JP2023128103A - grease composition - Google Patents

Abstract

To provide a grease composition capable of reducing a steel-resin friction coefficient.SOLUTION: A grease composition according to the present invention contains a base oil having a kinematic viscosity at 100°C of 5-30 mm2/s, a thickener, a polymer having a weight-average molecular weight of 1,000-500,000, and an aliphatic amide compound and is used for sliding between steel and resin.SELECTED DRAWING: None

Description

The present invention relates to a grease composition used between steel and resin.

Grease compositions are mainly used for sliding bearings, rolling bearings, or sliding surfaces where it is difficult to keep a lubricating oil film attached because the contact surfaces move. The members that make up the sliding surface are mainly made of metal, but in recent years, resin materials are sometimes used for some of the sliding members for the purpose of reducing weight. However, the forms of friction and wear differ between sliding between steel (metal) and resin and sliding between metals, as well as the adsorption of the grease composition to the sliding surface and the reactivity of additives. Therefore, even if a grease composition suitable for sliding between metals is applied as is to the sliding portion between steel and resin, the expected performance may not always be obtained.

The grease composition used between steel and resin contains a base oil, a diurea compound as a thickener, and a chain hydrocarbon polymer, and the weight average molecular weight of the chain hydrocarbon polymer is 20,000 to 20,000. 30,000 has been proposed (Patent Document 1).
However, in recent years, in order to promote energy saving in sliding parts such as bearings, even lower friction is required for grease compositions applied to sliding parts.

International Publication 2016/104812

The problem to be solved by the present invention is to provide a grease composition that reduces the coefficient of friction between steel and resin.

In order to solve the above problems, the inventors of the present invention have conducted intensive studies and found that the use of a thickener, an aliphatic amide compound, and an oil-soluble polymer in the base oil is suitable for sliding between steel and resin. It has been found that a grease composition can be obtained which reduces the coefficient of friction.
The present invention was made based on this knowledge and consists of the following.

<1> Contains a base oil with a kinematic viscosity of 5 to 30 mm ² /s at 100°C, a thickener, a polymer with a weight average molecular weight of 1,000 to 500,000, and an aliphatic amide compound. , a grease composition used for sliding between steel and resin.
<2> The grease composition according to <1>, wherein the aliphatic amide compound is a saturated aliphatic amide compound.
<3> The grease composition according to <1> or <2>, wherein the thickener is a urea-based thickener.
<4> The grease composition according to <3>, wherein the urea-based thickener is a diurea compound represented by the following formula (1).
R ¹ -NHCONH-R ² -NHCONH-R ³ (1)
(In formula (1), R ¹ and R ³ are an aliphatic hydrocarbon group having 4 to 24 carbon atoms which may have a substituent, a fatty acid having 6 to 15 carbon atoms which may have a substituent) Represents a cyclic hydrocarbon group or an aromatic hydrocarbon group having 6 to 15 carbon atoms which may have a substituent, and R ² is a divalent group having 6 to 15 carbon atoms which may have a substituent. represents an aromatic hydrocarbon group.)
<5> The grease composition according to any one of <1> to <4>, wherein the base oil contains a poly-α-olefin.

The grease composition of the present invention has a special effect of reducing the coefficient of friction in sliding between steel and resin.

Hereinafter, the present invention will be explained in detail based on its preferred embodiments. In this specification, unless otherwise specified, the notation "X to Y" for numerical values X and Y means "more than or equal to X and less than or equal to Y." In such a notation, if a unit is attached only to the numerical value Y, the unit shall also be applied to the numerical value X.

The grease composition of the present invention includes a base oil, a thickener, a polymer having a weight average molecular weight of 1,000 to 500,000, and an aliphatic amide compound.

[Base oil]
As the base oil of the present invention, either mineral base oil or synthetic base oil can be used. The kinematic viscosity at 100°C of the base oil of the present invention is 5 to 30 mm ² /s, preferably 8 mm ² /s or more, more preferably 10 mm ² /s or more, and preferably 27 mm ² /s or less, more Preferably it is 25 mm ² /s or less. In one embodiment, the kinematic viscosity at 100° C. is preferably 8 to 27 mm ² /s, more preferably 10 to 25 mm ² /s. When the kinematic viscosity at 100° C. is at least the above lower limit, the coefficient of friction between steel and resin can be reduced, and when it is at or below the above upper limit, the low temperature fluidity of the grease composition is improved.

