SG181737A1

SG181737A1 - System lubricant oil composition for crosshead-type diesel engine

Info

Publication number: SG181737A1
Application number: SG2012044277A
Authority: SG
Inventors: Shigeki Takeshima
Original assignee: Jx Nippon Oil & Energy Corp
Priority date: 2009-12-24
Filing date: 2010-10-08
Publication date: 2012-07-30
Also published as: EP2518135A4; WO2011077811A1; EP2518135B1; CN102686712A; EP2518135B2; CN102686712B; KR101728192B1; KR20120123374A; US20120258898A1; EP2518135A1

Abstract

SYSTEM LUBRICATING OIL COMPOSITION FOR CROSSHEAD-TYPEThe present invention provides a system lubricating oil composition for a crosshead-type diesel engine, which can prevent fuel efficiency deterioration by suppressing the viscosity increase and comprises a mineral base oil and/or a synthetic base oil, (A) (a-1) a star polymer having a vinyl aromatic hydrocarbon structure in the molecule and/or (a-2) an ethylene-a-olefin copolymer or a hydrogenated compound thereof and having a base number of 4 to 20 mgKOH/g and a 100°C kinematic viscosity of 7.5 to 15.0 mm2/s.[NO FIGURE]

Description

SYSTEM LUBRICATING OIL COMPOSITION FOR CROSSHEAD-TYPE

DIESEL ENGINE

Technical Field

[0001] The present invention relates tc a system lubricating oil composition for a crosshead-Lype diesel engine.

Background Art i0G02] For a crosshead-type diesel engine, a cylinder oll for lubricating the friction point between the cylinders and pistons and a system oil for lubricating and cocling other portions have been used.

The cylinder oil is required to have a sultable viscosity needed to lubricate a friction portion between a cylinder and a piston (piston ring) and a function to maintain detergency needed to allow a piston and a plston ring to move appropriately.

Furthermore, since for this engine, a high-sulfur content fuel 1s generally used for the economy reason, it has a problem that acidic components such as sulfuric acid generated by the combustion of the fuel corrode a cylinder. In order to avoid this problem, the cylinder oil is required to have a function to neutralize the acidic components such as sulfuric acid

So as to prevent corrosion.

Whereas, the system oil dees not contact combustion gas unlike the usual diesel engine oil and is a lubricating oil which is stored in a tank and supplied to hearings with a circulation pump for lubrication and cooling and is thus reguired to maintain a suitable viscosity for a long period of time becauss 1% is used for a long time unlike the cylinder oll (see, for example, Patent Literature 1 below).

However, a crosshead-type engine for ships has a problem that the system oll is eventually increased in viscosity by being mixed with a drip oil, and how such viscosity increase should be suppressed has become a longstanding problem. Inparticular, due to the recent growing environment issue, emphasis has bessn on avoidance of a deterioration in fuel efficiency resulting from the increased friction loss at bearings involving the viscosity increase or of a decrease in the heat-exchange efficiency at piston surfaces to be cooled.

Citation List

Patent Literature [6G03] Patent Literature 1: Japanese Patent

Laid-Open Publication No. 2002-275491

Summary of Invention

Tachnical Problem — Pe

[00G4] The present invention has an objsct to provide a system lubricating oll composition for a crosshead-type diesel engine, which can prevent fuel efficiency detericration by suppressing the viscosity increase.

Solution to Problem

[0005] As the results of extensive study and research, the present invention was accomplished on the basis of the finding that a lubricating oil composition containing a specific polymer can balance a viscosity increase caused by bsing mixed with a drip oil and a viscosity decrease due to thermal decomposition of a polymer and thus is an advantageously effective system lubricating oil composition for a crosshead-type diesel engine,

Epecifically, a system oil comprising a lubricating base oil blended with a star polymer having a vinyl aromatic hydrocarbon structure in the molecule and/or an olefin copolymer, which have characteristics that are ezcellent in shear stability but likely to decompose with heat makes it possible to decrease the viscosity of the system oil by the decomposition of the polymer at piston surfaces to be cooled and thus balance out the viscosity increase caused by being mixed with a cylinder drip oil thereby suppressing fuel efficiency deterioration.

[0006] That is, the present invention relates toc a system lubricating ¢ll composition for a crosshead-type diesel engine comprising a mineral base oil and/or a synthetic base cil, and (BR) (a-1) a =tar polymar having a vinyl aromatic hydrocarben structure in the molecule and/or {a-2) an ethylene-a-olefin copolymer or a hydrogenated compound thereof, and having a base number of 4 to 20 mgKOH/qg and a 100°C kinematic viscosity of 7.5 to 15.0 mm?/s. 0007] The present invention also relates to the foregoing system lubricating oil composition for a crosshead-type diesel engine wherein Component (a-1) is a compound having a structure wherein the polymer or copolymer of a diene extends radially from the core of the vinyl aromatic hydrocarbon located in the center of the molecule.

The present invention also relates to the foregoing system lubricating oil composition for a crosshead-type diesel engine wherein the vinyl aromatic hydrocarbon is divinylbenzene.

The present invention also relates to the foregoing system lubricating oil composition for a crosshead-type diesel engines wherein the polymer or copolymer of a diene is pclyisoprene or an —d]

isoprene-styrene copolymsar. [C008] The present invention alse relates to the foregoing system lubricating oil composition for a crosshead-type diesel engine further comprising at least one type selected from the group consisting of (B) metal detergents, (CC) zincdialkyldithiophosphates, {DY rust inhibitors and {EB} ashless dispersants,

The present invention also relates to the foregoing system lubricating oil composition for a crosshead-type diesel engine wherein the base oll has 2 100°C kinematic viscosity of 3.5 to 95.3 mm?/s.

Advantageous Effects of Invention

[00089] The use of the system lubricating oil composition for a crosshead-type diesel engine of the present invention makes it possible to suppress the viscosity from increasing, resulting in inhibition of fuel efficiency deterioration.

Description of Embodiments

[0010] The present invention will be described in details below.

