A method for using a lubricating oil composition between a sliding member and a sealing member, and a lubricating oil composition

Abstract

To easily control the coefficient of friction between the sliding member and the sealing member. [Solution] A method for using a lubricating oil composition containing a base oil and additives between a sliding member and a sealing member, wherein the sealing member contains an ashless friction modifier, and if it is desired to increase the coefficient of friction between the sliding member and the sealing member, a metal dithiophosphate salt is selected as the additive; and if it is desired to decrease the coefficient of friction between the sliding member and the sealing member, at least one selected from the group consisting of phosphite esters, acidic phosphate esters, and organic salts of acidic phosphate esters is selected as the additive.

Description

[Technical Field]

[0001] The present invention relates to a method of using a lubricating oil composition between a sliding member and a seal member, and to a lubricating oil composition. [Background Art]

[0002] Lubricating oil compositions for improving the lubricity of sliding members are used in mechanical elements such as hydraulic machinery, compression machinery, turbines, gear elements, and bearings in automobiles, industrial machinery, and the like, and seal members (oil seals) are provided to prevent the lubricating oil composition from leaking from the mechanical elements.

[0003] Sliding members such as rotating shafts and hydraulic cylinders come into contact with and slide against seal members. Therefore, for such sliding members, there is a demand for a seal member that has high sealing performance and is reduced in friction so as to lower sliding resistance. On the other hand, phosphorus-based additives such as metal dithiophosphate and phosphite esters are often added to lubricating oil compositions (for example, Patent Document 1). [Prior Art Documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Unexamined Patent Application Publication No. 2024-093384 [Summary of the Invention] [Problems to be Solved by the Invention]

[0005] According to studies conducted by the present inventors, depending on the application and other factors, there are cases where it is desired to increase the coefficient of friction between a sliding member and a seal member (hereinafter simply referred to as "coefficient of friction"), and cases where it is desired to decrease the coefficient of friction, but controlling the increase or decrease of the coefficient of friction is not necessarily easy.

[0006] Accordingly, an object of one aspect of the present invention is to easily control the coefficient of friction between a sliding member and a seal member. [Means for Solving the Problems]

[0007] The inventors have discovered that when using a sealing member containing an ashless friction modifier, the coefficient of friction between a sliding member and a sealing member can be easily controlled simply by selecting the type of additive to be blended into the base oil. Specifically, when using a sealing member containing an ashless friction modifier, if a metal dithiophosphate salt is selected as the additive and blended into the base oil, the coefficient of friction can be increased compared to when no additive is used. On the other hand, if at least one additive selected from the group consisting of phosphite esters, acidic phosphate esters, and organic salts of acidic phosphate esters is selected and blended into the base oil, the coefficient of friction can be decreased compared to when no additive is used.

[0008] The present invention includes the following aspects.

[0009] [1] A method for using a lubricating oil composition containing a base oil and additives between a sliding member and a sealing member, wherein the sealing member contains an ashless friction modifier, and if it is desired to increase the coefficient of friction between the sliding member and the sealing member, a metal dithiophosphate salt is selected as the additive; and if it is desired to decrease the coefficient of friction between the sliding member and the sealing member, at least one selected from the group consisting of phosphite esters, acidic phosphate esters, and organic salts of acidic phosphate esters is selected as the additive. [2] The method according to [1], wherein the ashless friction modifier comprises a fatty acid ester compound. [3] The method according to [1] or [2], wherein, in order to increase the coefficient of friction between the sliding member and the sealing member, a fatty acid ester compound is further selected as an additive in addition to the metal dithiophosphate salt. [4] A lubricating oil composition comprising a base oil and at least one additive selected from the group consisting of metal dithiophosphate salts, phosphite esters, acidic phosphate esters, and organic salts of acidic phosphate esters, and used together with a sealing member containing an ashless friction modifier. [5] The lubricating oil composition according to [4], comprising a fatty acid ester compound as an ashless friction modifier. [6] The lubricating oil composition according to [4] or [5], wherein the additive comprises a metal dithiophosphate salt and further comprises a fatty acid ester compound. [Effects of the Invention]

[0010] According to one aspect of the present invention, the coefficient of friction between the sliding member and the sealing member can be easily controlled. [Modes for carrying out the invention]

[0011] Embodiments of the present invention will be described in detail below. One embodiment of the present invention is a method for using a lubricating oil composition containing a base oil and additives between a sliding member and a sealing member. This method includes a step (selection step) in which, if it is desired to increase the coefficient of friction between the sliding member and the sealing member, a metal dithiophosphate salt is selected as the additive, and if it is desired to decrease the coefficient of friction between the sliding member and the sealing member, at least one selected from the group consisting of phosphite esters, acidic phosphate esters, and organic salts of acidic phosphate esters is selected as the additive.

[0012] Examples of base oils included in lubricating oil compositions include hydrocarbon oils and oxygen-containing oils. Examples of hydrocarbon oils include mineral oil, isoparaffin, alkylbenzene, alkylnaphthalene, poly-α-olefin or its hydride, polybutene or its hydride, and ethylene-α-olefin copolymer. Examples of oxygen-containing oils include esters and ethers. Examples of esters include monoesters, diesters, polyol esters, and complex esters. Examples of ethers include polyalkylene glycol and polyvinyl ether.

