JPH08170B2 - Air filter material - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an air filter material, and more particularly to an air filter material suitable for an air cleaner for an internal combustion engine and an air filter for various air conditioners.

[Prior Art and Problems] Conventionally, in an air filter material, a filter including a fiber sheet in which fibers are bonded with an adhesive resin has been widely used. As a means for applying this adhesive resin,
A means for applying a solution-like material to the fiber sheet by spraying and a means for impregnating the fiber sheet are usually adopted, but in the former case, if the fiber sheet is thick, the adhesive resin does not enter the inside, and peeling easily occurs. Therefore, there is a problem in strength, and the latter is excellent in strength because the resin is spread all over, but the thickness of the sheet tends to decrease due to impregnation, the density of the sheet increases and the ventilation resistance increases, and the dust of the filter material becomes large. There is a drawback that the holding capacity becomes small and the life becomes short.

Further, conventionally, in order to enhance the cleaning effect, a density gradient type filter material (Japanese Patent Laid-Open No. 53-67176) in which the density of the inflow side of the air flow is made rough and the outflow side is made dense is known. In the filter material of (3), since the adhesive resin is apt to be unevenly distributed in the dense layer, there is a drawback that the dense layer is easily clogged and the life is easily shortened.

[Object of the Invention] The present invention has been made to solve the above-mentioned drawbacks of the prior art, and has the strength and over-efficiency required for an air filter material, a large dust holding capacity, and a long service life. The purpose is to provide wood.

[Structure of the Invention] The present invention provides an air filter material having a fiber layer in which fibers are bonded by an adhesive resin, in which expandable intumescent spheres are arranged in the adhesive resin, and an overwind speed of 0.1
The present invention relates to an air filter material having an initial pressure loss of 100 mmAq or less at ~ 5 m / sec.

That is, the present invention is made by arranging the expansive small spheres in the resin for bonding the fibers, thereby making the apparent total volume of the air filter material larger than the volume increase due to the expansion of the expansive small spheres. It increases the apparent volume of the air filter material, increases the dust holding capacity, and extends the service life without increasing the fiber amount, and thus substantially increasing the air flow resistance. It was done.

The adhesive resin used in the present invention includes polyacrylate,
Suitable are styrene-butadiene copolymer, nitrile-butadiene copolymer, polyurethane, ethylene-vinyl acetate copolymer, polyvinyl acetate, polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, polyester and copolymers containing them. . These adhesive resins are impregnated into the fiber layer as a solution such as an emulsion and dried to bond the fibers. At this time, the resin solution tends to collect at the intersections of the fibers, but this is preferable because it gives strength to the filter material without increasing ventilation resistance as much as possible. In particular, when a surfactant or the like is added to the solution and the resin solution is impregnated in a foamed state, this tendency is promoted. In addition, a crosslinking agent, a flame retardant, a filler, and the like may be added to the resin solution, if necessary.

The fibers used in the present invention are not particularly limited, and synthetic fibers such as polyester fibers, polyamide fibers, polyacrylonitrile fibers, polyvinyl chloride fibers, polyolefin fibers, rayon, and recycled cupra. Fiber, semi-synthetic fiber such as acetate fiber, natural fiber such as cotton, hemp, silk, or glass fiber,
All fibers such as mineral fibers, inorganic fibers such as metal fibers can be used. These fibers are accumulated by a known web forming method such as a dry method or a wet method to form a fiber layer.

The expandable small spheres referred to in the present invention are hollow spheres made of a thermoplastic resin and containing an expanding agent inside. Polystyrene, polyvinyl chloride, polyvinylidene chloride and copolymers thereof are suitable for this thermoplastic resin, and chemical or physical expanding agents such as azodicarbonamide, isobutane and freon are suitable for the expanding agent. Used. In particular, the one using vinylidene chloride-acrylonitrile copolymer as the thermoplastic resin and isobutane as the expanding agent is preferable from the viewpoints of stability and expansion degree of spheres. In addition, the expandable spherules have a diameter of 3 to 20 μm in the unexpanded state.
After expansion, the thickness is preferably 10 to 200 μm.

Although the expansive small spheres may burst under some expansion conditions, even in such a case, voids due to the expansion of the expansive small spheres remain in the adhesive resin, and the expansive small spheres are substantially expanded. Since it has the same effect that a sphere exists,
In the present invention, a thing in which the expansive small spheres are ruptured is also included in the expanded expansive small spheres referred to here.

The expandable spherules are added to the adhesive resin solution and impregnated in the fiber layer to adhere to the fibers together with the adhesive resin. At this time, since the expandable small spheres have a very fine diameter, they easily follow the behavior of the adhesive resin and easily gather together with the adhesive resin near the intersection of the fibers. In this case, if the volume of a sphere such as a glass balloon does not change and the diameter is large from the beginning, steric hindrance occurs and the sphere can enter only at a location away from the fiber intersection. Next, in the drying step for removing the solvent of the adhesive resin solution, or in the case where the adhesive resin is of a type that crosslinks and hardens, in the heating step for crosslinking and hardening, expansion of the expansive small spheres is carried out. As a result, the apparent volume of the air filter material increases and the thickness increases. It is considered that this is because the fibers are pushed apart by the expansion of the expandable small spheres existing near the fiber intersection. When the expandable small spheres are expanded, the adhesive resin is presumed to be in a state capable of being deformed with the expansion of the expandable small spheres, so that the bond between the fibers is almost maintained and the air filter material is kept. The required strength is obtained.

The air filter material having a fiber layer obtained in this manner maintains a bulky state without being crushed in thickness despite impregnating the adhesive resin, and has a very high dust holding capacity. However, if the amount of expandable spherules contained is too large, expanded swelling spherules will be present in many places other than near the intersection of the fibers, and the voids between the fibers will be blocked. This is offset by the increase in the apparent volume and the increase in the number of voids, which increases the ventilation resistance and reduces the dust holding capacity. Therefore, it is desirable that the amount of expandable spherules contained in the fiber layer is 10% by weight or less, especially 5% by weight or less. On the other hand, in order to obtain the effect of the present invention by using the expandable small spheres, it is desirable that the fiber layer contains the expandable small spheres in an amount of at least 0.5% by weight or more.

The initial pressure loss of the air filter material obtained as described above needs to be 100 mmAq or less at an overwind speed of 0.1 to 5 m / sec, and if the initial pressure loss is higher than this, it is not suitable for the air filter material. Especially desirable initial pressure drop of air filter material is less than 50mmAq.

The above-mentioned fiber layer may be a single layer or a plurality of layers of two or more layers, and a fiber layer containing no expandable microspheres or a fiber material such as woven fabric, knitted fabric, felt or mesh. It may be laminated with a material, a metal mesh, a perforated film, or the like. When laminating a plurality of fiber layers, it is more desirable to arrange a low-density layer on the inflow side of the air flow containing dust and a high-density layer on the outflow side to have a density gradient. In the case of such an arrangement, in the conventional case, since the resin is concentrated in the high-density layer, the density becomes excessively high and clogging is likely to occur, but in the present invention, due to the presence of the expanded inflatable small spheres. Since the voids are secured, it is possible to obtain a filter having a proper density, high dust collection efficiency, and a long life.

Hereinafter, the air filter material of the present invention will be described more specifically by way of examples, but the present invention is not limited to these examples.

Example 1 A 100 g / m ² fiber web layer composed of 60% polyester short fibers of 14 denier and 40% polyester short fibers of 1.5 denier was added to an adhesive resin having the composition shown in Table A below and expandable spherules (isobutane). An aqueous dispersion (150 g / l) containing polyvinylidene chloride-acrylonitrile copolymer microspheres encapsulating the above was stirred and bubbled with a mixer to impregnate. Then, this fiber layer is dried by a hot air dryer at a temperature of 135 ° C., cured and expanded to expand expansive small spheres, and the basis weight is 130 g / m ² and the thickness is 51 mm.
An air filter material having a thickness of 20 g / cm ² under pressure was obtained.

The obtained filter material was measured for performance as a filter according to the AFI gravimetric method, and was found to be suitable for an air conditioning filter. The measurement results are shown in Table 1.

Table A Acrylic ester 12 parts Methylol melamine 2 parts Catalyst 0.01 parts Alkylbenzene sulfonate 0.8 parts Expandable spheres 2.8 parts Water 82.39 parts (Test conditions of AFI gravimetric method) Test wind speed: 2.5m / sec Effective excess area: 0.225m ² Test dust: AFI test dust Dust concentration: 22.3mg / m ³ Full life designated pressure loss: + 20mmAq [Example 2] 1.5 denier A unit weight of 80 g / m consisting of polyester short fibers
² g of a fiber web layer and a fiber web layer of 100 g / m ^{2 having} a basis weight of 3 denier polyester short fibers were laminated, and 200 g / l of the dispersion shown in Table A as in Example 1 was mixed with a mixer. Stir foam to impregnate. Then, this fiber layer is dried, cured and expanded into small spherical spheres with a hot air dryer at a temperature of 140 ° C. to give a basis weight of 240 g / m ² , a thickness of 4.3 mm (20
An air filter material having a density gradient of (g / cm ^{2 when} pressed) was obtained.

The obtained air filter material was measured for performance as a filter according to JIS-D-1612, and as a result, it was suitable for an air cleaner for an internal combustion engine. The measurement results are shown in Table 2.

