Grease composition

Abstract

To provide a grease composition having excellent wear resistance and extreme pressure property.SOLUTION: A grease composition contains a base oil, a thickener, an extreme pressure agent, and an anti-wear agent, the composition satisfying all of the following formulas 1, 2, and 3 when the amount of the extreme pressure agent is X mass% and the amount of the anti-wear agent is Y mass% relative to the total amount of the grease composition: Y≥-0.5X+2.1 (Formula 1), Y≤0.5X+0.65 (Formula 2), X≤5.0 (Formula 3).SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to a grease composition. [Background Art]

[0002] Grease compositions are used in various applications such as tools including power tools, and industrial machine parts. In recent years, along with the achievement of both miniaturization and higher output of machinery and equipment, grease tends to be used under higher loads and higher temperatures, and the usage environment of grease has become harsher.

[0003] Grease compositions applied to tools and the like are required to have wear resistance in order to improve the service life of machinery. When used in members subjected to large load, not only wear resistance but also extreme pressure properties are required. For example, Patent Document 1 discloses a grease composition that can be used in geared motors and the like, the grease composition comprising a base oil and a thickener, and as extreme pressure additives, at least one of dithiocarbamate and zinc dithiocarbamate in an amount of 0.01% by mass to 1% by mass in terms of sulfur content based on the total mass of the composition, and a phosphorus-based extreme pressure agent in an amount of 150 mass ppm to 4000 mass ppm in terms of phosphorus content based on the total mass of the composition. [Prior Art Literature] [Patent Literature]

[0004] [Patent Document 1] Japanese Unexamined Patent Publication No. 2008-143927 [Summary of the Invention] [Problem to be Solved by the Invention]

[0005] An object of an embodiment of the present disclosure is to provide a grease composition excellent in wear resistance and extreme pressure properties. [Means for Solving the Problem]

[0006] As a result of diligent research to solve the above problems, the present inventors have found that in a grease composition containing a base oil, a thickener, an extreme pressure agent, and an anti-wear agent, when the content of the extreme pressure agent (X mass%) and the content of the anti-wear agent (Y mass%) relative to the total amount of the grease composition satisfy a specific relationship, both the anti-wear properties and extreme pressure properties are remarkably excellent. That is, the means for solving the above problems include the following embodiments.

[0007] <1> It contains a base oil, a thickener, an extreme pressure agent, and an anti-wear agent. When the total amount of the grease composition is given by X mass% of the anti-wear agent and Y mass% of the extreme pressure agent, all of the following equations 1, 2, and 3 are satisfied: Grease composition. Y≧-0.5X+2.1 (Formula 1) Y≦0.5X+0.65 (Formula 2) X≦5.0 (Formula 3) <2> wear-resistant agent However, containing zinc dialkyldithiophosphate, <1> The grease composition described above. <3> Extreme pressure agent However, it contains sulfide esters, <1> or <2> The grease composition described above. <4> The thickener contains lithium soap, <1> ~ <3> A grease composition as described in any one of the following. [Effects of the Invention]

[0008] According to one embodiment of the present disclosure, a grease composition is provided that is excellent in wear resistance and extreme pressure properties. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 shows the relationship between Equations 1 and 2 and the mass percentages of X and Y in the group of examples and the group of comparative examples. [Modes for carrying out the invention]

[0010] Hereinafter, specific embodiments of the grease composition according to the present disclosure will be described in detail. However, the grease composition according to the present disclosure is not limited to the following embodiments in any way, and modifications may be made as appropriate within the scope of the purpose of the present disclosure.

[0011] In the present disclosure, a numerical range indicated using "~" means a range that includes the numerical values described before and after "~" as the minimum value and maximum value, respectively. In the numerical ranges described stepwise in the present disclosure, the upper limit or lower limit described for a certain numerical range may be replaced with the upper limit or lower limit of the numerical range described in another stepwise description. In addition, in the numerical ranges described in the present specification, the upper limit or lower limit described for a certain numerical range may be replaced with the values shown in the examples. In the present disclosure, a combination of two or more preferred embodiments is a more preferred embodiment. In the present disclosure, "mass %" is synonymous with "weight %". In the present disclosure, when there are a plurality of types of substances corresponding to each component, the amount of each component means the total amount of the plurality of types of substances unless otherwise specified. In the present disclosure, "JIS" is used as an abbreviation for Japanese Industrial Standards.

