Grease composition

Abstract

The present invention provides a grease composition that does not contain PFAS (perfluoroalkyl compounds and polyfluoroalkyl compounds) and exhibits excellent oil non-diffusivity. [Solution] The grease composition of the present invention contains a base oil, a thickener, and a nonionic surfactant, wherein the nonionic surfactant has a surface tension of 22.5 to 26.5 mN / m when its concentration in PGMEA is 0.05% by mass, and does not contain PFAS (perfluoroalkyl compounds and polyfluoroalkyl compounds).

Description

[Technical Field]

[0001] This invention relates to a grease composition. [Background technology]

[0002] Grease is used in the sliding parts of automotive parts and mechanical components of office automation equipment and audiovisual equipment. Under particularly high-temperature conditions, the oil contained in the grease may separate, and the separated oil can cause contamination of the mechanical components or lead to malfunctions. Various technologies have been proposed as additives for grease. Patent Document 1 discloses an oil non-diffusion additive comprising a fluorine copolymer having perfluoroalkyl groups and polyoxypropylene units, which suppresses the diffusion (seepage) of the base oil. Patent Document 2 discloses a grease composition containing a base oil, a thickener, a fluorine surfactant, and a styrene block copolymer, in which a fluorine copolymer obtained by polymerizing a perfluoroaliphatic hydrocarbon group-containing ethylenically unsaturated monomer (A), a polyoxyalkylene unit-containing ethylenically unsaturated monomer (B), and / or a non-fluorine alkyl-containing ethylenically unsaturated monomer other than (B) (C) is used as the fluorine surfactant.

[0003] Perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA), which are types of perfluoroalkyl and polyfluoroalkyl compounds (PFAS), are subject to international discussion and regulation regarding target values ​​and standards from the perspective of protecting human health. In addition, the management of PFAS other than PFOS and PFOA is also being discussed in various countries and organizations. The U.S. Environmental Protection Agency (USEPA) and the European Chemicals Agency (ECHA) are moving to manage PFAS as a group, not just individual substances, and there is a possibility that regulations will expand further. Therefore, there is a need for a technology that suppresses oil diffusion using additives that do not contain PFAS, rather than conventional oil diffusion prevention additives made of fluorine copolymers. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 08-81690 [Patent Document 2] Japanese Patent Publication No. 2007-297422 [Overview of the project] [Problems that the invention aims to solve]

[0005] The object of this invention is to provide a grease composition that does not contain PFAS (perfluoroalkyl compounds and polyfluoroalkyl compounds) and has excellent oil non-diffusivity properties. [Means for solving the problem]

[0006] The present invention solves the above problems by using a nonionic surfactant that does not contain PFAS (perfluoroalkyl compounds and polyfluoroalkyl compounds). That is, the present invention has the following configuration. [1] A grease composition containing a base oil, a thickener, and a nonionic surfactant, wherein the nonionic surfactant has a surface tension of 22.5 to 26.5 mN / m when its concentration in PGMEA is 0.05% by mass, and is free of PFAS (perfluoroalkyl compounds and polyfluoroalkyl compounds). [2] The grease composition according to [1], wherein the content of the nonionic surfactant is 0.05 to 15% by mass. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a grease composition that does not contain PFAS (perfluoroalkyl compounds and polyfluoroalkyl compounds) and has excellent oil non-diffusivity properties. [Modes for carrying out the invention]

