JP2007002235A - Polyethylene resin, method for producing the same, and pipe and joint produced by using the resin - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polyethylene resin having excellent slow crack growth, a method for producing the resin and a resin especially useful for pipes and joints. <P>SOLUTION: The polyethylene resin and its production method can be achieved by satisfying the formula logT≥-2.9×logHLa+5.1×logCa+6.8 wherein (a) HLa is a specific high-load melt flow rate (HLMFR), (b) Da is a specific density, (c) Ca is a specific α-olefin content and (d) T is a breaking time measured by notched Lander ESCR. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention relates to a polyethylene resin, and particularly relates to a resin excellent in durability for pipe use, a method for producing the same, and a pipe and a joint made thereof. More specifically, the present invention relates to a polyethylene resin particularly suitable for water distribution pipes and excellent in low-speed crack growth (SCG), a method for producing the same, and a pipe and a joint made thereof.
In addition, the polyethylene resin and pipes and joints obtained by the method of the present invention are excellent in the balance between molding processability and rigidity and the mechanical properties of SCG, and are excellent in homogeneity, so that water pipes, sewer pipes, rehabilitation pipes, etc. Suitable for a wide range of pipe applications.

Polyethylene resin is excellent in molding processability and various physical properties, and is highly economical and adaptable to environmental problems. Therefore, it is used as a material in a very wide technical field and is used for a wide range of applications. One field of its use is the pipe field, and its use for gas pipes, water distribution pipes, etc. is increasing based on the track record of durability during earthquakes.
The resin currently used for gas pipes and water distribution pipes needs to satisfy excellent long-term durability such as PE80 (MRS: Minimum Required Strength = 8 MPa) and PE100 (MRS = 10 MPa) defined by ISO 9080 and ISO 12162. Recently, due to changes in the pipe laying construction method, even if the surface of the molded pipe is damaged, it has excellent long-term durability, that is, slow crack growth such as the notched pipe test defined in ISO 13479 (Slow Crack Growth). = SCG), an excellent polyethylene resin has been demanded.

These polyethylene resins for pipes are manufactured by copolymerization of ethylene and α-olefin by multistage polymerization in the presence of a Philips catalyst or Ziegler catalyst. Durability is difficult, and highly durable polyethylene resin for water distribution pipes that satisfies PE100 is produced exclusively by the latter Ziegler catalyst.
Polyethylene resin for pipes obtained by copolymerization of ethylene and α-olefin by multi-stage polymerization using Ziegler catalyst has many prior arts, but satisfies the standards of PE100 and has SCG, rigidity, fluidity, homogeneity It is very difficult to produce a polyethylene resin excellent in

For example, although an ethylene polymer composed of a high molecular weight component and a low molecular weight component in which a comonomer is selectively introduced on the high molecular weight side, a polyethylene pipe excellent in stress crack resistance and fracture toughness has been proposed (Patent Document 1). It is inferior in the balance between fluidity and stress crack resistance, and if it is attempted to increase the stress crack resistance, the fluidity is inferior.
JP-A-8-301933

In addition, polyethylene resins and pipes and pipe joints focusing on tie molecules have been presented (Patent Documents 2 to 6). However, since SCG is not determined solely by tie molecules, the tie molecule existence probability (Patent Document 2) and Even if the tie molecule formation probability (Patent Documents 3 and 4) is high, the SCG is not high. Japanese Patent Laid-Open No. 2000-109521 (Patent Document 5) presents a polyethylene pipe satisfying the relationship that there is a component amount having a molecular weight of 100,000 or more by cross fractionation and an elution temperature of 90 ° C. or more (Patent Document 5). Although a multimodal polyethylene for producing a high molecular weight ethylene copolymer after a low molecular weight component ethylene homopolymer has been proposed (Patent Document 6), both examples use 1-butene as a comonomer, The balance of SCG is inferior.
Japanese Patent Laid-Open No. 9-286820 JP-A-11-228635 JP 2003-64187 A JP 2000-109521 A Japanese translation of PCT publication No. 2003-519496

Therefore, recently, polyethylene using 1-hexene as a comonomer in bimodal polyethylene composed of a low molecular weight component and a high molecular weight component has been proposed (Patent Documents 7 to 8), and improvement of SCG is expected. However, the examples in each of these patent documents are so-called reverse two-stage polymerizations in which a low molecular weight ethylene homopolymer is first produced and then a high molecular weight ethylene / 1-hexene copolymer is produced. Compared to so-called sequential two-stage polymerization for producing low molecular weight, there is a disadvantage that the equipment for purging unreacted hydrogen after production of the low molecular weight component is necessary, and the homogeneity of mixing of the low molecular weight component and the high molecular weight component is inferior. is doing.
Special table 2003-504442 Special table 2003-53233 gazette

In addition to the Ziegler catalyst, a polyethylene pipe comprising a high molecular weight component and a low molecular weight component in which the slope of the linear approximation of the temperature-molecular weight of cross fractionation is -0.5 to 0 using a metallocene catalyst is disclosed in Although it is proposed in 199719 (Patent Document 9), it is a metallocene catalyst, the molecular weight distribution of each component is narrower than Ziegler catalyst, and is inferior in moldability and homogeneity.
JP 11-199719 A

  Under such circumstances, the subject of the present invention is polyethylene that not only satisfies PE100 in the field of pipes, particularly water distribution pipes, but also has excellent low-speed crack growth (SCG) and sufficient fluidity, homogeneity, etc. The present invention provides a resin, a production method thereof, and a pipe / joint using the resin.

In order to solve such problems, the present inventors preferably specify various physical properties of a polyethylene-based polymer, make a composition of the polymer, and copolymerize or copolymerize with an α-olefin in a polyethylene resin using a Ziegler catalyst. The material which can solve said subject was calculated | required considering and examined focusing on the combination of a polymer. As a result, polyethylene resin with HLMFR and density range specified, fracture time by notched Lander method-ESCR specified as HLMFR and α-olefin content is effective in solving problems, and excellent physical properties as pipes and joints It was found to have
That is, the polyethylene resin of the present invention has a constitution that defines HLMFR, density and α-olefin content and is specified by a notched Lander method-ESCR, and more preferably a specific α-olefin copolymer in this resin. It is also characterized by combining the coalescence and using a specific multistage polymerization method, and particularly satisfies the PE100 in a pipe molded product and enables a very excellent SCG.
The present invention will be described in detail below.

[1] A first aspect of the present invention is (A) a polyethylene resin for pipes that satisfies the following requirements (a) to (d).
(A) High load melt flow rate (HLMFR, HLa) is 5 to 20 g / 10 min. (B) Density (Da) is 0.945 to 0.965 g / cm ^3.
(C) α-olefin content (Ca) of 0.05 to 1.5 mol%
(D) Notched Lander method-ESCR destruction time (T), HLa and Ca satisfy the following formula: logT ≧ −2.9 × logHLa + 5.1 × logCa + 6.8
[2] A second aspect of the present invention is a polyethylene resin characterized in that the (A) polyethylene resin is composed of the following polyethylene polymers (B) and (C).
(B) Polyethylene polymer having an HLMFR (HLb) of 0.01 to 3 g / 10 min and an α-olefin content (Cb) other than ethylene of 3.0 mol% or less is a polymerization amount ratio (Xb) of 20 to 60 weights. % Percentage,
(C) A polyethylene polymer having an MFR (MFRc) of 1 to 1000 g / 10 min and an α-olefin content (Cc) other than ethylene of 0.5 mol% or less is a polymerization amount ratio (Xc) of 40 to 80% by weight. Percentage

[3] A third aspect of the present invention is a polyethylene resin in which the main α-olefin having the largest content of the polyethylene polymer has 6 or more carbon atoms.
[4] The fourth aspect of the present invention is that the polyethylene resin (A) satisfies the relationship of α-olefin content in the low molecular weight component / α-olefin content in the high molecular weight component ≦ 0.20. It is.
[5] The fifth aspect of the present invention is that a chain in which two α-olefins are continuous (Tβδ) and a chain in which α-olefins are isolated with respect to the main α-olefin having the highest content in the ethylene polymer ( The polyethylene resin is characterized in that a value obtained by further dividing the ratio of Tδδ) by the α-olefin content is 0.15 or less.
[6] In the sixth aspect of the present invention, the polyethylene resin (A) first produces a high molecular weight component, and then transfers the reaction liquid containing the high molecular weight component to the next polymerization reactor as it is to produce a low molecular weight component. It is a polyethylene resin characterized by being produced by sequential multistage polymerization.
[7] A seventh aspect of the present invention is the polyethylene resin, wherein the (A) polyethylene resin is obtained by multistage polymerization using a Ziegler catalyst.
[8] An eighth aspect of the present invention is a polyethylene resin characterized in that (d) the fracture time (T) by notched Lander method-ESCR, HLa and Ca satisfy the following formula.
T ≧ 10 ^ (− 2.9 × log HLa + 5.1 × log Ca + 6.8) +50
[9] A ninth aspect of the present invention is a pipe and joint formed using the polyethylene resin according to any one of [1] to [8].

