Grease composition

Abstract

To provide a grease composition capable of reducing a steel-resin friction coefficient.SOLUTION: A grease composition according to the present invention contains a base oil having a kinematic viscosity at 100°C of 5-30 mm2 / s, a thickener, a polymer having a weight-average molecular weight of 1,000-500,000, and an aliphatic amide compound and is used for sliding between steel and resin.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a grease composition used between steel and resin.

Background Art

[0002] Grease compositions are mainly used for sliding bearings, rolling bearings (bearings), or sliding surfaces where it is difficult to maintain a lubricating oil film due to the movement of the contact surface. The members constituting the sliding surface are mainly made of metal, but in recent years, for the purpose of weight reduction, a resin material may be used for a part of the sliding member. However, in addition to the different forms of friction and wear between steel (metal)-resin sliding and metal-metal sliding, the adsorption of the grease composition to the sliding surface and the reactivity of the additives are different. Therefore, even if a grease composition suitable for metal-metal sliding is directly applied to the sliding part between steel and resin, the expected performance may not be obtained.

[0003] As a grease composition used between steel and resin, a grease composition for resin lubrication containing a base oil, a diurea compound as a thickener, and a chain hydrocarbon polymer with a weight average molecular weight of 20,000 to 30,000 has been proposed (Patent Document 1). However, in recent years, in order to promote energy saving in sliding parts such as bearings, further reduction of friction is required for the grease composition applied to the sliding parts.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The problem to be solved by the present invention is to provide a grease composition that reduces the friction coefficient between steel and resin. [Means for solving the problem]

[0006] In order to solve the above problems, the inventors conducted diligent research and found that by using a thickener, an aliphatic amide compound, and an oil-soluble polymer in the base oil, it is possible to create a grease composition that is suitable for sliding between steel and resin and reduces the coefficient of friction. This invention is based on the aforementioned findings and consists of the following:

[0007] <1> Kinematic viscosity at 100°C is 5-30 mmHg 2 A grease composition containing a base oil of / s, a thickener, a polymer with a weight-average molecular weight of 1,000 to 500,000, and an aliphatic amide compound, used for sliding between steel and resin. <2> The aliphatic amide compound is a saturated aliphatic amide compound. <1> The grease composition described above. <3> The thickener is a urea-based thickener. <1> or <2> The grease composition described above. <4> The urea thickener is a diurea compound represented by the following formula (1). <3> The grease composition described above. R 1 -NHCONH-R 2 -NHCONH-R 3 (1) (In formula (1), R 1 and R 3 R represents an aliphatic hydrocarbon group having 4 to 24 carbon atoms that may have substituents, an alicyclic hydrocarbon group having 6 to 15 carbon atoms that may have substituents, or an aromatic hydrocarbon group having 6 to 15 carbon atoms that may have substituents. 2 (This represents a divalent aromatic hydrocarbon group having 6 to 15 carbon atoms, which may have substituents.) <5> The base oil contains poly-α-olefins. <1> ~ <4> A grease composition as described in any of the following. [Effects of the Invention]

[0008] The grease composition of the present invention has a special effect of reducing the friction coefficient in the sliding between steel and resin.

Mode for Carrying Out the Invention

[0009] Hereinafter, the present invention will be described in detail according to its preferred embodiments. In this specification, unless otherwise specified, the notation "X to Y" for numerical values X and Y means "X or more and Y or less". In such notation, when only the numerical value Y is provided with a unit, the unit shall also apply to the numerical value X.

[0010] The grease composition of the present invention contains a base oil, a thickener, a polymer having a weight average molecular weight of 1,000 to 500,000, and an aliphatic amide compound.

[0011] 〔Base Oil〕 As the base oil of the present invention, either a mineral oil-based base oil or a synthetic oil-based base oil can be used. The kinematic viscosity of the base oil of the present invention at 100 °C is 5 to 30 mm 2 / s, preferably 8 mm 2 / s or more, more preferably 10 mm 2 / s or more, preferably 27 mm 2 / s or less, more preferably 25 mm 2 / s or less. In one embodiment, the kinematic viscosity at 100 °C is preferably 8 to 27 mm 2 / s, more preferably 10 to 25 mm 2 / s. When the kinematic viscosity at 100 °C is at least the above lower limit value, the friction coefficient between steel and resin can be reduced, and when it is at most the above upper limit value, the low-temperature fluidity of the grease composition is improved.