The kinematic viscosity at 40°C of the base oil of the present invention is preferably 40 mm ² /s or more, more preferably 60 mm ² /s or more, and preferably 300 mm ² /s or less, for the same reason as the kinematic viscosity at 100°C. , more preferably 230 mm ² /s or less. In one embodiment, the kinematic viscosity at 40° C. is preferably 40 to 300 mm ² /s, more preferably 60 to 230 mm ² /s.
Note that in this specification, the kinematic viscosity at 100°C or 40°C means the kinematic viscosity at 100°C or 40°C, respectively, as measured in accordance with JIS K2283:2000.

The viscosity index of the base oil of the present invention is preferably 90 or higher, more preferably 120 to 150, the pour point is preferably -10°C or lower, more preferably -15°C or lower, and the flash point is preferably 200°C or lower. ℃ or higher.
In this specification, the viscosity index means the numerical value measured according to JIS K2283:2000, the pour point according to JIS K2269:1987, and the flash point according to JIS K2265-4:2007.

Examples of mineral base oils include base oil fractions obtained by distilling crude oil under normal pressure or further distilling it under reduced pressure and refining distillate oil through various refining processes. The refining process includes hydrorefining, solvent extraction, solvent dewaxing, hydrodewaxing, sulfuric acid washing, clay treatment, etc., and a mineral base oil can be obtained by combining these in an appropriate order. Also useful is a mixture of a plurality of refined oils with different properties obtained from different crude oils or distillate oils by different process combinations and sequences. Either method can be used preferably by adjusting the properties of the base oil obtained so that it satisfies the above-mentioned physical properties.

As the synthetic base oil, it is preferable to use a base material with excellent hydrolytic stability, such as polyolefins such as poly-α-olefins, polybutenes, and copolymers of two or more various olefins, diesters, polyol esters, etc. Examples include ester-based synthetic oils, ether-based synthetic oils such as alkyldiphenyl and polypropylene glycol, polyalkylene glycols, alkylbenzenes, and alkylnaphthalenes. Among these, poly-α-olefin is preferred in terms of oxidation stability and low-temperature fluidity.

As the base oil, the exemplified synthetic base oils can be used alone or in combination of two or more. Furthermore, it can also be used in combination with the mineral base oil.
When using a mixture of multiple base oils, including synthetic base oils, as long as the base oil mixture satisfies the above physical properties, the individual base oils before mixing must be outside the range of physical properties. can also be used. Therefore, each synthetic base oil does not necessarily have to satisfy the above-mentioned physical properties, but preferably falls within the range of the above-mentioned physical properties.

The base oil content is preferably 50% by mass or more, more preferably 60% by mass or more, and preferably 95% by mass or less, more preferably 85% by mass or less, based on the total amount of the grease composition. In one embodiment, the base oil content is preferably 50-95% by weight, more preferably 60-85% by weight. When the base oil content is at least the above lower limit value, appropriate lubricity can be ensured, and when it is at most the above upper limit value, the base oil is easily retained in the grease composition.

[Thickener]
As the thickener of the present invention, both urea-based thickeners and metal soap-based thickeners can be used.

<Urea-based thickener>

As the urea-based thickener, for example, a diurea compound obtained by a reaction between a diisocyanate and a monoamine, a polyurea compound obtained by a reaction between a diisocyanate and a monoamine or a diamine, etc. can be used.

A diisocyanate is a compound in which two hydrogen atoms of a hydrocarbon are replaced with isocyanate groups. The hydrocarbon may be an acyclic hydrocarbon or a cyclic hydrocarbon, and may be an aromatic hydrocarbon, an alicyclic hydrocarbon, or an aliphatic hydrocarbon. The hydrocarbon preferably has 6 to 15 carbon atoms, more preferably 8 to 14 carbon atoms. Preferred specific examples of the diisocyanate include phenylene diisocyanate, tolylene diisocyanate, biphenyl diisocyanate (diphenyl diisocyanate), diphenylmethane diisocyanate, hexane diisocyanate, decane diisocyanate, and the like. One type of diisocyanate may be used alone, or two or more types may be used in combination.

