JPH06246115A - Felt filter medium for wet-filtering and compacting magnetic powdery material - Google Patents

Abstract

PURPOSE:To provide a felt filter medium used in a wet-compacting process in which a magnetic powdery material such as ferrite is slurried, dehydrated by filtration and compacted into a prescribed shape. CONSTITUTION:A 1st layer brought into direct contact with a material to be compacted is made of a layer of thermoplastic synthetic fibers surface- smoothened and fixed by hot melting and calendering, a substrate made to coarse leno cloth is interposed between the 1st and 2nd layers to obtain the objective felt filter medium for wetfiltering and compacting a magnetic powdery material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a felt filter medium used in wet molding in which a magnetic powder material such as ferrite is slurried, filtered and dehydrated to be molded into a predetermined shape.

[0002]

2. Description of the Related Art In the wet manufacturing of ferrite magnets,
As shown in FIG. 1, the filter paper (1) is installed near the upper punch (2).
At least a woven cloth between the filter paper and the upper punch, or
Two filter cloths (3) (4) made of non-woven fabric are arranged, and a slurry of magnetic powder material (7) is injected into a space formed by a fixed die (5) and a vertically movable lower punch (6). Then
It is common to pressurize this with a lower punch to carry out filtration dehydration, and to discharge the filtrate from the drain hole (8) of the upper punch to obtain a molded body.

In this structure / mechanism, slurry injection, filtration, dehydration, and mold release are repeated, but the filtration and dehydration properties of the filter paper and filter cloth are extremely important in terms of the quality of the molded product. That is, in ordinary filter paper and filter cloth, clogging gradually progresses as the number of times of filtration overlaps, and the dewatering property deteriorates. Therefore, if it exceeds the permissible range, the single weight of the powder material after molding is reduced. The rate of occurrence of quality defects such as variations, uneven density, and cracks increases.

Therefore, the role of the filter paper in direct contact with the slurry is particularly large. If you simply try to omit the filter paper from this configuration and try to mold it, the outflow of powder particles in the slurry,
Premature clogging of the filter cloth occurs, and fluffing of the filter cloth occurs on the surface where the filter cloth comes into contact with the molded body, which makes it difficult to separate the molded body after dehydration from the filter cloth. In order to solve such a problem, a filter paper, which is cheaper than a filter cloth, is interposed between the slurry and the filter cloth to obtain good filtration, dewatering and peeling properties, thereby extending the life of the filter cloth.

However, since the filter paper used in this method has a pore size smaller than that of the filter cloth, it is easily clogged, and its strength is weaker than that of the filter cloth. It was necessary to replace with a new filter paper after each molding. This causes a decrease in productivity such as time and effort for changing the filter paper, stopping the machine, and disposing of a huge amount of used filter paper requires a lot of space and cost, which is a problem. For the purpose of eliminating such defects, needle punching felts (hereinafter simply referred to as felts) that can be molded without using filter paper as described in Japanese Utility Model Laid-Open No. 63-107714 and Japanese Patent Laid-Open No. 63-166410. ) Has been proposed.

[0006]

However, from the viewpoint of the filter cloth, the felt generally has much more filtrate flow passages and a narrower flow path than the woven fabric of the same basis weight. For this reason, it has an excellent collecting property, but on the other hand, it can be said that the structure easily causes clogging. Therefore, even when the felt is used, the number of times of good dewatering is not sufficient for all products having different moldability due to the clogging peculiar to the felt structure.

That is, in a normal felt, as shown in FIG. 4, webs (b ₁ ) and (b ₂ ) are arranged above and below a base fabric (a) made of plain weave multifilament, and needle punching is used from above and below to form the base fabric ( Fibers of a) and webs (b ₁ ) and (b ₂ ) are entwined and integrated, and one surface, for example, the surface on the web (b ₁ ) side, is optionally calcined and calendered to be smoothed and molded. It prevents the entanglement of the ferrite powder with the solid matter via the fluff and the deterioration of the peeling.

