WO2011098616A1

WO2011098616A1 - Grease composition

Info

Publication number: WO2011098616A1
Application number: PCT/EP2011/052217
Authority: WO
Inventors: Tetsuya Katou; Koichi Numazawa; Takahiro Ozaki
Original assignee: Shell Internationale Research Maatschappij B.V.
Priority date: 2010-02-15
Filing date: 2011-02-15
Publication date: 2011-08-18
Also published as: JP5643634B2; JP2011184680A

Abstract

Grease composition comprising (a) a base oil, (b) a thickener, (c) tricalcium phosphate, and (d) at least one compound selected from the group consisting of alkaline earth metal salts, alkali metal salts, amine salts or zinc salts of oxidised waxes, petroleum sulphonic acids, alkyl aromatic sulphonic acids or such salts which are salicylates or phenates, and mixtures thereof. The grease composition of the present invention has excellent anti-fretting corrosion properties, so that it is possible to achieve a satisfactory lubricating function even under the severe conditions accompanying microvibrations.

Description

GREASE COMPOSITION

Technical Field of the Invention

This invention relates to a grease composition with excellent anti-fretting corrosion characteristics.

Background of the Invention

Fretting corrosion, also called abrasion-corrosion, rubbing corrosion and microvibration wear, is a wear phenomenon which occurs when two objects pressed together at any pressure repeatedly slide relative to each other with very small amplitudes in the contact space. When microvibrations and microsliding occur between the two objects, the frictional dust which arises in the case of steel-steel microvibrations in the atmosphere turns to a fine brown iron oxide ( Fe₂0₃) . This gets mixed in the grease and turns it brown. The phenomenon of the grease becoming brown occurs in various kinds of machinery, accompanying microvibrations and microsliding between two objects in contacts, as for example in automobile wheel bearings, bolt-tightened flanges and laminated springs. Fretting corrosion promotes wear in machine parts and bearings, and is also a cause of noise.

The mechanism of fretting corrosion has often been investigated but even now it is still unclear. Although they have not been obtained logically from the fretting corrosion mechanism, greases which are acknowledged to have an effect against the phenomenon on the basis of test results or practical experience are being used.

In other words, lubricating greases used in the past at lubrication points where fretting corrosion occurs have been highly paraffinic low-viscosity base oils with high penetration (soft greases of penetration not less than 320 are especially effective (NLGI Spokesman, Vol. 45, 1 (1982))), but satisfactory effectiveness has not necessarily been achieved.

Also, what is already known as means to reduce this fretting corrosion is a grease composition for use in automobile wheel bearings in which an organic molybdenum compound has been added to a urea grease (Japanese Laid- Open Patent 2006-77056), a lithium soap grease

composition in which at least one additive selected from organic molybdenum compounds, organic fatty acid

compounds or organic fatty acid derivatives, and

organophosphorus compounds has been added (Japanese Laid- Open Patent 2001-335792), and a grease composition in which calcium sulphonate has been added to a lithium soap grease using an ester oil for the base oil (Japanese

Laid-Open Patent 2003-147378) .

The aim of this invention is to offer a lubricating grease which will improve the anti-fretting corrosion characteristics compared to the lithium soap greases and urea greases of the prior art.

Summary of the Invention

According to the present invention there is provided a grease composition comprising (a) a base oil, (b) a thickener, (c) tricalcium phosphate, and (d) at least one kind of salt selected from the group consisting of alkaline earth metal salts, alkali metal salts, amine salts or zinc salts of oxidised waxes, petroleum

sulphonic acids, alkyl aromatic sulphonic acids or such salts which are salicylates or phenates; and mixtures thereof.

Detailed Description of the Invention

The grease composition of this invention can improve anti-fretting corrosion characteristics. Also, it need not be the highly paraffinic low-viscosity base oils with high penetration (soft greases: penetration not less than 320) deemed necessary in the past, as mentioned above, and in this invention it is possible to obtain excellent anti-fretting corrosion characteristics also in cases where a high viscosity oil or a naphthene-based base oil is used in part, and even if the hardness is of Grade 2 Penetration [penetration grade of the NLGI (US grease institute) classification] .

