JPH10195135A - Ethylenic polymer and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ethylenic polymer which does not suffer from sagging (draw down) in blow molding, especially large-scale blow molding and can give blow moldings having good surface appearance (skin), high impact resistance and excellent environmental stress cracking resistance. SOLUTION: An ethylene homopolymer or a copolymer of ethylene with a 3-20C α-olefin having a density of 0.945-0.970g/cm<3> , a melt flow rate under a load of 21.6kg (HLMFR) of 1.5-10g/10min and a terminal vinyl bond content of 3/1,000C and satisfying the relationship: logMS>=-0.336×logMFR+0.82 (MS is the melt tension, and MFR is the melt flow rate under a load of 2.16kg) is used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a novel ethylene polymer and a method for producing the same. More specifically, in blow molding, especially in large blow molding, there is no sagging (drawdown) during molding, the surface state (skin) is good, and the rigidity and impact resistance of the obtained blow molded article are high.
The present invention relates to an ethylene polymer having excellent environmental stress cracking resistance (ESCR) and a method for producing the same.

[0002]

2. Description of the Related Art In the field of blow molding applications such as blow containers, it has mechanical strength such as rigidity and impact resistance.
In order to obtain a blow-molded body having a good environmental stress cracking resistance (ESCR) and a uniform thickness without sagging (drawdown) during molding, and a blow-molded body having a good surface condition (skin). In order to obtain, it is desirable to use an ethylene polymer having a high molecular weight and a wide molecular weight distribution. In particular, for large containers such as 50 liters or more, whose use has recently been expanded and demand is growing, and particularly for plastic drums and the like having a volume of 200 liters or more, the parison (the molten resin extruded in blow molding) has a large weight. It is necessary to prevent drawdown at the time.

[0003]

However, an ethylene polymer having these characteristics in a well-balanced manner has not been obtained. For example, an ethylene polymer obtained by polymerization with a Phillips catalyst (which can be identified by detecting Cr atoms from polymer ash) generally has the advantage that there is no drawdown and that the skin can be molded well. ,
The polymer has many drawbacks, such as having many vinyl bonds at the terminal of the polymer, and has the disadvantage that the polymer is easily deteriorated and the ESCR is low. ESCR is improved by increasing the comonomer content in the ethylene-based polymer, but at a reduced density and reduced stiffness. A blow molded article manufactured using an ethylene polymer having low rigidity is not preferable because buckling or deformation occurs when containers are stacked.

Further, an ethylene polymer using a Ziegler catalyst (which can be identified by detecting Ti, Mg, Cl atoms, etc. from polymer ash) generally has a small number of vinyl bonds at the polymer terminal, Strong against polymer degradation and excellent in ESCR. However, the drawdown property is inferior to the polymer obtained using a Phillips catalyst. If the molecular weight of the polymer is increased in order to improve the drawdown property, the skin of the molded article becomes worse (melfrah, shark skin, raggedness, etc.), and a polymer having an excellent balance of these properties has been desired.

[0005]

Means for Solving the Problems Accordingly, the present inventors have
As a result of intensive studies to achieve the above object, ethylene homopolymer or ethylene and α having 3 to 20 carbon atoms
An olefin and a copolymer having a density and 2
Melt flow rate at 1.6 kg load (HLMF
R) is in a specific range, the number of terminal vinyl bonds in the polymer is equal to or less than a specific number, and the melt tension (MS) and 2.16 k
The melt-flow rate (MFR) at a g load is an ethylene polymer having a specific relationship, and the blow-molded article obtained has no drawdown in blow molding, especially large-size blow molding, and has good skin during molding. Of the present invention have been found to have high rigidity and impact resistance and to be excellent in ESCR, and have completed the present invention.

That is, the present invention relates to an ethylene homopolymer or an ethylene copolymer comprising ethylene and an α-olefin having 3 to 20 carbon atoms, wherein (1) the density is 0.945 to 0.970 g. / Cm ³ , (2) 21.6k
Melt flow rate (HLMFR) under g load is 1.5
(3) The number of terminal vinyl bonds is 3 or less per 10,000 carbon atoms. (4) The relationship between the melt tension (MS) and the melt flow rate (MFR) under a load of 2.16 kg is logMS. ≧ −0.336 × logMFR +
The present invention relates to an ethylene polymer having a ratio of 0.82 and a method for producing the same.

