JP3031650B2 - Fluororesin composition for sliding members - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin composition comprising a polytetrafluoroethylene resin as a main component for producing a sliding member having excellent wear resistance and strength.

[0002]

2. Description of the Related Art Polytetrafluoroethylene resin (hereinafter referred to as "PTFE resin") is an engineering material having low friction properties as well as heat resistance, weather resistance, cold resistance, nonflammability, chemical resistance and the like. It is a plastic and is widely used as various sliding component materials (for example, dry bearings, bushes, ball seats, piston rings, sliding pads, ring seals, lip seals, etc.). Further, as a device for improving the abrasion resistance and sliding characteristics, various filler materials such as asbestos fiber, glass fiber, potassium titanate fiber, carbon fiber, organic heat-resistant fiber (polyamide resin fiber) are added to PTFE resin. Many proposals have been made for resin compositions containing metal fibers (stainless steel fibers, etc.), inorganic powders (mica, silica, alumina, zirconia, etc.), and metal powders (lead, zinc, etc.) (for example, JP-A-55-18430, JP-A-55-50052, JP-A-58-167696, JP-A-60-25005
No. 4, JP-A-62-146944, etc.).

[0003]

In recent years, the usage and usage of sliding part materials mainly composed of PTFE resin have been expanded and diversified, and the sliding conditions have become more severe as seen in dry bearings and the like. With the progress of high speed and high surface pressure, there is a strong demand for further improvement in durability, stable use, sliding characteristics and the like. Therefore, the present invention improves the mechanical properties such as abrasion resistance and rigidity while maintaining characteristics such as a low coefficient of friction peculiar to PTFE resin, and can withstand severe sliding conditions such as high speed and high surface pressure operation. An object is to provide a resin composition capable of forming a moving member.

[0004]

SUMMARY OF THE INVENTION The fluororesin composition for a sliding member of the present invention is a polytetrafluoroethylene resin (P
TFE resin) as the main component, and the length (the
Length and diameter): 5 to 100 μm, width (minimum in the surface direction)
Diameter: 1 to 30 μm, aspect ratio (length /
It is characterized in that flaky potassium titanate particles having a width of 3 or more and a thickness of 0.01 to 2 μm are blended. The compounding amount of the flaky potassium titanate particles is preferably 2 to 40% by weight.

[0005]

The flaky potassium titanate particles, which are mixed in an appropriate amount in the PTFE resin, have the effect of the flaky shape by strengthening the sliding member in multiple layers, thereby increasing the wear resistance of the sliding surface and increasing the strength. , Increase rigidity, etc. Further, the flaky potassium titanate particles in the resin absorb and relax internal stress caused by rising and falling of the temperature of the sliding surface, and prevent peeling and cracking of the sliding member. Good sliding characteristics are maintained without impairing the low friction coefficient and the like, which are the characteristics of the main component resin, by the addition of the flaky potassium titanate particles. The mixing effect of the flaky potassium titanate particles shows that even with the same potassium titanate particles, as compared with the potassium titanate particles (whiskers) having a needle-like morphology, as shown in the examples described later, the low friction coefficient Excellent in securing μ and improving effects such as abrasion resistance and rigidity. The flaky potassium titanate particles have a Mohs hardness of about 3.5, which is moderately soft as compared with glass fiber or the like, and have low aggressiveness to the mating material.

Hereinafter, the components of the resin composition of the present invention and the production of a sliding member comprising the composition will be described in detail. The flaky potassium titanate particles blended as a filler material in the resin composition of the present invention have a general formula: K ₂ O
A polycrystalline synthetic inorganic compound represented by nTiO ₂ (n is a positive integer). In particular, potassium tetratitanate (K ₂
Ti ₄ O ₉ ), potassium hexatitanate (K ₂ Ti
Flaky particles such as ₆ O ₁₃ ) and potassium octa titanate (K ₂ Ti ₈ O ₁₇ ) are suitably used from the viewpoint of heat resistance and reinforcing effect. These flaky potassium titanate particles have the following properties.
Only the species may be used, or two or more species may be used in combination.

