JP2006241451A - Polyethylene composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polyethylene composition, especially the polyethylene composition suitable for use in high speed blow molding, which is excellent in the physical properties such as stiffness and impact resistance and in the moldability such as draw-down resistance and fusibility and also gives a molded article with a good external appearance. <P>SOLUTION: The polyethylene composition comprises (A) a polyethylene manufactured by using a chromium-based catalyst and (B) a polyethylene manufactured by using a titanium-based catalyst and has a content in the composition of (A) the polyethylene of 5-95% by weight, an MFR of the composition of 0.4-2.0 g/10 min, a density of 940-965 kg/m<SP>3</SP>, a molecular weight distribution (a value of Mw/Mn) of 7-20, a melt viscosity at 230&deg;C and a shear rate of 1,598 sec<SP>-1</SP>of 180-230 Pa s, and also has such a relationship between the G"/G' and the MFR as expressed by the formula: Log(MFR)+1.5&le;G"/G'&le;Log(MFR)+2.5, wherein G' is a storage modulus and G" is a loss modulus, each determined by the dynamic viscoelasticity measurement at 170&deg;C and a frequency of 0.01 rad/sec. <P>COPYRIGHT: (C)2006,JPO&amp;NCIPI

Description

  The present invention relates to a polyethylene composition. More specifically, the present invention relates to a polyethylene composition having excellent physical properties such as rigidity and impact resistance and moldability such as drawdown resistance and fusing property, and is suitable for hollow molding, injection molding, extrusion molding, film / sheet molding. The present invention relates to a polyethylene composition suitable for various containers, lids, bottles, pipes, films, sheets, packaging materials, and the like, and particularly suitable for high-speed hollow molding applications.

Conventionally, polyethylene produced using a chromium-based catalyst (hereinafter referred to as “chromium-catalyzed polyethylene”) is generally used as a polyethylene suitable for hollow molding because of its relatively wide molecular weight distribution. However, although such chromium-catalyzed polyethylene has a suitable melt tension and swell that facilitate hollow molding, it has the disadvantage of insufficient environmental stress crack resistance (hereinafter referred to as “ESCR”).
On the other hand, polyethylene produced by single-stage or multistage polymerization using a Ziegler catalyst is disclosed in, for example, Patent Documents 1 to 3 as polyethylene having a wide molecular weight distribution suitable for hollow molding. However, although the polyethylene obtained by such a method has excellent physical properties such as high ESCR, it has a drawback of low melt tension, swell, and draw-down resistance and is difficult to be hollow-molded.

As a method for improving these disadvantages, it is known that a method of mixing chromium-catalyzed polyethylene and polyethylene produced by multistage polymerization using a titanium-based catalyst is effective, and molding fields such as hollow molding and extrusion molding It is widely put into practical use. A polyethylene composition comprising such a chromium-catalyzed polyethylene and polyethylene produced by multistage polymerization using a titanium-based catalyst is an example of a polyethylene composition having excellent physical properties such as ESCR and molding processability. It is disclosed in Documents 4-9.
In recent years, efforts to save resources have become stronger due to the response to environmental problems, and there has been an increasing demand for thinning to reduce the thickness of molded products such as hollow molded products, and there is also a high demand for high-speed molding from the viewpoint of economy. Further improvement of moldability is desired. However, in the prior art, when thin-wall molding is performed at high speed, unevenness called melt fracture occurs on the surface of the parison (cylindrical molten resin that is extruded during hollow molding), and the appearance of the molded product deteriorates significantly. There is a problem that the resin temperature rises due to heat generation during extrusion and the fusing property is lowered, and it has not been possible to sufficiently meet such demands for thinning and high speed.

Japanese Patent Laid-Open No. 02-123108 Japanese Patent Laid-Open No. 04-018407 Japanese Patent Laid-Open No. 05-230136 Japanese Examined Patent Publication No. 01-012777 Japanese Patent Publication No. 01-012778 Japanese Patent Publication No. 01-012781 Japanese Patent Laid-Open No. 11-302465 JP 2004-059650 A JP 2004-168817 A

  The present invention improves the drawbacks of the prior art, and is a polyethylene composition having excellent physical properties such as rigidity and impact resistance, excellent moldability such as drawdown resistance and fusing property, and good appearance of the molded body. In particular, a polyethylene composition suitable for high-speed hollow molding applications is provided.

  As a result of intensive studies to improve the drawbacks of the prior art, the present inventor has obtained a specific polyethylene composition comprising a polyethylene produced using a chromium-based catalyst and a polyethylene produced using a titanium-based catalyst. The present inventors have found that the above-mentioned problems can be solved and have reached the present invention.

That is, the present invention
(1) A polyethylene (A) produced using a chromium-based catalyst and a polyethylene (B) produced using a titanium-based catalyst, and the amount of polyethylene (A) in the composition is 5 to 95% by weight. The weight average molecular weight Mw and the number determined by gel permeation chromatography (GPC), the MFR of the composition is 0.4 to 2.0 g / 10 min, the density is 940 to 965 kg / m ³ The molecular weight distribution (Mw / Mn value), which is the ratio of the average molecular weight Mn, is 7 to 20, the measurement temperature is 230 ° C., the melt viscosity is 180 to 230 Pa · s at a shear rate of 1598 sec ⁻¹ , the measurement temperature is 170 ° C., and the frequency is 0 The relationship between the ratio G ″ / G ′ of the storage elastic modulus G ′ and the loss elastic modulus G ″ obtained from dynamic viscoelasticity measurement at 0.01 rad / sec and MFR is Log (MFR) +1.5 ≦ G ″ /G′≦Log(MFR)+2.5, a polyethylene composition,
(2) The polyethylene composition as described in (1) above, wherein the polyethylene (A) is produced by a catalyst system comprising a combination of a chromium-based catalyst treated with an organometallic compound and a promoter. object,
(3) The polyethylene composition according to (1) or (2), wherein the polyethylene (B) is produced by two-stage polymerization,
(4) A hollow molded article comprising the polyethylene composition according to any one of (1) to (3),
It is.

  The polyethylene composition of the present invention is excellent in physical properties such as rigidity and impact resistance and moldability such as drawdown resistance and fusing property, and it is possible to obtain a hollow molded body having a good appearance even in high-speed hollow molding. It is. In particular, it can be suitably used for high-speed hollow molding applications and thin-walled hollow molding applications.

