WO1992013933A1

WO1992013933A1 - Demulsification of oils

Info

Publication number: WO1992013933A1
Application number: PCT/EP1992/000242
Authority: WO
Inventors: Alan Aries; Adrian Dunn
Original assignee: Exxon Chemical Patents Inc.
Priority date: 1991-01-31
Filing date: 1992-01-31
Publication date: 1992-08-20
Also published as: EP0523213A1; GB9102097D0; BR9204108A; JPH05505420A; EP0523213B1; ES2068704T3; FI924378A0; FI924378A

Abstract

The action of a crosslinked polyoxyalkylene polyiol demulsifier for a water-in-oil emulsion containing an ashless dispersant additive is enhanced by the use of a free dicarboxylic acid or anhydride. The invention has particular relevance to lubricating oils for marine use, especially trunk piston engine oils and system oils.

Description

Deaulsiffication gf oils The invention relates to improvements in oil compositions, particularly in lubricating oil compositions. The invention has particular relevance to lubricating oils for marine engines, but is not limited thereto.

Oils for use in marine engines generally fall into one of three main classes, namely marine diesel cylinder lubricants (NDCLs) and trunk piston engine oils (TPEOs), and system oils. Under the crankcase conditions in which TPEOs are normally used (the presence of condensation, the possibility of water contamination, and the use of a lubricant purification system) , there is a tendency for water to form an emulsion with the oil, which will normally contain a dispersant and a metal-containing detergent. Emulsion formation may also be a problem with system oils, although, as system oils normally contain less metal-containing detergent than TPEOs, or no metal- containing detergent at all, the tendency of system oils to form emulsions is generally lower than for TPEOs.

The formation of emulsions is undesirable, as an emulsion may interfere with the working of the oil and/or of parts of the engine, and/or the intimate association of the oil and the water in the emulsion may result in an increased tendency for additives in the oil to become dissolved or dispersed in the water and to be lost from the oil when the oil is purified by the removal of water. Further, the presence of an emulsion may also result in blocking of filters and reduced efficiency of centrifuges used in purification of the oil.

There have been numerous proposals to incorporate demulsifiers in oil compositions. Thus, for example, European Specification No. 333 141 A discloses the use of adducts of specified alkylene oxide block copolymers and specified polyglycidyl ethers as demulsifiers for water- in-oil emulsions, while U.S. Specification No. 3 752 657 discloses fuels containing a dispersant having a long chain aliphatic hydrocarbon group bonded to an ethylene polyaraine, and a demulsifier, of specified formula, which is a polyalkyleneoxy-modified poly(alkylphenol)- formaldehyde polymer. Further, U.S. Specification No. 4 398 921 discloses the use in fuels of a specified Hannich dispersant and a two-component demulsifying agent comprising a specified oil-soluble oxyalkylene polyether and a specified oxyalkylated phenol formaldehyde resin. The fuels also contain a corrosion inhibitor which is a hydrocarbyl succinic acid or anhydride having from 12 to 30 carbon atoms.

European Specification No. 330 522 λ discloses an oil-soluble mixture useful as an oil additive which comprises a specified lubricating oil ashless additive, a demulsifier additive comprising the reaction product of an alkylene oxide and an adduct of a bis-epoxide and a polyhydric alcohol, and a compatibility additive for enhancing the solubility of the demulsifier in the oil solutions in which it is used. The compatibility additive comprises an alcohol, for example, a glycol, ester or hydroxyamide derivative of a carboxylic acid having a total of from 24 to 90 carbon atoms and at least one carboxylic group per molecule, preferred compatibility additives being dimer acid esters, the dimer acids being cyclohexene dicarboxylic acids formed from C₁₈ to C₂2 unsaturated fatty acids.

In a number of prior proposals, the starting materials from which the demulsifiers are prepared include dicarboxylic acids or derivatives thereof, the acids/derivatives reacting with one or more other components during the preparation of the demulsifiers.

U.S. Specification No. 4 440 902 discloses the use of a bisester of an alkenylsuccinic anhydride of specified formula and an ethylene oxide/propylene oxide block polymer of specified formula as a demulsifier for oil-water emulsions.

U.S. Specification No. 4 885 110 discloses the use of the reaction product of specified proportions of an oxyalkylated primary fatty amine of specified formula, an at least trihydric oxyalkylated alkanol containing specified units, and a dicarboxylic acid/anhydride, as a demulsifier for breaking crude oil emulsions.

British Specification No. 2 008 146 λ discloses a demulsifier for water-in-oil emulsions, especially water- - H - in-crude oil emulsions, which comprises a polyester obtained by the condensation of an alk(en)yl succinic anhydride wherein the alk(en)yl group has 9 to 18 carbon atoms, a polyalkylene glycol of specified molecular weight and properties, and a polyhydric alcohol having three or more hydroxyl groups capable of reacting with the anhydride, the reactants being used in specified proportions.

U.S. Specification No. 4 705 834 discloses the use of crosslinked oxyalkylated polyalkylenepolyamines for breaking water-in-oil emulsions which occur in oil production. The crosslinked compounds are prepared by crosslinking polyalkylene polyamines, which are completely oxyalkylated at the nitrogen atoms, with a crosslinking compound which possesses two or more functional groups which are capable of reacting with the terminal alcohol groups of the oxyalkylated polyalkylenepolyamines. As examples of crosslinking compounds there are mentioned aliphatic and aromatic diisocyanates , dicarboxylic acids, diesters of dicarboxylic acids with lower alcohols, and bisglycidyl ethers of aliphatic and aromatic polyhydroxy compounds.

German Specification No. 3 635 489 A discloses demulsifiers for water-containing crude oils, the demulsifiers being formed by a process in which free hydroxyl groups in copolymers of (meth)acrylic esters of mixtures of polyglycols and polyglycol ethers with - S - ethylenically unsaturated monomers are etherified , esterified or converted to urethane groups and/or an acid used as a catalyst is neutralised by addition of an amine .

European Specification No. 333 135 A discloses reaction products of (1) alkoxylated primary fatty amines, (2) adducts of ethylene oxide/propylene block copolymers and glycidyl ethers and (3) dicarboxylic acids. The reaction products may be used as demulsifiers.

British Specification No. 1 186 659 discloses the use of demulsifiers, particularly polyoxyalkylene polyol block copolymers, in lubricating compositions containing dispersants comprising specified derivatives of succinic acids having a substituent containing at least fifty aliphatic carbon atoms.

