Ethylene-based polymer composition and its use

Abstract

An ethylene-based polymer composition according to the present invention contains 100 parts by mass of an ethylene-based polymer component (A), which has a limiting viscosity [η] measured in a decalin solvent at 135°C of 1.5-10 dl / g, and a density of 930-980 kg / m3, and 1-100 parts by mass of carbon fibers (B), wherein the ethylene-based polymer component (A) contains an ultrahigh molecular weight ethylene polymer (a1) which has a a limiting viscosity [η] measured in a decalin solvent at 135°C of 10-40 dl / g.

Description

[Technical Field]

[0001] The present invention relates to an ethylene-based polymer composition and its use. [Background technology]

[0002] Polyethylene resin is widely used as a molding material because it is easy to mold, has various excellent physical properties, and is economical. For example, Patent Document 1 discloses a high-density polyethylene resin composition containing a high-density polyethylene resin and a layered silicate, and an injection-molded article of this composition. Furthermore, Patent Document 2 discloses a resin composition comprising a polyolefin resin (polyethylene resin, polypropylene resin, etc.), multi-walled carbon nanotubes, and an inorganic filler, and a molded article of this composition.

[0003] On the other hand, Patent Document 3 discloses an ethylene polymer composition containing an ethylene polymer including ultra-high molecular weight polyethylene and low- to high-molecular weight polyethylene, and carbon nanotubes, and describes that the resin composition has low surface resistivity and volume resistivity and good thermal conductivity, and that a molded article obtained from the ethylene polymer composition has good sliding properties and rigidity. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-19733 [Patent Document 2] Japanese Patent Application Laid-Open No. 2010-196012 [Patent Document 3] International Publication No. 2022 / 038941 Summary of the Invention [Problem to be solved by the invention]

[0005] However, conventional ethylene polymer compositions containing inorganic fillers or carbon nanotubes do not necessarily have sufficient moldability, and there is room for further improvement from the viewpoint of obtaining molded articles excellent in rigidity, electrical conductivity, abrasion resistance, and heat resistance.

[0006] Therefore, an object of the present invention is to provide an ethylene polymer composition which has excellent moldability and from which molded articles having excellent rigidity, electrical conductivity, abrasion resistance and heat resistance can be obtained, and a molded article thereof. [Means for solving the problem]

[0007] An example of the present invention is given below. [1] The intrinsic viscosity [η] measured in decalin solvent at 135°C is 1.5 to 10 dl / g, and the density is 930 to 980 kg / m 3 and 1 to 100 parts by mass of carbon fiber (B), The ethylene polymer component (A) is an ethylene polymer composition containing an ultra-high molecular weight ethylene polymer (a1) having an intrinsic viscosity [η] of 10 to 40 dl / g as measured in decalin solvent at 135°C.

[0008] [2] The ethylene polymer composition according to item [1], wherein the ethylene polymer component (A) contains a low-molecular-weight to high-molecular-weight ethylene polymer (a2) having an intrinsic viscosity [η] of 0.1 to 9 dl / g measured in decalin solvent at 135°C.

[0009] [3] The ethylene polymer component (A) contains 10 to 90% by mass of an ethylene polymer component (AI) and 90 to 10% by mass of an ethylene polymer component (AII) (the total amount of the components (AI) and (AII) being 100% by mass), the ethylene polymer component (AI) is a multistage polymer comprising more than 35% by mass and not more than 90% by mass of the ultra-high molecular weight ethylene polymer (a1) and 10% by mass or more and less than 65% by mass of the low- to high-molecular weight ethylene polymer (a2) (the total amount of polymer (a1) and polymer (a2) being 100% by mass), Item [2]. The ethylene polymer composition according to item [2], wherein the ethylene polymer component (AII) contains an ethylene polymer (a3) ​​having an intrinsic viscosity [η] of 0.1 to 2.9 dl / g as measured in decalin solvent at 135°C.

[0010] [4] The ethylene polymer composition according to item [3], wherein the ethylene polymer component (AI) is obtained by a multistage polymerization method including a step of producing the ultra-high molecular weight ethylene polymer (a1) and a step of producing the low-molecular weight to high-molecular weight ethylene polymer (a2).

[0011] [5] The ethylene polymer composition according to any one of items [1] to [4], wherein the carbon fiber (B) is a surface-treated carbon fiber. [6] The ethylene polymer composition according to item [5], wherein the surface treatment of the carbon fiber (B) is a sizing treatment using an olefin polymer, a urethane polymer, a nylon polymer, or an epoxy polymer.

[0012] [7] The ethylene polymer composition according to any one of items [1] to [6], wherein the carbon fibers (B) extracted from the ethylene polymer composition have an average fiber length of 100 μm or more and 400 μm or less. [8] The ethylene polymer composition according to any one of items [1] to [7], wherein the carbon fibers (B) extracted from the ethylene polymer composition contain carbon fibers having a fiber length of 100 μm or more and 300 μm or less at a rate of 30% or more.

[0013] [9] The ethylene polymer composition according to any one of items [1] to [8], which contains a modified olefin polymer (C).

[10] The ethylene polymer composition according to any one of items [1] to [9], wherein the content of the carbon fiber (B) is 20 to 60 parts by mass per 100 parts by mass of the ethylene polymer component (A).

[0014]

[11] A molded article comprising the ethylene polymer composition according to any one of items [1] to

[10] .

[12] The molded body according to item

[11] , wherein the proportion of carbon fibers having an acicular ratio of 1.5 or more among the carbon fibers (B) contained in the molded body is 30% or more.

[0015]

[13] The molded article according to item

[11] or

[12] , wherein the shrinkage rate of the molded article in both the length direction and the width direction is 2.0% or less.

[14] The molded article according to any one of items

[11] to

[13] , wherein the molded article has a flexural modulus of elasticity of 5000 MPa or more.

[0016]

[15] The molded article according to any one of items

[11] to

[14] , wherein the number of repetitions when the displacement reaches 8 mm in a vibration fatigue test (35 MPa) of the molded article is 1500 or more.

[16] The molded article according to any one of items

[11] to

[15] , which is an injection molded article.

[17] The molded article according to any one of items

[11] to

[16] , which is a coating material or a sliding material. [Effects of the Invention]

[0017] According to the present invention, it is possible to provide an ethylene polymer composition which has excellent moldability and from which a molded article having excellent rigidity, electrical conductivity, abrasion resistance and heat resistance can be obtained, and a molded article thereof. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 1 is a schematic diagram illustrating a location from which an observation sample for evaluating orientation in the examples is taken from an ASTM D671 Type A test piece (molded product) and an observation surface of the observation sample. DETAILED DESCRIPTION OF THE INVENTION

[0019] The present invention will be described in detail below. In this specification, a numerical range expressed using "to" means a range that includes the numerical values ​​before and after "to" as the lower and upper limits.

[0020] The ethylene polymer composition according to the present invention (hereinafter also simply referred to as "the composition of the present invention") has an intrinsic viscosity [η] of 1.5 to 10 dl / g and a density of 930 to 980 kg / m 3 and 1 to 100 parts by mass of carbon fiber (B), wherein the ethylene polymer component (A) contains an ultra-high molecular weight ethylene polymer (a1) having an intrinsic viscosity [η] of 10 to 40 dl / g.