No particular limitation is imposed on the type of lubricating bass 0il to be used in the system ‘ lubricating oil composition for a crosshead-type diesel engine of the present invention (hereinafter merely referred to as “the lubricating oil composition -k —

of the praesent invention”), which may be a mineral oil, a synthetic oil, or a mixture thereof.

[0031] Specific examples of the mineral base o1l include those which can be produced by subjecting a lubricating cil fraction produced by vacuum-distilling an atmospheric distillation bottom oil resulting from atmospheric distillaticn of a crude oil, to any ons Or more treatments selected from solvent deasphalting, solvent extraction, hydrocracking, solvent dewaxing, and hydrorefining; wax-isomerized mineral oils; and those produced by isomerizing GTL WAX (Gas to Liguid

Wax} produced through Fischer-Tropsch process. 100121 Specific examples of the synthetic base oil include polybutenes and hydrogenated compounds thereof; poly-a-clefins such as 1l-octene oligomer and l-decene cligomer, and hydrogenated compounds thereof; copolymers of ethylene having a welght average molecular weight of 8,000 or less and aw-clefins having 3 to 30 carbon atoms; diesters such as ditridecyl glutarate, di-2-ethylhexyl adipate, diisodecyl adipate, ditridecyl adipate and di-Z-ethylhexyl sebacate; polyol esters such as trimethylolpropane caprylate, trimethylolpropane pelargonate, pentaerythritol Z-ethylhexancate and pentaerythritol pelargonate; copolymers of dicarboxylic acids such as —

dibutyl maleate and w-olefins having 2 to 30 carbon atoms; aromatic synthetic oils such as alkylnaphthalenes, alkvlbenzenes, and aromatic esters; and mixtures of the foregoing. [00137 The lubricating base oil used in the lubricating oil composition of the present invention may be any one or more type of the mineral bases oils or synthetic base oils or a mixture of one or more of the mineral base oils and one or more of the synthetic base oils.

F00147 The 100°C kinematic viscosity of the lubricating hase oil used in the present invention is preferably 9.3 mn®/s or lower, more preferably 8.5 mm®/s or lower, more preferably 8.0 mn®/s or lower. Whereas, the 100°C kinematic viscosity is preferably 3.5 mm?/s or higher, more preferably 3.8 mm/s or higher, more preferably 4.0 mm?/s or higher. The 100°C kinematic viscosity referred herein denctes one defined by ASTM

D-445. If the 100°C kinematic viscosity is higher than 9.3 mm?/s, the resulting composition would be less in viscosity decrease and thus could not exhibit the effect of suppressing the viscosity increase when mixed with a cylinder drip oil. If the 100°C kinematic viscosity is lower than 3.5 mm®/s, the resulting } composition would be decreased in viscosity toc much —-

and thus could be deteriorated in oil film formation capability at bearings, possibly causing seizure. (00153 No particular limitation is imposed on the 40°C kinematic viscosity of the lubricating base oil used ln the present invention, which 1s, however, preferably 150 mn®/s or lower, more preferably 120 mm®/= or lower, more preferably 90 mm®/s or lower. Whereas, the 40°C kinematic viscosity is preferably 15 mm?/s or higher, more preferably 20 mn®/s or higher, more preferably 25 mm/s or higher. If the 40°C kinematic viscosity is higher than 200 mm®/s, the resulting composition would be less in viscosity decrease and thus could not exhibit the effect of suppressing the viscosity increase when mixad with a cylinder drip oil.

If the 40°C kinematic viscosity 1s lower than 50 mm?/s, the resulting composition would bs decreassd in viscosity too much and thus could be deteriorated in oil film formation capability at bearings, possibly causing seizure.

[0018] The viscosity index of the lubricating base oil used in the present invention 1s preferably 85 or greater, more preferably 90 or greater, more preferably 9% or greater. No particular limitation is imposed on the upper limit of the viscosity index. Normal paraffin, slack wax or GTL wax or lsoparaffinic mineral oils produced by isomerizing the foregoing may also be uzed,

The viscosity index referred herein denctes one measured in accordance with JIS K 2283-1993. [00171 The lubricating oil composition cof the present invention contains necessarily (a-1) a star polymer having a vinyl aromatic hydrocarbon structure in the molecule and/or (a-2) an ethylene-o-olefin copolymer or a hydrogenated compound thersof, as

Component (A).

Faoig] The star polymer having a vinyl arematic hydrocarbon structure in the molecule that is Component {a-1) is a compound having a structure wherein the arms of polymers or copolymers of a number of (two or more) dienes extend radially from the core of the vinyl aromatic hydrocarbon located in the center of the molecule. 10019; Examples of the vinyl aromatic hydrocarbon located in the center of the molecule include divinyibenzene, trivinylbenzene, tetravinylbenzene, divinylortho-, divinvlmetha- or divinylpara-xylene, trivinylortho-, trivinylmetha- or trivinylpara-zylene, tetravinylortho-, tetravinylmetha- or tetravinylpara-xylene, divinylnaphthalene, divinylethylbenzene, divinylbiphenyl,

diisobutenylbenzene, diisopropenylbenzene, and diiscpropenylbiphenyl. Among these compounds, preferred is divinylbenzene.

[0020] The diens monomer constituting the polymer or copolymer of dienes has preferably 4 to 12 carbon atoms. Specific examples include 1,3-butadiene, isoprene, piperylene, methvipentadiene, phenylbutadine, 3,4-dimethvi-1,3-hexadiene, and 4,5h~diethyl-~1,3~o0ctadiene. Preferred are 1,3~putadiene and isoprene.

Examples of the polymer cor copolymer of dienes that will be a star polymer include homopolymers of diene such as polyisoprene and copolymers of diene such as isoprene-putadiene copolymer. Alternatively, copolymers of diene and other monomer that is not diene (for example, isoprene-styrene copolymer) may be used,

The copolymer may be a random copolymer or a block copolymer. : [oo21] Component {(a-1) that is a star polymer having a vinyl aromatic hydrocarbon structure in the molecule used as Component (A) in the present invention has a welght average molecular weight (Mw) of preferably 10,000 or greater, more preferably 50,000 or greater, more preferably 100,000 or greater and preferably 1,000,000 or less, more preferably 800,000 or less, wl more preferably 500,000 or less. If the weight average molecular weight is less than 10,000, the resulting composition could not exhibit sufficiently an viscosity adjustment effect but also the production cost could be increased. If the weight average molecular weight is greater than 1,000,000, the resulting composition could be poor in shear stability and could not exhibit an viscosity adjustment effect as well.

