Lubricating oil composition and the use of an additive.

Description

11 Lubricating oil composition and use of an additive. Field of the invention.

[001] This invention relates to an industrial lubricating oil composition and to improved air release in industrial lubricating oil compositions. Background of the invention

[002] Lubricating oil compositions are used to protect and lubricate surfaces in contact and can also be used to transmit energy. Lubricating oil compositions are required in all industrial equipment with moving parts. Industrial lubricating oil compositions therefore include hydraulic oils, gear oils, compressor oils, circulating oils, and turbine oils, etc. Such industrial lubricating oil compositions generally comprise one or more base oils and one or more additives. Typically, the additive treatment rate for industrial lubricating oil compositions is considerably lower than for motor oil compositions, with additive treatment rates of less than 10% by weight being routine, and additive treatment rates of less than 5% by weight being normally preferred.

[003] Air entrainment is known to reduce the effectiveness of lubricating oil compositions, particularly those used as industrial lubricating oil compositions. Air entrainment is a phenomenon in which air bubbles (typically less than 1 mm in diameter) are dispersed throughout the lubricating oil. Entrained air can be distinguished from free air (an air pocket trapped in part of the system), dissolved air (lubricating oils can contain between 6 and 12 percent dissolved air by volume), and foam (air bubbles typically larger than 1 mm in diameter that gather on the surface of the oil). Air entrainment can have a number of negative consequences, including loss of Petition 870250089881, dated 02 / 10 / 2025, page 12 / 26 / 11 lubricity, possible oxidation of the lubricant oil composition, noisy operation, lower efficiency and higher oil temperatures.

[004] Of particular relevance are the compositions of industrial lubricating oil used in hydraulic systems. Current trends in hydraulic system design are towards smaller reservoirs, low oil residence times, and high power output. These changes are leading to increased air entrainment problems.

[005] The air entrainment properties of a lubricating oil are typically measured using the ASTM D3427 air release test. This test measures the time required for entrained air in the oil to reduce in volume to 0.2% under the specified test conditions and temperature.

[006] Document WO2017089354 describes a method comprising mixing an alkyl acrylate additive into a lubricating oil using a high shear mixer to improve air release. Document WO2017089357 teaches an improvement in the air release properties of a lubricating oil suitable for use as a hydraulic fluid, wherein at least 70% by mass of the base oil is GTL.

[007] Citric acid is known to be a demulsifier / demetallizing agent for crude oil, see, for example, documents US4439345 and EP0612548.

[008] The present inventors sought to improve the air entrainment properties of lubricating oil compositions, particularly those used in hydraulic systems. Summary of the invention

[009] The present invention provides a lubricating oil composition comprising at least 80%, by weight, based on the total weight of the lubricating oil composition, of base oil, wherein the base oil is selected from base oils derived from Group II, Group III and Fischer Petition 870250089881, dated 02 / 10 / 2025, page 13 / 26 / 11 Tropsch and mixtures thereof, one or more additives, except citric acid, selected from the group consisting of anti-wear additives, rust and corrosion inhibitors, dispersants, extreme pressure additives, friction modifiers, viscosity index improvers, pour point depressants, antioxidants and one or more of citric acid and a derivative thereof.

[0010] The present invention also provides the use of an additive selected from one or more citric acids and their derivatives in a lubricating oil composition comprising at least 80%, by weight, based on the total weight of the lubricating oil composition of base oil, wherein the base oil is selected from base oils derived from Group II, Group III and Fischer-Tropsch and mixtures thereof and one or more additives, except citric acid, selected from the group consisting of anti-wear additives, rust and corrosion inhibitors, dispersants, extreme pressure additives, friction modifiers, viscosity index improvers, pour point depressants, antioxidants, in order to improve the air release properties of said lubricating oil composition, as measured by ASTM D3427. Detailed description of the invention

[0011] One or more specific embodiments of the present disclosure will be described below. These described embodiments are examples of the composition and methods currently disclosed. Additionally, in an effort to provide a concise description of these embodiments, not all features of an actual implementation can be described in the descriptive report.

