JP4073508B2 - Water-absorbing composite and water-absorbing article - Google Patents
Water-absorbing composite and water-absorbing article Download PDFInfo
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- JP4073508B2 JP4073508B2 JP24069396A JP24069396A JP4073508B2 JP 4073508 B2 JP4073508 B2 JP 4073508B2 JP 24069396 A JP24069396 A JP 24069396A JP 24069396 A JP24069396 A JP 24069396A JP 4073508 B2 JP4073508 B2 JP 4073508B2
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- Prior art keywords
- water
- absorbing
- sheet
- weight
- absorbing polymer
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- 239000002245 particle Substances 0.000 claims description 37
- 239000011230 binding agent Substances 0.000 claims description 36
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 32
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- XRUKRHLZDVJJSX-UHFFFAOYSA-N 4-cyanopentanoic acid Chemical compound N#CC(C)CCC(O)=O XRUKRHLZDVJJSX-UHFFFAOYSA-N 0.000 description 2
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Description
【０００１】
【発明の属する技術分野】
本発明は、新規な吸水性複合体および吸水性物品に関するものである。詳しくは、漏れが生じず、かつ吸水力、保水力および柔軟性に優れた新規な吸収性構体およびこれを用いた吸水性物品に関するものである。
【０００２】
【従来の技術】
従来より、生理用ナプキンや紙おむつ等の吸水性物品では、吸水力、保水力に優れる吸水性ポリマーが、パルプや吸水紙等に代わる吸収素材として注目を集め、応用開発が進められてきた。この吸水性ポリマーは、体液の吸収速度に限度があり、また、体液に濡れないと体液を吸収できないため、吸水性物品では、吸収速度の速いパルプ等と併用して用いられることが多い。
【０００３】
しかし、吸水性物品中のパルプは乾燥時にはある程度の圧縮及び曲げ回復性を示すが、湿潤時には極度に強度が低下し、殆どそれらの回復性を示さない。このため、従来の吸水性物品では、体液で湿潤した吸水性物品に人体の運動による複雑な応力が加わると、パルプが変形して吸水性物品にヨレや片寄りを生じ、体液がそのヨレを伝わって流れ、横漏れを生ずるという問題があった。また、体液で湿潤することによりパルプの嵩が減少し、これにより吸水性物品と人体との間に隙間をつくる原因となり、同様に漏れを生じていた。
【０００４】
そこで、これらの問題点を解決すべく現在までに各種の検討が行われてきた。たとえば、特公平３−６７７１２号公報には、吸水性ポリマーを支持体上に固定しシート化したものを吸水性物品中に使用することにより、装着時の応力に対するヨレ、片寄りを防止する方法が示されている。しかし、これらのシートは吸水時の膨張異方性が低く、吸水性物品と人体との密着性については改善されていない。また、特開平３−１６２８５５号公報、特開平２−２８９６０８号公報には、異方膨張性を有したセルローススポンジ、ポリウレタンフォームを吸水性物品中に使用することにより、吸収速度および人体との密着性を改善したものが示されている。しかし、いずれの方法も、圧縮されたスポンジやフォームが水と接触したときに発現する弾性復元力だけを利用したもので、吸水性物品に含有される吸水性ポリマーは、保水能力の低いスポンジやフォームに一時的に保持された水分を吸収し保水するだけにしか用いられておらず、吸収体自身の膨張には殆ど寄与していない。そのため、おむつ等の吸水性物品に必要とされる高加圧下での吸収力が低いという欠点を有していた。また、これらのスポンジ、フォーム中に吸水性ポリマーを、膨張異方性が発現するように高濃度に分散固定し、かつ柔軟性を損なわないように形成することは非常に困難であった。
【０００５】
【発明が解決しようとする課題】
本発明は、かかる従来技術の有する問題点に鑑みなされたものであり、その目的とするところは、漏れが生じない新規な吸水性複合体およびこれを用いた吸水性物品を提供することにある。
【０００６】
本発明の他の目的は、吸水力、保水力および柔軟性に優れ、一方向に特異的に膨張する機能を有した新規な吸水性複合体およびこれを用いた吸水性物品を提供することにある。
【０００７】
【課題を解決するための手段】
上記課題は、本発明の吸水性複合体及びこれを用いた吸水性物品により解決される。
【０００８】
すなわち、本発明は、支持体としての繊維状物、および、アニオン性吸水性ポリマー粒子を含むシート状吸水性複合体であって、少なくとも総重量に対し３０重量％の前記アニオン性吸水性ポリマー粒子を含有し、液体を吸収したときの下記式で特定される厚み方向の膨張異方性が５以上であることを特徴とするシート状吸水性複合体である。
【０００９】
膨張異方性＝（Ｅｚ／Ｅｘ＋Ｅｚ／Ｅｙ）／２
（ただし、Ｅｘ、ＥｙおよびＥｚは、それぞれ、Ｘ軸方向、Ｙ軸方向およびＺ軸（厚み）方向の線膨潤倍率である。）
【００１０】
本発明はさらに、総重量に対し８０〜９９重量％の前記アニオン性吸水性ポリマー粒子を含有し、かつ、０．９％食塩水からなる生理食塩水に対する遠心分離操作後の吸収倍率（３０分）が１０ｇ／ｇ以上である前記シート状吸水性複合体である。
【００１１】
本発明はまた、前記アニオン性吸水性ポリマーが、バインダーとしてカチオン性架橋吸水性ポリマーを介して、支持体としての繊維状物に固着されている、前記シート状吸水性複合体である。本発明はまた、前記支持体に前記アニオン性吸水性ポリマー粒子が、前記カチオン性架橋吸水性ポリマーを介して固定され厚み方向に圧縮されてなる前記シート状吸水性複合体である。本発明はまた、前記カチオン性架橋吸水性ポリマーは、０．９％食塩水からなる生理食塩水に対する遠心分離操作後の吸収倍率（３０分）が５ｇ／ｇ以上である前記シート状吸水性複合体である。
【００１２】
本発明はさらに、厚さが０．２ｍｍ以上であり、生理食塩水に対する垂直吸引力（６０分）が５ｃｍ以上であり、ガーレー剛性（ＪＩＳ−Ｌ−１０９６）が１０００ｍｇｆＮ以下である前記シート状吸水性複合体である。本発明は、また、０．４％食塩水に対する５０ｇ／ｃｍ ２ での加圧下吸水量（３０分）が２０ｇ／ｇ以上である前記シート状吸水性複合体である。
【００１３】
また、本発明は、生理用ナプキンまたは紙おむつからなる衛生用吸水性物品であって、液体透過性表面シートと、液体非透過性裏面シートとの間に、前記シート状吸水性複合体を含む衛生用吸水性物品である。
【００１４】
【発明の実施の形態】
本発明の吸水性複合体は、液体を吸収したときの下記式で特定される膨張異方性が３以上であることを特徴とするものである。
【００１５】
膨張異方性＝（Ｅｚ／Ｅｘ＋Ｅｚ／Ｅｙ）／２
（ただし、Ｅｘ、ＥｙおよびＥｚは、それぞれ、Ｘ軸方向、Ｙ軸方向およびＺ軸方向の線膨潤倍率である。）
該膨張異方性は、後述する方法により測定されるものであり、吸水性複合体が液体を吸収したときの、Ｘ軸方向およびＹ軸方向に対するＺ軸方向への膨張性の度合いを表す指標である。すなわち、本発明の吸水性複合体は、液体を吸収したときの体積膨張が異方性を有し、主として厚み方向に膨張する。したがって、吸水性物品が体液で湿潤しても嵩が減少することなく逆に嵩が増加するので、人体とのフィット性が高まり漏れの生じない吸水性物品を得ることができるものである。吸水性複合体の前記膨張異方性が３未満では、人体との十分なフィット性が得られず好ましくない。さらに、前記膨張異方性が５以上であることが特に好ましい。
【００１６】
また、本発明の吸水性複合体は、少なくとも総重量に対し３０重量％以上の吸水性ポリマーを含有するものである。吸水性ポリマーの重量比を３０重量％以上とすることにより、吸水性複合体の膨張異方性、吸収力がより高くなり、該吸水性複合体を含む吸水性物品を薄型化、コンパクト化することができる。特に、吸水性ポリマーの重量比が８０〜９９重量％のものが好ましい。
【００１７】
本発明で用いられる吸水性ポリマーには、後述する吸水性複合体中の吸水性ポリマーおよび該吸水性ポリマーを支持体に固定する吸水性バインダーが含まれる。具体的には、架橋または架橋されていない親水性の天然高分子および合成高分子を使用することができる。天然高分子としては、でんぷん系、セルロース系等、合成高分子としては、ポリアクリル酸およびポリアクリル酸塩系、ポリビニルアルコール系、ポリアクリルアミド系、ポリオキシエチレン系等が挙げられるが、これらの中では、ポリアクリル酸塩系およびポリアクリルアミド系高分子が好適に使用される。
【００１８】
本発明の吸水性複合体としては、たとえば、支持体に吸水性ポリマーが吸水性バインダーを介して固定され厚み方向に圧縮された構造のものが挙げられる。
【００１９】
