JPH0245485B2 - ROZAI - Google Patents

Description

[Detailed description of the invention]

TECHNICAL FIELD This invention relates to air filter element materials, and more particularly to materials that have special structural features to form gradient fiber density nonwoven filter elements. Conventionally, a filter element made of a nonwoven fabric with a fiber density gradient type has a nonwoven fabric with a fiber density gradient in the thickness direction, which is folded by pleating in order to increase the overarea of the material stored in the filter element and increase the amount of dust held. Formation is performed by Such pleating processing methods include creating streaks on the non-woven fabric using mechanical pressure and using that area as a crease, or creating narrow streaks about half the thickness of the non-woven fabric using heat-pressure processing and using that area as a crease. However, the current situation is that none of these methods has achieved satisfactory results in terms of securing the effective area of the material. That is, FIGS. 2 and 3 are schematic cross-sectional views of typical examples of nonwoven fabric materials formed by such conventional methods, and as is clear from these figures, the materials formed by folding the nonwoven fabric 1 do not have mountain folds. Not only can the valleys 2 become clogged and the periphery of the peaks 3 undergo compression deformation, but also the distribution of space on the dirty side 4 and clean side 5 is inappropriate, causing the clean side 5 to become extremely crowded. It was never sufficient in terms of effectively securing the surface area of the nonwoven fabric material, such as narrowing, and even more so, the amount of dust retained per element was not satisfactory. The reason why the pleat shape of the nonwoven material is insufficient is that the thickness of the nonwoven material is large, and due to the fiber density gradient, the layer on the clean side of the filter element has high rigidity and the layer on the dirty side has low rigidity. This was due to the inherent properties of the fiber density gradient type nonwoven fabric material. The present invention has been made in order to eliminate these drawbacks in the conventional technology, and provides a material that enables the formation of a folded filter element having a pleated shape that can hold a large amount of dust per element. be. That is, in the present invention, on the front side of a fiber density gradient type nonwoven fabric in which the fiber density gradually increases from the front side to the back side,
Welding recesses A having a width of 1.5 to 3.0 times the thickness of the nonwoven fabric and welding recesses B having a width of at least 0.3 times the thickness of the nonwoven fabric are alternately formed at a constant rate in a direction perpendicular to the length direction of the nonwoven fabric. This relates to a material that is formed at intervals and is foldable by folding the fused recesses A and B. The material 1 according to the present invention will be described in more detail below with reference to the present invention and the drawings. Composed of vertically long non-woven fabric. This nonwoven fabric is made of thermoplastic synthetic resin fibers or a fiber material containing the same. In addition, the fiber density gradient means that the fiber density is low in the layer on the front side (the inlet side, i.e., the dirty side) and high in the layer on the back side (the outflow side, i.e., the clean side), and this gradient is gradual. It may be either a change or a continuous change. The thickness of this non-woven fabric is at least 1 mm, preferably 2 to 5 mm. In the case of a material with a homogeneous fiber density, such as paper, if the material is made with mechanical pressure and then folded into creases, the material can be folded straight into a zigzag shape without any curvature. On the other hand, when folding a fiber density gradient type nonwoven fabric with the clean side layer with a high fiber density inside, the layer with a high fiber density will fold at an acute angle, and the dirty side layer with a low fiber density will fold as shown in Figure 2. When deformed, the original fiber density of the material is lost, and when folded with the dirty side layer with a lower fiber density inside, the layer with a higher fiber density does not break and bends into a U-shape to wrap around the layer with a lower fiber density. The mountain folds take on a curved shape. In the case of a folding structure having such a shape, the surface of the material does not work effectively, so the amount of dust held per element becomes small. The present invention uses a fiber density gradient type nonwoven fabric and forms specific recesses on the surface side of the nonwoven fabric in order to enable a folded shape that does not have the above-mentioned drawbacks. That is, as shown in FIG. 4, in the material 1 of the present invention, a fiber density gradient type vertically elongated nonwoven fabric is coated with 1.5 of the thickness of the nonwoven fabric in a direction perpendicular to the length direction of the nonwoven fabric on the surface side (lower fiber density side). A fusion recess A having a width of ~3.0 times and at least the thickness of the nonwoven fabric
Fusion recesses B having a width of 0.3 times (preferably 0.5 to 2.0 times) are formed alternately at regular intervals. In the present invention, these recesses are an important requirement, so that when this material is folded to form a filter element, the amount of dust held per element volume can be maximized. . Note that when this material is folded to form a filter element, the recesses A will correspond to the valleys of the mountain folds, and the recesses B will correspond to the peaks of the mountain folds. The depth of such a welding recess is 40% or less, preferably 10 to 30%, of the thickness of the nonwoven fabric. Such a welding recess can be formed by subjecting the surface (dirty side surface) of the nonwoven fabric to a heat-pressure welding process such as a heat-pressure process, an ultrasonic welder process, a high-frequency welder process, or the like. Further, each of these welding recesses is normally formed in the shape of a single groove as shown in FIGS. 4 and 5a, but in some cases, as shown in FIGS. It is also possible to form a pattern in which the fused portions 6 and the non-fused portions 7 coexist as shown in c and d. By the above-described fusing process, the bottom of the recess and the adjacent fiber layer portion with a low fiber density are fixed to the side of the fiber layer portion with a high fiber density in the form of a film. This phenomenon combined with the above-mentioned specific width of the recesses means that when the material of the present invention is folded alternately along the recesses A and B, the troughs and peaks are straight without being curved, as shown in Figure 1. This allows the filter element to be folded into a zigzag shape, thus creating a filter element with an ideal shape. Since the filter element obtained in this way has a folded structure with a pleated shape, the amount of dust retained per element is significantly larger than that of a conventional filter element with a folded structure, even if the same nonwoven fabric is used. The reason why the amount of dust retained per element is large is that only a small area (only the valleys and peaks of the welded mountain folds) works effectively as a material compared to the total area of the mountain folds of the material. This is because the original excessive performance of the fiber density gradient type nonwoven fabric can be demonstrated in other parts, and the areas around the valleys and peaks of the mountain folds, which are seen in conventional seed materials, are not affected. This is because excessive performance deterioration and overlapping of mountain folds do not occur. Hereinafter, the present invention will be specifically explained with reference to Examples. As shown in Table 1, there is a fusion recess A on the surface (lower fiber density side) of a three-layer laminated fiber type density gradient nonwoven fabric made of polyester and rayon fibers with a basis weight of 300 g/m ² and a thickness of 3.0 mm. (corresponding to the valleys of the mountain folds of the material) and fusion concave portions B (corresponding to the peaks of the mountain folds of the material) were formed with various widths at regular intervals of 35 mm by fusion processing using an ultrasonic welder. Ta. In both cases, the depth of the recess was 0.5 mm. The thus obtained material was folded along the concave portion and stored in a frame with a width of 170 mm, depth of 40 mm, and height of 50 mm, and the surrounding area was fixed with adhesive (the number of threads was as shown in Table 1). Example 1 , 2 and Comparative Examples 1 and 2,
I created 3 and 4 filter elements. Using these filter elements, the test air volume was 1 cm ³ /
A dust test was conducted with a dust concentration of 1 g/m ² (using the 8th class test dust according to JIS-Z-8901) and a lifetime of increased resistance of 300 mmH ₂ O. The results are shown in Table 1. As is clear from these results, there is almost no difference in cleaning efficiency between the Examples and the Comparative Examples, but the amount of dust retained in Examples 1 and 2 of the present invention was significantly larger than in any of the Comparative Examples.

