JP2000109521A - Resin having excellent molding processability useful for polyethylene pipe and joint - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an ethylene/α-olefin copolymer resin having a specific density, a specific α-olefin content, a specific MFR, a specific mol.wt. distribution, or the like, having excellent molding processability, and useful for polyethylene pipes and joints. SOLUTION: This ethylene/α-olefin copolymer resin has (A) a density (ρ) of 0.945-0.60 g/cm3, (B) an α-olefin content (Y) of 0.30-1.50 mol.%, (C) a MFR (load: 5 kg, temperature: 190 deg.C) of 0.25-0.50 g/10 min, (D) a mol.wt. distribution (an Mw/Mn ratio) of 25-40 determined by gel permeation chromatography, and (E) a ratio (R, wt.%) of the integrated elution amount of eluted components having mol.wts. of >=100,000 and elution temperatures of <=90 deg.C to the total integrated eluted amount is not less than an equation: R0=17.37(Y)1.59 in the correlation of a mol.wt. - elution temperature - eluted amount which is determined by a cross fractionation of a temperature-rising elution fractionation with gel permeation chromatography.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyethylene pipe and a resin for a joint using a material classified as PE100 described in the ISO9080 standard. PE1
00 is the minimum guaranteed stress after 50 years at 20 ° C (hereinafter referred to as Min)
It refers to a polyethylene resin having an immuqreRequirementStrength (MSR) of 10 Mpa or more.

[0002]

2. Description of the Related Art Conventionally, polyethylene has a creep property,
Excellent environmental stress cracking resistance, impact properties, and flexibility,
Widely used as piping material. The piping material described in the present invention refers to water and sewage pipes, gas pipes, and water supply pipes. recent years,
Polyethylene pipes have been demonstrated to be superior to pipe types such as steel pipes and ductile cast iron pipes because of their properties such as the ability of the pipes to expand and follow the ground changes in response to earthquakes. Unlike mechanical joints such as steel pipes and ductile cast iron pipes, the joints are welded to the pipes by EF (electrofusion) joints.
The construction is simple and has excellent characteristics of earthquake resistance.
Due to such characteristics, attention has been paid to piping materials for water and sewage pipes, gas pipes, water supply pipes and the like.

[0003] Further, there is a high demand for safety required for each pipe material, and PE80 is used for gas pipes, and PE10 is used for water pipes.
Pipes made of materials with a rating of 0 are being used. The PE 100 described here is ISO908
In a hot internal pressure creep test described at 0, measurements of stress-rupture time curves at three different levels of temperature were performed for at least 9000 hours, resulting in a 5
The value obtained by estimating the minimum guaranteed stress after 0 years is ISO12162.
Is a polyethylene which is classified into PE100 in the classification table specified in the above. When resin for polyethylene pipes 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 when buried, so stress concentration occurs at minute structural defects in the pipe, resulting in brittleness. Severe destruction may occur. Under such severe conditions in which stress is applied over a long period of time, the conventional performance is not sufficiently satisfactory to provide a material that does not cause brittle fracture cracking.

A new polyethylene resin material-PE100 having improved long-term properties with improved brittle fracture due to resin origin
However, depending on the resin design, it is possible to obtain this PE100 classified polyethylene pipe and fitting resin, although the long-term properties are brittle, depending on the resin design. . In particular, brittle fracture is remarkable under the internal pressure creep test condition at 80 ° C.
Even if it is classified as PE100 described in SO, it can be said that PE100 is brittle under high temperature. When estimating long-term creep properties, brittle fractures are more likely to fracture than ductile fractures, so it is difficult to predict the fracture, making them unsuitable for materials used in lifelines such as water pipes. It is.

If it is only necessary to improve the long-term properties and elongation properties in order to obtain the polyethylene classified as PE100, it is not so difficult as a resin design. Materials with good processability are very difficult with current technology. In particular, the pipe and the joint are preferably made of the same resin from the viewpoint of fusion. Considering the joint formed by injection molding, polyethylene of PE100 not only has excellent mechanical properties as a pipe but also has excellent moldability. Is required.

