JPH0827211A - Polyethylene having environmental stress-crack resistance(escr) - Google Patents

Abstract

PURPOSE:To obtain a new environmental stress-crack resistant polyethylene having improved ESCR and high strength and further excellent in fatigue resistance, abrasion resistance, dimensional stability, chemical resistance, moldability, etc. CONSTITUTION:This environmental stress-crash resistant polyethylene satisfies the relation P>=0.18-0.05logMFR. Here, MFR is a melt flow rate determined by JIS K7210 and P is tie-molecular ratio obtained from long periodic length of a lamella and a weight-average molecular weight. The polyethylene is obtained by the polymerization in the presence of a catalyst obtained by bringing a magnesium alkoxide, into contact with a halogenated hydrocarbon and a titanium compound.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to polyethylene,
More particularly, it relates to polyethylene with improved environmental stress crack resistance (ESCR).

[0002]

2. Description of the Related Art Polyethylene has excellent chemical resistance and electrical properties, and also has good rigidity, tensile strength, optical characteristics, and processability. Therefore, polyethylene, injection molding, film molding, extrusion molding,
It is used for blow molding and is widely used as pipes, plates, sheets, etc.

One of the key performances of polyethylene homopolymers and copolymers, among others, is ESCR.
Most polymerization processes involve decreasing the MFR and / or density and / or 1 in the case of copolymers.
-ESCR by increasing the olefin content
Can be improved. However, simply lowering the MFR or density or increasing the comonomer content of the copolymer is not always practical as it adversely affects other performance. Therefore, the development of polyethylene having improved ESCR has been required, and devises such as a polymerization catalyst and a polymerization method have been made. However, although these improve ESCR to some extent, they are still insufficient.

[0004]

DISCLOSURE OF THE INVENTION The present invention has improved ESCR and high strength, and further has fatigue characteristics, wear resistance,
Provided is a novel environmental stress crack resistant polyethylene excellent in dimensional stability, chemical resistance and moldability.

[0005]

As a result of intensive studies, the inventors of the present invention have found that it is necessary to increase the number of tie molecules in order to improve the ESCR of polyethylene. When the Thai molecular ratio (P) obtained from the cycle length and the weight average molecular weight is adopted, ESCR
Was found to vary depending on the melt flow rate (MFR) of polyethylene, and P and MFR are expressed by the following formula: P ≧ 0.18-0.05 logMFR When the above relationship is satisfied, the polyethylene has excellent ESC.
The inventors have found that R is expressed and completed the invention of the present application. Further, although the polyethylene can be produced by various polymerization catalysts and polymerization means, it was found that the polyethylene can be easily produced by using a specific polymerization catalyst component, and the second invention of the present application was completed. It was

SUMMARY OF THE INVENTION That is, the gist of the present invention is that the tie molecular ratio (P) obtained from the melt flow rate (MFR) measured according to JIS K7210, the long period length of the lamella and the weight average molecular weight.
And P satisfy the relationship of P ≧ 0.18-0.05 log MFR, which is an environmental stress crack resistant polyethylene, and a catalyst component obtained by contacting a magnesium alkoxide, a halogenated hydrocarbon and a titanium compound. Is a polyethylene obtained by polymerizing by using, and the melt flow rate (MFR) measured according to JIS K7210 and the tie molecular ratio (P) determined from the long period length of the lamella and the weight average molecular weight are P ≧ 0.18− An environmental stress crack resistant polyethylene characterized by satisfying a relationship of 0.05 log MFR.

Here, the tie molecular ratio (P) in the present invention is a basic idea that the tie molecule can be formed if the spread of the molecular chain of polyethylene in the molten state is larger than the long period length of the lamella. And P is
J. Mat. Sci, 23 , 3648 (1988). The details will be described below. When this basic idea is formulated, from the solution theory of the polymer, the probability W (r) that the end of the molecular chain is the distance r is

[0008]

(Equation 1) It is known that P follows from the following formula:

[0009]

(Equation 2) And the following equation (1) is obtained.

[0010]

(Equation 3) Here, L is a long period length of the lamella, the L can be measured by using a small angle scattering device, and b ² is a weight average molecular weight measured by gel permeation chromatography (GPC) or the like. (Mw) has a relation of the following equation (2), and when the relational expression (2) is substituted into the relational expression (1), a relational expression (3) is obtained. By substituting the value into the relational expression (3), the value of P can be calculated.

