JPH0532958A - Friction material - Google Patents

Abstract

PURPOSE:To obtain a friction material exhibiting stable friction effect and abrasion resistance in a wide temperature range from a low temperature to a high temperature and useful for the brake-lining of automobile, etc., by bonding and forming a base fiber composed of a specific fibrous compound with an organic binder, etc. CONSTITUTION:The objective friction material is produced by bonding and forming a base fiber composition (preferably surface-treated with a silane coupling agent, etc.) composed of 3-50wt.% of a fibrous compound of formula (A is Na or K; x is 0-0.5) having orthorhombic crystal form and tunnel structure and 1-60wt.% of other fibers (e.g. aramid fiber) with an organic or inorganic binder.

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 vehicles, aircrafts, industrial machines and the like.

[0002]

2. Description of the Related Art As a typical sliding member in the above braking device, asbestos fiber has been used as a base fiber in the past and dispersed in an organic or inorganic binder, and a friction / wear modifier (sulfuric acid) is added as necessary. Friction materials have been used which have been added with barium or the like) and binding-molded under heat and pressure. In addition, with regard to the improvement of the friction performance, many proposals have been made so far, such as the addition of various additives.

[0003]

However, although the conventional friction material using asbestos fiber as the base fiber shows stable and good friction and wear characteristics in a low temperature range, when the friction surface temperature exceeds about 200 ° C. , Wear increases sharply,
Further, there is a problem that the friction coefficient also greatly decreases from a temperature of about 350 ° C. and a fade phenomenon appears. Recently, from the standpoint of environmental hygiene such as the improvement of heat resistance, the demand for improvement and stabilization of friction and wear characteristics in high temperature range, and the problem of carcinogenicity pointed out in asbestos fibers, alternatives Development is strongly demanded. The present invention provides a new friction material to meet the above demand.

[0004]

Means and Actions for Solving the Problems The present invention is directed to a friction material obtained by binding and molding base fibers with an organic or inorganic binder to form A _1-X Ti _{2 + X} as the base fibers. Al _5-X O ₁₂ ... [I] [wherein A is Na or K and x is 0 to 0.5], and 3 to 50 parts by weight of a fibrous compound having an orthorhombic tunnel structure. It is characterized by being blended.

The compound represented by the above formula [I], which is the base fiber of the friction material of the present invention, is described in "Journal of the Ceramic Society of Japan, 98 [10] P. 1169-71 (199).
0) ”, four AlO ₆ and 2
Octahedral six pieces of TiO ₆ (both octahedral coordination), and 4 AlO ₄ formed in tetrahedral coordination AlO ₄ 2 pieces and of
-(AlO ₆ -TiO ₆ ) -AlO ₆ [Shape sharing in brackets, vertex sharing in other brackets] A ion (Na ⁺ or K ⁺⁾ within the framework of an octagonal tunnel consisting of two-fold symmetry.
Has a coordinated crystal structure. Although the stoichiometric composition is x = 0.2, it can be put to practical use as a fiber having the above crystal structure in the range of x = 0 to 0.5.

The fibrous compound has a high melting point and a high hardness. For example, Na _0.8 Ti _2.2 Al _4.8 O _{12 has} a melting point of about 1418 ° C. and a Mohs hardness of 5-6. In the actual use of a friction material such as a brake pad for an automobile, the friction surface is locally 1000 due to the generation and accumulation of friction heat.
It is presumed that the temperature rises above ℃. By using the fibrous compound as a base fiber of such a friction material,
As the effect of improving the heat resistance and wear resistance of the friction surface, as shown in the examples described below, the friction coefficient is excellent in the low temperature range as well as in the high temperature range of over 300 ° C to around 400 ° C. And wear resistance is ensured.

When the content of the fibrous compound in the friction material of the present invention is 3% by weight or more, when the content is less than that,
This is because the effect of improving the friction and wear characteristics cannot be sufficiently obtained, and the upper limit of 50% by weight is that there is no advantage in compounding a large amount beyond that.

The size of the above fibrous compound compounded as the base fiber is not particularly limited, and for example, the cross-sectional diameter is about 5 to 20.
μm, length about 50-100 μm, or cross-section diameter about 20
Single crystal or polycrystalline fibers of various sizes, such as .about.50 .mu.m and length 100 to 300 .mu.m can be used. It should be noted that it is considered harmful for environmental hygiene to have extra fine fiber pieces (cross-sectional diameter of about 1 μm or less) mixed in the dust generated from the friction surface during actual use of brakes, etc. If the fiber has a diameter of about 5 μm or more, such a safety problem can be avoided.

