JP2004001355A - Absorber, absorbent article, water absorbent resin, and its manufacturing method and evaluating method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an absorber, an absorbent article and a water absorbent resin which can be used suitable for this absorber, the absorbent article which realize both diffusing capability and storing capability of liquid, realize in dry feeling and return volume of liquid and which provides thin shape more and weight reduction. <P>SOLUTION: The absorber includes a liquid diffusing member and the water absorbent resin. When a capillary absorption index in height of 40cm of the liquid diffusing member is referred to as A (concerning A≥0.10), a capillary absorption index B in height of 40cm as the water absorbing resin satisfies formula 1 (B/A≥0.7) is used. <P>COPYRIGHT: (C)2004,JPO

Description

【０１５４】
【表２】

【０１５５】
（参考例８）吸水性樹脂（４）の製造方法
アクリル酸ナトリウム（中和率７５モル％）の３３重量％水溶液５５００部に、ポリエチレングリコールジアクリレート（ｎ＝８）４．９部を溶解させて反応液とした。次に、この反応液を窒素ガス雰囲気下で３０分間脱気した。次いで、開閉可能な蓋付きのシグマ型羽根を２本有するジャケット付きステンレス製双腕型ニーダーに、上記反応液を供給し、反応液を３０℃に保ちながら系を窒素ガス置換した。続いて、反応液を撹拌しながら、過硫酸アンモニウム２．４部およびＬ−アスコルビン酸０．１２部を添加したところ、凡そ１分後に重合が開始した。そして、３０〜９０℃で重合を行い、重合を開始して６０分後に含水ゲル状重合体を取り出した。
【０１５６】
得られた含水ゲル状重合体は、その径が約５ｍｍに細分化されていた。この細分化された含水ゲル状重合体を５０メッシュの金網上に広げ、１５０℃で９０分間熱風乾燥した。次いで、乾燥物を振動ミルを用いて粉砕し、さらに２０メッシュの金網で分級することにより、重量平均粒子径が３４０μｍで、しかも、粒径が１０６μｍ未満の粒子の割合が３重量％の不定形破砕状の樹脂を得た。
得られた樹脂１００重量部に、エチレングリコールジグリシジルエーテル０．０５重量部と、プロピレングリコール０．９重量部と、水３重量部、イソプロピルアルコール１重量部とからなる表面架橋剤組成液を混合した。上記の混合物を１９５℃で４０分間加熱処理することにより、吸水性樹脂（４）を得た。吸水性樹脂（４）の重量平均粒子径は３４７μｍであった。また吸水性樹脂（４）の０ｃｍの高さにおける毛管吸収倍率は３９．９（ｇ／ｇ）、４０ｃｍの高さにおける毛管吸収倍率Ｄは１１．４（ｇ／ｇ）、４０ｃｍの高さにおける毛管吸収指数Ｂは０．２９であった。
【０１５７】
（参考例９）吸水性樹脂（５）の製造方法
アクリル酸ナトリウム（中和率７１モル％）の３８重量％水溶液５５００部に、ポリエチレングリコールジアクリレート（ｎ＝８）８．１部を溶解させて反応液とした。次に、この反応液を窒素ガス雰囲気下で３０分間脱気した。次いで、開閉可能な蓋付きのシグマ型羽根を２本有するジャケット付きステンレス製双腕型ニーダーに、上記反応液を供給し、反応液を３０℃に保ちながら系を窒素ガス置換した。続いて、反応液を撹拌しながら、過硫酸アンモニウム２．４部およびＬ−アスコルビン酸０．１２部を添加したところ、凡そ１分後に重合が開始した。そして、２０〜９５℃で重合を行い、重合を開始して６０分後に含水ゲル状重合体を取り出した。
【０１５８】
得られた含水ゲル状重合体は、その径が約５ｍｍに細分化されていた。この細分化された含水ゲル状重合体を５０メッシュの金網上に広げ、１５０℃で９０分間熱風乾燥した。次いで、乾燥物を振動ミルを用いて粉砕し、さらに目開き８５０μｍの篩を通過し１０６μｍの篩上に残る、重量平均粒子径が４００μｍの不定形破砕状の樹脂を得た。
得られた樹脂１００重量部に、１，４−ブタンジオール０．３重量部と、プロピレングリコール０．５重量部、水３重量部とからなる表面架橋剤組成液を混合した。上記の混合物を２１０℃で３０分間加熱処理したあと親水性二酸化ケイ素微粉末（日本アエロジル社製、アエロジル２００）０．５部を加えて表面部分にコーティングし、吸水性樹脂（５）を得た。吸水性樹脂（５）の重量平均粒子径は５００μｍであった。また吸水性樹脂（５）の０ｃｍの高さにおける毛管吸収倍率は３７．４（ｇ／ｇ）、４０ｃｍの高さにおける毛管吸収倍率Ｄは２．８（ｇ／ｇ）、４０ｃｍの高さにおける毛管吸収指数Ｂは０．０８であった。
【０１５９】
（参考例１０）液獲得部材（１）
液獲得部材として、市販の子供用おむつ（Ｐ＆Ｇパンパースさらさらケア、サイズＬ，おむつ重量５７ｇ）に用いられていた上下を不織布で覆われた状態の架橋セルロースをとりだし、８ｃｍ×３０ｃｍの大きさで液獲得部材（１）として使用した。また液獲得部材（１）の０ｃｍの高さにおける毛管吸収倍率は１４．４（ｇ／ｇ）、４０ｃｍの高さにおける毛管吸収倍率Ｃは０．１８（ｇ／ｇ）、４０ｃｍの高さにおける毛管吸収指数Ａは０．０１４であった。
（参考例１１）液獲得部材（２）
液獲得部材として、子供用おむつに使用する綿状パルプ３ｇを８ｃｍ×３０ｃｍの大きさに広げシート化し、液獲得部材（２）として使用した（密度０．０３ｇ／ｃｍ^３で坪量２６０ｇ／ｍ^２）。液獲得部材（２）の０ｃｍの高さにおける毛管吸収倍率は１３．８（ｇ／ｇ）、４０ｃｍの高さにおける毛管吸収倍率Ｃは０．５３（ｇ／ｇ）、４０ｃｍの高さにおける毛管吸収指数Ａは０．０３８であった。
【０１６０】
（実施例８）
吸水性樹脂（４）１６．４ｇを１２×３８ｃｍの面積に散布して散布量３６０ｇ／ｍ^２の吸水性樹脂層を形成させ、その上に前述の作成方法に従い液獲得部材（１）（１２×２４ｃｍ、重量３．８ｇ）を載置した吸収体（１２）を得た。液獲得部材（１）の４０ｃｍの高さにおける毛管吸収指数Ａに対する吸水性樹脂（４）の４０ｃｍの高さにおける毛管吸収指数Ｂの比Ｂ／Ａ＝２０．７、液獲得部材（１）の４０ｃｍの高さにおける毛管吸収倍率Ｃは０．１８（ｇ／ｇ）であり、吸水性樹脂（４）の４０ｃｍの高さにおける毛管吸収倍率Ｄは１１．４（ｇ／ｇ）あった。
【０１６１】
吸収体（１２）を用いて前述の作成方法に従いモデルおむつとしての吸収性物品（１２）を作成し、通液時間、白化時間、液獲得部材中の残存液量、戻り量を求めた。結果を表３に示したが、白化時間も速く、液獲得部材中の残存液量が少なく、戻り量も少ないことから、液獲得部材から吸水性樹脂層が液を良好に吸収しドライ感に優れたおむつが得られることがわかる。
（実施例９）
実施例８と同様にして吸水性樹脂（２）と液獲得部材（１）を組合わせた吸収体（１３）を得た。液獲得部材（１）の４０ｃｍの高さにおける毛管吸収指数Ａに対する吸水性樹脂（２）の４０ｃｍの高さにおける毛管吸収指数Ｂの比Ｂ／Ａ＝４１．０、液獲得部材（１）の４０ｃｍの高さにおける毛管吸収倍率は０．１８（ｇ／ｇ）であり、吸水性樹脂（２）の４０ｃｍの高さにおける毛管吸収倍率Ｄは１９．４（ｇ／ｇ）あった。
【０１６２】
吸収体（１３）を用いて前述の作成方法に従いモデルおむつとしての吸収性物品（１３）を作成し、通液時間、白化時間、液獲得部材中の残存液量、戻り量を求めた。結果を表３に示したが、白化時間も速く、液獲得部材中の残存液量が少なく、戻り量も少ないことから、液獲得部材から吸水性樹脂層が液を良好に吸収しドライ感に優れたおむつが得られることがわかる。
（実施例１０）
実施例８と同様にして吸水性樹脂（１）と液獲得部材（１）を組合わせた吸収体（１４）を得た。液獲得部材（１）の４０ｃｍの高さにおける毛管吸収指数Ａに対する吸水性樹脂（１）の４０ｃｍの高さにおける毛管吸収指数Ｂの比Ｂ／Ａ＝４３．０、液獲得部材（１）の４０ｃｍの高さにおける毛管吸収倍率は０．１８（ｇ／ｇ）であり、吸水性樹脂（１）の４０ｃｍの高さにおける毛管吸収倍率Ｄは２７．４（ｇ／ｇ）あった。
【０１６３】
吸収体（１４）を用いて前述の作成方法に従いモデルおむつとしての吸収性物品（１４）を作成し、通液時間、白化時間、液獲得部材中の残存液量、戻り量を求めた。結果を表３に示したが、白化時間も速く、液獲得部材中の残存液量が少なく、戻り量も少ないことから、液獲得部材から吸水性樹脂層が液を良好に吸収しドライ感に優れたおむつが得られることがわかる。
（実施例１１）
実施例８と同様にして吸水性樹脂（４）と液獲得部材（２）を組合わせた吸収体（１５）を得た。液獲得部材（２）の４０ｃｍの高さにおける毛管吸収指数Ａに対する吸水性樹脂（４）の４０ｃｍの高さにおける毛管吸収指数Ｂの比Ｂ／Ａ＝７．６、液獲得部材（２）の４０ｃｍの高さにおける毛管吸収倍率は０．５３（ｇ／ｇ）であり、吸水性樹脂（４）の４０ｃｍの高さにおける毛管吸収倍率Ｄは１１．４（ｇ／ｇ）あった。
【０１６４】
吸収体（１５）を用いて前述の作成方法に従いモデルおむつとしての吸収性物品（１５）を作成し、通液時間、白化時間、液獲得部材中の残存液量、戻り量を求めた。結果を表３に示したが、白化時間も速く、液獲得部材中の残存液量が少なく、戻り量も少ないことから、液獲得部材から吸水性樹脂層が液を良好に吸収しドライ感に優れたおむつが得られることがわかる。
（比較例５）
実施例８と同様にして吸水性樹脂（５）と液獲得部材（１）を組合わせた吸収体（１６）を得た。液獲得部材（１）の４０ｃｍの高さにおける毛管吸収指数Ａに対する吸水性樹脂（５）の４０ｃｍの高さにおける毛管吸収指数Ｂの比Ｂ／Ａ＝５．４、液獲得部材（１）の４０ｃｍの高さにおける毛管吸収倍率は０．１８（ｇ／ｇ）であり、吸水性樹脂（５）の４０ｃｍの高さにおける毛管吸収倍率Ｄは２．８（ｇ／ｇ）あった。
【０１６５】
吸収体（１６）を用いて前述の作成方法に従いモデルおむつとしての吸収性物品（１６）を作成し、通液時間、白化時間、液獲得部材中の残存液量、戻り量を求めた。結果を表４に示したが、白化時間が遅く、液獲得部材中の残存液量、戻り量も多くことから液獲得部材から吸水性樹脂層への液の吸収がスムーズに行えていないことがわかる。
（比較例６）
実施例８と同様にして吸水性樹脂（３）と液獲得部材（１）を組合わせた吸収体（１７）を得た。液獲得部材（１）の４０ｃｍの高さにおける毛管吸収指数Ａに対する吸水性樹脂（３）の４０ｃｍの高さにおける毛管吸収指数Ｂの比Ｂ／Ａ＝８．１、液獲得部材（１）の４０ｃｍの高さにおける毛管吸収倍率は０．１８（ｇ／ｇ）であり、吸水性樹脂（３）の４０ｃｍの高さにおける毛管吸収倍率Ｄは４．３（ｇ／ｇ）あった。
【０１６６】
吸収体（１７）を用いて前述の作成方法に従いモデルおむつとしての吸収性物品（１７）を作成し、通液時間、白化時間、液獲得部材中の残存液量、戻り量を求めた。結果を表４に示したが、白化時間が遅く、戻り量も多いことから液獲得部材から吸水性樹脂層への液の吸収がスムーズに行えていないことがわかる。
（比較例７）
吸水性樹脂（４）８．２ｇと子供用おむつに使用する綿状パルプ８．２ｇを混合し、１２×３８ｃｍのブレンドコアを作成した。このものの毛管吸収能力を表４に示した。液獲得部材（１）と上記ブレンドコアを表４に記載の使用量で組み合わせ、吸収体（１８）を得た。液獲得部材（１）の４０ｃｍの高さにおける毛管吸収指数Ａに対する上記ブレンドコアの４０ｃｍの高さにおける毛管吸収指数Ｂの比Ｂ／Ａ＝５．６、液獲得部材（１）の４０ｃｍの高さにおける毛管吸収倍率は０．１８（ｇ／ｇ）であり、上記ブレンドコアの４０ｃｍの高さにおける毛管吸収倍率は２．３（ｇ／ｇ）あった。
【０１６７】
吸収体（１８）を用いて前述の作成方法に従いモデルおむつとしての吸収性物品（１８）を作成し、吸液速度、液拡散材のドライ速度、１時間後の液獲得部材中の残存液量、戻り量を求めた。結果を表４に示したが、白化時間が遅く、液獲得部材中の残存液量、戻り量も多くことから液獲得部材から吸水性樹脂層への液の吸収がスムーズに行えていないことがわかる。
（比較例８）
実施例８において液拡散部材を用いない他は同様の操作を行いモデルおむつとしての吸収性物品（１９）を作成し、吸液速度、液拡散材のドライ速度、１時間後の液獲得部材中の残存液量、戻り量を求めた。結果を表４に示したが、通液時間が非常に遅く、液がスムーズに吸収されないことがわかる。
【０１６８】
【表３】

【０１６９】
【表４】

【０１７０】
（参考例１２）吸水性樹脂（６）の製造方法
アクリル酸ナトリウム（中和率７５モル％）の３３重量％水溶液５５００部に、ポリエチレングリコールジアクリレート（ｎ＝８）４．９部を溶解させて反応液とした。次に、この反応液を窒素ガス雰囲気下で３０分間脱気した。次いで、開閉可能な蓋付きのシグマ型羽根を２本有するジャケット付きステンレス製双腕型ニーダーに、上記反応液を供給し、反応液を３０℃に保ちながら系を窒素ガス置換した。続いて、反応液を撹拌しながら、過硫酸アンモニウム２．４部およびＬ−アスコルビン酸０．１２部を添加したところ、凡そ１分後に重合が開始した。そして、３０〜９０℃で重合を行い、重合を開始して６０分後に含水ゲル状重合体を取り出した。
【０１７１】
得られた含水ゲル状重合体は、その径が約５ｍｍに細分化されていた。この細分化された含水ゲル状重合体を５０メッシュの金網上に広げ、１５０℃で９０分間熱風乾燥した。次いで、乾燥物を振動ミルを用いて粉砕し、さらに３０メッシュの金網で分級することにより、重量平均粒子径が２８０μｍで、しかも、粒径が１０６μｍ未満の粒子の割合が５重量％の不定形破砕状の吸水性樹脂前駆体を得た。
得られた吸水性樹脂前駆体１００重量部に、エチレングリコールジグリシジルエーテル０．０５重量部と、プロピレングリコール０．９重量部と、水３重量部、イソプロピルアルコール１重量部とからなる表面架橋剤組成液を混合した。上記の混合物を１９５℃で４０分間加熱処理することにより、吸水性樹脂（６）を得た。吸水性樹脂（６）の重量平均粒子径は２６５μｍであった。また吸水性樹脂（６）の４０ｃｍの高さにおける毛管吸収倍率Ｄは１１．４（ｇ／ｇ）であった。吸水性樹脂（６）の粒度分布は、１５０〜８５０μｍの粒子が９０重量％、１５０μｍ未満の粒子が１０重量％であった。
【０１７２】
（参考例１３）水分散性微粒子の分散液
水分散性微粒子として、アエロジル２００（超微粒子の酸化硅素、日本アエロジル株式会社製）５重量部をイオン交換水７０重量部を高速攪拌混合機（２０００ｒｐｍ）で２時間混合させた。混合後、２４時間で室温放置し、水分散性微粒子の分散液を得た。水分散性微粒子の粘度は１０００ｃｐｓであった。
（実施例１２）
吸水性樹脂（６）１００重量部に対して、参考例１３で得た水分散性粒子の分散液を７重量部添加混合し、６０℃で３０分放置後、混合物を解砕し、全ての粒子を８５０μｍの開孔を有する金網を通過せしめ本発明の吸水性樹脂粒子（１）を得た。この物の粒度分布は、１５０〜８５０μｍの粒子が９７重量％、１５０μｍ以下の粒子が３重量％であった。また重量平均粒子径は５００μｍであった。結果を表５に示した。
【０１７３】
得られた吸収性樹脂粒子（１）と液獲得部材（２）を用い、前述の方法に従い、モデルおむつとしての吸収性物品（２０）を作成し、通液時間、拡散面積、戻り量を上記評価方法に従って評価し表５に示した。
（実施例１３）
参考例１３で得た水分散性粒子の分散液を７重量部とイオン水１３重量部を混合し分散液を得た。吸水性樹脂（２）１００重量部に対して、分散液を２０重量部添加混合し、６０℃で３０分放置後、混合物を解砕し、全ての粒子を８５０μｍの開孔を有する金網を通過せしめ本発明の吸水性樹脂粒子（２）を得た。この物の粒度分布は、１５０〜８５０μｍの粒子が８５重量％、１５０μｍ以下の粒子が１５重量％であった。また重量平均粒子径は３０８μｍであった。
【０１７４】
得られた吸収性樹脂粒子（２）と液獲得部材（２）を用い、前述の方法に従い、モデルおむつとしての吸収性物品（２１）を作成し、通液時間、拡散面積、戻り量を上記評価方法に従って評価し表５に示した。
（比較例９）
吸水性樹脂（２）１００重量部に対して、アエロジル２００（二酸化珪素微粉末、日本アエロジル株式会社製）を０．５重量部を加えて吸収性樹脂を混合し、更にイオン交換水２０重量部を添加混合した。６０℃で３０分放置後、混合物を解砕し、全ての粒子を８５０μｍの開孔を有する金網を通過せしめ吸水性樹脂粒子（３）を得た。この物の粒度分布は、１５０〜８５０μｍの粒子が５９重量％、１５０μｍ以下の粒子が４１重量％であった。また重量平均粒子径は１７４μｍであった。
【０１７５】
得られた吸収性樹脂粒子（３）と液獲得部材（２）を用い、前述の方法に従い、モデルおむつとしての吸収性物品（２２）を作成し、通液時間、拡散面積、戻り量を上記評価方法に従って評価し表５に示した。
（比較例１０）
吸水性樹脂（２）１００重量部に対して、イオン交換水２０重量部を添加混合し、６０℃で３０分放置後、混合物を解砕し、全ての粒子を８５０μｍの開孔を有する金網を通過せしめ吸水性樹脂粒子（４）を得た。この物の粒度分布は、１５０〜８５０μｍの粒子が６１重量％、１５０μｍ以下の粒子が３９重量％であった。また重量平均粒子径は１８０μｍであったが、脆く崩壊し易いものであった。
【０１７６】
得られた吸収性樹脂粒子（４）と液獲得部材（２）を用い、前述の方法に従い、モデルおむつとしての吸収性物品（２３）を作成し、通液時間、拡散面積、戻り量を上記評価方法に従って評価し表５に示した。
（比較例１１）
得られた吸収性樹脂（２）と液獲得部材（２）を用い、前述の方法に従い、モデルおむつとしての吸収性物品（２４）を作成し、通液時間、拡散面積、戻り量を上記評価方法に従って評価し表５に示した。吸収体を作成の際、粉塵が飛散し取扱い性が困難であった。
【０１７７】
（比較例１２）
得られた吸収性樹脂（３）と液獲得部材（２）を用い、前述の方法に従い、モデルおむつとしての吸収性物品（２５）を作成し、通液時間、拡散面積、戻り量を上記評価方法に従って評価し表５に示した。
【０１７８】
【表５】

【０１７９】
【発明の効果】
本発明によれば、液拡散部材および吸水性樹脂を用いる吸収体や吸収性物品において、表面積の大きい材料等の補助材料を用いずとも液拡散部材から吸水性樹脂に液が十分に受け渡され吸収される、すなわち液の拡散能力および貯蔵能力の両者に優れた吸収体、吸収性物品、および該吸収体、吸収性物品に好適に使用できる吸水性樹脂を提供することができ、また、液獲得部材および吸水性樹脂を用いる吸収体や吸収性物品において、吸水性樹脂濃度をより高めた場合であっても、液獲得部材から吸水性樹脂に液が良好に移行し、繰り返し液を吸収してもその液獲得機能が大きく低下せず、ドライ感、液の戻り量に優れ、かつより薄型、軽量化を実現する吸収体、吸収性物品、および該吸収体、吸収性物品に好適に使用できる吸水性樹脂を提供することができる。
【図面の簡単な説明】
【図１】本発明における毛管吸収倍率、毛管吸収指数を求めるための測定に用いる測定装置の概略の断面図である。この装置では４０ｃｍの高さの毛管吸収倍率が測定される。
【図２】本発明における毛管吸収倍率、毛管吸収指数を求めるための測定に用いる測定装置の概略の断面図である。この装置では０ｃｍの高さの毛管吸収倍率、および吸水性樹脂の加圧下の吸収倍率が測定される。
【図３】本発明における吸収性物品の概略の斜視図。
【図４】本発明における吸収性物品の概略の断面図。
【符号の説明】
１　　多孔質ガラス板
２　　グラスフィルター
３　　導管
４　　液溜容器
５　　支持リング
６　　生理食塩水
７　　天秤
８　　スタンド
９　　測定試料（吸水性樹脂または液拡散部材）
１０　荷重（０．４１ｋＰａ（０．０６ｐｓｉ））
１１　外気吸入パイプ
１２　導管
１３　ガラスフィルター
１４　生理食塩水
１５　液溜容器
１６　天秤
１７　ろ紙
１８　金網
１９　プラスチック円筒
１０　荷重（０．４１ｋＰａ（０．０６ｐｓｉ））
２０　荷重（２．０７ｋＰａ（０．３ｐｓｉ））
２１　荷重（４．８３ｋＰａ（０．７ｐｓｉ））
３１　液透過性ポリエステル不織布
３２　吸水性樹脂
３３　液拡散部材
３４　液非透過性ポリエチレンフィルム
３５　ヒートロンペーパー
３６　接着テープ[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to sanitary materials such as disposable diapers and sanitary napkins, so-called incontinence pads, dew condensation and water absorption sheets, agricultural and horticultural water-retaining materials, water-blocking materials for civil engineering, medical sheets and other medical materials, food freshness retaining materials, food drip absorbing materials, and the like. TECHNICAL FIELD The present invention relates to an absorbent body, an absorbent article, a water-absorbent resin, and a production method and an evaluation method thereof, which are suitably used for the above-mentioned applications.
[0002]
[Prior art]
At present, hygienic materials such as disposable diapers and sanitary napkins, so-called incontinence pads, are used for the purpose of absorbing body fluids. Water-swellable crosslinked polymers mainly composed of hydrophilic fibers such as pulp and acrylic acid (salt). Is widely used as a constituent material thereof. In recent years, sanitary materials such as disposable diapers and sanitary napkins have become highly functional and thinner, and the amount of water-absorbent resin used per sanitary material and the total amount of absorbent made of water-absorbent resin and hydrophilic fibers, etc. The weight ratio of the water absorbent resin tends to increase. In other words, by reducing the number of hydrophilic fibers having a low bulk specific gravity, excellent in water absorption, and by using a large amount of a water-absorbing resin having a large bulk specific gravity, the ratio of the water-absorbing resin in the absorber is increased, thereby increasing the water absorption. The sanitary material is made thinner without lowering it.
[0003]
However, sanitary materials with a reduced ratio of hydrophilic fibers and an increased amount of water-absorbent resin are preferred in terms of simply storing liquids, but the distribution and diffusion of liquids in actual diaper use situations. If you think about it, a problem arises rather. A large amount of water-absorbent resin becomes a soft gel due to water absorption, causing a phenomenon called gel blocking, which greatly hinders the diffusion of the liquid. In order to avoid such a problem and maintain the absorption characteristics of the absorber, the ratio between the hydrophilic fiber and the water-absorbent resin is naturally limited, and there is a limit to the reduction in thickness of the sanitary material.
