Grease composition for bearing for elevator hoist or elevator pulley

Abstract

Provided is a grease composition for a bearing for an elevator hoist or an elevator pulley, the grease composition having excellent low torque properties due to a reduction in power consumption, excellent shear stability in order to suppress leakage from the bearing, and little oil separation. A grease composition for a bearing for a hoist of an elevator or a pulley of an elevator, which contains (a) a base oil and (b) an alicyclic aliphatic diurea thickener, and (c) as additives (c1) a dibasic acid metal salt, (c2) at least one amine-based antioxidant having a diphenylamine structure, and (c3) at least one phenolic antioxidant. The grease composition has a 60-order working penetration of 220-315 as measured in accordance with JIS K 2220.7.

Description

Technical Field

[0001] The present invention relates to a grease composition for a bearing for an elevator traction machine or an elevator pulley, and a bearing for an elevator traction machine or an elevator pulley filled with the grease composition. Background Art

[0002] The elevator traction mechanism is formed by using a bearing installed in a bearing seat to support the rotating shaft of the motor and the sheave so that it can rotate. In addition, a car is suspended at one end of the rope wound around the sheave, and a counterweight is suspended at the other end. When the motor is driven, the car rises and falls as the rotor, the rotating shaft and the sheave rotate. Grease is used as a lubricant for the bearing.

[0003] Elevators are used for a long time and are regularly maintained and inspected, so the bearings of the traction machine are also expected to be used for a long time. Grease is regularly replenished to the bearings, but from the perspective of long-term use, the grease is required to have not only rust resistance and resistance to oxidation degradation, but also leakage resistance to prevent softened grease and oil generated by the grease from scattering from the bearing and adhering to the surrounding area.

[0004] In recent years, the number of high-rise buildings with a lifting stroke exceeding 200 meters has increased, and accordingly, the weight of the rope, car, and counterweight of the elevator has also increased, and thus the load applied to the traction machine has also increased.

[0005] In order to cope with the increase in load, the bearings of the traction machine have become larger, and as the speed of the elevator increases, the rotation speed also increases. Therefore, from the viewpoint of power consumption, the torque generated by the bearing cannot be ignored.

[0006] Therefore, elevator traction machine bearings require grease that has two properties: resistance to grease softening due to shearing and resistance to oil leakage outside the bearings after oil separation, i.e., so-called leakage resistance and low torque.

[0007] For example, in Patent Document 1, the following method is used: by using the waste heat from the motor generated during elevator operation to increase the grease temperature, the torque is reduced by softening the grease due to heat. As buildings become taller, the performance and efficiency of motors are continuously improved, so the waste heat during operation is reduced. In addition, the reduction of torque based on waste heat can be applied to the operation of elevators during the day, but it cannot be applied to environments where the entire device is cooled, such as in the morning after a long stop or in cold regions. In addition, the reduction of torque is based on the waste heat of the traction machine, not on the performance of the grease.

[0008] For example, Patent Document 2 proposes a grease that uses a specific urea compound as a thickener and has a kinematic viscosity of 20 to 55 mm at 40°C. 2 / s pentaerythritol ester oil as a base oil is a mixture of at least one selected from the group consisting of polyol ester-based rust inhibitors and at least one selected from the group consisting of organic sulfonate-based rust inhibitors, but due to its low viscosity, it does not meet the lubrication life required of traction machine bearings.

[0009] For example, Patent Document 3 proposes a grease containing ester oil in a base oil, using a specific urea compound as a thickener, and having a diurea content of 18% by mass or less, and discloses that the bearing rotation torque can be suppressed to a low level by increasing the shear stress and the channeling property of the grease. In addition, it is disclosed that the grease leakage can be prevented because the shear viscosity at high temperature can be increased.

[0010] However, it cannot fully prevent the softening of grease due to additives and the leakage of oil due to oil separation when the grease is subjected to shear.

[0011] Prior art literature

[0012] Patent Literature

[0013] Patent Document 1: Japanese Patent Application Publication No. 2012-076897

[0014] Patent Document 2: Japanese Patent Application Publication No. 2012-197401

[0015] Patent Document 3: Japanese Patent Application Publication No. 2018-065971 Summary of the invention

[0016] Problems to be solved by the invention

[0017] As elevators become taller and faster, the efficiency of traction machines has become a must as a measure for energy saving. Although research has been conducted to reduce the power consumption caused by the traction machine structure by using a special motor with high torque to achieve gearless operation, there has been no research on reducing the torque of the bearings by using grease as a lubricant.

