JP2014091762A - Sliding grease composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide means capable of substantialLy preventing or reducing the seizure, excessive wear and/or the increase of friction force, and the like of a slide part even in a boundary lubrication region to a mixed lubrication region, particularly, in an ordinary temperature environment.SOLUTION: Provided is a sliding grease composition comprising: a base oil; and a porous organic fiber having opening holes at the surface, in which the average fiber size lies in the range of 0.2 to 5 μm, the average fiber length lies in the range of 5 to 50 μm, the average diameter of the opening holes lies in the range of 5 to 100 nm, and the percentage of the area of the opening holes to the total surface area of the organic fiber lies in the range of 1 to 10%.

Description

  The present invention relates to a sliding grease composition.

  Sliding grease used in automobiles usually contains a base oil and a thickener. Examples of the thickener contained in the sliding grease include soap-based materials and non-soap-based materials. As the soap material, for example, lithium soap or the like is used. As the non-soap material, for example, an inorganic material such as silica powder, titania, alumina, or carbon fiber is used in addition to an organic material such as a diurea compound or fluorine powder. These thickeners usually have a smooth surface and are not porous.

  For example, Patent Document 1 is a lubricant composition containing a thickener and fine particles, wherein the lubricant is a combination of silica and another thickener as a thickener. The agent composition is described. The reference describes, as thickeners other than silica, inorganic non-soap materials such as bentonite and boron nitrite, diurea compounds, allyl urea compounds, polyurea compounds, phthalocyanine compounds, terephthalamate compounds, Organic non-soap materials such as Len and Ameline are described.

  Patent Document 2 describes the composition of the content of the conductivity-imparting additive in a conductive grease composition containing a base oil, a conductivity-imparting additive, a dispersant, and inorganic compound fine particles having an average particle size of 2 μm or less. 0.1 to 10% by mass of the total, the content of the dispersant is 0.1 to 10% by mass of the entire composition, and the content of the inorganic compound fine particles is 0.05 to 7% by mass of the total composition. A functional grease composition is described. This document describes that urea compounds or metal soaps are preferred as thickeners.

  In addition to the base oil and the thickener, the sliding grease may contain an additive such as an extreme pressure agent or an antiwear agent as a means for maintaining or improving the sliding characteristics. Examples of the additive include an S-based additive, a P-based additive, and a Mo-based additive.

JP 2005-47938 A Japanese Patent Laid-Open No. 2004-123954

  The above-mentioned additives contained in the sliding grease maintain or improve the sliding characteristics by a chemical reaction. For this reason, the effect is remarkably exhibited only in a high temperature region (for example, 40 to 120 ° C.) where the chemical reaction proceeds rapidly. When sliding grease is used in a room temperature (for example, about 30 ° C.) environment, the chemical reaction proceeds only moderately. Therefore, in the normal temperature environment, the effect of maintaining or improving the sliding characteristics by the additive is limited.

  When the sliding grease is used in the boundary lubrication region to the mixed lubrication region, the oil film layer is not formed at all in the sliding portion, or the oil film layer is formed only in a part of the sliding portion. For this reason, if sliding continues in the above-mentioned lubrication region, seizure of the sliding portion, excessive wear and / or increase in frictional force may occur. For example, thickeners of inorganic materials such as silica, titania or alumina have high hardness. For this reason, when a sliding grease containing these thickeners is used in the boundary lubrication region to the mixed lubrication region, the thickener acts as a foreign substance (abstractive action), and seizure of the sliding portion is excessive. The possibility of occurrence of wear and / or increased frictional force is further increased. In addition, although carbon fiber thickeners include porous carbon fibers, porous carbon fibers have low rigidity. For this reason, when a sliding grease containing such porous carbon fiber as a thickener is used in the lubricating region, the fiber structure may be destroyed by the high surface pressure of the sliding portion. .

  Therefore, the present invention provides means capable of substantially preventing or reducing seizure of the sliding portion, excessive wear and / or increase in frictional force even in the boundary lubrication region to the mixed lubrication region, particularly in a room temperature environment. The purpose is to do.

  As a result of various studies on means for solving the above-mentioned problems, the present inventor has optimized the shape and material of the thickener contained in the sliding grease to thereby determine the shear stability and seizure of the sliding grease. The inventors have found that the characteristics can be improved and completed the present invention.