[Table] Next, filter elements of Examples 3 and 4 and Comparative Examples 5 and 6 were prepared by changing only the number of threads in Example 1 and Comparative Example 1 as shown in Table 2, and a dust test was conducted under the same conditions. I did this. For reference, a dust test was also conducted on a filter element that was manually pleated without forming any fused recesses. These results are shown in Table 2.
From this result, it was recognized that the superiority of the present invention did not change even if the number of threads was changed, and that Comparative Example 7, which was a manually folded filter element, was also far inferior to the Examples of the present invention.

【table】 [Brief explanation of drawings]

FIG. 1 is a perspective view of a filter element formed using a material according to an embodiment of the present invention, FIGS. 2 and 3 are sectional views of a material formed by pleating by a conventional method, and FIG. A perspective view of an embodiment of the material of the present invention, and FIGS. 5a, b, c, and d are partial schematic plan views of the material showing the patterns of the fused portions in the material of the present invention, respectively. 1... Material, 2... Valley part, 3... Mountain part, 4...
Dirty side space, 5... Clean side space, 6... Fusion processed part, 7... Non-fused processed part,
A... Fusion recess, B... Fusion recess.

Claims (1)

[Claims] 1. On the front side of a fiber density gradient type nonwoven fabric in which the fiber density gradually increases from the front side to the back side, 1.5 to 1.5 of the thickness of the nonwoven fabric in a direction perpendicular to the length direction of the nonwoven fabric.
Welding recess A having a width of 3.0 times and welding recess B having a width of at least 0.3 times the thickness of the nonwoven fabric.
A material made of sheets formed alternately at regular intervals and made foldable by folding the fused parts A and B.