JP2003096127A - Production method for ethylene polymer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing an ethylene polymer having a lower mol.wt. and a narrower mol.wt. distribution than those of an ethylene polymer obtained by using a generally used Phillips catalyst; and a method for producing an ethylene polymer having a good balance between environmental stress crack resistance (ESCR) and impact resistance and having a mol.wt. distribution widened by multistep polymerization. SOLUTION: This method for producing an ethylene polymer uses an organoaluminum-compound-carrying chromium catalyst which is prepared by causing an inorganic oxide carrier to carry a chromium compound of which at least a part of chromium atoms become hexavalent when activated by baking in a non-reducing atmosphere, activating the chromium compound by baking, causing the chromium compound to carry an organoaluminum compound in an inert hydrocarbon solvent, and removing the solvent to dry. An ethylene polymer prepared by the method is also provided.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing an ethylene polymer. More specifically, the present invention relates to a method for producing an ethylene-based polymer in which ethylene or (co) polymerization of ethylene and an α-olefin having 3 to 8 carbon atoms is carried out using a catalyst in which a specific organoaluminum compound is supported on a chromium catalyst. The ethylene-based polymer obtained by the method of the present invention has a wide range of manufacturable molecular weights, and has a low molecular weight and a narrow molecular weight distribution, and therefore is suitable for an injection-molded product. Also, it is possible to broaden the molecular weight distribution by carrying out multistage polymerization. It is suitable for blow molding products that have a good balance of environmental stress crack resistance (hereinafter sometimes abbreviated as ESCR) and rigidity.

[0002]

2. Description of the Related Art Ethylene polymers are widely used as resin materials for various molded articles, but the characteristics of the ethylene polymers differ depending on the molding method and application. For example, a polymer having a relatively low molecular weight and a narrow molecular weight distribution is suitable for a product molded by an injection molding method. On the other hand, a polymer having a relatively high molecular weight and a wide molecular weight distribution is suitable for a product molded by blow molding or inflation molding.

Conventionally, a chromium compound is supported on an inorganic oxide carrier, and is activated by firing in a non-reducing atmosphere so that at least a part of the supported chromium atoms is a hexavalent chromium catalyst (so-called Phillips catalyst. It is known that an ethylene-based polymer can be obtained by using a chromium catalyst hereinafter).

However, chromium catalysts generally produce ethylene polymers having a relatively high molecular weight and a relatively wide molecular weight distribution. Although a great deal of effort has been made to reduce the molecular weight of the ethylene polymer obtained by using a chromium catalyst, a sufficient result has not been obtained yet. Unlike Ziegler catalysts and metallocene catalysts, chromium catalysts with relatively high molecular weight can be obtained.
This is partly because hydrogen does not easily act as a chain transfer agent in a chromium catalyst system, and it is difficult to obtain a low molecular weight ethylene polymer.

Generally, in the polymerization with a chromium catalyst, the molecular weight is controlled by the polymerization temperature. To obtain a low molecular weight ethylene polymer, it is necessary to raise the polymerization temperature, but when the polymerization temperature is raised, the produced ethylene polymer melts in the polymerization reactor. There is a problem in the process such as the viscosity of the internal solution becomes high. Further, even if a low-molecular weight ethylene polymer is obtained, the molecular weight distribution is often still wide, and therefore a low-molecular weight component (hereinafter referred to as an extremely low-molecular weight component) that causes smoke and mesiness during molding. Will exist. Therefore, it has been difficult to produce an ethylene polymer suitable for injection and the like using a chromium catalyst.

Further, in the chromium-based catalyst, it is possible to lower the molecular weight by using an organoaluminum compound as a co-catalyst at the time of polymerization or by adding hydrogen as described later, but in this case, α-olefin is not produced during ethylene polymerization. As a by-product, and this by-product α-olefin is copolymerized with ethylene, the density of the resulting ethylene-based polymer may be reduced, and in a chromium-based catalyst using an organoaluminum compound as a co-catalyst, high-density ethylene is used. The polymer was difficult to obtain.

Further, in recent years, there has been a demand for higher quality ethylene polymers suitable for small blow molding products such as edible oil bottles and detergent bottles. For example,
There is a demand for smaller blow molding products that have a balance between ESCR and rigidity and that can be made thinner. However, when a blow molding product is produced from an ethylene polymer obtained by a conventional chromium catalyst, the molecular weight distribution of the ethylene polymer is not wide enough, so that the ESCR
It is hard to say that the balance between the rigidity and the rigidity is not sufficient and the customer's request can be sufficiently satisfied.

In order to develop a balance between ESCR and rigidity, an ethylene polymer component having a low molecular weight and a high density is generally used (hereinafter sometimes abbreviated as a low molecular weight component).
It is possible to improve these balances by combining an ethylene polymer component having a high molecular weight and a low density (hereinafter sometimes abbreviated as a high molecular weight component). Further, as the low molecular weight component, a component having a narrow molecular weight distribution is preferable in order to reduce an extremely low molecular weight component which causes smoke and mesiness during molding. It is possible to improve these balances by producing each of these components by multistage polymerization. However, as described above, as long as the conventional chromium catalyst is used, it is difficult to produce a low molecular weight component, so there is a limit to broadening the molecular weight distribution even if multi-step polymerization is performed, and even if multi-step polymerization is performed, these There is a limit to improving the balance.

As a method for obtaining an ethylene polymer having a low molecular weight, a method of combining an organic aluminum compound with a chromium catalyst is disclosed in, for example, Japanese Patent Publication Nos. 47-1365, 47-23176 and 49-.
9108, 49-13230 and the like. In these, a chromium catalyst and an organoaluminum compound are separately introduced into a polymerization reactor, or they are mixed in advance and introduced into a polymerization reactor to polymerize ethylene. A method of making a coalescence is disclosed. In the technology described in these publications, hydrogen acts as a chain transfer agent, unlike a general chromium catalyst,
As a result, an ethylene polymer having a relatively low molecular weight can be obtained. However, there is a limit to lowering the molecular weight, and a sufficiently low molecular weight was not achieved. Furthermore, the low molecular weight ethylene polymers obtained by these methods have a wide molecular weight distribution and a large amount of extremely low molecular weight components. Further, it was difficult to obtain a high-density product due to the by-produced α-olefin. Therefore, with these catalysts, it is difficult to obtain an ethylene-based polymer having a good balance between ESCR and rigidity even if multi-stage polymerization is performed.

Japanese Unexamined Patent Publication (Kokai) No. 51-17993 discloses a method for producing an ethylene polymer using a chromium catalyst treated with a specific organoaluminum compound (dihydrocarbylaluminum hydrocarbyl oxide). However, even in this method, similarly to the prior art publication using the above-mentioned chromium catalyst and organoaluminum compound, there is a limit in lowering the molecular weight, and it cannot be said that a sufficiently low molecular weight is achieved. Further, the obtained ethylene-based polymer has a wide molecular weight distribution and contains many extremely low molecular weight components.

WO94 / 13708 discloses a method for producing an ethylene polymer by using a chromium catalyst carrying a specific organoaluminum compound (dialkylaluminum ethoxide). Although the molecular weight can be controlled by hydrogen in this method, if the disclosed specific organoaluminum compound (dialkylaluminum ethoxide) is supported, there is a limit to lowering the molecular weight, and a sufficiently low molecular weight can be achieved. Was not done.

Further, JP-A-57-70109 discloses a method of improving ESCR by carrying out two-step polymerization by combining a chromium catalyst and a specific organoaluminum compound. However, this method is a method similar to the technique described in the above-mentioned publication in which the chromium catalyst and the organoaluminum compound are separately introduced into the polymerization reactor, and α-olefins mainly containing 1-hexene are by-produced, which is low. It has the drawback of introducing short chain branching into the molecular weight component. Therefore, it is difficult to obtain an ethylene polymer having a good balance between ESCR and rigidity. As described above, it has been difficult to produce an ethylene polymer having a low molecular weight, a narrow molecular weight distribution, and a high density by the conventional method using a chromium catalyst.

[0013]

The object of the present invention is to solve the above problems of the prior art and to produce an ethylene polymer having a high density and a low molecular weight and a narrow molecular weight distribution,
Another object of the present invention is to provide a method for producing an ethylene-based polymer having a wide molecular weight distribution by multistage polymerization, high environmental stress crack resistance (ESCR) and high rigidity, and an excellent balance of both properties.

[0014]

Means for Solving the Problems As a result of intensive studies in view of the above-mentioned problems, the present inventors have brought an organoaluminum compound into contact with a calcination-activated chromium catalyst in an inert hydrocarbon solvent and further removed the solvent. -By using a catalyst which is dried and supports an organoaluminum compound, an ethylene-based polymer having a low molecular weight, a narrow molecular weight distribution and a small amount of extremely low molecular weight components can be obtained. The present invention has been completed by finding that an ethylene-based polymer having an excellent balance of rigidity and a small amount of extremely low molecular weight components can be obtained.

That is, the present invention has solved the above-mentioned problems by developing a method for producing an ethylene polymer according to the following [1] to [8] and an ethylene polymer according to [9] to [13]. .

[1] A chromium compound is supported on an inorganic oxide carrier and activated by firing in a non-reducing atmosphere to make a chromium compound-carrying inorganic oxide carrier in which at least a part of chromium atoms are hexavalent. A chromium catalyst in which an organoaluminum compound represented by the following general formula (1), (2) or (3) is brought into contact in a hydrogen solvent, the solvent is removed and dried to support the organoaluminum compound is used. Method for producing ethylene-based polymer:

[Chemical 4] (In the formula, R ¹ , R ² , R ³ , R ⁴ and R ⁵ may be the same or different and each represents an alkyl group having 1 to 18 carbon atoms.)

[Chemical 5] (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 , R ⁹ and R ¹⁰ may be the same or different and each is a hydrogen atom or Represents an alkyl group having 1 to 18 carbon atoms, provided that
At least two substituents of R ^8, R ^9, R ¹⁰ is an alkyl group. )

[Chemical 6] (Wherein, R ¹¹ and R ¹² may be the same or different, each represents an alkyl group having 1 to 18 carbon atoms, R ^13, R
¹⁴ , R ¹⁵ , R ¹⁶ and R ¹⁷ may be the same or different,
Each represents a hydrogen atom, an alkyl group having 1 to 18 carbon atoms, a halogen atom, an alkoxy group, or a nitrile group. ).

[2] When the organoaluminum compound is brought into contact with an inert hydrocarbon solvent and the solvent is removed and dried,
2. The method for producing an ethylene polymer as described in 1 above, wherein the treatment with the solvent is performed so as to be as short as possible. [3] The method for producing an ethylene polymer as described in 1 or 2 above, wherein the molar ratio of the organoaluminum compound to chromium atoms is 0.1 to 10. The method for producing an ethylene-based coalescence according to the above 1, wherein the inorganic oxide carrier is silica.