[0008] <Base oil> The base oil used in the grease composition of the present invention is not particularly limited. For example, mineral oil, ester-based synthetic oils such as diesters and polyol esters, synthetic hydrocarbon oils such as poly-α-olefin (PAO), co-oligomers of ethylene and α-olefin, and polybutene, ether-based synthetic oils such as alkyl diphenyl ether and polypropylene glycol, silicone oil, and fluorinated oil can be used. The synthetic oil may be a so-called biomass oil, which is produced using biological resources derived from plants and animals as raw materials. For example, biomass ester oils synthesized from various fatty acids and alcohols derived from vegetable oils, or biomass hydrocarbon oils using vegetable oils such as palm oil, corn oil, and soybean oil can be used. Two or more base oils may be used in combination. In the present invention, from the viewpoint of lubricity, the base oil is preferably mineral oil, synthetic hydrocarbon oil (particularly PAO), or ester-based synthetic oil. In this invention, from the viewpoint of low-temperature properties, the kinematic viscosity of the entire base oil at 40°C is 15 to 800 mm². 2 It is preferable that the value be / s, and 15-600mm 2 It is more preferable that the speed be / s, and the range is 15-410 mm. 2 It is even more preferable that the viscosity is / s. Furthermore, from the viewpoint of low-temperature properties and heat resistance, the kinematic viscosity of the entire base oil at 100°C should be 3.9 to 150 mm². 2 It is preferable that the value be / s, and the range is 3.9 to 100 mm. 2 It is more preferable that the interval be / s, and the interval be 3.9 to 50 mm. 2 It is even more preferable that the kinematic viscosity is / s. In this specification, the kinematic viscosity is the value measured in accordance with JIS K2283. The content of the base oil in the grease composition of the present invention is preferably 65 to 94.95% by mass, more preferably 70 to 94.95% by mass, and even more preferably 75 to 92.95% by mass based on the total mass of the composition. When the content of the base oil is within such a range, the lubricity is excellent.

[0009] <Thickener> The thickener used in the grease composition of the present invention is not particularly limited. For example, soap-based thickeners represented by lithium soap or complex lithium soap, urea-based thickeners represented by diurea, inorganic thickeners represented by organic modified clay or silica, and organic thickeners represented by PTFE can be mentioned. Examples of lithium soap include lithium stearate (LiSt), lithium 12-hydroxystearate (12(OH)StLi), and the like. As the complex lithium soap, those composed of a lithium salt of a hydroxy fatty acid having 12 to 24 carbon atoms and having one or more hydroxyl groups and a lithium salt of a fatty acid dicarboxylic acid having 2 to 12 carbon atoms are preferred. Examples of the hydroxy fatty acid include 12-hydroxystearic acid, 12-hydroxylauric acid, 16-hydroxypalmitic acid, etc., and 12-hydroxystearic acid is preferred. Examples of the aliphatic dicarboxylic acid include azelaic acid, sebacic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, speric acid, undecanedioic acid, dodecanedioic acid, etc., and azelaic acid is preferred. From the viewpoint of shear stability, the complex lithium soap is preferably composed of a lithium salt of 12-hydroxystearic acid and a lithium salt of azelaic acid. Examples of the urea-based thickener include diurea compounds represented by formula (I). R 1 -NHCONH-R 2 -NHCONH-R 3 (I) In the formula, R 1 and R 3These may be the same or different from each other, and are an alkyl group having 6 to 30 carbon atoms, an aryl group having 6 to 7 carbon atoms, or a cyclohexyl group, and are preferably an alkyl group having 6 to 30 carbon atoms or a cyclohexyl group, R 1 and R 2 Both are alkyl groups with 6 to 30 carbon atoms (aliphatic diurea), or R 1 and R 2 It is more preferable that one of the groups is an alkyl group having 6 to 30 carbon atoms and the other is a cyclohexyl group (alicyclic aliphatic diurea). Among alkyl groups having 6 to 30 carbon atoms, linear alkyl groups having 8 to 20 carbon atoms are more preferred, linear alkyl groups having 8 to 18 carbon atoms are even more preferred, and linear alkyl groups having 8 carbon atoms or linear alkyl groups having 18 carbon atoms are particularly preferred. Examples of aryl groups having 6 to 7 carbon atoms include phenyl groups and tolyl groups, with tolyl groups being preferred. R 2 The group is a divalent aromatic hydrocarbon group having 6 to 15 carbon atoms, preferably derived from tolylene diisocyanate or diphenylmethane-4,4'-diisocyanate, and more preferably derived from diphenylmethane-4,4'-diisocyanate. As a thickening agent, soap-based or urea-based thickening agents are preferred from the viewpoint of shear stability and heat resistance, and more preferably lithium stearate, lithium 12-hydroxystearate, a complex Li soap consisting of a lithium salt of 12-hydroxystearate and a lithium salt of azelaic acid, or a urea-based thickening agent. The consistency of the grease composition of the present invention is preferably 175 to 475, more preferably 220 to 430, and even more preferably 250 to 430, from the viewpoint of the grease composition maintaining appropriate hardness and achieving both applicability and appropriate fluidity. In this specification, consistency refers to the 60-compound consistency measured according to JIS K 2220 7. The content of the thickener in the grease composition of the present invention may be an amount suitable for adjusting the consistency within the above range, and based on the total mass of the composition, it is preferably 5 to 30% by mass, more preferably 5 to 27% by mass, and even more preferably 7 to 25% by mass.

