KR20130035227A - Lubricating oil composition - Google Patents

Abstract

PURPOSE: A lubricating oil composition is provided to desirably use for lubrication of an internal combustion engine operated using low sulfur hydrocarbon fuel. CONSTITUTION: A lubricating oil composition of an internal combustion engine for lubrication includes less than 0.5 wt% of sulfur, base oil having lubrication viscosity and additive component of a) to e). a) 0.5-5.0 wt% of alkenyl- or alkyl-succinimide or ashless dispersant including its derivative b) 0.5-5.0 wt% of alkenyl- or alkyl-succinic acid ester or ashless dispersant including its derivative c) 50-1200 wt% of molybdenum composite of a basic nitrogen containing compound based on molybdenum content d) 0.05-1.0 wt% of akaline earth metal containing detergency having 10-400 mg·KOH/g of TBN e) 0.05-0.5 wt% of anti-abrasive The sulfur content is 0.01 to 0.2 wt%. The lubricating oil composition additionally contains a viscosity index improver and is multi-grade engine oil classified as 0W5, 0W10, 0W15, 0W20, 0W30, 5W20, 5W30, 10W20, or 10W30.

Description

Lubricating Oil Composition

The present invention relates to a lubricating oil composition which can advantageously be used for the lubrication of internal combustion engines such as diesel engines and gasoline engines. More specifically, the present invention has a low sulfur content of about 0.5% by weight or less, in particular about 0.2% by weight or less, thereby reducing friction and producing excellent internal combustion engines mounted on land mobile vehicles using low sulfur hydrocarbon fuels. A lubricating oil composition exhibiting high temperature cleaning power.

Sulfur contained in fuels such as gasoline or diesel fuel used for operation of internal combustion engines is oxidized when the fuel is burned in the engine to emit sulfur oxides such as sulfuric acid. Some sulfur oxides enter the lubricant used to lubricate the engine, and the remaining sulfur oxides are discharged along with the other emissions. Sulfur oxides emitted with other emissions cause environmental pollution. To date, sulfur content in fuels has been controlled under strict regulations. Restrictions on sulfur content were initially applied to gasoline (fuel for gasoline engines). However, restrictions on sulfur content have also been applied until recently for diesel fuels with higher sulfur content. Sulfur content in diesel fuel has until recently been regulated to less than 0.0010% by weight.

The reduction of sulfur content reduces the contamination of the lubricating oil produced when the fuel is burned with sulfur oxides such as sulfuric acid. This means that the amount of overbasic metal containing detergent in the lubricating oil can be reduced. Basic metal-containing cleaners are provided to neutralize sulfur oxides in the lubricant.

When fuel is combusted in an engine, not only the fuel but also some lubricant is combusted in the engine. The gas produced by the burned lubricating oil is discharged along with other exhaust gases. Therefore, it is desirable to reduce the sulfur content of lubricating oil.

By the way, recently used lubricating oils for internal combustion engines include base oils (hydrocarbon oils with lubricating viscosity) and produced basic metal-containing detergents for neutralizing sulfur oxides, antioxidants for maintaining the function of base oils from rot under elevated temperatures, Dispersant for dispersing soot produced by combustion of fuel and residue produced by decay of base oil and metal-containing detergent in base oil, extreme pressure agent to prevent piston and cylinder from shutting down, between piston and cylinder It contains various additives (ie lubricant additives) such as friction reducers (friction modifiers) to reduce the friction generated.

Therefore, the phosphorus and metal components included in the additive located in the lubricating oil composition are decomposed when the lubricating oil composition is burned and included in the exhaust gas in the form of phosphorus oxide and metal oxide. Phosphorus oxide and metal oxide contained in the exhaust gas are contacted with an oxidation catalyst or a reduction catalyst located in the exhaust gas scrubber to deactivate the catalyst.

For the reasons described above, there is a need to reduce the sulfurized ash content, phosphorus content and sulfur content of lubricating oil compositions.

Patent publication 1 (JP 2002-53888 A) discloses a lubricating oil composition which is preferably used for lubricating internal combustion engines, in particular diesel engines, which operate using fuel oils having a low sulfur content. The disclosed lubricating oil composition comprises a base oil having a sulfur content of 0.1 wt% or less (preferably 0.03 wt% or less) and the following additives:

a) ashless dispersant comprising alkenyl- or alkyl-succinimide or derivatives thereof, 0.01 to 0.3% by weight based on nitrogen atom content;

b) a metal containing detergent having a TBN of 10 to 350 mg KOH / g and a sulfur content of up to 3% by weight, 0.1 to 1% by weight, based on the ash content of sulphide;

c) zinc dialkyldithiophosphate, 0.01 to 0.12 weight percent based on phosphorus content; And

d) from 0.01 to 5% by weight of an antioxidant phenol compound and / or an antioxidant amine compound,

The lubricating oil composition may comprise 0.1-1 wt% sulphide ash content, 0.01-0.1 wt% phosphorus content, 0.01-0.3 wt% sulfur content, 40 wtppm or less chlorine content, and 0.2-7 wt% (preferably 0.5-5% by weight, more preferably 1.0-3% by weight) of the metal-containing detergent-derived organic acid salt,

Wherein the content and amount are expressed based on the amount of lubricating oil composition.