[0021] In the present invention, the intrinsic viscosity [η] is the intrinsic viscosity [η] measured in decalin solvent at 135° C. unless otherwise specified.

[0022] <Ethylene-based polymer component (A)> The ethylene polymer component (A) is a homopolymer of ethylene or a copolymer of ethylene and an α-olefin, and is a polymer mainly composed of ethylene, generally known as high-pressure low-density polyethylene (HP-LDPE), linear low-density polyethylene (LLDPE), medium-density polyethylene (MDPE), high-density polyethylene (HDPE), ultra-high molecular weight ethylene polymer, or the like.

[0023] When the ethylene polymer component (A) is a copolymer, it may be a random copolymer or a block copolymer.

[0024] The α-olefin copolymerized with ethylene is preferably an α-olefin having 3 to 20 carbon atoms, and specific examples thereof include propylene, 1-butene, 4-methyl-1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, 1-undecene, 1-dodecene, 1-tridecene, 1-tetradecene, 1-pentadecene, 1-hexadecene, 1-heptadecene, 1-nonadecene, 1-eicosene, 9-methyl-1-decene, 11-methyl-1-dodecene, and 12-ethyl-1-tetradecene. These α-olefins may be used singly or in combination of two or more.

[0025] The ethylene polymer component (A) may be a single polymer or a composition (mixture) of two or more ethylene polymers.

[0026] The ethylene polymer component (A) has an intrinsic viscosity [η] of 1.5 to 10 dL / g, preferably 2.0 to 8.0 dL / g, and more preferably 2.5 to 7.0 dL / g. When the ethylene polymer component (A) has an intrinsic viscosity [η] within the above range, the composition of the present invention can provide a molded article having an excellent balance of properties such as abrasion resistance, self-lubrication, impact strength, chemical resistance, appearance, and moldability.

[0027] The density of the ethylene polymer component (A) (measured in accordance with ASTM D1505) is 930 to 980 kg / m 3 , preferably 940 to 970 kg / m 3 When the ethylene polymer component (A) has a density within the above range, a molded article having excellent abrasion resistance and flexibility can be obtained.

[0028] The ethylene polymer component (A) contains an ultra-high molecular weight ethylene polymer (a1) (hereinafter also referred to as "polymer (a1)") having an intrinsic viscosity [η] of 10 to 40 dL / g. Since the ethylene polymer component (A) contains the polymer (a1), the composition of the present invention can provide a molded article having excellent abrasion resistance, self-lubrication, impact strength, chemical resistance, etc.

[0029] The intrinsic viscosity [η] of the polymer (a1) is preferably 15 to 35 dl / g, more preferably 20 to 35 dl / g.

[0030] The ethylene polymer component (A) may contain a low-molecular-weight to high-molecular-weight ethylene polymer (a2) (hereinafter also referred to as "polymer (a2)") having an intrinsic viscosity [η] of 0.1 to 9 dL / g. The polymer (a2) may be a wax.

[0031] The intrinsic viscosity [η] of the polymer (a2) is preferably 0.1 to 5 dl / g, more preferably 0.5 to 3.0 dl / g, and even more preferably 1.0 to 2.5 dl / g.

[0032] The composition of the present invention preferably contains, as the ethylene polymer component (A), the ultra-high molecular weight ethylene polymer (a1) being more than 35% by mass and not more than 90% by mass; 10 to 90% by mass of an ethylene polymer component (AI) which is a multistage polymer containing 10% by mass or more but less than 65% by mass of the low-molecular-weight to high-molecular-weight ethylene polymer (a2) (the total amount of polymer (a1) and polymer (a2) being 100% by mass), and It contains 90 to 10 mass % (the total amount of components (AI) and (AII) is taken as 100 mass %) of an ethylene polymer component (AII) having an intrinsic viscosity [η] of 0.1 to 2.9 dl / g.

[0033] The ethylene polymer component (AI) can be obtained preferably by a multistage polymerization method including a step of producing the ultra-high molecular weight ethylene polymer (a1) and a step of producing the low-molecular weight to high-molecular weight ethylene polymer (a2).

[0034] In the multi-stage polymerization method, the polymer (a1) is usually produced in the first stage, and then the polymer (a2) is produced in the second stage.

[0035] The proportion of the ethylene polymer component (AI) is preferably 15 to 90 mass %, more preferably 20 to 80 mass %. % The proportion of the ethylene polymer component (AII) is preferably 85 to 10 mass%, more preferably 80 to 20 mass%, and even more preferably 73.3 to 51 mass% (the total amount of components (AI) and (AII) being 100 mass%).

[0036] Ethylene polymer component (AI) The ultra-high molecular weight ethylene polymer (a1) constituting the ethylene polymer component (AI) is usually obtained in the first stage polymerization in a multi-stage polymerization method.

[0037] The low-molecular-weight to high-molecular-weight ethylene polymer (a2) constituting the ethylene polymer component (AI) is usually obtained in a second-stage polymerization after polymerization of the polymer (a1) in a multistage polymerization method.

[0038] The ethylene polymer component (AI) can be produced by polymerizing ethylene and, if desired, an α-olefin in multiple stages in the presence of a catalyst, and the multiple stage polymerization can be carried out by a method similar to the polymerization method described in JP-A-2-289636.

[0039] Furthermore, by polymerizing the polymer (a1) and then post-polymerizing the polymer (a2), the ethylene polymer component (AI) has excellent compatibility with the ethylene polymer component (AII). As a result, the ultra-high molecular weight ethylene polymer (a1) is uniformly dispersed in the composition of the present invention, and the ultra-high molecular weight ethylene polymer (a1) is bonded to the ethylene polymer component (AII). That is, the interfacial strength between the polymer (a1) and the ethylene polymer component (AII) is increased. Therefore, by containing the components (AI) and (AII), the composition of the present invention has an excellent balance of properties such as wear resistance, self-lubrication, impact strength, chemical resistance, appearance, and moldability, and is particularly excellent in the balance of wear resistance, appearance, and moldability.

[0040] The ethylene polymer component (AI) contains the ultra-high molecular weight ethylene polymer (a1) in an amount of preferably more than 35% by mass and not more than 90% by mass, more preferably more than 40% by mass and not more than 80% by mass, and even more preferably 41 to 75% by mass, and the low-molecular weight to high-molecular weight ethylene polymer (a2) in an amount of preferably 10% by mass or more and less than 65% by mass, more preferably 20% by mass or more and less than 60% by mass, and even more preferably 25 to 59% by mass.

[0041] By setting the ratio of polymer (a1) to polymer (a2) within the above range, the compatibility between component (AI) and component (AII) is improved, and the composition of the present invention is excellent in particular in abrasion resistance, appearance, and moldability.

[0042] The ethylene polymer component (AI) substantially comprises only an ultra-high molecular weight ethylene polymer (polymer (a1)) and a low- to high-molecular weight ethylene polymer (polymer (a2)).