Hereinafter, the present invention will be described in detail. The ethylene polymer of the present invention comprises an ethylene homopolymer or an ethylene copolymer composed of ethylene and an α-olefin having 3 to 20 carbon atoms. Examples of the α-olefin having 3 to 20 carbon atoms include propylene, butene-1, pentene-1, hexene-1, octene-1, decene-1,
Eicosene-1, 4-methylpentene-1 and the like.

The ethylene polymer of the present invention has a density of 0.1.
It is necessary to be 945 to 0.970 g / cm ³ . If the density is less than 0.945 g / cm ³ , the rigidity decreases,
When stacking blow molded articles, buckling and deformation occur, which is not preferable. When the density exceeds 0.970 g / cm ³ ,
ESCR is undesirably reduced.

Further, the ethylene polymer of the present invention has a
Melt flow rate at 1.6 kg load (HLMF
R) needs to be in the range of 1.5 to 10 g / 10 minutes. If the HLMFR exceeds 10 g / 10 minutes,
Mechanical strength such as impact resistance and ESCR decrease, and
It is not preferable because the drawdown becomes easy. Also, HL
If the MFR is less than 1.5 g / 10 minutes, the flow of the molten resin during molding is poor, and the skin of the molded body is poor. The skin can be improved by increasing the molding temperature, but it is not preferable because the tension at the time of molding is reduced and drawdown becomes easy, and it takes time for the molten resin to solidify and the molding cycle becomes longer, which is not preferable.

[0010] The ethylene-based polymer of the present invention needs to have no more than 3 vinyl bonds per 10,000 carbon atoms. If the number of terminal vinyl bonds exceeds this range, problems such as deterioration of the polymer and reduction of the ESCR occur.

In the ethylene polymer of the present invention, the relationship between the melt tension (MS) and the melt flow rate (MFR) at a load of 2.16 kg must satisfy logMS ≧ −0.336 × logMFR + 0.82. It is. If the MS is lower than this relationship, drawdown occurs due to low melt tension, and it becomes difficult to obtain a blow molded body having a uniform thickness. A blow-molded body having an uneven thickness has a low mechanical strength in a thinned portion, and therefore needs to have a large overall thickness, which is not preferable in terms of weight reduction and cost saving.

Furthermore, it is desirable that the ethylene polymer of the present invention has a specific molecular weight and a specific molecular weight distribution. That is, gel permeation chromatography (G
(I) the number average molecular weight (Mn) obtained by (PC) is 1.5
(Iii) weight average molecular weight (Mw) of 15
(Iii) a ratio of the weight average molecular weight to the number average molecular weight (Mw / Mn) of 4 to 15, preferably (i) a number average molecular weight (Mn) of 170000 to 35,000, (Ii) weight average molecular weight (Mw) of 150,000 to 230,000; (iii) ratio of weight average molecular weight to number average molecular weight (Mw / Mn) of 6 to
It is preferable that the ethylene polymer has a molecular weight and a molecular weight distribution in the range of 12. When Mn is smaller than this range, mechanical strength such as impact resistance and ESCR decrease,
Further, it is not preferable because the draw-down becomes easy. Mn
However, if it is larger than this range, the flow of the molten resin at the time of molding is poor, and the skin of the molded body is unfavorably deteriorated. Also, Mw
Is larger than this range, the flow of the molten resin during molding is poor, the skin of the molded body is deteriorated, and the molding cycle is undesirably long. If the Mw is smaller than this range, the mechanical strength such as impact resistance and the ESCR decrease, and the drawdown tends to occur. Also, Mw / Mn
Is smaller than this range, the skin of the molded body is deteriorated, and when Mw / Mn is larger than this range, the fusion of the pinch-off portion of the blow molded body (the fusion portion where the parison is sandwiched between the molds) is performed. Even if the strength becomes weak and the strength of the ethylene polymer itself is sufficient,
Since the molded body is easily broken from this pinch-off part,
Mw / Mn is desirably 4 to 15, preferably 6 to 12.

