JP2006117741A - Gel-like lubricant composition and lubricant for sintered oil-containing bearing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a gel-like lubricant composition presenting semi-solid gel-like form similar to grease in its service bulk temperature region to enable oil leakage to be prevented, and having outstanding low-frictional properties impossible for grease to realize, therefore presenting significant energy-saving performance when adsorption film of a higher fatty acid is formed once. <P>SOLUTION: The gel-like lubricant composition is obtained by compounding a mineral oil-based and/or synthetic liquid lubricating oil with a higher fatty acid capable of forming a uniform gel. Preferably, this composition is obtained by compounding 100 pts.wt. of the above liquid lubricating oil with 1-200 pt(s). wt. of the above higher fatty acid. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a gel lubricant composition and a lubricant for sintered oil-impregnated bearings. In particular, when impregnated and used for sintered oil-impregnated bearings, oil leakage and oil separation are unlikely to occur, and gel characteristics such as fluidity and consistency can be adjusted over a wide range according to the application, and at a predetermined temperature or less. As long as it is used, the present invention relates to a gel-like lubricant composition that exhibits significantly lower frictional properties than ordinary lubricants.

  Lubricants include lubricating oils that are liquid at room temperature, mainly composed of base oils such as mineral oils and synthetic oils, and semi-solid gel greases in which thickeners such as metal soaps and urea are dispersed. Each of these lubricants has advantages and disadvantages, and is selected according to the conditions, environment, and usage.

  In recent years, machines are becoming increasingly sophisticated, high-performance, high-speed, downsized and long-life. Therefore, especially in the sliding part of the bearing system used in these machines, the lubrication conditions are severe and the required performance for the lubricant is also increasing. In order to maintain stable sliding characteristics and lubrication characteristics over a long period of time, it is necessary to reduce lubrication failure due to lubricant consumption, loss, and deterioration as much as possible. In particular, in DVD equipment and the like, since the bearing rotates at an ultra-high speed, oil is likely to be scattered due to centrifugal force, so that long-term stable operation is an issue. Also, these machines often incorporate complex electronic control circuits, and it is necessary to prevent system contamination due to leaked lubricant or volatile components as much as possible. Oil leaks inside precision instruments that handle paper, such as copiers and printers, also cause the oil to bleed out into the printing paper, so oil-free sintered bearings are usually used. Liquid lubricants are easy to spread because of their high wettability, and when used in small precision machines such as cameras, it is necessary to take measures to prevent the oil from spreading, such as applying an oil repellent treatment to the surface of the system material as necessary. Yes.

  Furthermore, in office equipment such as printers, facsimiles, and copiers, there are many bearing systems with relatively low speed rotation, but since there are many bearings, the energy saving effect due to low friction is high. It is conceivable that energy saving by reducing friction of sliding parts can be dealt with by reducing the viscosity of liquid lubricating oil. However, low-viscosity oil is not only prone to system contamination and evaporation loss due to oil leakage, but also lubrication. There was a limit to lowering the viscosity because the ability to form an oil film at the site decreased and poor lubrication occurred.

  Therefore, it is conceivable to use a semi-solid gel grease for this kind of application, for example, a lubricant impregnated in a sintered oil-impregnated bearing, which is excellent in terms of preventing system contamination. However, general grease often cannot be impregnated even when heated to a high temperature.

It has been proposed to use an amino acid-based gelling agent as the contact grease (see Patent Document 1). However, since non-aqueous gelling agents are required to have optical activity, there are not many types of gelling agents that are put into practical use in terms of ease of purification and cost (see Non-Patent Document 1). The triamide compound, which is one of the few non-aqueous gelling agents, is not very good in lubrication performance, so there is a problem that a gel-like lubricant showing sufficient low friction properties cannot be obtained by adjusting the type and concentration of the triamide compound alone. .
In addition, a lubricating composition characterized by blending a wax component such as paraffin wax or beeswax into a liquid lubricating oil has been proposed (see, for example, Patent Document 2). However, although oil leakage can be prevented by blending the wax component, there is a problem that the frictional properties do not have sufficient performance.
Japanese Unexamined Patent Publication No. Sho 63-221198 JP-A-10-246230 Kenji Ei, et al .: “Surface”, Vol.36, No.6, 291-301, 2003

  The present invention solves the above problems, and the object of the present invention is a semi-solid gel like the grease in the use bulk temperature range, but not only can be easily impregnated into the sintered oil-impregnated bearing but also realized with the grease. It is an object of the present invention to provide a gel-like lubricant composition that has outstanding low friction characteristics and exhibits significant energy saving performance.

