JPH07196817A - Friction material - Google Patents

Abstract

(57) [Abstract] [Purpose] To improve the friction and wear characteristics (friction coefficient, wear resistance) of friction materials that compose braking devices for automobiles. [Structure] Polycrystalline fiber of sodium hexatitanate [K ₂ Ti ₆ O ₁₃ ] is used as a base fiber in a friction material obtained by binding and molding a mixture of a base fiber and a resin as a binder. Blending amount: 3 to 50% by weight. The fiber size is about 10 to 60 μm in diameter, about 80 to 400 μm in length, and about 3 to 70 in aspect ratio. Other known fibers may be compounded and mixed. If desired, a friction modifier (barium sulfate, etc.) and other additives (lubricant, etc.) are mixed in appropriate amounts. Due to the heat resistance and reinforcing properties of the base fiber, the high friction coefficient of the sliding surface is stably maintained over a wide temperature range from low temperature to high temperature, and the abrasion resistance is also high. The dust generated from the sliding surface during use does not contain extra fine fiber fragments that are harmful to health.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a friction material constituting a sliding surface such as a brake lining, a disc pad, a clutch facing, etc. in a braking device for automobiles, railway vehicles, aircrafts, industrial machines and the like.

[0002]

2. Description of the Related Art Conventionally, as a friction material for the above braking device,
Resin binder (pheno
Resin, epoxy resin, etc.)
Add a mixture with a friction / wear modifier (barium sulfate, etc.)
Friction materials that have been binding-molded under heat and pressure have been used.
Friction materials that use asbestos fiber as the base fiber
Shows good friction and wear characteristics, but is suitable for high temperature friction surfaces.
Along with this, the fiber reinforcing effect is reduced, and wear damage is significantly increased.
And the coefficient of friction drops sharply when the temperature exceeds 300 ° C.
Performance deterioration at high temperatures, such as
large. In addition, asbestos fibers also point out the problem of carcinogenicity
Therefore, from the viewpoint of environmental hygiene, the development of alternative products has been demanded.
Has been. From this point of view, instead of asbestos fiber,
Potassium titanate fiber [K₂Ti ₆O₁₃]
A friction material using potassium titanate fiber as the base fiber is proposed.
Therefore, attempts have been made to put it into practical use (see, for example, Japanese Patent Laid-Open No.
61-191599, Japanese Patent Laid-Open No. 1-294553.
Gazette). Potassium hexatitanate fiber has excellent heat resistance
And has no hygroscopicity and does not react with water.
Asbestos fiber as the base fiber that constitutes the friction material
Have desirable characteristics.

[0003]

A friction material produced by using potassium hexatitanate fiber as a base fiber has dramatically improved abrasion resistance as compared with a conventional friction material using asbestos fiber. It has improved friction and wear characteristics that do not cause a sharp decrease in the friction coefficient even in a high temperature range exceeding ℃. However, the coefficient of friction in the low temperature range is
Lower than those using asbestos fiber. In order to cope with high speed of automobiles, downsizing and weight reduction of braking devices, etc., it has excellent wear resistance and has a higher friction coefficient, and the high friction coefficient extends from low temperature range to high temperature range. It must be able to be stably maintained in a wide temperature range. It is an object of the present invention to provide a friction material having improved friction and wear characteristics that can satisfy such requirements.

[0004]

The friction material of the present invention is a friction material obtained by binding and molding a kneaded material containing a base fiber with a resin as a binder, and sodium hexatitanate polycrystal is used as the base fiber. It is characterized in that the fibers are blended in an amount of 3 to 50% by weight.

