JP2017025339A - Polyethylene resin composition, pipe and joint - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyethylene resin composition classified to PE100 by ISO9080 specification, having excellent in long term property with 100 years guarantee and further excellent molding processability, a pipe containing the same and a joint.SOLUTION: There is provided a polyethylene resin composition containing an ethylene single polymer and/or a copolymer of ethylene and α-olefin having 3 to 20 carbon atoms and satisfying following (1) to (4). (1) density is 946 to 953 kg/m. (2) melt flow rate (code T) is 0.15 to 0.50 g/10 min. (3) molecular weight distribution is 15 to 40. (4) a ratio of slope of a plot line in logarithm of leap pressure to logarithm of breakage time has the following relationship in a hot inner pressure creep test at 20°C defined in ISO 9080. slope by 1000 hr/slop after 1000 hr>1.5.SELECTED DRAWING: None

Description

  The present invention relates to a polyethylene resin composition, a pipe including the same, and a joint.

  Polyethylene resins have excellent creep characteristics, environmental stress crack resistance, impact characteristics, and flexibility, and have been widely used as piping materials. In this specification, “piping material” refers to pipes and joints used as water and sewage pipes, gas pipes, and water supply pipes. In recent years, it has been demonstrated that polyethylene pipes are superior to pipe types such as steel pipes and ductile cast iron pipes in that they have characteristics such as pipes extending and following ground changes even with earthquakes. Unlike mechanical joints such as steel pipes and ductile cast iron pipes, polyethylene joints can be welded to pipes with EF (electrofusion) joints, so that construction is simple and excellent in earthquake resistance. . Due to these characteristics, polyethylene resin has attracted attention as piping materials for water and sewage pipes, gas pipes, water supply pipes and the like.

  Further, there is a high demand for safety required for each piping material, and pipes made of materials that have acquired PE80 as a gas pipe and PE100 as a water supply pipe have come to be used. Here, “PE100” means that, in the hot internal pressure creep test described in ISO 9080, a stress-fracture time curve at three different temperatures was measured up to at least 9000 hours, and the 50 ° C. at 20 ° C. This refers to polyethylene classified as PE100 in the classification table stipulated in ISO12162, with a value of 97.5% lower confidence limit (hereinafter referred to as LPL) of the estimated minimum guaranteed stress after the year. . When polyethylene pipe resin is used as a water distribution pipe for a long time, stress is applied due to water pressure from the inside of the pipe or earth pressure from the outside during embedding. Disruption can occur. Improvements have been made to provide a material that does not cause brittle fracture cracking under such severe conditions of stress over a long period of time.

  In recent years, the number of pipes that have passed for a long time since the installation of water pipes and gas pipes has increased, and the proportion of so-called aging pipes that exceed the legal service life of 40 years has increased since laying, and leakage due to pipe breakage has become a problem. Yes. Since PE100 polyethylene pipe has a 50-year warranty, renewal is desired before 50 years, but the annual renewal rate is only 1%. Therefore, it is desired to develop a material having a 100-year warranty, which has a longer service life guaranteed for the pipe than the 50-year warranty for PE100.

  When an internal pressure is applied to a pipe at a constant temperature, a ductile fracture occurs in which a bulge occurs after a certain period of time and breaks. Between the fracture time of this ductile fracture and the stress due to the internal pressure, there is a stress-fracture time creep relationship in which the lower the stress, the longer the fracture time. This relationship is known to be lower stress and shorter time as the test temperature is higher, and higher stress and longer time as the density of the polyethylene resin is higher. Therefore, if the density of the polyethylene resin is increased, the stress on the long time side increases. However, when the density is increased, brittle fracture proceeds rapidly. In the conventional polymerization design, for example, at 20 ° C., brittle fracture occurs before 100 years. In the stress-fracture time creep diagram, ductile fracture occurs. This leads to the generation of creep curve bending (Knee Point) due to the transition from brittle fracture. For this reason, it has been difficult to achieve a material having a lifetime of 100 years with a conventional resin design.

  Depending on the conventional resin design, even if the long-term characteristics are brittle, it is possible to obtain PE100 classified polyethylene pipe and joint resin. In particular, brittle fracture is noticeable in the internal pressure creep test condition at 80 ° C., and even if such a material is classified as PE100 described in ISO, it can be said to be brittle PE100 at high temperature. When estimating long-term creep characteristics, brittle fracture progresses more rapidly than ductile fracture, making it difficult to predict fracture, and brittle PE100 is a material used in lifelines such as water pipes. It is inappropriate.

  Also, if only long-term properties and elongation properties are to be obtained in order to obtain polyethylene classified as PE100, it is not so difficult as a resin design. Developing excellent materials is very difficult with current technology. In particular, since the pipe and the joint are preferably made of the same resin from the viewpoint of fusion, the polyethylene of PE100 is excellent not only in mechanical properties as a pipe but also in molding processability, considering the joint formed by injection molding. Will be needed.

  Accordingly, there is a demand for a material that is excellent in mechanical properties, brittle fracture resistance, elongation properties, and moldability over a long period of time. As described above, a polyethylene resin composition classified based on the classification table defined in ISO12162 by measurement in conformity with ISO9080, which is excellent in molding processability and has a 100-year warranty, is a lifeline. It is a material that is highly expected to be used for sewer pipes, gas pipes, water supply pipes, etc.

  On the other hand, conventionally, in order to improve the long-term mechanical properties of polyethylene, widening of the molecular weight distribution and introduction of a copolymerizable comonomer as a side chain during polymerization have been performed (for example, Patent Document 1, 2).

  In addition, in order to improve long-term characteristics and impact resistance, control the distribution of comonomer, pay attention to the contribution of the comonomer to the high molecular weight side, and further determine the molecular weight required by temperature-elution fractionation and GPC cross-fractionation- It is known to improve the design of polyethylene by paying attention to the correlation between elution temperature and elution amount (for example, see Patent Document 3).

  Further, mechanical properties comprising polyethylene having two molecular weight distributions and having a melt flow rate (code T) (JIS K7210-1999, code T: hereinafter referred to as “MFR5”) of 0.35 g / 10 min or less. (See, for example, Patent Document 4).

Furthermore, a composition composed of two components having different intrinsic viscosities and densities is disclosed (see, for example, Patent Document 5). When a pipe molded body is molded using this composition, the hot internal pressure is obtained as a characteristic of the pipe. It has been proposed that creep tests, tensile creep tests, tensile fatigue tests, and the like are dramatically improved over conventional materials. According to this, the density and intrinsic viscosity of a composition comprising two components of low molecular weight, high density polyethylene and high molecular weight, low density polyethylene are 0.945 to 0.970 g / cm ³ (JIS K7112-1999), 2 in the range of .41~6.3dyne / cm ^2, the compositions shear rate when shear stress of the capillary at 190 ° C. is reached ^{2.4 × 10 6 dyne / cm 2} (FI) is 350Sec ^-1 or less It is said that it is possible to form a pipe excellent in formability, pipe fatigue characteristics, etc. Furthermore, it describes also about the polyethylene pipe and its pipe joint (for example, refer patent document 6).

  In addition, a resin composition for pipes and joints has been disclosed that is excellent in moldability and fatigue characteristics when used as a pipe and also excellent in injection moldability of joints and the like (see, for example, Patent Document 7).

Japanese Examined Patent Publication No. 61-42736 Japanese Patent Publication No. 61-43378 JP 10-17619 A JP-A-8-301933 JP-A-8-134285 Japanese Patent Laid-Open No. 9-286820 JP 2000-109521 A

  However, in Patent Documents 1 and 2, the molecular weight distribution is broadened and a copolymerizable comonomer is only introduced as a side chain during polymerization, and is insufficient for improving the long-term mechanical properties required for PE100.

  Further, the resin design in Patent Document 3 cannot obtain a polyethylene resin classified as PE100.

  Furthermore, in Patent Document 4, there is a possibility that a polyethylene resin excellent in mechanical properties and classified as PE100 may be obtained. However, the molecular weight or density is constantly increased by increasing the molecular weight or introducing a comonomer to decrease the density. It is expected that molding processability will be very poor, or that the PE100 requirement will not be met due to a decrease in density because no improvements have been made.

Furthermore, with the resin in Patent Document 5, pipe properties such as fatigue resistance are certainly improved due to an increase in molecular weight, but the molding processability is inferior, and in particular, injection molding for molding a joint becomes difficult. In addition, as can be seen from the examples where the value called the flow index (FI) is FI ≦ 350 sec ⁻¹ and the MFR of the comparative example, the resin design is made higher in molecular weight to improve the physical properties, so it is clearly molded. Inferior in workability. Further, the resin in Patent Document 5 does not necessarily satisfy the requirements of PE100.

Furthermore, Patent Document 6 describes a resin having an FI value of 100 to 400 sec ⁻¹ , but it is difficult to form a joint by a molding method in a high shear rate region by injection molding. In addition, the tie molecule existence probability is improved by increasing the lamellar thickness due to the increase in molecular weight and density. Examples of means for improving long-term mechanical properties include increasing the molecular weight and broadening the molecular weight distribution. However, simply increasing the molecular weight by such a method is not suitable for forming a pipe from the viewpoint of molding processability. . In addition, the flowability is improved by widening the molecular weight distribution, but the properties such as elongation and impact properties are deteriorated. Furthermore, when extruded as a pipe, not only is the surface roughened, but also the surface of the molded product is roughened even by injection molding of a joint.

  In addition, although the resin in Patent Document 7 satisfies the 50-year warranty as PE100, the LPL at 20 ° C. when it is 100 years is somewhat insufficient. Therefore, a design in which the creep line of the stress-fracture time is further improved is required, but the generation of KneePoint is expected in the case of simple densification, and thus a new resin design that has never been seen before is required.

  The present invention has been made in view of the above problems, and is classified as PE100 according to the ISO 9080 standard and has a long-term property that is guaranteed for 100 years, and in addition, polyethylene having excellent moldability. It aims at providing the resin composition, the pipe containing the same, and a coupling.

As a result of intensive studies to solve the above problems, the present inventors have found that a polyethylene composition satisfying all specific constituent conditions can achieve the above object, and have reached the present invention.
That is, the present invention is as follows.

[1]
A polyethylene resin composition comprising an ethylene homopolymer and / or a copolymer of ethylene and an α-olefin having 3 to 20 carbon atoms and satisfying the following (1) to (4).
(1) The density is 946 to 953 kg / m ³ .
(2) The melt flow rate (code T) is 0.15 to 0.50 g / 10 min.
(3) The molecular weight distribution is 15-40.
(4) In the hot internal pressure creep test at 20 ° C. specified by ISO 9080, the ratio of the slope of the plot line of the logarithm of the hoop pressure to the logarithm of the fracture time has the following relationship.
Slope less than 1000 hours / Slope after 1000 hours> 1.5
[2]
An ethylene homopolymer and / or a copolymer of ethylene and an α-olefin having 3 to 20 carbon atoms, a density of 967 to 977 kg / m ³ , and a melt flow rate (Code D) of 40 to 300 g / 48-60 parts by mass of polyethylene resin, which is 10 minutes,
A polyethylene resin having a copolymer of ethylene and an α-olefin having 3 to 20 carbon atoms, a density of 895 to 949 kg / m ³ , and a weight average molecular weight of 500,000 to 1,000,000. Including 52 parts by mass,
The polyethylene resin composition according to the preceding item [1].
[3]
Obtained by a two-stage polymerization method in which an ethylene homopolymer is produced in a first-stage polymerization tank, and a copolymer of ethylene and an α-olefin having 3 to 20 carbon atoms is produced in a second-stage polymerization tank. The polyethylene resin composition according to [1] or [2].
[4]
An organomagnesium compound (i) soluble in a hydrocarbon solvent represented by the following formula (1) and a chlorosilane compound (ii) represented by the following formula (2) are mixed in a (ii) / (i) molar ratio of 0.00. The reaction is carried out in the range of 01 to 100 to obtain a solid (A-1a),
0.01-1 mol of alcohol (A-2) is reacted with 1 mol of C—Mg bond contained in the solid (A-1a) to obtain a solid (A-1b),
The solid (A-1b) is reacted with an organometallic compound (A-3) represented by the following formula (3) to obtain a solid (A-1c).
The above-mentioned item obtained by using the polymerization catalyst containing the solid catalyst component [A] and the organoaluminum compound [B] obtained by supporting the titanium compound (A-4) on the solid (A-1c). The polyethylene resin composition according to any one of [1] to [3].
(Al) _a (Mg) _b (R ¹ ) _c (R ² ) _d (OR ³ ) _e Expression (1)
(In the formula (1), R ¹ , R ² and R ³ are hydrocarbon groups having 2 to 20 carbon atoms, and a, b, c, d and e are numbers satisfying the following relationship: 0 ≦ a , 0 <b, 0 ≦ c, 0 ≦ d, 0 ≦ e, 0 <c + d, 0 ≦ e / (a + b) ≦ 2, 3a + 2b = c + d + e)
H _h SiCl _i R ⁴ _{4- (h + i)} (2)
(In the formula (2), R ⁴ is a hydrocarbon group having 1 to 20 carbon atoms, and h and i are numbers satisfying the following relationship: 0 <h, 0 <i, h + i ≦ 4)
AlR ⁵ _s Q _3-s ... Formula (3)
(In the formula (3), R ⁵ is a hydrocarbon group having 1 to 20 carbon atoms, and Q is selected from the group consisting of OR ⁶ , OSiR ⁷ R ⁸ R ⁹ , NR ¹⁰ R ¹¹ , SR ¹² and halogen. R ⁶ , R ⁷ , R ⁸ , R ⁹ , R ¹⁰ , R ¹¹ , R ¹² are hydrogen atoms or hydrocarbon groups, and s is a number that satisfies the following relationship: 0 <s <3 )
[5]
The polyethylene resin composition according to any one of [1] to [4] above, which is for polyethylene piping material.
[6]
A pipe comprising the polyethylene resin composition according to any one of [1] to [5] above.
[7]
A pipe joint comprising the polyethylene resin composition according to any one of [1] to [5] above.
[8]
The pipe according to [6] above, which is for water supply.
[9]
The pipe joint according to [7], which is for water supply.

