JP7610403B2 - Olefin-based polymer composition and its use - Google Patents

Description

The present invention relates to an olefin polymer composition having excellent sliding properties and heat resistance, and its uses.

Ethylene polymers with extremely high molecular weights, so-called ultra-high molecular weight ethylene polymers, have superior impact resistance, abrasion resistance, chemical resistance, and strength compared to general-purpose ethylene polymers, and have excellent characteristics as engineering plastics.

It is known that such ultra-high molecular weight ethylene polymers can be obtained using known catalysts such as so-called Ziegler catalysts consisting of halogen-containing transition metal compounds and organometallic compounds, or magnesium compound-supported catalysts.

Due to the high molecular weight of ultra-high molecular weight ethylene polymers, it is difficult to perform melt molding, a common molding method for resins. The ram extrusion method is already a commonly used method for producing molded bodies of ultra-high molecular weight ethylene polymers (Patent Document 1).

In addition, as a method for improving the sliding properties, abrasion resistance, heat resistance, and rigidity of an olefin resin composition, it has been proposed to add a particulate inorganic filler such as talc to the olefin resin composition (Patent Document 2).

Japanese Unexamined Patent Publication No. 55-28896 Japanese Patent Application Publication No. 01-272646

However, olefin polymers have inferior heat resistance compared to engineering plastics such as polyamide resins, polyacetal resins, polyester resins, polyphenylene sulfide resins, and polycarbonate resins. Therefore, there is a demand for compositions that have improved heat resistance without impairing the inherent sliding properties and abrasion resistance of olefin polymers.

The object of the present invention is to provide an olefin-based polymer composition that has excellent sliding properties and heat resistance.

As a result of intensive research, the inventors discovered that the above problems could be solved by adding specific amounts of a propylene-based polymer, an inorganic filler, and a fatty acid amide to a specific ethylene-based polymer composition, and thus completed the present invention.

The present invention relates to the following [1] to [8].
[1] An olefin-based polymer composition comprising an ethylene-based polymer composition (A), a propylene-based polymer (B), an inorganic filler (C) and a fatty acid amide (D), wherein the ethylene-based polymer composition (A) comprises an ultra-high molecular weight ethylene-based polymer (component (a-1)) having an intrinsic viscosity [η] of 10 to 40 dl/g as measured in decalin solvent at 135°C, and a low- to high-molecular weight ethylene-based polymer (component (a-2)) having an intrinsic viscosity [η] of 0.1 to 5 dl/g as measured in decalin solvent at 135°C, wherein the component (a-1) is in the range of 15 to 75 mass% and the component (a-2) is in the range of 85 to 25 mass%, where the total mass of the components (a-1) and (a-2) is 100 mass%, the density is in the range of 930 to 980 kg/ ^m3 , and the intrinsic viscosity [η] of the component (a-1) is in the range of 15 to 75 mass% and the component (a-2) is in the range of 85 to 25 mass%, respectively, and the density is in the range of 930 to 980 kg/m3. The intrinsic viscosity [η] of the component (a-1) is in the range of 5 to 35 dl/g as measured in decalin solvent at 135°C.

[2] The olefin polymer composition according to [1], wherein the propylene polymer (B) is a composition of a propylene homopolymer (b-1) and a propylene-α-olefin copolymer (b-2).

[3] The olefin-based polymer composition according to [1] or [2], in which the content of the ethylene-based polymer composition (A) is 10 to 50% by mass, the content of the polypropylene (B) is 30 to 70% by mass, and the content of the inorganic filler (C) is in the range of 0.1 to 30% by mass (wherein the olefin-based polymer composition is taken as 100% by mass).

[4] The olefin polymer composition according to any one of [1] to [3], further comprising a modified olefin polymer (E).
[5] The olefin polymer composition according to [4], wherein the content of the modified olefin polymer (E) is in the range of 0.1 to 5 mass % (wherein the olefin polymer composition is taken as 100 mass %).

[6] The olefin polymer composition according to any one of [1] to [5], wherein the content of the fatty acid amide (D) is in the range of 0.1 to 15% by mass (wherein the olefin polymer composition is taken as 100% by mass).

