JPH0940939A - Filler for friction material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a filler for a friction material, prepared by adhering and bonding an expandable thermosetting resin to the surface of a flaky solid and giving a friction material (e.g. brake lining) having improved mechanical strengths. SOLUTION: This filler for a friction material is prepared by adhering and bonding an expandable thermosetting resin to the surface of a flaky solid. The expandable thermosetting resin used is, for example, a phenol resin or a urethane resin containing a blowing agent and has a porosity of 50 to below 100vol.%. In an actual example, 100 pts.wt. Suzolite mica 150S and 8 pts.wt. expandable phenolic resin are kneaded, the obtained mixture is expanded and cured by heating, and the obtained product is disintegrated to obtain a filler for a friction material. Because this filler has a high affinity for the phenol resin as a binder, it can give a friction material having mechanical strengths higher than those of the conventional ones in spite of its high porosity.

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, and a phenol resin or the like is further mixed as a binder, and the mixture is preformed and then heat-cured to be processed into a friction material molded body. It Fillers include cashew dust and rubber powder as organic components, and calcium carbonate, barium sulfate, mica, graphite and the like as inorganic components.

Among the inorganic components, mica and graphite have a flake-like shape, and are used in friction materials with the expectation of a damping action and a lubricating action due to the shape.

[0004]

However, since the surface area of the flake-like solid is small, and the affinity for the phenol resin, which is a binder generally used in friction materials, is low, the flake-like solid is solid. The decrease in the strength of the friction material due to the use of objects is unavoidable. In addition, since the flaky solids are oriented in a specific direction during molding of the friction material, it is inevitable that the shear stress of the friction material in the oriented direction is reduced.

On the other hand, the reliability required of friction materials has become higher with the speeding up of transportation facilities and the deterioration of traffic conditions in the past ten years. Therefore, an object of the present invention is to improve the affinity with a phenolic resin, and to increase the surface area of the flake-like solid matter, thereby not deteriorating the strength of the friction material, and especially the flake-like solid matter. It is intended to provide a flake filler which does not reduce the shear stress in the orientation direction.

[0006]

As a method for solving the above-mentioned problems, the present inventors have studied to increase the contact area between the flaky solid matter and a binder such as a phenol resin. It is arguable that increasing the specific surface area of the flaky solids is most effective for that purpose. However, as a method of increasing the specific surface area of the flake-like solid,
There is no choice but to grind the flaky solids into fine particles, which results in a significant reduction of the high aspect ratio characteristic of the flaky solids.

From this point of view, the present inventors have focused on providing a porous structure by introducing another substance to the surface of the flake-like solid material. Then, the present inventors have found that it is very effective to coat the surface of the flaky solid material with a foaming substance as a method for realizing the above-mentioned point of view, and have completed the present invention. .

That is, in the present invention, the foamable thermosetting resin is adhered and bonded to the surface of the flake-shaped solid material, and the affinity with the binder constituting the friction material is remarkably improved. The present invention is characterized in that it is possible to provide a filler for a friction material, which is composed of a flake-shaped solid material.

In order to achieve the object of the present invention, the amount of the expandable thermosetting resin added is 50% or less (not including 0) based on the weight of the flaky solid material.

In order to achieve the object of the present invention, the porosity of the expandable thermosetting resin is 50 to 100% (1
00 is not included).

The reason why the upper limit of the amount of addition is set is that if the amount of addition is too large, the amount of powder of only the expandable thermosetting resin is increased in the manufacturing process, and the function as a flake solid is impaired. This is because it causes deterioration of the characteristics of the friction material.

The reason why the lower limit of the porosity of the thermosetting resin is set is that when the porosity is too small, the shape of the surface of the flake-like solid material is before the adhesive bonding of the foamable thermosetting resin. This is because there is not much difference. The upper limit was not set for the porosity of the foamable thermosetting resin. Even if the porosity is considerably large, the foamable thermosetting resin has flexibility such as urethane resin. This is because the porous structure can be sufficiently maintained by adopting a material having a high content.