Despite the above proposals there remains a need for additives having a highly effective demulsifying action and, in particular, having a highly effective demulsifying action in TPEOs and system oils.

The present invention provides the use of a free (as hereinafter defined) dicarboxylic acid or anhydride to enhance the action of a demulsifier for a water-in-oil emulsion containing an ashless dispersant additive, the demulsifier comprising a crosslinked polyoxyalkylene polyol. The invention also provides a lubricating composition comprising an oil of lubricating viscosity, an ashless dispersant additive, a demulsifier comprising a crosslinked polyoxyalkylene polyol, and a free (as hereinafter defined) dicarboxylic acid or anhydride.

The invention further provides a lubricating composition comprising a blend of an oil of lubricating viscosity, a lubricating oil ashless dispersant additive, a demulsifier comprising a crosslinked polyoxyalkylene polyol, and a dicarboxylic acid or anhydride.

A lubricating composition in accordance with the invention may comprise one or more additional additives, particularly one or more overbased metal detergent additives and/or one or more zinc dihydrocarbyl dithiophosphates (ZODPs) .

In a preferred aspect of the invention, the lubricating oil is suitable for marine use, particularly for use as a TPEO or a system oil, and is formulated using constituents, and proportions of constituents, appropriate to such use. A lubricating oil suitable for use as a TPEO will normally contain at least one overbased metal detergent and at least one ZDDP, and will normally a Total Base Number (TBN) in the range of from 9 to 40. The TBN of a system oil will normally be in the range of from 0 to 6. All TBNs indicated in this specification are measured according to ASTM D2896. - 1 - The invention also provides a concentrate useful as an additive for a lubricating oil which concentrate comprises an ashless dispersant additive, a demulsifier comprising a crosslinked polyoxyalkylene polyol, a free

(as hereinafter defined) dicarboxylic acid or anhydride, an overbared metal detergent, a ZDDP, and base oil.

Where the lubricating oil is a TPEO, the concentrate preferably has a TBN in the range of from 150 to 250.

The invention further provides a method for preparing a lubricating composition which comprises blending, in any order, an oil of lubricating viscosity, an ashless dispersant additive, a demulsifier and a free (as hereinafter defined) dicarboxylic acid or anhydride. When the method is used to prepare a concentrate as defined above, the demulsifier is preferably added to a mixture of the ashless dispersant additive, the dicarboxylic acid and the overbased metal detergent additive, and the ZDDP is then added to the mixture so obtained.

The use in accordance with the invention of a demulsifier and a dicarboxylic acid/anhydride makes it possible to obtain oil compositions, particularly lubricating oil compositions, and especially TPEOs and system oils, with little or no tendency to form emulsions, even when used in the presence of water or water vapour. -tf- By a free dicarboxylic acid or anhydride is meant an acid or anhydride which is mixed as such with at least the first of the other components of the composition or blend. Thus, for example, the acid or anhydride is introduced as such into the vessel or other container in which a mixture of components is to be prepared. As indicated above, dicarboxylic acids or anhydrides are used in the preparation of certain demulsifiers.

Dicarboxylic acid/anhydride-derived groups which are chemically incorporated in demulsifiers or other components by reaction at one or both of the car oxy1 groups before the dicarboxylic acid/anhydride is blended with the ashless dispersant additive and the demulsifier used in accordance with the invention, or with whichever of the dispersant additive and the demulsifier is blended first with the acid/anhydride, are not free dicarboxylic acids/anhydrides.

The dicarboxylic acid used in accordance with the invention (or the dicarboxylic acid from which an anhydride used in accordance with the invention is derived) preferably has the general formula

H0₂C-(R)-C0₂H

wherein R represents a divalent hydrocarbyl group. A hydrocarbyl group consists essentially of hydrogen and carbon atoms but may, if desired, contain other atoms as or in βubstituents or as chain members provided that the presence of such atoms or groups containing them does not result in undesired reactions occurring during the use of the dicarboxylic acid or anhydride. The hydrocarbyl group may be, for example, a divalent aromatic group, but is advantageously a straight or branched chain, saturated or unsaturated, divalent aliphatic radical.

Advantageously, at most three chain atoms separate the two carboxyl groups, and, in preferred acids/anhydrides, the carboxyl groups are separated by two chain carbon atoms.

Especially advantageous for use in accordance with the invention are alk(en)yl succinic acids and anhydrides, the alk(en)yl radical preferably having 9 to 18 carbon atoms. Anhydrides containing an alkenyl radical may be prepared, for example, by an addition reaction between a monoolefin and maleic acid or anhydride at an elevated temperature, usually in the presence of a catalyst; if desired, such acids or anhydrides can then be hydrogenated to give the corresponding alkyl compounds. Straight or branched- chain mono-olefins may be used, although in some cases the branched-chain olefins may be preferred as giving liquid anhydrides.

Suitable monoolefins for use in preparing the succinic anhydrides are alpha-olefins, for example, those obtained from cracking wax. Examples of suitable alpha- - lo - olefins are 1-dodecene, 1-tridecene, 1-tetradecene and

1-pentadecene. other suitable olefins are low molecular weight polymers of a C₂ to C₄ olefin (that is, an oligomer of a C₂ to C₄ olefin) , examples of such oligomers being tetrapropylene, triisobutylene and tetraisobutylene. A preferred alkenyl succinic anhydride is dodecenyl succinic anhydride (DDSA), especially the branched chain form thereof, tetrapropenyl succinic anhydride (TPSA).

The optimum amount of dicarboxylic acid/anhydride to be used for a particular oil will depend on the nature of the acid/anhydride and the nature and proportions of the other constituents of the oil, and can be determined by routine experiment. For guidance, in a TPEO the acid/anhydride and demulsifier will generally be used in a mass ratio of about 0.1:1 to 10:1, on an active ingredient basis, more specifically, 0.5:1 to 5:1. In one particular system with a TBN of 40, a ratio in the range of from about 1:1 to 3:1 was found to be advantageous. Mixtures of two or more acids or anhydrides, or at least one acid and at least one anhydride, may of course be used.

The demulsifiers used in accordance with the invention comprise at least one crosslinked polyoxyalkylene polyol, and may also comprise one or more other constituents which, together with the crosslinked polyoxyalkylene polyol, impart demulsifying properties to - li ¬ the mixture.