[7] The olefin polymer composition according to any one of [1] to [6], wherein the inorganic filler (C) is a glass fiber.
[8] A molded article obtained by injection molding the olefin polymer composition according to any one of [1] to [7].

The present invention provides an olefin polymer composition that improves sliding properties and suppresses deformation even when used at high temperatures, and a molded article obtained from the olefin polymer composition.

The present invention will be specifically described below.
<<Ethylene-based polymer composition (A)>>
The ethylene polymer composition (A), which is one of the components of the olefin polymer composition of the present invention, contains an ultra-high molecular weight ethylene polymer (component (a-1)) having an intrinsic viscosity [η] measured in decalin solvent at 135° C. in the range of 10 to 40 dl/g, and a low- to high-molecular weight ethylene polymer (component (a-2)) having an intrinsic viscosity [η] measured in decalin solvent at 135° C. in the range of 0.1 to 5 dl/g.

<Component (a-1)>
The ultra-high molecular weight ethylene polymer (component (a-1)) constituting the ethylene polymer composition (A) according to the present invention preferably has an intrinsic viscosity [η] in the range of 10 to 35 dl/g, more preferably 12.5 to 35 dl/g.

By containing the component (a-1) having an intrinsic viscosity [η] within the above range, the resulting olefin polymer composition is excellent in self-lubrication, impact strength, chemical resistance, and the like.
The component (a-1) according to the present invention is a homopolymer of ethylene or a copolymer of ethylene and an α-olefin such as propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 1-decene, 1-dodecene, 4-methyl-1-pentene, or 3-methyl-1-pentene. Of these, it is preferable to use a homopolymer of ethylene or a copolymer of ethylene and the above-mentioned α-olefins, which is composed mainly of ethylene, and it is particularly preferable to use a homopolymer of ethylene.

<Component (a-2)>
The low- to high-molecular-weight ethylene polymer (component (a-2)) constituting the ethylene polymer composition (A) according to the present invention preferably has an intrinsic viscosity [η] in the range of 0.3 to 3 dl/g, more preferably 0.5 to 2.5 dl/g.

By containing the component (a-2) having an intrinsic viscosity [η] within the above range, the resulting olefin polymer composition has good melt fluidity.
The component (a-2) according to the present invention is a homopolymer of ethylene or a copolymer of ethylene and an α-olefin. The α-olefin constituting the copolymer is a linear or branched α-olefin having 3 to 20 carbon atoms, specifically, propylene, 1-butene, 1-pentene, 3-methyl-1-butene, 1-hexene, 4-methyl-1-pentene, 3-methyl-1-pentene, 3,4-dimethyl-1-pentene, 4-methyl-1-hexene, 3-ethyl-1-pentene, 3-ethyl-4-methyl-1-pentene, 3,4-dimethyl-1-hexene, 4-methyl-1-heptene, 3,4-dimethyl-1-heptene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, 1-eicosene, and the like. Among these, ethylene homopolymers are preferably used from the viewpoint of the self-lubricating properties of the resulting olefin polymer and molded article.

In the ethylene polymer composition (A) according to the present invention, the total mass of the above components (a-1) and (a-2) is taken as 100 mass%, and the content of component (a-1) is in the range of 15 to 75 mass%, preferably 20 to 60 mass%, and more preferably 25 to 50 mass%, and the content of component (a-2) is in the range of 85 to 25 mass%, preferably 80 to 40 mass%, and more preferably 75 to 50 mass%, respectively.

An olefin-based polymer composition containing an ethylene-based polymer composition (A) in which the amounts of component (a-1) and component (a-2) contained in the ethylene-based polymer composition (A) satisfy the above ranges has excellent self-lubricity, impact strength, chemical resistance, etc.

The ethylene polymer composition (A) according to the present invention has a density in the range of 930 to 980 kg/m ³ , preferably 940 to 975 kg/m ³ , and more preferably 950 to 970 kg/m ³ .

An olefin polymer composition containing the ethylene polymer composition (A) having a density falling within the above range is excellent in self-lubrication, impact strength, chemical resistance, and the like.
The density was measured in accordance with ASTM D1505.

