WO2022207407A1

WO2022207407A1 - Grease composition

Info

Publication number: WO2022207407A1
Application number: PCT/EP2022/057465
Authority: WO
Inventors: Hiroki Yano; Kunitoshi ABE; Keiji Tanaka
Original assignee: Shell Internationale Research Maatschappij B.V.; Shell Usa, Inc.
Priority date: 2021-03-30
Filing date: 2022-03-22
Publication date: 2022-10-06
Also published as: JP2024012214A

Abstract

The present invention provides a grease composition comprising: a lubricating oil belonging to Group 1 to 5 of the base oil categories defined by the American Petroleum Institute (API) or mixed oils thereof as a base oil; particles expressed by the following structural formula (1) as a thickener [A_0-0.2][B_1-8][C_0-5|D_2nO_5n]·mH₂O … (1) wherein: A: [Ca, Ba, K, Na, Rb, Cs, NH₄] B: [Ti, Al, Cr, V, Fe, Mn, Mg, Li] C: [S, OH, F, Cl] D: [Si, Al, Fe, B, Be] n = 1-10 m = 5-15.

Description

GREASE COMPOSITION

Field of the Invention

The present invention relates to a grease composition containing a specific clay mineral, and to a grease composition that has high environmental compatibility and key characteristics as a grease.

Background of the Invention

The environment in which grease is used has changed significantly over the years due to advances in machine technology. For example, automobiles and electrical equipment have become smaller and lighter along with increases in output, which has made operating conditions hotter and lubrication conditions harsher. Grease used in continuous steel casting equipment and rolling mills for hot rolling equipment requires excellent heat resistance and oxidation stability. In addition to improving performance at high temperatures, grease must also be a material that meets higher standards for environmental compatibility (such as being safer to humans during use and reducing the burden that manufacturing places on the environment). Lithium grease currently makes up more than 50% of the grease market. Lithium grease has become an all-purpose grease because it can be used up to a maximum temperature of about 120°C, has relatively good shear stability and water resistance, uses readily available and easy to handle raw materials such as fats and oils and fatty acids, and can be produced at relatively low cost. A lithium complex grease has also been proposed that can be used as a grease over a wider temperature range than ordinary lithium grease (JP H01-170691 A). However, the lithium hydroxide used to saponify the fats and oils and fatty acids used as raw materials in lithium grease has handling restrictions because it is a toxic substance. There is also concern about changes in the status of lithium grease as an all-purpose grease due to the gradual rise in demand for lithium in a diverse range of applications.

Greases other than lithium grease include sodium grease and aluminum grease, but sodium grease becomes fluid when mixed with water, causing it to ooze out of bearings, etc. As a result, it is gradually being eliminated from the grease market. Also, because aluminum grease has an operating temperature range that is no better than calcium grease, its use is limited to specific applications.

One means that has been considered for increasing the environmental compatibility of grease is the use of naturally-derived minerals and artificially synthesized inorganic compounds as raw materials for grease. For example, JP2011057761 A has disclosed a grease composition that uses a naturally-derived mineral or artificially synthesized inorganic compound as a grease thickener. This grease can meet the demand for reducing the burden on the environment, but the grease cannot maintain its structure unless a large amount of thickener is used. It also becomes soft when exposed to water and reduces rust prevention.

Urea grease can be used as a heat-resistant grease. Because urea grease can be used at even higher temperatures than lithium complex grease, it is a high performance grease composition used in a wide variety of applications requiring heat resistance. JP2008094991 A has disclosed a grease composition obtained by mixing a polyurea compound with a solid lubricant such as calcium carbonate, polytetrafluoroethylene, or graphite, which are all inorganic compounds. This grease composition has excellent heat resistance and extreme pressure properties at high temperatures and under heavy loads, and can even suppress the hardening of grease when locally exposed to high temperatures.

However, urea grease has low environmental compatibility due to safety and handling problems with the isocyanates and amines that are raw materials in urea grease. Also, because it requires advanced production technologies and equipment, urea grease is expensive. This limits its use in certain applications.

In view of these circumstances, it is an object of the present invention to provide a grease composition having excellent key characteristics (miscibility, dropping point, heat resistance) as a grease and excellent environmental compatibility.

Summary of the Invention

The present invention provides [1] to [4] below.

