JP7148426B2 - Lubricating compositions and rolling bearings - Google Patents

Description

TECHNICAL FIELD The present invention relates to a lubricating composition for use in a high-temperature atmosphere of, for example, 300 to 500° C., and a rolling bearing containing the lubricating composition.

Rolling bearings incorporated in various industrial machines and vehicles are filled with a lubricating composition (grease, lubricating oil, etc.) to provide lubricity. Lubricating compositions are required to have different properties depending on the operating conditions of the rolling bearing, and lubricating compositions used under high temperature conditions are required to have heat resistance and the like.

For example, in rolling bearings for tenter clips that are used in high-temperature air, fluoro-greases containing fluororesin as a thickener are widely used in consideration of heat resistance. In addition, solid lubricants and the like are also blended as additives. The fluorine grease described in Patent Document 1 contains fluorine oil, polytetrafluoroethylene resin powder as a thickener, and a predetermined additive such as molybdenum disulfide. By adding a predetermined additive to the fluorine grease, leakage of the fluorine grease is suppressed even in an environment where ester oil, which has a strong affinity for metals, enters the bearing.

Patent Literature 2 proposes a lubricating coating composition that forms a solid coating film for the purpose of preventing seizure of threaded parts used in a high-temperature environment. This lubricating coating composition comprises a solid component and an organic solvent, the solid component being an organosilicon polymer having a polycarbosilane skeleton crosslinked by a metal element, and at least one of molybdenum disulfide, boron nitride, graphite and mica. It contains a solid lubricant consisting of seeds.

Further, Patent Document 3 proposes a solid lubricated rolling bearing having a member obtained by firing a solid lubricant such as graphite as a rolling bearing that can be used even in a high temperature range where fluorine grease cannot be used.

Japanese Patent No. 4277521 Japanese Patent No. 5763494 Japanese Patent No. 6196514

In recent years, the conditions under which rolling bearings are used have become increasingly severe due to the increasing speed and performance of various industrial machines. Therefore, there is a demand for a lubricating composition that can be used even at extremely high temperatures such as 300° C. or higher.

Since the fluorine grease described in Patent Document 1 decomposes at around 300° C., it is difficult to use in a high temperature range higher than that. Even if a heat-resistant solid lubricant is blended as an additive, the blending ratio is small, and it is difficult to continue lubricating after the grease deteriorates. Further, the lubricating coating composition described in Patent Document 2 contains an organosilicon polymer as a solid component. However, there is no example of enclosing a lubricating composition containing such an organosilicon polymer in a rolling bearing, and the composition is not suitable as a lubricating composition to be enclosed in a rolling bearing. In addition, the solid lubricated rolling bearing that can be used in a high temperature range of 300 ° C. or higher described in Patent Document 3 has a special shape that incorporates a member made of sintered solid lubricant powder, unlike general-purpose rolling bearings. There is a concern that the manufacturing cost will increase.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and provides a lubricating composition capable of maintaining a lubricating function for a long time even under high-temperature atmospheric conditions and having excellent bearing life, and a rolling bearing containing the lubricating composition. With the goal.

The lubricating composition of the present invention is a lubricating composition containing fluorine oil as a main component and at least one solid lubricant selected from molybdenum disulfide, boron nitride, and graphite, wherein the lubricating composition is the solid It is a paste-like composition containing a lubricant as a thickening agent, and is characterized in that the kinematic viscosity of the fluorine oil at 40° C. is 700 mm ² /s or more. Here, having a fluorine oil as a main component means that the content (% by mass) of the fluorine oil with respect to the entire lubricating composition is 50% by mass or more.

The solid lubricant is molybdenum disulfide. Further, the lubricating composition is characterized by containing 10 to 30% by mass of the solid lubricant with respect to the entire lubricating composition, and the balance other than the solid lubricant being the fluorine oil.

The fluorine oil is characterized by having a kinematic viscosity at 40° C. of 1000 mm ² /s or more.