In the past, various methods for distributing and diffusing liquids and liquid diffusion members have been studied in order to enhance the diffusion of liquid in the absorber and use the absorbing material more efficiently, and various absorbent articles using these members have been studied. Are known. Examples of these are an absorbent pad (US Pat. No. 4,781,710) in which specific regions of hydrophilic fibers of the absorbent are compressed at a high density, and wet molding of two or more fibers having different strengths and specific surface areas. US Patent No. 5,387,207, combined, fluid distribution material with specific wicking properties (WO 97/45087), open-cell foamed absorbent material manufactured using a high internal phase emulsion. U.S. Pat. No. 5,134,007; U.S. Pat. No. 6,107,538), which preferably have a narrow crotch width using a foamed absorbent material having open cells, and the absorption capacity of the crotch region is greater than that of the absorbent core. Absorbent cores that are 40% or less of the total absorption capacity (International Patent Publication No. 98/43573, Japanese Translation of PCT International Publication No. 2000-510365), and the like.
[0004]
In addition, a member for obtaining a liquid has been proposed in order to increase and maintain the liquid absorption efficiency of an absorbent article such as a disposable diaper. As such a liquid acquisition member, crosslinked cellulose (JP-A-63-264971), a discharge treatment layer having a specific liquid permeability index (JP-A-5-261126), and the like are known.
However, when a water-absorbent resin is used as a storage material for storing the liquid distributed and diffused by the liquid diffusion member, depending on the liquid diffusion member used, most of the liquid therein is transferred to and absorbed by the water-absorbent resin. It was found that the water-absorbent resin did not work efficiently as a liquid storage member. In particular, when a material having a very high suction capacity in the vertical direction is used as the liquid diffusion member, for example, a porous polymer having fine open cells inside manufactured by using a high internal phase emulsion as described above is used. Surprisingly, it has been found that, depending on its properties, the water-absorbent resin can hardly absorb the liquid from the porous polymer, and cannot exhibit the original storage function of the water-absorbent resin at all. For this reason, even if the liquid can be diffused sufficiently in the absorber, the function of storing the liquid does not work well, and the phenomenon that the liquid leaks from the absorbent article with a much smaller capacity than the expected absorption amount may occur. Admitted.
[0005]
Techniques to solve this problem include an osmotic absorbing material such as the above-mentioned water-absorbing resin and a material having a large surface area (for example, a particulate porous foam having open cells produced using the above-mentioned high internal phase emulsion). A liquid storage member having a high capillary absorption capacity in combination with an absorbent material and glass microfibers has been disclosed (for example, see Patent Documents 1 and 2).
However, according to this method, since a plurality of materials as described above are used in combination as a liquid storage member, a new apparatus for manufacturing a liquid storage material by combining these materials is required, and not only the process becomes complicated, but also However, even if a material having a large surface area exists around the water absorbing resin, there is a problem that the water absorbing resin still has a low absorption capacity. Further, when a material having a large surface area has a lower absorption capacity than a water-absorbent resin, there is a problem that the liquid absorption and storage capacity of the entire liquid storage member is reduced.
[0006]
In addition, as described above, the presence of the liquid acquisition member ensures that the liquid is quickly taken into the absorber in the initial state, but as the amount of absorption increases, the water-absorbing resin and the hydrophilic Absorbers made of fibers or the like were unable to absorb the liquid present in the liquid acquiring member, and there were cases where the absorption rate was conversely reduced and the amount of return increased.
In addition, even the current thin absorbent products are still heavy and thick, and are not yet satisfactory in the distribution, display space, purchase, use when going out, etc. of products. There is a demand for thinning. For this reason, when the concentration of the water-absorbent resin in the absorber is further increased, for example, the amount of the bulky hydrophilic fiber used is reduced, and the water-absorbent resin layer mainly composed of the water-absorbent resin is used as the liquid storage member. In such a case, the problem of gel blocking of the water-absorbing resin as described above is further highlighted, and the desired absorption capacity may not be realized.
[0007]
Techniques for using a water-absorbent resin layer mainly composed of a water-absorbent resin as a liquid storage member include a first structure made of a first fiber material and a first superabsorbent material, a second fiber material and a first fiber material. An absorbent core having a second structure made of a second superabsorbent material having a higher absorption rate than that of the superabsorbent material (for example, see Patent Document 3), a liquid trapping layer and a gel layer having a permeation value of a specific amount or more. An upper assembly comprising a superabsorbent layer made of a superabsorbent material, and an upper assembly having a void space for storage of liquid and a lower layer containing a superabsorbent layer having a specific range of absorption capacity under pressure. An absorbent body having a lower assembly having a structure (for example, see Patent Document 4), a first absorbent layer in which a water-absorbing polymer is held between fibers of a nonwoven fabric, and a second absorbent layer made of an aggregate of hydrophilic fibers. The first absorbent layer is located on the liquid-permeable topsheet side. Absorbent articles (see, for example, Patent Document 5), an absorbent without gel blocking comprising a wettable fiber and a surface-crosslinked water-absorbent resin, comprising a fiber and a water-absorbent resin in the surface-crosslinked water-absorbent resin. Absorbers having a weight ratio of 75 to 95% by weight and a volume increase rate under load of 15% or more after 600 seconds (for example, see Patent Document 6) are known.
[0008]
Patent Literature 3 and Patent Literature 4 disclose a technology relating to the configuration of the absorber that moves the liquid storage position in the absorber from the lower portion to the upper portion. Patent Literature 5 discloses a technology for eliminating the roughness of the back sheet of the diaper. Patent Literature 6 discloses a technique in which the porosity of the absorbent in the swollen state is specified, but does not disclose the liquid distribution relationship between the liquid acquisition member that has received the liquid and the water absorbent resin layer.
In addition, a body fluid absorbing article in which the ratio of the water-absorbing resin to the total amount of the pulp and the water-absorbing resin is 10 to 90% by weight. The body fluid suction / absorbing performance is specified to transfer the liquid held in the pulp fiber space to the polymer. (See, for example, Patent Document 7).
[0009]
However, the polymer used in this case is a polymer having a relatively low bulk specific gravity and a high degree of irregularity, and the so-called water absorption speed, which is to quickly absorb the liquid held in the gaps of the pulp around the polymer, is important. Similarly, there is no description of the liquid distribution relationship between the liquid acquisition member and the water-absorbent resin layer.
In addition, as an example of measuring the absorption capacity of a water-absorbent resin, there is a disclosure of measurement of the absorption capacity in the absence of negative pressure (for example, see Patent Document 8).
[0010]
[Patent Document 1]
International Publication No. 99/47184 pamphlet
[0011]
[Patent Document 2]
U.S. Pat. No. 6,107,538
[0012]
[Patent Document 3]
Japanese Unexamined Patent Publication No. Hei 8-519773
[0013]
[Patent Document 4]
Japanese Patent Publication No. Hei 8-511974
[0014]
[Patent Document 5]
JP 2000-286505 A
[0015]
[Patent Document 6]
WO 01/30290 pamphlet
[0016]
[Patent Document 7]
JP 2001-276124 A
[0017]
[Patent Document 8]
International Publication No. 88/01282 pamphlet
[0018]
[Problems to be solved by the invention]
Therefore, an object of the present invention is to solve the above-described problems by using a liquid diffusion member and an absorbent or absorbent article using a water-absorbing resin, without using an auxiliary material such as a material having a large surface area. The liquid is sufficiently transferred to and absorbed by the water-absorbent resin, that is, the absorbent, the absorbent article, and the water-absorbent which can be suitably used for the absorbent and the absorbent article, which are excellent in both the diffusion ability and the storage ability of the liquid. Providing the resin, and in the absorbent or absorbent article using the liquid acquisition member and the water-absorbent resin, even when the water-absorbent resin concentration is further increased, the liquid is good from the liquid acquisition member to the water-absorbent resin. The absorbent, the absorbent article, and the absorbent that realizes a dry feeling, excellent liquid return amount, and realizes a thinner and lighter weight even when the liquid is repeatedly absorbed and the liquid acquiring function is not significantly reduced. Body, absorbent And to provide a suitably water-absorbent resin which can be used for.
[0019]
[Means for Solving the Problems]
As a result of intensive studies to achieve the above object, the present inventor has focused on the performance of the water-absorbent resin, which has not been known as a water-absorbent resin, in terms of the capillary absorption capacity of a single water-absorbent resin. By establishing the specific relationship described below between the capillary absorption capacity of the water-absorbent resin and the capillary absorption capacity of the water-absorbent resin, the surface area as described in Patent Document 1 (International Patent Publication No. WO 99/47184) is established. That the water-absorbent resin can well absorb the liquid from the liquid diffusion member without using other auxiliary wicking materials such as a large material, and that the water-absorbent resin can well absorb the liquid from the liquid acquisition member. I found something. The capillary absorption capacity, which will be described in detail later, is measured using an apparatus schematically shown in FIG. 1, and a measurement sample (water-absorbent resin) is measured several tens of meters from the surface of physiological saline in a liquid storage container. It is placed at a height of cm and measures the ability of the capillary to absorb liquid against the negative pressure of the water column at that height. Conventionally, there is an example in which the absorption capacity is measured in a state where there is no negative pressure, that is, when the liquid surface of the liquid reservoir and the sample position are at the same height (Patent Document 8: International Publication No. 88/01282 pamphlet). For the water-absorbent resin alone, there is no example in which the capillary absorption capacity under such a negative pressure was measured, and the correlation between the capillary absorption capacity of the water-absorbent resin measured by the method of the present invention and the performance of the absorber was also observed. Was not known. That is, if an absorbent body and an absorbent article are made using a water-absorbent resin having the performance of maintaining the above-described relationship in accordance with the characteristics of the liquid diffusion member and the liquid acquisition member, storage from the diffusion of the liquid in the absorber, It has been found that the system from acquisition to storage or from acquisition to storage / diffusion works well, and it is possible to provide an absorbent and an absorbent article exhibiting excellent liquid absorption capacity in a very simple manufacturing process. It was completed.
[0020]
Furthermore, the weight average particle diameter (the method for measuring the weight average particle diameter of the water-absorbent resin of the present invention, which is determined by sieving as described later, is the weight average of the sieve diameter) is in a specific range, Using as a raw material powder a water-absorbent resin having a specific range of the inter-particle gap ratio at the time of saturation swelling under no pressure and the average inter-particle radius at the time of saturation swelling under no pressure when liquid is absorbed into the particles, And, when the dispersion of the water-dispersible fine particles is used as a binder, the water-absorbent resin fine powder can be granulated extremely efficiently, and the adhesive of the present invention has strong adhesiveness and redispersibility. The present inventors have found that water-absorbent resin particles suitable for use in absorbent articles can be easily obtained and have excellent absorption properties, and have completed the present invention.
[0021]
That is, the absorber according to the present invention is an absorber containing a liquid diffusion member and a water-absorbing resin, and the capillary absorption index at a height of 40 cm of the liquid diffusion member is A (where A ≧ 0.10). In some cases, the water-absorbent resin has a capillary absorption index B at a height of 40 cm that satisfies the following expression.
B / A ≧ 0.7 (Formula 1)
Another absorbent body according to the present invention is an absorbent body containing a liquid diffusion member and a water-absorbing resin, wherein the liquid absorption member has a capillary absorption capacity at a height of 40 cm of C (where C ≧ 2.0 (g / g)), wherein the water-absorbent resin has a capillary absorption capacity D at a height of 40 cm that satisfies the following expression.
[0022]
D / C ≧ 0.7 (Equation 2)
Another absorbent body according to the present invention is an absorbent body including a liquid diffusion member and a liquid storage member, wherein the liquid diffusion member has a suction height of 30 cm or more, and the liquid storage member has a capillary absorption at a height of 40 cm. It is characterized by using a water-absorbing resin having a magnification D of 15 (g / g) or more.
Another absorber according to the present invention is an absorber including a liquid diffusion member and a liquid storage member, a member having a suction height of 30 cm or more as the liquid diffusion member, and a surface-crosslinked weight averaged as the liquid storage member. It is characterized by using a water-absorbing resin having a particle diameter of 250 μm or less.
[0023]
Another absorber according to the present invention is an absorber containing a liquid diffusion member and a water-absorbing resin containing a polyacrylic acid (salt) -based crosslinked polymer as a main component, wherein the liquid diffusion member contains a high internal phase emulsion. A porous polymer obtained by polymerization, wherein a weight ratio of the water-absorbent resin to the total weight of the liquid diffusion member and the water-absorbent resin is 75% by weight or more and 90% by weight or less.
Another absorber according to the present invention has a spraying amount of the liquid acquisition member and the water-absorbing resin of 250 g / m2.²An absorbent body including the above-described water-absorbent resin layer, wherein the water-absorbent resin has a height of 40 cm when the capillary absorption index at a height of 40 cm of the liquid acquisition member is E (where E <0.1). And a capillary absorption index B satisfying the following expression.
[0024]
B / E ≧ 10 ° (Equation 3)
Another absorber according to the present invention has a spraying amount of the liquid acquisition member and the water-absorbing resin of 250 g / m2.²An absorbent body including the above-described water-absorbent resin layer, wherein a capillary absorption index at a height of 40 cm of the liquid acquisition member is E (where E <0.1). The capillary absorption index F at the height satisfies the following expression.
F / E ≧ 10 ° (Equation 4)
Another absorber according to the present invention has a spraying amount of the liquid acquisition member and the water-absorbing resin of 250 g / m2.²An absorbent body including the above-described water-absorbent resin layer, wherein a capillary absorption capacity G at a height of 40 cm of the liquid acquisition member is 1.0 (g / g) or less, and a height of 40 cm as the water-absorbent resin. Is characterized in that a capillary absorption ratio D of 5 (g / g) or more is used.
[0025]
Another absorber according to the present invention has a spraying amount of the liquid acquisition member and the water-absorbing resin of 250 g / m2.²An absorbent body including the above-described water-absorbent resin layer, wherein a capillary absorption ratio G at a height of 40 cm of the liquid acquisition member is 1.0 (g / g) or less, and a height of 40 cm of the water-absorbent resin layer. In this case, the capillary absorption capacity H is 5 (g / g) or more.
An absorbent article according to the present invention includes the absorbent body of the present invention.
The water-absorbent resin particles according to the present invention have a weight-average particle diameter of 50 to 300 μm, and a void ratio between particles during saturated swelling under no pressure when saturatedly swelled in a physiological saline solution (0.9% by weight NaCl aqueous solution). Are water-absorbent resin particles obtained by granulating a water-absorbent resin having a particle diameter of 30 to 50% and an average gap radius between particles during saturation swelling under no pressure of 80 to 150 μm, wherein the weight average of the water-absorbent resin particles is The particle diameter is increased by 50% or more before granulation.
[0026]
Another water-absorbent resin particle according to the present invention is a water-absorbent resin particle containing a polyacrylic acid (salt) -based crosslinked polymer as a main component, and has a capillary absorption capacity D at a height of 40 cm of 25 (g / g). ) That is all.
The method for producing water-absorbent resin particles according to the present invention is characterized in that particles having a weight-average particle diameter of 50 to 300 μm and saturated swelling in a physiological saline solution (0.9% by weight NaCl aqueous solution) under no pressure are used. The weight-average particle diameter is reduced by adding a dispersion of water-dispersible fine particles to a water-absorbent resin having an inter-gap ratio of 30 to 50% and an average inter-gap radius of 80 to 150 μm during saturation swelling under no pressure. It is characterized by being raised by 50% or more.
[0027]
The absorbent article according to the present invention contains the water-absorbent resin particles of the present invention.
The water-absorbent resin according to the present invention is a water-absorbent resin containing a polyacrylic acid (salt) -based crosslinked polymer as a main component, and has a capillary absorption capacity D at a height of 40 cm of 25 (g / g) or more. .
The absorbent article according to the present invention contains the water absorbent resin of the present invention.
The method for evaluating a water-absorbent resin according to the present invention includes a method for measuring a liquid absorbed by a water-absorbent resin within a predetermined time in a state where the height H1 of the liquid absorption position is higher than the height H2 of the liquid level of the liquid storage container. Measure the absorption capacity.
[0028]
BEST MODE FOR CARRYING OUT THE INVENTION
[1] Capillary absorption capacity
Capillary absorption capacity used in the present invention is generally an evaluation item conventionally used to evaluate the absorptive power of a material that absorbs and absorbs a liquid by a capillary phenomenon such as paper and pulp, and will be described later. By measuring the amount of liquid absorbed per unit weight of the sample while changing the liquid absorption position to various heights using a device that performs the evaluation, the capillary absorption power of the sample and the liquid absorption capacity are evaluated. . The specific method for measuring the capillary absorption capacity, which is the capillary absorption capacity in the present invention, will be described in detail in Examples below, but a measurement method based on the same principle is described in, for example, {Textile Research} Journal Vol. 57, 356 (1967), "Absorbency" (Chaterjee, Textile Science and Technology, Vol. 7, 1985), JP-A-8-52349, International Patent 99/47184, and the like.
[0029]
In the present invention, a water-absorbent resin for measuring the absorption capacity of a liquid absorbed by a water-absorbent resin within a predetermined time in a state where the height H1 of the liquid absorbing position is higher than the height H2 of the liquid level of the liquid storage container. By performing the above-described method for the first time with a water-absorbent resin, the evaluation method can correctly determine the ability of the water-absorbent resin to absorb liquid from other base materials such as a liquid diffusion member and a liquid acquisition member, based on the value. It was found. In order to increase the measurement accuracy and increase the correlation with the performance of the absorber, the evaluation is performed in a state where the height difference between the height H1 of the liquid absorption position and the height H2 of the liquid surface of the liquid storage container is 20 to 60 cm. It is more preferable to provide an altitude difference of 30 to 50 cm.
[0030]
There are two types of capillary absorption capacity in the present invention: capillary absorption capacity and capillary absorption index. The capillary absorption capacity in the present invention measures the amount (magnification) of the liquid absorbed by the sample in 30 minutes with a difference in height between the liquid absorption position and the liquid level of the liquid storage container. The case where the height difference between the liquid absorption position and the liquid level of the liquid storage container is 40 cm is “capillary absorption capacity at a height of 40 cm”, and the case where the height difference between the liquid absorption position and the liquid level of the liquid storage container is 0 cm is “ Capillary absorbency at 0 cm height ".
In addition, the capillary absorption index in the present invention is a value of the capillary absorption ratio at which the sample absorbs for 30 minutes in a state where a difference in height is provided between the liquid absorption position and the liquid surface of the liquid storage container, and the liquid absorption container liquid level. Is determined by dividing the difference in the capillary absorption capacity at a height of 0 cm at which the sample absorbs in 30 minutes with the difference in height of the sample being 0 cm. The “capillary absorption index at a height of 40 cm” refers to the value of “capillary absorption ratio at a height of 40 cm” when the height difference between the liquid absorption position and the liquid level of the liquid storage container is 40 cm, It is determined by dividing by the value of "capillary absorption capacity at a height of 0 cm" when the height difference from the surface is 0 cm.
[0031]
The water-absorbing resin currently marketed and used in large quantities for sanitary materials is a polyacrylic acid (salt) crosslinked polymer whose main raw material is acrylic acid (salt). The mechanism of absorbing liquid is similar to that of pulp. It is not derived from capillary absorption but basically originates from the osmotic pressure difference between the liquid to be absorbed and the polymer itself, which is a polymer electrolyte. However, the ability of the water-absorbent resin to absorb the liquid held by the liquid diffusion member or the liquid acquisition member, which has an excellent ability to absorb liquid in the vertical direction, is generally known to date as the ability of the water-absorbent resin. It could not be predicted at all only from the absorption characteristics such as absorption capacity, water absorption rate, absorption capacity under pressure, and liquid permeability of the gel layer.
[0032]
The present inventors have focused on the ability of the water-absorbent resin as well as the liquid-diffusing member and the liquid-acquisition member, focusing on the capability of capillary absorption. By using a water-absorbent resin having a specific relationship with the capillary absorption capacity of the liquid acquisition member or the liquid acquisition member in combination with the liquid diffusion member or the liquid acquisition member, the water absorption resin is removed from the liquid diffusion member or the liquid acquisition member. Was found to be able to be absorbed and stored well. Furthermore, absorbents designed to maintain this relationship exhibit extremely excellent liquid absorption efficiency, and absorbent articles such as disposable diapers using such absorbents are highly effective in absorbing water over the entire diaper. Because it can be used for diapers, the absorption capacity of the diaper as a whole can be very large, and by adjusting this high absorption capacity to the desired actual use level absorption capacity, a thinner, more mobile diaper with fewer components can be manufactured. Was found.
[0033]
In the present invention, in order to express the capillary absorption ability of the water-absorbent resin, the capillary suction force derived from the physical shape of the water-absorbent resin and the osmotic pressure of various polymers themselves developed by surface crosslinking treatment. The balance with the water absorption properties is considered to be very important.
[2] Absorber containing liquid diffusion member and water absorbent resin
(2-1) Relationship between liquid diffusion member and capillary absorption capacity of water absorbent resin
The relationship between the liquid diffusion member and the capillary absorption capacity of the water absorbent resin in the present invention will be described.
[0034]
As the water-absorbent resin that can be used in the present invention, when the capillary absorption index at a height of 40 cm of the liquid diffusion member is A (where A ≧ 0.10), the water-absorbent resin has a height of 40 cm. The capillary absorption index B satisfies the following equation.
B / A ≧ 0.7 (Formula 1)
The value of the capillary absorption index B at a height of 40 cm of the water-absorbent resin required for the present invention depends on the characteristics of the liquid diffusion member used, that is, the capillary absorption index A at a height of 40 cm of the liquid diffusion member used. If the relationship of ≧ 0.7 is satisfied, the liquid is satisfactorily distributed from the liquid diffusion member to the water-absorbent resin, and the water-absorbent resin can satisfactorily absorb and store the liquid. When B / A is less than 0.7, it is difficult for the water-absorbing resin to absorb the liquid from the liquid diffusion member, and the liquid distribution rate from the liquid diffusion member becomes low. In some cases, the absorption amount of the water-absorbent resin does not improve, and the water-absorbent resin does not work well as a liquid storage member. Preferably, the water-absorbent resin satisfies B / A ≧ 1.3, and more preferably, the water-absorbent resin satisfies B / A ≧ 1.5. If the value of B / A exceeds 2.0, the liquid diffusivity of the liquid diffusing member may decrease, so caution is required. Hereinafter, the value of B / A may be referred to as liquid diffusion storage coefficient 1.
[0035]
Another water-absorbent resin that can be used in the present invention is a liquid-diffusion member having a capillary absorption capacity at a height of 40 cm of C (where C ≧ 2.0 (g / g)). Capillary absorption capacity D at a height of 40 cm as a water absorbent resin satisfies the following expression.
D / C ≧ 0.7 (Equation 2)
The value of the capillary absorption ratio D at a height of 40 cm of the water-absorbent resin required for the present invention depends on the characteristics of the liquid diffusion member used, that is, the capillary absorption ratio C at a height of 40 cm of the liquid diffusion member used. As long as the relationship of ≧ 0.7 is satisfied, the liquid is distributed well from the liquid diffusion member to the water-absorbing resin, and the water-absorbing resin can satisfactorily absorb and store the liquid. When D / C is less than 0.7, it is difficult for the water-absorbing resin to absorb the liquid from the liquid diffusion member, and does not work well as a liquid storage member. The water-absorbing resin preferably satisfies D / C ≧ 1.3, and more preferably the water-absorbing resin satisfies D / C ≧ 1.5. If the value of D / C exceeds 10, the liquid diffusivity of the liquid diffusing member may decrease, so caution is required. Hereinafter, the value of D / C may be referred to as liquid diffusion storage coefficient 2.
[0036]
In the present invention, it is more preferable that both the liquid diffusion storage coefficient 1 and the liquid diffusion storage coefficient 2 satisfy the range of the present invention. If only one of them is satisfied, care should be taken because the liquid absorbing ability of the water-absorbent resin from the liquid diffusion member may not be sufficiently exhibited depending on the use conditions.
The present invention is an absorber composed of a liquid diffusion member having a specific relationship and an absorbent resin, but also functions as a liquid transfer / absorption system composed of a liquid diffusion member having a specific relationship and an absorbent resin. That is, the present invention relates to an absorbent body containing a liquid diffusion member and a water-absorbing resin, wherein the liquid absorption member has a capillary absorption index at a height of 40 cm where A (where A ≧ 0.10), A liquid transfer / absorption system, characterized in that a resin having a capillary absorption index B at a height of 40 cm that satisfies the following formula is used as the conductive resin:
B / A ≧ 0.7 (Formula 1)
And an absorber containing a liquid diffusion member and a water-absorbent resin, wherein the capillary absorption capacity at a height of 40 cm of the liquid diffusion member is C (where C ≧ 2.0 (g / g)). A liquid transfer / absorption system, wherein a capillary absorption capacity D at a height of 40 cm that satisfies the following expression is used as the water-absorbent resin.
D / C ≧ 0.7 (Equation 2)
Can also be provided.
(2-2) Liquid diffusion member
The liquid diffusion member that can be used in the present invention is that the capillary absorption index A at a height of 40 cm is 0.10 or more, and the capillary absorption ratio C at a height of 40 cm is 2.0 (g / g). The above is defined as a material having essentially no hydrogel-forming ability, and is a material for diffusing a liquid added to an absorber or an absorbent article having an absorber over a larger area of the absorber. In particular, it has a porous structure and excellent liquid suction capability in the vertical direction in order to sufficiently exhibit such a function even in a practical use form. More preferably, the liquid diffusion member itself has a certain level of liquid holding, absorbing, and storing ability.
