CA2173895A1

CA2173895A1 - Lubricant oil composition

Info

Publication number: CA2173895A1
Application number: CA002173895A
Authority: CA
Inventors: Satoshi Asano; Katsuya Arai
Original assignee: Individual
Current assignee: Tonen General Sekiyu KK
Priority date: 1995-04-14
Filing date: 1996-04-11
Publication date: 1996-10-15
Also published as: EP0737735A3; SG54284A1; EP0737735A2; AU5062796A; JPH08283762A

Abstract

A lubricant oil composition produced by blending (A) a molybdenum-containing friction conditioner, (B) a boron-containing compound and (C) an antioxidant if necessary, with a lubricant base oil, wherein the content of the molybdenum derived from the molybdenum-containing friction condi-tioner is 100 to 2,000 ppm (as the ratio by weight) and the content of the boronderived from the boron-containing compound is 0.015% by weight or more, to the total weight of the composition.

The lubricant oil compositions of the present invention are the lubricant oil compositions blended with a molybdenum-containing friction conditioner and a boron-containing compound, and are capable of decreasing coking deposit in internal combustion engines such as automobile engines, which is advantageous for sustaining a fuel-efficiency property for a long term. Hence, the compositions can be used preferably for automobile lubricant oils.

Description

; 21738~5 BACKGROUND OF THE rNVENTION

FIELD OF THE INVENTION

The present invention relates to a novel lubricant oil composition.
More specifically, the present invention relates to a lubricant oil composition with a small friction coefficient under a wide variety of applicable conditions,particularly under operating conditions at a medium to low oil temperature and alow-speed rotation, which is preferable as a lubricant oil composition for intPrn~l combustion eng-nes such as automobile engines for sustaining a fuel-efficiency.

DESCRIPTION OF THE RELATED ART

So as to smoothly operate internal combustion engines, driving systems such as automatic tr~n~mi~ions, buffers, and power steerings, and gears, use has been made therein of lubricant oils. Lubricant oils for internal combustion engines, in particular, have roles in lubricating principally a variety of sliding parts such as piston rings/cylinder liners, bearings of a crank shaft and connecting rods, valve meçhAnism inclusive of cams and valve lifters, and the like, as well as in cooling the inside of an engine and cleaning to disperse combustion products and furthermore preventing rust and corrosion.

As has been described above, a wide variety of efficiencies are demanded of lubricant oils for internal combustion engines. In recent years, furthermore, higher efficiency has been required therefor, as intern~l combustion engines have acquired higher performance and higher output and the operating conditions have become more severe. In order to satisfy such demanded propellies, thus, a variety of additives including for example wear preventing agents, metal cleaning agents, non-ash dispersants, antioxidants and the like have been added to lubricant oils for internal combustion engines.

For the filn~ment~l functions of lubricant oils for int~rn~l combustion engines, smooth operation of internal combustion engines under any of the conditions, in particular, is significant, so as to prevent wear and seizure.
Lubricated engine parts are mostly in the state of fluid lubrication, but valve systems and top and bottom dead centers of pistons are likely to be put in the ~17;38~S

state of boundary lubrication. The wear preventing property in such a state of boundary lubrication is generally given by the addition of zinc dithiophosphate and zinc dithioc~l,~,late. The energy loss due to friction of moving parts involving lubricant oils is so large in internal combustion engines that use is made of a lubricant oil in combination with a variety of additives primarily including a friction conditioner, as a measure for decreasing a frictional loss or for increasing the fuel efficiency (for example, see Japanese Patent PublicationNo. 23595/1991).

Automobile internal combustion engines are operated at a wide range of oil temperature, and rates of rotation and load, and so as to promote the fuel-efficiency, lubricant oils for intçrn~l combustion engines should have greater friction properties under a wide variety of applicable conditions. How-ever, the friction properties may be sometimes deteriorated by generated coking deposit and the like. Thus, so as to m~int~in the fuel-efficiency for a long term, less coking deposit should be demanded. Hence, the standard ILSAC GF-2 specifying such demand is now going to be established.

On the other hand, so as to lower the friction coefficient, use has been made of molybdenum-cont~inin~ friction conditioners such as sulfoxy-molybdenum dithiocarbamate. When the improvement of the fuel-efficiency is intended by decreasing the friction coefficient by means of the molybdenum-co~ friction conditioner, the coking deposit is increased in proportion to the molybd~Pnllm content thereof, disadvantageously, involving sometimes the occurrence of such a drawback that the fuel-efficiency property which has been laboriously re~li7ed cannot be m~int~ined.

