JPH0260694B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a conductive sliding resin material, and more specifically, it can be used for VTR cassette reels, copy machine paper feeding rotating members, other office machines or electronic equipment parts, etc. The present invention relates to a resin material that has sliding properties and conductivity that can be applied to. (Conventional technology) Demand for VTRs has been increasing rapidly in recent years, but
Since cassette reels tend to generate static electricity due to friction and peeling when the tape runs, it is possible to use antistatic resin in the cassette reel to prevent the electrification of the cassette reel from adversely affecting images.
It has contributed greatly to improving the quality of VTRs and to their widespread use. In addition, the reel stand of a VTR is integrated with a pulley and driven by a belt, but the friction between the belt and the reel causes the reel stand to become electrically charged, and the charge is discharged from the reel stand to the IC, causing VTR failure. This problem is also being solved by antistatic resins. Furthermore, plastic bearings have recently been used to support paper feed rollers in electrostatic copying machines, etc., but static electricity charged on the paper can cause uneven copying, inaccurate feeding due to adhesion of the paper to the shaft, and problems with the shaft. There is a problem with discharge. Providing an antistatic mechanism or a peeling mechanism for peeling off the paper adhered to the rollers would complicate the mechanism, potentially reducing the reliability of the copying machine, and increasing weight and cost. Polymeric materials such as plastics are usually
It has a volume resistivity of 10 ¹⁴ Ω・cm or more, and is easily charged by friction. Due to such electrification, polymeric materials may attract dust or be subjected to electric shocks, and as a countermeasure to this, materials in which antistatic agents are mixed into plastic are supplied as necessary. however,
Materials such as the VTR reel stand mentioned above cannot be satisfied with simply preventing static electricity; they also require conductivity with a low resistance value, and in order to further improve image quality, it is necessary to actively dissipate the charge to the ground. ing.
Additionally, in the United States, there are regulations regarding radio wave containment in order to eliminate radio wave interference in electronic devices such as microcomputers and VCRs, and for this purpose, it has become necessary to impart conductivity to the plastic materials used in the housings of electronic devices. There is. Methods for making plastic conductive include (1) addition of conductive carbon, (2) addition of metal powder or fiber, (3) addition of carbon fiber, or (4)
The surface of the molded product is metallized. (Four)
Metallizing can be applied to housings such as electronic devices or ICs, but it cannot be applied to members that involve movement such as rotation or sliding. (2) and (3)
When the addition of metal powder, fiber or carbon fiber is applied to a sliding member, for example, there is a problem in that it damages the mating material. Furthermore, when carbon fiber-added plastics are used as sliding members, for example, there is the disadvantage that the coefficient of friction increases with time of use. Addition of conductive carbon (1) is a method of adding carbon black (amorphous carbon), which has the lowest specific volume resistance among carbon materials, to plastic. By this method, a conductive resin material having a specific volume resistivity of about 10 ² to ^{10 3} Ω·cm can be obtained by adding 8 to 15% by weight of carbon black to the polyacetal resin. However, although this conductive resin material has conductivity, its sliding properties are inferior to those without carbon black added thereto. In particular, the conductive resin material described above is unsuitable for use as a bearing. (Problems to be Solved by the Invention) As described above, proposals have been made to impart conductivity to resin materials, but sliding properties have not been taken into account. Therefore, an object of the present invention is to provide a resin material that has both electrical conductivity and sliding properties. (Means for Solving the Problems) According to the present invention, the above-mentioned objects are achieved by: 2 to 30% by weight of carbon black, 0.1 to 30% by weight of fibrous dispersed fluororesin, 0.5 to 30% of graphite Aito,
This can be achieved by using a conductive sliding resin material characterized by being made of the remaining thermoplastic resin. Note that the symbol "%" is often used below, but this symbol is used unless otherwise specified.
As above, it should be understood that "% by weight" is meant. In the sliding material of the present invention, the resin material serving as the base material is a thermoplastic material. The fluororesin, which is an essential component of this base material, is a component that has the effect of improving sliding properties, as will be described in detail later.
