JP6184342B2 - Filter media - Google Patents

Description

The present invention relates to a filter medium used in, for example, a vehicle air conditioner such as an automobile, a home air conditioner such as a home air cleaner, or an air conditioner installed in a building, factory, office, or the like.

2. Description of the Related Art In recent years, due to an increasing desire to improve the living environment, it has been required that volatile organic compounds (VOC) can be removed by filter media in addition to dust present in the air to clean the air. For example, aldehyde-based compounds such as formaldehyde and acetaldehyde are known as VOCs which are both offensive odor substances and may cause health threats as causative substances such as sick house syndrome.
In particular, in a vehicle such as an automobile, since there are many parts using a binder or paint in a narrow space, VOC tends to exist at a high concentration, and efficient removal of VOC is required.

In response to the above request, a filter medium having excellent VOC adsorption performance has been studied. For example, in JP 2000-279500 A (hereinafter sometimes referred to as Patent Document 1), an adsorbent in which a compound having an amino group is supported on silicon dioxide is attached to a porous body such as a nonwoven fabric with a binder. A prepared air filter is disclosed.
In the cited document 1, it is disclosed that an adsorbent having an average particle size of 0.01 to 50 μm can be used. Moreover, the air filter formed by giving the liquid mixture which mixed the binder of 2 times mass with respect to the mass of adsorption agent to the nonwoven fabric is disclosed by the Example.

JP 2000-279500 A (Claims, 0004, 0009, 0016, 0020-00021, Examples, etc.)

The inventors of the present application employ an adsorbent having an average particle diameter of 1 μm or less because efficient adsorption of VOC can be expected due to a large surface area relative to mass. And as patent document 1 discloses, the liquid mixture (mass ratio of an adsorbent and a binder is 33 mass%: 67 mass%) which mixed the binder twice the mass with respect to the mass of an adsorbent is provided to the said nonwoven fabric. Then, the preparation of a filter medium having VOC adsorption performance was examined.
However, the VOC adsorption performance of the filter medium having the above-described configuration is lower than expected, and it was thought that the VOC adsorption performance of the filter medium was hindered for some reason.

An object of the present invention is to provide a filter medium having excellent VOC adsorption performance.

The present invention
“A filter medium comprising a nonwoven fabric carrying an adsorbent with a binder,
The adsorbent is a particle having an average particle diameter of 1 μm or less,
The filter medium whose mass ratio of the said adsorption agent and the said binder is 93 mass%: 7 mass%-99.5 mass%: 0.5 mass%. "
It is.

As a result of continuous investigations by the inventors, in a filter medium including a nonwoven fabric in which an adsorbent, which is a particle having an average particle diameter of 1 μm or less, is supported by a binder, the mass ratio of the binder and the adsorbent included in the filter medium is within the scope of the present invention. It was found that the VOC adsorption performance of the filter medium is efficiently exhibited by adjusting so as to be.

The reason for this is not completely understood, but it is thought that the filter medium of the present invention is a filter medium that prevents the following causes from occurring.
1. When the mass ratio of the binder is larger than the range of the present invention, the binder included in the filter medium is larger than the binder necessary for supporting the adsorbent on the non-woven fabric, so that the excess binder covers the surface of the adsorbent. Thus, the VOC adsorption performance of the adsorbent is considered to be hindered.
2. When the mass ratio of the binder is less than the range of the present invention, the binder provided in the filter medium is less than the binder required for supporting the adsorbent on the nonwoven fabric, and the adsorbent is easily peeled off from the filter medium. It is thought that the VOC adsorption performance decreases.

Therefore, the filter medium of the present invention is a filter medium excellent in VOC adsorption performance.

The adsorbent referred to in the present invention may be any adsorbent that can adsorb VOCs such as aldehyde compounds, and the type and composition of the adsorbent are appropriately adjusted. For example, titanium oxide, zinc oxide, or silicon dioxide has an amino group. An adsorbent in which a compound is supported can be employed.
Examples of the compound having an amino group herein include aromatic compounds having an amino group such as aniline, and aliphatic compounds having an amino group represented by the following chemical structural formula.

_{H 2 N- (CH 2 CH 2} -NH) n-CH 2 CH 2 NH 2
(N is an integer from 0 to 3)

In addition, it is preferable that the compound having an amino group is a compound having a primary amino group because it is excellent in the ability to adsorb VOCs such as aldehyde compounds.

