WO2011070140A2

WO2011070140A2 - Lubricating oil composition

Info

Publication number: WO2011070140A2
Application number: PCT/EP2010/069350
Authority: WO
Inventors: Akiko Fujita; Hiroshi Kaneko; Mitsuhiro Nagakari; Hirohiko Ohtsu; Ayano Otsuka
Original assignee: Shell Internationale Research Maatschappij B.V.
Priority date: 2009-12-10
Filing date: 2010-12-10
Publication date: 2011-06-16
Also published as: WO2011070140A3; JP2011140642A

Abstract

A lubricating oil composition characterised in that it comprises a succinic acid derivative and an amide compound as additives, and a base oil selected from a mineral oil, a synthetic oil, and mixtures thereof. The lubricating oil composition of the present invention has excellent rust-preventing properties, a reduced friction coefficient and excellent energy-saving characteristics.

Description

LUBRICATING OIL COMPOSITION Technical Field of the Invention

This invention relates to lubricating oil

compositions such as industrial lubricating oils using refined base oils, and in particular it relates to lubricating oil compositions useful as machine oils, hydraulic oils, turbine oils, compressor oils, gear oils and bearing oils.

Background of the Invention

Good rust-preventing properties and friction

characteristics are required of lubricating oil

compositions, including those used as industrial

lubricating oil compositions. If they have a low friction coefficient (μ) , it is possible efficiently to reduce friction losses in mechanical apparatus and to achieve high energy savings.

For example, hydraulic apparatus is widely used in construction machinery and the like, and if the friction coefficient of the lubricating oils used for the

hydraulic oil actuating the machinery is high, the phenomenon of minute stick-slip may occur in the sliding friction parts of the packing owing to the reciprocating movement of the hydraulic cylinders, and chatter, vibration, squealing and other abnormal sounds may occur in the cylinders, so that it becomes impossible to control the hydraulic plant with satisfactory precision (Japanese Laid-open Patent H9-111277 (1997)). As a consequence it is necessary to reduce the friction coefficient of the lubricating oil so that the hydraulic cylinders move accurately and smoothly.

A fundamental requirement to maintain performance of a lubricating oil used in mechanical apparatus is rust prevention. This is because the lubricating oil

temperature within tanks in the mechanical apparatus rises and falls in accordance with conditions of use, and therefore the lubricating oil within the tanks may be subject to admixture with condensed water, or to

admixture with moisture because of leaks from cooling- water pipes.

This invention is intended to reduce the friction coefficient exhibited by lubricating oils so as to obtain an industrial lubricating oil which offers high energy savings. In addition, the intention is that, if such a lubricating oil composition is used as a hydraulic oil in hydraulic apparatus, the phenomena of chatter, vibration, squealing and other abnormal sounds in the cylinders will not occur, so that it will become possible to control the hydraulic apparatus with satisfactory precision and to inhibit the occurrence of rust and so impart excellent rust-prevention properties. The intention is, by this means, to obtain a lubricating oil composition which has excellent rust-prevention properties, which offers substantial energy savings because of low friction characteristics and which has good operating efficiency. Summary of the Invention

According to the present invention there is provided a lubricating oil composition, such as a hydraulic oil, comprising a succinic acid derivative and an amide compound as additives, and a base oil selected from a mineral oil, a synthetic oil and mixtures thereof.

Further, it is possible to obtain a lubricating oil composition with even better rust-prevention properties and with superior energy savings by further adding a polyhydric alcohol ester as an additive. According to this invention, it is possible to reduce the friction losses in all kinds of industrial apparatus to great effect and to bring about energy savings. Also, in the case of use as a hydraulic oil, it is possible to control the hydraulic apparatus with precision by reducing the friction coefficient and so not giving rise to phenomena in the hydraulic apparatus such as chatter, vibrations, squealing and other abnormal sounds in the hydraulic cylinders. Further, it is

possible to inhibit the occurrence of rust and so obtain a lubricating oil composition with substantial rust- prevention properties. Also, it is possible to obtain a lubricating oil composition with even more substantial rust-prevention properties such that no rust occurs even if lower fatty acids such as formic acid and acetic acid are present in the hydraulic apparatus and accumulate in the oil.

Detailed Description of the Invention

For the base oil of the present lubricating oil composition it is possible to use mineral oils or

synthetic oils as normally used for lubricating oils. In particular it is possible to use, singly or as mixtures, base oils which belong to Group I, Group II, Group III and Group IV of the API (American Petroleum Institute) base oil categories.

Group I base oils include, for example, paraffinic mineral oils obtained by 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. The viscosity index should be 80 to 120 and

preferably 95 to 110. The kinetic viscosity at 40°C should preferably be 2 to 680 mm²/s and even more preferably 8 to 220 mm²/s. The total nitrogen content should be less than 50 ppm and preferably less than 25 ppm. In addition, oils with an aniline point of 80 to 150°C and preferably 90 to 120°C should be used.

Group II base oils include, for example, paraffinic mineral oils obtained by 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 this invention. The viscosity of these base oils is not specially limited, but the viscosity index should be 90 to 125 and preferably 100 to 120. The kinetic viscosity at 40°C should preferably be 2 to 680 mm²/s and more preferably 8 to 220 mm²/s. Also, the total sulphur content should be less than 700 ppm, preferably less than 100 ppm and even more preferably less than 10 ppm. The total nitrogen content should also be less than

10 ppm and preferably less than 1 ppm. In addition, oils with an aniline point of 80 to 150°C and preferably 100 to 135°C should be used.

