Grease composition

Abstract

Provided is a grease composition that does not contain PFAS (perfluoroalkyl compounds and polyfluoroalkyl compounds) and has a superior ability to prevent the diffusion of oil. This grease composition contains a base oil, a thickener, and a nonionic surfactant. The nonionic surfactant has a surface tension of 22.5-26.5 mN / m when the concentration in PGMEA is 0.05 mass%. The grease composition does not not contain any PFAS (perfluoroalkyl compounds and polyfluoroalkyl compounds).

Description

Grease composition

[0001] This invention relates to a grease composition.

[0002] Grease is used in the sliding parts of automotive parts and mechanical components of office automation equipment and AV equipment. Under particularly high-temperature conditions, the oil contained in the grease may separate, and the separated oil can cause contamination of mechanical components or lead to malfunctions. Various technologies have been proposed as additives for grease. Patent Document 1 discloses an oil non-diffusion additive that suppresses the diffusion (seepage) of the base oil, consisting of a fluorine copolymer having perfluoroalkyl groups and polyoxypropylene units. 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 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 technology to suppress oil diffusion using additives that do not contain PFAS, rather than conventional oil diffusion-preventing additives made of fluorine copolymers.

[0004] Japanese Patent Publication No. 08-81690 Japanese Patent Publication No. 2007-297422

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

[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 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 does not contain 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.

[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.

[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 represented by diesters and polyol esters, synthetic hydrocarbon oils represented by poly-α-olefin (PAO), co-oligomers of ethylene and α-olefin, and polybutene, ether-based synthetic oils represented by alkyl diphenyl ether and polypropylene glycol, silicone oil, fluorinated oil, etc., 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 using vegetable oils as raw materials, 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, mineral oil, synthetic hydrocarbon oil (especially PAO), or ester-based synthetic oil is preferred as the base oil. In the present invention, from the viewpoint of low-temperature performance, the kinematic viscosity of the entire base oil at 40°C should be 15 to 800 mm². 2It is preferable that the value be / s, and the range is 15 to 600 mm. 2 It is more preferable that the value be / s, and the range is 15 to 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 value be / s, and the range is 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 base oil content 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. Having a base oil content within this range provides excellent lubricity.

[0009] <Thickener> The thickener used in the grease composition of the present invention is not particularly limited. For example, soap-based thickeners represented by Li soap and composite Li soap, urea-based thickeners represented by diurea, inorganic thickeners represented by organic modified clay and silica, and organic thickeners represented by PTFE can be mentioned. As the Li soap, lithium stearate (LiSt), lithium 12-hydroxystearate (12(OH)StLi), etc. can be mentioned. As the composite Li 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 preferable. Examples of the hydroxy fatty acid include 12-hydroxystearic acid, 12-hydroxylauric acid, 16-hydroxypalmitic acid, etc., and 12-hydroxystearic acid is preferable. 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, and azelaic acid is preferable. From the viewpoint of shear stability, the composite Li soap is preferably composed of a lithium salt of 12-hydroxystearic acid and a lithium salt of azelaic acid. As the urea-based thickener, a diurea compound represented by the formula (I) can be mentioned. 1 -NHCONH-R 2 -NHCONH-R 3 (I) In the formula, R 1 and R 3 may be the same as 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, preferably an alkyl group having 6 to 30 carbon atoms or a cyclohexyl group, and R 1 and R 2 are both alkyl groups having 6 to 30 carbon atoms (aliphatic diurea), or R 1 and R 2It 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 the alkyl groups having 6 to 30 carbon atoms, linear alkyl groups having 8 to 20 carbon atoms are more preferable, linear alkyl groups having 8 to 18 carbon atoms are more preferable, and linear alkyl groups having 8 carbon atoms or linear alkyl groups having 18 carbon atoms are particularly preferable. Examples of aryl groups having 6 to 7 carbon atoms include phenyl groups and tolyl groups, with tolyl groups being preferred. 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 thickener, from the viewpoint of shear stability and heat resistance, soap-based thickeners or urea-based thickeners are preferred, 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 thickener. 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 is defined as JIS K 2220 7. This refers to the consistency after 60 mixings as measured according to [the formula]. The amount of thickener in the grease composition of the present invention should be an amount suitable for adjusting the consistency to the above range, preferably 5 to 30% by mass, more preferably 5 to 27% by mass, and even more preferably 7 to 25% by mass, based on the total mass of the composition.

[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 its concentration in PGMEA is 0.05% by mass, and does not contain PFAS (perfluoroalkyl compounds and polyfluoroalkyl compounds). "PFAS" is an organofluorine 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 either perfluoroalkyl compounds or polyfluoroalkyl compounds, that the surfactant does not contain PFAS, and more preferably that the grease composition does not contain PFAS. In the present invention, it is preferable that the nonionic surfactant 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, preferably 22.5 to 26.0 mN / m, and more preferably 22.5 to 25.5 mN / m, when the nonionic surfactant is dissolved in PGMEA (propylene glycol monomethyl ether acetate) at a concentration of 0.05% by mass (0.05% by mass PGMEA solution). By using a nonionic surfactant with a surface tension in this range, excellent oil non-diffusivity is achieved. In this specification, surface tension refers to the 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. Including the nonionic surfactant within this range provides superior oil non-diffusivity.

