JP2005105026A - Water resistant grease composition and rolling bearing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a water resistant grease composition having an improved durability and a stronger heat resistance and a rolling bearing having stronger water and heat resistances to be built in water-contacting equipment such as a water pump. <P>SOLUTION: The water resistant grease composition contains 0.5-10 mass% of a base oil, a thickener and an N-vinylamide resin to the total amount of the grease composition. The rolling bearing has the water resistant grease composition filled in it. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a water resistant grease composition and a rolling bearing in which the water resistant grease composition is enclosed.

  Mixing water into the bearings of the device is not preferable. However, there are many places where water mixes in the usage environment and structure of the equipment, and the bearings often cause poor lubrication.

  For example, the bearing for water pumps incorporated in the water pump attached to the radiator etc. of a motor vehicle is mentioned. As shown in FIG. 1, this water pump 1 circulates cooling water by the rotation of an impeller 2, and the impeller 2 has a shaft 4 by the rotation of a pulley 3 connected to an engine (not shown) by a belt. Driven through. A water pump bearing 7 including a roller row 5 and a ball row 6 is fitted on the shaft 4. Further, the water channel 8 side where the impeller 2 is disposed and the water pump bearing 7 side are partitioned by a mechanical seal 9 with a waterproof structure. Further, a drain hole 10 is formed on the water pump bearing 7 side in case water leaks from the water channel 8 side.

  Grease lubrication is generally used for the water pump bearing 7, but it is inevitable that water will penetrate into the bearing due to long-term use. As a result, the grease will soften and flow out, reducing the lubrication performance and extending the service life. is there. Accordingly, the grease sealed in the water pump bearing 7 is required to have water resistance, and lithium soap-mineral oil type or synthetic hydrocarbon oil-urea type grease is generally used.

Also, in industrial machinery, there is a possibility that water will enter the parts where cooling water is used due to the process of the equipment. In the rolling device used in such an environment, moisture enters the inside and is enclosed. There is a problem that water is easily mixed in the grease. Therefore, water resistance has been improved by various techniques so far. For example, an additive comprising a copolymer of a polyoxyalkylene derivative and maleic anhydride, or a hydrolyzate or a salt of the hydrolyzate is used. An added water-resistant grease is known (see Patent Document 1).
JP-A-4-46997

  With the above-mentioned advances in equipment, grease compositions used for bearings in these equipment are required to have a performance that can withstand higher temperatures and higher rotations. There is also a demand for improvement. However, it is difficult for conventional lithium soap-mineral oil-based greases and synthetic hydrocarbon oil-urea-based greases to sufficiently meet these requirements. Further, although the water resistant grease composition described in Patent Document 1 is expected to improve water resistance, the additive itself has difficulty in heat resistance, so that it is durable while being used at a higher temperature. Is expected to be a problem.

  Therefore, an object of the present invention is to provide a water-resistant grease composition with enhanced heat resistance in addition to improved durability. Another object of the present invention is to provide a rolling bearing that is incorporated in a device that comes into contact with water, such as a water pump, and has further enhanced water resistance and heat resistance.

In order to solve such problems, the present invention provides the following water-resistant grease composition and rolling bearing.
(1) A grease composition containing a base oil and a thickener, wherein a compound represented by the following general formula (I) and a compound represented by the following general formula (II) are (I) by weight ratio: (II) = 70 to 99.9: N-vinylamide resin formed by polymerization crosslinking at 30 to 0.1 is added in an amount of 0.5 to 10% by mass based on the total amount of the grease composition. Water-resistant grease composition.
CH ₂ = CR ¹ NR ² COR ³ (I)
CH ₂ = CR ⁴ CO (OX) _n OR ⁵ (II)
(Wherein, R ¹ to R ⁵ may be different from each other in the same, represent a hydrogen atom, a methyl group or an ethyl group, X represents an alkylene group having 2 or 3 carbon atoms, n represents 2 to 30 Represents an integer.)
(2) An inner ring, an outer ring, and a plurality of rolling elements disposed between the inner ring and the outer ring so as to be freely rollable. The rolling elements are disposed between the inner ring and the outer ring. A rolling bearing characterized in that the water-resistant grease composition is sealed in the gap.