Patent Publication 1 further discloses an operational embodiment in which the disclosed lubricating oil composition shows good high temperature cleaning power in an internal combustion engine.

The patent publication 1 further discloses that the lubricating oil composition may contain molybdenum containing compounds which can act as friction modifiers, antioxidant papers and anti-wear agents. Molybdenum containing compounds may be known molybdenum containing compounds such as molybdenum complexes of sulfoxyolibdenium dithiocarbamate, sulfoxymolybdenum dithiophosphate and possibly sulfur containing succinimide.

Patent Publication 2 (JP 2004-149802 A) describes a low sulfurized ash content, low phosphorus content, containing base oil, ethylene carbonate aftertreatment ashless dispersant, borate treated ashless dispersant, overbased metal containing detergents and phosphorus compounds. A lubricating oil composition (ie engine oil) which is preferably used for the lubrication of internal combustion engines with a low sulfur content is disclosed. Patent Publication 2 further discloses that the disclosed lubricating oil composition may comprise a blebdenium-succinimide complex. In the working example of Patent Publication 2, experimental data shows that the lubricating oil composition exhibits excellent oxidative stability and good anti-wear performance.

Patent Publication 3 discloses low sulfurized ash, low phosphorus, low containing sulphurous base oils, boron containing ashless dispersants, molybdenum containing friction modifiers, metal containing detergents such as sulfonates, phenates or salicylates, and zinc dithiophosphate. Sulfur engine oil (engine oil composition) is disclosed. The molybdenum-containing friction modifiers include molybdenum diorgano-dithiocarbamate, molybdenum diorgano-dithiophosphate, molybdenum carboxylate, and Mo ₃ S ₇ ( trinuclear molybdenum compounds such as dtc) ₄ or Mo ₃ S ₄ (dtc) ₄ . In an operational embodiment, experimental data indicate that the lubricating oil composition has a particularly good high temperature oxidative stability and good friction reducing performance using the trinuclear molybdenum compound mentioned above.

As described above, the molybdenum containing compounds are particularly effective as friction modifiers included in lubricating oil compositions.

As known molybdenum containing compounds, molybdenum diorgano dithiocarbamate and molybdenum diorgano dithiophosphate are most commonly used. However, the molybdenum diorgano dithiocarbamate compound has a disadvantage in that it contains sulfur (S) in the molecular structure, and the molybdenum diorgano dithiophosphate compound contains phosphorus (P) in the molecular structure. Therefore, when lubricating oil is combusted in the internal combustion engine, toxic gases such as sulfur oxide gas and phosphorus oxide gas are produced, resulting in inactivation of the catalyst of the exhaust gas scrubbing apparatus. As described above, Patent Publication 3 describes that trinuclear molybdenum compounds such as Mo ₃ S ₇ (dtc) ₄ or Mo ₃ S ₄ (dtc) ₄ exhibit excellent friction modifying function (friction reduction function). However, such trinuclear molybdenum compounds contain sulfur atoms in the molecular structure of their ligand residues, i.e., dithiocarbamate, dtc, and further include other sulfur atoms directly attached to the molybdenum atoms. Nuclear molybdenum compounds inherently contain a relatively large amount of sulfur in the compound. Therefore, it is not preferred that the trinuclear molybdenum compound be used to be mixed into the lubricating oil composition if the purpose is to reduce the sulfur content in the oil composition.

Accordingly, it is an object of the present invention to provide a conventionally used friction reducing agent, for example molybdenum diorgano dithiocarbamate, which contains or does not contain relatively small amounts of sulfur and phosphorus. , A molybdenum-containing friction reducing agent which is preferably used in place of trinuclear molybdenum compounds such as molybdenum diorgano dithiophosphate, molybdenum carboxylate and Mo ₃ S ₇ (dtc) ₄ or Mo ₃ S ₄ (dtc) ₄ To provide.

The inventors have found that if a known molybdenum complex of a basic nitrogen-containing compound has a specially selected amount of alkenyl- or alkyl-succinimide or derivative thereof (known as ashless dispersant) and alkenyl- or alkyl-succinic acid ester (succinate) or It has been found that when mixed with its derivatives (known as ashless dispersants) and mixed in a lubricating oil composition, the friction reducing function of molybdenum composites, for example molybdenum-succinimide composites, has been found to be significantly improved.

The present invention has been invented on the basis of the novel findings of the inventors mentioned above. The lubricating oil compositions which contain the molybdenum complexes of the basic nitrogen-containing compounds mentioned above, but which do not contain succinimide or derivatives thereof (in addition no succinate or derivatives thereof), do not exhibit improved resistance to oxidation at high temperatures. However, it was further found that the oil composition showed little reduction in the coefficient of friction.