As to the applications of this grease composition, whilst it can naturally be used in generally used

machines, bearings and gears, it displays excellent performance under the rather more rigorous conditions which accompany microvibrations. For example, it can be suitably used in automobile parts such as the needle bearings of universal joints, constant velocity joints (CVJ) , wheel bearings, ball screws, screws, flexible couplings, various kinds of gears, cams and chains.

For the base oil used in the grease composition of this invention it is possible to use the mineral oils, synthetic oils and mixtures thereof normally used for lubricating oils. Their kinematic viscosity at 40°C should preferably be approximately 20 to 400 mm²/s.

In particular, it is possible to use, singly or as mixtures, base oils which belong to Group I, Group II,

Group III, Group IV and Group V of the API (American Petroleum Institute) base oil categories.

Group I base oils include, for example, paraffinic mineral oils obtained by appropriate use of a suitable combination of refining processes such as solvent

refining, hydrorefining, and dewaxing in respect of lubricating oil fractions obtained by atmospheric distillation of crude oil. Group II base oils include, for example, paraffinic mineral oils obtained by appropriate use of a suitable combination of refining processes such as hydrorefining and dewaxing in respect of lubricating oil fractions obtained by atmospheric distillation of crude oil. Group

II base oils refined by hydrorefining methods such as the Gulf Company method have a total sulphur content of less than 10 ppm and an aromatic content of not more than 5% and so are suitable for use in this invention.

Group III and Group 11+ base oils include paraffinic mineral oils manufactured by a high degree of

hydrorefining in respect of lubricating oil fractions obtained by atmospheric distillation of crude oil, base oils refined by Isodewaxing which dewaxes and substitutes the wax produced by the dewaxing process with

isoparaffins, and base oils refined by the Mobil wax isomerisation process. These too are suitable for use in this invention.

Also, GTLs (gas to liquid) synthesised by the

Fischer-Tropsch method of converting natural gas to liquid fuel have a very low sulphur content and aromatic content compared with mineral oil base oils refined from crude oil and have a very high paraffin constituent ratio, and so have excellent oxidative stability, and because they also have extremely small evaporation losses, they are suitable as base oils for this

invention .

Group V base oils include, for example, naphthenic mineral oils obtained by appropriate use of a suitable combination of refining processes such as solvent

refining, hydrorefining, and dewaxing in respect of lubricating oil fractions obtained by atmospheric

distillation of crude oil. It is also possible to use mixtures of the above mentioned paraffinic mineral oils and naphthenic mineral oils .

As examples of synthetic oils mention may be made of polyolefins, dibasic acid diesters such as dioctyl sebacate, polyol esters, alkylbenzenes ,

alkylnaphthalenes , esters, polyoxyalkylene glycols, polyoxyalkylene glycol esters, polyoxyalkylene glycol ethers, polyphenyl ethers, dialkyldiphenyl ethers, fluorine-containing compounds (perfluoropolyethers, fluorinated polyolefins) and silicones.

The aforementioned polyolefins include polymers of various olefins or hydrides thereof. Any olefin may be used, and as examples mention may be made of ethylene, propylene, butene and -olefins with five or more

carbons. In the manufacture of polyolefins, one kind of the aforementioned olefins may be used singly or two or more kinds may be used in combination. Particularly suitable are the polyolefins called poly- -olefins (PAO) . These are base oils of Group IV.

In general, it is possible to use for the

aforementioned thickening agent one kind, or two or more kinds in combination, of generally already known urea compounds, alkali metal soaps, alkali metal complex soaps, alkaline earth metal soaps, alkaline earth metal complex soaps, alkali metal sulphonates, alkaline earth metal sulphonates, aluminium soaps, aluminium complex soaps, metal terephthalamate salts, clays,

polytetrafluoroethylenes, silica aerogels (silicon oxide), and so on. In particular, lithium soaps and urea-based thickeners will often be preferred as they have few drawbacks and are excellent for practical use. The tricalcium phosphate in this invention is one having the chemical structure of a hydroxyapatite

composition as generally represented by [Ca₃ (PO₄)

2] 3-Ca(OH) 2 , but it is also possible to use those

represented by Ca₃ (P0₄) ₂-

In the examples described below for this invention, [Ca3 (P0₄) 2l 3-Ca(OH) 2 is used, and the content is shown as the mass based on this.

The tricalcium phosphate preferably will have an average granularity of not more than 5 μιη diameter in order to increase the penetration yield of the grease, but it may be used without problems so long as the average granularity is not more than 100 μιη diameter.

