JP2008127578A - Lubricating oil composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an advanced means for decreasing an amount of consumption of fuel when operating an internal combustion engine. <P>SOLUTION: An automotive lubricating oil composition comprises (A) an oil of a lubricating viscosity in a major amount and (B) as an additive component in a minor amount, an oil-soluble or oil-dispersible 4-oxobutanoic acid or its salt, having the moiety: -CO(CH<SB>2</SB>)COOH. The moiety -CO(CH<SB>2</SB>)COOH is bonded to (i) an OR<SP>1</SP>group where R<SP>1</SP>is a 10-30C hydrocarbyl group; or to (ii) X of an aromatic group substituted with at least one 10-30C hydrocarbyl group; or to (iii) an NR<SP>2</SP>R<SP>3</SP>group where either or both of R<SP>2</SP>and R<SP>3</SP>is a 10-30C hydrocarbyl group, and either but not both of R<SP>2</SP>and R<SP>3</SP>may be a hydrogen atom. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an automotive lubricating oil composition, more particularly a composition suitable for use in crankcase lubrication of piston engines, particularly gasoline (spark ignition) and diesel (compression ignition) engines. Such compositions are referred to as crankcase lubricants); and the use of additives in friction modification. The present invention relates to the use of friction modifiers in automotive lubrication.

  Crankshaft lubricant is an oil used for general lubrication in an engine where an oil sump is located under the crankshaft of the engine and the circulating oil is returned. It is well known to include additives in crankcase lubricants for various purposes. Friction modifiers, also referred to as friction reducers, may be boundary additives that operate by reducing the coefficient of friction, thereby improving fuel economy. The use of glycerol monoesters as friction modifiers is described in the art, for example, in US-A-4,495,088; US-A-4,683,069; EP-A-0 092 946; and WO-A-01 / 72933. Yes. Glycerol monoester friction modifiers have been used commercially and are still in use.

GB-A-2 106 106 reduces the fuel consumption of an internal combustion engine by lubricating an operating engine with a lubricating composition containing a small proportion of at least one ester having the formula R ¹ (COOR ⁴ ) _m Is described.
Wherein R ¹ is an aliphatic hydrocarbon-based radical free of acetylenic unsaturation, containing from about 10 to about 35 carbon atoms, at least 8 of which are in a straight chain structure Present in
Each R ⁴ is independently hydrogen or an alkyl or alkenyl radical containing up to about 18 carbon atoms, at least one R ⁴ is alkyl or alkenyl; and
m is an integer of 2-5. )

  Lubricant formulators are continually seeking additional means to reduce the amount of fuel consumed when operating an internal combustion engine.

(Summary of the Invention)
Surprisingly, the present invention provides an improvement in friction relief over glycerol ester additives by employing butanoic acid or its salts, as evidenced by the data herein.

In the first aspect, the present invention provides:
(A) a large proportion of oil of lubricating viscosity; and (B) a small proportion of 4-oxobutanoic acid having a —CO (CH ₂ ) ₂ COOH moiety as an oil-soluble or oil-dispersible additive component, The CO (CH ₂ ) ₂ COOH moiety
(I) bonded to the OR ¹ group to provide a half-acid half ester (wherein R ¹ is a hydrocarbyl group having 10 to 30 carbon atoms); or (ii) bonded to the X group A keto acid (wherein X is an aromatic group substituted with at least one hydrocarbyl group having 10 to 30 carbon atoms); or (iii) an NR ² R ³ group binding to the providing half acid half amides (wherein one or both of R ² and R ³ is a hydrocarbyl group having 10 to 30 carbon atoms, one of R ² and R ³ May be a hydrogen atom, but both are not hydrogen atoms), 4-oxobutanoic acid or a salt thereof,
And a lubricating oil composition for an auto-propelled body manufactured by mixing them.

In a second aspect, the present invention is a method of lubricating an internal combustion engine comprising: (a) providing the crankcase with the composition of the first aspect of the present invention; and (b) providing the engine. Providing the method.
In a third aspect, the invention is defined in the first aspect of the invention as an additive component in a lubricating oil composition for enhancing the friction improving properties of the lubricating oil composition during lubrication of an internal combustion engine. The use of oil-soluble or oil-dispersible 4-oxobutanoic acid or salt thereof is provided.