[0013]

The filler for a friction material according to the present invention naturally has a large contact area with the binder due to its large specific surface area, but due to its characteristic surface structure, the binder caused by the so-called anchoring effect. It can be expected to improve the affinity with. Further, the smooth surface of the flake-like solid has many irregularities due to foaming of the expandable thermosetting resin, and the specific surface area of the smooth surface increases, so that the contact area with the binder increases and the orientation direction Shear stress increases significantly.

Now, a method for producing the filler for friction material of the present invention will be described.

In this manufacturing method, (1) the flaky solid matter and the expandable thermosetting resin are weighed in the required ratios.

(2) The weighed materials are kneaded by using an appropriate kneading device.

(3) The mixture is left standing or heated to foam and cure the thermosetting resin.

(4) The cured product is crushed and adjusted to the required particle size. Therefore, it is a feature of the present invention that no special device is required.

Next, the foamable thermosetting resin usable in the present invention will be described. In the present invention, a so-called foaming agent uniformly mixed with a phenol resin, a urethane resin or the like can be used, but the invention is not limited thereto.
As the foaming method, so-called chemical foaming, gas foaming and the like can be applied. However, it goes without saying that it is not limited to these.

[0020]

[Description of Embodiments] Next, the embodiments will be described in more detail.

(Example) Szolite Mica 150S:
100 parts by weight and expandable phenol resin: 8 parts by weight were weighed and kneaded for 10 minutes using a pressure kneader.
This mixture was kept for 60 minutes in a dryer maintained at a temperature of 90 ± 10 ° C. to foam the phenol resin and heat-set it.

The cured product was crushed using an atomizer until it passed through a sieve having a mesh opening of 1.18 mm to obtain a filler for friction material. The main properties are shown in Table 1. As a comparative example, Table 1 also shows the properties of mica to which no expandable thermosetting resin is attached.

It can be seen from Table 1 that the examples have a large specific surface area despite the coarse particle size.

Then, a friction material was prepared in accordance with the composition shown in Table 2 by using the above-mentioned two types of friction material fillers.

Regarding these friction materials, JIS D431
Bending strength, bending strain and shear stress were measured according to No. 1 and the results are shown in Table 3.

Further, a rubbing test was conducted by using the friction material, the fluctuation of the friction coefficient (μ) was measured, and the braking stability was examined. The results are shown in Table 4.

Further, the amount of abrasion during the rubbing test was measured, and the results are shown in Table 5.

[0028]

As described above in detail, the friction material using the filler for friction materials obtained according to the present invention has improved mechanical strength despite having higher porosity than the conventional one. . It is clear that this effect is due to the fact that the foamable thermosetting resin is adhered and bonded to the surface of the flaky solid material.

In general, flake-like solids may have a problem of low dispersibility in the friction material due to the coarseness of the particle size, but the present invention is also effective for this. There can be expected a secondary effect.

Therefore, the present invention greatly contributes to the improvement of the reliability of the friction material and is extremely useful in industry.

[0031]

[Table 1]

[0032]

[Table 2]

[0033]

[Table 3]

[0034]

[Table 4]

[0035]

[Table 5]

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Tadao Katahira 7-9-4 Nishigotanda, Shinagawa-ku, Tokyo Within Tohoku Kako Co., Ltd. (72) Inventor Mikio Nishimura 7-9-4 Nishigotanda, Shinagawa-ku, Tokyo No. Tohoku Kako Co., Ltd.

Claims (3)

[Claims] 1. A filler for a friction material, characterized in that a foamable thermosetting resin is adhered and bonded to the surface of a flaky solid material. 2. The filler for a friction material according to claim 1, wherein the ratio of the expandable thermosetting resin to the flake-like solid matter is 50% or less (not including 0) by weight. 3. The porosity of the expandable thermosetting resin is 5 by volume.
It is 0% -100% (100 is not included), The filler for friction materials of Claim 1 characterized by the above-mentioned.