JP2939604B2 - Friction material - Google Patents

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 disc pad, a clutch facing, etc., constituting a braking device for an automobile, a railway vehicle, an aircraft, an industrial machine, and the like.

[0002]

2. Description of the Related Art As a typical sliding member in the above-mentioned braking device, asbestos fiber is conventionally used as a base fiber, which is dispersed in an organic or inorganic binder, and if necessary, a friction / wear adjusting agent (sulfuric acid) is used. A friction material manufactured by binding and kneading a kneaded material to which barium or the like has been added under heat and pressure has been used.

[0003]

The conventional friction material using asbestos fiber as a base fiber shows excellent friction characteristics in a low temperature range, but as the friction surface becomes higher in temperature, the asbestos fiber releases water of crystallization. When the temperature exceeds about 200 ° C., wear of the friction surface rapidly increases. There is also a problem that the coefficient of friction is greatly reduced from a temperature of about 350 ° C. and a fade phenomenon appears,
In order to cope with an increase in the speed of a vehicle and the like, improvement of its friction and wear characteristics is strongly demanded. Recently, the carcinogenicity of asbestos fiber has been pointed out, and the development of alternatives has been requested from the viewpoint of environmental health. The present invention provides a new friction material that meets the above demand.

[0004]

[Where x is 0.5-3]

Wherein octotitanate fibers having a hollandite structure represented by the formula (1) are blended in an amount of 3 to 50% by weight.

[0005]

The crystal fiber of octotitanate having a hollandite structure represented by the above formula (1) is (Ti, A
l) A synthetic inorganic compound having a one-dimensional tunnel structure in which K ions are coordinated in the frame of a tunnel formed by an O ₆ octahedron [Research Report on Inorganic Materials, No. 57, p. the study"〕. It has a high melting point (about 1
It has a melting point of 400 ° C. or more, for example, K _1.5 Al _1.5 Ti _6.5 O ₁₆ , and has excellent heat resistance and reinforcing effect, and its hardness is about 5 to 6 in Mohs hardness.
In actual use of friction materials such as automotive brake pads,
The friction surface locally generates 1 by the generation of frictional heat and heat storage.
It is estimated that the temperature rises to 000 ° C. or higher. By using the octo titanate fiber as the base fiber of the friction material exposed to such harsh use conditions, the heat resistance and wear resistance of the friction surface are enhanced, as shown in Examples described later. A high degree of wear resistance and a stable coefficient of friction are secured over a high temperature range exceeding 300 ° C. and around 400 ° C.

Hereinafter, the friction material of the present invention will be described in detail. The compounding ratio of the octo titanate fiber, which is the base fiber of the friction material of the present invention, is required to be at least 3% by weight in order to sufficiently exhibit the effect of improving the friction and wear properties.
Formulations up to 50% by weight are sufficient and beyond that there is no benefit in formulating large amounts. Therefore, the content is set to 3 to 50% by weight. Although the shape of the octotitanate fiber is not particularly limited, the fiber length is about 30 to 70 μm, and the fiber diameter is about 10 to 20.
Those having a fiber form of μm, aspect ratio: about 3 to 5 are excellent in uniformity of kneading and dispersion in a resin, a reinforcing effect, and the like. In addition, it is considered that it is harmful to the environment and sanitation that ultra-fine fiber fragments (cross-sectional diameter of about 1 μm or less) are mixed in dust generated from a friction surface during actual use of a brake or the like. In such a case, such ultra-fine pieces are not generated, and safety is ensured.

[0007] The friction material of the present invention, as a base fiber, together with the octo titanate fiber, other fibers such as aramid fiber, steel fiber, stainless fiber, copper fiber, brass fiber, carbon fiber, glass fiber, ceramics Fiber, rock wool, wood pulp and the like may be used in combination. The blending amount of these other kinds of fibers can be about 1 to 60% by weight. The base fiber may be used, if necessary, in order to improve dispersibility, binding property with a binder resin, etc., with a silane coupling agent (aminosilane, vinylsilane, epoxysilane, methacryloxysilane, mercaptoxysilane, etc.). ),
Alternatively, a surface treatment (coupling treatment) with a titanate-based coupling agent (isopropyl triisostearoyl titanate, di (dioctyl pyrophosphate) ethylene titanate, or the like) is performed before use.

