Improvement of solubility of choline carboxylates in base oils

Abstract

The present invention relates to a composition comprising a choline carboxylate, a base oil and specific ester(s), to a blend of choline carboxylate and specific ester(s), and to their applications in lubricant filed.

Description

[0001] The present invention relates to a composition comprising a choline carboxylate, a base oil and specific ester(s), to a blend of choline carboxylate and specific ester(s), and to their applications in lubricant filed.

[0002] Choline carboxylate is an ionic liquid.

[0003] Ionic liquids are composed of cations and anions. They present many properties, such as low temperature fluidity, high thermal oxidation stability, low volatility and high electrical conductivity.

[0004] Also, they are of particular interest in the lubricant field for various applications such as in electric motors, electric vehicle powertrains, wind turbines.

[0005] The function of ionic liquids in lubricants includes reduction of wear, mitigating of electrical pitting issues, and preventing or minimizing electrostatic discharge and dielectric breakdown.

[0006] However, ionic liquids tend to have low solubility in base oils, which are the major constituents (the constituents whose content is the highest), of lubricants. In particular, most ionic liquids are insoluble in Poly Alpha Olefin (PAO), non-polar base oils, but are nevertheless commonly used in industrial lubricants and engine oils.

[0007] The ionic liquids that are soluble in base oils, are not environmentally friendly and are toxic. With the rise in awareness on environmentally acceptable lubricants (EAL), more environmentally friendly alternatives are required.

[0008] Therefore, there is still a need for a method for improving the solubilization of environmentally friendly ionic liquids in base oils.

[0009] Choline carboxylates are composed of cholinium as cation and carboxylate as anion, and thus form environmentally friendly ionic liquids, which are low toxic and halogen free ionic liquids.

[0010] However, as for other tetra-alkylammonium ionic liquids, the solubility these quaternary ammonium ionic liquids in base oil is also an issue. Improvement of the solubility of choline based ionic liquids in base oils has become critical to promote the use of choline based ionic liquid.

[0011] The inventors found that choline carboxylates could be solubilized in specific esters. Moreover, the presence of one or more of those specific esters enables the solubilization of the choline carboxylate in base oils.

[0012] In addition, the inventor found a new process for preparing the blend of choline carboxylate and specific ester(s).

[0013] Accordingly, the present invention relates to a composition comprising: at least 0.1 wt% of a choline carboxylate; at least 1 wt% of one polyol fatty acid ester or a mixture of polyol fatty acid esters; at least 50 wt % of one or more base oil(s); weight percentages being based on the weight of the composition; wherein the one or more base oil(s) is / are not a polyol fatty acid ester.

[0014] Choline carboxylate is an ionic liquid formed by a cholinium cation and a monocarboxylate anion.

[0015] Preferably, the carboxylate comprises from 6 to 24 carbon atoms, more preferably, from 6 to 22 carbon atoms, even more preferably from 6 to 18 carbon atoms.

[0016] In the present application, unless otherwise indicated, all ranges of values used are to be understood as being inclusive limits.

[0017] Preferably, the choline carboxylate is represented by the Formula I: wherein R represents an hydrocarbon chain, straight or branched, saturated or unsaturated, comprising from 5 to 23 carbon atoms.

[0018] Preferably, the choline carboxylate is selected from the group consisting of choline oleate, choline isostearate, choline myristate, choline caprate, choline caprylate and mixtures thereof.

[0019] Preferably, the choline carboxylate is choline oleate or choline isostearate.

[0020] The polyol fatty acid ester is a straight or branched hydrocarbon chain comprising two or more hydroxyl groups.

[0021] Preferably, the polyol fatty acid ester comprises at least three carbon atoms.

[0022] The polyol preferably consists solely of carbon, oxygen and hydrogen atoms.

[0023] Preferably, the polyol is saturated.

[0024] Preferably, the polyol is glycerol, polyglycerol, trimethylolpropane, pentaerythritol or sorbitan.

[0025] Preferably, the polyol fatty acid ester comprises at least one hydroxy group.

[0026] In the composition according to the invention, preferably, the polyol of at least one polyol fatty acid ester is partially esterified.

[0027] By "polyol partially esterified", it is intended to mean that at least one hydroxy group of the polyol is not esterified.

[0028] Preferably, the polyol fatty acid ester or the mixture of polyol fatty acid esters has a hydroxyl value greater than 0 as measured according to standard AOCS Cd 13-60.

