JP2005239750A - Ethylene polymer for pipe and pipe made of ethylene polymer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an ethylene polymer for a pipe excellent in moldability and particularly excellent in long-life property, and to provide a pipe molded product made of the ethylene polymer. <P>SOLUTION: The ethylene polymer for the pipe has an intrinsic viscosity [η] (dl/g) of 2.7-4.1 as measured in decalin at 135°C, a density (d) (kg/m<SP>3</SP>) of 952-962 kg/m<SP>3</SP>for a sample which is straightly cooled down to room temperature in one hour after one hour annealing at 120°C as measured using a density gradient tube, a weight-average molecular weight(Mw)/number-average molecular weight (Mn) ratio of at least 11 and at most 50 as measured by GPC (gel permeation chromatography), and the actual stress (S) (MPa) of 19.4-27.2 when the number of cycles until breakage in the tensile fatigue characteristics is measured at 23°C is 10,000. The pipe is made of the ethylene polymer. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an ethylene polymer for pipes excellent in moldability and long life and a pipe comprising the ethylene polymer.

    High-density polyethylene used in a wide range of applications such as films, pipes, and bottle containers has been conventionally produced using Ziegler-Natta catalysts and chromium catalysts. However, due to the properties of these catalysts, there is a limit to the control of the molecular weight distribution and composition distribution of the polymer.

  In recent years, ethylene homopolymers or ethylene / α-olefin copolymers with a relatively low molecular weight have been used with a single-site catalyst or a catalyst with a single-site catalyst supported on a carrier that can easily control the composition distribution. Have disclosed several methods for producing an ethylene polymer having excellent moldability and mechanical strength, including a large ethylene homopolymer or ethylene / α-olefin copolymer, by a continuous polymerization method.

  JP-A-11-106432 discloses a low molecular weight polyethylene and a high molecular weight ethylene / α-olefin copolymer obtained by polymerization using a supported geometrically constrained single site catalyst (CGC / Borate catalyst). A composition prepared by melt blending is disclosed. However, since the molecular weight distribution of the composition is not wide, the fluidity of the composition may be inferior. Further, in the claims of the above publication, the preferred carbon number range of the α-olefin copolymerized with ethylene is not disclosed, but if the carbon number is less than 6, the mechanical strength may not be sufficiently developed. is expected. Furthermore, since the molecular weight distribution (Mw / Mn) of the single-stage polymer is wide, it is expected that the mechanical properties such as impact strength are not sufficient as compared with the narrow molecular weight distribution of the single-stage product. The forecast that the above-mentioned strength is inferior when the composition distribution of the single-stage polymer is wide is that of CMC Publishing Co., Ltd., “Functional Materials”, Cross Separation (CFC) data described on page 50 of the March 2001 issue. This is also clear from the cross fractionation (CFC) data described in FIG. 2 of the Kaihei 11-106432 publication.

WO01 / 25328 discloses an ethylene polymer obtained by solution polymerization using a catalyst system comprising CpTiNP ( ^t Bu) ₃ Cl ₂ and borate or alumoxane. In this ethylene-based polymer, since the component having a low molecular weight is branched, the crystal structure is weak, and therefore, it is expected that the mechanical strength is inferior. Further, since the molecular weight of the low molecular weight component is relatively large, it is expected that the fluidity is inferior. Further, in the claims of the publication, the preferred carbon number range of the α-olefin copolymerized with ethylene is not disclosed, but if the carbon number is less than 6, the mechanical strength may not be sufficiently developed. It is done.

  EP1201711A1 discloses ethylene obtained by slurry polymerization in the presence of a catalyst system consisting of ethylene bis (4,5,6,7-tetrahydro-1-indenyl) zirconium dichloride and methylalumoxane supported on silica. System polymers are disclosed. Among these ethylene polymers, the single-stage polymer has a wide molecular weight distribution (Mw / Mn), and therefore, it is expected that the impact strength and the like are inferior to those of the single-stage product having a narrow molecular weight distribution. In addition, when the molecular weight distribution is wide, it is presumed that the active species are non-uniform. As a result, there is a concern that the composition distribution is widened and the fatigue strength is lowered. In addition, in some examples of the publication, a single-stage polymer product having a low molecular weight and a single-stage polymer product having a high molecular weight are melt-kneaded. In such a kneading method, a continuous crystal structure exceeding 10 μm is often generated, and it is expected that sufficient strength may not be exhibited.

  JP 2002-53615 discloses an ethylene polymer obtained by slurry polymerization using a catalyst system comprising a zirconium compound having a specific salicylaldimine ligand supported on silica and methylalumoxane. ing. Although the preferred carbon number range of the α-olefin copolymerized with ethylene is not disclosed in the claims of the publication, 1-butene (the number of carbon atoms) used as the α-olefin in the examples of the publication = 4) It is assumed that the ethylene polymer obtained in 4) has a small number of carbon atoms and does not exhibit sufficient mechanical strength.

  In general, an ethylene polymer exhibits a multimodal molecular weight distribution. When the molecular weight difference between the multimodal peaks is large, it is difficult to mix them by melt-kneading, so that multistage polymerization is usually employed. In general, multistage polymerization is often performed continuously. In such a continuous multistage polymerization, the residence time in the polymerization vessel in a polymerization environment that produces a low molecular weight product and the residence time in the polymerization environment in a polymerization environment that produces a high molecular weight product. In general, there is a difference in the molecular weight between particles in the case of a polymerization method in which the polymer takes a particle shape, such as a gas phase method or a slurry method. . Such a difference in molecular weight was recognized even when using a Ziegler catalyst described in Japanese Patent No. 821037, etc., but because the catalyst is multi-site, the molecular weight distribution is wide, and therefore normal melt-kneading. Even in the pelletization by, the polymer particles were well mixed. On the other hand, when a single site catalyst is used, since the molecular weight distribution is narrow, pelletization by ordinary melt-kneading often does not sufficiently mix the polymer particles. Therefore, a history of the shape of the polymer particles remains, which may cause flow disturbance and deteriorate the appearance, or may not exhibit sufficient mechanical strength. Moreover, in such an ethylene polymer, the smoothness coefficient calculated | required from the surface roughness of an extrusion strand tends to become large.

  The ethylene (co) polymer using a Ziegler catalyst described in Japanese Patent No. 821037 and the like has methyl branches in the molecular chain because methyl branches are by-produced during the polymerization. Methyl branching is known to be incorporated into crystals and weaken the crystals (see, for example, Polymer, Vol. 31, page 1999, 1990), which causes the mechanical strength of ethylene (co) polymers. Was lowering. In addition, in the copolymerization of ethylene and α-olefin, a hard and brittle component is formed when almost no α-olefin is contained, whereas when α-olefin is excessively copolymerized, it is soft and has a crystal structure. As a result of generation of weak components, stickiness may be caused. Furthermore, since the molecular weight distribution is wide, there has been a problem that a low molecular weight body exhibits a phenomenon of adhering to the surface of the molded product as a powdery substance.

  In an ethylene polymer obtained by polymerization using a metallocene catalyst described in JP-A-9-183816 and the like, methyl branches are present in the molecular chain as a result of by-production of methyl branches during the polymerization. The methyl branch is incorporated into the crystal and weakens the crystal structure. This has been a cause of lowering the mechanical strength. Further, an ethylene polymer having an extremely large molecular weight has not been disclosed so far.

  The ethylene-based polymer obtained by polymerization using a chromium-based catalyst has long chain branching and thus has a small molecular spread, and therefore has poor mechanical strength. Further, methyl branching was present in the molecular chain because methyl branching was by-produced during the polymerization. The methyl branch is incorporated into the crystal and weakens the crystal structure. This has been a cause of lowering the mechanical strength. In addition, in the case of a copolymer of ethylene and α-olefin, a hard and brittle component is formed when almost no α-olefin is contained, whereas when α-olefin is excessively copolymerized, stickiness may be caused. Or a soft component with a weak crystal structure was formed.

  The ethylene polymer obtained by polymerization using a constrained geometric catalyst (CGC) described in WO 93/08221 and the like has a methyl branch as a by-product during the polymerization, and therefore has a methyl branch in the molecular chain. It was. The methyl branch is incorporated into the crystal and weakens the crystal structure. This has caused a decrease in mechanical strength. Moreover, since the long-chain branching is contained, the molecular spread is small, so that the mechanical strength is insufficient.

The ethylene polymer obtained by the high-pressure radical polymerization method has methyl branches and long chain branches in the molecular chain because methyl branches and long chain branches are by-produced during the polymerization. The methyl branch is incorporated into the crystal and weakens the crystal strength. This has been a cause of lowering the mechanical strength. In addition, since it contains long-chain branches, the molecular spread is small and the molecular weight distribution is wide, so that the mechanical strength is poor.
An ethylene-based polymer obtained by low-temperature polymerization using a catalyst containing Ta or Nb complex described in JP-A-6-323323 and the like has a weight average molecular weight (Mw) and a number average molecular weight (Mn) measured by GPC. Since the ratio of (Mw / Mn) is small, the moldability may not be sufficient.

