CN113631692A

CN113631692A - Grease composition

Info

Publication number: CN113631692A
Application number: CN202080022892.9A
Authority: CN
Inventors: 中西祐辅
Original assignee: Idemitsu Kosan Co Ltd
Current assignee: Idemitsu Kosan Co Ltd
Priority date: 2019-03-22
Filing date: 2020-02-27
Publication date: 2021-11-09
Also published as: US20220145207A1; EP3943583A1; JPWO2020195509A1; EP3943583A4; WO2020195509A1

Abstract

The present invention addresses the problem of providing a grease composition for a speed reducer and a speed increaser, which is excellent in both leak resistance and energy transmission efficiency, and which is used for a speed reducer and a speed increaser, and which contains a base oil (A) and nanofibers (B) having a thickness (d) of 1 to 500nm, wherein the nanofibers (B) are at least 1 type selected from the group consisting of cellulose nanofibers (B1) and modified cellulose nanofibers (B2).

Description

Grease composition

Technical Field

The present invention relates to a grease composition. More specifically, the present invention relates to a grease composition used for a speed reducer and a speed increaser.

Background

The grease is easier to seal than a lubricating oil, and can reduce the size and weight of a machine to which the grease is applied. Therefore, lubricating oil compositions have been widely used for lubricating various sliding parts of automobiles, electric devices, industrial machines, and the like.

In recent years, grease is used also in a speed reducer used in an industrial robot or the like, a speed increaser used in a wind power generation plant, or the like (for example, see patent document 1).

The speed reducer has a mechanism for applying torque to an input side to reduce the speed and transmitting the torque to an output side.

The speed-increasing gearbox includes a mechanism that increases speed by applying torque to an input side and transmits torque to an output side.

Grease used in lubrication portions of a speed reducer and a speed increaser is required to have excellent energy transmission efficiency from the viewpoint of suppressing loss of torque (energy) applied to an input side and transmitting the torque to an output side without loss.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2017-203069

Disclosure of Invention

Problems to be solved by the invention

In the case of producing a grease excellent in energy conduction efficiency, a soft grease is generally obtained by increasing the working penetration. However, when a soft grease having a high penetration depth is used, there is a problem that the grease leakage prevention performance is lowered.

If the leakage prevention performance of the grease is lowered and the grease leaks out, the grease adheres to products manufactured by a device provided with a speed reducer, a device provided with a speed increaser, or the like, and the product yield is lowered. In addition, in the case of food products produced by food production apparatuses and the like, it is strongly required to prevent the mixing of foreign substances into the food products from the viewpoint of safety and the like. From this viewpoint, prevention of adhesion of grease to the food is strongly required.

Therefore, although it is expected to improve the grease leakage prevention performance, if the working penetration of the grease is increased in order to improve the energy transmission efficiency, there is a problem that the grease leakage prevention performance cannot be sufficiently ensured.

The purpose of the present invention is to provide a grease composition for a speed reducer and a speed increaser, which is excellent in both leak resistance and energy transmission efficiency.

Means for solving the problems

The present inventors have found that a grease composition containing a base oil and specific nanofibers can solve the above problems, and have completed the present invention.

That is, the present invention relates to the following [1] to [10 ].

[1] A grease composition for a speed reducer and a speed increaser, comprising a base oil (A) and a nanofiber (B) having a thickness (d) of 1 to 500nm,

the nanofibers (B) are at least 1 type selected from the group consisting of cellulose nanofibers (B1) and modified cellulose nanofibers (B2).

[2] The grease composition according to the above [1], wherein the content of the nanofibers (B) is 0.1 to 20% by mass based on the total amount of the grease composition.

[3] The grease composition according to the above [1] or [2], further comprising an organobentonite (C),

the nanofibers (B) include the cellulose nanofibers (B1).

[4] The grease composition according to the above [3], wherein the content of the organobentonite (C) is 0.01 to 15 mass% based on the total amount of the grease composition.

[5] The grease composition according to the above [3] or [4], wherein the content ratio [ B1/C ] of the cellulose nanofibers (B1) to the organobentonite (C) is 0.05 to 5.0 in terms of mass ratio.

[6]According to the above [1]～[5]A grease composition according to any one of the preceding claims, wherein the base oil (A) is a mixed base oil comprising a low-viscosity base oil (A1) and a high-viscosity base oil (A2)The kinematic viscosity of the low-viscosity base oil (A1) at 40 ℃ is 5-150 mm²(S) the kinematic viscosity of the high-viscosity base oil (A2) at 40 ℃ is 200-1000 mm²/s。

[7] The grease composition according to any one of the above [1] to [6], which has a working penetration at 25 ℃ of 220 to 440.

[8] The grease composition according to any one of the above [1] to [7], which is used for a food machine equipped with a speed reducer or a food machine equipped with a speed increaser.

[9] A method of lubricating a lubricated part of a speed reducer or a speed increaser with the grease composition according to any one of [1] to [7 ].

[10] A method of lubricating a lubricated part of a food machine equipped with a speed reducer or a speed increaser with the grease composition according to any one of [1] to [7 ].

Effects of the invention

According to the present invention, a grease composition for a speed reducer and a speed booster excellent in both leak resistance and energy transmission efficiency can be provided.

Drawings

Fig. 1 is a schematic view of an apparatus used in the present example for measuring the torque transmission efficiency as an index of the energy transmission efficiency.

Detailed Description

In the present specification, for a preferable numerical range (for example, a range of contents), the lower limit value and the upper limit value described in the stepwise may be independently combined. For example, according to the description of "preferably 10 to 90, more preferably 30 to 60", the "preferred lower limit value (10)" and the "more preferred upper limit value (60)" may be combined to obtain "10 to 60".

In the present specification, the numerical values of the examples are numerical values that can be used as upper limit values or lower limit values.

[ embodiment of the grease composition of the present invention ]

The grease composition of the present invention is a grease composition for a speed reducer and a speed increaser, and comprises a base oil (A) and nanofibers (B) having a thickness (d) of 1 to 500nm, wherein the nanofibers (B) are at least 1 selected from the group consisting of cellulose nanofibers (B1) and modified cellulose nanofibers (B2).

In the grease composition of the present invention, the thickness (d) of the nanofibers (B) contained in the grease composition is defined. That is, the thickness (d) of the nanofibers (B) dispersed in the base oil (a) is specified.

By satisfying this specification, the nanofibers (B) are likely to form a higher-order structure in the base oil (a). In addition, it is easy to uniformly disperse the nanofibers (B) in the base oil (a). As a result, even if the content of the nanofibers (B) is small, the adjustment to an appropriate working penetration is easy, and a grease composition excellent in both the leakage prevention performance and the energy transmission efficiency can be obtained.

In the present specification, the "base oil (a)" and the "nanofibers (B)" will also be referred to as "component (a)" and "component (B)" respectively in the following description. The "cellulose nanofiber (B1)" and the "modified cellulose nanofiber (B2)" are also referred to as a "component (B1)" and a "component (B2)", respectively.

