JP5291284B2 - Lubricating oil composition - Google Patents

Abstract

The present invention relates to a method of lubricating a passenger car motor vehicle engine having a rotating tappet, comprising lubricating the engine with a lubricating oil composition having up to 0.09 wt % phosphorus, 0.4 wt % sulphur and 1.0 wt % sulphated ash, and being substantially free of friction-modifier.

Description

  The present invention relates to a passenger car automobile lubricating oil composition. In particular, but not exclusively, the present invention relates to passenger car automotive lubricant compositions that exhibit improved wear performance.

Lubricating oil compositions used to lubricate internal combustion engines include a base oil of lubricating viscosity, or a mixture of such oils, and additives used to improve the performance characteristics of the oil. For example, additives are used to improve detergency, reduce engine wear, provide oxidation stability, reduce friction loss, increase fuel economy, and inhibit corrosion. Certain additives, such as dispersant-viscosity modifiers, offer many benefits. Other additives improve one property of the lubricating oil but are detrimental to another property.
Friction modifiers, such as molybdenum-containing compounds, and / or organic friction modifiers, such as glycerol monooleate, are used in passenger cars to reduce friction between moving engine parts and improve fuel economy. Improvements have been known for many years.
For example, U.S. Pat. Nos. 4,164,473 and 4,479,883, European Patent No. 13469, and British Patent No. 2068380 disclose various oil-soluble molybdenum-containing compounds that are suitable as friction reducing additives for passenger car vehicles. US Pat. No. 6,723,685 discloses a composition comprising a molybdenum additive and an organic friction modifier in an amount sufficient to pass the sequence VIB fuel economy test.
In addition, International Patent Application No. WO-A-03 / 064568 discloses the use of friction modifiers as additives in lubricating oil compositions to reduce internal combustion engine wear.
In addition, as the acceptable levels of sulfated ash, phosphorus and sulfur (SAPS) emissions from passenger car vehicles decrease, the level of additives such as metal dialkyldithiophosphates that can be used is reduced. This results in an imbalance of additive combinations that are commonly used in passenger car vehicles and allows formulators to consider new additive combinations to meet the requirements of vehicle manufacturers.
Passenger car automobile internal combustion engines have many different conformations with different lubrication requirements. One problem associated with low SAPS lubricants is increased engine wear due to reduced phosphorus levels that limit the amount of normal antiwear additives that can be used. This problem is particularly apparent with rotating tappets in valve trains, which can stall when lubricated with low SAPS lubricants and can exhibit unacceptable wear.
US 2003 / 0148895A discloses a lubricating oil composition aimed at reducing wear in the Peugeot TU3M scuffing test. This test is aimed at examining the wear of cams and tappets of internal combustion engines. The disclosure in this document preferably cams relatively high levels of boron (derived from a boronated dispersant), enriched with a significant amount of molybdenum (eg, derived from a trinuclear molybdenum additive). And what is needed to reduce tappet wear to an acceptable level.
WO 03/064568 A2 discloses a lubricating oil composition for use with a low sulfur fuel in an internal combustion engine. Lubricants result in increased wear (cam nose wear and overall wear) when tested in the sequence IVA test. This is because the molybdenum concentration and boron concentration are lowered. Other adverse effects are also evident.
The preferred embodiment of the present invention seeks to provide a method of lubricating an engine containing a rotating tappet to provide improved wear performance, especially with low SAPS formulations.

The present invention provides a method of lubricating an internal combustion engine having a cam and a rotating tappet associated with the cam, the method being specified by claim 1 according to the description of the invention. Preferred and optional features of the invention are the subject matter of the claims that are directly or indirectly dependent on claim 1.
The invention, in another aspect, provides a combination comprising an internal combustion engine having a rotating tappet and a lubricating composition, the lubricating composition having the characteristics specified for the lubricating composition of claim 1.
In yet another aspect, the present invention provides the use of a lubricating oil composition to pass the 650 hour Volkswagen (trademark) RNT test (PV1473 draft), and optionally the VW (trademark) PV1451 FE test. The lubricating oil composition has one or more features of the claims specified for the lubricating oil of claim 1 and, optionally, dependent directly and / or indirectly on claim 1.

