RUST-PREVENTIVE LUBRICATING OIL COMPOSITION

Abstract

A rust-preventive lubricating oil composition comprising a base oil; a sorbitan fatty acid ester; an overbased magnesium sulfonate; and at least one additive selected from the group consisting of a calcium sulfonate, a calcium sulfonate complex, a zinc sulfonate, a barium sulfonate, a fatty acid zinc, an oleic acid amine salt, an alkenyl succinic acid polyimide, and a benzotriazole derivative.

Claims

1. A rust-preventive lubricating oil composition comprising: a base oil; a sorbitan fatty acid ester; an overbased magnesium sulfonate; and at least one additive selected from the group consisting of a calcium sulfonate, a calcium sulfonate complex, a zinc sulfonate, a barium sulfonate, a fatty acid zinc, an oleic acid amine salt, an alkenyl succinic acid polyimide, and a benzotriazole derivative.

2. The rust-preventive lubricating oil composition of claim 1, wherein a total content of the overbased magnesium sulfonate and the additive is 5 to 40% by mass.

3. The rust-preventive lubricating oil composition of claim 1, wherein a content of the overbased magnesium sulfonate with respect to a total content of the overbased magnesium sulfonate and the additive is 25 to 90% by mass.

4. The rust-preventive lubricating oil composition of claim 1, wherein a content of the sorbitan fatty acid ester is 10 to 40% by mass.

5. The rust-preventive lubricating oil composition of claim 1, further comprising 0.1 to 10% by mass of amine-based antioxidant.

6. The rust-preventive lubricating oil composition of claim 1, further comprising 0.1 to 10% by mass of wax.

7. A wire rope, wherein the rust-preventive lubricating oil composition of claim 1 is filled at least in a void between a core strand and a side strand.

8. A window regulator comprising the wire rope of claim 7.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] FIG. 1 is a cross-sectional view showing one example of the structure of a wire rope according to the present embodiment.

EMBODIMENT FOR CARRYING OUT THE INVENTION

[0018] A method of manufacturing a rust-preventive lubricating oil composition according to the present embodiment (hereinafter merely referred to as a lubricating oil composition) will be described in detail below. Besides, the description below shows an example to describe the present embodiment and is not intended to limit the technical scope of the present invention only to the scope of the description. Besides, in a case that a numerical range is indicated using to in the present specification, the numerical values at both ends of the range are to be included therein.

<Lubricating Oil Composition>

[0019] The lubricating oil composition according to the present embodiment comprises a base oil, a sorbitan fatty acid ester, an overbased magnesium sulfonate, and a calcium sulfonate as essential components. A content of each of the above-described components comprised in the lubricating oil composition according to the present embodiment can be appropriately selected respectively within the range described such that a total content of the above-described components in the lubricating oil composition is less than or equal to 100% by mass.

(Base Oil)

[0020] The base oil is not particularly limited, and any arbitrary one can be appropriately selected from the following ones that are conventionally used as a base oil for a lubricating oil: a mineral oil, a synthetic oil, a gas liquified oil synthesized by the Fischer-Tropsch process from natural gas and the like (a GTL oil), a vegetable oil, an animal oil, and the like. One of the base oils may be used alone, or two or more thereof may be used in combination.

[0021] Examples of mineral oils include topped crudes obtained through atmospheric distillation of crude oils such as paraffin-based mineral oils, intermediate-based mineral oils, naphthene-based mineral oils, and the like; distillates obtained through reduced-pressure distillation of these topped crudes; mineral oils obtained by purifying the distillates through one or more purification treatments of solvent deasphalting, solvent extraction, hydro-finishing, solvent dewaxing, catalytic dewaxing, dewaxing by isomerization, reduced-pressure distillation, and the like. One of the mineral oils may be used alone, or two or more thereof may be used in combination.

