JP3292973B2 - 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 constituting a sliding surface such as a brake lining, a disc pad, a clutch facing and the like in a braking device of an automobile, a railway vehicle, an aircraft, an industrial machine and the like.

[0002]

2. Description of the Related Art The friction material of the above-mentioned braking device uses a resin (phenol resin, epoxy resin, etc.) as a binder, disperses a base material into the binder, and adds a friction / wear adjusting agent (barium sulfate, etc.) as necessary. It is manufactured by binding and forming the mixture under heat and pressure. Conventionally, a friction material containing asbestos fiber as a base component has been used, but wear and damage due to a high temperature of the friction surface is remarkable, and a rapid decrease in friction coefficient and a fading phenomenon are liable to occur. In addition, carcinogenicity of asbestos fibers has been pointed out. For this reason, asbestos substitutes have been developed, and potassium hexatitanate (K ₂ Ti ₆ O
Practical use of alkali metal titanate fibers represented by ₁₃ ) has been attempted. Alkali metal titanate powder is mainly manufactured as a powder composed of whisker or polycrystalline fibrous particles, but from the viewpoint of uniform dispersibility in resin, reduction of deformation (warpage / strain) of friction material, improvement of dimensional accuracy, etc. From
It has also been proposed to use a powder composed of spherical particles instead of a fibrous one (JP-A-7-53214).

[0003]

In order to meet the demands for downsizing and lightening of a brake device for an automobile, it has a high coefficient of friction and stably maintains the high coefficient of friction from a low speed to a high speed range. A friction material that can be used is required. The alkali metal titanate powder such as the above potassium hexatitanate is a material having excellent strength, heat resistance, abrasion resistance, reinforcing property, etc., and having an appropriate hardness as a friction material. It is possible to obtain improved friction and wear characteristics over conventional friction materials. An object of the present invention is to provide a friction material having further improved friction and wear characteristics while utilizing characteristics of an alkali metal titanate.

[0004]

The friction material of the present invention is a friction material obtained by binding and molding a mixture of a resin and a base material, wherein the base material is TiO ₂ or TiO ₂ by heating.
Compound powder and A ₂ O (A is alkali gold)
Genus) or alkali metalization to produce A ₂ O by heating
Alkali metal titanate crystal grains, which are the product of the calcination reaction with the compound powder, and one or more
Alternatively, it is characterized in that alkali metal titanate-based composite compound powder composed of composite particles in which two or more kinds of inorganic oxide particles having a Mohs hardness of 6 to 8 are combined.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The alkali metal titanate-based composite compound powder blended in a resin as a base material component contains an alkali metal titanate crystal as a basic constituent phase and an inorganic oxide having a Mohs' hardness of 6 to 8. The effect of having a composite particle structure in which the particles are combined is that the friction material cannot be obtained with a single phase powder of alkali metal titanate or a mere mixed powder of alkali metal titanate powder and the above-mentioned inorganic oxide particles. And enables a high friction coefficient to be stably maintained from a low speed range to a high speed range without attacking a partner material.

[0006] In the above alkali metal titanate is a basic configuration phase of the complex compound powder of composite particles, the following formula (1) _{A 2 Ti n O 2n + 1} ... [1] [wherein, A is K, Na , Li, Rb, etc., and n is 3 to 8]. Specific examples thereof include sodium trititanate (Na ₂ Ti ₃ O ₇ ), potassium tetratitanate (K ₂ Ti ₄ O ₉ ), potassium hexatitanate (K ₂ Ti ₆ O ₁₃ ), and the like. In particular, potassium hexatitanate is most suitable as a basic constituent phase in terms of thermal stability, abrasion resistance, strength and the like.

The inorganic oxide grains having a Mohs' hardness of 6 to 8, which combine with alkali metal titanate crystal grains to form composite particles,
For example, MgO (Mohs hardness: 6), Fe ₃ O ₄ (same:
6), ZrO ₂ (same: 7.5), SiO ₂ (same: 7),
SiZrO ₄ (zircon) (7.5: Cr ₂ O ₃ )
(Id .: 6.5). Oxide-based ceramics have heat resistance, chemical stability, and the like required as a base component of a friction material. Grade of inorganic oxide particles, Mohs hardness 6 ~
It is limited to those having a hardness of less than 8 that particles having higher hardness have no combined effect with alkali metal titanate crystals (for example, Mohs hardness of potassium hexatitanate is about 3 to 4), and particles of higher hardness. In this case, the friction material has poor facing damage.