[0012] [Grease Composition] The grease composition according to the present disclosure contains a base oil, a thickener, an extreme pressure agent, and an antiwear agent, and based on the total amount of the grease composition, wear-resistant agent let the content be X mass%, Extreme pressure agent when the content is defined as Y mass%, the grease composition satisfies all of the following Formula 1, Formula 2, and Formula 3. Y≧-0.5X+2.1 (Formula 1) Y≦0.5X+0.65 (Formula 2) X≦5.0 (Formula 3)

[0013] Grease compositions applied to tools and the like are required to achieve both wear resistance and extreme pressure properties at high levels in order to improve mechanical service life. Generally, phosphorus-based additives are used to improve wear resistance, and sulfur-based additives are used to improve extreme pressure properties. Blending a phosphorus-based additive into a grease composition can improve wear resistance, but blending a sulfur-based additive is effective in extreme pressure regions with high reaction temperatures. However, adding a large amount of a sulfur-based additive may inhibit the wear resistance imparted by the phosphorus-based additive, and wear resistance and extreme pressure properties have tended to be in a trade-off relationship. Furthermore, the extreme pressure grease composition described in Patent Document 1 does not necessarily exhibit sufficient lubricating performance, and metal parts of machinery and devices may reach the end of their service life earlier than expected. With the grease composition of Patent Document 1, there is a possibility that sufficient wear resistance cannot be obtained under load-bearing conditions.

[0014] Under such circumstances, the grease composition according to the present disclosure contains a base oil, a thickener, an extreme pressure agent, and an anti-wear agent, and is excellent in wear resistance and extreme pressure properties by satisfying both Formula 1 and Formula 2. The reason why the grease composition according to the present disclosure exhibits such effects is not clear, but the present inventors infer as follows. That is, the mechanism of action of both the extreme pressure agent and the anti-wear agent contained in the grease composition is adsorption onto the metal surface, resulting in competitive adsorption, which can bring about a trade-off relationship between wear resistance and extreme pressure properties. However, when all of Formula 1, Formula 2, and Formula 3 are satisfied, the cooperative action of the extreme pressure agent and the anti-wear agent is exhibited specifically and remarkably. Therefore, it is inferred that the grease composition according to the present disclosure is excellent in both wear resistance and extreme pressure properties. The above inference is not intended to limit the interpretation of the grease composition of the present disclosure, and is described as an example only.

[0015] In this disclosure, "extreme pressure resistance" is determined by the weld point (WP, unit: N) obtained by performing a four-ball extreme pressure test in accordance with ASTM D2596. In this disclosure, "excellent extreme pressure resistance" is determined by the weld point (WP) of the grease composition being 1961 N or higher. In this disclosure, "wear resistance" shall be evaluated by the Last Non-Seizure Load (LNSL, in N) determined by performing a four-ball extreme pressure test in accordance with ASTM D2596. In this disclosure, "excellent wear resistance" is determined by the Last Non-Seizure Load (LNSL) of the grease composition being 981 N or higher. The test conditions applicable to the above four-ball extreme pressure test are: rotation speed: 1770 ± 60 rpm (revolutions per minute), time: 10 seconds, and temperature: 27°C.

[0016] <Matters concerning Formulas 1, 2, and 3> The grease composition relating to this disclosure is, in relation to the total amount of the grease composition, wear-resistant agent Let the content be X by mass%, Extreme pressure agent When the content of is Y by mass%, both Formula 1 and Formula 2 below are satisfied. As a result, the grease composition according to this disclosure is excellent in both wear resistance and extreme pressure properties. Y≧-0.5X+2.1 (Formula 1) Y≦0.5X+0.65 (Formula 2)

[0017] Content of extreme pressure agent Y (As mass%), from the viewpoint of thermal stability and cost, the formula is 4 : Y ≤5.0 Y is preferable. ≤4.0 twist Preferably, 0.5 ≤ Y ≤2.5 moreover Preferably, 1.0 ≤ Y A value of ≤2.0 is particularly preferable. Content of abrasion-resistant agent X (As mass%), from the viewpoint of thermal stability and cost, the formula is 3 : X ≤5.0 and ,X ≤4.0 is more preferable, and 1.5 ≤ X ≤3.5 is even better stomach.

[0018] The following describes each component contained in the grease composition.