Suitable Group III base oils and Group 11+ base oils include, for example, 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 the

Isodewax process which dewaxes and substitutes the wax produced by the dewaxing process with isoparaffins, and base oils refined by the Mobil wax isomerisation process. The viscosity of these base oils is not specially

limited, but the viscosity index should be 95 to 145 and preferably 100 to 140. The kinetic viscosity at 40°C should preferably be 2 to 680 mm²/s and more preferably 8 to 220 mm²/s. Also, the total sulphur content should be 0 to 100 ppm and preferably less than 10 ppm. The total nitrogen content should also be less than 10 ppm and preferably less than 1 ppm. In addition, oils with an aniline point of 80 to 150°C and preferably 110 to 135°C should be used.

As examples of synthetic oils mention may be made of polyolefins, alkylbenzenes , alkylnaphthalenes , esters, polyoxyalkylene glycols, polyphenyl ethers,

dialkyldiphenyl ethers, fluorine-containing compounds (perfluoropolyethers, fluorinated polyolefins) and silicone oils.

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.

The viscosity of these synthetic oils is not

specially limited, but the kinetic viscosity at 40°C should preferably be 2 to 680 mm²/s and more preferably 8 to 220 mm²/ s .

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. The viscosity of GTL base oils is not specially limited, but normally the viscosity index should be 130 to 180 and preferably 140 to 175. Also, the kinetic viscosity at 40°C should be 2 to 680 mm²/s and preferably 5 to 120 mm²/s. Normally the total sulphur content is also less than 10 ppm and the total nitrogen content less than 1 ppm. A commercial example of such a GTL base oil is Shell XHVI (registered trademark) .

The amount of the aforementioned base oil to be incorporated in the present lubricating oil composition is not specially limited, but, taking as a basis the total amount of the lubricating oil composition, should be at least 60% by mass, preferably at least 80% by mass, more preferably at least 90% by mass, and yet more preferably at least 95% by mass.

The succinic acid derivatives are as shown by general formula (1) : coox

In the aforementioned general formula 1, Xi and X₂ are each hydrogen or alkyl groups, alkenyl groups or hydroxyalkyl groups with 3 to 6 carbons which may be the same or different, and preferably should be hydrogen atoms, 1-hydroxypropyl groups, 2-hydroxypropyl groups, 2- methylpropyl groups or tertiary butyl groups. X3 has 1 to

30 carbons and is an alkyl group or an alkenyl group, or an alkyl group having ether bonds, or a hydroxyalkyl group, for example, a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a 2-ethylhexyl group, a nonyl group, a decyl group, an undecyl group, a dodecyl group, a dodecylene group, a tridecyl group, a tetradecyl group, a tetradecylene group, a pentadecyl group, a hexadecyl group, a heptadecyl group, an

octadecyl group, an octadecylene group, an eicosyl group, a docosyl group, an alkoxypropyl group, a 3-(Cg- Cis) hydrocarbonoxy (C₃-C₆) alkyl group, and more preferably a tetraisopropyl group, an oleyl group, a

cyclohexyloxypropyl group, a 3-octyloxypropyl group, a 3- isooctyloxypropyl group, a 3-decyloxypropyl group, a 3- isodecyloxypropyl group and a 3- (Ci₂-Ci₆) alkoxypropyl group are suitable. Aminated forms of these compounds are also suitable.

The aforementioned succinic acid derivatives should have an acid number as determined by JIS K2501 in the range of from 10 to 300 mgKOH/g and preferably in the range of from 30 to 200 mgKOH/g. The amount of succinic acid derivatives used in the lubricating oil composition is in the range of from 0.001 to 0.5% by mass, preferably in the range of from 0.001 to 0.1% by mass and more preferably in the range of from 0.005 to 0.1% by mass. One kind or a mixture of several kinds of these succinic acid derivatives may be used.

For the amide compounds in this invention, mention may be made of the amide compounds, shown in general formula (2), which are products based on fatty acids and monoamines, or amide compounds which are products based on the reaction of fatty acids and polyamines.

X4CONH2 (2) Assuming the amide compound is based on a fatty acid and a monoamine, in the aforementioned general formula 2, X₄ is an alkyl group or alkenyl group having from 1 to 30 carbon atoms. For example, mention may be made of

laurylamide, coconut amide, n-tridecylamide,

myristylamide, n-pentadecylamide, n-palmitylamide, n- heptadecylamide, n-stearylamide, isostearylamide, n- nononadecylamide, n-eicosylamide, n-heneicosylamide, n- docosylamide, n-tricosylamide, n-pentacosylamide,

oleylamide, beef tallow amide, hydrogenated beef tallow amide and soybean amide. The number of carbon atoms in X₄ is preferably in the range of from 8 to 24 and more preferably in the range of from 12 to 18. The alkyl group or alkenyl group may also be a straight-chain aliphatic, a branched aliphatic or a tertiary alkyl group.

Assuming the amide compound is based on a polyamine and a fatty acid, mention may be made for example of reaction products of aliphatic amines or polyamines and saturated or unsaturated fatty acids having from 1 to 24 carbon atoms, such as isostearic acid triethylene

tetramide, isostearic acid tetraethylene pentamide, oleic acid diethylene triamide and oleic acid diethanol amide.