[0018] The low torque due to grease lubrication reduces the stirring resistance in the bearing.

[0019] Lowering the base oil viscosity of grease can also reduce torque, but since the bearings rotate forward and reverse when the elevator is moving up and down, it is difficult to maintain the oil film during deceleration and stopping. Therefore, if the base oil viscosity of the lithium grease used in the past is reduced, durability problems will arise.

[0020] By using urea as the thickener, the oil film at low speed is thicker than that of lithium grease, so the base oil viscosity can be reduced. Since the grease softens when sheared, the stirring resistance is also reduced.

[0021] However, in the case of a large bearing, since shear is applied to the entire grease in the bearing, the general low-torque urea grease softens and leaks.

[0022] The problem to be solved by the present invention is to provide a grease composition for an elevator traction machine or a pulley bearing, and an elevator traction machine or a pulley bearing filled with the grease composition, wherein the grease composition has excellent low torque performance due to reduced power consumption, excellent shear stability for suppressing leakage from the bearing, and little oil separation.

[0023] Methods for solving problems

[0024] According to the present invention, there are provided the following grease composition and a bearing for an elevator traction machine or a pulley.

[0025] 1. A grease composition for a bearing of an elevator traction machine or an elevator pulley, comprising:

[0026] (a) base oil,

[0027] (b) a thickener comprising 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),

[0028] R 1 -NHCONH-R 2 -NHCONH-R 1 (1)

[0029] R 1 -NHCONH-R 2 -NHCONH-R 3 (2)

[0030] R 3 -NHCONH-R 2 -NHCONH-R 3 (3)

[0031] In the formula, R 1 Represents cyclohexyl, 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, represented by {(R 3 The number of moles) / (R 1 Number of moles + R 3 The mole % of the alkyl group represented by (the number of moles of)}×100 is more than 10% and less than 30%, and

[0032] (c) as additives (c1) a dibasic acid metal salt, (c2) at least one amine antioxidant having a diphenylamine structure, and (c3) at least one phenolic antioxidant;

[0033] The grease composition has a 60-stroke cone penetration of 220 to 315 as measured in accordance with JIS K 2220.7.

[0034] 2. The grease composition according to item 1 above, wherein the (c1) dibasic acid metal salt is sodium sebacate.

[0035] 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% by mass based on the total mass of the composition.

[0036] 4. The grease composition according to 1 or 2 above, wherein the antioxidant (c3) comprises octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate.

[0037] 5. The grease composition according to 1 or 2 above, wherein the thickener is R 1 is a urea compound of cyclohexyl, wherein R 1 is cyclohexyl and R 3 is a urea compound having an alkyl group with 18 carbon atoms, wherein R 3 The mixture of urea compounds having an alkyl group having 18 carbon atoms has the above mol % of 15 to 25%.

[0038] 6. The grease composition according to item 1 or 2 above, wherein the content of the thickener is 5 to 15% by mass based on the total mass of the composition.

[0039] 7. The grease composition according to 1 or 2 above, wherein the base oil (a) is at least one selected from the group consisting of mineral oil, synthetic hydrocarbon oil, ester oil and ether oil.

[0040] 8. A bearing for an elevator hoisting machine or an elevator pulley, which is filled with the grease composition described in 1 above.

[0041] Effects of the Invention

[0042] According to the present invention, it is possible to provide a grease composition which is excellent in low torque properties and shear stability and has little oil separation. DETAILED DESCRIPTION

[0043] [(a) Base oil]

[0044] The base oil used in the grease composition of the present invention is not particularly limited. For example, all base oils headed by mineral oil can be used. In addition to mineral oil, various synthetic oils such as ester-based synthetic oils represented by diesters and polyol esters, synthetic hydrocarbon oils represented by polyalphaolefins and polybutene, ether-based synthetic oils represented by alkyl diphenyl ethers and polypropylene glycol, and silicone oil can also be used. Preferably, ester-based synthetic oils, synthetic hydrocarbon oils, and ether-based synthetic oils with excellent low temperature resistance and heat resistance are used. More preferably, ester-based synthetic oils and synthetic hydrocarbon oils are used. Further more preferably, synthetic hydrocarbon oils are used. The kinematic viscosity of synthetic hydrocarbon oils caused by temperature changes is small, and the fluidity at low temperatures is excellent, so the low torque at low temperatures is excellent, and the oil film thickness at high temperatures can also be ensured, so the durability at high temperatures is also excellent. From the viewpoint of low traction coefficient and low temperature properties, polyalphaolefins are preferred.