This tricalcium phosphate is added to the

aforementioned grease composition, and it is best if it is blended in an amount, relative to the total amount of the grease composition, of from 0.1 to 20% by mass, but preferably from 1 to 15% by mass, and more preferably from 2 to 10% by mass.

If the aforementioned tricalcium phosphate is blended in the aforementioned base oil, a thickening effect is exhibited because of the tricalcium phosphate. Even if the previously mentioned lithium soaps, ureas or other thickeners are reduced, it is possible to form the compositions into a grease state, and further into pastes and compounds .

If the amount of this tricalcium phosphate in the blend is less than 0.1% by mass, it will not be possible to maintain superior anti-fretting corrosion properties. If it exceeds 20% by mass, the grease composition may harden and may not become a slippery semi-solid, and there will be many difficulties with its manufacture. Alkaline earth metal salts which are the

aforementioned (d) include alkaline earth metal salts of oxidised waxes, alkaline earth metal salts of petroleum sulphonic acids, alkaline earth metal salts of alkyl aromatic sulphonic acids, alkaline earth metal salts which are salicylates, and alkaline earth metal salts which are phenates.

In addition, they include overbased versions

thereof, that is overbased alkaline earth metal salts of oxidised waxes, overbased alkaline earth metal salts of petroleum sulphonic acids, overbased alkaline earth metal salts of alkyl aromatic sulphonic acids, overbased alkaline earth metal salts which are salicylates, and overbased alkaline earth metal salts which are phenates. Salts of the aforementioned petroleum sulphonic acids and alkyl aromatic sulphonic acids are generally known as sulphonates .

As examples of the aforementioned alkaline earth metals, mention may be made of calcium, magnesium and barium.

For this alkaline earth metal salt it is possible to use one of the aforementioned kinds, or two or more together .

Alkali metal salts which are the aforementioned (d) include alkali metal salts of oxidised waxes, alkali metal salts of petroleum sulphonic acids, alkali metal salts of alkyl aromatic sulphonic acids, alkali metal salts which are salicylates, and alkali metal salts which are phenates. In addition, they include overbased

versions thereof, that is overbased alkali metal salts of oxidised waxes, overbased alkali metal salts of petroleum sulphonic acids, overbased alkali metal salts of alkyl aromatic sulphonic acids, overbased alkali metal salts which are salicylates, and overbased alkali metal salts which are phenates.

As examples of the aforementioned alkali metals, mention may be made of lithium, sodium and potassium.

For this alkali metal salt it is possible to use one of the aforementioned kinds, or two or more together.

Similarly, amine salts which are the aforementioned (d) include amine salts of oxidised waxes, amine salts of petroleum sulphonic acids, amine salts of alkyl aromatic sulphonic acids, amine salts which are salicylates, and amine salts which are phenates. In addition, they include overbased versions thereof, that is overbased amine salts of oxidised waxes, overbased amine salts of petroleum sulphonic acids, overbased amine salts of alkyl aromatic sulphonic acids, overbased amine salts which are salicylates, and overbased amine salts which are

phenates .

As examples of substances forming the aforementioned amine salts, mention may be made of ammonia,

ethylenediamine and diethylenetriamine .

For this amine salt it is possible to use one of the aforementioned kinds, or two or more together.

Zinc salts which are the aforementioned (d) include zinc salts of oxidised waxes, zinc salts of petroleum sulphonic acids, zinc salts of alkyl aromatic sulphonic acids, zinc salts which are salicylates, and zinc salts which are phenates.

For this zinc salt, in the same way as mentioned above, it is possible to use one of the aforementioned kinds, or two or more together.

As examples of the aforementioned alkyl aromatic sulphonic salts, mention may be made of those of General Formula (1) and General Formula (2), these being salts of alkyl benzene sulphonic salts or of alkyl naphthalene sulphonic acids.

General Formula 1 :

General Formula 2 :

In General Formulae (1) and (2), M is selected from alkaline earth metal, alkali metal, amine or zinc, and Rn¹ and R_n ² are each independently selected from hydrogen atoms or a hydrocarbyl group having from 1 to 30 carbon atoms, preferably an alkyl group having from 6 to 18 carbon atoms, n is an integer of from 1 to 3, and h and k are each an integer of 1 or 2. Where there is more than one R¹ group, these may the same or different. Where there is more than one R² group, these may the same or different .