The amide compounds are used in the lubricating oil composition in an amount in the range of from 0.001 to 0.5% by mass, but preferably in the range of from 0.001 to 0.1% by mass and more preferably in the range of from 0.005 to 0.1 % by mass. These amide compounds may be used singly or in mixtures.

It is possible to incorporate esters of polyhydric alcohols in the lubricating oil composition of this invention. These polyhydric alcohol esters are those used in the prior art as oiliness improvers. For example, it is possible to use partial or complete esters of saturated or unsaturated fatty acids having from 1 to 24 carbon atoms and polyhydric alcohols such as glycerol, sorbitol, alkylene glycol, neopentyl glycol,

trimethylolpropane, pentaerythritol and xylidol.

As specific examples of such, mention may be made of glycerol esters such as glycerol monolaurylate, glycerol monostearate, glycerol monopalmitate, glycerol

monooleate, glycerol dilaurylate, glycerol distearate, glycerol dipalmitate and glycerol dioleate.

For sorbitol esters mention may be made of sorbitol monolaurylate, sorbitol monopalmitate, sorbitol

monostearate, sorbitol monooleate, sorbitol dilaurylate, sorbitol dipalmitate, sorbitol distearate, sorbitol dioleate, sorbitol tristearate, sorbitol trilaurylate, sorbitol trioleate, sorbitol sesquioleate and sorbitol tetraoleate .

Alkylene glycol esters include ethylene glycol monolaurylate, ethylene glycol monostearate, ethylene glycol monooleate, ethylene glycol dilaurylate, ethylene glycol distearate, ethylene glycol dioleate, propylene glycol monolaurylate, propylene glycol monostearate, propylene glycol monooleate, propylene glycol

dilaurylate, propylene glycol distearate and propylene glycol dioleate.

For neopentyl glycol esters mention may be made of neopentyl glycol monolaurylate, neopentyl glycol

monostearate, neopentyl glycol monooleate, neopentyl glycol dilaurylate, neopentyl glycol distearate and neopentyl glycol dioleate.

Trimethylolpropane esters include trimethylolpropane monolaurylate, trimethylolpropane monostearate,

trimethylolpropane monooleate, trimethylolpropane dilaurylate, trimethylolpropane distearate and trimethylolpropane dioleate.

Pentaerythritol esters include pentaerythritol monolaurylate, pentaerythritol monostearate,

pentaerythritol monooleate, pentaerythritol dilaurylate, pentaerythritol distearate, pentaerythritol dioleate and dipentaerythritol monooleate.

For such fatty acid esters of polyhydric alcohols it is preferable to use partial esters of polyhydric

alcohols and unsaturated fatty acids.

These fatty acid esters of polyhydric alcohols are used in the lubricating oil composition in an amount in the range of from 0.01 to 5% by mass, but preferably in the range of from 0.05 to 2% by mass. If the amount used is outside this range, the effect on reducing the

friction coefficient may be weakened.

Apart from the aforementioned constituents, it is possible, in order to improve performance further, to make appropriate use, as required, of various additives. Mention may be made of anti-oxidants , metal deactivators, extreme-pressure additives, oiliness improvers, defoaming agents, viscosity index improvers, pour-point

depressants, detergent dispersants, rust preventatives, demulsifiers and so on, as well as other known

lubricating oil additives.

For the anti-oxidants used in this invention, those used in lubricating oils are preferred for practical use, and mention may be made of phenolic anti-oxidants , amine- based anti-oxidants and sulphur-based anti-oxidants .

These anti-oxidants may be used in the lubricating oil composition singly or in mixtures in the range of from

0.01 to 5% by mass.

As examples of the aforementioned amine-based anti^¬ oxidants, mention may be made of dialkyldiphenylamines such as p, p ' -dioctyldiphenylamine (Nonflex OD-3, made by Seiko Chemical Ltd), p, p ' -di- -methylbenzyldiphenylamine 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 octylphenyl-l-naphthylamine and N-t-dodecylphenyl-1- naphthylamine, 1-naphthylamine, arylnaphthylamines 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 .

As examples of sulphur-based anti-oxidants , mention may be made of dialkyl sulphides such as didodecyl sulphide and dioctadecyl sulphide, thiodipropionate esters such as didodecyl thiodipropionate, dioctadecyl thiodipropionate, dimyristyl thiodipropionate and

dodecyloctadecyl thiodipropionate, and 2- mercaptobenzoimidazole .

Phenolic 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 (Yoshinox 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 and

benzenepropanoic acid 3 , 5-bis ( 1 , 1-dimethyl-ethyl ) -4- hydroxy-C₇-Cg 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 ' ' , 4 ' ' -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 phosphorus-based anti-oxidants mention may be made of triarylphosphites such as

triphenylphosphite and tricresylphosphite,

trialkylphosphites such as trioctadecylphosphite and tridecylphosphite, and tridodecyltrithiophosphite .

