JP2000264692A - Friction material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a friction material excellent in frictional/abrasive characteristics at high temperatures and mechanical strengths by compounding, as friction regulator, a grainy alkali metal titanate of specific shape and a fibrous alkali metal titanate. SOLUTION: This friction material is obtained by compounding pref. a total of 3-50 wt.% of a grainy alkali metal titanate 3-100 μm in average grain size and a fibrous alkali metal titanate 0.1-1 μm in average fiber diameter and >=6 in average aspect ratio in the weight ratio of the former to the latter of pref. (1:1) to (10:1); wherein the above two kinds of alkali metal titanate are shown by the general formula: M2O.nTiO2 (M is an alkali metal such as K, Na or Li; n is 2-12), being pref. potassium octatitanate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to an automobile, an aircraft,
The present invention relates to a friction material suitable as a material for a braking member, for example, a material for a clutch facing, a material for a brake, and the like used in a braking device of a railway vehicle and industrial equipment.

[0002]

2. Description of the Related Art
As a friction material for the braking member, a friction material obtained by dispersing asbestos in an organic or inorganic binder and binding and forming the same has been used. However, this kind of friction material
Since friction and wear properties such as heat resistance are insufficient, and asbestos has environmental health problems such as carcinogenicity, development of alternative products is strongly demanded.

[0003] In response to such demands, friction materials using potassium titanate fibers as base fibers or friction modifiers have been proposed. Potassium titanate fiber does not have carcinogenic properties like asbestos, has excellent heat resistance, and has excellent characteristics that it is effective in preventing a fade phenomenon and improving thermal stability of friction characteristics.

However, potassium titanate fiber has a bulky shape due to its fiber shape, and when blended with a friction material, becomes structurally sparse, which is one of the causes of a decrease in strength after a high temperature history. I have.

To solve such a problem, Japanese Patent Laid-Open Publication No. Hei 4-3
No. 18093 proposes that the aspect ratio of potassium titanate be 8 or less. However, even with this method, the structure cannot be made sufficiently dense.
Further, when only potassium titanate having a small aspect ratio is used, a friction material having sufficiently high strength cannot be obtained, and there is a drawback that applications are restricted.

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above-mentioned conventional problems, and has as its object to provide a friction material which is excellent in friction and wear characteristics and has excellent strength even at high temperatures.

[0007]

According to the present invention, as a friction modifier, a granular alkali metal titanate having an average particle diameter of 3 to 100 μm and a fibrous titanate having an average fiber diameter of 0.1 to 1 μm and an aspect ratio of 6 or more are used. A friction material containing an alkali metal salt (claim 1). Also,
The present invention relates to a friction material in which both the granular alkali metal titanate and the fibrous alkali metal titanate are potassium octitanate (Claim 2). Further, the present invention relates to any one of the friction materials, wherein a mixing ratio of the granular alkali metal titanate and the fibrous alkali metal titanate is in a range of 1: 1 to 10: 1 by weight. 3). In addition, the present invention relates to any one of the friction materials, wherein the granular alkali metal titanate and the fibrous alkali metal titanate are mixed in a total amount of 3 to 50% by weight (claim 4).

The granular alkali metal titanate used in the present invention is an abbreviation of potassium titanate represented by the general formula M ₂ O.nTiO ₂ (M is an alkali metal such as potassium, sodium, lithium, etc., n = 2 to 12). These are spherical, generally cubic, or irregularly shaped particles. Examples of the particle diameter of the granular alkali metal titanate include those having an average particle diameter of 3 to 100 μm, preferably 5 to 80 μm. To these granular alkali metal titanates, various metal oxides and the like are added (the term “addition” in the present specification includes coating, supporting, interlayer introduction or solid solution). You may.

Preferred specific examples of the granular alkali metal titanate include granular potassium titanate and granular sodium titanate. Examples of the granular potassium titanate include granular potassium dititanate with n = 2, granular potassium tetratitanate with n = 4, granular potassium hexatitanate with n = 6, and granular potassium octa titanate with n = 8. . As the granular sodium titanate, n = 3 granular 3
Sodium titanate, and granular sodium titanate with n = 5.

Among these granular alkali metal titanates, granular potassium tetratitanate, granular potassium hexatitanate, and granular potassium octa titanate can be produced, for example, by the following production method.

