Grease composition

Abstract

The present invention provides a lubricating grease composition for use in bearings, the lubricating grease composition comprising: 1 X-(R 2 )-NH3+n( - OOCR 3 ) wherein R 1 is C 12 ~C 20 and X is selected from saturated or unsaturated branched or linear hydrocarbyl groups, + NH2 and N-(R 4 )-NH3+, and R 2 and R 4 are independently selected from C2 to C8 saturated or unsaturated branched or linear hydrocarbyl groups and may be the same or different; R 3 is C 12 ~C 26 wherein n is 1 or 2; and (ii) a mineral base oil having a saturated or unsaturated, branched or linear hydrocarbyl group selected from:

Description

[Technical Field]

[0001] The present invention relates to a lubricating grease composition that increases bearing life. [Background technology]

[0002] Bearings are used in almost every industry to support rotating shafts such as wheels, gears, turbines, rotors, etc. To keep bearings running smoothly, they must be properly lubricated to reduce friction, minimize wear and tear on moving parts, and help maintain cooler operating temperatures. Providing the correct lubricant composition for bearings helps keep machines in optimum operating condition and extend their useful life.

[0003] Bearing lubrication creates a barrier between the softer material of the bearing and the rest of the machine. This keeps the bearing running smoothly and prevents wear and tear. However, over time, bearings inevitably wear out and require replacement. This necessitates that the machine be taken out of service while maintenance is performed. It is important to extend the length of time a bearing can be used without requiring replacement or major maintenance.

[0004] Due to their simplicity of design, reduced sealing requirements, and reduced maintenance needs, greases are almost universally given the first consideration for lubricating ball and roller bearings. Lubricating grease compositions primarily comprise a base oil and a thickener, with suitable additives depending on the application and conditions of use.

[0005] Many greases are thickened with soaps, which generally fall into two categories. So-called "simple" soaps are formed by the reaction of a metal hydroxide (often lithium hydroxide) with a single fatty acid. To make a complex-thickened grease, the fatty acid is combined with a short-chain complexing acid. The acid mixture is then combined with a metal hydroxide to form the complex thickener. Like simple soaps, "complex" soaps generally require a single metal hydroxide, such as lithium hydroxide.

[0006] Lithium complex greases, such as those disclosed in WO 2020139333 and U.S. 2010 / 298187, are known to have excellent performance and provide excellent service life when used to lubricate bearings. It has also been reported that the use of certain synthetic base oils and base oil blends can result in greases that support extended bearing life. Summary of the Invention

[0007] Extending the life of bearings lubricated with simple lithium soap-based greases without the use of synthetic base oils remains a challenge. The present invention provides a lubricating grease composition for use in bearings, the lubricating grease composition comprising: (i) a mineral base oil containing one or more ammonium salts of an aliphatic carboxylic acid of formula (I), R 1 X-(R 2 )-NH3 + n( - OOCR 3 ) (I) In the formula, R 1 is C 12 ~C 20 and X is selected from saturated or unsaturated branched or linear hydrocarbyl groups, + NH2 and N-(R 4 )-NH3 + Selected from R 2 and R 4 are independently selected from C2 to C8 saturated or unsaturated branched or linear hydrocarbyl groups and may be the same or different; R 3 is C 12 ~C 26 wherein n is 1 or 2; and (ii) a simple lithium soap thickener; The lubricating grease compositions are prepared by a process comprising combining a mineral base oil with one or more ammonium salts of an aliphatic carboxylic acid of formula (I) and then thickening the base oil-ammonium salt of an aliphatic carboxylic acid mixture with a simple lithium soap thickener.

