JP4679725B2 - A durable and wettable liquid permeable web made using an indirect plasma polymerization method - Google Patents

Description

【００３１】
ｈ）一般式（Ｒ²）（Ｒ²）Ｃ＝Ｃ（Ｒ²）−ＯＣ（Ｏ）ＣＨ₃のビニルアセテート、
ｉ）一般式Ｒ²ＣＨ＝ＣＨＲ³の脂肪族ビニル化合物、およびこれらの混合物。
【００３２】
ここで、各Ｒ²は独立に、水素またはＣ₁−Ｃ₁₀アルキル、好ましくはＣ₁−Ｃ₅アルキルであり、各Ｒ³は独立に、炭素原子が約１０以下の脂肪族炭化水素基であり、この脂肪族炭化水素基は、置換されていないか、１または複数種の極性基たとえばカルボキシ基、ヒドロキシ基、アミノ基、および（ポリ）エチレンオキシド基によって置換されているか、１または複数種のサルフェート基、ホスフェート基、スルホナート基またはこのような基の混合物によって置換されている。
【００３３】
好ましいアクリル誘導体の具体的な例としては、以下のものが挙げられる。
アクリル酸、メタクリル酸、ヒドロキシエチルメタクリレート（ＨＥＭＡ）、メチルメタクリレート（ＭＭＡ）、ジメチルアミノエチル−メタクリレート（ＤＭＡＥＭＡ）、２−ヒドロキシエチルアクリラート（ＨＥＡ）、Ｎ,Ｎ−ジメチルアクリルアミド（ＤＭＡ）、Ｎ−アクリロイルモルホリン（ＮＡＭ）、およびエチレングリコールジメタクリレート（ＥＧＤＭＡ）。好適なビニルエーテルの具体的な例は、メチルビニルエーテル、エチルビニルエーテル、およびメトキシエチルビニルエーテルである。また、好適な親水性モノマーには、エチレングリコーヅ、エチレンオキサイド、およびプロピレンオキサイドも含まれる。モノマーは、個別に用いても良いし、モノマーの混合物として用いても良い。
【００３４】
モノマーを、チャンバーに導入する前に十分な温度に加熱して、化合物を気化させ、コーティングが適切な速度で堆積するように蒸気圧を十分に発生させる。典型的に、温度は、約４０℃ないし約１００℃、より典型的には約４０℃ないし約６０℃である。気体のモノマー化合物と一緒に、気体状態の酸素とアルゴンとを同時に堆積チャンバー内に供給する。しかし酸素とアルゴンとは、それぞれ別の供給手段および別のマスフローコントローラーを用いて供給する。用途に依存して、Ｏ₂の流量は約５ｃｍ³／分（標準状態）（「ｓｃｃｍ」）ないし約１２００ｓｃｃｍ、気体モノマー化合物の流量は約１ｓｃｃｍないし約２５０ｓｃｃｍ、Ａｒの流量は約１ｓｃｃｍないし約１５０ｓｃｃｍである。アルゴンを用いると、使用している気体材料の堆積速度が上がる。従って、アルゴンをプロセスに用いるのが好ましい。
【００３５】
代替的に、米国特許第4,842,893号（Yializisに1988年4月29日に付与）に記載されたフラッシュ気化技術を用いて、モノマー堆積を実現しても良い。この文献の開示は、本明細書において参照により取り入れられている。
【００３６】
低温プラズマを減圧ガス雰囲気中で発生させ、その圧力は、約０．００１ないし約１０Ｔｏｒｒ、好ましくは約０．０１ないし約５Ｔｏｒｒ、より好ましくは約０．０５ないし約１Ｔｏｒｒ、最も好ましくは約０．０５ないし約０．４Ｔｏｒｒであり、使用するプロセスおよび処理中のウェブに依存する。
【００３７】
出発ウェブに関しては、ウェブは平坦（２次元）であっても良いし、複雑（３次元。あらかじめ開口部が設けられたフィルムなど）であっても良い。すなわちプラズマ重合を、ウェブに開口部を形成する前に行っても良いし、形成した後に行っても良い。好ましい実施形態においては、開口部を形成した後にプラズマ処理を行って、均一な親水性コーティングをフィルム表面上により良好に保持する。
【００３８】
上述した、HIMONT Plasma Scienceから販売される最新式のプラズマシステムたとえばPS0500D反応装置にはスロットルバルブが取り付けられており、ガス流量を同じにしたままでプロセス圧力を変えることが可能になっている。
【００３９】
望ましい親水性コーティングを得るためのプラズマ処理時間は、典型的に約０．１分ないし約１０分、好ましくは約１．５分ないし約４分、最も好ましくは約１．５分ないし約２．５分である。気相の反応を起こすために用いるＲＦ電力は、好ましくは約１０ないし約１０００Ｗ、より好ましくは約５０ないし約５００Ｗ、最も好ましくは約７５ないし約２５０Ｗである。使用するＲＦ電力は、約１００ないし約２５００Ｗであり、処理中の基体およびスループット要求に依存する。結果として生じる親水性コーティングは、いろいろな厚みで作製できるが、典型的には約０．０１ないし約２．５μｍ、好ましくは約０．５ないし約１μｍである。
【００４０】
間接プラズマ重合を行っている間、ウェブはプラズマゾーンから下方に約１ないし約４０ｃｍの距離に配置されていることが好ましい。同様に、モノマー入口は、プラズマゾーンから下方に約１ないし約３５ｃｍの距離に配置されていることが好ましい。プラズマゾーンから下流（すなわち下方）のウェブの距離は、より好ましくは約２ないし約２０ｃｍであり、最も好ましくは約３ｃｍないし約１０ｃｍである。プラズマゾーンから下流のモノマー入口の距離は、好ましくは約２ないし約２０ｃｍであり、最も好ましくは約３ｃｍないし約１０ｃｍである。
【００４１】
１つの好ましい実施形態においては、本発明に係る重合可能な不飽和化合物の間接プラズマ重合を、以下のプラズマ条件の下で行うことが好ましい。
【００４２】
電力＝１０ないし１００Ｗ、
電圧＝８×１０²ないし４×１０³Ｖ、
プラズマガス流量＝１ないし１００ｓｃｃｍ（標準立方センチメートル）、
モノマー流量＝１ないし５０ｍｇ／分、
供給ガス流量＝１ないし１００ｓｃｃｍ
モノマー源の温度＝−８０℃ないし＋８０℃
周波数＝１ｋＨｚないし２７．１２ＭＨｚ、最も好ましくは１３．６ＭＨｚまたは２７．１２ＭＨｚ、
プラズマガス＝Ａｒ、Ｈｅ、Ｎ₂、
圧力＝０．０１ないし１Ｔｏｒｒ
本発明のポリマーコーティングは、ウェブとプラズマゾーンとの間およびモノマー入口とプラズマゾーンとの間の距離に関する前述した条件の下で、重合可能な不飽和化合物をウェブ上で間接プラズマ誘導重合することによって得ることができる。本発明に係るコーティングは、イングロー（または直接）プラズマ誘導重合によって得られるコーティングとは反対に、ポリマー鎖の繰り返し単位の大部分が、個々の不飽和化合物を非プラズマラジカル重合して得られる繰り返し単位と、構造が同一であるという事実によって特徴付けられる。典型的に、約７０％ないし約９８％、より典型的には約７６％ないし約９８％、最も典型的には約８２％ないし約９８％の繰り返し構造単位が、同じモノマーの非プラズマラジカル重合によって得られるポリマーと同じ構造を示す。典型的に、約２％ないし約３０％、より典型的には約２％ないし約２４％、さらにより典型的には約２％ないし約１８％の残りの構造単位が、処理されたウェブに対する共有結合基（covalent linking groups）として、または隣接するポリマー鎖の間の架橋部位として機能する。
【００４３】
本発明のプラズマ誘導ポリマーコーティングの定性的および定量的な特性は、典型的に後に略述するようにして測定することができる。
【００４４】
コーティングの均一な構造および制御可能な比較的度合いの低い架橋が、驚くことに、基台およびモノマー入口の位置の特定の条件下で、重合可能な不飽和化合物を間接プラズマ重合することによって達成される。このような構造および架橋によって、処理されたウェブの耐久的な湿潤性をもたらすコーティング特性が形成される。コーティングの具体的な利点は、処理されたウェブ表面への強い粘着力であり、これはかなりの程度、ウェブの性質（nature）とは無関係に得られる。
【００４５】
すでに述べたように、プラズマ誘導親水性コーティングは水に対する接触角が９０°未満を示し、ウェブ上に垂らしたわずかな水または水性ベースの液体も、ウェブのコーティングされた表面に自然に広がる。好ましい実施形態においては、処理されたウェブを、低温プラズマガス組成物（本明細書においては「表面改質ガスの流れ」とも言う）にさらして、または赤外線、電子ビーム、熱電子線または紫外線など（しかしこれらに限定されない）を放出する装置のようなエネルギー源にさらすことによって、さらに処理しても良い。後者は本明細書においては「放射線硬化」とも言う。本発明におけるエネルギー源として好適な装置が、米国特許第4,842,893号（Yializisに1988年4月29日に付与）に開示されている。この文献の開示は本明細書において参照により取り入れられている。
【００４６】
表面改質ガスの流れの実施形態においては、親水性コーティングの湿潤性を高めるために、表面改質ガスの流れにＮ₂ＯとＣＯ₂とが含まれていることが好ましい。このような好ましい実施形態の１つにおいては、プラズマガス組成物は、約８０ないし約４０モル％のＮ₂０と約２０ないし約６０モル％のＣＯ₂、好ましくは約７０ないし約４５モル％のＮ₂０と約３０ないし約５５モル％のＣＯ₂、最も好ましくは約６０ないし約４５モル％のＮ₂０と約４０ないし約５５モル％のＣ０₂（なお、混合物中のＮ₂ＯおよびＣＯ₂の量は、１００ないし１０モル％に等しい）を、親水性コーティングの表面を改質してその湿潤性を高めるのに十分な時間の間、含有する。
【００４７】
放射線硬化の実施形態においては、放射線源はガス放電電子ビーム銃であることが好ましい。電子銃は、電子の流れをエミッターウィンドウを通してモノマー上に送ってモノマーをさらに硬化させて、親水性コーティングの湿潤性を高める。硬化は、電子ビームの電圧をモノマーコーティングの誘電厚み（dielectric thickness）に合わせることによって制御される。例えば１０Ｋ電子ボルトでは、堆積されたモノマー中を約１μｍだけ進む。
【００４８】
プラズマプロセスは、通常以下のように行う。処理すべきウェブを真空チャンバー内に配置した後、チャンバー圧力を典型的に約０．００５Ｔｏｒｒまで下げる。使用するプロセスガスまたはプロセスガス混合物をチャンバー内に導入して、チャンバー圧力を０．０４ないし０．４Ｔｏｒｒで一定にする。作業領域の内部寸法は、およそ１．７３×０．７６×１．０２ｍ（幅×高さ×奥行き）で、全作業容積は１．３４ｍ³である。好適な高周波の形態のエネルギー（典型的に１３．５６ＭＨｚの無線周波数エネルギー）を用いて、プラズマを発生させる。上述したシステムにおいては、全電力入力容量が２５００Ｗ以下で行う。ＲＦエネルギーによってガスが解離して、特有のグローを特徴とするプラズマが発生する。プロセスを減圧下で行うため、ガスのバルク温度は周囲温度に近い。そのため、低温ガスプラズマ、グロー放電、または低温ガスグロー放電と言われる。プラズマ中で生成される電子またはイオンが、ウェブ表面に衝撃を与えて、原子を取り去るか結合を切り、フリーラジカルを生成する。これらのフリーラジカルは不安定であるため、プラズマガス内でフリーラジカルまたは基と反応してより安定な状態を満たそうとし、ウェブ表面に新たな部分（moieties）が形成される。加えて、グロー放電内の高エネルギー電子によって気相状態の分子が壊されて複雑な化学反応が起こり、その結果、薄い親水性コーティングがウェブの少なくとも１つの表面に堆積する。
【００４９】
典型的に、かつ好ましくは、親水性コーティングをプラズマ堆積させる前に、初期工程を行う。この工程の目的は、処理すべきウェブ表面をクリーニングして、その後に堆積される薄い親水性コーティングの付着力を高めることである。クリーニングは、赤外線、電子ビーム、熱電子線および紫外線など（しかしこれらに限定されない）のエネルギー源からの放射線にウェブ表面をさらすこと（本明細書において放射線クリーニングと言う）によって、またはプラズマクリーニングによって行うことができる。本発明でのエネルギー源として好適な装置が、米国特許第4,842,893号（1988年4月29日にYializisに付与）に開示されている。この開示は本明細書において参照により取り入れられている。放射線クリーニングの実施形態においては、放射線源はガス放電電子ビーム銃であることが好ましい。電子銃は、電子の流れをエミッターウィンドウを通してウェブ表面へ送って、原子を取り去るか結合を切り、フリーラジカルを生成する。これらのフリーラジカルは不安定であるためより安定な状態を満たそうとし、その結果、フリーラジカルは、ウェブの親水性コーティングの形成に用いられるモノマーに対する結合部位（bonding site）の役目を果たす。クリーニングは、電子ビームの電圧を誘電厚みまたは所望するクリーニング深さに合わせることによって制御される。例えば１０Ｋ電子ボルトでは、フィルム中を約１μｍの深さだけ進む。