Practically, some lubricant oil compositions blended with such molybdPnllm-co~ & friction conditioners have a drawback such that in a deposit test according to the hot tube coking test of the GF-2 standard, they absolutely cannot satisfy the standard [the deposit content at the hot tube coking (at 310C for 16 hours) should be 100 mg or less] because occlusion develops in them through the coking deposit.

The objective of the present invention is to improve the property of sll~ ~e fuel-coefficiency of a lubricant oil composition with a smaller 2~7389~

friction coefficient, the composition being blended with a molybdenum-co~ g friction conditioner, more specifically, to provide a lubricant oil composition blended with a molybdenllm-cont~ining friction conditioner, the composition satisfying the coke deposit criterion of the GF-2 standard on hot tube coking test.

DESCRIPTION OF THE FIGURES

Figure 1 is a graph representing the relation between the molybdenum content and the amount of deposit generated.

Figure 2 is a graph representing the relation between the boron content and the amount of deposit generated.

DESCRIPTION OF THE INVENTION

It has been discovered that coke deposit can be decreased prol"illently by adding a specific amount of a specific compound having a higherboron content into a lubricant oil composition with friction properties improvedby use of a molybdenum series additive.

More specifically, the present invention is to provide:

(1) a lubricant oil composition produced by blending (A) a molybdenum-CO.~t~ g friction conditioner and (B) a boron-containing compound with a lubricant base oil, wherein the content of the molybdenum derived from the molybdenum-cont~ining friction conditioner is 100 to 2,000 ppm (as the ratio by weight) and the content of the boron derived from the boron-col.l;.il-il~g compound is 0.015% by weight or more, to the total weight of the composition; and (2) a lubricant oil composition produced by blending (A) a molybenum-COI~ g friction conditioner, (B) a boron-cont~ining compound and (C) a minor amount of an antioxidant with a lubricant base oil, wherein the conlent of the molybdenu-m derived from the molybdenum-col~
friction conditioner is 100 to 2,000 ppm (as the ratio by weight) and the content of the boron derived from the boron-co~ compound is 0.015% by weight or more, to the total weight of the composition.

Furthermore, prefelable embodiments of the present invention include:

(3) a lubricant oil composition according to 1 or 2 above, wherein the molybdenum-co~ friction conditioner is sulfoxymolybdenum dithioc~l,~nate;

(4) a lubricant oil composition according to 1, 2 and 3 above, wherein the boron-co~ g compound is boron-cont~inin~ succinimide or boron-CO~ g succinate ester;

(5) a lubricant oil composition according to 2 to 4 above, wherein the content of the antioxidant is 0.05 to 5.0% by weight, to the total weight of the composition; and (6) a lubricant oil composition according to 2 to 5 above, wherein the anti-oxidant is phenol sulfide.

In the lubricant oil compositions in accordance with the present invention, any lubricant base oil may be used with no specific limitation; use may be made of those base oils conventionally used as the base oils of lubricantoils, for example, mineral oils and synthetic oils. Mineral oils include, for example, r~ffin~te produced through the solvent refining of lubricant oil raw materials in aromatic extraction solvents such as phenol,N-methylpyrolidone and furfural; hydrogenated oils produced by hydrogenation using a hydrogenation catalyst such as cobalt and molybdenum on a carrier silica-alumina; or mineral oils such as lubricant fractions produced by isomerization of wax, for example, 60 Neutral Oil, 100 Neutral Oil, 150 Neutral Oil, 300 Neutral Oil, 500 Neutral Oil, bright stock and the like. Alternatively, synthetic oils include poly(a-olefin oligomer), polybutene, aLkylbenzene, polyol ester, polyglycol ester, dibasic acid ester, ~hosphate ester, silicone oil and the like may be used. These base oils may be used singly or in combination with two or more thereof. Likewise, mixlu~es of such mineral oil and such synthetic oil may be used. Preferably the base oil 217389~

S

has a lrinem~tic viscosity generally in a range of 3 to 20 mm2/s at a temperature of 100C.