Accordingly, such long-lasting mechanical properties,
There is a demand for a material having excellent brittle fracture resistance and elongation characteristics and excellent moldability. Thus, the ISO 908
PE100 excellent in moldability, classified by the classification table defined in ISO12162 by measurement based on 0, is a material that is highly expected in the future for use in water and sewage pipes, gas pipes, water supply pipes and the like as lifelines. is there. Until now, polyethylene has been improved by widening the molecular weight distribution and introducing a copolymerizable comonomer as a side chain during polymerization in order to improve long-term mechanical properties (Japanese Patent Publication No. 61-42736, , Tokiko Sho 61-4
No. 3,378), it was difficult to improve the long-term mechanical properties required of PE100 by itself.

Japanese Patent Application Laid-Open No. H10-17619 discloses a method of controlling the distribution of comonomer in order to improve long-term properties and impact resistance, and to determine the contribution of the comonomer to the high molecular weight side by temperature-eluting fractionation and cross-fractionation with GPC. Focusing on the correlation between required molecular weight-elution temperature-elution amount, the design of polyethylene has been improved, but in order to obtain a polyethylene resin classified as PE100, it is impossible to obtain PE100 unless the resin design is further limited. Can not. JP-A-8-301933 describes a polyethylene pipe having excellent mechanical properties. The polyethylene forming this pipe is made of polyethylene having two molecular weight distributions and has a high molecular weight due to a design in which MFR5 is 0.35 g / 10 min or less, and it is highly possible that such a material has excellent mechanical properties and is PE100. However, the molding processability is poor, and in the production of pipes and fittings by actual extrusion molding and injection molding, it is expected that productivity will be extremely poor especially in injection molding. Also, Japanese Patent Application Laid-Open No. 8-134285
Discloses a composition comprising two components having different intrinsic viscosities and densities. When a pipe molded body is formed using this composition, the properties of the pipe include a hot internal pressure creep test, a tensile creep test, and a tensile fatigue test. It has been proposed that the above-mentioned properties are dramatically improved over conventional materials.

According to this, the density and intrinsic viscosity of the two-component composition of low molecular weight, high density polyethylene and high molecular weight, low density polyethylene are 0.945 to 0.945 respectively.
0.970 g / cm3, 2.41 to 6.3 dyne / c
m2, and a shear rate (FI) when the shear stress of the capillary at 190 ° C. reaches 2.4 × 10 6 dyne / cm 2 is 350 sec -1 or less. sometimes,
It is said that it is possible to mold pipes with excellent moldability, pipe fatigue properties, etc., but such a composition has a high molecular weight, etc., but pipe properties such as fatigue properties certainly increase, Conversely, it means a composition that tends to deteriorate in terms of moldability, especially in injection molding for forming a joint.

[0009] Judging from the MFR of Examples and Comparative Examples in which the value referred to as the fluidity index (FI) in the text is FI ≤ 350 sec-1, since the design is on the high molecular weight side taking physical properties into consideration, it is almost impossible to form It cannot be said that the workability is excellent. Similarly, JP-A-9-286820
In the publication, there is also a polyethylene pipe and its pipe joint, but the described FI value is 100 to 400 sec.
-1 is not suitable for a joint formed by a molding method in a high shear rate region by injection molding.

[0010]

SUMMARY OF THE INVENTION The present invention provides a long-term property and an elongation property, particularly under high temperature acceleration conditions, while maintaining rigidity.
An object of the present invention is to provide a polyethylene pipe and a resin for a joint obtained by using a novel high-density polyethylene which is very excellent in impact resistance and also excellent in processability.

[0011]

Means for Solving the Problems As a result of intensive studies, the present inventors have found that a polyethylene satisfying all the specific constitutional conditions can achieve the above object, and have reached the present invention. That is, the present invention relates to a copolymer of ethylene and another α-olefin, wherein (a) density (ρ): 0.9
45 to 0.960 g / cm3 (b) α-olefin content (Y): 0.30 to 1.50 mol% (c) MFR (load 5 kg, temperature 190 ° C., hereinafter MFR5) 0.25
0.50 g / 10 min (d) Molecular weight distribution: Mw and M determined by gel permeation chromatography
n (Mw / Mn) is 25 to 40, and (e) the molecular weight is 100,000 or more in the correlation between molecular weight, elution temperature, and elution amount obtained by cross-fractionation between elevated temperature elution fractionation and gel permeation chromatography. R0 is the ratio (R, unit: wt%) of the integrated elution amount of the elution component having an elution temperature of 90 ° C. or less to the total integrated elution amount.
that's all,

[0012]

(Equation 2)

[0013] A polyethylene pipe and a joint resin. In addition, low molecular weight component (A)
And the high molecular weight component (B). The low molecular weight component (A) has a density of 0.970 to 0.980 g / cm 3 and has an MFR (load of 2.16 kg, temperature of 190 ° C .; hereinafter MFR of 2.16). ) Is 50 to 300 g / 10 min, and the high molecular weight component (B) has a density of 0.896 to 0.952 g / cm3 and a weight average molecular weight of 480,000 to 45 to 60% by weight. 1.15 million ethylene copolymers are 40 to 55% by weight, and the total weight (A +
Weight ratio of high molecular weight component (B) to B) (B / A + B)
Is the polyethylene resin for pipes and joints described above, which has a value of 0.40 to 0.55.

