CA2171538C

CA2171538C - Lubricant composition containing antiwear additive combination

Info

Publication number: CA2171538C
Application number: CA002171538A
Authority: CA
Inventors: David Gary Lawton Holt; Patrick Desmond Fraser Vernon; John Ian Atherton
Original assignee: Exxon Research and Engineering Co
Current assignee: ExxonMobil Technology and Engineering Co
Priority date: 1993-09-13
Filing date: 1994-09-09
Publication date: 2004-10-26
Anticipated expiration: 2014-09-09
Also published as: JPH09506910A; DE69415817T2; KR100237074B1; ES2128581T3; CA2171538A1; KR960705009A; DE69415817D1; EP0719314B1; ATE175438T1; EP0719314A1; WO1995007964A1; SG47398A1; HK1014024A1; MY116337A

Abstract

A lubricant composition is described, particularly for engine oils, comprising a base oil of viscosity from 3 to 26 cSt (mm2/s) at 100°C
and an antiwear additive combination comprising (a) an oil soluble or oil dispersible phosphorus-free organo-molybdenum compound, (b) an ashless, sulphur-containing organo-phosphorus compound and optionally (c) a zinc thiophosphate compound selected from one or more of zinc dialkyldithiophosphate, zinc diaryldithiophosphate zinc alkylaryldithiophosphate and zinc arylalkyldithiophosphate. The molybdenum compound may be a carbamate, e.g. molybdenum dithiocarbamate (MoDTC) but is preferably nitrogen-free, e.g. a carboxylate.