[0022] The PSS8I (permanent shear stability index) of {(a-1l} the star polymer having a vinyl aromatic hydrocarbon structure in the molecule used in the present invention is prefsrably from 1 to 40, more preferably from 1 to 35, more preferably 1 toe 30, particularly preferably from 1 to 25. If the PSSI is greater than 40, the resulting composition is poor in shear stability and thus could not exhibit sufficiently an viscosity adjustment effect. If the PS3I iz less than 1, the resulting composition could not exhibit sufficiently an viscosity adjustment effect as well.

The term "P5SIY used herein denotes the permanent shear stability index of a polymer calculated on the basls of the data measurasd with ASTM D 6278-02 (Test Method for Shear Stability of Polymer Containing

Fluids Using a Buropean Diesel Injector Apparatus) in -171- 5 conformity with ASTM D 6022-01 (Standard Practice for

Calculation of Permanent Shear Stability Index).

[0023] The ethylene~a~olefin copolymer or a hydrogenated compound thereof that is Component {(a-2) is a copolymer of ethylene and an a-olefin or a compound produced by hydrogenating the copolymer. Specific examples of the w-olefin include propylene, isobutylene, l-hutene, l-pentene, l-hexene, l-cctene, l-decene, and l-dodecesns. The ethylene-o~clefin copolymer may be one consisting of hydrocarbons that is of non-dispersant type or one produced by rsacting a copolymer with a polar compound such as a nitrogen-containing compound that is a dispersant~type ethylene~a~olefin copolymer. Among these compounds, the most preferred is an ethylene-a-propyvlene copolymer,

[0024] The ethylene-u-clefin copclymer or a hydrogenated compound thereof that is {a-Z} used as

Component (A} in the present invention has a weight average molecular weight (Mw) of preferably 10,000 or greater, mores preferably 20,000 or greater, more preferably 50,000 and preferably 500,000 or less, mors preferably 400,000 or less, more preferably 300,000.

If the weight average molecular weight is less than 10,000, the resulting composition could not exhibit —1 7 sufficiently an viscosity adjustment effect but also the production cost could be increased. If the weight average molecular weight is greater than 500,000, the resulting composition could be poor in shear stability and thus could not exhibit an viscosity adjustment effect as well.

[0025] The P3331 (permanent shear stability index} of {a-2) the ethylene-w-~oclefin copolymer or a hydrogenated compound thereof 1s preferably from 1 to 7h, more preferably from 3 to 50, more preferably from to 30, particularly preferably from 10 to 28. If the

PSSI is greater than 75, Component (a-2) would be poor in shear stability and thus could not exhibit a viscosity adjustment effect when added to a systemoil.

If the PSST is less than 1, the resulting composition could not exhibit a viscosity adjustment effect as well. 10026] The content of Component {A) in the lubricating oil composition of the present invention is preferably from 1 to 20 percent by mass, more preferably from 2 to 15 percent by mass, more prafarabliy from 3 to 12 percent by mass, most preferably from 4 to 10 percent by mass on the basis of the total mass of the composition. If the content is less than 1 percent by mass, the resulting composition could not exhibit sufficiently a viscosity adjustment effect.

If the content is more than 20 percent by mass, the resulting composition could be poor in handling properties, possibly causing adverse affects on the producticn of the composition and also could be deteriorated in detergency due to the generation of deposit caused by the dsgradation ¢f the polymer.

The ethylene-o-olefin copolymer or hydrogenated compound thereof is provided in a state wherein it is diluted with 1 to 90 percent by mass of a mineral oil.

[0027] The lubricating oil composition of the present invention contains preferably at least one type selected from the group consisting of (B) metal detergents, (CC) zinc dialkvldithiophosphates, {D) rust inhibitors and (D) ashless dispersants. inp28] Component (8) that is a2 metal detergent may be cone or more metal detergents selected from phenate detergents, sulfonate detergents, salicylate detergants, carboxylate detergents and phosphonate detergents. [00291 The phenate metal detergent is a phenate metal detergent containing analkaline earth metal salt of an alkvlphenol, an alkylphenolsulfide or a Mannich reaction product of an alkylphenol represented by formulas (1) to (3) below or an {overbased)basic salt cf the alkaline earth metal salt.

Examples of the alkaline sarth metal include magnesium, barium, and calcium. Preferred are magnesium and calcium, and particularly preferred is calcium.

[0030]

Orne Me)

A Py —— ——

Ly NLR? (1)

Rem a

N72 x 2 Lo 2 : 2

OM nO O— M—20 Oh — OH mo ; i

TN TX 7X

Cr co Lf | {27 sells By— ss v sft) | (2) - Z - ya 1/ 4 / 3/ th 5 i

R: R R R m[ R [nn % 42

Qrrrmnmees Wrmrnene (

L t aN ~ 6 | . i 7 {3} ~~ ~~

[0031] In formulas (1) to (3), R', R?, RR? R', RY, 7 . cs 1a = ~ 5 1

B® and R' may be the same or different from each other and are each independently a straight-chain or branched alkyl group having 4 to 30 carbon atoms, preferably § to 18 carbon atoms. If the carbon number is fewer than 4, Component (B) would be poor in dissolubility in the lubricating base oil. If the carbon number is more than 30, Component (B) wouldbe difficult to produce and poor in heat resistance. Specific examples of the alkyl group for R', R?, R*, r?, R®, R®, and R” are butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, coctadecyl, nonadecyl, eicosyl, henelcosyl, docosyl, triceosyl, tetracosyl, pentacosyl, hexacosyl, heptacosyl, octacesyl, nonacosyl, and triacontyl groups. These alkyl groups may be straight-chain or . branched and may be of primary, secondary, or tertiary.