By a polyoxyalkylene polyol is meant any compound containing at least two oxyalkylene units and at least two hydroxyl groups. The term "crosslinked polyoxyalkylene polyol" includes not only compounds made by reactinj one or more polyoxyalkylene polyols with a crosslinking agent but also, for example, compounds in which a difunctional compound, for example, one of those mentioned below as being suitable for use as a crosslinked agent, is treated with one or more alkylene oxides to give a product containing at least two oxyalkylene chains.

Preferred demulsifiers for use in accordance with the invention are produced by reacting with a crosslinking agent a polyoxyalkylene polyol produced by reacting a polyol with one or more alkylene oxides or oxyalkylene mono- or copolymers. Suitable polyols include, for example, alkylene glycols, alkylene triols and alkylene tetrols, for example, ethylene glycol, propylene glycol, dipropylene glycol, glycerol, and pentaerythritol. Aromatic hydroxyl compounds, for example, alkylated mono-and polyhydric phenols and naphthols can also be used.

The total number of carbon atoms in alkylene oxides from which oxyalkylene groups are derived advantageously does not exceed 10, and is preferably 2 to 4. Examples of such alkylene oxides are ethylene oxide, propylene oxide, 1,2-epoxy butane, 2,3-epoxy butane, 1,2-epoxy pentane, 2,3-epoxy pentane, 1,2-epoxy hexane, 2,3-epoxy hexane, 3,4-epoxy hexane, and l,2-epoxy-3-methylbutane. Particularly preferred alkylene oxides are ethylene oxide and propylene oxide. The alkylene oxides may, if desired, contain non-hydrocarbon substituents provided that these do not interfere with the use of the alkylene oxides or demulsifiers derived therefrom.

When a polyoxyalkylene polyol contains units derived from more than one alkylene oxide, these units may be randomly distributed (if a mixture of two or more different alkylene oxides is used) or in blocks (if different alkylene oxides are added sequentially to the reaction vessel). Where block polymers are prepared, the nature of the alkylene oxides used in forming the blocks, and the number of repeating units, may be chosen by the person skilled in the art having regard to the properties desired for the block polymers. Thus, for example, oxypropylene blocks are normally relatively hydrophobic and oxyethylene blocks relatively hydrophilic.

Preferred polyoxyalkylene polyols from which crosslinked compounds for use in accordance with the invention may be derived are obtained by reacting dipropylene glycol or a triol with propylene oxide. Crosslinking of polyoxyalkylene polyols may be effected using a crosslinking compound which possesses two or more functional groups which are capable of reacting with hydroxyl groups (normally terminal hydroxyl groups) in the polyoxyalkylene polyols. Preferred crosslinking agents for use in preparing crosslinked polyoxyalkylene polyols for use in accordance with the invention are dicarboxylic acids and diglycidyl ethers of aliphatic and aromatic polyhydroxy compounds. Examples of suitable dicarboxylic acids are glutaric acid and, preferably, adipic acid, while examples of suitable diglycidyl ethers are the diglycidyl ethers of the hydroxy compounds diphenylolmethane, pentaerythritol, trimethylolpropane, ethane-1,2-diol, propane-1,2-diol, butane-l,2-diol, butane-2,3-diol, glycerol and, especially, bisphenol A.

As indicated above, the demulsifier used in accordance with the invention may comprise one or more other constituents which, together with the crosslinked polyoxyalkylene polyol, impart demulsifying properties to the mixture. Examples of suitable additional constituents are crosslinked polyoxyalkylene polyols which have been reacted with one or more alkylene oxides, for example ethylene oxide and/or propylene oxide, and esters of oxyalkylated phenol formaldehyde resins.

Examples of oxyalkylated phenol formaldehyde resins which may be esterified to give a demulsifier constituent for use in accordance with the invention are resins of the formula:

wherein A represents an alkylene group containing from 2 to about 10 carbon atoms, m has an average value of from about 4 to about 200, R represents an alkyl group having 1 to about 20 carbon atoms, and x is an integer greater than 1. The use of such resins as a demulsifier component is described in, for example, U.S. Specification No. 4 398 921 referred to above. The group represented by R preferably has at least four carbon atoms and may be, for example, an isobutyl, tert.butyl or nonyl radical.

A demulsifier constituent for use in accordance with the invention may be prepared by esterifying an oxyalkylated phenol formaldehyde resin with, for example, a monocarboxylic acid, advantageously a saturated or unsaturated, straight or branched chain, monocarboxylic acid, which acid preferably contains about 12 to 20 carbon atoms. Because of their ready availability, mixtures of acids containing C₁₆ to C₁₈ fa ty acids are particularly preferred.

The optimum amount of demulsifier to be used for a particular oil will depend on the nature and proportions of the other constituents of the oil, and can be determined by routine experiment. For guidance, the demulsifier/dispersant mass ratio in a TPEO may be, for example, in the range of from about 0.001:1 to 0.1 : 1, more especially 0.002 : 1 to 0.07 : 1, calculated on an active ingredient basis.

The ashless dispersant additive for use in accordance with the invention may comprise an ashless dispersant and/or a viscosity index improver dispersant. Suitable ashless dispersants for use in accordance with the invention include, for example, the reaction products of amines, including amino-alcohols, with a hydrocarbyl-substituted mono-or dicarboxylic acid or a derivative thereof, long chain aliphatic hydrocarbons having one or more polyamine molecules attached directly thereto as shown in, for example, U.S. Specifications Nos. 3 275 554 and 3 565 804 (in which the halogen group in a halogenated hydrocarbon is displaced using an alkylene polyamine) , and Mannich condensation products containing a long chain hydrocarbyl group, for example as a substituent of a phenol.

Preferred ashless dispersant additives used in accordance with the invention comprise, for example, at least one member selected from the group consisting of: (1) ashless dispersant comprising (i) oil soluble salts, amides, imides, oxazolines and esters, or mixtures thereof, of long chain hydrocarbon-substituted mono- and dicarboxylic acids or their derivatives; (ii) long chain aliphatic hydrocarbons having a polyamine attached directly thereto; and (iii) Mannich condensation products formed by condensing a long chain hydrocarbon-substituted phenol with formaldehyde and a polyalkylene polyamine; the long chain hydrocarbon group in (i), (ii) or (iii) advantageously being a polymer of a C₂ to C₁₀, ^for example, C₂ to C₅ monoolefin, said polymer having a number average molecular weight of at least about 900; and (2) polymeric viscosity index improver dispersants.