A minimum internal stress (hereinafter, referred to as MRS) after 50 years at 20 ° C. is 10 MPa or more by a hot internal pressure creep test according to the method described in ISO9080. Resin. In addition, in the creep test of the internal pressure under hot pressure according to the method described in ISO9080, the creep diagram of the stress-rupture time at 80 ° C. shows that KneePoi due to brittle fracture was observed.
The polyethylene pipe and the joint resin described above, wherein nt is not observed within 10,000 hours.

Further, a value obtained by dividing the extrusion amount (Q) at a screw rotation speed of 40 rpm by the rotation speed (Ns) under the extrusion conditions set at 170 ° C. to 210 ° C. with a screw diameter of 65 mmφ full flight (Ns) Q / Ns) is 0.70 (kg / hr / rpm) or more, and a spiral flow at 230 ° C. by injection molding (hereinafter, S;
FD) The above-mentioned polyethylene pipe and resin for a joint having excellent fluidity having a value of 35 cm or more. Also,
The resin for a polyethylene pipe and the joint as described above, wherein the ash content is 0.07% by weight or less. In addition, among the polyethylene pipes and fitting resins described above, there are provided polyethylene pipes and fitting resins characterized by being used for water supply.

The polyethylene pipe and the joint resin described in the present invention are a material of PE100 having excellent long-term properties, elongation properties, and impact resistance, and are excellent in moldability and workability. As a result of earnest studies, it has been obtained that the resin design in a very narrow area is limited in order to obtain such high-density polyethylene. Therefore, the polyethylene mentioned in the examples has a design that emphasizes the improvement of physical properties at the expense of moldability, and the material PE100 with excellent moldability reported in this report is a new polyethylene pipe and joint resin that has never been seen before. It is.

[0017] PE100 with good moldability can be achieved with a very narrow and limited design. The polyethylene pipe and the joint resin of the present invention are:
By using PE100 which is more excellent in moldability than the conventional polyethylene pipe and fitting resin, long-term characteristics are dramatically improved and the productivity is very high. Also, when producing polyethylene pipes and joints, they are usually provided in a colored form together with a coloring pigment in order to limit the use as pipes.

Taking a polyethylene pipe for water supply as an example, when tap water in Japan is used, bubbles are generated due to chlorine water and the surface layer is peeled off due to this. Become. As described above, if the polyethylene pipe and the joint resin containing the coloring pigment contain a large amount of ash, it is considered that the chlorine water resistance may be reduced.
No. 6762 for polyethylene pipes for water supply. As described above, the polyethylene pipe and the joint resin excellent in pipe characteristics, moldability, and chlorine water resistance are novel polyethylene resin materials that have never existed before.

If the density is less than 0.945 g / cm 3, the rigidity of the tube is insufficient, and 0.960 g / cm 3
If it exceeds 3, the rigidity of the tube is high, but the ESCR and elongation characteristics under high temperature accelerated conditions deteriorate, and if used for a long time, cracks occur and brittle fracture such as low-speed crack fracture occurs. In particular, in the case of hot internal pressure creep, the creep characteristics on the short-term side are high, but on the long-term side, brittle fracture occurs suddenly regardless of the operating pressure, and the long-term properties cannot be satisfied.

Next, the (b) α-olefin content (Y) of the high-density polyethylene of the present invention is from 0.30 to 1.5
0 mol%, preferably 0.50 to 1.00 mo
1%. Here, α-olefin content refers to other α-olefin content.
-The total content of olefins. If the α-olefin content (Y) is less than 0.30 mol%, the ESCR and elongation characteristics under high-temperature acceleration conditions are reduced. It is difficult to produce a high-density polyethylene having an α-olefin content (Y) of more than 1.50 mol%, and the resulting composition also deteriorates mechanical properties due to generation of a gel. Means for improving long-term mechanical properties include increasing the molecular weight and widening the molecular weight distribution. However, simply increasing the molecular weight by such a method is not suitable for forming pipes from the viewpoint of moldability. No Further, although the fluidity is improved by widening the molecular weight distribution, properties such as elongation properties and impact properties are deteriorated.