[5] The method for producing an ethylene polymer as described in 1 above, wherein hydrogen is introduced during the polymerization to carry out the polymerization. [6] Polymerization of ethylene or ethylene and 3 carbon atoms by multi-stage polymerization using a plurality of polymerization reactors connected in series
8. The method for producing an ethylene-based polymer as described in 1 above, wherein the α-olefin of any one of 8 to 8 is copolymerized. [7] The method for producing an ethylene polymer according to the above item 6, wherein hydrogen is introduced into an arbitrary polymerization reactor to polymerize ethylene or copolymerize ethylene with an α-olefin having 3 to 8 carbon atoms. [8] MFR obtained by the method for producing an ethylene-based polymer as described in any one of 1 to 5 above is 0.5 to 50 g.
Ethylene polymer having a density of 0.940 to 0.970 g / cm ³ for 10 minutes.

[9] The HLMFR obtained by the method for producing an ethylene polymer according to the above 6 or 7 is 1 to HLMFR.
An ethylene polymer having a density of 100 g / 10 minutes and a density of 0.935 to 0.965 g / cm ³ . [10] An injection-molded product comprising the ethylene polymer according to the above item 8. [11] A blow-molded product comprising the ethylene polymer according to the above item 9. [12] With a chromium catalyst in which at least a part of chromium atoms is hexavalent by supporting a chromium compound on an inorganic oxide carrier and activating it by firing in a non-reducing atmosphere, ethylene or ethylene and a carbon atom having 3 to 8 carbon atoms are used. An ethylene polymer having an MFR of 20 to 50 g / 10 minutes and a molecular weight distribution (Mw / Mn) of 3 to 6, which is obtained by a method for producing an ethylene polymer that (co) polymerizes an α-olefin. [13] The method for producing an ethylene-based polymer is the same as in the above items 1 to 5.
13. The M as described in 12 above, which is the method according to any one of 1.
FR is 20 to 50 g / 10 minutes, molecular weight distribution (Mw / M
Ethylene polymer in which n) is 3 to 6.

The present invention will be specifically described below. A chromium catalyst in which at least a part of the chromium atoms becomes hexavalent by supporting a chromium compound on an inorganic oxide carrier and activating by firing in a non-reducing atmosphere is generally known as a Phillips catalyst. By MP McDaniel, Advances in Cata
An overview of this catalyst is given in literatures such as lysis, Volume 33, p. 47, 1985.

As the inorganic oxide carrier, there are No. 2 of the periodic table,
Oxides of Group 4, 13 or 14 metals are preferred. Specifically, magnesia, titania, zirconia, alumina,
Examples thereof include silica, thoria, silica-titania, silica-zirconia, silica-alumina, and mixtures thereof, with silica being preferred. In the case of silica-titania, silica-zirconia, and silica-alumina, those containing titanium, zirconium or aluminum atom as a metal component other than silica in an amount of 0.2 to 10%, preferably 0.5 to 7%, more preferably 1 to 5%. Is used. CE Marsden, Preparation of Catalysts, Volu describes the process, physical properties, and characteristics of carriers suitable for these chromium catalysts.
meV, 215 pages, 1991, Elsevier Science Publishers
, CE Marsden, Plastics, Rubber and Composit
es Processing and Applications, Volume 21, 193 pages,
It is described in literatures such as 1994.

These carriers have a specific surface area of 100 to 1000.
m ² / g, preferably 150~800m ² / g, more preferably in the range of 200~600m ² / g is used. The pore volume is 0.5 to 3.5 cm ³ / g, preferably 0.7 to 3.2 cm ³ / g, and more preferably 1.0 to 3.0 c.
Those having a range of m ³ / g are used. The average particle size is 10 to 200 μm, preferably 20 to 150 μm,
It is more preferably used in the range of 30 to 100 μm.

A chromium compound is supported on the above-mentioned inorganic oxide carrier. As the chromium compound, any compound may be used as long as it is a compound in which at least a part of the chromium atoms becomes hexavalent by being activated by firing in a non-reducing atmosphere after being supported, and examples thereof include chromium oxide, chromium halides, oxyhalides, and chromium. Examples thereof include acid salts, dichromates, nitrates, carboxylates, sulfates, chromium-1,3-diketo compounds, chromates and the like. Specific examples include chromium trioxide, chromium trichloride, chromyl chloride, potassium chromate, ammonium chromate, potassium dichromate, chromium nitrate, chromium sulfate, chromium acetate, tris (2-ethylhexanoate) chromium, Chromium acetylacetonate, bis (te
rt-Butyl) chromate and the like, among which chromium trioxide, chromium nitrate, 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 portion is burned during the firing activation treatment in a non-reducing atmosphere described later, and finally chromium trioxide is used. It is known that it reacts with the hydroxyl groups on the surface of the inorganic oxide carrier in the same manner as described above, and at least some of the chromium atoms become hexavalent and are immobilized in the structure of chromate ester.

The supporting of the chromium compound on the inorganic oxide carrier can be carried out by a known method such as impregnation, solvent removal, sublimation and the like. An appropriate method may be used depending on the type of chromium compound used. The amount of chromium compound supported is 0.2 to 2.0 as a chromium atom with respect to the inorganic oxide support.
% (Mass%, the same applies hereinafter), preferably 0.3 to 1.7%, more preferably 0.5 to 1.5%.

After supporting the chromium compound, it is activated by baking treatment. The calcination activation treatment can be carried out in a non-reducing atmosphere substantially free of water, such as oxygen or air. At this time, an inert gas may coexist. Preferably, the molecular sieves and the like are circulated and sufficiently dried air is used to carry out the activation treatment in a fluidized state. The firing activation is 400 to 900 ° C., preferably 450 to 850.
C., more preferably 500 to 800.degree. C., for 30 minutes to 48 hours, preferably 1 hour to 24 hours, more preferably 2 hours to 12 hours. By this calcination activation, at least a part of the chromium atoms of the chromium compound supported on the inorganic oxide carrier is oxidized into hexavalent and chemically fixed on the carrier.

From the above, the chromium catalyst used in the present invention can be obtained. In the present invention, before or after supporting the chromium compound and before firing activation, titanium alkoxides such as titanium tetraisopropoxide, zirconium alkoxides such as zirconium tetrabutoxide, and aluminum tributoxide such as Ethylene by adding metal alkoxides or organometallic compounds typified by aluminum alkoxides, organoaluminums such as trialkylaluminum, organomagnesiums such as dialkylmagnesium, and fluorine-containing salts such as ammonium silicofluoride. Polymerization activity, α
-A known method for controlling the copolymerizability with an olefin and the molecular weight and molecular weight distribution of the resulting ethylene polymer may be used in combination.

These metal alkoxides or organometallic compounds are burnt at a non-reducing atmosphere to burn their organic groups, and are oxidized into metal oxides such as titania, zirconia, alumina, or magnesia to be incorporated into the catalyst. included. In the case of fluorine-containing salts, the inorganic oxide carrier is fluorinated. These methods are described by CE Marsden,
Plastics, Rubber and Composites Processing and Ap
Replications, Volume 21, 193 pages, 1994 etc.

In the present invention, the calcination activated chromium catalyst is brought into contact with an organoaluminum compound in an inert hydrocarbon solvent, and then the solvent is removed and dried to be used as a chromium catalyst carrying an organoaluminum compound.

The organoaluminum compound is a dialkylaluminum alkoxide represented by the following general formula (1).

[Chemical 7] (In the formula, R ¹ , R ² , R ³ , R ⁴ and R ⁵ may be the same or different and each represents an alkyl group having 1 to 18 carbon atoms),

Dialkylaluminum siloxide represented by the following general formula (2)

[Chemical 8] (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 , R ⁹ and R ¹⁰ may be the same or different and each is a hydrogen atom or Represents an alkyl group having 1 to 18 carbon atoms, provided that
At least two substituents of R ^8, R ^9, R ¹⁰ is an alkyl group. )

Dialkylaluminum phenoxide represented by the following general formula (3)

[Chemical 9] (Wherein, R ¹¹ and R ¹² may be the same or different, each represents an alkyl group having 1 to 18 carbon atoms, R ^13, R
¹⁴ , R ¹⁵ , R ¹⁶ and R ¹⁷ may be the same or different,
Each represents a hydrogen atom, an alkyl group having 1 to 18 carbon atoms, a halogen atom, an alkoxy group, or a nitrile group. ) Is used.

It is essential that the carbon atom of the alkoxide group of the diethylaluminum alkoxide represented by the general formula (1) is a tertiary carbon, and the substituents (R ^{3 to} R ⁵ ) of the tertiary carbon are alkyl groups. is there. When the carbon atom of the alkoxide group is primary or secondary, or when it is a substituent other than an alkyl group even if it is tertiary, it is an ethylene-based resin having the same molecular weight as that when no dialkylaluminum alkoxide is supported, at the same polymerization temperature. Only polymers are available.

Further, it is essential that all three silicon atom substituents of the siloxide group of the dialkylaluminum siloxide represented by the general formula (2) be an alkyl group or an alkyl group and two hydrogen atoms. When the substituent of the silicon atom of the siloxide group is a combination of substituents other than these, only an ethylene-based polymer having a molecular weight equivalent to that when no dialkylaluminum siloxide is supported is obtained.

In the dialkylaluminum alkoxide represented by the general formula (1), specific examples of R ¹ , R ² , R ³ , R ⁴ and R ⁵ are methyl, ethyl, n-propyl, i-propyl and n-. Butyl, i-butyl, sec-butyl, tert-butyl, n-hexyl, n-octyl, n
-Decyl, n-dodecyl, cyclohexyl, etc., but for R ¹ and R ² , methyl, ethyl, n-
Butyl, i-butyl, n-hexyl and n-octyl are preferred. Methyl and ethyl are preferable for R ³ , R ⁴ and R ⁵ .

Specific examples of the dialkylaluminum alkoxide represented by the general formula (1) include dimethylaluminum 2-methyl-2-propoxide, dimethylaluminum 2-methyl-2-butoxide, dimethylaluminum 3-methyl-3-pentoxide. , Dimethylaluminum 3-ethyl-3-pentoxide, diethylaluminum 2-methyl-2-propoxide, diethylaluminum 2-methyl-2-butoxide, diethylaluminum 3-methyl-3-pentoxide, diethylaluminum 3-ethyl-3- Pentoxide,

Di-n-butylaluminum 2-methyl-
2-propoxide, di-n-butylaluminum 2-methyl-2-butoxide, di-n-butylaluminum 3
-Methyl-3-pentoxide, di-n-butylaluminum 3-ethyl-3-pentoxide, di-i-butylaluminum 2-methyl-2-propoxide, di-i-butylaluminum 2-methyl-2-butoxide, di-i-
Butylaluminum 3-methyl-3-pentoxide,
Di-i-butylaluminum 3-ethyl-3-pentoxide,

Di-n-hexyl aluminum 2-methyl-2-propoxide, di-n-hexyl aluminum 2
-Methyl-2-butoxide, di-n-hexyl aluminum 3-methyl-3-pentoxide, di-n-hexyl aluminum 3-ethyl-3-pentoxide, di-n-octyl aluminum 2-methyl-2-propoxide,
Di-n-octyl aluminum 2-methyl-2-butoxide, di-n-octyl aluminum 3-methyl-3-
Examples include pentoxide and di-n-octylaluminum 3-ethyl-3-pentoxide. Among these, among these,

Dimethyl aluminum 2-methyl-2-
Propoxide, diethylaluminum 2-methyl-2
-Propoxide, di-n-butylaluminum 2-methyl-2-propoxide, di-i-butylaluminum 2
-Methyl-2-propoxide, di-n-hexyl aluminum 2-methyl-2-propoxide and di-n-octyl aluminum 2-methyl-2-propoxide are preferred.