  According to the present invention, a polyethylene resin composition having excellent long-term characteristics classified into PE100 described in the ISO 9080 standard and guaranteed for 100 years, and having excellent moldability, and the like are included. Pipes and joints can be realized at low cost.

It is a figure which shows the relationship (creep curve) of the fracture time and hoop pressure of the general polyethylene obtained by ISO9080. It is a figure which shows the relationship between the fracture time in the polyethylene resin composition of Example 1, and a hoop pressure. It is a figure which shows the relationship between the fracture time in the polyethylene resin composition of the comparative example 1, and a hoop pressure. It is a figure which shows the relationship between the fracture time in the polyethylene resin composition of the comparative example 2, and a hoop pressure. It is a correlation diagram which shows the correlation of molecular weight-elution temperature-elution amount in temperature rising elution fractionation GPC cross fractionation.

  Hereinafter, a mode for carrying out the present invention (hereinafter, referred to as “the present embodiment”) will be described in more detail. However, the present invention is not limited to this, and various modifications can be made without departing from the gist of the present invention. Deformation is possible.

[Polyethylene resin composition]
First, the polyethylene resin composition will be described. The polyethylene resin composition of the present embodiment is
Including an ethylene homopolymer and / or a copolymer of ethylene and an α-olefin having 3 to 20 carbon atoms, the following (1) to (4) are satisfied.
(1) The density is 946 to 953 kg / m ³ .
(2) The melt flow rate (code T) is 0.15 to 0.50 g / 10 min.
(3) The molecular weight distribution is 15-40.
(4) In the hot internal pressure creep test at 20 ° C. specified by ISO 9080, the ratio of the slope of the plot line of the logarithm of the hoop pressure to the logarithm of the fracture time has the following relationship.
Slope less than 1000 hours / Slope after 1000 hours> 1.5

[(1) Density]
The density (JIS K7112-1999) of the polyethylene resin composition of this embodiment is 946-953 kg / m < ³ >, Preferably it is 948-951 kg / m < ³ >, More preferably, it is 948-950 kg / m < ³ >. When the density is 946 kg / m ³ or more, the rigidity as a tube is sufficient. In addition, since it is 953 kg / m ³ or less, environmental stress cracking resistance (ESCR) and elongation characteristics under high temperature acceleration conditions become sufficient, and low speed due to generation of cracks even after long-term use. It is possible to suppress brittle fracture such as crack fracture. In particular, in the case of hot internal pressure creep, the creep characteristics on the short-term side are high, and on the long-term side, sudden brittle fracture that does not depend on the operating pressure does not occur and the long-term characteristics are satisfied. The density of the polyethylene resin composition can be controlled by the amount of comonomer added during polymerization. Moreover, a density can be measured by the method as described in an Example.

[(2) Melt flow rate (Code T)]
The melt flow rate and code T (hereinafter also referred to as “MFR5”) of the polyethylene resin composition of the present embodiment are 0.15 to 0.50 g / 10 minutes, preferably 0.30 to 0.45 g / 10. Min, more preferably 0.30 to 0.40 g / 10 min. When the MFR5 exceeds 0.50 g / 10 min, the moldability is good, but the long-term life and elongation characteristics of the hot internal pressure creep test are lowered, and the impact resistance is also poor. High-density polyethylene having an MFR5 of less than 0.15 g / 10 minutes improves mechanical properties but has poor molding processability, making injection molding particularly difficult. The melt flow rate of the polyethylene resin composition can be controlled by the temperature during polymerization, the amount of hydrogen to be added, and the like. The melt flow rate (code T) can be measured by the method described in the examples.

[(3) Molecular weight distribution]
The molecular weight distribution of the polyethylene resin composition of the present embodiment is a ratio (Mw / Mn) of the weight average molecular weight (Mw) and the number average molecular weight (Mn) determined by gel permeation chromatography, and the value is 15 to 40, preferably 20-38, more preferably 25-35. If Mw / Mn is less than 15, the long-term life and elongation characteristics of the hot internal pressure creep deteriorate, the molding processability is poor, and melt fracture occurs particularly during injection molding. In addition, when Mw / Mn exceeds 40, molding processability and the like are improved due to the influence of components on the low molecular weight side, but in addition to inferior hot internal pressure creep characteristics and impact resistance, the components on the high molecular weight side also increase. Surface roughness of the molded product is likely to occur. The molecular weight distribution of the polyethylene resin composition can be controlled by the catalyst used, the polymerization temperature, the amount of hydrogen to be added, and the like, and can also be controlled by mixing two or more polyethylene resins having different molecular weights. Moreover, molecular weight distribution can be measured by the method as described in an Example.

[(4) Ratio of slope of plot line]
In the polyethylene resin composition of the present embodiment, the logarithm (logσ) of the hoop pressure (σ) against the logarithm (logT) of the fracture time (T) was plotted in the hot internal pressure creep test at 20 ° C. specified by ISO 9080. The slope of the plot line (logσ / logT) is different before and after 1000 hours, and the ratio of the slope of the plot line of less than 1000 hours to the slope of the plot line after 1000 hours is 1.5 times or more, preferably 2 0.0 times or more, more preferably 2.5 times or more. The slope of the plot line can be obtained by the method described in the examples. In addition, the ratio of the slope of less than 1000 hours to the slope after 1000 hours is not particularly limited and is preferably as high as possible.

  ISO 9080 measures stress-fracture time curves up to at least 9,000 hours, calculates long-term hydrostatic strength (LTHS) using multiple correlation average, and extrapolates minimum guaranteed stress after 50 years at 20 ° C (Refer to the circled area in FIG. 1). The lower confidence limit of the value estimated by extrapolation is called extrapolated lower confidence limit (LPL). The classification of PE 100 or the like is determined by determining whether or not this LPL is equal to or greater than the minimum required strength (MRS) defined in the standard. Therefore, the long-term slope of the creep curve at 20 ° C. within the measurement range (approximately 40 hours to 10,000 hours) is important. FIG. 1 shows a general polyethylene creep curve (20 ° C., 60 ° C., 80 ° C.) obtained by ISO9080. 1 in FIG. 1 indicates ductile fracture and means the time when ductile fracture occurred at the test hoop pressure. Further, □ indicates brittle fracture and means the time when brittle fracture occurred at the test hoop pressure. Further, Δ indicates mixed fracture, meaning that ductile fracture and brittle fracture occurred at the same time. Furthermore, ◇ indicates that the test is in progress and ◇ indicates that the test was interrupted midway.

  In the conventional polyethylene material, the slope of the creep curve in the ductile fracture region is almost constant within the measurement range. Therefore, in order to increase the minimum guaranteed stress value after 50 years obtained by extrapolation, it is conceivable to increase the density of polyethylene and shift the creep curve to the right (to the long time side). When the amount is increased, the amount of comonomer decreases, so that the number of tie molecules between the crystalline lamellae of polyethylene decreases. Therefore, brittle fracture that breaks between lamellae occurs on the low pressure and long time side, and KneePoint appears.

  On the other hand, in the polyethylene resin composition of the present embodiment, the slope after 1,000 hours becomes gentler than the slope of less than 1,000 hours, and thus after 50 years obtained by extrapolation without increasing the density. The value of the minimum guaranteed stress after 100 years can be increased.

  In order to control the ratio of the slope below 1,000 hours to the slope after 1,000 hours to 1.5 times or more (that is, to make the slope of the region after 1,000 hours gentle), The presence of a tie molecule can be mentioned. In the region of less than 1,000 hours (high pressure region), the crystal lamella is loosened, and the molecular chain is stretched through a so-called shishikabab structure. Therefore, the strength of the lamella is directly affected. On the other hand, in the region after 1,000 hours (relatively low pressure region), not only the lamella but also the effect of the tie molecule between the lamellae is added, and as a result, the slope of the creep curve is estimated to be gentle. .

  In order to generate tie molecules between lamellae, there are methods such as increasing the molecular weight of components in the polyethylene resin composition and introducing a comonomer into the high molecular weight polyethylene resin contained in the composition. The lamella is formed by folding a polyethylene chain. At that time, the higher the polyethylene resin contained in the composition, the easier it will pop out from the folding, and the more the branch due to the comonomer will pop out. In this way, the molecular chain jumping out from the lamella forms another layer of lamella and becomes a tie molecule that connects the lamellae. The introduction of the comonomer into the high molecular weight polyethylene component can be achieved, for example, by preparing a mixture of a high molecular weight polyethylene copolymer and a low molecular weight polyethylene (homopolymer).

  Thus, the polyethylene resin composition of the present embodiment has a specific density, MFR5, molecular weight distribution, and a ratio of the slope of the creep curve, whereby the minimum guaranteed stress after 50 years and even after 100 years. It exhibits excellent long-term creep characteristics such as high and excellent moldability.

[Cross fractionation gel permeation chromatography]
In addition, the polyethylene resin composition of the present embodiment has a molecular weight of 200,000 or more and an elution temperature of 85 ° C. in the correlation of molecular weight-elution temperature-elution amount determined by cross-fractionation between temperature rising elution fractionation and gel permeation chromatography. The ratio (R, unit: wt%) of the total elution amount of the following elution components to the total elution amount is preferably 1.0 wt% or more, more preferably 3.0 wt% or more, and further preferably 4 0.0 wt% or more. The elution component having a molecular weight of 200,000 or more and an elution temperature of 85 ° C. or less corresponds to a component having a high molecular weight and a large amount of comonomer, and if R is 1.0 wt% or more, there are many components that tend to be tie molecules. This is preferable because long-term creep characteristics tend to be excellent. The cumulative elution amount of elution components having a molecular weight of 200,000 or more and an elution temperature of 85 ° C. or less can be measured by the temperature rising elution fractionation GPC cross fractionation described in Examples.

[Polyethylene resin]
The polyethylene resin composition of the present embodiment includes an ethylene homopolymer and / or a copolymer of ethylene and an α-olefin having 3 to 20 carbon atoms. The polyethylene resin composition of the present embodiment is preferably a mixture of a low molecular weight polyethylene resin and a high molecular weight polyethylene resin. This may be a mixture of a low molecular weight polyethylene resin and a high molecular weight polyethylene resin, or may be obtained by polymerizing a low molecular weight component and a high molecular weight component in multiple stages by a method called multistage polymerization. Good.

(Low molecular weight polyethylene resin)
Although the low molecular weight polyethylene resin according to the present embodiment is not particularly limited, specifically, an ethylene homopolymer and / or a copolymer of ethylene and an α-olefin having 3 to 20 carbon atoms. Can be mentioned. Preferably the low molecular weight polyethylene resin density (JIS K7112-1999) is 967~977kg / m ^3, more preferably from 970~977kg / m ^3, more preferably a 973~977kg / m ³ .

By setting the density to 967 kg / m ³ or more, sudden brittle fracture on the long-term side hardly occurs in the hot internal pressure creep characteristics, and the long-term characteristics tend to be sufficient. The low molecular weight polyethylene resin may contain a comonomer, but is preferably a polyethylene homopolymer. In the case of a homopolymer, if the melt flow rate, code D (JIS K7210-1999, code D: hereinafter also referred to as “MFR 2.16”) is in the range of 40 to 300 g / 10 min, 977 kg / m ^It tends to be less than ³ .

  The MFR 2.16 of the low molecular weight polyethylene resin is preferably 40 to 300 g / 10 minutes, more preferably 50 to 250 g / 10 minutes, and further preferably 100 to 200 g / 10 minutes. When MFR 2.16 is 300 g / 10 min or less, the long-term life and elongation characteristics of the hot internal pressure creep are improved, and the impact resistance tends to be excellent. If MFR2.16 is 40 g / 10 min or more, the molding processability tends to be excellent, and injection molding is particularly easy.

  The weight average molecular weight of the low molecular weight polyethylene resin is preferably 1,000 to 500,000, more preferably 3,000 to 50,000, and further preferably 5,000 to 30,000. preferable. When the weight average molecular weight is 1,000 or more, there is no stickiness or deterioration in long-term characteristics, and the dispersibility with a high molecular weight component tends to be excellent. Moreover, it exists in the tendency for a moldability to become favorable because a weight average molecular weight is 500,000 or less. The weight average molecular weight of the low molecular weight polyethylene resin can be measured by gel permeation chromatography (GPC) when polymer components and low molecular components are separately polymerized and mixed. On the other hand, in the polymerization by multistage polymerization, since the low molecular weight polyethylene resin component cannot be isolated and the weight average molecular weight cannot be measured, the conversion is performed by the conversion method described later.

