JP2020079363A - Lubricating composition and rolling bearing - Google Patents

Abstract

To provide the lubricating composition and the rolling bearing in which the lubricating composition is encapsulated, wherein the lubricating composition can maintain a lubricating function for a long time even under high temperature conditions and has an excellent bearing life.SOLUTION: The lubricating composition encapsulated in a deep groove ball bearing 1 used at high temperature 7 comprises: a base oil; molybdenum disulfide; and an additive, wherein the lubricating composition is a paste-like composition, the lubricating composition is a paste-like composition whose main component is molybdenum disulfide, the additive contains sulfur powder, the sulfur powder is contained in an amount of 8 to 20 mass% with respect to the entire lubricating composition, and the base oil is poly-α-olefin oil.SELECTED DRAWING: Figure 2

Description

  TECHNICAL FIELD The present invention relates to a lubricating composition enclosed in a rolling bearing incorporated in various industrial machines and the like, and particularly to a lubricating composition suitable for a rolling bearing used in a tenter clip used in a film stretching apparatus.

  BACKGROUND ART Rolling bearings incorporated in various industrial machines and vehicles are filled with a lubricating composition (grease, lubricating oil, etc.) in order to impart lubricity. The required characteristics of the lubricating composition differ depending on the usage conditions of the rolling bearing, and the lubricating composition used under high temperature conditions is required to have heat resistance and the like.

  For example, fluorine grease is widely used for rolling bearings for tenter clips in consideration of heat resistance. The fluorine grease described in Patent Document 1 contains fluorine oil, a polytetrafluoroethylene resin powder that is a thickener, and a predetermined additive such as molybdenum disulfide. By adding a predetermined additive to the fluorine grease, the leakage of the fluorine grease is suppressed even in an environment in which ester oil having a strong affinity for metals enters the inside of the bearing.

  Patent Document 2 describes a lubricating coating composition that forms a solid coating film for the purpose of preventing seizure of screw parts and the like used in a high temperature environment. This lubricating coating composition comprises a solid component and an organic solvent, and the solid component is an organosilicon polymer in which a polycarbosilane skeleton is cross-linked with a metal element, and at least one of molybdenum disulfide, boron nitride, graphite and mica. And a solid lubricant consisting of seeds.

  Further, Patent Document 3 describes a lubricating composition for the purpose of reducing noise of a speed reducer and steering torque of an electric power steering device. This lubricating composition contains a lubricating oil and cushioning material particles, and a solid lubricant such as molybdenum disulfide or graphite is used as a component of the cushioning material particles.

Japanese Patent No. 4277521 Japanese Patent No. 5763494 JP, 2008-106204, A

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

  The fluorine grease described in Patent Document 1 decomposes at around 300° C., so that it is difficult to use in the higher temperature range. Further, the lubricating coating composition described in Patent Document 2 contains an organic silicon polymer as a solid component. However, there is no example in which a lubricating composition containing such an organosilicon polymer is enclosed in a rolling bearing, and the composition is not suitable as a lubricating composition enclosed in a rolling bearing. Further, since the lubricating composition described in Patent Document 3 contains buffer material particles that decompose in a high temperature atmosphere, it is not a composition suitable for a rolling bearing used under high temperature conditions.

  The present invention has been made in view of the above circumstances, and it is possible to provide a lubricating composition that can maintain a lubricating function for a long time even under high temperature conditions and that has an excellent bearing life, and a rolling bearing in which the lubricating composition is encapsulated. To aim.

  The lubricating composition of the present invention is a lubricating composition containing a base oil, molybdenum disulfide, and an additive, wherein the lubricating composition is a paste composition containing molybdenum disulfide as a main component. The additive contains sulfur powder, and the sulfur powder is contained in an amount of 8 to 20 mass% with respect to the entire lubricating composition. Here, having molybdenum disulfide as a main component means that the content (mass %) of molybdenum disulfide with respect to the entire lubricating composition is equal to or more than the content (mass %) of the base oil.

  In the lubricating composition, the balance other than the molybdenum disulfide and the sulfur powder is the base oil.

  The base oil is contained in an amount of 28 to 46 mass% with respect to the entire lubricating composition, and the molybdenum disulfide is included in an amount of 40 to 52 mass% with respect to the entire lubricating composition.

  The base oil is poly-α-olefin oil (PAO oil).

  The rolling bearing of the present invention is a rolling bearing in which a lubricating composition is enclosed, and the lubricating composition is the lubricating composition of the present invention.

  The rolling bearing is a bearing used for a tenter clip for a film stretching device.

  The lubricating composition of the present invention contains a base oil, molybdenum disulfide, and sulfur powder, and is a paste-like composition containing molybdenum disulfide as a main component. Since a predetermined amount of sulfur powder is contained, it is possible to use it in a high temperature environment. The formation of the molybdenum disulfide coating on the sliding surface is maintained even after the base oil has evaporated. Thereby, the lubricating function can be maintained for a long time even under a high temperature condition of, for example, 300° C. or higher.

  Since the rolling bearing of the present invention encapsulates the lubricating composition of the present invention, the lubricating function can be maintained and an excellent bearing life can be exhibited even when used under high temperature conditions. Further, the bearing used for the tenter clip for the film stretching apparatus is supposed to be used at high temperature (for example, around 250° C.), but the rolling bearing of the present invention has excellent heat resistance, and therefore is suitable for this application. Is.

It is a figure which shows an example of a tenter clip. It is an axial sectional view showing an example of a rolling bearing of the present invention. It is a perspective view showing an example of a film stretching device. It is a figure which shows the guide rail of the horizontal stretching apparatus of FIG.

  The present inventors have investigated 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. Solid lubricants are widely used in lubricating compositions such as grease to impart lubricity. The solid lubricant forms a lubricating coating on the sliding surface when the bearing is started to be used. The present inventors have paid attention to molybdenum disulfide among solid lubricants, and have earnestly studied to make molybdenum disulfide existing on a sliding surface function even under high temperature conditions. As a result, they have found that by adding a predetermined amount of sulfur powder (sulfur simple substance) to the molybdenum disulfide paste, molybdenum disulfide functions properly and the lubricity is maintained. The present invention is based on such knowledge.

  The lubricating composition of the present invention comprises base oil, molybdenum disulfide, and sulfur powder as an additive. The lubricating composition is a paste composition containing molybdenum disulfide as a main component. Since the lubricating composition of the present invention has an excellent lubricating function even under high temperature conditions, it is preferably used at a high temperature of 200°C or higher, more preferably 300°C or higher.

  The base oil used in the present invention can be used without particular limitation as long as it is usually used for rolling bearings. For example, mineral oils such as paraffinic mineral oils and naphthenic mineral oils, polybutene oils, PAO oils, hydrocarbon synthetic oils such as alkylbenzene oils and alkylnaphthalene oils, or natural oils and fats, polyol ester oils, phosphate ester oils, diester oils, Examples include non-hydrocarbon synthetic oils such as polyglycol oil, silicone oil, polyphenyl ether oil, alkyldiphenyl ether oil, and fluorinated oil. These base oils may be used alone or in combination of two or more. Among these base oils, it is preferable to use PAO oil because it is excellent in heat resistance and lubricity.

  PAO oil is a mixture of α-olefins or oligomers or polymers of isomerized α-olefins. Specific examples of α-olefins include 1-octene, 1-nonene, 1-decene, 1-dodecene, 1-tridecene, 1-tetradecene, 1-pentadecene, 1-hexadecene, 1-heptadecene, 1-octadecene, 1 -Nonadecene, 1-eicosene, 1-dococene, 1-tetradococene and the like can be mentioned, and a mixture thereof is usually used.

The kinematic viscosity of the base oil (in the case of a mixed oil, the kinematic viscosity of the mixed oil) is preferably 10 to ²⁰⁰ mm ² /s at 40°C. More preferably, it is 10 to 120 mm ² /s.

  The molybdenum disulfide used in the present invention is widely used as a solid lubricant such as a grease composition. As a lubrication mechanism, it is known that it has a layered lattice structure and is easily sheared into a thin layer by a sliding motion to reduce frictional resistance.

  The lubricating composition of the present invention contains molybdenum disulfide as a main component. As molybdenum disulfide, powdery one is used. Due to the high content of molybdenum disulfide, the lubricating composition becomes a paste. It is preferable that the lubricating composition of the present invention does not contain a thickening agent such as metallic soap or a urea compound. Molybdenum disulfide is contained in an amount of 40 to 52% by mass based on the entire lubricating composition after the content (% by mass) of molybdenum disulfide based on the entire lubricating composition is set to be equal to or more than the content (% by mass) of the base oil. It is preferable that the content is 45 to 50% by mass. By setting the content of molybdenum disulfide to 40% by mass or more, molybdenum disulfide tends to be evenly present on the sliding surface even after the base oil is evaporated. Further, by setting the content of molybdenum disulfide to be 52% by mass or less, uniform dispersibility is ensured and a good lubricating function is easily exhibited.

The sulfur powder used in the present invention is a powder of elemental sulfur. Cyclic S ₈ sulfur is generally known as sulfur, and three types of S ₈ sulfur are α sulfur (orthogonal sulfur), β sulfur (monoclinic sulfur), and γ sulfur (monoclinic sulfur). There is a crystalline form. It is preferable to use α-sulfur because it is stable at room temperature. Further, the purity of sulfur is preferably 98% or more.

  The content of the sulfur powder is 8 to 20 mass% with respect to the entire lubricating composition. By setting the content of the sulfur powder within the above range, it becomes easy to promote the formation of the molybdenum disulfide coating. The content of the sulfur powder is preferably 10 to 15% by mass.

Further, the mass ratio (Mo ₂ S/S) of molybdenum disulfide and sulfur powder is preferably 3 to 5, and more preferably 3.5 to 4.5. By setting the mass ratio of the both to 3 to 5, sulfur acts on molybdenum disulfide existing on the sliding surface, the molybdenum disulfide coating film is easily formed, and the lubricating function is maintained.

  The lubricating composition of the present invention contains three components of a base oil, molybdenum disulfide and sulfur powder as essential components, but in addition to these, other additives may be added within a range not impairing the object of the present invention. Good. For example, extreme pressure agents such as organozinc compounds and organomolybdenum compounds, antioxidants such as amine-based compounds, phenol-based compounds, sulfur-based compounds, antiwear agents such as sulfur-based and phosphorus-based compounds, and rust preventives such as polyhydric alcohol esters. Agents, friction reducing agents such as graphite, and oiliness agents such as esters and alcohols. However, the lubricating composition of the present invention is preferably one in which the balance other than molybdenum disulfide and sulfur powder consists of base oil.

  The mixing consistency (JIS K2220) of the lubricating composition is preferably in the range of 200 to 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 easily flows out of the bearing, which is not preferable.

  In view of the above, a more preferred form of the lubricating composition of the present invention is composed of only three elements: PAO oil as a base oil, molybdenum disulfide as a solid lubricant, and sulfur powder as an additive, The composition contains sulfur powder in an amount of 8 to 20% by mass based on the entire lubricating composition. More preferably, the composition contains 8 to 20% by mass of sulfur powder, 28 to 46% by mass of base oil, and 40 to 52% by mass of molybdenum disulfide with respect to the entire lubricating composition.

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

  As shown in FIG. 4, the longitudinally stretched sheet is heat-treated in the transverse stretching device 13 in a state where both ends thereof are continuously sandwiched by a plurality of tenter clips 15 to be formed on the widened portions 12 a and 12 b of the guide rail 12. The film is stretched in the width direction of the sheet, and is a biaxially stretched film stretched in both longitudinal and transverse directions. The stretched biaxially stretched film is wound by the draw winder 14.

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

  As shown in FIGS. 1 and 4, the tenter clip 15 orbits in the lateral stretching device 13 along the guide rail 12. The vertically stretched sheet is gripped at one end 16 of the sheet at the guide rail inlet 12c by the grip portion 17, and is horizontally stretched at the guide rail widened portions 12a and 12b by the running of the tenter clip 15 while being heated. This longitudinally stretched and transversely stretched sheet becomes a biaxially stretched film. At the guide rail outlet 12d, the grip portion 17 releases the gripped state, and the tenter clip 15 returns to the inlet along the guide rail 12 to the lateral stretching device 13.

  The rolling bearing 18 for the tenter clip is exposed to heat treatment in the lateral stretching device 13 and spray of ester oil to assist the running of the tenter clip 15. An amine-based additive is added to the ester oil in order to prevent oxidative deterioration of the ester oil under high temperature conditions in the stretching device, and the outer ring of the bearing 18 and the guide rail 12 are lubricated by the ester oil. To be done.

  An example of the rolling bearing of the present invention is shown in FIG. FIG. 2 is a sectional view of the deep groove ball bearing. In a deep groove ball bearing 1 used as a rolling bearing for a tenter clip, an inner ring 2 having an inner ring raceway surface 2a on the outer peripheral surface and an outer ring 3 having an outer ring raceway surface 3a on the inner peripheral surface are concentrically arranged, and an inner ring raceway surface 2a A plurality of rolling elements 4 are arranged between the outer raceway surface 3a and the outer ring raceway surface 3a. The rolling element 4 is held by a retainer 5, and the lubricating composition 7 of the present invention is enclosed at least around the rolling element 4. The seal member 6 is fixed to the outer ring 3 and the like at the axially opposite end openings 8a and 8b of the inner ring 2 and the outer ring 3, respectively. The seal member 6 prevents the lubricating composition 7 from leaking, and also prevents intrusion of ester oil sprayed as a travel aid and mixing of foreign matter.

