Lubricating oil composition

Abstract

This lubricating oil composition comprises a base oil and at least one friction modifier selected from the group consisting of a fatty acid ester-based compound, an amine-based compound, an amide-based compound, an imide-based compound, a phosphorus-based compound, a sulfur-based compound, and a phosphorus-sulfur-based compound, and is used together with an oil seal including an inorganic filler.

Description

lubricating oil composition

[0001] The present invention relates to a lubricating oil composition.

[0002] Mechanical systems that make up automobiles and the like use lubricating oil to lubricate the sliding parts of the mechanical systems, and are provided with oil seals to prevent the lubricating oil from leaking from static or dynamic gaps that occur in the mechanical systems (see, for example, Patent Document 1).

[0003] JP 2018-84301 A

[0004] In recent years, as the sliding speed in mechanical systems increases, the frictional resistance of oil seals tends to increase. Since increased frictional resistance can lead to a decrease in the energy efficiency of the mechanical system and to deterioration of the oil seal due to frictional heat, which can result in oil leakage, reducing frictional resistance is desirable. However, according to the inventors' research, not all types of oil seals can effectively reduce friction.

[0005] Therefore, one aspect of the present invention has an object to provide a lubricating oil composition that exhibits a significant friction-reducing effect when used with an oil seal containing an inorganic filler.

[0006] The present inventors have studied the friction characteristics of lubricating oil compositions used with oil seals containing inorganic fillers and have found that the friction-reducing effect (the degree of reduction in the coefficient of friction when a friction modifier is added relative to the coefficient of friction when only the base oil is used) is greater when a specific friction modifier is added to the base oil.

[0007] The present invention includes the following aspects. [1] A lubricating oil composition containing a base oil and at least one friction modifier selected from the group consisting of fatty acid ester compounds, amine compounds, amide compounds, imide compounds, phosphorus compounds, sulfur compounds, and phosphorus-sulfur compounds, and used with an oil seal containing an inorganic filler. [2] The lubricating oil composition according to [1], wherein the oil seal further contains a friction modifier. [3] The lubricating oil composition according to [1] or [2], wherein the oil seal further contains at least one friction modifier selected from the group consisting of fatty acid ester compounds, amine compounds, amide compounds, imide compounds, phosphorus compounds, sulfur compounds, and phosphorus-sulfur compounds. [4] The lubricating oil composition according to [2], wherein the friction modifiers in the lubricating oil composition and the oil seal are fatty acid ester compounds. [5] The lubricating oil composition according to any one of [1] to [4], wherein the fatty acid ester compound contains a compound having a hydrocarbon group, an ester group, and a hydroxyl group. [6] The lubricating oil composition according to any one of [1] to [5], wherein the inorganic filler is an iron-based filler.

[0008] According to one aspect of the present invention, it is possible to provide a lubricating oil composition that exhibits a significant friction-reducing effect when used with an oil seal containing an inorganic filler.

[0009] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention is a lubricating oil composition containing a base oil and a friction modifier.

[0010] Examples of base oils include hydrocarbon oils and oxygenated oils. Examples of hydrocarbon oils include mineral oil, isoparaffin, alkylbenzene, alkylnaphthalene, poly-α-olefin or its hydrogenated derivative, polybutene or its hydrogenated derivative, and ethylene-α-olefin copolymer. Examples of oxygenated oils include esters and ethers. Examples of esters include monoesters, diesters, polyol esters, and complex esters. Examples of ethers include polyalkylene glycols and polyvinyl ethers.

[0011] The hydrocarbon oil is preferably mineral oil or isoparaffin. Examples of mineral oil include paraffinic mineral oil (normal paraffin, isoparaffin, etc.), naphthenic mineral oil, aromatic mineral oil, etc., obtained by refining a lubricating oil fraction obtained by atmospheric distillation and / or vacuum distillation of crude oil through a single or suitable combination of two or more refining processes such as solvent deasphalting, solvent extraction, hydrocracking, solvent dewaxing, catalytic dewaxing, hydrorefining, sulfuric acid washing, and clay treatment. The isoparaffin may contain, as a main component, isoparaffin obtained by hydrocracking and / or hydroisomerization of a paraffin wax component obtained by the dewaxing process or Fischer-Tropsch synthesis.

[0012] The oxygenated oil is preferably a polyol ester, which is an ester of a polyhydric alcohol and a carboxylic acid, and preferably an ester of a polyhydric alcohol and a fatty acid.

[0013] The polyhydric alcohol constituting the polyol ester may be a polyhydric alcohol having 2 to 6 hydroxyl groups. The number of carbon atoms in the polyhydric alcohol may be 4 to 12. Examples of polyhydric alcohols include hindered alcohols such as neopentyl glycol, trimethylolethane, trimethylolpropane, trimethylolbutane, di-(trimethylolpropane), tri-(trimethylolpropane), pentaerythritol, and dipentaerythritol. The polyhydric alcohol is preferably at least one selected from the group consisting of trimethylolpropane, pentaerythritol, and dipentaerythritol.

[0014] The fatty acid constituting the polyol ester may be a saturated fatty acid or an unsaturated fatty acid. In one embodiment, when the polyhydric alcohol is trimethylolpropane, the fatty acid preferably comprises an unsaturated fatty acid. In another embodiment, when the polyhydric alcohol is pentaerythritol or dipentaerythritol, the fatty acid preferably comprises a saturated fatty acid.

[0015] The number of carbon atoms of the unsaturated fatty acid may be 14 or more and 20 or less. Examples of the unsaturated fatty acid include physeteric acid, myristoleic acid, palmitoleic acid, heptadecenylene acid, petroselaidic acid, elaidic acid, oleic acid, and vaccenic acid. The unsaturated fatty acid preferably includes oleic acid.