[0019] <Base oil> The base oil is not particularly limited and may be, for example, mineral oil, synthetic oil, or a mixture thereof. The base oil may be used alone or in combination of two or more types. In one embodiment, the base oil is preferably mineral oil.

[0020] Examples of mineral oils include those obtained by refining the lubricating oil fraction of crude oil using a combination of refining methods such as solvent refining, hydrorefining, hydrocracking, and hydrodeswaxing. Other examples of mineral oils include paraffinic mineral oils that have been highly refined by subjecting hydrorefined oils, catalytic isomerized oils, etc., to treatments such as solvent dewaxing or hydrodeswaxing.

[0021] Examples of synthetic oils include ether-based synthetic oils such as alkyldiphenyl ethers; ester-based synthetic oils such as diesters, polyol esters, and complex-type polyol esters; synthetic hydrocarbon oils such as polyalphaolefins; and alkylnaphthalene-based synthetic oils.

[0022] The kinematic viscosity of the base oil at 40°C is 10 mm 2 / s~500mm 2 / s is preferred, 30mm 2 / s~300mm 2 / s is more preferable, and particularly preferable, 50 mm 2 / s~200mm 2 It is / s.

[0023] In this disclosure, the kinematic viscosity of the base oil at 40°C refers to the value measured according to JIS K 2283:2000 "Kinematic Viscosity Test Method".

[0024] There are no particular restrictions on the base oil content, and it can be appropriately adjusted within the range of 85% to 95% by mass relative to the total mass of the grease composition.

[0025] <Thickener> The grease composition according to this disclosure contains a thickener. The thickener is not limited as long as it is a thickener that can be applied to the grease composition, and can be appropriately determined considering the desired physical properties of the grease composition, the environment in which the grease composition is used, etc. Examples of thickeners include lithium soap, lithium complex soap, calcium soap, calcium complex soap, diurea compounds, etc.

[0026] Among these, the grease composition according to this disclosure preferably contains at least one compound selected from the group consisting of lithium soap and lithium complex soap.

[0027] Lithium soap is a lithium salt of a higher fatty acid. Lithium complex soap is a complex soap that combines a lithium salt of a higher fatty acid with a lithium salt of a dicarboxylic acid.

[0028] From the viewpoint of heat resistance, lithium soap is preferably a lithium salt of a monocarboxylic acid having 12 to 24 carbon atoms. From the viewpoint of heat resistance, lithium-complex soaps are preferably complexes that combine a lithium salt of a monocarboxylic acid having 12 to 24 carbon atoms and a lithium salt of a dicarboxylic acid having 2 to 12 carbon atoms. Suitable monocarboxylic acids include stearic acid and 12-hydroxystearic acid. Suitable dicarboxylic acids include succinic acid, malonic acid, adipic acid, pimelic acid, azelaic acid, and sebacic acid.

[0029] As a thickener, lithium soap is more preferred in terms of availability and ease of handling.

[0030] The grease composition relating to this disclosure may contain only one type of thickener, or it may contain two or more types.

[0031] The amount of thickener can be adjusted as appropriate according to the desired consistency, preferably 5% to 20% by mass, and more preferably 5% to 15% by mass, relative to the total mass of the grease composition.

[0032] <Extreme pressure agent> The grease composition relating to this disclosure contains an extreme pressure agent. The grease composition may contain only one extreme pressure agent, or it may contain two or more extreme pressure agents.

[0033] The extreme pressure agent is preferably at least one selected from the group consisting of polysulfides, sulfurized olefins, sulfurized oils and fats, and sulfurized esters, and more preferably at least one selected from the group consisting of sulfurized oils and fats and sulfurized esters, with sulfurized esters being more preferred.

[0034] Examples of polysulfides include diisobutyl disulfide, dioctyl polysulfide, di-tert-butyl polysulfide, and di-tert-benzyl polysulfide. Examples of sulfurized olefins include those obtained by sulfidizing olefins such as polyisobutylene and terpenes with sulfur or other sulfiding agents. Sulfurized fats and oils are reaction products of fats and oils and sulfur. They are obtained by sulfurizing animal and vegetable fats and oils such as lard, beef tallow, whale oil, palm oil, coconut oil, and rapeseed oil. The reaction product is not a single substance but a mixture of various substances, and its chemical structure itself is not clearly defined. Sulfurized esters are obtained by sulfurizing fatty acid esters, which are produced by the reaction of the above-mentioned oils and fats with various alcohols. Similar to sulfurized oils and fats, their chemical structure itself is not clearly defined.

