Resin composition for sliding element and sliding element

Abstract

The present invention provides a resin composition for sliding elements and a sliding element with excellent moldability and sliding performance, which contains a polyethylene resin of plant origin as a main component. In the resin composition for sliding elements, in addition to the polyethylene resin of plant origin as the main component, 0.1-20% by mass of polyethylene resin of petroleum origin as an additive, 0.1-10% by mass of modified polyolefin resin, 0.5-5% by mass of lubricating oil, and 0.1-50% by mass of filler of plant origin are mixed. The sliding element is produced by molding this resin composition for sliding elements.

Description

Technical Field

[0001] The present invention relates to a resin composition for sliding elements, which contains a plant-derived polyethylene resin as a main component, and a sliding element such as a bearing having excellent friction and wear characteristics. Background Art

[0002] In recent years, due to the increasing awareness of preventing global warming and reducing the amount of petroleum used as a declining resource, lactic acid polymers, plant-derived polyethylene resins, etc. have attracted attention. Lactic acid polymers are produced by lactic acid fermentation of sugars obtained by decomposing carbohydrates (starch, etc.) contained in grains, beans, potatoes, etc. or sugars contained in sugar cane as a raw material. Plant-derived polyethylene resins are produced based on ethylene extracted from bioethanol (which is produced from corn, etc. as a raw material).

[0003] For example, as a resin composition using a lactic acid polymer, a biodegradable lubricating resin composition (Patent Document 1) has been proposed. The lubricating resin composition comprises an aliphatic polyester having a lactic acid content of 50-100% by volume as a main component, and comprises 5-30% by volume of one or more solid lubricants selected from polytetrafluoroethylene resin, graphite and mica. However, polylactic acid resin (which is the main component of the lubricating resin composition) is not suitable for sliding applications because it has low mechanical strength and can cause hydrolysis.

[0004] In addition, a sliding element containing a polyamide containing one type of dicarboxylic acid and one type of diamine and an inorganic filler has been proposed (Patent Document 2). In addition, a sliding element with a high biomass content using plant-derived decamethylenediamine as a diamine has been proposed. However, such a sliding element causes stick-slip motion (adhesion-slip) between friction surfaces during sliding.

[0005] On the other hand, as a technology using plant-derived polyethylene resins, packaging containers or packaging laminates using plant-derived polyethylene resins have been proposed in Patent Documents 3-6, etc. Some of them have been put into practical use. However, the fact is that they have not yet been proposed for sliding applications such as mechanical elements such as sliding bearings.

[0006] Citation list

[0007] Patent Literature

[0008] Patent Document 1: Japanese Patent Application Laid-Open No. 10-212400

[0009] Patent Document 2: Japanese Patent Application Publication No. 2015-129244

[0010] Patent Document 3: Japanese Patent Application Publication No. 2014-30942

[0011] Patent Document 4: Japanese Patent Application Publication No. 2015-231870

[0012] Patent Document 5: Japanese Patent Application Publication No. 2018-135133

[0013] Patent Document 6: Japanese Patent Application Publication No. 2019-34519 Summary of the invention

[0014] Technical issues

[0015] Due to the above circumstances, the present inventors have continued to study the use of plant-derived polyethylene resins for sliding applications. As a result, the present inventors found that by blending a predetermined amount of additives with a plant-derived polyethylene resin, it can be applied to sliding applications such as sliding bearings, etc. Therefore, an object of the present invention is to provide a resin composition for a sliding element and a sliding element having excellent moldability and sliding properties, which contain a plant-derived polyethylene resin as a main component.

[0016] Problem Solution

[0017] The resin composition for sliding elements of the present invention (hereinafter referred to as the resin composition) contains, as additives, 0.1-20% by mass of a petroleum-derived polyethylene resin, 0.1-10% by mass of a modified polyolefin resin, 0.5-5% by mass of a lubricating oil, and 0.1-50% by mass of a plant-derived filler in addition to the plant-derived polyethylene resin as a main component.

[0018] According to the resin composition of the present invention, the molding material made of this resin composition has good bite performance into the screw of the molding machine and excellent molding processability, and the surface of the molded product has excellent surface conditions. According to the sliding element manufactured by using this resin composition, the mechanical strength of the polyethylene resin of plant origin as the main component is improved. And for the sliding friction of the relative element, the sliding characteristics including low friction and wear resistance can be improved.

[0019] The resin composition of the present invention may contain, as additional components, a lubricant in a ratio of 0.1 to 5% by mass and a colorant in a ratio of 1 to 5% by mass.

[0020] The lubricant as an additional component acts as a release agent, which improves the demoulding property of the resin composition in molding, and also acts as a carrier for absorbing and retaining lubricating oil. Thus, the exudation of lubricating oil can be suppressed. Therefore, not only the mixing amount of lubricating oil can be increased, but also the sliding property of the sliding element can be further improved by fusing the lubricating oil and the lubricant.

[0021] Advantageous Effects of the Invention

[0022] According to the present invention, there are provided a resin composition and a sliding element which have good molding processability such as bite performance into a molding machine screw, and can improve the mechanical strength of a plant-derived polyethylene resin as a main component, and further can improve sliding properties including low friction and wear resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is a perspective illustration to explain the jab test method. DETAILED DESCRIPTION

[0024] In addition to the main component plant-derived polyethylene resin, the resin composition of the present invention further contains as additives 0.1-20 mass % of petroleum-derived polyethylene resin, 0.1-10 mass % of modified polyolefin resin, 0.5-5 mass % of lubricating oil, and 0.1-50 mass % of plant-derived filler.

