DESCRIPTION

IMPREGNATING OIL COMPOSITION FOR SINTERED BEARING, BEARING APPARATUS AND SLIDING MEMBER

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to an impregnating oil composition for a sintered bearing to be used as a sliding part or the like in slide-bearing apparatuses which have been used industrially; and more specifically, the invention relates to the impregnating oil composition capable of forming films and contributing to lengthening life-times of bearing apparatuses. The invention also relates to a bearing apparatus employing the composition.

2. Related Art

One feature of a bearing apparatus, employing a sintered body impregnated with lubricating oil as a sliding plane, resides in that it can work without refueling, and, thus, it has been employed in small size motors which can be operated relatively high speed or are used for relatively light load. Along with the popularization of small size motors, such bearing apparatuses have been employed in the various technical fields such as automobiles, audio equipments, office equipments, home electric equipments and agricultural machines. And, along with the advance in qualities of such various equipments or the like, the requests for ^' qualities of bearings employed in such equipments have been higher and more diversified, and, in order to respond such requests, it is necessary to provide high lubricating techniques. Although, previously, researches and developments have been made on materials to be used as bearing members, recently, there is tendency to think that researches and developments on impregnating lubricant oils for bearing members are more important than those on materials of bearing members. One of the grounds thereof is that lubricant oils, employed in bearing apparatuses, are used in nearly equal to a boundary lubrication state rather than in a fluid lubrication state. The bearing ability of a bearing apparatus may remarkably depend on the property of lubricant oil

with which the sintered body is impregnated. And, lubricant oils exhibiting a high ability of forming films are required.

Generally, bearing oils are required to exhibit a low current value (i.e. to use much less power), to penetrate readily, to deteriorate with age hardly (i.e. to exhibit a high ability of forming films) , to work with a wide service temperature range from a low temperature to a high temperature (for example, from -40 to 120°C) , to withstand high speed (about 30, 000 rpm) and low speed (60-180 rpm) and the like.

Examples of the conventional impregnating oil for a sintered bearing, include mineral oil such as paraffin-base or naphthene-base crude oil; and synthetic oil such as diester, polyol ester and poly-alpha-olefin, and they may be selected depending on their properties. However, they are not provided as exclusively-used bearing oils, and, at present, they are selected from commercially available hydraulic actuation oils and engine oils.

Generally, mineral base oil in mineral oil-base lubricant may be added with various additives such as an antioxidant, an anti-rusting agent, an anti-wear agent, an antifoaming agent and an metal deactivator, and, if necessary, other additives such as a detergent additive, an viscosity index improver and a pour-point depressant.

Automotive engine oils and poly-alpha-olefin hydrides employed in various applications such as ATF have been considered as appropriate base oils which can be employed in lubricants with a wide service temperature range from a low temperature to a high temperature, since they exhibit good properties in a low temperature range and small evaporative loss. If mineral oil is used as base oil, paraffin ingredients in mineral oil may precipitate as wax at a low temperature, and such precipitation may result in an increase of the current value; and impurities or additives reacting therewith in mineral oil may precipitate as sludge at a high temperature, and such precipitation may accelerate bearing wear and also result in the increase of the current value. Therefore, synthetic oils, not containing impurities and exhibiting a high dissolving power for sludge, may be preferably used.

A bearing oil composition for sintered oil-impregnated body, which is a long-life oil, does not form sludge during service, and can be used with a wide service temperature range of service temperature, is disclosed in JPANo. hei 7-53984 (the term "JPA" as used herein means an "unexamined published Japanese patent application (Kohkai Tokkyo Kohou) ") . The composition is prepared by adding at least one additive selected from zinc dialkyldithiophosphate, Mo dialkyldithiocarbamate, Mo dialkyldithiophosphate and a sulfur-phosphorus extreme pressure additive to particular synthetic base oil.

A bearing oil composition for sintered oil-impregnated body, which is capable of manifesting excellent oil film-forming properties, can be used with a wide service temperature range, exhibits good lubricating properties and is a long-life oil, is disclosed in JPA No. hei 10-287892. The composition is prepared by adding a predetermined amount of a phosphoric ester to particular synthetic base oil.

SUMMARY OF THE INVENTION

One object of the present invention is to provide an impregnating oil composition for a sintered bearing, which exhibits a high ability of forming films and excellent lubricating properties, can be used with a wide service temperature range and is long-life.

Another object of the invention is to provide a bearing apparatus which is long-life and is capable of working stably, and to provide a sliding member useful for a bearing apparatus.

In one aspect, the invention provides an impregnating oil composition for a sintered bearing, comprising: a base oil, at least one compound represented by a formula (1) shown below:

Formula (1)

R—X- -D m

where D represents an m-valent cyclic group capable of

binding to ^Nλ m" of -X-R; each X represents a single bond or a bivalent linking group selected from the group consisting of NR ¹ , where R ¹ is a hydrogen atom or a C ₁ - ₃₀ alkyl group, oxygen, sulfur, carbonyl, sulfonyl and any combinations thereof; each R represents a substituted or non-substituted, alkyl group, alkenyl group, alkynyl group, aryl group or heterocyclic group, or a halogen atom, hydroxy, amino, mercapto, cyano, sulfide, carboxy or salt thereof, sulfo or salt thereof, hydroxylamine, ureido or urethane; and m is an integer from 2 to 11.

The base oil may contain synthetic hydrocarbon; the impregnating oil composition, wherein the base oil contains at least one type of poly-alpha-olefin, poly-alpha-olefin hydrate, ethylene-alpha-olefin copolymer, ethylene-alpha-olefin copolymer hydrate, a mixture of poly-alpha-olefin or hydrate thereof and alkyl naphthalene, a mixture of ethylene-alpha-olefin copolymer or hydrate thereof and alkyl naphthalene.

As embodiments of the invention, the impregnating oil composition comprising the compound represented by the formula (1) in an amount from 0.1 to 10 weight % with respect to the total weight of the composition; and the impregnating oil composition wherein the base oil comprises alkyl naphthalene in an amount from of 50 to 99.9 weight % and poly-alpha-olefin hydrate or ethylene-alpha-olefin copolymer hydrate in an amount from 50 to 0.1 weight % with respect to the total weight of the base oil; are provided.

