Grease composition for elevator winch or elevator pulley bearing

Abstract

To provide a grease composition for use in an elevator winch or an elevator pulley bearing that is excellent in low torque characteristics contributing to reducing power consumption and in shear stability contributing to preventing its leakage from a bearing and allowing slight oil separation.SOLUTION: A grease composition for use in an elevator winch or an elevator pulley bearing comprises (a) base oil, (b) an alicyclic aliphatic diurea thickener (provided that the mole% of an alkyl group derived from an aliphatic amine in the urea compound is more than 10% and less than 30%), and additives (c) including (c1) a dibasic acid metal salt, (c2) at least one species of amine-based antioxidants having a diphenylamine structure, and (c3) at least one species of phenol-based antioxidant, and having a 60-time worked penetration measured according to JIS K 2220.7 ranging from 220 to 315.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a grease composition for use in an elevator hoist or elevator pulley bearing, and to an elevator hoist or elevator pulley bearing filled with the grease composition. [Background technology]

[0002] An elevator hoist is constructed by supporting a rotating shaft, to which a rotor and sheave of an electric motor are attached, rotatably by bearings provided on a bearing stand. A car is hung from one end of a rope wound around the sheave, and a weight is hung from the other end. When the electric motor is driven, the rotor, rotating shaft, and sheave rotate, causing the car to rise and fall. Grease is used as a lubricant for the bearings. Elevators are used for long periods of time with regular maintenance inspections, so the bearings of the hoisting machine are also expected to be used for a long time. The bearings are periodically replenished with grease, and from the perspective of long-term use, the grease must not only be rust-resistant and resistant to oxidation deterioration, but also leak-resistant to prevent softened grease from the bearings and oil generated from the grease from scattering and adhering to the surrounding area. In recent years, the number of high-rise buildings with lifting distances exceeding 200m has increased, and the weight of elevator ropes, cars and weights has correspondingly increased, which has resulted in an increase in the load placed on the hoisting machine. In order to accommodate the increased load, the bearings of the hoisting machine have become larger, and as the speed of elevators increases, the rotation speed also increases, so the torque generated by the bearings has become non-negligible from the perspective of power consumption. As a result, elevator traction machine bearings are now required to have grease that is both leak-resistant and has low torque properties, that is, grease that is resistant to softening due to shear and prevents separated oil from leaking outside the bearing. For example, Patent Document 1 uses a method in which waste heat generated from the motor during elevator operation is used to increase the grease temperature, and the heat softens the grease to reduce torque. As buildings become taller, motors are becoming more powerful and efficient, leading to a decrease in the amount of waste heat during operation. In addition, torque reduction using waste heat can be applied when elevators are operating during the day, but cannot be applied when the elevator is operating in the early morning after a long stop, for example, or in cold regions where the entire device is cooled. In addition, torque reduction is achieved by using waste heat from the hoist, not by the performance of the grease. For example, in Patent Document 2, a specific urea compound is used as a thickener, and the kinetic viscosity at 40°C is 20 to 55 mm 2 A grease has been proposed that uses a pentaerythritol ester oil having a viscosity of 1000 to 15000 psi as a base oil, and is a mixture of at least one selected from the group consisting of polyhydric alcohol ester-based rust inhibitors and at least one selected from the group consisting of organic sulfonate-based rust inhibitors. However, because of its low viscosity, it does not satisfy the lubrication life required for a traction machine bearing. For example, Patent Document 3 proposes a grease containing an ester oil as a base oil, a specific urea compound as a thickener, and a diurea content of 18 mass% or less, and discloses that the bearing rotation torque can be kept low by increasing the shear stress and improving the channeling property of the grease. It also discloses that the shear viscosity at high temperatures can be increased, which can prevent grease leakage. However, this does not satisfy the problem of softening of the grease due to additives when subjected to shear stress, or leakage of oil due to oil separation. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2012-076897 A [Patent Document 2] JP 2012-197401 A [Patent Document 3] JP 2018-065971 A Summary of the Invention [Problem to be solved by the invention]