The ethylene polymer composition (A) according to the present invention has an intrinsic viscosity [η] measured in decalin solvent at 135° C. in the range of 5 to 35 dl/g, preferably 10 to 30 dl/g, more preferably 15 to 25 dl/g.
The olefin polymer composition containing the ethylene polymer composition (A) having an intrinsic viscosity [η] falling within the above range is excellent in self-lubricity, impact strength, chemical resistance, and the like.

<Production method of ethylene-based polymer composition (A)>
The ethylene polymer composition (A) according to the present invention can be produced by mixing the previously obtained components (a-1) and (a-2). As preferred embodiments, the following methods (M-1) and (M-2) can be exemplified.

(M-1) A method of producing the component (a-1) and the component (a-2) in advance in the presence of a known olefin polymerization catalyst, and then mixing or kneading the components.
(M-2) A production method by a multi-stage polymerization method including at least two steps, namely, a first step of producing component (a-1) in the presence of a known olefin polymerization catalyst, and a second step of producing component (a-2).

In this case, the olefin such as ethylene used in the polymerization can be any of the various olefins described in the above items of component (a-1) and component (a-2) without any restrictions.
Any known olefin polymerization catalyst can be used without any particular limitation as long as it can produce the above-mentioned components (a-1) and (a-2). Specific examples of such catalysts include Ziegler-Natta catalysts made of titanium tetrachloride or titanium trichloride, solid titanium catalysts supported on a carrier such as magnesium, metallocene catalysts, and postmetallocene catalysts.

As a method for producing the ethylene polymer composition (A) according to the present invention, among the above, the method of polymerization in multiple stages as shown in (M-2) is preferably used because it is possible to obtain a homogeneous ethylene polymer composition (A) by finely dispersing component (a-1) in component (a-2).

Furthermore, by post-polymerizing the component (a-2) together with the component (a-1), the compatibility between the ethylene polymer composition (A) and the propylene polymer (B) is improved, and as a result, the ethylene polymer composition (A) is uniformly dispersed or bonded, and an olefin polymer composition having an excellent balance of properties such as self-lubricity, impact strength, chemical resistance, appearance and moldability, and particularly excellent self-lubricity and moldability, can be obtained.
The multi-stage polymerization method can be carried out in the same manner as the polymerization method described in JP-A-1-129047, for example.

<<Propylene-Based Polymer (B)>>
The propylene polymer (B), which is one of the components of the olefin polymer composition of the present invention, is a propylene homopolymer (b-1) or a copolymer of propylene with ethylene or an α-olefin having 4 or more carbon atoms, specifically, 1-butene, 1-pentene, 1-hexene, 1-octene, 1-decene, 1-dodecene, 4-methyl-1-pentene or 3-methyl-1-pentene, etc., and is a propylene-α-olefin copolymer (b-2) having an α-olefin content of usually 50 mol % or less, preferably 40 mol % or less, and more preferably 20 mol % or less.

The propylene polymer (B) according to the present invention is not particularly limited as long as the moldability of the olefin polymer composition containing the propylene polymer (B) is not impaired, but typically has a melt flow rate (MFR) (ASTM D-1238, 230°C, load 2160 g) in the range of 0.01 to 100 g/10 min, preferably 0.1 to 80 g/10 min.

The propylene polymer (B) according to the present invention is preferably a mixture (composition) of a propylene homopolymer (b-1) and a propylene-α-olefin copolymer (b-2). The mixture ratio of the propylene homopolymer (b-1) and the propylene-α-olefin copolymer (b-2) is particularly preferably in the range of 20 to 80% by mass for the propylene homopolymer (b-1) and 80 to 20% by mass for the propylene-α-olefin copolymer (b-2), when the total amount of (b-1) and (b-2) is taken as 100% by mass, from the viewpoint of the heat resistance of the olefin polymer composition containing the propylene polymer (B).