前記支持体は、圧縮弾性率が６０％以上のものが好ましく、特に三次元骨格構造や連続気泡構造を有するものが吸水時の復元力が強いので好ましい。圧縮弾性率が６０％未満では、吸水時の復元力が弱く、高い膨張異方性が達成されず好ましくない。このような支持体としては、発泡ポリウレタンのような発泡体、粉末状、粒子状、シート状、短冊状、繊維状等の形態またはそれらの結合体が挙げられるが、好ましくは繊維状支持体である。繊維状支持体としては、天然または合成繊維、天然または合成パルプ等から作られる繊維状物、特に繊維シートが好適に使用される。繊維シートとしては、織布、不織布、紙、編地などが挙げられるが、各種繊維ウェブから作られる不織布が好適である。繊維は親水性繊維、疎水性繊維のいずれでも使用でき、親水性繊維としては、木材パルプ、綿、羊毛、レーヨン、アセテート、ビニロン等、疎水性繊維としては、ポリエステル、アクリル、ナイロン、ポリエチレン、ポリプロピレン、ポリ塩化ビニル等が挙げられ、これらの混紡繊維も使用することができる。繊維状シートは、例えば、テープ状のものも含まれ、その厚みも特に限定はないが、例えば、０．０１〜１００ｍｍ、好ましくは０．１〜１０ｍｍのものが使用される。繊維シートとして長尺物を使用し、これを連続的に供給しながら製造することができ、このようにすると生産性良く、吸水性複合体を得ることができる。また、これらの繊維の直径は０．１〜１，０００μｍ、好ましくは１〜１００μｍである。
【００２０】
また、前記吸水性バインダーは、支持体、吸水性ポリマー及びバインダー同士を接着固定するために、吸水性複合体の柔軟性と密接な関係がある。そのため、前記バインダーは柔軟性のあるものがよく、具体的には、ガラス転移点が室温以下の架橋重縮合物が好適に用いられる。また、該バインダーは、それ自身が吸水膨張性を有することが望ましい。該バインダーを吸水膨張性とすることにより、得られる吸水性複合体の膨張異方性が向上し、さらに、優れた吸水力、保水力、柔軟性等が達成されるとともに、吸水性複合体中の吸水性ポリマー量を増加させ、相対的に支持体量を減らし、得られる吸水性複合体を薄型化することができる。具体的には、前記吸水性バインダーは、生理食塩水に対する遠心分離操作後の吸収倍率が５ｇ／ｇ以上であることが好ましい。該吸収倍率は、後述の方法で測定されるものであり、吸水性複合体の保水性を評価する指標である。該吸収倍率が５ｇ／ｇ未満では、膨張異方性、吸収力が向上せず、また、吸水性複合体の薄型化に寄与しないので好ましくない。このような吸水性バインダーとしては、ポリアリルアミン、ポリアルキレンポリアミン、ポリエチレンイミン、ポリビニルアミン、ポリ（メタ）アクリルアミドのマンニッヒ反応物、ポリ（メタ）アクリルアミン、ジアルキルアミノアルキル（メタ）アクリレートのホモポリマーまたは（メタ）アクリルアミドとのコポリマー、ジアルキルアミノアルキル（メタ）アクリレートをハロゲン化アルキル（例えば塩化メチル、塩化エチル、臭化メチル等）で４級化アンモニウム塩としたもののホモポリマーまたはその（メタ）アクリルアミドとのコポリマー、ポリジアルキルアリルアミン４級アンモニウム塩、４級化ビニルベンジルアミンのポリマー、キトサンのアセチル化物、エピクロルヒドリンと多価アミンまたはモノアミンとの縮合反応物等が挙げられる。これらのポリマーの重合中、または重合後に架橋剤を加えて架橋させたバインダーは、多数のカチオン性基を持ったポリカチオンであり、アニオン性の吸収性ポリマーと強いイオン結合を形成するため吸水膨張後も強い接着力を持つことができるので、吸水性バインダーとして好ましく用いられる。
【００２１】
前記吸水性バインダーの製造に用いられるジアルキルアミノアルキル（メタ）アクリレートのハロゲン化アルキル４級塩としては、例えばＮ，Ｎ−ジメチルアミノエチル（メタ）アクリレート、Ｎ，Ｎ−ジメチルアミノプロピル（メタ）アクリレート、Ｎ，Ｎ−ジチルアミノブチル（メタ）アクリレート、Ｎ，Ｎ−ジエチルアミノエチル（メタ）アクリレート、Ｎ，Ｎ−ジエチルアミノプロピル（メタ）アクリレート等のモノマーのハロゲン化アルキル４級塩が挙げられる。
【００２２】
これらの吸水性バインダーは、重合後のポリマーを溶液、その他の形態で前記支持体に噴霧、塗布等の手段によって固着させてもよいが、モノマーもしくはモノマー混合物またはその水溶液の状態で前記支持体に含浸または付着させたのち、該モノマーまたはモノマー混合物を重縮合させて吸水性バインダーを前記支持体に固着させる方法が望ましい。
【００２３】
前記モノマーまたはモノマー混合物の重合は、重合開始剤の存在下に０〜２００℃、好ましくは５０〜１５０℃の温度で行なわれる。
【００２４】
重合開始剤としては、水溶性または水と混合・分散可能な酸化性またはアゾ系のラジカル性重合開始剤が好適である。例えば、酸化性重合開始剤としては、過硫酸ナトリウム、過硫酸カリウム、過硫酸アンモニウム等の過硫酸塩、過酸化水素、ジ第３ブチルペルオキシド、アセチルペルオキシド等の有機過酸化物等が挙げられ、アゾ系重合開始剤としては、２，２´−アゾビス（２−アミジノプロパン）２塩酸塩、２，２´−アゾビス（Ｎ，Ｎ´−ジメチレンイソブチルアミジン）２塩酸塩、４，４´−アゾビス（４−シアノ吉草酸）等のアゾ化合物を挙げることができる。
【００２５】
また、必要によりこれらの酸化性重合開始剤とアゾ系重合開始剤の併用に加え、さらに上記重合開始剤を複数併用したり亜硫酸塩やＬ−アスコルビン酸等の還元性物質を添加してレドックス重合を行なってもよい。重合開始剤は、前記モノマーの合計量に対して０．００１〜１０重量％、好ましくは０．０１〜１重量％用いられる。
【００２６】
この際、必要に応じ前記モノマーの合計量に対して０．０００１〜１０重量％、好ましくは０．０１〜２重量％の架橋剤が必要により配合される。架橋剤としては、分子中に２個以上の不飽和二重結合を有する化合物、例えばＮ，Ｎ´−メチレンビス（メタ）アクリルアミド、（ポリ）エチレングリコールジ（メタ）アクリレート、（ポリ）プロピレングリコールジ（メタ）アクリレート、トリメチロールプロパントリ（メタ）アクリレート、トリメチロールプロパンジ（メタ）アクリレート、グリセリントリ（メタ）アクリレート、グリセリンアクリレートメタクリレート、エチレンオキサイド変性トリメチロールプロパントリ（メタ）アクリレート、ペンタエリスリトールテトラ（メタ）アクリレート、ジペンタエリスリトールヘキサ（メタ）アクリレート、トリアリルシアヌレート、トリアリルイソシアヌレート、トリアリルホスフェート、トリアリルアミン、ポリ（メタ）アリロキシアルカン、グリシジル（メタ）アクリレート、Ｎ−メチロールアクリルアミド、（ポリ）エチレングリコールジグリシジルエーテル、グリセロールジグリシジルエーテル等を挙げることができる。
【００２７】
前記支持体１００重量部に対する前記吸水性バインダーの固着量は１〜１０，０００重量部、好ましくは１０〜５，０００重量部、最も好ましくは５０〜１，０００重量部である。
【００２８】
つぎに、前記吸水性ポリマーとしては、水溶性のエチレン性不飽和モノマーのホモポリマーまたはコポリマー等が挙げられる。このようなモノマーとしては、例えば、アクリル酸、メタクリル酸、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、（メタ）アリルスルホン酸、および、それらのアルカリ金属塩やアンモニウム塩等のアニオン性吸水性ポリマーを挙げることができ、これらの１種または２種以上を用いることができる。好ましくはアクリル酸またはその塩である。
【００２９】
前記モノマー中には、必要によりモノマーの合計量に対して０．０００１〜１０重量％、好ましくは０．０１〜２重量％の架橋剤が配合される。架橋剤としては、分子中に２個以上の不飽和二重結合を有する化合物、例えばＮ，Ｎ´−メチレンビス（メタ）アクリルアミド、（ポリ）エチレングリコールジ（メタ）アクリレート、（ポリ）プロピレングリコールジ（メタ）アクリレート、トリメチロールプロパントリ（メタ）アクリレート、トリメチロールプロパンジ（メタ）アクリレート、グリセリントリ（メタ）アクリレート、グリセリンアクリレートメタクリレート、エチレンオキサイド変性トリメチロールプロパントリ（メタ）アクリレート、ペンタエリスリトールテトラ（メタ）アクリレート、ジペンタエリスリトールヘキサ（メタ）アクリレート、トリアリルシアヌレート、トリアリルイソシアヌレート、トリアリルホスフェート、トリアリルアミン、ポリ（メタ）アリロキシアルカン、グリシジル（メタ）アクリレート、Ｎ−メチロールアクリルアミド、（ポリ）エチレングリコールジグリシジルエーテル、グリセロールジグリシジルエーテル、エチレングリコール、ポリエチレングリコール、プロピレングリコール、グリセリン、ペンタエリスリトール、エチレンジアミン、ポリエチレンイミン、硫酸アルミニウムなどを挙げることができる。
【００３０】
これら吸水性ポリマーは、予め重合器中で重合され、必要により乾燥、粉砕されて粒子として得られる。すなわち、前記モノマーもしくはモノマー混合物またはその水溶液を、重合器中で重合開始剤の存在下に０〜２００℃、好ましくは５０〜１５０℃の温度で重合する。
【００３１】
重合開始剤としては、水溶性または水と混合・分散可能な酸化性またはアゾ系のラジカル性重合開始剤が好適である。例えば、酸化性重合開始剤としては、過硫酸ナトリウム、過硫酸カリウム、過硫酸アンモニウム等の過硫酸塩；過酸化水素；ジ第３ブチルペルオキシド、アセチルペルオキシド等の有機過酸化物等が挙げられ、アゾ系重合開始剤としては、２，２´−アゾビス（２−アミジノプロパン）２塩酸塩、２，２´−アゾビス（Ｎ，Ｎ´−ジメチレンイソブチルアミジン）２塩酸塩、４，４´−アゾビス（４−シアノ吉草酸）等のアゾ化合物を挙げることができる。
【００３２】
また、必要によりこれらの酸化性重合開始剤とアゾ系重合開始剤の併用に加え、さらに上記重合開始剤を複数併用したり亜硫酸塩やＬ−アスコルビン酸等の還元性物質を添加してレドックス重合を行なってもよい。重合開始剤は、前記モノマーの合計量に対して０．００１〜１０重量％、好ましくは０．０１〜１重量％用いられる。得られる吸水性ポリマー粒子の平均粒径は、１，０００〜１０μｍ、好ましくは６００〜１００μｍである。
【００３３】
