阅读说明：本技术 润滑方法 (Lubrication method ) 是由 辰巳刚 设乐裕治 于 2020-04-28 设计创作，主要内容包括：公开一种使用润滑油组合物对一对滑动构件进行润滑的润滑方法。该润滑方法中,一对滑动构件中的至少一者为包含工程塑料的构件,润滑油组合物含有润滑油基础油和抗磨剂,所述抗磨剂选自由作为构成元素包含磷并且不含硫的抗磨剂、作为构成元素包含硫并且不含磷的抗磨剂、以及作为构成元素包含磷和硫的抗磨剂组成的组中的至少1种。(A lubricating method for lubricating a pair of sliding members using a lubricating oil composition is disclosed. In the lubricating method, at least one of the pair of sliding members is a member comprising an engineering plastic, and the lubricating oil composition contains a lubricating oil base oil and an antiwear agent selected from at least 1 of the group consisting of an antiwear agent containing phosphorus as a constituent element and not containing sulfur, an antiwear agent containing sulfur as a constituent element and not containing phosphorus, and an antiwear agent containing phosphorus and sulfur as a constituent element.)

1. A lubricating method for lubricating a pair of sliding members with a lubricating oil composition,

at least one of the pair of sliding members is a member comprising engineering plastic,

the lubricating oil composition contains a lubricating oil base oil and an antiwear agent, the antiwear agent being at least 1 selected from the group consisting of an antiwear agent containing phosphorus as a constituent element and containing no sulfur, an antiwear agent containing sulfur as a constituent element and containing no phosphorus, and an antiwear agent containing phosphorus and sulfur as a constituent element.

2. The lubrication method according to claim 1, wherein one of the pair of sliding members is a member containing an engineering plastic, and the other is a member containing an iron-based material.

Technical Field

The present invention relates to a lubrication method.

Background

In a mechanical device or the like having a metal material as a sliding member, various lubricants are used for lubricating the sliding member. As the lubricant, a lubricant, grease, or the like, which is blended with various additives as necessary, is used.

In recent years, the use of resin materials as sliding members has been studied in many applications from the viewpoints of weight reduction of parts, ease of processing, and the like in the background of fuel economy and the like. However, the resin material is inferior in mechanical strength to the metal material, and abrasion, breakage, and the like may occur.

For example, patent document 1 discloses that a lubricant (refrigerator oil) containing at least 1 selected from mineral oil, synthetic alicyclic hydrocarbon compounds and synthetic aromatic hydrocarbon compounds as a main component and having a kinematic viscosity at 40 ℃ of 1 to 8mm is applied to a sliding portion formed of polyphenylene sulfide or the like, or a sliding portion having a polymer coating film or an inorganic coating film²A base oil per second.

Documents of the prior art

Patent document

Patent document 1: international publication No. 2007/058072

Disclosure of Invention

Problems to be solved by the invention

When a resin material (particularly, a member made of an engineering plastic) is used as the sliding member, it is necessary to improve the sliding property as compared with the case of using a metal material. However, the conventional lubricating method is not necessarily sufficient from the viewpoint of improving the sliding property, and there is room for improvement.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a lubrication method capable of improving slidability when a resin material is used as a sliding member.

Means for solving the problems

The invention provides a lubricating method for lubricating a pair of sliding members with a lubricating oil composition. In the lubricating method, at least one of the pair of sliding members is a member comprising an engineering plastic, and the lubricating oil composition contains a lubricating oil base oil and an antiwear agent selected from at least 1 of the group consisting of an antiwear agent containing phosphorus as a constituent element and not containing sulfur, an antiwear agent containing sulfur as a constituent element and not containing phosphorus, and an antiwear agent containing phosphorus and sulfur as a constituent element. According to such a lubrication method, when a resin material is used as the sliding member from the viewpoint of weight reduction, the friction coefficient between the sliding members can be reduced, the wear resistance can be improved, and the sliding property can be improved.

Preferably, one of the pair of sliding members is a member made of engineering plastic, and the other is a member made of iron-based material.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, a lubrication method capable of improving the slidability in the case of using a resin material as a sliding member is provided.

Detailed Description

Hereinafter, embodiments for carrying out the present invention will be described in detail. However, the present invention is not limited to the following embodiments.

The lubricating method of one embodiment is a method of lubricating a pair of sliding members (which are relatively moved in opposite directions) with a lubricating oil composition.