[0010] <Nonionic surfactant> The grease composition of the present invention contains a nonionic surfactant. The nonionic surfactant of the present invention is a surfactant having a surface tension of 22.5 to 26.5 mN / m when the concentration in PGMEA is 0.05% by mass, and does not contain PFAS (perfluoroalkyl compounds and polyfluoroalkyl compounds). "PFAS" is an organic fluorine compound and is a general term for perfluoroalkyl compounds and polyfluoroalkyl compounds. In the present invention, it is preferable that the nonionic surfactant does not contain perfluoroalkyl compounds or polyfluoroalkyl compounds, and it is more preferable that the grease composition does not contain PFAS. In the present invention, the nonionic surfactant preferably has an HLB value of 0 to 6. The nonionic surfactant of the present invention has a surface tension of 22.5 to 26.5 mN / m in a solution (0.05% by mass PGMEA solution) prepared by dissolving the nonionic surfactant in PGMEA (propylene glycol monomethyl ether acetate) so that the concentration of the nonionic surfactant is 0.05% by mass. It is preferably 22.5 to 26.0 mN / m, and more preferably 22.5 to 25.5 mN / m. By using a nonionic surfactant having a surface tension within such a range, excellent oil non-diffusibility can be obtained. In this specification, the surface tension means a value measured at a temperature of 25°C by the Wilhelmy method. As the nonionic surfactant, it is preferable to use MEGAFACE EFS801 manufactured by DIC Corporation. The content of the nonionic surfactant is preferably 0.05 to 15.0% by mass, more preferably 0.05 to 12.5% by mass, and even more preferably 0.05 to 10.0% by mass based on the total mass of the grease composition. By including the nonionic surfactant within such a range, the oil non-diffusibility is more excellent.

[0011] <Other additives> In addition to the above nonionic surfactant, the grease composition of the present invention may further contain other additives. As the other additives, any additives generally used in grease compositions can be used as necessary, and examples include antioxidants, rust preventives, metal corrosion inhibitors, oiliness agents, viscosity index improvers, and the like. Examples of the antioxidant include amine-based, phenol-based, quinoline-based, sulfur-based, zinc dithiophosphate, and the like. Examples of the rust preventive include zinc-based, carboxylic acid-based, carboxylate-based, amine-based, sulfonate-based, and the like. Examples of the metal corrosion inhibitor include benzimidazole-based, benzotriazole-based, and the like. Examples of the oiliness agent include fatty acids, fatty acid esters, phosphate esters, and the like. Examples of the viscosity index improver include polymethacrylate-based, polyisobutylene-based, ethylene-propylene copolymer-based, styrene-butadiene hydrogenated copolymer-based, and the like. The content of these other additives is usually from 0.01 to 20% by mass, preferably from 0.05 to 15% by mass, and more preferably from 0.05 to 10% by mass based on the total mass of the grease composition.

[0012] The grease composition of the present invention can be easily produced by mixing the above base oil, thickener, and components of the nonionic surfactant, and other additives as necessary, in a desired blending ratio by a conventional method. The grease composition of the present invention can be used for lubricating various mechanical parts. The type of mechanical part to which the grease composition of the present invention can be used is not limited to, and examples include automotive parts and mechanical parts of office automation equipment and AV equipment. [Examples]