MY, M® and M° are each independently an alkaline earth metal, preferably calcium and/or magnesium, xX, vy and z are each independently an integer of 1 to 3, m is 0, 1 or 2, and n is 0 or 1, 10032] The sulfonate detergent may be an alkali metal salt or alkaline earth metal salt of an alkyl aromatic sulfonic acid produced by sulfonating an alkyl aromatic compound having a molecular weight of 300 ox more, preferably 400 to 700 and/or an {(overbased) basic salt of the atkali metal salt or alkaline earth metal salt. Examples of the alkall metal or alkaline earth metal include sodium, potassium, magnesium, barium and calcium. Preferred are magnesium and/or calcium, .

Particularly preferred is calcium. (00333 Specific examples of the alkyl arcmatic sulfonic acid include petroleum sulfonic acids and synthetic sulfonic acids. The petroleum sulfonic acids may be those produced by suifonating an alkyl aromatic compound containad in the lubricant fraction of a mineral oll cr may be mahogany acld by-produced upen production of white oll. The synthetic sulfonic acids may be those produced by sulfonating an alkyl benzene having a straight-chain ox branched alkyl group, produced as a by-product from a plant for producing an alkyl benzene used as the raw material of a detergent or produced by alkylating polyolefin to benzene, or those produced by sulfeonating alkylnaphthalenes such as dinonylnaphthalene. No particular limitation is imposed on the sulfonating agent used for sulfonating these alkyl aromatic compounds. In general, fuming sulfuric acids or sulfuric acid may be used.

[0034] The salicylate detergent may be an alkali metal or alkaline earth metal salicylate having one hydrocarbon group having 1 tec 18 carbon atoms and/or an {overbased)} basic salt thereof; an alkali metal or alkaline earth metal salicylate having one hydrocarbon group having 20 te 40 carbon atoms and/or an {overbased) basic salt thereof; or analkali metal or alkaline earth metal salicylate having two or more hydrocarbon groups having 1 to 40 carbon atoms and/or an {(overbased) basic salt therecf (these alkyl groups may be the same or different). Among these compounds, preferred are alkalimetal or alkaline earth metal salicylates having cone hydrocarbon group having 8 te 1% carbon atoms and/or {everbased) basic salts thereof because they are excellent in low-temperature flowability. Examples of the alkali metal or alkaline earth metal include sodium, potassium, magnesium, barium, and calcium.

Preferred are magnesium and/or calcium. Particularly preferred 1s calcium.

[0035] The base number of Component (B) that is a metal detergent used in the present invention is preferably from 50 te 500 mgKOH/g, more preferably from 100 to 450 mgKOH/g, more preferably from 150 to 350 mgKOH/g. If the base number iz less than 100 mgKQH/g, corrosive wear could be increased because the resulting composition could be insufficient in acid neutralization properties. If the base number is greater than 500 mgKOH/g, a problem regarding . dissolubility would arise.

The term "base number" used herein denotes ~ lf

K2501 "Petroleum products and lubricants-Determination of neutralization number".

[00386] No particular limitation is imposed on the metal ratio of (B) the metal detergent. The lower limit is, however, 1 or greater, preferably 2 or greater, rarticuiarly preferably 2.5 or greater while the upper limit is 20 or less, preferably 1% or less, more preferably 10 or less.

The term “metal ratio” used herein is represented by "valence of metal =slement x metal element content {(mole%) / soap group content {mole%)” in {B) the metal detergent”. The metal element denotes an alkaline earth metal such as calcium and magnesium.

The scap group denotes phenol group.

[0037] The content of (B} the metal detergent if contained in the composition of the present invention is usually from 0.5 to 15 percent by mass, preferably from 1 te 12 percent by mass, particularly preferably from 1.5% te 10 percent by mass. {0038 The lubricating oil composition of the present invention contains preferably (CL) zinc dialkyldithiophosphates represented by formula (4):

rR'0. 8 sor

No NLS PEN

Zn OF (4) 2.7 NA 4 N 4

RO 5 S OR

[0039] in formula (4), R', R®, R® and R! may be the same or different from each other and are each independently an alkyl group having 1 to 30 carbon atoms, which may be straight-chain or branched and of primary, secondary, or an alkylaryl group having 7 to 30 carbon atoms.

[0040] No particular limitation is imposed on the method for producing zinc dithicphosphates that is

Component {(C) since any conventional method may be used.

For example, an alcohol having alkyl groups corresponding to RY, R?, BR’ and R* above is reacted with ghosphorus pentasulfide to produce dithiophosphoric acid, which is then neutralized with zinc oxide thereby } synthesizing zinc dithiophesphate.

[0041] The content of {CC} the zing dithiophasphats if centained in the lubricating oll composition of the present invention is preferably from 0.005 to 0.12 percent by mass, more preferably from 0.01 to 0.10 percent by mass, more preferably from 0.02 to 0.08 percent by mass on the basis of phosphorus of the total mass of the compesition. If the content is less than

0.005 percent by mass, the resulting composition would fail to obtain extreme pressure properties or gear characteristics required for a system oil. If the content is more than 0.12 percent by mass, the resulting composition could corrodes bearings, seal rings in a staffing box or oil scraper rings. [0042 The lubricating oil composition of the present invention contains preferably (D) rust inhibitors. Examples of the rust inhibitors include sulfonic acid salts (salts of sodium, calcium or barium}, succinic acid derivatives, organic acid esters such as fatty acid esters and sorbitan acid esters, carboxylic acid salts (sodium, magnesium, barium and zinc salts of stearic acid or naphthenic acid), polyhydric alcohol partial esters such as sorbitan monoester and pentaerythritol monocester, oxidized paraffin {oxidized wax), carboxylic acid, and phosphoric acid esters. Preferred are sulfonates.

[0043] The content of (DD) the rust inhibitor if centained in the lubricating oil composition of the present invention is preferably from ¢.005 to 5 percent by mass on the basis of the total mass of the composition. }

[0044] The lubricating oil composition of the present invention contains preferably (BE) ashless —-7 1 dispersants.

The ashless dispersant may be any ashless dispersant that has been used in a lubricating oil. The ashless dispersant may be succinic acid imide, benzylamine, or polyamine having in thelr molecules at least one straight-chain or branched alkyl or alkenyl group having 40 to 400, preferably 60 to 350 carbon atoms, or modified products thereof.