Also, overbased compounds of alkaline earth metal and the aforementioned alkyl aromatic sulphonic acids may be obtained in respect of the normal salt by reacting excess of an alkaline earth metal salt or a carbonate or a borate which is an alkaline earth metal salt in the presence of carbon dioxide gas. The aforementioned salicylates include alkaline earth metal salts, alkali metal salts, amine salts and zinc salts, and mention may be made for example of the salicylates of the General Formula (3) below.

General Formula 3 :

In the General Formula (3), M is selected from alkaline earth metal, alkali metal, amine or zinc, preferably alkaline earth metal, more preferably calcium or magnesium. Each R³ group is independently selected from hydrogen or a hydrocarbyl group having from 1 to 40 carbon atoms, preferably an alkyl group having from 6 to 22 carbon atoms. n is an integer of from 1 to 4, and j is an integer of 1 or 2. Where there is more than one R³ group present, these may be the same or different.

For example, for a Ca type salicylate the normal salt can be used as is, but it is also possible to use a basic Ca salicylate obtained by heating the normal salt of a Ca type salicylate in the presence of excess Ca salt or Ca base and water, or an overbased Ca salicylate obtained by reacting a Ca carbonate or borate with the normal salt of a Ca type salicylate in the presence of carbon dioxide gas. Other overbased salts can be

obtained in accordance with the above.

As examples of phenate salts, mention may be made, as regards alkaline earth metal salts, of alkaline earth metal salts of alkylphenols , alkylphenol sulphides or Mannich reaction products of alkylphenols, and in particular magnesium salts or calcium salts among others. Specifically, mention may be made of the examples

represented by the General Formulae (4), (5) and (6) below .

General Formula 4: -M-

General Formula 5:

General Formula 6 :

R⁵ and R⁶ in Formula 4, R⁷ and R⁸ in Formula 5, and R⁹ and R¹⁰ in Formula 6 may be the same or different, and are each independently selected from a hydrocarbyl group, preferably a hydrocarbyl group having from 4 to 30 carbon atoms, more preferably an alkyl group having from 9 to 22 carbon atoms.

In Formulae 4 ,5 or 6, M is an alkaline earth metal, preferably calcium, barium or magnesium, and x is in the range of 1 to 3 depending on which metal is used. For the purposes of this invention, calcium phenate and magnesium phenate are preferred. Also, multiple phenate rings may be formed as opposed to the discrete formulae above.

Phenates or overbased alkaline earth metals are alkaline earth metal salts of alkylphenols or sulphurised alkylphenols , and are normally obtained by the method of carbonating alkaline earth metal salts of alkyl phenols or sulphurised alkylphenols.

One of these alkaline earth metal salts, alkali metal salts, amine salts or zinc salts which constitute the aforementioned (d) may be selected or they may be used in conjunction with each other, and such salts should be used in the blend in an amount of from 0.1 to 10% by mass relative to the total amount of the grease composition, but preferably from 1 to 8% by mass and more preferably from 2 to 7% by mass.

If the amount thereof added to the blend is less than 0.1% by mass, it will not be possible to maintain superior anti-fretting corrosion properties, and if the amount in the blend exceeds 10% by mass, an increased effect as regards an improvement in anti-fretting

corrosion properties will often not be apparent.

In addition to the aforementioned constituents, it is possible to use also extreme pressure agents,

dispersants, surfactants, adhesion improvers (polymers, etc.), oiliness agents, friction reducers, wear

inhibitors, rust inhibitors, corrosion inhibitors, solid lubricants and other additives as required by the

application.

For the aforementioned anti-oxidants it is possible to use amine-based, phenol-based, phosphite-based, sulphur-based and dialkyldithiophosphate-based anti- oxidants, but phenol-based and amine-based anti-oxidants will often be particularly preferred as they have

superior oxidative stability at high temperatures.