The ethylene polymer having the above-mentioned properties is
It can be produced by polymerizing under specific conditions using a so-called Ziegler catalyst or metallocene catalyst, and then subjecting the resulting polymer to a crosslinking treatment. Particularly, a Ziegler catalyst is preferable. When polymerized with a Philips catalyst, the resulting ethylene polymer has many vinyl bonds at the polymer terminal, etc.
The polymer tends to deteriorate and the ESCR is low. Metallocene catalysts generally have a narrower molecular weight distribution than Ziegler catalysts, and it is difficult to obtain a molded body with good skin when manufacturing a large blow container such as a plastic drum.

Next, an example of the method for producing the ethylene polymer of the present invention will be described, but the ethylene polymer of the present invention is not limited to the following production method.

As the Ziegler-based catalyst, Mg, Ti,
Examples include a solid catalyst component (A) containing halogen as an essential component and a catalyst containing an organoaluminum compound (B) as main components. A specific example of the solid catalyst component (A) is disclosed in
JP-A-66178, JP-A-50-51587, JP-A-50-51587
5-78005, JP-A-56-61406, JP-A-57-212210, JP-A-60-262802,
JP-A-7-41513 is an example. Also,
It is also possible to use a catalyst using Ti and Zr or V as the transition metal. Specifically, Japanese Patent Application Laid-Open No. 51-4638
7, JP-A-51-138785, JP-A-56-15
No. 1704, JP-A-60-101105, JP-A-5-101
No. 9216, and the like. As the organic aluminum compound (B), an aluminum compound having a linear or branched alkyl group having 1 to 20 carbon atoms, which is generally used in the art, is used. Specific examples include trimethylaluminum, triethylaluminum, tri-i-butylaluminum, tri-n-butylaluminum, tri-n-hexylaluminum, diethylaluminum chloride and the like.

Examples of the metallocene catalyst include Group IVB transition metal compounds containing a ligand having a cyclopentadienyl skeleton. Specifically, JP-A-61-31
No. 404, JP-A-61-108610, JP-A-63-108610
No. 152608 and the like.

Ethylene alone or ethylene and carbon number 3
The polymerization of the α-olefin of No. 20 to 20 can be carried out under general reaction conditions of the so-called Ziegler method. That is,
The polymerization is carried out at a temperature of from 20 to 110 ° C. in a continuous or batch manner. The polymerization pressure is not particularly limited, but the use of 1.5 to 100 kg / cm ² G under pressure is particularly suitable. When the polymerization is carried out in the presence of an inert solvent, any one commonly used as an inert solvent can be used. Particularly suitable are alkanes or cycloalkanes having 3 to 20 carbon atoms, such as propane, isobutane, pentane, hexane, cyclohexane and the like.

When the polymerization is carried out in the gas phase in the absence of an inert solvent, the reaction is carried out at a temperature lower than the melting point of the polymer in the presence of an olefin gas.

As the reactor used in the polymerization step, a fluid bed type stirrer, a stirring tank type stirrer, etc., which are commonly used in the technical field, can be appropriately used. When using a fluidized bed stirrer, by blowing gaseous olefin and or inert gas into the system,
The reaction is performed while maintaining the reaction system in a fluid state. When a stirring tank type stirrer is used, various types of stirrers such as an squid type stirrer, a screw type stirrer, and a ribbon type stirrer can be used.

The polymerization can be carried out by a single polymerization or a multi-stage polymerization of two or more stages. However, in order to obtain an ethylene polymer having a relatively wide molecular weight distribution, it is desirable to carry out a multi-stage polymerization of two or more stages. Even when a Ziegler-based catalyst is used, the molecular weight distribution of the ethylene-based polymer obtained by the one-stage polymerization is relatively narrow, and when producing a large blow container such as a plastic drum, a molded product with good skin can be obtained. Is difficult.

When an ethylene polymer is produced by multistage polymerization of two or more stages, polymers having different molecular weights are produced in each stage, but the order is arbitrary. The molecular weight of the produced polymer can be adjusted by a known method, that is, a method of allowing an appropriate amount of hydrogen to exist in the reaction system.
As for the supply amount of the comonomer, the density of the ethylene polymer finally obtained is 0.945 to 0.970 g.
/ Cm ³ can be adjusted arbitrarily, but high ESC
In order to obtain a polymer having R, it is desirable to supply a large amount of comonomer to the step of producing a polymer having a higher molecular weight.

