JP3555969B2

JP3555969B2 - Water absorbent material and water absorbent article

Info

Publication number: JP3555969B2
Application number: JP20642093A
Authority: JP
Inventors: 卓己初田; 一正小西
Original assignee: Nippon Shokubai Co Ltd
Current assignee: Nippon Shokubai Co Ltd
Priority date: 1992-08-28
Filing date: 1993-08-20
Publication date: 2004-08-18
Anticipated expiration: 2019-08-18
Also published as: JPH06256536A

Description

【０００１】
【産業上の利用分野】
本発明は、新規な吸水性材料および吸水性物品に関する。更に詳しくは、しなやかな風合い、良好なる吸水性を有する可撓性のシート状吸水性材料、および大きい吸水速度、優れた柔軟性を有する可撓性のシート状吸水性材料であって、吸水性樹脂粒子と水とからなり、任意の大きさまたは形状に切断できる吸水性材料、および該吸水性材料を収納した吸水性物品に関する。
【０００２】
【従来の技術】
吸水性樹脂として、ポリアクリル酸部分中和物架橋体、アクリル酸エステル−酢酸ビニル共重合体のケン化物、架橋ポリビニルアルコール変成物、架橋イソブチレン−無水マレイン酸共重合体、澱粉−アクリロニトリルグラフト重合体の加水分解物、澱粉−アクリル酸グラフト重合体、ポリエチレンオキサイドの部分架橋体等が知られており、該吸水性樹脂は、生理用ナプキン、紙おむつ等の衛材用吸収剤あるいは農園芸用分野、土木業分野において保水剤、脱水剤等の巾広い用途に応用されている。
【０００３】
用いられる吸水性樹脂は一般に粉末状、粒子状であり、実使用する場合の多くは、紙とのサンドイッチ、パルプに混入させてエンボス加工等の圧着処理、あるいは熱可塑性樹脂等による溶封等の複合化を行い、シート状やフィルム状等の形状に変えて用いられる。
【０００４】
従来、吸水性樹脂を基材に付与して固着化処理を行い、シート状にして利用するための提案が種々なされている。吸水性樹脂を製造した後これをシート状にする方法と、吸水性樹脂の製造とシート化とを同時に行う方法に大別できる。前者の方法には吸水性樹脂粉末をシート状の基材に付与して固着化処理を行う方法（ａ）と、繊維状の吸水性樹脂をシート化する方法（ｂ）がある。（ｂ）の方法は、繊維状の吸水性樹脂を得ること自体がコスト高となるうえ、得られる吸水性シートの吸水能が低くあまり一般的でない。（ａ）の方法の固着化処理として、基材シートに吸水性樹脂粉末を散布し、これに別のシートを重ねエンボス加工を施す方法、基材シートと吸水性樹脂粉末を混合しエンボス加工を施す方法、吸水性樹脂粉末に少量の水分を与え、基材シートと強固な固着を実現しようとする方法（例えば、ＵＳＰ３９５９５６９、特開昭５１−４０４９７号、特開昭５４−１２３２９３号、特開昭５４−１４１０９９号および特開昭５８−３６４５２号）、あるいは樹脂バインダーを用いて、吸水性樹脂粉末と基材シートとの固着を実現しようとする方法（例えば、特開昭５８−１０１０４７号、特開平４−５０４２３４号、ＵＳＰ５１２８０８２）等がある。また特開平１−２３０６７１号には、吸水性樹脂に水性液を組み合わせて水化物を形成する吸水性樹脂の不動化方法が提案されている。しかしながら、吸水性シートを得るためのこれらの方法にはいくつかの問題点があった。例えば、シート状態を保持するためには基材が必須であり、基材と吸水性樹脂粉末との複合化工程が繁雑であったり、粉塵がたつ等の作業環境が悪かったり、得られるシートの強度あるいは柔軟度が不十分であったりした。また、単位面積当たりの吸水性樹脂量を高くできないため、吸水量が小さかったり、吸水速度が小さかったりした。単位面積当たりの吸水性樹脂量を高くすると、シートが硬くなったり、吸水性樹脂粉末がシートからこぼれ出たりした。
【０００５】
一方、基材シート上で単量体を直接重合することにより吸水性樹脂の製造とシート化を同時に行う方法がいくつか提案されている（例えば、特開昭６０−１４９６０９号、特開昭６２−５３３０９号、特開昭６２−６２８２９号および特開昭６２−９７９７９号等がある）。しかしながら、これらの方法はいずれも次のような欠点を有する。すなわち、重合に用いた重合開始剤やその他の添加剤および比較的多くの単量体が残存する可能性が高い。これらの物質の安全性が懸念される場合には、衛材用途あるいは食品用途等に製品を使用する際に問題となる。また反応のコントロールが困難であったり、生産性が低かったりした。さらに得られるシートの吸水性能あるいは柔軟度が不十分であったりした。
【０００６】
おむつ、失禁パッド、生理用品等の衛材製品に組み込まれる吸水性物品が知られており（例えばＵＳＰ４６９９６１９、ＵＳＰ４７９８６０３およびＵＳＰ４８３４７３５等）、一般にこれらの吸水性物品は繊維状のマトリックスおよび必要により吸水性樹脂から成っている。繊維状マトリックスは木材パルプフラッフとして知られているセルロース繊維あるいはセルロース繊維と合成繊維とから成っている。
【０００７】
従来の吸水性物品の内、吸水性樹脂を用いないものは、必然的に容積が大きいものとなり、取扱いが極めて不便であった。即ち、木材パルプフラッフの単位重量当たりの吸水量は比較的小さく（約７〜９ｇ／ｇ）、所定の吸水量を達成するために比較的大量の木材パルプフラッフを使うことが必要となり、その結果比較的大きく、厚い吸水性物品となった。これに対して、吸水性樹脂はかなり大きい吸水量（少なくとも１５ｇ／ｇ）を有しており、吸水性樹脂を吸水性物品に導入することで木材パルプフラッフの使用量を低減することが可能となった。そして吸水性樹脂を使用することで、小さく薄い吸水性物品を製造することがが可能となった。しかしながら、従来の吸水性物品は、まだ比較的低い吸水性樹脂量（一般的に約５０重量％以下）から成っており、十分に小さく薄い吸水性物品を提供しているとはいえない。単位重量当たりの吸水量を考えれば、吸水性樹脂量を高くすることでコンパクトで薄型の吸水性物品がえられるはずである。ＥＰ４４３６２７において、吸水性樹脂量を多くした吸水性物品が提案されている。
【０００８】
しかしながら、従来公知の吸水性樹脂を用い、その樹脂量を高くした吸水性物品をつくったのでは、種々の問題を生じるであろう。ひとつの問題点はゲルブロッキング現象である。一般に吸水性樹脂は吸水して膨潤した際に変形し、吸水性樹脂粒子間、および吸水性樹脂粒子と繊維状マトリックス間に当初あった空間を塞ぎ、その結果、該空間を流れていた流体の流れを妨げるのである。吸水性樹脂量が小さい場合には繊維状マトリックスが吸水性樹脂粒子同士の接近を少なくすることができ、流体がマトリックス中を流れるのに十分なキャピラリー構造を保つことができる。もう一つの問題点は、吸水性樹脂の吸水速度不足である。一般に吸水性樹脂の吸水速度は木材パルプフラッフに比べて小さく、実使用時に吸水性物品に適用される流体の速度に対応できない。したがって木材パルプフラッフのような繊維状マトリックスが、吸水性物品に適用される流体の一次貯蔵層として機能しているのが現状である。
【０００９】
ＥＰ４４３６２７では、吸水速度を高めた吸水性樹脂を用いることで吸水性樹脂量を多くした吸水性物品を提案している。しかしながらＥＰ４４３６２７で提案されているような、粒子状の吸水性樹脂の固定化の役目をしていた繊維状マトリックスが少ないか、あるいはない場合には、吸水性物品中での吸水性樹脂の移動や偏りの問題が生じることが予想される。吸水性樹脂が吸液、膨潤というその役目を果たす時点まで、該樹脂を所定の位置に固定化するための新たな工夫が必要となる。さらにまた吸水性樹脂を乾燥粉末として用いようとすると、微細なため漏れや空中飛散が多く、極めて扱いにくい。このことは機械的大量生産において安定な運転を大いに阻害する。
【００１０】
コンパクトで薄型の吸水性物品およびそれをを得るための吸水速度が大きく、しかも柔軟性があり、該吸水性物品の所望の位置に固定化できる吸水性材料の登場が待ち望まれていた。
【００１１】
【発明が解決しようとする課題】
本発明は、前述した従来の吸水性樹脂あるいは吸水性物品、およびそれらの製造方法が有する欠点を改良し、しなやかで、良好なる吸水性（吸水速度および吸水量）を有し、任意の大きさまたは形状に切断でき、しかも安全性の高い吸水性材料を提供することを目的とする。また該吸水性材料を得るための簡便で生産性が高く、製品性能のコントロールの容易な製造方法を提供することを目的とする。さらに該吸水性材料を用い、コンパクトで薄型の吸水性物品を提供することを目的とする。
【００１２】
【課題を解決するための手段】
本発明者らは、吸水性樹脂の有する特性に着目し研究を重ねた結果、下記のごとき吸水性材料および吸水性物品が、前記目的を達成することを見出だし、本発明を完成するに至った。
【００１３】
すなわち前記目的は、吸水性樹脂粒子１００重量部に対して水１５〜１５０重量部が配合された吸水性材料であって、該吸水性材料は、厚みが約０．３〜５ｍｍのシート状態であって、該シート状態は前記吸水性樹脂粒子同士の接着に起因したものであることを特徴とする吸水性材料によって達成される。
【００１４】
前記目的は、吸水性樹脂粒子１００重量部に対して水１５〜１５０重量部、および水不溶性微粒子、界面活性剤および繊維よりなる群から選ばれた少なくとも１種の吸水助剤０．１〜１０重量部が配合された吸水性材料であって、該吸水性材料は、厚みが約０．３〜５ｍｍのシート状態であって、該シート状態は前記吸水性樹脂粒子同士の接着に起因したものであることを特徴とする吸水性材料によっても達成される。
【００１５】
前記目的は、上記の吸水性材料を、少なくとも片面側を水透過性シートによって形成した袋体の内部に収納したことを特徴とする吸水性物品によっても達成される。
【００１６】
前記目的は、吸水性樹脂粒子１００重量部を支持体上に、厚みを約０．３〜５ｍｍに規制して面状に流展し、この面状態を保持しながら水および／または水蒸気１５〜１５０重量部を加えて接触させることを特徴とする吸水性材料の製造方法によっても達成される。
【００１７】
前記目的は、吸水性樹脂粒子１００重量部と、水不溶性微粒子、界面活性剤および繊維よりなる群から選ばれた少なくとも１種のものである吸水助剤０．１〜１０重量部とを支持体上に、厚みを約０．３〜５ｍｍに規制して面状に流展し、この面状態を保持しながら水および／または水蒸気１５〜１５０重量部を加えて接触させることを特徴とする吸水性材料の製造方法によっても達成される。
【００１８】
以下本発明を詳しく説明する。
【００１９】
本発明に用いる吸水性樹脂粒子は、吸水性樹脂の粒子状物であって、水を吸収して体積膨脹を起こすものであれば特に制限はないが、一般に水溶性不飽和単量体を重合させることにより得られる。これらの水溶性不飽和単量体の例としては、（メタ）アクリル酸、（無水）マレイン酸、フマル酸、クロトン酸、イタコン酸、２−（メタ）アクリロイルエタンスルホン酸、２−（メタ）アクリロイルプロパンスルホン酸、２−（メタ）アクリルアミド−２−メチルプロパンスルホン酸、ビニルスルホン酸、スチレンスルホン酸、等のアニオン性単量体やその塩；（メタ）アクリルアミド、Ｎ−置換（メタ）アクリルアミド、２−ヒドロキシエチル（メタ）アクリレ−ト、２−ヒドロキシプロピル（メタ）アクリレ−ト、メトキシポリエチレングリコ−ル（メタ）アクリレ−ト、ポリエチレングリコ−ル（メタ）アクリレ−ト、等のノニオン性親水性基含有単量体；Ｎ，Ｎ−ジメチルアミノエチル（メタ）アクリレ−ト、Ｎ，Ｎ−ジメチルアミノプロピル（メタ）アクリレ−ト、Ｎ，Ｎ−ジメチルアミノプロピル（メタ）アクリルアミド、等のアミノ基含有不飽和単量体やそれらの４級化物等を具体的に挙げることがでる。また、得られる重合体の親水性を極度に阻害しない程度の量で、例えば、メチル（メタ）アクリレ−ト、エチル（メタ）アクリレ−ト、ブチル（メタ）アクリレート等のアクリル酸エステル類や酢酸ビニル、プロピオン酸ビニル等の疎水性単量体を使用してもよい。単量体成分としてはこれらのうちから１種または２種以上を選択して用いることができるが、最終的に得られる吸水性材料の吸水諸特性を考えると（メタ）アクリル酸（塩）、２−（メタ）アクリロイルエタンスルホン酸（塩）、２−（メタ）アクリルアミド−２−メチルプロパンスルホン酸（塩）、（メタ）アクリルアミド、メトキシポリエチレングリコ−ル（メタ）アクリレ−ト、Ｎ，Ｎ−ジメチルアミノエチル（メタ）アクリレ−トまたはその４級化物からなる群から選ばれる１種以上のものが好ましく、（メタ）アクリル酸（塩）を必須成分として含むものがさらに好ましい。この場合（メタ）アクリル酸の３０〜９０モル％が塩基性物質で中和されているものが最も好ましい。また、吸水性樹脂としての吸水倍率は、生理食塩水中のティーバッグ法による値で、２０〜６０ｇ／ｇ程度有することが好ましい。未架橋成分、いわゆる水可溶成分の割合は２０重量％以下が好ましく、より好ましくは１０重量％以下、さらに少ないほど好ましい。
【００２０】
本発明に用いる吸水性樹脂は、架橋剤を使用せずに得られる自己架橋型のものでも、重合性不飽和基および／または反応性官能基を有する架橋剤を、得られる吸水性樹脂粒子の諸特性が所望の基準に達する範囲で用いて得られるものでもよい。
【００２１】
これらの架橋剤の例としては、例えばＮ，Ｎ´−メチレンビス（メタ）アクリルアミド、（ポリ）エチレングリコ−ル（メタ）アクリレ−ト、グリセリントリ（メタ）アクリレ−ト、トリメチロ−ルプロパントリ（メタ）アクリレ−ト、トリアリルアミン、トリアリルシアヌレ−ト、トリアリルイソシアヌレ−ト、グリシジル（メタ）アクリレ−ト、（ポリ）エチレングリコ−ル、ジエチレングリコ−ル、（ポリ）グリセリン、プロピレングリコ−ル、ジエタノ−ルアミン、トリメチロ−ルプロパン、ペンタエリスリト−ル、（ポリ）エチレングリコ−ルジグリシジルエ−テル、（ポリ）グリセロ−ルポリグリシジルエ−テル、エピクロルヒドリン、エチレンジアミン、ポリエチレンイミン、（ポリ）塩化アルミニウム、硫酸アルミニウム、塩化カルシウム、硫酸マグネシウム等を具体的に挙げることができ、これらのうち反応性を考慮して、１種または２種以上を用いることができる。
【００２２】
また吸水性樹脂を得るにあたっては、デンプン、セルロ−ス、ポリビニルアルコ−ル等の親水性高分子の存在下で上記単量体成分を重合させることによって、重合と同時にグラフト結合やコンプレックスを形成させてもよい。
【００２３】
これらの単量体成分を重合させるにあたり、重合開始剤として、過硫酸アンモニウム、過硫酸カリウム、過酸化水素、ｔ−ブチルハイドロパ−オキサイド、２、２´−アゾビス−アミジノプロパン二塩酸塩等の水溶性ラジカル重合開始剤を用いればよい。重合方法は何等制限されることなく、例えば塊状重合、水溶液重合、逆相懸濁重合等の方法によれば良い。
【００２４】
これらの吸水性樹脂は、単独または２種あるいはそれ以上の混合物の形で使用される。
【００２５】
本発明に使用される吸水性樹脂粒子の粒子の形は、特に限定されない。ドラムで乾燥することにより得られるフレーク状であってもよく、塊状の樹脂を粉砕して得られる不定形状であってもよい。また逆相懸濁重合により得られる球状であってもよい。一般に逆相懸濁重合により得られる粒子は、その表面に分散剤あるいは界面活性剤を有しており、この様な粒子の場合には、追加の粉砕を加えたのち、本発明に使用することが好ましい場合がある。
【００２６】
本発明に用いる吸水性樹脂粒子は、本発明の目的が達成できる程度の粒子状であればよく、その大きさは特に限定されない。本発明の吸水性材料の内、引張降伏強さおよび引張降伏伸びの大きい吸水性材料を得るには、一般に、粒子サイズが小さいほど強さ、伸びとも大きくなる傾向がみらる。したがって吸水性樹脂粒子は、１０００μｍよりも大きな粒子を実質的に含まず、かつ１５０μｍ以下の粒子が２０％以上である粒度分布を有することが、得られる吸水性材料の引張降伏強さおよび引張降伏伸びをバランス良く満足する点で好ましく、８５０μｍよりも大きな粒子を実質的に含まず、かつ１５０μｍ以下の粒子が２０％以上である粒度分布を有することがより好ましい。一方、吸水速度および柔軟度の大きい吸水性材料を得るには、１０００μｍよりも大きな粒子を実質的に含まず、かつ１５０μｍ以下の粒子が１０％以下である粒度分布を有することが、得られる吸水性材料の吸水速度および柔軟度をバランス良く満足する点で好ましく、８５０μｍよりも大きな粒子を実質的に含まず、かつ１５０μｍ以下の粒子が１０％以下である粒度分布を有することがより好ましい。さらに好ましくは、６００μｍよりも大きな粒子を実質的に含まず、かつ１５０μｍ以下の粒子が５％以下である粒度分布を有する。本発明は、特に吸水速度に優れる吸水性材料として、水不溶性微粒子、界面活性剤および繊維よりなる群から選ばれた少なくとも１種の吸水助剤を含有する吸水性材料をも提供する。吸水助剤を含有する場合には、比較的広い粒度分布を有する吸水性樹脂粒子を用いても、大きい吸水速度を有する吸水性材料を得ることが可能になる。吸水助剤を含有する場合には、むしろ１５０μｍ以下の粒子を含有していることが得られる吸水性材料の強度および吸水速度の点で好ましい。したがって、１０００μｍよりも大きな粒子を実質的に含まず、かつ１５０μｍ以下の粒子が１０％以上である粒度分布を有することが、好ましい。１５０μｍ以下の粒子の含有量が少ない場合には、シート状の吸水性材料を作ることが困難となる場合がある。吸水性樹脂粒子の平均粒子径が小さいほど吸水速度は大きくなる傾向がある。
【００２７】
本発明において、吸水速度の大きい吸水性材料は、吸水性樹脂粒子に加重下の吸収倍率が大きいものを用いることが好ましい。加重下の吸収倍率の測定方法は後述するが、少なくとも２０ｇ／ｃｍ^２の加重下で０．９％食塩水を少なくとも２０ｍｌ／ｇ吸収するものが好ましい。少なくとも２４ｍｌ／ｇ吸収するものがより好ましく、少なくとも２８ｍｌ／ｇ吸収するものがさらに好ましい。この加重下の吸収倍率が、特定の値よりも大きい吸水性樹脂粒子を用いた吸水性材料は特に吸水速度に優れたものとなる。このような加重下の吸収倍率が大きい吸水性樹脂粒子は、例えば、後述するような吸水性樹脂粒子の表面を架橋処理することによって得られる。
【００２８】
本発明に用いる吸水性樹脂粒子は、表面架橋されていることが好ましい場合がある。吸水性樹脂粒子と該粒子の有する少なくとも２個の官能基と反応し得る基を有する架橋剤とを混合、反応し、吸水性樹脂粒子の表面近傍の架橋密度を高くした吸水性樹脂粒子を用いることで、特に吸水速度に優れる吸水性材料を得ることができる。吸水性樹脂粒子に、例えば、架橋剤として多価アルコールを用いる方法（特開昭５８−１８０２３３号、特開昭６１−１６９０３号）、多価グリシジル化合物、多価アジリジン化合物、多価アミン化合物、多価イソシアネート化合物を用いる方法（特開昭５９−１８９１０３号）、グリオキサールを用いる方法（特開昭５２−１１７３９３号）、多価金属を用いる方法（特開昭５１−１３６５８８号、特開昭６１−２５７２３５号、特開昭６２−７７４５号）、シランカップリング剤を用いる方法（特開昭６１−２１１３０５号、特開昭６１−２５２２１２号、特開昭６１−２６４００６号）、エポキシ化合物とヒドロキシ化合物を用いる方法（特開平２−１３２１０３号）、アルキレンカーボネートを用いる方法（ＤＥ−４０２０７８０）等に知られている表面架橋を施すことで、表面架橋された吸水性樹脂粒子を得ることができる。また、架橋反応時に不活性無機粉末を存在させる方法（特開昭６０−１６３９５６号、特開昭６０−２５５８１４号）、二価アルコールを存在させる方法（特開平１−２９２００４号）、水とエーテル化合物を存在させる方法（特開平２−１５３９０３号）等も知られている。
【００２９】
本発明に使用される吸水性樹脂粒子の含水率は、吸水性樹脂が粒子として取り扱える範囲であればとくに限定されない。吸水性樹脂粒子１００重量部に対して１５〜１５０重量部の水および／または水蒸気を加えて接触させたのち、得られた吸水性材料が、実質的に乾燥した吸水性樹脂１００重量部に対して１５〜１５０重量部の水からなっていればよい。好ましくは含水率０〜４０％、より好ましくは含水率０〜３０％の吸水性樹脂粒子を用いることが作業性の点でよい。
