JPS60137954A - Electrically conductive sliding material composition - Google Patents

Abstract

PURPOSE:To produce the titled composition imparted with electrical conductivity keeping excellent abrasion resistance of the base resin, by compounding a tetrafluoroethylene resin with a specific amount of a mixture of powdery nickel and carbon fiber at a specific ratio. CONSTITUTION:The objective composition is produced by compounding (A) 100pts.(vol.) of a tetrafluoroethylene resin having an average particle diameter of <=40mum with (B) 30-150pts., preferably 50-100pts. of a mixture of (i) flaky nickel powder or chain-like nickel powder consisting of amorphous particles having small cross-sectional area and (ii) carbon fiber having diameter of <=20mum, preferably 15-6mum and length of <=1mm., preferably 0.3-0.02mm., at a volume ratio (i/ii) of 15:80-80:20, preferably 40:60-70:30.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a conductive sliding material composition which is intended to have a low coefficient of friction, high wear resistance, and at the same time low volume resistivity.

It is well known that fluororesins (particularly tetrafluoroethylene resin) are widely used as various engineering plastics in applications that require a low coefficient of friction, heat resistance, chemical resistance, etc. However, this resin has poor abrasion resistance and compression creep resistance, so various fillers must be used in combination, and the resin itself has excellent electrical insulation properties and has a volume resistivity of 10'4 Ω・cm or more. It has the characteristic that it shows the rate.

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 containing graphite and conductive carbon have good sliding properties, their volume resistivity is 101 to 10.
It is only about 2Ω・(111Ω), so it cannot be said to be a preferable material. In addition, powders of gold, silver, copper, aluminum, nickel, etc. are used as metal powders, and gold and silver are chemically stable and have high resistance. Because they are conductive or extremely expensive, copper, aluminum, nickel, etc. are used for the chopsticks.However, copper and aluminum are easily oxidized at the molding temperature of tetrafluoroethylene resin, so these materials are not added. Since the conductivity of the product becomes unstable, it is not suitable as a conductivity improving material for tetrafluoroethylene.On the other hand, nickel powder is relatively stable and can be obtained by adding it to tetrafluoroethylene resin. Although the product has good conductivity and stability, its wear resistance is extremely poor.Furthermore, metal fJII
Even if brass fibers, aluminum fins, etc. are commercially available for K and Ilj, they are not only easily oxidized like the powdered ones mentioned above, making them undesirable materials, but also those that are normally commercially available. Most have a diameter of 60μ■
11. It has a large length of 3 mm, and is a filler for sliding materials (if used, it would protrude from the surface of the material and damage the surface of the mating material, so it is not a desirable material at all).

This invention was made in view of the current situation, and for 100 parts by volume of tetrafluoroethylene resin,
The present invention provides a conductive sliding material composition characterized in that 30 to 150 parts by volume of a mixture of nickel powder and carbon fiber having a volume ratio in the range of 15:80 to 80:20 is added.

The details will be described below.

The tetrafluoroethylene resin in this invention is a polymer of tetrafluoroethylene, including Alboflon, Teflon,
It is a type of fluororesin that is commercially available under registered trademarks such as Fluon and Polyfluoro.

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 so that decomposition usually occurs only at temperatures above 400'C. Powdered resin is put into a mold and gradually added (100 to 600 kg/ctn") using the method described in
) LT A method of firing at around 350 to 3'80°C after forming is adopted. Here, pressurize at room temperature,
If a preformed product is sintered under normal pressure, the resulting compact will have a low packing density and a high volume resistivity, so in this invention it is desirable to apply pressure and heat at the same time. .

Next, the shape of the nickel powder in this invention is not particularly limited as long as it has conductivity, but since it is desirable that the powder particles have good continuity even when added in a small amount, it is preferable to use a scaly shape. (for example, Nickel Powder 255 or 287 manufactured by Inco, Inc., USA) or chain-shaped particles composed of irregularly shaped particles with a small cross-sectional area (for example, Nickel Powder 255 or 287 manufactured by Inco, Inc.)
etc. can be said to be more preferable.

Furthermore, the carbon fibers in this invention play the role of improving wear resistance and creep resistance, but are used for the purpose of increasing the overall electrical conductivity by contacting the dispersed nickel powder. Therefore, it goes without saying that the carbon fiber itself needs to have good conductivity, but it also needs to have an even higher degree of conductivity. When n-electrification is required, metals (
It is also possible to use carbon fiber coated with nickel (for example, a product of Toho Bethlon Co., Ltd.). In this invention, from the viewpoint of ease of mixing, molding, etc. and prevention of protrusion from the molding surface, the carbon fiber has a diameter of 20 μm or less, preferably 15 to 6 μIn, and a length of 1 nm or less, preferably 0.3 to 3 nm.
A thickness of 0.02 mm is desirable, and commercial products such as Torayka MLD-39 (manufactured by Toshisha Co., Ltd.) and +1 (+1) manufactured by Kureha Chemical Industry Co., Ltd. (Kureno 1 Carbon Phino<-M2O2S) can be exemplified.

In this invention, the mixing ratio of the tetrafluoroethylene resin, nickel powder, and carbon fiber is shown in terms of volume ratio, but the reason for this is that in weight ratio, normal carbon fiber and metal-coated carbon fiber are different. This is because vehicles are significantly different, and the same volume has different weights, so expressing the compounding ratio by weight makes it impossible and undesirable to express the structure of this invention in a clear range. 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 nickel powder and carbon fiber is 80: even if the nickel powder is less than 15:80.
If the ratio is more than 20, it will not be possible to have both conductivity and sliding properties, so preferably 40:60 to 70:
It is recommended that it be within the range of 30. Such a mixture of nickel powder and carbon fiber is added in an amount of 30 to 150 parts by volume, preferably 50 to 1 part by volume, per 100 parts by volume of tetrafluoroethylene resin.
The reason for mixing 00 parts by volume is that if the mixture is less than 30 parts by volume, sufficient conductivity cannot be obtained, and if it is more than 150 parts by volume, the sliding properties may deteriorate or the molded product may become very difficult to obtain. This is because it becomes brittle, which is not desirable.

