WO2015026566A1

WO2015026566A1 - Lubricant having improved antiwear properties

Info

Publication number: WO2015026566A1
Application number: PCT/US2014/050678
Authority: WO
Inventors: Anantha Desikan; Eric Burkhardt; Sergei V. Levchik; Andrew Piotrowski
Original assignee: Icl-Ip America Inc.
Priority date: 2013-08-20
Filing date: 2014-08-12
Publication date: 2015-02-26

Abstract

There is provided herein a lubricant comprising a major amount of natural and/or synthetic basestock and a minor amount of aryl bisphosphate ester of the general formula wherein each R is independently an alkyl group of from 1 to about 4 carbon atoms and wherein R¹ is selected from a divalent phenyiene group such that the aryl bisphosphate ester is a hydroquinone bisphosphate wherem the divalent phenyiene group is optionally substituted with an R* group wherein R* is R or H; a divalent phenyiene group such that the aryl bisphosphate ester is a resorcinol bisphosphate wherein the divalent phenyiene group is optionally substituted with at least one R* group; a divalent neopentyl group; and, a divalent bisphenylene group containing an isopropylene bridge, and wherein a is 1 or 2.

Description

LUBRICANT HAVING IMPROVED ANTI WEAR PROPERTIES

FIELD OF THE INVENTION

(00 1] This invention relates to a lubricant, in particular a lubricant comprising an aryl bisphosp ate esters. The aryl bisphosphate esters provide for improved stability of lubricating oils such as natural and synthetic lubricants.

DETAILED DESCRIPTION OF THE RELATED ART

[OOffi] High temperature lubrication, for example from about 150 degrees Celsius

(°C) to about 350° C, requires a natural [ubricant and/or a synthetic ester lubricant such as a polyol ester, a diester or certain phosphate esters. Antiwear compounds are

conventionally added to lubricants to enhance their lubricity. Such lubricants can be used in automotive, aeronautical and industrial uses such as foe!s, oils and functional fluids. Unfortunately, typical iy available antiwear additives degrade or volatilize too rapidly at high use temperatures. For example, neutral triaryl phosphate esters are used as antiwear additives in lubricants and hydraulic fluids but due to lower thermal stability and relatively high volatility, may not perform well in high temperature applications.

SUMMARY OF THE INVENTION

(0003) The present invention provides for an ar l bisphosphate ester with reduced volatility and a higher hydrolytic stability then conventional antiwear additives (e.g., those outside the definition of general formulae (I)-(V) herein). Such an aryl

bisphosphate ester may be employed to provide improved lubricity in fuels, oils and functional fluids for automotive, aeronautical and industrial uses.

(0004] There is provided herein a lubricant comprising a major amount of natural and/or synthetic basestock (natural and/or synthetic lubricant.) and a minor amount of aryl bisphosphate ester of the general formula (I):

wherein each R is independently an alkyl group of from 1 to about 4 carbon atoms and wherein R¹ is selected from a divalent phenylene group such that the aryl bisphosphate ester is a fiydroquinone bisphosphate wherein the divalent phenylene group is optionally substituted with at least one R* group wherein R* is R or H; a divalent phenylene group such that the aryl bisphosphate ester is a resorcino! bisphosphate wherein the divalent phenylene group is optionally substituted with at least one R* group; a divalent neopentyl group; and, a divalent bisphenylene group containing an isopropylene bridge, and wherein a is 1 or 2.

(0005) There is also provided herein a concentrate for addition to a natural and/or synthetic basestock comprising an aryl bisphosphate ester of the general formula (I) described above and a liquid carrier compatible with the natural and/or synthetic basestock.