【００５０】
プラズマクリーニングの実施形態においては、ガスは典型的にＡｒ単独か、Ｏ₂単独か、またはＡｒとＯ₂との混合物（たとえば１：１の比率）である。ガス流量は典型に、約２０ないし約１００ｓｃｃｍ（標準状態でのｃｃ／分）、好ましくは約４０ないし８０ｓｃｃｍ、最も好ましくは約５０ないし約６０ｓｃｃｍである。ＲＦ電力は約１１００ワットであり、プロセス圧力は約０．０４Ｔｏｒｒである。随意的な初期工程の後の次の工程は、上述した親水性コーティングのプラズマ堆積である。この工程は、後の実施例でより詳細に述べる。
【００５１】
親水性コーティングを得るためにプラズマ処理するポリマーフィルムとして有用な材料は、熱可塑性ポリマーから得られる。本明細書において用いる用語「熱可塑性ポリマー」は、概略的に、フィルムの作製に使用できるどんな熱可塑性ポリマーをも意味する。熱可塑性ポリマーの例には（実例としてのみだが）、以下のものがある。エンドキャップされた（end-capped）ポリアセタール、たとえばポリ（オキシメチレン）またはポリホルムアルデヒド、ポリ（トリクロロアセトアルデヒド）、ポリ（ｎ−バレルアルデヒド）、ポリ（アセトアルデヒド）、ポリ（プロピオンアルデヒド）など；アクリルポリマー、たとえばポリアクリルアミド、ポリ（アクリル酸）、ポリ（メタクリル酸）、ポリ（エチルアクリラート）、ポリ（メチルメタクリレート）など；フルオロカーボンポリマー、たとえばポリ（テトラフルオロエチレン）、ペルフルオリネーティッド（perfluorinated）エチレン−プロピレンコポリマー、エチレン−テトラフルオロエチレンコポリマー、ポリ（クロロトリフルオロエチレン）、エチレン−クロロトリフルオロエチレンコポリマー、ポリ（ビニリデンフルオリド）、ポリ（ビニルフルオリド）など；ポリアミド、たとえばポリ（６−アミノカプロン酸）またはポリ（ε−カプロラクタム）、ポリ（ヘキサメチレンアジパミド）、ポリ（ヘキサメチレンセバカミド）、ポリ（１１−アミノウンデカン酸）など；ポリアラミド、たとえばポリ（イミノ−１,３−フェニレンイミノイソフタロイル）またはポリ（ｍ−フェニレンイソフタルアミド）など；ポリアリーレン、たとえばポリ−ｐ−キシリレン、ポリ（クロロ−ｐ−キシリレン）など；ポリアリールエーテル、たとえばポリ（オキシ−２,６−ジメチル−１,４−フェニレン）またはポリ（ｐ−フェニレンオキシド）など；ポリアリールスルホン、たとえばポリ（オキシ−１,４−フェニレンスルホニル−１,４−フェニレンオキシ−１,４−フェニレン−イソプロピリデン−１、４−フェニレン）、ポリ（スルホニル−１,４−フェニレンオキシ−フェニレン−スルホニル−４,４'−ビフェニレン）など；ポリカーボネート、たとえばポリ（ビスフェノールＡ）またはポリ（カルボニルジオキシ−１,４−フェニレン−イソプロピリデン−１,４−フェニレン）など；ポリエステル、たとえばポリ（エチレンテレフタレート）、ポリ（テトラメチレンテレフタレート）、ポリ（シクロヘキシレン−１,４−ジメチレンテレフタレート）またはポリ（オキシメチレン−１,４−シクロヘキシル−エネメチレンオキシテレフタロイル）など；ポリアリールスルフィド、たとえばポリ（ｐ−フェニレンスルフィド）またはポリ（チオ−１,４−フェニレン）など；ポリイミド、たとえばポリ（ピロメリトイミド−１,４−フェニレン）など、ポリオレフィン、たとえばポリエチレン、ポロプロピレン、ポリ（１−ブテン）、ポリ（２−ブテン）、ポリ（１−ペンテン）、ポリ（２−ペンテン）、ポリ（３−メチル−１−ペンテン）、ポリ（４−メチル−１−ペンテン）、１,２−ポリ−１,３−ブタジエン、１,４−ポリ−１,３−ブタジエン、ポリイソプレン、ポリクロロプレン、ポリアクリロニトリル、ポリ（ビニルアセテート）、ポリ（ビニリデンクロライド）、ポリスチレンなど；上述したものからなるコポリマー、たとえばアクリロニトリル−ブタジエン−スチレン（ＡＢＳ）コポリマーなど。
【００５２】
好ましいポリマーはポリオレフィンとポリエステルであり、ポリオレフィンがより好ましい。さらにより好ましいのは、水素原子と炭素原子のみを含有し、１または複数種の不飽和モノマーの付加重合によって作製されたポリオレフィンである。このようなポリオレフィンの例としては、特にポリエチレン、ポリプロピレン、ポリ（１−ブテン）、ポリ（２−ブテン）、ポリ（１−ペンテン）、ポリ（２−ペンテン）、ポリ（３−メチル−１−ペンテン）、ポリ（４−メチル−１−ペンテン）、１,２−ポリ−１,３−ブタジエン、１,４−ポリ−１,３−ブタジエン、ポリイソプレンなどが挙げられる。また、このような用語は、２種類以上のポリオレフィンのブレンド、２種類以上の異なる不飽和モノマーから作られるランダムコポリマーおよびブロックコポリマーを含むことを意味する。その商業的な重要性から、最も好ましいポリオレフィンはポリエチレンとポリプロピレンである。
【００５３】
ポリマーフィルム以外に、本発明に係る耐久的に湿潤性である液体透過性ウェブの作製に使用できるウェブとしては、スパンボンドされた不織布、ハイドロエンタングルされた不織布、ニードルされた不織布、および重合結合（polymericly bound）された不織布などがあるが、これらに限定されない。好ましい不織ウェブは典型的に、以下のような有機織物（textile）繊維から形成されるが、これらに限定されるわけではない。綿、ウール、木材、ジュート、ビスコースレーヨン、ナイロン、ポリエステル、ポリオレフィン、カーボン、またはこれらの混合物。無機繊維たとえばガラスおよび金属を、単独で、または組み合わせて用いても良いし、さらに有機繊維と組み合わせても良い。ステープル繊維の場合は、繊維長は約１／４インチないし約２インチまたはそれ以上である。スパンボンドされたウェブの場合、繊維長は決まっていない。ハイドロエンタングルされた不織布、ニードルされた不織布、および重合結合された不織布で使用するステープル繊維は、従来の織物機械によって加工処理される。
【００５４】
例えば、重合結合された不織ウェブを作製する場合、カード機を用いて、カードされたウェブとして知られる連続長のある程度２次元的に緩く結びついた繊維を形成しても良い。これらのウェブを集めて、かなりの重さ（例えばヤードあたりおよそ数グラムないし数千グラム）の多層繊維ウェブまたは３次元繊維ウェブを形成しても良い。連続した不織繊維ウェブでは、織物繊維をウェブの長さ方向の軸に対して様々な角度で配置する。カード機を動作させてウェブを形成すると、通常、繊維の大部分は機械の進行方向に配向されるが、一方では、等方的なウェブを例えばエアレイによって形成することができる。上述した繊維ウェブには典型的に、重合結合剤が含侵されている（重合結合されている）。好ましい形態においては、重合結合剤を、アクリル、ポリビニルアセテート、または同様のポリマー種（nature）、およびこれらの混合物のエマルションとして加える。好ましくは、繊維は不織であって、実質的にデタラメに配向され、重合結合剤とともに粘着によって結合している。
【００５５】
ハイドロエンタングルされたウェブおよびニードルされたウェブは、主として繊維の物理的な絡み合いに依存してウェブの結合性を得る点で、重合結合されたウェブと区別される。重合結合されたウェブおよび物理的に絡められたウェブとは対照的に、スパンボンドされたウェブは典型的に、溶媒処理または融解処理によって互いに結合された非常に長い繊維からなる。
【００５６】
すでに述べたように、ウェブは、２次元であっても良いし、従来の技術で論じた参照文献の教示に従って作製された開口部が設けられた３次元構造であっても良い。コーティングは耐久的であり、ウェブの表面エネルギーを増加させて、結果として生じる処理されたウェブをより湿潤性にする。コーティングは、水その他の水性液にさらした後であっても長い間保持されるという点で、耐久的である。このことに関して本発明のウェブは、１つの点において、長期間の間および／または液体にさらした後でも湿潤性を保つ能力という点から記述される。長期間の間湿潤性を保つ能力は、処理されたウェブのエージング後の接触角の測定によって評価する。この測定は、接触角の測定前に、プラズマ処理されたウェブを７４℃で１６時間保存して、サンプルを人為的にエージングさせることを伴う。液体にさらした後に湿潤性を保つ能力は、処理されたウェブのウォッシング後の接触角の測定によって評価する。この測定は、接触角の測定前に、２インチ×２インチの処理されたウェブを６５℃の２５０ｍＬ水槽に９０秒間浸して強制的に攪拌することを伴う。液体とウェブ表面との間の接触角を測定する手順および装置は、当該技術分野において周知である。しかし、出願人が開示している処理されたウェブについては、T565pm-96の暫定的方法およびACCUC DYNE TEST（Diversified Enterprises（ASTM D2578-84方法に基づく））によって指定された手順に従って、表面と水滴との接触角および表面エネルギーを試験する。接触角の値は、５サンプルについての測定値の平均値として報告される。
【００５７】
ある態様においては、本発明の処理されたウェブは、エージング後の接触角が処理されたウェブのエージング前の接触角（すなわち、７４℃で１６時間保存する前に測定した接触角）よりも、約６０°以下だけ大きい。好ましくは、処理されたウェブは、エージング後の接触角がエージング前の接触角よりも、約４０°以下だけ、より好ましくは約２０°以下だけ、さらにより好ましくは約１０°以下だけ大きい。他の態様においては、本発明の処理されたウェブは、ウォッシング後の接触角が処理されたウェブのウォッシング前の接触角（すなわち、処理されたウェブを６５℃の２５０ｍＬ水槽に９０秒間浸して強制的に攪拌する前に測定した接触角）よりも約６０°以下だけ大きい。この点に関して、処理されたウェブは好ましくは、ウォッシング後の接触角がウォッシング前の接触角よりも約４０°以下だけ、より好ましくは約２０°以下だけ、さらにより好ましくは約１０°以下だけ大きい。好ましい態様においては、本発明の処理されたウェブは、上述したエージング後およびウォッシング後に要求されるものを両方示す。
【００５８】
本発明の耐久的に湿潤性である液体透過性ウェブは、エージング後の接触角とウォッシング後の接触角の何れか一方（好ましくは両方）が、約９０°未満、好ましくは約７０°以下、より好ましくは約５０°以下、さらにより好ましくは約３０°以下、最も好ましくは約２０°以下である。
【００５９】
ＩＩ．吸収性用品
本明細書で用いる場合、用語「吸収性用品」は、一般に身体滲出物を吸収して収容するために用いられる器具を指し、より具体的には、着用者の身体またはその付近に配置されて、身体から放出される様々な滲出物を吸収し収容する器具を指す。用語「吸収性用品」には、おむつ、月経パッド、タンポン、生理ナプキン、失禁用パッド、トレーニングパンツなどの他に、ワイプ、包帯、傷口手当て用品も含まれることが意図されている。用語「使い捨て」は本明細書で用いる場合、洗濯もそうでなければ修復も吸収性用品としての再使用も意図していない吸収性用品を指す（すなわち、それらをある程度使用したら捨て、好ましくはリサイクルし、環境と共存できる方法で堆肥にしそうでなければ処理することが意図される）。「単一の」吸収性用品は、ただ１つの構造としてか、または合体されて整合された実体（coordinated entity）を構成する別個の部品として形成されるため、別個のホルダーおよびパッドのような別個の操作部品（manipulative parts）を必要としない吸収性用品を指す。
