COMPRISING IONS

Technical field

The present invention relates to anti-wear and friction-reducing lubricant components, comprising selected ionic liquids as well as a lubricant comprising the lubricant component.

Background

Improper lubrication may result in high, friction and wear losses, which can in turn adversely affect the fuel, economy, durability of engines, environment and human health, Developing new technological solutions, such as use of lightweight non-ferrous materials, less harmful fuels, controlled fuel combustion processes or more efficient exhaust gas after-treatment., are possible ways to reduce the economical and environmental impact of machines. The commercially available lubricants are yet not. appropriate for lightweight, non-ferrous materials,

Ionic liquids (ILs) are purely ionic, salt-like materials that are usually liquid at low temperatures (below 100 °C). Some IL have melting points below 0 °C. ILs have already found their diverse applications as catalysts, liquid crystals, green solvents in organic synthesis, in separation of metal ions, electrochemistry, photochemistry. CO ₂ storage devices, etc. ILs have a number of attractive properties, such as negligible volatility,, negligible flammability, high thermal and chemical stability, low melting point and controllable irascibility with organic compounds and base oils. Recently, it was found that ILs can act as versatile lubricants and lubricant components in base oils and greases for different sliding pairs, see e.g. US Patent 3,239,463; US Patent Application Publication 2010/0227783 A1 ; US Patent Application Publication 2010/0187481 A1; US Patent 7,754,664 B2, Jul. 13, 2010; US Patent Application Publication 2010/0105586 A1. Due to their molecular structure and charges, ILs can be readily adsorbed on the sliding surfaces in frictionai pa s, forming a boundary tribofilm, which reduces both friction and wear at low and high loads.

The choice of cations has an impact on properties of ILs and often, but. not always defines their stability. Functionality of ILs is, in general, controlled by a choice of both the cation and the anion. Different, combinations of a broad variety of already know cations and anions lead to a theoretically possible number of 10 . Today only about KMX) ILs are described in the literature, and approximately 300 of them are commercially available, ILs with cations iinidazolium, ammonium and phosphonium and halogen-containing anions, tetrafluoroborates and

hexafluorophosphates, are the most commonly used in tribological studies. Alkyiimidazoliiim tetrafluoroborates and hexafluorophosphates have shown promising lubricating properties as base oils for a variety of contacts. However, some ILs with halogen atoms in their structure, for example, with tetrafluoroborates or/and hexafluorophosphates, are very reactive that may increase a risk for tribocorrosion in ferrous and non- ferrous contacts.

Imidasolium and other iLt with Bf^aman: A literature survey shows that most of the IL lubricants successfully employed during the past decade in various ferrous and non-ferrous tribological contacts are based o boron-based anion, tetrafiuoroborale [BR*]- (Ye, C, Liu, W., Chen, Y., Yu _s L.: Room-temperature ionic liquids: a novel versatile lubricant. Chem. Commun. 2244-2245 (2001 ). Liu, W., Ye, G, Gong, Q., Wang, H„ Wang, P.: Tribological performance of room-temperature ionic liquids as lubricant. Tribal. Lett. 13 (2002) 8.1-85. Chen, Y.X., Ye, C.F., Wang, H.Z., Liu, W.M.: Tr ibological performanc of an ionic liquid as a lubricant for steei/aiuminiuirc contacts. J. Synth. Lubrf. 20 (2003) 217-225. Jimenez, A.E., Be mudez, Ml)., Iglesias, P., Carrion, FX, Mait iezrNicolas, G.: l-N-alkyl~3-methylhn.ida7.ol.ium ionic liquids as neat lubricants and lubricant, components in steel aluminum . contacts. 260 (2006) 766-782, Yu, G., Zhou, F,, Liu, W., Liang, Y,, Yan, S.: Preparation, of .functional ionic liquids and tribological investigatio of their ultra-thin films. Wear 260 (2006) 1076- 1080.]

Zhang ei al. have reported that nitrile-functionalized ILs with BIY anion have considerably better tribological performance in steel-steel and steel-aluminium contacts than ILs with TiV and (C ) ₂ ^' anions [Q. Zhang, Z. Li, I Zhang, S. Zhang, L. Zhu, J. Yang _* X. Zhang, Y. J. Deng. Physieochetnical properties of nitrile-fimctionalizcd ionic liquids. J. Phys. Chem. B, 2007, 11 1, 2864-2872.] it has been suggested that the BF4 ^" anion has excellent tribological performance but unfortunately the detailed mechanism was not described,

A comparison of the film formation properties of iinidazolium ILs based on IV and !¾ ^' anions in rolling-sliding steel-steel contacts using mini-traction machine (MT .) revealed that F4- anion develop thicker tribofilm and provides lower friction (u ^« * 0. 1) compared to PF<j ^' (μ~ 0.03) [H. Arora, P.M. Cann. Lubricant film formation properties of alkyl imidazolium tetraftuoroborate and hexafluorophosphate ionic liquids. Trib&L Int. 43 (2010) 1 08- 1916. J The same family of ILs in titanium-steel contacts has shown that BF^ anion- ased IL tails above room, temperature while BF a on- bascd IL perform better up to 200 "C { A. E. Jimenez, M, D. Bermudez. Ionic liquids as lubricants of titanium- steel contact, pan 2: friction., wear and surface interactions at high temperature. TriboL Lett. 37 (2010) 431-443.] in steel -aluminium contacts, phosphonium IL with BP_f anion showed superior tribological properties including friction- reducing, antiwear and load carrying capacity to conventional imidazolium IL based on PF'Y anion [X. Liu, F. Zhou, Y. Liang, W. Liu. Tribological performance of phosphonium based ionic liquids for an aluminum-on-steel system and opinions on lubrication mechanism. Wear 2 1 (2006) 1 174- 1 179.] Similarly, phosphon un IL with. BF* ^' anion exhibited excellent tribological performance at 20 **C and 100 X in steel-steel contacts as compared to invidazoIium-PFff and conventional high temperature lubricants such as X- I P and peril uoropolyefher PFPE [L. Wenga, X. Liu. Y, Liang, Q. Xue. Efiect of tetraalkyiphosphorvium based ionic liquids as lubricants on the tribological performance of it steel-on-steel system. Tribal Lett. 26 (2007) 1.1.-17.] However, the sensitivity of [ Et] ^' anion to moisture make such ILs undesirable in tribological and other industrial applications. During the past, few years., efforts have been made by researchers to desig and synthesize hydrolyticatly stable halogen-free boron-based ILs with improved performance.