[0016] The number of carbon atoms in the saturated fatty acid may be preferably 4 or more, and preferably 20 or less, more preferably 18 or less, and even more preferably 9 or less. Examples of saturated fatty acids include butanoic acid, pentanoic acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, undecanoic acid, dodecanoic acid, tridecanoic acid, tetradecanoic acid, pentadecanoic acid, hexadecanoic acid, heptadecanoic acid, octadecanoic acid, nonadecanoic acid, and icosanoic acid. These saturated fatty acids may be linear or branched.

[0017] In one embodiment, the complex ester may be a complex ester of a polyhydric alcohol, a polycarboxylic acid, and at least one selected from the group consisting of a monocarboxylic acid and a monohydric alcohol. Examples of the polyhydric alcohol constituting the complex ester may be the same as the examples of the polyhydric alcohol constituting the polyol ester described above. The polycarboxylic acid constituting the complex ester may be a dicarboxylic acid. The carbon number of the dicarboxylic acid may be 2 or more, preferably 4 or more, and may be 12 or less, preferably 10 or less. Examples of the polycarboxylic acid include succinic acid, adipic acid, azelaic acid, and sebacic acid.

[0018] The monocarboxylic acid constituting the complex ester may be a fatty acid. Examples of the fatty acid may be the same as the examples of the fatty acid constituting the polyol ester described above. The number of carbon atoms of the monohydric alcohol constituting the complex ester may be 2 or more, preferably 4 or more, and 20 or less, preferably 10 or less. Examples of the monohydric alcohol include ethanol, butanol, hexanol, octanol, nonanol, decanol, etc.

[0019] The base oils are classified into API base oil Group I (viscosity index of 80 or more but less than 120, sulfur content exceeding 0.03% by mass and / or saturated content less than 90% by mass; solvent refined base oil), Group II (viscosity index of 80 or more but less than 120, sulfur content of 0.03% by mass or less, and saturated content of 90% by mass or more: hydrotreated base oil), Group III (viscosity index of 120 or more, sulfur content of 0.03% by mass or less, and saturated content of 90% by mass or more: hydrocracked / hydroisomerized oil), Group IV (poly-α-olefin base oil), and Group V (base oil not belonging to any of Groups I to IV).

[0020] The base oil may contain, as a main component, at least one selected from the group consisting of base oils classified into any of these groups. The group may preferably be the group consisting of base oils classified into any of Group II, Group III, Group IV, and Group V, or may be the group consisting of base oils classified into Group III, Group IV, and Group V, or may be the group consisting of base oils classified into Group III or Group IV.

[0021] As these base oils, a base oil having a saturated content of 90 mass% or more, preferably 94 mass% or more, 97 mass% or more, or 99 mass% or more and an aromatic content of 10 mass% or less, preferably 6 mass% or less, 3 mass% or less, or 1 mass% or less may be used as a main component, and %C Ｐ is 60 or more, 70 or more, 75 or more, or 80 or more, % C Ｎ is 40 or less, 30 or less, or 25 or less, % C Ａ However, the %C may be 5 or less, 3 or less, 1 or less, or 0.1 or less as the main component. Ｐ , %C Ｎ , %C ＡThe "total of 100" refers to the weight ratio of the paraffinic carbon content, naphthenic carbon content, and aromatic carbon content to the total carbon content, respectively (determined in accordance with ASTM D 3238). The viscosity index of these base oils is preferably 80 or higher, and may be 90 or higher, 100 or higher, 120 or higher, 130 or higher, 140 or higher, or 150 or higher. Base oils classified into Group V include aromatic hydrocarbon base oils such as alkylbenzenes and alkylnaphthalenes, and oxygenated base oils such as esters and ethers, with ester-based base oils or ether-based base oils being preferred. The viscosity index of the ester-based base oil or ether-based base oil is preferably 80 or higher, and may be 90 or higher, 100 or higher, 120 or higher, 130 or higher, 140 or higher, or 150 or higher.

[0022] The kinematic viscosity of the base oil at 40°C is 3 mm ２ / s or more, 4mm ２ / s or more, or 5 mm ２ / s or more, and ２ / s or less, 300mm ２ / s or less, or 100 mm ２ The kinematic viscosity of the base oil at 100°C may be 1 mm / s or less. ２ / s or more or 2 mm ２ / s or more, and 100 mm ２ / s or less or 50 mm ２ The kinematic viscosity in this specification means a kinematic viscosity measured in accordance with JIS K2283:2000.

[0023] The content of the base oil may be 50 mass % or more, 60 mass % or more, 70 mass % or more, 80 mass % or more, or 90 mass % or more based on the total amount of the lubricating oil composition.

[0024] The friction modifier is at least one selected from the group consisting of fatty acid ester compounds, amine compounds, amide compounds, imide compounds, phosphorus compounds, sulfur compounds, and phosphorus-sulfur compounds, preferably fatty acid ester compounds. These friction modifiers may be compounds having a hydrocarbon group and a polar group. Examples of the hydrocarbon group include linear hydrocarbon groups, aromatic hydrocarbon groups, and alicyclic hydrocarbon groups. The hydrocarbon group may have two or more carbon atoms and may have 400 or less, 200 or less, or 40 or less carbon atoms. The hydrocarbon group may be a saturated hydrocarbon group or an unsaturated hydrocarbon group. Examples of the polar group include an ester group, a carboxy group, an amine group, an amide group, an imide group, and a phosphate group. These polar groups can be adsorbed to the surface of an inorganic filler. The friction modifier may be an ashless friction modifier.

[0025] The fatty acid ester compound is at least one selected from esters of fatty acids and monohydric alcohols or polyhydric alcohols, preferably esters of fatty acids and polyhydric alcohols. The fatty acid ester compound has a hydrocarbon group derived from a fatty acid or alcohol. The number of carbon atoms in the hydrocarbon group may be 2 or more, preferably 6 or more or 12 or more, and may be 40 or less, preferably 20 or less or 18 or less.