[0006] Further, there is also provided herein a process of purifying an aryl bisphosphate ester of the general formula (! ) which comprises washing the aryl bisphosphate ester with water and then distilling any remaining impurities by wiped film evaporation. DETAILED DESCRIPTION OF THE INVENTION

[0007] There is provided herein an aryl bisphosphate ester which has higher hydrolytic stability and lower volatility then conventional antiwear additives, which higher hydrolytic stability, and resultant antiwear improvement is due to the presence of the R aikyl subsiituent(s) on each of the terminal 4 phenyl groups of the general formula (I), most specifically wherein said aikyl subsiituents are linear or branched alkyls of up to 4 carbon atoms located in ortho position(s) on each of the terminal phenyl groups of the general formula (I), although meta and para placement independently of each of the R group(s) is also suitable in addition to, or in place of, the placement of the R group(s) on ortho position(s). While not wishing to be bound by theory it is believed that the presence of the R groups in the ortho position(s) and/or other positions noted herein, most specifically groups such as t-butyl, sec-butyl and isopropyl (although others noted herein are also suitable) provide for increased steric hindrance of the structure (as opposed to an unsubsfi lined structure) and a resultant unexpected hydrolytic stability and lower volatility which provides for improved antiwear properties as described herein.

[0008] It will be understood herein that the aikyl groups of the R and/or R* groups herein can be linear or branched aikyl groups.

[0009] It will be understood herein that any of the herein choices of R and R* can be applied to any of the formulae described herein independently in any of the ortho, para or meta placements of the respective formulae, such that, for exampl e one R and/or R* group i s on an ortho position and another R and/or R* is any of the meta or para positions, or wherein the R and/or R* groups are independently on exclusively the meta and/or para positions, it will be understood that due to the limited possibilities of the locations of the R and R* groups, that any and all permuatio s and combinations of placements of R and/or R* independently on any of the ortho, meta and para placements possible are included herein and no limitation on such placments is excluded. [0010] in one embodiment of general formula (1) the subscript a is one and each of the terminal R groups are independently selected from methyl, isopropyl, tert-butyl, isobutyl, sec-butyl, and are located in an ortho-position.

[0011] In another embodiment of the general formula (I), the subscript a is two and each of the terminal R groups are methyl groups of which one methyl group is located in an ortho-position and the other methyl group is located in a meta or para position.

[0012] The R alkyl substituents on the phenyl group(s) and on the R* groups of general formulae (I)-(V) include one or more linear or branched groups such as methyl, ethyl, n-propyl, isopropyl, tert-butyl, isobutyl and sec-butyl. Since the number, carbon content, structure and position of the alkyl substituents will influence solubility, both in hydrocarbons (natural lubricants) and in synthetic esters, the R groups will be selected, using routine screening procedures, to provide the desired solubility and insolubility.

[0013] Without wishing to be bound by theory it is believed that the placement of short chain alkyl group(s) (e.g., 4 or less carbon atoms) in ortho position(s) provides for increased steric hinderance in the molecule of formula (I), which improves the hydrolytic stability (and thus, the antiwear properties) of the resultant lubricant.

[0014) In one embodiment, the aryl bisphosphate ester herein can serve as an antiwear agent for addition to fuels such as gasoline, petroleum, kerosene, heating oils, as well as middle distillate fuels, such as diesel, jet and turbine fuels; to lubricants including natural lubricants and diester lubricants, such as motor oils; and to functional fluids such as hydraulic fluids. In addition, the aryl bisphosphate ester herein can also be used in machining oils and the like.

[0015] Some examples of natural lubricants (natural basestocks) that can be used herein are paraffin-type base oils, asphaltic or mixed base crude oils, and mixtures thereof. While derived principally from crude oil, these natural lubricants can also be derived from shale, tat- sands and the like. f Θ016] Some examples of synthetic lubricants (synthetic basestocks) include polyol esters, diesters and phosphate esters. Representative polyol esters are the reaction products of monocarboxylic acids (C2-C12 or higher) and po!yols such as neopentyl glycol, trimethylolpropane, pentaerythrito], dipentaerythritol, complexes and mixtures of any of the foregoing, and the like. Representati ve diesters include reaction products of monohydroxy alcohols (C1 -C6 or higher, both acyclic and cyclic) and dicarboxylic acids such as adipic, azelaic, sebaeic, phthalic acid, dimer acids, mixtures of any of the foregoing, and the like. The phosphate esters are those used as lubricants per se and generally comprise triaryl phosphates, trialkyi phosphates, phosphates having both aryl and substituents (sometimes called "mixed" phosphate esters), and any blends of the foregoing. The phosphate esters thus include tricresyl phosphate, trixylenyl phosphate, iribuiyl phosphate, tributoxyethyl phosphate, trioct l phosphate, isopropyl phenyl phosphate, and the like, and any blends thereof.

