JPH0657099A - Filler for friction material - Google Patents

Abstract

PURPOSE:To provide the filler, cashew dust, homogeneously dispersible in the texture of friction material. CONSTITUTION:Cashew dust is mixed with chopped fibers bearing specific physical properties to provide the surface of the cashew dust with implanted fibers as the raised chopped fibers. Thereby, the resulting cashew dust enhances the mechanical entanglement with the fibrous material comprising a friction material, leading to improving the dispersibility of the cashew dust in a friction material along with preventing the cashew dust from slipping off the friction material during its use.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a brake lining,
The present invention relates to a filler used for a friction material such as a disk pad.

[0002]

Friction materials such as brake linings and disc pads are generally manufactured by the following steps. That is, a fibrous substance is mixed with a filler or the like for improving friction performance, a phenol resin or the like is further added and mixed as a binder, the mixture is preformed, and then heat-cured to form a friction material molded body. Is processed. Cashew dust is generally used as the filler.

Cashew dust is obtained by crushing cashew polymer obtained by reaction hardening of cashew nut oil into fine particles, and by adding this to a friction material, a remarkable effect can be obtained in improving friction performance. Are known.

[0004]

However, in the mixing process with the fibrous substance and the other filler added to the friction material, cashew dust is more granular than other fillers such as barium sulfate. Since the diameter is large and the difference in apparent density is large, separation is easy, and as a result, poor dispersion is likely to occur. When cashew dust is poorly dispersed,
This causes cracks and cracks in the molded body, which causes a drop in friction performance due to the dropout of cashew dust when the product is used.

On the other hand, Japanese Patent Publication No. 51-34434 discloses a prior art example of mixing a fibrous substance into cashew dust. In this precedent, asbestos in cashew dust,
There is disclosed an example in which an organic fiber capable of forming a heat-resistant carbon skeleton is added by heating at a high temperature, such as an inorganic fiber such as glass or rock wool, or an acrylic fiber.

However, in this prior example, it is presumed that the deterioration of the friction performance of the friction material at high temperature is caused by cashew dust, so that the fibrous material excellent in heat resistance is simply mixed into the friction material. Was proposed for the purpose of improving the stability of the friction coefficient at high temperatures, and it was not possible to solve the above problem of poor dispersion.

An object of the present invention is to provide a filler for a friction material, which can be mechanically entangled with a fibrous substance constituting the friction material and uniformly dispersed in the structure of the friction material.

[0008]

In order to achieve the above-mentioned object, in the filler for friction material according to the present invention, chopped fibers which are erected and flocked on the surface of an amorphous solid mainly composed of cashew polymer. I have.

The amount of chop fiber mixed with the cashew polymer is 5% or less (not including 0).

The chop fiber has a diameter of 1 to 30 μm.
m.

The length of chop fiber is 0.5 to
It is 3.0 mm.

The elongation of chop fiber is 1.5% or more.

The tensile strength of chop fiber is 300
It is above MPa.

The elastic modulus of chop fiber is 5 GP.
It is a or more.

[0015]

[Operation] Attention was paid to the flocked structure of the fibrous material having an appropriate length for the purpose of mechanically entangled with the fibrous material of the friction material. As the experiment progressed, when simple inorganic fibers were selected as the fibrous substance to be added to cashew dust, the inorganic fibers were finely cut when the reaction-cured product of cashew nut oil and aldechts was crushed. As shown in (1), it was not possible to obtain a substantially flocked structure. It is considered that this is due to the fragility peculiar to inorganic fibers. In addition, although acrylic fibers have excellent heat resistance, they have properties similar to wool, so that it is impossible to obtain acrylic fibers having a structure intended by the present inventors. It is considered that the small elastic modulus of the acrylic fiber also contributes to this result. Further, even if the fiber has high strength, if the fiber length is long, the fibers are entangled with each other as shown in FIG. 4 even after crushing after reaction curing, and cashew dust in which hair is transplanted as desired cannot be obtained. .