[Comparative Example 1] 10 g / m ² (adhesion amount of solid content) of the adhesive resin dispersion shown in Table B was added to a laminated fibrous web layer having the same fiber blend as in Example 2.
Is applied by spraying, dried and cured by a hot air dryer at a temperature of 140 ° C. Then, 200 g / l of the adhesive resin dispersion shown in Table C was stirred and foamed by a mixer to impregnate it, followed by drying and curing with a hot air dryer at a temperature of 140 ° C.
An air filter material having a basis weight of 240 g / m ² and a thickness of 2.8 mm (20 g / cm ² pressure) was obtained.

Table 2 shows the results of measuring the performance of the obtained air filter material as a filter according to JIS-D-1612.

Table B Acrylic ester 8 parts Methylolmelamine 1 part Catalyst 0.01 part Alkylbenzenesulfonate 0.6 parts Water 90.39 parts Table C Acrylic ester 12 parts Methylolmelamine 2 parts Catalyst 0.01 parts Alkylbenzenesulfonate 0.8 parts Water 85.19 parts (Test condition of JIS-D-1612 method) Test wind speed: 20 cm / sec Effective area: 530 cm ² Test dust: JIS type 8 test dust Dust concentration: 1 g / m ³ Full life specified pressure loss: +300 mmAq Note that the initial cleaning efficiency is Efficiency when adding dust 2g / 100cm ² .

As is clear from Table 2, since the filter material of Example 2 uses the expandable small spheres, the initial pressure loss is lower and the dust holding capacity is higher than that of Comparative Example 1. You can see that it has a long life.

[Example 3] 73 g / m ^{2 of} basis weight made of polyester long fibers, thickness 0.16 mm
On the spunbonded non-woven fabric, a fiber web layer of 2 denier polyester core-sheath type heat-sealing fiber having a basis weight of 50 g / m ² is further formed, and further a 6 denier polyester staple fiber having a basis weight of 40 g / m ² The fibrous web layers of 1 are laminated and passed through hot air and between the rolls, one of which is a heating roll, to integrate the three layers. Then, in the same manner as in Example 2, the dispersion liquid having the composition of Table A was impregnated and treated with a hot air dryer to give a basis weight.
An air filter material having a thickness of 230 g / m ² and a thickness of 3.6 mm was obtained.

The obtained air filter material was measured for performance as a filter according to JIS-D-1612 and in the same manner as in Example 2, and as a result, it was suitable for an air cleaner for an internal combustion engine.

The measurement results are shown in Table 3.

[Comparative Example 2] 10 g / m ² (adhesion amount of solid content) of the adhesive resin dispersion shown in Table B was applied by spraying to the laminated fiber layer in which the three layers of Example 3 were integrated, and dried with hot air at a temperature of 140 ° C. Dry and cure with a machine. Next, 200 g / l of the adhesive resin dispersion shown in Table C was stirred and foamed with a mixer to impregnate the mixture, and then the temperature was 140 ° C.
With a hot air dryer, the product is dried and cured, with a basis weight of 230 g / m ² ,
An air filter material having a thickness of 3.0 mm (thickness when pressurized at 20 g / cm ² ) was obtained.

The obtained air filter material was measured for performance as a filter according to JIS-D-1612 and in the same manner as in Example 2, and the results are shown in Table 3.

As is clear from Table 3, since the filter material of Example 3 uses the expandable small spheres, the initial pressure loss is lower and the dust holding capacity is higher than that of Comparative Example 2. You can see that it has a long life.

[Effects of the Invention] As described above, in the air filter material of the present invention, since the expansive small spheres are arranged in the resin that bonds the fibers, the volume of the expansive small spheres is not less than the volume obtained by the expansion. In addition, the apparent total volume of the air filter material increases, and the porosity inside the filter material increases. For this reason, even if a means for impregnating the adhesive resin to bond the fibers is used, the thickness is not easily crushed and clogging is not likely to occur, and a small amount of fibers and a large thickness can be configured.

Therefore, the air filter material of the present invention has the strength required for the filter, the high collection efficiency, the low pressure loss, the large dust holding capacity, and the long life.

Further, the air filter material of the present invention can be manufactured by a simple process of impregnating an adhesive resin solution containing expansive small spheres and drying without requiring a complicated process.

As described above, the air filter material of the present invention can be easily manufactured and has excellent performance, and therefore is extremely useful as a filter used in various air conditioning equipment or an air cleaner for an internal combustion engine.

Claims (5)

[Claims] 1. An air filter material having a fiber layer in which fibers are bonded by an adhesive resin, in which expandable inflatable spherules are arranged in the adhesive resin, and an overwind speed of 0.1
An air filter material characterized by having an initial pressure loss of 100 mmAq or less at ~ 5 m / sec. 2. The air filter material according to claim 1, wherein the expandable microspheres are contained in an amount of 0.5 to 10% by weight. 3. The air filter material according to claim 1 or 2, wherein two or more fiber layers are laminated. 4. The air filter material according to any one of claims 1 to 3, wherein the fiber layer is laminated with a fibrous material containing no expandable small spheres. 5. The air filter material according to any one of claims 1 to 4, wherein the air filter material has a density gradient.