[0022] Examples of synthetic oils include diester-based synthetic oils such as dibutyl sebacate, di-2-ethylhexyl sebacate, dioctyl adipate, diisodecyl adipate, ditridecyl adipate, ditridecyl glutarate, methyl acetyl ricinoleate, and the like; aromatic ester-based synthetic oils such as trioctyl trimellitate, tridecyl trimellitate, tetraoctyl pyromellitate, and the like; polyol ester-based synthetic oils such as trimethylolpropane caprylate, trimethylolpropane pelargonate, pentaerythritol 2-ethylhexanoate, pentaerythritol pelargonate, and the like; ester-based synthetic oils such as complex ester oils that are oligoesters from a polyhydric alcohol and a dibasic acid/monobasic acid mixed fatty acid; polyglycol-based synthetic oils such as polyethylene glycol, polypropylene glycol, polyethylene glycol monoether, polypropylene glycol monoether, and the like; phenyl ether-based synthetic oils such as monoalkyl triphenyl ether, alkyl diphenyl ether, dialkyl diphenyl ether, pentaphenyl ether, tetraphenyl ether, monoalkyl tetraphenyl ether, dialkyl tetraphenyl ether, and the like; silicone-based synthetic oils such as dimethylpolysiloxane, dipheyl polysiloxane, alkyl-modified polysiloxane, and the like; fluoride-based synthetic oils such as perfluorinated polyether, and the like. One of the synthetic oils may be used alone, or two or more thereof may be used in combination.

[0023] A kinematic viscosity of the base oil is not particularly limited, and the kinematic viscosity at 40 C. can be brought to be in the ranges of 4 to 1,000 mm.sup.2/s, 5 to 800 mm.sup.2/s, 6 to 600 mm.sup.2/s, or 7 to 500 mm.sup.2/s, for example. Besides, the kinematic viscosity of the base oil in the present specification is in accordance with JIS K 2283:2000 and is a value measured using a glass capillary viscometer.

[0024] A content of the base oil in the lubricating oil composition is not particularly limited, and it is preferably 10 to 85% by mass, more preferably 14 to 75% by mass, further preferably 18 to 68% by mass, further preferably 20 to 63% by mass, and particularly preferably 22 to 58% by mass.

(Sorbitan Fatty Acid Ester)

[0025] The lubricating oil composition according to the present embodiment comprises a sorbitan fatty acid ester as an essential component. It can be compounded with the sorbitan fatty acid ester to improve the rust-preventive properties of the lubricating oil composition.

[0026] As a fatty acid constituting the sorbitan fatty acid ester, a fatty acid derived from saturated or unsaturated animal or vegetable fats and oils is suitably used. The number of carbons of the fatty acid is preferably 6 to 22, preferably 8 to 20, and further preferably 10 to 18. Besides, the number of carbons of the fatty acid as referred to herein is the number including that of carbon atoms in carboxylic acid groups. The fatty acid may be one of linear, branched, and cyclic, but it is preferably linear. Specific examples of the fatty acid include caproic acid, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, lignoceric acid, oleic acid, elaidic acid, linoleic acid, linolenic acid, erucic acid, and the like.

[0027] The sorbitan fatty acid ester may be one in which at least one of the hydroxyl groups in sorbitan is esterified with a fatty acid. Specific examples of the sorbitan fatty acid ester include sorbitan monooleate, sorbitan monostearate, sorbitan monoisostearate, sorbitan monopalmitate, sorbitan monolaurate, sorbitan trioleate, sorbitan tristearate, sorbitan sesquistearate, sorbitan sesquioleate, sorbitan sesquiisostearate, sorbitan coconut oil fatty acid, and the like. In particular, the lubricating oil composition preferably comprises sorbitan mono-fatty acid esters. One of these sorbitan mono-fatty acid esters may be used alone, or two or more thereof may be used in combination.

[0028] A content of the sorbitan fatty acid ester in the lubricating oil composition is, from a viewpoint of rust-preventive properties, preferably 10 to 40% by mass, more preferably 12 to 38% by mass, further preferably 15 to 35% by mass, and particularly preferably 18 to 32% by mass.