[1] A grease composition comprising a base oil (a) and a thickener (b), wherein the thickener (b) is composed of particles (with a primary particle size, for example, of 0.1 to 200 pm) expressed by the following structural formula (1) [A0-0.2][B1-8][Co-5ID2n05n]PTBO ... (1)

A: [Ca, Ba, K, Na, Rb, Cs, NH]

B: [Ti, Al, Cr, V, Fe, Mn, Mg, Li]

C: [S, OH, F, Cl]

D: [Si, Al, Fe, B, Be] n = 1-10 m = 5-15. [2] A grease composition according to [1], wherein elements A, B, C and D in the thickener (b) are the following

A: None

B: [Mg, Mn, Fe]

C: [OH]

D: [Si].

[3] A grease composition according to [1] or [2], wherein the thickener (b) is from 0.1 to 10% by mass relative to the overall mass of the grease composition at 100% by mass.

[4] A grease composition according to any one of [1] to [3], wherein the grease composition further comprises a stabilizer (c), the stabilizer (c) being a dihydric alcohol or trihydric alcohol having from 2 to 5 carbon atoms, and the amount of stabilizer (c) being from 0.1 to 5% by mass relative to the overall mass of the grease composition at 100% by mass. Detailed Description of the Invention

As a result of extensive research conducted to achieve this object, the present inventors discovered that a specific naturally produced inorganic compound has environmental compatibility and can improve the key characteristics of a grease composition such as miscibility. The present invention is able to provide a grease composition having excellent key characteristics (miscibility, dropping point, heat resistance) as a grease and excellent environmental compatibility.

A powder represented by structural formula (1) is added as a thickener to a grease composition in the present embodiment. Specific components, amounts of components, production methods, physical properties, and applications for the grease composition of the present embodiment will be described in detail below, but the present invention is not limited to these examples. For example, a powder represented by structural formula (1) is added as a thickener to a grease composition in the present embodiment, but it should be understood that grease compositions containing a powder represented by structural formula (1) for a purpose other than that of thickener also belong to the technical scope of the present invention as long as the effects of the present invention are realized. Also, the expression "a to b" in the present specification and claims means "a or more and b or less" unless otherwise specified.

There are no particular restrictions on the base oil used in the present invention as long as the effects of the present invention are not impaired. The base oil can be a mineral oil, synthetic oil, animal or vegetable oil, or any mixture thereof. Specific examples are those in Groups 1 to 5 of the base oil categories of the American Petroleum Institute (API). The API base oil categories are a broad classification of base oil materials defined by the American Petroleum Institute in order to create guidelines for base oils used in lubricating oils.

There are no particular restrictions on the mineral oils used in the present invention. However, preferred examples include paraffin-based or naphthene-based mineral oils obtained by applying one or more refining means, such as solvent degassing, solvent extraction, hydrocracking, solvent dewaxing, catalytic dewaxing, hydrorefining, sulfuric acid washing and clay treatment, to a lubricating oil fraction obtained by atmospheric distillation and vacuum distillation of crude oil. These can be used alone or in combinations of two or more.

There are no particular restrictions on the synthetic oils used in the present invention. However, preferred examples include poly a-olefins (PAO) and hydrocarbon synthetic oils (oligomers). A PAO is an a-olefin homopolymer or copolymer. An a-olefin is a compound with a C-C double bond at the terminal, and specific examples include butene, butadiene, hexene, cyclohexene, methylcyclohexene, octene, nonene, decene, dodecene, tetradecene, hexadecene, octadecene, and eicosene. Examples of hydrocarbon synthetic oils (oligomers) include ethylene, propylene, and isobutene homopolymers or copolymers. These can be used alone or in combinations of two or more. These compounds may have any isomeric structure as long as they have a C-C double bond at the terminal, and may have a branched structure or a linear structure. These structural isomers and positional isomers with double bonds can be used in combinations of two or more. Among these olefins, a linear olefin having from 6 to 30 carbon atoms is preferred because the flash point is low when the number of carbon atoms is five or less, and the viscosity is high and the olefin impractical when the number of carbon atoms is 31 or higher.

In the present invention, a gas-to-liquid (GTL) base oil synthesized using the Fischer-Tropsch method for converting natural gas into liquid fuel can be used as the base oil. Compared to a mineral base oil refined from crude oil, a GTL base oil has a very low sulfur and aromatic content and a very high paraffin component ratio. As a result, it has excellent oxidative stability and very low evaporation loss, and is ideal for use as a base oil in the present invention.