[0029] Preferably, the polyol fatty acid ester or the mixture of polyol fatty acid esters has a hydroxyl value of at least 10, 11, 12, 13 such as 13.6, 14, 15, 16, 17 such as 17.5, 18, 19 or 20 mgKOH / g as measured according to standard AOCS Cd 13-60.

[0030] In the present disclosure, unless otherwise indicated, the hydroxy value is measured according to standard AOCS Cd 13-60.

[0031] Preferably, the polyol fatty acid ester or the mixture of polyol fatty acid esters is selected from the group consisting of monoglycerides such as glycerol monooleate and glycerol monoisostearate; diglycerides such as glycerol dioleate; pentaerythritol esters such as pentaerythritol mono-, di-, tri- and tetra-oleate, and pentaerythritol mono-, di-, tri- and tetra -isostearate; trimethylolpropane esters such as trimethylolpropane mono, di, tri-oleate, trimethylolpropane C36 dimerate, and trimethylolpropane mono, di, and tri-isostearate; polyglycerol esters; sorbitan esters; and mixtures thereof.

[0032] The base oils have been categorized by the American Petroleum Institute (API) into five categories (API 1509, Appendix E).

[0033] Group I-III base oils are refined from petroleum crude oils.

[0034] Group IV base oils are full synthetic (polyalphaolefin) oils.

[0035] Group V base oils are all other base oils not included in Groups I through IV. In particular, Group V includes alkylated naphthalenes and esters.

[0036] Preferably, the weight ratio choline carboxylate / (polyol fatty ester or a mixture of polyol fatty acid esters) is comprised between 0.01 and 1.

[0037] In a first embodiment of the composition according to the invention, the choline carboxylate and the polyol fatty acid ester(s) are used separately. The choline carboxylate, the polyol fatty acid ester or the mixture of polyol fatty acid esters are individually and / or successively brought into contact with the base oil(s).

[0038] Preferably, in the composition of the first embodiment, the quantity of choline carboxylate is of at least 0.3 wt%, more preferably at least 0.5 wt%, even more preferably of at least 1 wt% based on the weight of the composition.

[0039] Preferably, in the composition of the first embodiment, the quantity of choline carboxylate is of at most 25 wt%, more preferably of at most 20 wt%, even more preferably of at most 15 wt%, such as 10 wt% based on the weight of the composition.

[0040] Preferably, in the composition of the first embodiment, the quantity choline carboxylate, is comprised between 0.1 and 25 wt%, more preferably between 0.3 and 20 wt%, such as 0.5-20 wt%, 0.5-15 wt%, and 0.5-10 wt%, even more preferably between 1 and 20 wt%, such as 1-15 wt% and 1-10 wt% based on the weight of the composition.

[0041] Preferably, in the composition of the first embodiment, the quantity of polyol fatty acid ester or mixture of polyol fatty acid esters is of at least 1.4 wt% based on the weight of the composition.

[0042] Preferably, in the composition of the first embodiment, the quantity of polyol fatty acid ester or mixture of polyol fatty acid esters is of at most 25 wt%, more preferably of at most 20 wt%, even more preferably of at most 15 wt% based on the weight of the composition.

[0043] Preferably, in the composition of the first embodiment, the quantity of polyol fatty acid ester or mixture of polyol fatty acid esters, is comprised between 1 and 25 wt%, more preferably between 1 and 20 wt% such as between 1.4 and 20 wt% based on the weight of the composition.

[0044] In a second embodiment of the composition according to the invention, the choline carboxylate and the polyol fatty acid ester(s) are used simultaneously, for example in the form of a blend. The choline carboxylate and the polyol fatty acid ester or the mixture of polyol fatty acid esters are first blended together to form a blend.

[0045] Thus, the composition according to the invention preferably comprises: at least 0.1 wt% of a blend comprising: ∘ a choline carboxylate; and ∘ a polyol fatty ester or a mixture of polyol fatty acid esters; at least 50 wt% of one or more base oil(s); weight percentages being based on the weight of the composition; wherein the one or more base oil(s) is / are not a polyol fatty acid ester.

[0046] Preferably, in the blend, the weight ratio choline carboxylate / (polyol fatty ester or a mixture of polyol fatty acid esters) is comprised between 0.01 and 1.

[0047] Preferably, in the composition of the second embodiment, the blend comprises at least 1 wt% of choline carboxylate based on the weight of the blend.