[0012] The kinematic viscosity of the base oil of the present invention at 40 °C is preferably 40 mm 2 / s or more, more preferably 60 mm 2 / s or more, preferably 300 mm 2 / s or less, more preferably 230 mm 2It is less than or equal to / s. In one embodiment, the kinematic viscosity at 40°C is preferably 40 to 300 mm². 2 / s, more preferably 60~230mm 2 It is / s. In this specification, kinematic viscosity at 100°C or 40°C refers to the kinematic viscosity at 100°C or 40°C measured in accordance with JIS K2283:2000, respectively.

[0013] The viscosity index of the base oil of the present invention is preferably 90 or higher, more preferably 120 to 150, the pour point is preferably -10°C or lower, more preferably -15°C or lower, and the flash point is preferably 200°C or higher. In this specification, viscosity index refers to values ​​measured in accordance with JIS K2283:2000, pour point in accordance with JIS K2269:1987, and flash point in accordance with JIS K2265-4:2007.

[0014] Mineral oil-based base oils include base oil fractions obtained by distilling crude oil at atmospheric pressure, or by further distilling it under reduced pressure, and then refining the distillate through various refining processes. Refining processes include hydrorefining, solvent extraction, solvent dewaxing, hydrodewaxing, sulfuric acid washing, and clay treatment, and mineral oil-based base oils can be obtained by combining these processes in an appropriate order. Mixtures of multiple refined oils with different properties obtained by combining and ordering different crude oils or distillates are also useful. In any of these methods, the properties of the resulting base oil can be preferably used after adjusting them to satisfy the aforementioned physical properties.

[0015] As the synthetic base oil, it is preferable to use a base material with excellent hydrolysis stability. Examples include polyolefins such as poly-α-olefins, polybutenes, and copolymers of two or more olefins; ester-based synthetic oils such as diesters and polyol esters; ether-based synthetic oils such as alkyldiphenyls and polypropylene glycols; polyalkylene glycols, alkylbenzenes, and alkylnaphthalenes. Among these, poly-α-olefins are preferred in terms of oxidation stability and low-temperature fluidity.

[0016] The base oil can be the synthetic base oils exemplified, either alone or in a mixture of two or more. Furthermore, it can also be used in a mixture with the mineral oil-based base oil. When using a mixture of multiple base oils, including synthetic base oils, the mixture can be used even if the individual base oils before mixing fall outside the range of the above-mentioned physical properties, as long as the mixture satisfies the above-mentioned physical properties. Therefore, individual synthetic base oils do not necessarily need to satisfy the above-mentioned physical properties, but it is preferable that they are within the range of the above-mentioned physical properties.

[0017] The base oil content is preferably 50% by mass or more, more preferably 60% by mass or more, preferably 95% by mass or less, and more preferably 85% by mass or less, based on the total amount of the grease composition. In one embodiment, the base oil content is preferably 50 to 95% by mass, more preferably 60 to 85% by mass. By having a base oil content above the lower limit, appropriate lubricity can be ensured, and by having a base oil content below the upper limit, the base oil is more easily retained in the grease composition.

[0018] [Thickener] In the present invention, either a urea-based thickener or a metal soap-based thickener can be used.

[0019] <Urea-based thickeners>

[0020] Examples of urea-based thickeners that can be used include diurea compounds obtained by the reaction of diisocyanate with a monoamine, and polyurea compounds obtained by the reaction of diisocyanate with a monoamine or diamine.

[0021] A diisocyanate is a compound in which two hydrogen atoms of a hydrocarbon are replaced by an isocyanate group. The hydrocarbon may be an acyclic or cyclic hydrocarbon, and may be an aromatic hydrocarbon, an alicyclic hydrocarbon, or an aliphatic hydrocarbon. The number of carbon atoms in the hydrocarbon is preferably 6 to 15, more preferably 8 to 14. Preferred specific examples of diisocyanates include phenylenediisocyanate, tolylene diisocyanate, biphenyl diisocyanate (diphenyl diisocyanate), diphenylmethane diisocyanate, hexane diisocyanate, decanediisocyanate, and the like. Diisocyanates may be used individually or in combination of two or more types.

