LUBRICATING OIL COMPOSITION FOR DIESEL ENGINES
Lubricating oil composition for use in diesel engines which comprises, in the base oil, not more than 0.3% by mass of sulphated ash, from 0.01 to 0.2% by mass of nitrogen in succinimides, from 0.05 to 0.12% by mass of zinc in zinc dithiophosphates, from 0.02 to 0.3% by mass of nitrogen in amine-based anti-oxidants, and from 0.01 to 0.08% by mass of boron, which further has a total value of [(zinc amount in zinc dithiophosphates)×(nitrogen amount in succinimides)] and [(zinc amount in zinc dithiophosphates)×(nitrogen amount in amine-based anti-oxidants)] as regards the aforementioned of from 0.015 to 0.06, and which does not contain salicylate, phenate or sulphonate metallic detergents. The intention is to obtain a lubricating oil composition for use in diesel engines which does not contain a metallic detergent yet maintains excellent engine (piston) detergency while preventing DPF clogging, and which reduces valve-train wear.
This invention relates to a lubricating oil composition for diesel engines, and in particular relates to a lubricating oil composition for diesel engines having excellent engine (piston) detergency while being extra low ash despite not incorporating metallic detergents.
BACKGROUND OF THE INVENTIONA diesel particulate filter (hereafter DPF), which is regarded as an effective way of cleaning the particulate matter (hereafter PM) in the exhaust gases of diesel engines, may be subject to clogging of the filter because of metal constituents in the engine oil used. For example, it is known that the ash deriving from diesel engine oils accumulates in the DPF, and that this gives rise to a reduction in the PM cleaning efficiency and a reduction in the life of the DPF, so that it is considered necessary to reduce the sulphated ash in the diesel engine oil, in other words to lower the ash content.
This has meant that engine oils, and diesel engine oils in particular, have had a history of changing because of changes in the fuel. For example, particulates, carbon monoxide and NOx emissions from atmospheric pollution due to exhaust gases are now a problem, and in particular the sulphur content in diesel oils has sharply decreased over the past ten or more years, from not more than 500 ppm to not more than 10 ppm. Because of these exhaust-gas countermeasures, it has come about that a post-treatment device known as a DPF has been installed in diesel engines. But in order to prevent clogging of the DPFs, a need has arisen for low-ash engine oils.
Also, in the case of the sulphur content, given that sulphuric acid is formed by combustion and that the sulphuric acid so formed has a deleterious effect on piston detergency and on wear, and given that phosphorus in the engines oils is known to poison the exhaust gas purification catalysts, it is now conceivable that a trend favouring low ash/low phosphorus/low sulphur, known as “low SAPS” engine oils is becoming ever stronger.
In this move towards lower ash, which has a major effect on the required performance of the aforementioned diesel engines oils, it is necessary to reduce the blended amounts of additives which contain metals, such as metallic detergents which impart engine detergency, and zinc dialkylthiophosphates (ZnDTP), which impart anti-wear performance.
In order to prevent the aforementioned clogging of the DPF, a low ash engine oil composition that contains no metallic additives can be considered, but if the metallic component is simply reduced compared to engine oil compositions of the prior art, the result will be a reduction in important functions, namely engine detergency, anti-wear performance and oxidative stability of the engine oil composition.
For example, Japanese Laid-open Patent 2007-254559 (Patent Reference 1) has as its objective a low-ash diesel engine oil composition, but the sulphated ash is still considerable at up to 0.6% by mass, and it further contains a metallic detergent, so that so long as it uses a small amount of metallic detergent, the situation is that it is continuing the prior art even with the objective of a low-ash engine oil.
Also, Japanese Laid-open Patent 2006-176672 (Patent Reference 2) has as its objective a lubricating oil for internal combustion engines with superior oxidative stability because of a low-ash component. It attempts to offer an increased viscosity and acid number in this low-ash oil, but it does not specially focus on piston detergency. Furthermore, the sulphated ash in the examples is extremely large, at 0.99 to 1.01% by mass.
This invention is intended to obtain a lubricating oil composition for use in diesel engines such that excellent engine (piston) detergency is maintained while clogging of the DPF is prevented and wear on valve trains is reduced, even without the inclusion of a metallic detergent.