[0017] I will be understood herein that the "major amount" of natural and/or synthetic bases toe k is 50% or greater weight percent of the lubricant (lubricant composition) based on the total weight of the lubricant (lubricant composition), more specifically 75% or greater, even more specifically 95% or greater and most specifically 98% or greater.

(00181 In one embodiment the aryl bisphosphate ester of the general formula 0) is part of an aryl bisphosphate ester composition containing no more than 2 wt % triaryl phosphate, more specificall no more than I wt % triaryl phosphate and most specificall no more than 0.5 wt %. Surprisingly, although the aryl bisphosphate ester of formula (I) in comparison with triaryl phosphate esters is stable at high temperature lubricating conditions, it gives poor antiwear results when used alone per se as a high temperature lubricant. In contrast, the lubricant containing the aryl bisphosphate ester of general formula (I) when used in minor amounts in a natural and/or synthetic ester basestock, provides excellent antiwear at high temperature.

[0019] It will be understood herein that the "minor amount" of aryl bisphosphate ester of the general formula (I) is less than 50 weight percent of the lubricant (lubricant composition) based on the total weight of the lubricant (lubricani composition), more specifically 25 or less weight percent, even more specifically 5 or less weight percent and most specifically 2 or less weight percent.

[0020] In one embodiment the aryl bisphosphate ester of the general formula ( I) is such that the subscript a is two. In one other embodiment the aryl bisphosphate ester of the general formula (I) is such that each R group(s) is in ortho position(s), and in another embodiment the aryl bisphosphate ester of the general formula (I) is such that the subscript a is two and each R group is in ortho positions.

[0021] In one specific embodiment the aryl bisphosphate ester of the general formula ( !) is such that R¹ is selected from a divalent phenylene group such that the aryl bisphosphate ester is a hydroquinone bisphosphate wherein the divalent phenylene group is optionally substituted with at least one R* group wherein R* is R or H and wherein the subscript a is two and each of the R and R* groups are in ortho positions, such as the general formula (II):

[9022] Although general formula (II) above could also be modified such that the

R* groups on the central phenyl group of the hydroquinone moiety are on the right side in the ortho positions of the central phenyl group, or even further wherein one R* group is on one of the ortho locations on the central phenyl group on the left and the other R* group is on one of the ortho locations on the central phenyl group on the right, In one embodiment the general formula (II) above could also be modified such that there is only one R* group on the central divalent phenylene group, located in an ortho position.

10023] In one other specific embodiment, the aryl bisphosphate of the general formula (I) is such that R* is a divalent phenylene group such that the aryl bisphosphate ester is a resorcinol bisphosphate, wherein the divalent phenylene group is optionally substituted with at least one R* group, more specifically two R* groups wherein R* is R or H, even more specifically wherein a is two and each R and R* group on the phenyl groups is in an ortho position, such as in the general formula (III):

[0024] Although general formula (III) above could also be modified such that one of the R groups on the central, phenyl group of the resorcinol moiety could be relocated to an ortho position on the right side of the central phenyl group, or even further each of the R groups of formula (III) could be in one of the ortho positions on the left and the right, side of the central phenyl group. In another embodiment of formula (III) above one of R* groups could be on one of the oriho locations and another R* group could be on the respective meta position.

[0025] in one other specific embodiment, the ary! bisphosphate of the general formula (I) is such that R¹ is a neopentyl group and wherein a is two and the R groups are in oriho positions such as the general formula (IV):

[0026] In one other specific embodiment, the aryl bisphosphate of the general formula (I) is such that R¹ is a divalent bisphenylene group containing an isopropviene bridge and where a is two and R groups are in ortho positions, such as the general formula (V):

[0027] In another aspect of the invention, the aryl bisphosphate ester of general formula (I) may be formulated as a concentrate in a liquid carrier compatible with a natural and/or synthetic lubricant basestock, for addition to the basestock in amounts effective to improve antiwear properties of lubricant end products. Such an addition is also suitable for the fuels and functional fluids herein. In addition it will be understood herein that any reference to a lubricant (lubricant composition) herein will also apply to wherein the natural and/or synthetic basestock in the lubricant can be replaced by a fuel or functional fluid as described herein.