[0022] A monoamine is a compound in which one hydrogen atom of ammonia is replaced by a hydrocarbon group, while a diamine is a compound in which two hydrogen atoms of ammonia are replaced by hydrocarbon groups. Preferably, the monoamines used are aliphatic amines in which one hydrogen atom of ammonia is substituted with an aliphatic hydrocarbon group having 4 to 24 carbon atoms, alicyclic amines in which one hydrogen atom of ammonia is substituted with an alicyclic hydrocarbon group having 6 to 15 carbon atoms, or aromatic amines in which one hydrogen atom of ammonia is substituted with an aromatic hydrocarbon group having 6 to 15 carbon atoms. The substituents of the aliphatic amine, alicyclic amine, and aromatic amine may each have further substituents. Preferred examples of monoamines include octylamine, dodecylamine, hexadecylamine, octadecylamine, oleylamine, aniline, p-toluidine, and cyclohexylamine. Preferred examples of diamines include ethylenediamine, propanediamine, butanediamine, hexanediamine, octanediamine, phenylenediamine, tolylenediamine, xylenediamine, and diaminodiphenylmethane.

[0023] As a urea-based thickener, a diurea compound obtained by the reaction of the above-mentioned diisocyanate with a monoamine and represented by the following formula (1) is preferred.

[0024] (chemical 1) R 1 -NHCONH-R 2 -NHCONH-R 3 (1) In formula (1), R 1 and R 3 R represents an aliphatic hydrocarbon group having 4 to 24 carbon atoms that may have substituents, an alicyclic hydrocarbon group having 6 to 15 carbon atoms that may have substituents, or an aromatic hydrocarbon group having 6 to 15 carbon atoms that may have substituents. 2 This represents a divalent aromatic hydrocarbon group having 6 to 15 carbon atoms, which may have substituents. R 1 and R 3 If it is an aliphatic hydrocarbon group, the number of carbon atoms is more preferably 8 to 18; if it is an alicyclic hydrocarbon group, the number of carbon atoms is more preferably 6 to 12; and if it is an aromatic hydrocarbon group, the number of carbon atoms is more preferably 7.

[0025] R 1 and R 3 These may be the same or different, but from the viewpoint of raising the droplet point of the grease composition, it is preferable that at least one of them be an alicyclic hydrocarbon group.

[0026] <Metal soap-based thickeners> Examples of metal soap-based thickeners include single soaps and complex soaps. A single soap is a metal soap produced by saponifying fatty acids or oils with alkali metal hydroxides or alkaline earth metal hydroxides. A complex soap is a compound formed by combining the fatty acids used in single soaps with organic acids having different molecular structures. The fatty acid may be a fatty acid derivative having a hydroxyl group, etc. A monovalent or divalent aliphatic carboxylic acid is preferred as the fatty acid. A fatty acid with 6 to 20 carbon atoms is preferred, and a monovalent aliphatic carboxylic acid with 12 to 20 carbon atoms or a divalent aliphatic carboxylic acid with 6 to 14 carbon atoms is more preferred. A monovalent aliphatic carboxylic acid containing one hydroxyl group is preferred as the fatty acid. As the organic acid to be combined with the fatty acid in the complex soap, acetic acid, azelaic acid, sebacic acid, or other dibasic acids, or benzoic acid are preferred. As metal soap thickeners, alkali metals such as lithium and sodium, alkaline earth metals such as calcium, or amphoteric metals such as aluminum are used.

[0027] This thickener may be formulated in the form of a metal soap, or it may be formulated by separately combining a carboxylic acid and a metal source (metal salt, metal salt hydroxide, etc.) and reacting them during grease preparation to produce a metal soap thickener. Such metal carboxylate salts may be used individually or in combination of several types. For example, a mixture of lithium 12-hydroxystearate and lithium azelaate is preferred.

[0028] The thickener of the present invention may be used as a single type or as a mixture of multiple types. The content of the thickener should be such that the desired consistency is obtained, for example, preferably 2 to 30% by mass, more preferably 5 to 20% by mass, based on the total amount of the grease composition. As the thickener of the present invention, it is preferable to use a urea-based thickener from the viewpoint of heat resistance at high temperatures and the lubricity of the thickener itself.