In the formula (1), D may represent a cyclic group of any one of formulae [1] to [74]:

[7] [8] [9] [11]

[12] [13] [14] [15]

[16] [17] [18] [19]

[21] [22] [23]

[20]

[28] [29] [30]

[31] [32] [33]

[34] [35] [36]

[46] [47] [48]

[49] [50] [51]

[52] [53] [54]

[55] [56] [57]

[58] [59] [60]

[61] [62] [63]

and R ¹³ respectively represent a substituted or non-substituted, alkyl group, alkenyl group, alkynyl group, aryl group or heterocyclic group, or a halogen atom, hydroxy, amino, mercapto, cyano, sulfide, carboxy or salt thereof, sulfo or salt thereof, hydroxylamine, ureido or urethane; Formula (3)

where X ²¹ , X ²² and X ²³ respectively represent a single bond or a bivalent linking group selected from the group consisting of NR ¹ , where R ¹ is a hydrogen atom or a C^o alkyl group, oxygen, sulfur, carbonyl, sulfonyl and any combinations thereof; R ²¹ , R ²² and R ²³ respectively represent a substituent; and a21, a22 and a23 respectively represent an integer from 1 to 5.

In another aspect, the invention provides a bearing apparatus for bearing a rotating element rotatably comprising a sliding part wherein at least a part of the sliding part is a sintered body impregnated with a composition of the invention; and a sliding member comprising a sintered body impregnated with a composition of the invention.

PREFERRED EMBODIMENT OF THE INVENTION

The present invention will be described in detail. It is to be understood, in this description, that the term "... to ..." is used as meaning a range inclusive of the lower and upper values disposed therebefore and thereafter.

The invention relates to an impregnating oil composition for a sintered bearing. The composition of the invention comprises at least one compound selected from the group represented by a formula (1) .

Formula (1)

R—X-) D i m

In the formula, D represents anm-valent cyclic group capable of binding to ^λλ m" of -X-R; each X represents a single bond or a bivalent linking group selected from the group consisting of NR ¹ , where R ¹ is a hydrogen atom or a Ci-30 alkyl group, oxygen, sulfur, carbonyl, sulfonyl and any combinations thereof; each R represents a substituted or non-substituted, alkyl group, alkenyl group, alkynyl group, aryl group or heterocyclic group, or a halogen atom, hydroxy, amino, mercapto, cyano, sulfide, carboxy or salt thereof (carboxylate) , a sulfo or salt thereof (sulfate), hydroxylamine, ureido or urethane; and m is an integer from 2 to 11.

The compound represented by the formula (1) has a cyclic group, "D", and m, representing an integer from 2 to 11, of side chains, "[R-X-)". In this description, the term of "discotic compound" is used for any compounds having a discotic segment in the central portion of a molecule structure. The discotic segment is a central segment without the side chain segment, and to use an original form thereof, namely a hydrogenised compound, as an example, the structural feature of such a central segment can be explained as follows:

A molecular size of a hydrogenised compound, which can be an original form of a discotic compound, may be obtained by 1) to 5) steps.

1) To create a possible planar, desirably an exact planar, molecule structure for a target molecule. For creating, standard bond-length and bond-angle values based on orbital hybridization are desirably used, and such standard values can be obtained with reference to the 15th chapter in the second volume of "Chemical Handbook, revised version 4, Foundation Section (Kagaku Binran. Kaitei 4 Kisohen) " compiled by The Chemical Society of Japan, published by MARUZEN in 1993.

2) To optimize a molecular structure using the above-obtained planar structure as a default by molecular orbital method or molecular mechanics method. Examples of such methods

include Gaussian92, MOPAC93, CHARMm/QUANTA and MM3, and Gaussian92 is desirably selected.

3) To move a centroid of the optimized structure to an origin position and to create a coordinate having an axis equal to a principal axis of inertia (a principal axis of a inertia tensor ellipsoid) .

4) To set a sphere defined by van der Waals radius in each atom positions thereby drawing a molecular structure.

5) To calculate lengths along to three coordinate axes on van der Waals surface thereby obtaining ^λλ a", ^λλ b" and "c".

Using ^λλ a", ^λλ b" and ^Nλ c" obtained trough the steps 1) to 5), "a discotic structure" can be defined as a structure which satisfies a ≥ b > c and a ≥ b ≥ a/2, and a preferred example of the discotic structure is a structure which satisfying a ≥ b > c and a ≥ b ≥ 0.7a or b/2 > c.

Examples of the hydrogenated compound, which can be an original form of a discotic compound, include mother cores and derivatives described in various literatures such as "Ekisho no Kagaku (Science of Liquid Crystal) , edited by the Chemical Society of Japan, Seasonal Chemical Review No.22, Chapter 5, and Chapter 10, Section 2 (1994); C. Destrade et al. , MoI. Crysr. Liq. Cryst., vol. 71, p. Ill (1981); B. Kohne et al. , Angew. Chem. Vol. 96, p. 70; compounds described in J.M.Lehn et al. , J. Chem. Soc. Chem. Commun., p. 1794(1985); and J. Zhang et al., J. Am. Chem. Soc, vol. 116, p. 2655 (1994) . More specific examples of the hydrogenated compound include benzene derivatives, tri phenylene derivatives, truxene derivatives, phthalocyanine derivatives, porphyrin derivatives, anthracene derivatives hexaethynylbenzene derivatives, dibenzopyrene derivatives, coronene derivatives and phenylacetylene macrocycl derivatives . The examples also include cyclic compounds described in "Chemical Review (Kagaku Sousetsu) No. 15 Chemistry of Novel Aromatic Series (Atarashii Houkouzoku no Kagaku) " compiled by the Chemical Society of Japan, published by University of Tokyo Press in 1977; and electronic structures such as heteroatom-substituted compounds thereof.

Examples of the cyclic group represented by D include aryl groups and heterocyclic groups. Examples of the aryl rings in the aryl group include a benzene ring, an indene ring, a naphthalene

ring, a triphenylene ring, a fluorene ring, a phenanthrene ring, an anthracene ring and a pyrene ring. The aryl group may have one or more substituents .