The friction material of the present invention may be, if desired, a known friction and wear modifier, for example, organic powders such as vulcanized or unvulcanized natural or synthetic rubber powder, cashew resin powder, resin dust, rubber dust, and the like. Inorganic powders such as natural and artificial graphite, molybdenum disulfide, antimony disulfide, barium sulfate, calcium carbonate, metal powders such as copper, aluminum, zinc, iron, etc., alumina, silica, chromium oxide, copper oxide, antimony trioxide, oxidation One or two or more components selected from oxide powders such as titanium and iron oxide are added in an appropriate amount (generally 20 to 20) for the purpose of improving the friction and wear characteristics (friction coefficient, wear resistance, vibration characteristics, pear, etc.). 70% by weight).
Further, the friction material of the present invention, various additives, for example, a rust inhibitor,
Lubricants, abrasives, and the like may be blended in an appropriate amount (for example, 50% by weight or less) in accordance with the use and usage mode, etc., and do not differ from ordinary friction materials.

[0009] The resin component as a binder in the friction material of the present invention is a commonly used material type, for example, phenol resin,
Examples thereof include thermosetting resins such as formaldehyde resins and epoxy resins, and thermosetting resins thereof (modified with cashew oil and dryness), and rubber resins such as natural rubber, styrene butadiene rubber, and nitrile rubber. Except that the friction material of the present invention uses the above octo titanate fiber as a base fiber, its component composition is not different from that of a conventional friction material using asbestos fiber or the like as a base fiber, and its manufacturing process No special conditions are added or restricted. That is, a base fiber is dispersed in a binder resin, and a friction and wear adjuster and a rust preventive are added as required.
Lubricants, abrasives, etc. are added and uniformly kneaded to prepare a raw material composition. Then, binding molding is performed under heat and pressure by die molding, etc., and heat treatment is performed if necessary. The molded body is subjected to machining and polishing to finish the friction material having a predetermined shape. As another method, the raw material composition is dispersed and suspended in water or the like, paper-milled by a paper net, squeezed to form a sheet, and an appropriate number of the sheets are stacked and bound and formed under heat and pressure. The molded body is machined and polished to obtain a predetermined friction material.

[0010]

EXAMPLE 1 Octo-titanate fiber [K _1.6 Al _1.6
Ti _6.4 O ₁₆ ] (according to a reference example described later), the following raw material composition is prepared, and then subjected to binding molding with a mold (pressure: 1).
(4.7 MPa = 150 kgf / cm ² , temperature: 170 ° C, pressurization holding time: 5 minutes). After molding, the mold is released and heat-treated in a drying furnace (held at 180 ° C for 3 hours). After that, it is cut to a predetermined size, and polished to provide a friction material for testing (disk pad)
I got This test material is designated as A1. Base fiber 30% by weight Binder resin (phenol resin) 20% by weight Friction modifier (barium sulfate) 50% by weight Comparative example 1 Asbestos fiber (6 class) is used as the base fiber instead of octo titanate fiber A test friction material (disk pad) was obtained by the same raw material composition and manufacturing process as in Example 1 except for the above. This test material (conventional type)
Is B1.

[Friction and wear test] The test disk A1
(Invention Example) and B1 (Comparative Example)
The coefficient of friction and the specific wear rate (cm ³ / Kgm) were measured by a constant speed friction and wear test specified in “Automotive Brake Lining”, and the results shown in FIGS. 1 and 2 were obtained [FIG. 1: Friction coefficient, FIG. 2: Specific wear rate]. Disc friction surface: FC25 gray cast iron, surface pressure: 10 kgf / cm ² , friction speed: 7 m / sec.

Example 2 Using octo titanate fiber (same as that in Example 1) as a base fiber, the following raw material composition was prepared, and binding molding was performed using a mold under the same conditions as in Example 1. After the heat treatment and the heat treatment, mechanical processing and polishing were performed to obtain a test friction material (disk pad). This test material is designated as A2. Base fiber: 28% by weight Binder resin Phenolic resin: 10% by weight Friction and wear modifier Cashew dust: 8% by weight Others Barium sulfate powder, metal powder, oxide powder, graphite powder, etc. 54% by weight Comparative Example 2 base material A test friction material (disk pad) was obtained by the same raw material composition and manufacturing process as in Example 2 except that asbestos fibers (six classes) were used instead of octotitanate fibers. This test material (conventional type)
Is B2.

