Grease composition

Abstract

Provided is a grease composition containing a base oil (A), hydrophilic nanofibers (B) having a roughness (d) of 1 nm to 500 nm, and particles (C) having a structure in which the hydrophilic nanofibers (B) are one or more types selected from the group consisting of cellulose nanofibers (B1) and modified cellulose nanofibers (B2), the particles (C) having a hydrophobic group on the outermost surface of the hydrophilic matrix structure, and having a hydrophobic group on the outermost surface of the hydrophilic matrix structure. In the grease composition, the average particle diameter of the particles (C) is 1 nm to 500 nm, and the grease composition has an appropriate oil separation degree and excellent water resistance despite the use of hydrophilic nanofibers.

Description

TECHNICAL FIELD

[0001] The present application relates to a grease composition. BACKGROUND

[0002] Greases are easy to seal compared to lubricating oils, and enable miniaturization and weight reduction of the applied machinery. Therefore, they have been widely used for lubrication of various sliding portions of automobiles, electric devices, industrial machines, and industrial machinery, etc.

[0003] In recent years, in order to provide a grease composition with low environmental burden, a grease composition obtained using a thickening agent having biodegradability has also been proposed. For example, in Patent Literature 1, a grease composition using cellulose nanofiber (hereinafter also referred to as "CNF") as a thickening agent is proposed.

[0004] PRIOR ART DOCUMENTS PATENT LITERATURE Patent Literature 1: Japanese Patent Application Laid-Open No. 2017-210612 SUMMARY

[0005] PROBLEMS TO BE SOLVED BY THE INVENTION However, a grease composition using a hydrophilic nanofiber such as CNF as a thickening agent is prone to oil separation, and has insufficient water resistance.

[0006] Therefore, a grease composition having appropriate oil separation and excellent water resistance despite using such a hydrophilic nanofiber is desired.

[0007] Thus, an object of the present application is to provide a grease composition having appropriate oil separation and excellent water resistance despite using a hydrophilic nanofiber.

[0008] MEANS FOR SOLVING THE PROBLEMS The present inventors found that a grease composition containing a base oil, a specific hydrophilic nanofiber, and a specific particle can solve the above problems, and thus completed the present application.

[0009] That is, the present application provides the following [1].

[0010] [1] A grease composition containing a base oil (A), a hydrophilic nanofiber (B) having a roughness (d) of 1 nm to 500 nm, and a particle (C), the aforementioned hydrophilic nanofiber (B) is one or more selected from the group consisting of cellulose nanofiber (B1) and modified cellulose nanofiber (B2), the aforementioned particle (C) has a structure in which a hydrophobic group is present on the outermost surface of a hydrophilic base structure, and in the grease composition, the average particle diameter of the particle (C) is 1 nm to 500 nm.

[0011] Effects of Invention According to the present application, a grease composition having appropriate oil repellency and excellent water resistance can be provided even though hydrophilic nanofibers are used. DETAILED DESCRIPTION

[0012] The upper limit value and the lower limit value of the numerical range described in the present specification can be combined arbitrarily. For example, when "A ~ B" and "C ~ D" are described as numerical ranges, the numerical ranges of "A ~ D" and "C ~ B" are also included in the range of the present application.

[0013] In addition, the numerical range "lower limit value ~ upper limit value" described in the present specification means the value equal to or higher than the lower limit value and equal to or lower than the upper limit value unless otherwise specified.

[0014] In addition, in the present specification, the numerical value of the examples is a numerical value that can be used as the upper limit value or the lower limit value.

[0015] [Grease composition] The grease composition of the present embodiment is a grease composition containing a base oil (A), a hydrophilic nanofiber (B) having a roughness (d) of 1 nm to 500 nm, and a particle (C), The aforementioned hydrophilic nanofiber (B) is one or more selected from the group consisting of a cellulose nanofiber (B1) and a modified cellulose nanofiber (B2), The aforementioned particle (C) is a structure having a hydrophobic group on the outermost surface of a hydrophilic base structure, and in the grease composition, the average particle diameter of the particle (C) is 1 nm to 500 nm.

[0016] In order to solve the above problem, the present inventors have conducted intensive studies.

[0017] As a base material of a grease composition having biodegradability and excellent lubricity and heat resistance, it is useful to use a cellulose nanofiber as a thickening agent.

[0018] Here, the cellulose nanofiber is easily hygroscopic due to high hydrophilicity, and there is a problem that it is washed away by water and does not easily remain in the sliding portion. In addition, there is a problem that oil separation is easy.

[0019] In order to solve this problem, the present inventors have repeatedly conducted intensive studies, and as a result, it has been found that a grease composition into which a particle (C) having a hydrophobic group on the outermost surface of a hydrophilic base structure and having a specific particle diameter is compounded can solve these problems.

[0020] Here, in the base oil (A), the hydrophilic nanofiber (B) easily forms a high-order structure. In addition, the hydrophilic nanofiber (B) easily disperses uniformly in the base oil (A).

[0021] In addition, the grease composition of the present embodiment contains the particle (C) as a necessary component. The particle (C) is a particle having a structure in which a hydrophobic group is present on the outermost surface of a hydrophilic base structure, and in the grease composition, the average particle diameter of the particle (C) is 1 nm to 500 nm.

[0022] The particle (C) imparts an appropriate oil separation degree to the grease composition, and imparts water resistance. The detailed mechanism thereof is not clear, but it can be conjectured as follows.

[0023] It can be conjectured that the hydrophilic nanofiber (B) and the particle (C) form some kind of higher-order structure, and the grease composition has an appropriate oil separation degree and excellent water resistance. In addition, as a result of forming this higher-order structure, it can be considered that even if the content of the hydrophilic nanofiber (B) is small and the content of the particle (C) is small, it is easy to have a moderate working cone penetration.

[0024] Note that in the following description, the "base oil (A)", "hydrophilic nanofiber (B)", and "particle (C)" are also referred to as "component (A)", "component (B)", and "component (C)", respectively.

[0025] In the grease composition of the present embodiment, the total content of the component (A), component (B), and component (C) is preferably 60% by mass or more, more preferably 70% by mass or more, further preferably 80% by mass or more, and more further preferably 90% by mass or more, based on the total amount (100% by mass) of the grease composition. In addition, it is usually 100% by mass or less, preferably less than 100% by mass, more preferably 99% by mass or less, and further preferably 98% by mass or less.

[0026] Note that in the grease composition of the present embodiment, other components than the component (A), component (B), and component (C) can be contained within a range that does not impair the effects of the present application.

[0027] As described later, the "antioxidant (D)", "antirust agent (E)", and "additive (F)" that can be contained in the grease composition of the present embodiment are also referred to as "component (D)", "component (E)", and "component (F)", respectively.

[0028] The total content of the component (A), the component (B), the component (C), the component (D), the component (E), and the component (F) in the grease composition of the present embodiment is preferably 60% by mass or more, more preferably 70% by mass or more, further preferably 80% by mass or more, and more further preferably 90% by mass or more, based on the total amount (100% by mass) of the grease composition. In addition, it is generally 100% by mass or less, preferably less than 100% by mass, more preferably 99% by mass or less, and further preferably 98% by mass or less.

[0029] Note that the grease composition of the present embodiment can contain other components than the component (A), the component (B), the component (C), the component (D), the component (E), and the component (F) within a range not impairing the effects of the present application.

[0030] <Base oil (A)> The grease composition of the present embodiment contains a base oil (A).

[0031] As the base oil (A), one or more selected from the group consisting of mineral oils, synthetic oils, and vegetable oils, for example, can be cited.

[0032] As the mineral oil, for example, atmospheric residue obtained by subjecting paraffin-based crude oil, intermediate-based crude oil, naphthene-based crude oil, or the like to atmospheric distillation; distillate oil obtained by subjecting these atmospheric residues to vacuum distillation; mineral oil obtained by subjecting the distillate oil to one or more of solvent deasphalting, solvent extraction, hydrocracking, solvent dewaxing, contact dewaxing, hydrogenation refining, or the like; wax isomerized mineral oil; and the like can be cited.

[0033] Note that the mineral oil can be used alone as one kind or in combination with two or more kinds.

[0034] As the synthetic oil, for example, hydrocarbon-based oil, aromatic-based oil, ester-based oil, ether-based oil, fatty acid ester, and the like can be cited.

[0035] Note that the synthetic oil can be used alone as one kind or in combination with two or more kinds.

[0036] As the hydrocarbon-based oil, for example, n-paraffin, i-paraffin, polybutene, polyisobutylene, 1-decene oligomer, copolymerization oligomer of 1-decene and ethylene, poly-α-olefin (PAO), and hydrogenated products thereof, and the like can be cited.

[0037] As the aromatic-based oil, for example, alkylbenzene such as monoalkylbenzene and dialkylbenzene; alkyl naphthalene such as monoalkylnaphthalene, dialkylnaphthalene, and polyalkylnaphthalene; and the like can be cited.