[0026] In one embodiment, the fatty acid ester compound may have the hydrocarbon group, an ester group, and a hydroxyl group (i.e., may be a partial ester of a fatty acid and a polyhydric alcohol). The fatty acid ester compound may contain 10% by mass or more of the partial ester of a fatty acid and a polyhydric alcohol as a main component (e.g., 50% by mass or more, preferably 60% by mass or more, 70% by mass or more, 80% by mass or more, or 90% by mass or more, and 100% by mass or less).

[0027] The number of carbon atoms in the fatty acid constituting the fatty acid ester-based compound may be 2 or more, preferably 6 or more, and may be 30 or less, preferably 20 or less. The fatty acid may more preferably include a saturated or unsaturated fatty acid having 12 to 18 carbon atoms, and may include at least one selected from the group consisting of lauric acid, myristic acid, palmitic acid, stearic acid, and oleic acid.

[0028] The monohydric alcohol constituting the fatty acid ester-based compound may be an aliphatic alcohol. The carbon number of the aliphatic alcohol may be 2 or more, preferably 6 or more, and may be 30 or less, preferably 20 or less. More preferably, the monohydric alcohol may include a saturated or unsaturated aliphatic alcohol having 12 to 18 carbon atoms, and may include at least one selected from the group consisting of lauryl alcohol, myristyl alcohol, palmityl alcohol, stearyl alcohol, and oleyl alcohol.

[0029] The polyhydric alcohol constituting the fatty acid ester-based compound may have 2 to 6 hydroxyl groups. The number of carbon atoms in the polyhydric alcohol may be 2 or more, preferably 3 or more, and may be 12 or less, preferably 6 or less. The polyhydric alcohol may more preferably include a polyhydric alcohol having 3 to 6 carbon atoms and 2, 3, or 4 hydroxyl groups, and may include at least one selected from the group consisting of glycerin, sorbitan, neopentyl glycol, trimethylolpropane, and pentaerythritol.

[0030] Specific examples of these fatty acid ester compounds include fatty acid monoesters having a hydrocarbon group containing 12 to 18 carbon atoms, such as oleyl oleate and stearyl stearate. Other specific examples of fatty acid ester compounds include polyhydric alcohol fatty acid esters having a hydrocarbon group containing 12 to 18 carbon atoms, such as glycerin fatty acid esters, sorbitan fatty acid esters, neopentyl glycol fatty acid esters, trimethylolpropane fatty acid esters, and pentaerythritol fatty acid esters. These polyhydric alcohol fatty acid esters may be partial esters, and more specifically, may be glycerin monooleate, sorbitan monooleate, trimethylolpropane partial decanoate (main components: monoesters and diesters), pentaerythritol partial oleate (main components: monoesters, diesters, and triesters), etc. Other specific examples of fatty acid ester compounds include polymethacrylic acid esters having a hydrocarbon group containing 1 to 40 carbon atoms.

[0031] Examples of amine compounds include alkylamines, alkenylamines, and alkylene oxide adducts thereof, and alkanolamines. The alkylamines may be monoalkylamines, dialkylamines, or trialkylamines. The alkenylamines may be monoalkenylamines, dialkenylamines, or trialkenylamines.

[0032] The number of carbon atoms in the hydrocarbon group in the alkylamine or alkenylamine may be 1 or more, 6 or more, or 12 or more, and may be 30 or less, 20 or less, or 18 or less. An example of an alkylamine is stearylamine. An example of an alkenylamine is oleylamine. Examples of alkanolamines include N,N-bis(2-hydroxyethyl)stearylamine, oleyldiethanolamine, etc. Examples of the above alkylene oxide adducts include ethylene oxide adducts of alkyl or alkenylamines.

[0033] Examples of amide compounds include oleoyl sarcosine, fatty acid amides, fatty acid monoamides such as oleyl oleic acid monoamide and stearyl oleic acid monoamide, fatty acid diamides such as ethylene bisstearic acid diamide and ethylene bisoleic acid diamide, etc. The number of carbon atoms in the hydrocarbon group in the amide compound may be 1 or more, 6 or more, or 12 or more, and may be 30 or less, 20 or less, or 18 or less.

[0034] Examples of imide compounds include alkyl or alkenyl succinimides and their boron adducts. Specific examples of these include succinimides having a hydrocarbon group with 30 or less carbon atoms, such as oleyl succinimide, and boron adducts thereof, such as polymeric poly(iso)butenyl succinimide and boric acid-modified products thereof. The number of carbon atoms in the hydrocarbon group in the imide compound may be 1 or more, 6 or more, or 12 or more, and 30 or less, 20 or less, or 18 or less. The average number of carbon atoms in the poly(iso)butenyl succinimide group may be 40 or more, 60 or more, or 80 or more, and 400 or less, 200 or less, or 150 or less.

[0035] The phosphorus-based compound is a compound containing phosphorus as a constituent element (excluding compounds containing sulfur as a constituent element). Examples of the phosphorus-based compound include phosphites, orthophosphates, amine salts of acidic phosphates, phosphonates, and phosphinates. The phosphorus-based compound may have a hydrocarbon group. The number of carbon atoms in the hydrocarbon group in the phosphorus-based compound may be 1 or more, 6 or more, or 12 or more, and may be 30 or less, 20 or less, or 18 or less.

[0036] The phosphorus-based compound is preferably at least one selected from the group consisting of phosphites, orthophosphates, and amine salts of acidic phosphates.

[0037] Examples of the phosphite include dialkyl hydrogen phosphite, dialkenyl hydrogen phosphite, diaryl hydrogen phosphite, trialkyl phosphite, trialkenyl phosphite, and triaryl phosphite. The phosphite is preferably at least one selected from the group consisting of dialkenyl hydrogen phosphite and diaryl hydrogen phosphite.