[0037]
The liquid diffusion member that can be used in the present invention is excellent in the ability to diffuse and suck up liquid, and it is necessary that the capillary absorption index A at a height of 40 cm is 0.10 or more. Capillary absorption index A at a height of 40 cm of a flap pulp or the like used for a conventional disposable diaper is 0.05 or less according to the measurement method of the present invention, and a material having such a capillary absorption index A of less than 0.10. In this case, the ability of the liquid to be sucked up in the vertical direction is small, and it is difficult to diffuse the liquid over the entire surface of the diffusion member and the entire absorber, and the material of the entire absorber is not used efficiently. Preferably, the capillary absorption index A at a height of 40 cm is 0.20 or more, more preferably 0.30 or more, and most preferably 0.40 or more.
[0038]
The liquid diffusion member that can be used in the present invention preferably has a capillary absorption capacity at a height of 0 cm of 10 (g / g) or more. The higher the capillary absorption capacity at a height of 0 cm, the larger the liquid transport capacity as a liquid diffusion member, and it can function from the viewpoint of absorption, retention, and storage of the liquid, so that an excellent absorber can be obtained. More preferably, the capillary absorption capacity at a height of 0 cm is 20 (g / g) or more, and further preferably the capillary absorption capacity at a height of 0 cm is 30 (g / g) or more.
Another liquid diffusion member that can be used in the present invention needs to have a capillary absorption capacity C at a height of 40 cm of 2.0 (g / g) or more. The capillary absorption capacity C at a height of 40 cm of a flap pulp or the like used for a conventional disposable diaper is 1.0 (g / g) or less, and the capillary absorption capacity C at such a height of 40 cm is 2.0 (g / g). With a material less than g / g), the liquid has a small ability to siphon the liquid in the vertical direction, making it difficult to diffuse the liquid over the entire surface of the liquid diffusion member and the entire absorber, and the material of the entire absorber is not used efficiently. The capillary absorption capacity C at a height of 40 cm is preferably 5.0 (g / g) or more, more preferably 10.0 (g / g) or more.
[0039]
Similarly, another liquid diffusion member that can be used in the present invention preferably has a capillary absorption capacity at a height of 0 cm of 10 (g / g) or more. The higher the capillary absorption capacity at a height of 0 cm, the larger the liquid transport capacity as a liquid diffusion member, and it can function from the viewpoint of absorption, retention, and storage of the liquid, so that an excellent absorber can be obtained. More preferably, the capillary absorption capacity at a height of 0 cm is 20 (g / g) or more, and further preferably the capillary absorption capacity at a height of 0 cm is 30 (g / g) or more.
The liquid diffusion member that can be used in the present invention satisfies the above conditions, and is used in combination with a water-absorbing resin for an absorber.
[0040]
As described above, when the capillary absorption index at a height of 40 cm of the liquid diffusion member is A, the capillary absorption index B at a height of 40 cm of the water-absorbing resin is B / A ≧ 0.7. When satisfying, preferably satisfying B / A ≧ 1.3, or when the capillary absorption capacity at a height of 40 cm of the liquid diffusion member is C (where C ≧ 2.0 (g / g)) In addition, it is necessary that the water absorbing resin has a capillary absorption ratio D at a height of 40 cm satisfying D / C ≧ 0.7, preferably satisfying D / C ≧ 1.3. It is more preferable that both satisfy B / A ≧ 0.7 and D / C ≧ 0.7 at the same time. More preferably, both should satisfy B / A ≧ 1.3 and D / C ≧ 1.3 at the same time.
[0041]
The liquid diffusion member that can be used in the present invention preferably has a suction height of 30 cm or more, more preferably 40 cm or more, and still more preferably 50 cm or more. Things. When it is 30 cm or less, the liquid diffusivity of the absorber is low, and the entire absorber cannot be used effectively.
The shape of the liquid diffusion member may be a sheet, a fiber, a particle, a strip, or the like, but a sheet is generally preferred. At this time, the basis weight of the liquid diffusion member is 50 to 500 g / m.²Degree is preferable, and more preferably 100 to 200 g / m.²It is about.
[0042]
When the liquid diffusion member has a density difference or a density gradient, a diffusion capability difference or a diffusion capability gradient within the member, or when a second liquid diffusion member that does not satisfy the relationship of the present invention is further used, the water absorption It is preferable that the capillary absorption capacity of the liquid diffusion member closer to the resin satisfies the above relationship.
Examples of such a liquid diffusion member include a porous polymer obtained by polymerizing a high internal phase emulsion (HIPE), a fiber material having a predetermined density (for example, cellulose pulp or nonwoven fabric), and a foam material such as urethane sponge or cellulose sponge. Is mentioned. Preferably, it has excellent vertical wicking capacity, wicking amount, and wicking speed, and among others, a porous polymer obtained by polymerizing a high internal phase emulsion (HIPE) described below is preferable.
[0043]
a. Liquid diffusion member made of porous polymer obtained by polymerizing high internal phase emulsion (HIPE)
The porous polymer that can be suitably used as the liquid diffusion member in the present invention has a ratio (W / O ratio) of an aqueous phase as an internal phase and an oil phase as an external phase of about 3/1 or more. Obtained by polymerizing a high internal phase emulsion (HIPE). Methods for producing a porous polymer from HIPE include, for example, US Pat. No. 5,189,070, US Pat. No. 5,250,576, US Pat. No. 5,252,619, US Pat. No. 5,290,820. No. 5,358,974, US Pat. No. 5,252,619, US Pat. No. 5,670,101, US Pat. No. 6,204,298, etc. The porous polymer is a low-density foam state of fine pores of open cells, and a polymer having desired absorption properties, for example, excellent liquid diffusion / wicking properties, etc. by selecting conditions. Forms can be manufactured.
[0044]
The raw materials used for HIPE are a polymerizable monomer component, an oil phase containing a surfactant, and an aqueous phase containing water. As the polymerizable monomer component, an intramolecular molecule capable of forming a crosslinked structure by polymerization is used. A polymerizable monomer having one polymerizable unsaturated group and / or a crosslinkable monomer having at least two polymerizable unsaturated groups in a molecule. Further, if necessary, the composition may contain a polymerization initiator, salts, and other additives as optional components constituting the oil phase and / or the aqueous phase.
As the polymerizable monomer, preferably, at least a part thereof contains a (meth) acrylic acid ester, specifically, an arylene monomer such as styrene; styrene, ethyl styrene, alpha methyl styrene, vinyl Monoalkylene arylene monomers such as toluene and vinylethylbenzene; methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, isobutyl (meth) acrylate, isodecyl (meth) acrylate, ( (Meth) acrylates such as 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, cyclohexyl (meth) acrylate, and benzyl (meth) acrylate; vinyl chloride, vinylidene chloride, Chlorine-containing monomers such as chloromethylstyrene; acrylonitrile Acrylonitrile compounds such as acrylonitrile and methacrylonitrile; vinyl acetate, vinyl propionate, N- octadecyl acrylamide, ethylene, propylene, butene and the like. These may be used alone or in combination of two or more.
[0045]
The crosslinkable monomer may be a compound having at least two polymerizable unsaturated groups in the molecule or a compound capable of forming a crosslinked structure by polymerization, and may be dispersed similarly to the polymerizable monomer. Alternatively, there is no particular limitation as long as it can be polymerized in a water-in-oil type high dispersion phase emulsion. Specifically, examples of the crosslinkable monomer include divinylbenzene, trivinylbenzene, divinyltoluene, divinylxylene, p-ethyl-vinylbenzene, divinylnaphthalene, divinylalkylbenzenes, divinylphenanthrene, divinylbiphenyl, and divinyldiphenylmethane. , Divinylbenzyl, divinylphenyl ether, aromatic monomers such as divinyldiphenylsulfide; oxygen-containing monomers such as divinylfuran; sulfur-containing monomers such as divinylsulfide and divinylsulfone; butadiene, isoprene, pentadiene and the like. Aliphatic monomers; ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate , 1,3-butanediol di (meth) acrylate, 1,4-butanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, octanediol di (meth) acrylate, decanediol di (meth) ) Acrylate, trimethylolpropane di (meth) acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol di (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol di ( (Meth) acrylate, dipentaerythritol tri (meth) acrylate, dipentaerythritol tetra (meth) acrylate, N, N'-methylenebis (meth) acrylamide, triallyl isocyanurate , Triallylamine, tetraallyloxyethane, and ester compounds of acrylic acid or methacrylic acid with polyhydric alcohols such as hydroquinone, catechol, resorcinol, and sorbitol. These may be used alone or in combination of two or more.
[0046]
The amount of the crosslinkable monomer used is in the range of 0.1 to 90% by weight based on the total weight of the polymerizable monomer and the polymerizable monomer component composed of the crosslinkable monomer. Is more preferable, more preferably 1 to 70% by weight, particularly preferably 5 to 50% by weight.
The surfactant used in the oil phase is not particularly limited as long as it can emulsify the aqueous phase, and conventionally known nonionic surfactants, cationic surfactants, anionic surfactants, and amphoteric surfactants Activators and the like can be used. In particular, the combined use of a nonionic surfactant and a cationic surfactant may improve the stability of HIPE in some cases.
[0047]
The amount of the surfactant to be used is preferably 1 to 30 parts by weight, more preferably 1 to 30 parts by weight, based on 100 parts by weight of the entire polymerizable monomer component comprising a polymerizable monomer and a crosslinkable monomer. Is 3 to 15 parts by weight.
As the water, tap water, pure water, ion-exchanged water, or waste water obtained by producing a porous polymer as it is, or water subjected to a predetermined treatment can be used. The amount of water used can be appropriately selected depending on the desired liquid diffusion performance. That is, the amount of water used is adjusted so that the porosity of the porous polymer is determined by changing the water / oil phase (W / O) ratio of the HIPE, so that the porosity matches the purpose. If the user selects the W / O ratio, the determination is made naturally.
[0048]
Any polymerization initiator may be used as long as it can be used in ordinary polymerization, and azo compounds such as 2,2′-azobis (2-amidinopropane) dihydrochloride; ammonium persulfate, potassium persulfate, and sodium persulfate; Persulfate: Any of water-soluble polymerization initiators such as peroxides such as potassium peracetate, sodium peracetate, potassium percarbonate and sodium percarbonate, and oil-soluble polymerization initiators can be used. Further, a redox polymerization initiator system obtained by combining the above polymerization initiator and a reducing agent may be used. In this case, any of water-soluble and oil-soluble polymerization initiators can be used, and a water-soluble redox polymerization initiator system and an oil-soluble redox polymerization initiator system may be used in combination.
[0049]
Salts may be used if necessary to improve the stability of HIPE. Specific examples of the salts include water-soluble salts such as alkali metals such as calcium chloride, sodium sulfate, sodium chloride, and magnesium sulfate, halides of alkaline earth metals, sulfates, and nitrates. These salts may be used alone or in combination of two or more. These salts are preferably added to the aqueous phase. Among them, polyvalent metal salts are preferred from the viewpoint of the stability of HIPE during polymerization.
The amount of such salts to be used is preferably 0.1 to 20 parts by weight, more preferably 0.5 to 10 parts by weight, based on 100 parts by weight of water.
[0050]
Furthermore, if it is possible to improve the performance of the porous polymer as a liquid diffusion member by adding the performance / function of other various additives, even if such various additives are appropriately used. For example, a base and / or a buffer may be added for pH adjustment. Examples of such additives include activated carbon, inorganic powder, organic powder, metal powder, deodorant, antibacterial agent, fungicide, fragrance, various polymers, surfactant and the like.
The method of emulsifying HIPE that can be used in the present invention is not particularly limited, but includes, for example, a polymerizable monomer component and a surfactant, a polymerization initiator that can be added as necessary, and other The components constituting the oil phase composed of the additives are stirred at a predetermined temperature to prepare a uniform oil phase, while the polymerization initiator and salts which can be added to water in a desired amount in water as needed. Then, the mixture is stirred while adding the components constituting the aqueous phase composed of other additives, and heated to a predetermined HIPE temperature to prepare a uniform aqueous phase. Next, the oil phase prepared as described above, which is a mixture of a polymerizable monomer component and a surfactant, and an aqueous phase which is a mixture of water, a water-soluble salt, and the like are combined to form a predetermined HIPE. HIPE can be stably prepared by mixing and stirring efficiently at the emulsification temperature, applying an optimal shearing force, and emulsifying.
[0051]
The water phase / oil phase (W / O) ratio (weight ratio) of HIPE can be appropriately selected and is not particularly limited, and may be 3/1 or more as defined above. The ratio is preferably 10/1 to 250/1, particularly 10/1 to 100/1. By changing the W / O ratio, the porosity of the porous polymer is determined, whereby the liquid diffusion ability, liquid suction ability, and liquid holding ability of the liquid diffusion member can be changed. Therefore, when manufacturing the liquid diffusion member intended for the present invention, the W / O ratio is about 10/1 to 100/1, more preferably about 20/1 to 80/1.
[0052]
The HIPE manufacturing apparatus is not particularly limited, and conventionally known manufacturing apparatuses, for example, blade agitators such as propeller type, paddle type, and turbine type, homomixers, pin mixers, and line mixers , Static mixers, etc., and these may be used alone or in various combinations.
The emulsification temperature of HIPE in the emulsification step for forming a water-in-oil type high dispersion phase emulsion is usually in the range of 40 to 110 ° C.
The HIPE mixed with the polymerization initiator is formed into a desired form. In the present invention, in order to use the obtained porous polymer as a liquid diffusion member, the shape of the molding is preferably a sheet shape, but it may be cut into a sheet shape after adding and polymerizing HIPE in a cylindrical container. Alternatively, a porous polymer in various forms (particle, fiber, film, etc.) may be processed into a form having a liquid diffusion function as a final product. In the case of a sheet, the thickness is not limited, but the thickness of the final product is preferably 10 mm or less, more preferably 5 mm or less, still more preferably 3 mm or less, particularly preferably 1 mm or less, and most preferably 0.5 mm or less. It is about. If the thickness is too large, there is a possibility that the wearing feeling may be reduced when the liquid diffusion member is used for an absorbent article.
[0053]
The polymerization method of HIPE is not particularly limited, and a conventionally known HIPE polymerization method can be appropriately used. Usually, polymerization is performed by applying heat by a static polymerization method under a condition that the structure in the HIPE is not destroyed. In this case, batch polymerization in which the HIPE is polymerized batch by batch, or continuous polymerization in which the HIPE is continuously cast and polymerized while being fed into a heating zone, for example, may be used. The polymerization temperature is usually in the range of 40 to 110 ° C, but in consideration of productivity, the polymerization temperature is preferably higher, for example, preferably about 60 ° C to 110 ° C, and more preferably about 80 ° C to 105 ° C. From the viewpoint of productivity, it is preferable to obtain a porous polymer having a uniform property within a polymerization time of several tens of seconds to 30 minutes. The details of these production methods are described in Japanese Patent Application No. 2000-203744.
[0054]
The porous polymer obtained after the polymerization is usually dehydrated by compression, suction under reduced pressure, or a combination thereof, and depending on the type, can be in a form compressed to a fraction of the original thickness. Further, for the purpose of improving the surface state of the porous polymer, for example, the porous polymer may be washed with pure water or an aqueous solution containing any additive, or a solvent, and then, if necessary, hot air, Heating and drying may be performed by infrared rays, microwaves, or the like, or moisture may be adjusted by humidification. Further, it may be cut into a desired shape and size for use in a final product, and processed into products according to various uses.
b. Other liquid diffusion members
Other liquid diffusing members that can be used in the present invention include foams made of synthetic polymers such as polyurethane, polystyrene, polyethylene, polypropylene, polyester, polyvinyl alcohol, butadiene styrene rubber (SBR), and nitrile butadiene rubber; polyethylene, Fiber aggregate obtained by bonding or bonding synthetic fibers such as polypropylene, polyethylene terephthalate, and nylon; rayon fibers; fibers obtained by pressing, bonding, or bonding hydrophilic fibers such as cellulose fibers such as cellulose, cellulose acetate, and nitrocellulose; and polyamide fibers. An aggregate is exemplified, and examples of the shape include a sheet, a fiber, and a particle. Among them, a sheet is preferable. Preferably, it is a fiber aggregate in which hydrophilic fibers such as cellulose fibers and rayon fibers are pressure-bonded, bonded or bonded. These liquid diffusion members may be manufactured in a line at the time of manufacturing an absorber or an absorbent article.
[0055]
These a. b. The required performance of the liquid diffusion member shown in (1) is as described above.
(2-3) Water absorbent resin
The water-absorbing resin of the present invention is a hydrophilic cross-linked polymer, and when the aqueous liquid comes into contact with, for example, the particulate polymer, the polymer particles swell by absorbing the liquid into the particles, A polymer having a property of forming a hydrogel containing a liquid (a water-swellable water-insoluble hydrogel-forming polymer); and an additive added to the water-swellable water-insoluble hydrogel-forming polymer. The amount of the additive is less than 30% by weight based on the total amount of the water-swellable water-insoluble hydrogel-forming polymer and the additive.
[0056]
Until now, water-absorbent resins have been used as liquid storage members such as disposable diapers as those that absorb liquid by the difference in osmotic pressure between the inside and outside of the resin. It was noted that even when the known physical properties are the same, the absorption behavior differs greatly when absorbing liquid from a liquid diffusion member or the like depending on the type of resin. And the present inventor has studied diligently and found that even the water-absorbent resin alone has a large difference in the capillary absorption capacity, and the specific conditions in which the relationship between the capillary absorption capacity of the liquid diffusion member and the capillary absorption capacity of the water-absorbency resin is satisfied. In some cases, it has been found that the water-absorbent resin can receive and store the liquid better than the liquid diffusion member.
[0057]
As described above, the water-absorbent resin that can be used in the present invention is 40 cm as the water-absorbent resin when the capillary absorption index at a height of 40 cm of the liquid diffusion member is A (where A ≧ 0.10). Having a capillary absorption index B at a height of B / A ≧ 0.7, preferably satisfying B / A ≧ 1.3, more preferably satisfying B / A ≧ 1.40. It is.
The value of the capillary absorption index B at a height of 40 cm of the water-absorbent resin required for the present invention depends on the characteristics of the liquid diffusion member used, that is, the capillary absorption index A at a height of 40 cm of the liquid diffusion member used. If the relationship of ≧ 0.7 is satisfied, the liquid is satisfactorily distributed from the liquid diffusion member to the water-absorbing resin, and the water-absorbing resin can satisfactorily absorb and store the liquid. Preferably, the water-absorbing resin has a capillary absorption index B at a height of 40 cm of 0.4 or more, more preferably 0.5 or more, and still more preferably 0.6 or more.
[0058]
Further, the water-absorbent resin used in the present invention preferably has a capillary absorption capacity at a height of 0 cm of 30 (g / g) or more. As the capillary absorption capacity at a height of 0 cm is higher, a larger amount of the liquid sucked up from the liquid diffusion member can be grasped, so that an excellent absorbent can be obtained from the viewpoint of the liquid absorption capacity. More preferably, it is a water-absorbent resin having a capillary absorption capacity at a height of 0 cm of 40 (g / g) or more, and further preferably 50 (g / g) or more at a height of 0 cm.
Another water-absorbent resin that can be used in the present invention is a liquid-diffusion member having a capillary absorption capacity at a height of 40 cm of C (where C ≧ 2.0 (g / g)). A water-absorbent resin having a capillary absorption capacity D at a height of 40 cm satisfying D / C ≧ 0.7, preferably satisfying D / C ≧ 1.3, more preferably D / C ≧ 1.40. Is satisfied.
[0059]
The value of the capillary absorption capacity D at a height of 40 cm of another water-absorbent resin required for the present invention depends on the characteristics of the liquid diffusion member to be used, that is, the capillary absorption capacity C at a height of 40 cm of the used liquid diffusion member. If the relationship of D / C ≧ 0.7 is satisfied, the liquid is well distributed from the liquid diffusion member to the water-absorbing resin, and the water-absorbing resin can absorb and store the liquid well. Preferably, the water absorption resin has a capillary absorption capacity D at a height of 40 cm of 15 (g / g) or more, more preferably 20 (g / g) or more, still more preferably 25 (g / g) or more, and most preferably 30 or more. (G / g) or more.
[0060]
Similarly, the water absorbing resin used in the present invention preferably has a capillary absorption capacity at a height of 0 cm of 30 (g / g) or more. As the capillary absorption capacity at a height of 0 cm is higher, a larger amount of the liquid sucked up from the liquid diffusion member can be grasped, so that an excellent absorbent can be obtained from the viewpoint of the liquid absorption capacity. More preferably, it is a water-absorbent resin having a capillary absorption capacity at a height of 0 cm of 40 (g / g) or more, and further preferably 50 (g / g) or more at a height of 0 cm.
Further, when the water-absorbing resin used in the present invention has a water absorption ratio of 20 to 50 g / g under a pressure of 2.07 kPa (0.3 psi), it is good even when the absorber is in a pressurized state. It is preferable because it is possible to maintain a good absorbency, and more preferably 25 to 40 g / g.
[0061]
The water-absorbing resin which can be used in the present invention satisfies the above conditions, and is used in combination with a liquid diffusion member for an absorber.
The shape of the water-absorbent resin can be in the form of particles, fibers, sheets, strips, and the like, but in general, particles are preferred. Preferably, the basic particles mainly composed of acrylic acid (salt) have a weight average particle diameter of 250 μm or less, and the particle diameter distribution of the particles is narrow. As the production method, aqueous solution polymerization, reversed phase suspension polymerization and the like can be used, but those obtained by reversed phase suspension polymerization are preferred. From the viewpoint of handleability, the water-absorbent resin composed of the above basic particles may be granulated while maintaining the capillary absorption capacity of the present invention, and the weight average particle diameter may be out of the above range.
[0062]
In the present invention, a resin satisfying the above relationship and a water absorbing resin not satisfying the above relationship may be used in combination as the water absorbing resin, but in order to maximize the effect of the present invention, only the resin satisfying the above relationship is used. Is preferred. Further, it is preferable that the resin is arranged so that the capillary absorption capacity of the water absorbing resin in a portion closer to the liquid diffusion member satisfies the above relationship.
Examples of the water-absorbent resin that can be used in the present invention include, for example, a water-swellable crosslinked polymer that can be obtained by polymerizing a hydrophilic monomer, among which acrylic acid or a salt thereof as a main component Polyacrylic acid (salt) -based crosslinked polymers are preferred. Specifically, partially neutralized crosslinked polyacrylic acid polymers (US Pat. Nos. 4,625,001, 4,654,039, 5,250,640, 5,275,773, and EP 456136) are crosslinked and partially neutralized. Starch-acrylic acid graft polymer (US Pat. No. 4,076,663), isobutylene-maleic acid copolymer (US Pat. No. 4,389,513), saponified vinyl acetate-acrylic acid copolymer (US Pat. No. 4,124,748), A hydrolyzate of an acrylamide (co) polymer (US Pat. No. 3,959,569) and a hydrolyzate of an acrylonitrile polymer (US Pat. No. 3,935,099) are exemplified. As the polyacrylic acid (salt) -based crosslinked polymer, it is preferable that 50 to 90 mol% of the acid groups in the polymer is neutralized, and examples of the salt include alkali metal salts, ammonium salts, amine salts and the like. You can do it.
[0063]
The water-absorbing resin used in the present invention and the polyacrylic acid (salt) -based crosslinked polymer preferably used in the present invention may be used in combination with a monomer used as a main component (for example, the above acrylic acid or a salt thereof). Other monomers may be copolymerized. Specific examples of other monomers include methacrylic acid, maleic acid, vinylsulfonic acid, styrenesulfonic acid, 2- (meth) acrylamido-2-methylpropanesulfonic acid, 2- (meth) acryloylethanesulfonic acid, Anionic unsaturated monomers such as 2- (meth) acryloylpropanesulfonic acid and salts thereof; acrylamide, methacrylamide, N-ethyl (meth) acrylamide, Nn-propyl (meth) acrylamide, N-isopropyl (meth) ) Acrylamide, N, N-dimethyl (meth) acrylamide, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, methoxypolyethylene glycol (meth) acrylate, polyethylene glycol mono (meth) acrylate, vinylpyridyl , N-vinylpyrrolidone, N-acryloylpiperidine, N-acryloylpyrrolidine, and other nonionic hydrophilic group-containing unsaturated monomers; N, N-dimethylaminoethyl (meth) acrylate, N, N-diethylaminoethyl (meth) Examples thereof include cationic unsaturated monomers such as acrylate, N, N-dimethylaminopropyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylamide and quaternary salts thereof. The amount of the monomer other than these acrylic acids to be used is generally preferably 0 to 30 mol%, more preferably 0 to 10 mol%, based on all monomers.
[0064]
As a method for introducing a crosslinked structure into the water-absorbing resin used in the present invention, there are a self-crosslinking type without using a crosslinking agent, an internal having at least two polymerizable unsaturated groups or at least two reactive groups. Examples thereof include those that copolymerize or react a crosslinking agent. Preferably, an internal crosslinking agent is copolymerized or reacted.
Specific examples of these internal crosslinking agents include, for example, N, N′-methylenebis (meth) acrylamide, (poly) ethylene glycol di (meth) acrylate, (poly) propylene glycol di (meth) acrylate, trimethylolpropanetri (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) allyloxyalkane, (poly) ethyl Glycol diglycidyl ether, glycerol diglycidyl ether, ethylene glycol, polyethylene glycol, propylene glycol, glycerol, pentaerythritol, ethylenediamine, polyethyleneimine, and glycidyl (meth) acrylate can be mentioned. Further, two or more of these internal crosslinking agents may be used. Among them, a compound having two or more polymerizable unsaturated groups is preferably used as an internal cross-linking agent in view of the water-absorbing properties of the obtained water-absorbing resin, and the amount thereof is preferably based on the amount of the monomer component. The content is 0.005 to 3 mol%, more preferably 0.01 to 1.5 mol%.
