KR20120123374A - System lubricant oil composition for crosshead-type diesel engine - Google Patents

Abstract

By suppressing a rise in viscosity, a system lubricating oil composition for a crosshead diesel engine that can prevent fuel deterioration is disclosed. The system lubricating oil composition comprises a mineral oil base oil and / or a synthetic oil base oil, and (A) a molded polymer having a vinyl aromatic hydrocarbon structure in the molecule (a-1) and / or (a-2) an ethylene-α-olefin air. It comprises a coalescence or a hydrogenated compound thereof, the base number (base number) is characterized in that 4 to 20 mgKOH / g, 100 ℃ kinematic viscosity is 7.5 to 15.0 mm 2 / s.

Description

System lubricant composition for crosshead diesel engines {SYSTEM LUBRICANT OIL COMPOSITION FOR CROSSHEAD-TYPE DIESEL ENGINE}

The present invention relates to a system lubricating oil composition for a crosshead diesel engine.

In crosshead diesel engines, cylinder oil for lubricating the friction point between the cylinder and the piston and system oil for lubricating and cooling other parts are used. Cylinder oil is required to maintain the proper viscosity needed to lubricate the frictional area between the cylinder and the piston (piston ring) and the cleanliness required to properly move the piston and piston ring. In addition, since these engines are generally used for fuels of high sulfur content for economic reasons, there is a problem that acidic components such as sulfuric acid generated during combustion of the fuel corrode the cylinder. To avoid this problem, cylinder oils require the ability to neutralize acidic components such as sulfuric acid to prevent corrosion.

On the other hand, unlike conventional diesel engine oils, system oils are lubricating oils stored in tanks without contact with combustion gases and supplied to bearings by circulation pumps for lubrication and cooling, unlike cylinder oils. It is necessary to hold | maintain (for example, refer patent document 1 below). However, there is a problem in the cross-hair type engine for ships that the system oil is actually mixed with drip oil, the viscosity is increased, and how to suppress this increase in viscosity is a long-term problem. In particular, in recent years, environmental problems have emerged, and it is important to avoid deterioration in fuel efficiency due to increased friction loss in the bearings with increasing viscosity or deterioration in heat exchange efficiency at the piston surface to be cooled.

Patent Document 1: Japanese Patent Laid-Open No. 2002-275491

It is an object of the present invention to provide a system lubricating oil composition for a crosshead diesel engine, which can suppress an increase in viscosity and prevent fuel economy deterioration.

As a result of intensive studies and investigations, the present invention can balance the increase in viscosity due to the mixing of a lubricating oil composition containing a specific polymer with the drip oil and the decrease in viscosity due to thermal decomposition of the polymer, thereby providing a system lubricating oil composition for a crosshead diesel engine. Based on the finding that it was beneficially effective.

Specifically, system oils comprising lubricating base oils blended with star polymers and / or olefin copolymers with vinyl aromatic hydrocarbon structures in the molecule, which have good shear stability but are easy to decompose by heat, can be cooled. The polymer may decompose at the piston surface to reduce the viscosity of the system oil, thereby balancing fuel viscosity deterioration with increased viscosity due to mixing with the cylinder drip oil.

That is, the present invention comprises a mineral oil base oil and / or a synthetic oil base oil, and (A) a molded polymer having a vinyl aromatic hydrocarbon structure in the molecule (a-1) and / or (a-2) ethylene-α-olefin air A system lubricating oil composition for crosshead diesel engines comprising coalescing or hydrogenated compounds thereof, having a base number of 4 to 20 mgKOH / g and a 100 ° C kinematic viscosity of 7.5 to 15.0 mm 2 / s.

The present invention also relates to a system lubricating oil composition for a crosshead diesel engine, wherein the component (a-1) is a compound having a structure in which a polymer or copolymer of diene extends radially from the nucleus of a vinyl aromatic hydrocarbon located at the center of the molecule. will be.

The present invention further relates to a system lubricating oil composition for the crosshead diesel engine, wherein the vinyl aromatic hydrocarbon is divinylbenzene.