(C) MF of the high-density polyethylene of the present invention
R5 is 0.25 to 0.50 g / 10 minutes, preferably 0.30 to 0.45 g / 10 minutes. If the MFR5 exceeds 0.50 g / 10 minutes, the moldability is good, but the long-term life and elongation characteristics of the internal creep during hot work are reduced, and the impact resistance tends to be poor. MFR5 is 0.
High-density polyethylene of less than 25 g / 10 minutes improves mechanical properties but makes molding processability, especially injection molding difficult. Further, as an index of the molecular weight distribution (d) of the high-density polyethylene of the present invention, the ratio of Mw to Mn (Mw / Mn) determined by gel permeation chromatography.
Mn) is 25-40. If the Mw / Mn is less than 25, the long-term life and elongation characteristics of the internal creep during hot work are reduced, and the moldability, especially the injection molding, tends to deteriorate. Also,
When Mw / Mn exceeds 40, the moldability and the like are improved due to the influence of the low molecular weight component, but the creep characteristics and the impact resistance under hot internal pressure tend to be inferior.

The high-density polyethylene of the present invention comprises:
(E) In the correlation of molecular weight-elution temperature-elution amount determined by cross-fractionation between temperature-elution fractionation and gel permeation chromatography, the integrated elution amount of the elution component having a molecular weight of 100,000 or more and an elution temperature of 90 ° C or less is obtained. The ratio (R, unit: wt%) to the total integrated elution amount is R0 or more determined by the following equation,

[0023]

(Equation 3)

It is necessary that If R is less than R0, the long-term life in hot internal pressure creep is inferior and the impact resistance tends to decrease. In addition, as a guide to the molding processability, the ratio of the length to the die diameter of the extruder (L / D) is 2
2. The discharge rate (Q) when extruded at a screw rotation speed of 40 rpm under the condition that the compression ratio is 3.1 / 1, the temperature from the cylinder to the die temperature is 170 ° C. to 210 ° C., and the screw diameter is 65 mmφ (full flight). Rotation speed (N
s; 40 rpm). The compression ratio mentioned here is the ratio S (F) / S of the area S (F) of the feed zone to the area S (M) of the metering zone.
(M), and each area is calculated from the groove depth of each screw as follows. Screw outer diameter to R
And the groove depth of the metering zone is tM, and the groove depth of the feed zone is tF. Here, π indicates the pi.

[0025]

(Equation 4)

When the value of Q / Ns is 0.70 (kg / hr)
/ Rpm) or higher, preferably 1.0 or higher, more preferably 1.5 or higher. If the value of Q / Ns is less than 0.7, the ejection amount is further reduced in actual production, and the resin pressure tends to increase. In addition, when spiral flow is performed by injection molding under the condition of 230 ° C., a material having an SFD value of 35 cm or less is inferior in moldability when molding a joint or the like, and alignment distortion or the like due to residual stress or the like is likely to occur. . Therefore, in order to improve the long-term properties more effectively without impairing the fluidity by increasing the molecular weight, it is necessary to use the above-described polyethylene in which a comonomer is selectively introduced on the high molecular weight side.
At this time, the ratio of the high molecular weight of the polymer obtained by the comonomer selectively introduced to the high molecular weight side is the molecular weight-elution temperature-obtained by cross-fractionation between temperature-elution fractionation and gel permeation chromatography. In the correlation diagram of the elution amount, the molecular weight is 100,000 or more and the elution temperature is 90 ° C.
This can be limited by the fact that the integrated elution amount of the following eluted components is R0 or more (R, unit: wt%) with respect to the total integrated elution amount.

[0027] The present invention relates to a polyethylene pipe and a resin for a joint, characterized in that the above-mentioned polyethylene pipe and the resin for a joint are formed by using the polyethylene resin classified as PE100 described above. The high-density polyethylene of the present invention is polymerized by a Ziegler-type catalyst or a Phillips-type catalyst. A Ziegler-type catalyst is preferred, and a high-activity Ziegler-type catalyst supported on a solid support is particularly preferred. Representative examples of the solid carrier include a halogen-containing magnesium compound, and specific examples include magnesium dihalide and oxymagnesium halogenide. Specific examples of the transition metal compound which is a main component of the catalyst include titanium tetrachloride, titanium trichloride, titanium dichloride, tetrabutoxy titanium, tributoxy titanium chloride, dibutoxy titanium dichloride, vanadium tetrachloride, vanadium oxychloride, and vanadium. , Vanadium trichloride and the like, and these can be used alone or in combination.

