JPH059462A - Friction material - Google Patents

Abstract

(57) [Abstract] [Purpose] Improving the friction characteristics and durability of friction materials used as sliding members for automobile brake pads, etc. [Constitution] Base fiber binding with organic or inorganic binder 98% purity as the base fiber in the friction material
The above-mentioned potassium titanate fiber is mixed in an amount of 3 to 50% by weight. [Effect] Stable friction coefficient is maintained and wear resistance is high even under high temperature use conditions where the friction surface temperature exceeds 350 ° C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a friction material useful as a sliding member for a brake lining, a disk pad, a clutch facing, etc., which constitutes a braking device in automobiles, railway wheels, aircrafts, industrial machinery and the like.

[0002]

2. Description of the Related Art As a typical sliding member in the above braking device, a friction material has been conventionally used in which asbestos fiber is used as a base fiber, and this is dispersed in an organic or inorganic binder to form a binder. However, there is a strong demand for the development of alternatives in view of the demands of the automobile industry regarding the improvement of frictional properties such as heat resistance, and the environmental hygiene such as the carcinogenic problem pointed out in asbestos fibers.

In response to the demand, a friction material has been proposed in which potassium titanate fiber is used as a base fiber instead of asbestos fiber (JP-A 61-191599 and JP-A 1-294553).
No. The potassium titanate fiber is a synthetic inorganic fiber typified by potassium hexatitanate fiber (K ₂ Ti ₆ O ₁₃ ). The above publication discloses a friction material having a base fiber of potassium titanate fiber produced by a so-called melting method using natural rutile sand or the like as a titanium oxide source, which has good thermal stability and is a conventional friction material using asbestos fiber. Shows a fading phenomenon at around 230 ° C, but maintains a stable friction performance without a fading phenomenon up to a temperature of around 350 ° C, and has good wear resistance in the high temperature range. It is disclosed along with specific data for the wear test.

[0004]

However, the high-temperature characteristics of the friction material using the above-mentioned potassium titanate fiber as the base fiber, in particular, exceeding the specified temperature of the constant speed friction wear test in JIS D4411 "Brake lining for automobiles" 400 Looking at the frictional characteristics near ℃, although it is superior to the conventional material using asbestos fiber, a fade phenomenon in which the friction coefficient is significantly reduced is clearly observed, and the wear resistance is also greatly reduced.

The object of the present invention is to improve the friction and wear characteristics in such a high temperature range. As a result of detailed research, potassium titanate obtained from the above-mentioned natural rutile sand etc. as a titanium oxide source. Fiber (derived from its raw material Fe,
It has been found that the above object can be achieved by using high-purity potassium titanate fiber instead of containing a large amount of impurities such as Zr and Si and having a purity as low as about 96%.

[0006]

Means for Solving the Problems The present invention provides a friction material obtained by binding and molding base fibers with an organic or inorganic binder, wherein the titanic acid having a purity of 98% or more is used as the base fibers. It is characterized by containing 3 to 50% by weight of potassium fiber.

The potassium titanate fibers, which are the base fibers of the friction material of the present invention, are limited to those having a purity of 98% or more.
The higher the purity, the more advantageous it is to improve the friction and wear characteristics in the high temperature range, preferably 99% or more. The lower limit of the purity is specified as 98% because the high purity gives the fiber a high melting point and high thermal conductivity, and as a result, the thermal stability of the friction material is improved and the high temperature range is improved. This is because it is possible to obtain a remarkable effect of improving the friction coefficient and the wear resistance.

That is, the melting point of potassium titanate fiber obtained by using the natural rutile sand or the like as a titanium oxide raw material is at most about 1330 ° C., and its thermal conductivity κ is 0.017.
The melting point of high-purity potassium titanate fiber of 98% or more is about 1370 ° C or more, and the thermal conductivity κ is about 0.026 w / cm · k, which is about w / cm · k. It has a high thermal conductivity of over 1.5 times.

In the actual use of a friction material such as a brake pad for an automobile, it is estimated that the friction surface is locally heated to 1000 ° C. or higher due to the generation of friction heat and the accumulated heat. By using the high-purity potassium titanate fiber as a base fiber in such a friction material, the fiber has a high melting point and a high thermal conductivity (the higher the thermal conductivity, the more advantageous the relaxation of heat accumulation on the friction surface). As a result of the improvement of the thermal stability, the improved friction coefficient and wear resistance are assured in the high temperature region around 400 ° C. as shown in the following examples.

The high-purity potassium titanate fiber used in the present invention uses industrially purified titanium oxide (purity: about 99%) as titanium oxide in the starting material, as shown in Reference Example 1 below. Except for this point, it can be manufactured by the general conditions and process of the melting method. The potassium titanate fiber contains potassium hexatitanate (K ₂ Ti ₆
O ₁₃ ), potassium tetratitanate (K ₂ Ti ₄ O ₉ ), potassium octatitanate (K ₂ Ti ₈ O ₁₇ ), and the like. Any one of these fibers may be used alone, or any two or more thereof may be used in combination.