In a first further aspect, the present invention provides an engine with a lubricating oil composition having up to 0.09 wt% phosphorus, up to 0.4 wt% sulfur and up to 1.0 wt% sulfated ash, based on the total weight of the composition. To provide a method for lubricating a passenger car automobile engine having a rotating tappet, the lubricating oil composition comprising an oil of lubricating viscosity and substantially free of a friction modifier.
In a second further aspect, the present invention provides an engine with a lubricating oil composition having up to 0.09 wt% phosphorus, up to 0.4 wt% sulfur and up to 1.0 wt% sulfated ash, based on the total weight of the composition. A method for reducing wear of a passenger car engine having a rotating tappet, wherein the lubricating oil composition comprises an oil of lubricating viscosity and is substantially free of a friction modifier.
In a third further aspect, the present invention provides an engine with a lubricating oil composition having up to 0.09 wt% phosphorus, up to 0.4 wt% sulfur and up to 1.0 wt% sulfated ash, based on the total weight of the composition. Providing a method of reducing engine wear with rotating tappets and maintaining fuel economy performance, the composition comprising an oil of lubricating viscosity and substantially comprising a friction modifier Absent.
In a fourth further aspect, the present invention has up to 0.09 wt.% Phosphorus, up to 0.4 wt.% Sulfur and up to 1.0 wt.% Sulfated ash, based on the total weight of the engine and composition having a rotating tappet. A combination of lubricating oil compositions is provided, the lubricating oil composition comprising an oil of lubricating viscosity and substantially free of a friction modifier.
In a fifth further aspect, the present invention is based on the total weight of the composition to pass the 650 hour VW RNT engine test (PV1473 draft), up to 0.09 wt% phosphorus, up to 0.4 wt% sulfur and Provided is the use of a lubricating oil composition having a sulfated ash content of up to 1.0% by weight, the composition comprising an oil of lubricating viscosity and substantially free of a friction modifier.
In a sixth further aspect, the present invention relates to up to 0.09 wt% phosphorus, based on the total weight of the composition to pass both the VW PV1451 FE test and the 650 hour VW RNT engine test (PV1473 draft), Provided is the use of a lubricating oil composition having up to 0.4 wt% sulfur and up to 1.0 wt% sulfated ash, the composition comprising an oil of lubricating viscosity and substantially free of friction modifiers.

The engine of the present invention is an internal combustion engine, such as a passenger car automobile engine. The engine may be a spark ignition engine or a compression ignition engine.
Oils of lubricating viscosity useful in the practice of the present invention, measured at 100 ° C., from about 2 mm ² / sec (centistokes) to about 40 mm ² / sec, especially from about 3 mm ² / sec to about 20 mm ² / sec, Most preferably, it may have a viscosity from about 5 mm ² / sec to about 15 mm ² / sec.
Natural oils include animal and vegetable oils (eg, castor oil, lard oil), liquid petroleum and paraffinic, naphthenic and mixed paraffin-naphthene hydrorefined, solvent-treated or acid-treated mineral oils. Oils of lubricating viscosity derived from coal or shale can also be used as useful base oils.
Synthetic lubricating oils include hydrocarbon oils and halo-substituted hydrocarbon oils, such as polymerized olefins and copolymerized olefins (eg, polybutylene, polypropylene, propylene-isobutylene copolymer, chlorinated polybutylene, poly (1-hexene), poly (1- Octene), poly (1-decene)), alkylbenzenes (eg, dodecylbenzene, tetradecylbenzene, dinonylbenzene, di (2-ethylhexyl) benzene), polyphenyls (eg, biphenyl, terphenyl, alkylated polyphenols), And alkylated diphenyl ethers and alkylated diphenyl sulfides and their derivatives, analogs and homologues.

Alkylene oxide polymers and copolymers and their derivatives (the terminal hydroxyl groups of which have been modified by esterification, etherification, etc.) constitute another class of known synthetic lubricating oils. These are polyoxyalkylene polymers prepared by polymerization of ethylene oxide or propylene oxide, and alkyl and aryl ethers of polyoxyalkylene polymers (eg, methyl-polyisopropylene glycol ether having a molecular weight of 1000 or a molecular weight of 1000-1500 And the monocarboxylic and polycarboxylic acid esters thereof, for example, tetraethylene glycol acetate, mixed C ₃ -C ₈ fatty acid esters and C ₁₃ oxo acid diesters.
Another suitable class of synthetic lubricants are dicarboxylic acids (eg, phthalic acid, for example) with various alcohols (eg, butyl alcohol, hexyl alcohol, dodecyl alcohol, 2-ethylhexyl alcohol, ethylene glycol, diethylene glycol monoether, propylene glycol). Including esters of succinic acid, alkyl succinic acid and alkenyl succinic acid, maleic acid, azelaic acid, suberic acid, sebacic acid, fumaric acid, adipic acid, linoleic acid dimer, malonic acid, alkylmalonic acid, alkenylmalonic acid) . Specific examples of such esters include dibutyl adipate, di (2-ethylhexyl) sebacate, di-n-hexyl fumarate, dioctyl sebacate, diisooctyl azelate, diisodecyl azelate, dioctyl phthalate, didecyl phthalate, Diaicosyl sebacate, 2-ethylhexyl diester of linoleic acid dimer, and a complex ester formed by reacting 1 mole of sebacic acid with 2 moles of tetraethylene glycol and 2 moles of 2-ethylhexanoic acid Is mentioned.

