JP2002220582A - Filler for friction material and friction material using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a change in coefficient of friction of a friction material caused by thermal decomposition of an organic substance component in a friction material comprising a fibrous base, a binder and a filler at a high temperature. SOLUTION: This filler for a friction material is obtained by adding an iron compound represented by an iron oxide to cashew dust being one of a filler of a friction material. A thermal decomposition product on the surface of the friction material is rapidly burned by using a catalytic action based on the change of iron in an oxidation state to actualize the stabilization of coefficient of friction.

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 brake lining, a brake pad, and the like, which is used for a braking device of a vehicle such as an automobile, various industrial machines, and more particularly to a friction material excellent in fade resistance. About materials.

[0002]

2. Description of the Related Art Friction materials used for brake pads of braking devices such as automobiles include various fibrous base materials, fillers such as friction modifiers, and various thermosetting polymers for bonding them. And the like. The friction material is manufactured by filling a mixture of these components into a mold, and then pressurizing and heating to cure the binder.

The fibrous base material includes organic fibers such as polyamide fibers and aramid fibers, ceramic fibers,
Synthetic inorganic compound fibers such as glass fiber, rock wool, and potassium titanate are used, and various inorganic compound powders such as barium sulfate and calcium carbonate, and metal powders are used as the filler. Also, for the purpose of friction adjustment,
Solid lubricants such as graphite and molybdenum disulfide,
Cashew dust and the like are added.

The characteristics required of the friction material include a large braking force, a high abrasion resistance, a small and stable change in the braking force due to a change in temperature, pressure, etc., a water resistance, It has oil resistance and high mechanical strength. Then, depending on the device into which the friction material is incorporated, which characteristics are emphasized is different, and accordingly, the blending and prescription of each raw material is also different.

[0005] The above-mentioned change in the braking force includes a phenomenon called a fade. Particularly, in a vehicle, there is an example in which a runaway accident caused by the phenomenon occurs. This phenomenon is caused by the high temperature of the friction material, the organic compound component in the friction material is thermally decomposed into gas or liquid, and intervenes between the friction surface of the brake such as a disc brake and the friction material, causing extreme friction. To significantly increase the braking distance of the vehicle.

Specifically, when the vehicle travels on a long-distance downhill, the vehicle may travel with the brakes operated, and the temperature of the friction material and the friction surface of the brakes rises. Such a phenomenon occurs.

As described above, the main cause of the fade phenomenon is as follows.
Since the organic matter component in the friction material is thermally decomposed, paying attention to the organic matter component contained in the friction material, cashew dust is one of the components that cause the thermal decomposition. Cashew dust is a highly reactive oil (cashew nut shell liquid, hereinafter referred to as CNSL) contained in the shell covering the seeds of cashew nuts produced in the tropics. Obtained.

The function of cashew dust in a friction material is such that a tar-like component generated by thermal decomposition imparts appropriate lubricity by coating the friction material surface, thereby improving the wear resistance of the friction material. Or to prevent an unpleasant sound generated during braking, that is, "squeal".

[0009] For this reason, cashew dust is an essential component of the friction material, but may generate volatile components, tar components, and powder by thermal decomposition at a high temperature, and may promote the fade phenomenon. In particular, the tar component has a remarkable lubricating effect, and it is necessary to suppress the production amount to a certain level or less.

[0010] For this purpose, a method of obtaining a resin powder by mixing and curing components that provide a heat-resistant resin, such as a phenol resin or a xylene resin, or curing a mixture of these components and CNSL. Is being done.
However, although these resins have better heat resistance than conventional cashew dust, they result in impairing flexibility, which is an important feature of cashew dust.

In addition, a large amount of powder of an inorganic compound such as an oxide is filled in cashew dust, whereby the amount of volatile matter and tar generated at high temperatures can be reduced. However, it is inevitable that the flexibility of cashew dust is impaired. That is, in the conventional method, it was impossible to suppress the amount of volatile matter and tar generated at high temperature while maintaining the flexibility of cashew dust.

[0012]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to reduce the amount of volatiles and tar components generated at high temperatures while maintaining the characteristics of cashew dust, thereby reducing friction including cashew dust. It is to improve the fade resistance of the material.