Representative examples of the organometallic compounds constituting the catalyst include alkylaluminum compounds, trialkylaluminums, dialkylaluminum allides, alkylaluminum dihalides, alkylaluminum sesquihydrides, dialkylaluminum hydrides, and alkylaluminum dihydrides. In general,
Trimethylaluminum, triethylaluminum, tripropylaluminum, tri-n-butylaluminum, tri-i-butylaluminum, tri-n-hexylaluminum, tri-n-octylaluminum, diethylaluminum chloride, diethylaluminum iodide, ethylaluminum dichloride, ethylaluminum There are sesquichloride, diethylaluminum hydride and the like.

The high-density polyethylene of the present invention is produced by a method such as slurry polymerization, bulk polymerization, gas polymerization, and solution polymerization. The high-density polyethylene of the present invention can be produced by one-stage polymerization, two-stage polymerization, or a multistage polymerization of more than one stage.However, in order to satisfy the constituent conditions of the present invention, α-olefin which is a comonomer is emphasized. It is necessary to copolymerize to the high molecular weight part of the polymer. An example of a preferred two-stage polymerization used in the present invention is described below with reference to FIG.

In the polymerization vessel 1, ethylene, hexane, hydrogen, a catalyst component and the like are supplied from a line 2. No α-olefin is supplied. Thereby, low molecular weight homopolyethylene is polymerized. The polymerization pressure is 1-30 kg / cm2G,
Preferably, the polymerization temperature is 3 to 25 kg / cm2G and the polymerization temperature is 60
C. to 100.degree. C., preferably 70 to 90.degree. The slurry in the polymerization vessel 1 is led to a flash drum 3 to remove unreacted ethylene and hydrogen. The removed ethylene and hydrogen are returned to the polymerization reactor 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 polymerization vessel 6, ethylene, α-olefin comonomer,
By supplying hexane, hydrogen, catalyst components, etc.,
High-molecular-weight polyethylene in which an α-olefin is copolymerized is polymerized. The polymerization pressure is 0.5 to 30 kg / cm2
G, preferably 0.5 to 20 kg / cm 2 G, 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 step.

The high-density polyethylene of the present invention may be obtained by mixing by a known mixing method, for example, kneading with a single-screw or twin-screw extruder or a Banbury mixer. In this case, the obtained polymer is also used. α-
It is necessary to select polyethylene before mixing so that the olefin is mainly copolymerized into the high molecular weight part of the polymer.

The high-density polyethylene of the present invention may contain, if necessary, phenol-based, phosphorus-based, sulfur-based antioxidants, metal soaps such as calcium stearate and magnesium stearate, ultraviolet absorbers, and light stabilizers. Known additives such as antistatic agents, antifogging agents, and color pigments can be mixed and used, but the ash content shown in JIS, K6762 is reduced to 0.07.
The formula must be less than wt%.

As a method of forming a pipe using the high-density polyethylene of the present invention, high-density polyethylene, which is PE100 described above, is melted at a temperature of 170 ° C. to 220 ° C., and is extruded into a Φ65 mm extruder (manufactured by Toshiba Plastic Engineering Co., Ltd.). Extruded into a cylindrical shape from the attached outer diameter 80 mm, inner diameter 68 mm die, and passed through a sizing plate in a sizing tank to form the outer diameter, and as a primary cooling, the sizing tank water temperature was cooled at 20 ° C to 60 ° C. After leaving the sizing tank, the pipes cooled at a water temperature of 15 ° C. to 25 ° C. as secondary cooling are taken out by a take-up machine so that SDR (outer diameter / thickness ratio) = 11, nominal diameter 50 mm, meat A 5.5 mm thick tubular pipe was formed.

The polyethylene pipe and the joint resin using the high-density polyethylene of the present invention are superior to conventional polyethylene pipe and the joint resin in the hot internal pressure creep property, so that they can be used for a long time and can be used for gas pipes and the like. As compared with the resin for medium density polyethylene pipes, it is possible to enhance the long-term safety without breaking even in a higher stress region in the long-term mechanical properties.