The present invention further relates to a system lubricating oil composition for the crosshead diesel engine, wherein the polymer or copolymer of the diene is a polyisoprene or isoprene-styrene copolymer.

In addition, the present invention further comprises at least one member selected from the group consisting of (B) metal detergents, (C) zinc dialkyldithiophosphates, (D) rust inhibitors, and (E) ashless dispersants. A system lubricating oil composition for a diesel engine.

The present invention further relates to a system lubricating oil composition for a crosshead diesel engine having a 100 ° C kinematic viscosity of base oil of 3.5 to 9.3 mm 2 / s.

Use of the system lubricating oil composition for crosshead diesel engines of the present invention can suppress the increase in viscosity and prevent fuel economy deterioration.

Hereinafter, the present invention will be described in more detail.

There is no particular limitation on the type of lubricating oil base oil used in the system lubricating oil composition (hereinafter, abbreviated as "lubricating oil composition" of the present invention) for the crosshead diesel engine of the present invention, and may be mineral oil, synthetic oil, or a mixture thereof.

Specific examples of mineral oil base oils include lubricating oil fractions produced by vacuum distillation of atmospheric distillation bottom oil obtained by atmospheric distillation of crude oil in solvent deasphalting, solvent extraction, hydrocracking, solvent dewaxing and hydrogenation purification. Capable of producing by carrying out any one or more treatments selected; Wax-isomerized mineral oil; And isomerized GTL WAX (gas-liquid wax) produced by the Fischer-Tropsch process.

Specific examples of the synthetic oil base oil include polybutene and hydrogenated compounds thereof; Poly-α-olefins such as 1-octene oligomers and 1-decene oligomers, and hydrogenated compounds thereof; A copolymer of ethylene having a weight average molecular weight of 8,000 or less and an α-olefin having 3 to 30 carbon atoms; Diesters such as ditridecyl glutarate, di-2-ethylhexyl adipate, diisodecyl adipate, ditridecyl adipate and di-2-ethylhexyl sebacate; Polyol esters such as trimethylolpropane caprylate, trimethylolpropane pelaronate, pentaerythritol 2-ethylhexanoate and pentaerythritol pelaronate; Copolymers of dicarboxylic acids such as dibutyl maleate with α-olefins having 2 to 30 carbon atoms; Aromatic synthetic oils such as alkylnaphthalenes, alkylbenzenes and aromatic esters; And mixtures thereof.

The lubricating oil base oil used in the lubricating oil composition of the present invention may be at least one kind of mineral oil base oil or synthetic oil base oil, or may be a mixture of one or more mineral oil base oils and one or more synthetic base oils.

The 100 ° C. kinematic viscosity of the lubricating oil base oil used in the present invention is preferably 9.3 mm 2 / s or less, more preferably 8.5 mm 2 / s or less, more preferably 8.0 mm 2 / s or less. On the other hand, 100 degreeC dynamic viscosity becomes like this. Preferably it is 3.5 mm <2> / s or more, More preferably, it is 3.8 mm <2> / s or more, More preferably, it is 4.0 mm <2> / s or more. 100 ° C. kinematic viscosity as referred to herein is defined as defined by ASTM D-445. If the 100 ° C kinematic viscosity is higher than 9.3 mm 2 / s, there is little viscosity decrease in the final composition, so that the effect of suppressing the viscosity increase upon mixing with the cylinder drip oil cannot be exhibited. If the 100 ° C. kinematic viscosity is lower than 3.5 mm 2 / s, the final composition may decrease the viscosity too much, resulting in a decrease in the oil film forming ability in the bearings, which may cause seizure.

Further, there is no particular limitation on the 40 ° C kinematic viscosity of the lubricant base oil used in the present invention, but it is preferably 150 mm 2 / s or less, more preferably 120 mm 2 / s or less, and more preferably 90 mm 2 / s. Or less. On the other hand, 40 degreeC dynamic viscosity becomes like this. Preferably it is 15 mm <2> / s or more, More preferably, it is 20 mm <2> / s or more, More preferably, it is 25 mm <2> / s or more. If the 40 ° C kinematic viscosity is higher than 200 mm 2 / s, there is little viscosity decrease in the final composition, which may not exhibit the effect of inhibiting viscosity increase when mixed with the cylinder drip oil. If the 40 ° C kinematic viscosity is lower than 50 mm 2 / s, the final composition may decrease the viscosity too much, which may lower the oil film-forming ability in the bearing and cause a scissor to occur.

