EP2290041A2

EP2290041A2 - A lubricating oil composition

Info

Publication number: EP2290041A2
Application number: EP10171303A
Authority: EP
Inventors: Stuart James Mctavish; Keith Strickland; Robert Shaw
Original assignee: Infineum International Ltd
Current assignee: Infineum International Ltd
Priority date: 2009-08-24
Filing date: 2010-07-29
Publication date: 2011-03-02
Anticipated expiration: 2030-07-29
Also published as: EP2290041A3; EP2290041B1

Abstract

A lubricating oil composition comprising: (A) an oil of lubricating viscosity in a major amount, comprising a Group III base stock; (B) as an additive component in a minor amount, an oil-soluble boron containing compound; and, wherein the lubricating oil composition is contaminated with at least 0.3 mass %, based on the total mass of the lubricating oil composition, of a biofuel or a decomposition product thereof and mixtures thereof.

Description

FIELD OF THE INVENTION

The present invention relates to automotive lubricating oil compositions, more especially to automotive lubricating oil compositions for use in gasoline (spark-ignited) and diesel (compression-ignited) internal combustion engines fuelled at least in part with a biofuel, especially compression-ignited internal combustion engines fuelled at least in part with a biodiesel fuel and spark-ignited internal combustion engines fuelled at least in part with bioethanol fuel, crankcase lubrication, such compositions being referred to as crankcase lubricants.
In particular, although not exclusively, the present invention relates to automotive lubricating oil compositions, preferably having low levels of phosphorus and also low levels of sulfur and/or sulfated ash, which exhibit an improved inhibition of corrosion of the metallic engine parts during operation of the engine which is fuelled with a biofuel; and to the use of additives in such compositions for improving the anti-corrosion properties of the lubricating oil composition.

BACKGROUND OF THE INVENTION

A crankcase lubricant is an oil used for general lubrication in an internal combustion engine where an oil sump is situated generally below the crankshaft of the engine and to which circulated oil returns. The contamination or dilution of the crankcase lubricant in internal combustion engines, especially engines fuelled at least in part with a biofuel, is a concern.
Biodiesel fuels include components of low volatility which are slow to vaporize after injection of the fuel into the engine. Typically, an unburnt portion of the biodiesel and some of the resulting partially combusted decomposition products become mixed with the lubricant on the cylinder wall and are washed down into the oil sump, thereby contaminating the crankcase lubricant. The biodiesel fuel in the contaminated lubricant may form further decompositions products, due to the extreme conditions during lubrication of the engine. It has been found that the presence of biodiesel fuel and the decomposition products thereof in the crankcase lubricant promotes the corrosion of the metallic engine parts; particularly the softer metallic (i.e. non-ferrous metallic) engine parts such as the lead and copper based bearing materials. Moreover, it has been found that this problem is significantly worse in diesel engines which employ a late post-injection of fuel into the cylinder (e.g. light duty, medium duty and passenger car diesel engines) to regenerate an exhaust gas after-treatment device.
Exhaust gas after-treatment devices, such as a diesel particulate filter (DPF), require periodical regeneration to remove the build up of soot and to prevent them from having a detrimental effect on engine performance. One way to create conditions for initiating and sustaining regeneration of a DPF involves elevating the temperature of the exhaust gases entering the DPF to burn the soot. As a diesel engine runs relatively cool and lean, this may be achieved by adding fuel into the exhaust gases optionally in combination with the use of an oxidation catalyst located upstream of the DPF. Heavy duty diesel (HDD) engines, such as those in trucks, typically employ a late post-injection of fuel directly into the exhaust system outside of the cylinder, whilst light duty and medium duty diesel engines typically employ a late post-injection of fuel directly into the cylinder during an expansion stroke. Surprisingly, it has been found that the corrosion of the softer metallic (i.e. non-ferrous metallic) engine components increases significantly in a diesel engine fuelled at least in part with biodiesel when the engine employs a late post-injection of fuel directly into the cylinder. Although only theory, it is believed this increased engine corrosion is due to more biodiesel being absorbed by the lubricant on the more exposed cylinder wall, thereby increasing contamination of the lubricant in the sump.
A similar increase in the corrosion of the metallic engine parts, particularly the softer metallic (i.e. non-ferrous metallic) engine components, has also been found to occur in spark-ignited internal combustion engines fuelled at least in part with an alcohol based fuel (e.g. bioethanol) due to the presence of the alcohol based fuel and the decomposition products thereof in the crankcase lubricant.
Additionally, it has been found that contamination of a crankcase lubricant with a biofuel (e.g. biodiesel or bioethanol), especially with biodiesel, and the decomposition products thereof accelerates oxidation of the lubricant. Oxidation of the lubricant yields corrosive acids and an undesirable increase in viscosity, thereby shortening the useful life of the lubricant.
Accordingly, lubricating oil compositions which exhibit improved anti-corrosion properties in respect of the metallic engine components, particularly the softer metallic (i.e. non-ferrous metallic) engine components such as those containing copper and/or lead (e.g. bearing materials), must be identified. Accordingly, lubricants with improved antioxidant properties also need to be identified.

SUMMARY OF THE INVENTION

The present invention is based on the discovery that a lubricating oil can be formulated which exhibits significantly improved anti-corrosion properties, particularly in respect of the softer metallic (i.e. non-ferrous metallic) engine components, such as those containing lead and/or copper, and/or improved antioxidant properties.
In accordance with a first aspect, the present invention provides a lubricating oil composition comprising:

(A) an oil of lubricating viscosity in a major amount, comprising a Group III base stock;
(B) as an additive component in a minor amount, an oil-soluble boron containing compound; and,

Preferably, the lubricating oil composition according to the present invention is a crankcase lubricant.
It has unexpectedly been found that the inclusion of an oil-soluble boron containing compound in a lubricating oil composition, particularly a lubricating oil composition including a Group III base stock, provides a lubricant that exhibits an improved inhibition and/or a reduction in the corrosion of the metallic engine components, particularly the softer metallic (i.e. non-ferrous metallic) engine components, in use, in the lubrication of a spark-ignited or compression-ignited internal combustion engine which is fuelled at least in part with a biofuel. Additionally, or alternatively, the inclusion of an oil-soluble boron containing compound in a lubricating oil composition, particularly one including a Group III base stock, improves the antioxidant properties of the lubricant, in use, in the lubrication of an internal combustion engine which is fuelled at least in part with a biofuel. In particular, the inclusion of such an oil-soluble boron containing compound in a lubricant comprising a Group III base stock provides, in use, a positive credit in terms of reduced corrosion of the metallic engine components and/or reduced oxidation of the lubricant.
According to a second aspect, the present invention provides a method of lubricating a spark-ignited or compression-ignited internal combustion engine which is fuelled at least in part with a biofuel, comprising operating the engine with a lubricating oil composition comprising: (A) an oil of lubricating viscosity in a major amount, comprising a Group III base stock; and, (B) as an additive component in a minor amount, an oil-soluble boron containing compound.
Suitably, the method of the second aspect reduces and/or inhibits the corrosion of the metallic, especially the non-ferrous metallic, engine components. Preferably, the metallic engine components comprise lead, copper or mixtures thereof, especially copper.
According to a third aspect, the present invention provides a method of reducing and/or inhibiting the corrosion of the metallic engine components, especially the softer metallic (i.e. non-ferrous metallic) engine components, of a spark-ignited or compression-ignited internal combustion engine which is fuelled at least in part with a biofuel, the method comprising lubricating, preferably operating, the engine with a lubricating oil composition, particularly a crankcase lubricating oil composition, comprising: (A) an oil of lubricating viscosity in a major amount, comprising a Group III base stock; and, (B), as an additive component in a minor amount, an oil-soluble boron containing compound.
According to a fourth aspect, the present invention provides the use, in the lubrication of a spark-ignited or compression-ignited internal combustion engine which is fuelled at least in part with a biofuel, of a lubricating oil composition comprising: (A) an oil of lubricating viscosity in a major amount, comprising a Group III base stock; and, (B) as an additive component in a minor amount, an oil-soluble boron containing compound, to reduce and/or inhibit the corrosion of the metallic engine components, especially the softer metallic (i.e. non-ferrous metallic) engine components, during operation of the engine.
According to a fifth aspect, the present invention provides the use, in the lubrication of a spark-ignited or compression-ignited internal combustion engine which is fuelled at least in part with a biofuel, of an oil-soluble boron containing compound, as an additive component in a minor amount in a lubricating oil composition, to reduce and/or inhibit the corrosion of the metallic engine components, especially the softer metallic (i.e. non-ferrous metallic) engine components, during operation of the engine. Preferably, the lubricating oil composition comprises a major amount of an oil of lubricating viscosity comprising a Group III base stock.
According to a sixth aspect, the present invention provides the use, in the lubrication of a spark-ignited or compression-ignited internal combustion engine which is fuelled at least in part with a biofuel, of an oil-soluble boron containing compound, as an additive component in a minor amount in a lubricating oil composition, to reduce and/or inhibit oxidation of the lubricating oil composition, during operation of the engine. Preferably, the lubricating oil composition comprises a major amount of an oil of lubricating viscosity comprising a Group III base stock.
According to a seventh aspect, the present invention provides a method of reducing and/or inhibiting the oxidation of a lubricating oil composition in the lubrication of a spark-ignited or compression-ignited internal combustion engine which is fuelled at least in part with a biofuel, the method comprising lubricating the engine with a lubricating oil composition, particularly a crankcase lubricating oil composition, comprising an oil of lubricating viscosity and an oil-soluble boron containing compound, as an additive component in a minor amount, and operating the engine. Preferably, the oil of lubricating viscosity comprises a Group III base stock. According to an eighth aspect, the present invention provides a spark-ignited or compression-ignited internal combustion engine comprising a crankcase containing a lubricating oil composition comprising: (A) an oil of lubricating viscosity in a major amount, comprising a Group III base stock; and, (B) as an additive component in a minor amount, an oil-soluble boron containing compound, wherein the engine is fuelled at least in part with a biofuel. Preferably, the engine is operating with a fuel comprising a biofuel and the engine is being lubricated with the lubricating oil composition.
The oil-soluble boron containing compound may be any borated conventional lubricant additive. Preferably, the oil-soluble boron containing compound is a borated dispersant or a borated detergent.
Preferably, the lubricating oil compositions as defined in the second to eighth aspects of the invention are each independently contaminated with at least 0.3 mass %, based on the total mass of the lubricating oil composition, of a biofuel or a decomposition product thereof and mixtures thereof.
Preferably, the oil-soluble boron containing compound (i.e. additive component (B)) forms part of an additive package which also includes a diluent, preferably a base stock, and one or more co-additives in a minor amount, other than additive component (B), selected from ashless dispersants, metal detergents, corrosion inhibitors, antioxidants, antiwear agents, friction modifiers, demulsifiers and antifoam agents; the additive package being added to the oil of lubricating viscosity comprising the Group III base stock.
Suitably, the lubricating oil composition may include one or more co-additives in a minor amount, other than additive components (B), selected from ashless dispersants, metal detergents, corrosion inhibitors, antioxidants, pour point depressants, antiwear agents, friction modifiers, demulsifiers, antifoam agents and viscosity modifiers.
Preferably, the soft metallic (i.e. non-ferrous metallic) engine components of the third, fourth and fifth aspects comprise components which include copper or lead and mixtures thereof, especially lead, such as the lead and copper based bearing materials.
Preferably, the spark-ignited internal combustion engine is fuelled at least in part with an alcohol based fuel, especially an ethanol based fuel such as bioethanol fuel.
Preferably, the compression-ignited combustion engine is fuelled at least in part with a biodiesel fuel.
Preferably, the engine of the second to eighth aspects comprises a compression-ignited combustion engine.
Preferably, the biofuel of each aspect of the invention is biodiesel.
In this specification, the following words and expressions, if and when used, have the meanings ascribed below:

"active ingredients" or "(a.i.)" refers to additive material that is not diluent or solvent;
"alcohol based fuel" refers to a fuel including an alcohol, irrespective of the source of the alcohol, such as methanol, ethanol, propanol and butanol, especially ethanol. The term "alcohol based fuel" embraces pure alcohol based fuel (i.e. pure ethanol) and also alcohol based fuel blends comprising, for example, a mixture of an alcohol and petroleum gasoline;
"ethanol based fuel" refers to a fuel including ethanol and is otherwise defined in the same way as "alcohol based fuel";
"biofuel" refers to a biodiesel fuel, a bioalcohol fuel and an alcohol based fuel as defined herein (i.e. a fuel that does not consist of solely petroleum gasoline or petroleum diesel fuel). Preferably, the biofuel comprises biodiesel fuel, bioalcohol fuel and ethanol fuel as defined herein. More preferably, the term
"biofuel" means a fuel derived at least in part from a renewable biological resource e.g. biodiesel fuel or bioalchohol fuel. Even more preferably the biofuel comprises biodiesel or bioethanol as defined herein, especially biodiesel;
"biodiesel fuel" refers to a fuel derived at least in part from a renewable biological resource (e.g. derivable from a natural oil/fat, such as vegetable oils or animal fats) comprising at least one alkyl ester, typically a mono-alkyl ester, of a long chain fatty acid. The term "biodiesel fuel" embraces pure biodiesel fuel (i.e. B100 as defined by ASTM D6751-08 (USA) and EN 14214 (Europe)) and also biodiesel fuel blends comprising a mixture of biodiesel fuel and another fuel, such as petroleum diesel fuel;
"bioalcohol fuel" refers to fuel including an alcohol derived from a renewable biological resource (e.g. fermented sugar) and is otherwise defined in the same way as "alcohol based fuel";
"bioethanol fuel" refers to fuel including ethanol derived from a renewable biological resource and is otherwise defined in the same way as "ethanol based fuel". The term "bioethanol fuel" embraces pure bioethanol fuel (i.e. pure bioethanol E100) and also bioethanol fuel blends comprising, for example, a mixture of bioethanol and petroleum gasoline;
"petroleum gasoline" refers to a gasoline fuel produced from petroleum;
"petroleum diesel fuel" refers to a diesel fuel produced from petroleum;
"bioethanol" refers to ethanol derived from a renewable biological resource;
"comprising" or any cognate word specifies the presence of stated features, steps, or integers or components, but does not preclude the presence or addition of one or more other features, steps, integers, components or groups thereof. The expressions "consists of or "consists essentially of" or cognates may be embraced within "comprises" or cognates, wherein "consists essentially of" permits inclusion of substances not materially affecting the characteristics of the composition to which it applies;
"hydrocarbyl" means a chemical group (i.e. substituent) of a compound that contains hydrogen and carbon atoms and that is bonded to the remainder of the compound directly via a carbon atom. The group may contain one or more atoms other than carbon and hydrogen provided they do not affect the essentially hydrocarbyl nature of the group. Such substituents include the following:
1. 1. Hydrocarbon substituents, that is, aliphatic (for example alkyl or alkenyl), alicyclic (for example cycloalkyl or cycloalkenyl) substituents, aromatic-, aliphatic- and alicyclic-substituted aromatic nuclei and the like, as well as cyclic substituents wherein the ring is completed through another portion of the ligand (that is, any two indicated substituents may together form an alicyclic group);
2. 2. Substituted hydrocarbon substituents, that is, those containing non-hydrocarbon groups which, in the context of this invention, do not alter the predominantly hydrocarbyl character of the substituent. Those skilled in the art will be aware of suitable groups (e.g., halo, especially chloro and fluoro, amino, alkoxyl, mercapto, alkylmercapto, nitro, nitroso, sulfoxy, etc.).
"halo" or "halogen" includes fluoro, chloro, bromo and iodo;
"oil-soluble" or "oil-dispersible", or cognate terms, used herein do not necessarily indicate that the compounds or additives are soluble, dissolvable, miscible, or are capable of being suspended in the oil in all proportions. These do mean, however, that they are, for example, soluble or stably dispersible in oil to an extent sufficient to exert their intended effect in the environment in which the oil is employed. Moreover, the additional incorporation of other additives may also permit incorporation of higher levels of a particular additive, if desired;
"major amount" means in excess of 50 mass % of a composition;
"minor amount" means less than 50 mass % of a composition, expressed in respect of the stated additive and in respect of the total mass of all the additives present in the composition, reckoned as active ingredient of the additive or additives;
"ppm" means parts per million by mass, based on the total mass of the lubricating oil composition;
"soft metal" means a non-ferrous metal or an alloy thereof, preferably a metal or an alloy thereof comprising lead, copper, tin or aluminium and mixtures thereof, preferably lead or copper and mixtures thereof, especially copper;
"soft metallic engine component" means an engine component which includes a soft metal as defined herein;
"soft metal corrosion" is measured by the High Temperature Bench Corrosion Test (HTCBT) in accordance with ASTM D6594 and, when appropriate, modified accordingly by the addition of a biofuel;
"TBN" means total base number as measured by ASTM D2896 (mg KOH/g);
"phosphorus content" is measured by ASTM D5185;
"sulfur content" is measured by ASTM D2622; and,
"sulfated ash content" is measured by ASTM D874.
All percentages reported are mass % on an active ingredient basis, i.e., without regard to carrier or diluent oil, unless otherwise stated.
Also, it will be understood that various components used, essential as well as optimal and customary, may react under conditions of formulation, storage or use and that the invention also provides the product obtainable or obtained as a result of any such reaction.
Further, it is understood that any upper and lower quantity, range and ratio limits set forth herein may be independently combined.

DETAILED DESCRIPTION OF THE INVENTION

The features of the invention relating, where appropriate, to each and all aspects of the invention, will now be described in more detail as follows:

OIL OF LUBRICATING VISCOSITY (A)

The oil of lubricating viscosity (sometimes referred to as "base stock" or "base oil") is the primary liquid constituent of a lubricant, into which additives and possibly other oils are blended, for example to produce a final lubricant (or lubricant composition). A base oil is useful for making concentrates as well as for making lubricating oil compositions therefrom, and may be selected from natural (vegetable, animal or mineral) and synthetic lubricating oils and mixtures thereof.
The oil of lubricating viscosity comprises a Group III base stock. The base stock groups are defined in the American Petroleum Institute (API) publication "Engine Oil Licensing and Certification System", Industry Services Department, Fourteenth Edition, December 1996, Addendum 1, December 1998. Typically, the base stock will have a viscosity preferably of 3-12, more preferably 4-10, most preferably 4.5-8, mm²/s (cSt) at 100°C.
Definitions for the base stocks and base oils in this invention are the same as those found in the American Petroleum Institute (API) publication "Engine Oil Licensing and Certification System", Industry Services Department, Fourteenth Edition, December 1996, Addendum 1, December 1998. Said publication categorizes base stocks as follows:

a) Group I base stocks contain less than 90 percent saturates and/or greater than 0.03 percent sulphur and have a viscosity index greater than or equal to 80 and less than 120 using the test methods specified in Table E-1.
b) Group II base stocks contain greater than or equal to 90 percent saturates and less than or equal to 0.03 percent sulphur and have a viscosity index greater than or equal to 80 and less than 120 using the test methods specified in Table E-1.
c) Group III base stocks contain greater than or equal to 90 percent saturates and less than or equal to 0.03 percent sulphur and have a viscosity index greater than or equal to 120 using the test methods specified in Table E-1.
d) Group IV base stocks are polyalphaolefins (PAO).
e) Group V base stocks include all other base stocks not included in Group I, II, III, or IV.

Table E-1: Analytical Methods for Base Stock

Property	Test Method
Saturates	ASTM D 2007
Viscosity Index	ASTM D 2270
Sulphur	ASTM D 2622
	ASTM D 4294
	ASTM D 4927
	ASTM D 3120

