Grease composition

Abstract

The grease composition contains a base oil, a diurea compound as a thickener, and at least one wax selected from the group consisting of rice wax, lanolin wax, carnauba wax, and castor wax.

Description

Grease composition

[0001] The present invention relates to a grease composition suitable for use in an environment where water may be present or where humidity is high and shear stress is applied.

[0002] When water gets into grease, it softens and leaks, so the grease itself needs to have improved water resistance. Greases used in work roll bearings of hot rolling mills in steelmaking facilities are exposed to large amounts of cooling water and strong shear, so they require excellent water shear stability. Greases used in rolling bearings of air conditioner fan motors or ventilation fans are used in high-humidity environments where they are subject to shear, so they also require excellent water shear stability. Greases used in rolling bearings of automobile hub units are used in environments where they are exposed to water contamination during car washes, rainwater, and rough roads, and are subject to shear, so they also require excellent water shear stability. Greases used in automotive rack and pinion gears, worm gears in electric power steering, and worm gears in power window motors are particularly required to have excellent water shear stability, as they are used in environments where they are exposed to water contamination and shear due to weather conditions. Non-Patent Document 1 reports that when a grease consisting only of mineral oil and a diurea thickener was tested using a mechanical shear stability evaluation device (ASTM D 1831) at 10 wt% water and 80°C, it became fluid. To solve the problem of water resistance, when a diurea compound is selected as a thickener, a method has been reported in which a metal salt compound selected from the group consisting of basic metal sulfonates, basic metal salicylates, and basic metal phenates is included (Patent Document 1). Another method is to use a component with excellent water absorption properties, such as barium sulfate, as the thickener (Patent Document 2).

[0003] JP 2002-053884 A JP 2016-121336 A

[0004] Tribologist Vol. 35 No. 5 (1990) 343-348

[0005] Therefore, an object of the present invention is to provide a grease composition that has excellent water-containing shear stability.

[0006] The present invention provides the following grease compositions: 1. A grease composition comprising a base oil, a diurea compound as a thickener, and at least one wax selected from the group consisting of rice wax, carnauba wax, lanolin wax, and castor wax. 2. The grease composition according to claim 1, wherein the wax is rice wax or carnauba wax. 3. The grease composition according to claim 1, wherein the wax is rice wax. 4. The grease composition according to any one of claims 1 to 3, wherein the diurea compound contains a diurea compound represented by the following formula (1): R 1 -NHCONH-R 2 -NHCONH-R 3 (1) (wherein, R 2 represents an aromatic hydrocarbon group having 6 to 15 carbon atoms, and R 1 and R 3 may be the same or different and represent an aliphatic hydrocarbon group having 8 to 20 carbon atoms or an aromatic hydrocarbon group having 6 to 15 carbon atoms; R 1 and R 3 The proportion of aliphatic hydrocarbon groups in the total of (a) and (b) is 40 to 100 mol %. 5. The grease composition according to any one of (a) to (b) above, wherein the diurea compound contains a diurea compound represented by the following formula (1): 1 -NHCONH-R 2 -NHCONH-R 3 (1) (wherein, R 2 represents an aromatic hydrocarbon group having 6 to 15 carbon atoms, and R 1 and R 3may be the same or different and are aliphatic hydrocarbon groups having 8 to 20 carbon atoms.) 6. The grease composition according to any one of 1 to 5 above, further containing a rust inhibitor. 7. The grease composition according to 6 above, wherein the rust inhibitor comprises at least one of a succinic acid derivative, a metal sulfonate, and an organic acid metal salt. 8. The grease composition according to 6 above, wherein the rust inhibitor is at least one selected from the group consisting of dodecenyl succinic anhydride, an alkenyl succinimide, zinc dinonylnaphthalenesulfonate, and sodium sebacate. 9. The grease composition according to 6 above, wherein the content of the rust inhibitor is 0.01 to 5 mass % relative to the total mass of the composition. 10. The grease composition according to any one of 1 to 9 above, which is for use in rolling bearings or gears.

