RU2768169C2 - Lubricating composition - Google Patents

Abstract

FIELD: lubricants.

SUBSTANCE: present invention relates to a lubricating oil composition suitable for lubricating internal combustion engines and providing a reduced wear rate, to reduce wear in the presence of a zinc dialkyl dithiophosphate compound and soot, wherein the nitrogen-containing ashless dispersant has a functionality (F) of 1.5 to 1.9, wherein functionality (F) is defined in accordance with the following formula: F = (SAP × Mn)/((1122 × A.I.) − (SAP × MW)) (1), where SAP is a saponification number, wherein the saponification number is the number of milligrams of KOH, consumed with complete neutralization of acid groups in one gram of amber group-containing reaction product, as determined in accordance with ASTM D94; Mn denotes the number-average molecular weight of the starting olefin polymer; AI denotes the percentage of the active ingredient of the reaction product containing an amber group; and MW denotes the molecular weight of the dicarboxylic acid-producing moiety, said nitrogen-containing ashless dispersant comprises polyisobutylene succinimide, and said nitrogen-containing ashless dispersant is present in the lubricating composition in such an amount to provide a nitrogen level of 0.05 to 0.1 wt. % relative to the weight of the lubricating composition.

EFFECT: reduced wear when using lubricating compositions containing zinc dithiophosphate compounds in the presence of soot.

1 cl, 2 tbl, 4 ex

Description

Field of invention

The present invention relates to a lubricating composition, in particular to a lubricating oil composition suitable for lubricating internal combustion engines and providing reduced wear.

State of the art

Systematic tightening of automotive emissions and fuel efficiency regulations is placing ever greater demands on both engine and lubricant manufacturers, who must offer increasingly efficient solutions to improve fuel economy.

A flexible solution to a growing problem is the optimization of lubricants through the use of high performance base oils and the latest additives.

Low viscosity lubricants help reduce fuel consumption, but such compounds cause increased wear, and anti-wear additives are important to mitigate the resulting problems; various additives of this type are already known in the art.

A well-known anti-wear additive that is commonly used in lubricating compositions is zinc dithiophosphate, such as, for example, zinc dialkyl, diaryl or alkylaryl zinc dithiophosphates. Zinc dithiophosphate is conveniently described by the general formula II:

where R ² -R ⁵ may be the same or different, and each of them represents a primary alkyl group containing from 1 to 20 carbon atoms, preferably from 3 to 12 carbon atoms, a secondary alkyl group containing from 3 to 20 carbon atoms , preferably 3 to 12 carbon atoms, an aryl group or an aryl group substituted with an alkyl group, said alkyl substituent having 1 to 20 carbon atoms, preferably 3 to 18 carbon atoms.

Examples of suitable zinc dithiophosphates that are commercially available include those supplied by Lubrizol Corporation under the trade names "Lz 1097" and "Lz 1395", supplied by Chevron Oronite under the trade names "OLOA 267" and "OLOA 269R", and supplied by Afton Chemical under the trade name "HITEC 7197"; C9417, zinc dithiophosphates such as those supplied by Infineum under the trade name Infineum C9417, supplied by Lubrizol Corporation under the trade names "Lz 677A", "Lz 1095" and "Lz 1371", supplied by Chevron Oronite under the trade name "OLOA 262" and supplied by Afton Chemical under the trade name "HITEC 7169"; and zinc dithiophosphates such as those supplied by Lubrizol Corporation under the trade names "Lz 1370" and "Lz 1373" and supplied by Chevron Oronite under the trade name "OLOA 260".

Although zinc dithiophosphate compounds in lubricating compositions are useful in reducing wear, a previously unknown wear mechanism has recently been discovered whereby zinc dithiophosphates can cause an undesirable increase in wear in the presence of soot. The corrosion/abrasion wear mechanism was identified and published in 2010, see Olomolehin, Y., Kapadia, R.G., Spikes, H.A., “Antagonistic interaction of antiwear additives and carbon black.” Trib Letters 37, 49-58, (2009) . This mechanism has recently been reaffirmed in a later work, see Salehi, F. Motamen, D.N. Khaemba, A. Morina, and A. Neville, “Corrosive-Abrasive Wear Induced by Soot in Boundary Lubrication Regime.” Trib Letters 63, 1-11, (2016).

Therefore, there is a need to find a way to reduce wear when using lubricant compositions containing zinc dithiophosphate compounds in the presence of soot.

It has recently been surprisingly discovered that by using certain nitrogen-containing ashless dispersants, a lubricating oil composition can be obtained that provides reduced wear in the presence of zinc dithiophosphate compounds and carbon black.

The essence of the invention

Accordingly, in the present invention, in order to reduce wear in the presence of zinc dithiophosphate compounds and carbon black, the use of a nitrogen-containing ashless dispersant in a lubricant composition is proposed, wherein the nitrogen-containing ashless dispersant has a functionality (F) greater than 1.4.

Detailed description of the invention

As used herein, the term "soot" means a deep black powdery or flaky substance composed primarily of amorphous carbon. Gaseous soot contains polycyclic aromatic hydrocarbons (PAH). Soot is formed as a result of the incomplete combustion of organic substances such as hydrocarbon-based fuels. It consists of agglomerated nanoparticles with a diameter of 6 to 30 nm. The soot particles may be mixed with metal oxides and minerals, and may be coated with sulfuric acid. In the case of an internal combustion engine, soot can move from the combustion chamber into the lubricant and can accumulate in the lubricant.

In the context of the present invention, the amount of carbon black in a lubricant composition containing a zinc dithiophosphate compound is usually from 0.1% wt. up to 10% wt. In one implementation, the level of soot is from 2 to 7% wt. relative to the weight of the lubricant composition. In another implementation, the level of soot is from 3.5 to 7% wt. relative to the weight of the lubricant composition. In another implementation, the level of soot is from 5 to 6% wt. relative to the weight of the lubricant composition.

