Grease composition

Abstract

To provide a urea-based grease composition having oxidation stability equivalent to that of a fluorine-based grease, being also excellent in oil separation property, and capable of maintaining the performance of the fluorine-based grease even when blended with the fluorine-based grease.SOLUTION: A urea-based grease composition of the present invention is characterized by containing methylphenyl silicone as a base oil and an aromatic urea compound as a thickener, and the urea-based grease composition can be a grease composition containing a fluorine-based grease composition comprising a straight-chain or side-chain perfluoropolyether as a base oil and polytetrafluoroethylene (PTFE) as a thickener.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a grease composition having suitable oil separation properties and excellent oxidation stability. [Background technology]

[0002] Grease is a semi-solid lubricating oil made by mixing a base oil with thickeners and additives. Among these, fluorine-based grease, which mixes perfluoropolyether as a base oil with polytetrafluoroethylene (PTFE) as a thickener, is known to have excellent lubricity, heat resistance, oxidation stability, etc., and is suitable for use in high-temperature environments, and is used in a variety of products such as automobiles, home appliances, and copiers (see Patent Documents 1 and 2 below, etc.).

[0003] Taking advantage of the suitability of such fluorine-based greases in high-temperature environments, so-called hybrid greases have been developed by mixing them with other greases to improve their properties. For example, a grease composition has been developed in which a fluorine-based grease is mixed with a synthetic hydrocarbon oil as a base oil and a urea-based grease using a urea compound as a thickener (see Patent Document 3 below). Furthermore, a lubricating grease has been developed in which a fluorine-based grease is mixed with an ester oil as a base oil and a urea-based grease using a urea compound as a thickener (see Patent Document 4 below).

[0004] On the other hand, hybrid greases that do not contain fluorine-based greases have also been developed. For example, hybrid greases that combine greases based on synthetic hydrocarbon oil, mineral oil, or polyglycol with silicone greases based on silicone oil have been developed (see Patent Document 5 below). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2022-96698 [Patent Document 2] Patent No. 6122191 [Patent Document 3] Japanese Patent Application Laid-Open No. 2017-211068 [Patent Document 4] Japanese Patent Application Laid-Open No. 2004-26941 [Patent Document 5] Special Publication No. 2021-508750 Summary of the Invention [Problem to be solved by the invention]

[0006] Fluorine-based grease is easy to handle, has high performance, and is used for a variety of purposes, but has the disadvantage of being expensive. In recent years, fluorine compounds have tended to be legally restricted as substances harmful to the human body, as seen in the restrictions on PFAS, a type of organic fluorine compound. Therefore, it is hoped that the use of fluorine-based grease will decrease in the future and will eventually be eliminated altogether.

[0007] As a result of extensive research, the present inventors have developed a grease composition that has oxidation stability equivalent to that of fluorine-based grease, and have found that the above-mentioned problems can be solved.

[0008] Therefore, an object of the present invention is to provide a urea-based grease composition that has oxidation stability equivalent to that of fluorine-based grease, is resistant to oxidative degradation, and has excellent oil separation properties.Furthermore, by mixing this urea-based grease composition with fluorine-based grease to form a hybrid grease, it is possible to reduce the amount of fluorine compound used while maintaining the performance of the fluorine-based grease. [Means for solving the problem]

[0009] A urea-based grease composition according to one embodiment of the present invention is characterized by containing methylphenyl silicone as a base oil and an aromatic urea compound as a thickener.

[0010] In the urea-based grease composition of the above aspect, the methylphenyl silicone is preferably diphenyldimethicone, and the aromatic urea compound is preferably an aromatic diurea compound.

[0011] The urea-based grease of the above embodiment preferably has a worked penetration within the range of 200-350.

[0012] A grease composition according to another embodiment of the present invention can be a grease composition comprising the urea-based grease composition according to the above-described embodiment, and a fluorine-based grease composition comprising a linear or branched chain perfluoropolyether as a base oil and polytetrafluoroethylene (PTFE) as a thickener.

[0013] The grease composition of the other embodiment described above preferably contains a linear perfluoropolyether as the base oil.

[0014] In the grease composition of the other embodiment described above, the blending ratio of the urea-based grease composition in the grease composition is preferably 60% by mass or more and less than 100% by mass. [Effects of the Invention]

[0015] The urea-based grease composition of one embodiment of the present invention has oxidation stability equivalent to that of fluorine-based grease and also has excellent oil separation properties. Furthermore, by mixing this urea-based grease composition with fluorine-based grease to form a hybrid grease, the grease composition of one embodiment of the present invention can maintain the performance of fluorine-based grease while reducing the amount of fluorine compound used. DETAILED DESCRIPTION OF THE INVENTION

[0016] The present invention will be described below based on one embodiment, but the present invention is not limited to this embodiment.