[0012] In introducing elements of various modalities of the present disclosure, the articles “a”, “an”, “the” and “the” are intended to mean that there is one or more of the elements. The terms “comprising”, “including” and “having” are intended to be inclusive and mean that there may be Petition 870250089881, dated 02 / 10 / 2025, p. 14 / 26 / 11 additional elements different from the elements mentioned. Additionally, it should be understood that references to “a modality” or “a modality” of this disclosure are not intended to be interpreted as excluding the existence of additional modalities that also incorporate the aforementioned features.

[0013] The present inventors have discovered that the addition of one or more of citric acid and a derivative thereof to a lubricating oil composition comprising at least 80% by weight, based on the total weight of the lubricating oil composition, of base oil, wherein the base oil is selected from base oils derived from Group II, Group III and FischerTropsch and mixtures thereof, and one or more additives selected from the group consisting of anti-wear additives, rust and corrosion inhibitors, dispersants, extreme pressure additives, friction modifiers, viscosity index improvers, pour point depressants, antioxidants, provides an unexpected improvement in relation to the air release properties of said lubricating oil composition.

[0014] The lubricating oil composition is preferably an industrial lubricating oil composition. Industrial lubricating oil compositions include, but are not limited to, those used as hydraulic oils, gear oils, compressor oils, circulating oils, and turbine oils. In a preferred embodiment of the invention, the lubricating oil is formulated for use in a hydraulic fluid. Hydraulic fluids are used in many different types of hydraulic machines and are used not only to lubricate the machines but also to transmit pressure. Air entrainment can be a significant problem in hydraulic systems, causing spongy or erratic operation of the hydraulic system.

[0015] A lubricating oil composition, according to the present invention, comprises at least one base oil and at least one Petition 870250089881, dated 02 / 10 / 2025, page 15 / 26 / 11 additive, as well as citric acid or a derivative thereof.

[0016] Industrial lubricating oil compositions contain lower amounts of additives compared to, for example, motor oils. Therefore, the lubricating oil composition comprises at least 80% by weight of base oil. Preferably, the lubricating oil composition comprises at least 85% by weight, more preferably at least 90% by weight of base oil based on the total weight of the lubricating oil composition. Suitably, the lubricating oil composition comprises no more than 99.5% by weight of base oil based on the total weight of the lubricating oil composition.

[0017] The base oil used in the present invention is preferably from Group II or Group III, including Fischer-Tropsch-derived base oils, according to the API base oil categories. Preferably, the base oil comprises at least one Fischer-Tropsch-derived base oil. Fischer-Tropsch-derived base oils are synthesized by converting, for example, natural gas or biomass into liquid fuel. They have very low sulfur and aromatic content compared to refined mineral oil base oils from crude oil and have a very high paraffin constituent ratio.

[0018] The kinematic viscosity of the Fischer-Tropsch-derived base oil at 100 °C is preferably 2 to 20 mm² / s, more preferably 3 to 15 mm² / s, with the highest preference being 3 to 10 mm² / s. The viscosity is suitably measured using ASTM D445.

[0019] Preferably, the total amount of additives in the lubricating oil composition is less than 20% by weight, more preferably less than 10% by weight, and even more preferably less than 5% by weight, based on the total weight of the lubricating oil composition. Suitablely, the total amount of additives in the lubricating oil composition is at least 0.5% by weight, based on the total weight of the oil composition. Petition 870250089881, dated 02 / 10 / 2025, page 16 / 26 / 11 lubricant. Additives may be incorporated into the composition of lubricating oil individually or as part of one or more additive packages. If added individually or in additive packages, a diluent oil may be included with the additive and form part of the finished lubricating oil composition.

