Polyethylene resin composition and molded article

Abstract

To provide an ultra-high molecular weight polyethylene resin composition that enables the formation of molded articles with enhanced conductivity, slidability, and wear resistance.SOLUTION: A polyethylene resin composition comprises ultra-high molecular weight polyethylene and a conductive filler.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present disclosure relates to a polyethylene resin composition and a molded article. [Background technology]

[0002] Polyethylene with a particularly large molecular weight, so-called ultra-high molecular weight polyethylene, is superior in impact resistance and strength to general-purpose polyethylene (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2010-106257 A Summary of the Invention [Problem to be solved by the invention]

[0004] Depending on the application, there may be a demand for an ultra-high molecular weight polyethylene resin composition capable of forming a molded article having excellent electrical conductivity, sliding properties, and abrasion resistance. One of the objects of the present disclosure is to provide an ultra-high molecular weight polyethylene resin composition capable of forming a molded article having excellent electrical conductivity, sliding properties, and abrasion resistance. [Means for solving the problem]

[0005] One embodiment of the polyethylene resin composition of the present disclosure contains ultra-high molecular weight polyethylene and a conductive filler. Effect of the Invention

[0006] According to the present disclosure, it is possible to provide an ultra-high molecular weight polyethylene resin composition capable of forming a molded article having excellent electrical conductivity, sliding properties and abrasion resistance. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0007] In this specification, the numerical range n1 to n2 means n1 or more and n2 or less. Here, n1 and n2 are any numbers that satisfy n1 < n2. For example, the numerical range 1 to 10 means 1 or more and 10 or less. In this specification, when a plurality of lower limit values and upper limit values are described for a certain element, a numerical range formed by combining a value arbitrarily selected from the described lower limit values and a value arbitrarily selected from the described upper limit values is also considered to be described.

[0008] [Polyethylene resin composition] The polyethylene resin composition of the present disclosure (hereinafter, also simply referred to as "polyethylene resin composition") contains ultra-high molecular weight polyethylene and a conductive filler.

[0009] <Ultra-high molecular weight polyethylene> The polyethylene resin composition contains ultra-high molecular weight polyethylene. Such a polyethylene resin composition can form a molded article excellent in, for example, slidability, abrasion resistance, impact resistance, and strength. Ultra-high molecular weight polyethylene is a polyethylene having a particularly large molecular weight compared to general polyethylene (for example, high-density polyethylene or low-density polyethylene having a weight average molecular weight of 20,000 to 300,000).

[0010] Ultra-high molecular weight polyethylene is, for example, a homopolymer of ethylene or a copolymer of ethylene and an α-olefin. Examples of the α-olefin include α-olefins 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. The above copolymer is a copolymer having a constituent unit derived from ethylene as a main component. The main component means the constituent unit having the highest content ratio (mol%) among the constituent units contained in the copolymer.

[0011] The ultra-high molecular weight polyethylene may have only structural units derived from raw material monomers derived from fossil fuels, may have only structural units derived from raw material monomers derived from biomass, or may have both structural units derived from raw material monomers derived from fossil fuels and structural units derived from raw material monomers derived from biomass. Examples of the raw material monomers include ethylene and α-olefins.

[0012] Biomass-derived feedstock monomers are feedstock monomers made from any (renewable) natural raw material, such as from plants or animals, including fungi, yeasts, algae and bacteria, as well as their residues. Biomass-derived feedstock monomers include, for example, those that contain carbon 14 C isotope 1×10 -12 and has a biomass carbon concentration (unit: pMC) of about 100 pMC as measured in accordance with ASTM D6866. The biomass-derived raw material monomer can be obtained, for example, by a conventionally known method.

[0013] Ultra-high molecular weight polyethylene having structural units derived from raw material monomers derived from biomass is preferred from the viewpoint of reducing the environmental load (mainly reducing greenhouse gas emissions).