[0048] Preferably, in the composition of the second embodiment, the blend comprises at most 40 wt%, more preferably at most 30 wt% of choline carboxylate based on the weight of the blend.

[0049] Preferably, in the composition of the second embodiment, the blend comprises between 1 and 40 wt%, more preferably between 1 and 30 wt% of choline carboxylate based on the weight of the blend.

[0050] Preferably, in the composition of the second embodiment, the blend comprises at least 50 wt%, more preferably at least 60 wt%, even more preferably at least 70 wt% of polyol fatty acid ester or mixture of polyol fatty acid esters based on the weight of the blend.

[0051] Preferably, in the composition of the second embodiment, the blend comprises at most 99 wt% of polyol fatty acid ester or mixture of polyol fatty acid esters based on the weight of the blend.

[0052] Preferably, in the composition of the second embodiment, the blend comprises between 50 and 99 wt%, more preferably between 60 and 99 wt%, even more preferably between 70 and 99 wt% of polyol fatty acid ester or mixture of polyol fatty acid esters based on the weight of the blend.

[0053] Whatever the embodiment, the hydroxyl value of the mixture polyol fatty acid ester(s) and base oil(s) present in the composition according to the invention, is of at least 3, 4, 5, 6, 7, 8, 9 or 10 mgKOH / g as measured according to standard AOCS Cd 13-60.

[0054] Preferably, the hydroxyl value of the composition is of at least 4, 5, 6, 7, 8, 9, 10 or 11 mgKOH / g as measured according to standard AOCS Cd 13-60.

[0055] The composition according to the invention is preferably monophasic, e.g. the whole quantity of choline carboxylate present in the composition according to the invention is solubilized.

[0056] As shown in Examples 3 and 4, at least 1 wt% of choline carboxylates are soluble in a base oil, when at least a polyol fatty acid ester is present in the base oil.

[0057] The present invention also relates to a process for preparing a composition according to the invention, by mixing a choline carboxylate, a polyol fatty acid ester or a mixture of polyol fatty acid esters, and base oil(s).

[0058] In a first embodiment, the choline carboxylate and the polyol fatty acid ester(s) are used separately. The choline carboxylate, the polyol fatty acid ester or the mixture of polyol fatty acid esters are individually and / or successively brought into contact with the base oil(s).

[0059] In a second embodiment, the choline carboxylate and the polyol fatty acid ester(s) are used simultaneously, for example in the form of a blend.

[0060] Advantageously, in the process for preparing a composition according to the invention, the choline carboxylate and the polyol fatty acid ester or the mixture of polyol fatty acid esters are first blended together to form a blend.

[0061] The blend may be prepared by mixing the choline carboxylate with the polyol fatty acid ester or the mixture of polyol fatty acid esters.

[0062] Preferably, the blend is prepared by reacting an equimolar quantity of choline hydroxide or choline chloride, with one or more monocarboxylic acid(s) in the presence of one polyol fatty acid ester or a mixture of polyol fatty acid esters.

[0063] In the process according to the invention, during the mixing, the composition may be heated to 40°C or up to 80°C.

[0064] The mixing lasts preferably at least 15 min, more preferably at least 30 min, even more preferably at least 1 hour.

[0065] The present disclosure also concerns a method for improving solubilization of a choline carboxylate in base oil(s) representing at least 50 wt% of a composition, by adding at least 1 wt% of one polyol fatty acid ester or a mixture of polyol fatty acid esters in said composition, weight percentages being based on the weight of the composition.

[0066] The choline carboxylate, the polyol fatty acid ester, the mixture of polyol fatty acid esters, and the base oil are as described above, including preferential features and embodiments.

[0067] In the method according to the invention, the polyol fatty acid ester or mixture of polyol fatty acid esters, may be added simultaneously or separately from the choline carboxylate.

[0068] As shown in Examples 1 and 2, it is possible to solubilize large quantities, such as 30 wt%, of different choline carboxylates in polyol fatty acid ester(s).

[0069] The present invention also concerns a blend comprising or consisting of: 1-50 wt% of a choline carboxylate; 50-99 wt% of one polyol fatty acid ester or a mixture of polyol fatty acid esters, weight percentages being based on the weight of the blend.

[0070] The choline carboxylate, the polyol fatty acid ester and the mixture of polyol fatty acid esters, are as described above, including preferential features and embodiments.

[0071] Preferably, the blend according to the invention comprises 1-40 wt%, more preferably 1-30 wt% of choline carboxylate based on the weight of the blend.