[0029] 〔polymer〕 The polymer of the present invention has a weight-average molecular weight of 1,000 to 500,000. Preferably, the weight-average molecular weight is 2,000 or more, more preferably 5,000 or more, even more preferably 100,000 or more, preferably 450,000 or less, more preferably 400,000 or less, and even more preferably 300,000 or less. In one embodiment, the weight-average molecular weight is preferably 2,000 to 450,000, more preferably 5,000 to 400,000, and even more preferably 100,000 to 300,000. When the weight-average molecular weight is above the lower limit, the lubricity of the grease composition is improved, and when it is below the upper limit, the low-temperature fluidity is improved.

[0030] In this specification, the weight-average molecular weight of the polymers refers to the value obtained by gel permeation chromatography (GPC) (molecular weight obtained in terms of polystyrene equivalent). The measurement conditions are as follows: [GPC measurement conditions] Equipment: Waters Corporation ACQUITY® APC UV RI system Columns: Two Waters Corporation ACQUITY® APC XT900A columns (gel particle size 2.5 μm, column size (inner diameter x length) 4.6 mm x 150 mm) and one Waters Corporation ACQUITY® APC XT200A column (gel particle size 2.5 μm, column size (inner diameter x length) 4.6 mm x 150 mm) are connected in series from upstream to downstream. Column temperature: 40℃ Sample solution: 1.0% by mass tetrahydrofuran solution of the sample. Flow rate: 0.8mL / min Detection device: Differential refractive index detector Reference material: Standard polystyrene (Agilent EasiCal® PS-1, manufactured by Agilent Technologies) 8 points (molecular weight: 2,698,000, 660,500, 325,600, 128,600, 69,650, 30,230, 9,960, 2,980)

[0031] The polymers of the present invention are not limited to the following, but examples include ethylene-α-olefin copolymers, poly(meth)acrylates, styrene-diene copolymers, and polybutenes.

[0032] <Ethylene-α-olefin copolymer> Ethylene-α-olefin copolymers contain ethylene and α-olefins having 3 or more carbon atoms as monomer units. Examples of α-olefins having 3 or more carbon atoms include propylene, 1-butene, 1-pentene, 3-methyl-1-butene, 1-hexene, 4-methyl-1-pentene, 3-methyl-1-pentene, 1-octene, and 1-decene, with propylene being preferred.

[0033] The ethylene unit content in the ethylene-α-olefin copolymer may be, for example, 30-80 mol%, 35-75 mol%, or 40-70 mol%, based on the total amount of monomer units. Furthermore, the α-olefin unit content in the ethylene-α-olefin copolymer may be, for example, 20-70 mol%, 25-65 mol%, or 30-60 mol%, based on the total amount of monomer units.

[0034] <Poly(meth)acrylate> The poly(meth)acrylate preferably contains a structural unit represented by the following general formula (2). In this specification, "(meth)acrylate" means "acrylate and / or methacrylate". JPEG0007843155000001.jpg4161 (in formula (2), R 4 R represents a hydrogen or methyl group. 5 (This represents a linear or branched hydrocarbon group with 1 to 18 carbon atoms.) In one embodiment, R 5 These are hydrocarbon groups with 1 to 5 carbon atoms, hydrocarbon groups with 6 to 18 carbon atoms, or combinations thereof.

[0035] <Styrene-diene copolymer> Styrene-diene copolymers contain, as monomer units, one or more styrene-based monomers selected from styrene and its hydrides, and one or more diene-based monomers selected from dienes and their hydrides. Examples of dienes include butadiene and isoprene.

[0036] The content of styrene monomer units in the styrene-diene copolymer may be, for example, 1 to 30 mol% or 5 to 20 mol% based on the total amount of monomer units. Furthermore, the content of diene monomer units in the styrene-diene copolymer may be, for example, 70 to 99 mol% or 80 to 95 mol% based on the total amount of monomer units.

[0037] <Polybutene> Polybutene is a polymer obtained by polymerizing butenes having double bonds. Polybutene may be a polymer represented by the following general formula (3), for example.

[0038] [ka]

[0039] In equation (3), n represents an integer between 5 and 90.

[0040] Polybutene may be used as a commercially available product or manufactured by a known method. One example of a method for producing polybutene is to remove butadiene from the C4 fraction produced by naphtha cracking and polymerize it using an acid catalyst.

[0041] The polymer of the present invention may be used alone or in combination of two or more polymers. From the viewpoint of further reducing friction in the grease composition, it is preferable to use an ethylene-α-olefin polymer.