【００６０】
本発明の耐久的に湿潤性である液体透過性のウェブを取り入れるかまたは一緒に用いる吸収性用品の全体のサイズ、形状、および／または構成は、それが何であれ、本発明の原理に対して何らの重要性も機能上の関連性も持たないことを理解されたい。しかしこのようなパラメーターは、ウェブの適切な形状を決めるときに、意図する液体と意図する機能性とともに考慮しなければならない。
【００６１】
また吸収性用品は、本発明の耐久的に湿潤性である液体透過性のウェブ以外に、吸収されたどんな身体液体をも保有するための吸収性コアを備える。本発明における吸収性コアとして用いる典型的な吸収性構造が、以下の文献に記載されている。米国特許第4,950,264号（Osbornに1990年8月21日に付与）、米国特許第4,610,678号（Weismanらに1986年9月9日に付与）、米国特許第4,834,735号（Alemanyらに1989年5月30日に付与）、欧州特許出願第0198683号（Procter&Gamble社、1986年10月22日にDuenkらの名義で公開）、米国特許第4,673,402号（Weismanらに1987年6月16日に付与）、米国特許第4,888,231号（Angstadtに1989年12月19日に付与）。吸収性コアは、吸収性貯蔵コアの上に配置された化学的に剛化された繊維からなる捕捉コア／分配コアを含む二重コアシステムをさらに備えていても良い。これは、米国特許第5,234,423号「Absorbent Article With Elastic Waist Feature and Enhanced Absorbency」（Alemanyらに1993年8月10日に付与）、および米国特許第5,147,345号「High Efficiency Absorbent Articles For Incontinence Management」（Young、LaVon、Taylorに1992年9月15日に付与）に詳細に説明されている。これら全ての特許の開示は、本明細書において参照により取り入れられている。
【００６２】
本発明に係る単一の使い捨て吸収性用品の好ましい実施形態は、月経パッド、生理ナプキンである。ここで用いる場合、用語「生理ナプキン」は、女性が外陰部領域の付近（通常、泌尿生殖器の外側）に着用し、月経からの液体およびその他の着用者の身体からの膣放出物（例えば、血液、メンス、尿）を吸収し収容するための吸収性用品を指す。着用者の膣前庭の内部および外部にそれぞれ部分的に配置される陰唇間の器具も、本発明の範囲内である。好適な女性用衛生用用品が以下の文献に開示されている。米国特許第4,556,146号（Swansonらに1985年12月3日に付与）、米国特許第4,589,876号（Van Tilbergらに1993年4月27日に付与）、米国特許第4,687,478号（Van Tilburgに1987年8月18日に付与）、米国特許第4,950,264号（Osborn,IIIに1990年8月21日に付与）、米国特許第5,009,653号（Osborn,IIIに1991年4月23日に付与）、米国特許5,267,992号（Van Tilburgに1993年12月7日に付与）、米国特許第5,389,094号（Lavashらに1995年2月14日に付与）、米国特許第5,413,568号（Roachらに1995年5月9日に付与）、米国特許第5,460,623号（Emenakerらに1995年10月24日に付与）、米国特許第5,489,283号（Van Tilburgに1996年2月6日に付与）、米国特許第5,569,231号（Emenakerらに1996年10月29日に付与）、米国特許第5,620,430号（Bamberに1997年4月15日に付与）。各文献の開示は、本明細書において参照により取り入れられている。
【００６３】
本発明の好ましい実施形態においては、生理ナプキンは、それぞれ吸収性コアの側端部に隣接してそこから横方向に延びる２つのフラップを有する。フラップはクロッチ領域において着用者のパンティの端部を覆うため、フラップは着用者のパンティの端部と大腿部との間に配置される。フラップは、少なくとも２つの目的のために機能する。第１に、フラップは、着用者の身体およびパンティが月経からの液体によって汚れることを、好ましくは二重壁バリアーをパンティの端部に沿って形成することによって防止する役目を果たす。第２に、好ましくはフラップの衣類側表面にアタッチメント手段が設けられていて、フラップをパンティの下側に折り返してパンティの衣類を向く側の面に取り付けることができる。このように、フラップは生理ナプキンをパンティの適切な位置に保持する役目を果たす。フラップは、トップシート、バックシート、ティシューと同様の材料またはこれらの材料の組み合わせなどの様々な材料から作ることができる。またフラップは、ナプキンの本体に取り付ける別個の部材であっても良く、またはトップシートおよびバックシートの拡張部分を構成しても良い（すなわち単一である）。本発明の生理ナプキンとの使用に好適なまたは適合するフラップを有する多くの生理ナプキンが、米国特許第4,687,478号「Shaped Sanitary Napkin With Flaps」（Van Tilburg に1987年8月18日に付与）、米国特許第4,589,876号「Sanitary Napkin」（Van Tilburgに1986年5月20日に付与）に開示されている。各特許の開示は、本明細書において参照により取り入れられている。
【００６４】
本発明の好ましい実施形態においては、トップシートと吸収性コアとの間に捕捉層を配置しても良い。捕捉層は、吸収性コア上または内部への滲出物の排出（wicking）を改善する等のいくつかの機能を果たすことができる。滲出物の排出を改善することがなぜ重要なのかについては、いくつかの理由がある。例えば、吸収性コアの至るところで滲出物をより均一に配分して、生理ナプキンを比較的薄く作製できるようにする。本明細書で述べる排出には、液体を１方向、２方向、または全ての方向（すなわち、ｘ−ｙ平面内および／またはｚ−方向）に輸送することが含まれていても良い。捕捉層は、以下の材料からなる不織ウェブまたは織りウェブを初めとする様々な異なる材料から構成されていても良い。合成繊維たとえばポリエステル、ポリプロピレン、ポリエチレン；天然繊維たとえば綿、セルロース；このような繊維のブレンド；何らかの同等の材料または材料の何らかの組み合わせ。捕捉層とトップシートとを有する生理ナプキンの例が、米国特許第4,950,264号（Osbornに付与）、米国特許出願第07/810,774号「Absorbent Article Having Fused Layers」（1991年12月17日にCreeらの名義で出願）に、より十分に記載されている。各参照文献の開示は、本明細書において参照により取り入れられている。好ましい実施形態においては、ウェブを互いに接合するための従来手段の何れかを用いて、最も好ましくは融着（参照したCreeの出願でより十分に説明されている）によって、捕捉層とトップシートとを接合しても良い。
【００６５】
月経パッドを以下のように作製しても良い。シリコーンコートされたリリースペーパー上に、螺旋パターンのH2031Findlayホットメルト粘着剤を０．０４ｇ／ｉｎ²で塗る。副トップシートとコートされたリリースペーパーとをハンドローラーで一緒に巻くことによって、この粘着剤層を副トップシートの上面（着用者を向く面）に移す。副トップシートは、Fort James Airlaid Tissue, Grade 817（Fort James社（Green Bay、ウィスコンシン州）から販売される）として知られる不織材料で作製する。本発明のトップシートを副トップシートの粘着剤面に貼り付けた後、両者をハンドローラーで静かにプレスして接合する。１／４インチ両面テープの２本の細片を、ポリエチレンのバックシートの長い両端に沿って貼り付ける。吸収性コアを加えて、完全な吸収性構造が作製される。
【００６６】
ここで用いる場合、用語「おむつ」は、通常幼児および失禁者が着用し、着用者の胴体の下部の辺りに着用される衣類を指す。しかし、本発明はその他の吸収性用品たとえば失禁用ブリーフ、失禁用パッド、トレーニングパンツ、おむつインサート、テッシュペーパー、ペーパータオルなどにも適用できることを理解されたい。本発明のおむつは、通常、本発明の耐久的に湿潤性である液体透過性のウェブを備えるトップシートと、このトップシートに結合された液体不透過性バックシートと、トップシートとバックシートとの間に配置される吸収性コアとを備える。また、付加的な構造部材たとえばおむつを着用者の所定の位置に固定するための弾性部材および締結手段（たとえばテープタブ留め具）を備えていても良い。
【００６７】
トップシート、バックシート、および吸収性コアを、周知の様々な構成で組み合わせることができるが、おむつの好ましい構成が、米国特許第3,860,003号（Buellに1975年1月14日に付与）に概略的に記載されている。この文献の開示は本明細書において参照により取り入れられている。代替的に、本明細書における使い捨ておむつの好ましい構成が、以下の文献にも開示されている。米国特許第4,808,178号（Azizらに1989年2月28日に付与）、米国特許第4,695,278号（Lawsonに1987年9月22日に付与）、米国特許第4.816,025号（Foremanに1989年3月28日に付与）。各特許の開示は、本明細書において参照により取り入れられている。成人着用者に対して好適な失禁用品が以下の文献に記載されている。米国特許第4,253,461号（Stricklandらに1981年3月3日に付与）、米国特許第4,597,760号および第4,597,761号（Buellに付与）、米国特許第4,704,115号、米国特許第4,909,802号（Ahrらに付与）、米国特許第4.964,860号（Gipsonらに1990年10月23日に付与）、米国特許出願第07/637,090号（Noelらによって1991年1月3日に出願）（国際公開WO92/11830（1992年7月23日に公開））。各参照文献の開示は、本明細書において参照により取り入れられている。
【００６８】
おむつの吸収性コアは、トップシートとバックシートとの間に配置される。吸収性コアは、様々なサイズおよび形状（例えば矩形、砂時計、非対称など）で作製することができる。しかし、吸収性コアの全吸収容量は、吸収性用品またはおむつの意図される用途に対するデザイン液体ローディング（loading）に適合しなければならない。また、吸収性コアのサイズおよび吸収容量は、幼児から成人までの着用者に適合するように変えることができる。
【００６９】
すでに述べたように、吸収性コアは液体分配部材を備えていても良い。好ましい構成においては、吸収性コアは、液体分配部材と液体を連絡し液体分配部材とトップシートとの間に配置される捕捉層または捕捉部材を、さらに備えることが好ましい。捕捉層または捕捉部材は、以下の材料からなる不織ウェブまたは織りウェブを始めとする様々な異なる材料から構成されていても良い。合成繊維たとえばポリエステル、ポリプロピレン、ポリエチレン；天然繊維たとえば綿、セルロース；このような繊維のブレンド；何らかの同等の材料または材料の何らかの組み合わせ。
【００７０】
好ましい実施形態においては、おむつは、伸縮性レッグカフスを備える。伸縮性レッグカフスは、以下の文献に記載されているものを初めとする多くの異なる構成で作製することができる。米国特許第3,860,003号、米国特許第4,909,803号（Azizらに1990年3月20日に付与）、米国特許第4,695,278号（Lawsonに1987年9月22日に付与）、米国特許第4,795,454号（Dragooに1989年1月3日に付与）。各文献は、本明細書において参照により取り入れられている.