However, in this felt, the fibers are extremely strongly and intensively entangled with each other in the base cloth layer, so that the particles invading from the surface are strongly trapped in the base cloth layer and fixed to this layer to cause clogging. . In order to solve this, in Japanese Utility Model Laid-Open No. 63-107714, a monofilament base cloth is arranged on the surface, but since the monofilament is arranged on the surface, the surface is hard,
It is rigid and the surface roughness remains even after calendering. For this reason, the surface bond between the molded body and the filter medium is strong, and the releasability is not satisfactory, and even if the molded body can be followed when it is a flat plate, in the case of an arc segment-shaped molded body due to the rigidity of the surface Cannot be used satisfactorily because it cannot follow the complicated shape change of the forming punch filter chamber.

Japanese Patent Laid-Open No. 63-166410 has a structure in which multifilaments are arranged on a surface base fabric, and hygroscopic fibers are used for the base fabric constituting yarns. The hygroscopic fiber of the surface base cloth tries to improve the dehydration property by maintaining the moisture absorption and drainage of the filter paper (cellulose pulp). However, in this structure, a large amount of web fibers are exposed to the surface by needle punching and adhere to the base cloth during surface scouring and calendering, and the fibers substantially cover the surface. Therefore, the fibers of the web that have come out on the surface are contaminated with the slurry, and the solids are entangled with the fibers, causing early clogging on the surface.

Therefore, an object of the present invention is to eliminate the above-mentioned drawbacks of the prior art, to eliminate the need for filter paper, to mold even products with high molding difficulty, and to significantly improve productivity and eliminate costs related to filter paper. Is to provide.

[0011]

In order to achieve the above object, the present invention provides a thermoplastic synthetic fiber layer in which the surface of the first layer, which is in direct contact with the molding target, is hot melt calendered and smoothed and fixed. A technical means was adopted in which the subsequent second layer was a synthetic fiber elastic layer, and a coarsely knitted woven base fabric was arranged between the first layer and the second layer.

[0012]

The present inventors conducted a detailed investigation of the clogging condition of the above-mentioned ordinary felt, and found that the clogging of the filter medium was concentrated in the base fabric layer, and that the web fibers that were filled up with the base fabric texture were Since this layer is concentrated and dense due to the entanglement of the base cloth yarns, even if the solid substance of the magnetic powder for molding is dispersed and filtered in water, it is possible to filter the slurry in which the inorganic particles are dispersed in water. It was found that the drainage rate of the filter medium did not decrease so much that it could be discussed on the table as well as the felt characteristics in the paper. In addition, in ferrite molding, a mineral oil-based release agent with a high viscosity is used in combination so that the molded body and the filter medium, mold, etc. can be easily peeled off, which takes in particles of the slurry and firmly adheres to the synthetic fibers. It was also found that the release agent forms an oil film and causes early clogging, and that these ordinary felts cannot completely prevent defects due to cracks caused by stress after molding.

Therefore, in order to obtain a felt which can be filtered and dehydrated without clogging without using a filter paper, A. The surface filtration layer should be provided with a fiber assembly that exhibits strong antifouling properties against oily substances dispersed in water. B. The base fabric layer should have a structure in which the entanglement of the yarns does not deviate and the yarns are not dispersed even with the needle punch. C. The filter medium should have elastic recovery so as not to cause thickness reduction even under intermittent pressure under wet conditions. We thought that it was necessary to have the basic structural functions of, and repeated research and experiments on its realization.

As a result, the surface filtration layer is not
Hydrophilicity is required to maintain drainage. Also hydrophilic
And fiber-processing agent that exhibits strong antifouling property against oily substances dispersed in water
Mainly polyethylene glycol carbamate as
Then, the fiber (the basic fiber is, for example, 2^d× 51mm cut
Is a polyester fiber. ) Is a hydrophobic bond and
The structure that exposes hydrophilic groups on the surface is the most effective
I found out. Furthermore, the base fabric is nylon multifilament  (420^D/ 1 x 840^D/ 1) / (24 / in × 13
Book / in) entangled woven fabric with needle punching
It was possible to prevent the deviation. Also, the structure with good elastic recovery
3 to make a filter with an appropriate fiber thickness as a filter medium
Made from 10 denier 66 nylon fiber web
Let The hydrophilicity of the surface constituent fibers is
You can also do it, or you can apply hydrophilic treatment in the state of the fiber web.
You can go there. From the actual state of the felt manufacturing process
For example, the hydrophilic treatment is performed in the state of the fiber web, and
Cost effective to manufacture by felt manufacturing process
Is.