Preferably, the oil of lubricating viscosity comprises greater than or equal to 10 mass %, more preferably greater than or equal to 20 mass %, even more preferably greater than or equal to 25 mass %, even more preferably greater than or equal to 30 mass %, even more preferably greater than or equal to 40 mass %, even more preferably greater than or equal to 45 mass % of a Group III base stock, based on the total mass of the oil of lubricating viscosity. Even more preferably, the oil of lubricating viscosity comprises greater than 50 mass %, preferably greater than or equal to 60 mass %, more preferably greater than or equal to 70 mass %, even more preferably greater than or equal to 80 mass %, even more preferably greater than or equal to 90 mass % of a Group III base stock, based on the total mass of the oil of lubricating viscosity. Most preferably, the oil of lubricating viscosity consists essentially of a Group III base stock. In some embodiments the oil of lubricating viscosity consists solely of Group III base stock. In the latter case it is acknowledged that additives included in the lubricating oil composition may comprise a carrier oil which is not a Group III base stock.
Other oils of lubricating viscosity which may be included in the lubricating oil composition are detailed as follows:
Natural oils include animal and vegetable oils (e.g. castor and lard oil), liquid petroleum oils and hydrorefined, solvent-treated mineral lubricating oils of the paraffinic, naphthenic and mixed paraffinic-naphthenic types. Oils of lubricating viscosity derived from coal or shale are also useful base oils.
Synthetic lubricating oils include hydrocarbon oils such as polymerized and interpolymerized olefins (e.g. polybutylenes, polypropylenes, propylene-isobutylene copolymers, chlorinated polybutylenes, poly(1-hexenes), poly(1-octenes), poly(1-decenes)); alkylbenzenes (e.g. dodecylbenzenes, tetradecylbenzenes, dinonylbenzenes, di(2-ethylhexyl)benzenes); polyphenols (e.g. biphenyls, terphenyls, alkylated polyphenols); and alkylated diphenyl ethers and alkylated diphenyl sulfides and the derivatives, analogues and homologues thereof.
Another suitable class of synthetic lubricating oils comprises the esters of dicarboxylic acids (e.g. phthalic acid, succinic acid, alkyl succinic acids and alkenyl succinic acids, maleic acid, azelaic acid, suberic acid, sebasic acid, fumaric acid, adipic acid, linoleic acid dimer, malonic acid, alkylmalonic acids, alkenyl malonic acids) with a variety of alcohols (e.g. butyl alcohol, hexyl alcohol, dodecyl alcohol, 2-ethylhexyl alcohol, ethylene glycol, diethylene glycol monoether, propylene glycol). Specific examples of these esters include dibutyl adipate, di(2-ethylhexyl) sebacate, di-n-hexyl fumarate, dioctyl sebacate, diisooctyl azelate, diisodecyl azelate, dioctyl phthalate, didecyl phthalate, dieicosyl sebacate, the 2-ethylhexyl diester of linoleic acid dimer, and the complex ester formed by reacting one mole of sebacic acid with two moles of tetraethylene glycol and two moles of 2-ethylhexanoic acid.
Esters useful as synthetic oils also include those made from C₅ to C₁₂ monocarboxylic acids and polyols, and polyol ethers such as neopentyl glycol, trimethylolpropane, pentaerythritol, dipentaerythritol and tripentaerythritol.
Unrefined, refined and re-refined oils can be used in the compositions of the present invention. Unrefined oils are those obtained directly from a natural or synthetic source without further purification treatment. For example, a shale oil obtained directly from retorting operations, a petroleum oil obtained directly from distillation or ester oil obtained directly from an esterification process and used without further treatment would be unrefined oil. Refined oils are similar to the unrefined oils except they have been further treated 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. Re-refined oils are obtained by processes similar to those used to obtain refined oils applied to refined oils which have been already used in service. Such re-refined oils are also known as reclaimed or reprocessed oils and often are additionally processed by techniques for approval of spent additive and oil breakdown products.
Other examples of base oil are gas-to-liquid ("GTL") base oils, i.e. the base oil may be an oil derived from Fischer-Tropsch synthesised hydrocarbons made from synthesis gas containing H₂ and CO using a Fischer-Tropsch catalyst. These hydrocarbons typically require further processing in order to be useful as a base oil. For example, they may, by methods known in the art, be hydroisomerized; hydrocracked and hydroisomerized; dewaxed; or hydroisomerized and dewaxed.
The oil of lubricating viscosity may also comprise a Group I, Group II, Group IV or Group V base stocks or base oil blends of the aforementioned base stocks.
Preferably, the volatility of the oil of lubricating viscosity or oil blend, as measured by the NOACK test (ASTM D5880), is less than or equal to 16%, preferably less than or equal to 13.5%, preferably less than or equal to 12%, more preferably less than or equal to 10%, most preferably less than or equal to 8%. Preferably, the viscosity index (VI) of the oil of lubricating viscosity is at least 95, preferably at least 110, more preferably at least 120, even more preferably at least 125, most preferably from about 130 to 140.
The oil of lubricating viscosity is provided in a major amount, in combination with a minor amount of additive component (B), as defined herein and, if necessary, one or more co-additives, such as described hereinafter, constituting a lubricating oil composition. This preparation may be accomplished by adding the additives directly to the oil or by adding them in the form of a concentrate thereof 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, at the same time as, or after addition of other additives.
Preferably, the oil of lubricating viscosity is present in an amount of greater than 55 mass %, more preferably greater than 60 mass %, even more preferably greater than 65 mass %, based on the total mass of the lubricating oil composition. Preferably, the oil of lubricating viscosity is present in an amount of less than 98 mass %, more preferably less than 95 mass %, even more preferably less than 90 mass %, based on the total mass of the lubricating oil composition.
The lubricating oil compositions of the invention comprise defined components that may or may not remain the same chemically before and after mixing with an oleaginous carrier. This invention encompasses compositions which comprise the defined components before mixing, or after mixing, or both before and after mixing.
When concentrates are used to make the lubricating oil compositions, they may for example be diluted with 3 to 100, e.g. 5 to 40, parts by mass of oil of lubricating viscosity per part by mass of the concentrate.
Preferably, the lubricating oil composition of the present invention contains low levels of phosphorus, namely up to 0.12 mass %, preferably up to 0.11 mass %, more preferably not greater than 0.10 mass %, even more preferably up to 0.09 mass %, even more preferably up to 0.08 mass %, even more preferably up to 0.06 mass % of phosphorus, expressed as atoms of phosphorus, based on the total mass of the composition.
Typically, the lubricating oil composition may contain low levels of sulfur. Preferably, the lubricating oil composition contains up to 0.4, more preferably up to 0.3, most preferably up to 0.2, mass % sulfur, expressed as atoms of sulfur, based on the total mass of the composition.
Typically, the lubricating oil composition may contain low levels of sulphated ash. Preferably, the lubricating oil composition contains up to and including 1.2, more preferably up to 1.1, even more preferably up to 1.0, even more preferably up to 0.8, mass % sulphated ash, based on the total mass of the composition.
Suitably, the lubricating oil composition may have a total base number (TBN) of 4 to 15, preferably 5 to 12. In heavy duty diesel (HDD) engine applications the TBN of the lubricating composition ranges from about 4 to 12, such as 6 to 12. In a passenger car diesel engine lubricating oil composition (PCDO) and a passenger car motor oil for a spark-ignited engine (PCMO), the TBN of the lubricating composition ranges from about 5.0 to about 12.0, such as from about 5.0 to about 11.0.
Preferably, the lubricating oil composition is a multigrade identified by the viscometric descriptor SAE 20WX, SAE 15WX, SAE 10WX, SAE 5WX or SAE 0WX, where X represents any one of 20, 30, 40 and 50; the characteristics of the different viscometric grades can be found in the SAE J300 classification. In an embodiment of each aspect of the invention, independently of the other embodiments, the lubricating oil composition is in the form of an SAE 10WX, SAE 5WX or SAE 0WX, preferably in the form of an SAE 5WX or SAE 0WX, wherein X represents any one of 20, 30, 40 and 50. Preferably X is 20 or 30.

BORON COMPOUND (B)