得られた吸水性ポリマー粒子は、前記吸水性バインダー粒子が固着されている支持体上に、散布、その他の方法で均一に分散されたのち、プレス等の手段で該吸水性バインダー表面に固着される。その量は、該吸水性バインダー１００重量部に対して、１０〜１０，０００重量部、好ましくは１００〜１，０００重量部である。
【００３４】
このようにして得られた吸水性複合体は、例えば支持体として繊維状物を使用した場合には、繊維に固着した吸水性バインダーを介して吸水性ポリマー粒子が繊維に固着した状態になっている。
【００３５】
本発明の吸水性複合体は、さらに高い膨張異方性を付与するため、上記により得られた吸水性複合体をさらに加圧したり、複数枚重ね合わせて加圧した構造とすることが好ましい。複数枚の吸水性複合体を重ね合わせるには、単に加圧してもよいが、必要に応じて接合表面を加湿してもよい。
【００３６】
また、本発明の吸水性複合体は、吸水性複合体の表面近傍に親水性を付与し、液体の拡散吸水速度を改善するため、微小親水性繊維を該吸水性複合体の表面近傍に付着させることが好ましい。微小親水性繊維としては、セルロースパウダー、ミルトファイバー等が挙げられる。また、該微小親水性繊維の付着量は、前記吸水性複合体の総重量に対し０．０１〜５重量％がよい。該微小親水性繊維の付着量が０．０１重量％未満では微小親水性繊維の添加の効果が得られず、５重量％を超えると戻り量が増えコストも高くなるので好ましくない。
【００３７】
本発明の吸水性複合体は、前述の生理食塩水に対する遠心分離操作後の吸収倍率が１０ｇ／ｇ以上であることが好ましい。吸水性複合体の該吸収倍率が１０ｇ／ｇ未満では、膨張異方性、吸収力が低くなり吸収物品に使用した際の性能が上がらないため好ましくない。
【００３８】
前記の方法で作成された吸水性複合体は、高い圧縮弾性率をもつ支持体空間中に、吸水性ポリマーをイオン性接着力を有する柔軟なバインダーを介して固定した構造をもつ。また、該構造体の総重量に対する吸水性ポリマーの含有量は３０重量％以上の高濃度である。このような構造体に水性液体を接触させると、水性液体は支持体間、または支持体と吸水性ポリマーおよびバインダー間の空間を毛細管現象によって瞬時に拡散し、水性液体が保持される。これと同時に吸水性ポリマーの吸水膨張が始まり、前記の効果を助長し、構造体をさらに膨張させる。しかし、吸水性ポリマーはバインダーを介して支持体に固定されているため、等方向には膨張できず、所定の一方向にのみ膨張し、該吸水性複合体は膨張異方性を示すものである。また、該吸水性複合体における膨張力は、主に吸水性ポリマーの吸水膨張に起因しているため、高加圧下状態においても良好な膨張異方性、吸収力を示す。さらに、吸水性複合体が複数枚加圧されている場合については、上記の現象がより顕著に現れるため、膨張異方性はより大きくなる。
【００３９】
つぎに、本発明の吸水性物品は、液体透過性の表面シートと、液体非透過性の裏面シートとの間に前記吸水性複合体を含むものであればよく、該吸水性複合体の機能を阻害しない範囲であれば、紙、繊維、無機粒子等の他の素材を含んでもよい。前記表面シートとしては、液体透過性を有するものであれば特に限定されるものではなく、たとえば不織布、織布、紙、メッシュシート等を用いることができるが、中でもポリエチレン、ポリプロピレン、ポリエステル、ポリアミド等の合成繊維からなる不織布シートが好適に用いられる。また、前記裏面シートとしては、非透水性のものであれば特に限定されるものではないが、たとえば、ポリエチレン、ポリプロピレン、ポリ塩化ビニル、ポリ塩化ビニリデン、ポリビニルアルコール等の合成樹脂フィルムが好適に用いられる。
【００４０】
また、本発明の吸水性複合体の用途は、前記衛生材用吸水性物品に限定されるものでなく、該吸水性複合体の膨張異方性を利用した機能性材料やおもちゃ等の分野にも使用することができる。
【００４１】
なお、本発明の吸水性複合体を吸水性物品として利用する場合は、少なくとも５ｃｍ3 、好ましくは１０〜２００ｃｍ3 の体積を有し、厚さが０．２ｍｍ以上、好ましくは０．５〜５ｍｍ、密度が０．３〜１．１ｇ／ｃｍ3 、好ましくは０．３〜１．０ｇ／ｃｍ3 の範囲であるシート状物が好ましい。また、その垂直吸引力が５ｃｍ以上、好ましくは６．５〜１０ｃｍ、加圧下吸水量が２０ｇ／ｇ以上、好ましくは２３ｇ／ｇ以上、ガーレー剛性が１０００ｍｇｆＮ以下、好ましくは０〜５００ｍｇｆＮであるものが好ましい。ただし、本発明の吸水性複合体を前記の機能を利用した新規な吸収体として用いる場合にはこの限りではない。
【００４２】
【実施例】
つぎに、実施例を挙げて本発明をさらに詳細に説明する。
【００４３】
なお、本発明の参考例、実施例および比較例で得られた吸水性ポリマーまたは吸水性複合体の吸収特性は、以下の方法により測定した。
【００４４】
（１）吸収倍率
０．２ｇの吸水性ポリマー粒子または吸水性複合体を６ｃｍ×６ｃｍの不織布のティーバッグ式袋に入れて縁部をヒートシールした。これを生理食塩水（０．９％食塩水）に３０分間浸漬し、その後遠心分離器（２５０Ｇ）で３分間余剰の生理食塩水を除去して重量（Ｗ１）を測定した。別に吸水性ポリマー粒子または吸水性複合体を入れずに同様の操作を行いブランク値の重量（Ｗ０）とした。（Ｗ１）より（Ｗ０）を差し引いた値を、吸水性ポリマー粒子または吸水性複合体の重量（０．２ｇ）で除して吸収倍率（ｇ／ｇ）とした。
【００４５】
（２）加圧下吸収量
内径１６０ｍｍ、高さ２０ｍｍのガラスシャーレ中に直径１２０ｍｍのガラスフィルター板（Ｇ＃１）を置き、０．４％食塩水をガラスフィルター板の頂部まで満たして、濾紙（東洋濾紙会社製 ＦＩＬＴＥＲ ＰＡＰＡＥＲ Ｎｏ．２）をガラスフィルター板の上に載せた。つぎに、内径６０ｃｍ、高さ６０ｃｍの円筒の底部に４００メッシュのステンレス製の金網を固定したアクリル樹脂容器中に０．９ｇの吸水性ポリマー粒子を均一に散布し、さらに円筒内部に５０ｇ／ｃｍ2 の加重を載せて円筒集合体とし、重量（Ｗ１）を測定した。この円筒集合体を濾紙上に載せ、３０分間０．４％食塩水を吸収させた。吸収中はガラスシャーレ中の０．４％食塩水の液量を一定に保持した。３０分後に円筒集合体の重量（Ｗ２）を測定し、（Ｗ２）より（Ｗ１）を差し引いた値を吸収前の吸水性樹脂の重量で除して加圧下吸収量（ｇ／ｇ）とした。
【００４６】
吸水体が吸水性複合体の場合は、３．１ｃｍ×３．１ｃｍの大きさに打ち抜いて秤量してアクリル容器底部に置き、荷重が５０ｇ／ｃｍ2 となるように調整して同様の操作で加圧下吸収量（ｇ／ｇ）を求めた。
【００４７】
（３）吸水速度
１平方インチ（２．５４ｃｍ×２．５４ｃｍ）に打ち抜いた吸水性複合体の重量を秤量し、つぎに、内径Φ５．５ｃｍ、高さ１．５ｃｍのポリプロピレン容器内に、吸水性複合体の重量の１０倍の０．４％食塩水を注いだ。打ち抜いた吸水性複合体を液中に投入し、すべての液を吸収するまで（４５度に傾けて液だまりができない状態）の時間を測定し、吸水速度（秒）とした。
【００４８】
（４）垂直吸引力
吸水性複合体を２ｃｍ×１０ｃｍの帯状に切り取り、生理食塩水中に吸水性複合体の先端が２ｍｍ浸漬するようにして垂直に吊り下げた。６０分後に吸水性複合体の先端から垂直方向に液を吸い上げた距離を測定し垂直吸引力（ｃｍ）とした。
【００４９】
（５）柔軟性
吸水性複合体を２．５４ｃｍ×８．８９ｃｍ（１インチ×３．５インチ）の帯状に打ち抜き、温度２５℃および湿度５０％中においてＪＩＳ−Ｌ−１０９６に規定されたガーレー剛性の測定法に基づいて柔軟性を測定した。さらに、これを温度７０℃で３時間乾燥させた後、同様にして測定した。
【００５０】
（６）圧縮弾性率
吸水性複合体の支持体不織布を５ｃｍ×５ｃｍの試験片に打ち抜き３枚に重ねＪＩＳ−Ｌ−１０９６記載の方法に準じた圧縮弾性度試験機（押金５ｃｍ）により初期荷重７ｇ／ｃｍ2 のもとで厚さ（Ｔ０）を測り、次に荷重を１５０ｇ／ｃｍ2 にして１分間放置して厚さ（Ｔ１）を測った。その後荷重を除き１分間放置した後、再び荷重を初期荷重と同じ７ｇ／ｃｍ2 にして厚さ（Ｔ２）を測り、次式により圧縮弾性率（％）を算出した。圧縮弾性率の測定は５回行い、その平均値を採用した。
【００５１】
圧縮弾性率（％）＝｛（Ｔ２）−（Ｔ１）｝／｛（Ｔ０）−（Ｔ１）｝×１００
（７）膨張異方性
吸水性複合体を５ｃｍ×５ｃｍの試験片に打ち抜き各辺の長さ、Ｘ軸方向長さ（Ｘ０）、Ｙ軸方向長さ（Ｙ０）、Ｚ軸方向長さ（Ｚ０）を測定した。試験片を生理食塩水に３０分間浸漬し、その後遠心分離機（２５０Ｇ）で３分間余剰の生理食塩水を除去した。膨張した吸水性複合体のＸ軸（Ｘ１）、Ｙ軸（Ｙ１）、Ｚ軸（Ｚ１）長さを測定し次式により膨張異方性を算出した。
【００５２】
Ｘ軸方向の線膨潤倍率（Ｅｘ）＝（Ｘ１）／（Ｘ０）
Ｙ軸方向の線膨潤倍率（Ｅｙ）＝（Ｙ１）／（Ｙ０）
Ｚ軸方向の線膨潤倍率（Ｅｚ）＝（Ｚ１）／（Ｚ０）
膨張異方性＝（Ｅｚ／Ｅｘ＋Ｅｚ／Ｅｙ）／２
（８）傾斜流出試験
縦１５ｃｍ×横７ｃｍに切断した吸水性複合体を４５度に傾けた傾斜面に取り付け、シート上端面より７ｍｌ／秒の速度で生理食塩水を滴下し吸水シートに吸水させた。吸水シートが液を吸収しきれなくなり下方から溢れ出る時を終点とし、注入開始から終点までの時間（秒）と、終点までに吸水シートが吸収した液重量（ｇ）を測定した。
【００５３】
（９）戻り量
１２ｃｍ×２５ｃｍの大きさに切断した吸水性複合体の上に子供用おむつ（商品名：パンパース プロクター・アンド・ギャンブル・ ファーイースト・インク社製）と称する紙おむつから取り出した不織布を重ね合わせ同じ大きさに切断することにより簡易吸収体を作成した。作成した簡易吸収体を２枚のアクリル板間に挟んで載置した。なお、上側のアクリル板は簡易吸収体の中央部に対応する位置に内径２３ｍｍの液注入管を備えた構造になっており、簡易吸収体の中央に吸収液を注入することができる。この状態で液注入管に生理食塩水５０ｍｌを３０分おきに計３回注入し、３回目の操作を行ってから３０分後に上面のアクリル板を取り外し、あらかじめブランク重量を測定したキッチンタオル（商品名：ネピア 新王子製紙株式会社製）１０枚を二つ折りにして簡易吸収上に載置し、その上に荷重を載せて５７ｇ／ｃｍ2 の圧力がかかるようにした。１分後にキッチンタオル１０枚を取り出して重量を測定し、あらかじめ測定しておいたキッチンタオル１０枚のブランク重量を差し引いて増加分の重量を求め、戻り量（ｇ）とした。