[10] A tenth aspect of the present invention is a polymerization apparatus in which two or more reactors are connected in series using a Ziegler catalyst containing at least titanium and magnesium. (B) HLMFR (HLb) of 0.01 to 3 g / 10 min and α-olefin content other than ethylene (Cb) of 3.0 mol% or less is a polymerization amount ratio (Xb) of 20 to 60 The reaction solution containing the high molecular weight component was transferred to the next reactor as it was, and the low molecular weight component (C) MFR (MFRc) was 1-1000 g / 10 minutes and the content of α-olefin other than ethylene A polyethylene polymer having a (Cc) of 0.5 mol% or less is continuously subjected to suspension polymerization at a polymerization amount ratio (Xc) of 40 to 80% by weight. (A) is a method for producing a polyethylene resin for pipes, which satisfies the following requirements (a) to (d).
(A) High load melt flow rate (HLMFR, HLa) is 5 to 20 g / 10 min. (B) Density (Da) is 0.945 to 0.965 g / cm ^3.
(C) α-olefin content (Ca) of 0.05 to 1.5 mol%
(D) Notched Lander method-ESCR destruction time (T), HLa and Ca satisfy the following formula: logT ≧ −2.9 × logHLa + 5.1 × logCa + 6.8
[11] The method for producing a polyethylene resin, wherein a main α-olefin having the largest content among the α-olefins of the ethylene-based polymer has 6 to 12 carbon atoms.
[12] A method for producing a polyethylene resin, wherein the (d) notched Lander method-breaking time (T) by ESCR, HLa, and Ca satisfy the following formula.
T ≧ 10 ^ (− 2.9 × log HLa + 5.1 × log Ca + 6.8) +50

  The polyethylene resin of the present invention has very high durability for fluidity (HLMFR) and α-olefin content (influence on density, index of rigidity), and in the field of pipes, particularly water distribution pipes, PE100 In addition to satisfying the above, it is possible to provide a pipe and a joint that are excellent in low-speed crack growth (SCG) and excellent in fluidity, moldability, rigidity, and homogeneity.

Since the present invention has been generally described along the basic configuration of the present invention as means for solving the problem, embodiments of the present invention will be described in detail below.
1. (A) Constituent Elements in Polyethylene Resin The properties of the (A) polyethylene resin of the present invention are as follows: (a) High load melt flow rate (HLMFR, HLa) is 5 to 20 g / 10 min, (b) Density (Da) is 0 945 to 0.965 g / cm ³ , (c) α-olefin content (Ca) of 0.05 to 1.5 mol%, and (d) Notched Lander method—destruction time (T) by ESCR and HLa It is necessary to satisfy the requirement that Ca satisfies the following formula.
log T ≧ −2.9 × log HLa + 5.1 × log Ca + 6.8

(1) HLMFR
The polyethylene resin (A) of the present invention has (a) a high load melt flow rate (HLMFR, HLa) measured at a temperature of 190 ° C. and a load of 21.6 kgf, 5 to 20 g / 10 minutes, preferably 7 to 15 g / 10 minutes. Should be in the range.
If the HLMFR is less than 5 g / 10 min, the fluidity decreases, and if it exceeds 20 g / 10 min, the long-term durability such as SCG and the notched Lander method-ESCR and the sag (sag characteristics) during pipe forming may be inferior. Arise.
The high load melt flow rate is measured at a temperature of 190 ° C. and a load of 211.82 N according to Table 1-Condition 7 of JIS K-7210 (1996 edition).
The high load melt flow rate can be increased or decreased by changing the polymerization temperature or the amount of chain transfer agent. That is, by increasing the polymerization temperature of ethylene and α-olefin, the molecular weight can be decreased and as a result, the high load melt flow rate can be increased, and by decreasing the polymerization temperature, the molecular weight can be increased and as a result, the high load melt flow rate can be increased. Can be reduced. In addition, by increasing the amount of hydrogen (chain transfer agent) that coexists in the copolymerization reaction of ethylene and α-olefin, the molecular weight can be lowered and as a result, the high load melt flow rate can be increased. By reducing the (chain transfer agent amount), the molecular weight can be increased and, as a result, the high load melt flow rate can be reduced.

(2) Density of the present invention (A) a polyethylene resin has a density (Da) is 0.945~0.965g / cm ^3, preferably should be in the range of 0.947~0.960g / cm ^3.
When the density is less than 0.945 g / cm ³ , the rigidity is lowered, and when it exceeds 0.965 g / cm ³ , long-term durability such as SCG or notched Lander method-ESCR may be deteriorated.
The density is measured according to JIS K-7112 (1996 edition).
The density can be increased or decreased by increasing or decreasing the amount of α-olefin (number of short chain branches) copolymerized with ethylene.

(3) α-olefin content The (A) polyethylene resin of the present invention has an α-olefin content (Ca) in the range of 0.05 to 1.5 mol%, preferably 0.1 to 1.0 mol%. Should.
If the α-olefin content is 0.05 mol% or less, long-term durability such as SCG and notched Lander-ESCR is lowered, and if it exceeds 1.5 mol%, the rigidity may be inferior. The α-olefin content mentioned here includes not only the α-olefin fed to the reactor and copolymerized during polymerization, but also short-chain branches (for example, ethyl branches and methyl branches) due to by-products.
The α-olefin content is measured by 13C-NMR.
The α-olefin content can be increased or decreased by increasing or decreasing the supply amount of α-olefin to be copolymerized with ethylene.

(4) Notdered Lander method-ESCR
In the polyethylene resin (A) of the present invention, it is necessary that the fracture time (T) by notched Lander method-ESCR, HLMFR (HLa), and α-olefin content (Ca) satisfy the following relational expression.
log T ≧ −2.9 × log HLa + 5.1 × log Ca + 6.8
Preferably, log T ≧ −2.9 × log HLa + 5.1 × log Ca + 6.9.

Therefore, the present inventors have come up with a notched Lander method-ESCR that has a good correlation with the notched pipe test and can be evaluated in a short time with a small amount of sample. Although the correlation of both data is shown in FIG. 1, it is a fairly good correlation, the notched Lander method-ESCR can be used as a long-term durability evaluation method, and the fracture time (T) is an index of long-term durability. . Furthermore, the present inventors examined the relationship between the fracture time of the notched Lander method-ESCR and the HLMFR and α-olefin contents. That is, if the HLMFR is generally low (= high molecular weight) or the α-olefin content is increased, the fracture time of the notched Lander method-ESCR, which is an indicator of long-term durability, is improved. This results in a decrease in rigidity. And in order to have not only excellent SCG but also excellent fluidity and rigidity over polyethylene currently used as a polyethylene resin for pipes, from a comparative study including currently used polyethylene shown in a comparative example, It has been found that the above formula should be satisfied.
Here, the notched Lander method-ESCR is a constant stress environmental stress crack test apparatus stipulated in JIS K 6922-2: 1997 annex, the test temperature is 80 ° C., and the test solution is 1 wt%. A higher alcohol sodium sulfonate aqueous solution is used, and an initial tensile stress is measured at 60 kg / cm ^{2. A} 1 mm thick and 6 mm wide press sheet is used as a test piece, and 0.4 mm in the central thickness direction of the tensile portion. Using a leather notch, the time to break is measured.
This test method correlates with the notched pipe test method specified in ISO13479. FIG. 1 and Table 3 show the relationship between both data of notched Lander-ESR and notched pipe tests defined in ISO 13479 for various polyethylene samples.

In the above data sample, A is the high-density polyethylene of Example 4 described later. B to F are high density polyethylenes made by conventional techniques. The high load melt flow rate (HLMFR) and density of each sample are as follows.
Sample A: HLMFR = 12 g / 10 min, density = 0.951 g / cm ³
Sample B: HLMFR = 11 g / 10 min, density = 0.948 g / cm ³
Sample C: HLMFR = 26 g / 10 min, density = 0.948 g / cm ³
Sample D: HLMFR = 13g / 10 min, density = 0.954 g / cm ³
Sample E: HLMFR = 10 g / 10 min, density = 0.952 g / cm ³
Sample F: HLMFR = 9.9 g / 10 min, density = 0.951 g / cm ³
As can be seen from FIG. 1, the two data have a fairly good correlation, and the fracture time (T) according to this test method is an index of long-term durability, and can be used sufficiently as an evaluation method for long-term durability.
The fracture time (T) by the notched Lander method-ESCR of the present invention is 100 hours or longer, preferably 200 hours or longer, more preferably 300 hours or longer. When the value of T is less than 100 hours, the value in the notched pipe test is less than about 1200 hours, and the SCG remains uneasy. When the value of T is less than 100 hours and less than 1200 hours, the characteristics as a pipe can be expressed.