[0038] As the ester-based oil, there can be mentioned, for example, dibutyl sebacate, di-2-ethylhexyl sebacate, dioctyl adipate, diisodecyl adipate, di-tridecyl adipate, di-tridecyl glutarate, methyl acetyl ricinoleate, and the like. As the aromatic ester-based oil, there can be mentioned, for example, trioctyl trimellitate, tridecyl trimellitate, and the like. As the polyol ester-based oil, there can be mentioned, for example, trimethylolpropane octanoate, trimethylolpropane nonanoate, pentaerythritol-2-ethylhexanoate, pentaerythritol nonanoate, and the like. As the complex ester-based oil, there can be mentioned, for example, oligoesters formed from a polyhydric alcohol and a mixed fatty acid of a dibasic acid and a monobasic acid, and the like.

[0039] As the ether-based oil, there can be mentioned, for example, polyglycols, polypropylene glycols, polyglycol monoethers, polypropylene glycol monoethers, and the like. As the phenyl ether-based oil, there can be mentioned, for example, monoalkyl triphenyl ethers, alkyl diphenyl ethers, dialkyl diphenyl ethers, penta phenyl ethers, tetraphenyl ethers, monoalkyl tetraphenyl ethers, dialkyl tetraphenyl ethers, and the like.

[0040] As the fatty acid constituting the fatty acid ester, a fatty acid having 8 to 22 carbon atoms is preferred, and specifically, there can be mentioned, for example, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, erucic acid, palmitoleic acid, oleic acid, linoleic acid, linolenic acid, isostearic acid, arachidic acid, ricinoleic acid, 12-hydroxystearic acid, and the like.

[0041] As the specific fatty acid ester, there can be mentioned, for example, glycerin fatty acid esters, polyglycerin fatty acid esters, propylene glycol fatty acid esters, and the like.

[0042] As the glycerin fatty acid ester, there can be mentioned, for example, glycerin monooleate, glycerin monostearate, glycerin monocaprylate, glycerin dioleate, glycerin distearate, glycerin dicaprylate, and the like.

[0043] As the polyglycerin fatty acid ester, for example, diglycerin monooleate, diglycerin monoisostearate, diglycerin dioleate, diglycerin trioleate, diglycerin monostearate, diglycerin distearate, diglycerin tristearate, diglycerin triisostearate, diglycerin mono- octanoate, diglycerin dioctanoate, diglycerin trioctanoate, triglycerin monooleate, triglycerin dioleate, triglycerin trioleate, triglycerin tetraoleate, triglycerin monostearate, triglycerin distearate, triglycerin tristearate, triglycerin tetra- stearate, triglycerin mono-octanoate, triglycerin dioctanoate, triglycerin tri- octanoate, triglycerin tetraoctanoate, diglycerin monooleate monostearate, diglycerin monooleate distearate, diglycerin mono-octanoate monostearate, triglycerin monooleate monostearate, triglycerin dioleate distearate, triglycerin dioleate monostearate, triglycerin monooleate monostearate mono-octanoate, diglycerin monolaurate, diglycerin dilaurate, triglycerin monolaurate, triglycerin trilaurate, triglycerin trilaurate, diglycerin monomyristate, diglycerin dimyristate, triglycerin monomyristate, triglycerin dimyristate, triglycerin trimyristate, diglycerin mono- linoleate, diglycerin dilinoleate, triglycerin monolinoleate, triglycerin dilinoleate, triglycerin trilinoleate, decaglycerin monooleate, decaglycerin monostearate, decaglycerin mono-octanoate monoleate, and the like can be exemplified.

[0044] As the propylene glycol fatty acid ester, for example, propylene glycol monooleate, propylene glycol monostearate, propylene glycol mono-octanoate, propylene glycol monolaurate, and the like can be exemplified.

[0045] <<Vegetable oil (A1)>> The base oil (A) preferably contains a vegetable oil (A1).

[0046] By causing the aforementioned base oil (A) to contain a vegetable oil (A1), it is possible to suppress environmental burden, and it is possible to improve the safety of the grease composition.

[0047] As the vegetable oil (A1), for example, a crude oil obtained by pressing or extracting a natural vegetable oil raw material; a refined oil obtained by performing various refining treatments such as filtration to remove floating impurities contained in the crude oil, degumming to remove phospholipids and the like, deacidification to remove free fatty acids, bleaching to remove pigments, dewaxing to remove wax components, and the like; a processed oil obtained by further performing treatments such as solidification, fractionation, transesterification, hydrogenation, and the like can be exemplified.

[0048] As the vegetable oil (A1), specifically, plant-derived oils, for example, rapeseed oil, peanut oil, corn oil, cottonseed oil, canola oil, soybean oil, camellia oil, olive oil, peanut oil, sunflower oil (preferably high-oleic type), safflower oil (preferably high-oleic type), safflower seed oil (preferably high-oleic type), palm oil, palm kernel oil, coconut oil, rice bran oil, hemp oil, perilla oil, linseed oil, grape seed oil, and the like, plant-derived base oils such as oligomerized lactide, and the like can be exemplified.

[0049] The vegetable oil (A1) can be composed of only one kind of vegetable oil, or can be a mixed vegetable oil composed of two or more kinds of vegetable oils.

[0050] As the fatty acid constituting the vegetable oil (A1), for example, one or more selected from the group consisting of oleic acid, linoleic acid, linolenic acid, palmitic acid, stearic acid, palmitoleic acid, arachidic acid, eicosenoic acid, behenic acid, erucic acid, lauric acid, myristic acid, and the like can be exemplified, and specifically, oleic acid can be exemplified as a representative.

[0051] Note that the "fatty acid constituting the vegetable oil (A1)" refers to the fatty acid in a compound in which the fatty acid constituting the vegetable oil is ester-bonded to glycerol.

[0052] From the viewpoint of further easily improving the oxidation stability of the grease composition, among the fatty acids constituting the vegetable oil (A1), the content of oleic acid is preferably 50% by mass or more, based on the total amount of the constituent fatty acids in the vegetable oil (A1). From the same viewpoint, the content of oleic acid is more preferably 55% by mass or more, further preferably 60% by mass or more, based on the total amount of the constituent fatty acids in the vegetable oil (A1). In addition, the content of oleic acid is usually less than 85% by mass, based on the total amount of the constituent fatty acids in the vegetable oil (A1).

[0053] As a method for measuring the fatty acid composition of the vegetable oil (A1), for example, a method in which a lipid is extracted from the vegetable oil (A1) using an organic solvent, the organic solvent is then distilled off, and then, fatty acid methyl esters are prepared from the obtained lipid, and subjected to gas chromatography mass spectrometry (GC-MS analysis) can be exemplified.

[0054] From the viewpoint of further easily improving the oxidation stability of the grease composition, among the fatty acids constituting the vegetable oil (A1), the content of saturated fatty acids is preferably 3% by mass or more, more preferably 4% by mass or more, further preferably 5% by mass or more, based on the total amount of the constituent fatty acids in the vegetable oil (A1).

[0055] The total content of oleic acid, linoleic acid, and linolenic acid among the fatty acids constituting the vegetable oil (Al) is preferably 50% by mass or more, more preferably 70% by mass or more, and further preferably 80% by mass or more, based on the total amount of the fatty acids constituting the vegetable oil (Al) described above.

[0056] The content of erucic acid among the fatty acids constituting the vegetable oil (Al) is preferably 0% to 45% by mass, more preferably 1% to 35% by mass, and further preferably 2% to 20% by mass, based on the total amount of the fatty acids constituting the vegetable oil (Al) described above.

[0057] The content of the vegetable oil (Al) is appropriately adjusted depending on the composition of the vegetable oil (Al). For example, the content of the vegetable oil (Al) is 10% by mass or more, 20% by mass or more, 30% by mass or more, 40% by mass or more, 50% by mass or more, 60% by mass or more, 70% by mass or more, 80% by mass or more, 90% by mass or more, or 100% by mass, based on the total amount of the base oil (A).

[0058] The kinematic viscosity at 40°C of the base oil (A) used in the present embodiment is preferably 10 mm 2 / s or more, more preferably 20 mm 2 / s or more, further preferably 30 mm 2 / s or more, more further preferably 35 mm 2 / s or more.

[0059] In addition, the kinematic viscosity at 40°C of the base oil (A) of the present embodiment is preferably 120 mm 2 / s or less, more preferably 100 mm 2 / s or less, further preferably 90 mm 2 / s or less, more further preferably 80 mm 2 / s or less.

[0060] The upper limit value and the lower limit value of these numerical ranges can be combined arbitrarily. Specifically, it is preferable that the kinematic viscosity at 40°C of the base oil (A) be 10 to 120 mm 2 / s, more preferably 20 to 100 mm 2 / s, further preferably 30 to 90 mm 2 / s, more further preferably 35 to 80 mm 2 / s.

[0061] The kinematic viscosity at 100°C of the base oil (A) used in the present embodiment is preferably 2.0 mm 2 / s or more, more preferably 3.0 mm 24.0 mm or more, further preferably 4.0 mm or more 2 4.0 mm or more.

[0062] Further, from the viewpoint of easily exerting the effects of the present application, the kinematic viscosity at 100°C of the base oil (A) of the present embodiment is preferably 20 mm 2 18 mm or less, more preferably 18 mm or less 2 16 mm or less, further preferably 16 mm or less 2 18 mm or less.

[0063] The upper limit value and the lower limit value of these numerical ranges can be combined arbitrarily. Specifically, 2.0 to 20 mm 2 3.0 to 18 mm, more preferably 2 4.0 to 16 mm, further preferably 2 18 mm.