[0008] The kind of the inorganic oxide particles contained in the composite compound powder is not necessarily limited to one kind, but has a particle structure in which two or more kinds of inorganic oxide particles are combined with alkali metal titanate crystal grains. It may be. The content of the inorganic oxide particles in the composite compound powder (the total amount when two or more types of inorganic oxide particles are mixed) is preferably in the range of 1 to 30% by weight. If the content is less than this, the composite effect of the inorganic oxide particles is not sufficiently exhibited, and if the content is larger than this, the characteristics of the alkali metal titanate crystal, which is the basic constituent phase, are weakened. is there.

The average particle diameter of the composite compound powder is about 10 to 10 from the viewpoint of mixing operability and dispersion effect in the resin.
A range of 0 μm is appropriate. The particle size of the inorganic oxide particles is preferably about 1 to 10 μm. Particle size 1μm
If the particle diameter is less than 0.1 μm, it is difficult to maintain a stable high coefficient of friction, and if the particle diameter is larger than 10 μm, the face-to-face damage is deteriorated. The compounding ratio of the composite compound powder to the resin is suitably in the range of about 3 to 50% by weight. If it is less than about 3% by weight, the compounding effect is small,
On the other hand, if it exceeds 50% by weight, the effect of improving the friction and wear characteristics is saturated, and there is no benefit of further increasing the amount.

The composite compound powder includes TiO ₂ (or a titanium compound that generates TiO ₂ by heating) powder,
A ₂ O (or alkali metal compound to produce a A ₂ O by heating) was mixed with the powder, one inorganic oxide powder having a Mohs' hardness of 6-8 or two or more, appropriate grain by which granulation process It is manufactured by firing treatment as granulated powder having a diameter. The particle size of the powder can be controlled by the particle size of the granulated powder. That is, after the granulated powder is fired, the fired product is subjected to a simple crushing process such as a vibrating sieve, and is made of composite particles having a spherical shape and a particle diameter almost similar to a true sphere almost the same as the granulated powder. A powder can be obtained (see Reference Example below).

In the friction material of the present invention, a known other material can be compounded as a base component together with the composite compound powder. For example, polyamide (nylon) fiber,
Examples include aramid fiber, steel fiber, stainless fiber, copper fiber, brass fiber, carbon fiber, glass fiber, alumina / silica fiber, rock wool, and wood pulp. One or more of these may be arbitrarily selected, and the blending amount is not particularly limited.
You may mix | blend in the range which becomes 0-65 weight%. The base material may be a silane-based coupling agent (aminosilane, vinylsilane, epoxysilane, methacryloxysilane, mercaptooxysilane, etc.) or titanate for the purpose of improving dispersibility and binding with a binder resin, if necessary. Based coupling agents (isopropyl triisostearoyl titanate,
Surface treatment (coupling treatment) with di (dioctyl pyrophosphate) ethylene titanate or the like is performed according to a conventional method and used.

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 / 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, etc., 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 (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, it is not different from ordinary friction materials in that various additives, for example, rust preventives, lubricants, abrasives, and the like are blended in an appropriate amount (for example, 50% by weight or less) according to the use and usage mode.

[0013] The resin component serving as a binder may be a commonly used material such as a phenol resin, a formaldehyde resin,
Examples thereof include thermosetting resins such as epoxy resins and silicone resins, and thermosetting resins thereof (modified with cashew oil and dryness), and rubber resins such as natural rubber, styrene butadiene rubber, and nitrile rubber.

The preparation of the raw material composition for producing the friction material of the present invention does not differ from the conventional friction material except that the composite compound powder is used as a base material component. There are no special conditions or restrictions. That is, a base material is dispersed in a binder resin, and a friction and wear modifier, a rust preventive, a lubricant, a grinding agent, and the like, which are added as necessary, are added, and the mixture is uniformly mixed to prepare a raw material composition. Then, after the preforming, by molding and the like, under heating and pressurizing (pressure: about 10 to 40 MPa, temperature: about 150 to 200 MPa)
C.), and after taking out from the mold, heat-treating (temperature: about 150 to 200 ° C., holding time: about 1 to 12 hours) if necessary in a heating furnace, and thereafter, machining and polishing the formed body It is processed into a friction material having a predetermined shape. As another method, a step of dispersing and suspending the raw material composition in water or the like, making it through a paper net, squeezing water to form a sheet, stacking an appropriate number of sheets, and binding and forming the sheet under heating and pressure. , The molded body can be machined or polished to obtain a predetermined friction material.

[0015]

【Example】

(1) Preparation of raw material composition See Table 2. Composite compound powder P ₁ to P ₅ of the base component column are as follows (see the following Reference Examples the preparation of the powder P ₁ ~P _5). In the comparative examples (No. 11 to No. 13), the average particle diameters of the potassium hexatitanate crystal powder and the inorganic oxide powder blended as the base components were 40 μm and 5 μm, respectively.
m.