Metal deactivators that can be used together with the composition of this invention include benzotriazole and benzotriazole derivatives which are 4-alkyl- benzotriazoles such as 4-methyl-benzotriazole and 4- ethyl-benzotriazole, 5-alkyl-benzotriazoles such as 5- methyl-benzotriazole and 5-ethyl-benzotriazole, 1-alkyl- benzotriazoles such as l-dioctylaminomethyl-2 , 3- benzotriazole and 1-alkyl-tolutriazoles such as 1- dioctylaminomethyl-2 , 3-tolutriazole, and benzoimidazole and benzoimidazole derivatives which are 2- ( alkyldithio ) - benzoimidazoles such as 2- (octyldithio) -benzoimidazole, 2- (decyldithio ) -benzoimidazole and 2- (dodecyldithio ) - benzoimidazole and 2- ( alkyldithio ) toluimidazoles such as

2- (octyldithio) -toluimidazole, 2- (decyldithio) - toluimidazole and 2- (dodecyldithio ) toluimidazole .

Also, mention may be made of indazole, indazole derivatives which are toluindazoles such as 4-alkyl- indazoles and 5-alkyl-indazoles , benzothiazole, and benzothiazole derivatives which are 2- mercaptobenzothiazole derivatives (Thiolite B-3100, made by Chiyoda Chemical Industries Ltd.)_? 2-

( alkyldithio ) benzothiazoles such as 2- (hexyldithio ) benzothiazole and 2-

(octyldithio) benzothiazole, 2- (alkyldithio) toluthiazoles such as 2- (hexyldithio ) toluthiazole and 2-

( octyldithio ) toluthiazole, 2- (N, -dialkyldithiocarbamyl ) - benzothiazoles such as 2- (N, N-diethyldithiocarbamyl ) - benzothiazole, 2- (N, N-dibutyldithiocarbamyl ) - benzothiazole and 2- (N, N-dihexyldithiocarbamyl ) - benzothiazole, and 2- (N, N-dialkylydithiocarbamyl ) - toluthiazoles such as 2- (N, N-diethyldithiocarbamyl ) - toluthiazole, 2- (N, -dibutyldithiocarbamyl ) -toluthiazole and 2- (N, N-dihexyldithiocarbamyl ) -toluthiazole .

Further, mention may be made of benzooxazole

derivatives which are 2- ( alkyldithio ) benzooxazoles such as 2- (octyldithio) benzooxazole, 2- (decyldithio ) benzooxazole and 2- (dodecyldithio ) benzooxazole or which are 2-

( alkyldithio ) toluoxazoles such as 2-

( octyldithio ) toluoxazole, 2- (decyldithio ) toluoxazole and 2- (dodecyldithio) toluoxazole, thiadiazole derivatives which are 2 , 5-bis ( alkyldithio ) -1 , 3 , 4-thiadiazoles such as 2, 5-bis (heptyldithio ) -1,3,4-thiadiazole, 2,5- bis (nonyldithio) -1, 3, 4-thiadiazole, 2, 5- bis (dodecyldithio ) -1 , 3 , 4-thiadiazole and 2,5- bis (octadecyldithio) -1, 3, 4-thiadiazole, 2,5-bis(N,N- dialkyldithiocarbamyl ) -1 , 3 , 4-thiadiazoles such as 2,5- bis (N, -diethyldithiocarbamyl )-l, 3, 4-thiadiazole, 2,5- bis (N, -dibutyldithiocarbamyl ) -1 , 3 , 4-thiadiazole and 2,5- bis (N, -dioctyldithiocarbamyl ) -1 , 3 , 4-thiadiazole and 2- N, -dialkyldithiocarbamyl-5-mercapto-l , 3, 4-thiadiazoles such as 2-N, N-dibutyldithiocarbamyl-5-mercapto-l , 3 , 4- thiadiazole and 2-N, N-dioctyldithiocarbamyl-5-mercapto- 1,3,4-thiadiazole, and triazole derivatives which are, for example, l-alkyl-2 , 4-triazoles such as 1-di- octylaminomethyl-2 , 4-triazole.

These metal deactivators may be used in the

lubricating oil composition singly or in mixtures in the range of from 0.01 to 0.5% by mass.

It is also possible to add phosphorus compounds to the lubricating oil composition of this invention and thereby further impart anti-wear properties and extreme- pressure properties. As examples of phosphorus compounds suitable for this invention, mention may be made of phosphate esters, acidic phosphate esters, amine salts of acidic phosphate esters, chlorinated phosphate esters, phosphite esters, phosphorothionates , zinc

dithiophosphates , esters of dithiophosphates and alkanols or polyether-type alcohols or derivatives thereof, phosphorus-containing carboxylic acids and phosphorus- containing carboxylic acid esters.

These phosphorus compounds may be used singly or in mixtures in the range of from 0.01 to 2% by mass in the lubricating oil composition. As examples of the aforementioned phosphate esters, mention may be made of tributyl phosphate, tripentyl phosphate, trihexyl phosphate, triheptyl phosphate, trioctyl phosphate, trinonyl phosphate, tridecyl

phosphate, triundecyl phosphate, tridodecyl phosphate, tritridecyl phosphate, tritetradecyl phosphate,

tripentadecyl phosphate, trihexadecyl phosphate,

triheptadecyl phosphate, trioctadecyl phosphate, trioleyl phosphate, triphenyl phosphate, tris(iso- propylphenyl ) phosphate, triaryl phosphate, tricresyl phosphate, trixylenyl phosphate, cresyldiphenyl phosphate and xylenyldiphenyl phosphate.