【００３０】
本発明の吸水性材料は、吸水性樹脂粒子１００重量部に対し、１５〜１５０重量部の水が配合されて成り、かつ該吸水性樹脂粒子同士の接着に起因してシート状態となったものである。１５０重量部を越える水の量では吸水性材料中の吸水性樹脂含量が低くなり、得られる吸水性材料の吸水量が低くなると共に、吸水性材料の強度が弱くなる。一方、１５重量部未満の水の量では十分な強度あるいは目的の吸水速度および柔軟度を有する吸水性材料が得られない。より好ましい水の量は、吸水性樹脂粒子１００重量部に対し２５〜１００重量部の範囲であり、最も好ましくは３０〜８０重量部の範囲である。驚くべきことに、ばらばらの吸水性樹脂粒子の状態よりも、本発明のシート状吸水性材料とすることで吸水速度が著しく向上するのである。
【００３１】
本発明にいうシート状態とは、少なくとも一部が連続する面を有していればよく、例えば任意の形状の貫通孔を１個あるいは複数個有しているシートでもよい。またウエーブがかかっていたり、ヒダ状であってもよい。好ましくは片面（表面あるいは裏面）が、５ｃｍ^２以上、より好ましくは１０ｃｍ^２以上、さらに好ましくは１５ｃｍ^２以上の面積を有するものである。さらに本発明の吸水性材料は、吸水性樹脂粒子同士の接着に起因するシート状態を呈する材料である。すなわち、例えば接着剤や繊維状の基材のような第３物質を介して連続的なシート状態になっているのではなく、吸水性樹脂粒子同士が直接接着することによって連続的なシート状態を形成しているものである。ここで吸水性樹脂粒子同士の接着とは、複数の吸水性樹脂粒子が接触しているところに、水分を与えることにより形成される接着であり、元の吸水性樹脂粒子同士の間に共有結合等の化学結合は生じていない。このことは、本発明の吸水性材料が吸液して膨潤する際に、ばらばらの吸水性樹脂粒子にもどることから推察できる。
【００３２】
本発明の吸水性材料は、厚みが０．３〜５ｍｍのシート状である。厚みが０．３ｍｍ未満ではシートの強度が小さくなるとともに、取扱い性が悪くなる。また単位面積当たりの吸水性樹脂量が小さすぎ、膨潤速度あるいは吸水速度も小さいものになる。一方厚みが５ｍｍを越えると均質な吸水性シートを得にくくなるばかりか、かえって膨潤速度あるいは吸水速度が小さくなる傾向がある。より好ましくは、厚みが０．５〜３ｍｍのシート状である。先に述べたように吸水性樹脂粉末を基材シート上に散布し、これに別のシートを重ね、必要により水を与えてシート化する技術は公知である。しかしながら、従来の技術は吸水性樹脂粒子同士の接近をできるだけ避けるように配慮され、したがって吸水性樹脂粒子の散布量は高々１００ｇ／ｍ^２であった。この様に低い散布量では本発明でいうところの吸水性樹脂粒子同士の接着はほとんど起こらず、したがって、粒子同士の接着に起因したシート状態は実現し得ない。本発明のシートは、一体のシートとして取り扱える範囲のものであり、吸水性樹脂粒子同士の接着によりシートの形態を保つものである。
【００３３】
本発明の吸水性材料は、吸水性樹脂粒子同士の接着に起因するシート状物であるが、被吸収液、すなわち水性媒体と接触することにより実質的に個々の吸水性樹脂粒子に分解されるものである。このことが良好なる吸水性を示す要因であると考えられる。従来公知の可撓性を有する吸水性シートに、例えば薄膜状の含水ゲル状重合体（特開平４−２３６２０３号）、ポリビニルアルコールとポリアクリル酸（塩）からなるフィルム（特公昭６２−９２１号、特公平２−４８０２４号等）等があるが、いずれも吸液により一体のゲル状を呈するものであり、吸水倍率が小さすぎたり、吸収速度が小さすぎるものであった。
【００３４】
本発明の好ましい実施態様は、引張降伏強さが０．５ｋｇ／ｃｍ^２以上で、かつ引張降伏伸びが１０％以上の吸水性材料である。大量の吸水性材料を取り扱う際に、引張り降伏強さが小さいと取扱いが困難となることがある。また吸水性材料を取り扱う際に、引張降伏伸びが小さいと柔軟性に欠け取扱いが困難となることがある。吸水性樹脂粒子として、１０００μｍよりも大きな粒子を実質的に含まず、かつ１５０μｍ以下の粒子が２０％以上である粒度分布を有するものを用いることが、このような吸水性材料を得るうえで好ましい。８５０μｍよりも大きな粒子を実質的に含まず、かつ１５０μｍ以下の粒子が２０％以上である粒度分布を有することがより好ましい。しかしながら、一般に、シートとしての強さ、あるいはしなやかさを高くすると、膨潤速度あるいは吸水速度が小さくなる傾向がある。
【００３５】
本発明の別の好ましい実施態様は、吸水速度が５０秒以下、より好ましくは３０秒以下で、かつ柔軟度が９０度以上の吸水性材料である。吸水速度の測定方法の詳細は後述するが、所定の面積を有する吸水性材料に一定量の人工尿を与え、これを完全に吸水する時間を本発明の吸水速度と定義する。木材パルプフラッフの使用量を低減し、小さく薄い吸水性物品を製造するうえで、この吸水速度を大きくすることが重要であることがわかった。柔軟度の測定方法の詳細は後述するが、吸水性材料のしなやかさ、外力が加わった際の微粉粒子の発生のし難さを表す指標が、本発明の柔軟度である。柔軟度が不足すると、硬くゴワゴワした感触が強くなり、使用に耐えないものとなったり、シートが崩壊し、吸水性樹脂粒子が発生したりする。吸水性樹脂の粒子同士の接着に起因するシート状材料でこれらの物性を同時に満足する材料は従来知られていなかった。吸水性樹脂粒子として、１０００μｍよりも大きな粒子を実質的に含まず、かつ１５０μｍ以下の粒子が１０％以下である粒度分布を有するものを用いることが、このような吸水性材料を得るうえで好ましい。８５０μｍよりも大きな粒子を実質的に含まず、かつ１５０μｍ以下の粒子が１０％以下である粒度分布を有することがより好ましく、６００μｍよりも大きな粒子を実質的に含まず、かつ１５０μｍ以下の粒子が５％以下である粒度分布を有することがさらに好ましい。また、吸水性樹脂粒子は、前述のように加重下の吸収倍率が少なくとも２０ｍｌ／ｇであるものが好ましく、表面架橋されたものであることが好ましい。
【００３６】
本発明は、吸水性樹脂粒子１００重量部に対して水１５〜１５０重量部、および水不溶性微粒子、海面活性剤および繊維よりなる群から選ばれた少なくとも１種の吸水助剤０．１〜１０重量部が配合された吸水性材料であって、該吸水性材料は、厚みが約０．３〜５ｍｍのシート状態であって、該シート状態は前記吸水性樹脂粒子同士の接着に起因したものであることを特徴とする吸水性材料をも提供する。特定の吸水助剤を含有させることによって、特に吸水速度に優れる吸水性材料が得られる。ここで吸水助剤とは、本発明の吸水性材料が吸水する際にその吸水速度を高める作用をするものである。これらは水不溶性微粒子（無機微粒子および有機微粒子）界面活性剤および繊維よりなる群から選ばれる少なくとも１種であって、具体例としては以下のものを挙げることができる。界面活性剤としては、ポリオキシエチレンアルキルエーテル、ポリオキシエチレンアルキルフェノールエーテル、ソルビタン脂肪酸エステル、ポリオキシエチレンソルビタン脂肪酸エステル、ポリオキシエチレンアシルエステル、オキシエチレンオキシプロピレンブロック共重合体、ショ糖脂肪酸エステル等を挙げることができる。無機微粒子としては、雲母、パイロフィライト、カオリナイト、ハルサイト、および他の類似した粘土鉱物および主に５０μｍ以下の平均粒子径を有する二酸化ケイ素粒子から成るアエロジル２００（日本アエロジル株式会社製）およびカープレックス＃８０（シオノギ株式会社製）のような微粒子状のシリカ等を挙げることができる。有機微粒子としては、カーボンブラック、活性炭およびパルプ粉等を挙げることができる。なかでも微粒子状シリカが吸水速度を高める作用が大きく好ましい。これらの吸水助剤の使用量は、０．１〜１０重量部、好ましくは０．５〜５重量部、最も好ましくは０．７〜２重量部である。前記重量が１０重量部を越えるならば、該超過は、使用量に比例する効果を得ることができず、そればかりかむしろ、吸水量が減少し、場合によっては、シートの形成をを困難にする。０．１重量部未満の使用量ではその使用効果が得られない。
【００３７】
本発明の特に好ましい実施態様である、吸水速度が３０秒以下で、かつ柔軟度が９０度以上である吸水性材料は、１０００μｍよりも大きな粒子を実質的に含まず、かつ１５０μｍ以下の粒子が１０％以上である粒度分布を有する吸水性樹脂粒子を用いると共に、吸水助剤を用いるのが好適である。１５０μｍ以下の粒子の含有量が少ない場合には、シート状の吸水性材料を作ることが困難となる場合がある。また、吸水助剤およびこのような特定の粒度分布とともに、前述のような特定の加重下吸収倍率を有する吸水性樹脂粒子を用いることが、吸水速度の大きい吸水性材料を得るうえで好ましい。また表面架橋された吸水性樹脂粒子であることが好ましい。
【００３８】
本発明は上記の吸水性材料を生産性良く製造するための方法も提供する。そのような製造方法は、吸水性樹脂粒子１００重量部を支持体上に、厚みを約０．３〜５ｍｍに規制して面状に流展し、この面状態を保持しながら水および／または水蒸気１５〜１５０重量部を加えて接触させることにより達成される。本発明の別の製造方法は、吸水性樹脂粒子１００重量部、および水不溶性微粒子、界面活性剤および繊維よりなる群から選ばれた少なくとも１種の吸水助剤０．１〜１０重量部を支持体上に、厚みを約０．３〜５ｍｍに規制して面状に流展し、この面状態を保持しながら、水および／または水蒸気１５〜１５０重量部を加えて接触させることにより達成される。厚みを規制して流展した吸水性樹脂粒子に、その面状態を保持しながら水および／または水蒸気を加えて接触させるとは、吸水性樹脂粒子に実質的に剪断力がかからない状態で水および／または水蒸気を加えることを意味し、例えば、支持体上に、厚みを約０．３〜５ｍｍに規制して流展した吸水性樹脂粒子に、水を噴霧する方法、飽和水蒸気をかける方法、および相対湿度５０％以上の雰囲気中で、吸水性樹脂粒子を厚みを規制して流展した支持体を保持する方法等が挙げられる。吸水性樹脂粒子と水との接触が不均一である場合には均質なシートが得られないことがあるが、水との接触後、水を飛ばさないように、例えば密封し、好ましくは３０℃以上の温度をかけて放置すると、均質なシートが得られる。吸水性樹脂粒子に水分を加える際に、例えば、吸水性樹脂粒子と水とを組合わせて掻き混ぜるというような剪断力が加わると、得られる吸水性材料の吸水速度が小さくなるため好ましくない。その様な操作を行うと、吸水性樹脂粒子は塊状となる傾向がある。この塊状のものを本発明の目的であるシート状に成型することは困難である。例えば、押し出し機等を用い、この塊状のものをシート状に成型することは不可能ではないが、その様な操作は非常に多くのエネルギーを必要とするばかりか、吸水性樹脂粒子同士の接着が過度に進行し、極端な場合には粒子間の界面が消失する。この様にして得られたシートは吸水速度が著しく低下する傾向がある。本発明の吸水性材料が得られた後も、該吸水性材料に剪断力が加わらないようにすることが好ましい。
【００３９】
本発明の製造方法において、吸水性樹脂粒子と水および／または水蒸気とを接触させる際に、吸水性樹脂粒子を支持体上に厚みを約０．３〜５ｍｍに規制して流展する。厚みが０．３ｍｍ未満ではシートの強度が小さくなり取扱い性が悪くなったり、単位面積当たりの吸水性樹脂量が小さすぎ、得られる吸水性材料の吸水速度も小さいものになる。また、シートとしての形態保持が困難になる。この様な厚みを達成するためには、一般に２００ｇ／ｍ^２以上、好ましくは２５０ｇ／ｍ^２以上、さらに好ましくは３００ｇ／ｍ^２以上の吸水性樹脂粒子が必要である。一方厚みが５ｍｍを越えると得られる吸水性材料の吸水速度がかえって小さくなる傾向があり、また均質な吸水性材料を得るための、吸水性樹脂粒子と水および／または水蒸気とを接触させるための時間が著しく長くなる傾向がある。
【００４０】
本発明の製造方法において、吸水性樹脂粒子に加える水分量は、吸水性樹脂粒子１００重量部に対し、１５〜１５０重量部の量である。ここで吸水性樹脂粒子は、前記の如くもともといくらかの水を含有していてもよく、粒子として取り扱える範囲のものであればよい。吸水性樹脂粒子が水を含有している場合は、得られる吸水性材料中の水が、吸水性樹脂粒子１００重量部に対し１５〜１５０重量部となる量で添加する。但し、本発明の方法においては、シート状の吸水性材料とする為に、吸水性樹脂粒子１００重量部に対し水を少なくとも１５重量部加える必要があるので、吸水性樹脂粒子１００重量部に対する水の量が１５重量部の吸水性材料を得る場合は、水の含有量が０の吸水性樹脂粒子を用いなければならない。１５０重量部を越える水の量では、得られる吸水性材料の吸水量が低くなるだけでなく、シート状の吸水性材料を製造する工程で破損が生じる場合がある。一方、１５重量部未満の水の量では、目的の吸水速度および柔軟度を有する吸水性材料が得られないだけでなく、吸水性樹脂粒子同士の接着が不十分で強度が劣ったものとなる場合がある。より好ましい水の量は、吸水性樹脂粒子１００重量部に対し２５〜１００重量部の範囲であり、最も好ましくは３０〜８０重量部の範囲である。
【００４１】
吸水性樹脂粒子と吸水助剤を組み合わせる際の組合わせの手順は特に制限されない。吸水性樹脂粒子と吸水助剤とをあらかじめ混合しておき、該混合物に水を接触させる方法でもよく、吸水助剤を溶解あるいは分散させた水を吸水性樹脂粒子に接触させる方法でもよい。
【００４２】
本発明の吸水性材料の製造方法において、吸水性樹脂粒子を支持体上に流展して水および／または水蒸気と接触させる際に、その流展する方法は任意である。すなわち吸水性樹脂粒子を一面に均一な厚みに広げれば、均一な厚みを有する一体のシート状の吸水性材料が得られ、任意の厚み、任意のパターンに広げれば、それに応じた吸水性材料が得られる。
【００４３】
本発明の吸水性材料の製造方法において、水は蒸留水、イオン交換水、水道水、工業用純水等のいずれであってもよく、これらの水の中に無機物あるいは有機物が溶解あるいは分散しているものであってもよい。
【００４４】
本発明は、上述の吸水性材料の少なくとも片面に水透過性シートを配してなる積層吸水性材料をも提供する。本発明の積層吸水性材料において、水透過性シートは前記吸水性材料の少なくとも片面に配すればよいが、両面に配してもよく、場合によっては、片面に水透過性シート、他面に水不透過性シートを配してもよい。このような積層吸水性材料は、水透過性シートまたは水不透過性シートを前記吸水性材料と重ね合わせるだけでえられるが、必要であればエンボス加工を施してもよい。ただし、吸水速度を重要と考える際は、プレスあるいはエンボス等の圧力あるいは剪断力をかける操作は好ましくない。また、水透過性シートまたは水不透過性シート上で、前記吸水性材料を形成することでもこのような積層吸水性材料が得られる。
【００４５】
水透過性シートとしては、例えば再生セルロース系不織布、綿状パルプ、レーヨン、コットンカードウエブあるいは紙等を挙げることができ、水を透過しやすい構造を持っているものが好ましい。また水不透過性シートとしては、例えばナイロン、ポリエチレン、ポリプロピレン、ポリスチレンおよびポリ塩化ビニルのフィルムを挙げることができる。
【００４６】
本発明の吸水性材料および積層吸水性材料はしなやかで強靱な風合い、良好なる吸水性を有し、任意の大きさまたは形状に切断できるため、種々の用途に使用できる。
【００４７】
本発明の方法に従って得られた吸水性材料および積層吸水性材料は該材料と水溶性高分子、消臭剤、香料、薬剤、植物育成助剤、殺菌剤、防黴剤、発泡剤、顔料、カーボンブラック、活性炭、短繊維等とを混合し、得られた吸水性材料に新たな機能を付与することもできる。
【００４８】
本発明の吸水性材料および積層吸水性材料はセルロース繊維あるいはそのウェブ、合成繊維あるいはそのウェブ等と組み合わせることにより、例えば衛生材料の吸水層として好適な吸水性物品とすることができる。例えば、セルロース繊維あるいは合成繊維からなる紙、不織布やマットに該吸水性材料を挟持する方法、セルロース繊維と該吸水性材料を短冊状としたものとをブレンドする方法等、吸水性物品を得るための公知の手段を適宜選択できる。なかでも本発明の吸水性材料を少なくとも片面側を透水性シートによって形成した袋体の内部に収納した吸水性物品は、従来の吸水性物品に比べ薄くコンパクトであるにもかかわらず、従来と同等以上の吸水性能を示す。
【００４９】
本発明の吸水性材料および積層吸水性材料は、大きい吸収速度を有する柔軟度の大きいシート状吸水性材料であるので、ゲルブロッキングを防止するために従来の吸水性樹脂粒子のように繊維状マトリックス中に比較的低い濃度で組み込む必要がなく、吸水性物品中に比較的高い濃度で組み込むことができる。特に、本発明の吸水性物品は、吸水性物品の全重量に対し約５０〜８５重量％の（実質的に乾燥した）吸水性樹脂含有量である。好ましくは約６０〜８５重量％、より好ましくは約７０〜８５重量％である。このような高い樹脂濃度の吸水性物品を作成しても、本発明の吸水性材料は柔軟なシート状であるので、吸水性物品の製造工程、包装工程および輸送工程で、吸水性物品内での吸水性樹脂の移動および吸水性樹脂のこぼれがなく、しかも吸水性物品の風合いを損なうことがない。
【００５０】
本発明の吸水性物品は、前記のように吸水性樹脂含有量を高くできるため、従来の吸水性物品と同等以上の吸水性能を有しながら、薄くコンパクトである。また柔軟性が高いため体によくフィットし、使い勝手がよい。
【００５１】
本発明の吸水性物品は、尿、経血および血液のような体液をはじめとする多くの流体を吸収するのに好適であり、おむつ、失禁用品、ベッドパッドのような製品、生理用ナプキン、タンポンのような生理用品およびタオル、包帯のような製品に適用可能である。
【００５２】
【発明の効果】
本発明の吸水性材料は、不純物を含有しないために安全性が高く、しなやかで強靱な風合い、良好なる吸水性を有しており、吸水ないし吸湿を目的とする種々の用途に用いることができる。例えば、衛生材料の吸水層、結露吸水シート、農業用保水シート、土木用止水剤、メディカルシーツ、食品用鮮度保持剤、雑貨用吸水剤等の用途が挙げられる。また、本発明の吸水性材料の製造方法により、上記の吸水性材料を極めて容易にかつ安価に製造することができる。本発明の吸水性物品は、吸水性樹脂含有量を高くできるため、従来の吸水性物品と同等以上の吸水性能を有しながら、薄くコンパクトである。また柔軟性が高いため体によくフィットし、使い勝手がよい。
【００５３】
【実施例】
以下、実施例により本発明をさらに説明するが、本発明はこれに限定されるものではない。
【００５４】
（参考例１）吸水性樹脂粒子（Ａ）の合成例
内容積１０リットル、シグマ型羽根を２本有するジャケット付きステンレス製ニーダーに、アクリル酸ナトリウム７５モル％とアクリル酸２５モル％とからなる単量体の水溶液５５００ｇ（単量体濃度３８％）と、架橋剤としてのトリメチロールプロパントリアクリレート３．５ｇ（対単量体０．０５モル％）とを投入し、窒素ガスを吹き込み反応系内を窒素置換した。ジャケットに３５℃の温水を通じて加温し、シグマ型羽根を４０ｒｐｍで回転撹拌させながら、重合開始剤として過硫酸ナトリウム２．８ｇとｌ−アスコルビン酸０．１ｇを添加し、重合を開始させた。重合反応は１時間行った。反応終了後、細分化された含水ゲル状重合体を目開き０．３ｍｍの金網上に広げ、１６０℃で１時間乾燥した。得られた乾燥物（ｐｐＡ）をハンマーミルを用いて粉砕し、８５０μｍを通過する吸水性樹脂粒子（Ａ）を得た。吸水性樹脂粒子（Ａ）のうち１５０μｍを通過するものの割合は２１重量％であった。
【００５５】
（実施例１）
１４０×１００ｍｍの型枠に１０ｇの吸水性樹脂粒子（Ａ）を均一に広げ、このものを４５℃、相対湿度８０％の恒温恒湿器に放置した。１２０分後に厚みが約１．３ｍｍの吸水性材料（１）が得られた。重量測定により、３．８ｇの水分が吸水性樹脂粒子（Ａ）に与えられたことがわかった。得られた吸水性材料を下記の方法で評価し、得られた結果を表１に示した。
【００５６】
Ａ：引張降伏強さおよび引張降伏伸び
ＪＩＳＫ７１２７に準じて測定を行った。
【００５７】
試験装置インストロンモデル４３０１型
試験片５号形
試験速度２００ｍｍ／ｍｉｎ．
Ｂ：吸水倍率
吸水性材料を吸水性樹脂粒子換算で０．５ｇ精秤し、不織布製のティ−バッグ式袋に入れ、０．９重量％食塩水に浸漬し、６０分後の重量を測定し、下記の数式１に従って吸水倍率を求めた。
【００５８】
【数１】

