JP4759165B2

JP4759165B2 - Organic / inorganic composite hydrogel and method for producing the same

Info

Publication number: JP4759165B2
Application number: JP2001158634A
Authority: JP
Inventors: 和敏原口
Original assignee: Kawamura Institute of Chemical Research
Current assignee: Kawamura Institute of Chemical Research
Priority date: 2000-05-29
Filing date: 2001-05-28
Publication date: 2011-08-31
Anticipated expiration: 2021-05-28
Also published as: JP2002053629A

Description

【０００１】
【発明の属する技術分野】
本発明は、水溶性有機高分子と、水に均一分散可能な水膨潤性粘土鉱物とが複合化して形成された三次元網目の中に水が包含されている有機・無機複合ヒドロゲル、その乾燥体、及びその製造方法に関する。
【０００２】
【従来の技術】
ゲルは液体と固体の中間の性質を有するもので、有機高分子などの三次元網目（ネットワーク）の中に溶媒を安定的に取り込んだものである。特に溶媒として水を用いたゲル（以下、ヒドロゲルもしくは水性ゲルと呼ぶ）は生体において重要な構成素材であり、これまで食品・包装、衛生用品、化粧品などの医薬・医療・食品分野の他、農業、土木、工業分野においても広く利用されている（例えば、長田義仁、梶原莞爾編”ゲルハンドブック”株式会社エヌ・ティー・エス、１９９７年）。
【０００３】
ヒドロゲルは少なくとも２種の構成成分を含んでいる。即ち、種々の方式で橋架けされた三次元網目と水である。三次元網目の構成成分としては、有機化合物又は無機物のいずれもが可能である。例えば、有機化合物のヒドロゲルでは、有機高分子又は有機分子が共有結合、水素結合、イオン結合、疎水結合などにより架橋するか、又は物理的絡み合いや微結晶などを架橋点として三次元網目を形成している。
【０００４】
具体的に三次元網目を形成する有機分子としては、疎水結合により架橋が形成される卵白アルブミンや血清アルブミン、ヘリックス形成によるゼラチンやアガロース、アルカリ土類金属イオンとの配位結合により架橋を形成するポリアクリル酸やポリスチレンスルホン酸、イオン結合により架橋する２種の高分子（ポリカチオンとポリアニオン）複合系、水素結合で架橋される完全けん化ポリビニルアルコール等のほか、熱、放射線、光、プラズマを照射したり、有機架橋剤添加により、有機高分子間に共有結合による架橋を形成させたものが多く知られている。
【０００５】
一方、無機物で三次元網目を形成するものとしては、金属アルコキシドの加水分解重縮合（いわゆるゾル-ゲル反応）により調製される金属酸化物や層間にカチオンを有する層状粘土鉱物が知られており、イオン相互作用などによる微粒子の凝集により三次元網目を形成し、無機物と水からなるゲルが調製される。
【０００６】
無機物のヒドロゲルは強度や伸びが小さく脆い性質を有しているため、単独のヒドロゲル材料として用いられることは少ない。これに対して有機化合物、特に共有結合などによる有機高分子の三次元網目と水からなるヒドロゲルは力学物性が無機物ヒドロゲルより良好であることや、有機高分子の持つ特性をヒドロゲル中で発揮できる可能性を有することから、ソフトマテリアルや機能性ゲル材料として幅広い産業分野で用途開拓が進められている。
【０００７】
このような有機架橋ヒドロゲルの有用性を拡大させる為に、ゲルの均一性、透明性、力学物性、及び機械的性質等を更に向上させたり、吸収（吸水）特性を更に向上させたり、ヒドロゲル中で有機高分子の特性をより効果的に発現させる新しいヒドロゲルの開発が望まれている。
【０００８】
【発明が解決しようとする課題】
本発明が解決しようとする課題は、優れた、均一性、透明性、力学物性、吸水性、及び膨潤・収縮特性を有する新規な有機・無機複合ヒドロゲル、その製造方法及び該ヒドロゲルから水分を除去して得られる有機・無機複合ヒドロゲルの乾燥体を提供することにある。
【０００９】
【課題を解決するための手段】
本発明者らは、上記課題を解決すべく鋭意研究に取り組んだ結果、水に均一分散可能な水膨潤性粘土鉱物と水との共存下に、水溶性有機高分子を構成する成分モノマーを重合させると、（Ａ）水溶性有機高分子と（Ｂ）水に均一分散可能な水膨潤性粘土鉱物とが分子レベルで複合化して形成された三次元網目の中に水が包含されている新規な有機・無機複合ヒドロゲル（以下、有機・無機複合ヒドロゲルと呼ぶ）が得られることを見出し、本発明を完成するに至った。
【００１０】
即ち、本発明は、（Ａ）水溶性有機高分子と、（Ｂ）水に均一分散可能な水膨潤性粘土鉱物とが複合化して形成された三次元網目の中に（Ｃ）水が包含されている有機・無機複合ヒドロゲルであり、（Ｂ）水に均一分散可能な水膨潤性粘土鉱物と、（Ｃ）水との共存下に、（Ａ）水溶性有機高分子の構成成分モノマー（Ａ’）を重合させて得られる有機・無機複合ヒドロゲルである。また本発明は、有機・無機複合ヒドロゲルから水分を除去して得られる有機・無機複合ヒドロゲルの乾燥体を提供する。
【００１１】
更に本発明は、（Ａ）水溶性有機高分子の構成成分であるモノマー（Ａ’）と、（Ｂ）水に均一分散可能な水膨潤性粘土鉱物と、（Ｃ）水とを含む均一溶液を調製し、（Ｂ）水の共存下に水溶性有機高分子の構成成分であるモノマー（Ａ’）を重合させる、有機・無機複合ヒドロゲルの製造方法を提供する。
【００１２】
【発明の実施の形態】
本発明でいう（Ａ）水溶性有機高分子とは、水に溶解するもののほか、水に膨潤する性質の有機高分子も含まれる。なお、かかる水溶解性や水膨潤性は特定の高分子濃度、温度、圧力条件や他の添加成分共存下などで達成されるものであっても良い。また水溶性有機高分子は単一モノマーからの重合体でも、複数種のモノマーが重合して得られる共重合体でも良い。
【００１３】
本発明に用いられる（Ａ）水溶性有機高分子は（Ｂ）水に均一分散可能な水膨潤性粘土鉱物と相互作用を有するものが好ましく、例えば（Ｂ）と水素結合、イオン結合、配位結合、共有結合等を形成できる官能基を有するものが好ましい。
【００１４】
これらの官能基を有する有機高分子としては、具体的には、アミド基、アミノ基、水酸基、テトラメチルアンモニウム基、シラノール基、エポキシ基などを有する有機高分子が挙げられる。更に本発明に用いる水溶性有機高分子としては、機能性を有しているものが特に好ましく、例えば、水溶液中でのポリマー物性（例えば親水性と疎水性）がＬＣＳＴ（下限臨界共溶温度、Lower Critical Solution Temperature）前後のわずかな温度変化により大きく変化する特性をもつ有機高分子などが挙げられる。
【００１５】
（Ａ）水溶性有機高分子の具体例として、アクリルアミド、Ｎ−置換アクリルアミド誘導体、Ｎ，Ｎ−ジ置換アクリルアミド誘導体、Ｎ−置換メタクリルアミド誘導体、Ｎ，Ｎ−ジ置換メタクリルアミド誘導体の中から選択される一つ又は複数を重合して得られる水溶性有機高分子が挙げられる。また上記モノマーとその他の有機モノマーとをあわせて用いることも均一な有機・無機複合ヒドロゲルを形成する限りにおいて可能である。
【００１６】
かかる水溶性有機高分子としては、ポリ（アクリルアミド）、ポリ（Ｎ−メチルアクリルアミド）、ポリ（Ｎ−エチルアクリルアミド）、ポリ（Ｎ−シクロプロピルアクリルアミド）、ポリ（Ｎ−イソプロピルアクリルアミド）、ポリ（メタクリルアミド）、ポリ（Ｎ−メチルメタクリルアミド）、ポリ（Ｎ−シクロプロピルメタクリルアミド）、ポリ（Ｎ−イソプロピルメタクリルアミド）、
【００１７】
ポリ（Ｎ,Ｎ−ジメチルアクリルアミド）、ポリ（Ｎ，Ｎ−ジメチルアミノプロピルアクリルアミド）、ポリ（Ｎ−メチル−Ｎ−エチルアクリルアミド）、ポリ（Ｎ−メチル−Ｎ−イソプロピルアクリルアミド）、ポリ（Ｎ−メチル−Ｎ−ｎ−プロピルアクリルアミド）、ポリ（Ｎ,Ｎ−ジエチルアクリルアミド）、ポリ（Ｎ−アクリロイルピロリディン）、ポリ（Ｎ−アクリロイルピペリディン）、ポリ（Ｎ−アクリロイルメチルホモピペラディン）、ポリ（Ｎ−アクリロイルメチルピペラディン）等が例示される。
【００１８】