A monoamine is a compound in which one hydrogen of ammonia is substituted with a hydrocarbon group, and a diamine is a compound in which two hydrogens of ammonia are substituted with a hydrocarbon group.
Monoamines include aliphatic amines in which one hydrogen of ammonia is substituted with an aliphatic hydrocarbon group having 4 to 24 carbon atoms, and aliphatic amines in which one hydrogen of ammonia is substituted with an alicyclic hydrocarbon group having 6 to 15 carbon atoms. Preferably used are alicyclic amines in which one hydrogen of ammonia is substituted with an aromatic hydrocarbon group having 6 to 15 carbon atoms. The substituents of the aliphatic amine, alicyclic amine, and aromatic amine may each have a further substituent.
Preferred specific examples of monoamines include octylamine, dodecylamine, hexadecylamine, octadecylamine, oleylamine, aniline, p-toluidine, and cyclohexylamine. Preferred specific examples of diamine include ethylenediamine, propanediamine, butanediamine, hexanediamine, octanediamine, phenylenediamine, tolylenediamine, xylenediamine, diaminodiphenylmethane, and the like.

As the urea-based thickener, a diurea compound obtained by the reaction of the above diisocyanate and a monoamine and represented by the following formula (1) is preferable.

(Chem.1)
R ¹ -NHCONH-R ² -NHCONH-R ³ (1)
In formula (1), R ¹ and R ³ are an aliphatic hydrocarbon group having 4 to 24 carbon atoms which may have a substituent, and an alicyclic group having 6 to 15 carbon atoms which may have a substituent. represents a hydrocarbon group of the formula hydrocarbon group, or an aromatic hydrocarbon group having 6 to 15 carbon atoms which may have a substituent, and R ² is a divalent hydrocarbon group having 6 to 15 carbon atoms which may have a substituent. Represents an aromatic hydrocarbon group.
When R ¹ and R ³ are aliphatic hydrocarbon groups, the number of carbon atoms is more preferably 8 to 18, and when R 1 and R 3 are alicyclic hydrocarbon groups, the number of carbon atoms is more preferably 6 to 12. , when it is an aromatic hydrocarbon group, the number of carbon atoms is more preferably 7.

R ¹ and R ³ may be the same or different, but from the viewpoint of increasing the dropping point of the grease composition, it is preferable that at least one of them is an alicyclic hydrocarbon group.

<Metallic soap-based thickener>
Metal soap thickeners include single soaps and complex soaps. A single soap is a metal soap obtained by saponifying fatty acids or fats and oils with an alkali metal hydroxide or an alkaline earth metal hydroxide. Complex soaps are complex soaps that combine the fatty acids used in single soaps with organic acids with different molecular structures.
The fatty acid may be a fatty acid derivative having a hydroxy group or the like. As the fatty acid, monovalent or divalent aliphatic carboxylic acids are preferred. The fatty acid is preferably an aliphatic carboxylic acid having 6 to 20 carbon atoms, more preferably a monovalent aliphatic carboxylic acid having 12 to 20 carbon atoms or a divalent aliphatic carboxylic acid having 6 to 14 carbon atoms. The fatty acid is preferably a monovalent aliphatic carboxylic acid containing one hydroxy group. The organic acid to be combined with the fatty acid in the complex soap is preferably a dibasic acid such as acetic acid, azelaic acid or sebacic acid, or benzoic acid.
As the metal of the metal soap thickener, alkali metals such as lithium and sodium, alkaline earth metals such as calcium, or amphoteric metals such as aluminum are used.

This thickener may be blended in the form of a metal soap, but the carboxylic acid and the metal source (metal salt, metal salt hydroxide, etc.) are blended separately and reacted during grease production to form a metal soap. May also be used as a soap thickener.
Such carboxylic acid metal salts may be used alone or in combination of a plurality of types. For example, a mixture of lithium 12-hydroxystearate and lithium azelaate is preferred.

The thickener of the present invention may be used alone or in combination of a plurality of types. The content of the thickener may be sufficient as long as a desired consistency can be obtained, and is, for example, preferably 2 to 30% by mass, more preferably 5 to 20% by mass, based on the total amount of the grease composition. As the thickener of the present invention, it is preferable to use a urea-based thickener from the viewpoint of heat resistance at high temperatures and lubricity of the thickener itself.