As used herein, the following words and expressions have the following meanings.
“Active ingredient” or “(ai)” refers to an additive material that is not a diluent or solvent.
"Including" or any similar term specifies the presence of the stated feature, step, integer or component, but excludes the presence or addition of one or more other features, steps, integers, components or groups thereof do not do. “Consisting of” or “consisting essentially of” or similar expressions may be included within the scope of “including” or similar terms, “consisting essentially of” The inclusion of substances that do not substantially affect the properties of the composition to be allowed.

“Hydrocarbyl” means a chemical group of a compound containing hydrogen and carbon atoms that is bonded directly to the remainder of the compound by a carbon atom. The group may contain one or more atoms other than carbon and hydrogen (“heteroatoms”) provided that they do not affect the intrinsic hydrocarbyl nature of the group.
“Major amount” means greater than 50% by weight of the composition.
“Minor amount” means less than 50% by weight of the composition.

Also, the various essential, optimal and customary components used may react under the conditions of formulation, storage or use, and the present invention is also available as a result of any such reaction It is understood that the present invention also provides the product or product obtained.
Furthermore, it will be appreciated that any upper and lower amounts, range limitations, and ratio limitations described herein may be independently combined.
(Detailed description of the invention)
The features of the invention relating to each and every aspect of the invention are described in more detail as follows, as necessary.

(Oil of lubricating viscosity (A))
Oils of lubricating viscosity (sometimes referred to as “base stock” or “base oil”) are used to produce additives and lubricants, for example, to produce the final lubricant (or lubricant composition). Other possible oils are the main liquid component of the lubricant to be incorporated.

The base oil is useful for making concentrates and for making lubricating oil compositions therefrom, and may be selected from natural lubricating oils (vegetable oils, animal oils or mineral oils) and synthetic lubricating oils and mixtures thereof. Viscosity ranges from light distillate mineral oils to heavy lubricating oils such as gas engine oils, mineral lubricating oils, autopropellant oils and heavy vehicle diesel oils. In general, the viscosity of the oil ranges from ² to 30 mm ² s ⁻¹ , in particular from 5 to 20 mm ² s ⁻¹ at 100 ° C.
Natural oils include animal oils and vegetable oils (eg, castor oil and lard oil), liquid petroleum and paraffinic, naphthenic and mixed paraffin-naphthenic type hydrorefining, solvent-treated mineral lubricating oils, and the like. Oils of lubricating viscosity derived from coal or shale are also useful base oils.

  Synthetic lubricating oils include polymerized and copolymerized olefins (eg, polybutylene, polypropylene, propylene-isobutylene copolymer, chlorinated polybutylene, poly (1-hexene), poly (1-octene), poly (1-decene)), etc. Hydrocarbon oils, alkylbenzenes (eg dodecylbenzene, tetradecylbenzene, dinonylbenzene, di (2-ethylhexyl) benzene), polyphenols (eg biphenyl, terphenyl, alkylated polyphenols) and alkylated diphenyl ethers and alkylated diphenyl sulfides And derivatives, analogs and homologues thereof.

Other suitable types of synthetic lubricating oils include dicarboxylic acids (eg, phthalic acid, succinic acid, alkyl succinic acid and alkenyl succinic acid, maleic acid, azelaic acid, suberic acid, sebacic acid, fumaric acid, adipic acid, linoleic acid. Includes esters of acid dimer, malonic acid, alkylmalonic acid, alkenylmalonic acid) with various alcohols (eg butyl alcohol, hexyl alcohol, dodecyl alcohol, 2-ethylhexyl alcohol, ethylene glycol, diethylene glycol monoether, propylene glycol) It is. Specific examples of these esters include dibutyl adipate, di (2-ethylhexyl) sebacate, di-n-hexyl fumarate, dioctyl sebacate, diisooctyl azelate, diisodecyl azelate, dioctyl phthalate, phthalic acid Examples include didecyl, diacosyl sebacate, 2-ethylhexyl diester of linoleic acid dimer, and a complex ester formed by reaction of 1 mol of sebacic acid with 2 mol of tetraethylene glycol and 2 mol of 2-ethylhexanoic acid.
Esters useful as synthetic oils include those produced from C ₅ -C ₁₂ monocarboxylic acids and polyhydric alcohols, and those such as neopentyl glycol, trimethylolpropane, pentaerythritol, dipentaerythritol and tripentaerythritol. And polyhydric alcohol ethers.