本発明に用いられる（Ａ）水溶性有機高分子としては、水に溶解・膨潤するもののほか、水と水と混和する有機溶媒との混合溶媒に溶解したり、膨潤するものであっても良い。水と水と混和する有機溶媒との混合溶媒としては、水及び水と混和する（均一相を形成する）一種又は複数の有機溶媒とを混合したものが用いられる。これらの有機溶媒としては、メタノール、アセトン、メチルエチルケトン、テトラヒドロフランなどの極性溶媒が例示される。水とこれらの有機溶媒との混合割合は水膨潤性粘土（Ｂ）が均一分散出来る範囲で任意に選択できる。
【００１９】
本発明でいう（Ｂ）水に均一分散可能な水膨潤性粘土鉱物とは、粘土鉱物のうち水に膨潤し均一分散可能なものであり、特に好ましくは水中で分子状（単一層）又はそれに近いレベルで均一分散可能な層状粘土鉱物である。例えば、水膨潤性スメクタイトや水膨潤性雲母などが用いられ、具体的には、ナトリウムを層間イオンとして含む水膨潤性ヘクトライト、水膨潤性モンモリロナイト、水膨潤性サポナイト、水膨潤性合成雲母などが挙げられる。
【００２０】
また本発明において、水膨潤性粘土鉱物は水溶性有機高分子のモノマーが重合する前の水溶液中で微細、且つ均一に分散していることが必要であり、特に水溶液中に溶解していることが望ましい。ここで溶解とは、粘土鉱物の沈殿もしくは濁った水溶液となるような大きな粘土鉱物凝集体が無い状態を意味する。より好ましくは１〜１０層程度のナノメーターレベルの厚みで分散しているもの、特に好ましくは１又は２層程度の厚みで分散しているものである。
【００２１】
本発明の構成成分である（Ｃ）水としては、水、もしくは水と混和する有機溶媒と水との混合溶媒であってよく、水膨潤性粘土鉱物及び有機モノマーを均一分散するものが用いられる。混合溶媒を用いた場合は、ゲル中に水に加えて有機溶媒を含むが、ここでは便宜上、これらを含めて全てヒドロゲルと称する。
【００２２】
本発明の有機・無機複合ヒドロゲルは、（Ａ）水溶性有機高分子と、（Ｂ）水に均一分散可能な水膨潤性粘土鉱物とが複合化して形成された三次元網目の中に（Ｃ）水が包含されている有機・無機複合ヒドロゲルである。即ち、（Ａ）と（Ｂ）とが水中で分子レベルで複合化することで、（Ａ）が（Ｂ）により橋架けされたか、又は（Ｂ）が（Ａ）により橋架けされた、（Ａ）と（Ｂ）からなる三次元架橋物が水を含んで形成されていることを特徴とする。
【００２３】
即ち、本発明における有機・無機複合ヒドロゲルは、有機架橋剤無しで形成可能なヒドロゲルであり、従来から知られている有機モノマーに有機架橋剤を添加し重合して得られる有機高分子架橋物のヒドロゲル（以下有機架橋ヒドロゲルと呼ぶ）とは異なる、優れた特性を有する。
【００２４】
また本発明における有機・無機複合ヒドロゲルの乾燥体も、いったんはかかる有機・無機複合ヒドロゲルを形成することが必要であり、それらを乾燥することで、有機・無機複合ヒドロゲルの乾燥体が得られる。
【００２５】
例えば、比較例５〜８に示すように、（Ａ）と（Ｂ）の各々の水溶液を調製した後に、単純に混合した場合は、たとえ、本発明と同一の成分組成からなる場合でも、本発明の有機・無機複合ヒドロゲルは得られない。
【００２６】
本発明の有機・無機複合ヒドロゲルにおける（Ａ）水溶性有機高分子と（Ｂ）水に均一分散可能な水膨潤性粘土鉱物との比率は、（Ａ）と（Ｂ）とからなる三次元網目を有する有機・無機ヒドロゲルが調製されれば良く、また用いる（Ａ）や（Ｂ）の種類によっても異なり必ずしも限定されないが、ヒドロゲル合成の容易さや均一性の点からは、好ましくはＢ／Ａの重量比が０．０１〜１０、より好ましくは０．０３〜２．０、特に好ましくは０．１〜１．０である。
【００２７】
Ｂ／Ａの重量比が０．０１未満では、本発明でいうゲル特性が充分でない場合が多く、１０を越えては、得られたヒドロゲルが脆くなったり、水を多量に使うなどの製造上の問題が生じる。一方、（Ａ＋Ｂ）に対する（Ｃ）水の比率は、重合過程での水量調整、もしくはその後の膨潤や乾燥により、目的に応じて０から非常に大きい値まで広い範囲で任意に設定できる。
【００２８】
本発明で得られる有機・無機複合ヒドロゲルに含まれる水の最大量、即ち、平衡膨潤時の最大吸水量（Ｃｍａｘ）は、ＡやＢの成分の種類及び比率、また温度やｐＨなどの環境条件などにより異なるが、本発明の有機・無機複合ヒドロゲルはＣｍａｘが従来の有機架橋ヒドロゲルに比べて大きいことが特徴である。
【００２９】
一般にはＢ／Ａが大きいほどＣｍａｘは小さくなる。ある条件での（Ｃ）の最大量（平衡膨潤吸水量Ｃｍａｘ）は有機・無機複合ヒドロゲルを、その条件下で過剰の水の中に長時間保持することにより測定される。例えば、ある水含有率で合成した有機・無機複合ヒドロゲルを２０℃の温度の過剰な水の中に保持すると、ヒドロゲル中に更に水が取り込まれ最終的に２０℃での平衡膨潤（最大膨潤）へ達する。
【００３０】
従って、過剰水中に浸漬したヒドロゲルを時々取り出して重量測定することにより、ヒドロゲルの膨潤の時間依存性や平衡膨潤時の水含有率を知ることができる。平衡膨潤時の水含有率〔｛Ｃｍａｘ／（Ａ＋Ｂ）｝×１００］は、上述したようにＡとＢの成分種や組成により、また温度、ｐＨ、又は塩濃度などの環境条件により異なり、例えば１００重量％以下の低い値から１０００００重量％以上の高い値まで変化することが可能である。
【００３１】
本発明における有機・無機複合ヒドロゲルはＣｍａｘが従来の有機架橋ヒドロゲルに比べて大きいことが特徴であり、本発明の有機・無機複合ヒドロゲルを、例えば、２０℃で平衡膨潤させた場合、｛Ｃｍａｘ／（Ａ＋Ｂ）｝×１００］としては、通常、２０００重量％以上であり、より好ましくは３０００重量％以上、特に好ましくは４０００重量％以上である。
【００３２】
また本発明における有機・無機複合ヒドロゲルは、膨潤（吸水）速度が従来の有機架橋ヒドロゲルに対して大きい特徴も有する。これは（Ａ）と（Ｂ）との三次元架橋が（Ａ）の吸水特性を阻害せず、且つ均一に形成されることによると推定される。また（Ａ）が下記に述べるように温度変化によりに膨潤収縮する性質を有する場合は、膨潤だけでなく収縮する速度も大きい特徴を有する。
【００３３】
本発明の有機・無機複合ヒドロゲルには、低温側で透明及び／又は膨潤状態にあり、且つ高温側で不透明及び／又は体積収縮状態となる臨界温度（Ｔｃ）を有し、Ｔｃを境にした上下の温度変化により透明性や体積を可逆的に変化できる特徴を有するものが含まれる。
【００３４】
このような有機・無機複合ヒドロゲルは、有機高分子として水溶液中でＬＣＳＴ（下限臨界共溶温度）を示す有機高分子を用いて調製できる。有機・無機複合ヒドロゲルのＴｃは有機高分子のＬＣＳＴと同じ温度か変化する場合がある。
【００３５】
本発明の有機・無機複合ヒドロゲルは、従来の有機架橋ヒドロゲルと比べて、高い吸水率を有する他、高い透明性、Ｔｃ前後での膨張時と収縮時での高い体積比や透明性の変化、大きい膨潤及び／又は収縮速度、優れた力学物性や機械的性質などの特徴の一部又は全部をあわせもつものが含まれる。
【００３６】
例えば、有機架橋ヒドロゲルでは、架橋剤濃度を上げ架橋密度を大きくすると、架橋が不均一になり、透明性が失われる場合がある（比較例４、及び、Ｔ.Ｔａｎａｋａ、ＳｃｉｅｎｔｉｆｉｃＡｍｅｒｉｃａｎ、２４４巻、１１０〜１２３頁、１９８１年）のに対し、同じ有機高分子を用いた、本発明の有機・無機複合ヒドロゲルでは、均一性は失われず、高い透明性を示す。
【００３７】
具体的には、本発明の有機・無機複合ヒドロゲルには、（Ａ）水溶性有機高分子の１０倍量（重量比）の（Ｃ）水が含まれている厚み２５ｍｍの有機・無機複合ヒドロゲルにおいて、可視光の光透過率が８０％以上であり、より好ましくは８５％以上、特に好ましくは９０％以上であるものが含まれる。また有機・無機複合ヒドロゲルを乾燥して得られる乾燥体においても水膨潤性粘土鉱物が微細分散しているため透明性を有することができる。
【００３８】
また本発明の有機・無機複合ヒドロゲルはＴｃでの明確な転移特性を保持するため、図１に示すように、架橋密度の比較的高い有機架橋ヒドロゲル（比較例４）がＴｃ前後で透明性変化が殆ど無いのに対して、それ以上の力学物性を有し、且つＴｃ前後で高い透明性変化を可逆的に示す（実施例１）。
【００３９】
更に、Ｔｃ前後でのヒドロゲルの膨潤、収縮についても、図２に示すように有機・無機複合ヒドロゲル（実施例１）は有機架橋ヒドロゲル（比較例４）と比べて、膨潤時と収縮時での体積比が高い特徴を有する。本発明の有機・無機複合ヒドロゲルの膨潤時と収縮時での体積比は、目的に応じて設定することができ、一般には同じ水溶性有機高分子を用いた有機架橋ヒドロゲルより膨潤／収縮の体積比は大きく、通常は１０以上、好ましくは２０以上、より好ましくは３０以上である。
【００４０】