Accordingly, the present invention provides a lubricating oil composition for lubrication of an internal combustion engine having a sulfur content of 0.5 wt% or less, containing a base oil having a lubricating viscosity, and having the additive component of a) to e) below:

a) 0.5-5.0 weight percent ashless dispersant comprising alkenyl- or alkyl-succinimide or derivatives thereof;

b) 0.5-5.0 weight percent ashless dispersant comprising alkenyl- or alkyl-succinic acid esters or derivatives thereof;

c) molybdenum complex of basic nitrogen containing compound, 50-1,200 ppm by weight, based on molybdenum content;

d) alkaline earth metal containing detergent having a TBN of 10 to 400 mg · KOH / g, 0.05-1.0 wt% based on alkaline earth metal content; And

c) 0.05-0.5% by weight of anti-wear agents

The present invention further provides a method of operating an internal combustion engine mounted on a land vehicle using a fuel having a sulfur content of 0.001% by weight or less under lubrication with the lubricating oil composition according to the invention mentioned above.

Preferred embodiments of the invention are described below.

(1) The lubricating oil composition has a sulfur content of 0.01 to 0.2% by weight.

(2) The lubricating oil composition has a sulfur content of 0.05 to 0.12% by weight.

(3) The lubricating oil composition is a multi-grade engine oil which further contains a viscosity index improver and is classified into 0W5, 0W10, 0W15, 0W20, 0W30, 5W20, 5W30, 10W20, or 10W30.

(4) The lubricating oil composition comprises 1.0-4.0% by weight of component a) i.e. alkenyl- or alkyl-succinimide or derivatives thereof.

(5) The lubricating oil composition comprises 1.0-4.0% by weight of component b) ie alkenyl- or alkyl-succinic acid esters or derivatives thereof.

(6) The lubricating oil composition comprises component a) and component b) in a ratio of 1: 4 to 4: 1.

(7) Molybdenum composite of component c), i.e., basic nitrogen containing compound, contains less than 1% by weight of sulfur.

(8) Molybdenum composite of component c), i.e., basic nitrogen containing compound, contains 0.05 to 0.5% by weight of sulfur.

(9) Component c) is a molybdenum composite of succinimide.

(10) Component d) contains alkaline earth metal salicylate.

(11) The antiwear agent is zinc dialkyldithiophosphate.

(12) The lubricating oil composition further contains an antioxidant.

(13) The lubricating oil composition is used for lubrication of internal combustion engines operated using fuel oil having a sulfur content of 0.001% by weight or less.

The lubricating oil compositions of the present invention comprise molybdenum complexes of basic nitrogen-containing compounds together with known dispersants, i.e. alkenyl- or alkyl-succinimides or derivatives thereof and specific amounts of alkenyl- or alkyl-succinic acid esters (succinates) or derivatives thereof. Include. Therefore, the lubricating oil composition can be prepared to contain low levels of sulfur. Nevertheless, the lubricating oil compositions of the present invention exhibit a remarkably good friction reducing function.

Base oils and additives usable for the preparation of the lubricating oil compositions of the present invention will be described in more detail below.

Base oil

Base oils are mineral or synthetic oils which generally exhibit a dynamic viscosity of 2 to 50 mm ² / s at 100 ° C. There is no particular limitation on the properties and other properties of the mineral oil and the synthetic oil. However, the sulfur content of the base oil is less than 0.1% by weight. Preferably, the sulfur content is less than 0.03% by weight, more preferably less than 0.005% by weight.

The mineral oil is an oil obtained by treating the lubricating oil distillate of the mineral oil with solvent purification, hydrogenation, or a combination thereof. Particularly preferably hydrocracked oil having high hydrocracked oil (viscosity index in the range from 100 to 150, aromatic content up to 5% by weight, nitrogen content up to 50 ppm and sulfur content up to 50 ppm) Corresponding to). Particularly preferred are, for example, high viscosity index base oils having a viscosity index of 140-160 obtained by hydroisomerization of slack wax or GTL wax (gas to liquid).

Examples of synthetic oils (synthetic lubricating base oils) include poly-α-olefins, ie polymer compounds of α-oliphenes having 3-12 carbon atoms; Esters of alcohols having 4 to 18 carbon atoms and dibasic acids such as sebacic acid, azelaic acid or adipic acid, for example dioctyl sebacate Phosphorus dialkyl esters; Polyol esters which are esters of monobasic acids having 3-18 carbon atoms with 1,1,1-tri-methylpropane or pentaerythritol; And alkylbenzenes having alkyl groups having 9-40 carbon atoms. Synthetic oils contain little sulfur, have good oxidative stability and good heat resistance and produce a small amount of residual carbon and soot upon combustion. Therefore, the synthetic oil is preferably used for the lubricating oil composition of the present invention. Especially preferably, it is a poly-alpha-olefin from the viewpoint of the objective of this invention.