(Overbased Magnesium Sulfonate)

[0029] The lubricating oil composition according to the present embodiment comprises an overbased magnesium sulfonate (overbased Mg sulfonate) as an essential component. The synergistic effects of the overbased magnesium sulfonate with the additive to be described below make it possible to significantly improve the rust-preventive properties of the lubricating oil composition. One of these overbased magnesium sulfonates may be used alone, or two or more thereof may be used in combination.

[0030] The base number of the overbased magnesium sulfonate is preferably 100 to 500 mgKOH/g, more preferably 150 to 500 mgKOH/g, further preferably 200 to 500 mgKOH/g, and particularly preferably 250 to 450 mgKOH/g. Besides, in the present specification, the base number is measured by a potentiometric titration method (base number (hydrochloric acid method)) in accordance with JIS K 2501:2003.

[0031] A content of the overbased magnesium sulfonate in the lubricating oil composition is, from a viewpoint of the rust-preventive properties, preferably 1 to 35% by mass, more preferably 2 to 30% by mass, further preferably 3 to 25% by mass, further preferably 4 to 21% by mass, and particularly preferably 5 to 18% by mass.

(Additive)

[0032] The lubricating oil composition according to the present embodiment is characterized in that at least one additive is used in combination with the overbased magnesium sulfonate, which at least one additive is selected from the group consisting of a calcium sulfonate, a calcium sulfonate complex, a zinc sulfonate, a barium sulfonate, a fatty acid zinc, an oleic acid amine salt, an alkenyl succinic acid polyimide, and a benzotriazole derivative. Among them, at least one additive selected from the group consisting of the calcium sulfonate, the calcium sulfonate complex, the zinc sulfonate, and the barium sulfonate is preferable, the calcium sulfonate and/or the calcium sulfonate complex is more preferable, and the calcium sulfonate is further preferable.

[0033] The calcium sulfonate according to the present embodiment can be a neutral salt, a basic salt, an overbased salt, or a mixture thereof. Examples of the calcium sulfonate include a neutral calcium sulfonate (neutral Ca sulfonate) obtained by directly reacting an alkylbenzene sulfonic acid with a base of a calcium oxide, a calcium hydroxide, and the like, or once converting the alkylbenzene sulfonic acid to an alkaline metal salt such as sodium salt, potassium salt, and the like, and then replacing the alkaline metal salt with calcium, and the like; a basic calcium sulfonate (basic Ca sulfonate) obtained by reacting the neutral calcium sulfonate with a calcium oxide and/or a calcium hydroxide; and an overbased calcium sulfonate (overbased Ca sulfonate) obtained by reacting the neutral Ca sulfonate or the basic Ca sulfonate with an excess of calcium oxide and/or calcium hydroxide under the presence of a carbonic acid gas or a boric acid or a boric acid salt. Moreover, the calcium sulfonate may comprise a calcium carbonate. One of such calcium sulfonates may be used alone, or two or more thereof may be used in combination.

[0034] The base number of calcium sulfonate is not particularly limited. The base number of neutral calcium sulfonate is preferably 0 to 50 mgKOH/g, more preferably 0 to 30 mgKOH/g, and further preferably 0 to 20 mgKOH/g. The base number of basic calcium sulfonate or overbased calcium sulfonate is preferably more than 50 mgKOH/g and not more than 500 mgKOH/g, more preferably 70 to 500 mgKOH/g, and further preferably 70 to 450 mgKOH/g. Among them, the base number of overbased calcium sulfonate is preferably 100 to 500 mgKOH/g, more preferably 150 to 500 mgKOH/g, further preferably 200 to 500 mgKOH/g, and particularly preferably 250 to 450 mgKOH/g.

[0035] The calcium sulfonate complex according to the present embodiment is a combination of calcium sulfonate and calcium carbonate, and a calcium salt (calcium soap) selected from (i) a higher fatty acid calcium salt such as calcium behenate, calcium stearate, calcium hydroxy stearate, calcium palmitate, calcium octylate, and the like; (ii) a lower fatty acid calcium salt such as calcium acetate, and the like; and (iii) an inorganic acid calcium salt such as calcium borate and the like. Among them, the lubricating oil composition is preferably compounded with calcium sulfonate and calcium carbonate and at least two selected from the group consisting of calcium behenate, calcium stearate, calcium hydroxy stearate, calcium acetate, and calcium borate.