本発明の有機・無機複合ヒドロゲルには、強度、伸び、タフネスなどの優れた力学物性をもつものが含まれる。特に上記の高い水吸収性、透明性、及び透明性変化や体積変化などの諸特性と共に、優れた機械的性質を併せ持つものが含まれることが特徴である。有機・無機複合ヒドロゲルの力学物性は、ヒドロゲルの水含有率により異なるため、本発明の有機・無機複合ヒドロゲルの力学物性や機械的性質は、一定範囲内の水含有率をもつヒドロゲルを用いて試験した結果で表わされる。
【００４１】
具体的には｛Ｃ／（Ａ＋Ｂ）｝×１００が６００〜１０００、即ち、（Ｃ）水を有機＋無機成分（Ａ＋Ｂ）に対して６００〜１０００重量％含むヒドロゲルを用いるか、もしくは（Ａ）水溶性有機高分子の１０倍量（重量比）の（Ｃ）水を含んだものを用いて試験した結果で表わされる。
【００４２】
更に、本発明における有機・無機複合ヒドロゲルは、破断伸びが大きく、断面積が試験途中で変化するため、試験開始時のヒドロゲルの断面積（初期断面積）を０．２３７ｃｍ²（半径０．２７５ｃｍの円に相当）にしたものを試験材料として用いて規定した。
【００４３】
本発明の有機・無機複合ヒドロゲルには上記の水含有率と初期断面積、即ち、｛Ｃ／（Ａ＋Ｂ）｝×１００で定義される水含有率が６００〜１０００重量％、初期断面積が０．２３７ｃｍ²であるヒドロゲルを用いて測定した、引っ張り破断荷重が０．１Ｎ以上、好ましくは０．５Ｎ以上、より好ましくは１Ｎ以上、特に好ましくは２Ｎ以上であるものが含まれる。
【００４４】
また本発明の有機・無機複合ヒドロゲルには上記の水含有率と初期断面積のヒドロゲルを用いて測定した、引っ張り破断伸びが１００％以上、より好ましくは２００％以上、更に好ましくは３００％以上、特に好ましくは５００％以上であること、更に引っ張り伸び１００％での荷重が０．０１Ｎ以上、より好ましくは０．０５Ｎ以上であること、特に好ましくは０．１Ｎ以上である特徴を有するものが含まれる。
【００４５】
これに対して比較例３や比較例４や比較例９〜１２に示した有機架橋ヒドロゲルは、本発明の有機・無機複合ヒドロゲルと比べて極めて弱く、引っ張り試験のチャックへの装着が脆くて出来ない場合が殆どで、たとえ工夫して装着しても試験直後の破壊により、物性値は測定できなかった。
【００４６】
また本発明の有機・無機複合ヒドロゲルは、吸水時にも良好な機械的性質を示し、例えば圧縮や引っ張り、又は曲げ変形に対して耐えるタフネスを有する。
具体的には、（Ａ）水溶性有機高分子に対して１０倍量（重量比）の（Ｃ）水を含んだ直径５．５ｍｍ、長さ３０ｍｍの有機・無機複合ヒドロゲルを厚み方向で１／３以下の厚みに、好ましくは１／５以下の厚みに圧縮変形されること、及び／又は長さ方向で２倍以上の長さに、好ましくは４倍以上の長さに延伸変形されること、及び／又は長さ中心点で１００度以上の角度に、好ましくは１５０度以上の角度に曲げ変形されること等によっても、形状が破壊されないものが含まれる。
【００４７】
これに対して（Ｂ）水膨潤性粘土鉱物の代わりに、有機架橋剤を用いた以外は同一組成の有機架橋ゲルは、上述のいずれか又は全ての変形操作によって、クラックが生じて形状が破壊されたり、欠損が生じる。
【００４８】
本発明の有機・無機複合ヒドロゲルは、有機高分子と粘土鉱物からなる３次元網目が形成される必要があり、以下の方法で製造できる。（Ａ’）水溶性有機高分子（Ａ）のモノマーと、（Ｂ）水に均一分散可能な水膨潤性粘土鉱物と、（Ｃ）水とを含む均一溶液を調製後、（Ｂ）の共存下に（Ａ’）の重合を行わせる。これにより（Ａ）と（Ｂ）との分子レベルでの微細な複合化が達成され、三次元網目形成によりゲル化した有機・無機複合ヒドロゲルが得られる。
【００４９】
具体的には、（Ａ’）、（Ｂ）、（Ｃ）を必須成分として含む組成の溶液を用い、水中に微細分散した（Ｂ）共存下に（Ａ’）をラジカル重合させる有機・無機複合ヒドロゲルの製造方法であって、好ましくは１〜１０層、より好ましくは１又は２層程度のナノメーターレベルで均一分散した粘土鉱物が、（Ａ’）の架橋剤の働きをして、（Ａ）と（Ｂ）が（Ｃ）中で複合化して三次元網目を形成する方法である。
【００５０】
上記のラジカル重合反応は、分子状酸素の不存在下で過酸化物の存在及び／又は紫外線照射など公知の方法により行わせることができる。更に、この重合反応は加熱又は紫外線照射により加速することもできる。ラジカル重合開始剤及び触媒としては、公知慣用のラジカル重合開始剤及び触媒を適時選択して用いることができる。好ましくは水分散性を有し、系全体に均一に含まれるものが用いられる。
【００５１】
具体的には、重合開始剤として、水溶性の過酸化物、例えばペルオキソ二硫酸カリウムやペルオキソ二硫酸アンモニウム、水溶性のアゾ化合物、例えばＶＡ−０４４、Ｖ−５０、Ｖ−５０１（いずれも和光純薬工業株式会社製）の他、ポリエチレンオキシド鎖を有する水溶性のラジカル開始剤などが例示される。一方、触媒としては、３級アミン化合物であるＮ，Ｎ，Ｎ’，Ｎ’−テトラメチルエチレンジアミンや、β−ジメチルアミノプロピオニトリルなどが好ましく用いられる。
【００５２】
重合温度は、重合触媒や開始剤の種類に合わせて０℃〜１００℃の範囲で設定できる。重合時間も触媒、開始剤、重合温度、重合溶液量（厚み）など重合条件によって異なり、一般に数十秒〜数時間の間で行える。また系全体で均一に重合を行わせるために、例えば（Ｂ）と水を予め均一混合したものに、（Ａ’）と水に溶かした重合開始剤を加え均一溶液を調製後、最後に水に溶かした重合触媒を添加する方法をとるなどの工夫を行うことは有効である。
【００５３】
上記のラジカル重合反応において更に公知の界面活性剤を共存させ、得られる有機・無機複合ヒドロゲルを微粒子形態で製造することも可能である。
本発明の有機・無機複合ヒドロゲルの重合では、（Ａ’）の重合収率が高く、且つ重合して得られる水溶性有機高分子はヒドロゲル内部に粘土鉱物と共に取り込まれ、水可溶性成分として溶出する量が少ない。このことは、水洗浄後の重合収率が高いことによって確認される。かかる結果は、（Ｂ）共存下での（Ａ’）の重合において、微細分散した粘土層が水溶性有機高分子の効果的な架橋剤として働くことによる効果と推定される。
【００５４】
更に本発明においては、有機・無機複合ヒドロゲルの特性を改良する目的で、必要に応じて水溶液中に必須成分である（Ａ’）、（Ｂ）と共に有機架橋剤を含ませても良い。含まれる有機架橋剤濃度は特に限定されず、目的に応じて選択できる。
【００５５】
必要に応じて含ませることが可能な有機架橋剤としては、従来から公知のＮ，Ｎ’−メチレンビスアクリルアミド、Ｎ，Ｎ’−プロピレンビスアクリルアミド、ジ（アクリルアミドメチル）エーテル、１，２−ジアクリルアミドエチレングリコール、１，３−ジアクリロイルエチレンウレア、エチレンジアクリレート、Ｎ，Ｎ’−ジアリルタータルジアミド、Ｎ，Ｎ’−ビスアクリリルシスタミンなどの二官能性化合物や、トリアリルシアヌレート、トリアリルイソシアヌレートなどの三官能性化合物が例示される。
【００５６】
本発明の有機・無機複合ヒドロゲルの製造においては、容器の形状を変化させることで種々の形状をもったヒドロゲルを調製できる。例えば、繊維状、棒状、平板状、円柱状、らせん状、球状など任意の形状を有する有機・無機複合ヒドロゲルが調製可能である。
【００５７】
また本発明における有機・無機複合ヒドロゲル及びその乾燥体には（Ａ）、（Ｂ）、（Ｃ）以外に必要に応じて、例えば陰イオン活性剤や有機染料や有機顔料のような有機分子、水溶性ポリマーや水に溶解しない繊維状物質のような有機高分子、炭素、シリカやチタニアのような無機微粒子成分などを製造の任意の段階で含ませることが可能である。更に目的に応じて他素材と複合化（分散、積層など）することも可能である。
【００５８】
本発明には、本発明の有機・無機複合ヒドロゲルから水分を除去して得られる有機・無機複合ヒドロゲルの乾燥体が含まれる。水分を除去する方法は特に限定されないが、温度、気流、減圧等の条件を適宜、変化させて行える。具体的には、熱風循環乾燥機や減圧乾燥機などが用いられる。ヒドロゲルからの水分の除去量も特に限定されず、完全に水分を除去したものから、必要に応じて水分を残存させたものまで任意に調製することができる。
【００５９】
本発明の有機・無機複合ヒドロゲルの乾燥体は粘土鉱物を含んでいるが、粘土鉱物が微細に分散した状態のため、透明であることが可能である。従って、ヒドロゲル又はその乾燥物に色のついた水溶液などを吸収させる場合は、吸収の様子を光透過や光反射により検知することが可能である特徴を有する。また予め、他の有機成分や無機成分をヒドロゲル中に分散させておく場合も、分散状態を明確に把握できる利点がある。
【００６０】