[0065]
In the polymerization, hydrophilic polymers such as starch / cellulose, starch / cellulose derivatives, polyvinyl alcohol, polyacrylic acid (salt), cross-linked polyacrylic acid (salt), hypophosphorous acid A chain transfer agent such as an acid (salt) may be added.
When polymerizing the above-described monomer containing acrylic acid or a salt thereof as a main component in order to obtain the water-absorbent resin used in the present invention, bulk polymerization or precipitation polymerization can be performed. From the viewpoint of easy control of polymerization, it is preferable to perform aqueous solution polymerization and reverse phase suspension polymerization using the monomer as an aqueous solution. Such a polymerization method is conventionally known, for example, U.S. Patent Nos. 4,625,001, 4,769,427, 4,873,299, 4,093,776, 4,369,323, 4,446,261, 4,683,274, 4,690,996, and 4,721,647, Nos. 4738867 and 4748076.
[0066]
In performing the polymerization, a radical polymerization initiator such as potassium persulfate, ammonium persulfate, sodium persulfate, t-butyl hydroperoxide, hydrogen peroxide, 2,2′-azobis (2-amidinopropane) dihydrochloride, Active energy rays such as ultraviolet rays and electron beams can be used. When an oxidizing radical polymerization initiator is used, redox polymerization may be performed by using a reducing agent such as sodium sulfite, sodium hydrogen sulfite, ferrous sulfate, or L-ascorbic acid in combination. The amount of these polymerization initiators used is usually 0.001 to 2 mol%, preferably 0.01 to 0.5 mol%.
[0067]
The shape of the water-absorbent resin obtained by the above-mentioned polymerization is generally an irregular crushed shape, spherical shape, fibrous shape, rod shape, substantially spherical shape, flat shape, or the like.
In order to obtain a water-absorbent resin having a high capillary absorption index and a high capillary absorption capacity at a height of 40 cm used in the present invention, it is preferable that the particle surface is cross-linked by a surface cross-linking agent.
Examples of the surface cross-linking agent that can be used for the surface cross-linking of the water-absorbent resin include ethylene glycol, diethylene glycol, propylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, 1,3-propanediol, dipropylene glycol, 2,4-trimethyl-1,3-pentanediol, polypropylene glycol, glycerin, polyglycerin, 2-butene-1,4-diol, 1,3-butanediol, 1,4-butanediol, 1,5-pentane Diol, 1,6-hexanediol, 1,2-cyclohexanedimethanol, 1,2-cyclohexanol, trimethylolpropane, diethanolamine, triethanolamine, polyoxypropylene, oxyethylene-oxypro Polyhydric alcohol compounds such as ren block copolymer, pentaerythritol and sorbitol; ethylene glycol diglycidyl ether, polyethylene diglycidyl ether, glycerol polyglycidyl ether, diglycerol polyglycidyl ether, polyglycerol polyglycidyl ether, propylene glycol diglycidyl ether , Polypropylene glycol diglycidyl ether, epoxy compounds such as glycidol; polyamine compounds such as ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, polyethyleneimine, and inorganic or organic salts thereof (for example, 2,4-tolylene diisocyanate, hexamethylene diisocyanate A polyvalent isocyanate compound such as 1,2-ethylenebisoxazoline; a polyvalent oxazoline compound such as 1,2-ethylenebisoxazoline; 1,3-dioxolan-2-one; 4-methyl-1,3-dioxolan-2-one; Dimethyl-1,3-dioxolan-2-one, 4,4-dimethyl-1,3-dioxolan-2-one, 4-ethyl-1,3-dioxolan-2-one, 4-hydroxymethyl-1,3 -Dioxolan-2-one, 1,3-dioxan-2-one, 4-methyl-1,3-dioxan-2-one, 4,6-dimethyl-1,3-dioxan-2-one, 1,3 Alkylene carbonate compounds such as dioxopan-2-one; haloepoxy compounds such as epichlorohydrin, epibromohydrin, α-methylepichlorohydrin, and polyamines thereof (Eg, Hercules-made sponge; registered trademark); silane coupling agent such as γ-glycidoxypropyltrimethoxysilane, γ-aminopropyltriethoxysilane; hydroxylation of zinc, calcium, magnesium, aluminum, iron, zirconium, etc. And polyvalent metal compounds such as chlorides.
[0068]
Among them, it is preferable to use surface cross-linking agents having different solubility parameters in combination. Preferably, the solubility parameter is 25.6 [(J / cm³)^1/2] (12.5 [(cal / cm³)^1/2]) The above first surface crosslinking agent, the solubility parameter is 25.6 [(J / cm³)^1/2] (12.5 [(cal / cm³)^1/2]) Less than the second surface cross-linking agent. The solubility parameter of the surface cross-linking agent is described in U.S. Pat. No. 5,422,405.
The use amount of the surface crosslinking agent is preferably about 0.001 to 5 parts by weight based on 100 parts by weight of the water absorbent resin. If the amount is more than 5 parts by weight or less than 0.001 part by weight, it may be difficult to obtain a surface crosslinked layer within the range of the present invention.
[0069]
Water may be used when mixing the surface cross-linking agent of the present invention with a water-absorbing resin. In general, the amount of water used is more than 0.5 part by weight and preferably 10 parts by weight or less, more preferably 1 part by weight to 5 parts by weight based on 100 parts by weight of the solid content of the water-absorbent resin.
When mixing the surface crosslinking agent or the aqueous solution thereof, a hydrophilic organic solvent or a third substance may be used. When a hydrophilic organic solvent is used, for example, lower alcohols such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, t-butyl alcohol; ketones such as acetone; Ethers such as dioxane, tetrahydrofuran and methoxy (poly) ethylene glycol; amides such as ε-caprolactam and N, N-dimethylformamide; sulfoxides such as dimethyl sulfoxide; ethylene glycol, diethylene glycol, propylene glycol, triethylene glycol and tetra Ethylene glycol, polyethylene glycol, 1,3-propanediol, dipropylene glycol, 2,2,4-trimethyl-1,3-pentanediol, polypropylene Glycol, glycerin, polyglycerin, 2-butene-1,4-diol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,2-cyclohexane Examples include dimethanol, 1,2-cyclohexanol, trimethylolpropane, diethanolamine, triethanolamine, polyoxypropylene, oxyethylene-oxypropylene block copolymer, polyhydric alcohols such as pentaerythritol and sorbitol. The amount of the hydrophilic organic solvent used depends on the type, particle size, water content, etc. of the water-absorbing resin, but is preferably 50 parts by weight or less, and more preferably 0.1 part by weight, based on 100 parts by weight of the solid content of the water-absorbing resin. More preferably, the amount is in the range of 10 parts by weight to 10 parts by weight. Further, inorganic acids, organic acids, polyamino acids and the like described in European Patent No. 0668080 may be present as the third substance.
[0070]
The mixing method for mixing the water-absorbent resin and the surface cross-linking agent is not particularly limited. For example, a surface obtained by immersing the water-absorbent resin in a hydrophilic organic solvent and dissolving in water and / or a hydrophilic organic solvent as necessary. Examples of the method include a method of mixing a crosslinking agent, and a method of directly spraying or dropping a surface crosslinking agent dissolved in water and / or a hydrophilic organic solvent on a water-absorbent resin and mixing. Also, by controlling the mixing temperature, that is, the temperature of the water-absorbent resin powder before mixing, and the temperature of the treating agent including the surface cross-linking agent, both within a specific range, the thickness and weight ratio of the surface cross-linked layer are controlled within the range of the present invention. May be easier to do. In the case of mixing using water, fine powder insoluble in water, a surfactant, or the like may be allowed to coexist.
[0071]
After mixing the water-absorbent resin and the surface cross-linking agent, a heat treatment is usually performed to carry out a cross-linking reaction. The heating temperature depends on the surface cross-linking agent used, but it is preferable that the temperature of the water-absorbent resin powder be 40 ° C. or more and 250 ° C. or less. When the treatment temperature is lower than 40 ° C., it may not be possible to obtain a water absorbing agent having excellent water absorbing properties. If the treatment temperature exceeds 250 ° C., the water-absorbent resin may be deteriorated, and the performance may be reduced. The heat treatment time is about 1 minute to 2 hours, preferably about 5 minutes to 1 hour.
Among the methods described above, preferred methods for obtaining a water-absorbent resin excellent in the capillary absorption index B at a height of 40 cm and the capillary absorption ratio D at a height of 40 cm that can be used in the present invention include:
(1) A water-absorbent resin precursor having a carboxyl group having a weight average particle diameter of 250 µm or less, preferably 40 to 200 µm, more preferably 70 to 150 µm, can react with the carboxyl group and has a solubility parameter of 25. 6 [(J / cm³)^1/2] (12.5 [(cal / cm³)^1/2]) The above first surface cross-linking agent and a solubility parameter of 25.6 [(J / cm³)^1/2] (12.5 [(cal / cm³)^1/2A) heat treatment in the presence of less than a second surface cross-linking agent;
(2) A water-absorbent resin precursor having a carboxyl group having a weight average particle diameter of 250 μm or less, preferably 40 to 200 μm, more preferably 70 to 150 μm, obtained by reverse phase suspension polymerization, having a water content of 10 % Or less, the absorption capacity under pressure under 2.07 kPa (0.3 psi) in the presence of a surface crosslinking agent is 20 (g / g) or more, preferably 25 (g / g) or more, and preferably 30 (g / g) or more. / G) a method of treating with a solvent after heat treatment so as to be not less than
(3) A water-absorbing resin precursor having a carboxyl group having a weight-average particle diameter of 100 to 1000 μm is subjected to a surface cross-linking treatment in the presence of a polyhydric alcohol or an alkylene carbonate, and then classified by a sieve having a specific particle size. A method for obtaining particles having a diameter of 300 μm or less, preferably having a weight average particle diameter of 10 to 250 μm, more preferably 70 to 150 μm,
Etc. can be exemplified.
[0072]
By such a method, a water-absorbing resin having a capillary absorption capacity D at a height of 40 cm of, for example, 15 (g / g) or more, preferably 20 (g / g) or more, and most preferably 25 (g / g) or more is obtained. It is obtained and can be suitably used in the present invention. In addition, a water-absorbing resin having a capillary absorption index B at a height of 40 cm of, for example, 0.4 or more, preferably 0.5 or more, and more preferably 0.6 or more is obtained by the above method, and can be suitably used in the present invention.
Above all, a water-absorbing resin whose main component is a polyacrylic acid (salt) -based crosslinked polymer obtained by reverse phase suspension polymerization having a weight average particle diameter of 250 μm or less subjected to the surface crosslinking treatment by the method (2) above is preferable. By selecting the conditions, it is possible to obtain an unprecedented resin having a capillary absorption magnification D at a height of 40 cm of, for example, 25 (g / g) or more. The presence or absence of the surface crosslinking treatment can be determined by the method described in Japanese Patent Application No. 11-309105.
[0073]
The water-absorbent resin of the present invention further comprises a water-swellable water-insoluble hydrogel-forming polymer, silicon dioxide, titanium dioxide, aluminum oxide, magnesium oxide, zinc oxide, talc, calcium phosphate, barium phosphate, silicic acid or a salt thereof, clay, Water-insoluble particulate inorganic powders such as diatomaceous earth, zeolite, bentonite, kaolin, hydrotalcite, active white salts, etc .; deodorants, fragrances, antibacterial agents, cationic polymer compounds such as polyamines, adhesives, adhesives, Addition of additives such as a foaming agent, a pigment, a dye, a fertilizer, an oxidizing agent, a reducing agent, and water to be included in or adhered to the water-swellable water-insoluble hydrogel-forming polymer, so that the water-absorbing resin has a further function. May be added or increased. The proportion of the additive used is preferably less than 30% by weight, more preferably less than 10% by weight, even more preferably less than 5% by weight, based on the total amount of the water-swellable water-insoluble hydrogel-forming polymer and the additive. Particularly preferably, it is less than 1% by weight.
(2-4) Absorber
The absorber of the present invention is obtained by combining the liquid diffusion member and the water-absorbing resin so as to satisfy the liquid diffusion storage coefficient 1 and / or the liquid diffusion storage coefficient 2 of the present invention.
[0074]
The absorbent of the present invention can also be obtained by using a liquid-absorbing resin having a capillary absorption capacity D of 15 (g / g) or more at a height of 40 cm for a liquid diffusion member having a suction height of 30 cm or more and a liquid storage member. Can be
Further, the absorbent body of the present invention can be obtained by using a liquid diffusion member having a suction height of 30 cm or more and a water-absorbing resin having a weight average particle diameter of 250 μm or less subjected to a surface cross-linking treatment for a liquid storage member.
The absorber of the present invention may use other materials besides the liquid diffusion member and the water absorbent resin as long as the liquid diffusion / storage system intended by the present invention is not hindered. Examples of other materials include hydrophilic fiber, non-woven fabric, paper, tissue and the like. Examples of the hydrophilic fibers include cellulose fibers such as mechanical pulp, chemical pulp, semi-chemical pulp, and dissolved pulp obtained from wood, and fibers such as rayon and acetate. Among the fibers exemplified above, cellulose fibers are preferred. Further, the hydrophilic fibers may contain synthetic fibers such as polyamide, polyester, and polyolefin. In addition, the hydrophilic fiber is not limited to the fiber exemplified above. Examples of the nonwoven fabric include nonwoven fabrics such as polyester such as spunbond, chemical bond, and spunlace, polyethylene, polypropylene, nylon, and rayon.
[0075]
The ratio of the water-absorbent resin and the liquid diffusion member in the absorber can be selected in an arbitrary range, but the weight ratio of the water-absorbent resin to the total amount of the water-absorbent resin and the liquid diffusion member is preferably 5% by weight to 99%. % By weight, more preferably from 20% by weight to 90% by weight, still more preferably from 30% by weight to 80% by weight.
In particular, when the weight ratio of the water-absorbent resin to the total amount of the water-absorbent resin and the liquid diffusion member is 75% by weight or more and 90% by weight or less, the use amount of the liquid diffusion member can be relatively reduced. In terms of shape, it is preferable because a lighter and thinner absorber can be manufactured. In order to manufacture an absorbent body in which the weight of the water-absorbent resin is 75% by weight or more and 90% by weight or less based on the total amount of the water-absorbent resin and the liquid diffusion member, the water-absorbent resin is made of a capillary at a height of 40 cm. It is more preferable to use one having an absorption capacity D of 15 (g / g) or more. In the case of using a water-absorbent resin having a capillary absorption capacity D at a height of 40 cm of 15 (g / g) or more, the transfer and distribution of the liquid from the liquid diffusion member to the water-absorbent resin are improved. The storage capacity of the liquid diffusion member is not required so much, and the amount of the liquid diffusion member used can be greatly reduced. The liquid diffusion member at that time is preferably a porous polymer obtained by polymerizing a high internal phase emulsion and having a suction height of 30 cm or more.
[0076]
As the arrangement position of the water-absorbent resin, the back surface of the liquid diffusion member, the front surface of the liquid diffusion member, a part of the back side of the liquid diffusion member, a part of the front side of the liquid diffusion member, between the liquid diffusion members, the liquid diffusion member Medium or the like can be exemplified, and these arrangement methods may be combined. Above all, it is preferable to arrange a water-absorbing resin on the back side of the liquid diffusion member, and it is preferable that the water-absorbing resin is present in a layered form. Further, the basis weight of the water-absorbent resin is 50 to 500 g / m.²It is about.
As the arrangement state of the water-absorbent resin, there are a state where the water-absorbing resin is uniformly present on the entire surface of the liquid-diffusing member, a state where the resin is present in a specific pattern, a state where it is present with a density gradient, and , A state existing only before and after the liquid diffusion member, and the like.
[0077]
In addition, the water-absorbing resin itself is formed into a sheet by a conventionally known method, or sprayed on a substrate to be immobilized, packed in a bag, or provided with tackiness and then combined with a liquid diffusion member. Is also good. Further, the water-absorbing resin and the liquid diffusion member may be bonded using an adhesive binder.
Examples of the adhesive binder include polyethylene, polypropylene, ethylene-propylene copolymer, heat-fusible fibers such as polyolefin fibers such as 1-butene-ethylene copolymer, adhesive emulsions, and hot melt adhesives. Can be illustrated. These adhesive binders may be used alone or as a mixture of two or more.
[0078]
In the absorber of the present invention, further, silicon dioxide, titanium dioxide, aluminum oxide, magnesium oxide, zinc oxide, talc, calcium phosphate, barium phosphate, silicic acid or a salt thereof, clay, diatomaceous earth, zeolite, bentonite, kaolin, hydrogel Water-insoluble particulate inorganic powders such as talcite and active white salts; deodorants, fragrances, antibacterial agents, cationic polymer compounds such as polyamines, foaming agents, pigments, dyes, hydrophilic short fibers, fertilizers, oxidation Additives, reducing agents, water and the like can be added to give the absorber a further function.
[3] Absorber including liquid acquisition member and water absorbent resin layer
(3-1) Relationship between Capillary Absorption Capability of Liquid Acquisition Member and Water Absorbent Resin (Layer)
The relationship between the liquid acquisition member and the capillary absorption capacity of the water absorbent resin (layer) in the present invention will be described.
[0079]
The water-absorbent resin layer combined with the liquid acquisition member has a water-absorbent resin content of 250 g / m2.²It is preferable that the water-absorbing resin is contained in the above-mentioned spray amount, and the water-absorbing resin is formed into a substantially continuous layer when swollen. 250g / m²If it is less than 3, the saturated absorption amount of the absorber becomes small, the liquid acquisition layer cannot be dried sufficiently, the dry feeling is inferior, and the return amount of the liquid tends to increase. More preferably, the spray amount of the water absorbent resin layer is 300 g / m.²Above, more preferably 350 g / m²Above, particularly preferably 400 g / m²That is all.
The water-absorbent resin layer is composed of only the water-absorbent resin or a mixture of the water-absorbent resin and another water-absorbent or hydrophilic material. Examples of the water-absorbing or hydrophilic material other than the water-absorbing resin include natural fibers such as pulp, rayon, polyester, and nylon, fibers such as regenerated fibers and synthetic fibers, and hydrophilically treated products thereof. . The proportion of the water-absorbing resin in the water-absorbing resin layer is preferably 70% by weight or more, more preferably 80% by weight or more, and still more preferably 90% by weight or more, from the viewpoint of making the absorber thinner and increasing the water absorption. It is particularly preferable that the resin is composed of only a water-absorbing resin (that is, 100% by weight).
[0080]
As the water-absorbing resin that can be used in the present invention, when the capillary absorption index at a height of 40 cm of the liquid acquisition member is E (where E <0.1), the water-absorbing resin has a height of 40 cm. Is such that the capillary absorption index B satisfies the following expression.
B / E ≧ 10 ° (Equation 3)
Further, the water-absorbent resin layer that can be used in the present invention, when the capillary absorption index at a height of 40 cm of the liquid acquisition member is E (where E <0.1), The capillary absorption index F at a height of 40 cm satisfies the following equation.
[0081]
F / E ≧ 10 ° (Equation 4)
The value of the capillary absorption index B or F at a height of 40 cm of the water-absorbent resin or the water-absorbent resin layer required for the present invention is the characteristic of the liquid acquisition member used, that is, the capillary absorption index at a height of 40 cm of the liquid acquisition member used. If the relationship of B / E ≧ 10 or F / E ≧ 10 is satisfied, the liquid is satisfactorily absorbed from the liquid acquisition member to the water-absorbent resin, and the water-absorbent resin sufficiently dries the liquid acquisition member. be able to. When B / E or F / E is less than 10, the water-absorbent resin cannot sufficiently absorb the liquid from the liquid acquisition member, the liquid acquisition member remains wet, and the next liquid can be received instantaneously. Can not. The water-absorbent resin preferably satisfies B / E ≧ 20 or F / E ≧ 20, and more preferably the water-absorbent resin satisfies B / E ≧ 30 or F / E ≧ 30. Hereinafter, the value of B / E or F / E may be referred to as liquid acquisition storage coefficient 1. B represents the water-absorbing resin alone, and F represents the capillary absorption index obtained by using the water-absorbing resin layer as it is when it is difficult to isolate the water-absorbing resin from the water-absorbing resin layer.
[0082]
As an absorbent that can be used in the present invention, the capillary absorption ratio G at a height of 40 cm of the liquid acquisition member is 1.0 (g / g) or less, and the capillary absorption at a height of 40 cm of the water absorbent resin. Magnification D is 5 (g / g) or more.
Further, as another absorber that can be used in the present invention, a capillary absorption capacity G at a height of 40 cm of the liquid acquisition member is 1.0 (g / g) or less, and 40 cm of the water-absorbent resin layer. The capillary absorption capacity H at a height of 5 g / g or more.
If the liquid acquisition member and the water-absorbent resin or the water-absorbent resin layer satisfy these relationships, the liquid is well distributed from the liquid acquisition member to the water-absorbent resin, and the water-absorbent resin dries the liquid acquisition member well, And the liquid can be absorbed and stored.
[0083]
When D or H is less than 5 (g / g), it is difficult for the water-absorbing resin to sufficiently absorb the liquid from the liquid acquisition member, and the liquid acquisition member does not dry and has a very large return amount. . Preferably, the value of the capillary absorption ratio D or H at a height of 40 cm of the water-absorbent resin or the water-absorbent resin layer required for the present invention is 10 (g / g) or more, more preferably 15 (g / g) or more. Most preferably, it is 20 (g / g) or more. Further, hereinafter, when the value of D / F or H / F of the liquid acquisition member is set as the liquid acquisition storage coefficient 2, this value is preferably 30 or more, more preferably 50 or more.
In the present invention, it is more preferable that all the values of the liquid acquisition storage coefficients 1, D, and H satisfy the range of the present invention. It should be noted that when only one of them is satisfied, the ability of the water absorbing resin to absorb the liquid from the liquid acquiring member may not be sufficiently exhibited depending on the use conditions. As described above, D means the water-absorbing resin alone, and H means the capillary absorption capacity obtained by using the water-absorbing resin layer as it is when it is difficult to isolate the water-absorbing resin from the water-absorbing resin layer.
(3-2) Liquid acquisition member
The liquid acquisition member that can be used in the present invention is a member that plays a role in capturing the liquid added to the absorber or the absorbent article having the absorber instantaneously and not out of the absorber, It is defined as a material having a capillary absorption index E at a height of 40 cm of less than 0.10 and a capillary absorption capacity G at a height of 40 cm of 1.0 (g / g) or less. It has a structure capable of maintaining a space for capturing the liquid even after applying force or absorbing water.
[0084]
The liquid obtaining member that can be used in the present invention is excellent in liquid obtaining ability and liquid discharging ability, and it is necessary that the capillary absorption index E at a height of 40 cm is less than 0.1. . The capillary absorption index E at a height of 40 cm of a flap pulp or the like used for a conventional disposable diaper is 0.04 according to the measuring method of the present invention, and such a substance can be used as the liquid acquisition member of the present invention. Although it is possible, it is preferable that this value is small because the liquid acquisition property and the liquid release property are excellent. A material having a capillary absorption index E of 0.10 or more retains the liquid relatively strongly inside the material, and when the liquid is repeatedly absorbed, the liquid acquisition performance sharply decreases. It is difficult to improve the return amount. Preferably, the capillary absorption index E at a height of 40 cm is 0.03 or less.
[0085]
Further, the liquid acquisition member that can be used in the present invention preferably has a capillary absorption capacity at a height of 0 cm of 5 (g / g) or more. As the capillary absorption capacity at a height of 0 cm is higher, the amount of liquid obtained as a liquid obtaining member is larger, and an absorber excellent in instantaneous absorption and temporary storage of liquid can be obtained. More preferably, the capillary absorption capacity at a height of 0 cm is 10 (g / g) or more, and further preferably the capillary absorption capacity at a height of 0 cm is 15 (g / g) or more.
Another liquid acquisition member that can be used in the present invention is required to have a capillary absorption capacity G at a height of 40 cm of 1.0 (g / g) or less. The capillary absorption capacity G of a conventional flap pulp or the like used for disposable diapers at a height of 40 cm is about 0.5 (g / g), and such a substance can be used as the liquid acquisition member of the present invention. It is preferable that this value is small, because the liquid obtaining property and the liquid releasing property are excellent. A material having a capillary absorption ratio G of more than 1.0 (g / g) at a height of 40 cm holds the liquid relatively strongly inside the member, and when the liquid is repeatedly absorbed, the liquid acquisition performance sharply increases. As a result, leakage, wet feeling, return amount, and the like are hardly improved. The capillary absorption capacity G at a height of 40 cm is preferably 0.4 (g / g) or less, more preferably 0.2 (g / g) or less.
[0086]
Similarly, another liquid acquisition member that can be used in the present invention preferably has a capillary absorption capacity at a height of 0 cm of 5 (g / g) or more. This is not the case. However, in general, the higher the capillary absorption capacity at a height of 0 cm, the greater the amount of liquid obtained as a liquid obtaining member, and an absorber excellent in instantaneous absorption and temporary storage of liquid can be obtained. More preferably, the capillary absorption capacity at a height of 0 cm is 10 (g / g) or more, and further preferably the capillary absorption capacity at a height of 0 cm is 15 (g / g) or more.