The size of the flaky potassium titanate particles is as follows:
If it is too coarse, the uniformity in the resin composition will be poor, and if it is too fine, the reinforcing effect based on the morphological characteristics of the flaky particles (the effect of improving abrasion resistance, strength, rigidity, etc.) ) Becomes weaker. Further, regarding the thickness of the flake, if it is too thick, it impairs the smoothness of the sliding surface, and if it is too thin, on the other hand, the flake shape is easily damaged in the mixed preparation of the resin composition, and its compounding effect can be secured. It will be difficult. From these points, it is preferable that the size (measured in the plane direction) is about 1 to 100 μm and the thickness is about 0.01 to 2 μm. In particular, regarding the size, the length (the maximum length in the plane direction) is about 5 to 100 μm, the width (the minimum length in the plane) is about 1 to 30 μm, and the aspect ratio “length / width” is about Those having a form of 3 or more are most preferably used in terms of uniformity of kneading / dispersion, reinforcing effect, and the like.

The mixing ratio of the flaky potassium titanate particles in the PTFE resin depends on the intended use and use conditions of the sliding member. However, in order to sufficiently exhibit the mixing effect, the mixing ratio is preferably about 2% by weight or more. Good to do. The heat resistance, abrasion resistance, load resistance, etc. are improved as the amount is increased. However, if the amount is too large, uniform kneading / dispersion becomes difficult.
The binding of the FE resin is weakened, resulting in a decrease in strength. In the firing step, the tendency of cracks and cracks to occur increases.
Therefore, it is appropriate that the upper limit is about 40% by weight.

Prior to the preparation of the resin composition, the above-mentioned flaky potassium titanate particles may be added to the surface of the PTFE resin, if necessary, in order to improve the dispersibility in the PTFE resin as a main component and the binding property with the resin. , Silane coupling agents (aminosilane, vinylsilane, epoxysilane, methacryloxysilane,
It is used after being subjected to a coupling treatment with a mercaptoxylan or the like or a titanate coupling agent (such as isopropyltriisostearoyl titanate or di (dioctyl pyrophosphate) ethylene titanate). In addition, the resin composition of the present invention may contain a known solid lubricant (for example, graphite, lead oxide, etc.) in an appropriate amount (for example, 2 to 10% by weight), if desired.

The preparation of the resin composition of the present invention and the production of a sliding member made of the resin composition can be carried out in a conventional manner, except that flaky potassium titanate particles are mixed with the PTFE resin. . That is, a predetermined amount of flaky potassium titanate particles is added to PTFE resin powder,
If necessary, a solid lubricant is blended and uniformly kneaded to prepare a resin composition. This is filled in a mold, and an appropriate pressure is applied at room temperature, for example, 10 to 30 MPa (about 100 to 300 kg / cm).
After compression molding in ² ), the molded body is taken out of the mold and is heated in a sintering furnace at a temperature of about 350 to 400 ° C. for an appropriate time (for example,
４4Hr) to achieve the sintering process. The resulting sintered product has a high density, abrasion resistance, strength and strength.
In order to increase the rigidity, it is preferable to add a compression molding process. The compression molding is achieved by immediately charging the sintered body taken out of the furnace into a mold and holding it under pressure (about 20 to 50 MPa) for an appropriate time (for example, 2 to 10 minutes). After the pressure forming, the formed body is subjected to machining and necessary polishing to finish the friction material.

[0011]

【Example】

[1] Preparation of resin composition and production of sliding member: PTF
Flake-like potassium titanate particles or needle-like potassium titanate particles are blended with the E resin powder as a filler, and uniformly mixed with a mixer to prepare a resin composition. This is filled in a mold, and a pressure of 24.5 MPa (250 kg / c
After compression molding in m ² ), it is charged into a firing furnace. Temperature 3
After sintering was achieved by holding at 80 ° C. for about 3 hours, it was taken out of the furnace, immediately put into a mold, and 34.4 MPa
(350 kg / cm ² ), and then cooled. This is subjected to machining to obtain a test piece. Table 1 shows the resin composition of the test materials. Nos. 1-3 are invention examples using flaky potassium titanate particles as fillers, Nos. 11-13 are comparative examples in which acicular potassium titanate particles are blended, and No. 14 is PTFE resin alone without fillers Material. PTFE resin: "Polyflon TFE" manufactured by Daikin Industries, Ltd.
Molding powder M-15 ”, Flaky potassium titanate particles:“ TXA ”manufactured by Kubota Corporation
X-SA "[particle shape: length 10 to 70 μm, width 3 to 1
5 μm, thickness: 0.2 to 1 μm], Acicular potassium titanate particles: “Tismo-D” manufactured by Otsuka Chemical Co., Ltd. [particle shape: 0.2 to 0.5 μm in diameter, length 1]
0-20 μm].