In general, the relationship between long-term durability (notched Lander method-ESCR fracture time (T)), high load melt flow rate (HLa), and α-olefin content (Ca) is low in HLa (= high in molecular weight). ) Or as Ca increases, the value of T, which is an indicator of long-term durability, increases (is improved). That is, if the material is designed so that the value of the relational expression on the right side of the above formula increases, the long-term durability will increase. Therefore, satisfying the above formula means that excellent fluidity and rigidity can be achieved while maintaining excellent long-term durability.
The relationship between the fracture time (T) by the notched Lander method-ESCR of the present invention, the high load melt flow rate (HLa), and the α-olefin content (Ca) preferably satisfies the following formula. This formula clearly distinguishes between a region that cannot be achieved by a conventionally known material and a region that can achieve an excellent effect in the present invention in terms of long-term durability. Incidentally, the area | region distinguished by this type | formula and the graph which plotted the Example and the comparative example data are shown in FIG.
T ≧ 10 ^ (− 2.9 × log HLa + 5.1 × log Ca + 6.8) +50
A method for controlling the fracture time (T) by the notched Lander method-ESCR and a method for satisfying the above formula will be described later.

2. (A) Identification of Component in Polyethylene Resin (1) Identification of Component (A) The polyethylene resin of the present invention is basically composed of a polymer alone that satisfies the above requirements, has a wide molecular weight distribution, and is on the high molecular weight side. This satisfies the condition that more α-olefin is introduced.
As another aspect, it is preferably composed of the following two types of (B) polyethylene polymer component and (C) component by multistage polymerization of a Ziegler catalyst.
(B) Polyethylene polymer having an HLMFR (HLb) of 0.01 to 3 g / 10 min and an α-olefin content (Cb) other than ethylene of 3.0 mol% or less is a polymerization amount ratio (Xb) of 20 to 60 weights. % Percentage,
(C) A polyethylene polymer having an MFR (MFRc) of 1 to 1000 g / 10 min and an α-olefin content (Cc) other than ethylene of 0.5 mol% or less is a polymerization amount ratio (Xc) of 40 to 80% by weight. Percentage

Examples of specific polymers of the polyethylene resin (A) of the present invention include ethylene-propylene copolymer, ethylene-1-butene copolymer, ethylene-1-pentene copolymer, and ethylene-1-hexene copolymer. Examples thereof include a polymer, an ethylene-4-methyl-1-pentene copolymer, an ethylene-1-octene copolymer, and an ethylene-1-decene copolymer. A plurality of these may be used.
The density (Da) of this (A) polyethylene resin is in the range of 0.945 to 0.965 g / cm ³ , preferably 0.947 to 0.960 g / cm ³ as described above. In terms of molecular weight, a number average molecular weight of about 5000 to 40000 is used.

  One of the embodiments of the (A) polyethylene resin is a comparatively different one from a substantially higher molecular weight polyethylene component (also referred to as “(B) polyethylene polymer component”). It is composed of at least two kinds of polyethylene components composed of a polyethylene component having a low molecular weight (also referred to as “(C) polyethylene polymer component”). This is composed of two or more types of polyethylene component (A) polyethylene resin is prepared by polymerizing (B) polyethylene polymer component prepared in advance and (C) polyethylene polymer component polyethylene by conventional polymer blend. it can. Of course, the polymer composition comprising the (B) polyethylene polymer component and the (C) polyethylene polymer component includes various other general-purpose polyethylenes, ethylene-propylene copolymers, and ethylene-propylene as the third component. The inclusion of a diene copolymer, natural rubber, synthetic rubber and the like can be blended within a range that does not change the properties of the polyethylene resin for pipes.

  However, (A) One of the practical methods for producing a polyethylene resin is that in a multi-stage polymerization step in a reactor, (B) a polyethylene-based polymer component is prepared in the previous step in advance, and (C) polyethylene-based in the next step. By adjusting the polymer component, it can be achieved by a method in which both components are blended in an appropriate amount in the final step. The composition ratio of the (B) polyethylene polymer component and the (C) polyethylene polymer component can be arbitrarily changed. However, in order to properly express the characteristics as a pipe in a specific application for a pipe. The composition ratio naturally has an appropriate range. The formulation depends solely on the polymerization process and, depending on the adjustment, some of the (B) polyethylene polymer component and (C) polyethylene polymer component do not belong to any of them. Other polyethylene-based polymer components may be mixed, but it is not a problem that they are mixed in a slight proportion that does not hinder the properties for pipes.

(2) Component (B) In the (B) polyethylene polymer which is the component (B) of the present invention, the HLMFR (HLb) measured at a temperature of 190 ° C. and a load of 21.6 kgf is 0.01 to 3 g / 10. Minutes, preferably 0.02 to 1 g / 10 min. Moreover, alpha-olefin content (Cb) should be 3.0 mol% or less, Preferably, it exists in the range of 0.1-2.0 mol%. When the amount of α-olefin is more than 3.0 mol%, the density of the polyethylene resin is lowered and the rigidity may be lowered.
If the HLb is less than 0.01, the fluidity is deteriorated and the dispersion is poor. If the HLb is more than 3, the long-term durability such as SCG or notched Lander ESCR and the sag (sag characteristics) may be inferior. Arise.
The high load melt flow rate is measured at a temperature of 190 ° C. and a load of 211.82 N according to Table 1-Condition 7 of JIS K-7210 (1996 edition).
The high load melt flow rate can be increased or decreased by changing the polymerization temperature or the amount of chain transfer agent.
The α-olefin content is measured by 13C-NMR.
The α-olefin content can be increased or decreased by increasing or decreasing the supply amount of α-olefin to be copolymerized with ethylene.

If the concrete thing of the (B) polyethylene-type polymer of this invention is illustrated, the alpha-olefin content (Cb) will be 3.0 mol% or less, ethylene-propylene copolymer, ethylene-1-butene copolymer weight Examples thereof include a copolymer, an ethylene-1-pentene copolymer, an ethylene-1-hexene copolymer, an ethylene-4-methyl-1-pentene copolymer, and an ethylene-1-octene copolymer. Examples of these are binary and ternary copolymers used in plural.
As described above, the density (Db) of the polyethylene polymer (B) is preferably 0.910 to 0.940 g / cm ³ , preferably 0.915 to 0.935 g / cm ^3. Although it can be changed depending on the composition ratio with the other component (C), it is not limited to the density range. In terms of molecular weight, those having a number average molecular weight of about 10,000 to 300,000 are used. Preferably, those having a number average molecular weight of about 50,000 to 200,000 are used.

(3) (C) component In the (C) polyethylene polymer which is the (C) component of the present invention, the MFR (MFRc) measured at a temperature of 190 ° C and a load of 2.16 kgf is 1-1000 g / 10 min. Preferably, it should be in the range of 5 to 500 g / 10 min. The α-olefin content (Cb) should be in the range of 0.5 mol% or less, preferably 0.3 mol% or less. When the amount of α-olefin is more than 0.5 mol%, the density of the polyethylene resin is lowered and the rigidity may be lowered.
When MFRc is less than 1, fluidity is lowered, and when MFRc is more than 1000, long-term durability and impact strength such as SCG and notched Lander method ESCR may be deteriorated. The melt flow rate (hereinafter also referred to as “MFR”) is measured at a temperature of 190 ° C. and a load of 21.18 N according to Table 1-Condition 4 of JIS K-7210 (1996 edition).
The α-olefin content is measured by 13C-NMR.
The α-olefin content can be increased or decreased by increasing or decreasing the supply amount of α-olefin to be copolymerized with ethylene.

If the concrete thing of the (C) polyethylene-type polymer of this invention is illustrated, the alpha-olefin content (Cc) will be 0.5 mol% or less, ethylene-propylene copolymer, ethylene-1-butene copolymer weight Examples thereof include a copolymer, an ethylene-1-pentene copolymer, an ethylene-1-hexene copolymer, an ethylene-4-methyl-1-pentene copolymer, and an ethylene-1-octene copolymer. Examples of these are binary and ternary copolymers used in plural.
As described above, the density (Dc) of the polyethylene resin (C) can be suitably used within the range of 0.935 to 0.980 g / cm ³ , preferably 0.935 to 0.960 g / cm ^3. The property varies depending on the composition ratio with the other component (C), and is not limited to the density range. In terms of molecular weight, those having a number average molecular weight of about 1000 to 200000 are used. Preferably, those having a number average molecular weight of about 2000 to 10,000 are used.