The viscosity index of the lubricating oil base oil used in the present invention is preferably 85 or more, more preferably 90 or more, more preferably 95 or more. There is no particular limitation on the upper limit of the viscosity index. In addition, normal paraffin, slack wax or GTL wax or isoparaffinic mineral oil produced by isomerization thereof may also be used.

Viscosity index referred to herein means measured according to JIS K 2283-1993.

The lubricating oil composition of the present invention must necessarily contain, as component (A), a molded polymer having a vinyl aromatic hydrocarbon structure in the molecule (a-1) and / or (a-2) an ethylene-α-olefin copolymer or a hydrogenated compound thereof. do.

Molded polymers having a vinyl aromatic hydrocarbon structure in the molecule of component (a-1) have radial arms of polymers or copolymers of many (two or more) dienes from the nucleus of the vinyl aromatic hydrocarbon located at the center of the molecule. It is a compound with an extended structure.

Examples of vinyl aromatic hydrocarbons located at the molecular center are divinylbenzene, trivinylbenzene, tetravinylbenzene, divinylortho-, divinylmetha- or divinylpara-xylene, trivinylorto-, trivinylmetha- or tri Vinylpara-xylene, tetravinylortho-, tetravinylmetha- or tetravinylpara-xylene, divinylnaphthalene, divinylethylbenzene, divinylbiphenyl, diisobutenylbenzene, diisopropenylbenzene and diiso Propenylbiphenyl. Of these compounds, divinylbenzene is preferred.

The diene monomer constituting the polymer or copolymer of the diene preferably has 4 to 12 carbon atoms. Specific examples include 1,3-butadiene, isoprene, piperylene, methylpentadiene, phenylbutadiene, 3,4-dimethyl-1,3-hexadiene and 4,5-diethyl-1,3-octadiene . 1,3-butadiene and isoprene are preferred.

Examples of polymers or copolymers of dienes to be shaped polymers include homopolymers of dienes such as polyisoprene and copolymers of dienes such as isoprene-butadiene copolymers. Alternatively, copolymers of dienes with monomers other than dienes (eg, isoprene-styrene copolymers) may be used. This copolymer can be a random copolymer or a block copolymer.

Component (a-1), which is a molded polymer having a vinyl aromatic hydrocarbon structure in its molecule, used as component (A) of the present invention, has a weight average molecular weight (Mw) of preferably 10,000 or more, more preferably 50,000 or more, further Preferably it is 100,000 or more, Preferably it is 1,000,000 or less, More preferably, it is 800,000 or less, More preferably, it is 500,000 or less. If the weight average molecular weight is less than 10,000, the final composition may not only exhibit a sufficient viscosity adjustment effect, but also increase the production cost. If the weight average molecular weight is more than 1,000,000, the final composition may have poor shear stability and may not exhibit a viscosity adjustment effect.

As used herein, the PSSI (Permanent Shear Stability Index) of the molded polymer (a-1) having a vinyl aromatic hydrocarbon structure in the molecule is preferably 1 to 40, more preferably 1 to 35, more preferably 1 To 30, particularly preferably 1 to 25. If the PSSI is greater than 40, the final composition may have poor shear stability, thereby not exhibiting sufficient viscosity adjustment effect. If the PSSI is less than 1, the final composition may also not sufficiently exhibit a viscosity adjustment effect.

As used herein, the term "PSSI" is used to measure shear stability of polymer-containing fluids using ASTM D 6278-02 (European diesel injector device), in accordance with ASTM D6022-01 (Standard Practice for Calculating Permanent Shear Stability Index). Permanent shear stability index of the polymer calculated based on the data measured by the test method).

