JPH0522733B2 - - Google Patents

Description

[Detailed description of the invention]

(1) Industrial Application Field The present invention relates to a conductive sliding material composition that has a low coefficient of friction, excellent wear resistance, and at the same time low volume resistivity. (2) Conventional technology It is well known that fluorine resins (particularly tetrafluoroethylene resins) are widely used as various engineering plastics in applications that require low friction coefficients, heat resistance, chemical resistance, etc. However, this resin has poor abrasion resistance and compression creep resistance, so various fillers must be used together, and the resin ^itself has excellent electrical insulation properties, so It has characteristics such as exhibiting volume resistivity. Recently, with the rapid progress of office mechanization, there has been a strong demand for sliding materials that have both sliding properties and excellent conductivity. Materials containing fillers such as graphite, conductive carbon, metal powder, and metal fibers have been developed for the purpose of improving wear resistance and imparting electrical conductivity. However, although materials to which graphite and conductive carbon are added have good sliding properties, their volume resistivity is only about 10 ¹ to ^{10 2} Ω·cm, which is not a desirable material. In addition, powders of gold, silver, copper, aluminum, nickel, etc. are used as metal powders, and although gold and silver are chemically stable and highly conductive, they are extremely expensive, so copper powder is often used. , aluminum, nickel, etc. are used. However, copper and aluminum are easily oxidized at the molding temperature of tetrafluoroethylene resin, and the conductivity of products to which they are added becomes unstable, so they are not suitable as conductivity imparting materials for tetrafluoroethylene. On the other hand, nickel powder is relatively stable, and although the product obtained by adding it to tetrafluoroethylene resin has good conductivity and stability, its wear resistance is extremely poor. Furthermore, even if metal fibers such as brass fibers and aluminum fibers are commercially available, they are not only easily oxidized and undesirable as a material like the powdered ones, but most of the commercially available ones have a diameter of 60 μm. It has a large length of 3 mm, and if used as a filler for a sliding material, it would protrude from the surface of the material and damage the surface of the other material, so it cannot be said to be a desirable material. For this reason, the inventor coated a lubricating material with metal and filled it into tetrafluoroethylene resin in as large a quantity as possible to conduct an experiment to confirm its properties, but good conductivity was not obtained. I couldn't help it. (3) Problems to be solved by the invention As is clear from the above, graphite and conductive carbon are added to tetrafluoroethylene resin to improve wear resistance and provide excellent conductivity. ,
Filling with metal powder, metal fiber, etc. each has serious drawbacks, and the conventional techniques cannot satisfy the strong demands of the public. (4) Means for Solving the Problems In order to solve the above problems, the present invention proposes to reduce the volume of the solid lubricant whose surface is coated with nickel and the carbon fibers to 100 parts by volume of tetrafluoroethylene resin. Mixtures with ratios ranging from 15:80 to 80:20,
The present invention provides a conductive sliding material composition characterized in that 30 to 150 parts by volume is added thereto, the details of which will be described below. The tetrafluoroethylene resin in this invention is a polymer of tetrafluoroethylene, and is a type of fluororesin commercially available under registered trademarks such as Algoflon, Teflon, Fluon, and Polyflon.
It is a resin that does not absorb water, is non-flammable, extremely stable against strong acids, strong alkalis, and organic solvents, and has good heat resistance such that decomposition usually occurs at temperatures above 400°C, so it is normally used in the same way as powder metallurgy. In the method of
Powdered resin is placed in a mold and pressure is gradually applied (100~
600Kg/cm ² ), molded, and then fired at around 350 to 380°C. Here, if a pre-formed product is pressurized at room temperature and sintered under normal pressure, the resulting compact will have a low packing density and a high volume resistivity. It is desirable to perform both heating and heating at the same time. Next, the solid lubricant of this invention whose surface is coated with nickel (hereinafter referred to as nickel coating material) is not particularly limited in type as long as it is conductive, but the surface is coated with nickel by electroless plating. Examples include mica coated with (for example, a Mitsubishi Metals product), graphite, and aromatic polyamide fibers. Furthermore, the carbon fibers in this invention play the role of improving wear resistance and creep resistance, but are also used for the purpose of increasing the overall electrical conductivity by contacting the dispersed nickel coating material. It goes without saying that the carbon fiber itself must have good conductivity, but when a higher degree of conductivity is required, carbon fiber coated with metal (for example, nickel) (for example, Toho Beslon) is required. You can also use products such as
