Ethylene-based polymer composition and pipe made thereof

Abstract

[Problem] The purpose of the present invention is to produce an ethylene-based polymer composition suitable for a polyethylene pipe having all of PE112 (MRS 11.2 MPa or more) performance in which higher creep strength is required, excellent moldability and low sagging properties. [Solution] The present invention relates to an ethylene-based polymer composition comprising 40 to 60% by mass of an ethylene homopolymer (A) that has an MFR (MFR2) value of 100 to 600 g / 10 min when measured at a temperature of 190°C under a load of 2.16 kg and 60 to 40% by mass of a copolymer (B) of ethylene and an α-olefin having 4 or more carbon atoms [i.e., an ethylene-(α-olefin) copolymer (B)] [wherein the total amount of the components (A) and (B) is 100% by mass], the ethylene-based polymer composition being characterized by satisfying the following requirements (i) to (iii). (i) The density is within the range from 940 to 960 kg / m3. (ii) The amount of a component having logM of ≥7 is within the range from 0.35 to 0.80% when measured by GPC. (iii) The amount of a component having logM of ≤3 is 1.85% or less when measured by GPC.

Description

[Technical Field]

[0001] The present invention relates to an ethylene polymer composition suitable for producing extrusion molded articles such as pipes which have excellent moldability and excellent long-term performance, and to a pipe made thereof. [Background technology]

[0002] Ethylene-based polymers are molded using various molding methods and are used in a wide range of applications. For example, high-pressure low-density polyethylene (LPPE), produced by high-pressure radical polymerization, is known to have long-chain branching and excellent processability. Linear low-density ethylene-α-olefin copolymers, produced by polymerizing ethylene and α-olefins using Ziegler-Natta catalysts, are known to have excellent mechanical strength, such as tensile strength, tear strength, and impact strength, as well as long-term durability, typified by environmental stress cracking (ESCR), hot internal pressure creep properties, and slow crack growth (SCG) properties for pipes. Linear low-density ethylene-α-olefin copolymers, produced by polymerizing ethylene and α-olefins using metallocene catalysts, are known to have excellent impact strength and ESCR. High-density polyethylene (HPE) is obtained by copolymerizing ethylene or ethylene with α-olefins using Ziegler-Natta catalysts, chromium catalysts, metallocene catalysts, etc., and is known to have excellent rigidity and heat resistance.

[0003] Since a single ethylene polymer cannot satisfy the physical properties required depending on the application, many methods have been proposed in which two types of ethylene polymers having different MFRs, densities, etc. are mixed (for example, Patent Documents 1 to 3). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-218324 [Patent Document 2] EP3293208 [Patent Document 3] Special Publication No. 2003-531233 Summary of the Invention [Problem to be solved by the invention]

[0005] While the properties of conventional polyethylene pipes are sufficient in many cases, higher pressure resistance is required for applications where higher pressure resistance is required, such as pipes that are subjected to internal fluid pressure for long and / or short periods of time.Currently, the MRS is obtained from the classification table of ISO 12162 based on the lower confidence limit determined in accordance with ISO 9080, and the type-specific design stress class is generally PE100 (MRS 10.0 MPa).

[0006] An object of the present invention is to obtain an ethylene polymer composition suitable for polyethylene pipes which combines the performance of PE112 (MRS of 11.2 MPa or more and less than 12.5 MPa) for which higher creep strength is required, or even higher performance, such as PE125 (MRS of 12.5 MPa or more and less than 14.0 MPa), with excellent moldability and low sagging properties. [Means for solving the problem]

[0007] The present invention relates to the following [1] to

[12] .

[0008] [1] An ethylene-based polymer composition comprising 40 to 60 mass% of an ethylene homopolymer (A) having an MFR (MFR2) in the range of 100 to 600 g / 10 min measured at a temperature of 190°C and a load of 2.16 kg, and 60 to 40 mass% of a copolymer (B) of ethylene and an α-olefin having 4 or more carbon atoms [ethylene-α-olefin copolymer (B)] (where the total amount of (A) + (B) is 100 mass%), wherein the ethylene-based polymer composition satisfies the following requirements (i) to (iii): (i) Density is 940 to 960 kg / m 3 is in the range. (ii) The amount of components with logM≧7 measured by GPC is in the range of 0.35 to 0.80%. (iii) The amount of components with logM≦3 as measured by GPC is 1.85% or less.

[0009] [2] Item [1]. The ethylene polymer composition according to item [1], wherein the α-olefin having 4 or more carbon atoms is 1-butene or 1-hexene.

[0010] [3] Item [1] or [2], wherein the ethylene-α-olefin copolymer (B) has an intrinsic viscosity [η] in the range of 7.0 to 14.0 dl / g.

[0011] [4] Item [1] - [3], wherein the ethylene polymer composition has an MFR (MFR5) measured at a temperature of 190°C and a load of 5 kg in the range of 0.03 to 0.3 g / 10 min.

[0012] [5] The ethylene polymer composition according to any one of items [1] to [4], wherein the ethylene polymer composition has a molecular weight distribution (Mw / Mn) in the range of 30 to 70 as measured by GPC.

[0013] [6] The ethylene polymer composition according to any one of items [1] to [5], wherein the ethylene homopolymer (A) and the ethylene-α-olefin copolymer (B) are polymerized using a Ziegler-Natta catalyst.

[0014] [7] A pipe made of the ethylene polymer composition according to any one of items [1] to [6].

[0015] [8] The pipe according to item [7], characterized in that the pipe simultaneously satisfies the following (a) to (d) in a hot internal pressure creep test measured in accordance with ISO 1167: (a) The time to failure at a test temperature of 20°C and a test circumferential stress of 12.7 MPa is 500 hours or more, (b) The time to failure at a test temperature of 80°C and a test circumferential stress of 6.3 MPa is 100 hours or more; (c) The time to failure at a test temperature of 80°C and a test circumferential stress of 6.1 MPa is 1,000 hours or more, (d) The time to failure is 3,000 hours or more at a test temperature of 80°C and a test circumferential stress of 5.7 MPa.

[0016] [9] Item [7] or [8], wherein 0.01 to 3 parts by mass of one or more pigments selected from titanium oxide, titanium yellow, phthalocyanine blue, isoindolinone, quinacridone compounds, condensed azo compounds, ultramarine blue, and cobalt blue are added to 100 parts by mass of the ethylene polymer composition.

[0017]

[10] An ethylene-based polymer composition comprising an ethylene homopolymer and a copolymer of ethylene and an α-olefin having 4 or more carbon atoms, and satisfying the following requirements (i) to (vi): (i) Density is 940 to 960 kg / m 3 is in the range. (ii) The amount of components with logM≧7 measured by GPC is in the range of 0.35 to 0.80%. (iii) The amount of components with logM≦3 as measured by GPC is 1.85% or less. (iv) The MFR (MFR5) measured at a temperature of 190°C and a load of 5 kg is in the range of 0.03 to 0.3 g / 10 min. (v) The molecular weight distribution (Mw / Mn) measured by GPC is in the range of 30 to 70. (vi) The obtained pipe simultaneously satisfies the following (a) to (d) in a hot internal pressure creep test measured in accordance with ISO1167: (a) The time to failure at a test temperature of 20°C and a test circumferential stress of 12.7 MPa is 500 hours or more, (b) The time to failure at a test temperature of 80°C and a test circumferential stress of 6.3 MPa is 100 hours or more; (c) The time to failure at a test temperature of 80°C and a test circumferential stress of 6.1 MPa is 1,000 hours or more, (d) The time to failure is 3,000 hours or more at a test temperature of 80°C and a test circumferential stress of 5.7 MPa.