The ethylene-α-olefin copolymer or hydrogenated compound thereof as component (a-2) is a copolymer of ethylene and α-olefin or a compound produced by hydrogenating this copolymer. Specific examples of α-olefins include propylene, isobutylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 1-decene and 1-dodecene. The ethylene-α-olefin copolymer may be produced by reacting a copolymer with a polar compound such as a nitrogen-containing compound, which is composed of a hydrocarbon having a non-dispersant type or a ethylene-α-olefin copolymer having a dispersant type. Most preferred of these compounds are ethylene-α-propylene copolymers.

The ethylene-α-olefin copolymer or hydrogenated compound thereof (a-2) used as component (A) in the present invention preferably has a weight average molecular weight (Mw) of 10,000 or more, more preferably 20,000 or more, further Preferably it is 50,000, Preferably it is 500,000 or less, More preferably, it is 400,000 or less, More preferably, it is 300,000. If the weight average molecular weight is less than 10,000, the final composition may not sufficiently exhibit the viscosity adjustment effect and the production cost may increase. If the weight average molecular weight exceeds 500,000, the final composition may have poor shear stability, so that the viscosity adjusting effect may not be exhibited either.

(a-2) The PSSI (Permanent Shear Stability Index) of the ethylene-α-olefin copolymer or hydrogenated compound thereof is preferably 1 to 75, more preferably 3 to 50, more preferably 5 to 30, especially Preferably it is 10-28. If the PSSI is greater than 75, component (a-2) has poor shear stability and may not exhibit a viscosity adjustment effect when added to the system oil. If the PSSI is less than 1, the final composition may also exhibit no viscosity adjustment effect.

The content of component (A) present in the lubricating oil composition of the present invention is preferably 1 to 20 mass%, more preferably 2 to 15 mass%, more preferably 3 to 12 mass, based on the total mass of the composition. %, Most preferably 4 to 10 mass%. If the content is less than 1 mass%, the final composition may not sufficiently exhibit the viscosity adjusting effect. If the content is more than 20% by mass, the final composition may have poor handleability and adversely affect the production of the composition, and there is a fear that detergency is deteriorated due to generation of precipitates due to decomposition of the polymer.

The ethylene-α-olefin copolymer or hydrogenated compound thereof is provided in a diluted state with 1 to 90 mass% of mineral oil.

It is preferable that the lubricating oil composition of this invention contains 1 or more types chosen from the group which consists of (B) metal detergent, (C) zinc dialkyl dithiophosphate, (D) rust inhibitor, and (E) ashless dispersing agent.

Component (B), which is a metal detergent, may be one or more metal detergents selected from phenate detergents, sulfonate detergents, salicylate detergents, carboxylate detergents and phosphonate detergents.

Phenate metal detergents contain (overbased) basic salts of alkaline earth metal salts or alkaline earth metal salts of Mannich reaction products of alkylphenols, alkylphenolsulfides or alkylphenols of the structures represented by the formulas (1) to (3) It is a phenate metal detergent.

Examples of alkaline earth metals include magnesium, barium and calcium. Magnesium and calcium are preferred, and calcium is particularly preferred.

Formula (1)

Formula (2)

(3)

In the formulas (1) to (3), R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ⁶ and R ⁷ may be the same or different from each other, each independently having 4 to 30 carbon atoms, preferably Preferably 6 to 18 straight or branched alkyl groups. If the carbon number is less than 4, the component (B) will have poor solubility in lubricating oil base oil. If the carbon number is more than 30, component (B) will be difficult to produce and have poor heat resistance. R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ⁶ and R ⁷ Specific examples of alkyl groups include butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, nonadecyl, eicosyl, Hencosyl, docosyl, tricosyl, tetracosyl, pentacosyl, hexacosyl, heptacosyl, octacosyl, nonacosyl and triacontyl groups. Such alkyl groups may be straight or branched chains and may be primary, secondary or tertiary groups.