(4) Blending ratio The blending ratio of the (B) component (B) polyethylene polymer and the (C) component (C) polyethylene polymer is (B) / (C) component: 20 to 60% by weight / 80. -40% by weight, preferably (B) / (C) component: 30-55% by weight / 70-45% by weight.
When the component (B) is less than 20% by weight and the component (C) exceeds 80% by weight, SCG may decrease, the component (B) exceeds 60% by weight, and the component (C) If it is less than 40% by weight, the fluidity may be lowered.

3. Kind of α-olefin of polyethylene resin Although the type of α-olefin constituting the (A) polyethylene resin in the present invention is not particularly limited as long as it is an α-olefin copolymerizable with ethylene, it has 3 to 12 carbon atoms. Typical examples include propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-octene and the like. A plurality of these may be used.
In a polyethylene resin based on a Ziegler catalyst, a plurality of short-chain branched species are often observed not only in the case of copolymerization of a plurality of α-olefins but also in the case of copolymerization of one type of α-olefin. This is due to a by-product. For example, the methyl branch contains propylene and the ethyl branch contains 1-butene in the α-olefin content.
And since the polyethylene resin in this invention becomes the outstanding low-speed crack progress (SCG), it is desirable for carbon number of the main alpha olefin to be the range of 6 or more and 12 or less. Here, the α-olefin mainly means an α-olefin having the largest number of short chain branches, for example, 1-hexene in the case of butyl branch and 1-butene in the case of ethyl branch. As the α-olefin having 6 or more carbon atoms, 1-hexene, 1-heptene, 1-octene, 1-decene, 4-methyl-1-pentene and the like are used.

4). Production of Polyethylene Resin (1) Production Method The polymerization catalyst and production method of the polyethylene resin (A) of the present invention are not particularly limited as long as the constituent requirements of the present invention are satisfied.
In order to satisfy the constituent requirements of the present invention with a polymer alone, that is, single-stage polymerization, it is only necessary to satisfy a molecular structure like multistage polymerization of Ziegler catalyst. Specifically, the molecular weight distribution is wide, and short chain branching by α-olefin copolymerization may be selectively introduced on the high molecular weight side. JP-A-2003-105016 can be cited as an example of such a catalyst.
In multi-stage polymerization of two or more stages, either a Ziegler catalyst or a metallocene catalyst may be used. In general, although a metallocene catalyst has a narrow composition distribution but a narrow molecular weight distribution, a Ziegler catalyst is preferably used. And the method of manufacturing continuously the (B) polyethylene polymer which is a high molecular weight (B) component and the (C) polyethylene polymer which is a low molecular weight (C) component by multistage polymerization is desirable.
In addition, Philips catalysts can be raised as a single-stage polymerization. However, since long-chain branching occurs in the molecular structure, there is a possibility that improvement in slow crack propagation (SCG) may not be expected. It is desirable.

(2) Ziegler catalyst The Ziegler catalyst used in the present invention is a well-known one. For example, JP-A-53-78287, JP-A-54-21383, JP-A-55-71707, The catalyst system described in each publication such as 58-225105 is used.
Specifically, a solid catalyst component obtained by contacting a tetravalent titanium compound with a co-pulverized product obtained by co-pulverizing aluminum trihalide, an organosilicon compound having a Si-O bond, and magnesium alcoholate And a catalyst system composed of an organoaluminum compound.
The solid catalyst component preferably contains 1 to 15% by weight of titanium atoms. As the organosilicon compound, those having a phenyl group or an aralkyl group, for example, diphenyldimethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, triphenylethoxysilane, triphenylmethoxysilane and the like are preferable.
In producing the co-ground product, the proportions of aluminum trihalide and organosilicon compound used per mol of magnesium alcoholate are generally 0.02 to 1.0 mol, particularly 0.05 to 0.20. Mole is preferred. The ratio of aluminum atoms of aluminum trihalide to silicon atoms of the organosilicon compound is preferably 0.5 to 2.0 molar ratio.
In order to produce a co-ground product, a conventional method is applied by using a grinding machine such as a rotating ball mill, a vibrating ball mill, and a colloid mill, which are generally used in producing this type of solid catalyst component. do it. The average particle size of the obtained co-ground product is usually 50 to 200 μm, and the specific surface area is 20 to ²⁰⁰ m ² / g.
A solid catalyst component is obtained by bringing the co-ground product obtained as described above and a tetravalent titanium compound into contact with each other in a liquid phase.
The organoaluminum compound used in combination with the solid catalyst component is preferably a trialkylaluminum compound, and examples thereof include triethylaluminum, trin-propylaluminum, trin-butylaluminum, and trii-butylaluminum.

(3) Polymerization The (A) polyethylene resin of the present invention may be the above homopolymer, but is preferably produced by multistage polymerization.
Thus, using the transition metal catalyst, the (B) polyethylene polymer that is the high molecular weight component (B) by multistage polymerization, and the (C) polyethylene polymer that is the low molecular weight component (C) (A) polyethylene resin of this invention is manufactured by manufacturing continuously.
One of the most preferable production methods of (A) polyethylene resin by multi-stage polymerization is a polymerization apparatus in which two or more reactors are connected in series using the above transition metal catalyst, and a high molecular weight in one or more reactors in the previous stage. (B) component is produced by continuous suspension polymerization of the low molecular weight component (C) in the subsequent reactor, or the low molecular weight component (C) and the high molecular weight component (B) in this order. Is the method. The former is called forward multi-stage polymerization, and the latter is called reverse multi-stage polymerization. In reverse multi-stage polymerization, equipment that purges unreacted hydrogen after the production of low molecular weight components is required. The mixture of low molecular weight components and high molecular weight components is homogeneous. The former sequential multi-stage polymerization is preferred because it has the disadvantage of being inferior in properties.
That is, in a polymerization apparatus in which two or more reactors are connected in series using a Ziegler catalyst containing at least titanium and magnesium, the high molecular weight component (B) HLMFR (HLb) is 0 in one or more reactors in the previous stage. 0.01 to 3 g / 10 min and α-olefin content other than ethylene (Cb) is 3.0 mol% or less, and (B) polyethylene polymer is produced in a polymerization amount ratio (Xb) of 20 to 60% by weight, The reaction liquid containing the high molecular weight component is transferred to the next reactor as it is, and the low molecular weight component (C) MFR (MFRc) is 1-1000 g / 10 min and the α-olefin content other than ethylene (Cc) is 0.5 mol. % Of (C) polyethylene polymer by continuous suspension polymerization at a polymerization amount ratio (Xc) of 40 to 80% by weight. (A) A method for producing a polyethylene resin, which satisfies the following requirements (a) to (d).
(A) High load melt flow rate (HLMFR, HLa) is 5 to 20 g / 10 min. (B) Density (Da) is 0.945 to 0.965 g / cm ^3.
(C) α-olefin content (Ca) of 0.05 to 1.5 mol%
(D) Notched Lander method-ESCR destruction time (T), HLa and Ca satisfy the following formula: logT ≧ −2.9 × logHLa + 5.1 × logCa + 6.8

[11] The method for producing a polyethylene resin according to (A), wherein the main α-olefin having the largest content among the α-olefins of the ethylene-based polymer has 6 to 12 carbon atoms.
The polymerization conditions in each reactor are not particularly limited as long as the desired components can be produced. Usually, the polymerization temperature is 50 to 110 ° C., and the pressure is 20 minutes to 6 hours. Depending on the type of solvent to be used, it is carried out at 0.2 to 10 MPa.
In a polymerization apparatus in which 2 or 3 pipe loop reactors are connected in series, a high molecular weight (B) component is continuously added to the preceding 1 or 2 reactors, and a low molecular weight (C) component is continuously added to the last 1 reactor. In the first and second stage reactors, the copolymerization of ethylene and α-olefin is carried out by the weight ratio or partial pressure ratio of the hydrogen concentration to the ethylene concentration, or the polymerization temperature. Alternatively, the polymerization reaction is carried out while adjusting the molecular weight by both, and adjusting the density by the weight ratio or partial pressure ratio of the α-olefin concentration to the ethylene concentration. Here, when the high molecular weight component is produced in two reactors, substantially the same high molecular weight component is produced in the first-stage and second-stage reactors.
In the last reactor, there are ethylene, hydrogen and α-olefin in the reaction mixture flowing from the reactor producing the first stage or second stage high molecular weight component, but the necessary ethylene or hydrogen is added. To manufacture.
The polymerization reaction mixture obtained by polymerization in the first stage reactor is transferred to the second stage reactor through the connecting pipe by a differential pressure, and when there are three reactors, the third reactor is further fed through the connecting pipe by a differential pressure. It is transferred to.
For polymerization, any method such as a slurry polymerization method in which polymer particles are dispersed in a solvent, a solution polymerization method in which polymer particles are dissolved in a solvent, or a gas phase polymerization method in which polymer particles are dispersed in a gas phase can be applied. .
Examples of the hydrocarbon solvent used in the slurry polymerization method and the solution polymerization method include propane, n-butane, isobutane, n-pentane, isopentane, hexane, heptane, octane, decane, cyclohexane, benzene, toluene, and xylene. Single or mixtures of activated hydrocarbons are used. In the case of slurry polymerization, propane, n-butane, and isobutane are preferable as the solvent in order to maintain the slurry state because the produced polyethylene polymer hardly dissolves in the solvent even when the polymerization temperature is raised.
In polymerization using a solid Ziegler catalyst, hydrogen is usually used as a so-called chain transfer agent for adjusting the molecular weight. The hydrogen pressure is not particularly limited, but is usually 1.0 × 10 ^{−5 to} 1.0 × 10 ⁻¹ wt%, preferably 5.0 × 10 ^{−4 to} 5 as the hydrogen concentration in the liquid phase. 0.0 × 10 ⁻² wt%.