According to the present invention, the nitrogen-containing ashless dispersant is present in the lubricating composition in such a concentration as to provide a nitrogen level of from 0.001 to 0.15% wt., preferably from 0.05 to 0.1% wt. relative to the weight of the lubricant composition.

According to the present invention, a nitrogen-containing ashless dispersant is used to reduce the wear that a lubricating composition exhibits in the presence of zinc dithiophosphate compounds and carbon black. Therefore, the term "wear reduction" as used herein means reducing wear to a level below that exhibited by a lubricant composition containing zinc dithiophosphate and carbon black, but which does not contain the nitrogen-containing ashless dispersant described herein.

In a preferred embodiment of the present invention, a nitrogen-containing ashless dispersant is used to reduce wear by at least 5%, more preferably at least 10%, even more preferably at least 50%, and most preferably at least 80%, even more preferably at least 90%, compared to a similar lubricant composition that contains zinc dithiophosphate and carbon black, but which does not contain the nitrogen-containing ashless dispersant described herein.

Suitable dispersants for use in the present invention include an oil-soluble polymeric long chain structure having functional groups capable of binding to the particles to be dispersed. Typically, such dispersants have amine, amino alcohol, or amide polar moieties attached to the polymer backbone, often via a bridging group. The dispersant may be selected, for example, from oil-soluble salts, esters, amino esters, amides, imides and oxazolines of long chain hydrocarbon-substituted mono- and polycarboxylic acids or their anhydrides; thiocarboxylate derivatives of long chain hydrocarbons; long chain aliphatic hydrocarbons having polyamine moieties attached directly to them; and Mannich condensation products formed by the condensation of a substituted long chain phenol with formaldehyde and polyalkylene polyamine.

In general, 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 amount of nucleophilic groups in the finished dispersant.

PIB Description

The polyalkenyl moiety of the dispersant used in the present invention has a number average molecular weight of from about 700 to about 3000, preferably from 950 to 3000, such as from 950 to 2800, more preferably from about 950 to 2500, and most preferably from about 950 to about 2400. The molecular weight of the dispersant is usually expressed in terms of the molecular weight of the polyalkenyl moiety, since the exact molecular weight range of the dispersant depends on numerous parameters, including the type of polymer used to form the dispersant, the number of functional groups, and the type of nucleophilic group used.

The polyalkenyl moiety from which high molecular weight dispersants are derived preferably has a narrow molecular weight distribution (MWD), also referred to as polydispersity, which is defined as the ratio of weight average molecular weight (M _w ) to number average molecular weight (M _n ). In particular, the polymers from which the dispersants used in the present invention are derived have M _w /M _n 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 used in the formation of the dispersants used in the present invention include homopolymers, interpolymers or lower molecular weight hydrocarbons. One family of such polymers includes polymers of ethylene and/or at least one C ₃ -C ₂₈ alpha-olefin having the formula H ₂ C=CHR ¹ where R ¹ is a linear or branched alkyl radical containing from 1 to 26 carbon atoms , and the polymer contains carbon-carbon unsaturation, preferably a high degree of terminal ethenylidene unsaturation. Preferably, such polymers include interpolymers of ethylene and at least one alpha-olefin of the above formula, where R ¹ is alkyl with 1-18 carbon atoms, and more preferably is alkyl with 1-8 carbon atoms, and even more preferably , with 1-2 carbon atoms. Therefore, useful alpha-olefin monomers and comonomers include, for example, propylene, butene-1, hexene-1, octene-1, 4-methylpentene-1, decene-1, dodecene-1, tridecene-1, tetradecene-1, pentadecene -1, hexadecene-1, heptadecene-1, octadecene-1, nonadecene-1 and mixtures thereof (eg mixtures of propylene and butene-1, etc.). Examples of such polymers are propylene homopolymers, butene-1 homopolymers, ethylene-propylene copolymers, ethylene-butene-1 copolymers, propylene-butene copolymers, and the like, wherein the polymer contains at least several terminal and/or internal unsaturations. Preferred polymers are unsaturated ethylene-propylene and ethylene-butene-1 copolymers. The copolymers used in the present invention may contain a small amount, for example, from 0.5 to 5 mol% non-conjugated C ₄ -C ₁₈ diolefin comonomer. However, it is preferred that the polymers used in the present invention contain only alpha-olefin homopolymers, alpha-olefin comonomer interpolymers, and ethylene-alpha-olefin comonomer interpolymers. The molar content of ethylene in the polymers used in this invention is preferably in the range of 0 to 80% and more preferably 0 to 60%. When propylene and/or butene-1 are used as comonomer(s) with ethylene, the ethylene content of such copolymers is most preferably 15 to 50%, although higher or lower ethylene content may be present.

These polymers can be prepared by polymerizing an alpha-olefin monomer, or mixtures of alpha-olefin monomers, or mixtures containing ethylene and at least one C ₃ -C ₂₈ alpha-olefin monomer, in the presence of a catalyst system containing at least one metallocene (for example , a cyclopentadienyl-transition metal compound) and an alumoxane compound. Using this process, a polymer can be obtained in which 95% or more of the polymer chains have ethenylidene-type terminal unsaturation. The percentage of polymer chains having terminal ethenylidene unsaturation can be determined by FTIR spectroscopic analysis, titration, or C ¹³ NMR. Copolymers of this latter type may be represented by the formula POLY-C(R ¹ )=CH ₂ where R ¹ is C ₁ -C ₂₆ alkyl, preferably C ₁ -C ₁₈ alkyl, more preferably C ₁ -C ₈ alkyl and, most preferably C ₁ -C ₂ alkyl (eg methyl or ethyl) and wherein POLY is a polymer chain. The chain length of the R ¹ alkyl group will vary depending on the comonomer(s) chosen to be used in the polymerization. A small number of polymer chains may contain terminal ethenyl, i.e. vinyl, unsaturation, i.e., POLY-CH=CH ₂ , and some of the polymers may contain internal monounsaturation, for example, POLY-CH=CH(R ¹ ), where R ¹ corresponds to the above definition. These terminally unsaturated interpolymers can be prepared using methods known in metallocene chemistry as well as those described in US Pat. Nos. 5,498,809; 5663130; 5705577; 5814715; 6022929 and 6030930.