[0043] Component (AI) may contain additives that are typically added to polyolefins (for example, stabilizers such as heat stabilizers and weather stabilizers, crosslinking agents, crosslinking aids, antistatic agents, slip agents, antiblocking agents, antifogging agents, lubricants, dyes, mineral oil-based softeners, petroleum resins, waxes, etc.), and the composition of the present invention may contain the additives added to component (AI) as long as the effects of the present invention are not impaired.

[0044] The density of the ethylene polymer component (AI) (measured in accordance with ASTM D1505) is usually 930 to 980 kg / m 3 , preferably 940 to 970 kg / m 3 is. The intrinsic viscosity [η] of the ethylene polymer component (AI) is usually 3.0 to 10.0 dl / g, preferably 3.0 to 8.0 dl / g, and more preferably 3.0 to 7.0 dl / g.

[0045] When the ethylene polymer component (AI) has the density as described above, the coefficient of dynamic friction of the molded article is reduced, and therefore, a molded article having excellent self-lubricating properties can be obtained. Furthermore, when the ethylene polymer component (AI) has an intrinsic viscosity [η] within the above range, the ethylene polymer component (AI) and the ethylene polymer component (AII) are well dispersed.

[0046] That is, the polymer (a2) contained in the ethylene polymer component (AI) and the ethylene polymer component (AII) melt-blended in an extruder or the like are mutually finely dispersed to form a uniform dispersion state, and therefore, by using the ethylene polymer component (AI), a molded article excellent in abrasion resistance, self-lubrication, impact strength, chemical resistance, appearance, moldability, etc. can be obtained from the composition of the present invention.

[0047] Ethylene-based polymer component (AII) The ethylene polymer component (AII) preferably contains an ethylene polymer (a3) ​​having an intrinsic viscosity [η] of 0.1 to 2.9 dl / g.

[0048] Examples of the ethylene polymer (a3) ​​include high-pressure polyethylene (HP-LDPE), linear low-density polyethylene (LLDPE), medium-density polyethylene (MDPE), high-density polyethylene (HDPE), ethylene-α-olefin copolymers, ethylene-vinyl alcohol copolymers, ethylene-vinyl acetate copolymers, saponified ethylene-vinyl acetate copolymers, ethylene-(meth)acrylic acid copolymers, and ethylene-α-olefin-diene (triene, polyene) terpolymers. Examples of α-olefins include those having 3 to 20 carbon atoms, such as propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 1-decene, 1-dodecene, 4-methyl-1-pentene, and 3-methyl-1-pentene. Examples of dienes (trienes, polyenes) include conjugated or non-conjugated dienes, trienes, and polyenes, such as 5-ethylidene-2-norbornene and vinylnorbornene.

[0049] The ethylene polymer component (AII) may be a single ethylene polymer (a3), a composition of two or more ethylene polymers (a3), or a composition of the ethylene polymer (a3) ​​and a polyolefin (such as polypropylene or polybutene). The ethylene polymer component (AII) may also be a wax.

[0050] Of the above-mentioned ethylene polymers (a3), high density polyethylene (HDPE) and low density polyethylene (LDPE) are preferred, with high density polyethylene (HDPE) being more preferred.

[0051] The density of the ethylene polymer (a3) ​​(measured in accordance with ASTM D1505) is usually 820 to 980 kg / m 3 , preferably 930 to 980 kg / m 3 , more preferably 950 to 980 kg / m 3 is.

[0052] The intrinsic viscosity [η] of the ethylene polymer (a3) ​​is usually 0.1 to 2.9 dl / g, preferably 0.3 to 2.8 dl / g, more preferably 0.5 to 2.5 dl / g, and even more preferably 1.0 to 2.5 dl / g.

[0053] Since the ethylene polymer component (AII) contains the ethylene polymer (a3), it disperses well when mixed with the ethylene polymer component (AI). That is, during melt blending in an extruder or the like, the ethylene polymer component (AII) and the low-molecular-weight to high-molecular-weight ethylene polymer (a2) contained in the ethylene polymer component (AI) are finely dispersed with each other, resulting in a uniform dispersion state. Therefore, by using the ethylene polymer component (AI) and the ethylene polymer component (AII) as the ethylene polymer component (A), molded articles excellent in wear resistance, self-lubrication, impact strength, chemical resistance, appearance, flexibility, moldability, etc. can be obtained.

[0054] Component (AII) may contain additives that are typically added to polyolefins (e.g., stabilizers such as heat stabilizers and weather stabilizers, crosslinking agents, crosslinking aids, antistatic agents, slip agents, antiblocking agents, antifogging agents, lubricants, dyes, mineral oil-based softeners, petroleum resins, waxes, etc.), and the composition of the present invention may contain the additives added to component (AII) as long as the effects of the present invention are not impaired.

[0055] <Carbon fiber (B)> The carbon fiber (B) is not particularly limited, and various known carbon fibers can be used. For example, polyacrylic B Examples of carbon fibers include nitrile-based, rayon-based, pitch-based, polyvinyl alcohol-based, regenerated cellulose-based, and pitch-based carbon fibers produced from mesophase pitch. These may be used alone or in combination of two or more.

[0056] The carbon fiber (B) may be a general-purpose fiber or a high-strength fiber, and may be a long fiber, a short fiber, a chopped fiber, or a recycled fiber.

[0057] The carbon fiber (B) is preferably a surface-treated carbon fiber. The surface treatment of the carbon fiber may be carried out by a commonly used known method, such as electrolytic surface treatment of the carbon fiber with an acid or alkaline aqueous solution to impart functional groups to the carbon fiber surface, or treatment using a sizing agent. Among these, sizing treatment using an olefin polymer, an epoxy polymer, a nylon polymer, or a urethane polymer is preferred.

[0058] The average length of the carbon fibers (B), i.e., the average fiber length, is preferably 0.1 mm or more and 15.0 mm or less, more preferably 0.3 mm or more and 13.0 mm or less, and even more preferably 0.5 mm or more and 13.0 mm or less. When the average fiber length is equal to or more than the lower limit, the reinforcing effect of the carbon fibers on mechanical properties tends to be sufficiently exhibited. When the average fiber length is equal to or less than the upper limit, the carbon fibers are dispersed in the ethylene polymer composition, and the appearance of the molded article tends to be good.

[0059] The average fiber length of the carbon fibers (B) extracted from the composition of the present invention is preferably 100 μm or less. m The average fiber length of the carbon fibers (B) extracted from the composition of the present invention is preferably in the range of 120 μm to 380 μm, and more preferably in the range of 150 μm to 360 μm. When the average fiber length of the carbon fibers (B) extracted from the composition of the present invention is in the above range, the processability during the production of molded articles is improved. On the other hand, when the average fiber length is outside the above range, it becomes difficult to uniformly mix the carbon fibers and the resin during molding, which may cause a deterioration in the physical properties of the composition and the molded article.

[0060] Furthermore, the proportion of carbon fibers having a fiber length of 100 μm or more and 300 μm or less among the carbon fibers (B) extracted from the composition of the present invention is preferably 30% or more, more preferably 35 to 99%, and even more preferably 40 to 98%. By ensuring that the proportion of carbon fibers having a fiber length of 100 μm or more and 300 μm or less is within the above range, it is possible to increase the mechanical strength and obtain a molded product having excellent abrasion resistance. The fiber length and average fiber length of the carbon fibers (B) extracted from the composition of the present invention can be determined, for example, by the method described in the examples below.