  The present inventors can prevent oil leakage because a semi-solid gel similar to grease can be obtained by blending a predetermined amount of a higher fatty acid having a melting point of several tens to one hundred and ten degrees C. into a base oil. Once the adsorption film was formed, it was considered that the above problems could be solved all at once by utilizing the low friction characteristics of higher fatty acids in the temperature range below the melting point. As a result of intensive studies based on this idea, it was confirmed that the expected effect was exhibited, and the present invention was completed.

  The present invention comprises blending a higher fatty acid that produces a uniform gel into a mineral and / or synthetic liquid lubricating oil, and preferably 1 to 200 higher fatty acids per 100 parts by weight of the liquid lubricating oil. It is a gel lubricant composition containing parts by weight.

  The present invention is also a lubricant for sintered oil-impregnated bearings comprising the gel lubricant composition.

  The gel-like lubricant composition of the present invention is a semi-solid gel like the grease at the bulk temperature in the machine element as well as at room temperature, but it is not possible to achieve with the grease below the melting point of higher fatty acids. The low friction characteristics achieved by fatty acids enable a significant energy-saving design.

  The gel-like lubricant composition of the present invention contains a predetermined amount of a higher fatty acid in a liquid lubricating oil, and is stirred naturally at a temperature about 5 to 10 ° C. higher than the highest melting point of the fatty acid, and then naturally cooled. Can be obtained.

As the liquid lubricating oil used in the present invention, any of mineral oils, synthetic oils, or mixtures thereof can be used as long as they are usually used as lubricating oils. The physical properties of the lubricating oil, kinematic viscosity at 40 ° C. can be used those 3~500mm ² / s, it is more preferable in 8~100mm ² / s. Furthermore, it is preferable that the viscosity index is 90 or more, the pour point is −10 ° C. or less, and the flash point is 150 ° C. or more. In the case of a mixture, as long as the mixture satisfies the above physical properties, it can be used even if the oil before mixing deviates from the above physical properties other than the flash point.

  Mineral oil-based lubricating oil is generally a base oil that is a distillate obtained by subjecting crude oil to atmospheric distillation or further distillation under reduced pressure by various refining processes. It is prepared by blending various additives. The refining process includes hydrorefining, solvent extraction, solvent dewaxing, hydrodewaxing, sulfuric acid washing, clay treatment, etc., and these are combined in an appropriate order for treatment, thereby providing a mineral oil-based lubrication suitable for the present invention. An oil base oil can be obtained. A mixture of a plurality of refined oils having different properties obtained by combining different crude oils or distillate oils with different process combinations and sequences can also be used as a suitable base oil.

  Synthetic oil-based lubricating oils with high heat resistance such as poly-α-olefin (PAO), low molecular weight ethylene / α-olefin copolymer, fatty acid ester, silicone oil, fluorinated oil, alkylnaphthalene, etc. as base oil It can be used as it is or by blending various additives and the like.

  The higher fatty acid in the present invention has a monovalent or higher carboxylic acid group, the alkyl group is linear and / or branched, and has 7 to 30 carbon atoms, preferably from the viewpoint of availability and cost. 8 or more and 24 or less are desirable. For example, octanoic acid, decanoic acid, lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid and the like can be mentioned.

  The amount of higher fatty acid blended in the liquid lubricating oil is preferably in the range of 1 to 200 parts by weight with respect to 100 parts by weight of the liquid lubricating oil. When the amount is 1 part by weight or more, sufficient low friction characteristics can be obtained, and when the amount is 200 parts by weight or less, the amount of liquid lubricant in the sliding portion can be sufficiently maintained, and an increase in friction can be prevented.

  Further, the lubricant composition of the present invention contains additives commonly used in lubricating oils such as antioxidants, antiwear agents, rust inhibitors, pour point depressants, metal deactivators, and antifoaming agents. Needless to say, it can be contained if necessary.

  EXAMPLES Hereinafter, although this invention is demonstrated in detail based on an Example, this invention is not limited to an Example.

