JPS6211604B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a nonwoven filter. More specifically, the present invention relates to a high-performance filter with excellent cleaning efficiency and dust-holding properties. Conventionally, paper, non-woven fabrics, woven fabrics, etc. have been used as filter materials, but paper has poor dust-holding properties at high flow rates and is easily clogged, non-woven fabrics have poor cleaning efficiency, and woven fabrics have poor cleaning efficiency and dust-holding properties. The drawback was that both of its performance were poor. The present invention relates to a high-performance nonwoven filter that eliminates these drawbacks. That is, the present invention consists of a coarse layer with a pore volume of 75 to 98%, in which continuous filaments with a fineness of 5d or more are intertwined three-dimensionally by needle punching, and a continuous filament with a fineness of less than 5d is two-dimensionally entangled. A nonwoven fabric comprising at least two layers, a dense scale-like layer and a dense scale-like layer having 65 to 80% pore volume arranged in the same manner, and wherein the filaments of the scale-like layer are partially fused. It is related to filters. FIG. 1 shows a nonwoven fabric filter of the present invention. To explain the present invention with reference to FIG. 1, 1 is a dense scale-like layer in which continuous filaments are two-dimensionally arranged;
2 is a coarse layer in which continuous filaments are three-dimensionally entangled, and 3 is an adhesive layer. The continuous filament referred to in the present invention is a continuous fiber obtained by continuously drawing and opening a spun fiber using an ejector as shown in FIG. be. Furthermore, the term "scaly" refers to a scale-like laminated unit consisting of a fiber group in which the constituent fibers in the nonwoven sheet are not arranged in the thickness direction, but are arranged randomly only in the plane direction. The two-dimensional arrangement in the present invention refers to a structure in which the continuous filaments are arranged in a two-dimensional random manner only in the planar direction of a scale, which is one laminated unit, and there is no filament arrangement in the thickness direction. Furthermore, three-dimensional entanglement refers to continuous filaments having a random arrangement in the plane direction of the sheet and the thickness direction of the sheet by needle punching, and the continuous filaments having mutual entanglement. When the nonwoven fabric filter of the present invention is cut along the XYZ plane of FIG. 1, it is as shown in FIG. 2. Layer 1 has a structure in which scales in which continuous filaments 4 are two-dimensionally arranged are stacked at an angle α (<XYZ). This structural arrangement increases the packing density of the fibers,
Moreover, the pores are fine, and the pores are long and widen in the direction of the laminated surface of the scales. Therefore, the angle α is preferably 90 degrees, that is, slightly angled rather than completely parallel to the sheet plane, and from the viewpoint of filter performance, it is usually greater than 90 degrees and particularly preferably in the range of 110 degrees or less. In this way, in the present invention, since the dense layer 1 has a scaly shape, the minute dust that passes through the coarse layer 2 under high flow velocity does not directly blow through, but collides with the fibers of the coarse layer 1 and is collected. or collected by elongated stomata. As shown in FIGS. 1 and 2, layer 2 has a bulky, rough structure with a large pore volume in which continuous filaments 5 are three-dimensionally entangled. This coarse layer 2 blocks the inflowing dust,
Collects dust and improves its dust holding properties. Since the pore volume varies depending on the purpose, it is difficult to define it unconditionally, but 75 to 98% is usually suitable. Here, the pore volume is the volume ratio of pores in a material as defined by JIS-L1079. The adhesive layer 3 is preferably bonded using a method that reduces pressure loss as much as possible, such as thermal bonding using a low melting point resin powder, low melting point fiber, low melting point perforated film, rubber adhesive, resin, etc. that has good adhesion to the constituent fibers. Or it can be chemically glued. In particular, the intermittent bonding method is suitable because it can reduce the bonding area and reduce fluid pressure loss. It is also possible to use mechanical adhesion by entangling fibers. The dense layer 1 is produced by jetting the filament onto a moving conveyor and suctioning it as shown in FIG. That is, a filament 7 is spun from a spinneret 6, drawn by an ejector 8, opened and jetted onto a conveyor 9, and at the same time, a scaly web 11 is deposited while being sucked by a suction box 10. The stacking angle α of the scales can be adjusted as appropriate by the degree of spreading of the injected fibers on the conveyor 9, the amount of fibers to be injected, the speed of the injection, the speed of the conveyor, and the like. Next, thermal bonding or chemical bonding is performed to make the scale-like web layer dense