The alkyl or alkenyl group may be straight-chain or branched but 1s preferably a branched alkyl or alkenyl group derived from oligomsrs of olefins such as propylene, l-butene or isobutylene or a cooligomer of ethylene and propylene.

[0045] Among these compounds, preferred are succinimide or products modified with boron represented by the following formulas:

Rr AP (CHLCHNE ©) wy —{(CHCHNH)- H a 0 2

RB “ PO O N 0 [ y~ctcupa canes | (6) < po

Ny 0 0 7

[0046] In formula (5), R' is an alkyl or alkenyl _3 group having 40 to 400, preferably 60 to 350, and h 1s an integer of 1 to 5, preferably 2 to 4. In formula (6), B% and B® are each independently an alkyl or alkenyl group having 40 to 400, preferably 60 to 350 carbon atoms, and particularly preferably polybuteny] group, and i is an integer of 0 to 4, preferably 1 to 3.

[0047] The content of the ashless dispersant if contained in the lubricating oil composition of the present invention is preferably from 1 to 8 percent by mass ¢n the basis of the total mass of the composition, [00487 In addition to the above-described components in order to further improve the properties of the lubricating cil composition of the present invention or add other required properties thereto, any additives that have been conventionally used in a lubricating oil may be added in accordance with the purposes, Examples of such additives include antioxidants, extreme pressure additives, corrosion inhibitors, demulsifiers, metal deactivators, pour point depressants, and anti-foaming agents.

[0049] Examples of the antioxidants include phenolic anticoxridants such as DBPL, bisphencol, and hindered phenols, aminic antioxidants such as diphenylamine and N-phenyl-g-naphthylamine, and metal antioxidants such copper and molybdenum antioxidants,

The content of the antioxidant if contained in the lubricating oil composition is preferably from 0.05 to 5 percent by mass on the basis of the total mass of the composition. {GO050] Eligible extreme pressure additives are any extreme pressure additives and anti~wear agents that have been used in a lubricating oil. For example, sulfuric~, phosphoric- and sulfuric-phosphoric extremes pressure additives may be used. Specific examples include phosphorus acid esters, thiophosphorus acid esters, dithiophosphorus acid esters, trithiophosphorus acid esters, phosphoric acid esters, thiophosphoric acid esters, dithiophosphoric acid esters, trithiophosphoric acid esters, amine salts, metal salts or derivatives thereof, dithiocarbamates, zinc dithioccaramates, molybdenum dithiocarbamates, disulfides, polysulfides, sulfurized olefins, and sulfurized fats and oils.

The content of the extreme pressure additive if contained in the lubricating oil composition of the present invention is preferably from 0.05 to 5 percent by mass on the basis of the total mass of the : composition. [00511 Examples of the corrosion inhibitor include benzotriazole~, tolyltrizzole-, thiadiazole-, and —2d -

imidazole~types compounds.

[0052] Examples cf the demulsifier include polvalkylene glycol-based non-ionic surfactants such as polyoxyethylenealkyl ethers, polyoxyethylenealkyvlphenyl ethers, and polvoxyethyvlensalkylnaphthyl ethers,

[0053] Examples of the metal deactivator include imidazolines, pyrimidine derivatives, alkvyithiadiazoles, mercaptobenzothiazoles, benzcoctriazoles and derivatives thereof, 1,3,4-thiadiazolepolysulfide, 1,3,d~thiadiazolyl-2,5-bisdialkyldithiocarbamate, 2-{alkyldithiolbenzoimidazcles, and

B-{oc-carboxybenzylthio)propionitrile, 0054) The pour point depressant may be a polymethacrylate polymer that is suitable for a lubricating base cil to be used. [G055] Examples of the anti-foaming agent include silicone oil with a 25°C kinematic viscosity of 100 to 100,000 mmi/s, alkenylsuccinic acid derivatives, esters of polyhydroxy aliphatic alcohols and long-chain fatty acids, aromatic amine salts of methylsalicylate and o-hydroxybenzyl alcohol, aluminum stearate, potassium oleate,

N-dialkyl-allylamine nitrcaminoalkanol, and -2 5 isgamyloctylphosphate, alkylalkylensdiphosphates, metal derivatives of thipethers, metal derivatives of disulfides, fluorine compounds of aliphatic hydrocarbons, triethylsilane, dichlorosilane, alkvlphenyl polvethylene glycol ether sulfide, and fluoroalkyl ethers.

[0056] When these additives are contained in the lubricating oil composition of the present invention, the corrosion inhibitor, rust inhibitor and demulsifier are each contained in an amcunt of usually 0.005 to 5 percent by mass, the metal deactivator is usually contained in an amount cf usually 0.005 to 1 percent by mass, and the anti-feaming agent is usually contained in an amount of usually 0.0005 to 1 percent by mass, all on the basis of the total mass of the composition. ro05713 The kinematic viscosity at 100°C of the lubricating oil composition of the present invention is necessarily 7.5mm?/s or higher, preferably 9.3 mm?/s or higher, more preferably 10 mm?/s or higher. The kinematic viscosity at 100°C is necessarily 15.0 mm?/s or lower, preferably 14.5 mm®/s cr lower, more preferably 12.5 mm’/s or lower. If the 100°C kinematic viscosity is lower than 7.5 mm?/s, the resulting composition would be poor in film formation capability and thus could cause selzure at bearings. If the 100°C kinematic viscosity is higher than 15.0 mm’/s, the resulting composition could not sufficiently cool piston surfaces to be cooled, causing burn of pistons and also could deteriorate fuel efficiency due to the increased friction loss.

[00581] The base number of the lubricating oil composition of fhe present invention is necessarily from 4 to 20 mgKOH/g. The lower limit is preferably mgKOH/g or greater, more prefsrably 5.5 mgKOH/g or greater while the upper limit is preferably 15 mgKQOH/qg or less, more preferably 10 mgKOH/g or less. If the base number 1s less than 4 mgKOH/g, the resulting composition could be poor in detergency. If the base number 1s greater than 20 mgKOH/g, the composition could be less likely to remove mixed foreign substances in a purifier, [C0593 The lubricating oil composition of the present invention is not only suitably applicable as a system oll for a crosshead-type diasel engine but also can be used for trunk-piston-type diesel engines as well as gasoline, diesal and gas engines of motorcycles, automebiles, power generators and cogeneration units.