As specific examples of the aforementioned acidic phosphate esters, mention may be made of monobutyl acid phosphate, monopentyl acid phosphate, monohexyl acid phosphate, monoheptyl acid phosphate, monooctyl acid phosphate, monononyl acid phosphate, monodecyl acid phosphate, monoundecyl acid phosphate, monododecyl acid phosphate, monotridecyl acid phosphate, monotetradecyl acid phosphate, monopentadecyl acid phosphate,

monohexadecyl acid phosphate, monoheptadecyl acid

phosphate, monooctadecyl acid phosphate, monooleyl acid phosphate, dibutyl acid phosphate, dipentyl acid

phosphate, dihexyl acid phosphate, diheptyl acid

phosphate, dioctyl acid phosphate, dinonyl acid

phosphate, didecyl acid phosphate, diundecyl acid

phosphate, didodecyl acid phosphate, ditridecyl acid phosphate, ditetradecyl acid phosphate, dipentadecyl acid phosphate, dihexadecyl acid phosphate, diheptadecyl acid phosphate, dioctadecyl acid phosphate and dioleyl acid phosphate .

As examples of the aforementioned amine salts of acidic phosphate esters, mention may be made of the methylamine, ethylamine, propylamine, butylamine,

pentylamine, hexylamine, heptylamine, octylamine,

dimethylamine, diethylamine, dipropylamine, dibutylamine, dipentylamine, dihexylamine, diheptylamine, dioctylamine, trimethylamine, triethylamine, tripropylamine,

tributylamine , tripentylamine, trihexylamine,

triheptylamine and trioctylamine salts of the previously mentioned acidic phosphate esters.

As examples of the aforementioned phosphite esters, mention may be made of dibutyl phosphite, dipentyl phosphite, dihexyl phosphite, diheptyl phosphite, dioctyl phosphite, dinonyl phosphite, didecyl phosphite,

diundecyl phosphite, didodecyl phosphite, dioleyl

phosphite, diphenyl phosphite, dicresyl phosphite, tributyl phosphite, tripentyl phosphite, trihexyl

phosphite, triheptyl phosphite, trioctyl phosphite, trinonyl phosphite, tridecyl phosphite, triundecyl phosphite, tridodecyl phosphite, trioleyl phosphite, triphenyl phosphite and tricresyl phosphite.

As examples of the aforementioned

phosphorothionates , mention may be made specifically of tributyl phosphorothionate, tripentyl phosphorothionate, trihexyl phosphorothionate, triheptyl phosphorothionate, trioctyl phosphorothionate, trinonyl phosphorothionate, tridecyl phosphorothionate, triundecyl phosphorothionate, tridodecyl phosphorothionate, tritridecyl

phosphorothionate, tritetradecyl phosphorothionate, tripentadecyl phosphorothionate, trihexadecyl

phosphorothionate, triheptadecyl phosphorothionate, trioctadecyl phosphorothionate, trioleyl

phosphorothionate, triphenyl phosphorothionate, tricresyl phosphorothionate, trixylenyl phosphorothionate,

cresyldiphenyl phosphorothionate, xylenyldiphenyl phosphorothionate, tris (n-propylphenyl )

phosphorothionate, tris ( isopropylphenyl )

phosphorothionate, tris (n-butylphenyl ) phosphorothionate, tris ( isobutylphenyl ) phosphorothionate, tris(s- butylphenyl) phosphorothionate and tris ( t-butylphenyl ) phosphorothionate. Mixtures of these may also be used.

As examples of the aforementioned zinc

dithiophosphates, mention may be made in general of zinc dialkyl dithiophosphates, zinc diaryl dithiophosphates and zinc arylalkyl dithiophosphates. For example, zinc dialkyl dithiophosphates where the alkyl groups of the zinc dialkyl dithiophosphates have primary or secondary alkyl groups having from 3 to 22 carbon atoms or

alkylaryl groups substituted with alkyl groups having from 3 to 18 carbon atoms may be used.

As specific examples of zinc dialkyl

dithiophosphates, mention may be made of zinc dipropyl dithiophosphate, zinc dibutyl dithiophosphate, zinc dipentyl dithiophosphate, zinc dihexyl dithiophosphate, zinc diisopentyl dithiophosphate, zinc diethylhexyl dithiophosphate, zinc dioctyl dithiophosphate, zinc dinonyl dithiophosphate, zinc didecyl dithiophosphate, zinc didodecyl dithiophosphate, zinc dipropylphenyl dithiophosphate, zinc dipentylphenyl dithiophosphate, zinc dipropylmethylphenyl dithiophosphate, zinc

dinonylphenyl dithiophosphate and zinc didodecylphenyl dithiophosphate .

Phosphorus-containing carboxylic compounds such as phosphorus-containing carboxylic acids and their acid esters should include both a carboxyl group and a

phosphorus atom in the same molecule. Their structure is not specially limited but normally, from the standpoint of extreme pressure properties and thermal and oxidative stability, phosphorylated carboxylic acids or

phosphorylated carboxylic acid esters are preferred. As examples of phosphorylated carboxylic acids or

phosphorylated carboxylic acid esters, mention may be made of compounds as exemplified by the following general formula ( 3 ) .

In the aforementioned general formula (3), R4 and R5 may be the same or different and each denotes a hydrogen atom or a hydrocarbon group having from 1 to 30 carbons atoms. R6 denotes an alkylene group having from 1 to 20 carbons atoms. R₇ denotes a hydrogen atom or a

hydrocarbon group having from 1 to 30 carbons. Xi, X2, X3 and X₄ may be the same or different and each denotes an oxygen atom or a sulphur atom.