[0045] The base oil is preferably contained in an amount of 80 to 95% by mass, more preferably 83 to 93% by 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 ensured, and excellent durability can be exerted.

[0046] The kinematic viscosity of the base oil used in the grease composition of the present invention at 40°C is not particularly limited. When the kinematic viscosity is too low, the low torque property is excellent, but the durability is reduced. On the other hand, when the kinematic viscosity is too high, the durability is improved, but the low torque property is reduced. Therefore, it is preferably 50 to 300 mm 2 / s, more preferably 60 to 200 mm 2 / s, more preferably 80 to 130 mm 2 / s.

[0047] [(b) Thickener]

[0048] 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 reactants of the alicyclic monoamine and the aliphatic monoamine with the diisocyanate, the reactants of the alicyclic monoamine and the diisocyanate (so-called alicyclic diurea compound) and the reactants of the aliphatic monoamine and the diisocyanate (so-called aliphatic diurea compound) are also included.

[0049] 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), from the viewpoint of low torque properties and shear stability.

[0050] R 1 -NHCONH-R 2 -NHCONH-R 3 (1)

[0051] R 1 -NHCONH-R 2 -NHCONH-R 1 (2)

[0052] R 3 -NHCONH-R 2 -NHCONH-R 3 (3)

[0053] In the formula, R 2 represents a divalent aromatic hydrocarbon group having 6 to 15 carbon atoms. 1 Represents cyclohexyl. 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 The number of moles / (R 1 Number of moles + R 3 The molar ratio of the alkyl group is preferably greater than 10% and less than 30%. By using such a thickener, the target consistency can be adjusted with a small amount of thickener, so that the stirring resistance of the grease composition can be reduced to achieve low torque performance, and a grease composition with excellent durability can be prepared. The molar ratio of the alkyl group is more preferably 15 to 25%, and particularly preferably 18 to 22%.

[0054] As the thickener of the present invention, the preferred thickener is R 1 is a urea compound of cyclohexyl, wherein R 1 is cyclohexyl and R 3 is a urea compound having an alkyl group with 18 carbon atoms, and R in the formula (3) 3 The mixture of urea compounds having an alkyl group having 18 carbon atoms has the above mol % of 15 to 25%.

[0055] In particular, as the thickener of the present invention, the following mixture is most preferred from the viewpoints of thickening ability (i.e., ability to prepare a grease of desired hardness with a relatively small amount of the thickener) and shear stability, and further from the viewpoints of low torque and durability: wherein R in formula (1) 1 is cyclohexyl and R 2 is a group derived from 4,4'-diphenylmethane diisocyanate and R 3 is a straight-chain alkyl group having 18 carbon atoms, and R in the formula (2) 1 is cyclohexyl and R 2A compound wherein R 2 is a group derived from 4,4'-diphenylmethane diisocyanate and R 3 The mixture of compounds having a linear alkyl group having 18 carbon atoms has the above-mentioned molar ratio of 18 to 22%.

[0056] The thickener is preferably contained in an amount of 5 to 15% by mass, more preferably 6 to 12% by mass, based on the total mass of the composition. When the content of the thickener is within such a range, the grease has a low stirring resistance and excellent channeling properties, thereby achieving a satisfactory level of low torque.

[0057] [(c1) Additives]

[0058] The additive (c1) of the present invention is a dibasic acid metal salt. Dibasic acid metal salts are generally used as rust inhibitors in the technical field of the present invention. The present inventors have conducted research using various additives and found that when dibasic acid metal salts are used in combination with amine antioxidants and phenolic antioxidants, the grease composition containing alicyclic aliphatic diurea thickeners exhibits excellent shear stability. As specific examples, metal salts such as dodecanedioic acid and sebacic acid can be cited. Sodium sebacate is particularly preferred.