[0020] The lubricating oil composition comprises one or more additives, in addition to citric acid, selected from the group consisting of anti-wear additives, rust and corrosion inhibitors, dispersants, extreme pressure additives, friction modifiers, viscosity index improvers, pour point depressants, and antioxidants. Such additives are known in many types of lubricating compositions. The typical total amounts of these one or more additives are in the range of 0.001% by weight to 10.0% by weight, based on the total weight of the lubricating oil composition.

[0021] Suitable anti-wear additives may be selected from zinc salts, such as zinc dialkyl or diaryl dithiophosphates, borates, substituted thiadiazoles, nitrogen / phosphorus polymeric compounds made, for example, by the reaction of a dialkylamine with a substituted organic phosphate, amine phosphates, sulfur oils of natural or synthetic origin, sulfurized lard, sulfur esters, sulfur fatty acid esters and similar sulfur materials, organophosphates and triphenyl phosphorothionate.

[0022] Rust and corrosion inhibitors include zinc dithiophosphate, metallic phenolates, calcium or magnesium sulfonates, and amines.

[0023] Dispersing additives may be reaction products of polyisobutenyl succinic anhydride and an amine or ester.

[0024] Extreme pressure additives are typically selected from sulfur-based derivatives, for example, DMTD, sulfurized olefins, sulfurized fats and oils or dithiocarbamates, and molybdenum-based additives, for example, dithiocarbamates or dithiophosphates.

[0025] Friction modifiers are typically selected from Petition 870250089881, dated 02 / 10 / 2025, page 17 / 26 / 11 organomolybdenum compounds, for example, molybdenum diothiocarbamates and molybdenum dithiophosphates, or are selected from ashless esters or amides, such as oleyl amide or glycerol monooleate.

[0026] Viscosity index improvers include, but are not limited to, olefin polymers such as polyisobutylenes, methacrylates, dienes and alkylated styrenes.

[0027] Pour point depressants include alkylated naphthenic products, polymethacrylates, and phenolic polymers.

[0028] The antioxidant may be a so-called phenolic or hindered amine antioxidant, for example, naphthols, sterically hindered monohydric, dihydric and trihydric phenols, hindered dinuclear, trinuclear and polynuclear phenols, alkylated or styrenated diphenylamines or hindered ionol-derived phenols.

[0029] Preferably, the lubricating oil composition does not contain any additives classified as demulsifiers or foam inhibitors, other than citric acid. More preferably, the lubricating oil composition does not contain demulsifiers selected from the list consisting of polyalkylene derivatives of alkyl phenols, fatty alcohols, fatty acids, fatty amines, fatty amides and / or polyols (including cross-linked polyols). Even more preferably, the lubricating oil composition does not contain foam inhibitors selected from the list consisting of polydimethylsiloxane, organo-modified siloxanes, polyacrylates and / or nonionic / anionic surfactants.

[0030] The composition of lubricating oil comprises one or more citric acids and derivatives thereof. Citric acid has the chemical formula HOC(CO2H)(CHiCOiH)2 and may also be known by the IUPAC name 2-hydroxypropane-1,2,3-tricarboxylic acid. Citric acid derivatives are preferably citrates, including salts and esters of citric acid. Such salts and esters may include mono-, di- and triesters and / or salts of tricarboxylic acid. Petition 870250089881, dated 02 / 10 / 2025, p. 18 / 26 / 11 and mixtures thereof. A mixture of citric acid and its derivatives may be present in the composition of finished lubricating oil. However, a preferred additive is citric acid. This is typically available in solid form, but may be more appropriately used in a diluted form in a non-aqueous carrier fluid. Typically, such a diluted form contains in the range of 40 to 60%, by weight, of citric acid.

[0031] Preferably, citric acid and / or its derivatives are present or added to the lubricating oil composition in an amount in the range of 0.005% by weight to 0.1% by weight, preferably in the range of 0.02% by weight to 0.08% by weight, relative to the total weight of the lubricating oil composition.