<<Inorganic Filler (C)>>
The inorganic filler (C), which is one of the components of the olefin polymer composition of the present invention, is a known material used as a reinforcing material or filler for rubber, resin, etc., and specific examples thereof include silicas such as dry process amorphous silica (aerosil), wet process amorphous silica (white carbon), crystalline silica (cristobalite, quartz), and diatomaceous earth; aluminas such as alumina (α-alumina), aluminum hydroxide or alumina gel (gibbsite, boehmite); aluminum silicates such as synthetic aluminum silicate (amorphous) and natural aluminum silicate (kaolin, calcined kaolin); natural magnesium silicate (talc), synthetic magnesium silicate, and synthetic basic magnesium silicate; natural or synthetic smectite clay minerals (bentonite, montmorillonite); synthetic aluminosilicates (zeolites); alkaline earth metal salts such as calcium carbonate, magnesium carbonate, and barium sulfate; powdery or granular materials such as magnesium oxide and magnesium hydroxide, and fibrous materials such as carbon fiber, alumina fiber, ceramic fiber, silica fiber, and glass fiber. Among these inorganic fillers (C), fibrous materials are preferred, and glass fibers are particularly preferred from the viewpoint of heat resistance.

<Glass fiber>
The glass fiber according to the present invention is not particularly limited, and examples thereof include borosilicate glass, E glass, S glass, A glass, AR glass, C glass, D glass, T glass, NE glass, H glass, quartz, low dielectric constant glass, and high dielectric constant glass. Among these, D glass is preferred because it is easy to obtain glass fibers having a refractive index within the above range. The glass fiber may be one type or two or more types.

The glass fibers according to the present invention may be long fibers, short fibers, or chopped fibers, and the cross-sectional shape perpendicular to the longitudinal direction of the glass fibers is not particularly limited, but is preferably circular.

The glass fibers according to the present invention may be fibers whose surfaces have been treated with a surface treatment agent such as a silane coupling agent, a titanate coupling agent, a boron coupling agent, an aluminate coupling agent, or a zircoaluminate coupling agent, or a conventionally known sizing agent.

The glass fiber according to the present invention preferably has an average fiber diameter of more than 6.5 μm and not more than 20 μm, more preferably 8 to 19 μm, and even more preferably 10 to 18 μm. When glass fibers having an average fiber diameter within the above range are used, the fibers are less likely to break when a molded article is formed from the olefin polymer composition of the present invention, and a molded article having excellent impact strength, appearance, rigidity, heat resistance, etc. can be easily formed.

The glass fiber according to the present invention has an average fiber length of preferably 0.1 to 15 mm, more preferably 0.3 to 13 mm, and further preferably 0.5 to 13 mm. When the glass fiber having an average fiber length within the above range is used, the reinforcing effect of the glass fiber on mechanical properties is easily exhibited, and a composition having excellent dispersibility can be easily obtained, which is preferable.
The average fiber diameter and the average fiber length of the glass fibers are values calculated by visually measuring the lengths of 100 glass fibers using an optical microscope.

<<Fatty acid amide (D)>>
The fatty acid amide (D), which is one of the components of the olefin polymer composition of the present invention, is usually a fatty acid amide having 12 or more carbon atoms. Specific examples thereof include saturated fatty acid amides such as lauric acid amide, palmitic acid amide, stearic acid amide, and behenic acid amide; unsaturated fatty acid amides such as erucic acid amide, oleic acid amide, brassidic acid amide, and elaidic acid amide; fatty acid bisamides such as methylene bisstearic acid amide, ethylene bisstearic acid amide, and ethylene bisoleic acid amide; and saturated or unsaturated fatty acid alkylamides such as fatty acid methylamide and fatty acid ethylamide.
Among these fatty acid amides, erucic acid amide is particularly preferred from the viewpoint of sliding properties.

<<Modified Olefin Polymer (E)>>
The modified olefin polymer (E), which is one of the components of the olefin polymer composition of the present invention, is a polymer containing an olefin-derived structural unit as a main component and a structural unit having a functional group containing a heteroatom (hereinafter, also simply referred to as a "functional group") in a proportion of preferably 0.1 to 10 mass%, more preferably 0.5 to 5 mass%. This proportion can be specified, for example, by the method described in paragraphs [0067] to [0071] of WO 2015/011935.