[0011] <Other Additives> In addition to the nonionic surfactant described above, the grease composition of the present invention may further contain other additives. Any additives commonly used in grease compositions can be used as needed, such as antioxidants, rust inhibitors, metal corrosion inhibitors, oiliness agents, viscosity index improvers, etc. Examples of antioxidants include amine-based, phenol-based, quinoline-based, sulfur-based, and zinc dithiophosphate. Examples of rust inhibitors include zinc-based, carboxylic acid-based, carboxylate-based, amine-based, and sulfonate-based agents. Examples of metal corrosion inhibitors include benzimidazole-based and benzotriazole-based agents. Examples of oiliness agents include fatty acids, fatty acid esters, and phosphate esters. Examples of viscosity index improvers include polymethacrylate-based, polyisobutylene-based, ethylene-propylene copolymer-based, and styrene-butadiene hydrogenated copolymer-based agents. The content of these other additives is usually 0.01 to 20% by mass, preferably 0.05 to 15% by mass, and more preferably 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 manufactured by mixing the above-mentioned base oil, thickener, and nonionic surfactant components, as well as other additives as needed, in desired proportions using a standard method. The grease composition of the present invention can be used for lubricating various machine parts. The type of machine 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.

[0013] [Preparation of Grease Compositions] The grease compositions of Examples 1 to 12 and Comparative Examples 1 to 9 were prepared by the following method. Similarly, the grease compositions of Standards 1 to 11, which do not contain any surfactants, were also prepared. ・Examples 1 to 8, Comparative Examples 1 to 5, and Standards 1 to 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 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, was the value listed in the table below. ・Example 9, Comparative Example 6, and Standard 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. To this, a solution of lithium hydroxide monohydrate dissolved in water and heated 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. To this, a solution of lithium hydroxide monohydrate dissolved in water and heated was added, and the saponification reaction of azelaic acid was carried out while stirring. Next, the above mixture was gradually heated to 200°C. After that, 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., was adjusted to the value shown in the table below. Examples 10-12, Comparative Examples 7-9, and References 9-11: Base oil was reacted with 1 mole of 4,4'-diphenylmethane diisocyanate (MDI) at 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, was the value shown in the table below. The base oils, thickeners, and additives in the table are as follows.Unless otherwise specified, the component numbers in the table represent mass percentages based on the total mass of the composition. The remainder, excluding thickeners 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-α-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 in accordance with JIS K 2283. <Thickeners> ・LiSt: Lithium stearate ・12(OH)StLi: Lithium 12-hydroxystearate ・Li complex: A complex Li soap consisting of the lithium salt of 12-hydroxystearate and the lithium salt of azelaic acid ・Aromatic diurea: Reaction product of 4,4'-diphenylmethane diisocyanate and p-toluidine ・Aliphatic diurea: Reaction product of 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, PFAS-containing, 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% by mass PGMEA solution was measured at 25°C using the Wilhelmy method. Specifically, it was measured on a platinum plate using a high-performance surface tension meter DY-500 (manufactured by Kyowa Interface Science Co., Ltd.).

[0015] [Test Methods and Evaluation Methods] A frosted glass diffusion test was performed on each of the example, comparative example, and reference grease compositions to investigate oil non-diffusivity. (Frosted Glass Diffusion Test) Grease was applied to frosted glass to a diameter of 10 mm and a thickness of 2 mm. After standing in an 80°C constant temperature bath for 24 hours, the diffusion diameter (mm) of the oil was measured. (Presence or Absence of PFAS) PFAS-free: ○ PFAS-containing: ×

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[0021]

[0022] In grease compositions containing lithium stearate as a thickener, the diffusion diameters of the grease compositions of Examples 1 to 7 were 15 to 35 mm, which was 56 to 86% suppressed compared to the diffusion diameters of 45 to 105 mm of the standard grease compositions 1 to 6 that did not contain any surfactants (diffusion suppression 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 diffusion diameters of the grease compositions of Examples 1 to 7 were similar to those of the grease compositions of Comparative Examples 1, 3, and 4 containing nonionic surfactant B, which had a diffusion diameter of 15 to 35 mm, and they exhibited equivalent or better 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 thickener, the grease composition of Example 8 showed an 86% reduction in diffusion diameter compared to the grease composition of Reference 7, which contained no surfactants. Furthermore, the grease composition of Example 8 exhibited oil non-diffusivity equivalent to that of the grease composition of Comparative Example 5, which contained nonionic surfactant B.

[0024] In a grease composition containing a complex Li soap as a thickener, the grease composition of Example 9 showed a 40% reduction in diffusion diameter compared to the 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 grease compositions of Examples 10 to 12 showed a diffusion diameter suppressed by 40 to 85% compared to the standard grease compositions of Reference 9 to 11, which did not contain any surfactants. Furthermore, the grease compositions of Examples 10 to 12 had oil non-diffusivity equivalent to or better than the grease compositions of Comparative Examples 7 to 9, which contained nonionic surfactant B. Thus, the grease composition of the present invention, by not containing PFAS and using a nonionic surfactant with a predetermined surface tension range, significantly improved oil non-diffusivity compared to grease compositions that did not contain any surfactants, and also had oil non-diffusivity equivalent to or better than conventional grease compositions containing surfactants including PFAS.

Claims

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 (propylene glycol monomethyl ether acetate) is 0.05% by mass, and 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.

3. The grease composition according to claim 1 or 2, wherein the base oil is mineral oil, synthetic hydrocarbon oil, or ester-based synthetic oil.

4. The kinematic viscosity of the base oil at 100°C is 3.9 to 100 mm². 2 The grease composition according to claim 1 or 2, wherein the ratio is / s.

5. The grease composition according to claim 1 or 2, wherein the thickener is Li soap, a complex Li soap, or a diurea compound.

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