Therefore, the present inventors think that when the structure of cashew dust is modeled as shown in FIG. 2, it is ideal that the short fibers 2 stand upright on the surface of the cashew dust 1 and are planted. It was

That is, when chopped fibers are erected on the surface of an amorphous solid granular material containing cashew polymer as a main component, and the chopped fibers are mechanically entangled with the fibers in the friction material. As a result, cashew dust is trapped in each part of the fibers in the friction material, and the cashew dust is uniformly dispersed in the structure of the friction material. Chop fibers are long fibers with a smooth surface cut into short pieces.
In order to strengthen the mechanical entanglement, the following physical properties, that is, (1) the diameter is 1 to 30 μm,
(2) The length is 0.5 to 3.0 mm, (3)
The elongation is 1.5% or more, and (4) the tensile strength is
300 MPa or more, (5) Elastic modulus is 5G
It is desirable that it is Pa or more.
The reason for this will be described below.

When the fiber diameter is 1 μm or less, the resistance against bending deformation is too small to easily bend. Therefore, it is difficult to obtain a flocked structure in which fibers are erected on the surface of the granular material. Further, even if the diameter of the fiber is 30 μm or more, there is substantially no difference in the hair-implanted state as compared to the area of the diameter of 1 to 30 μm, and the surface area per unit weight of the fiber is small, and the bonding Adhesion by the agent becomes insufficient. Therefore, the loss of the filler during use of the product increases.

FIG. 5 shows the relationship between the fiber diameter and the bulk density of the filler. The change in the bulk density depends on the degree of protrusion of the fiber on the surface of the filler, and thus ideal flocking is possible. It suggests that the bulk density drops to a constant value when the condition is realized. Therefore, FIG. 4 supports the reason why the range of the fiber diameter is limited in relation to the bulk density.

When the length of the fiber is 0.5 mm or less, it becomes shorter than 0.7 mm which is the approximate maximum particle size of the filler, and the fiber may not project on the surface of the granular material. FIG. 6 shows the relationship between the fiber length and the bulk density of the filler. For the same reason as above, FIG. 6 supports the reason why the length of the fiber used in the present invention is limited in relation to the bulk density. Further, if the length of the fiber is longer than 3 mm, the viscosity coefficient of the mixture becomes too large in the step of mixing the cashew nut oil and the fiber, and the mixing becomes substantially impossible.

When the elongation of the fiber is 1.5% or less, the toughness of the fiber becomes insufficient, and the fiber is often broken in the step of mixing the cashew nut oil and the fiber, so that the desired flocked structure cannot be obtained. FIG. 7 shows the relationship between the elongation of the fiber and the bulk density of the filler. FIG. 7 similarly supports the reason why the elongation of the fiber is limited in relation to the bulk density.

When the tensile strength of the fiber is 300 MPa or less,
The tensile strength of the fiber is insufficient, and the fiber is often broken in the step of mixing the cashew nut oil and the fiber, so that the desired hair transplant structure cannot be obtained. FIG. 7 shows the relationship between the tensile strength of the fiber and the bulk density of the filler. Similarly, FIG. 7 supports the reason why the tensile strength of the fiber is limited in relation to the bulk density.

When the elastic modulus of the fiber is 5.0 GPa or less,
The fiber has insufficient rigidity, and in the step of mixing the fiber with cashew nut oil, the fiber is easily bent, and it becomes substantially impossible to obtain a flocked structure in which the fiber is erected on the surface of the granular material. FIG. 8 shows the relationship between the elastic modulus of the fiber and the bulk density of the filler. Similarly, FIG. 9 supports the reason why the elastic modulus of the fiber is limited in relation to the bulk density.

From these viewpoints, typical examples of the material of the chop fiber that can be used include aramid and aromatic polyester, but the material is not limited to these. In addition, these fibers have an operating temperature of 400
The temperature is not less than ℃, the heat resistance is excellent, and the effect of improving the friction performance of the friction material at high temperature is also recognized.