In the lubricating oil composition according to one embodiment of the present invention, the total content of the component (a) and the component (B) is preferably 50% by mass or more, more preferably 60% by mass or more, further preferably 70% by mass or more, and still further preferably 80% by mass or more, based on the total amount (100% by mass) of the grease composition.

In the grease composition according to one embodiment of the present invention, the upper limit of the total content of the component (a) and the component (B) may be adjusted by the relationship with the content of the additive other than the component (B), and is preferably 99 mass% or less, more preferably 95 mass% or less, and still more preferably 92 mass% or less.

The base oil (a) and the nanofibers (B) will be described in detail below.

< base oil (A) >

The base oil (a) contained in the grease composition of the present invention is not particularly limited, and examples thereof include mineral oil, synthetic oil, animal oil, vegetable oil, and liquid paraffin.

The base oil (a) may be a base oil containing only 1 type, or may be a mixed base oil obtained by combining 2 or more types.

(mineral oil)

Examples of the mineral oil include distillate oil obtained by atmospheric distillation of a paraffinic crude oil, a medium base crude oil, or a naphthenic crude oil, or distillate oil obtained by vacuum distillation of an atmospheric distillation residue; refined oils (specifically, solvent refined oils, hydrorefined oils, dewaxed oils, clay-treated oils, etc.) obtained by subjecting these distillate oils to one or more refining treatments selected from refining treatments such as solvent deasphalting, solvent extraction, hydrocracking, and hydrorefining, and refining treatments such as solvent dewaxing and catalytic dewaxing; and so on.

Of these mineral oils, mineral oils classified as group 3 in the API (American Petroleum institute) base oil category are preferred.

(synthetic oil)

Examples of the synthetic oil include hydrocarbon oils, aromatic oils, ester oils, ether oils, and fatty acid esters.

Examples of the hydrocarbon-based oil include poly- α -olefins (PAOs) such as normal paraffins, isoparaffins, polybutenes, polyisobutylenes, 1-decene oligomers, and 1-decene-ethylene co-oligomers, and hydrogenated products thereof. Further, there may be mentioned a GTL synthetic oil obtained by isomerizing a WAX produced by a Fischer-Tropsch method or the like (Gas To Liquids WAX).

Examples of the aromatic oil include alkylbenzenes such as monoalkylbenzenes and dialkylbenzenes; alkylnaphthalenes such as monoalkylnaphthalenes, dialkylnaphthalenes, and polyalkylnaphthalenes; and so on.

Examples of the ester-based oil include diester-based oils such as dibutyl sebacate, di (2-ethylhexyl) sebacate, dioctyl adipate, diisodecyl adipate, ditridecyl glutarate, and methyl acetylricinoleate; aromatic ester-based oils such as trioctyl trimellitate, tridecyl trimellitate, and tetraoctyl pyromellitate; polyol ester oils such as trimethylolpropane caprylate, trimethylolpropane pelargonate, pentaerythritol 2-ethylhexanoate, pentaerythritol pelargonate and the like; complex ester oils such as oligoesters (oligoesters) of a mixed fatty acid of a dibasic acid and a monobasic acid with a polyhydric alcohol; and so on.

Examples of the ether oil include polyglycols such as polyethylene glycol, polypropylene glycol, polyethylene glycol monoether, and polypropylene glycol monoether; phenyl ether oils such as monoalkyltriphenyl ether, alkyldiphenyl ether, dialkyldiphenyl ether, pentaphenyl ether, tetraphenyl ether, monoalkyltetraphenyl ether, and dialkyltetraphenyl ether; and so on.

The fatty acid constituting the fatty acid ester is preferably a fatty acid having 8 to 22 carbon atoms, and specific examples thereof include 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, and 12-hydroxystearic acid.

Specific examples of the fatty acid ester include glycerin fatty acid ester, polyglycerin fatty acid ester, propylene glycol fatty acid ester, and the like.

Examples of the glycerin fatty acid ester include glycerin monooleate, glycerin monostearate, glycerin monocaprylate, glycerin dioleate, glycerin distearate, and glycerin dicaprylate.

Examples of the polyglycerin fatty acid ester include diglycerin monooleate, diglycerin monoisostearate, diglycerin dioleate, diglycerin trioleate, diglycerin monostearate, diglycerin distearate, diglycerin tristearate, diglycerin triisostearate, diglycerin monocaprylate, diglycerin dioctanoate, diglycerin tricaprylate, triglycerol monooleate, triglycerol dioleate, triglycerol trioleate, triglycerol tetraoleate, triglycerol monostearate, triglycerol distearate, triglycerol tristearate, triglycerol tetrastearate, triglycerol monocaprylate, triglycerol dioctanoate, triglycerol tricaprylate, triglycerol tetracaprylate, diglycerin monooleate monostearate, diglycerin monooleate distearate, diglycerin monocaprylate monostearate, triglycerol monooleate, triglycerol trioleate, triolein, or, Triglycerol dioleate distearate, triglycerol dioleate monostearate, triglycerol monooleate monostearate monocaprylate, diglycerol monolaurate, diglycerol dilaurate, triglycerol monolaurate, triglycerol trilaurate, diglycerol monomyristate, diglycerol dimyristate, triglycerol trimyristate, diglycerol monolinoleate, diglycerol dilinoleate, triglycerol monolinoleate, triglycerol dilinoleate, triglycerol trilinoleate, decaglycerol monooleate, decaglycerol monostearate, decaglycerol monocaprylate, and the like.

Examples of the propylene glycol fatty acid ester include propylene glycol monooleate, propylene glycol monostearate, propylene glycol monocaprylate, and propylene glycol monolaurate.

(vegetable oil)

The vegetable oil is an oil derived from a plant, and specific examples thereof include rapeseed oil, peanut oil, corn oil, cottonseed oil, canola oil, soybean oil, sunflower oil, palm oil, coconut oil, safflower oil, camellia oil, olive oil, peanut oil, and the like.

(animal oil)

The animal oil is an oil derived from animals, and specific examples thereof include lard, neatsfoot oil, silkworm pupa oil, sardine oil, herring oil, and the like.

(liquid Paraffin)

The liquid paraffin may have C_mH_n(m is a carbon number, n < 2m +2), a branched structure, a cyclic structure, or a mixture thereof.

Among the above base oils, the base oil (a) contained in the grease composition according to one embodiment of the present invention preferably contains 1 or more selected from mineral oils, synthetic oils, plant oils, animal oils, fatty acid esters, and liquid paraffins classified as group 3 in the API base oil category, and more preferably contains 1 or more selected from mineral oils and synthetic oils classified as group 3 in the API base oil category. As synthetic oil, preferably poly-alpha-olefins (PAO) are used.

