JP2008101074A - Resin composition for polyethylene piping materials - Google Patents

Abstract

[PROBLEMS] To provide a new high density that has excellent long-term characteristics, elongation characteristics, impact resistance, and molding processability, particularly in high-temperature acceleration conditions, while maintaining rigidity, and also has excellent eye properties during molding. It aims at providing the resin composition for polyethylene piping materials obtained using polyethylene.
The present invention provides a resin composition for a polyethylene piping material produced by using a composition in which two or more kinds of polyethylene resins specified by MFR and density are blended at a specified mixing ratio.
[Selection figure] None

Description

  The present invention relates to a polyethylene resin composition that is suppressed from being generated in the eyes during molding, has excellent physical properties and long-term characteristics when used as a pipe, and excellent productivity when used as a joint.

  Polyethylene resins are excellent in creep characteristics, environmental stress crack resistance, impact characteristics, and flexibility, and have been widely used as piping materials. The piping material described in the present invention refers to pipes and joints used as water and sewage pipes, gas pipes, and water supply pipes. In recent years, polyethylene pipes have been proven to be superior to pipe types such as steel pipes and ductile cast iron pipes because they have characteristics such as the pipes extending and following ground changes in response to earthquakes. Unlike mechanical joints such as steel pipes and ductile cast iron pipes, the pipes and joints are welded by EF (electrofusion) joints, so that the construction is simple and excellent in earthquake resistance. Due to these characteristics, it has been attracting attention as piping materials for water and sewage pipes, gas pipes, water supply pipes and the like.

  In addition, there is a high demand for safety required for each piping material, and pipes made of materials that have obtained PE80 for gas pipes and PE100 for waterworks pipes have come to be used. Here, PE100 refers to a stress-fracture time curve measured at three different temperatures in a hot internal pressure creep test described in ISO 9080 up to at least 9000 hours, and after 50 years at 20 ° C. The polyethylene is classified as PE100 in the classification table defined in ISO12162, in which the estimated value of the minimum guaranteed stress (hereinafter sometimes referred to as MRS) is 10 MPa or more. When polyethylene pipe resin is used for a long time as a water distribution pipe, stress is applied due to water pressure from the inside of the pipe or earth pressure from the outside at the time of embedding, so stress concentration occurs in the minute structural defects in the pipe, making it brittle. Destruction can occur. In order to provide a material that does not cause brittle fracture cracking under such severe conditions where stress is applied for a long period of time, improvements have been made so far.

  However, some polyethylene resin materials classified as PE100 may be brittle in long-term characteristics depending on the resin design. In particular, brittle fracture is noticeable under the internal pressure creep test conditions at 80 ° C., and it can be seen that there are many brittle polyethylene resins at high temperatures even if classified as PE100 in the ISO description. When estimating long-term creep characteristics, brittle fracture progresses more rapidly than ductile fracture, making it difficult to predict fracture and is inappropriate as a material used in lifelines such as water pipes. .

  In addition to long-term properties and elongation properties, materials that are excellent in molding processability are very difficult with the current technology. In particular, it is desirable that the pipe and the joint are made of the same resin from the viewpoint of fusion, and considering that the joint is formed by injection molding, PE100 is excellent not only in mechanical properties as a pipe but also in molding processability. Of polyethylene will be needed.

  In Japanese Patent Publication No. 61-42736 (Patent Document 1) and Japanese Patent Publication No. 61-43378 (Patent Document 2), a molecular weight distribution is broadened and a copolymerizable comonomer is polymerized in order to improve long-term mechanical properties. Although it has been disclosed that it is sometimes introduced as a side chain, improvement of mechanical properties over a long period of time is insufficient.

  In JP-A-10-17619 (Patent Document 3), the distribution of comonomer is controlled in order to improve long-term characteristics and impact resistance, and the contribution of comonomer to the high molecular weight side is determined by temperature rising elution fractionation and GPC. A method for improving the design of polyethylene has been proposed by paying attention to the correlation between molecular weight-elution temperature-elution amount obtained by cross-fractionation. However, to obtain a polyethylene resin classified as PE100, a more limited resin design is required.

  JP-A-8-301933 (Patent Document 4) and the like disclose a polyethylene pipe excellent in mechanical properties. The polyethylene forming this pipe is made of polyethylene having two molecular weight distributions, The flow rate (code T) (JIS K7210-1999, code T: hereinafter referred to as MFR5) is 0.35 g / 10 min or less, the molecular weight is high, and the molding processability is poor. Therefore, in the production of pipes and joints by actual extrusion molding and injection molding, productivity is expected to be very poor particularly in injection molding. In addition, when the resin is taken out from the extruder into a cylindrical shape during pipe production, a large amount of eyes are generated at the outlet of the die and the eyes are transferred to the surface of the molded product, or the deposited eyes are damaged on the surface of the pipe. This will not only eliminate the commercial value of the pipe, but it will also be the starting point for brittle fracture of the pipe, so in order to remove the eyes and eyes, it is necessary to interrupt the pipe molding and clean the die at the extruder outlet several times a day There was a problem.

JP-A-8-134285 (Patent Document 5) discloses a composition comprising two components having different intrinsic viscosities and densities. If a pipe molded body is molded using this composition, the results of a hot internal pressure creep test, a tensile creep test, a tensile fatigue test, and the like are said to be dramatically improved over conventional materials. According to this, the density and intrinsic viscosity of a composition composed of 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). ) in the range of 2.41~6.3dyne / cm ^2, at a shear rate at which the 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 when a pipe molded body is formed from a composition characterized by a certain characteristic, it is possible to mold a pipe excellent in moldability, pipe fatigue characteristics, and the like. However, in such a composition, pipe properties such as fatigue characteristics are certainly improved due to an increase in molecular weight and the like. However, in terms of moldability, it is adversely affected, particularly in injection molding for forming a joint. It is guessed that there is a tendency to become. Judging from the MFR of the examples and comparative examples where the value called flow index (FI) is FI ≦ 350 sec- ^1, it is a high molecular weight design that takes into account the physical properties, so that the molding processability is excellent. It is thought that it cannot be said.

Similarly, Japanese Patent Application Laid-Open No. 9-286820 (Patent Document 6) discloses a polyethylene pipe and its pipe joint. When the described FI value is 100 to 400 sec- ¹ , high shear by injection molding is disclosed. Not suitable for joints made by molding in the speed range.

JP 2000-109521 A (Patent Document 7) discloses a resin composition for pipes and joints. The resin composition obtained by this method is excellent in pipe characteristics such as moldability and fatigue characteristics when formed into a pipe, and also has excellent moldability in injection molding of joints and the like. However, when the resin is discharged from the extruder into a cylinder during pipe production, a large amount of eyes are generated at the die outlet and the eyes are transferred to the surface of the molded product, or the deposited eyes damage the surface of the pipe. This will not only eliminate the commercial value of the pipe, but it will also be the starting point for brittle fracture of the pipe, so in order to remove the eyes and eyes, it is necessary to interrupt the pipe molding and clean the die at the extruder outlet several times a day There was a problem.
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

  The present invention uses a new high-density polyethylene that has excellent long-term characteristics and elongation characteristics under high-temperature acceleration conditions, impact resistance, and molding processability while maintaining rigidity, and also has excellent eye properties during molding. It aims at providing the resin composition for polyethylene piping materials obtained by this.

  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
[1] An ethylene homopolymer 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 100 to 300 g / 10 A low molecular weight component (A) of 57 to 52 parts by weight, 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 50. And a high molecular weight component (B) of 43 to 48 parts by weight, a density of 943 to 957 kg / m ³ , an α-olefin content (Y) of 0.30 to 1.50 mol%, a melt flow The ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn) determined by gel permeation chromatography (M) with a rate (code T) of 0.25 to 0.50 g / 10 min (M / Mn) of from 25 to 40, a polyethylene pipe materials for the resin composition;
[2] The resin composition for polyethylene piping material according to [1] above, wherein the tensile elongation when the ratio of the notch depth to the thickness is 11% in a high-speed tensile test is 7% or more;
[3] The above-mentioned [1], wherein when formed into a pipe, the minimum guaranteed stress after 50 years at 20 ° C. is 10 MPa or more in a hot internal pressure creep test performed on the pipe by the method described in ISO 9080. ] Or the resin composition for polyethylene piping materials according to [2];
[4] When formed into a pipe, in a hot internal pressure creep test performed on the pipe by the method described in ISO 9080, a KneePoint due to brittle fracture is observed within 10,000 hours in a stress-fracture time creep diagram at 80 ° C. The resin composition for polyethylene piping materials according to any one of the above [1] to [3], wherein
[5] A value (Q / Ns) obtained by dividing the extrusion amount (Q) at a screw rotation speed of 45 rpm by the rotation speed (Ns) under the extrusion conditions set at 200 ° C. with a screw diameter of 50 mmφ full flight. The above [1], characterized in that it is 0.25 (kg / hr / rpm) or more, and the spiral flow (SFD) value by injection molding at a cavity width of 10 mm and a thickness of 2 mm at 230 ° C. is 35 cm or more. ]-The resin composition for polyethylene piping materials in any one of [4];
[6] The resin composition for polyethylene piping material according to any one of the above [1] to [5], wherein the ash content is 0.07% by weight or less;
[7] Pipes and joints molded from the resin composition for polyethylene piping materials according to any one of [1] to [6] above;
[8] The pipe and joint according to [7], which are used for water supply.

  The composition of the present invention is a material classified as PE100 that is excellent in long-term characteristics, elongation characteristics, and impact resistance, has good molding processability, and is less likely to cause eyes during molding. Because of its excellent moldability, pipes and joints that are piping materials can be manufactured from the same resin composition, which not only dramatically improves productivity, but also fuses pipes and joints well. Can be worn. In addition, the eye property during molding is improved, and the molded product has a good balance of mechanical properties. The pipe and the joint formed by the composition of the present invention are favorably used as a water and sewage pipe, a gas pipe and a water supply pipe as a lifeline.

The present invention will be specifically described below.
The polyethylene pipe material resin composition according to the present invention includes a low molecular weight component (A) and a high molecular weight component (B).

[Low molecular weight component (A)]
First, the polyethylene resin low molecular weight component (A) will be described.
The density (JIS K7112-1999) of the low molecular weight component (A) of the polyethylene resin is 967 to 977 kg / m ³ , preferably 970 to 977 kg / m ³ , and more preferably 973 to 977 kg / m ³ .
When the density is 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 are sufficient. Moreover, although a comonomer may be included, it is more preferable that it is a polyethylene homopolymer. In the case of a homopolymer, the density depends on the melt flow rate, and the melt flow rate, code D (JIS K7210-1999, code D: hereinafter referred to as “MFR 2.16”) is in the range of 50 to 300 g / 10 min. The density does not practically exceed 977 kg / m ³ .