The thickener used in the present embodiment is a powder represented by structural formula (1). Examples include lizardite, antigorite, caryopilite, berthierine, kaolinite, dickite, nacrite, meta-halloysite, pyrophyllite, talc, bementite, iron pyrophyllite, and manganese pyrophyllite. Powders represented by structural formula (1) are widely used in industry as, for example, adsorbents and non-metallic conductive fillers. As minerals present in nature, they are inorganic materials that are highly environmentally compatible (safe to humans during use and reducing the burden that manufacturing places on the environment). The affinity of these powders with solvents can be enhanced by including a surface-modifying additive. An example of a modifying additive is treatment with a quaternary ammonium salt.

Commonly used greases include soap-based greases.

Among these, lithium soap greases have excellent consistency yield (extent to which the grease hardens) and shear stability, and are the most widely used as all-purpose greases. The advantages mentioned above are a major reason. The structure of a lithium soap grease features a three- dimensional fiber structure in which the string-like lithium stearate thickener is dispersed in and becomes entangled with the base oil. In its basic form, the base oil is retained by this fiber structure so that the grease maintains the physical properties of a semi-solid grease. Most of these soap-based greases are composed of stearates with a relatively long chain length. This occurs because the equilibrium between the retaining power of the hydrocarbon base oil and the intramolecular force of the micelles constituting the fibers is optimal. As a result, the consistency yield is good and shear stability is effectively improved.

Meanwhile, the inorganic particles, which do not have a three-dimensional fiber structure, are dispersed in the base oil and often become gelled due to the interaction with, for example, intramolecular forces to maintain the grease structure. For example, bentonite gels and becomes semi-solid because it forms a "house of cards" structure in which the crystals swell in the solvent (aqueous system) due to the electrostatic bond between crystals. However, electrostatic bonding does not readily occur in base oils constituting greases, and swelling, gelling, and formation of a strong grease structure cannot occur. Therefore, a water-soluble polar solvent is often added as a binder in order to promote swelling. Unfortunately, most inorganic substances do not swell much in a base oil and have almost no action that contributes to realizing the basic properties of a grease (becoming semi-solid so that the consistency can be measured). Greases using inorganic thickeners other than bentonite are commercially available such as silica greases.

In these circumstances, powders represented by structural formula (1) in the present invention when used as thickeners have a significant effect as grease thickeners. This is because powders represented by structural formula (1) have voids in the structure and form secondary particles that are strongly aggregated from primary particles. In this structure, the lubricating oil is readily absorbed in the voids created between the secondary particles. Because the bulk specific gravity of these powders is high (the specific surface area is large), dispersibility in lubricating oil is also high. It is believed that these combine to produce an excellent thickening effect.

A powder represented by structural formula (1) in the present embodiment preferably has an average primary particle size of 200 pm or less, more preferably 150 pm or less, and even more preferably 100 pm or less. There are no particular restrictions on the lower limit value for the average primary particle size, but 0.1 pm or more is preferred. Fine powders such as powders represented by structural formula (1) form secondary particles that are aggregates of primary particles. Therefore, the powder is treated with a crystallization inhibitor or a dispersant in order to suppress this aggregation. However, there are no particular restrictions on the surface treatment method used on powders represented by structural formula (1) in the present invention. A powder represented by structural formula (1) with a smaller primary particle size contains voids with a larger surface area between secondary particles when aggregated and absorbs a greater amount of oil. This is believed to increase the thickening effect and produce a harder grease. The average primary particle size can be measured using the laser diffraction method, dynamic light scattering method, centrifugal sedimentation method, field flow fractionation (FFF) method, or electrical detector method. The average primary particle size in the present invention is the volume average particle size, but may also be determined in terms of the number average particle size.

Element A in the structural formula (1) of components according to the present embodiment is preferably Ca, Ba, K, Na, Rb, Cs or NH4, more preferably Ca, Ba, K or Na, and even more preferably Ca, K or Na. Element B is preferably Ti, Al, Cr, V, Fe, Mn, Mg or Li, more preferably Fe, Mn or Mg, and even more preferably Mg. Element C is preferably S, OH, F or Cl, more preferably S or OH, and even more preferably OH. Element D is preferably Si, Al, Fe, B or Be, more preferably Si, Al or Fe, and even more preferably Si. This is because a structure composed of Si and OH is a porous structure, the insertion of Fe, Mn or Mg into this structure tends to yield a porous structure that is a strong mineral structure, and the porosity increases the number of places where the base oil can be retained, thereby increasing the thickening effect.

