JP2893513B2 - Porous granular molded product - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic fibrous porous granular material useful for producing a friction material in a braking device for various vehicles and industrial machines.

[0002]

2. Description of the Related Art Ceramic fibers have excellent heat resistance, abrasion resistance, chemical resistance and the like, and are therefore used as molding materials, reinforcing materials, fillers and the like for various molded articles. The form used depends on the application, but is often a short fiber whose length has been adjusted to an appropriate range. In that case, the fibers are mixed homogeneously with the other molding materials, shaped and evenly distributed in the shaped body. The porosity of the molded body is determined by the presence or absence of the porous material and the molding conditions, and the use of ceramic fibers does not directly affect the porosity.

On the other hand, Japanese Patent Application Laid-Open No. 63-50373 discloses a method in which a binder is added to fine ceramic fibers or whiskers having a diameter of 0.1 to 5 μm and an aspect ratio of 50 to 500 to obtain a granule having a particle size of 10 to 3000 μm. , Apparent density 0.6-0.6.
It describes that a porous granular molded article of about 9 g / cm ³ is used for a fire-resistant heat insulating material, a pore filter and the like. When a molded article is manufactured using such a granular molded article as a part of the material, the fibers are distributed in the molded article as the granular molded article, and fine voids are introduced into the molded article.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a ceramic fibrous granular molding which can be used as a porous porous filler having a high porosity.

[0005]

Means for Solving the Problems A ceramic fibrous porous granular molded product successfully provided by the present invention is a finely divided ceramic fiber having an average fiber length of 50 to 150 μm, and 100 parts by weight of the ceramic fiber. A mixture of not more than 300 parts by weight of barium sulfate and 1 to 40 parts by weight of a binder has an average particle size of 0.1 to 5 mm and a bulk density of 0.2 to 2.0 g / c.
It is those formed by granulating the granules of m ^3.

[0008] The porous granular molded product of the present invention having the above-mentioned structure is characterized in that it is not easily deformed or collapsed because the fine powder of barium sulfate is filled between the ceramic fibers. It has advantageous properties such as uniform dispersibility when mixed with On the other hand, since the bulk density is suppressed to 2.0 g / cm ³ or less, the volume ratio in the particles is about 7%.
It is a porous material having fine voids of 0 to 90%. Those having a bulk density of more than 2.0 g / cm ³ have a low porosity and cannot be a porous granular molded product for introducing fine pores.

Hereinafter, the porous granular molded product of the present invention will be described with reference to the production method. The raw material ceramic fiber is not particularly limited, but is most preferable because aluminosilicate fiber can be obtained relatively inexpensively and easily, and is preferable in terms of physical properties and granulation is easy. Other suitable ceramic fibers include rock wool, alumina fibers, carbon fibers, and the like. Incidentally, usually available ceramic fibers have a length of several millimeters or more.However, in order to reduce the length of the ceramic fibers to a length suitable for the production of the granular molded product, a wet or dry pulverizer is used. It should be processed.

In the present invention, barium sulfate (preferably having an average particle size of 0.5 to 10 μm) is blended in the ceramic fiber as a friction modifier. Powders such as wollastonite, cashew dust, carbon powder, calcium carbonate, and the like can be used in combination, whereby the physical properties of the granular molded product can be adjusted according to the application (hereinafter, if necessary, barium sulfate and Barium sulfate is sometimes referred to as a filler in the sense of including heat-resistant fine powder used in combination.)

[0009] A binder is used in addition to the ceramic fiber and the filler. Preferred examples thereof include a sol binder such as colloidal silica and colloidal alumina; ethyl silicate; and an organic binder such as polyvinyl alcohol, CMC and phenol resin. Etc. These may be used in combination of two or more.

The above-mentioned raw materials are desirably used in an amount of 1 to 300 parts by weight (particularly preferably 50 to 200 parts by weight) with respect to 100 parts by weight of the ceramic fiber, and 1 to 40 parts of the inorganic binder.
Parts by weight (as solid content) and 5 parts by weight or less of an organic binder are mixed and stirred in a well-known agitation-type granulator used for granulating powder.

Normally, raw fibers are compressed in a package to form various sized masses. When this is stirred in a granulator, the disintegration of large lumps and the reassembly of single fibers progress, and an aggregate having a uniform particle size is formed. During this process, the filler is attached to the fiber surface by the binder. The aggregated ceramic fibers are initially in a loosely engaged state, but the packing density gradually increases due to a compressive stress accompanying stirring. Then, when stirring is further continued, the packing density measured in the form of bulk density does not change much, but becomes a more stable aggregate state. Here, the agitation granulation is discontinued, and the binder is cured by heating and drying. By selecting the raw material blending and stirring conditions, the average particle size is 0.1 to 5 mm and the bulk density is 0.2 to 2.0 g / c.
An m ³ porous granular molded product can be obtained.