In the dialkylaluminum siloxide represented by the general formula (2), specific examples of the alkyl groups of R ⁶ , R ⁷ , R ⁸ , R ⁹ and R ¹⁰ 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 can be mentioned, but for R ⁶ and R ⁷ , methyl,
Ethyl, n-butyl, i-butyl, n-hexyl, n-
Octyl is preferred. Further, R ⁸ , R ⁹ and R ¹⁰ are preferably methyl, ethyl and i-propyl.

Specific examples of the dialkyl aluminum siloxide represented by the general formula (2) include dimethyl aluminum trimethyl siloxide and dimethyl aluminum.
Triethylsiloxide, dimethylaluminum tri i
-Propyl siloxide, diethyl aluminum trimethyl siloxide, diethyl aluminum triethyl siloxide, diethyl aluminum tri i-propyl siloxide,

Di-n-butyl aluminum trimethylsiloxide, di-n-butyl aluminum triethyl siloxide, di-n-butyl aluminum tri i-propyl siloxide, di i-butyl aluminum trimethyl siloxide, di i-butyl aluminum triethyl siloxide , I-butylaluminum tri-i-propylsiloxide,

Di-n-hexylaluminum trimethylsiloxide, di-n-hexylaluminum triethylsiloxide, di-n-hexylaluminum tri-i-propylsiloxide, di-n-octylaluminum trimethylsiloxide, di-n-octylaluminum triethylsiloxide Di-n-octyl aluminum tri i-propyl siloxide dimethyl aluminum dimethyl hydrosiloxide diethyl aluminum dimethyl ethyl siloxide diethyl aluminum ethyl hydromethyl siloxide di n-butyl aluminum n-butyl dimethyl siloxide di n-butyl aluminum n-butyl hydromethyl Siloxide di i-butyl aluminum i-butyl dimethyl siloxide di i-butyl aluminum i-butyl hydromethyl siloxy Sidodi n-hexyl aluminum dimethyl n-hexyl siloxide di n-hexyl aluminum n-hexyl hydromethyl siloxide di n-octyl aluminum dimethyl n-octyl siloxide di n-octyl aluminum Hydromethyl n-octyl siloxide is mentioned among these. ,

Dimethylaluminum trimethylsiloxide, diethylaluminum trimethylsiloxide,
Di-n-butylaluminum trimethylsiloxide, di-i-butylaluminum trimethylsiloxide, di-n
-Hexylaluminum trimethylsiloxide, di-n
Octylaluminum trimethylsiloxide diethylaluminum dimethylethylsiloxide diethylaluminum ethylhydromethylsiloxide is preferred.

In the dialkylaluminum phenoxide represented by the general formula (3), specific examples of R ¹¹ and R ¹² include methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl and sec-butyl. , Tert-butyl, n-hexyl, n-octyl, n-decyl, n-
Dodecyl, cyclohexyl and the like can be mentioned, but methyl, ethyl, n-butyl, i-butyl, n-hexyl,
N-octyl is preferred. In addition, R ¹³ , R ¹⁴ , R ¹⁵ and R ¹⁶
Specific examples of R ¹⁷ and R ¹⁷ include hydrogen, an alkyl group such as methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, sec-butyl, tert-butyl and n-butyl.
Hexyl, n-octyl, n-decyl, n-dodecyl,
Cyclohexyl, halogen as fluorine, chlorine, bromine,
Examples of iodine and alkoxy groups include methoxy, ethoxy, and nitrile. Hydrogen, methyl, fluorine, chlorine, methoxy, and nitrile are preferable, and hydrogen is particularly preferable.
Methyl, fluorine and methoxy are preferred.

Specific examples of the dialkylaluminum phenoxide represented by the general formula (3) include dimethylaluminum phenoxide, dimethylaluminum 4-methylphenoxide, dimethylaluminum 2,6-dimethylphenoxide, dimethylaluminum 2,4.
6-trimethylphenoxide, dimethyl aluminum
2-fluorophenoxide, dimethyl aluminum 3
-Fluorophenoxide, dimethyl aluminum 4-
Fluorophenoxide, dimethylaluminum 2-methoxyphenoxide, dimethylaluminum 4-methoxyphenoxide,

Diethylaluminum phenoxide, diethylaluminum 4-methylphenoxide, diethylaluminum 2,6-dimethylphenoxide, diethylaluminum 2,4,6-trimethylphenoxide, diethylaluminum 2-fluorophenoxide, diethylaluminum 3-fluorophenoxide, diethylaluminum. 4-fluorophenoxide, diethylaluminum 2-methoxyphenoxide, diethylaluminum 4-methoxyphenoxide,

Di-n-butyl aluminum phenoxide, di-n-butyl aluminum 4-methylphenoxide, di-n-butyl aluminum 2,6-dimethylphenoxide, di-n-butyl aluminum 2,4,6-trimethylphenoxide, di-n-butyl Aluminum 2
-Fluorophenoxide, di-n-butylaluminum
3-fluorophenoxide, di-n-butylaluminum 4-fluorophenoxide, di-n-butylaluminum 2-methoxyphenoxide, di-n-butylaluminum 4-methoxyphenoxide,

Di-butyl aluminum phenoxide, di-butyl aluminum 4-methylphenoxide, di-butyl aluminum 2,6-dimethylphenoxide, di-butyl aluminum 2,4,6-trimethylphenoxide, di-butyl Aluminum 2
-Fluorophenoxide, di-butyl aluminum
3-fluorophenoxide, di-i-butylaluminum 4-fluorophenoxide, di-i-butylaluminum 2-methoxyphenoxide, di-i-butylaluminum 4-methoxyphenoxide,

Di-n-hexyl aluminum phenoxide, di-n-hexyl aluminum 4-methylphenoxide, di-n-hexyl aluminum 2,6-dimethylphenoxide, di-n-hexyl aluminum 2,4,4
6-trimethylphenoxide, di-n-hexylaluminum 2-fluorophenoxide, di-n-hexylaluminum 3-fluorophenoxide, di-n-hexylaluminum 4-fluorophenoxide, di-n-hexylaluminum 2-methoxyphenoxide, di-n-
Hexylaluminum 4-methoxyphenoxide,

Di-n-octyl aluminum phenoxide, di-n-octyl aluminum 4-methylphenoxide, di-n-octyl aluminum 2,6-dimethylphenoxide, di-n-octyl aluminum 2,4,4
6-trimethylphenoxide, di-n-octylaluminum 2-fluorophenoxide, di-n-octylaluminum 3-fluorophenoxide, di-n-octylaluminum 4-fluorophenoxide, di-n-octylaluminum 2-methoxyphenoxide, di-n-
Octylaluminum 4-methoxyphenoxide may be mentioned. Among these, among these,

Dimethyl aluminum phenoxide, diethyl aluminum phenoxide, di-n-butyl aluminum phenoxide, di i-butyl aluminum
Phenoxide, di-n-hexyl aluminum phenoxide, di-n-octyl aluminum phenoxide, dimethyl aluminum 4-methylphenoxide, diethyl aluminum 4-methylphenoxide, di-n-butyl aluminum 4-methylphenoxide, di-butyl aluminum 4-methylphenoxide, Di-n-hexyl aluminum 4-methylphenoxide and di-n-octyl aluminum 4-methylphenoxide are preferable.

Among the organoaluminum compounds used in the present invention, the organoaluminum compound represented by the general formula (1) or (2) is preferable, and the organoaluminum compound represented by the general formula (2) is particularly preferable. These organoaluminum compounds are (1) a method in which a trialkylaluminum is reacted with a tertiary alcohol, silanols or phenols, respectively, and (ii) a dialkylaluminum halide is reacted with a metal alkoxide, a metal siloxide or a metal phenoxide, respectively. It can be easily synthesized by a method of reacting (iii) trialkylaluminum with poly (dialkylsiloxane) or poly (alkylhydrosiloxane).

That is, when synthesizing the dialkylaluminum alkoxide represented by the general formula (1), the method (i) or (ii) can be adopted. (1) Method of reacting trialkylaluminum with tertiary alcohols As shown in the following formula, trialkylaluminum and tertiary alcohols are reacted at a molar ratio of 1: 1 (here,
R may be the same as or different from R ¹ or R ² and has 1 carbon atom.
Represents an alkyl group of -18. R ^{1 to} R ⁵ are represented by the general formula (1)
Has the same meaning as. ).

[Chemical 10] (Ii) Method of reacting dialkylaluminum halide with metal alkoxide As shown in the following formula, a dialkylaluminum halide and a metal alkoxide of a tertiary alcohol are reacted at a molar ratio of 1: 1 (R ^{1 to} R ⁵ are represented by the general formula). It has the same meaning as (1).

[Chemical 11] X in the dialkylaluminum halide (R ¹ R ² AlX) is fluorine, chlorine, bromine or iodine, and chlorine is particularly preferably used. Further, M in the metal alkoxide (R ³ R ⁴ R ⁵ COM) of the tertiary alcohol is an alkali metal, and lithium, sodium and potassium are particularly preferably used.

When synthesizing the dialkylaluminum siloxide represented by the general formula (2), the above (i) is used.
The method of (iii) can be adopted. (1) Method of reacting trialkylaluminum with silanols A trialkylaluminum and silanols are reacted at a molar ratio of 1: 1 as follows (where R is the same as or different from R ⁶ or R ^7). May also represent an alkyl group having 1 to 18 carbon atoms, and R ^{6 to} R ¹⁰ have the same meanings as in formula (2).

[Chemical 12] (Ii) Method of reacting dialkyl aluminum halide with metal siloxide As shown in the following formula, dialkyl aluminum halide and metal siloxide are reacted at a molar ratio of 1: 1 (R ⁶
~ R ¹⁰ has the same meaning as in formula (2). ).

[Chemical 13] (Iii) Trialkylaluminum and poly (dialkylsiloxane) or poly (alkylhydrosiloxane)
Method of reacting with trialkylaluminum and poly (dialkylsiloxane) or poly (alkylhydrosiloxane) as shown in the following formula, where the atomic ratio of aluminum to silicon is 1: 1.
(R ^{6 to} R ¹⁰ have the same meanings as in formula (2)).