[0025] In the resin composition of the present invention, the plant-derived polyethylene resin is a homopolymer of plant-derived ethylene derived from bioethanol obtained from plants such as sugar cane or corn, or a copolymer of such plant-derived ethylene and another monomer. Here, the polymerization reaction from ethylene to polyethylene (PE) is the same as the case of polymerizing petroleum-derived ethylene.

[0026] Specifically, high-density polyethylene, medium-density polyethylene, high-pressure low-density polyethylene, linear low-density polyethylene and mixtures thereof (which are obtained by polymerizing ethylene of plant origin derived from the above-mentioned bioethanol) can be exemplary. Other monomers (comonomers) intended to be copolymerized with the ethylene of plant origin are α-olefins having 3 to 20 carbon atoms, preferably 4 to 8 carbon atoms. Specific examples are propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 1-heptene, 4-methyl-pentene-1,4-methyl-hexene-1,4,4-dimethylpentene-1, etc.

[0027] In the present invention, the preferred density of the plant-derived polyethylene resin is 0.910-0.960 g / cm 3 In addition, it is preferred that the plant-derived polyethylene has a plant degree (%) (ASTM6866, measurement of the content of radiocarbon 14C) of 80% or more. When the plant degree is 80% or more, CO2 is reduced by about 70-74% compared to petroleum-derived polyethylene. Thus, it is possible to effectively use the attenuation resources and reduce the amount of CO2 produced, which significantly causes greenhouse gases.

[0028] From the viewpoint of extrusion processability, the melt flow rate (JIS K7210, temperature: 190° C., load: 2.16 kg) of the plant-derived polyethylene resin is preferably 0.5-10 g / 10 min, particularly preferably 1.0-5.0 g / 10 min. When the melt flow rate is 0.5-10 g / 10 min, extrusion processability can be well maintained.

[0029] Specific examples of plant-derived polyethylene resins include plant-derived high-density polyethylene resin (HDPE) "GREEN-SHE150, -SGF 4960" (both trade names) and linear low-density polyethylene resin (LLDPE) "GREEN-SLH118", manufactured by Braskem SA. For sliding applications, plant-derived high-density polyethylene resins are suitable.

[0030] The polyethylene resin of the petroleum origin mixed in the resin combination of the present invention is finely dispersed in the polyethylene resin of the plant origin as the main component.Thus, the sliding property such as friction and wear of the molded product (hereinafter referred to as sliding element) made by this resin combination is improved.As the polyethylene resin of petroleum origin, high-density polyethylene resin, ultra-high molecular weight polyethylene resin, acid-modified ultra-high molecular weight polyethylene resin etc. are used.As acid-modified ultra-high molecular weight polyethylene resin, preferably maleic anhydride acid-modified ultra-high molecular weight polyethylene resin.

[0031] High-density polyethylene resin (HDPE) is an ethylene homopolymer produced by a medium / low pressure process and its density is usually 0.940-0.970 g / cm 3. Examples of high-density polyethylene resins (HDPE) include "HI-ZEX (trade name)" manufactured by Prime Polymer Co., Ltd., "Novatec (trade name)" manufactured by Japan Polyethylene Corporation, and the like. As the ultra-high molecular weight polyethylene resin (UHPE), a resin having a final viscosity [η] of 10 dl / g or more measured in a decanoic acid solvent at 135° C. and a viscosity-average molecular weight of 500,000 to 6,000,000 can be used. Examples of ultra-high molecular weight polyethylene resins (UHPE) include "HI-ZEX Million (trade name)" manufactured by Mitsui Chemicals, Inc., "MIPELON (trade name)" manufactured by Mitsui Chemicals, Inc., and "SUNFINE (trade name)" manufactured by Asahi Kasei Chemicals Co., Ltd., and the like. In addition, as the ultra-high molecular weight polyethylene resin, a resin composed of an ultra-high molecular weight polyethylene resin (whose final viscosity [η] at 135° C. is 10-40 dl / g) and a low molecular weight or high molecular weight polyethylene resin (whose final viscosity [η] at 135° C. is 0.1-5 dl / g) can be used. Examples of the ultra-high molecular weight polyethylene resin include "LUBMER (trade name)" manufactured by Mitsui Chemicals, Inc. Examples of the acid-modified ultra-high molecular weight polyethylene resin include "MODIFIED LUBMER (trade name)" manufactured by Mitsui Chemicals, Inc., which is modified with maleic anhydride.

[0032] One or more of the above-mentioned petroleum-derived polyethylene resins are selected, and the blending amount is 0.1-20% by mass, preferably 0.5-15% by mass. If the blending amount is less than 0.1% by mass, there is no effect of improving the sliding characteristics of the sliding element made of the resin composition. On the other hand, if the blending amount exceeds 20% by mass, the melt viscosity of the resin composition in molding is increased, so that the fluidity tends to deteriorate, and the appearance of the molded product will deteriorate.

[0033] The modified polyolefin resin mixed in the resin combination of the present invention is a modified polyolefin resin, which can interact with the polyethylene resin of plant origin as the main component. The modified polyolefin resin serves as a compatibilizer, which finely disperses the polyethylene resin of petroleum origin in the matrix of the polyethylene resin of plant origin as the main component, and disperses the filler of plant origin described later in the matrix of the polyethylene resin of plant origin. Thus, the modified polyolefin resin significantly improves the sliding properties including low friction and wear resistance, without reducing the mechanical strength of the sliding element made of the resin combination.