The liquid acquisition member that can be used in the present invention satisfies the above conditions, and is used in combination with a water-absorbing resin (layer) for an absorber.
[0087]
As described above, when the capillary absorption index at a height of 40 cm of the liquid acquisition member is E (where E <0.1) as described above, the capillary absorption index B at a height of 40 cm of the water absorbent resin is It is necessary that B / E ≧ 10 or that the water-absorbent resin layer has a capillary absorption index F at a height of 40 cm that satisfies F / E ≧ 10.
Further, the relationship between the two is that when the capillary absorption ratio at a height of 40 cm of the liquid acquisition member is G (where G ≦ 1.0 (g / g)), the capillary absorption at a height of 40 cm is used as the water-absorbing resin. It is necessary that the magnification D satisfies 5 (g / g) or more, or that the water absorption resin layer has a capillary absorption magnification H at a height of 40 cm of 5 (g / g) or more.
[0088]
It is more preferable that both satisfy B / E ≧ 10 and D ≧ 5.0 at the same time, or that both satisfy F / E ≧ 10 and H ≧ 5.0 at the same time.
The shape of the liquid acquisition member may be a sheet shape, a fiber shape, a fiber aggregate, a particle shape, a strip shape, or the like, but a sheet shape is generally preferable. At that time, the basis weight of the liquid acquisition member is 50 to 500 g / m.²Degree is preferable, and more preferably 100 to 200 g / m.²It is about.
Further, when the liquid acquisition member has a density difference or a density gradient within the member, an acquisition capability difference or an acquisition capability gradient, or when further using a second liquid acquisition member / liquid diffusion member that does not satisfy the relationship of the present invention. It is preferable that the capillary absorption capacity of the liquid acquisition member in a portion closer to the water absorbent resin satisfies the above relationship.
[0089]
Examples of the liquid acquisition member that can be used in the present invention include flap pulp, crosslinked cellulose fibers, synthetic fibers such as nonwoven fabrics having a bulky structure, and porous heavy particles obtained by polymerizing a high internal phase emulsion (HIPE). Foam composed of synthetic polymer such as coalesced, polyurethane, polystyrene, polyethylene, polypropylene, polyester, polyvinyl alcohol, butadiene styrene rubber (SBR), and nitrile butadiene rubber; bonded or bonded with synthetic fibers such as polyethylene, polypropylene, polyethylene terephthalate, and nylon Rayon fibers; cellulose fibers such as cellulose, cellulose acetate and nitrocellulose; and fiber aggregates obtained by pressing, bonding or bonding hydrophilic fibers such as polyamide fibers. Preferably, it is a crosslinked cellulose fiber, a synthetic fiber such as a nonwoven fabric having a bulky structure, or a porous polymer obtained by polymerizing a high internal phase emulsion (HIPE).
(3-3) Water absorbent resin
Until now, water-absorbent resins have been used as liquid storage members such as disposable diapers as those that absorb liquid by the difference in osmotic pressure between the inside and outside of the resin. It was noted that even when the known physical properties are the same, when the liquid is absorbed from the liquid acquisition member or the like, the absorption behavior greatly differs depending on the type of the resin. And the present inventor has studied diligently and found that even the water-absorbent resin alone has a large difference in the capillary absorption capacity, and a specific condition having a relationship between the capillary absorption capacity of the liquid acquisition member and the capillary absorption capacity of the water-absorbency resin is satisfied. In some cases, it has been found that the water-absorbent resin can receive and store the liquid better than the liquid acquisition member.
[0090]
As described above, the water-absorbent resin that can be used in the present invention is 40 cm as the water-absorbent resin when the capillary absorption index at a height of 40 cm of the liquid acquisition member is E (where E <0.10). The capillary absorption index B at the height of satisfies B / E ≧ 10, preferably satisfies B / E ≧ 20, and more preferably satisfies B / E ≧ 30. The water-absorbent resin may be measured as it is with the absorbent resin layer taken out of the absorber. In this case, the water-absorbent resin layer has a capillary absorption index F at a height of 40 cm satisfying F / E ≧ 10. , Preferably satisfying F / E ≧ 20, and more preferably satisfying F / E ≧ 30.
[0091]
The values of the capillary absorption index B at a height of 40 cm of the water-absorbent resin and the capillary absorption index F at a height of 40 cm of the water-absorbent resin layer required for the present invention are the characteristics of the liquid acquisition member used, that is, 40 cm of the liquid acquisition member used. Depends on the capillary absorption index E at the height of the liquid, and if the relationship of B / E ≧ 10 or F / E ≧ 10 is satisfied, the liquid can be favorably transferred from the liquid acquisition member to the water-absorbent resin or the water-absorbent resin layer. As a result, the water-absorbent resin can absorb and store the liquid well, and dry the liquid obtaining member. Preferably, the water-absorbent resin has a capillary absorption index B at a height of 40 cm or a capillary absorption index F at a height of 40 cm of the water-absorbent resin layer of 0.2 or more, more preferably 0.4 or more, still more preferably 0.6 or more. That's all.
[0092]
The water-absorbent resin used in the present invention preferably has a capillary absorption capacity at a height of 0 cm of 20 (g / g) or more. As the capillary absorption capacity at a height of 0 cm is higher, a larger amount of liquid sucked from the liquid acquisition member can be grasped, so that an excellent absorbent is obtained from the viewpoint of liquid absorption capacity. More preferably, it is a water-absorbent resin having a capillary absorption capacity at a height of 0 cm of 30 (g / g) or more, more preferably 40 (g / g) or more at a height of 0 cm, and still more preferably 0 cm. Is a water-absorbent resin having a capillary absorption capacity of 50 (g / g) or more. If the capillary absorption capacity of the height of 0 cm is too high, even if a liquid diffusion member is used, the absorption capacity of the absorbent may be reduced. Care must be taken because the liquid may be difficult to enter inside.
[0093]
As another water-absorbent resin that can be used in the present invention, the water-absorbent resin has a capillary absorption capacity D at a height of 40 cm of preferably 5 (g / g) or more, more preferably 10 (g / g). g) or more, more preferably 15 (g / g) or more, most preferably 20 (g / g) or more. The water-absorbent resin may be measured as it is with the absorbent resin layer taken out from the absorber. In this case, the water-absorbent resin layer has a capillary absorption capacity H at a height of 40 cm, preferably 5 (g / g) or more. , More preferably 10 (g / g) or more, still more preferably 15 (g / g) or more, and most preferably 20 (g / g) or more.
[0094]
The water-absorbing resin which can be used in the present invention satisfies the above conditions, and is used in combination with a liquid obtaining member satisfying the requirements of the present invention for an absorber.
The shape of the water-absorbent resin can be in the form of particles, fibers, sheets, strips, and the like, but in general, particles are preferred. As the production method, aqueous solution polymerization, reverse phase suspension polymerization and the like can be used.
In the present invention, a resin satisfying the above relationship and a water absorbing resin not satisfying the above relationship may be used in combination as the water absorbing resin, but in order to maximize the effect of the present invention, only the resin satisfying the above relationship is used. Is preferred. In addition, it is preferable that the resin is disposed so that the capillary absorption capacity of the water-absorbing resin in a portion closer to the liquid acquisition member satisfies the above relationship.
[0095]
Examples of the water-absorbent resin that can be used in the present invention, examples and amounts of monomers used as raw materials of the water-absorbent resin, a method for introducing a crosslinked structure, a description on internal crosslinking, and examples of additives in polymerization. The amount used, the polymerization method, the shape of the obtained water-absorbent resin, the description of the surface crosslinking, and the description of the additive for imparting a further function to the water-absorbent resin are the same as those described in the above section (2-3). The same is true.
Preferred methods for obtaining a water-absorbent resin having an excellent capillary absorption index B at a height of 40 cm and a capillary absorption magnification D at a height of 40 cm that can be used in the present invention include:
(1) A water-absorbent resin precursor having a carboxyl group having a weight average particle diameter of 100 to 500 μm, more preferably 200 to 400 μm, can be reacted with the carboxyl group and has a solubility parameter of 25.6 [(J / cm³)^1/2] (12.5 [(cal / cm³)^1/2]) The above first surface cross-linking agent and a solubility parameter of 25.6 [(J / cm³)^1/2] (12.5 [(cal / cm³)^1/2A) heat treatment in the presence of less than a second surface cross-linking agent;
(2) A water-absorbent resin precursor having a carboxyl group having a weight average particle diameter of 250 μm or less, preferably 40 to 200 μm, more preferably 70 to 150 μm, obtained by reverse phase suspension polymerization, having a water content of 10 % And an absorption capacity under pressure of 0.3 (psi) in the presence of a surface crosslinking agent of 20 (g / g) or more, preferably 25 (g / g) or more, and more preferably 30 (g / g) or more. A method of treating with a solvent after heat treatment so that
(3) A water-absorbent resin precursor having a carboxyl group having a weight average particle diameter of 100 to 600 μm is treated in the presence of a polyhydric alcohol or an alkylene carbonate so as to have a specific surface crosslinked layer, and then a sieve having a specific particle size. A method of obtaining particles having a weight average particle diameter of 400 μm or less, preferably a weight average particle diameter of 100 to 400 μm,
Etc. can be exemplified.
[0096]
By such a method, a water-absorbing resin having a capillary absorption capacity D at a height of 40 cm of, for example, 10 (g / g) or more, preferably 15 (g / g) or more, and most preferably 25 (g / g) or more is obtained. It is obtained and can be suitably used in the present invention. In addition, a water-absorbing resin having a capillary absorption index B at a height of 40 cm of, for example, 0.2 or more, preferably 0.4 or more, and more preferably 0.6 or more at a height of 40 cm is obtained by the above method, and can be suitably used in the present invention.
(3-4) absorber
The absorber of the present invention is obtained by combining a liquid acquisition member and a water-absorbing resin layer satisfying the above characteristics. The water-absorbing resin layer has the same water-absorbing resin amount and constitution as described above.
[0097]
In the absorber of the present invention, the water-absorbing resin layer has a thickness of 250 g / m2.²It is preferable that the spraying amount is as described above, and the water-absorbing resin is configured to form a substantially continuous layer when swollen. 250g / m²If it is less than 3, the saturated absorption amount of the absorber becomes small, the liquid acquisition layer cannot be dried sufficiently, the dry feeling is inferior, and the return amount of the liquid tends to increase. Preferably, the spray amount of the water-absorbent resin layer is 300 g / m.²Or more, more preferably 350 g / m²Or more, more preferably 400 g / m²That is all.
The water-absorbent resin that can be used in the present invention, as long as it does not interfere with the liquid acquisition / storage system intended by the present invention, can be used in combination with a small amount of hydrophilic fiber, another base material such as a synthetic fiber to the water-absorbent resin. However, in order to maximize the transfer of the liquid from the liquid acquisition member, it is preferable to spray the water-absorbing resin itself to form the water-absorbing resin layer having the above-mentioned spray amount.
[0098]
In the absorber of the present invention, in addition to the liquid acquisition member and the water absorbent resin, other materials may be used as long as the liquid acquisition and storage system intended by the present invention is not hindered. Examples of other materials include hydrophilic fiber, non-woven fabric, paper, tissue and the like. Examples of the hydrophilic fibers include cellulose fibers such as mechanical pulp, chemical pulp, semi-chemical pulp, and dissolved pulp obtained from wood, and fibers such as rayon and acetate. Among the fibers exemplified above, cellulose fibers are preferred. Further, the hydrophilic fibers may contain synthetic fibers such as polyamide, polyester, and polyolefin. In addition, the hydrophilic fiber is not limited to the fiber exemplified above. Examples of the nonwoven fabric include nonwoven fabrics such as polyester such as spunbond, chemical bond, and spunlace, polyethylene, polypropylene, nylon, and rayon.
[0099]
In the absorber of the present invention, it is preferable that the liquid acquisition member and the water-absorbing resin layer are each composed of one layer. When there are two or more liquid acquisition members, the liquid is not sufficiently absorbed from all the liquid acquisition members in the absorbent article into the water-absorbent resin layer, and the dryness and the return amount may be poor. .
The ratio between the water absorbing resin layer and the liquid acquisition member in the absorber can be selected in an arbitrary range. Preferably, there is. More preferably, the content is 80% by weight or more and 95% by weight or less.
[0100]
The weight ratio of the liquid absorption of the water-absorbent resin layer to the liquid saturation absorption of the absorber is preferably 80% by weight or more. More preferably, it is 80% by weight or more and 95% by weight or less, further preferably 90% by weight or more and 95% by weight or less.
Although the amount of the liquid acquisition member of the present invention and the amount of the water-absorbent resin layer to be used depends on the size of the intended absorbent article, the liquid acquisition member is preferably 0.5 to It is about 4 g, more preferably about 1 to 2 g, preferably about 10 to 30 g, more preferably about 15 to 20 g for the water-absorbent resin layer.
The water-absorbent resin layer may be disposed on the back side of the liquid acquisition member (the liquid-impermeable back sheet side of the absorbent article), the front side of the liquid acquisition member, a part of the back side of the liquid acquisition member, or the front side of the liquid acquisition member. Part of the side, between the liquid acquisition members, inside the liquid acquisition member, etc. can be exemplified, and these arrangement methods may be combined. In particular, it is preferable to dispose a water-absorbing resin layer on the back side of the liquid acquisition member. The water-absorbent resin layer is arranged uniformly over the entire surface of the liquid acquisition member, in a specific pattern, in a streak, or with a density gradient. State, the state existing only at the center of the liquid acquisition member, the state existing only before and after the liquid acquisition member, and the like. It is preferable that the existing area is larger. Preferably, the area ratio of the water absorbent resin layer to the area 1 of the liquid acquisition member is 1.2 or more, more preferably 2 or more.
[0101]
In addition, the water-absorbing resin or the water-absorbing resin layer itself is formed into a sheet by a conventionally known method, sprayed on a substrate to be immobilized, packed in a bag, or provided with tackiness, and You may combine with an acquisition member. Further, the water absorbing resin layer and the liquid obtaining member may be bonded using an adhesive binder.
Examples of the adhesive binder include polyethylene, polypropylene, ethylene-propylene copolymer, heat-fusible fibers such as polyolefin fibers such as 1-butene-ethylene copolymer, adhesive emulsions, and hot melt adhesives. Can be illustrated. These adhesive binders may be used alone or as a mixture of two or more. In this case, it is more preferable that not only the water-absorbing resin alone but also the capillary-absorbing ability of the water-absorbing resin layer in a fixed state satisfies the range of the present invention.
[0102]
In the absorber of the present invention, further, silicon dioxide, titanium dioxide, aluminum oxide, magnesium oxide, zinc oxide, talc, calcium phosphate, barium phosphate, silicic acid or a salt thereof, clay, diatomaceous earth, zeolite, bentonite, kaolin, hydrotalcite Water-insoluble particulate inorganic powders such as active white salts; deodorants, fragrances, antibacterial agents, cationic polymer compounds such as polyamines, foaming agents, pigments, dyes, hydrophilic short fibers, fertilizers, oxidizing agents, A reducing agent, water or the like may be added to give the absorber an additional function.
The absorber according to the present invention, that is, the absorber including the liquid acquisition member and the water-absorbent resin layer, may further include the liquid diffusion member described above. In this case, both of the above-described features of the absorbent including the liquid diffusion member and the water absorbent resin according to the present invention and the features of the absorbent including the liquid acquisition member and the water absorbent resin layer according to the present invention are combined. The absorber is preferable because the effects of the present invention can be further exhibited.
[4] Absorbent articles
The absorbent article according to the present invention is generally the absorbent according to the present invention having the above structure, that is, the absorbent including the liquid diffusion member and the water absorbent resin, or the liquid acquisition member and the water absorbent resin. An absorber including a layer is sandwiched between a liquid-permeable sheet and a liquid-impermeable sheet. And since the said absorbent article has the absorber of the said structure, it is provided with the above-mentioned excellent water absorption characteristics. Specific examples of the absorbent article include, but are not particularly limited to, sanitary materials such as disposable diapers and sanitary napkins, so-called incontinence pads, medical sheets, and dew-absorbing sheets. Since the absorbent article of the present invention has excellent water absorption properties, for example, when the absorbent article is a disposable diaper, the liquid absorption efficiency becomes extremely high, and it is possible to prevent leakage of urine. That is, a so-called dry feeling can be imparted, and a reduction in thickness and weight can be realized.
[0103]
Examples of the material referred to as the liquid permeable sheet include materials having a property of transmitting an aqueous liquid, such as a nonwoven fabric; a woven fabric; and a porous synthetic resin film made of polyethylene, polypropylene, polyester, polyamide, or the like. The liquid impermeable sheet is made of a material having a property of impervious to an aqueous liquid, for example, a synthetic resin film made of polyethylene, polypropylene, ethylene vinyl acetate, polyvinyl chloride, or the like; Film; a film made of a composite material of the above synthetic resin and woven fabric. The liquid impermeable sheet may have a property of transmitting vapor.
[0104]
As described above, in the present invention, a water-absorbing resin having a capillary absorption capacity having a specific relationship with the capillary diffusion capacity of the liquid diffusion member or the liquid acquisition member is used in combination with the liquid diffusion member or the liquid acquisition member. And the water-absorbent resin can absorb and store the liquid well from the liquid acquisition member, and exhibit extremely excellent liquid absorption efficiency. That is, according to the present invention, an absorber and an absorbent article exhibiting a very excellent liquid diffusion / storage ability in a very simple manufacturing process by a system from liquid diffusion to storage work well.
Absorbent articles such as disposable diapers and sanitary napkins, so-called incontinence pads, etc. manufactured using such an absorber have a high liquid absorption efficiency of the member, so the entire member is effectively used for liquid absorption, and has a high absorption capacity. Is shown. In addition, when the absorption capacity of such an absorbent or absorbent article having a high absorption efficiency is designed to be equal to the absorption level of a conventional commercially available diaper, a liquid diffusion member, a liquid acquisition member, or a water-absorbent resin to be used is used. The amount of used diapers can be reduced more than conventional products, and light, thin diapers can be economically manufactured.
[5] Water-absorbing resin particles
The water-absorbing resin that can be used for the water-absorbing body and the water-absorbing article according to the present invention is as described above, but as a particularly preferable water-absorbing resin, in the present invention, the water-absorbing resin described below is used. A resin particle and a method for producing the same are also provided.
[0105]
The method for producing water-absorbent resin particles according to the present invention is characterized in that particles having a weight-average particle diameter of 50 to 300 μm and saturated swelling in a physiological saline solution (0.9% by weight NaCl aqueous solution) under no pressure are used. The weight-average particle diameter is reduced by adding a dispersion of water-dispersible fine particles to a water-absorbent resin having an inter-gap ratio of 30 to 50% and an average inter-gap radius of 80 to 150 μm during saturation swelling under no pressure. It is characterized by being raised by 50% or more.
The water-absorbent resin that can be used in the method for producing water-absorbent resin particles according to the present invention has a weight-average particle diameter of 50 to 300 μm and has no weight loss when saturated and swollen in physiological saline (0.9% by weight aqueous NaCl solution). It has a particle porosity of 30 to 50% during saturated swelling under pressure and an average particle radius of 80 to 150 μm during saturated swelling under no pressure.
[0106]
These are to optimize the weight-average particle diameter, particle size distribution, surface cross-linking agent, thickness of the surface cross-linking layer, etc. when producing the water-absorbent resin used for the water-absorbent body and the water-absorbent article of the present invention described above. Is obtained. For example, the technique
(1) a water-absorbent resin having a carboxyl group is heat-treated in the presence of a surface crosslinking agent capable of reacting with the carboxyl group such as a polyhydric alcohol, an epoxy compound, an oxazoline compound, or an alkylene carbonate, or an oxazolidone compound; A method of performing a surface cross-linking treatment so that the surface cross-linked layer is within a certain range,
(2) a method of heat-treating a water-absorbent resin having a carboxyl group in the presence of a surface crosslinking agent capable of reacting with the carboxyl group, and adding a cationic polymer having a specific range of molecular weight;
Etc. can be exemplified. The method for determining the thickness of the surface crosslinked layer is described in Japanese Patent Application No. 2000-329501. The cationic polymer is exemplified in JP-A-5-31360, JP-A-6-370 and the like.
[0107]
The water-absorbent resin obtained by such a method having an interparticle gap ratio of 30 to 50% at the time of saturated swelling under no load and an average interparticle gap radius of 80 to 150 μm at the time of saturated swelling under no load is used as a raw material powder. Use as
Further, the water-absorbent resin particles of the present invention have strong granulating properties when dried, but lose their bond when in contact with a large amount of liquid and have redispersibility. When the granulated particles are saturated and swelled in, for example, a physiological saline solution (a 0.9 wt% NaCl aqueous solution), the particles are redispersed to freely absorb and swell, and the particles at the time of saturated swelling under no pressure are applied. It has a gap ratio of 30 to 50% and an average gap radius between particles at the time of saturation swelling under no pressure of 80 to 150 μm.
[0108]
The weight-average particle size of the water-absorbent resin that can be used in the method for producing the water-absorbent resin particles according to the present invention is 50 to 300 μm, but in order to more effectively obtain the water-absorbent resin particles according to the present invention, Preferably it is 100 to 300 μm, more preferably 150 to 250 μm.
The water-absorbent resin which can be used in the method for producing water-absorbent resin particles according to the present invention, is obtained by swelling saturated in physiological saline (0.9% by weight aqueous NaCl solution) under no pressure between particles during saturated swelling. The porosity is 30 to 50%, but is preferably 35 to 45% in order to obtain the water-absorbent resin particles according to the present invention more effectively.
[0109]
The average gap radius between particles of the water-absorbent resin that can be used in the method for producing water-absorbent resin particles according to the present invention at the time of saturation swelling under no pressure is 80 to 150 μm.
The method for producing water-absorbent resin particles according to the present invention is characterized in that the weight-average particle diameter is increased by 50% or more by adding a dispersion of water-dispersible fine particles to a water-absorbent resin having the above-described characteristics. .
Examples of the water-dispersible fine particles usable in the present invention include, for example, powdered inorganic substances such as silicon dioxide, aluminum oxide, zinc oxide, magnesium oxide, titanium dioxide, calcium phosphate, barium phosphate, calcium carbonate, talc, and magnesium phosphate. , Calcium sulfate, silicic acid or a salt thereof, viscosity, diatomaceous earth, bentonite, zeolite, kaolin, hydrotalcite, water-insoluble particulate inorganic powders such as activated white salts, and other metal oxides. Particularly, silicon dioxide, aluminum oxide, and titanium dioxide are preferable.
[0110]
The water-dispersible fine particles generally have a weight-average primary particle size (weight-average particle size of individual particles. When a plurality of particles are aggregated or granulated, they are aggregated or granulated. It is preferable that the weight average particle diameter of the previous individual particles is 3.0 μm or less, more preferably 3.0 μm to 0.005 μm, and very fine particles having an average of 0.1 μm or less. It is preferably an object.
The amount of the water-dispersible fine particles to be contained is generally preferably from 0.1 to 5 parts by weight, and more preferably from 0.3 to 2.0 parts by weight, based on 100 parts by weight of the water absorbent resin. It is. In general, if the amount of the powdered inorganic substance is less than 0.1 part by weight, a granulated product cannot be obtained, or if obtained, the effect is poor. On the other hand, if the amount of the dispersed fine particles is more than 5 parts by weight, agglomerated materials may be obtained as granules, or even if granulated materials may be obtained, they may become coarse particles and adversely affect absorption performance. It is uneconomical because no further effect can be expected. By changing the addition amount in these ranges, particles having an arbitrary particle size with a narrow range of the particle size distribution can be obtained.
[0111]
The water-dispersible fine particles used in the present invention have the property of not impairing the water permeability and the swelling property of the water-absorbing resin, and the components to be bound do not prevent the liquid from penetrating and absorbing, and do not cause blocking during swelling. The water-absorbing resin is fully utilized. The granulated water-absorbent resin particles have strong granulation properties, and there is no dust when dried, and when absorbing liquid, the water-dispersible fine particles introduce and distribute water and dissociate, and the water-absorbent resin becomes loose. It has been found that it has the property of freely absorbing and swelling.
In the present invention, the above water-dispersible fine particles are used as a dispersion obtained by dispersing the particles in water or an aqueous medium.
[0112]
The amount of the dispersion used is preferably in the range of 3 to 100 parts by weight based on 100 parts by weight of the water absorbent resin. If the amount of the dispersion is less than 3 parts by weight, no granulated product can be obtained, or if obtained, the effect is poor. On the other hand, if the amount of the dispersion exceeds 100 parts by weight, agglomerated material is obtained as a granulated product, or even if a granulated product is obtained, it becomes undesirably coarse particles.
The water-dispersible fine particles exhibit a so-called structural viscosity when dispersed in an aqueous medium, and the viscosity of a 6.7% by weight concentration dispersion (Brookfield rotational viscometer, 6 rpm, 25 ° C.) is 0.5 Pa · s. Those described above are preferred.
[0113]
The amount of the water-dispersible fine particles and the amount of water in the dispersion liquid need to be set and selected according to the surface area and the surface state of the water-absorbent resin in order to obtain an optimum granulation state.