  That is, the gist of the present invention is as follows.

  (1) Base oil and porous organic fibers having open pores on the surface, the average fiber diameter is in the range of 0.2 to 5 μm, the average fiber length is in the range of 5 to 50 μm, A sliding grease composition comprising the organic fiber having an average diameter in the range of 5 to 100 nm and a percentage of the area of the open pores in the range of 1 to 10% with respect to the total surface area of the organic fiber.

  (2) The sliding grease according to (1), wherein the organic fiber is a polyester fiber selected from the group consisting of polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, and polybutylene naphthalate. Composition.

  According to the present invention, it is possible to provide means capable of substantially preventing or reducing seizure of a sliding portion, excessive wear and / or increase in frictional force even in a boundary lubrication region to a mixed lubrication region, particularly in a normal temperature environment. It becomes possible.

FIG. 1 is a diagram showing test results of seizure characteristics of greases of Examples 1 to 4 and Comparative Examples 1 to 9.

<1. Sliding grease composition>
The present invention relates to a sliding grease composition containing a base oil and organic fibers.

  The organic fiber contained in the sliding grease composition of the present invention needs to be a porous organic fiber having an open hole on the surface. The inventor has improved the seizure characteristics of the sliding grease by using a porous organic fiber having a specific shape having an open hole on the surface as a thickener contained in the sliding grease. I found out that I could do it. The reason why the sliding grease composition of the present invention exhibits high seizure characteristics can be explained as follows. In addition, the effect of this invention is not limited to the following principles. The porous organic fiber having an open hole on the surface thereof contained in the sliding grease composition of the present invention can retain the base oil inside the open hole existing on the surface. In the boundary lubrication region to the mixed lubrication region, the organic fiber holding the base oil inside the open hole is elastically deformed by coming into contact with the sliding member. At this time, the base oil held inside the open hole is leached and supplied to the surface of the sliding member. Thereafter, when the contact with the sliding member is released, the elastically deformed organic fiber recovers its original shape. At this time, since the pressure inside the open hole is lowered, the base oil is filled inside the open hole. Thereby, the organic fiber can hold | maintain base oil again inside an open hole. In this way, the sliding characteristics are maintained by the continuously supplied base oil, and as a result, high seizure characteristics can be exhibited.

  The seizure characteristics of the sliding grease composition are not limited, but can be evaluated by, for example, a ball-on-plate test using an SRV friction and wear tester.

  The organic fiber contained in the sliding grease composition of the present invention needs to have an average fiber diameter in the range of 0.2 to 5 μm. The average fiber diameter of the organic fibers is preferably in the range of 1 to 5 μm. When the average fiber diameter is 0.2 μm or more, the fiber strength of the organic fiber is increased. For this reason, the stability with respect to the mechanical shear by sliding improves. When the shear stability of the organic fiber is improved, cutting of the organic fiber due to mechanical shearing is substantially prevented or suppressed. Therefore, as a result, a rapid change in consistency of the sliding grease composition can be prevented or suppressed. When the average fiber diameter is 5 μm or less, the thickening effect of retaining the base oil between the organic fibers becomes high. For this reason, even if it is a case where external forces, such as a centrifugal force, act, for example, the phenomenon which an organic fiber and base oil isolate | separate can be suppressed.

  The average fiber diameter of the organic fiber is not limited, but is determined by, for example, observing the organic fiber with a scanning electron microscope (SEM) and averaging measured values of several fiber diameters. be able to.

  The shear stability of the sliding grease composition is not limited, but can be evaluated by, for example, a sliding test using a four-ball frictional wear tester.

  The organic fiber contained in the sliding grease composition of the present invention needs to have an average fiber length in the range of 5 to 50 μm. The average fiber length of the organic fibers is preferably in the range of 20 to 50 μm. When the average fiber length is 5 μm or more, the thickening effect for retaining the base oil between the organic fibers becomes high. For this reason, even if it is a case where external forces, such as a centrifugal force, act, for example, the phenomenon which an organic fiber and base oil isolate | separate can be suppressed. When the average fiber length is 50 μm or less, organic fibers can be dispersed substantially uniformly in the sliding grease composition without being unevenly distributed. For this reason, even if it is a case where external forces, such as a centrifugal force, act, for example, the phenomenon which an organic fiber and base oil isolate | separate can be suppressed. Further, when the average fiber length is 50 μm or less, stability against mechanical shear due to sliding is improved.