【００５４】
［参考例１］
坪量３０ｇ／ｍ2 、圧縮弾性率７２％のポリエステル不織布（厚さ２ｍｍ）に対して、Ｎ，Ｎ−ジメチルアミノエチルアクリレート塩化メチル４級塩（７９％水溶液）１００重量部、トリメチロールプロパントリアクリレート０．４９重量部、ヒドロキシエチルセルロース１．２重量部、過硫酸ナトリウム０．２９重量部および脱イオン水４５．５重量部よりなる単量体水溶液をその付着量が１２７ｇ／ｍ2 となるように付着せしめた。ついで、該単量体水溶液が付着した不織布を窒素雰囲気下に１００℃で１０分間保持して単量体の重合を行い、吸水性バインダーが不織布に固着した支持体シートを得た。得られた支持体シートの吸水性バインダー付着量は７０ｇ／ｍ2 、吸収倍率は１０ｇ／ｇであった。
【００５５】
［参考例２］
窒素シールされた除熱可能な反応容器中、７５モル％の中和率を有するアクリル酸ナトリウム塩の水溶液５５００重量部（単量体濃度３７％）に、架橋剤としてトリメチロールプロパントリアクリレート１．７重量部を溶解し、窒素ガスで３０分間脱気後過硫酸アンモニウム２．８重量部およびＬ−アスコルビン酸０．１４重量部を添加し、反応温度３０〜７０℃で重合を行った。重合開始６０分後に重合物を約５ｍｍの径に細分化された含水ゲル重合体として取り出し、該含水ゲル状重合体の細粒化物を５０メッシュ金網に広げて１５０℃で９０分間熱風乾燥を行った。乾燥物をロール型粉砕機を組み合わせて粉砕し、粒子径が１５０〜８５０μｍである吸収倍率３５ｇ／ｇの吸水性ポリマー粒子を得た。得られた吸水性ポリマー粒子１００重量部に対し、グリセリン０．５重量部、水２重量部およびエチルアルコール０．５重量部からなる架橋剤水溶液を添加混合し、得られた混合物を１９６℃で４５分間加熱処理して吸水性ポリマー粒子を得た。吸収倍率は３０ｇ／ｇ、加圧下吸収倍率は２９ｇ／ｇであった。
【００５６】
［参考例３］
参考例２と同様の反応容器中で８０モル％の中和率を有するアクリル酸ナトリウム塩の水溶液５５００重量部（単量体濃度３５％）に、架橋剤としてポリエチレングリコールジアクリレート５．２重量部を溶解し、窒素ガスで３０分間脱気後、過硫酸アンモニウム２．８重量部、２−２’−アゾビス（２−メチルプロピオンアミジン）二塩酸塩０．２重量部およびＬ−アスコルビン酸０．１４重量部を添加し２−２’−アゾビス（２−メチルプロピオンアミジン）二アクリル酸塩を析出させた後、参考例２と同条件下で重合し、粒子径が１５０〜８５０μｍの発泡体である吸水性ポリマー粒子を得た。この吸水性ポリマー粒子を参考例２と同様に後架橋することによって吸水性ポリマー粒子を得た。得られた吸水性ポリマー粒子の吸収倍率は４０ｇ／ｇ、加圧下吸収倍率２８ｇ／ｇで多数の気泡を有した発泡粒子であった。
【００５７】
［参考例４］
参考例１で得られた吸水性バインダーが固着した支持体シートを１０ｃｍ×３０ｃｍの大きさに裁断し、シート全体に参考例２で得られた吸水性ポリマー粒子を添加し、さらに圧力２ｋｇ／ｃｍ2 でプレスし付着させて参考用吸水性複合体を得た。得られた参考用吸水性複合体の坪量は３００ｇ／ｍ2 、厚さは０．７ｍｍ、密度は０．４３ｇ／ｃｍ3 、体積は２１ｃｍ3 であり、吸水性ポリマー粒子の付着量は２００ｇ／ｃｍ2 であった。
【００５８】
［参考例５］
参考例４と同様の操作で、参考例１で得られた吸水性バインダーが固着した支持体シートに参考例３で得られた吸水性ポリマー粒子を付着させ、参考用吸水性複合体を得た。得られた参考用吸水性複合体の坪量は３００ｇ／ｃｍ2 、厚さは０．７ｍｍ、密度は０．４３ｇ／ｃｍ3 、体積は２１ｃｍ3 であり、アニオン性吸収性ポリマー粒子の付着量は２００ｇ／ｃｍ2 であった。
【００５９】
［実施例１］
参考例４で得られた参考用吸水性複合体を２枚重ね合わせてアクリル版に挟み盤面Φ１７ｃｍの簡易プレス機で５ｋｇｆ／ｃｍ2 、１分間プレスした後、表面にセルロースパウダー（ＣＦ１１／Ｗａｔｍａｎ Ｂｉｏ Ｓｙｓｔｅｍｓ Ｌｔｄ製）を３０ｇ／ｍ2 付着させて厚さ１．０ｍｍ、密度０．６ｇ／ｃｍ3 の本発明の吸水性複合体を作成した。
【００６０】
［実施例２］
参考例５で得られた参考用吸水性複合体を２枚使用し、実施例１と同様の操作を繰り返し、厚さ１．０ｍｍ、密度０．５８ｇ／ｃｍ3 の本発明の吸水性複合体を作成した。
【００６１】
［実施例３］
参考例４で得られた参考用吸水性複合体を４枚使用し、実施例１と同様の操作を繰り返し、厚さ１．５ｍｍ、密度０．７７ｇ／ｃｍ3 の本発明の吸水性複合体を作成した。
【００６２】
［実施例４］
参考例５で得られた参考用吸水性複合体を４枚使用し、実施例１と同様の操作を繰り返し、厚さ１．６ｍｍ、密度０．７ｇ／ｃｍ3 の本発明の吸水性複合体を作成した。
【００６３】
［実施例５］
参考例１と同様の操作で坪量１２０ｇ／ｃｍ2 、圧縮弾性率７５％、厚さ８ｃｍのポリエステル不織布に吸水性バインダーを重合、付着させ、２８０ｇ／ｍ2 の吸水性バインダーが固着した支持体シートを作成した。つぎに、参考例４と同様の操作で作成した吸水性バインダーシートに、参考例２で得られた吸水性ポリマー粒子８００ｇ／ｍ2 を付着させ、さらに、実施例１の方法で厚さ１．６ｍｍ、密度０．７ｇ／ｃｍ3 の本発明の吸水性複合体を作成した。
【００６４】
［実施例６］
坪量３０ｇ／ｍ2 、圧縮弾性率７２％のポリエステル不織布（厚さ２ｍｍ）に対して、ポリエチレンイミン（３０％水溶液）２０重量部、エチレングリコールジグリシジルエーテル０．０２５重量部を混合した単量体水溶液をその付着量が４１７ｇ／ｍ2 となるように付着せしめた。ついで、該単量体水溶液が付着した不織布を窒素雰囲気下に８０℃で３０分間保持して、吸水性バインダーが不織布に固着した支持体シートを得た。得られた支持体シートの吸水性バインダー付着量は１２５ｇ／ｍ2 、吸収倍率は５ｇ／ｇであった。
【００６５】
上記で得られた吸水性バインダーが固着した支持体シートを１０ｃｍ×３０ｃｍの大きさに裁断し、シート全体に参考例２で得られた吸水性ポリマー粒子を添加し、さらに圧力２ｋｇ／ｃｍ2 でプレスし付着させて吸水性複合体を得た。得られた吸水性複合体の坪量は３１７ｇ／ｍ2 、厚さは０．７ｍｍ、密度は０．４５ｇ／ｃｍ3 、体積は２１ｃｍ3 であり、吸水性ポリマー粒子の付着量は１６２ｇ／ｍ2 であった。
【００６６】
さらに、この吸水性複合体を４枚使用し、実施例１と同様の操作を繰り返し、厚さ１．６ｍｍ、密度０．７９ｇ／ｃｍ3 の本発明の吸水性複合体を作成した。
［比較例１］
参考例２で得られた吸水性ポリマー粒子５５重量部と、親水性繊維としての木材粉砕パルプ４５重量部とを、ミキサーを用いて乾式混合した。得られた混合物３６ｇを３０ｃｍ×１０ｃｍの枠内に均一に広げて噴霧加温した後、アクリル板に挟み盤面Φ１７ｃｍの簡易プレス機で５ｋｇｆ／ｃｍ2 、１分間プレスし厚さ２．０ｍｍ、密度０．６０ｇ／ｃｍ3 の比較用吸水性複合体を作成した。
【００６７】
［比較例２］
市販されているパルプスポンジ（日本ポリエステル株式会社製）厚さ１．８ｍｍ、密度０．４４ｇ／ｃｍ3 を切断して比較用吸水性複合体とした。
【００６８】
［比較例３］
坪量３０ｇ／ｍ2 、圧縮弾性率７２％のポリエステル不織布に対し、７５％中中和アクリル酸カリウム１００重量部、トリメチロールプロパントリアクリレート０．１７重量部、ヒドロキシエチルセルロース１．２４重量部、過硫酸ナトリウム０．２９重量部および脱イオン水４５．１重量部よりなる単量体水溶液をその付着量が７９０ｇ／ｃｍ2 となるように付着せしめた。ついで、該単量体水溶液が付着した不織布を窒素雰囲気下に１２０℃で３分間保持して単量体の重合を行い、吸水性ポリマーが不織布に固着した吸収倍率１７ｇ／ｇの支持体シートを得た。この支持体シート１００重量部にエチレングリコールジグリシジルエーテル０．５重量部、水３重量部、イソプロピルアルコール１重量部からなる架橋剤水溶液を噴霧添加し、１００℃で３０分間加熱処理して吸収倍率１５ｇ／ｇの吸水性複合体を得た。こうして得られた吸水性複合体を４枚重ね合わせてアクリル板に挟み盤面Φ１７ｃｍの簡易プレス機で５ｋｇｆ／ｃｍ2 、１分間プレスした後、表面にセルロースパウダー（ＣＦ１１／Ｗａｔｍａｎ Ｂｉｏ Ｓｙｓｔｅｍｓ Ｌｔｄ製）を３０ｇ／ｍ2 付着させて厚さ３．０ｍｍ、密度０．６９ｇ／ｃｍ3 の比較用吸水性複合体を作成した。
【００６９】
実施例１〜６および比較例１〜３で得られた吸水性複合体の物性を表１に、吸収特性を表２に示した。
【００７０】
【表１】
【表２】
【発明の効果】
このように、本発明の吸水性複合体は、液体を吸収すると体積が主として厚み方向に膨張し、吸水性物品が体液で湿潤しても嵩が減少することなく逆に嵩が増加するので、人体とのフィット性が高まり漏れの生じない吸水性物品を得ることができる。また、支持体、例えば繊維状物の含有量が少ないので、極めて薄型の吸水性物品を得ることができる。
【００７３】
さらに、本発明の吸水性複合体は、加圧下吸水量が大きいので、漏れの少ない吸水性物品を得ることができる。また、垂直吸引力が大きいので、おむつ等の吸水性物品の全体が使用できる。さらに、ガーレー剛性が小さいので、柔軟性があり、型くずれせずヨレが生じにくいので横漏れ等がなく、装着感にも優れた吸水性物品を得ることができる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a novel water absorbent composite and a water absorbent article. Specifically, the present invention relates to a novel absorbent structure that does not leak and has excellent water absorption, water retention, and flexibility, and a water absorbent article using the same.