[0004] As elevator speeds increase in high-rise buildings, it has become essential to improve the efficiency of traction machines as an energy-saving measure. Although there have been studies on reducing power consumption from the perspective of traction machine structure, such as making them gearless by applying dedicated electric motors with high torque, no efforts have been made to reduce the torque of bearings by using grease as a lubricant. The low torque provided by grease reduces the stirring resistance within the bearing. Although torque can be reduced by lowering the viscosity of the grease's base oil, since the bearings of an elevator rotate forward and backward when ascending and descending, it becomes difficult to maintain the oil film when decelerating and stopping. Therefore, lowering the viscosity of the base oil in conventional lithium grease causes durability problems. By using urea as a thickener, the oil film at low speeds is thicker than that of lithium grease, allowing the viscosity of the base oil to be reduced, and the stirring resistance is also reduced because the grease softens when subjected to shear. However, in the case of large bearings, the entire grease inside the bearing is subjected to shear stress, which causes the grease to soften and leak if using typical low-torque urea grease. The problem that the present invention aims to solve is to provide a grease composition for use in an elevator hoisting machine or a pulley bearing, which has excellent low torque properties for reducing power consumption, excellent shear stability for suppressing leakage from the bearing, and little oil separation, and to provide an elevator hoisting machine or a pulley bearing filled with the grease composition. [Means for solving the problem]

[0005] According to the present invention, there is provided the following grease composition and elevator hoist or pulley bearing. 1.(a) base oil; (b) a thickener containing a mixture of a urea compound represented by the following formula (1), a urea compound represented by the following formula (2), and a urea compound represented by the following formula (3), and R1 -NHCONH-R 2 -NHCONH-R 1 (1) R 1 -NHCONH-R 2 -NHCONH-R 3 (2) R 3 -NHCONH-R 2 -NHCONH-R 3 (3) (In the formula, R 1 represents a cyclohexyl group, and R 2 represents a divalent aromatic hydrocarbon group having 6 to 15 carbon atoms, R 3 represents an alkyl group having 8 to 22 carbon atoms, {(R 3 (number of moles of R 1 moles + R 3 The molar percentage of alkyl groups represented by {number of moles of alkyl groups per mole}×100 is greater than 10% and less than 30%. (c) As an additive, (c1) metal salts of dibasic acids, (c2) at least one amine antioxidant having a diphenylamine structure, and (c3) at least one phenolic antioxidant; and having a worked penetration of 220 to 315 after 60 tries as measured in accordance with JIS K 2220.7. 2. The grease composition according to 1 above, wherein (c1) the dibasic acid metal salt is sodium sebacate. 3. The grease composition according to 1 or 2 above, wherein the content of the dibasic acid metal salt (c1) is 0.1 to 2 mass % based on the total mass of the composition. 4. (c3) A grease composition according to 1 or 2 above, comprising octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate as an antioxidant. 5. The thickener is represented by the formula (1), R 1 a urea compound in which R 1 is a cyclohexyl group, and R 3a urea compound in which R 3 3. The grease composition according to 1 or 2 above, wherein the urea compound is a mixture of the urea compound having an alkyl group having 18 carbon atoms, and the mol % is 15 to 25%. 6. The grease composition according to 1 or 2 above, wherein the content of the thickener is 5 to 15 mass % based on the total mass of the composition. 7. The grease composition according to 1 or 2 above, wherein the (a) base oil is at least one oil selected from the group consisting of mineral oils, synthetic hydrocarbon oils, ester oils, and ether oils. 8. A bearing for an elevator hoist or elevator pulley, filled with the grease composition described in 1 above. Effect of the Invention

[0006] According to the present invention, it is possible to provide a grease composition which is excellent in low torque properties and shear stability and also causes little oil separation. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0007] (a) Base oil The base oil used in the grease composition of the present invention is not particularly limited. For example, all base oils including mineral oils can be used. In addition to mineral oils, various synthetic oils such as ester-based synthetic oils represented by diesters and polyol esters, poly-α-olefins, synthetic hydrocarbon oils represented by polybutenes, ether-based synthetic oils represented by alkyl diphenyl ethers and polypropylene glycols, and silicone oils can be used. Preferred are ester-based synthetic oils, synthetic hydrocarbon oils, and ether-based synthetic oils, which are excellent in low temperature properties and heat resistance. More preferred are ester-based synthetic oils and synthetic hydrocarbon oils. Even more preferred are synthetic hydrocarbon oils. Synthetic hydrocarbon oils have a small change in kinetic viscosity due to temperature change, and have excellent fluidity at low temperatures, so they are excellent in low torque at low temperatures, and can also ensure oil film thickness at high temperatures, so they are also excellent in durability at high temperatures. Poly-α-olefins are preferred from the viewpoint of low traction coefficient and low temperature properties. The base oil is preferably contained in an amount of 80 to 95 mass %, more preferably 83 to 93 mass %, based on the total mass of the composition. When the content of the base oil is within such a range, a sufficient amount of oil for lubrication can be secured, and excellent durability can be exhibited. The kinematic viscosity at 40°C of the base oil used in the grease composition of the present invention is not particularly limited, but if the kinematic viscosity is too low, the low torque performance is excellent but the durability is reduced, whereas if the kinematic viscosity is too high, the durability is improved but the low torque performance is reduced. 2 / s is preferable, and 60 to 200 mm 2 / s is more preferable, and 80 to 130 mm 2 / s is even more preferable.