【００５９】
Ｃ：膨潤速度
１００ｍｌビ−カ−に０．９重量％食塩水５０ｍｌとスタ−ラ−チップを入れ、６００ｒｐｍで攪拌した。吸水性材料を約１ｃｍ角に切り、吸水性樹脂粒子換算で２．０ｇをビ−カ−内へ瞬時に投入し、ストップウォッチをスタ−トさせた。食塩水の流れの中心部で露出しているスタ−ラ−チップが膨潤したゲルで隠れた時点でストップウォッチを止め、得られた時間を膨潤速度とした。この時間の短いものほど膨潤速度が大きい。
【００６０】
Ｄ：水分量
吸水性材料１．０ｇを精秤し、アルミニウムカップ（Ｗ_１ｇ）に入れた。このものを１８０℃に調整された乾燥器に入れ、３時間放置した。乾燥器から取り出した吸水性材料の入ったアルミニウムカップをデシケーター中で放冷後、重量（Ｗ_２ｇ）を測定した。下記の数式２に従って実質的に乾燥した吸水性樹脂粒子１００重量部当たりの水分量を求めた。
【００６１】
【数２】

【００６２】
Ｅ：吸水性樹脂粒子の粒度分布
ＪＩＳ標準フルイの網目が１６メッシュ、１８．５メッシュ、３０メッシュ、５０メッシュ、１００メッシュおよび受け皿の分級皿を重ね、その上に約３０ｇの吸水性樹脂粒子をいれ、フルイ振とう器で１０分間振とうさせた。その後、それぞれのフルイ上の分級物の重量を秤量し、仕込み吸水性樹脂粒子重量に対する重量％で表示した。
【００６３】
Ｆ：吸水性樹脂粒子の加重下の吸収倍率
第１図に示す装置を用いて加重下の吸収倍率を測定する。ビュレット１の上口２に栓３をし、測定台４と空気口５を等高位にセットする。測定台４の中央部にある直径７０ｍｍのガラスフィルター６上にろ紙７を載せる。一方、直径５５ｍｍの支持円筒１０の下端部に不織布８を固定させ、不織布８上に吸水性樹脂粒子０．２ｇを均一に散布し、さらに２０ｇ／ｃｍ^２の加重９を載せる。この不織布８−吸水性樹脂粒子−加重９を支持円筒１０ごとガラスフィルター６上のろ紙７上に載せ、３０分間にわたって吸収した０．９％食塩水の量（Ａｍｌ）を測定し、下記の数式３に従って加重下の吸収倍率を求めた。
【００６４】
【数３】