As examples of the hydrocarbon groups having from 1 to 30 carbons atoms in R₄ and R₅ in the aforementioned general formula (3), mention may be made of alkyl groups, alkenyl groups, aryl group, alkylaryl groups and

arylalkyl groups.

β-dithiophosphorylated propionic acids, which are useful examples of the aforementioned β- dithiophosphorylated carboxylic acids, have the structure shown in the following general formula (4) :

As a specific example of these β- dithiophosphorylated propionic acids, mention may be made of 3- (di-isobutoxy-thiophosphorylsulphanyl ) -2-methyl propionic acid.

The amount of phosphorus-containing carboxylic acid compound in the present lubricating oil composition is not specially limited, but is preferably in the range of from 0.001 to 1% by mass and more preferably in the range of from 0.002 to 0.5% by mass in the lubricating oil composition. If the amount of phosphorus-containing carboxylic acid compound is less than the above-mentioned lower limit, there will be a likelihood of satisfactory lubricating qualities not being obtained. On the other hand, even if the above-mentioned upper limit is

exceeded, it is likely that an effect in improving the lubrication properties matching the amount added will not be obtained. Furthermore, there is a risk that the thermal and oxidative stability and the hydrolytic stability will be reduced, which is not desirable.

The amount of the compound where R7 is a hydrogen atom in a phosphorylated carboxylic acid as expressed by the aforementioned general formula (3) is in the range of from 0.001 to 0.1% by mass, preferably in the range of from 0.002 to 0.08% by mass, more preferably in the range of from 0.003 to 0.07% by mass, still more preferably in the range of from 0.004 to 0.06% by mass, and even more preferably in the range of from 0.005 to 0.05% by mass.

In order to improve the low-temperature flow

characteristics and viscosity characteristics, pour-point depressants and viscosity-index improvers may also be added to the lubricating oil composition of this

invention .

As examples of viscosity-index improvers mention may be made of non-dispersant type viscosity-index improvers such as polymethacrylates and olefin polymers such as ethylene-propylene copolymers, styrene-diene copolymers, polyisobutylene and polystyrene, and dispersant type viscosity-index improvers where nitrogen-containing monomers have been copolymerised with these. As regards the amount to be added, they may be used within the range of from 0.05 to 20% by mass in the lubricating oil composition .

As examples of pour-point depressants mention may be made of polymethacrylate-based polymers. They may be used in an amount in the range of from 0.01 to 5% by mass in the lubricating oil composition.

Defoaming agents may also be added in order to impart defoaming characteristics to the lubricating oil composition of this invention. As examples of such defoaming agents suitable for this invention, mention may be made of organosilicates such as dimethylpolysiloxane, diethylsilicate and fluorosilicone, and non-silicone type defoaming agents such as polyalkylacrylates . As regards the amount to be added, they may be used singly or in mixtures in the range of from 0.0001 to 0.1% by mass in the lubricating oil composition.

As examples of demulsifiers suitable for this invention, mention may be made of those in the known art normally used as additives for lubricating oils. They may be used in an amount in the range of from 0.0005 to 0.5% by mass in the lubricating oil composition.

Examples

The invention is explained in specific detail below by means of examples and comparative examples, but the invention is not limited to only these examples.

For preparation of the examples and comparative examples, the compositions and materials mentioned below were used.

1. Base Oils

(1-1) Base Oil 1: A paraffinic mineral oil obtained by use of a suitable combination of refining processes such as hydrocracking and dewaxing in respect of a lubricating oil fraction obtained by atmospheric distillation of crude oil, and classified as Group II according to the API (American Petroleum Institute) base oil

classification. (Characteristics: kinetic viscosity at

100°C, 5.35 mm²/s; kinetic viscosity at 40°C, 31.4 mm²/s; viscosity index, 103; sulphur content (as converted to elemental sulphur) , less than 10 ppm; nitrogen content (as converted to elemental nitrogen) , less than 1 ppm; aniline point, 110°C; density at 15°C: 0.864; density at

20°C: 0.860; refractive index at 20°C: 1.472; molecular weight (ASTM D2502): 411; ring-analysis paraffin content according to the method of ASTM D3238, 62%; naphthene content according to the method of ASTM D3238, 38%;

aromatic content according to the method of ASTM D3238, less than 1%; initial boiling point temperature according to gas chromatography distillation by the method of ASTM D5480, 312°C) .

(1-2) Base Oil 2: A paraffinic mineral oil obtained by appropriate use of a suitable combination of

refining processes such as hydrocracking and dewaxing in respect of a lubricating oil fraction obtained by atmospheric distillation of crude oil, and classified as Group III according to the API (American Petroleum Institute) base oil classification. (Characteristics: kinetic viscosity at 100°C: 6.57 mm²/s, kinetic

viscosity at 40°C: 37.5 mm²/s, viscosity index: 130, sulphur content (as converted to elemental sulphur) : less than 10 ppm, nitrogen content (as converted to elemental nitrogen) : less than 1 ppm, aniline point: 123°C, 15°C density: 0.844, 20°C density: 0.841, 20°C refractive index: 1.465, molecular weight (ASTM