[0002]
[Prior art]
Conventionally, in a water-absorbing article such as a sanitary napkin or a paper diaper, a water-absorbing polymer excellent in water-absorbing power and water-holding power has attracted attention as an absorbent material to replace pulp and water-absorbing paper, and application development has been promoted. This water-absorbing polymer has a limit on the absorption rate of body fluids and cannot absorb body fluids unless it is wet with body fluids. Therefore, water-absorbing articles are often used in combination with pulp having a high absorption rate.
[0003]
However, the pulp in the water-absorbent article exhibits a certain degree of compression and bending recovery when dried, but extremely decreases in strength when wet and hardly exhibits such recovery. For this reason, in conventional water-absorbent articles, when complex stress due to the movement of the human body is applied to the water-absorbent article wetted with body fluid, the pulp is deformed, causing the water-absorbent article to be twisted or offset, and the body fluid is distorted. There was a problem that it flowed and caused a side leak. Moreover, the wetness of the body fluid reduced the bulk of the pulp, thereby causing a gap between the water-absorbent article and the human body, and leaking in the same manner.
[0004]
Therefore, various studies have been conducted so far to solve these problems. For example, Japanese Examined Patent Publication No. 3-67712 discloses a method for preventing twisting and deviation from the stress at the time of wearing by using a water-absorbing polymer in a water-absorbing article which is fixed on a support. It is shown. However, these sheets have low expansion anisotropy at the time of water absorption, and the adhesion between the water absorbent article and the human body has not been improved. In addition, in JP-A-3-162855 and JP-A-2-289608, by using cellulose sponge and polyurethane foam having anisotropic expansion property in a water-absorbent article, the absorption rate and adhesion to the human body are disclosed. An improvement in sex is shown. However, both methods use only the elastic restoring force that appears when the compressed sponge or foam comes into contact with water, and the water-absorbing polymer contained in the water-absorbing article is a sponge or It is used only to absorb and retain moisture temporarily held in the foam, and hardly contributes to the expansion of the absorber itself. For this reason, it has the disadvantage that the absorbency under high pressure required for water-absorbing articles such as diapers is low. Further, it has been very difficult to form a water-absorbing polymer in these sponges and foams so as to be dispersed and fixed at a high concentration so as to exhibit expansion anisotropy and not to impair flexibility.
[0005]
[Problems to be solved by the invention]
The present invention has been made in view of the problems of the prior art, and an object of the present invention is to provide a novel water-absorbent composite that does not leak and a water-absorbent article using the same. .
[0006]
Another object of the present invention is to provide a novel water-absorbent composite having excellent water absorption, water retention and flexibility and having a function of specifically expanding in one direction, and a water-absorbent article using the same. is there.
[0007]
[Means for Solving the Problems]
The above problems are solved by the water-absorbent composite of the present invention and the water-absorbent article using the same.
[0008]
That is, the present inventionA fibrous material as a support, and a sheet-like water-absorbing composite containing anionic water-absorbing polymer particles,At least 30% by weight of the total weightThe anionic water-absorbing polymer particlesSpecified by the following formula when liquid is absorbedThickness directionExpansion anisotropy5It is characterized by the aboveSheetIt is a water-absorbing complex.
[0009]
Expansion anisotropy = (Ez / Ex + Ez / Ey) / 2
(Ex, Ey, and Ez are the X-axis direction, Y-axis direction, and Z-axis, respectively.(Thickness)The linear swelling ratio in the direction. )
[0010]
The present invention further includesThe absorption capacity (30 minutes) after centrifugation for physiological saline containing 80% to 99% by weight of the anionic water-absorbing polymer particles with respect to the total weight is 10 g / g. The sheet-like water-absorbing composite as described above.
[0011]
The present invention also providesThe anionic water-absorbing polymer isCationic crosslinked water-absorbing polymer as binderIs fixed to a fibrous material as a support,The sheet-like water-absorbing composite. The present invention also provides the sheet-like water-absorbing composite in which the anionic water-absorbing polymer particles are fixed to the support through the cationic crosslinked water-absorbing polymer and compressed in the thickness direction. In the present invention, the cationic cross-linked water-absorbing polymer has a sheet-like water-absorbing composite having an absorption capacity (30 minutes) after centrifuging with respect to a physiological saline composed of 0.9% saline of 5 g / g or more. Is the body.
[0012]
The present invention further includesThe sheet-like water-absorbing composite having a thickness of 0.2 mm or more, a vertical suction force (60 minutes) with respect to physiological saline of 5 cm or more, and a Gurley rigidity (JIS-L-1096) of 1000 mgfN or less. . The present invention also provides 50 g / cm for 0.4% saline. 2 The sheet-like water-absorbing composite having a water absorption amount under pressure (30 minutes) of 20 g / g or more.
[0013]
The present invention also provides:A sanitary water-absorbing article comprising a sanitary napkin or a paper diaper, the sanitary water-absorbing article including the sheet-like water-absorbing composite between a liquid-permeable top sheet and a liquid-impermeable back sheet. .
[0014]
DETAILED DESCRIPTION OF THE INVENTION
The water-absorbent composite of the present invention is characterized in that the expansion anisotropy specified by the following formula when a liquid is absorbed is 3 or more.
[0015]
Expansion anisotropy = (Ez / Ex + Ez / Ey) / 2
(Ex, Ey, and Ez are linear swelling ratios in the X-axis direction, the Y-axis direction, and the Z-axis direction, respectively.)
The expansion anisotropy is measured by a method to be described later, and is an index representing the degree of expansion in the Z-axis direction with respect to the X-axis direction and the Y-axis direction when the water-absorbing composite absorbs liquid. It is. That is, the water-absorbent composite of the present invention has an anisotropic volume expansion when absorbing a liquid, and expands mainly in the thickness direction. Therefore, even if the water-absorbent article is wetted with body fluid, the bulk does not decrease and conversely increases in volume. Therefore, the water-absorbent article can be obtained with improved fit to the human body and no leakage. When the expansion anisotropy of the water-absorbent composite is less than 3, it is not preferable because sufficient fit with a human body cannot be obtained. Furthermore, the expansion anisotropy is particularly preferably 5 or more.
[0016]
The water-absorbing composite of the present invention contains at least 30% by weight of a water-absorbing polymer with respect to the total weight. By setting the weight ratio of the water-absorbing polymer to 30% by weight or more, the expansion anisotropy and absorptive power of the water-absorbing composite become higher, and the water-absorbing article containing the water-absorbing composite is made thinner and more compact. be able to. In particular, the weight ratio of the water-absorbing polymer is preferably 80 to 99% by weight.
[0017]
The water-absorbing polymer used in the present invention includes a water-absorbing polymer in a water-absorbing composite described later and a water-absorbing binder for fixing the water-absorbing polymer to a support. Specifically, hydrophilic natural polymers and synthetic polymers that are cross-linked or not cross-linked can be used. Examples of natural polymers include starch and cellulose, and examples of synthetic polymers include polyacrylic acid and polyacrylate, polyvinyl alcohol, polyacrylamide, and polyoxyethylene. In this case, polyacrylate and polyacrylamide polymers are preferably used.
[0018]
Examples of the water-absorbing composite of the present invention include a structure in which a water-absorbing polymer is fixed to a support through a water-absorbing binder and compressed in the thickness direction.
[0019]
The support preferably has a compressive elastic modulus of 60% or more, and in particular, a support having a three-dimensional skeleton structure or an open cell structure is preferable because of its strong restoring force upon water absorption. If the compression modulus is less than 60%, the restoring force at the time of water absorption is weak, and high expansion anisotropy is not achieved, which is not preferable. Examples of such a support include foams such as foamed polyurethane, powders, particles, sheets, strips, fibers, and the like, or a combination thereof, preferably a fiber support. is there. As the fibrous support, a fibrous material made of natural or synthetic fiber, natural or synthetic pulp, or the like, particularly a fiber sheet is preferably used. Examples of the fiber sheet include woven fabric, non-woven fabric, paper, and knitted fabric, but non-woven fabric made from various fiber webs is preferable. The fibers can be either hydrophilic fibers or hydrophobic fibers. The hydrophilic fibers are wood pulp, cotton, wool, rayon, acetate, vinylon, etc. The hydrophobic fibers are polyester, acrylic, nylon, polyethylene, polypropylene And polyvinyl chloride, and these blended fibers can also be used. The fibrous sheet includes, for example, a tape-like sheet, and the thickness thereof is not particularly limited. For example, a sheet having a thickness of 0.01 to 100 mm, preferably 0.1 to 10 mm is used. A long sheet is used as the fiber sheet, and it can be produced while being continuously supplied. In this way, a water-absorbing composite can be obtained with good productivity. The diameter of these fibers is 0.1 to 1,000 μm, preferably 1 to 100 μm.
[0020]
The water-absorbing binder has a close relationship with the flexibility of the water-absorbing composite in order to adhere and fix the support, the water-absorbing polymer and the binder. For this reason, the binder is preferably flexible, and specifically, a crosslinked polycondensate having a glass transition point of room temperature or lower is preferably used. Further, it is desirable that the binder itself has water absorbability. By making the binder water-swellable, the expansion anisotropy of the resulting water-absorbing composite is improved, and further, excellent water-absorbing power, water-holding power, flexibility, etc. are achieved, and in the water-absorbing composite The amount of the water-absorbing polymer can be increased, the amount of the support can be relatively decreased, and the resulting water-absorbing composite can be thinned. Specifically, the water-absorbing binder preferably has an absorption capacity of 5 g / g or more after a centrifugal separation operation with respect to physiological saline. The absorption rate is measured by a method described later, and is an index for evaluating the water retention of the water-absorbing composite. If the absorption ratio is less than 5 g / g, the expansion anisotropy and the absorption power are not improved, and it does not contribute to the thinning of the water-absorbent composite. Such water-absorbing binders include polyallylamine, polyalkylenepolyamine, polyethyleneimine, polyvinylamine, Mannich reaction product of poly (meth) acrylamide, homopolymer of poly (meth) acrylamine, dialkylaminoalkyl (meth) acrylate or Copolymer with (meth) acrylamide, homopolymer of dialkylaminoalkyl (meth) acrylate converted to quaternized ammonium salt with alkyl halide (eg methyl chloride, ethyl chloride, methyl bromide, etc.) or its (meth) acrylamide and Copolymer, polydialkylallylamine quaternary ammonium salt, quaternized vinylbenzylamine polymer, acetylated product of chitosan, condensation reaction product of epichlorohydrin and polyvalent amine or monoamine And the like. The binder that is crosslinked by adding a crosslinking agent during or after the polymerization of these polymers is a polycation with a large number of cationic groups, and forms a strong ionic bond with the anionic absorbent polymer to absorb water. Since it can have strong adhesive force later, it is preferably used as a water-absorbing binder.