[0034] The modified polyolefin resin is selected from unsaturated carboxylic acids, polyolefin resins grafted and modified with anhydrides or derivatives thereof, and saponified polyolefin resins obtained by saponifying polyolefin resins having acetoxy groups in the molecular chain with alkali. Examples of polyolefin resins include homopolymers of α-olefins, copolymers of two or more types of α-olefins, or copolymers of α-olefins and other compounds capable of copolymerizing with α-olefins. Examples of α-olefins include α-olefins having 2 to 20 carbon atoms such as ethylene, propylene, 1-butene, 1-hexene, 4-methyl-1-pentene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene and 1-eicosene. Examples of other compounds include compounds having polyunsaturated bonds, vinyl acetate and acrylates. Examples of polyunsaturated bonds include conjugated dienes and non-conjugated dienes.

[0035] Suitable examples of polyolefin resins include low-density, medium-density or high-density polyethylene, linear low-density polyethylene, polypropylene, α-olefin copolymers [ethylene-propylene copolymers, ethylene-vinyl acetate copolymers (EVA), ethylene-butene copolymers, ethylene-hexene copolymers, ethylene-octene copolymers, ionically crosslinked olefin copolymers (ionomers)] and the like.

[0036] Unsaturated carboxylic acids, their anhydrides or derivatives are compounds having an ethylenically unsaturated bond and a carboxyl group, anhydride or derivative group in one molecule. Specific examples of unsaturated carboxylic acids include: unsaturated carboxylic acids such as acrylic acid, methacrylic acid, α-ethylacrylic acid, maleic acid, fumaric acid, tetrahydrophthalic acid, methyltetrahydrophthalic acid, itaconic acid, citraconic acid, crotonic acid, isocrotonic acid, endo-bicyclo[2.2.1]hept-5-ene-2,3-dicarboxylic acid [nadic acid], methyl-endo-bicyclo[2.2.1]hept-5-ene-2,3-dicarboxylic acid [methylnadic acid]; anhydrides of these unsaturated carboxylic acids; and derivatives such as unsaturated carboxylic acid halides, unsaturated carboxylic acid amides, and unsaturated carboxylic acid imides. More specifically, there can be mentioned maleic chloride, maleimide, N-phenylmaleimide, maleic anhydride, itaconic anhydride, citraconic anhydride, monomethyl maleate, dimethyl maleate, glycidyl maleate, etc. Among them, acrylic acid, methacrylic acid, maleic acid, maleic anhydride and itaconic anhydride are preferred, and maleic anhydride is particularly preferred.

[0037] Examples of maleic anhydride-modified polyolefin resins include maleic anhydride-modified polyethylene resins, maleic anhydride-modified polypropylene resins, maleic anhydride-modified ethylene-α-olefin copolymers (ethylene-propylene copolymers, ethylene-vinyl acetate copolymers, ethylene-butene copolymers, ethylene-hexene copolymers, ethylene-octene copolymers, etc.), and maleic anhydride-modified styrene-ethylene / butylene-styrene copolymers (SEBS), etc.

[0038] A preferred example of the saponified polyolefin resin is a saponified ethylene-vinyl acetate copolymer.

[0039] The modified polyolefin resin used in the present invention complies with JIS K7210 (2014). Its melt flow index (MFR) measured at a temperature of 190° C. or 230° C. under a load of 2.16 kg is preferably 0.1-100 g / 10 min, particularly preferably 0.1-50 g / 10 min. If the melt flow index is less than 0.1 g / 10 min, the viscosity becomes too high and the fluidity of the resin composition is poor. As a result, the moldability of melt extrusion, etc., is deteriorated. On the other hand, if the melt flow rate exceeds 100 g / 10 min, the moldability becomes unstable. As a result, the mechanical strength of the sliding element can be reduced.

[0040] Specific examples of modified polyolefin resins used in the present invention are shown below. Examples of maleic anhydride-modified polyethylene resins and maleic anhydride-modified polypropylene resins include "ADMER (trade name)" manufactured by Mitsui Chemicals, Inc. and "Modic (trade name)" manufactured by Mitsubishi Chemical Corporation, etc. Examples of maleic anhydride-modified ethylene-propylene copolymers include "TAFMER (trade name)" manufactured by Mitsui Chemicals, Inc. Examples of maleic anhydride-modified ethylene-butene copolymers include "TAFMER (trade name)" manufactured by Mitsui Chemicals, Inc. Examples of maleic anhydride-modified styrene-ethylene / butene-styrene copolymers include "Tuftec (trade name)" manufactured by Asahi Kasei Corp., "SEPTON (trade name)" manufactured by Kuraray Co., Ltd., and "KRATON (trade name)" manufactured by Kraton Polymer Japan Corp. Examples of the saponified ethylene-vinyl acetate copolymer include "Technolink (trade name)" manufactured by Taoka Chemical Co., Ltd., "MELTHENE (trade name)" manufactured by Tosoh Corporation, "EVAL (trade name)" manufactured by Kuraray Co., Ltd., and "Soarnol (trade name)" manufactured by Mitsubishi Chemical Corporation.

[0041] The blending amount of the modified polyolefin resin is 0.1-10% by mass, preferably 1-5% by mass. If the blending amount is less than 0.1% by mass, the mechanical strength, particularly the load capacity and the sliding characteristics of the sliding element made of the resin composition cannot be improved due to the improvement of the compressive strength. On the other hand, if the blending amount exceeds 10% by mass, the moldability of the resin composition is deteriorated.

[0042] The plant-derived filler mixed in the resin composition of the present invention is dispersed and contained in a sliding element made of the resin composition to improve the mechanical strength, particularly the compressive strength, of the sliding element and to function as a carrier for absorbing and retaining lubricating oil, as described later. In this plant-derived filler, the filler surface is coated with a modified polyolefin resin, which acts as a compatibilizer to improve compatibility with the resin composition and dispersibility of the plant-derived filler.