  As the comonomer, an α-olefin having 3 to 20 carbon atoms is used. For example, propylene, 1-butene, 1-pentene, 3-methyl-1-butene, 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-hexadiene, 1,7-o Tajien and cyclohexadiene, and the like.

  The MFR 2.16 of the low molecular weight component (A) is 100 to 300 g / 10 minutes, preferably 100 to 250 g / 10 minutes, and more preferably 125 to 200 g / 10 minutes. When the MFR 2.16 exceeds 300 g / 10 min, the moldability is good, but the long-term life and elongation characteristics of the hot internal pressure creep are lowered, and the impact resistance is also inferior. High density polyethylene having an MFR of 2.16 less than 100 g / 10 min improves mechanical properties but is inferior in molding processability, and is particularly difficult to injection mold.

[High molecular weight component (B)]
Next, the high molecular weight component (B) of the polyethylene resin will be described.
The high molecular weight component (B) is a copolymer of ethylene and an α-olefin having 3 to 20 carbon atoms. Since the thing similar to what was demonstrated by the low molecular weight component (A) can be used for C3-C20 alpha-olefin used as a comonomer, description is abbreviate | omitted here.

The density (JIS K7112-1999) of the high molecular weight component (B) of the polyethylene resin is 895 to 949 kg / m ³ , preferably 900 to 945 kg / m ³ , more preferably 910 to 940 kg / m ³ , Preferably it is 916-933 kg / m < ³ >.
For density 895kg / m ³ or more, the rigidity of the molded tube becomes sufficient, 949kg / m ³ in the following cases, environmental stress crack resistance time of a high temperature accelerated conditions (hereinafter, referred to as "ESCR") And elongation characteristics do not deteriorate, and brittle fractures such as generation of cracks and low-speed crack fracture due to long-term use are not caused.

The weight average molecular weight is 500,000 to 1,000,000, preferably 600,000 to 950,000, and more preferably 700,000 to 900,000. When the weight average molecular weight is 500,000 or more, the moldability is good, the long-term life and elongation characteristics of the hot internal pressure creep are good, and the impact resistance is sufficient. When the weight average molecular weight is 1,000,000 or less, the mechanical properties are sufficient, and the moldability, particularly the injection moldability, is good.
In general, the weight average molecular weight of the high molecular weight component is measured by gel permeation chromatography (GPC) when the high molecular weight component and the low molecular weight component are separately polymerized and mixed. However, the polyethylene resin composition of the present invention is also preferably produced by multistage polymerization using at least two polymerization vessels. In the polymerization by multistage polymerization, the high molecular weight component cannot be isolated and the weight average molecular weight cannot be measured. Therefore, the MFR 2.16 of the high molecular weight component (B) is calculated from the MFR 2.16 of the low molecular weight component (A) and the composition (C) by the following method, and the weight average molecular weight of the high molecular weight component (B) is further calculated. calculate. By adjusting the weight average molecular weight to be 500,000 to 1,000,000, the polyethylene pipe material resin composition according to the present invention can be obtained.
i) Conversion from MFR 2.16 of low molecular weight component (A) and composition (C) to MFR 2.16 of high molecular weight component (B).
When mixing polyethylenes having different MFRs, it is known that the MFR after mixing can be calculated as follows.
(MFRfinal) ^-0.175 =
(1-R) × (MFR1st) ^−0.175 + R × (MFR2nd) ^−0.175 (Equation 1)
In the formula, MFR2.16 of the low molecular weight component is MFR1st, MFR2.16 of the high molecular weight component is MFR2nd, MFR2.16 of the composition is MFRfinal, and the ratio of the high molecular weight component amount to the sum of the high molecular weight component amount and the low molecular weight component amount (Mixing ratio) is indicated by R.
From (Formula 1), MFR2nd of the high molecular weight component can be expressed as follows.
MFR2nd = (((MFRfinal) ^-0.175
− (1-R) × (MFR1st) ^−0.175 ) / R) ^{−0.175 / 1} (Formula 2)
ii) Conversion of MFR 2.16 from high molecular weight component to 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)
In the formula, Mw represents a weight average molecular weight.
From (Formula 2) and (Formula 3), the weight average molecular weight Mw is expressed as follows.
Mw = 13.291 × 10 ⁻⁴ × ((((MFRfinal) ^−0.175
-(1-R) × (MFR1st) ^-0.175 ) / R) ^{-0.175 / 1} ) ^-0.2842

[Resin composition for polyethylene piping materials]
Next, the resin composition for polyethylene piping material according to the present invention will be described.
The density (JIS K7112-1999) of the resin composition for polyethylene piping materials is 943 to 957 kg / m ³ , preferably 945 to 955 kg / m ³ , and more preferably 947 to 953 kg / m ³ .
When the density is 943 kg / m ³ or more, the rigidity of the tube is sufficient, and when it is 957 kg / m ³ or less, the ESCR and elongation characteristics under high temperature acceleration conditions are sufficient, and cracks are generated even after long-term use. Does not cause brittle fracture such as low-speed crack fracture. In particular, in the case of hot internal pressure creep, the creep property on the short-term side is high, and on the long-term side, the sudden long brittle fracture that does not depend on the working pressure does not occur and the long-term property is satisfied.

  Next, the α-olefin content (Y) of the resin composition for polyethylene piping material of the present invention is 0.30 to 1.50 mol%, preferably 0.40 to 1.20 mol%, more preferably. 0.50 to 1.00 mol%. Here, the α-olefin content is the total content of α-olefin in the resin composition. If the α-olefin content (Y) is less than 0.30 mol%, the ESCR and elongation characteristics under high temperature acceleration conditions deteriorate. High-density polyethylene having an α-olefin content (Y) exceeding 1.50 mol% is difficult to produce, and the mechanical properties of the resulting composition also deteriorate due to the generation of gel.

  MFR5 of the resin composition for polyethylene piping materials of this invention is 0.25-0.50g / 10min, Preferably it is 0.30-0.45g / 10min. If 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 are lowered, and the impact resistance is also inferior. High density polyethylene having an MFR5 of less than 0.25 g / 10 min improves mechanical properties, but is inferior in molding processability, and particularly difficult to injection mold.

  Furthermore, the ratio (Mw / Mn) of Mw and Mn determined by gel permeation chromatography as an index of the molecular weight distribution of the resin composition for polyethylene piping materials of the present invention is 25 to 40, preferably 28 to 38. is there. If Mw / Mn is less than 25, the long-term life and elongation characteristics of hot internal pressure creep are lowered, and the molding processability, particularly injection molding, is also deteriorated. On the other hand, when Mw / Mn exceeds 40, moldability and the like are improved due to the influence of low molecular weight components, but the hot internal pressure creep characteristics and impact resistance are also inferior.

The mixing ratio of the low molecular weight component (A) and the high molecular weight component (B) constituting the resin composition for polyethylene piping material of the present invention is such that the low molecular weight component (A) is 57 to 52 parts by weight, and the high molecular weight component (B ) Is 43 to 48 parts by weight, preferably the low molecular weight component (A) is 56 to 54 parts by weight, and the high molecular weight component (B) is 44 to 46 parts by weight. By setting the proportion of the high molecular weight component (B) to 43 parts by weight or more, rough skin when a pipe is molded can be suppressed, and the eyes generated on the extruder die can be effectively suppressed. On the other hand, when the proportion is 48 parts by weight or less, the high molecular weight component is sufficient, and the long-term life, elongation characteristics and impact resistance of the hot internal pressure creep are sufficient.
For example, increasing the mixing ratio without changing the melt flow rate of the resin composition relates to lowering the molecular weight of the high molecular weight component that affects rough skin and increasing the molecular weight of the low molecular weight component that affects the eyes.
When the low molecular weight component is large, it tends to occur in the eyes and when it is small, the melt flow rate is lowered and the extrudability and rough skin property are deteriorated. In order to maintain the melt flow rate even when the low molecular weight component is decreased, it is conceivable to lower the molecular weight of the high molecular weight component or to reduce the ratio of the high molecular weight component. However, since both the physical properties and long-term physical properties are decreasing, it is necessary 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, and the composition ratio of both components.

Further, the resin composition for polyethylene piping material of the present invention has a molecular weight of 100,000 or more and an elution temperature of 90 in the correlation of molecular weight-elution temperature-elution amount determined by cross-fractionation between temperature rising elution fractionation and gel permeation chromatography. It is preferable that the ratio (R (wt%)) of the total elution amount of the elution component of elution components at or below C is equal to or higher than R0 obtained by the following formula.
R0 = 17.73 (Y) ^1.59 (5)
Here, (Y) represents the α-olefin content (mol%).
When R is less than R0, the long-term life in hot internal pressure creep is inferior, and the impact resistance is also lowered.

Moreover, it is preferable that the branch parameter of the resin composition for polyethylene piping materials of this invention is 0 or more and 2 or less. In the present invention, the term “branch parameter” refers to a least-squares approximate linear relationship C (M (i)) = P × log (M (M (i)) of the number of branches per 1000 carbon atoms C (M (i)) and molecular weight M (i). i)) + Q (Formula 6)
The coefficient P in is shown. In the present invention, 0 ≦ P ≦ 2 is preferable, more preferably 0.1 ≦ P ≦ 1.5, and still more preferably 0.5 ≦ P ≦ 1.0.
When P is smaller than 0 (that is, negative), it indicates that the comonomer concentration in the polymer region of the polyethylene composition is low, and the ESCR decreases. Even when P is 0 or less, if the comonomer content is increased, the ESCR is improved to some extent, but this is not preferable because the density is lowered and the rigidity is lowered. On the other hand, lowering the MFR also improves the ESCR, but it is not preferable because molding processability decreases. Therefore, in order to increase ESCR without deteriorating rigidity and moldability, it is necessary to set P to 0 or more. Moreover, it is practically difficult to obtain a polyethylene composition in which P exceeds 2.
Here, when calculating P, C (M (i)) at the point where the peak value of the GPC curve is small is not used for the calculation because the accuracy decreases. Further, C (M (i)) in the region below the maximum value M (max) of the GPC curve is not used for calculation because the influence of the terminal methyl groups at both ends of the molecule is large. In the present invention, the polymer side from M (max) is set as the P calculation region within a range that is 30% or more of the peak value of M (max).
In the present invention, in order to control P to 0 or more, for example, in the production of the low molecular weight component (A), homopolymerization of ethylene is performed, and in the production of the high molecular weight component (B), ethylene and α-olefin are mixed. Copolymerization may be performed. Further, in the production of the high molecular weight component (B), it is desirable to use a catalyst having good copolymerization, that is, a catalyst capable of introducing a large amount of comonomer into the high molecular weight region.
The density and melt flow rate of the low molecular weight component (A) and the high molecular weight component (B) can be varied by changing the polymerization conditions. That is, the melt flow rate can be lowered by raising the polymerization temperature, raising the polymerization pressure, or raising the hydrogen concentration. The density can be lowered by lowering the amount of α-olefin.