  In the water-resistant grease composition of the present invention, the N-vinylamide resin has a high ability to absorb moisture in the grease and is also excellent in heat resistance. It can be significantly improved.

Hereinafter, the present invention will be described in detail.
(Water-resistant grease composition)
The water-resistant grease composition of the present invention contains a base oil and a thickener, and further has the following general formula (I
) And a compound represented by the following general formula (II) by weight ratio (I) :( II) = 70-99.9: 30-0.1 N-vinylamide obtained by crosslinking A resin is added.
CH ₂ = CR ¹ NR ² COR ³ (I)
CH ₂ = CR ⁴ CO (OX) _n OR ⁵ (II)
In the formula, R ^{1 to} R ⁵ may be the same or different and each represents a hydrogen atom, a methyl group or an ethyl group, X represents an alkylene group having 2 or 3 carbon atoms, and n represents 2 to 30 Represents an integer.

Specifically, examples of the compound represented by the general formula (I) include N-vinylformamide, N-vinylacetamide, N-vinylformamide and the like, and N-vinylacetamide is particularly preferable. Examples of the compound represented by the general formula (II) include methoxydiethylene glycol methacrylate, methoxypolyethylene glycol methacrylate, methoxytriethylene glycol methacrylate (n = 4 to 30), and methoxypolyethylene glycol methacrylate is particularly preferable.

The N-vinylamide resin is obtained, for example, by the method described in JP-A-10-226715. That is, the compound represented by the general formula (I), the monomer of the compound represented by the general formula (II) and the crosslinking agent are dissolved in an organic solvent, the dissolved oxygen is sufficiently removed, and the temperature is raised to the reaction temperature. The reaction is carried out by adding an initiator to precipitate in the solvent as fine particles, which are filtered, dried and crushed to obtain a powdered N-vinylamide resin.

  In the above production process, the solvents include aromatic or aliphatic hydrocarbons such as benzene, toluene, xylene, hexane, heptane, and octane, aliphatic ketones such as acetone, methyl ethyl ketone, and methyl isobutyl ketone, ethyl acetate, butyl acetate, and acetic acid. Esters such as isopropyl, alkylamides such as dimethylformamide and dimethylacetamide, sulfoxides such as dimethylsulfoxide, and the like can be used, and benzene, acetone, methyl ethyl ketone, ethyl acetate, and isopropyl acetate are preferable. These are used in an amount equivalent to the monomer to 20 times, preferably 5 times to 15 times, particularly preferably 5 times to 10 times (weight).

  Initiators include benzoyl peroxide, t-butyl peroxide, t-amyl peroxide, cumyl peroxide, lauroyl peroxide, t-butyl hydroperoxide, cyclohexyl hydroperoxide, tetralin hydroperoxide, t-butyl peroxide. Acetate, bis (2-ethylhexylperoxydicarbonate), 2,2′-azobisisobutyronitrile, phenylazotriphenylmethane, 2,2′-azobis (4-methoxy-2,4-dimethylvaleronitrile) 2,2′-azobis (2-methylpropionitrile), 2,2′-azobis (2-methylbutyronitrile), 1,1′-azobis (cyclohexane-1-carbonitrile), dimethyl 2,2 '-Azobis (2-methylpropionate) Used it can, benzoyl peroxide, 2,2'-azobisisobutyronitrile, dimethyl 2,2'-azobis (2-methyl propionate) are preferred. The amount of these initiators used is in the range of 0.01 to 5 mol%, preferably 0.05 to 3 mol%, particularly preferably 0.1 to 2 mol%, based on the monomer.

  The polymerization initiation temperature is suitably 50 ° C. to the boiling point of the solvent, and the reaction time is suitably about 3 to 8 hours.

  The water-resistant grease composition of the present invention is more excellent in water resistance and heat resistance than before, but the reason is not clear, but is estimated as follows. The principle of the softening and leakage of grease due to moisture is considered to be caused by the destruction of the three-dimensional network structure of the thickener, as described in Patent Document 1, but the N-vinylamide resin absorbs water. Due to its high performance, the moisture in the grease is absorbed before the network structure of the thickener is destroyed. On the other hand, the N-vinylamide resin that has absorbed moisture swells into a soft gel and becomes a grease property. maintain. Further, since N-vinylamide resin is polymerized and cross-linked, it hardly undergoes thermal decomposition or thermal deterioration, and has excellent heat resistance.

  Considering these, the N-vinylamide resin is preferably a powder having an average particle size in a dry state of 0.01 to 2 μm. In the grease for rolling bearings, particles having a size exceeding 2 μm generally act as a foreign substance, so that the N-vinylamide resin is preferably 2 μm or less. Further, since the N-vinylamide resin swells by absorbing moisture, the average particle size in a dry state is more preferably 1 μm or less. However, if it is smaller than 0.01 μm, secondary agglomeration is likely to occur, and it is not well dispersed in the grease, so that the water resistance performance may not be sufficiently exhibited.

  Further, the content of the N-vinylamide resin is 0.5 to 10% by mass of the total amount of the grease, and if the content is less than 0.5% by mass, the content does not sufficiently contribute to the improvement of water resistance and heat resistance. When it exceeds 10% by mass, the content of the base oil and the thickener is relatively reduced, and the lubricating performance and the like become inferior. Moreover, 1-7 mass% is more preferable, and, as for content of N-vinylamide resin, 3-5 mass% is especially preferable.

  In the water-resistant grease composition of the present invention, the base oil and the thickener are not limited, but the base oil is preferably a synthetic hydrocarbon oil, an ether oil or a mixed oil thereof, and the thickener is a diurea compound. preferable. Synthetic hydrocarbon oils, ether oils and diurea compounds are originally excellent in water resistance and heat resistance, and are suitable as base oils or thickeners for high temperature greases. Further, since the urea bond of the diurea compound has good compatibility with the amide bond portion of the N-vinylamide resin, the N-vinylamide resin is well dispersed and excellent water resistance is obtained.

  There are no limitations on the synthetic hydrocarbon oil and the ether oil, and publicly known ones can be used. However, as the synthetic hydrocarbon oil, a poly α-olefin can be preferably used, and as the ether oil, an alkyl diphenyl ether oil is preferable.

The base oil preferably has a kinematic viscosity at 40 ° C. of ²⁰ to 400 mm ² / s. When the kinematic viscosity at 40 ° C. is less than 20 mm ² / s, it tends to evaporate, and when it exceeds 400 mm ² / s, it becomes difficult to satisfy the torque performance. More preferably, it is set to 30 to 350 mm ² / s. In particular, when it is used for lubricating a water pump bearing of an automobile, 100 to 300 mm ² / s is most preferable.

  There are no restrictions on the diurea compound, and known ones can be used, but aliphatic and alicyclic diurea compounds are preferred, and it is desirable to use them alone or as a mixture. More preferred is diurea in which a cyclohexyl group and an octadecyl group are mixed at both ends. When an aromatic group is introduced into the end group of diurea, the fluidity of the grease tends to deteriorate. For example, a water pump bearing that sometimes uses a roller as a rolling element may cause poor lubrication.

  The content of the thickener is not particularly limited as long as the blending degree of 200 to 350 can be obtained, but is usually 5 to 30% by mass of the entire grease composition. If it is less than 5% by mass, the amount of the thickener is too small and it becomes difficult to form grease. Moreover, since the quantity of base oil will decrease that it is more than 30 mass%, lubricity may become inadequate. In order to make it difficult to cause such a problem, the content of the thickener is more preferably 8 to 25% by mass of the entire grease composition. More preferably, when the thickener is the above-mentioned preferable alicyclic diurea or aliphatic diurea, the amount is from 10 to 18% by mass based on the entire grease composition.