This invention, without the inclusion of a metallic detergent, maintains excellent engine piston detergency while preventing clogging of the DPF and wear on valve trains, by creating a balance between zinc dithiophosphates, succinimides and amine-based anti-oxidants added to the base oil.
SUMMARY OF THE INVENTIONAccording to the present invention there is provided a lubricating oil composition for use in diesel engines which comprises, in the base oil, not more than 0.3% by mass of sulphated ash, 0.01 to 0.2% by mass of nitrogen in succinimides, 0.05 to 0.12% by mass of zinc in zinc dithiophosphates, 0.02 to 0.3% by mass of nitrogen in amine-based anti-oxidants, and 0.01 to 0.08% by mass of boron, which further has a total value of [(zinc amount in zinc dithiophosphates)×(nitrogen amount in succinimides)] and [(zinc amount in zinc dithiophosphates)×(nitrogen amount in amine-based anti-oxidants)]as regards the aforementioned of from 0.015 to 0.06, preferably 0.015 to 0.04 and more preferably 0.015 to 0.04, and which does not contain salicylate, phenate or sulphonate metallic detergents.
DETAILED DESCRIPTION OF THE INVENTIONWhat is meant herein by not containing metallic detergents is a lubricating oil composition wherein the metal component deriving from metallic detergents is not more than 0.01% by mass.
The aforementioned base oil is preferably one that is a base oil or a base oil mixture selected from Group II, Group III, Group IV and Group V and where the sulphur component of the base oil is not more than 50 ppm.
In addition, this lubricating oil composition for use in diesel engines is such that the TGF in JASO M336:1998 Detergency Test Procedure is not more than 30%, and the cam nose wear in JASO M354:1998 Valve-train Wear Test Procedure is not more than 95 μm.
With this invention it is possible to obtain a lubricating oil composition for use in diesel engines such that no metallic detergent is included and there is a low amount of ash, while at the same time excellent piston detergency of the engine is maintained, clogging of the DPF is prevented and wear on valve trains is reduced, so that there is a reduction in the burden on the environment.
For the base oil used in the lubricating oil composition for diesel engines of the present invention it is possible in particular to use as appropriate mineral oils, synthetic oils and mixtures thereof as normally used for lubricating oils. In particular, it is possible to use, singly or as mixtures, oils which belong to categories Group II, Group III, Group IV and Group V of the API (American Petroleum Institute) base oil categories.
The aforementioned Group II base oils include, for example, paraffinic mineral oils obtained by appropriate use of a suitable combination of refining processes such as hydrocracking 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 can be used for this invention.
The viscosity of these base oils is not specially limited, but the viscosity index should be 80 to 120 and preferably 100 to 120. The kinematic 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 300 ppm, preferably less than 100 ppm and 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.
Group 2 Plus base oils, which possess the viscosity index higher than 115, can be specified as a preferable Group 2 base oil.
Group III 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 Isodewaxing which dewaxes and substitutes with isoparaffins waxes produced by dewaxing processes, and base oils refined by the Mobil wax isomerisation process. These are also suitable for use in this invention.
The viscosity of these base oils is not specially limited, but the viscosity index should be 120 to 160 and preferably 120 to 150. The kinematic 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 300 ppm, preferably less than 100 ppm and 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 110 to 135° C. should be used.
Group 3 Plus base oils, which possess the viscosity index higher than 130, can be specified as a preferable Group 3 base oil.
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 so on), 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 α-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-α-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 characteristics of GTL base oils are not specially limited, but normally the viscosity index should be 120 to 180, preferably 130 to 175, and more preferably 140 to 175. Also, the kinematic 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).
Base oils specified above can be used singly or as mixtures, and their sulphur content should be less than 50 ppm, preferably less than 10 ppm and more preferably less than 1 ppm.
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 of 3 to 22 carbons or alkylaryl groups substituted with alkyl groups of 3 to 18 carbons may be used. For example, zinc dialkyl dithiophosphates where the alkyl groups of the zinc dialkyl dithiophosphates have primary or secondary alkyl groups of 3 to 12 carbons or zinc diaryl dithiophosphates where the aryl groups are phenyl or alkylaryl groups substituted with alkyl groups of 1 to 18 carbons may be used.