[0011]

[Chemical 4]

[0012]

Embedded image In addition, melt flow rate (MFR) is JIS K7
210 is a value measured according to 210, and is a value obtained by measuring the mass of a sample extruded for 10 minutes under the conditions of 190 ° C. and a load of 2.16 kg. Furthermore, ESCR is JIS K6
It is the value measured according to 760. The tie molecular ratio (P) of polyethylene in the present invention is 0.18-0.05lo.
gMFR or more, preferably 0.19-0.05 logM
FR or more and the value is 0.18-0.05 log MF
If it is less than R, the ESCR of polyethylene is insufficient and a molded product that can be used for a long time cannot be obtained.

The catalyst for producing the polyethylene of the present invention and the polymerization method are not limited, but as for the polymerization catalyst, the polyethylene of the present invention can be prepared by using a catalyst component obtained by contacting magnesium alkoxide, halogenated hydrocarbon and titanium compound. Can be easily manufactured.

The polymerization catalyst used in the present invention will be described in more detail. (1) Magnesium alkoxide The magnesium alkoxide used in the present invention is
It is a compound represented by the general formula Mg (OR) (OR ′). In the formula, R and R ′ are alkyl, alkenyl, cycloalkyl, aryl and aralkyl groups having 1 to 20 carbon atoms, preferably 1 to 10 carbon atoms. R and R'may be the same or different. To illustrate these compounds,
Mg (OCH ₃ ) ₂ , Mg (OC ₂ H ₅ ) ₂ , Mg (O
_{CH 3) (OC 2 H 5} ), Mg (Oi-C 3 H 7) 2,
Mg (OC ₃ H ₇ ) ₂ , Mg (OC ₄ H ₉ ) ₂ , Mg
_{(Oi-C 4 H 9)} 2, Mg (OC 4 H 9) (Oi-C
₄ H ₉ ), Mg (OC ₄ H ₉ ) (Osec-C
_{4 H 9), Mg (OC} 6 H 13) 2, Mg (OC 8 H 17)
₂ , Mg (OC ₆ H ₁₁ ) ₂ , Mg (OC ₆ H ₅ ) ₂ , M
_{g (OC 6 H 4 CH 3} ) 2, Mg (OCH 2 C 6 H 5)
₂ etc. can be mentioned. When these magnesium alkoxides are used, they are preferably dried, particularly preferably dried by heating under reduced pressure, and it is more preferable to use those dried and pulverized.

(2) Halogenated Hydrocarbon The halogenated hydrocarbon used in the present invention has 1 to 1 carbon atoms.
Mono- and polyhalogenated versions of two saturated or unsaturated, aliphatic, alicyclic and aromatic hydrocarbons. Specific examples of those compounds include, in aliphatic compounds, methyl chloride, methyl bromide, methyl iodide, methylene chloride, methylene bromide, methylene iodide, chloroform, bromoform, iodoform, carbon tetrachloride, carbon tetrabromide, and tetrachloride. Carbon iodide, ethyl chloride,
Ethyl bromide, ethyl iodide, 1,2-dichloroethane, 1,2-dibromoethane, 1,2-diiodoethane, methyl chloroform, methyl bromoform,
Methyl iodoform, 1,1,2-trichloroethylene, 1,1,2-tribromoethylene, 1,1,2,2
-Tetrachloroethylene, pentachloroethane, hexachloroethane, hexabromoethane, n-propyl chloride, 1,2-dichloropropane, hexachloropropylene, octachloropropane, decabromobutane, chlorinated paraffins are alicyclic compounds; Chlorocyclopropane, tetrachlorocyclopentane, hexachlorocyclopentadiene and hexachlorocyclohexane are aromatic compounds such as chlorobenzene, bromobenzene, o-dichlorobenzene, p-dichlorobenzene, hexachlorobenzene, hexabromobenzene and benzo. Examples thereof include trichloride and p-chlorobenzotrichloride.
These compounds may be used alone or in combination of two or more.