Examples of the functional group include a carboxylic acid group (including a carboxylic anhydride group), an ester group, an ether group, an aldehyde group, and a ketone group. A structural unit having a functional group can be introduced, for example, by subjecting an olefin polymer to a modification reaction.

The modified olefin polymer (E) according to the present invention preferably contains an olefin polymer modified with an unsaturated compound having at least one group selected from a carboxyl group and an acid anhydride group.

Specific examples of the unsaturated compound include unsaturated carboxylic acids or unsaturated dicarboxylic acids such as acrylic acid, methacrylic acid, α-ethylacrylic acid, maleic acid, fumaric acid, itaconic acid, citraconic acid, tetrahydrophthalic acid, methyltetrahydrophthalic acid, and endo-cis-bicyclo[2,2,1]hept-5-ene-2,3-dicarboxylic acid (Nadic acid (trademark)), as well as derivatives such as acid halides, amides, imides, acid anhydrides, and esters thereof. Among these, unsaturated dicarboxylic acids or their acid anhydrides are preferred, maleic acid, Nadic acid, and their acid anhydrides are more preferred, and maleic anhydride is particularly preferred. Maleic anhydride has a relatively high reactivity with olefin polymers before modification, is less likely to polymerize with maleic anhydride itself, and tends to be stable as a basic structure, which provides various advantages such as the ability to obtain modified olefin polymers of stable quality.

Examples of the olefin skeleton portion of the modified olefin polymer (E) according to the present invention include ethylene polymers, propylene polymers and 1-butene polymers.
An example of a method for producing the modified olefin polymer (E) according to the present invention is a method in which an unmodified olefin polymer is graft-modified with a modifying agent (for example, an unsaturated carboxylic acid or a derivative thereof).

The graft modification of the olefin polymer can be carried out by a known method, for example, by dissolving the olefin polymer in an organic solvent, adding an unsaturated carboxylic acid or its derivative and a radical initiator to the resulting solution, and reacting the mixture at a temperature of preferably 60 to 350°C, more preferably 80 to 190°C, for preferably 0.5 to 15 hours, more preferably 1 to 10 hours.

Examples of organic solvents that dissolve olefin polymers include aromatic hydrocarbon solvents such as benzene, toluene, and xylene, and aliphatic hydrocarbon solvents such as pentane, hexane, and heptane.

Another example of a method for graft-modifying an olefin polymer is to react the olefin polymer with a modifier (e.g., an unsaturated carboxylic acid and its derivatives) using a radical initiator in an extruder or the like in the absence of a solvent. In this case, the reaction temperature is usually above the melting point of the olefin polymer, for example, 100 to 350°C, and the reaction time is usually 0.5 to 10 minutes.

Examples of radical initiators include known radical initiators such as dicumyl peroxide, di-t-butyl peroxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexyne-3,2,5-dimethyl-2,5-di(t-butylperoxy)hexane, and 1,4-bis(t-butylperoxyisopropyl)benzene. The radical initiator is preferably used in a ratio of 0.001 to 1 part by mass per 100 parts by mass of the olefin polymer before modification.

<Olefin Polymer Composition>
The olefin polymer composition of the present invention is a composition containing the ethylene polymer composition (A), the propylene polymer (B), the inorganic filler (C) and the fatty acid amide (D), and contains the ethylene polymer composition (A) in an amount of preferably 10 to 50 mass%, more preferably 20 to 45 mass%, and even more preferably 25 to 40 mass%, the propylene polymer (B) in an amount of preferably 30 to 70 mass%, more preferably 35 to 65 mass%, and even more preferably 40 to 60 mass%, the inorganic filler (C) in an amount of preferably 0.1 to 30 mass%, more preferably 1 to 30 mass%, and even more preferably 5 to 30 mass%, and the fatty acid amide (D) in an amount of preferably 0.1 to 15 mass%, more preferably 0.5 to 13 mass%, and even more preferably 1 to 12 mass%, based on 100 mass% of the olefin polymer composition.