[0015]

The present invention will be described in the following felt manufacturing example. Felt Manufacturing Example 1 As Manufacturing Example 1, an actual manufacturing example of the present invention is shown in Table 1, and the structure is shown in FIG.

[0016]

[Table 1]

Felt Production Example 2 As Production Example 2, Table 2 shows the production specifications of a felt (comparative example) made of 100% polyester fiber, and the structure is shown in FIG.

[0018]

[Table 2]

Example of Using Felt Using the felts of Production Example 1 and Production Example 2, a ferrite magnet was produced under the following conditions, and the felt was evaluated. The results are shown in Table 3.

[0020] Ferrite powder with an average particle size of 0.7 μm (S
rO ・ 6Fe₂O₃) To the water, adding a solids concentration of 40%
I created a rally. This slurry is shown in FIG.
400kg / cm in the magnetic field by the device²Wet at pressure
Molding is performed, and the obtained molded body is baked at a temperature of 1200 ° C.
Bonded to obtain a ferrite magnet.

[0021]

[Table 3]

As shown in Table 1, the felt of the present invention is
The surface is laminated with hydrophilic polyester fiber web, needle punched and then fluffed, and heat roll press processing is applied, so the surface is fluff-free and smooth, and there is no entanglement between the molded product and the felt surface and it is smooth. The cake is peeled off. Further, by the action of the web of hydrophilic polyester fiber on the surface, the binding of the ferrite powder to the felt surface through the oil-based mold release agent and the promotion of clogging are prevented. Therefore, as shown in Table 3, the usable number of times is significantly increased as compared with the conventional one. Furthermore, 6 nylon and 66 nylon with excellent elastic recovery performance are placed on the base fabric and back layer (second layer), and since relatively thick 66 nylon fiber is used for the web, repeated filtration and Even when pressed, the felt thickness is reduced very little and stable drainage performance is maintained. The inherent hydrophilicity of nylon also contributes to the retention of drainage. Further, even with respect to the stress after molding, the felt of this structure has a cushioning property and easily absorbs the stress, and as shown in Table 3, due to the cracks caused by the stress, which cannot be dealt with by the conventional filter media. The defect rate was also greatly reduced.

The molding difficulty depends on the size of the ferrite raw material particles, the cohesiveness, the predetermined shape of the molded body, etc.
When the raw material particles are large and the cohesiveness is good, and the oily release agent is not required, the surface polyester fibers of the felt do not necessarily have to be hydrophilized.

[0024]

As described above, when ferrite is wet-molded by using the felt filter medium of the present invention, the use of the filter paper which is necessary in the magnetic material slurry having a particularly high molding difficulty can be omitted, A molded product of good quality can be obtained. In addition, the felt filter medium can be used for a long time without replacement, which can contribute to the improvement of productivity.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a molding apparatus used in a wet magnetic ferrite molding method.

FIG. 2 is a schematic view showing an embodiment of the felt of the present invention.

FIG. 3 is a schematic view showing an example of a conventional felt.

FIG. 4 is a schematic view showing an example of a normal felt.

[Explanation of symbols]

 1 Filter Paper 2 Upper Punch 3, 4 Woven or Non-woven Fabric 5 Die 6 Lower Punch 7 Slurry 8 Drainage Hole

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Akio Nagai 1-1-1, Matsubara, Konosu City, Saitama Prefecture (72) Inventor Sai Nishihara 15-25, Ohji, Kusatsu City, Shiga Prefecture

Claims (2)

[Claims] 1. A thermoplastic synthetic fiber layer in which the surface of the first layer, which is in direct contact with the molding target, is subjected to hot melt calendering and smoothed and fixed to form a thermoplastic synthetic fiber layer, and the subsequent second layer is a synthetic fiber elastic layer. A felt filter material for wet filtration molding of magnetic powder material, characterized in that a coarsely entangled woven base fabric is arranged between the first layer and the second layer. 2. The first layer is made of a hydrophilized polyethylene fiber, the second layer is made of a 3 to 10 denier 66 nylon fiber web, and the base layer is made of a woven nylon multifilament woven fabric. The felt according to claim 1.