[0035] The content of the extreme pressure agent (X mass%) is as previously explained in the section "Matters concerning Formulas 1, 2, and 3," so the explanation is omitted here.

[0036] < Abrasion-resistant agent ( Anti-wear agent ) > The grease composition relating to this disclosure is Abrasion-resistant agent ( Anti-wear agent ) It contains. The grease composition may contain only one type of anti-wear agent, or it may contain two or more types.

[0037] Examples of anti-wear agents include zinc-based, phosphorus-based, sulfur-based, amine-based, and ester-based anti-wear agents, with zinc dialkyldithiophosphate being more preferred.

[0038] The alkyl group in zinc dialkyldithiophosphate may be a primary type alkyl group, a secondary type alkyl group, or a compound having both a primary type alkyl group and a secondary type alkyl group in a single molecule. There are no particular restrictions on the number of carbon atoms in the alkyl group, but it is preferably 3 to 12, and more preferably 3 to 8, in that it provides better wear resistance.

[0039] The content of the anti-wear agent (Y mass%) has already been explained in the section on "Quantitative Relationship between Extreme Pressure Agent and Anti-wear Agent," so the explanation will be omitted here.

[0040] <Other additives> The grease composition relating to this disclosure may, if necessary, contain other additives in addition to the base oil, thickener, extreme pressure agent, and anti-wear agent described above. Other additives may include antioxidants, corrosion inhibitors, rust inhibitors, and so on. These other additives may be used individually or in combination of two or more.

[0041] Examples of antioxidants include alkylphenols such as 2,6-di-tert-butyl-p-cresol, bisphenols such as 4,4'-methylenebis-(2,6-di-t-butylphenol), phenolic compounds such as n-octadecyl-3-(4'-hydroxy-3',5'-di-t-butylphenol)propionate, aromatic amine compounds such as naphthylamines, diphenylamines, and dialkyldiphenylamines, and zinc thiophosphate compounds.

[0042] Examples of corrosion inhibitors include benzotriazole and benzimidazole.

[0043] Examples of rust inhibitors include various rust inhibitors such as metal sulfonate salt compounds and sorbitan compounds.

[0044] <Properties of the grease composition> • Mixing consistency The consistency of the grease composition is preferably 220 to 430, more preferably 265 to 385. The consistency of the mixture is measured according to the values ​​obtained in accordance with JIS K 2220:2013.

[0045] <Method for preparing a grease composition> The method for preparing the grease composition according to this disclosure is not particularly limited and can be prepared by conventionally known methods. The grease composition according to this disclosure can be prepared, for example, by appropriately mixing a base oil, a thickener, an anti-wear agent, and an extreme pressure agent, in addition to other additives as needed.

[0046] <Target Uses of Grease Composition> The grease composition according to this disclosure can be applied to the sliding parts, gear parts, bearing parts, etc. of power tools, and can be particularly suitably applied to the sliding parts or gear parts of power tools. [Examples]

[0047] The grease compositions relating to this disclosure will be described in detail below with reference to examples. However, the grease compositions relating to this disclosure are not limited in any way by these examples.

[0048] (Components of the grease composition) The details of each component contained in the grease composition are as follows:

[0049] <Base oil> • Base oil: Solvent-refined mineral oil (kinematic viscosity at 40°C: 110 mm) 2 / s)

[0050] <Thickener> • Lithium soap: Lithium soap was synthesized by mixing the raw materials for lithium soap with a base oil using the following manufacturing procedure and reacting the raw materials in the base oil.

[0051] ~Manufacturing Procedure (Lithium Soap)~ Base oil and 12-hydroxystearic acid as a thickening agent were added to a heat-resistant container, and the mixture was heated to approximately 90°C while stirring. Then, an aqueous lithium hydroxide solution was added, and the mixture was saponified for approximately 60 minutes. After that, the mixture was heated to 200°C while stirring to dissolve the lithium fatty acid salt, and then rapidly cooled to obtain lithium soap.

[0052] <Abrasion-resistant agent> • Zinc dialkyldithiophosphate (product name: HiTEC 7197, manufactured by Afton Chemical Japan Co., Ltd.)