As a method of evaluating long-term properties, a hot internal pressure creep test is widely performed. However, polyethylene pipes and fittings used for water supply are excellent in long-term mechanical properties. Even if the measurement is performed for a sufficiently long time (at least one year or more) below, brittle fracture may not be observed. Therefore, long time measurement evaluation is required for material determination. Also, if high stress is applied to the pipe, ductile fracture due to plastic deformation becomes dominant,
A material having high rigidity is unlikely to undergo plastic deformation in a high stress region, and tends to have excellent long-term mechanical properties during a short test period. However, the fracture mode of a pipe under low stress may show brittle fracture without plastic deformation, contrary to ductile fracture with plastic deformation, and in such a case, the pipe must be left under low stress for a long time. Therefore, a material that does not easily undergo plastic deformation in a high stress region is not necessarily a material having excellent long-term characteristics.

The high-density polyethylene which is 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 the joint are made of the same resin. In the case where fusion is performed, injection molding on the joint side becomes difficult, and therefore PE100 excellent in moldability is desired in the market.

[0037]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to embodiments, but the present invention is not limited to these embodiments unless it exceeds the gist. Hereinafter, a method for measuring the basic physical properties of the material used in the present invention will be described. (1) Density (ρ, unit: g / cm3) According to ASTM-D1505, density gradient tube method (23
° C). (2) α-olefin content (Y, unit: mol%) Model is JEOR, α400, measurement mode: 13C-NM
R, temperature 135 ° C, number of integration 10,000 times, sample 30
μg / 0.4cc orthodichlorobenzene, reference substance:
It measured with deuterated benzene (C6D6). The calculation of the α-olefin content was carried out by the following equation.

[0038]

(Equation 5)

Where X is an α-olefin unit, E
Represents a unit of ethylene, and is calculated assuming only a chain (dyad structure) in which two units are connected. (XE) is a chain of α-olefin and ethylene, (E)
E) shows a chain of ethylene and ethylene, and is calculated assuming that the sum of (EE) and (XE) is 100 mol%. Melt flow index (unit: g / 10 minutes) JIS, K,
Measured at 190 ° C. under a load of 5 kg according to 6760. (4) Molecular weight distribution (Mw / Mn) It is a ratio between Mw and Mn determined by measurement by gel permeation chromatography. The device is Water
Using two 150 cm columns manufactured by Tosoh Corporation and two AT-807 / S columns manufactured by Showa Denko K.K.
The measurement was performed at 140 ° C. using 2,4-trichlorobenzene as a solvent. (5) The ratio (R, unit: wt%) of the total eluted amount of the eluted components having a molecular weight of 100,000 or more and an elution temperature of 90 ° C. or less to the total total eluted amount
0 was calculated from the correlation of molecular weight-elution temperature-elution amount determined by cross-fractionation between temperature-elution fractionation and gel permeation chromatography. FIG. 3 is a schematic diagram showing the elution amount by a contour line. The integrated elution amount of the elution component having a molecular weight of 100,000 or more and an elution temperature of 90 ° C. or less corresponds to a hatched portion in FIG. The ratio to the total integrated elution amount is R
It is. The measuring device is C manufactured by Dia Instruments Co., Ltd.
FC-T-150A type was used. As columns for gel permeation chromatography, three AD-806MS columns manufactured by Showa Denko KK were used. Ortho-dichlorobenzene was used as the solvent, and the measurement was always performed at 140 ° C. except for the heated and eluted fractionation part. (6) Flexural modulus (unit: kgf / cm2) Measured according to JIS-K7203. (7) 80 ° C.-ESCR (unit: hr) According to JIS-K6760, the water temperature of the constant temperature water tank is 8
The measurement was performed after changing to 0 ° C. As a test solution, a 10% by weight aqueous solution of Liponox NC-140 manufactured by Lion Corporation was used. (8) Tensile breaking elongation (l, unit:%) According to JIS-K6760, the test speed is 10 mm
/ Sec, and the tensile elongation at break (l) was calculated by the following equation. l = (L−L0) / L0 × 100 (where,
l: tensile elongation at break, L: distance between grips at break (m
m), L0; indicates the original distance (mm) between the gripping tools.) (9) Izod impact strength (Iz, unit: kgf · cm)
/ Cm2) In accordance with JIS-K7110, the test piece shape was measured at 23 ° C. using a No. 2 type A type. (10) Spiral flow length (SFD, unit: cm) An injection temperature of 230 ° C., an injection pressure of 100 kg / cm 2, and a mold having a spiral cavity having a thickness of 2 mm were used.
The sample was injection-molded under a molding condition of a mold temperature of 50 ° C., and the length of the formed spiral was measured. As a molding machine, an injection molding machine IS150EN manufactured by Toshiba Machine was used. Extrusion amount per rotation (Q / Ns, Q: kg / hr, Ns: rp
m) Using a Toshiba extruder (screw diameter 65 mmφ), the cylinder temperature and the die temperature were measured under the following conditions, the discharge rate at a rotation speed of 40 rpm was measured, and this was divided by the rotation speed. Cylinder temperature: C1: C2: C3 = 170: 190:
210 ° C. Die temperature: H: D1: D2: D3 = 210: 210: 2
10: 210 ° C. Die outer diameter: 80 mm, die inner diameter: 68 mm, clearance 6 mm. (12) Hot internal pressure creep test A three-level temperature of 20 ° C., 60 ° C., and 80 ° C. was selected by a test method described in ISO9080 using a pipe (50A) having a diameter for a polyethylene pipe for gas described in JIS, K6774. A hot internal pressure creep test was performed at an arbitrary hoop stress so as to include at least one point of data of 9000 hours or more. Ash test According to the ash test for polyethylene pipes for water supply described in JIS, K6762, 10 g of a sample is put into a crucible, carbonized in an electric furnace, the sample weight before and after carbonization is measured, and the sample weight before carbonization. The sample weight after carbonization was calculated in%.