[0059] 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 resistance and low torque properties can be achieved.

[0060] [(c2) Antioxidant]

[0061] Antioxidants are known as inhibitors of oxidative degradation of greases. The amine antioxidant of the present invention is a combination of (c2) an amine antioxidant having a diphenylamine structure and (c3) a phenolic antioxidant.

[0062] Examples of the (c2) amine antioxidant having a diphenylamine structure include a reaction product of N-phenylaniline and 2,4,4-trimethylpentene, octylated diphenylamine (CAS 68411-46-1, a reaction product of N-phenylaniline and 2,4,4-trimethylpentene), and 4,4'-tetramethyl-diaminodiphenylmethane. The (c2) amine antioxidant is preferably a reaction product of N-phenylaniline and 2,4,4-trimethylpentene.

[0063] Examples of the phenolic antioxidant (c3) include 2,6-di-tert-butyl-p-cresol (BHT), 2,2'-methylenebis(4-methyl-6-tert-butylphenol), 4,4'-butylenebis(3-methyl-6-tert-butylphenol), 2,6-di-tert-butylphenol, 2,4-dimethyl-6-tert-butylphenol, tert-butylhydroxyanisole (BHA), 4,4'-butylenebis(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. As the phenolic antioxidant (c3), octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate is preferred.

[0064] The content of the amine antioxidant (c2) is preferably 0.5 to 5% by mass, more preferably 1 to 3% by mass, and even more preferably 1.5 to 2.5% by mass based on the total mass of the composition. By including the amine antioxidant (c2) in such an amount, even if it exceeds 5%, it is difficult to confirm further improvement in the effect.

[0065] The content of the phenolic antioxidant (c3) is preferably 0.2 to 3% by mass, more preferably 0.5 to 3% by mass, and even more preferably 0.5 to 1.5% by mass based on the total mass of the composition. By containing the phenolic antioxidant (c3) in such an amount, low torque at low temperatures can be maintained.

[0066] Based on the total mass of the composition, the content of the (c2) amine antioxidant is preferably 0.5 to 5 mass %, and the content of the (c3) phenolic antioxidant is preferably 0.2 to 3 mass %, more preferably the content of the (c2) amine antioxidant is 1 to 3 mass %, and the content of the (c3) phenolic antioxidant is 0.5 to 3 mass %, and further preferably the content of the (c2) amine antioxidant is 1.5 to 2.5 mass %, and the content of the (c3) phenolic antioxidant is 0.5 to 1.5 mass %. By including the (c2) amine antioxidant and the (c3) phenolic antioxidant in such amounts, an oxidative degradation inhibitory effect can be expected in a wide temperature range, and the oxidative degradation inhibitory effect can be enhanced by the combination.

[0067] The working penetration of the grease composition of the present invention is preferably 220 to 315. When the working penetration is within this range, the channeling of the grease composition is excellent. Generally, the grease inside the rolling bearing flows by rotation. As a result, a small amount of grease remains in the part where the rolling element travels. The remaining large proportion of grease does not flow and remains on the retainer, or is pushed out to the side seal. Such behavior of grease that is partially excluded from the rolling element to form a channel is called channeling. Excellent channeling means that the amount of grease attached to the rolling element surface and the raceway surface is reduced, which can achieve a reduction in rotational torque. The working penetration of the composition of the present invention is preferably 235 to 315, and more preferably 265 to 295. It should be noted that the working penetration in the present invention refers to 60 working penetrations, which is a value measured in accordance with JIS K 2220 7.

[0068] Example

[0069] For a grease composition containing an alicyclic aliphatic diurea thickener ("urea" in the table) as a thickener, a predetermined amount of amines (cyclohexylamine and stearylamine) as a raw material were reacted in a ratio of 2 mol to 1 mol of 4,4'-diphenylmethane diisocyanate in a base oil, heated and then cooled to prepare a base grease. A predetermined amount of additives was mixed with the base oil, added to the base grease and mixed thoroughly, and kneaded with a three-roll mill to prepare a grease composition with a predetermined working cone penetration.