In this invention, from the viewpoint of ease of mixing, molding, etc. and prevention of protrusion from the molding surface, the
A length of 20 μm or more, preferably 15 to 6 μm, and a length of 1 mm or less, preferably 0.3 to 0.02 mm, is generally a commercially available product such as Torayca MLD-30 manufactured by Toray Industries or Kureha Carbon Fiber M202S manufactured by Kureha Chemical Industry Co., Ltd. can be exemplified. In this invention, the compounding ratio of the tetrafluoroethylene resin, the nickel coating material, and the carbon fiber is shown in terms of volume ratio. This is because it is impossible and undesirable to express the composition of the present invention in a clear range if the compounding ratio is expressed as a weight ratio, since the weight is different even if the volume is the same. A method was adopted in which the true specific gravity was measured and the weight was divided by the true specific gravity. Here, the mixing ratio of the nickel coating material and carbon fiber is such that both conductivity and sliding properties can be achieved even if the nickel coating material is less than 15:80 or greater than 80:20. The ratio should preferably be within the range of 40:60 to 70:30. The reason why the mixture of nickel coating material and carbon fiber is mixed in an amount of 30 to 150 parts by volume, preferably 50 to 100 parts by volume, per 100 parts by volume of tetrafluoroethylene resin is that the mixture is more than 30 parts by volume. If the amount is less than 150 parts by volume, sufficient conductivity cannot be obtained, and if the amount is more than 150 parts by volume, the sliding properties may deteriorate or the molded product may become very brittle, which is undesirable. In order to make the dispersion of the nickel coating material and carbon fibers mixed with the tetrafluoroethylene resin as described above more uniform, it is desirable that the particle size of the tetrafluoroethylene resin is smaller, and the average particle size is usually 40μ.
There is no problem if it is less than m. A mixture of these three materials was placed in a mold and preformed at a pressure of 400 to 1000 kg/cm ² (higher than when using only tetrafluoroethylene resin, then returned to normal pressure and heated to 350 to 380°C. After that, pressurize again or heat while pressurizing to sufficiently sinter the particles, then cool and adjust the shape as necessary to meet the required dimensional stability and shape. By making adjustments, the desired molded product can be obtained. (5) Effect The conductive slide of the present invention in which the tetrafluoroethylene resin, the nickel coating material, and the carbon fibers are uniformly dispersed in the above-mentioned compounding ratio. The solid lubricant built into the nickel coating material also appears on the polished surface (sliding surface) of the animal composition. As a result, the solid lubricant helps improve lubricity, and at the same time the nickel coating layers form electrical paths in close contact with each other and the carbon fibers, contributing to increased electrical conductivity. (6) Examples Examples and comparative examples are shown below. Example 1 Tetrafluoroethylene resin (manufactured by Asahi Glass Co., Ltd.: Fluon
G163) phlogopite with an average particle size of 12 μm in 100 parts by volume,
Nickel coated mica with nickel electroless plating (manufactured by Mitsubishi Metals) 48 volume parts and carbon fiber with nickel plating on the surface (manufactured by Toho Veslon)
HTCF/Ni, fiber diameter 7.5 μm, fiber length 300 μm, average nickel film thickness 0.25 μm) was thoroughly mixed in a Henschel mixer, then filled into a cylindrical mold with an inner diameter of 30 mm, and the mixture was packed at 800 kg/cm ² It was preformed under pressure. The mold containing the preform was heated under normal pressure and held at 360° C. for 1 hour. After holding, a pressure of 800 Kg/cm ² was applied again, and the molded product was cooled as it was. Friction and wear tests and measurements of volume resistivity were attempted on the molded product obtained. Here, the friction coefficient is measured using a thrust type friction tester under the conditions of a sliding speed of 100 m/min and a load of 1 kg/ ^cm2 , and the wear coefficient is measured under the conditions of a sliding speed of 128 m/min and a load of 1.6 kg/ ^cm2 . A thrust type wear tester was used, and bearing steel SUJ-2 (quenched and ground) was used as the mating material in both cases.
The results obtained are summarized in Table 1.