The first production method comprises mixing a titanium-containing compound and a potassium-containing compound with at least 5 parts by weight of a boron-containing compound in terms of oxide based on 100 parts by weight of oxide of the titanium-containing compound. is there. Here, the titanium-containing compound can be appropriately selected from titanium oxide or a compound that produces titanium oxide by heating, such as rutile-type titanium oxide, anatase-type titanium oxide, brookite-type titanium oxide, and monoclinic titanium oxide. Titanium oxide, orthotitanic acid, metatitanic acid / orthotitanate (M ₂ TiO ₃ , M ₄ TiO ₂ , M is an alkali metal such as sodium, potassium, lithium, etc.), TiOSO ₄ , Ti
Cl ₂ , TiCl ₃ , TiCl ₄ , Ti (SO ₄ ) ₂ , Ti
S ₂ (SO ₄ ) ₃ , Ti ₂ O ₃ , H ₄ TiO ₄ , H ₂ TiO ₃ ,
Ti (OH) _{4 and the} like can be exemplified. These can be used alone or in combination of two or more. The potassium-containing compound can be appropriately selected from potassium oxide or a compound that generates potassium oxide by heating, and examples thereof include potassium oxide, potassium hydroxide, potassium carbonate, and potassium oxalate. These can be used alone or in combination of two or more.

The boron-containing compound can be appropriately selected from boron oxide and a compound capable of producing boron oxide by heating. Boron oxide, boron, boric acid and salts thereof (sodium salts, alkali metal salts of potassium salts,
Calcium salts, magnesium salts, alkaline earth metal salts such as barium salts, ammonium salts, etc.), metaboric acid and its salts (sodium salts, alkali metal salts of potassium salts,
Alkaline earth metal salts such as calcium salts, magnesium salts, and barium salts, and ammonium salts). Of these, boron oxide and boric acid are preferred. These can be used alone or in combination of two or more.

The mixing ratio of the titanium-containing compound and the potassium-containing compound can be appropriately selected depending on the kind of the intended potassium titanate. For example, when producing granular potassium hexatitanate, the potassium-containing compound and the titanium-containing compound are mixed with potassium oxide. : About 1: 2 to 6 in conversion ratio of titanium oxide;
Preferably, it is good to be about 1: 3-5. The compounding amount of the boron-containing compound is usually 5 parts by weight or more, preferably 5 to 100 parts by weight, more preferably 10 to 40 parts by weight, based on 100 parts by weight of the titanium-containing compound in terms of boron oxide. It is good to use parts by weight. If the amount of the boron-containing compound is less than 5 parts by weight, the production of fibrous potassium titanate increases, which is not preferable. On the other hand, 10
Even if the amount is more than 0 parts by weight, the effect is not changed, so that it is uneconomical.

In the first production method, the target substance, granular potassium titanate, can be produced by mixing a titanium-containing compound, a potassium-containing compound, and a boron-containing compound and firing the mixture. Mixing can be performed in any order by any means. The calcination is carried out in the air or in an oxidizing atmosphere, usually at about 650 to 1200 ° C., preferably at 7 ° C.
It may be carried out at 50 to 1100 ° C. for usually 0.5 to 20 hours, preferably 2 to 10 hours. In firing, a flux such as potassium chloride, potassium sulfate, or potassium molybdate may be used. After calcination, the mixture is cooled, and if necessary, the obtained calcination product is pulverized, pulverized, and classified to obtain granular potassium titanate used as the friction modifier of the present invention.

The first production method is a method particularly suitable for producing granular potassium hexatitanate. The second method for producing granular potassium titanate is a method of obtaining granular potassium tetratitanate by washing the granular potassium dititanate with water, removing a portion of potassium ions, and firing. Until now,
Although a method for efficiently producing granular potassium tetratitanate has not been known, according to this method, a large amount of 4
Potassium titanate can be produced. Here, the granular potassium dititanate can be produced by calcining titanium oxide and potassium carbonate at 900 ° C. for 1 to 5 hours in the presence of potassium chloride, followed by crushing and classification. In addition, granular 2
Washing of potassium titanate with water can be performed by charging granular potassium dititanate into water to form a slurry and stirring for 1 to 5 hours. Baking is 750-1000 °
C, preferably at about 900 ° C. for about 1 to 3 hours.