Although high-density polyethylene excellent in moldability and mechanical strength has been desired for a long time, there has been a limit to its realization. In view of such conventional technology, the present inventors have studied an ethylene-based polymer that is excellent in moldability and has a particularly excellent mechanical strength, and has obtained a specific molecular weight and molecular weight. By having a distribution, the present inventors have found an ethylene polymer for pipes having excellent moldability (fluidity) and extremely excellent fatigue characteristics, and a pipe molded body made of the ethylene polymer, thereby completing the present invention.
Japanese Patent Laid-Open No. 11-106432 Japanese Patent Laid-Open No. 11-106432 WO01 / 25328 EP1201711A1 Publication JP 2002-53615 A Japanese Patent No. 821037 JP-A-9-183816 WO93 / 08221 Publication Japanese Unexamined Patent Publication No. 6-23723 CMC Publishing Co., Ltd., “Functional Materials”, March 2001, page 50 Polymer, Vol. 31, 1999, 1990

  An object of the present invention is to provide an ethylene polymer for pipes that is excellent in moldability and has a particularly long lifetime, and a pipe molded body made of the ethylene polymer.

The ethylene-based polymer for pipes according to the present invention has an intrinsic viscosity [η] (dl / g) measured in decalin of 135 ° C. in the range of 2.7 to 4.1, and after annealing at 120 ° C. for 1 hour, over 1 hour linearly density measured by a density gradient tube of the sample was allowed to cool to room temperature ^{(d) (kg / m 3} ) is in the range of 952~962kg / m ^3, weight average molecular weight measured by GPC ( Mw) / number average molecular weight (Mn) is 11 or more and 50 or less, and the actual stress (S) (MPa) is 19.4 when the number of times to break is 10,000 with the tensile fatigue characteristics measured at 23 ° C. In the range of ˜27.2 or the intrinsic viscosity [η] (dl / g) measured in 135 ° C. decalin is in the range of 2.7 to 4.1, and after annealing at 120 ° C. for 1 hour, Sample density gradient tube linearly cooled to room temperature over time More measured density ^{(d) (kg / m 3} ) is in the range of 952~962kg / m ^3, or less weight-average molecular weight (Mw) / number average molecular weight (Mn) of 11 or more 50 measured by GPC, and The actual stress (S) (MPa) and density (d) when the number of times to break is 10,000 with tensile fatigue characteristics measured at 23 ° C satisfy the following relational expression (Eq-1) And

The ethylene-based polymer for pipes according to the present invention preferably satisfies at least one of the following requirements (1-1) to (1-6) in addition to the above requirements.
(1-1) The smoothness coefficient R obtained from the surface roughness of the extruded strand should not exceed 20 μm.
(1-2) Be soluble in decane at 140 ° C.
(1-3) Pipes are used for transporting liquids such as waterworks.
(1-4) 0.01 to 3% by weight of a pigment such as blue, yellow and black is blended.
(1-5) An ethylene polymer for pipe joints or a pipe joint made of the ethylene polymer.
(1-6) An ethylene polymer for pipe joints containing 0.01 to 3% by weight of a pigment such as blue, yellow and black, or a pipe joint made of the ethylene polymer.

  The pipe-based ethylene polymer according to the present invention is excellent in moldability, mechanical strength, excellent fatigue characteristics, and has a strong creep strength, and is particularly suitable for pipe applications such as water pipes and gas pipes. Yes.

  Hereinafter, the ethylene polymer for pipes according to the present invention will be specifically described.

Ethylene Polymer The ethylene polymer according to the present invention has an intrinsic viscosity [η] (dl / g) measured in decalin of 135 ° C. of 2.7 to 4.1, preferably 2.8 to 4.1. Is in range. When [η] is smaller than this range, sufficient mechanical strength cannot be obtained, and when [η] is larger than this range, the formability is poor. When performing a multistage polymerization as described later using a catalyst system as described later, an ethylene polymer having [η] within this range can be produced by controlling the molecular weight and the polymerization amount ratio of each component. . For example, in the slurry polymerization as in Example 1 in which the solvent is hexane, the catalyst used in Example 1 is used as the catalyst while stirring the system uniformly, under the conditions described in Example 1. When polymerized, [η] = 3.10 dl / g. Here, when the ethylene supplied to the second polymerization tank is changed from 4.0 kg / h to 2.5 kg / hr while maintaining the ratio of hydrogen and ethylene, [η] = 2.7 dl / g is obtained. When the ethylene supplied to the tank is changed from 4.0 kg / hr to 6.5 kg / hr, [η] = 3.9 dl / g.

In addition, the ethylene polymer according to the present invention has a density (d) (kg / m ³ ) measured by a density gradient tube of a sample that is annealed at 120 ° C. for 1 hour and then linearly cooled to room temperature over 1 hour. Is in the range of 952 to 962 kg / m ³ . If the density is lower than this range, the modulus of elasticity is low, so that the resin stretches even under a low stress load, and fatigue strength under high stress is not exhibited. If the density is higher than this range, it will be too brittle. When carrying out multistage polymerization as described later using a catalyst system as described later, by controlling the α-olefin content and the polymerization amount ratio of each component, an ethylene polymer having a density in this range can be obtained. Can be manufactured. For example, in the slurry polymerization as in Example 1 in which the solvent is hexane, the catalyst used in Example 1 is used as the catalyst while stirring the system uniformly, under the conditions described in Example 1. When polymerized, d = 953 kg / m ³ . Here, when 1-hexene fed to the second polymerization tank was changed from 130 g / h to 160 g / hr while maintaining other conditions, d = 952 kg / m ³ , and 1-hexene fed to the second polymerization tank Is changed to 60 g / hr, d = 958 kg / m ³ . When the supply amount of 1-hexene is more than 160 g / hr, the density of the obtained ethylene polymer is not lower than the claimed range, and when the supply amount of 1-hexene is more than 60 g / hr, the resulting ethylene system is obtained. The density of the polymer will be higher than claimed.

  Further, the pipe-based ethylene polymer according to the present invention usually has an Mw / Mn (Mw: weight average molecular weight, Mn: number average molecular weight) measured by gel permeation chromatography (GPC) of 11 to 50, preferably 11. It is in the range of ~ 40. When a multistage polymerization as described later is carried out using a catalyst system as described later, an ethylene polymer within this range can be produced by controlling the molecular weight and the polymerization amount ratio of each component. For example, Mw / Mn increases as the molecular weight difference between the components increases. A polymer having Mw / Mn in the above range is excellent in balance between mechanical strength and moldability. Specifically, in the slurry polymerization as in Example 1 using hexane as the solvent, the catalyst used in Example 1 was used as the catalyst while stirring the system so as to be uniform. When polymerization is performed under the conditions, Mw / Mn is 14.8. Here, when the ethylene supplied to the first polymerization tank is changed from 5.0 kg / hr to 7.0 kg / hr and the hydrogen is changed from 57 N-liter / hr to 125 N-liter / hr, the ethylene weight generated in the first polymerization tank is increased. By reducing the molecular weight of the coalescence, Mw / Mn is about 18, while ethylene supplied to the second polymerization tank is from 4.0 kg / hr to 3.3 kg / hr and hydrogen is from 0.2 N-liter / hr to 0 When changed to 0.07 N-liter / hr, the molecular weight of the ethylene polymer produced in the second polymerization tank is increased, so that Mw / Mn is about 22. Alternatively, if hydrogen supplied to the first polymerization tank is 52 N-liter / hr, ethylene supplied to the second polymerization tank is 6.0 kg / hr, hydrogen is 0.45 N-liter / hr, and 1-hexene is 200 g / hr. , Mw / Mn is about 12.

In addition, the ethylene polymer according to the present invention has an actual stress (S) (MPa) of 19 when the number of times of rupture is 10,000 with tensile fatigue characteristics measured at 23 ° C. without notching the sample. In the range of 4 to 27.2 MPa, preferably in the range of 19.6 to 27.2 MPa, or the ethylene-based polymer according to the present invention breaks at a tensile fatigue property measured at 23 ° C. without notching the sample. The actual stress (S) (MPa) when the number of times to reach 10,000 times and the density measured by a density gradient tube of a sample that was annealed at 120 ° C. for 1 hour and then linearly cooled to room temperature over 1 hour ( d) (kg / m ³ ) satisfies the following relational expression (Eq-1),

好ましくは、下記関係式(Eq-2)を満たすことを特徴とする。

Preferably, the following relational expression (Eq-2) is satisfied.

Increasing the density, that is, making it harder may improve the tensile fatigue properties measured at 23 ° C without notching, but changing the density may change other mechanical properties. It was also expressed in the relational expression. Therefore, this relational expression means that the tensile fatigue characteristics measured at 23 ° C. without notching the sample are superior to the conventional one, although the density (hardness) is the same. In addition, the basis of the formula defining the lower limit of S (MPa) is obtained from the relationship between the tensile fatigue property and density measured at 23 ° C. without an notch for the ethylene-based polymer obtained by the prior art, and the present invention. This is a formula obtained by plotting the relationship between the tensile fatigue property measured at 23 ° C. without density and the density and distinguishing the two, and is illustrated in [Example]. The basis for the equation defining the upper limit of S (MPa) is that the relationship between the tensile fatigue property measured at 23 ° C. and the density measured at 23 ° C. without the notch obtained in the present invention, and the region where there is an actual measurement value. This is an expression obtained for distinguishing from a region where there is no actual measured value with a high value as described above, and is shown in [Example]. When performing multistage polymerization as described later using a catalyst system as described later, the molecular weight of each component, the amount of α-olefin copolymerized with ethylene, the composition distribution, the polymerization amount ratio, and the compatibility are controlled. Thus, an ethylene polymer in this range can be produced. For example, a specific single site catalyst is used, [η] is increased within the scope of the claims, an α-olefin having 6 to 10 carbon atoms is selected as the α-olefin to be copolymerized, and the α-olefin in the copolymer The fatigue strength can be further increased within the scope of the claims by reducing the amount in the range of 0.1 to 2.0 mol% and selecting the polymerization conditions so that the composition distribution becomes narrow. Specifically, in the slurry polymerization as in Example 1 using hexane as the solvent, the catalyst used in Example 1 was used as the catalyst while stirring the system so as to be uniform. And granulated under the conditions described in Example 1, the density (d) = 953 kg / m ³ , and the actual results when the number of times of rupture was 10,000 with the tensile fatigue characteristics measured at 23 ° C. The stress (S) is 20.2 MPa. When the density (d) = 953 kg / m ³ , the claimed range of claim 2 of (S) is 19.5 to 21.8 MPa.