[0008] The present invention further provides a process for producing a lubricating grease composition, the process comprising: (i) combining a mineral base oil with one or more ammonium salts of an aliphatic carboxylic acid of formula (I); R 1 X-(R 2 )-NH3 + n( - OOCR 3 ) (I) In the formula, R 1 is C 12 ~C 20 and X is selected from saturated or unsaturated branched or linear hydrocarbyl groups, + NH2 and N-(R 4 )-NH3 + Selected from R 2 and R 4 are independently selected from C2 to C8 saturated or unsaturated branched or linear hydrocarbyl groups and may be the same or different; R 3 is C 12 ~C 26 wherein n is 1 or 2, forming a base oil / ammonium salt of an aliphatic carboxylic acid mixture; (ii) thickening the base oil / ammonium salt of an aliphatic carboxylic acid mixture with a simple lithium soap.

[0009] The present invention further provides the use of the grease composition of the present invention to extend bearing life. DETAILED DESCRIPTION OF THE INVENTION

[0010] The present inventors have developed a grease composition that has been demonstrated to provide a significant improvement in bearing life according to the FE09 bearing life test (DIN 51821). The grease of the present invention is produced by adding an ammonium carboxylate salt to a mineral base oil during the grease manufacturing process. The base oil is then thickened with a simple lithium soap. Advantageously, the lubricating grease composition of the present invention requires only a simple mineral base oil and a simple lithium soap.

[0011] As used herein, base oil refers to a mineral base oil. Mineral base oils include paraffinic, naphthenic, or mixed paraffinic / naphthenic liquid petroleum oils and solvent- or acid-treated mineral lubricating oils that can be further refined by hydrofinishing processes and / or dewaxing. Mineral base oils are Group I, Group II, and / or Group III base oils according to the American Petroleum Institute (API) Category I, II, and III definitions. These API categories are defined in API Publication 1509, 15th Edition, Appendix E, April 2002.

[0012] Suitable base oils have a kinematic viscosity at 40°C in the range of 50 to 250 cSt, preferably in the range of 70 to 220 cSt, and even more preferably in the range of 80 to 120 cSt. Typically, the amount of base oil in the grease composition of the present invention (not including the amount of ammonium salt of an aliphatic carboxylic acid) is at least 70 wt.%, preferably at least 75 wt.%, based on the total weight of the grease composition. Typically, the amount of base oil in the grease composition (not including the amount of ammonium salt of an aliphatic carboxylic acid) is at most 90 wt.%, preferably at most 85 wt.%, based on the total weight of the grease composition.

[0013] In the grease composition of the present invention, one or more ammonium salts of aliphatic carboxylic acids of formula (I), R 1 X-(R 2 )-NH3 + n(- OOCR 3 ) (I) is mixed with the base oil.

[0014] R 1 is C 12 ~C 20 The saturated or unsaturated, branched or straight chain hydrocarbyl groups are selected from the group consisting of: X is NH, + NH2 and N-(R 4 )-NH3 + Selected from R 2 and R 4 are each independently selected from C2 to C8 saturated or unsaturated branched or straight chain hydrocarbyl groups. 2 and R 4 is (CH2) m and m is independently selected from 2, 3, or 4. Most preferably, R 2 and R 4 is (CH2)3.

[0015] R 3 is C 12 ~C 26 Preferably, R 3 is C 16 ~C 24 , and even more preferably C 18 ~C 24 The saturated or unsaturated, branched or straight chain hydrocarbyl groups are selected from the group consisting of:

[0016] In the grease composition during use, the fatty acid carboxylic acid ammonium salt may be present as the parent salt or as the corresponding amide (e.g., the amide of general formula (II)).

[0017] R 1 X-(R 2 )-NC(=O)R 3 (II) That is, due to the conditions under which the grease is prepared or used, the parent amine R 1 X-(R 2 )-NH2 and parent acid R3 A reaction has occurred between the ammonium salt of a fatty acid carboxylic acid and the COOH. In some embodiments, further intermolecular and intramolecular reactions may also occur. In reality, a mixture of the ammonium salt of a fatty acid carboxylic acid, the amide, and any other reaction products is likely to be present in the lubricating grease composition.

[0018] In the process of the present invention, the base oil is mixed with the ammonium salt of a fatty acid carboxylate. Typically, this can be done by melting the ammonium salt of a fatty acid carboxylate (if solid) and mixing it with the base oil. This must be done before the base oil is thickened with the simple lithium soap.