有機・無機複合ヒドロゲルはヒドロゲル又は乾燥途中又はゲル乾燥体としてから、粉砕、分級、成形などを行うことができ、搬送、加工及び使用目的に適した形態をとることができる。具体的には、球状、鱗片状、粉末状、フィルム状、繊維状、ペレット状などである。また大きさについても、例えば粉末状の場合、平均粒径が通常１０〜１０００μｍのものが用いられるが、特に限定されない。
【００６１】
有機・無機複合ヒドロゲル乾燥体は、水、水溶液、湿気など水分と接触させることで再びヒドロゲルに可逆的に戻すことができる。本発明の新規な有機・無機複合ヒドロゲル及びその乾燥体は、生活用品、医薬・医療、農業、土木、工業分野等の広い分野で有用である。
【００６２】
【実施例】
次いで本発明を実施例により、より具体的に説明するが、もとより本発明は、以下に示す実施例にのみ限定されるものではない。
【００６３】
（実施例１）
粘土鉱物として、［Ｍｇ_５．３４Ｌｉ_０．６６Ｓｉ_８Ｏ_２０（ＯＨ）_４］Ｎａ^＋ _０．６６の組成を有する水膨潤性合成ヘクトライト（商標ラポナイトＸＬＧ、日本シリカ株式会社製）を１００℃で２時間真空乾燥して用いた。有機モノマーは、Ｎ−イソプロピルアクリルアミド（ＩＰＡＡ：興人株式会社製）をトルエンとヘキサンの混合溶媒（１／１０重量比）を用いて再結晶し無色針状結晶に精製してから用いた。
【００６４】
重合開始剤は、ペルオキソ二硫酸カリウム（ＰＰＳ：関東化学株式会社製）をＰＰＳ／水＝０．３８４／２０（ｇ／ｇ）の割合で純水で希釈し、水溶液にして使用した。触媒は、Ｎ,Ｎ,Ｎ’,Ｎ’−テトラメチルエチレンジアミン（ＴＭＥＤＡ：関東化学株式会社製）をＴＭＥＤＡ／水＝１６０μｌ／２０ｇの割合で薄めて使用した。水はイオン交換水を蒸留した純水を用いた。水は全て高純度窒素を予め３時間以上バブリングさせ含有酸素を除去してから使用した。
【００６５】
２０℃の恒温室において、内部を窒素置換した内径２５ｍｍ、長さ８０ｍｍの平底ガラス容器に、純水１６．９６ｇとテフロン製攪拌子を入れ、攪拌しながら０．６６２ｇのラポナイトＸＬＧを気泡が入らないように注意しながら少量ずつ加え、無色透明の溶液を調製した。
【００６６】
これにＩＰＡＡ２．０ｇを加え５分間攪拌して無色透明溶液を得た。次いで、ＰＰＳ水溶液１．０６ｇとＴＭＥＤＡ水溶液２．０ｇを攪拌して加え、１５秒ほど更に攪拌して（Ｄ）無色透明溶液を得た。（Ｄ）の一部（３ｍｌ×３）を底の閉じた内径５．５ｍｍ、長さ１５０ｍｍのガラス管容器３本に酸素にふれないようにして移した後、上部に密栓をし、２０℃で１５時間静置して重合を行った。
【００６７】
残りの溶液（Ｄ）も平底ガラス容器内で２０℃、１５時間静置し重合を行った。なお、これらの溶液調製から重合までの操作は全て酸素を遮断した窒素雰囲気下で行った。１５時間後に平底ガラス容器内、及びガラス管容器内に弾力性、タフネスのある無色透明・均一な円柱状、及び棒状のゲルが生成しており、両容器から注意深く取り出した。
【００６８】
ゲル中に粘土鉱物などによる不均一又は不透明な凝集は何ら観測されなかった。ゲルを１００℃の真空乾燥機で重量一定になるまで乾燥させることにより、｛Ｃ／（Ａ＋Ｂ）｝×１００＝７５０重量％の水を含むヒドロゲルであることがわかった。取り出したヒドロゲルに以下の精製操作を３回繰り返して、精製ヒドロゲルを得た。
【００６９】
精製は（２Ｌの水に２日浸漬して取り出し、次いで７０℃の水１Ｌに２時間浸漬して取り出し）を繰り返した。精製ヒドロゲルを１００℃、減圧下にて乾燥して水分を除いたヒドロゲル乾燥体を得た。ゲル乾燥体を２０℃に水に浸漬することにより、乾燥前と同じ形状の弾性のあるヒドロゲルに戻ることが確認された。
【００７０】
ゲル乾燥体のＫＢｒ法によるフーリエ変換赤外線吸収スペクトル（ＦＴ−ＩＲ）測定を行い（日本分光株式会社製フーリエ変換赤外分光光度計ＦＴ／ＩＲ−５５０を使用）、ポリ（Ｎ−イソプロピルアクリルアミド）に固有な赤外線吸収（例えば１４６０ｃｍ^-1、１５５０ｃｍ^-1、１６５０ｃｍ^-1、２９２０ｃｍ^-1、２９７０ｃｍ^-1）及びラポナイトＸＬＧに固有な赤外線吸収（例えば４６０ｃｍ^-1、６５０ｃｍ^-1、１００５ｃｍ^-1）が観測された。
【００７１】
またゲル乾燥体の熱重量分析（セイコー電子工業株式会社社製ＴＧ−ＤＴＡ２２０：空気流通下、１０℃／分で６００℃まで昇温）を行い、Ｂ／Ａ＝０．３３３（重量比）を得た。
【００７２】
以上から、本実施例で得られたゲルは、仕込み組成に沿った成分比を有する、有機高分子（ポリ（Ｎ−イソプロピルアクリルアミド））と粘土鉱物と水からなるヒドロゲルであること、有機高分子の合成において架橋剤を添加していないにもかかわらず、無色、透明、均一なヒドロゲルとなること、ヒドロゲルから水分を除いて得られるゲル乾燥体（固体）を水に浸漬することにより再びもとの形状のヒドロゲルに戻ること等から、有機高分子と粘土鉱物が分子レベルで複合化した三次元網目が水中で形成されていると結論された。なお、粘土鉱物を共存させない以外は同様な条件で合成した有機高分子は高分子水溶液となりヒドロゲルとはならなかった。
【００７３】
未精製の棒状の有機・無機複合ヒドロゲル（断面積＝０．２３７ｃｍ²）をチャック部での滑りの無いようにして引っ張り試験装置（株式会社島津製作所製、卓上型万能試験機ＡＧＳ−Ｈ）に装着し、評点間距離＝２０ｍｍ、引っ張り速度＝１００ｍｍ／分にて引っ張り試験を行った結果、破断荷重が１．１Ｎ、破断伸びが５５０％、引っ張り伸び１００％での荷重が０．０９Ｎであった。
【００７４】
長さ１０ｍｍに切り出した棒状の有機／無機複合ヒドロゲルを精製した後、２０℃から５０℃の範囲の６点の温度の水に浸漬し、１日間静置して体積を測定し、温度による膨潤、収縮の変化を測定した。結果を、比較例４（有機架橋ヒドロゲル）の結果と合わせて図１に示す。
【００７５】
本実施例で得られた有機・無機複合ヒドロゲルは上記のようなタフネスを持つと共に臨界温度（Ｔｃ）を有し、Ｔｃ以下の温度では膨潤し、Ｔｃ以下の温度では収縮した。２０℃と５０℃での膨潤時と収縮時の体積比は２４の高い値を示した。
【００７６】
平底ガラス容器から取り出した円柱状の有機・無機複合ヒドロゲルを精製した後、２０℃〜５０℃の５点の温度での水に浸漬したものを厚み２ｍｍで切り出し、日本電色工業株式会社製ＮＤＨ−３００Ａを用いて光透過率測定を行った。結果を比較例４の結果と併せて図２に示す。本実施例で得られた有機・無機複合ヒドロゲルはＴｃを境にして明確な透明性の変化を示し、Ｔｃ以下の温度で高い透明性を、Ｔｃ以下の温度で不透明（白濁）となった。
【００７７】
（実施例２〜４）
粘土鉱物（ラポナイトＸＬＧ）の量を０．１３２ｇ（実施例２）、０．２６４ｇ（実施例３）、１．３２２ｇ（実施例４）に変えた以外は、実施例１と同様にして重合を行い、有機・無機複合ヒドロゲルを調製した。実施例２〜４では、いずれも室温で無色透明な均一ヒドロゲルが得られた。
【００７８】
実施例１と同様にして測定したヒドロゲル評価結果を以下に示す。｛Ｃ／（Ａ＋Ｂ）｝×１００は９４０重量％（実施例２）、８８０重量％（実施例３）、６００重量％（実施例４）、またＢ／Ａ比は０．０６５（実施例２）、０．１３５（実施例３）、０．６６（実施例４）であった。
【００７９】
得られたヒドロゲルの温度を上昇させると、いずれも３５℃付近に臨界温度（Ｔｃ）を有し、Ｔｃ以下では無色透明で、Ｔｃ以上では白濁不透明になり収縮した。２０℃と５０℃の水中での膨潤時と収縮時の体積比は３１（実施例２）と１３（実施例４）であった。また、収縮は温度変化により１分以内の短い時間で起こり、膨潤も比較例３より短時間で生じた。
【００８０】
また引っ張り試験測定の結果は、破断荷重が０．６５Ｎ（実施例３）、７．０Ｎ（実施例４）、破断伸びが４３０％（実施例３）、６５０％（実施例４）、伸び１００％での荷重が０．０３３Ｎ（実施例３）、０．４０Ｎ（実施例４）であった。また得られたヒドロゲルを５ｍｍ角に切断後、２０℃の水中で平衡膨潤させたヒドロゲルに含まれる水含有率｛Ｃｍａｘ／（Ａ＋Ｂ）｝×１００は、１１３００重量％（実施例２）、７２００重量％（実施例３）、５０００重量％（実施例４）であった。
【００８１】
（実施例５〜７）
有機モノマーとして、実施例５では前記のＩＰＡＡを、実施例６ではＮ,Ｎ−ジメチルアクリルアミド（ＤＭＡＡ：和光純薬工業株式会社）を、実施例７ではＮ,Ｎ−ジエチルアクリルアミド（ＤＥＡＡ：和光純薬工業株式会社）を用いた。なお、ＤＭＡＡ及びＤＥＡＡはシリカゲルカラム（メルク社製）を有機モノマー１００ｍｌに対して８０ｍｌの容積で用いて重合禁止剤を取り除いてから使用した。
【００８２】
２０℃の恒温室において、内部を窒素置換した内径２５ｍｍ、長さ８０ｍｍの平底ガラス容器に、純水１８．９６ｇとテフロン製攪拌子を入れ、攪拌しながら０．６６２ｇのラポナイトＸＬＧを気泡が入らないように注意しながら少量ずつ加え、無色透明の溶液を調製した。これにＩＰＡＡ２．０ｇ（実施例５）、又はＤＭＡＡ２．０ｇ（実施例６）、又はＤＥＡＡ２．０ｇ（実施例７）を加え無色透明溶液になるまで攪拌した。