  In addition, the penetration degree here means the value measured according to Japanese Industrial Standard (JIS) K2220. If the penetration is less than 200, the grease composition is too hard when it is sealed in the rolling bearing, resulting in poor torque performance. If it exceeds 350, the grease composition is inherently too soft and the grease may flow out of the bearing. There is.

  In order to further improve various performances, the water resistant grease composition of the present invention may be mixed with various additives as necessary. For example, antioxidants such as amines, phenols, sulfurs, zinc dithiophosphates, rust inhibitors such as petroleum sulfonates, calcium sulfonates, sorbitan esters, molybdenum-based, phosphorus-based extreme pressure agents, fatty acids, Examples thereof include oil improvers such as animal and vegetable oils and metal deactivators such as benzotriazole. These can be used alone or in combination of two or more. In addition, the addition amount of these additives will not be specifically limited if it is a grade which does not impair the objective of this invention.

(Rolling bearing)
Although not shown in the drawings, the rolling bearing of the present invention includes an inner ring, an outer ring, and a plurality of rolling elements arranged so as to be able to roll between the inner ring and the outer ring, and between the inner ring and the outer ring. The above water-resistant grease composition is sealed in a gap formed in the above and in which the rolling elements are disposed. Since this water-resistant grease composition is enclosed, this rolling bearing has excellent water resistance, rust prevention, and heat resistance, such as water pump bearings. It is suitable for the member to contact.

  EXAMPLES The present invention will be further described below with reference to examples, but the present invention is not limited thereto.

(Examples 1-5, Comparative Examples 1-3)
A grease composition having the composition shown in Table 1 was prepared, and the following (1) water injection durability test and (2) rust prevention test were performed. The N-vinylamide resin uses N-vinylacetamide as the general formula (I) and methoxypolyethylene glycol methacrylate (n = 30) as the general formula (II). Both are dissolved in ethyl acetate and boiled to start. 1.0 part of dimethyl 2,2′-azobis (2-methylpropionate) was added as an agent, and the boiling state was maintained as it was for 5 hours. After standing to cool, the precipitate was suction filtered and vacuumed at 50 ° C. for 24 hours. After drying, the mixture was crushed and classified into an average particle size of 0.5 μm by a centrifugal separation method.

Further, each of the diurea compound A and the diurea compound B is represented by the following general formula (III), and the diurea compound A has R ⁶ and R ⁸ in the formula of cyclohexylamine: stearylamine = 1: 9. Diurea compound B is obtained by changing R ⁶ and R ⁸ in the formula to stearylamine: octylamine = 7: 3. R ⁷ is all MDI (4,4′-diphenylmethane diisocyanate).
R ⁶ —NHCO (R ⁷ ) NH—R ⁸ (III)

  In addition, "NASUL BSN" made by KING is used as a rust preventive, and 0.9% by weight of antioxidant ("Irganox L57" made by Ciba Geigy) and corrosion inhibitor (made by Ciba Geigy) are used for all grease compositions. "Irgamet 39") 0.1% by weight was added.

(1) Water injection durability test Each grease composition is enclosed in a deep groove ball bearing (inner diameter 85 mm, outer diameter 130 mm, width 22 mm) manufactured by NSK Ltd. and rotated at an inner ring rotational speed of 1000 min ^−1. Every 48 hours, 0.3 mL of water was injected into the enclosed grease. And time (endurance time) until it was seized was measured. The results are shown in Table 1 as relative values with the durability time of Comparative Example 1 as 1.

  From Table 1, it can be seen that the grease compositions of the examples are superior in water injection durability as compared with the grease compositions of the comparative examples. Further, as shown in Example 5, the best water-injection durability was obtained when a mixed oil of ether oil and poly-α-olefin oil was used as the base oil and diurea compound A was used as the thickener.