[0007] The grease composition of the present invention exhibits excellent shear stability even when water is present. The reason for the improved water-containing shear stability achieved by the present invention can be explained in principle as follows. Specifically, the diurea thickener, a grease component, exists as fine particles in the base oil. The network structure formed by these particles retains the base oil through capillary forces, forming a semi-solid or solid grease. When the grease is subjected to shear, the thickener network structure is destroyed, causing the grease to soften. In particular, aliphatic diurea greases tend to show a significant decrease in oil film thickness and accelerate shear softening when water is present. Looking at this at the crystalline level, as described in Non-Patent Document 1, the crystal form immediately after the reaction of isocyanate and amine, the raw materials for the diurea thickener, is a stable α-type. This phase transition occurs during the temperature rise in the grease production process, and when water-containing shear is applied to the diurea grease after the phase transition, it returns to the α-type before the phase transition. While the α type tends to form clumps as a whole, the β type, which is a thin, elongated fibrous particle, has a greater ability to retain the base oil by capillary force, allowing it to maintain sufficient hardness as a grease. In other words, the fact that the crystal form returns to the α type upon hydrous shear means that the grease softens. Without being bound by any theory, in the present invention, at least one wax selected from the group consisting of rice wax, carnauba wax, lanolin wax, and castor wax plays a role in preventing the diurea thickener from returning to the molecular arrangement (α type) before the phase transition, and as a result, it is presumed that the grease composition of the present invention has excellent hydrous shear stability.

[0008] <Base Oil> The type of base oil used in the present invention is not particularly limited. Examples include various synthetic oils such as naphthenic and paraffinic mineral oils, synthetic hydrocarbon oils such as poly-α-olefins (PAO) and polybutene, ether-based synthetic oils such as alkyl diphenyl ethers and polypropylene glycols, ester-based synthetic oils such as diesters and polyesters, silicone oils, and fluorinated oils. The synthetic oil may be a so-called biomass oil produced from biological resources derived from animals and plants. For example, biomass ester oils synthesized from various fatty acids and alcohols derived from vegetable oils, or biomass hydrocarbon oils derived from vegetable oils such as palm oil, corn oil, and soybean oil, can also be used. The base oils may be used alone or in combination of two or more. The kinematic viscosity at 40°C of the base oil of the present invention is, for example, 17 to 600 mm 2 The content of the base oil in the composition of the present invention is preferably 70 to 97 mass %, more preferably 80 to 96 mass %, and even more preferably 85 to 95 mass %, based on the total mass of the composition. By including the base oil in such a range, it is possible to ensure lubricity at the application location of the grease composition.

[0009] <Thickener> The thickener used in the present invention is a diurea compound. The diurea compound can be represented by the following formula (1): R 1 -NHCONH-R 2 -NHCONH-R 3 (1) In the formula, R 2 represents an aromatic hydrocarbon group having 6 to 15 carbon atoms, and R 1 and R 3may be the same or different and represent an aliphatic hydrocarbon group having 8 to 20 carbon atoms, an aromatic hydrocarbon group having 6 to 15 carbon atoms, or a cyclohexyl group. Examples of diurea compounds include: - aromatic-aliphatic urea compounds in which the raw amine is a mixture of aromatic amine and aliphatic amine; - aromatic urea compounds in which the raw amine is an aromatic amine; - aliphatic urea compounds in which the raw amine is an aliphatic amine; - alicyclic urea compounds in which the raw amine is an alicyclic amine; - alicyclic-aliphatic urea compounds in which the raw amine is a mixture of alicyclic amine and aliphatic amine; or - combinations of two or more of these. Among these, aromatic-aliphatic urea compounds, aliphatic urea compounds, and alicyclic-aliphatic urea compounds are preferred. When the raw amine is a mixture, the resulting diurea compound is also a mixture. A diurea compound represented by formula (1), R 1 and R 3 may be the same or different and represent an aliphatic hydrocarbon group having 8 to 20 carbon atoms or an aromatic hydrocarbon group having 6 to 15 carbon atoms; R 1 and R 3 It is preferable that the diurea compound contains a diurea compound in which the ratio of aliphatic hydrocarbon groups to the total of R 1 and R 3 However, it may be the same or different, and it is also preferable to contain a diurea compound which is an aliphatic hydrocarbon group having 8 to 20 carbon atoms.

[0010] The worked penetration of the grease composition of the present invention is preferably 180 to 400. The content of the thickener in the composition of the present invention may be any amount suitable for adjusting the penetration to the above range, for example, 2.0 to 25 mass% based on the total mass of the composition. In this specification, when simply referring to "consistency," it refers to the 60-stroke worked penetration measured in accordance with JIS K 2220 7.