使用する際、おむつを着用者に取り付けるには、背部ウェイストバンド部分を着用者の背中の下方に位置決めした後、おむつの残り部分を着用者の両脚の間に引っ張って、前部ウェイストバンド部分を着用者の前部に位置決めする。次に、テープタブその他の留め具を、好ましくはおむつの外側を向く領域に固定する。
【００７１】
【実施例】
以下の実施例は説明のためのものであり、本明細書において開示されクレームされる発明を何ら限定することを意味しない。
【００７２】
（実施例１）
ポリエチレンフィルム材料からなるテスト用ウェブ（３０ｃｍ×２０ｃｍ）を、プラズマ放電ユニット（ＡＰＳ社モデルＤ）の真空チャンバーの底部（底部電極の２０ｃｍ下方）に置く。プラズマチャンバーを排気する。チャンバー内圧力が２０ｍＴｏｒｒに到達した時点で、チャンバー内部にキャリアガス（Ａｒ）を一定の流量（１０ｓｃｃｍ）で連続的に導入し、連続排気とキャリアガスの導入とをバランスさせてチャンバー内圧力を６３ｍＴｏｒｒに保つ。上述した状態を維持しながら、１００Ｗの高周波電力を周波数４０ｋＨｚで供給してチャンバー内部に低温プラズマを１分間発生させ、フィルム表面を低温プラズマにさらす。次に、モノマー（アクリル酸）をチャンバー内部に一定の流量で導入して、チャンバー内を一定の圧力（１６５ｍＴｏｒｒ）に保つ。上述の状態を維持しながら、低温プラズマ（１００Ｗ、４０ｋＨｚ）をチャンバー内部に１０分間発生させる。処理後、チャンバーを排気し（３０ｍＴｏｒｒ）、その後大気空気で満たす。処理されたウェブを、表面と水滴との接触角および表面エネルギーについて試験する。試験は、T565pm-96の暫定的方法およびACCUC DYNE TEST（Diversified Enterprises（ASTM D2578-84方法に基づく））によって指定された手順に従って行う。結果を下表１に示す。
【表１】

【００７３】
（比較例２ないし４）
この比較例では、接触角データ（上表１と比較するために下表２に示す）を、プラズマ放電させることなくキャリアガス（Ａｒ）とモノマー（アクリル酸）とにさらしたポリエチレンフィルム（比較例２）、キャリアガス（Ａｒ）とプラズマ放電（１００Ｗ）とに１１分間さらしたフィルム（比較例３）、およびキャリアガス（Ａｒ）とモノマー（アクリル酸）とプラズマ放電（１００Ｗ、１１分間）とにさらした電極間に配置されたフィルム（直接プラズマ）（比較例４）に対して示す。表１と比較すると、直接プラズマ重合などの種々の他の条件下で作製されたウェブと比べて、その親水性を加速エージングの後により良好に保持するウェブが、間接プラズマによって得られることが分かる。
【表２】

[0001]
BACKGROUND OF THE INVENTION
This application is a continuation-in-part of co-pending application 09 / 157,840 (filed September 29, 1998).
[0002]
The present invention relates to a durable and wettable liquid-permeable web that is particularly suitable as a topsheet for absorbent articles. More particularly, the present invention relates to a polymer film or non-woven fabric having a thin organic material applied to at least one surface. The thin organic coating is in the form of a polymer and is obtained by plasma-induced polymerization of a polymerizable unsaturated compound, preferably a polymerizable vinyl compound or isopropenyl compound, under certain plasma conditions. can get. The invention also relates to a method for producing a liquid permeable web that is durable and wettable, and an article comprising the liquid permeable web that is durable and wettable as a topsheet.
[0003]
[Prior art]
Polymer webs and nonwoven webs are common components such as disposable absorbent articles, dryer sheets and the like. More specifically, a macroscopically expanded three-dimensional polymer film is used as the topsheet material for disposable absorbent articles. As used herein, the term “macroscopically expanded”, when used to describe a three-dimensional web, is made to follow the surface of a certain three-dimensional molded structure, and both surfaces are three-dimensional of that molded structure. Refers to a web that exhibits morphology, or a web that has a unique three-dimensional morphology due to web structure. Regardless of whether the three-dimensional form is unique or made by a molding process, if the vertical distance between the viewer's eye and the plane of the web is about 12 inches, this form Can be easily seen with the naked eye. In contrast, the term “flat”, as used herein to describe nonwovens and polymer films, refers to the state of the entire web when viewed with the naked eye on a macroscopic scale. In this context, a “flat” web includes fine scale surface aberrations that are not readily visible to the naked eye when the vertical distance between the viewer's eye and the web plane is about 12 inches or greater. May be included on one or both sides.
[0004]
After the liquid deposited on one surface is transferred to the opposite surface, the macroscopically expanded three-dimensional with openings is particularly suitable for keeping the transferred liquid isolated from the wearer's skin One polymer web is disclosed in commonly assigned US Pat. No. 3,929,135 (assigned to Thompson on Dec. 30, 1975). This disclosure is incorporated herein by reference. Thompson describes a macroscopically expanded three-dimensional web (e.g., a topsheet) made of a liquid impermeable material but provided with a tapered capillary form. The capillary has a bottom opening in the plane of the topsheet and a vertex opening away from the topsheet plane, the vertex opening being in direct contact with the absorbent pad used in the disposable absorbent article. ing. The Thompson topsheet allows liquid to move freely from the wearer's body into the absorbent member of the device, but this liquid backflow is suppressed. This results in a very dry surface in contact with the user compared to what was previously available. Another macroscopically expanded three-dimensional plastic web with openings, suitable for use as an absorbent article, for example as a sanitary napkin topsheet, is disclosed in US Pat. No. 4,342,314 (August 1982) with the same assignee. Granted to Radal et al. On the 3rd). This patent is incorporated herein by reference. The macroscopically expanded three-dimensional plastic web disclosed in this Radal patent has a fiber-like appearance and is well received by consumers when used as a contact surface with the wearer. Indicates. According to the same assignee patents for Thompson and Radal et al., Webs of the type described above apply pressure to the web while supporting the web on a three-dimensional molded structure, which is macroscopic. Can be made by following the three-dimensional cross section of the molded structure that is expanded to support the web. When it is required to provide an opening in a macroscopically expanded three-dimensional web, pressure (vacuum is described) until the opening is completely formed in the area of the web that coincides with the opening of the forming structure. Apply the difference.
[0005]
Also, a liquid-based multi-stage process such as US Pat. No. 4,609,518 (granted to Curro et al. On September 2, 1986) (hereinafter referred to as the “518 patent”), the disclosure of which is incorporated herein by reference. Have been developed for the purpose of providing a film having very small and very large openings adjacent to each other. As disclosed in this patent, by forming a very small opening (such as a micron size) in the opposite direction to the opening formed for the large opening, the liquid that was not initially absorbed is The possibility of running off the web surface is hindered. As a result, liquid that was not transported immediately through the large opening is restrained from flowing off the web surface and is then absorbed through the relatively large opening to provide an absorbent article that uses the web as a topsheet material. Deposit on the core. Also, these small openings formed outward reduce the degree of web / skin contact and reduce the stiffness of the film. As a result, the feel to the user is more comfortable. There are reports from the wearer that the surface of such a topsheet is soft and silky. Separately, the 518 patent discloses a film in which very small openings and large openings are formed in the same direction.
[0006]
In the above reference, when a wettable film material is required, such a structure is generally obtained by surface treatment of an originally hydrophobic polymer web with a wetting agent, regardless of the method used to form the opening. Have gained. The surface treatment is usually performed by spraying a surfactant on the web surface or immersing the web in a bath containing the surfactant. In addition to the fact that the surface treatment and level cannot be precisely controlled using any of these methods, the surface treatment has a significant amount of surface activity when the web is used as a topsheet for absorbent articles. There is a problem in that the agent moves into the opening and other components (for example, the absorbent core) and has an adverse effect. Furthermore, the surface treatment has the disadvantage that the desired wetting agent or surfactant tends to run off after multiple exposures to the liquid as described above. Thus, the treated web loses its ability to transport liquid from the skin into the core of the absorbent article when used many times as a topsheet of the absorbent article.
[0007]
In U.S. Pat. No. 4,535,020 (provided by Thomas et al. On Aug. 13, 1985), surface treatment of a vacuum formed film having openings is applied to a polymer resin prior to extrusion for film forming. Some of the problems associated with mixing (referred to herein as “surfactant mixed with resin” or “RIS”) are addressed. (See also: US patent application Ser. No. 08 / 713,377 (filed by YPLee et al. On September 13, 1996), US Pat. No. 4,923,914 (Nohr et al. US Pat. No. 5,057,262 (Granted to Nohr et al. On Oct. 15, 1991), US Pat. No. 5,120,888 (Granted to Nohr et al. On Jun. 9, 1992)) Thomas teaches According to this, after the resin / surfactant mixture is extruded and then the openings are formed, the non-coexisting surfactant eventually blooms to the film surface, making it more durable and wettable. The web that is is obtained. However, as in the case of surface treatment, there are some problems with the RIS, such as when the openings of the web are formed using a liquid pressure difference, and the surfactant runs off during use and / or manufacturing. Also, hydrophilic webs formed using RIS technology are not immediately wettable and do not become wettable for some time depending on the relationship between resin, surfactant and environmental conditions. There is. Similarly, when such webs are used in absorbent articles, there is some time delay before the surfactant (runs down during wear) is replenished to the web surface.
[0008]
Durable wettable liquid permeable web or film having improved durable wettability after time and / or after exposure to liquid attack despite teachings in the related art There is still a need for materials. Such treated webs are particularly suitable for use in disposable absorbent structures. There also remains a need for a process that provides such a durable and wet web.
[0009]
[Problems to be solved by the invention]
Accordingly, it is an object of the present invention to provide a liquid permeable web that is durable and wettable with improved durable wettability.
[0010]
[Means for Solving the Problems]
This durable wettability is achieved by applying a plasma-induced hydrophilic coating on at least one surface of the starting web to make the resulting web durable and hydrophilic. In particular, plasma induced coating is achieved using a “plasma-separated” or “remote” plasma polymerization process.
[0011]
The present invention relates to a durable, wettable, liquid permeable web that is particularly useful as a topsheet material for absorbent articles. In one respect, the present invention is a liquid permeable web that is durable and wettable,
(I) a web having openings selected from the group consisting of polymer films or nonwovens;
(Ii) a substantially continuous hydrophilic coating having a thickness of less than about 2.5 μm applied to at least one surface of the web by an indirect plasma polymerization process;
With
At least one surface of the liquid permeable web that is durable and wettable relates to a liquid permeable web having a contact angle after aging that is no more than about 60 ° greater than the contact angle before aging.
[0012]
In a similar aspect, at least one surface of the treated web has a contact angle after washing that is no more than about 60 ° greater than the contact angle before washing. Preferably both states are in one web.
[0013]
The present invention is also an absorbent article comprising a liquid-permeable topsheet that is durable and wettable, the topsheet comprising a web and a hydrophilic coating on at least one surface of the web, the hydrophilic article The coating relates to an absorbent article that is applied to the web by an indirect plasma polymerization process. In other words, the absorbent article topsheet comprises the durable, wettable, liquid permeable web of the present invention.
[0014]
Finally, the present invention relates to an indirect plasma polymerization process for producing a durable, wettable liquid permeable web as described herein.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
I. A liquid-permeable web that is durable and wettable
As described in detail below, the present invention relates to a durable, wettable, liquid permeable web made by applying a hydrophilic coating to a starting polymer film or starting nonwoven fabric by a radiation curing process.
[0016]
As used herein, the term “web” refers to a starting substrate (ie, a polymer film or nonwoven) to which a hydrophilic coating is applied. Conversely, the term “durable wet liquid permeable web” or “treated web” refers to the final product—a polymer film or nonwoven with a durable hydrophilic coating.