[0018]

[11] Item

[10] The ethylene polymer composition according to item

[10] , further satisfying the following requirement (vii): (vii) The chart measured by GPC shows a bimodal distribution, and the ratio of the low molecular weight component to the high molecular weight component determined by peak separation is in the range of 40:60 to 60:40.

[0019]

[12] Item

[11] The ethylene polymer composition according to item

[11] , wherein the low-molecular-weight component comprises an ethylene homopolymer, and the high-molecular-weight component comprises a copolymer of ethylene and an α-olefin having 4 or more carbon atoms. [Effects of the Invention]

[0020] The ethylene polymer composition of the present invention is excellent in long-term creep strength and pipe formability, and a pipe using the ethylene polymer composition of the present invention has excellent long-term creep strength and exhibits a performance of MRS of 11.2 MPa or more (PE112) as classified based on ISO 9080 and 12162. Because of its moderate fluidity, the composition has excellent formability and low sagging properties without impairing extrudability during molding.

[0021] A pipe made of the ethylene polymer composition of the present invention is suitable for use as a water pipe, a gas pipe, or the like. DETAILED DESCRIPTION OF THE INVENTION

[0022] Specific embodiments of the present invention will be described in detail below, but the present invention is not limited to the following embodiments and can be practiced with appropriate modifications within the scope of the object of the present invention. In this specification, the term "polymer" is used to include homopolymers and copolymers unless otherwise specified.

[0023] <Ethylene homopolymer (A)> The ethylene homopolymer (A) [hereinafter, sometimes referred to as "component (A)" or "homopolymer (A)], which is one of the components constituting the ethylene polymer composition of the present invention, has an MFR (MFR2) measured at a temperature of 190°C and a load of 2.16 kg in the range of 100 to 600 g / 10 min, preferably 200 to 500 g / 10 min, and is preferably an ethylene homopolymer polymerized with a Ziegler-Natta catalyst.

[0024] Component (A) according to the present invention may contain structural units derived from at least one or more biomass-derived monomers (ethylene). The same type of ethylene constituting component (A) may be biomass-derived ethylene only, or may contain both biomass-derived ethylene and fossil fuel-derived ethylene. Biomass-derived ethylene is ethylene obtained from any renewable natural raw material, such as a plant-derived or animal-derived material, including fungi, yeast, algae, and bacteria, and its residues, and contains as carbon 14 C isotope 10 -12 The biomass carbon concentration (pMC) measured in accordance with ASTM D 6866 is about 100 (pMC). Biomass-derived ethylene can be obtained by a conventionally known method.

[0025] It is preferable that the component (A) according to the present invention contains biomass-derived ethylene from the viewpoint of reducing the environmental load.

[0026] When the MFR2 of component (A) according to the present invention satisfies the above range, the shear viscosity of the ethylene polymer composition containing component (A) does not become too high, the resin pressure in the extruder is reduced, and moldability is improved. In addition, the content of low-molecular-weight components does not become too high, and therefore short-term creep strength is improved.

[0027] The MFR2 of the component (A) according to the present invention was measured in accordance with JIS K7210-1.

[0028] The component (A) according to the present invention preferably has an intrinsic viscosity [η] measured in decalin solvent at 135°C in the range of 0.55 to 0.75 dL / g, more preferably 0.58 to 0.72 dL / g. When the intrinsic viscosity [η] is within the above range, the shear viscosity of the ethylene polymer composition containing component (A) does not become too high, the resin pressure in the extruder decreases, and moldability improves. In addition, the low molecular weight component does not become too high, and therefore short-term creep strength improves.

[0029] Component (A) according to the present invention preferably has a density of 960 kg / m 3 More preferably, 965 kg / m 3 More preferably, it is 963 to 973 kg / m 3 , and more preferably 965 to 971 kg / m 3 When the density of component (A) is within this range, it becomes easy to adjust the density of the ethylene polymer composition containing component (A) to a range that satisfies the following requirement (i).

[0030] The component (A) according to the present invention also has a molecular weight distribution (Mw / Mn) measured by GPC of preferably 3.0 to 7.0, more preferably 4.0 to 6.0. The molecular weight distribution (Mw / Mn) of the component (A) can be determined by a method using GPC peak separation of the ethylene polymer composition, which will be described later. Alternatively, it can be determined by collecting a sample of the component (A) during the production process of the ethylene polymer composition and subjecting it to GPC measurement.

[0031] <Ethylene-α-olefin copolymer (B)> The ethylene-α-olefin copolymer (B) [hereinafter, sometimes referred to as "component (B)"], which is one of the components constituting the ethylene polymer composition of the present invention, is a copolymer of ethylene and an α-olefin having 4 or more carbon atoms, having an intrinsic viscosity [η] measured in decalin solvent at 135°C, preferably in the range of 7.0 to 14 dl / g, more preferably 8.0 to 12 dl / g. The α-olefin having 4 or more carbon atoms preferably has 20 or less carbon atoms. The density of component (B) is preferably 920 to 945 kg / m 3, more preferably 925 to 940 kg / m 3 , particularly preferably 930 to 935 kg / m 3 The molecular weight distribution (Mw / Mn) measured by GPC is preferably in the range of 4.0 to 8.0, more preferably 5.0 to 7.0. The molecular weight distribution (Mw / Mn) of component (B) can usually be determined by a method of GPC peak separation of the ethylene polymer composition, which will be described later. Alternatively, when only component (B) can be collected in the production process of the ethylene polymer composition, the molecular weight distribution (Mw / Mn) can be determined by GPC measurement of component (B).

[0032] When the intrinsic viscosity [η] of component (B) is within the above range, the creep strength of the ethylene polymer composition containing component (B) becomes good.

[0033] As the α-olefin having 4 or more carbon atoms constituting component (B) according to the present invention, multiple α-olefins may be used, and specific examples include 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-heptene, 1-octene, and 1-decene. Among these α-olefins, 1-butene or 1-hexene is preferred, with 1-butene being more preferred. While 1-butene is more preferred in terms of production costs, 1-hexene is more preferred in terms of the creep strength of the resulting ethylene polymer composition and molded article.

[0034] Component (B) according to the present invention may contain at least one or more types of biomass-derived ethylene and / or biomass-derived α-olefins. The same type of ethylene and / or α-olefins constituting component (B) may be biomass-derived ethylene and / or biomass-derived α-olefins only, or may contain both biomass-derived ethylene and / or biomass-derived α-olefins and fossil fuel-derived α-olefins and / or fossil fuel-derived ethylene. Biomass-derived ethylene and biomass-derived α-olefins are ethylene and α-olefins derived from any renewable natural raw material and its residue, such as plant-derived or animal-derived, including fungi, yeast, algae, and bacteria, and contain 10 carbon isotopes of 14C. -12 The biomass carbon concentration (pMC) measured in accordance with ASTM D 6866 is about 100 (pMC). Biomass-derived ethylene and biomass-derived α-olefins can be obtained by conventionally known methods.

[0035] It is preferable from the viewpoint of reducing the environmental load that the component (B) according to the present invention contains biomass-derived ethylene and / or α-olefin.

[0036] The component (B) according to the present invention preferably has a density of 910 to 960 kg / m 3 , more preferably 922 to 948 kg / m 3 When the density of component (B) is within this range, it becomes easy to adjust the density of the ethylene polymer composition containing component (B) to a range that satisfies the following requirement (i).

[0037] The method for producing component (B) according to the present invention is not particularly limited as long as it has the above-mentioned properties. However, polymers polymerized using a multi-site catalyst are preferred because they have a broad molecular weight distribution and improve moldability.

