JP6158061B2 - Air filter media - Google Patents
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Description
本発明は、支持体上に静電紡糸法を用いて形成されたナノ繊維層を有するエアフィルタ用濾材に関する。 The present invention relates to a filter medium for an air filter having a nanofiber layer formed on a support using an electrospinning method.
近年のエレクトロニクス技術の細密化及びエネルギーコストの削減などの要望から、エアフィルタ用濾材の更なる高性能化が望まれている。エアフィルタ用濾材の高性能化を達成するためには、圧力損失がより低く、かつ、より高い捕集効率が必要となる。一般的に濾材を構成する繊維径が細ければ細いほど、繊維１本の粒子捕集効率は良くなることが知られており、ナノ繊維をエアフィルタ用濾材に利用することは有効である。 Due to recent demands for finer electronics technology and reduced energy costs, further enhancement of air filter media is desired. In order to achieve high performance of the air filter media, lower pressure loss and higher collection efficiency are required. In general, it is known that the smaller the diameter of the fiber constituting the filter medium, the better the particle collection efficiency of one fiber, and it is effective to use nanofibers as a filter medium for air filters.
ナノ繊維の製造方法の一つとして、静電紡糸法（エレクトロスピニング法）がある。静電紡糸法とは、ポリマーの溶液に高電圧をかけて紡糸することによって、繊維径が１μｍ未満のナノ繊維を容易に作製することができる方法である。 One method for producing nanofibers is an electrostatic spinning method (electrospinning method). The electrospinning method is a method by which nanofibers having a fiber diameter of less than 1 μm can be easily produced by spinning a polymer solution under high voltage.
静電紡糸法によるナノ繊維を用いた高性能エアフィルタ用濾材として、アルミニウム板上に直にナノ繊維層だけを堆積させて作製した高性能エアフィルタ用濾材が提案されている（例えば、特許文献１を参照。）。また、通気性を有する支持体の表面に、粒子を分散したポリマー溶液を静電紡糸してナノ繊維層を設けたエアフィルタ用濾材が提案されている（例えば、特許文献２を参照。）。 As a filter medium for high-performance air filters using nanofibers by electrostatic spinning, a filter medium for high-performance air filters produced by depositing only a nanofiber layer directly on an aluminum plate has been proposed (for example, patent literature) 1). There has also been proposed an air filter medium in which a nanofiber layer is provided by electrostatic spinning of a polymer solution in which particles are dispersed on the surface of a support having air permeability (see, for example, Patent Document 2).
しかし、特許文献１に記載の方法ではアルミニウム板上に直にナノ繊維層だけを堆積させているため、堆積後の取り扱いにおいて、ナノ繊維の脱落又は破損が生じやすいといった強度面での問題がある。従って、特許文献２のエアフィルタ用濾材のように、通気性を有する支持体の表面に静電紡糸によるナノ繊維層を設けることが理想的であるが、このようなエアフィルタ用濾材においても、更なる低圧力損失化及び高捕集効率化が求められている。本発明は、支持体上に、静電紡糸法によるナノ繊維層を設けたエアフィルタ用濾材において、低圧力損失及び高捕集効率のエアフィルタ用濾材を提供することを課題とする。 However, in the method described in Patent Document 1, since only the nanofiber layer is deposited directly on the aluminum plate, there is a problem in strength that nanofibers are likely to fall off or break in handling after deposition. . Therefore, it is ideal to provide a nanofiber layer by electrostatic spinning on the surface of a support having air permeability, like the filter medium for air filter of Patent Document 2, but in such a filter medium for air filter, There is a need for further lower pressure loss and higher collection efficiency. An object of the present invention is to provide an air filter medium having a low pressure loss and a high collection efficiency in an air filter medium having a nanofiber layer formed by electrostatic spinning on a support.
上記課題を解決するため鋭意検討した結果、同一のナノ繊維層を使用しても、支持体の平均孔径の違いによってエアフィルタ用濾材のフィルタ性能が違うこと、フィルタ性能がより高くなる支持体の孔径が存在することを見出した。 As a result of intensive studies to solve the above problems, even when the same nanofiber layer is used, the filter performance of the filter medium for the air filter is different due to the difference in the average pore diameter of the support, and the support with higher filter performance. It was found that there was a pore size.
すなわち、本発明に係るエアフィルタ用濾材は、支持体と、該支持体上に静電紡糸法を用いて形成された、ナノ繊維からなるナノ繊維層とを有するエアフィルタ用濾材であり、前記支持体の平均孔径が１５〜３５μｍ、前記支持体は平均繊維径が０．６５〜９．０μｍのガラス繊維を含有し、前記ナノ繊維層の目付質量が０．２〜２．５ｇ／ｍ２、前記ナノ繊維層の密度が０．０１５〜０．０４５ｇ／ｃｍ３、前記ナノ繊維の平均繊維径が２５０ｎｍ以下であり、ＪＩＳ Ｂ ９９０８：２０１１「換気用エアフィルタユニット・換気用電気集じん器の性能試験方法」に記載された除電処理である「（２）ＩＰＡ飽和蒸気曝露法」に準拠して除電処理した後における、数１の式により示される対象粒子径０．３μｍのＰＦ値が２０以上であることを特徴とする。除電処理後のＰＦ値が２０以上であることで、時間の経過とともに電荷が消失しても高い捕集効率を維持することができる。
本発明に係るエアフィルタ用濾材では、前記支持体に使用する主体繊維は、平均繊維径が５μｍ以上９．０μｍ以下の第１繊維と平均繊維径が１μｍを超え５μｍ未満の第２繊維とからなり、全繊維質量に対する前記第１繊維の配合率が０質量％を超え８０質量％未満であることが好ましい。本発明に係るエアフィルタ用濾材では、前記支持体に使用する主体繊維は、平均繊維径が５μｍ以上９．０μｍ以下の第１繊維と平均繊維径が０．６５μｍ以上１μｍ以下の第３繊維とからなり、全繊維質量に対する前記第１繊維の配合率が６０質量％以上９５質量％以下であることが好ましい。 From the filter medium for an air filter according to the present invention, main fiber to be used for the support has an average fiber diameter of the 9.0μm or less of the first fibers or 5μm average fiber diameter of the second fiber is less than 5μm exceed 1μm becomes, it is preferable that mixing ratio of the first fiber to the total mass of the fiber is less than 80 wt% more than 0 mass%. In the filter medium for an air filter according to the present invention, the main fibers used for the support are first fibers having an average fiber diameter of 5 μm to 9.0 μm and third fibers having an average fiber diameter of 0.65 μm to 1 μm. It is preferable that the blending ratio of the first fiber with respect to the total fiber mass is 60% by mass or more and 95% by mass or less.
本発明に係るエアフィルタ用濾材では、前記ナノ繊維の構成成分が、重量平均分子量１５万以上のポリアクリロニトリルであることが好ましい。通風時のナノ繊維層の空隙を維持することができる。 In the air filter medium according to the present invention, the constituent component of the nanofiber is preferably polyacrylonitrile having a weight average molecular weight of 150,000 or more. The voids of the nanofiber layer during ventilation can be maintained.
本発明によれば、支持体上に静電紡糸法によるナノ繊維層を有する、低圧力損失で高捕集効率なエアフィルタ用濾材を提供することができる。 ADVANTAGE OF THE INVENTION According to this invention, the filter medium for air filters which has the nanofiber layer by an electrospinning method on a support body, and is a low pressure loss and high collection efficiency can be provided.
次に、本発明について実施形態を示して詳細に説明するが、本発明はこれらの記載に限定して解釈されない。本発明の効果を奏する限り、実施形態は種々の変形をしてもよい。 Next, the present invention will be described in detail with reference to embodiments, but the present invention is not construed as being limited to these descriptions. As long as the effect of the present invention is exhibited, the embodiment may be variously modified.
本実施形態に係るエアファイルタ用濾材は、支持体と、支持体上に静電紡糸法を用いて形成された、ナノ繊維からなるナノ繊維層とを有するが、支持体の平均孔径、ナノ繊維層の目付質量、ナノ繊維層の密度及びナノ繊維層に含まれるナノ繊維の繊維径を、それぞれ一定の範囲とすることで、低圧力損失で高捕集効率なエアフィルタ用濾材とするものである。 The air filter filter medium according to the present embodiment has a support and a nanofiber layer made of nanofibers formed on the support by using an electrospinning method. A filter medium for air filters with low pressure loss and high collection efficiency by keeping the weight per unit area of the fiber layer, the density of the nanofiber layer, and the fiber diameter of the nanofiber contained in the nanofiber layer within a certain range. It is.
本発明に用いる支持体としては、実用上十分な強度を有していること、静電紡糸用の装置に設置可能なシート状であること及びエアフィルタ用濾材としての性能を損なわないように高い通気性を有していることが必要である。従って、本発明に用いる支持体としては、例えば、紙、不織布、織布などの多孔質の繊維シートを用いる。 The support used in the present invention has a practically sufficient strength, is a sheet that can be installed in an apparatus for electrospinning, and is high so as not to impair the performance as a filter material for an air filter. It must be breathable. Accordingly, as the support used in the present invention, for example, a porous fiber sheet such as paper, nonwoven fabric, or woven fabric is used.
支持体の平均孔径は１５〜３５μｍの範囲とする。ナノ繊維層のナノ繊維の平均繊維径及びナノ繊維層の目付質量を同一条件として比較した場合、理由は定かでないが、支持体の平均孔径がこの範囲内であるときに低圧力損失であり高捕集効率といったフィルタ性能が向上する。支持体の平均孔径が１５μｍより小さいと圧力損失が高くなりやすい傾向がある。逆に支持体の平均孔径が３５μｍよりも大きいと支持体の大きい孔径内にナノ繊維が入り込みやすくなり、支持体の孔を詰まらせたり、ナノ繊維の脱落を起こしたりするためか、低圧力損失であり高捕集効率といったフィルタ性能が低下してしまう。支持体の平均孔径は、１８〜３０μｍであることがより好ましい。支持体の平均孔径は、例えば、細孔径分布測定装置（パームポロメーター）を用いて測定できる。 The average pore diameter of the support is in the range of 15 to 35 μm. When the average fiber diameter of the nanofiber layer and the mass per unit area of the nanofiber layer are compared under the same conditions, the reason is not clear, but when the average pore diameter of the support is within this range, low pressure loss and high Filter performance such as collection efficiency is improved. If the average pore diameter of the support is less than 15 μm, the pressure loss tends to increase. Conversely, if the average pore diameter of the support is larger than 35 μm, the nanofibers will easily enter the large pore diameter of the support, which may clog the holes in the support or cause the nanofibers to drop, or low pressure loss. Therefore, filter performance such as high collection efficiency is deteriorated. The average pore diameter of the support is more preferably 18 to 30 μm. The average pore diameter of the support can be measured using, for example, a pore diameter distribution measuring device (palm porometer).