The water-absorbent resin particles of the present invention are obtained by mixing a water-absorbent resin and a dispersion of water-dispersible fine particles, and heating and drying the resulting mixture. As a method of mixing the dispersion of the water-absorbent resin and the water-dispersible fine particles, it is general to spray, drop, or mix the treatment solution on the water-absorbent resin powder. As a mixer used for mixing, a mixer having a large mixing power is preferable for uniform mixing, but a usual mixer or kneader can be used. For example, a cylindrical mixer, a double cone mixer, a V mixer, a ribbon mixer, a screw mixer, a fluidizing mixer, a rotating disk mixer, an air mixer, a double arm kneader Examples include a Japanese machine, an internal mixer, a Muller-type kneader, a roll mixer, and a screw-type extruder. In order to heat the mixture obtained by mixing these treatment solutions with the water-absorbent resin powder, a usual dryer or heating furnace can be used. For example, a channel-type stirring dryer, a rotary dryer, a disk dryer, a kneading dryer, a fluidized-bed dryer, a flash dryer, an infrared dryer, a dielectric heating dryer, and the like. The heat treatment temperature is preferably in the range of 40 to 250C, more preferably 80 to 200C.
[0114]
In the method for producing water-absorbent resin particles according to the present invention, the weight-average particle diameter of the obtained water-absorbent resin particles is increased by 50% or more from before the addition by adding the dispersion of the water-dispersible fine particles.
The water-absorbent resin particles of the present invention obtained by the above method have absorption characteristics, such as high capillary attraction, which cannot be obtained by the conventional method. Furthermore, since the dispersion of the water-soluble fine particles acts as an excellent binder, the mechanical strength of the obtained granules is remarkably improved, and in actual use, scattering of the water-absorbent resin fine powder can be significantly suppressed. You can do it.
[0115]
That is, the water-absorbent resin particles according to the present invention have a weight-average particle diameter of 50 to 300 μm, and have a weight-average particle diameter of 50 to 300 μm when saturatedly swelled in physiological saline (0.9% by weight aqueous NaCl solution). A water-absorbent resin particle obtained by granulating a water-absorbent resin having a void ratio of 30 to 50% and an average void radius between particles at the time of saturation swelling under no pressure of 80 to 150 μm. The weight average particle diameter is increased by 50% or more before granulation.
The weight average particle diameter of the water-absorbent resin particles according to the present invention is preferably 150 to 600 μm, more preferably 200 to 500 μm, and further preferably 200 to 400 μm.
[0116]
The water-absorbent resin particles according to the present invention preferably have a capillary absorption capacity at 40 cm of 7 g / g or more, more preferably 15 g / g or more, and still more preferably 25 g / g or more.
The water-absorbent resin particles of the present invention exhibit particularly excellent effects when used, for example, by being mixed with a pulverizing valve because of their improved absorption characteristics. The mixture with the pulverized pulp can be suitably used as a water-absorbent resin layer of an absorber such as a disposable diaper or a sanitary napkin by being formed into a mat shape. The inventor has demonstrated that making the absorption rate as high as possible conversely reduces the absorption rate under that load. Therefore, it is particularly preferable for this application that the absorption rate be controlled in an appropriate range. Controlling the capillary absorption capacity at 40 cm to a range of 7 (g / g) or more has a critical meaning in the present invention. Furthermore, the water-absorbent resin particles of the present invention have the advantage of less scattering of dust because the ratio of particles passing through a 150-μm wire mesh is 50% or less before granulation. It is intended to provide conductive resin particles.
[0117]
【Example】
Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited thereto. In addition, various properties of the liquid diffusion member, the liquid acquisition member, the water absorbent resin, the absorber, and the absorbent article were measured by the following methods.
As the sample such as the water-absorbent resin, a sample stored in a moisture-impermeable container such as a polypropylene sealed container was used, and the following various measurements were performed at 25 ± 1 ° C. and 60 ± 5% RH.
1. Capillary absorption capacity and capillary absorption index
The capillary absorption capacity and the capillary absorption index of the present invention are determined to be 0.419 kPa (0.419 kPa) for the water absorbing resin and the liquid diffusion member or the liquid acquisition member within a predetermined time at a negative pressure gradient of 0 cm (equal water level) and 40 cm. (0.06 psi) measured under load. With reference to FIGS. 1 and 2, an apparatus and method for measuring their capillary absorption capacity will be described.
1-A. Capillary absorption capacity at a height of 40 cm (Fig. 1)
1) Glass filter 2 having a liquid absorption surface of porous glass plate 1 and having a diameter of 60 mm (Glass filter particle number # 3, Buchner type filter manufactured by Mutual Physics Glass Co., Ltd., TOP17G-3 (code No. 1175-03) )), A conduit 3 is connected thereto, and this conduit 3 is connected to a port provided at a lower part of a liquid reservoir 4 having a diameter of 10 cm. The porous glass plate of the glass filter has an average pore diameter of 20 to 30 μm, and even when a difference in liquid level of 60 cm is provided due to its capillary force, the porous glass plate is placed inside the porous glass plate against the negative pressure of the water column. Water can be retained, and a state without introduction of air can be maintained. A support ring 5 for raising and lowering the height is fitted to the glass filter 2, the system is filled with a physiological saline solution (0.9 wt% NaCl aqueous solution) 6, and the liquid container is placed on a balance 7. After confirming that there is no air in the conduit and in the lower part of the porous glass plate of the glass filter, the liquid level of the saline solution 6 in the reservoir 4 and the level of the upper part of the porous glass plate 1 are increased. The glass filter is fixed to the stand 8 by adjusting the difference in height to 40 cm.
2) A measurement sample 9 (a water-absorbing resin, a liquid diffusion member or a liquid acquisition member) is placed on the porous glass plate 1 under the following conditions, and a load 10 (0.06 psi) having a diameter of 59 mm is further placed thereon. , The value of physiological saline absorbed in the measurement sample 9 after 30 minutes (W₄₀) Is measured.
When the measurement sample 9 is a water-absorbent resin: 0.44 g is quickly and uniformly sprayed on the glass filter in the funnel.
In the case where the measurement sample 9 is a liquid diffusion member or a liquid acquisition member: A sample punched into a circle having a diameter of 57 mm is prepared, and the weight (Wi) in a dry state is measured, and then placed on the porous glass plate 1 for measurement.
1-B. Capillary absorption capacity at 0 cm height (Figure 2)
A measuring apparatus shown in FIG. 2 having an outside air suction pipe 11, a conduit 12, a glass filter 13, a liquid reservoir 15 for storing physiological saline 14, and a balance 16 (however, the lower end of the outside air suction pipe 11 is The filter paper 17 was placed on the glass filter 13 of which the glass filter 13 was fixed at a position slightly higher than the lower end of the outside air suction pipe 11). The entire surface of the filter paper 17 is wet with physiological saline.
[0118]
The measurement sample 9 is placed under the above conditions on a metal mesh of a plastic cylinder 19 having a diameter of 60 mm having a wire mesh 18 of 400 mesh (aperture 38 μm) adhered to the bottom, and a load 10 (0.06 psi) having a diameter of 59 mm is further placed thereon. A mounted suction device was prepared. The liquid absorbing device was placed on the filter paper 17 on the glass filter 13 and after 30 minutes, the value of the physiological saline absorbed in the measurement sample 9 (W₀) Is measured.
The capillary absorption capacity and the capillary absorption index of the present invention are determined by the following equations.
1) Capillary absorption capacity C (g / g) of liquid diffusion member at a height of 40 cm = absorption amount (W₄₀) (G) / Weight of measurement sample before liquid absorption (Wi) (g)
2) Capillary absorption capacity G (g / g) of the liquid acquisition member at a height of 40 cm = absorption amount (W₄₀) (G) / Weight of measurement sample before liquid absorption (Wi) (g)
3) Capillary absorption capacity D (g / g) of water-absorbent resin at a height of 40 cm = absorption amount (W₄₀) (G) /0.44 (g)
4) Capillary absorption capacity (g / g) at 0 cm height of liquid diffusion member = absorption amount (W₀) (G) / Weight of measurement sample before liquid absorption (Wi) (g)
5) Capillary absorption capacity (g / g) at 0 cm height of liquid acquisition member = absorption amount (W₀) (G) / Weight of measurement sample before liquid absorption (Wi) (g)
6) Capillary absorption capacity of water-absorbent resin at 0 cm height (g / g) = absorption amount (W₀) (G) /0.44 (g)
7) Capillary absorption index A at a height of 40 cm of the liquid diffusion member A = capillary absorption ratio C of the liquid diffusion member at a height of 40 cm (g / g) / capillary absorption ratio at a height of 0 cm of the liquid diffusion member (g / g) g)
8) Capillary absorption index E at 40 cm height of liquid acquisition member E = capillary absorption ratio G (g / g) at 40 cm height of liquid acquisition member / capillary absorption ratio (g / g) at 0 cm height of liquid acquisition member g)
9) {Capillary absorption index B of the water-absorbent resin at a height of 40 cm = Capillary absorption ratio D of the water-absorbent resin at a height of 40 cm D (g / g) / capillary absorption ratio of the water-absorbent resin at a height of 0 cm (g / g)
2. Siphon height
A liquid diffusion member is prepared in a state of 2 cm in width and 90 cm in length. The liquid diffusion member is set upright at 90 degrees so that about 2 cm of the lower end of the liquid diffusion member is immersed in physiological saline. The height at which the liquid has been absorbed is determined after 72 hours without evaporation of the liquid. The absorption capacity at the lower end 0 to 10 cm of the liquid diffusion member is set to 100, and the material is cut using a cutter knife at intervals of 2 cm in the height direction to determine each absorption capacity, and the absorption capacity at 90% of the absorption capacity at the lower end is calculated. The indicated height was defined as the suction height (cm) of the liquid diffusion member.
3. Absorption capacity
About 0.20g (W_p1) Was uniformly placed in a nonwoven fabric bag (60 × 60 mm) and immersed in a 0.9% by weight aqueous sodium chloride solution (physiological saline). After 60 minutes, the bag was pulled out, and after draining at 250 G for 3 minutes using a centrifuge, the weight Wa (g) was measured. The same operation was performed without using a water-absorbing resin, and the weight Wb (g) at that time was measured. Then, from these weights Wa and Wb, the absorption capacity (g / g) of the water absorbent resin was calculated according to the following equation.
[0119]
Absorbency (g / g) = [Wa (g) -Wb (g)] / W of the water-absorbent resin_p1(G)
4. Absorption capacity under pressure
Using the same apparatus shown in FIG. 2 as in 1-B, the absorption capacity under pressure was measured. Instead of the load 10, a load 20 and a load 21 were prepared by increasing the weight and adjusting the pressures to 2.07 kPa (0.3 psi) and 4.83 kPa (0.7 psi), respectively. Approximately 0.44 g of water-absorbing resin (W_p2) And apply the above-mentioned load 20 (at 2.07 kPa (0.3 psi)) or load 21 (at 4.83 kPa (0.7 psi)) on the glass filter 13 in FIG. After 30 minutes from placing on the filter paper 17, the value (Wc) of the physiological saline absorbed by the water-absorbent resin is measured. The absorption capacity under pressure of 2.07 kPa (0.3 psi) and 4.83 kPa (0.7 psi) was determined using the following equation.
[0120]
Absorption capacity under pressure (g / g) = Wc / W_p2
5. Particle size distribution and weight average particle size
The water-absorbent resin is classified using sieves having openings of 850 μm, 600 μm, 500 μm, 300 μm, 150 μm, 75 μm, and 45 μm (if necessary, further add a JIS standard sieve), and the weight of the resin remaining on each sieve The ratio was determined. The weight average particle diameter was classified, and the residual percentage R was plotted on log probability paper, and the particle diameter corresponding to R = 50% was defined as the weight average particle diameter.
6. Liquid distribution rate from liquid diffusion member to water absorbent resin
The liquid diffusion member was cut into a circle having a diameter of 57 mm, dried and weighed (Wd) (g) in advance, and then immersed in a sufficient amount of physiological saline (0.9% by weight NaCl aqueous solution). The sample swollen by absorbing the liquid was taken out of the container, suspended for one minute while supporting one end of the sample, drained, and immediately measured the weight (We) (g) of the sample that absorbed the liquid.
[0121]
On the liquid diffusion member after draining, 0.44 g of a water-absorbent resin was evenly dispersed to prepare an absorber. The weight (Wf) (g) of the liquid diffusion member after contacting the water-absorbent resin under a load of 0.41 kPa (0.06 psi) for 30 minutes was measured again, and from the liquid diffusion member of the absorber, the following formula was used. Was measured.
Liquid distribution ratio (%) = (We-Wf) / (We-Wd) × 100
7. Manufacturing example of absorber and absorbent article including liquid diffusion member and performance evaluation of absorbent article (model diaper)
About 14 g of the water-absorbing resin was added to heatron paper (GSP-22, Teikoku Pulp & Paper Co., Ltd., basis weight 22.4 g / m2).²) Was sprayed uniformly over a range of 11 x 38 cm, and then the water-absorbent resin was wetted by spraying with 5 to 10% by weight of ion-exchanged water to form a sheet of the water-absorbent resin. After the sheet is left to dry overnight, various liquid diffusion members having a size of 11 × 38 cm are laminated thereon, and the entire sheet is wrapped with an excess portion of heatron paper, and the present invention comprises the liquid diffusion member and a water-absorbing resin. Was made.
[0122]
A liquid-impermeable rectangular polyethylene film having a size of 12 × 40 cm (basis weight 18 g / m 2²), The absorbent is placed so that the liquid diffusion member is on top, and a liquid-permeable polyester non-woven fabric having a size of 12 × 40 cm is laminated from above, and the sides are adhered with tape to form an absorbent article (model A diaper was produced (FIGS. 3 and 4).
A PVC pipe having a diameter of 14.7 cm and a length of 46 cm was cut in half in the vertical direction, and a plate having a size of 20 × 30 cm was attached to both ends of the half cylinder and tangential directions to prepare a U-shaped device. The U-shaped device was placed in a state of being tilted 90 degrees (shape of ⊂), and the model diaper was fixed inside the device. In this state, the child is assumed to be wearing a diaper in which the child is lying face down. The diaper was kept at 37 ° C. together with the above-mentioned apparatus, and purifying was continued until 50 cc of physiological saline leaked from the center of the diaper at intervals of 20 minutes, assuming that the diaper was lying down.
[0123]
When the leak occurs, the diaper is taken out, the diffusion rate of the liquid in the liquid diffusion member (%), the total absorption amount of the diaper at the time of the leak (diaper final weight-diaper weight before liquid absorption) (g), diaper The liquid absorption amount (g) of the water-absorbent resin in the inside and the liquid absorption amount (g) of the water-absorbent resin in the upper half of the diaper (the butt side assuming prone sleeping) were determined.
8. Absorbent including liquid acquisition member, manufacturing example of absorbent article and method of evaluating performance of absorbent article A rectangular polyethylene film of 14 × 40 cm in size (basis weight 18 g / m 2) as a liquid-impermeable back sheet²) Was sprayed with 16.4 g of a water-absorbent resin over an area of 12 × 38 cm (amount of the water-absorbent resin sprayed was 360 g / m 2).²). Considering the urination position, a size of 8 x 24 cm (basis weight 160 g / m²The liquid acquisition member of (1) was laminated to constitute an absorber.
[0124]
A 12 × 40 cm rectangular polyester non-woven fabric (basis weight 20 g / m 2) was formed thereon as a liquid-permeable surface material.²) To obtain a model absorbent article.
The absorbent article is fixed on a desk in a flat shape, and a 12 × 40 cm acrylic plate (having a 70 mm diameter cylinder for liquid injection at the center) and a 1.3 kg load are placed thereon. Was.
75 ml of physiological saline adjusted to 37 ° C. is poured into the cylinder, and the time when the liquid has been completely absorbed into the absorbent article from the topsheet (liquid passing time) and the liquid is obtained from the liquid-permeable surface material Alternatively, a time (whitening time) until air was introduced into the vicinity of the surface of the liquid-permeable surface material after being absorbed by the water-absorbent resin and the surface of the surface material became white was measured.
[0125]
After a lapse of 60 minutes, the liquid acquisition member was taken out of the absorbent article and its weight was measured. The original liquid acquisition member weight was subtracted from the value to determine the remaining liquid amount in the liquid acquisition member. After the measurement, the article was returned to the original absorbent article.
Further, these operations were repeated a total of four times, every 60 minutes. After 60 minutes from the fourth injection, the acrylic plate was removed, the weight of the liquid acquisition member was measured, and after returning to the absorbent article, the absorbent article was removed. Cover 15 sheets of kitchen paper (Oji Paper Co., Ltd., Napier, 46 x 22 cm) with a stack of them, apply a 12 kg load (including acrylic plate 14 x 40 cm) for 1 minute, and return the amount of liquid (return amount) ) Was measured.
[0126]
Also, 60 minutes after the fourth injection, the liquid diffusion area in the absorbent core was measured from above the liquid-permeable surface material (Scm²).
The diffusion area in the absorbent article of the present invention is determined by the following equation.
Diffusion area (%) = liquid diffusion area (Scm²) / Absorber area (12 × 38cm)
9. Gap ratio between particles at the time of saturated swelling of the water-absorbent resin and average gap radius between particles of the water-absorbent resin, porosity at the time of saturated swelling of the water-absorbent resin particles, and average gap radius of the water-absorbent resin particles
The gap ratio and the average gap radius at the time of saturated swelling of the water-absorbent resin and the water-absorbent resin particles were measured using the measuring device shown in FIG.
[0127]
The height h at which the liquid rises through a tube having a radius R due to the capillary force is expressed as h = 2γcos θ / ρgR, where γ is the surface tension of the liquid, θ is the contact angle, g is the gravitational acceleration, and ρ is the density of the liquid. (PK Chatterjee, edited by "ABSORBENCY" (ELSEVIER) p36, Equation (2) p = 2γcosθ / Rc (Laplace equation), and Equation (5) Leq = p / ρg of p37, Leq is represented by h and Rc is represented by R). By raising the head difference between the tank and the measuring cell from 0 to h (cm) in the apparatus of FIG. 1, R (R) of the liquid existing between the gel particles in the swollen gel or the absorber or in the gap between the absorbers is obtained. The gap water held at a diameter larger than the capillary radius (gap) of μm) is released and escapes. Therefore, the gel that is saturated and swelled and completely fills the interstitial space with liquid is raised from a height of 0 cm, and by measuring the remaining interstitial liquid amount of the gel layer at each predetermined height, The distribution of the gap radius (capillary radius) is determined.
[0128]
Hereinafter, in the present invention, the value of the capillary radius R of the sample obtained at each height h is defined as the gap radius of the sample using the equation h = 2γ cos θ / ρgR. A gap having a value of R corresponding to each height by gradually raising the head difference between the tank and the measuring cell from 0 to 60 (cm) as 1 cm, 2 cm, 5 cm, 10 cm, 20 cm, 30 cm, and 60 cm. The liquid held in the liquid is discharged. By measuring the amount of the discharged liquid, the distribution of the gap radius (capillary radius) of the sample can be calculated. The value is plotted on log probability paper, and the value of d50 is defined as the average gap radius. In this embodiment, in the equation of h = 2γ cos θ / ρgR, γ: surface tension (0.0728 N / m) of physiological saline (0.9 wt% NaCl aqueous solution), θ: contact angle (0 °), ρ: physiological salt Water density (1000kg / m³), G: gravitational acceleration 9.8 m / s²Shall be used. Thus, the liquid held at the positions of 1 cm, 2 cm, 5 cm, 10 cm, 20 cm, 30 cm, and 60 cm respectively has a gap radius (capillary radius of 1485, 743, 297, 149, 74.3, 49.5, 24.8 μm). ) Is required.
10. No-load gap ratio and average gap radius
1) A glass having a diameter of 60 mm having a liquid absorbing surface of a porous glass plate 1 (glass filter particle number # 3; an average pore diameter of about 20 to 30 μm and a height difference of 60 cm and no introduction of air) A conduit 3 is connected to a lower part of the filter 2 and connected to a port provided at a lower part of a liquid reservoir 4 having a diameter of 10 cm. A support ring 5 for raising and lowering the height is fitted to the glass filter 2, the system is filled with physiological saline 6, and the liquid reservoir is placed on a balance 7. After confirming that there is no air in the conduit and in the lower part of the porous glass plate of the glass filter, the liquid level of the saline solution 6 in the reservoir 4 and the level of the upper part of the porous glass plate 1 are increased. The glass filter is fixed to the stand 8 by adjusting the difference in height to 60 cm, and the value of the balance is set to 0.
2) The measurement sample 9 (water-absorbent resin, absorber) is placed on the porous glass plate 1 under the following conditions.
When the measurement sample 9 is a water-absorbent resin: about 0.9 g (W) is uniformly and quickly sprayed on the porous glass plate 1 of the glass filter.
When the measurement sample 9 is an absorber: A sample punched into a circle having a diameter of 57 mm is prepared, and the weight (W) in a dry state is measured, and then placed on the porous glass plate 1 for measurement.
3) The difference between the liquid level above the physiological saline 6 in the liquid reservoir 4 and the level above the porous glass plate 1 is set to -3 cm (the position where the porous glass plate 1 is lower) 20 Let the sample swell for a minute. At this time, the sample is completely immersed in a physiological saline solution so that there is no air bubble.
4) The height difference between the liquid level above the physiological saline solution 6 in the liquid reservoir 4 and the level above the porous glass plate 1 is set to 0 cm. (A0). In the case of a sample that does not swell in 40 minutes, the time may be extended.
5) The height difference between the liquid level above the physiological saline 6 in the liquid reservoir 4 and the level above the porous glass plate 1 is set to 1 cm, and the value on the balance is recorded after 7 minutes (A1). In some cases, it is better to extend the equilibrium time until the gap water is discharged depending on the gap diameter of the sample.
6) Similarly, the difference between the liquid level above the physiological saline 6 in the liquid reservoir 4 and the level above the porous glass plate 1 is increased to 2, 5, 10, 20, 30, 60 cm. After 7 minutes each time, the value of the balance is recorded (A2, A5, A10, A20, A30, A60).
7) A sample is taken out and centrifuged in order to completely remove pore water held at a height difference of 60 cm between the liquid level above the physiological saline 6 in the liquid reservoir 4 and the level above the porous glass plate 1. (250 G, 6 minutes) and measure its weight B.
8) (A0-B) is the total amount of interstitial water in the sample, and the value obtained by subtracting the value of B from (A1, A2, A5, A10, A20, A30, A60) is 1, 2, 5, At the heights of 10, 20, 30, and 60 cm, the cumulative crevice water amount is obtained. As described above, the liquid held at the positions of 1 cm, 2 cm, 5 cm, 10 cm, 20 cm, 30 cm, and 60 cm has a gap radius of 1485, 743, 297, 149, 74.3, 49.5, and 24.8 μm, respectively. (Capillary radius), the percentage of the cumulative interstitial water amount at each height with respect to the total interstitial water amount (A0-B) is calculated, and this value and the value of the capillary radius are log-probable. Plot on paper (for example, the value of (A2-B) / (A0-B) × 100 is plotted on 743 μm of the graph). The value (d50) of the gap radius corresponding to 50% of the cumulative gap amount in this graph is obtained and defined as the average gap radius (μm) of the sample.
9) The sample gap ratio is obtained by the following equation.
[0129]
Gap ratio = (A0−B) / {A0 + W / (true specific gravity of sample)} × 100
10) In order to further confirm the measured values, the average gap radius was determined by this method using spherical glass beads of 350 to 500 μm and 1000 to 1180 μm as standard samples, and were found to be 86 μm and 217 μm, respectively.
(Reference Example 1) Method for producing water-absorbent resin (1)
28.6 parts of acrylic acid and 228.6 parts of a 37% by weight aqueous solution of sodium acrylate, 0.0185 part of N, N'-methylenebisacrylamide (0.01 mol% based on monomer), 0.106 parts of hydroxyethylcellulose, ions Using 53 parts of exchanged water, an aqueous monomer solution having a monomer concentration of 35% by weight and a neutralization rate of 75% was obtained, and 0.09 part of potassium persulfate was dissolved in the aqueous monomer solution. Kicked out.
[0130]
800 parts of cyclohexane is placed in a four-necked separable flask equipped with a stirrer, a reflux condenser, a thermometer, a nitrogen gas inlet tube and a dropping funnel, and 4 parts of sucrose fatty acid ester (HLB = 6) is added as a dispersant. And dissolved oxygen, and dissolved oxygen was blown out by blowing nitrogen gas. Next, the monomer aqueous solution was added to the above separable flask with stirring to disperse. Thereafter, the bath temperature was raised to 65 ° C. to start the polymerization reaction, and then the temperature was maintained at this temperature for 2 hours to complete the polymerization. After completion of the polymerization, most of the water was removed by azeotropic dehydration, followed by filtration and further drying under reduced pressure at 100 ° C. to obtain a resin having a water content of 8%. In a stainless steel beaker, 100 parts of the obtained resin were mixed with 0.1 part of ethylene glycol diglycidyl ether, 3 parts of water, and 1 part of isopropanol, and the resulting mixture was subjected to a heat treatment at 120 ° C. for 30 minutes. The particles were transferred to a separable flask similar to the above, and 5 times the amount (weight) of methanol was added to the particles, and the mixture was stirred at 60 ° C for 10 minutes, and then filtered through filter paper to separate the particles. Drying was performed under reduced pressure of 50 to 100 mmHg for a time to obtain a water-absorbent resin (1). The weight average particle diameter of the water absorbent resin (1) was 105 μm. Further, the capillary absorption capacity at a height of 0 cm of the water absorbent resin is 45.5 (g / g), the capillary absorption capacity D at a height of 40 cm is 27.4 (g / g), and the capillary absorption index at a height of 40 cm. B was 0.60.