[0038] Here, the multi-site catalyst is a conventionally known catalyst having many active sites, such as a Ziegler-Natta catalyst (hereinafter sometimes referred to as a "Ziegler catalyst"), a chromium-based catalyst (Phillips catalyst), or a standard catalyst, with the Ziegler catalyst being preferred.

[0039] <Ethylene-based polymer composition> The ethylene polymer composition of the present invention (hereinafter, may be referred to as "polymer composition") comprises 40 to 60 mass%, preferably 45 to 58 mass%, and more preferably 50 to 56 mass% of the component (A) and 60 to 40 mass%, preferably 55 to 42 mass%, and more preferably 50 to 44 mass% of the component (B) (where the total amount of (A) + (B) is 100 mass%), and is characterized by satisfying the following requirements (i) to (iii):

[0040] <Requirement (i)> Density: 940-960 kg / m 3 , preferably 945 to 958 kg / m 3 , more preferably 948 to 956 kg / m 3 is in the range.

[0041] When the polymer composition satisfies the above range, the long-term creep strength is improved.

[0042] <Requirement (ii)> The amount of components with logM≧7 measured by GPC is in the range of 0.35 to 0.80%, preferably 0.38 to 0.75%, and more preferably 0.40 to 0.70%.

[0043] A polymer composition satisfying the requirement (ii) can be obtained by adjusting the amounts of component (A) and component (B) contained in the polymer composition to fall within the above ranges. Furthermore, by increasing the intrinsic viscosity [η] of component (B), the amount of components with logM≧7 can be controlled to be large. Furthermore, in an ethylene polymer composition, the amount of components with logM≧7 tends to increase as the Mz value, which will be described later, increases.

[0044] When the polymer composition satisfies the above range, the shear viscosity does not become too high, and the long-term creep strength is good. If the amount of the component with log M ≥ 7 is too large, the shear viscosity of the polymer composition becomes too high, which may increase the resin pressure in the extruder and deteriorate moldability. In addition, there is a risk of the appearance being deteriorated when the polymer composition is made into a pipe. If the amount of the component with log M ≥ 7 is too small, there is a risk of the long-term creep strength of the polymer composition being reduced.

[0045] <Requirement (iii)> The amount of components with logM≦3 as measured by GPC is 1.85% or less, preferably 1.75% or less.

[0046] A polymer composition satisfying requirement (iii) can be obtained by adjusting the amounts of components (A) and (B) contained in the polymer composition to fall within the above ranges. The amount of components with logM≦3 is affected by the type and concentration of the catalyst and electron donor used during production, as well as other polymerization conditions. Generally, the amount of components with logM≦3 can be reduced by increasing the intrinsic viscosity [η] of component (A). In addition to the intrinsic viscosity [η] of component (A), the content of component (A) also affects the amount of components with logM≦3. Generally, reducing the content of component (A) reduces the amount of components with logM≦3. Furthermore, with regard to the hexane used as the polymerization solvent, increasing the proportion of hexane solvent (recycled hexane) obtained by centrifuging the polymer slurry containing the mother liquor after the reaction in the second polymerization vessel back into the polymerization vessel results in a greater incorporation of low-molecular-weight components contained in the recycled hexane into the polymer, thereby increasing the amount of components with logM≦3. In other words, decreasing the proportion of recycled hexane returned to the polymerization vessel can reduce the amount of components with logM≦3.

[0047] There is no particular lower limit to the amount of components with logM≦3 in the polymer composition, but it is usually 0.50% or more, or 1.00% or more.

[0048] By suppressing the amount of components with logM≦3 in the polymer composition to 1.85% or less, the long-term creep strength is improved.

[0049] In addition to the above requirements (i) to (iii), the ethylene polymer composition of the present invention has a molecular weight distribution (Mw / Mn) measured by GPC of preferably 30 to 70, more preferably 40 to 65, even more preferably 45 to 65, and particularly preferably 50 to 65.

[0050] If the Mw / Mn ratio of the polymer composition of the present invention is too low, the shear viscosity of the polymer composition may become too high, which may increase the resin pressure in the extruder and deteriorate moldability.On the other hand, if the Mw / Mn ratio is too high, poor mixing of components (A) and (B) may occur, which may deteriorate the appearance when molded into a pipe.

[0051] The chart of the polymer composition of the present invention measured by GPC usually shows a bimodal molecular weight distribution.

[0052] In addition to the above requirements (i) to (iii), the ethylene polymer composition of the present invention preferably has a Z-average molecular weight (Mz) measured by GPC of 2.0 × 10 6 More preferably, 3.0 × 10 6 More preferably, 4.0 × 10 6 The upper limit is usually 5.5 × 10 6 or less, or 5.0 x 10 6 The following is the result.

[0053] In the ethylene polymer composition of the present invention, the ratio of Mw / Mn of component (A) to Mw / Mn of component (B), (Mw / Mn(B)) / (Mw / Mn(A)), is preferably greater than 0.9, more preferably 1.0 or greater, and even more preferably 1.1 or greater.

[0054] The polymer composition of the present invention preferably has an MFR (MFR5) measured at a temperature of 190° C. and a load of 5 kg in the range of 0.03 to 0.3 g / 10 min, more preferably 0.05 to 0.25 g / 10 min.

[0055] When the MFR5 of the copolymer composition satisfies the above range, the creep strength becomes good while maintaining moldability and low sagging properties.

[0056] The ethylene polymer composition of the present invention has a melt flow rate (MFR) of 190°C under a load of 21.6 kg (hereinafter referred to as MFR 21.6 ) and MFR5 (MFR 21.6 / MFR5) is 40 or more, preferably 50 or more. 21.6 and MFR5 ratio (MFR 21.6 / MFR5) is usually less than 100. 21.6 By using an ethylene polymer composition having / MFR5 in the above range, a polyethylene pipe having excellent moldability, fracture resistance and hot internal pressure creep resistance can be obtained.

[0057] The MFR (MFR5 and MFR 21.6 ) was measured in accordance with JIS K7210-1.

[0058] Ethylene-based polymer composition 2 The ethylene polymer composition of the present invention can also be defined as follows (hereinafter referred to as "ethylene polymer composition 2").

[0059] The ethylene polymer composition 2 of the present invention is an ethylene polymer composition comprising an ethylene homopolymer and a copolymer of ethylene and an α-olefin having 4 or more carbon atoms, and satisfies the following requirements (i) to (vi). (i) Density is 940 to 960 kg / m 3 is in the range. (ii) The amount of components with logM≧7 measured by GPC is in the range of 0.35 to 0.80%. (iii) The amount of components with logM≦3 as measured by GPC is 1.85% or less. (iv) The MFR (MFR5) measured at a temperature of 190°C and a load of 5 kg is in the range of 0.03 to 0.3 g / 10 min. (v) The molecular weight distribution (Mw / Mn) measured by GPC is in the range of 30 to 70. (vi) The obtained pipe simultaneously satisfies the following (a) to (d) in a hot internal pressure creep test measured in accordance with ISO1167: (a) The time to failure at a test temperature of 20°C and a test circumferential stress of 12.7 MPa is 500 hours or more, (b) The time to failure at a test temperature of 80°C and a test circumferential stress of 6.3 MPa is 100 hours or more; (c) The time to failure at a test temperature of 80°C and a test circumferential stress of 6.1 MPa is 1,000 hours or more, (d) The time to failure is 3,000 hours or more at a test temperature of 80°C and a test circumferential stress of 5.7 MPa.

[0060] The above requirements (i) to (v) have already been described in detail in this specification, and requirement (vi) will be described later in the section on pipes.