【００６５】
（実施例２）
実施例１と同様の型枠に１０ｇの吸水性樹脂粒子（Ａ）を均一に広げ、スプレーをもちいた噴霧によって６．２ｇの水を与えた。型枠全体をポリエチレン製の袋で密封し、４５℃で放置した。１８０分後に袋から取り出すと厚みが約１．４ｍｍの吸水性材料（２）が得られた。得られた吸水性材料（２）を実施例１と同様の方法で評価し、得られた結果を表１に示した。
【００６６】
（実施例３）
実施例１と同様の操作を行い、６５分後に厚みが約１．２ｍｍの吸水性材料（３）が得られた。重量測定により２．０ｇの水分が吸水性樹脂粒子（Ａ）に与えられたことがわかった。得られた吸水性材料（３）を実施例１と同様の方法で評価し、得られた結果を表１に示した。
【００６７】
（比較例１）
実施例１と同様の操作を行い、０．５ｇの水分を吸水性樹脂粒子（Ａ）に与えた。得られたものは非常に硬くてもろく、シートとして取り扱うことが困難であった。
【００６８】
（比較例２）
実施例２と同様の操作を行い、４７ｇの水分を吸水性樹脂粒子（Ａ）に与えた。得られたものは非常に柔らかくてもろく、シートとして取り扱うことが困難であった。
【００６９】
（比較例３）
実施例１と同様の型枠に６７ｇの吸水性樹脂粒子（Ａ）を均一に広げ、スプレーをもちいた噴霧によって２２ｇの水を与えた。型枠全体をポリエチレン製の袋で密封し、４５℃で１６時間放置した。袋から取り出すと厚みが約８ｍｍの不均質な比較吸水性材料（３ａ）が得られた。得られた比較吸水性材料（３ａ）を実施例１と同様の方法で評価し、得られた結果を表１に示した。
【００７０】
（比較例４）
吸水性樹脂粒子（Ａ）１０ｇをミキサーに入れて撹拌しながら、水３．８ｇを滴下投入した。すぐに塊状の、吸水性樹脂と水からなる組成物が得られた。このものは強い弾性を有しており、引きちぎって小粒塊にすることはできたが、均一なシート状に成型することは困難であった。
【００７１】
（比較例５）
実施例１において、１．４ｇの吸水性樹脂粒子（Ａ）（坪量１００ｇ／ｍ^２に相当）を用いる以外は実施例１と同様の操作を繰り返した。部分的に粒子同士が集まった造粒物が見られたが、一体のシートとしての取扱いは不可能であった。（実施例４）
吸水性樹脂粒子（Ａ）を１５０μｍで分級し、１５０μｍを通過する吸水性樹脂粒子（Ｂ）を得た。吸水性樹脂粒子（Ｂ）を用いる以外は実施例１と同様の操作を行い、３．８ｇの水分を吸水性樹脂粒子（Ｂ）に与えた。厚みが約１．３ｍｍの吸水性材料（４）が得られた。得られた吸水性材料（４）を実施例１と同様の方法で評価し、得られた結果を表１に示した。
【００７２】
（参考例２）吸水性樹脂粒子（Ｃ）の合成例
参考例１と同様のニーダーにアクリル酸１１００ｇ、２重量％酸化デンプン水溶液２５００ｇ、水１８５０ｇおよび架橋剤としてのＮ，Ｎ´−メチレンビスアクリルアミド２．７ｇ（対単量体０．１１モル％）を投入し、窒素ガスを吹き込み反応系内を窒素置換した。ジャケットに８℃の水を通じ、シグマ型羽根を４０ｒｐｍで回転撹拌させながら、重合開始剤として２，２´−アゾビスアミジノプロパン二塩酸塩３．３ｇ、Ｌ−アスコルビン酸０．３ｇおよび３５重量％過酸化水素水３．１ｇを添加し、重合を開始させた。重合開始後、シグマ型羽根の回転を止め、重合反応を３時間行った。反応終了後、シグマ型羽根を４０ｒｐｍで回転し、生成した含水ゲル状重合体を細分化した。次いで４８重量％水酸化ナトリウム水溶液９５０ｇを投入し、更に回転撹拌を続けた。中和熱により発熱し８６℃になった含水ゲル状重合体に後架橋剤として３．３ｇのエチレングリコールジグリシジルエーテルおよび水７０ｇから成る水溶液を投入し、回転撹拌を続けた。得られた含水ゲル状重合体を目開き０．３ｍｍの金網上に広げ、１２０℃で３時間乾燥した。得られた乾燥物（ｐｐＣ）をハンマーミルを用いて粉砕し、８５０μｍを通過する吸水性樹脂粒子（Ｃ）を得た。吸水性樹脂粒子（Ｃ）のうち１５０μｍを通過するものの割合は２５重量％であった。
【００７３】
（実施例５）
吸水性樹脂粒子（Ｃ）を用いる以外は実施例１と同様の操作を行い、３．６ｇの水分を吸水性樹脂粒子（Ｃ）に与えた。厚みが約１．３ｍｍの吸水性材料（５）が得られた。得られた吸水性材料（５）を実施例１と同様の方法で評価し、得られた結果を表１に示した。
【００７４】
（実施例６）
実施例１において、型枠にかえて１４０×１００ｍｍの紙（Ａ）（目付け１５ｇ／ｍ^２）の上に吸水性樹脂粒子を広げる以外は実施例１と同様の操作を繰り返した。厚みが約１．３ｍｍの吸水性材料（１）と紙（Ａ）とが一体化したシート状物が得られた。得られたシート状物の吸水性材料（１）側に、紙（Ａ）と同じ紙（Ａ）を載せ、手で軽く押さえた。吸水性材料（１）が２枚の紙（Ａ）に挟持された積層吸水性材料が得られた。
【００７５】
【表１】

【００７６】
（参考例３）吸水性樹脂粒子（Ｄ）の合成例
参考例１で得られた吸水性樹脂粒子（Ａ）の加重下吸収倍率は１６ｍｌ／ｇであった。吸水性樹脂粒子（Ａ）１００重量部を、グリセリン０．５重量部、水３重量部およびイソプロパノール２重量部からなる水性混合物と混合した。得られた混合物を、オイルバス（１９５℃）に漬けられたボウルに投入し、撹拌下で４０分間熱処理し、８５０μｍを通過する吸水性樹脂粒子（Ｄ）を得た。吸水性樹脂粒子（Ｄ）のうち１５０μｍを通過するものの割合は１３重量％であった。また吸水性樹脂粒子（Ｄ）の加重下吸収倍率は２６ｍｌ／ｇであった。
【００７７】
（実施例７）
１５０×２００ｍｍの型枠に１５ｇの吸水性樹脂粒子（Ａ）を均一に広げた。この時、吸水性樹脂粒子（Ａ）は約０．７ｍｍの厚みで平面状に流展された状態であった。このものを４５℃、相対湿度８０％の恒温恒湿器に放置した。１２０分後にシート状の吸水性材料（７）が得られた。５．７ｇの水分が吸水性樹脂粒子（Ａ）に与えられた。得られた吸水性材料（７）を実施例１と同様の方法および下記の方法で評価し、得られた結果を表２に示した。
【００７８】
Ｇ：吸水速度
吸水性材料を４５×４５ｍｍの正方形にカットし、このものを水平な台上においた底面６ｃｍ径の円筒形の容器に入れ、上から２２℃の人工尿２０ｇをいっきに投入した。同時にストップウォッチをスタートさせた。人工尿の組成は、
ＫＣｌ２．０ｇ／ｌ；
Ｎａ_２ＳＯ_４２．０ｇ／ｌ；
（ＮＨ_４）Ｈ_２ＰＯ_４０．８５ｇ／ｌ；
（ＮＨ_４）_２ＨＰＯ_４０．１５ｇ／ｌ；
ＣａＣｌ_２０．１９ｇ／ｌ；
ＭｇＣｌ_２０．２３ｇ／ｌ
である。人工尿が吸水性材料に完全に吸収された時点でストップウォッチを止め、得られた時間を吸水速度とした。この時間の短いものほど吸水速度が大きい。
【００７９】
Ｈ：柔軟度
少なくとも２ｃｍの幅を有する吸水性材料を水平に置き、該吸水性材料の面積を概略２等分する直線を中心にして吸水性材料の半分を平面を保ちながらゆっくり回転させた。その際、吸水性材料に実質的な亀裂が入る時点の、回転を開始した水平面からの角度を柔軟度とした。この角度が大きいほど柔軟度が大きい。
【００８０】
（実施例８）
１５０×２００ｍｍの型枠に１５ｇの吸水性樹脂粒子（Ｄ）を均一に広げた。この時、吸水性樹脂粒子（Ｄ）は約０．７ｍｍの厚みで平面状に流展された状態であった。このものを４５℃、相対湿度８０％の恒温恒湿器に放置した。１５０分後にシート状の吸水性材料（８）が得られた。６．１ｇの水分が吸水性樹脂粒子（Ｄ）に与えられた。得られた吸水性材料（８）を実施例７と同様の方法で評価し、得られた結果を表２に示した。
【００８１】
（実施例９）
吸水性樹脂粒子（Ｄ）１５ｇと水不溶性の微粒子状シリカ（アエロジル２００、日本アエロジル株式会社製）０．１５ｇとを混合し、得られた混合物を１５０×２００ｍｍの型枠に均一に広げた。この時、吸水性樹脂粒子（Ｄ）および微粒子状シリカの混合物は約０．７ｍｍの厚みで平面状に流展された状態であった。このものを４５℃、相対湿度８０％の恒温恒湿器に放置した。１５０分後にシート状の吸水性材料（９）が得られた。６．２ｇの水分が吸水性樹脂粒子（Ｄ）に与えられた。得られた吸水性材料（９）を実施例７と同様の方法で評価し、得られた結果を表２に示した。
【００８２】
（参考例５）吸水性樹脂粒子（Ｅ）の合成例
５００ｍｌの円筒形セパラブルフラスコに、２−スルホエチルメタクリレートのナトリウム塩８．６ｇ、７５モル％がナトリウム塩により中和されたアクリル酸３５．４ｇと、架橋剤としてのトリメチロールプロパントリアクリレート０．０７７ｇ（対単量体０．０６モル％）および水６９ｇからなる単量体水溶液を仕込んだ。撹拌下に反応系内の窒素置換を行い、単量体水溶液の温度を３０℃にした。次いで１０％過硫酸ナトリウム水溶液０．５ｇおよび０．５％ｌ−アスコルビン酸水溶液０．４ｇを添加し、撹拌を停止して重合を開始させた。重合開始後１５分で系内温度は７０℃に上昇した。系内温度が下がり始めたのを確認した後、重合系を外部加熱し、７５℃で１時間保持した。得られた含水ゲル状重合体を細分化し、１５０℃で９０分間乾燥した。得られた乾燥物（ｐｐＥ）をハンマーミルで粉砕し、３００μｍを通過する吸水性樹脂粒子（ｐＥ）を得た。吸水性樹脂粒子（ｐＥ）１００重量部を、グリセリン１重量部、水１重量部およびイソプロパノール２重量部からなる水性混合物と混合した。得られた混合物を、オイルバス（１９５℃）に漬けられたボウルに投入し、撹拌下で３０分間熱処理し、３００μｍを通過する吸水性樹脂粒子（Ｅ）を得た。吸水性樹脂粒子（Ｅ）のうち１５０μｍを通過するものの割合は２７重量％であった。また吸水性樹脂粒子（Ｅ）の加重下吸収倍率は２４ｍｌ／ｇであった。
【００８３】
（実施例１０）
吸水性樹脂粒子（Ｅ）１５ｇを１５０×２００ｍｍの型枠に均一に広げた。この時、吸水性樹脂粒子（Ｅ）は約０．７ｍｍの厚みで平面状に流展された状態であった。このものに霧吹きによって５．９ｇの水分を与え、シート状の吸水性材料（１０）が得られた。得られた吸水性材料（１０）を実施例７と同様の方法で評価し、得られた結果を表２に示した。
【００８４】
（実施例１１）
吸水性樹脂粒子（Ｅ）１５ｇと水不溶性の微粒子状シリカ（アエロジル２００、日本アエロジル株式会社製）０．１５ｇとを混合し、得られた混合物を１５０×２００ｍｍの型枠に均一に広げた。この時、吸水性樹脂粒子（Ｅ）および微粒子状シリカの混合物は約０．７ｍｍの厚みで平面状に流展された状態であった。このものに霧吹きによって６．２ｇの水分を与え、シート状の吸水性材料（１１）が得られた。得られた吸水性材料（１１）を実施例７と同様の方法で評価し、得られた結果を表２に示した。
【００８５】
（実施例１２）
参考例５で得られた吸水性樹脂粒子（Ｅ）を１５０μｍで分級し、３００μｍから１５０μｍの吸水性樹脂粒子（Ｆ）を得た。吸水性樹脂粒子（Ｆ）の加重下吸収倍率は２８ｍｌ／ｇであった。吸水性樹脂粒子（Ｆ）を用いること以外は実施例１０と同様の操作を繰り返し、シート状の吸水性材料（１２）が得られた。得られた吸水性材料（１２）を実施例７と同様の方法で評価し、得られた結果を表２に示した。
【００８６】
（比較例６）
実施例８と同様の操作を繰り返し、吸水性樹脂粒子（Ｄ）を均一に広げた型枠を４５℃、相対湿度８０％の恒温恒湿器に放置した。恒温恒湿器に入れて１００分後に型枠を取り出し、湿った吸水性樹脂粒子（Ｄ）の上を金属製のへらでこすった。その後さらに５０分間恒温恒湿器に放置し、取り出した吸水性樹脂粒子（Ｄ）の上を再び金属製のへらでこすった。６ｇの水分が吸水性樹脂粒子（Ｄ）に与えられた。得られた比較吸水性材料（６ｃ）を実施例７と同様の方法で評価し、得られた結果を表２に示した。
【００８７】
（比較例７）
吸水性樹脂粒子（Ｅ）１５ｇをミキサ−に入れて撹拌しながら、水６ｇを滴下投入した。すぐに塊状の、吸水性樹脂と水からなる組成物が得られた。このものは強い弾性を有しており、引きちぎって小粒塊にすることはできたが、均一なシ−ト状に成型することは困難であった。
【００８８】
（比較例８）
実施例８において、０．８ｇの水分を吸水性樹脂粒子（Ｄ）に与えた以外は実施例８と同様の操作を繰り返した。造粒された粒子が一部みられたが、粒子状のままでシートを形成しなかった。
【００８９】
（比較例９）
実施例９において、吸水性樹脂粒子（Ｄ）４．２ｇと水不溶性の微粒子状シリカ（アエロジル２００、日本アエロジル株式会社製）０．０４ｇとを混合し、得られた混合物を１５０×２００ｍｍの型枠に均一に広げた以外は実施例９と同様の操作を繰り返した。このものを４５℃、相対湿度８０％の恒温恒湿器に放置し、１．７ｇの水分が吸水性樹脂粒子（Ｄ）に与えられた。造粒された粒子が一部みられたが、粒子状のままでシートを形成しなかった。
【００９０】
（実施例１３）
実施例９において、水不溶性の微粒子状シリカ（アエロジル２００、日本アエロジル株式会社製）０．１５ｇにかえて、ＫＣフロックＷ−３００（セルロースパウダー、山陽国策パルプ株式会社製）０．７５ｇを用いること以外は実施例９と同様の操作を繰り返した。６．２ｇの水分が吸水性樹脂粒子（Ｄ）に与えられた。得られた吸水性材料（１３）を実施例７と同様の方法で評価し、得られた結果を表２に示した。
【００９１】
【表２】

【００９２】
（実施例１４）
実施例７において、型枠にかえて１５０×３００ｍｍのヒートロンペーパーＧＳ２２（南国パルプ工業株式会社製）を水平な台上に広げ、その上に実施例７の操作を繰り返し、約０．５ｍｍの厚みの吸水性材料がヒートロンペーパーＧＳ２２に載った積層シートを作成した。一方、市販の使い捨ておむつピンポンパンツＬサイズ（株式会社資生堂製）のポリエチレンフィルムからなる防水材シートの中央を縦方向に切断し、吸水性樹脂、綿状パルプおよび吸水紙からなる吸収体を取り除いた。この様にして得られた使い捨ておむつのシャシーに、前述の積層シートを吸水性材料がシャシーの表面材（ポリプロピレン不織布）側にくるように組み込み、防水材シートの切れ目を粘着テープで塞いだ。得られた吸水性物品（１）を下記の方法で評価し、結果を表３に示した。
【００９３】
Ｉ：吸水性物品の評価方法
体重１０ｋｇの幼児をもとにした、排尿管を備えたベビーモデルを作成した。実施例１３で作成した吸水性物品（１）を上記ベビーモデルに装着し、人工尿を５０ｍｌ／１０ｓｅｃの速度で排出させた。５０分後に同様の排尿操作を行い、人工尿が吸水性物品から漏れ出るまでに吸収された人工尿の量により尿漏れを評価した。
【００９４】
（実施例１５〜１９）
実施例１４において、吸水性材料の作成は実施例８〜１２操作を繰り返す以外は、実施例１４と同様の操作を行い、吸水性材料がヒートロンペーパーＧＳ２２に載った積層シートをそれぞれ作成した。以後実施例１４の操作を繰り返して、吸水性物品（２〜６）を得た。得られた吸水性物品（２〜６）を実施例１４と同様の方法で評価し、結果を表３に示した。
【００９５】
（比較例１０）
実施例１４において、吸水性材料の作成を比較例８の操作を繰り返す以外は、実施例１４と同様の操作を行い、吸水性樹脂粒子（Ｄ）が載ったシートを作成した。吸水性樹脂粒子（Ｄ）は、ほとんど固定化されておらず非常に取扱い難いものであったが、以後実施例１４の操作を繰り返して、比較吸水性物品（１ｃ）を得た。得られた比較吸水性物品（１ｃ）を実施例１４と同様の方法で評価し、結果を表３に示した。比較吸水性物品（１ｃ）内で吸水性樹脂粒子の移動、偏りがみられた。
【００９６】
【表３】