The olefin polymer composition of the present invention has excellent sliding properties by containing the ethylene polymer composition (A) and the like in the above ranges.
The olefin polymer composition of the present invention is excellent in strength because it contains the modified olefin polymer (E) in addition to the above components.

When the olefin polymer composition of the present invention contains the modified olefin polymer (E), the content is usually in the range of 0.1 to 5% by mass, preferably 0.5 to 4% by mass (the olefin polymer composition is taken as 100% by mass).

The olefin polymer composition of the present invention may contain thermoplastic resins such as other polyolefin resins, and resin additives (for example, stabilizers such as heat stabilizers and weather stabilizers, crosslinking agents, crosslinking assistants, antistatic agents, slip agents, antiblocking agents, antifogging agents, lubricants, dyes, pigments, fillers, mineral oil-based softeners, petroleum resins, waxes, etc.) within the scope of the present invention.

<<Method for producing olefin polymer composition>>
The olefin polymer composition of the present invention can be produced by various known methods, for example, by melt-kneading and dry-blending the ethylene polymer composition (A), the propylene polymer (B), the inorganic filler (C), the fatty acid amide (D) and, if necessary, the modified olefin polymer (E).

<Molded body>
The molded article of the present invention contains the olefin polymer composition of the present invention.
[0043] Specific examples of the molding method according to the present invention 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 olefin polymer composition of the present invention is preferably processed by injection molding to obtain a molded article containing the olefin polymer composition of the present invention.

The injection molded article obtained by injection molding the olefin polymer composition of the present invention can simultaneously achieve high heat resistance (high deflection temperature under load (HDT)), high self-lubricity, and a low wear coefficient.

Specifically, the resulting injection molded product has a heat distortion temperature (ISO 75-1,2) of 140°C or higher at 0.45 MPa and 120°C or higher at 1.8 MPa, and a dynamic wear coefficient of 0.2 or less.

The molded article of the present invention may be a molded article formed from the olefin polymer composition of the present invention, or may be a molded article having a portion, such as a surface layer, formed from the olefin polymer composition of the present invention.

Furthermore, the molded article made of the olefin polymer composition of the present invention is also excellent in mechanical properties.
Specific examples of the molded article of the present invention include those used in a wide range of applications, from household goods such as daily necessities and recreational uses to general industrial and industrial products, such as home appliance material parts, communication device parts, electric 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.

The molded article of the present invention can be widely used in conventional polyethylene applications, but since it has an excellent balance of properties such as abrasion resistance, self-lubrication, impact strength, and thin-wall molding, it can be used in applications requiring these properties, such as gears, various bearings, cams, sliders, reels, cylinders, impellers, axial fans, rollers, bushes, various guide rails and rail guides, seat belt through anchors, various protective liner materials, steel pipes, electric wires, metal coatings (laminations) such as automobile sliding door rails, pressure-resistant rubber hoses, automobile door gaskets, clean room door gaskets, automobile glass run channels, automobile weather strips, and various rubber coatings (laminations) such as linings for hoppers and chutes.

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. In the following description of the examples, "parts" refers to "parts by mass" unless otherwise specified.
The ethylene polymer compositions (A) and the like used in the examples and comparative examples are shown below.

(1) Ethylene-based polymer composition (A-1)
Production of Ethylene-Based Polymer Composition (A-1) [Catalyst Preparation]
In a 10 L reactor equipped with a stirrer that had been thoroughly purged with nitrogen, 4.0 L of purified hexane and 95 g of anhydrous magnesium chloride were added, and 350 ml of ethanol was added dropwise at room temperature over a period of 2 hours while stirring, followed by mixing at room temperature for about 1 hour. Next, 330 ml of diethylaluminum chloride was added dropwise over a period of 2 hours, and the mixture was mixed at room temperature for about 1 hour after the dropwise addition, followed by dropwise addition of 1.3 L of titanium tetrachloride over a period of 1 hour, followed by reaction at 80°C for 1 hour.