(High molecular weight polyethylene resin)
On the other hand, the high molecular weight polyethylene resin according to the present embodiment is not particularly limited, but specifically, a copolymer of ethylene and an α-olefin having 3 to 20 carbon atoms is preferable. Density of the high molecular weight polyethylene resin (JIS K7112-1999) is preferably 895~949kg / m ^3, more preferably from 900~945kg / m ^3, still to be 910~940kg / m ³ It is preferably 920 to 930 kg / m ³ . When the density is 895 kg / m ³ or more, the rigidity of the molded tube tends to be sufficient. In addition, since it is 949 kg / m ³ or less, ESCR and elongation characteristics under high temperature acceleration conditions are not deteriorated, and brittle fracture such as generation of cracks and low-speed crack fracture due to long-term use is further suppressed. It tends to be.

  The weight average molecular weight of the high molecular weight polyethylene resin is preferably 500,000 to 1,000,000, more preferably 600,000 to 950,000, and further preferably 700,000 to 900,000. preferable. When the weight average molecular weight is 500,000 or more, the molding processability is good, the long-term life and elongation characteristics of the hot internal pressure creep are good, and the impact resistance tends to be excellent. Further, when the weight average molecular weight is 1,000,000 or less, the mechanical properties are sufficient, and the moldability, particularly the injection moldability, tends to be good.

  The weight average molecular weight of the high molecular weight polyethylene resin can be measured by gel permeation chromatography (GPC) when polymer components and low molecular components are separately polymerized and mixed. On the other hand, in polymerization by multistage polymerization, since a high molecular weight polyethylene resin component cannot be isolated and a weight average molecular weight cannot be measured, conversion is performed by the following method.

(Conversion method)
i) Conversion from MFR 2.16 of low molecular weight polyethylene resin component and polyethylene resin composition to MFR 2.16 of high molecular weight polyethylene resin component.
When mixing polyethylene resins having different MFR (MFR1st, MFR2nd), it is known that MFRfinal after mixing can be calculated as follows.
(MFRfinal) ^-0.175 =
(1-R) × (MFR1st) ^−0.175 + R × (MFR2nd) ^−0.175 (Equation 1)
Here, MFR2.16 of the low molecular weight polyethylene resin component is MFR1st, MFR2.16 of the high molecular weight polyethylene resin component is MFR2nd, MFR2.16 of the polyethylene resin composition is MFRfinal, and the amount of the high molecular weight polyethylene resin component and the amount of the low molecular weight polyethylene resin component The ratio (mixing ratio) of the amount of the high molecular weight polyethylene resin component to the sum of R is represented by R.
Therefore, MFR2nd of the high molecular weight polyethylene resin component can be expressed as follows.
MFR2nd = (((MFRfinal) ^−0.175 −
(1-R) × (MFR1st) ^−0.175 ) / R) ^{−1 / 0.175} (Equation 2)

ii) Conversion from MFR 2.16 of the high molecular weight polyethylene resin component to the respective weight average molecular weight.
It is known that MFR 2.16 and weight average molecular weight have the following relationship.
Mw × 10 ⁻⁴ = 13.291 × MFR ^{2.16 −0.2842} (Equation 3)
From the above, the weight average molecular weight Mw is expressed as follows. In addition, although the conversion method of the weight average molecular weight of high molecular weight polyethylene resin was shown above, the conversion method of the weight average molecular weight of a low molecular weight polyethylene resin component can be performed similarly.
Mw = 13.291 × 10 ⁻⁴ × ((((MFRfinal) ^−0.175 −
(1-R) × (MFR1st) ^−0.175 ) / R) ^{−1 / 0.175} ) ^−0.2842 (Equation 4)

  As described above, in order to generate tie molecules between crystal lamellae, it is preferable that the molecular chain protruding from the lamella has a high molecular weight. Therefore, the high molecular weight polyethylene resin is preferably a copolymer of ethylene and an α-olefin having 3 to 20 carbon atoms.

  In the present embodiment, the α-olefin having 3 to 20 carbon atoms is not particularly limited. Specifically, propylene, 1-butene, 1-pentene, 3-methyl-1-butene, and 3-methyl-1- Pentene, 1-hexene, 4-methyl-1-pentene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, 1-icocene, cyclopentene, cyclohexene, cycloheptene, norbornene, Dicyclopentadiene, 5-methyl-2-norbornene, tetracyclododecene, 2-methyl-1,4: 5,8-dimethano-1,2,3,4,4a, 5,8,8a-octahydronaphthalene Styrene, vinylcyclohexane, 1,3-butadiene, 1,4-pentadiene, 1,5-hexadiene, 1,4-he Sajien, 1,7-octadiene and cyclohexadiene, and the like.

  The α-olefin content is not particularly limited, but is preferably 0.30 to 1.50 mol%, more preferably 0.40 to 1.20 mol%, and 0.50 to 1.00 mol%. More preferably. Here, the α-olefin content is the total content of α-olefin in the polyethylene resin. When the α-olefin content is 0.30 mol% or more, ESCR and elongation characteristics under high temperature acceleration conditions tend to be improved. Moreover, when the α-olefin content is 1.50 mol% or less, the polyethylene resin can be easily produced, and the resulting composition tends to suppress gel generation and improve mechanical properties.

  Moreover, it is preferable to manufacture the polyethylene resin composition of this embodiment by the multistage polymerization superposed | polymerized using an at least 2 superposition | polymerization device. In particular, it is obtained by a two-stage polymerization method in which an ethylene homopolymer is produced in the first stage polymerization tank, and a copolymer of ethylene and an α-olefin having 3 to 20 carbon atoms is produced in the second stage polymerization tank. It is preferable that Polyethylene with excellent long-term properties and moldability by polymerizing polyethylene with different molecular weights in multiple polymerization vessels by multi-stage polymerization, and widening the molecular weight distribution of the entire polyethylene resin crude product mixed with the polyethylene A resin can be obtained. Here, since it is preferable that the molecular weight of polyethylene polymerized in each polymerizer is different, when comparing the molecular weight of the component polymerized in each polymerizer, the lower molecular weight side is the polyethylene resin low molecular weight component, molecular weight The larger side is called a polyethylene resin high molecular weight component. When polymerization is performed by multistage polymerization, polymerization is performed in the first-stage polymerization apparatus, transferred to the polymerization apparatus in the second and subsequent stages, and polymerization is performed. Polyethylene resins having different molecular weights are polymerized in two or more polymerization apparatuses. There is a method of obtaining a polyethylene resin by slurry mixing, powder mixing, or pellet mixing later, among which continuous polymerization is preferable. Alternatively, the polyethylene low molecular weight component may be polymerized in the first stage and then the polyethylene high molecular weight component may be polymerized in the second stage or after the high molecular weight component is polymerized in the first stage. May be polymerized. The polyethylene resin is preferably produced by polymerizing ethylene and one or more comonomers selected from α-olefins having 3 to 20 carbon atoms in such a ratio that the desired density is obtained. . At that time, in order to obtain a desired molecular weight and MFR, a molecular weight regulator such as hydrogen may be used.

  When the polyethylene resin composition of the present embodiment includes a low molecular weight polyethylene resin and a high molecular weight polyethylene resin, the ratio of the low molecular weight polyethylene resin to the high molecular weight polyethylene resin is 48 to 60 parts by mass of the low molecular weight polyethylene resin. It is preferably 50 to 58 parts by mass, more preferably 52 to 58 parts by mass. Moreover, it is preferable that it is 40-52 mass parts, as for high molecular weight polyethylene resin, it is more preferable that it is 42-50 mass parts, and it is further more preferable that it is 42-48 mass parts. By setting the ratio of the high molecular weight polyethylene resin to 40 parts by mass or more and the ratio of the low molecular weight polyethylene resin to 60 parts by mass or less, it is possible to suppress rough skin when the pipe is molded, and it is effective for the eyes generated in the extruder die. Tend to be suppressed. Further, by setting the ratio of the high molecular weight polyethylene resin to 52 parts by mass or less and the ratio of the low molecular weight polyethylene resin to 48 parts by mass or more, the high molecular weight component becomes sufficient, and the life and elongation on the long side of the hot internal pressure creep are increased. The properties and impact resistance tend to be sufficient. For example, bringing the mixing ratio close to 50 parts by mass without changing the melt flow rate of the entire polyethylene resin composition decreases the molecular weight of the high molecular weight component that affects rough skin and increases the molecular weight of the low molecular weight component that affects the eyes. Means that.

  When the low molecular weight component contained in the resin is reduced, the generation of the eye can be suppressed, and when the low molecular weight component is increased, the melt flow rate is increased and the extrudability and rough skin property tend to be improved. In addition, when the low molecular weight component is decreased, the molecular weight of the high molecular weight component is lowered or the ratio of the high molecular weight component is lowered to ensure moldability and maintain the melt flow rate as the composition. Furthermore, there is a tendency that mechanical properties and long-term physical properties are improved by increasing the molecular weight of the high molecular weight component or increasing the ratio of the high molecular weight component. As described above, it is preferable to balance both components such as the low molecular weight component, the molecular weight and molecular weight distribution of each of the high molecular weight components, the composition ratio of both components, and the like.

  The density and melt flow rate of each of the low molecular weight polyethylene resin and the high molecular weight polyethylene resin can be controlled by changing the polymerization conditions (polymerization temperature, pressure, added hydrogen concentration, comonomer amount, etc.).

[Method for producing polyethylene resin composition]
The polyethylene resin composition of the present embodiment, specifically, the low molecular weight polyethylene resin and / or the high molecular weight polyethylene resin is a Bessel type using a Ziegler catalyst, a Phillips type catalyst, or a supported geometrically constrained single site catalyst. It can be produced by a slurry polymerization method. Among these, it is particularly preferable to use a Ziegler catalyst and a supported geometrically constrained single site catalyst.

  The Ziegler catalyst in the present embodiment is an olefin polymerization catalyst having a titanium chloride compound and an alkylaluminum compound as essential components (see, for example, P.836 of Riken Dictionary 5th edition (Iwanami Shoten)). In the present embodiment, the method for producing a Ziegler catalyst is not particularly limited, but a Ziegler catalyst produced by the following production method is preferred.

  The polyethylene resin composition of the present embodiment is preferably produced by a Ziegler catalyst containing a solid catalyst component [A] and an organoaluminum compound [B].

Here, the solid catalyst component [A] comprises an organomagnesium compound (i) soluble in a hydrocarbon solvent represented by the following formula (1) and a chlorosilane compound (ii) represented by the following formula (2) ( ii) / (i) A solid (A-1a) is obtained by reacting in a molar ratio range of 0.01 to 100, and alcohol is contained with respect to 1 mol of C—Mg bonds contained in the solid (A-1a) 0.01-1 mol is obtained to obtain a solid (A-1b), and the solid (A-1b) is further reacted with an organometallic compound represented by the following formula (3) to obtain a solid (A-1c). And a Ziegler catalyst for olefin polymerization produced by supporting the organometallic compound represented by the following formula (5) and the titanium compound (A-4) on the solid (A-1c). Is preferred. Although it does not specifically limit as a titanium compound, Specifically, the titanium compound (A-4) represented by following formula (4) is preferable.
(Al) _a (Mg) _b (R ¹ ) _c (R ² ) _d (OR ³ ) _e (1)
(In the formula (1), R ¹ , R ² and R ³ are hydrocarbon groups having 2 to 20 carbon atoms, and a, b, c, d and e are numbers satisfying the following relationship: 0 ≦ a 0 <b, 0 ≦ c, 0 ≦ d, 0 ≦ e, 0 <c + d, 0 ≦ e / (a + b) ≦ 2, 3a + 2b = c + d + e)
H _h SiCl _i R ⁴ _{(4- (h + i))} (2)
(In the formula (2), R ⁴ is a hydrocarbon group having 1 to 20 carbon atoms, and h and i are numbers satisfying the following relationship: 0 <h, 0 <i, h + i ≦ 4).
AlR ⁵ _s Q _3-s (3)
(In the formula (3), R ⁵ is a hydrocarbon group having 1 to 20 carbon atoms, and Q is selected from the group consisting of OR ⁶ , OSiR ⁷ R ⁸ R ⁹ , NR ¹⁰ R ¹¹ , SR ¹² and halogen. R ⁶ , R ⁷ , R ⁸ , R ⁹ , R ¹⁰ , R ¹¹ , R ¹² are hydrogen atoms or hydrocarbon groups, and s is a number that satisfies the following relationship: 0 <s <3 )
Ti (OR ⁵ ) _j X _(4-j) (4)
(In Formula (4), j is a real number of 0 or more and 4 or less, R ⁵ is a hydrocarbon group having 1 to 20 carbon atoms, and X is a halogen atom.)