M ¹ , M ² and M ³ are each independently alkaline earth metals, preferably calcium and / or magnesium, x, y and z are each independently an integer from 1 to 3, m is 0, 1 or 2, n is 0 or 1;

Sulfonate detergents (overbased of alkali metal salts or alkaline earth metal salts and / or alkali metal salts or alkaline earth metal salts of alkyl aromatic sulfonic acids produced by sulfonating alkyl aromatic compounds having a molecular weight of at least 300, preferably 400 to 700 Basic salts). Examples of alkali or alkaline earth metals include sodium, potassium, magnesium, barium and calcium. Magnesium and / or calcium are preferred. Calcium is particularly preferred.

Specific examples of alkyl aromatic sulfonic acids include petroleum sulfonic acid and synthetic sulfonic acid. Petroleum sulfonic acid may be produced by sulfonating an alkyl aromatic compound contained in the lubricant fraction of mineral oil or mahogany acid produced as a by-product in the production of white oil. Synthetic sulfonic acids are produced as by-products from plants for producing alkyl benzene used as raw materials for detergents, or by sulfonating alkyl benzenes having straight or branched alkyl groups produced by alkylating polyolefins with benzene, or dinonyl It may be produced by sulfonating alkylnaphthalene such as naphthalene. There is no particular limitation on the sulfonating agent used to sulfonate such alkyl aromatic compounds. In general, fuming sulfuric acid or sulfuric acid may be used.

Salicylate detergents include alkali or alkaline earth metal salicylates with one hydrocarbon group having 1 to 19 carbon atoms and / or (overbased) basic salts thereof; Alkali metal or alkaline earth metal salicylates having one hydrocarbon group having 20 to 40 carbon atoms and / or (overbased) basic salts thereof; Or an alkali or alkaline earth metal salicylate having two or more hydrocarbon groups of 1 to 40 carbon atoms and / or (overbased) basic salts thereof (the alkyl groups may be the same or different). Among these compounds, alkali metal or alkaline earth metal salicylates having one hydrocarbon group having 8 to 19 carbon atoms and / or (overbased) basic salts thereof are preferred because of their low temperature fluidity. Examples of alkali or alkaline earth metals include sodium, potassium, magnesium, barium and calcium. Magnesium and / or calcium are preferred. Calcium is particularly preferred.

50-500 mg KOH / g is preferable, as for the base value of the component (B) which is a metal detergent used for this invention, 100-450 mg KOH / g is more preferable, 150-350 mg KOH / g is more preferable. If the base value is less than 100 mg KOH / g, since the final composition may have insufficient acid neutralization, there is a fear that corrosion wear increases. When the base value exceeds 500 mg KOH / g, there is a concern that solubility problems occur.

The term "base" as used herein means a value measured by perchlorate potentiometric titration according to section 7 of JIS K2501 "Petroleum products and lubricants-Determination of neutralization number".

(B) The metal ratio of the metal cleaning agent is not particularly limited. However, the lower limit is at least 1, preferably at least 2, particularly preferably at least 2.5, and the upper limit is at most 20, preferably at most 15, more preferably at most 10.

"Metal ratio" as used herein denotes "a valence x metal element content (mol%) / soap group content (mol%) of metal element" in the metal cleaning agent (B). Metal element means alkaline earth metals such as calcium and magnesium. Soap group means a phenol group.

If contained in the composition of the present invention, the content of the metal detergent (B) is usually 0.5 to 15% by mass, preferably 1 to 12% by mass, particularly preferably 1.5 to 10% by mass.

It is preferable that the lubricating oil composition of this invention contains the dialkyl dithiophosphate (C) represented by following formula (4):

Formula (4)

In formula (4), R ¹ , R ² , R ³ and R ⁴ may be the same or different from each other, and each independently an alkyl group having 1 to 30 carbon atoms or an alkylaryl group having 7 to 30 carbon atoms, and Alkyl groups may be straight or branched, and may be primary or secondary groups.

The method for producing zinc dithiophosphate as component (C) is not particularly limited because any conventional method can be used. For example, an alcohol having an alkyl group corresponding to R ¹ , R ² , R ^3, and R ⁴ may be reacted with phosphorus penta sulfide to form dithiophosphoric acid, and then neutralized with zinc oxide to synthesize zinc dithiophosphate. have.