[0017] <Urea-based grease composition> A urea-based grease composition according to one embodiment of the present invention (hereinafter also referred to as the present urea-based grease composition) is characterized by containing methylphenyl silicone as a base oil and an aromatic urea compound as a thickener.

[0018] (base oil) The base oil of the present urea-based grease composition contains the methylphenyl silicone shown in formula (1) below, and the base oil preferably contains 95% by mass or more of methylphenyl silicone, more preferably 98% by mass or more, and particularly preferably 99% by mass or more (including 100% by mass).

[0019] TIFF2025159412000001.tif71170

[0020] In the above formula (1), the values ​​of x and y are not particularly limited, but diphenyl dimethicone where x=2 and y=2 is preferred.

[0021] The methylphenyl silicone is preferably for high temperature use (for example, −30° C. to +250° C.), and the kinematic viscosity at 25° C. is not particularly limited, but is preferably 300 to 500 mm 2 / s range is preferable, and 400 mm 2 The kinematic viscosity can be measured, for example, in accordance with JIS K2283.

[0022] The pour point of the methylphenyl silicone is not particularly limited, but is preferably −30° C. or lower.

[0023] The flash point of the methylphenyl silicone is not particularly limited, but is preferably 300° C. or higher.

[0024] A specific example of the methylphenyl silicone used as the base oil of the present urea-based grease composition is "KF-54" manufactured by Shin-Etsu Chemical Co., Ltd.

[0025] (thickener) The thickener for the present urea-based grease composition may be an aromatic urea compound, and among these, an aromatic diurea compound is preferably used.

[0026] Aromatic diurea compounds are obtained by reacting a diisocyanate component with a monoamine component. Examples of the diisocyanate component include phenylene diisocyanate and diphenylmethane diisocyanate (MDI), and examples of the monoamine component include aromatic monoamines (p-toluidine, etc.). The chemical formula of MDI is shown in formula (2) below, and the chemical formula of p-toluidine is shown in formula (3) below.

[0027] TIFF2025159412000002.tif44170

[0028] TIFF2025159412000003.tif44170

[0029] A specific example of MDI is "Millionate MT" manufactured by Tosoh Corporation, and a specific example of p-toluidine is "p-Toluidine" manufactured by Lanxess AG.

[0030] (Other additives) The urea-based grease composition may further contain other additives within the scope of the present invention, such as extreme pressure agents such as organic zinc compounds and organic molybdenum compounds, antioxidants such as amine-based, phenol-based, and calcium-based compounds, rust inhibitors such as sulfonates and polyhydric alcohol esters, and oiliness agents such as esters and alcohols. When other additives are added, the amount added to the urea-based grease composition is preferably 5% by mass or less, more preferably 2% by mass or less, and particularly preferably 1% by mass or less (including 0% by mass).

[0031] The present urea-based grease composition preferably has a worked penetration within the range of 200 to 350, more preferably within the range of 250 to 300. The worked penetration can be measured, for example, based on JIS K2220.

[0032] The oil separation rate of the present urea-based grease composition at 180°C is preferably within the range of 0.5 to 2.0 mass %, more preferably within the range of 0.6 to 1.5 mass %. The degree of oil separation can be measured, for example, based on JIS K2220.

[0033] The dropping point of the present urea-based grease composition is preferably in the range of 260°C or higher. The dropping point can be measured, for example, based on JIS K2220.

[0034] The urea-based grease composition preferably has an accelerated oxidation stability within the range of 22 to 28 [hr], more preferably within the range of 27 to 28 [hr]. The accelerated oxidation stability can be measured, for example, based on ASTM D8206. Specifically, 4 g of grease is weighed out into a petri dish so that the surface is flat, the dish is placed in a measuring device, and the grease is placed in a high-pressure oxygen atmosphere at high temperature (160°C), and the time until the pressure drops to the specified level is measured.

[0035] (Manufacturing method) The present urea-based grease composition can be produced by blending a base oil, a thickener, and, if necessary, additives, and milling the mixture to achieve the worked consistency within the above-mentioned range. Milling can be carried out using, but is not particularly limited to, a stirring / dispersing device such as a hand mixer, a three-roll mill, a milling dispersion device, a homogenizer, or a colloid mill.