[0011] <Wax> The wax used in the present invention is at least one selected from the group consisting of rice wax, carnauba wax, lanolin wax, and castor wax. Rice wax or carnauba wax is particularly preferred. In this specification, wax refers to an organic substance having an alkyl group that is solid or semi-solid at room temperature (25°C), melts in a temperature range of approximately 35°C to 110°C, and has a low melt viscosity. Rice wax refers to a wax refined from wax oil separated during the refining of rice bran and rice bran oil, and has a CAS number of 8016-60-2. Rice wax is primarily composed of esters of fatty acids (C16 (approximately 5%), C22 (approximately 20%), C24 (approximately 60%), and the remainder being others) with alcohol. Rice wax preferably has an acid value of 15 or less, a saponification value of 60 to 100, or an iodine value of 20.0 or less. That is, partially saponified rice wax (the CAS number for Ca partially saponified rice wax is 1850357-57-1) can be used, or hydrogenated rice wax can be used. This improves shear stability when hydrated. The ratio of the fatty acids can be measured by gas chromatography. The acid value can be measured according to ISO 2114. The saponification value can be measured according to ISO 3681. The iodine value can be measured according to the standard method for the analysis of fats, oils, and related materials. Of these, rice wax is preferred, and rice wax having an acid value of 15 or less and a saponification value of 60 to 100, or rice wax having an acid value of 15 or less and an iodine value of 20.0 or less is particularly preferred.

[0012] Carnauba wax refers to wax extracted and refined from the leaves of the carnauba palm tree, and its CAS number is 8015-86-9. Carnauba wax is primarily composed of esters of fatty acids (C20 (approximately 7%), C22 (approximately 7%), C24 (approximately 25%), C26 (approximately 10%), C28 (approximately 15%), C30 (approximately 4%), C32 (approximately 6%), and the remainder being others) with alcohol. Carnauba wax preferably has an acid value of 12 or less, a saponification value of 70 to 100, and an iodine value of 4 to 15 or less, which improves shear stability when hydrated. The ratio of the fatty acids can be measured by gas chromatography. The acid value can be measured according to ISO 2114. The saponification value can be measured according to ISO 3681. The iodine value can be measured according to the Standard Methods for the Analysis of Fats, Oils, and Related Compounds. The content of the wax in the composition of the present invention is preferably 0.1 to 5.0 mass%, more preferably 0.1 to 3.0 mass%, and even more preferably 0.2 to 1.5 mass%, based on the total mass of the composition. By including the wax in such a range, the water-containing shear stability can be improved.

[0013] <Optional Additives> In addition to the above components, the grease composition of the present invention can further contain additives that are commonly used in grease compositions. Examples of such optional additives include rust inhibitors, antioxidants, metal corrosion inhibitors, anti-wear agents, extreme pressure agents, and solid lubricants. Of these, it is particularly preferable to include a rust inhibitor. Another wax may be included as long as it does not inhibit the effects of the grease composition of the present invention. However, the grease composition of the present invention does not contain lithium soap.

[0014] <Rust Inhibitor> The rust inhibitor that can be used in the present invention may be an alkaline earth metal phenate or salicylate, a partial organic acid ester, a succinic acid derivative, or a metal sulfonate compound. These may be used alone or in combination. In this specification, the term "succinic acid derivative" includes unsubstituted succinic acid. As the succinic acid derivative, succinic acid, dodecenyl succinic anhydride, or alkenyl succinimide is preferred, and dodecenyl succinic anhydride or alkenyl succinimide is more preferred. As the metal sulfonate compound, an alkaline earth metal sulfonate such as zinc sulfonate or calcium sulfonate is preferred. Zinc dinonylnaphthalene sulfonate is more preferred. Of these, succinic acid derivatives are preferred, and dodecenyl succinic anhydride is more preferred. The content of the rust inhibitor in the composition of the present invention is preferably 0.01 to 2 mass %, more preferably 0.1 to 1.0 mass %, and even more preferably 0.1 to 0.5 mass %, based on the total mass of the composition. By including the rust inhibitor in such a range, the rust prevention properties and water-containing shear stability are improved.

[0015] Examples of antioxidants include amine-based, phenol-based, quinoline-based, sulfur-based, and zinc dithiophosphate. Examples of metal corrosion inhibitors include thiadiazole-based, benzimidazole-based, and benzotriazole-based. Examples of anti-wear agents and extreme pressure agents include phosphorus-based compounds (tricresyl phosphate, tri-2-ethylhexyl phosphate, etc.), sulfur-based compounds (dibenzyl disulfide, various polysulfides, etc.), sulfur-phosphorus compounds (triphenyl phosphorothioate), organometallic extreme pressure agents (dialkyldithiophosphate salts of Zn, Mo, Sb, Bi, etc., dialkyldithiocarbamate salts of Zn, Mo, Sb, Ni, Cu, Bi, etc.), and others (ashless dithiocarbamate, ashless dithiophosphate carbamate). Examples of solid lubricants include molybdenum disulfide, graphite, polytetrafluoroethylene, and melamine cyanurate. Examples of waxes other than the essential components include petrolatum, ethylene-propylene copolymer, octadecaneamide, etc. The content of such optional additives is, for example, 0.1 to 20.0% by mass, preferably 0.1 to 15.0% by mass, based on the total mass of the composition.