In advantageous dispersants for use in accordance with the invention, the hydrocarbyl-substituted carboxylic acid or acid derivative comprises a hydrocarbon chain, generally a polyolefin chain, to which is grafted a substance containing at least one ethylenic bond and at least one carboxylic acid or anhydride group, or a polar group which is convertible into a carboxylic group by oxidation or hydrolysis. Preferably there are two such carboxylic acid groups (or derivatives thereof), and α-or 5-unsaturated C to Cι₂ dicarboxylic acids or derivatives thereof are particularly advantageous. Examples of suitable acids and anhydrides are itaconic acid, maleic acid, maleic anhydride, chloromaleic acid, dimethyl fumarate, succinic anhydride, chloromaleic anhydride, acrylic acid, methacrylic acid, crotonic acid, and cinnamic acid. Preferably, the dispersant product contains from 0.5 to 2, preferably 0.8 to 1.7, more preferably 1.0 to 1.5, for example, 1.05 to 1.2 acid groups, for example succinic groups, per mole of polyolefin starting material employed.

Preferred olefin polymers for reaction with the unsaturated carboxylic acids or derivatives thereof are those polymers derived from a major molar amount of C₂ to ClO' ^e*9-' ^c2 ^{to c}5/ monoolefin. Such olefins include, for example, ethylene, propylene, butylene, isobutylene, pentene, octene-1, and styrene. The polymers may be homopolymers, for example, polyisobutylene or copolymers of two or more of such olefins. These include copolymers of: ethylene and propylene; butylene and isobutylene: and propylene and isobutylene. Other copolymers include those in which a minor molar amount of the copolymer monomers, for example, 1 to 10 mole percent, is a C to C₁₈ diolefin, for example, a copolymer of isobutylene and butadiene or a copolymer of ethylene, propylene and 1,4- hexadiene.

In some cases, the olefin polymer may be completely saturated, for example an ethylene-propyler-? copolymer made by a Ziegler-Natta synthesis using hydrogen as a moderator to control molecular weight.

An especially suitable starting material for a dispersant additive is polyisobutylene.

The olefin polymers will usually have number average molecular weights above about 700, preferably above about 900, including number average molecular weights within the range of from 1,500 to 5,000 with approximately one double bond per polymer chain. The number average molecular weight for such polymers can be determined by any suitable technique. A convenient method for such determination is by gel permeation chromatography (GPC) which additionally provides molecular weight distribution information (see W. W. Yua, J. J. Kirkland and D. D. Bly, "Modern Size Exclusion Liquid Chromatography," John Wiley and Sons, New York, 1979).

Any suitable process may be used for reacting the olefin polymer with the unsaturated carboxylic acid or derivative thereof; a number of such processes are known in the art. For example, the olefin polymer and the carboxylic acid or acid derivative may simply be heated together as disclosed in U.S. Specifications Nos. 3 361 673 and 3 401 118 to cause a thermal "ene" reaction to take place. Alternatively, the olefin polymer can first be halogenated, for example, chlorinated or brominated, for example to about 1 to 8, preferably 3 to 7, weight percent chlorine or bromine, based on the weight of polymer, by passing the chlorine or bromine through the polyolefin at a temperature of 100" to 250^*C, for example 120^* to 160^*C, for about 0.5 to 10, preferably 1 to 7, hours. The halogenated polymer may then be reacted with sufficient unsaturated acid or acid derivative at 100^* to 250^*, for example 180^* to 220^*C, for from 0.5 to 10, for example, 3 to 8 hours. Processes of this general type are taught, for example, in U.S. Specifications Nos. 3 087 436, 3 172 892, and

3 272 746. In a further process, the olefin polymer and the unsaturated acid material are mixed and heated while adding chlorine to the hot material. Processes of this type are disclosed in U.S. Specifications

Nos. 3 215 707, 3 231 587, 3 912 764, 4 110 349 and

4 234 435 and British Specification No. 1 440 219.

When halogen is used, from 65 to 95 weight percent of the polyolefin will normally react with the carboxylic acid or derivative thereof. Thermal reactions, that is, those carried out without the use of halogen or a catalyst, normally cause only from 50 to 75 weight percent of the polyolefin to react. It is apparent, therefore, that chlorination helps to increase the reactivity.

Useful amine compounds for reaction with the hydrocarbyl substituted carboxylic acid or derivative thereof include mono- and polyamines having from 2 to 60, for example, 3 to 20, carbon atoms and from 1 to 12, for example 2 to 8, nitrogen atoms in a molecule. These amines may be hydrocarbyl amines, which may include other groups such, for example, as hydroxy groups, alkoxy groups, amide groups, nitrile groups and imidazoline groups. Hydroxy amines with 1 to 6 hydroxy groups, preferably 1 to 3 hydroxy groups, are particularly useful. Preferred amines are aliphatic saturated amines, including those of the general formulae:

R-N-R', and R-N(CH )_S

wherein R, R' and R" are independently selected from the group consisting of hydrogen, C to C₂₅ alkyl radicals, C to C₁₂ alkoxy radicals, C₂ to C_§ alkylene radicals, C₂ to C₁₂ alkylamino radicals, and C₂ to C₆ alkylene radicals; s and ε' can be the same or different and each is a number of from 2 to 6, preferably 2 to 4; and t is a number of from 0 to 10, preferably 2 to 7. At least one of R, R' or R" must be a hydrogen atom.

Non-limiting examples of suitable amine compounds include: 1,2-diaminoethane; 1,3-diaminopropane: 1,4-diaminobutane; l,6-diaminohexane; poly(ethyleneamines) such, for example, as diethylene triamine, triethylene tetramine and tetraethylene pentamine; poly(propylene amines) such, for example, as 1,2-propylenβ diamine, di-(l,2-propylene) triamine, and di-(1,3-propylene)triamine; N,N-dimethyl-1,3-diamino- propane; ³M,N-di-(2-aminoethyl) ethylene diamine; N,N-di- (2-hydroxyethyl)-1,3-propylene diamin ; 3-dodecyloxy- propyla ine; N-dodecyl-l,3-propane diamine; tris hydroxy- methylaminomethane (THAM); diisopropanol amine; diethanol amine; triethanol amine; and amino morpholines such, for example, as N-(3-amino-propyl)morpholine.

Other useful amine compounds include: alicyclic diamines such, for example, as l,4-di-(aminomethyl) cyclohexane, and heterocyclic nitrogen compounds such, for example, as imidazolines, and N-aminoalkyl piperazines of the general formula:

wherein p-^ and p₂ are the same or different and each is an integer of from 1 to 4, and n^, n₂ and n₃ are the same or different and each is an integer of from 1 to 3. Non-limiting examples of such amines include 2-pentadecyl imidazoline and N-(2-aminoethyl) piperazine.