[0036] As a fatty acid constituting the fatty acid zinc, one similar to the fatty acid constituting the sorbitan fatty acid ester can be suitably used.

[0037] Examples of the oleic acid amine salt include an oleic acid dicyclohexylamine salt, a polyether amine oleic acid salt, a tallow diamine oleic acid salt, and the like.

[0038] Examples of the benzotriazole derivative include 1,2,3-benzotriazole, N,N-bis(2-ethylhexyl)-(4 or 5)-methyl-1H-benzotriazole-1-methylamine, 1-[N,N-bis(2-ethylhexyl)aminomethyl]-benzotriazole, 1-[(2-ethylhexyl)aminomethyl]-benzotriazole, and the like.

[0039] A content of the additive in the lubricating oil composition is, from a viewpoint of the rust-preventive properties, preferably 1 to 30% by mass, more preferably 2 to 25% by mass, further preferably 3 to 21% by mass, further preferably 4 to 18% by mass, and particularly preferably 5 to 15% by mass.

[0040] A total content of the overbased magnesium sulfonate and the additive in the lubricating oil composition is, from a viewpoint of the rust-preventive properties, preferably 5 to 40% by mass, more preferably 7 to 35% by mass, further preferably 9 to 30% by mass, and particularly preferably 10 to 25% by mass.

[0041] A content of the overbased magnesium sulfonate with respect to a total content of the overbased magnesium sulfonate and the additive is preferably 20 to 98% by mass, more preferably 25 to 95% by mass, further preferably 25 to 90% by mass, further preferably 30 to 90% by mass, further preferably 32 to 85% by mass, further preferably 35 to 85% by mass, further preferably 40 to 80% by mass, further preferably 45 to 80% by mass, and particularly preferably 50 to 80% by mass. The content of the overbased magnesium sulfonate with respect to the total content of the overbased magnesium sulfonate and the additive can be brought to be in the above-described ranges to significantly improve the rust-preventive properties of the lubricating oil composition.

(the Other Compounding Agents)

[0042] The lubricating oil composition according to the present embodiment can further comprise one or more of compounding agents listed below. Examples of the other compounding agents include the other metal-based detergents besides the overbased magnesium sulfonate, the calcium sulfonate, the calcium sulfonate complex, the zinc sulfonate, the barium sulfonate, and the fatty acid zinc, a rust-preventive agent besides the sorbitan fatty acid ester, a tackiness agent, a wax, an antioxidant, an abrasion-resistant agent, a friction adjusting agent, an extreme pressure agent, an ashless dispersant, a viscosity index improver, a metal deactivator, an oiliness agent, a pour point depressant, a defoaming agent, and the like.

[0043] Examples of the other metal-based detergents include a metal salicylate such as a calcium salicylate and the like, a metal phenate such as a calcium phenate and the like, a magnesium sulfonate whose base number is less than 100 mgKOH/g (neutral magnesium sulfonate), a metal sulfonate besides the calcium sulfonate, the calcium sulfonate complex, the zinc sulfonate, and the barium sulfonate, and the like. One of these other metal-based detergents may be used alone, or two or more thereof may be used in combination.

[0044] When the lubricating oil composition comprises the other metal-based detergent, a content of the other metal-based detergent in the lubricating oil composition is preferably not more than 5.0% by mass, more preferably not more than 3.0% by mass, further preferably not more than 1.0% by mass, further preferably not more than 0.5% by mass, and further preferably not more than 0.1% by mass, and particularly preferably the other metal-based detergent is not comprised in the lubricating oil composition. Moreover, the content can be brought to be not less than 0.1% by mass, not less than 0.5% by mass, or not less than 1.0% by mass, for example.