[0014] If the production conditions such as polymerization catalyst, polymerization process, and polymerization temperature are the same, polyethylene having structural units derived from biomass-derived raw materials can be produced. 14 C isotope 1.0×10 -14 ~1.0×10 -12 The molecular structure and physical properties, etc., other than the inclusion of structural units derived from biomass-derived raw material monomers in a proportion of about 100% are equivalent to those of polyethylene having only structural units derived from raw material monomers derived from fossil fuels. Therefore, the performance of polyethylene having structural units derived from biomass-derived raw material monomers is considered to be equivalent to the performance of polyethylene having only structural units derived from raw material monomers derived from fossil fuels.

[0015] Ultra-high molecular weight polyethylene can be produced, for example, by polymerizing monomers containing at least ethylene in the presence of a known olefin polymerization catalyst.

[0016] The polyethylene resin composition may contain one type of ultra-high molecular weight polyethylene, or may contain two or more types of ultra-high molecular weight polyethylene.

[0017] <Conductive filler> The polyethylene resin composition contains a conductive filler. Such a polyethylene resin composition can be formed into, for example, a molded article having high electrical conductivity.

[0018] Examples of the conductive filler include conductive carbon. Examples of the conductive carbon include carbon nanotubes, carbon powder, carbon fibers, and fullerenes. Among these, carbon nanotubes are preferred from the viewpoint of being able to satisfactorily reduce the surface resistivity and volume resistivity of the molded body.

[0019] The average diameter of the carbon nanotubes may be, for example, 0.5 to 300 nm or 1 to 200 nm. The average fiber length of the carbon nanotubes may be, for example, 0.01 to 100 μm or 1 to 10 μm. The average diameter of the carbon nanotubes is determined by observing the carbon nanotubes with a scanning electron microscope (SEM) and taking the arithmetic average of the respective diameters. The average fiber length of the carbon nanotubes is determined by observing the carbon nanotubes with a SEM and taking the arithmetic average of the respective fiber lengths.

[0020] The secondary particle shape of the carbon nanotubes is not particularly limited. For example, the carbon nanotubes may be in a state where the carbon nanotubes have a general shape and are intricately entangled, or may be an aggregate of linear carbon nanotubes that are easy to disentangle.

[0021] The carbon nanotubes may be surface-treated. The carbon nanotubes may have a functional group such as a carboxy group. The carbon nanotubes may be multi-walled carbon nanotubes or single-walled carbon nanotubes.

[0022] Carbon nanotubes can be produced by, for example, a laser ablation method, an arc discharge method, a thermal chemical vapor deposition (CVD) method, a plasma CVD method, or a combustion method. Commercially available carbon nanotubes may also be used.

[0023] Examples of carbon powder include carbon black. Examples of carbon black include furnace black, acetylene black, and ketjen black. Carbon black can be produced by decomposition methods such as the thermal black method and the acetylene black method, or by incomplete combustion methods such as the channel black method, the gas furnace black method, the oil furnace black method, the pine smoke method, and the lamp black method.

[0024] The polyethylene resin composition may contain one type of conductive filler, or may contain two or more types of conductive fillers.

[0025] The content of the conductive filler in the polyethylene resin composition is preferably 1 to 30 parts by mass, more preferably 5 to 25 parts by mass, and further preferably 7 to 15 parts by mass, based on 100 parts by mass of the ultra-high molecular weight polyethylene. Such a polyethylene resin composition can form, for example, a molded article having high electrical conductivity and excellent sliding properties and abrasion resistance.

[0026] <Other ingredients> The polyethylene resin composition may further contain a thermoplastic resin such as a polyolefin resin other than the ultra-high molecular weight polyethylene.