【図面の簡単な説明】
【図１】本発明において使用した加重下の吸収倍率測定装置の断面図である。
（符号の説明）
１・・・ビュレット
２・・・ビュレットの上端部
３・・・栓
４・・・測定台
５・・・空気取り入れ口
６・・・ガラスフィルター
７・・・ろ紙
８・・・不織布
９・・・加重
１０・・・支持円筒[0001]
[Industrial applications]
The present invention relates to a novel water absorbent material and a water absorbent article. More specifically, a flexible sheet-like water-absorbing material having a supple texture, good water absorption, and a flexible sheet-like water-absorbing material having a high water absorption rate and excellent flexibility, The present invention relates to a water-absorbing material comprising resin particles and water, which can be cut into any size or shape, and a water-absorbing article containing the water-absorbing material.
[0002]
[Prior art]
As the water-absorbing resin, a crosslinked product of partially neutralized polyacrylic acid, a saponified acrylate-vinyl acetate copolymer, a crosslinked polyvinyl alcohol modified product, a crosslinked isobutylene-maleic anhydride copolymer, a starch-acrylonitrile graft polymer Hydrolysates, starch-acrylic acid graft polymers, partially crosslinked polyethylene oxide and the like are known, and the water-absorbing resin is used for sanitary napkins, absorbents for sanitary materials such as disposable diapers, or agricultural and horticultural fields. It is applied to a wide range of uses such as water retention agents and dehydrating agents in the field of civil engineering.
[0003]
The water-absorbing resin used is generally in the form of powder and particles, and in many cases of actual use, sandwiching with paper, pressure bonding such as embossing by mixing with pulp, or sealing with thermoplastic resin, etc. It is used after being compounded and changed into a sheet or film shape.
[0004]
Conventionally, various proposals have been made for applying a water-absorbing resin to a base material, performing a fixing treatment, and using the resultant in the form of a sheet. The method can be broadly classified into a method in which a water-absorbent resin is produced and then formed into a sheet, and a method in which the production and sheeting of the water-absorbent resin are simultaneously performed. The former method includes a method (a) in which a water-absorbent resin powder is applied to a sheet-like substrate to perform a fixing treatment, and a method (b) in which a fibrous water-absorbent resin is formed into a sheet. In the method (b), obtaining a fibrous water-absorbent resin itself is expensive, and the resulting water-absorbent sheet has a low water-absorbing ability and is not very common. As the fixing treatment in the method (a), a method in which a water-absorbent resin powder is sprayed on a base sheet, another sheet is stacked on the base sheet and embossed, and the base sheet and the water-absorbent resin powder are mixed and embossed. Application method, a method of giving a small amount of water to the water-absorbent resin powder to achieve strong fixation with the base sheet (for example, US Pat. No. 3,959,569, JP-A-51-40497, JP-A-54-123293, JP-A-54-141099 and JP-A-58-36452), or a method for realizing fixation of a water-absorbent resin powder to a substrate sheet by using a resin binder (for example, JP-A-58-11047, JP-A-4-504234, U.S. Pat. No. 5,128,082). Japanese Patent Application Laid-Open No. Hei 1-230671 proposes a method for immobilizing a water-absorbing resin in which a hydrate is formed by combining an aqueous liquid with the water-absorbing resin. However, these methods for obtaining a water-absorbent sheet have some problems. For example, in order to maintain the sheet state, the base material is essential, the complexing process of the base material and the water-absorbent resin powder is complicated, or the working environment such as dust is bad, or the obtained sheet Insufficient strength or flexibility. Further, since the amount of the water-absorbing resin per unit area cannot be increased, the amount of water absorption was small, and the water absorption rate was low. When the amount of the water-absorbing resin per unit area was increased, the sheet became hard or the water-absorbing resin powder spilled out of the sheet.
[0005]
On the other hand, there have been proposed several methods for simultaneously producing a water-absorbent resin and forming a sheet by directly polymerizing a monomer on a base sheet (for example, JP-A-60-149609, JP-A-62). No. 53309, JP-A-62-62829 and JP-A-62-79779). However, each of these methods has the following disadvantages. That is, there is a high possibility that the polymerization initiator and other additives used in the polymerization and a relatively large number of monomers remain. If the safety of these substances is concerned, it becomes a problem when using the products for sanitary use or food use. In addition, it was difficult to control the reaction and the productivity was low. Furthermore, the water absorption performance or flexibility of the obtained sheet was insufficient.
[0006]
There are known water-absorbing articles to be incorporated into sanitary products such as diapers, incontinence pads, sanitary articles (for example, US Pat. No. 4,699,619, US Pat. No. 4,798,603 and US Pat. No. 4,834,735). Consists of The fibrous matrix is composed of cellulose fibers, known as wood pulp fluff, or cellulose fibers and synthetic fibers.
[0007]
Among conventional water-absorbent articles, those that do not use a water-absorbent resin necessarily have a large volume and are extremely inconvenient to handle. That is, the water absorption of wood pulp fluff per unit weight is relatively small (about 7 to 9 g / g), and it is necessary to use a relatively large amount of wood pulp fluff to achieve a predetermined water absorption. A relatively large and thick water-absorbent article was obtained. On the other hand, the water-absorbent resin has a considerably large water absorption (at least 15 g / g), and it is possible to reduce the amount of wood pulp fluff used by introducing the water-absorbent resin into the water-absorbent article. became. By using a water-absorbing resin, a small and thin water-absorbing article can be manufactured. However, conventional water-absorbent articles still consist of relatively low amounts of water-absorbent resin (generally less than about 50% by weight), and cannot be said to provide sufficiently small and thin water-absorbent articles. Considering the amount of water absorption per unit weight, a compact and thin water-absorbent article should be obtained by increasing the amount of water-absorbing resin. EP 443627 proposes a water-absorbent article with a large amount of water-absorbent resin.
[0008]
However, if a conventionally known water-absorbing resin is used to produce a water-absorbing article with a higher resin content, various problems will occur. One problem is the gel blocking phenomenon. In general, the water-absorbent resin deforms when it swells by absorbing water, and closes the space between the water-absorbent resin particles and between the water-absorbent resin particles and the fibrous matrix, and as a result, the fluid flowing through the space It blocks the flow. When the amount of the water-absorbent resin is small, the fibrous matrix can reduce the approach between the water-absorbent resin particles and maintain a capillary structure sufficient for the fluid to flow through the matrix. Another problem is insufficient water absorption speed of the water absorbent resin. Generally, the water absorption rate of the water-absorbent resin is smaller than that of the wood pulp fluff, and cannot correspond to the speed of the fluid applied to the water-absorbent article during actual use. Therefore, at present, a fibrous matrix such as wood pulp fluff functions as a primary storage layer of a fluid applied to a water absorbent article.
[0009]
EP 443627 proposes a water-absorbent article in which the amount of water-absorbent resin is increased by using a water-absorbent resin having an increased water-absorbing speed. However, when there is little or no fibrous matrix that has been used to fix the particulate water-absorbing resin as proposed in EP 443627, the movement of the water-absorbing resin in the water-absorbing article can be reduced. It is expected that a bias problem will occur. Until the water-absorbing resin fulfills its role of liquid absorption and swelling, a new device for fixing the resin in a predetermined position is required. Furthermore, when the water-absorbent resin is used as a dry powder, it is very difficult to handle because it is so fine that there are many leaks and scattering in the air. This greatly hinders stable operation in mechanical mass production.
[0010]
There has been a long-awaited need for a compact and thin water-absorbing article and a water-absorbing material that has a high water absorption rate for obtaining the article and is flexible and can be fixed at a desired position on the water-absorbing article.
[0011]
[Problems to be solved by the invention]
The present invention improves the drawbacks of the above-mentioned conventional water-absorbent resin or water-absorbent article and the method for producing the same, and is flexible, has good water absorption (water absorption rate and water absorption), and has an arbitrary size. Another object of the present invention is to provide a water-absorbing material which can be cut into a shape and has high safety. Another object of the present invention is to provide a simple and high-productivity production method for obtaining the water-absorbing material, which can easily control product performance. It is another object of the present invention to provide a compact and thin water-absorbent article using the water-absorbent material.
[0012]
[Means for Solving the Problems]
The present inventors have focused on the characteristics of the water-absorbent resin and conducted repeated studies.As a result, they have found that the following water-absorbent material and water-absorbent article achieve the above objects, and have completed the present invention. Was.
[0013]
That is, the object is a water-absorbing material in which 15 to 150 parts by weight of water is blended with respect to 100 parts by weight of the water-absorbing resin particles, and the water-absorbing material has a thickness of about 0.3 to 5 mm in a sheet state. The sheet state is achieved by the water-absorbing material, which is caused by the adhesion between the water-absorbing resin particles.
[0014]
The object is to provide 15 to 150 parts by weight of water with respect to 100 parts by weight of the water-absorbing resin particles, and at least one water-absorbing aid selected from the group consisting of water-insoluble fine particles, surfactants and fibers. A water-absorbing material in which parts by weight are blended, wherein the water-absorbing material is in a sheet state having a thickness of about 0.3 to 5 mm, and the sheet state is caused by the adhesion between the water-absorbing resin particles. This is also achieved by a water-absorbing material characterized by the following.
[0015]
The above object is also achieved by a water-absorbent article characterized in that the above-described water-absorbent material is housed inside a bag formed on at least one side by a water-permeable sheet.
[0016]
The object is to spread 100 parts by weight of the water-absorbent resin particles on the support in a planar state with the thickness regulated to about 0.3 to 5 mm, and to maintain the planar state with water and / or steam 15 to 15 parts by weight. It is also achieved by a method for producing a water-absorbing material, characterized by adding and contacting 150 parts by weight.
[0017]
The object is to provide a support comprising 100 parts by weight of water-absorbent resin particles and 0.1 to 10 parts by weight of a water-absorbing aid, which is at least one selected from the group consisting of water-insoluble fine particles, surfactants and fibers. A water absorption method characterized in that the thickness is regulated to about 0.3 to 5 mm, and the resultant is flown in a planar state, and while maintaining this planar state, 15 to 150 parts by weight of water and / or steam is added and brought into contact. This is also achieved by a method for producing a conductive material.
[0018]
Hereinafter, the present invention will be described in detail.
[0019]
The water-absorbent resin particles used in the present invention are not particularly limited as long as they are water-absorbent resin particles and absorb water to cause volume expansion, but generally polymerize a water-soluble unsaturated monomer. It is obtained by doing. Examples of these water-soluble unsaturated monomers include (meth) acrylic acid, (anhydride) maleic acid, fumaric acid, crotonic acid, itaconic acid, 2- (meth) acryloylethanesulfonic acid, 2- (meth) Anionic monomers such as acryloylpropanesulfonic acid, 2- (meth) acrylamide-2-methylpropanesulfonic acid, vinylsulfonic acid and styrenesulfonic acid, and salts thereof; (meth) acrylamide, N-substituted (meth) acrylamide Nonionic properties of 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, methoxypolyethylene glycol (meth) acrylate, polyethylene glycol (meth) acrylate, etc. Hydrophilic group-containing monomer; N, N-dimethylaminoethyl (meth) acrylate, N, N-dimethylamine Nopuropiru (meth) acrylate - DOO, N, N-dimethylaminopropyl (meth) acrylamide, specific mention is leaving the amino group-containing unsaturated monomers and their quaternary products etc., and the like. In addition, an amount of an acrylic ester such as methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, or acetic acid in an amount that does not extremely impair the hydrophilicity of the obtained polymer. Hydrophobic monomers such as vinyl and vinyl propionate may be used. One or more of these can be selected and used as the monomer component. However, considering the various water absorbing properties of the finally obtained water absorbing material, (meth) acrylic acid (salt), 2- (meth) acryloylethanesulfonic acid (salt), 2- (meth) acrylamido-2-methylpropanesulfonic acid (salt), (meth) acrylamide, methoxypolyethylene glycol (meth) acrylate, N, N One or more selected from the group consisting of -dimethylaminoethyl (meth) acrylate or a quaternary compound thereof is preferable, and one containing (meth) acrylic acid (salt) as an essential component is more preferable. In this case, it is most preferable that 30 to 90 mol% of the (meth) acrylic acid is neutralized with a basic substance. The water absorption capacity of the water-absorbing resin is preferably about 20 to 60 g / g as measured by a tea bag method in physiological saline. The proportion of the uncrosslinked component, the so-called water-soluble component, is preferably 20% by weight or less, more preferably 10% by weight or less, and the smaller the ratio, the better.
[0020]
The water-absorbing resin used in the present invention may be a self-crosslinking resin obtained without using a crosslinking agent, or a crosslinking agent having a polymerizable unsaturated group and / or a reactive functional group. It may be obtained by using various characteristics in a range that reaches a desired standard.
[0021]
Examples of these crosslinking agents include, for example, N, N'-methylenebis (meth) acrylamide, (poly) ethylene glycol (meth) acrylate, glycerin tri (meth) acrylate, trimethylolpropane tri (meth) Acrylate, triallylamine, triallyl cyanurate, triallyl isocyanurate, glycidyl (meth) acrylate, (poly) ethylene glycol, diethylene glycol, (poly) glycerin, propylene glycol , Diethanolamine, trimethylolpropane, pentaerythritol, (poly) ethyleneglycoldiglycidylether, (poly) glycerolpolyglycidylether, epichlorohydrin, ethylenediamine, polyethyleneimine, (poly) chloride Aluminum, aluminum sulfate, Of calcium, it can be specifically exemplified magnesium sulfate or the like, in consideration of the reactivity of these, can be used either alone or in combination.
[0022]
In order to obtain a water-absorbent resin, the above monomer components are polymerized in the presence of a hydrophilic polymer such as starch, cellulose, polyvinyl alcohol, etc., so that a graft bond or complex is formed simultaneously with the polymerization. You may.
[0023]
In polymerizing these monomer components, water-soluble polymerization initiators such as ammonium persulfate, potassium persulfate, hydrogen peroxide, t-butyl hydroperoxide, 2,2′-azobis-amidinopropane dihydrochloride, etc. What is necessary is just to use an acidic radical polymerization initiator. The polymerization method is not limited at all, and may be, for example, a method such as bulk polymerization, aqueous solution polymerization, or reverse phase suspension polymerization.
[0024]
These water absorbent resins are used alone or in the form of a mixture of two or more.
[0025]
The shape of the water-absorbent resin particles used in the present invention is not particularly limited. It may be in the form of flakes obtained by drying with a drum, or may be in the form of irregular shapes obtained by pulverizing a lump of resin. It may also be a sphere obtained by reverse phase suspension polymerization. Generally, particles obtained by reverse-phase suspension polymerization have a dispersant or a surfactant on the surface, and in the case of such particles, after additional pulverization is added, the particles may be used in the present invention. May be preferred.
[0026]
The water-absorbent resin particles used in the present invention need only be in the form of particles capable of achieving the object of the present invention, and the size is not particularly limited. In order to obtain a water-absorbent material having a high tensile yield strength and a high tensile yield elongation among the water-absorbent materials of the present invention, generally, the smaller the particle size, the higher the strength and elongation. Therefore, the water-absorbent resin particles are substantially free from particles larger than 1000 μm and have a particle size distribution in which particles having a size of 150 μm or less are 20% or more. It is preferable in that the elongation is satisfied in a well-balanced manner, and it is more preferable that particles having a particle size of 850 μm or less are not substantially contained and the particles having a particle size of 150 μm or less have a particle size distribution of 20% or more. On the other hand, in order to obtain a water-absorbing material having a high water absorption rate and a high degree of softness, it is necessary that the particles having a particle size distribution substantially not containing particles larger than 1000 μm and having particles having a particle size of 150 μm or less being 10% or less are used. It is preferable in that the water absorption rate and the flexibility of the conductive material are satisfied in a well-balanced manner, and it is more preferable that the particles have a particle size distribution substantially not containing particles larger than 850 μm, and particles having a size of 150 μm or less being 10% or less. More preferably, the particles have a particle size distribution substantially free of particles larger than 600 μm and 5% or less of particles of 150 μm or less. The present invention also provides a water-absorbing material containing at least one water-absorbing aid selected from the group consisting of water-insoluble fine particles, a surfactant, and a fiber, as a water-absorbing material having an excellent water-absorbing speed. When a water-absorbing aid is contained, a water-absorbing material having a high water-absorbing rate can be obtained even when water-absorbing resin particles having a relatively wide particle size distribution are used. In the case where a water-absorbing aid is contained, it is more preferable to contain particles of 150 μm or less in view of the strength and the water-absorbing speed of the obtained water-absorbing material. Therefore, it is preferable that particles having a particle size larger than 1000 μm are not substantially contained and particles having a size of 150 μm or less have a particle size distribution of 10% or more. When the content of particles having a size of 150 μm or less is small, it may be difficult to produce a sheet-like water-absorbing material. The smaller the average particle size of the water-absorbent resin particles, the higher the water absorption rate tends to be.
[0027]
In the present invention, as the water absorbing material having a high water absorption rate, it is preferable to use a water absorbing resin particle having a large absorption capacity under load. The method for measuring the absorption capacity under load will be described later, but at least 20 g / cm.²Preferably, it absorbs at least 20 ml / g of 0.9% saline under a load of 0.1%. Those that absorb at least 24 ml / g are more preferred, and those that absorb at least 28 ml / g are even more preferred. A water-absorbing material using water-absorbing resin particles whose absorption capacity under this load is larger than a specific value has particularly excellent water absorption speed. Such water-absorbent resin particles having a large absorption capacity under load can be obtained, for example, by subjecting the surface of the water-absorbent resin particles to a cross-linking treatment as described below.
[0028]
In some cases, the water-absorbent resin particles used in the present invention are preferably surface-crosslinked. Water-absorbent resin particles and a cross-linking agent having a group capable of reacting with at least two functional groups of the particles are mixed and reacted to use water-absorbent resin particles having a high crosslink density near the surface of the water-absorbent resin particles. This makes it possible to obtain a water-absorbing material having an excellent water-absorbing speed. For the water-absorbent resin particles, for example, a method using a polyhydric alcohol as a cross-linking agent (JP-A-58-180233, JP-A-61-16903), a polyvalent glycidyl compound, a polyvalent aziridine compound, a polyamine compound, A method using a polyvalent isocyanate compound (JP-A-59-189103), a method using glyoxal (JP-A-52-117393), a method using a polyvalent metal (JP-A-51-136588, JP-A-61-1986) JP-A-257235, JP-A-62-7745), a method using a silane coupling agent (JP-A-61-211305, JP-A-61-252212, JP-A-61-264006), an epoxy compound and a hydroxy compound. A method using a compound (JP-A-2-132103) and a method using an alkylene carbonate (DE-4020780) By performing the surface cross-linking known, it is possible to obtain a water-absorbent resin particles surface crosslinked. Also, a method in which an inert inorganic powder is present during the crosslinking reaction (JP-A-60-163956, JP-A-60-255814), a method in which a dihydric alcohol is present (JP-A-1-292004), water and ether A method in which a compound is present (JP-A-2-153903) is also known.
[0029]
The water content of the water-absorbent resin particles used in the present invention is not particularly limited as long as the water-absorbent resin can be handled as particles. After 15 to 150 parts by weight of water and / or steam are added to and contacted with 100 parts by weight of the water-absorbent resin particles, the obtained water-absorbent material is substantially dried with respect to 100 parts by weight of the water-absorbent resin. It is sufficient if it is composed of 15 to 150 parts by weight of water. It is preferable in terms of workability to use water-absorbent resin particles having a water content of preferably 0 to 40%, more preferably 0 to 30%.
[0030]
The water-absorbing material of the present invention is formed by mixing 15 to 150 parts by weight of water with respect to 100 parts by weight of the water-absorbing resin particles, and is in a sheet state due to the adhesion between the water-absorbing resin particles. It is. If the amount of water exceeds 150 parts by weight, the content of the water-absorbing resin in the water-absorbing material will be low, and the water-absorbing amount of the obtained water-absorbing material will be low, and the strength of the water-absorbing material will be weak. On the other hand, if the amount of water is less than 15 parts by weight, a water-absorbing material having sufficient strength or desired water absorption rate and flexibility cannot be obtained. A more preferred amount of water is in the range of 25 to 100 parts by weight, most preferably in the range of 30 to 80 parts by weight, per 100 parts by weight of the water absorbent resin particles. Surprisingly, the water absorption rate is remarkably improved by using the sheet-shaped water-absorbing material of the present invention as compared with the state of the discrete water-absorbing resin particles.
[0031]