[0045] Examples of the rust-preventive agent besides the sorbitan fatty acid ester include an alkyl or alkenyl succinic acid derivative such as a dodecenyl succinic acid half ester, an octadecenyl succinic anhydride, a dodecenyl succinic acid amide, and the like; a polyhydric alcohol fatty acid ester such as a glycerol fatty acid ester, a pentaerythritol fatty acid ester, and the like; a rosin amine, a N-oleyl sarcosine, a dialkyl phosphite amine, and the like. One of these rust-preventive agents besides the sorbitan fatty acid ester may be used alone, or two or more thereof may be used in combination.

[0046] When the lubricating oil composition comprises the rust-preventive agent besides the sorbitan fatty acid ester, a content in the lubricating oil composition of the rust-preventive agent besides the sorbitan fatty acid ester is preferably not more than 10.0% by mass, more preferably not more than 5.0% by mass, further preferably not more than 1.0% by mass, further preferably not more than 0.5% by mass, and further preferably not more than 0.1% by mass, and particularly preferably the rust-preventive agent besides the sorbitan fatty acid ester is not comprised in the lubricating oil composition. Moreover, the content can be brought to be not less than 0.1% by mass, not less than 0.5% by mass, or not less than 1.0% by mass.

[0047] The tackiness agent is not particularly limited as long as it is a known tackiness agent used in a lubricating oil. Examples of the tackiness agent include a polymethacrylate, an alpha-olefin copolymer and a hydrogenated product thereof, a polybutene and a hydrogenated product thereof, a polyisobutene and a hydrogenated product thereof, a polyisobutylene and a hydrogenated product thereof, a styrene-diene copolymer and a hydrogenated product thereof, a styrene-maleic anhydride ester copolymer, and the like. Among them, one or more selected from the group consisting of the polymethacrylate and the alpha-olefin copolymer is preferable and the polymethacrylate is more preferable. These tackiness agents may be of the dispersion type or of the non-dispersion type.

[0048] When the lubricating oil composition comprises the tackiness agent, a content of the tackiness agent in the lubricating oil composition is preferably not less than 1% by mass, more preferably not less than 3% by mass, further preferably not less than 5% by mass, and particularly preferably not less than 7% by mass. Moreover, the content is preferably not more than 30% by mass, more preferably not more than 28% by mass, further preferably not more than 26% by mass, and particularly preferably not more than 24% by mass.

[0049] As a wax, a plant-based wax, an animal-based wax, a petroleum-based wax, and the like that are known can be used, for example. Examples of the plant-based wax include a rice wax, a carnauba wax, a candelilla wax, and the like. Examples of the animal-based wax include beeswax, lanolin, a spermaceti wax, and the like. Examples of the petroleum-based wax include a microcrystalline wax, a paraffin wax, and the like. Examples of a synthetic wax include a Fischer-Tropsch wax, a polyethylene wax, a polypropylene wax, an oil and fat-based wax (ester, ketones, amide), a hydrogenated wax, and the like.

[0050] When the lubricating oil composition comprises the wax, a content of the wax in the lubricating oil composition is preferably not less than 0.1% by mass, more preferably not less than 0.5% by mass, and further preferably not less than 1.0% by mass. Moreover, the content is preferably not more than 10.0% by mass, more preferably not more than 8.0% by mass, further preferably not more than 6.0% by mass, and particularly preferably not more than 4.0% by mass.

[0051] Examples of the antioxidant include an amine-based antioxidant, a phenol-based antioxidant, a sulfur-based antioxidant, a phosphorus-based antioxidant, a molybdenum amine complex-based antioxidant, and the like, and the amine-based antioxidant is preferable. One of these antioxidants may be used alone, or two or more thereof may be used in combination.