Another useful class of polymers are polymers obtained by cationic polymerization _of isobutene, styrene, and the like. and an isobutene content of from about 30 to about 60% by weight, in the presence of a Lewis acid catalyst such as aluminum trichloride or boron trifluoride. A preferred monomer source for producing poly-n-butenes are petroleum feed streams such as raffinate II. In the art, this feed is disclosed, for example, in US patent No. 4952739. In this invention, polyisobutylene is the most preferred base, because it is easily obtained by cationic polymerization from butene streams (for example, using AlCl ₃ or BF ₃ catalysts). Such polyisobutylenes typically contain a residual unsaturation of about one ethylene double bond per polymer chain along the chain. In a preferred embodiment of the invention, polyisobutylene derived from pure isobutylene stream or raffinate stream I is used to produce reactive isobutylene polymers with vinylidene olefin terminals. Preferably, these polymers, referred to as highly reactive polyisobutylene (HR-PIB), have a vinylidene terminal content of at least %, for example 70%, more preferably at least 80%, most preferably at least 85%. The preparation of such polymers is described, for example, in US Pat. No. 4,152,499. HR-PIB is known and commercially available under the trade names Glissopal ^TM (by BASF) and Ultravis ^TM (by BP-Amoco).

Suitable polyisobutylene polymers are typically based on a hydrocarbon chain of about 700 to 3000. Methods for producing polyisobutylene are known. Polyisobutylene can be functionalized by halogenation (eg, chlorination), thermal "ene" reaction or free radical grafting using a catalyst (eg, peroxide), which are described below.

The hydrocarbon or polymer backbone can be functionalized, for example, with carboxylic acid-producing moieties (preferably acid or anhydride moieties), either selectively, at centers of carbon-carbon unsaturation in the polymer or hydrocarbon chains, or randomly along the chains, using any of the three methods mentioned above or a combination of them in any order.

Methods for reacting polymeric hydrocarbons with unsaturated carboxylic acids, anhydrides, or esters and obtaining derivatives from such compounds are disclosed in US Pat. Nos. 3,087,936; 3172892; 3215707; 3231587; 3272746; 3275554; 3381022; 3442808; 3565804; 3912764; 4110349; 4234435; 5777025; 5891953; and also in EP 0382450 B1; CA-1335895 and GB-A-1440219.

The polymer or hydrocarbon may be functionalized, for example, with carboxylic acid (preferably acidic or anhydride) producing moieties, by reacting the polymer or hydrocarbon under conditions which result in the addition of functional groups or agents, i.e., acidic, anhydride, ester fragments, etc. onto polymer or hydrocarbon chains, primarily at centers of carbon-carbon unsaturation (also called ethylene or olefin unsaturation), using a halogen-assisted functionalization process (eg, chlorination) or a thermal "ene" reaction.

Functionalization

Selective functionalization can be achieved by halogenation, such as chlorination or bromination of the unsaturated α-olefin polymer to a content of about 1-8% wt., preferably from 3 to 7% wt. chlorine or bromine, relative to the weight of the polymer or hydrocarbon, by passing chlorine or bromine through the polymer at a temperature of from 60 to 250°C, preferably from 110 to 160°C, for example, from 120 to 140°C, for 0.5 up to 10, preferably from 1 to 7 hours. The halogenated polymer or hydrocarbon (hereinafter referred to as the main chain) is then reacted with a sufficient amount of a monounsaturated reagent capable of adding the required amount of functional groups to the main chain, such as a monounsaturated carboxylic reagent, at a temperature of from 100 to 250 ° C, usually from about 180 to 235 ° C, for about 0.5 to 10, such as 3 to 8 hours, such that the resulting product will contain the desired number of moles of monounsaturated carboxylic reactant per mole of halogenated backbones. Alternatively, the backbone and the monounsaturated carboxylic reactant are mixed and heated while adding chlorine to the hot material.

Although chlorination generally improves the reactivity of the starting olefin polymers with the monounsaturated functionalizing agent, it is not necessary for some of the polymers or hydrocarbons contemplated for use in the present invention, especially for those preferred polymers or hydrocarbons that have a high content of end bonds. and high reactivity. Therefore, it is preferred that the backbone and the reactant with monounsaturated functionality, such as the carboxylic reactant, are brought into contact at an elevated temperature so that the initial thermal "ene" reaction occurs. Enovye reactions are known in the industry.

The hydrocarbon or polymer chain can be functionalized by random attachment of functional moieties along the polymer chains in a variety of ways. For example, a polymer in solution or in solid phase can be grafted with a monounsaturated carboxylic reagent as described above in the presence of a free radical initiator. When this operation is carried out 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 is carried out in a mineral lubricating oil solution containing, for example, from 1 to 50 wt %, preferably from 5 to 30 wt %. polymer relative to the initial total oil solution.