[0028] In still another aspect of the invention, lubricant of the invention can be used as the lubricant in the lubrication systems of engines.

[0029] In one embodiment herein the aryl bisphosphate ester of the general formula (I) has a purity of greater than 98 weight percent.

[0030] In one embodiment the lubricant as described herein has a hydroiytic stability greater than that of lubricant containing an aryl bisphosphate other than the aryl bisphosphate ester of the general formula (I), wherein the greater hydroiytic stability is determined by ASTM3537 and D3850. [6031 J in one embodiment herein the lubricant as described herein has a greater antiwear property than that of an equivalent lubricant which contains an aryl

bisphosphate ester other than the aryl bisphosphate ester of the general formula (I), wherein the greater antiwear property is determined by ASTM 2266,

[0032] The lubricant of the invention will have a viscosity of at least 140 cSt at

100°F (about 38° C), specifically 150 cSt at 25°C. As described above, the aryl bisphosphate ester composi tion can comprise aryl bisphosphate ester of the general formula (!) and the triaryl phosphate byproduct, the aryl bisphosphate ester composition will normally also contain minor amounts (about 0.01 -10 wt. %) of a diaryl hydroxyaryl phosphate component and oligomer byproducts of unknown composition. The proportions of the latter component and oligomers can be controlled by reactant ratios and other process conditions and the amounts are reflected in total acid number of the lubricant

[0033] It will be understood herein that the aryl bisphosphate ester composition as described herein can be the aryl bisphosphate ester of the general formula (I) used in the lubricant described herein, i.e., the aryl bisphosphate ester of the genera] formula (1) employed in the lubricant described herein may contain certain amounts of aryl triphosphate ester, diaryl hydroxyaryl phosphate and oligomer byproducts as described herein as a matter of being byproducts of the formation of the aryl bisphosphate ester of general formula (I).

[0034] It is believed that the hydrolytic stability, low acidity, high viscosity and titer properties provided by the aryl bisphosphate ester of general formula (I) in natural and/or synthetic ester base stocks are achieved by controlling the process conditions for production of the aryl bisphosphaie ester with further reduction of triaryl phosphate ester content to no more than 2 wt % as is known in the art.

[0035] in the process of preparation, an excess of phosphorus oxytrichloride

(POCK) is first reacted with a dihydroxy aryl compound, such as resorcinol, in the presence of a Lewis acid catalyst. Unreaeted POC1? is then removed, followed by reaction of the intermediate with a monohydroxy aryl compound, such as phenol, again in the presence of a Lewis acid catalyst. Finally, the reaction product is treated with alkali without hydro lyzing the product. The total acidity of the reaction product is thereby reduced to 0.15 mg KOH/g or less measured in accordance with ASTM D974. Thus, in one embodiment herein the acid number of the aryl bisphosphate ester of the general formula (!) is less than 0.15 mg KOH/g.

[0036] Di hydroxy aryl compounds useful in preparing the aryl bisphosphate ester antiwear additives include resorcinol, hydroquinone and bisphenols such as bisphenol A. The reaction product can be a liquid or solid depending on whether the dihydroxy aryl reactant is unsymmetricai or symmetrical, respectively.

[0037] The aryl bisphosphate ester of general formula (I) may also be blended with carrier liquids, compatible with natural and/or synthetic ester basestocks, to provide concentrates suitable for addition to natural and/or synthetic ester basestocks to form lubricant end products. Such concentrates may facilitate mixing, blending, pouring or transferring (bulk or line) of the aryl bisphosphate ester of the general formula (I).

Typically, the liquid carrier for the aryl bisphosphate ester will be a portion of the natural and/or synthetic ester intended as the basestock for the end product lubricant, but other carriers may be employed, together with other lubricant additives. Addition of the concentrates to natural and/or synthetic ester basestocks to form end product lubricants may be batchwise, for example from unit containers of concentrates sold at retail, or may be added by metering at production or distribution sites. The amount of aryl bisphosphate ester of the general formula (I) in the concentrate may vary, depending on concentrate properties for ease of blending, such as viscosity. Generally, about 10% to 90% by weight of aryl bisphosphate ester in the carrier liquid is suitable, more specifically about 20% to 50% by weight.