Examples

[0060] The present invention will ke described in more detall with reference to the following Examples and Comparative Examples but are net limited thereto.

[0061] (Examples 1 to 18, and Comparative Examples 1 to 4)

Lubricating oil compositions of the present invention {Examples 1 to 18) and those for comparison {Comparative Examples 1 to 4} as set forth in Tables 1 and 2 were prepared. Each of the resulting compositions was subjected to a hot tube test, and the results thereof are also set forth in Tables 1 and 2.

For Examples 1 to 7 and 10 to 16 and Comparative Examples 1, 3 and 4, the content of the polymer compound and the ratio of the base oil were adjusted so that the 100°C kinematic viscosity of each composition mixed with additives was 11.5 mm®/s. [00627 {Base 011)

Base 011 A: 100 neutral (kinematic viscosity at 100°C: 4.42 mm?/s)

Base 011 B: 250 neutral {kinematic viscosity at 100°C: 7.12 mm/s)

Base 011 C: 500 neutral (kinematic viscosity at 100°C: 10.8 mm*/s)

Base Qil D: 150 bright stock (kinematic viscosity at 100°C: 31.7 mm®/s) (Additive)

{l) Polymer Compound

A-1: Polyisoprene star polymer {polymer wherein polyisoprens bonds as arms to dibinylbenzene,

P33I=2)

A-Z: Polyisoprene-polystyrene star polymex {polymer wherein an isoprene-styrene copolymer bonds as arms to dibinylbenzene, P851=25)

A-3: Ethylene-propylene copolymer {P35I=25)

PMA: Polymethacrylate (PE3I=35)

FB: Polybutene {molecular weight: 800) {2} Additives other than the polymer compounds

B-1: Metal Detergent {overbased basic calcium phenate, base number: 235 mgKCH/g, Ca content: 2.25 mass)

B-2: Metal Detergent (overbased calcium salicylate, base number: 170 mgKCH/g, Ca content: 6.72 massy) zinc dialkyldithiophosphate: Primary zinc dialkyldithiocphosphate (alkyl=2-ethylhexyl, P content: 7.4 mass%)

Rust Inhibitor: Neutral calcium sulfonate (base number: 20 mgKCH/g, Ca content: 2.35 percent by mass)

Ashless Dispersant: alkenyl succinimide {bis-type, nitrogen content: 1 mass$]

Other Additives {(anticxidant, extreme pressure additive, pour point depressant, anti-foaming agent) [00631 (Foot Tube Test)

This test was carrled cut in accordance with

JPI~-58-55-99. At a test temperature of 250°C, each oil flowing out form a glass tube is collected, and the viscosity of the oil was measured with an automatic capillary viscometer (CACV) manufactured by Canon Inc.

Siz types of sample oils were tested for the following

TWO Cases.

A} Fresh Oil 100%

B} Mixture of 85% fresh oil and 15 mass% of cylinder drip oil collected form a crosshead-type diesel engine mounted on VLCC (Middle East to Japan), properties of the cylinder drip oil are as follows: kinematic viscosity (100°C): 28.1 mm‘/s, acid number: 7.5 mgKOH/g, base numper {perchloric acid method): 24.1 mgKOH/g, pentane insoluble (A method): 6.0 mass%

r Fr f y

[0064] rp

Fon 5 [Table 13 2 v hrm mr AA RA 2 i i EE

Ho i i i i i 7 oni gE im i Po ! ! - o£ ia i i [I fad i | i T £3 {= i Pia a wud § | i i 1 hl] i i 3 |= 12 ER R- = uy i i i oi i i ES I 2% 13 wooed woo i i i io Pd i =] mow i - a woo i i | { i i i i = : [x] EE

Ee i : i ! i i — 2 wo

EH i i + } i i

Bx [I { i i 1 i gE HE i ! i 3 3 2a Ped wn | wl whe i 4 53 i + 2 B&H 2 wn ; i oS i | od Soe = = = uy « 4 i - i | i | o Fe i oon moo pd od aa iV 1 i 0 5 ne —

EN i FT : ! Pod oo 5B {a ! | i i T + i aE iG i bod wl i i J £2 [a 3 To 1a ws dou f { 3 i

Sd i boo 121 1813 3 ¢ ol i i i ! I PT oer = oui i pC = ool ! Po | | m= T £- a - i [od i Se

T + i it id i i i - = © 3 i i | Tt i i ! i | = = oh | ! I. i ed 81 i {om | § i i i a = i = fw wi oc i i i i Pe HE] FRR] 0 wr | i t i i | ood 3 ti <0 goal i wy s : | i | i 2d = Hon i PON =e el ) i i i i oon + of i [I fmm ence i i i | == ii bod bod at i Pood i | t + ; — 1 wi | 1 i = | PE 8 wiw| ja Pood i { | io woe = i i i | Hi ow = 8 = i o i i i i jo o 2 wi Bi o oy @ a . ~ } i i i i 2 om = 5 i i i i 1 ~ — ‘ 2 i t i i esa rmpmem remem 2 ls | pe 1 1 a - Sslwim|e i i da] | sSiaig|8iz 2 4 fw wl : dief- =o coo pI qn © 1 ! i i - == oe © ] + i i i = i ! =z 1 3 io i { £1 18 - ! bo i ! gi 17 = iia! izig|algl :

EY : PERL 18121213) wa i - i i al -lol = wd id of 3 « w ¥ i i i - - = soz fr: i i tra i - a o | | | i i = i i i i § — i og Ve i ' 3 i © isl Imia|glz] = i ¢ {es a “4 LI 0 i i i i oe i — : 2 3 i = . ewe smnnades i i i i ef Toa = Zi 3 <= < fomere ee eehmrne i i i TOT o = a i frm freee enh i : ~~ a | ¢ i i i £ 8 i i i i {