[0070] For a grease composition containing a lithium complex soap ("Li-comp" in the table) as a thickener, 12-hydroxystearic acid and azelaic acid are mixed in a base oil (12-hydroxystearic acid / zelaic acid = 2 / 1 by mass ratio), lithium hydroxide is mixed therein, and the mixture is stirred while heating to react, and then cooled after heating to prepare a base grease. A predetermined amount of additives is mixed with the base oil, added to the base grease and mixed thoroughly, and kneaded with a three-roll mill to prepare a grease composition with a predetermined working cone penetration.

[0071] 1. Low torque evaluation

[0072] Bearing outer ring temperature measurement during bearing rotation test:

[0073] In the test, a specified amount of grease is filled into a specified bearing, and then the bearing is placed in a testing machine. The inner ring is rotated at a specified speed by a motor, and the outer ring temperature of the bearing is read. It should be noted that this test is an element test, and is conducted in a laboratory under conditions that produce a heating temperature equivalent to that of a large bearing.

[0074] Bearing type: 6204 (inner diameter 20mm, outer diameter 47mm)

[0075] ·Material of retainer: Metal retainer

[0076] Inner ring speed: 5000rpm

[0077] Test load (axial load): 100N

[0078] Test load (radial load): 200N

[0079] ·Atmosphere temperature: 25℃

[0080] Grease filling amount: 2.0g

[0081] ·Measurement time: 60 minutes

[0082] <Evaluation>

[0083] The arithmetic mean of the bearing outer ring temperatures measured multiple times within the last minute of the bearing rotation is taken as the measurement result.

[0084] Bearing outer ring temperature:

[0085] Below 85℃: 0 (qualified),

[0086] Above 85℃: × (unqualified).

[0087] 2. Leakage resistance evaluation (shear stability and oil separation resistance)

[0088] The leakage resistance was evaluated by the roller stability test method of ASTM D 1831 and the oil separation test method of JIS K 2220 11.

[0089] 2.1 Roller stability test (shear stability evaluation)

[0090] The grease was operated at 40°C for 24 hours using an apparatus used in the roller stability test method of ASTM D 1831, and the evaluation was performed based on the non-worked cone penetration of the grease before and after the test. The non-worked cone penetration was measured in accordance with JIS K2220.7.

[0091] Non-working cone penetration is below 380: 0 (qualified)

[0092] Non-working cone penetration exceeds 380: × (unqualified)

[0093] 2.2 Oil separation test (oil separation resistance evaluation)

[0094] The oil separation resistance was evaluated by the oil separation test method of JIS K 2220 11 (100° C., 24 h).

[0095] Less than 2.5%: 0 (qualified)

[0096] 2.5% or more: × (unqualified)

[0097] The results are shown in Table 1.

[0098] [Table 1]

[0099]

Claims

1. A grease composition for use in a traction machine of an elevator or a bearing for a pulley of an elevator, comprising: (a) base oil, (b) a thickener comprising 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 -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 cyclohexyl, 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, represented by {(R 3 The number of moles) / (R 1 Number of moles + R 3 The mole % of the alkyl group represented by (the number of moles of)}×100 is more than 10% and less than 30%, and (c) as additives (c1) a dibasic acid metal salt, (c2) at least one amine antioxidant having a diphenylamine structure, and (c3) at least one phenolic antioxidant; The grease composition has a 60-stroke cone penetration of 220 to 315 as measured in accordance with JIS K 2220.

7.

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

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% by mass based on the total mass of the composition.

4. The grease composition according to claim 1 or 2, wherein (c3) The antioxidant comprises octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate.

5. The grease composition according to claim 1 or 2, wherein: The thickener is R in formula (1) 1 is a urea compound of cyclohexyl, wherein R 1 is cyclohexyl and R 3 is a urea compound having an alkyl group with 18 carbon atoms and R in the formula (3) 3 A mixture of urea compounds having an alkyl group having 18 carbon atoms, wherein the mole % is 15 to 25%.

6. The grease composition according to claim 1 or 2, wherein: The content of the thickener is 5 to 15% by mass based on the total mass of the composition.

7. The grease composition according to claim 1 or 2, wherein: The (a) base oil is at least one selected from the group consisting of mineral oil, synthetic hydrocarbon oil, ester oil and ether oil.

8. A bearing for an elevator hoisting machine or an elevator pulley, which is filled with the grease composition according to claim 1.

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