  First, the organic magnesium compound (i) will be described. The organomagnesium compound (i) is shown as a complex form of organomagnesium soluble in an inert hydrocarbon solvent, but includes all dihydrocarbylmagnesium compounds and complexes of this compound with other metal compounds. To do. The symbols a, b, c, d and e in the formula (1) satisfy the relational expression 3a + 2b = c + d + e, which indicates the stoichiometry between the valence of the metal atom and the substituent.

In the above formula, the hydrocarbon group having 2 to 20 carbon atoms represented by R ¹ and R ² is not particularly limited, and specific examples thereof include an alkyl group, a cycloalkyl group and an aryl group. Methyl, ethyl, propyl, butyl, propyl, hexyl, octyl, decyl, cyclohexyl, phenyl group and the like. Of these, R ¹ and R ² are preferably each an alkyl group.

The ratio b / a of magnesium to aluminum is not particularly limited, but is preferably 0.1 to 30, and more preferably 0.5 to 10. Further, when a = 0, for example, R ¹ is preferably 1-methylpropyl or the like, whereby the organomagnesium compound (i) tends to be more soluble in an inert hydrocarbon solvent. In the formula (1), when a = 0, R ¹ and R ² satisfy any one of the following three groups (1), (2), and (3). preferable.

Group (1) Preferably, at least one of R ¹ and R ² is a secondary or tertiary alkyl group having 4 to 6 carbon atoms, and both R ¹ and R ² have 4 to 6 carbon atoms, More preferably, one is a secondary or tertiary alkyl group.
Group (2) R ¹ and R ² are preferably alkyl groups having different carbon numbers, R ¹ is an alkyl group having 2 or 3 carbon atoms, and R ² is an alkyl group having 4 or more carbon atoms. More preferably.
Group (3) Preferably, at least one of R ¹ and R ² is a hydrocarbon group having 6 or more carbon atoms, and is an alkyl group in which the sum of the carbon numbers contained in R ¹ and R ² is 12 or more. More preferred.

  Hereinafter, these groups are specifically shown. Specific examples of the secondary or tertiary alkyl group having 4 to 6 carbon atoms in the group (1) include 1-methylpropyl, 2-methylpropyl, 1,1-dimethylethyl, 2-methylbutyl, 2 -Ethylpropyl, 2,2-dimethylpropyl, 2-methylpentyl, 2-ethylbutyl, 2,2-dimethylbutyl, 2-methyl-2-ethylpropyl group and the like can be mentioned. Of these, a 1-methylpropyl group is preferable.

  Next, in the group (2), specific examples of the alkyl group having 2 or 3 carbon atoms include ethyl, 1-methylethyl, and propyl groups, and an ethyl group is particularly preferable. Further, the alkyl group having 4 or more carbon atoms is not particularly limited, and specific examples thereof include butyl, pentyl, hexyl, heptyl, octyl group and the like. Of these, butyl and hexyl groups are preferable.

  Furthermore, in the group (3), the hydrocarbon group having 6 or more carbon atoms is not particularly limited, and specific examples include hexyl, heptyl, octyl, nonyl, decyl, phenyl, 2-naphthyl group and the like. Among the hydrocarbon groups, an alkyl group is preferable, and among the alkyl groups, hexyl and octyl groups are particularly preferable.

  In general, when the number of carbon atoms contained in the alkyl group increases, it tends to be easily dissolved in an inert hydrocarbon solvent. However, it is preferable to use an alkyl group having a chain length as necessary in order to increase the viscosity of the solution. The organomagnesium compound (i) is used in the state of an inert hydrocarbon solution. Even if trace amounts of Lewis basic compounds such as ethers, esters and amines are contained or remain in the solution. It can be used without any problem. In addition, although it does not specifically limit as an inert hydrocarbon solvent in this embodiment, Specifically, Aliphatic hydrocarbons, such as pentane, hexane, and heptane; Aromatic hydrocarbons, such as benzene and toluene; And cyclohexane, methyl Examples include alicyclic hydrocarbons such as cyclohexane.

Next, the alkoxy group (OR ³ ) will be described. Although it does not specifically limit as a C2-C20 hydrocarbon group represented by R < ³ >, Specifically, a C2-C20 alkyl group or an aryl group is preferable, and a C3-10 alkyl group is preferable. Or an aryl group is more preferable. Although it does not specifically limit as a C2-C20 alkyl group or an aryl group, Specifically, methyl, ethyl, propyl, 1-methylethyl, butyl, 1-methylpropyl, 1,1-dimethylethyl, pentyl Hexyl, 2-methylpentyl, 2-ethylbutyl, 2-ethylpentyl, 2-ethylhexyl, 2-ethyl-4-methylpentyl, 2-propylheptyl, 2-ethyl-5-methyloctyl, octyl, nonyl, decyl, A phenyl, a naphthyl group, etc. are mentioned. Of these, butyl, 1-methylpropyl, 2-methylpentyl and 2-ethylhexyl groups are more preferred.

In the present embodiment, the method for synthesizing the organomagnesium compound (i) is not particularly limited, but the formulas R ¹ MgX and R ¹ ₂ Mg (R ¹ is the same group as described above, and X is a halogen atom. In an inert hydrocarbon solvent and an organometallic compound belonging to the group consisting of the formulas AlR ² ₃ and AlR ² ₂ H (R ² is the same group as described above). It can obtain by making it react at the temperature of 25 to 150 degreeC. If necessary, this reaction is followed by an alcohol having a hydrocarbon group represented by R ³ (R ³ is the same group as described above), or an R ³ soluble in an inert hydrocarbon solvent. The method of making it react with the alkoxymagnesium compound which has the hydrocarbon group represented by these, and / or an alkoxyaluminum compound is preferable.

  Among these, when reacting an organomagnesium compound soluble in an inert hydrocarbon solvent with an alcohol, the order of the reaction is not particularly limited, and a method of adding alcohol to the organomagnesium compound, organomagnesium in the alcohol. Either a method of adding a compound or a method of adding both at the same time can be used. In the present embodiment, the reaction ratio between the organomagnesium compound soluble in the inert hydrocarbon solvent and the alcohol is not particularly limited. However, as a result of the reaction, the alkoxy group-containing organomagnesium compound has an alkoxy group with respect to all metal atoms. The molar composition ratio e / (a + b) is 0 ≦ e / (a + b) ≦ 2, and preferably 0 ≦ e / (a + b) <1.

Next, the chlorosilane compound (ii) will be described. The chlorosilane compound (ii) is a silicon chloride compound having at least one Si—H bond represented by the formula (2).
H _h SiCl _i R ⁴ _{(4- (h + i))} (2)
(In the formula, R ⁴ is a hydrocarbon group having 1 to 20 carbon atoms, and h and i are numbers satisfying the following relationship: 0 <h, 0 <i, h + i ≦ 4).

Although it does not specifically limit as a C1-C20 hydrocarbon group represented by R < ⁴ > in Formula (2), Specifically, an aliphatic hydrocarbon group, an alicyclic hydrocarbon group, or aromatic hydrocarbon Examples thereof include a hydrogen group, and examples thereof include methyl, ethyl, propyl, 1-methylethyl, butyl, pentyl, hexyl, octyl, decyl, cyclohexyl, and phenyl groups. Among these, an alkyl group having 1 to 10 carbon atoms is preferable, and an alkyl group having 1 to 3 carbon atoms such as methyl, ethyl, propyl, and 1-methylethyl group is more preferable. H and i are numbers greater than 0 satisfying the relationship of h + i ≦ 4, and i is preferably 2 to 3.

The chlorosilane compound (ii) is not particularly limited, and specifically, HSiCl ₃ , HSiCl ₂ CH ₃ , HSiCl ₂ C ₂ H ₅ , HSiCl ₂ (C ₃ H ₇ ), HSiCl ₂ (2- _{C 3 H 7), HSiCl 2} (C 4 H 9), HSiCl 2 (C 6 H 5), HSiCl 2 (4-Cl-C 6 H 4), HSiCl 2 (CH = CH 2), HSiCl 2 (CH ₂ C ₆ H ₅ ), HSiCl ₂ (1-C ₁₀ H ₇ ), HSiCl ₂ (CH ₂ CH═CH ₂ ), H ₂ SiCl (CH ₃ ), H ₂ SiCl (C ₂ H ₅ ), HSiCl (CH ₃ ) ₂ , HSiCl (C ₂ H ₅ ) ₂ , HSiCl (CH ₃ ) (2-C ₃ H ₇ ), HSiCl (CH ₃ ) (C ₆ H ₅ ), HSiCl (C ₆ H ₅ ) _{2 and the} like. It is done. Among these, HSiCl ₃ , HSiCl ₂ CH ₃ , HSiCl (CH ₃ ) ₂ , and HSiCl ₂ C ₂ H ₅ are preferable, and HSiCl ₃ and HSiCl ₂ CH ₃ are more preferable. A chlorosilane compound may be used individually by 1 type, or may use 2 or more types together.

  Next, the reaction between the organomagnesium compound (i) and the chlorosilane compound (ii) will be described. In the reaction, the chlorosilane compound (ii) is previously treated with an inert hydrocarbon solvent; chlorinated hydrocarbons such as 1,2-dichloroethane, o-dichlorobenzene and dichloromethane; ether-based media such as diethyl ether and tetrahydrofuran; or a mixed medium thereof. It is preferable to use after diluting with an inert hydrocarbon solvent in view of the performance of the catalyst. The reaction ratio between the organomagnesium compound (i) and the chlorosilane compound (ii) is not particularly limited, but the silicon atoms contained in the chlorosilane compound (ii) with respect to 1 mol of magnesium atoms contained in the organomagnesium compound (i) are 0.01 mol to It is preferably 100 mol or less, and more preferably 0.1 mol to 10 mol.

  There is no restriction | limiting in particular about the reaction method of organomagnesium compound (i) and chlorosilane compound (ii), The method of simultaneous addition which reacts, introducing organomagnesium compound (i) and chlorosilane compound (ii) into a reactor simultaneously. , A method of introducing the organomagnesium compound (i) into the reactor after the chlorosilane compound (ii) is previously charged into the reactor, or a chlorosilane compound (ii) after the organomagnesium compound (i) is charged into the reactor in advance However, it is preferable to introduce the organomagnesium compound (i) into the reactor after the chlorosilane compound (ii) is charged into the reactor in advance. The solid (A-1a) obtained by the above reaction is preferably separated by filtration or decantation, and then thoroughly washed with an inert hydrocarbon solvent to remove unreacted products or by-products. .

  The reaction temperature of the organomagnesium compound (i) and the chlorosilane compound (ii) is not particularly limited, but is preferably 25 ° C to 150 ° C, more preferably 40 ° C to 150 ° C, and more preferably 50 ° C to 150 ° C. More preferably, it is 150 degreeC. In the simultaneous addition method in which the organomagnesium compound (i) and the chlorosilane compound (ii) are simultaneously introduced into the reactor and reacted, the temperature of the reactor is adjusted to a predetermined temperature in advance, and the simultaneous addition is performed in the reactor. It is preferable to adjust the reaction temperature to a predetermined temperature by adjusting the temperature of the above to a predetermined temperature. In the method in which the organomagnesium compound (i) is introduced into the reactor after the chlorosilane compound (ii) is charged into the reactor in advance, the temperature of the reactor charged with the chlorosilane compound (ii) is adjusted to a predetermined temperature, It is preferable to adjust the reaction temperature to a predetermined temperature by adjusting the temperature in the reactor to a predetermined temperature while introducing the magnesium compound (i) into the reactor. In the method of introducing the chlorosilane compound (ii) into the reactor after the organomagnesium compound (i) is charged in the reactor in advance, the temperature of the reactor charged with the organomagnesium compound (i) is adjusted to a predetermined temperature, The reaction temperature can be adjusted to a predetermined temperature by adjusting the temperature in the reactor to a predetermined temperature while introducing the chlorosilane compound (ii) into the reactor.

The reaction between the organomagnesium compound (i) and the chlorosilane compound (ii) can also be performed in the presence of a solid. This solid may be either an inorganic solid or an organic solid, but it is preferable to use an inorganic solid. The following are mentioned as an inorganic solid.
(I) Inorganic oxide (II) Inorganic carbonate, silicate, sulfate (III) Inorganic hydroxide (IV) Inorganic halide (V) Double salt, solid solution, or mixture comprising (I) to (IV)

Specific examples of the inorganic solid are not particularly limited. Specifically, silica, alumina, silica / alumina, hydrated alumina, magnesia, tria, titania, zirconia, calcium phosphate / barium sulfate, calcium sulfate, magnesium silicate, magnesium · Calcium, aluminum silicate [(Mg · Ca) O · Al ₂ O ₃ · 5SiO ₂ · nH ₂ O], potassium silicate · aluminum [K ₂ O · 3Al ₂ O ₃ · 6SiO ₂ · 2H ₂ O], magnesium silicate Examples include iron [(Mg · Fe) ₂ SiO ₄ ], aluminum silicate [Al ₂ O ₃ · SiO ₂ ], calcium carbonate, magnesium chloride, magnesium iodide, and the like. Of these, silica, silica / alumina, and magnesium chloride are preferable. The specific surface area of the inorganic solid is preferably 20 m ² / g or more, more preferably 90 m ² / g or more.