Further, as a guideline for expressing the moldability, the ratio of length to the die diameter (L / D) of the extruder is 20, the compression ratio is 3.6 / 1, the cylinder to the die temperature is 200 ° C., and the screw diameter is 50 mmφ ( Evaluation was made by dividing the extrusion amount (Q) when extruded at a screw rotation speed of 45 rpm under the condition of full flight by the rotation speed (Ns; 45 rpm) at that time. The compression ratio referred to here is the ratio S (F) / S (M) of the area S (F) of the feed zone to the area S (M) of the metering zone, and each area is the groove depth of each screw. From this, it is calculated as follows. When the screw outer diameter is R and the groove depth of the metering zone is tF, the groove depth of the tM feed zone is tF. Here, π represents a circumference ratio.
S (M) = (R ² − (R−tF) ² ) π (Expression 7)
S (F) = (R ² − (R−tM) ² ) π (Formula 8)
The Q / Ns value is 0.25 (kg / hr / rpm) or more, preferably 0.28 or more, and more preferably 0.30 or more. If the Q / Ns is less than 0.25, the extrusion rate tends to decrease further in the actual production, and the resin pressure tends to increase. On the other hand, the melt flow rate region does not substantially exceed 0.40. In addition, when spiral flow is performed by injection molding under the conditions of a cavity width of 10 mm, thickness of 2 mm, and 230 ° C., a material having an SFD value of less than 35 cm has poor molding processability when molding a joint or the like, and residual stress It is easy to cause orientation distortion due to the above. Accordingly, in order to improve the long-term characteristics more effectively without increasing the fluidity by increasing the molecular weight, it is necessary to use the above polyethylene in which a comonomer is selectively introduced on the high molecular weight side.

  Next, the polyethylene pipe material resin composition of the present invention preferably has a tensile elongation of 7% or more when the ratio of the notch depth to the thickness is 11% in the high-speed tensile test. The high-speed tensile test evaluates the ease of destruction when a pipe is damaged when a sudden force is applied to a pipe embedded in an earthquake, etc., and the tensile elongation decreases even when the pipe is damaged. What you do not want is good. When the ratio of the notch depth to the thickness (hereinafter referred to as notch ratio) is 11%, the tensile elongation is 7% or more, so that pipe breakage when a sudden force is applied is less likely to occur. On the other hand, it is desirable that the tensile elongation is large, but practically does not exceed 30%.

  The amount of ash by ashing by an electric furnace in the resin composition for polyethylene piping material of the present invention is 0.07% by weight or less. 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. In particular, when there is a large amount of ash in polyethylene pipes and joint resins containing colored pigments, it is considered that the chlorine-resistant water resistance is lowered. Therefore, it is stated in JIS K6762 that the ash is limited to a predetermined amount or less. ing. In the resin composition according to the present invention, catalyst residues and additives having an ash content exceeding 0.07% by weight lead to generation of water bubbles on the pipe surface when the pipe is exposed to tap water containing chlorine.

The resin composition for polyethylene piping material of the present invention is suitable for forming polyethylene pipes and joints.
Using the resin composition for polyethylene piping material of the present invention, a pipe is formed by extrusion molding and a pipe joint is formed by injection molding, and a hot internal pressure creep test is performed by the method described in ISO 9080 using the molded pipe or joint. Then, the MRS after 50 years at 20 ° C. is required as 10 MPa or more as a standard, and is certified as PE100.

Further, when a hot internal pressure creep test is performed by the method described in ISO 9080 using the above-described formed pipe or joint, a Knee Point that changes from ductile fracture to brittle fracture in the stress-fracture time creep diagram at 80 ° C. is 10,000 hours. Not seen within. When Knee Point is shorter than 10,000 hours, brittle fracture may occur during long-term use.
In order to achieve the MRS and KneePoint time, the molecular weight of the polyethylene resin is increased, the mixing ratio of the polyethylene resins (A) and (B) is decreased to widen the molecular weight distribution of the composition (C), the high molecular weight This is achieved by introducing α-olefin intensively into component (B).

  In addition, the resin composition for polyethylene piping material of the present invention is usually provided in a colored form together with a coloring pigment in order to limit the use as a pipe when producing polyethylene pipes and joints. It is.

  Next, the multistage polymerization method will be described as an example of the method for producing the resin composition for polyethylene piping material of the present invention. The multistage polymerization method includes, for example, Japanese Patent Publication No. 35-15246, Japanese Patent Publication No. 46-11349, Japanese Patent Publication No. 48-42716, Japanese Patent Publication No. 51-47079, Japanese Patent Publication No. 52-19788, Patent This is a known technique reported in Japanese Patent No. 2505752 and the like, and is a method in which an α-olefin is homopolymerized or copolymerized by a multistage polymerization apparatus in which a plurality of polymerization vessels are usually connected in series.

The hydrogen concentration in the polymerization vessel is preferably 40 mol% or more and 90 mol% or less, and more preferably 45 mol% or more and 80 mol% or less during the production of the low molecular weight component. If it is 40 mol% or more, it is possible to produce a polyolefin excellent in molding processability, the molecular weight can be sufficiently controlled, and if it is 90 mol% or less, impact strength can be improved. The hydrogen concentration in the polymerization vessel means the hydrogen concentration (unit: mol / L) obtained by analyzing the gas phase portion in the polymerization vessel using gas chromatography and the α-olefin concentration (unit: mol). / L) is a value calculated according to the following mathematical formula, and the unit is mol%.
Hydrogen concentration (mol%) =
Hydrogen concentration (mol / L) / {Hydrogen concentration (mol / L)
+ Α-olefin concentration (mol / L)} (Formula 9)
In olefin polymerization, the molecular weight is generally controlled by the hydrogen concentration (mol%) in the polymerization vessel, and the higher the hydrogen concentration (mol%) in the polymerization vessel, the lower the molecular weight of the polyolefin produced. Therefore, in order to produce a low molecular weight component by the above-described multistage polymerization method, it is necessary to increase the hydrogen concentration in the polymerization vessel. On the other hand, it is generally known that the polymerization activity decreases when the hydrogen concentration is increased. At the time of polymerization at a high hydrogen concentration, it has been found that the activity is significantly reduced when oxygen-containing compounds and sulfur-containing compounds are mixed into the α-olefin. Although the cause of this is not clear, it has become possible to suppress this decrease in activity.

The average residence time during the production of the low molecular weight component in the multistage polymerization is preferably 1.5 hours or more and 10 hours or less, and more preferably 2 hours or more and 6 hours or less. When the average residence time is 1.5 hours or more, the productivity of the polyolefin per catalyst is sufficiently high, so that the chlorine water resistance and elution resistance are improved. When the average residence time is 10 hours or less, the unit time is high. Polyolefins can be produced with high productivity. The average residence time in the present invention is an average time during which the catalyst and the monomer are reacted in the polymerization vessel. In the case of batch polymerization, the average residence time in the present invention is the time from the start of the reaction between the catalyst and the monomer in the reactor to the termination of the polymerization reaction in the polymerization vessel. In this case, the value is obtained by dividing the sum of the volume of the solvent in the polymerization vessel and the volume of the polyolefin by the rate per volume at which the solvent and the polyolefin are constantly withdrawn from the polymerization vessel. That is, in order to extend the average residence time, it is necessary to reduce the speed per unit volume withdrawn constantly from the polymerization vessel with respect to the sum of the volume of the solvent in the polymerization vessel and the volume of the polyolefin. Therefore, in order to keep the productivity per unit time constant while extending the average residence time, it is necessary to keep the amount of polyolefin constantly withdrawn constant. There is a need to increase the ratio of polyolefin to solvent. On the other hand, there is a limit to the ratio of polyolefin to the solvent in the polymerization vessel, and this limit varies depending on the polymerization conditions, but if this limit is exceeded, the flowability of the slurry in the polymerization vessel deteriorates and a polyolefin lump is generated. There is a possibility that stable production may become difficult due to problems such as these.
Next, the solid catalyst [A] suitable for polymerization of the resin composition for polyethylene piping material of the present invention will be described. The solid catalyst [A] is reacted with an organomagnesium compound that is soluble in an inert hydrocarbon solvent represented by the following general formula (formula 10) and a chlorinating agent represented by the following general formula (formula 11). It is prepared by supporting a titanium compound (A-2) represented by the following general formula (Formula 12) on the prepared carrier (A-1).
(M ¹ ) α (Mg) β (R ¹ ) _a (R ² ) _b (OR ³ ) _c (Equation 10)
(Wherein 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 , R ² and R ³ are each a carbon number. 2 or more and 20 or less, and α, β, a, b and c are real numbers satisfying the following relationship: 0 ≦ α, 0 <β, 0 ≦ a, 0 ≦ b, 0 ≦ c, 0 <a + b, 0 ≦ c / (α + β) ≦ 2, kα + 2β = a + b + c (where k is the valence of M ¹ ))
H _d SiCl _e R ⁴ _{(4- (d + e))} (Formula 11)
(Wherein R ⁴ is a hydrocarbon group having 1 to 12 carbon atoms, and d and e are numbers satisfying the following relationship: 1 ≦ d, 1 ≦ e, 2 ≦ d + e ≦ 4)
Ti (OR ⁵ ) _f X _(4-f) (Equation 12)
(In the formula, f is a real number of 0 or more and 4 or less, R ⁵ is a hydrocarbon group of 1 to 20 carbon atoms, and X is a halogen atom.)

  Next, the inert hydrocarbon solvent suitable for the polymerization of the resin composition for polyethylene piping material of the present invention will be described. The inert hydrocarbon solvent in the present invention is an aliphatic hydrocarbon compound such as pentane, hexane or heptane, an aromatic hydrocarbon compound such as benzene or toluene, or an alicyclic hydrocarbon compound such as cyclohexane or methylcyclohexane. An aliphatic hydrocarbon is preferable.