[0013]

Means for Solving the Problems As a solution to the above-mentioned problem, the present inventors have proposed that if the generated tar component can be quickly removed from the friction material surface rather than suppressing the generation of tar component at a high temperature, cashew dust Without impairing the original characteristics,
The inventors considered that the anti-fade property can be improved and studied a specific method, and as a result, the present invention has been accomplished.

That is, the present invention is a filler for a friction material, comprising a cured product mainly composed of CNSL and containing an iron compound.

Further, in the present invention, in the filler for a friction material, the iron compound may include goethite (α-FeOO).
H), akagenite (β-FeOOH), lepicrosite (γ-FeOOH), hematite (α-Fe
₂ O ₃ ), at least one selected from maghemite (β-Fe ₂ O ₃ ), and magnetite (Fe ₃ O ₄ ).

Further, the present invention provides the filler for a friction material, wherein the content of the iron compound is 0.1% by weight to 30% by weight.
% By weight.

Further, the present invention is a friction material comprising a fibrous base material, a binder, and a filler, wherein the friction material includes the above-mentioned filler for a friction material.

[0018]

In general, an oxide of iron, which is a kind of transition metal, exhibits a catalytic action caused by a change in oxidation state and is used industrially. In particular, it is presumed that the catalytic ability in the combustion reaction is caused by repeating oxidation-reduction between Fe (III) in which iron oxide is in a high oxidation state and Fe (II) in which oxidation state is low.

Therefore, by adding iron oxide to cashew dust, tar components caused by cashew dust and other organic substances are quickly pyrolyzed or burned to gasify at a high temperature at which fade occurs, and the friction material surface Can be removed.

[0019] The iron compound used in the present invention basically contains iron ions or if it produces iron ions.
There is no particular limitation, and for example, iron powder may be used. However, considering ease of handling and cost, goethite (α-FeOOH), akagenite (β-FeOOH), and lepiclosite (γ-FeOO)
H), hematite (α-Fe ₂ O ₃ ), maghemite (β-Fe ₂ O ₃ ), and magnetite (Fe ₃ O ₄ ) are desirable.

In addition, from the viewpoint of use in mixing with a friction material and from the viewpoint of catalytic activity, it is desirable that the powder be in the form of a powder and have as large a specific surface area as possible. Therefore, it is preferable that the particle shape of the powder be flat or needle-like rather than spherical, and among the above iron compounds, goethite or the like corresponds thereto.

The reason why the content of the iron compound of cashew dust is limited to 0.1% by weight to 30% by weight is that when the content is less than this range, the effect of the iron compound as a catalyst is insufficient. In the above, the effect of the iron compound is not different from the case where the content is set at around 30% by weight, and the flexibility of cashew dust is impaired.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION Next, an embodiment of the present invention will be described.
Specific examples will be described in detail. Here, a material in which an iron compound was added to a raw material and a material in which iron compound was not added were prepared, and cashew dust was manufactured by the same method as in the usual case, and the characteristics of each were evaluated.

First, a polymer obtained by polymerizing CNSL with an acid (hereinafter referred to as cashew polymer)
, Hexamethylenetetramine, and goethite powder were weighed so as to have three compositions shown in Table 1. After stirring the mixture until it became uniform, the mixture was poured into a stainless steel container, and kept in a thermostat at a temperature of 200 ° C. for 24 hours to be cured. This was pulverized to a predetermined particle size by a pulverizer to obtain three types of cashew dust.

[0024]

[Table 1]

Next, using these three types of cashew dust, each component was weighed in the composition shown in Table 2 and thoroughly mixed with a V blender. Then, the mixture is filled in a preforming mold and pressurized at normal temperature at a pressure of 20 MPa for 1 minute.
At 10 ° C for 10 minutes at a pressure of 40 MPa.
For 3 hours to obtain a friction material sample.

[0026]

[Table 2]

Next, regarding these samples, JIS-D-
A friction test according to 4411 was performed. Table 3 shows the results. As is clear from Table 3, cashew dust to which no goethite was added was used in Samples 2 and 3, which are friction materials using cashew dust added with 1 part by weight and 5 parts by weight of goethite, respectively. As compared with Sample 1, which is a friction material, a change in friction coefficient at a high temperature is hardly observed.