The sheet state referred to in the present invention may be a sheet having at least a part of a continuous surface, for example, a sheet having one or a plurality of through holes of an arbitrary shape. It may be waved or pleated. Preferably one side (front or back) is 5 cm²Above, more preferably 10 cm²Above, more preferably 15 cm²It has the above area. Furthermore, the water-absorbing material of the present invention is a material that exhibits a sheet state due to the adhesion between the water-absorbing resin particles. That is, for example, instead of being in a continuous sheet state via a third substance such as an adhesive or a fibrous base material, a continuous sheet state is formed by directly adhering water-absorbing resin particles to each other. It is forming. Here, the adhesion between the water-absorbent resin particles is an adhesion formed by applying water to a place where a plurality of water-absorbent resin particles are in contact, and is covalently bonded between the original water-absorbent resin particles. And no such chemical bond has occurred. This can be inferred from the fact that when the water-absorbing material of the present invention absorbs liquid and swells, it returns to discrete water-absorbing resin particles.
[0032]
The water-absorbing material of the present invention is a sheet having a thickness of 0.3 to 5 mm. When the thickness is less than 0.3 mm, the strength of the sheet is reduced and the handleability is deteriorated. In addition, the amount of the water-absorbing resin per unit area is too small, and the swelling speed or the water absorption speed becomes low. On the other hand, when the thickness exceeds 5 mm, not only is it difficult to obtain a uniform water-absorbing sheet, but also the swelling speed or the water absorbing speed tends to decrease. More preferably, it is a sheet having a thickness of 0.5 to 3 mm. As described above, a technique is known in which a water-absorbent resin powder is sprinkled on a base sheet, another sheet is stacked on the base sheet, and water is applied as necessary to form a sheet. However, the prior art is designed to avoid the approach of the water-absorbent resin particles as much as possible, and therefore the amount of the water-absorbent resin particles sprayed is at most 100 g / m2.²Met. With such a low spraying amount, the adhesion between the water-absorbent resin particles as referred to in the present invention hardly occurs, and therefore, a sheet state due to the adhesion between the particles cannot be realized. The sheet of the present invention is within a range that can be handled as an integral sheet, and maintains the form of the sheet by bonding between water-absorbing resin particles.
[0033]
The water-absorbing material of the present invention is a sheet-like material resulting from the adhesion between the water-absorbing resin particles, but is substantially decomposed into individual water-absorbing resin particles by contact with the liquid to be absorbed, that is, the aqueous medium. Things. This is considered to be a factor indicating good water absorption. Conventionally known flexible water-absorbing sheets include, for example, a thin film-like hydrogel polymer (Japanese Patent Application Laid-Open No. 4-236203) and a film composed of polyvinyl alcohol and polyacrylic acid (salt) (Japanese Patent Publication No. 62-921). And JP-B 2-48024), all of which exhibited an integral gel state due to liquid absorption, and had too low a water absorption capacity or too low an absorption rate.
[0034]
A preferred embodiment of the present invention has a tensile yield strength of 0.5 kg / cm.²This is a water-absorbing material having a tensile yield elongation of 10% or more. When handling a large amount of water-absorbing material, handling may be difficult if the tensile yield strength is low. Further, when handling a water-absorbing material, if the tensile yield elongation is small, it may lack flexibility and handling may be difficult. As the water-absorbent resin particles, it is preferable to use particles having a particle size distribution in which substantially no particles larger than 1000 μm and particles of 150 μm or less are 20% or more, in order to obtain such a water-absorbent material. . More preferably, particles having a particle size of 850 μm or less are substantially not contained and particles having a size of 150 μm or less have a particle size distribution of 20% or more. However, generally, when the strength or flexibility of the sheet is increased, the swelling rate or the water absorption rate tends to decrease.
[0035]
Another preferred embodiment of the present invention is a water-absorbing material having a water absorption speed of 50 seconds or less, more preferably 30 seconds or less, and a flexibility of 90 degrees or more. The details of the method of measuring the water absorption speed will be described later, but the time during which a certain amount of artificial urine is applied to a water-absorbing material having a predetermined area and the water is completely absorbed is defined as the water absorption speed of the present invention. In order to reduce the amount of wood pulp fluff used and to produce small and thin water-absorbent articles, it has been found that it is important to increase the water absorption rate. Although the details of the method of measuring the flexibility will be described later, an index representing the flexibility of the water-absorbing material and the difficulty of generating fine powder particles when an external force is applied is the flexibility of the present invention. If the degree of softness is insufficient, the hard and rough feel becomes strong, and the sheet becomes unusable or the sheet collapses and water-absorbent resin particles are generated. A sheet-like material that simultaneously satisfies these properties has not been known as a sheet-like material resulting from the adhesion of the particles of the water-absorbing resin. It is preferable to use, as the water-absorbent resin particles, particles that do not substantially contain particles larger than 1000 μm and have a particle size distribution in which particles having a size of 150 μm or less are 10% or less. . More preferably, particles having a particle size of 850 μm or less and particles having a particle size of 150 μm or less have a particle size distribution of 10% or less. More preferably, it has a particle size distribution of 5% or less. As described above, the water-absorbent resin particles preferably have an absorption capacity under load of at least 20 ml / g, and are preferably surface-crosslinked.
[0036]
The present invention relates to water-absorbent resin particles of 100 parts by weight, water of 15 to 150 parts by weight, and at least one water-absorbing aid selected from the group consisting of water-insoluble fine particles, surfactants and fibers. A water-absorbing material in which parts by weight are blended, wherein the water-absorbing material is in a sheet state having a thickness of about 0.3 to 5 mm, and the sheet state is caused by the adhesion between the water-absorbing resin particles. The present invention also provides a water-absorbing material characterized by the following. By including a specific water-absorbing aid, a water-absorbing material having particularly excellent water-absorbing speed can be obtained. Here, the water-absorbing aid functions to increase the water absorption rate when the water-absorbing material of the present invention absorbs water. These are at least one selected from the group consisting of water-insoluble fine particles (inorganic fine particles and organic fine particles) surfactants and fibers, and specific examples include the following. Examples of the surfactant include polyoxyethylene alkyl ether, polyoxyethylene alkyl phenol ether, sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene acyl ester, oxyethylene oxypropylene block copolymer, and sucrose fatty acid ester. Can be mentioned. Aerosil 200 (manufactured by Nippon Aerosil Co., Ltd.) composed of mica, pyrophyllite, kaolinite, halcite, and other similar clay minerals and silicon dioxide particles having an average particle diameter of mainly 50 μm or less include inorganic fine particles. Fine particle silica such as Carplex # 80 (manufactured by Shionogi) can be used. Examples of the organic fine particles include carbon black, activated carbon, and pulp powder. Among them, finely divided silica is preferable because it has a large effect of increasing the water absorption rate. The amount of the water-absorbing aid used is 0.1 to 10 parts by weight, preferably 0.5 to 5 parts by weight, and most preferably 0.7 to 2 parts by weight. If the weight exceeds 10 parts by weight, the excess may not have an effect proportional to the amount used, but rather, the water absorption may be reduced, and in some cases, the sheet may be difficult to form. I do. If the amount is less than 0.1 part by weight, the effect cannot be obtained.
[0037]
A water-absorbing material having a water absorption rate of 30 seconds or less and a flexibility of 90 degrees or more, which is a particularly preferred embodiment of the present invention, contains substantially no particles larger than 1000 μm and particles of 150 μm or less. It is preferable to use water-absorbing resin particles having a particle size distribution of 10% or more and to use a water-absorbing aid. When the content of particles having a size of 150 μm or less is small, it may be difficult to produce a sheet-like water-absorbing material. It is preferable to use the water-absorbing resin particles having the above-mentioned specific absorption capacity under load together with the water-absorbing aid and such specific particle size distribution in order to obtain a water-absorbing material having a high water absorption rate. Further, it is preferable that the surface-crosslinked water-absorbent resin particles are used.
[0038]
The present invention also provides a method for producing the above water-absorbing material with high productivity. In such a production method, 100 parts by weight of the water-absorbent resin particles are spread on a support in a planar state with the thickness being regulated to about 0.3 to 5 mm, and water and / or water is maintained while maintaining this planar state. This is achieved by adding and contacting 15 to 150 parts by weight of steam. Another manufacturing method of the present invention supports 100 parts by weight of water-absorbing resin particles, and 0.1 to 10 parts by weight of at least one water-absorbing aid selected from the group consisting of water-insoluble fine particles, surfactant and fiber. It is achieved by flowing on the body in a planar state with the thickness being regulated to about 0.3 to 5 mm, and maintaining the surface state by contacting with 15 to 150 parts by weight of water and / or steam. You. Water and / or steam is added to and contacted with the water-absorbent resin particles that have flowed while regulating the thickness, and the water-absorbent resin particles are brought into contact with water and / or steam in a state where shear force is not substantially applied thereto. Means to add water vapor, for example, a method of spraying water, a method of applying saturated water vapor to the water-absorbent resin particles having a thickness regulated to about 0.3 to 5 mm on a support, and flowing, And a method in which the thickness of the water-absorbent resin particles is regulated and held in an atmosphere having a relative humidity of 50% or more, and the support is held. If the contact between the water-absorbent resin particles and water is not uniform, a uniform sheet may not be obtained. However, after contact with water, the sheet is sealed, for example, preferably at 30 ° C. so as not to splash the water. When left at the above temperature, a homogeneous sheet is obtained. When water is added to the water-absorbent resin particles, for example, if a shearing force such as a combination of stirring the water-absorbent resin particles and water is applied, the water-absorbing material obtained has a low water absorption rate, which is not preferable. When such an operation is performed, the water-absorbent resin particles tend to be clumpy. It is difficult to form this lump into a sheet which is the object of the present invention. For example, it is not impossible to mold this lump into a sheet using an extruder or the like, but such an operation not only requires a great deal of energy but also bonds the water-absorbent resin particles together. Progresses excessively, and in an extreme case, the interface between particles disappears. The sheet thus obtained tends to have a significantly reduced water absorption rate. Even after the water-absorbing material of the present invention is obtained, it is preferable that shearing force is not applied to the water-absorbing material.
[0039]
In the production method of the present invention, when the water-absorbent resin particles are brought into contact with water and / or water vapor, the water-absorbent resin particles are flowed on the support with a thickness regulated to about 0.3 to 5 mm. When the thickness is less than 0.3 mm, the strength of the sheet is reduced and the handleability is deteriorated, the amount of the water-absorbing resin per unit area is too small, and the water-absorbing speed of the obtained water-absorbing material becomes small. Further, it becomes difficult to maintain the form as a sheet. In order to achieve such a thickness, generally 200 g / m²Or more, preferably 250 g / m²Above, more preferably 300 g / m²The above water-absorbing resin particles are required. On the other hand, when the thickness exceeds 5 mm, the water absorption rate of the obtained water-absorbing material tends to be rather small, and in order to obtain a uniform water-absorbing material, it is necessary to bring the water-absorbing resin particles into contact with water and / or steam. Time tends to be significantly longer.
[0040]
In the production method of the present invention, the amount of water added to the water-absorbent resin particles is 15 to 150 parts by weight based on 100 parts by weight of the water-absorbent resin particles. Here, the water-absorbent resin particles may originally contain some water as described above, and may be in a range that can be handled as particles. When the water-absorbing resin particles contain water, the water in the obtained water-absorbing material is added in an amount of 15 to 150 parts by weight based on 100 parts by weight of the water-absorbing resin particles. However, in the method of the present invention, it is necessary to add at least 15 parts by weight of water to 100 parts by weight of the water-absorbing resin particles in order to obtain a sheet-like water-absorbing material. In order to obtain a water-absorbing material having an amount of water of 15 parts by weight, water-absorbing resin particles having a water content of 0 must be used. If the amount of water exceeds 150 parts by weight, not only the amount of water absorption of the obtained water-absorbing material becomes low, but also breakage may occur in the step of manufacturing the sheet-like water-absorbing material. On the other hand, if the amount of water is less than 15 parts by weight, not only a water-absorbing material having the desired water-absorbing speed and flexibility is not obtained, but also the strength of the water-absorbing resin particles is poor due to insufficient adhesion between the water-absorbing resin particles. There are cases. A more preferred amount of water is in the range of 25 to 100 parts by weight, most preferably in the range of 30 to 80 parts by weight, per 100 parts by weight of the water absorbent resin particles.
[0041]
The combination procedure when combining the water-absorbing resin particles and the water-absorbing auxiliary is not particularly limited. A method in which the water-absorbing resin particles and the water-absorbing auxiliary are mixed in advance and water is brought into contact with the mixture, or a method in which water in which the water-absorbing auxiliary is dissolved or dispersed is brought into contact with the water-absorbing resin particles may be used.
[0042]
In the method for producing a water-absorbent material of the present invention, when the water-absorbent resin particles are spread on a support and brought into contact with water and / or water vapor, the method of spreading is optional. That is, if the water-absorbent resin particles are spread over the entire surface to a uniform thickness, an integrated sheet-like water-absorbent material having a uniform thickness can be obtained. can get.
[0043]
In the method for producing a water-absorbing material of the present invention, water may be any of distilled water, ion-exchanged water, tap water, industrial pure water, and the like, in which inorganic or organic substances are dissolved or dispersed. May be used.
[0044]
The present invention also provides a laminated water-absorbing material comprising a water-permeable sheet disposed on at least one surface of the above-described water-absorbing material. In the laminated water-absorbent material of the present invention, the water-permeable sheet may be disposed on at least one side of the water-absorbent material, but may be disposed on both sides, and in some cases, the water-permeable sheet on one side and the other side. A water-impermeable sheet may be provided. Such a laminated water-absorbing material can be obtained by simply superposing a water-permeable sheet or a water-impermeable sheet on the water-absorbing material, but may be embossed if necessary. However, when it is considered that the water absorption rate is important, an operation of applying pressure or shearing force such as pressing or embossing is not preferable. Further, such a laminated water-absorbing material can also be obtained by forming the water-absorbing material on a water-permeable sheet or a water-impermeable sheet.
[0045]
Examples of the water-permeable sheet include regenerated cellulose-based nonwoven fabric, cotton-like pulp, rayon, cotton card web, paper, and the like, and those having a structure that easily allows water to permeate are preferable. Examples of the water-impermeable sheet include films of nylon, polyethylene, polypropylene, polystyrene, and polyvinyl chloride.
[0046]
The water-absorbing material and the laminated water-absorbing material of the present invention have a supple and tough feel, have good water absorption, and can be cut into any size or shape, so that they can be used for various applications.
[0047]
The water-absorbing material and the laminated water-absorbing material obtained according to the method of the present invention are used in combination with the material and a water-soluble polymer, a deodorant, a fragrance, a drug, a plant growth aid, a bactericide, a fungicide, a foaming agent, a pigment, A new function can be imparted to the obtained water-absorbing material by mixing carbon black, activated carbon, short fibers and the like.
[0048]
By combining the water-absorbing material and the laminated water-absorbing material of the present invention with cellulose fiber or its web, synthetic fiber or its web, or the like, a water-absorbing article suitable as a water-absorbing layer of a sanitary material can be obtained. For example, paper made of cellulose fiber or synthetic fiber, a method of sandwiching the water-absorbing material on a nonwoven fabric or a mat, a method of blending a cellulose fiber and a strip of the water-absorbing material, and the like to obtain a water-absorbing article. Can be appropriately selected. Above all, a water-absorbent article in which the water-absorbent material of the present invention is housed inside a bag formed on at least one side by a water-permeable sheet is equivalent to the conventional one despite being thinner and more compact than the conventional water-absorbent article. The above water absorption performance is shown.
[0049]
Since the water-absorbing material and the laminated water-absorbing material of the present invention are sheet-like water-absorbing materials having a high absorption rate and a high degree of flexibility, a fibrous matrix such as conventional water-absorbing resin particles is used to prevent gel blocking. There is no need to incorporate a relatively low concentration therein, and a relatively high concentration can be incorporated into the absorbent article. In particular, the water-absorbent articles of the present invention have a (substantially dry) water-absorbent resin content of about 50-85% by weight relative to the total weight of the water-absorbent article. Preferably it is about 60-85% by weight, more preferably about 70-85% by weight. Even if a water-absorbent article having such a high resin concentration is produced, the water-absorbent material of the present invention is in a flexible sheet form, and therefore, in the water-absorbent article manufacturing step, the packaging step, and the transportation step, the water-absorbent article is formed inside the water-absorbent article. No migration of the water-absorbent resin and no spillage of the water-absorbent resin, and the texture of the water-absorbent article is not impaired.
[0050]
As described above, the water-absorbent article of the present invention can have a high water-absorbent resin content, and therefore is thin and compact while having water absorption performance equal to or higher than that of a conventional water-absorbent article. In addition, because it is highly flexible, it fits well on the body and is easy to use.
[0051]
The water-absorbent articles of the present invention are suitable for absorbing many fluids, including body fluids such as urine, menses and blood, diapers, incontinence products, products such as bed pads, sanitary napkins, Applicable to sanitary products such as tampons and products such as towels and bandages.
[0052]
【The invention's effect】
The water-absorbing material of the present invention has high safety because it does not contain impurities, has a supple and tough texture, has good water absorption, and can be used for various purposes for water absorption or moisture absorption. . For example, applications such as a water-absorbing layer of a sanitary material, a condensation water-absorbing sheet, a water-retaining sheet for agriculture, a waterproofing agent for civil engineering, medical sheets, a freshness-retaining agent for food, and a water-absorbing agent for miscellaneous goods are listed. Further, the method for producing a water-absorbing material of the present invention makes it possible to produce the above-described water-absorbing material extremely easily and at low cost. The water-absorbent article of the present invention can have a high water-absorbent resin content, so that it is thin and compact while having water absorption performance equal to or higher than that of a conventional water-absorbent article. In addition, because it is highly flexible, it fits well on the body and is easy to use.
[0053]
【Example】
Hereinafter, the present invention will be further described with reference to Examples, but the present invention is not limited thereto.
[0054]
(Reference Example 1) Synthesis example of water-absorbent resin particles (A)
In a stainless steel kneader with an inner volume of 10 liters and two sigma type blades, 5500 g of an aqueous solution of a monomer composed of 75 mol% of sodium acrylate and 25 mol% of acrylic acid (monomer concentration: 38%), 3.5 g of trimethylolpropane triacrylate (0.05 mol% based on monomer) as a cross-linking agent was charged, and nitrogen gas was blown into the reaction system to replace the inside of the reaction system with nitrogen. The jacket was heated with warm water at 35 ° C., and 2.8 g of sodium persulfate and 0.1 g of 1-ascorbic acid were added as polymerization initiators while rotating and stirring the sigma type blades at 40 rpm to initiate polymerization. The polymerization reaction was performed for one hour. After the completion of the reaction, the finely divided hydrogel polymer was spread on a metal mesh having an aperture of 0.3 mm, and dried at 160 ° C. for 1 hour. The obtained dried product (ppA) was pulverized using a hammer mill to obtain water-absorbent resin particles (A) passing through 850 μm. The proportion of the water-absorbent resin particles (A) passing through 150 μm was 21% by weight.
[0055]
(Example 1)
10 g of the water-absorbent resin particles (A) were uniformly spread on a 140 × 100 mm formwork, and this was left in a thermo-hygrostat at 45 ° C. and a relative humidity of 80%. After 120 minutes, a water absorbing material (1) having a thickness of about 1.3 mm was obtained. It was found from the weight measurement that 3.8 g of water was given to the water-absorbent resin particles (A). The obtained water-absorbing material was evaluated by the following methods, and the obtained results are shown in Table 1.
[0056]
A: Tensile yield strength and tensile yield elongation
The measurement was performed according to JIS K7127.
[0057]
Test equipment Instron Model 4301
Test piece No.5
Test speed 200 mm / min.
B: Water absorption ratio
0.5 g of the water-absorbing material was precisely weighed in terms of water-absorbing resin particles, placed in a non-woven tea bag type bag, immersed in 0.9% by weight saline solution, and weighed after 60 minutes. The water absorption ratio was determined according to Equation 1.
[0058]
(Equation 1)