[0008] [(b) Thickener] The thickener contained in the composition of the present invention is an alicyclic aliphatic diurea compound. The alicyclic aliphatic diurea compound is obtained by reacting an alicyclic monoamine and an aliphatic monoamine with a diisocyanate. Therefore, in addition to the reaction product of an alicyclic monoamine and an aliphatic monoamine with a diisocyanate, the thickener includes a reaction product of an alicyclic monoamine and a diisocyanate (so-called an alicyclic diurea compound) and a reaction product of an aliphatic monoamine and a diisocyanate (so-called an aliphatic diurea compound). From the viewpoints of low torque and shear stability, the thickener of the present invention is preferably a mixture of a compound represented by the following formula (1), a compound represented by the following formula (2), and a urea compound represented by the following formula (3). R 1 -NHCONH-R 2 -NHCONH-R 3 (1) R 1 -NHCONH-R 2 -NHCONH-R 1 (2) R 3 -NHCONH-R 2 -NHCONH-R 3 (3) In the formula, R 2R represents a divalent aromatic hydrocarbon group having 6 to 15 carbon atoms. 1 R represents a cyclohexyl group. 3 represents a linear or branched alkyl group having 8 to 22 carbon atoms, preferably a linear alkyl group having 16 to 20 carbon atoms, and most preferably a linear alkyl group having 18 carbon atoms. The ratio of the number of moles of the linear or branched alkyl group having 8 to 22 carbon atoms to the total number of moles of the cyclohexyl group and the linear or branched alkyl group having 8 to 22 carbon atoms (R 3 moles / (R 1 moles + R 3 The molar ratio of alkyl groups is more preferably 15 to 25%, and particularly preferably 18 to 22%, and more preferably 18 to 22%. The use of such a thickener allows the consistency to be adjusted to the desired consistency with a small amount of thickener, thereby reducing the stirring resistance of the grease composition to achieve low torque properties and at the same time providing a grease composition with excellent durability. The molar ratio of alkyl groups is more preferably 15 to 25%, and particularly preferably 18 to 22%.

[0009] The thickener of the present invention is represented by the formula (1): 1 a urea compound in which R 1 is a cyclohexyl group, and R 3 a urea compound in which R 3 A thickener which is a mixture of a urea compound in which the alkyl group has 18 carbon atoms and the urea compound is a mixture in which the mol % is 15 to 25% is preferred. In particular, the thickener of the present invention is a compound represented by the formula (1): 1 is a cyclohexyl group, and R 2 is a group derived from 4,4'-diphenylmethane diisocyanate, and R 3 is a linear alkyl group having 18 carbon atoms, and in formula (2), R 1 is a cyclohexyl group, and R 2 is a group derived from 4,4'-diphenylmethane diisocyanate, and 2 is a group derived from 4,4'-diphenylmethane diisocyanate, and R 3A mixture in which the molar ratio is 18 to 22% and a compound in which the molar ratio is a linear alkyl group having 18 carbon atoms is the most preferable from the standpoints of thickening ability (i.e., the ability to prepare a grease with a desired hardness with a small content) and shear stability, and ultimately from the standpoints of low torque properties and durability. The thickener is preferably contained in an amount of 5 to 15 mass %, more preferably 6 to 12 mass %, based on the total mass of the composition. When the content of the thickener is within this range, the stirring resistance of the grease is small and the grease has excellent channeling properties, so that a satisfactory level of low torque can be achieved.

[0010] [(c1) Additives] The additive (c1) of the present invention is a dibasic metal salt. Dibasic metal salts are usually used as rust inhibitors in the technical field of the present invention. As a result of the investigation by the present inventors using various additives, it was found that when a dibasic metal salt is used in combination with an amine-based antioxidant and a phenol-based antioxidant, a grease composition containing an alicyclic aliphatic diurea thickener exhibits excellent shear stability. Specific examples include metal salts of dodecanoic acid, sebacic acid, dodecanoic acid, etc. In particular, sodium sebacate is preferred. The content of the dibasic acid metal salt is preferably 0.1 to 2 mass%, more preferably 0.3 to 1.5 mass%, and even more preferably 0.3 to 1 mass%, based on the total mass of the composition. By including the dibasic acid metal salt in such an amount, both rust prevention and low torque properties can be achieved.