[Chemical 14] The poly (dialkylsiloxane) or poly (alkylhydrosiloxane) may have a linear structure or a cyclic structure, but the cyclic structure is preferable from the viewpoint of the purity of the product. n is 2 or more, but 4 or more is preferable. These poly (dialkylsiloxanes) or poly (alkylhydrosiloxanes) having various viscosities are used, and those having a viscosity at 30 ° C. of 10 to 1000 centistokes are particularly preferably used.

Further, when synthesizing the dialkylaluminum phenoxide represented by the general formula (3), the above method (1) or (ii) can be adopted. (1) Method of reacting trialkylaluminum with phenols As shown in the following formula, a trialkylaluminum and phenols are reacted at a molar ratio of 1: 1 (where R is the same as R ¹¹ or R ^12). May be different, having 1 to 1 carbon atoms
Represents 18 alkyl groups. R ^{11 to} R ¹⁷ are represented by general formula (3)
Has the same meaning as. ).

[Chemical 15] As shown in the following formula, a dialkylaluminum halide and a metal phenoxide are reacted at a molar ratio of 1: 1 (R
^{11 to} R ¹⁷ have the same meanings as in formula (3). ).

[Chemical 16] X in the dialkylaluminum halide (R ¹¹ R ¹² AlX) is fluorine, chlorine, bromine or iodine, and chlorine is particularly preferably used. In addition, metal phenoxide (C ₆
M in R ¹³ R ¹⁴ R ¹⁵ R ¹⁶ R ¹⁷ OM) is an alkali metal, and lithium, sodium and potassium are particularly preferably used.

The by-product RH is an inactive alkane, and when it has a low boiling point, it volatilizes out of the system during the reaction process, or when it has a high boiling point, it remains in the solution, but remains in the system. However, it is inactive in the subsequent reaction. Also a by-product M
-X is an alkali metal halide, which 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.
Perform above ℃. 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 used as it is for the reaction with the chromium catalyst, or the reaction product may be isolated by removing the solvent, but it is preferable to use the solution as it is because it is simple.

The synthesis method and physical / chemical properties of these organoaluminum compounds are described by T. Mole et al.
Organoaluminum Compounds, 3rd.ed., 1972, Elsevi
It is written in detail in er etc.

The amount of the supported organoaluminum compound is
The molar ratio of the organoaluminum compound to the chromium atom is
0.1-10, preferably 0.5-7, more preferably 1-
The range of 5 is preferable. By setting the molar ratio to 0.1 to 10, as compared with the case where the organoaluminum compound is not supported, an ethylene polymer having a low molecular weight is obtained at the same polymerization temperature, and further by introducing hydrogen during the polymerization, if necessary. Furthermore, an ethylene polymer having a significantly low molecular weight is obtained. When the molar ratio of the organoaluminum compound to the chromium atom is less than 0.1, the effect of supporting the organoaluminum compound is less likely to appear, and the molecular weight at the same polymerization temperature is not so different from that when the organoaluminum compound is not supported. If the molar ratio exceeds 10, the ethylene polymerization activity will be lower than in the case where the organoaluminum compound is not supported, and the molecular weight distribution of the low molecular weight ethylene polymer obtained by introducing hydrogen will be broad,
Very low molecular weight components increase. Although the details of the reason for this activity reduction and broad distribution are unknown, it is considered that the excess organoaluminum compound binds to the chromium active site to inhibit the ethylene polymerization reaction and further change the active site to an unfavorable structure. To be

The method of supporting the organoaluminum compound is not particularly limited as long as it is a method of contacting the chromium catalyst after calcination activation in a liquid phase in an inert hydrocarbon. For example, an inert hydrocarbon solvent such as propane, n-butane, isobutane, n-pentane, isopentane, hexane, heptane, octane, decane, cyclohexane, benzene, toluene and xylene is mixed with a chromium catalyst after calcination activation. A method of forming a slurry state and adding an organoaluminum compound thereto is preferable.

The organoaluminum compound to be added may be diluted with the above-mentioned inert hydrocarbon solvent or may be added to the solvent without being diluted. The diluting solvent and the supporting solvent may be the same or different.

The amount of the inert hydrocarbon solvent used is arbitrary, but it is preferably an amount sufficient for at least stirring in a slurry state in preparation of the catalyst. The amount of the solvent used is not particularly limited as long as it is such an amount, but is, for example, 3 to 30 ml as the amount of the solvent per 1 g of the chromium catalyst after calcination activation.

In the present invention, a supporting operation for supporting an organoaluminum compound on a chromium catalyst in an inert hydrocarbon solvent is carried out. At this time, the order of adding the organoaluminum compound and the chromium catalyst to the solvent is arbitrary, but specifically, the chromium catalyst is suspended in an inert hydrocarbon solvent, the organoaluminum compound is added, and the mixture is stirred. Therefore, it is preferable to carry out the operation of the supporting reaction.

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 1 ~ 4 hours. The organoaluminum compound reacts with chromium atoms, at least a part of which has become hexavalent due to activation by firing, and reduces the chromium atoms to low-valent chromium atoms. This phenomenon can be easily confirmed from the fact that the chromium catalyst after firing activation exhibits an orange color peculiar to the hexavalent chromium atom, while the chromium catalyst subjected to the loading operation with the organoaluminum compound is green or blue green. . It is presumed that at least a part of hexavalent chromium atoms is reduced to trivalent or divalent chromium atoms due to the change in color of the catalyst.

After the stirring is stopped and the supporting operation is completed, rapid drying is carried out under reduced pressure to remove the solvent. At this time, filtration may be used together. The reduced pressure and drying are performed so that the organoaluminum compound-supported chromium catalyst becomes a free-flowing powder. After the completion of loading, it is necessary to remove the solvent promptly. 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, the molecular weight distribution of the low molecular weight ethylene polymer obtained by introducing hydrogen becomes broad, and the extremely low molecular weight component increases. Therefore, it is preferable to shorten the contact time with the solvent as much as possible, including the contact with the solvent at the time of loading, and quickly separate and remove the solvent. No conventional technique has been found that clearly describes the effect of rapid solvent separation / removal on the polymerization activity and molecular weight distribution, and separating the solvent is one of the features of the present invention. The details of the reason why this effect is obtained are unclear, but in the presence of a solvent, the reaction between the chromium active site and the organoaluminum compound continues to proceed, resulting in a overreduction reaction and the catalyst inhibiting the ethylene polymerization reaction. ,
Furthermore, it is considered that the active site is changed to an unfavorable structure. Therefore, it is necessary to shorten the supporting reaction time as much as possible so that the contact time with the solvent is as short as possible, and then quickly separate the solvent so that the over-reduction reaction does not proceed. The time required for separating and drying the solvent is preferably within 3 times, preferably within 2 times, and more preferably within 1 time of the supporting reaction time after completion of the supporting reaction.

The total time from the start of loading to the completion of solvent removal and completion of drying is 5 minutes to 24 hours, preferably 30 minutes to 18 hours, and more preferably 1 to 12 hours. After the completion of drying, the organoaluminum compound-supported chromium catalyst is preferably in a free flowing, free-flowing state. As a physical property measure, the residual mass of the solvent is 1/10 or less, preferably 1/3, of the mass obtained by multiplying the pore volume of the chromium catalyst by the density of the solvent.
0, and more preferably 1/100 or less. Here, the pore volume is obtained by the BET method by nitrogen adsorption, and the residual mass of the solvent is obtained by the following equation.

## EQU00001 ## Remaining mass of solvent = (mass of organoaluminum compound-supported chromium catalyst after drying)-{(mass of organoaluminum compound) + (mass of chromium catalyst)}

As a method of using the organoaluminum compound in combination with the chromium catalyst, in addition to the method of preliminarily supporting the catalyst as in the present invention, the chromium catalyst and the organoaluminum compound may be used in the presence or absence of a diluting solvent. Direct feed to the reactor separately, chromium catalyst and organoaluminum compound premixed or contacted in a solvent in the reactor, or chromium catalyst and organoaluminum compound in a prereactor separate from the reactor There is a method of mixing or pre-contacting them and feeding the mixed slurry to the reactor.

However, these methods are not preferable because the obtained ethylene-based polymers have a broad molecular weight distribution and a large amount of extremely low molecular weight components. According to the method of preliminarily supporting the organoaluminum compound of the present invention on the chromium catalyst, the molecular weight distribution of the obtained ethylene polymer is narrowed, and the extremely low molecular weight component is reduced. In particular, when hydrogen is introduced during polymerization to obtain a low molecular weight ethylene polymer, the molecular weight distribution of the obtained ethylene polymer is narrower than that when hydrogen is not introduced, and the extremely low molecular weight component can be reduced.

According to the organoaluminum compound-supporting chromium catalyst of the present invention, an ethylene polymer having a lower molecular weight can be obtained at the same polymerization temperature as compared with the case where the organoaluminum compound is not supported on the chromium catalyst. Therefore, when hydrogen is introduced, the catalyst of the present invention makes it possible to obtain an ethylene polymer having a lower molecular weight at the same polymerization temperature.

That is, in the case of producing a low molecular weight component with a conventional chromium catalyst, the molecular weight cannot be lowered sufficiently, or even if the molecular weight can be lowered, the molecular weight distribution is wide and the extremely low molecular weight component cannot be reduced. When the organoaluminum compound-supported chromium catalyst of the present invention is used, an ethylene polymer having a sufficiently low molecular weight, a narrow molecular weight distribution and a small amount of extremely low molecular weight components can be obtained.

Therefore, the catalyst of the present invention is the above-mentioned ESCR.
It is also preferably used in a method of combining a high molecular weight component and a low molecular weight component for producing an ethylene polymer having excellent rigidity and rigidity.

Further, when the above-mentioned organoaluminum compound is used in combination without being supported on a chromium catalyst, an α-olefin mainly containing 1-hexene is by-produced, and this is copolymerized with ethylene to form an ethylene-based polymer. Density tends to decrease. That is, the above-mentioned method cannot produce an ethylene polymer component having a low molecular weight and a high density, whereas the organoaluminum compound-supported chromium catalyst of the present invention can suitably obtain a sufficiently high-molecular-weight low-molecular weight component. .

As described above, by supporting the organoaluminum compound, the molecular weight is low and the molecular weight distribution is narrow.
No conventional technique has been found that clearly describes the effect of increasing the density, and supporting an organoaluminum compound on a chromium catalyst is one of the important features of the present invention.

Further, in the method in which the organoaluminum compound is not supported on the chromium catalyst and the organoaluminum compound is used in combination, the chromium catalyst and the organoaluminum compound are separately supplied to the reactor for continuous production.
In that case, unless the amount and ratio of the chromium catalyst and the organoaluminum compound continuously supplied are adjusted accurately,
The polymerization activity and the molecular weight of the ethylene-based polymer fluctuate, and it is difficult to continuously obtain the same specifications.