As the molybdenum-cont~ining friction conditioner to be used for the friction conditioner of the present invention, any molybdenum-cont~inin~;
compound may be used with no specific limitation, provided that the compound has an action of decreasing the friction property when added to a lubricant oil.For example, use may be made of sulfoxymolybdenum dithiocarbamate, sulfoxy-molybdenum dithiophosphate, molybdenum oxide ester and molybdenum amine salt and the like, and the derivatives thereof, having an alkyl sub~ elll with 1 to 18 carbon atoms.

As the molybdenum-cont~inin~ friction conditioner in accordance with the present invention, use may be made of one or two or more of these molybdenum compounds preferably.

In accordance with the present invention, the molybdenum-Co~ friction conditioner may be blended within a range of having the effect of decreasing a friction coefficient, that is, at such an amount that thecontent of the molybdenum derived from the molybdenum-cont~ining friction conditioner should be 100 to 2,000 ppm (as the ratio by weight), preferably 200 to 2,000 ppm (as the ratio by weight), more preferably 400 to 1,500 ppm (as the ratio by weight) and most preferably 600 to 1,300 ppm (as the ratio by weight) to the total weight of the lubricant oil composition. When the molybdenum-Co~ g friction conditioner is blended at such an amount that the content of the molybdenum derived from the molybdenum-co~ il-il-g friction conditioner is below 100 ppm (as the ratio by weight) to the total weight of the composition, the effect of improving the friction property cannot be s~ti~f~ctorily exerted.
When the molybdenum-co~ -il-g friction conditioner is blended at such an amount that the content of the molyb-lenllm derived from the molybdenum-co.~ friction conditioner is above 2,000 ppm (as the ratio by weight) to thetotal weight of the composition, the improvement in the friction decreasing effect cannot be brought about in proportion to the amount; additionally, such an amount is likely to cause the generation of coking deposit.

21.7~8g5 When only the molybdenum-cont~ining friction conditioner is added into a lubricant oil, the lubricant oil rapidly falls into an occlusive state supposing the molybdenum content is àbove 100 ppm at the hot coking test as shown in Figure 1.

As the sulfoxymolybdenum dithiocarbamate to be used preferably in the lubricant oil composition of the present invention with respect to the effect of decreasing friction, prefelably, use may be made of a compound represented by the general formula [1]:

/N C S Mo2SmOn [ 1 ]

wherein Rl and R2 are hydrocarbon groups with 8 to 18 carbon atoms, respectively, and they may be the same or different from each other; "m" and "n" are individually positive integers in which the sum thereof is 4.

The hydrocarbon groups with 8 to 18 carbon atoms, represented by Rl and R2 in the general formula [1], include for example hydrocarbon groups such as alkyl groups with 8 to 18 carbon atoms; alkenyl groups, with 8 to 18 carbon atoms; cycloaLkyl groups with 8 to 18 carbon atoms; allyl groups, alkyl-allyl groups and allylaLkyl groups with 8 to 18 carbon atoms. The alkyl groups and the alkenyl groups may be in the form of a straight chain or otherwise in the form of a branched chain. The hydrocarbon groups represented by R1 and R2 have particularly ~,efelably eight carbon atoms in the lubricant oil compositionof the present invention.

Specific examples of the hydrocarbon groups represented by Rl and R2 include octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, octenyl, nonenyl, decenyl, lmdecenyl, dodecenyl, tridecenyl, tetradecenyl, hexadecenyl, oct~dec~nyl, dimethylcyclohexyl, ethylcyclohexyl, methylcyclohexylmethyl, 217389~
.

cyclohexylethyl, propylcyclohexyl, butylcyclohexyl, hepthylcyclohexyl, di-methylphenyl, methylbenzyl, phenetyl, naphthyl, dimethylnaphthyl and the like.

For the lubricant oil composition of the present invention, one type of sulfoxymolybdenum dithiocarbamates may be used; otherwise, two types or more thereof may be used mixed with each other. Additionally, sulfoxymolyb-denum dithiocarbamate may be blended at such an amount that the content of the molybdenllm derived from sulfoxymolybdenum dithiocarbmate should be 100 to 2,000 ppm (as the ratio by weight), preferably 200 to 2,000 ppm (as the ratio byweight), more ~rerelably 400 to 1,500 ppm (as the ratio by weight) and most ~-~relably 600 to 1,300 ppm (as the ratio by weight), to the total weight of thecomposition. When sulfoxymolybdenum dithiocarbamate is blended at such an amount that the content of the molybdenum derived from sulfoxymolybdenum dithioc~l,~ate is below 100 ppm (as the ratio by weight) to the total weight of the composition, the effect of improving the friction property cannot s~ticfactorily be exerted; otherwise, when sulfoxymolybdenum dithiocarbamate is blended at such an amount that the content of the molybdenum derived from sulfoxymolybdenum dithiocarbamate is above 2,000 ppm (as the ratio by weight) to the total weight of the composition, the effect of decreasing the friction prope, l~ cannot be improved in proportion to the content; furthermore, the generation of coking deposit might be likely to be caused.