As base material components other than fluororesin, polyphenylene oxide, polyphthalene phthalate, polyamide (for example, trade name nylon), polycarbonate, and polyacetal are preferable, and polyacetal is particularly preferable. As polyacetal,
Of the copolymer type and the homopolymer type, the former is preferred. The fluororesin may be a PTFE powder for extrusion molding called fine powder, and by thoroughly kneading this with other components, these powders are dispersed in the form of fibers. When the total weight is 100%, the proportion of fibrous dispersed fluororesin is 0.1 to 30
Weight percent is preferred. More preferably 0.2% to 10%.
If this proportion is less than 0.1% by weight, the effect of the fibrous fluororesin will not be sufficient, while if it exceeds 30% by weight, molding of the resin will become difficult. The thickness of the fibrous dispersed fluororesin dispersed in the base material is generally about 0.1 to 10 μm. The characteristics of the fluororesin component in the conductive sliding resin material according to the present invention are that the fibrous dispersed fluororesin is exposed on the surface of the sliding part, thereby reducing the coefficient of friction with the mating material; Since the fluororesin exists in the resin material as a three-dimensionally dispersed fiber, it reinforces the base material, and especially if solid additives are present, they hold them and prevent them from falling off. This means that superior wear resistance can be obtained. FIG. 2 is an electron micrograph (magnification: 150 times) obtained by bending and breaking a 5 mm thick plate made of the resin material of the present invention, and depositing an electrode on a part of the plate. In this drawing, the matrix (base material)
is polyacetal resin. It is clear from this drawing that the fluororesin has a fibrous shape. Carbon black, which is one component of the sliding material of the present invention, is a component that imparts electrical conductivity. The upper limit of the amount of carbon black added coincides with the upper limit of the amount added to the resin by kneading. However, it is preferable to select the following range depending on particularly desired characteristics. That is, if high electrical conductivity is particularly desired as a property of the sliding material of the present invention, the amount of carbon black added is preferably 2-30%, and if good sliding properties are desired, the amount of carbon black added is preferably 3-10%. If you want something with good both properties, 7-10% is good. There are no particular restrictions on the type of carbon black, but acetylene black (amorphous carbonized acetylene) is preferred, or ultrafine carbon black with a particle size of 10 Å or less (for example, a special furnace type carbon black such as Ketsutien Black) is preferred. Particularly preferred are those commercially available under the name ). Next, the interaction of the sliding material components of the present invention will be explained. Figure 1 shows data obtained in accordance with JISK6911 resin volume resistivity measurement method, indicated by the solid line, for a slider made of 4% polytetrafluoroethylene, carbon black (addition amount shown on the horizontal axis), and the remainder polyacetal resin. It is a graph showing specific volume resistivity (ρ) of a dynamic material. The dotted line in FIG. 1 is a graph showing the specific volume resistivity (ρ) of a carbon black added polyacetal resin (prior art) that does not contain polytetrafluoroethylene. From FIG. 1, it can be seen that polytetrafluoroethylene slightly lowers the conductivity. Since polytetrafluoroethylene is originally insulating, it is thought that addition of this insulating component reduces conductivity depending on the amount added. On the other hand, it can be seen from Figure 1 that the sliding material of the present invention and the material of the prior art have the same tendency, and the specific volume resistivity (ρ) decreases depending on the amount of carbon black added. It is recognized that fluoroethylene does not take away the original conductivity imparting effect of carbon black. Carbon black is a component that degrades the sliding properties of thermoplastic resin by increasing the coefficient of friction, reducing load capacity, and increasing the amount of wear.However, carbon black coexists with fluororesin, which is dispersed in the form of fibers. As a result, the sliding properties are improved more than when carbon black is added. Therefore, by appropriately selecting the amount of each component added, the sliding material of the present invention has a conductivity equal to or higher than that of conventional conductive resin materials, and is superior to conventional conductive resin materials. A sliding material is provided that has unprecedented lubricity, low friction, load capacity and stability of these properties. Note that if the load capacity decreases, the sliding material will break under low load due to the load received from the mating material, or even if it does not lead to breakage, fatigue will easily occur, resulting in poor sliding characteristics. The following table shows the difference in friction coefficient reduction effect between two types of polytetrafluoroethylene.