The heterocyclic group is desirably selected from 5-, 6- or 7-membered heterocyclic groups, more desirably from 5- or 6-membered heterocyclic groups, and much more desirably from 6-membered heterocyclic groups . One or more hetero atoms embedded in the heterocycle are desirably selected from the group consisting of nitrogen, oxygen and sulfur atoms. Aromatic heterocycles are preferred. An aromatic heterocycle usually belongs to the group of unsaturated heterocycles, and unsaturated heterocyclic groups having maximum double bonds are more preferred. Examples of the heterocycle include furan ring, thiophene ring, pyrrole ring, pyrroline ring, pyrrolizine ring, oxazole ring, isoxazole ring, thiazole ring, isothiazole ring, imidazole ring, imidazoline ring, imidazolidine ring, pyrazole ring, pyrazoline ring, pyrazolidine ring, triazole ring, furazan ring, tetrazole ring, pyrane ring, thyine ring, pyridine ring, piperidine ring, oxazine ring, morpholine ring, thiazine ring, pyridazine ring, pyrimidine ring, pyrazine ring, piperazine ring and triazine ring. Triazine ring is preferred and 1, 3, 5-triazine ring is more preferred. The heterocycle may be condensed with other heterocycle ( s ) , or at least one aliphatic ring or aryl ring. Mono heterocyclic groups are preferred.

Preferred examples of the cyclic group D include the groups [1] to [74] shown below:

[36] [37] [38]

[39] [40]

[41] [42] [43]

[44] [45]

[46] [47] [48]

[49] [50] [51]

[52] [53] [54]

[55] [56] [57]

[58] [59] [60]

[61] [62] [63]

[64] [65] [66]

[67] [68] [69]

In the formula, n is an integer of 2 or more, and is preferably 3 or more.

In the formula, "*" shows a position capable of binding to a side chain. When two or more positions are marked by "*", it is not necessary that all positions marked by ^λλ *" are binding to side chains.

In the formula, M is a metal ion or two hydrogen atoms.

It is preferred that the mother core is a pi-conjugated system skeleton in which at least one polar atom is embedded. Among the above, the groups of [1], [2], [3], [6], [11], [12], [21], [23], [28] and [56] are preferred; the groups of [1], [2], [3], [β], [11] and [21] are more preferred; and the groups of [1], [2] and [3] are much more preferred.

In the formula (1) , each X represents a single bond or a bivalent linking group selected from the group consisting of NR ¹ , where R ¹ is a hydrogen atom or a Ci_ ₃ o alkyl group, oxygen, sulfur, carbonyl, sulfonyl and any combinations thereof. In the case that X is a single bond, it may bind directly to nitrogen atom, having free atomic valence, of a heterocyclic group such as a piperidine residue, or may bind to a heteroatom not having free atomic valence

to form an onium salt such as an oxonium salt, sulfonium salt or ammonium salt. It is preferred that X is a sulfur atom or NR ¹ in where R ¹ is preferably a hydrogen atom or a C3 or shorter alkyl group .

In the formula (1), each R represents a substituted or non-substituted, alkyl group, alkenyl group, alkynyl group, aryl group or heterocyclic group, or a halogen atom, hydroxy, amino, mercapto, cyano, sulfide, carboxy or slat thereof, sulfo or salt thereof, hydroxylamine, ureido or urethane.

In the case that R is an alkyl group, R is preferably selected from Ci- ₄₀ , more preferably from C ₂ -20 and much more preferably from C ₆ - ₃₀ alkyl groups. The alkyl group may have a linear or branched chain structure. And the alkyl group may have one or more substituents. Examples of the substituent include halogen atoms, Ci-40/' preferably Cχ-20r alkoxy groups such as methoxy, ethoxy, methoxyethoxy and phenoxy; Ci-40, preferably Ci_ ₂ o _r alkylthio groups and C ₆ - _40λ preferably C6-20, arylthio groups such as methylthio, ethylthio, propylthio and phenylthio; Ci-40, preferably C _I _ _20λ alkylamino groups such as methylamino and propylamino; Ci- ₄₀ , preferably Cχ-2 _0/ - acyl groups such as acetyl, propanoyl, octanoyl and benzoyl; C1-. ₄₀ , preferably C2- _20λ acyloxy groups such as acetoxy, pivaloyloxy and benzoyloxy; hydroxyl, mercapto, amino, carboxyl, sulfo, carbamoyl, sulfamoyl and ureido.

In the case that R is an alkenyl group or an alkynyl group, R is preferably selected from C2- _40λ more preferably from € ₂ - ₃₀ ^ much more preferably from C ₄ - ₃ 0 and further much more preferably from C ₆ - ₃₀ alkenyl or alkynyl groups. The alkenyl or alkynyl group may have a linear or branched chain structure. The alkenyl or alkynyl group may have one or more substituents selected from the groups exemplified above as substituents of the alkyl group.

In the case that R is an aryl group, it is preferred that R is phenyl, indenyl, alpha-naphthyl, beta-naphthyl, fluorenyl, phenanthryl, anthracenyl or pyrenyl; and it is more preferred that it is phenyl or naphthyl. The aryl group may have one or more substituents. Examples of the substituent include Ci_ ₄ o alkyl groups and those exemplified above as substituents of the alkyl group. It is preferred that the aryl group has one or more substituents including a Cs-30 linear or branched alkyl residue,

such as alkyl groups (e.g. octyl, decyl, hexadecyl and 2-ethylhexyl) ; alkoxy groups (e.g. dodecyloxy and hexadecyloxy) ; sulfide groups (e.g. hexadecylthio) ; substituted amino groups (e.g. heptadecyl amino), octyl carbamoyl, octanoyl and decyl sUlfamoyl. The aryl group preferably has two or more substituents selected from the substituents containing a Cs- ₃ o linear or branched alkyl residue. The aryl group may have one or more substituents selected from other substituents such as halogen atoms, hydroxyl, cyano, nitro, carboxyl and sulfo.

In the case that R is a heterocyclic group, R is preferably selected from 5-, 6- or 7-membered heterocyclic groups, more preferably selected from 5- or 6- membered heterocyclic groups, and much more preferably selected from 6-membered heterocyclic groups. Specific examples of such skeletons can be found in heterocycles listed in "Iwanami Rikagaku Jiten (Iwanami's Physicochemical Dictionary; Iwanami Shoten, Publishers) , the 3rd edition, supplement Chapter 11 "Nomenclature for Organic Chemistry", Table 4 "Names of Principal Hetero Monocyclic Compounds" on page 1606, and Table 5 "Names of Principal Condensed Heterocyclic Compounds" on page 1607. The heterocyclic groups are, similarly to the foregoing aryl group, preferably substituted with a substituent including a Ce- ₃₉ linear or branched alkyl chain, where substitution by two or more groups is more preferable. Specific examples of the substituent including such chain are same as those described in the above. The heterocyclic group may also be substituted by halogen atom, hydroxyl, cyano, nitro, carboxyl, sulfo or the like, besides the foregoing substituents.