[0052] Examples of the amine-based antioxidant include diphenylamine-based antioxidants such as diphenylamine, monooctyl diphenylamine, monononyl diphenylamine, dibutyl diphenylamine, monobutylphenylmonooctylphenylamine, dihexyl diphenylamine, dioctyl diphenylamine, dinonyl diphenylamine, tetrabutyl diphenylamine, tetrahexyl diphenylamine, tetraoctyl diphenylamine, tetranonyl diphenylamine, N,N-diphenyl-p-phenylenediamine, and the like; phenylenediamine-based antioxidants such as N,N-diisopropyl-p-phenylenediamine, N,N-diphenyl-p-phenylenediamine, N-cyclohexyl-N-phenyl-p-phenylenediamine, and the like; naphthylamine-based antioxidants such as alpha-naphthylamine, phenyl-alpha-naphthylamine, butylphenyl-alpha-naphthylamine, hexylphenyl-alpha-naphthylamine, octylphenyl-alpha-naphthylamine, nonylphenyl-alpha-naphthylamine, and the like, and the diphenylamine-based antioxidants are preferable.

[0053] When the lubricating oil composition comprises the antioxidant (preferably the amine-based antioxidant), a content of the antioxidant in the lubricating oil composition is preferably not less than 0.1% by mass, more preferably not less than 0.2% by mass, and further preferably not less than 0.3% by mass. Moreover, the content is preferably not more than 10.0% by mass, more preferably not more than 8.0% by mass, further preferably not more than 6.0% by mass, further preferably not more than 4.0% by mass, and particularly preferably not more than 2.0% by mass.

[0054] Examples of the abrasion-resistant agent include an organic sulfur-based abrasion-resistant agent such as a sulfurized olefin, a dialkylpolysulfide, a diallylalkyl polysulfide, a diallyl polysulfide, and the like; an organic phosphorus-based abrasion-resistant agent such as a phosphate ester, a thiophosphate ester, a phosphite ester, an alkyl hydrogen phosphite, a phosphate ester amine salt, a phosphite ester amine salt, and the like; an organic zinc-based abrasion-resistant agent such as a dialkyl dithiophosphate zinc (ZnDTP), a dialkyl dithiocarbamate zinc (ZnDTC), and the like; an organic molybdenum-based abrasion-resistant agent such as a dialkyl dithiophosphate molybdenum (MoDTP), a dialkyl dithiocarbamate molybdenum (MoDTC), and the like, and the organic zinc-based abrasion-resistant agent is preferable. One of these abrasion-resistant agents may be used alone, or two thereof may be used in combination.

[0055] When the lubricating oil composition comprises the abrasion-resistant agent (preferably the organic zinc-based abrasion-resistant agent), a content of the abrasion-resistant agent in the lubricating oil composition is preferably not less than 0.1% by mass, more preferably not less than 0.5% by mass, and further preferably not less than 1.0% by mass. Moreover, the content is preferably not more than 10.0% by mass, more preferably not more than 8.0% by mass, further preferably not more than 6.0% by mass, and particularly preferably not more than 4.0% by mass.

[0056] The lubricating oil composition according to the present embodiment is not particularly limited as long as it is liquid at room temperature (25 C.). The pour point of the lubricating oil composition according to the present embodiment is preferably not higher than 0 C., more preferably not higher than 5 C., further preferably not higher than 10 C., and particularly preferably not higher than 15 C. Besides, the pour point of the lubricating oil composition according to the present embodiment is measured in accordance with JIS K 2269:1987.

[0057] The lubricating oil composition according to the present embodiment is manufactured by mixing each of the base oil, the sorbitan fatty acid ester, the overbased magnesium sulfonate, and the calcium sulfonate and adding the above-described additive as needed using a known method.

<Wire Rope>

[0058] One example of the structure of a wire rope according to the present embodiment is shown in FIG. 1, but the present disclosure is not limited to such an aspect. A wire rope 1 shown in FIG. 1 has a so-called multiple twist structure in which a core strand 11 and eight side strands 12 around the core strand 11 are twisted together. The core strand 11 and the side strands 12 are formed by 19 element wires being twisted together into a Warrington twist and by 7 element wires being twisted together (W(19)+87), respectively.