The content of the above potassium titanate fiber in the friction material of the present invention is set to 3% by weight or more, because if it is less than that, the effect of improving the friction and wear characteristics cannot be sufficiently obtained. % Is set as the upper limit because there is no advantage in blending a large amount beyond that.

The size of the potassium titanate fiber is not particularly limited, and various sizes produced by the above melting method (the fiber size can be adjusted within a relatively wide range depending on the treatment process and conditions after heating and melting). ) Polycrystalline fiber, for example, a relatively coarse size having a cross-sectional diameter of about 20-50 μm and a length of about 100-300 μm, or a relatively small size having a cross-sectional diameter of about 5-10 μm and a length of 15-100 μm Etc. can be used appropriately.

The friction material of the present invention, as the base fiber, together with the above-mentioned potassium titanate fiber, other types of fiber such as resin fiber such as aramid fiber, steel fiber, carbon fiber, glass fiber, ceramic fiber, rock wool and wood pulp. Etc. can be used in a composite manner for reinforcing the friction material.
The blending amount of these other kinds of fibers may be appropriately determined within the range of about 1 to 60% by weight. Prior to the preparation of the raw material composition, each of these base fibers has a silane coupling agent (vinyl silane, epoxy silane, methacrylic acid) for the purpose of improving the dispersibility and the adhesiveness with the binder, if necessary. Roxylan, mercaptoxylan, etc.) or titanate coupling agent (isopropyltriisostearoyl titanate, di (dioctyl pyrophosphate))
Surface treatment with ethylene titanate).

The friction material of the present invention does not require addition of special conditions or steps except that the above-mentioned potassium titanate fiber or a mixture of this and other kinds of fibers is used as the base fiber. That is, first, the base fiber is dispersed in the binder,
If necessary, a raw material composition is prepared by adding an appropriate amount of a friction / wear modifier, or an anticorrosive agent, a lubricant, an abrasive, etc., and then binding molding is performed under heat and pressure by die molding or the like, or The raw material composition is dispersed and suspended in water, etc., drawn up on a paper making net, water-pressed to form a paper-like or sheet-like paper, and then binding-molded under heat and pressure, after which the binding is carried out. Appropriate mechanical processing and polishing processing are applied to the bonded product to obtain the desired friction material.

As an example of the binder in the preparation of the above raw material composition, a thermosetting resin such as a phenol resin, a formaldehyde resin, an epoxy resin, or a modified thermosetting resin (cashew oil, dry modified etc.), a natural rubber. Examples thereof include rubber-based resins such as styrene-butadiene rubber and nitrile rubber.

As the friction / wear modifier, organic powder such as vulcanized or unvulcanized natural / synthetic rubber powder, cashew resin powder, resin dust, rubber dust, or natural / artificial graphite, molybdenum disulfide, sulfuric acid is used. Examples thereof include inorganic powders such as barium and calcium carbonate, metal powders such as copper, aluminum, zinc and iron, oxide powders such as alumina, silica, chromium oxide, titanium oxide and iron oxide. They are,
They may be blended alone or in combination of two or more, depending on the frictional characteristics required for the product, for example, the friction coefficient, wear resistance, vibration characteristics, naki and the like.

The blending amount of each additive in the above raw material composition is appropriately determined depending on the use of the friction material, required performance, etc. For example, the binder is 10 to 40% by weight, and the friction / wear modifier is , 20 to 80% by weight, and other auxiliary agents can be 0 to 60% by weight.

[0018]

EXAMPLES Example 1 (1) Test Material A mold was filled with the following composition containing potassium titanate fiber as a base fiber and binding molding was performed (pressing force: 150 kgf / cm ² , temperature:
170 ℃, time: 5 minutes), after molding, mold release and heat treatment (hold at 180 ℃ for 3 hours). After that, polishing is applied to obtain a test pad. Base fiber 30 parts by weight Binder (phenol resin) 20 parts by weight Friction modifier (barium sulfate) 50 parts by weight Potassium titanate fibers used were those produced in Reference Example 1 or Reference Example 2 below. A test material, which is an invention example using the high-purity potassium hexatitanate fiber (purity: 99.1%) of Reference Example 1, was designated as A1, and the test material using the potassium hexatitanate fiber (Purity: 96.3%) of Reference Example 2 was used. Test material (comparative example)
Be B1. Further, as another comparative example, a test pad C1 manufactured under the same conditions as above except that asbestos fiber (6 class) was used as the base fiber was prepared.

(2) Friction and wear test A test piece was cut out from each of the test pads A1, B1, C1 and JI
S D4411 Constant velocity friction wear test (disc friction surface: FC25 gray cast iron, surface pressure: 10 kgf / cm ² , friction speed: 7 m / sec) in accordance with the regulations of "Brake lining for automobiles" and wear rate (cm ³ / Kgm) and the friction coefficient (μ) were measured. The measurement results are shown in FIGS. 1 and 2 (FIG. 1:
Wear rate, Fig. 2: Friction coefficient).