[0005]

[Function] Sodium hexatitanate [K₂Ti₆O₁₃〕fiber
The friction material of the present invention using as a base fiber is potassium hexatitanate.
The base fiber has the same properties as the friction material using
Asbestos fiber has the effect of good heat resistance and reinforcement.
Outstanding wear resistance that far exceeds conventional friction materials used
And even with potassium hexatitanate fiber friction material
Has a high coefficient of friction that cannot be
Holds stable over a wide temperature range from degrees to high temperatures
It This improved friction characteristic of the friction material of the present invention is
In the process, the base fiber resin (binder)
This is due to the difference in the size of the "Kaliatack" tendency. That is, six
Crystals of potassium titanate and sodium hexatitanate are the same
Same crystal structure (TiO ₆Toe formed by a chain of octahedra
Alkali metal ions are distributed within the tunnel frame.
But is located within the tunnel frame.
Na ions are more stable than the coordination of K ions. this
Therefore, during the actual use process of friction materials under high surface pressure,
In the friction material using potassium titanate fiber,
Kio is applied to the ultrathin skin layer (area of about 100 to 200 μm).
Deterioration of the binder resin (softening,
Sodium hexatitanate fiber
In the friction material of the present invention in which the base fiber is
And the deterioration tendency of the resin due to it can be suppressed to a slight extent. This
Is the high friction coefficient of the friction material of the present invention over a wide temperature range.
It is thought that this has made it possible to maintain stable numbers.

The present invention will be described in detail below. The blending ratio of the sodium hexatitanate polycrystal fiber, which is the base fiber of the friction material of the present invention, is limited to the range of 3 to 50% by weight because if it is less than 3% by weight, the blending effect is insufficient. The reason why the upper limit is 50% by weight is that if the amount exceeds 50% by weight, the effect of improving the friction and wear characteristics is saturated, and there is no benefit of increasing the amount further. The purpose of limiting the sodium hexatitanate fiber to the polycrystalline fiber is to eliminate the use of ultrafine single crystal fibers such as whiskers. By using the polycrystalline fibers, it is possible to avoid difficulties and problems in mixing the raw material composition and using the friction material when the whisker is used. The size of the sodium hexatitanate polycrystal fiber is about 80 to 400 μm in fiber length, about 10 to 60 μm in fiber diameter, and the aspect ratio (length / diameter) in view of uniformity of mixing and dispersion in the resin and reinforcing effect. Those of 3 to 7 are preferably used.

The friction material of the present invention, as the base fiber, together with the sodium hexatitanate polycrystal fiber, other known fibers such as polyamide (nylon) fiber, aramid fiber, steel fiber, stainless fiber, copper fiber, One or more kinds of fibers selected from brass fiber, carbon fiber, glass fiber, ceramics fiber, rock wool, wood pulp, etc. are compounded (for example, the total amount with the sodium hexatitanate polycrystal fiber is about 10 to 65% by weight) may be used. These base fibers are silane coupling agents (aminosilane, vinylsilane, epoxysilane, methacryloxylan, mercaptoxylan, etc.) for the purpose of improving dispersibility and binding property with binder resin, etc., if necessary. ),
Alternatively, a surface treatment (coupling treatment) with a titanate-based coupling agent (isopropyltriisostearoyl titanate, di (dioctylpyrophosphate) ethylene titanate, etc.) is performed according to a conventional method and then used.

If desired, the friction material of the present invention is a known friction and wear modifier, for example, vulcanized or unvulcanized natural / synthetic rubber powder, cashew resin powder, organic powder such as resin dust and rubber dust, Natural / artificial graphite, molybdenum disulfide, antimony trisulfide, inorganic powder such as barium sulfate, calcium carbonate, metal powder such as copper, aluminum, zinc, iron, alumina, silica, chromium oxide, copper oxide, antimony trioxide, oxidation One or more components selected from oxide powders such as titanium and iron oxide are used in an appropriate amount (for example, 20 to 20) for the purpose of improving friction and wear characteristics (friction coefficient, wear resistance, vibration characteristics, pear, etc.). 70% by weight). Also, it is no different from ordinary friction materials that various additives, for example, rust preventive agents, lubricants, abrasives, and the like are blended in appropriate amounts (for example, 50% by weight or less) depending on the application and usage.

The resin component which is a binder is a commonly used material such as phenol resin, formaldehyde resin,
Examples thereof include thermosetting resins such as epoxy resins and silicone resins, thermosetting resins modified with these (cashew oil modification, dry modification, etc.), rubber-based resins such as natural rubber, styrene-butadiene rubber, nitrile rubber and the like.