【００８３】
これにＴＭＥＤＡ１６０μｌを加え、次いで、ＰＰＳ水溶液１．０６ｇを攪拌して加え、５分間攪拌して無色透明溶液（Ｄ’）を得た。（Ｄ’）溶液から攪拌子を取り除き、密栓状態にして２０℃で静置し、系全体をゲル化（容器を横にしても内容物が動かない状態）させた。以上の操作は全て酸素を遮断した窒素雰囲気下で行った。その後、Ｎ₂雰囲気を保ちながら７０℃の水槽中で２時間静置し重合した。２時間後、平底ガラス容器に生成した円柱状のゲルを容器から注意深く取り出した。
【００８４】
実施例５と実施例７は弾力性、タフネスのある均一白濁ゲルが、実施例６では同じく弾力性、タフネスのある透明ゲルが得られた。白濁ゲル中に粘土鉱物などによる不均一又は不透明な凝集はいずれも観測されなかった。
【００８５】
実施例１と同様にして測定した｛Ｃ／（Ａ＋Ｂ）｝×１００はいずれも７５０重量％、Ｂ／Ａはいずれも０．３３であり、有機高分子、粘土鉱物、水からなる均一な有機／無機複合ヒドロゲルであることがわかった。実施例５と実施例７の白濁ヒドロゲルは温度を下げても透明に変化することはなかった。また実施例６の透明ヒドロゲルは温度を０〜７０℃で変化させても白濁することなく、透明のままであった。
【００８６】
（実施例８〜１２）
有機モノマーとして、実施例８では前記のＮ−イソプロピルアクリルアミド（ＩＰＡＡ）を、実施例９では前記のＮ,Ｎ−ジメチルアクリルアミド（ＤＭＡＡ）を、実施例１０では前記のＮ,Ｎ−ジエチルアクリルアミド（ＤＥＡＡ）を、実施例１１ではアクリロイルモルフォリン（ＡＣＭＯ；興人株式会社製）を、実施例１２ではＮ，Ｎ−ジメチルアミノプロピルアクリルアミド（ＤＭＡＰＡ；興人株式会社製）を用いた。
【００８７】
なお、ＩＰＡＡ（実施例８）は、ＩＰＡＡの０．７５倍量（重量比）のトルエンを加え、４０℃で溶解後室温に戻してから７．５倍量（重量比）のヘキサンを加え良く攪拌し、針状の無色結晶を得た。最後に溶媒を濾過と室温真空乾燥により取り除いて得たＩＰＡＡを使用した。ＤＭＡＡ（実施例９）、ＤＥＡＡ（実施例１０）及びＡＣＭＯ（実施例１１）は実施例６及び実施例７と同様にして重合禁止剤を取り除いて使用した。
【００８８】
またＤＭＡＰＡ（実施例１２）はアセトンをＤＭＡＰＡの２０体積％加え、粘性を低くしてから活性アルミナカラム（８０ｃｃ／１００ｍｌモノマー）で重合禁止剤を取り除き、その後、ロータリーエバポレーターでアセトンを取り除いて使用した。
【００８９】
使用する水は全てイオン交換水を蒸留した純水に、予め高純度窒素ガスを３時間以上バブリングさせ、含有酸素を除去してから使用した。なお、本実施例においては重合前の全ての操作（溶液準備からヒドロゲルを取り出すまでの全操作）を酸素を除去した窒素雰囲気又は窒素気流下で行った。また触媒及び開始剤水溶液の準備においても上記操作と同様に酸素を遮断した窒素雰囲気で行った。
【００９０】
２０℃の水浴中に設置した内部を窒素置換した二口フラスコに、上記の溶存酸素を除去した純水８５．３ｇとテフロン攪拌子を入れ、攪拌しながら２．９８ｇのラポナイトＸＬＧを気泡が入らないように注意しながら少量ずつ加え、無色透明の溶液を調製した。これにＩＰＡＡ９．０ｇ（実施例８）、又はＤＭＡＡ９．０ｇ（実施例９）、又はＤＥＡＡ９．０ｇ（実施例１０）、又はＡＣＭＯ９．０ｇ（実施例１１）、又はＤＭＡＰＡ９．０ｇ（実施例１２）を加え、均一透明溶液になるまで攪拌した。
【００９１】
ＸＬＧ／モノマーの重量比はいずれも０．３３１である。ついで、フラスコを氷浴中にて冷却した状態にして、別途、氷浴冷却していたＴＭＥＤＡ７２μｌを加え３０秒間攪拌させた後、次いで、同様に別途、氷浴中で冷却していた実施例１と同じＰＰＳ水溶液４．７７ｇを攪拌して加え、３０秒間攪拌させ均一透明溶液を得た。該溶液を１５℃の水浴で２０時間静置し重合を完了させた。
【００９２】
実施例８から実施例１２のいずれにおいてもフラスコ内に、系全体がゲル化（容器を横にしても内容物が動かない状態）した弾力性のあるヒドロゲルが得られた。ヒドロゲル中に不均一又は不透明な粘土鉱物やポリマーによる凝集はいずれも観測されなかった。重合して得られたヒドロゲルの透明性を氷浴温度（約１℃）にて調べた結果、実施例８、９、１１及び１２が均一透明で、実施例１０が均一な半透明であった。
【００９３】
厚み２５ｍｍにカットしたヒドロゲルの可視光での光透過率を日本電色工業株式会社製ＮＤＨ−３００Ａを用いて測定した結果、全透過率が９５％（実施例８）、８１％（実施例９）、４０％（実施例１０）、８５％（実施例１１）、９０％（実施例１２）であった。
【００９４】
次いで、氷浴を５０℃の温水浴に変えて透明性変化を調べた。実施例９、１１及び１２では透明性は殆ど変化しなかったが、実施例８と実施例１０では共に全透過率が１０％以下の不透明に変化した。
【００９５】
一方、重合して得られたヒドロゲルを直径５．５ｍｍ、長さ３０ｍｍの棒状に切り出し、厚み方向に１／３及び１／５にまで圧縮する試験と、長さ方向に２倍及び４倍にまで延伸する試験と、長さ中心点で１００度、１５０度及びそれ以上の角度に曲げ変形する試験を行った。その結果、実施例９〜１２のいずれのサンプルも上記の試験において、形状が破壊されたり、クラックが生じたり、欠損が生じることはなく、元の状態に戻った。
【００９６】
また曲げ変形試験では１８０度以上の変形でもいずれも破壊、クラックなどが生じることなく、試験後もとの状態に戻った。さらに得られたヒドロゲルを直径５．５ｍｍ（断面積０．２３７ｃｍ^２）、長さ５０ｍｍに切り出し、上下１０ｍｍを傷つけず、且つ滑らぬように丸形のサンドペーパーで挟み、実施例１と同じ引っ張り試験装置を用いて、標点間距離＝３０ｍｍ、引っ張り速度＝１００ｍｍ／分にて引っ張り試験を行った。
【００９７】
その結果、実施例８では破断荷重が２．９Ｎ、破断伸びが１００１％、引っ張り伸び１００％での荷重が０．１０３Ｎであり、実施例９では破断荷重が２．４Ｎ、破断伸びが１１１２％、引っ張り伸び１００％での荷重が０．０８９Ｎであり、実施例１０では破断荷重が４．８Ｎ、破断伸びが８９２％、引っ張り伸び１００％での荷重が０．１７３Ｎであった。
【００９８】
また、得られたヒドロゲルを５ｍｍ角に切断後、２０℃水中で平衡膨潤させたヒドロゲルに含まれる水含有率｛Ｃｍａｘ／（Ａ＋Ｂ）｝×１００は、６２００重量％（実施例８）、５０００重量％（実施例９）、３７００重量％（実施例１０）、４７００重量％（実施例１１）であった。また、実施例１と同様に精製して得られた乾燥体の重量測定により、モノマーの重合収率は実施例８〜１１のいずれもが９９％以上であり、高い収率であることが示された。
【００９９】
（実施例１３）有機モノマーとしてエタノールとトルエンを用いて精製したアクリルアミド（ＡＡＭ：関東化学株式会社製）３．１５ｇを用いること、水膨潤性層状粘土鉱物ＸＬＧを２．８ｇ用いること（ＸＬＧ／モノマー＝０．８９重量比）、水として計５０ｇを用いること、開始剤としてペルオキソ二硫酸カリウムを０．０５ｇ用いること、及び重合温度を２３℃にしたこと以外は、実施例８と同様にして重合実験及び評価試験を行った。
【０１００】
その結果、測定温度１℃での透明性（全透過率）が２５ｍｍ厚において８５％であり、且つタフネスのある均一透明な有機・無機複合ヒドロゲルが得られた。また透明性の測定温度を５０℃にしても全透過率は殆ど変化しなかった。
【０１０１】
（実施例１４）
粘土鉱物としてＸＬＧを１．７８８ｇ用いること、またそれと共に有機架橋剤（Ｎ、Ｎ’−メチレンビスアクリルアミド：ＢＩＳ：関東化学株式会社製）を有機モノマーの０．５モル％用いること、重合温度を３０℃とすること以外は実施例９と同様にして重合溶液の調製及び重合実験と評価試験を行った。
【０１０２】
その結果、透明で且つタフネスのある有機・無機複合ヒドロゲルゲルが得られた。厚さ２５ｍｍでの全透過率（測定温度１℃）は９０％であり、測定温度を５０℃にしても殆ど透明性は変化しなかった。直径５．５ｍｍ、長さ３０ｍｍに切り出した棒状ヒドロゲルは厚み方向１／５までの圧縮変形試験、また長さ方向４倍の延伸変形試験、また長さ中心での１８０度までの曲げ変形試験のいずれにおいても、形状が破壊されることはなく、試験後もとの形状に戻った。
【０１０３】
（実施例１５〜１７）
水の代わりに水とメタノールの混合溶媒を用いること、水：メタノールの混合溶媒比率（重量比）が８０：２０（実施例１５）、６０：４０（実施例１６）、４０：６０（実施例１７）であること、及び重合温度を１５℃とすること以外は、実施例２と同様にして、重合実験を行った。