  The particle shape of the adsorbent can be adjusted as appropriate. For example, it can be appropriately selected from spherical (substantially spherical or true spherical), fibrous, needle-like, flat plate, irregular shape, polyhedron shape, feather shape, tetrapod shape, etc. Since the surface area with respect to mass becomes an adsorbent having excellent VOC adsorption performance, the adsorbent having a spherical particle shape is preferable.

The average particle size of the adsorbent is adjusted to 1 μm or less so that a filter medium having excellent VOC adsorption performance can be prepared. However, the smaller the average particle size, the better the VOC adsorption performance by increasing the surface area relative to the mass. It is preferable that it is 100 nm or less. The lower limit of the average particle diameter of the adsorbent is larger than 0 nm and is adjusted as appropriate, but it is realistic that it is 5 nm or more.
In the present invention, the average particle diameter of the adsorbent is a value measured using a dynamic light scattering method (CONTIN method measurement) by subjecting the particles to FPRA1000 (measurement range: 3 nm to 5000 nm) manufactured by Otsuka Electronics Co., Ltd. Point to.

As the adsorbent described above, for example, Kesmon (registered trademark, model number: KS-210, KS-730, etc.) of Toagosei Co., Ltd., Kiraku (registered trademark, model number: AL-07), etc. of Nikka Chemical Co., Ltd. are used. can do.
In addition, an adsorbent may be used individually by 1 type, or may mix and use 2 or more types.

  The binder serves to hold the adsorbent on the nonwoven fabric by holding the adsorbent to the fibers constituting the nonwoven fabric.

  For example, the binder is selected and used depending on the type of fiber constituting the adsorbent or the nonwoven fabric. For example, polyolefin (modified polyolefin, etc.), ethylene vinyl alcohol copolymer, ethylene-ethyl acrylate Copolymers and other ethylene-acrylate copolymers, various rubbers and their derivatives [styrene-butadiene rubber (SBR), fluorine rubber, urethane rubber, ethylene-propylene-diene rubber (EPDM), etc.], cellulose derivatives [carboxymethylcellulose (CMC) ), Hydroxyethyl cellulose, hydroxypropyl cellulose, etc.], polyvinyl alcohol (PVA), polyvinyl butyral (PVB), polyvinyl pyrrolidone (PVP), polyurethane, epoxy resin, polyvinylidene fluoride PVdF), vinylidene fluoride - hexafluoropropylene copolymer (PVdF-HFP), and acrylic resins can be used.

  In particular, it is preferable to use a binder made of a resin that hardly releases an aldehyde compound as the binder because a filter medium excellent in VOC adsorption performance can be prepared without impairing the VOC adsorption performance of the filter medium. Examples of such a binder include Nipol (registered trademark) LX874, 855EX1, and LX852, which are acrylate latex binders manufactured by Nippon Zeon Co., Ltd., and AN-1170 and AN-1190 manufactured by DIC Corporation.

In addition, these binders may be used individually by 1 type, or may use 2 or more types together.

  The fibers constituting the nonwoven fabric include, for example, polyolefin resins (polyethylene, polypropylene, polymethylpentene, polyolefin resins having a structure in which a part of hydrocarbon is substituted with a cyano group or a halogen such as fluorine or chlorine), styrene resins, Polyether resins (polyether ether ketone, polyacetal, phenolic resin, melamine resin, urea resin, epoxy resin, modified polyphenylene ether, aromatic polyether ketone, etc.), polyester resins (polyethylene terephthalate, polytrimethylene) Terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polycarbonate, polyarylate, wholly aromatic polyester resin, unsaturated polyester resin, etc.), polyethylene Imide resin, polyamideimide resin, polyamide resin (for example, aromatic polyamide resin, aromatic polyetheramide resin, nylon resin), resin having nitrile group (for example, polyacrylonitrile), urethane resin, epoxy Resin, polysulfone resin (polysulfone, polyethersulfone, etc.), fluorine resin (polytetrafluoroethylene, polyvinylidene fluoride, etc.), cellulose resin, polybenzimidazole resin, acrylic resin (for example, acrylic ester or methacrylic acid) Polyacrylonitrile resins copolymerized with acid esters and the like, modacrylic resins copolymerized with acrylonitrile and vinyl chloride or vinylidene chloride, and the like) can be used.