(3) Titanium Compound The titanium compound is a compound of divalent, trivalent and tetravalent titanium. Examples thereof include titanium tetrachloride, titanium tetrabromide, trichloroethoxytitanium, trichlorobutoxytitanium and dichlorotitanium. Examples thereof include rudiethoxy titanium, dichlorodibutoxy titanium, dichlorodiphenoxy titanium, chlorotriethoxy titanium, chlortributoxy titanium, tetrabutoxy titanium and titanium trichloride. Among these, tetravalent titanium halides such as titanium tetrachloride, trichloroethoxy titanium, dichlorodibutoxy titanium, and dichlorodiphenoxy titanium are preferable, and titanium tetrachloride is particularly preferable.

Method for Preparing Catalyst Component The catalyst component of the present invention can be obtained by contacting a magnesium alkoxide, a halogenated hydrocarbon and a titanium compound. The contact methods of these three are: (a) magnesium alkoxide and halogen A method of contacting with a titanium compound after contacting with a modified hydrocarbon,
(B) A method of simultaneously contacting a magnesium alkoxide, a halogenated hydrocarbon and a titanium compound can be mentioned. Hereinafter, these methods (a) and (b) will be described.

Method (a) Contact between magnesium alkoxide and halogenated hydrocarbon The contact between magnesium alkoxide and halogenated hydrocarbon is a mixture of magnesium alkoxide and solid or liquid halogenated hydrocarbon in a solid or slurry mixture. Is mechanically co-pulverized, or simply contacted by stirring. Among these,
A contact method of mechanical co-pulverization is preferable, and as the halogenated hydrocarbon, any compound may be used as long as it is the above compound, but a polyhalide of a hydrocarbon having 2 or more carbon atoms is preferable. The contact ratio between the magnesium alkoxide and the halogenated hydrocarbon is 0.01 to 20 mol, preferably 0.1 to 2.0 mol, of the halogenated hydrocarbon per mol of the magnesium alkoxide.

The contact between the two is
It may be carried out by using an ordinary crusher used for obtaining a crushed product, and examples of the crusher include a rotary ball mill, a vibrating ball mill and an impact mill. The co-grinding treatment can be carried out, if necessary, under reduced pressure or in an atmosphere of an inert gas, and in a state where water, oxygen, etc. are substantially absent. The contact temperature for mechanical co-milling is 0
~ 200 ° C, contact time 0.5 ~ 100 hours,
Further, the contact temperature in the case of the contact method of simply stirring is 0 to 20.
The contact time is 0.5 to 100 hours at 0 ° C.

Contact with Titanium Compound The contact product of magnesium alkoxide and halogenated hydrocarbon (hereinafter referred to as “the contact product”) is then contacted with the titanium compound to form the catalyst component of the present invention. The contact product may be washed with a cleaning agent, for example, an inert hydrocarbon such as hexane, heptane, octane, cyclohexane, benzene, toluene, xylene, etc., before being brought into contact with the titanium compound. The contact product and the titanium compound may be contacted with each other as they are, but by a method of mixing and agitating both in the presence of a hydrocarbon and / or a halogenated hydrocarbon, a method of mechanically co-grinding, or the like. It is preferable to carry out.

The hydrocarbon is preferably a saturated aliphatic, saturated alicyclic or aromatic hydrocarbon having 6 to 12 carbon atoms exemplified as the detergent, and the halogenated hydrocarbon is brought into contact with the magnesium alkoxide. Any compound can be used as long as it is a compound used at that time. The ratio of both used in the contact between the contact product and the titanium compound is 0.1 gram mol or more of the titanium compound per gram atom of magnesium in the contact product, preferably 1
~ 5 grams mol. When the contacting operation is carried out in the presence of hydrocarbon and / or halogenated hydrocarbon,
To 200 ° C for 0.5 to 20 hours, preferably 60 to 15
It is 1-5 hours at 0 degreeC.

Method (b) The simultaneous contact of magnesium alkoxide, halogenated hydrocarbon and titanium compound is carried out in the presence or absence of an inert hydrocarbon such as hexane, heptane, octane, cyclohexane, benzene, toluene and xylene. The contact method by mechanical pulverization or the contact method by mixing and stirring is performed. The use ratio of the magnesium alkoxide, the halogenated hydrocarbon and the titanium compound may be the same as in the case of the above method (a). That is, magnesium alkoxide 1
The amount of the halogenated hydrocarbon is 0.01 to 20 mol, preferably 0.1 to 2.0 mol, and the titanium compound is 0.1 mol or more, preferably 1 to 5 mol, per mol.