[0032] The kinematic viscosity at 40 °C (KV40) of the lubricating oil composition is preferably in the range of 20 to 75 mm2 / s, more preferably in the range of 30 to 75 mm2 / s, more preferably in the range of 40 to 75 mm2 / s.

[0033] The present invention also provides the use of an additive selected from one or more citric acids and their derivatives in a lubricating oil composition comprising at least 80% by weight, based on the total weight of the lubricating oil composition, of base oil, wherein the base oil is selected from base oils derived from Group II, Group III and Fischer-Tropsch and mixtures thereof, and one or more additives, except citric acid, selected from the group consisting of anti-wear additives, rust and corrosion inhibitors, dispersants, extreme pressure additives, friction modifiers, viscosity index improvers, pour point depressants, antioxidants, in order to improve the air release properties of said lubricating oil composition, as measured by ASTM D3427.

[0034] ASTM D3247 is a standard test method for air release properties of hydrocarbon-based oils. It measures the time Petition 870250089881, dated 02 / 10 / 2025, page 19 / 26 / 11 necessary for the air trapped in the oil to be released and the oil density to return to 99.8% of the initial density.

[0035] The air release properties are improved compared to the air release properties achieved using a lubricating oil composition that does not contain one or more citric acids and their derivatives. Preferably, the air release properties are improved without worsening the foaming performance, as measured by ASTM D892. Preferably also, the air release properties are improved and there is no worsening of the demulsification performance as measured by ASTM D1401. More preferably, the air release properties are improved without worsening the foaming performance, as measured by ASTM 892, and without worsening the demulsification performance, as measured by ASTM D1401.

[0036] The invention will now be further illustrated with reference to the following non-limiting examples. Examples

[0037] Various hydraulic oil compositions, as shown in Table 1, were mixed according to standard procedures.

[0038] The base oil used was a Group III base oil derived from Fischer-Tropsch. The additive package was a standard hydraulic oil additive package comprising detergent, anti-wear, antioxidant, corrosion inhibitors and no demulsifier or citric acid. The acrylic copolymer additive was supplied at a concentration of 1 to 2% active content. The citric acid additive was supplied at a concentration of 40 to 60% active content in liquid form. Table 1 Component (% by weight) Ex. 1* Ex. 2* Ex. 3* Ex. 4 Ex. 5 Ex. 6 Additive package 1.00 1.00 1.00 1.00 1.00 1.00 VM Methacrylate 8.50 8.50 8.50 8.50 8.50 8.50 Base oil 90.50 90.47 87.50 90.50 90.49 90.40 Petition 870250089881, dated 02 / 10 / 2025, page 20 / 26 / 11 Acrylic copolymer additive 0 0.03 3.00 0 0 0 Citric acid additive 0 0 0 0.003 0.010 0.100 Comparative examples

[0039] The examples were all tested for demulsification and air release properties, as shown in Table 2. bee 2 Test Ex. 1* Ex. 2* Ex. 3* Ex. 4 Ex. 5 Ex. 6 ASTM D892 Seq II, Trend 0 min, ml 40 40 50 30 50 40 Seq II, Stability 10 min, ml 0 0 0 0 0 0 Seq III, Trend 0 min, ml 310 300 330 280 280 210 Seq III, Stability 10 min, ml 0 0 0 0 0 0 ASTM D3427 Air release at 50 °C, min 2.1 1.9 10.1 1.7 1.4 0.7 ASTM D1401 at 54 °C Time to <3 ml of emulsion, min 25 20 10 25 25 20 Time to >37 ml of water, min 25 20 10 25 25 20 Complete separation, min 25 >30 >30 >30 >30 >30 Appearance after mixing Bright and clear yellow, very light Bright and clear yellow, very light Opaque / cloudy yellow Bright and clear yellow, very light Bright and clear yellow, very light Slightly opaque yellow, very light

[0040] As can be seen from the data reported in the table 2. The addition of an additive containing citric acid increases the air release rate of the tested hydraulic oil formulation and does not significantly affect the foaming or demulsification performance of the hydraulic oil. In some examples, the foaming performance is even slightly improved.