According to the method of preliminarily supporting the organoaluminum compound of the present invention on the chromium catalyst, the molar ratio of the organoaluminum compound to the chromium atom in the reactor is always constant, and as a result, products of the same standard can be stably continuously produced. It can be produced and the method of the present invention is suitable for continuous production.

When an ethylene polymer is produced using the organoaluminum compound-supported chromium catalyst of the present invention, any method such as slurry polymerization or gas phase polymerization can be employed.

The slurry polymerization method is usually carried out in a hydrocarbon solvent. Hydrocarbon solvents include propane, n-butane,
Isobutane, n-pentane, isopentane, hexane,
Inert hydrocarbons such as heptane, octane, decane, cyclohexane, benzene, toluene, xylene are used alone or as a mixture thereof. Particularly, propane, n-butane and isobutane are preferable as the solvent because the ethylene polymer is difficult to dissolve in the solvent and the slurry state can be maintained even if the polymerization temperature is raised to produce an ethylene polymer having a low molecular weight.

As the gas phase polymerization method, a commonly known polymerization method such as a fluidized bed or a stirring bed can be adopted in the presence of an inert gas. In some cases, a so-called condensing mode in which a medium for removing the heat of polymerization coexists can be adopted.

The polymerization temperature in the slurry or gas phase polymerization method is generally 0 to 300 ° C., and practically 20
-200 degreeC, Preferably it is 50-180 degreeC, More preferably, it is 70-150 degreeC. Particularly in the case of slurry polymerization, the temperature is 60 to 120 ° C, preferably 70 to 110 ° C, more preferably 80 to 105 ° C. The catalyst concentration and ethylene concentration in the reactor can be any concentration sufficient to drive the polymerization. For example, the catalyst concentration can range from about 0.0001 to about 5% based on the weight of the reactor contents for slurry polymerization.

In the polymerization method according to the present invention, hydrogen can coexist if necessary. Here, hydrogen acts as a so-called chain transfer agent for controlling the molecular weight, as in the case of polymerization using a Ziegler catalyst or a metallocene catalyst. Of course, the high molecular weight component can also be obtained by lowering the polymerization temperature. Even in this case, according to the organoaluminum-supporting chromium catalyst of the present invention, it is possible to obtain a target high molecular weight component at a sufficiently practical polymerization temperature.

The hydrogen pressure is not particularly limited, but in the case of the slurry polymerization method, the hydrogen concentration in the liquid phase is usually 1.
0 × 10 ^{-5 to} 1.0 × 10 ^-1 %, preferably 5.0 × 10 ^-4 to
5.0 × 10 ^-2 %, in the case of the vapor phase polymerization method, the hydrogen partial pressure in the vapor phase is 1.0 × 10 ^{-3 to} 10.0 MPa, preferably 5.0 × 1.
It is in the range of 0 ^{-2 to} 5.0 MPa. The ethylene pressure is also not particularly limited, but in the case of the slurry polymerization method, it is usually 1.0 to 20.0% as the ethylene concentration in the liquid phase, preferably 2.0 to
15.0%, in the case of the gas phase polymerization method, the ethylene partial pressure in the gas phase is in the range of 1.0 to 20.0 MPa, preferably 2.0 to 15.0 MPa.

For the purpose of density adjustment, α-olefins such as propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene and 1-octene may be used alone or in combination of two or more kinds. Can be introduced into the copolymer for copolymerization. Here, the α-olefin content is preferably 15 mol% or less, and particularly preferably 10 mol% or less in the ethylene polymer.

The ethylene-based polymer obtained by the method of the present invention preferably has a low MFR of 20 to 50 g / 10 min and a molecular weight distribution (Mw / Mn) of 3 to.
It is as narrow as 6. Furthermore, its density is 0.960 or higher. Such an ethylene-based polymer has not been obtained by using a conventional Phillips catalyst (chromium catalyst). Therefore, ethylene polymerization using a Phillips catalyst (chromium catalyst) or a catalyst based on it is Alternatively, it is a novel ethylene polymer as an ethylene polymer obtained by copolymerization with an α-olefin containing ethylene as a main component.

In the present invention, whichever of the above polymerization methods is used, not only single-stage polymerization for producing an ethylene polymer by using one reactor but also at least two reactors for broadening the molecular weight distribution It is possible to carry out a multi-stage polymerization in which a high molecular weight component and a low molecular weight component are respectively produced by linking In the case of multi-stage polymerization, a two-stage polymerization 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 to polymerize preferable.

The multi-stage polymerization will be described by taking the two-stage polymerization as an example.
The transfer from the first-stage reactor to the second-stage reactor is performed by a differential pressure due to continuous discharge of the polymerization reaction mixture from the second-stage reactor through a connecting pipe. The order of producing the high molecular weight component and the low molecular weight component is as follows: the high molecular weight component in the first stage reactor, the low molecular weight component in the second stage reactor, or the low molecular weight component in the first stage reactor, the second stage reactor. Although any method of producing a high molecular weight component may be used, a method of producing a high molecular weight component in the first stage reactor and a low molecular weight component in the second stage reactor,
It is more preferable in terms of productivity because an intermediate hydrogen flash tank is not required for the transition from the first stage to the second stage.

In the first stage, ethylene homopolymerization or, if necessary, copolymerization with α-olefin is carried out while controlling the molecular weight by the mass ratio or partial pressure ratio of hydrogen concentration to ethylene concentration, polymerization temperature or both. , Again
-The polymerization reaction is performed while adjusting the density by the mass ratio or partial pressure ratio of the olefin concentration to the ethylene concentration.

In the second stage, hydrogen and α-olefin which flow in from the first stage are contained in the reaction mixture, and hydrogen and α-olefin can be newly added, respectively, if necessary. Therefore, also in the second stage, while adjusting the molecular weight by the mass ratio or partial pressure ratio of hydrogen concentration to ethylene concentration, the polymerization temperature or both, the density is adjusted by the mass ratio or partial pressure ratio of α-olefin concentration to ethylene concentration. While carrying out the polymerization reaction. As for the catalyst, not only the polymerization reaction may be continuously performed in the second stage by the catalyst flowing from the first stage, but the catalyst may be newly supplied in the second stage. Moreover, you may add an organometallic compound in each step as needed.

When multistage polymerization is carried out in order to obtain an ethylene polymer having a high balance between ESCR and rigidity, the catalyst of the present invention is used, and hydrogen introduction is preferably suppressed in the first stage. The introduction of the α-olefin produces a high molecular weight, low density component. Further, in order to generate a higher molecular weight component,
It is also possible to carry out the polymerization at a polymerization temperature of the first stage lower than that of the second stage. Next, in the second stage, hydrogen is introduced, and the α-olefin is preferably polymerized while suppressing the inflow from the preceding stage to produce a low-molecular-weight and high-density component.

The ratio of the high molecular weight component to the low molecular weight component in the case of the two-step polymerization is 10 for the high molecular weight component.
To 90 parts by mass, the low molecular weight component is 90 to 10 parts by mass, preferably the high molecular weight component is 20 to 80 parts by mass, the low molecular weight component is 80 to 20 parts by mass, and more preferably the high molecular weight component is 30 to 70 parts by mass, The low molecular weight component is 70 to 30 parts by mass. The HLMFR of the high molecular weight component is 0.01-10.
0 g / 10 minutes, preferably 0.01 to 50 g / 10 minutes, and the MFR of the low molecular weight component is 0.1 to 1000 g / 10 minutes, preferably 0.1 to 500 g / 10 minutes.

The ethylene polymer obtained by the method of the present invention has a lower molecular weight and a narrower molecular weight distribution than those obtained by conventional chromium catalysts, and is suitable for injection molded products.
In case of multi-stage polymerization, the molecular weight distribution is wide and ESCR
Since it has high rigidity and high balance, it is very effective for blow molding products, especially small blow molding products. MFR of ethylene polymer for injection molding products is 0.
5 to 50 g / 10 min and a density of 0.940 to 0.970 g / cm ^3, HLMFR of the ethylene-based polymer for blow molding product 1
100g / 10min, density 0.935 ~ 0.965g / cm ³ , HLMF of ethylene polymer especially for small blow molding products
R is 20 to 50 g / 10 minutes, density is 0.940 to 0.965 g / c
m is ^3.

The ethylene polymer obtained by multistage polymerization is preferably kneaded after the production. The kneading can be appropriately performed using a conventionally known single-screw or twin-screw extruder or a continuous kneader.

[0092]

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

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

B) Melt flow rate (MFR): JI
According to Condition 1 of Table 1 of SK-7210 (1996 edition),
The measured value at a temperature of 190 ° C. and a load of 21.18 N is shown as MFR. c) High load melt flow rate (HLMFR): J
According to Table 1 of IS K-7210 (1996 edition), condition 7, the measured value at a temperature of 190 ° C. and a load of 211.82 N is HL.
Shown as MFR. d) Density: Measured according to JIS K-7112 (1996 version).

E) Molecular weight distribution (Mw / Mn): number average molecular weight (Mn) determined by gel permeation chromatography (GPC) of the produced ethylene polymer under the following conditions.
And the weight average molecular weight (Mw). [Gel Permeation Chromatographic Measurement Conditions] Device: WATERS 150C model, column: Shodex-HT806M, solvent: 1,2,4-trichlorobenzene, temperature: 135 ° C, universal evaluation using a monodisperse polystyrene fraction. Regarding the molecular weight distribution represented by the ratio of Mw to Mn (Mw / Mn) (the larger the Mw / Mn, the broader the molecular weight distribution) is "size exclusion chromatography (polymer high performance liquid chromatography)" (Mori Sadao, Kyoritsu Shuppan, page 96)
The sensitivity of the molecular weight M represented by the following equation was determined by applying the data of alkane and the fractional linear polyethylene with Mw / Mn ≦ 1.2, and the actual measurement value of the sample was corrected.

## EQU2 ## Sensitivity of molecular weight M = a + b / M a and b are constants, a = 1.032 and b = 189.2.

F) Environmental stress crack resistance (ESCR): JIS
The F50 value measured by the BTL method according to K-6760 (1996 edition) was used as the value of ESCR (hr). g) Rigidity: The flexural modulus measured according to JIS K-7203 (1996 version) was used as the value of rigidity.

Example 1 (1) Synthesis of diethylaluminum 2-methyl-2-propoxide 48 mL of distilled and purified hexane was placed in a 100 mL flask which had been sufficiently replaced with nitrogen, and 1.37 mL (10 mmol) of triethylaluminum manufactured by Tosoh Finechem Co., Ltd. Was added and dissolved. Then 2-methyl-2-propanol
0.96 mL (10 mmol; Aldrich) was added.
The flask was heated with an oil bath and hexane was refluxed for 2 hours to complete the reaction. It was cooled to room temperature as it was, and diethylaluminum 2-methyl-2-propoxide was added to 0.
A 2 mol / L-hexane solution was obtained.