[0019] The simple lithium soap thickener is produced by the reaction of lithium hydroxide with a fatty acid component. Examples of suitable fatty acid components for preparing the simple lithium soap thickener in the grease composition include hydrogenated castor oil (HCO), hydrogenated castor oil fatty acid (HCOFA), and combinations thereof, preferably hydrogenated castor oil fatty acid (HCOFA). Hydrogenated castor oil (HCO) is a triglyceride of 12-hydroxystearic acid. 12-hydroxystearic acid is the preferred fatty acid for use herein.

[0020] Hydrogenated castor oil fatty acids (referred to herein as HCOFA) generally contain at least 85% by weight of 12-hydroxystearic acid, based on the total weight of the HCOFA. HCOFA may contain small amounts of additional components. Examples of additional components include palmitic acid (C 16 ), stearic acid (C 18 ), arachidic acid (C 20 As used herein, the term "hydrogenated castor oil fatty acid" ("HCOFA") refers to a composition comprising an amount of 12-hydroxystearic acid, generally an amount comprising at least 85% by weight of 12-hydroxystearic acid based on the total weight of the HCOFA, and preferably an amount comprising in the range of 85-87% by weight of 12-hydroxystearic acid based on the total weight of the HCOFA.

[0021] The lithium hydroxide used to make the lithium soap is preferably present at a level in the range of 0.5% to 3% by weight, more preferably 1% to 3% by weight, by weight of the metal complex grease composition.

[0022] The total content of the simple lithium soap thickener is preferably in the range of 5 to 15% by weight, more preferably in the range of 8 to 13% by weight, based on the total weight of the grease composition. Greases may be thickened with simple lithium soap thickeners using any suitable method. A typical process for the production of lithium soap thickened greases is described herein for purposes of illustration and is not intended to be limiting.

[0023] The slurry is prepared in a dedicated slurry tank. This is accomplished by adding solids (e.g., lithium hydroxide) and liquids (water, base oil, additives, etc.) together to form a dispersion or "suspension" before transferring to the autoclave. The slurry is mixed in a high shear mixer.

[0024] In the present invention, the base oil in the slurry already contains an ammonium salt of an aliphatic carboxylic acid. After thorough mixing, the slurry is contacted with a fatty acid component to carry out the saponification reaction, which is carried out at a temperature of at least 80°C, preferably at least 100°C.

[0025] Next, at least a portion, preferably all, of the water is removed from the product of the saponification reaction. Preferably, the water is removed by evaporation in a so-called "degassing step." Water removal is preferably carried out by heating the product of the saponification reaction to a temperature of at least 100°C, more preferably at least 130°C, and even more preferably at least 150°C.

[0026] The product is then subjected to a heating step, where it is heated to a temperature of at least 190°C, preferably in the range of 190-230°C, more preferably in the range of 195-225°C, even more preferably in the range of 200-220°C.

[0027] The product of the heating step is then subjected to a cooling step, which is preferably carried out in a grease kettle. Performance additives may be added to the lubricating grease composition. Preferably, such additives are added in the grease kettle.

[0028] The lubricating grease compositions of the present invention may incorporate various conventional grease additives in amounts normally used in this field of application to impart certain desirable properties to the grease, such as oxidation stability, tack, extreme pressure properties and corrosion inhibition.

