JP3014439B2 - Filter media - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a filter medium, and more particularly to a filter medium for an oil filter or an air filter of an internal combustion engine such as an engine.

[Prior art] Conventionally, filter media for filters include wood pulp, cotton, hemp,
There is a filter paper made from rayon or the like by a wet papermaking method, a filter paper impregnated with a resin to increase strength and workability, and a filter paper impregnated with oil to improve life performance.

However, since the filter paper type filters out most of the dust on the surface, the pressure loss of the filter medium itself is large and the life is short, so that it is necessary to increase the filtration area, and a large amount of filter medium is required. Oil-impregnated oils have a long life but low filtration performance and a large pressure loss, and therefore also require a large filtration area.

Further, although the fiber diameter is relatively large, relatively large particles are collected by filtration by inertia, but finer particles such as carbon dust leak from the filter medium greatly.

On the other hand, in recent years, a fiber obtained by laminating fiber layers in a density gradient type using synthetic fibers as a raw material and solidifying with a binder, and further impregnating with a resin have been newly used.

The density gradient filter medium is formed such that the filter medium density changes from coarse to dense from upstream to downstream. In these filter media, the density is controlled by increasing the diameter of the fiber forming the layer, increasing the number of thick fibers upstream, and increasing the number of thin fibers downstream (for example, Japanese Patent Publication No. 54-40778,
JP-A-57-59614, JP-B-2-45484), those in which the distribution of the binder in the powder is controlled and the density is controlled (for example, JP-A-57-75117), only the density and basis weight are measured. Specified (for example, JP-A-62-279817)
Are disclosed. In the examples of JP-A-52-112859, the average pore size of each layer is described, but the upstream pore size is very large. Conventionally, no finding has been found that controlling the pore diameter of the layers on the upstream and downstream sides of the filter medium within a specific range improves the filter medium performance.

In any of the above filter media, large-sized particles are captured in the low-density layer on the upstream side, and fine particles are captured in the high-density layer, so that the life can be improved.

However, these filter media can hardly perform surface filtration,
There is a drawback that clogging easily occurs inside the filter medium and pressure loss increases. In addition, since the filtration on the surface of the filter medium is hardly performed, there is a limit in improving the life.

In addition, because of the density gradient, relatively small particles are collected by filtration by diffusion, but the filter medium has a large pore size to reduce pressure loss, and the collection efficiency of relatively large particles is not always satisfactory. It is not what you go for.

In addition, the filter media using synthetic fibers has the advantage of reducing the density of constituent fibers in the high-density layer and increasing the resin impregnation to a relatively thick layer in order to enhance the dust collection performance. Although the thickness of the layer is increased, the thickness of the entire filter medium becomes unnecessarily large, causing a problem that the pressure loss increases and the processing is hindered.

[Problems to be Solved by the Invention] The present invention is to solve the above-mentioned conventional problems, and an object of the present invention is to provide a filter medium having a high filtration efficiency, a small pressure loss, and a long life.

[Means for Solving the Problems] The present inventors have conducted intensive research to solve the above problems. As a result, at least two layers or more are used, and specific fine fibers are used in a layer arranged downstream from the dust inflow side, and the pore diameters of the upstream layer and the downstream layer are within a predetermined range. Thus, the present inventors have found that a filter medium having high collection efficiency, low pressure loss, and long life can be obtained, and the present invention has been completed.

That is, the present invention provides an organic synthetic fiber having a structure in which at least two layers or more, and a layer disposed downstream of a layer disposed upstream which is a side where a fluid containing dust flows into the filter medium has a fiber diameter of 1 μm or less. The maximum pore diameter of the layer disposed upstream is 120 to 250 μm, the average pore diameter is 40 to 90 μm, and the maximum pore diameter of the layer containing organic synthetic fibers having a fiber diameter of 1 μm or less is
The present invention relates to a filter medium having a diameter of 10 to 50 μm and an average pore diameter of 5 to 20 μm.

 Hereinafter, the present invention will be described in detail.

The filter medium of the present invention has a structure of at least two layers,
Each has a specific pore size, and contains a specific organic synthetic fine fiber in a downstream layer.

By specifying the upstream pore diameter, the filtration is collected without being concentrated on the surface or inside the filter medium, so that the life of the filter medium is increased.

In addition, by specifying the downstream hole diameter, the collection efficiency can be improved.