[0009] The fibrous compound as a base fiber, as shown in the following Reference Examples, the Na ₂ O or K ₂ O (Na ₂ O by heating, may be compounds which decompose to K ₂ O),
TiO ₂ (a compound that turns into TiO ₂ by heating may be used)
And a Al ₂ O ₃ compound (which may be a compound that becomes Al ₂ O _{3 when} heated) are used as a raw material, or a flux method is used as a raw material, which is a composition that is mixed with a flux component. It is possible to use the one that has been made. In the flux method, the fiber morphology (cross-sectional diameter, length, etc.) of the obtained fibrous compound is adjusted by adjusting the mixing ratio of the crystal component and the flux component in the raw material composition, and the cooling conditions in the slow cooling operation after heating and melting. In addition, in the firing method, the size can be adjusted as a single crystal fiber or a polycrystalline fiber depending on the mixing ratio of Na ₂ O and K ₂ O in the raw material composition and the firing conditions.

The friction material of the present invention, as the base fiber, together with the above fibrous compound, other types of fibers such as resin fiber such as aramid fiber, steel fiber, carbon fiber, glass fiber, ceramic fiber, rock wool, wood pulp, etc. Can be used in combination for reinforcing the friction material. The blending amount of these other kinds of fibers can be about 1 to 60% by weight. Prior to the preparation of the raw material composition, each of the base fibers has a silane coupling agent (aminosilane, vinylsilane, epoxysilane, methacrylic acid) for the purpose of improving the dispersibility and the adhesiveness with the binder, if necessary. Roxylan,
A surface treatment with a mercapto xylan or the like) or a titanate coupling agent (such as isopropyltriisostearoyl titanate or di (dioctylpyrophosphate) ethylene titanate) is performed according to a conventional method.

The friction material of the present invention does not require any special conditions or steps except that the above fibrous compound or a mixture of the fibrous compound and fibers of other kinds is used as the base fiber. That is, first, the base fiber is dispersed in a binder, and if necessary, an appropriate amount of a friction / wear modifier, a rust preventive agent, a lubricant, an abrasive, etc. is mixed to prepare a raw material composition, and then a mold is prepared. Binder molding is performed under heat and pressure by molding or the like, or the raw material composition is dispersed and suspended in water or the like, made up on a making net, and squeezed to form a paper or sheet. After that, the binder is molded under heat and pressure, and then the binder molded product is machined,
Polishing is applied to obtain the desired friction material.

As an example of the binder in the preparation of the above-mentioned raw material composition, a thermosetting resin such as phenol resin, formaldehyde resin, epoxy resin, or a thermosetting resin modified with these (cashew oil, dry modified etc.), 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,
These may be blended alone or in combination of two or more, depending on the frictional characteristics required for the product, such as friction coefficient, wear resistance, vibration characteristics, and pear.

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

[0015]

Example 1 (1) Specimen material Using the following composition as a raw material, the composition was filled in a mold and subjected to binding molding (pressure: 150 kgf / cm ² , temperature: 170 ° C., time: 5 minutes). After molding and molding, the mold is released and heat treatment (holding at 180 ° C. for 3 hours) is performed. After that, it is cut into a predetermined size and subjected to polishing to obtain a test pad. Base material fiber 30 parts by weight Binder (phenol resin) 20 parts by weight Friction modifier (barium sulfate) 50 parts by weight The above base material fiber is produced by Reference Example 1 (flux method) or Reference Example 2 (firing method) described below. using the ones _{(both, Na 0.8 Ti 2.2 Al 4.8 O} 12). The test material which is an example of the invention using the fibrous compound of Reference Example 1
A2 is a test material which is an invention example using the fibrous compound of Reference Example 2. In addition, as a comparative example, a test pad B1 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, A2, B1 and JI
S D4411 Constant speed friction wear test based on the regulations of "Brake lining for automobiles" (disc friction surface: FC25 gray cast iron, surface pressure: 10 kgf / cm ² , friction speed: 7 m / sec)
Specific wear rate (cm ³ / kgm) and friction coefficient (μ)
Was measured. The measurement results are shown in FIGS. 1 and 2 (FIG. 1: specific wear rate, FIG. 2: friction coefficient).

Example 2 (1) Test Material Using the following composition as a raw material, under the same conditions as in the above-mentioned Example 1, a binding test, a heat treatment, and a polishing process were carried out using a mold to obtain a test pad. Base fiber: 28 parts by weight Binder (phenol resin): 10 parts by weight Organic additive (cashew dust, etc.): 8 parts by weight Others (lubricant such as graphite, inorganic powder such as barium sulfate, metal powder, oxide powder) 54 parts by weight As the base fiber, the fibrous compound (Na _0.8 Ti _2.2 Al _4.8 O ₁₂ ) produced in Reference Example 1 described later was used. This test pad (invention example) is designated as A3. Also, as a comparative example, a test pad B2 was prepared under the same conditions as above except that the base fiber was changed to asbestos fiber (6 class).