and to bond the scales together. In the case of thermal bonding, a dense layer with low pressure loss can be obtained by using low-melting fibers or by self-bonding of the fibers. In the case of chemical adhesion, after applying pressure, impregnation, spraying, coating, etc. are performed with adhesive. In the case of thermal bonding, if the fibers are fused together using a heat embossing roll with unevenness, a dense layer with unevenness can be obtained. If the dense layer 1 and the coarse layer 2 are bonded together, as shown in FIG. 4, the area through which the fluid passes increases due to the unevenness, so that a filter with less pressure loss can be obtained. In addition, the dense layer 1 provides a filter with fewer pores. Further, in order to reduce the pore size of the dense layer 1, the fineness of the constituent fibers is preferably less than 5 d, and the pore volume is preferably smaller than that of the coarse layer 2, and is preferably 65 to 80%. Further, the usually coarse layer 2 is obtained by punching a continuous filament web using a needle punching machine and intertwining the web in three dimensions. In this case, it is more preferable to use fibers that are thicker, more rigid, or have crimps than those used in the dense layer 1. The fineness of the coarse layer 2 is 5d or more.
As the rigid fiber used for the coarse layer 2, fibers such as polyester and polyolefin are suitable. The three-dimensional entangled structure maintains stable performance even when folded and bent during use. Further, in order to further stabilize the three-dimensional entangled structure, the present invention may be achieved by adhering with a rubber adhesive or the like to an extent that does not increase pressure loss. Furthermore, in order to further improve the filter performance, a multilayer structure as shown in FIG. 5, for example, is suitable. That is, 2a is a coarse layer, 2b is a coarse layer, 1
3 is a dense scale-like layer, and 3a and 3b are adhesive layers.
The dust-holding property is high due to the thick layer of roughness.
Furthermore, since there is a coarse and dense structure within the coarse layer, the effect of blocking dust is large, and the combined effect with the dense layer of 1 provides an even higher cleaning effect. The fibers used are natural fibers, synthetic organic polymer fibers,
Either can be used. In particular, filters made of synthetic organic polymer filaments are characterized in that even if there are few fusion points or adhesion points, a dense layer 1 with a stable shape can be formed, and a bulky coarse layer 2 can also be easily formed. Note that the filter of the present invention may be used by impregnating it with a known rubbery substance or resin. As mentioned above, the filter of the present invention is an excellent filter that has high dust holding properties under high-speed fluid and high cleaning efficiency. Therefore, it can be used in a wide range of applications such as automobile filters, vacuum cleaner filters, air conditioning filters, oil filters, and industrial filters. Example 1 Fineness manufactured by the method shown in Figure 3 as layer 1
A web made of polyethylene terephthalate filament having a fabric weight of 150 g/m ² and having a fabric weight of 150 g/m 2 was bonded under pressure using a heat embossing roll with unevenness to form a sheet with a two-dimensional arrangement of uneven scales. As the second layer, a three-dimensional entangled sheet was used, which was made by processing a polyethylene terephthalate filament web with a fineness of 15 d and a basis weight of 100 g/m ² using a needle punching machine at a needle density of 120 needles/cm ² . The two sheets were bonded together by intermittent bonding using a hot embossing roll with a thin sheet made of low melting point fiber sandwiched between the two sheets. In the filter of the present invention having the above configuration, the thickness of the first layer is 0.46 mm, the pore volume is 76%, and the thickness of the second layer is 1.49 mm.
mm, and the pore volume was 95.2%. The performance of the filter was measured under conditions according to the measurement method of JIS B-9908, and the cleaning efficiency was 99.9.
% and dust holding property of 182 g/m ² . Comparative Example 1 A scale-like sheet made of polyethylene terephthalate with a fineness of 3d and a basis weight of 150 g/m ² was used as the first layer.
A needle-punched sheet made of polyethylene terephthalate with a fineness of 10 d and a basis weight of 150 g/m ² was used as the second layer, and both sheets were bonded together under pressure and heat using polyethylene powder. In the filter thus obtained, the first layer had a thickness of 0.25 mm and the pore volume was 62%, and the second layer had a thickness of 0.36 and a pore volume of 70%. When the filter performance was measured under the same conditions as in Example 1, the results were excellent compared to Example 1 with a cleaning efficiency of 99.6% and dust holding property of 65 g/m ² . Comparative Examples 2 to 6 Table 1 shows the results of measuring the filter performance under the same conditions as in Example 1 when the pore volume of each layer was varied.