[0038] Examples of alkyl groups in dialkyl hydrogen phosphites and trialkyl phosphites include butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, and didodecyl groups. Examples of alkenyl groups in dialkenyl hydrogen phosphites and trialkenyl phosphites include oleyl groups. Examples of aryl groups in diaryl hydrogen phosphites and triaryl phosphites include phenyl and cresyl groups.

[0039] Examples of orthophosphate esters include trialkyl phosphate, trialkenyl phosphate, and triaryl phosphate. Examples of alkyl groups in trialkyl phosphates include butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, decyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, and octadecyl groups. Examples of alkenyl groups in trialkenyl phosphates include oleyl groups. Examples of aryl groups in triaryl phosphates include phenyl, cresyl, ethylphenyl, butylphenyl, and xylenyl groups. The orthophosphate ester is preferably triaryl phosphate, and more preferably tricresyl phosphate.

[0040] Examples of the acid phosphate ester in the amine salt of an acid phosphate ester include monoalkyl acid phosphate, monoalkenyl acid phosphate, dialkyl acid phosphate, and dialkenyl acid phosphate.

[0041] Examples of the alkyl group in the monoalkyl acid phosphate and dialkyl acid phosphate include a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, a decyl group, an undecyl group, a dodecyl group, a tridecyl group, a tetradecyl group, a pentadecyl group, a hexadecyl group, a heptadecyl group, and an octadecyl group. Examples of the alkenyl group in the monoalkenyl acid phosphate and dialkenyl acid phosphate include an oleyl group.

[0042] Examples of the amine in the amine salt of an acidic phosphoric acid ester include mono-, di-, and tri-alkylamines. Examples of the alkyl group in these amines include methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, and octyl groups.

[0043] The sulfur-based compound is a compound containing sulfur as a constituent element (excluding compounds containing phosphorus as a constituent element). Examples of the sulfur-based compound include sulfurized olefins, sulfurized fats and oils, sulfurized esters, thiazoles, thiadiazoles, dithiocarbamates, and sulfides. The sulfur-based compound may have a hydrocarbon group. The number of carbon atoms in the hydrocarbon group in the sulfur-based compound may be 1 or more, 6 or more, and 30 or less, 20 or less, or 18 or less.

[0044] The sulfur-based compound is preferably a sulfide. The sulfide may be a monosulfide or a polysulfide. An example of the sulfide is a dialkyl sulfide. The dialkyl sulfide is preferably a dialkyl polysulfide. The number of carbon atoms in the alkyl group in the dialkyl sulfide (dialkyl polysulfide) may be 1 or more, preferably 4 or more or 6 or more, and may be 12 or less, preferably 10 or less. The sulfur-based compound may also be a dithiocarbamate. Specific examples thereof include dialkyldithiocarbamate esters. The number of carbon atoms in the alkyl group in the dialkyldithiocarbamates may be 1 or more, preferably 4 or more or 6 or more, and may be 12 or less, preferably 10 or less.

[0045] Phosphorus-sulfur compounds are compounds containing phosphorus and sulfur as constituent elements. Examples of phosphorus-sulfur compounds include thiophosphate esters or derivatives thereof having 1 to 3, preferably 1 or 2, sulfur atoms. The number of carbon atoms in the hydrocarbon group in the phosphorus-sulfur compound may be 1 or more, 4 or more, or 6 or more, and may be 30 or less, 20 or less, or 18 or less. Specific examples of phosphorus-sulfur compounds include phosphorothioates such as triphenylphosphorothionate, dialkyldithiophosphates, and dialkyldithiophosphorylated carboxylic acids or esters thereof, such as 3-diisobutoxyphosphinothioylsulfanyl-2-methylpropanoic acid or esters thereof.

[0046] The content of the friction modifier may be 0.01 mass % or more, 0.05 mass % or more, or 0.1 mass % or more, based on the total amount of the lubricating oil composition, and may be 10 mass % or less, 5 mass % or less, or 3 mass % or less.

[0047] The lubricating oil composition may further contain additives other than friction modifiers. Examples of other additives include antioxidants, acid scavengers, metal deactivators, viscosity index improvers, pour point depressants, and detergent-dispersants. The total content of the additives may be 0.1 mass % or more, 0.5 mass % or more, or 1 mass % or more, and 5 mass % or more, 4 mass % or less, or 3 mass % or less, based on the total amount of the lubricating oil composition.

[0048] The kinematic viscosity of the lubricating oil composition at 40°C is 3mm ２ / s or more, 4mm ２ / s or more, or 5 mm ２ / s or more, and ２ / s or less, 300mm ２ / s or less, or 100 mm ２ The kinematic viscosity of the lubricating oil composition at 100°C may be 1 mm / s or less. ２ / s or more or 2 mm ２ / s or more, and 100 mm ２ / s or less or 50 mm ２ / s or less.

[0049] The lubricating oil composition is used together with an oil seal (sealing member) containing an inorganic filler. More specifically, in one embodiment, the lubricating oil composition is used in an oil / seal lubrication system including an oil seal (sealing member) containing an inorganic filler and a sliding member that moves relative to the oil seal (sealing member) and contacts the oil seal (sealing member) via the lubricating oil composition. As a result, the lubricating oil composition is interposed between the oil seal (sealing member) and the sliding member to reduce friction.