支持体の平均孔径は、例えば、使用する繊維の繊維径、配合率又は目付質量を調整することによってコントロールすることができる。支持体の平均孔径は、繊維径の大きい繊維（例えば、平均繊維径が５μｍ以上）を多く配合するほど、また、目付質量を小さくするほど大きくなる傾向となる。逆に、繊維径の小さい繊維（例えば、平均繊維径が１μｍ以下）を多く配合するほど、また、目付質量を高くするほど支持体の平均孔径は小さくなる傾向となる。支持体に使用する繊維の配合率の好ましい形態例としては、例えば、支持体が繊維径の大きい繊維（例えば、平均繊維径が５μｍ以上）及び繊維径の中程度の繊維（例えば、平均繊維径が１μｍを超え５μｍ未満）からなるとき、全繊維質量に対する繊維径の大きい繊維の配合率が０質量％を超え８０質量％未満であることが好ましく、２０質量％以上７０質量％以下であることがより好ましい。また、支持体が繊維径の大きい繊維（例えば、平均繊維径が５μｍ以上）及び繊維径の小さい繊維（例えば、平均繊維径が１μｍ以下）からなるとき、全繊維質量に対する繊維径の大きい繊維の配合率は、６０質量％以上９５質量％以下であることが好ましく、６５質量％以上９０質量％以下であることがより好ましい。 The average pore diameter of the support can be controlled, for example, by adjusting the fiber diameter, blending ratio, or basis weight of the fibers used. The average pore diameter of the support tends to increase as the number of fibers having a large fiber diameter (for example, the average fiber diameter is 5 μm or more) is increased and the basis weight decreases. Conversely, the more the fibers having a smaller fiber diameter (for example, the average fiber diameter is 1 μm or less) are added, and the average pore diameter of the support tends to be smaller as the basis weight is increased. As a preferable example of the mixing ratio of the fibers used for the support, for example, the support is a fiber having a large fiber diameter (for example, an average fiber diameter of 5 μm or more) and a medium fiber (for example, an average fiber diameter). Is more than 1 μm and less than 5 μm), the blending ratio of the fiber having a large fiber diameter with respect to the total fiber mass is preferably more than 0% by mass and less than 80% by mass, and 20% by mass or more and 70% by mass or less. Is more preferable. In addition, when the support is composed of fibers having a large fiber diameter (for example, an average fiber diameter of 5 μm or more) and fibers having a small fiber diameter (for example, an average fiber diameter of 1 μm or less), The blending ratio is preferably 60% by mass or more and 95% by mass or less, and more preferably 65% by mass or more and 90% by mass or less.
支持体の目付質量は特に限定するものではないが、目付質量が少なすぎると支持体の強度の低下が生じ、濾材加工時での強度不足となる場合がある。また、目付質量が多すぎると、濾材全体の厚みが大きくなりすぎ、エアフィルタユニット加工後での構造圧損が高くなる問題となる場合がある。従って、支持体の目付質量は１０〜１００ｇ／ｍ２とすることが好ましい。支持体の目付質量は、より好ましくは２０〜９０ｇ／ｍ２である。 The mass per unit area of the support is not particularly limited. However, if the mass per unit area is too small, the strength of the support may be lowered, and the strength during processing of the filter medium may be insufficient. Moreover, when there are too many basis weights, the thickness of the whole filter medium will become large too much, and the structure pressure loss after an air filter unit process may become a problem which becomes high. Therefore, the basis weight of the support is preferably 10 to 100 g / m 2 . The weight per unit area of the support is more preferably 20 to 90 g / m 2 .
支持体を構成する主体繊維の種類については、例えば、ガラス繊維などの無機繊維、ポリエステル繊維、アクリル繊維、セルロース繊維、再生セルロース繊維、ポリアミド繊維、ポリエチレン繊維などの有機主体繊維、又はパルプ繊維であり、これらを単独で又は２種類以上を混合して使用してもよい。また、芯鞘繊維、全融繊維なども使用できる。ここで用いる主体繊維の平均繊維径は特に限定するものではないが、０．６５〜９．０μｍの範囲であることが好ましい。主体繊維の平均繊維径は、より好ましくは０．６５〜６．０μｍである。平均繊維径が０．６５μｍ未満では、支持体の平均孔径を前述の範囲にするためには目付質量を極端に少なくする必要があり、支持体の強度が低くなるおそれがある。また、平均繊維径が９．０μｍより大きいと支持体の平均孔径を前述の範囲にするためには目付質量を極端に多くする必要があり、濾材全体の厚みが大きくなりすぎ、エアフィルタユニット加工後での構造圧損が高くなるおそれがある。主体繊維の平均繊維径は、次に従って測定する。エアフィルタ用濾材の支持体側の表面を、例えば電界放出型走査電子顕微鏡を用いて観察し、視野をずらした４箇所について観察画像を得る。観察の倍率は、１枚の画像中に繊維が６０〜１００本存在する条件を満たす倍率とする。得られた４枚の観察画像について、すべての繊維の繊維径を計測する。計測した値を大きい順に並べて、上位５％、下位５％となる値を除き、残った値の平均値を求め、平均繊維径とする。 The types of main fibers constituting the support are, for example, inorganic fibers such as glass fibers, polyester fibers, acrylic fibers, cellulose fibers, regenerated cellulose fibers, polyamide fibers, polyethylene fibers, and other organic main fibers, or pulp fibers. These may be used alone or in admixture of two or more. Moreover, a core-sheath fiber, a total melt fiber, etc. can also be used. The average fiber diameter of the main fibers used here is not particularly limited, but is preferably in the range of 0.65 to 9.0 μm. The average fiber diameter of the main fibers is more preferably 0.65 to 6.0 μm. When the average fiber diameter is less than 0.65 μm, it is necessary to extremely reduce the mass per unit area in order to make the average pore diameter of the support within the above range, and the strength of the support may be lowered. Also, if the average fiber diameter is larger than 9.0 μm, it is necessary to extremely increase the mass per unit area in order to make the average pore diameter of the support within the above-mentioned range, the thickness of the entire filter medium becomes too large, and the air filter unit is processed. Later structural pressure loss may be high. The average fiber diameter of the main fiber is measured according to the following. The surface on the support side of the filter medium for air filter is observed using, for example, a field emission scanning electron microscope, and observation images are obtained at four locations where the fields of view are shifted. The magnification for observation is a magnification that satisfies the condition that 60 to 100 fibers are present in one image. The fiber diameters of all the fibers are measured for the obtained four observation images. The measured values are arranged in descending order, and the average value of the remaining values is obtained by excluding the upper 5% and lower 5% values, and the average fiber diameter is obtained.
また、支持体には、強度付与のために、合成樹脂バインダー又はバインダー繊維などを使用してもよい。合成樹脂バインダーとしては、例えば、アクリル系ラテックス、ＮＢＲ系ラテックス、酢ビ系ラテックス、オレフィン系ラテックス、ポリビニール系ラテックスであり、これらを単独又は２種類以上で用いることができる。また、本発明の目的とする効果を損なわない範囲で、撥水剤、難燃剤、その他薬剤を合成樹脂バインダーに添加して使用しても差し支えない。バインダー繊維は、主体繊維よりも融点の低い（例えば８０℃〜１６０℃）の合成繊維であり、例えば、ポリエチレン繊維、変性ポリエステル繊維、芯鞘合成繊維、ポリビニルアルコール（ＰＶＡ）繊維であり、これらを単独又は２種以上で用いることができる。 Moreover, you may use a synthetic resin binder or a binder fiber for a support body for intensity | strength provision. Examples of the synthetic resin binder include acrylic latex, NBR latex, vinyl acetate latex, olefin latex, and polyvinyl latex, and these can be used alone or in combination of two or more. In addition, a water repellent, a flame retardant, and other chemicals may be added to the synthetic resin binder and used as long as the effects of the present invention are not impaired. The binder fiber is a synthetic fiber having a melting point lower than that of the main fiber (for example, 80 ° C. to 160 ° C.), such as polyethylene fiber, modified polyester fiber, core-sheath synthetic fiber, and polyvinyl alcohol (PVA) fiber. It can be used alone or in combination of two or more.
支持体の形成方法については、特に限定するものではなく、湿式法、乾式法、スパンボンド法、メルトブロー法などが利用できるが、支持体自体の均一性が高い方が濾材の均一性も良くなり、フィルタ性能も高くなるため、湿式法を用いることが好ましい。 The method for forming the support is not particularly limited, and wet methods, dry methods, spunbond methods, melt blow methods, etc. can be used, but the higher the uniformity of the support itself, the better the uniformity of the filter medium. Since the filter performance is also improved, it is preferable to use a wet method.
本発明においては、支持体上に静電紡糸法を用いてナノ繊維層を設ける。静電紡糸法とは、エレクトロスピニング法とも呼ばれ、繊維となるポリマーの溶液にプラスの高電圧を与え、これがアース又はマイナスに帯電したターゲットに向かってスプレーされる過程において繊維化を起こさせる方法であり、近年、ナノオーダーの繊維径を有するナノ繊維を製造する有効な方法として利用されている。ナノオーダーの繊維径とは、１ｎｍ以上１０００ｎｍ未満であり、本発明において、ナノ繊維とはこのようなナノオーダーの繊維径を有する極細繊維をいう。ナノ繊維の繊維径は、例えば、静電紡糸法における印加電圧、ターゲットドラムの回転数、ノズルとターゲット間の距離によって、適宜調整が可能である。ナノ繊維層は、支持体の一方の表面に設けるか、又は両面に設けてもよいが、ナノ繊維層の強度を考慮して、ナノ繊維層を支持体の一方の表面に設けることがより好ましい。 In the present invention, a nanofiber layer is provided on a support using an electrospinning method. Electrospinning method, also called electrospinning method, is a method in which a positive high voltage is applied to a polymer solution that becomes a fiber, and fiberization occurs in the process of being sprayed toward a grounded or negatively charged target. In recent years, it has been used as an effective method for producing nanofibers having a nano-order fiber diameter. The nano-order fiber diameter is 1 nm or more and less than 1000 nm. In the present invention, the nano fiber refers to an ultrafine fiber having such a nano-order fiber diameter. The fiber diameter of the nanofiber can be appropriately adjusted depending on, for example, the applied voltage in the electrostatic spinning method, the number of rotations of the target drum, and the distance between the nozzle and the target. The nanofiber layer may be provided on one surface of the support or may be provided on both surfaces, but it is more preferable to provide the nanofiber layer on one surface of the support in consideration of the strength of the nanofiber layer. .
本発明におけるナノ繊維層には前述のナノ繊維を用いるが、ナノ繊維層を構成するナノ繊維の平均繊維径は２５０ｎｍ以下とする。ナノ繊維の平均繊維径は、より好ましくは、２３０ｎｍ以下である。ナノ繊維の平均繊維径が２５０ｎｍより大きいとナノ繊維層の表面積が足りず十分な捕集効率が得られない。ナノ繊維の平均繊維径の下限は特に限定するものではないが、ナノ繊維層の強度を考慮すると、１０ｎｍ以上であることが好ましい。より好ましくは、５０ｎｍ以上である。ナノ繊維の平均繊維径は、次に従って測定する。エアフィルタ用濾材のナノ繊維層側の表面を、例えば電界放出型走査電子顕微鏡を用いて観察し、視野をずらした４箇所について観察画像を得る。このとき、観察画像中に節状の塊を有する繊維が含まれないようにする。また、観察の倍率は、１枚の画像中に繊維が６０〜１００本存在する条件を満たす倍率とする。観察画像では、現実には連続する１本の繊維であるのに、画像外で折り返されていて繊維が複数本であるかのようにみえる場合がある。本明細書では、繊維が画像外で連続しているか否かを問わず、画像中に現れている繊維の一端又は両端が画像のいずれかの辺に接している場合は、繊維が画像のいずれかの辺に接している部分で途切れているものとみなす。得られた４枚の観察画像について、すべての繊維の繊維径を計測する。計測した値を大きい順に並べて、上位５％、下位５％となる値を除き、残った値の平均値を求め、平均繊維径とする。ナノ繊維層の支持体側とは反対側の表面に、後述する不織布層が設けられている場合は、支持体又は不織布層を剥離してナノ繊維層の表面を剥き出しとした後、平均繊維径の測定を行う。 The nanofiber layer described above is used for the nanofiber layer in the present invention, and the average fiber diameter of the nanofibers constituting the nanofiber layer is 250 nm or less. The average fiber diameter of the nanofiber is more preferably 230 nm or less. If the average fiber diameter of the nanofibers is larger than 250 nm, the surface area of the nanofiber layer is insufficient and sufficient collection efficiency cannot be obtained. The lower limit of the average fiber diameter of the nanofiber is not particularly limited, but is preferably 10 nm or more in consideration of the strength of the nanofiber layer. More preferably, it is 50 nm or more. The average fiber diameter of the nanofiber is measured according to the following. The surface on the nanofiber layer side of the filter material for air filter is observed using, for example, a field emission scanning electron microscope, and observation images are obtained at four locations with different visual fields. At this time, the observation image is made not to include fibers having a knot-like lump. In addition, the magnification of observation is a magnification that satisfies the condition that 60 to 100 fibers are present in one image. In the observed image, although it is actually one continuous fiber, it may be folded outside the image and appear to be a plurality of fibers. In this specification, regardless of whether the fiber is continuous outside the image, if one or both ends of the fiber appearing in the image is in contact with either side of the image, the fiber is It is considered that it is broken at the part in contact with that side. The fiber diameters of all the fibers are measured for the obtained four observation images. The measured values are arranged in descending order, and the average value of the remaining values is obtained by excluding the upper 5% and lower 5% values, and the average fiber diameter is obtained. When the nonwoven fabric layer to be described later is provided on the surface opposite to the support side of the nanofiber layer, after peeling the support or the nonwoven fabric layer to expose the surface of the nanofiber layer, the average fiber diameter Measure.
ナノ繊維となるポリマーは、水又は有機溶媒などの溶媒に溶解できるものであれば、特に限定されるものではない。例えば、水に溶解可能なポリマーとしては、ポリビニルアルコール、ポリビニルピロリドン、セルロース誘導体などが挙げられる。また、有機溶媒に溶解可能なポリマーとしては、ポリアクリロニトリル、ポリウレタン、ナイロン、ポリエステルなどが挙げられる。本発明においては、これらのポリマーの中でも、重量平均分子量が１５万以上のポリアクリロニトリルを用いることが好ましい。ナノ繊維のポリマーの種類又は平均繊維径によっては、ナノ繊維の剛性が低くなることがあり、エアフィルタとしたときに通風時の圧力に負けてナノ繊維層の空隙を維持し難くなることがある。しかし、重量平均分子量が１５万以上のポリアクリロニトリルをナノ繊維とするポリマーに用いることによって、剛性の比較的高いナノ繊維を得ることができ、エアフィルタとしたときに通風時のナノ繊維層の空隙を維持しやすくなる。ポリアクリロニトリルの重量平均分子量は、より好ましくは３０万以上である。また、ポリアクリロニトリルの重量平均分子量の上限は、特に制限はないが、溶解度の点から１００万以下であることが好ましく、５０万以下であることがより好ましい。 The polymer that becomes the nanofiber is not particularly limited as long as it can be dissolved in a solvent such as water or an organic solvent. Examples of the polymer that can be dissolved in water include polyvinyl alcohol, polyvinyl pyrrolidone, and cellulose derivatives. Examples of the polymer that can be dissolved in an organic solvent include polyacrylonitrile, polyurethane, nylon, and polyester. In the present invention, among these polymers, it is preferable to use polyacrylonitrile having a weight average molecular weight of 150,000 or more. Depending on the polymer type or the average fiber diameter of the nanofiber, the rigidity of the nanofiber may be low, and when it is used as an air filter, it may be difficult to maintain the voids of the nanofiber layer under the pressure of ventilation. . However, by using a polyacrylonitrile having a weight average molecular weight of 150,000 or more as a polymer containing nanofibers, nanofibers having relatively high rigidity can be obtained. It becomes easy to maintain. The weight average molecular weight of polyacrylonitrile is more preferably 300,000 or more. The upper limit of the weight average molecular weight of polyacrylonitrile is not particularly limited, but is preferably 1,000,000 or less and more preferably 500,000 or less from the viewpoint of solubility.
本実施形態に係るエアフィルタ用濾材では、静電防止法で用いるポリマー溶液が粒子を含有しないことが好ましい。本実施形態に係るエアフィルタ用濾材は、静電防止法で用いるポリマー溶液が粒子を含有しなくても、支持体の平均孔径、ナノ繊維層の目付質量、ナノ繊維層の密度及びナノ繊維層に含まれるナノ繊維の繊維径を、それぞれ一定の範囲とすることで、低圧力損失化及び高捕集効率化を実現できる。 In the air filter medium according to the present embodiment, it is preferable that the polymer solution used in the antistatic method does not contain particles. Even if the polymer solution used in the antistatic method does not contain particles, the filter medium for an air filter according to the present embodiment has an average pore diameter of the support, a mass per unit area of the nanofiber layer, a density of the nanofiber layer, and a nanofiber layer. By making the fiber diameters of the nanofibers contained in each of a certain range, low pressure loss and high collection efficiency can be realized.
本発明において、支持体上に設けるナノ繊維層の目付質量は０．２〜２．５ｇ／ｍ２とする。ナノ繊維層の目付質量は、より好ましくは０．５〜２．０ｇ／ｍ２である。ナノ繊維層の目付質量が０．２ｇ／ｍ２より少ないと、ナノ繊維層におけるナノ繊維の絶対本数が不足して十分な捕集高効率を得ることができない。また、ナノ繊維層の目付質量が２．５ｇ／ｍ２よりも多いと圧力損失が高くなりすぎてしまう。ナノ繊維層の目付質量は、例えば紡糸時間によってコントロールする。紡糸時間を長くすると目付質量は大きくなり、時間を短くすると目付質量は小さくなる。ナノ繊維層の目付質量は、例えば、支持体とナノ繊維層との合計目付質量から支持体だけの目付質量を引いて求めることができる。また、支持体の目付質量が不明で、支持体とナノ繊維層とが一体となっているエアフィルタ用濾材のナノ繊維層の目付質量を測定するためには、（支持体＋ナノ繊維層）の目付質量からナノ繊維層のみを取り除いた後の支持体の目付質量を引き、その差の値をナノ繊維層目付質量として求めることができる。 In the present invention, the mass per unit area of the nanofiber layer provided on the support is 0.2 to 2.5 g / m 2 . The mass per unit area of the nanofiber layer is more preferably 0.5 to 2.0 g / m 2 . When the mass per unit area of the nanofiber layer is less than 0.2 g / m 2 , the absolute number of nanofibers in the nanofiber layer is insufficient, and sufficient collection efficiency cannot be obtained. On the other hand, if the mass per unit area of the nanofiber layer is more than 2.5 g / m 2 , the pressure loss becomes too high. The mass per unit area of the nanofiber layer is controlled by, for example, the spinning time. When the spinning time is lengthened, the mass per unit area increases, and when the time is shortened, the mass per unit area decreases. The basis weight of the nanofiber layer can be determined, for example, by subtracting the basis weight of only the support from the total basis weight of the support and the nanofiber layer. In order to measure the mass per unit area of the filter medium for air filter in which the mass of the support is unknown and the support and the nanofiber layer are integrated, (support + nanofiber layer) Subtracting the basis weight of the support after removing only the nanofiber layer from the basis weight, the difference value can be determined as the nanofiber layer basis weight.
本発明におけるナノ繊維層の密度は０．０１５〜０．０４５ｇ／ｃｍ３とする。ナノ繊維層の密度は、より好ましくは０．０２０〜０．０４０ｇ／ｃｍ３である。ナノ繊維層の密度が０．０１５ｇ／ｃｍ３より小さいとナノ繊維層自体の強度が低く、また、ナノ繊維層の剥離が発生し易くなる問題がある。また、ナノ繊維層の密度が０．０４５ｇ／ｃｍ３より高いと圧力損失が高くなりすぎてフィルタのフィルタ寿命が短くなってしまう。ナノ繊維層の密度は、例えば紡糸溶液の温度、ポリマーの分子量、紡糸溶液の固形分濃度、紡糸環境湿度などの各種紡糸条件によってコントロールすることができる。例えば、温度を低くすると密度は高くなり、温度を高くすると密度は低くなる。 The density of the nanofiber layer in the present invention is 0.015 to 0.045 g / cm 3 . The density of the nanofiber layer is more preferably 0.020 to 0.040 g / cm 3 . If the density of the nanofiber layer is less than 0.015 g / cm 3 , the strength of the nanofiber layer itself is low, and the nanofiber layer is liable to be peeled off. On the other hand, if the density of the nanofiber layer is higher than 0.045 g / cm 3 , the pressure loss becomes too high and the filter life of the filter is shortened. The density of the nanofiber layer can be controlled by various spinning conditions such as the temperature of the spinning solution, the molecular weight of the polymer, the solid content concentration of the spinning solution, and the spinning environment humidity. For example, when the temperature is lowered, the density is increased, and when the temperature is increased, the density is decreased.
本発明におけるエアフィルタ用濾材は、ＪＩＳ Ｂ ９９０８：２０１１「換気用エアフィルタユニット・換気用電気集じん器の性能試験方法」に記載された除電処理である「（２）ＩＰＡ飽和蒸気曝露法」に準拠して処理した後のフィルタ性能を示す指標であるＰＦ値が２０以上であることが好ましい。ＰＦ値は、より好ましくは２１．５以上である。静電紡糸法で製造されたナノ繊維はその製造法ゆえ、電荷を帯びた状態でナノ繊維層を形成するため、ナノ繊維層にはエレクトレット効果が働いている。そのため、静電紡糸法によって製造されたエアフィルタ用濾材は、一般的に初期捕集効率が非常に高く、使用初期では超高性能濾材となるが、時間の経過とともに電荷が消失するにつれて捕集効率が落ちていく問題があり信頼性に欠ける。電荷消失後のフィルタ性能を示す指標であるＰＦ値が２０以上であれば十分に高性能エアフィルタ用濾材であるといえる。 The filter medium for air filter in the present invention is “(2) IPA saturated vapor exposure method” which is a static elimination treatment described in JIS B 9908: 2011 “Performance test method of air filter unit for ventilation / electric dust collector for ventilation”. It is preferable that the PF value, which is an index indicating the filter performance after processing in accordance with, is 20 or more. The PF value is more preferably 21.5 or more. Since the nanofibers manufactured by the electrospinning method are manufactured, the nanofiber layer is formed in a charged state, and thus the electret effect works on the nanofiber layer. Therefore, the filter medium for air filters manufactured by the electrospinning method generally has a very high initial collection efficiency, and becomes an ultra-high performance filter medium in the initial stage of use. There is a problem that efficiency decreases and it is not reliable. If the PF value, which is an index indicating the filter performance after charge loss, is 20 or more, it can be said that the filter medium is sufficiently high-performance air filter.