D2502): 479, ring-analysis paraffin content according to the method of ASTM D3238: 79%, aromatic content ditto: less than 1%, poly aromatic content according to the method of IP 346: 0.2%, initial boiling point temperature according to gas chromatography

distillation by the method of ASTM D5480: 306°C) (1-3) Base Oil 3: A GTL base oil synthesised by the Fischer-Tropsch method, and classified as Group III according to the API (American Petroleum Institute) base oil classification. (Characteristics: kinetic viscosity at 100°C: 5.10 mm²/s, kinetic viscosity at 40°C: 23.5 mm²/s, viscosity index: 153, sulphur content (as converted to elemental sulphur) , less than 10 ppm: nitrogen content (as converted to elemental nitrogen) : less than 1 ppm, aniline point: 126°C, 15°C density: 0.821, 20°C density, 0.817: 20°C refractive index: 1.456, molecular weight (ASTM

D2502): 447, ring-analysis paraffin content according to the method of ASTM D3238: 95%, aromatic content ditto: less than 1%, initial boiling point

temperature according to gas chromatography

distillation by the method of ASTM D5480: 365°C) (1-4) Base Oil 4: A synthetic oil being a poly- - olefin (PAO) with the general name PA06, and

classified as Group IV according to the API (American Petroleum Institute) base oil classification.

(Characteristics: kinetic viscosity at 100°C: 5.89 mm²/s, kinetic viscosity at 40°C: 31.2 mm²/s,

viscosity index: 135, sulphur content (as converted to elemental sulphur) : less than 10 ppm, nitrogen content (as converted to elemental nitrogen) : less than 1 ppm, aniline point: 128°C, 15°C density:

0.827, 20°C density: 1.460, initial boiling point temperature according to gas chromatography

distillation by the method of ASTM D5480: 403°C)

2. Additives

(2-1) Additive Al : Succinic acid derivative:

tetrapropenyl succinic acid, 1 , 2-propanediol half ester (acid number by the method of JIS K2501: 160 mgKOH/g)

(2-2) Additive A2 : Succinic acid derivative:

tetrapropenyl succinic acid, 1 , 3-propanediol half ester (acid number by the method of JIS K2501: 160 mgKOH/g)

(2-3) Additive A3: Succinic acid derivative:

RheinChemie RC4802 (acid number by the method of ASTM D3739: 55mgKOH/g)

(2-4) Additive Bl : oleyl amide

(2-5) Additive B2 : amide of polyamine (the main

constituent being isostearic acid triethylene

tetramide) (base number by the method of JIS K2501: 7 mgKOH/g)

(2-6) Additive CI: sorbitan sesquioleate (hydroxyl number by the method of JIS K0070: 200 mgKOH/g)

(2-7) Additive C2 : glycerol monoisostearate (hydroxyl number by the method of JIS K0070: 313mgKOH/g)

Examples 1-7 and Comparative Examples 1 to 3

Using the aforementioned compositions and materials, the lubricating oil compositions of Examples 1-7 and

Comparative Examples 1 to 3 were prepared according to the constituent amounts shown in Tables 1 and 2. Tests

The following tests were carried out on the

lubricating oil compositions of the aforementioned

Examples 1-7 and Comparative Examples 1 to 3 in order to observe their performance.

Friction Coefficient

The friction coefficient was measured using a Masuda pendulum-type oiliness tester manufactured by Shinko Machine Manufacturing Co. Ltd. In this test the oil being tested is supplied to the friction portion of the

pendulum fulcrum, the pendulum is made to move, and the friction coefficient is obtained from the reduction in oscillations .

The evaluation of the tests was made according to the following criteria:

Friction coefficient 0.135 or less 0 (Excellent )

Friction coefficient 0.136 to less than 0.150 0 (Good)

Friction coefficient 0.150 or more X

(Not acceptable)

Rust Prevention Tests

Following JIS K2510, 300 ml of test oil was taken and put in a container disposed in a constant-temperature bath. It was agitated at a speed of 1000 turns per minute. When the temperature reached 60 °C, an iron test specimen was inserted into the oil being tested and 30 ml of artificial sea water was also added. Keeping the temperature at 60°C, agitation was continued for 24 hours. Then the specimen was removed and assessed

visually for occurrence of any rust.

The evaluation of the tests was made according to the following criteria: No rust 0 (pass)

Rust is observed X (fail)

Test Results

The results of the tests are shown in Tables 1 and 2.

Discussion

As is clear from the results in Tables 1 and 2, the case of using a base oil combined with a succinic acid derivative (Additive Al ) and an aliphatic amide (Additive Bl) as in Example 1 was Excellent (0) with a low friction coefficient, and it passed (0) in the artificial sea- water rust-prevention test with no occurrence of rust. The case of using a base oil combined with a succinic acid derivative (Additive Al ) , an aliphatic amide

(Additive Bl) and a polyhydric alcohol ester (Additive

CI) as in Example 2 also proved to be Excellent (0) with a low friction coefficient and it passed (0) in the artificial sea-water rust-prevention test with no

occurrence of rust .

Example 3, comprising Base Oil 2, succinic acid derivative (Additive A2 ) , fatty amide (Additive Bl) and polyalcohol ester (Additive C2), was Excellent (0) with a low friction coefficient, and it passed (0) in the artificial sea-water rust-prevention test with no

occurrence of rust.