These organic polymers may be either linear polymers or branched polymers, and the organic polymer may be a block copolymer or a random copolymer, and the three-dimensional structure or crystal of the organic polymer. The presence or absence of sex is not particularly limited. Furthermore, what mixed the some organic polymer may be sufficient, and it does not specifically limit.

The fibers constituting the nonwoven fabric may be composed of one or more types of resin components, and are generally referred to as composite fibers, for example, core-sheath type, sea-island type, side-by-side type, orange type, etc. Can be used. In addition, you may use the composite fiber in which one fiber component was provided with heat bonding components, such as a thermoplastic resin, and the latent crimpable composite fiber provided with several resin from which a thermal contraction rate differs.

The average fineness of the fibers constituting the nonwoven fabric is adjusted as appropriate so that a filter medium with excellent VOC adsorption performance can be prepared, but it is 5-30 dtex because it is easy to provide a filter medium with a low initial pressure loss and a large amount of dust retention. Is preferred. If the density is less than 5 decitex, the nonwoven fabric has a fine mesh, so that the filtration efficiency of the filter medium is increased, but the initial pressure loss is increased, and the dust holding amount may be reduced. On the other hand, if it exceeds 30 dtex, the non-woven fabric becomes too coarse, and the filtration efficiency of the filter medium and the amount of dust retained may be reduced. The average fineness of the fibers constituting the nonwoven fabric is more preferably 8 to 20 dtex.
In addition, as a calculation method of the average fineness of a constituent fiber, the fineness of each fiber contained in the nonwoven fabric is a decitex, b decitex, c decitex, etc., and the content ratio of each fiber is a ′ mass% and b ′ mass, respectively. %, C ′ mass%, the relational expression “(a ′ / a) + (b ′ / b) + (c ′ / c)... = (100 / x)” is established. The average fineness x can be obtained.

As an example of the manufacturing method of a nonwoven fabric, a nonwoven fabric can be manufactured by preparing a fiber web using a dry method, a wet method, etc., and intertwining and / or integrating the fibers which comprise a fiber web. As a method of entanglement and / or integration of the fibers constituting the fiber web, for example, a method of entanglement with a needle or a water flow, a method of integration of fibers with a binder, or the fiber web contains a thermoplastic resin. In this case, there can be mentioned a method in which the fibers are integrated by melting the thermoplastic resin by heat-treating the fiber web.
In addition, as a method of heat-processing a fiber web, the method of heating and pressurizing with a calender roll, the method of heating with a hot air dryer, the method of irradiating infrared rays etc. can be used, for example.

As another method for producing a nonwoven fabric, a spinning solution or a melted resin can be thinned and spun using a direct spinning method, and fibers can be collected to prepare a nonwoven fabric. In addition, you may use for the method of intertwining and / or integrating the fibers mentioned above using the nonwoven fabric prepared using the direct spinning method.

In addition, in order to improve the filtration performance of a nonwoven fabric, electrification may be performed and the constituent fibers may be converted into electrets. Since the effect of the electret is easily lost by heating at a relatively high temperature, it is preferable to perform a charging process after forming the nonwoven fabric by a heat treatment.
The method for electretizing the nonwoven fabric is appropriately selected and is not limited, but for example, means for charging by injecting ions such as plasma charging treatment or corona charging, charging by applying a force via a polar liquid Well-known means such as a means for making them rub, a means for frictionally charging a plurality of types of fiber components, and the like can be appropriately selected or used in combination.

The thickness of the non-woven fabric is appropriately adjusted so that a filter medium having excellent VOC adsorption performance can be prepared, but is preferably 1 to 5 mm because it is easy to provide a filter medium having a low initial pressure loss and a large amount of dust retention. If it is less than 1 mm, the amount of dust retained in the filter medium may be reduced. When the thickness exceeds 5 mm, when the filter medium is folded in pleats, the wall surfaces of the filter medium come into contact with each other at the ridge or valley portion of the pleat, and the portion that does not contribute to gas filtration or has very little contribution (hereinafter referred to as dead space and As a result, the initial pressure loss increases and the dust holding amount may decrease. As for the thickness of a nonwoven fabric, it is more preferable that it is 1.5-4.5 mm, and it is most preferable that it is 2-4 mm.
The “thickness” as used in the present invention means the thickness shown when a load of ² g is applied per 1 cm ^{2 of} the main surface, and the main surface means a surface having a large area.

The basis weight of the nonwoven fabric is appropriately adjusted so that a filter medium excellent in VOC adsorption performance can be prepared, but it is preferably 50 to 400 g / m ^{2 because} it is easy to provide a filter medium with a low initial pressure loss and a large amount of dust retention. . If it is less than 50 g / m ² , the amount of dust retained in the filter medium may decrease. ^{On the other hand} , if it exceeds 400 g / m ² , dead space is generated when the filter medium is folded in pleats. As a result, the initial pressure loss is increased, and the dust holding amount may be reduced. Basis weight of the nonwoven fabric, more preferably from 75~300g / ^{m 2,} most preferably a 90 to 200 g / ^{m 2.}
In the present invention, “weight per unit area” refers to the mass per 1 m ² area of the main surface.

When the mass ratio of the adsorbent and the binder is 93% by mass: 7% by mass to 99.5% by mass: 0.5% by mass, a filter medium having excellent VOC adsorption performance can be provided. When the mass ratio of the binder is more than 7% by mass, the excess binder tends to cover the surface of the adsorbent and the VOC adsorption performance of the filter medium tends to decrease, and the mass ratio of the binder is less than 0.5% by mass. Then, the adsorbent peels off from the filter medium, and the VOC adsorption performance of the filter medium tends to decrease.
The mass ratio between the adsorbent and the binder is appropriately adjusted as long as it is within the above range, but is more preferably 95% by mass: 5% by mass to 99.5% by mass: 0.5% by mass.

Each various properties such as basis weight and thickness of the filter medium is appropriately adjusted so as to provide filter media which is excellent in VOC adsorption performance, for example, is preferably basis weight is ^{50g / m 2 ~400g / m 2} , 75g / more preferably from ^{m 2} ~300g / m ^2, and even most preferably ^{90g / m 2 ~200g / m 2} . Further, the thickness of the filter medium in a flat plate state is preferably 1 mm to 5 mm, more preferably 1.5 mm to 4.5 mm, and most preferably 2 mm to 4 mm.

The total mass of the binder and the adsorbent contained in the filter medium is appropriately adjusted so as to provide a filter medium excellent in VOC adsorption performance. However, if the total mass is too large, the voids in the filter medium are blocked, the initial pressure loss increases, and the dust is increased. The retention amount tends to decrease, and if the total mass is too small, the VOC adsorption performance of the filter medium tends to decrease. Therefore, the total weight of the binder and adsorbent filter medium comprises ^is preferably from ^{1g / m 2 ~50g / m 2} , more preferably from ^{5g / m 2 ~40g / m 2} , 10g / m 2 ~ Most preferred is 35 g / m ² .

Hereinafter, the method for preparing the filter medium of the present invention will be described.
The method of preparing the nonwoven fabric carrying the adsorbent with a binder can be selected as appropriate, for example,
1. A method of removing the dispersion medium and the binder solvent after mixing the adsorbent and the binder into the dispersion medium and the binder solvent, and applying the prepared mixed liquid to the nonwoven fabric,
2. A method of cooling the binder after applying the melted binder to the nonwoven fabric, and then adsorbing the adsorbent on the melted binder,
3. A method of removing the solvent after applying the binder solution to the non-woven fabric and then attaching an adsorbent onto the binder solution;
4). A method of cooling the binder after applying the adsorbent and the binder to the nonwoven fabric and then melting the binder;
And so on.

  In addition, although the method of giving a liquid mixture and a binder solution to a nonwoven fabric is selected suitably, for example, the method of spraying a liquid mixture or a binder solution on a nonwoven fabric, the method of immersing a nonwoven fabric in a liquid mixture or a binder solution, a foamed liquid mixture, Examples thereof include a method of applying the binder solution to the nonwoven fabric, and a method of applying the mixed solution and the binder solution to the nonwoven fabric using a coating apparatus such as a gravure coater. Moreover, although the method of providing the melt | dissolved binder to a nonwoven fabric is selected suitably, the method of spraying the melted binder to a nonwoven fabric etc. can be mentioned, for example.

  The method for melting the binder is appropriately selected, and examples thereof include a method for supplying to a dry heat dryer, a method for supplying to a dryer device, and a method for supplying to an infrared heater.

  The method for removing the dispersion medium and the solvent is also appropriately selected. However, the method mentioned in the method for melting the binder described above, and the method for leaving the dispersion medium and the solvent at room temperature if they have a property of evaporating under room temperature conditions. And so on.

Further, the method for cooling the binder is appropriately selected and is not limited, and examples thereof include a method for supplying to a cooling device such as a refrigerator and a method for leaving at room temperature.

In order to prepare a filter medium having a low initial pressure loss, excellent dust holding capacity, and improved VOC adsorption performance more efficiently, it is preferable to prepare the filter medium using a pleated nonwoven fabric or to pleat the filter medium. In addition, as a method of pleat folding a nonwoven fabric or a filter medium, a method using a pleating machine such as a reciprocating type or a rotary type, a method of pressing with a pressing die formed in a zigzag shape, etc. can be adopted. The pleat interval, the angle of the pleats, etc. are adjusted as appropriate.

The nonwoven fabric carrying the adsorbent prepared as described above with a binder can be used as a filter medium as it is. However, for the purpose of reinforcement, improvement of filtration performance, imparting flame retardancy, etc., for example, a separately prepared fabric (nonwoven fabric, knitted fabric or knitted fabric) Other breathable materials such as fabrics may be laminated.

In order to improve the shape retention of the filter medium, an end plate may be provided on the side surface of the filter medium (a surface parallel to the thickness direction). Even if the end plate is provided on all side surfaces of the filter medium, when the filter medium is rectangular when viewed from the main surface side, the end plate is provided on two sides facing each other on the side surface of the filter medium. It may be an embodiment. In the case of a pleated filter medium, it is preferable that an end plate be provided on the side surface intersecting the ridge line of the pleated filter medium so as to be excellent in the shape retention of the pleat shape.

Although the kind of end plate is adjusted suitably, breathable materials, such as an organic resin plate, a metal plate, a glass plate, a wood board, a cloth, etc. are employable, for example.
In particular, if the end plate is a breathable material that has dust collection performance and VOC adsorption performance, the end plate can also function as a filter medium, so that the initial pressure loss is low, dust retention is excellent, and VOC adsorption is achieved. A filter medium with improved performance is more preferable. Although the preparation method of the end plate which has such a characteristic is selected suitably, the nonwoven fabric prepared similarly to the nonwoven fabric which comprises a filter medium is employable.

In addition, when the end plate is provided with a non-woven fabric containing a heat-adhesive fiber or a non-woven fabric containing a binder, the end plate is attached to the filter medium by melting and adhering the heat-adhesive fiber or the binder by heating. A filter medium that is strong and easily bonded and excellent in shape retention can be preferably prepared.

The method of integrating the end plate and the filter medium is appropriately adjusted. For example, the method of bonding and integrating using a binder, the method of melting and integrating by ultrasonic welding or the like, the filter medium and / or the end plate by heat treatment, etc. And a method of melting and bonding the binder and heat-adhesive fibers contained in the adhesive.

Examples of the present invention will be described below, but these are only suitable examples for facilitating the understanding of the present invention, and the present invention is not limited to the contents of these examples.

(Measurement method of VOC adsorption performance of filter media)
A chamber having an internal volume of 1 m ³ was prepared. And the fan which equips an upstream part with the filter medium cut | disconnected so that it might become a square shape of 30 mm on one side was prepared, and the said fan was installed in the chamber. Next, acetaldehyde gas was introduced into the chamber to adjust the acetaldehyde concentration in the chamber to 40 ppb.
By operating the fan for 15 minutes, the gas in the chamber was passed through the filter medium.
Thereafter, 50 L of gas in the chamber was supplied to a DNPH cartridge (manufactured by Waters), so that acetaldehyde remaining in the chamber was adsorbed to the DNPH cartridge.
And the mass of the acetaldehyde which the DNPH cartridge adsorb | sucked was calculated | required using the high speed ion chromatography, and the acetaldehyde density | concentration (A, unit: ppb) in the chamber after operating a fan for 15 minutes was computed.

From the results of the above measurements, the formaldehyde adsorption rate (Fre, unit:%) of the filter medium was calculated based on the following formula, and the calculated value was taken as the VOC adsorption rate (unit:%) of the filter medium.
Fre = {(40−A) / 40} × 100
A filter medium having a VOC adsorption rate of 60% or more was evaluated as a filter medium excellent in VOC adsorption performance, and a filter medium having an adsorption rate of less than 60% was evaluated as a filter medium inferior in VOC adsorption performance.

(Evaluation method of VOC specific adsorption performance of filter media)
By dividing the value of the VOC adsorption rate of the filter medium calculated by the above-described (measurement method of the VOC adsorption performance of the filter medium) by the value of the mass of the adsorbent contained in the filter medium, per 1 g / m ² contained in the filter medium. The adsorption performance of VOC exhibited by the adsorbent (hereinafter referred to as VOC specific adsorption performance) was evaluated. In Tables 1 and 2, the figures are rounded to the first decimal place.
The higher the VOC specific adsorption performance, the more efficient the VOC adsorption performance of the adsorbent.

(Whether or not the filter medium is powdered)
It was confirmed by visual observation whether or not powder was generated from the filter medium by applying the filter medium to the above-described method for measuring the VOC adsorption performance of the filter medium.

(Measurement method of filtration performance of filter media-mass method)
In the test method specified in ASHRAE 52.1-1992, SAE FINE dust is supplied at an air speed of 0.5 m / sec until the initial pressure loss reaches 200 Pa, and the collection efficiency (unit:%) and dust of the filter medium are reduced. The holding amount (unit: g / m ² ) was determined. The initial pressure loss (unit: Pa) of the filter medium is a value measured at a wind speed of 0.1 m / sec.

(Test method for flame retardancy of filter media)
The flame retardancy of the filter media is measured according to US automobile safety standard FMVSS No. Measured according to the combustion test specified in 302.
The burning rate is 100 mm / min. The following filter media were evaluated as filter media excellent in flame retardancy, and the burning rate was 100 mm / min. Faster filter media were evaluated as filter media with poor flame retardancy.

Example 1
(Nonwoven fabric preparation method)
65% by mass of a composite fiber (fineness: 20 dtex, fiber length: 64 mm) composed of a polyester resin having a melting point of 248 ° C. and a sheath component having a melting point of 72 ° C., and a polyester resin having a melting point of 248 ° C. And a composite fiber (fineness: 6.6 decitex, fiber length: 51 mm) 35% by mass comprising a polyester resin having a melting point of 72 ° C., and a fiber web (average fineness: 11.7 dtex) was prepared.
Next, this fiber web was heated and bonded with hot air at 150 ° C. using an air-through dryer, and then passed through a water-cooled roll equipped with a 1 mm slit gauge, and a nonwoven fabric (weight per unit: 150 g / m ² , (Thickness: 3 mm) was prepared.

(Method for preparing filter medium)
Adsorbent in which a compound having an amino group is supported on silicon dioxide (manufactured by Toagosei Co., Ltd., Kesmon (registered trademark) KS-730, particle shape: spherical, average particle diameter: 20 nm), 99.5% by mass, acrylate latex A mixed liquid was prepared by mixing 0.5% by mass of a binder (Nipol (registered trademark) LX874, manufactured by Nippon Zeon Co., Ltd.) with water.
After immersing the non-woven fabric prepared as described above in the liquid mixture, the filter medium (weight per unit: 165.6 g / m ² , thickness: 3 mm, total of binder and adsorbent contained in the filter medium is obtained by removing water by drying. Mass: 15.6 g / m ² ). The mass ratio of the adsorbent and the binder contained in the filter medium was adsorbent mass: binder mass = 99.5 mass%: 0.5 mass%.

(Example 2-5, Comparative Example 1-2)
Filter media of Example 2-5 and Comparative Example 1-2 were prepared in the same manner as in Example 1 except that the mass ratio between the adsorbent and the binder contained in the mixed solution was changed.

(Example 6)
After immersing the nonwoven fabric prepared in Example 1 in the mixed solution used in Example 5, the filter medium (weight per unit: 180.2 g / m ² , thickness: 3 mm, binder contained in the filter medium is removed by drying to remove water. And the total mass of the adsorbent: 30.2 g / m ² ). The mass ratio of the adsorbent and the binder contained in the filter medium was adsorbent mass: binder mass = 93 mass%: 7 mass%.

The composition of each filter medium prepared as described above and the results subjected to each measurement method are summarized in Table 1.