Each of the mineral oil and the synthetic oil may be used singly. However, if desired, two or more mineral oils may be used in combination, and two or more synthetic oils may be used in combination. The mineral oil and the synthetic oil may be used in combination in an optional ratio.

Ashless Dispersant

The lubricating oil compositions of the invention comprise at least two different ashless dispersants, i.e., alkenyl- or alkyl-succinimides or derivatives thereof (component a) and alkenyl- or alkyl-succinic acid esters or derivatives thereof (component b), respectively. -5.0 wt%, preferably 1.0-4.0 wt% (amount based on total amount of lubricating oil composition). Component a) and component b) are preferably included in a weight ratio of 1: 4 to 4: 1, more preferably 1: 2 to 2: 1.

Component a), ie alkenyl- or alkyl-succinimides or derivatives thereof, may be known alkenyl- or alkyl-succinimides or derivatives thereof. For example, alkenyl- or alkyl-succinimides derived from polyolefins or derivatives thereof can be used. Representative succinimides can be obtained by reaction between succinic anhydrides having substituents of high molecular weight alkenyl or alkyl and polyalkylene polyamines having an average nitrogen atom number of 4 to 10 (preferably 5 to 7). High molecular weight alkenyls or alkyls are preferably derived from polybutenes (particularly highly reactive polybutenes having vinylidene ends) having an average molecular weight of about 900 to 3,000.

The preparation of polybutenyl succinic anhydride through the reaction of polybutene with maleic anhydride is generally carried out by a chlorination process using a chlorine compound. The chlorination process is advantageous in terms of reaction yield. However, the reaction product obtained by the chlorination process contains a large amount (eg about 2,000 to 3,000 ppm) chlorine. In contrast, the reaction product contains an extremely low chlorine content (eg 0-30 ppm) if a thermal reaction without chlorine compounds is used. Therefore, it is preferable to prepare succinimide from polybutenyl succinic anhydride obtained by thermal reaction, whereby the chlorine content of the resulting succinimide is 0 to 30 ppm by weight. The succinimide can be reacted with boric acid, alcohols, aldehydes, ketones, alkylphenols, cyclic carbonates, organic acids and the like to provide modified succinimides. In particular, borate alkenyl- (or alkyl-) succinimides obtained by reaction with boric acid or boron containing compounds are advantageous in terms of thermal stability and oxidative stability.

The component b), ie the alkenyl- or alkyl-succinic acid esters or derivatives thereof, may be known alkenyl- or alkyl-succinic acid esters or derivatives thereof. For example, alkenyl- or alkyl-succinic esters derived from polyolefins or derivatives thereof can be used. Representative succinic esters can be prepared by the reaction between succinic anhydrides substituted with high molecular weight alkenyl or alkyl and alcohols containing, on average, 1 to 6 hydroxyl groups in one molecule. The high molecular weight alkenyl or alkyl is preferably derived from polybutenes (especially high reactive polybutenes having vinylidene ends) having an average molecular weight of about 900 to 3,000.

The lubricating oil composition of the present invention may comprise other ashless dispersants, such as alkenylbenzylamine ashless dispersants, in addition to ashless dispersant a) (ie component a)) and ashless dispersant b) (ie component b)).

Molybdenum complex of basic nitrogen-containing compound ( molybdenum complex )

The lubricating oil composition of the present invention may further comprise a molybdenum complex of the basic nitrogen-containing compound in an amount of 50-1,200 wt. Ppm based on molybdenum content. The molybdenum composite is known as a multifunctional additive. The molybdenum complex of the basic nitrogen-containing compound may contain a small amount of sulfur.

The molybdenum complex of the basic nitrogen-containing compound may act as an oxidation inhibitor, an anti-wear agent or a friction modifier in the lubricating oil composition.

The molybdenum complex of the basic nitrogen-containing compound may preferably be an oxymolybdenum complex obtained by the reaction of an acidic molybdenum compound with a basic nitrogen-containing compound. In this case, examples of the acidic molybdenum compound include molybdic acid, ammonium molybdate, and an alkali metal salt of molybdate, and examples of the basic nitrogen-containing compound include succinimide (suc- cin-imide, carboxylic amide, hydrocarbylamine, and Mannich basic compound. Further, examples of the molybdenum complex of the basic nitrogen-containing compound may include a molybdenum complex of succinimide and a molybdenum complex of secondary aliphatic amine.

The basic nitrogen-containing compound may be used after the reaction with a small amount of sulfur-containing compound, and in particular, a reaction product by sulfidation at low temperature of the molybdenum complex of succinimide may be used. The reaction product may then contain sulfur in a relatively small amount of less than 10% by weight. Such sulfooxymolybdenum complexes can be prepared according to the methods set forth in Examples C-H of US Pat. No. 6,562,765.