[0013] Hydrocarbon oil is preferably mineral oil or isoparaffin. Mineral oils include, for example, paraffinic mineral oils (normal paraffin, isoparaffin, etc.), naphthenic mineral oils, aromatic mineral oils, etc., obtained by refining a lubricating oil fraction obtained by atmospheric distillation and / or vacuum distillation of crude oil, using one or more refining processes such as solvent dewaxing, solvent extraction, hydrocracking, solvent dewaxing, catalytic dewaxing, hydrorefining, sulfuric acid washing, and clay treatment, either individually or in appropriate combinations of two or more. Isoparaffin may mainly contain isoparaffin obtained by hydrocracking and / or hydroisomerizing paraffin wax components obtained in the dewaxing process or Fischer-Tropsch synthesis, etc.

[0014] The oxygen-containing oil is preferably a polyol ester. The polyol ester is an ester of a polyhydric alcohol and a carboxylic acid, and preferably an ester of a polyhydric alcohol and a fatty acid.

[0015] 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. Preferably, the polyhydric alcohol is at least one selected from the group consisting of trimethylolpropane, pentaerythritol, and dipentaerythritol.

[0016] The fatty acids constituting the polyol ester may be saturated fatty acids or unsaturated fatty acids. In one embodiment, when the polyhydric alcohol is trimethylolpropane, the fatty acids preferably include unsaturated fatty acids. In another embodiment, when the polyhydric alcohol is pentaerythritol or dipentaerythritol, the fatty acids preferably include saturated fatty acids.

[0017] The number of carbon atoms in unsaturated fatty acids may be 14 or more, or 20 or less. Examples of unsaturated fatty acids include ficeteric acid, myristoleic acid, palmitoleic acid, heptadecenilenic acid, petroseradicic acid, elaidic acid, oleic acid, and vaccenic acid. The unsaturated fatty acid preferably includes oleic acid.

[0018] The number of carbon atoms in saturated fatty acids may preferably be 4 or more, 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 eicosanic acid. These saturated fatty acids may be linear or branched.

[0019] In one embodiment, the complex ester may be a complex ester of a polyhydric alcohol, a polyhydric carboxylic acid, and at least one selected from the group consisting of monohydric acids and monohydric alcohols. Examples of polyhydric alcohols constituting the complex ester may be the same as examples of polyhydric alcohols constituting the polyol ester described above. The polyhydric carboxylic acid constituting the complex ester may be a dihydric acid. The number of carbon atoms in the dihydric carboxylic acid may be 2 or more, preferably 4 or more, 12 or less, and preferably 10 or less. Examples of polyhydric acids include succinic acid, adipic acid, azelaic acid, and sebacic acid.

[0020] The monocarboxylic acid constituting the complex ester may be a fatty acid. Examples of fatty acids may be the same as the examples of fatty acids constituting the polyol ester described above. The number of carbon atoms in the monohydric alcohol constituting the complex ester may be 2 or more, preferably 4 or more, 20 or less, and preferably 10 or less. Examples of monohydric alcohols include ethanol, butanol, hexanol, octanol, nonanol, decanol, etc.

[0021] Base oils are classified into the following groups according to the API base oil classification: Group I (viscosity index of 80 or more and less than 120, sulfur content exceeding 0.03% by mass and / or saturation content less than 90% by mass; solvent-refined base oils), Group II (viscosity index of 80 or more and less than 120, sulfur content of 0.03% by mass or less and saturation content of 90% or more by mass: hydrorefined base oils), Group III (viscosity index of 120 or more, sulfur content of 0.03% by mass or less and saturation content of 90% or more by mass: hydrocracking / hydrogenated isomerized oils), Group IV (poly-α-olefin base oils), and Group V (base oils not belonging to any of Groups I to IV).

[0022] The base oil may contain as its main component at least one selected from the group consisting of base oils classified into any of these groups. The group may preferably consist of base oils classified into any of Group II, Group III, Group IV, and Group V, or it may consist of base oils classified into any of Group III, Group IV, and Group V, or it may consist of base oils classified into Group III or Group IV.

[0023] These base oils may be mainly composed of base oils with a saturated content of 90% by mass or more, preferably 94% by mass or more, 97% by mass or more, or 99% by mass or more, and an aromatic content of 10% by mass or less, preferably 6% by mass or less, 3% by mass or less, or 1% by mass or less, %C P However, 60 or higher, 70 or higher, 75 or higher, or 80 or higher, %C N However, 40 or less, 30 or less, or 25 or less, %C A, a base oil of 5 or less, 3 or less, 1 or less, or 0.1 or less may be used as the main component. Here, %C P , %C N , %C A (total 100) respectively mean the weight ratio of paraffin carbon content, naphthene carbon content, and aromatic carbon content to the total carbon content (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. Examples of base oils classified into Group V include aromatic hydrocarbon base oils such as alkylbenzene and alkylnaphthalene, oxygen-containing base oils such as ester and ether, etc., with ester base oils or ether base oils being preferred. The viscosity index of the ester base oil or ether 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.

[0024] The kinematic viscosity of the base oil at 40°C is 3 mm 2 / s or more, 4 mm 2 / s or more, or 5 mm 2 / s or more, and may be 500 mm 2 / s or less, 300 mm 2 / s or less, or 100 mm 2 / s or less. The kinematic viscosity of the base oil at 100°C is 1 mm 2 / s or more, or 2 mm 2 / s or more, and may be 100 mm 2 / s or less, or 50 mm 2 / s or less. The kinematic viscosity referred to in the present specification means the kinematic viscosity measured in accordance with JIS K2283:2000.

[0025] The content of the base oil, based on the total mass of the lubricating oil composition, may be 50% by mass or more, 60% by mass or more, 70% by mass or more, 80% by mass or more, or 90% by mass or more.

[0026] In the selection process, the additive to be blended into the base oil is selected. In the selection process, if it is desired that the friction coefficient will be higher when the additive is blended into the base oil compared to when it is not blended into the base oil, a metal dithiophosphate salt is selected as the additive.

