JP6722379B2 - Grease composition, method for producing the same, and rolling bearing in which the grease composition is enclosed - Google Patents

Description

The present invention relates to a grease composition, a method for producing the same, and a rolling bearing in which the grease composition is enclosed.

For example, products such as a semiconductor manufacturing device, a liquid crystal manufacturing device, a computer, and a printed circuit board manufacturing device are sensitive to foreign matter and dust, and thus need to be maintained in a clean state. Therefore, the lubricant (grease composition) used for the lubricated parts in this type of product is required to have low dust generation property in order to prevent the product from being contaminated by scattering.
As a low dust-generating grease composition, for example, Patent Document 1 discloses a grease containing a base oil composed of ester oil and poly-α-olefin, and a thickener composed of lithium stearate and lithium 12-hydroxystearate. A composition is disclosed.

JP-A-8-143884

In addition, as a low dust-generating grease, one having a penetration consistency of 200 or less is in circulation.
However, if the workability is 200 or less, the hardness is maintained even when subjected to shearing, so that the fluidity is poor and it is difficult to seal the bearing.
Therefore, an object of the present invention is to achieve both low noise and low dust generation, to exhibit torque stability, and further to suppress a decrease in bearing productivity, and a method for producing the same, and It is intended to provide a rolling bearing in which the grease composition is encapsulated.

The rolling bearing (1) of the present invention for solving the above-mentioned problems includes a base oil which is at least a poly-α-olefin, an amine selected from hexylamine, heptylamine, octylamine, nonylamine and decylamine, and diphenylmethane diisocyanate. A grease composition (G) containing a thickener, which is a diurea obtained by reacting with a., and an additive comprising glycerol monooleate, and having an immiscibility of 200 or less and a miscibility of 250 or more. ) Is enclosed (Claim 1).
According to this grease composition, when it is subjected to shearing by roll treatment or the like, it becomes soft and fluidity increases, so that it can be easily enclosed in a lubricating component such as a bearing. Therefore, it is possible to suppress a decrease in productivity even when the bearing is produced.

On the other hand, since the impermeability is 200 or less and the hardness can be relatively maintained in a stationary state, dust generation due to scattering can be suppressed.
Further, since polyoxyethylene alkylamine is oil-soluble, it easily dissolves in the base oil and acts as a surfactant. As a result, the interaction between the base oil and the thickener can be strengthened, and the hardness (concentration) of the grease composition in a stationary state can be increased. Thereby, the low dust generation performance can be improved. On the other hand, glycerol monooleate is insoluble in oil, but can be dispersed in the base oil and enter the network formed by the thickener. As a result, the interaction between the fibers of the thickener can be strengthened, and the hardness (concentration) of the grease composition in a stationary state can be increased. Thereby, the low dust generation performance can be improved.
Further, according to the rolling bearing of the present invention, since the grease composition is encapsulated, it is possible to provide a rolling bearing capable of achieving both low noise and low dust generation and exhibiting torque stability.
In the rolling bearing of the present invention, the difference between the immiscible consistency and the miscible consistency may be 100 or more (claim 2).
With this configuration, it is possible to increase the difference in properties of the grease composition between the sheared state and the static state.

The rolling bearing of the present invention may contain 0.5% by mass to 2% by mass of the additive (claim 3).
According to this configuration, the above-described effects can be exhibited without affecting the blending ratio of the main components of the grease composition such as the base oil and the thickener.
The grease composition may be obtained by roll-treating a mixture of the base oil and the thickener and then mixing the additive.

According to this configuration, the thickener is dispersed in the base oil by the roll treatment and then the additive is mixed, so that the additive can be satisfactorily spread over the entire grease composition.
In the rolling bearing of the present invention, the thickening agent may have an average particle size of 10 μm or less (claim 4 ).
According to this structure, the thickener is well dispersed in the entire base oil, so that the interaction between the base oil and the thickener can be strengthened.

The method for producing the grease composition is a diurea obtained by reacting a base oil which is a poly-α-olefin with any one of hexylamine, heptylamine, octylamine, nonylamine and decylamine and diphenylmethane diisocyanate. a step of roll processing the mixture of thickener, to the mixture, which is rolled, a step of mixing an additive comprising a glycerol monooleate may be free Ndei.

By this method, the grease composition of the present invention can be manufactured. Moreover, since the thickener is dispersed in the base oil by the roll treatment and then the additive is mixed, the additive can be satisfactorily spread throughout the grease composition.