The solid (A-1a) obtained as described above is further reacted with an alcohol (A-2) to obtain a solid (A-1b). Although it does not specifically limit as alcohol (A-2) used in this case, Specifically, C1-C20 saturated or unsaturated alcohol can be illustrated, for example, methyl alcohol, ethyl alcohol, Propyl alcohol, iso-propyl alcohol, butyl alcohol, iso-butyl alcohol, sec-butyl alcohol, tert-butyl alcohol, n-amyl alcohol, iso-amyl alcohol, sec-amyl alcohol, tert-amyl alcohol, hexyl alcohol, cyclo Examples include hexanol, phenol, cresol and the like. Of these, C ₃ to C ₈ linear alcohols, iso-butyl alcohol, and iso-amyl alcohol are preferred.

  Next, the amount of alcohol (A-2) used is preferably 0.01 to 1 mol, more preferably 0.05 to 0.5 mol, per 1 mol of C-Mg bonds contained in the solid (A-1a). More preferably, it is the range of 0.1-0.25 mol. The reaction of the solid (A-1a) and the alcohol (A-2) can be performed in the presence or absence of an inert medium. As the inert medium, any of the above-described aliphatic, aromatic, and alicyclic hydrocarbons may be used. Although the temperature at the time of reaction is not specifically limited, Preferably it can implement at room temperature-200 degreeC.

Next, the solid (A-1b) obtained by the reaction between the solid (A-1a) and the alcohol (A-2) is reacted with the organometallic compound (A-3) represented by the following formula (3). Thus, a solid (A-1c) can be obtained.
AlR ⁵ _s Q _3-s ... Formula (3)
(In the formula (3), R ⁵ is a hydrocarbon group having 1 to 20 carbon atoms, and Q is selected from the group consisting of OR ⁶ , OSiR ⁷ R ⁸ R ⁹ , NR ¹⁰ R ¹¹ , SR ¹² and halogen. R ⁶ , R ⁷ , R ⁸ , R ⁹ , R ¹⁰ , R ¹¹ , R ¹² are hydrogen atoms or hydrocarbon groups, and s is a number that satisfies the following relationship: 0 <s <3 ).

  The organometallic compound (A-3) is not particularly limited, and specifically, trimethylaluminum, triethylaluminum, tri-n-propylaluminum, tri-n-butylaluminum, triiso-butylaluminum, tri-n-amyl. Trialkylaluminum such as aluminum, triiso-amylaluminum, tri-n-hexylaluminum, tri-n-octylaluminum, tri-n-decylaluminum; diethylaluminum chloride, ethylaluminum dichloride, diiso-butylaluminum chloride, ethylaluminum sesquichloride Aluminum halides such as diethylaluminum bromide; alkoxyaluminums such as diethylaluminum ethoxide and diiso-butylaluminum butoxide ; Dimethylhydrosiloxy aluminum dimethyl, ethyl methyl hydro siloxy aluminum diethyl, ethyl dimethylsiloxy aluminum diethyl acyloxyalkyl aluminum and the like; and mixtures thereof. Among these, aluminum halide is preferable, and dimethylaluminum chloride, methylaluminum dichloride, diethylaluminum chloride, ethylaluminum dichloride, dipropylaluminum chloride, and dibutylaluminum chloride are more preferable.

  The reaction between the solid (A-1b) obtained by the reaction between the solid (A-1a) and the alcohol (A-2) and the organometallic compound (A-3) is preferably performed using an inert reaction medium. Can do. Such an inert reaction medium is not particularly limited, and specifically includes aliphatic hydrocarbons such as hexane and heptane; aromatic hydrocarbons such as benzene and toluene; alicyclic carbonization such as cyclohexane and methylcyclohexane. Hydrogen etc. are mentioned. Of these, aliphatic hydrocarbons are preferred. The amount of the organometallic compound (A-3) used is preferably 0.5 mol or less, particularly preferably 0.1 mol or less, per mol of C—Mg bonds contained in the solid component (A-1a). Although it does not specifically limit about reaction temperature, It is preferable to carry out in the range of room temperature-150 degreeC.

Next, the titanium compound (A-4) will be described. In the present embodiment, the titanium compound (A-4) is preferably a titanium compound represented by the above formula (4).
Ti (OR ⁵ ) _j X _(4-j) Expression (4)
(In Formula (4), j is a real number of 0 to 4, R ⁵ is a hydrocarbon group having 1 to 20 carbon atoms, and X is a halogen atom.)

The hydrocarbon group having 1 to 20 carbon atoms represented by R ⁵ is not particularly limited, and specifically, methyl, ethyl, propyl, butyl, pentyl, hexyl, 2-ethylhexyl, heptyl, octyl, decyl, Aliphatic hydrocarbon groups such as allyl groups; alicyclic hydrocarbon groups such as cyclohexyl, 2-methylcyclohexyl, and cyclopentyl groups; aromatic hydrocarbon groups such as phenyl and naphthyl groups. Among these, an aliphatic hydrocarbon group is preferable. Examples of the halogen represented by X include chlorine, bromine and iodine, with chlorine being preferred. A titanium compound (A-4) can be used individually by 1 type, or can be used in mixture of 2 or more types.

  Although there is no restriction | limiting in particular in the usage-amount of a titanium compound (A-4), 0.01-20 are preferable by molar ratio with respect to the magnesium atom contained in solid (A-1c), and 0.05-10 are especially preferable.

  Although it does not specifically limit about reaction temperature of solid (A-1c) and a titanium compound (A-4), It is preferable to carry out in the range of 25 to 150 degreeC.

  In the present embodiment, the method for supporting the titanium compound (A-4) on the solid (A-1c) is not particularly limited, and an excess of the titanium compound (A-4) is reacted with the solid (A-1c). Although the method of carrying | supporting a titanium compound (A-4) efficiently by using the method to make or a 3rd component may be used, a titanium compound (A-4) and an organometallic compound (A-5) A method of supporting by reaction is preferred.

Next, the organometallic compound (A-5) will be described. As (A-5), what is represented by following formula (5) and formula (6) is preferable.
(M ¹ ) _a (Mg) _b (R ¹ ) _c (R ² ) _d Y _e (5)
(In Formula (5), M ¹ is a metal atom other than magnesium belonging to the group consisting of Group 1, Group 2, Group 12 and Group 13 of the Periodic Table, and R ¹ and R ² are as described above. Y is alkoxy, siloxy, allyloxy, amino, amide, —N═C—R ⁶ , R ⁷ , —SR ⁸ , β-keto acid residue (where R ⁶ , R ⁷ and R ⁸ are carbon Represents a hydrocarbon group of 1 to 20. When e is 2 or more, Y may be different from each other), and a, b, c, d, and e have the following relationship: 0 ≦ a, 0 <b, 0 ≦ c, 0 ≦ d, 0 ≦ e, 0 <c + d, 0 ≦ e / (a + b) ≦ 2, f × a + 2b = c + d + e (where f is M ¹ valence.))
M ² R ⁹ _k Q _(mk) (6)
(In Formula (6), M ² is a metal atom belonging to the group consisting of Group 1, Group 2, Group 12, Group 13 of the Periodic Table, and R ⁹ is a hydrocarbon group having 1-20 carbon atoms. Q represents a group belonging to the group consisting of OR ¹⁰ , OSiR ¹¹ R ¹² R ¹³ , NR ¹⁴ R ¹⁵ , SR ¹⁶ and halogen, and R ¹⁰ , R ¹¹ , R ¹² , R ¹³ , R ¹⁴ , R ¹⁵ R ¹⁶ is a hydrogen atom or a hydrocarbon group, k is a real number greater than 0, and m is a valence of M ^2. )

  Hereinafter, the organometallic compounds represented by the above formulas (5) and (6) are referred to as an organometallic compound (A-5a) and an organometallic compound (A-5b), respectively.

  First, the organometallic compound (A-5a) will be described. The usage-amount of an organometallic compound (A-5a) is 0.1-10 in the molar ratio of the magnesium atom contained in the organometallic compound (A-5a) with respect to the titanium atom contained in a titanium compound (A-4). It is preferable that it is 0.5-5. The temperature of the reaction between the titanium compound (A-4) and the organometallic compound (A-5a) is not particularly limited, but is preferably -80 ° C to 150 ° C, and is in the range of -40 ° C to 100 ° C. More preferably.

  Although there is no restriction | limiting in particular about the density | concentration at the time of use of an organometallic compound (A-5a), It is preferable that it is 0.1 mol / L-2 mol / L on the basis of the magnesium atom contained in an organometallic compound (A-5a). More preferably, it is 0.5 mol / L to 1.5 mol / L. In addition, it is preferable to use an inert hydrocarbon solvent for the dilution of the organometallic compound (A-5a).

  There are no particular restrictions on the order of addition of the titanium compound (A-4) and the organometallic compound (A-5a) to the solid (A-1c), and the organometallic compound (A-5a) follows the titanium compound (A-4). ), The organometallic compound (A-5a) is added followed by the titanium compound (A-4), and the titanium compound (A-4) and the organometallic compound (A-5a) are added simultaneously. Although a method is also possible, the method of adding a titanium compound (A-4) and an organometallic compound (A-5a) simultaneously is preferable. The reaction between the titanium compound (A-4) and the organometallic compound (A-5a) is carried out in an inert hydrocarbon solvent, but it is preferable to use an aliphatic hydrocarbon solvent such as hexane or heptane. The catalyst thus obtained is used as a slurry solution using an inert hydrocarbon solvent.

  Next, the organometallic compound (A-5b) will be described. The organometallic compound (A-5b) is an organometallic compound represented by the formula (6).

In the above formula (6), M ² is a metal atom belonging to the group consisting of Group 1, Group 2, Group 12, Group 13 of the Periodic Table, and is not particularly limited. Sodium, potassium, beryllium, magnesium, boron, aluminum, zinc, etc. are mentioned. Among these, magnesium, boron, and aluminum are preferable. Although it does not specifically limit as a C1-C20 hydrocarbon group represented by R < ⁹ >, Specifically, an alkyl group, a cycloalkyl group, or an aryl group is mentioned, For example, methyl, ethyl, propyl, butyl , Pentyl, hexyl, octyl, decyl, cyclohexyl, phenyl group and the like. Among these, an alkyl group is preferable.

Q represents a group belonging to the group consisting of OR ¹⁰ , OSiR ¹¹ R ¹² R ¹³ , NR ¹⁴ R ¹⁵ , SR ¹⁶ and halogen, and R ¹⁰ , R ¹¹ , R ¹² , R ¹³ , R ¹⁴ , R ¹⁵ , R ¹⁶ Is a hydrogen atom or a hydrocarbon group, and Q is preferably a halogen atom.

  The organometallic compound (A-5b) is not particularly limited, and specifically, methyllithium, butyllithium, methylmagnesium chloride, methylmagnesium bromide, methylmagnesium iodide, ethylmagnesium chloride, ethylmagnesium bromide. , Ethylmagnesium iodide, butylmagnesium chloride, butylmagnesium bromide, butylmagnesium iodide, dibutylmagnesium, dihexylmagnesium, triethylboron, trimethylaluminum, dimethylaluminum bromide, dimethylaluminum chloride, dimethylaluminum methoxide, methylaluminum dichloride, methylaluminum Sesquichloride, triethylaluminum, diethylaluminum chloride , Diethylaluminum bromide, diethylaluminum ethoxide, ethylaluminum dichloride, ethylaluminum sesquichloride, tripropylaluminum, tributylaluminum, tri (2-methylpropyl) aluminum, trihexylaluminum, trioctylaluminum, tridecylaluminum, etc. It is done. Among these, an organoaluminum compound is preferable. Moreover, these compounds can be used individually by 1 type, or 2 or more types can be mixed and used for them. k is a real number larger than 0, and is preferably a real number larger than 0.5.

The amount of the organic metal compound (A-5b) is 0.1 to 10 at a molar ratio of M ² atoms contained in the titanium compound organometallic compound to titanium atom contained in the (A-4) (A- 5b) It is preferable that the ratio is 0.5 to 5. The temperature of the reaction between the titanium compound (A-4) and the organometallic compound (A-5b) is not particularly limited, but is preferably 20 ° C to 150 ° C, and more preferably 40 ° C to 100 ° C. .

Although there is no restriction | limiting in particular about the density | concentration at the time of use of an organometallic compound (A-5b), It is 0.1 mol / L- ² mol / L on the basis of M2 atom contained in an organometallic compound (A-5b). Preferably, it is 0.5 mol / L to 1.5 mol / L. In addition, it is preferable to use an inert hydrocarbon solvent for the dilution of the organometallic compound (A-5b).

  There are no particular limitations on the method of adding the titanium compound (A-4) and the organometallic compound (A-5b) to the solid (A-1c). First, the titanium compound (A-4) is added, followed by the organic compound. Method of adding metal compound (A-5b), first adding organometallic compound (A-5b), followed by adding titanium compound (A-4), titanium compound (A-4) and organic Any method of adding the metal compound (A-5b) at the same time is possible. First, the organometallic compound (A-5b) is added, and then the titanium compound (A-4) is added. Is preferred. The reaction between the titanium compound (A-4) and the organometallic compound (A-5b) is carried out in an inert hydrocarbon solvent, but it is preferable to use an aliphatic hydrocarbon solvent such as hexane or heptane. The catalyst thus obtained is used as a slurry solution using an inert hydrocarbon solvent.