The third method for producing granular potassium titanate is to subject the granular potassium tetratitanate obtained in the second production method to an acid treatment or a neutralization treatment to further remove potassium ions and to obtain an appropriate titanium / potassium. After adjusting to the ratio, by firing treatment, granular potassium hexatitanate,
This is a method for obtaining granular potassium octitanate. Here, examples of the acid used in the acid treatment or the neutralization treatment include sulfuric acid, nitric acid, hydrochloric acid, boric acid, and carbonic acid. The production of granular potassium octa titanate is performed, for example, by adding granular potassium tetratitanate into water to form a slurry, adding an acid with stirring, maintaining the pH at about 7.5, treating for 1 to 10 hours, and then heating at 900 ° C. It can be performed by firing for 0.5 to 10 hours.

The granular sodium titanate can be produced, for example, by the following production method. That is, the molar ratio of the titanium oxide source and the sodium oxide source (TiO ₂ / N
a ₂ O) 1: 1 to 1: 6, preferably 2: 1 to 4: 1
At a rate of 800-1350 ° C., preferably 90 ° C.
It can be produced by baking in a temperature range of 0 to 1050 ° C. for 3 to 15 hours, preferably 3 to 8 hours. At this time, depending on the raw material molar ratio and the firing conditions, the granular sodium trititanate and the granular sodium pentatitanate can be obtained either alone or as a mixture thereof. In the present invention, any of them is preferably used. Can be.

As the titanium oxide source, high-purity purified titanium oxide (rutile, anatase or monoclinic), titanium hydroxide, metatitanic acid, rutile sand, anatase sand,
Titanium slag and the like can be exemplified. Examples of the sodium oxide source include sodium carbonate, sodium hydroxide, and sodium nitrate.

The mixing of the raw materials can be performed by any means such as powder mixing. The raw material mixture may be formed into a pressure-formed block prior to the sintering step, and the raw material mixture formed into a paste by adding water may be extruded into pellets, or the raw material mixture formed into a slurry by adding water may be spray-dried. May be used for granulation. The firing can be performed by any means such as a rotary kiln, an electric furnace, a fluidized-bed firing furnace, and a tunnel kiln.

Sodium trititanate or sodium pentatitanate or a mixture thereof can be used as it is as a friction modifier for the friction material of the present invention. If necessary, treatment such as washing with water, pickling, drying, classification and the like can be used. May be used.

In the friction material of the present invention, the fibrous alkali metal titanate used together with the particulate alkali metal titanate includes potassium titanate fibers having an average fiber diameter of 0.1 to 1 μm and an average aspect ratio of 6 or more, Sodium acid fiber is exemplified, and among them, potassium dititanate fiber, potassium hexatitanate fiber, potassium titanate fiber, potassium titanate fiber, potassium titanate fiber and potassium titanate fiber are preferably used. Among them, potassium octitanate fiber is preferable. The fibrous potassium octitanate is commercially available from Otsuka Chemical Co., Ltd. under the trade name "Tismo D".

In the friction material of the present invention, the combination of the granular alkali metal titanate and the fibrous alkali metal titanate is not particularly limited. Particularly preferred. In the friction material of the present invention, the mixing ratio of the granular alkali metal titanate and the fibrous alkali metal titanate is such that the structure of the friction material is made dense, and from the viewpoint of ensuring strength, the granular alkali metal titanate is in a weight ratio. : Fibrous alkali metal titanate = 1: 1 to 10: 1.

In the friction material of the present invention, it is preferable that the total amount of the granular alkali metal titanate and the fibrous alkali metal titanate is 3 to 50% by weight in the friction material. . When the amount is 3% by weight or more, the effect of improving friction characteristics can be sufficiently exhibited. Also, there is no benefit of blending over 50% by weight. Examples of the friction material of the present invention include a friction material comprising a base fiber, a friction modifier and a binder, and the mixing ratio of each component in the friction material is 1 to 60 parts by weight of the base fiber, The agent contains 20 to 80 parts by weight, including granular alkali metal titanate and fibrous alkali metal titanate, binder 10 to 40 parts by weight.
Parts by weight, and 0 to 60 parts by weight of other components.