The zinc dithiophosphates with secondary alkyl groups having 3 to 12 carbon atoms, preferably 3 to 8 carbon atoms and more preferably 3 to 6 atoms are preferred.
As specific examples of zinc diallyl 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.
These zinc dithiophosphates are incorporated so that the amount of zinc is 0.05 to 0.12% by mass, but preferably 0.06 to 0.12% by mass, of the lubricating oil composition. Zinc dithiophosphates are, as mentioned above, effective anti-wear additives, but they contain phosphorus (P). Phosphorus compounds are said to poison exhaust-gas catalysts, and if the phosphorus content in the composition increases, there is a heightened possibility of a deleterious effect on the exhaust-gas cleaning catalyst. For this reason, if the zinc dithiophosphate is incorporated so that the amount of zinc exceeds 0.12% by mass, there will be a concomitant increase in the amount of phosphorus in the composition, which is not desirable. Also, if the aforementioned upper limit is exceeded, the effect of being a wear additive will be saturated, so that an effect matching the expenditure will not be obtained and this will not be efficient. On the other hand, if the amount is less than 0.05% by mass, the result in terms of being an anti-wear additive may not be effectual.
In the lubricating oil composition of this invention, an alkenyl succinimide or an alkyl succinimide and/or a boron-modified derivative thereof is used for the aforementioned succinimide. It has the function of being an ashless dispersant.
As suitable examples of an alkenyl or an alkyl succinimide mention may be made of the alkenyl or alkyl succinic monoimides represented by General Formula (1) and the alkenyl or alkylsuccinic bisimides represented by General Formula (2).
In the aforementioned General Formula (1) and General Formula (2), R1, R3 and R4 each denote an alkenyl group or an alkyl group with a weight-average molecular weight of from 500 to 3,000, and R3 and R4 may be the same or different. R2, R5 and R6 each denote an alkylene group having from 2 to 5 carbons, and R5 and R6 may be the same or different. m is an integer of from 1 to 10 and n is 0 or an integer of from 1 to 10.
The weight-average molecular weight of each of R1, R3 and R4 in General Formulae (1) and (2) is, as aforementioned, from 500 to 3,000, but preferably from 1,000 to 3,000. If the weight-average molecular weight is less than 500, solubility in the base oil will be reduced, and if it exceeds 3,000 detergency will decrease, so that there will be a risk that the target functions will not be achieved.
Also, the aforementioned m is an integer of from 1 to 10, but preferably from 2 to 5, and more preferably from 3 to 4. If m exceeds 2, there will be good detergency. If m is less than 5 solubility in the base oil will be good.
In General Formula (2), n is 0 or an integer of from 1 to 10, but preferably from 1 to 4 and more preferably from 2 to 3. If n exceeds 1, there will be good detergency, and if n is less than 4 solubility in the base oil will be good.
As examples of the alkenyl groups in General Formulae (1) and (2), mention may be made of polybutenyl groups, polyisobutenyl groups, and ethylene-propylene copolymers. Alkyl groups include hydrogenated forms thereof. As typical examples of suitable alkenyl groups mention may be made of polybutenyl groups and polyisobutenyl groups. These polybutenyl groups are obtained by polymerising mixtures of 1-butene and isobutene or highly refined isobutene.
Also, hydrogenated forms of polybutenyl groups or polyisobutenyl groups are typical examples of suitable alkyl groups.
The aforementioned alkenyl or alkyl succinimides can normally be prepared by reacting with a polyamine an anhydrous alkenyl succinimide obtained by a reaction between a polyolefin and maleic anhydride, or an anhydrous alkyl succinimide obtained by hydrogenating same.
The aforementioned succinic monoimides and bisimides may be prepared by varying the reaction proportions of anhydrous alkenyl succinic acids or anhydrous alkyl succinic acids and polyamines.
For the olefin monomer that forms the aforementioned polyolefin, it is possible to use mixtures of one or two or more kinds of α-olefins having from 2 to 8 carbons, and it is possible to use satisfactorily mixtures of isobutene and butene-1.
As examples of the aforementioned polyamines, mention may be made of unitary diamines such as ethylene diamine, propylene diamine, butylene diamine and pentylene diamine, and of polyalkylene polyamines such as diethylene triamine, triethylene tetramine, tetraethylene pentamine, pentaethylene hexamine, di(methylethylene) triamine, dibutylene triamine, tributylene tetramine and pentapentylene hexamine.