[Table 1] Inorganic oxide particles Composite particles Powder Phase structure of composite particles Content Average particle size Average particle size P ₁ K ₂ Ti ₆ O ₁₃ -MgO 8 wt% 5 μm 40 μm P ₂ K ₂ Ti ₆ O ₁₃ -Fe ₃ O ₄ 10 wt% 1 μm 40 μm P ₃ K ₂ Ti ₆ O ₁₃ -ZrO ₂ 5 wt% 1 μm 40 μm P ₄ K ₂ Ti ₆ O ₁₃ -SiZrO ₄ 20 wt% 1 μm 40 μm P ₅ K ₂ Ti ₆ O _13- SiO ₂ 15 wt% 3 μm 40 μm P ₆ K ₂ Ti ₆ O ₁₃ −Cr ₂ O ₃ 10 wt% 3 μm 40 μm

(2) Molding of friction material After the raw material composition is preformed (pressing force: 15 MPa, temperature: normal temperature, time: 1 minute), it is bonded and formed by a die (pressing force: 15 MPa, temperature: 170 ° C.). , Pressure holding time: 5 minutes), after molding, release and heat treatment in a drying furnace (180 ° C)
For 3 hours). After that, it is cut to a predetermined size and polished to obtain a test friction material (disk pad).

(3) Friction test A second effectiveness test was performed on each friction material to be tested according to JASO C 406, "Dynamometer Test Method for Passenger Car Brake Devices," and the results shown in the lower column of Table 2 were obtained. "Face-to-face damage"
This is a comparison of the abrasion state of the friction surface of the mating material (material type: FC 250) after the test by visual observation (◎: extremely small wear damage, ○: slight, Δ: slightly large). (Test conditions) Initial braking speed: 50 km / h _, 100 km / h. Deceleration: 0.3G

[0018]

[Table 2]

The friction materials of the invention examples (Nos. 1 to 6) using the composite compound powder as the base material include the friction materials No. 11 (base material: potassium hexatitanate powder) of the comparative examples and No. 12 (Base material:
Higher coefficient of friction μ is stably maintained as compared to No. 13 (inorganic oxide powder) and No. 13 (base material: mixed powder of potassium hexatitanate powder and inorganic oxide powder). In addition, the aggressiveness of the opponent material is also the friction material No. 12 (base material: inorganic oxide powder) and No. 1
3 (base material: mixed powder of potassium hexatitanate powder and inorganic oxide powder).
It has good face-to-face damage properties according to (base material: potassium hexatitanate powder).

[0020]

[Reference example]

(Production of alkali metal titanate composite compound powder) A powder of titanium oxide (purified anatase), a powder of an alkali metal compound, and an inorganic oxide powder having a Mohs hardness of 6 to 8 are blended. An appropriate amount of water is added to this to prepare a slurry, which is treated with a wet spray drier (spray drier) to obtain a granulated powder (average particle size of about 40 μm) as a dried product. The dried product is placed in an alumina crucible and fired in an electric furnace (processing time: 2
Hr). After the calcination treatment, the calcination reaction product is passed through a vibrating sieve to obtain a composite compound powder. Table 3 shows the composition of the raw material powder mixture, the firing temperature, and the particle structure of the obtained composite compound powder. The composite compound powder has a mixed phase structure composed of potassium hexatitanate crystals and inorganic oxide particles. The shape (spherical shape) and particle size of the particles are substantially the same as those of the granulated powder.

[0021]

[Table 3]

[0022]

The friction material of the present invention has improved friction and wear characteristics as an effect of compounding the alkali metal titanate composite compound powder, and constitutes a braking device for automobiles, vehicles, aircraft, and various industrial machines. It is useful as a brake lining, disc pad, clutch facing, etc., which makes it possible to cope with downsizing and weight reduction of a braking device, and contributes to improvement / stabilization of braking function and improvement of durability. .

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C08J 5/14 C01G 23/00-23/08 F16D 69/02

Claims (3)

(57) [Claims] A friction material obtained by binding and forming a mixture of a resin and a base material, wherein the base material is TiO ₂ or
Titanium compound powder that generates TiO ₂ by heating and A ₂
O (A is an alkali metal) or A ₂ O is generated by heating
And <br/> alkali metal titanate crystal grains is sintered reaction product of the alkali metal compound powder, previously during the sintering raw material
A friction material comprising an alkali metal titanate-based composite compound powder composed of composite particles in which one or two or more inorganic oxide particles having a Mohs hardness of 6 to 8 are combined. 2. An average particle diameter of the composite particles: 10 to 100 μm
The friction material according to claim 1, wherein m, average particle diameter of the inorganic oxide particles: 1 to 10 µm, and content of the inorganic oxide particles: 1 to 30% by weight. 3. The friction material according to claim 1, wherein the alkali metal titanate crystal is a potassium hexatitanate crystal.