FIG. 1 is a sectional view showing a rolling bearing according to an embodiment of the present invention. FIG. 2 is a schematic diagram of a bearing rotation torque measuring device. FIG. 3 is a diagram showing the penetrations of Examples and Comparative Examples.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a sectional view showing a rolling bearing 1 according to an embodiment of the present invention.
The rolling bearing 1 is composed of an inner ring 3 and an outer ring 4 as a pair of raceway members that define an annular region 2 therebetween, and a plurality of rolling elements arranged in the region 2 and rolling with respect to the inner ring 3 and the outer ring 4. Balls 5, a retainer 6 arranged in the area 2 for holding each ball 5, a grease G filled in the area 2, and a pair of annular seal members 7 fixed to the outer ring 4 and slidingly contacting the inner ring 3. , 8 and.

Each of the seal members 7, 8 has an annular core metal 9, 9 and an annular rubber body 10, 10 baked on the core metal 9, 9. The outer peripheral portions of the respective seal members 7 and 8 are fitted and fixed to the groove portions 11 and 11 formed on both end surfaces of the outer ring 4, and the inner peripheral portions thereof are fixed to the groove portions 12 and 12 formed on both end surfaces of the inner ring 3. It is fitted and fixed.
The grease G is enclosed in the area 2 defined by the pair of seal members 7 and 8 between the wheels 3 and 4 so that the grease G is almost full.

Next, the grease composition constituting the grease G will be described in detail.
The grease composition of the present invention contains a base oil, a thickener and an additive.
As the base oil, for example, synthetic oil or mineral oil is used, but preferably synthetic oil is used. Synthetic oils have no impurities or little impurities, so that the lubricating performance of the grease composition can be improved. In addition, the kinematic viscosity and pour point of the base oil can be selected in a wide range according to the molecular weight and the molecular structure.

Examples of the synthetic oil include synthetic hydrocarbon oil, ester oil, silicone oil, fluorine oil, phenyl ether oil, polyglycol oil, alkylbenzene oil, alkylnaphthalene oil, biphenyl oil, diphenylalkane oil, di(alkylphenyl)alkane oil. Fluorine compounds such as polyglycol oil, polyphenyl ether oil, perfluoropolyether, and fluorinated polyolefin. Of these, synthetic hydrocarbon oils are preferably used.

Specific examples of the synthetic hydrocarbon oil include those obtained by polymerizing α-olefins produced by using ethylene, propylene, butene and their derivatives as raw materials, alone or in combination of two or more. As the α-olefin, those having 6 to 20 carbon atoms are preferably used, and more preferably, poly-α-olefin (PAO) which is an oligomer of 1-decene or 1-dodecene is used.

Examples of the mineral oil include paraffinic mineral oil, naphthenic mineral oil, intermediate base mineral oil, and the like.
The physical properties of the base oil is not particularly limited, for example, kinematic viscosity (according to JIS K 2283) is ^{preferably, 20mm 2 / s~50mm 2 / s} (40 ℃), more preferably, 30 mm ² /S to 50 mm ² /s (40° C.).

Further, the blending amount of the base oil is preferably 75% by mass to 85% by mass with respect to the total amount of the grease composition.
As the thickener, a urea compound is preferably used. Examples of the urea thickeners include urea compounds such as diurea compounds, triurea compounds, tetraurea compounds, polyurea compounds (excluding diurea compounds, triurea compounds and tetraurea compounds), urethane compounds such as urea/urethane compounds and diurethanes, or these And the like. Of these, diurea compounds are preferably used, and more preferably diurea compounds obtained by reacting an aliphatic amine with a diisocyanate compound are used. This combination of diurea compounds can improve the heat resistance of the grease composition.

Examples of the aliphatic amine include those having a carbon chain length of 10 or less, and examples thereof include hexylamine (carbon chain length is 6), heptylamine (carbon chain length is 7), and octylamine (carbon chain length is 8). , Nonylamine (having a carbon chain length of 9), decylamine (having a carbon chain length of 10), and the like.
Examples of the diisocyanate compound include aliphatic diisocyanate, alicyclic diisocyanate, aromatic diisocyanate and the like. Examples of the aliphatic diisocyanate include diisocyanates having saturated and/or unsaturated linear or branched hydrocarbon groups, and specifically, octadecane diisocyanate, decane diisocyanate, hexane diisocyanate (HDI) and the like. Are listed. Examples of the alicyclic diisocyanate include cyclohexyl diisocyanate and dicyclohexylmethane diisocyanate. Examples of aromatic diisocyanates include phenylene diisocyanate, tolylene diisocyanate (TDI), diphenyl diisocyanate and diphenylmethane diisocyanate (MDI). Of these, aromatic diisocyanates are preferably used, and more preferably diphenylmethane diisocyanate (MDI) is used. That is, as the thickener, an aliphatic diurea composed of a combination of an aliphatic amine (having a carbon chain length of 10 or less) and diphenylmethane diisocyanate (MDI) is preferably used.