本実施形態に係るエアフィルタ用濾材にはナノ繊維層の保護を目的として、圧力損失の低い不織布層などを貼り合わせても問題はない。不織布層の圧力損失は、３５Ｐａ以下であることが好ましく、３０Ｐａ以下であることがより好ましい。また貼り合せの方法としては特に限定はしないが、一部又は全量に熱融着繊維を使用した不織布をドライヤーや熱風乾燥にてナノ繊維層側に貼り付ける方法がある。 For the purpose of protecting the nanofiber layer, there is no problem even if the nonwoven fabric layer having a low pressure loss is bonded to the air filter medium according to the present embodiment. The pressure loss of the nonwoven fabric layer is preferably 35 Pa or less, and more preferably 30 Pa or less. Further, the bonding method is not particularly limited, and there is a method in which a non-woven fabric using heat-bonded fibers in part or in whole is bonded to the nanofiber layer side by a dryer or hot air drying.
本実施形態に係るエアフィルタ用濾材は、エアフィルタとするとき、１枚だけで使用するか、又は２枚以上を重ね合わせて使用してもよい。２枚以上を重ね合わせて使用するときは、支持体層とナノ繊維層とが交互に配置されるように重ねることが好ましい。また、重ね合わせたエアフィルタ用濾材同士は、接着しないことが好ましい。 When the air filter medium according to the present embodiment is used as an air filter, only one sheet may be used, or two or more sheets may be used in an overlapping manner. When two or more sheets are used in an overlapped manner, it is preferable that the support layers and the nanofiber layers are stacked alternately. Moreover, it is preferable that the overlapped air filter media are not bonded to each other.
次に、実施例を挙げて本発明をより具体的に説明するが、本発明はこれら実施例に限定されるものではない。なお、添加部数は、固形分換算の値である。 Next, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples. The number of added parts is a value in terms of solid content.
＜実施例１＞
（支持体の製作）
平均繊維径２．６μｍのガラス繊維９９．３質量部及び繊維状ＰＶＡバインダー（商品名：ＳＰＧ０５６−１１、クラレ社製）０．７質量部を配合し、パルパーにてｐＨ３．０に調整した水中に離解後、抄紙機にて抄紙し、１２０℃の多筒式ドライヤーで乾燥して、目付質量６３．８ｇ／ｍ２の支持体を得た。
（ナノ繊維構造体の製作）
得られた支持体を静電紡糸法シート製造装置（商品名：ＮＵＥナノファイバーエレクトロスピニングユニット、カトーテック社製）のターゲットドラムに設置した。次いで、分子量３０万のポリアクリロニトリル樹脂をＮ，Ｎ‐ジメチルホルムアミド溶媒に溶解させ、該樹脂の固形分濃度が４．０質量％のポリマー溶液を得た。このポリマー溶液をノズルがセットされたシリンジに入れ、前記ターゲットドラムに設置した支持体上に静電紡糸を行い、目付質量１．２ｇ／ｍ２のナノ繊維層を形成した。この時の静電紡糸条件は、紡糸環境湿度５０％ＲＨ、溶液紡糸温度を２５℃、印加電圧２０ｋＶ、ターゲットドラム回転速度６ｍ／分、ノズルーターゲット間距離１５ｃｍとした。こうして、支持体の一方の面に目付質量１．２ｇ／ｍ２のナノ繊維層を設け、エアフィルタ用濾材を得た。
<Example 1>
(Production of support)
Underwater adjusted to pH 3.0 with a pulper containing 99.3 parts by weight of glass fibers having an average fiber diameter of 2.6 μm and 0.7 parts by weight of fibrous PVA binder (trade name: SPG056-11, manufactured by Kuraray Co., Ltd.) After disaggregation, the paper was made with a paper machine and dried with a multi-cylinder dryer at 120 ° C. to obtain a support having a basis weight of 63.8 g / m 2 .
(Production of nanofiber structure)
The obtained support was placed on a target drum of an electrospinning method sheet manufacturing apparatus (trade name: NUE nanofiber electrospinning unit, manufactured by Kato Tech Co., Ltd.). Next, a polyacrylonitrile resin having a molecular weight of 300,000 was dissolved in an N, N-dimethylformamide solvent to obtain a polymer solution having a solid content concentration of 4.0% by mass. This polymer solution was put into a syringe in which a nozzle was set, and electrospinning was performed on a support placed on the target drum to form a nanofiber layer having a basis weight of 1.2 g / m 2 . Electrospinning conditions at this time were as follows: spinning environment humidity 50% RH, solution spinning temperature 25 ° C., applied voltage 20 kV, target drum rotation speed 6 m / min, and nozzle-target distance 15 cm. In this way, a nanofiber layer having a basis weight of 1.2 g / m 2 was provided on one surface of the support to obtain a filter medium for air filter.
＜実施例２＞
（支持体の製作）
実施例１と同様にして、目付質量６３．８ｇ／ｍ２の支持体を得た。
（ナノ繊維構造体の製作）
紡糸溶液温度を２８℃とした以外は実施例１と同様にして、エアフィルタ用濾材を得た。
<Example 2>
(Production of support)
In the same manner as in Example 1, a support having a basis weight of 63.8 g / m 2 was obtained.
(Production of nanofiber structure)
An air filter medium was obtained in the same manner as in Example 1 except that the spinning solution temperature was 28 ° C.
＜実施例３＞
（支持体の製作）
実施例１と同様にして、目付質量６３．８ｇ／ｍ２の支持体を得た。
（ナノ繊維構造体の製作）
分子量３０万のポリアクリロニトリル樹脂をＮ，Ｎ‐ジメチルホルムアミド溶媒に溶解させ、該樹脂の固形分濃度が４．５質量％のポリマー溶液とし、紡糸環境湿度を５０％ＲＨ、紡糸溶液温度を３２℃とした以外は実施例１と同様にして、エアフィルタ用濾材を得た。
<Example 3>
(Production of support)
In the same manner as in Example 1, a support having a basis weight of 63.8 g / m 2 was obtained.
(Production of nanofiber structure)
A polyacrylonitrile resin having a molecular weight of 300,000 is dissolved in an N, N-dimethylformamide solvent to form a polymer solution having a solid content concentration of 4.5% by mass, a spinning environment humidity of 50% RH, and a spinning solution temperature of 32 ° C. Except that, an air filter medium was obtained in the same manner as in Example 1.
＜実施例４＞
（支持体の製作）
平均繊維径２．６μｍのガラス繊維５８質量部、平均繊維径５．５μｍのガラス繊維４１．３質量部及び繊維状ＰＶＡバインダー（商品名：ＳＰＧ０５６−１１、クラレ社製）０．７質量部を配合した以外は実施例１と同様にして、目付質量６４．１ｇ／ｍ２の支持体を得た。
（ナノ繊維構造体の製作）
分子量３０万のポリアクリロニトリル樹脂をＮ，Ｎ‐ジメチルホルムアミド溶媒に溶解させ、該樹脂の固形分濃度が３．５質量％のポリマー溶液とし、紡糸環境湿度を４５％ＲＨ、紡糸溶液温度を２９℃とした以外は実施例１と同様にして、エアフィルタ用濾材を得た。
<Example 4>
(Production of support)
58 parts by mass of glass fibers having an average fiber diameter of 2.6 μm, 41.3 parts by mass of glass fibers having an average fiber diameter of 5.5 μm, and 0.7 parts by mass of a fibrous PVA binder (trade name: SPG056-11, manufactured by Kuraray Co., Ltd.) A support having a mass per unit area of 64.1 g / m 2 was obtained in the same manner as Example 1 except for the blending.
(Production of nanofiber structure)
A polyacrylonitrile resin having a molecular weight of 300,000 is dissolved in a N, N-dimethylformamide solvent to obtain a polymer solution having a solid content concentration of 3.5% by mass, a spinning environment humidity of 45% RH, and a spinning solution temperature of 29 ° C. Except that, an air filter medium was obtained in the same manner as in Example 1.
＜実施例５＞
（支持体の製作）
実施例４と同様にして、目付質量６４．１ｇ／ｍ２の支持体を得た。
（ナノ繊維構造体の製作）
分子量３０万のポリアクリロニトリル樹脂をＮ，Ｎ‐ジメチルホルムアミド溶媒に溶解させ、該樹脂の固形分濃度が３．５質量％のポリマー溶液とし、紡糸環境湿度を４５％ＲＨ、溶液紡糸温度を２６℃とした以外は実施例１と同様にして、エアフィルタ用濾材を得た。
<Example 5>
(Production of support)
In the same manner as in Example 4, a support having a basis weight of 64.1 g / m 2 was obtained.
(Production of nanofiber structure)
A polyacrylonitrile resin having a molecular weight of 300,000 is dissolved in an N, N-dimethylformamide solvent to obtain a polymer solution having a solid content concentration of 3.5% by mass, a spinning environment humidity of 45% RH, and a solution spinning temperature of 26 ° C. Except that, an air filter medium was obtained in the same manner as in Example 1.
＜実施例６＞
（支持体の製作）
実施例４と同様にして、目付質量６４．１ｇ／ｍ２の基材を得た。
（ナノ繊維構造体の製作）
実施例２と同様にして、エアフィルタ用濾材を得た。
<Example 6>
(Production of support)
In the same manner as in Example 4, a substrate having a basis weight of 64.1 g / m 2 was obtained.
(Production of nanofiber structure)
In the same manner as in Example 2, a filter medium for air filter was obtained.
＜実施例７＞
（支持体の製作）
実施例４と同様にして、目付質量６４．１ｇ／ｍ２の支持体を得た。
（ナノ繊維構造体の製作）
実施例１と同様にして、エアフィルタ用濾材を得た。
<Example 7>
(Production of support)
In the same manner as in Example 4, a support having a basis weight of 64.1 g / m 2 was obtained.
(Production of nanofiber structure)
In the same manner as in Example 1, an air filter medium was obtained.
＜実施例８＞
（支持体の製作）
実施例４と同様にして、目付質量６４．１ｇ／ｍ２の支持体を得た。
（ナノ繊維構造体の製作）
実施例３と同様にして、エアフィルタ用濾材を得た。
<Example 8>
(Production of support)
In the same manner as in Example 4, a support having a basis weight of 64.1 g / m 2 was obtained.
(Production of nanofiber structure)
In the same manner as in Example 3, a filter medium for air filter was obtained.
＜実施例９＞
（支持体の製作）
実施例４と同様にして、目付質量６４．１ｇ／ｍ２の支持体を得た。
（ナノ繊維構造体の製作）
分子量３０万のポリアクリロニトリル樹脂をＮ，Ｎ‐ジメチルホルムアミド溶媒に溶解させ、該樹脂の固形分濃度が４．５質量％のポリマー溶液とし、紡糸環境湿度を５５％ＲＨ、紡糸溶液温度を３２℃とした以外は実施例１と同様にして、エアフィルタ用濾材を得た。
<Example 9>
(Production of support)
In the same manner as in Example 4, a support having a basis weight of 64.1 g / m 2 was obtained.