It is preferred that at least one of R contains one or more ester bonds; and it is more preferred that at least one of R is an alkoxy group having one or more substituents containing a linear or branched alkyl residue containing one or more ester bonds.

Further, it is preferred that each R contains one or more ester bonds; and it is more preferred that each R is an alkoxy group having one or more substituents containing a linear or branched alkyl residue containing one or more ester bonds.

Namely, it is preferred that at least one of R contains a group represented by a formula (4a) or (4b) described below; and it is more preferred that at least one of R contains a group

represented by any of formulae (4) to (6) described below.

It is also preferred that at least one of R-X- is a group represented by a formula (7) described below; and it is more preferred that each R-X- is a group represented by the formula (7).

Among the compounds represented by the formula (1) , the compounds having at least one side chain, i.e., R-X-, containing one or more ester bonds are preferred. Especially, the compounds having at least one side chain, i.e., R-X-, containing a group represented by the formula (4a) or (4b) described below. It is noted that the left end, i.e., -X ⁰ , in the formula (4a) or (4b) binds to D in the formula (1) .

Formula (4a)

O

—X°-L°-C—O-R°

Formula (4b)

In the formula, X ⁰ is a single bond or a bivalent linking group selected from the group consisting of NR ¹ , where R ¹ is a hydrogen atom or a C ₁ - _S0 alkyl group, oxygen, sulfur, carbonyl, sulfonyl and any combinations thereof.

In the formulae, L ⁰ represents a bivalent linking group selected from the group consisting of linear, branched or cyclic, preferably C _I - _2Oλ alkylene groups, NR ¹ , where R ¹ is a hydrogen atom or Ci- ₃₀ alkyl group, oxygen, sulfur, carbonyl, sulfonyl or any combinations thereof. The bivalent linking group may be substituted or non-substituted. L ⁰ preferably represents an alkylene group.

Preferred examples of the combination of X ⁰ and L ⁰ , namely -X°-L ⁰ -, include -0 (C=O) -alkylene- and -0 (C=O) -cycloalkylene- .

R ⁰ , which is located at the end of the side chain, represents

a substituted or non-substituted alkyl group or aryl group. Preferred examples or definitions of the alkyl and aryl groups represented by R ⁰ are same as those described above for the alkyl and aryl groups represented by R.

It is preferred that at least one of side chains contains the group represented by the formula (4a) ; and it is more preferred that at least one of side chains contains the group represented by a formula (4) described below. It is noted that the left end, i.e., -L ⁰¹ , in the formula (4) binds to D in the formula (1).

Formula (4)

In the formula, L ⁰¹ has the same meaning of X ⁰ . L ⁰¹ is desirably selected from the group consisting of oxygen atom, sulfur atom, -(C=O)O- and -NH-(C=O)O-. R ⁰¹ is a substituted or non-substituted Ci_3o alkyl group; and p and q respectively represent an integer. R ⁰¹ is desirably selected from substituted or non-substituted Ci- ₄ 0 alkyl groups, and more desirably selected from Ci- ₂ 0 alkyl groups. Examples of the substituent for the alkyl group include halogen atoms, alkoxy groups such as methoxy, ethoxy, methoxyethoxy and phenoxy; sulfide groups such as methylthio, ethylthio and propylthio; alkylamino groups such as methylamino and propylamino; acyl groups such as acetyl, propanoyl, octanoyl and benzoyl; acyloxy groups such as acetoxy, pivaloyloxy and benzoyloxy; aryl groups, heterocyclic groups, hydroxyl, mercapto, amino, cyano, nitro, carboxyl, sulfo, carbamoyl, sulfamoyl and ureido. In the formula, p is desirably an integer selected from 1 to 20, and more desirably selected from 2 to 10. In the formula, q is desirably an integer selected from 1 to 10, and is more desirably an integer from 1 to 5.

The compounds in which at least one of the side chains contains the group represented by a formula (5) or (6) described below are also preferred.

Formula (5)

O O —O-C—(-CH ₂ ^-0-0-(-CH ₂ CH ₂ O)-R ⁰¹

In the formula, R ⁰¹ represents a substituted or non-substituted C ₁ -. ₃ 0 alkyl group; and m and n respectively represent an integer. The definition and examples of R ⁰¹ in the formula (5) are same as it in the formula (4) .

Formula (6)

In the formula, R ²⁵ represents a substituent and a24 is an integer from 1 to 5.

The compounds in which at least one of the side chains contains the group represented by a formula (7) described below are also preferred.

Formula (7)

In the formula, L ²¹ represents a single bond or a bivalent linking group selected from the group consisting of NR ¹ , where R ¹ is a hydrogen atom or a Ci_ ₃ o alkyl group, oxygen, sulfur, carbonyl, sulfonyl and any combinations thereof. L ²¹ preferably represents an oxygen atom, an oxyalkylene group, an oxycarbonyl group, an aminocarbonyl group, a carbonyloxy group or a carbonyl group; and more preferably represents an oxycarbonyl group or a carbonyl group.

Examples of the substituent R ²⁵ , R ⁷¹ or R ⁷² include halogen atoms such as fluorine, chlorine and bromine; Ci-4 ₀ , preferably Ci_ _20c alkyl groups such as methyl, ethyl, propyl, hexyl, octyl, 2-ethylhexyl, decyl, dodecyl, tetradecyl, hexadecyl and octadecyl; C2- ₄₀ , preferably C2-20, alkenyl groups such as vinyl, 2-butene-l-yl andoleyl; 02-4O _r preferably C2- _20r alkynyl groups such as propargyl; Z^-w, preferably C ₆ - ₂ o^ aryl groups such as phenyl and naphthyl; Ci- ₄₀ , preferably Ci_ ₂ o, heterocyclic groups such as 2-furyl, 2-thienyl, 4-pyridyl, 2-imidazolyl, 2-benzothiazolyl, 2-benzoxazolyl and 1-benzoimidazolyl; cyano, hydroxyl, nitro, carboxyl, Ci_ ₄₀ , preferably Ci-20, alkoxy groups such as methoxy,