[0021]
Examples of the halogenated alkyl quaternary salt of dialkylaminoalkyl (meth) acrylate used in the production of the water-absorbing binder include N, N-dimethylaminoethyl (meth) acrylate and N, N-dimethylaminopropyl (meth) acrylate. And alkyl halide quaternary salts of monomers such as N, N-diethylaminobutyl (meth) acrylate, N, N-diethylaminoethyl (meth) acrylate, and N, N-diethylaminopropyl (meth) acrylate.
[0022]
These water-absorbing binders may be obtained by fixing the polymer after polymerization to the support in the form of a solution or other forms by means of spraying, coating, etc., but in the state of a monomer or a monomer mixture or an aqueous solution thereof. After impregnation or adhesion, a method is preferred in which the monomer or monomer mixture is polycondensed to fix the water-absorbing binder to the support.
[0023]
The polymerization of the monomer or monomer mixture is performed in the presence of a polymerization initiator at a temperature of 0 to 200 ° C, preferably 50 to 150 ° C.
[0024]
As the polymerization initiator, an oxidizing or azo radical polymerization initiator that is water-soluble or can be mixed / dispersed with water is suitable. Examples of the oxidative polymerization initiator include persulfates such as sodium persulfate, potassium persulfate, and ammonium persulfate, and organic peroxides such as hydrogen peroxide, di-tert-butyl peroxide, and acetyl peroxide. Examples of the polymerization initiator include 2,2′-azobis (2-amidinopropane) dihydrochloride, 2,2′-azobis (N, N′-dimethyleneisobutylamidine) dihydrochloride, 4,4′-azobis An azo compound such as (4-cyanovaleric acid) can be mentioned.
[0025]
If necessary, in addition to the combined use of these oxidative polymerization initiators and azo polymerization initiators, redox polymerization may be performed by further using a plurality of the above polymerization initiators or adding a reducing substance such as sulfite or L-ascorbic acid. May be performed. The polymerization initiator is used in an amount of 0.001 to 10% by weight, preferably 0.01 to 1% by weight, based on the total amount of the monomers.
[0026]
At this time, if necessary, a crosslinking agent of 0.0001 to 10% by weight, preferably 0.01 to 2% by weight, based on the total amount of the monomers is blended as necessary. Examples of the crosslinking agent include compounds having two or more unsaturated double bonds in the molecule, such as N, N′-methylenebis (meth) acrylamide, (poly) ethylene glycol di (meth) acrylate, and (poly) propylene glycol diester. (Meth) acrylate, trimethylolpropane tri (meth) acrylate, trimethylolpropane di (meth) acrylate, glycerin tri (meth) acrylate, glycerin acrylate methacrylate, ethylene oxide modified trimethylolpropane tri (meth) acrylate, pentaerythritol tetra ( (Meth) acrylate, dipentaerythritol hexa (meth) acrylate, triallyl cyanurate, triallyl isocyanurate, triallyl phosphate, triallylamine, poly (meth) allylo Shiarukan, glycidyl (meth) acrylate, N- methylol acrylamide, and (poly) ethylene glycol diglycidyl ether, glycerol diglycidyl ether.
[0027]
The amount of the water-absorbing binder fixed to 100 parts by weight of the support is 1 to 10,000 parts by weight, preferably 10 to 5,000 parts by weight, and most preferably 50 to 1,000 parts by weight.
[0028]
Next, examples of the water-absorbing polymer include homopolymers or copolymers of water-soluble ethylenically unsaturated monomers. Examples of such monomers include acrylic acid, methacrylic acid, 2- (meth) acryloylethanesulfonic acid, 2- (meth) acryloylpropanesulfonic acid, 2- (meth) acrylamido-2-methylpropanesulfonic acid, vinyl Examples thereof include sulfonic acid, (meth) allylsulfonic acid, and anionic water-absorbing polymers such as alkali metal salts and ammonium salts thereof, and one or more of these can be used. Acrylic acid or a salt thereof is preferable.
[0029]
If necessary, the monomer contains 0.0001 to 10% by weight, preferably 0.01 to 2% by weight of a crosslinking agent based on the total amount of monomers. Examples of the crosslinking agent include compounds having two or more unsaturated double bonds in the molecule, such as N, N′-methylenebis (meth) acrylamide, (poly) ethylene glycol di (meth) acrylate, and (poly) propylene glycol diester. (Meth) acrylate, trimethylolpropane tri (meth) acrylate, trimethylolpropane di (meth) acrylate, glycerin tri (meth) acrylate, glycerin acrylate methacrylate, ethylene oxide modified trimethylolpropane tri (meth) acrylate, pentaerythritol tetra ( (Meth) acrylate, dipentaerythritol hexa (meth) acrylate, triallyl cyanurate, triallyl isocyanurate, triallyl phosphate, triallylamine, poly (meth) allylo Sialkane, glycidyl (meth) acrylate, N-methylol acrylamide, (poly) ethylene glycol diglycidyl ether, glycerol diglycidyl ether, ethylene glycol, polyethylene glycol, propylene glycol, glycerin, pentaerythritol, ethylenediamine, polyethyleneimine, aluminum sulfate, etc. Can be mentioned.
[0030]
These water-absorbing polymers are polymerized in advance in a polymerization vessel and, if necessary, dried and pulverized to obtain particles. That is, the monomer or monomer mixture or an aqueous solution thereof is polymerized in a polymerization vessel in the presence of a polymerization initiator at a temperature of 0 to 200 ° C, preferably 50 to 150 ° C.
[0031]
As the polymerization initiator, an oxidizing or azo radical polymerization initiator that is water-soluble or can be mixed / dispersed with water is suitable. Examples of the oxidative polymerization initiator include persulfates such as sodium persulfate, potassium persulfate, and ammonium persulfate; hydrogen peroxide; organic peroxides such as di-tert-butyl peroxide and acetyl peroxide. Examples of the polymerization initiator include 2,2′-azobis (2-amidinopropane) dihydrochloride, 2,2′-azobis (N, N′-dimethyleneisobutylamidine) dihydrochloride, 4,4′-azobis An azo compound such as (4-cyanovaleric acid) can be mentioned.
[0032]
If necessary, in addition to the combined use of these oxidative polymerization initiators and azo polymerization initiators, redox polymerization may be performed by further using a plurality of the above polymerization initiators or adding a reducing substance such as sulfite or L-ascorbic acid. May be performed. The polymerization initiator is used in an amount of 0.001 to 10% by weight, preferably 0.01 to 1% by weight, based on the total amount of the monomers. The average particle diameter of the water-absorbing polymer particles obtained is 1,000 to 10 μm, preferably 600 to 100 μm.
[0033]
The obtained water-absorbing polymer particles are dispersed and uniformly dispersed on the support on which the water-absorbing binder particles are fixed, and then fixed to the surface of the water-absorbing binder by means such as a press. The The amount thereof is 10 to 10,000 parts by weight, preferably 100 to 1,000 parts by weight with respect to 100 parts by weight of the water-absorbing binder.
[0034]
In the water-absorbing composite obtained in this way, for example, when a fibrous material is used as the support, the water-absorbing polymer particles are fixed to the fiber via the water-absorbing binder fixed to the fiber. Yes.
[0035]
The water-absorbing composite of the present invention preferably has a structure in which the water-absorbing composite obtained as described above is further pressurized or a plurality of sheets are stacked and pressed in order to impart higher expansion anisotropy. In order to superimpose a plurality of water-absorbing composites, pressure may be simply applied, but the bonding surfaces may be humidified as necessary.
[0036]
In addition, the water-absorbent composite of the present invention attaches minute hydrophilic fibers to the vicinity of the surface of the water-absorbent composite in order to impart hydrophilicity to the vicinity of the surface of the water-absorbent composite and improve the diffusion water absorption rate of the liquid. It is preferable to make it. Examples of the micro hydrophilic fiber include cellulose powder and milt fiber. The adhesion amount of the micro hydrophilic fibers is preferably 0.01 to 5% by weight with respect to the total weight of the water-absorbent composite. If the adhesion amount of the micro hydrophilic fiber is less than 0.01% by weight, the effect of adding the micro hydrophilic fiber cannot be obtained, and if it exceeds 5% by weight, the amount of return increases and the cost increases.
[0037]
The water-absorbing complex of the present invention preferably has an absorption capacity of 10 g / g or more after the centrifugation operation with respect to the aforementioned physiological saline. If the absorption capacity of the water-absorbent composite is less than 10 g / g, the expansion anisotropy and the absorptive power are lowered, and the performance when used in an absorbent article is not preferable.
[0038]
The water-absorbing composite prepared by the above method has a structure in which a water-absorbing polymer is fixed via a flexible binder having an ionic adhesive force in a support space having a high compression modulus. The content of the water-absorbing polymer with respect to the total weight of the structure is a high concentration of 30% by weight or more. When the aqueous liquid is brought into contact with such a structure, the aqueous liquid instantaneously diffuses between the supports or between the support and the water-absorbing polymer and the binder by capillary action, and the aqueous liquid is retained. At the same time, the water-absorbing polymer begins to absorb water, promotes the above effects, and further expands the structure. However, since the water-absorbing polymer is fixed to the support through a binder, it cannot expand in the same direction, and expands only in one predetermined direction, and the water-absorbing composite exhibits expansion anisotropy. is there. Further, since the expansion force in the water-absorbing composite is mainly due to the water absorption expansion of the water-absorbing polymer, it exhibits good expansion anisotropy and absorption power even under a high pressure condition. Furthermore, in the case where a plurality of water-absorbing composites are pressurized, the above phenomenon appears more remarkably, so that the expansion anisotropy becomes larger.
[0039]
Next, the water-absorbent article of the present invention only needs to include the water-absorbing composite between the liquid-permeable top sheet and the liquid-impermeable back sheet, and the function of the water-absorbing composite is as follows. Other materials such as paper, fiber, and inorganic particles may be included as long as they do not interfere with the above. The surface sheet is not particularly limited as long as it has liquid permeability, and for example, a nonwoven fabric, a woven fabric, paper, a mesh sheet or the like can be used, among which polyethylene, polypropylene, polyester, polyamide, etc. The nonwoven fabric sheet which consists of these synthetic fibers is used suitably. Further, the back sheet is not particularly limited as long as it is water-impermeable, but for example, a synthetic resin film such as polyethylene, polypropylene, polyvinyl chloride, polyvinylidene chloride, and polyvinyl alcohol is preferably used. It is done.
[0040]
The use of the water-absorbing composite of the present invention is not limited to the water-absorbing article for sanitary materials, but in the field of functional materials and toys that utilize the expansion anisotropy of the water-absorbing composite. Can also be used.
[0041]
When the water-absorbing composite of the present invention is used as a water-absorbing article, at least 5 cmThree, Preferably 10-200cmThreeThe thickness is 0.2 mm or more, preferably 0.5 to 5 mm, and the density is 0.3 to 1.1 g / cm.Three, Preferably 0.3 to 1.0 g / cmThreeThe sheet-like material which is the range of these is preferable. Further, the vertical suction force is 5 cm or more, preferably 6.5 to 10 cm, the water absorption under pressure is 20 g / g or more, preferably 23 g / g or more, and the Gurley rigidity is 1000 mgfN or less, preferably 0 to 500 mgfN. preferable. However, this is not the case when the water-absorbing composite of the present invention is used as a novel absorber utilizing the above-mentioned function.