[0013] [Preparation of grease composition] The grease compositions of Examples 1-12 and Comparative Examples 1-9 were prepared by the following method. Similarly, the grease compositions of Standards 1-11, which did not contain any surfactants, were also prepared. Examples 1-8, Comparative Examples 1-5, and References 1-7 Stearic acid or 12-hydroxystearic acid was completely dissolved in the base oil at 90°C. In a separate container, lithium hydroxide was completely dissolved in pure water at 90°C. The two were mixed and heated to 220°C, then cooled to below 100°C while stirring to form the base grease. The above base grease was diluted with an additional base oil, the additives listed in the table below were added, and the mixture was kneaded in a three-roll mill until the consistency after 60 mixing cycles, as measured according to JIS K2220 7, reached the values ​​listed in the table below. • Example 9, Comparative Example 6, and Reference 8 12-hydroxystearic acid was added to the base oil and heated to a temperature (80-90°C) where it became a completely transparent liquid. A solution of lithium hydroxide monohydrate dissolved in water was added, and the saponification reaction of 12-hydroxystearic acid was carried out while stirring to form the lithium salt of 12-hydroxystearic acid. Next, the base oil and azelaic acid were added and stirring continued until a homogeneous state was reached. A solution of lithium hydroxide monohydrate dissolved in water was added, and the saponification reaction of azelaic acid was carried out while stirring. Next, the above mixture was gradually heated to 200°C. Afterward, it was cooled to below 100°C while stirring to obtain the base grease. The above base grease was diluted with additional base oil, the additives listed in the table below were added, and the mixture was kneaded in a three-roll mill until the consistency after 60 mixing cycles, as measured according to JIS K2220 7, reached the values ​​listed in the table below. Examples 10-12, Comparative Examples 7-9, and References 9-11 A base oil was reacted with 1 mole of 4,4'-diphenylmethane diisocyanate (MDI) in a ratio of 2 moles of a predetermined amine, and the mixture was heated and cooled while stirring to obtain a base grease. This base grease was diluted with additional base oil, the additives listed in the table below were added, and the mixture was kneaded in a three-roll mill until the consistency after 60 mixing cycles, as measured according to JIS K2220 7, reached the values ​​listed in the table below. The base oil, thickener, and additives listed in the table are as follows. Unless otherwise specified, the numbers for the components in the table represent mass percentages based on the total mass of the composition. The remainder, excluding the thickener and additives, represents the mass percentage of the base oil.

[0014] <Base oil> • PAO A: Poly-alpha-olefin (kinematic viscosity at 40°C: 30.2 mm) 2 / s) • PAO B: Poly-alpha-olefin (kinematic viscosity at 40°C: 407.6 mm) 2 / s) • Ester oil: Polyol ester (kinematic viscosity at 40°C: 32.5 mm) 2 / s) • Mineral oil: Paraffinic mineral oil (K40, manufactured by ENEOS Corporation, kinematic viscosity at 40°C: 39.0 mm) 2 / s) The kinematic viscosity was measured according to the method compliant with JIS K 2283. <Thickener> • LiSt: Lithium stearate • 12(OH)StLi: Lithium hydroxystearate (12) • Li Complex: A complex Li soap consisting of lithium salt of 12-hydroxystearic acid and lithium salt of azelaic acid. • Aromatic diurea: Reaction product of 4,4'-diphenylmethane diisocyanate and p-toluidine • A reaction product of alicyclic aliphatic diurea: 4,4'-diphenylmethane diisocyanate with cyclohexylamine and stearylamine (molar ratio of cyclohexylamine to stearylamine is 7:1) • Aliphatic diurea: Reaction product of 4,4'-diphenylmethane diisocyanate with octylamine and stearylamine (molar ratio of octylamine to stearylamine is 5:5) <Additives> • Nonionic surfactant A: MEGAFACE EFS801, manufactured by DIC Corporation, surface tension of 0.05% by mass PGMEA solution: 25.19 mN / m, PFAS-free. • Nonionic surfactant B: Megafac F-430, manufactured by DIC Corporation, surface tension of 0.05% by mass PGMEA solution: 22.35 mN / m, fluorine-based, contains PFAS. • Nonionic surfactant C: Marialim AAB-0851, manufactured by NOF Corporation, surface tension of 0.05% by mass PGMEA solution: 27.60 mN / m, high molecular weight carboxylic acid, PFAS-free. The surface tension of the 0.05 mass% PGMEA solution was measured at 25°C using the Wilhelmy method. Specifically, it was measured using a platinum plate with a high-performance surface tension meter DY-500 (manufactured by Kyowa Interface Science Co., Ltd.).