[0072] Preferably, the blend according to the invention comprises 60-99 wt% more preferably 70-99 wt% of one polyol fatty acid ester or a mixture of polyol fatty acid esters based on the weight of the blend.

[0073] The blend according to the invention is preferably a monophasic liquid.

[0074] The blend according to the invention is preferably a transparent liquid.

[0075] The blend may be prepared by mixing a choline carboxylate with polyol fatty ester(s).

[0076] The choline carboxylate may be prepared according to any method known by the person skilled in the art. The choline carboxylate may be prepared using acetone or methanol as disclosed in the following publications: Mu et al., ACS Appl. Mater. Interfaces, 2016, 8, 7, 4977-4984; and Ali et al., Journal of Colloid and Interface Science, 551, 2019, 72-80.

[0077] Preferably, the choline carboxylate is prepared in polyol fatty acid ester(s).

[0078] The present invention also concerns a process for preparing a blend according to the invention, by reacting an equimolar quantity of choline hydroxide or choline chloride, with one or more monocarboxylic acid(s) in the presence of one polyol fatty acid ester or a mixture of polyol fatty acid esters.

[0079] The one or more monocarboxylic acid(s) comprise(s) preferably from 6 to 24 carbon atoms.

[0080] The one or more monocarboxylic acid(s) may be saturated or unsaturated, straight or branched.

[0081] The monocarboxylic acid preferably consists solely of carbon, oxygen and hydrogen atoms.

[0082] Preferably, the monocarboxylic acid is obtained from renewable resources, such as vegetable oils. In particular, the monocarboxylic acid is a fatty acid.

[0083] Preferably, the fatty acid comprises from 6 to 22 carbon atoms, more preferably from 6 to 18 carbon atoms.

[0084] Preferably, the reaction mixture is stirred for at least 15 minutes, more preferably at least 30 mins, even more preferably at least 2 hours, such as 24 hours.

[0085] Advantageously, the process for preparing a blend according to the invention, comprises the following steps of: i) mixing the one or more monocarboxylic acid(s) with the polyol fatty ester or the mixture of polyol fatty acid esters); ii) adding the choline hydroxide or choline chloride into the mixture obtained in step i).

[0086] The process for preparing a blend according to the invention, is preferably conducted at a temperature comprised between 20 and 35°C.

[0087] In step ii), the addition of choline hydroxide or choline chloride is preferably done drop by drop.

[0088] Preferably, choline hydroxide or choline chloride is added with stirring.

[0089] Preferably, the reaction mixture is stirred for at least 30 minutes, more preferably at least 2 hours, even more preferably at least 24 hours, after step ii).

[0090] In the process for preparing a blend according to the invention, water is the only byproduct.

[0091] Thus, it is particularly interesting to prepare choline carboxylate by the process according to the invention, since no hazardous solvent is required.

[0092] The blend according to the invention may be obtained directly by the process for preparing a blend according to the invention.

[0093] Advantageously, in the process for preparing a blend according to the invention, the water formed during the reaction is removed.

[0094] Indeed, water is formed when the choline hydroxide or choline chloride reacts with the monocarboxylic acid(s).

[0095] The water may be removed during the reaction or at the end of the reaction.

[0096] Preferably, the water is removed at the end of the reaction.

[0097] Preferably, the water is removed by subjecting the mixture to vacuum.

[0098] Preferably, when the reaction mixture is under vacuum, the reaction mixture is heated at a temperature of at least 50°C, more preferably of at least 60°C.

[0099] The present invention also concerns an use of the blend according to the invention, as a conductive additive in a lubricant.

[0100] A lubricant typically comprises a base oil, usually the major constituent (the constituent whose content is the highest), and one or more additive(s).

[0101] An additive is used to enhance one or more intrinsic property(ies) of the base oil(s) and / or provide it with one or more additional property(ies).

[0102] A conductive additive is a chemical used to provide the required level of electrical conductivity.

[0103] The lubricant is preferably an engine oil, a hydraulic oil, a gear oil, a transmission oil, a metalworking oil, a fuel or a grease.

[0104] The quantity of the blend according to the invention in the lubricant is preferably comprised between 0.1 and 40 wt%, more preferably between 1 and 30 wt%, even more preferably between 5 and 25 wt%, based on the weight of the lubricant.

