JPH0726032A - Friction material - Google Patents

Abstract

PURPOSE:To improve the coefficient of friction and abrasion resistance of a friction material used for a brake of an automobile, etc. CONSTITUTION:A friction material is produced by molding a mixture comprising a binder resin and a base material comprising an octotitanate of a hollandite structure of the formula: KXBaYAlX+2YTi8-X-2YO16 (wherein X is 0.2-1.4; and Y is 0.2-1.4) in an amt. of about 3-50wt.%. Other known fibers may be used jointly. Suitable amts. of a friction-adjusting agent (e.g. barium sulfate) and other ingredients (e. g. a rust preventive) may be compounded if necessary.

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 such as a brake lining, a disk pad, a clutch facing, etc., which constitutes a braking device for automobiles, railway vehicles, aircrafts, industrial machines and the like.

[0002]

2. Description of the Related Art As a friction material in the above-mentioned braking device, asbestos fiber has been used as a base material and dispersed in a resin binder (phenol resin, epoxy resin, etc.), and a friction / wear modifier (barium sulfate) is used as necessary. Friction materials produced by binding and molding a kneaded product to which is added under heat and pressure have been used.

[0003]

In order to cope with higher speeds of automobiles and downsizing and weight reduction of brake devices, the coefficient of friction is high, and the high coefficient of friction has a wide temperature range from low temperature to high temperature. A friction material that is stably maintained in the region and has excellent abrasion resistance is required. Friction materials based on asbestos fibers have been used as friction materials with excellent friction and wear characteristics, but wear increases markedly as the friction surface becomes hot, and the friction coefficient at high temperatures increases. The performance deteriorates significantly in the high temperature range, such as a fade phenomenon in which the temperature rapidly decreases. Further, even in a low temperature range which is considered to have excellent friction and wear characteristics, the coefficient of friction is relatively low, and the above requirements cannot be met. Further, recently, the problem of carcinogenicity of asbestos fibers has been pointed out, and development of a substitute for the same has been demanded from the viewpoint of environmental hygiene. In view of the above, the present invention intends to provide a friction material which has improved friction and wear characteristics in order to eliminate the use of asbestos fibers and to meet the demands for higher speed and smaller and lighter brake devices. It is a thing.

[0004]

DISCLOSURE OF THE INVENTION The present invention provides a friction material obtained by binding and molding a kneaded material containing a base material using a resin as a binder, and the base material has the following formula [1] K _x Ba _Y Al _{x + 2Y} Ti _8-X-2Y O ₁₆ [1] 3 to 50 parts by weight of octotitanate having a hollandite type structure represented by the formula [wherein X is 0.2 to 1.4 and Y is 0.2 to 1.4] It is characterized by being blended in%.

[0005]

The crystal of octotitanate having the hollandite type structure represented by the above formula [1] is (Ti, Al) O ₆
It is a synthetic inorganic compound having a one-dimensional tunnel structure in which K ⁺ and Ba ⁺⁺ ions are coordinated in the frame formed by an octahedron [Inorganic Material Research Institute Research Report No. 57, pages 4 to 7 "Study on material synthesis" ]]. This has a high melting point [about 1450 ° C. or higher, for example, K _0.7 Ba _0.7 Al _2.1 Ti _5.9 O ₁₆ (X = Y =
0.7) has a melting point of about 1510 ° C.] and has excellent heat resistance and reinforcing effect, and its hardness is about 5 to 6 in Mohs hardness,
It has an appropriate hardness as a friction material. In the actual use of a friction material such as an automobile brake pad, it is estimated that the friction surface locally heats up to 1000 ° C. or higher due to frictional heat generation and heat accumulation. By blending the octotitanate as the base material of the friction material exposed to such severe usage conditions, as shown in the examples below, the wear resistance and the high friction coefficient are excellent even in the high temperature range. Is secured. The temperature dependency of the improved friction and wear characteristics is extremely small, and is stably maintained in a wide temperature range from low temperature to high temperature.