[0059]
C: swelling speed
50 ml of 0.9% by weight saline solution and a stirrer chip were placed in a 100 ml beaker and stirred at 600 rpm. The water-absorbing material was cut into about 1 cm squares, and 2.0 g of water-absorbing resin particles were instantaneously charged into the beaker, and the stopwatch was started. The stopwatch was stopped when the stirrer tip exposed at the center of the saline flow was hidden by the swollen gel, and the time obtained was taken as the swelling speed. The shorter the time, the higher the swelling rate.
[0060]
D: moisture content
1.0 g of the water-absorbing material is precisely weighed and placed in an aluminum cup (W₁ g). This was put in a dryer adjusted to 180 ° C. and left for 3 hours. The aluminum cup containing the water-absorbing material taken out of the dryer was allowed to cool in a desiccator, and then the weight (W)₂ g) was measured. The water content per 100 parts by weight of the substantially dried water-absorbent resin particles was determined according to the following formula 2.
[0061]
(Equation 2)

[0062]
E: Particle size distribution of water absorbent resin particles
The mesh of JIS standard sieve is 16 mesh, 18.5 mesh, 30 mesh, 50 mesh, 100 mesh and a classifying dish of a saucer are overlapped, and about 30 g of the water-absorbent resin particles are put thereon, and the sieve is shaken for 10 minutes. Shake. Thereafter, the weight of the classified material on each screen was weighed, and expressed as a percentage by weight based on the weight of the charged water-absorbent resin particles.
[0063]
F: Absorption capacity under load of water-absorbent resin particles
The absorption capacity under load is measured using the apparatus shown in FIG. The upper port 2 of the buret 1 is plugged with the stopper 3, and the measuring table 4 and the air port 5 are set at the same height. The filter paper 7 is placed on a glass filter 6 having a diameter of 70 mm at the center of the measuring table 4. On the other hand, the non-woven fabric 8 is fixed to the lower end of the support cylinder 10 having a diameter of 55 mm, and 0.2 g of the water-absorbent resin particles are evenly spread on the non-woven fabric 8, and further 20 g / cm²The weight 9 is placed. The nonwoven fabric 8-water-absorbent resin particles-weight 9 was placed on the filter paper 7 on the glass filter 6 together with the supporting cylinder 10, and the amount (Aml) of 0.9% saline absorbed over 30 minutes was measured. The absorption capacity under load was determined according to 3.
[0064]
(Equation 3)

[0065]
(Example 2)
10 g of the water-absorbent resin particles (A) were uniformly spread on the same mold as in Example 1, and 6.2 g of water was given by spraying using a spray. The entire mold was sealed with a polyethylene bag and left at 45 ° C. After taking out from the bag after 180 minutes, a water-absorbing material (2) having a thickness of about 1.4 mm was obtained. The obtained water-absorbing material (2) was evaluated in the same manner as in Example 1, and the obtained results are shown in Table 1.
[0066]
(Example 3)
The same operation as in Example 1 was performed, and a water-absorbing material (3) having a thickness of about 1.2 mm was obtained after 65 minutes. It was found by weight measurement that 2.0 g of water was given to the water-absorbent resin particles (A). The obtained water-absorbing material (3) was evaluated in the same manner as in Example 1, and the obtained results are shown in Table 1.
[0067]
(Comparative Example 1)
The same operation as in Example 1 was performed to give 0.5 g of water to the water-absorbent resin particles (A). The resulting product was very hard and brittle, and was difficult to handle as a sheet.
[0068]
(Comparative Example 2)
The same operation as in Example 2 was performed to give 47 g of water to the water-absorbent resin particles (A). The resulting product was very soft and brittle, and was difficult to handle as a sheet.
[0069]
(Comparative Example 3)
67 g of the water-absorbent resin particles (A) were uniformly spread on the same mold as in Example 1, and 22 g of water was given by spraying using a spray. The entire mold was sealed with a polyethylene bag and left at 45 ° C. for 16 hours. Upon removal from the bag, a heterogeneous comparative water-absorbent material (3a) having a thickness of about 8 mm was obtained. The obtained comparative water-absorbing material (3a) was evaluated in the same manner as in Example 1, and the obtained results are shown in Table 1.
[0070]
(Comparative Example 4)
While putting 10 g of the water-absorbent resin particles (A) in a mixer and stirring, 3.8 g of water was dropped thereinto. Immediately, a clumpy composition comprising a water-absorbent resin and water was obtained. This material had a strong elasticity and could be torn into small agglomerates, but it was difficult to mold it into a uniform sheet.
[0071]
(Comparative Example 5)
In Example 1, 1.4 g of the water-absorbent resin particles (A) (basis weight: 100 g / m2)²The same operation as in Example 1 was repeated, except that (equivalent to) was used. Although a granulated product in which particles were partially gathered was observed, it was impossible to handle as an integrated sheet. (Example 4)
The water-absorbent resin particles (A) were classified at 150 μm to obtain water-absorbent resin particles (B) passing through 150 μm. The same operation as in Example 1 was performed except that the water-absorbent resin particles (B) were used, to give 3.8 g of water to the water-absorbent resin particles (B). A water absorbing material (4) having a thickness of about 1.3 mm was obtained. The obtained water-absorbing material (4) was evaluated in the same manner as in Example 1, and the obtained results are shown in Table 1.
[0072]
(Reference Example 2) Synthesis example of water-absorbent resin particles (C)
In a kneader similar to that of Reference Example 1, 1100 g of acrylic acid, 2500 g of a 2% by weight aqueous oxidized starch solution, 1850 g of water, and 2.7 g of N, N'-methylenebisacrylamide as a cross-linking agent (0.11 mol% of monomer) were used. Then, nitrogen gas was blown into the reaction system to replace the inside of the reaction system with nitrogen. Water of 8 ° C. is passed through the jacket, and while rotating the sigma type blade at 40 rpm, 3.3 g of 2,2′-azobisamidinopropane dihydrochloride, 0.3 g of L-ascorbic acid and 35% by weight as a polymerization initiator 3.1 g of aqueous hydrogen peroxide was added to initiate polymerization. After the start of the polymerization, the rotation of the sigma type blade was stopped, and the polymerization reaction was performed for 3 hours. After completion of the reaction, the sigma-type blade was rotated at 40 rpm to fragment the formed hydrogel polymer. Next, 950 g of a 48% by weight aqueous sodium hydroxide solution was added thereto, and the rotation and stirring were further continued. An aqueous solution composed of 3.3 g of ethylene glycol diglycidyl ether and 70 g of water was added as a post-crosslinking agent to the hydrogel polymer heated to 86 ° C. due to the heat of neutralization, and the rotational stirring was continued. The obtained hydrogel polymer was spread on a metal mesh having a mesh size of 0.3 mm, and dried at 120 ° C. for 3 hours. The obtained dried product (ppC) was pulverized using a hammer mill to obtain water-absorbent resin particles (C) passing through 850 μm. The proportion of the water-absorbent resin particles (C) passing through 150 μm was 25% by weight.
[0073]
(Example 5)
The same operation as in Example 1 was performed except that the water-absorbent resin particles (C) were used, to give 3.6 g of water to the water-absorbent resin particles (C). A water absorbing material (5) having a thickness of about 1.3 mm was obtained. The obtained water-absorbing material (5) was evaluated in the same manner as in Example 1, and the obtained results are shown in Table 1.
[0074]
(Example 6)
In Example 1, paper (A) of 140 × 100 mm (basis weight 15 g / m²The same operation as in Example 1 was repeated except that the water-absorbent resin particles were spread on the above). A sheet was obtained in which the water-absorbing material (1) having a thickness of about 1.3 mm and the paper (A) were integrated. The same sheet of paper (A) as the sheet of paper (A) was placed on the water-absorbent material (1) side of the obtained sheet, and was lightly pressed by hand. A laminated water-absorbing material in which the water-absorbing material (1) was sandwiched between two sheets of paper (A) was obtained.
[0075]
[Table 1]