〔polymer〕
The polymer of the present invention has a weight average molecular weight of 1,000 to 500,000. The weight average molecular weight is preferably 2,000 or more, more preferably 5,000 or more, even more preferably 100,000 or more, and preferably 450,000 or less, more preferably 400,000 or less, and still more preferably 300,000. It is as follows. In one embodiment, the weight average molecular weight is preferably 2,000 to 450,000, more preferably 5,000 to 400,000, even more preferably 100,000 to 300,000. When the weight average molecular weight is at least the above lower limit, the lubricity of the grease composition is improved, and when it is at most the above upper limit, the low temperature fluidity is improved.

In this specification, the weight average molecular weight of a polymer means a value determined by gel permeation chromatography (GPC) (molecular weight obtained in terms of polystyrene). The measurement conditions are as follows.
[GPC measurement conditions]
Equipment: ACQUITY (registered trademark) APC UV RI system manufactured by Waters Corporation Column: From the upstream side, ACQUITY (registered trademark) APC XT900A manufactured by Waters Corporation (gel particle size 2.5 μm, column size (inner diameter x length) 4.6 mm x 150 mm) and one ACQUITY (registered trademark) APC XT200A (gel particle size 2.5 μm, column size (inner diameter x length) 4.6 mm x 150 mm) manufactured by Waters Corporation are connected in series. Column temperature: 40 ℃
Sample solution: Tetrahydrofuran solution with sample concentration of 1.0% by mass Flow rate: 0.8mL/min
Detection device: Differential refractive index detector Reference material: Standard polystyrene (Agilent EasiCal (registered trademark) PS-1 manufactured by Agilent Technologies) 8 points (molecular weight: 2698000, 660500, 325600, 128600, 69650, 30230, 9960, 2980 )

Examples of the polymer of the present invention include, but are not limited to, ethylene-α-olefin copolymers, poly(meth)acrylates, styrene-diene copolymers, polybutenes, and the like.

<Ethylene-α-olefin copolymer>
The ethylene-α-olefin copolymer contains ethylene and an α-olefin having 3 or more carbon atoms as monomer units. Examples of α-olefins having 3 or more carbon atoms include propylene, 1-butene, 1-pentene, 3-methyl-1-butene, 1-hexene, 4-methyl-1-pentene, and 3-methyl-1-pentene. , 1-octene, and 1-decene, with propylene being preferred.

The content of ethylene units in the ethylene-α-olefin copolymer may be, for example, 30 to 80 mol%, 35 to 75 mol%, or 40 to 70 mol%, based on the total amount of monomer units. It may be. Further, the content of α-olefin units in the ethylene-α-olefin copolymer may be, for example, 20 to 70 mol%, 25 to 65 mol%, or 30 to 65 mol%, based on the total amount of monomer units. It may be up to 60 mol%.

<Poly(meth)acrylate>
It is preferable that the poly(meth)acrylate contains a structural unit represented by the following general formula (2). As used herein, "(meth)acrylate" means "acrylate and/or methacrylate."
(In formula (2), R ⁴ represents hydrogen or a methyl group, and R ⁵ represents a linear or branched hydrocarbon group having 1 to 18 carbon atoms.)
In one embodiment, R ⁵ is a hydrocarbon group having 1 to 5 carbon atoms, a hydrocarbon group having 6 to 18 carbon atoms, or a combination thereof.

<Styrene-diene copolymer>
The styrene-diene copolymer contains, as monomer units, one or more styrene monomers selected from styrene and its hydrides, and one or more diene monomers selected from dienes and its hydrides. including. Examples of the diene include butadiene and isoprene.

The content of styrene monomer units in the styrene-diene copolymer may be, for example, 1 to 30 mol%, or 5 to 20 mol%, based on the total amount of monomer units. Further, the content of diene monomer units in the styrene-diene copolymer may be, for example, 70 to 99 mol%, or 80 to 95 mol%, based on the total amount of monomer units.

<Polybutene>
Polybutene is a polymer obtained by polymerizing butenes having double bonds. The polybutene may be, for example, a polymer represented by the following general formula (3).

In formula (3), n represents an integer from 5 to 90.

As the polybutene, a commercially available product may be used as is, or one produced by a known method may be used. Examples of methods for producing polybutene include a method in which butadiene is removed from a C4 fraction produced by naphtha decomposition and polymerized using an acid catalyst.

As the polymer of the present invention, one type may be used alone, or two or more types of polymers may be used in combination. As the polymer, it is preferable to use an ethylene-α-olefin polymer from the viewpoint of lowering the friction of the grease composition.