For measurement of pore size, see ASTM F-316 (American Socie
ety for Testing and Metirials), BS 6410 and 332
The method described in No. 1 (British Standard) was used in which the pressure applied to a filter medium filled with voids (holes) was increased and the manner in which the liquid was discharged from the holes during the process was monitored. These are common methods by which the maximum and average pore sizes of membranes and filters can be measured.

The layer arranged on the upstream side preferably has a maximum diameter of 120 to 250 μm and an average pore diameter of 40 to 90 μm.

When the maximum pore diameter on the upstream side exceeds 250 μm or when the average pore diameter exceeds 90 μm, since filtration on the surface of the filter medium is difficult to be performed, dust is trapped in the deep layer inside the filter medium, and the pressure loss of the filter medium rapidly increases, The life of the filter media is shortened.

When the maximum pore size on the upstream side is smaller than 120 μm or when the average pore size is smaller than 40 μm, the pressure loss of the filter medium increases, which is not preferable.

Further, downstream of this layer, organic synthetic fibers having a fiber diameter of 1 μm or less are contained, the maximum pore diameter is 10 to 50 μm, and the average pore diameter is 5 μm.
Arrange layers with 2020 μm.

When the maximum pore size on the downstream side exceeds 50 μm or when the average pore size is
If it exceeds 20 μm, the collection efficiency of the filter medium becomes small, which is not preferable.

When the maximum pore diameter on the downstream side is smaller than 10 μm, and when the average pore diameter is smaller than 5 μm, the pressure loss of the filter medium increases, which is not preferable.

The filter material layer has a sheet-like structure, and the material is not particularly limited, but a material using a fibrous material is preferable. Examples of the sheet forming method include a dry method, a spun bond method, a melt blow method, and a wet papermaking method. However, it is difficult to produce a uniform sheet by the dry method, and the pore size distribution is not uniform, which is not preferable. In the spun bond method and the melt blow method, it is difficult to mix a plurality of fibers, for example, fibers having different fiber diameters and fiber lengths, fibers having different materials and shapes, and it is difficult to satisfy the physical properties of the filter medium of the present invention.

For this reason, it is preferable to use a wet papermaking method as the sheet forming method. The method for laminating the sheets is not particularly limited. Examples thereof include a method of laminating by a wet papermaking method, a method of heat-sealing wet-sheeted sheets, and a method of integrating with a needle or a high-pressure water flow.

Also, if necessary, within the range that does not hinder the performance of the filter medium,
Further, a sheet of a dry method or a sheet of a wet method can be further laminated on the sheet.

The layer disposed on the upstream side can be used by appropriately mixing organic fibers and inorganic fibers. For example, polyester fibers, polyolefin fibers, polyamide fibers, polyimide fibers, rayon fibers, polyacrylonitrile fibers, organic fibers such as polyvinyl alcohol fibers, ceramic fibers,
Carbon fiber, activated carbon fiber, glass fiber, rock wool fiber, sepiolite fiber and the like can be used. These may be used alone or in combination of two or more. However, when used in an internal combustion engine, glass fibers are not preferred.

The binder is preferably a fibrous organic fiber, and more preferably has a core-sheath structure, is made of a heat-meltable resin, and has a sheath whose melting point is lower than the core by 40 ° C. or more. The heat-meltable resin is preferably a polyester-based or polyolefin-based resin. The compounding amount of the fibrous binder is preferably in the range of 5 to 40% by weight based on the weight of the entire fiber.

The fiber diameter of the fiber that can satisfy the physical properties of the above-mentioned filter medium is 1 to 10 denier, preferably 1 to 6 denier. It is preferable that the fiber having this diameter is contained in 50% by weight or more of the fiber weight.
Use of a fiber finer than 1 denier in a range exceeding 50% by weight is not preferable because the pore size becomes small and the pressure loss increases. If it is larger than 10 denier, the pore size becomes large and dust enters the inside of the filter medium, causing a pressure loss. And the life of the filter medium is shortened.

The layer disposed downstream of this layer contains organic synthetic fibers having a fiber diameter of 1 μm or less as essential components.