[0016] The grease composition of the present invention can be suitably used for, for example, rolling bearings or gears. Examples of rolling bearings include rolling bearings in steelmaking continuous casting equipment, rolling bearings in air conditioner fan motors or ventilation fans, and rolling bearings in hub units. Examples of gears include rack and pinion gears in automobiles, worm gears in electric power steering, and worm gears in power window motors.

[0017] Preferred embodiments according to the intended use will be described in further detail below. (1) First Aspect: Grease Composition for Iron and Steel Making The grease composition for iron and steel making continuous casting equipment will be described below. In this specification, the "grease composition for iron and steel making continuous casting equipment" may also be referred to as the "grease composition for iron and steel making". From the viewpoint of economy, mineral oil is preferred as the base oil. Since the grease composition for iron and steel making is pumped through piping so that it can be used in a centralized greasing facility, the kinematic viscosity of the base oil at 40°C is 70 to 600 mm2 / s is preferred, and 90 to 500 mm 2 / s is more preferable, and 120 to 500 mm 2 The content of the base oil in the grease composition for steel making of the present invention is preferably 70 to 97 mass %, more preferably 80 to 95 mass %, and even more preferably 85 to 95 mass %, based on the total mass of the composition.

[0018] As the thickener, a diurea compound is preferred from the viewpoint of heat resistance, and an aliphatic urea compound or an aromatic-aliphatic urea compound is preferred from the viewpoint of pumpability. 1 and R 3 The aromatic-aliphatic urea compound is particularly preferably an aromatic diurea compound represented by the formula (1) above, wherein R 1 and R 3 one of which is a C8 alkyl and the other is a phenyl group, and R 1 and R 3 An aromatic-aliphatic diurea compound in which the proportion of octyl groups in the total of 1 and R 3 one of which is a C8 alkyl and the other is a para-toluyl group, 1 and R 3 An aromatic-aliphatic diurea compound in which the proportion of octyl groups in the total of the above is 40 to 100 mol % is more preferred.

[0019] The consistency of the grease composition for steel making of the present invention is preferably 250 to 400, more preferably 265 to 385, and even more preferably 300 to 385, and the content of the thickener is the amount necessary to achieve this consistency. In the grease composition for steel making of the present invention, the proportion of the thickener is preferably 2 to 20 mass%, more preferably 2.5 to 15 mass%, and even more preferably 2.5 to 10 mass%. From the viewpoint of water-containing shear stability, the grease composition for steel making of the present invention preferably contains rice wax, carnauba wax, lanolin wax, or castor wax, and more preferably contains rice wax or carnauba wax. From the viewpoint of water-containing shear stability, the content of these waxes is preferably 0.1 to 5.0 mass%, more preferably 0.1 to 3.0 mass%, based on the total mass of the grease composition for steel making of the present invention. The grease composition for iron and steel of the present invention may also contain, as additives, rust inhibitors, antioxidants, metal corrosion inhibitors, anti-wear agents, extreme pressure agents, solid lubricants, etc. The content of these optional additives is preferably 0.1 to 20.0 mass %, and more preferably 0.1 to 15.0 mass %, based on the total mass of the grease composition for iron and steel of the present invention.

[0020] The grease composition for steel of the present invention is, in particular, a grease composition for steel of which the base oil has a kinematic viscosity at 40°C of 90 to 500 mm 2 / s, and the thickener is a mineral oil represented by the formula (1), R 1 and R 3 and an aliphatic diurea compound in which both of R 1 and R 3 one of which is a C8 alkyl and the other is a phenyl group, and R 1 and R 3 An aromatic-aliphatic diurea compound in which the proportion of octyl groups in the total of 1 and R 3 one of which is a C8 alkyl and the other is a para-toluyl group, 1 and R 3and the grease composition is an aromatic-aliphatic diurea compound in which the ratio of octyl groups to the total of (a) and (b) is 40 to 100 mol %, and the grease composition may contain, as additives, 0.1 to 3.0 mass % of rice wax or carnauba wax, and 0.01 to 0.5 mass % of a rust inhibitor, based on the total mass of the composition, and has a consistency of 265 to 385.