Commercial mixtures of amine compounds may advantageously be used. For example, one process for preparing alkylene amines involves the reaction of an alkylene dihalide (such, for example, as ethylene dichloride or propylene dichloride) with ammonia, which results in a complex mixture of alkylene amines wherein pairs of nitrogen atoms are joined by alkylene groups, forming such compounds as diβthylene triamine. triethylene tetramine, tetraethylene pentamine and corresponding pipera2ines. Low cost poly(ethyleneamine) compounds averaging about 5 to 7 nitrogen atoms per molecule are available commercially under trade names such, for example, as "Polyamine H," "Polyamine 400" and "Dow Polyamine E-100". Mixtures of alkylene amines are described in, for example, the Encyclopedia of Chemical Technology (Kirk Othmer), Interscience Publishers, New York, (1950), Volume 5, pages 898 to 905, under the headline "Ethylene Amines".

Useful amines also include polyoxyalkylene polyamines such, for example, as those of the formulae:

(i) NH₂—alkylene (— 0-alkylene ^ NH₂

where m has a value of from 3 to 70 and preferably 10 to 35; and

(ii) R ( alkylene—f— O-alkylene ^γ_j—NH₂)₃_₆

where n has a value of about 1 to 40 with the proviso that the sum of all the n's is from 3 to 70 and preferably from 6 to 35, and R is a saturated hydrocarbon radical of up to ten carbon atoms, wherein the number of substituents on the R group is from 3 to 6. The alkylene groups in formula (i) and formula (ii) may be straight or branched chains containing about 2 to 7, and preferably about 2 to 4, carbon atoms.

The polyoxyalkylene polyamines above, which are preferably polyoxyalkylene diamines and polyoxyalkylene triamines, may have average molecular weights ranging from 200 to 4,000 and preferably from 400 to 2,000. The preferred polyoxyalkylene polyamines include the polyoxyethylene and polyoxypropylene diamines and the polyoxypropylene triamines having average molecular weights ranging from 200 to 2,000. The polyoxyalkylene polyamines are commercially available and may be obtained, for example, from the Jefferson Chemical Company, Inc. under the trade names "Jeffamines D-230, D-400, D-1000, D-2000, T-403," etc.

The amine may be reacted with the carboxylic acid or derivative thereof, for example, alkenyl succinic anhydride, by any suitable method. Thus, for example, an oil solution containing 5 to 95 weight percent of the carboxylic acid material may be heated to from 100 to 250^*C, preferably 125 to 175^*C, generally for 1 to 10, e.g., 2 to 6 hours, until the desired amount of water is removed. The heating is preferably carried out to favour formation of imides or mixtures of imides and amides, rather than amides and salts. Reaction ratios can vary considerably, depending upon, for example, the reactants, amounts of excess amine, and type of bonds formed. Generally from 0.3 to 2, preferably from 0.3 to 1.0, for example, 0.4 to 0.8 mole of amine, for example, di- primary amine is used, per mole of the carboxylic acid moiety content, for example, grafted maleic anhydride content. For example, when one mole of olefin reacted with sufficient maleic anhydride to add 1.10 mole of maleic anhydride groups per mole of olefin is to be converted to a mixture of amides and imides, about 0.55 moles of amine with two primary groups would preferably be used, that is, 0.50 mole of amine per mole of carboxylic acid moiety.

The nitrogen-containing dispersant can if desired be further treated by boration as generally taught in U.S. Specifications Nos. 3 087 936 and 3 254 025 (the disclosures of which are hereby incorporated by reference in their entirety).

Tris (hydroxymethyl) amino methane (THAM) can be reacted with the aforesaid acid material to form amides, imides or ester type additives as taught by British Specification No. 984 409, or to form oxazoline compounds and borated oxazoline compounds as described, for example, in U.S. Specifications Nos. 4 102 798, 4 116 876 and 4 113 639.

The dispersant say also be derived from an amino- alcohol including, for example, the amino-alkylene-, and amino-arylene-substituted alcohols having one or more amino-alkylene or amino-arylene or amino-arylene oxy- arylene radicals. They may be exemplified by N,N,N',N'~ tetrahydroxy-tri-methylene diamine. Other hydroxyamines which can be reacted with the hydrocarbon substituted carboxylic acid or acid derivative to form dispersants include 2-amino-l-butanol, 2-amino-2-methyl-l-propanol, p-(beta-hydroxy-ethyl)-aniline, 2-amino-l-propanol, 3- amino-1-propanol, 2-amino-2-methyl-l,3-propanediol, 2- amino-2-ethyl-l,3-propanediol, N-(beta-hydroxy propyl)- N'-(beta-amino-ethyl)-piperazine, tris (hydroxy methyl) aminomethane (also known as trismethylolaminomethane) , ethanolamine, and beta-(beta-hydroxyethoxy)-ethylamine. Mixtures of these or similar amines can also be employed.

Certain nitrogen-containing Mannich base type dispersants such, for example, as those described in U.S. Specifications Nos. 3 649 229 and 3 798 165 (the disclosures of which are hereby incorporated by reference in their entirety) may also be used. Such Mannich base dispersants can, for example, be formed by reacting a high molecular weight hydrocarbyl-substituted mono- or polyhydroxy benzene (for example, having a number average molecular weight of 1,000 or greater) with an amine (for example, a polyalkyl polyamine, a polyalkenyl polyamine, an aromatic amine, or a carboxylic acid-substituted polyamine or the succinimide formed from any one of these with an olefinic succinic acid or anhydride) and a carbonyl compound (e.g., formaldehyde or para formaldehyde). A very suitable dispersant for use in lubricating oil compositions is one derived from polyisobutylene substituted with succinic anhydride groups and reacted with a polyethylene amine, for example, tetraethylene pentamine, pentaethylene hexamine, polyoxyethylene or polyoxypropylene amine, for example, polyoxypropylene diamine, trismethylolaminomethane or pentaerythritol, and combinations thereof. One preferred dispersant combination involves a combination of (A) polyisobutene substituted with succinic anhydride groups and reacted with (B) a hydroxy compound, e.g., pentaerythritol, (C) a polyoxyalkylene polyamine, e.g., polyoxypropylene diamine, and (D) a polyalkylene polyamine, e.g., polyethylene diamine and tetraethylene pentamine using from 0.3 to 2 moles each of (B) and (D) and from 0.3 to 2 moles of (C) per mole of (A) as described in U.S. Specification No. 3 804 763.