Phenol-based anti-oxidants include 2-t-butylphenol ,

2-t-butyl-4-methylphenol , 2-t-butyl-5-methylphenol , 2,4- di-t-butylphenol , 2 , 4-dimethyl-6-t-butylphenol , 2-t- butyl-4-methoxyphenol , 3-t-butyl-4-methoxyphenol , 2,5-di- t-butylhydroquinone (Antage DBH, made by Kawaguchi

Chemical Industry Co. Ltd.), 2 , 6-di-t-butylphenol , 2,6- di-t-butyl-4-alkylphenols such as 2 , 6-di-t-butyl-4- methylphenol and 2 , 6-di-t-butyl-4-ethylphenol , and 2,6- di-t-butyl-4-alkoxyphenols such as 2 , 6-di-t-butyl-4- methoxyphenol and 2 , 6-di-t-butyl-4-ethoxyphenol .

Also, there are 3 , 5-di-t-butyl-4- hydroxybenzylmercapto-octylacetate, alkyl-3- (3, 5-di-t- butyl-4-hydroxyphenyl ) propionates such as n-octadecyl-3- ( 3 , 5-di-t-butyl-4-hydroxyphenyl ) propionate (Tominox SS, made by Yoshitomi Fine Chemicals Ltd.), n-dodecyl-3- ( 3 , 5- di-t-butyl-4-hydroxyphenyl ) propionate and 2 ' -ethylhexyl-

3- (3, 5-di-t-butyl-4-hydroxyphenyl ) propionate,

benzenepropanoic acid 3 , 5-bis ( 1 , 1-dimethyl-ethyl ) -4- hydroxy-C7-C9 side-chain alkyl esters (Irganox L135, made by Ciba Specialty Chemicals Ltd.), 2 , 6-di-t-butyl- - dimethylamino-p-cresol , and 2 , 2 ' -methylenebis ( 4-alkyl-6- t-butylphenol ) s such as 2 , 2 ' -methylenebis ( 4-methyl-6-t- butylphenol) (Antage W-400, made by Kawaguchi Chemical Industry Ltd.) and 2 , 2 ' -methylenebis ( 4-ethyl-6-t- butylphenol) (Antage W-500, made by Kawaguchi Chemical Industry Ltd) .

Furthermore, there are bisphenols such as 4,4'- butylidenebis ( 3-methyl-6-t-butylphenol ) (Antage W-300, made by Kawaguchi Chemical Industry Ltd.), 4,4'- methylenebis ( 2 , 6-di-t-butylphenol ) (Ionox 220AH, made by Shell Japan Ltd.)_? 4 , 4 ' -bis ( 2 , 6-di-t-butylphenol ) , 2,2- (di-p-hydroxyphenyl ) propane (Bisphenol A, made by Shell Japan Ltd.), 2 , 2-bis ( 3 , 5-di-t-butyl-4- hydroxyphenyl ) propane, 4,4' -cyclohexylidenebis (2, 6-t- butylphenol ) , hexamethylene glycol bis [ 3- ( 3 , 5-di-t-butyl- 4-hydroxyphenyl ) propionate ] (Irganox L109, made by Ciba Specialty Chemicals Ltd.), triethylene glycol bis[3-(3-t- butyl-4-hydroxy-5-methylphenyl ) propionate ] (Tominox 917, made by Yoshitomi Fine Chemicals Ltd.), 2,2'-thio- [diethyl-3-(3, 5-di-t-butyl-4-hydroxyphenyl ) propionate (Irganox L115, made by Ciba Specialty Chemicals Ltd.), 3 , 9-bis { 1 , l-dimethyl-2- [3- ( 3-t-butyl-4-hydroxy-5- methylphenyl ) propionyloxy] ethyl } 2,4,8,10- tetraoxaspiro [ 5 , 5 ] undecane (Sumilizer GA80, made by

Sumitomo Chemicals), 4 , 4 ' -thiobis ( 3-methyl-6-t- butylphenol) (Antage RC, made by Kawaguchi Chemical Industry Ltd.) and 2 , 2 ' -thiobis ( 4 , 6-di-t-butyl- resorcinol ) .