[0040]

Example 1 In the two-stage polymerization process of FIG.
In order to produce a low-molecular-weight homopolyethylene, polymerization was carried out in a polymerization vessel 1 having a reaction volume of 170 L. The polymerization temperature is 85 ° C,
The polymerization pressure is 8 kg / cm2G. In this polymerization vessel 1, triisobutylaluminum was added at a rate of 0.8 mmol (based on Ti atom) / hr with titanium tetrachloride supported on a solid support containing magnesium chloride as a basic component.
At a rate of 0 mmol (based on metal atoms) / hr, purified hexane is supplied at a rate of 40 L / hr, and ethylene is added at a rate of 1 L / hr.
At a rate of 1 kg / hr, polymerization is carried out by supplying hydrogen as a molecular weight regulator so that the gas phase concentration becomes about 50 mol%.
The pressure of the polymer slurry in the polymerization vessel 1 is 0.5 kg / cm.
It is led to a flash drum 3 of 2 G and a temperature of 70 ° C. to separate unreacted ethylene and hydrogen, and then pressurized and introduced into a polymerization vessel 6 by a slurry pump 5. The removed ethylene and hydrogen are returned to the polymerization reactor 1 whose pressure has been increased by the compressor 4. In the polymerization vessel 6, a temperature of 65 ° C. and a pressure of 2 kg were used to produce a high molecular weight polyethylene in which butene-1 was copolymerized.
/ Cm2G. The polymerization vessel 6 has an internal volume of 110 L. In the polymerization vessel 6, 15
At a rate of mmol (based on metal atoms) / hr, purified hexane is supplied at a rate of 60 L / hr, ethylene is supplied at a rate of 9 kg / hr, and hydrogen and butene-1 are supplied at a gas phase concentration of about 0.7 mol% and about 0.7 mol%, respectively. It was introduced so as to be 8 mol%, and polymerization was carried out. The polymer in the polymerization vessel 6 is obtained as pellets after a drying step and a granulation step. Table 1 shows the obtained high-density polyethylene and the measurement results of its physical properties.

[0041]

Comparative Example 1 Two-stage polymerization was carried out in the same manner as in Example 1 except that butene 1 was also introduced into a polymerization vessel 1 for polymerizing low molecular weight polyethylene, to obtain a high-density polyethylene shown in Table 1.
Table 2 shows the measurement results of physical properties of the obtained high-density polyethylene.

[0042]

Comparative Examples 2 to 9 In the same manner as in Example 1, the amount and polymerization of butene-1 and the like were adjusted so that the density, α-olefin content, molecular weight distribution, and R (ratio of the integrated elution amount) shown in Table 2 were obtained. The two-stage polymerization was carried out by appropriately changing the conditions to obtain a high-density polyethylene shown in Table 2. Table 2 shows the measurement results of physical properties of the obtained high-density polyethylene.