[0064] Note that the base oil (A) used in the present embodiment can use a mixed base oil in which a high-viscosity base oil and a low-viscosity base oil are combined and the kinematic viscosity is adjusted to the above range.

[0065] As the viscosity index of the base oil (A) used in the present embodiment, from the viewpoint of easily exerting the effects of the present application, it is preferably 90 or more, more preferably 110 or more, further preferably 130 or more.

[0066] Note that in the present specification, the kinematic viscosity and the viscosity index of the base oil (A) refer to values measured or calculated according to JIS K 2283:2000.

[0067] In the grease composition of the present embodiment, the content of the base oil (A) is preferably 50% by mass or more, more preferably 60% by mass or more, further preferably 70% by mass or more, and more further preferably 80% by mass or more, based on the total amount (100% by mass) of the grease composition. In addition, the content of the base oil (A) is preferably 100% by mass or less, more preferably 98% by mass or less, further preferably 97% by mass or less, and more further preferably 95% by mass or less, based on the total amount (100% by mass) of the grease composition.

[0068] <Hydrophilic nanofiber (B)> The hydrophilic nanofiber refers to a fiber-like substance having a thickness of 500 nm or less, which is composed of a forming material containing a compound having hydrophilicity, and is distinguished from a particulate substance.

[0069] The hydrophilic nanofiber (B) has low environmental burden and excellent human safety. Therefore, by containing the hydrophilic nanofiber (B), it is possible to suppress the environmental burden and improve the safety of the grease composition.

[0070] ("Hydrophilic" Judgment Criteria) Whether or not the nanofiber is "hydrophilic" is judged as follows.

[0071] The nanofiber (fibrous material) to be the subject is molded into a sheet, and a water droplet is added to the surface of the sheet. At this time, (1) when the contact angle with water is 90° or less, or (2) when the added water droplet is rapidly absorbed by the sheet, the nanofiber is judged to be "hydrophilic".

[0072] ("Thickness" of Hydrophilic Nanofiber) Further, the "thickness" of the hydrophilic nanofiber is defined the same as the related definition of the thickness of a general fibrous material.

[0073] Specifically, in a cross section when the tangent direction with respect to an arbitrary point on the side surface of the hydrophilic nanofiber is vertically cut, if the cross section is a circle or an ellipse, the diameter or the major diameter is the "thickness" of the hydrophilic nanofiber. If the cross section is a polygon, the diameter of the circumscribed circle of the polygon is the "thickness" of the hydrophilic nanofiber.

[0074] When a hydrophilic compound having a size of several μm or more in a flaky, powdery, or particulate shape is compounded into a base oil as a thickening agent, the hydrophilic compound is aggregated in the base oil, and a so-called "lump" is easily formed. As a result, the aggregate of the hydrophilic compound is precipitated on the surface of the obtained grease composition, and the dispersion state is easily non-uniform. In this case, in order to increase the working cone penetration of the obtained grease composition, a large amount of the hydrophilic compound needs to be added. However, since particles larger than the oil film thickness are contained, a grease composition having poor wear resistance is formed.

[0075] On the other hand, in the grease composition of the present application, since a hydrophilic nanofiber having a thickness (d) of 1 nm to 500 nm is compounded into a base oil, the hydrophilic nanofiber is not aggregated in the base oil, and the hydrophilic nanofiber is uniformly dispersed and a high-order structure is formed using the hydrophilic nanofiber. As a result, a grease composition having a moderate working cone penetration can be produced even with a small amount of the hydrophilic nanofiber.

[0076] (Thickness (d) and Aspect Ratio of Hydrophilic Nanofiber) In the present application, the "thickness (d) of the hydrophilic nanofiber" indicates the thickness of the hydrophilic nanofiber dispersed in the base oil, and is distinguished from the "thickness (d') of the hydrophilic nanofiber" as a raw material before being compounded into the base oil described later.

[0077] The "thickness (d) of the hydrophilic nanofiber dispersed in the base oil" is almost the same as the "thickness (d') of the hydrophilic nanofiber as a raw material before compounding into the base oil". Therefore, the "thickness (d) of the hydrophilic nanofiber dispersed in the base oil" and the "thickness (d') of the hydrophilic nanofiber as a raw material before compounding into the base oil" can be regarded as substantially the same.

[0078] The thickness (d) of the hydrophilic nanofiber dispersed in the base oil is 1 nm to 500 nm, preferably 3 nm to 300 nm, more preferably 5 nm to 200 nm, further preferably 10 nm to 100 nm, more further preferably 15 nm to 70 nm, and still further preferably 20 nm to 50 nm, from the viewpoint of forming a higher-order structure using the hydrophilic nanofiber in the base oil and the viewpoint of more uniformly dispersing the hydrophilic nanofiber.

[0079] Note that, with respect to the hydrophilic nanofiber contained in the grease composition of the present application, a hydrophilic nanofiber having a thickness (d) outside the above range can be dispersed, provided that the dispersion of at least a hydrophilic nanofiber having a thickness (d) within the above range is confirmed.

[0080] In the grease composition of one embodiment of the present application, the average value of the thickness (d) of 10 hydrophilic nanofibers arbitrarily selected from among the hydrophilic nanofibers dispersed in the base oil is 1 nm to 500 nm, preferably 3 nm to 300 nm, more preferably 5 nm to 200 nm, further preferably 10 nm to 100 nm, more further preferably 15 nm to 70 nm, and still further preferably 20 nm to 50 nm, from the viewpoint of forming a higher-order structure using the hydrophilic nanofiber in the base oil and the viewpoint of more uniformly dispersing the hydrophilic nanofiber.

[0081] In addition, from the above viewpoints, the number of hydrophilic nanofibers having a thickness (d) within the above range is preferably one or more (more preferably five or more, and further preferably seven or more) in 10 arbitrarily selected from among the hydrophilic nanofibers contained in the grease composition of the present application, and more preferably the thickness (d) of all of the 10 arbitrarily selected hydrophilic nanofibers is within the above range.

[0082] In the grease composition of one embodiment of the present application, the aspect ratio of the hydrophilic nanofiber is preferably 5 or more, more preferably 10 or more, further preferably 15 or more, more further preferably 30 or more, and still further preferably 50 or more.

[0083] In the present specification, the "aspect ratio" means the ratio of the length of the hydrophilic nanofiber as an observation object to the thickness (length / thickness). The "length" of the hydrophilic nanofiber means the distance between the two points farthest apart in the hydrophilic nanofiber.

[0084] In addition, when a part of the hydrophilic nanofiber as an observation object is in contact with other hydrophilic nanofibers and it is difficult to determine the "length", only the length of the part for which the thickness can be measured is measured among the hydrophilic nanofibers as observation objects, as long as the aspect ratio of the part is in the above range.

[0085] Further, the average value of the aspect ratios of 10 arbitrarily selected hydrophilic nanofibers (hereinafter also referred to as "average aspect ratio") is preferably 5 or more, more preferably 10 or more, further preferably 15 or more, more further preferably 30 or more, and still more further preferably 50 or more.

[0086] (Thickness (d') and aspect ratio of hydrophilic nanofiber) The thickness (d') of the hydrophilic nanofiber as a raw material before mixing with the base oil is 1 nm to 500 nm, preferably 3 nm to 300 nm, more preferably 5 nm to 200 nm, further preferably 10 nm to 100 nm, more further preferably 15 nm to 70 nm, and still more further preferably 20 nm to 50 nm.

[0087] In addition, the average aspect ratio of the hydrophilic nanofiber as a raw material before mixing with the base oil is preferably 5 or more, more preferably 10 or more, further preferably 15 or more, more further preferably 30 or more, and still more further preferably 50 or more.

[0088] Note that in the present specification, the "thickness (d)" of the hydrophilic nanofiber dispersed in the base oil and the "thickness (d')" of the hydrophilic nanofiber as a raw material before compounding in the base oil, and the aspect ratios of these hydrophilic nanofibers are values measured using an electron microscope or the like.

[0089] (Forming material of hydrophilic nanofiber) The hydrophilic nanofiber used in one embodiment of the present application can be composed of a forming material containing a compound having hydrophilicity. As the compound having hydrophilicity, a compound having a functional group such as a hydroxyl group or an amino group having a hydrogen-bonding hydroxyl group, a metal oxide, or the like can be given.

[0090] Among them, from the viewpoint of making a grease composition with low environmental burden in production and excellent human body safety, and the viewpoint of making good affinity with base oil, as the hydrophilic nanofiber used in one embodiment of the present application, it is preferable to contain polysaccharides, more preferable to contain one or more polysaccharides selected from the group consisting of cellulose, carboxymethyl cellulose, chitin, and chitosan, further preferable to contain cellulose, and more further preferable to be cellulose nanofiber.

[0091] As a raw material of the cellulose nanofiber, lignocellulose can also be used. It is known that lignocellulose is a complex hydrocarbon polymer constituting a plant cell wall, and is mainly composed of cellulose and hemicellulose which are polysaccharides, and lignin which is an aromatic polymer. The cellulose constituting the cellulose nanofiber can be one or more selected from the group consisting of lignocellulose and acetylated lignocellulose. In addition, the cellulose nanofiber can contain one or more selected from the group consisting of hemicellulose and lignin. Furthermore, the cellulose constituting the cellulose nanofiber can be chemically bonded to one or more selected from the group consisting of hemicellulose and lignin.