[0036] (Application) The present urea-based grease composition can be used as a substitute for products that have previously used conventional fluorine-based grease, and can be suitably used for, for example, automobile parts, precision machine parts, and other mechanical parts. Examples of automobile parts include door locks, gear shift levers, window regulators, fan control levers, door mirrors, etc. In addition to automobile parts, examples of the products include home appliances such as air conditioners, game console controllers, electronic musical instruments such as electronic pianos, and welfare equipment such as nursing bed lifting devices.

[0037] (effect) Although the present urea-based grease composition does not contain any fluorine compounds, it has oxidation stability equivalent to that of fluorine-based grease and also has excellent oil separation properties, making it suitable as a substitute for fluorine-based grease.

[0038] <Grease composition> A grease composition according to another embodiment of the present invention (hereinafter also referred to as the present grease composition) is characterized in that it is a grease composition, a so-called hybrid grease composition, comprising the above-mentioned present urea-based grease composition and a fluorine-based grease composition containing a linear or branched chain perfluoropolyether as a base oil and polytetrafluoroethylene (PTFE) as a thickener.

[0039] (Base oil of fluorine-based grease composition) The base oil of the above-mentioned fluorine-based grease composition contains a linear or branched chain perfluoropolyether, and the base oil preferably contains 95% by mass or more of perfluoropolyether, more preferably 98% by mass or more, and particularly preferably 99% by mass or more (including 100% by mass).

[0040] As the perfluoropolyether, a linear perfluoropolyether represented by the following formula (4) or a side-chain perfluoropolyether represented by the following formula (5) can be used, and among these, a linear perfluoropolyether is preferred.

[0041] F-(CF2CF2CF2O) n -CF2CF3 formula (4)

[0042] F-(CF2CF2O)n -CF2CF3 formula (5) | CF2

[0043] In the above fluorine-based grease composition, n in the above formula (4) is preferably an integer in the range of 10 to 60. Furthermore, n in the above formula (5) is preferably an integer in the range of 10 to 60. In the above fluorine-based grease composition, the linear perfluoropolyether preferably has a weight average molecular weight in the range of 3,000 to 10,000, more preferably in the range of 6,000 to 9,000, and the side chain perfluoropolyether preferably has a weight average molecular weight in the range of 3,000 to 10,000, more preferably in the range of 5,000 to 8,000.

[0044] Specific examples of linear perfluoropolyethers in the base oil of this fluorine-based grease composition include "Demnum S200" (weight average molecular weight 8400) manufactured by Daikin Industries, Ltd., and specific examples of side-chain perfluoropolyethers include "PT-57" (weight average molecular weight 7500) manufactured by Nicca Chemical Co., Ltd.

[0045] (Thickener for fluorine-based grease composition) The thickener of the present fluorine-based grease composition can be polytetrafluoroethylene (PTFE).

[0046] The PTFE may be any conventionally used PTFE, but preferably has an average particle size of 0.2 μm to 1.0 μm, more preferably 0.2 μm to 0.5 μm. The average particle size can be measured, for example, by a microtrac.

[0047] A specific example of PTFE is "TLP-10F-1" (average particle size 0.2 μm) manufactured by Mitsui-Chemours Fluoroproducts Co., Ltd.

[0048] (Other additives) The fluorine-based grease composition may further contain other additives within the scope of the present invention, such as extreme pressure agents such as organic zinc compounds and organic molybdenum compounds, antioxidants such as amine-based, phenol-based and calcium-based compounds, rust inhibitors such as sulfonates and polyhydric alcohol esters, and oiliness agents such as esters and alcohols. When other additives are added, the amount added to the fluorine-based grease composition is preferably 5% by mass or less, more preferably 2% by mass or less, and particularly preferably 1% by mass or less (including 0% by mass).

[0049] (Method for producing fluorine-based grease composition) The fluorine-based grease composition can be produced by blending a base oil, a thickener, and, if necessary, additives in the blending ratios described below, followed by milling to achieve a worked penetration within the range shown below. Milling can be carried out using, but is not particularly limited to, a stirring / dispersing device such as a hand mixer, a three-roll mill, a milling dispersion device, a homogenizer, or a colloid mill.

[0050] The kinematic viscosity of the fluorine-based base oil at 40°C is not particularly limited, but is preferably 20 to 500 mm 2 / s, and 200 to 400 mm 2 It is more preferable that the kinematic viscosity is in the range of 1 / s. The kinematic viscosity can be measured, for example, based on JIS K2283.

[0051] The present fluorine-based grease composition preferably has a worked penetration within the range of 200-350, more preferably within the range of 250-300. The worked penetration can be measured, for example, based on JIS K2220.