In the present invention, the molecular weight and the production ratio of the polymer formed in each stage are not particularly limited as long as an ethylene-based polymer having a molecular weight distribution in the above specific range is obtained. Low molecular weight components in one polymerization vessel,
In the case of the two-stage polymerization in which the high molecular weight component is polymerized in the second polymerization vessel, the MFR of the low molecular weight component is 1 to 200 g / 10 min, preferably 2 to 100 g / 10 min, more preferably 5 to 10 g / 10 min.
50 g / 10 min, the production ratio is the production ratio of low molecular weight components:
20:80 to 80:20, preferably 30:70 to 60:40, more preferably 4 in terms of the production ratio of the high molecular weight component.
It is desirable to manufacture at 0:60 to 50:50. When the MFR of the low molecular weight component is smaller than this range, the flow of the molten resin during molding is poor, and the skin of the molded product is deteriorated, and the molding cycle is undesirably long. If the MFR of the low molecular weight component is larger than this range, the mechanical strength such as impact resistance decreases, which is not preferable.

In the two-stage polymerization in which a high molecular weight component is polymerized in the first polymerization reactor and a low molecular weight component is polymerized in the second polymerization reactor, the intrinsic viscosity ([η]) of the high molecular weight component is 2.0 to 20 dl /.
g, preferably 2.0 to 10 dl / g, particularly preferably 2.5 to 7 dl / g, and the production ratio is 20:80 to 8
0:20, preferably 30:70 to 60:40, more preferably 40:60 to 50:50. When [η] is less than this range, mechanical strength such as impact resistance is reduced, and when [η] is more than this range, the flow of the molten resin during molding is poor, and the skin of the molded article is deteriorated. The molding cycle is undesirably long.

When the production ratio of the low molecular weight component is smaller than the above range, the fusion strength of the pinch-off portion becomes weak, and the molded product is easily broken from the pinch-off portion by impact due to dropping, and the low molecular weight component is reduced. If the formation ratio is larger than the above range, the flow of the molten resin during molding is poor, and the skin of the molded body is unfavorably deteriorated.

The ethylene copolymer of the present invention can be produced by using the above-mentioned catalyst, polymerizing under specific conditions, and subjecting the obtained polymer to a crosslinking treatment. The cross-linking treatment is performed, for example, by using the following methods alone or in combination to generate radicals in the polymer chain, and the polymer in which the radicals are generated reacts with the polymer itself or another polymer to form a new one. This is performed by generating a suitable carbon-carbon bond. That is,
A method in which a polymer is melt-kneaded in the presence of oxygen. A method in which an organic peroxide is added to a polymerized polymer, and the mixture is heated or melt-kneaded at a temperature not lower than the decomposition temperature of the organic peroxide. A method of irradiating the polymer with radiation is exemplified. Among these methods, a method of melt-kneading the polymer in the presence of oxygen and a method of adding an organic peroxide to the polymer and kneading the polymer at a temperature not lower than the decomposition temperature of the organic peroxide are particularly preferable.

As the organic peroxide, for example, di-t-
Butyl peroxide, dicumyl peroxide, t-
Butyl cumyl peroxide, 2,5-dimethyl-2,
5-bis (t-butylperoxy) hexane, 2,5-
Dialkyl peroxides such as dimethyl-2,5-bis (t-butylperoxy) hexyne-3, α, α′-bis (t-butylperoxy) diisopropylbenzene, and 2,5-dimethyl-2,5- Peroxyesters such as bis (benzoylperoxy) hexane, t-hexylperoxybenzoate, t-butylperoxy-m-toluylbenzoate, t-butylperoxybenzoate, bis (t-butylperoxy) isophthalate, 1,1-bis (t-butylperoxy) 3,
3,5-trimethylcyclohexane, 1,1-bis (t
-Hexylperoxy) cyclohexane, 1,1-bis (t-hexylperoxy) 3,3,5-trimethylcyclohexane, 1,1-bis (t-butylperoxy)
Cyclohexane 1,1-bis (t-butylperoxy)
Peroxy ketals such as cyclododecane and n-butyl 4,4-bis (t-butylperoxy) valerate are exemplified. Among them, dialkyl peroxides, especially α, α'-bis (t-butylperoxy)
Diisopropylbenzene, 2,5-dimethyl-2,5-
It is preferable to use bis (t-butylperoxy) hexyne-3.