[Table] Example 2 Example 1 except that 37 parts by volume of carbon fiber manufactured by Toray Industries, Ltd. with a fiber diameter of 7 μm and a fiber length of 30 μm was used.
A compression and heating molded body was obtained in exactly the same manner as described above.
This molded body was also subjected to friction and wear tests and volume resistivity measurements in the same manner as in Example 1, and the results are also listed in Table 1. Example 3 Compression heating was performed using the same raw materials and method as in Example 1, except that the mixing ratio of nickel-coated mica and carbon fiber was 73 parts by volume and 70 parts by volume, respectively, with respect to 100 parts by volume of tetrafluoroethylene resin. A molded body was obtained. Friction and wear tests and volume resistivity measurements were carried out on this molded body in the same manner as in Example 1, and the results are also listed in Table 1. Comparative Examples 1 to 3 The same tetrafluoroethylene resin as in Example 1, nickel-coated mica or nickel powder (manufactured by Inco, USA: Nickel Powder 255), and the same carbon fiber as in Example 2 were mixed at the blending ratio shown in Table 2. Since I did it

[Table] A compression and heating molded body was obtained in exactly the same manner as in Example 1 except for the following. These molded bodies were also subjected to friction and wear tests and volume resistivity measurements in the same manner as in Example 1.
The results are summarized in Table 3.

[Table] In order to clarify the properties of each of the molded bodies of Examples 1 to 3 and Comparative Examples 1 to 5 shown in Tables 1 and 3, especially the relationship between volume resistivity and wear coefficient, When each measured value is entered in a diagram with volume resistivity on the horizontal axis and wear coefficient on the vertical axis (both axes are on a logarithmic scale), the result is as shown in the figure. Here, 1 to 1 marked with □
3 indicates Examples 1 to 3, and 1 to 5 marked with an x indicate Comparative Examples 1 to 5, respectively. In the comparative examples, Comparative Example 1 has a significantly large wear coefficient even though the volume resistivity is low. , 2 and 5, or Comparative Examples 3 and 4, in which the volume resistivity was extremely high even though the wear coefficient was small, the expected properties were not obtained, but the results of Examples 1 to 3 were all It can be clearly seen that the material exhibits favorable performance in that the volume resistivity is low and the wear coefficient is also very small. (7) Effects The molded product obtained from the composition of the present invention has a low coefficient of friction unique to tetrafluoroethylene resin, and also has excellent wear resistance and conductivity due to the addition of a nickel coating material and carbon fiber. Since it is also endowed with properties, it is ideal for bearing materials that require both wear resistance and conductivity at the same time, and the significance of this invention can be said to be extremely large.

[Brief explanation of drawings]

The figure is a drawing showing the relationship between volume resistivity and wear coefficient of molded bodies obtained in Examples and Comparative Examples of the present invention. □...Example, ×...Comparative example.

Claims (1)

[Claims] 1 For 100 parts by volume of tetrafluoroethylene resin,
A conductive sliding material composition characterized by adding 30 to 150 parts by volume of a mixture of a solid lubricant whose surface is coated with nickel and carbon fiber in a volume ratio in the range of 15:80 to 80:20. .