The lubricating oil composition of the present invention may further contain other molybdenum-containing compounds such as sulfooxymolybdenum dithiocarbamate, sulfooxymolybdene dithiophosphate and oxymolybdenum monoglyceride. It may include.

Alkaline Earth Metal-Containing Cleaner

The lubricating oil composition of the present invention may further comprise an alkaline earth metal-containing detergent having a TBN value in the range of 10 to 400 mg · KOH / g in an amount of 0.05-1.0% by weight based on alkaline earth metal. As the alkaline earth metal-containing detergent, a known detergent having a TBN value in the range of 10 to 400 mg · KOH / g may be used, and preferably, a calcium alkylsalicylate detergent may be used. The calcium alkylsalicylate detergent may be one containing an organic acid salt in an amount of preferably 0.2-7% by weight, more preferably 0.5-5% by weight, most preferably 1.0-3% by weight. The calcium alkyl salicylate detergent may preferably include an unsulfurized calcium alkyl-sali-cylate detergent having 14-18 carbon atom-containing alkyl groups. The unsulfated calcium alkyl salicylic trichloride detergent having 14-18 carbon atom-containing alkyl groups may be used together with the unsulfated calcium alkyl salicylic trichloride detergent having 20-28 carbon atoms-containing alkyl groups. Specifically, the unsulfated calcium alkylsalicylic trisalt cleaner having 14-18 carbon atom-containing alkyl groups is a nonsulfated calcium alkylsalicylic trisalt cleaner having an alkyl group having 14-18 carbon atoms-containing alkyl groups of at least 90 mole%. Unsulfated calcium alkylsalicylic trisalt cleaner having 20-28 carbon atom-containing alkyl groups also has the same meaning. That is, a non-sulfurized calcium alkyl salicylic trichloride detergent having 20 to 28 carbon atom-containing alkyl groups means a non-sulfurized calcium alkyl salicylic trichloride detergent having an alkyl group having 20 to 28 carbon atom-containing alkyl groups of at least 90 mole%. do.

The unsulfated calcium alkylsalicylate may preferably be a calcium salt of alkylsalicylic acid, which may be prepared from alkylphenols (produced by the reaction of α-olefins with preferred carbon atoms with phenols) by the Kolbe-Schmidt reaction. Typically, the calcium salt of alkylsalicylic acid can be overbased using lime and carbon dioxide, and thus can be in the form of overbased calcium salicylate.

In addition, the calcium salt of the alkyl salicylic acid may be prepared by a process of neutralizing phenol to generate the calcium salt and then performing carbonation.

The calcium alkylsalicylate detergent is preferably in the range of 0.2 to 7% by weight, preferably 0.5 to 5% by weight, more preferably 1.0 to 3% by weight, of the amount of the organic acid salt contained in the calcium alkylsalicylate detergent. It may be included in the lubricating oil composition of the present invention. Specifically, the calcium alkylsalicylate detergent is an organic acid metal salt (usually a soap component) dispersed in an oily medium and basic inorganic salt microparticles (eg calcium carbonate particles) aggregated around the organic acid metal salt. It may be an oily dispersion (oily dispersion) comprising a. Typically the dispersion may comprise an oily medium in an amount of 30 to 50% by weight. Even if the content of the calcium alkylsalicylate detergent is reduced, the content of the organic acid metal salt is adjusted so that the high tem-perature detergency of the lubricating oil composition (that is, the internal space retention of the engine operating at a high temperature) is not substantially lowered. Can be.

The alkaline earth metal-containing detergent may be an alkaline earth metal salt of an organic acid or phenol derivative having a carbon-nitrogen bond. The detergent may have a high TBN value regardless of the amount of sulfated ash when the amine compound is treated, wherein the amine compound has a base number derived from basic nitrogen elements. For example, metal salts of aminecarboxylic acids can be used, preferably unsulfurized alkylphenate (ie alkaline earth metal salts) having a Mannich base structure. The compound may be prepared by a process of obtaining an aminomethylated phenol through a Mannich reaction using alkylphenol, formaldehyde and an amine or an amine compound, and then neutralizing the reaction product with a base such as calcium hydroxide.

The alkaline earth metal-containing detergent may also be an alkaline earth metal salt of sulfonic acid (ie, sulfonate) obtained from petroleum sulfonic acid, alkylbenzenesulfonic acid or alkyltoluenesulfonic acid.

In addition, the alkaline earth metal-containing detergent may be an alkaline earth metal salt of sulfurized alkyl phenol, that is, sulfurized phenate.