  Unrefined, refined and rerefined oils can be used in the compositions of the present invention. Unrefined oils are those obtained directly from natural or synthetic sources without further purification. For example, shale oil obtained directly from retorting operations, petroleum oil obtained directly from distillation or ester oil obtained directly from an esterification process and used without further treatment is an unrefined oil. Refined oils are similar to unrefined oils except that they are further processed in one or more purification steps to improve one or more properties. Many such purification techniques, such as distillation, solvent extraction, acid or base extraction, filtration and percolation are known to those skilled in the art. The re-refined oil is obtained by a method similar to that used to obtain a refined oil that is already used in service and applied to the refined oil. Such rerefined oils are also known as reclaimed or reprocessed oils and are often further processed by techniques for the approval of used additives and oil breakdown products.

Another example of a base oil is a synthetic gas-to-liquid (“GTL”) base oil. That is, the base oil may be an oil derived from a Fischer-Tropsch synthesized hydrocarbon produced from a synthesis gas containing H ₂ and CO using a Fischer-Tropsch catalyst. These hydrocarbons typically require further processing in order to be useful as base oils. For example, it may be hydroisomerized; hydrocracked and hydroisomerized; dewaxed; or hydroisomerized and dewaxed by methods known in the art.

Base oils may be classified into groups I to V according to the definition of API EOLCS 1509.
When producing a concentrate using an oil of lubricating viscosity, it is present in a concentrate formation amount (eg, 30-70% by weight such as 40-60% by weight), for example, 10-80% by weight, preferably Is an additive which is component B in combination with one or more co-additives or an additive which is component (B) above, such as 20 to 80% by weight, more preferably 20 to 70% by weight, such as 20 to 70% by weight. A concentrate containing the active ingredient of the agent is provided. The oil of lubricating viscosity used in the concentrate is a suitable oily, typically hydrocarbon carrier fluid (eg, mineral lubricating oil or other suitable solvent). Oils of lubricating viscosity as described herein as well as aliphatic hydrocarbons, naphthene hydrocarbons and aromatic hydrocarbons are also examples of suitable carrier fluids for concentrates.

  Concentrates provide a convenient means of treating the additives prior to their use and facilitate dissolution or dispersion of the additives in the lubricating oil composition. In preparing a lubricating oil composition that includes one or more types of additives (sometimes referred to as “additive components”), each additive is incorporated separately, each in the form of a concentrate. Also good. In many cases, however, so-called additive “packages” (also referred to as “adpacks”) comprising one or more co-additives as described below are provided in a single concentrate. Is convenient.

  In the present invention, the oil of lubricating viscosity provided in a large proportion is combined with a small proportion of at least one additive and, if necessary, one or more co-additives as described below in the specification. And constitutes a lubricating oil composition. This production may be accomplished by adding the additive directly to the oil or by adding the additive in the form of its concentrate to disperse or dissolve the additive. Additives may be added to the oil by any method known to those skilled in the art, either before, simultaneously with, or after the addition of other additives.

  As used herein, the terms “oil-soluble” or “oil-dispersible” or similar terms are used to indicate that the compound or additive is soluble, miscible, miscible in any proportion in the oil. It does not necessarily represent what is or can be suspended. However, these are, for example, those compounds or additives that are soluble or stably dispersible in the oil to an extent sufficient to exert their intended effect in the environment in which the oil is employed. It means that. Furthermore, further mixing of other additives may also allow higher levels of mixing of certain additives, if necessary.

The lubricating oil composition of the present invention is particularly useful for lubricating mechanical engine components by adding the composition thereto, for example, in a two-stroke or four-stroke reciprocating engine with spark ignition or compression ignition. You may use in such an internal combustion engine. Preferably, the composition is a crankcase lubricant.
The lubricating oil composition (and also the concentrate) of the present invention is defined so that it may or may not remain chemically the same before and after mixing with the oily carrier. Contains ingredients. The present invention encompasses compositions comprising components defined before or after mixing or both before and after mixing.
When concentrates are used to produce lubricating oil compositions, they are, for example, from 3 to 100 percent, for example from 5 percent to 1 percent by mass of oil of lubricating viscosity per 1 percent of the mass of the concentrate. You may dilute at 40 percent.