Mention may also be made of polyphenols such as tetrakis [methylene-3- (3, 5-di-t-butyl-4-hydroxyphenyl ) propionate ] methane (Irganox L101, made by Ciba Specialty Chemicals Ltd.), 1 , 1 , 3-tris ( 2-methyl-4-hydroxy-5-t- butylphenyl ) butane (Yoshinox 930, made by Yoshitomi Fine Chemicals Ltd.), 1 , 3 , 5-trimethyl-2 , 4 , 6-tris ( 3 , 5-di-t- butyl-4-hydroxybenzyl ) benzene (Ionox 330, made by Shell Japan Ltd.), bis- [ 3 , 3 ' -bis- ( 4 ' -hydroxy-3 ' -t-butylphenyl ) butyric acid] glycol ester, 2- ( 3 ' , 5 ' -di-t-butyl-4- hydroxyphenyl ) methyl-4- ( 2^{1 1} , 4^{1 1} -di-t-butyl-3 ' ' - hydroxyphenyl ) methyl-6-t-butylphenol and 2, 6, -bis (2 '- hydroxy-3 ' -t-butyl-5 ' -methyl-benzyl) -4-methylphenol , and phenol-aldehyde condensates such as condensates of p-t- butylphenol and formaldehyde and condensates of p-t- butylphenol and acetaldehyde . As examples of amine-based anti-oxidants , mention may be made of dialkyl-diphenylamines such as ρ,ρ'- dioctyl-diphenylamine (Nonflex OD-3, made by Seiko

Chemical Ltd), p, p ' -di- -methylbenzyl-diphenylamine and N-p-butylphenyl-N-p ' -octylphenylamine,

monoalkyldiphenylamines such as mono-t-butyldiphenylamine and monooctyldiphenylamine, bis (dialkylphenyl ) amines such as di ( 2 , 4-diethylphenyl ) amine and di ( 2-ethyl-4- nonylphenyl ) amine, alkylphenyl-l-naphthylamines such as octyl-phenyl-l-naphthylamine and N-t-dodecylphenyl-1- naphthylamine, 1-naphthylamine, aryl-naphthylamines such as phenyl-l-naphthylamine, phenyl-2-naphthylamine, N- hexylphenyl-2-naphthylamine and N-octylphenyl-2- naphthylamine, phenylenediamines such as Ν,Ν'- diisopropyl-p-phenylenediamine and N, N ' -diphenyl-p- phenylenediamine, and phenothiazines such as

Phenothiazine (made by Hodogaya Chemical Ltd.) and 3,7- dioctylphenothiazine .

For the aforementioned extreme pressure agents and wear inhibitors it is possible to use sulphurised oils and fats, sulphurised olefins, sulphur compounds such as dithiocarbamates like zinc dithiocarbamates and

molybdenum dithiocarbamates, phosphorus compounds such as phosphate esters, acidic phosphate esters, phosphite esters, acidic phosphite esters, amine salts of phosphate esters, amine salts of phosphite esters, amine salts of acidic phosphate esters and amine salts of acidic

phosphite esters, thiophosphate esters, sulphur compounds such as dithiophosphates like zinc dithiophosphates and molybdenum dithiophosphates, or other molybdenum

compounds such as molybdenum amine compounds. Organic molybdenum compounds, which have superior friction and wear characteristics, are especially preferred. For rust inhibitors and corrosion inhibitors mention may be made of those that are generally used, for example, organic acid derivatives, among which

particularly preferred for use are succinic acid ester derivatives, aspartic acid derivatives, sarcosinic acid derivatives, and 4-nonylphenoxyacetic acids.

Mention may also be made of organic amine

derivatives and organic amide derivatives, among which diethanolamines , monoalkyl primary amines,

diamine/difatty acid salts, diamines, amides of

isostearic acid and amides of oleic acid are preferred.

As other preferred examples, mention may be made of sulphurised fatty acids, and surfactants (sorbitan trioleate, sorbitan tristearate, sorbitan monolaurate, stearic acid/oleic acid mono/diglycerides).

In addition, those selected from naphthenic acid salts, alkali metal salts of dibasic acids, alkaline earth metal salts of dibasic acids, or benzotriazole derivatives, benzoimidazole derivatives and

thiocarbamates are also suitable, and as preferred examples mention may be made of sodium sebacate or benzotriazole, or these combined.

As examples of solid lubricants, mention may be made of molybdenum disulphide, graphite, melamine cyanurate, boron nitride, mica, and PTFE (polytetrafluoroethylene) .

The aforementioned other additives may of course also be used in a form where they have been pre-added to commercial lubricating oils or semi-solid lubricating oils .

Examples

Further explanation is given below by way of examples and comparative examples, but the invention is not thereby limited. The following compositions and materials were used in preparation of the examples and comparative examples.