[0092] In addition, the hydrophilic nanofiber used in one embodiment of the present application can use a substance in which a modification treatment is performed on the surface thereof.

[0093] More specifically, a hydrophilic nanofiber in which one or more modification treatments selected from the group consisting of esterification such as acetylation, phosphorylation, carbamoylation, urea formation, etherification, carboxymethylation, TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl) oxidation, and periodate oxidation are performed on the surface of the hydrophilic nanofiber can also be used.

[0094] In the hydrophilic nanofiber used in one embodiment of the present application, the content of the polysaccharide is preferably 60% by mass or more and 100% by mass or less, more preferably 70% by mass or more and 100% by mass or less, further preferably 80% by mass or more and 100% by mass or less, and more further preferably 90% by mass or more and 100% by mass or less, based on the total amount of the hydrophilic nanofiber (100% by mass).

[0095] The degree of polymerization of the polysaccharide is preferably 50 or more and 3,000 or less, more preferably 100 or more and 1,500 or less, further preferably 150 or more and 1,000 or less, and more further preferably 200 or more and 800 or less.

[0096] Note that in the present application, the degree of polymerization of the polysaccharide macromolecule refers to a value measured by a viscosity method.

[0097] (Content of hydrophilic nanofiber) The content of the hydrophilic nanofiber (B) in the grease composition of one embodiment of the present application is preferably from 0.1% by mass to 15% by mass, more preferably from 0.5% by mass to 13% by mass, further preferably from 0.7% by mass to 10% by mass, more further preferably from 1.0% by mass to 8.0% by mass, and still further preferably from 1.5% by mass to 6.0% by mass, relative to the total amount (100% by mass) of the grease composition.

[0098] If the content of the hydrophilic nanofiber (B) is 0.1% by mass or more, it is easy to produce a grease composition having a moderate working cone penetration. In addition, if the content of the hydrophilic nanofiber (B) is 20% by mass or less, it is easy to produce a grease composition.

[0099] <Particle (C)> The grease composition of the present embodiment contains a particle (C).

[0100] The particle (C) has a structure in which a hydrophobic group is present on the outermost surface of a hydrophilic base structure, and in the grease composition, the average particle diameter of the particle (C) is from 1 nm to 500 nm.

[0101] By containing the particle (C) in the grease composition of the present embodiment, it is possible to provide a grease composition having an appropriate oil separation degree and excellent water resistance, even though a hydrophilic nanofiber is used.

[0102] The average particle diameter (average particle diameter of primary particles) of the particle (C) is preferably from 3 nm to 400 nm, and more preferably from 5 nm to 300 nm.

[0103] The average particle diameter of the particle (C) can be measured, for example, from an image of primary particles obtained by observing the grease composition with an electron microscope.

[0104] The hydrophilic base structure possessed by the particle (C) is not particularly limited as long as it makes it possible to control the particle (C) to have an average particle diameter in the above range, and is not particularly limited as long as the material constituting it is a hydrophilic material.

[0105] Here, from the viewpoint of satisfying the average particle diameter of from 1 nm to 500 nm, as the hydrophilic material constituting the hydrophilic base structure of the particle (C), a mineral material such as bentonite, a metal oxide material such as silicon dioxide and alumina can be given.

[0106] Among these, from the viewpoint of improving the effects of the present application, silicon dioxide is preferable, and fumed silica is more preferable.

[0107] Further, as the hydrophobic group possessed by the particle (C), there is no particular limitation as long as it is a hydrophobic group capable of bonding to the most surface of the hydrophilic base structure.

[0108] For example, when the material constituting the hydrophilic base structure is silica, the silica preferably has one or more hydrophobic groups selected from the group consisting of dimethylsilyl group, trimethylsilyl group, and dimethylpolysiloxane. These hydrophobic groups can be formed on the surface of the silica by surface treatment of the silica with one or more surface treatment agents selected from the group consisting of dimethyldicyclo silane, hexamethyldisilazane, and silicone oil.

[0109] As the particle (C), as a more preferable mode, fumed silica preferably has one or more (preferably dimethylsilyl group) hydrophobic groups selected from the group consisting of dimethylsilyl group, trimethylsilyl group, and dimethylpolysiloxane. These substituents can be formed on the surface of the fumed silica by surface treatment of the fumed silica with one or more surface treatment agents (preferably dimethyldicyclosilane) selected from the group consisting of dimethyldicyclosilane, hexamethyldisilazane, and silicone oil.

[0110] As the particle (C), for example, Aerosil (registered trademark) series (Aerosil (registered trademark) R972, R974, R9200, R976, R976S, NX130, RY200S, R202, RX200, R8200, RY200, RY200L, RX300, R812, R812S, RY300) manufactured by EVONIK Co., Ltd., HDK (registered trademark) series (HDK (registered trademark) H15, H15P, H17, H18, H20, H30, H2000) manufactured by Wacker Asahikasei Silicone Co., Ltd., and the like can be suitably used.

[0111] The particle (C) can be used alone or in combination with two or more.

[0112] The content of the particle (C) is preferably 6.0% by mass or more, more preferably 6.5% by mass or more, further preferably 7.0% by mass or more, and still further preferably 10.0% by mass or more, and is preferably 20.0% by mass or less, more preferably 18.0% by mass or less, and further preferably 16.0% by mass or less, based on the total amount (100% by mass) of the grease composition.

[0113] <Antioxidant (D)> The grease composition of the present embodiment can contain an antioxidant (D).

[0114] When the base oil (A) in the grease composition of the present embodiment contains the vegetable oil (A1), the oxidation stability of the grease composition can be improved by causing the grease composition to also contain the antioxidant (D).

[0115] As the antioxidant (D), for example, a phenol-based antioxidant (D1), a naphthylamine-based antioxidant (D2), a diphenylamine-based antioxidant (D3), and the like can be exemplified.

[0116] Among these, from the viewpoint of improving the antioxidant effect, the phenol-based antioxidant (D1) and the naphthylamine-based antioxidant (D2) are preferable.

[0117] <<Phenol-based antioxidant (D1)>> As the phenol-based antioxidant (D1), a phenol-based antioxidant not containing phosphorus that is generally used as an antioxidant for a lubricating oil composition can be used.

[0118] The phenol-based antioxidant (D1) can be used alone or in combination with two or more kinds.

[0119] From the viewpoint of further easily improving the effects of the present application, the phenol-based antioxidant (D1) preferably contains a compound (D1-1) represented by the following general formula (d1-1).

[0120] From the same viewpoint, the content of the compound (D1-1) in the phenol-based antioxidant (D1) is preferably 50% by mass or more and 100% by mass or less, more preferably 60% by mass or more and 100% by mass or less, further preferably 70% by mass or more and 100% by mass or less, more further preferably 80% by mass or more and 100% by mass or less, still further preferably 90% by mass or more and 100% by mass or less, and yet further preferably 95% by mass or more and 100% by mass or less, based on the total amount of the phenol-based antioxidant (D1).

[0121] [Chemical Formula 1] In the above general formula (d1-1), R d1 is an alkylene group having 1 to 5 carbon atoms.

[0122] From the viewpoint of more easily improving the effects of the present application, the number of carbon atoms of the alkylene group that can be selected as R d1 is preferably 1 to 4, more preferably 1 to 3, and further preferably 1 to 2.

[0123] As a specific example of the alkylene group that can be selected as R d1 , straight-chain alkylene groups such as a methylene group, an ethylene group, a n-propylene group, a n-butylene group, and a n-pentylene group; branched-chain alkylene groups such as an i-propylene group, an i-butylene group, a sec-butylene group, a t-butylene group, an i-pentylene group, and a neo-pentylene group; and the like can be exemplified.

[0124] In the above general formula (d1-1), R d2 is an alkyl group having 1 to 25 carbon atoms.

[0125] From the viewpoint of more easily improving the effects of the present application, the number of carbon atoms of the alkyl group that can be selected as R d2 is preferably 2 or more, more preferably 4 or more, and further preferably 6 or more. In addition, it is preferably 22 or less, more preferably 21 or less, and further preferably 20 or less. The upper limit value and the lower limit value of these numerical ranges can be combined arbitrarily. Specifically, it is preferably 2 to 20, more preferably 4 to 15, and further preferably 6 to 10.

[0126] As a specific example of the alkyl group that can be selected as R d2 , a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, a decyl group, a undecyl group, a dodecyl group, a tridecyl group, a tetradecyl group, a pentadecyl group, a hexadecyl group, a heptadecyl group, an octadecyl group, a nonadecyl group, an icosyl group, a hendecyl group, a docosyl group, a tricosyl group, a tetracosyl group, a pentacosyl group, and the like can be given. They can be linear or branched.

[0127] The compound (D1-1) can be used alone as one kind, or two or more kinds can be used in combination.

[0128] <<Naphthylamine-based antioxidant (D2)>> As the naphthylamine-based antioxidant (D2), a naphthylamine-based antioxidant that is generally used as an antioxidant for a lubricating oil composition can be used.