The following liquid lubricants, higher fatty acids, and waxes were mixed in the proportions shown in Table 2 to prepare lubricant compositions of Examples and Comparative Examples.
1. Liquid lubricating oil The liquid lubricating oil having the properties shown in Table 1 was used. This lubricating oil is pre-mixed with a predetermined amount of an additive such as an antioxidant, and has basic performance (such as antioxidant properties) as a lubricating oil.

2. Higher fatty acid stearic acid [melting point: 70 ° C]
Behenic acid [melting point: 80 ° C]

3. Wax (comparative example)
Paraffin wax [Melting point: 95 ° C]

4). Test method The above liquid lubricating oil, higher fatty acid, and wax are blended in the proportions (weight ratio) shown in Table 2, heated to the melting point or higher, and after stirring, confirmed to be uniformly dissolved, cooled to room temperature, The lubricant compositions of Examples and Comparative Examples were prepared. These prepared lubricant compositions were subjected to state observation and consistency tests by the following test methods, and were further impregnated into bronze-based sintered oil-impregnated bearings to measure and compare their friction characteristics. As a reference example, a commercially available Li-based grease No. 2 was also tested in the same manner.

(State observation)
Whether the lubricant composition prepared by heating and dissolving the liquid lubricating oil and higher fatty acid maintains a uniform gel form from the appearance after one day has passed, is not layer-separated, or has higher fatty acid not precipitated? Etc. were confirmed visually.

(Consistency)
Based on JIS K2220, the immiscible penetration was measured with a 1/4 penetration meter.

(Impregnation and friction characteristics of sintered bearings)
The gel-like lubricant composition was dissolved by heating to the melting point or higher, and impregnated into a bronze-based sintered oil-impregnated bearing [inner diameter: 4.007 mm] under vacuum. The oil content is about 20% by mass. A steel shaft [outer diameter 3.994 mm] was passed through the impregnated bearing material, a load [3.7 kgf / cm ² ] was applied from above, and a sliding test was performed at rotation speeds of 100 rpm and 4000 rpm. The friction characteristics were evaluated by the friction coefficient. The experiment was performed three times at room temperature, and the average value of the friction coefficient that became steady was recorded. Further, the time (familiar time) at which the friction coefficient at 100 rpm becomes steady was also measured.

5. Test results Examples, comparative examples and reference examples are shown in Table 2. All the examples in which a higher fatty acid was blended with a base oil to prepare a gel composition formed a uniform gel. Furthermore, since these gel-like compositions are semi-solid having an appropriate consistency, they were confirmed to be effective in preventing oil leakage as compared with a liquid base oil alone. In addition, the friction characteristics are also superior to those of the base oil alone, and it can be seen that a particularly excellent reduction in friction can be realized by adding a higher fatty acid.
Further, Comparative Example 2 containing 20 parts by weight of paraffin wax was a uniform gel. About the Example and the comparative example, the sliding test in the bearing which carried out the vacuum impregnation to the sintered bearing was implemented. As a result, it can be seen that by adding higher fatty acids, the friction coefficient is greatly reduced as shown in Examples 1 to 4, as compared with the case of only the base oil of Comparative Example 1. On the other hand, in the case of the paraffin wax of Comparative Example 2, the friction coefficient is lower than that of the base oil in the low speed range, but not as low as that of the higher fatty acid (Example). The coefficient of friction was much larger than that of the examples, and practically sufficient friction characteristics were not obtained. In addition, the commercially available Li-based grease shown as a reference example was a uniform gel, but it did not show thermoreversibility, and separation of oil and soap components was recognized by heating, and vacuum impregnation into sintered bearings in a uniform state I couldn't.

The gel-like lubricant composition of the present invention hardly causes oil leakage, can reduce the friction of sliding parts, and is used as a lubricant for sintered oil-impregnated bearings of various general machines such as automobiles and precision machines. Applicable.

Claims (3)

  A gel-like lubricant composition in which a higher fatty acid is blended with a mineral oil-based and / or synthetic liquid lubricant.   The gel lubricant composition according to claim 1, wherein 1 to 200 parts by weight of a higher fatty acid is blended with 100 parts by weight of the liquid lubricating oil.   A lubricant for sintered oil-impregnated bearings comprising the gel-like lubricant composition according to claim 1 or 2.