【０１０４】
その結果、実施例１５〜１７のいずれにおいてもポリ（Ｎ−イソプロピルアクリルアミド）とＸＬＧと水とメタノールとからなる均一でタフネスのある有機・無機複合ヒドロゲルが得られた。重合後のヒドロゲルの透明性（氷浴温度：約１℃で測定）は、実施例１５が透明、実施例１６と１７が不透明であった。特に実施例１７は完全な白色であった。
【０１０５】
その後、実施例１と同様な方法により純水を用いて精製を行った。精製後、２０℃の水中で膨潤させた有機・無機複合ヒドロゲルを用いて、水温を変化させてＴｃを測定した。その結果、実施例１５〜１７で得られた有機・無機複合ヒドロゲルはいずれも３３℃に臨界温度（Ｔｃ）を示し、それより以下の温度では無色透明で膨潤しており、Ｔｃ以上では白色不透明へ変化し、体積収縮を生じた。
【０１０６】
以上の結果より、水と水と混和する有機溶媒との混合溶媒を用いても、本発明における有機・無機複合ヒドロゲルが得られることが示された。なお、乾燥体の熱重量分析の結果、Ｂ／Ａ（重量比）はいずれも０．０６６であった。
【０１０７】
（実施例１８〜２１）
重合温度が５０℃であること以外は実施例１８では実施例８と、実施例１９では実施例９と、実施例２０では実施例１０と、実施例２１では実施例１１と同様にして重合を行い、いずれもタフネスのある均一な有機・無機複合ヒドロゲルを得た。
【０１０８】
重合直後の重合温度における透明性は実施例１９及び実施例２１では透明、実施例１８と実施例２０では白色不透明であった。その後、１℃まで冷却した場合、実施例１８、実施例１９、実施例２１では透明、実施例２０では不透明〜半透明であった。得られたヒドロゲルを厚み２５ｍｍにカットして１℃にて測定した可視光の全透過率は８４％（実施例１８）、９３％（実施例１９）、３０％（実施例２０）、８８％（実施例２１）であった。
【０１０９】
（実施例２２）
有機モノマーとして、Ｎ−イソプロピルアクリルアミド（ＩＰＡＡ）を４．５ｇ、Ｎ,Ｎ−ジメチルアクリルアミド（ＤＭＡＡ）を３．９４ｇ用いる以外は実施例８と同様にして、水（８５．３ｇ）、ＸＬＧ（２．９８ｇ）、ＴＭＥＤＡ（７２μｌ）、ＰＰＳ（水溶液で４．７７ｇ）を含む均一溶液を調製し、１５℃で重合させた。弾力性のある均一な半透明のヒドロゲルが得られた。
【０１１０】
ヒドロゲル中に不均一又は不透明な粘土鉱物やポリマーによる凝集はいずれも観測されなかった。重合して得られたヒドロゲルを２５ｍｍ幅にカットし、その透明性を温度を変化させながら測定した結果、半透明（全透過率４０〜３５％程度）から不透明（全透過率５％以下）への変化（ＬＣＳＴ）が約４０℃〜５０℃にて生じた。ＩＰＡＡ単独を用いた実施例８では３２℃〜３４℃で透明（全透過率９０％）から、不透明（全透過率６％）まで急速に変化したのに比べると、変化は高温側にずれるとともに、幅広くなった。
【０１１１】
一方、重合して得られたヒドロゲルを直径５．５ｍｍ、長さ３０ｍｍの棒状に切り出し、厚み方向に１／３及び１／５にまで圧縮する試験と、長さ方向に２倍及び４倍まで延伸する試験と、長さ中心点で１００度、１５０度及びそれ以上の角度に曲げ変形する試験を行った。その結果、いずれの試験においても、形状が破壊されたり、クラックが生じたり、欠損が生じることはなく、元の状態に戻った。また曲げ変形試験では１８０度以上の変形でもいずれも破壊、クラックなどが生じることなく、試験後、元の状態に戻った。
【０１１２】
（実施例２３及び２４）
水膨潤性粘土鉱物ＸＬＧと有機モノマーＩＰＡＡの量を、実施例２３ではＸＬＧ＝２．９８ｇ、ＩＰＡＡ＝０．４５ｇ、ＸＬＧ／ＩＰＡＡ＝６．６２重量比であること、実施例２４ではＸＬＧ＝０．０５９６ｇ、ＩＰＡＡ＝４．５ｇ、ＸＬＧ／ＩＰＡＡ＝０．０１３としたこと以外は、いずれも実施例８と同様にして実験を行った。その結果、実施例２３も実施例２４も、均一溶液を調製でき、また重合の結果、均一な透明ゲルが得られた。厚み２５ｍｍにカットしたゲルの全透過率は９５．１％（実施例２３）と９８．２％（実施例２４）であった。
【０１１３】
（実施例２５及び２６）
水膨潤性粘土鉱物としてＸＬＧの代わりに実施例２５ではＸＬＳ（ＸＬＳに６重量％のピロリン酸ナトリウムを解膠剤を含ませたもの：日本シリカ工業株式会社製）、実施例２６では合成スメクタイトＳＷＮ（コープケミカル株式会社製）を用いる以外は、いずれも実施例８と同様にして実験を行った。その結果、実施例２５も実施例２６も、均一溶液を調製でき、また重合の結果、均一な透明ゲルが得られた。厚み２５ｍｍにカットしたゲルの全透過率は９０．４％（実施例２５）と８３．８％（実施例２６）であった。
【０１１４】
（比較例１）
粘土鉱物を添加しないこと以外は実施例１と同様にして、２０℃で１５時間重合を行った。平底ガラス容器及びガラス管容器のいずれでも、ポリ（Ｎ−イソプロピルアクリルアミド）が水に溶解した無色透明溶液が得られたのみで、ゲルは生じなかった。また、溶液の温度を上昇させると約３２℃以上で白濁したポリマーゲルが水と分離した状態で得られ、次いで温度を２０℃に下げると再び水溶液に戻った。
【０１１５】
尚、得られた溶液中のポリマーの確認は５Ｌの水に薄め、５０℃の水槽中に保持して、溶解物を白濁凝集させ、遠心分離（２０℃、１０，０００ｒｐｍ、６０分）にて分離し、更に、水、アセトン、ヘキサンを用いて再沈精製を行った後のサンプルの分析（赤外線吸収スペクトル測定、核磁気共鳴スペクトル測定)により行った。
【０１１６】
（比較例２）
ＮａＯＨを添加してｐＨ１１にした以外は比較例１と同様にして、重合を行った結果、比較例１と同様にポリ（Ｎ−イソプロピルアクリルアミド）の無色透明溶液が得られゲルは一切生じなかった。このことより、実施例１の粘土鉱物添加に伴うｐＨ増加の影響が無いことが確認された。
【０１１７】
（比較例３及び４）
粘土鉱物を用いないで、ＩＰＡＡモノマーを添加した後、有機架橋剤をＩＰＡＡの１モル％（比較例３）、５モル％（比較例４）添加して用いること以外は実施例１と同様にして、２０℃で１５時間重合を行った。有機架橋剤としては、Ｎ,Ｎ’−メチレンビスアクリルアミド（ＢＩＳ）（関東化学株式会社製）をそのまま使用した。比較例３では無色透明ゲルが、比較例４では白濁したゲルが得られた。実施例１と同様にして測定した結果、｛Ｃ／（Ａ）｝×１００は９９０重量％（比較例３）と９３５重量％（比較例４）であり、有機架橋ヒドロゲルであることが確認された。
【０１１８】
比較例３では、Ｔｃが３３℃付近であり、Ｔｃより低温側で透明、膨潤状態にあり、Ｔｃより高温側で白濁、収縮状態を示した。２０℃と５０℃での膨潤時と収縮時の体積比は約８であった。一方、比較例４では温度を変化させても全て白濁状態のままであった。約３３℃を境に低温側で膨潤、高温側で収縮状態となったが、２０℃と５０℃での膨潤時と収縮時の体積比は約５であった。比較例４での温度変化による体積及び全透過率の変化の様子を図１及び図２に実施例１の結果と合わせて示す。
【０１１９】
（比較例５及び６）
比較例１で得られたポリ（Ｎ−イソプロピルアクリルアミド）１ｇを水１０ｇに溶かした水溶液に、粘土鉱物（ラポナイトＸＬＧ）０．３３１ｇ（比較例５）又は０．０６６ｇ（比較例６）を攪拌しながら添加して、実施例１及び実施例２と同一組成の有機高分子と粘土鉱物と水からなる複合体を調製しようとしたが、いずれの場合も、均一なタフネスのあるヒドロゲルは得られなかった。
【０１２０】
（比較例７）
ＤＥＡＡモノマーを用いる以外は、比較例１と同様にして得られたポリ（Ｎ,Ｎ−ジエチルアクリルアミド）０．１５ｇを水１４．８５ｇに溶かした透明水溶液に、粘土鉱物（ラポナイトＸＬＧ）０．２ｇを水９．８ｇに溶かした透明溶液を徐々に攪拌しながら添加し、混合物を調製した。ＸＬＧ水溶液を０．８８ｇ（Ｂ／Ａ＝０．１１７）まで添加した場合、ＸＬＧ添加量に応じて溶液中に白色浮遊物が析出し、白濁溶液に変化していった。更に添加を続けて、例えば添加量＝３．８８ｇ（Ｂ／Ａ＝０．５１７）でも混合物は白濁溶液のままであった。
【０１２１】
これらの白濁混合溶液は水中に白色凝集物が浮遊した不均一溶液であり、これを加熱すると約２８℃を境にそれ以上の温度で更に白濁度が増すことが観測された。しかしいずれの場合も均一なヒドロゲルは得られなかった。更に粘土添加量を増したり、初期ポリマー溶液濃度を増したものを用いた場合も、実施例で得られるような均一でタフネスのあるヒドロゲルは得られなかった。
【０１２２】
（比較例８）
ＸＬＧ水溶液１０ｇにポリ（Ｎ,Ｎ−ジエチルアクリルアミド）水溶液を徐々に添加すること以外は比較例７と同様にして、有機高分子と粘土鉱物と水を含む混合物を調製した。添加混合により白濁溶液となり、Ｔｃ以上への加温で更に白濁度の増した不均一溶液となるだけで、いずれの場合も均一なタフネスのあるヒドロゲルは得られなかった。