[0041] As measured by ASTM D3427 at 50 °C, the time required to release air from the tested hydraulic oils decreases with the Petition 870250089881, dated 02 / 10 / 2025, page 21 / 26 / 11 addition of citric acid additive. The hydraulic oil with 25 ppm and 100 ppm of the additive containing citric acid is able to release air in 1.7 min and 1.4 min, which is faster than comparative example 1 (a hydraulic oil without demulsifier) ​​and comparative example 2 (hydraulic oil with acrylic copolymer). Petition 870250089881, dated 02 / 10 / 2025, pp. 22 / 26

Claims

1 / 3 CLAIMS 1. Lubricating oil composition, characterized in that it comprises at least 80%, by weight, based on the total weight of the lubricating oil composition, of base oil, wherein the base oil is selected from base oils derived from Group II, Group III and FischerTropsch and mixtures thereof, one or more additives, except citric acid, selected from the group consisting of anti-wear additives, rust and corrosion inhibitors, dispersants, extreme pressure additives, friction modifiers, viscosity index improvers, pour point depressants, antioxidants and one or more of citric acid and a derivative thereof.

2. Lubricating oil composition according to claim 1, the lubricating oil composition being characterized by being formulated for use in a hydraulic fluid.

3. Lubricating oil composition according to claim 1 or claim 2, the lubricating oil composition being characterized in that it comprises at least 85% by weight, more preferably at least 90% by weight, and not more than 99.5% by weight, of base oil based on the total weight of the lubricating oil composition.

4. Lubricating oil composition according to any one of claims 1 to 3, characterized in that the base oil comprises at least one Fischer-Tropsch derived base oil.

5. Lubricating oil composition according to any one of claims 1 to 4, characterized in that one or more additives, except citric acid, selected from the group consisting of anti-wear additives, rust and corrosion inhibitors, dispersants, extreme pressure additives, friction modifiers, viscosity index improvers, pour point depressants, antioxidants are present in the lubricating oil composition in an amount in the range of 0.001%, Petition 870250089881, dated 02 / 10 / 2025, page 23 / 26 2 / 3 by weight, to 10.0%, by weight, based on the total weight of the lubricating oil composition.

6. Lubricating oil composition according to any one of claims 1 to 5, characterized in that one or more of the following are present in or added to the lubricating oil composition in an amount ranging from 0.005% by weight to 0.1% by weight relative to the total weight of the lubricating oil.

7. Lubricating oil composition according to any one of claims 1 to 6, said lubricating oil composition being characterized in that it has a kinematic viscosity at 40 °C in the range of 20 to 75 mm² / s, more preferably in the range of 30 to 75 mm² / s, with the highest preference in the range of 40 to 75 mm² / s.

8. Use of an additive selected from one or more citric acids and their derivatives, characterized in that it is intended for a lubricating oil composition comprising at least 80% by weight, based on the total weight of the lubricating oil composition, of base oil, wherein the base oil is selected from base oils derived from Group II, Group III and Fischer-Tropsch and mixtures thereof, and one or more additives, except citric acid, selected from the group consisting of anti-wear additives, rust and corrosion inhibitors, dispersants, extreme pressure additives, friction modifiers, viscosity index improvers, pour point depressants, antioxidants, in order to improve the air release properties of said lubricating oil composition, as measured by ASTM D3427.

9. Use according to claim 8, characterized in that the air release properties are improved without worsening the foaming performance, as measured by ASTM D892.

10. Use according to claim 8 or claim 9, characterized in that the air release properties are improved without worsening the demulsification performance, as measured by ASTM D1401.