[0042]
【Example】
Next, the present invention will be described in more detail with reference to examples.
[0043]
The absorption characteristics of the water-absorbing polymers or water-absorbing composites obtained in Reference Examples, Examples and Comparative Examples of the present invention were measured by the following method.
[0044]
(1) Absorption rate
0.2 g of the water-absorbing polymer particles or the water-absorbing composite was placed in a 6 cm × 6 cm non-woven tea bag bag, and the edges were heat sealed. This was immersed in physiological saline (0.9% saline) for 30 minutes, and then excess physiological saline was removed for 3 minutes with a centrifuge (250G), and the weight (W1) was measured. Separately, the same operation was performed without adding the water-absorbing polymer particles or the water-absorbing composite, and the weight of the blank value (W0) was obtained. The value obtained by subtracting (W0) from (W1) was divided by the weight (0.2 g) of the water-absorbent polymer particles or the water-absorbent composite to obtain the absorption capacity (g / g).
[0045]
(2) Absorption under pressure
Place a glass filter plate (G # 1) with a diameter of 120 mm in a glass petri dish with an inner diameter of 160 mm and a height of 20 mm, fill 0.4% saline solution to the top of the glass filter plate, and filter paper (FILTER PAPAER No. manufactured by Toyo Roshi Kaisha Co., Ltd.) .2) was placed on a glass filter plate. Next, 0.9 g of water-absorbing polymer particles are uniformly dispersed in an acrylic resin container in which a 400-mesh stainless steel wire mesh is fixed to the bottom of a cylinder having an inner diameter of 60 cm and a height of 60 cm, and further 50 g / cm inside the cylinder.2The weight (W1) was measured. This cylindrical assembly was placed on a filter paper and absorbed with 0.4% saline for 30 minutes. During absorption, the amount of 0.4% saline in the glass petri dish was kept constant. After 30 minutes, the weight (W2) of the cylindrical assembly was measured, and the value obtained by subtracting (W1) from (W2) was divided by the weight of the water-absorbent resin before absorption to obtain the amount absorbed under pressure (g / g). .
[0046]
When the water-absorbing body is a water-absorbing composite, it is punched into a size of 3.1 cm × 3.1 cm, weighed and placed on the bottom of the acrylic container, and the load is 50 g / cm.2The amount of absorption under pressure (g / g) was determined by the same operation.
[0047]
(3) Water absorption speed
The weight of the water-absorbing composite punched out to 1 square inch (2.54 cm × 2.54 cm) was weighed, and then the weight of the water-absorbing composite was placed in a polypropylene container having an inner diameter of Φ5.5 cm and a height of 1.5 cm. 10 times of 0.4% saline was poured. The punched water-absorbing composite was put into the liquid, and the time until all the liquid was absorbed (tilted at 45 degrees and no liquid pool was possible) was measured and taken as the water absorption speed (seconds).
[0048]
(4) Vertical suction force
The water-absorbing composite was cut into a 2 cm × 10 cm band and suspended vertically so that the tip of the water-absorbing composite was immersed 2 mm in physiological saline. After 60 minutes, the distance at which the liquid was sucked up vertically from the tip of the water-absorbing composite was measured and used as the vertical suction force (cm).
[0049]
(5) Flexibility
The water-absorbing composite was punched into a 2.54 cm × 8.89 cm (1 inch × 3.5 inch) belt and measured for Gurley stiffness as defined in JIS-L-1096 at a temperature of 25 ° C. and a humidity of 50%. Flexibility was measured on the basis. Further, this was dried at a temperature of 70 ° C. for 3 hours and then measured in the same manner.
[0050]
(6) Compression modulus
The support nonwoven fabric of the water-absorbing composite is punched into 5 cm × 5 cm test pieces, stacked on 3 sheets, and the initial load is 7 g / cm by a compression elasticity tester (presser 5 cm) according to the method described in JIS-L-1096.2Measure the thickness (T0) under the load, then load 150g / cm2And left for 1 minute to measure the thickness (T1). Then, after removing the load and leaving it for 1 minute, the load is again 7 g / cm which is the same as the initial load.2Then, the thickness (T2) was measured, and the compression modulus (%) was calculated by the following formula. The compression modulus was measured 5 times and the average value was adopted.
[0051]
Compression modulus (%) = {(T2) − (T1)} / {(T0) − (T1)} × 100
(7) Expansion anisotropy
The water-absorbing composite was punched into a 5 cm × 5 cm test piece, and the length of each side, the X-axis direction length (X0), the Y-axis direction length (Y0), and the Z-axis direction length (Z0) were measured. The test piece was immersed in physiological saline for 30 minutes, and then the excess physiological saline was removed with a centrifuge (250G) for 3 minutes. The X axis (X1), Y axis (Y1), and Z axis (Z1) lengths of the expanded water-absorbing composite were measured, and the expansion anisotropy was calculated according to the following formula.
[0052]
X-axis direction linear swelling ratio (Ex) = (X1) / (X0)
Y axis direction linear swelling ratio (Ey) = (Y1) / (Y0)
Z-axis direction linear swelling ratio (Ez) = (Z1) / (Z0)
Expansion anisotropy = (Ez / Ex + Ez / Ey) / 2
(8) Inclined runoff test
The water-absorbing composite cut to 15 cm in length and 7 cm in width was attached to an inclined surface inclined at 45 degrees, and physiological saline was dropped from the upper end surface of the sheet at a rate of 7 ml / second to allow the water-absorbing sheet to absorb water. When the water absorbent sheet could not absorb the liquid and overflowed from below, the end point was measured, and the time (seconds) from the start of injection to the end point and the liquid weight (g) absorbed by the water absorbent sheet up to the end point were measured.
[0053]
(9) Return amount
A non-woven fabric taken from a paper diaper called a children's diaper (trade name: Pampers Procter & Gamble Far East, Inc.) is superposed on the water-absorbent composite cut into a size of 12 cm x 25 cm. A simple absorbent was prepared by cutting into pieces. The prepared simple absorbent was placed between two acrylic plates. The upper acrylic plate has a structure including a liquid injection tube having an inner diameter of 23 mm at a position corresponding to the central portion of the simple absorbent body, and can absorb the absorbent into the center of the simple absorbent body. In this state, 50 ml of physiological saline was injected into the liquid injection tube every 30 minutes for a total of 3 times, and after 30 minutes from the third operation, the top acrylic plate was removed, and the blank weight was measured beforehand. Name: Napier Shin Oji Paper Co., Ltd.) 10 sheets folded in two and placed on a simple absorbent, and a load is placed on top of it to 57 g / cm2The pressure was applied. One minute later, 10 kitchen towels were taken out and weighed, and the weight of the increment was obtained by subtracting the blank weight of 10 kitchen towels measured in advance, and used as the return amount (g).
[0054]
[Reference Example 1]
Basis weight 30g / m2, 100 parts by weight of N, N-dimethylaminoethyl acrylate methyl chloride quaternary salt (79% aqueous solution), 0.49 parts by weight of trimethylolpropane triacrylate with respect to a polyester nonwoven fabric (thickness 2 mm) having a compression modulus of 72% A monomer aqueous solution consisting of 1.2 parts by weight of hydroxyethyl cellulose, 0.29 parts by weight of sodium persulfate and 45.5 parts by weight of deionized water has an adhesion amount of 127 g / m.2It was made to adhere so that it might become. Subsequently, the nonwoven fabric to which the aqueous monomer solution was adhered was held at 100 ° C. for 10 minutes in a nitrogen atmosphere to polymerize the monomer, thereby obtaining a support sheet in which the water-absorbing binder was fixed to the nonwoven fabric. The amount of water-absorbing binder attached to the obtained support sheet is 70 g / m.2The absorption capacity was 10 g / g.
[0055]
[Reference Example 2]
In a nitrogen-sealed reaction vessel capable of removing heat, 5500 parts by weight of an aqueous solution of sodium acrylate having a neutralization rate of 75 mol% (monomer concentration: 37%), trimethylolpropane triacrylate as a crosslinking agent After dissolving 7 parts by weight and degassing with nitrogen gas for 30 minutes, 2.8 parts by weight of ammonium persulfate and 0.14 part by weight of L-ascorbic acid were added, and polymerization was carried out at a reaction temperature of 30 to 70 ° C. 60 minutes after the start of the polymerization, the polymer was taken out as a hydrogel polymer that had been subdivided to a diameter of about 5 mm, and the fine granule of the hydrogel polymer was spread on a 50 mesh wire net and dried with hot air at 150 ° C. for 90 min. It was. The dried product was pulverized in combination with a roll-type pulverizer to obtain water-absorbing polymer particles having an absorption ratio of 35 g / g and a particle diameter of 150 to 850 μm. To 100 parts by weight of the obtained water-absorbing polymer particles, an aqueous solution of a crosslinking agent consisting of 0.5 parts by weight of glycerin, 2 parts by weight of water and 0.5 parts by weight of ethyl alcohol was added and mixed, and the resulting mixture was heated at 196 ° C. Water-absorbing polymer particles were obtained by heat treatment for 45 minutes. The absorption capacity was 30 g / g, and the absorption capacity under pressure was 29 g / g.
[0056]
[Reference Example 3]
In the same reaction vessel as in Reference Example 2, 5500 parts by weight of an aqueous solution of sodium acrylate having a neutralization rate of 80 mol% (monomer concentration 35%) and 5.2 parts by weight of polyethylene glycol diacrylate as a crosslinking agent After degassing with nitrogen gas for 30 minutes, 2.8 parts by weight of ammonium persulfate, 0.2 part by weight of 2-2′-azobis (2-methylpropionamidine) dihydrochloride and 0.14 of L-ascorbic acid After adding 2 parts by weight and precipitating 2-2'-azobis (2-methylpropionamidine) diacrylate, it is polymerized under the same conditions as in Reference Example 2 and is a foam having a particle size of 150 to 850 μm. Water-absorbing polymer particles were obtained. The water absorbent polymer particles were post-crosslinked in the same manner as in Reference Example 2 to obtain water absorbent polymer particles. The obtained water-absorbing polymer particles had an absorption rate of 40 g / g and an absorption rate of 28 g / g under pressure, and were foamed particles having many bubbles.
[0057]
[Reference Example 4]
The support sheet to which the water-absorbent binder obtained in Reference Example 1 was fixed was cut into a size of 10 cm × 30 cm, the water-absorbing polymer particles obtained in Reference Example 2 were added to the entire sheet, and the pressure was further 2 kg / cm.2To obtain a water-absorbing composite for reference. The basis weight of the obtained water-absorbing composite for reference is 300 g / m2, Thickness is 0.7mm, density is 0.43g / cmThreeThe volume is 21cmThreeThe amount of water-absorbing polymer particles deposited is 200 g / cm2Met.
