JPH06254321A - Air filter paper - Google Patents

Abstract

PURPOSE:To provide a novel density gradient type air filter paper having high dust capturing efficiency and long service life. CONSTITUTION:Fiber layers consisting of low-density layers and high-density layers are adhered by moisture curing type adhesives. The low-density layers are functioned as a prefilter and the closing of the gaps of the high-density layers is prevented, by which a sufficient filtration life is obtd. The dust past the low-density layers are captured by the high-density layers and the filter medium having high performance is obtd. Film formability is extremely little as compared with the conventional water-soluble or non-solvent type adhesives if the moisture curing type adhesives are used to integrate both layers having different functions and, therefore, the possibility of closing the inter-fiber gaps is drastically reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air filter filter paper, and more particularly to a density gradient type air filter filter paper having a high dust collection efficiency and a long service life.

[0002]

2. Description of the Related Art A conventional air filter paper is mainly made of glass fiber, and is made by adding a synthetic fiber binder or a liquid binder thereto. To enhance the dust collection effect of the air filter paper (hereinafter referred to as filter material),
In order to extend the life of the filter medium, a method has been proposed in which the filter medium has a density gradient composed of a coarse layer having a large fiber diameter and a dense layer having a small fiber diameter in the air flow direction (Japanese Patent Application Laid-Open No. Hei 4). -59007, JP-A-62-33514).

[0003]

If a conventional paper machine is used to make papers having different fiber diameters as in the above-mentioned prior art, they will not be mixed and will not have a density gradient. A special paper machine is required to hold it. In addition, it is possible to make two types of filter media, one with a low density layer and the other with a high density layer, using a general paper machine, and integrate them. In this case, the pressure of the integrated filter media is The loss is larger than the pressure loss of the simple sum of two types of filter media, one having a low density layer and the other having a high density layer. The reason is that, when the filter media are bonded to each other so as to be integrated, the adhesive blocks the inter-fiber voids, and the pressure loss increases more than that of the simple sum of the pressure losses of the filter media. . Further, since the adhesive fills the voids between the fibers, there is a drawback that the dust collecting performance of the obtained filter medium is deteriorated. Therefore, an object of the present invention is to provide a novel density gradient type air filter paper which has a high dust collection efficiency and a long service life.

[0004]

The above objects of the present invention can be achieved by the following constitutions. That is, an integrated air filter paper comprising a low-density fiber layer on the upstream side of the filtered air stream and a high-density fiber layer on the downstream side, wherein the low-density fiber layer and the high-density fiber layer are moisture-curable adhesives. It is an integrated air filter paper. As the fiber of the low density layer, it is desirable to use a fiber having a fiber diameter of 20 to 50 μ and formed into a sheet at ²⁰ to 30 g / m ² . The fiber diameter of the fiber of the low density layer is 20 to 50 μm and the amount of the fiber used is 20 to 30 g / m ^{2, which} are selected for the following reasons. B) Reason for fiber diameter of 20 to 50 μ In order to form a density gradient by combining with a high density fiber layer, a fiber having a fairly large fiber diameter is required.
If it is less than 0 μ, a remarkable density gradient cannot be obtained, and if it exceeds 50 μ, the filtration performance is deteriorated and there is no point in providing a low density layer (interstices between fibers become large and the dust directly reaches a high density without being filtered). (B) Reason for use amount of 20 to 30 g / m ^{2 Since} the low density layer functions as a prefilter, it is desirable that the thickness is thin. 20 to form a uniform paper layer
A fiber amount equivalent to -30 g / m ² is required.

Further, it is desirable that the fibers of the high density layer have a fiber diameter of 1 to 9 μ and are formed into a sheet at 40 to 70 g / m ² . The fiber diameter of the fibers of the high-density layer is 1 to 9 μm and the amount of the fibers used is 40 to 70 g / m ² are values selected for the following reasons. The high-density layer is a portion that functions as a so-called filter paper. In order to exert the function as a filter paper, it is necessary to form a paper layer having a fiber diameter of 1 to 9 μm and 40 to 70 g / m ² . If it is out of this range, it will be unsuitable as a filter paper. As the material of the fibers, inorganic fibers and organic fibers, for example, synthetic fibers such as glass fibers and polypropylene fibers can be used.

A feature of the present invention is that a moisture-curable adhesive is used to integrate both layers of the fiber. The amount of moisture-curable adhesive applied is 2 to 6 g / m.
It is preferably used in the range of ² . Adhesive coating amount 2g
If it is less than / m ² , there is no adhesive effect, and if it exceeds 6 g / m ² , the voids between the fibers will be blocked by the adhesive, and the filtration performance of the obtained filter medium will deteriorate. A synthetic polymer resin is used as a specific example of the moisture-curable adhesive, but a reactive urethane resin is preferable, and more specifically, a reactive urethane polymer, Esdyne # 9607 (trade name). ), Sekisui Chemical Co., Ltd., etc. are preferable.