Esters useful as synthetic oils also include C ₅ -C ₁₂ monocarboxylic acids and polyols and polyol esters such as those made from neopentyl glycol, trimethylolpropane, pentaerythritol, dipentaerythritol and tripentaerythritol. It is done.
Silicon-based oils such as polyalkyl-, polyaryl-, polyalkoxy- or polyaryloxysilicone oils and silicate oils constitute another useful class of synthetic lubricants. Such oils include tetraethyl silicate, tetraisopropyl silicate, tetra- (2-ethylhexyl) silicate, tetra- (4-methyl-2-ethylhexyl) silicate, tetra- (p-tert-butyl-phenyl) silicate, hexa- Examples include (4-methyl-2-ethylhexyl) disiloxane, poly (methyl) siloxane, and poly (methylphenyl) siloxane. Other synthetic lubricating oils include liquid esters of phosphorus-containing acids (eg, tricresyl phosphate, trioctyl phosphate, diethyl ester of decylphosphonic acid) and polymeric tetrahydrofurans.
Another example of a base oil is a synthetic light oil (“GTL”) base oil, that is, a base oil is a Fischer-Tropsch synthetic hydrocarbon made from synthesis gas containing hydrogen and carbon monoxide using a Fischer-Tropsch catalyst. Oil derived from may be used. These hydrocarbons typically require further processing in order to be useful as a base oil. For example, they may be hydroisomerized by methods known in the art; hydrocracked and hydroisomerized; may be dewaxed; or hydroisomerized and dewaxed May be.
The definitions of base stock and base oil in the present invention can be found in American Petroleum Institute (API) publication 1509 “Engine Oil Licensing and Authorization System”, Volume 15, April 2002, Appendix E, November 2004 The same. The publication categorizes base stocks as follows:
a) Group I base stocks contain less than 90% saturates and / or more than 0.03% by weight sulfur and have a viscosity index greater than 80 and less than 120 using the test methods specified in Table 1.
b) Group II base stocks contain 90% or more of saturates and 0.03% or less by weight of sulfur and have a viscosity index of 80 and less than 120 using the test methods specified in Table 1.
c) Group III base stocks contain 90% or more of saturates and 0.03% by weight or less of sulfur and have a viscosity index of 120 or more using the test method specified in Table 1.
d) Group IV base stock is polyalphaolefin (PAO).
e) Group V base stock includes all other base stocks not included in Group I, II, III, or IV.

Table 1 Analysis method for base feedstock

The oil of lubricating viscosity of the present invention may comprise a Group I, Group II, Group III, Group IV or Group V base stock or a base oil blend of said base stock.
The oil of lubricating viscosity of the present invention preferably includes at least a portion of one or more Group IV base feedstocks. Suitably, the lubricating oil composition of the present invention comprises at least 25 wt%, preferably at least 35 wt%, more preferably at least 40 wt% Group IV base stock, based on the total weight of the composition. Suitably, the lubricating oil composition of the present invention is less than 85 wt%, preferably less than 75 wt%, more preferably less than 60 wt%, especially less than 55 wt% Group IV base, based on the total weight of the composition Contains raw oil.
The oil of lubricating viscosity of the present invention preferably comprises at least a portion of one or more Group III base feedstocks. Suitably, the lubricating oil composition of the present invention comprises at least 15 wt%, preferably at least 20 wt%, more preferably at least 25 wt% Group III base stock, based on the total weight of the composition. Suitably, the lubricating oil composition of the present invention comprises less than 80 wt%, preferably less than 60 wt%, most preferably less than 50 wt% Group III base stock, based on the total weight of the composition.
The lubricating composition of the present invention may comprise one or more Group V ester base feedstocks. Suitably, the lubricating composition comprises less than 25 wt%, preferably less than 10 wt%, more preferably 5 wt% or less of the ester base stock based on the total weight of the composition. Suitably, the lubricating oil composition of the present invention comprises at least 1% by weight, preferably at least 1.5% by weight, more preferably at least 3% by weight of an ester base stock.
It should be noted that any of the above base stocks may be provided to the composition as a separate component for blending. Also, any or all of the base stock may be provided to the composition as a diluent for another component of the lubricating oil composition.
Substantially free of friction modifiers means that the lubricating oil composition is less than 0.1% by weight, preferably less than 0.05% by weight (eg 0-0.4% by weight) or less than 0.04% by weight , preferably less than 0.01% by weight. It should be noted that it is defined herein to mean including, for example, 0-0.0075 wt%, most preferably no (0 wt%) friction modifier.

Friction modifier means a boundary lubricant additive that lowers the coefficient of friction and thus improves fuel economy and includes, but is not necessarily limited to, the following types of compounds:
(1) Organic, ashless (metal free), nitrogen free organic friction modifiers include esters produced by reacting carboxylic acids and acid anhydrides with alkanols. Such friction modifiers include aliphatic carboxylic acids, aliphatic carboxylic acid esters of polyols, such as glycerol esters of fatty acids, such as glycerol oleate, boric acid esters of glycerol fatty acid monoesters, long-chain polymers with diols. Esters of carboxylic acids such as butanediol esters of dimerized unsaturated fatty acids, aliphatic phosphonates, aliphatic phosphates, aliphatic thiophosphates, aliphatic thiophosphonates, aliphatic thiophosphates and oxazoline compounds. Aliphatic groups usually contain at least 8 carbon atoms so that the compound is preferably oil-soluble. Esters of carboxylic acids and anhydrides with alkanols are described in US Pat. No. 4,702,850. Examples of other common organic friction modifiers are M. Belzer “Journal of Tribology” (1992), 114, 675-682 and M. Belzer and S. Jahanmir “Lubrication Science” (1988), 1 Volume 3, page 3-26.
(2) Ashless amine friction modifiers include oil-soluble aliphatic amines, alkoxylated mono- and di-amines and aliphatic fatty acid amides. One common class of nitrogen-containing friction modifiers that do not contain such metals includes ethoxylated amines. These amines are, for example, in the form of adducts or reaction products with boron compounds such as boron oxides, boron halides, metaborates, boric acid or mono-, di- or tri-alkyl borate esters. May be. Other amine friction modifiers include alkoxylated alkyl-substituted mono-amines, diamines and alkyl ether amines such as ethoxylated tallow amine and ethoxylated tallow ether amine and aliphatic carboxylic ester-amides. Examples of fatty acid esters and amides as friction modifiers are disclosed in US Pat. No. 3,933,659.