Additive component B comprises an oil-soluble boron containing compound. The boron containing compound may comprise a borated dispersant, a borated detergent, a borated ester, a borated amide, or other boron containing additive, or a mixture thereof, or by addition of elemental boron or other boron compound.
Preferably, the oil-soluble boron containing compound comprises a borated dispersant, a borated detergent, a borated ester or a borated amide. More preferably, the oil-soluble boron containing compound comprises a borated dispersant, a borated detergent or a borated ester, even more preferably a borated dispersant or borated detergent, especially a borated dispersant.
Conveniently, the boron containing compound comprises a borated dispersant, preferably an ashless borated dispersant, especially an ashless nitrogen containing borated dispersant. Accordingly, the dispersants disclosed herein are preferably ashless (i.e. metal free) dispersants and are borated using conventional techniques.
A dispersant is an additive whose primary function is to hold solid and liquid contaminations in suspension, thereby passivating them and reducing engine deposits at the same time as reducing sludge depositions. For example, a dispersant maintains in suspension oil-insoluble substances that result from oxidation during use of the lubricant, thus preventing sludge flocculation and precipitation or deposition on metal parts of the engine.
Dispersants are usually "ashless", being non-metallic organic materials that form substantially no ash on combustion, in contrast to metal-containing, and hence ashforming materials. They comprise a long hydrocarbon chain (e.g. hydrocarbon polymer backbone) with a polar head, the polarity being derived from inclusion of e.g. an O, P, or N atom. Typically, such dispersants have amine, amine-alcohol or amide polar moieties attached to the hydrocarbon chain, often via a bridging group. The hydrocarbon chain is an oleophilic group that confers oil-solubility, having, for example 40 to 500 carbon atoms. Thus, ashless dispersants may comprise an oil-soluble polymeric backbone. A suitable ashless dispersant may be, for example, selected from oil soluble salts, esters, amino-esters, amides, imides and oxazolines of long chain hydrocarbon-substituted mono- and polycarboxylic acids or anhydrides thereof; thiocarboxylate derivatives of long chain hydrocarbons; long chain aliphatic hydrocarbons having polyamine moieties attached directly thereto; and Mannich condensation products formed by condensing a long chain substituted phenol with formaldehyde and polyalkylene polyamine.
It is preferred that all the dispersant or dispersants used (including all nitrogen-containing dispersant and any nitrogen-free dispersant) be derived from hydrocarbon polymers having an average number average molecular weight (M_n) of from about 600 to 3000, more preferably 700 to 2700, even more preferably 700 to 2500, even more preferably 800 to 2400, even more preferably 800 to 2000, especially 800 to 1250.
A highly preferred ashless dispersant comprises a dispersant that is derived from a polyalkenyl-substituted mono- or di- carboxylic acid, anhydride or ester, most preferably a dispersant that is derived from a polyisobutenyl-substituted mono- or dicarboxylic acid, anhydride or ester.
Preferably, the polyalkenyl moiety of the dispersant has a number average molecular weight of from 600 to 3000, more preferably 700 to 2700, even more preferably 700 to 2500, even more preferably 800 to 2400, even more preferably 800 to 2000, especially 800 to 1250. The molecular weight of a dispersant is generally expressed in terms of the molecular weight of the polyalkenyl moiety as the precise molecular weight range of the dispersant depends on numerous parameters including the type of polymer used to derive the dispersant, the number of functional groups, and the type of nucleophilic group employed.
Preferably, the dispersant has greater than 1.1, more preferably greater than or equal to 1.2, even more preferably greater than or equal to 1.25, most preferably greater than or equal to 1.3 functional groups (mono- or dicarboxylic acid producing moieties) per polyalkenyl moiety. Preferably, the dispersant has less than or equal to 1.9, more preferably less than or equal to 1.8, even more preferably less than or equal to 1.7, even more preferably less than or equal to 1.6, most preferably less than or equal to 1.5, functional groups (mono- or dicarboxylic acid producing moieties) per polyalkenyl moiety. Functionality (F) can be determined according to the following formula: $F = ({SAP x M}_{n}) / ((112, 200 x A . I .) - (SAP x Molecular weight of acylating agent))$
wherein SAP is the saponification number (i.e., the number of milligrams of KOH consumed in the complete neutralization of the acid groups in one gram of the succinic-containing reaction product, as determined according to ASTM D94); M_n is the number average molecular weight of the starting olefin polymer; and A.I. is the percent active ingredient of the succinic-containing reaction product (the remainder being unreacted olefin polymer, succinic anhydride and diluent).
Generally, each mono- or dicarboxylic acid-producing moiety will react with a nucleophilic group (amine or amide) and the number of functional groups in the polyalkenyl-substituted carboxylic acylating agent will determine the number of nucleophilic groups in the finished dispersant.
Preferably, the polyalkenyl moiety from which dispersants may be derived has a narrow molecular weight distribution (MWD), also referred to as polydispersity, as determined by the ratio of weight average molecular weight (M_w) to number average molecular weight (M_n). Specifically, hydrocarbon polymers, particularly the polyalkenyl moiety, from which the dispersants are derived have a M_w/M_n of from about 1.5 to about 2.0, preferably from about 1.5 to about 1.9, most preferably from about 1.6 to about 1.8.
Suitable hydrocarbons or polymers employed in the formation of the dispersants include homopolymers, interpolymers or lower molecular weight hydrocarbons. One family of such polymers comprise polymers of ethylene and/or at least one C₃ to C₂₈ alpha-olefin having the formula H₂C=CHR¹ wherein R¹ is straight or branched chain alkyl radical comprising 1 to 26 carbon atoms and wherein the polymer contains carbon-to-carbon unsaturation, preferably a high degree of terminal ethenylidene unsaturation. Preferably, such polymers comprise interpolymers of ethylene and at least one alpha-olefin of the above formula, wherein R¹ is alkyl of from 1 to 18 carbon atoms, and more preferably is alkyl of from 1 to 8 carbon atoms, and more preferably still of from 1 to 2 carbon atoms. Therefore, useful alpha-olefin monomers and comonomers include, for example, propylene, but-1-ene, hex-1-ene, oct-1-ene, 4-methylpent-1-ene, dec-1-ene, dodec-1-ene, tridec-1-ene, tetradec-1-ene, pentadec-1-ene, hexadec-1-ene, heptadec-1-ene, octadec-1-ene, nonadec-1-ene, and mixtures thereof (e.g., mixtures of propylene and but-1-ene, and the like). Exemplary of such polymers are propylene homopolymers, but-1-ene homopolymers, ethylene-propylene copolymers, ethylene-but-1-ene copolymers, propylene-butene copolymers and the like, wherein the polymer contains at least some terminal and/or internal unsaturation. Preferred polymers are unsaturated copolymers of ethylene and propylene and ethylene and but-1-ene. The interpolymers may contain a minor amount, e.g. 0.5 to 5 mole % of a C₄ to C₁₈ non-conjugated diolefin comonomer. However, it is preferred that the polymers comprise only alpha-olefin homopolymers, interpolymers of alpha-olefin comonomers and interpolymers of ethylene and alpha-olefin comonomers. The molar ethylene content of the polymers employed is preferably in the range of 0 to 80 %, and more preferably 0 to 60 %. When propylene and/or but-1-ene are employed as comonomer(s) with ethylene, the ethylene content of such copolymers is most preferably between 15 and 50 %, although higher or lower ethylene contents may be present.
These polymers may be prepared by polymerizing alpha-olefin monomer, or mixtures of alpha-olefin monomers, or mixtures comprising ethylene and at least one C₃ to C₂₈ alpha-olefin monomer, in the presence of a catalyst system comprising at least one metallocene (e.g., a cyclopentadienyl-transition metal compound) and an alumoxane compound. Using this process, a polymer in which 95 % or more of the polymer chains possess terminal ethenylidene-type unsaturation can be provided. The percentage of polymer chains exhibiting terminal ethenylidene unsaturation may be determined by FTIR spectroscopic analysis, titration, or C¹³ NMR. Interpolymers of this latter type may be characterized by the formula POLY-C(R¹)=CH₂ wherein R¹ is C₁ to C₂₆ alkyl, preferably C₁ to C₁₈ alkyl, more preferably C₁ to C₈ alkyl, and most preferably C₁ to C₂ alkyl, (e.g., methyl or ethyl) and wherein POLY represents the polymer chain. The chain length of the R¹ alkyl group will vary depending on the comonomer(s) selected for use in the polymerization. A minor amount of the polymer chains can contain terminal ethenyl, i.e., vinyl, unsaturation, i.e. POLY-CH=CH₂, and a portion of the polymers can contain internal monounsaturation, e.g. POLY-CH=CH(R¹), wherein R¹ is as defined above. These terminally unsaturated interpolymers may be prepared by known metallocene chemistry and may also be prepared as described in U.S. Patent Nos. 5,498,809 ; 5,663,130 ; 5,705,577 ; 5,814,715 ; 6,022,929 and 6,030,930 .
Another useful class of polymers is polymers prepared by cationic polymerization of isobutene, styrene, and the like. Common polymers from this class include polyisobutenes obtained by polymerization of a C₄ refinery stream having a butene content of about 35 to about 75% by wt., and an isobutene content of about 30 to about 60% by wt., in the presence of a Lewis acid catalyst, such as aluminum trichloride or boron trifluoride. A preferred source of monomer for making poly-n-butenes is petroleum feed streams such as Raffinate II. These feedstocks are disclosed in the art such as in U.S. Patent No. 4,952,739 . Polyisobutylene (PIB) is a most preferred backbone of the present invention because it is readily available by cationic polymerization from butene streams (e.g., using AlCl₃ or BF₃ catalysts). Such polyisobutylenes generally contain residual unsaturation in amounts of about one ethylenic double bond per polymer chain, positioned along the chain. In certain embodiments, the polyalkenyl moiety of the dispersant comprises a highly reactive polyisobutylene (HR-PIB), having a terminal vinylidene content of at least 65%, e.g., 70%, more preferably at least 80%, most preferably, at least 85%. The preparation of such polymers is described, for example, in U.S. Patent No. 4,152,499 . HR-PIB is known and HR-PIB is commercially available under the tradenames Glissopal^™ (from BASF) and Ultravis^™ (from BP).
The hydrocarbon or polymer backbone can be functionalized, e.g., with carboxylic acid producing moieties (preferably acid or anhydride moieties) selectively at sites of carbon-to-carbon unsaturation on the polymer or hydrocarbon chains, or randomly along chains using any of the three processes mentioned above or combinations thereof, in any sequence.
Processes for reacting polymeric hydrocarbons with unsaturated carboxylic acids, anhydrides or esters and the preparation of derivatives from such compounds are disclosed in U.S. Patent Nos. 3,087,936 ; 3,172,892 ; 3,215,707 ; 3,231,587 ; 3,272,746 ; 3,275,554 ; 3,381,022 ; 3,442,808 ; 3,565,804 ; 3,912,764 ; 4,110,349 ; 4,234,435 ; 5,777,025 ; 5,891,953 ; as well as EP 0 382 450 B1 ; CA-1,335,895 and GB-A-1,440,219 . The polymer or hydrocarbon may be functionalized, for example, with carboxylic acid producing moieties (preferably acid or anhydride) by reacting the polymer or hydrocarbon under conditions that result in the addition of functional moieties or agents, i.e., acid, anhydride, ester moieties, etc., onto the polymer or hydrocarbon chains primarily at sites of carbon-to-carbon unsaturation (also referred to as ethylenic or olefinic unsaturation) using the halogen assisted functionalization (e.g. chlorination) process or the thermal "ene" reaction.
Selective functionalization can be accomplished by halogenating, e.g., chlorinating or brominating the unsaturated α-olefin polymer to about 1 to 8 wt. %, preferably 3 to 7 wt. % chlorine, or bromine, based on the weight of polymer or hydrocarbon, by passing the chlorine or bromine through the polymer at a temperature of 60 to 250°C, preferably 110 to 160°C, e.g., 120 to 140°C, for about 0.5 to 10, preferably 1 to 7 hours. The halogenated polymer or hydrocarbon (hereinafter backbone) is then reacted with sufficient monounsaturated reactant capable of adding the required number of functional moieties to the backbone, e.g., monounsaturated carboxylic reactant, at 100 to 250°C, usually about 180°C to 235°C, for about 0.5 to 10, e.g., 3 to 8 hours, such that the product obtained will contain the desired number of moles of the monounsaturated carboxylic reactant per mole of the halogenated backbones. Alternatively, the backbone and the monounsaturated carboxylic reactant are mixed and heated while adding chlorine to the hot material.
While chlorination normally helps increase the reactivity of starting olefin polymers with monounsaturated functionalizing reactant, it is not necessary with some of the polymers or hydrocarbons contemplated for use in the present invention, particularly those preferred polymers or hydrocarbons which possess a high terminal bond content and reactivity. Preferably, therefore, the backbone and the monounsaturated functionality reactant, e.g., carboxylic reactant, are contacted at elevated temperature to cause an initial thermal "ene" reaction to take place. Ene reactions are known.