If contained in the lubricating oil composition of the present invention, the content of (C) zinc dithiophosphate is preferably 0.005 to 0.12 mass%, more preferably 0.01 to 0.10 mass%, more preferably based on phosphorus of the total mass of the composition. Is 0.02 to 0.08 mass%. If it is less than 0.005 mass%, the final composition may not obtain the extreme pressure or gear properties required for the system oil. If it is more than 0.12 mass%, the final composition may corrode bearings, seal rings of stepping boxes or oil scraper rings.

The lubricating oil composition of the present invention preferably contains (D) a rust preventive agent. Examples of 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 monoesters and pentaerythritol monoesters, oxidized paraffins (oxidized waxes), carboxylic acids and phosphoric acid esters. Sulfonates are preferred.

If the rust preventive agent (D) is contained in the lubricating oil composition of the present invention, the content thereof is preferably 0.005 to 5% by mass based on the total mass of the composition.

It is preferable that the lubricating oil composition of this invention contains the (E) ashless dispersing agent.

Ashless dispersants may be any ashless dispersants that have been used in lubricating oils. Ashless dispersants may be succinimides, benzylamines or polyamines, or modified products thereof, having at least one linear or branched alkyl or alkenyl group in the molecule of 40 to 400 carbon atoms, preferably 60 to 350 carbon atoms. have.

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

Among these compounds, products modified with succinimide or boron represented by the following formula are preferred:

Formula (5)

Formula (6)

In formula (5), R ¹ is an alkyl or alkenyl group having 40 to 400 carbon atoms, preferably 60 to 350 carbon atoms, and h is an integer of 1 to 5, preferably 2 to 4. In formula (6), R ² and R ³ are each independently an alkyl or alkenyl group having from 40 to 400 carbon atoms, preferably from 60 to 350 carbon atoms, particularly preferably a polybutenyl group, and i is from 0 to 4, Preferably it is an integer of 1-3.

If ashless dispersant is included in the lubricating oil composition of the present invention, the content is preferably 1 to 8% by mass based on the total mass of the composition.

In order to further improve the properties of the lubricating oil composition of the present invention or to add other necessary properties, in addition to the aforementioned components, any additives conventionally used in lubricating oils may be added according to the purpose. Examples of such additives include antioxidants, extreme pressure additives, preservatives, anti emulsifiers, metal deactivators, pour point depressants, and antifoaming agents.

Examples of antioxidants include phenolic antioxidants such as DBPC, bisphenol and hindered phenols, amine antioxidants such as diphenylamine and N-phenyl-α-naphthylamine, and metal antioxidants such as copper and molybdenum antioxidants. It includes.

When included in the lubricating oil composition, the content of antioxidant is preferably 0.05 to 5 mass% based on the total mass of the composition.

Suitable extreme pressure additives are any extreme pressure additives and antiwear agents used in lubricating oils. For example, sulfuric acid, phosphoric acid and sulfuric acid-phosphate extreme pressure additives may be used. Specific examples include phosphorous acid esters, thiophosphorous acid esters, dithiophosphorous acid esters, trithiophosphoric acid esters, phosphate esters, thiophosphoric acid esters, dithiophosphoric acid esters, trithiophosphoric acid esters, amine salts, metal salts or derivatives thereof, dithiocarbamate Zinc dithiocarbamate, molybdenum dithiocarbamate, disulfide, polysulfide, vulcanized olefins and vulcanized fats and oils.

If the extreme pressure additive is included in the lubricating oil composition of the present invention, the content is preferably 0.05 to 5 mass% based on the total mass of the composition.

Examples of corrosion inhibitors include benzotriazole-, tolyltriazole-, thiadiazole- and imidazole type compounds.

Examples of anti-emulsifiers include polyalkylene glycol based nonionic surfactants such as polyoxyethylenealkyl ethers, polyoxyethylenealkylphenyl ethers and polyoxyethylenealkylnaphthyl ethers.