Also, for boron-modified derivatives of alkenyl or alkyl succinimides it is possible to use those prepared by the usual methods. For example, they can be obtained after making the aforementioned polyolefins into anhydrous alkenyl succinimides by reacting them with maleic acid, by further imidification through reacting them with an intermediate obtained by reacting the aforementioned polyamines and a boron compound such as boron oxide, a boron halide, a boric acid, a boric anhydride, a boric ester or an ammonium salt of a boric acid.
The lubricating oil composition of this invention contains, in terms of the composition, from 0.01 to 0.2% by mass, calculated in terms of nitrogen content, of an alkenyl or alkyl succinic monoimide or bisimide and/or a boron-modified derivative thereof as an ashless dispersant, but preferably contains from 0.05 to 0.15% by mass.
If the content of the alkenyl or alkyl succinic monoimide or bisimide and/or boron-modified derivative thereof is less than 0.01% by mass, the effect as an ashless dispersant will not be satisfactorily displayed, and if it exceeds 0.2% by mass, deleterious influence on rubber parts such as elastomers used in engines can be seen.
Also, the content of a boron-modified derivative of an alkenyl or alkyl succinic monoimide in said ashless dispersant will be, calculated in terms of boron, from 0.01 to 0.08% by mass and preferably from 0.04 to 0.07% by mass.
Even if the boron-converted content of the alkenyl or alkyl succinic monoimide and/or boron-modified derivative thereof in the ashless dispersant is less than 0.01% by mass the effect of the anti-wear and high temperature detergency performance is not enough and if it exceeds 0.08% by mass, that effective performance will be saturated and the economic efficiency will decrease.
Also, boron derives from boron-modified forms of succinimides, and for the amount of succinimide added to be within the aforementioned range, it is often not desirable if the boron component is added in excess, because the excess of the boron component may cause the DPF clogging by increasing the sulphated ash derived by increased boron in the formulation.
For the amine-based anti-oxidants used in this invention, those used generally for lubricating oils are preferred for practical use, and it is possible to use them singly or in plural combinations in the lubricating oil composition within the range of from 0.02 to 0.3% by mass in terms of the nitrogen content.
Amine-based anti-oxidants structurally are prone to surface adsorption, and because the zinc dithiophosphate, the anti-wear agent, decomposes and the acidic intermediates are adsorbed on the surface, an excess added amount is again not desirable, so that it is best to control the upper limit.
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-α-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-1-naphthylamines such as octylphenyl-1-naphthylamine and N-t-dodecylphenyl-1-naphthylamine, 1-naphthylamine, arylnaphthylamines such as phenyl-1-naphthylamine, phenyl-2-naphthylamine, N-hexylphenyl-2-naphthylamine and N-octylphenyl-2-naphthylamine, phenylenediamines such as N,N′-diisopropyl-p-phenylenediamine and N,N′-diphenyl-p-phenylenediamine, and phenothiazines such as Phenothiazine (made by Hodogaya Chemical Ltd.) and 3,7-dioctylphenothiazine.
Apart from the amine-based anti-oxidants used in this invention, it is possible to use phenolic anti-oxidants. In the undermentioned examples, phenolic anti-oxidants and amine-based anti-oxidants are used in combination. These anti-oxidants may be used singly or in plural combinations within the range of from 0.01 to 5% by mass in the lubricating oil composition.
The combination of the amine-based anti-oxidants and phenolic anti-oxidants used in the Examples shown in Table 1.
As examples of sulphur-based anti-oxidants, mention may be made of dialkyl sulphides such as didodecyl sulphide, thiodipropionate esters such as 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, benzenepropanoic acid 3,5-bis(1,1-dimethyl-ethyl)-4-hydroxy-C7-C9 side-chain alkyl ester (Irganox L135, made by Ciba Specialty Chemicals Ltd.), 2,6-di-t-butyl-α-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{1,1-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.
In addition to the aforementioned constituents, where required by applications or performance, it is also possible to use as appropriate metal deactivators, corrosion inhibitors, viscosity index improvers, pour point depressants, defoaming agents and other additives in the lubricating oil composition for diesel engines of this invention.