(Additive component (B))
This is 4-oxobutanoic acid or a salt thereof, as described, wherein the number 2 and 3 carbon atoms are each unsubstituted, such that the acid comprises a —CO (CH ₂ ) ₂ COOH moiety. That is, they each have two hydrogen atoms and are part of a methylene group. Without being bound by any theory, the methylene group in the moiety gives the three O atoms in the moiety a better ability to bind iron at the surface, so that the moiety becomes part of the molecule. It is thought to improve the friction improving properties of the molecule.

Component (B) is “ashless” in the sense that it is a non-metallic organic material that contains metal and thereby forms substantially no ash upon combustion, as opposed to an ash-forming material. Also good. In order to provide oil solubility or oil dispersibility to the additive component, Component B has a suitable hydrocarbyl group as defined herein in each of (i), (ii) and (iii).
In (i), 4-oxobutanoic acid (B) is a half acid-half ester. The hydrocarbyl group R ¹ provides oil solubility and is linear or branched, preferably linear and preferably has 12 to 20 carbon atoms. The hydrocarbyl group R ¹ may be alkenyl or alkyl, preferably alkenyl, in which case it preferably has only one double bond. As an example of (i), when the group R ¹ is CH ₃ (CH ₂ ) ₇ CH═CH (CH ₂ ) ₈ , ie the group R ¹ is oleyl, R ¹ OCO (CH ₂ ) ₂ COOH may be mentioned.

US-A-4 096 077 (077) describes a lubricating oil composition comprising at least one half acid half ester of succinic acid and alcohol. 077 describes their use as antiwear agents, but does not describe combinations of benzotriazoles, C ₁ -C ₂₀ alkyl substituted benzotriazoles and maleic acid half-acid half-esters .
When additive component (B) is (i) or (iii), the composition of the present invention is preferably (a) a maleic acid half-ester and (b) benzotriazole or C1-C20 Either or both of the alkyl-substituted benzotriazoles are not included.

In (ii), (B) is 4-ketocarboxylic acid. The keto group is attached to an aromatic group such as an aryl or phenyl group that is successively substituted with hydrocarbyl, such as an alkyl group having 12 to 20 carbon atoms, to provide oil solubility or oil dispersibility. . Such keto compounds may be conveniently prepared by acylating alkyl-substituted benzenes with succinic anhydride.
In (iii), (B) is a half acid half group obtained by reacting succinic acid with a long-chain alkylamine having 12 to 20 carbon atoms, for example, wherein the hydrocarbyl group is an alkyl group. Monoamide.
As an example of 4-oxobutanoic acid, a salt formed by reacting a carboxylic acid group with a hydrocarbyl derivative of pyridine or a salt formed by reacting a carboxylic acid group with di-n-butylamine or tri-n-butylamine May be mentioned.

(Co-additive)
As co-additives in the compositions of the present invention, mention is made of other organic friction modifiers different from (B) such as those having a polar head group containing oxygen atoms or nitrogen atoms or both. Also good. They may be referred to as organic ashless (metal-free) friction modifiers and may be ester-based or amide-based (aminic) such as glycerol monooleate. In addition, inorganic friction modifiers, ie metal-containing friction modifiers, may be mentioned. When inorganic friction modifiers are provided, organomolybdenum compounds such as dinuclear molybdenum compounds or trinuclear molybdenum compounds are preferred and may be present in concentrations ranging from 0.1 to 2% by weight or of molybdenum atoms. It may be provided at least 10 ppm by weight, for example 50-2,000 ppm.

Preferably, the molybdenum compound molybdenum is present in an amount of 10-1,500 ppm, such as 20-1,000 ppm, more preferably 30-750 ppm, based on the total weight of the lubricating oil composition. For some applications, molybdenum is present in an amount greater than 500 ppm.
Other co-additives are listed below along with representative effective amounts. All values listed are presented as mass% active ingredients.

Additive mass% mass%
(Wide) (preferred)
Ashless dispersant 0.1-20 1-8
Metal detergent 0.1-15 0.2-9
Corrosion inhibitor 0-5 0-1.5
Dihydrocarbyl dithiophosphate metal 0-10 0-4
Antioxidant 0-5 0.01-3
Pour point depressant 0.01-5 0.01-1.5
Antifoam 0-5 0.001-0.15
Auxiliary antiwear agent 0-5 0-2
Viscosity improver (1) 0-6 0.01-4
Mineral base oil or synthetic base oil Balance Balance

The viscosity improver (1) is used only in multi-grade oils.
The final lubricating oil composition, which is generally produced by blending them or by mixing the respective additives into the base oil, is 5-25% by weight, preferably 5-18% by weight, generally 7-15%. It may contain% by weight of the concentrate, the rest being an oil of lubricating viscosity.
The co-additives described above are clarified in more detail as follows; as is known in the art, some additives can provide multiple effects, for example, one additive is a dispersant. And may function as an antioxidant.