[0021] The grease composition for steel of the present invention is particularly characterized in that the base oil has a kinematic viscosity of 120 to 500 mm at 40°C. 2 / s, and the thickener is a mineral oil represented by the formula (1), R 1 and R 3 and an aliphatic diurea compound in which both of R 1 and R 3 one of which is a C8 alkyl and the other is a phenyl group, and R 1 and R 3 and the grease composition is an aromatic-aliphatic diurea compound in which the ratio of octyl groups to the total of (a) and (b) is 70 to 90 mol %, and the grease composition may contain, as additives, 0.2 to 1.5 mass % of rice wax and 0.1 to 0.5 mass % of a rust inhibitor, based on the total mass of the composition, and has a consistency of 300 to 385.

[0022] (2) Second Aspect: Grease Composition for Rolling Bearings of Fan Motors of Air Conditioners or Ventilation Fans The following describes a grease composition for rolling bearings of fan motors of air conditioners or ventilation fans. In this specification, "grease composition for rolling bearings of fan motors of air conditioners or ventilation fans" may also be referred to as "grease composition for ventilation fans." As the base oil, PAO, ester oil, ether oil, or a mixture thereof is preferred from the viewpoints of economy, low temperature, and low torque. Grease compositions for ventilation fans are not used in environments exposed to as much water as rolling bearings for steel, but are used in environments that are high in humidity and subject to shear. In this case, from the viewpoints of low torque and bearing life, the kinematic viscosity of the base oil at 40°C is 30 to 100 mm 2 / s is preferred, 30 to 80 mm 2 / s is more preferable. The content of the base oil in the grease composition for ventilation fans of the present invention is preferably 70 to 93 mass%, more preferably 72 to 90 mass%, and even more preferably 75 to 88 mass%, based on the total mass of the composition. By including the base oil in such a range, it is possible to ensure lubricity at the application location of the grease composition.

[0023] As the thickener, an aliphatic urea compound, an alicyclic-aliphatic diurea compound, or an aromatic-aliphatic urea compound is preferred from the viewpoint of low torque and heat resistance. 1 and R 3 and R are both C8 alkyl, or 1 and R 3 The alicyclic-aliphatic diurea compound is particularly preferably an aliphatic diurea compound in which one of R is a C8 alkyl and the other is a C18 alkyl. 1 and R 3 one of which is a C18 alkyl and the other is a cyclohexyl group, and R 1 and R 3 The aromatic aliphatic urea compound is particularly preferably an alicyclic-aliphatic diurea compound in which the proportion of cyclohexyl groups in the total of 1 and R 3 one of which is a C8 alkyl and the other is a para-toluyl group, 1 and R 3 An aromatic-aliphatic diurea compound in which the proportion of octyl groups in the total of the above is 0 to 40 mol % is preferred.

[0024] The consistency of the grease composition for a ventilation fan of the present invention is preferably 180 to 350, more preferably 200 to 300, and the content of the thickener is the amount necessary to achieve this consistency. The proportion of the thickener is preferably 5 to 25 mass%, more preferably 6 to 20 mass%, and even more preferably 8 to 17 mass%. From the viewpoint of water-containing shear stability, the grease composition for a ventilation fan of the present invention preferably contains rice wax, carnauba wax, lanolin wax, or castor wax as the wax, and more preferably rice wax or carnauba wax. From the viewpoint of water-containing shear stability, the content of these waxes is preferably 0.1 to 5.0 mass%, more preferably 0.1 to 2.0 mass%, based on the total mass of the grease composition for a ventilation fan of the present invention. The grease composition for a ventilation fan of the present invention may also contain additives such as rust inhibitors, antioxidants, metal corrosion inhibitors, anti-wear agents, and extreme pressure agents. The content of these optional additives is preferably 1 to 20 mass %, more preferably 2 to 15 mass %, based on the total mass of the grease composition for ventilation fans of the present invention.

[0025] The grease composition for a ventilation fan of the present invention is, in particular, a grease composition for a ventilation fan of the present invention, 2 / s, and the thickener is a PAO, an ester oil, an ether oil, or a mixture thereof, wherein R 1 and R 3 and an aliphatic diurea compound in which both of R 1 and R 3 an aliphatic diurea compound in which one of R is a C8 alkyl and the other is a C18 alkyl; 1 and R 3 one of which is a C18 alkyl and the other is a cyclohexyl group, and R 1 and R 3 an alicyclic-aliphatic diurea compound in which the proportion of cyclohexyl groups in the total of 1 and R 3 one of which is a C8 alkyl and the other is a para-toluyl group, 1and R 3 and the grease composition is preferably an aromatic-aliphatic diurea compound in which the ratio of octyl groups to the total of (a) to (b) is 0 to 30 mol %, and the grease composition may contain, as additives, 0.1 to 2.0 mass % of rice wax or carnauba wax, and 0.1 to 6.0 mass % of an antioxidant, 0.1 to 8.0 mass % of a rust inhibitor, 0.01 to 3.0 mass % of a metal corrosion inhibitor, and 0.1 to 5.0 mass % of an anti-wear agent or an extreme pressure agent, based on the total mass of the composition, and has a consistency of 200 to 300.