[0043] Examples of plant-derived fillers include cellulose nanofibers obtained by mixing cellulose fibers (pulp fibers) of natural plant origin such as wood fibers (conifer pulp such as Japanese Masson pine, Japanese black pine, Sakhalin fir, fish scale pine, red pine, larch, fir, southern Japanese hemlock, Japanese white fir, larch, silver fir, Honshu pine, cypress, Douglas fir, hemlock, white fir, spruce, balsam fir, cedar, pine, southern Asian pine, radiata pine, etc., mixtures thereof, and broadleaf pulp such as beech, birch , alder, oak, red nanmu, castanopsis, birch, Japanese poplar, poplar, Japanese ash, sweet poplar, eucalyptus, mangrove, lauan wood, acacia, etc., and mixtures thereof), bamboo fiber, sugarcane fiber, seed fiber (cotton fiber (cotton linter), kapok, etc.), stem fiber (hemp, parchment, incense, etc.), leaf fiber (abaca, sisal, New Zealand hemp, ramie, etc.), fruit fiber (palm), rush, wheat straw, etc., cellulose particles (powder), and cellulose fiber are manufactured by mechanical fiber separation.

[0044] The average fiber length (L) of the cellulose fibers and cellulose nanofibers as plant-derived fillers is preferably 0.1-100 μm, particularly preferably 0.5-80 μm. Its average fiber diameter (diameter: D) is preferably 4 nm-100 μm, more preferably 4 nm-90 μm. The aspect ratio (L / D) is preferably 2-2,000, more preferably 20-1,000. In addition, the average particle size of the cellulose particles is 50 μm or less, preferably 40 μm or less. Fibers or particles having these properties can improve the dispersibility and affinity of plant-derived polyethylene resins. Therefore, the mechanical strength, especially the compressive strength, of the sliding element made of the resin composition can be improved.

[0045] Specific examples of cellulose fibers and cellulose nanofibers as plant-derived fillers used in the present invention include "Fibra Cel (trade name)" manufactured by Celite Corporation, "Nanoforest (trade name)" manufactured by Chuetsu Pulp & Paper Co., Ltd., "BiNFi-s (Binfis: trade name)" manufactured by Sugino Machine Limited, "cellenpia (trade name)" manufactured by Nippon Paper Industries Co., Ltd., "Serish (trade name)" manufactured by Daicelfinechem Ltd, and "fluorene cellulose (trade name)" manufactured by Osaka Gas Chemicals Co., Ltd. Specific examples of the cellulose particles include "KC flock (trade name)" manufactured by Nippon Paper Industries Co., Ltd., "CEOLUS (trade name)" manufactured by Asahi Kasei Corp., "Tosco hemp Cellulose powder, Tosco Silk Powder, Bamboo Powder (all trade names)" manufactured by TOSCO Co., Ltd., and "Cellulose Powder (trade name)" manufactured by Tdi corp.

[0046] The blending amount of the plant-derived filler is 0.1-50% by mass, preferably 2-30% by mass. If the blending amount is less than 0.1% by mass, the strength of the sliding element made of the resin composition cannot be improved. On the other hand, if the blending amount exceeds 50% by mass, the moldability will deteriorate.

[0047] The lubricating oil blended into the resin composition of the present invention imparts low friction to a sliding member made of the resin composition to improve sliding properties.

[0048] Examples of lubricating oils include paraffinic and cycloparaffinic mineral oils such as spindle oil, refrigeration oil, motor oil, turbine oil, engine oil, cylinder oil and gear oil, etc., animal oils such as whale oil, etc., vegetable oils (whose main components are unsaturated fatty acids such as oleic acid, linoleic acid and linolenic acid) such as linseed oil, tung oil, castor oil, safflower oil, soybean oil, cottonseed oil, palm oil, rapeseed oil, jojoba oil, linoleic acid and linolenic acid, etc., hydrocarbon synthetic oils such as α-olefin oligomers and hydrogenates thereof, α-olefin oligomers such as polybutene, polyisobutylene, 1-octene oligomers, 1-decene oligomers and ethylene-propylene copolymers, etc., and ether synthetic oils such as polyoxyalkylene glycol oils and polyphenyl ether oils, etc.

[0049] The amount of lubricating oil mixed is 0.5-5% by mass, preferably 1-3% by mass. If the amount is less than 0.5% by mass, the sliding property cannot be improved. On the other hand, if the amount exceeds 5% by mass, the mechanical strength of the sliding element decreases, the surface appearance of the sliding element deteriorates, and the biting into the screw occurs.

[0050] In the resin composition of the present invention, a lubricant and a colorant (pigment or dye) may be mixed as additional components.

[0051] In the case where a lubricant is used in combination with the lubricating oil mixed in the resin composition, the amount of the lubricant mixed can be increased because the lubricant acts as a carrier that absorbs and holds the lubricating oil. Thus, the sliding property of the resin composition can be further improved.

[0052] The lubricant is a lubricating oil that becomes liquid when heated for molding. Examples of the lubricant include waxy substances such as natural waxes such as montan wax and palm wax, hydrocarbon waxes, higher fatty acids, and waxes obtained by inducing higher fatty acids, and the like.

[0053] Examples of the hydrocarbon wax include paraffin wax, microcrystalline wax, polyethylene wax, polyethylene oxide wax and the like.