The rolling bearing of the present invention is a rolling bearing containing a lubricating composition, wherein the lubricating composition is the lubricating composition of the present invention, and the rolling bearing is used in a tenter clip for a film stretching device. It is characterized by being a bearing that can be

The lubricating composition of the present invention is a paste-like composition containing a fluorine oil as a main component and containing at least one solid lubricant selected from molybdenum disulfide, boron nitride, and graphite as a thickener. The kinematic viscosity at °C is 700 mm ² /s or more. That is, since a solid lubricant with high heat resistance is used as a thickener and a fluorinated oil for ultra-high temperatures is used as a base oil, the lubricating composition continues to function as a lubricating composition without being decomposed even in a high-temperature atmosphere. As a result, the lubricating function can be maintained for a long time even in a high-temperature atmosphere of, for example, 300° C. or higher, and the bearing life is excellent. In addition, the lubricating composition of the present invention is in the form of a paste like general grease and the like, and can be enclosed in rolling bearings, so that manufacturing costs can be reduced.

Since the rolling bearing of the present invention encloses the lubricating composition of the present invention, it is possible to maintain the lubricating function and exhibit excellent bearing life even when used under high-temperature atmospheric conditions. . In addition, it is assumed that bearings used in tenter clips for film stretching devices are used at high temperatures (e.g., around 250°C), and the rolling bearing of the present invention has excellent heat resistance, so it is suitable for this application. is.

FIG. 10 is a diagram showing an example of a tenter clip; 1 is an axial sectional view showing an example of a rolling bearing of the present invention; FIG. It is a perspective view which shows an example of a film stretching apparatus. FIG. 4 is a view showing guide rails of the transverse stretching device of FIG. 3; FIG. 3 is a diagram showing the results of thermogravimetric measurement of each base oil;

The present inventors have studied a lubricating composition to be sealed in a rolling bearing in order to obtain an excellent bearing life even in an environment of 300° C. or higher in the atmosphere, for example. As a result, by using a predetermined solid lubricant as a thickener and using a fluorine oil with a kinematic viscosity of 700 mm ² /s or more at 40 ° C. as a base oil, lubricity can be maintained even under high temperature atmospheric conditions. I found out. The present invention is based on such findings.

The lubricating composition of the present invention contains a fluorine oil as a main component and at least one solid lubricant selected from molybdenum disulfide, boron nitride, and graphite. The lubricating composition of the present invention does not contain a general thickening agent such as metallic soap or a urea compound, and contains a predetermined amount of a solid lubricant with high heat resistance as a thickening agent. A composition of the form is obtained.

The fluorine oil used in the present invention has extremely excellent heat resistance, and the kinematic viscosity of the fluorine oil is 700 mm ² /s or more at 40°C. This kinematic viscosity is preferably 800 mm ² /s or more, more preferably 1000 mm ² /s or more. Since the stirring torque increases, the upper limit of kinematic viscosity is 1500 mm ² /s or less.

The fluorine oil as the base oil is preferably contained in an amount of 50 to 90% by mass, more preferably 70 to 90% by mass, even more preferably 70 to 80% by mass, relative to the entire lubricating composition.

The content of the solid lubricant used in the present invention is preferably 10 to 40% by mass, more preferably 20 to 30% by mass, relative to the total lubricating composition. By setting the content of the solid lubricant to 10% by mass or more, the solid lubricant tends to be evenly distributed on the sliding surface even after the fluorinated oil evaporates, and the lubricating function can be easily maintained. On the other hand, by setting the content of the solid lubricant to 40% by mass or less, uniform dispersibility is ensured, and a good lubricating function can be easily exhibited.

Molybdenum disulfide is widely used as a solid lubricant such as grease. Molybdenum disulfide has a layered lattice structure and is known to be easily sheared into thin layers by sliding motion to reduce frictional resistance. Powdered molybdenum disulfide can be used.

Boron nitride has high thermal conductivity, high mechanical stability and chemical stability. Although boron nitride is not particularly limited, for example, hexagonal boron nitride can be used. The average grain size of hexagonal boron nitride is not particularly limited, but is, for example, 1 to 50 μm. The average particle size is a value measured by a laser diffraction/scattering method.