The concentration of oxygen and the concentration of organic peroxide during the crosslinking treatment are not particularly limited as long as the relationship between MS and MFR of the ethylene polymer after the crosslinking treatment falls within a specific range. When used, the gas atmosphere in the granulator is 100 ppm to 10% in oxygen concentration, preferably 0.1 to 5%, depending on the granulation speed and the supply speed of the oxygen-containing gas sent to the granulator. When an organic peroxide is used, the amount is preferably 1 to 10000 ppm, more preferably 5 to 1000 ppm, based on the polymer. If it is less than this range, the relationship between MS and MFR does not fall into a specific range, and drawdown occurs due to insufficient melt tension. On the other hand, if it is more than this range, the crosslinking proceeds, and the copolymer has poor elongation at the time of molding, so that a molded article having good skin cannot be obtained, or gel is easily generated due to local crosslinking. In extreme cases, oxidative degradation may occur.

[0028]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, which should not be construed as limiting the invention thereto. Various physical property tests in Examples and Comparative Examples were performed by the following methods.

(1) Density: Measured according to JIS K-6760 (1981).

(2) Melt flow rate The melt flow rate (MFR and HLMFR) under 2.16 kg and 21.6 kg load is JIS K-7.
The measurement was performed in accordance with conditions 4 and 7 of No. 210 (1976).

(3) Melt tension (MS) Using “Capillograph 1B” manufactured by Toyo Seiki Co., Ltd.
Ethylene polymer sample melted at 0 ° C was 2.1 m in diameter
m, 9.6m from the orifice with a length of 8mm
m, the tension at the time of extrusion at an extrusion speed of 10 mm / min and withdrawal at 10 m / min was determined.

(4) ESCR Measured in accordance with the measuring method of “constant strain environmental stress crack test” of JIS K-6760 (1981).

(5) Vinyl terminal bond: Using a "Fourier transform infrared spectrophotometer 1760X" manufactured by PERKIN-ELMER, the bond was determined from the absorbance at 909 cm ^-1 of a hot-pressed ethylene polymer sample.

(6) "GPC150C" manufactured by GPC WATERS (TSO manufactured by Tosoh Corporation)
K GEL GMHHR-H (S) column 7.8 × 30
The measurement of the ethylene polymer sample was carried out at 0 ° C., at a measurement temperature of 140 ° C., and in a measurement solvent of ortho-dichlorobenzene using three pieces of 0 mm. In addition, a standard polystyrene sample was measured under the same conditions, and the GP obtained by calibration based on the Q factor method was obtained.
From the curve C, the number average molecular weight and weight average molecular weight of the ethylene polymer were determined.

Example 1 (1) Preparation of solid catalyst component (A) In a 10-liter stainless steel autoclave equipped with a stirring device, 108.2 g (1.80 mol) of i-propanol and 134.6 g of n-butanol ( 1.82 mol), 2.0 g of iodine and 4 of magnesium metal powder
0 g (1.65 mol) and titanium tetrabutoxide 2
After adding 24.1 g (0.66 mol) and further adding 2.1 liter of hexane, the temperature was raised to 80 ° C., and the mixture was stirred for 1 hour under a blanket of nitrogen while removing generated hydrogen gas. Subsequently, the temperature was raised to 120 ° C., and the reaction was performed for 1 hour.
A homogeneous solution containing Mg and Ti was obtained. While maintaining the internal temperature of the autoclave at 45 ° C., 1.32 kg (3.3 mol) of a 30% hexane solution of diethylaluminum chloride was added over 1 hour. After adding all, the mixture was stirred at 60 ° C. for 1 hour. Next, 197.0 g (3.3 g atom of silicon) of methylhydropolysiloxane (viscosity of about 30 centistokes at 25 ° C.) was added, and the mixture was reacted under reflux for 1 hour. After cooling to 45 ° C., 2.81 kg (9.1 mol) of a 50% hexane solution of i-butylaluminum dichloride.
Was added over 2 hours. After adding all, at 70 ° C 1
The mixture was stirred for an hour to obtain a solid catalyst component (A). The obtained solid catalyst component (A) was used for the next polymerization step as a hexane slurry after removing remaining unreacted substances and by-products using hexane.