Another preferred dispersant combination involves the combination of (A) polyisobutenyl succinic anhydride with (B) a polyalkylene polyamine, for example, tetraethylene pentamine, and (C) a polyhydric alcohol or polyhydroxy-substituted aliphatic primary amine, for example, pentaerythritol or trismethylolaminomethane, as described in U.S. Specification No. 3 632 511.

Viscosity index improvers (or viscosity modifiers) impart high and low temperature operability to a lubricating oil and permit it to remain shear stable at - i? - elevated temperatures and also exhibit acceptable viscosity or fluidity at low temperatures. Viscosity index improver dispersants function as dispersants as well as viscosity index improvers. Examples of such viscosity index improver dispersants are compounds essentially similar to the dispersants described in detail above (that is, the reaction products of amines with a hydrocarbyl-substituted mono-or dicarboxylic acid or a derivative thereof) in which the hydrocarbyl substituent comprises a chain of sufficient length to impart viscosity index-improving properties to the compounds. Such compounds can be prepared in a manner generally similar to that described above in connection with the corresponding dispersants.

The optimum amount of dispersant will depend on the use for which the oil is intended, which will influence the precise nature and proportions of the other constituents in the oil. In a TPEO, the proportion of dispersant will typically be in the range of from 0.1 to 10 mass %, especially 0.2 to 5 mass %, calculated on an active ingredient basis. The person skilled in the art will readily be able to determine, by routine experiment, the proportion of dispersant most appropriate to a particular use. In one particular oil suitable for use as a TPEO, the most appropriate amount of dispersant was found to be in the range of from 0.25 to 2 mass %, calculated on an active ingredient basis. As indicated above, lubricating oils for marine use advantageously include at least one metal-containing detergent additive and at least one ZDDP.

Overbased metal-containing detergent additives for use in accordance with the invention include, for example, overbased phenates, sulphurized phenates, sulphonates, salicylates and naphthenates of the alkali metals, alkaline earth metals and magnesium. Overbased calcium sulphonates of CJ^-CS_Q alkyl-substituted benzene- or toluene sulphonic acids, and overbased calcium sulphurized phenates, having a TBN of from 200 to 500, typically 300 to 400, are preferred.

Highly basic metal sulphonates may be produced, for example, by heating a mixture comprising an oil-soluble alkaryl sulphonic acid or sulphonate, with an excess of alkali metal or alkaline earth metal compound or magnesium above that required for complete neutralization of any sulphonic acid present and forming a dispersed carbonate complex by reacting the excess metal with carbon dioxide to provide the desired overbasing. The sulphonic acids are typically obtained by the sulphonation of alkyl-substituted aromatic hydrocarbons such, for example, as hose obtained from the fractionation of petroleum by distillation and/or extraction or by the alkylation of aromatic hydrocarbons as for example those obtained by alkylating benzene, toluene, xylene, naphthalene, diphenyl and halogen - 3 - derivatives thereof, for example, chlorobenzene, chlorotoluene and chloronaphthalene. The alkylation may be carried out, in the presence of a catalyst, with an alkylating agent having from about 3 to more than 30 carbon atoms. For example, haloparaffins, olefins obtained by dehydrogenation of paraffins, and polyolefin polymers produced from ethylene and/or propylene are all suitable. The alkaryl sulphonates usually contain from 9 to 70 or more carbon atoms, preferably from 16 to 50 carbon atoms, per alkyl-substituted aromatic moiety.

Compounds which may be used in neutralizing these alkaryl sulphonic acids to orovide the sulphonates include the oxides and hydroxides, alkoxides, carbonates, carboxylates, sulphides, hydrosulphides, nitrates, borates and ethers of sodium, magnesium, calcium, strontium and barium. Examples of suitable compounds are calcium oxide, calcium hydroxide, magnesium oxide, magnesium acetate and magnesium borate. As noted, the metal compound is used in excess of that required for complete neutralization of the alkaryl sulphonic acids. Generally, the amount ranges from 100 to 220 percent, although it is preferred to use at least 125 percent, of the stoichiosetric amount of metal required for complete neutralization.

Various other preparations of basic alkaline earth metal alkaryl sulphonates are known, for example, from U.S. Patent No. 3 150 088 and 3 150 089 wherein overbasing is accompanied by hydrolysis of an alkoxide- carbonate complex with the alkaryl sulphonate in a hydrocarbon solvent-diluent oil.

A sulphurized metal phenate can be considered to be a metal salt of a phenol sulphide, for example, a metal salt, whether neutral or basic, of a compound of the general formula:

n wherein x = l or 2, n = 0, 1 or 2 or a polymeric form of such a compound, where R represents an alkyl radical, n and x are each integers from 1 to 4, and the average number of carbon atoms in all of the R groups is at least about 9 in order to ensure adequate solubility in oil. The individual R groups may each contain from 5 to 40, but as indicated above preferably contain from 9 to 12, carbon atoms.

Regardless of the manner in which they are prepared, the sulphurized alkyl phenols which are useful generally contain from 2 to 14% by weight, preferably 4 to 12 wt. % sulphur based on the weight of sulphurized alkyl phenol. The sulphurized alkyl phenol may be converted to a salt by reaction with a metal-containing material, for example, a metal oxide, hydroxide or complex, in an amount sufficient to neutralize the phenol and, if desired, to overbase the product to a desired basicity. A preferred process involves neutralization using a solution of metal in a glycol ether.

The neutral or normal sulphurized metal phenates are those in which the ratio of metal to phenol nucleus is substantially stoichiometric. The "overbased" or "basic" sulphurized metal phenates are sulphurized metal phenates wherein the ratio of metal to phenol is greater than that required by stoichiometry, e.g. basic sulphurized metal dodecyl phenate has a metal content up to and greater than 100% in excess of the metal present in the corresponding normal sulphurized metal phenates, the excess metal being present in oil-soluble or dispersible form (for example, by reaction with C0₂).

These overbased materials may be used as the sole metal detergent additive or in combination with the same additives in the neutral form.