[0052] In the present fluorine-based grease composition, the blending ratio of the base oil to the thickener is not particularly limited, but in order to ensure that the worked penetration falls within the above range, the base oil:thickener (mass ratio) is preferably within the range of 5:5 to 8:2, and more preferably within the range of 6:4 to 7:3.

[0053] The fluorine-based grease composition preferably has an accelerated oxidation stability within the range of 25 to 28 [hr], more preferably within the range of 27 to 28 [hr]. The accelerated oxidation stability can be measured, for example, based on ASTM D8206 as described above.

[0054] (Method for producing the present grease composition) The present grease composition can be produced by mixing the present urea-based grease composition with the above-mentioned fluorine-based grease composition. The mixing can be carried out using, but is not particularly limited to, a stirring / dispersing device such as a three-roll mill, a milling dispersing device, a homogenizer, or a colloid mill.

[0055] The blending ratio of the urea-based grease composition and the fluorine-based grease composition in the present grease composition is not particularly limited, but the urea-based grease composition is preferably contained in the present hybrid grease composition in an amount of 60% by mass or more and 100% by mass or less (or less than 100%), more preferably 60% by mass or more and 90% by mass or less, and particularly preferably 60% by mass or more and 70% by mass or less.

[0056] (Application) The present grease composition can be used as a substitute for products that have previously used conventional fluorine-based grease, and can be suitably used for, for example, mechanical parts such as automobile parts and precision machinery parts, in the same manner as the present urea-based grease composition described above.

[0057] (effect) The present grease composition can maintain the performance of fluorine-based grease while reducing the amount of fluorine compound used. In addition, since the amount of expensive fluorine-based grease used can be reduced, the product price of the present grease composition can be reduced. [Example]

[0058] The present invention will be described below based on an example, but the present invention is not limited to this example.

[0059] Examples 1 to 4 and Comparative Examples 1 to 5 shown below were prepared.

[0060] Example 1 As the base oil, methylphenyl silicone (diphenyl dimethicone, "KF-54" manufactured by Shin-Etsu Chemical Co., Ltd.) was used. An aromatic diurea compound was used as a thickener. This aromatic diurea compound was synthesized using "Millionate MT" manufactured by Tosoh Corporation as MDI and "p-Toluidine" manufactured by Lanxess AG as p-toluidine.

[0061] 7 g of the above MDI was added to 61.7 g of the above base oil, and the mixture was stirred and dissolved at 60°C. A solution of 23.3 g of the above base oil and 8 g of the above p-toluidine, dissolved at 60°C in a separate container, was added thereto. The mixture was heated to 100°C with stirring and maintained for a certain period of time. The mixture was then heated to 165°C with continued stirring, and further stirred while maintaining the temperature, after which it was allowed to cool. The mixture was then passed through a triple roll mill twice to produce the urea-based grease composition of Example 1.

[0062] <Comparative Example 1> As the base oil, a linear perfluoropolyether having a weight average molecular weight of 8400 ("Demnum S200" manufactured by Daikin Industries, Ltd.) was used. As a thickener, PTFE ("TLP-10F-1" manufactured by Mitsui-Chemours Fluoroproducts Co., Ltd.) with an average particle size of 0.2 μm was used.

[0063] 30 g of a thickener (PTFE) was added to 70 g of the above base oil and mixed together, and the mixture was passed through a triple roll mill twice to give a fluorine-based grease composition of Comparative Example 1.

[0064] <Comparative Example 2> As the base oil, a side-chain perfluoropolyether having a weight average molecular weight of 7500 ("PT-57" manufactured by Nicca Chemical Co., Ltd.) was used. As a thickener, PTFE ("TLP-10F-1" manufactured by Mitsui-Chemours Fluoroproducts Co., Ltd.) with an average particle size of 0.2 μm was used.

[0065] 30 g of a thickener (PTFE) was added to 70 g of the above base oil and mixed together, and the mixture was passed through a triple roll mill twice to give a fluorine-based grease composition of Comparative Example 2.

[0066] <Example 2> The urea-based grease composition of Example 1 and the fluorine-based grease composition of Comparative Example 1 were blended in a mass ratio of urea:fluorine = 60:40 and mixed with a hand mixer. Then, the mixture was passed through a triple roll mill twice to produce the hybrid grease composition of Example 2.

[0067] Example 3 The urea-based grease composition of Example 1 and the fluorine-based grease composition of Comparative Example 1 were blended in a mass ratio of urea:fluorine=70:30 and mixed with a hand mixer. Then, the mixture was passed through a triple roll mill twice to produce the hybrid grease composition of Example 3.