(2) Preparation of Chromium Catalyst A 500 mL beaker was loaded with silica (Daviso from WR Grace).
n952 grade; specific surface area 300 m ² / g, pore volume 1.6 c
m ³ / g, average particle size 80 μm) 20 g, put pure water 50
mL was added to make a slurry. A solution prepared by dissolving 0.40 g of anhydrous chromium trioxide (manufactured by Wako Pure Chemical Industries, Ltd.) in 10 mL of pure water was added to this with stirring, and the mixture was stirred at room temperature for 1 hour. Remove water by decantation, and use a constant temperature dryer at 110 ° C for 12 hours.
It was dried for an hour and the water was removed. 15 g of the obtained powder was placed in a quartz glass tube with a perforated plate and a tube diameter of 3 cm, set in an electric furnace for cylindrical firing, and fluidized with air passing through molecular sieves at a flow rate of 1.0 L / min. , 800 ° C
The firing activation was performed for 10 hours. An orange chromium catalyst was obtained which was shown to contain hexavalent chromium atoms. As a result of elemental analysis, the amount of carried chromium atoms was 1.01%.

(3) Chromium catalyst supporting organoaluminum compound In a 100 mL flask previously purged with nitrogen, the above (2) was added.
2 g of the chromium catalyst obtained in Step 1 was added, and 30 mL of distilled and purified hexane was added to form a slurry. 3.9 mL of a 0.2 mol / L-hexane solution of diethylaluminum 2-methyl-2-propoxide synthesized in (1) above (Al / C
r mol ratio = 2) was added, and the mixture was stirred at 40 ° C. for 2 hours. Immediately after completion of the stirring, the solvent was removed under reduced pressure over 30 minutes to obtain a free flowing organic aluminum compound-supported chromium catalyst. The catalyst showed a green color due to reduction of hexavalent chromium.

(4) Polymerization Into a 1.5 L autoclave that had been sufficiently replaced with nitrogen, 50 mg of the chromium catalyst supporting the organoaluminum compound obtained in (3) above and 0.7 L of isobutane were charged, and the internal temperature was adjusted to 1
The temperature was raised to 05 ° C. Polymerization was initiated by introducing ethylene, and polymerization was carried out at 105 ° C for 1 hour while maintaining the ethylene partial pressure at 1.4 MPa. Then, the content gas was discharged to the outside of the system to terminate the polymerization. As a result, 60 g of polyethylene was obtained. The polymerization activity per 1 g of catalyst per 1 hour of polymerization time is 1200 g / g · h.
It was r. Physical properties (MFR, HLMFR, HLMFR /
MFR, density, molecular weight (Mn, Mw), molecular weight distribution (M
The measurement results of w / Mn)) are shown in Table 1. An ethylene polymer having a lower molecular weight at the same polymerization temperature than that of a general chromium catalyst was obtained.

Example 2 (1) Synthesis of Diethylaluminum Trimethylsiloxide 48 mL of distilled and purified hexane was placed in a 100 mL flask thoroughly replaced with nitrogen, and triethylaluminum 1.
37 mL (10 mmol; manufactured by Tosoh Finechem Co., Ltd.) was added and dissolved. Next, trimethylsilanol 0.90g
(10 mmol; manufactured by Shin-Etsu Chemical) was added. The flask was heated with an oil bath and hexane was refluxed for 2 hours to complete the reaction. It was cooled to room temperature as it was, and a 0.2 mol / L-hexane solution of diethylaluminum trimethylsiloxide was obtained.

(2) Catalyst Preparation and Polymerization Instead of diethylaluminum 2-methyl-2-propoxide, 3.9 mL (Al / A) of 0.2 mol / L-hexane solution of diethylaluminum trimethylsiloxide synthesized in (1) above was used. A catalyst was prepared in the same manner as in Example 1 (3) except that Cr molar ratio = 2) was added to obtain an organoaluminum compound-supported chromium catalyst. Further Example 1
Polymerization was performed in exactly the same manner as (4). As a result, 63g
Polyethylene was obtained. The polymerization activity per 1 g of catalyst per 1 hour of polymerization time was 1260 g / g · hr.
The physical property measurement results are shown in Table 1. An ethylene polymer having a lower molecular weight at the same polymerization temperature than that of a general chromium catalyst was obtained.

Example 3 (1) Synthesis of Diethylaluminum Dimethylethylsiloxide In a 100 mL flask thoroughly replaced with nitrogen, 13.67 mL (100% of triethylaluminum manufactured by Tosoh Finechem Co., Ltd.) was added.
mmol) and octamethylcyclotetrasiloxane 7.76 mL (25 mmol; manufactured by Shin-Etsu Chemical Co., Ltd.) were added.
The flask was heated with an oil bath and reacted at 180 ° C. for 2 hours. It was cooled to room temperature as it was, and transferred to a 1 L flask in which the whole amount was replaced with nitrogen, and distilled and purified in hexane 479.
It was dissolved in mL. A 0.2 mol / L-hexane solution of diethylaluminum dimethylethyl siloxide was obtained.

(2) Catalyst Preparation and Polymerization In place of diethylaluminum 2-methyl-2-propoxide, 3.9 mL (Al) of a 0.2 mol / L-hexane solution of diethylaluminum dimethylethylsiloxide synthesized in (1) above was used. / Cr molar ratio = 2) A catalyst was prepared in the same manner as in Example 1 (3) except that the addition was performed to obtain an organoaluminum compound-supported chromium catalyst. Further, polymerization was carried out in exactly the same manner as in Example 1 (4). As a result, 6
6 g of polyethylene was obtained. The polymerization activity per 1 g of catalyst per 1 hour of polymerization time was 1320 g / g · hr. The physical property measurement results are shown in Table 1. An ethylene polymer having a lower molecular weight at the same polymerization temperature than that of a general chromium catalyst was obtained.

Example 4 (1) Synthesis of Diethylaluminum Ethylhydromethylsiloxide 48 mL of distilled and purified heptane was placed in a 100 mL pressure-resistant glass flask sufficiently purged with nitrogen, and 1.37 mL (10 mm of triethylaluminum manufactured by Tosoh Finechem Co., Ltd.).
ol) was added and dissolved. Then 1,3,5,7-tetramethylcyclotetrasiloxane 0.61mL (2.5mm
ol; manufactured by Shin-Etsu Chemical Co., Ltd.) was added. The flask was heated with an oil bath and reacted at 120 ° C. for 4 hours. It was cooled to room temperature as it was, and a 0.2 mol / L-heptane solution of diethylaluminum ethylhydromethylsiloxide was obtained.

(2) Preparation of catalyst, polymerization 0.2 mol / L- of diethylaluminum ethylhydromethylsiloxide synthesized in (1) above in place of diethylaluminum 2-methyl-2-propoxide.
A catalyst was prepared in the same manner as in Example 1 (3) except that 3.9 mL of a heptane solution (Al / Cr molar ratio = 2) was added,
An organoaluminum compound-supported chromium catalyst was obtained. Further, polymerization was carried out in exactly the same manner as in Example 1 (4). As a result, 62 g of polyethylene was obtained. Polymerization activity per 1 g of catalyst per 1 hour of polymerization time is 1240 g / g · h
It was r. The physical property measurement results are shown in Table 1. An ethylene polymer having a lower molecular weight at the same polymerization temperature than that of a general chromium catalyst was obtained.

Example 5 (1) Synthesis of diethylaluminum 4-methylphenoxide 48 mL of distilled and purified hexane was placed in a 100 mL flask which had been sufficiently replaced with nitrogen, and triethylaluminum 1.
37 mL (10 mmol; manufactured by Tosoh Finechem Co., Ltd.) was added and dissolved. Then 4-methylphenol (p-
Cresol) (1.08 g, 10 mmol; Aldrich) was added. The flask was heated with an oil bath and hexane was refluxed for 2 hours to complete the reaction. It was cooled to room temperature as it was, and a 0.2 mol / L-hexane solution of diethylaluminum 4-methylphenoxide was obtained.

(2) Preparation of catalyst, polymerization Instead of diethylaluminum 2-methyl-2-propoxide, 3.9 mL (Al) of a 0.2 mol / L-hexane solution of diethylaluminum 4-methylphenoxide synthesized in (1) above was used. / Cr molar ratio = 2) A catalyst was prepared in the same manner as in Example 1 (3) except that the addition was performed to obtain an organoaluminum compound-supported chromium catalyst. Further, polymerization was carried out in exactly the same manner as in Example 1 (4). As a result, 93
g of polyethylene was obtained. The polymerization activity per 1 g of catalyst per 1 hour of polymerization time was 1860 g / g · hr. The physical property measurement results are shown in Table 1. An ethylene polymer having a lower molecular weight than that of a general chromium catalyst was obtained at the same polymerization temperature.

Example 6 Instead of diethylaluminum 2-methyl-2-propoxide, 3.9 mL (Al / Cr mol) of a 0.2 mol / L-hexane solution of diethylaluminum trimethylsiloxide synthesized in Example 2 (1) was used. Ratio = 2) A catalyst was prepared in the same manner as in Example 1 (3) except that the catalyst was prepared to obtain an organoaluminum compound-supported chromium catalyst. Furthermore, in Example 1 (4), hydrogen was introduced at a partial pressure of 0.
Polymerization was performed in exactly the same manner as in Example 1 except that 2 MPa was introduced. As a result, 52 g of polyethylene was obtained. The polymerization activity per 1 g of catalyst per 1 hour of polymerization time was 1040 g / g · hr. The physical property measurement results are shown in Table 1. By introducing hydrogen, the molecular weight was further decreased, and the molecular weight distribution of the obtained ethylene polymer was relatively narrow.

Example 7 Instead of diethylaluminum 2-methyl-2-propoxide, 3.9 mL (Al / Cr mol) of a 0.2 mol / L-hexane solution of diethylaluminum trimethylsiloxide synthesized in Example 2 (1) was used. Ratio = 2) A catalyst was prepared in the same manner as in Example 1 (3) except that the catalyst was prepared to obtain an organoaluminum compound-supported chromium catalyst. Furthermore, in Example 1 (4), hydrogen was introduced at a partial pressure of 0.
Polymerization was performed in exactly the same manner as in Example 1 except that 4 MPa was introduced. As a result, 46 g of polyethylene was obtained. The polymerization activity per 1 g of catalyst per 1 hour of polymerization time was 920 g / g · hr. The physical property measurement results are shown in Table 1. By further increasing the hydrogen partial pressure, the molecular weight was greatly reduced, and the obtained ethylene-based polymer had a narrower molecular weight distribution.