The preparation of the raw material mixture for producing the friction material of the present invention is the same as the conventional friction material except that sodium hexatitanate polycrystal fiber is used as the base fiber, and No special conditions are added or restricted in the manufacturing process. That is, a base fiber is dispersed in a binder resin, and a friction and wear modifier is added as necessary,
And a rust preventive agent, a lubricant, an abrasive, etc. are added and mixed evenly to prepare a raw material composition, and pre-molding and then die molding are performed under heating and pressurization (pressurizing pressure of about 10 to 40 MPa, temperature). Binder molding is performed at about 150 to 200 ° C, and after taking out from the mold, heat treatment is performed in a heating furnace at a temperature of about 150 ° C if desired.
˜200 ° C., holding time: about 1 to 12 hours), and then the molded body is subjected to machining and polishing to finish into a friction material having a predetermined shape. Alternatively, a step of dispersing and suspending the raw material composition in water, etc., making a paper with a paper making net, squeezing water to make sheets, stacking an appropriate number of sheets, and binding-molding under heating and pressure. It is also possible to obtain a predetermined friction material by subjecting the molded body to mechanical processing or polishing processing via the above.

[0011]

【Example】

[Fabrication of test friction material] Sodium hexatitanate polycrystal fiber (according to a reference example described below) was used as a base fiber, and the following raw material composition was prepared and preformed (pressing force: 14.7 MPa =
150Kg / cm ² , temperature: normal temperature, time: 1 minute), and then perform binding molding (pressing force: 14.7MPa = 150Kg / cm ² , temperature: 170 ° C, pressure holding time: 5 minutes) using a mold. , After molding,
The mold is released and heat-treated in a drying oven (hold at 180 ° C for 3 hours). After that, it was cut into a predetermined size and subjected to polishing to obtain a test friction material (disk pad). This friction material is designated as A. Base material fiber (polycrystalline sodium hexatitanate fiber) 30% by weight Binder resin (phenolic resin) 20% by weight Friction modifier (barium sulfate) 50% by weight

[0012]

[Comparative Example 1] As a base fiber, potassium hexatitanate polycrystal fiber (fiber size is the same as that of sodium hexatitanate polycrystal fiber in Examples) was used to prepare the following raw material mixture. A test friction material was obtained under the same molding conditions as above. This friction material is designated as B. Base fiber (polycrystalline potassium hexatitanate fiber) 30% by weight Binder resin (phenolic resin) 20% by weight Friction modifier (barium sulfate) 50% by weight

[0013]

Comparative Example 2 Asbestos fiber (6 class) was used as the base fiber, the following raw material mixture was prepared, and a test friction material was obtained under the same molding conditions as in the above example. It was This friction material is designated as C. Base fiber (asbestos fiber, 6 classes) ... 30% by weight Binder resin (phenolic resin) ... 20% by weight Friction modifier (barium sulfate) ... 50% by weight

[Friction and Wear Test] Each of the above-mentioned test friction materials, namely, friction material A [base fiber: sodium hexatitanate polycrystal fiber] (invention example), friction material B [base fiber: hexatitanic acid] Potassium Polycrystalline Fiber] (Comparative Example 1) and Friction Material C [Base Fiber: Asbestos Fiber] (Comparative Example 2) were subjected to a constant speed friction wear test specified in JIS D4411 “Brake lining for automobiles” to determine the friction coefficient. The wear rate (cm ³ / N · m) was measured and the results shown in FIGS. 1 and 2 were obtained [FIG. 1: friction coefficient, FIG. 2: wear rate]. Disc friction surface: FC25 gray cast iron, surface pressure: 10Kg
/ cm ² , friction speed: 7 m / s.