Description

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LLT~FRICANT CO iFtJSITION CO'VT4INl.NG ]E~,~T3DIiITvv~ C~~T13IN~TI(~N
This iaavention relates to a lubricant coza~positiors containing a combination of additives providing antiwear properties, Find to the amtiwear additive combination eontained therein.
It is well-knos~-n to include an antiwear additive in lubricating oils such as ezza ne oils.
Wear results mainly from the nubbin; together o~ tyro metal surfaces, i.e. iaa boundary Iubricatio~ re~~imes, such a9 is found in v slue trains ire. interna!.1 combustion engines. It is believed that the antiweax additive acts to provide a protective films over th~ metal surfaces.
One well-known class of antawear additives is the metal al~ylphosphate, especially zinc 1Q disl~yldathiophosphate ("ZDBP"?. Generally ~I7I3P is employed at treat ltw-els of 1 to 2 wt.°f based on the total weight o~ the lubricant, which gives a ph~phorus level in the lubricant typically in the range of from 0.0a to 0.15 wt.%, and a zinc level of from 0.
i to 0.2 wt.°ib.
In recexit years there has beesa increasiazg concern that lubricant ash levels, such as that produced by the zinc in ZDF~I', contribute to particulate emissions from internal corubustion I5 engines. There as also concern that the phosphorus from the lubricant tends t~ poi_4on catalysis used in catalytic convex-tiers, thereby preventing them from funeta~r~ing to full 2~eet. I~owever, any reduction an ~D1~P treat levels has the disadvantage that it will reduce the aaatiweaz ga~operties of the lubricant.
'I'herc is therefore a need for an e~ectave anta~rear additive with reduced sane and 20 phosphorus levels,.
~~ a have found that a phosphorus-free org~ano-zzaoly$denum compound and' ara ashless Qulpl~ur-containing organo-phosphorus compound act together synergistically to provide inaprvved antiwear pergormance whexx, used in a lubricant composition. F3y using this combination of coangounds it bocomes possible to achieve the same or better perforanance than 25 that achieved x°ith Zl?I31', with signiicantIy lore er levels of phosphorus, Sulphur-containing organic phosphorus cosapourzds are known to be used as "extreane pressure compounds°° in hEavy.duty app3acations such as greases for constant velocSty aOIIlC~3. It is also known t~ use sulphur-contaia~ing orga~aic compounds of heavy metals such as molybdenum, tungsten and lead ~ such applicatioa~s. °I°hus (~B-A-~2553~6 describes aaa additive 30 fog grease used in constant vel~aty joints comprising in combination molybdenum sulphide dia)kylc3ithi~arbr~nate. zinc dithiophasphatc, a sulphur-phosphoru~ series extreme pressure compound, and lead dial~yldithioc:arhamate. It is stinted that the presence of the lead compound is ~ssential to achieve the desired perforrmance.
~~e~ s~E~r l?CV. 1l>\ : F~F':-~ -VI L~:Cti~~: U:3 : l:3 - .)-:-3 i : I ~> : '? ; : i) I
:3 t'?:.,':.'.:31 f3:i -» +~l.~j X3:3 '''.i:?J4-1-E1:; : il :~
i.: ~cr ~~ i i : c~ r r~-:n t~~v rra i tm ~ :~ i a trvm Y'HW t . V_i~J7 f1 L. I i US-r~-.464.8985 describes a Lead-free extreme pressure additive, generally for lubricants based on asphalt, utilising an organic phosphate in combination pith popper or molybdenuzr compounds selected frc;~ carboxylat2, phosp~hat~, thiophosphate anal thiocarbarnate, optionally with a metal-free thiocarbamate yr in, combination ~~zth a metal thi~arbamate (numerous metals being descril~d!- The preferred metals aze copper and zinc.
Organic phosphorus compounds are also used as eeshless dispexaants. Thus EP-%-05 Z 661 describes a dispersant additive for lubricating oils showing improved compatibility with elasto>!neric seal mat.er~ial which comprises in combination a metal dihydrooarbyl 1~ dathiocarbaanate ear dithiocarbamate and a phoephorg"lated ashless dispersant. Various metal compounds are described including ra~alybdenum dithiophpsphate.
EP-r1-0316610 describes a multipurpose antiwear, antiseizure and corrosion inhibiting additive for lubricating ~zls utilising a combination of sax organs-phosphorus Compound solectxd from various phosphines aaad phosphates and an o~rgano-molybdenuan compound selected ~rom l :i o~-ysa~lphidE al&ylphosphorodithioates and oxysulphide alkyl dithiocarbamates.
G~-A-13'13588 describes an anrivrear, antioxidant additive combination compassing a metal dialkyldithiacarbamate andlor a metal alkyl, aryl or aralkyl dithiophosphate and a metal-f~ ce phosphorus com.poun.d selected fr~x sulg~laurised sperm oil esteri~ed with dithiophosphate, sulphurised terpe>.~e esterificd with dithioph~phate, sulphurised and phosphated sperm oil and 20 phosphorus polysulphide. Many metals are mle;ationed zr~cluding molybdenu,°ra, sine and lead.
In one aspect the present invention pro°~idss a Lubricant composition comprising a base oil of viscosity from 3 to 26 cSt {xnm2ls) at 100°C and an antiwear additive combination comprising {a) an oil soluble or ail-dispersible ph~phorue-free organo-molybdenum eol~pound 25 where the orgar~o group of the molybdenum eomp~und is selected frox;ta carbamate, caxboxylz~te and ~canthate groups and mixtures thereof, which groups may be substituted with a hydrocarbyl group and/or one or more hetero atoms, and (b) an ashless, sulphur-containing organo phosphorus eorrupound selected ~rom:
{i) a phosphorothiolothionate of the formula so R,50 - ~' ~ Sft.?
~Rg ,~, ~H~,~ r ~~ A~,~~nt:

hC~ . t ()\ : i:1'1-Il( 't.\C:tfi:~. ():3 : L:a- :9-:J:; : 1'? : y7 : i l L:37~'_''?:31f3=p - +:i.c3 tj;J '?~3;3J~~=bl~;;i : ti ti d .3 5C t-' ~J l d : .J r K'.:!'I C55'~J YH I =I'dl 5 i V C!W ll'I t'Hl7C , vJ~~
.yg~ v~,, :~ "'/Y 1 f~.
wherein Ru, R~ and R7 are each independently an unsubstituted branched or straight chain hydrcxarbyl group or a branched or straight chain hydroearbyi 'coup substituted with ome or more functional groups or hetero atoms, {i~ a phosphorothionate of the f~rmu?a S
IE
R~C% "' ~ ° C7RI~
~~s wherein R.~, Rg, and Rlp are as defined fox R5, Rd, and R~ above; and .
(~ a mixture of (i) and (ii).
Furthermore, ire have found surprisi~sgly that compoc~r~ds (a), (b) wh,~n used in combination watka red~accd levels of a selected zinc thiophasphate, act synergi$tically to provide better wear protection than fleet achieved using a condparable amo~rnt (i.2.
ara asnour~t pxoviding a samil.ax total level of phosphorus) of the zanc thiophosph.ate alone.
~ 5 ~cordiingly ir3 a preferred. lubricant composition the combination includes, in addition to (a} and (b), a zinc thioghosphate coexipound (c) selected from one or me>re o~ zinc diail~yldithiophosphate, zinc diaryldithiogh~plsate, ziaac al~yla~ldithioghosphate and zinc arylal&y ldit3ziophghate_ This provides the advantage that the or°gano-raolybdenusn. compound can replace some .~S a~s.amu~u ~ 95/07964 PC1'/G~94101971 ~ '~' j ~ ~ n ~.. ~ l i ,~ ,.,> ~~
of the zinc thiophosphate compound used in lubricant compositions with the effect that the phosphorus level in the lubricant is reduced without substantially reducing, indeed increasing the antiwear perfor~cnance of the lubricant.
however it is known that I~oIW°C decomposes when heated in use to decomposition products which include free amine and carbon disulphide. both such products are aggressive towards copper which is present in the engine bearings. dear in bearings is particularly objectionable since repair involves complete dismantling of the engine. Carbon disulphide tends to boil off fairly rapidly and does not constitute a special problem. I~owever even small amounts of free amine can cause damage.
~e leave found that the synergisms described above extend not only to carbamates of molybdenum but also to molybdenum compounds which are nitrogen free and which therefore do not decompose to free amine. A preferred organo-molybdenum compound is also free from sulphur.
Accordingly in a preferred combination of (a) and (b) together optionally with (c) the organo-molybdenum compound is nitrogen-free. It is preferably selected from a carboxylate and a xanthate or mixtures thereof the organo groups) of which may be substituted with a hydrocarbyl group, again with the proviso that the organo group selected results in an organo-molybdenum compound that is oil-soluble or oil-dispersible, preferably oil-soluble.
The preferred organo-molybdenum compound comprises a carboxylate. Not only do such compounds contain no nitrogen or phosphorus but they are relatively cheap and contain a higher proportion of molybdenum than the more complex compounds. As will be described in more detail, it is believed that the effective additive content is governed by the metal content.
Thus only about one third of the amount e.g. of molybdenum 2-ethyl hexanoate need be used by comparison with molybdenum dithiocarbamate.
In another aspect the present invention provides an antiwear agent comprising a combination of (a) an organo-molybdenum compound as above described, (b) an ashless organo-phosphorus compound as above described and, optionally, (c) a zinc thiophosphate as above TITIJ'TE l' (L) <~ c ;; ~1 ~ ~ ~ ~-W~ ~510796~ l~C'~'/~~9~I~~~731 described.
ha ~ further aspect the present invention provides the use in ~ lubricant composition of the combination of (a) an organo-molybdenum coanpound as above described, (&~) an ashless organo-phosphorus compound as above described and, optionally, (c) ~ zinc thiophosphate as above described, as an antisvear agent.
In ~ yet further aspect the invention provides an additive concentrate comprising in combianation: (~) an organo-anolybdenurn compound as above described, (5) an ashless organo-phosplnorus compound as above described, optionally (c) a ~irac thiophosphate as above described and a carrier fluid.
1~ Where the organo group is a carbamate, the organo-molybdenum compound is preferably a molybdenum dithiocarbamate of tlae formula where Ry, I$2, R3 and R~ each independently represent a hydro~ea~ atom., a Cl to C2p all~yl group, a C6 to C20 cycloalkyl, aryl, alhylaryl or arall~yl group, or a C3 to C2p hydrocarbyl group containing an ester, ether, alcohol or carboxyl group; and ~g X2, ~'I and ~'2 each independently 20 represent a sulphur or oxygen atom.
Examples of suitable groups for each of Il.l, R,2, 1$3 and Iii include 2-ethylhexyl, nor~ylplaenyl, methyl, ethyl, n-propyl, iso-propyl, n-butyl, t-butyl, n-hexyl, n-octy~l, nonyl, decyh dodecyl, tridecyl, lauryl, oleyl, linoleyl, cy~clohexyl and pheny~lnaethyl.
Preferably I~,I to I~,~ are each C6 to Cog allbyl groups, snore preferably Clp to Cg~.
25 It is preferred that ~1 and X2 are the same, and Y~ and 'Y~ are the assns.
host preferably ~1 and ~2 are both sulphur atoms, and ~I and Y~ are both oxygen atoms.
'Thus in a preferred embodiment the organo-molybdenum compound is sulphurised oxymolybdenum dithiocarbamate s~herein the thiocarbaraiate groups contain Cg0 to Ci~ aryl groups. Such compounds are commercially available and are supplied, for example, by I~.1°.
so ~~~aerb~l~ C~~p~~y.
Where the organo group of the organo-molybdea~una cornpo~and is a carboxylate, this is ~ °~°6TE ET ~ ~~ ~