The boron-cont~ining compound cont~inin~ a high percentage of boron, capable of suppressing coking deposit, by which the present invention is characterized, has conventionally been added as a dispersant, for example, at a trace amount below 0.015% by weight as the boron content, to a lubricant oil.
However, so as to acquire the effect of preventing coking deposit in accordance with the present invention, the compound should necessarily be added above 0.015% by weight, calculated in terms of boron.

Embodying examples of the boron-containing compounds contain-ing a high percentage of boron, capable of ~upl)ressing coking deposit, by whichthe present invention is characterized, include boron-co~"~ succinimide, boron-col~ g succinate ester and the like. The boron-col.l;~ succinimide includes for example those represented by the following general formulas [2] and [3].

~ ~ ~ 73895 R3 Cll C~ _ _ ~N R4--NH nH [2]

1l R3 CH C~ Cl-l R3 ~N R4--N'l nR4 N~ [ 3 ]

Z O

where R3 represents a hydrocarbon group with 1 to 50 carbon atoms, R4 represents an aLkylene group with 2 to 5 carbon atoms, and "n" is an integer of 1 to 10; in the compound of the general formula [3], the two R3's may be the same or di~, clll from each other; the R4's of the number "n" in the general formula [2] and the R4's of the number "n+ 1 " in the general formula [3] may be the same or different from each other, respectively; Z represents a boron-containing substituent, including for example ~OH
~OH ~ B\
B O--B~ B~ O [4]
OH ~ O--B<
bH

More specifically, ECA 5025 (m~nllf~ctured by Exxon Chemical Co., Ltd.), LUBRIZOL 935 (~ .r~ctured by Lubrizol Co., Ltd.) and the like may be viewed as illustrative.

Furthermore, boron-cont~ining succiniate esters include for example those represented by the general formula [5].

21738~
g f H3 f H3 C H3 11 CH3 C~CH2 C~CH2--CH CH2 CH--C O
,R5 [5 ]

wherein "n" represents an integer of 1 to 20; R5 represents a straight or branched hydrocarbon group with 2 to 18 carbon atoms, which may contain any aromatic groups or double bonds; Y and Z are boron-cont~ining substit lçnts, respectively, at least one of which is bound through a coordinate bond to the succinate ester).

Specifically, for example, LUBRIZOL 936 (manufactured by Lubrizol Co., Ltd.) may be viewed as illustrative.

In accordance with the present invention, the effect of adding boron-cont~ining succinimide and/or boron-cont~inin~ succinate ester is necessary, and furthermore the amount thereof to be added is extremely critical.
For example, when the boron content is above 0.015% by weight to a lubricant oil composition having a molybdneum content of 1,000 ppm (as the ratio by weight), the coking deposit decreases along the steep curve as shown in Figure 2. The deposit amount rapidly decreases below 100 mg from the occlusive state.

Therefore, as shown in the figure, no specific adverse effect will be brought about by the addition thereof above the critical value, but the effect of decreasing the coking deposit will never be increased in proportion to the amount thereof to be added.

In the lubricant oil composition of the present invention, the boron-co~ compound should be blended at such an amount that the content of the boron derived from the boron-cont~ining compound is above 0.015% by weight~ l,r~ferably above 0.030% by weight, to the total weight of the composi-tion.

2i73895 When the boron-co~Ail-il-g compound is blended at such an amount that the content of the boron derived from the boron-cont~inin,e compound is below 0.015% by weight, the effect of preventing coking deposit is not s~tisf~ctorily exerted.

In the lubricant oil composition of the present invention, one type or a combination of two types or more of the boron-col~ compounds may be used.

The amount of deposit has some relation with the molybdenum content and the boron content. As shown in the examples described below, the ~uppressive effect of deposit gets higher at a lower molybdenum content, provided that the boron content is fixed at a given value. Furthermore, the ~upplessive effect of deposit gets higher at a higher boron content, provided that the molybdenum content is fixed at a given value.