[0061] The average diameter of the carbon fibers (B) is preferably 0.5 μm or more and 30 μm or less, more preferably 1 μm or more and 21 μm or less, and even more preferably 1 μm or more and 19 μm or less. When the average diameter of the carbon fibers is above the lower limit, the carbon fibers are less likely to break during molding, and the impact strength of the resulting molded article tends to be high. When the average diameter of the carbon fibers is below the upper limit, the appearance of the molded article tends to be good, and the aspect ratio of the carbon fibers does not decrease, and a sufficient reinforcing effect tends to be obtained in the mechanical properties such as rigidity and heat resistance of the molded article.

[0062] In the composition of the present invention, the content of the carbon fiber (B) is 1 to 100 parts by mass, preferably 4 to 70 parts by mass, more preferably 7 to 65 parts by mass, even more preferably 10 to 60 parts by mass, and particularly preferably 20 to 60 parts by mass, relative to 100 parts by mass of the content of the ethylene polymer component (A). When the content of the carbon fiber (B) is within the above range, the composition of the present invention has excellent moldability, and can also provide a molded article having excellent rigidity, electrical conductivity, abrasion resistance, and heat resistance.

[0063] Commercially available carbon fibers (B) include, for example, Tenax manufactured by Teijin Ltd. (HT P802 (polyolefin-based polymer sizing), HT C605 (nylon-based polymer sizing), HT C503 (urethane-based polymer sizing)), Toray Industries, Inc.'s Torayca Cut Fiber T008-006 (epoxy-based polymer sizing), and Japan Polymer Sangyo Co., Ltd.'s EX-1LC (epoxy-based polymer sizing).

[0064] <Modified olefin polymer (C)> The composition of the present invention may contain a modified olefin polymer (C). The modified olefin polymer (C) is used, for example, as a compatibilizer for improving the compatibility between the ethylene polymer component (A) and the carbon fiber (B).

[0065] The modified olefin polymer (C) is not particularly limited, and examples thereof include acid-modified products (e.g., maleic anhydride-modified products), air-oxidized products, and styrene-modified products of homopolymers or copolymers of ethylene and α-olefins having 3 to 12 carbon atoms. Among these, preferred are modified products of polymers selected from the group consisting of ethylene polymers (ethylene homopolymers and copolymers of ethylene and at least one α-olefin selected from α-olefins having 3 to 12 carbon atoms) and propylene polymers (propylene homopolymers and copolymers of propylene and at least one α-olefin selected from α-olefins having 4 to 12 carbon atoms).

[0066] Examples of the α-olefin (α-olefin having 3 to 12 carbon atoms or α-olefin having 4 to 12 carbon atoms) include propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, and 1-octene.

[0067] The modified olefin polymer (C) is preferably a modified ethylene polymer. The modified olefin polymer (C) is more preferably a modified ethylene polymer (c11) in which the following ethylene polymer (c1) is graft-modified with an unsaturated carboxylic acid or a derivative thereof.

[0068] The ethylene polymer (c1) has a density of 930 to 975 kg / m 3 and the melt flow rate (MFR) measured in accordance with ASTM D1238 at 190°C under a load of 2.16 kg is preferably 0.1 to 10 g / 10 min, or the melt flow rate (MFR) measured in accordance with ASTM D1238 at 190°C under a load of 10 kg is preferably 0.1 to 20 g / 10 min.

[0069] The density of the ethylene polymer (c1) is preferably 940 to 970 kg / m 3 When the density is within the above range, the ethylene polymer component (A) and the carbon fiber (B) have high compatibility.

[0070] The melt flow rate of the ethylene polymer (c1) (according to ASTM D1238, 190°C, 2.16 kg load) is preferably 0.2 to 8 g / 10 min, more preferably 0.5 to 6 g / 10 min, and even more preferably 0.5 to 3 g / 10 min. The melt flow rate of the ethylene polymer (c1) (according to ASTM D1238, 190°C, 10 kg load) is preferably 0.1 to 15 g / 10 min, more preferably 0.1 to 1 0g / 10 min, and more preferably 0.1 to 8 g / 10 min. When the melt flow rate is within the above range, the compatibility between the ethylene polymer component (A) and the carbon fiber (B) is high.

[0071] The graft amount of the unsaturated carboxylic acid or its derivative in the modified ethylene polymer (c11) is usually 0.01 to 10 mass%, preferably 0.02 to 10 mass%. When the graft amount is within this range, the compatibility between the ethylene polymer component (A) and the carbon fiber (B) is high.

[0072] Examples of the unsaturated carboxylic acid or its derivative include unsaturated carboxylic acids such as (meth)acrylic acid, maleic acid, fumaric acid, tetrahydrophthalic acid, itaconic acid, citraconic acid, crotonic acid, isocrotonic acid, and nadic acid (endo-cis-bicyclo[2.2.1]hept-5-ene-dicarboxylic acid), and derivatives thereof, such as acid halides, amide imides, anhydrides, and esters. Specific examples of the derivatives include maleic chloride. D Examples of suitable esters include esters and half esters of unsaturated dicarboxylic acids and their acid anhydrides, such as maleic anhydride, maleimide, maleic anhydride, citraconic anhydride, monomethyl maleate, dimethyl maleate, glycidyl maleate, methyl (meth)acrylate, ethyl (meth)acrylate, glycidyl (meth)acrylate, monoethyl maleate, diethyl maleate, monomethyl fumarate, dimethyl fumarate, monomethyl itaconic acid, and diethyl itaconic acid. Among these, unsaturated dicarboxylic acids and their acid anhydrides are preferred, and maleic acid, nadic acid, and their acid anhydrides are more preferred.

[0073] The modified ethylene polymer (c11) can be produced by various known methods. For example, an ethylene polymer is dissolved in an organic solvent, and then an unsaturated carboxylic acid or a derivative thereof, and optionally a radical initiator such as an organic peroxide, are added to the resulting solution, and the reaction is carried out usually at a temperature of 60 to 350°C, preferably 80 to 190°C, for 0.5 to 15 hours, preferably 1 to 10 hours. Alternatively, an extruder or the like is used to add an ethylene polymer, an unsaturated carboxylic acid or a derivative thereof, and optionally a radical initiator such as an organic peroxide, without a solvent, and the reaction is carried out usually at a temperature above the melting point of the ethylene polymer, preferably 160 to 350°C, for 0.5 to 10 minutes.

[0074] The ethylene polymer before modification can be produced by a known method, for example, a high-pressure method or a low-pressure method using a Ziegler-type Ti-based catalyst, a Co-based catalyst, a metallocene-based catalyst, or the like.

[0075] The ethylene polymer (c1) may contain one kind of ethylene polymer alone, or may contain two or more kinds of ethylene polymers. When the ethylene polymer (c1) contains two or more kinds of ethylene polymers, each of the two or more ethylene polymers satisfies the requirements for density and melt flow rate of the ethylene polymer (c1) described above.