Free radical initiators which may be used for this purpose are peroxides, hydroperoxides and azo compounds, preferably those which have a boiling point higher than about 100° C. and thermally decompose to form free radicals at temperatures within within the grafting temperature range. Representative of these free radical polymerization initiators are azobutyronitrile, 2,5-dimethylhex-3-en-2, 5-bis-tert-butyl peroxide and dicumene peroxide. The initiator, in cases where it is used, is usually used in an amount of from 0.005 to 1% wt. Relative to the mass of the solution of the reaction mixture. Typically, the above monounsaturated carboxylic reactant and free radical initiator are used in a weight ratio range of about 1.0:1 to 30:1, preferably 3:1 to 6:1. The grafting is preferably carried out under an inert atmosphere such as a nitrogen atmosphere. The resulting graft polymer is characterized by the presence of carboxylic acid (or ester or anhydride) fragments randomly attached along the polymer chains: it is understood, of course, that some of the polymer chains remain ungrafted. The free radical grafting described above can be used for other polymers and hydrocarbons used in the present invention.

Preferred monounsaturated reagents that are used to functionalize the backbone contain mono- and dicarboxylic acid moieties, i.e., acid, anhydride or acid ester moieties, including (i) a monounsaturated C ₄ -C ₁₀ dicarboxylic acid in which (a ) the carboxyl groups are vicinyl (i.e., located on adjacent carbons) and (b) at least one, preferably both, of said adjacent carbons are part of said monounsaturation; (ii) derivatives of (i) such as anhydrides or mono- or diesters of (i) derived from C ₁ -C ₅ alcohol; (iii) monounsaturated C ₃ -C ₁₀ monocarboxylic acid, in which the carbon-carbon double bond is conjugated with a carboxy group, ie, structures -C=C-CO-; and (iv) derivatives of (iii) such as mono- or diesters of (iii) derived from a C ₁ -C ₅ alcohol. Mixtures of monounsaturated carboxylic materials (i) - (iv) can also be used. Upon reaction with the main chain, the monounsaturation of the monounsaturated carboxylic reactant becomes saturated. Thus, for example, maleic anhydride becomes substituted succinic anhydride, and acrylic acid becomes substituted propionic acid. Examples of such monounsaturated carboxylic reagents 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. C ₁ -C ₄ alkyl), complex esters of the above acids, for example methyl maleate, ethyl fumarate and methyl fumarate.

To provide the desired functionality, a monounsaturated carboxylic reactant, preferably maleic anhydride, is usually used in an amount of from about equimolar to about 100% wt. excess, preferably from 5 to 50% wt. excess, based on the number of moles of polymer or hydrocarbon. Unreacted excess monounsaturated carboxylic reactant can be removed, if desired, from the final dispersant product, for example by distillation, usually under vacuum.

Derivatization

The functionalized oil-soluble polymeric hydrocarbon chain is then derivatized with a nitrogen-containing nucleophilic reagent such as an amine, an amino alcohol, an amide, or a mixture thereof, to form the corresponding derivative. Amine compounds are preferred. Useful amine compounds for derivatization of functionalized polymers contain at least one amine and may contain one or more additional amines or other reactive or polar groups. These amines may be hydrocarbylamines or may be predominantly hydrocarbylamines in which the hydrocarbyl group includes other groups such as hydroxy groups, alkoxy groups, amido groups, nitriles, imidazoline groups, and the like. Particularly useful amine compounds include mono- and polyamines, such as polyalkene and polyoxyalkylene polyamines. containing from about 2 to 60, for example, from 2 to 40 (for example, from 3 to 20) carbon atoms, having from about 1 to 12, for example, from 3 to 12, preferably 3-9, most preferably from 6 up to 7 nitrogen atoms per molecule. Mixtures of amine compounds, such as mixtures obtained by reacting an alkylene dihalide with ammonia, can be successfully used. 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 diethylenetriamine; triethylenetetramine; tetraethylenepentamine; and polypropyleneamines such as 1,2-propylenediamine; and di-(1,2-propylene)triamine. Such mixtures of polyamines, referred to as PAM, are commercially available. Particularly preferred polyamine mixtures are those obtained by stripping the light ends from the PAM products. The resulting mixtures, which are referred to as "heavy" PAM or HPAM, are also commercially available. The properties and characteristics of PAM and/or HPAM are described in, for example, US Pat. Nos. 4,938,881; 4927551; 5230714; 5241003; 5565128; 5756431; 5792730; 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. Representatives of another useful class of amines are polyamido and related amidoamines, as described in US patent No. 4857217; 4956107; 4963275; and 5,229,022. Tris(hydroxymethyl)aminomethane (TAM) can also be used as described in US Pat. Nos. 4,102,798; 4113639; 4116876; and GB 989409. Dendrimers, star amines and comb amines can also be used. Similarly, fused amines can be used as described in US Pat.

Preferred Dispersants

A preferred dispersant for use in the present invention is one that contains at least one polyalkenyl succinimide which is the reaction product of a polyalkenyl substituted succinic anhydride (e.g. PIBSA) and a polyamine (PAM) and has a binding factor 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 invention, "binding factor" can be defined as the ratio of the number of succinyl groups in PIBSA to the number of primary amino groups in the polyamine reagent .

Another class of high molecular weight ashless dispersants includes Mannich base condensation products. Typically, these products are prepared by the condensation of about one mole of long chain alkyl substituted mono- or polyhydroxybenzene with about 1-2.5 moles of carbonyl compound(s) (e.g., formaldehyde and paraformaldehyde) and about 0.5-2 moles of polyalkylenepolyamine, as described, for example, in US Pat. No. 3,442,808. Such Mannich base condensation products may include a polymeric metallocene-catalyzed polymerization product as a substituent on the benzene group, or may be reacted with a compound containing such a polymer substituted with succinic anhydride in a manner analogous to that described in US Patent No. 3,442,808. Examples of functionalized and/or derivatized olefin polymers synthesized using metallocene catalyst systems are described in the publications cited above.