ethoxy, hexyloxy, octyloxy, 2-ethylhexyloxy, decyloxy, dodecyloxy, tetradecyloxy, hexadecyloxy and octadecyloxy; C ₆ - ₄ o, preferably C ₆ _ ₂ o, aryloxy groups such as phenoxy and 1-naphthoxy; C ₃ - ₄₀ , preferably C ₃ _ _20, silyloxy groups such as trimethyl silyloxy; Ci-40, preferably C ₁ - _20, heterocyclic oxy groups such as 2-furyloxy, 2-tetrahydro pyranyloxy, 3-pyridyloxy and 2-imιidazolyloxy; C ₂ - _40, preferably C ₂ -2 _0c acyloxy groups such as acetoxy, butanoyloxy, octanoyloxy, dodecanoyloxy and benzoyloxy; Ci-4 ₀ , preferably C1-. ₂₀ , carbamoyloxy groups such as N,N-diethyl carbamoyloxy; C ₂ - _40A preferably c ₂ - ₂₀ , alkoxy carbonyloxy groups such as ethoxy carbonyloxy, butoxy carbonyloxy, 2-ethylhexyloxy carbonyloxy, dodecyloxy carbonyloxy and hexadecyloxy carbonyloxy; C ₇ - ₄ o, preferably C ₇ - _20, aryloxy carbonyloxy groups such as phenoxy carbonyloxy; Co- _40r preferably C0-20, amino groups such as non-substituted amino, N-methylamino, N-2-ethylhexylamino, N-tetradecylamino, N,N-diethylamino and N,N-dioctylamino; Ci- ₄₀ , preferably C1-2 _0, acyl amino groups such as acetylamino, octanoylamino and dodecanoylamino; Ci--4o, preferably Ci- ₂₀ , aminocarbonylamino groups such as N,N-dioctyl carbamoylamino; c ₂ - ₄₀ , preferably C2-2o _, alkoxy carbonylamino groups such as methoxy carbonylamino, ethoxy carbonylamino, 2-ethylhexyloxy carbonylamino and tetradecyloxy carbonylamino; C ₇ _ ₄₀ , preferably c7- _20r aryloxy carbonylamino groups such as phenoxy carbonylamino; Co- _40, preferably C ₀ - _20, sulfamoylamino groups such as N,N-dimetyl sulfamoylamino; Ci-4 ₀ , preferably C1-2 _0, alkyl- or aryl-sulfonylamino groups such as methyl sulfonylamino, butyl sulfonylamino, dodecyl sulfonylamino and p-toluene sulfonylamino; mercapto; C1-40, preferably C ₁ _ _20, alkylthio groups such as methylthio, ethylthio, 2-ethylhexylthio and dodecylthio; c6- _40, preferably 0 ₆ - _2O, arylthio groups such as phenylthio; Ci- ₄₀ , preferably Ci_2o _, heterocyclic thio groups such as 4-pyridyl thio, thiazole-2-yl thio, benzoxazole-2-yl thio, 1-phenyl tetrazole-5-yl thio and 1, 3, 4-thiadiazole-2-yl thio; Co- ₄₀ . preferably Co- ₂ o _, sulfamoyl groups such as non-substituted sulfamoyl, N,N-diethyl sulfamoyl and N-hexadecyl sulfamoyl; sulfo; C1_4o, preferably Ci-20, alkyl- or aryl- sulfinyl groups such as methylsulfinyl and phenylsulfinyl; Ci-^o, preferably Ci_ ₂ o, alkyl- or aryl-sulfonyl groups such as methylsulfonyl,

butylsulfonyl, hexadecylsulfonyl and p-tolylsulfonyl; C ₁ -. ₄₀ , preferably Ci- ₂ cu acyl groups such as acetyl, propionyl, isobutyl, tetradecanoyl and benzoyl; C-7-4 ₀ , preferably C ₇ _2 _0/ ' aryloxycarbonyl groups such as phenoxycarbonyl; C ₂ _4o, preferably 02-2 ₀ ^ alkoxycarbonyl groups such as ethoxycarbonyl, t-butoxycarbonyl and hexadecyloxycarbonyl; C ₁ - ₄₀ , preferably Cχ_2 _0/ carbamoyl groups such as non-substituted carbamoyl, N,N-diethylcarbamoyl and N-dodecylcarbamoyl; C _1-140 , preferably Ci_ ₂ o, aryl- or heterocyclic azo groups such as phenylazo, 3-methyl-l, 2, 4-oxadiazole-5-yl azo and 2-methylthio-l, 3, 4-thiadiazole-5-yl azo; C ₄ - ₄₀ , preferably C4-20A imido groups such as succinimido and phthalimido; C _o - ₄ o, preferably C ₀ -20r phosphino groups; C _o - _iO r preferably C ₀ -20 _r phosphinyl groups; C ₀ -40, preferably Co-2 ₀ , phosphinyloxy groups; Co-ior preferably C ₀ -20 _λ phosphinylamino; and C ₃ _4 ₀ , preferably C3-20 _r silyl groups such as trimethyl silyl and t-butyldimethyl silyl. Examples of R ²⁵ , R ⁷¹ or R ⁷² also include substituents having one or more substituents selected from these. Preferred examples of the substituent R ⁷¹ include alkoxy, alkoxycarbonyl and acyl groups having one or more substituents containing a linear or branched alkyl residue. In the formula, "a" is an integer from 0 to 5, and preferably from 1 to 3.

The carbon atom number of R ⁷¹ is preferably from 1 to 40 and more preferably from 1 to 20.

It is also preferred that at least one of m of the side chains, i.e., R-X-, includes a partially or totally fluorinated carbon group. Namely, it is preferred that at least one of the formulae (4a), (4b), (4), (5), (6) and (7) contains a partially or totally fluorinated carbon group. The fluorinated carbon groups may be selected from those containing one or more double bonds, those having a linear or branched chain structure or a cyclic structure, and those having one or more aryl rings.

Among the compounds represented by the formula (1), the compounds represented by the formula (2) are preferred.

Formula (2)

In the formula (2) , X ¹ , X ² and X ³ respectively represent a single bond or a bivalent linking group selected from the group consisting of NR ¹ , where R ¹ is a hydrogen atom or a Ci_ ₃₀ alkyl group, oxygen, sulfur, carbonyl, sulfonyl and any combinations thereof. In the case that X ¹ , X ² or X ³ is a single bond, it may bind directly to nitrogen atom, having free atomic valence, of a heterocyclic group such as a piperidine residue, or may bind to a heteroatom not having free atomic valence to form an onium salt such as an oxonium salt, sulfonium salt or ammonium salt. In the case that X ¹ , X ² or X ³ is not a single bond, it represents a bivalent linking group selected from the group consisting of NR ¹ , where R ¹ is a hydrogen atom or a Ci- ₃₀ alkyl group, oxygen, sulfur, carbonyl, sulfonyl and any combinations thereof such as an oxycarbonyl group, an aminocarbonyl group, ureylene group, oxysulfonyl group and sulfamoyl group. Among these, a sulfur atom or NR ¹ in which R ¹ is a hydrogen atom or a C ₃ or shorter alkyl group. Among these, imino, i.e., -NH-, is most preferred.