Dispersants are additives whose primary function is to keep the solid and liquid mixture in suspension, thereby passivating them, reducing engine deposits and reducing sludge deposition. For example, the dispersant maintains oil insoluble material in suspension due to oxidation during use of the lubricant, thereby inhibiting sludge flocculation and settling or deposition on engine metal parts.
Dispersants are typically “ashless” as described above, and are non-metallic organic materials that contain metals and thereby form virtually no ash upon combustion, in contrast to ash-forming materials. They contain long hydrocarbon chains with a polar head, the polarity resulting from, for example, containing O, P or N atoms. The hydrocarbon is an oleophilic group that imparts oil solubility and has, for example, 40 to 500 carbon atoms. Therefore, the ashless dispersant may contain an oil-soluble polymer skeleton.
A preferred class of olefin polymers is polybutenes, in particular C ₄ Les refinery streams (refinery, stream) Good polyisobutene (PIB) be prepared by polymerization or poly -n- butene.

  Examples of the dispersant include derivatives of a long-chain hydrocarbon-substituted carboxylic acid, such as a high-molecular-weight hydrocarbon-substituted succinic acid. Notable groups of dispersants are hydrocarbon-substituted types, preferably produced by reacting the above acids (or derivatives) with nitrogen-containing compounds, preferably by polyalkylene polyamines such as polyethylene polyamines. Succinimide. US-A-3,202,678; -3,154,560; -3,172,892; -3,024,195; -3,024,237, -3219,666; and -3,216,936; and reaction products of polyalkylene polyamines as described in BE-A-66,875 Are particularly preferred, and post-treatments such as boration (as described in US-A-3,087,936 and -3,254,025), fluorination and oxylamination may be used to improve their properties. For example, boration may be achieved by treating an acyl nitrogen-containing dispersant with a boron compound selected from boron oxide, boron halides, boron acids and esters of boron acids.

A detergent is an additive that reduces the formation of piston deposits in the engine, such as hot varnish and lacquer deposits; it usually has acid neutralizing properties and keeps fine solids in suspension. It is possible. Most detergents are based on metal “soaps”, which are metal salts of acidic organic compounds.
The detergent generally comprises a polar head having a long hydrophobic tail, the polar head comprising a metal salt of an acidic organic compound. The salts may contain substantially stoichiometric amounts of metals, in which case they are usually described as normal or neutral salts, typically 0-80 total. It will have a base number or TBN (as can be measured by ASTM D2896). Large amounts of metal base can be included by reacting excess metal compounds, such as oxides or hydrides, with acid gases, such as 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 higher, typically 250 to 500 or higher.

  Detergents which may be used include oil-soluble neutral and overbased sulfonates of metals, in particular alkali metals or alkaline earth metals such as sodium, potassium, lithium, calcium and magnesium, phenates, sulfurized phenates, Mention may be made of thiophosphonates, salicylates and naphthenates and other oil-soluble carboxylates. The most commonly used metals are calcium and magnesium, both of which may be present in the detergent used in the lubricant, and in a mixture of calcium and / or magnesium with sodium. There may be. Particularly advantageous metal detergents are neutral and overbased calcium sulfonates and sulfurized phenates having a TBN of 50 to 450.

Antioxidants are sometimes referred to as oxidation inhibitors; they increase the resistance of the composition to oxidation, in combination with peroxides and by decomposing peroxides or inactivating oxidation catalysts. May function by denature it to make it non-toxic. Oxidative degradation can be evidenced by sludge in the lubricant, varnish-like deposits on the metal surface, and by increased viscosity.
They include radical scavengers (eg, sterically hindered phenols, secondary aromatic amines and organic copper salts); hydroperoxide decomposers (eg, organic sulfur and organic phosphorus additives); and multifunctional agents (eg, antiwear additives). Dihydrocarbyl dithiophosphate that may also function as an organic molybdenum compound that may function as a friction modifier and antiwear additive.
Examples of suitable antioxidants are copper-containing antioxidants, sulfur-containing antioxidants, aromatic amine-containing antioxidants, hindered phenolic antioxidants, dithiophosphate derivatives, metal thiocarbamates and molybdenum-containing compounds. More selected.