Next, the organomagnesium compound that is soluble in the inert hydrocarbon solvent represented by the general formula (Formula 10) will be described. This organomagnesium compound is shown as a complex form of organomagnesium soluble in an inert hydrocarbon solvent, but encompasses all dihydrocarbylmagnesium compounds and complexes of this compound with other metal compounds It is. The relational expression kα + 2β = a + b + c of the symbols α, β, a, b, c indicates the stoichiometry between the valence of the metal atom and the substituent.
In the above general formula (Formula 10), the hydrocarbon group represented by R ¹ to R ² is an alkyl group, a cycloalkyl group or an aryl group, for example, methyl, ethyl, propyl, butyl, propyl, hexyl, octyl Decyl, cyclohexyl, phenyl group, etc., preferably R ¹ to R ² are alkyl groups. When α> 0, as the metal atom M ¹ , metal elements belonging to Groups 1 to 3 and 13 of the periodic table can be used. For example, lithium, sodium, potassium, beryllium, zinc, boron, aluminum Among them, aluminum, boron, beryllium, and zinc are particularly preferable.
The ratio β / α of magnesium to the metal atom M ¹ can be arbitrarily set, but is preferably 0.1 to 30, particularly preferably 0.5 to 10. In addition, when a certain organomagnesium compound in which α = 0 is used, for example, when R ¹ is 1-methylpropyl or the like, it is soluble in an inert hydrocarbon solvent, and such a compound is also used in the present invention. Gives favorable results. In the general formula (Formula 10), it is recommended that R ¹ and R ² when α = 0 is any ^{one of} the following three groups (1), (2), and (3).
(1) At least one of R ¹ and R ² is a secondary or tertiary alkyl group having 4 to 6 carbon atoms, preferably R ¹ and R ² both have 4 to 6 carbon atoms, At least one is a secondary or tertiary alkyl group.
(2) R ¹ and R ² are alkyl groups having different carbon atoms, preferably R ¹ is an alkyl group having 2 or 3 carbon atoms, and R ¹ is an alkyl group having 4 or more carbon atoms. Be a group.
(3) At least one of R ¹ and R ² is a hydrocarbon group having 6 or more carbon atoms, preferably an alkyl group that becomes 12 or more when the number of carbon atoms contained in R ¹ and R ² is added. .

  These groups are specifically shown below. The secondary or tertiary alkyl group having 4 to 6 carbon atoms in (1) includes 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 are used, and 1-methylpropyl group is particularly preferable. Next, in (2), examples of the alkyl group having 2 or 3 carbon atoms include ethyl, 1-methylethyl, propyl and the like, and an ethyl group is particularly preferable. Examples of the alkyl group having 4 or more carbon atoms include butyl, pentyl, hexyl, heptyl, octyl group and the like, and butyl and hexyl groups are particularly preferable.

  Furthermore, examples of the hydrocarbon group having 6 or more carbon atoms in (3) 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, an increase in the number of carbon atoms contained in an alkyl group facilitates dissolution in an inert hydrocarbon solvent. However, the use of an unnecessarily long alkyl group is not preferred in terms of handling because the solution viscosity increases. The organomagnesium compound is used as an inert hydrocarbon solution, but it can be used as long as a trace amount of Lewis basic compounds such as ethers, esters, and amines are contained or remain in the solution.

Next, the alkoxy group (OR ³ ) will be described. The hydrocarbon group represented by R ³ is preferably an alkyl group or aryl group having 1 to 12 carbon atoms, and particularly preferably an alkyl group or aryl group having 3 to 10 carbon atoms. Specifically, for example, methyl, ethyl, propyl, 1-methylethyl, butyl, 1-methylpropyl, 1,1-dimethylethyl, pentyl, hexyl, 2-methylpentyl, 2-ethylbutyl, 2-ethylpentyl, Examples include 2-ethylhexyl, 2-ethyl-4-methylpentyl, 2-propylheptyl, 2-ethyl-5-methyloctyl, octyl, nonyl, decyl, phenyl, naphthyl groups, and the like. Butyl, 1-methylpropyl, 2 -Methylpentyl and 2-ethylhexyl groups are particularly preferred.

These organomagnesium compounds include an organomagnesium compound belonging to the group consisting of the general formulas R ¹ MgX and R ¹ ₂ Mg (R ¹ is as defined above and X is halogen), and the general formula M ¹ R ² _k And an organometallic compound belonging to the group consisting of M ¹ R ² _(k-1) H (M ¹ , R ² , k are as defined above) in an inert hydrocarbon solvent at room temperature to 150 ° C. An alkoxymagnesium compound having a hydrocarbon group represented by R ³ that is soluble in an alcohol having an hydrocarbon group represented by R ³ or an inert hydrocarbon solvent, if necessary, and the like. It is synthesized by the method of reacting.

  Among these, when reacting an organomagnesium compound soluble in an inert hydrocarbon solvent with an alcohol, the order of the reaction is such that the alcohol is added to the organomagnesium compound, or the organomagnesium compound is added to the alcohol. Any method can be used, or a method of adding both at the same time. In the present invention, the reaction ratio between the organomagnesium compound soluble in the inert hydrocarbon solvent and the alcohol is not particularly limited, but as a result of the reaction, the alkoxy group-containing organomagnesium compound in the resulting alkoxy group-containing organomagnesium compound contains all of the alkoxy groups. The range of the molar composition ratio c / (α + β) is 0 ≦ c / (α + β) ≦ 2, and 0 ≦ c / (α + β) <1 is particularly preferable.

The chlorinating agent used when synthesizing the carrier (A-1) is a silicon chloride compound having at least one Si—H bond represented by the following general formula (formula 11).
H _d SiCl _e R ⁴ _{(4- (d + e))} (Formula 11)
(Wherein R ⁴ is a hydrocarbon group having 1 to 12 carbon atoms, and d and e are numbers satisfying the following relationship: 1 ≦ d, 1 ≦ e, 2 ≦ d + e ≦ 4)

In the above (Formula 11), the hydrocarbon group represented by R ⁴ is an aliphatic hydrocarbon group, an alicyclic hydrocarbon group, or an aromatic hydrocarbon group. For example, methyl, ethyl, propyl, 1- Examples thereof include methylethyl, butyl, pentyl, hexyl, octyl, decyl, cyclohexyl, phenyl group, etc., preferably an alkyl group having 1 to 10 carbon atoms, and 1 carbon atom such as methyl, ethyl, propyl, 1-methylethyl group, etc. An alkyl group of ˜3 is particularly preferred. D and e are one or more real numbers satisfying the relationship of 2 ≦ d + e ≦ 4, and e is particularly preferably 2 or more.

These compounds include HSiCl ₃ , HSiCl ₂ CH ₃ , HSiCl ₂ C ₂ H ₅ , HSiCl ₂ C ₃ H ₇ , HSiCl ₂ (1-CH ₃ C ₂ H ₅ ), 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 SiClCH ₃ , H ₂ SiClC ₂ H ₅ , HSiCl (CH ₃ ) ₂ , HSiCl (C ₂ H ₅ ) ₂ , HSiClCH ₃ (1-CH ₃ C ₂ H ₅ ), HSiClCH ₃ (C ₆ H ₅ ), HSiCl (C ₆ H ₅ ) _{2 and the} like, and a silicon chloride compound composed of these compounds or a mixture of two or more selected from these compounds is used. As the silicon chloride compound, trichlorosilane, monomethyldichlorosilane, dimethylchlorosilane, and ethyldichlorosilane are preferable, and trichlorosilane and monomethyldichlorosilane are particularly preferable.

  Next, the reaction between the organomagnesium compound and the chlorinating agent will be described. In the reaction between the organomagnesium compound and the chlorinating agent, the chlorinating agent is previously converted into a reaction solvent body, for example, a chlorinated hydrocarbon such as an inert hydrocarbon solvent, 1,2-dichloroethane, o-dichlorobenzene, dichloromethane, or the like. It is preferably used after being diluted with an ether-based medium such as diethyl ether or tetrahydrofuran, or a mixed medium thereof. In particular, in view of the performance of the catalyst, an inert hydrocarbon solvent is preferable. In the present invention, the reaction temperature is not particularly limited, but is preferably carried out at a temperature not lower than the boiling point of the silicon chloride compound used as a chlorinating agent or not lower than 40 ° C. for the progress of the reaction. Although there is no restriction | limiting in particular also in the reaction ratio of an organomagnesium compound and a silicon chloride compound, Usually, it is 0.01-100 mol of silicon chloride compounds with respect to 1 mol of organomagnesium compounds, Preferably, with respect to 1 mol of organomagnesium compounds, It is the range of 0.1-10 mol of silicon chloride compounds.

  With respect to the reaction method in the present invention, a method of simultaneous addition in which an organomagnesium compound and a silicon chloride compound are simultaneously introduced into the reactor, and a reaction is performed, and after the silicon chloride compound is charged in the reactor in advance, the organomagnesium compound is added to the reactor. There is a method of introducing or a method of introducing an organomagnesium compound into the reactor in advance and then introducing a silicon chloride compound into the reactor. However, the organomagnesium compound is introduced into the reactor after the silicon chloride compound is introduced into the reactor in advance. The method of introducing into is preferable. The solid component obtained by the above reaction is preferably separated by filtration or decantation, and then sufficiently washed with an inert hydrocarbon solvent to remove unreacted products or by-products.

In the present invention, the reaction between the organomagnesium compound and the silicon chloride compound can 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 oxides (ii) Inorganic carbonates, silicates, sulfates (iii) Inorganic hydroxides (iv) Inorganic halides (v) Double salts, solid solutions or mixtures of (i) to (iv) Inorganic solids Specific examples of 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 iron silicate [(Mg · Fe) ₂ SiO ₄ ], aluminum silicate _{[Al 2 O 3 · SiO 2} ], calcium carbonate, magnesium chloride, magnesium iodide and the like Particularly preferably, silica, silica-alumina or magnesium chloride is preferred. The specific surface area of the inorganic solid is preferably 20 m ² / g or more, particularly preferably 90 m ² / g or more.

Next, the titanium compound (A-2) will be described. In the production of the resin composition for polyethylene piping material of the present invention, a titanium compound represented by the following general formula (12) is used as the titanium compound (A-2).
Ti (OR ⁵ ) _f X _(4-f) (Equation 12)
(In the formula, f is a real number of 0 or more and 4 or less, R ⁵ is a hydrocarbon group of 1 to 20 carbon atoms, and X is a halogen atom.)

Examples of the hydrocarbon group represented by R ⁵ include aliphatic hydrocarbon groups such as methyl, ethyl, propyl, butyl, pentyl, hexyl, 2-ethylhexyl, heptyl, octyl, decyl, and allyl groups, cyclohexyl, and 2-methylcyclohexyl. , An alicyclic hydrocarbon group such as cyclopentyl group, and an aromatic hydrocarbon group such as phenyl and naphthyl group. An aliphatic hydrocarbon group is preferable. Examples of the halogen atom represented by X include chlorine, bromine and iodine, with chlorine being preferred. Specifically, titanium tetrachloride is preferable. It is possible to use a mixture of two or more of the titanium compounds (A-2) selected from the above.