Organic synthetic fibers having a fiber diameter of 1 μm or less have excellent dust collecting performance. As organic synthetic fibers, conventionally used flexible ones are not preferable because the pressure loss of the filter is high, which is not preferable. Therefore, the organic synthetic fibers are preferably as rigid as possible. Fiber is effective. The rigid linear polymer is a polymer having a chain length of 50 angstroms or more that maintains linearity in a solution, and examples thereof include poly (P-phenylene terephthalamide), poly (P-benzamide), and poly (P-benzamide). −
Examples include phenylene benzobisthiazole), poly (P-phenylene benzobisoxazole), poly (amide hydrazide), polyhydrazide, and poly (P-phenylene terephthalamide-3,4-diphenyl ether terephthalamide).

As an example of a method for obtaining a fiber having a fiber diameter of 1 μm or less, Japanese Patent Laid-Open Publication No.
Microfibrillated ones using the method disclosed in Japanese Patent Publication No. 0801 are mentioned. This method differs from the treatment by a refiner or the like used in a general papermaking process, in which a fiber or a pulp-like material is microfibrillated using a homogenizing device. That is, a fiber slurry obtained from a rigid linear polymer dispersed in water is passed through an orifice having a pressure difference of 200 kgf / cm ² or more at the front and back thereof at a high speed, and immediately decelerated to form slurry particles. When a shearing force is applied, the fibers become microfibrils vertically divided in the direction of the fiber axis. This is obtained by repeating this step. Specific examples include microfibrillated fibers of poly (P-phenylene terephthalamide) (MFC-400, manufactured by Daicel Chemical Industries, Ltd.).

The organic synthetic fiber used in the present invention has a fine fiber diameter of 1 μm or less, which cannot be obtained by a commonly used method of grinding or shearing a fiber. In addition, it is well entangled with other fibers, can easily form a uniform slurry with other fibers, can be easily transferred to the next step, and can be efficiently manufactured by ordinary papermaking equipment.

The amount of the organic synthetic fiber having a fiber diameter of 1 μm or less is 0.01 to 10% by weight with respect to the fiber weight of the layer containing the fiber.
When the layer contains a fiber having a diameter of 2 denier or more and having a crimped or irregular cross section, the amount of the organic synthetic fiber having a fiber diameter of 1 μm or less is in a range of 25% by weight or less based on the fiber. If so, this is not the case.

If the amount of the organic synthetic fiber having a fiber diameter of 1 μm or less is less than 0.1% by weight, good collection efficiency cannot be obtained. If the content is more than 10% by weight, the collection efficiency increases, but the pore size of the filter medium becomes small, and the pressure loss increases, which is not preferable.

In addition, as the fiber contained in the downstream layer, the same material as that of the upstream side can be used as a material. The same binder fiber can be used.

The filter medium thus produced can be further impregnated with a resin for the purpose of increasing strength and improving workability. The resin to be used may be any resin that can be cured by heat, an electron beam or ultraviolet light and plasticized. General resins such as phenol-based, acrylic-based, vinyl acetate-based, styrene-based, and polyester-based resins can be widely used. There is no particular limitation on the impregnation step.

Moreover, it is also possible to perform a water-repellent or oil-repellent process as needed.

[Function] The filter medium of the present invention is a high-performance filter medium achieved by using a layer having a specific pore diameter in the upstream and downstream layers and using specific fine fibers downstream.
In particular, it works effectively as a filter for an internal combustion engine.

[Examples] Hereinafter, the present invention will be described specifically with reference to Examples.
The present invention is not limited to this embodiment.

In the examples, all parts and percentages are by weight.

Example 1 80% PET fiber (A) (2 denier × 5 mm, manufactured by Teijin Limited) and 2% PET binder fiber (a) (2 denier × 5 mm, Melty 4080 core / sheath type, manufactured by Unitika Ltd.) were used as the upstream side.
0% was uniformly dispersed in water to prepare a slurry.

79.5% of PET fiber (B) (0.1 denier x 5 mm, manufactured by Teijin Limited) as the downstream side, 20 parts of PET binder fiber (a),
0.5% or less of organic synthetic fiber (MFC400, manufactured by Daicel) having a fiber diameter of 1 μm or less was uniformly dispersed in water together with a dispersant in water to prepare a slurry.

The upstream 70 g / m ^2, a downstream combined paper making a filter medium having a two-layer structure of 30 g / m ^2, dried at 120 ° C., subjected to heat treatment at 170 ° C., subjected to resin impregnation, after drying, at 0.99 ° C. Cure was performed. Further, the resultant was impregnated with a water repellent and dried to prepare a filter medium.