【０１２３】
（比較例９〜１２）
粘土鉱物を用いないで、ＤＥＡＡ（比較例９と１０）又はＡＣＭＯ（比較例１１と１２）を添加した後、有機架橋剤Ｎ,Ｎ’−メチレンビスアクリルアミド（ＢＩＳ）をＤＥＡＡ又はＡＣＭＯの１モル％（比較例９と１１）、５モル％（比較例１０と１２）添加して用いること以外は実施例１０又は実施例１１と同様にして、１５℃の水浴で２０時間静置し重合を完了させた。
【０１２４】
比較例９から比較例１２のいずれにおいてもフラスコ内に、系全体がゲル化（容器を横にしても内容物が動かない状態）したヒドロゲルが得られた。ヒドロゲル中に不均一な凝集はいずれも観測されなかった。重合して得られたヒドロゲルの透明性を氷浴温度（約１℃）にて調べた結果、比較例例９と１１は均一透明で、比較例１０と１２が不透明であった。厚み２５ｍｍにカットしたヒドロゲルの可視光での光透過率を日本電色工業株式会社製ＮＤＨ−３００Ａを用いて測定した結果、全透過率が９８％（比較例９）、２４％（比較例１０）、９８％（比較例１１）、２２％（比較例１２）であった。
【０１２５】
一方、比較例９〜１２で重合容器として内径５．５ｍｍ、長さ１５０ｍｍのガラスチューブを用いて上記の条件で重合して、棒状の有機架橋ヒドロゲルを得た。得られたヒドロゲルを長さ３０ｍｍの棒状に切り出し、厚み方向に１／３にまで圧縮する試験と、長さ方向に２倍まで延伸する試験と、長さ中心点で１００度の角度に曲げ変形する試験を行った。
【０１２６】
その結果、比較例９〜１２のいずれのサンプルも上記の試験において、クラックが生じ、形状が壊れたり、欠損が生じた。更に比較例９〜１２で得られたヒドロゲルを直径５．５ｍｍ（断面積０．２３７ｃｍ^２）、長さ５０ｍｍに注意深く切り出し、上下１０ｍｍを傷つけず、且つ滑らぬように丸形のサンドペーパーで挟み、実施例１と同じ引っ張り試験装置を用いて、標点間距離＝３０ｍｍ、引っ張り速度＝１００ｍｍ／分にて引っ張り試験を行おうとしたが、サンプルが脆くチャックに装着前に殆どのサンプルが壊れた。また、チャックに軽く装着したものでも試験直後に破断し、物性値は得られなかった。
【０１２７】
（比較例１３及び１４）
内径５．５ｍｍ、長さ１５０ｍｍのガラスチューブ容器を用いる以外は、比較例１３では比較例３と、また比較例１４では比較例４と同様の方法により、外径５．５ｍｍの棒状の有機架橋ヒドロゲルを重合して得た。得られたヒドロゲルを長さ３０ｍｍに切り出し、厚み方向に１／３まで圧縮する試験と、長さ方向に２倍まで延伸する試験と、長さ中心点で１００度の角度に曲げ変形する試験を行った。
【０１２８】
その結果、比較例１３と１４のいずれのサンプルも上記の試験において、クラックが生じ、形状が壊れたり、欠損が生じた。さらに長さ５０ｍｍに切り出し、上下１０ｍｍを傷つけず、且つ滑らぬように丸形のサンドペーパーで挟み、実施例１と同じ引っ張り試験装置を用いて、標点間距離＝３０ｍｍ、引っ張り速度＝１００ｍｍ／分にて引っ張り試験を行おうとしたが、サンプルが脆くチャックに装着前にいずれのサンプルが壊れ、物性値は得られなかった。
【０１２９】
更に、得られた有機架橋ヒドロゲルを約５ｍｍ角に切断後、２０℃の水中で平衡膨潤させた有機架橋ヒドロゲルに含まれる水含有率｛Ｃｍａｘ／（Ａ）｝×１００は１５００重量％（比較例１３）、８００重量％（比較例１４）であった。
【０１３０】
【発明の効果】
本発明は、均一性、透明性、力学物性、機械的性質や吸水性、膨潤・収縮特性等の優れた機能性を有する新規な有機・無機複合ヒドロゲル、その製造方法及び該ヒドロゲルから水分を除去して得られる有機・無機複合ヒドロゲルの乾燥体を提供することができる。
【０１３１】
本発明で得られる有機・無機複合ヒドロゲルには、強靱でタフネスのあるヒドロゲルや、透明又は均一白色のヒドロゲルや、低温側で透明及び／又は体積膨潤状態にあり、高温側で不透明及び／又は体積収縮状態に可逆的に変化する臨界温度（Ｔｃ）を有するものが含まれ、該有機・無機複合ヒドロゲルのゲル乾燥体は、水に浸漬することにより可逆的にヒドロゲルに戻すことができるものであり、生活用品、医薬・医療、農業、土木、工業分野等の広い分野で有用である。
【図面の簡単な説明】
【図１】実施例１で得られた有機・無機複合ヒドロゲル及び比較例４で得られた有機架橋ヒドロゲルの水中での温度による膨潤時と収縮時の体積変化を示す図である。縦軸はヒドロゲルの体積（ｍｍ^３）を横軸は温度（℃）を示す。
【図２】実施例１で得られた有機・無機複合ヒドロゲル及び比較例４で得られた有機架橋ヒドロゲルの温度による透明性の変化を示す図である。縦軸が全透過率（％）を横軸が温度（℃）を示す。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an organic / inorganic composite hydrogel in which water is contained in a three-dimensional network formed by combining a water-soluble organic polymer and a water-swellable clay mineral that can be uniformly dispersed in water, The present invention relates to a body and a manufacturing method thereof.
[0002]
[Prior art]
Gels have intermediate properties between liquids and solids, and are obtained by stably incorporating a solvent into a three-dimensional network such as an organic polymer. In particular, gels using water as a solvent (hereinafter referred to as hydrogels or aqueous gels) are important constituent materials in living organisms, and so far in the fields of medicine, medical care, foods such as food, packaging, hygiene products, and cosmetics, as well as agriculture. It is also widely used in the civil engineering and industrial fields (eg, Yoshihito Nagata, Sakakibara “Gel Handbook”, NTS Corporation, 1997).
[0003]
The hydrogel contains at least two components. That is, a three-dimensional network and water bridged in various ways. As a component of the three-dimensional network, either an organic compound or an inorganic substance can be used. For example, in a hydrogel of an organic compound, an organic polymer or an organic molecule is crosslinked by a covalent bond, a hydrogen bond, an ionic bond, a hydrophobic bond, or the like, or a physical entanglement or a microcrystal is used as a crosslinking point to form a three-dimensional network. ing.
[0004]