(2) Polymerization 168 liters / hr of dehydrated and purified hexane and 164 mm of triisobutylaluminum as an organoaluminum compound (B) were placed in a first-stage polymerization vessel having an internal volume of 370 liters.
ol / hr, 1.10 g / h of the solid catalyst component (A)
r at a rate of 85 ° C. while feeding the polymerization vessel at the required rate.
at a rate of r, maintaining an ethylene concentration of 0.5 wt%, a hydrogen to ethylene concentration ratio of 0.48 mol / mol, a total pressure of 30 kg / cm ² , and an average residence time of 1.6 hr. The first-stage polymerization was continuously performed. The hexane slurry containing the polymer obtained in the first stage polymerization vessel was flushed with unreacted hydrogen and ethylene in a flash tank (the MFR of the polymer in the first stage was 15 g /
10 minutes). Thereafter, the mixture was introduced into a second-stage polymerization vessel having an internal volume of 545 liters, and the solid catalyst component and the alkylaluminum were not added and supplied at 121 liters / hr of hexane.
While discharging the contents of the polymerization vessel at a required speed, at 80 ° C., 22 kg / hr of ethylene and 0.55
kg / hr, ethylene concentration 1.5wt
%, Hydrogen to ethylene concentration ratio 0.041 mol / mo
1, butene-1 to ethylene concentration ratio 0.15mol / m
ol, the second stage polymerization was carried out under the conditions of a total pressure of 20 kg / cm ² and an average residence time of 1.3 hr. The effluent from the second stage polymerization vessel is unreacted hydrogen in the flash tank,
After flashing ethylene and butene-1, a polymer powder was obtained through a separation and drying process.

(3) Production of Ethylene-Based Polymer To 100 parts by weight of the obtained polymer powder, 0.1 part by weight of Irganox 1010 (trade name, manufactured by Ciba Geigy), which is a phenol-based stabilizer, was added. 0.1 parts by weight of Irgafos 168 (trade name, manufactured by Ciba Geigy), 0.07 parts by weight of DSTP (trade name, manufactured by Yoshitomi Pharmaceutical Co., Ltd.), 0.15 parts by weight of calcium stearate, and an organic peroxide Α, α'-bis (t-
Butylperoxy) diisopropylbenzene in 0.01
The mixture was added in parts by weight and pelletized at 230 ° C. The density of the obtained ethylene polymer pellets is 0.954 g / cm ³ ,
MFR 0.038 g / 10 min, HLMFR 6.0 g
/ 10 minutes, MS was 22 g, and ESCR was 230 hr. When the terminal vinyl group was measured, the number of carbon atoms was 10,000.
One per C. The average molecular weight obtained by GPC was Mn = 190000, Mw = 19.20, and Mw / Mn
Was 10.1.

(4) Production of Plastic Drum and Drop Strength Test The ethylene polymer pellets were molded into a 200-liter closed-type plastic drum using a plastic drum molding machine manufactured by Fischer. The ethylene polymer was melted by setting the temperature of the cylinder portion to 175 to 200 ° C., the parison extruded at a head temperature of 190 to 205 ° C. was sandwiched by a mold at 20 ° C., and air was pressured at 6 kg / cm.
After press-fitting with ² , a plastic drum having a product weight of 10.5 kg was obtained. There was no drawdown at the time of molding, and the obtained plastic drum had good skin, and no merfra, shark skin, and nicks were observed.

A drop strength test was performed on the obtained plastic drum. A plastic drum was filled with 98% of a 50% aqueous solution of ethylene glycol, and the temperature of the container and the inside solution was cooled to -18 ° C. I checked for presence. As a result, the plastic drum of this example had no cracks and no liquid leakage.