[0029] Suitable additives include one or more extreme pressure / antiwear agents, for example, zinc salts such as zinc dialkyldithiophosphate or zinc diaryldithiophosphate, borates, substituted thiadiazoles, polymeric nitrogen / phosphorus compounds prepared by reacting, for example, dialkoxyamines with substituted organophosphates, amine phosphates, sulfurized sperm oil of natural or synthetic origin, sulfurized lard, sulfurized esters, sulfurized fatty acid esters, and similar sulfurized materials, for example, organophosphates according to the formula: (OR)3P=O, where R is an alkyl, aryl, or aralkyl group, and triflate. The additives include, for example, one or more overbased metal-containing detergents, such as calcium alkyl salicylate, magnesium alkyl salicylate, or alkylaryl sulfonate; one or more ashless dispersant additives, such as the reaction product of polyisobutenyl succinic anhydride with an amine or ester; one or more antioxidants, such as hindered phenols or amines, such as phenyl alpha naphthylamine; one or more rust inhibitors; one or more friction modifiers; one or more viscosity index improvers; one or more pour point depressants; and one or more tackifiers.Solid materials such as graphite, finely divided molybdenum disulfide, talc, metal powders, calcium carbonate, and various polymers, such as polyethylene wax, can also be added to impart special properties.

[0030] The invention will now be further described by reference to the following non-limiting examples. [Example]

[0031] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to these examples. The raw materials used are as follows. Unless otherwise specified, the amounts shown in the examples and comparative examples are as shown in Table 1 below. Furthermore, the amounts of raw materials disclosed in Table 1 (especially the amounts of lithium hydroxide and fatty acid) are the amounts of reagents. Therefore, the actual amounts of components in the composition are calculated based on the values shown in Table 1 and the purity given below.

[0032] Thickener raw materials Lithium hydroxide: Special grade, purity 56% Hydrogenated castor oil (HCO): Saponification value 180.5 mg / g KOH Base oil A: Paraffinic mineral oil obtained by dewaxing and solvent refining, Group 2 base oil, kinematic viscosity at 100°C 11.74 mm 2 / s, viscosity index 107 Base oil B: Paraffinic mineral oil obtained by dewaxing and solvent refining, Group 2 base oil, kinematic viscosity at 100°C 31.56 mm 2 / s, viscosity index 96 Base oil C: A blend of base oil A and 5% m / m of aliphatic ammonium carboxylate (I) Additive A: Overbased calcium alkylsalicylate. Mineral oil content approximately 30%. Additive B: Alkylmercaptothiadiazole mineral oil content 25.5% Additive C: A sulfurized mixture of highly refined natural triglycerides and natural fatty acid esters Additive D: Bismuth naphthenate, naphthenic acid, mineral oil content 29-31% Additive E: 55% zinc naphthenate in naphthenic base oil, 45% mineral oil content Additive F: Butylated / octylated diphenylamine Example Base oil C, containing 5% aliphatic ammonium carboxylate (I), was added to a grease manufacturing tank. Hydrogenated castor oil was added, and the mixture was heated to 90°C to melt the contents of the vessel. An appropriate amount of lithium hydroxide dispersed in water was then added to the mixture. Ester cleavage of the hydrogenated castor oil occurred during further heating of the mixture, and the grease thickener was continuously formed while the lithium hydroxide and fatty acids underwent a saponification reaction. Water was evaporated by continuing to heat to 220°C with vigorous stirring. After the mixture was cooled to below 100°C, additives A through F were added to the base grease. After the addition of the additives, the grease was cooled to room temperature and sheared in a high-pressure homogenizer, resulting in a homogeneous grease.

[0033] Comparative Example 1 Base oil A was added to a grease manufacturing tank. Following the procedure of the examples, a homogeneous grease was obtained.

[0034] Comparative Example 2 Base oil B was added to a grease manufacturing tank. Following the procedure of the example, a homogeneous grease was obtained.

[0035] Comparative Example 3 Base oil A was added to a grease manufacturing tank. A base grease was manufactured according to the procedure described in the Examples. After saponification and heating to 220°C, the resulting base grease was cooled to below 100°C. Ammonium aliphatic carboxylate (I) was added at a treat rate of 3.89% of the total formulation before the addition of additives A to F. The material was then sheared in a high-pressure homogenizer to obtain a uniform grease.