[0011] [(c2) Antioxidants] Antioxidants are known as agents for inhibiting oxidation deterioration of grease. The amine-based antioxidant of the present invention is a combination of (c2) an amine-based antioxidant having a diphenylamine structure and (c3) a phenol-based antioxidant. (c2) Examples of amine-based antioxidants having a diphenylamine structure include reaction products of N-phenylbenzenamine and 2,4,4-trimethylpentene, octylated diphenylamine (CAS 68411-46-1 (Japanese chemical product name: benzylamine, reaction product of 2,4,4-trimethylpentene and N-phenyl)), 4,4'-tetramethyl-di-aminodiphenylmethane, etc. As the (c2) amine-based antioxidant, reaction products of N-phenylbenzenamine and 2,4,4-trimethylpentene are preferred. (c3) Examples of phenol-based antioxidants include 2,6-di-tert-butyl-p-cresol (BHT), 2,2'-methylenebis(4-methyl-6-tert-butylphenol), 4,4'-butylidenebis(3-methyl-6-tert-butylphenol), 2,6-di-tert-butyl-phenol, 2,4-dimethyl-6-tert-butylphenol, tert-butylhydroxyanisole (BHA), 4,4'-butylidenebis(3-methyl-6-tert-butylphenol), 4,4'-methylenebis(2,3-di-tert-butylphenol), 4,4'-thiobis(3-methyl-6-tert-butylphenol), and octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate. (c3) As the phenolic antioxidant, octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate is preferred.

[0012] The content of the (c2) amine-based antioxidant is preferably 0.5 to 5 mass %, more preferably 1 to 3 mass %, and even more preferably 1.5 to 2.5 mass %, based on the total mass of the composition. By including the (c2) amine-based antioxidant in such an amount, it is difficult to see any further improvement in the effect even if the amount exceeds 5%. The content of the (c3) phenolic antioxidant is preferably 0.2 to 3 mass%, more preferably 0.5 to 3 mass%, and even more preferably 0.5 to 1.5 mass%, based on the total mass of the composition. By including the (c3) phenolic antioxidant in such an amount, low torque properties at low temperatures can be maintained. Based on the total mass of the composition, the content of the amine-based antioxidant (c2) is preferably 0.5-5 mass%, and the content of the phenol-based antioxidant (c3) is preferably 0.2-3 mass%, more preferably the content of the amine-based antioxidant (c2) is 1-3 mass%, and the content of the phenol-based antioxidant (c3) is more preferably 0.5-3 mass%, and even more preferably the content of the amine-based antioxidant (c2) is 1.5-2.5 mass%, and the content of the phenol-based antioxidant (c3) is 0.5-1.5 mass%. By including the amine-based antioxidant (c2) and the phenol-based antioxidant (c3) in such amounts, an effect of inhibiting oxidation degradation in a wide range of temperatures can be expected, and by combining them, the effect of inhibiting oxidation degradation can be enhanced.

[0013] The worked penetration of the grease composition of the present invention is preferably 220 to 315. When the worked penetration is in this range, the channeling property (sometimes called channeling property) of the grease composition is excellent. In general, the grease inside the rolling bearing flows due to rotation. As a result, a small amount of grease remains in the part where the rolling body runs. The remaining large proportion of grease does not flow and remains on the cage, or is pushed out to the side seal part. Such behavior of the grease that is removed from the rolling body part and forms a tunnel is called channeling. Excellent channeling property means that the amount of grease attached to the rolling body surface and the raceway surface is reduced, and the rotation torque can be reduced. The worked penetration of the composition of the present invention is preferably 235 to 315, more preferably 265 to 295. The worked penetration in the present invention refers to the 60-stroke worked penetration, and is a value measured in accordance with JIS K 2220 7. EXAMPLES

[0014] The grease composition containing an alicyclic aliphatic diurea thickener (referred to as "urea" in the table) as a thickener was prepared by reacting a predetermined amount of raw amines (cyclohexylamine and stearylamine) in a base oil at a ratio of 1 mole of 4.4'-diphenylmethane diisocyanate to 2 moles of the raw amines, which were heated and then cooled to form a base grease. A predetermined amount of the additive was mixed with the base oil, added to the base grease, mixed well, and kneaded with a three-roll mill to produce a grease composition with a predetermined worked penetration.