As the polymer of the present invention, a pure product may be used, or a diluted product diluted with light oil such as kerosene or light oil may be used.
The content of the polymer of the present invention (excluding diluent oil) is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, and even more preferably 0.4% by mass, based on the total amount of the grease composition. % or more, preferably 10% by mass or less, more preferably 8% by mass or less, still more preferably 6% by mass or less. In one embodiment, the polymer content is preferably 0.1 to 10% by weight, more preferably 0.2 to 8% by weight, even more preferably 0.4 to 6% by weight. When the polymer content range is at least the above lower limit, the friction coefficient between steel and resin is further reduced, and when it is at most the above upper limit, the low temperature fluidity of the grease composition is improved.

[Aliphatic amide compound]
The aliphatic amide compounds used in the present invention include aliphatic monoamides having one amide group (-NH-CO-), aliphatic bisamides having two amide groups, aliphatic triamides having three amide groups, and the like.
The monoamide may be either an acid amide of a monoamine or an acid amide of a monoacid, and a bisamide may be an acid amide of a diamine or an acid amide of a diacid.
Preferably used aliphatic amide compounds have a melting point of 40 to 180°C, more preferably 80 to 180°C, even more preferably 100 to 170°C, and a molecular weight of 242 to 932, more preferably 298 to 876. It is.
The aliphatic monoamide, aliphatic bisamide, and aliphatic triamide are represented by the following general formula (4), general formula (5) or (6), and general formula (7), respectively.

R ⁶ -CO-NH-R ⁷ ...(4)

R ⁶ -CO-NH-A ¹ -NH-CO-R ⁷ ...(5)

R ⁶ -NH-CO-A ¹ -CO-NH-R ⁷ ...(6)

R ⁶ -M-A ¹ -CH (A ² -M-R ⁷ )-A ³ -M-R ⁷ ...(7)

In each of the above formulas, R ⁶ and R ⁷ are each independently an aliphatic hydrocarbon group having 5 to 25 carbon atoms. The case of general formula (4) also includes the case where R ⁷ is hydrogen. The number of carbon atoms in R ⁶ and R ⁷ is preferably 10 or more, more preferably 15 or more, and preferably 20 or less, more preferably 17 or less. In one embodiment, the number of carbon atoms in R ⁶ and R ⁷ is preferably 10 to 20, more preferably 15 to 17. When the number of carbon atoms in R ⁶ and R ⁷ is at least the above lower limit, the friction coefficient between steel and resin is further reduced, and when it is at most the above upper limit, the low temperature fluidity of the grease composition is improved.
A ¹ , A ² , and A ³ are each independently an aliphatic hydrocarbon group, an alicyclic hydrocarbon group, or an aromatic hydrocarbon group having 1 to 10 carbon atoms, or a combination thereof. It is a divalent hydrocarbon group of number 1 to 10, and M is an amide group (-NH-CO- or -CO-NH-).
Note that when the aliphatic amide compound is a monoamide, R ⁷ is preferably hydrogen or an aliphatic hydrocarbon group having 10 to 20 carbon atoms.
When the aliphatic amide compound is a diamine acid amide, A ¹ is preferably a divalent saturated chain hydrocarbon group having 1 to 4 carbon atoms.
Furthermore, in formulas (5) and (6), some of the hydrogens in the hydrocarbon group represented by R ⁶ , R ⁷ , or A ¹ may be substituted with a hydroxyl group (-OH).

Specifically, aliphatic monoamides include saturated fatty acid amides such as lauric acid amide, palmitic acid amide, stearic acid amide, behenic acid amide, and hydroxystearic acid amide, and unsaturated fatty acid amides such as oleic acid amide and erucic acid amide. and substituted amides with saturated or unsaturated long-chain fatty acids and long-chain amines, such as stearyl stearamide, oleyl oleamide, oleyl stearamide, and stearyl oleamide.

Specifically, the diamine acid amide represented by formula (5) includes ethylene bisstearamide, ethylene bis isostearamide, ethylene bisoleic acid amide, methylene bislauric acid amide, and hexamethylene bisoleic acid amide. , hexamethylene bishydroxystearamide, and the like. Specific examples of the bisamide of the diacid represented by formula (6) include N,N'-bisstearyl sebacic acid amide and the like.