[0036] [Table 1]

[0037] Additional information and test data for the above examples are provided in Table 1. In all examples, homogeneous greases were obtained, and the basic test data provided shows similar results for most of the properties evaluated. Only the example in which base oil C containing 5% aliphatic ammonium carboxylate (I) was used showed significant improvements in roll stability according to ASTM D1831 and bearing life at 140°C according to DIN 51821. The example shows a 103% increase in bearing life based on F50 values compared to Comparative Example 1.

[0038] However, Comparative Example 3, in which the aliphatic ammonium carboxylate (I) was added late in the process in combination with the other additives A-F, does not show the same benefit. Instead, the application mode described for Comparative Example 3 reduces bearing life by 79%, based on the F50 value of Comparative Example 1, which does not contain the aliphatic ammonium carboxylate (I).

Claims

1. A lubricating grease composition for use in bearings, wherein the lubricating grease composition is (i) A mineral base oil containing one or more aliphatic carboxylate ammonium salts of formula (I), R １ X-(R ２ )-NH ３ ＋ n( － OOCR ３ ) (I) Wherein, R １ is selected from saturated or unsaturated branched or straight-chain hydrocarbyl groups of C １２ to C ２０ ; X is selected from NH, ＋ NH ２ and N-(R ４ )-NH ３ ＋ ; R ２ and R ４ are independently selected from saturated or unsaturated branched or straight-chain hydrocarbyl groups of C ２ to C ８ , and may be the same or different; R ３ is selected from saturated or unsaturated branched or straight-chain hydrocarbyl groups of C １２ to C ２６ ; n is 1 or 2; a mineral base oil, (ii) A simple lithium soap thickener, A lubricating grease composition prepared by a process comprising the steps of: combining a mineral base oil with one or more aliphatic ammonium carboxylate salts of formula (I); and then thickening the base oil aliphatic ammonium carboxylate mixture with a simple lithium soap thickener.

2. R ２ and R ４ is, (CH ２ ) ｍ The lubricating grease composition according to claim 1, wherein m is selected from 2, 3, or 4 independently.

3. R ３ C １６ ~C ２４ The lubricating grease composition according to claim 1 or 2, selected from saturated or unsaturated branched or linear hydrocarbyl groups.

4. The lubricating grease composition according to claim 1 or 2, wherein the simple lithium soap thickener is produced by the reaction of lithium hydroxide with a fatty acid component selected from hydrogenated castor oil (HCO), hydrogenated castor oil fatty acid (HCOFA), and combinations thereof.

5. The lubricating grease composition according to claim 1 or 2, wherein the total content of the simple lithium soap thickener is in the range of 5 to 15% by weight.

6. A process for manufacturing a lubricating grease composition, wherein the process is: (i) A step of combining a mineral base oil with one or more aliphatic carboxylate ammonium salts of formula (I), R １ X-(R ２ )-NH ３ ＋ n( － OOCR ３ ) (I) In the formula, R １ C １２ ~C ２０ Selected from saturated or unsaturated branched or linear hydrocarbyl groups, where X is NH, ＋ NH ２ and N-(R ４ )-NH ３ ＋ Selected from, R ２ and R ４ C ２ ~C ８ R is independently selected from saturated or unsaturated branched or linear hydrocarbyl groups, which may be the same or different. ３ C １２ ~C ２６ Selected from saturated or unsaturated branched or linear hydrocarbyl groups, where n is 1 or 2. (ii) A process comprising the step of thickening the base oil aliphatic carboxylate ammonium salt mixture with a simple lithium soap.

7. The process according to claim 6, wherein the simple lithium soap thickener is produced by the reaction of lithium hydroxide with hydrogenated castor oil (HCO), hydrogenated castor oil fatty acids (HCOFA), and a fatty acid component selected from combinations thereof.

8. R ２ and R ４ is, (CH ２ ) ｍ m is independently selected from 2, 3 or 4, and R ３ However, C １６ ~C ２４ The process according to claim 6 or 7, selected from saturated or unsaturated branched or linear hydrocarbyl groups.

9. Use of the lubricating grease composition according to claim 1 or 2 to increase bearing life.