.,5.
preferably a C1 to Cep, more preferably a Cg to Clg, carboxylate group.
Examples of suitable carboxylates include octoate, e.g. 2~ethyl hexanoate, naphthenate and stearate. These compounds may be prepared, for example, by reacting molybdenum trioxide with the alkali metal salt of the appropriate carboxylic acid under suitable conditions.
Where the organo group of the organo-molybdenum compound is a xanthate, the compound preferably has the formula Mo2 (RCCS~~ (III
where R ie a Cl to CsQ hydrocarbyl gmup, preferably an alkyl group. Examples of suitable molybdenum xanthate compounds and their method of preparation are described in European patent application Ep-A-433025.
The ashieea organo~phosphorus compound is selected from a phosphorothiolothion.ate, a phosphorothivnate and mixtures thereo~~
Phosphorothiolothionat~ have the general formula:

R5 0 - i~ : sR? (m?

where R5, R~ and R? each independent>,y represent a hydrocarbyl group which may be substituted with one or more functional groups or hetero atoms, or may be unsubstituted, and which may be branched or atraight~chaia.
Preferably R5 and R~ are each a Gl to Cgp alkyl group, or a Cg to Cgp cycloalkyl, aryl, aralkyl or alkylaryl group. R7 is preferably a G1 to C3p alkyl group, a Cg to Cg0 cycloalkyl, aryl, aralkyl or alkylaryl group, or a C1 to C3p hydrocarbyl group containing one or more carboocylic acid, ostEx, alcohol, ether or amine groups, ox an ammonium ion, preferably one or more carboxylic acid groups. Exataples a~f suitable phoephorothiolothionates which axe commercially available include VANLUBE ?2?, VANLUBE 7611 both supplied by R.T.
nH
Vanderbilt Crnoapany, IRGAI,UB~63 supplied by Ciba-Geigy, and ECA 6330 supplied by Exxon Chemical Company.

~I~ 95/07964 PCTIGB94101971 - ~ t ,'~ i ~~
Phosphorothionates have the general formula:
where Rg, Rg, and R10 each represent a hydrocarbyl group which may be substituted with one or more functional groups or hetero atoms, or may be unsubstituted, and which may be branched or straight-chairs.
IO Preferably Rg and Rg are each a C1 to C30 alkyl group or a Cg to C30 cycloalkyl, aryl, aralkyl or alkylaryl group. R10 is preferably a C1 to C30 alkyl group or a Cs to C30 cycloalkyl, aryl, aralkyl or alkylaryl group, or a C 1 to C30 hydrocarbyl group containing one or more amine, carboxylic acid, ester, alcohol or ether groups, or an ammonium ion, preferably an amine group or ammonium ion. Fxamples of suitable phosphorothionates which are commercially available 15 include IRGALLTBE TPPT supplied by Ciba-Geigy. Phosphorus thionates may also be obtained from the reaction of amines with dialkyIdithiophosphoric acids.
Z'he zinc thiophosphate compound (c) has the general formula Rlli ~~ I, II ~ R13 20 P- S -Zn-S - P
R12~ ~ ~ ~ ~ R

where R11, R12~ R13 and R14 each independently represent a hydrogen atom, a C1 to C20 alkyl group, a Cg to C26 cycloalkyl, aryl, alkylaryl or aralkyl group, or a C3 t~
C20 hydrocarbyl group containing an ester, ether, alcohol or carboxyl group. Preferably each of R11 to R14 is a C2 to 25 C13, more preferably C3 to CS, alkyl group which may be straight-chain or branched. Such compounds are commercially available and are supplied lby, for example, Exxon Chemical Company.
Z'lae amounts of each of the antiwear additives (a) and (b) to be included in the lubricant composition according to the invention are the amounts that are effective in providing 30 the desired level of antiwear performance, whilst reducing the amount of phosphorus to an acceptable level.
S STIT TE ~1 ET ~ L