[0068] Example 4 The urea-based grease composition of Example 1 and the fluorine-based grease composition of Comparative Example 2 were blended in a mass ratio of urea:fluorine = 60:40 and mixed with a hand mixer. The mixture was then passed through a triple roll mill twice to produce the hybrid grease composition of Example 4.

[0069] <Comparative Example 3> As the base oil, alkyl-substituted diphenyl ether ("Moresco Hi-Lube LB-100" manufactured by MORESCO Corporation) was used. As the thickener, an aromatic diurea compound (MDI was "Millionate MT" manufactured by Tosoh Corporation, and p-toluidine was "p-Toluidine" manufactured by Lanxess) was used. As antioxidants, a liquid high molecular weight phenol-based antioxidant ("Irganox L135" manufactured by BASF) and a liquid octylated / butylated diphenylamine-based antioxidant ("Irganox L57" manufactured by BASF) were used. As the rust inhibitor, a calcium-based rust inhibitor ("NA-SUL729" manufactured by King Industries) was used.

[0070] 9.6 g of the MDI was added to 59.5 g of the base oil, and the mixture was heated to 60°C and dissolved with stirring. A solution of 19.5 g of the base oil and 8.4 g of the p-toluidine dissolved at 60°C in a separate container was added thereto. The mixture was heated to 100°C with stirring and maintained for a certain period of time. The mixture was then heated to 165°C with continued stirring, and further stirred while maintaining the temperature, after which it was allowed to cool. 1 g each of antioxidant and rust inhibitor were added, and the mixture was passed through a triple-roll mill twice to produce an ether base oil / urea-based grease composition of Comparative Example 3.

[0071] <Comparative Example 4> The ether base oil urea-based grease composition of Comparative Example 3 and the fluorine-based grease composition of Comparative Example 1 were blended in a mass ratio of ether base oil urea:fluorine = 60:40 and mixed with a hand mixer. Then, the mixture was passed through a triple roll mill twice to obtain the hybrid grease composition of Comparative Example 4.

[0072] <Comparative Example 5> A commercially available urea-based grease composition using silicone oil as a base oil and the fluorine-based grease composition of Comparative Example 1 were blended in a mass ratio of urea:fluorine=60:40 and mixed with a hand mixer. The mixture was then passed through a triple roll mill twice to produce the hybrid grease composition of Comparative Example 5.

[0073] (test) The following tests were carried out on the grease compositions of Examples 1 to 4 and Comparative Examples 1 to 5. The results of these tests are shown in Table 1 below.

[0074] <Consistency> The penetration was measured in accordance with JIS K 2220. In Table 1 below, the value of 0W indicates unworked penetration, and the value of 60W indicates worked penetration.

[0075] <Dripping point> The dropping point was measured in accordance with JIS K2220. If the dropping point could not be measured, it was evaluated as "none."

[0076] <Oil separation degree> The oil separation rate was measured at 180°C for 24 hours in accordance with JIS K2220.

[0077] <Accelerated oxidation stability> Accelerated oxidation stability was measured as follows based on ASTM D8206. 4g of grease was measured out onto a petri dish so that the surface was flat, and the dish was set into a measuring instrument. The grease was then placed in a high-temperature (160°C) and high-pressure oxygen atmosphere, and the time until the pressure dropped to the specified level was measured.

[0078] [Table 1]

[0079] (result) It was confirmed that the grease compositions of Examples 1 to 4 had the same accelerated oxidation stability as the fluorine-based grease composition of Comparative Example 1, and were less susceptible to oxidative degradation. Furthermore, the grease compositions of Examples 1 to 4 have an oil separation rate of 0.6 to 1.2, which means that they have an appropriate oil retention capacity and little dripping. On the other hand, the fluorine-based grease compositions (Comparative Examples 1 and 2) have a high degree of oil separation and tend to drip oil. The hybrid grease composition of Comparative Example 4, which uses an ether base oil, and the hybrid grease composition of Comparative Example 5, which uses a silicone base oil, have a short accelerated oxidation stability and tend to deteriorate due to oxidation.

Claims

1. A urea-based grease composition comprising a methylphenyl silicone as a base oil and an aromatic urea compound as a thickener.

2. The urea-based grease composition according to claim 1; a fluorine-based grease composition containing a linear or branched chain perfluoropolyether as a base oil and polytetrafluoroethylene (PTFE) as a thickener;

3. 3. The grease composition according to claim 2, wherein the base oil comprises a linear perfluoropolyether.

4. The grease composition according to claim 3, wherein the blending ratio of the urea-based grease composition is 60% by mass or more and less than 100% by mass.

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