[0050] This oil / seal lubrication system is suitable for use in rotating shafts and hydraulic cylinders of various mechanical elements, such as automobiles, electric vehicles, motorcycles, bicycles, aircraft, railway vehicles, construction machinery, agricultural machinery, hydraulic machinery, compressors, robots, turbines, and semiconductor manufacturing equipment, as well as in information and electronic equipment, office automation equipment, home appliances, drones, gear elements, and bearings. For example, the higher the rotation speed of the rotating shaft, the greater the durability of the oil seal (sealing member), lubricating oil composition, and rotating shaft due to the energy savings and heat generation suppression achieved by reduced friction. Therefore, the lubricating oil composition of this embodiment is particularly suitable for use in oil / seal lubrication systems equipped with such high-speed rotating shafts. Note that while this embodiment has been described using application to rotating shafts as an example, in another embodiment, the oil / seal lubrication system can also be used in the above-mentioned mechanical elements, such as shock absorbers and hydraulic cylinders.

[0051] The lubricating oil composition according to this embodiment can be used as various lubricating oils and greases such as various engine oils (gasoline engine oil, diesel engine oil, gas engine oil, marine engine oil), turbine oil, automatic transmission oil, manual transmission oil, continuously variable transmission oil, final reduction gear oil, EV drive oil, e-axle oil, gear oil, compressor oil, vacuum pump oil, refrigeration oil, hydraulic oil for construction machinery, hydraulic oil for agricultural machinery, hydraulic oil for shock absorbers, oil for food machinery, bearing oil, grease, etc.

[0052] As the inorganic filler, from the viewpoint of availability and adsorption with the ashless friction modifier, metal oxides, metal hydroxides, or silicate minerals are preferred, iron (III) oxide, chromium (III) oxide, titanium dioxide, aluminum hydroxide, silica, wollastonite, or talc are preferred, iron (III) oxide, chromium (III) oxide, titanium dioxide, aluminum hydroxide, or wollastonite are more preferred, and iron (III) oxide, chromium (III) oxide, titanium dioxide, or aluminum hydroxide are even more preferred. From the viewpoint of obtaining a particularly significant effect of reducing friction by the friction modifier, iron-based fillers are preferred, and fillers composed of iron (III) oxide are more preferred.

[0053] The content of the inorganic filler per 100 parts by mass of the rubber component in the oil seal is preferably 10 parts by mass or more, more preferably 20 parts by mass or more, even more preferably 30 parts by mass or more, and particularly preferably 50 parts by mass or more, and is preferably 300 parts by mass or less, more preferably 250 parts by mass or less, even more preferably 200 parts by mass or less, and particularly preferably 150 parts by mass or less.

[0054] In one embodiment, the oil seal may be a vulcanized molded product (also referred to as a cross-linked molded product) of a rubber composition containing a rubber component and an inorganic filler. In other words, the oil seal may further contain a rubber component (vulcanized (cross-linked) rubber) in addition to the inorganic filler. The oil seal can be obtained by molding the rubber composition by, for example, heat pressing (primary vulcanization) at 160 to 200°C for 3 to 30 minutes, and, if necessary, secondary vulcanization at 150 to 250°C for 0.5 to 24 hours.

[0055] The type of rubber component is not particularly limited. Examples of the rubber component include natural rubber, styrene-butadiene rubber, butadiene rubber, chloroprene rubber, acrylonitrile-butadiene rubber (nitrile rubber, NBR), hydrogenated nitrile rubber, isoprene rubber, butyl rubber, ethylene-propylene rubber, ethylene-propylene-diene rubber (EPDM), acrylic rubber (ACM), fluororubber (FKM), and silicone rubber. The rubber component is preferably at least one selected from the group consisting of fluororubber (FKM), acrylonitrile-butadiene rubber (nitrile rubber, NBR), silicone rubber, and acrylic rubber (ACM).

[0056] Examples of the fluororubber include polyol-vulcanizable fluororubber and peroxide-crosslinkable fluororubber. The fluororubber is preferably polyol-vulcanizable fluororubber.

[0057] Examples of polyol-vulcanizable fluororubbers include homopolymers and copolymers (e.g., alternating copolymers) of fluorine-containing monomers such as vinylidene fluoride, hexafluoropropene, pentafluoropropene, trifluoroethylene, trifluorochloroethylene, tetrafluoroethylene, vinyl fluoride, perfluoroacrylic acid esters, perfluoroalkyl acrylate esters, perfluoro(methyl vinyl ether), perfluoro(ethyl vinyl ether), and perfluoro(propyl vinyl ether), as well as copolymers of these fluorine-containing monomers with propylene. Polyol-vulcanizable fluororubbers are preferably vinylidene fluoride-hexafluoropropene copolymers, vinylidene fluoride-hexafluoropropene-tetrafluoroethylene copolymers, and tetrafluoroethylene-propylene copolymers. Commercially available polyol-vulcanizable fluororubbers may be used as they are.

[0058] The peroxide-crosslinkable fluororubber may be a fluoroelastomer containing iodine and / or bromine in the molecule as a crosslinking site. The fluorine content in the peroxide-crosslinkable fluororubber may be 63 to 71% by weight. The Mooney viscosity ML of the peroxide-crosslinkable fluororubber １＋１０ (121°C) may be 20 to 100.

[0059] The introduction of iodine and / or bromine groups that enable peroxide crosslinking of fluororubber can be carried out by copolymerization reaction in the presence of an iodine and / or bromine group-containing saturated or unsaturated compound.

[0060] When the fluororubber is made to contain a bromine group and / or an iodine group in its side chain, a crosslinking site-forming monomer such as perfluoro(2-bromoethyl vinyl ether), 3,3,4,4-tetrafluoro-4-bromo-1-butene, 2-bromo-1,1-difluoroethylene, bromotrifluoroethylene, perfluoro(2-iodoethyl vinyl ether), or iodotrifluoroethylene can be copolymerized with the above-mentioned fluorine-containing monomer.