Preferred dispersants for use in the present invention have a functionality (F) greater than 1.4, more preferably greater than 1.5, such as about 1.5 to about 2.2, more preferably about 1.5 to about 2.0 or about 1.5 to about 1.9. Functionality (F) can be defined by the following formula:

F = (SAP x M _n )/((1122 x AI) - (SAP x MW)) (1),

where SAP is the saponification number (ie, the number of milligrams of KOH consumed in the complete neutralization of acid groups in one gram of the reaction product containing the succinic group, as determined in accordance with ASTM D94); M _n denotes the number average molecular weight of the original olefin polymer (polybutene); AI denotes the percentage of the active ingredient of the reaction product containing the succinic group (the remainder is unreacted polybutene and diluent); and MW is the molecular weight of the dicarboxylic acid producing moiety (98 for maleic anhydride). In general, each dicarboxylic acid producing moiety (succinic group) will react with a nucleophilic group (polyamine moiety) and the number of succinic groups in PIBSA will determine the amount of nucleophilic groups in the finished dispersant.

The molecular weight of the polymer, in particular M _n , can be determined by various known methods. One convenient method is gel permeation chromatography (GPC), which additionally provides information on molecular weight distribution (see WW Yau, JJ Kirkland and DD Bly, "Modern Size Exclusion Liquid Chromatography", John Wiley and Sons, New York, 1979) . Another useful method for determining molecular weight, especially for lower molecular weight polymers, is vapor pressure osmometry (see, for example, ASTM D3592).

Suitable hydrocarbons or polymers used in the formation of dispersants include polymers obtained by cationic polymerization of isobutene. Typical polymers of this class include polyisobutenes obtained by polymerization of a refinery C ₄ stream having a butene content of from about 35 to about 75 wt %. and an isobutene content of from about 30 to about 60% by weight, in the presence of a Lewis acid catalyst such as boron trifluoride (BF ₃ ). Preferably, the polyisobutylene is produced from a pure isobutylene stream or a raffinate stream I to produce vinylidene olefin-terminated reactive isobutylene polymers. Preferably, these polymers, referred to as highly reactive polyisobutylene (HR-PIB), have a vinylidene terminal content of at least 60%, such as 70%, more preferably at least 80%, most preferably at least 85%. The preparation of such polymers is described, for example, in US Pat. No. 4,152,499. Such polymers are commonly referred to as HR-PIB and HR-PIB is commercially available from Texas Petrochemical Corporation (TPC) or from BASF (under the trade names Glissopal ^TM ). Methods for thermally reacting HR-PIB with unsaturated carboxylic acids or anhydrides and further reacting the resulting acylating agents (PIBSA) with amines are well known in the industry and are described in, for example, US Pat. No. 4,152,499 and EP 0355895.

To provide the desired functionality, the monounsaturated carboxylic reactant (maleic anhydride) is typically used in an amount of from about 5 to about 300% excess, preferably from about 10 to 200%, for example, from 20 to 100% excess, based on moles of polymer. Unreacted excess monounsaturated carboxylic reactant can be removed from the final dispersant product if desired, for example by vacuum stripping.

Suitable polyamines for forming dispersants include polyamines having or having an average of 3 to 8 nitrogen atoms per molecule, preferably about 5 to about 8 nitrogen atoms per molecule. These amines may be hydrocarbylamines or may be predominantly hydrocarbylamines in which the hydrocarbyl group includes other groups, for example hydroxy groups, alkoxy groups, amido groups, nitriles, imidazoline groups, and the like. ammonia. Preferred amines are aliphatic saturated amines including, for example, polyethyleneamines such as diethylenetriamine; triethylenetetramine; tetraethylenepentamine; and polypropyleneamines such as di-(1,2-propylene)triamine. Such mixtures of polyamines, referred to as PAM, are commercially available. Useful mixtures of polyamines also include mixtures obtained by stripping light ends from PAM products. The resulting mixtures, which are referred to as "heavy" PAM or HPAM, are also commercially available. The properties and characteristics of PAM and/or HPAM are described in, for example, US Pat. Nos. 4,938,881; 4927551; 5230714; 5241003; 5565128; 5756431; 5792730; and 5,854,186.

The total amount of base oil included in the lubricating oil composition of the present invention is preferably in the range of 60 to 92% by weight, more preferably in the range of 75 to 90% by weight. and most preferably, in the range from 75 to 88% wt. based on the total weight of the lubricating oil composition.

The base oil used in the present invention is not particularly limited, and various conventional known mineral oils and synthetic oils can be successfully used.

The base oil used in the present invention may freely contain mixtures of one or more mineral oils and/or one or more synthetic oils.

Mineral oils include liquid petroleum oils and solvent-treated or acid-treated mineral lubricating oils of the paraffinic, naphthenic, or mixed paraffin/naphthenic type, which can be further refined by hydrotreating and/or dewaxing processes.

Naphthenic base oils have a low viscosity index (VI) (typically 40-80) and a low pour point. These base oils are produced from raw materials rich in naphthenes and low in wax content, they are used mainly for lubricants where color and color stability are important, and VI and oxidation stability are of secondary importance.

Paraffin base oils have a higher VI (typically >95) and a higher pour point. These base oils are produced from raw materials rich in paraffins and are used for lubricants where VI and oxidation stability are important.

As the base oil in the lubricating oil composition of the present invention, base oils derived from a Fischer-Tropsch process, such as those derived from a Fischer-Tropsch process as disclosed in EP-A-776959, EP-A, can be successfully used. -668342, WO-A-97/21788, WO-00/15736, WO-00/14188, WO-00/14187, WO-00/14183, WO-00/14179, WO-00/08115, WO-99 /41332, EP-1029029, WO-01/18156 and WO-01/57166.