The hydrocarbon or polymer backbone can be functionalized by random attachment of functional moieties along the polymer chains by a variety of methods. For example, the polymer, in solution or in solid form, may be grafted with the monounsaturated carboxylic reactant, as described above, in the presence of a free-radical initiator. When performed in solution, the grafting takes place at an elevated temperature in the range of about 100 to 260°C, preferably 120 to 240°C. Preferably, free-radical initiated grafting would be accomplished in a mineral lubricating oil solution containing, e.g., 1 to 50 wt. %, preferably 5 to 30 wt. % polymer based on the initial total oil solution.
The free-radical initiators that may be used are peroxides, hydroperoxides, and azo compounds, preferably those that have a boiling point greater than about 100°C and decompose thermally within the grafting temperature range to provide free-radicals. Representative of these free-radical initiators are azobutyronitrile, 2,5-dimethylhex-3-ene-2, 5-bis-tertiary-butyl peroxide and dicumene peroxide. The initiator, when used, typically is used in an amount of between 0.005% and 1% by weight based on the weight of the reaction mixture solution. Typically, the aforesaid monounsaturated carboxylic reactant material and free-radical initiator are used in a weight ratio range of from about 1.0:1 to 30:1, preferably 3:1 to 6:1. The grafting is preferably carried out in an inert atmosphere, such as under nitrogen blanketing. The resulting grafted polymer is characterized by having carboxylic acid (or ester or anhydride) moieties randomly attached along the polymer chains: it being understood, of course, that some of the polymer chains remain ungrafted. The free radical grafting described above can be used for the other polymers and hydrocarbons of the present invention.
The preferred monounsaturated reactants that are used to functionalize the backbone comprise mono- and dicarboxylic acid material, i.e., acid, anhydride, or acid ester material, including (i) monounsaturated C₄ to C₁₀ dicarboxylic acid wherein (a) the carboxyl groups are vicinyl, (i.e., located on adjacent carbon atoms) and (b) at least one, preferably both, of said adjacent carbon atoms are part of said mono unsaturation; (ii) derivatives of (i) such as anhydrides or C₁ to C₅ alcohol derived mono- or diesters of (i); (iii) monounsaturated C₃ to C₁₀ monocarboxylic acid wherein the carbon-carbon double bond is conjugated with the carboxy group, i.e., of the structure -C=C-CO-; and (iv) derivatives of (iii) such as C₁ to C₅ alcohol derived mono- or diesters of (iii). Mixtures of monounsaturated carboxylic materials (i) - (iv) also may be used. Upon reaction with the backbone, the monounsaturation of the monounsaturated carboxylic reactant becomes saturated. Thus, for example, maleic anhydride becomes backbone-substituted succinic anhydride, and acrylic acid becomes backbone-substituted propionic acid. Exemplary of such monounsaturated carboxylic reactants are fumaric acid, itaconic acid, maleic acid, maleic anhydride, chloromaleic acid, chloromaleic anhydride, acrylic acid, methacrylic acid, crotonic acid, cinnamic acid, and lower alkyl (e.g., C₁ to C₄ alkyl) acid esters of the foregoing, e.g., methyl maleate, ethyl fumarate, and methyl fumarate.
To provide the required functionality, the monounsaturated carboxylic reactant, preferably maleic anhydride, typically will be used in an amount ranging from about equimolar amount to about 100 wt. % excess, preferably 5 to 50 wt. % excess, based on the moles of polymer or hydrocarbon. Unreacted excess monounsaturated carboxylic reactant can be removed from the final dispersant product by, for example, stripping, usually under vacuum, if required.
The functionalized oil-soluble polymeric hydrocarbon backbone is then derivatized with a nitrogen-containing nucleophilic reactant, such as an amine, amino-alcohol, amide, or mixture thereof, to form a corresponding derivative. Amine compounds are preferred. Useful amine compounds for derivatizing functionalized polymers comprise at least one amine and can comprise one or more additional amine or other reactive or polar groups. These amines may be hydrocarbyl amines or may be predominantly hydrocarbyl amines in which the hydrocarbyl group includes other groups, e.g., hydroxy groups, alkoxy groups, amide groups, nitriles, imidazoline groups, and the like. Particularly useful amine compounds include mono- and polyamines, e.g., polyalkene and polyoxyalkylene polyamines of about 2 to 60, such as 2 to 40 (e.g., 3 to 20) total carbon atoms having about 1 to 12, such as 3 to 12, preferably 3 to 9, most preferably form about 6 to about 7 nitrogen atoms per molecule. Mixtures of amine compounds may advantageously be used, such as those prepared by reaction of alkylene dihalide with ammonia. Preferred amines are aliphatic saturated amines, including, for example, 1,2-diaminoethane; 1,3-diaminopropane; 1,4-diaminobutane; 1,6-diaminohexane; polyethylene amines such as diethylene triamine; triethylene tetramine; tetraethylene pentamine; and polypropyleneamines such as 1,2-propylene diamine; and di-(1,2-propylene)triamine. Such polyamine mixtures, known as PAM, are commercially available. Particularly preferred polyamine mixtures are mixtures derived by distilling the light ends from PAM products. The resulting mixtures, known as "heavy" PAM, or HPAM, are also commercially available. The properties and attributes of both PAM and/or HPAM are described, for example, in U.S. Patent Nos. 4,938,881 ; 4,927,551 ; 5,230,714 ; 5,241,003 ; 5,565,128 ; 5,756,431 ; 5,792,730 ; and 5,854,186 .
Other useful amine compounds include: alicyclic diamines such as 1,4-di(aminomethyl) cyclohexane and heterocyclic nitrogen compounds such as imidazolines. Another useful class of amines is the polyamido and related amido- amines as disclosed in U.S. Patent Nos. 4,857,217 ; 4,956,107 ; 4,963,275 ; and 5,229,022 . Also usable is tris(hydroxymethyl)amino methane (TAM) as described in U.S. Patent Nos. 4,102,798 ; 4,113,639 ; 4,116,876 ; and UK 989,409 . Dendrimers, star-like amines, and comb-structured amines may also be used. Similarly, one may use condensed amines, as described in U.S. Patent No. 5,053,152 . The functionalized polymer is reacted with the amine compound using conventional techniques as described, for example, in U.S. Patent Nos. 4,234,435 and 5,229,022 , as well as in EP-A-208,560 .
A highly preferred borated dispersant is an ashless nitrogen containing borated dispersant which is the reaction product of a polyalkenyl-substituted mono- or dicarboxylic acid, anhydride or ester, a polyamine and a boron containing compound. More preferably, the ashless nitrogen containing borated dispersant is the reaction product of a polyisobutenyl-substituted mono- or di- carboxylic acid, anhydride or ester, a polyamine and a boron containing compound.
A most preferred dispersant is one comprising at least one polyalkenyl succinimide, especially a polyisobutenyl succinimide, which is the reaction product of a polyalkenyl substituted succinic anhydride (e.g., PIBSA) and a polyamine (PAM). In other words, a most preferred ashless nitrogen containing borated dispersant comprises the reaction product of a polyalkenyl substituted succinic anhydride, especially a polyisobutenyl-substituted succinic anhydride (i.e. PIBSA), a polyamine (PAM) and a boron containing compound. Preferably, such dispersants have a coupling ratio of from about 0.65 to about 1.25, preferably from about 0.8 to about 1.1, most preferably from about 0.9 to about 1. In the context of this disclosure, "coupling ratio" may be defined as a ratio of the number of succinyl groups in the PIBSA to the number of primary amine groups in the polyamine reactant.
Another class of high molecular weight ashless dispersants comprises Mannich base condensation products. Generally, these products are prepared by condensing about one mole of a long chain alkyl-substituted mono- or polyhydroxy benzene with about 1 to 2.5 moles of carbonyl compound(s) (e.g., formaldehyde and paraformaldehyde) and about 0.5 to 2 moles of polyalkylene polyamine, as disclosed, for example, in U.S. Patent No. 3,442,808 . Such Mannich base condensation products may include a polymer product of a metallocene catalyzed polymerization as a substituent on the benzene group, or may be reacted with a compound containing such a polymer substituted on a succinic anhydride in a manner similar to that described in U.S. Patent No. 3,442,808 . Examples of functionalized and/or derivatized olefin polymers synthesized using metallocene catalyst systems are described in the publications identified supra.
The dispersant(s) are preferably non-polymeric (e.g., are mono- or bis-succinimides). It is further preferred that the dispersant or dispersants contribute, in total, from about 0.10 to about 0.20 wt. %, preferably from about 0.115 to about 0.18 wt. %, most preferably from about 0.12 to about 0.16 wt. % of nitrogen to the lubricating oil composition.
The dispersants can be borated by conventional means, as generally taught in U.S. Patent Nos. 3,087,936 , 3,254,025 and 5,430,105 . Boration of the dispersant is readily accomplished by treating an acyl nitrogen-containing dispersant with a boron compound such as boron oxide, boron halide boron acids, and esters of boron acids, in an amount sufficient to provide from about 0.1 to about 20 atomic proportions of boron for each mole of acylated nitrogen composition.
The boron, which appears in the product as dehydrated boric acid polymers (primarily (HBO₂)₃), is believed to attach to the dispersant imides and diimides as amine salts, e.g., the metaborate salt of the diimide. Boration can be carried out by adding a sufficient quantity of a boron compound, preferably boric acid, usually as a slurry, to the acyl nitrogen compound and heating with stirring at from about 135°C to about 190°C, e.g., 140°C to 170°C, for from about 1 to about 5 hours, followed by nitrogen stripping. Alternatively, the boron treatment can be conducted by adding boric acid to a hot reaction mixture of the dicarboxylic acid material and amine, while removing water. Other post reaction processes known in the art can also be applied. Non-dispersant boron containing compounds include boron oxide, boron oxide hydrate, boron trioxide, boron trifluoride, boron tribromide, boron trichloride, boron acid such as boronic acid, boric acid, tetraboric acid and metaboric acid, boron hydrides, boron amides and various esters of boron acids. Suitable "non-dispersant boron sources" may comprise any oil-soluble, boron-containing compound, but preferably comprise one or more boron-containing additives known to impart enhanced properties to lubricating oil compositions. Such boron-containing additives include, for example, borated dispersant VI improver; alkali metal, mixed alkali metal or alkaline earth metal borate; borated overbased metal detergent; borated epoxide; borate ester; and borate amide.
Alkali metal and alkaline earth metal borates are generally hydrated particulate metal borates, which are known in the art. Alkali metal borates include mixed alkali and alkaline earth metal borates. These metal borates are available commercially. Representative patents describing suitable alkali metal and alkaline earth metal borates and their methods of manufacture include U.S. Patent Nos. 3,997,454 ; 3,819,521 ; 3,853.772 ; 3,907,601 ; 3,997,454 ; and 4,089,790 .
The borated amines maybe prepared by reacting one or more of the above boron compounds with one or more of fatty amines, e.g., an amine having from four to eighteen carbon atoms. They may be prepared by reacting the amine with the boron compound at a temperature of from 50 to 300, preferably from 100 to 250 °C and at a ratio from 3:1 to 1:3 equivalents of amine to equivalents of boron compound.
Borated fatty epoxides are generally the reaction product of one or more of the above boron compounds with at least one epoxide. The epoxide is generally an aliphatic epoxide having from 8 to 30, preferably from 10 to 24, more preferably from 12 to 20, carbon atoms. Examples of useful aliphatic epoxides include heptyl epoxide and octyl epoxide. Mixtures of epoxides may also be used, for instance commercial mixtures of epoxides having from 14 to 16 carbon atoms and from 14 to 18 carbon atoms. The borated fatty epoxides are generally known and are described in U.S. Patent 4,584,115 . Borate esters may be prepared by reacting one or more of the above boron compounds with one or more alcohol of suitable oleophilicity. Typically, the alcohol contains from 6 to 30, or from 8 to 24, carbon atoms. Methods of making such borate esters are known in the art.
The borate esters can be borated phospholipids. Such compounds, and processes for making such compounds, are described in EP-A-0 684 298 . Borated overbased metal detergents are known in the art where the borate substitutes the carbonate in the core either in part or in full.
In an embodiment of the present invention a borated dispersant as defined herein represents the sole boron containing compound in the lubricating oil composition.
Preferably, the boron containing compound introduces into the lubricating oil composition greater than 100, more preferably greater than 150, even more preferably greater than 175, even more preferably greater than 200, most preferably greater than 225, ppm of boron, based on the total mass of the lubricating oil composition. Preferably, the boron containing compound introduces into the lubricating oil composition less than 10000, more preferably less than 7000, even more preferably less than 3000, even more preferably less than 1000, most preferably less than 500, ppm of boron, based on the total mass of the lubricating oil composition.