In a grease composition of the present embodiment, a thickener other than a powder represented by structural formula (1) (another thickener) may be used in addition to the thickener described above. Examples of these other thickeners include tertiary calcium phosphate, alkali metal soaps, alkali metal composite soaps, alkaline earth metal soaps, alkaline earth metal composite soaps, alkali metal sulfonates, alkaline earth metal sulfonates and other metal soaps, terephthalate metal salts, triurea monourethane, diurea, tetraurea and other polyureas, silicas (silicon oxides) such as barium sulfate, clays and silica aerogels, and fluororesins such as polytetrafluoroethylene. These can be used alone or in combinations of two or more. Any liquid substance that is able to impart a thickening effect can also be used.

A heat-resisting function can be imparted to a grease composition of the present embodiment by adding a specific additive to a grease composed of a thickener mentioned above. Alcohols that can be used in the present embodiment are polyhydric alcohols, and preferred examples of these polyhydric alcohols include 1,1-ethanediol, 1,2-ethanediol (ethylene glycol), 1,1-butanediol, 1,2-butanediol, 1,3- butanediol, 1,4-butanediol, 1,5-heptanediol, and 1,2,3- propanetriol (glycerin). One or more of these polyhydric alcohols can be used.

A quaternary ammonium salt used as an additive in the present embodiment is preferably a quaternary ammonium chloride salt. Examples of these salts include one or more types of quaternary ammonium salts selected from the group composed of hardened beef tallow alkyldimethylbenzyl ammonium chlorides, di-hardened beef tallow alkylmethylbenzyl ammonium chlorides, beef tallow alkyltrimethyl ammonium chlorides, hexadecyltrimethyl ammonium chlorides, and di-palm oil alkyldimethyl ammonium chlorides. These quaternary ammonium salts may be added at a ratio of 5 to 15% by mass per 100% by mass of a powder represented by structural formula (1) used as a thickener, that is, in any amount between 0.005 to 7.5% by mass per 100% by mass of the grease composition. The consistency yield of a powder represented by structural formula (1) can be improved by adding a quaternary ammonium salt, and this improves its function as a thickener.

Polyhydric alcohols and quaternary ammonium salts are used as oiliness improvers and dispersants in hydraulic oils, and are known to exhibit a lubricating effect when adsorbed on lubricated metal surfaces to form an adsorbed film. The functions of these additives when included in a grease containing a powder represented by structural formula (1) of the present invention as a thickener are not the same as those expected when used as additives in hydraulic oils. In the present invention, a polyhydric alcohol or quaternary ammonium salt keeps the powder represented by structural formula (1) in a homogeneously dispersed state in the base oil, and this improves the basic functions of the composition as a grease against structural weakening due to heat, weakening and softening of the grease structure due to moisture in the air and moisture mixed in from the outside, and rust and poor lubricity due to insufficient dispersibility in water.

A powder represented by structural formula (1) that is used as a thickener in the present invention basically has voids in the structure and forms secondary particles that are strongly aggregated from primary particles. In this structure, the lubricating oil is readily absorbed in the voids created between the secondary particles and this forms a network with the grease thickener. This structure is believed to be strengthened by the effect of the additives mentioned above, and can exhibit basic performance as grease. Therefore, the heat resistance and consistency yield of a grease can be improved by including these additives. Performance as a grease is the one necessary performance quality in a usage environment, and when these performance qualities are added, the grease composition can be used in a wider range.