Pyrrolidinium ILs with halogenated anions: The lubricating properties; of pyrrolidinium ILs with [BF. _¾ ] ^' anion a t? not reported yet. However, pyrrolidinium IL with other halogenated. anions are reported, in literature as excellent, lubricants and lubricant components for various tribological applications. Recently, pyrrolidinium ILs with halogenated anions have shown excellent lubrication performance in microelectromechanieai systems (MEMS) [J. .1, Namaparampil, K. C. Eapcn, J. H. Sanders, A. A. Voevodin, Ionic-Liquid Lubrication of Sliding MEMS Contacts: Comparison of AFM Liquid Cell and Device-Level Tests. J. Mfcroehctrormchamcal Systems 16 (2007) 836-843.] l-Butyl-l-methylpyrrolidinium irisfpentailuoroethyljtrifluorophosphate, as is known to possess promising lubricatin properties in non-ferrous coatings interfaces such as TIN, CrN and DLC [R. Gonzalez, A. H. Battez, D. Blanco, J. L. Viesca, A. FemandeK-Ganssalcz. Lubrication ofTiN, CrN and DLC PVD costings with I-Butyl-l -MethylpyiroIidinium

i.i½(pentaf{i).oroethyl)tnfliiorophosphiite. Tribal Lett. 40 (2010) 26 --277.]

C olmhim ILs with ha genated anions: Choline is biological molecule In the form of phosphatidylcholine (liposome), a major constituent of synovia) fluid surface active

phospholipids, are natural additives for cartilage lubricants in human beings [G, Verberae, A. Sehroeder, G. Halperin, Y. Baretiholz, L Etsion, Liposomes as potential biolubricarit components for wear reduction In human synovial joints. Wear 268 (201 ) 1037-1042.] These molecules are widely used in effective biolubricants for friction and wear reduction ia human synovial joints [S. Si van, A. Sehroeder, G. Verbeme, Y. Merkher, D. Diminsky, A, Priev, A. Maroudas, G. Halperin, D. Niixan, L Etsion, Barenholz. liposomes act as effective biolubricants for friction reduction in human synovial joints. Langmuir 26 (2010) 1107-1 1 16.]

Choiinium .La, choline chloride, has recently shown excellent friction reducing performance in steel-steel contacts comparable to fully formulated engine oil (SAE 5W30 grade) [S, D« A, Lawes, S. V, Hainssvorth, P, Blake, K. S, Ryder, A, P. Abbott. Lubrication of steel/steel contacts by choline chloride ionic liquids. Tribal. Left. 37 (2010) 03-1 10,] These I ts are believed as green lubricants and have been known to have excellent corrosion inhibition properties [C.

Gabler, C. Tomasiik, J. Brenner, L. Pisarova, N, Doerr, G. Allmaier. Com>skra properties of ammonium based ionic liquids evaluated by SEM-ED.X, XPS and ICP-OES. Green Chent, 13 (201 1) 2869-2877.] US 2009/0163394 discloses a. number of ionic liquids, for instance

Memyl-i butylbis(cliethylamino)"phosphonium bis(oxaIaio)boratc. It briefly mentions that lubrication oils as a general application for ionic liquids. One drawback of the compounds that sire disclosed is that the direct P-N bonds in cations of described phosphonium based ionic liquids are sensitive to hydrolysis, which is critical in many important applications including most of commercial lubricants with unavoidable presence of traces of water. Compounds with P- bonds are very sensitive to hydrolysis and may hydrolyne to produce reactive species.

Therefore, phosphonium cations with one and more P-N chemical bonds will be prone to hydrolysis in the presence of traces of water in a lubricant. Stability of a lubricant placed in a contact with, water is a very important technical characteristics. The most widely studied ionic liquids in iribologieal applications usually contain tetmfluoroborate (B j ^' ) and hexafiuorophosphate (PF _(> ) anions. Probably, the reason is that both boron and phosphorus atoms have excellent tribological properties under high pressure and elevated temperature in the interfacesS. However, BFj ^' and PFe ^' anions have high polarity and. absorb water in the system. These anions are very sensitive to moisture and may hydrolyze to produce hydrogen fluoride among other products. These products cause corrosion by various trihoehernical reactions, which can. damage the substrate in the mechanical system, in addition, halogen-containing ILs may release toxic and corrosive hydrogen halides to the surrounding environment. One major drawback of ionic liquids, which are known for lubrication purpose is that die halogens make them undesked lor instance from aji environmental perspective. Further corrosion may be a problem for some currently used ionic liquids in particular for hydropbilie ionic li uids.

Therefore, the development of new hydrophobic and haiogen-iree anions containing ILs is highly desired. Su m ma r of th e Ϊ » ven t i n

It is an object of the present invention to obviate at least some of the disadvantages in the prior art and provide an improved lubricant component as well as a lubricant comprising the component.

I a first aspect, there is provided a lubricant component, characterized in that it comprises; a) at least one anion selected from the group consisting of a mandelato borate anion, a salicylate) borate anion, an oxalate borate anion, a malonato borate anion, a succinate borate anion, a glutarato borate anion and ait a lipaio borate anion, and b) at least one cation selected from the group consisting of a teiraaJkylphosphomum cation, a choline cation, an imidazolium cation and a pyrrolidinium cation, wherein said at least one cation has at least, one alkyl group substituent with the general formula C Han _H* wherein 1 n . SO.

In one embodiment 1 < n < 60. In one embodiment the anion is selected from the group consisting of a bis(mandelato)borate anion, a bis(sa!icyiato)borate anion, and a bis(ma!oraato)horat.e anion, and wherein the cation is a tetiaalkylphospli niurn cation. in one embodiment the anion is bis(oxaia.to)bnn_te and wherein the cation is a

tetraalkylphosphonium cation.

In one embodiment the anion is a bis(succtnato)borate anion and wherein the cation is a tettaalkylphosphonium cation.

In one embodiment the anion is selected from the group consisting of a b.is(glutarato)borate anion and a bis(adipato)borale anion and wherein the cation is a tetraalkylphosphonium cation. In one embodiment the only cation is ietnuilkylphosphonium with the general formula PR *Rj ^f , wherein R' and R are C,,3 i2 _n - i.

In one embodiment R' is selected from the group consisting of C _¾ Hi? and C14H29, and wherein R is selected from die group consisting of and C<jHi3.

In one embodiment the lubricant, component comprises ai least, one selected from the group consisting of tributylociylphosphonium b.is(mandelato)borate; triburyltetradecylphospho iiim bi.s(mandelato)borate; trihexyltetradecylphosphonium bisfmandelatojborate,

tributyloclylphosphonium bis(aa.iieylato)borate ₅ tributyltetradecyiphosphonium

bis(salicylato)borate, trihexylteiradecylphosphonium bis(salicylato)borale,

ributyltetradecylphosphonium bis(oxaIato)borate, trihexyhetradecylphosphonium

bis{oxalato)borate _t thbutyltetradecylphosphonium bi&CmalonatoJboi-ate,

trihexyltetradecylphosphonium bi$(malonatO.)boratc, tributyltetradecyiphospho um

bis(succinato)borRte, trihexyltetradecylphosphonium bis(succinato)borate,

trlbutylteti'adecylphosphonium bisiglutaratojlwate, trihexyltetradecy!phospjioninni

bis(glutarat ^' o}borate, (ributyUetradecylphosphonium bis(adipato)bovate _f

trihexyltetradecylphosphonium bis(adipato)borate, choline b.is(sa ^' licylato)borate, A-cthyl-N- methylpyrrolidiftium

I -ethyl- 2,3 -dnnethylimidazolhim bis( rid io)b orate, .1 -ethy3-2,3-dimethyIiinida .o!.ium bis(saIicylato)borate, I -methylimidazoIe-trimethylamine- iis bis(maiidelato)borate, 1. ,2- dimethyliniklazole-trimethy^ l-methylimidazole- trimethylemme~BH?. bis(salicyLat ^' o) ai ^, ate, and 1,2-dimeUiylmudaz¾>le-trimethyIaraIne-BlIi bi s(sa1 icy! ato)borate.

In one embodiment the lubricant component comprises trihexyltetradecylphosphonium bis( m aridel at ) borate ,

In one embodiment the lubricant component comprises tribexyltetradecyiphosphonium bI,s(salicylato)bt>rat¾ in one embodiment the lubricant component comprises tfihexyltetiadecylphosphomum bis(ox alato)borate. In one embodiment the lubricant component comprises ttihexyltetradecylpbosphoviium his(iv>alonato)borate.

In a second aspect there is provided a lubricant comprising 0.05-100 wt% of the lubricant component described herein. The lubricant component can both be used in pure form and as an additive to other lubricants. If the lubricant component is used in pure form the lubricant component itself is the sole lubricant.

In one embodiment the lubricant comprises 0.05- 20 wt%, of the lubricant component as described herein, in one embodiment the lubricant comprises 0.1- 5 \vt%, of the lubricant component. In one embodiment the lubricant comprises 0.5« 5 wf%, of the lubricant component. n a third aspect, there is provided use of the lubricant component as described herein for at least one selected from reducing wear and reducing friction.

In a fourth aspect there is provided a method for reducing friction comprising use of & lubricant with the lubricant component as described herein. '

There is also provided a method for reducing wear comprising use of a lubricant with the lubricant component as described herein. Advantages of the invention include that the replacement of Bf-y _> PI and haloge containing ions with more hydrophobic and halogen-free anions will avoid corrosion and toxicity. Halogen- ree boron bused ionic liquids, ( - A/-Bll..s) with these novel halogen-free boron-based anions make a lubricant hydrolytically stable. This will aid to avoid the formation of

hydrofluoric acid (HF) in the lubricant in the course of exploitation of machines. HP is produced by the most commonly used anion <BF<0 and (PF< in ILs. The formation of HF from ionic liquids is one of the main limitations of -such lubricants, because HF is highly corrosive towards metals. The present novel A/-BILs according to the invention do not have such limitations,

Based on tribological studies of ionic liquids with imidazoiium, pyrrolidinium and choHniura (as cations) and halogen-baaed anions, we suggest that ionic liquids according to the invention, i.e. ionic liquids with . tetrualkylphosphonium, imidazolium, pynolidinium and eholtnium (as cations) and halogen-free orthoborate anions will have good tribological performance in addition to their advantage as being o^enrfree, Some exampl es of these halogen-free orthoborate anions are bis(mancielato)borate, bis(salicyiat.o)borate, bis(oxalato)borale, bis(malonato}boratc,

bis(su.cemato)bor8t.e, bis(ghuarato)borate and bis(adipato)borate. An outstanding antiwear and friction-reducing effect for steel-aluminium contacts has been proven for orthoborate based tetraalkylphosphonium ionic liquids and the "key" role is orthoborate anions in ILs as lubricants regarding these technical effects.

Short description of drawings

The invention will be described more in detail below with reference to the accompanying- drawings, in which: Figure 1 shows DSC thermograms of novel halogen-free boron based ionk /) -BlL« liquids.

Figure 2 shows densities of novel halogen-free boron based ionic liquids (A -BILs) as a function of temperature.