Hereinafter, the friction material of the present invention will be described in detail. The blending ratio of octotitanate, which is the base material of the friction material of the present invention, needs to be at least 3% by weight in order to exert the effect of improving friction and wear characteristics. However, the blending amount is sufficient up to 50% by weight, and there is no advantage of blending a large amount beyond that. Therefore, the amount is 3 to 50% by weight. The shape of octotitanate is not particularly limited, but those having a particle morphology with a major axis of about 10 to 100 μm, a minor axis of about 3 to 20 μm, and an aspect ratio of about 2 to 5 are uniformly kneaded and dispersed in a resin. Excellent in reinforcing effect. In addition, as pointed out in friction materials that use asbestos fibers, it is a matter of environmental hygiene that dust particles generated from the friction surface during actual use such as brakes contain ultrafine particles (cross-sectional diameter of about 1 μm or less). Although it is said to be harmful, if the particles have the above-mentioned grain size, such ultrafine pieces will not occur, and safety can be secured.

The friction material of the present invention, together with the octotitanate as the base material, other known fibers such as polyamide (nylon) fiber, aramid fiber, steel fiber, stainless fiber, copper fiber, brass fiber and carbon. One or more kinds of fibers selected from fibers, glass fibers, ceramic fibers, rock wool, wood pulp, etc. are combined (for example,
10 to 65% by weight in total with the octotitanate). The above-mentioned substrate is a silane coupling agent (aminosilane, vinylsilane, epoxysilane, methacryloxylan, mercapto) according to a conventional method for improving dispersibility, binding property with a binder resin, etc., if necessary. (Xylsilane, etc.) or a titanate-based coupling agent (isopropyl triisostearoyl titanate, di (dioctyl pyrophosphate) ethylene titanate, etc.) is used after being subjected to a surface treatment (coupling treatment).

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). Further, in the friction material of the present invention, it is usual that various additives such as rust preventives, lubricants, abrasives, etc. are blended in an appropriate amount (for example, 50% by weight or less) in accordance with the application / use mode thereof. It is no different from friction material.

The resin component, which is the binder in the friction material of the present invention, is a commonly used material such as phenol resin,
Thermosetting resins such as formaldehyde resin, epoxy resin, silicone resin, thermosetting resins modified with these (cashew oil modification, dry modification, etc.), rubber-based resins such as natural rubber, styrene butadiene rubber, nitrile rubber, etc. To be

The friction material of the present invention has the same component composition as the conventional friction material having asbestos fibers as a base material except that the above-mentioned octotitanate is used as the base material, and the manufacturing process thereof. Is not subject to any special conditions or restrictions. That is, a base material is dispersed in a binder resin, and a friction and wear modifier and a rust preventive agent, which are blended as needed,
Lubricants, abrasives, etc. are added, and the mixture is uniformly kneaded to prepare a raw material composition, which is then subjected to binding molding under heat and pressure by die molding or the like, and heat treatment if necessary, and thereafter. Machining and polishing are applied to the molded body to finish the friction material having a predetermined shape. Alternatively, the raw material composition is dispersed and suspended in water or the like, made with a paper making net, squeezed with water to make a sheet, and an appropriate number of sheets are stacked, and binding molding is performed under heating and pressure, The molded body is machined and polished to obtain a predetermined friction material.

[0011]

【Example】

[Production of test friction material] Octo titanate [K
_0.7 Ba _0.7 Al _2.1 Ti _5.9 O ₁₆ , X = Y = 0.7]
Using the following reference examples, prepare the following raw material compositions and bond molding with a die (pressing force: 14.7 MPa = 150 K)
gf / cm ² , temperature: 170 ° C, pressurization holding time: 5 minutes), after molding, release and heat-treat in a drying oven (holding 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 30% by weight Binder resin (phenolic resin) 20% by weight Friction modifier (barium sulfate) 50% by weight

Comparative Example The friction material (disc pad) to be tested was prepared by the same raw material composition and production process as in Example 1 except that asbestos fibers (6 class) were used as the base material instead of octotitanate. ) Got. This friction material (conventional type) is designated as B.

