JPH0510890Y2 - - Google Patents

Description

[Detailed explanation of the idea]

Industrial Application Field This invention relates to the improvement of a filter cloth used in a wet molding device that filters and compresses slurry magnetic material powder such as hard ferrite magnet material or soft ferrite magnet material and molds it into a desired shape. The present invention relates to a filter cloth for wet molding that has improved strength, excellent water drainage, uniform density of molded products, and has the effect of improving productivity and quality by reducing cracking. BACKGROUND ART Generally, when manufacturing ferrite magnets by wet molding, a molding apparatus as shown in FIG. 3 is used, and magnetic material powder is slurried in a molding space formed by a die 1 and a lower punch 2. That is, a slurry-like raw material 3 is filled, a filter paper 5 and a filter cloth 6 are arranged between the slurry-like raw material 3 and the upper punch 4, and then compressed with a required pressure and water is filtered and discharged. Obtain a molded body of the desired shape. In the production of heteromorphic ferrite magnets, a magnetic field in a predetermined direction is formed at least within the molding space during compression. Moisture in the compression process of the slurry raw material 3 passes through the filter paper 5 and the filter cloth 6, and is drained to the outside through the drain hole 7 provided in the upper punch 4. Therefore, it is essential for the filter paper 5 and the filter cloth 6 to be able to remove water uniformly and sufficiently during the water removal process, and to prevent the raw material powder from flowing out. In order to prevent this, various studies have been made on the structure of the filter paper 5 and the filter cloth 6, etc. As conventional filter cloths, woven fabrics made of natural or synthetic fibers, so-called non-woven fabrics made of short synthetic fibers, etc. have been used. In addition, for the purpose of improving the mechanical strength of the nonwoven fabric, short synthetic fibers are intertwined and integrated by needling on both sides of the base fabric 11 woven from synthetic multifilament yarns, as shown in Figure 4. A filter cloth 10 having a structure in which nonwoven fabric layers 12 and 13 are provided has been proposed. Problems to be solved by the invention In any of the above-mentioned filter cloths, in a molding device,
When filtering and compressing by directly contacting the slurry raw material, the raw material powder is likely to flow out together with the moisture in the raw material, leading to early clogging. It was necessary to replace it after using it in the compression process, and there was also the problem that it was difficult to separate from the molded body. For this reason, in order to extend the life of the filter cloth and improve the ease with which it can be separated from the molded body, a filter paper has been interposed. As mentioned above, the water removal rate and its uniformity of the molded body in the wet molding method have a large effect on the density of the molded body, and non-uniformity of the density of the molded body makes the magnetic properties of the obtained ferrite magnet unstable, and , which can cause cracks in molded bodies and sintered bodies, and therefore, in consideration of the economy of mass production, there is a strong desire for a filter cloth whose initial performance can be maintained even after many compression steps. In view of the current situation, this invention aims to provide a filter cloth that has excellent water removal properties, can maintain a uniform compact density, and has the effect of preventing cracks in compacts and sintered compacts in the wet forming method, and also has the initial performance. The purpose of the present invention is to provide a filter cloth that maintains the same properties and withstands repeated use, reduces the number of filter cloth replacements, and improves industrial productivity. Means to Solve the Problems This idea was developed as a result of various studies aimed at creating a filter cloth that has excellent water removal properties and can maintain a uniform compact density in wet molding methods. Contact side (molded object side)
By arranging a woven fabric using polyethylene monofilament yarns for the warp and weft, we have created a filter fabric with improved mechanical strength, superior water removal properties, and long service life compared to conventional filter fabrics. This is what I found out that it can be obtained. That is, this device consists of at least one 300-700 denier polyethylene monofilament yarn with a texture density of 20
A filter cloth for wet molding characterized by a structure in which ~50 stitches (number of pieces per 30.3 mm) of plain woven fabric are placed on the side of the object to be molded and are entangled and integrated with short chemical fibers by needling. be. Preferred embodiment of the invention In this invention, the yarn type and texture of the woven fabric are particularly
From the viewpoint of mechanical strength and economical efficiency, the fabric is a plain weave fabric using polyethylene monofilament yarn, and the yarn size is 300 to 300 mm depending on the position in the cross section of the filter cloth, the properties of the slurry-like raw material powder, the filtration compression conditions, etc. 700 denier, and the texture density of the woven fabric is appropriately selected in the range of 20 to 50 stitches. The preferred range of tissue density is 30 meshes. However, the unit of tissue density (mesh) is 30.3 mm (1
It is expressed by the number of warp and weft threads per length. Known fibers such as synthetic fibers such as polyester and polypropylene, recycled fibers, and semi-synthetic fibers can be used as short chemical fibers to be entangled and integrated with the above-mentioned polyethylene monofilament yarn woven fabric by needling. It is desirable to select the fiber thickness, fiber length, etc. appropriately according to the filtration molding conditions.