Metal deactivators that can be used together with the lubricating oil composition for diesel engines 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 1-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,N-dialkylydithiocarbamyl)-benzothiazoles such as 2-(N,N-diethyldithiocarbamyl)-benzothiazole, 2-(N,N-dibutyldithiocarbamyl)-benzothiazole and 2-(N,N-dihexyldithiocarbamyl)-benzothiazole, and 2-(N,N-dialkyldithiocarbamyl)-toluthiazoles such as 2-(N,N-diethyldithiocarbamyl)-toluthiazole, 2-(N,N-dibutyldithiocarbamyl)-toluthiazole and 2-(N,N-dihexyldithiocarbamyl)-toluthiazole.
Further, mention may be made of benzooxazole derivates 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,N-diethyldithiocarbamyl)-1,3,4-thiadiazole, 2,5-bis(N,N-dibutyldithiocarbamyl)-1,3,4-thiadiazole and 2,5-bis(N,N-dioctyldithiocarbamyl)-1,3,4-thiadiazole and 2-N,N-dialkyldithiocarbamyl-5-mercapto-1,3,4-thiadiazoles such as 2-N,N-dibutyldithiocarbamyl-5-mercapto-1,3,4-thiadiazole and 2-N,N-dioctyldithiocarbamyl-5-mercapto-1,3,4-thiadiazole, and triazole derivates which are, for example, 1-alkyl-2,4-triazoles such as 1-dioctylaminomethyl-2,4-triazole.
These metal deactivators may be used singly or in plural combinations within the range of from 0.01 to 0.5% by mass in the lubricating oil composition.
As examples of the aforementioned corrosion inhibitors, mention may be made of fatty acids, alkenylsuccinic half-esters, fatty acid soaps, alkyl sulphonic acid salts, sulphonates, and naphthenates of alkaline earth metals (calcium (Ca), magnesium (Mg), barium (Ba) and so on), polyhydric alcohol fatty acid esters, fatty acid amines, paraffin oxide, and alkylpolyoxyethylene ethers, and normally the amount thereof in the blend will be within the range of from 0.01 to 5% by mass on the basis of the total amount of the composition.
In order to improve the low-temperature flow characteristics and viscosity characteristics, pour-point depressants and viscosity-index improvers can 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 as well as ethylene-propylene copolymers, styrene-diene copolymers such as styrene-butadiene or olefin polymers such as 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 of the lubricating oil composition.
As examples of pour-point depressants mention may be made of polymethacrylate-based polymers. As regards the amount to be added, they may be used within the range of from 0.01 to 5% by mass of the lubricating oil composition. A polymethacrylate-based pour-point depressant was incorporated in the examples of this invention.
Defoaming agents may also be added in order to impart defoaming characteristics to the lubricating oil composition of this invention. As examples of preferred defoaming agents, mention may be made of organosilicates such as polydimethylsiloxane, 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 plural combinations within the range of from 0.0001 to 0.1% by mass in the lubricating oil composition.
Further explanation is given below by giving examples and comparative examples, but the invention is not limited by these.
In preparing the examples and comparative examples, the following compositions and materials were used.