[0027] An example of a metal dithiophosphate salt is zinc dithiophosphate. Zinc dithiophosphate can be represented, for example, by the following formula (1). [ka] In the formula, R 1 ~R 4 These elements may be identical or different, and each represents a monovalent hydrocarbon group.

[0028] R 1 ~R 4 Examples of monovalent hydrocarbon groups represented by include C1-C24 alkyl groups, C5-C7 cycloalkyl groups, C6-C11 alkylcycloalkyl groups, C6-C18 aryl groups, C7-C24 alkaryl groups, and C7-C12 aralkyl groups. The monovalent hydrocarbon group is preferably a C2-C10 linear or branched alkyl group, more preferably a C3-C8 linear or branched alkyl group. Among these, zinc dithiophosphate having a C3-C8 primary alkyl group or zinc dithiophosphate having a C3-C8 primary alkyl group is preferred. Here, the C3-C8 secondary alkyl group is -CH(R a )R b (R a and R b (These are independently linear or branched alkyl groups with 1 to 7 carbon atoms, and their total number of carbon atoms is 2 to 7) and primary alkyl groups with 3 to 8 carbon atoms are represented as -CH2R c (R c (where is a linear or branched alkyl group having 1 to 7 carbon atoms).

[0029] The zinc element content in zinc dithiophosphate may be 2% by mass or more, or 5% by mass or more, and 20% by mass or less, or 15% by mass or less, based on the total amount of zinc dithiophosphate. The phosphorus element content in zinc dithiophosphate may be 2% by mass or more, or 4% by mass or more, and 25% by mass or less, or 15% by mass or less, based on the total amount of zinc dithiophosphate. The sulfur element content in zinc dithiophosphate may be 10% by mass or more, or 15% by mass or more, and 30% by mass or less, or 25% by mass or less, based on the total amount of zinc dithiophosphate.

[0030] The amount of metal dithiophosphate added may be 0.01% by mass or more, 0.1% by mass or more, 0.3% by mass or more, or 0.4% by mass or more, based on the total amount of the lubricating oil composition, and may be 2% by mass or less, 1% by mass or less, 0.8% by mass or less, or 0.6% by mass or less. The amount of metal dithiophosphate added may be 0.001% by mass or more, 0.01% by mass or more, 0.03% by mass or more, or 0.04% by mass or more, based on the total amount of the lubricating oil composition, and may be 0.2% by mass or less, 0.1% by mass or less, 0.08% by mass or less, or 0.06% by mass or less, based on the content of the constituent metal elements (for example, zinc element in the case of zinc dithiophosphate).

[0031] In the selection process, if it is desired that the coefficient of friction be lower when the additive is added to the base oil compared to when it is not, at least one additive is selected from the group consisting of phosphite esters, acidic phosphate esters, and organic salts of acidic phosphate esters. The above-mentioned phosphite esters and acidic phosphate esters may have hydrocarbon groups, and their carbon number may be 1 or more, 6 or more, or 12 or more, and 30 or less, 20 or less, or 18 or less.

[0032] Examples of phosphite esters include dialkylhydrogen phosphites, diarylhydrogen phosphites, diarylhydrogen phosphites, trialkyl phosphites, trialkenyl phosphites, and triaryl phosphites. Preferably, the phosphite ester is at least one selected from the group consisting of diarylhydrogen phosphites and diarylhydrogen phosphites.

[0033] Examples of alkyl groups in dialkylhydrogen phosphites and trialkyl phosphites include butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, and didodecyl groups. An example of an alkenyl group in dialkenylhydrogen phosphites and trialkenyl phosphites is the oleyl group. Examples of aryl groups in diarylhydrogen phosphites and triaryl phosphites include phenyl and cresyl groups.

[0034] Examples of acidic phosphate esters, and examples of acidic phosphate esters in amine salts of acidic phosphate esters, include monoalkyl acid phosphates, monoalkenyl acid phosphates, dialkyl acid phosphates, and dialkenyl acid phosphates.

[0035] Examples of alkyl groups in monoalkyl acid phosphates and dialkyl acid phosphates include butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, and octadecyl groups. An example of an alkenyl group in monoalkenyl acid phosphates and dialkenyl acid phosphates is the oleyl group.

[0036] Examples of amines in amine salts of acidic phosphate esters include monoalkylamines, dialkylamines, and trialkylamines. Examples of alkyl groups in these amines include methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, and octyl groups.

[0037] The acid value of at least one selected from the group consisting of phosphite esters, acidic phosphate esters, and organic salts of acidic phosphate esters is not particularly limited, but from the viewpoint of achieving both low friction and stability, it is preferably 1 mg KOH / g or more, 3 mg KOH / g or more, 5 mg KOH / g or more, or 8 mg KOH / g or more, and may be 200 mg KOH / g or less, 100 mg KOH / g or less, 50 mg KOH / g or less, or 20 mg KOH / g or less.

[0038] The amount of at least one selected from the group consisting of phosphite esters, acidic phosphate esters, and organic salts of acidic phosphate esters may be 0.01% by mass or more, 0.1% by mass or more, or 0.3% by mass or more, and may be 2% by mass or less, 1% by mass or less, or 0.8% by mass or less, based on the total amount of the lubricating oil composition.

[0039] In the selection step, other additives may be further selected as additives, in addition to at least one additive selected from the group consisting of metal dithiophosphate salts, phosphite esters, acidic phosphate esters, and organic salts of acidic phosphate esters.