[0129] The naphthylamine-based antioxidant (D2) can be used alone as one kind, or two or more kinds can be used in combination.

[0130] As the naphthylamine-based antioxidant (D2), it can be unsubstituted or can have a substituent such as an alkyl group.

[0131] As the naphthylamine-based antioxidant (D2), from the viewpoint of more easily improving the effects of the present application, a compound (D2-1) represented by the following general formula (d2-1) is preferably contained.

[0132] From the same viewpoint, the content of the compound (D2-1) in the naphthylamine-based antioxidant (D2) is preferably 50% by mass or more, more preferably 60% by mass or more, further preferably 70% by mass or more, more further preferably 80% by mass or more, still more further preferably 90% by mass or more, and yet more further preferably 95% by mass or more, based on the total amount of the naphthylamine-based antioxidant (D2).

[0133] [Chemical 2] In General Formula (d2-1) above, R b1 is an alkyl group having 1 to 30 carbon atoms.

[0134] If the alkyl group has 1 to 30 carbon atoms, the effect of the present application is more easily improved.

[0135] From the viewpoint of more easily improving the effect of the present application, the number of carbon atoms of the alkyl group that can be selected as R b1 is each independently preferably 1 to 20, more preferably 4 to 16, and further preferably 4 to 14.

[0136] As specific examples of the alkyl group that can be selected as R b1 , the groups exemplified as the alkyl group that can be selected as R a1 and R a2 can be given. The alkyl group can be linear or branched.

[0137] In General Formula (d2-1) above, nb1 is an integer of 0 to 5.

[0138] From the viewpoint of more easily improving the effect of the present application, nb1 is preferably 0 or 1.

[0139] The compound (D2-1) can be used alone or in combination with two or more kinds.

[0140] <<Diphenylamine-based antioxidant (D3)>> As the diphenylamine-based antioxidant (D3), a diphenylamine-based antioxidant that is generally used as an antioxidant for lubricating oil compositions can be used.

[0141] The diphenylamine-based antioxidant (D3) can be used alone or in combination with two or more kinds.

[0142] From the viewpoint of more easily improving the effect of the present application, the diphenylamine-based antioxidant (D3) preferably contains a compound (D3-1) represented by General Formula (d3-1) below.

[0143] From the same viewpoint, the content of the compound (D3-1) in the diphenylamine-based antioxidant (D3) is preferably 50% by mass or more and 100% by mass or less, more preferably 60% by mass or more and 100% by mass or less, further preferably 70% by mass or more and 100% by mass or less, more further preferably 80% by mass or more and 100% by mass or less, still further preferably 90% by mass or more and 100% by mass or less, yet further preferably 95% by mass or more and 100% by mass or less, based on the total amount of the diphenylamine-based antioxidant (D3).

[0144] [Chemical Formula 3] In General Formula (d3-1) above, R a1 and R a2 each independently is an alkyl group having 1 to 30 carbon atoms.

[0145] If the alkyl group has 1 to 30 carbon atoms, the effect of the present application is easily improved.

[0146] From the viewpoint of more easily improving the effect of the present application, the number of carbon atoms of the alkyl group that can be selected as R a1 and R a2 is preferably independently 1 to 20, more preferably 4 to 16, and further preferably 4 to 14.

[0147] As specific examples of the alkyl group that can be selected as R a1 and R a2 , there can be mentioned methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, nonadecyl, eicosyl, heneicosyl, docosyl, tricosyl, tetracosyl, pentacosyl, hexacosyl, heptacosyl, octacosyl, nonacosyl, and tricontyl. They can be linear or branched.

[0148] In General Formula (d3-1) above, na1and na2are each independently an integer of 1 to 5.

[0149] From the viewpoint of more easily improving the effect of the present application, na1and na2are each independently preferably 1 to 3, more preferably 1 to 2, and further preferably 1.

[0150] The compound (D3-1) can be used alone or in combination of two or more.

[0151] The content of the antioxidant (D) is preferably 0.8% by mass or more, more preferably 1.0% by mass or more, further preferably 1.5% by mass or more, more further preferably 3.0% by mass or more, and still more further preferably 5.0% by mass or more, and is preferably 10% by mass or less, more preferably 9.0% by mass or less, and further preferably 8.0% by mass or less, based on the total amount (100% by mass) of the grease composition.

[0152] <Antirust agent (E)> The grease composition of the present embodiment can contain an antirust agent (E).

[0153] The grease composition of the present embodiment contains the hydrophilic nanofiber (B), and the hydrophilic nanofiber (B) is liable to absorb moisture due to high hydrophilicity, and sometimes rusts. Thus, by including the rust preventive (E) in the grease composition of the present embodiment, it is possible to improve the rust resistance of the grease composition.

[0154] As the rust preventive (E), for example, fatty acid soaps, carboxylic acid-based rust preventives, carboxylate-based rust preventives, metal sulfonates, organic phosphorous acid esters, organic phosphoric acid esters, amine salts of organic phosphoric acid esters, metal salts of organic phosphoric acid esters, alkenyl succinic acid esters, polyhydric alcohol esters of alkenyl succinic acid, amine-based rust preventives, fatty acid amines, thiadiazoles and derivatives thereof, benzotriazoles and derivatives thereof, and the like can be exemplified.

[0155] The rust preventive (E) can be used alone as one kind, or two or more kinds can be used in combination.

[0156] Among these, fatty acid soaps, amine salts of organic phosphoric acid esters, and metal sulfonates are preferable.

[0157] As the fatty acid soaps, there is no particular limitation, and for example, zinc salts of fatty acids, aluminum salts of fatty acids, calcium salts of fatty acids, magnesium salts of fatty acids, and the like can be exemplified.

[0158] Among these, zinc salts of fatty acids are preferable.

[0159] As the zinc salt of fatty acid, the number of carbon atoms is preferably 4 to 30, more preferably 6 to 24, and further preferably 8 to 20.

[0160] As the zinc salt of fatty acid, for example, zinc stearate, zinc neodecanoate, and the like can be exemplified.

[0161] As the amine salt of organic phosphoric acid ester, there is no particular limitation, and for example, organic phosphoric acid ester amine salts having a hydrocarbon group with a number of carbon atoms of 1 to 30, and the like can be exemplified. As the number of carbon atoms of the organic phosphoric acid ester amine salt, 4 to 24 is preferable, and 8 to 18 is more preferable.

[0162] The metal sulfonate is a metal salt of various sulfonic acids. As the various sulfonic acids forming the metal sulfonate, aromatic petroleum sulfonic acids, alkyl sulfonic acids, aryl sulfonic acids, alkyl aryl sulfonic acids, and the like can be exemplified, and more specifically, dodecylbenzenesulfonic acid, dilauryl cetylbenzenesulfonic acid, paraffin wax-substituted benzenesulfonic acid, polyolefin-substituted benzenesulfonic acid, polyisobutylene-substituted benzenesulfonic acid, naphthalenesulfonic acid, dinonyl naphthalenesulfonic acid, and the like can be preferably exemplified.

[0163] As the metal forming the metal sulfonate, sodium, magnesium, calcium, zinc, barium, and the like can be preferably exemplified.

[0164] There is no particular limitation on the base value of these, and they can be neutral or overbased.

[0165] As the rust preventive agent (E), a zinc salt of a fatty acid and an amine salt of an organic phosphoric acid ester are preferably contained together. As the zinc salt of a fatty acid to be used in combination with the amine salt of an organic phosphoric acid ester, for example, zinc stearate, zinc neodecanoate, and the like can be exemplified.

[0166] When the zinc salt of a fatty acid and the amine salt of an organic phosphoric acid ester are used together, as the total content of the zinc salt of a fatty acid and the amine salt of an organic phosphoric acid ester, from the viewpoint of rust prevention, it is preferable that it be 0.1 to 10.0 mass%, more preferable that it be 0.3 to 8.0 mass%, further preferable that it be 0.4 to 5.0 mass%, still further preferable that it be 0.5 to 3.0 mass%, and yet further preferable that it be 0.8 to 1.5 mass%.

[0167] When the zinc salt of a fatty acid and the amine salt of an organic phosphoric acid ester are used together, as the ratio of the zinc salt of a fatty acid to the amine salt of an organic phosphoric acid ester, it is preferable that it be 1 / 9 to 9 / 1, more preferable that it be 3 / 7 to 8 / 2, and further preferable that it be 5 / 5 to 7 / 3.

[0168] As the content of the rust preventive agent (E), it is preferable that it be 0.1 to 10.0 mass%, more preferable that it be 0.3 to 8.0 mass%, further preferable that it be 0.4 to 5.0 mass%, still further preferable that it be 0.5 to 3.0 mass%, and yet further preferable that it be 0.8 to 2.0 mass%, based on the total amount (100 mass%) of the grease composition.

[0169] <Additive (F)> In the grease composition of the present embodiment, an additive (F) that is ordinarily blended into a grease composition can be further contained within a range that does not impair the effects of the present application.

[0170] As the additive (F), for example, a dispersant, a lubricity improver, a thickening agent, a detergent dispersant, a preservative, an extreme pressure agent, a metal deactivator, and the like can be exemplified.

[0171] Note that these various additives can be used singly in one kind or in combination in two or more kinds.