By using the chopped fiber having the above physical properties, the fiber and cashew nut oil are mixed, reacted and hardened, and then crushed, which is a relatively simple process. The filler for the friction material can be obtained.

Further, the reason why the amount of chop fiber mixed with cashew polymer is limited to 5% or less is that when the amount of chop fiber mixed is too large, the viscosity coefficient of the mixture of cashew polymer and chop fiber increases, and substantially. This is because mixing becomes impossible.

[0027]

EXAMPLES The present invention will be described in detail below with reference to examples.

Example 1 An average length of 2.0 mm, an elongation of 2.1%, a tensile strength of 350 MPa and an elastic modulus of 6.8.
In GPa, diameter varies between 0.1 and 40.0 μm 12
Seed chop fiber, cashew nut oil, furfural, and phenolsulfonic acid were weighed and mixed in the ratios shown in Table 1.

[0029]

[Table 1]

After thoroughly stirring the above formulation, 160
The plate-like cured product was pulverized by firing at 24 ° C. for 24 hours to cause reaction curing, and the friction material filler shown in FIG. 1 was obtained. The obtained filler had chopped fibers that stood up on the surface of irregularly shaped particles and flocked. The bulk density of each filler was measured in order to evaluate the relationship between the diameter of the mixed chop fibers and the fiber-implanted state. That is, when the fibers were projected on the surface of the filler, the spacing between the filler particles was expanded, and the bulk density was lowered, so that the flocked state was evaluated. The result is shown in FIG. The vertical axis of this figure is the percentage when the bulk density of the filler without any flocking is 1.

According to this figure, in order for the fibers to sufficiently project from the particle surface, the fiber diameter is required to be 1 μm or more, and when the fiber length is 30 μm or more, it is 25 to 30 μm or less.
It can be seen that there is almost no difference with the area of.

(Example 2) Using 11 kinds of chopped fibers having the same other properties as those of Example 1 except that the average diameter was 12 μm and the average length was 0.3 to 4.0 mm, The same treatment was performed to obtain a friction material filler. These fillers were evaluated in the same manner as in Example 1. The result is shown in FIG.

From this figure, in the region where the fiber length is 0.5 mm or less, almost no fibers are projected on the surface of the filler, and in the region where the fiber length is 3.0 mm or more, the region near 3.0 mm or less is obtained. It can be seen that there is no noticeable difference.

(Example 3) Using 5 kinds of chopped fibers having the same average diameter as 12 μm and elongation of 0.5 to 2.5% and other physical properties as in Example 1, The same treatment was performed to obtain a friction material filler. These fillers were evaluated in the same manner as in Example 1. The result is shown in FIG. 7.

From this figure, it is understood that the elongation of the fiber is required to be 1.5% or more in order to obtain the filler in the hair-implanted state which the present inventors aimed for.

(Example 4) The same treatment as in Example 1 was carried out by using 8 kinds of chopped fibers having the same average diameter of 12 μm and tensile strength of 45 to 400 MPa and other physical properties same as those of Example 1. A filler for friction material was obtained. These fillers were evaluated in the same manner as in Example 1. The result is shown in FIG.

From this figure, in order to obtain the flocked filler intended by the present inventors, the tensile strength of the fiber was 300 MPa.
It turns out that more than a is necessary.

(Example 5) The same as Example 1 using 7 types of chop fibers having the same average diameter of 12 μm and different elastic modulus between 1.0 and 7.0 GPa and other physical properties as in Example 1. A treatment was performed to obtain a friction material filler. These fillers were evaluated in the same manner as in Example 1. The result is shown in FIG.

From this figure, it is understood that the elastic modulus of the fiber is required to be 5 MPa or more in order to obtain the flocked filler intended by the present inventors.

Example 6 The average diameter obtained in Example 1 is 12
Flocked cashew dust using μm chop fiber, and fibrous substance, calcium carbonate, and straight phenol resin were weighed in the ratios shown in Table 2.

[0041]

[Table 2]

After thoroughly stirring and mixing the above formulation,
It was processed into a molded body. In processing the molded body, after preforming, the binder was heated in the mold at a temperature of 160 ° C. for 15 minutes to cure the binder.