[0105] The lubricant may further comprise other additives usually used in the lubricant field. A person skilled in the art knows how to select the most suitable additive(s) depending on the lubricating application. By way of example, reference may be made to the following manuals: "Fuels and Lubricants Handbook: technology, properties performance and testing", by George E. Totten, 2003 and "Handbook of lubrification and tribology, vol II : Theory and Design", by Robert W. Bruce, 2012.

[0106] The additive(s) is / are preferably chosen from the group constituted by friction reducers; anti-wears; detergents; antioxidants; viscosity index improvers; pour point depressants; anti-foaming agents; de-emulsifiers; anti-corrosion (or anti-rust) agents; thickening agents; metal deactivators; and mixtures thereof.

[0107] The total quantity of the additional additives is preferably comprised between 2 and 25 wt%, more preferably between 5 and 20 wt% based on the weight of the lubricant.

[0108] The present invention also relates to a lubricant comprising the composition according to the invention.

[0109] The lubricant is as described above, including preferential features.

[0110] The lubricant according to the invention preferably further comprises additives usually used in the lubricant field.

[0111] The additive used in the field of lubricants is as described above.

[0112] The invention is further described in the following examples, given by way of illustration, with reference to the figures: Figure 1 represents a Fourier-transform infrared spectroscopy (FTIR) spectrum of choline oleate, glycerol monooleate, choline oleate added to glycerol monooleate , and choline oleate prepared in glycerol monooleate; Figure 2 represents a Fourier-transform infrared spectroscopy (FTIR) spectrum of choline isostearate, pentaerythritol monooleate, choline isostearate added to pentaerythritol monooleate and choline isostearate prepared in pentaerythritol monooleate. Example 1: Preparation of blends according to the invention 1. Chemicals used

[0113] Choline hydroxide solution (46 wt% choline hydroxide in water) from Merck; Fatty acids: ∘ oleic acid: Radiacid 0255 from Oleon; ∘ isostearic acid: Radiacid 0909 from Oleon; ∘ myristic acid: Apicid MA-1499 from PT Apical Kao Chemicals; ∘ capric / caprylic acids: Radiacid 0640 from Oleon; Polyol fatty acid esters: ∘ glycerol monooleate: Radiasurf 7161 from Oleon; with a Hydroxyl Value (HV) of 180.52 mgKOH / g; ∘ glycerol monoisostearate: Radiasurf 7263 from Oleon; with a HV=219.9 mgKOH / g; ∘ pentaerythritol monooleate: Radiasurf 7156 from Oleon; with a HV=118.5 mgKOH / g; Mixtures of polyol fatty acid esters were prepared by esterification reactions between fatty acid(s) and a polyol. By varying the reaction time, mixtures of polyol mono-, di-, tri and / or tetra-fatty acid(s) esters were obtained. The excess of fatty acid(s) was removed by distillation. ∘ mixture of pentaerythritol oleic acid esters (pentaerythritol oleates), with a HV=22.9 mgKOH / g; ∘ mixture of trimethylolpropane oleic / dimer of oleic acid esters, (trimethylolpropane oleate / C36 dimerate) with a HV=17.5 mgKOH / g; ∘ mixture of trimethylolpropane isostearic acid esters (trimethylolpropane isostearates), with a HV= 15.2 mgKOH / g; 2. Preparation2.1 In one step

[0114] The choline carboxylates were prepared in a polyol fatty acid ester using an equimolar quantity of fatty acid and choline hydroxide.

[0115] The fatty acid was first added into the polyol fatty acid ester.

[0116] Then, the choline hydroxide was added dropwise into the mixture of fatty acid and polyol fatty acid ester, at room temperature.

[0117] The resulting mixture was then left to stir at room temperature for 24h.

[0118] It was then subjected to vacuum drying at 60 °C for 5 hours.

[0119] The following blends were prepared: Blend 1-1: 30 wt% of choline oleate (COLE) prepared in 70 wt% of glycerol monooleate; Blend 1-2: 30 wt% of choline isostearate (CISO) prepared in 70 wt% of pentaerythritol monooleate; Blend 1-3: 3 wt% choline oleate (COLE) prepared in 97 wt% of pentaerythritol tetraoleate; Blend 1-4: 30 wt% choline oleate (COLE) prepared in 70 wt% of glycerol monoisostearate; Blend 1-5: 30 wt% choline myristate (CMYR) prepared in 70 wt% of pentaerythritol monooleate; Blend 1-6: 30 wt% choline myristate (CMYR) prepared in 70 wt% of glycerol monoisostearate. 2.2 In two stepsa) Preparation of choline carboxylates

[0120] The choline carboxylates were prepared in acetone (20 mL) using an equimolar quantity (0.071 mol) of fatty acid and choline hydroxide, as described in Mu et al., ACS Appl. Mater. Interfaces 2016, 8, 7, 4977-4984.