Additives such as antioxidants, rust inhibitors, oiliness agents, extreme pressure agents, anti-wear agents, solid lubricants, metal deactivators, polymers, non-metal detergents and colorants can be added to a grease composition of the present embodiment in an amount totaling from about 0.1 to 20% by mass per 100% by mass of the grease composition as a whole. Examples of antioxidants include 2,6-di-t-butyl- 4-methylphenol, 2,6-di-t-butylparacresol, r,r'- dioctyldiphenylamine, N-phenyl-a-naphthylamine, and phenothiazine. Examples of rust inhibitors include paraffin oxide, carboxylic acid metal salts, sulfonic acid metal salts, carboxylic acid esters, sulfonic acid esters, salicylic acid esters, succinic acid esters, sorbitan ester, and various amine salts. Examples of oiliness agents, extreme pressure agents, and anti-wear agents include zinc sulfide dialkyldithiophosphates, zinc sulfide diallyl dithiophosphates, zinc sulfide dialkyldithiocarbamates, zinc diallyl sulfide dithiocarbamates, molybdenum dialkyldithiophosphates, molybdenum diallyl sulfide dithiophosphates, molybdenum dialkyldithiocarbamates, molybdenum diallyl dithiocarbamates, organic molybdenum complexes, olefin sulfides, triphenylphosphate, triphenylphosphineate, tricresin phosphate, phosphoric acid esters, and sulfonated oils and fats. Examples of solid lubricants include molybdenum disulfide, graphite, boron nitride, melamine cyanurate, PTFE (polytetrafluoroethylene), tungsten disulfide, and graphite fluoride. Examples of metal deactivators include N,N'disalicylidene-1,2-diaminopropane, benzotriazole, benzimidazole, benzothiazole, and thiadiazole. Examples of polymers include polybutene, polyisobutene, polyisobutylene, polyisoprene, and polymethacrylate. Examples of non-metal-based detergents include succinimide.

The amounts of base oil, thickener, and additives included in a grease composition of the present embodiment will now be described. If necessary, any component may be added in the amounts mentioned above.

The amount of base oil added per 100% by mass of grease composition is preferably from 50 to 98% by mass, and more preferably from 70 to 97% by mass.

The amount of thickener added per 100% by mass of grease composition is preferably from 0.1 to 50% by mass, more preferably from 0.5 to 30% by mass, and even more preferably from 3 to 10% by mass.

As mentioned above, a grease composition in the present embodiment contains as a thickener at least a powder represented by structural formula (1), which may be combined with other thickeners when appropriate. When a powder represented by structural formula (1) is used alone as the thickener, a high thickening effect can be obtained (that is, a grease composition with a high thickening effect can be produced) without including a thickener other than a powder represented by structural formula (1). Because powders represented by structural formula (1) have high environmental compatibility, the proportion of other thickeners used is preferably reduced from the standpoint of improved environmental compatibility.

Therefore, in terms of the overall amount of thickener in a grease composition, the amount of powder represented by structural formula (1) used per 100% by mass of grease composition in preferably from 0.5 to 50% by mass, more preferably from 2 to 30% by mass, and even more preferably from 3 to 28% by mass. Also, the amount of thickener other than a powder represented by structural formula (1) (another thickener) is preferably 20% by mass or less, and more preferably 10% by mass or less.

When the additive is at least one type of polyhydric alcohol selected from the group composed of 1,1-ethanediol,

1,2-ethanediol (ethylene glycol), 1,1-butanediol, 1,2- butanediol, 1,3-butanediol, 1,4-butanediol, 1,5-heptanediol, and 1,2,3-propanetriol (glycerin), the amount of polyhydric alcohol used per 100% by mass of grease composition in preferably from 0.1 to 5% by mass, more preferably from 0.2 to 4% by mass, and even more preferably from 0.5 to 3% by mass.

When the additive is at least one type of quaternary ammonium salt selected from the group composed of hardened beef tallow alkyldimethylbenzyl ammonium chlorides, di- hardened beef tallow alkylmethylbenzyl ammonium chlorides, beef tallow alkyltrimethyl ammonium chlorides, hexadecyltrimethyl ammonium chlorides, and di-palm oil alkyldimethyl ammonium chlorides, the amount of quaternary ammonium salt used per 100% by mass of grease composition in preferably from 0.005 to 7.5% by mass, more preferably from 0.01 to 5% by mass, and even more preferably from 0.15 to 1.5% by mass. A grease composition in the present embodiment can be produced using any existing technique. For example, a grease composition can be produced by performing the following steps. A base oil, thickener, and additives are mixed together and placed in dedicated grease-manufacturing equipment (programmable grease prototype equipment). Next, stirring is performed at room temperature (for example, around 25°C) (at a stirring rotation speed of 20 to 300 rpm and stirring time of 10 to 15 minutes, for example), treatment is performed using a homogenizing device (such as a three-roll mill), and vacuum defoaming is performed to obtain a homogeneous grease composition. When any other component (such as an additive) is used, the base oil and the additive may be mixed together in advance at an appropriate temperature (such as a temperature from 80 to 100°C), and returned to room temperature before adding a powder represented by structural formula (1). (Alternatively, a powder represented by structural formula (1) may be mixed with the base oil at room temperature and the temperature raised before mixing in the additive.)