Examples of metal deactivators include imidazolines, pyrimidine derivatives, alkylthiadiazoles, mercaptobenzothiazoles, benzotriazoles and derivatives thereof, 1,3,4-thiadiazolepolysulfides, 1,3,4- Thiadiazolyl-2,5-bisdialkyldithiocarbamate, 2- (alkyldithio) benzoimidazole and β- (o-carboxybenzylthio) propionitrile.

Pour point depressants may be polymethacrylate polymers suitable for use with lubricant base oils.

Examples of antifoaming agents are silicone oils having a kinematic viscosity of 25 ° C. from 100 to 100,000 mm 2 / s, alkenylsuccinic acid derivatives, esters of polyhydric aliphatic alcohols and long chain fatty acids, aromatic amine salts of methylsalicylate and o-hydroxybenzyl alcohol, aluminum stearate Latex, potassium oleate, N-dialkyl-allylamine nitroaminoalkanol, and isoamyloctylphosphate, alkylalkylenediphosphate, metal derivatives of thioethers, metal derivatives of disulfides, fluorine compounds of aliphatic hydrocarbons, triethylsilane, dichloro Silanes, alkylphenyl polyethylene glycol ether sulfides and fluoroalkyl ethers.

When such additives are included in the lubricating oil composition of the present invention, corrosion inhibitors, rust inhibitors and anti-emulsifiers are usually included in amounts of 0.005 to 5 mass%, metal deactivators are usually included in amounts of 0.005 to 1 mass%, and antifoaming agents. Is generally included in amounts of 0.0005 to 1% by mass, all of which are based on the total mass of the composition.

The kinematic viscosity at 100 ° C. of the lubricating oil composition of the present invention should be at least 7.5 mm 2 / s, preferably at least 9.3 mm 2 / s, more preferably at least 10 mm 2 / s. The kinematic viscosity at 100 ° C. should be 15.0 mm 2 / s or less, preferably 14.5 mm 2 / s or less, more preferably 12.5 mm 2 / s or less. If the 100 ° C. kinematic viscosity is less than 7.5 mm 2 / s, the final composition will have poor film-forming ability, thereby causing a scissor in the bearing. If the 100 ° C. kinematic viscosity is greater than 15.0 mm 2 / s, the final composition may not sufficiently cool the piston surface to be cooled, which may cause ignition of the piston, which may worsen fuel efficiency due to an increase in friction loss.

The base value of the lubricating oil composition of the present invention should be 4 to 20 mg KOH / g. The lower limit is preferably at least 5 mgKOH / g, more preferably at least 5.5 mgKOH / g, while the upper limit is preferably at most 15 mgKOH / g, more preferably at most 10 mgKOH / g. If the base value is less than 4 mgKOH / g, the final composition may be poor in washability. If the base value exceeds 20 mgKOH / g, the composition may not be easy to remove entrained foreign matter in the purifier.

The lubricating oil compositions of the present invention can be suitably applied as system oils for crosshead diesel engines, as well as for trunk-piston type diesel engines, as well as gasoline, diesel and gas engines for two-wheelers, four-wheelers, power generation and cogeneration units. Can be used.

Example

The invention is described in more detail with reference to the following examples and comparative examples, but is not limited thereto.

(Examples 1 to 18 and Comparative Examples 1 to 4)

The lubricating oil compositions (Examples 1-18) and comparative lubricating oil compositions (Comparative Examples 1-4) of the present invention were prepared as shown in Tables 1 and 2. Hot tube tests were carried out with the resulting compositions, respectively, and the results are also shown in Tables 1 and 2. In 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 the additive was 11.5 mm 2 / s.