[0076] When the composition of the present invention contains the modified olefin polymer (C), the content of the modified olefin polymer (C) in the composition of the present invention is preferably 0.1 to 10 parts by mass, more preferably 0.3 to 8 parts by mass, and even more preferably 0.5 to 7 parts by mass, relative to 100 parts by mass of the ethylene polymer component (A). When the content of the modified olefin polymer (C) is within the above range, the ethylene polymer component (A) and the carbon fiber (B) can be well compatibilized.

[0077] <Optional ingredients> In addition to the above-mentioned ethylene polymer component (A), carbon fiber (B), and modified olefin polymer (C), the ethylene polymer composition of the present invention may contain, as necessary, various additives typically used in polyolefins, such as inorganic fillers other than carbon fiber (B), heat stabilizers, weather stabilizers, ultraviolet absorbers, light stabilizers, waxes, lubricants, slip agents, nucleating agents, antiblocking agents, antistatic agents, antifogging agents, dyes, dispersants, flame retardants, flame retardant aids, plasticizers, and compatibilizers, or impact modifiers such as elastomers, and polymers such as polyamides, within ranges that do not impair the effects of the present invention.

[0078] When the ethylene polymer composition of the present invention contains the additive or polymer, the amount thereof is not particularly limited, but is, for example, in the range of 0.01 to 30% by mass.

[0079] The additive is preferably a wax, and examples of the wax include polyethylene waxes (excluding those corresponding to the ethylene polymer component (AII)) and polypropylene waxes.

[0080] It is believed that when the ethylene polymer composition of the present invention contains a wax, aggregation of the carbon fibers (B) in the ethylene polymer component (A) is suppressed, making kneading easier and facilitating dispersion of the carbon fibers (B) in the ethylene polymer component (A).

[0081] When the ethylene polymer composition of the present invention contains a wax, the amount thereof is preferably in the range of 0.01 to 10% by mass based on the amount of the entire composition.

[0082] The MFR of the ethylene polymer composition of the present invention, measured in accordance with JIS K 7210-1:2014 at 190°C under a load of 10 kg, is preferably 0.01 to 20 g / 10 min, more preferably 0.01 to 10 g / 10 min.

[0083] <Method of producing ethylene polymer composition> The ethylene polymer composition of the present invention can be obtained by mixing the ethylene polymer component (A), the carbon fiber (B), optionally the modified olefin polymer (C), and optionally the optional components by a conventionally known method, for example, by dry-blending the components, melt-kneading them in a single-screw or twin-screw extruder, extruding them into strands, and granulating them into pellets.

[0084] The carbon fibers (B) may be used in the form of a masterbatch by being mixed in advance with a polymer component such as the ethylene-based polymer component (A).

[0085] <Molded body> The molded article of the present invention contains the ethylene polymer composition. Specific examples of the method for producing the molded article (molding method) include conventionally known polyolefin molding methods, such as extrusion molding, injection molding, film molding, inflation molding, blow molding, extrusion blow molding, injection blow molding, press molding, vacuum molding, powder slush molding, calendar molding, and foam molding. The ethylene polymer composition is preferably processed by injection molding to obtain a molded article containing the ethylene polymer composition.

[0086] The molded article may be a molded article formed from the ethylene polymer composition, or may be a molded article having a portion, such as a surface layer, formed from the ethylene polymer composition.

[0087] Of the carbon fibers (B) contained in the molded article of the present invention, the proportion of carbon fibers having an acicular ratio of 1.5 or more is preferably 30% or more, more preferably 30 to 70%, even more preferably 31 to 65%, and particularly preferably 32 to 60%. When the proportion of carbon fibers having an acicular ratio of 1.5 or more is within the above range, the mechanical strength of the molded article can be increased, and a molded article having excellent rigidity and fatigue resistance can be obtained. The proportion of carbon fibers having an acicular ratio of 1.5 or more can be determined by the method described in the Examples below.

[0088] The shrinkage percentage of the molded article of the present invention in both the longitudinal and transverse directions is preferably 2.0% or less, more preferably 1.5% or less, and particularly preferably 0.05 to 1.0%. The shrinkage percentage can be determined by the method described in the examples below.

[0089] The flexural modulus of the molded article of the present invention is preferably 5000 MPa or more, more preferably 6000 to 20000 MPa, and even more preferably 7000 to 15000 MPa. The flexural modulus can be determined by the method described in the examples below.

[0090] The number of repetitions at which the displacement of the molded article of the present invention reaches 8 mm in a vibration fatigue test (35 MPa) is preferably 1,500 or more, more preferably 2,000 or more, and even more preferably 5,000 or more. The upper limit of the number of repetitions is not particularly limited, as the higher the number the better, but is preferably 10 million, more preferably 1 million, and even more preferably 500,000. The number of repetitions can be determined by the method described in the Examples below.

[0091] Molded articles are used in a wide range of applications, including household goods for daily necessities and recreational purposes, general industrial applications, and industrial goods. Specific examples of molded articles include home appliance material parts, communication device parts, electrical parts, electronic parts, automobile parts, other vehicle parts, ship and aircraft materials, machine mechanism parts, building materials, civil engineering materials, agricultural materials, power tool parts, food containers, films, sheets, and fibers.

[0092] The molded article of the present invention can be widely used for conventionally known polyethylene applications, but since it has an excellent balance of properties such as abrasion resistance, rigidity, self-lubrication, impact strength, and thin-wall moldability, it can be used for applications requiring these properties, such as metal coating materials (laminates) for steel pipes, electric wires, and automobile sliding door rails; various rubber coating materials (laminates) for pressure-resistant rubber hoses, automobile door gaskets, clean room door gaskets, automobile glass run channels, and automobile weather strips; and sliding materials such as linings for hoppers, chutes, gears, bearings, rollers, tape reels, various guide rails and elevator rail guides, and various protective liner materials.

[0093] The molded article of the present invention also has excellent electrical conductivity, making it possible to suppress the electrostatic charge of various machine parts and sliding members, and is therefore suitable for use in applications requiring electrical conductivity and anti-static properties. [Example]

[0094] The present invention will be explained in more detail below based on examples, but the present invention is not limited to these examples in any way.

[0095] [Measurement method] The methods for measuring the physical properties of the polymers used in the examples, the compositions obtained in the examples, and the molded articles produced using the compositions are as follows.

[0096] [Intrinsic viscosity [η]] Measured in decalin at 135°C.

[0097] 〔density〕 The density of the ethylene polymer component (A) was measured by the density gradient method in accordance with ASTM D1505. The density of the compositions obtained in the examples and comparative examples was measured in water at 23°C by the liquid weighing method in accordance with JIS Z8807:2012.

[0098] [Fiber analysis of carbon fiber (B) extracted from ethylene polymer composition] <Pretreatment> The pellet-shaped composition obtained in the example or comparative example was heated in an electric furnace at 500 °C for 30 minutes in an air atmosphere.