(2) Rust prevention test 2.3 g of each grease composition was sealed in a deep groove ball bearing (inner diameter: 17 mm, outer diameter: 47 mm, width: 14 mm) manufactured by NSK Ltd. and rotated at 1800 min ⁻¹ for 1 minute. I let you. After the rotation, 0.5 mL of salt water having a concentration of 0.5% by mass was poured into the bearing and rotated again at 1800 min ⁻¹ for 1 minute. Next, it was allowed to stand for 120 hours under conditions of 50 ° C. and 95% RH and then decomposed, and the state of rust generation on the inner and outer raceway surfaces was observed. The evaluation is shown in Table 1 with 3 points for no rust, 2 points for spot or spot-like rust, 1 point for small rust, and 0 for large rust. Two or more points were accepted.

  From Table 1, it can be seen that the grease compositions of the examples are excellent in rust prevention properties, and show some degree of rust prevention properties without adding a rust inhibitor as shown in Example 5. This is considered to be due to the water absorption of the N-vinylamide resin.

(3) Verification of N-vinylamide resin content According to the composition of Example 1, the N-vinylamide resin content was changed to prepare a grease composition, and the above (1) water injection durability test was performed. The results are shown in a graph in FIG. 2, and the content of the N-vinylamide resin is preferably 0.5 to 10% by mass, more preferably 1 to 7% by mass, and particularly preferably 3 to 5% by mass.

(4) Verification of particle diameter of N-vinylamide resin A grease composition was prepared according to the composition of Example 1 using N-vinylamide resins having different average particle diameters in the dry state, and the following acoustic test was performed.

(Sound test)
2.3 g of each grease composition was enclosed in a deep groove ball bearing (inner diameter 17 mm, outer diameter 47 mm, width 14 mm) manufactured by NSK Ltd. and rotated for 1 minute at 1800 min ⁻¹ , NSK Anderon Meter Anderon value was measured using. The results are shown in FIG. 3 as relative values with a value of 1 when the grease composition of Example 1 (using an N-vinylamide resin having an average particle size of 0.5 μm) is enclosed. It can be seen that the average particle size in the state is preferably 2 μm or less, and particularly preferably 1 μm or less.

It is sectional drawing which shows an example of a water pump. It is a graph which shows the relationship between content of N-vinylamide resin and water injection durable life ratio which were obtained in the Example. It is a graph which shows the relationship between the average particle diameter and the Anderon value in the dry state of N-vinylamide resin obtained in the Example.

Explanation of symbols

1 Water Pump 2 Impeller 3 Pulley 4 Shaft 5 Roller Row 6 Ball Row 7 Water Pump Bearing 8 Water Channel 9 Mechanical Seal

Claims (4)

A grease composition containing a base oil and a thickening agent, which has the following general formula (I
) And a compound represented by the following general formula (II) by weight ratio (I) :( II) = 70-99.9: 30-0.1 N-vinylamide obtained by crosslinking A water resistant grease composition comprising 0.5 to 10% by mass of a resin based on the total amount of the grease composition.
CH ₂ = CR ¹ NR ² COR ³ (I)
CH ₂ = CR ⁴ CO (OX) _n OR ⁵ (II)
(Wherein, R ¹ to R ⁵ may be different from each other in the same, represent a hydrogen atom, a methyl group or an ethyl group, X represents an alkylene group having 2 or 3 carbon atoms, n represents 2 to 30 Represents an integer.) The water-resistant grease composition according to claim 1, wherein the N-vinylamide resin is in a powder form and has an average particle size in a dry state of 0.01 to 2 µm. The water resistant grease composition according to claim 1 or 2, wherein the base oil is at least one of a synthetic hydrocarbon oil and an ether oil, and the thickener is a diurea compound. An inner ring, an outer ring, and a plurality of rolling elements disposed between the inner ring and the outer ring so as to be freely rollable, and formed in the space between the inner ring and the outer ring and having the rolling elements disposed therein. A rolling bearing, wherein the water-resistant grease composition according to any one of claims 1 to 3 is enclosed.

Images