[0017]
As used herein, the term “liquid permeable” means that the web or processed web has been processed from one side of the web or processed web to the opposite side of the web or processed web. Refers to the ability to transport liquid in a sufficiently efficient manner so that the web can be used as a component of a disposable product. The web may originally be liquid permeable, or may be made liquid permeable by performing a processing step such as providing an opening.
As used herein, the term “substantially continuous” means sufficiently continuous to obtain hydrophilic or wettable properties as defined by the contact angle limitations described or claimed.
[0018]
As used herein, the terms “hydrophilic” and “wettable” are used interchangeably and mean a surface that is susceptible to being wetted by an aqueous liquid (eg, an aqueous body fluid) deposited thereon. To do. Hydrophilicity and wettability are typically defined by the contact angle and the surface tension of the liquid and solid involved. This is discussed in detail in the American Chemical Society publication "Contact Angle, Wettability and Adhesion" (Robert F. Gould) (Copyright 1964). The web surface is wetted by the liquid when the contact angle between the liquid and the web surface is below 90 ° or when the liquid tends to spread naturally on the web surface (both conditions usually occur simultaneously) (ie It is said to be hydrophilic. Conversely, a surface is considered hydrophobic when the contact angle is greater than 90 ° and the liquid does not spread naturally on the web surface. In general, the smaller the contact angle between the surface and the liquid, the more hydrophilic the surface.
[0019]
The durable and wettable liquid permeable webs according to the present invention maintain the hydrophilic properties produced in otherwise more hydrophobic films over time and after exposure to liquids. In such a range, “durable and wettable”. As noted above, conventional approaches that have been aimed at making hydrophobic films wettable initially have improved wettability, but do not improve wettability over long periods of time and / or when exposed to liquids. The result was an unexpected property of being lost. As used herein, durable wettability is a liquid permeable web that is durable wettable (as described above, "treated" herein to distinguish it from the starting "web". Web ") is described by its ability to maintain its wettability properties after aging (referred to as" after aging ") and / or after exposure to liquid (referred to as" after washing "). A method for measuring the contact angle after aging and the contact angle after washing will be described later.
[0020]
As already mentioned, the durable wettability of the polymer web is achieved using an indirect plasma process. Without being bound by theory, it is believed that typical hydrophilic polymers and surface treated (eg corona discharge treated) polymer systems undergo a “hydrophobic recovery” process. During the hydrophobic recovery process, the wettability of the surface tends to decrease with time. This is because it is thermodynamically advantageous to expose the molecular chain segment having a low surface energy to the polymer surface. During aging, the hydrophilic molecular segments reorient and fill themselves, exposing the hydrophobic segments to the polymer surface. When chemical cross-linking is induced on the polymer surface, the cross-linking limits the mobility of the polymer chain and significantly slows the “hydrophobic recovery” process, thus maintaining the wettability of the polymer surface for a long period of time. There is a tendency to be. Applicant's invention provides chemical cross-linking of the polymer by an indirect plasma polymerization process so that a liquid permeable web that is durable and wettable can be produced.
[0021]
As used herein, “indirect plasma” and “plasma-separated”, respectively, introduce monomers to the outside of the plasma zone or plasma glow, and the substrate to be surfaced to the outside of the plasma glow, usually Means disposing under the monomer introduction opening. An advantage gained from positioning outside the plasma zone is to avoid interaction of monomer molecules with plasma electrons and plasma ions, which causes undesirable monomer fragmentation. Since electrons and ions are short-lived chemical species, they are confined inside the plasma glow. As used herein, “plasma zone” and “plasma glow” each refer to a portion of the volume inside the chamber (usually between the electrodes) that is visibly brighter than the remaining volume because it is a visible glow. Visible glow occurs when a plasma-excited chemical species undergoes electron relaxation with light emission.
[0022]
The plasma is often said to be the fourth state of matter. When energy is applied to a solid (eg, a polymer film), the solid can undergo a transition to the liquid state. If more energy is applied, the liquid becomes a gas. When the appropriate type of energy is further applied, the gas dissociates into a plasma. In plasma polymerization to form a coating on a web (sometimes referred to as “plasma grafting”, “plasma deposition” or “plasma coating”), a suitable organic monomer or monomer having a polymerizable unsaturated group is used. The mixture is introduced into the plasma zone of the reactor. There, the monomers are crushed and / or activated to form further excited species in addition to a complex mixture of activated plasma gases. The excited species and monomer fragments recombine as soon as they come into contact with the web. The method of recombination is indeterminate and forms a highly indeterminate structure that includes a variety of different groups and chemical bonds, resulting in highly crosslinked polymers being deposited on the web. O ₂ , N ₂ Or polymer deposition if oxygen-containing or nitrogen-containing molecules are present in the plasma reactor during the plasma coating process or when the plasma-coated substrate is exposed to oxygen or air after the plasma process The object will contain various polar groups.
[0023]
In one of the plasma technologies (referred to herein as “in-glow” plasma polymerization or “direct” plasma polymerization), the web to be treated and the monomer to be reacted are fed into the plasma zone during the polymerization process. Place in. While this technique has proven useful for making durable, wettable webs useful as topsheets for absorbent articles (co-pending US patent application Ser. No. 09/157845 (1998)). (Applied by YP Lee et al. On Sep. 21, 2000) (see “DURABLY WETTABLE, LIQUID PERVIOUS POLYMERIC WEBS”), polymerization in the plasma zone has certain drawbacks. For example, the monomer may cause undesirable crushing before depositing on the film. Thus, the monomers that can be used are limited to some extent when direct plasma polymerization is used. In contrast, the treated webs of the present invention are made using plasma polymerization of “indirect” or “plasma-separated” (the terms are used interchangeably herein), so that excess Concerns about fragmentation are reduced. Indirect plasma polymerization is a process in which polymerization occurs in the presence of plasma, but not only the web but also the monomer feed inlet is located outside or away from the plasma zone (typically below the zone). . In this process, monomer molecules do not pass through the highly reactive plasma gas zone, so that fragmentation of the monomer molecules is significantly avoided. Thus, in this process, certain monomers that are desirable for the formation of a hydrophilic coating can be used. These monomers cannot be used when direct plasma polymerization is utilized. In the case of this process, the structure of the polymer to be deposited can be controlled within a certain range, the undesirable surface corrosion of sensitive substrates can be avoided, and the formation of polymer deposits is mainly based on radical reactions.
[0024]
Plasma exists in various forms. The plasma processes useful herein are indirect low pressure processes or vacuum processes that allow the web to be processed at or near ambient temperature (ie, about 20 ° C.). As a result, thermal degradation of the web being processed and / or thermal distortion of the formed web being processed is prevented. Within the plasma chamber, active species in the form of electrons, free radicals, ions, and high-energy neutral particles are formed and collide with the surface of a web such as a polymer (located outside the plasma chamber) to form molecular bonds. Cutting and creating new functional groups on the web surface. Also, as a result of the reaction of these active and high energy species in the gas phase, a thin coating is deposited on at least one surface of the web.
[0025]
A plasma system suitable for use in the present invention incorporates a parallel plate electrode design. In this design, the material to be processed is exposed to the primary field of RF energy but is not part of the circuit. Designed to generate a uniform laminar flow of process gas over the entire chamber volume, in the form of a gas delivery system when it comes to high pressure processes (but within the general definition of cold gas plasma) What was done is beneficial. In a multi-electrode / shelf design, it is important that the amount of RF energy received by each electrode is equal. In this method, a uniform glow discharge is generated between shelves or in each plasma zone. Process uniformity, efficiency, and repeatability are also ensured by solid state components and microprocessor control of system parameters (process time, flow rate, power level, and working pressure).
[0026]
Since the plasma is an electrically conductive atmosphere, the plasma has a characteristic impedance to the output of the RF generator. Therefore, the preferred plasma process always uses a matching network to match the plasma impedance to the output impedance of the RF generator. A state-of-the-art plasma system suitable for use in the present invention is sold by HIMONT Plasma Science (Foster City, Calif.) (An entity of HIMONT USA), which includes an automatic matching network. And error checking means during the process.
[0027]
A low temperature plasma is generated in a reduced pressure gas atmosphere and the pressure is from about 0.001 to about 10 Torr, preferably from about 0.01 to about 5 Torr, more preferably from about 0.05 to about 1 Torr, and most preferably about 0.1. 05 to about 0.4 Torr. Power can be supplied to the device at a radio high frequency of about 40 kHz to 3 GHz, preferably 13 to 27 MHz, most conveniently about 14 MHz. In order to achieve the desired plasma state in the gas atmosphere, the power delivered to the device is about 10 to about 10,600 W, preferably about 50 to about 5000 W, more preferably about 250 to about 3000 W, most preferably about 500 to It can be changed within a range of about 2500W. The power used depends somewhat on the working volume of the chamber. The most preferred range of about 500 to about 2500 W is suitable for the HIMONT Plasma Science PS0500D gas plasma apparatus having a working volume of about 5.0 cubic feet. The plasma treatment time is several seconds to several minutes, preferably about 20 seconds to about 30 minutes, and most preferably about 60 seconds to about 20 minutes.
[0028]
It should be understood that process pressure, time, and power are not independent and are interrelated variables. The level of effect selected for each of these variables determines the degree of web surface modification and / or coating thickness. Chamber volume and chamber shape are also related along with sample size and sample surface shape. Selecting the level of these variables is well within the normal skill of those skilled in the art to which this invention belongs.
[0029]
A hydrophilic coating layer is deposited on the surface of a suitable web (if the openings are pre-formed or not) by indirect plasma induced vapor deposition (ie polymerization) of the monomer or combination of monomers to make it hydrophilic Apply the coating to the web. Monomers that can be used to form a polymer coating by plasma-separated plasma-induced polymerization are polymerizable unsaturated compounds that can be vaporized and then introduced into the plasma separation zone of the plasma generator to contact the web placed inside the device. Anything is fine. Preferred monomers are vinyl compounds including, but not limited to:
[0030]
a) General formula H ₂ C = C (R ² ) -C (O) OH acrylic and methacrylic acid,
b) General formula H ₂ C = C (R ² ) -C (O) OR ^Three Acrylates and methacrylates,
c) General formula (R ² ) (R ² ) C = C (R ² ) -C (O) NHR ^Three Acrylamide and methacrylamide,
d) General formula HO (O) C—C (R ² ) = C (R ² ) -C (O) OH maleic acid and fumaric acid,
e) General formula R ^Three O (O) C-C (R ² ) = C (R ² ) C (O) OR ^Three Maleate and fumarate,
f) General formula (R ² ) (R ² ) C = C (R ² ) -O-R ^Three Vinyl ether,
[Chemical 2]

[0031]
h) General formula (R ² ) (R ² ) C = C (R ² ) -OC (O) CH _Three Vinyl acetate,
i) General formula R ² CH = CHR ^Three Aliphatic vinyl compounds, and mixtures thereof.
[0032]
Where each R ² Is independently hydrogen or C ₁ -C _Ten Alkyl, preferably C ₁ -C _Five Each alkyl is R ^Three Is independently an aliphatic hydrocarbon group of up to about 10 carbon atoms, which aliphatic hydrocarbon group is unsubstituted or one or more polar groups such as carboxy, hydroxy, amino, And substituted by (poly) ethylene oxide groups or by one or more sulfate groups, phosphate groups, sulfonate groups or mixtures of such groups.
[0033]
Specific examples of preferred acrylic derivatives include the following.
Acrylic acid, methacrylic acid, hydroxyethyl methacrylate (HEMA), methyl methacrylate (MMA), dimethylaminoethyl methacrylate (DMAEMA), 2-hydroxyethyl acrylate (HEA), N, N-dimethylacrylamide (DMA), N- Acryloylmorpholine (NAM), and ethylene glycol dimethacrylate (EGDMA). Specific examples of suitable vinyl ethers are methyl vinyl ether, ethyl vinyl ether, and methoxyethyl vinyl ether. Suitable hydrophilic monomers also include ethylene glycol soot, ethylene oxide, and propylene oxide. Monomers may be used individually or as a mixture of monomers.