[0172] (Dispersant) As the dispersant, any solvent that is compatible with both water and oil can be used, and for example, one or more kinds selected from among aprotic polar solvents such as N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), and N-methylpyrrolidone (NMP); alcohols such as propanol, ethylene glycol, propylene glycol, and hexylene glycol; surfactants such as polyglycerin fatty acid ester, sucrose fatty acid ester, citric acid monoglyceride, diacetyl tartaric acid monoglyceride, polyoxyethylene sorbitan ester, and sorbitan ester can be exemplified.

[0173] Specifically, for example, sorbitan trioleate, succinic acid half ester, urea, various surfactants, and the like can be cited.

[0174] The grease composition of one embodiment contains a dispersant. The content of the dispersant is preferably 0.01 mass% to 20 mass%, more preferably 0.1 mass% to 10 mass%, and further preferably 0.2 mass% to 5 mass% relative to the total amount of the grease composition (100 mass%).

[0175] (Lubricity improver) As the lubricity improver, for example, sulfur compounds (sulfurized fats, sulfurized olefins, polythioethers, sulfurized mineral oil, thiophosphoric acid compounds such as triphenyl phosphorothioate, thiocarbamic acid compounds, thioterpene compounds, thiodialkyl dipyridine compounds, and the like), phosphoric acid esters, phosphorous acid esters (tricresyl phosphate, triphenyl phosphite, and the like), and the like can be cited.

[0176] The grease composition of one embodiment contains a lubricity improver. The content of the lubricity improver is preferably 0.01 mass% to 20 mass%, more preferably 0.1 mass% to 10 mass%, and further preferably 0.2 mass% to 5 mass% relative to the total amount of the grease composition (100 mass%).

[0177] (Thickening agent) The thickening agent is a substance that increases the viscosity of the aforementioned base oil as needed, and is compounded in order to adjust the base oil containing the thickening agent to an appropriate kinematic viscosity.

[0178] As the thickening agent, for example, polymethacrylate (PMA), olefin copolymer (OCP), polyalkylstyrene (PAS), styrene-diene copolymer (SCP), and the like can be cited.

[0179] The grease composition of one embodiment contains a thickening agent. The content of the thickening agent is preferably 0.01 mass% to 20 mass%, more preferably 0.1 mass% to 10 mass%, and further preferably 0.2 mass% to 5 mass% relative to the total amount of the grease composition (100 mass%).

[0180] (Detergent dispersant, preservative, extreme pressure agent, metal deactivator) As the detergent dispersant, for example, succinimide, boron succinimide, and the like can be cited.

[0181] As the preservative, for example, benzotriazole compounds, thiazole compounds, and the like can be cited.

[0182] As the extreme pressure agent, for example, phosphorus compounds, zinc dithiophosphate, organic molybdenum, and the like can be cited.

[0183] As the metal inactivator, for example, benzotriazole and the like can be exemplified.

[0184] When the grease composition of the present embodiment contains these additives, each content of these additives is preferably 0.01 to 20 mass%, more preferably 0.1 to 10 mass%, further preferably 0.2 to 5 mass%, based on the total amount (100 mass%) of the grease composition.

[0185] [Properties of the grease composition] In the grease composition of the present embodiment, the hydrophilic group of the hydrophilic nanofiber (B) is protected by the particle (C), and thus the hydrophilic nanofiber (B) is pseudo-hydrophobized. Therefore, the grease composition of the present embodiment has an appropriate oil separation degree, and also has excellent water resistance.

[0186] In addition, the grease composition of the present embodiment easily forms a high-order structure using the hydrophilic nanofiber (B), and the hydrophilic nanofiber (B) is uniformly dispersed in the base oil (A). In addition, the particle (C) is also uniformly dispersed in the base oil (A). Therefore, the grease composition of the present embodiment easily has a moderate working cone penetration, even if the content of the hydrophilic nanofiber (B) and the particle (C) is small.

[0187] [Properties of the grease composition] <Working cone penetration> The working cone penetration of the grease composition of the present embodiment at 25°C is preferably 220 to 430, more preferably 240 to 400, further preferably 250 to 345, more further preferably 255 to 300, and still further preferably 265 to 295, from the viewpoints of pressure delivery and suppression of oil leakage.

[0188] Note that, in the present specification, the working cone penetration of the grease composition refers to a value measured at 25°C in accordance with JIS K2220:2013 (Article 7).

[0189] <Oil separation degree> The grease composition of the present embodiment can be evaluated for the oil separation degree by the method described in the Examples below.

[0190] From the viewpoint of suppressing oil leakage during use, the oil separation degree of the grease composition of the present embodiment is preferably 10 mass% or less, more preferably 8.0 mass% or less, further preferably 7.0 mass% or less, and preferably 0.5 mass% or more, more preferably 0.8 mass% or more, further preferably 1.0 mass% or more.

[0191] Note that in the present specification, the oil separation degree of the grease composition refers to a value measured under the conditions of temperature: 100°C, time: 24 hours, according to the oil separation degree test method of JIS K2220:2013 (Article 11).

[0192] <Water washing water tolerance> The grease composition of the present embodiment can evaluate the water tolerance by measuring the water washing water tolerance using the method described in the Examples below.

[0193] From the viewpoint of water tolerance, the water washing water tolerance of the grease composition of the present embodiment is preferably 10 mass% or less, more preferably 9.0 mass% or less, and further preferably 8.0 mass% or less.

[0194] Note that in the present specification, the water washing water tolerance of the grease composition refers to a value measured under the conditions of using 79°C water, according to the water washing durability test of JIS K2220:2013 (Article 16).

[0195] <Oxidation stability> The grease composition of the present embodiment can evaluate the oxidation stability by measuring the oxidation stability using the method described in the Examples below.

[0196] From the viewpoint of oxidation stability, the oxidation stability of the grease composition of the present embodiment is preferably 80 or less, more preferably 75 or less, and further preferably 70 or less.

[0197] Note that in the present specification, the oxidation stability of the grease composition refers to a value measured under the conditions of temperature: 99°C, time: 100 hours, oxygen pressure: 750 kPa, according to the oxidation stability test of JIS K2220:2013 (Article 12).

[0198] <Bearing rust prevention test> The grease composition of the present embodiment can evaluate the rust prevention property by performing the bearing rust prevention test using the method described in the Examples below.

[0199] From the viewpoint of rust prevention property, the grease composition of the present embodiment preferably does not show discoloration (rusting) in a reddish-brown or black color on the surface when evaluated using the method described in the Examples below.

[0200] Note that in the present specification, the rust prevention property of the grease composition refers to a value evaluated under the conditions of temperature: 52°C, time: 48 hours, according to the bearing rust prevention test of ASTM D 1743.

[0201] [Method for producing grease composition] The grease composition manufacturing method of the present embodiment preferably has the following steps (1) to (3).

[0202] • Step (1): a step of mixing an aqueous dispersion of hydrophilic nanofibers having a roughness (d') of 1 nm to 500 nm, preferably 3 nm to 300 nm, more preferably 5 nm to 200 nm, further preferably 10 nm to 100 nm, more further preferably 15 nm to 70 nm, still further preferably 20 nm to 50 nm, mixed in water, a base oil, and a dispersant, to prepare a mixed solution.

[0203] • Step (2): a step of removing water from the aforementioned mixed solution to prepare a grease.

[0204] • Step (3): a step of mixing the aforementioned particles (C) into the aforementioned grease.

[0205] Note that Step (2) can be a step of removing water and the aforementioned dispersant from the aforementioned mixed solution.

[0206] Regarding the grease composition obtained through such steps, the aggregation of the hydrophilic nanofibers in the base oil is inhibited, and the hydrophilic nanofibers having a roughness (d) of 1 nm to 500 nm, preferably 3 nm to 300 nm, more preferably 5 nm to 200 nm, further preferably 10 nm to 100 nm, more further preferably 15 nm to 70 nm, still further preferably 20 nm to 50 nm, are dispersed while maintaining the fiber shape. As a result, it is presumed that in the base oil, the hydrophilic nanofibers and the particles (C) form some kind of high-order structure, and a grease composition having a moderate oil separation degree and excellent water resistance is prepared.

[0207] Hereinafter, Steps (1) to (3) will be described.

[0208] <Step (1)> Step (1) is a step of mixing an aqueous dispersion of hydrophilic nanofibers having a roughness (d') of 1 nm to 500 nm, preferably 3 nm to 300 nm, more preferably 5 nm to 200 nm, further preferably 10 nm to 100 nm, more further preferably 15 nm to 70 nm, still further preferably 20 nm to 50 nm, mixed in water, a base oil, and a dispersant, to prepare a mixed solution.

[0209] The details of the hydrophilic nanofibers and the base oil used in Step (1) are as described above.

[0210] Note that the "thickness (d')" mentioned here, as described above, indicates the thickness of the hydrophilic nanofiber as a raw material before compounding into the base oil, water, and the like, and the suitable range of the "thickness (d')" is the same as described above.

[0211] The solid content concentration of the water dispersion liquid compounded from the hydrophilic nanofiber is, in general, 0.1 to 70 mass%, preferably 0.1 to 65 mass%, more preferably 0.1 to 60 mass%, further preferably 0.5 to 55 mass%, and more further preferably 1.0 to 50 mass%, based on the total amount (100 mass%) of the water dispersion liquid.

