JPH08283076A - Porous granular compact - Google Patents

Abstract

PURPOSE: To obtain ceramic fiber-contg. granular compacts usable as a porous granular filler having high porosity. CONSTITUTION: A mixture of 100 pts.wt. finely divided ceramic fibers having 50-150μm average fiber length with <=300 pts.wt. barium sulfate and 1-40 pts.wt. binder is granulated into granules having 0.1-5mm average diameter and 0.2-2.0g/cm<3> bulk density to obtain the objective granular compacts.

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 molding useful for producing friction materials in braking devices for various vehicles and industrial machines.

[0002]

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

On the other hand, in Japanese Patent Laid-Open No. 63-50373, 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 and granulated to obtain a particle size of 10 to 3000 μm. , Apparent density 0.6 to 0.
It is described that a porous granular molded product of about 9 g / cm ³ is used as a fireproof heat insulating material, a pore filter, or the like. When a molded product is produced by using such a granular molded product as a part of the material, the fibers are distributed in the molded product as the granular molded product, and fine voids are introduced into the molded product.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a ceramic fiber granular molding which can be used as a high-porosity porous granular filler.

[0005]

The porous granular molded article of ceramic fiber 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 less than 300 parts by weight of barium sulfate and 1 to 40 parts by weight of binder with an average particle size of 0.1 to 5 mm and a bulk density of 0.2 to 2.0 g / c.
It is formed by granulating m ³ granular material.

The porous granular molded product of the present invention having the above-mentioned structure is filled with barium sulfate fine powder between the ceramic fibers, so that it is not easily deformed or disintegrated, and is stable in shape, fluidity, and other granular materials. 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 0 to 90% of fine voids. 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.

The porous granular molded article of the present invention will be described below with reference to the production method. The starting ceramic fiber is not particularly limited, but the aluminosilicate fiber is the most preferable because it is relatively inexpensive and easily available, and it is preferable in terms of physical properties and easy to granulate. Other suitable ceramic fibers include rock wool, alumina fibers, carbon fibers and the like. In addition, although ceramic fibers which are usually easily available have a length of several millimeters or more, it is necessary to use a wet or dry pulverizer to refine the ceramic fibers into a suitable length for producing the above-mentioned granular molded product. Just process it.

In the present invention, barium sulfate (preferably having an average particle size of 0.5 to 10 μm) is blended with 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, these barium sulfate and Barium sulphate is sometimes referred to as the filler in the sense that it contains the heat resistant fine powder used together.

A binder is used in addition to the ceramic fiber and the filler, and preferred specific examples thereof include a sol binder such as colloidal silica and colloidal alumina; an ethyl silicate; 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 preferably 1 to 300 parts by weight (particularly preferably 50 to 200 parts by weight) of filler and 1 to 40 parts by weight of inorganic binder with respect to 100 parts by weight of ceramic fiber.
The mixture is mixed at a ratio of 5 parts by weight (as solid content) and 5 parts by weight or less of the organic binder, and the mixture is put in a well-known stirring type granulator used for granulating powder and stirred.

Usually, the raw material fibers are compressed in a package to form various large and small lumps. When this is stirred in a granulator, crushing of large lumps and reassembling of single fibers proceed, and aggregates with uniform particle size are formed. In this process, the filler adheres to the fiber surface by the binder. The assembled ceramic fibers are initially in a loose engagement state, but the packing density gradually increases due to the compressive stress associated with stirring. Then, when stirring is further continued, the packing density measured in the form of bulk density does not change much, but a more stable aggregated state is obtained. Here, the stirring granulation is cut off, and the binder is cured by heating and drying. The average particle size is 0.1 to 5 mm and the bulk density is 0.2 to 2.0 g / c by selecting the raw material composition and stirring conditions.
It is possible to obtain a porous granular molding of m ³ .

The "bulk density" is a value measured by the following method. Bulk density measurement method: Put 300 g of a sample in a vertically standing metal cylinder with an inner diameter of 150 mm and 50 g per 1 cm ^{2 of} the cylindrical opening surface.
The weight of is added by the 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 porous granular molded product obtained as described above has a very stable shape in a wide temperature range,
During normal handling and use as a molding material, or when it is heated to a high temperature, it hardly breaks into powder.

[0014]

[Example] Aluminosilicate fiber (commercial item, Al ₂ O
₃ 50%, SiO ₂ 50%) was treated with a dry crusher to obtain 95
Finely divided fibers having an average fiber length of 50 μm and having a weight percentage of 5 to 500 μm were obtained. After putting this in an agitation granulator with an equal amount of barium sulfate and stirring for 1 minute, colloidal silica of 30% by weight of aluminosilicate fiber and 1% by weight of polyvinyl alcohol were added as a solid content, and further stirred for 4 minutes. Continued. Initially, the raw material fibers formed lumps of uneven size, but the lumps were crushed as the stirring was continued, and on the other hand, they were formed into small granules with barium sulfate, and the diameter gradually increased to 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 0.4 mm, 95% by weight
The above was a particle size of 1 mm or less. 1 and 2 are scanning electron micrographs of this porous granular molding.

Next, as shown in Table 1, a mixture of 8 parts by weight of aramid fiber, 20 parts by weight of phenol resin, 5 parts by weight of cashew dust and barium sulfate was used with or without the above porous granular molding. Friction material by hot pressing
Nos. 1 to 7 were manufactured. The ceramic fibers used in Comparative Examples Nos. 2 to 4, which did not use the porous granular molded product, were the finely divided ceramic fibers used in the production of the granular molded product, and the numerical 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 molded product − − − − 5 10 20 Ceramic fiber − 5 10 20 − − Barium sulfate 67 62 57 47 62 57 47

The porosity and bending strength of each of the obtained friction materials were measured, and Tables 2 and 3 show the relationship between the content of the ceramic fibers and the table. From these tables, it is understood that in the friction materials No. 5 to 7 containing the ceramic fiber porous granular molding, the porosity could be increased without significantly lowering the bending strength. As a result of observation with an electron micrograph, the blended porous granular moldings were evenly distributed in the friction material as they were, and each porous granular molding maintained the porosity even in the friction material. Was.

[0019]

[Table 2] Change in porosity (%) Ceramic fiber content 0% 5% 10% 20% Granular molding compound 3.5 3.5 4.4 4.5 5.1 Non-granulated fiber products 3.5 2.7 2.7 3.9

[0020]

[Table 3] Bending strength (kgf / cm²)change of  Granular molding or ceramic fiber content0% 5% 10% 20% Granular molding compound 6.7 6.3 6.3 6.2 5.7Non-granulated fiber products 6.7 7.2 6.9 6.9

Next, friction materials No. 6 (invention product) and N
Wear test by a wear tester for o.3 (control example)
It was performed according to JIS D4411 "Brake lining for automobiles". The generation of squeaking was also tested. The results are shown in Table 4.

[0022]

[Table 4] No. 6 (invention product) No. 3 (control example) Abrasion 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 No squeal occurrence Yes

[0023]

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

[Brief description of drawings]

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

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

Claims (1)

[Claims] 1. Finely divided ceramic fibers having an average fiber length of 50 to 150 μm, 300 parts by weight or less of barium sulfate and 1 to 4 parts by weight per 100 parts by weight of the ceramic fibers.
A porous granular molded 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 .