Synthetic methods make it possible to build molecules from simpler substances or modify their structures in order to obtain exactly the required properties.

Synthetic oils include hydrocarbon oils such as olefin oligomers (PAO), diacid esters, polyol esters, and dewaxed wax raffinate. Synthetic hydrocarbon base oils supplied by the Royal Dutch/Shell group under the name "XHVI" (trademark) can be successfully used.

Preferably, the base oil contains mineral oils and/or synthetic oils that contain more than 80% wt. saturated hydrocarbons, preferably more than 90% wt., as measured in accordance with ASTM D2007.

In addition, it is preferable that the base oil contains less than 1.0% wt., preferably less than 0.1% wt. sulfur, calculated as elemental sulfur and when measured in accordance with ASTM D2622, ASTM D4294, ASTM D4927, or ASTM D3120.

Preferably, the viscosity index of the base fluid is greater than 80, more preferably greater than 120, as measured in accordance with ASTM D2270.

Preferably, the lubricating oil composition has a kinematic viscosity in the range of 2 to 80 mm ² /s at 100° C., more preferably 3 to 70 mm ² /s, most preferably 4 to 50 mm ² /s.

The total amount of phosphorus in the lubricating oil composition of the present invention is preferably in the range of 0.04 to 0.12% by weight, more preferably in the range of 0.04 to 0.09% by weight. and, most preferably, in the range from 0.045 to 0.08% wt. based on the total weight of the lubricating oil composition.

The lubricating oil composition of the present invention preferably has a sulfated ash content of not more than 2.0% by weight, more preferably not more than 1.0% by weight. and, most preferably, not more than 0.8% wt. based on the total weight of the lubricating oil composition.

The lubricating oil composition of the present invention preferably has a sulfur content of not more than 1.2% by weight, more preferably not more than 0.8% by weight. and, most preferably, not more than 0.2% wt. based on the total weight of the lubricating oil composition.

The lubricating oil composition of the present invention may further contain additional additives such as antioxidants, antiwear additives, detergents, dispersants, friction modifiers, viscosity index improvers, pour point depressants, corrosion inhibitors, defoamers, as well as sealing aids for fixation. or ensure seal compatibility.

Antioxidants that can be successfully used include those selected from the group of amine antioxidants and/or phenolic antioxidants.

In a preferred embodiment of the invention, these antioxidants are present in an amount in the range from 0.1 to 5.0% wt., more preferably, in an amount in the range from 0.3 to 3.0% wt. and, most preferably, in an amount in the range from 0.5 to 1.5% wt. based on the total weight of the lubricating oil composition.

Examples of amine antioxidants that can be successfully used include alkylated diphenylamines, phenyl-α-naphthylamines, phenyl-β-naphthylamines, and alkylated α-naphthylamines.

Preferred amine antioxidants include dialkyldiphenylamines such as p,p'-dioctyl-diphenylamine, p,p'-di-α-methylbenzyl-diphenylamine and N-p-butylphenyl-N-p'-octylphenylamine, monoalkyldiphenylamines such as mono-t -butyldiphenylamine and mono-octyldiphenylamine, bis(dialkylphenyl)amines such as di-(2,4-diethylphenyl)amine and di(2-ethyl-4-nonylphenyl)amine, alkylphenyl-1-naphthylamines such as octylphenyl-1- naphthylamine and n-t-dodecylphenyl-1-naphthylamine, 1-naphthylamine, arylnaphthylamines such as phenyl-1-naphthylamine, phenyl-2-naphthylamine, N-hexylphenyl-2-naphthylamine and N-octylphenyl-2-naphthylamine, phenylenediamines, such as N,N'-diisopropyl-p-phenylenediamine and N,N'-diphenyl-p-phenylenediamine, as well as phenothiazines such as phenothiazine and 3,7-dioctylphenothiazine.

Preferred amine antioxidants include those commercially available under the following trade names: "Sonoflex OD-3" (from Seiko Kagaku Co.), "Irganox L-57" (from Ciba Specialty Chemicals Co.) and phenothiazine (from Hodogaya Kagaku Co. .).