After the reaction was completed, the solid portion was separated using a filter and washed twice with refined hexane to obtain a solid titanium catalyst component. The titanium catalyst component had a titanium content of 6.8% by mass, a magnesium content of 15% by mass, and a chlorine content of 60% by mass. When the solid catalyst component was observed under an optical microscope at 390x magnification, it was observed to be an aggregate of multiple layers of fine solid particles of about 1 μm.

[Production of ethylene polymer composition (A-1)]
After 12 L of purified n-decane was added to a 24 L autoclave that had been fully substituted with nitrogen, the autoclave was heated to 50°C, and 12 mmol of triethylaluminum and 0.12 mmol of the above-mentioned solid titanium catalyst component in terms of titanium atom were added at the same temperature. The catalyst inlet was then closed, and ethylene was introduced so that the internal pressure of the autoclave became 3.8 kg/cm ² ·G, and the first-stage polymerization was carried out. The polymerization temperature was maintained at 45 to 46°C. After 45 minutes had elapsed after the introduction of ethylene, the pressure was quickly released, and when the pressure became normal, 5.0 kg/cm ² ·G of hydrogen was introduced, and 3.00 kg/cm ² of ethylene was further introduced to set the total pressure to 8 kg/cm ² ·G, and the polymerization temperature was raised to 80°C, and the second-stage polymerization was carried out. The second-stage polymerization time was 490 minutes. After the polymerization was completed, the temperature was lowered, and the solid white polymer was separated and dried. The yield of the resulting ethylene polymer composition (A-1) was 3,485 g, the intrinsic viscosity [η] was 5.73 dl/g, and the density was 970 kg/m ³ .

On the other hand, when the first-stage polymerization alone was separately carried out under the same conditions, the yield of ultra-high molecular weight polyethylene (ethylene homopolymer) [(a-1)-1] obtained was 595 g, and the intrinsic viscosity [η] was 28.0 dl/g. From this, the content of ultra-high molecular weight polyethylene [(a-1)-1] was estimated to be 17.1 mass%. From this, the intrinsic viscosity [η] of the low- to high-molecular weight polyethylene [(a-2)-1] produced in the second stage was calculated to be 1.15 dl/g using the following formula.

[η] all = [η] [ _(a-1)-1 ] × [(a-1)-1] mass% + [η] [ _(a-2)-1 ] × [(a-2)- 1] Mass%
[η]all: intrinsic viscosity [η] (dl/g) of the entire polymer [ethylene polymer composition (A-1)]
[η] [ _(a-1)-1 ]: Intrinsic viscosity [η] of [(a-1)-1] (dl/g)
[(a-1)-1]: mass% [(a-1)-1] content (mass%)
[η] [ _(a-2)-1 ]: Intrinsic viscosity of [(a-2)-1] (dl/g)
[(a-2)-1] mass%: content (mass%) of [(a-2)-1]

(2) Propylene-based polymer (B-1)
Propylene homopolymer [Homo PP(b-1)-1]
"Product name: Prime Polypro J105G" manufactured by Prime Polymer Co., Ltd.: MFR = 9.0 g/10 min. Propylene-α-olefin copolymer [random PP(b-2)-1]
Prime Polymer Co., Ltd. "Product name: Prime Polypro F744NP": MFR = 7.0 g/10 min

(3) Inorganic filler (C-1)
Glass fiber chopped strand: Nippon Electric Glass Co., Ltd. "Product name: ESC 03 T480H"

(4) Fatty acid amide (D-1)
Erucic acid monoamide: NOF Corporation, product name "Alflow P-10"

(5) Modified olefin polymer (E-1)
A propylene homopolymer (manufactured by Prime Polymer, trade name J106G: MFR = 15 g/10 min) (100 parts by mass), maleic anhydride (4.0 parts by mass), and an organic peroxide (manufactured by Nippon Oil & Fats Co., Ltd., trade name Perhexyne-25B) (0.35 parts by mass) were mixed in a Hexchel mixer, and the resulting mixture was melt-graft-modified in a 100 mmφ twin-screw extruder set at 270°C for a kneading time of about 1 minute and 30 seconds to obtain a modified polyolefin resin (E-1). The amount of maleic anhydride grafted in the resulting modified olefin polymer (E-1) was measured by IR analysis and found to be 3.0% by mass.