[0007]

In order for the air filter paper to have both functions of effectively filtering the dust present in the air to be filtered and maintaining good performance for a long period of time, (1) low density By providing the fiber layer, this low-density fiber layer acts as a prefilter and prevents the voids of the high-density fiber layer from being blocked by dust. (2) The dust that has passed through the low-density fiber layer is captured by the high-density layer. It is necessary to satisfy the following performance. In order to integrate both layers having different functions, it is important to select the type of adhesive and the amount used, and the use of moisture-curing adhesives makes it easier than conventional water-soluble or water-insoluble adhesives. In comparison, since the film-forming property is extremely small, it is possible to significantly reduce the risk of blocking the inter-fiber voids.

Here, the film forming property of the adhesive refers to the speed at which the adhesive forms a film and the stability of the resulting film. For example, when an adhesive is applied to the fibers of FIG. 1, it is said that the film-forming property is low when the adhesive remains at the intersections of the fibers as shown in FIG. 1A, and as shown in FIG. It can be said that the film forming property is great when the adhesive forms a film. Moisture-curing adhesives can self-crosslink by absorbing moisture in the air. Therefore, an ordinary cross-linking agent gradually reacts as compared with a solution-type or non-solution-type adhesive that requires it, so that the initial adhesive force is weak.
That is, it can be said that the moisture-curable adhesive has a large fluidity at the time of being applied to the fiber, and thus has essentially a low film-forming property. The present invention is characterized in that the properties of this moisture-curable adhesive are used as an adhesive between fiber layers having different densities.

[0009]

EXAMPLE An example of the present invention will be described. Example 1 Polypropylene fiber nonwoven fabric having a fiber diameter of 40 μm was 20 g / m ² as a low density layer, and average fiber diameter was 3 μ as a high density layer.
72 g / m ² of wet glass fiber paper of m, and a moisture-curable urethane resin adhesive (Esdyne # 9607, Sekisui Chemical Co., Ltd.) was used for adhesion of both fiber layers at an application amount of 3 g / m ^2. A filter paper for filters was produced.

Comparative Example 1 95 g / m ² of wet glass fiber paper having an average fiber diameter of 3 μm
A filter paper consisting of was prepared. Comparative Example 2 A low-density fiber layer and a high-density fiber layer having the same materials and contents as in Example 1 were used as a water-soluble acrylic emulsion (Boncoat SFC-55 (trade name), Dainippon Ink and Chemicals, Inc.).
A filter paper for an air filter was produced by adhering an adhesive consisting of (manufactured by K.K.) at an application amount of 3 g / m ² .

Comparative Example 3 A low-density fiber layer and a high-density fiber layer made of the same material and content as in Example 1 were made of a two-component urethane (Hybon XB (trade name), manufactured by Hitachi Chemical Polymer Co., Ltd.). The adhesive was adhered at a coating amount of 3 g / m ² to prepare a filter paper for air filter. Table 1 shows the results of comparing the air filter papers of Example 1 and Comparative Examples 1 to 3 with the JIS 15-class dust test.
Shown in. The test method was based on JIS D-1612, the filter paper had a filtration area of 11.4 m ² , a dust input amount of 2 g / min, and the filter paper life was full time when the pressure loss reached 30 mm of water column. Further, the measurement of the average collection efficiency was carried out by the colorimetric method of JIS Class 11 dust.

[0012]

[Table 1]

Comparing the performance of this example and the comparative example, in the case of this example, the service life of the air filter paper is long,
It is also found that when a non-woven fabric made of an organic polymer is used as the low-density fiber layer material, it acts as a reinforcing material and has high tensile strength and tear strength.

[0014]

According to the present invention, an air filter paper having a long service life can be obtained.

[Brief description of drawings]

FIG. 1 is a diagram illustrating a film forming property of an adhesive.

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Claims (2)

[Claims] 1. An integrated air filter paper comprising a low density fiber layer on the upstream side of the filtered air stream and a high density fiber layer on the downstream side, wherein the low density fiber layer and the high density fiber layer are moisture-curable. An air filter paper that is integrated with an adhesive. 2. The low-density fiber layer has a fiber diameter of 20 to 50 μm.
Glass fiber of 20 to 30 g / m ² is used as a sheet, and a glass fiber having a fiber diameter of 1 to 9 μ is sheeted at an amount of 40 to 70 g / m ^{2 in} the high-density fiber layer. ^2. The air filter paper according to claim 1, wherein the glass fiber layers are integrated in a moisture-curable adhesive in an amount of 2 to 6 g / m ² applied.