Examples of the base fiber include resin fibers such as aramid fibers, metal fibers such as steel fibers and brass fibers, carbon fibers, glass fibers, ceramic fibers, rock wool, and the like.
Wood pulp and the like can be mentioned. These base fibers are surface-treated with a silane coupling agent such as an aminosilane, an epoxysilane or a vinylsilane, a titanate coupling agent, or a phosphate ester in order to improve dispersibility and adhesion with a binder. May be used. As the friction modifier, in addition to the granular alkali metal titanate and the fibrous alkali metal titanate, other friction modifiers may be used in combination as long as the effects of the present invention are not impaired.

For example, vulcanized or unvulcanized natural or synthetic rubber powder, cashew resin powder, organic powder such as resin dust, rubber dust, carbon black, graphite powder, molybdenum disulfide, barium sulfate, calcium carbonate, clay, mica , Talc, diatomaceous earth, antigolite, sepiolite, montmorillonite, inorganic powders such as zeolite,
Metal powder such as copper, aluminum, zinc, iron, alumina,
Examples thereof include oxide powders such as silica, chromium oxide, titanium oxide, and iron oxide. As the binder, phenolic resin, formaldehyde resin, melamine resin, epoxy resin, acrylic resin, aromatic polyester resin, thermosetting resin such as urea resin, natural rubber, nitrile rubber, butadiene rubber, styrene butadiene rubber, chloroprene rubber, Elastomers such as polyisoprene rubber, acrylic rubber, high styrene rubber, styrene propylene diene copolymer, etc., polyamide resins, polyphenylene sulfide resins, polyether resins, polyimide resins, polyether ether ketone resins, thermoplastic liquid crystal polyester resins, etc. Organic binder such as resin and alumina sol,
Examples thereof include inorganic binders such as silica sol and silicone resin.

In the friction material of the present invention, components such as a rust preventive, a lubricant, and a grinding agent can be added, if necessary, in addition to the above components. The method for producing the friction material of the present invention is not particularly limited, and can be appropriately produced according to a conventionally known method for producing a friction material. As an example, a base fiber is dispersed in a binder, a friction modifier and other components that are blended as required are combined and blended, a friction material composition is prepared, and then the composition is placed in a mold. A method of injecting an object, heating under pressure, and performing binding molding can be exemplified.

As another example, the binder is melt-kneaded in a twin-screw extruder, and the base fiber, the friction modifier and other components, if necessary, are combined and compounded from the side hopper. After extrusion, a method of machining into a desired shape can be mentioned. Further, as another example, after the friction material composition is dispersed in water or the like, formed on a paper net, dewatered and formed into a sheet shape, and then subjected to heat and pressure by a press machine to perform binding and molding, The obtained friction material may be appropriately cut and polished to obtain a desired shape.

The friction material of the present invention uses a granular and fibrous alkali metal titanate in combination, so that a friction material having a dense structure can be obtained without deteriorating fade resistance and squealing performance. It is possible to prevent a decrease in strength after a high-temperature history.

[0029]

The present invention will be described in more detail with reference to the following Examples, Comparative Examples and Test Examples. Reference Example 1 Anatase-type titanium oxide, potassium carbonate, and potassium chloride were mixed at a weight ratio of 5: 4.5: 1, and calcined at 900 ° C. for 2 hours. Thus, granular potassium dititanate having an average particle diameter of 50 μm was obtained. Next, this was poured into water to form a slurry, stirred for 2 hours, filtered, dried and calcined at 900 ° C. for 2 hours, and the obtained sintered body was crushed to obtain an average particle diameter of 50 μm. Meter granular potassium tetratitanate was obtained. The obtained granular potassium tetratitanate is charged into water to form a slurry, and boric acid is added to maintain the pH of the slurry at 7.5 while maintaining the pH at 7.5.
After performing a neutralization treatment for an hour, filtering, and drying, the resultant was treated at 900 ° C. for 2 hours, and the obtained sintered body was crushed and classified to obtain granular potassium octitanate having an average particle diameter of 50 μm.