[0026] (3) Third Aspect: Grease Composition for Rolling Bearing of Hub Unit The grease composition for rolling bearing of hub unit will be explained below. In this specification, "grease composition for rolling bearing of hub unit" may also be referred to as "grease composition for hub unit".) As the base oil, from the viewpoints of economy and lubricity, mineral oil, PAO, ester oil, or a mixture of two or more of these is preferred, and mineral oil, PAO, a mixture of mineral oil and PAO, or a mixture of PAO and ester oil is more preferred. The kinematic viscosity of the base oil at 40°C is 20 to 300 mm from the viewpoints of wear resistance, peeling resistance, and low torque. 2 / s is preferred, and 20 to 200 mm 2 / s is more preferable, 30 to 100 mm 2 / s is even more preferable. The content of the base oil in the grease composition for a hub unit of the present invention is preferably 70 to 93 mass %, and more preferably 75 to 90 mass %, based on the total mass of the composition. By including the base oil in such a range, it is possible to ensure lubricity at the application location of the grease composition.

[0027] As the thickener, an aliphatic diurea compound or an alicyclic-aliphatic diurea compound is preferred from the viewpoint of heat resistance and acoustic properties. 1 and R 3 and are both C8 alkyl. The alicyclic-aliphatic diurea compound is preferably a compound represented by the formula (1) above, 1 and R 3 one of which is a C18 alkyl and the other is a cyclohexyl group, and R1 and R 3 An alicyclic-aliphatic diurea compound in which the proportion of cyclohexyl groups in the total of the above is 50 to 95 mol % is preferred.

[0028] The consistency of the grease composition for a hub unit of the present invention is preferably 200 to 350, more preferably 230 to 350, and the content of the thickener is the amount necessary to achieve this consistency. The proportion of the thickener is preferably 5 to 25 mass%, more preferably 7 to 15 mass%. From the viewpoint of water-containing shear stability, the grease composition for a hub unit of the present invention preferably contains rice wax, carnauba wax, lanolin wax, or castor wax as the wax, and more preferably contains rice wax or carnauba wax. From the viewpoint of water-containing shear stability, the content of these waxes is preferably 0.1 to 5.0 mass%, more preferably 0.1 to 2.0 mass%, based on the total mass of the grease composition for a hub unit of the present invention. The grease composition for a hub unit of the present invention may also contain additives such as rust inhibitors, antioxidants, metal corrosion inhibitors, anti-wear agents, extreme pressure agents, and solid lubricants. The content of these optional additives is preferably 1.0 to 20 mass %, and more preferably 1.5 to 15 mass %, based on the total mass of the grease composition for a hub unit of the present invention.

[0029] The grease composition for a hub unit of the present invention is particularly characterized in that the base oil has a kinematic viscosity of 20 to 200 mm at 40°C. 2 / s, mineral oil, PAO, ester oil, or a mixture of two or more thereof, and the thickener is 1 and R 3 and R are both C8 alkyl, or 1 and R 3 one of which is a C18 alkyl and the other is a cyclohexyl group, and R 1 and R 3and the ratio of cyclohexyl groups to the total of (a) to (b) is 60 to 90 mol %, and the grease composition contains, as additives, 0.1 to 2.0 mass % of rice wax or carnauba wax, and may contain, based on the total mass of the composition, 0.1 to 7.0 mass % of a rust inhibitor, 0.1 to 5.0 mass % of an antioxidant, 0.1 to 4.0 mass % of an anti-wear agent or extreme pressure agent, and 0.5 to 6.0 mass % of a solid lubricant, and has a consistency of 230 to 350.

[0030] The grease composition for a hub unit of the present invention comprises a base oil having a kinematic viscosity of 30 to 100 mm at 40°C. 2 / s, and the thickener is a mineral oil, a PAO, a mixture of a mineral oil and a PAO, or a mixture of a PAO and an ester oil, wherein R 1 and R 3 and R are both C8 alkyl, or 1 and R 3 one of which is a C18 alkyl and the other is a cyclohexyl group, and R 1 and R 3 and the grease composition is most preferably an alicyclic-aliphatic diurea compound in which the proportion of cyclohexyl groups to the total of (a) and (b) is 65 to 90 mol %, and the grease composition may contain, as additives, 0.1 to 2.0 mass % of rice wax or carnauba wax, 0.1 to 7.0 mass % of a rust inhibitor, 0.1 to 5.0 mass % of an antioxidant, 0.1 to 4.0 mass % of an anti-wear agent or extreme pressure agent, and 0.5 to 6.0 mass % of a solid lubricant, based on the total mass of the composition, and has a consistency of 230 to 350.