[0061] When the fluororubber has an iodine group and / or a bromine group at its terminal, the fluororubber may be a compound represented by the formula: X１ C ｎ F ２ｎ X ２ (X １ : F, Br or I, X ２ A terminally halogenated fluoroalkylene compound represented by the formula (n: Br or I, n: an integer of 1 to 12) is used. From the viewpoint of a balance between reactivity and handling, the terminally halogenated fluoroalkylene compound is preferably a compound in which n is 1 to 6. Specifically, a copolymer containing iodine groups and / or bromine groups is preferably used by copolymerizing a terminally halogenated fluoroalkylene compound such as 1-bromoperfluoroethane, 1-bromoperfluoropropane, 1-bromoperfluorobutane, 1-bromoperfluoropentane, 1-bromoperfluorohexane, 1-iodoperfluoroethane, 1-iodoperfluoropropane, 1-iodoperfluorobutane, 1-iodoperfluoropentane, or 1-iodoperfluorohexane with the above-mentioned fluorine-containing monomer.

[0062] X １ and X ２ When each is I or Br, a crosslinking point is introduced at the end of the fluororubber. １ and X ２ are I or Br, for example, 1-bromo-2-iodotetrafluoroethane, 1-bromo-3-iodoperfluoropropane, 1-bromo-4-iodoperfluorobutane, 2-bromo-3-iodoperfluorobutane, monobromomonoiodoperfluoropentane, monobromomonoiodoperfluoro-n-hexane, 1,2-dibromoperfluoroethane, 1,3-dibromoperfluoropropane, 1,4-dibromoperfluorobutane, 1,5-dibromoperfluoropentane, 1,6-dibromoperfluorohexane, 1,2-diiodoperfluoroethane, 1,3-diiodoperfluoropropane, 1,4-diiodoperfluorobutane, 1,5-diiodoperfluoropentane, 1,6-diiodoperfluorohexane, and the like.

[0063] The peroxide-crosslinkable fluororubber is preferably a copolymer elastomer such as the following.

[0064] Fluororubber in which iodine groups and / or bromine groups have been introduced into a copolymer elastomer having a copolymerization composition of about 50 to 80 mol % vinylidene fluoride, about 15 to 50 mol % hexafluoropropene, and about 30 to 0 mol % tetrafluoroethylene. Examples of such fluororubbers that can be used include commercially available products such as Viton GAL200S, GBL200S, GBL600S, GF200S, and GF600S manufactured by DuPont; Tecnoflon P457, P757, P459, and P952 manufactured by Solvay-Solex; and Dai-el G952, G901, G902, G912, and G801 manufactured by Daikin Corporation.

[0065] about 50 to 85 mol % vinylidene fluoride, formula: CF ２ =CFORf (Rf: perfluoroalkyl group having 1 to 10 carbon atoms (preferably perfluoromethyl group) or perfluorooxyalkyl group having 1 to 10 carbon atoms and one or more ether bonds in the carbon chain), and about 50 to 0 mol % of tetrafluoroethylene. Fluororubber in which iodine groups and / or bromine groups have been introduced into a copolymer elastomer having a copolymerization composition of about 5 to 50 mol % of perfluorovinyl ether and about 50 to 0 mol % of tetrafluoroethylene. Examples of such fluororubbers that can be used include commercially available products such as Viton GLT200S, GLT600S, GBLT200S, GBLT600S, GFLT200S, and GFLT600S manufactured by DuPont; Tecnoflon PL455, PL855, PL557, PL458, and PL958 manufactured by Solvay-Solex; and Dai-el LT302 and LT301 manufactured by Daikin Corporation.

[0066] The rubber composition may further contain a vulcanizing agent (crosslinking agent). Examples of the vulcanizing agent (crosslinking agent) include polyol and organic peroxide. When the fluororubber is a polyol-vulcanizable fluororubber, polyol is preferably used. When the fluororubber is a peroxide-crosslinkable fluororubber, organic peroxide is preferably used.

[0067] Examples of polyols include 2,2-bis(4-hydroxyphenyl)propane (bisnol A), 2,2-bis(4-hydroxyphenyl)perfluoropropane (bisphenol AF), bis(4-hydroxyphenyl)sulfone (bisphenol S), 2,2-bis(4-hydroxyphenyl)methane (bisphenol F), bisphenol A-bis(diphenyl phosphate), 4,4'-dihydroxydiphenyl, and 2,2-bis(4-hydroxyphenyl)butane. The polyol is preferably bisphenol A or bisphenol AF. These polyols may be in the form of alkali metal salts or alkaline earth metal salts.

[0068] The content of the polyol may be 2 parts by mass or more, preferably 2.5 parts by mass or more, and may be 20 parts by mass or less, preferably 15 parts by mass or less, based on 100 parts by mass of the polyol-vulcanizable fluororubber.

[0069] The polyol may be used in combination with a vulcanization accelerator. That is, the rubber composition may further contain a vulcanization accelerator. The vulcanization accelerator may be a quaternary onium salt, such as a quaternary phosphonium salt or a quaternary ammonium salt, and is preferably a quaternary phosphonium salt. The content of the quaternary onium salt may be 0.5 parts by mass or more, preferably 1 part by mass or more, and may be 10 parts by mass or less, preferably 5 parts by mass or less, relative to 100 parts by mass of the polyol-vulcanizable fluororubber.

[0070] The quaternary phosphonium salt has the formula: １ R ２ R ３ R ４ 〕 ＋ X － In the formula, R １ ~R ４ are each independently an alkyl group, an alkoxyl group, an aryl group, an alkylaryl group, an aralkyl group, or a polyoxyalkylene group having 1 to 25 carbon atoms; X － is Cl － ,Br － , I － , HSO ４ －, H ２ P.O. ４ － , RCOO － , ROSO ２ － , or CO ３ ２－ It is. １ ~R ４ Two or three of these may form a ring structure together with P.