Figure 3 shows an Arrhenius plot of viscosity for selected. ft/-B ^' lLs as a function of temperature.

Figure 4 shows the wear depths at 40 N load for KHX'r6 steel against AA2024 aluminum lubricated by f-Bl s in comparison with 15 W-50 engine oil.

Figure 5 shows the friction, coefficients at 40 N load for l OOOr steel against AA2024 aluminum lubricated by A/-IHLs in comparison with 15W-5G engine oil. Figure 6 shows the friction coefficient curves at 20 N load for tOOCrd steel against A.A2024 aluminium lubricated by f-BlLs in comparison with .15 W-50 engine oil.

Figure 7 shows the friction coefficient curves at 40 N load for 100Cr6 steel against AA2024 aluminum lubricated by hf-BlLs in comparison with 15 W-50 engine oil. Detailed description of the Invention

Regardin n in R, R' - C,,.!.,,* i of tetraalkylphosphonium cations, it is noted, that borate with shorter {both linear and branched) alkyl chains are less miscib!e in oils (in particular, with mineral oils), while longer chain alkyl groups (both linear and branched) have higher iscibility with mineral oils. Therefore, an increase in the length of alkyl groups (n) is expected to result in a more homogeneous lubricant. However, the length of and IV should be optimized for each specific type of the oil and an optimum temperature interval for the lubricant, because too long alkyl chains will lead to a lower mobility of the additive in lubricant and, therefore, to compromised hoth anti-wear and friction reducing efficiency of the additive. Therefore, n is at least 1 and could be up to about 80 without, negatively affecting the performance of the compound according to the invention.

In order to be well miscible with today's engine oils, such as POA 40 and POA 60 (Statoil) having carbon chain lengths of 40 and 60 carbon atoms, respectively, the value of n should be no less than 40 and 60, respectively. Thus, in one embodiment n < 60. The limit n < 80 is motivated by possible future prod ucts of motor oils with even longer alkyl chains, supposedly up to at least ii~80.

A skilled person can in the light of the description make a routine optimization experiment and determine a suitable value of n and branched or/and non-branched character of the alkyl groups in tetraalkylphosphonium, inmudazolium and pyrrol idinium cations. It is conceived to use the lubricant components for reducing friction and reducing wear on a number of different materials both metals and non-metals. Examples of non-metals include but are not limited to ceramics with/without DI..C (diamond-like-coaiings) or/and graphene-based coatings. Examples of metals include but are not. l imited to alloys, steel, and aluminium with/without DLC (diamond-like-coatings) or/and graphene-based coatings. A new family oi ;/-Bl.Ls was s nthesized and purified following an improved protocol and a detailed study of their Iribological and physicochemical properties i ncluding thermal behavior, density and viscosity, was earned out. The iribological properties were studied with 1 GGCro steel balls on an AA2024 aluminum disc in a rotating pin-on-disc test.

All compounds tested from this novel class of /i/ ^' BlLs have outstanding antiwear as well as friction performance as compared with the fully formulated engine oil

Synthesis schemes for the halogen free boron based ionic liquids according to the invention are shown below:

Scheme 2: Synthesis oi' bte(salfcyta to) borate based ///-BILs

Scheme 3: Synthesis of bhi(oxalato) borate based /? >B!Ls

Scheme 4: Synthesis of bts(maiona to) borate bused // -BILs

Synthesis

All novel halogen-free boron based ionic liquids (h -B!Ls) were synthesized and purified using modified literature methods.

Example 1 : Tributyloctylphosp onium bU(man<leteto)borate (JP4448HBMB])

Mandclic acid (3.043 g _f 20 mmol) was added slowly to an aqueous solution of lithium carbonate (0.369 g, 5 inmol) and boric acid (0.618 g, 0 mmol) hi 50 m.L water. The solution was heated up to about 60 ^ft C for two hours. The reaction was cooled to room tempera lure and

tri.butyloctylphosp onium. chloride (3.509 g, 10 mmol) was added, The reaction mixture was stirred for two hours at room temperature. The organic layer of reaction product, formed was extracted with 80 ml. of CHjClj. The CHjOa organic layer was washed three times with 60 mL water. The CH2CI3 was rotar evaporated at reduced pressure and product was dried in a vacuum oven at 60 for 2 days. A viscous colorless ionic liquid was obtained in 84 % yield (5.30 g). m ESI-MS (-): 31 1.0 [BMB] ^' ; mfc ESI-MS (+): 315.3 fP4448f.

Example 2: TributylietradecyiphospboiTHim bis(i«aTid.el8to)boi'ate ({P44414](BMB})

The procedure is similar to that used in the synthesis of [P4448][BMB]. The reaction started with (0.369 g, 5 mmol) of lithium carbonate, (0,618 g, 10 mmol) of boric acid, (3.043 g, 20 mmol) of mandelic acid and tributyltetradccylphosphomum chloride (4.349 g, 10 mmol). A viscous colorless ionic liquid was obtained in 81 % yield (5.75 g). mti ESI-MS (-): 1 .9 [BMB]-; mfz ESI-MS {+): 399.2 [P44414}\ apJc 3: TrihexyltetrmlecylphoKphoniinn bis{mandelato)borate ({P666.l4j|BMBl)

The procedure is similar to that used in the synthesis of [P4448][BMB]. The reaction started with (0.369 g, 5 mmol) of lithium caAonate, (0.618 g, 10 mmol) of boric acid, (3.043 g, 20 mmol) of mandelic acid and trihexylteiradeeylphospho iim chloride (5.189 g, 10 mmol). A viscous colorless ionic liquid was obtained in 91 % yield (7.25 g). m/z ESl-MS (■■): 31 1.0 [BMB]-; m/z ESl-MS ( ^'■ ! }; 483.3 [P66614 .