(Base oil)

Base oil A: 100 neutrals (Kinematic viscosity at 100 ° C: 4.42 mm2 / s)

Base oil B: 250 Neutral (Kinematic Viscosity at 100 ° C: 7.12 mm2 / s)

Base oil C: 500 Neutral (Kinematic viscosity at 100 ° C: 10.8 mm2 / s)

Base oil D: 150 bright stocks (Kinematic viscosity at 100 ° C: 31.7 mm 2 / s)

(additive)

(1) polymer compound

A-1: polyisoprene molded polymer (polymer in which polyisoprene is bound to divinylbenzene as an arm, PSSI = 2)

A-2: polyisoprene-polystyrene molding polymer (polymer in which isoprene-styrene copolymer is bound to divinylbenzene as an arm, PSSI = 25)

A-3: ethylene-propylene copolymer (PSSI = 25)

PMA: Polymethacrylate (PSSI = 5)

PB: Polybutene (Molecular Weight: 800)

(2) additives other than polymer compounds

B-1: metal detergent (overbasic basic calcium phenate, basic value: 255 mgKOH / g, Ca content: 9.25 mass%)

B-2: Metal cleaning agent (overbased calcium salicylate, base value: 170 mgKOH / g, Ca content: 6.2 mass%)

Dialkyldithiophosphate zinc: primary dialkyldithiophosphate zinc (alkyl = 2-ethylhexyl, P content: 7.4 mass%)

Antirust agent: Neutral calcium sulfonate (base: 20 mgKOH / g, Ca content: 2.35 mass%)

Ashless dispersant: alkenyl succinimide (bis type, nitrogen content: 1 mass%)

Other additives (antioxidants, extreme pressure additives, pour point depressants, antifoams)

(Hot tube test)

This test was performed according to JPI-5S-55-99. Collect each oil flowing out of the glass tube at a test temperature of 250 ° C. and measure the viscosity of the oil. It measured by the automatic capillary viscometer (CACV) which is a product. Six sample oils were tested for the following two cases.

A) 100% fresh oil

B) A mixture of 85% fresh oil and 15% by mass cylinder drip oil obtained from a crosshead diesel engine mounted on VLCC (Middle East to Japan); The properties of the cylinder drip oil are as follows: kinematic viscosity (100 ° C.): 28.1 mm 2 / s, acid value: 7.5 mgKOH / g, basic value (perchloric acid method): 24.1 mgKOH / g, pentane insoluble substance (method A): 6.0 mass %

Table 1

Table 2

As can be clearly seen from the results shown in Tables 1 and 2, the lubricant composition of the present invention showed no difference in viscosity change from the test results of 100% of the new oil, but the viscosity increase was higher than that of the comparative oil when the cylinder drip oil was mixed. Less.

Industrial availability

The lubricating oil composition of the present invention has a smaller viscosity increase even when mixed with the cylinder drip oil, so that the fuel economy is excellent and it is particularly effective as a system lubricating oil for crosshead diesel engines.

Claims (7)

(A) a molded polymer having a vinyl aromatic hydrocarbon structure in the molecule (a-1) and / or (a-2) an ethylene-α-olefin copolymer or hydrogenated thereof, including mineral oil base oil and / or synthetic oil base oil A system lubricating oil composition for a crosshead diesel engine comprising a compound, having a base number of 4 to 20 mgKOH / g and a 100 ° C kinematic viscosity of 7.5 to 15.0 mm 2 / s. The system lubricating oil composition for a crosshead diesel engine according to claim 1, wherein component (a-1) is a compound having a structure in which a polymer or copolymer of diene extends radially from the nucleus of a vinyl aromatic hydrocarbon located at the center of the molecule. The system lubricant oil composition for crosshead diesel engines according to claim 1 or 2, wherein the vinyl aromatic hydrocarbon is divinylbenzene. The system lubricant composition for a crosshead diesel engine according to any one of claims 1 to 3, wherein the polymer or copolymer of the diene is a polyisoprene or an isoprene-styrene copolymer. 5. The system lubricating oil composition of claim 1, wherein component (A) is included in an amount of 2 to 15 mass% based on the total mass of the composition. 6. At least one selected from the group consisting of (B) a metal detergent, (C) zinc dialkyldithiophosphate, (D) rust inhibitor, and (E) ashless dispersant. Further comprising, system lubricant oil composition for a crosshead diesel engine. The system lubricant oil composition for a crosshead diesel engine according to any one of claims 1 to 6, wherein the 100 ° C kinematic viscosity of the base oil is 3.5 to 9.3 mm 2 / s.