In the formula (2), R ¹¹ , R ¹² and R ¹³ respectively represent a substituted or non-substituted, alkyl group, alkenyl group, alkynyl group, aryl group or heterocyclic group, or a halogen atom, hydroxyl, amino, mercapto, cyano, sulfide, carboxy or salt threof (carboxylate) , sulfo or salt thereof (sulfate) , hydroxylamino, ureido or urethane .

The alkyl group represented by R ¹¹ , R ¹² or R ¹³ is desirably selected from C1-40 _r MORE desirably from C2-30, much more desirably from C ₄ - ₃₀ and further much more desirably from C6-30 alkyl groups. The alkyl group may have a linear or branched chain structure and may have one or more substituents . Examples of the substituent include halogen atoms, C1-.40, preferably CI_20 _, alkoxy groups such as methoxy, ethoxy, methoxyethoxy and phenoxy; Ci_ ₄₀ , preferably C _I _ _20, alkylthio and c6-40, preferably C6-20, arylthio groups such

as methylthio, ethylthio, propylthio and phenylthio; Ci_ ₄₀ , preferably Ci_ _20f alkylamino groups such as methylamino and propylamino; Ci- ₄₀ , preferably Ci-20, acyl groups such as acetyl, propanoyl, octanoyl and benzoyl; Ci-40, preferably C1-20/ acyloxy groups such as acetoxy, pivaloyloxy and benzoyloxy; hydroxyl, mercapto, amino, carboxyl, sulfo, carbamoyl, sulfamoyl and ureido.

In the case that R ¹¹ , R ¹² or R ¹³ is an alkenyl or alkynyl group, their preferred carbon numbers is from 2 to 40, more preferably from 2 to 30, much more preferably from 4 to 30 and further much more preferably from 6 to 30. The alkenyl or alkynyl group may have a linear or branched chain structure. The alkenyl or alkynyl group may have one or more substituents . Example of the substituent include those exemplified as the substituent of the alkyl group.

In the case that R ¹¹ , R ¹² or R ¹³ is an aryl group, it is preferred that R is phenyl, indenyl, alpha-naphthyl, beta-naphthyl, fluorenyl, phenanthryl, anthracenyl or pyrenyl, and it is more preferred that it is phenyl or naphthyl. The aryl group may have one or more substituents . Examples of the substituent include C ₁ - ₄₀ alkyl groups and those exemplified above as substituents of the alkyl group. It is preferred that the aryl group has one or more substituents containing a C ₈ _ ₃₀ linear or branched alkyl residue, such as alkyl groups (e.g. octyl, decyl, hexadecyl and 2-ethylhexyl) ; alkoxy groups (e.g. dodecyloxy, hexadecyloxy, 2~hexyldecyloxy and hexyloxyethyleneoxyethyleneoxy) ; sulfide groups (e.g. hexadecylthio) ; substituted amino groups (e.g. heptadecyl amino) , octyl carbamoyl, octanoyl and decyl sulfamoyl. The aryl group preferably has two or more substituents selected from the substituents containing a C ₈ - ₃₀ linear or branched alkyl residue . The aryl group may have one or more substituents selected from other substituents such as halogen atoms, hydroxyl, cyano, nitro, carboxyl and sulfo.

The heterocyclic group represented by R ¹¹ , R ¹² or R ¹³ , is, similarly to D in the formula (1), preferably selected from 5-, 6- or 7-membered heterocyclic groups, more preferably selected from 5- or 6- membered heterocyclic groups, and much more preferably selected from 6-membered heterocyclic groups.

Specific examples of such skeletons can be found in heterocycles listed in "Iwanami Rikagaku Jiten (Iwanami's Physicochemical Dictionary; Iwanami Shoten, Publishers), the 3rd edition, supplement Chapter 11 "Nomenclature for Organic Chemistry", Table 4 "Names of Principal Hetero Monocyclic Compounds" on page 1606, and Table 5 "Names of Principal Condensed Heterocyclic Compounds" on page 1607. The heterocyclic groups are, similarly to the foregoing aryl group, preferably have one ore more substituents containing a C ₈ - ₃ o linear or branched alkyl chain, where substitution by two or more groups is more preferable. Specific examples of the substituent containing such chain are same as those described in the above. The heterocyclic group may also be substituted by halogen atom, hydroxyl, cyano, nitro, carboxyl, sulfo or the like, besides the foregoing substituents.

It is preferred that at least one of R ¹¹ , R ¹² and R ¹³ contains one or more ester bonds, and, more preferably, is an alkoxy group having one or more substituents containing a linear or branched alkyl residue. It is more preferred that each of R ¹¹ , R ¹² and R ¹³ contains one or more ester bonds, and, more preferably, is an alkoxy group having one or more substituents including a linear or branched alkyl residue. Namely, it is preferred that at least one of R ¹¹ , R ¹² and R ¹³ contains a group represented by the formula (4a) or (4b) ; and, more preferably, contains a group represented by any one of the formulae (4) to (6) .

It is also preferred that at least one of R ³ ^-X ¹ -, R ¹² -X ² - and R ¹³ -X ³ - is a group represented by the formula (7) ; and it is more preferred that each of those is a group represented by the formula (7 ) .

Among the compounds represented by the formula (2) , the compounds represented by the following formula (3) are preferred.

Formula (3)

In the formula, X ²¹ , X ²² and X ²³ respectively represent a single bond or a bivalent linking group selected from the group consisting of NR ¹ , where R ¹ is a hydrogen atom or a Ci-. _3O alkyl group, oxygen, sulfur, carbonyl, sulfonyl and any combinations thereof. In the case that X ²¹ , X ²² or X ²³ is a single bond, it may bind directly to nitrogen atom, having free atomic valence, of a heterocyclic group such as a piperidine residue, or may bind to a heteroatom not having free atomic valence to form an onium salt such as an oxonium salt, sulfonium salt and ammonium salt. In the case that X ²¹ , X ²² or X ²³ is not a single bond, it represents a bivalent linking group selected from the group consisting of NR ¹ , where R ¹ is a hydrogen atom or a C ₁ -.3 ₀ alkyl group, oxygen, sulfur, carbonyl, sulfonyl and any combinations thereof such as an oxycarbonyl group, aminocarbonyl group, ureylene group, oxysulfonyl group and sulfamoyl group. Among these, a sulfur atom or NR ¹ in which R ¹ is a hydrogen atom or a C ₃ or shorter alkyl group. Among these, imino, i.e., -NH-, is most preferred.