The preparation of various test pieces of the olefin polymer compositions obtained in the examples and comparative examples and their physical properties were measured by the following methods.

[Creating test pieces]
Various test pieces were formed under the following conditions using an injection molding machine (J110-AD manufactured by Japan Steel Works, Ltd.).
Cylinder temperature (℃): 50/220/230/230/230/230/230
Injection pressure (kg/ ^cm2 ): 600
Screw rotation speed (rpm): 80
Mold temperature (℃): Water cooling (60℃)

[Thermal deformation test]
In accordance with ISO 75-1 and 2, the test specimen had a shape of 80 mm (length), 10 mm (width), and 4 mm (thickness), and the heat distortion temperature at a standard deflection of 0.36 mm was determined under loads of 0.45 MPa and 1.80 MPa and a heating rate of 120°C/h.

[Kinematic friction coefficient, specific wear rate]
The dynamic friction coefficient and specific wear rate were measured using a Matsubara friction and wear tester in accordance with JIS K7218 "Sliding wear test for plastics, method A". The test conditions were as follows: mating material: S45C, speed: 50 cm/sec, distance: 3 km, load: 15 kg, and measurement environment temperature: 23°C.

[Examples 1 to 4 and Comparative Examples 1 to 3]
The ethylene polymer composition (A-1), the propylene homopolymer [(b-1)-1], the propylene-α-olefin copolymer [(b-2)-1], the fatty acid amide (D-1) and the modified olefin polymer (E-1) were dry-blended in the amounts shown in Table 1 below, and fed into a twin-screw extruder (Toshiba Corporation, φ=26 mm, L/D=64, cylinder temperature: 230° C.), and the inorganic filler (C-1) was side-fed into the vicinity of cylinder C11 and melt-kneaded to obtain an olefin polymer composition. Test pieces were prepared from the obtained olefin polymer composition, and the physical properties were measured by the methods described above.

The results are shown in Table 1.

Claims (6)

The present invention comprises an ethylene-based polymer composition (A), a propylene-based polymer (B), an inorganic filler (C) and a fatty acid amide (D),
the ethylene polymer composition (A) comprises an ultra-high molecular weight ethylene polymer (component (a-1)) having an intrinsic viscosity [η] measured in a decalin solvent at 135° C. in the range of 10 to 40 dl/g, and a low- to high-molecular weight ethylene polymer (component (a-2)) having an intrinsic viscosity [η] measured in a decalin solvent at 135° C. in the range of 0.1 to 5 dl/g, wherein, when the total mass of the components (a-1) and (a-2) is 100 mass%, the component (a-1) is in the range of 15 to 75 mass% and the component (a-2) is in the range of 85 to 25 mass%, the density is in the range of 930 to 980 kg/m ³ , and the intrinsic viscosity [η] measured in a decalin solvent at 135° C. is in the range of 5 to 35 dl/g,
the propylene polymer (B) is a composition of a propylene homopolymer (b-1) and a propylene/α-olefin copolymer (b-2);
Further containing a modified olefin polymer (E),
An olefin polymer composition. The olefin polymer composition according to claim 1, wherein the content of the ethylene polymer composition (A) is in the range of 10 to 50 mass%, the content of the propylene polymer (B) is in the range of 30 to 70 mass%, and the content of the inorganic filler (C) is in the range of 0.1 to 30 mass% (wherein the olefin polymer composition is taken as 100 mass%). The olefin polymer composition according to claim 1 or 2 , wherein the content of the modified olefin polymer (E) is in the range of 0.1 to 5 mass % (wherein the olefin polymer composition is taken as 100 mass %). The olefin polymer composition according to any one of claims 1 to 3 , wherein the content of the fatty acid amide (D) is in the range of 0.1 to 15 mass% (wherein the olefin polymer composition is taken as 100 mass%). The olefin polymer composition according to any one of claims 1 to 4 , wherein the inorganic filler (C) is a glass fiber. A molded article obtained by injection molding the olefin polymer composition according to any one of claims 1 to 5 .