[0059] In the core strand 11, six core strand first side element wires 11b are arranged around one core strand core element wire 11a, and six core strand second side element wires 11c are arranged between the neighboring two core strand first side element wires 11b so as to be in contact with the two core strand first side element wires 11b. Moreover, six core strand third side element wires 11d, each having a diameter less than that of the core strand first side element wire 11b, are arranged between the six core strand second side element wires 11c and are formed such that the core strand second side element wires 11c and the core strand third side element wires 11d are inscribed in one circle. The side strands 12 are formed by six side strand side element wires 12b twisted together around a side strand core element wire 12a. A twisting method (S twist, Z twist, and the like) and a pitch of the core strand 11 and the side strand 12 may be changed appropriately in accordance with the application used. Moreover, the wire rope 1 shown in FIG. 1 has a Warrington type parallel twist structure, but it can be of a seal type, a filler type, a Warrington seal type, and the like, and it can also be cross-twisted. Furthermore, differences are provided in diameter for the element wires used, but the element wires can have the same diameter. Moreover, FIG. 1 shows the wire rope 1 that has a certain multiple twist structure, but the wire rope 1 can be configured to have a different multiple twist structure or a single twist structure. Furthermore, the diameter of each element wire used for the wire rope 1 or the diameter of the entire wire rope 1 can be changed appropriately in accordance with the application used.

[0060] The material for the wire rope 1 is not particularly limited, examples of the material include zinc plating, zinc-aluminum alloy plating, iron-zinc alloy plating, aluminum plating, tin plating, and the like, and zinc plating is suitably used. The element wires can be obtained by drawing these steel materials.

[0061] In the wire rope 1, the lubricating oil composition is filled at least in a void between the core strand 11 and the side strands 12. A sufficient amount of the lubricating oil composition is filled in a relatively large void between the core strand 11 and the side strands 12, and this lubricating oil composition further permeates between each of the element wires, thereby reducing the fretting wear of the element wire associated with the bending of the wire rope 1 and improving the bending fatigue resistance. Moreover, lubricating oil that permeates between the element wires seeps onto the surface of the wire rope 1, thereby reducing wear due to contact between the wire rope 1 and a guide roller. Therefore, it is believed that the durability of the wire rope 1 is improved and wire breakage is prevented over a long period of time. Besides, the lubricating oil composition can be impregnated when the element wires are twisted together or can be impregnated after the element wires are twisted together.

[0062] The wire rope according to the present embodiment is, for example, routed between an operating portion that is operated to pull or pull and push the wire rope, and an object to be operated that is operated at a position remote from the operating portion via the wire rope, which wire rope is pulled or pulled and pushed by the operating portion being operated. The operating portion is not particularly limited as long as it can operate the wire rope and the object to be operated is not particularly limited as long as it can be operated by the wire rope. The wire rope according to the present embodiment can be used for a window regulator, a parking brake, a fuel lid actuator, a bike screen, and the like. Moreover, the wire rope according to the present embodiment is also applicable to applications other than vehicles.

EXAMPLE

[0063] Below, the present embodiment will be described more specifically with reference to an Example, but the present embodiment is not limited thereto.

[0064] The following raw materials were used in the present Example: [0065] Sorbitan fatty acid ester: TFE-120SB (sorbitan monooleate), manufactured by TSUNO FOOD INDUSTRIAL CO., LTD. [0066] Overbased Mg sulfonate: Hybase M-401 (the base number: 394 mgKOH/g), manufactured by Lanxess USA [0067] Overbased Ca sulfonate: Infineum C9330 (the base number: 305 mgKOH/g), manufactured by Infineum International Limited [0068] Neutral Ca sulfonate: Sulfol CA-45N (the base number: 0.26 mgKOH/g), manufactured by MORESCO Co., Ltd. [0069] Antioxidant: Irganox L57 (diphenylamine-based antioxidant), manufactured by BASF AG [0070] Base oil 1: SNH-8 (naphthene-based mineral oil, kinematic viscosity at 40 C.: 8 mm.sup.2/s), manufactured by SANKYO YUKA KOGYO K.K. [0071] Base oil 2: SNH-46 (naphthene-based mineral oil, kinematic viscosity at 40 C.: 46 mm 2/s), manufactured by SANKYO YUKA KOGYO K.K. [0072] Base oil 3: SNH-440 (naphthene-based mineral oil, kinematic viscosity at 40 C.: 407 mm 2/s), manufactured by SANKYO YUKA KOGYO K.K. [0073] Tackiness agent: PLEXOL702 (polymethacrylate), manufactured by Evonik Industries AG