Here, when oxidation stability at high temperatures is required for the grease composition, it is preferable to use a synthetic oil, more preferably 1 or more selected from hydrocarbon-based oils, ester-based oils, and ether-based oils, and still more preferably a hydrocarbon-based oil. Further, when the hydrocarbon-based oil, the ester-based oil, and the ether-based oil are used in combination, a balance can be obtained between heat resistance, sealing resistance (Japanese: シ - ル resistance), and low-temperature characteristics, and from this viewpoint, the hydrocarbon-based oil is preferably used.

(kinematic viscosity and viscosity index of base oil (A))

The base oil (A) used in one embodiment of the present invention preferably has a kinematic viscosity at 40 ℃ (hereinafter also referred to as "40 ℃ kinematic viscosity") of 10 to 400mm²(ii) s, more preferably 15 to 300mm²More preferably 20 to 200mm in terms of a mass fraction of the total mass fraction²More preferably 20 to 130 mm/s²/s。

By adjusting the kinematic viscosity at 40 ℃ of the base oil (a) to the above range, the grease can be easily improved in leakage resistance and energy transmission efficiency.

The base oil (a) used in one embodiment of the present invention may be a mixed base oil in which the kinematic viscosity is adjusted to the above range by combining the low viscosity base oil (a1) and the high viscosity base oil (a 2).

The low-viscosity base oil (A1) preferably has a kinematic viscosity at 40 ℃ of 5-150 mm²(ii) s, more preferably 7 to 120mm²More preferably 10 to 100mm in terms of a mass fraction of the total mass fraction²/s。

The kinematic viscosity at 40 ℃ of the high-viscosity base oil (A2) is preferably 200-1000 mm²(ii) s, more preferably 250 to 800mm²More preferably 300 to 600mm in terms of a mass fraction of the total mass fraction²/s。

The viscosity index of the base oil (a) used in one embodiment of the present invention is preferably 60 or more, more preferably 70 or more, and still more preferably 80 or more.

In the present invention, the kinematic viscosity at 40 ℃ and the viscosity index are expressed in accordance with JIS K2283: 2000 measured or calculated values.

(content of base oil (A))

The content of the base oil (a) contained in the grease composition according to one embodiment of the present invention is preferably 50% by mass or more, more preferably 60% by mass or more, further preferably 70% by mass or more, and still further preferably 80% by mass or more, based on the total amount (100% by mass) of the grease composition.

< nanofiber (B) >

The nanofibers (B) contained in the grease composition of the present invention are 1 or more selected from the group consisting of cellulose nanofibers (B1) and modified cellulose nanofibers (B2).

By incorporating the nanofibers (B) into the grease composition, the nanofibers (B) are uniformly dispersed in the grease composition to form a higher-order structure. Since the nanofibers (B) have excellent mechanical stability, the high-order structure of the nanofibers (B) is stable to shear. Therefore, the shear stability of the grease composition is improved, and the leakage prevention performance of the grease is improved.

Further, even if the content of the nanofibers (B) is small, the working penetration of the grease composition can be adjusted to an appropriate range. Therefore, the proportion of the base oil (a) in the grease composition can be increased. Therefore, the lubricating property of the grease composition is improved, and the energy transmission efficiency is also easily improved.

(cellulose nanofiber (B1))

Cellulose nanofibers are fibrous materials having a thickness of 500nm or less produced by opening plant fibers to the nano level, and are distinguished from flakes, powders, and particles.

As a raw material of the cellulose nanofibers, lignocellulose may be used. Lignocellulose is known as a complex hydrocarbon polymer constituting plant cell walls, and is mainly composed of cellulose and hemicellulose, which are polysaccharides, and lignin, which is an aromatic polymer. The cellulose constituting the cellulose nanofibers may be 1 or more selected from the group consisting of lignocellulose and acetylated lignocellulose. In addition, the cellulose nanofibers may comprise 1 or more selected from hemicellulose and lignin. Further, the cellulose constituting the cellulose nanofibers may be chemically bonded to 1 or more selected from hemicellulose and lignin.

The degree of polymerization of cellulose constituting the cellulose nanofibers is preferably 50 to 3,000, more preferably 100 to 1,500, even more preferably 150 to 1,000, and even more preferably 200 to 800.

In the present specification, the polymerization degree of cellulose represents a value measured by a viscosity method.

(modified cellulose nanofiber (B2))

The modified cellulose nanofibers are fibers obtained by modifying cellulose nanofibers.

Specific examples of the modification treatment include esterification such as acetylation, phosphorylation, carbamation, urethanization, etherification, carboxymethylation, TEMPO (2, 2, 6, 6-tetramethylpiperidine-1-oxyl) oxidation, periodic acid oxidation, and the like.

The modified cellulose nanofibers used in the present invention may be fibers obtained by performing only 1 of these modification treatments, or may be fibers obtained by performing 2 or more of these modification treatments.

In addition, resin-reinforced fibers containing 1 or more selected from cellulose nanofibers and modified cellulose nanofibers and a thermoplastic resin are known. Such resin-reinforcing fibers are also included in the modified cellulose nanofibers.

At least 1 kind selected from the group consisting of cellulose nanofibers and modified cellulose nanofibers and the thermoplastic resin may be mixed or kneaded, or may be dispersed in each other.

Examples of the thermoplastic resin include polyethylene, polypropylene, polyvinyl chloride, polystyrene, polyvinylidene chloride, fluorine resins, (meth) acrylic resins, polyamide resins, polyesters, polylactic acid resins, copolymerized resins of polylactic acid and polyester, acrylonitrile-butadiene-styrene copolymers, polycarbonates, polyphenylene oxides, (thermoplastic) polyurethanes, polyacetals, vinyl ether resins, polysulfone resins, and cellulose resins (for example, triacetyl cellulose and diacetyl cellulose). In addition, (meth) acrylic acid means acrylic acid and/or methacrylic acid.

The thermoplastic resin can be used alone in 1, can also be combined with more than 2.

(thickness of nanofiber (B))

The definition of "thickness" of the nanofibers (B) is the same as that of the thickness of a conventional fibrous material.

Specifically, in a cutting plane when cutting is performed perpendicularly to a tangential direction at any point on a side surface of the nanofiber (B), if the cutting plane is a circle or an ellipse, the diameter or the major diameter is "thickness" of the nanofiber (B). If the cut surface is a polygon, the diameter of the circumscribed circle of the polygon is the "thickness" of the nanofiber (B).

When a flake, powder, or particle having a size of several μm or more (hereinafter also referred to as "fine particle") as a thickener is blended in the base oil (a), the fine particle is aggregated in the base oil (a), and is likely to be a so-called "agglomerate". As a result, aggregates of fine particles are deposited on the surface of the grease composition obtained, and the dispersion state tends to become uneven. In this case, in order to increase the working penetration of the grease composition obtained, it is necessary to add a large amount of fine particles. However, since the grease composition contains particles larger than the oil film thickness, the grease composition has poor wear resistance.