  The average fiber length of the organic fibers is not limited, but is determined by, for example, observing the organic fibers with a scanning electron microscope (SEM) and averaging measured values of several fiber lengths. be able to.

  The organic fiber contained in the sliding grease composition of the present invention needs to have an average diameter of open holes in the range of 5 to 100 nm. The average diameter of the open holes of the organic fibers is preferably in the range of 30 to 100 nm. When the average diameter of the open holes is 5 nm or more, an effective amount of base oil can be retained inside the open holes. For this reason, the base oil can be leached by the elastic deformation of the organic fiber and supplied to the surface of the sliding member. In addition, when the average diameter of the open holes is 100 nm or less, the fiber strength of the organic fiber is increased. For this reason, the stability with respect to the mechanical shear by sliding improves.

  In addition, although the average diameter of an open hole is not limited, For example, it can determine with the following method. The surface of the organic fiber is photographed at a magnification of 10,000 to 30,000 times using a scanning electron microscope (SEM). The SEM image of the surface of the obtained organic fiber is analyzed using image processing software. An open hole existing in the SEM image is detected as a pseudo circle, and the diameter of the pseudo circle is recorded as the diameter of the open hole. Of the open holes, those not detected as pseudo circles by the software may be measured by measuring the dimensions in the X direction and the Y direction and recording the average of both dimensions as the diameter of the open holes. By averaging the values thus recorded, the average diameter of the open holes is determined.

  The organic fiber contained in the sliding grease composition of the present invention preferably has an average diameter of open holes of 1/10 or less with respect to the average fiber diameter, more preferably 1/40 or less, Particularly preferred is / 50 or less. When the average diameter of the open holes satisfies the above ratio, stability against mechanical shear due to sliding is improved.

  The organic fiber contained in the sliding grease composition of the present invention has a percentage of the area of the open pores relative to the total surface area of the organic fibers (hereinafter also referred to as “pore area ratio”) in the range of 1 to 10%. It is necessary to be. The pore area ratio is preferably in the range of 5 to 10%. When the pore area ratio is 1% or more, an effective amount of base oil can be retained inside the open pores. For this reason, the base oil can be leached by the elastic deformation of the organic fiber and supplied to the surface of the sliding member. Further, when the pore area ratio is 10% or less, the fiber strength of the organic fiber is increased. For this reason, the stability with respect to the mechanical shear by sliding improves.

  In addition, although the total surface area of an organic fiber is not limited, For example, it can calculate based on the average fiber diameter and average fiber length of this organic fiber determined by the means demonstrated above. Moreover, the area of the open hole is not limited, but can be calculated based on the average diameter of the open hole determined by the means described above, for example.

  As explained above, the sliding grease composition of the present invention exhibits high shear stability and seizure characteristics because the base oil held inside the open hole is leached by elastic deformation of the organic fiber, This is considered to be caused by being supplied to the surface of the sliding member. Therefore, the organic fiber contained in the sliding grease composition of the present invention is a porous organic fiber capable of expressing the above-described effects, for example, various materials usually used as a thickener in the technical field. Porous organic fibers can be used. Examples of the organic fibers include, but are not limited to, for example, polyester fibers, polyurethane fibers, nylon fibers (Japanese Patent Laid-Open No. 2-175965), polyphenylene sulfide fibers, or porous organic fibers made of copolymers thereof. Can be mentioned. The organic fiber is a polyester fiber selected from the group consisting of polyethylene terephthalate (PET), polytrimethylene terephthalate (PTT), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), and polybutylene naphthalate (PBN). It is preferable that it is a PET fiber, and more preferably a PET fiber.

  The base oil contained in the sliding grease composition of the present invention is not particularly limited, and a base oil usually used in the technical field can be used.

  The sliding grease composition of the present invention preferably contains 70 to 90% by volume of the base oil based on the total volume. Moreover, it is preferable to contain 5-20 volume% organic fiber with respect to the total volume. When the base oil and the organic fiber are contained in the above ranges, the shear stability and seizure characteristics of the sliding grease composition can be improved.