Graphite is well known to have excellent properties as a solid lubricant. Graphite is roughly classified into natural graphite and artificial graphite, and both can be used. As for the shape, there are scaly, granular, spherical, etc., and any of them can be used.

As the graphite, graphite with fixed carbon of 97.5% or more is preferably used, and artificial graphite with fixed carbon of 98.5% or more is more preferable. Such graphite has a high compatibility with fluorinated oil, and even if the fluorinated oil does not adhere to a part of the surface, the lubricity is maintained by the trace amount of fluorinated oil impregnated in the graphite.

The solid lubricant used in the present invention may be one of molybdenum disulfide, boron nitride, and graphite, or may be used in combination. Among these solid lubricants, it is preferable to use molybdenum disulfide, which can prolong the life of the lubricant, as shown in the examples below. It is believed that molybdenum disulfide maintains the film formed on the sliding surface more easily than other solid lubricants.

The lubricating composition of the present invention contains fluorinated oil and a predetermined solid lubricant as essential components, but in addition to these, other additives may be added within a range that does not impair the object of the present invention. For example, extreme pressure agents such as organic zinc compounds and organic molybdenum compounds; antioxidants such as amine-based, phenol-based and sulfur-based compounds; anti-wear agents such as sulfur-based and phosphorus-based compounds; agents, esters, and oily agents such as alcohols. However, as the lubricating composition of the present invention, the balance other than the predetermined solid lubricant is preferably composed of fluorine oil.

The worked penetration (JIS K 2220) of the lubricating composition is preferably in the range of 200-350. If the consistency is less than 200, there is a risk of poor lubrication. On the other hand, if the consistency exceeds 350, the lubricating composition is soft and tends to flow out of the bearing, which is not preferable.

In consideration of the above, a more preferable form of the lubricating composition of the present invention is composed only of a fluorine oil having a kinematic viscosity of 700 mm ² /s or more at 40 ° C. and molybdenum disulfide as a solid lubricant, and the disulfide The composition contains 20 to 30% by mass of molybdenum based on the total lubricating composition. More preferably, it is a composition in which the kinematic viscosity of the fluorine oil at 40° C. is 1000 mm ² /s or more.

An example of a film stretching apparatus in which the rolling bearing of the present invention is used is shown in FIGS. 3 and 4. FIG. FIG. 3 is a perspective view of a film stretching device, and FIG. 4 is a diagram showing guide rails of the lateral stretching device of FIG. As shown in FIGS. 3 and 4, the film stretching apparatus includes an extruder 9 that melts and kneads a resin, a die head (T die) 10 that shapes and extrudes the melted and kneaded resin into a raw sheet, and a raw sheet. A longitudinal stretching machine 11 that stretches in the longitudinal direction, a transverse stretching device 13 that stretches the longitudinally stretched sheet in the sheet width direction, and a take-up winder that winds up the film biaxially stretched in the longitudinal and transverse directions. 14. The transverse stretching device 13 has a pair of circulating guide rails 12, a plurality of tenter clips 15 circulating on the guide rails 12 at regular intervals, and means for heating the sheet.

As shown in FIG. 4, the longitudinally stretched sheet is subjected to a heat treatment in a lateral stretching device 13 while being continuously sandwiched between a plurality of tenter clips 15 at both ends thereof, and stretched onto the widened portions 12a and 12b of the guide rails 12. A biaxially stretched film is stretched in the width direction of the sheet along both the longitudinal and lateral directions. The stretched biaxially stretched film is wound up by a take-up winder 14 .

The rolling bearing of the present invention used in the tenter clip 15 is exposed to high temperature conditions in the transverse stretching device 13 which performs heat treatment. Here, FIG. 1 shows a sectional view of an example of the tenter clip. As shown in FIG. 1, the tenter clip 15 includes a gripping portion 17 for gripping one end 16 of the sheet, and a plurality of tenter clip rolling bearings 18 for allowing the tenter clip main body 15a to travel while being guided by the guide rails 12. and are provided. The tenter clip rolling bearing 18 corresponds to the rolling bearing of the present invention.