  When the organometallic compound (A-5b) is used, before adding the titanium compound (A-4) and the organometallic compound (A-5b) to the solid (A-1c), the solid ( A-1c) is preferably reacted with alcohol in advance and further reacted with the organometallic compound (A-5b).

  Such alcohol is not particularly limited, but specifically, those having 1 to 10 carbon atoms are preferable. For example, methanol, ethanol, propanol, 2-propanol, 1-butanol, 2-butanol, 2- Examples include methyl-1-propanol, 1-methyl-2-propanol, 1-pentanol, 1-hexanol, 1-octanol, 2-ethyl-1-hexanol, and decanol. Among these, those having 2 to 6 carbon atoms are more preferable, for example, ethanol, propanol, 2-propanol, 1-butanol, 2-butanol, 2-methyl-1-propanol, 1-methyl-2-propanol, Examples thereof include 1-pentanol and 1-hexanol. Although it does not specifically limit about the usage-amount of alcohol, It is preferable that it is 0.01-1 with the molar ratio with respect to the magnesium atom contained in solid (A-1c), and it is still more preferable that it is 0.01-0.5. . The concentration of the alcohol at the time of use is not particularly limited, but it is preferably used after diluting to 0.1M to 2M using an inert hydrocarbon solvent. Although it does not specifically limit about the temperature of reaction with solid (A-1c) and alcohol, It is preferable that it is 25 to 150 degreeC, and it is more preferable that it is 40 to 80 degreeC.

  The reaction between the solid (A-1c) after the reaction with alcohol and the organometallic compound (A-5b) will be described. Although it does not specifically limit about the usage-amount of an organometallic compound (A-5b), It is preferable that it is 0.1-10 by molar ratio with respect to the used alcohol, and it is still more preferable that it is 0.5-5 times. Although there is no restriction | limiting in particular about the density | concentration at the time of use of an organometallic compound (A-5b), It is preferable that it is 0.1 mol / L-2 mol / L on the basis of M2 atom contained in an organometallic compound (A-5b). More preferably, it is 0.5 mol / L to 1.5 mol / L. In addition, it is preferable to use an inert hydrocarbon solvent for the dilution of the organometallic compound (A-5b). The temperature of the reaction between the solid (A-1c) after reacting with the alcohol and the organometallic compound (A-5b) is not particularly limited, but is preferably 25 ° C. to 150 ° C. or less, and 40 ° C. to 80 ° C. More preferably, the temperature is C.

  Next, the organometallic compound component [B] in the present embodiment will be described. The solid catalyst component [A] of the present embodiment becomes a highly active polymerization catalyst when combined with the organometallic compound component [B]. Although it does not specifically limit as organometallic compound component [B], Specifically, it is a compound containing the metal which belongs to the group which consists of a periodic table 1st group, 2nd group, 12th group, and 13th group. In particular, organoaluminum compounds and / or organomagnesium compounds are preferred.

As such an organoaluminum compound, a compound represented by the following formula (7) is preferably used alone or in combination.
AlR ¹⁷ _n Z _(3-n) (7)
(Wherein R ¹⁷ is a hydrocarbon group having 1 to 20 carbon atoms, Z is a group belonging to the group consisting of hydrogen, halogen, alkoxy, allyloxy, and siloxy groups, and n is a number of 2 to 3)

In the above formula (7), the hydrocarbon group having 1 to 20 carbon atoms represented by R ¹⁷ is not particularly limited, and specifically, aliphatic hydrocarbon, aromatic hydrocarbon, alicyclic carbonization. Examples include hydrogen, such as trimethylaluminum, triethylaluminum, tripropylaluminum, tributylaluminum, tri (2-methylpropyl) aluminum, tripentylaluminum, tri (3-methylbutyl) aluminum, trihexylaluminum, trioctyl. Trialkylaluminum such as aluminum and tridecylaluminum; diethylaluminum chloride, ethylaluminum dichloride, bis (2-methylpropyl) aluminum chloride, ethylaluminum sesquichloride, diethylaluminum bromide, etc. An aluminum aluminum compound; an alkoxyaluminum compound such as diethylaluminum ethoxide, bis (2-methylpropyl) aluminum butoxide; a siloxyaluminum compound such as dimethylhydrosiloxyaluminum dimethyl, ethylmethylhydrosiloxyaluminum diethyl, ethyldimethylsiloxyaluminum diethyl; and These mixtures are preferred. Among these, a trialkylaluminum compound is more preferable.

The organomagnesium compound is preferably an organomagnesium compound that is soluble in the inert hydrocarbon solvent represented by the above formula (8).
(M ¹ ) _a (Mg) _b (R ¹ ) _c (R ² ) _d (OR ³ ) _e Expression (8)
(In the formula, M ¹ is a metal atom other than magnesium belonging to the group consisting of Group 1, Group 2, Group 12, and Group 13 of the Periodic Table, and R ¹ and R ² each have 2 to 20 carbon atoms. R ³ is a hydrocarbon group having 1 to 20 carbon atoms, and a, b, c, d, and e are real numbers that satisfy the following relationship: 0 ≦ a, 0 <b, 0 ≦ c, 0 ≦ d, 0 ≦ e, 0 <c + d, 0 ≦ e / (a + b) ≦ 2, f × a + 2b = c + d + e (where f is the valence of M ¹ ))

Such organomagnesium compounds are shown as complex forms of organomagnesium soluble in inert hydrocarbon solvents, but all of dialkylmagnesium compounds and complexes of this compound with other metal compounds. Is included. Since this organomagnesium compound is preferably a compound having high solubility in an inert hydrocarbon solvent, b / a is preferably 0.5 to 10, and more preferably a compound in which M ¹ is aluminum.

  The method for adding the solid catalyst component [A] and the organometallic compound component [B] into the polymerization system under the polymerization conditions is not particularly limited, and both may be added separately into the polymerization system. You may add in a polymerization system, after making both react. Moreover, although there is no restriction | limiting in particular in the ratio of both to combine, It is preferable that organometallic compound [B] is 1 mmol-3,000 mmol with respect to 1 g of solid catalyst components [A].

  The organoaluminum compound [B] used together with the solid catalyst component [A] of the present embodiment is not particularly limited. Specifically, trimethylaluminum, triethylaluminum, tri-n-propylaluminum, tri-n-butylaluminum, tri trialkylaluminum such as iso-butylaluminum, tri-n-amylaluminum, triiso-amylaluminum, tri-n-hexylaluminum, tri-n-octylaluminum, tri-n-decylaluminum; diethylaluminum chloride, ethylaluminum dichloride, diiso -Aluminum halides such as butyl aluminum chloride, ethyl aluminum sesquichloride, diethyl aluminum bromide; diethyl aluminum ethoxide, diiso-butyl alcohol Alkoxyaluminum such as minium butoxide; siloxyalkylaluminum such as dimethylhydrosiloxyaluminum dimethyl, ethylmethylhydrosiloxyaluminum diethyl, ethyldimethylsiloxyaluminum diethyl; and mixtures thereof are used, especially trialkylaluminum has achieved the highest activity. Therefore, it is preferable.

  The solid catalyst component [A] and the organoaluminum compound may be added to the polymerization system under the polymerization conditions, or may be mixed in advance prior to the polymerization. The ratio of both components to be combined is defined by the molar ratio of Ti in the solid catalyst component [A] and Al in the organoaluminum compound [B], and is preferably Al / Ti = 0.3 to 1000.

  As the polymerization solvent, a hydrocarbon solvent usually used for slurry polymerization is used. Specific examples include aliphatic hydrocarbons such as hexane and heptane; aromatic hydrocarbons such as benzene, toluene and xylene; and alicyclic hydrocarbons such as cyclohexane and methylcyclohexane. These hydrocarbon solvents may be used alone or in admixture of two or more. The polymerization temperature is usually in the range of room temperature to 100 ° C, preferably 50 ° C to 90 ° C. The polymerization pressure is usually carried out in the range of normal pressure to 100 atm. The molecular weight of the resulting polymer can be adjusted by allowing hydrogen to be present in the polymerization system or changing the polymerization temperature.

  Further, a method of producing by a vessel type slurry polymerization method using a supported geometrically constrained single site catalyst can also be preferably used.

  The polyethylene resin composition obtained in this way is particularly preferable in that the amount of comonomer introduced into the high molecular weight polyethylene resin component can be increased, so that the high molecular weight polyethylene resin component easily forms a tie molecule.

(Other ingredients)
You may add an additive, a filler, etc. to the polyethylene resin composition of the said embodiment as needed. Although it does not specifically limit as an additive used, Specifically, various antioxidants, such as a phenolic antioxidant, phosphorus antioxidant, and sulfur type antioxidant; HALS type light stabilizer, benzophenone Various light stabilizers such as a light stabilizer and a benzotriazole ultraviolet absorber; neutralizers such as fatty acid metal salts and hydrotalcite; pigments and the like can be used. Further, the filler is not particularly limited, and specific examples include talc, silica, carbon, mica, calcium carbonate, magnesium carbonate, wood flour and the like. If necessary, it is possible to add titanium oxide or an organic pigment in a master batch.

[Use]
The polyethylene resin composition of the present embodiment is excellent in long-term creep characteristics, is classified as PE100 described in the ISO 9080 standard, has a high minimum guaranteed stress after 100 years, and is excellent in molding processability. Suitable for polyethylene piping materials. Further, the polyethylene resin composition of the present embodiment tends to be excellent in long-term characteristics, elongation characteristics, and impact resistance.

  Here, “PE100” means that at least 9000 stress-fracture time curves were measured at three different temperatures in which the maximum temperature and the minimum temperature were separated by 50 ° C. or more in the hot internal pressure creep test described in ISO 9080. The LPL value of the value estimated by extrapolating the minimum guaranteed stress after 50 years at 20 ° C. by the multiple correlation average is 10 MPa or more and 11.19 MPa or less in the classification table defined in ISO12162, Since the minimum guaranteed stress is 10 MPa, it refers to polyethylene classified as PE100. Specifically, it can be classified by the method described in the examples.

  “100 year warranty” refers to a polyethylene resin composition having a minimum guaranteed stress of 10 MPa or more by extrapolation after 100 years at 20 ° C. in the same manner as “PE100”. Specifically, it can be evaluated by the method described in Examples.

  The polyethylene resin composition of the present embodiment is superior in long-term characteristics and moldability to conventional polyethylene pipe material resin compositions, and the long-term characteristics are dramatically improved and the productivity is extremely high.

  The pipe of this embodiment and the joint of a pipe contain a polyethylene resin composition, Preferably they are for waterworks. Taking a polyethylene pipe for waterworks as an example, when tap water is used in Japan, the generation of bubbles due to chlorine water and the accompanying peeling of the surface layer occur, and so-called chlorine water resistance is required. Usually, when producing polyethylene pipes and joints, in order to limit the use as a pipe, it is usually provided in a colored form together with a coloring pigment. As described above, if the polyethylene pipe and the joint resin containing the color pigment contain a large amount of ash (component derived from the color pigment), it is considered that the chlorine resistance is lowered. Therefore, it is described in the polyethylene pipe for water supply of JIS K6762 that ash content is limited to a predetermined amount or less. The ash content in the pipe and the joint of the present embodiment is preferably 0.07% by mass or less, and more preferably 0.05% by mass or less.

Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples. The present invention is not limited in any way by the following examples.
In the present invention and the following examples and comparative examples, the symbols and measurement methods shown are as follows.

(1) Melt flow rate, code D (MFR 2.16):
It represents a melt index, and is a value obtained by measuring a polyethylene resin on the low molecular weight side according to JIS K7210 at a temperature of 190 ° C. and a load of 2.16 kg. The unit was g / 10 min.

(2) Melt flow rate, code T (MFR5):
It represents a melt index, and is a value obtained by measuring a polyethylene resin composition according to JIS K7210 at a temperature of 190 ° C. and a load of 5.00 kg. The unit was g / 10 min.

(3) Density:
It is the value which measured the polyethylene resin composition based on JISK7112. The unit was kg / m ³ .

(4) Molecular weight distribution (Mw / Mn):
It is a value obtained from the ratio of the weight average molecular weight (Mw) and the number average molecular weight (Mn) in the molecular weight distribution chart obtained by measuring the polyethylene resin composition by high temperature gel permeation chromatography (GPC). . For the high-temperature GPC measurement, Waters Alliance GPCV2000 was used, and for the column, Showa Denko Co., Ltd. AT-807S (one) and Tosoh Corporation GMHHR-H (S) HT (two) were used. Connected in series, mobile phase with orthodichlorobenzene (ODCB), column temperature 140 ° C, flow rate 1.0ml / min, sample concentration 20mg / solvent (ODCB) 10ml, sample dissolution temperature 140 ° C, sample dissolution time 1 hour Went under.

(5) Flexural modulus It is the value which measured the polyethylene resin composition based on JISK7171. The unit was MPa.

(6) Tensile elongation at break This is a value obtained by measuring the polyethylene resin composition in accordance with JIS K7161. The unit is%.