[0031] (4) Fourth Aspect: Grease Composition for Rack and Pinion The grease composition for rack and pinion will be described below. As the base oil, mineral oil, PAO, or a mixture thereof is preferred from the viewpoints of economy, lubricity, and low-temperature fluidity. The kinematic viscosity of the base oil at 40°C is 17 to 400 mm from the viewpoints of lubricity and durability. 2 / s is preferred, 17 to 65 mm 2 / s is more preferable. The content of the base oil in the grease composition for rack and pinion of the present invention is preferably 70 to 95 mass%, more preferably 70 to 90 mass%, and even more preferably 70 to 85 mass%, based on the total mass of the composition. By including the base oil in such a range, it is possible to ensure lubrication at the application location of the grease composition.

[0032] As the thickener, an aliphatic diurea compound is preferred from the viewpoint of heat resistance and lubricity. 1 and R 3 and R are both C8 alkyl, or 1 and R 3 Aliphatic diurea compounds in which one of the alkyl groups is a C8 alkyl and the other is a C18 alkyl are more preferred.

[0033] The consistency of the grease composition is preferably 250 to 390, and the content of the thickener is the amount necessary to achieve this consistency. The proportion of the thickener is preferably 3 to 15 mass%. The rack and pinion grease composition of the present invention preferably contains rice wax, carnauba wax, lanolin wax, or castor wax as the wax, and more preferably rice wax or carnauba wax. The content of these waxes is preferably 0.1 to 5.0 mass%, and more preferably 0.1 to 3.0 mass%, based on the total mass of the rack and pinion grease composition of the present invention. The rack and pinion grease composition of the present invention may also contain additives such as rust inhibitors, antioxidants, metal corrosion inhibitors, anti-wear agents, extreme pressure agents, and solid lubricants. The content of these optional additives is preferably 0.1 to 20 mass%, and more preferably 0.5 to 15 mass%, based on the total mass of the rack and pinion grease composition of the present invention.

[0034] The rack and pinion grease composition of the present invention is particularly characterized in that: the base oil has a kinematic viscosity at 40°C of 17 to 400 mm 2 / s, preferably 17 to 65 mm 2 / s, a mineral oil, a PAO, or a mixture thereof, and the thickener is 1 and R 3 and R are both C8 alkyl, or 1 and R 3 and the other is a C18 alkyl; and the grease composition contains, as additives, 0.1 to 3.0 mass% of rice wax or carnauba wax, based on the total mass of the composition, and may contain 0.1 to 5.0 mass% of a rust inhibitor, 0.1 to 1.0 mass% of an antioxidant, 0.01 to 1.0 mass% of a metal corrosion inhibitor, 0.1 to 10 mass% of an anti-wear agent or extreme pressure agent, and 0.1 to 10.0 mass% of a solid lubricant; and has a consistency of 250 to 390.

[0035] <Test Grease> 1 mole of diphenylmethane-4,4'-diisocyanate was reacted with 2 moles of aniline and octylamine in a base oil. The mixture was heated to a temperature at which the thickener fibers undergo a phase transition. During cooling, wax was added and dissolved according to the formulation shown in Tables 1 to 3 to obtain a base grease. Additional base oil was added to achieve a consistency of 370, and each additive was added in the proportions shown in Tables 1 to 3. The mixture was dispersed using a three-roll mill to obtain the grease compositions of the Examples and Comparative Examples. The consistency of the grease compositions was adjusted to 370. The blending ratios of each ingredient are shown in Tables 1 to 3. Note that the numbers in Tables 1 to 3 indicate the molar ratio of the aromatic amine (aniline) to the aliphatic amine (octylamine) for the thickener. All other values ​​indicate mass % based on the total mass of the composition. The kinematic viscosity of the base oil at 40°C was measured according to JIS K2220 23. The consistency of the grease composition was measured in accordance with JIS K2220 7. The grease compositions obtained above were tested and evaluated by the methods shown below. The results are shown in Tables 1 to 3.