1. Base oils
(1-1) Base Oil A: Fischer-Tropsch derived base oil (XHVI 5.2) [Characteristics: kinematic viscosity at 100° C., 5.2 mm2/s; viscosity index, 140; sulphur content, not more than 10 ppm by mass]
(1-2) Base Oil B: Fischer-Tropsch derived base oil (XHVI 8.2) [Characteristics: kinematic viscosity at 100° C., 8.2 mm2/s; viscosity index, 144; sulphur content, not more than 10 ppm by mass]
(1-3) Base Oil C: Co-oligomer of ethylene and α-olefins (Lucant HC40) [Characteristics: kinematic viscosity at 100° C., 40 mm2/s; viscosity index, 155; sulphur content, not more than 10 ppm by mass]
2. Zinc dithiophosphates
(2-1) ZnDTP-1: Zinc dialkyldithiophosphate having secondary alkyl groups with 3 to 6 carbons [Constituents (values for elemental analysis): Zn 11.1% by mass, P 10.0% by mass, S 21% by mass]
(2-2) ZnDTP-2: Zinc dialkyldithiophosphate having secondary alkyl groups with 4 to 6 carbons [Constituents (values for elemental analysis): Zn 7.7% by mass, P 7.2% by mass, S 15% by mass]
3. Ashless dispersants
(3-1) Succinimide-1: Borated polybutenyl succinimide (mono) [Constituents (values for elemental analysis): N 2.2% by mass, B 1.96% by mass]
(3-2) Succinimide-2: Polybutenyl succinimide (bis) [Constituents (values for elemental analysis): N 1.2% by mass]
(3-3) Succinimide-3: Borated polybutenyl succinimide (bis) [Constituents (values for elemental analysis): N 1.5% by mass, B 0.47% by mass]
(4-1) Anti-oxidant-1: Amine-based anti-oxidant (Irganox L57) [Constituents: nitrogen content 4.5% by mass]
(4-2) Anti-oxidant-2: Hindered phenol-based anti-oxidant (Irganox L135)
5. Metal deactivator: Benzotriazole derivative (Irgamet 39)
6. Viscosity index improver: styrene-butadiene-based viscosity index improver
7. Pour-point depressant: Polymethacrylate-based pour-point depressant
8. Defoaming agent: Polydimethylsiloxane-based defoaming agent
The component materials were mixed in the proportions shown in Tables 1 and 2, and lubricating oil compositions for use in diesel engine oils were obtained. The proportions shown in Tables 1 and 2 are mass % unless otherwise specified.
TestsThe following tests were carried out on Examples 1 to 4 and Comparative Examples 1 to 6 in order to compare their characteristics.
(1) Parameter CalculationTotal value of [(amount of zinc in zinc dialkyldithiophosphate)×(amount of nitrogen in polybutenyl succinimide)] and [(amount of zinc in zinc dialkyldithiophosphate)×(amount of nitrogen in amine-based anti-oxidant)]
The amount of zinc and nitrogen described here are expressed with % by mass.
Evaluation criterion:
0.015 or more . . . Acceptable
Under 0.015 . . . Not acceptable
If this value is less than 0.015, the TGF will exceed 30% or the amount of cam nose wear will exceed 95 μm, which is not desirable. If it is between 0.015 and 0.06, both the TGF and the amount of cam nose wear will be small, which means it is possible to achieve desirable results. If the value is more than 0.06, it is not favourable in terms of economic efficiency.
(2) Detergency Test Based on TGF Value (TGF Value Measured after Nissan TD25 Engine Test)
A test to evaluate piston detergency was carried out on the basis of the engine test procedure according to JASO M336:1998, which is a diesel-engine piston detergency test adopted also for JASO M355 (Automotive Diesel Engine Oil Standard).
Evaluation criterion:
30% or less . . . Acceptable
Over 30% . . . Not acceptable
(3) Valve-Train Wear TestsValve-train wear tests were carried out in accordance with JASO M354:1999 (using Mitsubishi 4D34T4 engine).
Evaluation criterion:
Wear on cam nose 95 μm or less . . . Acceptable
Over 95 μm . . . Not acceptable
The cam nose wear value limit is based on the pass criteria for JASO's DH-2.
In the case of the cam nose wear values used here, investigations were carried out using the actual measured values themselves and no conversions of any kind were carried out.
Test ResultsThe test results for Examples 1 to 4 and Comparative Examples 1 to 6 are given in Tables 1 and 2.
DiscussionExample 1 did not contain any metallic detergent. The succinimide-3 ashless dispersant gave a nitrogen amount of 0.15% by mass, the amine-based anti-oxidant gave a nitrogen amount of 0.08% by mass, and the succinimide-based dispersant gave a boron amount of 0.047% by mass, whilst the ZnDTP gave a Zn amount of 0.10% by mass, so that the parameter for zinc amount×(succinimide nitrogen amount+amine-based anti-oxidant nitrogen amount) had a value of 0.023, and the TGF was 12% and the cam nose wear was 7 μm. Furthermore, the sulphated ash was 0.23% by mass, meeting the criterion, so that satisfactory performance had been obtained.
Example 2 did not use a metallic detergent. The main points were that the total nitrogen amount of the mixture of succinimide-1, succinimide-2 and succinimide-3 gave a total nitrogen amount of 0.12% by mass, and the parameter value was therefore 0.020. The TGF was 12%, and the cam nose wear was 18 μm, which meant satisfactory performance had been achieved.