(Production of nanofiber structure)
A polyacrylonitrile resin having a molecular weight of 300,000 is dissolved in a N, N-dimethylformamide solvent to form a polymer solution having a solid content concentration of 4.5% by mass, a spinning environment humidity of 55% RH, and a spinning solution temperature of 32 ° C. Except that, an air filter medium was obtained in the same manner as in Example 1.
＜実施例１０＞
（支持体の製作）
平均繊維径２．６μｍのガラス繊維２０質量部、平均繊維径５．５μｍのガラス繊維７９．３質量部及び繊維状ＰＶＡバインダー（商品名：ＳＰＧ０５６−１１、クラレ社製）０．７質量部を配合した以外は実施例１と同様にして、目付質量６３．８ｇ／ｍ２の支持体を得た。
（ナノ繊維構造体の製作）
実施例１と同様にして、エアフィルタ用濾材を得た。
<Example 10>
(Production of support)
20 parts by mass of glass fibers having an average fiber diameter of 2.6 μm, 79.3 parts by mass of glass fibers having an average fiber diameter of 5.5 μm, and 0.7 parts by mass of a fibrous PVA binder (trade name: SPG056-11, manufactured by Kuraray Co., Ltd.) A support having a mass per unit area of 63.8 g / m 2 was obtained in the same manner as in Example 1 except that it was blended.
(Production of nanofiber structure)
In the same manner as in Example 1, an air filter medium was obtained.
＜実施例１１＞
（支持体の製作）
実施例１０と同様にして、目付質量６３．８ｇ／ｍ２の支持体を得た。
（ナノ繊維構造体の製作）
実施例２と同様にして、エアフィルタ用濾材を得た。
<Example 11>
(Production of support)
In the same manner as in Example 10, a support having a basis weight of 63.8 g / m 2 was obtained.
(Production of nanofiber structure)
In the same manner as in Example 2, a filter medium for air filter was obtained.
＜実施例１２＞
（支持体の製作）
実施例１０と同様にして、目付質量６３．８ｇ／ｍ２の支持体を得た。
（ナノ繊維構造体の製作）
実施例９と同様にして、エアフィルタ用濾材を得た。
<Example 12>
(Production of support)
In the same manner as in Example 10, a support having a basis weight of 63.8 g / m 2 was obtained.
(Production of nanofiber structure)
In the same manner as in Example 9, an air filter medium was obtained.
＜実施例１３＞
（支持体の製作）
実施例４と同様にして、目付質量６４．１ｇ／ｍ２の支持体を得た。
（ナノ繊維構造体の製作）
支持体の一方の面に設けるナノ繊維層の目付質量を０．２ｇ／ｍ２に変更した以外は、実施例２と同様にしてエアフィルタ用濾材を得た。
<Example 13>
(Production of support)
In the same manner as in Example 4, a support having a basis weight of 64.1 g / m 2 was obtained.
(Production of nanofiber structure)
A filter medium for an air filter was obtained in the same manner as in Example 2 except that the mass per unit area of the nanofiber layer provided on one surface of the support was changed to 0.2 g / m 2 .
＜実施例１４＞
（支持体の製作）
実施例４と同様にして、目付質量６４．１ｇ／ｍ２の支持体を得た。
（ナノ繊維構造体の製作）
支持体の一方の面に設けるナノ繊維層の目付質量を０．６ｇ／ｍ２に変更した以外は、実施例２と同様にしてエアフィルタ用濾材を得た。
<Example 14>
(Production of support)
In the same manner as in Example 4, a support having a basis weight of 64.1 g / m 2 was obtained.
(Production of nanofiber structure)
A filter medium for an air filter was obtained in the same manner as in Example 2 except that the basis weight of the nanofiber layer provided on one surface of the support was changed to 0.6 g / m 2 .
＜実施例１５＞
（支持体の製作）
実施例４と同様にして、目付質量６４．１ｇ／ｍ２の支持体を得た。
（ナノ繊維構造体の製作）
支持体の一方の面に設けるナノ繊維層の目付質量を２．５ｇ／ｍ２に変更した以外は、実施例２と同様にしてエアフィルタ用濾材を得た。
<Example 15>
(Production of support)
In the same manner as in Example 4, a support having a basis weight of 64.1 g / m 2 was obtained.
(Production of nanofiber structure)
A filter medium for an air filter was obtained in the same manner as in Example 2 except that the mass per unit area of the nanofiber layer provided on one surface of the support was changed to 2.5 g / m 2 .
＜実施例１６＞
（支持体の製作）
平均繊維径０．６５μｍのガラス繊維３０質量部、平均繊維径５．５μｍのガラス繊維６９．５質量部及び繊維状ＰＶＡバインダー（商品名：ＳＰＧ０５６−１１、クラレ社製）０．５質量部を配合した以外は実施例１と同様にして、目付質量２７．５ｇ／ｍ２の支持体を得た。
（ナノ繊維構造体の製作）
実施例１と同様にして、エアフィルタ用濾材を得た。
<Example 16>
(Production of support)
30 parts by mass of glass fibers having an average fiber diameter of 0.65 μm, 69.5 parts by mass of glass fibers having an average fiber diameter of 5.5 μm, and 0.5 parts by mass of a fibrous PVA binder (trade name: SPG056-11, manufactured by Kuraray Co., Ltd.) A support having a weight per unit area of 27.5 g / m 2 was obtained in the same manner as in Example 1 except that it was blended.
(Production of nanofiber structure)
In the same manner as in Example 1, an air filter medium was obtained.
＜実施例１７＞
（支持体の製作）
平均繊維径０．６５μｍのガラス繊維１７質量部、平均繊維径５．５μｍのガラス繊維８２．５質量部及び繊維状ＰＶＡバインダー（商品名：ＳＰＧ０５６−１１、クラレ社製）０．５質量部を配合した以外は実施例１と同様にして、目付質量２７．６ｇ／ｍ２の支持体を得た。
（ナノ繊維構造体の製作）
実施例２と同様にして、エアフィルタ用濾材を得た。
<Example 17>
(Production of support)
17 parts by mass of glass fibers having an average fiber diameter of 0.65 μm, 82.5 parts by mass of glass fibers having an average fiber diameter of 5.5 μm, and 0.5 parts by mass of a fibrous PVA binder (trade name: SPG056-11, manufactured by Kuraray Co., Ltd.) A support having a mass per unit area of 27.6 g / m 2 was obtained in the same manner as in Example 1 except that it was blended.
(Production of nanofiber structure)
In the same manner as in Example 2, a filter medium for air filter was obtained.
＜実施例１８＞
（支持体の製作）
平均繊維径２．６μｍのガラス繊維９９．５質量部及び繊維状ＰＶＡバインダー（商品名：ＳＰＧ０５６−１１、クラレ社製）０．５質量部を配合し、パルパーにてｐＨ３．０に調整した水中に離解後、抄紙機にて抄紙し、１２０℃の多筒式ドライヤーで乾燥し、目付質量３１．１ｇ／ｍ２の支持体を得た。
（ナノ繊維構造体の製作）
実施例２と同様にして、エアフィルタ用濾材を得た。
<Example 18>
(Production of support)
Water containing 99.5 parts by mass of glass fibers having an average fiber diameter of 2.6 μm and 0.5 parts by mass of fibrous PVA binder (trade name: SPG056-11, manufactured by Kuraray Co., Ltd.) and adjusted to pH 3.0 with a pulper. After disaggregation, the paper was made with a paper machine and dried with a multi-cylinder dryer at 120 ° C. to obtain a support having a basis weight of 31.1 g / m 2 .
(Production of nanofiber structure)
In the same manner as in Example 2, a filter medium for air filter was obtained.
＜実施例１９＞
（支持体の製作）
平均繊維径２．６μｍのガラス繊維３０質量部、平均繊維径５．５μｍのガラス繊維３０質量部及び平均繊維径９．０μｍのチョップドガラス繊維４０質量部を、パルパーにてｐＨ３．０に調整した水中に離解後、抄紙機にて抄紙した。次いで、アクリルラテックス９０質量部（商品名：ボンコートＡＮ−１５５、ＤＩＣ社製）及びフッ素系撥水剤（商品名：ＮＫガードＳ−０９、日華化学工業社製）１０質量部の混合バインダー液に含浸し、エアーサクションにて余分なバインダー液の除去を行い、１２０℃の多筒式ドライヤーで乾燥し、目付質量７０．６ｇ／ｍ２の支持体を得た。混合バインダー液の固形分含浸量は支持体に対して５．５質量％であった。
（ナノ繊維構造体の製作）
実施例２と同様にして、エアフィルタ用濾材を得た。
<Example 19>
(Production of support)
30 parts by mass of glass fiber having an average fiber diameter of 2.6 μm, 30 parts by mass of glass fiber having an average fiber diameter of 5.5 μm, and 40 parts by mass of chopped glass fiber having an average fiber diameter of 9.0 μm were adjusted to pH 3.0 with a pulper. After disaggregation in water, paper was made with a paper machine. Next, 90 parts by mass of acrylic latex (trade name: Boncoat AN-155, manufactured by DIC Corporation) and 10 parts by mass of a mixed binder solution of fluorine-based water repellent (trade name: NK Guard S-09, manufactured by Nikka Chemical Co., Ltd.) The excess binder solution was removed by air suction, and dried with a multi-cylinder dryer at 120 ° C. to obtain a support having a basis weight of 70.6 g / m 2 . The solid content impregnation amount of the mixed binder liquid was 5.5% by mass with respect to the support.
(Production of nanofiber structure)
In the same manner as in Example 2, a filter medium for air filter was obtained.
＜実施例２０＞
（支持体の製作）
平均繊維径０．６５μｍのガラス繊維５質量部、平均繊維径２．６μｍのガラス繊維９４．５質量部及び繊維状ＰＶＡバインダー（商品名：ＳＰＧ０５６−１１、クラレ社製）０．５質量部を配合し、パルパーにてｐＨ３．０に調整した水中に離解後、抄紙機にて抄紙し、１２０℃の多筒式ドライヤーで乾燥し、目付質量２７．３ｇ／ｍ２の支持体を得た。
（ナノ繊維構造体の製作）
実施例１と同様にして、エアフィルタ用濾材を得た。
<Example 20>
(Production of support)
5 parts by mass of glass fibers having an average fiber diameter of 0.65 μm, 94.5 parts by mass of glass fibers having an average fiber diameter of 2.6 μm, and 0.5 parts by mass of a fibrous PVA binder (trade name: SPG056-11, manufactured by Kuraray Co., Ltd.) After mixing in water adjusted to pH 3.0 with a pulper, paper was made with a paper machine and dried with a multi-cylinder dryer at 120 ° C. to obtain a support having a basis weight of 27.3 g / m 2 .
(Production of nanofiber structure)
In the same manner as in Example 1, an air filter medium was obtained.
＜実施例２１＞
（支持体の製作）
実施例１８と同様にして、目付質量３１．１ｇ／ｍ２の支持体を得た。
（ナノ繊維構造体の製作）
支持体の一方の面に設けるナノ繊維層の目付質量を０．６ｇ／ｍ２に変更した以外は、実施例２と同様にしてエアフィルタ用濾材を得た。このエアフィルタ用濾材を２枚製作した。
（重ね合わせシート製作）
得られた２枚のエアフィルタ用濾材を、ナノ繊維層／支持体層／ナノ繊維層／支持体層となるように貼り合せせずに重ね合わせ、ナノ繊維層の総目付質量が１．２ｇ／ｍ２となる、重ね合わせ形態のエアフィルタ用濾材を得た。
<Example 21>
(Production of support)
In the same manner as in Example 18, a support having a basis weight of 31.1 g / m 2 was obtained.