Example 4, comprising Base Oil 3, succinic acid derivative (Additive A3), fatty amide (Additive B2) and polyalcohol ester (Additive CI) was Excellent (0) with a low friction coefficient, and it passed (0) in the artificial sea-water rust-prevention test with no

occurrence of rust .

Example 5, comprising Base Oil 3, succinic acid derivative (Additive A3), fatty amide (Additive B2) and polyalcohol ester (Additive C2) was Excellent (0) with a low friction coefficient, and it passed (0) in the artificial sea-water rust-prevention test with no

occurrence of rust .

Example 6, comprising Base Oil 4, succinic acid derivative (Additive A3), fatty amide (Additive B2) and polyalcohol ester (Additive CI) was Excellent (0) with a low friction coefficient, and it passed (0) in the artificial sea-water rust-prevention test with no

occurrence of rust.

Example 7, comprising Base Oil 4, succinic acid derivative (Additive A3), fatty amide (Additive B2) and polyalcohol ester (Additive C2) was Excellent (0) with a low friction coefficient, and it passed (0) in the artificial sea-water rust-prevention test with no

occurrence of rust .

In contrast, in the case of the base oil only as in Comparative Example 1, the friction coefficient was extremely high and not acceptable (X) . It also failed in the artificial sea-water rust-prevention test (X) because of occurrence of rust. In the case of a succinic acid derivative (Additive A) added to the base oil as in

Comparative Example 2, there was no occurrence of rust and so it passed (0) the artificial sea-water rust- prevention test, but the friction coefficient was high and not acceptable (X) . Also, in the case of an aliphatic amide (Additive B) added to the base oil as in

Comparative Example 3, the friction coefficient was

Excellent (0) , being low, but rust occurred in artificial sea water in the rust-prevention test and so it failed

(X) .

It was thus observed as in Examples 1-7 that a lubricating oil composition in which a succinic acid derivative (Additive A1-A3) and an aliphatic amide

(Additive B1/B2) were added together in a base oil (Base Oil 1-4) or in which a polyhydric alcohol ester (Additive C1-C2) was further added had a low and Excellent (0) friction coefficient, and passed (0) the rust-prevention test with no occurrence of rust in artificial sea water, so that a reduction in the friction coefficient and improvement in rust-prevention properties were brought about .

Table 1

Table 2

Comp . Comp . Comp . Ex. 1 Ex. 2 Ex. 3 i_i _Ctomposon

lR_tessu Mass % Mass % Mass %

Base Oil 100.0 99.9 99.9

Additive A:

0.1

Succinic acid derivative

Additive B:

Oleylamide

0.1

Pendulum test X X 0 Friction coefficient 0.307 0.157 0.134

Rust (artificial

sea water only) X 0 X

Fail Pass Fail

Claims

C L A I M S

1. A lubricating oil composition comprising a succinic acid derivative and an amide compound as additives, and a base oil selected from a mineral oil, a synthetic oil, and mixtures thereof.

2. A lubricating oil composition according to Claim 1 additionally comprising a polyhydric alcohol ester as an additive .

3. A lubricating oil composition according to Claim 1 or Claim 2 wherein the succinic acid derivative has an acid number in the range of from 10 to 300 mgKOH/g (JIS K2501) .

4. A lubricating oil composition according to with any of Claims 1 to 3 wherein the amount of the aforementioned succinic acid derivative in the lubricating oil

composition is in the range of from 0.001 to 0.5% by mass and the amount of the amide compound is in the range of from 0.001 to 0.5% by mass.

5. A lubricating oil composition according to any of Claims 1 to 4 wherein the succinic acid derivative has the general formula (1) : coox₁

wherein Xi and X2 are each hydrogen or alkyl groups, alkenyl groups or hydroxyalkyl groups having from 3 to 6 carbons which may be the same or different, and X3 has 1 to 30 carbons and is an alkyl group or an alkenyl group, or an alkyl group having ether bonds, or a hydroxyalkyl group .

6. A lubricating oil composition according to Claim 5 wherein Xi and X₂ are each independently selected from hydrogen atoms, 1-hydroxypropyl groups, 2-hydroxypropyl groups, 2-methylpropyl groups and tertiary butyl groups.

7. A lubricating oil composition according to any of Claims 1 to 6 wherein the amide compound is selected from compounds of general formula (2), which are products based on fatty acids and monoamines or polyamines:

X₄CONH₂ (2) wherein X₄ is an alkyl group or alkenyl group having from 1 to 30 carbon atoms.

8. A lubricating oil composition according to Claim 7 wherein X₄ has from 8 to 24 carbon atoms, preferably from 12 to 18 carbon atoms.

9. A lubricating oil composition according to Claim 7 or 8 wherein X₄ is selected from laurylamide, coconut amide, n-tridecylamide, myristylamide, n-pentadecylamide, n-palmitylamide, n-heptadecylamide, n-stearylamide, isostearylamide, n-nononadecylamide, n-eicosylamide, n- heneicosylamide, n-docosylamide, n-tricosylamide, n- pentacosylamide, oleylamide, beef tallow amide,

hydrogenated beef tallow amide and soybean amide.

10. A lubricating oil composition according to any of Claims 1 to 9 wherein the base oil is selected from an

API (American Petroleum Institute) Group II base oil, an API Group III base oil, a GTL base oil and a

polyalphaolefin .

11. Use of a lubricating oil composition according to any of Claims 1 to 10 for reducing friction and/or for rust prevention.