Furthermore, it is not always necessary to use only the same type of fibers or the same length fibers. As short chemical fibers, known fibers having a fiber thickness of 0.5 to 3 deniers and a fiber length of 50 to 80 mm can be used. The needling conditions for entangling and integrating short chemical fibers into such a woven fabric are not particularly limited, but as will be described later, when integrating by entangling, the cross-sectional configuration of the filter fabric, that is, the number of monofilament yarn woven fabrics, The amount of chemical fibers in the short fibers, the amount of needling, the order of needling, etc. are appropriately selected depending on the location and location of the short fibers. The woven fabric made of polyethylene monofilament yarn does not necessarily need to be placed on the slurry raw material contact surface, and at least one of the woven fabrics is placed closer to the slurry raw material contact surface than the center of the thickness of the filter cloth, that is,
There may be a plurality of filter cloths as long as they are arranged near the slurry raw material contact surface, and the stacking position on the filter cloth can be arbitrarily selected. Furthermore, it is also possible to arrange the woven fabric at the central part of the thickness of the filter fabric and the surface that contacts the slurry raw material. Furthermore, the use of filter paper can be omitted by subjecting each surface of the filter cloth according to the present invention to surface treatments such as frizz treatment and calender treatment, depending on the properties of the slurry-like raw material powder, filtration compression conditions, etc. be able to. Furthermore, by applying a surface treatment such as calendering to the surface of the woven fabric made of polyethylene monofilament yarn that comes in contact with the slurry raw material, the monofilament yarn and short fibers are entangled and the strength of the filter cloth is improved. do. In addition, fibers that exhibit adhesive properties when heat treated are mixed uniformly or close to the woven fabric into the short chemical fibers that are entangled and integrated with the woven fabric, and by heat treatment, entanglement progresses in the same way as above, and filtration is performed. It can improve the strength of cloth. Furthermore, the thickness of the filter cloth according to this invention is preferably about 1 mm to 2 mm, considering the official moisture content, mechanical strength, and sealing performance of the molding space, and the air permeability is
Approximately 25 to 35 c.c./cm ² /sec is desirable. DISCLOSURE BASED ON DRAWINGS OF THE INVENTION FIGS. 1 and 2 are cross-sectional explanatory views of a filter cloth according to this invention. The filter cloth 20 shown in FIG. 1 is made by placing a required amount of polyester short fibers 22 on a plain-woven cloth 21 made of polyethylene monofilament yarn, entangling and integrating them by required needling to form a single filter cloth. The surface 23 on the woven fabric 21 side becomes the contact surface with the slurry raw material, and the short fibers 22 are entangled and integrated to such an extent that the surface is slightly covered.
Further, the surface on the upper punch contact side opposite to the surface 23 is calendered. The filter cloth 30 shown in FIG. 2 is made by placing a required amount of polyester staple fibers 32 on a plain weave cloth 31 made of polyethylene monofilament yarn, and then applying the required needling to the same woven cloth 33. A small amount of short polyester fibers 32 are placed and needled to form one filter cloth 30, and the surface 34 on the outermost woven cloth 31 side becomes the contact surface with the slurry raw material. The surface of the upper punch contact side opposite to the upper punch is calendered. Further, the woven fabric 33 located on the upper punch side has a coarser texture than the woven fabric 31 on the slurry raw material side, and is responsible for improving the mechanical strength of the filter fabric 30. Note that the layered structure and entangling method of the filter cloth are not limited to the above-mentioned methods, and any known method can be selected as appropriate. Example: A conventional filter cloth (corresponding to Fig. 4, filter cloth No. 1) in which short fibers are needled on both sides of a base cloth made of multifilament yarn, and a woven fabric made of monofilament yarn on the side in contact with the slurry raw material powder. A filter cloth based on this invention with cloth arranged (corresponding to Figure 1, filter cloth No.
2) Two types of filter cloths were manufactured using a woven cloth with the properties shown in Table 1 and short polyester fibers (fiber thickness: 1.5 denier, fiber length: 76 mm). The upper punch-side abutting surface of each filter cloth is calendered. Table 1 shows the properties of each filter cloth. Using these two types of filter cloth, the average particle size was 0.7 μm.
A slurry-like raw material powder of ~0.8 μm was molded in a magnetic field to obtain a large number of arch-shaped molded bodies in 5 lots. During compression molding, each filter cloth was used in combination with filter paper until the variation in density of the molded product started to become 5.0% or more of the unit weight of the molded product, and the number of times it was used (number of moldings) up to that point and the resulting molded material were measured. The incidence of cracks on the body was measured and the results are shown in Table 2. In addition,
The filter paper was replaced after each molding. As is clear from Table 2, it can be seen that the filter cloth according to this invention can be used for a significantly longer period of time than the conventional filter cloth at the same cracking rate. Furthermore, it was confirmed that when used the same number of times as the conventional filter cloth, the density of the compact was stable and defects such as cracks were significantly reduced.