[0040] Other additives are preferably ashless friction modifiers (excluding phosphite esters, acidic phosphate esters, and organic salts of acidic phosphate esters). Examples of such ashless friction modifiers include fatty acid ester compounds, phosphorus compounds (excluding phosphite esters, acidic phosphate esters, and organic salts of acidic phosphate esters), ether compounds, alcohol compounds, amide compounds, amine compounds, imide compounds, sulfur compounds, and phosphorus-sulfur compounds.

[0041] The ashless friction modifier may be a compound having a hydrocarbon group and a polar group. Examples of hydrocarbon groups include chain hydrocarbon groups, aromatic hydrocarbon groups, and alicyclic hydrocarbon groups. The number of carbon atoms in the hydrocarbon group may be 2 or more, and may be 400 or less, 200 or less, or 40 or less. The hydrocarbon group may be a saturated hydrocarbon group or an unsaturated hydrocarbon group. Examples of polar groups include ester groups, carboxyl groups, amine groups, amide groups, imide groups, and phosphate groups. These polar groups can be adsorbed onto the surface of the inorganic filler.

[0042] The fatty acid ester compound is at least one selected from esters of a fatty acid and a monohydric alcohol or a polyhydric alcohol, and is preferably an ester of a fatty acid and a polyhydric alcohol. The fatty acid ester compound has a hydrocarbon group derived from a fatty acid or an alcohol. The number of carbon atoms in the hydrocarbon group may be 2 or more, preferably 6 or more or 12 or more, may be 40 or less, and preferably 20 or less or 18 or less.

[0043] In one embodiment, the fatty acid ester compound may have the hydrocarbon group, the ester group, and the hydroxyl group (i.e., it 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, and may contain it as the main component (for example, 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, 100% by mass or less).

[0044] The number of carbon atoms in the fatty acid constituting the fatty acid ester compound may be 2 or more, preferably 6 or more, 30 or less, and preferably 20 or less. The fatty acid may more preferably include saturated or unsaturated fatty acids 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.

[0045] The monohydric alcohol constituting the fatty acid ester compound may be an aliphatic alcohol. The aliphatic alcohol may have 2 or more carbon atoms, preferably 6 or more, 30 or less, and preferably 20 or less. The monohydric alcohol may more preferably include saturated or unsaturated aliphatic alcohols 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 alcoholic acid.

[0046] The polyhydric alcohol constituting the fatty acid ester 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, 12 or less, and preferably 6 or less. The polyhydric alcohol may more preferably include polyhydric alcohols 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.

[0047] Specific examples of these fatty acid ester compounds include, for example, fatty acid monoesters having hydrocarbon groups with 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 hydrocarbon groups with 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, glycerin monooleate, sorbitan monooleate, trimethylolpropane decanoate (main components: monoester and diester), pentaerythritol oleate (main components: monoester, diester, and triester), etc. Other specific examples of fatty acid ester compounds include polymethacrylate esters having hydrocarbon groups with 1 to 40 carbon atoms.

[0048] Phosphorus compounds (excluding phosphite esters, acidic phosphate esters, and organic salts of acidic phosphate esters) are compounds containing phosphorus as a constituent element (excluding compounds containing sulfur as a constituent element). Examples of such phosphorus compounds include orthophosphate esters, hydrogen phosphites, phosphonic acid esters, and phosphinic acid esters. Phosphorus compounds may have a hydrocarbon group. The number of carbon atoms in the hydrocarbon group of a phosphorus 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.

[0049] Phosphorus compounds are preferably orthophosphate esters. Examples of orthophosphate esters include trialkyl phosphates, trialkenyl phosphates, and triaryl phosphates. 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. An example of an alkenyl group in trialkenyl phosphate is the oleyl group. Examples of aryl groups in triaryl phosphates include phenyl, cresyl, ethylphenyl, butylphenyl, and xylenyl groups. Orthophosphate esters are preferably triaryl phosphates, and more preferably tricresyl phosphates.

[0050] Ether compounds are compounds having a hydrocarbon group and an ether group. The number of carbon atoms in the hydrocarbon group 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. Examples of ether compounds include etherified polyhydric alcohols having hydrocarbon groups with 6 to 18 carbon atoms, such as glycerin oleyl ether, glycerin stearyl ether, glycerin 2-ethylhexyl ether, and glycerin hexyl ether, as well as etherified monohydric alcohols having hydrocarbon groups with 6 to 18 carbon atoms, such as dioctyl ether and diphenyl ether.

[0051] Alcohol compounds are compounds having a hydrocarbon group and a hydroxyl group. The number of carbon atoms in the hydrocarbon group 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. Examples of alcohol compounds include oleyl alcohol, lauryl alcohol, decyl alcohol, stearyl alcohol, cyclohexyl alcohol, phenol, and other alcohol compounds having hydrocarbon groups with 6 to 18 carbon atoms.

[0052] Examples of amide compounds include fatty acid monoamides such as oleoyl sarcosine, fatty acid amides, oleyl oleic acid monoamide, and stearyl oleic acid monoamide, and fatty acid diamides such as ethylenebisstearate diamide and ethylenebisoleic acid diamide. The number of carbon atoms in the hydrocarbon group of an 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.

[0053] Examples of amine compounds include alkylamines, alkenylamines, or their alkylene oxide adducts and alkanolamines. Alkylamines may be monoalkylamines, dialkylamines, or trialkylamines. Alkenylamines may be monoalkenylamines, dialkenylamines, or trialkenylamines.

[0054] The number of carbon atoms in the hydrocarbon group of an 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. Examples of alkylamines include stearylamine. Examples of alkenylamines include oleylamine. Examples of alkanolamines include N,N-bis(2-hydroxyethyl)stearylamine and oleyldiethanolamine. Examples of alkylene oxide adducts include ethylene oxide adducts of alkyl or alkenylamines.