ENGINES

The lubricating oil compositions of the invention may be used to lubricate mechanical engine components, particularly in internal combustion engines, e.g. spark-ignited or compression-ignited two- or four- stroke reciprocating engines, by adding the composition thereto. The engines may be conventional gasoline or diesel engines designed to be powered by gasoline or petroleum diesel, respectively; alternatively, the engines may be specifically modified to be powered by an alcohol based fuel or biodiesel fuel. Preferably, the lubricating oil compositions are crankcase lubricants. Preferably, the lubricating oil composition is for use in the lubrication of a compression-ignited internal combustion engine (diesel engine), especially a compression-ignited internal combustion engine which is fuelled at least in part with a biodiesel fuel. Such engines include passenger car diesel engines and heavy duty diesel engines, for example engines found in road trucks. More preferably, the lubricating oil composition is for use in the lubrication of a passenger car compression-ignited internal combustion engine (i.e. a light duty diesel engine), which is fuelled at least in part with a biodiesel fuel, especially such an engine which employs a late post-injection of fuel into the cylinder. More preferably, the lubricating oil composition is for use in the lubrication of the crankcase of the aforementioned engines.
When the lubricating oil composition, such as a crankcase lubricant, is used in the lubrication of a spark-ignited or compression-ignited internal combustion engine which is fuelled at least in part with a biofuel, the lubricant during operation of the engine becomes contaminated with biofuel and decomposition products thereof. Thus according to a preferred aspect of the present invention, the lubricating oil composition of the present invention comprises at least 0.3, preferably at least 0.5, more preferably at least 1, even more preferably at least 5, even more preferably at least 10, even more preferably at least 15, even more preferably at least 20, mass % of biofuel and/or a decomposition product thereof. Although the lubricating oil composition may comprise up to 50 mass % of biofuel and/or a decomposition product thereof, preferably it includes less than 35, more preferably less than 30, mass % of biofuel and/or a decomposition product thereof.
The biofuel comprises an alcohol based fuel in the case of spark-ignited internal combustion engines, preferably a bioalcohol fuel, especially bioethanol fuel.
The biofuel comprises biodiesel in the case of compression ignited internal combustion engines.

BIOFUELS

Biofuels include fuels that are produced from renewable biological resources and include biodiesel fuel as defined herein and bioethanol fuel which may be derived from fermented sugar. The term biofuel also embraces an "alcohol based fuel", such as "ethanol based fuel", irrespective of the source of the alcohol (i.e. the alcohol may be derived from a renewable biological source or a non-renewable source, such as petroleum).

Alcohol Based Fuels

Alcohol based fuels are employed in spark-ignited internal combustion engines. The alcohol based fuel may include one or more alcohols selected from methanol, ethanol, propanol and butanol. The alcohol may be derived from a renewable biological source or a non-renewable source, such as petroleum. The alcohol based fuel may comprise 100 % by volume of one or more alcohols (i.e. pure alcohol). Alternatively the alcohol based fuel may comprise a blend of an alcohol and petroleum gasoline; suitable blends include 5, 10, 15, 20, 25, 30, 35, 40, 50, 60, 70, 80, 85, and 90, vol.% of the alcohol, based on the total volume of the alcohol and gasoline blend.
Preferably, the alcohol based fuel comprises an ethanol based fuel. More preferably, the alcohol based fuel comprises a bioalcohol fuel, especially a bioethanol fuel.
The bioethanol fuel comprises ethanol derived from a renewable biological source (i.e. bioethanol), preferably ethanol derived solely from a renewable biological source. The bioethanol may be derived from the sugar fermentation of crops such as corn, maize, wheat, cord grass and sorghum plants. The bioethanol fuel may comprise 100% by volume bioethanol (designated as E100); alternatively, the bioethanol fuel may comprise a blend of bioethanol and petroleum gasoline. The bioethanol fuel blend may have the designation "Exx" wherein xx refers to the amount of E100 bioethanol in vol.%, based on the total volume of the bioethanol fuel blend. For example, E10 refers to a bioethanol fuel blend which comprises 10 volume % E100 bioethanol fuel and 90 volume % of petroleum gasoline. For the avoidance of doubt, the term "bioethanol fuel" includes pure bioethanol fuel (i.e. E100) and bioethanol fuel blends comprising a mixture of bioethanol fuel and petroleum gasoline fuel.
Typically, the bioethanol fuel comprises E100, E95, E90, E85, E80, E75, E70, E65, E60, E55, E50, E45, E40, E35, E30, E25, E20, E15, E10, E8, E6 or E5. Highly preferred blends include E85 (ASTM D5798 (USA)), E10 (ASTM D4806 (USA)) and E5 (EN 228:2004 (Europe)).

Biodiesel Fuels

The biodiesel fuel comprises at least one alkyl ester, typically a mono-alkyl ester, of a long chain fatty acid derivable from vegetable oils or animal fats. Preferably, the biodiesel fuel comprises one or more methyl or ethyl esters of such long chain fatty acids, especially one or more methyl esters.
The long chain fatty acids typically comprise long chains which include carbon, hydrogen and oxygen atoms. Preferably, the long chain fatty acids include from 10 to 30, more preferably 14 to 26, most preferably 16 to 22, carbon atoms. Highly preferred fatty acids include palmitic acid, stearic acid, oleic acid and linoleic acid.
The biodiesel fuel may be derived from the esterification or transesterification of one or more vegetable oils and animal fats, such as corn oil, cashew oil, oat oil, lupine oil, kenaf oil, calendula oil, cotton oil, hemp oil, soybean oil, linseed oil, hazelnut oil, euphorbia oil, pumpkin seed oil, palm oil, rapeseed oil, olive oil, tallow oil, sunflower oil, rice oil, sesame oil or algae oil. Preferred vegetable oils include palm oil, rapeseed oil and soybean oil.
Generally, a pure biodiesel fuel that meets the ASTM D6751-08 standard (USA) or EN 14214 standard (European) specifications is designated as B100. A pure biodiesel fuel may be mixed with a petroleum diesel fuel to form a biodiesel blend which may reduce emissions and improve engine performance. Such biodiesel blends are given a designation "Bxx" where xx refers to the amount of the B100 biodiesel in volume %, based on the total volume of the biodiesel blend. For example, B10 refers to a biodiesel blend which comprises 10 volume % B100 biodiesel fuel and 90 volume % of petroleum diesel fuel. For the avoidance of doubt, the term "biodiesel fuel" includes pure biodiesel fuel (i.e. B100) and biodiesel fuel blends comprising a mixture of biodiesel fuel and petroleum diesel fuel.
Typically, the biodiesel fuel comprises a B100, B95, B90, B85, B80, B75, B70, B65, B60, B55, B50, B45, B40, B35, B30, B25, B20, B15, B10, B8, B6, B5, B4, B3, B2 or B1. Preferably, the biodiesel fuel comprises a B50 designation or lower, more preferably a B5 to B40, even more preferably B5 to B40, most preferably B5 to B20.

CO-ADDITIVES

Co-additives, with representative effective amounts, that may also be present, different from additive component (B), are listed below. All the values listed are stated as mass percent active ingredient.

Additive	Mass %	Mass %
	(Broad)	(Preferred)
Ashless Dispersant	0.1 - 20	1 - 8

Metal Detergents	0.1 - 15	0.2 - 9
Friction modifier	0 - 5	0 - 1.5
Corrosion Inhibitor	0 - 5	0 - 1.5
Metal Dihydrocarbyl Dithiophosphate	0 - 10	0 - 4
Anti-Oxidants	0 - 5	0.01 - 3
Pour Point Depressant	0.01 - 5	0.01 - 1.5
Anti-Foaming Agent	0 - 5	0.001 - 0.15
Supplement Anti-Wear Agents	0 - 5	0 - 2
Viscosity Modifier (1)	0 - 6	0.01 - 4
Mineral or Synthetic Base Oil	Balance	Balance

(1) Viscosity modifiers are used only in multi-graded oils.