[0034]
The monomer is heated to a sufficient temperature prior to introduction into the chamber to vaporize the compound and to generate sufficient vapor pressure so that the coating is deposited at an appropriate rate. Typically, the temperature is about 40 ° C to about 100 ° C, more typically about 40 ° C to about 60 ° C. Along with the gaseous monomer compound, gaseous oxygen and argon are simultaneously fed into the deposition chamber. However, oxygen and argon are supplied using separate supply means and separate mass flow controllers. Depending on the application, O ₂ The flow rate of about 5cm ^Three / Min (standard state) (“sccm”) to about 1200 sccm, the flow rate of the gaseous monomer compound is about 1 sccm to about 250 sccm, and the flow rate of Ar is about 1 sccm to about 150 sccm. The use of argon increases the deposition rate of the gaseous material being used. Therefore, it is preferred to use argon in the process.
[0035]
Alternatively, monomer deposition may be achieved using the flash vaporization technique described in US Pat. No. 4,842,893 (granted to Yializis on April 29, 1988). The disclosure of this document is incorporated herein by reference.
[0036]
A low temperature plasma is generated in a reduced pressure gas atmosphere and the pressure is from about 0.001 to about 10 Torr, preferably from about 0.01 to about 5 Torr, more preferably from about 0.05 to about 1 Torr, and most preferably about 0.1. 05 to about 0.4 Torr, depending on the process used and the web being processed.
[0037]
With respect to the starting web, the web may be flat (2D) or complex (3D, such as a film previously provided with an opening). That is, the plasma polymerization may be performed before or after the opening is formed on the web. In a preferred embodiment, plasma treatment is performed after forming the openings to better maintain a uniform hydrophilic coating on the film surface.
[0038]
The above-described latest plasma system sold by HIMONT Plasma Science, such as the PS0500D reactor, is equipped with a throttle valve, which makes it possible to change the process pressure while keeping the gas flow rate the same.
[0039]
The plasma treatment time to obtain the desired hydrophilic coating is typically about 0.1 minutes to about 10 minutes, preferably about 1.5 minutes to about 4 minutes, and most preferably about 1.5 minutes to about 2. 5 minutes. The RF power used to initiate the gas phase reaction is preferably about 10 to about 1000 W, more preferably about 50 to about 500 W, and most preferably about 75 to about 250 W. The RF power used is about 100 to about 2500 W, depending on the substrate being processed and the throughput requirements. The resulting hydrophilic coating can be made in a variety of thicknesses, but is typically about 0.01 to about 2.5 μm, preferably about 0.5 to about 1 μm.
[0040]
During indirect plasma polymerization, the web is preferably positioned at a distance of about 1 to about 40 cm below the plasma zone. Similarly, the monomer inlet is preferably located at a distance of about 1 to about 35 cm below the plasma zone. The distance of the web downstream (ie, below) from the plasma zone is more preferably from about 2 to about 20 cm, and most preferably from about 3 cm to about 10 cm. The distance of the monomer inlet downstream from the plasma zone is preferably about 2 to about 20 cm, and most preferably about 3 cm to about 10 cm.
[0041]
In one preferred embodiment, the indirect plasma polymerization of the polymerizable unsaturated compound according to the present invention is preferably performed under the following plasma conditions.
[0042]
Power = 10 to 100W,
Voltage = 8 × 10 ² Or 4 × 10 ^Three V,
Plasma gas flow rate = 1 to 100 sccm (standard cubic centimeter),
Monomer flow rate = 1 to 50 mg / min,
Supply gas flow rate = 1 to 100 sccm
Monomer source temperature = -80 ° C to + 80 ° C
Frequency = 1 kHz to 27.12 MHz, most preferably 13.6 MHz or 27.12 MHz,
Plasma gas = Ar, He, N ₂ ,
Pressure = 0.01 to 1 Torr
The polymer coating of the present invention is obtained by indirect plasma induced polymerization of a polymerizable unsaturated compound on a web under the conditions described above with respect to the distance between the web and the plasma zone and between the monomer inlet and the plasma zone. Obtainable. In contrast to coatings obtained by in-grow (or direct) plasma-induced polymerization, the coating according to the present invention is a repeating unit in which most of the repeating units of the polymer chain are obtained by non-plasma radical polymerization of individual unsaturated compounds. And is characterized by the fact that the structure is identical. Typically, from about 70% to about 98%, more typically from about 76% to about 98%, and most typically from about 82% to about 98% of repeating structural units are non-plasma radical polymerizations of the same monomer Shows the same structure as the polymer obtained. Typically, from about 2% to about 30%, more typically from about 2% to about 24%, and even more typically from about 2% to about 18% of the remaining structural units are based on the treated web. It functions as covalent linking groups or as a cross-linking site between adjacent polymer chains.
[0043]
The qualitative and quantitative properties of the plasma-induced polymer coatings of the present invention can typically be measured as outlined below.
[0044]
The uniform structure of the coating and the relatively low degree of controllable crosslinking is surprisingly achieved by indirect plasma polymerization of polymerizable unsaturated compounds under specific conditions at the base and monomer inlet locations. The Such structure and cross-linking creates coating properties that provide durable wettability of the treated web. A particular advantage of the coating is its strong adhesion to the treated web surface, which is obtained to a large extent irrespective of the nature of the web.
[0045]
As already mentioned, plasma-induced hydrophilic coatings exhibit a contact angle with water of less than 90 °, and even a small amount of water or an aqueous based liquid hanging on the web will naturally spread over the coated surface of the web. In a preferred embodiment, the treated web is exposed to a low temperature plasma gas composition (also referred to herein as a “surface modified gas stream”), or infrared, electron beam, thermal electron beam, or ultraviolet light. Further processing may be performed by exposure to an energy source such as but not limited to a device that emits. The latter is also referred to herein as “radiation curing”. An apparatus suitable as an energy source in the present invention is disclosed in US Pat. No. 4,842,893 (assigned to Yializis on April 29, 1988). The disclosure of this document is incorporated herein by reference.
[0046]
In the surface reforming gas flow embodiment, the surface reforming gas flow may contain N to increase the wettability of the hydrophilic coating. ₂ O and CO ₂ And are preferably included. In one such preferred embodiment, the plasma gas composition is about 80 to about 40 mole percent N. ₂ 0 and about 20 to about 60 mol% CO ₂ Preferably from about 70 to about 45 mole percent N ₂ 0 and about 30 to about 55 mol% CO ₂ Most preferably from about 60 to about 45 mole percent N. ₂ 0 and about 40 to about 55 mol% C0 ₂ (In addition, N in the mixture ₂ O and CO ₂ In an amount equal to 100 to 10 mole%) for a time sufficient to modify the surface of the hydrophilic coating to increase its wettability.
[0047]
In the radiation curing embodiment, the radiation source is preferably a gas discharge electron beam gun. The electron gun sends a stream of electrons through the emitter window onto the monomer to further cure the monomer and enhance the wettability of the hydrophilic coating. Curing is controlled by matching the electron beam voltage to the dielectric thickness of the monomer coating. For example, at 10K electron volts, it travels about 1 μm through the deposited monomer.
[0048]
The plasma process is usually performed as follows. After placing the web to be processed in a vacuum chamber, the chamber pressure is typically reduced to about 0.005 Torr. The process gas or process gas mixture to be used is introduced into the chamber and the chamber pressure is kept constant between 0.04 and 0.4 Torr. The internal dimensions of the work area are approximately 1.73 x 0.76 x 1.02 m (width x height x depth) and the total work volume is 1.34 m. ^Three It is. A suitable high frequency form of energy (typically 13.56 MHz radio frequency energy) is used to generate the plasma. In the system described above, the total power input capacity is 2500 W or less. The gas is dissociated by the RF energy to generate a plasma characterized by a unique glow. Since the process is performed under reduced pressure, the bulk temperature of the gas is close to ambient temperature. Therefore, it is called low temperature gas plasma, glow discharge, or low temperature gas glow discharge. Electrons or ions generated in the plasma impact the web surface, removing atoms or breaking bonds and generating free radicals. Since these free radicals are unstable, they react with the free radicals or groups in the plasma gas to fill a more stable state and form new moieties on the web surface. In addition, the energetic electrons in the glow discharge break the molecules in the gas phase and cause complex chemical reactions, resulting in the deposition of a thin hydrophilic coating on at least one surface of the web.
[0049]
Typically and preferably, an initial step is performed prior to plasma depositing the hydrophilic coating. The purpose of this step is to clean the web surface to be treated and to increase the adhesion of the thin hydrophilic coating that is subsequently deposited. Cleaning is performed by exposing the web surface to radiation from an energy source (including but not limited to) infrared, electron beam, thermal electron beam, and ultraviolet light (referred to herein as radiation cleaning) or by plasma cleaning. be able to. A device suitable as an energy source in the present invention is disclosed in US Pat. No. 4,842,893 (assigned to Yializis on April 29, 1988). This disclosure is incorporated herein by reference. In radiation cleaning embodiments, the radiation source is preferably a gas discharge electron beam gun. The electron gun sends a flow of electrons through the emitter window to the web surface to remove or break atoms and generate free radicals. These free radicals are unstable and attempt to satisfy a more stable state, so that the free radicals serve as a bonding site for the monomers used to form the hydrophilic coating on the web. Cleaning is controlled by matching the electron beam voltage to the dielectric thickness or desired cleaning depth. For example, for a 10K electron volt, it travels through the film by a depth of about 1 μm.
[0050]
In plasma cleaning embodiments, the gas is typically Ar alone or O.sub.2. ₂ Alone or Ar and O ₂ (For example, a 1: 1 ratio). The gas flow rate is typically about 20 to about 100 sccm (cc / min under standard conditions), preferably about 40 to 80 sccm, and most preferably about 50 to about 60 sccm. The RF power is about 1100 watts and the process pressure is about 0.04 Torr. The next step after the optional initial step is plasma deposition of the hydrophilic coating described above. This process is described in more detail in a later example.
[0051]
Materials useful as polymer films that are plasma treated to obtain hydrophilic coatings are obtained from thermoplastic polymers. As used herein, the term “thermoplastic polymer” generally means any thermoplastic polymer that can be used to make a film. Examples of thermoplastic polymers (although only illustrative) include: End-capped polyacetals such as poly (oxymethylene) or polyformaldehyde, poly (trichloroacetaldehyde), poly (n-valeraldehyde), poly (acetaldehyde), poly (propionaldehyde), etc .; acrylic polymers, For example, polyacrylamide, poly (acrylic acid), poly (methacrylic acid), poly (ethyl acrylate), poly (methyl methacrylate), etc .; fluorocarbon polymers such as poly (tetrafluoroethylene), perfluorinated ethylene- Propylene copolymer, ethylene-tetrafluoroethylene copolymer, poly (chlorotrifluoroethylene), ethylene-chlorotrifluoroethylene copolymer, poly (vinylidene fluoride) ), Poly (vinyl fluoride), etc .; polyamides such as poly (6-aminocaproic acid) or poly (ε-caprolactam), poly (hexamethylene adipamide), poly (hexamethylene sebacamide), poly (11 -Aminoundecanoic acid) etc .; polyaramides such as poly (imino-1,3-phenyleneiminoisophthaloyl) or poly (m-phenyleneisophthalamide); polyarylenes such as poly-p-xylylene, poly (chloro-p A polyaryl ether such as poly (oxy-2,6-dimethyl-1,4-phenylene) or poly (p-phenylene oxide); a polyarylsulfone such as poly (oxy-1,4-phenylene) Sulfonyl-1,4-phenyleneoxy-1,4-phenylene -Isopropylidene-1,4-phenylene), poly (sulfonyl-1,4-phenyleneoxy-phenylene-sulfonyl-4,4'-biphenylene) and the like; polycarbonates such as poly (bisphenol A) or poly (carbonyldioxy- 1,4-phenylene-isopropylidene-1,4-phenylene); polyesters such as poly (ethylene terephthalate), poly (tetramethylene terephthalate), poly (cyclohexylene-1,4-dimethylene terephthalate) or poly (oxy) Methylene-1,4-cyclohexyl-enemethyleneoxyterephthaloyl); polyaryl sulfides such as poly (p-phenylene sulfide) or poly (thio-1,4-phenylene); polyimides such as poly (pyromellitoimi) -1,4-phenylene), polyolefins such as polyethylene, polypropylene, poly (1-butene), poly (2-butene), poly (1-pentene), poly (2-pentene), poly (3-methyl) -1-pentene), poly (4-methyl-1-pentene), 1,2-poly-1,3-butadiene, 1,4-poly-1,3-butadiene, polyisoprene, polychloroprene, polyacrylonitrile, Poly (vinyl acetate), poly (vinylidene chloride), polystyrene and the like; copolymers consisting of those mentioned above, such as acrylonitrile-butadiene-styrene (ABS) copolymers.