Example 4; Tributylocryiphosphonium bis(salicylato) oraie (|?4448][BScB|)

The procedure is simflar to thai used in the synthesis of [P4448][BMBj. The reaction started with (0.369 g, 5 mmol) of lithium carbonate, (0.618 g, 1.0 mmol) of boric acid, (2,762 g, 20 mmol) of salicylic acid and trlbutyloctyiphosphcmiurn chloride (3.509 g. 10 mmol). A viscous colorless ionic liquid was obtained in 88 % yield (5.28 g). otfe ESl-MS (-): 283.1 [BScB] ^" ; m z ESl-MS (+): 315.3 fP4448] ⁺ .

Example 5: Tributy etradccylphosphonium bis{salicylato)b rate (|P444l4j{BikB))

The procedure is similar to that used in the synthesis of P444Sj[BMB], The reaction started with (0.369 g, 5 mmol) of lithium carbonate, (0.618 g, 10 mmol) of boric add, (2.762 g, 20 mmol) of salicylic acid and tributyheuadeeylphosphonium chloride (4.349 g, .10 mmol). A viscous colorless ionic liquid was obtained in 94 % yield (6.44 g). m/z ES1- S (-): 283.0 [BScB]-; /z ES1-MS (+): 399.4 [P444l4f.

Exa m pi c 6 : Trf h .exylfctra decylph ospho niu m bie{sal icy to to) bo rate ((P66614} [BScB])

The procedure is similar to that used in the synthesis of Ρ4448][ΒΜΒ]. The reaction started with (0369 g, 5 mmol) of lilhium carbonate, (0. 38 g, 10 mmoi) of boric acid, (2.762 g, 20 mmol) of salicylic acid and trihexyltetradecylphosphonhim chloride ( 5.189 g, 1 mmol). A viscous colorless ionic liquid was obtained in 95 % yield (7,30 g). m/z E£SI~MS (-): 283.0

[BScB] ^' ; m/z ESI-MS (+): 483.5 ! 66614] \

Example 7: Tributyltetradeeylphosphonium bis(oxalaio)borafe ([P44414j{BOBV)

The procedure is similar to that, used in the synthesis of [P4448] BMB]. The reaction started with (0.369 g, 5 mmol) of lithium carbonate, (0.618 g, 10 mmol) of bor ic acid, (} .80 g, 20 mmol) of oxalic acid and Iributyhetradecylphosphonium chloride (4.349 g, 10 mmol). A viscous colorless ionic liquid was obtained.

Example 8: Tt ihexyltotrad cylphosph aitun bis(o alato)borate ((P66614}{BGBJ)

The procedure is similar to that used in the synthesis of [P4448][B B]. The reaction started with {0.369 g _f 5 rnruol) of lithium carbonate, (0.618 g, 10 mmol) of boric acid, (1.80 g, 20 mmol) of oxalic acid and trihexyltetradecylphosphoniuin chloride (5.189 g, 10 mmol). Λ viscous colorless ionic liquid was obtained, mk ESI-MS (-): [BOB] ^' ; m z ESI-MS (+): 483.5 [P<56614]\

Example 9: ributyUetntdecylphospIi niutn bis(maloiialo)br>rare ([P44 14][BMLB])

The procedure is similar to that, used in. the synthesis of P4448][B ^' MB]. The reaction started with (0.369 g, 5 mmol) of lithium carbonate, (0.618 g, 10 mmol) of boric acid, (2.081 g, 20 mmol) of makmic acid and tii utyltetredecylphoitphonium chloride (4.349 g _f 10 mmol). A viscous colorless ionic liquid was obtained.

Example 10: Trthexy!tetraclecylphosplionium bw(rnatonat«)borate ({P666.14HBMLB])

S

The procedure is similar to that used in the synthesis of [P4448][BMB]. The reaction started with (0,369 g, 5 mmol) of lithium carbonate, (0.618 g, 10 mmol) of boric acid, (2.081 g, 20 mmol) ofmalonic acid and tnhexyltettadecylphosphottium chloride (5.189 g _f 10 mmol). A0 viscous colorless ionic liquid was obtained, mhs ESI-MS (-): [B LB]-; m/z ESI-MS (·+·): 483,5

[P66614]*. xam le 11 : Tributyltetradeeylphosphonium bis(succinaio)l>orate ({} ^> 4 4l4](BSuB])

5 The procedure is similar to that used in the synthesis of |P4448][BMB], The reaction stalled with (0.369 g, 5 mmol) of lithium carbonate, (0.618 , 10 mmol) of boric acid, (2.362 g, 20 nrniol) of mslonic acid and tribu yltetradecylphosphontum chloride (4.349 g, 10 mmol). A viscous colorless ionic liquid was obtained.

Example 12: Tnhexyitetradecylphosphonium hrs(8uccinato)b<>rate ( P666J4] | S»B))

The procedure is similar to that used in the synthesis of [Ρ4448][.ΒΜΒ], The reaction started with (0.369 g, 5 mmo.1) of lithium carbonate, (0,618 g, 10 mmol) of boric acid, (2.362 g. 20 mmol) of malonic acid and trihexyt tetrad ecylphosphoni tun chloride (5.189 g, 10 mmol). A viscous colorless ionic liquid was obtained.

Example 13: Tributyltefradecylphosphoniuin bis(g_utarato)b raie ([P44414][I ilB])

The procedure is similar to that used in the synthesis of (P4448][BMB). The reaction .started with (0.369 g„ 5 mmol) of lithium carbonate, (0.618 g, 10 mmol) of boric acid, (2.642 g, 20 mmol) of malonic acid and tributyltetradecylphosphonium chloride (4.349 g„ 10 mmol). A viscous colorless ionic liquid was obtained.

Example 14: Trrhexylretnuie ylplwsphontuni bie(g it»rato)bontte ({P66614HI G1BD

The procedure is similar to that used in the synthesis of [i'4448]( B I3]. The reaction started with (0/369 g, 5 mmol) of lithium carbonate, (0.618 g _s 10 mmol) of boric acid, (2.642 g, 20 mmol) of malonk acid and trihexyltelrade yiplt sph nium chloride (5.189 g, 10 mmol). A viscous colorless ionic liquid was obtained.