[0071] Examples of quaternary phosphonium salts include tetraphenylphosphonium chloride, benzyltriphenylphosphonium bromide, benzyltriphenylphosphonium chloride, triphenylmethoxymethylphosphonium chloride, triphenylmethylcarbonylmethylphosphonium chloride, triphenylethoxycarbonylmethylphosphonium chloride, trioctylbenzylphosphonium chloride, trioctylmethylphosphonium chloride, trioctylethylphosphonium acetate, tetraoctylphosphonium chloride, trioctylethylphosphonium dimethylphosphate, etc. The quaternary phosphonium salt may be an equimolar compound of a polyhydroxy aromatic compound and a quaternary phosphonium compound, as described in JP-A-61-12741.

[0072] The quaternary ammonium salt has the formula: １ R ２ R ３ R ４ 〕 ＋ X － In the formula, R １ ~R ４ and X － is R in the above quaternary phosphonium salt １ ~R ４ and X － As the quaternary ammonium salt, for example, 1-alkylpyridinium salt, 5-aralkyl-1,5-diazabicyclo[4,3,0]-5-nonenium salt, 8-aralkyl-1,8-diazabicyclo[5,4,0]-7-undecenium salt, etc. may be used.

[0073] Examples of organic peroxides include dicumyl peroxide, cumene hydroperoxide, p-methane hydroperoxide, 2,5-dimethylhexane-2,5-dihydroperoxide, di-tert-butyl peroxide, benzoyl peroxide, m-toluyl peroxide, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexyne-3, 1,3 ... butylperoxyisopropyl)benzene, 2,5-dimethyl-2,5-dibenzoylperoxyhexane, (1,1,3,3-tetramethylbutylperoxy)2-ethylhexanoate, tert-butylperoxybenzoate, tert-butylperoxylaurate, di(tert-butylperoxy)adipate, di(2-ethoxyethylperoxy)dicarbonate, bis-(4-tert-butylcyclohexylperoxy)dicarbonate, and the like.

[0074] The content of the organic peroxide may be 0.5 parts by mass or more, preferably 1 part by mass or more, and may be 10 parts by mass or less, preferably 5 parts by mass or less, relative to 100 parts by mass of the peroxide-crosslinkable fluororubber.

[0075] From the viewpoint of improving the mechanical strength, compression set, etc. of the oil seal, organic peroxides are preferably used in combination with polyfunctional unsaturated compounds. Examples of polyfunctional unsaturated compounds include tri(meth)allyl isocyanurate, tri(meth)allyl cyanurate, triallyl trimellitate, N,N'-m-phenylene bismaleimide, diallyl phthalate, tris(diallylamine)-s-triazine, triallyl phosphite, ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, and 1,3-polybutadiene. Here, (meth)allyl means allyl or methallyl. (Meth)acrylate means acrylate or methacrylate.

[0076] The content of the polyfunctional unsaturated compound may be 0.1 parts by mass or more, preferably 0.5 parts by mass or more, and may be 20 parts by mass or less, preferably 10 parts by mass or less, relative to 100 parts by mass of the peroxide-crosslinkable fluororubber.

[0077] The oil seal preferably further contains a friction modifier. The friction modifier is preferably an ashless friction modifier, more preferably at least one selected from the group consisting of fatty acid ester compounds, amine compounds, amide compounds, imide compounds, phosphorus compounds, sulfur compounds, and phosphorus-sulfur compounds, and even more preferably a fatty acid ester compound. In particular, it is preferable that both the lubricating oil composition and the oil seal contain a fatty acid ester compound. Details of each friction modifier are the same as those described for the friction modifier contained in the lubricating oil composition.

[0078] The content of the friction modifier per 100 parts by mass of the rubber component in the oil seal is preferably 0.01 parts by mass or more, more preferably 0.1 parts by mass or more, even more preferably 1 part by mass or more, and is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, even more preferably 10 parts by mass or less.

[0079] The oil seal may further contain other components, such as various additives commonly used in the field of rubber compositions, such as an ashless friction modifier (described in detail below), an antioxidant, a plasticizer, a crosslinking agent, a crosslinking accelerator, an acid acceptor, and a processing aid.

[0080] The rubber composition is obtained by kneading the above-mentioned components using a kneader, an open roll, or the like. The oil seal is obtained by forming the obtained rubber composition into a ribbon-like or pellet-like preform using an extruder or the like as needed, and then appropriately molding and vulcanizing it. When an inorganic filler and a friction modifier are contained in the oil seal, the friction modifier and the inorganic filler may be added separately to the rubber component, or the surface of the inorganic filler may be treated in advance to adsorb the friction modifier, and the treated inorganic filler may then be added to the rubber component.

[0081] The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples.

[0082] (Preparation of Oil Seal 1) FKM (fluororubber, Technoflon (registered trademark) P757 manufactured by Solvay) was used as the rubber component, and 75 parts by mass of iron (III) oxide (Brown #601 manufactured by Resinocolor Kogyo Co., Ltd.) was used as the inorganic filler, and 5 parts by mass of a fatty acid ester compound (glycerin monooleate) was used as the friction modifier, relative to 100 parts by mass of FKM. The mixture was kneaded using a kneader and an open roll, and molded at 180°C for 6 minutes to prepare oil seal 1 measuring 40 x 40 x 2 mm.

[0083] (Preparation of Oil Seal 2) Oil seal 2 was prepared in the same manner as oil seal 1, except that iron (III) oxide and fatty acid ester-based compounds were not used.