The aliphatic amide compound of the present invention is preferably a saturated aliphatic amide in which at least one of R ⁶ and R ⁷ is a saturated aliphatic hydrocarbon group from the viewpoint of low friction.
Further, as the aliphatic amide compound of the present invention, an aliphatic bisamide or an aliphatic triamide is preferable from the viewpoint of low friction, and an aliphatic bisamide is more preferable.

The aliphatic amide compounds of the present invention may be used alone or in combination of two or more. The content of the aliphatic amide compound of the present invention is preferably 1% by mass or more, more preferably 2% by mass or more, even more preferably 4% by mass or more, and preferably 30% by mass or less, based on the total amount of the grease composition. , more preferably 20% by mass or less, still more preferably 15% by mass or less. In one embodiment, the content of the aliphatic amide compound is preferably 1 to 30% by weight, more preferably 2 to 20% by weight, and even more preferably 4 to 15% by weight. When the content of the aliphatic amide compound is at least the above lower limit, the friction coefficient between steel and resin is further reduced, and when it is at most the above upper limit, the low temperature fluidity of the grease composition is improved.
Note that when this aliphatic amide compound is heated and melted in the presence of base oil, the base oil is retained in the amide compound that forms a three-dimensional network structure, and the amide compound is simply dispersed and mixed into the grease. The coefficient of friction between the steel and the resin is lower than that in the case where the steel is used.

[Other additives]
In addition to the above-mentioned components, the grease composition of the present invention may optionally contain solid lubricants, anti-wear agents or extreme pressure agents, antioxidants, oil-based agents, and Rust agents, corrosion inhibitors, etc. can be added as appropriate.

Examples of the solid lubricant include graphite, graphite fluoride, melamine cyanurate, polytetrafluoroethylene, molybdenum disulfide, antimony sulfide, boron nitride, and alkali (earth) metal borates. When the grease composition contains a solid lubricant, its content is usually 0.1 to 20% by mass based on the total amount of the grease composition.

Examples of anti-wear agents or extreme pressure agents include organic zinc compounds such as zinc dialkyldithiophosphate and zinc dialkyldithiocarbamate, sulfur-containing compounds such as molybdenum dialkyldithiocarbamate, dihydrocarbyl polysulfide, sulfurized esters, thiazole compounds, and thiadiazole compounds. Compounds include phosphorus-based extreme pressure agents such as phosphoric acid esters, acidic phosphoric esters, amine salts of acidic phosphoric esters, and phosphorous esters. When the grease composition contains an anti-wear agent or an extreme pressure agent, the content is usually 0.1 to 10% by mass based on the total amount of the grease composition.

Examples of antioxidants include phenolic compounds such as 2,6-di-t-butylphenol and 2,6-di-t-butyl-p-cresol, diphenylamine, dialkyldiphenylamine, phenyl-α-naphthylamine, p- Examples include amine compounds such as alkylphenyl-α-naphthylamine. When the grease composition contains an antioxidant, the content thereof is usually 0.5 to 10% by mass, preferably 1 to 5% by mass, based on the total amount of the grease composition. The antioxidant may include both a phenol compound and an amine compound.

Examples of oily agents include amines such as laurylamine, myristylamine, palmitylamine, stearylamine, and oleylamine; higher alcohols such as lauryl alcohol, myristyl alcohol, palmityl alcohol, stearyl alcohol, and oleyl alcohol; lauric acid; Higher fatty acids such as myristic acid, palmitic acid, stearic acid, and oleic acid; fatty acid esters such as methyl laurate, methyl myristate, methyl palmitate, methyl stearate, and methyl oleate; glycerin oleate, glycerin stearate, etc. Examples include oils and fats. When the grease composition contains an oily agent, the content thereof is usually 0.01 to 5% by mass based on the total amount of the grease composition.

Examples of the rust preventive include amines, neutral or overbased petroleum-based or synthetic oil-based metal sulfonates, carboxylic acid metal salts, esters, phosphoric acid, phosphates, and the like. When the grease composition contains a rust preventive agent, the content thereof is usually 0.005 to 5% by mass based on the total amount of the grease composition.

As the corrosion inhibitor, for example, known corrosion inhibitors such as benzotriazole compounds, tolyltriazole compounds, thiadiazole compounds, and imidazole compounds can be used. When the grease composition contains a corrosion inhibitor, the content is usually 0.01 to 10% by mass based on the total amount of the grease composition.