[0036] <Test Method> ○ Hydrous Shell Roll Test (Based on ASTM D 1831) This test involves applying shear in a water-contaminated environment. This test was used to evaluate hydrous shear stability. [Test Conditions] - Grease Amount: 45g - Ion-exchanged Water: 5g - Rotational Speed: 165 rpm - Test Temperature: 80°C - Test Time: 24 hours [Evaluation] ◎: Difference in consistency before and after the test is 0-30 ○: Difference in consistency before and after the test is 31-60 ×: Difference in consistency before and after the test is 61 or more Note that grease consistency is classified by grade. JIS, ASTM, and NLGI all have a range of 30 (±15) with each grade separated by 45. While grease consistency varies depending on the application, a consistency difference of within 30 means that the grease can be used for the intended application without any problems.

[0037]

[0038]

[0039]

[0040] The components used to prepare the grease compositions of the Examples and Comparative Examples are as follows: <Base oil> Mineral oil A: paraffinic mineral oil, kinematic viscosity at 40°C: 130.0 mm 2 / s Mineral oil B: paraffinic mineral oil, kinematic viscosity at 40 ° C: 461.2 mm 2 / s PAO: Polyα-olefin, kinematic viscosity at 40 ° C: 48.5 mm 2 / s Ether oil: alkyl diphenyl ether, kinematic viscosity at 40 ° C: 68.5 mm 2The kinematic viscosity was measured in accordance with JIS K 2220 23. <Waxes> Rice wax: trade name: TOWAX-3F17, manufactured by Toa Kasei Co., Ltd. (acid value: 5.4, saponification value: 77.3, iodine value: 7.4) Lanolin wax: trade name: Lanolin Wax H, manufactured by Nippon Fine Chemicals Co., Ltd. Carnauba wax: trade name: Carnauba No. 2, manufactured by Toa Kasei Co., Ltd. (acid value: 10.0, saponification value: 89.4, iodine value: 8.5) Castor wax: trade name: Castor Wax A, manufactured by NOF Corporation Vaseline: Cas number: 8009-03-8 Ethylene-propylene copolymer: trade name: Licocene PP 3602 GR, manufactured by Clariant Chemicals Co., Ltd. Octadecanamide: trade name: Armoslip HT Powder, manufactured by Lion Specialty Chemicals <Rust inhibitors> Dodecenylsuccinic anhydride: Trade name: DSA, manufactured by Sanyo Chemical Industries, Ltd. Alkenyl succinimide: Trade name: OLOA 1200, manufactured by Chevron Japan Co., Ltd. Zinc dinonylnaphthalenesulfonate: Trade name: NA-SUL ZS, manufactured by KING INDUSTRIES, INC. Sodium sebacate: Trade name: IRGACOR DSSG, manufactured by BASF Japan Ltd.

Claims

1. A grease composition comprising a base oil, a diurea compound as a thickener, and at least one wax selected from the group consisting of rice wax, carnauba wax, lanolin wax, and castor wax.

2. The grease composition according to claim 1, wherein the wax is rice wax or carnauba wax.

3. The grease composition according to claim 1, wherein the wax is rice wax.

4. The grease composition according to claim 1, wherein the diurea compound contains a diurea compound represented by the following formula (1): 1 -NHCONH-R 2 -NHCONH-R 3 (1) (wherein, R 2 represents an aromatic hydrocarbon group having 6 to 15 carbon atoms; R 1 and R 3 may be the same or different and represent an aliphatic hydrocarbon group having 8 to 20 carbon atoms or an aromatic hydrocarbon group having 6 to 15 carbon atoms; R 1 and R 3 The proportion of aliphatic hydrocarbon groups in the total of is 40 to 100 mol %.) 5. The grease composition according to claim 1, wherein the diurea compound contains a diurea compound represented by the following formula (1): 1 -NHCONH-R 2 -NHCONH-R 3 (1) (wherein, R 2 represents an aromatic hydrocarbon group having 6 to 15 carbon atoms; R 1 and R 3 may be the same or different and are aliphatic hydrocarbon groups having 8 to 20 carbon atoms.

6. The grease composition according to claim 1, further comprising a rust inhibitor.

7. The grease composition according to claim 6, wherein the rust inhibitor comprises at least one of a succinic acid derivative, a metal sulfonate, and an organic acid metal salt.

8. The grease composition according to claim 6, wherein the rust inhibitor is at least one selected from the group consisting of dodecenylsuccinic anhydride, alkenylsuccinimide, zinc dinonylnaphthalenesulfonate, and sodium sebacate.

9. The grease composition according to claim 6, wherein the content of the rust inhibitor is 0.01 to 5 mass % based on the total mass of the composition.

10. The grease composition according to any one of claims 1 to 9, which is for use in rolling bearings or gears.

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