[0084] (Preparation of Lubricating Oil Composition) Base oil (Group III mineral oil, kinematic viscosity at 40°C: 32 mm ２ / s, kinematic viscosity at 100 ° C: 6 mm ２ / s, viscosity index: 134, sulfur content: less than 1 mass ppm, saturated content 99.5% by mass or more, aromatic content 0.5% or less, %C Ｐ : 79.2, % C Ｎ : 20.8, % C Ａ: 0.0), one of the following friction modifiers was added to prepare a lubricating oil composition. The type of friction modifier used in each example and comparative example is shown in Tables 1 to 3. In the tables, the numerical value in parentheses next to the type of friction modifier is the content (mass %) of the friction modifier based on the total amount of the lubricating oil composition, and "none" means that no friction modifier was added to the lubricating oil composition. Fatty acid ester compound (glycerin monooleate) Phosphorus compound 1 (diphenyl hydrogen phosphite) Phosphorus compound 2 (dioleyl hydrogen phosphite) Phosphorus compound 3 (tricresyl phosphate) Phosphorus compound 4 (amine salt of oleyl acid phosphate ester) Phosphorus-sulfur compound (3-diisobutoxyphosphinothioylsulfanyl-2-methylpropanoic acid) Amine compound (oleylamine) Amide compound (oleoyl sarcosine) Sulfur compound (dioctyl polysulfide) Imide compound (boron adduct of polybutenyl succinimide, average carbon number of polybutenyl group: 96) Ether compound (glycerin oleyl ether) Alcohol compound (oleyl alcohol)

[0085] (Evaluation of Friction Reduction Effect) The friction coefficient was measured under the following conditions using an MTM (MiniTraction Machine) testing machine (manufactured by PCS Instruments). Ball: ½-inch steel ball Disc: Any of Oil Seals 1 to 4 (40 × 40 × 2 mm) Load: 10 N Sliding ratio: 200% (complete sliding) Average speed: 0.1 m / s Oil temperature: 25°C Measurements were performed three times for each combination of oil seal and lubricating oil composition shown in Tables 1 to 3, and the average value of the friction coefficient obtained from the three measurements was calculated. The friction reduction effect was evaluated as a relative value, with the friction coefficient measured for Oil Seal 1 using a reference oil (Reference Example 1-1) consisting only of base oil being set at 100. The smaller this relative value, the greater the friction reduction effect. The results (relative values) are shown in Tables 1 to 3.

[0086]

[0087]

[0088]

[0089] (Preparation of Oil Seal 3) Oil seal 3 was prepared in the same manner as oil seal 1, except that no fatty acid ester compound was used.

[0090] (Preparation of lubricating oil compositions) Lubricating oil compositions were prepared in the same manner as described above. The types of friction modifiers used in each of the Examples and Comparative Examples are shown in Tables 4 to 6. In the tables, the numerical value in parentheses next to the type of friction modifier is the content (mass%) of the friction modifier based on the total amount of the lubricating oil composition, and "none" means that no friction modifier was added to the lubricating oil composition.

[0091] (Evaluation of Friction-Reducing Effect) The friction coefficient was measured in the same manner as above. Measurements were carried out three times for each combination of oil seal and lubricating oil composition shown in Tables 4 to 6, and the average value of the friction coefficient obtained from the three measurements was calculated. The friction-reducing effect was evaluated as a relative value when the friction coefficient measured for Oil Seal 3 using a reference oil (Reference Example 2-1) consisting only of base oil was set to 100. The smaller this relative value, the greater the friction-reducing effect. The results (relative values) are shown in Tables 4 to 6.

[0092]

[0093]

[0094]

[0095] As described above, for oil seals 1 and 3 containing iron oxide, which is an inorganic filler, by adding fatty acid ester compounds, amine compounds, amide compounds, imide compounds, phosphorus compounds, sulfur compounds, or phosphorus-sulfur compounds to the base oil, the relative value of the friction coefficient becomes smaller than when, for example, an ether compound or alcohol compound is added to the base oil, and it can be seen that a significant friction reduction effect is obtained.

[0096] (Preparation of Lubricating Oil Composition) Base oil (Group V ester, trimethylolpropane trioleate, kinematic viscosity at 40°C: 47.7 mm ２ / s, kinematic viscosity at 100 ° C: 9.5 mm ２

[0049] One of the above friction modifiers was added to a lubricating oil composition (lubricating oil composition: JIS K 1001 / s, viscosity index: 189, sulfur content: less than 1 ppm by mass) to prepare a lubricating oil composition. The type of friction modifier used in each example and comparative example is shown in Table 7. In the table, the number in parentheses next to the type of friction modifier is the content (mass%) of the friction modifier based on the total amount of the lubricating oil composition, and "none" means that no friction modifier was added to the lubricating oil composition.

[0097] (Evaluation of Friction-Reducing Effect) The friction coefficient was measured in the same manner as above. The measurement was carried out three times for each combination of oil seal and lubricating oil composition shown in Table 7, and the average value of the friction coefficient obtained from the three measurements was calculated. The friction-reducing effect was evaluated as a relative value when the friction coefficient measured for Oil Seal 2 using a reference oil (Reference Example 3-3) consisting only of base oil was set to 100. The smaller this relative value, the greater the friction-reducing effect. The results (relative values) are shown in Table 7.

[0098]

Claims

1. A lubricating oil composition comprising a base oil and at least one friction modifier selected from the group consisting of fatty acid ester compounds, amine compounds, amide compounds, imide compounds, phosphorus compounds, sulfur compounds, and phosphorus-sulfur compounds, the composition being used together with an oil seal containing an inorganic filler.

2. The lubricating oil composition of claim 1, wherein the oil seal further comprises a friction modifier.

3. The lubricating oil composition according to claim 1, wherein the oil seal further comprises at least one friction modifier selected from the group consisting of fatty acid ester compounds, amine compounds, amide compounds, imide compounds, phosphorus compounds, sulfur compounds, and phosphorus-sulfur compounds.

4. The lubricating oil composition according to claim 2, wherein the friction modifier in the lubricating oil composition and the friction modifier in the oil seal are fatty acid ester compounds.

5. The lubricating oil composition according to claim 4, wherein the fatty acid ester compound contains a compound having a hydrocarbon group, an ester group, and a hydroxyl group.

6. The lubricating oil composition according to any one of claims 1 to 5, wherein the inorganic filler is an iron-based filler.

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