Example 2 (1) Preparation of Solid Catalyst Component In a 3 liter glass flask equipped with a stirrer, 40 g (1.65 mol) of metallic magnesium powder and 224.5 g (0.66 mol) of titanium tetrabutoxide were placed. N-butanol in which 2.0 g of iodine was dissolved.
1 g (3.46 mol) was added over 2 hours at 90 ° C., and 1 g (14.6 g) was added under a nitrogen blanket while excluding further generated hydrogen gas.
Stirred at 40 ° C. for 2 hours. After setting this to 110 ° C,
36.9 g (0.18 mol) of tetraethoxysilane and 25.2 g (0.17 mol) of tetramethoxysilane were added, and the mixture was further stirred at 140 ° C. for 2 hours. Next, 2.1 liters of hexane was added to obtain a homogeneous solution containing Mg and Ti. This homogeneous solution was placed in a 10-liter stainless steel autoclave equipped with a stirrer, the internal temperature was maintained at 45 ° C, and 1.4 mol of diethylaluminum chloride and i-
0.74 kg of a hexane solution containing 0.56 mol of butylaluminum dichloride was added over 1 hour, and 6
Stirred at 0 ° C. for 1 hour. Then, a hexane solution containing 10.4 mol of i-butylaluminum dichloride.
2 kg was added and the mixture was stirred at 60 ° C. for 1 hour to obtain a solid catalyst component. The obtained solid catalyst component was used for the next polymerization step as a hexane slurry after removing remaining unreacted substances and by-products using hexane. (2) Polymerization 168 liters / hr of dehydrated and purified hexane in a first-stage polymerization vessel having an internal volume of 370 liters, and 164 mm of triisobutylaluminum as an organic aluminum compound (B).
ol / hr, 0.95 g / h of the solid catalyst component (A)
20 kg / h of ethylene at 85 ° C. while continuously feeding at a required speed and discharging the contents of the polymerization vessel at a required speed.
at an ethylene concentration of 0.5 wt%, a hydrogen to ethylene concentration ratio of 0.30 mol / mol, a total pressure of 30 kg / cm ² , and an average residence time of 1.6 hr. The first-stage polymerization was continuously performed. The hexane slurry containing the polymer obtained in the first stage polymerization vessel was flushed with unreacted hydrogen and ethylene in a flash tank (the MFR of the polymer in the first stage was 5 g / 1.
0 minutes). Thereafter, the mixture was introduced into a second-stage polymerization vessel having an internal volume of 545 liters. The solid catalyst component and alkylaluminum were not added, and hexane was supplied at 121 liters / hr. , 20 kg / hr of ethylene and 0.50 of butene-1
kg / hr, ethylene concentration 1.9wt
%, Hydrogen to ethylene concentration ratio 0.040 mol / mo
1, butene-1 to ethylene concentration ratio 0.15mol / m
ol, the second stage polymerization was carried out under the conditions of a total pressure of 20 kg / cm ² and an average residence time of 1.3 hr. The effluent from the second stage polymerization vessel is unreacted hydrogen in the flash tank,
After flashing ethylene and butene-1, an ethylene polymer powder was obtained through a separation and drying process.

(3) Production of ethylene polymer The same additives and organic peroxides as in Example 1 were added, and
Pelleted at 0 ° C. The density of the obtained ethylene polymer pellets was 0.955 g / cm ³ , and the MFR was 0.042.
g / 10 min, HLMFR 8.2 g / 10 min, MS 2
1 g, ESCR was 250 hr. When the terminal vinyl group was measured, it was one per 10,000 carbon atoms. The average molecular weight obtained by GPC is Mn = 2.1.
Mw = 16,000 and Mw / Mn was 7.8.

(4) Production of Plastic Drum and Drop Strength Test The above-mentioned ethylene polymer pellets were molded in the same manner as in Example 1. The obtained plastic drum had no drawdown at the time of molding, had good skin, and did not show any merhula, shark skin, or bruise. When a drop strength test was performed, no crack was generated by the drop and no liquid leakage occurred.