[0055] Examples of imide compounds include alkyl or alkenyl succinimides and their boron adducts. Specific examples include succinimides having hydrocarbon groups with 30 or fewer carbon atoms, such as oleyl succinimides, and boron adducts such as polymeric poly(iso)butenyl succinimides and their boric acid modified products. The number of carbon atoms in the hydrocarbon group of the imide 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. Furthermore, the average number of carbon atoms in the poly(iso)butenyl group of the poly(iso)butenyl succinimide may be 40 or more, 60 or more, or 80 or more, and may be 400 or less, 200 or less, or 150 or less.

[0056] Sulfur compounds are compounds that contain sulfur as a constituent element (excluding compounds that contain phosphorus as a constituent element). Examples of sulfur compounds include sulfurized olefins, sulfurized oils and fats, sulfurized esters, thiazoles, thiadiazoles, dithiocarbamates, and sulfides. Sulfur compounds may have hydrocarbon groups. The number of carbon atoms in the hydrocarbon group of a sulfur compound may be 1 or more, 6 or more, 30 or less, 20 or less, or 18 or less.

[0057] The sulfur-based compound is preferably a sulfide. The sulfides may be monosulfides or polysulfides. An example of a sulfide is a dialkyl sulfide. Dialkyl sulfides are preferably dialkyl polysulfides. The number of carbon atoms in the alkyl group of a dialkyl sulfide (dialkyl polysulfide) may be 1 or more, preferably 4 or more or 6 or more, 12 or less, and preferably 10 or less. The sulfur-based compound is also a dithiocarbamate. A specific example is a dialkyldithiocarbamate ester. The number of carbon atoms in the alkyl group of a dialkyldithiocarbamate may be 1 or more, preferably 4 or more or 6 or more, 12 or less, and preferably 10 or less.

[0058] Phosphorus-sulfur compounds are compounds that contain phosphorus and sulfur as constituent elements. Examples of phosphorus-sulfur compounds include thiophosphate esters or derivatives thereof having 1 to 3 sulfur atoms, preferably 1 or 2. The number of carbon atoms in the hydrocarbon group of a 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. Examples of phosphorus-sulfur compounds include thiophosphate esters such as phosphorothionate and triphenylphosphorothionate, and dialkyldithiophosphorylated carboxylic acids or esters thereof, such as 3-diisobutoxyphosphinotioylsulfanyl-2-methylpropanoic acid or its esters.

[0059] In the selection step, it is preferable to further select fatty acid ester compounds as other additives. In particular, when it is desired to increase the coefficient of friction between the sliding member and the sealing member in the selection step, it is preferable to further select fatty acid ester compounds as additives in addition to metal dithiophosphate salts, from the viewpoint of further increasing the coefficient of friction.

[0060] In the selection process, other additives may be further selected, such as anti-wear agents, extreme pressure agents, antioxidants, acid scavengers, metal deactivators, viscosity index improvers, pour point depressants, detergent dispersants, defoamers, thickeners, etc.

[0061] In one embodiment, in the selection step, in addition to dithiophosphate metal salts, antioxidants and viscosity index improvers may be further selected as additives, and ashless friction modifiers (excluding phosphite esters, acidic phosphate esters, and organic salts of acidic phosphate esters), antioxidants, and viscosity index improvers may be further selected. In another embodiment, in the selection step, in addition to at least one selected from the group consisting of phosphite esters, acidic phosphate esters, and organic salts of acidic phosphate esters, antioxidants and viscosity index improvers may be further selected as additives, and ashless friction modifiers (excluding phosphite esters, acidic phosphate esters, and organic salts of acidic phosphate esters) may be further selected as additives.

[0062] In these embodiments, the antioxidant is preferably a phenolic antioxidant. Examples of phenolic antioxidants include 2,6-di-tert-butyl-p-cresol (DBPC), 2,6-di-tert-butyl-phenol, 4,4'-methylenebis(2,6-di-tert-butyl-phenol), and octyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate. The amount of antioxidant added may be 0.01% by mass or more, 0.1% by mass or more, 5% by mass or less, 3% by mass or less, or 1% by mass or less, based on the total amount of the lubricating oil composition.

[0063] In these embodiments, the viscosity index improver is preferably a poly(meth)acrylate-based viscosity index improver. The weight-average molecular weight (Mw) of the viscosity index improver may be 5,000 or more, and may be 1,000,000 or less. In terms of excellent shear stability and stabilizing the coefficient of friction, it is preferably 10,000 or more, 20,000 or more, or 30,000 or more, and may be 500,000 or less, 200,000 or less, 90,000 or less, or 60,000 or less. The ratio (Mw / Mn) of the weight-average molecular weight (Mw) to the number-average molecular weight (Mn) of the viscosity index improver is preferably 1.2 or more, 1.4 or more, or 1.6 or more, and may be 5 or less, 3 or less, or 2 or less. The amount of viscosity index improver blended may be 0.1% by mass or more, or 1% by mass or more, or 20% by mass or less, 10% by mass or less, or 8% by mass or less, based on the total amount of the lubricating oil composition.

[0064] In the method according to this embodiment, the sealing member contains an ashless friction modifier. The ashless friction modifier may contain at least one selected from the group consisting of fatty acid ester compounds, phosphorus compounds, ether compounds, alcohol compounds, amide compounds, amine compounds, imide compounds, sulfur compounds, and phosphorus-sulfur compounds. The details of each ashless friction modifier are the same as those described for ashless friction modifiers that can be included in a lubricating oil composition.

[0065] The amount of ashless friction modifier contained in the sealing member 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, preferably 20 parts by mass or less, more preferably 15 parts by mass or less, and even more preferably 10 parts by mass or less, per 100 parts by mass of the rubber component in the sealing member.