(4) Blending method This blending method is a method in which a polymer blend consisting of a plurality of polymer components of different grades prepared by a multistage polymerization operation in a reactor is mixed to obtain a more uniform composition. It is to make a certain polyethylene resin for pipes. For example, a relatively high molecular weight (B) polyethylene-based polymer component is produced in the first step by a multistage polymerization operation, and in the next step, a relatively low molecular weight (C ) A material obtained by polymerizing a polyethylene polymer component is further mixed into a material having a uniform composition. If there is a non-uniform portion in the mixing of the component (B) and the component (C), it is feared that a non-uniform portion in the strength and the like is also generated in the pipe formed therefrom.
Furthermore, in order to increase the impact strength of the polyethylene resin at the blending stage, an ethylene copolymer such as E-P-R or E-P-D-M as a third component, a synthetic resin, or a synthetic rubber, if necessary. There is an advantage that the components can be easily adjusted such that various additives such as natural rubber, fillers, stabilizers, lubricants and the like can be arbitrarily selected and a predetermined amount can be blended. This blending method is preferably a method in which the degree of kneading is high. Conventional twin-screw extruders in the same direction or different directions, single-screw extruders, Banbury mixers, meshing or non-meshing continuous kneaders, Brabenders, Kneader Brabenders The blending method by etc. is mentioned.

(5) Control of notched Lander method-ESCR Control of requirements (a), (b) and (c) in the polyethylene resin satisfying the requirements (a) to (d) of claim 1 of the present invention. Although the method is a general method, in order to produce or control the polyethylene resin specified in the requirement (d), the following methods can be mentioned.
First, it is preferable that the molecular weight distribution is sufficiently wide. This is a necessary requirement for excellent notched Lander method-ESCR despite good flowability, that is, HLMFR is high, and it is preferable that the molecular weight distribution is double, but the high molecular weight component in the multistage polymerization of Ziegler catalyst. It can be easily realized by sufficiently separating the molecular weight of the low molecular weight component.
The molecular weight distribution is 10 to 50, preferably 15 to 40, as the ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) by gel permeation chromatography (GPC). If it is less than 10, it will be inferior to durability, such as the extrudability at the time of shaping | molding, and low-speed crack progress (SCG). On the other hand, if it exceeds 50, mechanical strength such as impact resistance is lowered, which is not preferable.
The molecular weight distribution can be adjusted by the type of catalyst in the polymerization of ethylene and α-olefin, the type of promoter, the polymerization temperature, the amount of chain transfer agent, the residence time in the polymerization reactor, the number of polymerization reactors, etc. It can be increased or decreased by adjusting the molecular weights of the high molecular weight component and the low molecular weight component and the mixing ratio thereof.
Next, with respect to the α-olefin, as is clear from the requirement (d), it is preferable to obtain a sufficient notched Lander method-ESCR while maintaining a small α-olefin content, that is, rigidity. According to the study by the present inventors, it was inferred that there are two factors as to when this is realized.
The first is that more α-olefin is introduced on the high molecular weight side. In the case of a polyethylene resin composed of a high molecular weight component and a low molecular weight component, the α-olefin content in the low molecular weight component / in the high molecular weight component It is desirable to satisfy the α-olefin content of ≦ 0.20. Here, the α-olefin content includes short chain branching due to by-products. In order to satisfy this in sequential multi-stage polymerization using a Ziegler catalyst, for example, a reactor in which α-olefin is highly copolymerized during production of a high molecular weight component and an unreacted α-olefin produces a low molecular weight component is used. You can reduce the amount that flows. Specifically, it can be controlled by using a Ziegler catalyst with excellent α-olefin copolymerization, increasing the polymerization temperature during production of high molecular weight components, or using multiple reactors for producing high molecular weight components. It is.

Second, the composition distribution of the copolymerized α-olefin is narrow. There are various methods for evaluating the composition distribution. For example, the ratio of the chain of two consecutive α-olefins and the chain of isolated α-olefins by 13C-NMR is further divided by the α-olefin content (= Tβδ / It was presumed that Tδδ / Ca (described later) preferably satisfies 0.15 or less. In calculating Tβδ / Tδδ / Ca, only the main α-olefin having the highest content is considered. As a method for achieving a value of 0.15 or less, a Ziegler catalyst that narrows the α-olefin composition distribution is used, and polymerization conditions that narrow the composition distribution particularly during the production of high molecular weight components (for example, increase the polymerization temperature). ) Etc. are considered.
In order to control the copolymerizability and composition distribution of these α-olefins, not only the polymerization conditions but also the selection of the Ziegler catalyst becomes important. Of the Ziegler catalysts mentioned above, JP-A-58-225105 can be shown as a suitable example.

(6) Additives, compounding agents In the polyethylene resin of the present invention, generally used antioxidants, heat stabilizers, light stabilizers, antifogging agents, flame retardants, within the scope not departing from the spirit of the present invention. Additives such as plasticizers, antistatic agents, mold release agents, foaming agents, nucleating agents, inorganic organic fillers, reinforcing agents, colorants, pigments, fragrances, and other thermoplastic resins can be used in combination.

5. Others (1) Molding method The polyethylene resin (A) of the present invention is formed by a molding method such as a film molding method, a hollow molding method, an injection molding method, an extrusion molding method, or a compression molding method that is generally used in the field of synthetic resins. Apply to shape into desired shape. In particular, an excellent pipe molded body can be obtained by molding by a pipe molding method.

(2) Applications Since the (A) polyethylene resin of the present invention has very excellent durability for fluidity (HLMFR) and α-olefin content (influence on density and stiffness index), In the field of pipes, especially water distribution pipes, it not only satisfies PE100, but also has excellent low-speed crack growth (SCG) and can be used as pipes and joints with excellent fluidity, moldability, rigidity, and homogeneity. it can.

In the following, the present invention will be described using examples. Each example and each comparative example is also for demonstrating the significance and rationality of the structure in this invention.
The analysis of the (A) polyethylene resin and (B) component and (C) component of this invention and the physical-property evaluation method were shown below.

[HLMFR]
According to Table 1-Condition 7 of JIS K-7210 (1996 edition), the measured value at a temperature of 190 ° C. and a load of 211.82 N was shown as HLMFR.
[MFR]
According to Table 1-Condition 4 of JIS K-7210 (1996 edition), the measured value at a temperature of 190 ° C. and a load of 21.18 N was shown as MFR.

[density]
It measured according to JIS K-7112 (1996 edition).

[Α-olefin content]
It was measured under the following conditions by 13C-NMR.
Device: JNM-GSX400 manufactured by JEOL Ltd.
Pulse width: 8.0 μsec (Flip angle = 40 °)
Pulse repetition time: 5 seconds Integration number: 5,000 times or more Solvent and internal standard: o-dichlorobenzene / benzene-d6 / hexamethyldishiro
Xanthine (mixing ratio: 30/10/1)
Measurement temperature: 120 ° C
Sample concentration: 0.3 g / ml
The spectrum obtained by the measurement is as follows. (1) For ethylene / 1-butene copolymer, “Macromolecules, 15, 353-360 (1982) (Eric T. Hsieh and James C. Randall)”, (2) Ethylene / For the 1-hexene copolymer, the α-olefin content was determined after assignment of the observed peak according to the document “Macromolecules, 15, 1402-1406 (1982) (Eric T. Hsieh and James C. Randall)”. . As for other short chain branches, for example, methyl branch, "J. Polym. Sci. Part A: Polym. Chem., 29, 1987-1990 (1991) (Atsushi Kagi, Yoshiko Akimoto, and Masao Murano)". According to the literature, after assignment of the observed peak, the number of short chain branches was determined. In addition, there is a relationship of α-olefin content = short chain branch number / 5 between the number of short chain branches (pieces / 1000 main chain carbons) and the α-olefin content (mol%).
As for the chain in which two α-olefins are continuous and the chain in which the α-olefin is isolated, the ethylene / 1-butene copolymer has 37.2 ppm (two consecutive) and 39.7 ppm (isolated), ethylene / 1 -It calculated | required from the peak of 36.0 ppm (two continuous) and 38.1 ppm (isolation) in the hexene copolymer. A chain in which two α-olefins are continuous is represented by Tβδ, a chain in which α-olefins are isolated is represented by Tδδ, and Tβδ / Tδδ / Ca calculated using the content of Ca (mol%) of α-olefin is represented by α- It was used as an index of olefin composition distribution. That is, the smaller this value, the greater the number of isolated chains and the narrower the composition distribution.