[0076]
(Reference Example 3) Synthesis example of water-absorbent resin particles (D)
The absorption capacity under load of the water-absorbent resin particles (A) obtained in Reference Example 1 was 16 ml / g. 100 parts by weight of the water-absorbent resin particles (A) were mixed with an aqueous mixture consisting of 0.5 parts by weight of glycerin, 3 parts by weight of water and 2 parts by weight of isopropanol. The obtained mixture was put into a bowl immersed in an oil bath (195 ° C.) and heat-treated under stirring for 40 minutes to obtain water-absorbent resin particles (D) passing through 850 μm. The proportion of the water-absorbent resin particles (D) passing through 150 μm was 13% by weight. The absorption capacity under load of the water-absorbent resin particles (D) was 26 ml / g.
[0077]
(Example 7)
15 g of the water-absorbent resin particles (A) were uniformly spread on a 150 × 200 mm formwork. At this time, the water-absorbent resin particles (A) were in a state of flowing about 0.7 mm in a plane. This was left in a thermo-hygrostat at 45 ° C. and a relative humidity of 80%. After 120 minutes, a sheet-like water-absorbing material (7) was obtained. 5.7 g of water was given to the water absorbent resin particles (A). The obtained water-absorbing material (7) was evaluated by the same method as in Example 1 and the following method, and the obtained results are shown in Table 2.
[0078]
G: Water absorption speed
The water-absorbing material was cut into a 45 × 45 mm square, placed in a cylindrical container having a diameter of 6 cm on a horizontal table, and 20 g of artificial urine at 22 ° C. was poured at once from the top. At the same time he started the stopwatch. The composition of artificial urine is
2.0 g / l KCl;
Na₂ SO₄   2.0 g / l;
(NH₄ ) H₂ PO₄   0.85 g / l;
(NH₄ )₂ HPO₄   0.15 g / l;
CaCl₂   0.19 g / l;
MgCl₂   0.23g / l
It is. The stopwatch was stopped when the artificial urine was completely absorbed by the water-absorbing material, and the obtained time was defined as the water absorption rate. The shorter the time, the higher the water absorption rate.
[0079]
H: Flexibility
A water-absorbing material having a width of at least 2 cm was placed horizontally, and half of the water-absorbing material was slowly rotated while keeping a plane about a straight line that roughly bisects the area of the water-absorbing material. At that time, the angle from the horizontal plane at which rotation started when the water-absorbing material substantially cracked was defined as the degree of flexibility. The greater the angle, the greater the flexibility.
[0080]
(Example 8)
15 g of the water-absorbent resin particles (D) were uniformly spread on a 150 × 200 mm mold. At this time, the water-absorbent resin particles (D) were in a state of being spread in a flat shape with a thickness of about 0.7 mm. This was left in a thermo-hygrostat at 45 ° C. and a relative humidity of 80%. After 150 minutes, a sheet-like water-absorbing material (8) was obtained. 6.1 g of water was given to the water-absorbent resin particles (D). The obtained water-absorbing material (8) was evaluated in the same manner as in Example 7, and the obtained results are shown in Table 2.
[0081]
(Example 9)
15 g of the water-absorbent resin particles (D) and 0.15 g of water-insoluble fine-particle silica (Aerosil 200, manufactured by Nippon Aerosil Co., Ltd.) were mixed, and the resulting mixture was uniformly spread on a 150 × 200 mm mold. At this time, the mixture of the water-absorbent resin particles (D) and the particulate silica was in a state of being spread in a plane with a thickness of about 0.7 mm. This was left in a thermo-hygrostat at 45 ° C. and a relative humidity of 80%. After 150 minutes, a sheet-like water-absorbing material (9) was obtained. 6.2 g of water was provided to the water-absorbent resin particles (D). The obtained water-absorbing material (9) was evaluated in the same manner as in Example 7, and the obtained results are shown in Table 2.
[0082]
(Reference Example 5) Synthesis example of water-absorbent resin particles (E)
In a 500-ml cylindrical separable flask, 8.6 g of sodium salt of 2-sulfoethyl methacrylate, 35.4 g of acrylic acid in which 75 mol% was neutralized with sodium salt, and 0.1 mL of trimethylolpropane triacrylate as a crosslinking agent. An aqueous monomer solution consisting of 077 g (based on 0.06 mol% of monomer) and 69 g of water was charged. The reaction system was replaced with nitrogen under stirring, and the temperature of the aqueous monomer solution was set to 30 ° C. Next, 0.5 g of a 10% aqueous sodium persulfate solution and 0.4 g of a 0.5% 1-ascorbic acid aqueous solution were added, and stirring was stopped to start polymerization. Fifteen minutes after the start of the polymerization, the temperature in the system rose to 70 ° C. After confirming that the temperature in the system had begun to decrease, the polymerization system was externally heated and kept at 75 ° C. for 1 hour. The obtained hydrogel polymer was subdivided and dried at 150 ° C. for 90 minutes. The obtained dried product (ppE) was pulverized with a hammer mill to obtain water-absorbent resin particles (pE) passing through 300 μm. 100 parts by weight of water-absorbent resin particles (pE) were mixed with an aqueous mixture consisting of 1 part by weight of glycerin, 1 part by weight of water and 2 parts by weight of isopropanol. The obtained mixture was put into a bowl immersed in an oil bath (195 ° C.), and heat-treated under stirring for 30 minutes to obtain water-absorbent resin particles (E) passing through 300 μm. The ratio of the water-absorbent resin particles (E) passing through 150 μm was 27% by weight. The absorption capacity under load of the water-absorbent resin particles (E) was 24 ml / g.
[0083]
(Example 10)
15 g of the water-absorbent resin particles (E) were uniformly spread on a 150 × 200 mm formwork. At this time, the water-absorbent resin particles (E) were in a state of flowing about 0.7 mm in a flat shape. 5.9 g of water was given to this by spraying to obtain a sheet-like water-absorbing material (10). The obtained water-absorbing material (10) was evaluated in the same manner as in Example 7, and the obtained results are shown in Table 2.
[0084]
(Example 11)
15 g of the water-absorbent resin particles (E) and 0.15 g of water-insoluble fine-particle silica (Aerosil 200, manufactured by Nippon Aerosil Co., Ltd.) were mixed, and the resulting mixture was uniformly spread on a 150 × 200 mm formwork. At this time, the mixture of the water-absorbent resin particles (E) and the particulate silica was in a state of being spread in a plane with a thickness of about 0.7 mm. This was sprayed with water to give 6.2 g of water, whereby a sheet-like water-absorbing material (11) was obtained. The obtained water-absorbing material (11) was evaluated in the same manner as in Example 7, and the obtained results are shown in Table 2.
[0085]
(Example 12)
The water-absorbent resin particles (E) obtained in Reference Example 5 were classified at 150 μm to obtain water-absorbent resin particles (F) of 300 μm to 150 μm. The absorption capacity under load of the water-absorbent resin particles (F) was 28 ml / g. The same operation as in Example 10 was repeated except that the water-absorbent resin particles (F) were used, and a sheet-like water-absorbent material (12) was obtained. The obtained water-absorbing material (12) was evaluated in the same manner as in Example 7, and the obtained results are shown in Table 2.
[0086]
(Comparative Example 6)
The same operation as in Example 8 was repeated, and the mold in which the water-absorbent resin particles (D) were uniformly spread was left in a thermo-hygrostat at 45 ° C. and a relative humidity of 80%. After 100 minutes in a thermo-hygrostat, the mold was taken out and rubbed over the wet water-absorbent resin particles (D) with a metal spatula. After that, it was left in a thermo-hygrostat for 50 minutes, and the water-absorbent resin particles (D) taken out were rubbed again with a metal spatula. 6 g of water was provided to the water absorbent resin particles (D). The comparative water-absorbing material (6c) obtained was evaluated in the same manner as in Example 7, and the results are shown in Table 2.
[0087]
(Comparative Example 7)
While stirring 15 g of the water-absorbing resin particles (E) in a mixer, 6 g of water was added dropwise thereto. Immediately, a clumpy composition comprising a water-absorbent resin and water was obtained. This product had strong elasticity and could be torn into small agglomerates, but it was difficult to mold it into a uniform sheet.
[0088]
(Comparative Example 8)
Example 8 was repeated except that 0.8 g of water was given to the water-absorbent resin particles (D). Some of the granulated particles were observed, but the particles were not formed and formed a sheet.
[0089]
(Comparative Example 9)
In Example 9, 4.2 g of the water-absorbent resin particles (D) and 0.04 g of water-insoluble particulate silica (Aerosil 200, manufactured by Nippon Aerosil Co., Ltd.) were mixed, and the resulting mixture was molded into a 150 × 200 mm mold. The same operation as in Example 9 was repeated except that the film was uniformly spread on the frame. This was left in a thermo-hygrostat at 45 ° C. and 80% relative humidity to give 1.7 g of water to the water-absorbent resin particles (D). Some of the granulated particles were observed, but the particles were not formed and formed a sheet.
[0090]
(Example 13)
In Example 9, 0.75 g of KC Floc W-300 (cellulose powder, manufactured by Sanyo Kokusaku Pulp Co., Ltd.) was used instead of 0.15 g of water-insoluble particulate silica (Aerosil 200, manufactured by Nippon Aerosil Co., Ltd.) Except for this, the same operation as in Example 9 was repeated. 6.2 g of water was provided to the water-absorbent resin particles (D). The obtained water-absorbing material (13) was evaluated in the same manner as in Example 7, and the obtained results are shown in Table 2.
[0091]
[Table 2]

[0092]
(Example 14)
In Example 7, instead of the mold, 150 × 300 mm heatron paper GS22 (manufactured by Nankoku Pulp Industry Co., Ltd.) was spread on a horizontal table, and the operation of Example 7 was repeated thereon to obtain about 0.5 mm. A laminated sheet was prepared in which a thick water-absorbing material was placed on Heatron paper GS22. On the other hand, the center of a commercially available disposable diaper ping-pong pants L-size (made by Shiseido Co., Ltd.) polyethylene film waterproof sheet was cut in the vertical direction to remove the absorbent made of water-absorbent resin, cotton-like pulp and water-absorbing paper. . The above-described laminated sheet was incorporated into the thus obtained disposable diaper chassis such that the water-absorbing material came to the surface material (polypropylene nonwoven fabric) of the chassis, and the cuts in the waterproof material sheet were closed with adhesive tape. The obtained water-absorbent article (1) was evaluated by the following method, and the results are shown in Table 3.
[0093]
I: Method for evaluating water-absorbent articles
A baby model with a ureter based on an infant weighing 10 kg was created. The water absorbent article (1) prepared in Example 13 was attached to the baby model, and artificial urine was discharged at a rate of 50 ml / 10 sec. After 50 minutes, the same urination operation was performed, and urine leakage was evaluated based on the amount of artificial urine absorbed before the artificial urine leaked out of the absorbent article.
[0094]
(Examples 15 to 19)
In Example 14, the same operations as in Example 14 were carried out except that the operations of Examples 8 to 12 were repeated to prepare the water-absorbing material, and laminated sheets in which the water-absorbing material was placed on the heatron paper GS22 were prepared. Thereafter, the procedure of Example 14 was repeated to obtain water-absorbent articles (2 to 6). The obtained water-absorbent articles (2 to 6) were evaluated in the same manner as in Example 14, and the results are shown in Table 3.
[0095]
(Comparative Example 10)
In Example 14, the same operation as in Example 14 was performed, except that the preparation of the water-absorbing material was repeated as in Comparative Example 8, to prepare a sheet on which the water-absorbing resin particles (D) were placed. Although the water-absorbent resin particles (D) were hardly fixed and very difficult to handle, the operation of Example 14 was repeated to obtain a comparative water-absorbent article (1c). The obtained comparative water-absorbent article (1c) was evaluated in the same manner as in Example 14, and the results are shown in Table 3. In the comparative water-absorbent article (1c), movement and deviation of the water-absorbent resin particles were observed.
[0096]
[Table 3]

[Brief description of the drawings]
FIG. 1 is a cross-sectional view of an apparatus for measuring an absorption capacity under load used in the present invention.
(Explanation of reference numerals)
1 ... Bullet
2 ... Upper end of burette
3 ... stopper
4 ... Measuring table
5 ・・・ Air intake
6 ... Glass filter
7 ... Filter paper
8 ... non-woven fabric
9 ... weight
10 ... Support cylinder

Claims

A water absorbent material of water 15 to 150 parts by weight is blended with respect to 100 parts by weight of the water-absorbent resin particles, water-absorbing material, thickness 0. A water-absorbent material in a sheet state of 3 to 5 mm, wherein the sheet state is caused by adhesion between the water-absorbent resin particles.

Tensile yield strength, at 5 kg / cm ² or more, and tensile yield elongation, water-absorbing material according to claim 1 is 20% or more.

Water-absorbing material according to claim 2 water-absorbent resin particles containing first particles larger than 1000 .mu.m, and the following particle 150μm and has a particle size distribution is 20% by weight or more.

15 to 150 parts by weight of water and 0.1 to 10 parts by weight of at least one water-absorbing aid selected from the group consisting of water-insoluble fine particles, surfactants and fibers are mixed with 100 parts by weight of water-absorbent resin particles. a water absorbent material that is, water-absorbing material, thickness 0. A water-absorbent material in a sheet state of 3 to 5 mm, wherein the sheet state is caused by adhesion between the water-absorbent resin particles.

Water-absorbing resin particles, water-absorbing material according to claim 1 or 4 in which at least 20 ml / g absorbs 0.9% saline under a force of at least 20 g / cm ^2.

The water-absorbing material according to claim 1 or 4 , wherein the water-absorbing resin particles are surface-crosslinked.

Water-absorbing material according to claim 1 or 4 water-absorbent resin particles containing first particles larger than 1000 .mu.m, and those having a particle size distribution 150μm or less of the particles is 10 wt% or more.

Absorbent material, absorbent material according to claim 1 or 4 by contacting with an aqueous liquid, it is intended to be broken down into the water-absorbent resin particles of the individual.

Laminated absorbent material formed by arranging water-permeable sheet on at least one surface of the water-absorbing material according to claim 1 or 4.

100 parts by weight of the water-absorbent resin particles were placed on a support, and the thickness was set to 0 . A method for producing a water-absorbing material, characterized in that the material is flowed in a planar shape with the surface regulated at 3 to 5 mm, and 15 to 150 parts by weight of water and / or steam is added while maintaining the planar state.

The water absorbing resin particles 100 parts by weight of water-insoluble particles, and at least one water-absorbing additive 0.1 to 10 parts by weight selected from surfactants and the group consisting of fibers on a support, the thickness of 0. A method for producing a water-absorbing material, characterized in that the material is flowed in a planar shape with the surface regulated at 3 to 5 mm, and 15 to 150 parts by weight of water and / or steam is added while maintaining the planar state.

A water-absorbent article characterized in that the water-absorbent material according to any one of claims 1, 4 and 9 is housed in a bag formed on at least one side by a water-permeable sheet.