(7) Charpy impact strength This is a value obtained by measuring a polyethylene resin composition in accordance with JIS K7111. The unit is kJ / m ² .

(8) Hot internal pressure creep (pipe hoop):
(8-1) Pipe molding The physical properties of the pipe were measured by molding the pipe as follows using a polyethylene resin composition. The pipe is melted at a resin temperature of 220 ° C. using a 65 mm diameter extruder (manufactured by Toshiba Plastic Engineering), extruded into a cylindrical shape from a die with an outer diameter of 80 mm and an inner diameter of 68 mm attached to the extruder, and a sizing plate in a sizing tank The outer diameter is formed by passing through, and the sizing tank water temperature is cooled at 25 ° C. as primary cooling, and the pipe is cooled at 20 ° C. as secondary cooling in the next water tank after leaving the sizing tank. Was taken with a take-up machine so that the outer diameter / thickness ratio = 11, and a tubular pipe having an outer diameter of 63 mm and a wall thickness of 5.8 mm was formed.

(8-2) PE class:
Three levels of temperatures of 20 ° C., 60 ° C., and 80 ° C. are selected by the test method described in ISO 9080, and a hot internal pressure test is performed at an arbitrary hoop stress on each of the molded pipes at 30 points or more at each temperature level. And it measured so that the data after 9000 hours may be included at least one point. The logarithmic value of the test time and the logarithmic value of the hoop pressure were subjected to multiple correlation averaging at three temperatures, and the hoop pressure after 50 years was calculated by extrapolation for the lower confidence limit of 97.5% for the 20 ° C. line. Based on this, the PE class was determined from the range of σLCL corresponding to the minimum guaranteed stress according to the standard described in ISO12162.
Evaluation standard of PE class PE100: MRS = 10 MPa: 10 ≦ LCL ≦ 11.19
PE80: MRS = 80 MPa: 8 ≦ σLCL ≦ 9.99

(8-3) Hoop pressure after 100 years:
Three levels of temperatures of 20 ° C., 60 ° C., and 80 ° C. are selected by the test method described in ISO 9080, and a hot internal pressure test is performed at an arbitrary hoop stress on each of the molded pipes at 30 points or more at each temperature level. And it measured so that the data after 9000 hours may be included at least one point. Regarding the logarithmic value of the test time and the logarithm value of the hoop pressure, when there is no knee point, the model RI described in ISO / TR9080 is used, and when the knee point is present, the model RII is used, and a multiple correlation average is performed at three temperatures. The hoop pressure after 100 years was calculated by extrapolation for the lower confidence limit of 97.5% for the 20 ° C line. Based on this, the 100-year warranty was determined according to the following evaluation criteria.
Evaluation criteria for 100-year warranty ○: Estimated value after 100 years is 10 MPa or more ×: Less than 10 MPa

(8-4) Calculation of slope ratio:
The slope ratio was determined by linear regression using a linear model using a least squares method for the slope of the plot line of less than 1000 hours and the slope of the plot line after 1000 hours in the hot internal pressure test at 20 ° C. The ratio of the slope of the plot line less than 1000 hours to the slope after 1000 hours was calculated (slope less than 1000 hours / slope after 1000 hours).

(8-5) Knee Point judgment:
Knee Point is a hot internal pressure test at 80 ° C. using an unnotched pipe based on ISO 9080, and changes from ductile fracture on the low time side to brittle fracture on the high time side when expressing hoop stress with respect to elapsed time (Knee). ) Was evaluated according to the following evaluation criteria.
"Yes": Change (Knee) appears
“No”: No change (Knee), only ductile fracture

(9) Temperature rising elution fractionation GPC cross fractionation:
The fraction (R, unit: wt%) of the total elution amount of elution components with a molecular weight of 200,000 or more and an elution temperature of 85 ° C or less to the total integrated elution amount, cross-separation between temperature rising elution fractionation and gel permeation chromatography It calculated from the correlation of molecular weight-elution temperature-elution amount calculated | required by. The cumulative elution amount of elution components having a molecular weight of 200,000 or more and an elution temperature of 85 ° C. or less corresponds to the hatched portion in FIG. The ratio to the total accumulated elution amount is R. As a measuring device, a CFC manufactured by Polymer char was used. As a column for gel permeation chromatography, AT-807S (1) manufactured by Showa Denko KK and GMHHR-H (S) HT (2) manufactured by Tosoh Co., Ltd. are connected in series, and the mobile phase is ortho. Measurements were always made at 140 ° C. except for dichlorobenzene (ODCB), column temperature 140 ° C., flow rate 1.0 ml / min, sample concentration 20 mg / solvent (ODCB) 10 ml, sample dissolution temperature 140 ° C., temperature elution fractionation part.

  The sample concentration was 0.1 to 0.3 wt / vol%, the injection amount was 0.5 ml, and the flow rate was 1.0 ml / min. The sample was heated at 140 ° C. for 2 hours, then cooled to 20 ° C. at 10 ° C./hr, and further held at 20 ° C. for 60 minutes to coat the sample. An infrared spectrometer was used as a detector, and infrared light of 3.42 μm was detected. The elution temperature was 40 ° C. to 140 ° C., and it was divided into 1 ° C. fractions in the vicinity of the elution peak. The molecular weight of the eluted fraction at each temperature was measured. Next, an elution amount having a molecular weight of 200,000 or more and an elution temperature of 85 ° C. or less was calculated from the integrated value for each molecular weight of each fraction, and the total amount ratio was taken as R.

(10) Molding workability The surface of a molded product molded by injection molding was visually evaluated, and those having no rough skin, flow marks, and peeling were evaluated as “good”, and those having rough skin, flow marks, and peeling were evaluated as “x”.

[Example 1]
[Preparation of catalyst]
(Preparation of solid catalyst component [A])
(1) Synthesis of magnesium-containing solid by reaction with chlorosilane compound 2740 mL of trichlorosilane (HSiCl ₃ ) (component (ii)) as a 2 mol / L n-heptane solution was charged into a fully nitrogen-substituted 15 L reactor. The mixture is kept at 65 ° C. with stirring, and the formula AlMg ₆ (C ₂ H ₅ ) ₃ (iC ₄ H ₉ ) _10.8 (Oi C ₄ H ₉ ) _1.2
7 L (5 mol in terms of magnesium) of an organomagnesium component (component (i)) represented by the formula (1) was added over 1 hour, and 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 L of n-hexane to obtain a solid slurry. As a result of separating and drying this solid (A-1a) and analyzing it, it contained Mg 8.62 mmol, Cl 17.1 mmol and i-butoxy group (Oi-C ₄ H ₉ ) 0.84 mmol per 1 g of the solid.
(2) Preparation of Solid Catalyst A slurry containing 500 g of the solid (A-1a) was mixed with 2160 mL of 1-mol / L n-hexane solution of iso-butyl alcohol (component (A-2)) at 50 ° C. with stirring. Reacted for hours. After completion of the reaction, the supernatant was removed and washed once with 7 L of n-hexane to obtain a solid slurry (A-1b). This solid slurry (A-1b) was kept at 50 ° C., and 970 mL of 1 mol / L n-hexane solution of diethylaluminum chloride (component (A-3)) was added with stirring to react for 1 hour. After completion of the reaction, the supernatant was removed and washed twice with 7 L of n-hexane to obtain a solid slurry (A-1c). The solid slurry (A-1c) was kept at 50 ° C., and 270 mL of n-hexane solution of 1 mol / L of diethylaluminum chloride and 270 mL of n-hexane solution of 1 mol / L of titanium tetrachloride (component (A-4)) were added. Reacted for 2 hours. After completion of the reaction, the supernatant was removed and washed with 7 L of n-hexane four times while maintaining the internal temperature at 50 ° C. to obtain a solid catalyst component (component [A]) as a hexane slurry solution. The chlorine ion concentration in the supernatant of the solid catalyst slurry solution was 2.5 mmol / L, and the aluminum ion concentration was 4.5 mmol / L.

(3) Polymerization Two-stage polymerization by two polymerization tanks connected in series by a continuous slurry polymerization method using a polymerization catalyst containing the solid catalyst component [A] obtained above and triethylaluminum (component [B]). Went. The comonomer used was 1-butene. The first stage polymerization tank is supplied with only ethylene as a monomer and polymerized at a temperature of 85 ° C., a pressure of 7.2 kg / cm ³ G, and a hydrogen concentration of 48%, and the second stage contains ethylene and 1-butene. The polymerization was carried out at 70 ° C., 2.3 kg / cm ³ G, hydrogen concentration 1.5%, and 1-butene concentration 9.0%. The production ratio of the low molecular weight polyethylene resin component (A) made of an ethylene homopolymer obtained in the first stage polymerization tank is 55 wt%, and the high molecular weight polyethylene resin component made of a copolymer obtained in the second stage polymerization tank. The proportion of the production amount of (B) was set to 45 wt%, and a powder with an MFR5 of 0.86 g / 10 minutes and a density of 948 kg / m ³ was obtained.

The powder obtained by the above polymerization was dried, and 1000 ppm of tri (2,4-di-t-butylphenyl) phosphate as a secondary antioxidant and tetrakis (3 as a heat-resistant stabilizer) with respect to 100 parts by mass of the powder. -(4'-hydroxy-3 ', 5'-di-t-butylphenyl) propionate) methane at 1500 ppm and 2- (3-t-butyl-5-methyl-2-hydroxyphenyl) -5- as weathering agent By extruding and granulating 400 ppm chlorobenzotriazole, 300 ppm calcium stearate, Nippon Steel's TEX-44 type extruder (screw diameter 44 mm, L / D = 42) at a set temperature of 200 ° C. and a resin extrusion rate of 40 kg / hr. Pellets were obtained. The pellet had an MFR5 of 0.33 g / 10 min and a density of 948 kg / m ³ . A test piece was prepared using this pellet, and physical properties were measured.

  Further, a pipe having an outer diameter of 63 mm was formed using the pellet, and the physical properties of the pipe were measured. The results are shown in Table 1. The relationship between time and hoop pressure is shown in FIG. In FIG. 2, plots of less than 1000 hours are indicated by ♦, plots after 1000 hours are indicated by □, and each plot is calculated by regression using a least square method of a linear equation, and the plot lines are indicated by straight lines.

[Comparative Example 1]
A stainless steel autoclave with an internal volume of 20 L that has been sufficiently purged with nitrogen is charged with 4 L of a 1 mol / L hydroxytrichlorosilane hexane solution and stirred at 50 ° C., while the composition formula AlMg ₅ (C ₄ H ₉ ) ₁₁ (OC ₂ H ₅ ) 9 L of a hexane solution of the organomagnesium compound represented by ₂ (equivalent to 6.5 mol of magnesium) was added dropwise over 4 h, and the reaction was further continued at 50 ° C. with stirring for 1 h. After completion of the reaction, the supernatant was removed and washed 4 times with 7 L of hexane to obtain a carrier. As a result of analyzing this carrier, the amount of magnesium contained in 1 g of the carrier was 8.44 mmol.

  While stirring at 50 ° C., 450 mL of a 1 mol / L 1-propanol hexane solution was added to 13 L of hexane slurry containing 500 g of the carrier over 30 minutes. After the addition, the reaction was continued at 50 ° C. for 1 hour. After completion of the reaction, 7 L of the supernatant was removed, 6.4 L of hexane was added, the temperature was 65 ° C., and 600 ml of a 1 mol / L diethylaluminum chloride hexane solution was added over 1 hour 30 minutes. After the addition, the reaction was continued at 65 ° C. for 1 hour. After completion of the reaction, 7 L of the supernatant was removed and washed 4 times with 7 L of hexane to obtain a slurry. Remove 600 mL of the supernatant of the slurry after washing, add 265 mL of a 1 mol / L diethylaluminum chloride hexane solution over 5 minutes while stirring at 50 ° C., and subsequently add 265 mL of a 1 mol / L titanium tetrachloride hexane solution for 5 minutes. Added over time. After the addition, the reaction was continued at 50 ° C for 2 hours. After completion of the reaction, 7 L of the supernatant was removed, and the solid catalyst component was prepared by washing 4 times with 7 L of hexane. The amount of titanium contained in 1 g of this solid catalyst component was 0.52 mmol.

  First, in the first stage polymerization, a stainless polymerizer 1 having a reaction volume of 300 L was used to produce a low molecular weight component. The sum of the volume of the solvent in the polymerization vessel and the volume of the polyolefin measured by a liquid level meter using γ rays is 170 L, and the rate per volume at which the solvent and the polyolefin are regularly extracted from the polymerization vessel is 51 L. / H. Therefore, the average residence time in the first stage was 3.3 hours. Low molecular weight components were withdrawn from the polymerization vessel 1 at a rate of 10 kg / h. Under the conditions of a polymerization temperature of 85 ° C. and a polymerization pressure of 1 MPa, the above solid catalyst was introduced as a catalyst in an amount of 0.5 mmol / h in terms of Ti atoms, and the above organoaluminum compound was introduced in an amount of 20 mmol / h in terms of Al atoms, Hexane was introduced at a rate of 40 L / h. Hydrogen is used as the molecular weight regulator, and is supplied so that the gas phase molar concentration (hydrogen / (ethylene + hydrogen)) of the sum of ethylene and hydrogen is 65 mol%, and the supply amount of ethylene is 10 kg / h. Then, the polymerization was carried out by supplying the polymerization vessel.