Comparative Example 1 (1) Polymerization 168 liter / hr of dehydrated and purified hexane and 164 mm of triisobutylaluminum as an organoaluminum compound (B) in a first-stage polymerization vessel having an internal volume of 370 liters.
ol / hr, the solid catalyst component (A) of Example 1 was 1.20
g / hr at a rate of 85.degree. C. while discharging the polymerization vessel contents at the required rate.
g / hr, ethylene concentration 0.5 wt%,
The hydrogen to ethylene concentration ratio was maintained at 0.55 mol / mol, the total pressure was 30 kg / cm ² , and the average residence time was 1.6 hr.
The first-stage polymerization was continuously performed in a liquid-filled state under the conditions described in (1).
The hexane slurry containing the polymer obtained in the first stage polymerization vessel was flushed with unreacted hydrogen and ethylene in a flash tank (the MFR of the polymer in the first stage was 50 g / 10 min). Thereafter, the mixture was introduced into a second-stage polymerization vessel having an internal volume of 545 liters. The solid catalyst component and alkylaluminum were not added, and hexane was supplied at a rate of 121 liters / hr.
At 20 ° C., ethylene was supplied at a rate of 20 kg / hr and butene-1 was supplied at a rate of 0.60 kg / hr.
2 wt%, hydrogen to ethylene concentration ratio 0.025 mol /
mol, butene-1 to ethylene concentration ratio 0.20mol
/ Mol, the total pressure was 20 kg / cm ² , and the average residence time was 1.3 hr. The unreacted hydrogen, ethylene, and butene-1 were flushed from the discharge from the second-stage polymerization tank in a flash tank, followed by separation and drying steps to obtain an ethylene polymer powder.

(3) Production of ethylene polymer The same additives as in Example 1 were added except that α, α'-bis (t-butylperoxy) diisopropylbenzene which was an organic peroxide was not added. Pelleted at 230 ° C. The density of the obtained ethylene polymer pellet is 0.95.
3 g / cm ³ , MFR 0.024 g / 10 min, HLM
FR: 5.7 g / 10 min, MS: 19 g, ESCR: 5
00 hr. When the terminal vinyl group was measured, it was one per 10,000 carbon atoms. The average molecular weight obtained by GPC was Mn = 15,000 and Mw = 22.7.
Mw / Mn was 15.4 in 10,000.

(4) Production of Plastic Drum and Drop Strength Test The above-mentioned ethylene polymer pellets were molded in the same manner as in Example 1. The obtained plastic drum had good skin, and did not show any merhula, shark skin, or kerf, but it did draw down during molding. When a drop strength test was performed, cracks occurred from the pinch-off portion of the top plate due to a drop from a height of 1.9 m, the molded body was broken, and the content liquid flowed out.

[0046]

[Table 1]

[0047]

As described above, the novel ethylene polymer of the present invention is free from sagging (drawdown) during molding and has a good surface condition (skin) in blow molding, especially in large blow molding. The obtained blow molded article has high rigidity and impact resistance, and is excellent in environmental stress crack resistance (ESCR).

[0048]

Claims (6)

[Claims] 1. An ethylene homopolymer or an ethylene copolymer comprising ethylene and an α-olefin having 3 to 20 carbon atoms, wherein (1) the density is 0.945 to 0.97.
0 g / cm ³ , (2) melt flow rate (HLMFR) under a load of 21.6 kg is 1.5 to 10 g / 10 min,
(3) The number of terminal vinyl bonds is 3 out of 10,000 carbon atoms.
(4) An ethylene polymer, wherein the relationship between the melt tension (MS) and the melt flow rate (MFR) under a load of 2.16 kg is logMS ≧ −0.336 × logMFR + 0.82. 2. A gel permeation chromatography (GPC) obtained (i) a number average molecular weight (Mn) of 15,000 to 35,000, and (ii) a weight average molecular weight (Mw) of 150,000 to 25. (Iii) the ratio of the weight average molecular weight to the number average molecular weight (Mw /
The ethylene polymer according to claim 1, wherein Mn) is 4 to 15. 3. A gel permeation chromatography (GPC) obtained (i) a number average molecular weight (Mn) of 170000 to 35,000 or more, and (ii) a weight average molecular weight (Mw) of 150,000 or more. (Iii) ratio of weight average molecular weight to number average molecular weight (Mw /
2. The ethylene polymer according to claim 1, wherein Mn) is 6 to 12. 4. A cross-linking treatment is performed after ethylene alone or ethylene and an α-olefin having 3 to 20 carbon atoms are polymerized by multistage polymerization.
3. The method for producing an ethylene-based polymer according to item 1. 5. The method for producing an ethylene-based polymer according to claim 4, wherein a Ziegler-based catalyst is used as the catalyst. 6. The method for producing an ethylene polymer according to claim 4, wherein ethylene alone or two-stage polymerization of ethylene and an α-olefin having 3 to 20 carbon atoms is carried out.