Examples of phenolic antioxidants that can be successfully used include C7-C9 branched alkyl esters of 3,5-bis(1,1-dimethyl-ethyl)-4-hydroxy-benzenepropanoic acid, 2-t-butylphenol, 2-t-butyl -4-methylphenol, 2-t-butyl-5-methylphenol, 2,4-di-t-butylphenol, 2,4-dimethyl-6-t-butylphenol, 2-t-butyl-4-methoxyphenol, 3-t -butyl-4-methoxyphenol, 2,5-di-t-butylhydroquinone, 2,6-di-t-butyl-4-alkylphenols such as 2,6-di-t-butylphenol, 2,6-di-t -butyl-4-methylphenol and 2,6-di-t-butyl-4-ethylphenol, 2,6-di-t-butyl-4-alkoxyphenols such as 2,6-di-t-butyl-4-methoxyphenol and 2,6-di-t-butyl-4-ethoxyphenol, 3,5-di-t-butyl-4-hydroxybenzylmercaptooctyl acetate, alkyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionates, such as n-octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, n-butyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate and 2' -ethylhexyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, 2,6-d-t-butyl-α-dimethylamino-p-cresol, 2,2'-methylenebis(4-alkyl -6-t-butylphenol), such as 2,2'-methylenebis(4-methyl-6-t-b utilphenol and 2,2-methylenebis(4-ethyl-6-t-butylphenol), bisphenols such as 4,4"-butylidenebis(3-methyl-6-t-butylphenol), 4,4'-methylenebis(2, 6-di-t-butylphenol), 4,4'-bis(2,6-di-t-butylphenol), 2,2-(di-p-hydroxyphenyl)propane, 2,2-bis(3,5- di-t-butyl-4-hydroxyphenyl)propane, 4,4'-cyclohexylidenebis(2,6-t-butylphenol), hexamethylene glycol-bis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate ], triethylene glycolbis[3-(3-t-butyl-4-hydroxy-5-methylphenyl) propionate], 2,2'-thio-[diethyl-3-(3,5-di-t-butyl-4-hydroxyphenyl) )propionate], 3,9-bis{1,1-dimethyl-2-[3-(3-t-butyl-4-hydroxy-5-methylphenyl)propionyloxy]ethyl}2,4,8,10-tetraoxaspiro [ 5,5]undecane, 4,4'-thiobis(3-methyl-6-t-butylphenol) and 2,2'-thiobis(4,6-di-t-butylresorcinol), polyphenols such as tetrakis[methylene- 3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate]methane, 1,1,3-tris(2-methyl-4-hydroxy-5-t-butylphenyl)butane, 1,3,5 -trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene, bis-[3,3'-bis(4'-hydroxy-3'-t-butylphenyl)butyric acids]glycol ether, 2-(3',5'-di-t -butyl-4-hydroxyphenyl) methyl-4-(2',4'-di-t-butyl-3'-hydroxyphenyl)methyl-6-t-butylphenol and 2,6-bis(2'-hydroxy-3' -t-butyl-5'-methylbenzyl)-4-methylphenol and p-t-butylphenol-formaldehyde condensates and p-t-butylphenol-acetaldehyde condensates.

Preferred phenolic antioxidants are those commercially available under the following trade names: "Irganox L-135" (from Ciba Specialty Chemicals Co.), "Yoshinox SS" (from Yoshitomi Seiyaku Co.), "Antage W-400" (from Kawaguchi Kagaku Co.), "Antage W-500" (by Kawaguchi Kagaku Co.), "Antage W-300" (by Kawaguchi Kagaku Co.), "Irganox L109" (by Ciba Specialty Chemicals Co.), "Tominox 917" (by Yoshitomi Seiyaku Co.), "Irganox L115" (by Ciba Specialty Chemicals Co.), "Sumilizer GA80" (by Sumitomo Kagaku), "Antage RC" (by Kawaguchi Kagaku Co.), "Irganox L101" (by Ciba Specialty Chemicals Co.), "Yoshinox 930" (from Yoshitomi Seiyaku Co.).

The lubricating oil composition of the present invention may contain mixtures of one or more phenolic antioxidants with one or more amine antioxidants.

In a preferred embodiment, the lubricating oil composition may contain, as antiwear additives, one zinc dithiophosphate or a combination of two or more zinc dithiophosphates, each zinc dithiophosphate being selected from dialkyl, diaryl, or alkylaryl zinc dithiophosphates.

Zinc dithiophosphate compounds are present in the lubricant composition in an amount providing a phosphorus content, preferably from 0.01 to 0.16% wt., more preferably from 0.06 to 0.12% wt. by weight of the lubricant composition.

Zinc dithiophosphate is an additive well known in the art, this compound can be described by the general formula II;

where R ² -R ⁵ may be the same or different and each of them represents a primary alkyl group containing from 1 to 20 carbon atoms, preferably from 3 to 12 carbon atoms, a secondary alkyl group containing from 3 to 20 carbon atoms, preferably 3 to 12 carbon atoms, an aryl group or an aryl group substituted with an alkyl group, said alkyl substituent having 1 to 20 carbon atoms, preferably 3 to 18 carbon atoms.

Zinc dithiophosphate compounds in which all R ² -R ⁵ are different can be used alone or in admixture with zinc dithiophosphate compounds in which all R ² -R ⁵ are the same.

Preferably, one or each zinc dithiophosphate compound used in the present invention is a zinc dialkyl dithiophosphate.

Examples of suitable commercially available zinc dithiophosphates include those sold by Lubrizol Corporation under the trade names "Lz 1097" and "Lz 1395", sold by Chevron Oronite under the trade names "OLOA 267" and "OLOA 269R", and also sold by Afton Chemical under the trade names "OLOA 267" and "OLOA 269R". trade name "HITEC 7197"; zinc dithiophosphates, such as those supplied by Infineum under the trade name Infineum C9417, supplied by Lubrizol Corporation under the trade names "Lz 677A", "Lz 1095" and "Lz 1371", supplied by Chevron Oronite under the trade name "OLOA 262" and supplied by Afton Chemical under the trade name "OLOA 262" trade name "HITEC 7169"; and zinc dithiophosphates such as those supplied by Lubrizol Corporation under the trade names "Lz 1370" and "Lz 1373" and also supplied by Chevron Oronite under the trade name "OLOA 260".

The composition of the lubricating oil according to the present invention can usually contain from 0.4 to 1.2% wt. zinc dithiophosphate based on the total weight of the lubricating oil composition.

In the composition of the present invention, additional or alternative antiwear additives can be successfully used.

Typical detergents that can be used in the lubricating oil of the present invention include one or more salicylate and/or phenolate and/or sulfonate detergents.

However, since organometallic and inorganic base salts used as detergents can increase the content of sulphated ash in the lubricating oil composition, in the preferred embodiment of the present invention, the amount of such additives is kept to a minimum.

In addition, for reasons of low sulfur levels, it is preferable to use salicylate detergents.

Thus, in a preferred embodiment, the lubricating oil composition of the present invention may contain one or more salicylate detergents.