On the other hand, in the grease composition of the present invention, since the nanofibers (B) having a thickness (d) of 1 to 500nm are blended in the base oil (a), the nanofibers (B) do not aggregate in the base oil (a), but form a higher-order structure due to the nanofibers (B) while uniformly dispersing the nanofibers (B). As a result, a grease composition having an appropriate working penetration can be obtained even if the content of the nanofibers (B) is small.

(thickness (d) and aspect ratio of nanofiber (B))

In the present invention, "the thickness (d) of the nanofibers (B)" represents the thickness of the nanofibers (B) dispersed in the base oil (a), and is different from "the thickness (d') of the nanofibers (B)" as a raw material before blending in the base oil (a).

However, the "thickness (d) of the nanofibers (B)" dispersed in the base oil (a) is almost the same as the "thickness (d') of the nanofibers (B)" as a raw material before blending in the base oil (a). Therefore, the "thickness (d) of the nanofibers (B)" dispersed in the base oil (a) can be considered to be substantially the same as the "thickness (d') of the nanofibers (B)" as the raw material before blending in the base oil (a).

The thickness (d) of the nanofibers (B) dispersed in the base oil (A) is 1 to 500nm, but is preferably 1 to 300nm, more preferably 1 to 200nm, and even more preferably 2 to 100nm, from the viewpoint of forming a higher-order structure by the nanofibers (B) in the base oil (A) and from the viewpoint of dispersing the nanofibers (B) more uniformly.

The nanofibers (B) contained in the grease composition of the present invention may be dispersed with at least nanofibers (B) having a thickness (d) within the above range, or with nanofibers (B) having a thickness (d) outside the above range.

However, in the grease composition according to one embodiment of the present invention, from the viewpoint of forming a higher-order structure by the nanofibers (B) in the base oil (a) and from the viewpoint of dispersing the nanofibers (B) more uniformly, the average value of the thickness (d) of 10 nanofibers (B) arbitrarily selected from the nanofibers (B) dispersed in the base oil (a) is preferably 1 to 500nm, more preferably 1 to 300nm, even more preferably 1 to 200nm, and even more preferably 2 to 100 nm.

From the above viewpoint, the number of nanofibers (B) having a thickness (d) in the above range among the arbitrarily selected 10 nanofibers (B) contained in the grease composition of the present invention is preferably 1 or more, more preferably 5 or more, further preferably 7 or more, and more preferably all nanofibers (B) having a thickness (d) in the above range among the selected 10 nanofibers (B).

In the grease composition according to one embodiment of the present invention, the aspect ratio of the nanofibers (B) is preferably 5 or more, more preferably 10 or more, further preferably 15 or more, still more preferably 30 or more, still more preferably 50 or more, still more preferably 70 or more, still more preferably 90 or more, and still more preferably 100 or more.

In the present specification, the "aspect ratio" refers to the ratio of the length to the thickness (length/thickness) of the nanofibers (B) to be observed, and the "length" of the nanofibers (B) refers to the distance between 2 points at which the distance of the nanofibers (B) is the largest.

In addition, in the case where a part of the nanofibers (B) to be observed is in contact with other nanofibers (B) and it is difficult to determine the "length", the length may be measured only for a part of the nanofibers (B) to be observed, the thickness of which can be measured, and the aspect ratio of the part may be in the above range.

The average aspect ratio (hereinafter, also referred to as "average aspect ratio") of the aspect ratios of the 10 nanofibers (B) arbitrarily selected from the nanofibers (B) contained in the grease composition of the present invention is preferably 5 or more, more preferably 10 or more, further preferably 15 or more, further preferably 30 or more, further preferably 50 or more, further preferably 70 or more, further preferably 90 or more, and further preferably 100 or more.

(thickness (d') and aspect ratio of nanofiber (B))

The thickness (d') of the nanofibers (B) as a raw material before blending in the base oil (A) is preferably 1 to 500nm, more preferably 1 to 300nm, still more preferably 1 to 200nm, and still more preferably 2 to 100 nm.

The average aspect ratio of the nanofibers (B) as a raw material before mixing with the base oil (a) is preferably 5 or more, more preferably 10 or more, further preferably 15 or more, further preferably 30 or more, further preferably 50 or more, further preferably 70 or more, further preferably 90 or more, and further preferably 100 or more.

In the present specification, the "thickness (d)" of the nanofibers (B) dispersed in the base oil (a), the "thickness (d') of the nanofibers (B) as a raw material before blending in the base oil (a), and the aspect ratio of the nanofibers (B) are measured by an electron microscope or the like.

(content of nanofiber (B))

As described above, the grease composition according to one embodiment of the present invention can adjust the working penetration to an appropriate range even when the content of the nanofibers (B) is small. Specifically, in the grease composition according to one embodiment of the present invention, the content of the nanofibers (B) is preferably 0.1 to 20% by mass, more preferably 0.5 to 18% by mass, even more preferably 0.8 to 15% by mass, even more preferably 1.0 to 12% by mass, even more preferably 1.0 to 10% by mass, and even more preferably 1.0 to 9.0% by mass, based on the total amount (100% by mass) of the grease composition.

If the content of the nanofibers (B) is 0.1 mass% or more, the grease composition having a high dropping point can be easily prepared.

On the other hand, if the content of the nanofibers (B) is 20 mass% or less, a grease composition having excellent wear resistance can be easily produced.

Further, by adjusting the content of the nanofibers (B) to the above range, the working penetration of the grease composition can be easily adjusted to an appropriate range.

Hereinafter, a preferred embodiment of the grease composition according to one embodiment of the present invention, that is, an embodiment further containing an organobentonite (C), will be described.

< Organobentonite (C) >

In the grease composition according to one embodiment of the present invention, it is preferable that the base oil (a) and the nanofibers (B) further contain an organobentonite (C). Further, the nanofibers (B) preferably comprise cellulose nanofibers (B1).

As described above, by incorporating the nanofibers (B) in the grease composition, the nanofibers (B) are uniformly dispersed in the grease composition to form a higher-order structure. When the nanofibers (B) include the cellulose nanofibers (B1), the cellulose nanofibers (B1) are also uniformly dispersed in the grease composition to form a high-order structure. In addition, the organobentonite (C) is dispersed in the vicinity of the uniformly dispersed cellulose nanofibers (B1) by adsorbing the hydrophilic groups of the cellulose nanofibers (B1) on the hydrophilic surface (surface having hydrophilic groups) or by bringing the hydrophilic surface close to the hydrophilic groups of the cellulose nanofibers (B1). As a result, the organobentonite (C) is arranged as if it were uniformly dispersed so as to surround the hydrophilic groups of the cellulose nanofibers (B1).

Here, as described above, the nanofibers (B) are excellent in mechanical stability. The cellulose nanofibers (B1) also had excellent mechanical stability. Further, the organobentonite (C) is also excellent in mechanical stability. Therefore, the higher-order structure of the nanofibers (B) (cellulose nanofibers (B1)) and the organobentonite (C) dispersed in the grease composition are stable to shear. Therefore, the shear stability of the grease composition is improved, and the leakage prevention performance of the grease is improved.

