JP2958602B2 - 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 Conventionally, as a friction material in the above-mentioned braking device, asbestos fiber is used as a base material, which is dispersed in a resin binder (phenol resin, epoxy resin, etc.). And the like. A friction material produced by binding and kneading the kneaded material to which the above-described compound has been added under heat and pressure has been used.

[0003]

In order to cope with an increase in the speed of an automobile or the like and a reduction in the size and weight of a brake device, the friction coefficient is high, and the high friction coefficient has a wide temperature range from a low temperature to a high temperature. A friction material which is stably maintained in a region and has excellent wear resistance is required. Friction materials based on asbestos fibers have been used as friction materials with excellent friction and wear characteristics.However, as the friction surface increases in temperature, wear increases significantly, and in the high temperature range, the friction coefficient increases. The performance degradation in a high temperature range is large, such as the occurrence of a fade phenomenon in which the temperature decreases rapidly. Further, even in a low temperature range where the friction and wear characteristics are considered to be excellent, the friction coefficient is relatively low, and cannot meet the above demand. Furthermore, recently, the problem of carcinogenicity of asbestos fibers has been pointed out, and the development of alternatives has been requested from the viewpoint of environmental health. In view of the above, the present invention seeks to eliminate the use of asbestos fibers, and to provide a friction material having improved friction and wear characteristics for responding to demands for higher speed, a smaller and lighter brake device, and the like. Things.

[0004]

SUMMARY OF THE INVENTION The present invention relates to a friction material obtained by binding and forming a kneaded product containing a base material using a resin as a binder, wherein the base material is represented by the following formula (1): K _x Ba _Y Al _{x + 2Y} Ti _8-X-2Y O ₁₆ ... [1] wherein the octo titanate having a hollandite structure represented by the formula, wherein X is 0.2 to 1.4 and Y is 0.2 to 1.4, is 3 to 50% by weight. %.

[0005]

The crystal of octotitanate having the hollandite 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 an octahedral frame [Inorganic Materials Research Institute Research Report No. 57, p. ]]. It 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.], is excellent in heat resistance and reinforcing effect, and has a hardness of about 5 to 6 in Mohs hardness.
It has moderate hardness as a friction material. In actual use of friction materials such as brake pads for automobiles, it is estimated that the friction surface locally rises in temperature to 1000 ° C. or higher due to generation of frictional heat and heat storage. By blending the above octotitanate as a base material of a friction material exposed to such severe use conditions, as shown in Examples described later, outstanding wear resistance and a high friction coefficient even in a 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 a low temperature to a high temperature.

Hereinafter, the friction material of the present invention will be described in detail. The mixing 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 compounding amount is sufficient up to 50% by weight, and there is no advantage of compounding a large amount beyond that. Therefore, the content is set to 3 to 50% by weight. The shape of the octotitanate is not particularly limited, but those having a particle shape of 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 have uniform kneading and dispersion in a resin. Good properties and excellent reinforcement effect. In addition, as pointed out in friction materials using asbestos fibers, the inclusion of ultra-fine pieces (cross-sectional diameter of about 1 μm or less) in dust generated from friction surfaces during actual use of brakes, etc. Although it is considered to be harmful to the above, if it is of the above-mentioned particle size, such ultra-fine pieces are not generated, and safety is also ensured.

The friction material of the present invention comprises, as a base material, other known fibers such as polyamide (nylon) fiber, aramid fiber, steel fiber, stainless fiber, copper fiber, brass fiber, carbon fiber together with the above octotitanate. One or two or more fibers selected from fibers, glass fibers, ceramic fibers, rock wool, wood pulp, etc.
About 10 to 65% by weight in total with the above octotitanate). The above-mentioned base material may be used, if necessary, in order to improve dispersibility, binding property with a binder resin, etc., according to a conventional method using a silane coupling agent (aminosilane, vinylsilane, epoxysilane, methacryloxysilane, mercaptosilane). Xylan) or a surface treatment (coupling treatment) with a titanate-based coupling agent (isopropyl triisostearoyl titanate, di (dioctyl pyrophosphate) ethylene titanate, etc.).

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 trisulfide, barium sulfate, calcium carbonate, metal powders such as copper, aluminum, zinc, iron, alumina, silica, chromium oxide, copper oxide, antimony trioxide, and oxide One or two or more components selected from oxide powders such as titanium and iron oxide are added in an appropriate amount (for example, 20 to 20) for the purpose of improving the friction and wear characteristics (friction coefficient, wear resistance, vibration characteristics, naki, etc.). 70% by weight). In addition, the friction material of the present invention is usually mixed with an appropriate amount (for example, 50% by weight or less) of various additives, for example, a rust inhibitor, a lubricant, a grinding agent, and the like, according to the use and usage mode. Not different from friction material.