The contact temperature is 0 to 200 ° C., preferably 20 to 150 ° C., and the contact time is 0.5 to 100 hours, preferably 1 to 50 hours. When contacting in the presence of a hydrocarbon, it is preferable to use the hydrocarbon in an amount such that the solid substance in the contact system is 10 to 300 g per liter of the liquid substance. The solid substance obtained as described above is separated from the liquid substance, and if necessary, hexane, heptane, octane, cyclohexane, benzene,
Wash with an inert hydrocarbon such as toluene or xylene,
The catalyst component of the present invention is obtained by drying.

The catalyst component of the present invention has a specific surface area of 20 measured at the adsorption temperature of liquid nitrogen by the BET method.
0-650 m ² / g, pore volume 0.1-0.4 cc /
g, the pore radius is mainly 10 to 13Å, the particle size distribution is narrow and the sizes are uniform, and the composition is such that the magnesium atom is 10 to 20% by weight and the titanium atom is 5 to 1%.
5% by weight, 50 to 65% by weight of halogen atoms, and other organic compounds and the like. The substance contains a small amount of the halogenated hydrocarbon and / or its conversion substance used in the preparation of the catalyst component.

Ethylene Polymerization Catalyst The catalyst component of the present invention is used as an ethylene polymerization catalyst in combination with an organoaluminum compound and optionally an electron donating compound. Organoaluminum Compound An organoaluminum compound to be combined with a catalyst component when polymerizing ethylene is represented by the general formula R _n AlX _3-n (wherein R is an alkyl group or an aryl group, X is a halogen atom, an alkoxy group or a hydrogen atom). , N is an arbitrary number within the range of 1 ≦ n ≦ 3), and examples thereof include trialkyl aluminum, dialkyl aluminum monohalide, monoalkyl aluminum dihalide, alkyl aluminum sesquihalide, dialkyl aluminum mono. Particularly preferred are alkylaluminum compounds having 1 to 18 carbon atoms, preferably 2 to 6 carbon atoms, such as alkoxides and dialkylaluminum monohydride, or mixtures or complex compounds thereof.

Specifically, trialkyl aluminum such as trimethyl aluminum, triethyl aluminum, tripropyl aluminum, triisobutyl aluminum, trihexyl aluminum, dimethyl aluminum chloride, diethyl aluminum chloride, diethyl aluminum bromide, diethyl aluminum iodide, diisobutyl aluminum. Dialkyl aluminum monohalides such as chloride, methyl aluminum dichloride, ethyl aluminum dichloride, ethyl aluminum dibromide, ethyl aluminum diiodide, monoalkyl aluminum dihalides such as isobutyl aluminum dichloride, alkyl aluminum sesquihalides such as ethyl aluminum sesquichloride, dimethyl Aluminum Dialkyl aluminum monoalkoxides such as um methoxide, diethyl aluminum ethoxide, diethyl aluminum phenoxide, dipropyl aluminum ethoxide, diisobutyl aluminum ethoxide, diisobutyl aluminum phenoxide, dimethyl aluminum hydride, diethyl aluminum hydride, dipropyl aluminum hydride, diisobutyl aluminum hydride, etc. Dialkylaluminum hydride may be mentioned.

Among these, trialkylaluminums, particularly triethylaluminum and triisobutylaluminum are preferable. Further, these trialkylaluminums are other organoaluminum compounds, for example,
It can be used in combination with industrially easily available diethylaluminum chloride, ethylaluminum dichloride, ethylaluminum sesquichloride, diethylaluminum ethoxide, diethylaluminum hydride or a mixture or complex compound thereof. Further, the organoaluminum compound is used alone, but may be used in combination with an electron donating compound, and examples of the electron donating compound include carboxylic acids, carboxylic acid anhydrides, carboxylic acid esters, carboxylic acid halides, Alcohols, ethers, ketones, amines, amides, nitrites, aldehydes, alcoholates, phosphorus, arsenic and antimony compounds bonded to organic groups through carbon or oxygen, phosphoamides, thioethers, thioesters Examples thereof include carboxylic acid esters, alcohols and ethers.