The "bulk density" is a value measured by the following method. Bulk density measurement method: a metal cylinder vertically erected inner diameter 150mm putting sample 300g cylindrical opening surface 1 cm ² per 50g
Is applied by a weight. After 5 minutes, the height of the sample is measured to determine the volume V (cm ³ ). Bulk density (g / cm ³ ) = 300 / V

The shape of the porous granular molded product obtained as described above is extremely stable over a wide temperature range.
During normal handling and use as a molding material, or when heated to a high temperature, it hardly breaks and becomes powder.

[0014]

EXAMPLE Aluminosilicate fiber (commercially available, Al ₂ O)
₃ 50%, SiO ₂ 50%) in a dry mill.
The weight% or more was in the range of 5 to 500 µm in fiber length, and the refined fiber having an average fiber length of 50 µm was obtained. This was put in a stirring granulator together with an equal amount of barium sulfate and stirred for 1 minute. Then, as solids, 30% by weight of colloidal silica and 1% by weight of polyvinyl alcohol based on aluminosilicate fiber were added, and the mixture was further stirred for 4 minutes. Continued. At first, the raw material fibers were formed into lumps of irregular sizes, but as the stirring continued, the lumps were broken up, and on the other hand, formed into small granules together with barium sulfate, gradually having a diameter of about 0.1 to 5 mm. Only particulate matter became visible.

The obtained granular molded product has a bulk density of 0.80 g / c.
m ³ , porosity 75.0%, average particle size 0.4mm, 95% by weight
These were those having a particle size of 1 mm or less. 1 and 2 are scanning electron micrographs of the porous granular molded product.

Next, as shown in Table 1, a mixture of 8 parts by weight of aramid fiber, 20 parts by weight of phenolic resin, 5 parts by weight of cashew dust and barium sulfate was used with or without the above porous granular molded product. Hot pressing, friction material
Nos. 1 to 7 were manufactured. The ceramic fibers used in Comparative Examples Nos. 2 to 4 using no porous granular molded product were the fine ceramic fibers used in the production of the granular molded product, and the values in the table are parts by weight.

[0017]

Table 1 No.1 No.2 No.3 No.4 No.5 No.6 No.7 Porous granular molding ----- 5 10 20 Ceramic fiber-5 10 20---Barium sulfate 6762 57 47 62 57 47

The porosity and flexural strength of each of the obtained friction materials were measured, and Tables 2 and 3 show the relationship between the porosity and the ceramic fiber content. It can be seen from these tables that the porosity could be increased without significantly lowering the flexural strength of the friction materials Nos. 5 to 7 in which the ceramic fibrous porous granular moldings were blended. Observation with an electron microscope photograph shows that the compounded porous granular molded product is uniformly distributed in the friction material as it is, and each porous granular molded product maintains porosity even in the friction material. Was.

[0019]

[Table 2] Change in porosity (%) Ceramic fiber content 0% 5% 10% 20% Granular molded product blended product 3.5 4.4 4.5 5.1 Product using non-granulated fiber 3.5 2.7 2.7 3.9

[0020]

[Table 3] Change in bending strength (kgf / cm ² ) Granular molded product or ceramic fiber content 0% 5% 10% 20% Granular molded product compound 6.7 6.3 6.2 5.7 Product using non-granulated fiber 6.7 7.2 6.9 6. .9

Next, friction material No. 6 (product of the present invention) and N
o.3 (control example)
The test was performed according to JIS D4411 "Brake lining for automobiles". The occurrence of squeal was also tested. Table 4 shows the results.

[0022]

Table 4 No. 6 (product of the present invention) No. 3 (control) Wear rate (× 10 ⁻⁷ cm ³ / kg · m) 100 ° C. 1.6 1.5 150 ° C. 0.9 1.0 200 ℃ 1.0 1.2 250 ℃ 1.3 1.5 Squealing No Yes

[0023]

As described above, according to the present invention, a heat-resistant porous granular molded product useful for producing a friction material is provided.

[Brief description of the drawings]

FIG. 1 is a scanning electron micrograph (× 40) of an example of a porous granular molded product according to the present invention.

FIG. 2 is a scanning electron micrograph (magnification: 2) of the embodiment of FIG.
00 times).

Claims (1)

(57) [Claims] 1. Finely divided ceramic fibers having an average fiber length of 50 to 150 μm, barium sulfate of 300 parts by weight or less based on 100 parts by weight of the ceramic fibers, and 1 to 4 parts by weight.
A porous granulated product obtained by granulating a mixture of 0 parts by weight of a binder into granules having an average particle size of 0.1 to 5 mm and a bulk density of 0.2 to 2.0 g / cm ³ .