  The amount of the titanium compound (A-2) supported on the carrier (A-1) is preferably 0.01 or more and 20 or less, and 0.05 or more and 10 or less in terms of a molar ratio with respect to the magnesium atom contained in the carrier (A-1). Particularly preferred. If the amount of the titanium compound (A-2) supported on the carrier (A-1) is 0.01 or more in terms of the molar ratio to the magnesium atom contained in the carrier (A-1), the polymerization activity per catalyst is sufficiently high. If it is high and 20 or less, the polymerization activity per titanium is sufficiently high. In the present invention, the reaction temperature at the time of loading is not particularly limited, but it is preferably carried out in the range of room temperature to 150 ° C.

  In the present invention, the solid catalyst [A] is a carrier (A-1), an alcohol (A-3), an organometallic compound (A-4), an organometallic compound (A-5), a titanium compound (A-2). It is preferable that it consists of.

  Next, alcohol (A-3) is demonstrated. In the preparation of the solid catalyst [A] in the present invention, the carrier (A-1) and the alcohol (A-3) are brought into contact with each other before the titanium compound (A-2) is supported on the carrier (A-1). Is preferred. The alcohol (A-3) in the present invention is preferably a saturated or unsaturated alcohol having 1 to 20 carbon atoms. Such alcohols include methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 2-methyl-1-propanol, 2-methyl-2-propanol, 1-pentanol, 1-pentanol, Examples include hexanol, 1-heptanol, 1-octanol, 2-ethyl-1-hexanol, cyclohexanol, phenol, cresol, and the like, and linear alcohols having 3 to 8 carbon atoms are particularly preferable. It is also possible to use a mixture of these alcohols.

  The amount of the alcohol (A-3) used is preferably greater than 0 and 10 or less, more preferably 0.05 or more and 5 or less, in terms of a molar ratio to the magnesium atom contained in the carrier (A-1). 1 or more and 3 or less are more preferable. The reaction of the carrier (A-1) and the alcohol (A-3) is carried out in the presence or absence of an inert hydrocarbon solvent. The temperature during the reaction is not particularly limited, but it is preferably carried out in the range of 25 ° C. or more and 200 ° C. or less.

Next, the organometallic compound (A-4) in the present invention will be described. In the preparation of the solid catalyst [A] in the present invention, it is more preferable to react the support (A-1) and the alcohol (A-3) and then react the organometallic compound (A-4). In the present invention, the organometallic compound (A-4) is represented by the following general formula (Formula 13).
General formula, M ² R ⁷ _s Q _(ts) (Formula 13)
(In the formula, M ² is a metal atom belonging to the group consisting of Group 1, Group 2 and Group 13 of the Periodic Table, R ⁷ is a hydrocarbon group having 1 to 20 carbon atoms, and Q is OR ⁸ , OSiR. ⁹ R ¹⁰ represents a group belonging to the group consisting of R ¹¹ , NR ¹² R ¹³ , SR ¹⁴ and halogen, and R ⁸ , R ⁹ , R ¹⁰ , R ¹¹ , R ¹² , R ¹³ , R ¹⁴ are hydrogen atoms or hydrocarbons A group, s is a real number greater than 0, and t is the valence of M ² )

M ² is a metal atom belonging to the group consisting of Group 1, Group 2 and Group 13 of the Periodic Table, and examples thereof include lithium, sodium, potassium, beryllium, magnesium, boron, aluminum and the like. Boron and aluminum are particularly preferred. The hydrocarbon group represented by R ⁵ is an alkyl group, a cycloalkyl group or an aryl group, and examples thereof include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, an octyl group, a decyl group, a cyclohexyl group and a phenyl group. Is an alkyl group. Q represents a group belonging to the group consisting of OR ⁸ , OSiR ⁹ R ¹⁰ R ¹¹ , NR ¹² R ¹³ , SR ¹⁴ and halogen, and R ⁸ , R ⁹ , R ¹⁰ , R ¹¹ , R ¹² , R ¹³ , R ¹⁴ Is a hydrogen atom or a hydrocarbon group, and Q is particularly preferably a halogen.

Examples of the organometallic compound (A-4) in the present invention include 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 Romido, diethylaluminum ethoxide, ethylaluminum dichloride, ethylaluminum sesquichloride, tripropylaluminum, tributylaluminum, tri (2-methylpropyl) aluminum, trihexylaluminum, trioctylaluminum, tridecylaluminum, etc., organic aluminum Compounds are particularly preferred.
It is also possible to use a mixture of these compounds.

  The use amount of (A-4) is preferably 0.01 times or more and 20 times or less, and more preferably 0.1 times or more and 10 or less, in a molar ratio to (A-3). The amount of (A-4) used is preferably 0.01 times or more and 20 times or less, and 0.05 times or more and 10 times or less in terms of a molar ratio to the magnesium atom contained in the carrier (A-1). More preferably it is. Although there is no restriction | limiting in particular about the temperature of reaction, The range which is 25 degreeC or more and 200 degrees C or less and less than the boiling point of a reaction medium is preferable.

  Next, the organometallic compound (A-5) in the present invention will be described. In the present invention, when the carrier (A-1) is brought into contact with the alcohol (A-3) and then reacted with the organometallic compound (A-4) and then the titanium compound (A-2) is supported, the titanium compound It is preferable to carry | support by making (A-2) and an organometallic compound (A-5) react. The organometallic compound (A-5) is an organometallic compound represented by the above general formula (formula 13), and may be the same as or different from the organometallic compound (A-4).

  Examples of the organometallic compound (A-5) in the present invention include 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 Romido, diethylaluminum ethoxide, ethylaluminum dichloride, ethylaluminum sesquichloride, tripropylaluminum, tributylaluminum, tri (2-methylpropyl) aluminum, trihexylaluminum, trioctylaluminum, tridecylaluminum, etc., organic aluminum Compounds are particularly preferred.

  There is no restriction | limiting in particular in the addition order of a titanium compound (A-2) and an organometallic compound (A-5), and an organometallic compound (A-5) is added following a titanium compound (A-2). Any method of adding a titanium compound (A-2) and an organometallic compound (A-5) at the same time by adding a titanium compound (A-2) following (A-5) is possible. It is preferable to add the organometallic compound (A-5) following (A-2). The molar ratio of the organometallic compound (A-5) to the titanium compound (A-2) is preferably 0.1 to 10, particularly preferably 0.5 to 5. The reaction between the titanium compound (A-2) and the organometallic compound (A-5) is carried out in an inert hydrocarbon solvent, but it is preferable to use an aliphatic hydrocarbon solvent such as hexane or heptane. Although there is no restriction | limiting in particular about the temperature of reaction, The range which is 25 degreeC or more and 200 degrees C or less and less than the boiling point of a reaction medium is preferable.

Next, the organoaluminum compound [B] used as the organometallic compound (A-4) or (A-5) will be described. The organoaluminum compound [B] in the present invention is represented by the following general formula (Formula 14).
General formula R ⁶ _h AlZ _(3-h) (Formula 14)
(Wherein R ⁶ is a hydrocarbon group having 1 to 12 carbon atoms, Z is a group belonging to the group consisting of hydrogen, halogen, alkoxy, allyloxy and siloxy groups, and h is a real number of 2 to 3) is there.)

Examples of R ⁶ include methyl, ethyl, propyl, butyl, 2-methylpropyl, pentyl, 3-methylbutyl, hexyl, octyl, decyl, phenyl, tolyl and the like. Of these, an ethyl group and a 2-methylpropyl group are particularly preferable. Two or more kinds of these hydrocarbon groups may be contained. h is preferably 0.05 or more and 1.5 or less, and particularly preferably 0.1 or more and 1.2 or less.

  The organoaluminum compound [B] is preferably synthesized by mixing trihydrocarbyl aluminum and dihydrocarbyl aluminum hydride when Z in (Formula 14) is hydrogen. Specifically, a synthesis method such as mixing triisobutylaluminum and diisobutylaluminum hydride, mixing triethylaluminum and diisobutylaluminum hydride, or mixing triethylaluminum and diethylaluminum hydride is preferable. The mixing conditions are not particularly limited, but it is preferable to mix by stirring at a temperature of 0 ° C. or higher and 80 ° C. or lower.

  When Z in (Formula 14) is other than hydrogen, for example, trimethylaluminum, triethylaluminum, tripropylaluminum, tributylaluminum, tri (2-methylpropylaluminum, tripentylaluminum, tri (3-methylbutyl) aluminum, trihexylaluminum , Trialkylaluminum such as trioctylaluminum and tridecylaluminum, diethylaluminum chloride, ethylaluminum dichloride, bis (2-methylpropyl) aluminum chloride, ethylaluminum sesquichloride, diethylaluminum bromide and other aluminum halide compounds, diethylaluminum ethoxy , Alkoxy aluminum compounds such as bis (2-methylpropyl) aluminum butoxide, dimethyl Le hydro siloxy aluminum dimethyl, ethyl methyl hydro siloxy aluminum diethyl, ethyl dimethylsiloxy aluminum diethyl etc. siloxy aluminum compounds and mixtures thereof are preferred, trialkylaluminum compounds are preferred.

  Examples of the α-olefin used in the present invention include ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, 1-eicocene, cyclopentene, cyclohexene, cycloheptene, norbornene, 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-hexadiene, Examples include 1,7-octadiene and cyclohexadiene.

In the present invention, the polyolefin production method is not particularly limited, and can be applied to any of the commonly used solution methods, high-pressure methods, high-pressure bulk methods, gas methods, and slurry methods.
For example, the polymerization pressure is from 0.1 MPa to 200 MPa as the gauge pressure, the polymerization temperature is from 25 ° C. to 250 ° C., and propane, butane, isobutane, hexane, cyclohexane or the like is used as the solvent.

  The resin composition for polyethylene piping material of the present invention is produced by methods such as slurry polymerization, bulk polymerization, gas polymerization, solution polymerization and the like. The resin composition for polyethylene piping material of the present invention can be produced by one-stage polymerization, two-stage polymerization, or more multistage polymerization, etc. In order to satisfy the constitutional conditions of the present invention, α is a comonomer. -It is necessary to copolymerize olefins mainly in the high molecular weight part of the polymer. An example of a preferred two-stage polymerization used in the present invention will be described below with reference to FIG.