[0054] Examples of higher fatty acids include higher saturated fatty acids having 10 or more carbon atoms, preferably 12 or more carbon atoms, such as lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, arachidic acid, cerotic acid, montanic acid and melissic acid, and unsaturated fatty acids having 12 or more carbon atoms, such as oleic acid, linoleic acid, linolenic acid, elaidic acid, octadecenoic acid, arachidonic acid, eicos-9-enoic acid, erucic acid and octadecatetraenoic acid.

[0055] Examples of the wax obtained by inducing the above-mentioned higher fatty acids include higher fatty acid esters, higher fatty acid amides, higher fatty acid salts and the like.

[0056] The higher fatty acid ester is an ester obtained by reacting a higher fatty acid with an aliphatic alcohol such as a monohydric saturated fatty acid alcohol, a monounsaturated fatty acid alcohol and a polyhydric alcohol.

[0057] Examples of higher fatty acid esters include esters of higher fatty acids having 12 to 26 carbon atoms and monoalcohols having 12 to 24 carbon atoms such as stearyl stearate and behenyl behenate, esters of alkylene glycols having 2 to 6 carbon atoms and higher fatty acids having 12 to 26 carbon atoms such as ethylene glycol mono- or dipalmitate, ethylene glycol mono- or distearate, ethylene glycol mono- or dibehenate, ethylene glycol mono- or dimontanate, triols having 3 to 6 carbon atoms (glycerol, etc.) and esters of alkylene glycols having 12 to 26 carbon atoms Mono-, di- or tri-esters of higher fatty acids having 4 carbon atoms, such as glycerol mono-, di- or tripalmitate, glycerol mono-, di- or tristearate, glycerol mono-, di- or tribehenate, and glycerol mono-, di- or trimontanate; mono-, di-, tri- or tetra-esters of pentaerythritol and higher fatty acids having 14 to 24 carbon atoms, such as pentaerythritol mono-, di-, tri- or tetrapalmitate, pentaerythritol mono-, di-, tri- or tetrastearate, pentaerythritol mono-, di-, tri- or tetrabehenate, and pentaerythritol mono-, di-, tri- or tetramontanate.

[0058] Examples of higher fatty acid amides include saturated higher fatty acid amides such as lauric acid amide, palmitic acid amide, stearic acid amide and behenic acid amide; unsaturated higher fatty acid amides such as erucic acid amide, oleic acid amide, brassinoic acid amide and elaidic acid amide; substituted amides such as N-stearyl stearic acid amide, N-oleyl oleic acid amide, N-stearyl oleic acid amide, N-oleyl stearic acid amide, N-stearyl erucic acid amide and N-oleyl palmitic acid amide; hydroxymethyl amides such as hydroxymethyl stearic acid amide and hydroxymethyl behenic acid amide; saturated fatty acid bisamides such as methylene bis stearic acid amide. Acid amides, ethylene biscapric acid amide, ethylene bislauric acid amide, ethylene bisstearic acid amide (ethylene bisstearyl amide), ethylene bisisostearic acid amide, ethylene bishydroxystearic acid amide, ethylene bisbehenic acid amide, hexamethylene bisstearic acid amide, hexamethylene bisbehenic acid amide, hexamethylene bishydroxystearic acid amide, N,N'-distearyl adipamide and N,N'-distearyl sebacic acid amide; unsaturated fatty acid bisamides such as ethylene bisoleic acid amide, hexamethylene bisoleic acid amide, N,N'-dioleoyl adipamide and N,N'-dioleoyl sebacic acid amide.

[0059] Higher fatty acid salts (metal soaps) are salts of higher fatty acids and alkali metals, alkaline earth metals or zinc. Examples of alkali metals include lithium, sodium and potassium. Examples of alkaline earth metals include magnesium, calcium and barium. Specific examples of the higher fatty acid salts include lithium stearate, calcium stearate, magnesium stearate, zinc stearate, etc.

[0060] Specific examples of these lubricants include “LICOWAX (trade name)” manufactured by Clariant Plastics & Coatings (Japan) KK (as polyethylene oxide wax, which is a hydrocarbon wax), “ANSTEX (trade name)” manufactured by TOHO Chemical Industry Co., Ltd. and “Rikemar (trade name)” manufactured by RIKEN VITAMIN Co., Ltd. (as glyceryl monostearate, which is a higher fatty acid ester), “Diamid (trade name)” manufactured by Mitsubishi Chemical Corporation (as lauric acid amide, which is a higher fatty acid amide, palmitic acid amide and palmitic acid amide), “Kaowax (trade name)” manufactured by Kao Corporation (as ethylene bisstearic acid amide), “Calcium stearate” manufactured by TAIHEI CHEMICAL INDUSTRIAL CO., LTD. (as calcium stearate, which is a higher fatty acid salt) and “zinc stearate” manufactured by NITTO KASEI KOGYO KK (as zinc stearate).

[0061] The amount of lubricant mixed depends on considerations in the amount of lubricating oil mixed. The amount of lubricant mixed is 0.1-5% by mass, preferably 0.5-3% by mass. If the amount mixed is less than 0.1% by mass, the lubricant cannot act as a carrier for absorbing and holding the lubricating oil. On the other hand, if the amount mixed exceeds 5% by mass, the mechanical strength of the sliding element decreases, the surface appearance of the sliding element deteriorates, and poor biting into the screw occurs.

[0062] There is no particular limitation on the colorant. Examples of the colorant include dyes such as azo, anthraquinone and triphenylmethane, and pigments such as titanium dioxide, cadmium sulfide, phthalocyanine and carbon black. The amount of the colorant is 1-5% by mass, preferably 1-3% by mass. If the amount of the colorant is less than 1% by mass, the effect as a colorant is not achieved. On the other hand, if the amount of the colorant exceeds 5% by mass, the sliding property of the sliding element is adversely affected.