No cracks or cracks were found in this molded product. For comparison, using the cashew dust of FIG. 3 which has not been implanted with chop fibers at all,
A molded body was produced with the same composition as in the above table. Cracks or cracks were found in 13% of this molded body.

[0044]

As described above in detail, according to the present invention, cashew dust having chopped fibers on its surface can be easily obtained. Since the cashew dust according to the present invention has a more uniform dispersion in the friction material as compared with the conventional one, not only can cracks and cracks in the product be eliminated, but also cashew dust can be prevented from falling off during use. it can. Therefore, the present invention is extremely useful in improving the performance of the friction material and reducing the manufacturing cost, and is extremely useful industrially.

[Brief description of drawings]

FIG. 1 is a micrograph (magnification: 40 times) of cashew dust for a friction material according to the present invention.

FIG. 2 is a view showing a model of an ideal hair transplant state.

FIG. 3 is a photomicrograph (40 × magnification) of cashew dust when inorganic fibers are used for flocking.

FIG. 4 is a photomicrograph (magnification: 40 times) of cashew dust in which long fibers are used for flocking.

5 is a diagram showing the relationship between the diameter of chop fibers and the relative bulk density of the obtained cashew dust in Example 1. FIG.

FIG. 6 is a diagram showing the relationship between the length of chop fibers and the relative bulk density of the obtained cashew dust in Example 2.

FIG. 7 is a diagram showing the relationship between the elongation of chop fibers and the relative bulk density of the obtained cashew dust in Example 3.

FIG. 8 shows the tensile strength of chop fibers in Example 4,
It is a figure which shows the relationship with the relative bulk density of the obtained cashew dust.

FIG. 9 shows the elastic modulus of chop fiber in Example 5,
It is a figure which shows the relationship with the relative bulk density of the obtained cashew dust.

[Explanation of symbols]

 1 Cashew dust 2 Flocked fibers

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[Procedure amendment]

[Submission date] July 14, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Figure 1

[Correction method] Change

[Correction content]

FIG. 1 is a particle structure of cashew dust for a friction material according to the present invention.
It is a micrograph showing the structure (magnification 40 times).

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] Figure 3

[Correction method] Change

[Correction content]

FIG. 3 is a micrograph (40 × magnification) showing the particle structure of cashew dust when inorganic fibers are used for flocking.

[Procedure 3]

[Document name to be amended] Statement

[Name of item to be corrected] Figure 4

[Correction method] Change

[Correction content]

FIG. 4 is a micrograph (magnification: 40 times) showing a particle structure of cashew dust in which long fibers are used for flocking.

[Procedure amendment 4]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 1

[Correction method] Change

[Correction content]

[Figure 1]

[Procedure Amendment 5]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 3

[Correction method] Change

[Correction content]

[Figure 3]

[Procedure correction 6]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 4

[Correction method] Change

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[Figure 4]

Claims (7)

[Claims] 1. A filler for a friction material, which comprises chopped fibers which are erected and planted on the surface of an amorphous solid mainly composed of cashew polymer. 2. The filler for a friction material according to claim 1, wherein the amount of chop fiber mixed with the cashew polymer is 5% or less (not including 0). 3. The filler for a friction material according to claim 1, wherein the chop fiber has a diameter of 1 to 30 μm. 4. The length of chop fiber is 0.5 to 3.0.
It is mm, The filler for friction materials of Claim 1, 2 or 3 characterized by the above-mentioned. 5. The filler for a friction material according to claim 1, 2, 3 or 4, wherein the elongation of the chop fiber is 1.5% or more. 6. The tensile strength of chop fiber is 300MP.
It is a or more, The filler for friction materials of Claim 1, 2, 3, 4 or 5 characterized by the above-mentioned. 7. The friction material filler according to claim 1, 2, 3, 4, 5 or 6, wherein the chop fiber has an elastic modulus of 5 GPa or more.