(1) Base Oil A: A paraffin-based mineral oil, with a 40°C kinematic viscosity of 144.1 mm²/s and viscosity index 96.

(2) Base Oil B: A paraffin-based and naphthene-based oil, with a 40°C kinematic viscosity of 130.2 mm²/s and viscosity index 79.

(3) Base Oil C: A paraffin-based mineral oil belonging to API category Group III which is produced by a high degree of hydrorefining in respect of a lubricating oil fraction obtained by atmospheric distillation of crude oil, with a 40°C kinematic viscosity of 46.87 mm²/s and viscosity index 127.

(4) Base Oil D: A poly- -olefin (PAO) , with a 40°C kinematic viscosity of 46.24 mm²/s and viscosity index 137.

(5) Lithium soap: lithium-12-hydroxystearate .

(6) Diurea compound: reaction product of 2 mol octylamine (C₈H₁₇NH₂) and 1 mol MDI ( 4 , 4 ' -diphenylmethane

diisocyanate ) .

(7) Tricalcium phosphate: [Ca₃ (P0₄) ₂] 3-Ca(OH) ₂, average granularity 5 μηι diameter.

(8) Calcium sulphonate (King Industries, Inc.; trade name Na-SUL 729) .

(9) Calcium salicylate (Infineum Japan Ltd.; trade name Infineum M7121) .

(10) Calcium phenate (Oronite Chemical Co.; trade name Oloa 229) .

(11) Calcium salt of oxidised wax (Lubrizol Corporation; trade name ALOX 165) .

(12) Barium sulphonate (King Industries, Inc.; trade name Na-SUL BSN) . (13) Lithium sulphonate (King Industries, Inc, ; trade name Na-SUL 707) .

(14) Sodium sulphonate (King Industries, Inc.; trade name Na-SUL SS) .

(15) Ammonium sulphonate (King Industries, Inc.; trade name Na-SUL AS) .

(16) Diethylene triamine sulphonate (King Industries, Inc.; trade name Na-SUL DTA) .

(17) Ethylene diamine sulphonate (King Industries, Inc.; trade name Na-SUL EDS) .

(18) Zinc sulphonate (King Industries, Inc.; trade name Na-SUL ZS-HT)

Examples and Comparative Examples

The compositions were mixed in the blending

proportions (mass%) shown in Tables 1, 2 and 3. They were treated in a three-roll mill and finished to a uniform state to give the grease compositions for

Examples 1 to 22.

Using the blending proportions shown in Tables 4, 5 and 6, Comparative Examples 1 to 20 were obtained in similar fashion to the aforementioned examples.

Tests

The following tests were carried out on Examples 1 to 22 and Comparative Examples 1 to 20 in order to compare their characteristics.

(1) Penetration: the worked penetration (25°C, 60W) was measured for penetration in the grease state as

stipulated in JIS K2220 (ASTM D1403) .

Here, a small value for the penetration shows a high consistency.

(2) Fretting corrosion test: carried out in accordance with ASTM D4170. Test bearings: Thrust bearing 51203 (made by

Nippon Seiko Co. Ltd.)

Amount of grease: 1.0 ± 0.05 g in upper and lower bearings

Thrust load: 2450 N (550 lb)

Amplitude: 0.21 radian (12°)

Oscillations: 30 Hz (1800 cycles/min)

Test temperature: Room temperature

Test duration: 22 hours

The anti-fretting corrosion characteristic was calculated as the loss (mg) being the race weight loss (wear loss) per each bearing using the formula (weight loss in upper bearing race + weight loss in lower bearing race) / 2.

Also, an evaluation was made by the following criteria, expressed by a score of 1 to 4. A lower wear loss is preferred.

Score 1: Amount of fretting wear not more than 3.0 mg Score 2: Amount of fretting wear More than 3.0 mg and less than 4.5 mg

Score 3: Amount of fretting wear 4.5 mg and above and less than 10.0 mg

Score 4: Amount of fretting wear 10.0 mg and above. Test Results

The results of the various tests are shown in Tables

1, 2, 3, 4, 5 and 6.