[0063] The resin combination of the present invention is easily prepared by a known method that is usually used as a method for preparing a conventional resin combination. For example, the polyethylene resin of plant origin as an additive, the polyethylene resin of petroleum origin, the modified polyolefin resin as an additive, the lubricating oil as an additive, and the filler of plant origin as an additive, or the lubricant and colorant in addition are weighed so that each of them becomes a predetermined amount. They are mixed by a mixer such as a Henschel mixer, a super mixer, a ball mill and a drum mixer to prepare a mixture. Then, the mixture is put into a uniaxial or biaxial screw type extruder, and melt kneading is used to form a rope-shaped molded product (strip material). Thereafter, the rope-shaped molded product is cut to prepare pellets as a molding material. For another example, the polyethylene resin of petroleum origin as an additive, the modified polyolefin resin as an additive, the lubricating oil as an additive and the filler of plant origin as an additive, or the lubricant and colorant in addition are weighed so that each of them becomes a predetermined amount. They are mixed by the same mixer as above to prepare a mixture. Then, the mixture is put into a uniaxial or biaxial screw type extruder and melt-kneaded to form a rope-shaped molded product. Thereafter, the rope-shaped molded product is cut to prepare pellets. Then, these pellets are mixed with a plant-derived polyethylene resin as a main component in a predetermined amount to be used as a molding material.

[0064] The resin composition of the present invention has good bite performance into the screw of the molding machine and excellent molding processability. In addition, the sliding element manufactured according to the resin composition improves the mechanical strength of the plant-derived polyethylene resin and improves the sliding characteristics including low friction and wear resistance in the sliding friction with the matching material.

[0065] Example

[0066] Hereinafter, the present invention will be described in more detail with reference to Examples. However, the present invention is not limited to the following Examples as long as the scope of the present invention is not exceeded. The moldability of the resin composition to the molding material, the moldability of the molding material to the sliding element, and the friction and wear characteristics of the sliding element manufactured from the resin composition were evaluated by the following method.

[0067] <Moldability (1)>

[0068] In the case where the mixture (resin composition) was melt-kneaded using an extruder to form a rope-shaped molded product and then cut to produce pellets, the rope-shaped molded product was visually observed for the presence or absence of cracks (cuts), the biting properties into the screw, and the surface conditions of the pellets (generation of voids (bubbles), etc.). Evaluation was performed according to the evaluation criteria in Table 1.

[0069] Table 1

[0070] ◎…Excellent

[0071] ○…Good

[0072] ×…Impossible

[0073] <Moldability (2)>

[0074] In the case where the sliding element was molded from pellets using an injection molding machine, the biting characteristics into the screw, the demoldability of the sliding element from the mold, and the surface conditions (peeling, etc.) of the sliding element product were visually observed.

[0075] Table 2

[0076] ◎…Excellent

[0077] ○…Good

[0078] ×…Impossible

[0079] <Friction and wear characteristics>

[0080] The friction coefficient and wear volume were measured using a piercing tester under the conditions shown in Table 3. Figure 1 As shown, a square bearing test piece (sliding element) 1 with a side length of 30 mm and a thickness of 3 mm is fixed to the test bench. Then, when a predetermined load is applied to one surface 3 of the bearing test piece 1 from a cylinder 2 as a relative element in a direction X perpendicular to the surface 3, the cylinder 2 rotates around the axis 4 of the cylinder 2 in a direction Y. And the friction coefficient between the bearing test piece 1 and the cylinder 2 and the amount of wear on the surface 3 of the bearing test piece 1 after the test are measured. The friction coefficient is shown by the friction coefficient of the stability time from 1 hour after the start of the test to the end of the test. The wear amount is shown by the amount of dimensional change of the sliding surface after a test time of 8 hours.

[0081] Table 3

[0082]

[0083]

[0084] In the following examples, the following materials were used as plant-derived polyethylene resin, petroleum-derived polyethylene resin, modified polyolefin resin, lubricating oil, plant-derived filler, lubricant and colorant. The following materials all represent trade names.

[0085] [A] Plant-derived polyethylene resin

[0086] (A-1) Plant-derived high-density polyethylene resin (HDPE)

[0087] "GREEN-SHE 150", manufactured by Braskem SA. Density 0.948 g / cm 3 , MFR (melt flow rate: temperature 190°C, load 2.16kg) 1.0g / 10min;

[0088] [B] Petroleum-derived polyethylene resin

[0089] (B-1) High-density polyethylene resin

[0090] "HI-ZEX (trade name)", manufactured by Prime Polymer Co., Ltd.

[0091] (B-2) Ultra-high molecular weight polyethylene resin

[0092] "MIPELON (trade name)", manufactured by Mitsui Chemicals, Inc.

[0093] (B-3) Maleic anhydride acid-modified ultra-high molecular weight polyethylene resin

[0094] "MODIFIED LUBMER (trade name)", manufactured by Mitsui Chemicals, Inc.

[0095] [C] Modified polyolefin resin

[0096] (C-1) Saponified ethylene-vinyl acetate copolymer

[0097] "Technolink K431-80", manufactured by Taoka Chemical Co., Ltd. (vinyl acetate content before saponification: 28 mass %, saponification degree: 80%, MFR: 4 g / 10 min: 190°C, load: 2.16 kg).

[0098] (C-2) Saponified ethylene-vinyl acetate copolymer

[0099] "MELTHENE H-6051", manufactured by Tosoh Corporation (vinyl acetate content before saponification: 28 mass %, saponification degree: 100%, MFR: 5.5 g / 10 min: 190°C, load: 2.16 kg).

