JPH0779933B2 - Air filter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION A. Purpose of the invention Industrial field of application The present invention relates to air cleaners for automobiles, air filters for air conditioning, back filters for electric vacuum cleaners, and other air cleaners. It's about filters.

Conventional technology and its problems Conventionally, air filters have a density gradient from the air inflow side to the air outflow side from coarse to dense 2-3
Layered fibrous structures are mainly used.

In this density gradient type air filter, the dense layer is an important layer in order to improve the filtration accuracy and the filtration efficiency, and the constituent fibers of this dense layer are thinned to a relatively thick layer, or the resin impregnation amount. The fiber gap is made finer by increasing the amount.

As a result, the overall thickness of the filter becomes unnecessarily large and the ventilation resistance increases, which are unavoidable drawbacks.

Various proposals have been made in order to solve this drawback, that is, to reduce the thickness of the dense layer as much as possible and to reduce the ventilation resistance, but a satisfactory product has not yet been developed.

For example, although it has been attempted to use a filter paper or a spunbonded non-woven fabric as the dense layer, it cannot be said that it is sufficient in terms of its filtration efficiency and the amount of retained dust, and it is regenerated by removing dust. Therefore, there are problems such as low property.

The present invention has been made to solve this problem,
It is intended to provide an air filter having high filtration efficiency, low airflow resistance, and excellent dust retention and reproducibility.

(B) Structure of the Invention The structure of the present invention is a fiber structure sheet comprising at least two layers so as to have a density gradient from a coarse layer to a dense layer, and the dense layer has a fiber areal weight of 20 to 100 g / m ² . Wet non-woven fabric composed mainly of non-crimped synthetic fibers having a fiber diameter of 2 to 15 μm and used in combination with an adhesive fiber or an adhesive resin, and having an apparent density of 0.3 g / cm ³ or less. The air filter is characterized in that the rough layer is composed of fibers having a fiber diameter of 10 to 50 μm and is composed of a dry nonwoven fabric having a fiber basis weight of 20 to 200 g / m ² .

Means for solving the problem A wet non-woven fabric mainly composed of crimp-free synthetic fibers such as polyester fibers having a fiber diameter of 20 μ or less,
Fiber weight is 20-100g / m ² and overall apparent density is 0.3g / cm ³
By using the following as a dense layer and using a dry non-woven fabric as a rough layer, we have found that an air filter with low ventilation resistance, high filtration efficiency and high dust retention, and excellent recyclability can be obtained. is there.

The wet non-woven fabric in the present invention is obtained by paper-making a slurry in which short fibers are uniformly dispersed in water and drying, and if the weight and thickness are appropriately selected, one fiber
Since the books are uniformly dispersed, the structure is very uniform, which is extremely effective in terms of filtration accuracy and filtration efficiency.

The present invention uses a wet non-woven fabric capable of obtaining such a uniform structure in a dense layer of an air filter.

As the synthetic fiber used in the dense layer of the present invention, for example, synthetic fiber such as polyester, polyamide, aromatic polyamide and polypropylene can be used, and these may be used alone or in combination of two or more kinds. Is.

This synthetic fiber is required not to be crimped, and if crimped, it is difficult to be dense and non-uniform, so that the object of the present invention cannot be achieved.

The thickness of this synthetic fiber has a fiber diameter of 20 μ or less, and if the fiber diameter exceeds 20 μ, the fiber gap will be too large even with a uniform distribution, so the dense surface of the filter will be filtered. This is not preferable because it lowers the efficiency. In the present invention, the thickness in this range may be appropriately selected depending on the purpose and application, but it is more preferably 2 to 15 μm. For example, for an automobile (engine) air cleaner, the fiber diameter is 5 to 5 μm. A value of 10μ gives good results.

The synthetic fiber may have any length as long as it can be formed by a wet method, and usually has a length of 3 to 20 mm, preferably 5 to 10 mm.

If necessary, other fibers such as rayon and pulp may be appropriately mixed in the wet non-woven fabric mainly composed of this synthetic fiber, so that the total fiber constitutional weight is 20 to 100 g / m ^2. It forms a layer.

If the fiber basis weight of this dense layer is less than 20 g / m ² , the fiber gap becomes large and the filtration efficiency decreases, while if it exceeds 100 g / m ² , the pressure loss becomes large, which is not preferable as an air filter.

The thickness of the dense layer depends on the basis weight and is selected from the above range according to the purpose and application, but a fiber basis weight of 30 to 50 g / m ² is suitable for automobile air cleaners. ing.