[Bending elastic modulus]
The measurement was performed at a test speed of 2 mm / min in accordance with JIS K 7171.
[Lander method with notch-ESCR]
JIS K 6922-2: 1997 Using the constant stress environmental stress cracking test apparatus specified in the annex, the test temperature is set to 80 ° C., and the test solution is a 1 wt% higher alcohol sodium sulfonate aqueous solution. The stress was measured as 60 kg / cm ² . The test piece used was a 1 mm thick and 6 mm wide press sheet with a 0.4 mm leather notch in the direction of the center thickness of the tensile part, and the time until breakage was measured.

[Pipe molding]
For notched pipe test and rapid crack growth test (RCP) evaluation: UH-70-32DN type single screw extruder (70 mmφ, L / D = 32) manufactured by Hitachi Zosen Co., Ltd., at a die temperature of 190 ° C. A pipe having an outer diameter of 110 mm and a wall thickness of 10 mm as defined in ISO 4427 was molded.

  For MRS evaluation: Using a KME1-45-33B single screw extruder (45 mmφ, L / D = 45) manufactured by Krauss-Maffei, an outer diameter of 32 mm and a wall thickness of 3 mm specified by ISO 4427 at a die temperature of 190 ° C. A pipe was formed.

[Notched pipe test]
In accordance with ISO 13479, a pipe with an outer diameter of 110 mm and a wall thickness of 10 mm as defined in ISO 4427 is provided in a circumferential direction so that a notch with a length of 110 mm and a tip angle of 60 ° is 10 mm in the tube axis direction and the remaining wall thickness is 10 mm. An internal pressure creep test was conducted at four locations at equal intervals, under conditions of a test temperature of 80 ° C. and an internal pressure of 4.6 bar.

[MRS (Minimum Required Strength) Evaluation]
The test was carried out in accordance with ISO 9080 and ISO 12162 with a pipe having an outer diameter of 32 mm and a wall thickness of 3 mm defined in ISO 4427.

[RCP (rapid crack growth test)]
An RCP-S4 test was performed on a pipe having an outer diameter of 110 mm and a wall thickness of 10 mm specified in ISO 4427 in accordance with ISO 13477 at a test temperature of 0 ° C. to determine the limit pressure (Pc, _S4 ).

[Example 1]
(Preparation of solid catalyst component)
20 g of commercially available magnesium ethylate (average particle size 860 μm) in a nitrogen atmosphere in a pot (crushing vessel) with a capacity of 1 L containing about 700 magnetic balls with a diameter of 10 mm, 1.66 g of granular aluminum trichloride and diphenyl 2.72 g of diethoxysilane was added. These were co-ground for 3 hours using a vibrating ball mill under the conditions of an amplitude of 6 mm and a frequency of 30 Hz. After co-grinding, the contents were separated from the magnetic balls in a nitrogen atmosphere.
5 g of the co-ground product obtained as described above and 20 ml of n-heptane were added to a 200 ml three-necked flask. While stirring, 10.4 ml of titanium tetrachloride was added dropwise at room temperature, the temperature was raised to 90 ° C., and stirring was continued for 90 minutes. Then, after cooling the reaction system, the supernatant was extracted and n-hexane was added. This operation was repeated three times. The obtained pale yellow solid was dried at 50 ° C. under reduced pressure for 6 hours to obtain a solid catalyst component.

(Manufacture of polyethylene resin)
The first polymerization liquid-filled loop reactor having an internal volume of 200 L was dehydrated and purified by isobutane at a rate of 102 L / hr, triisobutylaluminum at a rate of 54 g / hr, and the solid catalyst at a rate of 3.7 g / hr. Is 14 kg / hr, hydrogen is 0.32 g / hr, and 1-hexene as a comonomer is continuously fed at a rate of 0.97 kg / hr, under conditions of 90 ° C., polymerization pressure 4.2 MPa, and average residence time 0.9 hr. Under the copolymerization of ethylene and 1-hexene. As a result of collecting a part of the polymerization reaction product and measuring the physical properties, HLMFR was 0.19 g / 10 min, the density was 0.927 g / cm ³ , and the α-olefin content was 0.87 mol%.
Next, the entire amount of isobutane slurry containing the first step polymerization product was introduced as it was into the second step reactor having an internal volume of 400 L, and 87 l / hr of isobutane and 18 kg / hr of ethylene were added without adding catalyst and 1-hexene. Then, hydrogen was continuously supplied at a rate of 45 g / hr, and polymerization in the second step was performed under the conditions of 85 ° C., a polymerization pressure of 4.1 MPa, and an average residence time of 1.6 hr. The HLMFR after drying of the polyethylene polymer discharged from the second step reactor was 13 g / 10 minutes, the density was 0.949 g / cm ³ , and the α-olefin content was 0.48 mol%. In addition, the ratio of the high molecular weight component (the polymer produced in the first step) was 45% by weight.
On the other hand, the MFR of the low molecular weight component polyethylene polymer produced in the second step was determined by separately polymerizing under the second stage polymerization conditions, and the MFR was 70 g / 10 min. In addition, the α-olefin content of the low molecular weight component polyethylene polymer produced in the second step is a weight percentage between the α-olefin content after the second step and the α-olefin content after the first step. We demanded that additivity about
In summary, Table 1 shows the polymerization conditions, and Table 2 shows the results of the polyethylene polymer after each step.

0.05% by weight of a phenolic antioxidant (Ciba Geigy, brand: Irganox 1010) and 0.15 wt. Of a phosphorus antioxidant (Ciba Geigy, brand: Irgaphos 168) in the powder after the second step %, 0.15% by weight of calcium stearate was added, and the mixture was kneaded with a 50 mm single screw extruder at 200 ° C. to 90 rpm. HLMFR after kneading is 9.9 g / 10 min and a density of 0.949 g / cm ^3.
The polyethylene resin thus obtained was used to evaluate the notched Lander method-ESCR, which was 300 hours (Table 2).

[Example 2]
In Example 1, the polymerization conditions in the first step and the second step were changed as shown in Table 1 to obtain a polyethylene polymer. The results after each step of the obtained polymer are shown in Table 2. Thereafter, the same additive as in Example 1 was added, and kneaded in the same manner with a single screw extruder. The HLMFR after kneading was 10 g / 10 minutes, and the density was 0.950 g / cm ³ .
The polyethylene resin thus obtained was used to evaluate the notched Lander method-ESCR, which was 180 hours (Table 2).