[Table] In Table 1, samples 2 and 3 contain 4% polytetrafluoroethylene, 6% carbon black, 20% graphite, and the remainder of polyacetal, and samples 4 and 5 contain 5% polytetrafluoroethylene. %, carbon black 6%, oil 2
%, and the blending amount of the remaining polyacetal was used. Samples 2 and 4 used polytetrafluoroethylene (trade name: Polyflon M12) which could be made into fibers, and polytetrafluoroethylene (trade name: Lublon) which could be dispersed into granules was used for samples 3 and 5. From the data in Table 1, it is clear that the sliding material of the present invention in which the fibrous dispersed resin (polytetrafluoroethylene) is present has a much better effect of reducing the coefficient of friction than the comparative example. be. In addition,
Graphite, which is an optional component of the sliding material of the present invention, is a component that improves the sliding properties by particularly increasing the electrical conductivity and the lubricating properties. Carbon black, which is one of the components of the sliding material of the present invention, deteriorates the sliding characteristics compared to a material without carbon additives, but graphite compensates for the deterioration in sliding characteristics caused by carbon black, and also has no carbon additives. Achieves better sliding characteristics than those of
Furthermore, although graphite has a specific volume resistivity that is more than 10 ^-10 times lower than that of resin materials, it is difficult to impart conductivity to the resin when added alone; A large amount of graphite addition of 40% (weight percentage) or more is required. However, when graphite coexists with carbon black, a significant improvement in conductivity is realized even if the amounts of graphite and carbon black added are small. The fluororesin that is one component of the sliding material according to the present invention is a resin that alone has excellent heat resistance but does not have very good wear resistance. The coexistence of fluororesin and carbon black provides the sliding material of the present invention with extremely excellent resistance to uneven wear. That is, the sliding material of the present invention exhibits an extremely small amount of wear when used as a one-sided sliding portion to which a load is applied non-uniformly. The upper limit of the amount of graphite added may be the same as the upper limit of the amount of graphite that can be kneaded with the resin material, and usually the upper limit of the amount of graphite added is about 40%. However, if the amount of graphite is large, the strength of the sliding material will be reduced and the sliding properties will be insufficient. is 30%
It is preferably at most 25%, more preferably at most 25%. Furthermore, from the viewpoint of sliding properties, the graphite content is preferably 5% or more, more preferably 15% or more. In the sliding material of the present invention, the amount of graphite added is generally 0.5-30%, most preferably about 20%.
When graphite is used in conjunction with lubricant retention as described below, the amount of graphite added is preferably 10-25%. In the sliding material of the present invention, the amount of graphite added is generally 3-40%, most preferably about 20%. As graphite, naturally occurring earthy graphite and scaly graphite are used, as well as artificial graphite obtained by crystallizing amorphous carbon obtained from coal, oil, coke, etc. by heating. However, artificial graphite improves the sliding properties measured by the amount of wear by about 10 times (1/10 times the amount of wear) than natural graphite. There is no particular restriction on the particle size of graphite used in the sliding material of the present invention, but it is preferably 50 μm or less. Lubricating oil, which is an optional component of the sliding material of the present invention, is a component that imparts lubricating performance. In the sliding material of the present invention, excellent lubrication performance can be obtained due to the improvement in sliding performance due to graphite and the improvement in lubrication performance due to the lubricating oil. Such lubricating oil may be contained in the resin material, contained (oil-impregnated) in graphite, or both simultaneously. The type of lubricating oil is preferably one having heat resistance up to 250°C, but there is no particular restriction. Jet engine oil is particularly preferred, but general engine oil (having heat resistance up to 180°C) may also be used. In addition, the amount of lubricating oil added is preferably 10% or less, and approximately 1.5~
3.5% is particularly preferred. The method for manufacturing the sliding material according to the present invention will be explained below.