Example 2 (1) Specimen Material The following composition containing potassium titanate fiber as a part of the base fiber was used as a raw material, and binding molding, heat treatment, and Polishing is performed to obtain a test pad. Base fiber Potassium titanate fiber 16 parts by weight Aramid fiber ("Kevlar pulp" (length 3 mm), manufactured by Toray Industries, Inc.) 3 parts by weight Binder (phenolic resin) 9 parts by weight Organic additive (cashew dust) Etc.) 9 parts by weight Others (lubricant such as graphite, inorganic powder such as barium sulfate, metal powder, oxide powder) 63 parts by weight As a base fiber, high purity potassium hexatitanate fiber of Reference Example 1 (purity: 99.1) %) Is used as the test material (invention example), and potassium hexatitanate fiber of Reference Example 2 (purity:
The test material (comparative example) using 96.3%) is designated as B2. In addition, as another comparative example, a test pad C2 was prepared under the same conditions as above except that asbestos fibers (6 class) were used instead of potassium titanate fibers.

(2) Friction and Wear Test A constant velocity friction and wear test similar to that of Example 1 was performed on each of the test materials A2, B2 and C2, and the results of FIG. 3 (wear rate) and FIG. 4 (friction coefficient) were obtained. Obtained.

FIGS. 1, 3 (wear rate) and FIGS. 2, 4
From the comparison of each test pad in (friction coefficient), the test pad A1, which uses potassium titanate fiber as the base fiber,
A2, B1 and B2 have dramatically improved wear resistance compared to the test pads C1 and C2 using asbestos fibers (Figs. 1 and 3), and the friction coefficient in the temperature range over 250 ° C. Is also small (Figs. 2 and 4). Further, comparing the friction and wear characteristics of the test pad materials using potassium titanate fiber, the test material B1 using low purity fiber
B2 shows a fade phenomenon in which the friction coefficient greatly decreases in the temperature range of 350 ° C. or higher, and wear also significantly increases, whereas the test pad A of the invention example using high-purity fiber
It can be seen that 1 and A2 have an extremely small change in the friction coefficient even in the temperature range exceeding 350 ° C., and have a relatively low decrease in friction resistance and improved friction and wear characteristics.

Reference Example 1 (Production of high-purity potassium hexatitanate fiber) A mixture (TiO ₂ / K) with purified anatase (TiO ₂ : 99.2%) as a titanium oxide source and industrial potassium carbonate (purity: 99.5%). _A potassium hexatitanate fiber is manufactured by the following process using a ₂ O molar ratio of 2.0) as a starting material. (1) Heating and melting The starting raw material powder was put into a platinum crucible and heated and melted at 1050 ° C for 40 minutes. (2) Cooling and solidification The heated melt is poured into a dish-shaped copper container to be rapidly cooled and solidified, and potassium dititanate fiber (K ₂ Ti) which is a primary phase fiber.
_A cooled solidified product which is a bundle-shaped aggregate of ₂ O ₅ ) is obtained. (3) Potassium removal and defibration treatment The coagulated product was added to a washing liquid (150 times the amount of water) and K ⁺ was added under stirring with a propeller until the TiO ₂ / K ₂ O molar ratio reached about 6.
Dissolve ions as well as elute them. (4) Baking treatment The defibrated fibers (hydrated potassium titanate polycrystal fiber having a composition equivalent to potassium hexatitanate) are recovered from the washing solution, dehydrated and dried, put in an alumina crucible, and baked in a furnace. (Ten
00 ℃ x 3 hours). The potassium hexatitanate fiber obtained through the firing treatment is a white plate-like polycrystalline fiber. Purity: 99.1%, average cross-sectional diameter: 20 μm, average length: 200 μ
m.

Reference Example 2 Potassium hexatitanate was prepared by the same steps and conditions as in Reference Example 1 except that natural rutile sand (Australia, TiO ₂ : 95.6%) was used as the titanium oxide source instead of purified anatase. Produce fiber. The obtained potassium hexatitanate fiber is a plate-like polycrystalline fiber that exhibits a pale yellow color. Purity: 96.3%, average cross-sectional diameter / average length: same as in Reference Example 1.

[0025]

The friction material of the present invention has excellent and stable friction effect and wear resistance over a wide temperature range from low temperature to high temperature. In particular, it does not lose its stable friction coefficient even at high temperatures exceeding 350 ° C, and it has great wear resistance.
Therefore, when it is used as a brake lining, a clutch facing, a disk pad or the like in a braking device of an automobile, a vehicle, an aircraft or various industrial machines, the effect of improving / stabilizing the braking function and improving the useful life can be obtained.

[Brief description of drawings]

FIG. 1 is a graph showing wear rate measurement results by a constant speed friction wear test.

FIG. 2 is a graph showing the results of friction coefficient measurement by a constant speed friction wear test.

FIG. 3 is a graph showing wear rate measurement results by a constant speed friction wear test.

FIG. 4 is a graph showing the results of friction coefficient measurement by a constant speed friction and wear test.

Claims (1)

Claim: What is claimed is: 1. A friction material obtained by binding and molding base fibers with an organic or inorganic binder, wherein the base fibers are three potassium titanate fibers having a purity of 98% or more. Friction material characterized by being blended up to 50% by weight.