Further, since the cellulose nanofibers (B1) and the organobentonite (C) are easily uniformly dispersed in the base oil (a), even if the content of the cellulose nanofibers (B1) is small and the content of the organobentonite (C) is small, a grease composition having an appropriate working penetration can be obtained, and therefore, the proportion of the base oil (a) in the grease composition can be increased. Therefore, the lubricating property of the grease composition is improved, and the energy transmission efficiency is also easily improved.

Since the organobentonite (C) is uniformly dispersed and arranged so as to surround the hydrophilic group of the cellulose nanofiber (B1), the cellulose nanofiber (B1) is hydrophobized as if it were, and excellent water resistance is imparted to the grease composition.

The phrase "the content of the organobentonite (C) is small" means that the content of the organobentonite (C) is 0.01 to 15 mass%, preferably 0.1 to 10 mass%, and more preferably 1.0 to 8.0 mass% based on the total amount (100 mass%) of the grease composition.

If the content of the organobentonite is 0.01 mass% or more, a grease composition having more excellent water resistance can be easily produced.

On the other hand, if the content of the organobentonite is 15 mass% or less, a grease composition excellent in energy transfer efficiency can be easily produced.

In addition, when the grease composition according to one embodiment of the present invention contains the organobentonite (C), the content of the cellulose nanofibers (B1) is preferably 60 to 100 mass%, more preferably 70 to 100 mass%, even more preferably 80 to 100 mass%, and even more preferably 90 to 100 mass% based on the total amount of the nanofibers (B), from the viewpoint of maximizing the effect obtained by the inclusion of the organobentonite (C).

In the grease composition according to one embodiment of the present invention, the total content of the base oil (a), the nanofibers (B), and the organobentonite (C) is preferably 50 mass% or more, more preferably 60 mass% or more, even more preferably 70 mass% or more, even more preferably 80 mass% or more, and even more preferably 90 mass% or more, based on the total amount (100 mass%) of the grease composition.

In the grease composition according to one embodiment of the present invention, the content ratio [ (B1)/(C) ] of the cellulose nanofibers (B1) to the organobentonite (C) is preferably 0.05 to 5.0, more preferably 0.1 to 2.0, and even more preferably 0.1 to 1.0 in terms of a mass ratio, from the viewpoint of obtaining a grease composition having excellent leakage prevention performance and energy transmission efficiency and excellent water resistance.

The organic bentonite (C) is obtained by modifying the crystal surface of montmorillonite which is a clay mineral by treatment with a quaternary ammonium compound or the like.

The quaternary ammonium compound is not particularly limited as long as it can modify the crystal surface of the montmorillonite which is the clay mineral, and examples thereof include dimethylalkylammonium such as dimethyldioctadecylammonium, trimethylalkylammonium such as trimethyloctadecylammonium, and trialkylbenzylammonium, and among them, dimethylalkylammonium such as dimethyldioctadecylammonium is preferable.

The quaternary ammonium compound may be used alone in 1 kind, or may be used in combination in 2 or more kinds.

Further, the organobentonite (C) may be used alone in 1 kind, or may be used in combination in 2 or more kinds.

Generally, the organobentonite (C) functions as a thickener by being cleaved by shear in the presence of a polar compound in a base oil. However, it is difficult to uniformly disperse bentonite such as organobentonite in the base oil. Therefore, a grease composition using bentonite as a thickener, bentonite grease) is generally blended with a large amount of bentonite to adjust the penetration of the working cone. Specifically, the bentonite is generally blended in an amount of 18 mass% or more, and further 20 mass% or more, based on the total amount (100 mass%) of the grease composition.

In contrast, the grease composition according to one embodiment of the present invention can uniformly disperse the organobentonite (C) in the base oil by using the cellulose nanofibers (B1) and the organobentonite (C) in combination.

The method for producing organobentonite is disclosed in detail in, for example, Japanese patent application laid-open Nos. 62-83108 and 53-72792.

< various additives >

The grease composition according to one embodiment of the present invention may further contain various additives that are blended in a general grease composition, within a range that does not impair the effects of the present invention.

Examples of the various additives include an extreme pressure agent, a rust preventive, an antioxidant, a detergent dispersant, an anticorrosive agent, an antifoaming agent, and a metal deactivator.

These various additives may be used alone, or 2 or more of them may be used in combination.

In the grease composition according to one embodiment of the present invention, the dispersant and water used for the grease formation may be contained within a range in which the state of the grease can be maintained.

Examples of the dispersant include compounds exemplified in the method for producing the grease composition of the present invention described below.

In the grease composition according to one embodiment of the present invention, the total content of the dispersant and water is preferably 0 to 60 mass%, more preferably 0 to 30 mass%, even more preferably 0 to 10 mass%, and even more preferably 0 to 5 mass%, based on the total amount (100 mass%) of the grease.

(extreme pressure agent)

Examples of the extreme pressure agent include 1 or more selected from phosphorus-based extreme pressure agents and sulfur-phosphorus-based extreme pressure agents.

Examples of the phosphorus-based extreme pressure agent include 1 or more kinds of phosphates selected from orthophosphates, hydrogenphosphates, polyphosphates, phosphites, and metaphosphates.

Examples of the polyphosphate salt include pyrophosphate (diphosphate), tripolyphosphate, and tetrapolyate.

The phosphate is preferably an alkali metal salt. The alkali metal salt is preferably a sodium salt, a potassium salt, and a lithium salt, and particularly preferably a sodium salt.

Examples of the sulfur-phosphorus-based extreme pressure agent include 1 or more selected from thiophosphate and an amine salt of thiophosphate.

Examples of the thiophosphate include monothiophosphate, dithiophosphate, trithiophosphate, monothiophosphite, dithiophosphite, trithiophosphite, and the like, and among these, trithiophosphate is preferable.

Examples of the trithiophosphate ester include trialkyl thiophosphates such as tributyl thiophosphate, tripentyl thiophosphate, trihexyl thiophosphate, triheptyl thiophosphate, trioctyl thiophosphate, trinonyl thiophosphate, tridecyl thiophosphate, triundecyl thiophosphate, tripentadecyl thiophosphate, and trihexadecyl thiophosphate; triaryl thiophosphates such as triphenyl thiophosphate, tricresyl thiophosphate, and trixylyl thiophosphate; tri (n-propylphenyl) thiophosphate, tri (isopropylphenyl) thiophosphate, tri (n-butylphenyl) thiophosphate, tri (isobutylphenyl) thiophosphate, tri (sec-butylphenyl) thiophosphate, tri (tert-butylphenyl) thiophosphate, tri (2, 4-C) thiophosphate₉，C₁₀Tri (alkylphenyl) thiophosphates such as isoalkylphenyl) thiophosphates.

Examples of the amine salt of thiophosphate include the amine salts of thiophosphate exemplified above.