~ 95/07964 PC"1'/G1394/01971 ~- -~ r., ;, _7_ Whilst not being limited to any particular theory, it is lbelieved that the antiwear properties of the organo-molybdenum compound (a) are generally attributable to the presence of the molybdenum. Thus when determining the amount of organo-molybdenum compound to be incorporated into the lubricant composition, one fu°st needs to determiaae the desired amount of molybdenum. Preferably the amount of molybdenum contained in the lubricant composition is from 0.001 to 0.5 wt.%, more preferably 0.005 to 0.2 wt.%, and most preferably 0.01 to 0.05 wt.%, based on the total weight of the lubricant composition. The amount of organo-molybdenum compound that this corresponds to depends upon the type of compound selected.
Where the organo-molybdenum compound is a dithiocarbamate, the amount of compound used depends on the molecular weight of the R groups contained in the thiocarbamate groups, as defined in formula (I) above. Typically, however, the amount of molybdenum dithiocarbamate used is preferably from 0.01 to 3.0 wt.%, more preferably from 0.02 to 2.0 wt.%, and most preferably from 0.05 to 1.0 wt.°/, based on the total weight of the lubricant composition.
1~ Where the organo-molybdenum compound is a carboxylate, the amount of compound used depends upon the molecular weight of the carboxylate group selected. For example, where the carboxylate is 2-ethyl hexanoate, the amount of molybdenum carboxylate used is preferably from 0.005 to 2.5 'vt.%, more preferably from 0.025 to 1.0 wt.%, and most preferably from 0.05 to 0.25 wt.%, based on the total weight of the lubricant composition.
Where the organo-molybdenum compound is a xanthate, the amount of compound used depends upon the nnolecular weight of the hydrocarbyl, e.g. alkyl, groups contained in the xanthate groups. Typically, however, the amount of molybdenum xanthate used is preferably from 0.003 to 2.0 'vt.%, more preferably from 0.01 to 0. r wt.°/ and most preferably from 0.03 to 0.2 wt.%, based on tine total weight of the lubricant composition.
Similarly, it is believed that the anti'vear properties of the ashless organo-phosphorus compound (b) and the zinc thiophosphate, when used, are generally attributable to the presence of the phosphorus. Thus, when determining the amounts of these compounds to incorporate, one first needs to determine the desired amount of phosphorus in the lubricant composition.
Preferably the total amount of phosphorus contained ira.the lubricant composition is from 0.001 to 0.3 wt.%, more preferably from 0.01 to 0.2 wt.%, and most preferably from 0.02 to 0.1 wt.%, based on the total weight of the lubricant composition.
The amount of ashless organo-phosphorus compound and zinc thiophosphate compound (when used) that this corresponds to depends on the relative proportions of these compounds and the molecular weights of the particular compounds selected. Typically, however, the TITIlI'E S T ( LE ) ~'~ 95/~79Cr~ °'~~ i' '~ ~~ c~'E~~t'ic~~9~9fog971 ~. s -amount of ashless organo-phosphorus compound incorporated into the lubricant cognposition is preferably from 0.01 to 3.0 wt.%, more preferably from 0.1 to 2.0 wt.°/~, and r~aost preferably from 0.2 to 1.0 wt.°/~, based on the total weight of the lubricant coa~l~ositio~a, and the alllount of zinc thiophosphate colylpound is preferably from 0.01 to 3.0 wt, more preferably 0.1 to 2.0 wt.°/~, and most preferably 0.2 to 1.0 wt. % based on the total weight of the lubricant cohrlpositiola.
Tlle ratio of organo-molybdenulll compound (a) to ashless organo-phosphorus compound (b) is preferably such that the weight ratio of naolybden~am to phosphorus in the lubricant coaanposition, due to the presence of compounds (a) and (b), is f°rolll 1:~0 to 100:1, lxlore preferably from 1:10 to 20:1, and most preferably from 1:1 to 10:1. Tlle weight ratio of phosphorus derived from the ashless orgallo-phosphorus compound (lb) to zinc tlliophosphate compound (c) (when used) is preferably from 10:1 to 1:20, more preferably from n:l to 1:15 and most preferably 1:1 to 1:10.
The base oil employed in tile lubricant composition according to tile inventiola lBlay be any base oil having a viscosity suitable for use of tile lubricant in an engine e.g. as a cranl~case oil or gear oil. Thus tile base oil may be, for example, a conventionally refined mineral oil, an oil derived from coal tar or shale, a vegetable oil, an animal oil, a hydrocrac~ed oil, or a synthetic oil, or a mixture of two or more of these types of oils. Exalllples of synthetic oils include hydroisomerised para~firls, polyalphaolefills, polybutene, alhylbenzenes, polyglycols, esters such as polyol esters or dibasic carboxylic acid esters, allsylene oxide polymers, and silicone oils. The viscosity of tile base oil depends upon the intended use, but generally is ill tile range of from ~ to 26 cSt (nlm2/s)at 100°C, preferably frol%1 3 to 20 cSt (ar11112/s)at 100°C.
The antiwear additive colrlpounds (a) and (b), and (c) when used, may be mixed directly with the base oil, but, for ease of handling and ialtroduction of the compounds to tlne base oil, are preferably in the form of additive concelatrate colnprisaaag the additive compound, or lllixture of both compounds, contained in a carrier fluid. The carrier fluid is typically an oil and nay be, for exaallple, any of the oils mentioned above ill the description of the base oil. alternatively, it may be an organic solvent, for example naphtha, benzene, toluene, xylene and the life. Tlle carrier fluid should be coallpatible with the base oil of the lubricant composition, but other~~ise is preferably arlert. Clenerally the concentrate will comprise from 10 to 00 wt.
% of the additive(s), preferably from 30 to ?0 wt.°/, tile balance being tile carrier fluid.
The lubricant colllpositioll according to tile invention may also contain other additives, which lnay be added directly to tile base oil, as a separate additive concentrate, or included in tile concealtrate of the aTltlb~'ear addltl~'es. for exaprlple, where tile lubricant is an engine oil, other additives that l~llay be iaucorporated include one or lllore of a detergent, dispersant, antioxidant, corrosion itlhibitor, extreme pressure agent, antifoaming agent, pour point corrosion inhibitor, extreme pressure agent, antifoaming agent, pour point depressant and viscosity index improver. Such additives are well-known and the selection of appropriate additives could readily be determined by a person skilled in the art of lubricant formulating.
The lubricant composition may find use in any application where the parts to be lubricated are subject to wear. It is especially suitable for use as an engine oil for internal combustion engines.
The invention is illustrated by the following Examples.
Examples I to 3 A number of engine oils were formulated by blending an organo-molybdenum compound and an ashless organo-phosphorus compound with a conventional engine oil formulation (the "basecase" oil) which was based on a conventionally refined mineral oil and contained standard engine oil additives except that ZDDP was omitted. For comparative purposes, further engine oils were formulated omitting one or more of the antiwear additives, and, in one example, ZDDP was added.
The formulations are listed in Table 1 below.
The organo-molybdenum compounds used were: (i) MOLYVAN 822 (trade name) a molybdenum dithiocarbamate supplied by R.T. Vanderbilt Company, (ii) MOLYNAPALL (trade name), a molybdenum naphthenate supplied by Mooney Chemicals, and (iii) MOLYHEXCEM
(trade name), molybdenum 2-ethyl hexanoate supplied by Mooney Chemicals. The molybdenum content of each of these compounds was determined using ICP (inductively-coupled plasma) analysis.
The ashless organo-phosphorus compounds used were: (i) 1RGALUBE TPPT (trade name), a phosphorothionate supplied by Ciba-Geigy, (ii) VANLUBE 727 (trade name), a phosphorothiolothionate supplied by R.T. Vanderbilt Company, and (iii) "Amine DDP", an amine derivative of a phosphorothionate obtained by reacting the amine PRIMENE IMT
(trade name) supplied by Rohm and Haas with dioctyldithiophosphoric acid. The phosphorus content of each of these compounds was determined using X-ray fluorescent analysis according to standard test AMS
86.002.
The ZDDP compound used was PARANOX 14 supplied by Exxon Chemical Company.
The phosphorus content of this compound was also determined using the above X-ray fluorescent analysis technique.