It should be noted that when the fabric weight increases, the air permeability naturally decreases, and for example,
When the air permeability of 60 g / m ² is measured with a pressure difference of 12.7 mmAq, it becomes 76 cc / cm ² / sec, and with the unit weight of 80 g / m ² , the air permeability also decreases to 61 cc / cm ² / sec. .

For the inter-fiber bonding of the dense layer in the present invention, the adhering fibers are used together during the wet papermaking, the adhesive resin is impregnated after the papermaking, or the resin is internally added during the papermaking.

When this adhesive fiber is blended, it is desirable to use the same thickness and length as the main synthetic fiber in order to achieve the object of the present invention.

When an adhesive resin is used in combination, the amount of this resin used is preferably in the range of 5 to 100 g / m ² in terms of solid content, particularly 8 to 20 g.
/ m ² is suitable.

The apparent density of the wet type nonwoven fabric configured as described above is
It needs to be 0.3 g / cm ³ or less.

If the apparent density exceeds 0.3 g / cm ³ , the density will be too high and the ventilation resistance will be large, and the object of the present invention will not be achieved.

The adjustment of the apparent density is performed by adjusting the heating and pressurizing after the wet papermaking.

Of course, if the apparent density of this dense layer is too low, the effect as a filter is reduced, and therefore, the appropriate apparent density of this dense layer is 0.07 to 0.2 g / cm ³ place, The apparent density of 0.3 g / cm ³ or less in the present invention means that the apparent density should not exceed the limited range although it is a dense layer as a dense layer in an air filter.

The air filter of the present invention is one in which a dense layer formed under such conditions is integrated with a rough layer. The means for integrating with the rough layer is a needle punch method, a discontinuous adhesion method by impregnating resin or fiber adhesion. Various methods such as a point adhesion method using a thermoplastic resin powder or an adhesive fiber in the rough layer can be cited, and it may be appropriately selected depending on the purpose and application.

As the rough layer, 1 to 2 layers are preferable, and even in the case of 1 layer, for example, 20 to 20 made of synthetic fiber having a thickness of 10 to 50 μ
It is desirable that the fiber layer of 0 g / m ² is formed by various known methods so as to have an appropriate density gradient while finishing the dry type nonwoven fabric as in the examples.

Action The present invention is configured as described above, and is mainly composed of a synthetic fiber having a uniform thickness without crimping, and a wet non-woven fabric formed by a wet method as a dense layer, and the amount of impregnated resin is comparative. Since it is configured to be relatively small, the fiber gaps in this dense layer are made fine and uniform, and the thickness is formed relatively thin.
Further, since the apparent density of this dense layer is 0.3 g / cm ³ or less, the ventilation resistance becomes small.

These actions work synergistically, and the synergistic effect of the rough layer of dry non-woven fabric is also added, improving filtration accuracy and filtration efficiency, increasing dust retention, reducing pressure loss (ventilation resistance), and excellent dust removal. Therefore, various remarkable effects such as excellent reproducibility are achieved.

Example 1 As a rough layer, a nonwoven fabric was prepared by entwining two webs of an outer layer and an intermediate layer as described below by needle punching, that is, a dry method.

Outer layer Polyester fiber (6d) 50% Polyester fiber (3d) 30% Polyester adhesive fiber (4d) 20% Middle layer Polyester fiber (3d) 20% Polyester fiber (1d) 30% Polyester adhesive fiber (4d) 50% The next dense layer was laminated on the surface of the intermediate layer side, and an appropriate amount of heat and pressure was applied between the heat rolls to join and integrate them.

Dense layer thickness 0.5d (fiber diameter 7μ), length 10mm polyester fiber is used to make a sheet with a basis weight of 40g / m ² by wet process, and adhesive resin (acrylic resin) Of 10 g / m ² (solid content) to give a wet non-woven fabric with a thickness of 0.4 mm and an apparent density of 0.1 g / cm ³ .

The rough layer and the dense layer are integrated, and 15 g / m ² of resin is impregnated to replenish the bonding of all layers and to add hardness (rigidity), and the thickness is 2.3 mm and the weight is 215 g / m. ^Two inventive air filters were obtained.

In addition, the following was created as a conventional air filter.

Rough layer Outer layer Polyester fiber (3d) 100% 50g / m ² Middle layer Polyester fiber (3d) 50% 25g / m ² Rayon fiber (1.5d) 50% 25g / m ² Dense layer Rayon fiber (1.5d) 100% 50 g / m ² This web composed of a total of 150 g / m ^{2 of} fibers was entangled with a needle punch to impregnate the resin with 100 g / m ² to obtain a conventional filter having a thickness of 3.5 mm and a weight of 250 g / m ² .