In order to keep the content of total sulphated ash in the lubricating oil composition of the present invention at a level preferably not exceeding 2.0% wt., more preferably at a level not exceeding 1.0% wt. and, most preferably, at a level not exceeding 0.8% wt. based on the total weight of the lubricating oil composition, these detergents are preferably used in amounts ranging from 0.05 to 20.0% wt., more preferably from 1.0 to 10.0% wt. and, most preferably, in the range from 2.0 to 5.0% wt. based on the total weight of the lubricating oil composition.

In addition, it is preferred that said detergents independently have a TBN value (total base number) in the range of 10 to 500 mg.KOH/g, more preferably in the range of 30 to 350 mg.KOH/g and , most preferably in the range of 50 to 300 mg.KOH/g when measured in accordance with ISO 3771.

Examples of viscosity index improvers that can be successfully used in the lubricating oil composition of the present invention include styrene-butadiene copolymers, star-shaped styrene-isoprene copolymers and polymethacrylate copolymer, as well as ethylene-propylene copolymers. Such viscosity index improvers can be successfully used in an amount in the range from 1 to 20% wt. based on the total weight of the lubricating oil composition.

Polymethacrylates can be successfully used in the lubricating oil compositions of the present invention as effective pour point depressants.

In addition, compounds such as alkenylsuccinic acids or their ester moieties, benzotriazole-based compounds and thiodiazole-based compounds can be successfully used in the lubricating oil composition of the present invention as corrosion inhibitors.

Compounds such as polysiloxanes, dimethylpolycyclohexane and polyacrylates can be successfully used in the lubricating oil composition of the present invention as defoamers.

Compounds that can be successfully used in the lubricating oil composition of the present invention as sealing aids for fixing or seal compatibility include, for example, commercially available aromatic esters.

The lubricant compositions provided herein can be successfully prepared using conventional preparation techniques by mixing a base oil with a liquid crystal compound and one or more additives at a temperature of 60°C.

The present invention is described below with reference to the following Examples, which are not intended to limit the scope of the present invention in any way.

Examples

Various lubricating compositions were prepared by combining a base oil (GTL 4, a Fischer-Tropsch base oil having a kinematic viscosity at 100° C. of approximately 4 cSt, supplied by Shell) with ZDTP (zinc dialkyl dithiophosphate). ZDTP was added in an amount at which the phosphorus content in the final lubricant composition was 0.08% wt. To obtain lubricating compositions with various amounts of nitrogen (0.05% wt. N, 0.07% wt. N or 0.1% wt. N, based on the weight of the final lubricating compositions), various amounts of a nitrogen-containing ashless dispersant ( designated in Table 1 below as D1, D2, D3 or D4). To simulate the effect of the presence of soot in the lubricant, carbon black was also added to the lubricant compositions in an amount of 5% wt. by weight of the final lubricating compositions.

The nitrogen-containing ashless dispersants used in the present examples were polyisobutylene succinimides, the properties of which are shown in Table 1 below:

Table 1

Dispersant number PIB Mn Functionality (Fv) Maleization method Boriding D1 2225 1.3 Chlorine Not D2 2300 1.4 Thermally Not D3 2225 1.5 Chlorine Not D4 2300 1.8 Thermally Not

Wear test, HFRR test

Lubricant formulations were subjected to the HFRR wear test. The HFRR (High Frequency Reciprocating Apparatus) is a controlled reciprocating friction and wear test rig used to evaluate the performance of fuels and lubricants. The test uses a 6 mm diameter steel ball loaded and reciprocating against a flat surface of a fixed steel disk immersed in lubricant. At the end of each test, the ball and disk were taken out of the test facility, washed with toluene and isopropanol, and then treated with a solution of 0.05% wt. ethylenediaminetetraacetic acid (EDTA) for 60 s. This was to remove any ZDTP anti-wear film on surfaces that could interfere with optical wear measurement. Then, topographic images were obtained and analyzed using the SWLI Veeco Wyko model NT9100 to determine the wear volumes on the ball and disc. The instrument was set to vertical scanning interferometry (VSI) mode and calibrated to measure rough surfaces with nanometer detection range.

The results of these wear tests are presented in Table 2 below.

table 2

Dispersant Wear Volume (µm ³ ) according to HFRR results 0.05% N 0.07% N 0.1% N D1 640818 367829 254700 D2 475946 402865 387829 D3 26865 28355 30466 D4 21960 20987 20412

The discussion of the results

From the results presented in Table 2, formulations containing polyisobutylene succinimide dispersants D3 and D4 (having functionality values of 1.5 and 1.8, respectively) exhibited reduced wear (low wear measurements) compared to formulations containing polyisobutylene succinimide dispersants. dispersants D1 and D2 (having Fv functionality values of 1.3 and 1.4, respectively.

Claims (5)

The use of a nitrogen-containing ashless dispersant in a lubricating composition as a wear reducing agent in the presence of a zinc dialkyldithiophosphate compound and carbon black, wherein the nitrogen-containing ashless dispersant has a functionality (F) of 1.5 to 1.9, wherein the functionality (F) is determined according to the following formula : F = (SAP x M _n )/((1122 x AI) - (SAP x MW)) (1), where SAP is the saponification number, and the saponification number is the number of milligrams of KOH consumed in the complete neutralization of acid groups in one gram of the reaction product containing the succinic group, as determined in accordance with ASTM D94; M _n denotes the number average molecular weight of the original olefin polymer; AI denotes the percentage of the active ingredient of the reaction product containing the succinic group; and MW is the molecular weight of the dicarboxylic acid producing moiety, wherein said nitrogen-containing ashless dispersant contains at least one polyisobutylene succinimide, and moreover, the specified nitrogen-containing ashless dispersant is present in the lubricating composition in such an amount to provide a nitrogen level of from 0.05 to 0.1% wt. relative to the weight of the lubricant composition.