When a grease composition is substantially free of a thickener other than a powder represented by structural formula (1), no special chemical reaction is involved in adding and stirring the thickener. As a result, a grease can be produced without having to raise the temperature. This saves energy and lowers costs. (Alternatively, if heating to a high temperature is needed to mix the additives together, the step of maintaining a high temperature can be shortened.) Note that, when stirring and mixing together a powder represented by structural formula (1), a base oil, and additives, heat treatment (at a temperature, for example, less than about 140°C) may be performed instead of performing the process at room temperature.

A method for producing a grease composition of the present embodiment by combining a powder represented by structural formula (1) with a thickener other than a powder represented by structural formula (1) (another thickener) to serve as the thickeners in the grease composition will now be explained. In this example, a urea thickener is used as the other thickener. First, the ingredients of the urea thickener (diisocyanate, primary monoamine, primary diamine, etc.) are mixed together and subjected to a synthetic reaction in the base oil. After raising the temperature to about 180°C and then cooling, the additives etc. are added at a temperature from 80 to 100°C and stirred in sufficiently before allowing the mixture to cool to room temperature. The powder represented by structural formula (1) is then added and stirred in to obtain a dispersion, which is subjected to homogenization using a kneader (such as a triple roll-mill) to obtain a grease composition.

When a thickener of the prior art is combined with a powder represented by structural formula (1), a grease composition can be formed with the thickener of the prior art using a grease production method common in the art, before adding the powder represented by structural formula (1) to improve the thickening and complete the grease composition. Alternatively, the powder represented by structural formula (1) and the other thickener may be added in the same step (at the same time) to produce a grease composition using a grease production method common in the art. Also, a grease composition created using a powder represented by structural formula (1) as the thickener and a grease composition created using a thickener other than a powder represented by structural formula (1) as the thickener may be produced separately and then mixed together.

The dropping point of a grease composition of the present embodiment is preferably 200°C or higher, more preferably 220°C or higher, and even more preferably 250°C or higher. When the dropping point of the grease composition is 200°C or higher, it is believed that the likelihood of lubrication problems such as loss of viscosity at high temperatures and the leakage and seizure accompanying a loss of viscosity can be suppressed. The dropping point is the temperature at which a viscous grease loses its structure as a thickener. The dropping point can be measured in accordance with JIS K 22208.

In miscibility testing, a grease composition of the present embodiment preferably has a consistency from No. 00 to No. 4 (175 to 430), and more preferably a consistency from

No. 1 to No. 3 (220 to 340). Consistency represents the physical hardness of the grease. Here, the miscibility value measured in accordance with JIS K 22207 is used as the consistency.

The grease composition in the present embodiment is preferably at 100°C, and more preferably at 150°C in heat resistance testing. The following method is used in the heat resistance test. A consistency measuring instrument is filled with the grease composition, heated, and allowed to stand for 2 hours before measuring the degree of immiscibility. When the amount of change in the immiscibility value at 25°C is within 100, the grease composition has heat resistance at a specified temperature in the heat resistance test. The test temperature is increased in 10°C increments from 80°C until the change in consistency exceeds 100. When the heat resistance is insufficient and the degree of consistency softens, the grease composition leaks and a sufficient amount of oil is not supplied to the lubricated interface, resulting in impaired lubricity.

A grease composition of the present embodiment can of course be used in machinery, bearings, gears, and ball screws where excellent performance can be exhibited as grease lubrication even in harsh environments. It is suitable for lubricating various automotive components, including components surrounding an engine such as water pumps, cooling fan motors, starters, alternators and actuators, as well as propeller shafts, constant velocity joints (CVJ), powertrain components such as wheel bearings and clutches, electric power steering (EPS) components, electric power window components, braking devices, ball joints, door hinges, handle components, and brake expanders. A grease composition of the present embodiment is preferably used on shafts and fittings that slide back and forth in construction machinery such as power shovels, bulldozers and mobile cranes, in the steel industry, in the paper industry, in forestry machinery, in agricultural machines, in chemical plants, in power generating equipment, and in train cars. Other applications include screw joints for seamless pipes and outboard motor bearings. A grease composition of the present embodiment is especially suitable for these applications.

Examples

The following is a detailed description of the invention with reference to examples and comparative examples. Note, however, that the present invention is not limited in any way to these examples.