Within the limits not detrimental to the objective of the present invention, a wide variety of additives conventionally used in lubricant oils, may be added ap~3rop,iately to the lubricant oil composition of the present invention, including for example antioxidants, metal cleaning agents, other friction condi-tioners, viscosity index improvers, pour point depressants, defoaming agents, other wear preventing agents, rust preventives, corrosion inhibitors and the like.
Preferably, these additives have a structure not subject to dehydrogenation reaction, from the viewpoint of decreasing coking deposit.

Among these additives, the antioxidants in particular are preferable because the generation of coking deposit can be decreased by suppressing the progress of radical polymerization. The antioxidants which can be used in the present invention include for example amine-series antioxidants such as alkylated diphenyl~mine, phenyl-a-naphthylamine, alkylated a-naphthyl~mine, and phenol-series antioxidants such as 2,6-di-t-butyl-4-methylphenol, 4,4'-methylenebis(2,6-di-t-butylphenol), phenol sulfide, etc. These are used general-ly at a ratio of 0.05 to 5% by weight. Among these antioxidants, a phenol-seriesantioxidant with greater radical-ca~lu.h~g function is preferable in particular.

217~89~

The metal-series cleaning agents include for example calcium sulfonate, magnesium sulfonate, barium sulfonate, calcium phenate, barium phPn~te, calcium salicylate, magnesium salicylate and the like, and these may beused generally at a ratio of 0.1 to 5 % by weight.

The friction conditioners include for example polyhydric alcohol partial ester, amine, amide, sulfide ester and the like.

The viscosity index improvers include for example polymeth-acrylate-series, polyisobutylene-series, ethylene-propylene copolymer-series, styrene-butadiene hydrogenated copolymer series and the like, and these may be used generally at a ratio of 0.5 to 35 % by weight.

The pour point depressants include for example polyalkyl-methacrylate, chlorinated pa~ -naphthalene cond-Pns~te and the like.

The defoaming agents include for example dimethylpolysiloxane, polyacrylic acid and the like.

The wear preventing agents include for example thiophosphate metal salt, thiocarbamate metal salt, sulfur compound, phosphate ester, phosphite ester and the like, and these may be used generally at a ratio of 0.05 to 5.0 % by weight.

The rust preventives include for example fatty acid, alkenyl-succiniate semi-ester, fatty acid soap, alkylsulfonate, fatty acid polyhydric alcohol ester, fatty acid amine, oxidized paraffin, alkylpolyoxyethylene ether and the like.

The corrosion inhibitors include for example benzotriazole, benzoimidazole and the like, th~ 7oles and the like.

The present invention will now be a~parellt from the following more particular description of the examples, but it will be understood that the examples do not purport to be wholly definitive with respect to the scope of themventlon.

21738~5 In the examples and con-palali~/e examples, herein, the hot tube cooling test was carried out and ~sessed by means of Hot Tube Coking Test (HTCT) m~mlf~Ghlred by Komatsu Kabushiki Kaisha. HTCT was carried out as follows: after passing individual sample oils through a glass tube having a 2 mminner diameter and a 300 mm length at air flow of 10 + 0.5 cc/min., oil flow of 0.31 + 0.01 cc/hour, a temperature of 310C for 16 hours, the glass tube was washed in n-hexane and dried sufficiently to measure the weight of the coking deposit attached to the inside of the glass tube.

A lubricant oil composition was prepared such that as a molybdenum-cont~ining friction conditioner, 1,000 or 1,500 ppm of sulfoxy-molybdneum-N,N-dioctyl dithocarbamate, calculated in terms of molybdenum, and as a boron-cont~ining compound, 0.015 to 0.140% by weight of borated succinimide (LUBRIZOL 935, manufactured by Lubrizol Co., Ltd.), calculated in terms of boron were contained, respectively, in a base oil (100 Neutral Oil with a viscosity of 4.4 mm2/s at 100C). The deposit was measured by the hot tube coking test. The results are shown in Table 1.

The lubricant oil compositions cont~ining 1,000 ppm molybdenum of Examples 1 to 5 in accordance with the present invention generated less HTCT coke deposit, which decreased as the increase in the boron content.
Additionally, the lubricant oil compositions having an increased molybdenum content of 1,500 ppm of Examples 6 and 7 generated less HTCT coke deposit.
However, when the compositions of Examples 3 and 6, both of which have the same boron content, are con~a~ed with each other and the compositions of Examples 5 and 7, both of which have the same boron content, are compared with each other, those of Examples 3 and 5, with a lower molybdenum content, generated less HTCT coke deposit, which indicates that those with a lower molyb~lçmlm content in such a range generate less HTCT coke deposit.