Discussion

What is shown for Examples 1 to 22 and Comparative Examples 1 to 20 is that the penetration is 272 to 295, so that in each case they display a grease hardness of

Penetration Grade 2 (worked penetration 265 to 295) of the NLGI (US grease institute) classification. It can be seen that the ant i-fretting corrosion characteristics of Examples 1 to 14 and 18 to 22 all gave an extremely good score of 1. Also, Examples 15 to 17 gave a score of "2" , which even if not as good as "1" is still excellent. In practical use they would not be inferior .

In addition, good results were obtained in each case even when using various base oils.

On the other hand, Comparative Examples 2 to 7, Comparative Example 9, Comparative Examples 11 to 15, and Comparative Examples 17 to 20 had a score of "3".

Comparative Example 1, Comparative Example 8, Comparative Example 10 and Comparative Example 16 has a score of "4", so that it was evident that they had greater weight loss and in this characteristic were inferior to the Examples of the invention.

Table 1

Table 2

Table 3

Table 4

Table 5

Table 6

Claims

C L A I M S

1. Grease composition comprising (a) a base oil, (b) a thickener, (c) tricalcium phosphate, and (d) at least one compound selected from the group consisting of alkaline earth metal salts, alkali metal salts, amine salts or zinc salts of oxidised waxes, petroleum sulphonic acids, alkyl aromatic sulphonic acids or such salts which are salicylates or phenates, and mixtures thereof.

2. Grease composition in accordance with Claim 1 characterised in that compound (d) is an alkaline earth metal salt selected from the group consisting of alkaline earth metal salts of oxidised waxes, alkaline earth metal salts of petroleum sulphonic acids, alkaline earth metal salts of alkyl aromatic sulphonic acids, alkaline earth metal salts which are salicylates, alkaline earth metal salts which are phenates, overbased alkaline earth metal salts of oxidised waxes, overbased alkaline earth metal salts of petroleum sulphonic acids, overbased alkaline earth metal salts of alkyl aromatic sulphonic acids, overbased alkaline earth metal salts which are

salicylates and overbased alkaline earth metal salts which are phenates, and mixtures thereof.

3. Grease composition in accordance with Claim 2 wherein the alkaline earth metal in the aforementioned alkaline earth metal salt (d) is calcium, magnesium or barium.

4. Grease composition in accordance with Claim 1 characterised in that compound (d) is an alkali metal salt selected from the group consisting of alkali metal salts of oxidised waxes, alkali metal salts of petroleum sulphonic acids, alkali metal salts of alkyl aromatic sulphonic acids, alkali metal salts which are

salicylates, alkali metal salts which are phenates, overbased alkali metal salts of oxidised waxes, overbased alkali metal salts of petroleum sulphonic acids,

overbased alkali metal salts of alkyl aromatic sulphonic acids, overbased alkali metal salts which are salicylates and overbased alkali metal salts which are phenates, and mixtures thereof.

5. Grease composition in accordance with Claim 4 wherein the alkali metal of the alkali metal salt which is the aforementioned (d) is selected from lithium or sodium .

6. Grease composition in accordance with Claim 1 characterised in that compound (d) is an amine salt selected from the group consisting of amine salts of oxidised waxes, amine salts of petroleum sulphonic acids, amine salts of alkyl aromatic sulphonic acids, amine salts which are salicylates, amine salts which are phenates, overbased amine salts of oxidised waxes, overbased amine salts of petroleum sulphonic acids, overbased amine salts of alkyl aromatic sulphonic acids, overbased amine salts which are salicylates and overbased amine salts which are phenates, and mixtures thereof.

7. Grease composition in accordance with Claim 1 characterised in that compound (d) is a zinc salt

selected from the group consisting of zinc salts of oxidised waxes, zinc salts of petroleum sulphonic acids, zinc salts of alkyl aromatic sulphonic acids, zinc salts which are salicylates and zinc salts which are phenates, and mixtures thereof.

8. Grease composition in accordance with any of Claims

1 to 7 characterised in that the aforementioned thickener is a lithium soap or a urea compound.

9. Grease composition in accordance with any of Claims 1 to 8 characterised in that the content of the

aforementioned tricalcium phosphate is 0.1 to 20% by mass relative to the grease composition.

10. Grease composition in accordance with any of Claims

1 to 9 characterised in that the content of the

aforementioned (d) being at least one compound selected from the group consisting of alkaline earth metal salts, alkali metal salts, amine salts and zinc salts is from 0.1 to 10% by mass relative to the grease composition.