【table】

[Table] As is clear from Table 1, Comparative Examples 3 and 4
Comparative Example 2 is satisfactory in terms of cleaning efficiency, but has poor dust holding property, while Comparative Example 5 has poor dust holding property. Although the cleaning efficiency was at a satisfactory level, the cleaning efficiency was extremely poor and none of them could be put to practical use. Examples 2 to 4 and Comparative Examples 7 to 9 This experiment was conducted using the nonwoven fabric filter of the present invention (Example 2
- 4), the nonwoven fabric filters (Comparative Examples 7, 8, and 9) according to Utility Model Application Publication No. 51-26569, which have a structure in which coarse layers and dense layers are intertwined three-dimensionally, have excessive precision (cleaning efficiency). This proves that it is significantly inferior in terms of evaluation of the maximum particle size passing through a filter, etc.). Examples 2 and 3 were manufactured according to the manufacturing method of Example 1, and Example 4 was manufactured according to the manufacturing method of Example 1, except that the layer 1 and the layer 2b were bonded by thermal bonding. Furthermore, each filter used a polyethylene terephthalate filament. Table 1 shows each filter configuration and evaluation results. In addition, in Table 1, overaccuracy is measured by the following method. Overaccuracy evaluation method: Using the evaluation apparatus shown above, 2g of glass beads were introduced from the top, and a collection test was conducted on each filter sample under the condition of an overflow speed of 20 m/min.
The glass beads that have passed through are completely collected by an absolute filter.

[Table] Glass bead weight Glass bead weight
〓100
Furthermore, the maximum particle diameter passing through the filter is the average value of the top five particles with the largest diameter among the glass beads that passed through the sample and were collected by the absolute filter. Initial pressure loss and final pressure loss indicate the pressure loss before and after glass beads were added to each sample. The glass beads used had a Min of 5μ, a Max of 120μ, a volume average particle diameter of 62μ, and a number average particle diameter of 39μ.

[Table] As is clear from the overperformance test results using glass beads shown in Table 1, the product according to Utility Model Application No. 51-26569 (in Comparative Examples 7 to 9, both the coarse layer and the dense layer had a three-dimensional structure) ) are significantly inferior to those according to the present invention (in Examples 2 to 4, the coarse layer has a three-dimensional structure and the dense layer has a two-dimensional structure and scale-like structure) in terms of cleaning efficiency and evaluation of the maximum particle size passing through the filter. . The reason for this is thought to be that in Comparative Examples 7 to 9, the dense layer has a three-dimensional structure, so there are many pinholes that facilitate the passage of dust. In particular, sheets with a three-dimensional structure created by needle punching have many pinholes in the sheet due to fiber convergence caused by the punching needles, so even large glass beads can pass through. . This can be measured using the evaluation item, the maximum particle diameter that passes through the filter. Moreover, such a structure naturally reduces the cleaning efficiency of the supplied glass beads. On the other hand, in the present invention, since the coarse layer has a three-dimensional structure and has a large fineness, most of the glass beads can be collected in this layer. Furthermore, since the layer is rough, the increase in pressure loss can be minimized even if glass beads are deposited. Next, glass beads having a relatively small particle size that could not be collected in the coarse layer are collected in the two-dimensional structure of the dense layer. This two-dimensional structure has fibers arranged two-dimensionally and in the form of scales, and there are no pinholes or fiber bundles, so it has small uniform voids that can collect even the smallest glass beads. I can do it.

[Brief explanation of the drawing]

Figures 1 and 2 show the filter of the present invention. Figure 3 shows a two-dimensional arrangement of filters in the filter of the present invention.
3 is a schematic diagram showing the manufacturing process of the layer of FIG. 4 and 5 are drawings showing embodiments of the filter of the present invention. 1: Two-dimensionally arranged scale-like dense layer, 2,2
a, 2b: Rough layer of three-dimensional entanglement, 3, 3a, 3
b: adhesive layer, 4, 5: continuous filament, 6: spinneret, 7: filament, 8: ejector,
9: conveyor, 10: suction box, 11: scaly web.

Claims (1)

[Claims] 1 A coarse layer with a pore volume of 75 to 98%, in which continuous filaments with a fineness of 5d or more are entangled three-dimensionally by needle punching, and pores in which continuous filaments with a fineness of less than 5d are arranged two-dimensionally. 1. A nonwoven fabric filter having a volume of 65 to 80% and comprising at least two layers, a dense layer having a scale shape, and wherein the filaments of the scale layer are partially fused.