[Friction and Wear Test] For the test disks A2 (inventive example) and B2 (comparative example), the friction coefficient and specific wear rate (cm ³ / Kgm) were determined by the same friction and wear test as described above.
Was measured, and the results shown in FIGS. 3 and 4 were obtained [FIG. 3: coefficient of friction, FIG. 4: specific wear rate].

FIGS. 1 and 3 (coefficient of friction) and FIGS. 2 and 4
As is clear from the comparison of each test material in (specific wear rate), the conventional test disks B1 and B2 using asbestos fiber as the base fiber, the wear rate increases as the temperature of the friction surface increases, and particularly, the wear rate increases. The wear resistance in the temperature range exceeding 200 ° C. is sharply reduced, and when the temperature of the friction surface rises to about 350 ° C. or more, a fade phenomenon in which the friction coefficient sharply decreases occurs. On the other hand, the test disks A1 and A2 of the invention have very little change in temperature of abrasion resistance, and have high abrasion resistance over a wide temperature range from a low temperature range to 400 ° C. Further, the temperature dependence of the friction coefficient is small, and a high friction coefficient is stably maintained from a low temperature range to a high temperature range.

[0015]

[Reference example]

[Production of octo titanate fiber having hollandite structure] (1) Raw material composition: potassium carbonate, aluminum oxide,
Titanium oxide is converted to K ₂ CO ₃ : Al ₂ O ₃ : TiO ₂ =
The mixture was mixed at a molar ratio of 0.9: 0.8: 6.4, mixed with a mixer for 10 minutes, filled in a mold, and dry-molded (pressing force: 10).
(MPa) to form a molded body. (2) Firing treatment: The compact is heated in a firing furnace at 900 ° C. for 2 hours.
After holding to release the CO ₂ of potassium carbonate (K ₂ CO ₃ ), the mixture is heated and maintained at 1350 ° C. for 3 hours to carry out a firing reaction (a reaction for producing and growing octotitanate fibers based on a solid phase reaction). And then cooled in the furnace. The calcined anti-product is
It is a lump in which fibers of octotitanate are consolidated. (3) Fibrillation treatment: The fired reaction product is roughly pulverized, passed through a 2 mm sieve, immersed in water for 5 hours, and further stirred for 10 minutes with a household mixer to break the fiber binding. The defibrated fibers are recovered from the water and dehydrated and dried. Fiber composition (X-ray powder diffraction): K _1.6 Al _1.6 Ti _6.4 O ₁₆ Fiber size (scanning electron microscope): length 30-70 μm
m, diameter 10-20 μm, aspect ratio 3-5.

[0016]

The friction material of the present invention has a high degree of wear resistance and a stable coefficient of friction. The temperature dependency of the friction and wear characteristics is extremely small, and is stably maintained over a wide temperature range from low temperature to 400 ° C. Therefore, cars,
It is useful as a brake lining, clutch facing, disc pad, etc. for braking devices for vehicles, aircraft, various industrial machines, etc., and has the effects of improving and stabilizing braking functions, improving durability, etc. It is possible to deal with such problems as

[Brief description of the drawings]

FIG. 1 is a graph showing a measurement result of 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.

FIG. 3 is a graph showing a measurement result of a friction coefficient by a constant speed friction and wear test.

FIG. 4 is a graph showing a measurement result of a specific wear rate by a constant speed friction wear test.

[Explanation of symbols]

 A1, A2: invention example, B1, B2: comparative example.

──────────────────────────────────────────────────続 き Continuation of front page (58) Field surveyed (Int. Cl. ⁶ , DB name) F16D 69/00-69/02 C01G 23/00-23/08 C08J 5/14 C09K 3/14

Claims (1)

(57) [Claims] 1. A friction material obtained by binding and forming a base fiber with an organic binder, wherein the base fiber is K _x Al _x Ti _8-x O ₁₆ [where x is 0.5 to 3]. A friction material comprising 3 to 50% by weight of an octo titanate fiber having a hollandite structure as shown.