[0100] (C-3) Maleic anhydride modified polyethylene resin

[0101] "ADMER-NF 518", manufactured by Mitsui Chemicals, Inc. (MFR 2.2 g / 10 min: 230°C, load 2.16 kg).

[0102] (C-4) Maleic anhydride modified ethylene-propylene copolymer

[0103] "TAFMER-MP 0620", manufactured by Mitsui Chemicals, Inc. (MFR 0.3 g / 10 min: 230°C, load 2.16 kg).

[0104] (C-5) Maleic anhydride modified ethylene-butene copolymer

[0105] "TAFMER-MH 7020", manufactured by Mitsui Chemicals, Inc. (MFR 1.5 g / 10 min: 230° C., load 2.16 kg).

[0106] (C-6) Maleic anhydride modified styrene-ethylene / butylene-styrene copolymer

[0107] "Tuftec H 1517", manufactured by Asahi Kasei Chemicals Co., Ltd. (MFR 3.0 g / 10 min: 230°C, load 2.16 kg).

[0108] [D] Lubricating oil

[0109] (D-1) Paraffin oil

[0110] "MORESCO WHITE P-350P", manufactured by MORESCO Corporation.

[0111] (D-2) Hydrocarbon-based synthetic oil (ethylene α-olefin oligomer)

[0112] "LUCANT", manufactured by Mitsui Chemicals, Inc.

[0113] (D-3) Vegetable oil (Jojoba oil)

[0114] "Jojoba golden", imported by Mitsuba Tratring Co., Ltd.

[0115] [E] Fillers of plant origin

[0116] (E-1) Cellulose fiber

[0117] "Fibra Cel SW-10: plant origin, average fiber diameter 20 μm, average fiber length 700 μm", manufactured by Celite Corporation.

[0118] (E-2) Cellulose nanofibers

[0119] "Serish KY-100G: average fiber diameter 100nm", manufactured by Daicel finechem Ltd,

[0120] (E-3) Cellulose particles (wood pulp)

[0121] "KC flock: average particle diameter 37 μm", manufactured by Nippon Paper Industries Co., Ltd.

[0122] (E-4) Bamboo fiber

[0123] “Bamboo powder: average particle size 178 μm”, manufactured by NAKAWOOD Co., Ltd.

[0124] (E-5) Hemp fiber

[0125] “Tosco hemp cellulose powder: average particle size 22 μm”, manufactured by TOSCO Co., Ltd.

[0126] (E-6) Tree Particles

[0127] “Cedar powder: average particle size 178 μm”, manufactured by NAKAWOOD Co., Ltd.

[0128] [F] Lubricant

[0129] (F-1) Hydrocarbon wax (polyethylene oxide wax)

[0130] "LICOWAX", manufactured by Clariant Plastics & Coatings (Japan) KK.

[0131] (F-2) Higher fatty acid amide (ethylene bisstearic acid amide)

[0132] "Kaowax", manufactured by Kao Corporation.

[0133] (F-3) Higher fatty acid ester (glyceryl monostearate)

[0134] "ANSTEX", manufactured by TOHO Chemical Industry Co., Ltd.

[0135] [G] Colorants

[0136] (G-1) Carbon black

[0137] "KETJENBLACK", manufactured by LION SPECIALTY CHEMICALS CO.,LTD.

[0138] (G-2) Phthalocyanine Blue

[0139] "Pigment Blue 15", manufactured by Tokyo Chemical Industry Co., Ltd.

[0140] Examples 1-20

[0141] A polyethylene resin of plant origin as a main component, a polyethylene resin of petroleum origin (B-1) to (B-3) as an additive, a modified polyolefin resin (C-1) to (C-6), a lubricating oil (D-1) to (D-3), a filler of plant origin (E-1) to (E-6), a lubricant (F-1) to (F-3), and a colorant (G-1) to (G-2) are prepared and weighed in the ratio of the amounts shown in Table 4-7. Next, they are mixed with a drum mixer to prepare a mixture. Then, the mixture is supplied to a twin-shaft screw discharge type extruder and melt-kneaded to form a rope-shaped molded product. Thereafter, the rope-shaped molded product is cut to prepare pellets, which are used as a molding material. In the manufacturing method, the presence or absence of cracks (cuts) in the rope-shaped molded product, the bite performance into the screw, and the surface conditions of the pellets (generation of voids, etc.) are visually observed. These evaluations are shown in the characteristics of Table 4-7.

[0142] Next, the molding material was supplied to a screw type injection molding machine, and injection molding was performed to produce a square type sliding element having a size of 30 mm side length and 3 mm thickness. In the manufacturing method, the bite performance of the pellets into the screw when the sliding element was molded from the pellets, the demoulding property of the square type sliding element from the mold, and the surface condition (peeling, etc.) of the sliding element were visually observed. These evaluations are shown in the characteristics of Table 4-7. In addition, the evaluation results of the friction coefficient and the wear amount of the square type sliding element based on the above evaluation method are shown in the characteristics of Table 4-7.

[0143] Comparative Examples 1-4

[0144] A polyethylene resin of plant origin, a polyethylene resin of petroleum origin (B-3), a modified polyolefin resin (C-2), a lubricating oil (D-3), a filler of plant origin (E-3), a lubricant (F-3) and a colorant (G-1) as additives similar to the above are prepared and weighed in the ratio of the amounts shown in Table 7. Next, they are mixed with a drum mixer to prepare a mixture. Then, the mixture is supplied to a twin-shaft screw discharge type extruder and melt-kneaded to form a rope-shaped molded product. Thereafter, the rope-shaped molded product is cut to prepare pellets, which are used as molding materials. In the manufacturing method, the presence or absence of cracks (cuts) in the rope-shaped molded product, the bite performance into the screw, and the surface conditions of the pellets (generation of voids, etc.) are visually observed. These evaluations are shown in the characteristics of Table 8.