The polymerization activity in the polymerization vessel 1 was 3200 g / g / h. The melt flow rate (MFR 2.16) of the low molecular weight component produced in Polymerizer 1 was 190 g / 10 min, and the density was 974 kg / m ³ .

  In order to remove hydrogen in the polymer slurry, the polymer slurry solution in the polymerization vessel 1 was led to a flash drum having a pressure of 0.1 MPa and a temperature of 75 ° C. at a rate of 51 L / h to separate unreacted ethylene and hydrogen.

  Next, in order to produce a high molecular weight component in the second-stage polymerization, a stainless polymerizer 2 having a reaction volume of 300 L is used, and the polymer slurry solution is 51 L / h and hexane 95 L / h, and the rate is 146 L / h. Was introduced into the polymerization vessel 2. The organoaluminum compound was introduced at 47 mmol / h in terms of Al atoms. The sum of the volume of the solvent in the polymerization vessel and the volume of the copolymer of ethylene and α-olefin measured by a liquid level meter using γ-ray is 146 L, and the solvent, ethylene and α-olefin are removed from the polymerization vessel. The volume per volume at which the copolymer was extracted constantly was 157 L / h. Therefore, the average residence time in the first stage was 0.90 hours. From the polymerization vessel 2, a polyethylene composition comprising a low molecular weight component and a high molecular weight component was withdrawn at a rate of 20 kg / h.

  In the polymerization vessel 2, the organoaluminum compound was introduced at a rate of 47.5 mmol / hr in terms of Al atoms under the conditions of a temperature of 70 ° C. and a pressure of 0.2 MPa. To this, ethylene, hydrogen, 1-butene, total pressure 0.2 MPa, hydrogen gas phase concentration 1.3 mol%, 1-butene gas phase concentration 4.3 mol%, ethylene supply amount and 1-butene The weight ratio of the low molecular weight portion produced in the polymerization vessel 1 to the high molecular weight portion produced in the polymerization vessel 2 (high molecular weight portion) / The high molecular weight portion was polymerized so that (low molecular weight portion) was 45/55.

A powdery polyethylene resin composition having a powdery MFR5 of 0.88 g / 10 min and a density of 950 kg / m ³ was produced.

Thereafter, extrusion was performed in the same manner as in Example 1 to obtain pellets having an MFR5 of 0.37 g / 10 min and a density of 950 kg / m ³ . Evaluation was performed in the same manner as in Example 1, and the results are shown in Table 1. The relationship between time and hoop pressure is shown in FIG. In FIG. 3, a plot of less than 1000 hours is indicated by ♦, a plot after 1000 hours is indicated by □, and each plot line is indicated by a straight line.

[Comparative Example 2]
The melt flow rate (MFR 2.16) of the low molecular weight component produced in the polymerization vessel 1 is 200 g / 10 min. The weight ratio of the low molecular weight portion produced in the polymerization vessel 1 to the high molecular weight portion produced in the polymerization vessel 2 (high Comparative Example 1 except that a powdered polyethylene having a molecular weight part) / (low molecular weight part) of 50/50, MFR5 in powder form of 0.44 g / 10 min and density of 952 kg / m ³ was produced. A pellet having an MFR5 of 0.22 g / 10 min and a density of 952 kg / m ³ was obtained. The measurement results are shown in Table 1. FIG. 4 shows the relationship between time and hoop pressure. In FIG. 4, plots of less than 1000 hours are indicated by ♦, plots after 1000 hours are indicated by □, and each plot line is indicated by a straight line.

[Comparative Example 3]
Polymerization is performed in the polymerization vessel 1 at a pressure of 8.0 kg / cm ³ G and a hydrogen concentration of 65%, and in the polymerization vessel 2, 2.4 kg / cm ³ G, a hydrogen concentration of 1.6%, and a 1-butene concentration of 9.7%. Polymerized as. The proportion of the production amount of the low molecular weight component (A) composed of the ethylene homopolymer obtained in the polymerizer 1 is 60 wt%, and the proportion of the production amount of the high molecular weight component (B) composed of the copolymer obtained in the polymerizer 2 is The MFR5 in the pellet was 0 in the same manner as in Example 1 except that a powdery polyethylene having an MFR5 in the powder form of 1.46 g / 10 min and a density of 950 kg / m ³ was produced by setting the powder to 40 wt%. A pellet with a density of 950 kg / m ³ was obtained at .51 g / 10 min. The measurement results are shown in Table 1.

  The polyethylene resin composition of the present invention is excellent in physical properties and long-term characteristics when used as a pipe, and productivity when used as a joint, and as a material for pipes and joints of water supply and sewerage, agricultural pipes and various transport pipes, etc. Is optimal.

[1]
Homopolymers of ethylene, and comprises a copolymer of ethylene and an α- olefin having 3 to 20 carbon atoms, the following (1) to (5) meet, 100-year warranty polyethylene piping materials for polyethylene resin composition.
(1) The density is 946 to 953 kg / m ³ .
(2) The melt flow rate (code T) is 0.15 to 0.50 g / 10 min.
(3) The molecular weight distribution is 15-40.
(4) In the hot internal pressure creep test at 20 ° C. specified by ISO 9080, the ratio of the slope of the plot line of the logarithm of the hoop pressure to the logarithm of the fracture time has the following relationship.
Slope less than 1000 hours / Slope after 1000 hours> 1.5
(5) In the correlation of molecular weight-elution temperature-elution amount obtained by cross-fractionation between temperature-programmed elution fractionation and gel permeation chromatography, the cumulative elution amount of elution components with molecular weight of 200,000 or more and elution temperature of 85 ° C. or less The ratio (R, unit: wt%) to the total accumulated elution amount is 1.0 wt% or more.
[2]
An ethylene homopolymer and / or a copolymer of ethylene and an α-olefin having 3 to 20 carbon atoms, a density of 967 to 977 kg / m ³ , and a melt flow rate (Code D) of 40 to 300 g / 48-60 parts by mass of polyethylene resin, which is 10 minutes,
A polyethylene resin having a copolymer of ethylene and an α-olefin having 3 to 20 carbon atoms, a density of 895 to 949 kg / m ³ , and a weight average molecular weight of 500,000 to 1,000,000. Including 52 parts by mass,
The polyethylene resin composition according to the preceding item [1].
[3]
Obtained by a two-stage polymerization method in which an ethylene homopolymer is produced in a first-stage polymerization tank, and a copolymer of ethylene and an α-olefin having 3 to 20 carbon atoms is produced in a second-stage polymerization tank. The polyethylene resin composition according to [1] or [2].
[4]
An organomagnesium compound (i) soluble in a hydrocarbon solvent represented by the following formula (1) and a chlorosilane compound (ii) represented by the following formula (2) are mixed in a (ii) / (i) molar ratio of 0.00. The reaction is carried out in the range of 01 to 100 to obtain a solid (A-1a),
0.01-1 mol of alcohol (A-2) is reacted with 1 mol of C—Mg bond contained in the solid (A-1a) to obtain a solid (A-1b),
The solid (A-1b) is reacted with an organometallic compound (A-3) represented by the following formula (3) to obtain a solid (A-1c).
The above-mentioned item obtained by using the polymerization catalyst containing the solid catalyst component [A] and the organoaluminum compound [B] obtained by supporting the titanium compound (A-4) on the solid (A-1c). The polyethylene resin composition according to any one of [1] to [3].
(Al) _a (Mg) _b (R ¹ ) _c (R ² ) _d (OR ³ ) _e Expression (1)
(In the formula (1), R ¹ , R ² and R ³ are hydrocarbon groups having 2 to 20 carbon atoms, and a, b, c, d and e are numbers satisfying the following relationship: 0 ≦ a , 0 <b, 0 ≦ c, 0 ≦ d, 0 ≦ e, 0 <c + d, 0 ≦ e / (a + b) ≦ 2, 3a + 2b = c + d + e)
H _h SiCl _i R ⁴ _{4- (h + i)} (2)
(In the formula (2), R ⁴ is a hydrocarbon group having 1 to 20 carbon atoms, and h and i are numbers satisfying the following relationship: 0 <h, 0 <i, h + i ≦ 4)
AlR ⁵ _s Q _3-s ... Formula (3)
(In the formula (3), R ⁵ is a hydrocarbon group having 1 to 20 carbon atoms, and Q is selected from the group consisting of OR ⁶ , OSiR ⁷ R ⁸ R ⁹ , NR ¹⁰ R ¹¹ , SR ¹² and halogen. R ⁶ , R ⁷ , R ⁸ , R ⁹ , R ¹⁰ , R ¹¹ , R ¹² are hydrogen atoms or hydrocarbon groups, and s is a number that satisfies the following relationship: 0 <s <3 )
[5]
The polyethylene resin composition according to any one of [1] to [4] above, which is for polyethylene piping material.
[6]
A pipe comprising the polyethylene resin composition according to any one of [1] to [5] above.
[7]
A pipe joint comprising the polyethylene resin composition according to any one of [1] to [5] above.
[8]
The pipe according to [6] above, which is for water supply.
[9]
The pipe joint according to [7], which is for water supply.

Claims (9)

A polyethylene resin composition comprising an ethylene homopolymer and / or a copolymer of ethylene and an α-olefin having 3 to 20 carbon atoms and satisfying the following (1) to (4).
(1) The density is 946 to 953 kg / m ³ .
(2) The melt flow rate (code T) is 0.15 to 0.50 g / 10 min.
(3) The molecular weight distribution is 15-40.
(4) In the hot internal pressure creep test at 20 ° C. specified by ISO 9080, the ratio of the slope of the plot line of the logarithm of the hoop pressure to the logarithm of the fracture time has the following relationship.
Slope less than 1000 hours / Slope after 1000 hours> 1.5 An ethylene homopolymer and / or a copolymer of ethylene and an α-olefin having 3 to 20 carbon atoms, a density of 967 to 977 kg / m ³ , and a melt flow rate (Code D) of 40 to 300 g / 48-60 parts by mass of polyethylene resin, which is 10 minutes,
A copolymer of ethylene and an α-olefin having 3 to 20 carbon atoms, having a density of 895 to 949 kg / m ³ and a weight average molecular weight of 500,000 to 1,000,000,
Including 40 to 52 parts by mass of polyethylene resin,
The polyethylene resin composition according to claim 1.   Obtained by a two-stage polymerization method in which an ethylene homopolymer is produced in a first stage polymerization tank, and a copolymer of ethylene and an α-olefin having 3 to 20 carbon atoms is produced in a second stage polymerization tank. Item 3. The polyethylene resin composition according to Item 1 or 2. An organomagnesium compound (i) soluble in a hydrocarbon solvent represented by the following formula (1) and a chlorosilane compound (ii) represented by the following formula (2) are mixed in a (ii) / (i) molar ratio of 0.00. The reaction is carried out in the range of 01 to 100 to obtain a solid (A-1a),
0.01-1 mol of alcohol (A-2) is reacted with 1 mol of C—Mg bond contained in the solid (A-1a) to obtain a solid (A-1b),
The solid (A-1b) is reacted with an organometallic compound (A-3) represented by the following formula (3) to obtain a solid (A-1c).
It is obtained using a polymerization catalyst containing the solid catalyst component [A] and the organoaluminum compound [B] obtained by loading the solid (A-1c) with the titanium compound (A-4). Item 4. The polyethylene resin composition according to any one of Items 1 to 3.
(Al) _a (Mg) _b (R ¹ ) _c (R ² ) _d (OR ³ ) _e Expression (1)
(In the formula (1), R ¹ , R ² and R ³ are hydrocarbon groups having 2 to 20 carbon atoms, and a, b, c, d and e are numbers satisfying the following relationship: 0 ≦ a , 0 <b, 0 ≦ c, 0 ≦ d, 0 ≦ e, 0 <c + d, 0 ≦ e / (a + b) ≦ 2, 3a + 2b = c + d + e)
H _h SiCl _i R ⁴ _{4- (h + i)} (2)
(In the formula (2), R ⁴ is a hydrocarbon group having 1 to 20 carbon atoms, and h and i are numbers satisfying the following relationship: 0 <h, 0 <i, h + i ≦ 4)
AlR ⁵ _s Q _3-s ... Formula (3)
(In the formula (3), R ⁵ is a hydrocarbon group having 1 to 20 carbon atoms, and Q is selected from the group consisting of OR ⁶ , OSiR ⁷ R ⁸ R ⁹ , NR ¹⁰ R ¹¹ , SR ¹² and halogen. R ⁶ , R ⁷ , R ⁸ , R ⁹ , R ¹⁰ , R ¹¹ , R ¹² are hydrogen atoms or hydrocarbon groups, and s is a number that satisfies the following relationship: 0 <s <3 )   The polyethylene resin composition according to any one of claims 1 to 4, which is used for a polyethylene piping material.   The pipe containing the polyethylene resin composition of any one of Claims 1-5.   The joint of a pipe containing the polyethylene resin composition of any one of Claims 1-5.   The pipe according to claim 6, which is used for water supply.   The pipe joint according to claim 7, which is used for water supply.