In the lubrication method according to the present embodiment, at least one of the pair of sliding members is a member made of engineering plastic (hereinafter, may be referred to as "engineering plastic"). Engineering plastics are generally referred to as: a plastic having a heat resistance of 100 ℃ or higher, a strength of 50MPa or higher, and a flexural modulus of 2.4GPa or higher. The engineering plastics also include Super engineering plastics (hereinafter, sometimes referred to as "Super engineering plastics") having heat resistance of 150 ℃.

The engineering plastic is not particularly limited, and examples thereof include amorphous resins such as Polycarbonate (PC) and modified polyphenylene ether (m-PPE), and (semi-) crystalline resins such as Polyacetal (POM), Polyamide (PA), polybutylene terephthalate (PBT) and polyethylene terephthalate (PET). Among these, the engineering plastic is preferably Polyacetal (POM) or Polyamide (PA).

The engineering plastic may be a super engineering plastic. The super engineering plastic is not particularly limited, and examples thereof include amorphous resins such as polyphenylsulfone (PPSU), Polysulfone (PSF), Polyarylate (PAR), Polyetherimide (PEI), and Polyamideimide (PAI), and (semi) crystalline resins such as Polyetheretherketone (PEEK), polyphenylene sulfide (PPS), Polyethersulfone (PES), Liquid Crystal Polymer (LCP), polyvinylidene fluoride (PVDF), and Polytetrafluoroethylene (PTFE). Of these, the super engineering plastic is preferably Polyetheretherketone (PEEK).

PEEK is 1 kind of semicrystalline polymer having a structure in which benzene rings are connected to each other with an ether bond or a carbonyl group. PEEK is, for example, a polymer having a structural unit represented by the following formula (a).

The number average molecular weight Mn of PEEK may be 20000 to 50000, and the weight average molecular weight Mw of PEEK may be 60000 to 150000. The Mw/Mn, which represents the molecular weight distribution, may be 2 to 4. The number average molecular weight Mn and the weight average molecular weight Mw are values measured by GPC and are relative values based on polystyrene.

The sliding member may be a member formed of an engineering plastic, and from the viewpoint of further improving the sliding property, the sliding member may be a member containing, as other components, a solid lubricant, a reinforcing fiber, a filler, an additive, and the like in addition to the engineering plastic.

Examples of the solid lubricant include boron nitride, molybdenum disulfide, fluorine resin, and a carbon-based solid lubricant (graphite, carbon black, etc.).

When the sliding member contains a solid lubricant, the content thereof may be 0.1 to 30% by mass or 0.5 to 20% by mass based on the total amount of the sliding member. When the content of the solid lubricant is 30% by mass or less based on the total amount of the sliding member, defects are less likely to occur in the step of producing pellets from the mixture, and the mechanical properties such as impact strength as a sliding member can be prevented from being significantly reduced. When the content of the solid lubricant is 0.1% by mass or more based on the total amount of the sliding member, the effect of containing the solid lubricant can be sufficiently obtained.

Examples of the reinforcing fiber include fibrous materials such as glass fiber, Carbon fiber (Carbon fiber), aramid fiber, and various whiskers. Among these, the reinforcing fiber is preferably a glass fiber, a carbon fiber, or an aramid fiber in terms of being able to further improve the sliding property, and more preferably a carbon fiber or an aramid fiber in terms of being able to further suppress the wear of the sliding member during sliding.

When the sliding member contains the reinforcing fiber, the content thereof may be 0.1 to 80 mass% or less or 0.5 to 70 mass% or less based on the total amount of the sliding member. When the content of the reinforcing fiber is 80% by mass or less based on the total amount of the member, defects are less likely to occur in the step of producing pellets from the mixture, and the mechanical properties such as impact strength as a sliding member can be prevented from being significantly reduced. When the content of the reinforcing fiber is 0.1% by mass or more based on the total amount of the sliding member, the effect of including the reinforcing fiber can be sufficiently obtained.

Examples of the filler include talc, mica, glass flake (glass flake), clay, sericite, calcium carbonate, calcium sulfate, calcium silicate, silica, alumina, aluminum hydroxide, calcium hydroxide, potassium titanate, titanium oxide, fluorocarbon resin fiber, fluorocarbon resin, barium sulfate, and various whiskers.

Examples of the additives include a colorant, a dispersant, a plasticizer, an antioxidant, a curing agent, a flame retardant, a heat stabilizer, an ultraviolet absorber, an antistatic agent, and a surfactant.

The total content of the filler and the additive is not particularly limited, and may be 10 mass% or less or 5 mass% or less based on the total amount of the sliding member.