Hereinafter, the present invention will be described in detail.
The MFR of the polyethylene composition of the present invention is 0.4 to 2.0 g / 10 minutes, preferably 0.4 to 1.5 g / 10 minutes, and more preferably 0.5 to 1.0 g / 10. Minutes, most preferably 0.6 to 0.9 g / 10 min. If the MFR is 0.4 g / 10 min or more, the occurrence of gels, fish eyes, etc. is suppressed and the appearance of the molded body is good. If the MFR is 2.0 g / 10 min or less, drawdown is difficult to occur and molding is difficult. It becomes easy.
The HLMFR of the polyethylene composition of the present invention is 20 to 100 g / 10 minutes, preferably 20 to 80 g / 10 minutes, more preferably 30 to 60 g / 10 minutes, and further preferably 30 to 50 g / 10 minutes. Yes, most preferably 35-45 g / 10 min. If the HLMFR is 20 g / 10 min or more, the resin pressure and the resin temperature will not increase during the molding process, and high-speed molding will be easy, and if it is 100 g / 10 min or less, a molded article having sufficient impact resistance can be obtained.

The density of the polyethylene composition of the present invention is 940-965 kg / m ³ , preferably 945-963 kg / m ³ , more preferably 950-960 kg / m ³ , most preferably 955-959 kg / m 3. ³ . If the density is 940 kg / m ³ or more, the molded body has sufficient rigidity, and if it is 965 kg / m ³ or less, the impact resistance is sufficient.
The molecular weight distribution (Mw / Mn) of the polyethylene composition of the present invention is 7 to 20, preferably 7 to 16, more preferably 8 to 13, and further preferably 9 to 11. When Mw / Mn is 7 or more, the resin pressure and the resin temperature do not increase at the time of molding, and high-speed molding becomes easy, and when it is 20 or less, gel and fish eye are hardly generated, and impact resistance is also improved. It is enough.
The melt viscosity of the polyethylene composition of the present invention at a measurement temperature of 230 ° C. and a shear rate of 1598 sec ⁻¹ is 180 to 230 Pa · s, preferably 190 to 230 Pa · s, more preferably 200 to 230 Pa · s. is there. When the melt viscosity is 230 Pa · s or less, the occurrence of melt fracture on the parison surface is suppressed during high-speed hollow molding, and the appearance of the molded body does not deteriorate. If the melt viscosity is 180 Pa · s or more, the impact resistance is sufficient.

  In the polyethylene composition of the present invention, the ratio G ″ / G ′ and MFR of the storage elastic modulus G ′ and the loss elastic modulus G ″ determined from the dynamic viscoelasticity measurement at a measurement temperature of 170 ° C. and a frequency of 0.01 rad / sec. Log (MFR) + 1.5 ≦ G ″ /G′≦Log(MFR)+2.5 is preferably satisfied (the base of the logarithm is e, the same applies hereinafter). Log (MFR) + 1.7 ≦ G It is more preferable that the condition of “/G′≦Log(MFR)+2.3 is satisfied, and it is more preferable that the condition of Log (MFR) + 2.0 ≦ G” /G′≦Log(MFR)+2.2 is satisfied. In a low frequency region such as a measurement frequency of 0.01 rad / sec, the fact that the value of G ″ / G ′ is smaller than the value of MFR means that the stress relaxation with respect to the strain of the resin is slow.

  If the stress relaxation is slow, when the molten resin flows into the minute gap between the die and the core in hollow molding, the stress against the received strain is difficult to be relaxed, and the stress is sufficiently retained near the die exit. Becomes larger. Since the stress relaxation becomes faster as the resin temperature increases, the relationship between G ″ / G ′ and MFR is necessary to maintain sufficient swell even in high-speed molding in which the resin temperature rises to 220 ° C. or higher due to extrusion load. Must satisfy the condition of G ″ /G′≦Log(MFR)+2.5. In the case of G ″ /G′>Log(MFR)+2.5, the swell is lowered particularly in the hollow molding at a resin temperature of 220 ° C. or higher, and it becomes difficult to adjust the thickness. If the speed is too low, the swell becomes too large, the time required to extrude the required length of the parison during hollow molding increases, and the molding cycle decreases, so G ″ /G′≧Log(MFR)+1.5 It is also necessary to satisfy the following conditions. In the production of polyethylene (A), a polyethylene composition having a large G ″ / G ′ can be obtained by using a chromium-based catalyst, and a polyethylene comprising a combination of a chromium-based catalyst treated with an organometallic compound and a cocatalyst. By manufacturing (A), G ″ / G ′ can be made larger. It is also possible to increase G ″ / G ′ by increasing the ratio of polyethylene (A) in the polyethylene composition.

The melt tension (Melt Tension: MT) of the polyethylene composition of the present invention is preferably 5 to 15 g, more preferably 7 to 12 g, and still more preferably 8 to 10 g. If MT is less than 5, drawdown is likely to occur, and if it exceeds 15 g, the problem that the thickness of the pinch-off fused portion (resin junction between the molds) is likely to be reduced.
The melt elongation (ME) of the polyethylene composition of the present invention is preferably 5 to 30 m / min, more preferably 8 to 20 m / min, and further preferably 10 to 15 m / min. When the ME is less than 5 m / min, the uniform stretchability of the molten resin is lowered, and thickness unevenness tends to occur in the hollow molded body, which is not preferable. When ME exceeds 30 m / min, the problem that the thickness of the pinch-off fusion part becomes thin is likely to occur.
The tensile impact strength of the polyethylene composition of the present invention is preferably 90 to 300 kg · cm / cm ² , more preferably 100 to 300 kg · cm / cm ² , and still more preferably 110 to 300 kg · cm / cm ^2. It is. When the tensile impact strength is less than 90 kg · cm / cm ^2, it becomes easy to break when a hollow molded container or the like filled with the content liquid is dropped. Moreover, it is practically difficult to obtain a polyethylene composition having an MFR of 0.4 g / 10 min or more with a tensile impact strength exceeding 300 kg · cm / cm ² .

The bending strength of the polyethylene composition of the present invention is preferably 24 to 32 MPa, more preferably 25 to 32 MPa, and still more preferably 27 to 32 MPa. If the bending strength is less than 24 MPa, the rigidity of the hollow molded container or the like is insufficient, and it is practically difficult to obtain a polyethylene composition having a bending strength exceeding 32 MPa and a density of 965 kg / m ³ or less.
In the polyethylene composition of the present invention, the number of terminal vinyl groups in 10,000 carbon atoms is preferably 10 or less, more preferably 7 or less, and even more preferably 6 or less. When the number of terminal vinyl groups is more than 10, the thermal stability at the time of molding processing is lowered, and resin degradation products such as crosslinked gel and koge are likely to occur.
The polyethylene composition of the present invention comprises two types of polyethylene (A) and (B).