粉落ちの有無：○・・・粉落ちは発生していなかった。×・・・粉落ちが発生していた。
難燃性：○・・・燃焼速度が１００ｍｍ／ｍｉｎ．以下であった。×・・・燃焼速度が１００ｍｍ／ｍｉｎ．よりも速かった。

Presence / absence of powder fall: ○ ... No powder fall occurred. X: Powder falling occurred.
Flame retardancy: ○ ... Combustion rate is 100 mm / min. It was the following. X: Combustion rate is 100 mm / min. It was faster.

(Example 7)
Except for using an adsorbent prepared by granulating the adsorbent used in Example 1 and having a compound having an amino group supported on silicon dioxide (average particle size: 1 μm), the same as in Example 1. Thus, a filter medium (weight per unit: 164.9 g / m ² , thickness: 3 mm, total mass of binder and adsorbent contained in the filter medium: 14.9 g / m ² ) was prepared. The mass ratio of the adsorbent and the binder contained in the filter medium was adsorbent mass: binder mass = 99.5 mass%: 0.5 mass%.

(Example 8-9, Comparative Example 3-4)
Filter media of Example 8-9 and Comparative Example 3-4 were prepared in the same manner as Example 7 except that the mass ratio of the adsorbent and binder contained in the mixed solution was changed.

(Example 10)
After immersing the nonwoven fabric prepared in Example 1 in the mixed solution used in Example 9, the filter medium (weight per unit: 180.6 g / m ² , thickness: 3 mm, filter medium included by drying and removing water) The total mass of the binder and the adsorbent: 30.6 g / m ² ) was prepared. The mass ratio of the adsorbent and the binder contained in the filter medium was adsorbent mass: binder mass = 93 mass%: 7 mass%.

The composition of each filter medium prepared as described above and the results subjected to each measurement method are summarized in Table 2.

粉落ちの有無：○・・・粉落ちは発生していなかった。×・・・粉落ちが発生していた。
難燃性：○・・・燃焼速度が１００ｍｍ／ｍｉｎ．以下であった。×・・・燃焼速度が１００ｍｍ／ｍｉｎ．よりも速かった。

Presence / absence of powder fall: ○ ... No powder fall occurred. X: Powder falling occurred.
Flame retardancy: ○ ... Combustion rate is 100 mm / min. It was the following. X: Combustion rate is 100 mm / min. It was faster.

The filter medium of the example was a filter medium excellent in VOC adsorption performance because the VOC adsorption rate was 60% or more. On the other hand, the filter media of Comparative Example 2 and Comparative Example 4 were inferior in VOC adsorption performance because the VOC adsorption rate was less than 60%.
In addition, as a result of comparing the values of the VOC specific adsorption performance applied to the filter media of Example 1-5 and Comparative Example 2, and Examples 7-9 and Comparative Example 4, the VOC specific adsorption is increased as the binder mass ratio increases. The performance value was found to be small. The reason for this was thought to be that the excess binder covered the surface of the adsorbent and the VOC adsorption performance of the adsorbent was hindered. The fact that the surface of the adsorbent was covered with an extra binder was considered to be the cause of the decrease in the VOC adsorption rate of the filter media of Comparative Examples 2 and 4.

Moreover, although it was thought that the filter media of Comparative Example 1 and Comparative Example 3 that did not have a binder for supporting the adsorbent had the maximum VOC specific adsorption performance, Example 1, Comparative Example 1, and Example 7 From the results of comparing the values of the VOC specific adsorption performance of the filter medium of Example 1 and Comparative Example 3, in fact, the filter medium of Comparative Example 1 and Comparative Example 3 were compared with the filter medium of Example 1 and Example 7 and the VOC specific adsorption performance. It was found that the value of decreased significantly. This is probably because the adsorbent peeled off (powder fall) from the filter medium and the VOC adsorption performance decreased. And it was thought that the adsorbent peeled off (powder-off) from the filter medium was the reason why the filter mediums of Comparative Example 1 and Comparative Example 3 could not efficiently exhibit the VOC adsorption performance.

From the above, the filter medium of the present invention is a filter medium excellent in VOC adsorption performance.

  The filter medium of the present invention can be suitably used in applications such as an automobile cabin air filter, an air purifier filter, and a building air conditioning filter.

Claims (1)

A filter medium comprising a nonwoven fabric carrying an adsorbent with a binder,
The adsorbent is a particle having an average particle diameter of 1 μm or less,
The filter medium whose mass ratio of the said adsorption agent and the said binder is 93 mass%: 7 mass%-99.5 mass%: 0.5 mass%.