[0212] The water dispersion liquid can be prepared by compounding the hydrophilic nanofiber, a surfactant, and the like, as necessary, into water, and sufficiently stirring using a hand or a blender.

[0213] Note that, as the hydrophilic nanofiber, a powdered hydrophilic nanofiber can be used, which is added to water to prepare a water dispersion liquid.

[0214] The compounding amount of the dispersant in the mixed liquid prepared by the process (1) is preferably 0.1 to 50 mass%, more preferably 0.5 to 40 mass%, further preferably 1.0 to 30 mass%, more further preferably 1.0 to 20 mass%, and still further preferably 1.0 to 10 mass%, based on the total amount (100 mass%) of the mixed liquid.

[0215] The compounding amount of water in the mixed liquid prepared by the process (1) is preferably 1 to 60 mass%, more preferably 3 to 50 mass%, and further preferably 5 to 40 mass%, based on the total amount (100 mass%) of the mixed liquid.

[0216] The compounding amount ratio (water / dispersant) of water and the dispersant in the mixed liquid prepared by the process (1) is preferably 0.01 to 600, more preferably 0.05 to 400, further preferably 0.1 to 300, and more further preferably 0.2 to 200, in terms of mass ratio.

[0217] In the mixed liquid, the above-described various additives that are generally compounded into the grease composition can be added at the same time as the water dispersion liquid compounded from the hydrophilic nanofiber, the base oil, and the dispersant. These components can be mixed and sufficiently stirred using a hand or a blender to prepare the mixed liquid.

[0218] <Process (2)> The process (2) is a process of removing at least water from the mixed liquid prepared by the process (1).

[0219] Note that in this process, water and the dispersant can be removed together from the mixed solution.

[0220] As the method for removing water and the dispersant, a method in which the mixed solution is heated to evaporate and remove water and the dispersant is preferable.

[0221] As the conditions when water is evaporated and removed, it is preferable that the mixed solution is heated at a temperature ranging from 0°C to 100°C in an environment with a pressure of 0.001 MPa to 0.1 MPa.

[0222] Further, as the conditions when the dispersant is evaporated and removed, it is preferable that the mixed solution is heated at a temperature ranging from [boiling point of the dispersant (°C)] - 120°C to [boiling point of the dispersant (°C)] - 0°C in an environment with a pressure of 0.001 MPa to 0.1 MPa.

[0223] Note that the evaporative removal of water and the dispersant can be performed by atmospheric distillation.

[0224] The grease is prepared by the process (2).

[0225] <Process (3)> The process (3) is a process in which the grease prepared by the process (2) is compounded with the particles (C).

[0226] Specifically, for example, the grease prepared by the process (2) is mixed with the particles (C), and homogenized or the like using a homogenizer, a roll mill, or the like, to prepare the grease composition of the present embodiment.

[0227] Further, as needed, the antioxidant (D), the rust preventive (E), and the additive (F) can be compounded at the time of mixing the particles (C).

[0228] [Use of the grease composition] The grease composition of the present embodiment has an appropriate oil separation degree even though hydrophilic nanofibers are used, and is also excellent in water resistance. Thus, in a hygroscopic environment, excellent lubricating properties can be exhibited.

[0229] As the mechanical parts to which the grease composition of the present embodiment can be applied, for example, bearings, gears, and the like can be listed, and more specifically, various bearings such as sliding bearings, rolling bearings, and the like, gears, internal combustion engines, brakes, parts for torque transmission devices, fluid joints, parts for compression devices, chains, parts for oil pressure devices, parts for vacuum pump devices, watch parts, parts for hard disks, parts for refrigerators, parts for cutting machines, parts for calenders, parts for drawbench, parts for roll forming machines, parts for forging machines, parts for heat treatment devices, parts for heat exchangers, parts for cleaning machines, parts for shock absorbers, parts for sealing devices, and the like can be listed.

[0230] Note that the grease of the present embodiment is also suitable for lubrication of sliding portions of general bearings, construction equipment bearings, and the like.

[0231] According to one embodiment of the present application, [1] to

[13] described below are provided.

[0232] [1] A grease composition containing a base oil (A), a hydrophilic nanofiber (B) having a roughness (d) of 1 nm to 500 nm, and a particle (C), The aforementioned hydrophilic nanofiber (B) is one or more selected from the group consisting of a cellulose nanofiber (B1) and a modified cellulose nanofiber (B2), The aforementioned particle (C) has a structure in which a hydrophobic group is present on the outermost surface of a hydrophilic base structure, and in the grease composition, the average particle diameter of the particle (C) is 1 nm to 500 nm.

[0233] [2] The grease composition according to the aforementioned [1], wherein the aforementioned base oil (A) contains a vegetable oil (A1).

[0234] [3] The grease composition according to the aforementioned [1] or [2], wherein the content of the aforementioned hydrophilic nanofiber (B) is 0.1 mass% to 20 mass% based on the total amount of the aforementioned grease composition.

[0235] [4] The grease composition according to any one of the aforementioned [1] to [3], wherein the aforementioned hydrophilic base structure contains a silica particle.

[0236] [5] The grease composition according to any one of the aforementioned [1] to [4], wherein the content of the aforementioned particle (C) is 6.0 mass% or more based on the total amount of the aforementioned grease composition.

[0237] [6] The grease composition according to any one of the aforementioned [1] to [5], further containing an antioxidant (D).

[0238] [7] The grease composition according to the aforementioned [6], wherein the aforementioned antioxidant (D) contains one or more selected from the group consisting of a phenol-based antioxidant and a naphthylamine-based antioxidant.

[0239] [8] The grease composition according to the aforementioned [6] or [7], wherein the content of the aforementioned antioxidant (D) is 0.8 mass% or more based on the total amount of the aforementioned grease composition.

[0240] [9] The grease composition according to any one of the aforementioned [1] to [8], further containing a rust preventive (E).

[0241]

[10] The grease composition according to the preceding [9], wherein the aforementioned rust preventive agent (E) contains a zinc salt of a fatty acid and an amine salt of an organic phosphoric acid ester.

[0242]

[11] The grease composition according to the preceding [9] or

[10] , wherein the content of the aforementioned rust preventive agent (E) is 0.5 mass% to 3.0 mass% based on the total amount of the aforementioned grease composition.

[0243]

[12] The grease composition according to any one of the preceding [1] to

[11] , which has a working cone penetration of 220 to 430 at 25°C.

[0244]

[13] A lubricating method for lubricating a lubrication site using the grease composition according to any one of the preceding [1] to

[12] . Examples

[0245] The present application is specifically described by the following examples, but the present application is not limited to the following examples.

[0246] [Various physical property values] The measurement methods of the various physical property values are shown below.

[0247] (1) 40°C kinematic viscosity and viscosity index of base oil (A) The measurement and calculation were performed in accordance with JIS K2283:2000.

[0248] (2) Roughness and aspect ratio of hydrophilic nanofiber of thickening agent (B) The roughness and length of 10 arbitrarily selected hydrophilic nanofibers were measured using a transmission electron microscope (TEM), and the value calculated from the "length" / "roughness" was set as the "aspect ratio" of the hydrophilic nanofiber that became the object.

[0249] (3) Working cone penetration (1 / 2) of grease composition The measurement was performed at 25°C in accordance with JIS K2220:2013 (Article 7).

[0250] [Raw materials] In Examples 1-1 to 1-4 and Comparative Examples 1-1 to 1-6, the base oil (A), the hydrophilic nanofiber dispersion liquid, the particles (C), and the dispersant used as raw materials for preparing the grease composition are shown below.

[0251] <Base oil (A)> ・Base oil (A1): vegetable oil (rapeseed oil, product name: FUMI SAWAYAKA OIL, manufactured by Showa Sangyo Co., Ltd., 40°C kinematic viscosity: 37.71, viscosity index: 208) • Base oil (A2): Poly-alpha-olefin (PAO) (40°C kinematic viscosity: 57.14, viscosity index: 146).

[0252] <Hydrophilic nanofiber (B)> • Hydrophilic nanofiber dispersion liquid (product name: nanoforest-S, manufactured by Chuetsu Pulp & Paper Co., Ltd., water dispersion liquid containing cellulose nanofiber (CNF) having a degree of polymerization of 600 (roughness (d'): 20 nm to 50 nm (average: 35 nm), aspect ratio: 100 or more (average: 100 or more)).

[0253] <Particle (C)> • Particle (C1): Hydrophobic silica gel (a substance in which dimethyldichlorosilane treatment is performed on the surface of fumed silica, product name: Aerosil (registered trademark) R972, manufactured by EVONIK Co., Ltd., average primary particle diameter: about 16 nm) • Particle (C2): Organic bentonite (product name: Baragel 3000, manufactured by ELEMENTIS Co., Ltd.) • Particle (C3): Organic bentonite (product name: Bentone (registered trademark) 27, manufactured by ELEMENTIS Co., Ltd.) • Particle (C4): Organic modified mineral (product name: GARAMITE (registered trademark) 7303, manufactured by BYK Co., Ltd.) • Comparative component (C'1): Polybutene • Comparative component (C'2): Polymethacrylate (PMA).