Example 3.5: Tributylietrmiecylphosphontutn bis(adipato)borate (|P44414|(BAdU])

The procedure is similar to that used in the synthesis of [P4448][BMB], The reaction started with (0.369 g, 5 mmol) of lithium carbonate, (0.618 g, 10 mmo.1) of boric acid, (2.923 g, 20 mmol) of malonic acid and ttibirtyltetradecylphosphomum chloride (4.349 g, 10 mmol). A viscous colorless ionic liquid was obtained.

Example 16: THhexyitetradccylphosphonium bis(adipato)borate ({P666.l4]lBAdB})

The procedure is similar to that used in the synthesis ofTI 448 ^' j[BMB]. The reaction started with (0.369 g, 5 mmol) olTithhtm carbonate, (0,618 g, .10 mmol) of boric acid, (2.923 g„ 20 mmol) of malonic acid and trihexyltelradecylphospbonium chloride (5,189 g, 10 mmol). A viscous colorless ionic liquid was obtained.

Example 17: Choline biis<salie la o)borate ([Choline] BSc ])

Salicylic acid (5.524 g, 40 mmol) was added slowly to an aqueous solution of lithium carbonate (0,738 g, 10 mmol) and boric acid ( 1.236 g, 20 mmol) in 40 mL water. The solution was heated upto about 60 °C for two hours. The reaction was cooled to room temperature and choline chloride (2,792 g, 20 mmol) was added. The reaction mixture was stirred for two hours at room temperature. The organic layer of reaction product formed was extracted with 80 mL of CHjCla. The I ¾CI ₂ organic layer was washed three times with 80 mL water. The CH2CI2 was rotary evaporated at reduced pressure and the product was dried in a vacuum oven at 60 for 2 days, A. white solid ionic: liquid was recrystalHzed from CH2CI3 (5,44 g, 70 % yield), mfo ESl- MS (-): 28.10 [BScB]-; m z ESI- S (+): 10 ,9 [Choline]".

Example 18: cthyt-jV-m thylpyriOlidinium bis(saiicylato)borate ([I£MFy]{BScB|)

Salicylic acid (5.524 g, 40 mmol.) was added slowly to an aqueous solution of lithium carbonate (0.738 g, 10 mmol) and boric acid (1 ,236 g, 20 mmol) i 40 mL water. The solution was heated upto about 60 °C for two hours. The reaction was cooled to room temperature and N- elhyl.-N-methylp>Trolidin.ium iodide (4,822 g, 20 mmol) was added. The reaction mixture was stirred for two hours at room temperature. The organic layer of reaction product formed was extracted with 80 ml of (¾0 _¾ . The CH2CI2 organic layer was washed, three times with 80 mL water. The CH2CI2 was rotary evaporated at reduced pressure and the product was dried in a vacuum oven at 60 for 2 days, A white solid ionic liquid was rocrystalliaed. from CH _¾ な f 6.167 g, 78 % yield), m/z ESi.- S (-): 283.0 [BScB]-; m z ESI-M8 (+): .1 1 .9 [EMPy .

Example 19: jlV-ethyt-iV-mctbylpyrralidininm bis(mandela.o)borare [EMPy||BMB|

S

The procedure is similar to that used in the synthesis of [EMPy][BScB]. The reaction started with lithium carbonate (0.369 g, 5 mmol), boric acid (0.618 g, 10 mmol), mandelic acid (3.043 g, 20 mmol) and JV-ethyl-.V-methylpvtiOlidini m iodide (2.41 g, 10 mmol). A viscous ionic liquid was obtained in 6? % yield (2.85 g). MS (ESI) ca!cd for [CsHj _f iNf nt z 1 14.2; found nth 1 14.1; calcd for [C, _(i H, ₂ O _f ,B]- m/z 31 1.0; found m/z 31 1.0.

Example 20: l-ethyI-2,3-dinieth> fcnklnKoHum bis(ma«de!ato)borate [EMlmjjBMB)

Mandelic acid (3.043 g, 20 mmol) was added slowly to an aqueous solution of lithium, carbonateS (0.369 g _s 5 mmol) and boric acid (0.618 g„ 10 mmol) in 50 mL water. The solution was heated npto about. 60 ^ft C for two hours. The reaction was cooled to room temperature and l-ethyl-2,3- cUmethylimidazolkun iodide (2.52 g, 10 mmol) was added. The reaction mixture was stirred for two hours at room temperature. The bottom layer of the reaction product formed was extracted with 80 mL of Cf C . The CHjCij organic layer was washed three times with 100 mL water.0 The CなC . was rotary evaporated at reduced pressure and the final product was dried in a vacuum oven at 60 °C for 2 days. A viscous ionic liquid was obtained in 78 % yield (3.40 g). MS (ESI) calcd for [C _? H)j ^' Na] ⁺ m/z 125.2; found m/z 125.2; calcd for [Ct«I I.|. ₂ 0«B] ^' m/z 1 1.0; found m/z 31 1.1. .Example 21: 1 -ethyl -.2 ^-dimeth l tmidaxolhini bis(saHcy.ato)borate |EMIm| [BScB]

The procedure is similar to that, used in the synthesis of [£MIm][BMB]. The reaction started with lithium carbonate (0,369 g, 5 mmol), boric acid (0.618 g, .10 mmol), salicylic acid (2.762 g, 20 mmol) and l-ethyl-2 _} 3-dimeihylimidazoliimi iodide (2.52 g, .10 mmol). A while solid product was obtained in 83 % yield (3.38 g). MS (ESI) ealed for [C^HuNaf mfz 1 5.2; found mfz 1.25,1; calcd for Ci HsO _e B3- m/z 283.0; found mfz 283.0, xam le 22: l-iut bylimidaz( fc riniet y}amitu BIi ₂ his(mandeIato)borate

|MImNmBHi][BMBl

Mandelie acid (3.043 g, 20 mmol) was added slowly to an aqueous solution of liihium carbonate (0.369 g, 5 mmol) and boric acid (0,618 g, 10 mmol) in 50 ml, water. The solution was heated upto about 60 °C I r two hours. The reaction was cooled to room temperature and 1 - methylimidazole trimethyiamine BHj iodide (2.81 g, 10 mmol) was added. The reaction mixture was stirred for two hours at room temperature. The bottom layer of the reaction produc formed was extracted with 80 mL ofCikCfe. The 0な<な organic layer was washed three times with 100 mL water. The (¾<な was rotary evaporated at reduced pressure and the final product was dried in a vacuum oven at. 60 °C for 2 days,