~ 951~7964 c~~ ~s f ~ I~EC~'/~~9~/~ff97E
_y~_ The resulting engine oils were tested for valve train wear by rrneasarrang camshaft wear and tappet scuff'ang using a motored cylinder head test rig which is e~aaivalent to the industry standard °l°[1-3 engine test CEC L-3S-T-S7, which test procedure i~ available frorrr flee C~~
Secretariat, O1 hlew ~avendish Street, hondon W 1 Sue.
The results are given in Table 1 bel~~r. X11 percentages are by weight based on the weight of the fully f~ranulated engine oil.
In Table 1 the following abbreviations are used:
PhT 14 - P ~X 14~
IX22 - ~h~I~T S22 .I~.~hL - NT~L~P~L
I~.~i.CEI~ - M~L~Ii~~CE
LTPPT - IRGU~~ TPPT
VI. 727 - ~lLITI3E 727 P.JMT - Pl?ITVIEhIE T reacted with dioctyldithiophosphoric acid (rood results are indicated by a low value for camshaft wear and a high value for tappet scuffing. From the results it can be seen that addition of an organo-molybdenum compound as the sole antiwear additive produces only a sma~ improvement in camshaft wear and some improvement ia~ tappet scuff'yrtg over the basecase oil containing no arrtiwear additive. l~il~ewise addition of solely an organo-phosphorus compound produces some improveBnent in camshaft wear and tappet scufl'ing. ~Iodvever addition of both compounds produces sagnrf'gcant antiwear improvement. Furthermore the improvement achieved is greater than that achieved using ZDI?P, even when the total active ingredient is higher for the ZI~l7P-containing formulation (Example lA) than the formulation according to the invention (Example lI~).
Furthermore, better results than with ZDI)P alone were achieved when the organo-~nolybdera~m compound was 2-ethyl hexanoate (ExaPraple 3E) the ~ces~alts being ~nly marginally less than with dithiocarbarrgate example 3C) and was achieved using only 0.07 wt.°/~
of the additive compound as against 0.2 wt.°/~ ire the case of dithi~carbaanate.
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T'IT TE E T ( LJ