[0038] In another embodiment there is provided herein a process of purifying an aryl bisphosphate ester of the general formula (I) which comprises washing (he aryl bisphosphate ester with water and then distilling any impurities by wiped film evaporation.

{0039] There is also provided herein a process of reducing wear in an engine lubrication system comprising utilizing the lubricant (lubricant composition) described herein. Further there is provided a fuel or a functional fluid comprising an aryl bisphosphate ester of the general formula (I).

[0040] Other agents which may be added to the lubricant or to the concentrates are well known and include lubricity agents, other anti-wear additives, antioxidants, metal passivators, rust and/or corrosion inhibitors, viscosity index (VI) improvers, deiergents/dispersants, defoamers/antifoamers, emulsion modifiers, seal swell agents, tackifiers, stabilizers, dyes, and perfumes and other odor masks.

[0041] Lubricity agents include fatty acids and their metal salts or esters and oxidized paraffins. Anti-wear additives include phosphate esters, zinc dialkyl dithiophosphates, and phosphorized fats and olefins.

[0042] Extreme pressure (EP) agents include chlorinated paraffins olefins and sulfurized paraffins, olefins or fats.

[0043] Antioxidants include hindered phenols, aromatic amines and zinc dialkyl dithiophosphates.

[0044] Corrosion inhibitors include metal sulfonates, metal phenate sulfides, acid phosphate esters and zinc dialkyl dithiophosphates.

[0045] Metal passivators include beuzotriazoles and phosphate esters. VI improvers include melhacrylate polymers, styrene butadiene copolymers and

polyisobulylenes. {0046 J Defoamers/antifoamers include silicones and organic copolymers.

[0047] Detergent/dispersants include metal sulfonates, metal phenate sulfides and polyamine succinimides.

{0048} Seal swell agents include alkyi phosphate esters and aromatic

hydrocarbons and esters.

(0049J Tackifiers include VI type poiymers and aluminum soaps of fatty acids.

[0050] Throughout this specification and claims all parts and percentages are by weight, all temperatures are centigrade, acid numbers are total acid numbers of aryi bisphosphaie ester as mg KOH/g measured by the procedure of ASTM 974-87, and residuals % are by high pressure liquid chromatographic (HFLC) analysis.

Claims

CLAIMS;

1 , A lubricant comprising a major amount of natural and/or synthetic basestock and a minor amo

(1) wherein each R is independently an alk l group of from 1 to about 4 carbon atoms and wherein R¹ is selected from a divalent phenylene group such that the aryl bisphosphate ester is a hydroquinoiie bisphosphate wherem the divalent phenylene group is optionally substituted with an R* group wherein R* is R or H; a divalent phenylene group such that the aryl bisphosphate ester is a resorcinol bisphosphate wherem the divalent phenylene group is optionally substituted with at least one R* group; a divalent neopentyl group; and, a divalent bisphenylene group containing an isopropylene bridge, and wherein a is 1 or 2.

2. The lubricant of Claim 1 wherein a is two.

3. The lubricant of Claim 1 wherein each R group is in an ortho position.

4. The lubricant of Claim 1 wherein a is two and each R group is in an ortho position.

5. The lubricant of Claim 1 wherein a is two and one R group is in an ortho position and the other R group is either a meta or para position.

6. The lubricant of Claim 1 wherein R is selected from a divalent phenylene group such that the aryl bisphosphate ester is a hydroquinone bisphosphate wherein the divalent phenylene group is optionally substituted with an R* group wherein R* is R or H and wherein a is two and each R group is in an ortho position,

7. The lubricant of Claim 1 wherein R^! is selected from a divalent phenylene group such that the aryl bisphosphate ester is a resorcinoi bisphosphate and wherein a is two and the divalent phenylene group is substituted with two independently selected R* groups in ortho positions.

7. The lubricant of Claim 1 wherein a is two and R* is a di valent neopentyl group,

8. The lubricant of Claim 1 wherein a is two and R¹ is a divalent bisphenylene group containing an isopropylene bridge.

9. The lubricant of Claim 1 wherein the aryl bisphosphate ester has the general formula (I ):

wherein R* is R as defined or H. The lubricant of Claim 1 wherein the aryl bisphosphate is of the general formula

wherein R* is R as defined or H.