As shown in FIG. 1 (friction coefficient) and FIG. 2 (wear rate), the friction material C (base fiber: asbestos fiber)
Has a low coefficient of friction at low and high temperatures, especially 30
The decrease is remarkable in the high temperature range over 0 ° C., and the wear resistance also sharply decreases with increasing temperature. Compared to the friction material C, the friction material B (base fiber: potassium hexatitanate polycrystal fiber) has less wear damage even in a high temperature range,
Although the friction coefficient is less likely to decrease with increasing temperature, the friction coefficient in the low temperature range is lower than that of the friction material C. On the other hand, in the friction material A of the invention example, the temperature dependence of the friction coefficient is extremely small, the high friction coefficient is stably maintained in a wide temperature range from low temperature to high temperature, and the wear resistance is, of course, low temperature range. That
Extremely negligible even at high temperatures above 300 ° C,
The effect of improving the wear characteristics is clear.

[0016]

[Reference Example] [Manufacture of sodium hexatitanate polycrystal fiber] [1] Preparation of raw material and heat melting treatment Purified anatase powder (purity 99.0%) and sodium carbonate powder (purity 99.2%) were mixed with TiO ₂ / Na. _The starting material is prepared by mixing the ₂ O _{2 in} a molar ratio of 2 and mixing them uniformly. Put this in a platinum crucible and put it in a heating furnace at a temperature of 1050 ° C for 1 hour.
The melting reaction is performed by heating and holding for a time.

[3] Cooling of Melt Product The melt product is poured into a copper dish and cooled and solidified as it is. The obtained lumps are sodium trititanate crystals (Na
₂ Ti ₃ O ₇ ) and octasodium pentatitanate crystal (Na ₈
Ti ₅ O ₁₄ ), a mixed phase (according to X-ray diffraction), sodium trititanate crystals having a fiber shape, and octasodium pentatitanate crystals being fine particles (according to a scanning electron microscope). [4] Wet defibration treatment The above lumps are immersed in water, allowed to stand for a day and night, and then stirred with a stirrer (about 10 minutes). Fine-grained sodium pentatitanate crystals float, and fibrous sodium trititanate crystals settle in the liquid. The sodium trititanate fiber is recovered by this gravity separation. Sodium trititanate fiber is polycrystalline (scanning electron microscope observation).

[5] Sodium elution treatment After dehydrating and drying the sodium trititanate polycrystalline fiber,
The mixture is poured into water (50 times volume), 0.5% by weight of sulfuric acid is added, the mixture is stirred for 1 hour, and then recovered from the treatment liquid. [6] Firing treatment The collected fibers are dehydrated and dried, and heat-treated at a temperature of 700 ° C for 2 hours. The fibers obtained are as follows. Chemical composition: Na ₂ Ti ₆ O ₁₃ (by X-ray diffraction) Fiber morphology: average fiber diameter 50 μm, average fiber length 300 μm,
Aspect ratio 5-7 (by scanning electron microscope).

[0019]

The friction material of the present invention has a high friction coefficient and wear resistance over a wide temperature range from low temperature to high temperature.
Therefore, brake linings, disc pads, etc. that constitute the braking devices for automobiles, vehicles, aircraft, and various industrial machines,
It is useful as a clutch facing, etc., and can respond to downsizing and weight reduction of a braking device, and is effective in improving and stabilizing a braking function and improving durability.

[Brief description of drawings]

FIG. 1 is a graph showing a measurement result of a friction coefficient by a friction and wear test.

FIG. 2 is a graph showing the results of measuring the wear rate by a friction wear test.

[Explanation of symbols]

A: invention example (base fiber: sodium hexatitanate polycrystal fiber), B: comparative example (base fiber: potassium hexatitanate polycrystal fiber), C: comparative example (base fiber: asbestos fiber, 6 class) ).

Claims (2)

[Claims] 1. A friction material obtained by binding and molding a kneaded material containing a base fiber with a resin as a binder.
A friction material comprising sodium hexatitanate polycrystalline fibers in an amount of 3 to 50% by weight. 2. A sodium hexatitanate polycrystal fiber having a fiber size of 10 to 60 μm in diameter and 80 to 400 μm in length.
The friction material according to claim 1, wherein the friction material has an m and an aspect ratio of 3 to 7.