The following raw material components were used in Examples 1 to 14 and Comparative Examples 1 to 4. Base Oil A: A paraffinic mineral oil with a kinematic viscosity at 40°C of 100.0 mm²/s and a kinematic viscosity at 100°C of 11.55 mm²/s that is a mixture of a paraffinic mineral oil with a kinematic viscosity at 40°C of 24.22 mm²/s and a kinematic viscosity at 100°C of 4.640 mm²/s and a paraffinic mineral oil with a kinematic viscosity at 40°C of 480.2 mm²/s and a kinematic viscosity at 100°C of 31.56 mm²/s.

Base Oil B: A naphthenic mineral oil with a kinematic viscosity at 40°C of 143.6 mm²/s and a kinematic viscosity at 100°C of 10.71 mm²/s.

Base Oil C: An unsaturated polyol ester oil with a kinematic viscosity at 40°C of 20.50 mm²/s and a kinematic viscosity at 100°C of 4.550 mm²/s.

Base Oil D: An alkyl diphenyl ether oil with a kinematic viscosity at 40°C of 102.2 mm²/s and a kinematic viscosity at 100°C of 12.64 mm²/s.

Base Oil E: A poly-a-olefin oil with a kinematic viscosity at 40°C of 100.0 mm²/s and a kinematic viscosity at 100°C of 15.14 mm²/s that is a mixture of a poly-a-olefin oil with a kinematic viscosity at 40°C of 30.50 mm²/s and a kinematic viscosity at 100°C of 6.340 mm²/s and a poly-a-olefin oil with a kinematic viscosity at 40°C of 396.5 mm²/s and a kinematic viscosity at 100°C of 39.99 mm²/s.

Base Oil F: A gas-to-liquid (GTL) oil synthesized using the Fischer-Tropsch method with a kinematic viscosity at 40°C of 44.61 mm²/s and a kinematic viscosity at 100°C of 7.640 mm²/s.

Powder A: A powder represented by Formula (2) with an average primary particle size of 65 pm:

Sii₂Mg₈0₃o(OH)4(OH₂)4-8H₂0 ... (2) Powder B: A powder represented by Formula (3) (Generic name: Bentonite):

Na₂Si₂₄ (Ali₀Mg₂)Oeo·(OH)i2 ... (3)

Powder C: A powder represented by Formula (4) (Generic name: Vermiculite):

(Mg, Fe²⁺, A1)₃(A1, Si)₄0io(OH)₂ ·4H₂0 ... (4)

Additive A: Glycerin (from Fujifilm Wako Pure Chemical Industries, Ltd.)

Additive B: Ethylene glycol (from Fujifilm Wako Pure Chemical Industries, Ltd.)

Additive C: Hardened beef tallow alkyldimethylbenzylammonium chloride (from Kao Corporation)

Example 1

Base oil A and powder A were measured out at the ratios shown in Table 1 to obtain a total amount of 500 g, which was placed in dedicated grease production equipment with an internal volume of 1.0 kg. The dispersion was stirred at room temperature at 200 rpm for 15 minutes and processed using a three-roll mill. The processed dispersion was then defoamed in a vacuum to obtain a homogeneous grease with a No. 2 consistency grade.

Example 2

Base oil A and powder A were mixed together in a grease kettle at the amounts shown in Table 1 and a homogenized grease with a No. 1 consistency grade was produced in the same manner as in Example 1.

Example 3

Base oil A and powder A were mixed together in a grease kettle at the amounts shown in Table 1 and a homogenized grease with a No. 3 consistency grade was produced in the same manner as in Example 1. Example 4

Base oil B and powder A were mixed together in a grease kettle at the amounts shown in Table 1 and a homogenized grease with a No. 2 consistency grade was produced in the same manner as in Example 1.

Example 5

Base oil C and powder A were mixed together in a grease kettle at the amounts shown in Table 1 and a homogenized grease with a No. 2 consistency grade was produced in the same manner as in Example 1.

Example 6

Base oil D and powder A were mixed together in a grease kettle at the amounts shown in Table 1 and a homogenized grease with a No. 2 consistency grade was produced in the same manner as in Example 1.

Example 7

Base oil E and powder A were mixed together in a grease kettle at the amounts shown in Table 1 and a homogenized grease with a No. 2 consistency grade was produced in the same manner as in Example 1.

Example 8

Base oil F and powder A were mixed together in a grease kettle at the amounts shown in Table 2 and a homogenized grease with a No. 2 consistency grade was produced in the same manner as in Example 1.