Anti-wear agents ( anti - wear agent )

The lubricating oil composition of the present invention may further comprise an antiwear agent (component e) in an amount of 0.05-5.0% by weight. The anti-wear agent is not particularly limited but known sulfur-containing anti-wear agents as well as known phosphorus-containing anti-wear agents may be used. Examples of the sulfur-containing anti-wear agents include sulfurized olefins, polysulfide compounds, sulfurized esters, sulfurized alcohols, sulfurized amides, sulfurized oils. Sulfurized oil / fat, ashless dithiocarbamate, metal (non-molybdenum) dithiocarbamate, mercapto thiadiazole, mercapto benzothiadiazole -thiadiazole) and mercapto thiazoline. Examples of phosphorus-containing anti-wear agents include phos-phoric acid esters, phosphorous acid esters, thiophosphoric acid esters, amine salts thereof, and zinc dialkyldithiophosphates. metal salts thereof, including dialkyldithiophosphate, zinc dihydrocarbylphos-phate, zinc dialkylphosphate, and the like.

The antiwear agent, ie component e), may preferably be zinc dialkyldithiophosphate or zinc dihydrocarbyl phosphate. Such zinc phosphate anti-wear agents are known in the art and can be readily prepared by conventional processes. The zinc phosphate anti-wear agent may be preferably used at 0.01-0.12% by weight, but is preferably used at 0.01-0.06% by weight in consideration of the low phosphorus content and the sulfur content.

The zinc dialkyl dithio phosphate may preferably contain an alkyl group or an aryl group having a C _{3 -18} alkyl group having from 3-18 carbon atoms, and most preferably derived from a secondary alcohol having from 3-18 carbon atoms Alkyl group-containing zinc dialkyldithiophosphates or zinc dialkyldithiophosphates containing alkyl group mixtures derived from mixtures of primary alcohols having 3-18 carbon atoms and secondary alcohols having 3-18 carbon atoms, Both compounds are particularly effective at reducing wear. Zinc dialkyldithiophosphates derived from primary alcohols exhibit good high temperature resistance. These zinc dialkyldithiophosphates can be used alone or together in the form of a mixture mainly comprising those derived from secondary alcohols and / or those derived from primary alcohols.

Antioxidants oxidation inhibitor )

The lubricating oil composition of the present invention may comprise 0.01-5% by weight of antioxidant, preferably 0.1-3% by weight. As the antioxidant, an antioxidant phenol compound (phenolic oxidation inhibitor) and an antioxidant amine compound (amine oxidation inhibitor) may be used. Lubricating oil compositions having a low sulfide ash content, a low phosphorus content and a low sulfur content may degrade high temperature cleansing, antioxidant and anti-wear properties due to the reduced content of metal-containing detergents and zinc dithiophosphate. Therefore, the lubricating oil composition of the present invention may preferably contain an antioxidant for improving this phenomenon and enhancing the effect.

Preferred examples of the antioxidant may include diarylamine antioxidants and hindered phenol antioxidants. Such antioxidants may also function to improve high temperature cleanability. Diarylamine antioxidants have the advantage of providing base water derived from nitrogen atoms, while hindered phenolic antioxidants have the advantage of not causing NO _x gas.

Examples of hindered phenol antioxidants include 2,6-di-t-butyl-p-cresol, 4,4'-methylenebis (2,6-di-t-butylphenol), 4,4'-methylenebis (6 -t-butylphenol-o-cresol), 4,4'-isopropylidenebis (2,6-di-t-butylphenol), 4,4'-bis (2,6-di-t-butylphenol ), 2,2'-methylenebis (4-methyl-6-t-butylphenol), 4,4'-thiobis (2-methyl-6-t-butylphenol), 2,2'-thio-di Ethylenebis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], octyl 3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate And octadecyl 3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate and octyl 3- (3,5-t-butyl-4-hydroxy-3-methylphenyl) propionate Etc. may be included.

Examples of diarylamine antioxidants include mixed alkyl group-containing alkyldiphenylamines having 4 to 9 carbon atoms, p, p'-dioctyldiphenylamine, phenyl-α-naphthylamine, phenyl-α-naphthylamine, alkylation Β-naphthylamine and alkylated phenyl-α-naphthylamine, and the like.

Each of the hindered phenolic antioxidants and the diarylamine antioxidants may be used alone or in combination, and preferably other oil soluble oxida-tion inhibitors may be used with the antioxidants.

Other additives

The lubricating oil composition of the present invention may further include an alkali metal borate hydrate for improving stability at high temperature and base number. Alkali metal borate hydrates can be prepared according to the methods set forth in US Pat. Nos. 3,929,650 and 4,089,790. The alkali metal borate hydrate is, for example, an alkali metal borate prepared by a process of carbonizing a neutral alkali metal or alkaline earth metal sulfone salt in the presence of an alkali metal hydroxide to obtain an overbased sulfonate and reacting it with boric acid. It may be in the form of a microparticle-containing dispersion of hydrate. At this time, it is preferable to add an ashless dispersant such as succinimide to the reaction mixture in the carbonization reaction. The alkali metal is preferably potassium or sodium, and the alkali metal borate hydrate may be a dispersion of KB ₃ O ₅ H ₂ O particles having a particle size of 0.3 μm or less dispersed in the presence of neutral calcium sulfonate and succinimide. have. In addition, potassium may be substituted for sodium in consideration of resistance to hydrolysis.