[0042] The polymer of the present invention may be used in its pure form, or as a diluted product obtained by diluting it with a light oil such as kerosene or diesel fuel. The polymer content of the present invention (excluding diluent oil) is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, even more preferably 0.4% by mass or more, preferably 10% by mass or less, more preferably 8% by mass or less, and even more preferably 6% by mass or less, based on the total amount of the grease composition. In one embodiment, the polymer content is preferably 0.1 to 10% by mass, more preferably 0.2 to 8% by mass, and even more preferably 0.4 to 6% by mass. When the polymer content is above the lower limit, the coefficient of friction between steel and resin is further reduced, and when it is below the upper limit, the low-temperature fluidity of the grease composition is improved.

[0043] [Aliphatic amide compounds] The aliphatic amide compounds used in the present invention include aliphatic monoamides having one amide group (-NH-CO-), aliphatic bisamides having two amide groups, and aliphatic triamides having three amide groups. The monoamide can be either a monoamine acid amide or a monoacid acid amide, and the bisamide can be either a diamine acid amide or a diacid acid amide. The aliphatic amide compounds that are preferably used have a melting point of 40 to 180°C, more preferably 80 to 180°C, and even more preferably 100 to 170°C, and a molecular weight of 242 to 932, more preferably 298 to 876. Aliphatic monoamides, aliphatic bisamides, and aliphatic triamides are represented by the following general formulas (4), (5) or (6), and (7), respectively.

[0044] R 6 -CO-NH-R 7 ...(4) R 6 -CO-NH-A 1 -NH-CO-R 7 ...(5) R 6-NH-CO-A 1 -CO-NH-R 7 ...(6) R 6 -MA 1 -CH(A 2 -MR 7 )-A 3 -MR 7 ...(7)

[0045] In each of the above formulas, R 6 and R 7 Each of these is an aliphatic hydrocarbon group having 5 to 25 carbon atoms. In the case of general formula (4), R 7 This also includes the case where R is hydrogen. 6 and R 7 The number of carbon atoms is preferably 10 or more, more preferably 15 or more, preferably 20 or less, and more preferably 17 or less. In one embodiment, R 6 and R 7 The number of carbon atoms is preferably 10 to 20, more preferably 15 to 17. 6 and R 7 When the number of carbon atoms is above the lower limit, the coefficient of friction between steel and resin is further reduced, and when it is below the upper limit, the low-temperature fluidity of the grease composition is improved. A 1 , A 2 , and A 3 Each of these is independently an aliphatic hydrocarbon group, an alicyclic hydrocarbon group, or an aromatic hydrocarbon group having 1 to 10 carbon atoms, or a divalent hydrocarbon group having 1 to 10 carbon atoms in combination thereof, and M is an amide group (-NH-CO- or -CO-NH-). Furthermore, if the aliphatic amide compound is a monoamide, R 7 Preferably, it is hydrogen or an aliphatic hydrocarbon group having 10 to 20 carbon atoms. Furthermore, if the aliphatic amide compound is a diamine acid amide, then A 1 Preferably, it is a divalent saturated chain hydrocarbon group having 1 to 4 carbon atoms. Furthermore, in equations (5) and (6), R 6 , R 7, or A 1 The hydrocarbon group represented by may have some of its hydrogen atoms replaced by hydroxyl groups (-OH).

[0046] Examples of aliphatic monoamides include saturated fatty acid amides such as lauric acid amide, palmitic acid amide, stearic acid amide, behenic acid amide, and hydroxystearic acid amide; unsaturated fatty acid amides such as oleic acid amide and erucic acid amide; and substituted amides with saturated or unsaturated long-chain fatty acids and long-chain amines, such as stearyl stearate amide, oleyl oleic acid amide, oleyl stearate amide, and stearyl oleic acid amide.

[0047] Examples of diamine acid amides represented by formula (5) include ethylenebisstearate, ethylenebisisostearate, ethylenebisoleamide, methylenebislaurate, hexamethylenebisoleamide, and hexamethylenebishydroxystearate. Examples of diacid bisamides represented by formula (6) include N,N'-bisstearylsebacinamide.