[0058]
[Reference Example 5]
In the same manner as in Reference Example 4, the water-absorbing polymer particles obtained in Reference Example 3 were adhered to the support sheet to which the water-absorbent binder obtained in Reference Example 1 was fixed, to obtain a water-absorbing composite for reference. . The basis weight of the obtained water-absorbing composite for reference is 300 g / cm2, Thickness is 0.7mm, density is 0.43g / cmThreeThe volume is 21cmThreeAnd the adhesion amount of the anionic absorbent polymer particles is 200 g / cm2Met.
[0059]
[Example 1]
Two superabsorbent composites for reference obtained in Reference Example 4 are overlapped and sandwiched between acrylic plates and 5 kgf / cm with a simple press machine with a disk surface of Φ17 cm.2After pressing for 1 minute, cellulose powder (CF11 / manufactured by Watman Bio Systems Ltd) is applied to the surface at 30 g / m.2Adhered to a thickness of 1.0 mm and a density of 0.6 g / cmThreeThe water-absorbing composite of the present invention was prepared.
[0060]
[Example 2]
Using two reference water-absorbing composites obtained in Reference Example 5 and repeating the same operation as in Example 1, the thickness was 1.0 mm and the density was 0.58 g / cm.ThreeThe water-absorbing composite of the present invention was prepared.
[0061]
[Example 3]
Using four reference water-absorbing composites obtained in Reference Example 4 and repeating the same operation as in Example 1, the thickness was 1.5 mm and the density was 0.77 g / cm.ThreeThe water-absorbing composite of the present invention was prepared.
[0062]
[Example 4]
Using four reference water-absorbing composites obtained in Reference Example 5 and repeating the same operation as in Example 1, the thickness was 1.6 mm and the density was 0.7 g / cm.ThreeThe water-absorbing composite of the present invention was prepared.
[0063]
[Example 5]
Basis weight 120g / cm in the same operation as Reference Example 1.2A water-absorbing binder is polymerized and adhered to a polyester nonwoven fabric having a compression modulus of 75% and a thickness of 8 cm, and 280 g / m.2A support sheet to which the water-absorbent binder was fixed was prepared. Next, 800 g / m of water-absorbing polymer particles obtained in Reference Example 2 were applied to the water-absorbing binder sheet prepared in the same manner as in Reference Example 4.2Further, a thickness of 1.6 mm and a density of 0.7 g / cm by the method of Example 1 were applied.ThreeThe water-absorbing composite of the present invention was prepared.
[0064]
[Example 6]
Basis weight 30g / m2The adhering amount of the monomer aqueous solution in which 20 parts by weight of polyethyleneimine (30% aqueous solution) and 0.025 parts by weight of ethylene glycol diglycidyl ether were mixed with a polyester nonwoven fabric (thickness 2 mm) having a compression modulus of 72%. 417g / m2It was made to adhere so that it might become. Subsequently, the nonwoven fabric to which the aqueous monomer solution was adhered was held at 80 ° C. for 30 minutes in a nitrogen atmosphere to obtain a support sheet in which the water-absorbing binder was fixed to the nonwoven fabric. The amount of water-absorbing binder attached to the obtained support sheet is 125 g / m.2The absorption capacity was 5 g / g.
[0065]
The support sheet to which the water-absorbing binder obtained above is fixed is cut into a size of 10 cm × 30 cm, the water-absorbing polymer particles obtained in Reference Example 2 are added to the whole sheet, and the pressure is further 2 kg / cm.2To obtain a water-absorbing composite. The basis weight of the water-absorbing composite obtained was 317 g / m2, Thickness is 0.7mm, density is 0.45g / cmThreeThe volume is 21cmThreeThe adsorbed amount of the water-absorbing polymer particles is 162 g / m2Met.
[0066]
Furthermore, using 4 sheets of this water-absorbing composite, the same operation as in Example 1 was repeated to obtain a thickness of 1.6 mm and a density of 0.79 g / cmThreeThe water-absorbing composite of the present invention was prepared.
[Comparative Example 1]
55 parts by weight of the water-absorbing polymer particles obtained in Reference Example 2 and 45 parts by weight of pulverized wood pulp as hydrophilic fibers were dry-mixed using a mixer. After 36 g of the obtained mixture was uniformly spread in a 30 cm × 10 cm frame and sprayed and heated, it was sandwiched between acrylic plates and 5 kgf / cm with a simple press machine with a disk surface of Φ17 cm.2Pressed for 1 minute, thickness 2.0mm, density 0.60g / cmThreeA comparative water-absorbing composite was prepared.
[0067]
[Comparative Example 2]
Commercially available pulp sponge (manufactured by Nippon Polyester Co., Ltd.) thickness 1.8 mm, density 0.44 g / cmThreeWas cut into a comparative water-absorbing composite.
[0068]
[Comparative Example 3]
Basis weight 30g / m2, 100% by weight of neutralized potassium acrylate in 75%, 0.17 parts by weight of trimethylolpropane triacrylate, 1.24 parts by weight of hydroxyethyl cellulose, 0.29 parts by weight of sodium persulfate with respect to a polyester nonwoven fabric having a compression modulus of 72% A monomer aqueous solution consisting of 45.1 parts by weight of deionized water and an adhesion amount of 790 g / cm2It was made to adhere so that it might become. Next, the nonwoven fabric to which the aqueous monomer solution was adhered was held at 120 ° C. for 3 minutes in a nitrogen atmosphere to polymerize the monomer, and a support sheet having an absorption rate of 17 g / g in which the water-absorbing polymer was fixed to the nonwoven fabric was obtained. Obtained. To 100 parts by weight of this support sheet, an aqueous solution of a crosslinking agent consisting of 0.5 parts by weight of ethylene glycol diglycidyl ether, 3 parts by weight of water, and 1 part by weight of isopropyl alcohol is added by spraying, followed by heat treatment at 100 ° C. for 30 minutes. A 15 g / g water-absorbing composite was obtained. Four sheets of water-absorbing composites obtained in this way are stacked and sandwiched between acrylic plates and 5 kgf / cm with a simple press machine with a disk surface of Φ17 cm.2After pressing for 1 minute, cellulose powder (CF11 / manufactured by Watman Bio Systems Ltd) is applied to the surface at 30 g / m.2Adhering to a thickness of 3.0mm, density 0.69g / cmThreeA comparative water-absorbing composite was prepared.
[0069]
Table 1 shows the physical properties of the water-absorbing composites obtained in Examples 1 to 6 and Comparative Examples 1 to 3, and Table 2 shows the absorption characteristics.
[0070]
[Table 1]
[Table 2]
【The invention's effect】
Thus, the water-absorbent composite of the present invention, when the liquid is absorbed, the volume mainly expands in the thickness direction, and even if the water-absorbent article is wet with body fluid, the bulk increases without decreasing, It is possible to obtain a water-absorbent article that is highly fit with the human body and does not leak. Moreover, since there is little content of a support body, for example, a fibrous material, an extremely thin water-absorbing article can be obtained.
[0073]
Furthermore, since the water-absorbent composite of the present invention has a large amount of water absorption under pressure, a water-absorbent article with little leakage can be obtained. Moreover, since the vertical suction force is large, the entire water-absorbing article such as a diaper can be used. Furthermore, since the Gurley rigidity is small, the water-absorbent article is flexible, does not lose its shape, and does not easily twist, so there is no side leakage and the like, and the water-absorbing article is also excellent in wearing feeling.
Claims (11)
少なくとも総重量に対し３０重量％の前記アニオン性吸水性ポリマー粒子を含有し、
前記アニオン性吸水性ポリマーが、バインダーを介して、支持体としての繊維状物に固着され、
液体を吸収したときの下記式で特定される厚み方向の膨張異方性が５以上であることを特徴とするシート状吸水性複合体。
膨張異方性＝（Ｅｚ／Ｅｘ＋Ｅｚ／Ｅｙ）／２
（ただし、Ｅｘ、ＥｙおよびＥｚは、それぞれ、Ｘ軸方向、Ｙ軸方向およびＺ軸（厚み）方向の線膨潤倍率である。）A fibrous material as a support, and a sheet-like water-absorbing composite containing anionic water-absorbing polymer particles,
Containing at least 30% by weight of the anionic water-absorbing polymer particles based on the total weight;
The anionic water-absorbing polymer is fixed to a fibrous material as a support through a binder,
A sheet-like water-absorbing composite having an expansion anisotropy in the thickness direction specified by the following formula when absorbing a liquid of 5 or more.
Expansion anisotropy = (Ez / Ex + Ez / Ey) / 2
(Ex, Ey, and Ez are the linear swelling ratios in the X-axis direction, the Y-axis direction, and the Z-axis (thickness) direction, respectively.)
液体透過性表面シートと、液体非透過性裏面シートとの間に、請求項１〜１０記載のシート状吸水性複合体を含む衛生用吸水性物品。A sanitary water-absorbent article comprising a sanitary napkin or a paper diaper,
Sanitary water-absorbent article comprising the sheet-like water-absorbent composite according to claim 1 between a liquid-permeable top sheet and a liquid-impermeable back sheet.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP24069396A JP4073508B2 (en) | 1996-07-12 | 1996-09-11 | Water-absorbing composite and water-absorbing article |
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
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| JP8-183816 | 1996-07-12 | ||
| JP18381696 | 1996-07-12 | ||
| JP24069396A JP4073508B2 (en) | 1996-07-12 | 1996-09-11 | Water-absorbing composite and water-absorbing article |
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| JP4073508B2 true JP4073508B2 (en) | 2008-04-09 |
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| JP24069396A Expired - Fee Related JP4073508B2 (en) | 1996-07-12 | 1996-09-11 | Water-absorbing composite and water-absorbing article |
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| WO2000055418A1 (en) | 1999-03-16 | 2000-09-21 | Mitsubishi Chemical Corporation | Water-absorbing composite and process for continuously producing the same |
| ATE507809T1 (en) | 2000-12-08 | 2011-05-15 | Daio Seishi Kk | ABSORPTION AGENT, METHOD FOR THE PRODUCTION THEREOF AND ABSORBENT ITEMS COMPRISING THE ABSORPTION AGENT |
| WO2004052985A1 (en) * | 2002-12-11 | 2004-06-24 | Corovin Gmbh | Hydrophilic polyolefin materials and method for producing the same |
| JP2005015995A (en) * | 2003-06-06 | 2005-01-20 | Mitsubishi Chemicals Corp | Process for producing absorbent article |
| JP4214868B2 (en) * | 2003-09-04 | 2009-01-28 | パナソニック株式会社 | Electroacoustic transducer and electronic device using the same |
| US8921244B2 (en) * | 2005-08-22 | 2014-12-30 | The Procter & Gamble Company | Hydroxyl polymer fiber fibrous structures and processes for making same |
| TWI780494B (en) * | 2019-10-09 | 2022-10-11 | 德商卡爾科德寶兩合公司 | Application of composite materials for absorption and distribution of liquids in actively and/or passively cooled energized systems |
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