Specific examples of the carboxylic acids include formic acid, acetic acid, propionic acid, butyric acid, isobutyric acid, valeric acid, caproic acid, pivalic acid, acrylic acid, methacrylic acid, crotonic acid and other aliphatic monocarboxylic acids, malonic acid. , Succinic acid, glutaric acid, adipic acid, sebacic acid, maleic acid, fumaric acid and other aliphatic dicarboxylic acids, tartaric acid and other aliphatic oxycarboxylic acids, cyclohexanemonocarboxylic acid, cyclohexenemonocarboxylic acid, cis-1,2- Cyclohexanedicarboxylic acid, cis-4-methylcyclohexene-1,
Alicyclic carboxylic acids such as 2-dicarboxylic acid, benzoic acid, toluic acid, anisic acid, aromatic monocarboxylic acids such as p-tertiary butyl benzoic acid, naphthoic acid and cinnamic acid, phthalic acid, isophthalic acid, Terephthalic acid, naphthalic acid, trimellitic acid, hemimellitic acid, trimesic acid, pyromellitic acid,
Examples thereof include aromatic polycarboxylic acids such as mellitic acid.

As the carboxylic acid anhydride, acid anhydrides of the above carboxylic acids can be used. As the carboxylic acid ester, a mono- or polyvalent ester of the above-mentioned carboxylic acids can be used, and specific examples thereof include butyl formate,
Ethyl acetate, butyl acetate, isobutyl isobutyrate, propyl pivalate, isobutyl pivalate, ethyl acrylate, methyl methacrylate, ethyl methacrylate, isobutyl methacrylate, diethyl malonate, diisobutyl malonate, diethyl succinate, dibutyl succinate, Diisobutyl succinate, diethyl glutarate, dibutyl glutarate, diisobutyl glutarate, diisobutyl adipate, dibutyl sebacate, diisobutyl sebacate, diethyl maleate, dibutyl maleate, diisobutyl maleate, monomethyl fumarate, diethyl fumarate,
Diisobutyl fumarate, diethyl tartrate, dibutyl tartrate, diisobutyl tartrate, ethyl cyclohexanecarboxylate, methyl benzoate, ethyl benzoate, methyl p-toluate, ethyl p-tertiary butyl benzoate, ethyl p-anisate, α- Ethyl naphthoate, α-isobutyl naphthoate, ethyl cinnamate, monomethyl phthalate, monobutyl phthalate, dibutyl phthalate, diisobutyl phthalate, dihexyl phthalate, dioctyl phthalate, di2-ethylhexyl phthalate, diallyl phthalate, Diphenyl phthalate, diethyl isophthalate, diisobutyl isophthalate, diethyl terephthalate, dibutyl terephthalate, diethyl naphthalate, dibutyl naphthalate, triethyl trimellitate, tributyl trimellitate, tetramethyl pyromelliticate , Tetraethyl pyromellitic acid, tetrabutyl pyromellitic acid and the like.

As the carboxylic acid halide, acid halides of the above carboxylic acids can be used,
As specific examples thereof, acetic acid chloride, acetic acid bromide, acetic acid iodide, propionic acid chloride, butyric acid chloride,
Butyric acid bromide, butyric acid iodide, pivalic acid chloride, pivalic acid bromide, acrylic acid chloride, acrylic acid bromide, acrylic acid iodide, methacrylic acid chloride, methacrylic acid bromide, methacrylic acid iodide, crotonic acid chloride, malonic acid chloride, malonic acid bromide, Succinic acid chloride, succinic acid bromide,
Glutaric acid chloride, glutaric acid bromide, adipic acid chloride, adipic acid bromide, sebacic acid chloride,
Sebacic acid bromide, maleic acid chloride, maleic acid bromide,