The following two types of filters were subjected to the following dust load test and air spray reproducibility test.

Dust load test According to JIS D-1612 (air cleaner test method), a flat plate test with an effective filtration area of 530 cm ² Type and amount of dust JIS 8 class 1 g / m ³ Wind speed 40 cm / sec Increase ventilation resistance 300 mm Aq until life.
(1 life) Air spray reproducibility test (Resilience by dust removal) Every time the dust resistance test increases the ventilation resistance by 300 mmAq, the height of 50 mm from the filter surface to 5 kg / cm ² from the nozzle of 1 mm in diameter. Pressurized air was blown twice alternately on the dense surface side → the rough surface side → the dense surface side → the rough surface side until the dust was not scattered. The dust load test was performed again on the sample after the dust was removed.

The reproducibility was evaluated from the deterioration of filtration performance due to this repetition.

The results of the dust load test and the reproducibility test are shown in Tables 1 to 4.

However, p in the table is initial ventilation resistance (mmAq), η is 2g / 100cm
² shows the initial filtration efficiency (%) under load, ηF is the average filtration efficiency (%) up to full life (at the time when the ventilation resistance increased by 300 mmAq), and DHC is the dust retention amount (g / 100 cm ² ). There is.

From the above table, the filter of the present invention has a filtration efficiency as high as that of the conventional thick filter,
The ventilation resistance, that is, the pressure loss, is considerably smaller than that of the conventional filter, and the excellentness of this pressure loss is very small with regeneration, and in this respect, it has a great difference from the conventional filter. In addition, the dust retention is equivalent to the thick conventional filter at the first time, and the retention amount is small even if the regeneration is repeated, and it is recognized that the conventional filter greatly reduces each time it is regenerated. .

Example 2 As a rough layer, a two-layer structure of a web made of 100% polyester fiber (3d) and a web made of 100% polyester fiber (2d) was used, and the two layers were partially fused (6% in area ratio).
Was adhered) to prepare a dry non-woven fabric having a basis weight of 30 g / m ² .

The same wet non-woven fabric as in Example 1 was used as a dense layer on this rough layer, and both were bonded with thermoplastic powder to obtain a filter of the present invention having a thickness of 0.83 mm and a weight of 130 g / m ² .

On the other hand, as a conventional filter, a filter paper type commercial air cleaner made of cotton linter pulp and an adhesive having a thickness of 0.82 mm and a weight of 174 g / m ² was prepared.

The same dust load test as in Example 1 was carried out on the above-mentioned two types of filters at a wind speed of 20 cm / min while regenerating similarly.

The results are shown in Tables 5 to 7.

The symbols and units in the table are the same as in Example 1.

From these tables, the filter of the present invention has the same thickness as the commercially available filter paper type air cleaner and has a small weight, but it has excellent filtration efficiency, and has a small pressure loss and dust. The holding amount is increasing.

Further, regarding the reproducibility, the filter of the present invention hardly has an increase in pressure loss and a slight decrease in the amount of dust retained, and it is recognized that the filter of the present invention has an excellent reproducibility.

C. Effect of the Invention The present invention is as described above. By using a dry non-woven fabric as a rough layer and a wet non-woven fabric having a uniform fiber gap as a dense layer, the thickness and the amount of resin impregnation are increased. It is an air filter that has excellent filtration accuracy and filtration efficiency without increasing the ventilation resistance, and thus it is also advantageous in terms of cost. It has various remarkable effects such as being extremely excellent, and exhibits extremely excellent usefulness as an air cleaner for automobiles, an air filter for air conditioning, and various other air cleaning filters.

Claims (1)

[Claims] 1. A fibrous structure sheet comprising at least two layers so as to have a density gradient from a coarse layer to a dense layer,
The dense layer is composed mainly of non-crimped synthetic fibers having a fiber basis weight of 20 to 100 g / m ² and a fiber diameter of ² to 15 μm, and is composed of an adhesive fiber or an adhesive resin in combination, and an apparent density of 0.3 g.
characterized in that it is composed of a wet non-woven fabric formed so as to be less than / cm ³ , and the coarse layer is composed of fibers having a fiber diameter of 10 to 50μ, and is composed of a dry non-woven fabric with a fiber basis weight of 20 to 200 g / m ^2. Air filter.