Then, the amine and the diisocyanate compound can be reacted under various methods and conditions. It is preferable to react in a base oil because a diurea compound having a thickening agent with high uniform dispersibility can be obtained. The reaction may be carried out by adding a base oil in which a diisocyanate compound is dissolved to a base oil in which an amine is dissolved, or by adding a base oil in which an amine is dissolved to a base oil in which a diisocyanate compound is dissolved. You may go. The temperature and time in these reactions are not particularly limited and may be the same as in ordinary reactions of this type. The reaction temperature is preferably 60°C to 170°C from the viewpoint of solubility and volatility of amine and diisocyanate. The reaction time is preferably 0.5 to 2.0 hours from the viewpoint of completing the reaction of the amine and the diisocyanate and improving the efficiency by shortening the production time.

The average particle size of the thickener is preferably 10 μm or less, more preferably 5 μm to 8 μm. The average particle size of the thickener may be measured by a known measurement method such as a laser diffraction method, a dynamic light scattering method, an image imaging method, a gravity sedimentation method, or the like. When the average particle size of the thickener is within the above range, the thickener is well dispersed in the entire base oil, so that the interaction between the base oil and the thickener can be strengthened.

Further, the compounding amount of the thickener is preferably 15% by mass to 25% by mass based on the total amount of the grease composition.
As the additive, at least one of polyoxyethylene alkylamine and glycerol monooleate is mentioned as an essential component, and as an optional component, for example, an extreme pressure agent, an oiliness agent, an antirust agent, an antioxidant, an antiwear agent, Examples include various additives such as dyes, hue stabilizers, thickeners, structure stabilizers, metal deactivators, and viscosity index improvers.

Examples of the polyoxyethylene alkylamine include polyoxyethylene lauryl amine, polyoxyethylene tallow amine, polyoxyethylene stearyl amine, polyoxyethylene oleyl amine, polyoxyethylene tallow propylene diamine, polyoxyethylene stearyl propylene diamine, polyoxyethylene. N-cyclohexylamine, polyoxyethylene metaxylenediamine, dodecyldioxyethylamine, tetradecyldioxyethylamine, octadecyldioxyethylamine, 16-oxyheptadecyldioxyethylamine, octadecyloxyethoxyethylamine, 17-octadecenyldioxyethylamine , 1-methylheptadecyldioxyethylamine and the like. For example, as a commercially available product, "ADEKAKI CLUB FM-812" manufactured by ADEKA can be used.

As the glycerol monooleate, for example, “ADEKAKI CLUB FM-210” manufactured by ADEKA can be used as a commercially available product.
The blending amount of polyoxyethylene alkylamine and/or glycerol monooleate (total amount when used in combination) is preferably 0.5% by mass to 2% by mass with respect to the total amount of the grease composition.

The reason for using polyoxyethylene alkylamine and/or glycerol monooleate as the additive as described above is as follows. That is, since polyoxyethylene alkylamine is oil-soluble, it easily dissolves in the base oil and acts as a surfactant. As a result, the interaction between the base oil and the thickener can be strengthened, and the hardness (concentration) of the grease composition in a stationary state can be increased. Thereby, the low dust generation performance can be improved. On the other hand, although glycerol monooleate is insoluble in oil, it can be dispersed in the base oil and enter the network formed by the thickener. As a result, the interaction between the thickener fibers can be strengthened, and the hardness (concentration) of the grease composition in a stationary state can be increased. Thereby, the low dust generation performance can be improved.

Then, in order to produce the grease composition of the present invention, for example, first, the base oil and the thickener are mixed and stirred. Next, the mixture is rolled (rolled) by passing it through a roll mill or the like. After the roll treatment, the mixture is added with polyoxyethylene alkylamine and/or glycerol monooleate as essential components, and if necessary, other additives and stirred. As described above, by dispersing the thickener in the base oil by roll treatment and then mixing the additive, the additive can be satisfactorily spread throughout the grease composition. The above grease composition can be obtained through the above steps.

The grease composition (grease G) obtained as described above has an immiscibility of 200 or less and a penetration of 250 or more.
Therefore, in FIG. 1, even when the grease G is sheared by the sliding between the inner ring 3 and the outer ring 4 and the ball 5, it is possible to reduce the deterioration of the acoustic characteristics and the torque stability due to the coarse particles. .. Further, when the workability is 250 or more, it becomes soft and fluidity increases when it is subjected to shearing by a roll treatment or the like, so that it can be easily enclosed in the rolling bearing 1, for example. Therefore, it is possible to suppress a decrease in productivity when the rolling bearing 1 is produced.