Example 8 G. Mabilon et al., Eur. Polym. J., Volume 21, p. 245,
A vertical vibration type reactor (capacity 150 cm ³ , diameter 50 mm, vibration speed 420 times / min (7 Hz), vibration distance 6 cm) similar to the fluidized bed reactor described in 1985 was prepared and gas phase polymerization was carried out. . Into a reactor previously purged with nitrogen, 20 mg of the organoaluminum compound-supported chromium catalyst obtained in Example 2 (2) sealed in an ampoule under a nitrogen atmosphere was placed, heated to 105 ° C., and then 0.03 MPa of hydrogen was introduced. After that, ethylene was introduced, vibration was started, and the ampoule was broken to initiate polymerization. As needed, ethylene was fed through a flexible joint so that the ethylene partial pressure in the reactor was maintained at 1.4 MPa. After polymerization was carried out at 105 ° C. for 1 hour, ethylene feeding was stopped, the reactor was cooled to room temperature, degassed, and the contents were taken out. As a result, 22 g of polyethylene was obtained. The polymerization activity per 1 g of catalyst per 1 hour of polymerization time is 1100.
It was g / g · hr. The physical property measurement results are shown in Table 1. Also in the gas phase polymerization, an ethylene-based polymer having a low molecular weight and a narrow molecular weight distribution similar to that in the slurry polymerization was obtained.

Example 9 Polymerization was carried out in the same manner as in Example 1 except that hydrogen was introduced at a partial pressure of 0.2 MPa in Example 1 (4). As a result, 50 g of polyethylene was obtained. The polymerization activity per 1 g of catalyst per 1 hour of polymerization time was 1000 g / g · hr. The physical property measurement results are shown in Table 1. By introducing hydrogen, the molecular weight was further decreased, and the molecular weight distribution of the obtained ethylene polymer was relatively narrow.

Example 10 120 L of isobutane was added to a first-stage reactor having an internal volume of 200 L.
/ Hr, the organoaluminum compound-supported chromium catalyst obtained in Example 2 (2) was continuously fed at a rate of 5 g / hr, and the contents of the reactor were discharged at a required rate in a liquid phase at 82 ° C. Ethylene concentration 6.0%, 1-hexene concentration
Supply ethylene and 1-hexene to maintain 0.35%,
First-stage polymerization was continuously carried out in a liquid-filled state under the conditions of a total pressure of 4.1 MPa and an average residence time of 1.0 hr. The isobutane slurry containing the polymer produced from the first-stage reactor was continuously withdrawn and introduced into a second-stage reactor having an internal volume of 400 L through a connecting pipe having an inner diameter of 50 mm. At that time, a part of the polymer was taken out of the system. HLMF of extracted polymer
R was 2.1 g / 10 minutes and the density was 0.9494 g / cm ³ . In the second stage reactor, 10
At 5 ℃, ethylene concentration 6.0%, hydrogen concentration 2.0 × 10 ^-2
Ethylene and hydrogen are supplied so that the total pressure is 4.1%.
a, the second stage polymerization was carried out under the conditions of an average residence time of 2.2 hours to obtain polyethylene. The ratio of high molecular weight components in the first stage is 4
8 parts by mass, the ratio of the second stage low molecular weight component was 52 parts by mass. The flexural modulus of the obtained polyethylene is 15100k.
J / m ² and ESCR were 65 hours. Table 1 shows the other physical property measurement results. An ethylene polymer having a high balance between rigidity and ESCR and excellent balance was obtained.

Comparative Example 1 Polymerization was carried out in the same manner as in Example 1 (4), using the chromium catalyst of Example 1 (2) without supporting diethylaluminum 2-methyl-2-propoxide. As a result, 54 g of polyethylene was obtained. Polymerization activity per 1 g of catalyst per hour of polymerization time is 1080 g / g · h
It was r. The physical property measurement results are shown in Table 1. Examples 1-5
It had a higher molecular weight and a broader molecular weight distribution.

Comparative Example 2 Diethylaluminum 2-methyl-2-propoxide was not supported, but the chromium catalyst of Example 1 (2) was used, and hydrogen was introduced at a partial pressure of 0.2 MPa before introducing ethylene. Polymerization was carried out in the same manner as in Example 1 (4). As a result, 50 g of polyethylene was obtained. Polymerization activity per 1 g of catalyst per hour of polymerization time is 1000 g / g.
It was hr. The physical property measurement results are shown in Table 1. Example 6,
The molecular weight was higher than those of Nos. 7 and 9, and the introduction of hydrogen did not significantly lower the molecular weight. The molecular weight distribution was also wide.

Comparative Example 3 Diethylaluminum 2-methyl-2-propoxide was replaced with a 0.2 mol / L-hexane solution of diethylaluminum ethoxide (Tosoh Akzo Co., Ltd.) in an amount of 3.9 m.
A catalyst was prepared in the same manner as in Example 1 (3) except that L (Al / Cr molar ratio = 2) was added to obtain an organoaluminum compound-supported chromium catalyst. Further, polymerization was carried out in exactly the same manner as in Example 1 (4). In this case, the carbon of the alkoxide group is a primary carbon. As a result, 67 g of polyethylene was obtained. The polymerization activity per 1 g of catalyst per 1 hour of polymerization time was 1340 g / g · hr. The physical property measurement results are shown in Table 1. The molecular weight was higher than that of Example 1 and was not so different from that of Comparative Example 1. The molecular weight distribution was also wide.

Comparative Example 4 (1) Synthesis of diethylaluminum 2-propoxide 48 mL of distilled and purified hexane was placed in a 100 mL flask that had been sufficiently replaced with nitrogen, and triethylaluminum 1.
37 mL (10 mmol; manufactured by Tosoh Finechem Co., Ltd.) was added and dissolved. Then 2-propanol 0.76 mL
(10 mmol; Aldrich) was added. The flask was heated with an oil bath and hexane was refluxed for 2 hours to complete the reaction. It was cooled to room temperature as it was, and a 0.2 mol / L-hexane solution of diethylaluminum 2-propoxide was obtained. In this case, the carbon of the alkoxide group is a secondary carbon.

(2) Preparation of catalyst, polymerization Instead of diethylaluminum 2-methyl-2-propoxide, 3.9 mL (Al) of a 0.2 mol / L-hexane solution of diethylaluminum 2-propoxide synthesized in (1) above was used. / Cr molar ratio = 2) A catalyst was prepared in the same manner as in Example 1 (3) except that the addition was performed to obtain an organoaluminum compound-supported chromium catalyst. Further Example 1
Polymerization was performed in exactly the same manner as (4). As a result, 59g
Polyethylene was obtained. The polymerization activity per 1 g of catalyst per 1 hour of polymerization time was 1180 g / g · hr.
The physical property measurement results are shown in Table 1. The molecular weight was higher than that of Example 1 and was not so different from that of Comparative Example 1. The molecular weight distribution was also wide.

Comparative Example 5 (1) Synthesis of Diethylaluminum Triphenylmethoxide 46 mL of distilled and purified hexane was placed in a 100 mL flask that had been sufficiently purged with nitrogen, and triethylaluminum 1.
37 mL (10 mmol; manufactured by Tosoh Finechem Co., Ltd.) was added and dissolved. Then triphenylmethanol 2.60
g (10 mmol; Aldrich) was added. The flask was heated with an oil bath and hexane was refluxed for 2 hours to complete the reaction. It is cooled to room temperature as it is, and 0.2 mol / L of diethylaluminum triphenylmethoxide is added.
A hexane solution was obtained. In this case, the carbon of the alkoxide group is a tertiary carbon, but the carbon substituent is a phenyl group.

(2) Catalyst Preparation and Polymerization Instead of diethylaluminum 2-methyl-2-propoxide, 3.9 mL (Al) of a 0.2 mol / L-hexane solution of diethylaluminum triphenylmethoxide synthesized in (1) above was used. / Cr molar ratio = 2) A catalyst was prepared in the same manner as in Example 1 (3) except that the addition was performed to obtain an organoaluminum compound-supported chromium catalyst. Further, polymerization was carried out in exactly the same manner as in Example 1 (4). As a result, 53
g of polyethylene was obtained. The polymerization activity per 1 g of catalyst per 1 hour of polymerization time was 1060 g / g · hr. The physical property measurement results are shown in Table 1. The molecular weight was higher than that of Example 1 and was not so different from that of Comparative Example 1. The molecular weight distribution was also wide.

Comparative Example 6 (1) Synthesis of Diethylaluminum Triphenylsiloxide 46 mL of distilled and purified hexane was placed in a 100 mL flask that had been sufficiently replaced with nitrogen, and triethylaluminum 1.
37 mL (10 mmol; manufactured by Tosoh Finechem Co., Ltd.) was added and dissolved. Then triphenylsilanol 2.76
g (10 mmol; Aldrich) was added. The flask was heated with an oil bath and hexane was refluxed for 2 hours to complete the reaction. It is cooled to room temperature as it is, and 0.2 mol / L of diethylaluminum triphenylsiloxide is added.
A hexane solution was obtained. In this case, the silicon substituent of the siloxide group is a phenyl group.

(2) Catalyst Preparation and Polymerization In place of diethylaluminum 2-methyl-2-propoxide, 3.9 mL (Al) of a 0.2 mol / L-hexane solution of diethylaluminum triphenylsiloxide synthesized in (1) above was used. / Cr molar ratio = 2) An organoaluminum compound-supported chromium catalyst was obtained in the same manner as in Example 1 (3) except that the addition was performed. Further, polymerization was carried out in exactly the same manner as in Example 1 (4). As a result, 52 g of polyethylene was obtained. The polymerization activity per 1 g of catalyst per 1 hour of polymerization time was 1040 g / g · hr. The physical property measurement results are shown in Table 1. The molecular weight was higher than that of Example 2 and was not so different from that of Comparative Example 1. The molecular weight distribution was also wide.

Comparative Example 7 Example 1 was carried out in a 1.5 L autoclave which had been thoroughly purged with nitrogen.
50 mg of the chromium catalyst obtained in (2) and isobutane
0.7 L was charged and the internal temperature was raised to 105 ° C. 0.02 mol / L-hexane solution 0.97 of diethylaluminum trimethylsiloxide diluted after synthesis in Example 2 (1)
mL (Al / Cr molar ratio = 2) was introduced under pressure with ethylene to start polymerization, and polymerization was carried out at 105 ° C. for 1 hour while maintaining the ethylene partial pressure at 1.4 MPa. Then, the content gas was discharged to the outside of the system to terminate the polymerization. As a result, 65 g of polyethylene was obtained. Polymerization activity is 1300 g per 1 g of catalyst per 1 hour of polymerization time.
/ G · hr. The physical property measurement results are shown in Table 1. Although the molecular weight is a little lower than that of Comparative Example 1, the molecular weight is obviously higher than that of Example 2. In addition, the density was greatly reduced and the molecular weight distribution was wide as compared with Example 2.