[0061] The ethylene polymer composition 2 preferably further satisfies the following requirement (vii). (vii) The chart measured by GPC shows a bimodal peak, and the ratio of the low molecular weight component to the high molecular weight component determined by peak separation is in the range of 40:60 to 60:40, more preferably 50:50 to 60:40, and even more preferably 55:45 to 60:40.

[0062] Peak separation in a GPC chart can be determined by curve fitting two normal distribution curves to bimodal peaks appearing in the molecular weight distribution curve and then separating the peaks. Alternatively, the entire sample can be measured by GPC, and the resulting multimodal molecular weight distribution curve can be separated using commercially available data analysis software, etc., and the component ratios can be calculated. For example, based on a program created using Microsoft Excel Visual Basic (registered trademark), the two peak curves to be separated are assumed to be log-normal distributions, and the molecular weight distribution curve is separated into two peak curves with different molecular weights by convergence calculation. The two separated peak curves are recombined and compared with the GPC chart, and calculations are performed while changing the initial values ​​so that the two curves approximately match. The calculation is performed by dividing Log(molecular weight) [LogM] into 0.02 intervals and normalizing the intensity so that the area of ​​the measured molecular weight curve and the area of ​​the recombined curve of the two separated peaks equal 1.

[0063] The low molecular weight component corresponds to the component (A) constituting the above-mentioned ethylene polymer composition, and the high molecular weight component corresponds to the component (B) constituting the above-mentioned ethylene polymer composition.

[0064] To achieve the physical properties specified in the above requirement (vi), the low-molecular-weight component is preferably made of an ethylene homopolymer. This can be achieved by producing an ethylene homopolymer (A) according to the production method described below. In this case, the high-molecular-weight component is made of a copolymer of ethylene and an α-olefin having 4 or more carbon atoms.

[0065] Other requirements that the ethylene-based polymer composition 2 preferably satisfies are as described above for the ethylene-based polymer composition.

[0066] Pigments and additives The ethylene polymer composition of the present invention preferably contains 0.01 to 3 parts by mass, more preferably 0.05 to 2 parts by mass, of one or more pigments selected from titanium oxide, titanium yellow, phthalocyanine blue, isoindolinone, quinacridone compounds, condensed azo compounds, ultramarine blue, and cobalt blue, per 100 parts by mass of the polymer composition (total amount of (A) + (B)). By adding such pigments, pipes suitable for water pipes or gas pipes can be obtained. The color of the pipes can be, for example, blue, yellow, orange, white, red, green, purple, etc.

[0067] Furthermore, the ethylene polymer composition of the present invention preferably contains 0.01 to 3 parts by mass, preferably 0.5 to 2.5 parts by mass, and more preferably 2.0 to 2.5 parts by mass of carbon black per 100 parts by mass of the polymer composition (total amount of (A) + (B)). By adding carbon black, a pipe suitable for water or gas pipes having excellent weather resistance can be obtained. In this case, the color of the pipe is black, gray, or the like.

[0068] The ethylene polymer composition of the present invention can be used for various molded articles, which will be described later, by adding other resins to the polymer composition. Examples of other resins include ethylene resins such as high-density polyethylene, low-density polyethylene, very-low-density polyethylene, and ultra-low-density polyethylene, and polyolefin rubber. The amount of the other resin added is, for example, 10 parts by mass or less per 100 parts by mass of the polymer composition (the total amount of (A) + (B)).

[0069] The ethylene polymer composition of the present invention may contain, as needed, additives that are usually used in olefin polymers, such as a weather resistance stabilizer, a heat resistance stabilizer, an antistatic agent, an antislip agent, an antiblocking agent, an antifogging agent, a lubricant, a dye, a nucleating agent, a plasticizer, an antioxidant, a hydrochloric acid absorbent, and an antioxidant, within the scope of the object of the present invention.

[0070] <<Method for producing ethylene polymer composition>> The polymer composition of the present invention is preferably produced by slurry polymerization using a MgCl2-based Ziegler-Natta catalyst, in which the ethylene homopolymer (A) and the ethylene-α-olefin copolymer (B) constituting the ethylene polymer composition are each independently polymerized, or in a multi-stage polymerization. When each is independently polymerized, the ethylene polymer composition is obtained by mixing or melt-kneading the components (A, B) using a conventionally known method. For example, the ethylene polymer composition can be obtained by melting and kneading the components (A, B) using an extruder, a Brabender Plastograph, a Banbury mixer, a kneader blender, or the like. In the case of multi-stage polymerization, the dispersibility of the components (A, B) is improved, resulting in a good appearance of the pipe molded from the ethylene polymer composition of the present invention.

[0071] <<Molded body, pipe>> The ethylene polymer composition of the present invention can be molded to obtain various molded articles, which can be used in various existing applications of ethylene resins. The ethylene polymer composition of the present invention is particularly suitable for pipe applications. The ethylene polymer composition of the present invention has excellent pipe moldability, and by molding it, pipes and multi-layer pipes with excellent long-term durability can be obtained. Here, this multi-layer pipe is formed with at least one layer comprising the copolymer composition of the present invention. In this multi-layer pipe molded article, the layer comprising the copolymer composition may be formed on only one side or on both sides, and one of the two sides may be formed with a pigment as one of the "other blending components." The substrate constituting this multi-layer pipe may be formed from the copolymer composition, or may be formed from a material other than the copolymer composition.

[0072] When the pipe is multi-layered, the other resins are not particularly limited and include, for example, crystalline resins, rubber, adhesive resins, and barrier resins. Specific examples include high-density polyethylene, low-density polyethylene, very low-density polyethylene, ultra-low-density polyethylene, polypropylene, ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, ethylene-acrylic acid ester copolymer, ethylene-methacrylic acid copolymer, ethylene-methacrylic acid ester copolymer, ethylene-vinyl alcohol copolymer, saponified ethylene-vinyl acetate copolymer, ethylene-styrene copolymer, ethylene-vinylcyclohexane copolymer, ethylene-norbornene copolymer, polyolefin rubber, styrene-butadiene rubber, styrene-butadiene-styrene block copolymer, isoprene rubber, styrene-isoprene rubber, isobutylene rubber, and the like, as well as acid-modified and hydrogenated products of these resins.

[0073] The pipe of the present invention is formed from the copolymer composition of the present invention by a known pipe-forming method, for example, by melting the copolymer composition at a temperature of 150 to 220°C, preferably 160 to 210°C, using an extruder of a pipe-making apparatus, extruding the composition through a die into a cylindrical shape, and then cooling with water.

[0074] The shape of the pipe of the present invention can be determined appropriately depending on the application of the pipe. Examples include polyethylene pipes molded to an outer diameter and wall thickness specified in ISO 4427, ISO 4437, JIS K6761, JIS K6762, or JIS K6774. These molded articles also include molded articles (such as laminates) containing a portion made of an ethylene polymer composition and a portion made of another resin.

[0075] The pipe of the present invention is characterized in that, in a hot internal pressure creep test measured in accordance with ISO 1167, it simultaneously satisfies the following (a) to (d): (a) The time to failure at a test temperature of 20°C and a test circumferential stress of 12.7 MPa is 500 hours or more, (b) The time to failure at a test temperature of 80°C and a test circumferential stress of 6.3 MPa is 100 hours or more; (c) The time to failure at a test temperature of 80°C and a test circumferential stress of 6.1 MPa is 1,000 hours or more, (d) The time to failure is 3,000 hours or more at a test temperature of 80°C and a test circumferential stress of 5.7 MPa. [Example]

[0076] The present invention will be explained in more detail below based on examples, but the present invention is not limited to these examples.

[0077] The methods for measuring the characteristics and physical properties of each component used in the examples are as follows.