The content of the extreme-pressure agent contained in the grease composition according to one embodiment of the present invention is preferably 0.01 to 5.0 mass%, more preferably 0.1 to 3.0 mass%, and still more preferably 0.5 to 2.0 mass%, based on the total amount (100 mass%) of the grease composition.

Examples of the extreme pressure agent other than the above extreme pressure agent include organic molybdenum and the like.

However, the grease composition according to one embodiment of the present invention preferably contains a small amount of molybdenum atoms. Specifically, the content of molybdenum atoms is preferably less than 50 mass ppm, more preferably less than 10 mass ppm, still more preferably less than 1 mass ppm, and still more preferably no molybdenum atoms, based on the total amount (100 mass%) of the grease composition.

(Rust preventive)

Examples of the rust inhibitor include a carboxylic acid-based rust inhibitor, an amine-based rust inhibitor, and a carboxylic acid salt-based rust inhibitor.

When the grease composition according to one embodiment of the present invention contains a rust inhibitor, the content of the rust inhibitor is preferably 0.1 to 10.0% by mass, more preferably 0.3 to 8.0% by mass, and still more preferably 1.0 to 5.0% by mass, based on the total amount (100% by mass) of the grease composition.

(antioxidant)

Examples of the antioxidant include amine-based antioxidants, phenol-based antioxidants, sulfur-based antioxidants, zinc dithiophosphates, and the like.

When the grease composition according to one embodiment of the present invention contains an antioxidant, the content of the antioxidant is preferably 0.05 to 10% by mass, more preferably 0.1 to 7% by mass, and still more preferably 0.2 to 5% by mass, based on the total amount (100% by mass) of the grease composition.

(detergent dispersant, anticorrosive agent, defoaming agent, metal deactivator)

Examples of the detergent dispersant include succinimide and boron-based succinimide.

Examples of the anticorrosive agent include benzotriazole compounds and thiazole compounds.

Examples of the defoaming agent include silicone compounds and fluorinated silicone compounds.

Examples of the metal deactivator include benzotriazole and the like.

When the grease composition according to one embodiment of the present invention contains these additives, the content of each of these additives is preferably 0.01 to 20% by mass, more preferably 0.1 to 10% by mass, and still more preferably 0.2 to 5% by mass, based on the total amount (100% by mass) of the grease composition.

[ characteristics of the grease composition of the present invention ]

(working cone penetration)

The working penetration at 25 ℃ of the grease composition according to one embodiment of the present invention is preferably 220 to 440, more preferably 240 to 400, even more preferably 250 to 380, and even more preferably 270 to 360.

In the grease composition according to one embodiment of the present invention, the grease composition has excellent leakage prevention performance even when the working penetration at 25 ℃ is adjusted to the above range, and a grease composition having excellent energy transmission efficiency and leakage prevention performance is obtained.

(shear stability)

The grease composition according to one embodiment of the present invention has a working cone penetration change in a roll stability test, which is measured and calculated by the method described in the examples described below, of preferably 50 or less, more preferably 40 or less, even more preferably 30 or less, and even more preferably 20 or less.

(efficiency of Torque conduction)

The grease composition according to one embodiment of the present invention has a torque transmission efficiency as an index of energy transmission efficiency, which is measured and calculated by the method described in the examples described below, of preferably 60.0% or more, more preferably 63.0% or more, and still more preferably 66.0% or more.

[ method for producing grease composition of the present invention ]

The method for producing the grease composition of the present invention is not particularly limited, but for example, the following step (1) is included, and the step (2) is performed as needed.

Step (1): a step for preparing a mixed solution in which nanofibers (B) having a thickness (d') of 1 to 500nm are dispersed in a base oil (A);

step (2): and removing unnecessary components from the mixed solution.

The nanofibers (B) are at least 1 selected from the group consisting of cellulose nanofibers (B1) and modified cellulose nanofibers (B2).

The grease composition obtained through such a step can disperse nanofibers having a thickness (d) of 1 to 500nm while maintaining the fiber shape by suppressing aggregation of nanofibers (B) in the base oil (a). As a result, a higher-order structure due to the nanofibers (B) can be formed in the base oil, and the nanofibers (B) can be uniformly dispersed in the base oil (a). Therefore, by adding a small amount of the nanofibers (B), a grease composition having an appropriate working penetration can be prepared, and a grease composition having excellent leakage prevention performance and excellent energy transmission efficiency can be obtained.

The steps (1) to (2) will be explained below.

< step (1) >

The step (S1a) is a step of preparing a mixed solution in which nanofibers (B) having a thickness (d') of 1 to 500nm are dispersed in a base oil (a).

The details of the nanofibers (B) and the base oil (a) used in the step (S1a) are as described above.

As described above, the "thickness (d ')" referred to herein indicates the thickness of the nanofibers (B) as a raw material before blending in the base oil (a), and suitable ranges of the "thickness (d')" are the same as those described above.

In one embodiment of the present invention, powdered cellulose nanofibers that can be dispersed in water, an organic solvent, or a base oil (a) may be used as the nanofibers (B), or a dispersion liquid that is dispersed in water, an organic solvent, or a base oil (a) may be used. Alternatively, the base oil (a) may be subjected to nanofibrillation by applying shear thereto. When an aqueous dispersion of nanofibers (B) dispersed in water or an organic solvent dispersion of nanofibers (B) dispersed in an organic solvent is used, the solid content concentration of these dispersions containing nanofibers (B) is usually 0.1 to 70% by mass, preferably 0.1 to 65% by mass, more preferably 0.1 to 60% by mass, even more preferably 0.5 to 55% by mass, and even more preferably 1.0 to 50% by mass, based on the total amount (100% by mass) of the dispersion.

This dispersion can be prepared by mixing the nanofibers (B) in water or an organic solvent, and if necessary, mixing a dispersant or the like in the case of using the aqueous dispersion, and sufficiently stirring the mixture by hand or a stirrer.

The dispersant is preferably selected from aprotic polar solvents such as N, N-Dimethylformamide (DMF), N-dimethylacetamide (DMAc), and N-methylpyrrolidone (NMP); alcohols such as propanol, ethylene glycol, propylene glycol, and hexylene glycol; more than 1 kind of surfactant selected from polyglycerol fatty acid ester, sucrose fatty acid ester, citric acid monoglyceride, diacetyl tartaric acid monoglyceride, polyoxyethylene sorbitan fatty acid ester, and sorbitan fatty acid ester (Japanese text: ソルビタン acid エステル).

When the aqueous dispersion is used, the amount of the dispersant added to the mixed solution prepared in the step (S1a) is preferably 0.1 to 50% by mass, more preferably 0.5 to 40% by mass, still more preferably 1.0 to 30% by mass, yet more preferably 1.0 to 20% by mass, and yet still more preferably 1.0 to 10% by mass, based on the total amount (100% by mass) of the mixed solution.