W~ 95/0794 I~~~'1~~~~I0~971i :~ , , _. .. ., ~~~pl~ ~
An engine oil was formulated by adding the following antiwear additives to ~
basecase oil consisting of conventional engine oil based on a conventionally refined gnineral oil and containarng standard engine oil additives othe~° than Z~I~Po (a) 0.2 wt. %~ 1!~~1..322 (nnolybden~adithiocarbamate as in E~a~a~le 1) (ia) 0.3 wt.~/~ ECA 6330, a plaosphorothiolothionate supplied by E~~on ~heangcal ~opa~y, and (c) 1.0 wt.~/ P ~X 14 (Z17~~ as in E~a~~le 1) ~'he amount of molybdenum contained in (a) was determined using l~h (inductively-coupled plasma) analysis. ~'lae am~unt of phosphorus c~a~tained in eacl~a ~f (b) and (c) was determined using X-ray fluorescent analysis acc~rding to standard test 3 36.002.
Comparative engine oils were formulated using the same basecase aril and omitting one or more of the above antibvear additives (a), (b) and (c).
~'he resulting engine oils were tested for valve train wear by measuring tappet wear according to the standard industry engine test 5106 Cam and °l°appet °l°est Qprocedure 1'-5106), which test procedure is available from AG, P~stfach 3130, ~Iolfsburg 1, ~er~nany Z"he resulting engine oils were tested for valve train wear by measuring tappet wear according to the standard industry engine test Wt15106 Cana and ~'appet l3.ig.
Z°lae results are given in Z'able 2 below. X11 percentages are by weight based on the weight of the fully formulated engine oil.
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~i'~ 95/07964 ~C7f'1G~94/01971 ~_. 1 !
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Example Organo-o Ashless-PZDDP /~ % /~Z'otal Ivlax.
NIo P Z"appet active wear (Esm) ingredient 0.2J 0.8% 1.0% 0.01 0.10 0.11 100 - 1.2% - 0.10 0.10 123 0.2% - 1.0! 0.01 0.09 0.10 127 4D ~ ~ 0.8% l.OS - 0.10 0.10 123 ! ~

~'he lower the tappet wear value the better the anti'vear pex°f~rmance of the lubricant.
Thus the results show that for the same level of total phosphorus a significant hnprovement in antiwear performance is achieved when the antiwear agent is a combination of organo-molybdenum oompou~nd, ashless organo-phosphorus compound and ZDDP.
STI'T T'5 El' ~ L)

Claims

CLAIMS:

1. An antiwear additive combination for use in a lubricant composition comprising:

(a) an oil soluble or oil-dispersible phosphorus-free organo-molybdenum compound wherein the organo group of the molybdenum compound is selected from carbamate, carboxylate and xanthate groups and mixtures thereof, which groups may be substituted with a hydrocarbyl group and/or one or more hetero atoms;

(b) an ashless, sulphur-containing organo phosphorus compound selected from:

(i) a phosphorothiolothionate of the formula:
wherein R5, R6, and R7 are each independently an unsubstituted branched or straight-chain hydrocarbyl group or a branched or straight-chain hydrocarbyl group substituted with one or more functional groups or hetero atoms, (ii) a phosphorothionate of the formula:
wherein R8, R9, and R10 are as defined for R5, R6, and R7 above; and (iii) a mixture of (i) and (ii); and, (c) a zinc thiophosphate compound selected from one or more of zinc dialkyldithiophosphate, zincdiaryldithiophosphate, zinc alkylaryldithiophosphate and zinc arylalkyldithiophosphate.