(Production of nanofiber structure)
A filter medium for an air filter was obtained in the same manner as in Example 2 except that the basis weight of the nanofiber layer provided on one surface of the support was changed to 0.6 g / m 2 . Two filter media for the air filter were produced.
(Overlay sheet production)
The obtained two filter media for air filter were laminated without being bonded so as to be a nanofiber layer / support layer / nanofiber layer / support layer, and the total mass of the nanofiber layer was 1.2 g. A filter medium for an air filter in a superposed form with a / m 2 was obtained.
＜実施例２２＞
（支持体の作製）
実施例４と同様にして、目付質量６４．１ｇ／ｍ２の支持体を得た。
（ナノ繊維構造体の製作）
分子量１５万のポリアクリロニトリル樹脂をＮ，Ｎ‐ジメチルホルムアミド溶媒に溶解させ、該樹脂の固形分濃度が５．５質量％のポリマー溶液とし、紡糸環境湿度を４０％ＲＨ、紡糸溶液温度を２９℃とした以外は実施例１と同様にして、エアフィルタ用濾材を得た。
<Example 22>
(Production of support)
In the same manner as in Example 4, a support having a basis weight of 64.1 g / m 2 was obtained.
(Production of nanofiber structure)
A polyacrylonitrile resin having a molecular weight of 150,000 is dissolved in a N, N-dimethylformamide solvent to obtain a polymer solution having a solid content concentration of 5.5% by mass, a spinning environment humidity of 40% RH, and a spinning solution temperature of 29 ° C. Except that, an air filter medium was obtained in the same manner as in Example 1.
＜実施例２３＞
（支持体の製作）
実施例４と同様にして、目付質量６４．１ｇ／ｍ２の支持体を得た。
（ナノ繊維構造体の製作）
分子量６万のポリアクリロニトリル樹脂をＮ，Ｎ‐ジメチルホルムアミド溶媒に溶解させ、該樹脂の固形分濃度が５．８質量％のポリマー溶液とし、紡糸環境湿度を７０％ＲＨ、紡糸溶液温度を３２℃とした以外は実施例１と同様にして、エアフィルタ用濾材を得た。
<Example 23>
(Production of support)
In the same manner as in Example 4, a support having a basis weight of 64.1 g / m 2 was obtained.
(Production of nanofiber structure)
A polyacrylonitrile resin having a molecular weight of 60,000 is dissolved in a N, N-dimethylformamide solvent to obtain a polymer solution having a solid content concentration of 5.8% by mass, a spinning environment humidity of 70% RH, and a spinning solution temperature of 32 ° C. Except that, an air filter medium was obtained in the same manner as in Example 1.
＜実施例２４＞
（支持体の製作）
実施例４と同様にして、目付質量６４．１ｇ／ｍ２の支持体を得た。
（ナノ繊維構造体の製作）
分子量７．５万のポリビニルアルコール（ＰＶＡ）樹脂をＮ，Ｎ‐ジメチルホルムアミド溶媒に溶解させ、該樹脂の固形分濃度が８質量％のポリマー溶液とし、紡糸環境湿度を２０％ＲＨ、紡糸溶液温度を３０℃とし、支持体の一方の面に設けるナノ繊維層の目付質量を２．５ｇ／ｍ２とした以外は実施例１と同様にして、エアフィルタ用濾材を得た。
<Example 24>
(Production of support)
In the same manner as in Example 4, a support having a basis weight of 64.1 g / m 2 was obtained.
(Production of nanofiber structure)
Polyvinyl alcohol (PVA) resin having a molecular weight of 75,000 is dissolved in a N, N-dimethylformamide solvent to form a polymer solution having a solid content concentration of 8% by mass, the spinning environment humidity is 20% RH, and the spinning solution temperature. Was set to 30 ° C., and a filter medium for an air filter was obtained in the same manner as in Example 1 except that the mass per unit area of the nanofiber layer provided on one surface of the support was 2.5 g / m 2 .
＜実施例２５＞
（支持体の製作）
平均繊維径０．６５μｍのガラス繊維１０質量部、平均繊維径１２．４μｍ、平均繊維長５ｍｍのポリエステル繊維（商品名ＴＴ０４Ｎ、帝人ファイバー社製）５０質量部及び平均繊維径１３．０μｍ、平均繊維長５ｍｍの芯鞘複合型バインダー繊維（ポリエチレン／ポリエステル）（商品名：ＴＪ０４ＣＮ、帝人ファイバー社製）１０質量部を配合し、パルパーにてｐＨ３．０に調整した水中に離解後、抄紙機にて抄紙し、１２０℃の多筒式ドライヤーで乾燥して、目付質量９１．３ｇ／ｍ２の支持体を得た。
（ナノ繊維構造体の製作）
実施例２と同様にして、エアフィルタ用濾材を得た。
<Example 25>
(Production of support)
10 parts by mass of glass fiber with an average fiber diameter of 0.65 μm, 50 parts by mass of polyester fiber (trade name TT04N, manufactured by Teijin Fibers Ltd.) with an average fiber diameter of 12.4 μm and an average fiber length of 5 mm, an average fiber diameter of 13.0 μm, and an average fiber Blended 10 parts by weight of 5 mm long core-sheath composite binder fiber (polyethylene / polyester) (trade name: TJ04CN, manufactured by Teijin Fibers Ltd.), disaggregated in water adjusted to pH 3.0 with a pulper, and then on a paper machine. Paper was made and dried with a multi-cylinder dryer at 120 ° C. to obtain a support having a basis weight of 91.3 g / m 2 .
(Production of nanofiber structure)
In the same manner as in Example 2, a filter medium for air filter was obtained.
＜比較例１＞
（支持体の製作）
実施例１において、平均繊維径０．６５μｍのガラス繊維５０質量部、平均繊維径５．５μｍのガラス繊維４９．５質量部及び繊維状ＰＶＡバインダー（商品名：ＳＰＧ０５６−１１、クラレ社製）０．５質量部を使用した以外は実施例１と同様にして、目付質量２７．４ｇ／ｍ２の支持体を得た。
（ナノ繊維構造体の製作）
実施例２と同様にして、エアフィルタ用濾材を得た。
<Comparative Example 1>
(Production of support)
In Example 1, 50 parts by mass of glass fibers having an average fiber diameter of 0.65 μm, 49.5 parts by mass of glass fibers having an average fiber diameter of 5.5 μm, and a fibrous PVA binder (trade name: SPG056-11, manufactured by Kuraray Co., Ltd.) 0 A support having a basis weight of 27.4 g / m 2 was obtained in the same manner as in Example 1 except that 0.5 part by mass was used.
(Production of nanofiber structure)
In the same manner as in Example 2, a filter medium for air filter was obtained.
＜比較例２＞
（支持体の製作）
実施例１同様にして、目付質量６３．８ｇ／ｍ２の支持体を得た。
（ナノ繊維構造体の製作）
分子量３０万のポリアクリロニトリル樹脂をＮ，Ｎ‐ジメチルホルムアミド溶媒に溶解させ、該樹脂の固形分濃度が４．０質量％のポリマー溶液とし、紡糸環境湿度を５０％ＲＨ、紡糸溶液温度を２２℃とした以外は実施例１と同様にして、エアフィルタ用濾材を得た。
<Comparative example 2>
(Production of support)
In the same manner as in Example 1, a support having a basis weight of 63.8 g / m 2 was obtained.
(Production of nanofiber structure)
A polyacrylonitrile resin having a molecular weight of 300,000 is dissolved in a N, N-dimethylformamide solvent to form a polymer solution having a solid content concentration of 4.0% by mass, a spinning environment humidity of 50% RH, and a spinning solution temperature of 22 ° C. Except that, an air filter medium was obtained in the same manner as in Example 1.
＜比較例３＞
（支持体の製作）
実施例１同様にして、目付質量６３．８ｇ／ｍ２の支持体を得た。
（ナノ繊維構造体の製作）
分子量３０万のポリアクリロニトリル樹脂をＮ，Ｎ‐ジメチルホルムアミド溶媒に溶解させ、該樹脂の固形分濃度が４．５質量％のポリマー溶液とし、紡糸環境湿度を５０％ＲＨ、紡糸溶液温度を３４℃とした以外は実施例１と同様にして、エアフィルタ用濾材を得た。
<Comparative Example 3>
(Production of support)
In the same manner as in Example 1, a support having a basis weight of 63.8 g / m 2 was obtained.
(Production of nanofiber structure)
A polyacrylonitrile resin having a molecular weight of 300,000 is dissolved in a N, N-dimethylformamide solvent to obtain a polymer solution having a solid content concentration of 4.5% by mass, a spinning environment humidity of 50% RH, and a spinning solution temperature of 34 ° C. Except that, an air filter medium was obtained in the same manner as in Example 1.
＜比較例４＞
（支持体の製作）
実施例４と同様にして、目付質量６４．１ｇ／ｍ２の支持体を得た。
（ナノ繊維構造体の製作）
比較例２と同様にして、エアフィルタ用濾材を得た。
<Comparative example 4>
(Production of support)
In the same manner as in Example 4, a support having a basis weight of 64.1 g / m 2 was obtained.
(Production of nanofiber structure)
In the same manner as in Comparative Example 2, a filter medium for air filter was obtained.
＜比較例５＞
（支持体の製作）
実施例４と同様にして、目付質量６４．１ｇ／ｍ２の基材を得た。
（ナノ繊維構造体の製作）
分子量３０万のポリアクリロニトリル樹脂をＮ，Ｎ‐ジメチルホルムアミド溶媒に溶解させ、該樹脂の固形分濃度が４．５質量％のポリマー溶液とし、紡糸環境湿度を５５％ＲＨ、紡糸溶液温度を３４℃とした以外は実施例１と同様にして、エアフィルタ用濾材を得た。
<Comparative Example 5>
(Production of support)
In the same manner as in Example 4, a substrate having a basis weight of 64.1 g / m 2 was obtained.
(Production of nanofiber structure)
A polyacrylonitrile resin having a molecular weight of 300,000 is dissolved in a N, N-dimethylformamide solvent to obtain a polymer solution having a solid content concentration of 4.5% by mass, a spinning environment humidity of 55% RH, and a spinning solution temperature of 34 ° C. Except that, an air filter medium was obtained in the same manner as in Example 1.
＜比較例６＞
（支持体の製作）
実施例４と同様にして、目付質量６４．１ｇ／ｍ２の支持体を得た。
（ナノ繊維構造体の製作）
分子量３０万のポリアクリロニトリル樹脂をＮ，Ｎ‐ジメチルホルムアミド溶媒に溶解させ、該樹脂の固形分濃度が４．５質量％のポリマー溶液とし、紡糸環境湿度を６５％ＲＨ、紡糸溶液温度を３２℃とした以外は実施例１と同様にして、エアフィルタ用濾材を得た。
<Comparative Example 6>
(Production of support)
In the same manner as in Example 4, a support having a basis weight of 64.1 g / m 2 was obtained.
(Production of nanofiber structure)
A polyacrylonitrile resin having a molecular weight of 300,000 is dissolved in a N, N-dimethylformamide solvent to form a polymer solution having a solid content concentration of 4.5% by mass, a spinning environment humidity of 65% RH, and a spinning solution temperature of 32 ° C. Except that, an air filter medium was obtained in the same manner as in Example 1.
＜比較例７＞
（支持体の製作）
実施例１０と同様にして、目付質量６３．８ｇ／ｍ２の支持体を得た。
（ナノ繊維構造体の製作）
比較例２と同様にして、エアフィルタ用濾材を得た。
<Comparative Example 7>
(Production of support)
In the same manner as in Example 10, a support having a basis weight of 63.8 g / m 2 was obtained.
(Production of nanofiber structure)
In the same manner as in Comparative Example 2, a filter medium for air filter was obtained.
＜比較例８＞
（支持体の製作）
実施例１０と同様にして、目付質量６３．８ｇ／ｍ２の基材を得た。
（ナノ繊維構造体の製作）
比較例３と同様にして、エアフィルタ用濾材を得た。
<Comparative Example 8>
(Production of support)
In the same manner as in Example 10, a base material having a basis weight of 63.8 g / m 2 was obtained.
(Production of nanofiber structure)
In the same manner as in Comparative Example 3, a filter medium for air filter was obtained.
＜比較例９＞
（支持体の製作）
平均繊維径２．６μｍのガラス繊維８質量部、平均繊維径５．５μｍのガラス繊維９１．３質量部及び繊維状ＰＶＡバインダー（商品名：ＳＰＧ０５６−１１、クラレ社製）０．７質量部を使用した以外は実施例１と同様にして、目付質量６４．５ｇ／ｍ２の支持体を得た。
（ナノ繊維構造体の製作）
実施例２と同様にして、エアフィルタ用濾材を得た。
<Comparative Example 9>
(Production of support)
8 parts by mass of glass fibers having an average fiber diameter of 2.6 μm, 91.3 parts by mass of glass fibers having an average fiber diameter of 5.5 μm, and 0.7 parts by mass of a fibrous PVA binder (trade name: SPG056-11, manufactured by Kuraray Co., Ltd.) A support having a basis weight of 64.5 g / m 2 was obtained in the same manner as in Example 1 except that it was used.
(Production of nanofiber structure)
In the same manner as in Example 2, a filter medium for air filter was obtained.
＜比較例１０＞
（支持体の製作）
実施例４と同様にして、目付質量６４．１ｇ／ｍ２の支持体を得た。
（ナノ繊維構造体の製作）
支持体の一方の面に設けるナノ繊維層の目付質量を０．１ｇ／ｍ２に変更した以外は、実施例２と同様にしてエアフィルタ用濾材を得た。
<Comparative Example 10>
(Production of support)
In the same manner as in Example 4, a support having a basis weight of 64.1 g / m 2 was obtained.
(Production of nanofiber structure)
A filter medium for an air filter was obtained in the same manner as in Example 2 except that the basis weight of the nanofiber layer provided on one surface of the support was changed to 0.1 g / m 2 .
＜比較例１１＞
（支持体の製作）
実施例４と同様にして、目付質量６４．１ｇ／ｍ２の支持体を得た。
（ナノ繊維構造体の製作）
支持体の一方の面に設けるナノ繊維層の目付質量を３．０ｇ／ｍ２に変更した以外は、実施例２と同様にしてエアフィルタ用濾材を得た。
<Comparative Example 11>
(Production of support)
In the same manner as in Example 4, a support having a basis weight of 64.1 g / m 2 was obtained.
(Production of nanofiber structure)
A filter medium for an air filter was obtained in the same manner as in Example 2 except that the mass per unit area of the nanofiber layer provided on one surface of the support was changed to 3.0 g / m 2 .
各実施例及び比較例で得られたエアフィルタ用濾材の評価結果を表１に示す。表１中の評価は、以下の方法で行った。なお、各評価を行う前に、次に示す方法によりエアフィルタ用濾材の除電処理を行った。
＜除電処理＞
「換気用エアフィルタユニット・換気用電気集じん器の性能試験方法」に記載された除電処理である「（２）ＩＰＡ飽和蒸気曝露法」に準拠して除電処理を行った。
Table 1 shows the evaluation results of the air filter media obtained in the examples and comparative examples. Evaluation in Table 1 was performed by the following method. In addition, before performing each evaluation, the static elimination process of the filter medium for air filters was performed by the method shown next.
<Static removal treatment>
The static elimination treatment was performed in accordance with “(2) IPA saturated vapor exposure method” which is a static elimination treatment described in “Performance test method of ventilation air filter unit / ventilation electric dust collector”.
＜支持体の平均孔径＞
パームポロメータ−（Ｐｏｒｏｕｓ Ｍａｔｅｒｉａｌｓ社製 Ａｕｔｏｍａｔｅｄ Ｐｅｒｍ Ｐｏｒｏｍｅｔｅｒ）にて支持体の孔の直径を測定し平均孔径を求めた。
<Average pore diameter of support>
The diameter of the hole of the support was measured with a palm porometer (Automated Perm Porometer manufactured by Porous Materials) to determine the average hole diameter.
＜ナノ繊維層の目付質量＞
支持体とナノ繊維層との合計目付質量から支持体だけの目付質量を引き、その差の値をナノ繊維層目付質量とした。
<Mass weight of nanofiber layer>
The mass per unit area of the support was subtracted from the total mass per unit area of the support and the nanofiber layer, and the difference value was defined as the mass per unit area of the nanofiber layer.
＜ナノ繊維の平均繊維径＞
電界放出型走査電子顕微鏡写真を用いて、エアフィルタ用濾材のナノ繊維層側の表面を倍率１５０００倍〜２００００倍で観察し、視野をずらした４箇所について観察画像を得た。このとき、観察画像中に節状の塊を有する繊維が含まれないようにした。ここでは、繊維が画像外で連続しているか否かを問わず、画像中に現れている繊維の一端又は両端が画像のいずれかの辺に接している場合は、繊維が画像のいずれかの辺に接している部分で途切れているものとみなした。得られた４枚の観察画像について、すべての繊維の繊維径を計測した。計測した値を大きい順に並べて、上位５％、下位５％となる値を除き、残った値の平均値を求め、平均繊維径とした。
<Average fiber diameter of nanofibers>
Using the field emission scanning electron micrograph, the surface on the nanofiber layer side of the filter medium for air filter was observed at a magnification of 15000 to 20000 times, and observation images were obtained at four locations where the field of view was shifted. At this time, fibers having nodular lumps were not included in the observed image. Here, regardless of whether the fiber is continuous outside the image, if one or both ends of the fiber appearing in the image is in contact with either side of the image, the fiber is either of the images It was assumed that the part touching the side was interrupted. The fiber diameters of all the fibers were measured for the obtained four observation images. The measured values were arranged in descending order, and the average value of the remaining values was determined by excluding the values of the upper 5% and the lower 5%, and the average fiber diameter was obtained.
＜圧力損失＞
圧力損失は、有効面積１００ｃｍ２のエアフィルタ用濾材に面風速５．３ｃｍ／ｓｅｃで通風したときの差圧について、微差圧計を用いて測定した。
<Pressure loss>
The pressure loss was measured using a micro differential pressure gauge for the differential pressure when air was passed through a filter medium having an effective area of 100 cm 2 at a surface wind speed of 5.3 cm / sec.
＜０．３μｍ透過率＞
ラスキンノズルで発生させた多分散ＤＯＰ粒子を含む空気を、有効面積１００ｃｍ２のエアフィルタ用濾材に面風速５．３ｃｍ／ｓｅｃで通風したときの上流及び下流の個数比からＤＯＰ透過率を、レーザーパーティクルカウンター（型番：ＫＣ−１８、リオン社製）を使用して測定した。なお、測定対象粒子径０．３μｍ単分散は粒子径０．３−０．４μｍと０．４−０．５μｍのＤＯＰ透過率の幾何平均を０．３μｍ単分散の透過率とした。ＤＯＰ捕集効率は、１００−（ＤＯＰ透過率）の式から求めた。また、上流側のＤＯＰ発生濃度は、０．１μｍ以下で約１×１０９個／ｆｔ３とした。
<0.3 μm transmittance>
DOP transmittance is calculated from the number ratio of upstream and downstream when air containing polydisperse DOP particles generated by a Ruskin nozzle is passed through an air filter medium having an effective area of 100 cm 2 at a surface wind speed of 5.3 cm / sec. Measurement was performed using a particle counter (model number: KC-18, manufactured by Rion Corporation). In addition, the monodispersion of the particle diameter of 0.3 μm to be measured was defined as the transmittance of 0.3 μm monodispersion, which is the geometric average of the DOP transmittances of the particle diameters of 0.3-0.4 μm and 0.4-0.5 μm. The DOP collection efficiency was determined from the equation 100- (DOP transmittance). The upstream DOP generation concentration was about 1 × 10 9 / ft 3 at 0.1 μm or less.
＜０．３μｍＰＦ値＞
濾紙のフィルタ性能の指標となるＰＦ値は、＜圧力損失＞と＜０．３μｍ透過率＞の測定に基づき、数１の式より求めた。ＰＦ値が高いほど、同一圧力損失で高捕集効率であることを示す。０．３μＰＦ値が２０以上を実用レベル、０．３μＰＦ値が２０未満を実用不適レベルとした。
<0.3 μm PF value>
The PF value, which is an index of the filter performance of the filter paper, was obtained from the formula 1 based on the measurement of <pressure loss> and <0.3 μm transmittance>. A higher PF value indicates a higher collection efficiency with the same pressure loss. A 0.3 μPF value of 20 or more was regarded as a practical level, and a 0.3 μPF value of less than 20 was regarded as a practical inappropriate level.
＜ナノ繊維層の密度＞
レーザー顕微鏡（キーエンス社製、ＶＫ‐９０００）を用いてナノ繊維層の厚さを測定し、ナノ繊維層の目付質量を、ナノ繊維層の厚さで除した値をナノ繊維層の密度とした。
<Nanofiber layer density>
The thickness of the nanofiber layer was measured using a laser microscope (manufactured by Keyence Corporation, VK-9000), and the value obtained by dividing the mass per unit area of the nanofiber layer by the thickness of the nanofiber layer was defined as the density of the nanofiber layer. .
表１からも明らかなように、実施例１〜２５で得られたエアフィルタ用濾材は、０．３μｍＰＦ値が２０以上であり、エアフィルタ用濾材としての性能を満足できるものであった。これに対し、比較例１〜１１で得られたエアフィルタ用濾材は、０．３μｍＰＦ値が２０未満であり、エアフィルタ用濾材としての性能を満足できるものではなかった。 As is clear from Table 1, the air filter media obtained in Examples 1 to 25 had a 0.3 μm PF value of 20 or more, and were able to satisfy the performance as air filter media. On the other hand, the air filter media obtained in Comparative Examples 1 to 11 had a 0.3 μm PF value of less than 20, and could not satisfy the performance as the air filter media.