After weighing and mixing the predetermined ingredients whose particle sizes have been adjusted, a coupling agent, a viscosity modifier, etc. are added as necessary, and then extruded using a kneading machine to form pellets, and then molded into a predetermined shape using a molding machine.
When graphite or carbon black is impregnated (oil-impregnated) with a lubricating oil, an oleoresin can be easily obtained by stirring the graphite or the like in the lubricating oil. (Example) Examples of the present invention will be described below with reference to Tables 2 to 4. In Tables 2 to 4, CB is carbon black (product name: KETSUCHEN BLACK), Gr is standard G117 artificial graphite, OIL is synthetic lubricating oil (SHC630), and 4F is polytetrafluoroethylene that can be made into fibers (product name: Polyflon). M12) and Gr
The remainder is a copolymer type polyacetal shown as POM. When the 4F used in the examples is sufficiently kneaded, it becomes fibrous in a thermoplastic base resin such as polyacetal. In Tables 2 to 4, "conductivity" refers to volume resistivity (ρ-
The unit is Ω・cm. ) "Wear" is a sliding distance of 10 km, and the first 10 minutes are
2.5Kg, thereafter 10Kg (constant) load, sliding speed
0.2m/sec, mating material SUJ2 (quenched), dry lubrication,
Shows the amount of wear (unit: mg) mixed under the conditions of a thrust type friction and wear tester. "μ" indicates the friction coefficient, and "load" indicates the load capacity (unit: Kg) measured under the above-mentioned load conditions. Load capacity measurement conditions: (a) Testing machine: Thrust type wear and friction tester (b) Sliding speed: 0.2m/sec (c) Load: Increase stepwise at 5Kg/hr (d) Compatible material: SUJ-2 (Quenching) (E) Lubrication: Dry condition (F) Load application method: Thrust load

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[Table] Similar properties were obtained when polyamide was used in place of POM. From Tables 2 to 4, conductivity (specific volume resistivity ρ)
is 10 ⁰ ~ 10 ¹⁴ Ω・cm・μ≒(=0.1)=～(=0.5=),
The characteristics change in the load (loading capacity) range of (25) to (60) kg, and it is possible to select a composition that has good conductivity or sliding characteristics, or both. I understand. (Effects) (a) Since the sliding material of the present invention not only has an antistatic function but also has conductive properties, it can be used as an electrical component that is energized or grounded, and can be used to prevent harmful effects caused by static electricity, such as image after-sound on a VTR. Thoroughly prevents paper from sticking to the copier. It can also be used as an IC package, and the IC package can be grounded. (b) Since the frictional properties of the sliding material of the present invention are extremely good and stable over a long period of time, the reliability of electrical components with rotating and sliding parts is improved. (c) Since the sliding material of the present invention has excellent wear resistance, when it is applied to electrical parts that rotate and slide, it is expected that parts replacement will be reduced and that maintenance will be free. (d) Taking advantage of the excellent load capacity and the effect of (a) above, the sliding material of the present invention can be used in small and lightweight bearing devices that require electricity. (e) Since the sliding material of the present invention has a high load capacity under thrust loads, it can also be used as an energized thrust bearing.

[Brief explanation of drawings]

FIG. 1 is a graph showing the relationship between the amount of carbon black added and the specific volume resistivity (ρ), and FIG. 2 is an electron micrograph showing the structure of fluororesin fibers.

Claims (1)

[Claims] 1 2-30% by weight carbon black, 0.1-30
% by weight of fibrous dispersed fluororesin, 0.5-30% by weight
A conductive sliding resin material characterized by comprising graphite, and a residual thermoplastic resin. 2. The conductive sliding resin material according to claim 1, further comprising 10% by weight or less of lubricating oil.