<Preparation of Lubricating Oil Composition and Wire Rope>

[0074] A lubricating oil composition for testing was prepared by thoroughly mixing various raw materials in accordance with formulations described in Table 1 and Table 2, respectively. Moreover, element wires were twisted together to prepare a wire rope with a diameter of 1.5 mm, which wire rope has a structure shown in FIG. 1, and the lubricating oil composition was filled in a void between the core strand 11 and the side strand 12. Besides, the pour point of the lubricating oil composition was not higher than 15 C. in all of Examples 1 to 10 and Comparative examples 1 to 3.

<Rust-Preventive Properties Test>

[0075] In accordance with JIS K 2510:1998, a generation rate of white rust and red rust was examined after storing, in an apparatus sprayed with neutral salt water for a specified time under an environment of 35 C., a zinc-plated wire rope test piece coated with a lubricating oil composition for testing, the zinc-plated wire rope test piece being cut to the length of approximately 100 mm. Table 1 shows a time period during which generation rate of rust was maintained at 0%. A performance target value for white rust shall be 300 hours or more and that for red rust shall be 500 hours or more.

TABLE-US-00001 TABLE 1 Example Compounding amount (% by mass) 1 2 3 4 5 6 7 8 9 10 Sorbitan fatty acid ester 30 30 30 30 30 30 30 20 30 30 Overbased Mg sulfonate 10 10 5 15 5 10 5 10 15 15 (base number: 394 mgKOH/g) Overbased Ca sulfonate 10 5 5 (base number: 305 mgKOH/g) Neutral Ca sulfonate 10 15 5 10 5 5 10 (base number: 0.26 mgKOH/g) Antioxidant 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 Base oil 1 29.7 29.7 29.7 29.7 32.7 32.7 35.7 35.7 22.5 5.4 Base oil 2 11.3 11.3 11.3 11.3 12.5 12.5 13.6 13.6 8.5 Base oil 3 21.6 Tackiness agent 8.5 8.5 8.5 8.5 9.3 9.3 10.2 10.2 18.5 22.5 White rust generation (h) 408 336 192 408 336 336 336 312 >700 >700 Red rust generation (h) >700 678 528 >700 528 600 576 576 >700 >700

TABLE-US-00002 TABLE 2 Comparative example Compounding amount (% by mass) 1 2 3 Sorbitan fatty acid ester 30 30 Overbased Mg sulfonate 10 5 (the base number: 394 mgKOH/g) Overbased Ca sulfonate (the base number: 305 mgKOH/g) Neutral Ca sulfonate 10 5 (the base number: 0.26 mgKOH/g) Antioxidant 0.5 0.5 0.5 Base oil 1 35.7 35.7 53.7 Base oil 2 13.6 13.6 20.4 Tackiness agent 10.2 10.2 15.4 White rust generation (h) 312 144 48 Red rust generation (h) 480 312 312

[0076] From the results shown in FIG. 1 and FIG. 2, it can be seen that a lubricating oil composition according to the present embodiment, which lubricating oil composition comprises a base oil, a sorbitan fatty acid ester, an overbased magnesium sulfonate, and predetermined additives, has good rust-preventive properties.

REFERENCE SIGNS LIST

[0077] 1 WIRE ROPE [0078] 11 CORE STRAND [0079] 11a CORE STRAND CORE ELEMENT WIRE [0080] 11b CORE STRAND FIRST CORE ELEMENT WIRE [0081] 11c CORE STRAND SECOND CORE ELEMENT WIRE [0082] 11d CORE STRAND THIRD CORE ELEMENT WIRE [0083] 12 SIDE STRAND [0084] 12a SIDE STRAND CORE ELEMENT WIRE [0085] 12b SIDE STRAND SIDE ELEMENT WIRE