  In the polymerization vessel 1, ethylene, hexane, hydrogen, catalyst components, and the like are supplied from the line 2. α-Olefin is not supplied. Thus, a low molecular weight homopolyethylene is polymerized. The polymerization pressure is 0.1 to 200 MPa as a gauge pressure, preferably 0.1 to 3 MPa, more preferably 0.1 to 2.5 MPa, and the polymerization temperature is 25 ° C. to 250 ° C., preferably 60 ° C. to 100 ° C. More preferably, it is 70-90 degreeC. The slurry in the polymerization vessel 1 is guided to the flash drum 3 to remove unreacted ethylene and hydrogen. The removed ethylene and hydrogen are returned to the polymerizer 1 whose pressure has been increased by the compressor 4. On the other hand, the slurry in the flash drum 3 is introduced into the second-stage polymerization vessel 6 by the pump 5. In the polymerizer 6, ethylene, α-olefin comonomer, hexane, hydrogen, a catalyst component, and the like are supplied from the line 7, whereby a high molecular weight polyethylene copolymerized with α-olefin is polymerized. The polymerization pressure is a gauge pressure of 0.1 to 3 MPa, preferably 0.1 to 2 MPa, and the polymerization temperature is 40 to 110 ° C., preferably 60 to 90 ° C. The polymer in the polymerization vessel 6 is taken out as a product through a post-treatment process.

  The resin composition for polyethylene piping material of the present invention may also be obtained by mixing by a known mixing method, for example, kneading with a single or twin screw extruder or a Banbury mixer. Therefore, it is necessary to select polyethylene before mixing so that α-olefin is mainly copolymerized with the high molecular weight part of the polymer.

  The resin composition for polyethylene piping material of the present invention includes, as necessary, antioxidants such as phenolic, phosphorous, and sulfur, metal soaps such as calcium stearate and magnesium stearate, ultraviolet absorbers, and light stability. Known additives such as an agent, an antistatic agent, an antifogging agent, and a coloring pigment can be mixed and used, but the ash content shown in JIS K6762 must be a prescription that makes 0.07% by weight or less.

  Next, a method for forming a pipe using the resin composition for polyethylene piping material of the present invention will be described. The high-density polyethylene PE100 described above is melted at a temperature of 170 ° C. to 220 ° C. and extruded into a cylindrical shape from a die with an outer diameter of 80 mm and an inner diameter of 68 mm attached to a 65 mmφ extruder (manufactured by Toshiba Plastic Engineering Co., Ltd.). The outer diameter is formed by passing through a sizing plate, and the sizing tank water temperature is cooled at 20 ° C. to 60 ° C. as primary cooling, and the water temperature is 15 ° C. to 25 ° C. as secondary cooling after leaving the sizing tank. The cooled pipe was taken up by a take-up machine so that SDR (outer diameter / thickness ratio) = 11, and a tubular pipe having a nominal diameter of 50 mm and a thickness of 5.5 mm was formed.

  The resin composition for polyethylene piping materials using the high-density polyethylene of the present invention is superior to the conventional resin composition for polyethylene piping materials in that it has excellent hot internal pressure creep characteristics, and can be used for a long time. Compared to the resin for medium density polyethylene pipe, the long-term safety can be improved without breaking even in the higher stress region in the long-term mechanical properties.

The hot internal pressure creep test is widely used as a method for evaluating long-term characteristics. However, polyethylene pipes and joint resins used for waterworks are excellent in long-term mechanical characteristics, so they are sufficient under accelerated test conditions at elevated temperatures. Even if measurement is performed for a long time (at least one year or more), brittle fracture may not be observed. Therefore, a long time measurement evaluation is necessary for the material determination. In addition, since ductile fracture due to plastic deformation becomes dominant when high stress is applied to the pipe, high-rigidity materials are unlikely to undergo plastic deformation in the high stress region, and have excellent long-term mechanical properties during a short test period. It shows such a tendency. However, the fracture mode of pipes under low stress may show brittle fracture without plastic deformation as opposed to ductile fracture with plastic deformation. In such a case, the pipe may be left under low stress for a long time. Therefore, a material that hardly undergoes plastic deformation in a high-stress region is not necessarily a material that has excellent long-term characteristics.
The high-density polyethylene PE100 described above can be obtained by designing the molecular weight, density, molecular weight distribution, and R0 at the expense of moldability, but the pipe and joint are the same resin and fused. In such a case, injection molding on the joint side becomes difficult. Therefore, PE100 excellent in moldability is desired in the market, and according to the present invention, such PE100 could be provided.

Next, the present invention will be described more specifically based on examples and reference examples.
The basic physical property measuring method used in the present invention will be described below.

(1) Density (ρ, unit: kg / m ³ )
Based on JIS K7112-1999, it measured by the density gradient tube method (23 degreeC).

(2) α-olefin content (Y, unit: mol%)
Model: JEOL Co., Ltd. JEOL, α400 nuclear magnetic resonance apparatus, measurement mode: ¹³ C-NMR, temperature 135 ° C., integration number 10,000 times, sample 30 μg / 0.4 cc orthodichlorobenzene, reference material: deuteration Measured with benzene (C ₆ D ₆ ). The α-olefin content was calculated by the following formula.
Y = 1/2 (XE) (Formula 15)
(EE) + (XE) = 100 mol% (Formula 16)
Here, X represents an α-olefin unit, and E represents an ethylene unit, which is calculated assuming only a chain (dyad structure) in which two units are connected. (XE) represents a chain of α-olefin and ethylene, (EE) represents a chain of ethylene and ethylene, and the sum of (EE) and (XE) is calculated as 100 mol%.

(3) Melt flow rate (unit: g / 10 minutes) Based on JIS K7210-1999, the cord D was measured at a load of 2.16 kg, and the cord T was measured at 190 ° C. under a load of 5 kg.

(4) Weight average molecular weight (Mw) and molecular weight distribution (Mw / Mn)
The molecular weight distribution (Mw / Mn) is a ratio of the weight average molecular weight Mw and the number average molecular weight Mn obtained by measurement by gel permeation chromatography (GPC).
GPC was measured using an Alliance GPCV2000 manufactured by Waters. The columns used were one Shodex AT-807S manufactured by Showa Denko KK and two TSK-gelGMH-H6 manufactured by Tosoh Corporation, first passing through one Shodex AT-807S and then two TSK-gelGMH. -Used in series connected through H6. As the mobile phase solvent, 1,2,4-trichlorobenzene containing 10 ppm by weight of pentaerythrityl tetrakis- [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate] was used. The measurement temperature was 140 ° C. The mobile phase solvent flow rate was 1.0 ml / min. A measurement sample was prepared by dissolving 20 mg of polymer in 20 ml of 1,2,4-trichlorobenzene containing 0.1% by mass of 2,6-di-t-butyl-4-methylphenol. A differential refraction type was used as the detector. The weight average molecular weight is 0.43 (polyethylene Q factor / polystyrene Q factor = 17.7) using a calibration curve prepared using a monodispersed polystyrene manufactured by Tosoh Corporation as a standard substance. /41.3).
The weight average molecular weight of the high molecular weight component is measured by gel permeation chromatography (GPC) when the high molecular component and the low molecular component are separately polymerized and mixed. On the other hand, in the case of multistage polymerization, the melt flow rate (MFR 2.16) of the high molecular weight component was obtained from the melt flow rate of the low molecular weight component and the melt flow rate of the composition, and the weight average molecular weight was calculated from the melt flow rate of the high molecular weight component. .

(5) GPC-FTIR (branch parameter)
A detector; FT-IR1760X manufactured by Perkin Elmer Co., Ltd. was connected to Waters Alliance GPCV2000 online, and the measurement was performed simultaneously with the GPC measurement. 2960 cm ^-1 measured wavelength is an absorption band of the methyl group, the 2930 cm ^-1 and 2980cm ^-1 based an absorption band of the methylene groups is measured every 6 seconds, after the peak separation by deconvolution, respectively The peak area was calculated, and the number of branches per 1000 carbon atoms at each GPC retention time was determined from the ratio. The number of branched carbon atoms per 1000 carbon atoms was corrected using values measured by nuclear magnetic resonance (NMR).

(6) Temperature rising elution fractionation GPC cross fractionation R0 is the temperature elution fractionation with respect to the ratio (R, unit: wt%) of the total elution amount of elution components with molecular weight of 100,000 or more and elution temperature of 90 ° C or less. It calculated from the correlation of molecular weight-elution temperature-elution amount calculated | required by the cross fractionation with a gel permeation chromatography. FIG. 3 is a schematic diagram showing the amount of elution with contour lines. The cumulative elution amount of elution components having a molecular weight of 100,000 or more and an elution temperature of 90 ° C. or less corresponds to the hatched portion in the figure. The ratio to the total accumulated elution amount is R. The measuring device used was CFC-T-150A manufactured by Dia Instruments Co., Ltd. As the column for gel permeation chromatography, three AD-806MS columns manufactured by Showa Denko K.K. were used. As the solvent, orthodichlorobenzene was used, and measurements were always made at 140 ° C. except for the temperature elution fractionated portion.
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 0 ° C. at 10 ° C./hr, and further kept at 0 ° C. for 60 minutes to coat the sample. An infrared spectrometer was used as a detector to detect 3.42 μm infrared light. The elution temperature was divided from 0 ° C. to 140 ° C., and was divided into 2 ° C. fractions in the vicinity of the elution peak. The molecular weight of the eluted fraction at each temperature was measured.

(7) ESCR (unit: hr)
Although it conforms to the JIS K6922-2 appendix, the water temperature of the thermostatic bath was changed to 80 ° C. and measured. As a test solution, a 10 wt% aqueous solution of Liponox NC-140 (registered trademark) manufactured by Lion Corporation was used.

(8) Tensile elongation (l, unit:%)
Although conforming to JIS K7113, the test speed was changed to 10 mm / sec, and the tensile elongation (l) at break was calculated by the following formula. l = (L−L0) / L0 × 100 (Expression 17)
(Where, l: elongation at the time of tensile failure, L: distance between grips at break (mm), L0: distance between original grips (mm))

(9) Tensile modulus (unit: MPa)
Although conforming to JIS K7113, the test speed was changed to 10 mm / sec, and the elongation was determined from the slope of 0 to 2%.

(10) High-speed tensile elongation (unit:%)
Although conforming to JIS K7113, the test speed was 100 mm / sec. The test piece used JIS No. 2 and a notch was made on one side with an ESCR blade in the center of the test piece, perpendicular to the tensile direction. The notch depth was determined by observation with a 210 × microscope. The ratio of the notch depth to the specimen thickness was defined as the notch ratio. The elongation was expressed as a ratio of the elongation to the chuck distance (80 mm). The notch ratio was measured at least 2 levels between 9 and 13%, and the elongation when the notch ratio was 11% was determined.

(11) Izod impact strength (IZOD, unit: kJ)
In accordance with JIS K7110, the test piece shape was No. 2 type A and measured at 23 ° C.

(12) Spiral flow length (SFD, unit: cm)
Using a mold having a spiral cavity with a width of 10 mm and a thickness of 2 mm, a sample was injection molded under molding conditions of an injection temperature of 230 ° C., an injection pressure of 100 kg / cm ² , and a mold temperature of 50 ° C. The length was measured. As the molding machine, an injection molding machine IS150EN manufactured by Toshiba Machine was used.