  When granulation is carried out at 20 ° φ single screw extruder (L / D = 28), 230 ° C setting, 100 rpm, full flight screw (compression ratio = 3), discharge rate 50 g / min, manufactured by Thermoplastic Co., measured at 23 ° C The actual stress at the time when the number of times of rupture is 10,000 due to the tensile fatigue characteristics is 19.2 MPa, which does not satisfy the claimed range. This is presumed to be due to the poor compatibility of the polymer particles. When granulation is performed under the conditions described in Example 1, the actual stress is 20.2 MPa when the number of times of fracture is 10,000 with the tensile fatigue characteristics measured at 23 ° C. By reducing the amount of hydrogen at the time of copolymerizing the comonomer with the same comonomer amount as in Example 1, the number of times to break even at the same density as the [η] of the resin approaches the upper limit of 3.7 dl / g. The actual stress increases when the value is 10,000. Further, even when the molecular structure is the same, when a low molecular weight ethylene homopolymer polymerized in a single stage and a high molecular weight ethylene / α-olefin copolymer polymerized in a single stage are melt-blended, 10 μm is reduced. The tensile fatigue measured at 23 ° C. without notching the sample because it has a continuous crystal structure exceeding 1, that is, a continuous structure exceeding 10 μm made of a low molecular weight ethylene homopolymer which is easy to break. Strength is not expressed. Furthermore, a component that weakens the crystal part as a molecular structure, that is, if the low molecular weight component contains short chain branches or the high molecular weight component contains too many short chain branches, the crystal lamella becomes thin. In this case, the crystal becomes weak or the short chain branch is incorporated into the crystal, so that the crystal becomes weak. Therefore, the tensile fatigue strength measured at 23 ° C. without notching the sample does not appear. Note that the continuous crystal structure exceeding 10 μm is not observed here when the microtome section of a 0.5 mm thick press sheet melted at 190 ° C. and cooled at 20 ° C. is observed with a polarizing microscope. Is not observed, and the ethylene-based polymer was melted at 190 ° C. using a hydraulic press molding machine manufactured by Shindo Metal Industry Co., Ltd., then formed into a sheet shape at a pressure of 10 MPa, and 20 ° C. A press sheet having a thickness of 0.5 mm is prepared with a cooling press set to, and then cut to about 0.5 mm (press sheet thickness) × 10 to 20 μm using a microtome, and then a small amount of glycerin is added to the cut piece. The sample was applied and brought into close contact with the preparation, and a cover glass was placed thereon to form an observation sample. This sample was set between crossed Nicols polarizing plates and observed with an optical microscope enlarged to about 75 times and 150 times. In the case where the crystal structure is observed only in a part of the field of view in FIGS. 1 and 2, an example in which there is no continuous crystal structure exceeding 10 μm and in the case where the crystal structure is observed in the entire field of view exceeds 10 μm An example of what exists as a continuous crystal structure is shown. The scale bar has a total length of 0.5 mm. FIG. 1 is a photograph observed at about 75 times and FIG. 2 at about 150 times.

In addition to the above requirements, the ethylene polymer according to the present invention preferably further satisfies at least one of the following requirements (1-1) to (1-2).
(1-1) It is preferable that the smoothness coefficient R obtained from the surface roughness of the extruded strand does not exceed 20 μm. When the ethylene polymer obtained by polymerization is in the form of particles, as in the gas phase polymerization method or slurry polymerization method, the polymer particles are not completely mixed and dispersed even after post-treatment such as melt kneading. In some cases, the portions having different viscosities may remain on the surface. In that case, when the molten resin is extruded in the form of a tube or a strand, the surface becomes rough. In that case, the same rough skin occurs when the product is molded. The degree is obtained by the smoothness coefficient R obtained from the surface roughness measurement. Usually, the size of ethylene polymer particles produced by gas phase polymerization method or slurry polymerization method is about several tens of μm to 2 mm. If the history of the shape of the polymer particles remains, the surface of the extrudate becomes rough. Thus, R becomes larger than 20 μm. For example, when a polymerization method as described below is selected, an ethylene polymer in which R does not exceed 20 μm, usually does not exceed 15 μm can be produced. R is further reduced by strengthening the kneading, but R no longer affects the strength as long as R does not exceed 20 μm. Melting an ethylene-based polymer with an R value exceeding 20 μm for a very long time such as 180 ° C., 50 rpm, 10 minutes using, for example, a lab plast mill (batch type different direction rotating biaxial kneader) manufactured by Toyo Seiki Co., Ltd. When kneaded, an ethylene polymer having an R of less than 20 μm can be obtained. It is possible to make R smaller by further lengthening the kneading time. However, there may be a structural change accompanying decomposition or crosslinking. In addition, an ethylene polymer having an R value exceeding 20 μm is dissolved at a rate of about 5 g with respect to 500 ml of a good solvent such as paraxylene, and then cooled with ice to give about 5 times as much as acetone. When it is deposited in a solvent at a rate of about 10 ml / min, dried and then melt-kneaded, an ethylene polymer having an R value of 10 μm or less can be obtained. A polymer in which R does not exceed the above-mentioned value is particularly excellent in mechanical strength because it has no history of polymer particles and is uniform in flow, so that the surface of the molded body is smooth and excellent in appearance.
(1-2) The ethylene polymer according to the present invention is preferably soluble in 140 decane. This means that the crosslinking step has not been performed. If the crosslinking step has not been performed, it can be remelted and reused, and the production process of the molded product is simpler and preferable.

  Hereinafter, various physical property measuring methods according to the present invention will be described.

Physical property measurement method [Preparation of sample for measurement]
0.1 parts by weight of tri (2,4-di-t-butylphenyl) phosphate as a secondary antioxidant and 100 parts by weight of a particulate ethylene (co) polymer as a heat stabilizer 0.1 parts by weight of n-octadecyl-3- (4′-hydroxy-3 ′, 5′-di-t-butylphenyl) propinate is mixed with 0.05 parts by weight of calcium stearate as a hydrochloric acid absorbent. Thereafter, using a lab plast mill (biaxial batch type melt kneader) manufactured by Toyo Seiki Co., Ltd., at a set temperature of 190 ° C., a resin charge amount of 40 g (apparatus batch volume = 60 cm ³ ), 50 rpm, 5 minutes or 50 rpm, melted for 10 minutes. After kneading, the sheet was taken out with a cooling press set at 20 ° C. and cut into an appropriate size to obtain a measurement sample. In addition, you may granulate using a normal extruder. However, when granulating a particulate ethylene (co) polymer that has undergone continuous two-stage polymerization, a device such as using a twin screw extruder with a long L / D is necessary to sufficiently homogenize the polymer particles. It is.

[Intrinsic viscosity ([η])]
It is a value measured at 135 ° C. using a decalin solvent. That is, about 20 mg of granulated pellets are dissolved in 15 ml of decalin, and the specific viscosity η _sp is measured in an oil bath at 135 ° C. After adding 5 ml of decalin solvent to this decalin solution for dilution, the specific viscosity η _sp is measured in the same manner. This dilution operation is further repeated twice, and the value of η _sp / C when the concentration (C) is extrapolated to 0 is obtained as the intrinsic viscosity.
[Η] = lim (η _sp / C) (C → 0)

[Weight average molecular weight (Mw), number average molecular weight (Mn), molecular weight curve]
It measured as follows using GPC-150C by Waters. The separation columns were TSKgel GMH6-HT and TSKgel GMH6-HTL, the column size was 7.5 mm in inner diameter and 600 mm in length, the column temperature was 140 ° C., and o-dichlorobenzene (Wako Pure Chemical Industries) was used as the mobile phase. Industrial) and BHT (Takeda Pharmaceutical) 0.025% by weight as an antioxidant, moved at 1.0 ml / min, sample concentration 0.1% by weight, sample injection volume 500 microliters, detector A differential refractometer was used. The standard polystyrene used was manufactured by Tosoh Corporation for molecular weights of Mw <1000 and Mw> 4 × 10 ⁶ , and used by Pressure Chemical Co. for 1000 ≦ Mw ≦ 4 × 10 ⁶ . The molecular weight calculation is a value obtained by universal calibration and conversion into polyethylene.

[Creation of a press sheet for measuring tensile fatigue strength]
3 mm dumbbell (ASTM-D-1822 Type S) shown in FIG. 3 was molded at a pressure of 100 kg / cm ² using a hydraulic hot press machine manufactured by Shindo Metal Industry Co., Ltd. set at 190 ° C. (spacer shape: 240 × By creating a shape of ASTM-D-1822 Type S on a 240 × 3 mm thick plate), and compressing it at a pressure of 100 kg / cm ² using another hydraulic heat press machine manufactured by Kamito Metal Industry Co., Ltd. set to 20 ° C. A sample for measurement was prepared by cooling. As the hot plate, a 5 mm thick SUS plate was used.