[0078] (1) 2.16 kg load melt flow rate (MFR2, g / 10 min) Measurement was carried out in accordance with JIS K7210-1 under conditions of 190°C and a load of 2.16 kg.

[0079] (2) 5 kg load melt flow rate (MFR5, g / 10 min) Measurement was carried out in accordance with JIS K7210-1 under conditions of 190°C and a load of 5 kg.

[0080] (3) 21.6 kg load melt flow rate (MFR 21.6 ,g / 10min) Measurement was carried out in accordance with JIS K7210-1 under conditions of 190°C and a load of 21.6 kg.

[0081] (4) Density (kg / m 3 ) The density was measured in accordance with JIS K7112 by heat treating the strand obtained during the MFR measurement at 100°C for 1 hour and then leaving it at room temperature for 1 hour, followed by measurement by the density gradient tube method.

[0082] The density (D B ) is the mass fraction BR of the ethylene homopolymer (A). A , density D A and the density D of the ethylene polymer composition C was calculated using the following equation (Eq-1).

[0083] BR B / D B =(1 / D C )-(BR A / D A ) -------- (Eq-1) (5) Intrinsic viscosity ([η], dl / g) For the intrinsic viscosity, approximately 20 mg of the measurement sample was dissolved in 15 ml of decalin, and the specific viscosity ηsp was measured in an oil bath at 135°C. 5 ml of decalin solvent was added to this decalin solution to dilute it, and the specific viscosity ηsp was measured in the same manner. This dilution procedure was repeated two more times, and the value of ηsp / C when the concentration (C) was extrapolated to 0 as shown in the following equation (Eq-2) was calculated as the intrinsic viscosity [η] (unit: dl / g).

[0084] [η]=lim(ηsp / C) (C→0) -------- (Eq-2) In addition, the intrinsic viscosity ([η] B ) is the mass fraction BR of ethylene homopolymer A , intrinsic viscosity [η] A and the intrinsic viscosity [η] of the ethylene polymer compositionC was calculated using the following equation (Eq-3).

[0085] [η] B =([η] C -[η] A ×BR A )) / (1-BR A ) -------- (Eq-3) (6)logM≧7 component amount, logM≦3 component amount The amount of log M≧7 components was measured using a gel permeation chromatograph HLC-8321 GPC / HT model manufactured by Tosoh Corporation as follows.

[0086] Analysis software: Chromatography Data System Empower3 (Waters, registered trademark); Column: TSKgel GMH6-HT x 2 + TSKgel GMH6-HTL x 2 (inner diameter 7.5 mm x length 30 cm, manufactured by Tosoh Corporation); Mobile phase: o-dichlorobenzene (special grade reagent, Wako Pure Chemical Industries, Ltd.); Detector: differential refractometer (built-in); Column temperature: 140°C; Flow rate: 1.0 mL / min; Injection volume: 400 μL; Sampling time interval: 0.5 seconds; Sample concentration: 0.1% (w / v); Molecular weight calibration: monodisperse polystyrene (manufactured by Tosoh Corporation); #3std set.

[0087] A molecular weight distribution curve was prepared in terms of standard polyethylene molecular weight according to the universal calibration procedure described in Z. Crubisic, P. Rempp, H. Benoit, J. Polym. Sci., B5, 753 (1967).

[0088] The amount of components with log M≧7 was calculated by the following method using the molecular weight distribution curve (G1) of the obtained ethylene polymer composition. In this specification, the term "molecular weight distribution curve" refers to a differential molecular weight distribution curve unless otherwise specified, and the term "area" of a molecular weight distribution curve refers to the area of ​​the region formed between the molecular weight distribution curve and the baseline.

[0089] For each numerical data of (G1), Log (molecular weight, hereinafter M) is divided into 0.02 intervals, and for each of (G1), the intensity [dwt / d(logM)] is normalized so that the area becomes 1.

[0090] Then, the sum of normalized dwt / dlogM for logM≧7 was calculated and used as the component amount for logM≧7. Similarly, the sum of normalized dwt / dlogM for logM≦3 was calculated and used as the component amount for logM≦3.

[0091] (7) Molecular weight distribution (Mw / Mn), average molecular weight (Mw,Mn,Mz) Using the method (6) above, Mw / Mn was calculated from the weight average molecular weight (Mw), number average molecular weight (Mn), and z average molecular weight (Mz) calculated in terms of standard polyethylene molecular weight.

[0092] (7-2) Peak separation of molecular weight distribution The bimodal peaks appearing in the molecular weight distribution curve were fitted with two normal distribution curves to separate the peaks, and the content ratio of each component, as well as the weight-average molecular weight (Mw), number-average molecular weight (Mn), and molecular weight distribution (Mw / Mn) of each component were determined.

[0093] (8) Hot internal pressure creep test - time to failure <Pipe forming method> The ethylene polymer composition (C) was extruded at a set temperature of 200°C and an extrusion rate of 22 kg / hr using a 65 mmφ, L / D=25 pipe molding machine manufactured by Ikegai Iron Works Co., Ltd. to obtain a polyethylene pipe having an SDR of 11 and a diameter of 60 mm.

[0094] <Internal pressure creep rupture time> Measurements were made according to ISO 1167 with a pipe length of 50 cm and temperatures of 20°C or 80°C, with hoop stresses ranging from 11 to 15 MPa at 20°C and 5 to 7 MPa at 80°C.

[0095] (9) 80℃ tensile fatigue strength (FNFT fracture stress: MPa) The obtained polyethylene pipe was cut into a rectangular column measuring 6 mm in length, 6 mm in width, and 60 mm in length to be used as an evaluation sample. Tensile fatigue strength (test specimen shape) was measured in accordance with JIS K6774. The test conditions for a full-circumference notch type with a notch depth of 1 mm are outlined below.

[0096] Measurements were taken at several points in the test specimen shape (6mm x 6mm x 60mm rectangular column with a notch), test waveform and test frequency (square wave, 0.5Hz), test temperature 80°C, and actual stress range of 10 to 18MPa, and the fatigue strength was determined as the number of fatigue cycles at which the specimen broke. Measurements were taken at at least three different actual stress points, over a range of three digits or more in the number of cycles to break or over an actual stress of 3MPa or more, and an approximate formula was created using the least squares method of power approximation to determine the actual stresses corresponding to 10,000 cycles and 100,000 cycles to break.

[0097] Example 1 <Production of Ethylene Homopolymer (A-1)> The catalyst used was a MgCl2-based Ziegler-Natta catalyst.

[0098] Internal volume 0.34m 3 To the first polymerization vessel, n-hexane was continuously fed at 70.7 L / hr, catalyst at 1.9 mmol-Ti / hr, and triethylaluminum at 11 mmol-Al / hr, and the contents of the polymerization vessel were continuously withdrawn to maintain a constant liquid level. Ethylene homopolymer (A) was polymerized under the conditions of a polymerization temperature of 85°C, a reaction pressure of 0.65 MPaG, and an average residence time of 2.0 hours. During the polymerization, ethylene, hydrogen, and nitrogen were continuously fed to maintain a constant gas composition (gas composition (molar ratio): hydrogen / ethylene = 5.4 mol / mol). The content continuously withdrawn from the first polymerization vessel is passed through a flash drum maintained at an internal pressure of 0.03 MPa and a temperature of 30°C, where unreacted ethylene and hydrogen are substantially removed.

[0099] The physical properties of the homopolymer (A-1) from which the unreacted ethylene and hydrogen had been substantially removed were measured by the methods described above.