Reference Example 2 Anatase type titanium oxide, potassium carbonate, potassium chloride, and boric acid were mixed at a weight ratio of 5: 2.5: 1: 1, and the temperature was raised to 1055 ° C. over 5 hours. After holding for one hour, it was cooled to 600 ° C. over one hour, and then cooled to room temperature. The obtained sintered body was crushed and classified to obtain granular potassium hexatitanate having an average particle diameter of 10 μm.

Reference Example 3 A mixture of titanium oxide and sodium carbonate at a molar ratio of 3: 1 was placed in a crucible and heated at 950 ° C. for 8 hours in an electric furnace. The product was pulverized, washed with water and dried. As a result, granular sodium trititanate having an average particle diameter of 13 μm was obtained.

Example 1 15 parts by weight of granular potassium octitanate obtained in Reference Example 1 and potassium octitanate fiber (trade name "Tismo D" manufactured by Otsuka Chemical Co., Ltd., average fiber diameter 0.5 μm, average fiber 13 μm length, average aspect ratio 26) 15 parts by weight, aramid fiber (trade name “Kevlar pulp” 3 mm length, manufactured by Toray Industries, Inc.) 3 parts by weight, binder (phenolic resin) 10
Parts by weight, 9 parts by weight of organic additives (cashew dust, etc.) and 48 parts by weight of others (lubricants such as graphite, metal powder, oxide powder) are sufficiently mixed, filled into a mold, and subjected to binding molding (pressing force). :
150 kgf / cm ² , temperature 170 ° C., 5 minutes), after molding, release from mold and heat treatment (hold at 180 ° C. for 3 hours)
Was given. Thereafter, polishing was performed to obtain the friction material of the present invention. The organic additives, lubricants, metal powders and oxide powders used were usually those added to the friction agent.

Example 2 15 parts by weight of granular potassium hexatitanate obtained in Reference Example 2 and potassium octa titanate fiber (trade name "Tismo D" manufactured by Otsuka Chemical Co., Ltd., average fiber diameter 0.5 μm, average fiber 13 μm length, average aspect ratio 26) 15 parts by weight, aramid fiber (trade name “Kevlar pulp” 3 mm length, manufactured by Toray Industries, Inc.) 3 parts by weight, binder (phenolic resin) 10
Parts by weight, 9 parts by weight of organic additives (cashew dust, etc.) and 48 parts by weight of others (lubricants such as graphite, metal powder, oxide powder) are sufficiently mixed and filled in a mold. Thus, the friction material of the present invention was obtained.

Example 3 15 parts by weight of granular sodium trititanate obtained in Reference Example 3 and potassium octa titanate fiber (trade name "Tismo D" manufactured by Otsuka Chemical Co., Ltd., average fiber diameter 0.5 μm, average fiber 13 μm length, average aspect ratio 26) 15 parts by weight, aramid fiber (trade name “Kevlar pulp” 3 mm length, manufactured by Toray Industries, Inc.) 3 parts by weight, binder (phenolic resin) 10
Parts by weight, 9 parts by weight of organic additives (cashew dust, etc.) and 48 parts by weight of others (lubricants such as graphite, metal powder, oxide powder) are sufficiently mixed and filled in a mold. Thus, the friction material of the present invention was obtained. Each of the friction materials obtained in Examples 1 to 3 had a small decrease in strength even after a high-temperature history, and had a reduced amount of wear at high temperatures.

[0035]

As described above, the friction material according to the present invention has improved thermal stability of friction and wear characteristics, has excellent friction and wear characteristics even at high temperatures, and has a reduced strength even after a high temperature history. It has the advantage of low strength and excellent strength.

Claims (4)

[Claims] An average particle size of 3 to 10 as a friction modifier.
A friction material comprising: a particulate alkali metal titanate of 0 μm; and a fibrous alkali metal titanate having an average fiber diameter of 0.1 to 1 μm and an average aspect ratio of 6 or more. 2. The friction material according to claim 1, wherein both the granular alkali metal titanate and the fibrous alkali metal titanate are potassium octa titanate. 3. The mixing ratio of the granular alkali metal titanate and the fibrous alkali metal titanate is 1: 1 by weight.
The friction material according to claim 1 or 2, wherein the ratio is in the range of 10 to 10. 4. The friction material according to claim 1, wherein the total amount of the granular alkali metal titanate and the fibrous alkali metal titanate is 3 to 50% by weight.