[0121] The fatty acid was first dissolved in acetone.

[0122] The choline hydroxide aqueous solution was added dropwise to the fatty acid with cooling at around 5°C.

[0123] The mixture was magnetically stirred at room temperature for 48 h.

[0124] Water and acetone were then removed under reduced pressure at 50 °C using a rotary evaporator.

[0125] Finally, the product was dried in a vacuum oven at 70 °C for 48 h.

[0126] The following choline carboxylates were prepared: choline oleate (COLE); choline isostearate (CISO); choline myristate (CMYR); choline caprate / caprylate (CCAP). b) Mixing of choline carboxylate with a polyol fatty acid ester

[0127] Following blends were prepared by mixing a choline carboxylate prepared in Example 1-2.2a) with a polyol fatty acid ester: Blend 2-1: 30 wt% of choline oleate (COLE) + 70 wt% of glycerol monooleate; Blend 2-2: 30 wt% of choline isostearate (CISO) + 70 wt% of pentaerythritol monooleate; Blend 2-3: 3 wt% of choline oleate (COLE) + 97 wt% of pentaerythritol tetraoleate; 3. Characteristics of blends

[0128] The characteristics of blends according to the invention respectively prepared in one and two steps were compared.3.1 Structure analysis

[0129] The structure of blends prepared in Example 1.2.1 in one step (Blend 1-1 and Blend 1-2), were analysed by Fourier-transform infrared spectroscopy (FTIR) and compared to blends prepared in Example 1.2.2 in two steps (Blend 2-1 and Blend 2-2), consisting of the same polyol fatty acid ester and choline carboxylate.

[0130] On Figures 1 and 2, for comparable blends (Blends 1-1 and 2-1, and blends 1-2 and 2-2), prepared respectively in one and two steps, same peaks corresponding to the choline carboxylate and to the polyol fatty acid ester, can be observed.

[0131] It can be concluded that the structure of a choline carboxylate in a polyol fatty acid ester is the same whether the choline carboxylate is produced directly in the polyol fatty acid ester or is mixed with the polyol fatty acid ester in a subsequent step.3.2 Titration

[0132] Blends 1-1, 1-2, 2-1 and 2-2 were titrated with hydrochloric acid, to quantify the amount of choline carboxylate in each blend.

[0133] Results are gathered in Table 1 below. Table 1: Amount of choline in blendsAmount of choline (g / g)COLE of Ex1-2.2a)0.2287Blend 1-130 wt% COLE prepared in 70 wt% glycerol monooleate0.0709Blend 2-130 wt% COLE + 70 wt% glycerol monooleate0.0705CISO of Ex1-2.2a)0.2202Blend 1-230 wt% CISO prepared in 70 wt% pentaerythritol monooleate0.0729Blend 2-230 wt% CISO + 70 wt% pentaerythritol monooleate0.0668

[0134] It can be observed that the amounts of choline in comparable blends (Blends 1-1 with 2-1, and blends 1-2 with 2-2) are similar whether the choline carboxylate is produced directly in the polyol fatty acid ester or is mixed with the polyol fatty acid ester in a subsequent step.3.3 Resistivity reduction ability

[0135] The resistivity ability of blends was evaluated according to the standard ASTM D1169.

[0136] Results are gathered in Table 2. Table 2: Resistivity of blends according to the inventionResistivity (10 10< Ωcm)Pentaerythritol tetraoleate12.00Blend 1-33 wt% COLE prepared in 97 wt% of pentaerythritol tetraoleate0.48Blend 2-33 wt% COLE + 97 wt% of pentaerythritol tetraoleate0.36

[0137] Whether the choline carboxylate is produced directly in the polyol fatty acid ester or is mixed with the polyol fatty acid ester in a subsequent step, all blends according to the invention enable a similar reduction of the resistivity.Example 2: Solubility of choline carboxylates in polyol fatty acid esters 1. Solubility according to the hydroxyl value

[0138] To evaluate the solubility and stability of choline carboxylate in polyol fatty acid ester, 1 wt% of a choline carboxylate was added to 99 wt% of one or more polyol fatty acid ester(s). The resulting mixture was: mixed at room temperature (25°C); heated at 80°C for 15 min; stirred for 30min at room temperature; centrifuged for 45min, 15000 rpm, 40°C.