(3) Additive that adheres molybdenum disulfide. Such molybdenum compounds include sulfur-containing, organic molybdenum compounds such as dithiocarbamates, dithiophosphates, dithiophosphinates, xanthates, thioxanthates, alkylthioxanthates and sulfides. Examples of such molybdenum compounds include acidic molybdenum compounds that react with basic nitrogen as measured by ASTM test D-664 or D-2896 titration operation and are typically hexavalent. Such compounds include molybdate, ammonium molybdate, sodium molybdate, potassium molybdate, and other alkaline earth metal molybdates and other molybdenum salts, such as sodium hydrogen molybdate, MoOCl ₄ , MoO ₂ Br ₂ , Mo ₂ O ₃ Cl ₆ , molybdenum trioxide and similar molybdenum compounds.
The lubricating oil composition of the present invention is preferably less than 1.0 wt% sulfated ash, preferably less than 0.9 wt%, more preferably less than 0.8 wt%, especially less than 0.7 wt%, based on the total weight of the composition. Contains sulfated ash. Advantageously, the lubricating oil composition of the present invention comprises no more than 0.6% by weight sulfated ash as measured using ASTM D874.
The lubricating oil composition of the present invention suitably comprises less than 0.09 wt%, preferably less than 0.08 wt%, more preferably less than 0.07 wt% phosphorus, based on the total weight of the composition. Advantageously, the lubricating oil composition of the present invention comprises 0.06 wt% or less phosphorus, as measured using ASTM D4951, based on the total weight of the composition.
The lubricating oil composition of the present invention is suitably less than 0.4 wt%, preferably less than 0.3 wt%, more preferably 0.2 wt%, as measured using ASTM 5185 or ASTM 2622, based on the total weight of the composition. Containing less than% sulfur.
The lubricating oil composition of the present invention suitably has a total alkali number (TBN) of 13 or less, preferably less than 10, more preferably 4-9, as measured using ASTM D2986.
The lubricating oil composition of the present invention may contain additional conventional additives. Examples of suitable additional additives are given in the section below.

Metal-containing or ash-forming detergents act as both detergents to reduce or remove deposits and as both acid neutralizers or rust inhibitors, thereby reducing wear and corrosion and extending engine life. The detergent generally includes a polar head with a long hydrophobic tail. The polar head includes a metal salt of an acidic organic compound. Salts may contain substantially stoichiometric amounts of metals, in which case they are usually described as normal or neutral salts, typically having a total alkali number or TBN of 0 to 80 (according to ASTM D2896). Will be able to measure). Large amounts of metal bases can be incorporated by reacting excess metal compounds (eg, oxides or hydroxides) with acid gases (eg, carbon dioxide). The resulting overbased detergent comprises a neutralized detergent as the outer layer of a metal base (eg, carbonate) micelle. Such overbased detergents may have a TBN of 150 or more, and typically will have a TBN of 250 to 450 or more.
Detergents that can be used in the lubricating oil compositions of the present invention include oil-soluble neutral sulfonates and overbases of metals, particularly alkali metals or alkaline earth metals such as barium, sodium, potassium, lithium, calcium, and magnesium. Sulfonated sulfonates, phenates, sulfurized phenates, thiophosphonates, salicylates, and naphthenates and other oil-soluble carboxylates. The most commonly used metals are calcium and magnesium (both may be present) and calcium and / or a mixture of magnesium and sodium. Particularly useful metal detergents are neutral and overbased calcium or magnesium sulfonates with a TBN of 20 to 450, neutral and overbased calcium or magnesium phenates and sulfurized phenates with a TBN of 50 to 450 and from 20 Neutral and overbased magnesium or calcium salicylates with up to 450 TBN. Combinations of detergents (whether overbased or neutral or both) may be used. Mixed surfactant systems such as those described in U.S. Patent Nos. 6,153,565, 6,281,179, 6,429,178, and 6,429,179 as generally useful detergents in formulations of lubricating oil compositions For example, “hybrid” detergents made with phenate / salicylate, sulfonate / phenate, sulfonate / salicylate, sulfonate / phenate / salicylate.