[0027] The polyethylene resin composition may contain additives. Examples of additives include heat stabilizers, antioxidants, ultraviolet absorbers, weathering agents, colorants (dyes, pigments, etc.), antistatic agents, fillers other than conductive fillers, flame retardants, flame retardant assistants, antifogging agents, lubricants, antiblocking agents, flow improvers, plasticizers, dispersants, antibacterial agents, release agents, foaming agents, tackifiers, sealability improvers, crosslinking agents, coupling agents, and surfactants. The polyethylene resin composition may contain one type of additive, or two or more types of additives.

[0028] The total content of the ultra-high molecular weight polyethylene and the conductive filler in the polyethylene resin composition is, in 100 mass% of the polyethylene resin composition, preferably 50 mass% or more, more preferably 60 mass% or more, even more preferably 70 mass% or more, still more preferably 80 mass% or more, particularly preferably 90 mass% or more, 95 mass% or more, 98 mass% or more, or 99 mass% or more.

[0029] <Preparation of Polyethylene Resin Composition> The polyethylene resin composition can be prepared, for example, by mixing ultra-high molecular weight polyethylene, a conductive filler, and other components as desired, for example, by melt kneading. The polyethylene resin composition can be prepared, for example, by dry blending ultra-high molecular weight polyethylene, a conductive filler, and other components as desired, and then melt kneading. Examples of the melt kneading method include a method using a single screw extruder, a multi-screw extruder, or a tandem extruder.

[0030] As the polyethylene resin composition, a commercially available product may be used. Examples of the commercially available polyethylene resin composition include LUBMER (registered trademark) LK4920 and LUBMER (registered trademark) LK6940 manufactured by Mitsui Chemicals, Inc.

[0031] [Molded body] The molded article of the present disclosure includes the polyethylene resin composition of the present disclosure. The molded article of the present disclosure can be produced, for example, by a conventionally known method for molding polyolefins. Examples of the method for molding polyolefins include injection molding, injection compression molding, extrusion molding, press molding, calendar molding, foam molding, pipe molding, inflation molding, and injection blow molding. The molded article of the present disclosure is preferably obtained by molding a polyethylene resin composition by injection molding. That is, the molded article of the present disclosure is preferably an injection molded article.

[0032] The molded article of the present disclosure may be a molded article formed from the polyethylene resin composition of the present disclosure. The molded article of the present disclosure may be a molded article having a portion, for example, a surface layer, formed from the polyethylene resin composition of the present disclosure.

[0033] [Uses of molded products] The molded article of the present disclosure may be, for example, a household product, a general industrial product, or an industrial product.The molded article of the present disclosure may be, for example, a communication device part, an electric part, an electronic part, an automobile part, a part of other vehicles, a home appliance material part, a ship part, an aircraft part, a machine mechanism part, a building material part, a civil engineering part, an agricultural material, an electric tool part, a food container, a film, a sheet, or a fiber.

[0034] The molded article of the present disclosure is excellent in electrical conductivity, slidability, and abrasion resistance, and therefore can be suitably used as a sliding material. In addition, the molded article of the present disclosure is excellent in electrical conductivity, and therefore can be suitably used in applications requiring antistatic properties, for example. Examples of the sliding material include oilless bearings, joints, bearings, gears, steel pistons, rollers; metal coating materials (laminated) such as steel pipes, electric wires, and automobile sliding door rails; pressure-resistant rubber hoses, gaskets for automobile doors, gaskets for clean room doors, automobile glass run channels, automobile weather strips, and various other rubber coating materials (laminated); and various protective liner materials for lining hoppers, chutes, and the like.

[0035] [Example of the situation] The present disclosure relates to, for example, the following [1] to [5]. [1] A polyethylene resin composition containing ultra-high molecular weight polyethylene and a conductive filler. [2] The polyethylene resin composition according to [1], which contains at least carbon nanotubes as the conductive filler. [3] A molded article comprising the polyethylene resin composition according to [1] or [2] above. [4] The molded article according to [3] above, which is an injection molded article. [5] The molded article according to [3] above, which is a sliding material. EXAMPLES

[0036] The polyethylene resin composition of the present disclosure will be described more specifically below based on examples, but the polyethylene resin composition of the present disclosure is in no way limited to these examples.