In the formula, R ²¹ , R ²² and R ²³ respectively represent a substituent. Examples of the substituent R ²¹ , R ²² or R ²³ include halogen atoms, alkyl groups, alkenyl groups, alkynyl groups, aryl groups, heterocyclic groups, cyano, hydroxyl, nitro, carboxyl, alkoxy groups, aryloxy groups, silyloxy groups, heteroxy groups, acyloxy groups, carbamoyloxy groups, alkoxycarbonyloxy groups, aryloxycarbonyloxy groups, amino groups, acylamino groups, aminocarbonylamino groups, alkoxy aminocarbonylamino groups, aryloxycarbonylamino groups, sulfamoylamino groups, alkyl- and aryl-sulfonylamino groups, mercapto, alkylthio groups, arylthio

groups, heterocyclic thio groups, sulfamoyl groups, sulfo groups, alkyl- and aryl-sulfinyl groups, alkyl- and aryl-sulfonyl groups, acyl groups, aryloxycarbonyl groups, alkoxycarbonyl groups, carbamoyl groups, aryl- and heterocyclic-azo groups, imido, phosphino groups, phosphinyl groups, phosphinyloxy groups, phosphinylamino groups and silyl groups. The preferred carbon numbers and preferred examples of these groups are same as those described above for the substituents R ²⁵ , R ⁷¹ and R ⁷² . Examples of the substituent R ²¹ , R ²² or R ²³ also include the substituents having one or more substituents selected from the examples exemplified above .

It is preferred that at least one of R ²¹ , R ²² and R ²³ contains one or more ester bonds, and, more preferably, is an alkoxy group having one or more substituents containing a linear or branched alkyl residue. It is more preferred that each of R ²¹ , R ²² and R ²³ contains one or more ester bonds, and, more preferably, is an alkoxy group having one or more substituents containing a linear or branched alkyl residue. Namely, it is preferred that at least one of R ¹¹ , R ¹² and R ¹³ contains a group represented by the formula (4a) or (4b); and, more preferably, contains a group represented by any one of the formulae (4) to (6) .

It is also preferred that at least one of (R ²¹ ) _a2 i-Ph-X ²¹ -, (R ²² ) _a22 -Ph-X ²² - and (R ²³ ) _a23 -Ph-X ²³ -R ^1:L -X ¹ - is a group represented by the formula (7); and it is more preferred that each of those is a group represented by the formula (7) .

In the formula, a21, a22 and a23 respectively represents an integer from 1 to 5.

Examples of the compound represented by the formula (1), which can be employed in the invention, include, but are not limited to, those shown below.

[H-29]

-C-OC ₂ H ₄ OC ₂ H ₄ OC ₆ H ₁₃ -Ii

O

[H-303 -C-OC ₂ H ₄ OC ₂ H ₄ OC ₆ H ₁₃ -Ii — NHCOC ₁₃ H ₂₅ -(I

— C-OC ₂ H ₄ OC ₂ H ₄ OC ₆ H ₁₃ -Ii — NHCOC ₁₃ H ₂₅ -Ii

R = -C-OC ₂ H ₄ OC ₂ H ₄ OC ₆ H ₁₃ -Ii

The compounds represented by the formula ( 1 ) can be synthesized by using cyanuric chloride , which is readily

commercially available, as a starting material.

The impregnating oil composition of the invention preferably comprises at least one compound represented by the formula (1) in an amount of 0.1 to 10 wt%, more preferably in an amount of 1 to 10 wt% and much more preferably in an mount of 1 to 5 wt%. The composition containing the compound in an amount falling within the above range is preferred in the view of improvement in ability of forming oil films and durability enhancement.

The impregnating oil composition of the invention comprises a base oil. Any types of base oil may be employed in the invention, and it may be selected from either mineral oils or synthetic oils. In the view of reduction of sludge, the base oils is preferably selected from synthetic oils and more preferably from synthetic carbon hydrate base oils. The composition, comprising, as base oil, at least one selected from the group consisting of poly-alpha-olefins, poly-alpha-olefin hydrates, ethylene-alpha-olefin copolymers, ethylene-alpha-olefin copolymer hydrates, mixtures of poly-alpha-olefin or hydrate thereof and alkyl naphthalene, mixtures of ethylene-alpha-olefin copolymer or hydrate thereof and alkyl naphthalene is preferred in the view of compatibility with the compound represented by the formula (1), reduction of sludge and durability enhancement.

Various types of poly alpha-olefin hydrates, referred to as "PAO" hereinafter, can be employed as base oil in the invention. In usual, PAO having a mean molecular weight of 200 to 1600 is preferred and PAO having a mean molecular weight of 400 to 800 is more preferred. Such PAO can be produced by hydrogenating the polymers which are produced by carrying out polymerization of 1-decene, isobutene or the like in the presence of catalyst such as Lewis acid complex and aluminum oxide catalyst. It is possible to improve durability of the composition and remarkably reduce the amount of sludge generated from the composition by employing such PAO as base oil.

Various types of ethylene-alpha-olefin copolymers, referred to as "PEAO" hereinafter, can be employed as base oil in the invention. PEAO may be produced by hydrogenating the polymers which are produced by carrying out polymerization of ethylene and alpha-olefin such as 1-decene and isobutene in the

presence of catalyst such as Lewis acid catalyst. In usual, PEAO having a mean molecular weight of 200 to 4000 is preferred and PEAO having a mean molecular weight of 1000 to 2000 is more preferred.

The alkyl naphthalene, which can be employed in the invention, is selected from any naphthalene derivatives having one or more substituents on the naphthalene ring. Mono- di- or tri-alkyl naphthalenes, in which the total carbon atom number of the alkyl group (s) is from 5 to 25 around carbon, are preferred; and, among these, naphthalenes having both of lower or higher alkyl groups are more preferred. Examples of the lower alkyl group include methyl, ethyl, propyl and isopropyl, and methyl is preferred. The higher alkyl group is not to be limited to a certain group, and is may be selected from linear and branched chain alkyl groups. In the view from viscosity index and lubricant property, the higher alkyl group is preferably a linear chain alkyl group. Examples of such alkyl naphthalene include dialkyl naphthalenes having a methyl and a secondary C ₁₀ -24 alkyl group and mixtures thereof which are described in JPA No. hei 8-302371. Known materials, especially commercially available materials, are preferred in the view of procurement easiness.