(13) Extrusion amount per rotation speed (Q / Ns, Q: kg / hr, Ns: rpm)
The cylinder temperature and die temperature were measured under the following conditions with a Plako extruder (screw diameter 50 mmφ, L / D = 20, CR = 3.6), and the discharge rate at 45 rpm was measured, and this was divided by the number of revolutions. did.
Cylinder temperature: C1: C2: C3 = 200: 200: 200 ° C.
Die temperature: H: D1: D2: D3 = 200: 200: 200: 200 ° C.
Die outer diameter: 15mm,
Die inner diameter: 10 mm.

(14) Pipe forming The physical properties of the pipe were measured by forming the pipe as follows.
The pipe is melted at a resin temperature of 220 ° C using a Φ65mm extruder (manufactured by Toshiba Plastic Engineering), extruded into a cylindrical shape from a die with an outer diameter of 80mm and an inner diameter of 68mm attached to the extruder, and a sizing plate is placed in a sizing tank. A pipe that has been cooled to a sizing bath water temperature of 25 ° C. as primary cooling and then cooled at a water temperature of 20 ° C. as a secondary cooling in the next water bath after the sizing bath has been cooled. The pipe was drawn with a take-up machine so that the outer diameter / thickness ratio = 11, and a tubular pipe having a nominal diameter of 50 mm and a wall thickness of 5.5 mm was formed.

(15) Measurement of chlorine water resistance The chlorine water resistance test was performed according to JIS-K6762 using a pipe having a nominal diameter of 50 mm.
Chlorine-resistant water test: chlorine concentration 2000ppm, immersion temperature 60 ° C, liquid pH 6.5 ± 0.5 (at the time of liquid change), liquid change every day, immersion after 336 hours (2 weeks), test It was confirmed whether water bubbles were generated on the piece. The case where the generation of water bubbles was observed was evaluated as x, and the case where the generation of water bubbles was not observed was determined as ○.

(16) Hot internal pressure creep test Using a pipe (50A) for a polyethylene pipe for gas described in JIS K6774, select three levels of temperatures of 20 ° C, 60 ° C and 80 ° C by the test method described in ISO 9080. The hot internal pressure test was performed at an arbitrary hoop stress so as to include at least one point of data for 9000 hours or more.
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). ) Appears as “Yes”, and only ductile fracture is indicated as “No”.

(17) Ash content A 100 ml magnetic crucible specified in JIS R1301 was washed and then heated and cooled in an electric muffle furnace at 700 to 800 ° C. for 1 hour. After putting 10 mg of sample and weighing the sample mass, it was carbonized with care so that no flame would appear on the electric heater, heated in an electric muffle furnace at 700 to 800 ° C. until it was ashed, and the mass of ash was weighed. The sample weight after ashing with respect to the sample weight before ashing was calculated in%.

(18) Measurement of moldability Using a φ65mm extruder (Toshiba Plastic Engineering Co., Ltd.), melt at a resin temperature of 220 ° C and extrude into a cylindrical shape from a die with an outer diameter of 80mm and an inner diameter of 68mm attached to the extruder. Judged the degree of rough. A smooth surface with no irregularities was evaluated as “◯”, and a rough surface was determined as “×”.

(19) Meiyani Toyo Seiki Co., Ltd. Laboplast mill, single screw extruder (L / D = 20), full flight screw (CR = 3.0), nozzle diameter (1.8) mm Teflon (registered) (Trademark) A processed nozzle was attached and extruded as a mesh of 80/100/400/100/80 mesh, a resin temperature of 180/200/200/180 ° C., and a screw rotation speed of 150 rpm.
Extrusion was continued for 3 hours, and many were observed around the nozzle.

[Reference Example 1]
Preparation of Solid Catalyst Component [A-1] (1) Synthesis of {(A-1) -1} Support 4 L of a 1 mol / L hydroxytrichlorosilane hexane solution was placed in a 20 L stainless steel autoclave that had been sufficiently purged with nitrogen. While stirring at 50 ° C., 9 L of a hexane solution of an organomagnesium compound represented by the composition formula AlMg ₅ (C ₄ H ₉ ) ₁₁ (OC ₂ H ₅ ) ₂ (equivalent to 6.5 mol of magnesium) was dropped over 4 hours. The mixture was further reacted 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. As a result of analyzing this support, the amount of magnesium contained per 1 g of the support was 8.44 mmol.
(2) Preparation of solid catalyst component [A-1] 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 with stirring at 50 ° C. 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 set to 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. 600 mL of the supernatant of the slurry after washing was removed, and 265 mL of 1 mol / L diethylaluminum chloride hexane solution was added over 5 minutes while stirring at 50 ° C., followed by 265 mL of 1 mol / L titanium tetrachloride hexane solution over 5 minutes. Added. After the addition, the reaction was continued at 50 ° C. for 2 hours. After completion of the reaction, 7 L of the supernatant liquid was removed, and the solid catalyst component [C] 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.

[Example 1]
(1) Polymerization As a catalyst, solid catalyst [A-1] and triisobutylaluminum [B-1] were used.
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 conditions of a polymerization temperature of 85 ° C. and a polymerization pressure of 1 MPa, the catalyst is the above solid catalyst [A-1] in terms of Ti atom of 0.5 mmol / h, and the above organoaluminum compound [B-1] in terms of Al atom. 20 mmol / h and hexane were introduced at a rate of 40 L / h. Hydrogen is used as the molecular weight regulator, and the hydrogen is supplied in such a way that the gas phase molar concentration (hydrogen / (ethylene + hydrogen)) with respect to the sum of ethylene and hydrogen is 65 mol%, and the supply amount of ethylene is 10 kg / h. Then, the polymerization was conducted by supplying to 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 the hydrogen in the polymer slurry, the polymer slurry solution in the polymerization vessel 1 is led to a flash drum at a pressure of 0.1 MPa and a temperature of 75 ° C. at a rate of 51 L / h, and after the unreacted ethylene and hydrogen are separated, the reaction The polymer slurry solution was mixed at a speed of 51 L / h and hexane was mixed at a speed of 95 L / h into the polymerization vessel 2 having a volume of 250 L, and the mixture was pressurized and introduced.
Next, in the second stage polymerization, a stainless polymerizer 2 having a reaction volume of 300 L was used to produce a high molecular weight component. The polymer slurry solution and hexane were combined and introduced into the polymerization vessel 2 at a rate of 146 L / h. Said organoaluminum compound [B-1] was introduce | transduced at 47 mmol / h in conversion of Al atom. The sum of the volume of the solvent in the polymerization vessel and the volume of the polyolefin measured by the liquid level system using γ-rays is 146 L, and the rate per volume at which the solvent and the polyolefin are constantly extracted from the polymerization vessel is 157 L. / H. Therefore, the average residence time in the first stage was 0.90 hours. A polyolefin composition comprising a low molecular weight component and a high molecular weight component was withdrawn from the polymerization vessel 2 at a rate of 20 kg / h.
In the polymerization vessel 2, the organoaluminum compound [B-1] 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 1 -The weight ratio between the low molecular weight portion produced in the polymerization vessel 1 and the high molecular weight portion produced in the polymerization vessel 2 (high molecular weight portion) introduced into the polymerization vessel so that the sum of the butene supply amount becomes 10 kg / h. ) / (Low molecular weight portion) was polymerized so that the high molecular weight portion was 45/55. The gas phase concentration of 1-butene is a value calculated by the following equation using a value obtained by gas phase analysis using gas chromatography.
1-butene gas phase concentration (mol%) =
1-butene gas phase concentration (mol / L) × 100 / {1-butene gas phase concentration (mol / L) + ethylene gas phase concentration (mol / L)} (Equation 18)
The polymerization activity in the polymerization vessel 2 was 9500 g / g / h.
A powdered polyethylene having an MFR5 of 0.88 g / 10 min and a density of 950 kg / m ³ was produced.
(2) Measurement of physical properties The powder obtained by the above polymerization was dried, and 1000 ppm of tri (2,4-di-t-butylphenyl) phosphate as a secondary antioxidant with respect to 100 parts by weight of the powder, stable against heat. Tetrakis (3- (4′-hydroxy-3 ′, 5′-di-t-butylphenyl) propionate) methane as an agent, 1500 ppm, and 2- (3-t-butyl-5-methyl-2-hydroxy as a weathering agent Phenyl) -5-chlorobenzotriazole 400 ppm, calcium stearate 300 ppm, Nippon Steel's TEX-44 extruder (screw diameter 44 mm, L / D = 42) Extruded at a set temperature of 200 ° C. and a resin extrusion rate of 40 kg / hr Pellet was obtained by granulation. The pellet had an MFR5 of 0.40 g / 10 min and a density of 950 kg / m ³ . A test piece was prepared using this pellet, and physical properties were measured.
Further, a 50φ pipe was formed using the pellets, and the physical properties of the pipe were measured.
The results are shown in Table 1.

[Example 2]
A low molecular weight component having a melt flow rate (MFR 2.16) of 120 g / 10 min and a density of 973 kg / m ³ is obtained when the gas phase molar concentration of the first stage hydrogen is 60 mol%, and the gas phase concentration of the second stage hydrogen is Except being 1.7 mol%, it carried out similarly to Example 1, and obtained the pellet of the melt flow rate (MFR5) 0.39g / 10min and the density of 950 kg / m < ³ >.

  Table 1 shows the results of the physical property measurement of the test piece and the pipe physical property measurement.

[Example 3]
A pellet with a melt flow rate (MFR5) of 0.44 g / 10 min and a density of 950 kg / m ³ was obtained in the same manner as in Example 1 except that the gas phase concentration of the second stage hydrogen was 1.5 mol%. It was.
Table 1 shows the results of physical property measurement and pipe physical property measurement.

[Example 4]
Pellets having a melt flow rate (MFR5) of 0.27 g / 10 min and a density of 955 kg / m ^{3 in} the same manner as in Example 1 except that the gas phase concentration of 1-butene in the second stage is 1.8 mol%. Got.
Table 1 shows the physical property measurements and the results of the pipe physical properties.

[Example 5]
Except that the gas phase concentration of hydrogen in the second stage is 1.8 mol%, pellets having a melt flow rate (MFR5) of 0.48 g / 10 min and a density of 949 kg / m ³ are obtained in the same manner as in Example 1. It was.
Table 1 shows the results of physical property measurement and pipe physical property measurement.

[Example 6]
The melt flow rate (MFR5) was set to 0.002 in the same manner as in Example 1 except that the gas phase concentration of hydrogen in the second stage was 1.0 mol% and the gas phase concentration of 1-butene was 2.9 mol%. A pellet having a density of 952 kg / m ³ was obtained at 26 g / 10 minutes.
Table 1 shows the results of physical property measurement and pipe physical property measurement.