The lubricating oil composition of the present invention may comprise a viscosity index improver in an amount of up to 20% by weight, preferably 1 to 20% by weight. Examples of the viscosity index improver include polyalkyl methacrylate, ethylene-propylene copol-ymer, styrene-butadiene copolymer and polyisoprene. May be included. Preferably, a viscosity index improver and a multifunctional viscosity index improver prepared by imparting dispersibility to the polymer may be used, and these viscosity index improvers may be used alone or in combination.

The lubricating oil composition of the present invention may further comprise small amounts of various auxiliary additives. Examples of such auxiliary additives are: benzotriazol compounds and thiadi-azol compounds, which act as metal deactivating agents; And co-pol-y-mers and polyoxyethylene-alkylphenyl ethers, which act as anti-rust and anti-emulsifying agents, and copolymers of ethylene oxide and propylene oxide. nonionic polyoxy-alkyl-ene surface active agents such as of eth-yl-ene oxide and propylene oxide. In addition, various compounds that act as foam inhibitors, pour point depressants and the like can be used together.

The coadditive may be included in the lubricant composition in an amount of 3% by weight or less, preferably 0.001-3% by weight.

Example

(1) Preparation of lubricating oil composition Test oil )

A lubricating oil composition having a low sulfur content (0.5 wt% or less) for oil performance evaluation was prepared as follows using base oil and additives. The lubricating oil composition was prepared to exhibit a viscosity grade (SAE viscosity grade) of 5W30 by the addition of a viscosity index improver.

(2) base oils and additives

1) base oil (a mixture of the base stock A and the base stock B in a weight ratio of 46:54)

Base stock A: Hydrocracked base stock showing a dynamic viscosity of 6.4 mm ² / s (100 ° C.), a viscosity index of 132, a saturated component content of 92 wt% and a sulfur content of less than 0.001 wt%

Base stock B: Hydrocracked base stock showing a dynamic viscosity of 4.1 mm ² / s (100 ° C.), a viscosity index of 127, a saturated component content of 92 wt% and a sulfur content of less than 0.001 wt%

2) additive

Ashless Dispersant A: Polybutene (average molecular weight about 2,200) and maleic anhydride were thermally reacted to obtain polyisobutylenesuccinic anhydride, about 2 moles of polyisobutenylsuccinic anhydride and 6.5 (average) per molecule Ethylene carbonate post-treatment succinate prepared by the process of reacting polyalkylene polyamine with nitrogen atom to obtain bis-type succinimide, and then reacting bis-type succinimide with ethylene carbonate Imide dispersant (nitrogen content: 0.85% by weight).

Ashless dispersant B: Thermal reaction of polybutene (average molecular weight about 1,000) with maleic anhydride to obtain polyisobutenylsuccinic anhydride followed by about 1.14 moles of polyisobutenylsuccinic anhydride and 1 mole pentaerythritol Alkenylsuccinic ester (TAN: 5 mg · KOH / g) prepared by the process of reacting ().

Mo complex of succinimide: A mono-type alkenylsuccinimide derived from polyisobutene having an average molecular weight of about 1,000 and molybdate are reacted to obtain a molybdenum complex A product prepared by reacting with a small amount of sulfur (Mo content: 4.5 wt%, N content: 2.1 wt%, S content: 0.16 wt%)

MoDTC: sulfoxymolybdenum dialkylthiocarbamate (Mo content: 10 wt%, S content: 11 wt%)

Ca-containing detergent A: calcium monoalkylsalicylate (alkyl containing about 14-18 carbon atoms, over-base degree: 2.0, Ca content: 6.2% by weight, S content: 0.12% by weight)

Ca-containing detergent B: calcium monoalkylsalicylate (alkyl containing about 20-28 carbon atoms, over-base degree: 8.2, Ca content: 11.4 wt%, S content: 0.17 wt%)

Ca-containing cleaner C: calcium sulfonate (neu-tral type, Ca content: 2.4 wt%, sulfur content: 2.7 wt%)

ZnDTP: zinc dialkyldithiophosphate (P content: 7.2 wt%, S content: 14.4 wt%, derived from a mixture of secondary alcohols having 4 carbon atoms and secondary alcohols having 6 carbon atoms)

Antioxidant: Mixture of dialkyldiphenylamine antioxidants and hindered phenol propionate antioxidants

Viscosity Index Enhancer (VII): non-dispersant type ethylene-propylene copolymer (Paratone 8057)

(3) coefficient of friction friction coefficient ) Measure

The coefficient of friction was measured using a high frequency reciprocating rig (HFRR) under the following conditions:

Oil temperature: 105 ° C., load: 400 g, friction length: 1,000 μm, reciprocating frequency: 20 Hz, test duration: 1 hour

(4) high temperature Deposits  Generation suppression evaluation

The ability to inhibit the formation of hot deposits was evaluated using a hot tube tester (HTT) under the conditions described below:

The glass tube (inner diameter: 2 mm) was placed vertically in the heater block. Test oil and air were fed to the tube through the bottom at a feed rate of 0.31 cc / hour to 10 cc / min. This procedure was performed for 16 hours while maintaining the heater temperature at 280 ° C. The glass tube was then removed from the heater block, washed with petroleum ether and dried. Deposits adhered to the inner surface of the glass tube were observed and scored according to overuse evaluation.