In the case of Example 3, the nitrogen amount of the succinimides was 0.15% by mass, and it was a mixture of succinimide-1 and succinimide-2. The Zn amount was 0.1% by mass, and the amine-based anti-oxidant gave a nitrogen amount of 0.0396% by mass, which meant that the parameter value was 0.019. The TGF value was 9% and the cam nose wear was 24.7 μm.
When the amine-based anti-oxidant nitrogen amount was 0.022% by mass, as in Example 4, the parameter value was 0.015, the TGF was 7% and the cam nose wear was 84.9 μm, but this was within the range of satisfactory performance.
On the other hand, in the case of Comparative Example 1, the succinimide-based dispersant gave a nitrogen amount of 0.075% by mass. Also, the Zn amount was 0.077% by mass, and no amine-based anti-oxidant was added, so that the parameter value was considerably reduced at 0.006, the TGF value was 47%, and there was a substantial increase in cam nose wear. In Comparative Example 2, the nitrogen amount from the succinimide-based dispersant was 0.12% by mass, and the nitrogen amount from the amine-based anti-oxidant was 0.08% by mass, whilst the Zn amount was 0.05% by mass. This meant the parameter value was outside the range at 0.010, and the TGF was 39% but the cam nose wear exceeded 95 μm at 217 μm.
Comparative Example 3 gave a Zn amount of 0.05% by mass, a succinimide nitrogen amount of 0.10% by mass, an amine-based anti-oxidant nitrogen amount of 0.0792% by mass, and a parameter value of 0.009, which was outside the range. The TGF value was 55 and the valve-train wear deteriorated further to 300 μm. In the case of Comparative Example 4, where the Zn amount was 0.06% by mass, the succinimide nitrogen amount was 0.15% by mass, and the amine-based anti-oxidant nitrogen amount was 0.0396% by mass, the parameter value was 0.011, the TGF was 14% and the cam nose wear exceeded 95 μm at 130.7 μm.
In Comparative Example 5, where the Zn amount was 0.07% by mass and the succinimide nitrogen amount was 0.12% by mass, the parameter value was 0.011, and the TGF was satisfactory at 24%, but the cam nose wear increased substantially to give 235.6 μm. In Comparative Example 6, the amount of succinimide-3 was made the same as in Example 1, and the Zn amount was 0.07% by mass, whilst the amine-based anti-oxidant nitrogen amount was 0.0396% by mass, which meant the parameter value was 0.013, the TGF was 11% and the cam nose wear was 99 μm, slightly exceeding the camshaft wear limit of 95 μm.
Claims
1. A lubricating oil composition for use in diesel engines which comprises, in the base oil, not more than 0.3% by mass of sulphated ash, from 0.01 to 0.2% by mass of nitrogen in succinimides, from 0.05 to 0.12% by mass of zinc in zinc dithiophosphates, from 0.02 to 0.3% by mass of nitrogen in amine-based anti-oxidants, and from 0.01 to 0.08% by mass of boron, which further has a total value of [(zinc amount in zinc dithiophosphates)×(nitrogen amount in succinimides)] and [(zinc amount in zinc dithiophosphates)×(nitrogen amount in amine-based anti-oxidants)] in an amount of not less than 0.015, and which does not contain salicylate, phenate or sulphonate metallic detergents.
2. The lubricating oil composition according to claim 1 wherein the base oil is a single base oil or a mixture selected from Group II, Group III, Group IV and Group V, and where the sulphur component of the base oil is not more than 50 ppm.
3. The lubricating oil composition according to claim 1 having a Top Groove fill according to Japanese Automobile Standards Organization M336:1998 Detergency Test Procedure of not more than 30%, and cam nose wear according to Japanese Automobile Standards Organization M354:1999 Valve-train Wear Test Procedure of not more than 95 μm.
4. The lubricating oil composition according to claim 1, wherein the base oil contains secondary alkyl zinc dithiophosphates, wherein the alkyl groups have from 3 to 12 carbon atoms.
Type: Application
Filed: May 11, 2011
Publication Date: Oct 10, 2013
Inventors: Kiyoshi Hanyuda (Aikou-Gun Aikou), Tetsuo Wakizono (Aikou-Gun Aikou)
Application Number: 13/696,841
International Classification: C10M 141/12 (20060101);