[0052]
Preferred polymers are polyolefins and polyesters, with polyolefins being more preferred. Even more preferred are polyolefins containing only hydrogen and carbon atoms and made by addition polymerization of one or more unsaturated monomers. Examples of such polyolefins are in particular polyethylene, polypropylene, poly (1-butene), poly (2-butene), poly (1-pentene), poly (2-pentene), poly (3-methyl-1- Pentene), poly (4-methyl-1-pentene), 1,2-poly-1,3-butadiene, 1,4-poly-1,3-butadiene, polyisoprene and the like. Such terms are also meant to include blends of two or more polyolefins, random copolymers and block copolymers made from two or more different unsaturated monomers. Due to their commercial importance, the most preferred polyolefins are polyethylene and polypropylene.
[0053]
In addition to polymer films, webs that can be used to make durable, wettable, liquid permeable webs according to the present invention include spunbonded nonwovens, hydroentangled nonwovens, needled nonwovens, and polymeric bonds ( Non-limiting examples include polymericly bound nonwovens. Preferred nonwoven webs are typically formed from organic textile fibers such as, but not limited to: Cotton, wool, wood, jute, viscose rayon, nylon, polyester, polyolefin, carbon, or mixtures thereof. Inorganic fibers such as glass and metal may be used alone or in combination, and may also be combined with organic fibers. In the case of staple fibers, the fiber length is from about 1/4 inch to about 2 inches or more. In the case of a spunbonded web, the fiber length is not fixed. Staple fibers for use in hydroentangled nonwovens, needled nonwovens, and polymerized bonded nonwovens are processed by conventional textile machines.
[0054]
For example, when making a polymerized bonded nonwoven web, a card machine may be used to form a continuous length of some length loosely tied fibers known as a carded web. These webs may be collected to form a multi-layered or three-dimensional fibrous web of considerable weight (eg, approximately a few to thousands of grams per yard). In a continuous nonwoven fibrous web, the woven fibers are arranged at various angles with respect to the longitudinal axis of the web. When the card machine is operated to form the web, usually the majority of the fibers are oriented in the direction of machine travel, while the isotropic web can be formed, for example, by air laying. The fiber web described above is typically impregnated (polymerized) with a polymeric binder. In a preferred form, the polymeric binder is added as an emulsion of acrylic, polyvinyl acetate, or similar polymer nature, and mixtures thereof. Preferably, the fibers are non-woven, substantially oriented in a tangled manner, and bonded together with a polymeric binder by adhesion.
[0055]
Hydroentangled webs and needled webs are distinguished from polymerized bonded webs in that they obtain web bondability primarily depending on the physical entanglement of the fibers. In contrast to polymer bonded webs and physically entangled webs, spunbonded webs typically consist of very long fibers bonded together by a solvent or melt process.
[0056]
As already mentioned, the web may be two-dimensional or a three-dimensional structure provided with openings made in accordance with the teachings of the references discussed in the prior art. The coating is durable and increases the surface energy of the web, making the resulting treated web more wettable. The coating is durable in that it is retained for a long time even after exposure to water or other aqueous liquids. In this regard, the webs of the present invention are described in one respect in terms of their ability to remain wet for extended periods of time and / or after exposure to liquids. The ability to remain wet for an extended period is assessed by measuring the contact angle after aging of the treated web. This measurement involves storing the plasma treated web at 74 ° C. for 16 hours and artificially aging the sample prior to contact angle measurement. The ability to remain wet after exposure to liquid is assessed by measuring the contact angle after washing of the treated web. This measurement involves forcing the 2 inch × 2 inch treated web into a 250 mL water bath at 65 ° C. for 90 seconds before forcibly stirring. Procedures and apparatus for measuring the contact angle between the liquid and the web surface are well known in the art. However, for processed webs that Applicants have disclosed, surface and water drops according to the procedures specified by the T565pm-96 tentative method and ACCUC DYNE TEST (Diversified Enterprises (based on ASTM D2578-84 method)). Test contact angle and surface energy. The contact angle value is reported as the average of the measurements for 5 samples.
[0057]
In some embodiments, the treated web of the present invention has a contact angle after aging that is greater than the contact angle of the treated web before aging (ie, the contact angle measured before storage at 74 ° C. for 16 hours). Larger by about 60 ° or less. Preferably, the treated web has a contact angle after aging that is about 40 ° or less, more preferably about 20 ° or less, and even more preferably about 10 ° or less than the contact angle before aging. In another embodiment, the treated web of the present invention is a prewashed contact angle of the treated web (ie, the treated web is forced by immersing the treated web in a 250 mL water bath at 65 ° C. for 90 seconds). Contact angle measured before mechanical stirring) by about 60 ° or less. In this regard, the treated web preferably has a contact angle after washing that is no more than about 40 °, more preferably no more than about 20 °, and even more preferably no more than about 10 ° than the contact angle before washing. . In a preferred embodiment, the treated web of the present invention exhibits both what is required after aging and after washing as described above.
[0058]
The durable and wettable liquid permeable web of the present invention has a contact angle after aging and a contact angle after washing (preferably both) of less than about 90 °, preferably about 70 ° or less, More preferably, it is about 50 ° or less, even more preferably about 30 ° or less, and most preferably about 20 ° or less.
[0059]
II. Absorbent article
As used herein, the term “absorbent article” generally refers to an instrument used to absorb and contain body exudates, and more specifically, disposed on or near the wearer's body. Refers to devices that absorb and contain various exudates released from the body. The term “absorbent article” is intended to include wipes, bandages, wound dressings as well as diapers, menstrual pads, tampons, sanitary napkins, incontinence pads, training pants and the like. The term “disposable” as used herein refers to absorbent articles that are not intended to be washed, otherwise repaired, or reused as an absorbent article (ie, discarded to some extent, preferably recycled) And is otherwise intended to be composted in a way that is compatible with the environment). A “single” absorbent article is formed as a single structure or as separate parts that are combined to form a coordinated entity, so that separate holders and pads are separate. Absorbent articles that do not require any manipulative parts.
[0060]
Whatever the overall size, shape, and / or configuration of the absorbent article that incorporates or uses the durable, wettable, liquid permeable web of the present invention, it is in accordance with the principles of the present invention. It should be understood that there is no significance or functional relevance. However, such parameters must be considered along with the intended liquid and intended functionality when determining the appropriate shape of the web.
[0061]
The absorbent article also includes an absorbent core for holding any absorbed body fluid in addition to the durable, wettable, liquid permeable web of the present invention. Typical absorbent structures used as the absorbent core in the present invention are described in the following documents. US Patent No. 4,950,264 (Osborn granted on August 21, 1990), US Patent No. 4,610,678 (Weisman et al. Granted on September 9, 1986), US Patent No. 4,834,735 (Alemany et al. May 1989) Granted on 30th), European Patent Application 0198683 (Procter & Gamble, published in the name of Duenk et al. On October 22, 1986), US Pat. No. 4,673,402 (granted on Weisman et al. On June 16, 1987), US Pat. No. 4,888,231 (granted to Angstadt on December 19, 1989). The absorbent core may further comprise a dual core system comprising a capture core / distribution core consisting of chemically stiffened fibers disposed on the absorbent storage core. This includes US Pat. No. 5,234,423 “Absorbent Article With Elastic Waist Feature and Enhanced Absorbency” (Alemany et al. Granted on August 10, 1993) and US Pat. No. 5,147,345 “High Efficiency Absorbent Articles For Incontinence Management” (Young , Granted on September 15, 1992 to LaVon, Taylor). The disclosures of all these patents are incorporated herein by reference.
[0062]
A preferred embodiment of a single disposable absorbent article according to the present invention is a menstrual pad, a sanitary napkin. As used herein, the term “sanitary napkin” is used by women in the vicinity of the vulva region (usually outside the urogenital region), and liquids from menstruation and other vaginal discharges from the wearer's body (eg, Absorptive article for absorbing and containing blood, mens, urine). Interlabial devices that are partially placed inside and outside the wearer's vaginal vestibule are also within the scope of the present invention. Suitable feminine hygiene products are disclosed in the following references. US Pat. No. 4,556,146 (granted to Swanson et al. On December 3, 1985), US Pat. No. 4,589,876 (granted to Van Tilberg et al. On April 27, 1993), US Pat. No. 4,687,478 (Van Tilburg, 1987) Granted on Aug. 18), U.S. Pat. No. 4,950,264 (Granted to Osborn, III on Aug. 21, 1990), U.S. Pat. No. 5,009,653 (granted to Osborn, III on Apr. 23, 1991), U.S. Patent 5,267,992 (granted to Van Tilburg on December 7, 1993), US Pat. No. 5,389,094 (granted to Lavash et al. On February 14, 1995), US Pat. No. 5,413,568 (Roach et al., May 9, 1995) U.S. Pat. No. 5,460,623 (Emenaker et al. Granted on Oct. 24, 1995), U.S. Pat. No. 5,489,283 (Van Tilburg granted Feb. 6, 1996), U.S. Pat. No. 5,569,231 (Emenaker et al.) Granted on October 29, 1996), US Pat. No. 5,620,430 (issued on April 15, 1997 to Bamber). The disclosures of each document are incorporated herein by reference.
[0063]
In a preferred embodiment of the present invention, the sanitary napkin has two flaps each extending adjacent to the lateral end of the absorbent core and extending laterally therefrom. Since the flap covers the end of the wearer's panty in the crotch region, the flap is placed between the end of the wearer's panty and the thigh. The flaps serve for at least two purposes. First, the flap serves to prevent the wearer's body and panty from becoming soiled by liquid from menstruation, preferably by forming a double wall barrier along the end of the panty. Second, attachment means are preferably provided on the garment-side surface of the flap so that the flap can be folded back to the underside of the panty and attached to the side of the panty facing the garment. Thus, the flap serves to hold the sanitary napkin in place on the panty. The flaps can be made from a variety of materials, such as topsheets, backsheets, similar materials to tissue, or combinations of these materials. The flap may also be a separate member attached to the body of the napkin, or may constitute an extended portion of the topsheet and backsheet (ie, a single piece). Many sanitary napkins having flaps suitable or compatible with the sanitary napkins of the present invention are described in US Pat. No. 4,687,478 “Shaped Sanitary Napkin With Flaps” (Van Tilburg, granted on Aug. 18, 1987), US Patent No. 4,589,876 “Sanitary Napkin” (granted to Van Tilburg on May 20, 1986). The disclosures of each patent are incorporated herein by reference.