[0012]

[Table 1]

[2] Evaluation of material properties (2.1) Friction and wear test: Friction coefficient μ and specific wear rate (mm ³ / Kgf · Km) were determined by a pin-on-disk friction and wear test.
Measure. Mating material: S45C carbon steel (surface roughness 1.6S), friction speed: 0.5 m / sec, friction distance: 4000 m, sliding surface pressure: 1 to 7 kgf. (2.2) Bending test: Bending strength (MPa) and flexural modulus (MPa) are determined in accordance with ASTM D790 “Bending test of plastic”. Test piece size (mm): 120 ^L x 13 ^W x 6 ^H , Span distance: 100 mm.

The results of the pin-on-disk friction and wear test are shown in FIGS. 1 and 2 (FIG. 1: specific wear rate, FIG. 2: friction coefficient). The bending test results are shown in FIGS. 3 and 4 (FIG. 3:
The flexural strength is shown in FIG. The reference numerals in the figures indicate the test material numbers. As shown in FIG. 1 (comparative material No. 14 in the upper left frame in the figure), Invention Examples No. 1 to 3 in which flaky potassium titanate particles were blended with PTFE resin were made of PT
Compared with No. 14 which is a single material of FE resin, it has remarkably high abrasion resistance, and its abrasion resistance is stably maintained even when the surface pressure increases. The test materials Nos. 11 to 13 to which the acicular potassium titanate particles were added also had higher abrasion resistance than the PTFE resin simple material No. 14, but the wear resistance increased with increasing surface pressure. Its properties decline rapidly and lack stability.

In addition, as is apparent from FIG. 2, the invention examples Nos. 1 to 3 in which the flaky potassium titanate particles are blended have the PT
It has a low friction coefficient equivalent to that of No. 14, which is a FE resin simple substance, and the low friction coefficient is stable over a wide range from low surface pressure to high surface pressure. Different from this, the friction coefficients of Comparative Examples Nos. 11 to 13 in which needle-like potassium titanate particles were blended were as follows:
It is even greater than No. 14 of the PTFE single material, and has an instability that its coefficient of friction changes with the change in surface pressure.

Further, looking at the mechanical properties (FIGS. 3 and 4),
Invention examples No. 1 to 3 using flaky potassium titanate particles
Comparative Examples No11 ~ using acicular potassium titanate particles
The effect of improving the flexural strength (FIG. 3) and the flexural modulus (FIG. 4) is greater than that of 13, especially the effect of improving the flexural modulus [rigidity] (FIG. 4) becomes remarkable with an increase in the blending amount. . The fact that Invention Examples Nos. 1 to 3 have a high modulus of elasticity means that, for example, in the application of dry bearings, deformation due to load and inconveniences such as lip and vibration due to the load hardly occur. It means that it is excellent in loadability and it is possible to secure stable rotational movement under high speed and high surface pressure operating conditions.

[0017]

The sliding member obtained by using the resin composition of the present invention has a low coefficient of friction unique to PTFE resin and the like.
It has high abrasion resistance, strength, rigidity, etc. due to the mixing effect of flaky potassium titanate particles. As a material for forming sliding members in various fields, durability and stability of members under severe sliding conditions The present invention meets the demand for improvement and the like. For example, it is possible to stably maintain a smooth rotational motion even in a dry bearing or the like under a high speed and high surface pressure sliding condition.

[Brief description of the drawings]

FIG. 1 is a graph showing a measurement result of friction coefficient-surface pressure.

FIG. 2 is a graph showing measurement results of specific wear rate-surface pressure.

FIG. 3 is a graph showing measurement results of bending strength.

FIG. 4 is a graph showing measurement results of flexural modulus.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C08L 27/18 C08K 3/24 C08K 7/00

Claims (2)

(57) [Claims] 1. A polytetrafluoroethylene resin as a main component, which has a length (the maximum length in the surface direction).
5 to 100 μm, width (minimum diameter in the surface direction): 1
３０30 μm, aspect ratio (length / width): 3 or more, and
A fluororesin composition for a sliding member, comprising flaky potassium titanate particles having a thickness of 0.01 to 2 μm . 2. A blending amount of flaky potassium titanate particles.
Is from 2 to 40% by weight.
The fluororesin composition for a sliding member according to the above.