Dihydrocarbyl dithiophosphate metal salts are often used as antiwear and antioxidant agents. The metal may be an alkali metal or alkaline earth metal, or aluminum, lead, tin, zinc, molybdenum, manganese, nickel or copper. Zinc salts are most commonly used, for example, 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. According to known techniques, they first form dihydrocarbyl dithiophosphate (DDPA), usually by reacting one or more alcohols or phenols with P ₂ S _5, and then neutralize the formed DDPA with a zinc compound. You may manufacture by doing. For example, dithiophosphoric acid can be produced by reacting a mixture of primary and secondary alcohols. Alternatively, complex dithiophosphoric acids can be prepared in which the hydrocarbyl group of one acid is completely secondary in nature and the hydrocarbyl group of the other acid is entirely primary in nature. Any basic or neutral zinc compound can be used to produce the zinc salt, but oxides, hydroxides and carbonates are most commonly employed. Commercial additives often contain excess zinc due to the use of excess basic zinc compounds in the neutralization reaction.

Antiwear agents are based on compounds containing sulfur or phosphorus or both that reduce friction and excessive wear and are typically capable of depositing polysulfide films, for example, on the included surfaces. Of note are dihydrocarbyl dithiophosphates, such as zinc dialkyldithiophosphates (ZDDP) discussed herein.
Examples of ashless antiwear agents include 1,2,3-triazole, benzotriazole, thiadiazole, sulfurized fatty acid esters, and dithiocarbamate derivatives.

The rust inhibitor and the corrosion inhibitor serve to protect the surface from rust and / or corrosion. Examples of the rust inhibitor include nonionic polyoxyalkylene polyhydric alcohols and esters thereof, polyoxyalkylene phenols and anionic alkyl sulfonic acids.
Pour point depressants , also known as lube oil flow improvers, lower the minimum temperature at which the oil will flow or can be poured. Such additives are well known. Typical examples of these additives are C ₈ -C ₁₈ dialkyl fumerate / vinyl acetate copolymers and polyalkyl methacrylates.
Polysiloxane type additives, such as silicone oil or polydimethyl siloxane, can provide foam control (foam control).

A small amount of a demulsifying component may be used. A preferred demulsifying component is described in EP-A-330,522. It can be obtained by reacting an adduct obtained by reacting a bisepoxide with a polyhydric alcohol and an alkylene oxide. The demulsifier should be used at a level not exceeding 0.1% by weight active ingredient. A treat rate of 0.001 to 0.05 mass% active ingredient is convenient.
The viscosity improver (or viscosity index improver) imparts high temperature workability and low temperature workability to the lubricating oil. Viscosity modifiers that also function as dispersants are also known and may be prepared as described above for ashless dispersants. In general, these dispersant viscosity modifiers are functionalized polymers that are then derivatized with, for example, alcohols or amines (eg, ethylene-propylene co-polymers that are post-grafted with an active monomer such as maleic anhydride. Polymer).
The lubricant may be formulated with or without conventional viscosity modifiers and with or without dispersant viscosity modifiers. Suitable compounds for use as viscosity modifiers are generally high molecular weight hydrocarbon polymers including polyesters. Oil soluble viscosity modifying polymers generally have a weight average molecular weight of 10,000 to 1,000,000, preferably 20,000 to 500,000, which may be measured by gel permeation chromatography or by light scattering.

The invention will be described in detail in the following examples, which are not intended to limit the scope of the claims.
In this example, the following additive components were used as examples of the present invention:
B1: 4-oxobutanoic acid in the form of 4-stearylbenzoylpropanoic acid (SBP); and B2: mono-oleyl succinate (MOS) used as a reference example known in the art; and mono-oleic acid glycerol friction modifier (GMO).

  Component B1 was synthesized by acylation of stearylbenzene with succinic anhydride according to literature procedures (P. Nuhn et al; Pharmazie 53, 12, 825, 1998). Accordingly, aluminum trichloride was added to a mixture of stearylbenzene and succinic anhydride in nitrobenzene at 5 ° C. After standing overnight, the mixture was poured onto ice and washed with water. The solvent was evaporated from the organic layer to give the product (SBP) with the desired purity. A total of 230 g of product was produced in three batches.