11, The lubricant of Claim 1 wherein the aryl bisphosphate is of the general formula (IV):

wherein R is as defined. The lubricant of Claim 1 wherein the aryl bisphosphate is of the general formula

wherein R is as defined.

13. The lubricant of Claim 1 wherein the aryl bisphosphate ester of the general formula (1) has a purity of greater than 98 weight percent.

14. The lubricant of Claim i wherein the aryl bisphosphate ester of the general formula (I) has a viscosity of at least 140 cSt at 38°C.

15. The lubricant of Claim 1 wherein the acid number of the aryl bisphosphate ester of the general formula (I) is less than 0.15 nig KOH/g.

16. The lubricant of Claim 1 wherein the aryl bisphosphate ester of the general formula (I) has a viscosity of at least 140 cSt at 3S°C and an acid number of less than 0.15 mg KOH/g.

17. The lubricant of Cl aim 1 which has a hydro! ytic stability greater than that of lubricant containing an aryl bisphosphate other than the aryl bisphosphate ester of the general formula (1).

38. The lubricant of Claim 17 wherein the greater hydrolytic stability is determined by AST 3537 and D3850.

19. The lubricant of Claim 1 which has a greater antiwear property than that of an equivalent lubricant which contains an. aryl bisphosphate ester other than the aryl bisphosphate ester of the general formula (I).

20. The lubricant of Claim 19 wherein the greater antiwear property is determined by AST 2266.

21. A concentrate for addition to a natural and/or synthetic basestock comprising an aryl bisp

wherein each R is independently an alkyl group of from 1 to about 4 carbon atoms and wherein R¹ is selected from a divalent phenylene grou such that the aryi bisphosphate ester is a hydroquinone bisphosphate wherein the divalent phenylene group is optionally substituted with an R* group wherein R* is R or H; a divalent phenylene group such that the aryl bisphosphate ester is a resorcinol bisphosphate wherein the divalent phenylene group is optionally substituted with at least one R* group; a divalent neopcntyl group; and, a divalent bisphenyiene group containing an isopropylene bridge, and wherein a is 1 or 2; and, a liquid carrier compatible with the natural and/or synthetic basestock, A proc a (I):

wherein each R is independentl an a!kyl group of from 1 to about 4 carbon atoms and wherein R¹ is selected from a divalent phenylene group such that the aryl bisphosphate ester is a hydroquinone bisphosphate wherein the divalent phenylene group is optionally substituted with an R* group wherein R* is R or H; a divalent phenylene group such that the aryl bisphosphate ester is a resorcinol bisphosphate wherein the divalent phenylene group is optionally substituted with at least one R* group; a divalent neopentyl group; and, a divalent bisphenylene group containing an isopropylene bridge, and wherein a is 1 or 2, which process comprises washing the aryl bisphosphate ester with water and then distilling the aryl bisphosphate ester by wiped film evaporation.

23, An aryl bisphosphate ester made by the process of Claim 22.

24. A process of reducing wear in an engine lubrication system comprising utilizing the lubricant of Claim 1. A fuel c :

wherein each R is independently an alkyi group of from 1 to about 4 carbon atoms and wherein R¹ is selected from a divalent phenylene group such that the aryl bisphosphate ester is a hydroquinone bisphosphate wherein the divalent phenylene group is optional ly substituted with an R* group wherein R* is R or II; a divalent phenylene group such that the aryl bisphosphate ester is a resorciool bisphosphate wherein the divalent phenylene group is optionally substituted with at least one R* group; a divalent neopentyl group; and. a divalent bisphenylene group containing an isopropyiene bridge, and wherein a is I or 2.

A functional fluid comprising an aryl bisphosphate of the general formula (1):

(I) wherein each R is independently an alkyl group of from 1 to about 4 carbon atoms and wherein R* is selected from a divalent phenylene group such that the aryl bisphosphate ester is a hydroquinone bisphosphate wherein the divalent phenylene group is optionally substituted with an R* group wherein R* is R or H; a divalent phenylene group such that the aryl bisphosphate ester is a resorcinoi bisphosphate wherein the divalent phenylene group is optionally substituted with at least one R* group; a divalent neopentyl group; and, a divalent bisphenylene group containing an isopropylene bridge, and wherein a is 1 or 2.