The detergent may be present in any suitable amount within the limits provided by the maximum sulfated ash level and sulfur level of the lubricating oil composition of the present invention. Detergents are measured as sulfated ash (SASH) content from about 0.05% to about 0.30%, such as from about 0.07% to about 0.25%, more preferably from about 0.8% to about 0.22%. Of calcium may be used in an amount to provide the lubricating oil composition.
Ashless dispersants include a hydrocarbon backbone of an oil-soluble polymer having one or more functional groups that can associate with the particles to be dispersed. Typically, the polymer backbone is functionalized with an amine polar moiety, an alcohol polar moiety, an amide polar moiety, or an ester polar moiety, often via a bridge group. Ashless dispersants include, for example, oil-soluble salts, esters, amino-esters, amides, imides, and oxazolines of long-chain hydrocarbon-substituted monocarboxylic acids and dicarboxylic acids or their anhydrides; thiocarboxylates of long-chain hydrocarbons Derivatives; long chain aliphatic hydrocarbons with directly attached polyamines; and Mannich condensation products produced by condensing long chain substituted phenols with formaldehyde and polyalkylene polyamines.
The oil soluble polymer hydrocarbon backbone of these dispersants is typically an olefin polymer or polyene, especially a majority (ie, greater than 50 mole percent) C ₂ -C ₁₈ olefin (eg, ethylene, propylene, butylene). , Isobutylene, pentene, octene-1, styrene), typically derived from polymers containing C ₂ -C ₅ olefins. The oil-soluble polymer hydrocarbon backbone is a homopolymer (eg, polypropylene or polyisobutylene) or a copolymer of two or more such olefins (eg, a copolymer of ethylene and an alpha-olefin such as propylene or butylene, or two A copolymer of different alpha-olefins). Other copolymers include copolymers in which a small molar amount, for example 1 to 10 mol%, of the copolymer monomer is an α, ω-diene, such as a C ₃ -C ₂₂ nonconjugated diolefin (eg, a copolymer of isobutylene and butadiene, or And copolymers of ethylene, propylene and 1,4-hexadiene or 5-ethylidene-2-norbornene). Polyisobutenyl (Mn400-2500, preferably 950-2200) succinimide dispersant is preferred. The lubricating oil composition of the present invention preferably comprises 0.005% to 0.08%, preferably 0.01% to 0.08%, most preferably about 0.05% to 0.08% total nitrogen. It is preferred that substantially all of the nitrogen in the lubricating oil composition is provided by the dispersant.

The lubricating oil composition of the present invention may contain one or more boron compound-treated dispersants. Such dispersants can generally be treated with boron compounds by conventional means such as taught in US Pat. Nos. 3,087,936, 3,254,025 and 5,430,105. Boration of the dispersant is sufficient to provide the acyl nitrogen-containing dispersant in a ratio of about 0.1 to about 20 atoms per mole of acylated nitrogen composition, such as a boron compound, such as boron oxide, Easily achieved by treatment with boron halide, boronic acid, and esters of boronic acid. The lubricating oil composition of the present invention preferably contains less than 100 ppm boron, such as less than 90 ppm boron, more preferably less than 80 ppm, such as less than 70 ppm boron.
Dihydrocarbyl dithiophosphate metal salts are frequently used as antiwear and antioxidant agents. The metal may be an alkali metal or alkaline earth metal, or aluminum, lead, tin, molybdenum, manganese, nickel or copper. Zinc salts are most commonly used in lubricating oils in amounts of 0.1 to 10% by weight, preferably 0.2 to 2% by weight, based on the total weight of the lubricating oil composition. They produce dihydrocarbyl dithiophosphate (DDPA) first by reaction of one or more alcohols or phenols with P ₂ S ₅ according to known techniques, and then neutralize the produced DDPA with a zinc compound. May be prepared. For example, dithiophosphoric acid may be made by reacting a mixture of primary and secondary alcohols. Also, a wide variety of dithiophosphoric acids can be prepared, in which one hydrocarbyl group is completely secondary and another hydrocarbyl group is completely primary. Any basic or neutral zinc compound can be used to make the zinc salt, but oxides, hydroxides and carbonates are most commonly used. Commercial additives frequently contain excess zinc due to excessive use of basic zinc compounds during the neutralization reaction.
A preferred zinc dihydrocarbyl dithiophosphate is an oil-soluble salt of dihydrocarbyl dithiophosphoric acid, which can be represented by the following formula:

In which R and R ′ may be the same or different hydrocarbyl groups containing 1 to 18, preferably 2 to 12 carbon atoms, alkyl groups, alkenyl groups, aryl groups, arylalkyls. Groups such as groups, alkaryl groups and alicyclic groups. Particularly preferred as R and R ′ groups are alkyl groups of 2 to 8 carbon atoms. Thus, these radicals are for example ethyl, n-propyl, i-propyl, n-butyl, i-butyl, sec-butyl, amyl, n-hexyl, i-hexyl, n-octyl, decyl, dodecyl, octadecyl. 2-ethylhexyl, phenyl, butylphenyl, cyclohexyl, methylcyclopentyl, propenyl, butenyl. In order to obtain oil solubility, the total number of carbon atoms (ie, R and R ′) in the dithiophosphoric acid will generally be about 5 or greater. Thus, zinc dihydrocarbyl dithiophosphate (ZDDP) can include zinc dialkyldithiophosphate. Although the lubricating oil composition of the present invention can provide superior performance in the presence of ZDDP in an amount that provides large amounts of phosphorus, the improved performance of the lubricating oil composition of the present invention is particularly evident with low SAPS formulations. And they generally have phosphorus levels of about 0.08% by weight (800 ppm) or less. Therefore, the lubricating oil composition of the present invention suitably contains less than 800 ppm, preferably less than 700 ppm, more preferably 600 ppm or less. The lubricating oil composition of the present invention suitably comprises at least 50 ppm, preferably at least 100 ppm, more preferably at least 200 ppm phosphorus.

Antioxidants or antioxidants reduce the tendency of mineral oil to deteriorate during use. Oxidative degradation can be evidenced by sludge in the lubricant, varnish-like deposits on the metal surface, and thickening. Such oxidation inhibitors include hindered phenols, preferably alkaline earth metal salts of alkylphenol thioesters having C ₅ -C ₁₂ alkyl side chains, calcium nonylphenol sulfides, oil-soluble phenates and sulfurized phenates, phosphosulfurized or sulfurized hydrocarbons. Or esters, phosphorus esters, ashless and metal-containing thiocarbamates, and oil-soluble copper compounds described in US Pat. No. 4,867,890.
Aromatic amines having at least two aromatic groups bonded directly to nitrogen constitute another class of compounds frequently used for antioxidant purposes. Typical oil-soluble aromatic amines having at least two aromatic groups bonded directly to one amine nitrogen contain from 6 to 16 carbon atoms. The amine may contain more than two aromatic groups. A total of at least three aromatic groups (two aromatic groups are bonded by a covalent bond or an atom or group (for example, an oxygen atom or a sulfur atom, or a —CO— group, a —SO ₂ — group or an alkylene group). Compounds that are directly bonded to one amine nitrogen are also considered aromatic amines having at least two aromatic groups bonded directly to the nitrogen, where the aromatic ring is typically an alkyl group, a cycloalkyl group, Substituted by one or more substituents selected from an alkoxy group, an aryloxy group, an acyl group, an acylamino group, a hydroxy group, and a nitro group, at least two aromatic groups directly bonded to one amine nitrogen Preferably the amount of such oil-soluble aromatic amines having no more than 0.4% by weight active ingredient.
The lubricating oil composition of the present invention is from about 0.05% to about 5%, preferably from about 0.10% to about 3%, most preferably about 0.20% by weight, based on the total weight of the lubricating oil composition. To about 2.5% by weight of a phenolic antioxidant, an amine antioxidant, or both.

If necessary, the lubricating oil composition of the present invention may contain a rust or corrosion inhibitor. Any suitable rust or corrosion inhibitor may be used. Examples of the rust inhibitor include nonionic polyoxyalkylene polyols and esters thereof, polyoxyalkylene phenols, and anionic alkyl sulfonic acids. The lubricating oil composition of the present invention preferably includes a rust inhibitor based on succinic acid and / or an alkyl-substituted phenol ethoxylate.
Corrosion inhibitors having copper and lead include thiadiazole polysulfides containing from 5 to 50 carbon atoms, their derivatives and polymers thereof. Such materials are widely known and disclosed, for example, in U.S. Pat. Nos. 2,719,125, 4,097,387 and British Patent 1560830.
When present, it is preferred that the rust or corrosion inhibitor is present in an amount not exceeding 1.0% by weight, preferably not exceeding 0.5% by weight, based on the total weight of the composition.
Foam control is provided by a polysiloxane type antifoaming agent such as silicone oil or polydimethylsiloxane.
In the present invention, it may be advantageous to include additives that maintain the viscosity stability of the blend. Additives that are effective in controlling this thickening include long chain carbonizations functionalized by reaction with monocarboxylic or dicarboxylic acids or acid anhydrides used in the preparation of the ashless dispersants disclosed above. Hydrogen is mentioned. In another preferred embodiment, the lubricating oil composition of the present invention is a long chain hydrocarbon functionalized by reaction with an effective amount of a mono- or dicarboxylic acid or anhydride (eg, polyisobutenyl succinic anhydride (PIBSA)). )including.
The viscosity index of the base stock may be increased or improved by incorporating therein certain polymeric materials that act as viscosity modifiers (VM) or viscosity index improvers (VII). In general, polymeric materials useful as viscosity modifiers are those having a number average molecular weight (Mn) of from about 5,000 to about 250,000, preferably from about 15,000 to about 200,000, more preferably from about 20,000 to about 150,000. The polymer molecular weight, in particular Mn, can be measured by various known techniques. One convenient method is Gel Permeation Chromatography (GPC), which provides further molecular weight distribution information ("Newest Size Exclusion Liquid Chromatography" by WW Yau, JJ Kirkland and DD Bly, John Wiley and Sons, New York , 1979). Another method useful for measuring molecular weight, particularly for low molecular weight polymers, is the vapor pressure osmometry (see, eg, ASTM D3592).

The viscosity index improver dispersant acts as both a viscosity index improver and a dispersant. Examples of viscosity index improver dispersants include amines, such as polyamines, and hydrocarbyl-substituted monocarboxylic or dicarboxylic acids (the hydrocarbyl substituent contains a chain long enough to impart viscosity index improving properties to the compound. ) Reaction products. Generally, the viscosity index improver dispersant is, for example, a C ₄ -C ₂₄ unsaturated ester of vinyl alcohol or a C ₃ -C ₁₀ unsaturated monocarboxylic acid or C ₄ -C ₁₀ dicarboxylic acid and 4 to 20 carbon atoms. Polymers of unsaturated nitrogen-containing monomers having: C ₂ -C ₂₀ olefins and polymers of unsaturated C ₃ -C ₁₀ mono- or di-carboxylic acids neutralized with amines, hydroxyamines or alcohols; or ethylene and C ₄ by grafting -C ₂₀ unsaturated nitrogen-containing monomer, or an unsaturated acid grafted to the polymer backbone, then the carboxylic acid groups of the amine of the grafted acid is reacted by reaction with hydroxylamine or an alcohol C ₃ -C ₂₀ olefin polymers may also be used. A preferred lubricating oil composition comprises the dispersant composition of the present invention, a base oil, and a viscosity index improver dispersant.
Pour point depressants (PPD) (otherwise also known as lube oil flow improvers (LOFI)) lower their temperature. Additives that improve the low temperature fluidity of liquids are C ₈ -C ₁₈ dialkyl fumarate / vinyl acetate copolymers, and polymethacrylates such as VM, LOFI can be grafted with graft materials such as maleic anhydride and grafted The material can be reacted with, for example, amines, amides, nitrogen-containing heterocyclic compounds or alcohols to produce multifunctional additives.
Some other of the above additives can also have many effects. Thus, for example, a single additive can act as a dispersant-oxidation inhibitor. This approach is known and need not be further described herein.
When the lubricating composition includes one or more of the above additives, each additive is typically blended into the base oil in an amount that allows the additive to perform its desired function. Representative effective amounts of such additives are listed below when used in crankcase lubricants.

One or more additive concentrates containing additives (concentrates are sometimes referred to as additive packages) can be prepared, whereby several additives can be added simultaneously to the oil to produce a lubricating oil composition That is not essential, but may be desirable.
The final composition may use a concentrate of 5% to 30% by weight, preferably 5% to 25% by weight, typically 10% to 20% by weight, the balance being the lubricating viscosity Of oil.
As used herein, the term “oil-soluble” or “oil-dispersible” does not necessarily indicate that a compound or additive is soluble, soluble, miscible, or can be suspended in oil in all proportions. . However, these mean that they are soluble or stably dispersible in the oil to an extent sufficient to provide their intended effect, for example, in the environment in which the oil is used. Furthermore, additional incorporation of other additives may also allow for the incorporation of high levels of special additives if desired.
In this specification, references to quantitative amounts of ingredients are given on an active ingredient basis. Some additives are usually combined with a diluent.

The present invention provides a method for reducing the wear of rotating tappets in passenger car automobile engines that are advantageously lubricated with low SAPS lubricants.
It is not expected that the removal of conventional friction modifier additives from the lubricating oil used to lubricate engines containing rotating tappets will provide improved wear performance, particularly for rotating tappets. It is particularly surprising that the present invention also exhibits acceptable fuel economy performance despite the absence of friction modifiers, which are normally considered necessary for acceptable fuel economy performance.
The invention will be further described, by way of example only, with reference to FIGS.
FIG. 1 shows the part of the engine valve train that contains the rotating tappet 6. It can be seen from FIG. 1 that the cam lobe 2 supported on the camshaft 4 contacts the end surface of the rotating tappet 6 (which is connected to the valve 10).
In use, the cam lobe 2 is rotated by the rotation of the camshaft 4 to which it is attached. There is a position of contact between the face of the cam lobe 2 and the rotating tappet 6. The action of the eccentric cam affects the linear reciprocation of the tappet 6. In moving to the distal limit (not shown) of this linear reciprocation, the tappet 6 starts the valve 10 and compresses the valve spring 8. As the camshaft 4 continues to rotate and the cam lobe 2 releases the tappet 6, the tappet moves back to the proximal limit of this linear motion by the relaxation of the valve spring closing the valve 10 (shown in FIG. 1). like).

During operation of the engine at operating temperature and hydraulic pressure, the camshaft (cam lobe 2 is part thereof) remains in constant contact with the surface of the tappet 6. As shown in FIG. 2, the position of contact between the cam 2 and the tappet 6 is offset from the axis of linear reciprocation by a distance X. Thus, in addition to the linear reciprocating motion, the rotational motion of the camshaft 4 also changes to the rotational motion of the tappet 6 about the axis of linear motion. This movement is clearly shown in FIG.
As the cam lobe 2 rotates, there is a sliding contact between the surface of the cam lobe 2 and the face of the tappet 6. The rotational movement of the tappet 6 means that the position of contact between the cam lobe 2 and the tappet 6 changes. Thus, the mechanical stress, deformation or wear of the tappet 6 due to the cam lobe 2 is not concentrated in a fixed or restricted area, but is evenly distributed over the working surface of the tappet 6.
The present invention advantageously facilitates tappet rotation, reduces tappet stall and thus affects improved wear performance.
The invention will be further understood with reference to the following examples, which include preferred embodiments of the invention. A composition described as “comprising” a plurality of specific ingredients should be considered to include a composition produced by mixing the plurality of specific ingredients.
Example