(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 A3 and B2, and FIG. 3 (specific wear rate) and FIG.
The results shown in (Friction coefficient) were obtained.

FIGS. 1, 3 (specific wear rate) and FIGS. 2, 4
As is clear from the comparison of each test pad in (friction coefficient), a test pad B using asbestos fiber as a base fiber
In No. 1 and B2 (conventional type), the wear rate increases as the friction surface temperature rises, and the wear resistance decreases sharply especially in the temperature range exceeding 200 ° C, and when the friction surface temperature rises above 350 ° C. , A friction phenomenon in which the coefficient of friction sharply decreases occurs, whereas the test pads A1, A2 of the invention example
A3 has very little change in wear resistance with temperature, has a high degree of wear resistance from a low temperature range to a high temperature range of 400 ° C, and has a small friction coefficient temperature change, exceeding 350 ° C. Also maintains a high friction coefficient.

Reference Example 1 (Production of Fibrous Compound by Flux Method) (1) Raw Material Composition A starting material is a mixture of the following crystal components and flux components. Crystal component Na ₂ CO ₃ ... 10.24% by weight TiO ₂ ... 7.68% by weight Al ₂ O ₃ ... 9.76% by weight Flux component Na ₂ CO ₃ ... 23.68% by weight MoO ₃ ... 48.64% by weight (Na ₂ C constituting the crystal component in the above raw material composition
The compounding molar ratio of O ₃ , TiO ₂ , and Al ₂ O ₃ is 1: 1:
1, the mixing molar ratio of Na ₂ CO ₃ and MoO _{3 as} the flux component is 1: 1.5, and the mixing molar ratio of the crystal component and the flux component is 3: 7.

(2) Heat Melt Treatment The above raw material composition was put in a platinum crucible and heated to 1300 ° C. for 10 minutes.
Hold for a while to heat and melt.

(3) Slow cooling treatment The above melt is gradually cooled to 1000 ° C. in 75 hours.
Then let cool to room temperature.

(4) Flux removal treatment The cooled solidified product was put in boiling water (water amount: about 200 g / l), and the flux components were eluted and separated with stirring for 1 hour, and then the fibrous compound was recovered. Washed with water and dried. Crystal phase: Na _0.8 Ti _2.2 Al _4.8 O ₁₂ Size: Cross-sectional diameter 30 to 150 μm, length 200 to
1000 μm

Reference Example 2 (Production of Fibrous Compound by Firing Method) (1) Raw Material Composition Na ₂ CO ₃ 13.0 wt% TiO ₂ 36.78 wt% Al ₂ O ₃ 50.14 wt% (the above raw materials Na ₂ CO ₃ , TiO ₂ , A in the composition
The compounding molar ratio of l ₂ O ₃ is 3:11:12, and Na ₂ CO ₃ is slightly excessive to promote fiber growth.)
The above raw material composition is mixed with a mixer, and 5% by weight of water is added and kneaded, followed by press molding (pressing force: 170 kg / c
m ² ).

(2) Baking treatment A molded body of the above raw material composition is dried and put in a platinum crucible,
A heating treatment is performed by heating and holding at 1350 ° C. for 5 hours.

(3) Pulverization and defibration treatment The above fired product was put in 70 l / g of water and wet defibration was performed with a household mixer. After defibration treatment, collect from water and dehydrate /
It was dried to obtain a fibrous compound. Fiber phase: Na _0.8 Ti _2.2 Al _4.8 O ₁₂ (trace amount of Na
-Β "alumina (with Na ₂ O.8Al ₂ O ₃ ) size: cross section diameter 20-100 μm, length 50-2
00 μm.

[0027]

INDUSTRIAL APPLICABILITY 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, and has stable friction even at a high temperature exceeding 350 ° C. The coefficient is maintained and the abrasion resistance is large. Therefore, brake linings, clutch facings in braking devices for automobiles, vehicles, aircraft, and various industrial machines,
By using it as a disk pad, etc., the braking function is improved and stabilized, and the useful life is improved.

[Brief description of drawings]

FIG. 1 is a graph showing the results of specific wear rate measurement 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 measurement results of specific wear rate 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)

Claims: 1. A friction material obtained by binding and molding base fibers with an organic or inorganic binder, wherein the base fibers are A _1-X Ti _{2 + X} Al _5-X. 3 to 50% by weight of a fibrous compound having an orthorhombic tunnel structure represented by O ₁₂ [wherein A is Na or K and x is 0 to 0.5]. And friction material.