[0048] As for the aliphatic amide compound of the present invention, from the viewpoint of reducing friction, R 6 and R 7 A saturated aliphatic amide is preferred in which at least one of the groups is a saturated aliphatic hydrocarbon group. Furthermore, as the aliphatic amide compound of the present invention, aliphatic bisamide or aliphatic triamide is preferred from the viewpoint of reducing friction, and aliphatic bisamide is more preferred.

[0049] The aliphatic amide compounds of the present invention may be used individually or in combination of two or more. The content of the aliphatic amide compounds of the present invention is preferably 1% by mass or more, more preferably 2% by mass or more, even more preferably 4% by mass or more, preferably 30% by mass or less, more preferably 20% by mass or less, and even more preferably 15% by mass or less, based on the total amount of the grease composition. In one embodiment, the content of the aliphatic amide compounds is preferably 1 to 30% by mass, more preferably 2 to 20% by mass, and even more preferably 4 to 15% by mass. When the content of the aliphatic amide compounds is above the lower limit, the coefficient of friction between steel and resin is further reduced, and when it is below the upper limit, the low-temperature fluidity of the grease composition is improved. Furthermore, when this aliphatic amide compound is heated and melted in the presence of a base oil, the base oil is retained within the amide compound, which forms a three-dimensional network structure. This results in a lower coefficient of friction between steel and resin compared to simply dispersing and mixing the amide compound in grease.

[0050] [Other additives] In addition to the above components, the grease composition of the present invention may optionally contain solid lubricants, anti-wear agents or extreme pressure agents, antioxidants, oiliness agents, rust inhibitors, corrosion inhibitors, and other substances commonly used in lubricating oils and greases.

[0051] Examples of solid lubricants include graphite, graphite fluoride, melamine cyanurate, polytetrafluoroethylene, molybdenum disulfide, antimony sulfide, boron nitride, and alkali (earth) metal borates. When a grease composition contains a solid lubricant, its content is usually 0.1 to 20% by mass based on the total amount of the grease composition.

[0052] Examples of anti-wear agents or extreme pressure agents include organozinc compounds such as zinc dialkyldithiophosphate and zinc dialkyldithiocarbamate, sulfur-containing compounds such as molybdenum dialkyldithiocarbamate, dihydrocarbyl polysulfide, sulfur esters, thiazole compounds, and thiadiazole compounds; and phosphorus-based extreme pressure agents such as phosphate esters, acidic phosphate esters, amine salts of acidic phosphate esters, and phosphite esters. When a grease composition contains an anti-wear agent or extreme pressure agent, its content is usually 0.1 to 10% by mass based on the total amount of the grease composition.

[0053] Examples of antioxidants include phenolic compounds such as 2,6-di-t-butylphenol and 2,6-di-t-butyl-p-cresol, and amine compounds such as diphenylamine, dialkyldiphenylamine, phenyl-α-naphthylamine, and p-alkylphenyl-α-naphthylamine. When a grease composition contains an antioxidant, its content is usually 0.5 to 10% by mass, preferably 1 to 5% by mass, based on the total amount of the grease composition. The antioxidant may contain both phenolic compounds and amine compounds.

[0054] Examples of oily agents include amines such as laurylamine, myristylamine, palmitylamine, stearylamine, and oleylamine; higher alcohols such as lauryl alcohol, myristyl alcohol, palmityl alcohol, stearyl alcohol, and oleyl alcohol; higher fatty acids such as lauric acid, myristic acid, palmitic acid, stearic acid, and oleic acid; fatty acid esters such as methyl laurate, methyl myristate, methyl palmitate, methyl stearate, and methyl oleate; and oils and fats such as glycerin oleate and glycerin stearate. When a grease composition contains an oily agent, its content is usually 0.01 to 5% by mass based on the total amount of the grease composition.

[0055] Examples of rust inhibitors include amines, neutral or overbasic petroleum-based or synthetic oil-based metal sulfonates, carboxylate metal salts, esters, phosphoric acid, and phosphates. When a grease composition contains a rust inhibitor, its content is usually 0.005 to 5% by mass based on the total amount of the grease composition.

[0056] As corrosion inhibitors, known corrosion inhibitors such as benzotriazole compounds, toltriazole compounds, thiadiazole compounds, and imidazole compounds can be used. When the grease composition contains a corrosion inhibitor, its content is usually 0.01 to 10% by mass based on the total amount of the grease composition.