The VW RNT test (draft PV1473) is one test used to assess cam and tappet wear. The test is a static engine bench test using a 1.91 TDI PD, 85kW VW diesel engine. This engine has a rotating tappet and cam design. The test is a continuous test for a period of 650 hours. Prior to testing, discharge cams and tappets (No. 1) are irradiated and wear is monitored online using radionuclide tracer technology.
The four oils were blended and tested in the VW RNT test (PV1473 draft) for 650 hours. Oils 1 and 2 are lubricating oil compositions of the present invention and do not contain a friction modifier. Oils A and B are comparative examples and contain glycerol monooleate friction modifier and oleamide friction modifier.
Oils 1, 2, A and B each had a sulfated ash content of 0.6% by weight, a phosphorus content of 0.06% by weight and a sulfur content of around 0.22% by weight. Each of the exemplary oils was blended to a viscosity rating of 5W-30 according to SAE J300 (May 2004).
The test results are shown in Table 2 below.

Table 2

The above results demonstrated that the lubricant without the friction modifier performed better in the 650 hour VW RNT test (PV1473 draft) than the comparable formulation with the friction modifier, which reduced the rotating tappet. Shows wear. In fact, oils 1 and 2 of the present invention passed the tests specified by the radial cam and tappet limitations, while comparative oils A and B failed.
It is not expected that the removal of friction modifiers from passenger car automotive lubricant compositions will give improved wear resistance of rotating tappets.

The VW PV 1451 FE test measures fuel economy. It involves a comparison of candidate oils against a specific reference oil (CEC RL 191).
Oil 2 and Oil C were tested in the VW FE PV1451 test. Oil C substantially corresponds to Oil B of Example 1 except that Oil C contained only a glycerol monooleate friction modifier. Each of oils 2 and C and reference oil CEC RL 191 were tested in a test and the fuel savings of oils 2 and C were measured relative to the reference oil.
The test results are shown in Table 3 below.

Table 3

  It can be seen from Table 3 that both Oils 2 and C pass the VW PV P1451 FE test for fuel economy. Therefore, the lubricant of the present invention not only passes the 650-hour VW RNT test (PV1473 draft), but also passes the VW PV 1451 FE test, thus giving an acceptable combination of wear resistance and fuel economy. I understand that. It is not expected that a lubricating oil composition for passenger car vehicles that is substantially free of friction modifiers will pass both industrial wear tests and fuel economy tests. This is especially unexpected for low SAPS oil compositions, which are inherently limited in the amount of metal dihydrocarbyl dithiophosphate antiwear additive that can be used in the composition.

1 is a schematic cross-sectional view of an engine valve train. 2 is a schematic diagram of cam and tappet action of the valve train cross section of FIG.

Explanation of symbols

2-cam lobe 4-cam shaft 6-rotating tappet 8-valve spring
10-valve

Claims (9)

A method for reducing the wear of a rotary tappet in an internal combustion engine having a cam and a rotary tappet, the phosphorus content in an amount of 50-900 ppm (mass basis), the sulfur content in an amount of 1500-3000 ppm (mass basis), 0.0-100 ppm Boron content in amount, and sulfated ash content in amount not exceeding 1.0% by mass, friction modifier base oil, friction modifier in an amount of 0.0-0.1% by mass based on the mass of the fully formulated lubricating oil composition , And metal-containing detergents or ash-forming detergents; ashless dispersants; boron compound-treated ashless dispersants; dihydrocarbyl dithiophosphate metal salts as antiwear and antioxidants; oxidation inhibitors or antioxidants; rust or corrosion inhibition Lubricating the engine with a lubricating composition comprising one or more additives selected from: an agent; a foam control agent; a viscosity stabilizer; a viscosity modifier; a pour point depressant; Features Said method.   The method of claim 1, wherein the lubricating oil composition comprises less than 0.05 weight percent friction modifier, based on the weight of the fully formulated oil composition.   The method of claim 1 or 2, wherein the friction modifier in the lubricating composition is selected from one or more of the following substances: glycerol esters of fatty acids; nitrogen-containing friction modifiers; and molybdenum compounds.   The method according to any one of claims 1 to 3, wherein a sulfated ash content of the lubricating oil composition is less than 0.7% by mass.   The method according to any one of claims 1 to 4, wherein the phosphorus content of the lubricating oil composition is 0.06% by mass or less based on the mass of the completely formulated composition.   The method according to any one of claims 1 to 5, wherein the boron content of the composition is less than 90 ppm (mass basis).   7. The lubricating oil composition according to any one of claims 1 to 6, wherein the lubricating oil composition comprises one or more nitrogen-containing dispersants, and the one or more dispersants may optionally provide 0.005 to 0.08 mass% nitrogen to the composition. the method of.   Use of a lubricating oil composition to pass a 650 hour Volkswagen RNA test (PV1473 draft) for cam and tappet wear, wherein the lubricating oil composition is as specified in claim 1 and optionally claimed. Use of a lubricating oil composition having the characteristics of any one of 2 to 7. Use of the composition according to claim 8 to pass both the 650 hour VW RNT test (PV1473 draft) for cam and tappet wear and the VW PV1451 test for fuel economy.

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