[0066] The sealing member may further include an inorganic filler. The shape of the inorganic filler may be, for example, particulate, fibrous, layered, lumpy, strip-shaped, or columnar.

[0067] As the inorganic filler, at least one selected from the group consisting of carbon black, metal oxides, metal hydroxides, and silicate minerals can be used. Examples of the metal oxides include iron(III) oxide (Fe2O3), chromium(III) oxide (Cr2O3), titanium dioxide (TiO2), aluminum oxide (Al2O3), magnesium oxide (MgO), and zinc oxide (ZnO). Examples of the metal hydroxides include magnesium hydroxide and aluminum hydroxide. Examples of the silicate minerals include silica, wollastonite, talc, and mica. Among these, metal oxides, metal hydroxides, or silicate minerals are preferred from the viewpoint of availability and adsorption with ashless friction modifiers, with iron(III) oxide, chromium(III) oxide, titanium dioxide, aluminum hydroxide, silica, wollastonite, or talc being preferred, iron(III) oxide, chromium(III) oxide, titanium dioxide, aluminum hydroxide, or wollastonite being more preferred, and iron(III) oxide, chromium(III) oxide, titanium dioxide, or aluminum hydroxide being even more preferred. As for inorganic fillers, iron-based fillers are preferred from the viewpoint of easily obtaining the effect of adjusting the friction coefficient by selecting additives, and fillers containing iron(III) oxide are particularly preferred.

[0068] The content of the inorganic filler 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, particularly preferably 50 parts by mass or more, 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, based on 100 parts by mass of the rubber component in the sealing member.

[0069] In one embodiment, the sealing member may be a vulcanized molded article (also called a crosslinked molded article) of a rubber composition containing a rubber component and an ashless friction modifier (and, if necessary, an inorganic filler). In other words, the sealing member may further contain a rubber component (vulcanized (crosslinked) rubber) in addition to the friction modifier (and, if necessary, an inorganic filler). The sealing member is obtained by molding the rubber composition, for example, by heat pressing (primary vulcanization) at 160-200°C for 3-30 minutes, and, if necessary, by secondary vulcanization at 150-250°C for 0.5-24 hours.

[0070] The type of rubber component is not particularly limited. Examples of rubber components 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. Preferably, the rubber component is at least one selected from the group consisting of fluororubber (FKM), acrylonitrile-butadiene rubber (nitrile rubber, NBR), silicone rubber, and acrylic rubber (ACM).

[0071] Examples of fluororubbers include polyol-vulcanizable fluororubbers and peroxide-crosslinkable fluororubbers. Preferably, the fluororubber is polyol-vulcanizable fluororubber.

[0072] Examples of polyol-vulcanizable fluororubbers include homopolymers, copolymers (e.g., alternating copolymers) of fluorine-containing monomers such as vinylidene fluoride, hexafluoropropene, pentafluoropropene, trifluoroethylene, trifluorochloroethylene, tetrafluoroethylene, vinyl fluoride, perfluoroacrylic acid esters, perfluoroalkyl acrylates, perfluoro(methyl vinyl ether), perfluoro(ethyl vinyl ether), and perfluoro(propyl vinyl ether), or copolymers of these fluorine-containing monomers with propylene. Preferably, polyol-vulcanizable fluororubbers are vinylidene fluoride-hexafluoropropene copolymers, vinylidene fluoride-hexafluoropropene-tetrafluoroethylene copolymers, and tetrafluoroethylene-propylene copolymers. Commercially available polyol-vulcanizable fluororubbers may be used as is.

[0073] Examples of peroxide-crosslinkable fluororubbers include fluorine-containing elastomers that contain iodine and / or bromine in the molecule as crosslinking sites. The fluorine content in the peroxide-crosslinkable fluororubber may be 63-71% by weight. Mooney viscosity of the peroxide-crosslinkable fluororubber: ML 1+10 (121℃) may be between 20 and 100.

[0074] The introduction of iodine and / or bromine groups, which enables peroxide crosslinking of fluororubber, can be carried out by copolymerization in the presence of saturated or unsaturated compounds containing iodine and / or bromine groups.

[0075] When bromine and / or iodine groups are included in the side chains of fluororubber, for example, crosslinking point-forming monomers 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), and iodotrifluoroethylene can be copolymerized with the above-mentioned fluorine-containing monomers.

[0076] When iodine groups and / or bromine groups are to be included at the ends of the fluororubber, use formula: X 1 C n F 2n X 2 (X 1 :F, Br or I, X 2 A terminally halogenated fluoroalkylene compound represented as (:Br or I, n: an integer from 1 to 12) is used. From the viewpoint of the balance between reactivity and handling, the terminally halogenated fluoroalkylene compound is preferably one in which n is 1 to 6. Specifically, copolymers containing iodine groups and / or bromine groups are preferably used by copolymerizing terminally halogenated fluoroalkylene compounds such as 1-bromoperfluoroethane, 1-bromoperfluoropropane, 1-bromoperfluorobutane, 1-bromoperfluoropentane, 1-bromoperfluorohexane, 1-iodoperfluoroethane, 1-iodoperfluoropropane, 1-iodoperfluorobutane, 1-iodoperfluoropentane, and 1-iodoperfluorohexane with the above-mentioned fluorine-containing monomer.

[0077] X 1 and X 2 If each of these is I or Br, a crosslinking point is introduced at the end of the fluororubber. 1 and X 2 Examples of compounds in which each of these is I or Br include 1-bromo-2-iodotetrafluoroethane, 1-bromo-3-iodoperfluoropropane, 1-bromo-4-iodoperfluorobutane, 2-bromo-3-iodoperfluorobutane, monobromomoniodoperfluoropentane, monobromomoniodoperfluoro-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, and 1,6-diiodoperfluorohexane.