[0064]
In a preferred embodiment of the present invention, a capture layer may be disposed between the topsheet and the absorbent core. The acquisition layer can serve several functions such as improving wicking of exudates on or into the absorbent core. There are several reasons why it is important to improve exudate emissions. For example, exudates are more evenly distributed throughout the absorbent core so that sanitary napkins can be made relatively thin. Discharge described herein may include transporting liquid in one direction, two directions, or all directions (ie, in the xy plane and / or z-direction). The acquisition layer may be composed of a variety of different materials, including nonwoven webs or woven webs of the following materials. Synthetic fibers such as polyester, polypropylene, polyethylene; natural fibers such as cotton, cellulose; blends of such fibers; any equivalent material or any combination of materials. Examples of sanitary napkins having a trapping layer and a topsheet are described in US Pat. No. 4,950,264 (Granted to Osborn), US Patent Application No. 07 / 810,774 “Absorbent Article Having Fused Layers” (Cree et al. On Dec. 17, 1991). In the name of this application). The disclosure of each reference is incorporated herein by reference. In a preferred embodiment, the acquisition layer and the topsheet are used by any conventional means for joining the webs together, most preferably by fusing (as described more fully in the referenced Cree application). May be joined.
[0065]
A menstrual pad may be made as follows. 0.04g / in of spiral pattern H2031Findlay hot melt adhesive on silicone coated release paper ² Paint with. The adhesive layer is transferred to the top surface of the secondary topsheet (the surface facing the wearer) by winding the secondary topsheet and the coated release paper together with a hand roller. The secondary topsheet is made of a non-woven material known as Fort James Airlaid Tissue, Grade 817 (sold by Fort James (Green Bay, Wis.)). After the top sheet of the present invention is attached to the pressure-sensitive adhesive surface of the sub top sheet, both are gently pressed with a hand roller to join them. Two strips of 1/4 inch double sided tape are applied along the long ends of the polyethylene backsheet. An absorbent core is added to create a complete absorbent structure.
[0066]
As used herein, the term “diaper” refers to clothing normally worn by infants and incontinent persons and worn around the bottom of the wearer's torso. However, it should be understood that the present invention is applicable to other absorbent articles such as incontinence briefs, incontinence pads, training pants, diaper inserts, tissue paper, paper towels and the like. The diaper of the present invention typically comprises a topsheet comprising the durable and wettable liquid permeable web of the present invention, a liquid impervious backsheet bonded to the topsheet, a topsheet and a backsheet. And an absorbent core disposed between the two. Moreover, you may provide the elastic member and fastening means (for example, tape tab fastener) for fixing an additional structural member, for example, a diaper to a wearer's predetermined position.
[0067]
Although the topsheet, backsheet, and absorbent core can be combined in a variety of well-known configurations, a preferred configuration for diapers is outlined in US Pat. No. 3,860,003 (granted to Buell on January 14, 1975). It is described in. The disclosure of this document is incorporated herein by reference. Alternatively, preferred configurations of disposable diapers herein are also disclosed in the following references. US Pat. No. 4,808,178 (Granted to Aziz et al. On February 28, 1989), US Pat. No. 4,695,278 (Granted to Lawson on September 22, 1987), US Pat. No. 4.816,025 (Foreman Granted on March 28). The disclosures of each patent are incorporated herein by reference. Incontinence articles suitable for adult wearers are described in the following references. US Pat. No. 4,253,461 (granted to Strickland et al. On March 3, 1981), US Pat. Nos. 4,597,760 and 4,597,761 (granted to Buell), US Pat. No. 4,704,115, US Pat. No. 4,909,802 (granted to Ahr et al.) ), US Pat. No. 4.964,860 (Gipson et al. Granted on Oct. 23, 1990), U.S. Patent Application No. 07 / 637,090 (Noel et al. Filed on Jan. 3, 1991) (International Publication WO 92/11830) (Published July 23, 1992)). The disclosure of each reference is incorporated herein by reference.
[0068]
The absorbent core of the diaper is disposed between the top sheet and the back sheet. The absorbent core can be made in a variety of sizes and shapes (eg, rectangular, hourglass, asymmetric, etc.). However, the total absorbent capacity of the absorbent core must be compatible with the design liquid loading for the intended use of the absorbent article or diaper. Also, the size and capacity of the absorbent core can be varied to suit wearers from infants to adults.
[0069]
As already mentioned, the absorbent core may comprise a liquid distribution member. In a preferred configuration, the absorbent core preferably further comprises a capture layer or capture member in fluid communication with the liquid distribution member and disposed between the liquid distribution member and the topsheet. The acquisition layer or acquisition member may be composed of a variety of different materials including a nonwoven web or a woven web made of the following materials. Synthetic fibers such as polyester, polypropylene, polyethylene; natural fibers such as cotton, cellulose; blends of such fibers; any equivalent material or any combination of materials.
[0070]
In a preferred embodiment, the diaper comprises stretchable leg cuffs. Stretch leg cuffs can be made in many different configurations, including those described in the following references. US Pat. No. 3,860,003, US Pat. No. 4,909,803 (granted to Aziz et al. On March 20, 1990), US Pat. No. 4,695,278 (granted to Lawson on September 22, 1987), US Pat. No. 4,795,454 (Dragoo) Granted on January 3, 1989). Each document is incorporated herein by reference.
In use, to attach the diaper to the wearer, position the back waistband part below the wearer's back and then pull the rest of the diaper between the wearer's legs so that the front wasteband part is Position at the front of the wearer. Next, a tape tab or other fastener is secured, preferably in the area facing the outside of the diaper.
[0071]
【Example】
The following examples are illustrative and are not meant to limit the invention disclosed and claimed herein.
[0072]
Example 1
A test web (30 cm × 20 cm) made of polyethylene film material is placed at the bottom of the vacuum chamber (20 cm below the bottom electrode) of the plasma discharge unit (APS model D). The plasma chamber is evacuated. When the pressure in the chamber reaches 20 mTorr, the carrier gas (Ar) is continuously introduced into the chamber at a constant flow rate (10 sccm), and the continuous pressure and the introduction of the carrier gas are balanced to adjust the pressure in the chamber to 63 mTorr. Keep on. While maintaining the above-described state, high-frequency power of 100 W is supplied at a frequency of 40 kHz to generate low-temperature plasma for 1 minute inside the chamber, and the film surface is exposed to low-temperature plasma. Next, a monomer (acrylic acid) is introduced into the chamber at a constant flow rate, and the inside of the chamber is maintained at a constant pressure (165 mTorr). While maintaining the above state, low temperature plasma (100 W, 40 kHz) is generated inside the chamber for 10 minutes. After treatment, the chamber is evacuated (30 mTorr) and then filled with atmospheric air. The treated web is tested for surface-to-water contact angle and surface energy. The test is performed according to the procedure specified by the T565pm-96 tentative method and the ACCUC DYNE TEST (Diversified Enterprises (based on ASTM D2578-84 method)). The results are shown in Table 1 below.
[Table 1]

[0073]
(Comparative Examples 2 to 4)
In this comparative example, contact angle data (shown in Table 2 below for comparison with Table 1 above) is exposed to a carrier gas (Ar) and a monomer (acrylic acid) without plasma discharge (Comparative Example) 2) A film exposed to carrier gas (Ar) and plasma discharge (100 W) for 11 minutes (Comparative Example 3), and carrier gas (Ar), monomer (acrylic acid) and plasma discharge (100 W, 11 minutes) Shown for film (direct plasma) (Comparative Example 4) placed between exposed electrodes. Compared to Table 1, it can be seen that indirect plasma results in a web that retains its hydrophilicity better after accelerated aging compared to webs made under various other conditions such as direct plasma polymerization. .
[Table 2]

Claims (12)

An absorbent article comprising a liquid permeable topsheet web that is durable and wettable, the topsheet web comprising:
(I) introducing the web into a plasma reaction chamber comprising a plasma reaction zone, the web being disposed outside the plasma reaction zone;
(Ii) coating at least one surface of the web with monomer polymerized by plasma polymerization, the coating being obtained from a flow of monomer gas having a thickness of less than 2.5 μm resulting in a hydrophilic coating during plasma polymerization A flow of monomer gas is introduced outside the plasma reaction zone;
Produced by an indirect plasma method including:
The web and monomer gas flows are located 2-20 cm below the plasma zone,
The web is selected from the group consisting of a polymer film, a polymer film having openings, a nonwoven fabric, and a nonwoven fabric having openings, and the polymerized monomer renders at least one surface of the web durable wettable,
At least one surface of a liquid permeable web that is durable and wettable is characterized in that the contact angle after aging is greater than the contact angle before aging by no more than 10 ° under conditions of storage at 74 ° C. for 16 hours. , Absorbent articles.   The absorbent article of claim 1, wherein at least one surface of the liquid permeable web that is durable and wettable has a contact angle after washing that is no more than 60 degrees greater than the contact angle before washing.   Prior to introducing the monomer gas stream of step (ii), the web surface is exposed to a plasma state or an energy source selected from the group consisting of infrared, electron beam, thermal electron beam, or ultraviolet light and mixtures thereof. The absorbent article according to claim 1, further comprising a step of cleaning the web surface. The step of cleaning the web surface by exposing the web to a plasma condition comprises introducing a flow of gas comprising a material selected from the group consisting of Ar, O ₂ and mixtures thereof. 3. Absorbent article according to 3. The web produced in step (ii) is selected from the group consisting of a flow of surface modifying gas comprising N ₂ O and CO ₂ or from infrared, electron beam, thermal electron beam, or ultraviolet light and mixtures thereof. The absorbent article according to any one of claims 1 to 4, further comprising a step of further modifying the hydrophilic surface by introducing it into an energy source.   6. Absorbent article according to any one of the preceding claims, further comprising a final step comprising providing openings in the coated web.   The absorbent article according to any one of claims 1 to 6, wherein the polymer film is obtained from a material selected from the group consisting of polyolefins, polyesters, and mixtures thereof.   Polymer films include polyethylene, polypropylene, poly (1-butene), poly (2-butene), poly (1-pentene), poly (2-pentene), poly (3-methyl-1-pentene), poly ( 4-methyl-1-pentene), 1,2-poly-1,3-butadiene, 1,4-poly-1,3-butadiene, polyisoprene, blends thereof, random copolymers thereof, and block copolymers thereof 8. Absorbent article according to claim 7, obtained from a material selected from the group consisting of:   9. Absorbent article according to any one of the preceding claims, characterized in that the flow of monomer gas comprises at least one monomer containing vinyl groups. The absorbent article of claim 9, wherein the monomer gas stream comprises a monomer selected from the group consisting of:
a) general formula ^{_{H 2 C = C (R 2}} ) -C (O) OH acrylic acid and methacrylic acid,
b) the general formula ^{_{H 2 C = C (R 2}} ) -C (O) OR 3 acrylates and methacrylates,
c) Acrylamide and methacrylamide of the general formula (R ² ) (R ² ) C═C (R ² ) —C (O) NHR ³
d) maleic and fumaric acids of the general formula HO (O) C—C (R ² ) ═C (R ² ) —C (O) OH,
e) Maleate and fumarate of the general formula R ³ O (O) C—C (R ² ) ═C (R ² ) C (O) OR ³ ,
f) vinyl ethers of the general formula (R ² ) (R ² ) C═C (R ² ) —O—R ³ ,

h) vinyl acetate of the general formula (R ² ) (R ² ) C═C (R ² ) —OC (O) CH ₃ ;
i) Aliphatic vinyl compounds of the general formula R ² CH═CHR ³ and mixtures thereof.
Wherein each R ² is independently hydrogen or C ₁ -C ₁₀ alkyl, each R ³ is independently 1 0 following aliphatic hydrocarbon group is a carbon atom, an aliphatic hydrocarbon group, Substituted by one or more carboxy, hydroxy, amino, or (poly) ethylene oxide groups, or substituted by one or more sulfate, phosphate, sulfonate groups or mixtures of such groups Yes.   The flow of monomer gas is acrylic acid, methacrylic acid, hydroxyethyl methacrylate, methyl methacrylate, dimethylaminoethyl methacrylate, 2-hydroxyethyl acrylate, N, N-dimethylacrylamide, N-acryloylmorpholine, ethylene glycol dimethacrylate, and these 11. The absorbent article of claim 10 comprising a monomer selected from the group consisting of:   The absorbent article according to any one of claims 1 to 11, wherein the gas in the flow of the monomer gas is ionized by high-frequency microwave or radio wave vibration.