WO2005063359A1 - Filter material for air filter and filter unit - Google Patents

Abstract

A filter material for an air filter, characterized in that it is a laminar structure which comprises a nonwoven fabric sheet being electrostatically treated and having a fiber density of 0.06 to 0.19 g/cm3 and a QF value of at least 0.1 Pa-1 and an aggregate sheet being composed of a fibrous material having a water content of 6 % or less and exhibiting a bending resistance at 65°C of at least 150 mg; and a filter unit comprising the filter material. The filter material exhibits a low pressure loss and excellent capturing efficiency, and also excellent heat resistance.

Description

 Description Air filter media and filter unit Technical field

 TECHNICAL FIELD The present invention relates to an air filter medium and a filter unit which can be suitably used for an on-vehicle or home air filter, particularly an on-vehicle air filter. Background art

 Since air filters for vehicles mounted on automobiles must collect relatively large dust, pollen, tobacco smoke, etc., they have conventionally been used as filter media such as short-fiber nonwoven fabric sheets or electret melt blown. Non-woven fabric sheets are often used (Japanese Patent Laid-Open No. 4-161209 (Table 1), etc.). However, the collection efficiency of the short-fiber nonwoven sheet filter material is low in spite of its high airflow resistance. Electretized melt-pro nonwoven sheet filter media have lower pressure loss and higher collection efficiency than short-fiber nonwoven sheet filter media, but their collection efficiency is still not sufficient.

 On the other hand, in-vehicle air filters can collect relatively large dust, pollen, tobacco smoke, etc., as well as obtain high air volume, low pressure loss, high collection efficiency, and the amount of dust retained by the filter media. High, the amount of filter media is small (filter volume is small), even in a car that has been left in the scorching sun and becomes hot, the pressure loss increases due to the deformation of the filter media, the filter media comes off from the frame, It is particularly required that no odor is generated. In addition, the cabin filter unit for automobiles is used regardless of weather conditions such as fog, rainy weather, snowy roads, etc., and water droplets and snow easily adhere to the filter unit.

 If water adheres to the filter unit, the filter medium absorbs water and swells, causing a change in size and a decrease in rigidity, and a rise in pressure loss due to the fact that the deformed filter medium does not return to its original state even when it dries. was there. '

Japanese Unexamined Patent Publication No. 2002-12020 ゃ Japanese Unexamined Patent Publication No. 2002-182 A filter medium in which an electret nonwoven sheet having a QF value of 0.5 Pa- ¹ is joined to an aggregate sheet using fiber fibers, polyvinyl alcohol fibers, rayon modified cross-section fibers, or the like is disclosed. When these filter media are exposed to a high humidity atmosphere or exposed to water, polyvinyl alcohol fibers and rayon shaped cross-section fibers expand, making it impossible to assemble a filter unit with the specified dimensional accuracy, or assembling the assembled filter unit. There were problems such as an increase in pressure loss. Furthermore, when used as a cabin filter unit, it is heated in a water-absorbing state, especially when it is parked under scorching sun after running in rainy weather in summer. If air is passed through the filter unit in this state, the rigidity of the filter material will decrease due to the effects of moisture and resin heating. I knew there was a problem going up.

 Furthermore, in the electret melt-blown nonwoven fabric sheet by the conventional corona discharge method, the nonwoven fabric sheet is charged into a discharge electric field formed between a grounded electrode and a corona discharge electrode provided in a space above the grounded electrode, and charges are injected. Therefore, as shown schematically in Fig. 1, one and + charges are formed at the top and bottom of the cross section of the fiber (the front and back sides of the nonwoven fabric sheet), and there is little charge at the middle position of the fiber cross section. State. In the non-woven fabric sheet, which is a collection of fibers having such a charged structure, no electric charge is applied (small) between the fibers as shown in the figure, and the relatively small particles are in a portion where the electric charge is weak. However, the relatively large particles passing between the fibers were trapped but had a structure that made it difficult for them to be trapped and their trapping performance deteriorated (see Fig. 1).

The tendency of the collection performance to decrease due to the electrostatic adsorption operation becomes more remarkable as the filtration wind speed is higher and the particle size is larger and heavier. For this reason, the filter unit, which is intended to reliably collect fine particles such as diesel smoke of about 0.3 to large particles of about 50 m such as pollen and dust, has been converted to an electret by the conventional corona discharge method. In order to make a melt-pro-woven nonwoven sheet, it was necessary to take measures such as making the fibers thinner to reduce the space distance between the fibers and increasing the basis weight to improve the collection performance. Then, the pressure drop becomes too high, and it has never been possible to make a filter unit with a low pressure drop and a high collection of -11 13 15 type 0 value 0.03 Pa- ¹ or more.

On the other hand, after the film is electretized, it is split into nonwoven sheets. A filter medium mainly using the electretized film split fiber is widely used in one unit of the cabin filter. Also in this case, the charge is reduced in the middle part of the film thickness. Since film split fibers are cut into fibers by cutting the film with a machine, there is a limit to thinning the fibers.Therefore, the filter medium mainly using these fibers is bulky, and the space between the fibers is very large. The collection efficiency is not sufficient because it is as large as 0 to 30 O ^ m or more. Furthermore, if dust adheres to the electret film split fiber having such a structure, the collection performance is particularly severely reduced, and fine particles to large particles, particularly large particles such as pollen, easily pass through. Therefore, it was impossible to increase the collection efficiency of JIS type 15 powders, which ranged from fine dust to large particles, similar to general atmospheric dust. Japanese Patent Application Laid-Open Publication No. Hei 9-1501604 discloses a “hydrocharging method” in which water is sprayed onto a nonwoven sheet to provide an electretized filter medium. Water is sprayed vigorously onto the nonwoven sheet, and the water that hits the fibers flows through the nonwoven sheet until the jetting energy is lost, thereby exfoliating the air on the fiber surface, promoting contact between water and the fibers, and performing charging. This method is an excellent method that can obtain a higher band S property than the corona discharge method. However, in the case of a non-woven fabric sheet with a small fiber basis weight and a large fiber diameter, water injected from nozzles arranged at a constant pitch penetrates the non-woven fabric sheet and escapes without remaining in the non-woven fabric sheet. Therefore, it is difficult for water to diffuse in the horizontal direction of the thickness of the nonwoven fabric sheet. For this reason, uneven charging tends to occur, and this method is not suitable for a cabin filter for a vehicle that filters at a high wind speed.