[Tensile fatigue strength]
A 3 mm dumbbell (ASTM-D-1822 Type S) shown in FIG. 3 was used as an evaluation sample.
The tensile fatigue strength was measured according to JIS K7118 using a Shimadzu servo pulsar EHF-FG10KN-4LA type.
The outline of the evaluation conditions is shown below.
Specimen shape: ASTM D1822 Type S Dumbbell described in FIG. 3, no notch
Test waveform and test frequency: Sine wave, 4 Hz
Test temperature: 23 ° C
In the tensile fatigue strength test, the load cell has a minimum load of 4.9 N (0.5 kgf) constant, and the actual stress corrected by the cross-sectional area of the central portion of the test piece before the test is in the range of 17 to 25 MPa. Several points were measured under the conditions (test temperature, test waveform and test frequency). When the sample was stretched 50%, it was considered as fracture, and the number of vibrations at this time was defined as the fatigue strength at the actual stress of the maximum load. Measured in the range of 1 digit or more in the number of times of rupture or 1 MPa or more in the actual stress, an approximate expression is created by the logarithm approximate least square method, and the actual stress corresponding to the number of times of rupture is 10,000 is obtained.

[Smoothness coefficient R]
The resin is extruded at a resin temperature of 200 ° C. and a speed of 50 mm / min (3.6 cm ³ / min) using a capillary flow characteristic tester Capillograph 1B manufactured by Toyo Seiki Co., Ltd. A nozzle having a length L = 60 mm and a diameter D = 1 mm, or a cylindrical die (outer diameter 4 mmφ, slit = 0.5 mm) capable of extruding a tube-shaped object is attached instead of a capillary die. Even if the polymer is pelletized, if the polymer particles polymerized in the gas phase or slurry phase are not sufficiently mixed together, the melted extrudate looks rough. The surface roughness is measured using the strand or tube thus obtained as the measurement surface. For the measurement, Surfcom 1400D manufactured by Tokyo Seimitsu Co., Ltd. was used. Measuring length = 10 mm, measuring speed = 0.06 mm / sec, sampling time = 0.01 sec, sampling pitch = 0.6 μm, measuring needle material is diamond, measuring needle tip = 5 μmφ, calculation standard JIS B0601-1982 Let the calculated ten-point average roughness be Rz. Rz is the value of the difference between the average value of the altitude of the peak from the highest to the fifth and the average value of the altitude of the bottom from the deepest to the fifth with respect to the average line of the measurement length of 10 mm. The measurement is performed three times at different locations, and the average value is defined as the dispersion coefficient R. Here, a standard deviation is obtained for Rz measured three times. When the value of the standard deviation is larger than ½ of the value of R, which is the average value of Rz measured three times, remeasurement is performed. When R exceeds 20 μm, the polymer particles are not sufficiently mixed. For this reason, even when a thick molded body such as a pipe or a blow bottle is molded, flow failure occurs and the surface skin is not smooth. Or stress concentration occurs between the polymer particles, and the mechanical strength is not sufficiently developed. On the other hand, if R is 20 μm or less, it can be said that no history of polymer particles remains.

[Density (d)]
A sheet of 0.5 mm thickness was formed at a pressure of 100 kg / cm ² using a hydraulic heat press machine manufactured by Shindo Metal Industry Co., Ltd. set at 190 ° C. (spacer shape: 45 × on a 240 × 240 × 0.5 mm thick plate) 45 × 0.5 mm, 9 pieces), using another hydraulic hot press machine manufactured by Shinfuji Metal Industry Co., Ltd. set to 20 ° C., and cooled by compressing at a pressure of 100 kg / cm ² to prepare a measurement sample. . As the hot plate, a 5 mm thick SUS plate was used. The press sheet was heat-treated at 120 ° C. for 1 hour, linearly cooled to room temperature over 1 hour, and then measured with a density gradient tube.

[Soluble in decane]
The gel content was determined according to JIS K 6796, except that decane controlled at 140 ° C. was used as the solvent, and the sample was cut from a 0.5 mm thick press sheet or granulated pellets and the concentration was 1 mg / 1 ml. When the measurement is performed and the gel fraction is 1 wt% or less, it is soluble in decane at 140 ° C.

Process for producing ethylene (co) polymer The ethylene polymer according to the present invention includes, for example, a transition metal in which a cyclopentadienyl group and a fluorenyl group are bonded by a covalent bond containing a group 14 atom. Compound (A) and (B)
(B-1) an organometallic compound,
(B-2) an organoaluminum oxy compound, and
(B-3) Is ethylene homopolymerized using an olefin polymerization catalyst formed from a carrier (C) and at least one compound selected from compounds that react with transition metal compounds to form ion pairs? Alternatively, it can be obtained by copolymerizing ethylene and an α-olefin having 6 to 20 carbon atoms.

More specifically, (A), (B) and (C) used this time are as follows.
(A) Transition metal compound The transition metal compound (A) is a compound represented by the following general formulas (1) and (2).

(In the above general formulas (1) and (2), R ⁷ , R ⁸ , R ⁹ , R ¹⁰ , R ¹¹ , R ¹² , R ¹³ , R ¹⁴ , R ¹⁵ , R ¹⁶ , R ¹⁷ , R ¹⁸ , R ¹⁹ and R ²⁰ are selected from a hydrogen atom, a hydrocarbon group, and a silicon-containing hydrocarbon group, and may be the same or different, and adjacent substituents from R ^{7 to} R ¹⁸ are bonded to each other to form a ring. A is a divalent hydrocarbon group having 2 to 20 carbon atoms which may partially contain an unsaturated bond and / or an aromatic ring, and forms a ring structure with Y. May contain two or more ring structures including a ring formed with Y, Y is carbon or silicon, M is a metal selected from Group 4 of the periodic table, Q is halogen, carbonized You may choose hydrogen groups, anionic ligands or neutral ligands that can coordinate with lone pairs in the same or different combinations j is an integer from 1 to 4.) Specifically, R ⁷ to R ¹⁰ are hydrogen, Y is carbon, M is Zr, and j is 2.

  The transition metal compound (A) used this time is specifically represented by the following formulas (3) and (4), but is not limited to this compound in the present invention.

The structure of the obtained transition metal compound is determined using 270 MHz ¹ H-NMR (JEOL GSH-270) and FD-mass spectrometry (JEOL SX-102A).

(B-1) Organometallic compounds (B-1) Organometallic compounds used as necessary in the present invention include organic compounds of Periodic Tables 1 and 2 and Groups 12 and 13 A metal compound is mentioned.

General formula R ^a _m Al (OR ^b ) _n H _p X _q
(In the formula, R ^a and R ^b may be the same or different from each other, each represents a hydrocarbon group having 1 to 15 carbon atoms, preferably 1 to 4 carbon atoms, X represents a halogen atom, and m represents 0. <M ≦ 3, n is 0 ≦ n <3, p is a number of 0 ≦ p <3, q is a number of 0 ≦ q <3, and m + n + p + q = 3). .

  The aluminum compound used this time is triisobutylaluminum or triethylaluminum.

(B-2) Organoaluminum Oxy Compound The organoaluminum oxy compound used as necessary in the present invention may be a conventionally known aluminoxane, and is exemplified in JP-A-2-78687. It may be a benzene-insoluble organoaluminum oxy compound.

  The organoaluminum oxy compound used this time is a commercially available MAO / toluene solution manufactured by Nippon Alkyl Aluminum Co., Ltd.

(B-3) Compound which reacts with transition metal compound to form ion pair Compound (B-3) which reacts with bridged metallocene compound (A) of the present invention to form ion pair (hereinafter referred to as “ionized ionic compound” Are referred to as JP-A-1-501950, JP-A-1-502036, JP-A-3-179005, JP-A-3-179006, JP-A-3-207703, JP-A-3. And Lewis acids, ionic compounds, borane compounds and carborane compounds described in JP-A-207704, USP-5321106, and the like. Furthermore, heteropoly compounds and isopoly compounds can also be mentioned. Such ionized ionic compounds (B-3) are used singly or in combination of two or more.
As the component (B), the two (B-1) and (B-2) shown above were used.

(C) Carrier The carrier (C) used as necessary in the present invention is an inorganic or organic compound and is a granular or fine particle solid. Among these, as the inorganic compound, a porous oxide, an inorganic halide, clay, clay mineral, or an ion-exchange layered compound is preferable. Such porous oxides have different properties depending on the type and production method, but the carrier preferably used in the present invention has a particle size of 1 to 300 μm, preferably 3 to 200 μm, and a specific surface area of 50 to 1000 m. ² / g, preferably in the range of 100 to 800 m ² / g, and the pore volume is in the range of 0.3 to 3.0 cm ³ / g. Such a carrier is used after being calcined at 80 to 1000 ° C., preferably 100 to 800 ° C., if necessary.

The carrier used this time was SiO ₂ manufactured by Asahi Glass Co., Ltd. having an average particle size of 12 μm, a specific surface area of 800 m ² / g, and a pore volume of 1.0 cm ³ / g.

  The olefin polymerization catalyst according to the present invention comprises the bridged metallocene compound (A), (B-1) an organometallic compound, (B-2) an organoaluminum oxy compound, and (B-3) an ionized ionic compound according to the present invention. A specific organic compound component (D) as described later can be included together with at least one selected compound (B) and, if necessary, the carrier (C) as necessary.

(D) Organic Compound Component In the present invention, the (D) organic compound component is used for the purpose of improving the polymerization performance and the physical properties of the produced polymer, if necessary. Examples of such organic compounds include, but are not limited to, alcohols, phenolic compounds, carboxylic acids, phosphorus compounds, and sulfonates.