The ZDDPs used as anti-wear agents, and also to provide antioxidant activity, may be prepared, for example, in accordance with known techniques by first forming a dithiophosphoric acid, usually by reaction of an alcohol or a phenol with P₂Ss, and then neutralizing the dithiophosphoric acid with a suitable zinc compound. Mixtures of alcohols may be used, including mixtures of primary and secondary alcohols, secondary alcohols generally imparting improved anti-wear properties, and primary alcohols giving improved thermal stability properties. Mixtures of the two are particularly useful. In general, any basic or neutral zinc compound could be used but the oxides, hydroxides and carbonates are most generally employed. Commercial additives frequently contain an excess of zinc because of the use of an excess of the basic zinc compound in the neutralization reaction.

The preferred zinc dihydrocarbyl dithiophosphates for use in the present invention are oil soluble salts of dialkyl esters of dithiophosphoric acids represented by the formula: [RO(R'0)PS ]₂Zn wherein R and R^/ may be the same or different alkyl radicals preferably containing 3 to 10, more preferably 3 to 8 carbon atoms and including n-propyl, i-propyl, n-butyl, i-butyl, sec-butyl, arayl, n-hexyl, i-hexyl, n-octyl, 2-ethylhexyl, cyclohexyl and methylcyclopentyl groups.

Other additives which may be used in formulating TPEOs are, for example, antioxidants, for example, alkylated diphenylamineε, and rust inhibitors, for example, alkyl thiodiazoles.

A wide variety of lubricating oil base stocks may be used in accordance with the invention, for example for preparing a lubricating composition or a concentrate in - 35 - accordance with the invention. Thus, for example, suitable base stocks include natural base oils and synthetic base oils such, for example, as alkyl esters of dicarboxylic acids, polyglycols and alcohols; polyalpha- olefins, polybutenes, alkyl benzenes, organic esters of phosphoric acids, and polysilicone oils.

Natural base oils include mineral lubricating oils which may vary widely as to their crude source, for example, as to whether they are paraffinic, naphthenic, mixed, or paraffinic-naphthenic, as well as to the details of their production, for example, distillation range, straight run or cracked, hydrofined, solvent extracted and the like.

More specifically, natural lubricating oil base stocks which can be used in accordance with the invention may be straight mineral lubricating oil or distillates derived from paraffinic, naphthenic, asphaltic, or mixed base crude oils. Alternatively, if desired, various blended oils may be employed as well as residual oils, particularly those from which asphaltic constituents have been removed. The oils may be refined by any suitable method, for example, using acid, alkali, and/or clay or other agents such, for example, as aluminium chloride, or they say be extracted oils produced, for example, by solvent extraction with solvents, for example, phenol, sulphur dioxide, furfural, dichlorodiethyl ether, nitrobenzene, or crotonaldehyde.

SUBSTITUTESHEET Lubricating oil base stocks suitable for use in preparing TPEOs conveniently have a viscosity of typically about 3 to about 15 cSt (about 3 x 10~⁶ to about 15 x 10~⁶ m²/s) at 100'C, although base stocks with other viscosities may also be used. Thus, for example, bright stocks, which typically has a viscosity of about 30 cSt. (about 30 x 10~⁶ m²/s) at 100^*C may be used in some applications.

The additives used in accordance with the invention are oil-soluble, dissolvable in oil with the aid of a suitable solvent, or are stably dispersible materials. Oil-soluble, dissolvable, or stably dispersible as that terminology is used herein does not necessarily indicate that the materials are soluble, dissolvable, miscible, or capable of being suspended in oil in all proportions. It does mean, however, that the additives are, for instance, 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.

Additives used in accordance with the present invention can be incorporated into the lubricating oil in any convenient way. Thus, they can be added directly to the oil by dispersing, or by dissolving them in the oil at the desired level of concentration. Such blending may be effected at room temperature or an elevated temperature.

Additives used in accordance with the present invention may be employed in a lubricating oil composition which comprises lubricating oil, typically in a major amount, and the additives, typically in a minor amount. Additional additives, for example, the additional additives indicated above, may be incorporated in the composition to enable it to meet particular requirements.

As indicated above, the present invention has special relevance to TPEOs. Typical proportions for additional additives for a TPEO in accordance with the invention are as follows:

Additive Mass % active ingredient Detergent(s) 1 to 10

ZDDP(s) 0.1 to 1.5

Antioxidant(ε) 0.2 to 2

Rust Inhibitor(s) 0.005 to 0.05

As also indicated above, it may be desirable, although not essential, to prepare additive concentrates comprising the additives (the concentrate sometimes being referred to herein as an additive package) whereby several additives can be added simultaneously to the base oil to form the lubricating oil composition. Dissolution of the additive concentrate into the lubricating oil may be facilitated by solvents and by mixing accompanied with mild heating, but this is not essential. The concentrate or additive package 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 is combined with a predetermined amount of base lubricant. Thus, one or more additives can be added to small amounts of base oil or other compatible solvents along with other desirable additives to form additive packages containing active ingredients in an amount of, for example, from about 20 to about 70 mass %, and preferably from about 40 to about 65 mass %, additives in the appropriate proportions with the remainder being base oil. The final formulations may employ typically about 4 to 20 mass % of the additive package with the remainder being base oil.

The following Examples illustrate the invention.

Example 1 and Comparative Examples Cl to C3

An ashless dispersant comprising a borated reaction product of a polyisobutenyl succinic anhydride with a polyamine was introduced into a reaction vessel, followed in turn by tetrapropenyl succinic anhydride (TPSA) (if used) and an overbased calcium sulphonate detergent. The contents of the vessel were mixed at 80^*C for 1 hour, then cooled to 60^*C, following which there were added a demulsifier (where indicated in Table 1), an antioxidant, a rust inhibitor, and base oil. The mixture was stirred for 1 hour at 60^*C, and a zinc dihydrocarbyl dithiophosphate was then added. The proportions of the components indicated above are shown in Table 1. The proportions of each of the dispersant, detergent, antioxidant, rust inhibitor and demulsifier were the same in each of the examples.

The demulsifier used in these examples was a blend (92 mass % active ingredient in diluent oil) of a propoxylated dipropylene glycol crosslinked with the diglycidylether of bisphenol A, and two different constituents prepared by reacting with propylene oxide, or ethylene oxide and propylene oxide, a propoxylated dipropylene glycol crosslinked with the diglycidyl ether of bisphenol A. The mixture obtained as described above, which had a TBN of 220, was suitable for use as a concentrate for addition to a base oil to form a lubricant composition suitable for use as a TPEO. Compositions suitable for use in Test Method ASTM D1401, which measures the ability of petroleum oils or synthetic fluids to separate from water (commonly referred to as the ability of the oils or other fluids to "shed" water), were prepared by mixing about 18 parts by mass of the concentrate with about 82 parts by mass of base oil. The final compositions had a TBN of 40. In accordance with Test Method D1401, 40 ml of the composition to be tested and 40 ml of water were mixed in a graduated cylinder and the separation (if any) of the emulsion so produced into oil and water were observed. Table 2 gives the proportions by volume of oil, water and emulsion obtained after the time specified in that table.