[0099] <Image analysis of carbon fiber (B)> A part of the ash obtained in the pretreatment was taken out on a slide glass, and after spreading with oil and covering with a cover glass, the prepared sample was used as an observation sample. Using the "Stereo Microscope SZX16" manufactured by Olympus Corporation, the sample was observed with a reflected bright-field image at a lens magnification of 4 times. A visual field containing fibers of 100 μm or more was selected from the observation visual field, and after acquiring an image, analysis was performed using image analysis software ("Win ROOF 2018" manufactured by MITANI Corporation) to determine the fiber length and the number of carbon fibers (B).

[0100] <Average fiber length of carbon fiber (B)> Based on the results obtained by the above image analysis, the average fiber length of the carbon fibers contained in the composition was calculated. <Ratio of carbon fiber (B) with fiber length of 100 to 300 μm> Based on the results obtained by the above image analysis, the ratio of fibers with a fiber length of 100 to 300 μm among all the analyzed fibers was calculated.

[0101] 〔Orientation〕 <Production of ASTM D671 Type A test piece> The composition obtained in the example or comparative example was put into the hopper part of the "EC-75SXIII molding machine" manufactured by Shibaura Machine Co., Ltd., melted at 230 °C, and injection molded into a mold to produce a plate-shaped ASTM D671 Type A test piece (molded body) having the outer shape shown in Fig. 1. The temperature of the mold during injection molding was 30 to 50 °C, the injection pressure was 90 to 110 MPa, and the holding pressure was 55 to 65 MPa.

[0102] <Production of observation sample> The ASTM D671 Type A test piece (molded body) shown in the schematic diagram in Figure 1 was first cut out in the same direction as the flow direction during injection molding (injection molding direction), i.e., in the direction of line AA in Figure 1, and the sample collection area was cut out. Next, the sample collection area was encapsulated in a resin. buried After that, the cut surface in the AA direction was polished, and further cut to the desired thickness using a microtome. Finally, carbon deposition was performed to prepare a sample for observation.

[0103] <Observation and analysis> The prepared observation sample was observed using a Hitachi High-Technologies Corporation "Scanning Electron Microscope S-3700N" at an accelerating voltage of 10 kV and a backscattered electron image at 150x magnification. The observation direction of the observation sample was set so that the polished surface of the section cut out from the molded body was the front, as shown in Figure 1, and the image was taken so that the observation surface seen from this observation direction was parallel to the long side of the image screen. The center of the image was set at a depth of 0.7 to 0.8 mm from the surface (top surface) of the molded body.

[0104] After acquiring the images, they were analyzed using image analysis software (MITANI Corporation's "Win ROOF 2018"). Carbon fibers (CFs) were extracted from the images as binary representations, and the acicular ratios of all extracted CFs were calculated and averaged. The acicular ratio was calculated from the absolute maximum length of the observed elliptical CFs and the ratio of the absolute maximum length to the perpendicular diagonal width (absolute maximum length / diagonal width).

[0105] [Conductivity (surface resistivity, volume resistivity)] <Preparation of a test piece measuring 120 mm long x 130 mm wide x 3 mm thick> The compositions obtained in the examples or comparative examples were placed in the hopper of an EC-75SXIII molding machine manufactured by Shibaura Machine Co., Ltd., melted at 230°C, and injection molded into a mold to prepare test pieces measuring 120 mm in length, 130 mm in width, and 3 mm in thickness. The mold temperature was 50 to 70°C, the injection pressure was 90 to 110 MPa, and the dwell pressure was 40 to 70 MPa.

[0106] <Measurement of surface resistivity and volume resistivity> Using a test piece measuring 120 mm long x 130 mm wide x 3 mm thick, the surface resistivity and volume resistivity were measured using an ADC "Digital Ultra-High Resistance / Fine Particle Ammeter 8340A" by the double ring method under the conditions of 23°C, humidity: 50%, applied voltage: 500 V, and application time: 60 seconds.

[0107] The surface resistivity in the above measurement was 1.0 × 10 7 The following standards were measured in accordance with JIS K7194:1994 using a "Loresta-GX-MCP-T700 low resistance resistivity meter" manufactured by Nitto Seiko Analytech Co., Ltd. under the following conditions: applied current: 1 mA, application time: 10 seconds, temperature: 23°C, humidity: 50%.

[0108] [Heat resistance (heat distortion temperature HDT)] The heat distortion temperature was determined in accordance with ISO-75-1, 2, using a test piece shaped as specified in JIS K7162 1A. The heat distortion temperature was measured at bending stresses of 0.45 MPa (HDT 0.45 MPa) and 1.80 MPa (HDT 1.80 MPa).

[0109] [Moldability (mold shrinkage)] Using the same method as described above, test pieces measuring 120 mm long, 130 mm wide, and 3 mm thick were prepared by injection molding. The dimensional change in the test piece size (length and width) after 3 days relative to the mold size (length and width) was calculated to evaluate moldability. Specifically, the injection-molded molded product (test piece) was removed from the mold and allowed to stand at room temperature for 3 days. The differences between the lengths of each length and width of the test piece and the lengths of each length and width of the injection mold were then measured for each of the four sides. The percentage of the difference relative to the length of the mold side was calculated for each of the four sides, and the average of these percentages was taken as the molding shrinkage. The molding shrinkage in the length direction was taken as the shrinkage MD, and the molding shrinkage in the width direction was taken as the shrinkage TD.

[0110] [Slidability (dynamic friction coefficient) and wear resistance (specific wear rate)] A test piece with a length of 120 mm, a width of 130 mm, and a thickness of 3 mm, produced by the same method as described above, was punched out to produce a test piece with a length of 30 mm, a width of 30 mm, and a thickness of 3 mm. Using this test piece, in accordance with JIS K7218 "Method A for Sliding Wear Test of Plastics", the dynamic friction coefficient and specific wear rate were measured using a Matsumoto-type friction and wear tester. The test conditions were as follows: counter material: S45C, speed: 50 cm / second, distance: 3 km, load: 15 kg, and measurement ambient temperature: 23°C.

[0111] 〔Tensile breaking strength, tensile breaking elongation and tensile modulus of elasticity〕 In accordance with ISO 527-1,2, with the test piece shape being the shape described in JIS K7162 1A and the tensile speed being 50 mm / min, the tensile breaking strength and tensile breaking elongation were determined. Also, in accordance with ISO 527-1,2, with the test piece shape being the shape described in JIS K7162 1A and the tensile speed being 1 mm / min, the tensile modulus of elasticity was determined.

[0112] 〔Flexural strength, flexural modulus of elasticity〕 <Production of JIS K7162 1A test piece> The composition obtained in the example or comparative example was put into the hopper part of an "EC-75SXIII type molding machine" manufactured by Shibaura Machine Co., Ltd., melted at 230°C, and injection molded into a mold to produce a JIS K7162 1A test piece. The mold temperature was 50 - 70°C, the injection pressure was 80 - 120 MPa, and the holding pressure was 60 - 90 MPa. However, only in the case of the composition obtained in Comparative Example 1, the injection pressure was changed to 70 - 90 MPa and the holding pressure was changed to 25 - 45 MPa.