Polyethylene (A) is polyethylene manufactured using a chromium-based catalyst.
Next, a catalyst for producing polyethylene (A) and a method for producing (A) will be described.
Examples of the chromium-based catalyst used for producing polyethylene (A) include known catalysts such as a solid catalyst in which a chromium compound is supported on an inorganic oxide carrier, or a catalyst in which the solid catalyst and an organometallic compound are combined. . Specifically, JP-B Nos. 44-2996, 47-1365, 44-3827, 44-2337, 47-19985, 45-40902, 49 No. 38986, No. 56-18132, No. 59-5602, No. 59-50242, No. 59-5604, Japanese Patent Publication No. 1-1277, No. 1-112778, No. 1 -12781, JP-A-11-302465, JP-A-9-25312, JP-A-9-25313, JP-A-9-25314, JP 7-503739, US Pat. No. 5,104,841 No. 5,137,997 and the like can be exemplified.

Among these known catalysts, those produced with a catalyst system comprising a chromium-based catalyst treated with an organometallic compound and a co-catalyst in particular have a good balance of MT, ME, swell, drawdown resistance, etc. Therefore, it is suitable as a chromium-based catalyst used in the present invention.
The polyethylene (A) of the present invention comprises a chromium oxide catalyst produced by the method described in JP-A-2001-294613 and the like, supported on a refractory compound and activated by heat treatment in a non-reducing atmosphere, It is further produced in the presence of a polymerization catalyst comprising a combination of a solid catalyst component obtained by mixing an organoaluminum compound containing both a group and a hydrosiloxy group with an organoaluminum compound containing an alkoxy group. Is preferred.

In order to obtain the polyethylene (A) of the present invention, the most preferable polymerization catalyst is a chromium oxide catalyst supported on a refractory compound and activated by heat treatment in a non-reducing atmosphere, and represented by the following general formula (1). A polymerization catalyst comprising a solid catalyst component obtained by mixing an organoaluminum compound containing both an alkoxy group and a hydrosiloxy group, and an organoaluminum compound containing an alkoxy group represented by the following general formula (2) It is.
_{^{AlR 1 p H q (OR 2}} ) x (OSiHR 3 R 4) y (1)
(Wherein p ≧ 1, 0 ≦ q ≦ 1, x ≧ 0.25, y ≧ 0.15, 0.5 ≦ x + y ≦ 1.5, and p + q + x + y = 3, R ¹ , R ² , R ³ , R ⁴ represents the same or different hydrocarbon group having 1 to 20 carbon atoms.)
AlR ⁵ _3-n (OR ⁶ ) _n (2)
(In the formula, 0 <n ≦ 1, R ⁵ and R ⁶ represent the same or different hydrocarbon groups having 1 to 20 carbon atoms.)

The polyethylene (A) of the present invention can be produced by a known method such as suspension polymerization, solution polymerization, or gas phase polymerization.
The MFR of polyethylene (A) is preferably 0.5 to 10 g / 10 minutes, more preferably 0.5 to 3 g / 10 minutes, and further preferably 0.8 to 2.0 g / 10 minutes. Most preferably, it is 1.0 to 1.6 g / 10 min. When the MFR is 0.5 g / 10 min or more, the generation of gel and fish eyes is small and the appearance of the molded body is good, and when it is 10 g / 10 min or less, drawdown is difficult to occur and molding is easy.
The HLMFR of polyethylene (A) is preferably 25 to 500 g / 10 minutes, more preferably 25 to 150 g / 10 minutes, still more preferably 40 to 100 g / 10 minutes, and most preferably 50 to 80 g / 10 minutes. It is. When the HLMFR is 25 g / 10 min or more, the resin pressure and the resin temperature are not increased during the molding process and high-speed molding is facilitated. When the HLMFR exceeds 500 g / 10 min, the impact resistance is insufficient.
The density of polyethylene (A) is preferably 945 to 970 kg / m ³ . A density of 945 kg / m ³ or more is preferable because sufficient rigidity of the polyethylene composition of the present invention can be secured. The density of polyethylene (A) is more preferably 955 to 970 kg / m ³ , still more preferably 960 to 967 kg / m ³ , and most preferably 963 to 966 kg / m ³ .

Polyethylene (B) is polyethylene produced using a titanium-based catalyst.
Next, a catalyst for producing polyethylene (B) and a method for producing (B) will be described.
As the titanium-based catalyst in the present invention, a porous polymer material (however, the matrix is, for example, polyethylene, polypropylene, polystyrene, ethylene-propylene copolymer, ethylene-vinyl ester copolymer, styrene-divinylbenzene copolymer). Thermosetting properties such as polymers, polyolefins such as ethylene-vinyl ester copolymer or completely saponified products, and modified products thereof, polyamides, polycarbonates, polyesters, thermoplastic resins, phenol resins, epoxy resins, urea resins, melamine resins, etc. Inorganic solid oxides of elements belonging to Groups 2 to 4, 13 or 14 of the periodic table (for example, silica, alumina, magnesia, magnesium chloride, zirconia, titania, boron oxide, calcium oxide, zinc oxide, Barium oxide, vanadium pentoxide, acid Chromium, the thorium oxide or mixtures or composite oxides thereof thereof) carrier such, include known catalysts such as a catalyst supporting titanium compound

Preferred catalysts in the present invention include, for example, (a) an organomagnesium compound represented by the following general formula (3), (b) a titanium compound containing at least one halogen atom, and (c) Al, B, Solid catalyst obtained by reacting (a) and (b) or (a) and (b) and (c) among (a) to (c) of halide compounds of Si, Ge, Sn, Te and Sb It consists of component [A] and organometallic compound [B].
MαMgβR ¹ _p R ² _q X _r Y _s (3)
(In the formula, α is 0 or a number greater than 0, p, q, r, and s are 0 or a number greater than 0 and have the relationship p + q + r + s = mα + 2 β, and M is a group 1 to 13 in the periodic table. A metal element belonging to the group, m is a valence of M, R ¹ and R ² are hydrocarbon groups having the same or different carbon atoms, X and Y are the same or different groups, halogen, OR ³ , OSiR ⁴ R ⁵ R ⁶ , NR ⁷ R ⁸ and SR ⁹ are represented, R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷ and R ⁸ are hydrogen atoms or hydrocarbon groups, and R ⁹ is a hydrocarbon group. .)