On the other hand, the impermeability is 200 or less, and the hardness can be relatively maintained in the stationary state. Therefore, for example, in the outer region 14 of the grease G, which is away from the interface (sliding surface 13) between the inner ring 3 and the outer ring 4 and the ball 5, the sliding effect of the ball 5 is less likely to cause the sliding. It can be kept harder than the inner region 15 near the surface 13. As a result, even when the inner region 15 is softened by shearing and has increased fluidity, the outer region 14 plays a role as a lid to prevent the grease G having increased fluidity from scattering and generate dust. Can be suppressed. Furthermore, if the difference between the immiscible consistency and the miscible consistency of the grease G is 100 or more, the difference in the properties of the grease G between the sheared state and the static state can be increased. As a result, the difference in properties between the inner region 15 which is susceptible to shearing and the stationary outer region 14 becomes noticeable. Therefore, while the grease G having high fluidity and excellent lubricating performance is mainly supplied to the sliding surface 13 from the inner region 15, the scattering of the grease G can be suppressed in the outer region 14.

Since the above effects can be achieved without significantly changing the amount of the thickener, it is possible to avoid affecting the blending ratio of the main components of the grease composition such as the base oil and the thickener. .. Therefore, the amount of base oil can be maintained at an amount suitable for lubrication, so that the base oil can be supplied to the contact portion (sliding surface 13) of the rolling bearing 1 for a long period of time. As a result, the life of the grease G can be extended.

It should be noted that the present invention is not limited to the above embodiment and can be implemented in other embodiments.
For example, in the above-described embodiment, an example in which grease (G) is filled in the rolling bearing 1 formed of a (double row) ball bearing has been described. However, a bearing in which grease of the grease composition of the present invention is filled is described. May be other rolling bearings such as needle bearings, roller bearings, etc. other than balls used as rolling elements.

Moreover, the additive of the essential component is not limited to polyoxyethylene alkylamine and glycerol monooleate, and any additive can be used as long as the grease composition can have an immiscibility of 200 or less and a miscibility of 250 or more. However, additives other than these may be used.
Further, in the above-described embodiment, the base oil and the thickener are pre-rolled and then the additive is mixed, but the base oil, the thickener and the additive are mixed first, and then the roll treatment is performed. Good.

Besides, various design changes can be made within the scope of the matters described in the claims.

Next, the present invention will be described based on Examples and Comparative Examples, but the present invention is not limited to the following Examples.
Examples 1-2 and Comparative Examples 1-2
<Grease composition>
A grease composition for test was prepared by blending the base oil and the thickener in the blending ratios shown in Table 1 for each of the Examples and Comparative Examples, rolling the mixture, and then mixing and stirring the additives. The following evaluation was performed on the obtained test grease composition. The evaluation results are shown in Table 1 and FIG. In Table 1, the kinematic viscosity of the base oil is a value measured according to JIS K 2283. In addition, Mo-DTC represents molybdenum dialkyldithiocarbamate, and Zn-St represents zinc stearate.
<Evaluation>
(I) Grease Penetration The immiscible penetration and the penetration consistency of each grease composition for test were measured according to JIS K2220.
(II) Measurement of Grease Bearing Rotational Torque A deep groove ball bearing 6202 with a non-contact seal having a crown type resin cage was evaluated by using two test grease compositions filled with a space volume ratio of 35%. .. In addition, 0.11 g of the base oil was dropped into a ball and used. Then, using the measuring device shown in FIG. 2, a tangential force acting on the housing when the inner ring was rotated at 1800 r/m at room temperature under an axial preload (axial load) of 44 N was measured with a load cell, and the outside of the housing was measured. The rotation torque was calculated from the diameter. The evaluation time is 1800 sec. And

Table 1 shows that Examples 1 and 2 can achieve low dust generation that cannot be achieved by Comparative Examples 1 and 2, while achieving torque performance equivalent to that of Comparative Examples 1 to 3.

1...Rolling bearing, G...Grease

Claims (4)

A base oil which is at least a poly-α-olefin, and a thickener which is a diurea obtained by reacting any amine of hexylamine, heptylamine, octylamine, nonylamine and decylamine with diphenylmethane diisocyanate, and glycerol monooleate. And an additive consisting of
A rolling bearing in which a grease composition is encapsulated , which has an impermeability of 200 or less and an intimacy of 250 or more. The rolling bearing according to claim 1, wherein a difference between the immiscible consistency and the miscible consistency is 100 or more. The rolling bearing according to claim 1, wherein the additive is contained in an amount of 0.5% by mass to 2% by mass. The rolling bearing according to claim 1, wherein the thickening agent has an average particle size of 10 μm or less.

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