Comparative Example 8 In Comparative Example 7, hydrogen was introduced at a partial pressure of 0.2 at a partial pressure before introduction of diethylaluminum trimethylsiloxide and ethylene.
Polymerization was carried out in the same manner as in Comparative Example 7 except that the introduction of MPa was performed. As a result, 61 g of polyethylene was obtained.
The polymerization activity per 1 g of catalyst per 1 hour of polymerization time is 12
It was 20 g / g · hr. The physical property measurement results are shown in Table 1.
Compared with Example 6, the molecular weight was high and the molecular weight distribution was wide. In addition, the density was greatly reduced as compared with Example 6.

Comparative Example 9 Example 1 was carried out in a 1.5 L autoclave which had been fully replaced with nitrogen.
50 mg of the chromium catalyst obtained in (2), Example 2 (1)
Diethyl aluminum trimethylsiloxide 0.02 mol / L-hexane solution 0.97 mL (A
1 / Cr molar ratio = 2) and 0.7 L of isobutane were charged, and the catalyst was brought into contact with the dialkylaluminum siloxide in advance. After stirring at 25 ° C for 15 minutes, the internal temperature was raised to 105 ° C. While introducing ethylene to start the polymerization and maintaining the ethylene partial pressure at 1.4 MPa,
Polymerization was carried out at 0 ° C for 1 hour. Then, the content gas was discharged to the outside of the system to terminate the polymerization. As a result, 60 g of polyethylene was obtained. Polymerization time 1 g per 1 g catalyst
The polymerization activity per hour was 1200 g / g · hr. The physical property measurement results are shown in Table 1. Although the molecular weight was lower than that of Comparative Example 1, the molecular weight was obviously higher than that of Example 2. Further, the density was greatly reduced and the molecular weight distribution was broader than that of Example 2.

Comparative Example 10 Example 1 was carried out in a 1.5 L autoclave which had been sufficiently replaced with nitrogen.
50 mg of the chromium catalyst obtained in (2), Example 2 (1)
Diethyl aluminum trimethylsiloxide 0.02 mol / L-hexane solution 0.97 mL (A
1 / Cr molar ratio = 2) and 0.7 L of isobutane were charged, and the catalyst was brought into contact with the dialkylaluminum siloxide in advance. After stirring at 25 ° C for 15 minutes, the internal temperature was raised to 105 ° C. After introducing hydrogen with a partial pressure of 0.2 MPa, ethylene is introduced to start the polymerization, and the ethylene partial pressure is 1.4 MPa.
Polymerization was carried out at 105 ° C. for 1 hour while maintaining the above condition. Then, the content gas was discharged to the outside of the system to terminate the polymerization. As a result, 52 g of polyethylene was obtained. The polymerization activity per 1 g of catalyst per 1 hour of polymerization time was 1040 g / g · hr. The physical property measurement results are shown in Table 1. Although the molecular weight was lower than that of Comparative Example 2, the molecular weight was obviously higher than that of Example 6. In addition, the density was significantly reduced and the molecular weight distribution was wide as compared with Example 6.

Comparative Example 11 Example 1 was carried out in a 1.5 L autoclave which had been fully replaced with nitrogen.
50 mg of the chromium catalyst obtained in (2), Example 1 (1)
Diethyl aluminum 2-methyl-
2-propoxide 0.02 mol / L-hexane solution 0.97
mL (Al / Cr molar ratio = 2) and isobutane 0.7L
Was charged, and the catalyst was brought into contact with the dialkylaluminum alkoxide in advance. After stirring at 25 ° C for 15 minutes, set the internal temperature to 1
The temperature was raised to 05 ° C. Polymerization was initiated by introducing ethylene, and polymerization was carried out at 105 ° C for 1 hour while maintaining the ethylene partial pressure at 1.4 MPa. Then, the content gas was discharged to the outside of the system to terminate the polymerization. As a result, 56 g of polyethylene was obtained. The polymerization activity per 1 g of catalyst per 1 hour of polymerization time is 1120 g / g · h.
It was r. The physical property measurement results are shown in Table 1. Although the molecular weight was lower than that of Comparative Example 1, the molecular weight was obviously higher than that of Example 1. In addition, the density was greatly reduced and the molecular weight distribution was wide as compared with Example 1.

Comparative Example 12 Example 1 was carried out in a 1.5 L autoclave which had been thoroughly purged with nitrogen.
50 mg of the chromium catalyst obtained in (2), Example 1 (1)
Diethyl aluminum 2-methyl-
2-propoxide 0.02 mol / L-hexane solution 0.97
mL (Al / Cr molar ratio = 2) and isobutane 0.7 L
Was charged, and the catalyst was brought into contact with the dialkylaluminum alkoxide in advance. After stirring at 25 ° C for 15 minutes, set the internal temperature to 1
The temperature was raised to 05 ° C. After introducing hydrogen at a partial pressure of 0.2 MPa,
Introduce ethylene to start polymerization and adjust ethylene partial pressure to 1.
Polymerization was carried out at 105 ° C. for 1 hour while maintaining 4 MPa. Then, the content gas was discharged to the outside of the system to terminate the polymerization. As a result, 53 g of polyethylene was obtained. The polymerization activity per 1 g of catalyst per 1 hour of polymerization time was 1060 g / g · hr. The physical property measurement results are shown in Table 1. Although the molecular weight was lower than that of Comparative Example 2, the molecular weight was obviously higher than that of Example 9. In addition, the density was greatly reduced and the molecular weight distribution was wide as compared with Example 9.

[0129]

[Table 1]

[0130]

[Table 2]

[0131]

EFFECTS OF THE INVENTION A chromium catalyst is contacted with an organoaluminum compound in an inert hydrocarbon solvent to remove the solvent.
By carrying out the polymerization of ethylene using the catalyst of the present invention which is dried and carrying an organoaluminum compound, an ethylene-based polymer having a low molecular weight and a narrow molecular weight distribution is obtained, and by further broadening the molecular weight distribution by multistage polymerization, ,
It is possible to produce an ethylene-based polymer having improved environmental stress crack resistance (ESCR) and rigidity and a good balance between them.

[Brief description of drawings]

FIG. 1 is a flow chart diagram of preparation of a catalyst for producing an ethylene-based polymer used in the present invention.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Hidenobu Torigoe             10-1 Chidori-cho, Kawasaki-ku, Kawasaki-shi, Kanagawa             The Polyolefin Co., Ltd., Technology Division Research Open             In the departure center (72) Inventor Shinya Waki             10-1 Chidori-cho, Kawasaki-ku, Kawasaki-shi, Kanagawa             The Polyolefin Co., Ltd., Technology Division Research Open             In the departure center F-term (reference) 4F071 AA16 AA16X AA17 AA17X                       AA81 AA82 AF14 AH05 AH19                       BA01 BB05 BB06 BC03 BC04                       BC07                 4J100 AA02P AA03Q AA04Q AA07Q                       AA16Q AA17Q AA19Q CA01                       CA04 DA04 DA42 DA43 FA19                       FA22 JA57 JA58                 4J128 AA01 AB00 AC42 AC43 BA01A                       BB01A BC24A BC28A BC29A                       CA24A CA25A CA27A CA28A                       CA29A DB04A DB09A EA01                       EA02 EB02 EB03 EB04 EB05                       EB09 EB10 EC01 EC02 ED01                       ED02 ED03 ED04 ED05 EF03                       FA02 FA04 GA02 GA05 GA06                       GA07 GA08 GB01

Claims (13)

[Claims] 1. A chromium compound-carrying inorganic oxide carrier in which at least a part of chromium atoms is hexavalent by supporting a chromium compound on an inorganic oxide carrier and activating by firing in a non-reducing atmosphere, an inert hydrocarbon is used. A chromium catalyst comprising an organoaluminum compound represented by the following general formula (1), (2) or (3) contacted in a solvent, the solvent is removed and dried to carry the organoaluminum compound. Method for producing ethylene-based polymer: (In the formula, R ¹ , R ² , R ³ , R ⁴ and R ⁵ may be the same or different and each represents an alkyl group having 1 to 18 carbon atoms.) (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 , R ⁹ and R ¹⁰ may be the same or different and each is a hydrogen atom or Represents an alkyl group having 1 to 18 carbon atoms, provided that
At least two substituents of R ^8, R ^9, R ¹⁰ is an alkyl group. ) [Chemical 3] (Wherein, R ¹¹ and R ¹² may be the same or different, each represents an alkyl group having 1 to 18 carbon atoms, R ^13, R
¹⁴ , R ¹⁵ , R ¹⁶ and R ¹⁷ may be the same or different,
Each represents a hydrogen atom, an alkyl group having 1 to 18 carbon atoms, a halogen atom, an alkoxy group, or a nitrile group. ). 2. The ethylene system according to claim 1, wherein the organoaluminum compound is brought into contact with an inert hydrocarbon solvent, and when the solvent is removed and dried, the contact time with the solvent is treated to be as short as possible. Method for producing polymer. 3. The method for producing an ethylene polymer according to claim 1, wherein the molar ratio of the organoaluminum compound to chromium atoms is 0.1 to 10. 4. The inorganic oxide carrier is silica.
The method for producing an ethylene-based polymer described in 1. 5. The method for producing an ethylene polymer according to claim 1, wherein hydrogen is introduced during the polymerization to carry out the polymerization. 6. The polymerization of ethylene or the copolymerization of ethylene and an α-olefin having 3 to 8 carbon atoms is carried out by multi-stage polymerization using a plurality of polymerization reactors connected in series.
The method for producing an ethylene-based polymer described in 1. 7. The method for producing an ethylene polymer according to claim 6, wherein hydrogen is introduced into any polymerization reactor to polymerize ethylene or copolymerize ethylene with an α-olefin having 3 to 8 carbon atoms. . 8. An MFR of 0.5 obtained by the method for producing an ethylene polymer according to claim 1.
An ethylene polymer having a density of 0.940 to 0.970 g / cm ³ for ˜50 g / 10 minutes. 9. The ethylene-based heavy according to claim 6 or 7.
HLMFR of 1 to 10 obtained by the method for producing a coalescence
0g / 10 minutes, density 0.935-0.965g / cm ³Echile of
Polymer. 10. An injection-molded product comprising the ethylene-based polymer according to claim 8. 11. A blow molded product comprising the ethylene polymer according to claim 9. 12. A chromium catalyst in which at least a part of chromium atoms is hexavalent by supporting a chromium compound on an inorganic oxide carrier and activating it by firing in a non-reducing atmosphere,
Obtained by a method for producing an ethylene-based polymer by (co) polymerizing ethylene or ethylene and an α-olefin having 3 to 8 carbon atoms, MFR is 20 to 50 g / 10 minutes, and molecular weight distribution (Mw / Mn) is 3 to. 6. Ethylene polymer of 6. 13. The method for producing an ethylene-based polymer is the production method according to any one of claims 1 to 5.
An ethylene-based polymer having an MFR of 20 to 50 g / 10 minutes and a molecular weight distribution (Mw / Mn) of 3 to 6 described in 1.