Performance in test D1401

As can be seen from the above tables, no separation of the oil and water had occurred after 60 minutes in Comparative Example Cl, where the composition contained no TPSA or demulsifier, or in Comparative Example C2, where the composition contained TPSA but no demulsifier. Further, in Comparative Example C3, where the composition being tested contained demulsifier but no TPSA, 10 volume % of emulsion remained after 60 minutes. In contrast, the composition in accordance with the invention, containing both the demulsifier and TPSA (Example 1), showed excellent performance, complete separation of the initial emulsion occurring in only 20 minutes. It can thus be seen that there is synergism between the demulsifier and the TPSA.

Example 2 and Comparative Example 4

A lubricating oil suitable for use as a TPEO was prepared by mixing an overbased calcium phenate detergent, the detergent used in Example 1, an ashless dispersant obtained by reacting a polyisobutenyl succinic anhydride with a polyamine, a ZDDP, a demulsifier and base oil.

The demulsifier used in Comparative Example 4 contained 15.7 % active ingredients and comprised a propoxylated triol crosslinked with adipic acid, an ethoxylated phenol formaldehyde resin esterified with a mixture of C₁₆ to C₁₈ fatty acids, and base solvents, while in the demulsifier used in Example 2, a proportion of the solvent mixture was replaced by TPSA to give a demulsifier/TPSA mixture containing about 75 mass % TPSA calculated on the demulsifier active ingredients. The total proportion of demulsifier, or demulsifier and TPSA, in the final oil was 0.02 mass %, and the TBN of the final oil was 40 in each case.

The results of testing the compositions of Comparative Example C4 and Example 2 in ASTM Test Method D1401 are given in Table 3:

Iabls_3.

Performance in Test D1401

Example C4 Ex. 2

40

0

45

It will be seen that the use in accordance with the invention of TPSA and a demulsifier results in a more complete separation of the oil and water, and a lower separation time.

Claims

OMMS:

1. The use of a free (as hereinbefore defined) dicarboxylic acid or anhydride to enhance the action of a demulsifier for a water-in-oil emulsion containing an ashless dispersant additive, the demulsifier comprising a crosslinked polyoxyalkylene polyol.

2. A lubricating composition comprising an oil of lubricating viscosity, an ashless dispersant additive, a demulsifier comprising a crosslinked polyoxyalkylene polyol, and a free (as hereinbefore defined) dicarboxylic acid or anhydride.

3. A lubricating composition comprising a blend of an oil of lubricating viscosity, a lubricating oil ashless dispersant additive, a demulsifier comprising a crosslinked polyoxyalkylene polyol, and a dicarboxylic acid or anhydride.

4. An invention as claimed in any one of claims 1 to 3, wherein the dicarboxylic acid, or the dicarboxylic acid from which the anhydride is derived, has the general formula

HO2C-(R)-C0₂H

wherein R represents a divalent hydrocarbyl group.

5. An invention as claimed in claim 4, wherein, in the formula given in claim 4, R represents a straight or branched chain, saturated or unsaturated, divalent aliohatic radical.

6. An invention as claimed in any one of claims 1 to 3, wherein the dicarboxylic acid or anhydride is an alk(en)yl succinic acid or anhydride.

7. An invention as claimed in any one of claims 1 to 3, wherein the dicarboxylic anhydride is tetrapropenyl succinic anhydride.

8. An invention as claimed in any one of claims 1 to 7, wherein the crosslinked polyoxyalkylene polyol is prepared by crosslinking the reaction product of a polyol and an alkylene oxide or a compound containing groups derived from an alkylene oxide.

9. An invention as claimed in claim 8, wherein the crosslinked polyoxyalkylene polyol is prepared by crosslinking the reaction product of an alkylene glycol or an alkylene triol and an alkylene oxide or a compound containing groups derived from an alkylene oxide .

10. An invention as claimed in claim 8 or claim 9, wherein the alkylene oxide is ethylene oxide and/or propylene oxide.

11. An invention as claimed in any one of claims 8 to 10, wherein crosslinking is effected using a dicarboxylic acid or a diglycidyl ether of an aliphatic or aromatic hydroxy compound.

12. An invention as claimed in any one of claims 1 to 11, wherein the demulsifier also comprises one or more additional constituents containing oxyalkylene groups.

13. An invention as claimed in any one of claims 1 to 12, wherein the ashless dispersant additive comprises and ashless dispersant selected from

(i) the reaction products of an amine with a long chain hydrocarbon-substituted mono- or dicarboxylic acid or a derivative thereof,

(ii) long chain hydrocarbons having one or more polyamine molecules attached directly thereto, and

(iii) Mannich condensation products containing a long chain hydrocarbon group, the long chain hydrocarbon group in (i) , (ii) and (iii) being a polymer of a C2 to Cχo monoolefin and having a number average molecular weight of at least about 900.

14. An invention as claimed in any one of claims 1 to 13, wherein the ashless dispersant additive comprises the reaction product of a polyamine with a hydrocarbyl- substituted succinic acid or anhydride.

15. An invention as claimed in claim 14, wherein said reaction product is borated.

16. An invention as claimed in any one of claims 2 to 5, wherein the composition also contains at least one metal-containing detergent additive and/or at least one zinc dihydrocarbyl dithiophosphate.

17. An invention as claimed in any one of claims 2 to 16, wherein the composition has a TBN in the range of from 9 to 40.

18. A method for preparing a lubricating composition which comprises blending, in any order, an oil of lubricating viscosity, an ashless dispersant additive, a demulsifier and a free (as hereinbefore defined) dicarboxylic acid or anhydride.

19. A concentrate useful as an additive for a lubricating oil which concentrate comprises an ashless dispersant additive, a demulsifier comprising a crosslinked polyoxyalkylene polyol, a free (as hereinbefore defined) dicarboxylic acid or anhydride, an overbased metal detergent, a ZDDP, and base oil.

20. A concentrate as claimed in claim 19 or claim 20, wherein the constituents are as specified in any one of claims 4 to 15.