【table】

[Table] Effects of the invention The filter cloth according to this invention consists of an optimal mesh structure density using polyethylene monofilament yarn on the side of the slurry raw powder contacting surface (the side to be molded) of the filter cloth made of non-woven fabric. The structure in which the woven fabric is arranged improves the mechanical strength of the filter fabric compared to the conventional base fabric using multifilament yarn, and in wet molding, it has excellent water removal properties and a uniform density of the molded product. It has the effect of preventing cracks in molded bodies and sintered bodies, and can also maintain such initial performance and withstand a greater number of uses than before, reducing the number of filter cloth replacements and improving productivity. . In other words, the mechanical strength of the filter cloth is improved, and by minimizing changes in the opening dimensions of the woven cloth during use, variations in water drainage can be reduced, which is advantageous in stabilizing the density of the molded product, and improving the density of the molded product. And the effect of preventing cracks in the sintered body can be obtained. In addition, by placing a woven fabric using polyethylene monofilament yarn on the side that comes in contact with the slurry raw powder, mechanical strength is improved, damage to the filter fabric can be reduced, and water flow in the non-woven fabric area is improved. This, combined with the clogging reduction effect, improves the water removal rate.

[Brief explanation of the drawing]

1 and 2 are cross-sectional explanatory views of the filter cloth according to this invention. FIG. 3 is an explanatory diagram of the main parts of the wet molding apparatus. FIG. 4 is an explanatory cross-sectional view of a conventional filter cloth. 20, 30... filter cloth, 21, 31, 33...
Woven fabric, 22, 32... short fibers, 23, 34... surface.

Claims (1)

[Scope of utility model registration request] Consisting of at least one 300-700 denier polyethylene monofilament yarn with a texture density of
A filter cloth for wet molding characterized by having a structure in which 20 to 50 stitches (number of threads per 30.3 mm) of plain woven fabric are placed on the side of the object to be molded and intertwined and integrated with short chemical fibers by needling. .