E - i “ i wy bow i 4 i a | 81818 2 wn 4 i i HES] oe oi = wooo refrac i i Po oi - @® - = = Le] on i ements i i i - —- 3 - 5 i {mmm i i i ~ pa 2 HI i a o i ! | i i

E 2 i = ; i i o had 1 o 3 1 $ i a PI Re] HE wi i i £ Y HERE wy wy : of fa = 2 = 5 =

PV i 3 j 1 i o | Zw — = = - i aw

N id i i i - = go a 7 = 3 T rtm mpm mime [+8 = i mmm — £ 2 “ { | i erm ees £ 2 y io i im 3 = } “1 wig wi a i i fal 3 < | oa ow = ; ; { i oi Zou - - “4 io

I i i - — = - = i fod i 7 i i 1 = os { ! i £ iS o {in | i i mn. ; 2 ! i : < al ielg| lel = wl of Pat hol ha nw : $9 si = = 2 QF i i = 5 a war los lagi Ld i - 2 =

SBIR IES we loo fwd la x “lei z FR a1 818 Biwi wo lazer fav oar

Il gi mip al oa C1 gigi ax BiwiEidl nm a » sl El El El & gt ale) aidld gigi ga: 4d Ga 2 i EE E|EjsjEiels gieidrs io oz so. om

E El BE i 5 3 w i i El EI ELEIEl EE) Ei EE} Et g a he + oa i i 3 Ej El EEE Zi E Bb g = es hh i i i = & E = e

Pod i E EE EE i Pod £ i i I" i i i i & El i f : 5 i | Poise 2 i | 2 S i i —1 Ble I i i rr] 42 = i | Eis | ad i i & = £2 i = Tig | Ei i i £ a a 2 i 5 SEE Eo i i &s ; a > i ~~ ed Si Six gi i i E = i i a gt ai i i Ro i i gmt) e 515 aR] ! ! £3 X 8 ! i NL = re t PT «© i F3 a a8 or { {EL EIE1E Lie 8 3 4 “ i “= £3 = 3 5 3 i {81 SI 518 gi9 {&i glol-ig i 2 3 o> = 5 = _lBleiglE ie |S Eiwigid i i = 2 i gS ui o_o = el 8 i i i = PE i i + i - CF d= 8 gigi s Hogg Pg) Sigiglg i. EI = = | SE =

Bio wmiZ ais if | B17 21 oun L iad wb ~~ a | & ai

ZiZ IRIE |S Zihik 3c s| 21518) 18 g2 2 ls | = El £5 — 3 = Pag hi 8 a a2 = Za moe TE ad Sis Cidigis [E128 21a iBlala 8 13d 5 Bi 5g

I] alialel 213 HERR aig2iZici dg 515 g IE. 2 Fi “yg ; mlm min P20 2 lm Fig) ald E 5.12 wr | = 5k

SIG |BIBIE ElT|E~l 5824182 S{E1E12 5 BIE | el 28 35 a = 2D Gl. Flag dE RiD Elias et Ld 2d EI ae qs .

HEE © o ol i oat a 2 xE i. =F Sialy < ew @ & wiz 8 1G Blog 212 l= E Sgt =! 2! 8} 3 sz} 2 = 519 | 5 x] 3 ef lgldid gia SITES sl 3T5 a8 aly g 3 Zim. T S Fie 82% = =i lal 2 ~~ T flames) Sa icBh miiivielzlilzi ge 2 =e 5 oe S15 gd 2 8] | 1 aigla|aln|d sls E 2 zi3%51 3% ¢ 2 8 &- BB on i a PS i £iG| an ¥ SFdl 8 2 3 2 Sa 2 ia i i a Pool mo gS dg = = i & 2a = 2 mE 6 £3 3 ! . 2

SL

. (Tabl le 2 2 ] £ orf wl F [= i 3 El t £8 !

ER f=) 8 = i - . i

Em

EH i i

RT ws i p=] or i 58 wa f . £8 of

J 2 ot 0 & iif 2 i i 212 - { = i | apn ! i | - Ie 2 i i 2

Ba { | | < wo £2 | | | = x iz i Pod a i w i gs Lo i aio 8 | Poo i

Su | Dogo | ! i J wn — i wr of i = i <= a a i — —t 1 zl | | nN | il d x Ee © eet | i i ! rem] i | “ | ? i | i i { mt | A | 3 <b { _. i i i fee | <2 po i | —_ Nd 2 | — i i | — | 3 { i “ . 8 | V | i va i emedn INI i ; =i g = Pod ; | i 9 |. Tr i i i [I | i i i 3 o {8 ie | tee i “+ i : i | i i t i i i [R19 mmm i Fe en £ = | bod i { i fod il gs rmsd i wd : — i | i i i i ii i a i i - i : Pod i jo Pod {i | |= A | = i 2 ! bo | o Vd Po t [= in | i i = = 2 | {i = I : Po i x | i = a. i i i i | i T i i = | i £ i i + i | in i : i — 2 {

E | Pod i § bod ! 3 |e io i i fed wl id | i w 3 |e | i i | i om | i + | 3G i | { i | i ERE i i i —- ws = | Pood { 51808 i ! = = a ! Pod i fp 181818 + - x,

T E i { = | i = i Sig i . . [= i i : 2 | i - i Pei i i o 3 i | { i = I | | ! z 3

Pa { i | i i i of ol © iB b i {uw | 4 i i — od = i fot | ioe i i 1 iw! [I 3 | | of ® | i ! - ia 2 | i | { : | wy b i Pod BiG bo | nw in i ga = t i i © 2 i= i t I {oe ew + —- i ; « i Te | i= | i ie X § i me {i o | <5 eg iB wa i | | 2 i ve ~

HS {2 : i 2 at - io@ 8 HG = ; i wt

I od ~ 0 i

Vd - i Sa wo 7 <Q [a le S32 i z2 o = Mz 2 i o = o w= 1 * 2 = i a 0 2 Z 2 ol 28 = = a g 1 i —_— == ia — = ol - a i i a slg 2 3 = = : |= | Hrs 0 = = io =~ 7 - = p T «3 £5 & od | 23 20%