Ethylene polymer according to Polymerization present invention can be obtained by using the olefin polymerization catalyst described above, is copolymerized homopolymerization is causing or ethylene and an olefin having 6 to 20 carbon atoms with ethylene . In the polymerization, the method of using each component and the order of addition are arbitrarily selected, and the following methods (P-1) to (P-10) are exemplified.
(P-1) Component (A) and at least one component (B) selected from (B-1) an organometallic compound, (B-2) an organoaluminum oxy compound, and (B-3) an ionized ionic compound (Hereinafter simply referred to as “component (B)”) in an arbitrary order to the polymerization vessel.
(P-2) A method in which a catalyst in which the component (A) and the component (B) are contacted in advance is added to the polymerization reactor.
(P-3) A method in which the catalyst component in which the component (A) and the component (B) are contacted in advance, and the component (B) are added to the polymerization vessel in an arbitrary order. In this case, each component (B) may be the same or different.
(P-4) A method in which the catalyst component having the component (A) supported on the particulate carrier (C) and the component (B) are added to the polymerization vessel in an arbitrary order.
(P-5) A method in which a catalyst in which the component (A) and the component (B) are supported on the particulate carrier (C) is added to the polymerization vessel.
(P-6) A method in which the catalyst component in which the component (A) and the component (B) are supported on the particulate carrier (C), and the component (B) are added to the polymerization vessel in an arbitrary order. In this case, each component (B) may be the same or different.
(P-7) A method in which the catalyst component having the component (B) supported on the particulate carrier (C) and the component (A) are added to the polymerization vessel in an arbitrary order.
(P-8) A method in which the catalyst component having component (B) supported on fine particle carrier (C), component (A), and component (B) are added to the polymerization vessel in any order. In this case, each component (B) may be the same or different.
(P-9) A method in which a catalyst in which a component (A) and a component (B) are supported on a particulate carrier (C) and a catalyst component that has been brought into contact with the component (B) in advance are added to a polymerization vessel. In this case, each component (B) may be the same or different.
(P-10) A catalyst in which component (A) and component (B) are supported on a particulate carrier (C), a catalyst component that has been previously contacted with component (B), and component (B) in any order A method of adding to the polymerization vessel. In this case, each component (B) may be the same or different.

  In each of the above methods (P-1) to (P10), at least two or more of the catalyst components may be contacted in advance.

  The solid catalyst component in which the component (A) and the component (B) are supported on the particulate carrier (C) may be prepolymerized with olefin. This prepolymerized solid catalyst component is usually prepolymerized at a ratio of 0.1 to 1000 g, preferably 0.3 to 500 g, particularly preferably 1 to 200 g of polyolefin per 1 g of the solid catalyst component. . Further, for the purpose of allowing the polymerization to proceed smoothly, an antistatic agent, an anti-fouling agent, or the like may be used in combination or supported on a carrier.

  The polymerization can be carried out by either a liquid phase polymerization method such as solution polymerization or suspension polymerization or a gas phase polymerization method, and suspension polymerization is particularly preferred. Specific examples of the inert hydrocarbon medium used in the liquid phase polymerization method include aliphatic hydrocarbons such as propane, butane, pentane, hexane, heptane, octane, decane, dodecane, and kerosene; cyclopentane, cyclohexane, and methylcyclopentane. Alicyclic hydrocarbons such as benzene, toluene, xylene and other aromatic hydrocarbons; halogenated hydrocarbons such as ethylene chloride, chlorobenzene and dichloromethane, or mixtures thereof, and the olefin itself is used as a solvent. You can also.

When (co) polymerization is carried out using the above olefin polymerization catalyst, component (A) is usually 10 ⁻¹² to 10 ⁻² mol, preferably 10 ⁻¹⁰ to 10 ⁻ , per liter of reaction volume. It is used in such an amount that it becomes ³ mol. The component (B-1) used as necessary has a molar ratio [(B-1) / M] of the component (B-1) and the transition metal atom (M) in the component (A). The amount used is from 0.01 to 100,000, preferably from 0.05 to 50,000. The component (B-2) used as necessary is a molar ratio of the aluminum atom in the component (B-2) and the transition metal atom (M) in the component (A) [(B-2) / M ] Is usually used in an amount of 10 to 500,000, preferably 20 to 100,000. The component (B-3) used as necessary has a molar ratio [(B-3) / M] of the component (B-3) and the transition metal atom (M) in the component (A). The amount used is 1 to 10, preferably 1 to 5.

  When the component (B) is the component (B-1), the molar ratio [(D) / (B-1)] is usually 0.01 to 10, and preferably used as necessary. Is an amount such that 0.1 to 5, and when component (B) is component (B-2), the molar ratio [(D) / (B-2)] is usually 0.001 to 2, When the component (B) is the component (B-3) in such an amount as preferably 0.005 to 1, the molar ratio [(D) / (B-3)] is usually from 0.01 to 10 The amount is preferably 0.1 to 5.

The polymerization temperature using such an olefin polymerization catalyst is usually in the range of −50 to + 250 ° C., preferably 0 to 200 ° C., particularly preferably 60 to 170 ° C. The polymerization pressure is usually from normal pressure to 100 kg / cm ² , preferably from normal pressure to 50 kg / cm ² , and the polymerization reaction can be performed in any of batch, batch, semi-continuous and continuous methods. Can also be done. Polymerization is carried out in the gas phase or a slurry phase in which polymer particles are precipitated in a solvent. Furthermore, the polymerization is carried out in two or more stages with different reaction conditions. Among these, it is preferable to carry out by a batch type. In the case of slurry polymerization or gas phase polymerization, the polymerization temperature is preferably 60 ° C to 90 ° C, more preferably 65 ° C to 85 ° C. By polymerizing in this temperature range, an ethylene polymer having a narrower composition distribution can be obtained. The obtained polymer is in the form of particles of about several tens to several thousand μmφ. When the polymerization is carried out in a continuous system comprising two polymerization vessels, it is necessary to perform operations such as dissolving in a good solvent and then precipitating in a poor solvent, or sufficiently melting and kneading with a specific kneader.

For example, when the ethylene polymer according to the present invention is produced in two stages, an ethylene homopolymer having an intrinsic viscosity of 0.3 to 1.8 dl / g is produced in the previous stage, and the intrinsic viscosity is 4.0 in the latter stage. A (co) polymer of ˜10.0 dl / g is produced. This order may be reversed.
Since such an olefin polymerization catalyst has extremely high polymerization performance even with respect to α-olefin (for example, 1-hexene) copolymerized with ethylene, an α-olefin content that is too high after a predetermined polymerization is completed. It is necessary to devise such that no copolymer is formed. For example, (i) a method of separating the polymer, the solvent, and the unreacted α-olefin with a solvent separator, as soon as possible or as soon as possible after the polymerization tank contents are withdrawn from the polymerization tank, and (ii) the contents. A method of forcibly discharging the solvent and unreacted α-olefin out of the system by adding an inert gas such as nitrogen, (iii) forcing the solvent and unreacted α-olefin to be controlled by controlling the pressure applied to the contents (Iv) a method of diluting unreacted α-olefin to a concentration at which it is considered that substantially no polymerization occurs by adding a large amount of solvent to the contents, (v) methanol, etc. Examples thereof include a method of adding a substance that deactivates the polymerization catalyst, and (vi) a method of cooling the contents to a temperature at which polymerization is considered not to occur. These methods may be carried out singly or in combination.

  The molecular weight of the resulting ethylene polymer can be adjusted by allowing hydrogen to be present in the polymerization system or changing the polymerization temperature. Furthermore, it can also adjust by the difference in the component (B) to be used.

The polymer particles obtained by the polymerization reaction may be pelletized by the following method.
(1) A method of mechanically blending ethylene (co) polymer particles and other components optionally added using an extruder, a kneader or the like, and cutting the mixture into a predetermined size.
(2) Dissolve the ethylene (co) polymer and other components optionally added in a suitable good solvent (eg, hydrocarbon solvents such as hexane, heptane, decane, cyclohexane, benzene, toluene and xylene), then A method of removing the solvent, and then mechanically blending using an extruder, kneader, etc., and cutting to a predetermined size.

  The ethylene (co) polymer is within a range that does not impair the object of the present invention, a weather resistance stabilizer, a heat resistance stabilizer, an antistatic agent, an anti-slip agent, an anti-blocking agent, an antifogging agent, a lubricant, a dye, a nucleating agent, Necessary additives such as plasticizers, anti-aging agents, hydrochloric acid absorbents, antioxidants, and pigments such as carbon black, titanium oxide, titanium yellow, phthalocyanine, isoindolinone, quinacridone compounds, condensed azo compounds, ultramarine, cobalt blue It may be blended accordingly.

  The ethylene (co) polymer according to the present invention can be formed into an extrusion-molded body such as a pipe or an irregular shape, an injection-molded body, or the like. These molded bodies include molded bodies (laminates and the like) including a portion made of an ethylene (co) polymer and a portion made of another resin.

  EXAMPLES Hereinafter, although this invention is demonstrated further more concretely based on an Example, this invention is not limited to these Examples. The pipe forming method and the internal pressure creep rupture time measuring method are as follows.

[Pipe molding]
The ethylene copolymer was extruded at a set temperature of 200 ° C. and an extrusion rate of 22 kg / h using an extruder manufactured by Ikekai Kikai Co., Ltd. having a diameter of 65 mmφ and L / D = 25. No. 1 as defined in JIS K6774 (SDR11) A pipe with a diameter of 50 mm was obtained.