[Friction and Wear Test] Above Friction Material A (Invention Example)
For B1 and B1 (comparative example), the friction coefficient and specific wear rate (cm ³ / N · m) were measured by the constant speed friction wear test specified in JIS D4411 “Brake lining for automobiles”. The obtained results were obtained [Fig. 1: friction coefficient, Fig. 2: specific wear rate]. Disc friction surface: FC25 gray cast iron, surface pressure: 10Kgf / cm ² , friction speed: 7m / sec.

FIG. 1 (friction coefficient) and FIG. 2 (specific wear rate)
As shown in, friction material B using asbestos fibers
Has a low coefficient of friction at low and high temperatures, especially 35
The drop in the high temperature region above 0 ° C is rapid. The wear resistance also decreases with increasing temperature, and the deterioration in the temperature range exceeding 300 ° C. is remarkable. On the other hand, the friction material A of the invention example has a high friction coefficient and its temperature dependence is extremely small, and the high friction coefficient is stably maintained in a wide temperature range from low temperature to high temperature, and the wear resistance is low. However, in the low temperature region, of course, the increase in the amount of wear in the high temperature region exceeding 300 ° C. is extremely small, and the difference from the friction and wear characteristics of the friction material B is obvious.

[0015]

[Reference example]

[Production of octotitanate having hollandite type structure] (1) Raw material composition: potassium carbonate, barium carbonate, aluminum oxide, titanium oxide, K ₂ CO ₃ : BaC
O ₃ : Al ₂ O ₃ : TiO ₂ = 0.7: 1.4: 2.
It is mixed in a molar ratio of 1: 11.8. After mixing with a mixer for 10 minutes and adding 5% by weight of water to the mixed powder, the mixture is filled in a mold and press-molded (pressing pressure 5.1 MPa). (2) Firing treatment: 900 mm of the above press-molded body in a firing furnace
Keep 2Hr at ℃ for CO of potassium carbonate (K ₂ CO ₃ ).
After releasing ₂ , the mixture is heated and held at 1350 ° C. for 3 hours to cause a firing reaction (octotitanate generation / growth reaction based on solid-phase reaction), and then cooled in the furnace. The calcined reaction product is a lump in which octotitanate is solidified. (3) Disentanglement treatment: The calcination reaction product was roughly crushed and passed through a 2 mm sieve, then 1 L of water was added and the mixture was mixed with a household mixer to 1
Stir for 0 minutes and wet defibration. After defibration, dehydration and drying. Composition (X-ray powder diffraction): K _0.7 Ba _0.7 Al _2.1 Ti
_5.9 O ₁₆ size (scanning electron microscope): major axis 10-50 μm, minor axis 3-20 μm, aspect ratio 2-3.

[0016]

The friction material of the present invention has a high coefficient of friction and outstanding wear resistance. The temperature dependence of the friction and wear characteristics is small, and it is stably maintained in a wide temperature range from low temperature to high temperature. Therefore, the friction material of the present invention is useful as a brake lining, a clutch facing, a disk pad, etc. of a braking device for automobiles, vehicles, aircrafts, various industrial machines, etc., and has a high speed and a small braking device.
It is possible to cope with weight reduction and the like, and also it is possible to improve and stabilize the braking function and improve durability.

[Brief description of drawings]

FIG. 1 is a graph showing the results of measuring a friction coefficient by a constant speed friction and wear test.

FIG. 2 is a graph showing a measurement result of a specific wear rate by a constant speed friction wear test.

[Explanation of symbols]

 A: invention example, B: comparative example.

Claims (1)

[Claims] 1. A friction material obtained by binding and molding a kneaded material containing a base material using a resin as a binder, wherein the base material has the following formula [1] K _x Ba _Y Al _{x + 2Y} Ti _8-x-2Y O ₁₆ ... [1] [wherein X is 0.2 to 1.4 and Y is 0.2 to 1.4], and 3 to 50% by weight of octotitanate having a hollandite type structure is blended. Friction material