[0037] [Polyethylene resin composition] · LK4920 LUBMER (registered trademark) LK4920, manufactured by Mitsui Chemicals, Inc. Conductive filler-containing ultra-high molecular weight polyethylene resin composition · LK6940 LUBMER (registered trademark) LK6940, manufactured by Mitsui Chemicals, Inc. Conductive filler-containing ultra-high molecular weight polyethylene resin composition

[0038] [Ultra-high molecular weight polyethylene] 320MU Million (registered trademark) 320MU, manufactured by Mitsui Chemicals, Inc. Ultra-high molecular weight polyethylene ·L3000 LUBMER (registered trademark) L3000, manufactured by Mitsui Chemicals, Inc. Ultra-high molecular weight polyethylene

[0039] [Example 1] The raw material polyethylene resin composition (LK4920) was melted at 270°C using an injection molding machine EC75SX-III manufactured by Shibaura Machine Co., Ltd., and molded at an injection pressure of 100 MPa and a holding pressure of 40 MPa to produce a molded body measuring 120 mm x 130 mm x 3 mmt.

[0040] [Example 2 and Comparative Example 2] Molded articles were produced in the same manner as in Example 1, except that the polyethylene resin composition or ultra-high molecular weight polyethylene shown in Table 1 was used as the raw material.

[0041] [Comparative Example 1] The raw material, ultra-high molecular weight polyethylene (320MU), was preheated for 5 minutes using a hydraulic heat press made by Shinto Metal Industry Co., Ltd. set at 220°C, and then pressurized at 10 MPa for 20 minutes. After that, the raw material was compressed and cooled for 10 minutes using another hydraulic press made by Shinto Metal Industry Co., Ltd. set at 20°C to produce a molded body measuring 100 mm x 100 mm x 3 mmt.

[0042] [Comparative Example 3] 91 parts by mass of high density polyethylene (manufactured by Prime Polymer Co., Ltd., product name Hi-Zex (registered trademark) 1700J) and 9 parts by mass of carbon nanotubes (manufactured by Nanocyl Corporation, NC7000) were mixed and melt-kneaded at 200°C using a BT-30 twin-screw extruder manufactured by Plastics Engineering Research Institute Co., Ltd. to produce a conductive filler-containing high density polyethylene resin composition (hereinafter also referred to as "CNT-HDPE"). A molded body was produced in the same manner as in Example 1, except that this CNT-HDPE was used as a raw material.

[0043] [Evaluation method] <Conductivity evaluation> The molded body obtained above was left to stand at room temperature of 23° C.±2° C. and humidity of 50%±5% for 24 hours or more. After this conditioning, the surface resistivity and volume resistivity of the molded body were measured using Loresta MCP-T700 manufactured by Nitto Seiko Analytech Co., Ltd.

[0044] <Sliding properties (dynamic friction coefficient) and wear resistance (specific wear rate)> The 120mm×130mm×3mmt and 100mm×100mm×3mmt compacts obtained above were punched out to 30mm×30mm×3mmt test pieces. The test pieces were used to measure the dynamic friction coefficient and specific wear rate under the following conditions using a friction and wear tester EFM-3H manufactured by A&D Co., Ltd. (conditions) Load: 15kgf Distance: 3km Speed: 0.5m / s Measurement temperature: room temperature (23±2℃) Mating material: Carbon steel (S45C)

[0045] [Table 1]

Claims

1. A polyethylene resin composition comprising ultra-high molecular weight polyethylene and a conductive filler.

2. The polyethylene resin composition according to claim 1 , which contains at least carbon nanotubes as the conductive filler.

3. A molded article comprising the polyethylene resin composition according to claim 1 or 2.

4. The molded article according to claim 3, which is an injection molded article.

5. The molded article according to claim 3, which is a sliding material.

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