[0057] [Grease composition] The consistency of the grease composition of the present invention is preferably 175 to 385, and more preferably 220 to 340, from the viewpoint of fluidity and ease of retention of the grease on sliding parts. Note that consistency represents the physical hardness of the grease. In this specification, consistency refers to the mixed consistency measured in accordance with JIS K2220:2013.

[0058] The dropping point of the grease composition of the present invention is preferably 180°C or higher, more preferably 200°C or higher, from the viewpoint of maintaining the durability of parts at high temperatures. The dropping point refers to the temperature at which a viscous grease loses its thickening agent structure as the temperature increases. Here, the dropping point can be measured in accordance with JIS K2220:2013.

[0059] [Preparation method] The grease composition of the present invention can be prepared using a general grease manufacturing method, but it is preferable to heat the mixture to a temperature above its melting point after mixing with the aliphatic amide compound. In other words, the aliphatic amide compound and the base oil may be heated to a temperature above the melting point of the aliphatic amide compound, cooled, and then physically mixed with a general grease consisting of a thickener and a base oil. Alternatively, all components, including the thickener, may be mixed first, and then heated to a temperature above the melting point of the aliphatic amide compound and cooled.

[0060] Thus, by heating an aliphatic amide compound above its melting point, at least once, in the presence of a base oil, the base oil is retained within the aliphatic amide compound, forming a three-dimensional network structure, resulting in a semi-solid gel. Microscopically, the base oil moves freely within the network structure. This indicates that, for example, when a gel-like lubricating composition comes into contact with the narrow voids of a porous material, the base oil in the gel can move from the gel to the narrow voids due to capillary action. Conversely, if there is an excess of base oil in the system, the three-dimensional structure of the gel causes capillary action, incorporating this excess base oil into the gel. In this state, a thickener can be added to improve consistency, reducing the coefficient of friction in sliding parts.

[0061] <Lubrication target> The grease composition of the present invention is suitably used for lubricating various resin sliding members and steel sliding members. Examples of resins include polyamide resin, polycarbonate, polyamide-imide resin, polyacetal resin, polybutylene terephthalate resin, and polyetheretherketone resin, and is particularly suitable for members using polyamide resin. Examples of steel sliding members include bearing steel, carbon steel, and stainless steel (SUS).

[0062] <Applications of grease compositions> The grease composition of the present invention can be used for sliding between steel and resin in commonly used machinery, bearings, gears, ball screws, etc., and can also exhibit excellent performance even in harsh environments. For example, in automobiles, it can be used for lubrication of engine parts such as water pumps, cooling fan motors, starters, alternators and various actuators, powertrain components such as propeller shafts, constant velocity joints (CVJs), wheel bearings and clutches, electric power steering (EPS), electric power windows, braking systems, ball joints, door hinges, steering wheels, brake expanders, and various other parts. Furthermore, it can be used in construction machinery such as power shovels, bulldozers and cranes, as well as in the steel industry, paper industry, forestry machinery, agricultural machinery, chemical plants, power generation equipment, railway vehicles, and various other shafts and mating parts that may undergo reciprocating sliding. Other applications include threaded joints in seamless pipes and bearings in outboard motors. [Examples]

[0063] The present invention will be described below using an embodiment that is one example of the present invention, but the present invention is not limited to the following embodiment.

[0064] Test grease compositions were prepared for each of Examples 1-11 and Comparative Examples 1-4 by blending the base oil, thickener, and additives in the proportions shown in Table 1. Unless otherwise specified, "mass%" in the table represents the amount of each ingredient relative to the total amount of the grease composition.

[0065] (1) Base oil Base oils 1 and 2 were mixed so that their kinematic viscosity at 100°C was as shown in Table 1. • Base oil 1: Poly-α-olefin (kinematic viscosity at 100°C: 8.0 mm) 2 / s, viscosity index: 136, pour point: <-45℃, flash point: 265℃) • Base oil 2: Poly-α-olefin (kinematic viscosity at 100°C: 40.0 mm) 2 / s), viscosity index: 149, pour point: <-30℃, flash point: 280℃) (2) Thickener The thickener used was a diurea synthesized from a monoamine and diphenylmethane diisocyanate (MDI). As the monoamine, cyclohexylamine (CHA) and / or octadecylamine (ODA) were used in the molar ratios shown in Table 1. (3) Polymers • Polymer A: Ethylene-propylene copolymer (weight-average molecular weight: 200,000, polymer concentration in diluent oil: 10%) • Polymer B: Ethylene-propylene copolymer (weight-average molecular weight: 300,000, polymer concentration in diluent oil: 10%) • Polymer C: Ethylene-propylene copolymer (weight-average molecular weight: 60,000, no diluent oil) • Polymer D: Styrene-diene copolymer (weight-average molecular weight: 440,000, polymer concentration in diluent oil: 10%) • Polymer E: Polymethacrylate (weight-average molecular weight: 400,000, polymer concentration in diluent oil: 20%) • Polymer F Polybutene (weight-average molecular weight: 2,000, no diluting oil) (4) Aliphatic amide compounds • Aliphatic amide: Ethylenebisstearic acid amide (5) Other additives • Antioxidant: Diphenylamine