The resin is acrylic resin (Primal HA-16, manufactured by Nippon Acrylic Chemicals Co., Ltd.), 9% of the sheet weight, and the water repellent is fluorine-based (Sumireze FP210, manufactured by Sumitomo Chemical Co., Ltd.)
It was adjusted to be 0.2% based on the sheet weight.

Example 2 The basis weight on the upstream side was 80 g / m ² , the composition on the downstream side was 75% of PET fiber (B), 20% of PET binder fiber (a), and 5% of organic synthetic fiber having a fiber diameter of 1 μm or less. , Its basis weight is 20
A filter medium was produced in the same manner as in Example 1 except that the filtration material was changed to g / m ² .

Example 3 A filter medium was produced in the same manner as in Example 1, except that the basis weight on the upstream side was 120 g / m ² and the basis weight on the downstream side was 30 g / m ² .

Example 4 The basis weight on the upstream side was 93 g / m ² , the blending on the downstream side was 10% of PET fiber (B), 20% of PET binder fiber (a), 5% of organic synthetic fiber having a fiber diameter of 1 μm or less, 6 PET fibers (A)
A filter medium was prepared in the same manner as in Example 1 except that the weight was 5% and the basis weight was 80 g / m ² .

Comparative Example 1 The upstream fiber was blended with PET fiber (C) (6 denier × 10 m
m, manufactured by Teijin Limited) was 50%, PET fiber was 30%, PET binder fiber (a) was 20%, and a filter medium was produced in the same manner as in Example 1 except that the basis weight was 130 g / m ² .

Comparative Example 2 The blending of the downstream side was performed using PET fiber (C) (0.5 denier x 5 mm,
A filter medium was prepared in the same manner as in Example 1 except that the ratio was 40%, the PET fiber (B) was 40%, the PET binder fiber (a) was 20%, and the basis weight was 70 g / m ² . .

Comparative Examples 3 and 4 Commercially available elements were purchased and the filter media used were evaluated. Comparative Example 3 is obtained by integrating a resin-impregnated dry nonwoven fabric and a resin-impregnated dry nonwoven fabric by a needle punch method, and Comparative Example 4 is a filter paper type in which softwood pulp and cotton pulp are made and phenol resin is impregnated.

Table 1 shows the physical properties of the filter medium. The pore diameter used was the method described in ASTM F-316.

* In Comparative Example 3 is 300 μm or more.

* Comparative Example 4 has a single-layer structure.

 Tables 2, 3, and 4 show the performance of the filter media.

The pressure loss and collection efficiency in Table 2 were measured at a wind speed of 5.3 cm / sec according to JIS-B9908 format 1. In addition, the measurement of collection efficiency is DO
P aerosol (dioctyl phthalate, particle size 0.3 μm) was used.

The initial pressure loss and collection efficiency in Tables 3 and 4 are rated flow 5.0m
^The measurement was performed using ³ / min, a filtration area of 1256 cm ² , JIS Class 8 dust, and carbon dust in light oil exhaust gas. The dust retention when the pressure loss increased by 100 mmAq was measured.

In addition, fold the filter media at 5 cm intervals, fold it,
The number of folds of the filter medium when a box-shaped element of 0 × 15 × 5 cm is produced is described.

From Tables 1 to 4, it has a specific pore size upstream and downstream,
In addition, it can be seen that the filter medium comprising a layer containing organic synthetic fine fibers on the downstream side has a high collection efficiency for both DOP, JIS Class 8 dust and carbon dust, and has a long life. Further, since a large number of filter media can be folded into an element of a specific size, it is possible to reduce the pressure loss of the element itself and extend its life.

[Effects of the Invention] The filter medium of the present invention has low pressure loss, high collection efficiency,
It is a long-life filter medium. It is effective as a filter, especially an air filter and an oil filter of an internal combustion engine.

Claims (1)

(57) [Claims] An organic synthetic fiber having a structure having at least two layers and having a fiber diameter of 1 μm or less, wherein a layer disposed downstream of an upstream layer on which a fluid containing dust flows into a filter medium is provided. And the maximum pore size of the layer arranged upstream is
120-250 μm, average pore size 40-90 μm, fiber diameter 1
The maximum pore size of the layer containing organic synthetic fibers of μm or less is 10 to
A filter medium having a size of 50 μm and an average pore size of 5 to 20 μm.