2. An additive combination according to claim 1 wherein (a) is a molybdenum dithiocarbamate of the formula:
where R1, R2, R3, and R4 are each independently a hydrogen atom, a C1-C20 alkyl group, a C6-C20 cycloalkyl, aryl, alkylaryl or arylalkyl group, or a C3-C20 hydrocarbyl group containing an ester, ether, alcohol or carboxyl group; and X1, X2, Y1, and Y2 are each independently a sulphur or an oxygen atom.

3. An additive combination according to claim 1 wherein (a) is a molybdenum carboxylate wherein the carboxylate group contains from 1 to 50 carbon atoms.

4. An additive combination according to claim 1 wherein (a) is a molybdenum xanthate of the formula Mo2(ROCS2)4 where R is a C1- C30 hydrocarbyl group.

5. An additive concentrate comprising a carrier fluid in which the components of the additive combination of any one of claims 1 to 4 is or are dispersed, dissolved or dispersed and dissolved.

6. A lubricant composition comprising a base oil viscosity of from 3 to 26 cSt (mm2/s) at 100C, and an anti-wear additive combination according to any one of claims 1 to 4.

7. A lubricant composition according to claim 6 wherein the base oil viscosity is from 3 to 20 cSt.

8. A lubricant composition according to claim 6 or 7 wherein the amount of organo-molybdenum compound contained in the lubricant composition is such that the amount of molybdenum contained in the lubricant composition is from 0.001 to 0.5 wt. %
based on the total weight of the lubricant composition and/or wherein the amount of ashless organo-phosphorus compound contained in the lubricant composition is such that the amount of phosphorus contained in the lubricant composition is from 0.001 to 0.3 wt. %
based on the total weight of the lubricant composition.

9. A lubricant composition according to claim 8 wherein the amount of molybdenum contained in the lubricant composition is from 0.005 to 0.2 wt.%.

10. A lubricant composition according to claim 8 or 9 wherein the amount of phosphorus contained in the lubricant composition is from 0.01 to 0.2 wt.%.

11. A lubricant composition according to any one of claims 6 to 10 wherein the ratio of organo-molybdenum compound to the ashless organo-phosphorus compound in the lubricant composition is such that the weight ratio of molybdenum to phosphorus in the lubricant composition is from 1:50 to 100:1.

12. A lubricant composition according to claim 11 wherein the weight ratio of molybdenum to phosphorus in the lubricant composition is from 1:10 to 20:1.

13. A lubricant composition according to any one of claims 6 to 12 wherein the amount of zinc thiophosphate compound and ashless organo-phosphorus compound contained in the lubricant composition is such that the amount of phosphorus contained in the lubricant composition is from 0.001 to 0.3 wt. % based on the total weight of the lubricant composition and/or wherein the ratio of organo-molybdenum compound to the ashless organo-phosphorus and zinc thiophosphate compounds in the lubricant composition is such that the weight ratio of molybdenum to phosphorus in the lubricant composition is from 1:50 to 100:1.

14. A lubricant composition according to claim 13 wherein the amount of phosphorus contained in the lubricant composition is from 0.01 to 0.2 wt.%.

15. A lubricant composition according to claim 13 or 14 wherein the weight ratio of molybdenum to phosphorus in the lubricant composition is from 1:10 to 20:1.

16. A lubricant composition according to any one of claims 6 to 12 wherein the weight ratio of phosphorus derived from the ashless organo-phosphorus compound to phosphorus derived from the zinc thiophosphate compound is from 10:1 to 1:20.

17. A lubricant composition according to claim 16 wherein the weight ratio of phosphorus derived from the ashless organo-phosphorus compound to phosphorus derived from the zinc thiophosphate compound is from 5:1 to 1:15.

18. Use of a combination of additives as an antiwear agent in a lubricant composition, the combination of additives being in accordance with any one of claims 1 to 4.