As shown in FIGS. 1 and 4, the tenter clips 15 are routed along the guide rails 12 within the transverse stretching device 13 . One end 16 of the longitudinally stretched sheet is gripped by the gripping portion 17 at the guide rail entrance 12c, and is laterally stretched by the guide rail widening portions 12a and 12b as the tenter clips 15 run while being heat-treated. The longitudinally stretched and transversely stretched sheet becomes a biaxially stretched film. At the guide rail exit 12d, the gripping portion 17 releases the gripping state, and the tenter clip 15 returns along the guide rail 12 to the entrance of the transverse stretching device 13. As shown in FIG.

The tenter clip rolling bearing 18 is subjected to heat treatment in the transverse stretching device 13 and sprayed with ester oil for assisting the running of the tenter clip 15 . An amine additive is added to the ester oil in order to prevent oxidation deterioration of the ester oil under high-temperature conditions in the drawing apparatus, and the outer ring of the bearing 18 and the guide rail 12 are lubricated by this ester oil. be done.

An example of the rolling bearing of the present invention is shown in FIG. FIG. 2 is a cross-sectional view of a deep groove ball bearing. A deep groove ball bearing 1 used as a rolling bearing for a tenter clip has an inner ring 2 having an inner ring raceway surface 2a on its outer peripheral surface and an outer ring 3 having an outer ring raceway surface 3a on its inner peripheral surface. and the outer ring raceway surface 3a. The rolling elements 4 are held by cages 5, and at least around the rolling elements 4 the lubricating composition 7 of the present invention is sealed. The seal members 6 are fixed to the outer ring 3 and the like and provided in the axial end openings 8a and 8b of the inner ring 2 and the outer ring 3, respectively. The sealing member 6 prevents leakage of the lubricating composition 7, and also prevents entry of ester oil sprayed as a driving aid and contamination with foreign matter.

The rolling bearing of the present invention is applicable not only to deep groove ball bearings but also to various types of rolling bearings. Examples include angular contact ball bearings, thrust ball bearings, cylindrical roller bearings, needle roller bearings, cylindrical thrust roller bearings, thrust needle roller bearings, tapered roller bearings, thrust tapered roller bearings, self-aligning ball bearings, self-aligning roller bearings Bearings, thrust self-aligning roller bearings, slide bearings, and the like.

Since the rolling bearing of the present invention can maintain the lubricating function for a long time even under high temperature conditions, it is particularly suitable for rolling bearings used under high temperature conditions, such as rolling bearings for tenter clips used in film stretching equipment. Suitable for

In the examples, base oils 1 to 3 shown below were used as base oils.
・Base oil 1: fluorine oil (XHT-1000 manufactured by Chemours); kinematic viscosity at 40 ° C. 1023 mm ² / s
- Base oil 2: poly-α-olefin oil (Synfluid 801 manufactured by Nippon Steel & Sumikin Chemical Co., Ltd.); kinematic viscosity at 40 ° C. 47 mm ² / s
- Base oil 3: fluorine oil (GPL105 manufactured by Chemours); kinematic viscosity at 40°C 160 mm ² /s

<Thermogravimetry test>
A thermogravimetry test was performed using the above base oils 1-3. In the test, the temperature was increased from 40° C. to 500° C. at an acceleration temperature of 10° C./min under an air atmosphere, and the weight of each base oil was measured over time. FIG. 5 shows a plot of the weight reduction rate of the base oil at different heating temperatures.

As shown in FIG. 5, base oil 2 and base oil 3 began to lose weight around 250°C and almost evaporated around 400°C, whereas base oil 1 showed weight loss up to around 350°C. The weight loss was less than 10% even at around 400°C. From the above, it was found that the fluorine oil of the base oil 1 has the highest heat resistance.

<Bearing life test>
Lubricating compositions were obtained by mixing base oil 1, base oil 2, molybdenum disulfide, boron nitride, and graphite in the composition (% by mass) shown in Table 1. Each obtained lubricating composition was sealed in a bearing (manufactured by NTN, SEB608ZZ) to obtain a test bearing.