[0015] [Test methods and evaluation methods] A ground glass diffusion test was performed on each of the example, comparative, and reference grease compositions to investigate their oil non-diffusivity. (Ground glass diffusion test) Grease was applied to frosted glass in a 10mm diameter, 2mm thick layer, and left to stand in an 80°C constant temperature bath for 24 hours. After that, the diffusion diameter (mm) of the oil was measured. (Contains PFAS or not) PFAS free:○ Contains PFAS: ×

[0016] [Table 1]

[0017] [Table 2]

[0018] [Table 3]

[0019] [Table 4]

[0020] [Table 5]

[0021] [Table 6]

[0022] In grease compositions containing lithium stearate as a thickening agent, the diffusion diameters of the grease compositions of Examples 1 to 7 were 15 to 35 mm, which was 56 to 86% lower than the diffusion diameters of 45 to 105 mm for the standard grease compositions 1 to 6 that did not contain any surfactants (diffusion inhibition rate = (diffusion diameter without surfactant - diffusion diameter with surfactant) / diffusion diameter without surfactant), comparison between Examples 1 and 2 and standard 1, comparison between Example 3 and standard 2, comparison between Example 4 and standard 3, comparison between Example 5 and standard 4, comparison between Example 6 and standard 5, and comparison between Example 7 and standard 6). Furthermore, the grease compositions of Examples 1 to 7 had diffusion diameters of approximately the same size as those of the grease compositions of Comparative Examples 1, 3, and 4 containing nonionic surfactant B (15 to 35 mm), and exhibited equivalent or superior oil non-diffusivity (for example, comparison between Examples 1 to 3, 5, and 7 and Comparative Example 1, comparison between Example 4 and Comparative Example 3, and comparison between Example 6 and Comparative Example 4). Furthermore, the diffusion diameter of the grease compositions in Examples 1 to 7 was significantly suppressed compared to the diffusion diameter of 105 mm of the grease composition in Comparative Example 2, which contained a nonionic surfactant C.

[0023] In a grease composition containing lithium 12-hydroxystearate as a thickening agent, the grease composition of Example 8 showed an 86% reduction in diffusion diameter compared to the standard grease composition of Reference 7, which did not contain any surfactants. Furthermore, the grease composition of Example 8 had oil non-diffusivity equivalent to that of the grease composition of Comparative Example 5, which contained a nonionic surfactant B.

[0024] In a grease composition containing a complex Li soap as a thickening agent, the grease composition of Example 9 showed a 40% reduction in diffusion diameter compared to the standard grease composition of Reference 8, which did not contain any surfactants. Furthermore, the grease composition of Example 9 had oil non-diffusivity equivalent to or better than that of the grease composition of Comparative Example 6, which contained a nonionic surfactant B.

[0025] In grease compositions containing a urea-based thickener, the diffusion diameter of the grease compositions of Examples 10 to 12 was suppressed by 40 to 85% compared to the standard grease compositions of Examples 9 to 11, which did not contain any surfactants. Furthermore, the grease compositions of Examples 10 to 12 exhibited oil non-diffusivity equivalent to or better than that of the grease compositions of Comparative Examples 7 to 9, which contained nonionic surfactant B. Based on the above, the grease composition of the present invention, by not containing PFAS and using a nonionic surfactant having a predetermined range of surface tension, significantly improved oil non-diffusivity compared to grease compositions that do not contain any surfactants, and had oil non-diffusivity equivalent to or better than conventional grease compositions containing surfactants including PFAS.

Claims

1. It contains a base oil, a thickener, and a nonionic surfactant. A grease composition in which the nonionic surfactant is a surfactant having a surface tension of 22.5 to 26.5 mN / m when its concentration in PGMEA is 0.05% by mass, and which does not contain PFAS (perfluoroalkyl compounds and polyfluoroalkyl compounds).

2. The grease composition according to claim 1, wherein the content of the nonionic surfactant is 0.05 to 15% by mass.

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