[0145] Next, the molding material was supplied to a screw type injection molding machine, and injection molding was performed to produce a square type sliding element having a size of 30 mm side length and 3 mm thickness. In the manufacturing method, the bite performance of the pellets into the screw when the sliding element was molded from the pellets, the demolding property of the square type sliding element from the mold, and the surface condition (peeling, etc.) of the sliding element were visually observed. These evaluations are shown in the characteristics of Table 8. In addition, the evaluation results of the friction coefficient and the wear amount of the square type sliding element based on the above evaluation method are shown in the characteristics of Table 8.

[0146] Table 4

[0147]

[0148]

[0149] Table 5

[0150]

[0151]

[0152] Table 6

[0153]

[0154]

[0155] Table 7

[0156]

[0157]

[0158] Table 8

[0159]

[0160]

[0161] From the above test results, Examples 1-20 of the resin composition have good biting performance into the screw during extrusion. In addition, no cracks (cuts) of the rope-shaped molded product were observed in the molding method of the rope-shaped molded product. In addition, it has been confirmed that the molding material (pellets) formed by the rope-shaped molded product has good biting performance into the screw of the molding machine and has excellent molding processability. In addition, it has been confirmed that the surface of the molded product does not have peeling and has excellent surface conditions. On the other hand, Comparative Examples 1-3 of the resin composition have no particular problems in terms of the biting performance into the screw during extrusion, the moldability of the rope-shaped molded product and the moldability of the molding material formed by the rope-shaped molded product. However, in Comparative Example 4 of the resin composition, the biting performance into the screw during extrusion is poor, and a good rope-shaped molded product cannot be obtained.

[0162] In addition, the sliding elements of Examples 1-20 manufactured by the resin composition all show low friction coefficients and small wear. On the other hand, the sliding element of Comparative Example 1 manufactured by the resin composition shows high friction coefficients and very large wear. Specifically, the sliding elements of Comparative Examples 2-3 manufactured by the resin composition show very large wear. In Comparative Example 4 of the resin composition, friction and wear characteristics were not tested because the molding material could not be obtained, so the sliding element could not be obtained. As can be seen from the above, the sliding element made of the resin composition of the embodiment has excellent sliding characteristics compared to the sliding element made of the resin composition of the comparative example.

[0163] As described above, the resin composition and sliding element of the present invention have good bite performance into the screw and excellent molding processability. In addition, the molded product has no peeling on the surface and has excellent surface conditions. In addition, according to the sliding element made of the resin composition, the sliding characteristics including low friction and wear resistance in the sliding friction of the relative element are significantly improved. Therefore, according to the present invention, such a resin composition and sliding element can be provided.

[0164] Reference numerals list

[0165] 1 Bearing test piece (sliding element)

[0166] 2 Cylinders (opposite components)

[0167] 4 Axis

Claims

1. A resin composition for a sliding element, comprising: a plant-derived polyethylene resin as a main component and having a plant degree of 80% or more, wherein the plant-derived polyethylene resin consists of a plant-derived high-density polyethylene resin, In addition, as additives, there are 0.1-20% by mass of polyethylene resin derived from petroleum, 0.1-10% by mass of modified polyolefin resin, 0.5-5% by mass of lubricating oil, and 0.1-50% by mass of plant-derived filler. The lubricating oil is selected from paraffinic and cycloparaffinic mineral oils, vegetable oils and hydrocarbon synthetic oils, The petroleum-derived polyethylene resin is selected from high-density polyethylene resin, ultra-high molecular weight polyethylene resin and acid-modified ultra-high molecular weight polyethylene resin, wherein the modified polyolefin resin is selected from a polyolefin resin graft-modified with an unsaturated carboxylic acid, an anhydride thereof or a derivative thereof, and a saponified polyolefin resin obtained by saponifying a polyolefin resin having an acetoxy group in the molecular chain with an alkali, and The plant-derived filler is selected from cellulose fibers, cellulose particles and cellulose nanofibers.

2. The resin composition for a sliding element according to claim 1, wherein: The polyolefin resin graft-modified with unsaturated carboxylic acid, its anhydride or its derivative is selected from maleic anhydride-modified polyethylene resin, maleic anhydride-modified polypropylene resin, maleic anhydride-modified ethylene-α-olefin copolymer and maleic anhydride-modified styrene-ethylene / butylene-styrene copolymer.

3. The resin composition for a sliding element according to claim 1, wherein: The saponified polyolefin resin consists of a saponified ethylene-vinyl acetate copolymer.

4. The resin composition for a sliding element according to any one of claims 1 to 3, wherein: As an additive, a lubricant selected from natural waxes, hydrocarbon waxes, higher fatty acids, higher fatty acid esters, higher fatty acid amides and higher fatty acid salts is mixed at a ratio of 0.1 to 5% by mass.

5. The resin composition for a sliding element according to any one of claims 1 to 3, wherein: As an additive, a colorant composed of a pigment or a dye is mixed at a ratio of 1 to 5% by mass.

6. The resin composition for a sliding element according to claim 4, wherein: As an additive, a colorant composed of a pigment or a dye is mixed at a ratio of 1 to 5% by mass.

7. A sliding element made of the resin composition for a sliding element according to any one of claims 1 to 6.

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