[Grease composition]
The consistency of the grease composition of the present invention is preferably 175 to 385, more preferably 220 to 340, from the viewpoint of fluidity and ease of retaining the grease on sliding parts. Note that consistency represents the physical hardness of grease.
Consistency in this specification means worked penetration measured in accordance with JIS K2220:2013.

The dropping point of the grease composition of the present invention is preferably 180°C or higher, more preferably 200°C or higher, from the viewpoint of maintaining the durability of parts at high temperatures. Note that the dropping point refers to the temperature at which viscous grease loses its thickener structure as the temperature is increased.
Here, the dropping point can be measured in accordance with JIS K2220:2013.

[Preparation method]
The grease composition of the present invention can be produced by a general grease manufacturing method, but it is preferable that the aliphatic amide compound is mixed and then heated once to a temperature above its melting point.
That is, a method may be used in which an aliphatic amide compound and a base oil are heated above the melting point of the aliphatic amide compound, cooled, and then physically mixed with a general grease consisting of a thickener and base oil. After mixing all the components including the agent, the mixture may be heated to a temperature higher than the melting point of the aliphatic amide compound and then cooled.

In this way, by heating the aliphatic amide compound once above the melting point of the aliphatic amide compound in the presence of at least the base oil, the base oil is retained in the aliphatic amide compound forming a three-dimensional network structure. It becomes a semi-solid gel. Microscopically, the base oil moves freely within the network structure. This indicates that, for example, when a gel-like lubricating composition comes into contact with narrow porous voids, the base oil in the gel can migrate from the gel to the narrow voids due to capillary action. Or, conversely, if excess base oil is present in the system, the three-dimensional structure of the gel induces capillary action to entrap these excess base oils within the gel. In such a state, consistency is imparted by the thickener, and the coefficient of friction in the sliding portion can be reduced.

<Lubrication target>
The grease composition of the present invention is suitably used for lubricating various resin sliding members and steel sliding members. Examples of the resin include polyamide resin, polycarbonate, polyamideimide resin, polyacetal resin, polybutylene terephthalate resin, polyether ether ketone resin, etc., and are particularly suitable for members using polyamide resin. Further, examples of the steel sliding member include bearing steel, carbon steel, stainless steel (SUS), and the like.

<Applications of grease composition>
The grease composition of the present invention can be used for sliding between steel and resin in commonly used machines, bearings, gears, ball screws, etc., and also exhibits excellent performance even under harsh environments. I can do it. For example, in automobiles, the water pump, cooling fan motor, starter, alternator, and various actuators around the engine, propeller shaft, constant velocity joint (CVJ), wheel bearings, clutches, and other parts of the power train, electric power steering (EPS), It can be used to lubricate various parts such as electric power windows, braking devices, ball joints, door hinges, handles, and brake expanders. Furthermore, various shafts and joints that may slide back and forth in construction machinery such as power shovels, bulldozers, and crane trucks, steel industry, paper manufacturing industry, forestry machinery, agricultural machinery, chemical plants, power generation equipment, and railway vehicles. It can also be used for. Other uses include threaded joints for seamless pipes and bearings for outboard motors.

The present invention will be described below using examples that are one embodiment of the present invention, but the present invention is not limited to the following embodiments.

Test grease compositions were prepared by blending the base oil, thickener, and each additive at the blending ratios shown in Table 1 for each of Examples 1 to 11 and Comparative Examples 1 to 4. Unless otherwise specified, "mass %" in the table represents each compounding amount based on the total amount of the grease composition.