[0131]
(Reference Example 2) Method for producing water-absorbent resin (2)
5 parts of polyethylene glycol diacrylate (n = 8) was dissolved in 5500 parts of a 33% by weight aqueous solution of sodium acrylate (neutralization ratio: 75 mol%) to prepare a reaction solution. Next, the reaction solution was degassed under a nitrogen gas atmosphere for 30 minutes. Next, the reaction solution was supplied to a jacketed stainless steel double-armed kneader having two sigma-type blades with a lid that can be opened and closed, and the system was purged with nitrogen gas while maintaining the reaction solution at 30 ° C. Subsequently, 2.4 parts of ammonium persulfate and 0.12 part of L-ascorbic acid were added while stirring the reaction solution, and polymerization started about 1 minute later. Then, polymerization was carried out at 30 to 90 ° C., and the hydrogel polymer was taken out 60 minutes after the initiation of the polymerization.
[0132]
The obtained hydrogel polymer was subdivided into a diameter of about 5 mm. The finely divided hydrogel polymer was spread on a 50-mesh wire net and dried with hot air at 150 ° C. for 90 minutes. Next, the dried product is pulverized using a vibration mill, and further classified by a 20-mesh wire net to form an amorphous material having a weight-average particle diameter of 360 μm and a particle size of less than 106 μm in which the proportion of particles is 3% by weight. A crushed resin was obtained.
Surface crosslinking comprising 0.05 parts by weight of ethylene glycol diglycidyl ether, 0.75 parts by weight of glycerin, 3 parts by weight of water, 0.3 part of lactic acid and 1 part by weight of isopropyl alcohol to 100 parts by weight of the obtained resin. The agent composition liquid was mixed. The mixture was heat-treated at 195 ° C. for 40 minutes to obtain a water-absorbent resin (2 ′). The obtained water-absorbent resin (2 ′) was further passed through a wire mesh having an aperture of 250 μm to obtain a water-absorbent resin (2) under a sieve. The weight average particle diameter of the water absorbent resin (2) was 120 μm. The capillary absorption capacity at a height of 0 cm of the water absorbent resin is 33.8 (g / g), the capillary absorption capacity D at a height of 40 cm is 19.4 (g / g), and the capillary absorption index at a height of 40 cm. B was 0.57. The particle size distribution of the water-absorbent resin (2) was 31% for 150 to 850 μm, and 69% for 150 μm or less.
[0133]
(Reference Example 3) Method for producing water-absorbent resin (3)
A reaction solution was prepared by dissolving 8.1 parts of polyethylene glycol diacrylate (n = 8) in 5500 parts of a 38% by weight aqueous solution of sodium acrylate (neutralization ratio: 71 mol%). Next, the reaction solution was degassed under a nitrogen gas atmosphere for 30 minutes. Next, the reaction solution was supplied to a jacketed stainless steel double-armed kneader having two sigma-type blades with a lid that can be opened and closed, and the system was purged with nitrogen gas while maintaining the reaction solution at 30 ° C. Subsequently, 2.4 parts of ammonium persulfate and 0.12 part of L-ascorbic acid were added while stirring the reaction solution, and polymerization started about 1 minute later. Then, polymerization was carried out at 20 to 95 ° C., and the hydrogel polymer was taken out 60 minutes after the polymerization was started.
[0134]
The obtained hydrogel polymer was subdivided into a diameter of about 5 mm. The finely divided hydrogel polymer was spread on a 50-mesh wire net and dried with hot air at 150 ° C. for 90 minutes. Next, the dried product was pulverized using a vibration mill, and further passed through a sieve having openings of 850 μm and remained on a sieve having a size of 106 μm to obtain an irregularly crushed resin having a weight average particle diameter of 400 μm.
To 100 parts by weight of the obtained resin, a surface cross-linking agent composition liquid composed of 0.3 parts by weight of 1,4-butanediol, 0.5 parts by weight of propylene glycol, and 3 parts by weight of water was mixed. The mixture was heat-treated at 210 ° C. for 30 minutes to obtain a water-absorbent resin (3). The weight average particle diameter of the water absorbent resin (3) was 420 μm. The capillary absorption capacity at a height of 0 cm of the water absorbent resin is 37.8 (g / g), the capillary absorption capacity D at a height of 40 cm is 4.30 (g / g), and the capillary absorption index at a height of 40 cm. B was 0.11. The particle size distribution of the water-absorbent resin (3) was 95% for 150 to 850 μm, and 5% for 150 μm or less.
[0135]
(Reference Example 4) Manufacturing method of liquid diffusion member (1)
A liquid diffusion member of a porous cross-linked polymer was manufactured using a high internal phase water-in-oil emulsion (HIPE). As an aqueous phase for forming HIPE, 20.7 parts of anhydrous calcium chloride and 0.415 part of potassium persulfate were dissolved in 394 parts of pure water. Separately, 0.654 parts of diglycerol monooleate was added to a mixture of 0.438 parts of styrene, 5.449 parts of 2-ethylhexyl acrylate, and 3.459 parts of 55% divinylbenzene to form an oil phase. The aqueous phase has a temperature of 80 ° C and a flow rate of 75.2cm³/ S, the oil phase is continuously supplied to a mixing device with a pin-type stirring blade at a temperature of 22 ° C. and a flow rate of 1.88 g / s, respectively, and stirred and mixed at 1600 rpm to obtain a high internal phase water at 79 ° C. A mold emulsion was obtained.
[0136]
The obtained high internal phase water-in-oil emulsion was formed on a drive belt covered with a PET film to a thickness of 5 mm, the top surface was further covered with a PET film, and the curing furnace set at an internal temperature of 95 ° C. was moved at a moving speed. The mixture was passed at 1.5 m / min and polymerized for 10 minutes to obtain a wet porous crosslinked polymer. The wet polymer was dehydrated and dried to a water content of 20% to obtain a liquid diffusion member (1) as a porous polymer having a thickness of 1 mm. The capillary absorption capacity at a height of 0 cm of the liquid diffusion member (1) is 33.6 (g / g), the capillary absorption capacity C at a height of 40 cm is 14.2 (g / g), and the capillary at a height of 40 cm. The absorption index A was 0.42. The siphoning height was 45 cm.
[0137]
(Reference Example 5) Manufacturing method of liquid diffusion member (2)
The oil phase used in the method for producing the liquid diffusion member (1) was mixed with a mixture of 1.649 parts of styrene, 5.449 parts of 2-ethylhexyl acrylate, and 2.248 parts of 55% divinylbenzene to obtain 0.654 of diglycerol monooleate. A liquid diffusing member (2) having a water content of 22% and a thickness of 1 mm was obtained by performing the same operation except that the liquid diffusion member was added. The capillary absorption capacity at a height of 0 cm of the liquid diffusion member (2) is 27.0 (g / g), the capillary absorption capacity C at a height of 40 cm is 7.6 (g / g), and the capillary at a height of 40 cm. The absorption index A was 0.28. The siphoning height was 35 cm.
[0138]
(Reference Example 6) Manufacturing method of liquid diffusion member (3)
The cotton-like pulp used in disposable diapers for children is moistened, compressed by suction, and has a density of 0.3 g / cm.³With a basis weight of 260 g / m²The liquid diffusion member (3) laminated on was obtained. The capillary absorption capacity at a height of 0 cm of the liquid diffusion member (3) is 6.6 (g / g), the capillary absorption capacity C at a height of 40 cm is 2.1 (g / g), and the capillary capacity at a height of 40 cm. The absorption index A was 0.32. The siphoning height was 30 cm.
(Reference Example 7) Manufacturing method of liquid diffusion member (4)
Cottony pulp used for disposable diapers for children (density 0.03 g / cm³With a basis weight of 260 g / m²) Was used as the liquid diffusion member (4). Capillary absorption at a height of 0 cm of the liquid diffusion member (4) is 13.7 (g / g), capillary absorption at a height of 40 cm C is 0.5 (g / g), and capillary at a height of 40 cm. The absorption index A was 0.04. The siphoning height was less than 10 cm.
[0139]
(Example 1)
The absorbent (1) obtained by combining the water-absorbent resin (1) and the liquid diffusion member (1) was obtained by the method described in the section of the production example of the absorbent including the liquid diffusion member and the absorbent article. The capillary absorption index and the capillary absorption ratio of the water-absorbent resin (1) and the liquid diffusion member (1) constituting the absorber are as shown in each of the reference examples, and the liquid absorption member (1) has a height of 40 cm. The ratio of the capillary absorption index B of the water-absorbent resin (1) to the capillary absorption index A at a height of 40 cm, B / A = 1.4, and the water absorption of the liquid diffusion member (1) to the capillary absorption capacity C at a height of 40 cm. The ratio of the capillary absorption capacity D at a height of 40 cm of the resin (1) was D / C = 1.9.
[0140]
The liquid distribution ratio from the liquid diffusion member to the water-absorbent resin is determined using the absorber (1), and an absorbent article (1) as a model diaper is formed using the absorber (1). , The total absorption of the diaper at the time of leakage, the liquid absorption of the water-absorbent resin in the diaper, and the liquid absorption of the upper half of the diaper. The results are shown in Table 1. The liquid distribution ratio from the liquid diffusion member to the water-absorbent resin and the absorption capacity of the water-absorbent resin liquid from the liquid diffusion member in the upper half of the diaper assuming lying down were 47%. 165 g, which was a very excellent value.
(Example 2)
An absorber (2) obtained by combining the water absorbent resin (2) and the liquid diffusion member (1) was obtained. The ratio of the capillary absorption index B at a height of 40 cm of the water-absorbent resin (2) to the capillary absorption index A at a height of 40 cm of the liquid diffusion member (1) is B / A = 1.4. The ratio of the capillary absorption capacity D at a height of 40 cm of the water-absorbent resin (2) to the capillary absorption capacity C at a height of 40 cm, D / C = 1.4.
[0141]
The liquid distribution ratio from the liquid diffusion member to the water-absorbent resin is determined using the absorber (2), and an absorbent article (2) as a model diaper is formed using the absorber (2). , The total absorption of the diaper at the time of leakage, the liquid absorption of the water-absorbent resin in the diaper, and the liquid absorption of the upper half of the diaper. The results are shown in Table 1. The liquid distribution ratio from the liquid diffusion member to the water-absorbent resin, and the absorption capacity of the water-absorbent resin liquid from the liquid diffusion member in the upper half of the diaper assuming lying down were 23%. , 102 g, an excellent value.
(Comparative Example 1)
An absorber (3) obtained by combining the water absorbent resin (3) and the liquid diffusion member (1) was obtained. The ratio of the capillary absorption index B at a height of 40 cm of the water-absorbent resin (3) to the capillary absorption index A at a height of 40 cm of the liquid diffusion member (1) is B / A = 0.3. The ratio of the capillary absorption capacity D at a height of 40 cm of the water-absorbent resin (3) to the capillary absorption capacity C at a height of 40 cm, D / C = 0.3.
[0142]
The liquid distribution ratio from the liquid diffusion member to the water-absorbent resin is determined using the absorber (3), and an absorbent article (3) as a model diaper is formed using the absorber (3). , The total absorption of the diaper at the time of leakage, the liquid absorption of the water-absorbent resin in the diaper, and the liquid absorption of the upper half of the diaper. The results are shown in Table 1. The liquid distribution ratio from the liquid diffusion member to the water-absorbent resin, and the absorption capacity of the water-absorbent resin liquid from the liquid diffusion member in the upper half of the diaper assuming lying down were 13%. , 33 g.
Even when the same liquid diffusing member is used than in Examples 1 and 2 and Comparative Example 1, the relationship between the capillary absorbent capacity of the water-absorbing resin satisfies the relationship of the present invention, and when the same is not satisfied, the liquid is distributed to the water-absorbing resin. The ratios differ, indicating that the absorbency of the water absorbent resin in the diaper is significantly different.
[0143]
(Example 3)
The liquid diffusion member (1) is further sliced so as to have a half thickness to obtain a liquid diffusion member (1 ′) having a thickness of about 0.5 mm, and the absorbent (4) combined with the water absorbent resin (1) is used. Obtained. The ratio of the capillary absorption index B at a height of 40 cm of the water-absorbent resin (1) to the capillary absorption index A at a height of 40 cm of the liquid diffusion member (1 ') B / A = 1.9, and the liquid diffusion member (1') ), The ratio of the capillary absorption capacity D at a height of 40 cm of the water-absorbent resin (1) to the capillary absorption capacity C at a height of 40 cm, D / C = 2.2. The weight ratio of the water absorbent resin to the total amount of the water absorbent resin and the liquid diffusion member was 80% by weight.
[0144]
The liquid distribution ratio from the liquid diffusion member to the water-absorbent resin is determined using the absorber (4), and an absorbent article (4) as a model diaper is formed using the absorber (4). , The total absorption of the diaper at the time of leakage, the liquid absorption of the water-absorbent resin in the diaper, and the liquid absorption of the upper half of the diaper. The results are shown in Table 1. The liquid distribution ratio from the liquid diffusion member to the water-absorbent resin, and the absorption capacity of the water-absorbent resin liquid from the liquid diffusion member in the upper half of the diaper assuming lying down were 52%. , 81 g, which is an excellent value.
The water-absorbent article (3) in which the amount of the liquid diffusion member is further reduced from the absorbent article (1) in Examples 1 and 3 and Comparative Example 4 is a member used as compared with the diaper of Comparative Example 4 which is a current commercial diaper. Despite the volume being reduced by as much as 30%, the total absorption of the liquid is still at a high level. As described above, the use of the absorber of the present invention makes it possible to design a lighter and thinner diaper.
[0145]
(Example 4)
An absorber (5) obtained by combining the water-absorbent resin (1) and the liquid diffusion member (2) was obtained. The ratio of the capillary absorption index B at a height of 40 cm of the water-absorbent resin (1) to the capillary absorption index A at a height of 40 cm of the liquid diffusion member (2) is B / A = 2.1. The ratio of the capillary absorption capacity D at a height of 40 cm of the water-absorbent resin (1) to the capillary absorption capacity C at a height of 40 cm, D / C = 3.6.
The liquid distribution ratio from the liquid diffusion member to the water-absorbent resin is determined using the absorber (5), and an absorbent article (5) as a model diaper is formed using the absorber (5). , The total absorption of the diaper at the time of leakage, the liquid absorption of the water-absorbent resin in the diaper, and the liquid absorption of the upper half of the diaper. The results are shown in Table 1. The liquid distribution rate from the liquid diffusion member to the water-absorbent resin, and the absorption capacity of the liquid-absorbent resin liquid from the liquid diffusion member in the upper half of the diaper assuming the lying down were 51%. , 77 g, which is an excellent value. In this case, the number of members used for the diaper can be reduced, and a diaper that is thinner and has excellent performance can be manufactured.
[0146]
(Comparative Example 2)
An absorber (6) obtained by combining the water absorbent resin (3) and the liquid diffusion member (2) was obtained. The ratio of the capillary absorption index B at a height of 40 cm of the water-absorbent resin (3) to the capillary absorption index A at a height of 40 cm of the liquid diffusion member (2) is B / A = 0.4. The ratio of the capillary absorption capacity D at a height of 40 cm of the water-absorbent resin (3) to the capillary absorption capacity C at a height of 40 cm, D / C = 0.6.
The liquid distribution ratio from the liquid diffusion member to the water-absorbing resin is determined using the absorber (6), and an absorbent article (6) as a model diaper is formed using the absorber (6). , The total absorption of the diaper at the time of leakage, the liquid absorption of the water-absorbent resin in the diaper, and the liquid absorption of the upper half of the diaper. The results are shown in Table 1. The liquid distribution ratio from the liquid diffusion member to the water-absorbent resin, and the absorption capacity of the water-absorbent resin liquid from the liquid diffusion member in the upper half of the diaper assuming lying down were 13%. , Was as low as 17 g.
[0147]
From Example 4 and Comparative Example 2, the same liquid diffusion member was used, but the relationship with the capillary absorption capacity of the water-absorbing resin satisfies the relationship of the present invention. It can be seen that the liquid distribution ratio to the resin and the amount of water-absorbent resin absorbed in the diaper are significantly different.
(Example 5)
An absorber (7) obtained by combining the water absorbent resin (1) and the liquid diffusion member (3) was obtained. The ratio B / A of the water-absorbent resin (1) at a height of 40 cm to the capillary absorption index A of the liquid diffusion member (3) at a height of 40 cm of the liquid diffusion member (3) is B / A = 1.9. The ratio of the capillary absorption capacity D at a height of 40 cm of the water-absorbent resin (1) to the capillary absorption capacity C at a height of 40 cm, D / C = 13.0.
[0148]
The liquid distribution ratio from the liquid diffusion member to the water-absorbent resin is determined using the absorber (7), and an absorbent article (7) as a model diaper is formed using the absorber (7). , The total absorption of the diaper at the time of leakage, the liquid absorption of the water-absorbent resin in the diaper, and the liquid absorption of the upper half of the diaper. The results are shown in Table 2. The liquid distribution ratio from the liquid diffusion member to the water-absorbent resin, and the ability of the water-absorbent resin to absorb the liquid from the liquid diffusion member in the upper half of the diaper assuming lying down were 87%. , 121 g. However, since the liquid diffusion member (3) had a low capillary absorption capacity at a height of 0 cm of 6.6 (g / g), the total absorption amount of the diaper was low.
[0149]
(Example 6)
An absorber (8) obtained by combining the water-absorbent resin (2) and the liquid diffusion member (3) was obtained. The ratio of the capillary absorption index B at a height of 40 cm of the water-absorbent resin (2) to the capillary absorption index A at a height of 40 cm of the liquid diffusion member (3) is B / A = 1.8. The ratio of the capillary absorption capacity D at a height of 40 cm of the water-absorbent resin (2) to the capillary absorption capacity C at a height of 40 cm, D / C = 9.2.
The liquid distribution ratio from the liquid diffusion member to the water-absorbent resin is determined using the absorber (8), and an absorbent article (8) as a model diaper is formed using the absorber (8). , The total absorption of the diaper at the time of leakage, the liquid absorption of the water-absorbent resin in the diaper, and the liquid absorption of the upper half of the diaper. The results are shown in Table 2. The liquid distribution ratio from the liquid diffusion member to the water-absorbent resin, and the absorption capacity of the water-absorbent resin liquid from the liquid diffusion member in the upper half of the diaper assuming lying down were 84%. , 122 g. However, since the liquid diffusion member (3) had a low capillary absorption capacity at a height of 0 cm of 6.6 (g / g), the total absorption amount of the diaper was low.
[0150]
(Example 7)
An absorber (9) obtained by combining the water-absorbent resin (3) and the liquid diffusion member (3) was obtained. The ratio of the capillary absorption index B at a height of 40 cm of the water-absorbent resin (3) to the capillary absorption index A at a height of 40 cm of the liquid diffusion member (3) is B / A = 0.4. The ratio of the capillary absorption capacity D at a height of 40 cm of the water-absorbent resin (3) to the capillary absorption capacity C at a height of 40 cm, D / C = 2.0.
The liquid distribution ratio from the liquid diffusion member to the water-absorbent resin is determined using the absorber (9), and an absorbent article (9) is created as a model diaper using the absorber (9). , The total absorption of the diaper at the time of leakage, the liquid absorption of the water-absorbent resin in the diaper, and the liquid absorption of the upper half of the diaper. The results are shown in Table 2. Although the liquid distribution ratio from the liquid diffusion member to the water-absorbent resin is excellent at 66%, the water-absorbent resin from the liquid diffusion member in the upper half of the diaper is assumed to be lying down. The liquid absorption capacity was 33 g. For this reason, the combination of the water-absorbent resin (3) and the liquid diffusion member (3) is cautious because the liquid-absorbing ability of the water-absorbent resin may hardly be exhibited depending on the usage method.
[0151]
Examples 5 to 7 are examples using a liquid diffusion member having a low capillary absorption capacity at a height of 0 cm or 40 cm. In Examples 5 and 6, the liquid distribution ratio of the water-absorbent resin from the liquid diffusion member is high, and the liquid distribution ratio from the liquid diffusion member to the water-absorbent resin and the amount of the water-absorbent resin absorbed in the diaper are large. Example 7 is an example in which only the liquid diffusion storage coefficient 2 is within the range of the present application. In Examples 5 to 7, the total absorption of the diaper is low because the capillary absorption capacity at the height of 0 cm and 40 cm of the liquid diffusion member is low.
(Comparative Example 3)
An absorber (10) obtained by combining the water-absorbent resin (3) and the liquid diffusion member (4) was obtained. The ratio of the capillary absorption index B at a height of 40 cm of the water-absorbent resin (3) to the capillary absorption index A at a height of 40 cm of the liquid diffusion member (4) is B / A = 2.9. The ratio of the capillary absorption capacity D at a height of 40 cm of the water-absorbent resin (3) to the capillary absorption capacity C at a height of 40 cm is D / C = 8.1, but the height of the liquid diffusion member (4) is 40 cm. Is 0.4 (g / g), the capillary absorption index A at a height of 40 cm of the liquid diffusion member (4) is as low as 0.04 (g / g), and the liquid diffusion ability is low. Things.
[0152]
The liquid distribution ratio from the liquid diffusion member to the water-absorbent resin is determined using the absorber (10), and an absorbent article (10) as a model diaper is formed using the absorber (10). , The total absorption of the diaper at the time of leakage, the liquid absorption of the water-absorbent resin in the diaper, and the liquid absorption of the upper half of the diaper. The results are shown in Table 2. Although the liquid distribution ratio from the liquid diffusion member to the water-absorbent resin is excellent at 84%, the liquid diffusion ratio in the diaper is as low as 64%, and the liquid of the water-absorbent resin in the upper half of the diaper is assumed to be lying down. The amount of absorption was also very low at 16 g.
(Comparative Example 4)
Instead of the absorber of the present invention, a commercially available diaper for children (P & G Pampers Smooth Care, size L, diaper weight 57 g, absorber weight 24.0 g: water absorbent resin 12.4 g, floc pulp 12.2 g) is absorbed It was set as the sexual article (11). The diffusivity of the liquid in the liquid diffusion member of the absorbent article (11) and the total absorption of the diaper at the time of leakage were determined. The results are shown in Table 2, but the liquid diffusion rate in the diaper was as low as 62%.
[0153]
[Table 1]

[0154]
[Table 2]

[0155]
(Reference Example 8) Method for producing water-absorbent resin (4)
4.9 parts of polyethylene glycol diacrylate (n = 8) was dissolved in 5500 parts of a 33% by weight aqueous solution of sodium acrylate (neutralization ratio: 75 mol%) to prepare a reaction solution. Next, the reaction solution was degassed under a nitrogen gas atmosphere for 30 minutes. Next, the reaction solution was supplied to a stainless steel double-armed kneader with a jacket having two sigma-type blades with a lid that can be opened and closed, and the system was purged with nitrogen gas while maintaining the reaction solution at 30 ° C. Subsequently, 2.4 parts of ammonium persulfate and 0.12 part of L-ascorbic acid were added while stirring the reaction solution, and polymerization started about 1 minute later. Then, polymerization was carried out at 30 to 90 ° C., and the hydrogel polymer was taken out 60 minutes after the initiation of the polymerization.
[0156]
The obtained hydrogel polymer was subdivided into a diameter of about 5 mm. The finely divided hydrogel polymer was spread on a 50-mesh wire net and dried with hot air at 150 ° C. for 90 minutes. Next, the dried product is pulverized using a vibrating mill, and further classified by a 20-mesh wire net, so that the weight-average particle size is 340 μm, and the ratio of particles having a particle size of less than 106 μm is 3% by weight. A crushed resin was obtained.
100 parts by weight of the obtained resin was mixed with a surface cross-linking agent composition solution composed of 0.05 parts by weight of ethylene glycol diglycidyl ether, 0.9 parts by weight of propylene glycol, 3 parts by weight of water, and 1 part by weight of isopropyl alcohol. did. The mixture was heated at 195 ° C. for 40 minutes to obtain a water-absorbent resin (4). The weight average particle diameter of the water absorbent resin (4) was 347 μm. The water-absorbent resin (4) has a capillary absorption capacity at a height of 0 cm of 39.9 (g / g), a capillary absorption capacity D at a height of 40 cm of 11.4 (g / g), and a water absorption capacity of 40 cm. The capillary absorption index B was 0.29.
[0157]
(Reference Example 9) Method for producing water-absorbent resin (5)
A reaction solution was prepared by dissolving 8.1 parts of polyethylene glycol diacrylate (n = 8) in 5500 parts of a 38% by weight aqueous solution of sodium acrylate (neutralization ratio: 71 mol%). Next, the reaction solution was degassed under a nitrogen gas atmosphere for 30 minutes. Next, the reaction solution was supplied to a stainless steel double-armed kneader with a jacket having two sigma-type blades with a lid that can be opened and closed, and the system was purged with nitrogen gas while maintaining the reaction solution at 30 ° C. Subsequently, 2.4 parts of ammonium persulfate and 0.12 part of L-ascorbic acid were added while stirring the reaction solution, and polymerization started about 1 minute later. Then, polymerization was carried out at 20 to 95 ° C., and the hydrogel polymer was taken out 60 minutes after the polymerization was started.