Fumaric acid chloride, fumaric acid bromide, tartaric acid chloride, tartaric acid bromide, cyclohexanecarboxylic acid chloride, cyclohexanecarboxylic acid bromide, 1
-Cyclohexenecarboxylic acid chloride, cis-4-methylcyclohexenecarboxylic acid chloride, cis-4-methylcyclohexenecarboxylic acid bromide, benzoyl chloride, benzoyl bromide, p-toluic acid chloride, p-toluic acid bromide, p-anisic acid chloride , P-anisic acid bromide, α-naphthoic acid chloride, cinnamic acid chloride, cinnamic acid bromide, phthalic acid dichloride, phthalic acid dibromide, isophthalic acid dichloride, isophthalic acid dibromide, terephthalic acid dichloride, naphthalic acid dichloride. Also, a monoalkyl halide of a dicarboxylic acid such as adipic acid monomethyl chloride, maleic acid monoethyl chloride, maleic acid monomethyl chloride, phthalic acid butyl chloride may be used.

Alcohols are represented by the general formula R ¹ OH. In the general formula, R ¹ is an alkyl, alkenyl, cycloalkyl, aryl or aralkyl group having 1 to 12 carbon atoms. Specific examples thereof include methanol, ethanol, propanol, isopropanol, butanol, isobutanol, pentanol, hexanol, octanol, 2-ethylhexanol, cyclohexanol, benzyl alcohol, allyl alcohol, phenol, cresol, xylenol, ethylphenol,
Examples include isopropylphenol, p-tertiarybutylphenol, and n-octylphenol.

The ethers are represented by the general formula R ² OR ³ . In the general formula, R ² and R ³ are alkyl, alkenyl, cycloalkyl, aryl and aralkyl groups having 1 to 12 carbon atoms, and R ² and R ³ may be the same or different. Specific examples thereof include diethyl ether, dipropyl ether, diisopropyl ether, dibutyl ether, diisobutyl ether, diisoamyl ether, di-2-ethylhexyl ether, diallyl ether, ethyl allyl ether, butyl allyl ether, diphenyl ether, anisole, ethyl phenyl. Ether and the like. These electron-donating compounds may be used in combination with an organoaluminum compound, or may be used after being brought into contact with the organoaluminum compound in advance. The amount of the organoaluminum compound used with respect to the catalyst component of the present invention is usually 1 to 1 gram atom of titanium in the catalyst component.
2000 gram moles, especially 20 to 500 gram moles are preferred. The ratio of the organoaluminum compound to the electron donating compound is selected from the range of 0.1 to 40 gram atom, preferably 1 to 25 gram atom of aluminum as the organoaluminum compound with respect to 1 mol of the electron donating compound.

Further, as a polymerization method, the polymerization reaction of ethylene may be in a gas phase or a liquid phase. When the polymerization is carried out in a liquid phase, normal butane, isobutane, normal pentane, isopentane, hexane, heptane, octane,
It can be carried out in an inert hydrocarbon such as cyclohexane, benzene, toluene or xylene. The polymerization temperature is usually in the range of -80 ° C to + 150 ° C, preferably 40 to 120 ° C, and the polymerization pressure may be, for example, 1 to 60 atm.
Further, the molecular weight of the obtained polymer is controlled by the presence of hydrogen or other known molecular weight regulator. The polymerization reaction is carried out by a continuous or batch reaction, and the conditions therefor may be those usually used. Moreover, the polymerization reaction may be carried out in one step or in two or more steps.

[0035]

EXAMPLES The present invention will be specifically described with reference to Examples and Comparative Examples. The percentages (%) in the examples are by weight unless otherwise specified. (Example 1) Preparation of catalyst component for polymerization Contact of magnesium diethoxide with hexachloroethane Commercially available magnesium ethoxide [Mg (OEt) ₂ ] 8
5 g and hexachloroethane (C ₂ Cl ₆ ) 79 g [C ₂
Cl ₆ / Mg (OEt) ₂ = 0.45 (molar ratio)] in a nitrogen gas atmosphere and having a diameter of 12 mm of stainless steel (SUS
316) It was placed in a stainless steel (SUS316) mill pot having an internal volume of 1 liter containing 340 balls and the mill pot was mounted on a shaker and shaken for 15 hours for contact to obtain a pulverized product.