[0113] <Measurement of flexural strength and flexural modulus of elasticity> Using a JIS K7162 1A test piece, in accordance with ISO 178, with the above test piece shape being 80 mm (length), 10 mm (width), 4 mm (thickness), the span distance being 64 mm, and the test speed being 2 mm / min, the flexural strength and flexural modulus of elasticity were determined.

[0114] 〔Flexural fatigue test〕 <Production of ASTM D671 Type A test piece> The compositions obtained in the examples or comparative examples were placed in the hopper of an EC-75SXIII molding machine manufactured by Shibaura Machine Co., Ltd., melted at 230°C, and injection molded into a mold to prepare ASTM D671 Type A test specimens. The mold temperature was 30 to 50°C, the injection pressure was 90 to 110 MPa, and the holding pressure was 55 to 65 MPa.

[0115] <Measurement of vibration fatigue count> An ASTM D671 Type A test piece was set in a Toyo Seiki Seisakusho B70-type cyclic vibration fatigue tester, and a vibration fatigue test was performed at room temperature, a frequency of 30 Hz, and a pressure of 35 MPa. The number of cycles until the displacement reached 8 mm was calculated as the fatigue resistance (cycles).

[0116] [Raw materials] The raw materials used in the examples and comparative examples are as follows.

[0117] (Ethylene polymer component (AI)) <<Production of Ethylene-Based Polymer Component (AI-1)>> Using a conventional method, an ultra-high molecular weight ethylene polymer (polymer (a1)) having an intrinsic viscosity [η] of 30 dL / g was polymerized in a first stage, and then a low molecular weight ethylene polymer (polymer (a2)) having an intrinsic viscosity [η] of 1.5 dL / g was polymerized in a second stage, in a mass ratio (polymer (a1) / polymer (a2)) of 41 / 59, to thereby obtain an ethylene polymer component (AI-1) having an intrinsic viscosity [η] of 4.4 dL / g.

[0118] <<Production of Ethylene-Based Polymer Component (AI-2)>> By a conventional method, an ultra-high molecular weight ethylene polymer (polymer (a1)) having an intrinsic viscosity [η] of 30 dL / g was produced in a first polymerization stage, and then a low molecular weight ethylene polymer (polymer (a2)) having an intrinsic viscosity [η] of 1.5 dL / g was produced in a second polymerization stage in a mass ratio (polymer (a1) / polymer (a2)) of 75 / 25 to produce an ethylene polymer component (AI-2) having an intrinsic viscosity [η] of 6.9 dL / g.

[0119] (Ethylene-based polymer component (AII)) The following ethylene polymer components were used: Ethylene polymer component (AII-1): Intrinsic viscosity [η] 1.1 dl / g, density 965 kg / m 3 High-density, low-molecular-weight polyethylene ("Hi-Zex 1700J" manufactured by Prime Polymer Co., Ltd.)

[0120] (Ethylene-based polymer component (A)) <<Production of Ethylene-Based Polymer Component (A-1)>> The ethylene polymer component (AI-1) and the ethylene polymer component (AII-1) were blended in a mass ratio ((AI-1) / (AII-1)) of 49 / 51, and melt-blended using an Ikegai PCM twin-screw extruder to obtain a pellet with an intrinsic viscosity [η] of 3.0 dl / g and a density of 968 kg / cm. 3 An ethylene polymer component (A-1) of the following formula was obtained: The content of the ultra-high molecular weight ethylene polymer (polymer (a1)) in the ethylene polymer component (A-1) was 20 mass %.

[0121] <<Production of Ethylene-Based Polymer Component (A-2)>> The ethylene polymer component (AI-2) and the ethylene polymer component (AII-1) were mixed in a mass ratio ((AI-2) / (AII-1)) of 33 / 67, and melt-blended using an Ikegai PCM twin-screw extruder to obtain a pellet with an intrinsic viscosity [η] of 5.8 dl / g and a density of 966 kg / cm. 3 An ethylene polymer component (A-2) of the following formula was obtained: The content of the ultra-high molecular weight ethylene polymer (polymer (a1)) in the ethylene polymer component (A-2) was 25 mass %.

[0122] (Carbon fiber (B)) The following carbon fibers were used: Carbon fiber (B-1): Teijin Limited's "Tenax HT P802" (polyolefin polymer sizing treatment, fiber length: 3 mm, diameter: 7 μm, carbon fiber content: 98% by mass) Carbon fiber (B-2): Teijin Limited's "Tenax HT C605" (nylon polymer sizing treatment, fiber length: 6 mm, diameter: 7 μm, carbon fiber content: 95.5% by mass) Carbon fiber (B-3): Toray Industries, Inc. "TORAYCA T008-006" (epoxy polymer sizing treatment, fiber length: 6 mm, diameter: 7 μm, carbon fiber content: 99% by mass)

[0123] (Other carbon-based fillers) The following carbon nanotubes were used: Carbon nanotubes: Nanosil "NC7000" (average diameter: 9.5 nm, average length: 1.5 μm)

[0124] <<Preparation of carbon nanotube masterbatch>> 15% by mass of the carbon nanotubes, 75% by mass of the ethylene-based polymer component (A-1), and 10% by mass of wax (polyethylene-based wax) were mixed by a conventional method to prepare a carbon nanotube-containing masterbatch.

[0125] (Modified olefin polymer (C)) The following modified olefin polymers were used as compatibilizers. Modified olefin polymer (C-1): A maleic acid-modified ethylene polymer (density: 965 kg / cm) produced based on the production method of ethylene polymer PE-0 described in WO 2019 / 208169, paragraphs

[0042] to

[0043] . 3 MFR (190°C, 2.16 kg load): 5 g / 10 min, Modification rate: 2.4) Modified olefin polymer (C-2): A maleic acid-modified ethylene polymer (density 967 kg / cm) produced based on the method for producing a modified polyolefin composition described in paragraph

[0083] of JP 2019-218568 A 3 , intrinsic viscosity [η]5dl / g、 MFR (190°C, 10kgf): 6.2, Modification rate: 0.8)

[0126] [Example 1] After dry-blending 78% by mass of ethylene polymer component (A-1), 20% by mass of carbon fiber (B-1), and 2% by mass of modified olefin polymer (C-1), the mixture was melt-extruded using a twin-screw kneading extruder "HK-25D" manufactured by Parker Corporation under conditions of a cylinder temperature of 260°C, a screw rotation speed of 200 rpm, and a discharge rate of 12 kg / h to obtain a composition. The blending amounts of each component in the obtained composition (based on 100 parts by mass of the total amount of ethylene polymer) are shown in Table 1. The physical properties of the obtained composition were also measured using the methods described above. The results are shown in Table 1.

[0127] [Example 2] A composition was produced in the same manner as in Example 1, except that the amounts of the ethylene polymer component (A-1), carbon fiber (B-1), and modified olefin polymer (C-1) were adjusted to the blending amounts shown in Table 1, and the physical properties of the composition were measured. The results are shown in Table 1.

[0128] [Example 3] A composition was produced in the same manner as in Example 1, except that the modified olefin polymer (C-2) was used instead of the modified olefin polymer (C-1), and the amounts of the ethylene polymer component (A-1), carbon fiber (B-1), and modified olefin polymer (C-2) were adjusted to the blending amounts shown in Table 1, and the physical properties of the composition were measured. The results are shown in Table 1.