[Comparative Example 1]
The gas phase concentration of 1-butene in the first stage is 0.4 mol%, the gas phase concentration of hydrogen in the second stage is 1.1 mol%, the gas phase concentration of 1-butene is 2.0 mol%, In the same manner as in Example 1 except that the weight ratio of the low molecular weight portion produced in step 1 and the high molecular weight portion produced in the polymerization vessel 2 was 49/51, the melt flow rate (MFR5) 0.32 g / 10 minutes, Pellets with a density of 954 kg / m ³ were obtained.
Table 2 shows the results of physical property measurement and pipe physical property measurement.
Since the amount of comonomer on the polymer side is small and the mixing ratio is large, the long-term physical properties are poor.

[Comparative Example 2]
The gas phase concentration of hydrogen in the first stage is 62 mol%, the gas phase concentration of 1-butene is 0.2 mol%, the polymerization pressure is 1.2 MPa, the melt flow rate (MFR 2.16) is 50 g / 10 min, and the density is 971 kg. / M ³ of low molecular weight component was obtained, the second stage polymerization temperature was 65 ° C., the polymerization pressure was 0.35 MPa, the second stage hydrogen gas phase concentration was 0.2 mol%, and the 1-butene gas phase concentration. In the same manner as in Example 1 except that the weight ratio of the low molecular weight portion produced in the polymerization vessel 1 and the high molecular weight portion produced in the polymerization vessel 2 is 40/60. (MFR5) A pellet having a density of 947 kg / m ³ and 0.35 g / 10 minutes was obtained.
Table 2 shows the results of physical property measurement and pipe physical property measurement.
Extrudability was poor and rough skin occurred.

[Comparative Example 3]
A low molecular weight component having a melt pressure (MFR 2.16) of 600 g / 10 min and a density of 977 kg / m ^{3 at} a first stage polymerization pressure of 1 MPa, a hydrogen gas phase concentration of 80 mol%, and a second stage polymerization temperature. In the same manner as in Example 1 except that the polymerization pressure is 0.3 MPa, the gas phase concentration of hydrogen is 1.0 mol%, and the gas phase concentration of 1-butene is 18.0 mol%. Pellets having a flow rate (MFR5) of 0.18 g / 10 min and a density of 951 kg / m ³ were obtained.
Table 2 shows the results of physical property measurement and pipe physical property measurement.
Although formability and rough skin are good, high-speed tensile property is remarkably bad.

[Comparative Example 4]
The first stage polymerization pressure is 1 MPa, the gas phase concentration of hydrogen is 80 mol%, and a low molecular weight component having a melt flow rate (MFR 2.16) of 600 g / 10 min and a density of 977 kg / m ³ is obtained. The gas phase concentration is 0.7 mol%, the gas phase concentration of 1-butene is 8.0 mol%, and 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 is 50 / Except that it was 50, it carried out similarly to Example 1, and obtained the pellet of melt flow rate (MFR5) 0.18g / 10min and density 951kg / m < ³ >.
Table 2 shows the results of physical property measurement and pipe physical property measurement.
Although formability and rough skin are good, high-speed tensile property is remarkably bad.

[Comparative Example 5]
A low molecular weight component having a melt pressure (MFR 2.16) of 100 g / 10 min and a density of 972 kg / m ³ is obtained at a first stage polymerization pressure of 12 MPa, a hydrogen gas phase concentration of 67 mol%, and a second stage polymerization temperature. Is 50 MPa, the polymerization pressure is 0.3 MPa, the gas phase concentration of hydrogen is 1.2 mol%, the gas phase concentration of 1-butene is 20.0 mol%, the low molecular weight portion produced in the polymerizer 1 and the polymerizer 2 A pellet with a melt flow rate (MFR5) of 0.40 g / 10 min and a density of 948 kg / m ³ was obtained in the same manner as in Example 1 except that the weight ratio with respect to the high molecular weight portion produced in step 1 was 50/50. .
Table 3 shows the results of the physical property measurement and the pipe physical property measurement.
Long-term characteristics are low and PE100 is not achieved.

[Comparative Example 6]
Example, except that the gas phase concentration of hydrogen in the second stage is 1.8 mol%, and the weight ratio of the low molecular weight portion produced in the polymerization vessel 1 and the high molecular weight portion produced in the polymerization vessel 2 is 50/50 In the same manner as in Example 1, pellets having a melt flow rate (MFR5) of 0.51 g / 10 min and a density of 950 kg / m ³ were obtained.
Table 3 shows the results of the physical property measurement and the pipe physical property measurement.
Long-term characteristics are low and PE100 is not achieved. There are very many occurrences in the eyes.

[Comparative Example 7]
The melt flow rate (MFR5) of 0. 2 was the same as in Example 1 except that the gas phase concentration of hydrogen in the second stage was 1.0 mol% and the gas phase concentration of 1-butene was 1.8 mol%. Pellets having a density of 955 kg / m ³ were obtained at 23 g / 10 minutes.
Table 4 shows the results of the physical property measurement and the pipe physical property measurement.
Appearance is poor due to rough skin during extrusion, and high-speed tensile properties are poor.

[Comparative Example 8]
A low molecular weight component having a polymerization pressure of 0.6 MPa in the first stage, a gas phase concentration of hydrogen of 79 mol%, a melt flow rate (MFR 2.16) of 800 g / 10 minutes, and a density of 977 kg / m ³ is obtained. In the same manner as in Example 1, except that the polymerization temperature was 50 ° C., the polymerization pressure was 0.3 MPa, the gas phase concentration of hydrogen was 7.0 mol%, and the gas phase concentration of 1-butene was 13 mol%. Pellets having a flow rate (MFR5) of 0.52 g / 10 min and a density of 950 kg / m ³ were obtained.
Table 4 shows the results of the physical property measurement and the pipe physical property measurement.
Extrudability is good, but long-term properties and high-speed tensile properties are extremely poor.

[Comparative Example 9]
The gas phase concentration of hydrogen in the second stage is 0.9 mol%, the gas phase concentration of 1-butene is 3.2 mol%, the low molecular weight portion produced in the polymerizer 1 and the high molecular weight portion produced in the polymerizer 2; Except that the weight ratio is 50/50, pellets having a melt flow rate (MFR5) of 0.18 g / 10 min and a density of 951 kg / m ³ were obtained in the same manner as in Example 1.
Table 4 shows the results of the physical property measurement and the pipe physical property measurement.
Long-term characteristics are satisfactory and PE100 is satisfied, but rough skin occurs during extrusion and the appearance is poor.

[Comparative Example 10]
The melt flow rate (MFR5) of 0. 2 was the same as in Example 1 except that the gas phase concentration of hydrogen in the second stage was 0.8 mol% and the gas phase concentration of 1-butene was 2.8 mol%. A pellet having a density of 951 kg / m ³ was obtained at 16 g / 10 minutes.
Table 4 shows the results of the physical property measurement and the pipe physical property measurement.
Long-term characteristics are satisfactory and PE100 is satisfied, but the high-speed tensile property is low, and the skin is roughened during extrusion and the appearance is poor.

[Comparative Example 11]
Example 1 except that the first stage polymerization pressure was 12 MPa, the gas phase concentration of hydrogen was 67 mol%, a low molecular weight component having a melt flow rate (MFR 2.16) of 100 g / 10 min and a density of 972 kg / m ³ was obtained. In the same manner as above, pellets having a melt flow rate (MFR5) of 0.35 g / 10 min and a density of 949 kg / m ³ were obtained.
Table 5 shows the results of physical property measurement and pipe physical property measurement.
Long-term characteristics are poor, and rough appearance occurs during extrusion, resulting in poor appearance.

[Comparative Example 12]
The melt flow rate (MFR5) of 0. 2 was the same as in Example 1 except that the gas phase concentration of the second stage hydrogen was 0.2 mol% and the gas phase concentration of 1-butene was 17.5 mol%. Pellets with a density of 948 kg / m ³ were obtained at 28 g / 10 min.
Table 5 shows the results of physical property measurement and pipe physical property measurement.
Brittle cracks occurred in a short time in the high hoop region.

  The resin composition of the present invention can be suitably used for polyethylene pipes for water pipes.

It is a flow sheet of the two-stage polymerization process of the embodiment of the present invention.

Explanation of symbols

1. Polymerizer 1
2. Line 3. 3. Flash drum 4. Compressor Pump 6. Polymerizer 2
7). line

Claims (8)

An ethylene homopolymer or a copolymer of ethylene and an α-olefin having 3 to 20 carbon atoms, having a density of 967 to 977 kg / m ³ and a melt flow rate (Code D) of 100 to 300 g / 10 min. Low molecular weight component (A) 57 to 52 parts by weight;
A copolymer of ethylene and an α-olefin having 3 to 20 carbon atoms, a high molecular weight component (B) of 43 to 48 weights having a density of 895 to 949 kg / m ³ and a weight average molecular weight of 500,000 to 1,000,000. And
Density is 943-957 kg / m ³ ,
α-olefin content (Y) is 0.30 to 1.50 mol%,
The melt flow rate (code T) is 0.25 to 0.50 g / 10 min,
The resin composition for polyethylene piping materials whose ratio (Mw / Mn) of the weight average molecular weight (Mw) and number average molecular weight (Mn) calculated | required by gel permeation chromatography is 25-40.   The resin composition for polyethylene piping material according to claim 1, wherein the tensile elongation when the ratio of the notch depth to the thickness is 11% in a high-speed tensile test is 7% or more.   When molded into a pipe, the minimum guaranteed stress after 50 years at 20 ° C. is 10 MPa or more in a hot internal pressure creep test performed by the method described in ISO 9080 on the pipe according to claim 1 or 2. The resin composition for polyethylene piping materials as described.   When it is molded into a pipe, the KneePoint due to brittle fracture is not observed within 10,000 hours in the stress-fracture time creep diagram at 80 ° C in the hot internal pressure creep test performed by the method described in ISO 9080. The resin composition for polyethylene piping material according to any one of claims 1 to 3, wherein   A value (Q / Ns) obtained by dividing the extrusion amount (Q) at a screw rotation speed of 45 rpm by the rotation speed (Ns) under an extrusion condition set at 200 ° C. with a screw diameter of 50 mmφ full flight is 0.25. (Kg / hr / rpm) or more, and the spiral flow (SFD) value at a cavity width of 10 mm, thickness of 2 mm, and 230 ° C. by injection molding is 35 cm or more. The resin composition for polyethylene piping materials according to any one of the above.   The resin composition for polyethylene piping material according to any one of claims 1 to 5, wherein the ash content is 0.07% by weight or less.   A pipe and a joint molded from the resin composition for polyethylene piping material according to any one of claims 1 to 6.   8. Pipe and fitting according to claim 7, characterized in that it is used for water supply.

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