In order to uniformly disperse the nickel powder and carbon fibers mixed in the tetrafluoroethylene resin as described above,
The smaller the particle size of the tetrafluoroethylene resin is, the more desirable it is, and normally there will be no problem if the average particle size is 40 μm or less.

400~t with 1 cup of molded mixture of these kings
o o o kg/cm2 (4 people, higher than when using only fluorinated ethylene resin) pressure to preform, return to normal pressure, heat to 350 to 380°C, and pressurize again, or pressurize again. The desired molded body can be obtained by heating while pressing to sufficiently sinter the particles, then cooling and adjusting the shape as necessary to meet the required dimensional stability and shape. can get.

The resulting molded product has a low coefficient of friction unique to tetrafluoroethylene resin, and it also has good abrasion resistance and conductivity due to the addition of nickel powder and carbon fiber, so it has excellent abrasion resistance. χ1 of this invention is the most suitable bearing material for which the two functions of conductivity and conductivity are required at the same time.
It can be said that righteousness is extremely strong.

Examples and comparative examples are listed below.

[Example 1] Tetrafluoroethylene resin (manufactured by Asahi Glass Co., Ltd.: Fluo 70163
) 100 parts by volume (Nickel powder with ζ chain structure (US/I)
Co., Ltd. - Nickel Powder 255) 48 volume parts and carbon fiber with nickel plating on the surface (manufactured by Toho Isufu Co., Ltd.: I-I TCF, /Ni, fiber diameter 75 μm, fiber length 30 Q 7 cm, average nickel film II O, 25
After thoroughly mixing 37 parts by volume (μm) in a Henschel mixer, the mixture was filled into a cylindrical mold with an inner diameter of 3 Q 111111, and preformed under a pressure of 800 kg/c+n2. The mold containing the preform is heated under normal pressure to 360
It was kept at ℃ for 1 hour. Holds 800 kg,
A pressure of /c+n2 was applied, the molded product was cooled as it was, and friction and wear tests and volume resistivity measurements were performed on the molded product obtained. Here, 1〒 double friction coefficient is 100 m/m/m
min, load 1 kg/con (7) X Measured using a last type friction tester, and the wear coefficient is sliding speed
2 B nyinin, load L 6 kg/cm2 (
y) % using a thrust type abrasion tester), and bearing steel 5UJ-2 (quenched and ground) was used as the mating material for both cases.The obtained results are as follows. Summarized in one table
child.

Table 1 [Example 2] The carbon fiber is made by Toshisha Co., Ltd. and has a fiber diameter of 7 μm.

37 volume parts of the molded product having a length of 30 μm were used.A compression molding of P45 molding was performed in exactly the same manner as in Example 1.
% resistance test and body resistivity were measured.The results are also listed in Table 1.

[Example 3] As the nickel powder, 48 parts by volume of flaky nickel powder (Novamet Nickel ocA-'1, manufactured by I7 Co., Ltd. in the United States) was used, and as the carbon fiber, the same nickel powder manufactured by Toshi Co., Ltd. used in Example 2 was used. A compression and heating molded body was obtained in the same manner as in Example 1 except that 37 parts by volume of carbon fiber #fli was used. This molded body was also subjected to the friction abrasion test and measurement of volume resistivity in the same manner as in Example 1. The results are also listed in Table 1.

[Example 4] The same raw materials and method as in Example 1 were used, except that the mixing ratio of nickel powder 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 compression and heating 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 5) The same method as in Example 1 was carried out except that the same tetrafluoroethylene resin and nickel powder as in Example 1 and the same carbon fiber as in Example 2 were mixed in the proportions shown in Table 2. The compression and heating molded bodies are shown in Table 2.Friction and wear tests and volume resistivity measurements were also performed on these molded bodies in the same manner as in Example 1, and the results are summarized in Table 3.

Table 3 In order to clarify the properties of each of the molded bodies of Examples 1 to 4 and Comparative Examples 1 to 5 shown in Tables 1 and 3, particularly the relationship between volume resistivity and wear coefficient. , horizontal volume resistivity: l
'+b, and each measured value is entered in a drawing with the wear coefficient on the vertical axis (both axes are on a logarithmic scale), and the result is as shown in Fig. 1. Here, 1 to 4 marked with ○ indicate Examples 1 to 4, respectively, and 1 to 5 marked with X indicate Comparative Examples 1 to 5, respectively. However, the wear coefficient is significantly large (ratio (bite examples 2 and 3) or the wear coefficient is
Even if the L coefficient is small, the volume resistivity is extremely high (Comparative Example 1)
．． 4 and 5), the expected properties r↓ were not obtained, or the results of Examples 1 to 4 all showed favorable performance with low volume resistivity and low wear coefficient. Clearly J! I'm about to cum.

[Brief explanation of the drawing]

Figure 2 is a drawing showing the relationship between the volume resistivity and the wear coefficient of molded bodies obtained in Examples and Comparative Examples of the present invention. 1', )...Example, X/Comparative example

Claims (1)

[Claims] The volume ratio of nickel powder and carbon fiber to 100 parts by volume of tetrafluoroethylene resin is 15:80 to 80:20.
An electrically conductive sliding material composition, characterized in that 30 to 150 parts by volume of a mixture in the range of: