JP3567480B2 - Filter medium and method for producing the same - Google Patents
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【０００１】
【産業上の利用分野】
本発明は、クリ−ンル−ム用エアフイルタ−、電子機器の洗浄に用いられる液体のフイルタ−、あるいは医薬の製造に用いられる液体や気体のプレフイルタ−等として使用される精密濾過用の濾材に関する。更に詳しくは、極細繊維の交点が熱融着した不織布と、熱融着性繊維製ネツトとが熱融着し、加熱による孔径変化がなく、ひだ折り等のぶ形性の良い精密濾過用濾材およびその製造方法に関する。
【０００２】
【従来の技術】
近年、エレクトロニクスやバイオケミカル等に関する産業が発達し、気体や液体を清浄化して用いられる機会が多くなつている。従来このような精密濾過用の濾材として、極細のガラス繊維不織布や合成繊維不織布等が使用されていた。しかし前記ガラス繊維不織布は耐アルカリに弱いとか、濾過表面積を多く取る目的で加工されるひだ折りや、種々な立体形状等に加工する際、いわゆるぶ形性が悪い等の課題がある。一方前記合成繊維不織布は、ガラス繊維不織布に較べ比重が小で軽量である、ぶ形性がガラス繊維不織布に較べて良い、安価である、濾材加工時にガラスの微粉が飛散せず取り扱い易い、等の利点があり、該合成繊維不織布濾材が急速に使用されるようになつてきた。
該合成繊維不織布濾材は、ポリエステルスパンボンド不織布やポリプロピレンメルトブロ−不織布等が使用されているが、加熱、振動、摩擦等により目開きし細孔径が大きくなる現象、即ち孔径安定性が劣るという課題がある。
【０００３】
不織布濾材のぶ形性を改良した物として、不織布とネツト状シ−トを融着した濾材が知られている。
特開平１−１９４９１２号公報に、エレクトレツト化された極細繊維不織布と網状物が熱融着したフイルタ−が、特開平４−３４６８０５号公報に、極細繊維不織布に熱融着性モノフイラメントと金属細線を併用したネツトを融着した濾材が開示されている。
前記不織布にネツト状シ−トを融着した物は、何れも不織布を構成する極細繊維として、メルトブロ−法ポリプロピレンやメルトブロ−法ポリエステル等のレギュラ−繊維が使用されている。該極細繊維ウェブをその繊維の交点が熱融着の無い状態で、又は該ウェブをエンボスロ−ルやカレンダ−ロ−ル等を使用し、繊維の交点を部分的に熱融着させたもの、あるいはネツトを該ウェブ又は熱圧着不織布に積層し、カレンダ−ロ−ルやドライヤ−等の加熱手段を用い、前記不織布とネツトとを融着させた物である。
【０００４】
ところで、不織布の熱融着状態をミクロ的に観た場合、前記のような不織布濾材は、濾材の通気抵抗を損なわずに繊維の交点を十分に熱融着させる事が困難である。例えばエンボスロ−ル法による物は、熱圧着部以外の部分は融着していず、カレンダ−ロ−ル法による物は、不織布の表面及び裏面は多く融着しているが、厚みの中央部分が融着部分が少ないか、多くあつても弱い融着状態である物となつている。このように繊維の融着状態が、その表面、中央、裏面で異なる不織布は、該不織布をひだ折りや、筒状に加工したり、筒状の両端面を合成樹脂端面部材でヒ−トシ−ルしたり、該端面部材をバインダ−等で接着したりする際の加熱や、濾材を加熱滅菌する際の加熱や、振動、衝撃、濾過時におけるハウジングの振動等で不織布に目開きが起き、最大孔径が著しく大きくなるという欠点、即ち孔径安定性が劣るという欠点がある。特に目付けが約２５ｇ／ｍ２ 以上の高目付けの物は、不織布厚みの中間部近傍の繊維の熱融着が不十分となり易く、孔径安定性が劣り、時には加熱後の最大孔径が２５％以上も大になる物であつた。
又、カレンダ−ロ−ル法等で高温かつ高圧で熱圧着した濾材は、孔径安定性が幾分改良されるが、繊維全体が溶融し膜状に変化するので通気抵抗が著しく高くなるという欠点がある。
【０００５】
【発明が解決しようとする課題】
本発明は、上記従来技術の課題である加熱や振動等により最大孔径が変化せず、しかも高強力でかつ山谷状に、或は他の複雑な形状等に容易に加工出来る精密濾過用の濾材を提供することを目的としたものである。
【０００６】
【課題を解決するための手段】
本発明者らは、上記課題を解決するために鋭意研究を重ねた結果、以下の構成をとることにより初期の目的が達成される事を知り、本発明を完成するに至った。 即ち本発明の構成は以下の通りである。
（１）繊維径１０μｍ以下の低融点極細繊維２０〜８０重量％と低融点極細繊維より融点が１０℃以上高い繊維径１０μｍ以下の高融点極細繊維８０〜２０重量％とからなり且つ低融点極細繊維によつて繊維同士が熱融着された不織布と、低融点成分と高融点成分の複合繊維を編織した熱融着性ネツトとを熱融着して得られる最大孔径が１２０μｍ以下の濾材であって、極細繊維の低融点樹脂とネツトに含有される低融点樹脂との融点差が１５℃以下であり、且つ繊維の交点部でお互いの低融点樹脂が相互侵入構造をとっている濾材。
（２）低融点極細繊維および高融点極細繊維の一方または両方が複合繊維であり、熱融着性ネツト用繊維の繊度が３０〜４０００デニ−ルであり、且つ熱融着性ネツトの低融点成分と低融点極細繊維の成分とが同種系であり、加熱後の最大孔径変化率が２０％以下である前記（１）項の濾材。
（３）ひだ折り加工された前記（１）〜（２）項のいずれかの濾材。
（４）エレクトレツト化され、通気度が０．１〜１００ｃｃ／ｃｍ２秒、引張強力が２〜１００ｋｇ／５ｃｍである前記（１）〜（３）項のいずれかの濾材。
（５）複数樹脂を口金から紡糸し、繊維径１０μｍ以下の低融点極細繊維２０〜８０重量％と該繊維より融点が１０℃以上高い繊維径１０μｍ以下の高融点極細繊維８０〜２０重量％とからなるウエブとし、該ウエブを熱処理し低融点極細繊維によつて繊維同士が熱融着された不織布を得、樹脂を口金から紡糸し低融点成分と高融点成分の複合繊維を得、該繊維を編織して得た熱融着性ネツトを得、上記の不織布と熱融着性ネツトとを積層し、熱処理し熱融着して、融点差が１５℃以下である極細繊維の低融点樹脂とネツトに含有される低融点樹脂とを繊維の交点部で相互侵入構造とする、最大孔径が１２０μｍ以下の濾材の製造方法。
（６）メルトブロ−法により紡糸した極細繊維ウエブを熱処理した不織布を用いた前記（５）項の濾材の製造方法。
【０００７】
本発明の濾材は、熱融着された極細繊維による不織布と、ネツトとが熱融着されたものであり、熱融着された濾材の最大孔径が１２０μｍ以下であり、
該不織布は、低融点極細繊維と高融点極細繊維が使用され、該低融点極細繊維によつて極細繊維同士が融着され、
低融点極細繊維２０〜８０重量％と高融点極細繊維８０〜２０重量％の比率からなり、
低融点極細繊維と高融点極細繊維との融点差が１０℃以上ある。
融点差が１０℃以上ある２種以上の熱可塑性樹脂を種々の方法により口金から紡糸し、混合し、得られたウェブを低融点極細繊維の熱融着温度以上に加熱し、極細繊維の交点を熱融着し不織布とし、
樹脂を口金から紡糸し繊維を得、該繊維を編織して得たネツトとし、
該不織布とネツトとを積層し、熱処理し熱融着し、
熱融着し最大孔径１２０μｍ以下の濾材の製造方法とする。
【０００８】
極細繊維の紡糸法は、低融点成分と高融点成分とを吐出する。成分の異なる２以上の口金を組み合わせたものでもよく、１個の口金に２以上の複成分を導入して１孔ごとに異なる成分を紡糸する、いわゆる単成分混繊紡糸法であってもよい。また第１の口金が複合紡糸で、第２の口金が単成分紡糸の２種の口金を用いる紡糸法でもよく、第１の口金、第２の口金ともに複合紡糸の２種の口金を用いる紡糸法でもよく、或は１個の口金に複合紡糸部分と、単成分紡糸部分を含むような、いわゆる単成分／複合混繊紡糸法等いずれも使用できる。
極細繊維の紡糸法として、メルトブロ−法、スパンボンド法
フラッシュ紡糸法、延伸紡糸法等があり、これらの複合紡糸法、混繊紡糸法がある。とりわけメルトブロ−法による混繊紡糸法は繊維がよく混合でき好ましい。さらに口金の導入溝を各成分ごとに変更できる口金であると、各成分（低融点成分、高融点成分）の比率を変更でき好ましい。複合紡糸口金として、並列型、鞘芯型、多分割型、海島型等種々の口金を用いることができる。又、２種の極細繊維を別々の口金から一旦紡糸し、その後ウェブを積層し、ニードルパンチ、ウオーターニードル等で混合してもよい。
【０００９】
本発明ではその用途が精密濾過用の濾材であるので極細繊維の径は、１０μｍ以下、好ましくは０．１〜１０μｍ、更に好ましくは０．２〜８μｍである。また本発明の濾材に使用される不織布には、上記極細繊維を主に用いるが、本発明の目的を損なわない範囲で繊維径２０μｍ以上の繊維が混合されてもよい。
【００１０】
本発明の極細繊維は、低融点極細繊維と高融点極細繊維との混合繊維であり、低融点極細繊維（単成分）と高融点極細繊維（単成分）との混合繊維とすることができ、低融点極細繊維（単成分）と高融点極細繊維（複合成分）との混合繊維とすることができ、低融点極細繊維（複合成分）と高融点極細繊維（単成分）との混合繊維とすることができ、低融点極細繊維（複合成分）と高融点極細繊維（複合成分）との混合繊維とすることができる。ただし複合成分繊維の融点は、低融点成分を熱融着するので、この低融点成分の融点とする。またこの複合繊維として融点差のない分子量、結晶化度の異なる同成分の組み合わせた複合繊維であってもよい。
極細繊維に使用できる熱可塑性樹脂には、ポリプロピレン、ポリエチレン、ポリ−４−メチルペンテン、プロピレンと他のαオレフィンとの２元又は３元共重合体、ポリエチレンテレフテレ−ト、ポリアミド、ポリカ−ボネ−ト等の樹脂がある。低融点極細繊維と高融点極細繊維との融点差は１０℃以上であり、１５℃以上１５０℃以下が好ましく、、さらに好ましくは２０〜１００℃であるような種々の組合せで混繊紡糸等をする。
低融点極細繊維（単成分）と高融点極細繊維（単成分）との混合繊維の組合せとしては、ポリエチレン：ポリプロピレン、プロピレン−エチレン−ブテン−１共重合体：ポリプロピレン、ポリプロピレン：ポリエチレンテレフタレ−ト、低融点ポリエステル：ポリエチレンテレフタレ−ト、ポリアミド：ポリエチレンテレフタレ−ト等を例示できる。
低融点極細繊維（単成分）と高融点極細繊維（複合成分）との混合繊維の場合、低融点極細繊維（単成分）として線状低密度ポリエチレン：高融点極細繊維（複合成分）としてポリプロピレン（鞘）／ポリアミド（芯）を例示でき、
低融点極細繊維（複合成分）と高融点極細繊維（単成分）との混合繊維の場合、低融点極細繊維（複合成分）として線状低密度ポリエチレン（並列）／ポリプロピレン（並列）：高融点極細繊維（単成分）としてポリエチレンテレフタレ−トを例示できる。
低融点極細繊維（複合成分）と高融点極細繊維（複合成分）との混合繊維の場合、低融点極細繊維（複合成分）として線状低密度ポリエチレン（並列）／ポリプロピレン（並列）：高融点極細繊維（複合成分）としてポリプロピレン（並列）／ポリエチレンテレフタレ−ト（並列）を例示でき、
低融点極細繊維（複合成分）として高密度ポリエチレン（鞘）／ポリエチレンテレフタレ−ト（芯）：高融点極細繊維（複合成分）としてポリプロピレン（鞘）／ポリエチレンテレフタレ−ト（芯）を例示できる。
【００１１】
メルトブロ−法等で融点に差がある２種の極細繊維を紡糸し、得られた２種のウェブを低融点極細繊維が溶融する温度以上に加熱し、繊維の交点が熱融着した不織布とする。
本発明において、不織布の低融点極細繊維の含有量が２０重量％未満の場合、ウェブを後記の熱処理をしても、繊維の融着点が少なく加熱後の孔径安定性がよい物が得られず、しかも毛羽立、強力不足等の課題がある。又低融点極細繊維の含有量が８０重量％を超えると後記の熱処理により、低融点極細繊維が完全に溶融し繊維の形態を失い、膜状化、繊維の収縮玉状化等が起き、通気抵抗が大になったり、濾過精度の悪い物になる等の課題がある。
【００１２】
熱処理は、乾熱循環型ドライヤ−、スル−エア−型ドライヤ−、カレンダ−ロ−ル、エンボスロ−ル等の加熱装置を用いて行う。前記加熱装置のうち、スル−エア−型ドライヤ−等のような、不織布にあまり圧力が掛からない状態で熱融着できる装置を用いて熱処理した物は、通気度が大きい不織布が得られる。又、カレンダ−ロ−ル等のような、熱圧着型の加熱装置を用いて熱圧着した物は、最大孔径の小さい不織布が得られる。
この熱処理は、不織布の熱融着、ネツトの熱融着、不織布とネツトとの熱融着に使用できる。
【００１３】
本発明の濾材に使用する不織布は、極細で且つ熱融着性のある低融点繊維が使用され、しかも熱処理により低融点繊維が溶融し繊維の交点が熱融着された物である。従って、熱処理温度を低融点繊維の軟化点以上、高融点繊維の融点以下の温度で行う事により、該高融点繊維が溶融せずに繊維の形状を保持し、繊維の交点が該低融点繊維の熱融着により不織布化されている。従って後工程での滅菌処理や高温濾過、振動等で目開せず、孔径が安定した物となる。又、繊維の完全溶融による一種の膜状化が起きず、起きたとしてもきわめて少ない。従って通気度が大でしかも孔径の小さい物が得られる。
【００１４】
一方、従来のメルトブロ−法等により得られた単成分極細繊維１００％の不織布は、不織布厚みの中央部付近に未融着繊維が多量に発生していたり、該中央部付近の融着部の結合がきわめて弱い不織布であるため、後記のネツトを不織布に融着後の物を、加熱滅菌処理、高温濾過等をしたり、或は振動等により目開きする。又、カレンダ−ロ−ル等で高温加熱した物は、繊維が完全溶融し、繊維の形状が消失し膜状化が起きる。スル−エア−型加熱機で高温で加熱した物は、繊維が溶融収縮したり、玉状に凝集したりする。このような物は、通気度が小でであつたり、最大孔径が大きい物となる。
【００１５】
本発明の濾材に使用される不織布は、目付け約３〜１０００ｇ／ｍ２ 、好ましくは４〜７００ｇ／ｍ２ の物が使用出来る。又、該不織布は、目付け、加熱温度、カレンダ−ロ−ルの線圧、処理時間、等の加工条件等を変える事により、不織布の孔径を変化させる事ができる。繊維の繊度が小、目付けが大、カレンダ−ロ−ルの線圧が大の条件で製造された物程、孔径小の不織布が得られる。
【００１６】
本発明の濾材は、上記不織布とネツトが熱融着された物であり、該ネツトは、熱可塑性樹脂を含有する繊維を編織り等した物である。ネツト用繊維は、２種以上の熱可塑性繊維を複合紡糸して得た熱処理により熱融着可能な複合繊維である。とりわけ融点差が１０℃以上ある少なくとも２種以上の熱可塑性樹脂を用いて、複合紡糸法により得た複合繊維がよい。熱融着性複合モノフイラメントを編織等をしネツト状とした物、或はこのネツトを熱融着温度以上で加熱し、繊維の交点を融着した物等が使用される。熱融着性ネツトに用いる複合成分の融点差は１０℃以上であり、好ましくは１５℃以上１５０℃以下、さらに好ましくは２０〜１００℃である。又、該ネツトは、ト−タル繊度が約３０〜４０００デニ−ルのネット用繊維を、織り密度約０．５〜２５本／２５ｍｍで織製した物が好ましい。
【００１７】
該ネツト用繊維の複合形態や、該ネツト用繊維に使用出来る樹脂や、樹脂の組合せ等は、前記不織布と熱融着するような樹脂の組合せ等である。極細繊維の低融点樹脂と、ネツトに含有される低融点樹脂との融点差は１５℃以下であり、後記の加熱処理により、繊維の交点部でお互いの低融点樹脂が相互侵入構造をとるので、不織布とネツトが強く熱融着し、その境界面で剥離しにくい。とりわけ低融点極細繊維の融点とネツトの低融点樹脂が、同種系の物、例えばポリオレフイン／ポリオレフイン、ポリエステル／ポリエステル等の物が好ましい。
以上
【００１８】
上記不織布とネツトを、不織布／ネツト、ネツト／不織布／ネツト等のように積層し、或は前記積層物を更に二段に積層した物等を、加熱圧着する。前記のような公知の加熱方法で加熱し、不織布とネツトが熱融着した濾材とする。加熱後ロール処理する方法、加熱ロールで熱圧着する方法であってもよい。ちろん該積層物に比較的太い繊度のスパンボンド不織布やステ−プルの熱融着不織布等を積層してもよい。
【００１９】
本発明の濾材は、ひだ折り等をせずに、ハウジング等に取り付けて使用できる。又、該濾材をひだ折り機や成型機等を使用し、鋭角な山谷状に、Ｕ状に、凹凸状等、任意の形状にぶ形し、ハウジングに取り付けて使用できる。又、前記種々の形状にぶ形後の濾材を、更に円筒状、渦巻状等に二次加工することもできる。円筒状にした場合、左右の端部は融着或はバインダ−等で接着する。
該ハウジングは濾過すべき用途に応じ、種々の形状の物が使用出来る。例えば、その側面に多数の開孔を有する円筒状の芯材、多孔性円筒状の外枠材、及び端面シ−ル部材を主構成部材とする円筒状のハウジングや、四角形の枠状のハウジング、及び金属ネツト等を主構成部材とする四角形のハウジング、或は、箱型で濾材を多層状に装着する箱型多層状のハウジング、その他濾過すべき場所に装着できる任意の形状のハウジングが使用できる。
【００２０】
又本発明の濾材は、エレクトレツト化した物であつてもよい。エレクトレツト化の方法としては、紡糸時繊維を捕集しながら、口金と捕集面間でエレクトレツト化する方法、紡糸した後ウェブ等を巻取るまでの間にエレクトレツト化する方法等がある。又、不織布や、不織布と熱融着性ネツトが熱融着された不織布、ひだ折りされた濾材、ハウジングに装着された濾材等をエレクトレツト化する方法等がある。該エレクトレツト化は、電圧約１〜３０キロボルトの直流コロナ放電等で処理する。又、該不織布は約１０〜４５ク−ロン／ｃｍ２ の表面電化密度を有するものが好ましい。
【００２１】
本発明の濾材は、繊維径１０μｍ以下の極細繊維が密度勾配型になつていてもよい。又、本発明の濾材は、繊維の素材、繊維径等の違う他の不織布やシ−ト等が積層された物であつてもよい。他の不織布等として、繊維径約５０μｍ以下の複合メルトブロ−法不織布、繊維径１００μｍ以下の熱融着性複合繊維不織布、或は該不織布と熱融着性ネツトとの積層シ−ト等が例示できる。
【００２２】
【実施例】
以下実施例、比較例により本発明を更に詳細に説明する。なお、各例において、濾材の物性や濾過性能等の評価は、以下に記載する方法で行った。
【００２３】
不織布の繊維径：ウェブ、不織布、或は濾材から小片を１０個切取り、走査型電子顕微鏡により倍率１００〜５０００倍の写真をとり、計１００本の繊維直径を測定し、その平均値（μｍ）を不織布の繊維径とした。
【００２４】
引張強力：引張強力試験機を用い、５ｃｍ幅の破断強力（ｋｇ／５ｃｍ）を求めた。
【００２５】
通気度：フラジ−ル型通気度試験機を用い、ＪＩＳ−Ｌ１００６Ａに定める方法で通気度を求めた。単位、ｃｃ／ｃｍ２ ．秒。
【００２６】
最大孔径：バブルポイントテスタ−を使用し、ＡＳＴＭ−Ｆ−３１６−８６に定める方法で最大孔径（μｍ）を求めた。
【００２７】
加熱後の最大孔径変化率：前記バブルポイントテスタ−を用い、前記同様の方法で、加熱前の最大孔径（Ａ）、及び８０℃１０分加熱後の最大孔径（Ｆ）を求め以下の式で算出した。
加熱後の最大孔径変化率（％）＝１００（Ｆ−Ａ）／Ａ
【００２８】
濾過精度：５０リツトルの水を入れた水槽、ポンプ、及びハウジング、濾過機からなる循環式濾過試験機を用いた。該濾過機のハウジングに濾材１本を取付、水を毎分３０リツトルの流量で循環させながら、水槽にケ−キ（カ−ボランダム＃４０００）を５ｇ添加する。ケ−キ添加より１分後に採取した濾過水１００ｃｃをメンブレンフイルタ−で濾過する。メンブレンフイルタ−上に捕集された粒子のサイズを粒度分布測定機で測定し、最も大きな粒子のサイズ（最大流出径、単位μｍ）を濾材の濾過精度とした。
【００２９】
圧力損失：前記、循環式濾過精度試験において、ケ−キを添加せず、水のみ毎分３０リツトルの流量で循環させる。循環開始１分後、圧力損失（ｋｇ／ｃｍ２）を求める。
【００３０】
実施例１〜３、比較例１〜３
２台の押出機及び、孔径０．３ｍｍ、孔数５０１のメルトブロ−紡糸口金を主構成要素とする混繊型メルトブロ−装置を用い、混繊紡糸をした。該口金は、２台の押出機から押し出された２種の溶融樹脂が各孔で混合せず、各孔毎に吐出し、しかも各孔から吐出する２種の溶融樹脂が種々の孔数比で変えられるような構造の口金になっている。
【００３１】
第１成分としてメルトフロレ−ト１２０（ＭＦＲ、ｇ／１０分、１９０℃）、融点１２１℃の線状低密度ポリエチレンを、第２成分としてメルトフロレ−ト１２０（ＭＦＲ、ｇ／１０分、２３０℃）、融点１６４℃のポリプロピレンを、溶融押出し、メルトブロ−紡糸した。紡糸条件は、紡糸温度が第１成分２６０℃、第２成分２８０℃一定とし、２種の成分が吐出する孔数比を種々変えて押出し、紡糸孔から吐出された繊維を、温度３６０℃の空気を圧力１．２ｋｇ／ｃｍ２ Ｇで導入し、噴出気体吸引装置付きのコンベア−ネツト上に吹き付けた。該極細繊維の繊維径は約３μｍであつた。このウェブをスル−エア−型加熱機を用い、温度１３５℃で１５秒間加熱し、繊維の交点が熱融着した目付け約１００ｇ／ｍ２ の不織布を得た。
【００３２】
鞘成分が、ＭＦＲ１８（ｇ／１０分、１９０℃）、融点１２４℃の線状低密度ポリエチレンで、芯成分がＭＦＲ８（ｇ／１０分、２３０℃）、融点１６４℃のポリプロピレンからなる複合比５０／５０（重量比）、繊度２５０ｄ／ｆの熱融着性複合モノフイラメントを使用し、経緯共１７×１７本／２５ｍｍの織り密度で平織布を織製し、その後ネツトをテンタ−型加熱機を用い温度１３５℃で加熱し、繊維の交点が熱融着したネツトを得た。
【００３３】
前記で得た物を、ネツト／不織布／ネツトの順に三層に積層し、スル−エア−型加熱機を用い、温度１４０℃で１５秒間加熱後、直ちに温度３０℃のカレンダ−ロ−ルで処理し、不織布とネツトが熱融着した濾材を得た。
【００３４】
前記濾材をひだ折り加工機を用い、ひだの高さ２０ｍｍ、ひだの形状がＷ状の濾材を得た。
該ひだ折りされた濾材を、その側面に多数の孔がある外形３０ｍｍ、高さ２５０ｍｍの中空状金属中芯に巻き付け、内径約３０ｍｍ、外形７０ｍｍの濾材を得た。該濾材の左右の合わせ目は熱融着した。更に上下両端部をバインダ−を用い、直径３０ｍｍの開口部がある金属製端面シ−ル部材を接着し、円筒状の濾材を得た。この濾材は、外形７０ｍｍのひだ折りなしの物に較べ、表面積が約９．１倍増加した。
【００３５】
表１に加熱前、加熱後の濾材の物性や、ひだ折りし且つ中空円筒状に加工された濾材の濾過性能等の試験結果を示す。
表１より、本発明の濾材（実施例１〜３）は、加熱後の最大孔径変化率が１０％以下であり、加熱に対する孔径安定性がよく、しかもひだ折り加工後の物は濾過精度が約４〜５μｍでありよい事が判る。
一方低融点極細繊維の含有量が２０％未満の場合（比較例１，２）には、加熱により目開きし、最大孔径が大になり、かつ濾過精度も悪い事が判る。又、低融点極細繊維１００％の物（比較例３）は、濾過精度がよいが通気度及び圧力損失が劣る事が判る。
【００３６】
実施例４
前記実施例２で得た混繊型メルトブロ−法極細繊維ウェブを、スル−エア−型加熱機を用い、温度１４０℃で処理し繊維の交点が熱融着した目付け９８ｇ／ｍ２ の不織布を得た。
【００３７】
鞘成分が融点１３３℃の高密度ポリエチレンで、芯成分がポリプロピレンからなる鞘芯型フイラメントであつて、単糸繊度が６ｄ／ｆ、フィラメント数６０のマルチフィラメントを用い、経緯共３本／２５ｍｍの構成で平織布を織製した。その後テンタ−型加熱機を用い、温度１３５℃で加熱し、繊維の交点が熱融着したネツトを得た。
【００３８】
前記不織布と前記ネツトとを、ネツト／不織布／ネツトの三層状に積層した。該積層物を、カレンダ−ロ−ルを用い、温度１２０℃で処理し、不織布とネツトが熱融着した濾材を得た。
この濾材を前記実施例（１）同様に、ひだ折り加工後、更に円筒状の濾材に加工した。この濾材は外形７０ｍｍのひだ折りなしの物に較べ、表面積が約９．１倍増加した。表１より、実施例（４）の濾材は、加熱後の最大孔径変化率が０％であり、孔径安定性がよく、ひだ折り加工後の物は濾過精度が１．１μｍとよい物であつた。
【００３９】
実施例５
前記実施例２で得た、不織布とネツトが熱融着した濾材を、ア−ス電極上に直接載せ、その上部の放電電極から１４ｋｖ／ｃｍの直流電圧を印加した高電界中で２０秒間処理し、エレクトレツト化した濾材を得た。該濾材を３０ｃｍ×３０ｃｍの大きさに切り取り、人の出入りの多い事務所のテ−ブル上に置き、浮遊塵を該濾材に自然吸着させた。６０日後、濾材表面の汚れ具合いを、ＪＩＳ−Ｌ０８０５規定の汚染用グレ−スケ−ル（１級：汚染が大、５級：汚染が小）で判定したところ２．５級であつた。一方エレクトレツト化しない前記実施例（２）で得た濾材も同時に汚れ具合いを観察したところ、４．５級であつた。
【００４０】
実施例６
ＭＦＲ４３（ｇ／１０分、１９０℃）、融点１３３℃の高密度ポリエチレンを第１成分とし、固有粘度０．６０、融点２５３℃のポリエチレンテレフタレ−トを第２成分とし、孔径０．３ｍｍ、孔数５０１の並列型メルトブロ−口金より、複合メルトブロ−紡糸し複合低融点極細繊維を得た。紡糸条件は、複合比が４０（第１成分）／６０（第２成分）（重量比）、紡糸温度が高密度ポリエチレンを２６０℃、ポリエチレンテレフタレ−トを２８０℃の条件で押出し、紡糸孔から吐出された繊維を、温度３９０℃の空気を圧力１．５ｋｇ／ｃｍ２ ．Ｇで導入し、噴出気体吸引装置付きのコンベア−ネツト上に吹き付けた。該複合低融点極細繊維ウェブは、目付けが４０ｇ／ｍ２、繊維径が４．０μｍであつた。
【００４１】
該ウェブと、前記比較例（１）で得たポリプロピレン１００％の高融点極細繊維からなる目付け１０１ｇ／ｍ２ 、繊維径３．３μｍのウェブとを積層し、圧力７０ｋｇ／ｃｍ２ の条件で、ウオタ−ニ−ドル処理をした。この不織布を、８０℃で乾燥後、スル−エア−型加熱機で、温度１４５℃で２０秒間熱処理し、その後直ちに温度３０℃のカレンダ−ロ−ルで処理し、繊維の交点が融着した不織布を得た。
【００４２】
前記不織布と実施例（１）で使用したネツトとを用い、ネツト／不織布／ネツトの順に積層した。該積層物を、カレンダ−ロ−ルを用い、温度１２０℃で処理し、不織布とネツトが熱融着した濾材を得た。
この濾材を前記実施例（１）同様に、ひだ折り加工後、更に円筒状の濾材に加工した。この濾材は外形７０ｍｍのひだ折りなしの物に較べ、表面積が約９．１倍増加した。
この濾材は、加熱前で、引張強力が４６．３ｋｇ／５ｃｍ、最大孔径が２６μｍであつた。８０℃１０分加熱後で、最大孔径が２７μｍであり最大孔径変化率が３．９％、通気度が１８．８ｃｃ／ｃｍ２ ．秒であつた。又ひだ折り後の物は、濾過精度が３μｍで圧力損失が０．０４ｋｇ／ｃｍ２ であつた。
【００４３】
実施例７
２台の押出機及び、１個の口金に単成分孔と複合成分孔を含む孔径０．３ｍｍ、低融点単成分孔１６７個、低融点成分と高融点成分との複合成分孔（並列型）１６７個、高融点単成分孔１６７個のメルトブロ−紡糸口金を用い混繊紡糸をした。低融点成分として実施例１と同じ線状低密度ポリエチレン、高融点成分として実施例１と同じポリプロピレンを使用しメルトブロー紡糸した。紡糸条件は、紡糸温度が低融点成分２４５℃、高融点成分２６０℃とし、低融点成分と高融点成分との複合比を１：１（重量％）で押出した。低融点（単成分）極細繊維：低融点（複合成分）極細繊維：高融点（単成分）極細繊維を１：１：１（重量％）に設定し押出し、紡糸孔から吐出された繊維を、温度３３０℃の空気を圧力１．２ｋｇ／ｃｍ２ Ｇで導入し、実施例１と同じコンベア−ネツト上に吹き付けた。該極細繊維の繊維径は約４μｍであつた。低融点（単成分）極細繊維が３．６μｍ、低融点（複合成分）極細繊維４．５μｍ、高融点（単成分）極細繊維 ３．７μｍであった。
このウェブを実施例１と同じ加熱機を用い、温度１４５℃で３０秒間加熱し、繊維の交点が熱融着した目付け約１００ｇ／ｍ２ の不織布を得た。
前記不織布と実施例１と同じネットを、ネツト／不織布／ネツトの順に三層に積層し、スル−エア−型加熱機を用い、温度１３５℃で１５秒間加熱後、直ちに温度３０℃のカレンダ−ロ−ルで処理し、不織布とネツトが熱融着した濾材を得た。
前記濾材を実施例１と同様にひだ折り加工し、金属製端面シ−ル部材を接着をし円筒状の濾材を得た。この濾材は、外形７０ｍｍのひだ折りなしの物に較べ、表面積が約９．１倍増加した。
この濾材は加熱前で、引張り強力が３１．８Ｋｇ／５ｃｍ、最大孔径が４０μｍであった。また８０℃１０分加熱後で最大孔径が４１μｍ、加熱後の最大孔径変化率が２．５％、通気度が３０ｃｃ／ｃｍ２秒であった。またひだ折り加工後の物は濾過精度が５．２μｍ、圧力損失が０．０４Ｋｇ／ｃｍ２であった。
本発明の濾材は、比較例１または２のものより繊維径が太いが濾過精度がよく、加熱後の最大孔径変化率が１０％以下であり良いものであった。
【００４４】
【発明の効果】
本発明の濾材は極細繊維の交点が熱融着された不織布と、繊度の大きい熱融着性繊維製ネツトが熱融着された物である。従って該濾材は、引張強力に優れ、圧力損失が小さく、５μｍ以下の微粒子をも捕捉でき、濾過精度に優れ、通気度も多く、加熱に対し孔径安定性が良く、加熱等により目開きしない。該濾材は加熱に対し孔径安定性が良いので、加熱滅菌や、高温濾過等を行っても、安定した高精度の濾過を行うことが出来る。
又、この濾材は、ひだ折りや凹凸状の加工が出来る。又、該ひだ折り加工された濾材は、前記効果に加え、濾過面積が多いので濾過ライフが長いという効果がある。又、不織布のウェブとして、メルトブロ−法ウェブを用いた物は、繊維に帯電防止剤等の仕上げ剤が付着していないので、食品分野の精密濾過用の濾材としても使用出来る。
【００４５】
【表１】
[Industrial applications]
The present invention relates to a filter medium for microfiltration used as an air filter for a clean room, a liquid filter used for cleaning electronic equipment, or a liquid or gas prefilter used for manufacturing a medicine. More specifically, a non-woven fabric in which the intersections of ultrafine fibers are heat-fused and a heat-fusible fiber net are heat-fused, there is no change in pore size due to heating, and a filter material for fine filtration with good shape such as folds and the like is provided. It relates to the manufacturing method.
[0002]
[Prior art]
2. Description of the Related Art In recent years, industries related to electronics, biochemicals, and the like have been developed, and there are many opportunities for purifying and using gases and liquids. Conventionally, ultrafine glass fiber nonwoven fabric, synthetic fiber nonwoven fabric, and the like have been used as a filter medium for such precision filtration. However, the glass fiber nonwoven fabric is problematic in that it is weak in alkali resistance, has folds formed for the purpose of increasing the filtration surface area, and has poor so-called convexity when processed into various three-dimensional shapes. On the other hand, the synthetic fiber nonwoven fabric has a smaller specific gravity and lighter weight than a glass fiber nonwoven fabric, has a better shape than a glass fiber nonwoven fabric, is inexpensive, is easy to handle without being scattered by fine glass powder when processing a filter material, and the like. The synthetic fiber non-woven fabric filter medium has come to be used rapidly.
As the synthetic fiber nonwoven fabric filter material, a polyester spunbonded nonwoven fabric or a polypropylene melt-blow nonwoven fabric is used. However, a phenomenon in which pores become large due to heating, vibration, friction, and the like, that is, pore diameter stability is poor, that is, pore diameter stability is poor. There is.
[0003]
A filter material obtained by fusing a nonwoven fabric and a net-like sheet is known as an improved non-woven fabric filter material.
Japanese Unexamined Patent Publication (Kokai) No. 1-194912 discloses a filter in which an electret ultrafine fiber nonwoven fabric and a net are heat-fused. A filter medium fused with a net using a thin wire is disclosed.
In all of the non-woven fabrics obtained by fusing the net-like sheet, regular fibers such as melt-blown polypropylene and melt-blown polyester are used as the ultrafine fibers constituting the non-woven fabric. The ultrafine fiber web in a state where the intersections of the fibers have no heat fusion, or the web is partially heat-sealed at the intersections of the fibers using an embossing roll or a calendar roll, etc. Alternatively, the net is laminated on the web or the thermocompression-bonded non-woven fabric, and the non-woven fabric and the net are fused by using a heating means such as a calendar roll or a drier.
[0004]
By the way, when the heat-sealing state of the nonwoven fabric is viewed microscopically, it is difficult for the above-mentioned nonwoven fabric filter medium to sufficiently heat-seal the intersections of the fibers without impairing the ventilation resistance of the filter medium. For example, in the case of the embossing roll method, the parts other than the thermocompression-bonded portion are not fused, and in the case of the calendar rolling method, the front and back surfaces of the nonwoven fabric are largely fused, but the central part of the thickness However, there are few or a large number of fused parts, and a weakly fused state is obtained. As described above, in the nonwoven fabric in which the fused state of the fibers is different between the front surface, the center, and the back surface, the nonwoven fabric is folded or processed into a cylindrical shape, or both end surfaces of the cylindrical shape are heat-sealed with synthetic resin end surface members. Or when the end face member is bonded with a binder or the like, or when heating and sterilizing the filter medium, vibration, impact, vibration of the housing at the time of filtration, etc. There is a disadvantage that the maximum pore diameter is significantly increased, that is, the pore diameter stability is poor. Especially the basis weight is about 25g / m2 The above-mentioned high-basis material is a material in which the heat fusion of the fiber near the middle part of the nonwoven fabric thickness tends to be insufficient, the pore diameter stability is poor, and sometimes the maximum pore diameter after heating is as large as 25% or more. .
The filter medium thermocompressed at a high temperature and high pressure by a calendar roll method or the like has a somewhat improved pore diameter stability, but the whole fiber melts and changes into a film, resulting in a remarkable increase in airflow resistance. There is.
[0005]
[Problems to be solved by the invention]
The present invention provides a filter medium for precision filtration that does not change its maximum pore diameter due to heating, vibration, or the like, which is a problem of the prior art, and that can be easily processed into a high-strength and valley-shaped or other complicated shape. The purpose is to provide.
[0006]
[Means for Solving the Problems]
The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, have found that the following objects can be achieved to achieve the initial object, and have completed the present invention. That is, the configuration of the present invention is as follows.
(1)Fiber diameter of 10μm or less20 to 80% by weight of low melting point ultrafine fiber, whose melting point is higher than that of low melting point ultrafine fiber by 10 ° C or moreFiber diameter of 10μm or lessA nonwoven fabric comprising 80 to 20% by weight of high-melting ultrafine fibers and heat-fused with each other by the low-melting ultrafine fibers;Weaving composite fiber of low melting point component and high melting point componentHeat-fusible netsToHeat fusioncan getFilter media with a maximum pore size of 120 μm or lessAnd,The melting point difference between the low melting point resin of the ultrafine fibers and the low melting point resin contained in the net is 15 ° C. or less, and the low melting point resins have an interpenetrating structure at the intersection of the fibers.Filter media.
(2) Low melting point ultrafine fiber and high melting point ultrafine fiberOne or both ofComposite fiber, heat-fusible netFiberAnd the low melting point component and the low melting point ultrafine fiber component of the heat-fusible net are of the same type, and the maximum pore diameter change rate after heating is 20% or less.The filter medium according to the above (1).
(3) FoldedItems (1) and (2)Any filter media.
(4) Electret and air permeability of 0.1 to 100 cc / cm2Seconds, tensile strength is 2-100kg / 5cmItems (1) to (3)Any filter media.
(5) Spin multiple resins from the die,Fiber diameter of 10μm or less20 to 80% by weight of low-melting ultrafine fiber, whose melting point is higher than that of the fiber by 10 ° C or moreFiber diameter of 10μm or lessA web composed of 80 to 20% by weight of high melting point ultrafine fibers is obtained, and the web is heat-treated to obtain a non-woven fabric in which the fibers are thermally fused to each other by the low melting point ultrafine fibers, and the resin is spun from a die.Combination of low melting point component and high melting point componentA fiber is obtained, a heat-fusible net obtained by knitting the fiber is obtained, the above-mentioned nonwoven fabric and the heat-fusible net are laminated, and heat treatment is performed.AndHeat fusiondo it,The low melting point resin of the ultrafine fiber having a melting point difference of 15 ° C. or less and the low melting point resin contained in the net have an interpenetrating structure at the intersection of the fibers.A method for producing a filter medium having a maximum pore size of 120 μm or less.
(6) The method for producing a filter medium according to the above (5), wherein a nonwoven fabric obtained by heat treating an ultrafine fiber web spun by a melt blow method is used.
[0007]
The filter medium of the present invention is obtained by heat-sealing a non-woven fabric of heat-fused ultrafine fibers and a net, and the maximum pore diameter of the heat-sealed filter medium is 120 μm or less,
The non-woven fabric is made of low-melting ultra-fine fibers and high-melting ultra-fine fibers, and the ultra-fine fibers are fused together by the low-melting ultra-fine fibers;
It comprises a ratio of 20 to 80% by weight of low melting point ultrafine fibers and 80 to 20% by weight of high melting point ultrafine fibers,
The difference in melting point between the low melting point ultrafine fiber and the high melting point ultrafine fiber is 10 ° C. or more.
Two or more kinds of thermoplastic resins having a melting point difference of 10 ° C. or more are spun from a die by various methods and mixed, and the obtained web is heated to a temperature equal to or higher than the heat fusion temperature of the low melting point ultrafine fibers, and the intersection of the ultrafine fibers Into a nonwoven fabric by heat fusion
A resin is spun from a die to obtain a fiber, and the fiber is knitted and obtained as a net,
The non-woven fabric and the net are laminated, heat-treated and heat-sealed,
A method for producing a filter medium having a maximum pore diameter of 120 μm or less by heat fusion.
[0008]
In the spinning method of ultrafine fibers, a low melting point component and a high melting point component are discharged. A so-called single-component mixed fiber spinning method in which two or more spinners having different components are combined and two or more multiple components are introduced into one spinneret and different components are spun for each hole may be used. . Alternatively, a spinning method in which the first spinneret is a composite spinning and the second spinneret uses two types of single component spinnerets, and both the first spinneret and the second spinneret use two types of spinning composite spinnerets. Or a so-called single component / composite mixed fiber spinning method in which a single spinneret includes a composite spinning portion and a single component spinning portion.
Melt blow method, spun bond method as spinning method of ultrafine fiber
There are a flash spinning method and a drawing spinning method, and a composite spinning method and a mixed fiber spinning method. In particular, the mixed fiber spinning method by the melt blow method is preferable since the fibers can be mixed well. Further, it is preferable to use a mouthpiece in which the inlet groove of the mouthpiece can be changed for each component because the ratio of each component (low melting point component, high melting point component) can be changed. Various spinnerets such as a parallel type, a sheath-core type, a multi-segment type, and a sea-island type can be used as the composite spinneret. Alternatively, two kinds of ultrafine fibers may be once spun from separate spinnerets, and then the webs may be laminated and mixed with a needle punch, a water needle or the like.
[0009]
In the present invention, since its use is a filter medium for microfiltration, the diameter of ultrafine fibers is10 μm or less, Preferably 0.1 to 10 µm, more preferably 0.2 to 8 µm. Although the above-mentioned ultrafine fibers are mainly used for the nonwoven fabric used in the filter medium of the present invention, fibers having a fiber diameter of 20 μm or more may be mixed as long as the object of the present invention is not impaired.
[0010]
The ultrafine fiber of the present invention is a mixed fiber of a low melting point ultrafine fiber and a high melting point ultrafine fiber, and can be a mixed fiber of a low melting point ultrafine fiber (single component) and a high melting point ultrafine fiber (single component), It can be a mixed fiber of a low melting point ultrafine fiber (single component) and a high melting point ultrafine fiber (composite component), and a mixed fiber of a low melting point ultrafine fiber (composite component) and a high melting point ultrafine fiber (single component). And a mixed fiber of a low melting point ultrafine fiber (composite component) and a high melting point ultrafine fiber (composite component). However, the melting point of the composite component fiber is the melting point of the low melting point component because the low melting point component is thermally fused. Further, the composite fiber may be a composite fiber having the same components having different molecular weights and different degrees of crystallinity without a difference in melting point.
Examples of the thermoplastic resin usable for the ultrafine fiber include polypropylene, polyethylene, poly-4-methylpentene, a binary or terpolymer of propylene and another α-olefin, polyethylene terephthalate, polyamide, polycarbonate and the like. -Resins such as The melting point difference between the low-melting ultrafine fiber and the high-melting ultrafine fiber is 10 ° C or higher, preferably 15 ° C or higher and 150 ° C or lower, more preferably 20-100 ° C. I do.
As a combination of a mixed fiber of a low melting point ultrafine fiber (single component) and a high melting point ultrafine fiber (single component), polyethylene: polypropylene, propylene-ethylene-butene-1 copolymer: polypropylene, polypropylene: polyethylene terephthalate And low-melting polyester: polyethylene terephthalate, polyamide: polyethylene terephthalate, and the like.
In the case of a mixed fiber of a low-melting point ultrafine fiber (single component) and a high-melting point ultrafine fiber (composite component), a linear low-density polyethylene is used as the low-melting point ultrafine fiber (single component); Sheath) / polyamide (core),
In the case of a mixed fiber of a low melting point ultrafine fiber (composite component) and a high melting point ultrafine fiber (single component), a linear low density polyethylene (parallel) / polypropylene (parallel) as a low melting point ultrafine fiber (composite component): high melting point ultrafine Polyethylene terephthalate can be exemplified as the fiber (single component).
In the case of a mixed fiber of a low melting point ultrafine fiber (composite component) and a high melting point ultrafine fiber (composite component), linear low density polyethylene (parallel) / polypropylene (parallel) as the low melting point ultrafine fiber (composite component): high melting point ultrafine Examples of the fiber (composite component) include polypropylene (parallel) / polyethylene terephthalate (parallel),
High-density polyethylene (sheath) / polyethylene terephthalate (core) as low melting point ultrafine fiber (composite component): Polypropylene (sheath) / polyethylene terephthalate (core) as high melting point ultrafine fiber (composite component). .
[0011]
Two types of ultrafine fibers having different melting points are spun by a melt blow method or the like, and the obtained two types of webs are heated to a temperature at which the low melting point ultrafine fibers are melted. I do.
In the present invention, when the content of the low-melting-point ultrafine fibers in the nonwoven fabric is less than 20% by weight, even if the web is subjected to the heat treatment described below, a product having a small fusion point of the fibers and having good pore diameter stability after heating can be obtained. In addition, there are problems such as fluffing and insufficient strength. If the content of the low-melting ultrafine fiber exceeds 80% by weight, the heat treatment described below completely melts the low-melting ultrafine fiber and loses the fiber form, resulting in film formation, fiber shrinking pilling, etc. There are problems such as an increase in resistance and a result of poor filtration accuracy.
[0012]
The heat treatment is performed using a heating device such as a dry heat circulation type dryer, a through-air type dryer, a calendar roll, and an emboss roll. Among the heating devices, non-woven fabrics having high air permeability can be obtained by heat-treating using a device such as a through-air type dryer capable of heat-sealing the non-woven fabric without applying much pressure. Further, a non-woven fabric having a small maximum pore diameter can be obtained from a thermocompression-bonded material such as a calendar roll using a thermocompression-type heating device.
This heat treatment can be used for heat fusion of the nonwoven fabric, heat fusion of the net, and heat fusion of the nonwoven fabric and the net.
[0013]
The non-woven fabric used for the filter medium of the present invention is a non-woven fabric that is made of ultra-fine and heat-fusible low-melting fiber, and that the low-melting fiber is melted by heat treatment and the intersection of the fibers is heat-sealed. Therefore, by performing the heat treatment at a temperature equal to or higher than the softening point of the low-melting fiber and equal to or lower than the melting point of the high-melting fiber, the high-melting fiber retains its shape without melting, and the intersection of the fibers is Is formed into a nonwoven fabric by heat fusion. Therefore, the pores are not opened due to sterilization treatment, high-temperature filtration, vibration, or the like in the subsequent process, and the pore diameter is stable. Further, a kind of film formation due to the complete melting of the fiber does not occur, and if it does occur, it is extremely small. Therefore, a product having high air permeability and small pore size can be obtained.
[0014]
On the other hand, in a nonwoven fabric of 100% single-component ultrafine fibers obtained by a conventional melt blow method or the like, a large amount of unfused fiber is generated near the center of the thickness of the nonwoven fabric, Since the non-woven fabric has an extremely weak bond, the material obtained by fusing the nets described below to the non-woven fabric is subjected to heat sterilization treatment, high-temperature filtration or the like, or is opened by vibration or the like. In the case of a material heated at a high temperature with a calendar roll or the like, the fibers are completely melted, the shape of the fibers is lost, and a film is formed. When heated at a high temperature by a through-air heater, the fibers melt and shrink or agglomerate into beads. Such a material has a small air permeability or a large maximum pore size.
[0015]
The nonwoven fabric used for the filter medium of the present invention has a basis weight of about 3 to 1000 g / m2.2 , Preferably 4 to 700 g / m2 Can be used. Further, the pore size of the nonwoven fabric can be changed by changing processing conditions such as the basis weight, the heating temperature, the linear pressure of the calendar roll, the processing time, and the like. A non-woven fabric having a smaller pore diameter can be obtained as the fiber is produced under the condition that the fineness of the fiber is small, the basis weight is large, and the linear pressure of the calendar roll is large.
[0016]
The filter medium of the present invention is obtained by heat-sealing the above-mentioned nonwoven fabric and net, and the net is obtained by knitting or weaving a fiber containing a thermoplastic resin. Netting fiber isTwo or moreComposite spinning of thermoplastic fibersdo itComposite fiber that can be thermally fused by the obtained heat treatmentIs. In particular, at least two or more kinds of thermoplastic resins having a melting point difference of 10 ° C. or more are used.make use ofA composite fiber obtained by a composite spinning method is preferred. The heat-fusible composite monofilament is made into a net by weaving or the like, or the net is heated at a heat-sealing temperature or higher to fuse the intersections of the fibers. The melting point difference of the composite component used for the heat-fusible net is 10 ° C or more, preferably 15 ° C or more and 150 ° C or less, more preferably 20 to 100 ° C. Preferably, the net is made by weaving net fibers having a total fineness of about 30 to 4000 denier at a weave density of about 0.5 to 25 fibers / 25 mm.
[0017]
The composite form of the netting fiber, the resin that can be used for the netting fiber, the combination of the resin, and the like are a combination of a resin that is heat-fused with the nonwoven fabric.To. Contained in ultra-fine fiber low melting point resin and netIsDifference from low melting point resinIs15 ° C or lessIsBy the heat treatment described below, the low-melting-point resins have an interpenetrating structure at the intersections of the fibers, so that the non-woven fabric and the net are strongly heat-sealed and are not easily separated at the boundary surface. In particular, it is preferable that the low-melting point resin of the low melting point ultrafine fiber and the low melting point resin of the net are of the same type, such as polyolefin / polyolefin and polyester / polyester.
that's all
[0018]
The nonwoven fabric and the net are laminated as a nonwoven fabric / net, a net / nonwoven fabric / net or the like, or a laminate obtained by further laminating the laminate in two steps, and the like are heated and pressed. The filter material is heated by the known heating method as described above, and the nonwoven fabric and the net are heat-sealed to obtain a filter medium. A method of performing a roll treatment after heating or a method of performing thermocompression bonding with a heating roll may be used. Of course, a spunbonded nonwoven fabric having a relatively large fineness, a staple heat-sealed nonwoven fabric, or the like may be laminated on the laminate.
[0019]
The filter medium of the present invention can be used attached to a housing or the like without folds or the like. Further, the filter medium can be formed into an arbitrary shape such as a sharp angled valley, a U shape, an uneven shape, or the like using a fold-folding machine or a molding machine, and attached to a housing for use. Further, the filter medium after being formed into the above-mentioned various shapes can be further processed into a cylindrical shape, a spiral shape or the like. In the case of a cylindrical shape, the left and right ends are bonded by fusion or a binder.
The housing can be of various shapes depending on the application to be filtered. For example, a cylindrical housing having a cylindrical core material having a large number of openings on its side surface, a porous cylindrical outer frame material, and an end face seal member as a main component, or a square frame-shaped housing And a rectangular housing having metal nets or the like as a main constituent member, a box-shaped multi-layer housing in which a filter medium is mounted in a multi-layer shape in a box shape, or a housing of any shape that can be mounted in a place to be filtered is used. it can.
[0020]
The filter medium of the present invention may be an electret material. As a method of electretization, there is a method of electret between a die and a collecting surface while collecting fibers at the time of spinning, a method of electreting before spinning a web or the like after spinning, and the like. . In addition, there is a method of electretizing a nonwoven fabric, a nonwoven fabric in which a nonwoven fabric and a heat-fusible net are heat-fused, a folded filter material, a filter material attached to a housing, and the like. The electretization is performed by a DC corona discharge having a voltage of about 1 to 30 kV. The non-woven fabric has a thickness of about 10 to 45 Clon / cm.2 Those having a surface electrification density of are preferred.
[0021]
In the filter medium of the present invention, ultrafine fibers having a fiber diameter of 10 μm or less may be in a density gradient type. Further, the filter medium of the present invention may be a material in which other nonwoven fabrics or sheets having different fiber materials and fiber diameters are laminated. Examples of other non-woven fabrics include a composite melt-blown non-woven fabric having a fiber diameter of about 50 μm or less, a heat-fusible composite fiber non-woven fabric having a fiber diameter of 100 μm or less, or a laminated sheet of the non-woven fabric and a heat-fusible net. it can.
[0022]
【Example】
Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. In each example, the evaluation of the physical properties, the filtration performance, and the like of the filter medium was performed by the methods described below.
[0023]
Fiber diameter of non-woven fabric: 10 small pieces are cut out from a web, non-woven fabric, or filter medium, taken with a scanning electron microscope at a magnification of 100 to 5000 times, and a total of 100 fiber diameters are measured. The average value (μm) Is the fiber diameter of the nonwoven fabric.
[0024]
Tensile strength: 5 cm width breaking strength (kg / 5 cm) was determined using a tensile strength tester.
[0025]
Air permeability: The air permeability was determined by a method specified in JIS-L1006A using a fragile type air permeability tester. Unit, cc / cm2 . Seconds.
[0026]
Maximum pore diameter: Using a bubble point tester, the maximum pore diameter (μm) was determined by the method specified in ASTM-F-316-86.
[0027]
Maximum pore diameter change rate after heating: Using the bubble point tester, the maximum pore diameter (A) before heating and the maximum pore diameter (F) after heating at 80 ° C. for 10 minutes are determined in the same manner as above using the following formula. Calculated.
Maximum pore diameter change rate after heating (%) = 100 (FA) / A
[0028]
Filtration accuracy: A circulating filtration tester comprising a water tank containing 50 liters of water, a pump, a housing, and a filter was used. One filter medium is attached to the housing of the filter, and 5 g of a cake (carborundum # 4000) is added to the water tank while circulating water at a flow rate of 30 liters per minute. One minute after the addition of the cake, 100 cc of the filtered water collected is filtered through a membrane filter. The size of the particles collected on the membrane filter was measured with a particle size distribution analyzer, and the largest particle size (maximum outflow diameter, unit μm) was taken as the filtration accuracy of the filter medium.
[0029]
Pressure loss: In the above-mentioned circulating filtration accuracy test, only water was circulated at a flow rate of 30 liters per minute without adding a cake. One minute after the start of circulation, the pressure loss (kg / cm2).
[0030]
Examples 1-3, Comparative Examples 1-3
Mixed fiber spinning was performed using two extruders and a mixed fiber type melt blower having a melt blow spinneret having a hole diameter of 0.3 mm and a number of holes of 501 as a main component. The die is such that the two types of molten resin extruded from the two extruders are not mixed in each hole, but are discharged in each hole, and the two types of molten resin discharged from each hole are mixed in various hole ratios. It is a base with a structure that can be changed with.
[0031]
Melt flow rate 120 (MFR, g / 10 minutes, 230 ° C.) as a first component, melt low rate 120 (MFR, g / 10 minutes, 230 ° C.) as a second component. A polypropylene having a melting point of 164 ° C. was melt-extruded and melt-blown. The spinning conditions were as follows: the spinning temperature was constant at 260 ° C. for the first component and 280 ° C. for the second component, and the fiber discharged from the spinning hole was extruded at a temperature of 360 ° C. Air pressure 1.2kg / cm2 It was introduced at G and sprayed onto a conveyor net equipped with a blast gas suction device. The fiber diameter of the ultrafine fibers was about 3 μm. The web was heated at 135 ° C. for 15 seconds using a through-air heater, and the basis weight at which the intersections of the fibers were thermally fused was about 100 g / m 2.2 Was obtained.
[0032]
The composite ratio of the sheath component is MFR18 (g / 10 min, 190 ° C.), linear low density polyethylene having a melting point of 124 ° C., and the core component is MFR8 (g / 10 min, 230 ° C.), polypropylene having a melting point of 164 ° C. / 50 (weight ratio), using a heat-fusible composite monofilament with a fineness of 250 d / f, weaving a plain woven fabric with a weave density of 17 × 17/25 mm in both directions, and then heating the net with a tenter type Heating was performed at a temperature of 135 ° C. using a machine to obtain a net where the intersections of the fibers were heat-sealed.
[0033]
The material obtained above was laminated in three layers in the order of net / nonwoven fabric / net, heated at a temperature of 140 ° C. for 15 seconds using a through-air type heater, and then immediately heated with a calendar roll at a temperature of 30 ° C. After the treatment, a filter medium in which the nonwoven fabric and the net were thermally fused was obtained.
[0034]
Using a fold-folding machine, the filter medium was used to obtain a filter medium having a fold height of 20 mm and a pleated W shape.
The crimped filter medium was wound around a hollow metal core having an outer diameter of 30 mm and a height of 250 mm having a large number of holes on its side surface to obtain a filter medium having an inner diameter of about 30 mm and an outer diameter of 70 mm. The right and left joints of the filter medium were heat-sealed. Further, a metal end seal member having an opening having a diameter of 30 mm was bonded to the upper and lower ends using a binder to obtain a cylindrical filter medium. The surface area of this filter medium was increased by about 9.1 times as compared with that of the unfolded one having an outer diameter of 70 mm.
[0035]
Table 1 shows the test results of the physical properties of the filter medium before and after heating, and the filtering performance of the filter medium folded and processed into a hollow cylindrical shape.
From Table 1, it can be seen that the filter medium of the present invention (Examples 1 to 3) has a maximum rate of change in pore size after heating of 10% or less, has good pore size stability with respect to heating, and has a high filtration accuracy after being folded. It can be seen that it may be about 4 to 5 μm.
On the other hand, when the content of the low-melting ultrafine fibers is less than 20% (Comparative Examples 1 and 2), it can be seen that the openings are opened by heating, the maximum pore diameter becomes large, and the filtration accuracy is poor. In addition, it can be seen that a product having 100% of low melting point ultrafine fibers (Comparative Example 3) has good filtration accuracy but is inferior in air permeability and pressure loss.
[0036]
Example 4
The mixed fiber melt-blown microfiber web obtained in Example 2 was treated at a temperature of 140 ° C. using a through-air type heating machine, and the basis weight at which the intersections of the fibers were thermally fused was 98 g / m 2.2 Was obtained.
[0037]
A sheath-core type filament having a sheath component of high-density polyethylene having a melting point of 133 ° C. and a core component of polypropylene. A plain woven fabric was woven in the configuration. Thereafter, heating was performed at a temperature of 135 ° C. using a tenter-type heater to obtain a net in which the intersections of the fibers were heat-sealed.
[0038]
The nonwoven fabric and the net were laminated in three layers of net / nonwoven fabric / net. The laminate was treated at a temperature of 120 ° C. using a calendar roll to obtain a filter medium in which the nonwoven fabric and the net were heat-sealed.
This filter medium was folded into a cylindrical filter medium in the same manner as in Example (1) after folding. The surface area of this filter medium was increased by about 9.1 times as compared with that of the unfolded filter having an outer diameter of 70 mm. From Table 1, the filter medium of Example (4) has a maximum pore diameter change rate of 0% after heating, has good pore diameter stability, and has a good filtration accuracy of 1.1 μm after the fold processing. Was.
[0039]
Example 5
The filter medium obtained in Example 2 where the nonwoven fabric and the net were heat-sealed was directly placed on the ground electrode, and treated for 20 seconds in a high electric field applied with a DC voltage of 14 kv / cm from the discharge electrode above the ground electrode. Then, an electret filter medium was obtained. The filter medium was cut into a size of 30 cm × 30 cm, placed on a table in an office where many people enter and exit, and airborne dust was naturally adsorbed to the filter medium. After 60 days, the degree of contamination on the surface of the filter medium was determined to be 2.5 grade by judging with a staining scale (grade 1: large pollution, grade 5: small pollution) specified in JIS-L0805. On the other hand, when the filter medium obtained in Example (2), which did not become electret, was also observed for the degree of contamination at the same time, it was rated 4.5.
[0040]
Example 6
MFR43 (g / 10 min, 190 ° C), high-density polyethylene having a melting point of 133 ° C as a first component, polyethylene terephthalate having an intrinsic viscosity of 0.60 and a melting point of 253 ° C as a second component, a pore diameter of 0.3 mm, Composite melt blow spinning was performed from a parallel type melt blow die having 501 holes to obtain a composite low melting point ultrafine fiber. The spinning conditions were as follows: the compounding ratio was 40 (first component) / 60 (second component) (weight ratio), the spinning temperature was 260 ° C for high-density polyethylene, and 280 ° C for polyethylene terephthalate. The fiber discharged from 390 ° C. is blown at a pressure of 1.5 kg / cm.2 . It was introduced at G and sprayed onto a conveyor net equipped with a blast gas suction device. The composite low melting point ultrafine fiber web has a basis weight of 40 g / m2The fiber diameter was 4.0 μm.
[0041]
The basis weight of the web and the 100% polypropylene high-melting ultrafine fibers obtained in Comparative Example (1) was 101 g / m2.2 And a web having a fiber diameter of 3.3 μm, and a pressure of 70 kg / cm.2 Under the conditions described above, water needle treatment was performed. This nonwoven fabric was dried at 80 ° C., heat-treated at 145 ° C. for 20 seconds by a through-air heater, and immediately thereafter treated with a calender roll at 30 ° C. to fuse the intersections of the fibers. A non-woven fabric was obtained.
[0042]
Using the nonwoven fabric and the net used in Example (1), lamination was performed in the order of net / nonwoven fabric / net. The laminate was treated at a temperature of 120 ° C. using a calendar roll to obtain a filter medium in which the nonwoven fabric and the net were heat-sealed.
This filter medium was folded into a cylindrical filter medium in the same manner as in Example (1) after folding. The surface area of this filter medium was increased by about 9.1 times as compared with that of the unfolded filter having an outer diameter of 70 mm.
Before heating, the filter medium had a tensile strength of 46.3 kg / 5 cm and a maximum pore size of 26 μm. After heating at 80 ° C. for 10 minutes, the maximum pore diameter is 27 μm, the maximum pore diameter change rate is 3.9%, and the air permeability is 18.8 cc / cm.2 . Seconds. The folds have a filtration accuracy of 3 μm and a pressure loss of 0.04 kg / cm.2 It was.
[0043]
Example 7
Two extruders, one die having a hole diameter of 0.3 mm including a single component hole and a multiple component hole, 167 low melting single component holes, a composite component hole of a low melting component and a high melting component (parallel type) Mixed fiber spinning was performed using a melt blow spinneret having 167 pieces and 167 high melting point single component holes. Melt blow spinning was performed using the same linear low density polyethylene as in Example 1 as the low melting point component and the same polypropylene as in Example 1 as the high melting point component. The spinning conditions were as follows: the spinning temperature was 245 ° C. for the low melting point component and 260 ° C. for the high melting point component, and the composite ratio of the low melting point component and the high melting point component was 1: 1 (weight%). The low melting point (single component) ultrafine fiber: the low melting point (composite component) ultrafine fiber: the high melting point (single component) ultrafine fiber is set at 1: 1: 1 (weight%), extruded, and the fiber discharged from the spinning hole is extruded. Air at a temperature of 330 ° C with a pressure of 1.2 kg / cm2 G and sprayed on the same conveyor net as in Example 1. The fiber diameter of the ultrafine fibers was about 4 μm. The low melting point (single component) ultrafine fiber was 3.6 μm, the low melting point (complex component) ultrafine fiber was 4.5 μm, and the high melting point (single component) ultrafine fiber was 3.7 μm.
This web was heated at a temperature of 145 ° C. for 30 seconds using the same heating machine as in Example 1, and the fiber intersection was heat-sealed at a basis weight of about 100 g / m 2.2 Was obtained.
The nonwoven fabric and the same net as in Example 1 were laminated in three layers in the order of net / nonwoven fabric / net, heated at 135 ° C. for 15 seconds using a through-air heater, and then immediately calendered at 30 ° C. The resultant was treated with a roll to obtain a filter medium in which the nonwoven fabric and the net were heat-sealed.
The filter medium was crimped in the same manner as in Example 1, and a metal end face sealing member was bonded to obtain a cylindrical filter medium. The surface area of this filter medium was increased by about 9.1 times as compared with that of the unfolded one having an outer diameter of 70 mm.
Before heating, the filter medium had a tensile strength of 31.8 kg / 5 cm and a maximum pore size of 40 μm. The maximum pore diameter after heating at 80 ° C. for 10 minutes is 41 μm, the maximum pore diameter change rate after heating is 2.5%, and the air permeability is 30 cc / cm.2Seconds. The material after the fold processing has a filtration accuracy of 5.2 μm and a pressure loss of 0.04 kg / cm.2Met.
The filter medium of the present invention had a larger fiber diameter than those of Comparative Examples 1 and 2, but had better filtration accuracy, and had a maximum rate of change in pore size after heating of 10% or less.
[0044]
【The invention's effect】
The filter medium of the present invention is a material obtained by heat-sealing a non-woven fabric in which the intersections of ultrafine fibers are heat-sealed and a heat-fusible fiber net having high fineness. Therefore, the filter medium is excellent in tensile strength, has a small pressure loss, can capture fine particles of 5 μm or less, has excellent filtration accuracy, has a high air permeability, has a stable pore diameter with respect to heating, and does not open due to heating or the like. Since the filter medium has good pore diameter stability against heating, stable high-precision filtration can be performed even when heat sterilization or high-temperature filtration is performed.
In addition, this filter medium can be processed into folds and irregularities. In addition to the above-described effects, the fold-folded filter medium has an effect that the filtration life is long because the filtration area is large. In addition, those using a melt-blown web as a nonwoven web can be used as a filter medium for microfiltration in the food field since a finishing agent such as an antistatic agent does not adhere to the fibers.
[0045]
[Table 1]
Claims (6)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP06681194A JP3567480B2 (en) | 1993-05-26 | 1994-03-09 | Filter medium and method for producing the same |
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP14695793 | 1993-05-26 | ||
| JP5-146957 | 1993-05-26 | ||
| JP06681194A JP3567480B2 (en) | 1993-05-26 | 1994-03-09 | Filter medium and method for producing the same |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH0788312A JPH0788312A (en) | 1995-04-04 |
| JP3567480B2 true JP3567480B2 (en) | 2004-09-22 |
Family
ID=26408006
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP06681194A Expired - Lifetime JP3567480B2 (en) | 1993-05-26 | 1994-03-09 | Filter medium and method for producing the same |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP3567480B2 (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR101354301B1 (en) * | 2012-04-06 | 2014-01-24 | 웅진케미칼 주식회사 | Filter assembly for fan type cooling apparatus |
| US20210257165A1 (en) * | 2018-08-24 | 2021-08-19 | Sekisui Chemical Co., Ltd. | Electret sheet and piezoelectric sensor |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP4556263B2 (en) * | 1999-11-11 | 2010-10-06 | チッソ株式会社 | Pleated net laminate |
| JP5600106B2 (en) * | 2009-08-10 | 2014-10-01 | 旭化成せんい株式会社 | Filter cloth for dust collector |
| JP7080102B2 (en) * | 2018-05-14 | 2022-06-03 | 積水樹脂株式会社 | Young tree protector |
| KR102362231B1 (en) * | 2018-06-19 | 2022-02-10 | 코오롱인더스트리 주식회사 | Non-woven for primary carpet backing and manufacturing method thereof |
| CN113750648B (en) * | 2020-06-01 | 2022-09-06 | 辽宁博联过滤有限公司 | Filter cloth for vertical filter press and preparation method thereof |
-
1994
- 1994-03-09 JP JP06681194A patent/JP3567480B2/en not_active Expired - Lifetime
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR101354301B1 (en) * | 2012-04-06 | 2014-01-24 | 웅진케미칼 주식회사 | Filter assembly for fan type cooling apparatus |
| US20210257165A1 (en) * | 2018-08-24 | 2021-08-19 | Sekisui Chemical Co., Ltd. | Electret sheet and piezoelectric sensor |
| US11908629B2 (en) * | 2018-08-24 | 2024-02-20 | Sekisui Chemical Co., Ltd. | Electret sheet and piezoelectric sensor |
Also Published As
| Publication number | Publication date |
|---|---|
| JPH0788312A (en) | 1995-04-04 |
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