[0139] The mixtures were then observed: if the mixture was transparent and homogeneous, then the choline carboxylate is soluble in the polyol fatty acid ester(s); if the mixture was cloudy and / or with sedimentation at the bottom, then the choline carboxylate is not soluble in the polyol fatty acid ester(s). Results are gathered in Table 3. Table 3: Solubility of 1 wt% of COLE in different polyol fatty acid estersPolyol fatty acid esterHV (mgKOH / g)1 wt% COLE1 wt% CCAPtrimethylolpropane oleate / C36 dimerate17.5solublesolubletrimethylolpropane triisostearate15.2solublenot solubletrimethylolpropane trioleate / trimethylolpropane oleate / C36 dimerate (w / w=40 / 60)13.6solublenot solubletrimethylolpropane trioleate / pentaerythritol tetraoleate (w / w=70 / 30)12.4not solublenot soluble1 wt% of choline oleate is soluble in polyol fatty acid ester(s) as long as the hydroxyl value of the latter is of at least 13.6 mgKOH / g. 1 wt% of choline caprate / caprylate is soluble in polyol fatty acid ester(s) as long as the hydroxyl value of the latter is of at least 17.5 mgKOH / g. 2. Maximum solubility

[0140] Different esterification reactions were conducted between oleic acid and trimethylolpropane by varying the reaction time to obtained different mixtures of trimethylolpropane mono-, di-, and / or tri-oleate with different hydroxyl values. The excess of oleic acid was removed by distillation.

[0141] Choline carboxylate was added to the different trimethylolpropane oleates obtained under mixing, until the mixture became cloudy and / or a sedimentation appeared (2 phases). Table 4: Solubility of COLE in trimethylolpropane trioleateHV (mgKOH / g)Maximum solubility of COLE7.90< 1 wt%14.003 wt%27.4120 wt%

[0142] It can be observed than the higher the hydroxyl value, the higher the solubility of choline oleate.Example 3: Solubility of blends according to the invention in base oils 1. Chemicals

[0143] Base oils: Group IV base oil: mixture of Poly Alpha Olefine 10 (SpectraSyn 10) and Poly Alpha Olefine 40 (SpectraSyn 40) from ExxonMobil with a kinematic viscosity at 40°C of 100 mm 2< / s measured according to standard ASTM D 445; Group III base oil: PX 38 from PT Pertamina Lubricants, kinematic viscosity at 40°C of 32.90 mm 2< / s measured according to standard ASTM D 445; 2. Preparation of compositions according to the invention

[0144] Each composition according to the invention was prepared by adding 10 wt% of a blend according to the invention into 90 wt% of a base oil at room temperature.

[0145] Upon mixing (at 1000 rpm), the compositions were heated at 80°C for 15 minutes, then for an additional 1 hour at 25°C.

[0146] The compositions were then centrifuged (at 15000 rpm) for 45mins at 40°C.

[0147] To compare the solubility of the blends according to the invention with the solubility of choline carboxylate solely, 3 wt% of each choline carboxylate us previously was also mixed with 97 wt% of the different base oils according to the method described above.

[0148] The solubility was evaluated based on visual inspection: if the composition was cloudy and / or presented sedimentation, then the choline carboxylate or the blend is not considered as soluble in the corresponding base oil.

[0149] Results are gathered in Table 5. Table 5: Solubility of choline carboxylates and blends according to the invention in base oilsCholine carboxylateBlend (choline carboxylate / polyol fatty acid ester, w / w=30 / 70)Base oilSolubilityCOLEGroup IVnot solubleCOLE and pentaerythritol monooleateGroup IVsolubleCOLE and glycerol monoisostearateGroup IVsolubleCOLEGroup IIInot solubleCOLE and pentaerythritol monooleateGroup IIIsolubleCOLE and glycerol monoisostearateGroup IIIsolubleCISOGroup IVnot solubleCISO and pentaerythritol monooleateGroup IVsolubleCISO and glycerol monoisostearateGroup IVsolubleCISOGroup IIInot solubleCISO and pentaerythritol monooleateGroup IIIsolubleCISO and glycerol monoisostearateGroup IIIsolubleCMYRGroup IVnot solubleCMYR and pentaerythritol monooleateGroup IVsolubleCMYRGroup IIInot solubleCMYR and pentaerythritol monooleateGroup IIIsoluble

[0150] The compositions according to the invention disclosed in Table 5 are all monophasic.