The performance of the filter unit manufactured by these conventional techniques is shown. In the case of a filter unit using a melt-blown non-woven sheet made of a corona discharge method electret, the JIS 15 type QF value is 0.01. 7 Pa- ¹ (pressure loss 210 Pa, JIS 1 5 class collection efficiency 97%, 0.3 Atm particle collection efficiency 11%), filter using electretized film split fiber filter media The unit has a JIS 15 class QF value of 0.025 Pa- ¹ (pressure loss 90 Pa, JIS 15 class 5 collection efficiency 89%, 0.3 μm particle collection efficiency 25) Met.

Each filter unit has a low collection efficiency of 0.3 m particles, and a filter that uses a melt-blown nonwoven sheet made of electret melted corona. The unit has the problem of high JIS 15 type collection efficiency but high pressure loss, and the filter unit using the electretized film split embroidery filter material has low pressure loss but JIS 15 type collection. There was a problem of low efficiency. DISCLOSURE OF THE INVENTION '' In view of the above-mentioned circumstances, the object of the present invention is to provide a low pressure loss and excellent collection efficiency, and to be suitable for a large air volume filter unit used under high wind speed conditions. It can reliably collect fine particles and particles larger than 50 / m, such as pollen and dust, and is also subject to the attachment of water droplets, high humidity and high temperature, etc. To provide an air filter medium with excellent moisture resistance, heat resistance and dimensional stability that can be used even in the use environment of, and to provide a filter unit with low pressure drop and high collection made of such an air filter medium To do that.

The present invention for achieving the above object, the fiber density ^{0. 0 6~0. 1 9 gZcm 3} , the electret non-woven fabric sheet QF value of at least 0. ¹ P a- 1, moisture content of 6% or less An air filter medium characterized by having a layered structure with an aggregate sheet having a stiffness at 65 ° C of at least 150 mg made of the above fiber material.

 Here, the QF value is obtained by the following equation. '

 Q F value = -1 n (T) / ε-where Τ represents the degree of penetration of 0.3 m atmospheric dust particles under a penetrating wind speed of 6.5 m and calculated by the following equation. ,

 T = 1 C

 In the above equation, C represents the degree of collection of particles, and the particle concentration C i (pieces m 1) on the upstream side of the filter medium and the particle concentration C on the downstream side under a penetrating wind speed of 6.5 mZ From 0 (pieces / m 1), the equation

 C = 1— (C o / C i)

Ask by. ε is the pressure loss (P a), which is obtained under the penetration wind speed of 6.5 mZ. The pressure difference between the upstream side and the downstream side of the filter medium is measured by a manometer. The rigidity is determined by the Gurley method specified in JISL 1085 “Test method for nonwoven fabric fabric”.

 In the above, the electretized nonwoven fabric sheet is, for example, an electret meltblown nonwoven fabric sheet.

 The aggregate sheet is made of a fibrous material with a moisture content of 6% or less, such as polyester, vinylon, polypropylene, and glass fiber, so that the filter medium does not change its dimensions due to moisture or water absorption. Similarly, there is a synthetic fiber nonwoven sheet net or the like in which fibers are bonded with a resin having a low water content and a glass transition point of at least 50 ° C. The aggregate sheet may be constituted by a sheet containing electretized film split fibers. Here, the electret film split fiber preferably has a fiber length in the range of 30 to 100 mm. The aggregate sheet may be constituted by a sheet including a net-like net in addition to the electret film split fiber. ''

 The air filter medium described above can be used as it is, or with a deodorant disposed downstream on the air flow direction. Also, the frame can be joined to form a filter unit. In this case, the joining of the pure bodies is preferably made of a hot melt resin having a softening point of at least 120 ° C.

 The air filter / filter medium / filtration unit of the present invention can be used in a home air cleaner, but is particularly suitable as an in-vehicle air filter.

 According to the air filter medium of the present invention described above, the pressure loss is low, the trapping efficiency is excellent, and the dimensional stability against heat resistance, moisture, and water adsorption is also excellent. A suitable air filter medium and filter unit can be obtained. Brief Description of Drawings

 FIG. 1 is a schematic diagram showing a dust collecting mechanism of an air filter-filter medium electretized by a conventional corona discharge method.

Fig. 2 shows the air filters electretized by the `` Hide port charging method ''. It is the schematic diagram showing the dust collection mechanism of the Luther filter medium.

 FIG. 3 is a schematic cross-sectional view showing one embodiment of an air filter medium according to the present invention.

 FIG. 4 is a perspective view showing an embodiment of a filter unit according to the present invention. Explanation of symbols

 1: Electretized nonwoven sheet layer

 2: Electretized fiber

 3: Dust

 4: Electrostatic adsorption

 5: Aggregate sheet layer

 6: Aggregate fiber

 7: Filter unit Best mode for carrying out the invention

The air filter medium according to the present invention has an electret nonwoven sheet having a fiber density of 0.06 to 0.19 gZcm ³ and a QF value of at least 0.1 Pa- ¹ and a water content of 6%. It is formed by laminating aggregate sheets each having a stiffness at 65 ° C. of at least 150 mg made of the following fiber materials.

The electrified nonwoven sheet is made of a polyester fiber having a fiber diameter of about 2 to 50 im, or a synthetic fiber such as a polypropylene fiber, a polycarbonate fiber, or a polylactic acid fiber. The basis weight is about 5 to 60 g / m ² . The electret nonwoven fabric sheet mainly but responsible for collecting dust contained in the air one, request QF value 0. l P a one ¹ less stuff than is described above as a vehicle, i.e. The requirements of low pressure loss, high collection efficiency under high air flow conditions, high retention of dust by filter media, and low filter media volume (small filter volume) cannot be met. . Such an electretized nonwoven fabric sheet having a QF value of at least 0.1 P a- ¹ can be obtained, for example, as an electret melted nonwoven fabric sheet as follows. That is, polymers such as polyester, polypropylene, polycarbonate, and polylactic acid are dry-spun at a temperature slightly lower than usual so that the single yarns do not join together, and collected while cooling so that they do not join together. Get a sheet. Although this non-woven fabric sheet was made so that the single yarns did not join with each other, there were some joints, so the non-woven fabric sheet could be further stretched, or high-pressure liquid could be sprayed or sucked. Or give a peeling force to the fiber, and separate the bonded parts. As a result, a nonwoven fabric sheet having a very small number of joined portions between the single yarns and a large bulk and a large total surface area of the single yarns can be obtained. This is subjected to electret processing using a hydrocharging method or the like to obtain an electret melt-blown nonwoven sheet. In the case where a high-pressure liquid is used to apply a peeling force to the fiber, it is advantageous to use pure water as the liquid, because it is possible to perform electret processing together with the peeling.

 The electret melt-blown nonwoven fabric sheet thus obtained has a low bulk and pressure loss due to its bulkiness, and also has an increased charge amount due to an increase in the total surface area of the single yarn, resulting in a high QF value.

Erekutoretsu preparative non-woven fabric sheet Ichito is preferably be such that strength at 3% elongation is within ^{1 X 1 0 5 ~ 3 5} X 1 0. 5 in range H. It is less than 1 X 1 0 ⁵ strength ones, easy fuzz due to the low entanglement of the single yarns to each other. On the other hand, those exceeding 35 × 10 ⁵ have a high fiber density and tend to increase pressure loss.

 The aggregate sheet collects relatively large dust and is joined to the electretized nonwoven fabric sheet so as to obtain the required rigidity as a filter medium. To do so, the bristles at 65 must be at least 15 Omg. The reason for setting the temperature at 65 ° C is to take into account the operating environment such as the interior of a car left under the scorching sun.

Examples of such an aggregate sheet include a non-woven sheet made of polyester fiber, polypropylene fiber, vinylon fiber, glass fiber, etc., an acrylic resin having a glass transition point of at least 50 ° C and low odor, and styrene. A non-woven fabric sheet formed by bonding fibers between fibers with a resin such as an acrylic resin or a mixed resin of an acryl resin and an epoxy resin can be used. The basis weight is 20 to: about 150 g Zm ² . Also use polypropylene or polyester resin nets, lattices, or honeycombs. be able to. Polypropylene resin and polyester resin have a high glass transition point, and nets, lattices and 82 cams have extremely low airflow resistance, so that a filter medium with excellent heat resistance and low pressure loss can be obtained.

 Moisture-curable urethane resin, ethylene vinyl acetate resin, ethylene vinyl chloride resin, polyamide copolymer resin, polyolefin resin, ultrasonic bonding, hot emboss bonding, etc. are used for joining the aggregate sheet and the electret nonwoven sheet. Can be used. Above all, it is preferable to use a moisture-curable urethane resin which is insoluble by reacting with the moisture in the air in a spider web shape in order to improve adhesiveness, heat resistance and air permeability.

Further, as the aggregate sheet, a sheet containing electretized film split fibers may be used. Electretized film split fiber is obtained by cutting the fiber length to a length within the range of 30 to 10 Omm, and then opening and carding in an atmosphere with a relative humidity of 50% or more. Can be. In addition, if the sheet containing the electretized film split fiber alone cannot provide the stiffness, it is preferable to install a mesh net or the like, but if the stiffness can be obtained, the net is limited to the net. Not something. If the basis weight of the electret film split fiber layer is too low, the dust retention amount cannot be expected. Further, if it is too high, the pressure loss increases, so that it is preferably in the range of 5 to 100 g Zm ² . More preferably, in the range of 1 0~ 5 0 g Zm ^2. The mesh net may be made of any of synthetic fibers, inorganic fibers, and metal fibers. The fineness is preferably 10 to 150 decitex, and the opening is preferably 9 mm ² or more. ,

The air filter medium of the present invention can be used as it is as a filter medium.However, when used, a deodorant is disposed on the surface that is on the downstream side in the air flow direction so that the filter medium has a further enhanced deodorizing function. it can. As the deodorant, activated carbon particles having a particle diameter of about 0.1 to 1 mm are suitable. Such activated carbon particles can be used by being sandwiched between nonwoven fabric sheets, supported on a net or an 82 cam, or supported on a foamed resin or foamed rubber. At this time, if a non-woven fabric sheet is stuck to at least the outer surface at the time of use, falling off of the activated carbon particles can be more completely prevented. Activated carbon impregnated with acids or alkalis, for example, amine dianiline The use of particles makes it possible to more effectively adsorb and remove acetoaldehyde, ammonia and the like contained in tobacco smoke.

 The above-mentioned air filter medium is usually joined to a body made of aluminum, plastic, non-woven cloth, paper, wood, foam, or the like to form a filter unit. It is preferable to use a hot melt resin for this bonding. Among them, polyethylene resins and polyamide resins having a high softening point of at least 120 ° C. and excellent heat resistance are preferred.

The filter unit using the air filter medium of the present invention can be suitably used as a cabin filter unit for automobiles. The required characteristics of an automotive cabin filter L-nit include the amount of dust that can be used without replacement during the period from the periodic inspection required for automobiles to the next periodic inspection, and diesel smoke centered on 0.1 um. From 5 to 100 / zm coarse particles such as pollen and dust, and low pressure loss. It is preferable that the filter unit has a filter unit of at least 0.33 Pa- ¹ if expressed as> 1 1 31 5 types 9 F value. This QF value can be achieved by setting the collection efficiency of JIS 1 class 5 powder including fine dust to coarse particles to 95% or more, and the collection efficiency of fine dust 0.3 im to 40% or more. Further, these performances are preferably realized with a filter unit pressure loss of 100 Pa or less in order to reduce noise in the vehicle interior.

 In order to achieve this, the electretized nonwoven fabric sheet used in the present invention may be a melt-blown nonwoven fabric or a spunbonded nonwoven fabric to which about 10 or OOO ppm of an antistatic agent, such as hinderedamine or triazine, is added. Is preferred.

The electret nonwoven fabric sheet used in the present invention is an electret-processed nonwoven fabric sheet by a pure water suction method disclosed in JP-A-2003-73971, and has a fiber density of 0.06- 0. 1 9 gZ cm ³ or less, preferably at 0. 0 6~0. 1 5 g / cm 3 range, is characterized by QF value uses those 1 P a- ¹ or 0.. At this time, the place where the hindered amine content is rich is charged to +, and the amount of hindered amine is small or close to 0, or the fiber part with the electron trapping body is charged to-and the schematic diagram shown in Fig. 2 As shown in the above, a positive charging zone or a single charging zone is formed at random on the entire surface of the fiber in contact with water. In particular, the characteristic of the electretized nonwoven fabric sheet obtained by the suction method is that the pure water is vigorously sucked into the nonwoven fabric through the nonwoven fabric that passes while contacting the upper part of the slit-shaped pure water suction port, and the air on the fiber surface is released. Separation and contact between pure water and fibers to conduct charging, water flows vigorously from the inflow side to the outflow side in the gap between the fibers, and the wide slit-shaped suction port keeps the entire width of the nonwoven fabric even. It is possible to perform electrification processing. Moreover, the suction method has a feature that the contact charging efficiency is increased and a higher charge is obtained between the fibers as compared with the water jetting technique described in the prior art which merely wets the fiber surface. The reason why a higher charge is obtained between the fibers is that water flows easily where the fiber openings are large. In addition, such a portion may cause the air to flow at a high speed, which may deteriorate the trapping performance. It is believed that the air adhering to the surface of the fiber is reliably peeled off to increase the contact charging efficiency with pure water, and that the rapid flow of water increases the friction band power, resulting in a high charge density due to a synergistic effect. ,

For this reason, even a non-woven fabric having a large opening between fibers and a low pressure loss can obtain a high collection efficiency with a small collection efficiency. In particular, as shown in Fig. 2, a high charged surface is generated between the fibers and the fibers, and the fine particles trying to pass through the space and the particles larger than 10 such as pollen and dust are reliably collected. However, it was possible to realize characteristics of 0.1 Pa- ¹ or more.

Further electret nonwoven fabric sheet for use in the present invention, the fiber density of 0. 0 6 ~ 0. 1 9 g Z cm 3 or less, preferably 0. 0 6~ 0. 1 5 g Z cm 3 because the ranges Suitable for collecting large or heavy particles. In particular, it is important to collect pollen with a particle size of 20 to 50 m for use in cabin filters. Small particles can be collected by electrostatic charging (electrostatic adsorption), but large particles are heavy, so it is difficult to obtain a sufficient collection effect only by electrostatic charging (electrostatic adsorption). Although this is disadvantageous in terms of pressure loss, it increases the fiber density and maximizes the mechanical trapping effect, while utilizing the two effects of electrostatic adsorption and the JIS 15 class 5 collection efficiency at the filter unit. A filter unit with a QF value of 0.3 Pa ¹ or more was obtained. JIS 15 class dust is artificial powder composed of 25% of fine dust JIS class 12 (carbon black), 72% of medium dust JIS class 8 (diatomaceous earth), and 3% of coarse particles of cotton phosphorus. It is a powder used in the evaluation method of air filter units for ventilation (JISB 9908; Model 3) as dust for life evaluation. Subsequent evaluations were made in accordance with Type 3 of this standard. .

 The JIS 15 class QF of the filter unit can be obtained by flowing air with the rated air volume through the test filter unit according to the evaluation method for ventilation air filter TU (JISB9908; model 3). Dust loading is carried out to the final pressure loss of 147 Pa by dispersing the body. The collection efficiency of JIS15 at this time? ? And the initial pressure loss (ε) of the filter unit.

 J I S 1 5 types QF value = — 1 n (D) / ε

 Here, D represents the degree of permeation of JIS 1 class 5 particles under the rated airflow, and is calculated by the following formula.

 D = 1-77

 In the above equation, 7? Represents the degree of collection of particles.From the total amount of dust D i (g) under the rated air flow and the amount of adhesion D o (g) to the filter unit, Expression,

 D = 1-(D o / D i)

Ask by. ε is the pressure loss (Pa), which is determined by measuring the pressure difference between the upstream and downstream sides of the filter media under the rated air flow before dust loading with a manometer.

Next will be described an example using the nonwoven aggregate sheet as filter media arrangement for achieving JIS 1 5 or QF value 0. 0 3 P a ¹ or more filters Interview knit performance.

The air filter media has a layered structure in which an aggregate sheet and an electret nonwoven sheet are laminated, but when an attempt is made to increase the dust holding capacity, an electret nonwoven sheet is used. Increasing the storage capacity tends to cause problems such as clogging. Therefore, it is preferable to adjust the holding capacity at the aggregate sheet portion. For example, if the dust holding capacity of the entire E Afiruta one filter medium was 34 gZm ^3, to retain its 7 0-9 0% 2 3. 8 ~ 3 0 .. 6 g / m 3 in the aggregate sheet portion Is preferred. In that case, the dust holding capacity of the electretized nonwoven fabric sheet is the remaining 3.4 ~ It is necessary to 1 0. 2 g / m ^3.

 In order to obtain JIS 1 5 class collection efficiency of 95% or more, the collection efficiency is initially lower than 95% when dust is not loaded, and the collection efficiency becomes 95% or more due to clogging of filter media. At this time, the rise in pressure loss and the increase in collection efficiency occur at the electretized nonwoven sheet layer rather than at the aggregate sheet layer, and therefore, depending on the initial collection efficiency of the electret layer and the degree of fiber opening. Dust holding capacity is greatly affected.

As described above, the electretized nonwoven fabric sheet must have a QF value of 0.1 lPa- ^{1 or more.} (Pressure loss of 7 Pa or less under the condition that the air flow through the filter medium is 6.5 m / min. 3 / im particle collection efficiency of about 50% or more). In order to obtain 3. 4- 1 0. 2 gZm ³ as a dust holding capacity required in order to be able to use two to three years period until the next periodic inspection of periodic inspection, fiber diameter 5 8 m, weight 15 to 30 gZm ³ are suitable.

That is, the following pressure drop 7 P a, 0. 3 collection efficiency 50% or more, JIS 1 5撑捕current efficiency 95% or more, the same E the four items of the dust storage capacitor 3. 4~ 1 0. 2 gZm ³ It must be achieved with a lectretized nonwoven sheet.

、 繊維密度 0. 0 6~0. 1 9 g/ c m³ 、 目付 5〜 1 2 0 g Zm³の狭い範囲に 限定された。 なお、.より好ましくは平均繊維径が 5. 0 ~ 7. 、 繊維密度QF value of electret nonwoven fabric sheet obtained is made to 0. ¹ P a- 1 by the choice of fiber diameter and basis weight for the relationship of the pressure loss and the collection efficiency can be made variously, dust holding capacity and It is extremely difficult to produce JIS 15 collection materials with the same collection efficiency. As a result of various studies, the average fiber diameter was 5.0 to 50

The fiber density was limited to a narrow range of 0.06 to 0.19 g / cm ³ and a basis weight of 5 to 120 g Zm ³ . The average fiber diameter is more preferably 5.0 to 7, and the fiber density is more preferable.

0. 1 0-0. 14 gZcm ^3, were those having a basis weight of 1 6~ 2 5 gZm ^3.

By subjecting the nonwoven fabric in this range to suction-type hydrocharge electret processing, the pressure loss is 7 Pa or less, the 0.3 um particle collection efficiency is 50% or more, and the QF value is 0.1 Pa- ^1. The above electreted nonwoven fabric sheet was obtained. The optimal amount of the dust holding ratio on the side of the electrified nonwoven fabric sheet is preferably within the range of 5 to 20% of the entire dust holding capacity in view of the life and the requirement of achieving JIS 15 type 5 collection efficiency.

Next, the means for achieving the dimensional stability of the air filter medium will be described. The dimensional change occurs due to water absorption of the fiber material constituting the aggregate sheet and the resin fixing the fibers. For this reason, it is recommended that the air filter medium be made of a material that absorbs as little water as possible. Moisture content of fiber (at 20 ° C 65% RH, moisture content of test method JISL 101 (filament) or JISL 101 (staple)) 6% or less, preferably 5% or less In addition, in order to prevent a decrease in rigidity due to a temperature rise, preferably, a nonwoven fabric aggregate sheet bonded between fibers using a resin having a Tg of 50 ° C or more is used to reduce the dimensional change of the air filter medium to 3% or less. Optimally, it can be less than 1%. Specifically, the rigidity at 65 is increased to 15 Omg by bonding between fibers using acrylic or epoxy resin with a low moisture content such as polyester fiber, vinylon fiber, glass fiber, etc. and a glass transition point of 50 ° C or more. By doing as described above, an air filter medium and a filter unit having little change in dimensions and pressure loss due to moisture and moisture adsorption and no change in pressure loss due to temperature rise can be produced.

 The method of calculating the dimensional change rate of the air filter media is as follows: 50 cm in the length (MD) direction and 20 cm in the width (CD) direction from a filter medium conditioned for 8 hours or more in an atmosphere of 20 ° C 'and 65% RH. Collect one or more samples, and draw 45 cm and 15 cm lines at the center of the sample using a water-insoluble ink.

 This is immersed in water for 3 hours after being immersed in a horizontal state, taken out, and the length is measured using a gold scale in a wet state.From the relationship between the length L 0 before immersion in water and the length L 1 after immersion in water, Find the rate of change.

 Dimensional change rate (%) = ((L 1 / L 0) 1 1) X 100

The dimensional change rate may be within the range of 13% to + 3% in either the length direction or the width direction. If the sample is small, it should be done in a size that can be collected. The air filter medium of the present invention is desirably flame retardant, but preferably does not contain a flame retardant harmful to the global environment or the human body in terms of environmental impact. Such a flame-retardant filter medium can be obtained by forming an electret nonwoven fabric sheet and an aggregate sheet from the same material. A preferred material composition is polypropylene.For example, a laminate obtained by laminating a polypropylene meltblown nonwoven fabric as an electret nonwoven fabric sheet having a QF value of 0.1 Pa- ¹ or more and a polypropylene spanbond nonwoven fabric as an aggregate sheet is used. No. In another embodiment, <3? The P a- ¹ or more electronics Bok Retsuto of polypropylene as non-woven sheet. Pyrene meltblown nonwoven adopts polypropylene main Rutoburo nonwoven with a fiber diameter 2 0 or more rigid as aggregate sheet, it includes those obtained by laminating them. In particular, the structure in which both the electreted nonwoven sheet and the aggregate sheet are made of a melt-blown nonwoven is excellent since high flame retardancy can be obtained. This is because when the fire source comes into contact with the filter media, the filter media itself exhibits heat shrinkage or a burning part that falls and exhibits self-extinguishing properties. Flame retardancy evaluation method conforms to FMV SS-302. Example

 (Example 1)

Electretized polypropylene melt professional non-woven fabric sheet (average fiber diameter: 6.3 m, basis weight: 22 g / m thickness: 0.18 mm, QF value: 0.22 Pa- \ collection efficiency: 65 %, Pressure loss: 5 Pa, fiber density: 0.12 gZcm ³ ), as an aggregate sheet, 16.5% by weight of 2.2 dte X polyester fiber (water content: 0.5%) 16.5% by weight of 1.7 dtex vinylon fiber (water content: 5%) and 22% by weight of 7.8 dte X vinylon fiber, 20% by weight, glass transition point Is a non-woven fabric sheet with a basis weight of 70 gZm ² (65 ° C rigidity) made of acrylic resin at 75 ° C and 25% by weight of decapromodiphenyl ether (flame retardant). : 20 Omg, air permeability: 330 ml / cm ² sec.) Using moisture-curable urethane resin and pleating (mountain height: 28 mm, pitch: 4.7 mm). Frame made of polyester non-woven fabric The bodies were joined using a polyethylene resin having a softening point of 124 ° C to obtain an air filter unit.

The performance of this unit is as follows: air filter media usage 0.50 m ² , rated air volume 8.Ym ³ , min, pressure loss 90 Pa, 0.3 πι collection efficiency 56%, JIS 15 class The collection efficiency was 98%, and the value of 13 1 5 species 0 was 0.04 Pa- ¹ .

 The dimensional change rate of the air filter medium is 0.2% in the length direction and 0.1% in the width direction.

In addition, one liter of water was sprayed on the filter unit, and the pressure loss after drying was confirmed to be 92 Pa without any problem. In addition, car cabin fill After installing and operating as a unit, the car was left in the scorching sun for 2 hours and then operated. The filter unit was collected and the pressure loss was measured. However, it was 91 Pa without any problem. The pleat shape and appearance of the filter medium of one filter unit were confirmed, but it was confirmed that there was no change from before the test. (Example 2)

Electretized polypropylene meltblown nonwoven fabric sheet (average fiber diameter: 5.5 m, basis weight: 18 gZm ² , thickness: 0.15 mm, QF value: 0.21 Pa a collection efficiency: 68% , Pressure loss: 5.5 Pa Fiber density: 0.12 gZcm ³ ) As an aggregate sheet, 16.5% by weight of 2.2 dte X polyester fiber (water content: 0.5%) 16.5% by weight of 1.7 dtex vinylon fiber (water content: 5%) and 22% by weight of 7.8 dte X vinylon fiber, and 20% by weight of glass transition point Non-woven fabric sheet with a basis weight of 70 gZm ² (65 ° C rigidity: 200 mg, made by inter-fiber bonding with acryl resin at 75 and 25% by weight of decabromodiphenyl ether) Air permeability: 330 m 1 / cm ² Z seconds) is bonded using moisture-curable urethane resin, pleated (mountain height: 28 mm, pitch: 4.7 mm), and made of polyester nonwoven fabric Soften the frame Points are joined with a polyethylene resin of 1 24 ° C, to obtain an air filter one unit.

The performance of this unit is as follows: filter media usage 0.50 m ² , rated air volume 8.7 m ³ Z min, pressure loss 91 Pa, 0. Collection efficiency 56%, JIS 15 type collection efficiency 99 %, J

The ISF5 QF value was 0.05 Pa- ¹ .

 The dimensional change rate of the air filter medium was 0.2% in the length direction and 0.1% in the width direction.

(Example 3).

Electretized polypropylene melt-blown nonwoven fabric sheet (average fiber diameter: 35 m, basis weight: 100 g / m ² , thickness: 0.66 mm, QF value: 0.16 Pa— \ collection efficiency: 75 %, pressure loss: 8. 2 P a, fiber density: 0.5 to 1 5 gZcm ^3), as aggregate sheet, basis weight of SO gZm ^2, Tan'ito径is 0. 3 mm, eye fit is 4 m m polyester net (65 ° C bending softness: 220 mg, moisture content: 0.5%) is dot-joined by ultrasonic bonding and pleated (height: 28 mm, pitch: 4. 7 mm), and a frame made of polyester non-woven was joined using a polyethylene resin having a softening point of 124 ° C to obtain an air filter unit.

The performance of this unit is as follows: filter media usage 0.50 m ² , rated air volume 8.7 m ³ Z min, pressure loss 99 Pa, 0.3 im collection efficiency 66%, JIS 15 type collection efficiency The JIS 1 class 5 QF value was 0.99%, and the value was 0.046 Pa- ¹ .

 This air filter medium contained no flame retardant, but passed FMVS S-302. The dimensional change rate of the filter medium was 0% in both the length and width directions.

(Example 4)

Electretized polypropylene meltblown nonwoven fabric sheet (average fiber diameter: 5, basis weight: 12 g / m thickness: 0.13 mm, QF value: 0.22 Pa- ¹ ; collection efficiency: 25%, pressure loss: 2 P a, fiber density: 0.09 gZcm ³ ) Electretized polypropylene melt professional nonwoven sheet as aggregate sheet (average fiber diameter: 35 ^ m, basis weight: 100 g / m thickness) : 0. 6 6 mm, QF value: 0. ¹ 6.P a - 1, collection efficiency: 7 5%, pressure loss: 8. 2 P a, fiber ^{density: 0. 1 5 g / cm 3} , 6 5 ° C bending resistance: 170 mg, moisture content: 0%), pleated (mountain height: 28 mm, pitch: 4.7 mm), and the softening point of the frame made of polyester nonwoven fabric Were joined by using a 124 ° C. polyethylene resin to obtain an air filter unit.

The performance of the unit, the filter medium usage 0. 4 0 m ^2, Teikakufuryou 8. 7 m ³ Bruno partial, pressure drop 9 9 P a, 0. 3 ^ m collecting efficiency 7 3%, capturing JIS 1 5 or The collection efficiency was 99.5%, and the JIS 15 class QF value was 0.05 Pa- ¹ .

This air filter medium contained no flame retardant, but passed FMVS S-302. The dimensional change rate was 0% in both the length and width directions. . (Example 5)

Electretized polypropylene melt professional non-woven fabric sheet (average fiber diameter: 6.3 μ, πι, basis weight: 22 g / thickness: 0.18 mm, QF value: 0.22 P ai i, collection efficiency: 65%, pressure loss: 5 Pa, fiber density: 0.12 gZcm ³ ), aggregate sheet, 70 g / m ² , 16.5% by weight, 2.2 dtex poly Ester fiber (water content: 0.5%), 16.5% by weight of 1.7 dtex pinion fiber (water content: 5%), and 22% by weight of 7.8 dtex vinylon fiber And 20% by weight of a resin obtained by mixing acrylic resin having a glass transition point of 75 ° C. and epoxy resin having a glass transition point of 80 ° C. in a mixing ratio of 73:27, and 25% by weight. A nonwoven fabric sheet (65 ° C softness: 250 mg, air permeability: 350 ml / cm ² / sec) made of fibers bonded with decabromodiphenyl ether using moisture-curable urethane resin Joining and pleating (mountain height: 2.8 mm, pitch: 4.7 mm), and a frame made of polyester non-woven fabric was joined using a polyethylene resin having a softening point of 124 ° C to obtain an air filter unit.

The performance of this unit is as follows: filter media usage 0.50 m ² , rated air volume 8.7 m ³ Z min, pressure loss 88 Pa, 0.3 <m collection efficiency 56%, JIS 15 type collection The efficiency was 98%, and the JIS Class 1 QF value was 0.044 Pa- ¹ .

 The dimensional change rate of the air filter media is 0.2% in the length direction and 0.1% in the width direction.

 In addition, one liter of water was sprayed on the above filter unit, and the pressure loss after drying was confirmed to be 88 Pa without any problem. Furthermore, the car was mounted as a car cabinet filter unit, the car was left in the scorching sun for 2 hours, and then operated.The filter unit was collected and the pressure loss was measured, but no problem was found at 89 Pa. . The shape of the filter and the shape of the pleats after the test were confirmed, but no change was confirmed. '

(Example 6)

The Erekutoretsuto polypropylene meltblown nonwoven sheet one bets used in Example 1, as an aggregate sheet, basis weight of 80 gZm ^2, Tan'ito径is 0. 3 mm, eye eye A 4mm polypropylene net (65 ° C softness: 29 Omg, moisture content: 0%) is bonded using a moisture-curable urethane resin, and the particle size on the net is 100 ~, Activated carbon particles in the range of 0 # are supported at a rate of 150 g / m ² using powder of ethylene vinyl acetate resin, and then a filter medium laminated with a cover nonwoven fabric is pleated (mounting height: 18 mm). The pitch was 8 mm), and a frame made of polyester non-woven fabric was joined using a polyethylene resin having a softening point of 124 ° C. to obtain one unit of an air filter.

This unit has a filter material usage of 0.3 m ² , a rated air volume of 8.7 m ³ / min, a pressure loss of 98 Pa, an initial collection efficiency of 42%, and a pressure loss required for in-vehicle use. The condition of 1 OOP a or less and the initial collection efficiency of 35% or more was sufficiently satisfied.

1 3 1 5 types (2 values were 0.03 Pa- ¹ ).

(Example 7) ',

 Polyester heat fusible fiber with a melting point of 110 ° C (9 dtex, moisture content: 0.5%) and polypropylene split fiber with a thickness of 8 m and an average width of 80 zm

(75 mm length, moisture content: 0%) was opened and carded under an atmosphere of 65% relative humidity to prepare a nonwoven fabric sheet having a basis weight of 30 gZm ² . In addition to this, a polypropylene net (65 ° C softness: 170 mg, water content: 0%) having a fiber diameter of 0.3 mm, a basis weight of 30 g / m and a basis weight of 5 mm was used as an intermediate layer, and Electretized Polypropylene Melt Pro—Nonwoven fabric sheets were laminated, heat-treated and integrated, and then electretized to obtain a laminated sheet.

 The laminated sheet was pleated (height: 20 mm, pitch: 8 mm) to obtain an air-fill unit.

This unit has a filter material usage of 0.35 m ² , a rated air volume of 8.9 m ³ Z, a pressure loss of 90 Pa, an initial collection efficiency of 65%, and a pressure loss required for in-vehicle use. The condition of Pa or less and the initial collection efficiency of 35% or more was sufficiently satisfied. Also, DFC

(Measurement method: based on JIS-B-9908 (Test method type 2: Dust retention capacity test)), the target of 20 g / un was achieved with a small amount of filter media. The DFC is the dust supply amount, and here represents the dust supply amount per filter unit. request The higher the DFC value up to the required pressure drop, the longer the life of the filter unit.

(Comparative Example 1)

Electretized polypropylene melt-blown nonwoven fabric sheet (average fiber diameter: 6.3 urn, basis weight: 22 g / m thickness: 0.18 mm, QF value: 0.04 Pa—, i, collection efficiency: 18% , Pressure loss: 5 Pa, fiber density: 0.12 g / cm ³ ), as aggregate sheet, 16.5 wt% of 2.2 dte X polyester fiber (moisture content:

0.5%), 16.5% by weight of 1.7 dte X vinylon fiber (moisture content: 5%) and 22% by weight of 7.8 dte X vinylon fiber, 20% by weight of, glass transition point is attached between the fibers with an acrylic resin and 2 5% by weight of decabromodiphenyl diphenyl ether of 7 5 ° C, a basis weight of 7 0 gZm ² of the nonwoven fabric sheet (6 51 bending resistance

: 2000 mg, air permeability: 330 ml / cm ² / sec) using moisture-curable urethane resin, and pre-processed (mountain height: 28 mm, pitch: 3.5 mm) A frame made of a polyester non-woven fabric was bonded to this using a polyethylene resin having a softening point of 124 to obtain an air filter unit.

 The performance of this unit is as follows: pressure drop 1 110 Pa, 0.3 m collection efficiency 11%, J

1 S 1 5 species collection efficiency 9 2%,] 1 3 1 5 species 0 value was 0.22 Pa- ¹ . It had high pressure loss and low dust and low JIS 15 collection performance.

(Comparative Example 2)

 A filter unit having exactly the same configuration as in Example 1 was prepared except that the electrified nonwoven fabric was changed to the following.

Elect 'Retsuto polypropylene Mel Bok blow nonwoven Sea Bok (average fiber diameter: 6. 3 m, basis weight: 40 g / m Thickness: 0. 2 5 mm, QF value: 0. 043 P a one ^1, collection efficiency: 3 8%, pressure drop: 11 Pa, fiber density 0.16 gZcm ³ ) The performance of this unit is pressure loss 2 10 Pa, 0.3 m collection efficiency 23%, JIS 15 class Collection efficiency 97%,] 13 15 species (3 values 0.025 Pa- ¹ .

Although the collection performance of JIS 15 type is high, the collection efficiency of 0.3 m fine dust is low, The pressure loss was higher.

(Comparative Example 3)

Aggregate sheet containing glass fiber (water content: 0.1% or less) (thickness: 0.19mm, fiber diameter: 13; um, basis weight: 25g / m Air permeability: 250m1Zcm Example 1 except that the binder was changed to ² sec, binder: vinyl acetate (moisture: 12%), polypinyl alcohol fiber (moisture: 10% or more), and 65 softness: 180mg. A filter with exactly the same configuration as was created. The performance of this unit is as follows: filter media usage 0.50 m ² , rated air volume 8.7 m ³ min, pressure loss 87 Pa, 0.3 im collection efficiency 5 '7%, JIS 1 class 5 collection efficiency 9 8%,] 1.3 1 5 types (3 values 0.044 Pa- ¹ ) However, since vinyl alcohol fiber (moisture content 10% or more) was contained, the dimensions of the air filter media were The rate of change is as large as 3.5% in the long direction and 4% in the width direction.One liter of water is sprayed on the above filter unit, and when the pressure loss is confirmed after drying, it increases to 130Pa and becomes unusable. When the shape of the filter medium after the test was confirmed, it was confirmed that the filter medium had swelled and blocked the flow path for air flow.

(Comparative Example 4) 'Aggregate sheet is a sheet containing rayon fiber having a Y-shaped cross section (water content: 14%) (fiber diameter: 7.3 dtex, basis weight: 40 g / m ³ , air permeability: 15) 0m l / cm ² / sec, thickness: 0. 1 9 mm, 6 5 in softness: 1 5 0 mg, binder: polyvinyl alcohol resin and polyvinyl alcohol fibers: the (water content 1 0% or more)) A filter unit having exactly the same structure as in Example 1 was prepared except for the change. The performance of this unit is as follows: filter media usage 0.50 m ² , rated air flow 8.7 m ³ min, pressure drop 93 Pa, 0.3 πι collection efficiency 57%, JIS 15 type collection Efficiency 98%,] 13 15 species <3 value 0.042 Pa- ¹ . However, since it contained rayon fiber, polyvinyl alcohol fiber (water content of 10% or more) and polyvinyl alcohol resin, the dimensional change rate of the air filter medium was as large as 6% in the length direction and 5% in the width direction. The spray was sprayed with 1 liter of water, and the pressure loss was confirmed after drying. It turned out to be unusable. When the pleated shape of the filter medium after the test was confirmed, it was confirmed that the filter medium swelled and blocked the air flow path. Industrial applicability

 According to the present invention, as is clear from the comparison between the example and the comparative example, the pressure loss is low and the collection efficiency is excellent, and the heat resistance, moisture, and dimensional stability against water adsorption are also excellent. In particular, it is possible to obtain a filter medium and a filter unit suitable for a vehicle-mounted air filter. '

Claims

The scope of the claims 1. fiber density 0. 06~0. Lg gZcm ^3, and Erekutoretsuto non-woven fabric Sea Bok a QF value of at least 0. l P a- ^1, moisture content is constituted by the fiber material than 6% 6 An air filter medium having a layered structure with a plaster sheet having a stiffness at 5 of at least 15 Omg. 2. The air filter medium according to claim 1, wherein the electretized nonwoven fabric sheet is an electret meltblown nonwoven fabric sheet. 3. The air filter medium according to claim 1, wherein the aggregate sheet is a synthetic fiber non-woven fabric sheet indirectly bonded with a resin having a glass transition point (Tg) of at least 0.50 ° C. 4. The air filter medium according to claim 3, wherein the synthetic fiber nonwoven fabric sheet is a short fiber resin processed nonwoven fabric sheet. 5. The resin having a glass transition point (Tg) of at least 50 ° C is at least one resin selected from an acrylic resin, a styrene acryl resin, and a mixed resin of an acryl resin and an epoxy resin. Item 7. The air filter medium according to Item 3 or 4. 6. The air filter medium according to claim 1, wherein the aggregate sheet is formed of a sheet including a synthetic resin net. 7. The air filter medium according to claim 1, wherein the aggregate sheet is formed of a sheet containing electretized film split fibers. 8. The air filter medium according to claim 1, wherein the aggregate sheet is formed of a sheet including a melt-blown nonwoven sheet. 9. The air filter medium according to claim 8, wherein the meltblown nonwoven fabric sheet is an electret meltblown nonwoven fabric sheet. 10. The air filter medium according to any one of claims 1 to 9, which has a deodorizing function. 1 1. A filter unit using the air filter medium according to any one of claims 1 to 10. 12. The filter unit according to claim 11, wherein the frame is attached to the filter unit with a hot melt resin having a softening point of at least 120 ° C. 1 3. The filter unit according to claim 11 or 12, wherein the filter unit is of a type of 13 15 (three values of 0.03 Pa- ¹ or more). 1. The filter unit according to any one of claims 11 to 13, wherein the filter unit is a car cabin filter. '