When the aqueous dispersion or the organic solvent dispersion is used, the amount of water or the organic solvent in the mixed solution prepared in the step (S1a) is preferably 1 to 60% by mass, more preferably 3 to 50% by mass, and still more preferably 5 to 40% by mass, based on the total amount (100% by mass) of the mixed solution.

When the aqueous dispersion is used, the mixing amount ratio (water/dispersion solvent) of water to the dispersion solvent in the mixed solution prepared in the step (S1a) is preferably 0.01 to 600, more preferably 0.05 to 400, even more preferably 0.1 to 300, and even more preferably 0.2 to 200 in terms of mass ratio.

The mixed solution is sufficiently stirred by hand or a stirrer, whereby a mixed solution in which nanofibers (B) having a thickness (d') of 1 to 500nm are dispersed in the base oil (A) can be prepared.

The mixed liquid in which the nanofibers (B) having a thickness (d') of 1 to 500nm are dispersed in the base oil (a) may be prepared by directly dispersing the nanofibers (B) in the base oil (a), or may be prepared by forming nanofibers by applying shear to a nanofiber raw material in the base oil (a).

< step (2) >

The step (2) is a step of removing unnecessary components from the mixed solution prepared in the step (1).

The unnecessary component is 1 or more selected from water, an organic solvent, and a dispersant in the mixed solution.

However, these components may not be completely removed when the grease composition can maintain the state of the grease.

As a method for removing 1 or more selected from water, an organic solvent, and a dispersant in the mixed solution, a method of heating the mixed solution to evaporate and remove the same is preferable.

The conditions for evaporation and removal are preferably set in a temperature range in consideration of 1 or more boiling points selected from the group consisting of organic solvents and dispersants under an environment of a pressure of 0.001 to 0.1MPa, and heating is performed. The heating temperature is, for example, 0 to 100 ℃.

The grease composition is prepared by the step (2).

In the case of preparing a grease composition containing the organobentonite (C) and other additives, the organobentonite (C) and other additives may be mixed into the mixed liquid in the step (1), or may be mixed into the grease composition prepared in the step (2) and then subjected to a treatment such as homogenization using a roll mill or the like.

< use of the grease composition of the present invention >

The grease composition of the present invention is excellent in both the leakage prevention performance and the energy transmission efficiency.

Therefore, the grease composition according to one embodiment of the present invention can be suitably used for a speed reducer provided in an industrial robot or the like and a speed increaser provided in a wind turbine generator.

Examples of the speed reducer and the speed increaser include a speed reducer including a gear mechanism and a speed increaser including a gear mechanism. However, the application object of the grease composition according to one embodiment of the present invention is not limited to a reduction gear including a gear mechanism and a speed increaser including a gear mechanism, and the grease composition may be applied to traction drive and the like.

In addition, one embodiment of the present invention provides a speed reducer or speed increaser having the grease composition of the present invention at a lubricated part.

In addition, an embodiment of the present invention provides a lubricating method for lubricating a lubricated part of a speed reducer or a speed increaser by using the grease composition of the present invention.

In addition, the nanofibers (B) have a low environmental burden and are highly safe to the human body. Therefore, the grease composition of the present invention can be suitably used for food machines equipped with a speed reducer, food machines equipped with a speed increaser, and the like.

Further, the organobentonite (C) is also low in environmental load and excellent in safety to the human body. Therefore, the grease composition according to one embodiment of the present invention containing the organobentonite (C) can be suitably used for food machines equipped with speed reducers, food machines equipped with speed boosters, and the like.

Accordingly, one embodiment of the present invention provides a food machine provided with a speed reducer or a speed increaser, which has the grease composition of the present invention at a lubricated part.

In addition, one embodiment of the present invention provides a lubricating method for lubricating a lubricated part of a food machine equipped with a speed reducer or a speed increaser with the grease composition of the present invention.

Examples

The present invention will be specifically described with reference to the following examples, but the present invention is not limited to the following examples.

[ physical Property values of raw materials ]

The physical property values of the raw materials were determined by the following methods.

(1) Thickness and aspect ratio of nanofiber (B)

The thickness and length of each of 10 arbitrarily selected hydrophilic nanofibers were measured by a Transmission Electron Microscope (TEM), and the value calculated from "length"/"thickness" was defined as the "aspect ratio" of the targeted hydrophilic nanofiber.

(2) Kinematic viscosity at 40 ℃ and viscosity index

According to JIS K2283: 2000 were measured and calculated.

Examples 1 to 5 and comparative examples 1 to 3

In examples 1 to 5 and comparative examples 1 to 3, the following raw materials were used.

< base oil (A) >

Combining a low viscosity base oil (A1) with a high viscosity base oil (A2) to prepare a kinematic viscosity at 40 ℃ of 60mm²(ii)/s, viscosity index 135.

Low viscosity base oil (a 1): polyalphaolefin, kinematic viscosity at 40 ℃ 46mm²S, viscosity index 137

High viscosity base oil (a 2): polyalphaolefin, kinematic viscosity at 40 ℃ of 403mm²S, viscosity index 150

< thickening agent >

Nanofiber (B): a product name "BiNFi-s" (an aqueous dispersion containing Cellulose Nanofibers (CNF) having a polymerization degree of 600 (a coarseness (d') of 20 to 50nm (an average value of 35nm) and an aspect ratio of 100 or more (an average value of 100 or more)) manufactured by Sugino Machine co. Hereinafter, the dispersion of cellulose nanofibers (B1) is also referred to as "dispersion liquid".

Organobentonite (C): elementis Specialties, Inc., product name "BARARAGEL (registered trademark) 3000"

Lithium stearate

Aluminum stearate

< extreme pressure Agents >

Phosphorus-based extreme pressure agent: sodium polyphosphate

Sulfur-phosphorus-based extreme pressure agents: triphenyl thiophosphate

< dispersant >

Sorbitan acid esters

< antioxidant >

Amine antioxidant

< example 1>

A mixed solution was prepared by mixing 75 parts by mass of a dispersion of cellulose nanofibers (B1) (CNF amount: 7.5 parts by mass), 89.7 parts by mass of base oil (a), and 0.8 part by mass of a dispersant, and sufficiently stirring at 25 ℃. The mixture was then heated to 150 ℃ and water was evaporated from the mixture.

Subsequently, after cooling to room temperature (25 ℃), 1.0 part by mass of a phosphorus-based extreme pressure agent, 0.5 part by mass of a sulfur-phosphorus-based extreme pressure agent, and 0.5 part by mass of an antioxidant were added to the mixed solution, and then the mixture was sufficiently stirred and homogenized by using a 3-roll mill, thereby preparing a grease composition having a formulation shown in example 1 of table 1.

In example 1, (B1)/(C) was 7.5/0 (mass ratio).

< example 2>

40 parts by mass of a dispersion of cellulose nanofibers (B1) (CNF content: 4.0 parts by mass), 84.8 parts by mass of base oil (A), and 0.4 part by mass of a dispersant were mixed and sufficiently stirred at 25 ℃ to prepare a mixed solution. The mixture was then heated to 150 ℃ and water was evaporated from the mixture.

Subsequently, after cooling to room temperature (25 ℃), 8.8 parts by mass of the organic bentonite (C), 1.0 part by mass of the phosphorus-based extreme pressure agent, 0.5 part by mass of the sulfur-phosphorus-based extreme pressure agent, and 0.5 part by mass of the antioxidant were added to the mixed solution, and then sufficiently stirred, followed by homogenization treatment using a 3-roll mill, thereby preparing a grease composition having the formulation shown in example 2 in table 1.

In example 2, (B1)/(C) was 0.45 (mass ratio).

< example 3>

A grease composition having a formulation shown in example 3 of table 1 was prepared under the same conditions as in example 2, except that the loading of the base oil (a) was changed to 85.8 parts by mass without adding a phosphorus-based extreme pressure agent.

In example 3, (B1)/(C) was 0.45 (mass ratio).

< example 4>

A mixed solution was prepared by mixing 28 parts by mass of a dispersion of cellulose nanofibers (B1) (CNF amount: 2.8 parts by mass), 88.4 parts by mass of base oil (a), and 0.3 part by mass of a dispersant, and sufficiently stirring at 25 ℃. The mixture was then heated to 150 ℃ and water was evaporated from the mixture.

Subsequently, after cooling to room temperature (25 ℃), 6.5 parts by mass of the organic bentonite (C), 1.0 part by mass of the phosphorus-based extreme pressure agent, 0.5 part by mass of the sulfur-phosphorus-based extreme pressure agent, and 0.5 part by mass of the antioxidant were added to the mixed solution, and then sufficiently stirred, followed by homogenization treatment using a 3-roll mill, thereby preparing a grease composition having the formulation shown in example 4 of table 1.

In example 4, (B1)/(C) was 0.43 (mass ratio).

< example 5>

A grease composition of the formulation shown in example 5 of table 1 was prepared under the same conditions as in example 3, except that the content of the base oil (a) was changed to 86.3 parts by mass without adding the sulfur-phosphorus extreme pressure agent.

In example 5, (B1)/(C) was 0.45 (mass ratio).

< comparative examples 1 to 3>

The components shown in table 1 were mixed in the proportions shown in table 1 to prepare lubricant compositions of comparative examples 1 to 3.

[ evaluation ]

The grease composition thus prepared was evaluated as follows.

< evaluation of penetration of working Cone >

According to JIS K22207: 2013 at 25 ℃.

< evaluation of shear stability >

The working cone penetration change in the roller stability test was measured by the method described in ASTM D1831. However, the temperature and time were changed to 80 ℃ and the reaction was carried out after 20 hours.

The smaller the working cone penetration change in the roller stability test, the more excellent the shear stability and the more excellent the leak resistance of the grease.

< evaluation of energy transfer efficiency >

The measuring apparatus 100 shown in fig. 1 is an apparatus in which an input-side motor unit 111, an input-side torque measuring device 112, an input-side speed reducer 113 (product name "CSG-40-100-2 UH" manufactured by Harmonic Drive Systems), an output-side torque measuring device 122, an output-side speed reducer 123 (product name "RV-125V" manufactured by Nabtesco) and an output-side motor unit 121 are connected in this order.

A grease-filled tank (internal temperature: 30 ℃) of an input-side reduction gear 113 of a measuring apparatus 1 shown in FIG. 1 was filled with 140g of mixed grease, the measuring apparatus 100 was operated under conditions of a load torque of 240Nm and an input-side rotation speed of 1600rpm, the rotation speeds and torques on the input side and the output side were measured, the torque transfer efficiency was calculated from the following formula (1), and the energy transfer efficiency was evaluated.

(torque transmission efficiency (%))) - (output side torque (Nm))/[ (input side torque (Nm)) × (reduction gear ratio) ] × 100 … (1)

The reduction ratio is 100.

The torque conduction efficiency is an index showing the amount of energy input to be lost until output, and is expressed as: the lower the torque conduction efficiency, the greater the energy loss, and conversely, the higher the torque conduction efficiency, the smaller the energy loss.

The results are shown in Table 1.

[ Table 1]

The following matters are apparent from table 1.

It is clear that the grease compositions of examples 1 to 5 have a moderate working penetration and are excellent in shear stability and energy transfer efficiency. Therefore, a grease composition excellent in leakage prevention performance and energy transmission efficiency is known.

On the other hand, it is found that the grease composition containing the organic bentonite without the nanofibers (B) as in the grease composition of comparative example 1 has a moderate working penetration, but is inferior in shear stability and energy transfer efficiency.

Further, like the grease compositions of comparative examples 2 and 3, the grease compositions using lithium stearate or aluminum stearate as a thickener had a moderate working penetration, but had poor shear stability and energy transfer efficiency.

In example 1, it was confirmed whether or not the thickness of the cellulose nanofibers (B1) changed before and after the preparation of the grease composition, and as a result, it was confirmed that: the thickness hardly changes before and after the manufacture. From this, it is understood that "the thickness (d) of the nanofibers (B)" dispersed in the base oil is almost the same as "the thickness (d') of the nanofibers (B)" as a raw material before blending in the base oil, and they can be regarded as substantially the same.

Claims

1. A grease composition for a speed reducer and a speed increaser,

the grease composition contains a base oil (A) and a nanofiber (B) having a thickness (d) of 1 to 500nm,

2. The grease composition of claim 1,

the content of the nanofibers (B) is 0.1 to 20 mass% based on the total amount of the grease composition.

3. Grease composition according to claim 1 or 2, wherein,

also contains organic bentonite (C),

the nanofiber (B) comprises the cellulose nanofiber (B1).

4. Grease composition according to claim 3, wherein,

the content of the organobentonite (C) is 0.01 to 15% by mass based on the total amount of the grease composition.

5. Grease composition according to claim 3 or 4, wherein,

the content ratio of the cellulose nanofibers (B1) to the organobentonite (C), namely B1/C, is 0.05-5.0 in terms of mass ratio.

6. A grease composition according to any one of claims 1 to 5,

the base oil (A) is a mixed base oil comprising a low-viscosity base oil (A1) and a high-viscosity base oil (A2),

the kinematic viscosity at 40 ℃ of the low-viscosity base oil (A1) is 5mm²/s～150mm²/s，

The kinematic viscosity of the high-viscosity base oil (A2) at 40 ℃ is 200mm²/s～1000mm²/s。

7. A grease composition according to any one of claims 1 to 6, having a working penetration at 25 ℃ of 220 to 440.

8. A grease composition according to any one of claims 1 to 7, which is used for a food machine equipped with a speed reducer or a food machine equipped with a speed reducer.

9. A method of lubricating a lubricated part of a speed reducer or a speed increaser with the grease composition according to any one of claims 1 to 7.

10. A method of lubricating a lubricated part of a food machine equipped with a speed reducer or a speed increaser with the grease composition according to any one of claims 1 to 7.