PE o 24 zo = 3 2 Bi 18 ji} TE p. | = ~N i r= je = oe -~ —1 1 = i "le 13 i = } AE i i ©) 2 = on — : + i ~“ os 5 of (a = " ! i x] )

Bi oe no | | a ¥ —3- — “ 4

Ed w | enn - | 7

FI oS S18 mnt i 1; | i i S aie wn — i ya | er] het i [= ~ manne | - = | 1 - ba | Poe - 4 BE: 21 Pod HE i i «= : i i -= a ai i |i | i | : = @ = © i Lo ; “| ; Tow i f gi & i i i 1 i i 818 i rs i gi = bod | TT i 21818] esr 2 oF . = i i Pod | } = Ea { i = =

S| Pod Pod | TY { i be = _ ! 1 i i i ! i 5 i i= * i i | i ia i i 5 i ies un 5 ] od 3 i i i | os i i i |= ? - : ri § T i i ! i i i i i — RY] - a | I Poo i [I id i ca = =i 3 i ¥ $ i i Poa b i i © 51 HI i] ! | | HI i i igi i i + i Poo uy i } wy gi 12 Pod Po 28 Pod woe } i | | i i + | = ~ {| - ~ i id | i i od - Ped - 4 i Pod | | o boi |S 1 a 8 i= 1 I. |e | Pod 3 wooo a EI Ld PT | je Pod = = - [a 61% i i i £ i | 8 i i = ow & FIR IY ed Po [a 31911) T £ i Po 10 i + © i Hh aed [od Big i 0 i i EIR Pas fas | i Go i. — ~ i io {21 | @ [I ’ {gi = or tod | Ei [41g i = i | i i | iE vo iat {=| uw 3 @

Pod | |=] E] i &1 3 2 | | = in - i i i | ' i iE i 2 a o a% + i i ! | i i i i i 8 i 8 |) at i + in i 1 i i i i i |. = | 4 a doa y = — i [EE | | io El é a G10 = 2 ~ i io bod ! i i El E & siz = = i i i ! iy {i £ EE ax - =

I i Jed if! Pai ELEY $3 59 ~~ 1% {51 PE | o = sl PE £1 PS PT E 5 a 215115) Eo | 2 2 28 18% SE 12 | PE = co gic 3 ig | [= E E Sr

EEE + 3k : 5 OE - i 212 < g 5 iz EE | = i 2 ale 2 18 i i o E =

Blix [Rg pos ERE Ele 12 Pod El g i < =e sie ¢ RF iE i i a = i az ols = g|E | 2 2 Z ~ iE i i E i = “— i { + x at oe @iee zie £15 & 21g io £ g 3 8 i E12 EIB gis 2 2 & 3 £ { i i = 2 o = } 212 aid HE el © £0 g bod | = 0 3 2 g1 3 PY =) Eig SE a z:.8 boi i bt 5 © ® = a ala zi Sig 212 - rr PE iB + @ = 5 + 4 @ ala @ 2d £15 ® AZ {8d HE Id = gs 2 He — . a = sis - pe I ] led iG Sn - o = Ea a gi? =e o 51S Ei a £2 — = 4 i a]

E14 <| 8 = 312 5g g 2 a 2 5 3 21% = g ~— S18 Eig ZF EZ = Q = % = a £12 — 21 =i0 2 5 Z 3 x ES 8 is is 1 od gig - Ss 5 i 3 7 Ea 5 5 Tia E Ei 2 < Ss iE @* z 5a = < Pe £1 8 a5 8 214 FE = 5 = i ~ 2 =| 2 uw € 7 — 5 gd th i Ef < 3 31, a2 Xo. 3 < <i E E =i 2 o zg 5 31 8 2 o a . 2 = = - § ¢ 3303 8 2 i JE = - = a ER a = oi 83 32- & pile 2 3 E £ 2 5 a 2

[0065] As apparent from The results set forth in

Tables 1 and 2, the lubricating oll compositions of the present invention has no difference in viscosity changes over those of Comparative Examples when tested by 100% fresh oils but are smaller in viscosity increase than the comparative coils when mixed with a cylinder drip oll.

Industrial Applicabilitvy

[0066] The lubricating oil composition of the present invention is smaller in viscosity increases even when mixed with a cylinder drip oil and thus excellent in fuel efficiency and exhibits excellent effects in particular as a system lubricating oil for a crosshead-type diesel engine.

Claims

CLAIMS {Claiml] A system lubricating oil composition for a crosshead-type diesel engine comprising: a mineral base oil and/or a synthetic hase oil; {A) (a-1) a star polymer having a vinyl aromatic hydrocarbon structure in the molecule and/or {a-2) an ethylene~a~olefin copolymer or a hydrogenated compound thersof, and having a pase number of 4 to 20 mgKOH/g and a 100°C kinematic viscosity of 7.5 to 15.0 l/s.

[Claim 2] The system lubricating oil composition for a crosshead-type diesel engine according to claim 1 wherein Component {a-1}) is a compound having a structure wherein the polymer or copolymer of a diene extends radially from the core ¢f the vinyl aromatic hydrocarbon located in the center of the molecule.

[Claim 3] The system lubricating oil composition for a crosshead-type diesel engine according to claim 1 ocr 2 wherein the vinyl aromatic hydrocarben is divinylbenzene. (Claim 4] The system lubricating oil composition for a crosshead-type diesel engine according to any one of claims 1 to 3 wherein the polymer or copolymer of a diene is polyisoprene or an lsoprene-styrene copolymer.

[Claim 5] The system lubricating oil composition for a crosshead~type diesel engine according to any one of claims 1 to 4 wherein Component (A) is contained in an amount of 2 to 135 percent by mass on the basis of the total mass of the composition. [Claim ©] The system lubricating cll composition for a crosshead-type diesel engine according to any one of claims 1 to 5 further comprising at least one type selected from the group consisting of (B) metal detergents, [(C) zinc dialkyldithiophosphates, (D) rust inhibitors and {Ej} ashless dispersants. [Claim 71 The system lubricating ¢il composition for a crosshead-type diesel engine according to any one of claims 1 to & wherein the base 0il has a 100°C kinematic viscosity of 3.5 to 9.3 mm?/s.