[Example 3]
In a first polymerization liquid-filled loop reactor having an internal volume of 100 L, dehydrated and purified isobutane was 63 L / hr, triisobutylaluminum was 20 g / hr, and the solid catalyst of Example 1 was 3.6 g / hr. Further, ethylene was continuously fed at a rate of 7 kg / hr, hydrogen at 0.15 g / hr, and 1-hexene as a comonomer at a rate of 0.73 kg / hr, 85 ° C., polymerization pressure 4.3 MPa, average residence time 0. Copolymerization of ethylene and 1-hexene was performed under the condition of 9 hours. As a result of collecting a part of the polymerization reaction product and measuring the physical properties, the HLMFR was 0.16 g / 10 min, the density was 0.923 g / cm ³ , and the α-olefin content was 1.03 mol%.
Next, the entire amount of isobutane slurry containing the first step polymerization product was introduced into the second step reactor having an internal volume of 200 L. Without adding a catalyst, isobutane was 40 L / hr, ethylene was 7 kg / hr, and hydrogen was 0. 0.07 g / hr, 1-hexene was continuously fed at a rate of 0.61 kg / hr, and polymerization in the second step was performed under the conditions of 85 ° C., polymerization pressure of 4.2 MPa, and average residence time of 0.9 hr. . In this second step, an amount of hydrogen (control of HLMFR) and 1-hexene (control of density and amount of α-olefin) were supplied so as to produce substantially the same polymer as in the first step. As a result of collecting a part of the polymerization reaction product after the second step and measuring physical properties, the HLMFR was 0.14 g / 10 min, the density was 0.923 g / cm ³ , and the α-olefin content was 1.00 mol%. It was.
Next, the entire amount of the isobutane slurry containing the second-stage polymerization product was introduced into a 400-L third-stage reactor as it was, without adding catalyst and 1-hexene, 87 L / hr of isobutane, 18 kg / hr of ethylene, hydrogen Was continuously fed at a rate of 40 g / hr, and polymerization in the third step was performed under the conditions of 90 ° C., a polymerization pressure of 4.1 MPa, and an average residence time of 1.5 hr. The HLMFR after drying of the polyethylene polymer discharged from the third step reactor was 15 g / 10 min, the density was 0.948 g / cm ³ , and the α-olefin content was 0.55 mol%. The ratio of the polymer (high molecular weight component) produced in the first step and the second step was 23% by weight.
On the other hand, the MFR of the low molecular weight component polyethylene polymer produced in the third step was determined by separately polymerizing under the polymerization conditions of the third third step, and the MFR was 120 g / 10 min. The α-olefin content of the low molecular weight component polyethylene polymer produced in the third step is a weight between the α-olefin content after the third step and the α-olefin content after the second step. %, And it was found to be 0.15 mol%.
The same additive as in Example 1 was added to the powder after the third step and then kneaded in the same manner. The HLMFR after kneading was 9.4 g / 10 minutes, and the density was 0.948 g / cm ³ .
Using the polyethylene resin thus obtained, the notched Lander method-ESCR was evaluated, and it was 533 hours (Table 2).

[Example 4]
In Example 3, the polymerization conditions of the first step, the second step, and the third step were changed as shown in Table 1 to obtain a polyethylene polymer. The results after each step of the obtained polymer are shown in Table 2. Thereafter, the same additive as in Example 1 was added, and kneaded in the same manner with a single screw extruder. The HLMFR after kneading was 12 g / 10 min and the density was 0.951 g / cm ³ .
Using the polyethylene resin thus obtained, the notched Lander method-ESCR was evaluated, and it was 285 hours (Table 2).

[Example 5]
In Example 1, the polymerization conditions in the first step and the second step were changed as shown in Table 1 to obtain a polyethylene polymer. The results after each step of the obtained polymer are shown in Table 2. Thereafter, the same additive as in Example 1 was added, and kneaded in the same manner with a single screw extruder. The HLMFR after kneading was 8.7 g / 10 minutes, and the density was 0.955 g / cm ³ .
Using the polyethylene resin thus obtained, the notched Lander method-ESCR was evaluated and it was 35 hours (Table 2).

[Example 6]
In Example 1, the polymerization conditions in the first step and the second step were changed as shown in Table 1 to obtain a polyethylene polymer. The results after each step of the obtained polymer are shown in Table 2. Thereafter, the same additive as in Example 1 was added, and kneaded in the same manner with a single screw extruder. The HLMFR after kneading was 15 g / 10 min, and the density was 0.947 g / cm ³ .
Using the polyethylene resin thus obtained, the notched Lander method-ESCR was evaluated, and it was 332 hours (Table 2).

[Comparative Example 1]
In Example 1, the polymerization conditions in the first step and the second step were changed as shown in Table 1 to obtain a polyethylene polymer. The major difference in the polymerization conditions from Example 1 is that the polymerization temperature in the first step is as low as 80 ° C, while the temperature in the second step is as high as 90 ° C. The results after each step of the obtained polymer are shown in Table 2. Thereafter, the same additive as in Example 1 was added, and kneaded in the same manner with a single screw extruder. The HLMFR after kneading was 9.0 g / 10 min, and the density was 0.949 g / cm ³ .
The polyethylene resin thus obtained was used to evaluate the notched Lander method-ESCR, which was 70 hours (Table 2), which was considerably shorter than Example 1.

[Comparative Example 2]
In Example 3, the polymerization conditions of the first step, the second step, and the third step were changed as shown in Table 1 to obtain a polyethylene polymer. The difference from Example 3 is that the polymerization temperature in the first step and the second step for producing a high molecular weight is 75 ° C., which is 10 ° C. lower than 85 ° C. in Example 3. The results after each step of the obtained polymer are shown in Table 2. Thereafter, the same additive as in Example 1 was added, and kneaded in the same manner with a single screw extruder. HLMFR after kneading 11g / 10 min and a density of 0.950 g / cm ^3.
Using the polyethylene resin thus obtained, the notched Lander method-ESCR was evaluated and found to be 150 hours (Table 2), which was only 1/3 or less of the corresponding Example 3.

[Comparative Example 3]
In Example 1, the polymerization conditions in the first step and the second step were changed as shown in Table 1 to obtain a polyethylene polymer. The major difference in the polymerization conditions from Example 1 is that the α-olefin supplied during the polymerization is not 1-hexene but 1-butene. The results after each step of the obtained polymer are shown in Table 2. Thereafter, the same additive as in Example 1 was added, and kneaded in the same manner with a single screw extruder. The HLMFR after kneading was 10 g / 10 min, and the density was 0.949 g / cm ³ .
Using the polyethylene resin thus obtained, the notched Lander method-ESCR was evaluated and found to be 86 hours (Table 2), which was considerably shorter than Example 1.

[Comparative Example 4]
TUB124 N1836 manufactured by BP-Solvay Co., Ltd. was evaluated. The results are summarized in Table 2. Since the main α-olefin is 1-butene, although the α-olefin content of the polyethylene resin is as large as 0.69 mol%, the notched Lander method-ESCR was inferior to 106 hours.

[Comparative Example 5]
TUB124 N2025 manufactured by BP-Solvay Co., Ltd. was evaluated. The results are summarized in Table 2. Since the main α-olefin is 1-butene, although the α-olefin content of the polyethylene resin is as large as 0.65 mol%, the notched Lander method-ESCR is 244 hours, and the α-olefin content is It was inferior to few Examples 1 and 3.

[Comparative Example 6]
CELL100 manufactured by Basell Co., Ltd. was evaluated. The results are summarized in Table 2. Since the main α-olefin is 1-butene, the polyethylene resin has a high α-olefin content of 0.61 mol% and a high molecular weight of HLMFR of 6.4 g / 10 min. The ESCR was 233 hours, which was inferior to Examples 1, 3 and 4 with low α-olefin content and high HLMFR.

[Comparative Example 7]
XS10H manufactured by Fina Co., Ltd. was evaluated. The results are summarized in Table 2. Since the main α-olefin is 1-hexene, although the notched Lander method-ESCR showed a relatively good number of 289 hours, Tβδ / Tδδ / Ca, which is an index of the composition distribution of the α-olefin, was 0.00. Since it showed a high value of 16 and the composition distribution was wide, it was inferior to Examples 1 and 3.

[Example 7] (Pipe evaluation)
Two kinds of colored pipes (outer diameter 110 mm—thickness 10 mm, outer diameter 32 mm—thickness 3 mm) defined in ISO 4427 by the above-described method are blended with the polyethylene resin of Example 3 and a blue-toned pigment compound. Was molded.
When MRS was evaluated based on ISO 9080 and ISO 12162 using a pipe having an outer diameter of 32 mm and a wall thickness of 3 mm, the lower reliability limit value (σLPL) of the predicted hydrostatic pressure strength at 20 ° C.-50 years is 10.2 MPa and MRS = 10 MPa (PE100).
In addition, using a pipe having an outer diameter of 110 mm and a wall thickness of 10 mm, a notched pipe test in accordance with ISO 13479 was performed at a test temperature of 80 ° C. and an internal pressure of 9.2 bar with a test score of 5 and a test time of 17,000 hours was obtained. Even after the lapse of time, the results were very excellent so that they were not destroyed.
Furthermore, when a rapid crack growth test (RCP-S4) based on ISO 13477 was performed at a test temperature of 0 ° C. using a pipe having an outer diameter of 110 mm and a wall thickness of 10 mm, the crack progressed even when the internal pressure of the pipe was increased to 25 bar. Did not occur, and excellent results were obtained such that the critical pressure (Pc, _S4 ) could not be observed.
Table 3 shows the correlation data between the notched Lander method-ESCR and the notched pipe test.