The organometallic compound [B] is a metal compound of Groups 1, 2, and 13 of the periodic table, and is particularly preferably an organoaluminum compound or an organomagnesium compound complex containing an organoaluminum compound.
The reaction between the catalyst component [A] and the organometallic compound component [B] can be carried out by adding both components into the polymerization system and proceeding with the polymerization under the polymerization conditions. May be implemented.
The reaction ratio of the catalyst component is preferably in the range of 1 to 3000 mmol of the [B] component with respect to 1 g of the [A] component.
Specifically, JP-B-52-36788, 52-36790, 52-36791, 52-35792, 52-50070, 52-36794, 52-36795, 52-36796, 52-36915 52-36917, 53-6019, JP-A-50-21876, 50-31835, 50-72044, 50-78619, 53-40696, International Publication No. 99/28353. There are things described in the pamphlet.

The polyethylene (B) of the present invention can be produced by a known method such as suspension polymerization, solution polymerization, or gas phase polymerization.
The polyethylene (B) is preferably a polymer composed of a low molecular weight portion and a high molecular weight portion, two-stage polymerized using a titanium-based catalyst, and the MFR of the low molecular weight portion is preferably 1 to 200 g / It is 10 minutes, More preferably, it is 5-100 g / 10min, More preferably, it is 10-50 g / 10min. The low molecular weight component has a density of preferably 945 to 975 kg / m ³ , more preferably 955 to 975 kg / m ³ , and is obtained by homopolymerizing ethylene or copolymerizing ethylene and an α-olefin having 3 to 20 carbon atoms. Obtained. When producing by suspension polymerization, the low molecular weight portion is preferably produced in a solvent containing 2.0 mol% or less of α-olefin.

The polyethylene (B) of the present invention is preferably obtained by copolymerizing ethylene and an α-olefin having 3 to 20 carbon atoms after homopolymerizing ethylene to produce a low molecular weight portion. The weight ratio of the low molecular weight part to the high molecular weight part (high molecular weight part) / (low molecular weight part) is preferably 40/60 to 60/40, and if the weight ratio of the high molecular weight part is higher than this range, Fracture is likely to occur, and if the weight ratio of the high molecular weight portion is lower than this range, gel and fish eye are likely to occur. More preferably, (high molecular weight portion) / (low molecular weight portion) = 40/60 to 55/45, still more preferably 40/60 to 50/50.
In the present invention, examples of the α-olefin having 3 to 20 carbon atoms include propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-octene, 1-decene, 1-decene, It is selected from the group consisting of dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, and 1-icocene.

The MFR of polyethylene (B) is preferably 0.1 to 5.0 g / 10 minutes, more preferably 0.2 to 2.0 g / 10 minutes, and further preferably 0.4 to 1.6 g / 10 minutes. Most preferably, it is 0.6 to 1.4 g / 10 min.
The HLMFR of polyethylene (B) is preferably 5 to 250 g / 10 minutes, more preferably 10 to 100 g / 10 minutes, still more preferably 20 to 80 g / 10 minutes, and most preferably 30 to 60 g / 10 minutes. .
The density of polyethylene (B) is preferably 935 to 970 kg / m ³ , more preferably 940 to 965 kg / m ³ , still more preferably 945 to 960 kg / m ³ , and most preferably 950 to 955 kg / m ³ .

In the present invention, polyethylene (A) and (B) are mixed to obtain the intended polyethylene composition.
The ratio of (A) to (B) is (A) / (B) = 5/95 to 95/5, preferably 30/70 to 70/30, more preferably 35/65 by weight. ~ 55/45, most preferably 35/65 to 45/55.
There is no restriction | limiting in particular in the mixing method in the case of manufacturing a polyethylene composition, Normal mixing methods, such as a powder state, a slurry state, a pellet state, are used. When kneading, it is carried out at a temperature of 150 to 300 ° C. with a uniaxial or biaxial extruder, a kneader or the like.
The polyethylene composition is a heat stabilizer, antioxidant, ultraviolet absorber, pigment, antistatic agent, lubricant, filler, other polyolefin, thermoplastic resin, rubber, etc. It can be used as needed. It is also possible to perform foam molding by mixing a foaming agent.

It is also possible to crosslink using a radical generator or oxygen. As a method for crosslinking the composition comprising (A) and (B), oxygen or a gas containing oxygen, such as air, or the oxygen concentration is used when the polyethylene composition powder is uniformly mixed. A method of thermal crosslinking at 210 to 300 ° C. in an atmosphere of less than 0.5 vol% is particularly preferable.
The polyethylene composition of the present invention is suitable for hollow molding, injection molding, extrusion molding, film / sheet molding, and can be used for various containers, lids, bottles, pipes, films, sheets, packaging materials and the like. Among them, it is suitable for high-speed hollow molding in which the amount of extruded resin per hour is 50 kg or more, and more suitable for ultra-high speed hollow molding in which the amount of extruded resin per hour is 200 kg or more. It is also suitable for thin-walled hollow molding, and is a thin-wall molding that molds a container having a value obtained by dividing the container internal volume (ml) by the container weight (g), preferably 20 ml / g or more, more preferably 25 ml / g or more. In the above, the characteristics of the polyethylene composition of the present invention become remarkable, and a product having a good appearance can be molded. Specific uses of the container include food multilayer containers such as edible oil containers.

The symbols, measurement methods, and measurement conditions shown in the present invention are as follows.
(1) MFR: Melt index, measured according to JIS-K-7210 under conditions of a temperature of 190 ° C. and a load of 2.16 kg, and the unit is g / 10 minutes.
(2) HLMFR: Represents a high load melt index, measured according to JIS-K-7210 under conditions of a temperature of 190 ° C. and a load of 21.6 kg, and the unit is g / 10 minutes.
(3) Density: A value measured according to JIS-K-7112, in units of kg / m ³ .
(4) Molecular weight distribution: The value of the ratio Mw / Mn of the weight average molecular weight (Mw) and the number average molecular weight (Mn) determined from gel permeation chromatography (GPC). GPC measurement is made by Waters; GPCV2000, Column Showa Denko Co., Ltd .; UT-807 (1) and Tosoh Corp .; GMHHR-H (S) HT (2) connected in series, Mobile phase trichlorobenzene (TCB), column temperature 140 ° C., flow rate 1.0 ml / min, sample concentration 20 mg / 15 ml (TCB), injection amount 413 μl, sample dissolution temperature 140 ° C., sample dissolution time 2 hours. The calibration of the molecular weight is performed at 12 points in which Mw of standard polystyrene manufactured by Tosoh Corporation is in the range of 1,050 to 2,060,000. Mw of each standard polystyrene is multiplied by a coefficient of 0.43 to obtain a molecular weight in terms of polyethylene, a primary calibration line is created from a plot of elution time and molecular weight in terms of polyethylene, and the molecular weight of each sample is determined.