Example 9

Base oil A, powder A, and additive A were mixed together in a grease kettle at the amounts shown in Table 2 and a homogenized grease with a No. 1 consistency grade was produced in the same manner as in Example 1. Example 10

Base oil A, powder A, and additive A were mixed together in a grease kettle at the amounts shown in Table 2 and a homogenized grease with a No. 2 consistency grade was produced in the same manner as in Example 1.

Example 11

Base oil A, powder A, and additive A were mixed together in a grease kettle at the amounts shown in Table 2 and a homogenized grease with a No. 3 consistency grade was produced in the same manner as in Example 1.

Example 12)

Base oil A, powder A, and additive B were mixed together in a grease kettle at the amounts shown in Table 2 and a homogenized grease with a No. 2 consistency grade was produced in the same manner as in Example 1.

Example 13

Base oil A, powder A, additive A, and additive C were mixed together in a grease kettle at the amounts shown in

Table 2 and a homogenized grease with a No. 3 consistency grade was produced in the same manner as in Example 1. Example 14)

Table 2 and a homogenized grease with a No. 3 consistency grade was produced in the same manner as in Example 1. Comparative Example 1)

Base oil A and powder B were mixed together in a grease kettle at the amounts shown in Table 3 and a homogenized grease with a No. 1 consistency grade was produced in the same manner as in Example 1. Comparative Example 2)

Base oil A and powder C were mixed together in a grease kettle at the amounts shown in Table 3 and production was conducted in the same manner as in Example 1, but the result was a fluid (non-grease) substance.

Comparative Example 3)

This was a commercially available all-purpose lithium- based grease using mineral oil-based lubricating oil as the base oil and lithium 12-hydroxystearate soap as the thickener (from Shell Lubricants Japan K.K.), and the viscosity of the base oil at 100°C was 12.2 mm²/s.

Comparative Example 4)

This was a commercially available urea-based grease using mineral oil-based lubricating oil as the base oil (from Shell Lubricants Japan K.K.), and the viscosity of the base oil at 100°C was 11.3 mm²/s.

Testing

The dropping point, miscibility, and heat resistance of the examples and comparative examples were tested using the methods described above. The physical properties of each grease in the examples and comparative examples are shown in Table 1, 2 and 3. As for the evaluation of "grain quality," n was assigned when the grain was fine, smooth and glossy, ; was assigned when the grain was fine and smooth but not glossy, D was assigned when the grain was somewhat coarse and not glossy, and x was assigned when the grain was coarse and not glossy. Grain is an indicator determined based on the feel and appearance of a test sample when touched directly with the fingers. As for the evaluation of viscoelasticity (stiffness), n was assigned when the stiffness was strong and elastic, ; was assigned when the stiffness was somewhat elastic, D was assigned when the stiffness was weak and inelastic, and x was assigned when no stiffness was felt at all (liquidy, etc.). Viscoelasticity is an indicator determined based on the feel of a test sample when touched directly with the fingers.

Table 1

Table 2

Table 3

As shown in Tables 1 and 2, Examples 1 to 14 all have excellent miscibility, dropping points, and heat resistance.

Claims

C LA IM S

1. A grease composition comprising a base oil (a) and a thickener (b), wherein the thickener (b) is composed of particles expressed by the following structural formula (1)

[A0-0.2][B1-8][Co-5ID2n05n]'PΐίBO ... (1) wherein:

A: [Ca, Ba, K, Na, Rb, Cs, NH₄]

B: [Ti, Al, Cr, V, Fe, Mn, Mg, Li]

C: [S, OH, F, Cl]

D: [Si, Al, Fe, B, Be] n = 1-10 m = 5-15.

2. A grease composition according to claim 1, wherein elements A, B, C and D in the thickener (b) are the following:

A: None

B: [Mg, Mn, Fe]

C: [OH]

D: [Si].

3. A grease composition according to claim 1 or 2, wherein the thickener (b) is from 0.1 to 10% by mass relative to the overall mass of the grease composition at 100% by mass.

4. A grease composition according to any one of claims 1 to 3, wherein the grease composition further comprises a stabilizer (c), the stabilizer (c) being a dihydric alcohol or trihydric alcohol having from 2 to 5 carbon atoms, and the amount of stabilizer (c) being from 0.1 to 5% by mass relative to the overall mass of the grease composition at 100% by mass.