[0028]

[Table 3]

The above three types of cashew dust were extracted with acetone, that is, the weight fraction of the soluble component of the cashew dust in acetone, and the volatilization loss at 400 ° C., that is, when the cashew dust was heat-treated at 400 ° C. for 2 hours. , And the acetone extraction rate of the sample for which the 400 ° C. acetone extraction rate, that is, the 400 ° C. volatilization loss rate, was measured. Table 4 shows the results.

[0030]

[Table 4]

According to the results shown in Table 4, there is no significant difference between the three types of cashew dust in the acetone extraction rate and 400 ° C. volatilization loss rate. The result was that the added cashew dust was smaller.

Generally, when cashew dust is treated at a high temperature, a tar component having a relatively low molecular weight is generated by thermal decomposition. Since the tar content is soluble in acetone, the acetone extraction rate increases as compared to before the heat treatment. From the results shown in Table 4, it can be seen that, as described above, the addition of goethite suppresses the amount of tar content generated when the treatment is performed at a high temperature, thereby suppressing the increase in the acetone extraction rate.

In the above, an example using goethite as an iron compound has been described. Next, as an iron compound, akagenite (β-FeOOH), lepiclosite (γ-FeO
OH), hematite (α-Fe ₂ O ₃ ), maghemite (β-Fe ₂ O ₃ ), and magnetite (Fe ₃ O ₄ ) will be described.

Here, 1 part by weight of the above five types of iron compounds and 8 parts by weight of hexamethylenetetramine were weighed with respect to 100 parts by weight of the cashew polymer, and the five types of iron compounds were weighed under exactly the same conditions as when goethite was used. Cashew dust was prepared. Using the obtained five types of cashew dust, the respective components were weighed with the compositions shown in Table 2, and five types of friction material samples were produced under exactly the same conditions as when goethite was used.

For these samples, JIS-D-4
A friction test according to 411 was performed. Table 5 summarizes these results. From Table 5, it can be seen that, similarly to the case where goethite was added to the cashew polymer, these samples showed little change in the friction coefficient at high temperatures.

[0036]

[Table 5]

Further, with respect to these five types of cashew dust, the acetone extraction rate, 400 ° C. volatilization loss rate,
The acetone extraction rate was measured at ℃. These results are summarized in Table 6, and it can be seen that, similarly to the case of using goethite, the production of tar is suppressed.

[0038]

[Table 6]

[0039]

As described in detail above, according to the present invention, cashew dust capable of preventing fade and a friction material using the same can be obtained easily and at low cost. As a result, it is possible to prevent a runaway accident of the vehicle due to the fade phenomenon, and it can be said that a significant contribution to safety is achieved.

Here, only an example in which the iron compounds are individually added to the cashew polymer has been described. From the above results, even when a plurality of iron compounds are used, the effect is exhibited and the fade phenomenon is reduced. It is clear that this can be prevented.

Continuing from the front page (72) Inventor Mikio Nishimura 7-9-4 Nishigotanda, Shinagawa-ku, Tokyo F-term in Tohoku Kako Co., Ltd. 3J058 BA34 DD11 EA10 EA15 EA28 FA01 FA11 GA07 GA13 GA20 GA24 GA26 GA28 GA32 GA35 GA37 GA39 GA55 GA92

Claims (4)

[Claims] 1. A filler for a friction material, comprising a cured product mainly composed of cashew nut shell liquid and containing an iron compound. 2. The filler for a friction material according to claim 1, wherein the iron compound is goethite (α-FeOOH),
Akagenite (β-FeOOH), lepiclosite (γ
-FeOOH), hematite (α-Fe ₂ O ₃ ), maghemite (β-Fe ₂ O ₃ ), magnetite (Fe ₃ O
₄ ) A friction material filler, which is at least one member selected from the group consisting of: 3. The friction material filler according to claim 1, wherein the content of the iron compound is 0.1% by weight to 30% by weight. Filler for materials. 4. A friction material comprising a fibrous base material, a binder, and a filler, as a filler.
A friction material, comprising the friction material filler according to any one of the above.