The sliding member may further contain a polymer other than engineering plastic within a range not significantly impairing the effects of the present invention. Examples of the polymer other than the engineering plastic include polyethylene, polystyrene, polypropylene, polyvinyl chloride, phenol resin, epoxy resin, and the like.

In the pair of sliding members that relatively move in opposite directions, both the sliding members may be members containing engineering plastic, or one of the sliding members may be a member containing engineering plastic and the other may be a member other than a member containing engineering plastic. Examples of such members include metallic materials such as iron-based materials, aluminum-based materials, and magnesium-based materials, polymers other than engineering plastics, and nonmetallic materials such as carbon. Among these, from the viewpoint of further improving the slidability, the other of the sliding members is preferably a member containing a metallic material, more preferably a member containing an iron-based material.

In the case where one of the sliding members is a member made of engineering plastic and the other is a member made of a metallic material, the lubricating method of the present embodiment can improve the sliding property even when the member made of a metallic material has a large surface roughness (arithmetic average roughness Ra). The surface roughness (arithmetic average roughness Ra) of the member made of the metal-based material may be, for example, 0.05 μm or more, 0.1 μm or more, or 0.3 μm or more.

The lubricating method of the present embodiment lubricates the above-described sliding member using the lubricating oil composition. The lubricating oil composition contains a lubricating oil base oil and a prescribed antiwear agent.

Examples of the lubricant base oil include hydrocarbon oils and oxygen-containing oils. Examples of the hydrocarbon oil include mineral oil-based hydrocarbon oils and synthetic hydrocarbon oils. Examples of the oxygen-containing oil include esters, ethers, carbonates, ketones, silicones, and polysiloxanes. The lubricant base oil may be used alone in 1 kind, or may be used in combination in 2 or more kinds at any ratio. The lubricant base oil preferably contains a hydrocarbon oil (mineral oil-based hydrocarbon oil or synthetic hydrocarbon oil).

Examples of the mineral oil-based hydrocarbon oil include paraffinic mineral oils (normal paraffins, isoparaffins, and the like), naphthenic mineral oils, and aromatic mineral oils obtained by purifying a lubricant fraction obtained by atmospheric distillation and/or vacuum distillation of crude oil by using purification treatments such as solvent deasphalting, solvent extraction, hydrogenolysis, solvent dewaxing, contact dewaxing, hydropurification, sulfuric acid washing, and clay treatment, alone or in combination of 2 or more as appropriate.

Examples of the synthetic hydrocarbon oil include alkylbenzenes, alkylnaphthalenes, Polyalphaolefins (PAOs), polybutenes, and ethylene- α -olefin copolymers.

The kinematic viscosity at 40 ℃ of the lubricant base oil may be, for example, 1mm from the viewpoint of slidability²5mm above/s²More than s, or 10mm²Is more than s, and can be 1000mm²600mm below s²200mm below/s²100mm below s²Less than s, or 50mm²The ratio of the water to the water is less than s. In the present specification, the kinematic viscosity at 40 ℃ means a kinematic viscosity according to JIS K2283: kinematic viscosity at 40 ℃ measured at 2000.

Other physical properties such as the kinematic viscosity at 100 ℃, viscosity index, NOACK evaporation amount, flash point, and pour point of the lubricant base oil used in the lubricating method of the present embodiment can be appropriately set.

The content of the lubricant base oil may be, for example, 70 mass% or more, 80 mass% or more, 85 mass% or more, 90 mass% or more, 95 mass% or more, or 97 mass% or more, and may be 99.9 mass% or less, 99.7 mass% or less, or 99.5 mass% or less, based on the total amount of the lubricant oil composition.

The antiwear agent is at least 1 selected from the group consisting of an antiwear agent containing phosphorus as a constituent element and containing no sulfur (hereinafter, sometimes referred to as "1 st antiwear agent"), an antiwear agent containing sulfur as a constituent element and containing no phosphorus (hereinafter, sometimes referred to as "2 nd antiwear agent"), and an antiwear agent containing phosphorus and sulfur as a constituent element (hereinafter, sometimes referred to as "3 rd antiwear agent").

As the 1 st antiwear agent, for example, zinc dialkylphosphate; phosphites (mono (alkyl or aryl) phosphites, di (alkyl or aryl) phosphites, tri (alkyl or aryl) phosphites, and the like) (phosphites); phosphate esters (mono (alkyl or aryl) Phosphate, di (alkyl or aryl) Phosphate, tri (alkyl or aryl) Phosphate, etc.) (phospate); amine salts, metal salts, derivatives of phosphoric or phosphorous acid esters; condensed phosphoric acid ester; phosphonates and the like. The 1 st antiwear agent may be, for example, a Phosphate ester (phospate) or a metal salt thereof.

The zinc salt of dialkyl phosphate (zinc dialkylphosphate) may be, for example, a compound represented by the following formula (C).

In the formula (C), R²¹～R²⁴Each independently represents a linear or branched alkyl group. The number of carbon atoms of the alkyl group may be 1 or more, or 3 or more, or 24 or less, 12 or less, or 8 or less.

Examples of the phosphite include di (alkyl or aryl) phosphites such as dibutyl phosphite, dipentyl phosphite, dihexyl phosphite, diheptyl phosphite, dioctyl phosphite, dinonyl phosphite, didecyl phosphite, diundecyl phosphite, didodecyl phosphite, dioleyl phosphite, diphenyl phosphite, and ditolyl phosphite; tributyl phosphite, tripentyl phosphite, trihexyl phosphite, triheptyl phosphite, trioctyl phosphite, trinonyl phosphite, tridecyl phosphite, triundecyl phosphite, tridodecyl phosphite, trioleyl phosphite, triphenyl phosphite, tricresyl phosphite and other tri (alkyl or aryl) phosphites, and the like. The alkyl group may be linear or branched and may have an unsaturated bond.

Examples of the phosphate ester include: di (alkyl or aryl) phosphates such as diethyl phosphate, dibutyl phosphate, dipentyl phosphate, dihexyl phosphate, diheptyl phosphate, dioctyl phosphate, dinonyl phosphate, didecyl phosphate, diundecyl phosphate, didodecyl phosphate, dioleyl phosphate, diphenyl phosphate, and ditolyl phosphate; tributyl phosphate, tripentyl phosphate, trihexyl phosphate, triheptyl phosphate, trioctyl phosphate, trinonyl phosphate, tridecyl phosphate, triundecyl phosphate, tridodecyl phosphate, tritridecyl phosphate, tritetradecyl phosphate, tripentadecyl phosphate, trihexadecyl phosphate, triheptadecyl phosphate, trioctadecyl phosphate, trioleyl phosphate, triphenyl phosphate, tricresyl phosphate, tris (ethylphenyl) phosphate, tris (propylphenyl) phosphate, tris (butylphenyl) phosphate, trixylyl phosphate, tolyldiphenyl phosphate, ditolyl diphenyl phosphate, etc. The alkyl group may be linear or branched and may have an unsaturated bond.

Examples of the condensed phosphate ester include resorcinol bis (diphenyl phosphate), resorcinol bis [ di (xylyl) phosphate ], bisphenol a bis (diphenyl phosphate), and the like.

Examples of the phosphonate ester include dialkyl phosphonoacetate, dialkyl hydroxymethyl phosphonate, dialkyl hydroxyethyl phosphonate, and dialkyl hydroxyundecyl phosphonate. The alkyl group of the phosphonate ester may be a linear or branched aliphatic group having 1 to 20 carbon atoms, for example.

Examples of the 2 nd antiwear agent include dithiocarbamates, zinc dithiocarbamates, molybdenum dithiocarbamates (MoDTC), disulfides, sulfurized olefins, and sulfurized fats and oils. The 2 nd antiwear agent may be, for example, a sulfurized olefin.

Examples of the 3 rd antiwear agent include: zinc dialkyldithiophosphates (ZnDTP); a thiophosphite ester; a dithiophosphoric phosphite; a trithiophosphite; a thiophosphate; a phosphorodithioate ester; a trithiophosphate ester; thiophosphites, dithiophosphites, trithiophosphites, thiophosphates, dithiophosphates, or amine salts, metal salts, derivatives of trithiophosphates, and the like. The 3 rd antiwear agent may be, for example, zinc dialkyldithiophosphate (ZnDTP).

The zinc dialkyldithiophosphate (ZnDTP) may be, for example, a compound represented by the following formula (B).

In the formula (B), R¹¹～R¹⁴Each independently represents a linear or branched alkyl group. The number of carbon atoms of the alkyl group may be 1 or more, or 3 or more, or 24 or less, 12 or less, or 8 or less.

The antiwear agent is at least 1 selected from the group consisting of a 1 st antiwear agent, a 2 nd antiwear agent, and a 3 rd antiwear agent. The antiwear agent is preferably the 1 st or 3 rd antiwear agent.

The content of the antiwear agent may be, for example, 0.01 mass% or more, 0.05 mass% or more, 0.1 mass% or more, 0.3 mass% or more, or 0.5 mass% or more, and may be 20 mass% or less, 15 mass% or less, 10 mass% or less, 5 mass% or less, or 3 mass% or less, based on the total amount of the lubricating oil composition.

The lubricating oil composition may further contain any additives for lubricating oils which are generally used depending on the purpose. Examples of such additives for lubricating oils include antioxidants, defoaming agents, metal deactivators, viscosity index improvers, pour point depressants, detergent dispersants, acid scavengers, and rust inhibitors. The content of these additives for lubricating oil may be, for example, 0.1 to 20% by mass based on the total amount of the lubricating oil composition.

The lubricating oil composition may have a kinematic viscosity at 40 ℃ of, for example, 1mm from the viewpoint of slidability²5mm above/s²More than s, or 10mm²Is more than s, and can be 1000mm²600mm below s²200mm below/s²100mm below s²Less than s, or 50mm²The ratio of the water to the water is less than s.

Other physical properties of the lubricating oil composition used in the lubricating method of the present embodiment, such as kinematic viscosity at 100 ℃, viscosity index, NOACK evaporation amount, flash point, and pour point, may be appropriately set.

The lubrication method of the present embodiment can be applied to lubrication systems of various devices. Examples of the lubricating system include a lubricating system for lubricating a portion requiring lubricity in a mechanical device such as a transport machine such as an (electric) automobile, a railway, or an aircraft, an industrial machine such as a machine tool or a robot, a household appliance such as a washing machine, a refrigerator, a room air conditioner, or a cleaner, or a precision machine such as a clock or a camera. Examples of the portion requiring lubricity include a portion (sliding portion) where components such as gears, bearings, pumps, vanes, rotors, and piston rings slide while contacting each other. Examples of the mechanical device including the sliding portion include an engine, a transmission, a compressor, a hydraulic mechanism, and a motor. As a mechanical device including the sliding portion, a compressor system including various cooling media and the like can be cited.

The method of supplying the lubricating oil composition to the sliding member in the lubricating system is not particularly limited. The lubricating system may be, for example, a system including a reservoir portion that contains a lubricating oil composition and a supply portion; the supply unit supplies the lubricating oil composition from the reservoir to the sliding member. The supply unit may be a circulation type supply unit that supplies the lubricating oil composition to the sliding member by a supply means such as a pump. The lubricating system may be a system in which the sliding member is impregnated with a lubricating oil composition. The lubricating system may be a system in which a lubricating oil composition is filled in a container having a sliding member, such as a compressor in a cooling medium circulation system of a refrigerator, a room air conditioner, or the like.

Examples

The present invention will be described more specifically below with reference to examples. However, the present invention is not limited to these examples.

(examples 1-1 and 1-2 and comparative examples 1-1 and 1-2)

(examples 2-1 to 2-4 and comparative example 2-1)

(examples 3-1 to 3-3 and comparative examples 3-1 and 3-2)

< preparation of lubricating oil composition >

Lubricating oil compositions were prepared by mixing the lubricating base oils shown in tables 1, 2, and 3 with an antiwear agent. The numerical values shown in tables 1, 2, and 3 refer to parts by mass.

The details of each component are as follows.

[ Lubricant base oils ]

Lubricating base oil 1: polyalphaolefin (PAO, trade name: Durasyn-164, manufactured by INEOS Inc., kinematic viscosity at 40 ℃ of 17.5mm²S, kinematic viscosity at 100 ℃: 4.0mm²/s)

Lubricating base oil 2: polyalphaolefin (PAO, trade name: Durasyn-168, manufactured by INEOS Inc., kinematic viscosity at 40 ℃ 46.0mm²S, kinematic viscosity at 100 ℃: 8.0mm²/s)

Lubricating base oil 3: mineral oil-based hydrocarbon oil (API 1509, base oil classification based on Appendix E: GroupIII, kinematic viscosity at 40 ℃: 20.3mm²S, kinematic viscosity at 100 ℃: 4.3mm²(s), viscosity index: 121. density at 15 ℃: 0.836g/cm³)

Lubricating oil base oil 4: mineral oil-based hydrocarbon oil (API 1509, base oil classification based on Appendix E: GroupI, kinematic viscosity at 40 ℃ 3.4 mm)²S, kinematic viscosity at 100 ℃: 1.3mm²(s), viscosity index: 84. density at 15 ℃: 0.830g/cm³)