  The sliding grease composition of the present invention can be produced using a method usually used in the art. The porous organic fiber material used as a thickener is, for example, melt-spun the resin raw material together with an open pore forming agent such as a hot water soluble polymer, and then removing the open pore forming agent to obtain a continuous porous material. A spun product may be prepared, or a porous long-fiber product made of the resin raw material may be purchased and prepared. Next, after freezing the porous organic fiber material, the frozen material is pulverized by pulverizing means (for example, several types of falling spheres having different masses and / or materials) set in several stages of conditions. A porous organic fiber having the following shape can be prepared. Then, the sliding grease composition of this invention can be obtained by mixing the said porous organic fiber and base oil.

  As described above, the sliding grease composition of the present invention can exhibit high shear stability and seizure characteristics even in a boundary lubrication region to a mixed lubrication region, particularly in a room temperature environment. Therefore, by using the sliding grease composition of the present invention as a lubricant for automobiles and the like, it is possible to substantially prevent or reduce seizure of the sliding portion, excessive wear and / or increase in frictional force, etc. Become.

  Hereinafter, the present invention will be described more specifically with reference to examples. However, the technical scope of the present invention is not limited to these examples.

<I: Preparation of grease>
[Example 1-3 and Comparative Example 1-8]
PET powder (Mitsui Pet; manufactured by Mitsui Chemicals) and hot water soluble polymer (Paogen PP-15; manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) are mixed at a specific ratio and 275 using a twin screw extruder kneader (HK25D; Parker Corporation). A polymer alloy was prepared by melt-kneading at ° C. Next, the polymer alloy is melt-spun while changing the melting part temperature (270 to 275 ° C.), the spinning temperature (250 to 275 ° C.) and the discharge amount (drawing amount) (5 to 10 m / min) within the above ranges. did. The obtained polymer alloy fiber was immersed in hot water at 100 ° C. for 2 hours to remove the hot water-soluble polymer contained in the fiber. As a result, porous PET fibers having open pores on the surface were obtained. The obtained PET fiber was frozen using liquid nitrogen. Using a freeze pulverizer (JFC-300; manufactured by Nihon Analytical Industrial Co., Ltd.), the obtained frozen PET fibers were pulverized with several types of falling balls having different masses to obtain PET fibers having a predetermined shape. The obtained PET fibers were added to a base oil (PAO10; manufactured by INEOS) so as to have a content of 10% by volume with respect to the total volume to prepare greases of Examples and Comparative Examples.

[Example 4]
The sliding grease composition of the present invention was prepared using a commercially available polyester fiber (Welky; manufactured by Teijin) having an open hole on the surface. The polyester fiber was freeze-ground by the same procedure as in Example 1-3 to obtain a polyester fiber having a predetermined shape. The obtained polyester fiber was added to a base oil (PAO10; manufactured by INEOS) so as to have a content of 10% by volume with respect to the total volume to prepare a grease of Example 4.

[Comparative Example 9]
This is a comparative example of a sliding grease of the prior art containing a diurea compound as a thickener, like the lubricant composition described in Patent Document 1.

  A diurea compound was prepared by reacting 2 mol (129 g) of amine (octylamine; manufactured by Tokyo Chemical Industry Co., Ltd.) and 1 mol (125 g) of isocyanate (diphenylmethane-4,4-diisocyanate; manufactured by Nikka Trading). . The obtained diurea compound was added to 2000 g of base oil (PAO10; manufactured by INEOS) to a content of 10% by volume with respect to the total volume. The obtained mixture was subjected to shearing using a shell roll tester (870-02; Co., Ltd.) and the grease of Comparative Example 9 containing a diurea compound having an average fiber length of 21 μm as a thickener. Prepared.

<II: Organic fiber shape analysis>
The shapes of the organic fibers contained in the greases of Examples 1 to 4 and Comparative Examples 1 to 9 were analyzed. The surface of the organic fiber used for the preparation of each grease was photographed at a magnification of 10,000 to 30,000 times using a scanning electron microscope (SEM) (JSM-6610; manufactured by JEOL). The SEM image of the surface of the obtained organic fiber was analyzed using image processing software (WINROOF; Mitani Corp.). Among the open holes present in the SEM image, those detected as pseudo circles by the software were recorded as the diameter of the open holes. Of the open holes, those not detected as pseudo circles by the software were measured for the dimensions in the X and Y directions, and the average of both dimensions was recorded as the diameter of the open holes. The processing was only performed on open holes capable of measuring 1 nm or more among open holes existing in the SEM image.