[0129] [Example 4] A composition was produced in the same manner as in Example 1, except that the ethylene polymer component (A-2) was used instead of the ethylene polymer component (A-1), and the amounts of the ethylene polymer component (A-2), carbon fiber (B-1), and modified olefin polymer (C-1) were adjusted to the blending amounts shown in Table 1, and the physical properties of the composition were measured. The results are shown in Table 1.

[0130] [Example 5] A composition was produced in the same manner as in Example 1, except that carbon fiber (B-2) was used instead of carbon fiber (B-1), and the amounts of ethylene polymer component (A-1), carbon fiber (B-2), and modified olefin polymer (C-1) were adjusted to the blending amounts shown in Table 1, and the physical properties of the composition were measured. The results are shown in Table 1.

[0131] [Example 6] A composition was produced in the same manner as in Example 1, except that carbon fiber (B-3) was used instead of carbon fiber (B-1), and the amounts of ethylene polymer component (A-1), carbon fiber (B-3), and modified olefin polymer (C-1) were adjusted to the blending amounts shown in Table 1, and the physical properties of the composition were measured. The results are shown in Table 1.

[0132] [Comparative Example 1] A composition was produced in the same manner as in Example 1, except that the ethylene polymer component (AII-1) was used instead of the ethylene polymer component (A-1), and the amounts of the ethylene polymer component (AII-1), carbon fiber (B-1), and modified olefin polymer (C-1) were adjusted to the blending amounts shown in Table 1, and the physical properties of the composition were measured. The results are shown in Table 1.

[0133] Comparative Example 2 A composition was produced in the same manner as in Example 1, except that only the ethylene polymer component (A-1) was used without using the carbon fiber (B-1) and the modified olefin polymer (C-1), and the physical properties thereof were measured. The results are shown in Table 1.

[0134] Comparative Example 3 After dry-blending 40% by mass of the ethylene polymer component (A-2) and 60% by mass of the carbon nanotube masterbatch, the mixture was melt-extruded using a twin-screw kneading extruder "HK-25D" manufactured by Parker Corporation under conditions of a cylinder temperature of 260°C, a screw rotation speed of 200 rpm, and a discharge rate of 12 kg / h to obtain a composition. The blending amounts of each component in the composition (based on 100 parts by mass of the total amount of the ethylene polymer) are shown in Table 1. The physical properties of the obtained composition were measured using the methods described above. The results are shown in Table 1.

[0135] Table 1

Claims

1. The intrinsic viscosity [η] measured in decalin solvent at 135°C is 1.5 to 10 dl / g, and the density is 930 to 980 kg / m 3 and 1 to 100 parts by mass of carbon fiber (B), The ethylene polymer component (A) is an ethylene polymer composition containing an ultra-high molecular weight ethylene polymer (a1) having an intrinsic viscosity [η] of 10 to 40 dl / g as measured in decalin solvent at 135°C, The ethylene-based polymer composition, wherein the carbon fibers (B) extracted from the ethylene-based polymer composition have an average fiber length of 100 μm or more and 400 μm or less.

2. The intrinsic viscosity [η] measured in decalin solvent at 135°C is 1.5 to 10 dl / g, and the density is 930 to 980 kg / m 3 and 1 to 100 parts by mass of carbon fiber (B), The ethylene polymer component (A) is an ethylene polymer composition containing an ultra-high molecular weight ethylene polymer (a1) having an intrinsic viscosity [η] of 10 to 40 dl / g as measured in decalin solvent at 135°C, an ethylene-based polymer composition, wherein the proportion of carbon fibers having a fiber length of 100 μm or more and 300 μm or less is 30% or more of the carbon fibers (B) extracted from the ethylene-based polymer composition.

3. The intrinsic viscosity [η] measured in decalin solvent at 135°C is 1.5 to 10 dl / g, and the density is 930 to 980 kg / m 3 the composition contains 100 parts by mass of an ethylene polymer component (A) represented by the formula (I), 1 to 100 parts by mass of carbon fiber (B), and a modified olefin polymer (C), The ethylene polymer component (A) is an ethylene polymer composition containing an ultra-high molecular weight ethylene polymer (a1) having an intrinsic viscosity [η] of 10 to 40 dl / g as measured in decalin solvent at 135°C.

4. The ethylene polymer composition according to any one of claims 1 to 3, wherein the ethylene polymer component (A) comprises a low- to high-molecular-weight ethylene polymer (a2) having an intrinsic viscosity [η] of 0.1 to 9 dl / g measured in decalin solvent at 135°C.

5. the ethylene polymer component (A) contains 10 to 90 mass% of an ethylene polymer component (AI) and 90 to 10 mass% of an ethylene polymer component (AII) (the total amount of the components (AI) and (AII) being 100 mass%); the ethylene polymer component (AI) is a multistage polymer comprising more than 35% by mass but not more than 90% by mass of the ultra-high molecular weight ethylene polymer (a1) and 10% by mass or more but not more than 65% by mass of the low- to high-molecular weight ethylene polymer (a2) (the total amount of polymer (a1) and polymer (a2) being 100% by mass), 5. The ethylene polymer composition according to claim 4, wherein the ethylene polymer component (AII) comprises an ethylene polymer (a3) ​​having an intrinsic viscosity [η] measured in decalin solvent at 135°C of 0.1 to 2.9 dl / g.

6. The ethylene polymer composition according to any one of claims 1 to 3, wherein the carbon fiber (B) is a surface-treated carbon fiber.

7. The ethylene polymer composition according to claim 6, wherein the surface treatment of the carbon fibers (B) is a sizing treatment using an olefin-based polymer, a urethane-based polymer, a nylon-based polymer, or an epoxy-based polymer.

8. 2. The ethylene polymer composition according to claim 1, wherein the carbon fibers (B) extracted from the ethylene polymer composition contain carbon fibers having a fiber length of 100 μm or more and 300 μm or less in a proportion of 30% or more.

9. The ethylene polymer composition according to claim 1 or 2, which comprises a modified olefin polymer (C).

10. The ethylene polymer composition according to any one of claims 1 to 3, wherein the amount of the carbon fiber (B) is 20 to 60 parts by mass per 100 parts by mass of the ethylene polymer component (A).

11. A molded article comprising the ethylene polymer composition according to any one of claims 1 to 3.

12. The molded body according to claim 11, wherein the proportion of carbon fibers having an acicular ratio of 1.5 or more in the carbon fibers (B) contained in the molded body is 30% or more.

13. The molded article according to claim 11, wherein the shrinkage rate of the molded article in both the length direction and the width direction is 2.0% or less.

14. The molded article according to claim 11, wherein the molded article has a flexural modulus of elasticity of 5000 MPa or more.

15. The molded article according to claim 11, wherein the number of repetitions when the displacement amount reaches 8 mm in a vibration fatigue test (35 MPa) of the molded article is 1,500 or more.

16. The molded article according to claim 11, which is an injection molded article.

17. The molded article according to claim 11, which is a coating material or a sliding material.

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