[0053] <Extreme pressure agent> • Sulfur ester (Product name: DAILUBE GS-230S, manufactured by DIC Corporation) • Sulfurized fats and oils (lard) (Product name: Mayco Base 1351, manufactured by Dover Chemical Corporation) • Molybdenum dithiocarbamate (product name: MOLYVAN A, manufactured by Vanderbilt Chemicals)

[0054] <Other additives> Additives containing antioxidants, corrosion inhibitors, and rust inhibitors.

[0055] [Examples 1-7 and Comparative Examples 1-10] Each grease composition for the examples and comparative examples was prepared by mixing the components of the grease composition to achieve the composition shown in the composition column of Table 1 (unit: mass%). In the composition column of the table, "-" indicates that the ingredient in question is not included.

[0056] Each grease composition obtained was evaluated for wear resistance and extreme pressure properties. The evaluation results are shown in Table 1.

[0057] [Matters concerning Formulas 1, 2, and 3] Figure 1 shows the relationship between formulas 1 and 2 and the group of examples and the group of comparative examples. wear-resistant agent Content (X mass%) and Extreme pressure agent The relationship with the content (Y mass%) is shown. In Figure 1, the "black circles" plots represent the example group, and the "black triangles" plots represent the comparative example group. In each grease composition wear-resistant agent Content (X mass%) and Extreme pressure agent The values ​​of the content (Y mass%) were substituted into Equation 1. If the value on the left side of Equation 1 was greater than or equal to the value on the right side, it was determined to be "S". If it was less than the value on the right side, it was determined to be "N". The results are shown in Table 1. In each grease composition wear-resistant agent Content (X: mass%) and Extreme pressure agent The values ​​of the content (Y: mass%) were substituted into Equation 2. If the value on the left side of Equation 1 was less than or equal to the value on the right side, it was determined to be "S". If it exceeded the value on the right side, it was determined to be "N". The results are shown in Table 1. Furthermore, for comparative examples of grease compositions that did not contain either or both of the wear-resistant agent and the extreme pressure agent, no evaluation was performed regarding Formulas 1 and 2. As shown in Table 1 and Figure 1, the group of examples and the group of comparative examples are as follows: wear-resistant agent The content (X by mass%) of each is such that X ≤ 5, and satisfies Equation 3.

[0058] [Measurement and Evaluation] The following measurements and evaluations were performed on each of the obtained grease compositions. The results are shown in Table 1.

[0059] (1) Mixing consistency Each grease composition was measured according to the consistency test method specified in JIS K 2220:2013.

[0060] (2) Evaluation of extreme pressure resistance and abrasion resistance For each grease composition, a four-ball extreme pressure test was conducted in accordance with ASTM D2596 to determine the Weld Point (WP, in N) and the Last Non-Seizure Load (LNSL, in N). The test conditions were: rotation speed: 1770 ± 60 rpm (revolutions per minute), time: 10 seconds, temperature: room temperature (27°C).

[0061] The higher the fusion load (WP) value, the better the extreme pressure resistance. A grease composition was evaluated as having excellent extreme pressure resistance if the fusion load (WP) value was 1961 or higher.

[0062] A higher Last Non-Seizure Load (LNSL) value indicates superior wear resistance. A grease composition was evaluated as having excellent wear resistance if the Last Non-Seizure Load (LNSL) value was 981 N or higher.

[0063] [Table 1]

[0064] As shown in Table 1, the grease composition of the example, which contains a base oil, a thickener, an extreme pressure agent, and an anti-wear agent, and satisfies all of Formulas 1, 2, and 3, is found to be superior in both wear resistance and extreme pressure properties compared to the grease composition of the comparative example.

Claims

1. It contains a base oil, a thickener, an extreme pressure agent, and an anti-wear agent. The extreme pressure agent comprises at least one selected from the group consisting of polysulfide, sulfurized olefin, sulfurized oil and fat, and sulfurized ester. The wear-resistant agent comprises zinc dialkyldithiophosphate, When the content of the extreme pressure agent is Y mass% and the content of the wear-resistant agent is X mass% relative to the total amount of the grease composition, all of the following formulas 1, 2 and 3 are satisfied: Grease composition. Y≧-0.5X+2.1 (Formula 1) Y≦0.5X+0.65 (Formula 2) X≦5.0 (Formula 3)

2. The grease composition according to claim 1, wherein the extreme pressure agent comprises a sulfur ester.

3. The grease composition according to claim 1 or claim 2, wherein the thickener comprises lithium soap.

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