The same procedure was carried out as in Examples 1 to 5, except that the boron-cont~ining succinimide to be blended was decreased to a content of 0.013% by weight, calcnl~ted in terms of boron. Then, the HTCT coke deposit was 211.8 mg in weight, which exceeded the GF-2 standard.

The same procedure was carried out as in Examples 1 to 5, except that succin~ ide was blended at 3.0% by weight, instead of the boron-co~
succinimide. The resulting composition did not contain boron. Occlusion occurred at the hot tube coking test.

The same procedure was carried out as in Examples 1 to 7, except that sulfoxymolybdenum-N,N-ditridecyl dithiocarbamate was used as the molybdenum-col.t~ il-g friction conditioner, which was blended at a content of 100 and 400 ppm, calc~ ted in terms of molybdenum. The results are shown in Table 2.

The lubricant oil compositions of Examples 8 to 13 generated less HTCT coke deposit. The same results are yielded as those in Examples 1 to 7 to the effect that the increase in the boron content decreased HTCT deposit and a lower molybdenum content generated less HTCT deposit in such a range, provided that the boron content was fixed at a given value.

The same procedure was carried out as in Examples 8 and 9, except that boron-col.~i~il-il-g succi~ nide to be blended was decreased to a content of 0.013% by weight, calc~ ted in terms of boron. The HTCT coke deposit was 132.9 mg in weight, which exceeded the GF-2 standard.

2173~

The same procedure was carried out as in Examples 1 to 5, except that boron-co.~ succinate ester (LUBRIZOL 936, manufactured by Lubrizol Co., Ltd.) was used as the boron-cont~inin~ compound, which was blended at a content of 0.015 or 0.030% by weight, calculated in terms of boron.The results are shown in Table 3.

The same procedure was calTied out as in Examples 8 and 9, except that boron-co~ succinate ester (LUBRIZOL 936, manufactured by Lubrizol Co., Ltd.) was used as the boron-cont~inin~ compound, which was blended at a content of 0.015 or 0.030% by weight, calculated in terms of boron.The results are shown in Table 4.

All the lubricant oil compositions of Examples 14 to 17 satisfy the GF-2 standard. However, boron-con~ ing succinimide to be used as the boron-cont~inin~ compound obtained slightly better results than boron-cont~ining succiniate ester, provided that the boron content was at a given value.

With respect to the lubricant oil compositions of Examples 1 to 5, to which was further added an antioxidant, an e~min~tion was made of their properties.

A lubricant oil composition was pl epared such that as a molybdenum-co~ friction conditioner, 1,000 ppm of sulfoxymolybdenum-N,N-dioctyl dithioc&~ te, calculated in terms of molybdenum, and as a boron-co~ compound, 0.015 to 0.140% by weight of succinimide (LUBRIZOL 935, m~mlf~ctured by Lubrizol Co., Ltd.) calculated in terms of boron, and as an antioxidant, 0.7 or 1.4% by weight of phenol sulfide were cont~ine-l respectively, in a base oil (100 Neutral Oil with a viscosity of 4.4 mm2/s at 100C). The deposit was measured by the hot tube coking test.
The results are shown in Table 5.

21738~1~

Colllp~il~g the results of Examples 18 to 22 with the results of Examples 1 to 5, it will be noted that the mixtures of the same amounts of the molybdenum-co~ g friction conditioner and the boron-cont~inin,e compound generated less HTCT coke deposit through the addition of the antioxidant.
Furthermore, COlll~ g the results of Examples 18 to 22 with the results of the Examples 23 to 26, it will be noted that less HTCT coke was deposited in the case of the same amounts of the molybdenum-cont~inin~ friction conditioner and the boron-col~ -g compound, as the amount of the antioxidant to be added in such a range was increased. Based on these results, the effect of the antioxidant were able to be verified in the lubricant oil compositions in accordance with the present invention.

Further adding an antioxidant, that is, phenol sulfide at 0.7% by weight to the compound of Example 14, a lubricant oil composition was prepa~ed. Then, the hot tube coking test was carried out. The HTCT coke deposit was 81.6 mg in weight.