Overuse evaluation was performed according to a known method based on 10 points. High scores indicate a high ability to inhibit the formation of deposits.

(5) Composition and measurement and evaluation result of test oil

Table 1 lists the test results of the test oils.

Base oils / additives Example 1 Comparative Example 1 Comparative Example 2 Ashless Dispersant A (wt%) 3.0 5.5 3.0 Ashless Dispersant B (wt%) 2.5 - 2.5 Succinimide Mo-Composite (Mo weight ppm) 220 220 - MoDTC (Mo weight ppm) - - 220 Ca cleaner A (Ca wt%) 0.19 0.19 0.19 Ca cleaner B (CA wt%) 0.06 0.06 0.06 Ca cleaner C (Ca wt%) 0.01 0.01 0.01 ZnDTP (P wt%) 0.04 0.04 0.04 Antioxidant (wt%) 1.0 1.0 1.0 VII (% by weight) 5.0 5.0 5.0 Base oil Balance Balance Balance S content (% by weight) 0.11 0.11 0.13 Coefficient of friction 0.05 0.12 0.05 HTT high score 7.5 7.5 5.5

The test results listed in Table 1 indicate the following:

The lubricating oil composition of the present invention (test oil of Example 1) comprising a succinimide-Mo composite, a succinimide dispersant (ashless dispersant A) and a succinic acid ester dispersant (ashless dispersant B), inhibited the formation of the same high temperature deposit. Lubricant compositions (test oils of Comparative Example 1), which showed the ability, but included a combination of the succinimide-Mo composite and the succinimide dispersant (ashless dispersant A) but did not include the succinic acid ester dispersant (ashless dispersant B) ), It showed a significantly lower coefficient of friction. The test oil of Comparative Example 2 prepared using the same amount of MoDTC (sulfoxy molybdenum dialkyldithiocarbamate) in place of the succinimide-Mo composite exhibited the same coefficient of friction but was not good at inhibiting the formation of high temperature deposits. Appeared.

Claims (15)

A lubricating oil composition for lubricating internal combustion engines having a sulfur content of 0.5% by weight or less, containing a base oil having a lubricating viscosity, and having the additive component of a) to e) below:
a) 0.5-5.0 weight percent ashless dispersant comprising alkenyl- or alkyl-succinimide or derivatives thereof;
b) 0.5-5.0 weight percent ashless dispersant comprising alkenyl- or alkyl-succinic acid esters or derivatives thereof;
c) molybdenum complex of basic nitrogen containing compound, 50-1,200 ppm by weight, based on molybdenum content;
d) alkaline earth metal containing detergent having a TBN of 10 to 400 mg · KOH / g, 0.05-1.0 wt% based on alkaline earth metal content; And
c) 0.05-0.5 weight percent anti-wear agent. The method of claim 1,
The sulfur content is a lubricant composition, characterized in that the range of 0.01 to 0.2% by weight. The method of claim 1,
The sulfur content is a lubricating oil composition, characterized in that the range of 0.05 to 0.12% by weight. The method of claim 1,
The lubricating oil composition is a lubricating oil composition, characterized in that it is a multi-grade engine oil further comprises a viscosity index improver classified into 0W5, 0W10, 0W15, 0W20, 0W30, 5W20, 5W30, 10W20, or 10W30. The method of claim 1,
The component a) is a lubricant composition, characterized in that it comprises in an amount of 1.0-4.0% by weight. The method of claim 1,
The component b) is a lubricant composition, characterized in that it comprises in an amount of 1.0-4.0% by weight. The method of claim 1,
The ratio of component a) to component b) is in the range of 1: 4 to 4: 1. The method of claim 1,
The component c) contains less than 1% by weight of sulfur. The method of claim 1,
The component c) comprises sulfur in the range of 0.05 to 0.5% by weight. The method of claim 1,
Said component c) is a molybdenum composite of succinimide. The method of claim 1,
The component d) is a lubricating oil composition, characterized in that it contains alkaline earth metal salicylate. The method of claim 1,
The anti-wear agent is a lubricant composition, characterized in that zinc dialkyldithiophosphate (zinc dialkyldithiophosphate). The method of claim 1,
The lubricant composition is a lubricant composition, characterized in that it further comprises an antioxidant. The method of claim 1,
The lubricating oil composition is used for lubricating an internal combustion engine operated using fuel oil having a sulfur content of 0.001% by weight or less. A method for operating an internal combustion engine mounted on a land vehicle using fuel having a sulfur content of 0.001% by weight or less under lubrication with the lubricating oil composition of claim 1.