[0100] <Production of Copolymer (B-1) and Copolymer Composition (C-1)> The contents are then poured into a 0.2m 3 The contents of the second polymerization vessel were continuously supplied with n-hexane at 57 L / hr, a polymerization temperature of 72°C, a reaction pressure of 0.30 MPaG, and an average residence time of 1.0 hr, and ethylene-1-butene copolymer (B-1) was polymerized. Ethylene, 1-butene, hydrogen, and nitrogen were continuously supplied to maintain a constant gas composition during the polymerization. The 1-butene to ethylene feed ratio was 0.031 kg / kg, and the hydrogen to ethylene gas composition (molar ratio): hydrogen / ethylene = 0.016 mol / mol. The contents of the second polymerization vessel were also continuously withdrawn to maintain a constant liquid level. The n-hexane and unreacted monomers were removed and dried using a solvent separator, yielding an ethylene polymer composition (C-1) containing homopolymer (A-1) and ethylene-1-butene copolymer (B-1). The yield of the resulting copolymer composition (C-1) was 16 kg / hr.

[0101] The amount and physical properties of the copolymer (B-1) contained in the composition (C-1), as well as the physical properties of the composition (C-1), were measured by the methods described above.

[0102] Next, 100 parts by mass of the copolymer composition was blended with 0.15 parts by mass of calcium stearate as a hydrochloric acid absorbent, 0.2 parts by mass of BASF's Irganox1010 and 0.1 parts by mass of BASF's Irgafos168 as antioxidants, and 0.1 parts by mass of BASF's Tinuvin622LD as a weather stabilizer. The mixture was then melt-kneaded using a GM40-28 extruder manufactured by GM Sansei Co., Ltd. at a set temperature of 200°C and a screw rotation speed of 80 rpm, extruded into a strand shape, and cut to obtain pellets.

[0103] The physical properties of the resulting pellets of the ethylene polymer composition are shown in Table 1. Furthermore, a pipe was formed by the above-mentioned method, and the performance thereof was evaluated. The results are shown in Table 2.

[0104] Example 2 Internal volume 0.34m 3To the first polymerization vessel, n-hexane was continuously fed at 71.8 L / hr, the same catalyst as in Example 1 at 1.9 mmol-Ti / hr, and triethylaluminum at 14 mmol-Al / hr, and the contents of the polymerization vessel were continuously withdrawn to maintain a constant liquid level in the polymerization vessel. Ethylene homopolymer (A-2) was polymerized under the same conditions as in Example 1, polymerization temperature, reaction pressure, and average residence time of 1.9 hr. During the polymerization, ethylene, hydrogen, and nitrogen were continuously fed to maintain a constant gas composition (gas composition (molar ratio): hydrogen / ethylene = 5.3 mol / mol). (A-2) extracted from the first polymerization reactor had an internal volume of 0.2 m 3 The resulting mixture was continuously fed to a second polymerization vessel, and an ethylene-1-butene copolymer (B-2) was polymerized under the same conditions as in Example 1. During the polymerization, ethylene, 1-butene, hydrogen, and nitrogen were continuously fed to maintain a constant gas composition. The feed ratio of 1-butene to ethylene was 0.031 kg / kg, and the gas composition (molar ratio) of hydrogen to ethylene was hydrogen / ethylene = 0.017 mol / mol. The solvent and unreacted monomers were separated from the resulting contents and dried in the same manner as in Example 1, yielding an ethylene polymer composition. The yield was 17 kg / hr.

[0105] In addition, the amount and physical properties of (B-2) contained in composition (C-2) in the same manner as in Example 1, as well as the physical properties of composition (C-2) and the results of performance evaluation after pipe molding are shown in Tables 1 and 2.

[0106] Example 3 Internal volume 0.34m 3 To the first polymerization vessel, n-hexane was continuously fed at 70.4 L / hr, the same catalyst as in Example 1 at 1.9 mmol-Ti / hr, and triethylaluminum at 11 mmol-Al / hr, and the contents of the polymerization vessel were continuously withdrawn to maintain a constant liquid level in the polymerization vessel. Ethylene homopolymer (A-3) was polymerized under the same conditions as in Example 1, polymerization temperature, reaction pressure, and average residence time of 1.9 hr. During the polymerization, ethylene, hydrogen, and nitrogen were continuously fed to maintain a constant gas composition (gas composition (molar ratio): hydrogen / ethylene = 5.2 mol / mol). The (A-3) extracted from the first polymerization reactor had an internal volume of 0.2 m 3 The resulting mixture was continuously fed to a second polymerization vessel, and an ethylene-1-butene copolymer (B-3) was polymerized under the same conditions as in Example 1. During the polymerization, ethylene, 1-butene, hydrogen, and nitrogen were continuously fed to maintain a constant gas composition. The feed ratio of 1-butene to ethylene was 0.018 kg / kg, and the gas composition (molar ratio) of hydrogen to ethylene was hydrogen / ethylene = 0.007 mol / mol. The solvent and unreacted monomers were separated from the resulting contents and dried in the same manner as in Example 1, yielding an ethylene polymer composition. The yield was 17 kg / hr.

[0107] In addition, the physical properties were measured in the same manner as in Example 1, and the pipe was molded to evaluate the performance. The results are shown in Tables 1 and 2.

[0108] Comparative Example 1 Internal volume 0.34m 3 To the first polymerization vessel, n-hexane was continuously fed at 70.3 L / hr, the same catalyst as in Example 1 at 1.9 mmol-Ti / hr, and triethylaluminum at 11 mmol-Al / hr, and the contents of the polymerization vessel were continuously withdrawn to maintain a constant liquid level in the polymerization vessel. Ethylene homopolymer was polymerized under the same conditions as in Example 1, polymerization temperature, reaction pressure, and average residence time of 1.9 hours. During the polymerization, ethylene, hydrogen, and nitrogen were continuously fed to maintain a constant gas composition (gas composition (molar ratio): hydrogen / ethylene = 5.2 mol / mol). The contents extracted from the first polymerization reactor had an internal volume of 0.2 m 3 The resulting mixture was continuously fed to a second polymerization vessel, and an ethylene-1-butene copolymer was polymerized under the same conditions as in Example 1. During the polymerization, ethylene, 1-butene, hydrogen, and nitrogen were continuously fed to maintain a constant gas composition. The feed ratio of 1-butene to ethylene was 0.043 kg / kg, and the gas composition (molar ratio) of hydrogen to ethylene was hydrogen / ethylene = 0.007 mol / mol. The solvent and unreacted monomers were separated from the resulting contents and dried in the same manner as in Example 1, yielding an ethylene polymer composition. The yield was 20 kg / hr.

[0109] In addition, the physical properties were measured in the same manner as in Example 1, and the pipe was molded to evaluate the performance. The results are shown in Tables 1 and 2.

[0110] Comparative Example 2 Internal volume 0.34m 3 To the first polymerization vessel, n-hexane was continuously fed at 73.6 L / hr, the same catalyst as in Example 1 at 1.9 mmol-Ti / hr, and triethylaluminum at 15 mmol-Al / hr, and the contents of the polymerization vessel were continuously withdrawn to maintain a constant liquid level in the polymerization vessel, while ethylene homopolymer was polymerized under the same conditions as in Example 1. During the polymerization, ethylene, hydrogen, and nitrogen were continuously fed to maintain a constant gas composition (gas composition (molar ratio): hydrogen / ethylene = 5.5 mol / mol). The contents extracted from the first polymerization reactor had an internal volume of 0.2 m 3 The resulting mixture was continuously fed to a second polymerization vessel, and an ethylene-1-butene copolymer was polymerized under the same conditions as in Example 1. During the polymerization, ethylene, 1-butene, hydrogen, and nitrogen were continuously fed to maintain a constant gas composition. The feed ratio of 1-butene to ethylene was 0.050 kg / kg, and the gas composition (molar ratio) of hydrogen to ethylene was hydrogen / ethylene = 0.025 mol / mol. The solvent and unreacted monomers were separated from the resulting contents and dried in the same manner as in Example 1, yielding an ethylene polymer composition. The yield was 17 kg / hr.