Further adding an antioxidant, that is, phenol sulfide at 0.7% by weight to the compound of Example 16, a lubricant oil composition was plel)aled. Then, ~e hot tube coking test was prepared. The HTCT coke deposit was 5.0 mg in weight.

The lubricant oil compositions of Examples 27 and 28 generated less HTCT coke deposit than the deposit generated from those with no blend of ~e corresponding antioxidant. In Example 28, in particular, the effect of the antioxidant was plo~ ent.

As is seen, the lubricant oil compositions of the present invention are the lubricant oil compositions blended with a molybdenum-cont~ining friction conditioner and a boron-co.~ -g compound, and are capable of decreasing coking deposit in internal combustion engines such as automobile 217389~

engines, which is advantageous for s~lst~inin~ a fuel-efficiency property for a long te-m. Hence, the compositions can be used p-efelably for automobile lubricant oils.

HTCT
Molybdenum (ppm) Boron (wt%) Deposit (mg) Example 1 1,000 0.015 82.5 Example 2 1,000 0.030 17.8 Example 3 1,000 0.050 1.8 Example 4 1,000 0.080 1.6 Example 5 1,000 0.140 1.4 Example 6 1,500 0.050 13.7 Example 7 1,500 0.140 1.7 Comparative 1,000 0.013 211 .8 Example 1 Compa~ali~re 1,000 0.000 occluded Example 2 21~389~
. ..~

HTCT
Molybdenum (ppm) Boron (wt%) Deposit (mg) Example 8 100 0.015 52.4 Example 9 100 0.030 0.8 Example 10 400 0.015 68.3 Example 11 400 0.030 1.9 Example 12 400 0.050 1.0 Example 13 400 0.140 0.3 Comp~ali~/e 100 0.013 132.9 Example 3 HTCT
Molybdenum (ppm) Boron (wt%) Deposit (mg) Example 14 1,000 0.015 93.9 Example 15 1,000 0.030 38.5 HTCT
Molybdenum (ppm) Boron (wt%) Deposit (mg) Example 16 100 0.015 66.9 Example 17 100 0.030 8.1 2~7~9~

Molyb~lenl-m BoronAntioxidant HTCT
(ppm) (wt%) (wt%) Deposit (mg) Example 18 1,000 0.015 0.7 73.2 Example 19 1,000 0.030 0.7 15.6 Example 20 1,000 0.050 0.7 1.6 Example 21 1,000 0.080 0.7 1.3 Example 22 1,000 0.140 0.7 1.2 Example 23 1,000 0.015 1.4 69.8 Example 24 1,000 0.030 1.4 13.7 Example 25 1,000 0.050 1.4 1.3 Example 26 1,000 0.140 1.4 1.1 Molybdenum BoronAntioxidant HTCT
(ppm) (wt%) (wt%) Deposit(mg) Example 27 1,000 0.015 0.7 81.6 Molybdenum BoronAntioxidant HTCT
(ppm) (wt%) (wt%) Deposit (mg) Example 27 1,000 0.015 0.7 5.0

Claims

1. A lubricant oil composition produced by blending (A) a molybdenum-containing friction and (B) a boron-containing compound with a lubricant base oil, wherein the content of the molybdenum derived from the molybdenum-containing friction conditioner is 100 to 2,000 ppm (as the ratio by weight) and the content of the boron derived from the boron-containing compound is 0.015% by weight or more, to the total weight of the composition.

2. A lubricant oil composition produced by blending (A) a molybdenum-containing friction conditioner, (B) a boron-containing compound and (C) an antioxidant with a lubricant base oil, wherein the content of the molybdenum derived from the molybdenum-containing friction conditioner is 100 to 2,000 ppm (as the ratio by weight) and the content of the boron derived from the boron-containing compound is 0.015% by weight or more, to the total weight of the composition.

3. The lubricant oil composition of claim 1 or 2 wherein the molybdenum containing friction conditioner is sulfoxymolybdenum dithio-carbamate.

4. The lubricant oil composition of claim 1 or 2 wherein the boron containing compound is selected from the group consisting of boron containing succinimide, boron containing succinate ester and mixtures thereof.

5. The lubricant oil composition of claim 2 wherein the anti-oxidant content is 0.05 to 5.0% by weight, to the total weight of the composition.

6. The lubricant oil composition of claim 2 or 5 wherein the anti-oxidant is phenol sulfide.