[0066] [Preparation method] The amine and isocyanate, which are the raw materials for the thickener, were reacted in the base oil in the proportions shown in Table 1, and the reaction product 1 was obtained by heating and cooling. Furthermore, an aliphatic amide compound was added to the same type of base oil taken in a separate container from the aforementioned base oil, heated to 150°C (above the melting point of the aliphatic amide compound), stirred with a magnetic stirrer, and then cooled to room temperature to obtain a semi-solid reaction product 2. Reactant 1 and Reactant 2 were mixed so that the aliphatic amide compound was present in the proportions shown in Table 1, and the remaining additives were added in the proportions shown in Table 1. The mixture was kneaded in a three-roll mill to obtain the test grease compositions shown in Table 1.

[0067] The obtained test grease compositions were evaluated as follows. The evaluation results are shown in Table 1.

[0068] [Evaluation Method] <Coefficient of friction> Evaluation tests were conducted using a ball-and-disc reciprocating friction testing machine. A 1 / 4-inch diameter SUJ-2 ball was used as the ball (steel sliding member), and a plate-shaped 66 nylon disc (TPS® N66(NC) manufactured by Toray Plastics Precision Co., Ltd.) was used as the disc (resin sliding member). Grease was applied to the disc, and the coefficient of friction was measured when it was slid at room temperature (25°C) under the following conditions: test load: 2000 gf, sliding speed: 10 mm / s, and amplitude: 20 mm.

[0069] [Evaluation Results] Comparative Example 1, which did not contain polymers or aliphatic amide compounds, showed a high coefficient of friction in sliding between steel and resin. Comparative Example 2, which contained only polymers, and Comparative Example 3, which contained only aliphatic amide compounds, showed a slight reduction in friction compared to Comparative Example 1, but it was not sufficient. In contrast, the grease composition of the present invention, containing polymers and aliphatic amide compounds, was found to exhibit a sufficient reduction in the coefficient of friction during sliding between steel and resin (Examples 1-11). Furthermore, the kinematic viscosity of the base oil at 100°C was 30 mmHg. 2 Comparative Example 4, which exceeded / s, showed insufficient reduction of the friction coefficient.

[0070] [Table 1] [Industrial applicability]

[0071] Because the grease composition of the present invention has excellent low friction properties, it can be applied to the lubrication of various joints, gears, bearings, etc., that have sliding parts between steel and resin.

Claims

1. The kinematic viscosity at 100°C is 5 to 30 mmHg. ２ A base oil of poly-α-olefin in a quantity of 50% by mass or more, Urea-based thickeners and 0.4 to 6% by mass of an ethylene-α-olefin copolymer, poly(meth)acrylate, styrene-diene copolymer, or polybutene, as a polymer having a weight-average molecular weight of 1,000 to 500,000, It contains 4 to 15% by mass of ethylenebisstearamide as an aliphatic amide compound. A grease composition used for sliding between steel and resin.

2. The grease composition according to claim 1, wherein the urea-based thickener is a diurea compound represented by the following formula (1). R １ -NHGNH-R ２ -NHGNH-R ３ (1) (In formula (1), R １ and R ３ R represents an aliphatic hydrocarbon group having 4 to 24 carbon atoms that may have substituents, an alicyclic hydrocarbon group having 6 to 15 carbon atoms that may have substituents, or an aromatic hydrocarbon group having 6 to 15 carbon atoms that may have substituents. ２ (This represents a divalent aromatic hydrocarbon group having 6 to 15 carbon atoms, which may have substituents.)

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