[Example 8] (Pipe evaluation)
Two kinds of colored pipes (outer diameter 110 mm-thickness 10 mm, outer diameter 32 mm-thickness 3 mm) defined by ISO 4427 by the above-described method are blended with the polyethylene resin of Example 4 and a blue-toned pigment compound. Was molded.
When MRS was evaluated based on ISO 9080 and ISO 12162 using a pipe having an outer diameter of 32 mm and a wall thickness of 3 mm, the lower reliability limit value (σLPL) of the predicted hydrostatic pressure strength at 20 ° C.-50 years is 10.4 MPa and MRS = 10 MPa (PE100).
Further, when a pipe with an outer diameter of 110 mm and a wall thickness of 10 mm was used and a notched pipe test in accordance with ISO 13479 was performed under the conditions of a test temperature of 80 ° C. and an internal pressure of 9.2 bar, the fracture time was 4200 hours and excellent results were obtained. Obtained.
[Comparative Example 8] (Pipe evaluation)
A pigment compound adjusted to blue is blended with the polyethylene resin of Comparative Example 1, a colored pipe having an outer diameter of 110 mm and a wall thickness of 10 mm as defined in ISO 4427 is molded by the above-described method, and a notched pipe test in accordance with ISO 13479 is performed. Was conducted under the conditions of a test temperature of 80 ° C. and an internal pressure of 9.2 bar.
[Example 9] (Pipe evaluation)
A pigment compound adjusted to blue is blended with the polyethylene resin of Example 5, a colored pipe having an outer diameter of 110 mm and a wall thickness of 10 mm as defined in ISO 4427 is formed by the above-described method, and a notched pipe test in accordance with ISO 13479 is performed. Was conducted under the conditions of a test temperature of 80 ° C. and an internal pressure of 9.2 bar, the result was that the destruction time was 450 hours.

[Results of Examples and Comparative Examples]
Since the polyethylene resins obtained in Examples 1 to 6 all satisfy the requirements of HLMFR, density, α-olefin content, notched Lander method-ESCR in the present invention, fluidity and rigidity And the balance of durability is excellent.
In Comparative Examples 1 and 2, since the polymerization temperature of the high molecular weight component is lower than that of the example and the polymerization temperature of the low molecular weight component is equal to or higher than that of the example, the relative 1-hexene copolymerization is high during the polymerization of the low molecular weight component. As a result, the α-olefin content in the low molecular weight component / the α-olefin content in the high molecular weight component exceeds 0.2. Therefore, the durability is inferior, the notched Lander method-ESCR does not satisfy the relational expression of the present invention, and the notched Lander method-ESCR is inferior to the control examples 2 and 4, respectively.
In Comparative Examples 3 to 6, since the main α-olefin is 1-butene, the notched Lander method-ESCR does not satisfy the relational expression of the present invention, and the notch is compared with Example 3 in which HLMFR and α-olefin content are close. Lander method-ESCR is inferior.
In Comparative Example 7, although the main α-olefin was 1-hexene, the ratio of the chain in which two α-olefins were continuous to the chain in which the α-olefin was isolated was further divided by the α-olefin content ( = Tβδ / Tδδ / Ca) exceeds 0.15, so the composition distribution is wide. Therefore, the notched Lander method-ESCR does not satisfy the relational expression in claim 1 and the notched Lander method-ESCR is inferior to that of Example 3 in which HLMFR and α-olefin content are close.
From the above results, the polyethylene resin of the present invention has significantly improved durability in the pipe molded product as compared with the prior art and the like seen in each comparative example, and the significance of the configuration of the present invention The rationality is proven.

  The polyethylene resin of the present invention is a polyethylene resin particularly excellent in low-speed crack growth (SCG), and is a general-purpose polyethylene application container, food packaging container, tank, bottle, various molded products, stretched Or it can be used in the same way as general-purpose polyethylene resin for various uses such as unstretched film, agricultural film, ultra-thin film, material, binding tape, pipe, etc. And as a specific application, it has excellent properties in applications related to pipes and fittings. It also has the use of general-purpose polyethylene such as water supply pipes, oil supply pipes, chemical supply pipes, porous underdrain drainage pipes, rainwater infiltration pipes, seawater pipes, etc. Exhibits excellent properties in a wide range of pipe applications such as rehabilitation pipes. Furthermore, the polyethylene resin of the present invention includes a joint attached to the polyethylene pipe and a part necessary for concretely laying the pipe such as an elbow molding material. Excellent properties not found in polyethylene resin

Notched Lander Method-Correlation between ESCR (modified Lander method ESCR) and SCG (Notch Pipe Test) Graph of relationship between notched Lander method-ESCR and formula value 10 ^ (-2.9 × log HLa + 5.1 × log Ca + 6.8) +50

Claims (12)

(A) A polyethylene resin for pipes that satisfies the following requirements (a) to (d).
(A) High load melt flow rate (HLMFR, HLa) is 5 to 20 g / 10 min. (B) Density (Da) is 0.945 to 0.965 g / cm ^3.
(C) α-olefin content (Ca) of 0.05 to 1.5 mol%
(D) Notched Lander method-ESCR destruction time (T), HLa and Ca satisfy the following formula: logT ≧ −2.9 × logHLa + 5.1 × logCa + 6.8 2. The polyethylene resin according to claim 1, wherein the (A) polyethylene resin is composed of the following polyethylene polymers (B) and (C).
(B) Polyethylene polymer having an HLMFR (HLb) of 0.01 to 3 g / 10 min and an α-olefin content (Cb) other than ethylene of 3.0 mol% or less is a polymerization amount ratio (Xb) of 20 to 60 weights. % Percentage,
(C) A polyethylene polymer having an MFR (MFRc) of 1 to 1000 g / 10 min and an α-olefin content (Cc) other than ethylene of 0.5 mol% or less is a polymerization amount ratio (Xc) of 40 to 80% by weight. Percentage The polyethylene resin according to claim 1 or 2, wherein the main α-olefin having the largest content of the polyethylene polymer (B) or (C) has 6 or more carbon atoms. The polyethylene resin according to claim 2 or 3, wherein the (A) polyethylene resin satisfies the following relationship.
Α-olefin content in low molecular weight component / α-olefin content in high molecular weight component ≦ 0.20 The ratio of the chain in which two α-olefins are continuous (Tβδ) and the chain in which the α-olefins are isolated (Tδδ) is further set to α-olefin with respect to the main α-olefin having the highest content in the polyethylene resin (A). The polyethylene resin according to any one of claims 2 to 4, wherein a value divided by the olefin content is 0.15 or less. The polyethylene resin (A) is produced by sequential multistage polymerization in which a high molecular weight component is first produced, and then a reaction liquid containing the high molecular weight component is transferred to the next polymerization reactor as it is to produce a low molecular weight component. The polyethylene resin according to claim 2, wherein the polyethylene resin is present. The polyethylene resin according to any one of claims 2 to 6, wherein the (A) polyethylene resin is obtained by multistage polymerization using a Ziegler catalyst. The polyethylene resin according to any one of claims 1 to 7, wherein the (d) notched Lander method-breaking time (T) by ESCR, HLa, and Ca satisfy the following expressions.
T ≧ 10 ^ (− 2.9 × log HLa + 5.1 × log Ca + 6.8) +50 The pipe and joint shape | molded using the polyethylene resin of any one of Claims 1-8. In a polymerization apparatus in which two or more reactors are connected in series using a Ziegler catalyst containing at least titanium and magnesium, the high molecular weight component (B) HLMFR (HLb) is 0.01 in one or more reactors in the previous stage. A polyethylene-based polymer having an α-olefin content (Cb) other than ethylene of 3.0 mol% or less is produced in a polymerization amount ratio (Xb) of 20 to 60% by weight, and then contains a high molecular weight component. The reaction solution is transferred to the next reactor as it is, and a polyethylene type having a low molecular weight component (C) MFR (MFRc) of 1 to 1000 g / 10 min and an α-olefin content (Cc) other than ethylene of 0.5 mol% or less. Obtained by continuously subjecting the polymer to suspension polymerization at a polymerization amount ratio (Xc) of 40 to 80% by weight (A) The manufacturing method of the polyethylene resin for pipes characterized by satisfying the requirements of ()-(d).
(A) High load melt flow rate (HLMFR, HLa) is 5 to 20 g / 10 min. (B) Density (Da) is 0.945 to 0.965 g / cm ^3.
(C) α-olefin content (Ca) of 0.05 to 1.5 mol%
(D) Notched Lander method-ESCR destruction time (T), HLa and Ca satisfy the following formula: logT ≧ −2.9 × logHLa + 5.1 × logCa + 6.8 11. The method for producing a polyethylene resin for pipes according to claim 10, wherein the main α-olefin having the largest content among the α-olefins has 6 to 12 carbon atoms. 12. The polyethylene resin for pipes according to claim 10, wherein the (d) notched Lander method-fracture time (T) by ESCR, HLa, and Ca satisfy the following formulas: Production method.
T ≧ 10 ^ (− 2.9 × log HLa + 5.1 × log Ca + 6.8) +50