  Table 1 shows the shapes of the organic fibers contained in the greases of Examples 1 to 4 and Comparative Examples 1 to 9 obtained by the shape analysis. In the table, the pore area ratio means the percentage of the area of the open pores with respect to the total surface area of the organic fibers.

<III: Performance evaluation of grease>
[Measurement test of shear stability]
The shear stability measurement test was performed according to the following procedure. The grease to be tested was filled in a test holder of a four-ball friction and wear tester (Shinko Engineering Co., Ltd.), and a sliding test was conducted under the conditions of 50 N load, room temperature, and 1 hour. Thereafter, the grease was collected from the test holder, and the consistency after the sliding test was measured using a consistency meter (800M-01; Co., Ltd.). Compared to the pre-measured consistency before the sliding test, “○” indicates that the consistency after the sliding test has not substantially changed, and “△” indicates that the consistency after the sliding test has increased. The case where the consistency after the sliding test was remarkably increased (viscosity decreased) was evaluated as “x”.

  Table 2 shows the measurement test results of the shear stability of the greases of Examples 1 to 4 and Comparative Examples 1 to 9.

  As shown in Table 2, the greases of Examples 1 to 4 did not substantially change the consistency before and after the sliding test. Therefore, it was revealed that the greases of Examples 1 to 4 have high shear stability. In contrast, when the average fiber diameter of the polyester fiber is thin (Comparative Example 1), when the average fiber length of the polyester fiber is long (Comparative Example 4), when the average diameter of the open holes of the polyester fiber is large (Comparative Example 6) When the open pore area ratio of the polyester fiber was large (Comparative Example 8), the shear stability was lowered. Further, when the average fiber diameter of the polyester fiber was large (Comparative Example 2) and when the average fiber length of the polyester fiber was short (Comparative Example 3), the shear stability was slightly lowered.

[Baking characteristics test]
The seizure characteristic test was performed according to the following procedure. Apply the grease to be tested to the sliding part of the SRV friction and wear tester (SRV4; manufactured by Optimol), and increase the test load while maintaining the test frequency of 50 Hz, test amplitude of 5 mm, and room temperature. A ball-on-plate test was performed. The test was terminated when seizure occurred, and the test load at that time was recorded as “seizure load”. The seizure load when measured using the grease of Comparative Example 9 was taken as 1, and the index for that value was calculated as the “seizure load index”.

  The test results of the seizure characteristics of the greases of Examples 1 to 4 and Comparative Examples 1 to 9 are shown in FIG.

  As shown in FIG. 1, the greases of Examples 1 to 4 have a seizure characteristic of 40 to 60% as compared with the grease of Comparative Example 9 which is a sliding grease of the prior art containing a diurea compound as a thickener. Improved. On the other hand, the polyester fiber is contained as a thickener, but the average fiber diameter, the average fiber length, the average diameter of the open holes and / or the open hole area ratio of the polyester fibers is not included in the predetermined range. The grease exhibited a seizure characteristic substantially the same as or lower than that of Comparative Example 9.

  As described above, the sliding grease composition of the present invention exhibits high seizure characteristics because the base oil is held inside the open holes present on the surface of the organic fiber contained as the thickener. I think that. In the boundary lubrication region to the mixed lubrication region, the organic fiber holding the base oil inside the open hole is elastically deformed by coming into contact with the sliding member. At this time, the base oil held inside the open hole is leached and supplied to the surface of the sliding member. Since the sliding characteristics are maintained by the base oil supplied in this manner, it is considered that high seizure characteristics are exhibited as a result.

Claims (2)

  Base oil and porous organic fibers having open pores on the surface, the average fiber diameter is in the range of 0.2 to 5 μm, the average fiber length is in the range of 5 to 50 μm, and the average diameter of the open pores is A sliding grease composition comprising the organic fiber in a range of 5 to 100 nm and a percentage of the area of the open pores in the range of 1 to 10% with respect to the total surface area of the organic fiber. 2. The sliding grease composition according to claim 1, wherein the organic fiber is a polyester fiber selected from the group consisting of polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, and polybutylene naphthalate.

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