[0078] Peroxide-crosslinkable fluororubber is preferably a copolymer elastomer as described below.

[0079] Fluororubber with iodine and / or bromine groups introduced into a copolymer elastomer having a copolymer composition of approximately 50-80 mol% vinylidene fluoride, approximately 15-50 mol% hexafluoropropene, and approximately 30-0 mol% tetrafluoroethylene. Examples of such fluororubbers that can be used include commercially available products such as DuPont's Viton GAL200S, GBL200S, GBL600S, GF200S, GF600S; Solvay Sorex's Technoflon P457, P757, P459, P952; and Daikin's Daiel G952, G901, G902, G912, G801.

[0080] Fluororubber having iodine and / or bromine groups introduced into a copolymer elastomer having a copolymer composition of approximately 50-85 mol% vinylidene fluoride, approximately 5-50 mol% perfluorovinyl ether represented by the formula: CF2=CFORf (Rf: perfluoroalkyl group having 1-10 carbon atoms (preferably a perfluoromethyl group) or perfluorooxyalkyl group having 1-10 carbon atoms having one or more ether bonds in the carbon chain), and approximately 50-0 mol% tetrafluoroethylene. Examples of commercially available fluororubbers that can be used include DuPont's Viton GLT200S, GLT600S, GBLT200S, GBLT600S, GFLT200S, GFLT600S, Solvay Sorex's Technoflon PL455, PL855, PL557, PL458, PL958, and Daikin's Daiel LT302, LT301.

[0081] The rubber composition may further contain a vulcanizing agent (crosslinking agent). Examples of vulcanizing agents (crosslinking agents) include polyols and organic peroxides. When the fluororubber is a fluororubber that can be vulcanized with a polyol, a polyol is preferably used. When the fluororubber is a fluororubber that can be crosslinked with a peroxide, an organic peroxide is preferably used.

[0082] 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 also be in the form of alkali metal salts or alkaline earth metal salts.

[0083] The polyol content 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, and preferably 15 parts by mass or less, per 100 parts by mass of polyol-vulcanizable fluororubber.

[0084] 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, which is 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, and preferably 5 parts by mass or less, per 100 parts by mass of polyol-vulcanizable fluororubber.

[0085] Quaternary phosphonium salts are given by formula: [PR 1 R 2 R 3 R 4 ] + X - It is a compound represented by [formula]. In the formula, R 1 ~R 4 Each of these is independently an alkyl group, alkoxyl group, aryl group, alkylaryl group, aralkyl group, or polyoxyalkylene group having 1 to 25 carbon atoms, and X - Cl- , Br - , I - HSO4 - H2PO4 - RCOO - ROSO2 - , or CO3 2- That is. R 1 ~R 4 Two or three of these may form a ring structure with P.

[0086] 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, and trioctylethylphosphonium dimethylphosphate. The quaternary phosphonium salt may also be a polyhydroxyaromatic compound-quaternary phosphonium compound, as described in Japanese Patent Publication No. 61-12741.

[0087] Quaternary ammonium salts are given by formula: [NR 1 R 2 R 3 R 4 ] + X - It is a compound represented by the formula. In the formula, R 1 ~R 4 and X - R in the above quaternary phosphonium salt is 1 ~R 4 and X - This is synonymous with quaternary ammonium salts, such as 1-alkylpyridinium salt, 5-aralkyl-1,5-diazabicyclo[4,3,0]-5-nonenium salt, and 8-aralkyl-1,8-diazabicyclo[5,4,0]-7-undecenium salt.

[0088] 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)hexine-3, and 1,3-di(tert-butylperoxy). Examples include (1,1,3,3-tetramethylbutylperoxy)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, and bis-(4-tert-butylcyclohexylperoxy)dicarbonate.

[0089] The content of 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, and preferably 5 parts by mass or less, per 100 parts by mass of peroxide crosslinkable fluororubber.

[0090] Organic peroxides are preferably used in combination with polyfunctional unsaturated compounds from the viewpoint of improving the mechanical strength and compression set of the sealing member. 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.

[0091] 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, and preferably 10 parts by mass or less, per 100 parts by mass of peroxide crosslinkable fluororubber.

[0092] The sealing member may further contain other components. Examples of other components include ashless friction modifiers (details will be described later) and reinforcing agents.

[0093] The rubber composition is obtained by kneading the above-mentioned components using a kneader or open roll. The sealing member is obtained by forming the obtained rubber composition into ribbon-shaped or pellet-shaped pre-molded products using an extruder or the like as needed, and then performing molding and vulcanization as appropriate. When the sealing member contains an inorganic filler and an ashless friction modifier, the ashless friction modifier and the inorganic filler may be added to the rubber component separately, or the inorganic filler may be treated in advance to adsorb the ashless friction modifier onto its surface, and then the treated inorganic filler may be added to the rubber component.

[0094] The sliding member and sealing member may be, for example, a rotating shaft (sliding member) of various industrial machines such as automobiles, electric vehicles, motorcycles, bicycles, aircraft, railway vehicles, construction machinery, agricultural machinery, hydraulic machinery, compressors, robots, turbines, semiconductor manufacturing equipment, information and electronic equipment, office automation equipment, home appliances, drones, gear elements, bearings, and other mechanical elements, and a sealing member (oil seal) that moves relative to the rotating shaft (sliding member). In another embodiment, the sliding member and sealing member may be a sliding member and sealing member in a shock absorber or hydraulic cylinder of a mechanical element.