The final lubricating oil composition, typically made by blending the or each additive into the base oil, may contain from 5 to 25, preferably 5 to 18, typically 7 to 15, mass % of the co-additives, the remainder being oil of lubricating viscosity.
The above mentioned co-additives are discussed in further detail as follows; as is known in the art, some additives can provide a multiplicity of effects, for example, a single additive may act as a dispersant and as an oxidation inhibitor.
A dispersant in addition to the borated dispersant (B), if present, may also be present in the lubricating oil composition. Such dispersants include non-borated hydrocarbon substituted succinimides, such as those made by reacting polyiosobutenyl substituted succinimide with a polyamine.
A detergent is an additive that reduces formation of piston deposits, for example high-temperature varnish and lacquer deposits, in engines; it normally has acid-neutralising properties and is capable of keeping finely divided solids in suspension. Most detergents are based on metal "soaps", that is metal salts of acidic organic compounds.
Detergents generally comprise a polar head with a long hydrophobic tail, the polar head comprising a metal salt of an acidic organic compound. The salts may contain a substantially stoichiometric amount of the metal when they are usually described as normal or neutral salts and would typically have a total base number or TBN (as may be measured by ASTM D2896) of from 0 to 80. Large amounts of a metal base can be included by reaction of an excess of a metal compound, such as an oxide or hydroxide, with an acidic gas such as carbon dioxide. The resulting overbased detergent comprises neutralised detergent as an outer layer of a metal base (e.g. carbonate) micelle. Such overbased detergents may have a TBN of 150 or greater, and typically of from 250 to 500 or more.
Detergents that may be used include oil-soluble neutral and overbased sulfonates, phenates, sulfurized phenates, thiophosphonates, salicylates, and naphthenates and other oil-soluble carboxylates of a metal, particularly the alkali or alkaline earth metals, e.g. sodium, potassium, lithium, calcium and magnesium. The most commonly-used metals are calcium and magnesium, which may both be present in detergents used in a lubricant, and mixtures of calcium and/or magnesium with sodium.
Particularly preferred metal detergents are neutral and overbased alkali or alkaline earth metal salicylates having a TBN of from 50 to 450, preferably a TBN of 50 to 250. Highly preferred salicylate detergents include alkaline earth metal salicylates, particularly magnesium and calcium, especially, calcium salicylates. Preferably, the alkali or alkaline earth metal salicylate detergent is the sole detergent in the lubricating oil composition.
Friction modifiers include glyceryl monoesters of higher fatty acids, for example, glyceryl mono-oleate; esters of long chain polycarboxylic acids with diols, for example, the butane diol ester of a dimerized unsaturated fatty acid; oxazoline compounds; and alkoxylated alkyl-substituted mono-amines, diamines and alkyl ether amines, for example, ethoxylated tallow amine and ethoxylated tallow ether amine.
Other known friction modifiers comprise oil-soluble organo-molybdenum compounds. Such organo-molybdenum friction modifiers also provide antioxidant and antiwear credits to a lubricating oil composition. Suitable oil-soluble organo-molybdenum compounds have a molybdenum-sulfur core. As examples there may be mentioned dithiocarbamates, dithiophosphates, dithiophosphinates, xanthates, thioxanthates, sulfides, and mixtures thereof. Particularly preferred are molybdenum dithiocarbamates, dialkyldithiophosphates, alkyl xanthates and alkylthioxanthates. The molybdenum compound is dinuclear or trinuclear.
One class of preferred organo-molybdenum compounds useful in all aspects of the present invention is tri-nuclear molybdenum compounds of the formula Mo₃S_kL_nQ_z and mixtures thereof wherein L are independently selected ligands having organo groups with a sufficient number of carbon atoms to render the compounds soluble or dispersible in the oil, n is from 1 to 4, k varies from 4 through to 7, Q is selected from the group of neutral electron donating compounds such as water, amines, alcohols, phosphines, and ethers, and z ranges from 0 to 5 and includes non-stoichiometric values. At least 21 total carbon atoms should be present among all the ligands' organo groups, such as at least 25, at least 30, or at least 35 carbon atoms.
The molybdenum compounds may be present in a lubricating oil composition at a concentration in the range 0.1 to 2 mass %, or providing at least 10 such as 50 to 2,000 ppm by mass of molybdenum atoms.
Preferably, the molybdenum from the molybdenum compound is present in an amount of from 10 to 1500, such as 20 to 1000, more preferably 30 to 750, ppm based on the total weight of the lubricating oil composition. For some applications, the molybdenum is present in an amount of greater than 500 ppm.
Anti-oxidants are sometimes referred to as oxidation inhibitors; they increase the resistance of the composition to oxidation and may work by combining with and modifying peroxides to render them harmless, by decomposing peroxides, or by rendering an oxidation catalyst inert. Oxidative deterioration can be evidenced by sludge in the lubricant, varnish-like deposits on the metal surfaces, and by viscosity growth.
They may be classified as radical scavengers (e.g. sterically hindered phenols, secondary aromatic amines, and organo-copper salts); hydroperoxide decomposers (e.g., organosulfur and organophosphorus additives); and multifunctionals (e.g. zinc dihydrocarbyl dithiophosphates, which may also function as anti-wear additives, and organo-molybdenum compounds, which may also function as friction modifiers and anti-wear additives).
Examples of suitable antioxidants are selected from copper-containing antioxidants, sulfur-containing antioxidants, aromatic amine-containing antioxidants, hindered phenolic antioxidants, dithiophosphates derivatives, metal thiocarbamates, and molybdenum-containing compounds. Preferred anti-oxidants are aromatic amine-containing antioxidants, molybdenum-containing compounds and mixtures thereof, particularly aromatic amine-containing antioxidants. Preferably, an antioxidant is present in the lubricating oil composition.
Anti-wear agents reduce friction and excessive wear and are usually based on compounds containing sulfur or phosphorous or both, for example that are capable of depositing polysulfide films on the surfaces involved. Noteworthy are dihydrocarbyl dithiophosphate metal salts wherein the metal may be an alkali or alkaline earth metal, or aluminium, lead, tin, molybdenum, manganese, nickel, copper, or preferably, zinc.
Dihydrocarbyl dithiophosphate metal salts may be prepared in accordance with known techniques by first forming a dihydrocarbyl dithiophosphoric acid (DDPA), usually by reaction of one or more alcohols or a phenol with P₂S₅ and then neutralizing the formed DDPA with a metal compound. For example, a dithiophosphoric acid may be made by reacting mixtures of primary and secondary alcohols. Alternatively, multiple dithiophosphoric acids can be prepared where the hydrocarbyl groups on one are entirely secondary in character and the hydrocarbyl groups on the others are entirely primary in character. To make the metal salt, any basic or neutral metal compound could be used but the oxides, hydroxides and carbonates are most generally employed. Commercial additives frequently contain an excess of metal due to the use of an excess of the basic metal compound in the neutralization reaction.
The preferred dihydrocarbyl dithiophosphate metal salts are zinc dihydrocarbyl dithiophosphates (ZDDP) which are oil-soluble salts of dihydrocarbyl dithiophosphoric acids and may be represented by the following formula:
wherein R¹ and R² may be the same or different hydrocarbyl radicals containing from 1 to 18, preferably 2 to 12, carbon atoms and include radicals such as alkyl, alkenyl, aryl, arylalkyl, alkaryl and cycloaliphatic radicals. Particularly preferred as R¹ and R² groups are alkyl groups of 2 to 8 carbon atoms, especially primary alkyl groups (i.e. R¹ and R² are derived from predominantly primary alcohols). Thus, the radicals may, for example, be ethyl, n-propyl, i-propyl, n-butyl, iso-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 (i.e. R¹ and R²) in the dithiophosphoric acid will
generally be about 5 or greater. Preferably, the zinc dihydrocarbyl dithiophosphate comprises a zinc dialkyl dithiophosphate.
Preferably, the lubricating oil composition contains an amount of dihydrocarbyl dithiophosphate metal salt that introduces 0.02 to 0.10 mass %, preferably 0.02 to 0.09 mass%, preferably 0.02 to 0.08 mass %, more preferably 0.02 to 0.06 mass % of phosphorus into the composition.
To limit the amount of phosphorus introduced into the lubricating oil composition to no more than 0.10 mass %, the dihydrocarbyl dithiophosphate metal salt should preferably be added to the lubricating oil compositions in amounts no greater than from 1.1 to 1.3 mass % (a.i.), based upon the total mass of the lubricating oil composition.
Examples of ashless anti-wear agents include 1,2,3-triazoles, benzotriazoles, sulfurised fatty acid esters, and dithiocarbamate derivatives.
Rust and corrosion inhibitors serve to protect surfaces against rust and/or corrosion. As rust inhibitors there may be mentioned non-ionic polyoxyalkylene polyols and esters thereof, polyoxyalkylene phenols, thiadiazoles and anionic alkyl sulfonic acids.
Pour point depressants, otherwise 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 of these additive are C₈ to C₁₈ dialkyl fumerate/vinyl acetate copolymers and polyalkylmethacrylates.
Additives of the polysiloxane type, for example silicone oil or polydimethyl siloxane, can provide foam control.
A small amount of a demulsifying component may be used. A preferred demulsifying component is described in EP-A-330,522 . It is obtained by reacting an alkylene oxide with an adduct obtained by reaction of a bis-epoxide with a polyhydric alcohol. The demulsifier should be used at a level not exceeding 0.1 mass % active ingredient. A treat rate of 0.001 to 0.05 mass % active ingredient is convenient.
Viscosity modifiers (or viscosity index improvers) impart high and low temperature operability to a 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 functionalised polymers (e.g. interpolymers of ethylene-propylene post grafted with an active monomer such as maleic anhydride) which are then derivatised with, for example, an alcohol or amine.
The lubricant may be formulated with or without a conventional viscosity modifier and with or without a dispersant viscosity modifier. Suitable compounds for use as viscosity modifiers are generally high molecular weight hydrocarbon polymers, including polyesters. Oil-soluble viscosity modifying polymers generally have weight average molecular weights of from 10,000 to 1,000,000, preferably 20,000 to 500,000, which may be determined by gel permeation chromatography or by light scattering.
The additives may be incorporated into an oil of lubricating viscosity (also known as a base oil) in any convenient way. Thus, each additive can be added directly to the oil by dispersing or dissolving it in the oil at the desired level of concentration. Such blending may occur at ambient temperature or at an elevated temperature. Typically an additive is available as an admixture with a base oil so that the handling thereof is easier.
When a plurality of additives are employed it may be desirable, although not essential, to prepare one or more additive packages (also known as additive compositions or concentrates) comprising additives and a diluent, which can be a base oil, whereby the additives, with the exception of viscosity modifiers, multifuntional viscosity modifiers and pour point depressants, can be added simultaneously to the base oil to form the lubricating oil composition. Dissolution of the additive package(s) into the oil of lubricating viscosity may be facilitated by diluent or solvents and by mixing accompanied with mild heating, but this is not essential. The additive package(s) will typically be formulated to contain the additive(s) in proper amounts to provide the desired concentration in the final formulation when the additive package(s) is/are combined with a predetermined amount of oil of lubricating viscosity. Thus, one or more detergents may be added to small amounts of base oil or other compatible solvents (such as a carrier oil or diluent oil) together with other desirable additives to form additive packages containing from 2.5 to 90, preferably from 5 to 75, most preferably from 8 to 60, mass %, based on the mass of the additive package, of additives on an active ingredient basis in the appropriate proportions. The final formulations may typically contain 5 to 40 mass % of the additive package(s), the remainder being oil of lubricating viscosity.
Preferably, the oil-soluble boron containing compound (i.e. additive component (B)) forms part of an additive package which also includes a diluent, preferably a base stock, and one or more co-additives in a minor amount, other than additive component (B), selected from ashless dispersants, metal detergents, corrosion inhibitors, antioxidants, antiwear agents, friction modifiers, demulsifiers and antifoam agents; the additive package being added to the oil of lubricating viscosity comprising a Group III base stock.

EXAMPLES

The invention will now be particularly described in the following examples which are not intended to limit the scope of the claims hereof.