[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,
Thermosetting resins such as formaldehyde resin, epoxy resin and silicone resin, or their modified (cashew oil modified, dry modified etc.) thermosetting resins, rubber resins such as natural rubber, styrene butadiene rubber, nitrile rubber, etc. Can be

The friction material of the present invention has the same composition as that of a conventional friction material using asbestos fiber or the like, except that the above octotitanate is used as a base material. No special conditions are added or restricted. That is, a base material is dispersed in a binder resin, and a friction and wear adjuster and a rust preventive, which are added as necessary,
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.

[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]
The following raw material composition was prepared by using (according to the reference example described later), and then subjected to binding molding with a mold (pressing force: 14.7 MPa = 150 K).
gf / cm ² , temperature: 170 ° C, pressure holding time: 5 minutes), after molding, release from the mold and heat treatment in a drying furnace (hold at 180 ° C for 3 hours). Thereafter, it was cut to a predetermined size, and polished 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 A friction material (disk pad) was prepared in the same manner as in Example 1 except that asbestos fibers (6 classes) were used instead of octotitanate as the base material. ) Got. This friction material (conventional type) is designated as B.

[Friction wear test] The above friction material A (inventive example)
The coefficient of friction and the specific wear rate (cm ³ / N · m) of B1 and B1 (Comparative Example) were measured by a constant-speed friction and wear test specified in JIS D4411 “Automotive Brake Lining”. The results shown were obtained (FIG. 1: coefficient of friction, FIG. 2: specific wear rate). Disc friction surface: FC25 gray cast iron, surface pressure: 10 kgf / cm ² , friction speed: 7 m / sec.

FIG. 1 (coefficient of friction) and FIG. 2 (specific wear rate)
As shown in the figure, friction material B using asbestos fiber
Has a low coefficient of friction at low and high temperatures, especially 35
The decrease in the high temperature range exceeding 0 ° C. is sharp. Abrasion resistance also decreases with increasing temperature, and degradation in a 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, the high friction coefficient is stably maintained in a wide temperature range from a low temperature to a high temperature, and the abrasion resistance is low. Of course, in the low temperature range, the increase in the wear amount in the high temperature range 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 blended in a molar ratio of 1: 11.8. After mixing with a mixer for 10 minutes, 5% by weight of water is added to the mixed powder, and the mixture is filled into a mold and press-molded (pressing force: 5.1 MPa). (2) Firing treatment: 900 g of the above pressed body in a firing furnace
C. for 2 hours while keeping the CO of potassium carbonate (K ₂ CO ₃ )
_{After 2} is removed, the mixture is heated and maintained at 1350 ° C. for 3 hours to cause a firing reaction (a reaction for producing and growing octotitanate based on a solid-phase reaction), and then cooled in a furnace. The sintering anti-product is a lump solidified with octotitanate. (3) Fibrillation treatment: The fired reaction product is coarsely pulverized and passed through a 2 mm sieve, and then 1 L of water is added.
The mixture is stirred for 0 minute and wet-laid. After defibration, dehydrate and dry. 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 to 50 μm, minor axis 3 to 20 μm, aspect ratio 2-3.

[0016]

The friction material of the present invention has a high coefficient of friction and excellent wear resistance. The temperature dependence of the friction and wear characteristics is small, and the friction and wear characteristics are stably maintained in a wide temperature range from a low temperature to a 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 of an automobile, a vehicle, an aircraft, various industrial machines, etc .;
It is possible to cope with a reduction in weight and the like, and also has an effect of improving and stabilizing a braking function, improving durability, and the like.

[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.

[Explanation of symbols]

 A: invention example, B: comparative example.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-6-330968 (JP, A) JP-A-3-181529 (JP, A) JP-A-6-9948 (JP, A) JP-A-4- 106183 (JP, A) JP-A-6-248091 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C08J 5/14 C09K 3/14 F16D 69/02

Claims (1)

(57) [Claims] 1. A friction material obtained by binding and forming a kneaded material containing a base material using a resin as a binder, wherein K _x Ba _Y Al _{x + 2Y} Ti _{8-x-2Y is} used as the base material. O ₁₆ ... [1] wherein X is 0.2 to 1.4 and Y is 0.2 to 1.4, wherein 3 to 50% by weight of an octotitanate having a hollandite structure is blended. Friction material.