[Internal pressure creep rupture time]
When the pipe length was 50 cm, the temperature was 20 ° C., or 80 ° C., and 20 ° C., the circumferential stress was in the range of 11 to 15 MPa, and in the case of 80 ° C., the circumferential stress was in the range of 5 to 7 MPa.

[Synthesis Example 1]
[Preparation of solid catalyst component]
After 8.5 kg of silica dried at 200 ° C. for 3 hours was suspended in 33 liters of toluene, 82.7 liters of methylaluminoxane solution (Al = 1.42 mol / liter) was added dropwise over 30 minutes. Next, the temperature was raised to 115 ° C. over 1.5 hours, and the reaction was carried out at that temperature for 4 hours. Thereafter, the temperature was lowered to 60 ° C., and the supernatant was removed by a decantation method. The obtained solid catalyst component was washed with toluene three times and then resuspended with toluene to obtain a solid catalyst component (α) (total volume 150 liters).

[Preparation of supported catalyst]
In a fully nitrogen-substituted reactor, 19.60 mol of the solid catalyst component (α) suspended in toluene was added in terms of aluminum, and the suspension was stirred at room temperature (20-23 ° C.). 2 liters (74.76 mmol) of a diphenylmethylene (cyclopentadienyl) (2,7-di-t-butylfluorenyl) zirconium dichloride 37.38 mmol / liter solution was added, followed by stirring for 60 minutes. After stopping the stirring, the supernatant liquid is removed by decantation, washing is performed twice using 40 liters of n-hexane, and the obtained supported catalyst is reslurried in n-hexane to form a 25 liter catalyst suspension as a solid catalyst. Component (β) was obtained.

[Prepolymerization of solid catalyst component (β)]
Into a reactor equipped with a stirrer, 15.8 liters of purified n-hexane and the above solid catalyst component (β) were charged in a nitrogen atmosphere, then 5 mol of triisobutylaluminum was added, and 3 g per 4 g of the solid component was added while stirring. The prepolymerization was carried out with a considerable amount of ethylene. The polymerization temperature was kept at 20-23 ° C. After completion of the polymerization, stirring was stopped, the supernatant was removed by decantation, washing was performed 4 times with 35 liters of n-hexane, and the obtained supported catalyst was made into a catalyst suspension with 20 liters of n-hexane. A solid catalyst component (γ) was obtained.

[polymerization]
In the first polymerization tank, hexane is 45 liters / hr, the solid catalyst component (γ) obtained in Synthesis Example 1 is 0.11 mmol / hr in terms of Zr equivalent atoms, triethylaluminum is 20 mmol / hr, and ethylene is 5. While continuously supplying 0 kg / hr, hydrogen at 57 N-liter / hr, and continuously withdrawing the contents of the polymerization tank so that the liquid level in the polymerization tank is constant, the polymerization temperature is 85 ° C. and the reaction pressure is 8 Polymerization was performed under the conditions of 0.5 kg / cm ² G and an average residence time of 2.5 hours. The contents continuously extracted from the first polymerization tank are substantially free of unreacted ethylene and hydrogen by a flash drum maintained at an internal pressure of 0.2 kg / m ² G and 65 ° C.

Thereafter, the contents were continuously supplied to the second polymerization tank together with hexane 35 liter / hr, ethylene 4.0 kg / hr, hydrogen 0.2 N-liter / hr, 1-hexene 130 g / hr, and a polymerization temperature of 80 Subsequently, polymerization was carried out under the conditions of a temperature of 4.5 ° C., a reaction pressure of 4.5 kg / cm ² G, and an average residence time of 1.2 hours.

  In the second polymerization tank, the contents of the polymerization tank were continuously withdrawn so that the liquid level in the polymerization tank was constant. In order to prevent unintended polymerization such as the production of a polymer containing a large amount of 1-hexene, methanol was supplied to the contents extracted from the second polymerization tank at 2 liter / hr to deactivate the polymerization catalyst. Thereafter, hexane and unreacted monomers in the contents were removed with a solvent separator and dried to obtain a polymer.

  Next, 0.1 part by weight of tri (2,4-di-t-butylphenyl) phosphate as a secondary antioxidant and n-octadecyl-as a heat stabilizer are added to 100 parts by weight of the polymer particles. 0.1 part by weight of 3- (4′-hydroxy-3 ′, 5′-di-t-butylphenyl) propinate and 0.05 part by weight of calcium stearate as a hydrochloric acid absorbent are blended. After that, granulation was performed at a set temperature of 260 ° C. and a resin extrusion rate of 22 g / min and 120 rpm using a Plavo twin screw extruder (30 mmφ, L / D = 46, rotating in the same direction, 4 needing zones). A sample for measurement was obtained. In observation with a polarizing microscope, there is no continuous crystal structure exceeding 10 μm. Moreover, it is soluble in 140 degreeC decane. Further, a press sheet was prepared using the sample, and the physical properties were measured. The results are shown in Tables 1-3. Further, a pipe was molded, and the hot internal pressure creep strength was measured. The results are shown in Table 4.

[polymerization]
In the first polymerization tank, hexane is 45 liters / hr, the solid catalyst component (γ) obtained in Synthesis Example 1 is 0.13 mmol / hr in terms of Zr equivalent atoms, triethylaluminum is 20 mmol / hr, and ethylene is 5. While continuously supplying 0 kg / hr, hydrogen at 55 N-liter / hr, and continuously withdrawing the contents of the polymerization tank so that the liquid level in the polymerization tank becomes constant, a polymerization temperature of 85 ° C. and a reaction pressure of 8 Polymerization was performed under the conditions of 0.1 kg / cm ² G and an average residence time of 2.6 hours.

Unreacted ethylene and hydrogen are substantially removed from the contents continuously extracted from the first polymerization tank by a flash drum maintained at an internal pressure of 0.35 kg / m ² G and 60 ° C. Thereafter, the contents were continuously supplied to the second polymerization tank together with hexane 35 liter / hr, ethylene 3.0 kg / hr, hydrogen 0.5 N-liter / hr, 1-hexene 130 g / hr, and a polymerization temperature of 80 Polymerization was subsequently carried out under the conditions of ° C., reaction pressure of 3.9 kg / cm ² G, and average residence time of 1.2 hr.

  In the second polymerization tank, the contents of the polymerization tank were continuously withdrawn so that the liquid level in the polymerization tank was constant. In order to prevent unintended polymerization such as the production of a polymer containing a large amount of 1-hexene, methanol was supplied to the contents extracted from the second polymerization tank at 2 liter / hr to deactivate the polymerization catalyst. Thereafter, hexane and unreacted monomers in the contents were removed with a solvent separator and dried to obtain a polymer.

  Next, 0.1 part by weight of tri (2,4-di-t-butylphenyl) phosphate as a secondary antioxidant and n-octadecyl-as a heat stabilizer are added to 100 parts by weight of the polymer particles. 0.1 part by weight of 3- (4′-hydroxy-3 ′, 5′-di-t-butylphenyl) propinate and 0.05 part by weight of calcium stearate as a hydrochloric acid absorbent are blended. After that, using a Placo single screw extruder (screw diameter 65 mm, L / D = 28, screen mesh # 300 × 4 sheets), granulate at a set temperature of 200 ° C. and a resin extrusion rate of 25 kg / hr, and a measurement sample. It was. In observation with a polarizing microscope, there is no continuous crystal structure exceeding 10 μm. Moreover, it is soluble in 140 degreeC decane. Further, a press sheet was prepared using the sample, and the physical properties were measured. The results are shown in Tables 1-3. Further, a pipe was molded, and the hot internal pressure creep strength was measured. The results are shown in Table 4.

[Preparation of solid catalyst component]
In a reactor sufficiently purged with nitrogen, 19.60 mol of the solid catalyst component (α) synthesized in Synthesis Example 1 suspended in toluene was added in terms of aluminum, and the suspension was stirred at room temperature (20 After adding 2 liters (62.12 mmol) of a 31.06 mmol / liter solution of di (p-tolyl) methylene (cyclopentadienyl) (octamethyloctahydrodibenzofluorenyl) zirconium dichloride at ˜25 ° C., the mixture was stirred for 60 minutes. . After the stirring is stopped, the supernatant is removed by decantation, washed twice with 40 liters of n-hexane, and the resulting supported catalyst is reslurried in n-hexane to form a 25 liter catalyst suspension as a solid catalyst. (T) was obtained. Into a reactor equipped with a stirrer, 15.8 liters of purified n-hexane and the above solid catalyst component (T) were added under a nitrogen atmosphere, 5 mol of triisobutylaluminum was added, and 3 g per 4 g of the solid component was added while stirring. The prepolymerization was carried out with a considerable amount of ethylene. The polymerization temperature was kept at 20 to 25 ° C. After completion of the polymerization, stirring was stopped, the supernatant was removed by decantation, washing was performed 4 times with 35 liters of n-hexane, and the obtained supported catalyst was made into a catalyst suspension with 20 liters of n-hexane. A solid catalyst component (ω) was obtained.

[polymerization]
In the first polymerization tank, hexane is 45 liters / hr, the solid catalyst component (ω) obtained in Synthesis Example 2 is 0.13 mmol / hr in terms of Zr equivalent atoms, triethylaluminum is 20 mmol / hr, and ethylene is 5. While continuously supplying 0 kg / hr, hydrogen at 67 N-liter / hr, and continuously withdrawing the contents of the polymerization tank so that the liquid level in the polymerization tank is constant, the polymerization temperature is 85 ° C., the reaction pressure is 7 Polymerization was conducted under the conditions of 0.4 kg / cm ² G and an average residence time of 2.7 hr.