[0111] In addition, the physical properties were measured in the same manner as in Example 1, and the pipe was molded to evaluate the performance. The results are shown in Tables 1 and 2.

[0112] Comparative Example 3 Internal volume 0.34m 3To the first polymerization vessel, n-hexane was continuously fed at 68 L / hr, the same catalyst as in Example 1 at 3.8 mmol-Ti / hr, and triethylaluminum at 50 mmol-Al / hr, and the contents of the polymerization vessel were continuously withdrawn to maintain a constant liquid level in the vessel. Ethylene homopolymer was polymerized at a polymerization temperature of 85°C, a reaction pressure of 0.6 MPaG, and an average residence time of 2.0 hours. During the polymerization, ethylene, hydrogen, and nitrogen were continuously fed to maintain a constant gas composition (gas composition (molar ratio): hydrogen / ethylene = 5.1 mol / mol). The contents extracted from the first polymerization reactor had an internal volume of 0.2 m 3 The resulting mixture was continuously fed to a second polymerization vessel, where an ethylene-1-butene copolymer was polymerized at a polymerization temperature of 72°C, a reaction pressure of 0.3 MPaG, and an average residence time of 1.0 hr. During the polymerization, ethylene, 1-butene, hydrogen, and nitrogen were continuously fed to maintain a constant gas composition. The feed ratio of 1-butene to ethylene was 0.077 kg / kg, and the gas composition (molar ratio) of hydrogen to ethylene was hydrogen / ethylene = 0.020 mol / mol. The resulting contents were separated from the solvent and unreacted monomers and dried in the same manner as in Example 1, yielding an ethylene-based polymer composition. The yield was 19 kg / hr.

[0113] In addition, the physical properties were measured in the same manner as in Example 1, and the pipe was molded to evaluate the performance. The results are shown in Tables 1 and 2.

[0114] Comparative Example 4 Internal volume 0.34m 3 To the first polymerization vessel, n-hexane was continuously fed at 68 L / hr, the same catalyst as in Example 1 at 3.2 mmol-Ti / hr, and triethylaluminum at 50 mmol-Al / hr, and the contents of the polymerization vessel were continuously withdrawn to maintain a constant liquid level in the polymerization vessel, while polymerizing ethylene homopolymer under the same conditions as in Comparative Example 3. During the polymerization, ethylene, hydrogen, and nitrogen were continuously fed to maintain a constant gas composition (gas composition (molar ratio): hydrogen / ethylene = 4.8 mol / mol). The contents extracted from the first polymerization reactor had an internal volume of 0.2 m 3The resulting mixture was continuously fed to a second polymerization vessel, where an ethylene-1-butene copolymer was polymerized under the same conditions as in Comparative Example 3, including polymerization temperature, reaction pressure, and average residence time of 1.1 hours. During the polymerization, ethylene, 1-butene, hydrogen, and nitrogen were continuously fed to maintain a constant gas composition. The feed ratio of 1-butene to ethylene was 0.077 kg / kg, and the gas composition (molar ratio) of hydrogen to ethylene was hydrogen / ethylene = 0.011 mol / mol. The resulting contents were separated from the solvent and unreacted monomers and dried in the same manner as in Example 1, yielding an ethylene polymer composition. The yield was 17 kg / hr.

[0115] In addition, the physical properties were measured in the same manner as in Example 1, and the pipe was molded to evaluate the performance. The results are shown in Tables 1 and 2.

[0116] Comparative Example 5 Internal volume 0.34m 3 To the first polymerization vessel, n-hexane was continuously fed at 68 L / hr, the same catalyst as in Example 1 at 3.1 mmol-Ti / hr, and triethylaluminum at 50 mmol-Al / hr, and the contents of the polymerization vessel were continuously withdrawn to maintain a constant liquid level in the polymerization vessel, while ethylene homopolymer was polymerized under the same conditions as in Comparative Example 3. During the polymerization, ethylene, hydrogen, and nitrogen were continuously fed to maintain a constant gas composition (gas composition (molar ratio): hydrogen / ethylene = 5.4 mol / mol). The contents extracted from the first polymerization reactor had an internal volume of 0.2 m 3 The resulting mixture was continuously fed to a second polymerization vessel, and an ethylene-1-butene copolymer was polymerized under the same conditions as in Comparative Example 3. During the polymerization, ethylene, 1-butene, hydrogen, and nitrogen were continuously fed to maintain a constant gas composition. The feed ratio of 1-butene to ethylene was 0.062 kg / kg, and the gas composition (molar ratio) of hydrogen to ethylene was hydrogen / ethylene = 0.017 mol / mol. The solvent and unreacted monomers were separated from the resulting contents and dried in the same manner as in Example 1, yielding an ethylene polymer composition. The yield was 19 kg / hr.

[0117] In addition, the physical properties were measured in the same manner as in Example 1, and the pipe was molded to evaluate the performance. The results are shown in Tables 1 and 2.

[0118] Example 4 Internal volume 60m 3 To the first polymerization vessel, 14,850 L / hr of n-hexane, 1.1 mol Ti / hr of the same catalyst as in Example 1, and 7.4 mol Al / hr of triethylaluminum were continuously fed, and the contents of the polymerization vessel were continuously withdrawn to maintain a constant liquid level in the polymerization vessel. Ethylene homopolymer was polymerized under the same conditions as in Comparative Example 3. During the polymerization, ethylene, hydrogen, and nitrogen were continuously fed to maintain a constant gas composition (gas composition (molar ratio): hydrogen / ethylene = 5.9 mol / mol). The contents extracted from the first polymerization reactor had an internal volume of 60m 3 The resulting mixture was continuously fed to a second polymerization vessel, and an ethylene-1-butene copolymer was polymerized under the same conditions as in Comparative Example 3. During the polymerization, ethylene, 1-butene, hydrogen, and nitrogen were continuously fed to maintain a constant gas composition. The feed ratio of 1-butene to ethylene was 0.018 kg / kg, and the gas composition (molar ratio) of hydrogen to ethylene was hydrogen / ethylene = 0.021 mol / mol. The solvent and unreacted monomers were separated from the resulting contents and dried in the same manner as in Example 1, yielding an ethylene polymer composition. The yield was 11,000 kg / hr.

[0119] Example 5 Internal volume 60m 3 To the first polymerization vessel, 14,850 L / hr of n-hexane, 1.1 mol Ti / hr of the same catalyst as in Example 1, and 7.4 mol Al / hr of triethylaluminum were continuously fed, and the contents of the polymerization vessel were continuously withdrawn to maintain a constant liquid level in the polymerization vessel. Ethylene homopolymer was polymerized under the same conditions as in Comparative Example 3. During the polymerization, ethylene, hydrogen, and nitrogen were continuously fed to maintain a constant gas composition (gas composition (molar ratio): hydrogen / ethylene = 5.9 mol / mol). The contents extracted from the first polymerization reactor had an internal volume of 60m 3The resulting mixture was continuously fed to a second polymerization vessel, and an ethylene-1-butene copolymer was polymerized under the same conditions as in Comparative Example 3. During the polymerization, ethylene, 1-butene, hydrogen, and nitrogen were continuously fed to maintain a constant gas composition. The feed ratio of 1-butene to ethylene was 0.010 kg / kg, and the gas composition (molar ratio) of hydrogen to ethylene was hydrogen / ethylene = 0.016 mol / mol. The solvent and unreacted monomers were separated from the resulting contents and dried in the same manner as in Example 1, yielding an ethylene polymer composition. The yield was 11,000 kg / hr.