[0015] The grease composition containing lithium complex soap ("Li-comp" in the table) as a thickener was prepared by mixing 12-hydroxystearic acid and azelaic acid in a base oil (mass ratio of 12-hydroxystearic acid / azelaic acid = 2 / 1), adding lithium hydroxide thereto, and reacting with stirring while heating, and then cooling after warming to obtain a base grease. A predetermined amount of additive was mixed with the base oil, added to the base grease, mixed well, and kneaded with a three-roll mill to produce a grease composition with a predetermined worked consistency.

[0016] 1. Low torque evaluation Measuring the temperature of the outer ring of a bearing during a bearing rotation test The test was carried out by filling a specified bearing with a specified amount of grease, setting it on a testing machine, rotating the inner ring at a specified rotation speed using a motor, and reading the temperature of the outer ring of the bearing. Note that this was an element test, and was carried out in a laboratory under selected conditions that would result in a heat generation temperature comparable to that of a large bearing. Bearing type: 6204 (inner diameter 20 mm, outer diameter 47 mm) -Cage material: Metal cage Inner wheel speed: 5000 rpm Test load (axial load): 100N Test load (radial load): 200N Ambient temperature: 25℃ Grease content: 2.0g Measurement time: 60 minutes <Evaluation> The measurement result was the arithmetic mean value of the bearing outer ring temperature measured multiple times during the last minute of bearing rotation. Bearing outer ring temperature: Less than 85°C: ◯ (pass) 85°C or higher: × (fail)

[0017] 2. Leak resistance evaluation (shear stability and oil separation resistance) The leak resistance was evaluated by the roll stability test method of ASTM D 1831 and the oil separation test method of JIS K 2220 11. 2.1 Roll stability test (shear stability evaluation) The test was performed for 24 hours at 40°C using an apparatus used in the roll stability test method of ASTM D 1831, and the unmixed penetration of the grease was evaluated before and after the test. The unmixed penetration was measured according to JIS K 2220.7. Unmixed penetration of 380 or less: 〇 (pass) Unmixed penetration exceeds 380: × (fail) 2.2 Oil separation test (evaluation of oil separation resistance) The oil separation resistance was evaluated according to the oil separation test method of JIS K 2220 11 (100°C, 24h). Less than 2.5%: 〇 (pass) 2.5% or more: × (fail) The results are shown in Table 1.

[0018] [Table 1]

Claims

1. (a) a base oil, (b) a thickener containing a mixture of a urea compound represented by the following formula (1), a urea compound represented by the following formula (2), and a urea compound represented by the following formula (3), R 1 -NHGNH-R 2 -NHGNH-R 1 (1) R 1 -NHGNH-R 2 -NHGNH-R 3 (2) R 3 -NHGNH-R 2 -NHGNH-R 3 (3) (In the formula, R 1 represents a cyclohexyl group, R 2 represents a divalent aromatic hydrocarbon group having 6 to 15 carbon atoms; R 3 represents an alkyl group having 8 to 22 carbon atoms, {(R 3 (number of moles of R 1 Number of moles of + R 3 The mole percentage of alkyl groups represented by the formula (number of moles of alkyl groups x 100) is greater than 10% and less than 30%. (c) as an additive, (c1) a dibasic acid metal salt, (c2) at least one amine antioxidant having a diphenylamine structure, and (c3) at least one phenolic antioxidant; and having a worked penetration of 220 to 315 at 60 tries as measured in accordance with JIS K 2220.

7.

2. 2. The grease composition according to claim 1, wherein the dibasic acid metal salt (c1) is sodium sebacate.

3. 3. The grease composition according to claim 1 or 2, wherein the content of the dibasic acid metal salt (c1) is 0.1 to 2 mass % based on the total mass of the composition.

4. The grease composition according to claim 1 or 2, which contains (c3) octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate as an antioxidant.

5. The thickener is represented by the formula (1), 1 is a cyclohexyl group, and a urea compound represented by the formula (2), 1 is a cyclohexyl group, R 3 a urea compound represented by the formula (3), 3 and a urea compound having an alkyl group having 18 carbon atoms, and the mol % is 15 to 25%.

6. 3. The grease composition according to claim 1, wherein the content of the thickener is 5 to 15 mass % based on the total mass of the composition.

7. 3. The grease composition according to claim 1, wherein the base oil (a) is at least one oil selected from the group consisting of mineral oils, synthetic hydrocarbon oils, ester oils, and ether oils.

8. 2. An elevator hoist or elevator pulley bearing filled with the grease composition according to claim 1.

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