[0158]
The obtained hydrogel polymer was subdivided into a diameter of about 5 mm. The finely divided hydrogel polymer was spread on a 50-mesh wire net and dried with hot air at 150 ° C. for 90 minutes. Next, the dried product was pulverized using a vibration mill, and further passed through a sieve having openings of 850 μm and remained on a sieve having a size of 106 μm to obtain an irregularly crushed resin having a weight average particle diameter of 400 μm.
To 100 parts by weight of the obtained resin, a surface cross-linking agent composition liquid composed of 0.3 parts by weight of 1,4-butanediol, 0.5 parts by weight of propylene glycol, and 3 parts by weight of water was mixed. After heat-treating the above mixture at 210 ° C. for 30 minutes, 0.5 parts of hydrophilic silicon dioxide fine powder (manufactured by Nippon Aerosil Co., Ltd., Aerosil 200) was added and the surface was coated to obtain a water-absorbent resin (5). . The weight average particle diameter of the water absorbent resin (5) was 500 μm. The water-absorbent resin (5) has a capillary absorption capacity at a height of 0 cm of 37.4 (g / g), a capillary absorption capacity D at a height of 40 cm of 2.8 (g / g), and a capacity of 40 cm. The capillary absorption index B was 0.08.
[0159]
(Reference Example 10) Liquid acquisition member (1)
As a liquid acquisition member, take out crosslinked cellulose covered with a nonwoven fabric on the top and bottom used in a commercially available children's diaper (P & G Pampers Smooth Care, size L, diaper weight 57 g), and measure the liquid in a size of 8 cm × 30 cm. Used as acquisition member (1). The capillary absorption capacity at a height of 0 cm of the liquid acquisition member (1) is 14.4 (g / g), the capillary absorption capacity C at a height of 40 cm is 0.18 (g / g), and the capacity at a height of 40 cm. The capillary absorption index A was 0.014.
(Reference Example 11) Liquid acquisition member (2)
As a liquid acquisition member, 3 g of cotton-like pulp used for a child's diaper was spread to a size of 8 cm × 30 cm to form a sheet, and used as a liquid acquisition member (2) (density: 0.03 g / cm).³With a basis weight of 260 g / m²). Capillary absorption at a height of 0 cm of the liquid acquisition member (2) is 13.8 (g / g), capillary absorption at a height of 40 cm C is 0.53 (g / g), and capillary at a height of 40 cm. The absorption index A was 0.038.
[0160]
(Example 8)
16.4 g of the water-absorbent resin (4) was sprayed over an area of 12 × 38 cm, and the spray amount was 360 g / m.²Was formed thereon, and an absorber (12) on which the liquid acquisition member (1) (12 × 24 cm, weight 3.8 g) was placed was obtained according to the above-described method. The ratio B / A of the water-absorbent resin (4) at a height of 40 cm to the capillary absorption index A at a height of 40 cm of the liquid acquisition member (1) at a height of 40 cm B / A = 20.7. The capillary absorption capacity C at a height of 40 cm was 0.18 (g / g), and the capillary absorption capacity D of the water absorbent resin (4) at a height of 40 cm was 11.4 (g / g).
[0161]
Using the absorbent body (12), an absorbent article (12) as a model diaper was prepared according to the above-mentioned preparation method, and the liquid passing time, the whitening time, the residual liquid amount in the liquid obtaining member, and the return amount were determined. The results are shown in Table 3. The whitening time was fast, the amount of the remaining liquid in the liquid acquiring member was small, and the amount of return was small. It can be seen that an excellent diaper can be obtained.
(Example 9)
In the same manner as in Example 8, an absorber (13) in which the water-absorbent resin (2) and the liquid acquisition member (1) were combined was obtained. The ratio of the capillary absorption index B at a height of 40 cm of the water-absorbent resin (2) to the capillary absorption index A at a height of 40 cm of the liquid acquisition member (1) is B / A = 41.0. The capillary absorption capacity at a height of 40 cm was 0.18 (g / g), and the water absorption resin (2) had a capillary absorption capacity D at a height of 40 cm of 19.4 (g / g).
[0162]
Using the absorber (13), an absorbent article (13) as a model diaper was prepared in accordance with the above-mentioned preparation method, and the liquid passing time, the whitening time, the residual liquid amount in the liquid obtaining member, and the return amount were determined. The results are shown in Table 3. The whitening time was fast, the amount of the remaining liquid in the liquid acquisition member was small, and the amount of return was small. It can be seen that an excellent diaper can be obtained.
(Example 10)
In the same manner as in Example 8, an absorbent (14) obtained by combining the water absorbent resin (1) and the liquid acquisition member (1) was obtained. The ratio B / A of the water-absorbent resin (1) at a height of 40 cm to the capillary absorption index A at a height of 40 cm of the liquid acquisition member (1) at a height of 40 cm B / A = 43.0. The capillary absorption capacity at a height of 40 cm was 0.18 (g / g), and the water absorption resin (1) had a capillary absorption capacity D at a height of 40 cm of 27.4 (g / g).
[0163]
Using the absorber (14), an absorbent article (14) as a model diaper was prepared in accordance with the above-described preparation method, and the liquid passing time, the whitening time, the remaining liquid amount in the liquid obtaining member, and the return amount were determined. The results are shown in Table 3. The whitening time was fast, the amount of the remaining liquid in the liquid acquisition member was small, and the amount of return was small. It can be seen that an excellent diaper can be obtained.
(Example 11)
In the same manner as in Example 8, an absorbent (15) in which the water absorbing resin (4) and the liquid acquisition member (2) were combined was obtained. The ratio B / A of the water-absorbent resin (4) at a height of 40 cm to the capillary absorption index A at a height of 40 cm of the liquid acquisition member (2) at a height of 40 cm is B / A = 7.6. The capillary absorption capacity at a height of 40 cm was 0.53 (g / g), and the water absorption resin (4) had a capillary absorption capacity D at a height of 40 cm of 11.4 (g / g).
[0164]
Using the absorber (15), an absorbent article (15) as a model diaper was prepared in accordance with the above-mentioned preparation method, and the liquid passing time, the whitening time, the remaining liquid amount in the liquid obtaining member, and the return amount were obtained. The results are shown in Table 3. The whitening time was fast, the amount of the remaining liquid in the liquid acquisition member was small, and the amount of return was small. It can be seen that an excellent diaper can be obtained.
(Comparative Example 5)
In the same manner as in Example 8, an absorbent (16) obtained by combining the water absorbent resin (5) and the liquid acquisition member (1) was obtained. The ratio B / A of the water absorption resin (5) at a height of 40 cm to the capillary absorption index A at a height of 40 cm of the liquid acquisition member (1) at a height of 40 cm, B / A = 5.4, of the liquid acquisition member (1). The capillary absorption capacity at a height of 40 cm was 0.18 (g / g), and the water absorption resin (5) had a capillary absorption capacity D at a height of 40 cm of 2.8 (g / g).
[0165]
Using the absorber (16), an absorbent article (16) as a model diaper was prepared in accordance with the above-mentioned preparation method, and the liquid passing time, the whitening time, the amount of liquid remaining in the liquid acquisition member, and the amount of return were determined. The results are shown in Table 4. As shown in Table 4, the whitening time was slow, and the amount of liquid remaining in the liquid acquisition member and the amount of return were large, so that the liquid was not smoothly absorbed from the liquid acquisition member to the water-absorbent resin layer. Understand.
(Comparative Example 6)
An absorber (17) in which the water absorbing resin (3) and the liquid acquisition member (1) were combined was obtained in the same manner as in Example 8. The ratio B / A of the water-absorbent resin (3) at a height of 40 cm to the capillary absorption index A at a height of 40 cm of the liquid acquisition member (1) at a height of 40 cm, B / A = 8.1, of the liquid acquisition member (1). The capillary absorption capacity at a height of 40 cm was 0.18 (g / g), and the water absorption resin (3) had a capillary absorption capacity D at a height of 40 cm of 4.3 (g / g).
[0166]
Using the absorber (17), an absorbent article (17) as a model diaper was prepared in accordance with the above-described preparation method, and the liquid passing time, the whitening time, the amount of liquid remaining in the liquid acquisition member, and the amount of return were determined. The results are shown in Table 4, which shows that the absorption of the liquid from the liquid acquisition member to the water-absorbent resin layer was not performed smoothly because the whitening time was long and the amount of return was large.
(Comparative Example 7)
8.2 g of the water-absorbent resin (4) and 8.2 g of cotton-like pulp used for a child's diaper were mixed to prepare a 12 x 38 cm blend core. Table 4 shows the capillary absorption capacity of this product. The liquid acquisition member (1) and the above blend core were combined in the amounts shown in Table 4 to obtain an absorber (18). The ratio of the capillary absorption index B at a height of 40 cm of the blend core to the capillary absorption index A at a height of 40 cm of the liquid acquisition member (1) B / A = 5.6, the height of the liquid acquisition member (1) of 40 cm The capillary absorption capacity at a height of 0.18 (g / g) and the capillary absorption capacity at a height of 40 cm of the blend core was 2.3 (g / g).
[0167]
Using the absorber (18), an absorbent article (18) as a model diaper is prepared according to the above-described preparation method, and the liquid absorption rate, the drying rate of the liquid diffusing material, and the amount of liquid remaining in the liquid acquisition member after 1 hour. And the amount of return was determined. The results are shown in Table 4. As shown in Table 4, the whitening time was slow, and the amount of liquid remaining in the liquid acquisition member and the amount of return were large, so that the liquid was not smoothly absorbed from the liquid acquisition member to the water-absorbent resin layer. Understand.
(Comparative Example 8)
An absorbent article (19) as a model diaper was prepared by performing the same operation as in Example 8 except that the liquid diffusion member was not used, and the liquid absorption rate, the drying rate of the liquid diffusion material, and the liquid acquisition member after one hour. And the amount of reversion was determined. The results are shown in Table 4, and it can be seen that the liquid passing time was extremely slow and the liquid was not absorbed smoothly.
[0168]
[Table 3]

[0169]
[Table 4]

[0170]
(Reference Example 12) Method for producing water-absorbent resin (6)
4.9 parts of polyethylene glycol diacrylate (n = 8) was dissolved in 5500 parts of a 33% by weight aqueous solution of sodium acrylate (neutralization ratio: 75 mol%) to prepare a reaction solution. Next, the reaction solution was degassed under a nitrogen gas atmosphere for 30 minutes. Next, the reaction solution was supplied to a stainless steel double-armed kneader with a jacket having two sigma-type blades with a lid that can be opened and closed, and the system was purged with nitrogen gas while maintaining the reaction solution at 30 ° C. Subsequently, 2.4 parts of ammonium persulfate and 0.12 part of L-ascorbic acid were added while stirring the reaction solution, and polymerization started about 1 minute later. Then, polymerization was carried out at 30 to 90 ° C., and the hydrogel polymer was taken out 60 minutes after the initiation of the polymerization.
[0171]
The obtained hydrogel polymer was subdivided into a diameter of about 5 mm. The finely divided hydrogel polymer was spread on a 50-mesh wire net and dried with hot air at 150 ° C. for 90 minutes. Next, the dried product is pulverized using a vibrating mill, and further classified by a 30-mesh wire net to form an amorphous material having a weight average particle size of 280 μm and a particle size of less than 106 μm in which the ratio of particles is 5% by weight. A crushed water absorbent resin precursor was obtained.
A surface crosslinking agent comprising 0.05 parts by weight of ethylene glycol diglycidyl ether, 0.9 parts by weight of propylene glycol, 3 parts by weight of water, and 1 part by weight of isopropyl alcohol based on 100 parts by weight of the obtained water-absorbent resin precursor. The composition liquid was mixed. The mixture was heated at 195 ° C. for 40 minutes to obtain a water-absorbent resin (6). The weight average particle diameter of the water absorbent resin (6) was 265 μm. The capillary absorption capacity D at a height of 40 cm of the water absorbent resin (6) was 11.4 (g / g). The particle size distribution of the water absorbent resin (6) was such that particles having a size of 150 to 850 μm were 90% by weight, and particles having a size of less than 150 μm were 10% by weight.
[0172]
(Reference Example 13) Dispersion of water-dispersible fine particles
As water-dispersible fine particles, 5 parts by weight of Aerosil 200 (ultrafine silicon oxide, manufactured by Nippon Aerosil Co., Ltd.) and 70 parts by weight of ion-exchanged water were mixed for 2 hours with a high-speed stirring mixer (2000 rpm). After mixing, the mixture was allowed to stand at room temperature for 24 hours to obtain a dispersion of water-dispersible fine particles. The viscosity of the water-dispersible fine particles was 1000 cps.
(Example 12)
7 parts by weight of the dispersion of the water-dispersible particles obtained in Reference Example 13 was added to 100 parts by weight of the water-absorbent resin (6), mixed and left at 60 ° C. for 30 minutes, and the mixture was crushed. The particles were passed through a wire mesh having openings of 850 μm to obtain water-absorbent resin particles (1) of the present invention. The particle size distribution of the product was 97% by weight of particles having a size of 150 to 850 μm, and 3% by weight of particles having a size of 150 μm or less. The weight average particle diameter was 500 μm. Table 5 shows the results.
[0173]
Using the obtained absorbent resin particles (1) and the liquid acquisition member (2), an absorbent article (20) as a model diaper is prepared according to the method described above, and the liquid passing time, the diffusion area, and the return amount are set as described above. The results were evaluated according to the evaluation methods and are shown in Table 5.
(Example 13)
7 parts by weight of the dispersion of the water-dispersible particles obtained in Reference Example 13 and 13 parts by weight of ionic water were mixed to obtain a dispersion. 20 parts by weight of the dispersion is added to 100 parts by weight of the water-absorbent resin (2), mixed and left at 60 ° C. for 30 minutes, then the mixture is crushed, and all the particles pass through a wire mesh having an opening of 850 μm. As a result, water-absorbent resin particles (2) of the present invention were obtained. The particle size distribution of this product was 85% by weight of particles of 150 to 850 μm, and 15% by weight of particles of 150 μm or less. The weight average particle size was 308 μm.
[0174]
Using the obtained absorbent resin particles (2) and the liquid acquisition member (2), an absorbent article (21) as a model diaper is prepared according to the method described above, and the liquid passing time, diffusion area, and return amount are set as described above. The results were evaluated according to the evaluation methods and are shown in Table 5.
(Comparative Example 9)
To 100 parts by weight of the water-absorbent resin (2), 0.5 parts by weight of Aerosil 200 (fine powder of silicon dioxide, manufactured by Nippon Aerosil Co., Ltd.) is added, the absorbent resin is mixed, and 20 parts by weight of ion-exchanged water is further added. Was added and mixed. After standing at 60 ° C. for 30 minutes, the mixture was pulverized, and all the particles were passed through a wire mesh having openings of 850 μm to obtain water-absorbent resin particles (3). The particle size distribution of this product was 59% by weight of particles having a size of 150 to 850 μm, and 41% by weight of particles having a size of 150 μm or less. The weight average particle size was 174 μm.
[0175]
Using the obtained absorbent resin particles (3) and the liquid acquisition member (2), an absorbent article (22) as a model diaper is prepared according to the method described above, and the liquid passing time, diffusion area, and return amount are set as described above. The results were evaluated according to the evaluation methods and are shown in Table 5.
(Comparative Example 10)
20 parts by weight of ion-exchanged water is added to and mixed with 100 parts by weight of the water-absorbent resin (2), and the mixture is left at 60 ° C. for 30 minutes. The water-absorbent resin particles (4) were passed through to obtain. The particle size distribution of this product was 61% by weight of particles of 150 to 850 μm, and 39% by weight of particles of 150 μm or less. The weight average particle diameter was 180 μm, but it was brittle and easily collapsed.
[0176]
Using the obtained absorbent resin particles (4) and the liquid acquisition member (2), an absorbent article (23) as a model diaper is prepared according to the method described above, and the liquid passing time, the diffusion area, and the return amount are set as described above. The results were evaluated according to the evaluation methods and are shown in Table 5.
(Comparative Example 11)
Using the obtained absorbent resin (2) and the liquid acquisition member (2), an absorbent article (24) as a model diaper is prepared according to the method described above, and the liquid passing time, the diffusion area, and the return amount are evaluated as described above. The results were evaluated according to the method and are shown in Table 5. When making the absorber, dust was scattered and handling was difficult.
[0177]
(Comparative Example 12)
Using the obtained absorbent resin (3) and the liquid acquisition member (2), an absorbent article (25) as a model diaper is prepared according to the method described above, and the liquid passing time, the diffusion area, and the return amount are evaluated as described above. The results were evaluated according to the method and are shown in Table 5.
[0178]
[Table 5]

[0179]
【The invention's effect】
According to the present invention, in an absorber or an absorbent article using a liquid diffusion member and a water absorbent resin, the liquid is sufficiently transferred from the liquid diffusion member to the water absorbent resin without using an auxiliary material such as a material having a large surface area. It is possible to provide an absorbent, an absorbent article, and a water-absorbent resin that can be suitably used for the absorbent, the absorbent, and the absorbent, which are excellent in both the ability to absorb and diffuse the liquid and the ability to store the liquid. In an absorber or an absorbent article using the acquisition member and the water-absorbent resin, even when the concentration of the water-absorbent resin is further increased, the liquid migrates favorably from the liquid acquisition member to the water-absorbent resin, and absorbs the liquid repeatedly. Even when the liquid acquisition function is not significantly reduced, the dryness and the amount of liquid returned are excellent, and the thinner and lighter material is realized. Providing water-absorbent resin It can be.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view of a measuring device used for measurement for obtaining a capillary absorption capacity and a capillary absorption index in the present invention. This device measures capillary absorption capacity at a height of 40 cm.
FIG. 2 is a schematic cross-sectional view of a measuring device used for measurement for obtaining a capillary absorption capacity and a capillary absorption index in the present invention. This apparatus measures the absorption capacity of a capillary at a height of 0 cm and the absorption capacity of a water-absorbent resin under pressure.
FIG. 3 is a schematic perspective view of an absorbent article according to the present invention.
FIG. 4 is a schematic sectional view of an absorbent article according to the present invention.
[Explanation of symbols]
1 Porous glass plate
2 Glass filter
3 conduit
4 Reservoir container
5 support ring
6 saline
7 balance
8 stand
9 Measurement sample (water-absorbent resin or liquid diffusion member)
10 ° load (0.41 kPa (0.06 psi))
11 ° outside air suction pipe
12 conduit
13 glass filter
14 saline
15 reservoir
16 balance
17 filter paper
18 wire mesh
19mm plastic cylinder
10 ° load (0.41 kPa (0.06 psi))
20mm load (2.07kPa (0.3psi))
21 ° load (4.83 kPa (0.7 psi))
31% liquid permeable polyester non-woven fabric
32 water absorbent resin
33 ° liquid diffusion member
34 liquid impermeable polyethylene film
35 Heatron Paper
36mm adhesive tape

Claims (26)

An absorbent body including a liquid diffusion member and a water-absorbent resin, wherein a capillary absorption index at a height of 40 cm of the liquid diffusion member is A (where A ≧ 0.10.) An absorbent body characterized in that a capillary absorption index B at a height satisfying the following expression is used.
B / A ≧ 0.7 (Equation 1) An absorber containing a liquid diffusion member and a water-absorbent resin, wherein the liquid absorption member has a capillary absorption capacity C at a height of 40 cm (where C ≧ 2.0 (g / g)); An absorbent, characterized in that a resin having a capillary absorption magnification D at a height of 40 cm that satisfies the following formula is used as the conductive resin.
D / C ≧ 0.7 (Equation 2) The absorber according to claim 1 or 2, wherein the water absorbing resin has a capillary absorption capacity D at a height of 40 cm of 15 (g / g) or more. An absorber including a liquid diffusion member and a liquid storage member, wherein the liquid diffusion member has a suction height of 30 cm or more, and the liquid storage member has a capillary absorption ratio D of 15 (g / g) or more at a height of 40 cm. An absorbent, characterized by using a water-absorbent resin of the above. An absorbent body including a liquid diffusion member and a liquid storage member, wherein a member having a suction height of 30 cm or more is used as the liquid diffusion member, and a surface-crosslinked water-absorbent resin having a weight average particle diameter of 250 μm or less is used as the liquid storage member. An absorber, characterized in that: The absorber according to any one of claims 1 to 5, wherein the liquid diffusion member is a porous polymer obtained by polymerizing a high internal phase emulsion. An absorbent comprising a liquid diffusion member and a water-absorbent resin containing a polyacrylic acid (salt) -based crosslinked polymer as a main component, wherein the liquid diffusion member is a porous polymer obtained by polymerizing a high internal phase emulsion. An absorbent, wherein the weight ratio of the water-absorbent resin to the total weight of the liquid diffusion member and the water-absorbent resin is 75% by weight or more and 90% by weight or less. The absorbent body according to claim 7, wherein a capillary absorption capacity D at a height of 40 cm of the water absorbent resin is 15 (g / g) or more. An absorbent article comprising the absorber according to any one of claims 1 to 8. An absorbent body comprising a liquid acquisition member and a water-absorbent resin layer in which the amount of the water-absorbent resin sprayed is 250 g / m ² or more, wherein a capillary absorption index of the liquid acquisition member at a height of 40 cm is E (where E <0. The absorbent body according to 1), wherein the water-absorbent resin has a capillary absorption index B at a height of 40 cm that satisfies the following expression.
B / E ≧ 10 (Equation 3) An absorbent body comprising a liquid acquisition member and a water-absorbent resin layer in which the amount of the water-absorbent resin sprayed is 250 g / m ² or more, wherein a capillary absorption index of the liquid acquisition member at a height of 40 cm is E (where E <0. The absorbent according to 1), wherein the capillary absorption index F at a height of 40 cm of the water-absorbent resin layer satisfies the following expression.
F / E ≧ 10 (Equation 4) An absorbent body including a liquid acquisition member and a water-absorbent resin layer in which the amount of the water-absorbent resin sprayed is 250 g / m ² or more, wherein a capillary absorption ratio G at a height of 40 cm of the liquid acquisition member is 1.0 (g / m ^2). g) or less, characterized by using a water-absorbent resin having a capillary absorption capacity D at a height of 40 cm of 5 (g / g) or more. An absorbent body including a liquid acquisition member and a water-absorbent resin layer in which the amount of the water-absorbent resin sprayed is 250 g / m ² or more, wherein a capillary absorption ratio G at a height of 40 cm of the liquid acquisition member is 1.0 (g / m ^2). g) or less, and the capillary absorption capacity H at a height of 40 cm of the water-absorbent resin layer is 5 (g / g) or more. 14. The absorber according to claim 10, wherein a weight ratio of the water absorbent resin layer to the total weight of the liquid acquisition member and the water absorbent resin layer is 70% by weight or more. An absorbent article comprising the absorber according to any one of claims 10 to 14. The weight average particle diameter is 50 to 300 μm, the gap between particles during saturated swelling under no pressure when saturated and swollen in physiological saline (0.9 wt% NaCl aqueous solution) is 30 to 50%, and under no pressure Water-absorbent resin particles obtained by granulating a water-absorbent resin having an average interparticle radius at saturation swelling of 80 to 150 μm, wherein the weight-average particle size of the water-absorbent resin particles is 50% or more from before the granulation Water-absorbing resin particles that have been raised. The water-absorbent resin particles according to claim 16, wherein the weight average particle diameter is 150 to 600 µm, and the capillary absorption capacity at a height of 40 cm is 7 (g / g) or more. The ratio of a particle diameter of 150 μm or less in the water-absorbent resin particles is 50% or less as compared with that before granulation, and the capillary absorption capacity at a height of 40 cm is 7 (g / g) or more. 18. The water-absorbent resin particles according to 17. Water-absorbent resin particles containing a polyacrylic acid (salt) -based crosslinked polymer as a main component and having a capillary absorption capacity D at a height of 40 cm of 25 (g / g) or more. The weight average particle diameter is 50 to 300 μm, the gap between particles during saturated swelling under no pressure when saturated and swollen in physiological saline (0.9 wt% NaCl aqueous solution) is 30 to 50%, and under no pressure A water-absorbent resin having a mean inter-particle radius at saturation swelling of 80 to 150 μm, wherein the weight-average particle diameter is increased by 50% or more by adding a dispersion of water-dispersible fine particles. A method for producing resin particles. The method for producing water-absorbent resin particles according to claim 20, wherein a powder having a weight average primary particle diameter of 3 µm or less is used as the water-dispersible fine particles. A water-absorbent article comprising the water-absorbent resin particles according to any one of claims 16 to 19. A water-absorbent resin containing a polyacrylic acid (salt) -based crosslinked polymer as a main component and having a capillary absorption capacity D at a height of 40 cm of 25 (g / g) or more. A water absorbent article comprising the water absorbent resin according to claim 23. A method for evaluating a water-absorbent resin, wherein the absorption capacity of a liquid absorbed by the water-absorbent resin within a predetermined time is measured in a state where the height H1 of the liquid absorption position is higher than the height H2 of the liquid level of the liquid storage container. 26. The method for evaluating a water-absorbent resin according to claim 25, wherein the height difference between the height H1 of the liquid absorbing position and the height H2 of the liquid level of the liquid storage container is 20 to 60 cm.

Images