Each test bearing was attached to a testing machine, and a bearing life test was conducted under the following conditions. The life form is seizure, and the torque rises sharply as the life is reached. In this test, the life was defined as the time (h) until the test machine stopped due to motor overload. Table 1 shows the results.
Test bearing: SEB608ZZ
Bearing dimensions: φ8mm×φ22mm×7mm
Axial load: 196 N (maximum point contact surface pressure: 1.7 GPa)
Rotation speed (inner ring): 1000min ^-1
Temperature: 350°C

As shown in Table 1, in Examples 1 to 3 in which a fluorine oil having a kinematic viscosity of 700 mm ² /s or more, which is base oil 1, and each solid lubricant were combined, only the fluorine oil (Comparative Example 1) or The life of the bearing was extended by about twice as much as that of PAO oil alone (Comparative Example 2). In the lubricating compositions of Examples 1 to 3, a fluorine oil with excellent heat resistance is further blended with a solid lubricant, and the solid lubricant forms a reaction film on the sliding surface, so that the lubricating function can be maintained for a long time. I was able to keep it. In general, solid lubricants have higher heat resistance than fluorine oil, so even if the fluorine oil decomposes or evaporates, the solid lubricant as a thickener will still function as a lubricant. This leads to longer bearing life.

Further, among Examples 1 to 3, Example 1 using molybdenum disulfide as the solid lubricant had the longest service life. Since boron nitride has a higher melting point than molybdenum disulfide, boron nitride is generally considered to have better heat resistance than molybdenum disulfide, but in Table 1, molybdenum disulfide has the best results. became.

The lubricating composition of the present invention can maintain the lubricating function for a long time even under high temperature conditions and has excellent bearing life. Therefore, it is suitable for rolling bearings used under high temperature conditions, and is particularly suitable as a lubricating composition for rolling bearings used in tenter clips for film stretching devices.

Reference Signs List 1 deep groove ball bearing 2 inner ring 3 outer ring 4 rolling element 5 retainer 6 sealing member 7 lubricating composition 8a opening 8b opening 9 extruder 10 T die 11 longitudinal stretching machine 12 guide rail 13 transverse stretching device 14 take-up winder 15 Tenter clip 15a Tenter clip main body 16 One end of sheet 17 Grip portion 18 Rolling bearing for tenter clip

Claims (5)

A lubricating composition containing a fluorine oil as a main component and a solid lubricant,
The lubricating composition is a paste composition containing the solid lubricant as a thickening agent, the solid lubricant being molybdenum disulfide,
The fluorine oil has a kinematic viscosity of 800 mm ² /s or more and 1500 mm ² /s or less at 40 ° C., and the temperature of the fluorine oil is increased from 40 ° C. at an acceleration temperature of 10 ° C./min in an air atmosphere. A lubricating composition characterized by a weight loss of less than 10% at 400°C in a thermogravimetric test in which the weight of the oil is measured over time . A lubricating composition containing a fluorine oil as a main component and a solid lubricant,
The lubricating composition is a paste-like composition containing the solid lubricant as a thickening agent, the solid lubricant being boron nitride,
The kinematic viscosity of the fluorine oil at 40 ° C. is 800 mm ² /s or more 1500mm ² / s or less, and the fluorine oil is 400 ° C. A lubricating composition characterized by a weight loss of less than 10% in 1 or 2, wherein the lubricating composition contains 10 to 30% by mass of the solid lubricant with respect to the entire lubricating composition, and the rest other than the solid lubricant is the fluorine oil. 3. The lubricating composition according to 2. The lubricating composition according to any one of Claims 1 to 3, wherein the fluorinated oil has a kinematic viscosity at 40°C of 1000 ^mm2 /s or more. A rolling bearing containing a lubricating composition,
The lubricating composition is the lubricating composition according to any one of claims 1 to 4,
A rolling bearing, wherein the rolling bearing is a bearing used in a tenter clip for a film stretching device.

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