[ anti-wear agent ]

Comparative antiwear agent: n-oleoyl sarcosine (trade name: Sarkosyl O, BASF corporation)

1-1 part of antiwear agent: triphenyl phosphate (trade name: TCP, product of Daba chemical industries, Ltd., No. 1 antiwear agent)

1-2 parts of antiwear agent: dioleyl phosphite (trade name: JP-218-OR, product of Tokyo chemical industry Co., Ltd., No. 1 antiwear agent)

1-3 parts of antiwear agent: di-n-butylzinc phosphate (phosphorus content: 13.2 mass%, sulfur content: 0 mass%, zinc content: 13 mass%, No. 1 antiwear agent)

2-1 part of antiwear agent: sulfurized olefin (trade name: GS-440L, DIC, 2 nd antiwear agent)

3-1 part of antiwear agent: zinc dialkyldithiophosphate (ZnDTP, trade name: HiTEC653, manufactured by Afton Chemical Corporation, 3 rd antiwear agent)

< evaluation of Friction characteristics >

The lubricating oil composition prepared above was subjected to a friction characteristic test under the following conditions using an mtm (mini Traction machine) tester (PCS Instruments), and the average friction coefficient (μ) of the last 10 minutes was obtained. As the ball, the following steel balls were used: a commercially available steel ball of 1/2 inches, high carbon chromium bearing steel (AISI52100), hardness 800-920HV and surface roughness <0.02 μm was prepared and treated by shot blasting to adjust the surface to 0.5 μm as an arithmetic average roughness (Ra). Further, as the disk, a PEEK sheet obtained by injection molding of polyetheretherketone (PEEK, super engineering plastic, ketarse (registered trademark) KT-820NT manufactured by Solvay) without filler addition and adjusted to a size of 40mm in length × 40mm in width × 2mm in thickness was used (PEEK disk). The results are shown in tables 1, 2 and 3. The smaller the friction coefficient, the more excellent the friction characteristics.

Oil temperature: 25 deg.C

Loading: 50N

Peripheral speed: 0.5m/s

And (3) slipping rate: 50 percent of

Test time: 60 minutes

< evaluation of abrasion characteristics >

The depth of the wear mark of the disc after the above-described friction characteristic test was measured to determine the volume wear amount. The results are shown in tables 1, 2 and 3. The smaller the volume abrasion amount, the more excellent the abrasion characteristics.

[ Table 1]

[ Table 2]

[ Table 3]

Comparative examples 4-1 and 4-2

< preparation of lubricating oil composition >

Lubricating oil compositions were prepared by mixing the lubricating base oil shown in Table 4 and an antiwear agent. The numerical values shown in table 4 refer to parts by mass. The details of each component are the same as described above.

< evaluation of Friction characteristics and abrasion characteristics >

The lubricating oil composition prepared in the above was subjected to the evaluation of frictional properties and the evaluation of wear characteristics in the same manner as described above except that the PEEK disk was changed to a steel disk (Standard Steel disk manufactured by PCS Co., Ltd., material: AISI 52100). The results are shown in Table 4. For comparison, data of comparative example 2-1 and example 2-3 are also shown.

[ Table 4]

As shown in tables 1, 2 and 3, in the examples using the lubricating oil composition containing the specific anti-wear agent, the friction coefficient between the sliding members can be reduced and the volume wear amount can be reduced, as compared with the comparative examples using only the lubricating oil base oil and the comparative examples using the lubricating oil composition containing no specific anti-wear agent. As shown in table 4, in the case where the pair of sliding members are a steel ball and a steel disc, the friction characteristics and the wear characteristics are inferior to those of comparative example 4-2 to which the specific anti-wear agent is added, compared with comparative example 4-1 to which the specific anti-wear agent is not added. On the other hand, in the case where the pair of sliding members were the steel ball and the PEEK disk, although there was a difference in absolute value of the volume abrasion loss depending on the kind of the disks of comparative example 4-1 and comparative example 4-2, example 2-3 to which the specific anti-wear agent was added was superior in the friction characteristics and the wear characteristics to comparative example 2-1 to which the specific anti-wear agent was not added. It is clear from this that the improvement of the sliding property by using the specific anti-wear agent is an effect which is specifically exhibited in the case where at least one of the pair of sliding members is a member containing engineering plastic. From the above, it was confirmed that: the lubricating method of the present invention can improve the sliding property in the case of using a resin material as a sliding member.