Example 23: 1,2-dimethyIitnidazoIe-tritncthyIamine-BI.j bis(mandel¾to)b»j ate

|ΜΜΪ mNll1HMb) [BiVtBj

The procedure is similar to that used in the synthesis of [MMLmN 1 1 1 Bな][BMB], The reaction started with lithium carbonate (0.369 g, 5 mmol), boric acid (0.618 g, 10 mmol), salicylic acid (2,762 g, 20 mmol) ami 1 ,2~diinettiylimidazole irimethylamine BHj iodide (2.84 Ig, 10 mmol) was added, A Liquid product was obtained.

Example 24: l-metliyiimidazole-trimetliyiamine-BHj bts(salicyhtto)borate

| ImNlllBH ₂ ][BScBI

Salicylic acid (5.524 g, 40 mmol) was added slowly to an aqueous solution of lithium carbonate (0,738 g, 10 mmol) and boric acid (1.236 g, 20 mmol) in 40 mL water. The solution was heated Hpto about. 60 °C for two hours. The reaction was cooled to room temperature and 1- methylimidaKOle trimethylamine Bな iodide (5.62 g, 20 mmol) was added. The reaction mixture was stirred for two hours at room temperature. The organic layer of reaction product formed was extracted with 80 ml of Cな(な, The C.H2CI2 organic layer was washed three times with 80 ml, water. The CHjG?. was rotary evaporated at reduced pressure and the product was dried in a vacuum oven at 60 for 2 days, A Liquid product was obtained. Exam le 25: 1 ,2-(iitnc ^> tLiyliiiiida2olc>trin ^> thy]amine>BIl2 bis(saSicy!a to) borate

[M lm lil ii;HBSc |

The procedure is similar to that used i the synthesis of [MlmN ^' l 1 I BIな][BSB]- The reaction started with lithium, carbonate (0,369 g _P 5 mmol), boric acid (0.618 g, 10 mmol), salicylic acid (2.762 g, 20 mmol) and l^-dimethylimidazole trimethylamine BH2 iodide (2.8 1 g, 10 mmol) was added. A liquid product, was obtained.

instrumentation used in the invention

NMR experiments were cotleeted on a Bniker Avance 400 (9.4 Tesla magnet) with a 5mm broadband autotunable probe with Z-gradients at 30 "C. NMR spectra were collected and processed using the spectrometer "Topspm" 2.1 software. ^T H and ^U C spectra were reference to internal TMS and CDClj. Externa! references were employed in the ^3V P (85% lijPO ) and ^M B (BtiO'BF ₃ ). The positive and negative ion eleetrospray .mass spectra were obtained ith a Mieromass Platform 2 ESI- MS instrument.

A. Q100 TA instrument was used for differential scanning calorimetrie (DSC) measurements to study the thermal behavior of hf-BlLs. An a erage weight, of 5-10 mg of each sample was sealed in an aluminum pan and cooled to -1.20 °C then heated upto 50 °C at a scanning rate of 10.0 °C/mi.n.

Viscosity of these hf-BlLs was measured with an AMVn Automated icroviscomcter in a temperature range from 20 to 90 °C using a sealed sample tube.

The wear tests were conducted at. room temperature (22"C) on a Nanovea phi-on-disk tester according to ASTM 099 using 6mm 100Cr6 balls on 45 mm diameter AA2024 aluminum disks. The composition, Vicker's ^' hardness and average roughness, Κ _ή) of the steel balls and aluminum disks are shown in Table 1. The disks were lubricated with 0.1 mL of lubricant. Experiments were conducted at loads of 2 and 0 N for a distance of 1000 m, with a wear track diameter of 20 mm and a speed of 0,2 m/s, The friction coefficient was recorded throughout the experiment. On completion of the wear tests, the wear depth was measured using a Dektak 150 stylus profiiometer.

Others 0.15 max

Fe 0.5 max Balance

Al Balance

Hardness (Vkkers) 145 850

R„ (μηι) 0.09 0.05 max

R sults and Discussion o» the invention

Thermal Behaviour of A/-BILS

Figure 1 shows the differentia:! scanning calorimetry (DSC) traces of A BILs under discussion. All these A/-B1L§ are liquids at room temperature and they exhibit glass transitions below room temperature (-44 °C io -73 °C). Glass transition temperatures (T _& ) for these A BILs a c also tabulated, in 'fable 2. t is known that T _g of orthoborate ionic liquids are higher than those for me corresponding salts of the fTu rhiated anions. T _s f the orthoborate ionic liquids with the cation P66614 ^* arid different anions decreases in the order BMB ^" > BScB- > BOB ^' > BMLB-, i ' BlLs with B B- and BScB- have considerably higher T _g values compared with these of A BlLs with BOB- arid BMLB-, most probably because of the phenyl rings present in the structure of the former anions (BMB- and BScB-).

For common orthoborate anions with different phosphonium cations, a decrease in T _g is observed with an increase in size of alkyl chains in the cations. This trend is more easily seen in A/ ^: BILs with the BScB- anion and different phosphonium cations: T _B fall in the order P4448* (- 49 °Q > P44414* (- 54 °C) > Ρ666Ί6* (- 56 °C) (see Table 2). Del Sesto et at have observed a similar (rend for ionic liquids of phosphonium cations with bistrifyl amide ( Ίな) and diihiomal.eon.itri.le (dtmn) anions. Lowest T _t of A BILs (clown to■■ 73 ¹ for P66614-BMLB) are reached with P666.16 ^" ' ^' as the cation, probably because of a larger size, lower symmetry and a low packing efficiency of this cation.