また、実施例２、６、１１、２１乃至２３で得られたエアフィルタ用濾材と、比較例１、９で得られたエアフィルタ用濾材の対比において、ナノ繊維層の密度、ナノ繊維平均繊維径及びナノ繊維層の目付質量は同等であるにもかかわらず、支持体の平均孔径が１５〜３５μｍである実施例２、６、１１、２１乃至２３が、０．３μｍＰＦ値が２０以上となり、支持体の平均孔径が１５μｍより小さい比較例１、及び支持体の平均孔径が３５μｍより大きい比較例９は、０．３μｍＰＦ値が２０未満となった。これにより、支持体の平均孔径を１５〜３５μｍとすることで０．３μｍＰＦ値が向上することがわかる。 Further, in the comparison of the air filter media obtained in Examples 2, 6, 11, 21 to 23 and the air filter media obtained in Comparative Examples 1 and 9, the density of the nanofiber layer and the nanofiber average fiber Examples 2, 6, 11, 21 to 23 in which the average pore diameter of the support is 15 to 35 μm, even though the diameter and the areal mass of the nanofiber layer are the same, the 0.3 μm PF value is 20 or more, Comparative Example 1 in which the average pore diameter of the support was smaller than 15 μm and Comparative Example 9 in which the average pore diameter of the support was larger than 35 μm had a 0.3 μm PF value of less than 20. Thereby, it turns out that 0.3 micrometer PF value improves by making the average hole diameter of a support body 15-35 micrometers.
また、比較例３、５、８で得られたエアフィルタ用濾材は、ナノ繊維層の密度が０．０１５ｇ／ｃｍ３未満であったため、ナノ繊維層の強度が低く、支持体からナノ繊維層が剥がれてしまう問題があり、圧力損失及び０．３μｍ透過率を測定することができず、０．３μｍＰＦ値を求めることができなかった。また、ナノ繊維層の密度が０．０４５ｇ／ｃｍ３より大きい比較例２、４、７で得られたエアフィルタ用濾材は０．３μｍＰＦ値が２０未満となった。これにより、ナノ繊維層の密度は０．０１５〜０．０４５ｇ／ｃｍ３とすることで０．３μｍＰＦ値が向上することがわかる。 Moreover, since the density of the nanofiber layer was less than 0.015 g / cm 3 in the filter medium for air filter obtained in Comparative Examples 3, 5, and 8, the strength of the nanofiber layer was low, and the nanofiber layer was separated from the support. However, the pressure loss and the 0.3 μm transmittance could not be measured, and the 0.3 μm PF value could not be obtained. Moreover, the filter medium for air filters obtained in Comparative Examples 2, 4, and 7 in which the density of the nanofiber layer is larger than 0.045 g / cm 3 has a 0.3 μm PF value of less than 20. Thereby, it turns out that the 0.3 micrometer PF value improves by the density of a nanofiber layer being 0.015-0.045 g / cm < 3 >.
また、比較例１０で得られたエアフィルタ用濾材は、ナノ繊維層の目付質量が０．２ｇ／ｍ２より小さかったため、支持体上のナノ繊維の絶対数が少なく、０．３μｍＰＦ値がエアフィルタ用濾材の測定箇所によりバラツキが大きくなったため、エアフィルタ用濾材として信頼性にかけるものとなった。また、比較例１１で得られたエアフィルタ用濾材は、ナノ繊維層の目付質量が２．５ｇ／ｍ２より大きいため、圧力損失が高くなりすぎ、０．３μｍＰＦ値が低下した。これより、ナノ繊維層の目付質量は０．２〜２．５ｇ／ｍ２の範囲が最適であることがわかる。 Moreover, since the filter medium for air filters obtained in Comparative Example 10 had a mass per unit area of the nanofiber layer smaller than 0.2 g / m 2 , the absolute number of nanofibers on the support was small, and the 0.3 μm PF value was air. As the variation in the measurement location of the filter medium for the filter increased, it became a reliable filter medium for the air filter. Moreover, since the filter medium for air filters obtained in Comparative Example 11 had a mass per unit area of the nanofiber layer larger than 2.5 g / m 2 , the pressure loss was too high and the 0.3 μm PF value was lowered. From this, it can be seen that the basis weight of the nanofiber layer is optimal in the range of 0.2 to 2.5 g / m 2 .
また、ナノ繊維の平均繊維径が２５０ｎｍより大きくなった比較例６で得られたエアフィルタ用濾材は、捕集に必要な表面積が不足し、その結果０．３μｍＰＦ値が低下した。これにより、ナノ繊維の平均繊維径は２５０ｎｍ以下が最適であることがわかる。 In addition, the air filter medium obtained in Comparative Example 6 in which the average fiber diameter of the nanofibers was larger than 250 nm lacked the surface area necessary for collection, and as a result, the 0.3 μm PF value decreased. This shows that the average fiber diameter of the nanofibers is optimally 250 nm or less.
＜参考評価１（支持体の平均孔径と支持体の目付量との関係）＞
支持体の平均孔径と支持体の目付量との関係を確認した。
<Reference evaluation 1 (Relationship between average pore diameter of support and basis weight of support)>
The relationship between the average pore diameter of the support and the basis weight of the support was confirmed.
（支持体の製作）
平均繊維径２．６μｍのガラス繊維（以降、繊維１という。）１００質量部を、パルパーにてｐＨ３．０に調整した水中に離解後、抄紙機にて抄紙し、１２０℃の多筒式ドライヤーで乾燥して、目付質量６３．３ｇ／ｍ２、５０．２ｇ／ｍ２、３６．５ｇ／ｍ２、２７．０ｇ／ｍ２、１７．７ｇ／ｍ２の支持体をそれぞれ得た。各支持体について、平均孔径を測定した。支持体の平均孔径と支持体の目付量との関係を表２に示す。
(Production of support)
100 parts by mass of glass fiber having an average fiber diameter of 2.6 μm (hereinafter referred to as fiber 1) was disaggregated in water adjusted to pH 3.0 with a pulper, and then paper-made with a paper machine, and a multi-cylinder dryer at 120 ° C. in dried, basis weight mass 63.3g / m 2, 50.2g / m 2, 36.5g / m 2, to obtain 27.0 g / m 2, the support of 17.7 g / m 2, respectively. The average pore diameter was measured for each support. Table 2 shows the relationship between the average pore diameter of the support and the basis weight of the support.
表２に示すように、支持体の平均孔径は、支持体の目付質量を小さくするほど大きくなり、支持体の目付質量を大きくするほど小さくなることが確認できた。 As shown in Table 2, it was confirmed that the average pore diameter of the support was increased as the basis weight of the support was decreased and decreased as the basis weight of the support was increased.
＜参考評価２（支持体の平均孔径と主体繊維の平均繊維径との関係）＞
支持体の平均孔径と主体繊維の平均繊維径との関係を確認した。
<Reference evaluation 2 (Relationship between average pore diameter of support and average fiber diameter of main fiber)>
The relationship between the average pore diameter of the support and the average fiber diameter of the main fibers was confirmed.
（支持体の製作）
繊維１に加えて、更に平均繊維径が０．６５μｍのガラス繊維（以降、繊維２という。）及び平均繊維径が５．５μｍのガラス繊維（以降、繊維３という。）の中から、適宜配合し、パルパーにてｐＨ３．０に調整した水中に離解後、抄紙機にて抄紙し、１２０℃の多筒式ドライヤーで乾燥して支持体を作製した。各支持体について、平均孔径を測定した。繊維１〜繊維３の配合率、支持体の目付量及び支持体の平均孔径を表３に示す。
(Production of support)
In addition to fiber 1, glass fiber having an average fiber diameter of 0.65 μm (hereinafter referred to as fiber 2) and glass fiber having an average fiber diameter of 5.5 μm (hereinafter referred to as fiber 3) are appropriately blended. Then, after disaggregation in water adjusted to pH 3.0 with a pulper, paper was made with a paper machine and dried with a multi-cylinder dryer at 120 ° C. to prepare a support. The average pore diameter was measured for each support. Table 3 shows the mixing ratio of the fibers 1 to 3, the basis weight of the support, and the average pore diameter of the support.
表３に示すように、支持体の平均孔径は、繊維径の大きい繊維（繊維３）を多く配合するほど大きくなり、繊維径の小さい繊維（繊維２）を多く配合するほど小さくなることが確認できた。参考評価１，２では、一例としてガラス繊維を用いて確認したが、他の繊維についても同様の傾向が見られる。 As shown in Table 3, it is confirmed that the average pore diameter of the support increases as more fibers (fibers 3) having a larger fiber diameter are added, and decreases as more fibers (fibers 2) having a smaller fiber diameter are added. did it. In the reference evaluations 1 and 2, it confirmed using glass fiber as an example, but the same tendency is seen also about other fibers.
本発明は、低圧力損失で高捕集効率を有したエアフィルタ用濾材としての産業用の利用の可能性を有している。 The present invention has a possibility of industrial use as a filter medium for air filters having low pressure loss and high collection efficiency.
Claims (4)
前記支持体の平均孔径が１５〜３５μｍ、前記支持体は平均繊維径が０．６５〜９．０μｍのガラス繊維を含有し、
前記ナノ繊維層の目付質量が０．２〜２．５ｇ／ｍ２、前記ナノ繊維層の密度が０．０１５〜０．０４５ｇ／ｃｍ３、前記ナノ繊維の平均繊維径が２５０ｎｍ以下であり、
ＪＩＳ Ｂ ９９０８：２０１１「換気用エアフィルタユニット・換気用電気集じん器の性能試験方法」に記載された除電処理である「（２）ＩＰＡ飽和蒸気曝露法」に準拠して除電処理した後における、数１の式により示される対象粒子径０．３μｍのＰＦ値が２０以上であることを特徴とするエアフィルタ用濾材。
The support has an average pore diameter of 15 to 35 μm, the support contains glass fibers having an average fiber diameter of 0.65 to 9.0 μm,
The mass per unit area of the nanofiber layer is 0.2 to 2.5 g / m 2 , the density of the nanofiber layer is 0.015 to 0.045 g / cm 3 , and the average fiber diameter of the nanofiber is 250 nm or less,
JIS B 9908: 2011 after performing static elimination processing in accordance with “(2) IPA saturated vapor exposure method” which is the static elimination processing described in “Performance Test Method of Ventilation Air Filter Unit / Ventilation Electric Dust Collector” A filter medium for an air filter, wherein a PF value of a target particle diameter of 0.3 μm represented by the formula 1 is 20 or more.
全繊維質量に対する前記第１繊維の配合率が０質量％を超え８０質量％未満であることを特徴とする請求項１に記載のエアフィルタ用濾材。 The metallic fibers used in the support has an average fiber diameter of the average fiber diameter and 9.0μm or less of the first fibers or 5μm is composed of a second fiber of less than 5μm exceed 1 [mu] m,
2. The air filter medium according to claim 1, wherein a blending ratio of the first fibers with respect to a total fiber mass is more than 0% by mass and less than 80% by mass.
全繊維質量に対する前記第１繊維の配合率が６０質量％以上９５質量％以下であることを特徴とする請求項１に記載のエアフィルタ用濾材。 The metallic fibers used in the support has an average fiber diameter of the average fiber diameter and 9.0μm or less of the first fibers or 5μm is composed of a 1μm or less of the third fiber least 0.65 .mu.m,
The air filter medium according to claim 1, wherein the mixing ratio of the first fibers with respect to the total fiber mass is 60 mass% or more and 95 mass% or less.
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