[0120] [Reference example 1] Internal volume 60m 3 To the first polymerization vessel, n-hexane was continuously fed at 20,200 L / hr, the same catalyst as in Example 1 at 1.6 mol Ti / hr, and triethylaluminum at 10 mol Al / hr, and the contents of the polymerization vessel were continuously withdrawn to maintain a constant liquid level in the polymerization vessel. Ethylene homopolymer was polymerized under the conditions of a polymerization temperature of 87°C, a reaction pressure of 0.6 MPaG, and an average residence time of 2.0 hours. During the polymerization, ethylene, hydrogen, and nitrogen were continuously fed to maintain a constant gas composition (gas composition (molar ratio): hydrogen / ethylene = 6.4 mol / mol). The contents extracted from the first polymerization reactor had an internal volume of 60m 3 The resulting mixture was continuously fed to a second polymerization vessel, where an ethylene-1-butene copolymer was polymerized at a polymerization temperature of 84°C, a reaction pressure of 0.3 MPaG, and an average residence time of 1.0 hr. During the polymerization, ethylene, 1-butene, hydrogen, and nitrogen were continuously fed to maintain a constant gas composition. The feed ratio of 1-butene to ethylene was 0.02 kg / kg, and the gas composition (molar ratio) of hydrogen to ethylene was hydrogen / ethylene = 0.047 mol / mol. The resulting contents were separated from the solvent and unreacted monomers and dried in the same manner as in Example 1 to obtain an ethylene polymer composition. The yield was 16,000 kg / hr.

[0121] [Reference example 2] Internal volume 60m 3To the first polymerization vessel, n-hexane was continuously fed at 19,600 L / hr, the same catalyst as in Example 1 at 1.3 mol Ti / hr, and triethylaluminum at 9.8 mol Al / hr, and the contents of the polymerization vessel were continuously withdrawn to maintain a constant liquid level in the polymerization vessel, while ethylene homopolymer was polymerized under the same conditions as in Comparative Example 3. During the polymerization, ethylene, hydrogen, and nitrogen were continuously fed to maintain a constant gas composition (gas composition (molar ratio): hydrogen / ethylene = 5.2 mol / mol). The contents extracted from the first polymerization reactor had an internal volume of 60m 3 The resulting mixture was continuously fed to a second polymerization vessel, and an ethylene-1-butene copolymer was polymerized under the same conditions as in Comparative Example 3. During the polymerization, ethylene, 1-butene, hydrogen, and nitrogen were continuously fed to maintain a constant gas composition. The feed ratio of 1-butene to ethylene was 0.069 kg / kg, and the gas composition (molar ratio) of hydrogen to ethylene was hydrogen / ethylene = 0.057 mol / mol. The solvent and unreacted monomers were separated from the resulting contents and dried in the same manner as in Example 1, yielding an ethylene polymer composition. The yield was 13,200 kg / hr. Comparison of Examples and Comparative Examples It is clear that all of Examples 1 to 3 have significantly superior internal pressure creep rupture times at 80°C and σ=5.7 MPa compared to Comparative Examples 3 to 5, in which the amount of components with logM≧7 does not satisfy requirement (ii).

[0122] It can be seen that, compared to Comparative Examples 1 and 2, in which the amount of components with logM≧7 satisfies requirement (ii) but the amount of components with logM≦3 does not satisfy requirement (iii), Examples 1 to 3 all have significantly superior internal pressure creep rupture times at 20°C, σ=12.7 MPa, 80°C, σ=6.3 MPa, and 80°C, σ=6.1 MPa.

[0123] In other words, the pipes obtained in Examples 1 to 3 are excellent in internal pressure creep rupture time under a wide range of temperature and pressure conditions.

[0124] [Table 1]

[0125] [Table 2] [Industrial Applicability]

[0126] The ethylene polymer composition of the present invention, which is excellent in moldability and mechanical strength, is suitably used for pipe applications such as water pipes and gas pipes.

Claims

1. An ethylene homopolymer (A) and an ethylene-α-olefin copolymer (B) are polymerized using a Ziegler-Natta catalyst, MFR (MFR) measured at a temperature of 190°C and a load of 2.16 kg 2 and 60 to 40% by mass of the ethylene-α-olefin copolymer (B), which is a copolymer of ethylene and an α-olefin having 4 or more carbon atoms (wherein the total amount of (A) + (B) is 100% by mass), wherein the ethylene-based polymer composition satisfies the following requirements (i) to (iii): (i) Density is 940 to 960 kg / m 3 is in the range. (ii) The amount of components with log M≧7 measured by GPC is in the range of 0.35 to 0.80%. (iii) The amount of components with log M≦3 as measured by GPC is 1.85% or less.

2. 2. The method for producing an ethylene polymer composition according to claim 1, wherein the α-olefin having 4 or more carbon atoms is 1-butene or 1-hexene.

3. 2. The method for producing an ethylene polymer composition according to claim 1, wherein the ethylene / α-olefin copolymer (B) has an intrinsic viscosity [η] in the range of 7.0 to 14.0 dl / g.

4. The ethylene polymer composition has an MFR (MFR 5 2. The method for producing an ethylene polymer composition according to claim 1, wherein the melt flow rate is in the range of 0.03 to 0.3 g / 10 min.

5. 2. The method for producing an ethylene polymer composition according to claim 1, wherein the ethylene polymer composition has a molecular weight distribution (Mw / Mn) in the range of 30 to 70 as measured by GPC.

6. An ethylene homopolymer and a copolymer of ethylene and an α-olefin having 4 or more carbon atoms are polymerized using a Ziegler-Natta catalyst, The present invention provides a method for producing an ethylene polymer composition comprising the ethylene homopolymer and the copolymer of ethylene and an α-olefin having 4 or more carbon atoms, the composition satisfying the following requirements (i) to (vi): (i) Density is 940 to 960 kg / m 3 is in the range. (ii) The amount of components with log M≧7 measured by GPC is in the range of 0.35 to 0.80%. (iii) The amount of components with log M≦3 as measured by GPC is 1.85% or less. (iv) MFR (MFR) measured at a temperature of 190°C and a load of 5 kg 5 ) is in the range of 0.03 to 0.3 g / 10 min. (v) The molecular weight distribution (Mw / Mn) measured by GPC is in the range of 30 to 70. (vi) The pipe obtained satisfies the following (a) to (d) simultaneously in a hot internal pressure creep test measured in accordance with ISO 1167: (a) The time to failure at a test temperature of 20°C and a test circumferential stress of 12.7 MPa is 500 hours or more; (b) The time to failure at a test temperature of 80°C and a test circumferential stress of 6.3 MPa is 100 hours or more; (c) The time to failure at a test temperature of 80°C and a test circumferential stress of 6.1 MPa is 1,000 hours or more; (d) The time to failure at a test temperature of 80°C and a test circumferential stress of 5.7 MPa is 3,000 hours or more.

7. The method for producing an ethylene polymer composition according to claim 6, further satisfying the following requirement (vii): (vii) The chart measured by GPC shows a bimodal peak, and the ratio of the low molecular weight component to the high molecular weight component determined by peak separation is in the range of 40:60 to 60:

40.

8. The method for producing an ethylene-based polymer composition according to claim 7, wherein the low-molecular-weight component comprises an ethylene homopolymer, and the high-molecular-weight component comprises a copolymer of ethylene and an α-olefin having 4 or more carbon atoms.

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