[0254] <Antioxidant (D)> • Antioxidant (D1): Phenol-based antioxidant (n-octyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate) • Antioxidant (D2): Phenol-based antioxidant (n-octadecyl 3-(3',5'-di-tert-butyl-4'-hydroxyphenyl)propionate) • Antioxidant (D3): Naphthylamine • Antioxidant (D4): Dinonyl diphenylamine.

[0255] <Antirust agent (E)> • Antirust agent (E1): Mixture of zinc stearate and organic phosphate amine salt (mass ratio of zinc stearate / organic phosphate amine salt = 7 / 3, number of carbon atoms of organic phosphate amine salt: 10 to 12) ・Rust preventive (E2): mixture of zinc neodecanoate and organic phosphate amine salt (product name: G-1340, manufactured by KING INDUSTRIES Co., Ltd., number of carbon atoms of organic phosphate amine salt: 10 to 12) ・Rust preventive (E3): zinc stearate ・Rust preventive (E4): organic phosphate amine salt ・Rust preventive (E5): mixture of calcium sulfonate and sodium sulfonate ・Rust preventive (E6): barium sulfonate (overbased) ・Rust preventive (E7): sodium sulfonate (neutral) ・Rust preventive (E8): sodium sulfonate (overbased).

[0256] <Additive (F)> ・Dispersant: sorbitan trioleate

[0257] (Example 1-1) A mixed solution was prepared by mixing 200 g of a hydrophilic nanofiber dispersion liquid (B) as the hydrophilic nanofiber (B) (amount of CNF therein: 20.0 g), 438 g of base oil (A1), and 2.0 g of a dispersant as the additive (F), and sufficiently stirring at 25°C.

[0258] Next, the mixed solution was heated to 90°C under normal pressure (atmospheric pressure), and water was removed from the mixed solution by evaporation.

[0259] Next, after cooling to room temperature (25°C), 40.0 g of the granule (C1) was added to the mixed solution and sufficiently stirred, and then a homogenization treatment was performed using a triple roll mill, to prepare the grease composition of Example 1-1.

[0260] (Examples 1-2 to 1-4 and Comparative Examples 1-1 to 1-6) The grease compositions of Examples 1-2 to 1-4 and Comparative Examples 1-1 to 1-6 were prepared by the same operation as the grease composition of Example 1-1, except that the components and contents shown in Tables 1 to 2 were changed.

[0261] Next, the oil separation degree and water resistance were evaluated for the grease compositions of Examples 1-1 to 1-4 and Comparative Examples 1-1 to 1-6.

[0262] [Evaluation of oil separation degree] The mass ratio of oil separated from the grease composition was measured under the conditions of temperature: 100°C, time: 24 hours, according to the oil separation degree test of JIS K2220:2013 (Article 11). Note that if the oil separation degree is 10 mass% or less, it is judged to be an appropriate oil separation degree.

[0263] [evaluation of water resistance] The water resistance was evaluated by measuring the water washable water resistance of the grease composition, using 79°C water, according to the water wash durability test of JIS K2220:2013 (Article 16), with respect to the mass of the grease composition before the test (100 mass%). Note that if the water washable water resistance is 10 mass% or less, the water resistance is judged to be good.

[0264] The compositions, physical property values, and evaluation results of the grease compositions of Examples 1-1 to 1-4 and Comparative Examples 1-1 to 1-6 are shown in Tables 1 to 2.

[0265] [Table 1] .

[0266] [Table 2] .

[0267] As shown in Table 1, the grease compositions of Examples 1-1 to 1-4 had appropriate oil separation, and the water resistance was also excellent.

[0268] (Example 2-1) Next, in Example 1-1, 40.0 g of the particles (C1) was added to the mixed solution, and 25 g of the antioxidant (D1) was also added, and otherwise, the same operation as in Example 1-1 was performed to produce the grease composition of Example 2-1.

[0269] (Examples 2-2 to 2-13) The same operation as in the grease composition of Example 2-1 was performed, except that the components and contents shown in Tables 3 to 4 were changed, to produce the grease compositions of Examples 2-2 to 2-13.

[0270] Next, the oil separation, water resistance, and oxidation stability were evaluated for the grease compositions of Examples 2-1 to 2-13.

[0271] [evaluation of oil separation] The measurement was performed by the same operation as in the above "evaluation of oil separation". Note that if the oil separation is 10 mass% or less, the oil separation is judged to be appropriate.

[0272] [evaluation of water resistance] The water washable water resistance was measured by the same operation as in the above "evaluation of water resistance". Note that if the water washable water resistance is 10 mass% or less, the water resistance is judged to be good.

[0273] [evaluation of oxidation stability] The pressure decrease was measured according to the oxidation stability test of JIS K2220:2013 (Article 12) under the conditions of temperature: 99°C, time: 100 hours, and oxygen pressurization: 750 kPa. Note that if the oxidation stability is 80 or less, the oxidation stability is judged to be good.

[0274] The compositions, physical property values, and evaluation results of the grease compositions of Examples 2-1 to 2-13 are shown in Tables 3 to 4.

[0275] [Table 3] .

[0276] [Table 4] .

[0277] As shown in Tables 3 to 4, the grease compositions of Examples 2-1 to 2-13 had appropriate oil separation, and also had excellent water resistance. In addition, the grease compositions of Examples 2-1 to 2-6, 2-8, and 2-11 exhibited excellent results in oxidation stability.

[0278] (Example 3-1) Next, in Example 1-1, while 20.0 g of the particles (C1) was added to the mixed solution, 25 g of the antioxidant (D1) and 5.0 g of the rust preventive (E1) were also added, and otherwise, the same operation as in Example 1-1 was performed to produce the grease composition of Example 3-1.

[0279] (Examples 3-2 to 3-8) The same operation as in the grease composition of Example 3-1 was performed except that the components and contents shown in Table 5 were changed to produce the grease compositions of Examples 3-2 to 3-8.

[0280] Next, the oil separation, water resistance, and rust resistance were evaluated for the grease compositions of Examples 3-1 to 3-8.

[0281] [Evaluation of Oil Separation] The measurement was performed by the same operation as in the above "Evaluation of Oil Separation". Note that if the oil separation is 10 mass% or less, the oil separation is judged to be appropriate.

[0282] [Evaluation of Water Resistance] The water washing water resistance was measured by the same operation as in the above "Evaluation of Water Resistance". Note that if the water washing water resistance is 10 mass% or less, the water resistance is judged to be good.

[0283] [Evaluation of Rust Resistance] Each of the grease compositions was put into a high-humidity thermostat at a temperature of 52°C and a time of 48 hours according to the bearing rust prevention test of ASTM D 1743, and whether rusting occurred was observed visually. Note that in the following evaluation criteria, if "A", it was judged that rust prevention was good.

[0284] Evaluation Criteria A: No reddish or blackish discoloration (rusting) was observed on the surface.

[0285] B: Reddish or blackish discoloration (rusting) was observed on the surface.

[0286] The composition, physical property values, and evaluation results of the grease compositions of Examples 3-1 to 3-8 are shown in Table 5.

[0287] [Table 5] .

[0288] As shown in Table 5, it was found that the grease compositions of Examples 3-1 to 3-8 had an appropriate oil separation degree, and the water resistance was also excellent. In addition, the grease compositions of Examples 3-1 to 3-2 exhibited excellent results in terms of rust prevention.

Claims

1. A grease composition comprising a base oil (A), hydrophilic nanofibers (B) with a coarseness (d) of 1 nm to 500 nm, and particles (C). The hydrophilic nanofibers (B) are selected from one or more of cellulose nanofibers (B1) and modified cellulose nanofibers (B2). The particle (C) has a structure with hydrophobic groups on the outermost surface of the hydrophilic parent structure, and in the grease composition, the average particle size of the particle (C) is 1 nm to 500 nm.

2. The grease composition according to claim 1, wherein, The base oil (A) comprises vegetable oil (A1).

3. The grease composition according to claim 1 or 2, wherein, The content of the hydrophilic nanofibers (B) is 0.1% to 20% by mass based on the total amount of the grease composition.

4. The grease composition according to any one of claims 1 to 3, wherein, The hydrophilic matrix structure contains silica particles.

5. The grease composition according to any one of claims 1 to 4, wherein, The content of the particles (C) is 6.0% by mass or more based on the total amount of the grease composition.

6. The grease composition according to any one of claims 1 to 5, further comprising an antioxidant (D).

7. The grease composition according to claim 6, wherein, The antioxidant (D) comprises one or more selected from phenolic antioxidants and naphthylamine antioxidants.

8. The grease composition according to claim 6 or 7, wherein, The content of the antioxidant (D) is 0.8% by mass or more based on the total amount of the grease composition.

9. The grease composition according to any one of claims 1 to 8, further comprising a rust inhibitor (E).

10. The grease composition according to claim 9, wherein, The rust inhibitor (E) comprises a zinc salt of fatty acids and an organophosphate amine salt.

11. The grease composition according to claim 9 or 10, wherein, The content of the rust inhibitor (E) is 0.5% to 3.0% by mass based on the total amount of the grease composition.

12. The grease composition according to any one of claims 1 to 11, wherein the working penetration at 25°C is 220 to 430.

13. A lubrication method comprising lubricating a lubrication part by means of the grease composition according to any one of claims 1 to 12.

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