(5) Melt viscosity: manufactured by Toyo Seiki Seisakusho Co., Ltd .; Capillograph 1C was used, a capillary having a diameter of 0.77 mm and a length of 50.8 mm was used, and the measurement was performed at 230 ° C. and a shear rate of 1598 sec ⁻¹ . The unit is Pa · s.
(6) Storage elastic modulus G ′ and loss elastic modulus G ″: manufactured by Rheometric; using ARES, a parallel plate having a diameter of 25 mm, measuring temperature 170 ° C., frequency 0.01 rad / sec, strain 7.0% The dynamic viscoelasticity measurement is performed under the following conditions to obtain the rates G ′ and G ″. The unit is Pa.
(7) Melt tension (MT): manufactured by Toyo Seiki Seisakusho; Capillograph 1C was used, and molten resin was applied under conditions of a temperature of 190 ° C., an orifice diameter of 2.095 mm, an orifice length of 8.02 mm, and a down speed of 0.6 cm / min. Extrusion and load when wound at a speed of 2.0 m / min by a winder, the unit is g.

(8) Melt elongation (ME): The molten resin is extruded under the same conditions as in the MT measurement, the strand winding speed is increased at a rate of 1 m / 1 min, and the winding speed at which the strand breaks is set to the melt elongation ( ME). The unit is m / min.
(9) Tensile impact strength: An S-type dumbbell test piece is cut from a press sheet having a thickness of 1.1 to 1.2 mm in accordance with ASTM-D1822, and measured at 23 ° C. The unit is J / m ² .
(10) Bending strength: A value measured according to JIS-K-7171, in units of MPa.
(11) Number of terminal vinyl groups: Using a “Fourier transform infrared spectrophotometer” manufactured by JASCO Corporation, it was determined from the absorbance at 909 cm ⁻¹ of the sheet-like polyethylene composition obtained by hot pressing.

(12) Hollow molding: a hollow molding machine with a screw system of 55 mm, manufactured by Plako Corporation; using SB-55, a die diameter of 48 mm, a core diameter of 46 mm, a cylinder temperature of 210 ° C., a mold temperature of 25 ° C., and a mold cooling time of 18 seconds. As a common condition, a hollow molded body with a handle having a container weight of 60 g and a container volume of 1700 ml was molded under two conditions of an extrusion rate of 25 kg / hour (condition 1) and 50 kg / hour (condition 2). Evaluate the resin temperature.
(I) Appearance: The appearance of the container is visually confirmed, and the quality is judged according to the following criteria.
○ The surface is smooth and glossy.
× Unevenness on the entire surface, rough skin, and no gloss.
(Ii) Gel: The number of gels per gram of the molded body in the container body is measured visually.
(Iii) Fusion property: The pinch-off part of the handle part is visually confirmed, and the quality is judged according to the following criteria.
○ Thickness of the fused part is sufficiently secured and there are no defects such as holes.
X The thickness of the fused part is thin and a hole is opened.
(Iv) Resin temperature: The resin temperature near the die outlet is measured with a contact-type thermometer.

Next, the present invention will be described more specifically with reference to examples and the like, but the present invention is not limited to these examples and the like.
[Example 1]
(1) Synthesis of chromium oxide catalyst (I) 4 mol of chromium trioxide was dissolved in 80 liters of distilled water, and 20 kg of silica (manufactured by WR Grace and Company; Grade 952) was immersed in this solution at room temperature. After stirring for 1 hour, the slurry was heated to distill off water, followed by drying under reduced pressure at 120 ° C. for 10 hours, followed by firing with flowing dry air at 600 ° C. for 5 hours, A chromium oxide catalyst (I) containing 0.0% by weight was obtained.

(2) Synthesis of organoaluminum compound (II) 100 moles of triethylaluminum, 50 moles of methyl hydropolysiloxane (viscosity at 30 ° C .: 30 centistokes) (Si standard), and 150 liters of n-hexane were weighed in a pressure-resistant container under a nitrogen atmosphere. The mixture was taken and reacted at 50 ° C. for 24 hours with stirring to prepare an Al (C ₂ H ₅ ) _2.5 (OSi · H · CH ₃ · C ₂ H ₅ ) _0.5 hexane solution. Next, 100 mol (Al basis) of this solution was transferred to a 600 liter reactor under a nitrogen atmosphere, and a mixed solution of 50 liters of ethanol and 50 liters of n-hexane was added with stirring at -10 ° C. The reaction was continued for 1 hour at this temperature to prepare an Al (C ₂ H ₅ ) _2.0 (OC ₂ H ₅ ) _0.5 (OSi · H · CH ₃ · C ₂ H ₅ ) _0.5 hexane solution.

(3) Synthesis of titanium catalyst (III) A 15-liter reactor fully purged with nitrogen was charged with 3 liters of trichlorosilane as a 2 mol / liter n-heptane solution and kept at 65 ° C. with stirring. AlMg ₆ (C ₂ H ₅ ) ₃ (n-C ₄ H ₉ ) _6.4 (On-C ₄ H ₉ ) 7 liters of an n-heptane solution of an organic magnesium component represented by _5.6 (5 mol in terms of magnesium) for 1 hour The mixture was further reacted with stirring at 65 ° C. for 1 hour. After completion of the reaction, the supernatant was removed and washed 4 times with 7 liters of n-hexane to obtain a solid material slurry. This solid was separated, dried and analyzed, and as a result, it contained 7.45 mmol of Mg per gram of the solid.
Of these, a slurry containing 500 g of solid was reacted with 0.93 liter of n-butyl alcohol 1 mol / liter n-hexane solution at 50 ° C. for 1 hour with stirring. After completion of the reaction, the supernatant was removed and washed once with 7 liters of n-hexane. This slurry was kept at 50 ° C., and 1.3 liters of n-hexane solution of 1 mol / liter of diethylaluminum chloride was added with stirring and reacted for 1 hour. After completion of the reaction, the supernatant was removed and washed twice with 7 liters of n-hexane. This slurry was kept at 50 ° C., 0.2 liter of n-hexane solution of 1 mol / liter of diethylaluminum chloride and 0.2 liter of n-hexane solution of 1 mol / liter of titanium tetrachloride were added and reacted for 2 hours. After completion of the reaction, the supernatant was removed and the solid catalyst was isolated and washed with hexane until no free halogen was detected. The solid catalyst had 2.3 wt% titanium.