[0095] Another embodiment of the present invention may be a lubricating oil composition used in the method described above. That is, another embodiment of the present invention may be a lubricating oil composition containing a base oil and at least one additive selected from the group consisting of metal dithiophosphate, phosphite, acidic phosphate, and organic salts of acidic phosphate, and used together with a sealing member containing an ashless friction modifier. Details of the sealing member containing the base oil, metal dithiophosphate, phosphite, acidic phosphate, organic salt of acidic phosphate, and ashless friction modifier are as described above. [Examples]

[0096] The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples.

[0097] (Manufacturing of sealing components) Rubber components, an ashless friction modifier, and an inorganic filler were kneaded in a kneader and open roll, and molded at 180°C for 6 minutes to obtain hemispherical rubber test pieces with a diameter of 5 mm. As the ashless friction modifier, a fatty acid ester-based ashless friction modifier was selected from the above ashless friction modifiers, and its blending amount was selected in the range of 0.1 parts by mass to 20 parts by mass per 100 parts by mass of rubber components. In this example, a fatty acid ester-based ashless friction modifier mainly composed of glycerin monooleate was used as the ashless friction modifier.

[0098] (Comparative lubricating oil composition) Base oil (GrII, 40℃ kinematic viscosity 8.0mm 2 A comparative lubricating oil composition was obtained containing a viscosity index of 100, a phenolic antioxidant, and a poly(meth)acrylate viscosity index improver.

[0099] (Lubricating oil composition L1) Lubricating oil composition L1 (40°C kinematic viscosity: 11.5 mm) contains the above base oil and a selected additive, zinc dialkyldithiophosphate having a primary alkyl group with 8 carbon atoms (0.5% by mass on a basis of the total lubricating oil composition (0.045% by mass in terms of zinc element content)).2 A solution with a viscosity index of 178 and a pour point of <-45°C was prepared (at a rate of 0.25°C).

[0100] (Lubricating oil composition L2) Lubricant composition L2 (kinematic viscosity at 40°C: 11.5 mm) contains the above base oil, and selected additives: zinc dialkyldithiophosphate having a primary alkyl group with 8 carbon atoms (0.5% by mass on a basis of the total lubricant composition (0.045% by mass in terms of zinc element content)), and a fatty acid ester-based ashless friction modifier mainly composed of glycerin monooleate (0.1% by mass on a basis of the total lubricant composition). 2 A solution with a viscosity index of 178 and a pour point of <-45°C was prepared (at a rate of 0.25°C).

[0101] (Lubricating oil composition L3) Lubricating oil composition L3 (40°C kinematic viscosity: 11.5 mm) contains the above base oil and a selected additive, dioylyl hydrogen phosphite (acid value: 10 mg KOH / g, 0.5% by mass based on the total amount of the lubricating oil composition). 2 A solution with a viscosity index of 178 and a pour point of <-45°C was prepared (at a rate of 0.25°C).

[0102] (Lubricating oil composition L4) Lubricant composition L4 (kinematic viscosity at 40°C: 11.5 mm) contains the above base oil, and selected additives: dioyl hydrogen phosphite (acid value: 10 mg KOH / g, 0.5% by mass based on the total amount of the lubricant composition) and a fatty acid ester-based ashless friction modifier mainly composed of glycerin monooleate (0.1% by mass based on the total amount of the lubricant composition). 2 A solution with a viscosity index of 178 and a pour point of <-45°C was prepared (at a rate of 0.25°C).

[0103] (Measurement of friction coefficient) A 30mm x 50mm x 2mm cold-rolled steel sheet (SPCC) was coated with a comparative lubricant composition and lubricant compositions L1 to L4. A dynamic friction test was performed with a sealing member using a reciprocating friction tester under the following conditions. Load: 3N Temperature: room temperature Speed: 0.01~5mm / s Table 1 shows the coefficient of friction at a speed of 1 mm / s.

[0104] [Table 1]

[0105] As can be seen from Table 1, when dithiophosphate metal salts are selected and blended as additives (lubricating oil compositions L1 and L2), the coefficient of friction can be increased compared to when they are not added (comparative lubricating oil composition). Furthermore, when phosphite esters are selected and blended as additives (lubricating oil compositions L3 and L4), the coefficient of friction can be decreased compared to when they are not added (comparative lubricating oil composition).

Claims

1. A method for using a lubricating oil composition containing a base oil and additives between a sliding member and a sealing member, The sealing member contains an ashless friction modifier, A method comprising the step of selecting a metal dithiophosphate salt as the additive if it is desired to increase the coefficient of friction between the sliding member and the sealing member, and selecting at least one selected from the group consisting of phosphite esters, acidic phosphate esters, and organic salts of acidic phosphate esters as the additive if it is desired to decrease the coefficient of friction between the sliding member and the sealing member.

2. The method according to claim 1, wherein the ashless friction modifier comprises a fatty acid ester compound.

3. The method according to claim 1 or 2, wherein, in order to increase the coefficient of friction between the sliding member and the sealing member, a fatty acid ester compound is further selected as the additive in addition to the metal dithiophosphate salt.

4. Base oil and, It contains at least one additive selected from the group consisting of metal dithiophosphate salts, phosphite esters, acidic phosphate esters, and organic salts of acidic phosphate esters, A lubricating oil composition used in conjunction with a sealing member containing an ashless friction modifier.

5. The lubricating oil composition according to claim 4, wherein the ashless friction modifier comprises a fatty acid ester compound.

6. The lubricating oil composition according to claim 4 or 5, wherein the additive comprises the metal dithiophosphate salt and further comprises a fatty acid ester compound.

Images