Corrosion Control: High Temperature Corrosion Bench Test (HTCBT)

Corrosion control is measured using the High Temperature Corrosion Bench Test (HTCBT) in accordance with ASTM D6594-06. This test method simulates the corrosion of non-ferrous metals, such as copper and lead found in cam followers and bearings, in lubricants; the corrosion process under investigation being induced by lubricant chemistry rather than lubricant degradation or contamination.
Four metal specimens of copper, lead, tin and phosphor bronze are immersed in a measured amount of a test lubricating oil (100 ml) within a sample tube. The sample tube is immersed in a heated oil bath so that the temperature of the test lubricating oil is heated to 135°C. The test lubricating oil is heated at 135°C for 168 hours and during this time dry air is blown through the heated oil at a rate of 5 litres per hour. After which, the test lubricating oil is cooled and the metal specimens removed and examined for corrosion. The concentration of copper, tin and lead in the test lubricating oil composition and a reference sample of the lubricating oil composition (i.e. a new sample of the test lubricating oil) is then determined in accordance with ASTM D5185. The difference between the concentration of each of the metal contaminants in the test lubricating oil composition and those of the reference sample lubricating oil composition provides a value for the change in the various metal concentrations before and after the test.
The industry standard limits to meet the requirements of API CJ-4, which involves testing the lubricant in the absence of any added fuel, are 20 ppm maximum for copper and 120 ppm maximum for lead (i.e. these are the test limits for the pure lubricant only). Suitably, when the test is performed with a lubricating oil composition which includes a biofuel or a petroleum fuel, then the test has essentially been modified and such compositions are not required to meet the requirements of API CJ-4; the results of the test being used for comparative purposes to assess the effects of certain additives in the presence of a biofuel.

Oxidative Stability: Hot Surface Oxidation Test

Oxidative stability is measured using the Hot Surface Oxidation Test which determines the Oxidation Induction Time (OIT) of a lubricating oil composition by Pressure Differential Scanning Calorimetry (PDSC).
A measured sample (3 mg) of a lubricating oil composition is placed in a test cell of a Pressure Differential Scanning Calorimeter (Netzsch 204 HPDSC) and the cell pressurised to 689.5 KPa (100 psi) with clean dry air. The cell is then heated at a rate of 40°C per minute until the isothermal test temperature of 210°C is attained and the sample maintained at this temperature for a maximum of 240 minutes. The calorimeter provides a value of the OIT i.e. the time taken for the sample to oxidise; a larger OIT indicates the sample is more stable to oxidation than a sample having a smaller OIT.
Unless otherwise specified, all of the additives described in the Examples are available as standard additives from lubricant additive companies such as Infineum UK Ltd, Lubrizol Corporation and Afton Chemicals Corporation, for example.

Example 1

A series of 5W-30 multigrade lubricating oil compositions, as detailed in Table 1, were prepared by admixing a Group III base stock with known additives including an overbased calcium salicylate detergent (TBN 350 mgKOH/g), a neutral calcium salicylate detergent (TBN 64), non-borated dispersants, ZDDP and a viscosity index improver concentrate. Reference Lubricant 1 did not include any biodiesel fuel (i.e. the lubricant per se), whereas Lubricant 1 of the invention and Comparative Lubricant 1 included B50 biodiesel fuel (10 mass %) to simulate contamination of the oil during operation of a diesel engine fuelled with biodiesel fuel. Reference Lubricant 1 and Lubricant 1 of the invention also included a low molecular weight ashless polyisobutenyl succinimide dispersant (1.3 mass % Boron), whereas Comparative Lubricant 1 did not include the overborated dispersant. Each of the lubricants had a phosphorus content of 800 ppm and a sulphated ash content of 1.2 mass %.
The Lubricants were evaluated for copper and lead corrosion control using the High Temperature Corrosion Bench Test. The results are also detailed in Table 1.

The results indicate that a lubricant including an overborated dispersant in the absence of biodiesel fuel (Reference Lubricant 1) displays excellent corrosion control performance, as expected. In the presence of biodiesel fuel, a lubricant including an overborated dispersant (Lubricant 1) still displays good copper and lead corrosion control performance. Moreover, the copper and lead corrosion control performance of a lubricant including an overborated dispersant (Lubricant 1), in the presence of biodiesel fuel, is far superior to that of a corresponding lubricant not including the overborated dispersant (Comparative Lubricant 1).

Table 1

	Reference Lubricant 1 (mass %)	Comparative Lubricant 1 (mass %)	Lubricant 1 (mass %)
Calcium salicylate detergent (TBN 350)	2.8	2.8	2.8
Calcium salicylate detergent (TBN 64)	0.25	0.25	0.25
Non-borated dispersants	11.0	14.0	11.0
Overborated dispersant	2.6	0	2.6
ZDDP	1.0	1.0	1.0
Viscosity modifier concentrate	9.1	7.8	7.8
B50 Biodiesel	0	10	10
Group III base stock	balance	balance	balance
Copper corrosion (ppm)	15.40	416.20	49.50
Lead corrosion (ppm)	10_.40	4221.70	417.30

Example 2

A series of 5W-30 multigrade lubricating oil compositions, as detailed in Table 2, were prepared by admixing a Group III base stock with known additives including an overbased calcium alkyl sulphonate detergent (TBN 300), an overbased calcium phenate detergent (TBN 145), non-borated dispersants, ZDDP, an aminic antioxidant, and a viscosity index improver concentrate. Lubricants 2, 3 and 4 of the invention and Comparative Lubricant 2 included B50 biodiesel fuel (10 mass %) to simulate contamination of the oil during operation of a diesel engine fuelled with biodiesel fuel. Comparative Lubricant 2 and Inventive Lubricant 3 contained a magnesium sulphonate detergent (TBN 400), whereas Lubricant 2 of the invention included a borated magnesium sulphonate detergent (TBN 337) instead at equivalent TBN and ash level as Comparative Lubricant 2.
Lubricant 3 of the invention included a borated ashless polyisobutenyl succinimide dispersant (1.3 mass % Boron) in place of some of the dispersant present in Comparative Lubricant 2. Each of the lubricants had a sulphated ash content of around 1.05 mass %.
Lubricant 4 of the invention included a borated ester and borated amide mixture (Vanlube 289™ available from R T Vanderbilt) in place of the borated dispersant of Lubricant 3 to provide a lubricant with an equivalent level of boron, ash and TBN. The Lubricants were evaluated for copper and lead corrosion control using the High Temperature Corrosion Bench Test and also for oxidative stability using the Hot Surface Oxidation Test. The results are also detailed in Table 2.
The results indicate that in the presence of biodiesel fuel, a lubricant including an overborated dispersant (Lubricant 3) displays good copper and lead corrosion control performance compared to an equivalent lubricant without boron (Comparative Lubricant 2). Moreover, the copper and lead corrosion control performance of a lubricant including an overborated detergent (Lubricant 2), in the presence of biodiesel fuel, is also improved compared to an equivalent lubricant with no boron (Comparative Lubricant 2).

Additionally, the results demonstrate that a lubricant including an oil-soluble boron containing compound (Lubricants 2 to 4) is far more stable to oxidation, in the presence of a biofuel, than a comparable lubricant which does not include an oil soluble boron containing compound (Comparative Lubricant 2).

Table 2

	Comparative Lubricant 2 (mass %)	Lubricant 2 (mass %)	Lubricant 3 (mass %)	Lubricant 4 (mass %)
Calcium sulphonate detergent (TBN 300)	0.9	0.9	0.9	0.9
Calcium phenate detergent (TBN 145)	2.0	2.0	2.0	2.0
Magnesium Sulphonate (TBN 400)	0.49	0	0.49	0.49
Borated Magnesium Sulphonate (TBN 337)	0	0.58	0	0
Borated Ester (Vanlube)	0	0	0	3.25
Non-borated dispersants	7.5	7.5	5.5	7.5
Overborated dispersant	0	0	2.6	0
ZDDP	1.0	1.0	1.0	1.0
Aminic Antioxidant	1.0	1.0	1.0	1.0
Viscosity modifier concentrate	5.5	5.5	5.5	5.5
B50 Biodiesel	10	10	10	10
Group III base stock	balance	balance	balance	balance
Nitrogen (mass %)	0.14	0.14	0.14	0.14
Boron (ppm)	0	336	338	338
TBN (mgKOH/g)	11.23	11.23	11.28	11.25
Ash (mass %)	1.04	1.08	1.08	1.08
Lead corrosion (ppm)	1648	1154	939	-
Copper corrosion (ppm)	272	136	130	-
Oxidation Induction Time (mins) Induction	78	295	235	309

Claims

The use, in the lubrication of a spark-ignited or compression-ignited internal combustion engine which is fuelled at least in part with a biofuel, of an oil-soluble boron containing compound, as an additive component in a minor amount, in a lubricating oil composition, to reduce and/or inhibit the corrosion of the metallic engine components, during operation of the engine.
The use as claimed in claim 1, wherein the oil-soluble boron containing compound comprises a borated dispersant, a borated detergent, a borated ester or borated amide.
The use as claimed in claim 1 or 2, wherein the oil-soluble boron containing compound comprises an ashless borated dispersant.
The use as claimed in claim 3, wherein the ashless borated dispersant comprises an ashless, nitrogen containing borated dispersant.
The use as claimed in claim 4, wherein the ashless, nitrogen containing borated dispersant comprises a borated polyalkenyl succinimide.
The use as claimed in claim 5, wherein the borated polyalkenyl succinimide comprises a borated polyisobutenyl succinimide.
The use as claimed in any one of the preceding claims, wherein the oil-soluble boron containing compound introduces greater than 100 ppm of boron into the lubricating oil composition.
The use as claimed in any one of the preceding claims, wherein the metallic engine components comprise lead, copper or mixtures thereof.
The use, in the lubrication of a spark-ignited or compression-ignited internal combustion engine which is fuelled at least in part with a biofuel, of an oil-soluble boron containing compound as defined in any one of claims 1 to 7, as an additive component in a minor amount, in a lubricating oil composition, to reduce and/or inhibit oxidation of the lubricating oil composition, during operation of the engine.
The use as claimed in anyone of the preceding claims, wherein the engine comprises a compression-ignited internal combustion engine which is fuelled at least in part with biodiesel.
The use as claimed in anyone of the preceding claims, wherein the lubricating oil composition is contaminated with at least 0.3 mass %, based on the total mass of the lubricating oil composition, of a biofuel or a decomposition product thereof and mixtures thereof.
The use as claimed in any one of the preceding claims, wherein the lubricating oil composition comprises an oil of lubricating viscosity in a major amount, comprising a Group III base stock.
A lubricating oil composition comprising:
(A) an oil of lubricating viscosity in a major amount, comprising a Group III base stock;

(B) as an additive component in a minor amount, an oil-soluble boron containing compound as defined in any one of claims 1 to 7; and, wherein the lubricating oil composition is contaminated with at least 0.3 mass %, based on the total mass of the lubricating oil composition, of a biofuel or a decomposition product thereof and mixtures thereof.
A method of lubricating a spark-ignited or compression-ignited internal combustion engine which is fuelled at least in part with a biofuel, comprising operating the engine with a lubricating oil composition as claimed in claim 13.
The use, in the lubrication of a spark-ignited or compression-ignited internal combustion engine which is fuelled at least in part with a biofuel, of a lubricating oil composition as claimed in claim 13, to reduce and/or inhibit the corrosion of the metallic engine components, during operation of the engine.