(4) Production of polyethylene (A) In a single-stage polymerization process, polymerization was performed in a polymerization vessel having a volume of 230 liters. The polymerization temperature is 78 ° C. and the polymerization pressure is 0.98 MPa. It is obtained by adding 5 mmol (Al basis) of the organoaluminum compound (II) prepared in (2) to 50 g of the chromium oxide catalyst (I) synthesized in (1) and reacting at room temperature for 1 hour. The organoaluminum compound obtained by reacting the solid catalyst with ethanol and trihexylaluminum at a molar ratio of 0.98: 1 at a rate of 2 g / hr resulted in a concentration of 0.08 mmol / liter in the polymerization vessel. It was supplied and adjusted. Purified hexane was supplied at a rate of 60 liters / hr, and ethylene was supplied at a rate of 12 kg / hr, and hydrogen was supplied as a molecular weight regulator so that the gas phase concentration was 16 mol%. The gas phase concentration of hydrogen is a value calculated by the following equation using a value obtained by gas phase analysis using gas chromatography.
Gas phase concentration of hydrogen (mol%) = Gas phase concentration of hydrogen (mol / liter) x 100
/ {Gas phase concentration of hydrogen (mol / liter) + gas phase concentration of ethylene (mol / liter)}
The polymer in the polymerization vessel was obtained as a powder after passing through a drying process. The powdered polyethylene (A-1) had an MFR of 1.2 g / 10 min, an HLMFR of 66 g / 10 min, and a density of 966 kg / m ^3. It was.

(5) Production of polyethylene (B) First, in order to produce a low molecular weight component by the first stage polymerization, a stainless polymerizer 1 having a reaction volume of 300 liters was used under the conditions of a polymerization temperature of 83 ° C and a polymerization pressure of 1 MPa. As the catalyst, the solid catalyst (III) described above was introduced at a rate of 1.4 mmol / hr in terms of Ti atoms, triisobutylaluminum was converted to 20 mmol / hr in terms of Al atoms, and hexane was introduced at a rate of 40 liters / hr. Hydrogen was used as a molecular weight regulator, and ethylene, hydrogen, and butene-1 were supplied so that the gas phase concentration of hydrogen was 38 mol% and the gas phase concentration of butene-1 was 0.8 mol%, and polymerization was performed. . The gas phase concentration of butene-1 is a value calculated by the following equation using a value obtained by gas phase analysis using gas chromatography.
Butene-1 gas phase concentration (mol%) = butene-1 gas phase concentration (mol / liter) × 100 / {butene-1 gas phase concentration (mol / liter) + ethylene gas phase concentration (mol / liter) )}

The polymer slurry solution in the polymerization vessel 1 was introduced into a flash drum having a pressure of 0.1 MPa and a temperature of 75 ° C., and unreacted ethylene and hydrogen were separated and then introduced into the polymerization vessel 2 having a reaction volume of 250 liters by increasing the pressure with a slurry pump. .
In the polymerization vessel 2, triisobutylaluminum was introduced at a rate of 7.5 mmol / hr and hexane was introduced at a rate of 40 l / hr under the conditions of a temperature of 83 ° C. and a pressure of 0.5 MPa. Ethylene, hydrogen, and butene-1 were introduced so that the gas phase concentration of hydrogen was 6.8 mol% and the gas phase concentration of butene was 4.0 mol%. The high molecular weight part was polymerized so that the weight ratio of the high molecular weight part produced in the polymerization vessel 2 (high molecular weight part) / (low molecular weight part) was 45/55, and the MFR was 1.3 g / 10 min. A powdery polyethylene (B-1) having an HLMFR of 69 g / 10 min and a density of 952 kg / m ³ was produced. The MFR of the low molecular weight portion produced in the polymerization vessel 1 was 30 g / 10 minutes, and the density was 962 kg / m ³ .

(6) Production of polyethylene composition The polyethylene (A-1) and (B-1) powders produced as described above were mixed at a weight ratio of 40/60, and then calcium stearate was added to this mixture. It added so that it might become a density | concentration of 60 ppm, and it stirred and mixed with the mixer. This mixture was extruded using a twin-screw extruder having a cylinder diameter of 44 mm (manufactured by Nippon Steel Works; TEX44HCT-49PW-7V) at a cylinder temperature of 200 ° C. and an extrusion rate of 45 kg / hour to extrude a polyethylene composition. Obtained.
As shown in Table 1, the performance of the polyethylene composition was excellent in physical properties such as rigidity and impact resistance. The hollow molding of condition 1 is inferior in fusibility, but the hollow molding of condition 2 has good fusibility, the number of gels is small, the skin is not rough due to melt fracture, and the appearance is good. Suitable for high-speed hollow molding It is.

[Example 2]
MFR obtained by polymerizing under the same conditions as in Example 1 except that the polymerization temperature is 86 ° C., the polymerization pressure is 0.84 MPa, and the gas phase concentration of hydrogen is 27 mol% as polyethylene (A). Was 1.2 g / 10 min, HLMFR was 66 g / 10 min, and powdered polyethylene (A-2) having a density of 966 kg / m ³ was used.
On the other hand, as the polyethylene (B), the polymerization temperature in the polymerization vessel 1 is 83 ° C., the polymerization pressure is 0.64 MPa, the gas phase concentration of hydrogen is 63 mol%, and the gas phase concentration of butene-1 is 0.8 mol%. Except that the polymerization temperature in the polymerization vessel 2 is 77 ° C., the polymerization pressure is 0.36 MPa, the gas phase concentration of hydrogen is 12 mol%, and the gas phase concentration of butene-1 is 4.9 mol%. Powdered polyethylene (B-2) obtained by polymerizing under the same conditions as in No. 1 and having an MFR of 0.9 g / 10 min, an HLMFR of 60 g / 10 min, and a density of 952 kg / m ³ was used. . The MFR of the low molecular weight portion produced in the polymerization vessel 1 was 31 g / 10 minutes, and the density was 962 kg / m ³ .
A polyethylene composition was produced in the same manner as in Example 1, and its performance was evaluated.
As shown in Table 1, the performance of the polyethylene composition was excellent in physical properties such as rigidity and impact resistance. The hollow molding of condition 1 is inferior in fusibility, but the hollow molding of condition 2 has good fusibility, the number of gels is small, the skin is not rough due to melt fracture, and the appearance is good. Suitable for high-speed hollow molding It is.