[0151] While it is not possible to solubilize 3 wt% of choline carboxylate in Group III and Group IV base oils, it is possible in presence of a polyol fatty acid ester. More particularly, it was possible to solubilize 3 wt% of choline oleate, choline isostearate, and choline myristate in 90 wt% of poly alpha olefines and Group III base oils in the presence of 7wt% of pentaerythritol monooleate or glycerol monoisostearate.Example 4: Solubility of choline carboxylates in base oils in presence of polyol fatty acid ester(s) 1. Chemicals

[0152] Base oils: Group IV base oil: mixture of Poly Alpha Olefine 10 (SpectraSyn 10) and Poly Alpha Olefine 40 (SpectraSyn 40) from ExxonMobil with a kinematic viscosity at 40°C of 100 mm 2< / s measured according to standard ASTM D 445; Group III base oil: PX 38 from PT Pertamina Lubricants, kinematic viscosity at 40°C of 32.90 mm 2< / s measured according to standard ASTM D 445; 2. Solubility according to the hydroxyl value

[0153] To evaluate the solubility and stability of choline carboxylate in a mixture of base oil and polyol fatty acid ester(s), 1 wt% of a choline carboxylate was added to 99 wt% of the said mixture. The resulting mixture was: mixed at room temperature (25°C); heated at 80°C for 15 min; stirred for 30min at room temperature; centrifuged for 45min, 15000 rpm, 40°C.

[0154] The mixtures were then observed: if the mixture was transparent and homogeneous, then the choline carboxylate is soluble; if the mixture was cloudy and / or with sedimentation at the bottom, then the choline carboxylate is not soluble.

[0155] Chemicals, quantities and results are gathered in Table 6. Table 6: Solubility of choline carboxylates and blends according to the invention in base oilsBase oilPolyol fatty acid esterHV of the mixture polyol fatty acid esters and base oils (mgKOH / g)1 wt% COLE1 wt% CISO95.78 wt% of Group IV4.22 wt% of pentaerythritol monooleate7.66solublesoluble97.19 wt% of Group IV2.81 wt% of glycerol monoisostearate4.09solublesoluble95.78 wt% of Group III4.22 wt% of pentaerythritol monooleate6.78solublesoluble98.56 wt% of Group III1.44 wt% of glycerol monoisostearate4.58solublesoluble1 wt% of choline oleate or choline isostearate is soluble in 99 wt % of a Group III or Group IV base oils, and glycerol monoisostearate or pentaerythritol monooleate, as long as the hydroxyl vale of the mixture is of at least 4.58 mgKOH / g.

Claims

1. Composition comprising: - at least 0.1 wt% of a choline carboxylate; - at least 1 wt% of one polyol fatty acid ester or a mixture of polyol fatty acid esters; - at least 50 wt % of one or more base oil(s); weight percentages being based on the weight of the composition; wherein the one or more base oil(s) is / are not a polyol fatty acid ester.

2. Process for preparing a composition according to claim 1, by mixing a choline carboxylate, a polyol fatty acid ester or a mixture of polyol fatty acid esters, and base oil(s).

3. Process according to claim 2, wherein the choline carboxylate and the polyol fatty acid ester or the mixture of polyol fatty acid esters are first blended together to form a blend.

4. Blend comprising or consisting of: - 1-50 wt% of a choline carboxylate; - 50-99 wt% of one polyol fatty acid ester or a mixture of polyol fatty acid esters, weight percentages being based on the weight of the blend.

5. Process for preparing a blend according to claim 4, by reacting an equimolar quantity of choline hydroxide or choline chloride, with one or more monocarboxylic acid(s) in the presence of one polyol fatty acid ester or a mixture of polyol fatty acid esters.

6. Process according to claim 5, comprising the following steps of: i) mixing the one or more monocarboxylic acid(s) with the one or more polyol fatty acid ester(s); ii) adding the choline hydroxide or choline chloride into the mixture obtained in step i).

7. Process according to claim 5 or 6, wherein the water formed during the reaction is removed.

8. Use of the blend according to the claim 4, as a conductive additive in a lubricant.

9. Lubricant comprising the composition according to the claim 1.

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