Density measurements of A/-BlLs

Figure 2 shows a linear variation of densities with temperature for A/-BlLs. By comparing the effect of anions on the densities of A/ ^: B:ILS _;> densities fall in the order BScB ^' > BMB- > BOB ^' > BMLB-. For the same anion, density of f- lLs decreases with an increase in the s ze f the cation as P 4 S* ^' > P44414* > ?666I6 ^÷ . The density values οΠ>44414-ΒΜΒ and P444 !4-BScB are very similar at all measured temperatures. Density of ?/ ^: BILs decreases with an increase in the length of alky! chains in cations, because the van der Walls interactions are reduced and that leads to a less efficient packing of ions. The parameters characterizing density of the.se A/-BlLs as a function of temperature are tabulated in Table 2. For increasing temperatures from f 20 to +90 °C, density of ttf-BlLs decreases linearly. This behaviour is usual for ionic liquids.

Dynamic viscosity of r/>BILs

Figure 3 shows temperature dependences of viscosities of hf-BILs. These dependences can be fit to the Arrhenius equation for viscosity, η - ₀ βχρ(Ε _¾ ( )/なι7), in the whole temperature range studied. Here, n ₀ i.s a constant and B _g (Vj) is the activation energy for viscous flows. Activation energies, Β ₃ ( ), for different hf-BILs are tabulated in Table 2.

Some of novel A BILs have shown very high viscosity in the temperature range between 20-30 "C, which was not measurable by the viscometer used in this study. However, viscosity of A BJLs decreases markedly with an increase in temperature (from ca 1000 cP at ca 20 °C down to ca 20 cP at ca 90 °C\ see Fig. 3 ). Viscosity of ionic liquids depends on electrostatic forces and van der Walls interactions, hydrogen bonding, mol ecular weight of the ions, geometry of cations and anions (a. conformational d egree of freedom, their sym etry and flexibility of alkyl chains), charge del.ocalizat.ion, nature of substituents and coordination ability. For a given cation, P66616 ^' \ viscosities fall in the order BMB ^" (E _a - 1 1.6 kcal mol ¹ ) > BOB ^' 11 -6 kcal mol ^-1 ) > BScB ^* (E _e ^» 10.6 kcal mol '} > B D3 ^' (な- 10.0 kcal mol ¹ ) (see Table 2).

Tribological Performance of A/-BIL$ Figure 4 compares the antiwear performance for h B\Ls with this for the 1.5W-50 engine oil at loads of 20 and 40 N for a sliding distance of 1000 in. The wear depths for t e 15 W-50 engine oil were 1.369 μηι and 8.686 μιη at 20 N and 40 N loads., respectively. N-ΒΠ. _* » have

considerably reduced wear of aluminum used in this study, in particular, at a high load. (40 N). For example, aluminum lubricated with P66614-BMB the wear depths were 0.842 μχη. and 1 ,984 pm at 20 and 40 N loads, respectively.

Mean friction coefficients for the selected ft -BILs in comparison with 15 W-50 engine oil are shown in Figure 5. The friction, coefficients for the 1.5W-50 engine oil were 0,093 and 0.102 at 20 N and 40 N, respectively. All the tested A/-BILs have lower mean friction coefficients compared with 15W-50 engine oil. For example, the friction coefficients forP666l4~B B were 0.066 and 0.067 at 20 N and 40 N loads, respecti vely.

Figures 6 and 7 show time-traces of the friction coefficient for the selected ft/ ^' BILs and the 15W- 50 engine oil. at 20 N (Fig. 6) and 40 N (Fig, 7} during 1000 m sliding distance. The friction coefficients are stable at 20 N both for 1 SW-50 engine oil and /?/-Bl ^" Ls, There is no an increase in the friction coefficients until the end. of the test for all lubricants examined here. The friction coefficients for /?/- ILs were lower than those for 15W-50 engine oil at ail times of the test (see Fig. 3).

At the load of 40 N the friction coefficient for the 15 W-50 engine oil varied considerably over a sliding distance. At the beginning of the test, the friction coefficient was stable but a sudden increase occurred at a sliding distance of c 200 m and remained that high far a 400 m sliding distance. In the beginning of the test a thin tribofilm separated the surfaces and prevented them from a direct metal - to-metal contact. A sudden increase in the friction coefficient is the evidence of that the tribofilm formed, by standard additi ves present in 15 W-50 engine oi l is not stable on aluminum surfaces. To the contrary, novel hf- iLs according to the invention exhibit a different trend compared to than in. the 15W-50 engine oil. In the ease of P66614--BMB and P66614-BMLB, there was no increase in the friction coefficient over the whole period of the tribological test. The friction coefficients, increased (for .P666i4-BSoB and P66614-BOB) in the very beginning of the test, but then they stabilized after a sliding distance of 50 m. Thus, stable tribofilms (at least until 1000 m sliding distances) are formed at aluminum surfaces lubricated with novel hf BiLs already after a short sliding distance.

Stability studies

The tetraalkylphosphomuni-orthoborate according to the invention based on hosphonium cations containing onl P-C bonds are considerably snore stable to hydrol sis compared for instance to compounds comprising P-K bonds. We have proven experimentally the hydrolytie stability of our novel hf-B!Ls. A small droplet of [ AMI!!BSCB] was put in distilled water and left inside water for .10 days to confirm the hydrolytie stability of these hf-BILs, There was no change in appearance. The sample was analysed by ESI -MS; peaks at m/z 483.5 and m z 283.0 for C}¾(¾P3 ⁺ and [C HgOeB]-, respecti vely, and the absence of other peaks in ESI-MS spectra confirmed the hydrolytie stability of these hf-BILs.