Titanium tetrachloride treatment 12 g of the pulverized product obtained above was treated under a nitrogen gas atmosphere for 5
Put it in a 00 ml flask and add 100 ml of toluene to it.
And 50 ml of titanium tetrachloride were added, and the mixture was stirred at 110 ° C. for 2 hours for contact, and then excess liquid was removed. Then, the solid substance was mixed with 100 ml of n-hexane at 65% each.
Washed 6 times at ℃, dried at 50 ℃ under reduced pressure for 1 hour, titanium content 10.7%, magnesium content 13.4%,
11.0 g of a catalyst component having a chlorine content of 57.1% was obtained. This catalyst component has a specific surface area of 560 m ² / g and a pore volume of 0.
It was 374 cc / g and the average pore radius was 13.4Å.

Polymerization of ethylene In a 1.5 liter autoclave equipped with a stirrer, 10 mg of the catalyst component for polymerization prepared by the above method, 1 mmol of triisobutylaluminum, 0.02 mmol of di-n-propyl ether and 700 ml of isobutane, 600 ml of hydrogen (0 ° C, under 1 atm) was introduced and the temperature was 85 ° C
Then, ethylene and butene-1 were introduced (the butene-1 concentration of the polymer finally obtained = 0.2%), and the polymerization was carried out for 1 hour while maintaining the ethylene partial pressure at 5 kg / cm ² .
The polyethylene thus obtained has an MFR of 0.14.
(G / 10 min), P = 0.26, ESCR = 35
It was (time).

(Examples 2 and 3) Polyethylenes shown in Table 1 were obtained in the same manner as in Example 1, except that the amount of butene-1 introduced and the amount of hydrogen were changed. Table 1 shows the results of measuring the physical properties of the obtained polyethylene. (Comparative Example 1) A 2.0-liter autoclave with a stirrer was impregnated with an organic Cr compound using silica xerogel as a carrier, and then 200 mg of a Cr-based catalyst (catalyst manufactured by Grace; 969MS) activated with dry air at 810 ° C. , Isobutane 800 ml, ethylene and butene-1 were introduced at a temperature of 93 ° C. (butene-1 concentration of the polymer finally obtained = 0.2%), and ethylene partial pressure 15 kg.
Polymerization was carried out for 30 minutes while maintaining the same at / cm ² . The polyethylene thus obtained had MFR = 0.14 (g / 10 mi
n), P = 0.20 and ESCR = 20 (hours). Table 1 shows the results of measuring the physical properties of the obtained polyethylene.

Comparative Example 2 The polymerization temperature was 98 ° C., butene
Polymerization was carried out under the same conditions as in Comparative Example 1 except that the concentration of 1 was 0.4%. The obtained polyethylene has MFR = 0.8
0 (g / 10min), P = 0.15, ESCR = 11
It was (time). Table 1 shows the results of measuring the physical properties of the obtained polyethylene.

[0040]

[Table 1]

[0041]

EFFECT OF THE INVENTION Environmental stress crack resistance (ES) of polyethylene
By improving CR), long-term use of blow molded products, construction,
It has become possible to use polyethylene pipes for civil engineering for a long time.

 ─────────────────────────────────────────────────── --- Continuation of the front page (72) Inventor Yoshihiro Nomoto 1-3-1 Nishitsurugaoka, Oi-cho, Iruma-gun, Saitama Tonen Co., Ltd. Research Institute (72) Masahide Murata Nishitsurugaoka, Oi-cho, Iruma-gun, Saitama Prefecture 1-72 3-1 Tonen Corporation Research Institute (72) Inventor Satoshi Ueki 1-3-1 Nishitsurugaoka, Oi-cho, Iruma-gun, Saitama Tonen Research Institute

Claims (2)

[Claims] 1. A melt flow rate (MFR) measured according to JIS K7210 and a tie molecular ratio (P) determined from a long period length of a lamella and a weight average molecular weight satisfy a relation of P ≧ 0.18-0.05 log MFR. An environmental stress crack resistant polyethylene characterized by being. 2. A polyethylene obtained by polymerizing a magnesium alkoxide, a halogenated hydrocarbon and a titanium compound, which are polymerized using a catalyst component in contact, according to JIS K7.
210 melt flow rate (MFR)
And the tie molecular ratio (P) determined from the long period length and the weight average molecular weight of the lamella satisfy the relationship of P ≧ 0.18-0.05 log MFR.