JPH0561305B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a conductive sliding material composition which aims to have a small coefficient of friction, excellent wear resistance, and at the same time a low volume resistivity. [Prior Art] In recent years, as electronic devices and electrical devices have become smaller and lighter, synthetic resins have come to be widely used for their parts. In particular, there was a strong demand for plastic sliding materials that had both sliding properties and electrical conductivity, and the aim was to use synthetic resin as a base material to improve wear resistance and impart electrical conductivity. As a result, materials containing fillers such as graphite, conductive carbon, metal powder, and metal fibers have been developed. However, when graphite or conductive carbon is added to a material, a volume resistivity of about 10 ¹ to ^{10 2} Ω·cm can be obtained, but when added to polyphenylene sulfide or the like, wear resistance is extremely poor. Furthermore, when adding metal powder, powders of gold, silver, copper, aluminum, nickel, etc. are used, but although gold and silver are chemically stable and highly conductive, they are extremely expensive. Therefore, copper and aluminum used as substitutes for these materials are easily oxidized during molding, and the resulting products have unstable conductivity, making them unsuitable as conductivity imparting materials. Further, nickel powder is chemically relatively stable, and although products obtained by adding it to synthetic resins have good conductivity and stability, their wear resistance is extremely poor.
In addition, metal fibers include brass fibers and aluminum fibers, but these are all easily oxidized like the powdered ones mentioned above, and most commercially available products are large, with a diameter of 60 μm and a length of 3 mm. When such large fibers are used as fillers for sliding materials, their ends may protrude beyond the surface of the material and damage the surface of the mating material, which is by no means desirable. As a result, the inventor tried to confirm the properties of a lubricating material by coating it with metal and filling it into a synthetic resin as much as possible, but he was unable to find the expected electrical conductivity. In addition, a composition was developed in which a combination of nickel powder or a coating material of nickel and carbon fiber was added to a polyolefin or an injection moldable fluororesin (for example, Japanese Patent Application No. 11361/1982, Japanese Patent Application No. 11360/1983).
Although these compositions have excellent sliding properties and good conductivity, injection moldable fluororesins are expensive to produce and are economically disadvantageous for use in office equipment. Moreover, even though polyolefins are inexpensive, their heat resistance is low and the environment in which they can be used is limited. Therefore, it cannot be said that any of them can be fully adapted to the demands of the market. [Problems to be solved by the invention] As described above, conventional conductive sliding material compositions have a small coefficient of friction, excellent wear resistance and conductivity, and have a wide range of service life and are inexpensive. There was a problem that needed to be solved: there was nothing that satisfied the various conditions. [Means for Solving the Problems] In order to solve the above problems, the present invention provides that, for 100 parts by volume of polyphenylene sulfide,
The capacity ratio of nickel-coated mica and carbon fiber is
A method is adopted in which the composition is added in a ratio of 15:80 to 80:20 in a total amount of 30 to 140 parts by volume. The details will be described below. First, polyphenylene sulfide (hereinafter abbreviated as PPS) in this invention has the following general formula: It is a synthetic resin shown by
It is marketed by Petroleum Corporation under the trademark "Ryton." The manufacturing method is US Patent No. 3354129
No. 45-3368 (corresponding patent No. 45-3368), according to which Ryton prepared p-dichlorobenzene and sodium disulfide in an N-methylpyrrolidone solvent at 160 to 250°C under pressure. It is produced by a reaction, and can be freely produced by subjecting the resin to various degrees of polymerization, from those with no cross-linking to those with partial cross-linking, by subjecting it to a post-heat treatment process. Therefore, it is possible to arbitrarily select and use those having melt viscosity characteristics suitable for the desired melt blend. Further, the nickel-coated mica in this invention is
The surface of mica powder such as phlogopite, which is known as a solid lubricant, is electrically or chemically plated with nickel to give it electrical conductivity. Furthermore, the carbon fibers in this invention play the role of improving wear resistance and creep resistance, but when the nickel-coated mica is dispersed, they come into contact with each other and try to uniformly increase the overall conductivity. Since the carbon fiber is used for this purpose, it goes without saying that the carbon fiber itself must have good electrical conductivity. Therefore, when a higher degree of conductivity is required, carbon fiber coated with a metal such as nickel (for example, HTCF/Ni manufactured by Toho Bethlon Co., Ltd.) may be used. In any case, such carbon fibers have a diameter of 20 μm or less, preferably 6 μm or less, from the viewpoint of ease of mixing and molding the composition of the present invention and protrusion from the molding surface.
~15μm, length less than 6mm, preferably 0.02~3.0
mm is preferable, and commercially available products such as Torayca MLD (manufactured by Toray Industries, Inc.) and Kureha Carbon Fiber (manufactured by Kureha Chemical Industry Co., Ltd.) can generally be used. In this invention, the reason why the mixing ratio of nickel-coated mica and carbon fiber is limited to a range of 15:80 to 80:20 by volume is that if the amount of nickel-coated mica is less than the lower limit, the conductivity cannot be expected, and conversely, if the amount exceeds the upper limit, even if conductivity is achieved, sliding properties cannot be obtained.