[Example 3]
As polyethylene (A), powdery polyethylene (A-2) was used in the same manner as in Example 2.
On the other hand, as polyethylene (B), the polymerization pressure in the polymerization vessel 2 is 0.32 MPa, the gas phase concentration of hydrogen is 8.3 mol%, and the gas phase concentration of butene-1 is 5.0 mol%. A powdery polyethylene (B-3) obtained by polymerization under the same conditions as in Example 2 and having an MFR of 0.6 g / 10 min, an HLMFR of 52 g / 10 min, and a density of 952 kg / m ³ was obtained. used.
A polyethylene composition was produced in the same manner as in Example 1, and its performance was evaluated.
As shown in Table 1, the performance of the polyethylene composition was excellent in physical properties such as rigidity and impact resistance. The hollow molding of condition 1 is inferior in fusibility, but the hollow molding of condition 2 has good fusibility, the number of gels is small, the skin is not rough due to melt fracture, and the appearance is good. Suitable for high-speed hollow molding It is.

[Example 4]
As polyethylene (A), powdery polyethylene (A-2) was used in the same manner as in Example 2.
On the other hand, as polyethylene (B), the polymerization pressure in the polymerization vessel 2 is 0.34 MPa, the gas phase concentration of hydrogen is 10.7 mol%, and the gas phase concentration of butene-1 is 4.9 mol%. Powdered polyethylene (B-4) obtained by polymerizing under the same conditions as in Example 2 and having an MFR of 0.8 g / 10 min, an HLMFR of 59 g / 10 min, and a density of 952 kg / m ³ was obtained. used.
A polyethylene composition was produced in the same manner as in Example 1, and its performance was evaluated.
As shown in Table 1, the performance of the polyethylene composition was excellent in physical properties such as rigidity and impact resistance. The hollow molding of condition 1 is inferior in fusibility, but the hollow molding of condition 2 has good fusibility, the number of gels is small, the skin is not rough due to melt fracture, and the appearance is good. Suitable for high-speed hollow molding It is.

[Example 5]
The polyethylene (A) was obtained by polymerization under the same conditions as in Example 2 except that the gas phase concentration of hydrogen was 31 mol%, and the MFR was 1.6 g / 10 minutes and the HLMFR was 75 g / 10. A powdery polyethylene (A-3) having a density of 966 kg / m ³ was used.
On the other hand, as polyethylene (B), the same conditions as in Example 2 except that the gas phase concentration of hydrogen in the polymerization vessel 2 is 15.1 mol% and the gas phase concentration of butene-1 is 2.0 mol%. The powdered polyethylene (B-5) obtained by polymerizing in step 1 and having an MFR of 0.8 g / 10 min, an HLMFR of 59 g / 10 min, and a density of 952 kg / m ³ was used.
A polyethylene composition was produced in the same manner as in Example 1, and its performance was evaluated.
As shown in Table 1, the performance of the polyethylene composition was excellent in physical properties such as rigidity and impact resistance. The hollow molding of condition 1 is inferior in fusibility, but the hollow molding of condition 2 has good fusibility, the number of gels is small, the skin is not rough due to melt fracture, and the appearance is good. Suitable for high-speed hollow molding It is.

[Example 6]
As polyethylene (A), powdery polyethylene (A-3) was used in the same manner as in Example 5.
On the other hand, as polyethylene (B), the same conditions as in Example 2 except that the gas phase concentration of hydrogen in the polymerization vessel 2 is 8.2 mol% and the gas phase concentration of butene-1 is 10.1 mol%. The powdery polyethylene (B-6) obtained by polymerizing in step 1 and having an MFR of 1.2 g / 10 min, an HLMFR of 68 g / 10 min, and a density of 947 kg / m ³ was used.
A polyethylene composition was obtained in the same manner as in Example 5 except that the obtained polyethylene (A-3) and polyethylene (B-6) powders were mixed at a weight ratio of 60/40.
As shown in Table 1, the performance of this polyethylene composition was excellent in physical properties such as rigidity and impact resistance. The hollow molding of condition 1 is inferior in fusibility, but the hollow molding of condition 2 has good fusibility, the number of gels is small, the skin is not rough due to melt fracture, and the appearance is good. Suitable for high-speed hollow molding It is.

[Comparative Example 1]
As polyethylene (A), powdery polyethylene (A-1) was used in the same manner as in Example 1.
On the other hand, as polyethylene (B), the temperature in the polymerization vessel 1 is 85 ° C., the gas phase concentration of hydrogen is 70 mol%, and the gas phase concentration of butene-1 is 1.0 mol%. Was obtained by polymerization under the same conditions as in Example 1, except that the gas phase concentration of hydrogen was 4.0 mol% and the gas phase concentration of butene-1 was 3.0 mol%. Powdered polyethylene (B-7) having an MFR of 0.52 g / 10 min, an HLMFR of 51 g / 10 min, and a density of 952 kg / m ³ was used. The MFR of the low molecular weight portion produced in the polymerization vessel 1 was 300 g / 10 minutes, and the density was 962 kg / m ³ .
A polyethylene composition was produced in the same manner as in Example 1, and its performance was evaluated.
As shown in Table 1, the performance of this polyethylene composition was excellent in rigidity and impact resistance, but had many gels and poor fusion properties.

[Comparative Example 2]
(1) Synthesis of chromium oxide catalyst (IV) 40 mmol of chromium trioxide was dissolved in 0.8 liter of distilled water, and 200 g of silica (manufactured by WR Grace and Company; Grade 952) was immersed in this solution at room temperature. After stirring for 1 hour at this temperature, this slurry was heated to distill off water, followed by drying under reduced pressure at 120 ° C. for 10 hours, followed by firing with flowing dry air at 800 ° C. for 5 hours. A solid catalyst component (IV) containing 1.0 wt% was obtained.
(2) Synthesis of organoaluminum compound (V) An organoaluminum compound (V) obtained by reacting methanol and aluminum trihexyl at a molar ratio of 0.96: 1 was obtained.

(3) Production of polyethylene (A) Polymerization was carried out with an isobutane solvent at a liquid level of 170 liters in a jacketed polymerization tank having an internal volume of 350 liters using the synthesized chromium oxide catalyst (IV). The solid catalyst component (IV) was supplied to the polymerization tank at a rate of 2.0 g / hr, and the organoaluminum compound (V) was supplied so as to have a concentration of 0.08 mmol / liter. Purified isobutane is supplied at a rate of 32 liters / hr and ethylene is supplied at a rate of 10 kg / hr. The temperature is 70 ° C., the gas phase concentration of hydrogen is 3 mol%, and the gas phase concentration of butene-1 is 1.6 mol. %, Continuous polymerization was performed at a total pressure of 2.4 MPa and an average residence time of 3.7 hours. The polymer in the polymerization vessel was obtained as a powder after passing through a drying process. The powdered polyethylene (A-4) had an MFR of 0.78 g / 10 min, an HLMFR of 37 g / 10 min, and a density of 957 kg / m ^3. It was. In the same manner as in the polyethylene composition of Example 1, calcium stearate was added to this polyethylene (A-4) and kneaded with a twin screw extruder to obtain a polyethylene resin.
As shown in Table 1, the performance of this polyethylene composition was excellent in rigidity and impact resistance, but in the high-speed hollow molding under Condition 2, melt fracture occurred and the appearance was poor.

[Comparative Example 3]
The polyethylene (A) was obtained by polymerization in the same manner as in Example 2 except that the polymerization temperature was 86 ° C., the polymerization pressure was 0.87 MPa, and the gas phase concentration of hydrogen was 40 mol%. The MFR was 2 Powdered polyethylene (A-5) having a density of ³ g / 10 min, an HLMFR of 77 g / 10 min, and a density of 966 kg / m ³ was used.
On the other hand, as polyethylene (B), the polymerization pressure in the polymerizer 1 is 0.51 MPa, the gas phase concentration of hydrogen is 64.5 mol%, and the gas phase concentration of butene-1 is 0 mol%. By polymerizing under the same conditions as in Example 2 except that the polymerization pressure of 0.39 MPa, the gas phase concentration of hydrogen is 9.4 mol%, and the gas phase concentration of butene-1 is 7.0 mol% The obtained powdery polyethylene (B-8) having an MFR of 1.2 g / 10 min, an HLMFR of 68 g / 10 min, and a density of 954 kg / m ³ was produced. The MFR of the low molecular weight portion produced in the polymerization vessel 1 was 30 g / 10 minutes, and the density was 962 kg / m ³ .
A polyethylene composition was produced in the same manner as in Example 1 except that the obtained polyethylene (A-5) and polyethylene (B-8) powders were mixed at a weight ratio of 30/70. evaluated.
As shown in Table 1, the performance of this polyethylene composition was excellent in physical properties such as rigidity and impact resistance, but resulted in poor fusibility in hollow molding.

[Comparative Example 4]
The polyethylene (A) was obtained by polymerizing under the same conditions as in Example 2 except that the gas phase concentration of butene-1 was 4.0 mol%. The MFR was 1.6 g / 10 min, and HLMFR. Was 75 g / 10 min and a powdery polyethylene (A-6) having a density of 959 kg / m ³ was used.
On the other hand, as polyethylene (B), the gas phase concentration of hydrogen in the polymerization vessel 1 is 58 mol%, the gas phase concentration of butene-1 is 0.8 mol%, the polymerization pressure in the polymerization vessel 2 is 0.34 MPa, hydrogen The MFR was 0.9 g / 10 obtained by polymerization in the same manner as in Example 2 except that the gas phase concentration of 11.4 mol% and butene-1 was 5.0 mol%. Minute, HLMFR was 58 g / 10 min, and a powdery polyethylene (B-9) having a density of 943 kg / m ³ was used. The MFR of the low molecular weight portion produced in the polymerization vessel 1 was 30 g / 10 minutes, and the density was 962 kg / m ³ .
A polyethylene composition was obtained in the same manner as in Example 1 except that the obtained polyethylene (A-6) and polyethylene (B-9) powders were mixed at a weight ratio of 40/60, and the performance was evaluated. did.
As shown in Table 1, the performance of this polyethylene composition is excellent in physical properties such as impact resistance and fusion property of hollow molding, but in the high-speed hollow molding of Condition 2, melt fracture occurs and the appearance is poor. became.

[Comparative Example 5]
As polyethylene (A), powdery polyethylene (A-1) produced in the same manner as in Example 1 was used.
On the other hand, as polyethylene (B), the gas phase concentration of hydrogen in the polymerizer 1 is 69 mol%, the gas phase concentration of butene-1 is 1.1 mol%, and the gas phase concentration of hydrogen in the polymerizer 2 is 6. The MFR was 1.0 g / 10 min and the HLMFR was 62 g obtained by polymerization under the same conditions as in Example 2 except that the gas phase concentration of 6 mol% and butene-1 was 8.2 mol%. / 10 minutes, powdery polyethylene (B-10) having a density of 951 kg / m ³ was used. The MFR of the low molecular weight portion produced in the polymerization vessel 1 was 70 g / 10 minutes, and the density was 962 kg / m ³ .
A polyethylene composition was obtained in the same manner as in Example 1 except that the obtained polyethylene (A-1) and polyethylene (B-10) powders were mixed at a weight ratio of 50/50.
As shown in Table 1, the performance of this polyethylene composition was such that melt fracture occurred and the appearance was inferior in the meltability of hollow molding and high-speed hollow molding under Condition 2.

  The polyethylene composition of the present invention can provide a hollow molded article having a good appearance in high-speed hollow molding. In particular, it can be suitably used for high-speed hollow molding applications and thin-walled hollow molding applications.

Claims (4)

It consists of polyethylene (A) produced using a chromium-based catalyst and polyethylene (B) produced using a titanium-based catalyst, and the amount of polyethylene (A) in the composition is in the range of 5 to 95% by weight. The composition has an MFR of 0.4 to 2.0 g / 10 min, a density of 940 to 965 kg / m ³ , and a weight average molecular weight Mw and a number average molecular weight Mn determined from gel permeation chromatography (GPC). The molecular weight distribution (Mw / Mn value) is 7 to 20, the measurement temperature is 230 ° C., the melt viscosity is 180 to 230 Pa · s at a shear rate of 1598 sec ⁻¹ , the measurement temperature is 170 ° C., and the frequency is 0.01 rad / The ratio G ″ / G ′ of the storage elastic modulus G ′ and the loss elastic modulus G ″ obtained from dynamic viscoelasticity measurement in sec is Log (MFR) + 1.5 ≦ G ″. /G'<=Log(MFR)+2.5, The polyethylene composition characterized by the above-mentioned.   2. The polyethylene composition according to claim 1, wherein the polyethylene (A) is produced by a catalyst system comprising a combination of a chromium-based catalyst treated with an organometallic compound and a co-catalyst.   The polyethylene composition according to claim 1 or 2, wherein the polyethylene (B) is produced by two-stage polymerization.   A hollow molded article comprising the polyethylene composition according to any one of claims 1 to 3.