From the contents continuously extracted from the first polymerization tank, unreacted ethylene and hydrogen are substantially removed by a flash drum maintained at an internal pressure of 0.30 kg / m ² G and 60 ° C. Thereafter, the contents were continuously supplied to the second polymerization tank together with hexane 43 liter / hr, ethylene 3.9 kg / hr, hydrogen 10.0 N-liter / hr, 1-hexene 110 g / hr, and a polymerization temperature of 75 Subsequently, polymerization was carried out under the conditions of a temperature of 4.5 ° C., a reaction pressure of 4.5 kg / cm ² G, and an average residence time of 1.1 hours.

  In the second polymerization tank, the contents of the polymerization tank were continuously withdrawn so that the liquid level in the polymerization tank was constant. In order to prevent unintended polymerization such as the production of a polymer containing a large amount of 1-hexene, methanol was supplied to the contents extracted from the second polymerization tank at 2 liter / hr to deactivate the polymerization catalyst. Thereafter, hexane and unreacted monomers in the contents were removed with a solvent separator and dried to obtain a polymer.

  Next, 0.1 part by weight of tri (2,4-di-t-butylphenyl) phosphate as a secondary antioxidant and n-octadecyl-as a heat stabilizer are added to 100 parts by weight of the polymer particles. 0.1 part by weight of 3- (4′-hydroxy-3 ′, 5′-di-t-butylphenyl) propinate and 0.05 part by weight of calcium stearate as a hydrochloric acid absorbent are blended. After that, using a Placo single screw extruder (screw diameter 65 mm, L / D = 28, screen mesh # 300 × 4 sheets), granulate at a set temperature of 200 ° C. and a resin extrusion rate of 25 kg / h, and a measurement sample. It was. In observation with a polarizing microscope, there is no continuous crystal structure exceeding 10 μm. Moreover, it is soluble in 140 degreeC decane. Further, a press sheet was prepared using the sample, and the physical properties were measured. The results are shown in Tables 1-3. Further, a pipe was molded, and the hot internal pressure creep strength was measured. The results are shown in Table 4.

After thoroughly drying and putting in a nitrogen-substituted polymerizer, 1200 liters of hexane, 650 mmol of triisobutylaluminum and 1.3 g of Epan 720 manufactured by Daiichi Kogyo Seiyaku Co., Ltd. are introduced, and then the nitrogen in the polymerizer is removed. Therefore, pressurization and depressurization with ethylene were repeated three times. When the temperature in the polymerization vessel was heated to 70 ° C., it was pressurized to 0.50 MPa with ethylene, and further pressurized with hydrogen so that the hydrogen concentration in the gas phase portion was 29 mol%. The solid catalyst component obtained in Synthesis Example 1 (gamma) and simultaneously introducing 1.6mmol in terms of Zr atom, ethylene 30 Nm ³ / hr, the hydrogen was fed at a rate of 0.2Nm ³ / hr, 80 ℃ The polymerization was started. After the ethylene supply integrated amount after starting to continuously supply ethylene reaches 52 Nm3, the supply of ethylene and hydrogen is stopped and the pressure in the system is depressurized and nitrogen is removed to remove the ethylene and hydrogen. The temperature was lowered to ° C. After removing ethylene and hydrogen in the system, the system was heated again to 70 ° C., 1.95 liters of 1-hexene was added, and then pressurized to 0.35 MPa with ethylene. Ethylene was fed at a rate of 24 Nm 3 / hr and hydrogen was fed at a rate of 1.0 N-liter / hr, and polymerization was resumed at 80 ° C. After the ethylene supply accumulated amount after starting ethylene supply continuously reaches 28 Nm3, the supply of ethylene and hydrogen is stopped, and the polymerization slurry is quickly transferred to another container, depressurized, and then supplied with nitrogen. While removing ethylene and hydrogen, the catalyst was deactivated by feeding methanol at 20 N-liter / hr for 1 hour. At this time, the temperature in the system was kept at 60 ° C.

  The polymer was separated from hexane by filtration, washed with excess hexane, and dried for 3 hours. The obtained polymer was 102.5 kg.

  Next, 0.1 part by weight of tri (2,4-di-t-butylphenyl) phosphate as a secondary antioxidant and n-octadecyl-as a heat stabilizer are added to 100 parts by weight of the polymer particles. 0.1 part by weight of 3- (4′-hydroxy-3 ′, 5′-di-t-butylphenyl) propinate and 0.05 part by weight of calcium stearate as a hydrochloric acid absorbent are blended. After that, using a Placo single screw extruder (screw diameter 65 mm, L / D = 28, screen mesh # 300 × 4 sheets), granulate at a set temperature of 200 ° C. and a resin extrusion rate of 25 kg / hr, and a measurement sample. It was. In observation with a polarizing microscope, there is no continuous crystal structure exceeding 10 μm. Soluble in decane at 140 ° C. Further, a press sheet was prepared using the sample, and the physical properties were measured. The results are shown in Tables 1-3.

Into a sufficiently dried and nitrogen-substituted polymerizer, 1200 liters of hexane was introduced, 650 mmol of triisobutylaluminum was introduced, and then pressure and depressurization with ethylene were repeated three times to remove nitrogen in the polymerizer. It was. When the temperature in the polymerization reactor was heated to 70 ° C., the pressure was increased to 0.50 MPa with ethylene, and further with hydrogen, the hydrogen concentration in the gas phase was 28 mol%. The solid catalyst component (γ) obtained in Synthesis Example 1 was converted to Zr atoms, and 1.6 mmol was charged. At the same time, ethylene was fed at a rate of 32 Nm ³ / hr and hydrogen was fed at a rate of 0.2 Nm ³ / hr, and 80 ° C. The polymerization was started. After the ethylene supply integration amount after starting ethylene supply continuously reaches 52 Nm ³ , the supply of ethylene and hydrogen is stopped and the pressure in the system is released while removing the ethylene and hydrogen with nitrogen. The temperature was lowered to 55 ° C. After removing ethylene and hydrogen in the system, the system was heated again to 70 ° C., 1.95 liters of 1-hexene was added, and then pressurized to 0.35 MPa with ethylene. Ethylene was fed at a rate of 26 Nm ³ / hr and hydrogen was fed at a rate of 1.1 N-liter / hr, and polymerization was resumed at 80 ° C. After the ethylene supply cumulative amount after starting to continuously supply ethylene reaches 23 Nm ³ , the supply of ethylene and hydrogen is stopped, and the polymerization slurry is quickly transferred to another container to depressurize and supply nitrogen. Then, the catalyst was deactivated by feeding methanol at 20 N-liter / hr for 1 hour while removing ethylene and hydrogen. At this time, the temperature in the system was kept at 60 ° C.

  The polymer was separated from hexane by filtration, washed with excess hexane, and dried for 3 hours. The obtained polymer was 99.5 kg. Next, 0.1 part by weight of tri (2,4-di-t-butylphenyl) phosphate as a secondary antioxidant and n-octadecyl-as a heat stabilizer are added to 100 parts by weight of the polymer particles. 0.1 part by weight of 3- (4′-hydroxy-3 ′, 5′-di-t-butylphenyl) propinate and 0.05 part by weight of calcium stearate as a hydrochloric acid absorbent are blended. After that, using a Placo single screw extruder (screw diameter 65 mm, L / D = 28, screen mesh # 300 × 4 sheets), granulate at a set temperature of 200 ° C. and a resin extrusion rate of 25 kg / hr, and a measurement sample. It was. In observation with a polarizing microscope, there is no continuous crystal structure exceeding 10 μm. Soluble in decane at 140 ° C. Further, a press sheet was prepared using the sample, and the physical properties were measured. The results are shown in Tables 1-3.

Into a sufficiently dried and nitrogen-substituted polymerizer, 1200 liters of hexane was introduced, 650 mmol of triisobutylaluminum was introduced, and then pressure and depressurization with ethylene were repeated three times to remove nitrogen in the polymerizer. It was. When the temperature in the polymerization vessel was heated to 70 ° C., it was pressurized to 0.50 MPa with ethylene, and further pressurized with hydrogen so that the hydrogen concentration in the gas phase portion was 29 mol%. The solid catalyst component (γ) obtained in Synthesis Example 1 was converted to Zr atoms, and 1.6 mmol was charged. At the same time, ethylene was fed at a rate of 32 Nm ³ / hr and hydrogen was fed at a rate of 0.1 Nm ³ / hr, and 80 ° C. The polymerization was started. After the ethylene supply integration amount after starting ethylene supply continuously reaches 40 Nm ³ , the supply of ethylene and hydrogen is stopped and the pressure in the system is released while removing the ethylene and hydrogen with nitrogen. The temperature was lowered to 55 ° C. After removing ethylene and hydrogen in the system, the inside of the system was again heated to 70 ° C., 1.39 liters of 1-hexene was added, and then pressurized to 0.35 MPa with ethylene. Ethylene was fed at a rate of 26 Nm ³ / hr and hydrogen was fed at a rate of 3.2 N-liter / hr, and polymerization was resumed at 80 ° C. After the ethylene supply cumulative amount after starting ethylene supply reaches 33 Nm3, the supply of ethylene and hydrogen is stopped, and the polymerization slurry is quickly transferred to another container, depressurized, and nitrogen is used. While removing ethylene and hydrogen, the catalyst was deactivated by feeding methanol at 20 N-liter / hr for 1 hour. At this time, the temperature in the system was kept at 60 ° C.

  The polymer was separated from hexane by filtration, washed with excess hexane, and dried for 3 hours. The obtained polymer was 91.0 kg. Next, 0.1 part by weight of tri (2,4-di-t-butylphenyl) phosphate as a secondary antioxidant and n-octadecyl-as a heat stabilizer are added to 100 parts by weight of the polymer particles. 0.1 part by weight of 3- (4′-hydroxy-3 ′, 5′-di-t-butylphenyl) propinate and 0.05 part by weight of calcium stearate as a hydrochloric acid absorbent are blended. After that, using a Placo single screw extruder (screw diameter 65 mm, L / D = 28, screen mesh # 300 × 4 sheets), granulate at a set temperature of 200 ° C. and a resin extrusion rate of 25 kg / hr. It was. In observation with a polarizing microscope, there is no continuous crystal structure exceeding 10 μm. Soluble in decane at 140 ° C. Further, a press sheet was prepared using the sample, and the physical properties were measured. The results are shown in Tables 1-3.

(1) Catalyst synthesis In a glove box, 0.18 g of di (p-tolyl) methylene (cyclopentadienyl) (octamethyloctahydrodibenzofluorenyl) zirconium dichloride was weighed in a 1 L four-necked flask. The flask was taken out, 46 mL of toluene and 140 mL of MAO / SiO ₂ / toluene slurry (a solid amount of 8.82 g) were added under nitrogen, and the mixture was stirred for 30 minutes to carry. The resulting di (p-tolyl) methylene (cyclopentadienyl) (octamethyloctahydrodibenzofluorenyl) zirconium dichloride / MAO / SiO ₂ / toluene slurry was 99% substituted with normal-heptane and finally The amount of slurry was 450 mL. This operation was performed at room temperature.

(2) Ethylene polymerization An autoclave with a stirrer having an internal volume of 200 L was charged with 86.5 L of heptane, 90 mmol of triisobutylaluminum, and 9 g of the solid catalyst component prepared in (1). The internal temperature was kept at 80 ° C., ethylene and hydrogen were charged, and the internal pressure was kept at 0.6 MPa / G for polymerization. The amount of ethylene charged was 13.7 kg.

  Subsequently, the pressure in the polymerization tank was depressurized to 0 MPa / G and replaced with nitrogen to remove hydrogen in the polymerization tank.

  Then, 340 mL of 1-hexene was charged. Polymerization was performed while maintaining the internal temperature at 65 ° C., charging ethylene and hydrogen, and maintaining the internal pressure at 0.5 MPa / G. The amount of ethylene charged was 9.0 kg.

The entire amount of the obtained polyethylene slurry was transferred to an autoclave with a stirrer having an internal volume of 500 L, and 10.7 mL of methanol was charged to deactivate the catalyst. This slurry was transferred to a filter dryer equipped with a stirrer, filtered, and then vacuum dried at 85 ° C. for 6 hours to obtain polyethylene powder.
Next, 0.1 part by weight of tri (2,4-di-t-butylphenyl) phosphate as a secondary antioxidant and n-octadecyl-as a heat stabilizer are added to 100 parts by weight of the polymer particles. 0.1 part by weight of 3- (4′-hydroxy-3 ′, 5′-di-t-butylphenyl) propinate and 0.05 part by weight of calcium stearate as a hydrochloric acid absorbent are blended. After that, Laboplast mill manufactured by Toyo Seiki Co., Ltd. (using a twin screw batch melt kneader, set temperature 190 ° C., polyethylene powder charge 40 g (device batch volume = 60 cm ³ ), 50 rpm, 5 minutes after melt kneading and taking out. Then, it was made into a sheet with a cooling press set at 20 ° C., and cut into an appropriate size to obtain a measurement sample, etc. In the observation with a polarizing microscope, there was no continuous crystal structure exceeding 10 μm. In addition, a press sheet was prepared using the sample, and the physical properties were measured.
Pipe molding was not performed.

(Ethylene polymerization)
An autoclave equipped with a stirrer with an internal volume of 200 L was charged with 86.5 L of heptane, 90 mmol of triisobutylaluminum, and 9 g of the solid catalyst component prepared in Example 7 (1). The internal temperature was kept at 80 ° C., ethylene and hydrogen were charged, and the internal pressure was kept at 0.6 MPa / G for polymerization. The amount of ethylene charged was 13.7 kg.

  Subsequently, the pressure in the polymerization tank was depressurized to 0 MPa / G and replaced with nitrogen to remove hydrogen in the polymerization tank.

  Then, 473 mL of 1-hexene was charged. Polymerization was performed while maintaining the internal temperature at 65 ° C., charging ethylene and hydrogen, and maintaining the internal pressure at 0.5 MPa / G. The amount of ethylene charged was 9.0 kg.

The entire amount of the obtained polyethylene slurry was transferred to an autoclave with a stirrer having an internal volume of 500 L, and 10.7 mL of methanol was charged to deactivate the catalyst. This slurry was transferred to a filter dryer equipped with a stirrer, filtered, and then vacuum dried at 85 ° C. for 6 hours to obtain polyethylene powder.
Next, 0.1 part by weight of tri (2,4-di-t-butylphenyl) phosphate as a secondary antioxidant and n-octadecyl-as a heat stabilizer are added to 100 parts by weight of the polymer particles. 0.1 part by weight of 3- (4′-hydroxy-3 ′, 5′-di-t-butylphenyl) propinate is mixed with 0.05 part by weight of calcium stearate as a hydrochloric acid absorbent. After that, Laboplast mill manufactured by Toyo Seiki Co., Ltd. (using a twin screw batch melt kneader, set temperature 190 ° C., polyethylene powder charge 40 g (device batch volume = 60 cm ³ ), 50 rpm, 5 minutes after melt kneading and taking out. Then, it was made into a sheet with a cooling press set at 20 ° C., and cut into an appropriate size to obtain a measurement sample, etc. In the observation with a polarizing microscope, there was no continuous crystal structure exceeding 10 μm. In addition, a press sheet was prepared using the sample, and the physical properties were measured.
Pipe molding was not performed.

[Comparative Example 1]
A breath sheet using a pellet made by Hi-Zex 7700M manufactured by Mitsui Chemicals, Inc. was prepared and used as a measurement sample. The comonomer is 1-butene. The results are shown in Tables 1-3. Further, a press sheet was prepared using the sample, and the physical properties were measured. The results are shown in Tables 1-3. Further, a pipe was molded, and the hot internal pressure creep strength was measured. The results are shown in Table 4. Compared to the examples, the creep strength is weak.

[Comparative Example 2]
Breath sheet using HDPE (trade name: Hostalene, brand name: CRP100) product pellets manufactured by Basel Co., Ltd. was prepared and used as a measurement sample. The comonomer is 1-butene. Further, a press sheet was prepared using the sample, and the physical properties were measured. The results are shown in Tables 1-3. Further, a pipe was molded, and the hot internal pressure creep strength was measured. The results are shown in Table 4. Compared to the examples, the creep strength is weak.

  FIG. 4 shows the results of the 23 ° C. tensile fatigue test of the example and the comparative example. FIG. 5 shows a plot of the 23 ° C. tensile fatigue test results of the example and the comparative example against the density of the sample. Thus, the X (MPa) lower limit expression in claim 2 is defined for the purpose of distinguishing between the prior art (comparative example) and the present invention, and the X (MP) in claim 2 is defined for the purpose of limiting the possible range of the present invention. MPa) The upper limit formula was obtained.

  The pipe-based ethylene polymer according to the present invention is excellent in moldability, mechanical strength, excellent fatigue characteristics, and has a strong creep strength, and is particularly suitable for pipe applications such as water pipes and gas pipes. Yes.

It is an example of the measurement result (75 times) of the crystal structure of an ethylene polymer. It is an example of the measurement result (150 times) of the crystal structure of an ethylene polymer. The dumbbell shape for 23 degreeC tensile fatigue strength measurement is shown. It is a 23 degreeC tension fatigue test result of an Example and a comparative example. It is the figure which plotted the 23 degreeC tension fatigue test result of the Example and the comparative example with respect to the density of the sample.

Claims (7)

Intrinsic viscosity [η] (dl / g) measured in decalin at 135 ° C. is in the range of 2.7 to 4.1. After annealing at 120 ° C. for 1 hour, the temperature is linearly lowered to room temperature over 1 hour. density measured by a density gradient tube of the sample ^{(d) (kg / m 3} ) is in the range of 952~962kg / m ^3, weight average molecular weight measured by GPC (Mw) / number average molecular weight (Mn) of 11 or more The actual stress (S) (MPa) and the density (d) when the number of times of rupture in the tensile fatigue characteristics measured at 23 ° C. is 50 or less and the density (d) are the following relational expression (Eq-1) An ethylene polymer and a pipe made of the ethylene polymer.

  The smoothness coefficient R calculated | required from the surface roughness of an extrusion strand does not exceed 20 micrometers, The pipe consisting of this ethylene-type polymer for pipes of Claim 1 characterized by the above-mentioned.   The pipe is made of an ethylene-based polymer for pipes according to claim 1 or 2, which is soluble in decane at 140 ° C.   The pipe made of an ethylene polymer for pipes according to any one of claims 1 to 3, wherein the pipe is used for liquid transportation such as water supply.   The pipe made of an ethylene-based polymer for pipes according to any one of claims 1 to 3, wherein pigments such as blue, yellow and black are blended in an amount of 0.01 to 3% by weight.   The pipe joint which consists of the ethylene-type polymer for pipe joints in any one of Claims 1-3, or this ethylene-type polymer.   The pipe joint made of the ethylene-based polymer for pipe joints according to any one of claims 1 to 3, wherein pigments such as blue, yellow and black are blended in an amount of 0.01 to 3% by weight.

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