Preferably it is in the range of 40:60 to 70:30. The reason why such a mixture of nickel-coated mica and carbon fiber, that is, the total amount thereof, is added in 30 to 140 parts by volume to 100 parts by volume of synthetic resin is that if it is less than 30 parts by volume, the expected conductivity will not be achieved. If the amount is more than 140 parts by volume, the sliding properties may deteriorate, or it may become difficult to mold, or even if it can be molded, the mechanical strength (for example, impact strength) of the molded product will decrease, which is undesirable. The amount is preferably from 50 to 100 parts by volume. The reason why all compounding ratios in this invention are expressed as volume ratios is that normal carbon fibers and metal-coated carbon fibers have significantly different specific gravity, and weight ratios cannot objectively indicate the range of composition of this invention. A method was used in which the weight and true specific gravity of each raw material were measured, and the volume was determined by dividing the weight by the true specific gravity. The method of mixing each raw material in a fixed amount is not particularly limited, and may be any commonly used method, such as
PPS resin, nickel-coated mica, carbon fiber, etc. are mixed individually or appropriately using a mixer such as a Henschel mixer, a ball mill, or a tumbler mixer, and then mixed in an injection molding machine or melt extrusion molding machine with good melt mixing properties. Alternatively, a method such as melt mixing in advance using a hot roll, kneader, Banbury mixer, melt extruder, etc. may be used. Furthermore, the method for molding the composition of the present invention is not particularly limited, and may be performed by a conventional method such as compression molding, extrusion molding, or injection molding, or by melt-mixing the composition. It is also possible to pulverize the powder using a jet mill, frozen pulverizer, etc. and classify it to the desired particle size, or to perform fluidized dip coating, electrostatic powder coating, etc. using the resulting powder without classifying it. be. In order to further improve the lubricity of the composition of the present invention, a lubricant such as polytetrafluoroethylene, graphite, molybdenum disulfide, or oil may be added. [Operation] In addition to the PPS phase and the nickel-coated phase, the surface of the molded product of the composition of the invention described above is polished and made into a sliding surface, and the solid contained in the nickel-coated mica Mica and carbon fibers serve as lubricants to improve lubricity, and the nickel coating layer forms an electrical path in close contact with each other or with carbon fibers, contributing to increased conductivity. [Example] The raw materials used in the Examples and Comparative Examples are as follows. Namely, polyphenylene sulfide (manufactured by Philips Petroleum Co., USA: Ryton P4), tetrafluoroethylene resin (manufactured by Mitsui Dupont Fluorochemical Co., Ltd.: Teflon 7J), nickel-coated mica (electroless phlogopite with an average particle size of 12 μm) nickel plating with an average thickness of 0.1 μm), nickel-coated carbon fiber (manufactured by Toho Veslon Co., Ltd.)
HTCF/Ni, fiber diameter 7.5 μm, fiber length 300 μm, average nickel film thickness 0.25 μm), nickel powder (manufactured by Inco, USA: Nickel Powder 255, average particle size 3 μm), carbon fiber (manufactured by Toray Industries, Inc.: Torayca MLD-300) , fiber diameter 7 μm, fiber length 300 μm). The blending ratio of each raw material in Examples 1 to 4 is based on 100 parts by volume of polyphenylene sulfide, and the blending ratio of each raw material in Comparative Examples 1 to 4 is also based on 100 parts by volume of polyphenylene sulfide. The values are expressed in terms of volumetric parts and are summarized in a table. These raw materials were thoroughly mixed in a Henschel mixer, then supplied to a twin-screw melt extruder, and extruded and granulated under melt mixing conditions of a cylinder temperature of 300° C. and a rotation speed of 100 rpm. The obtained pellets were injection molded under the following injection molding conditions: resin temperature 310℃, injection pressure 800Kg/cm ² , mold temperature 130℃, outer diameter 23mm, inner diameter 14mm,
Ring-shaped specimen with a length of 13 mm and a width of 12.7 mm, length
A plate-shaped test piece of 63 mm and 3 mm thickness was formed, and the ring-shaped test piece was used to measure the volume resistivity and perform a friction and wear test.
The bending strength was measured according to the following. Here, the friction coefficient is measured using a thrust type friction tester at a sliding speed of 100 m/min and a load of 1 kg/ ^cm2 , and the wear coefficient is measured at a sliding speed of 128 m/min and a load of 1.6 kg/ ^cm2 . The test results were determined using a thrust-type wear tester, and bearing steel SUJ-2 (quenched and ground) was used as the mating material in both cases. All the obtained results are summarized and listed in the table. As is clear from this table, Comparative Examples 1 to
4, even if the volume resistivity shows a low value, the wear coefficient is extremely large, or conversely, the wear coefficient is low.

【table】

〔effect〕

As described above, the molded article obtained from the composition of the present invention has a low coefficient of friction, and furthermore, the addition of nickel-coated mica and carbon fiber imparts electrical conductivity while maintaining excellent wear resistance. Therefore, it is suitable for applications that require both wear resistance and conductivity at the same time, such as ground buttons in floppy disk drives, current-carrying bearings in steering columns of automobiles, carriage bearings in OA equipment, and photocopying. It can be said that it is suitable as a base material for heat roll bearings and sliding bearings, such as machine grounding or current-carrying bearings. In addition, since injection molding is possible and molding is easy, it can be said that the significance of this invention is extremely large.

Claims (1)

[Claims] 1. For 100 parts by volume of polyphenylene sulfide, add nickel-coated mica and carbon fiber at a volume ratio of 15:80 to 80:20 and a total amount of 30 to 140 parts.
A conductive sliding material composition, characterized in that it is added in a capacitive part.