(1) Base oil Base oils 1 and 2 were mixed so that the kinematic viscosity at 100° C. was the value shown in Table 1.
・Base oil 1 Poly-α-olefin (kinematic viscosity at 100°C: 8.0 mm ² /s, viscosity index: 136, pour point: <-45°C, flash point: 265°C)
・Base oil 2 Poly-α-olefin (kinematic viscosity at 100°C: 40.0mm ² /s), viscosity index: 149, pour point: <-30°C, flash point: 280°C)
(2) Thickener Diurea synthesized from monoamine and diphenylmethane diisocyanate (MDI) was used as the thickener. As the monoamine, cyclohexylamine (CHA) and/or octadecylamine (ODA) were mixed and used at the molar ratio shown in Table 1.
(3) Polymer/Polymer A Ethylene-propylene copolymer (weight average molecular weight: 200,000, polymer concentration in diluent oil: 10%)
・Polymer B Ethylene-propylene copolymer (weight average molecular weight: 300,000, polymer concentration in diluent oil: 10%)
・Polymer C ethylene-propylene copolymer (weight average molecular weight: 60,000, no diluent oil)
・Polymer D Styrene-diene copolymer (weight average molecular weight: 440,000, polymer concentration in diluent oil: 10%)
・Polymer E Polymethacrylate (weight average molecular weight: 400,000, polymer concentration in diluent oil: 20%)
・Polymer F Polybutene (weight average molecular weight: 2,000, no diluent oil)
(4) Aliphatic amide compounds/aliphatic amide ethylene bisstearamide (5) Other additives/antioxidants diphenylamine

[Preparation method]
Reactant 1 was obtained by reacting amine and isocyanate, which are raw materials for a thickener, in base oil so that the proportions shown in Table 1 were achieved, and by raising and cooling the temperature. Furthermore, an aliphatic amide compound was added to the same type of base oil in a separate container from the base oil, heated to 150°C (above the melting point of the aliphatic amide compound), stirred with a magnetic stirrer, and then heated to room temperature. Semi-solid reaction product 2 was obtained by cooling to .
Reactant 1 and Reactant 2 were mixed so that the aliphatic amide compounds were in the proportions shown in Table 1, and the remaining additives were added in the proportions shown in Table 1. The mixture was kneaded in a three-roll mill to obtain test grease compositions shown in Table 1.

The following evaluations were performed on the obtained test grease composition. The evaluation results are shown in Table 1.

〔Evaluation methods〕
<Friction coefficient>
Evaluation tests were conducted using a ball and disc reciprocating friction tester. The ball (steel sliding member) was a SUJ-2 1/4 inch diameter ball, and the disk (resin sliding member) was a 66 nylon plate (TPS (registered trademark) N66 manufactured by Toray Plastics Seiko Co., Ltd.). NC)) was used.
Grease was applied to the disk, and the friction coefficient was measured when the disk was slid at room temperature (25° C.) under the conditions of test load: 2000 gf, sliding speed: 10 mm/s, and amplitude: 20 mm.

〔Evaluation results〕
Comparative Example 1, which did not contain a polymer or an aliphatic amide compound, showed a high coefficient of friction in sliding between steel and resin. Comparative Example 2, which contained only a polymer, and Comparative Example 3, which contained only an aliphatic amide compound, showed a slight reduction in friction compared to Comparative Example 1, but it was not sufficient.
On the other hand, it was found that the grease composition of the present invention containing a polymer and an aliphatic amide compound showed a sufficient reduction in the coefficient of friction in sliding between steel and resin (Examples 1 to 11). Furthermore, in Comparative Example 4, in which the base oil had a kinematic viscosity of more than 30 mm ² /s at 100° C., the friction coefficient was insufficiently reduced.

Since the grease composition of the present invention has excellent low friction properties, it can be applied to lubricate various joints, gears, bearings, etc. that have sliding parts between steel and resin.

Claims (5)

A base oil having a kinematic viscosity of 5 to 30 mm ² /s at 100°C;
A thickener,
A polymer having a weight average molecular weight of 1,000 to 500,000;
Contains an aliphatic amide compound,
Grease composition used for sliding between steel and resin. The grease composition according to claim 1, wherein the aliphatic amide compound is a saturated aliphatic amide compound. The grease composition according to claim 1 or 2, wherein the thickener is a urea-based thickener. The grease composition according to claim 3, wherein the urea-based thickener is a diurea compound represented by the following formula (1).
R ¹ -NHCONH-R ² -NHCONH-R ³ (1)
(In formula (1), R ¹ and R ³ are an aliphatic hydrocarbon group having 4 to 24 carbon atoms which may have a substituent, a fatty acid having 6 to 15 carbon atoms which may have a substituent) Represents a cyclic hydrocarbon group or an aromatic hydrocarbon group having 6 to 15 carbon atoms which may have a substituent, and R ² is a divalent group having 6 to 15 carbon atoms which may have a substituent. represents an aromatic hydrocarbon group.) Grease composition according to any one of claims 1 to 4, wherein the base oil comprises a poly-α-olefin.