Component B2 was prepared by reacting 0.5 mole succinic anhydride with 0.5 mole oleyl alcohol. The reactants were mixed with an overhead stirrer in a 500 mL flask equipped with a condenser at 120 ° C. for 6 hours under a nitrogen blanket. The resulting mono-oleyl succinate was used without further purification.
Using the same base oil, each of the above additive components was incorporated into the composition to provide examples of the invention and reference examples. The contents of the composition are shown below under the heading "Test and Results".

(Test and results)
A high frequency reciprocating rig (HFRR) was used to evaluate the coefficient of friction of each of the above compositions. Examples of the present invention were identified as Examples 1 and 2, and the corresponding reference examples were identified as Examples 1 ′ and 2 ′.

Experiment 1
The adopted HFRR test protocol was as follows.

The results obtained were as follows.

In this experiment, each oil composition contained 0.2% by weight of the active ingredients of the additives in the above table. The composition was exactly the same except for the identity of the additives shown in the table above.
The coefficient of friction measurement was the average value obtained after 60 minutes at 100 ° C.

Experiment 2
The adopted HFRR test protocol was as follows.

The results obtained were as follows.

In this experiment, each oil composition contained 0.2% by weight of the active ingredients of the additives in the above table. The composition was exactly the same except for the identity of the additives shown in the table above.
The coefficient of friction measurement was the average value obtained after 30 minutes at each of the indicated temperatures.
The above results show that the compositions of the invention (Examples 1 and 2) in all cases have a better (ie smaller) coefficient of friction than the corresponding reference compositions (Examples 1 ′ and 2 ′). Indicates that it was generated.

Claims (9)

(A) a large proportion of oil of lubricating viscosity; and (B) a small proportion of 4-oxobutanoic acid having a —CO (CH ₂ ) ₂ COOH moiety as an oil-soluble or oil-dispersible additive component, The CO (CH ₂ ) ₂ COOH moiety
(I) bonded to the OR ¹ group to provide a half-acid half ester (wherein R ¹ is a hydrocarbyl group having 10 to 30 carbon atoms); or (ii) bonded to the X group A keto acid (wherein X is an aromatic group substituted with at least one hydrocarbyl group having 10 to 30 carbon atoms); or (iii) an NR ² R ³ group binding to the providing half acid half amides (wherein one or both of R ² and R ³ is a hydrocarbyl group having 10 to 30 carbon atoms, one of R ² and R ³ May be a hydrogen atom, but both are not hydrogen atoms), 4-oxobutanoic acid or a salt thereof,
A lubricating oil composition for an auto-propelled body that is produced by mixing or mixing them. The composition of claim 1, wherein each of the R ¹ , R ² and R ³ groups and the hydrocarbyl group in the X group has from 12 to 20 carbon atoms. The 4-oxobutanoic acid has the formula R ¹ OCO (CH ₂ ) ₂ COOH where R ¹ is an alkenyl group such as a CH ₃ (CH ₂ ) ₇ CH═CH (CH ₂ ) ₈ group. The composition according to claim 1 or 2. When the 4-oxobutanoic acid has the formula R ¹ OCO (CH ₂ ) ₂ COOH or the formula R ² R ³ NCO (CH ₂ ) ₂ COOH, (a) a half acid half ester of maleic anhydride; and (b) 5. A composition according to claim 4, which does not contain either or both of benzotriazole or C1-C20 alkyl-substituted benzotriazole. The composition according to claim 1, wherein the 4-oxobutanoic acid has the formula XCO (CH ₂ ) COOH, wherein X is a stearyl-substituted phenyl group.   The composition of any one of Claims 1-5 in which the said additive component (B) does not contain a metal.   Different from (B), selected from ashless dispersants, metal detergents, corrosion inhibitors, dihydrocarbyl dithiophosphate metal salts, antioxidants, pour point depressants, friction modifiers, antifoaming agents and viscosity modifiers 7. A composition according to any one of claims 1 to 6, further comprising one or more co-additives.   A method of lubricating an internal combustion engine comprising: (a) providing the crankcase with the composition of any one of claims 1-7; and (b) operating the engine. , Said method.   The 4-oxobutanoic acid or a salt thereof according to any one of claims 1 to 6, as an additive component in the lubricating oil composition for enhancing the friction improving properties of the lubricating oil composition during lubrication of an internal combustion engine Use of.