As base oil to be employed in the invention, mixtures of PAO or PEAO and alkyl naphthalene are preferred. As to the mix proportion thereof, the proportion of the former is preferably from 0.1 to 50 wt% and more preferably from 2 to 40 wt%; and the proportion of the later is preferably from 50 to 99.9 wt% and more preferably from 60 to 98 wt% . The composition comprising, as base oil, the mixture of PAO or PEAO and alkyl naphthalene, having a mix proportion falling within the preferred range, may exhibit improved durability and improved ability of forming oil films.

The composition of the invention may comprise any known additives in order to attain practical performances adopted for the individual applications. Examples of the additive include wear preventive agents, extreme pressure agents, antioxidants, viscosity index raising agents, clean dispersion aids, metal passivation agents, corrosion preventive agents, rust preventive agents, and defoaming agents in an amount without lowering the effect of the invention.

The impregnating oil composition of the invention, with which a sintered body is impregnated, is employed in a bearing apparatus. The composition, for example, may be kept within pores of a porous sintered body. The sintered body impregnated with the composition of the invention may be employed in a part of a sliding part or as a sliding part of a bearing apparatus. The composition is fed from the oil-impregnated sintered bearing to a sliding site between a rotating element and a non-rotation body for bearing the rotating element, and contributes to reducing friction and wear. It can be thought that since the composition of the invention comprises a base oil and a particular class of discotic compound, employing the composition of the invention can achieve lower friction and, therefore, higher wear-resistance, compared with employing known compositions, comprising base oil and a metal compound such as molybdenum compound and zinc compound, or known compositions comprising base oil and ester phosphate.

The invention also relates to a bearing apparatus for bearing a rotating element rotatably comprising a sliding part wherein at least a part of the sliding part is a sintered body impregnated with the composition of the invention; and a sliding member comprising a sintered body impregnated with the composition of the invention. The porous sintered body is preferable, and employing the porous sintered body, the impregnating oil composition is kept within the pores of the porous sintered body. The sintered body made of any material can be employed in the invention, and, in usual, metal sintered bodies are employed. Metal sintered bodies may be produced by sintering metal powders, comprising, as a major material, one or more types of metal powders selected from the common metal powders such as copper, iron and aluminum powder, and, if necessary, one or more types of powders selected from tin, lead, graphite and their alloy metal powders. It is possible to provide a long-life and stably operable bearing apparatus by employing the sintered bearing of the invention for a sliding part.

The bearing apparatus of the invention can be employed as a small size motor in the various technical fields such as automobiles, audio equipments, office equipments, home electric equipments and agricultural machines .

EXAMPLES

The invention will be further specifically described below with reference to the following Examples. Materials, reagents, amounts and proportions thereof, operations, and the like as shown in the following Examples can be properly changed so far as the gist of the invention is not deviated. Accordingly, it should not be construed that the scope of the invention is limited to the following specific examples.

In the examples described below, each friction coefficient was measured by using a reciprocating type friction test machine

(SRV friction wear test machine) under conditions described below.

And each wear resistance was evaluated with wear depths measured by using a surface roughness measuring equipment.

Seven types of impregnating oil compositions, Example Nos. 1 to 7, were prepared by using the exemplified compounds N-8, N-28 N-34 and S-34 respectively. And Comparative Example Nos. 1 to 4 were prepared by using only base oils. [Test Condition]

Tests were subjected under Cylinder on Plate Test. Specimen (friction material) : SUJ-2 Plate : 24 mm in diameter, 6.9 mm thick Three plates, having thereon a sintered metal layer shown below respectively, were produced and the plates were impregnated with the compositions shown in Table 1 respectively.

Impregnated iron sintered layer, employed in Example Nos. 1, 4 to 7 and Comparative Example Nos. 1 to 4, was produced as follows :

Iron powder mixed with copper powder in an amount of 3 weight % and chemical carbon in an amount of 0.6 weight %, was disposed on a cast iron substrate, subjected to compression formation under 250 MPa, and sintered in a reduction atmosphere at 770 ⁰ C for an hour.

Impregnated copper sintered layer, employed in Example No. 2, was produced as follows:

Copper powder mixed with tin powder in an amount of 88 weight % and graphite in an amount of 2 weight %, was disposed on a cast iron substrate, subjected to compression formation under 250 MPa, and sintered in a reduction atmosphere at 770 ⁰ C for an

hour.

Impregnated TiC> ₂ sintered layer, employed in Example No.

3 produced as follows:

Ti (OC ₈ Hi ₇ -n) ₄ in an amount of 33 wt% added with TiO ₂ fine powder in an amount of 57 wt% and PEO(MW3000) was disposed on a cast iron substrate, and sintered under UV irradiation at 560 ⁰ C for three hours.

Cylinder : 15 mm in diameter, 22 mm long

Temperature : 50°C or 80 ⁰ C

Load : 5ON or IOON

Amplitude : 1.5 mm

Frequency : 50 Hz

Testing period : for 5 min. after the start of testing

The results of Example Nos. 1 to 6 are shown in Table 1 and the results of Example No. 7 and Comparative Example Nos. 1 to

4 are shown in Table 2. From the results shown in Table Nos. 1 and 2, it is understandable that Example Nos. 1 to 7 exhibited an excellent low-wear property respectively, compared with Comparative Example Nos. 1 to 4. It is also understandable that Example Nos. 1 to 6, containing synthetic hydrocarbon as base oil, exhibited an excellent low-wear property, compared with Example No. 7 containing mineral oil as base oil.

Table 1

Table 2

Industrial Applicability

According to the present invention, it is possible to provide an impregnating oil composition for a sintered bearing capable of improving film-forming ability of the bearing and of extending bearing life. It is also possible to provide a long-life bearing apparatus reduced in wearing at a sliding part and capable of working stably. It is also possible to provide a sliding member which is useful for such a bearing apparatus.

Cross-Reference to Related Applications

This application claims benefit of priority under 35 USC 119 to Japanese Patent Application No. 2005-246318 filed August 26, 2005.