As shown in Table 1, in the examples satisfying all the constituent conditions of the present invention, all the physical properties in the table are excellent, but as shown in Table 2, they do not satisfy any one of the constituent conditions. In the comparative example, the rigidity and ESC of high temperature acceleration conditions
It is clear that any of R, elongation characteristics, long-term creep characteristics, and fluidity are inferior.

[0044]

[Table 1]

[0045]

[Table 2]

[0046]

As described above, according to the present invention, while maintaining rigidity, it is very excellent in long-term characteristics, elongation characteristics and impact resistance, especially under high temperature acceleration conditions, and also excellent in moldability. The present invention can provide a polyethylene pipe and a resin for a joint obtained by using a novel high-density polyethylene.

[Brief description of the drawings]

FIG. 1 is a flow sheet of a polymerization process.

FIG. 2 shows the correlation between the α-olefin content (Y) and the ratio (R) of the total eluted amount of the eluted components having a molecular weight of 100,000 or more and an elution temperature of 90 ° C. or less to the total integrated elution amount in Examples and Comparative Examples of the present invention. FIG.

FIG. 3 is a contour diagram of CFC molecular weight-elution amount-temperature.

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[Procedure amendment]

[Submission date] October 15, 1998 (1998.10.
15)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0025

[Correction method] Change

[Correction contents]

[0025]

(Equation 4)

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat ゛ (Reference) B29L 23:00

Claims (7)

[Claims] 1. A copolymer of ethylene and another α-olefin, wherein (a) a density (ρ): 0.945 to 0.9
60 g / cm3 (b) α-olefin content (Y): 0.
30 to 1.50 mol% (c) MFR (load 5 kg, temperature 190 ° C., hereinafter MFR 5) 0.25 to 0.50 g / 1
0 min (d) Molecular weight distribution: ratio of Mw to Mn (Mw) determined by gel permeation chromatography
/ Mn) is 25 to 40, and (e) a correlation between molecular weight, elution temperature, and elution amount determined by cross-fractionation between the elevated temperature elution fractionation and gel permeation chromatography.
Ratio (R, unit: total integrated elution amount) of the integrated elution amount of the elution component having a molecular weight of 100,000 or more and an elution temperature of 90 ° C. or less.
wt%) is equal to or greater than R0 obtained by the following equation: A resin for a polyethylene pipe and a joint, characterized in that: 2. A low molecular weight component (A) comprising a low molecular weight component (A) and a high molecular weight component (B), wherein the low molecular weight component (A) has a density of 0.970 to 0.980 g / cm 3 and an MFR
(Load 2.16 kg, temperature 190 ° C; hereinafter MFR 2.1
6) is 45 to 60% by weight of an ethylene polymer having a content of 50 to 300 g / 10 min, the high molecular weight component (B) has a density of 0.896 to 0.952 g / cm3 and a weight average molecular weight of 480,000. Ethylene-based copolymer having a molecular weight of
0 to 55% by weight, and the weight ratio (B / A + B) of the high molecular weight component (B) to the total weight (A + B) is 0.40 to 0.
The polyethylene resin for pipes and joints according to claim 1, wherein the polyethylene resin is 55. 3. The minimum internal stress (hereinafter referred to as MRS) after 50 years at 20 ° C. in a hot internal pressure creep test according to a method described in ISO9080, and is at least 10 MPa. For polyethylene pipes and fittings. 4. A stress-rupture time creep diagram at 80 ° C. in a creep test under a hot internal pressure according to a method described in ISO9080, which shows a KneePoint due to brittle fracture.
2. is not seen within 10,000 hours
4. The resin for a polyethylene pipe and a joint according to claim 2 and claim 3. 5. An extrusion amount (Q) at a screw rotation speed of 40 rpm under an extrusion condition set at 170 ° C. to 210 ° C. with a screw diameter of 65 mmφ full flight.
Is divided by the number of rotations (Ns) (Q / Ns) is 0.7.
0 (kg / hr / rpm) or more and spiral flow at 230 ° C. by injection molding (hereinafter, SFD)
The polyethylene pipe and the joint resin according to claim 1, wherein the value is 35 cm or more, and the resin has excellent fluidity. 6. The resin for polyethylene pipes and joints according to claim 1, wherein the ash content is 0.07% by weight or less. 7. The method of claim 1, 2, 3
7. The polyethylene pipe and the joint resin according to claim 4, wherein the polyethylene pipe and the joint resin are water supply.