  The rolling bearing of the present invention is not limited to the deep groove ball bearing type, but can be applied to various types of rolling bearings. Examples include angular contact ball bearings, thrust ball bearings, cylindrical roller bearings, needle roller bearings, thrust cylindrical roller bearings, thrust needle roller bearings, tapered roller bearings, thrust tapered roller bearings, self-aligning ball bearings, self-aligning rollers. Bearings, thrust self-aligning roller bearings, slide bearings and the like can be mentioned.

  INDUSTRIAL APPLICABILITY The rolling bearing of the present invention can maintain a lubricating function for a long time even under high temperature conditions, and thus is particularly suitable for a rolling bearing used under high temperature conditions, for example, a rolling bearing for a tenter clip used in a film stretching device. Suitable for

Example 1, Comparative Examples 1 to 3
PAO oil and molybdenum disulfide (manufactured by Kojundo Chemical Laboratory Co., Ltd.) were mixed with the compounding composition (mass%) shown in Table 1 to form a molybdenum disulfide paste, and sulfur powder (manufactured by Fuji Film Wako Pure Chemical Industries) was added thereto. Was appropriately added to obtain a lubricating composition. Each of the obtained lubricating compositions was sealed in a bearing (SEB608ZZ, manufactured by NTN) to obtain a test bearing.

<Bearing life test>
Each test bearing was attached to a tester, and a bearing life test was performed under the following conditions. The life type is seizure, and the torque sharply increases as the life is reached. In this test, the time (h) until the tester stopped due to the overload of the motor was defined as the life. The results are also shown in Table 1.
Test bearing: SEB608ZZ
Bearing dimensions: φ8mm×φ22mm×7mm
Axial load: 196N (point contact maximum surface pressure: 1.7GPa)
Rotational speed (inner ring): 1000min ^-1
Temperature: 350°C

  As shown in Table 1, Example 1 had the longest bearing life. In Example 1, the bearing life was extended compared to Comparative Example 1 in which sulfur powder was not added, and it is considered that sulfur promoted the formation of the molybdenum disulfide coating on the sliding surface. On the other hand, even when sulfur powder was added (Comparative Example 2 and Comparative Example 3), it was found that if the sulfur content was not a certain amount or more, the bearing life was deteriorated. As described above, in the rolling bearing according to the embodiment of the present invention, molybdenum disulfide enclosed inside the bearing forms a reaction film on the sliding surface even in high temperature atmosphere, and therefore, even after the PAO oil evaporates. The lubrication function can be maintained for a long time.

  Since the lubricating composition of the present invention can maintain the lubricating function for a long time even under high temperature conditions and has an excellent bearing life, it can be used even under high temperature conditions of, for example, 300° C. or higher. Therefore, it is suitable for a rolling bearing used under high temperature conditions, and is particularly suitable as a lubricating composition for a rolling bearing used for a tenter clip for a film stretching device.

1 Deep Groove Ball Bearing 2 Inner Ring 3 Outer Ring 4 Rolling Element 5 Cage 6 Sealing Member 7 Lubricating Composition 8a Opening 8b Opening 9 Extruder 10 T Die 11 Vertical Stretching Machine 12 Guide Rail 13 Horizontal Stretching Machine 14 Winding Winder 15 Tenter clip 15a Tenter clip body 16 One end of seat 17 Grip 18 Rolling bearing for tenter clip

Claims (6)

A lubricating composition comprising a base oil, molybdenum disulfide, and an additive,
The lubricating composition is a paste composition containing the molybdenum disulfide as a main component,
The lubricating composition, wherein the additive contains sulfur powder, and the sulfur powder is contained in an amount of 8 to 20 mass% with respect to the entire lubricating composition.   The lubricating composition according to claim 1, wherein in the lubricating composition, the balance other than the molybdenum disulfide and the sulfur powder is the base oil.   The base oil is contained in an amount of 28 to 46% by mass based on the entire lubricating composition, and the molybdenum disulfide is included in an amount of 40 to 52% by mass based on the entire lubricating composition. Item 2. The lubricating composition according to item 2.   The lubricating composition according to any one of claims 1 to 3, wherein the base oil is a poly-α-olefin oil.   A rolling bearing in which a lubricating composition is enclosed, wherein the lubricating composition is the lubricating composition according to any one of claims 1 to 4.   The rolling bearing according to claim 5, wherein the rolling bearing is a bearing used for a tenter clip for a film stretching device.

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