Specifically, as an organic molecule that forms a three-dimensional network, a cross-link is formed by a coordinate bond with ovalbumin or serum albumin that is cross-linked by a hydrophobic bond, gelatin or agarose by a helix formation, or an alkaline earth metal ion. In addition to polyacrylic acid, polystyrene sulfonic acid, two types of polymer (polycation and polyanion) composites that crosslink by ionic bonds, fully saponified polyvinyl alcohol that crosslinks by hydrogen bonds, etc., heat, radiation, light, and plasma are irradiated. However, many are known in which a crosslink by a covalent bond is formed between organic polymers by adding an organic crosslinking agent.
[0005]
On the other hand, as a material that forms a three-dimensional network with inorganic substances, metal oxides prepared by hydrolysis polycondensation of metal alkoxides (so-called sol-gel reaction) and layered clay minerals having cations between layers are known, A three-dimensional network is formed by agglomeration of fine particles by ion interaction or the like, and a gel composed of an inorganic substance and water is prepared.
[0006]
Inorganic hydrogels are brittle with small strength and elongation, and are therefore rarely used as a single hydrogel material. On the other hand, hydrogels composed of organic compounds, especially organic polymer three-dimensional networks by covalent bonds, and water have better mechanical properties than inorganic hydrogels, and can exhibit the properties of organic polymers in hydrogels. Because of its properties, it is being developed as a soft material and a functional gel material in a wide range of industrial fields.
[0007]
In order to expand the usefulness of such organic cross-linked hydrogels, the gel uniformity, transparency, mechanical properties, mechanical properties, etc. are further improved, absorption (water absorption) characteristics are further improved, Therefore, the development of new hydrogels that more effectively express the properties of organic polymers is desired.
[0008]
[Problems to be solved by the invention]
The problem to be solved by the present invention is a novel organic / inorganic composite hydrogel having excellent uniformity, transparency, mechanical properties, water absorption, and swelling / shrinking properties, its production method, and removal of water from the hydrogel Another object of the present invention is to provide a dried product of the organic / inorganic composite hydrogel obtained as described above.
[0009]
[Means for Solving the Problems]
As a result of diligent research to solve the above-mentioned problems, the present inventors polymerized component monomers constituting a water-soluble organic polymer in the presence of water-swellable clay mineral that can be uniformly dispersed in water and water. Then, (A) a water-soluble organic polymer and (B) a water-swellable clay mineral that can be uniformly dispersed in water are combined in a three-dimensional network formed at the molecular level. It was found that an organic / inorganic composite hydrogel (hereinafter referred to as organic / inorganic composite hydrogel) was obtained, and the present invention was completed.
[0010]
That is, the present invention includes (C) water in a three-dimensional network formed by combining (A) a water-soluble organic polymer and (B) a water-swellable clay mineral that can be uniformly dispersed in water. In the presence of (B) water-swellable clay mineral that can be uniformly dispersed in water and (C) water, (A) the constituent monomer of the water-soluble organic polymer ( An organic / inorganic composite hydrogel obtained by polymerizing A ′). The present invention also provides a dried organic / inorganic composite hydrogel obtained by removing water from the organic / inorganic composite hydrogel.
[0011]
Furthermore, the present invention provides a homogeneous solution comprising (A) a monomer (A ′) that is a constituent of a water-soluble organic polymer, (B) a water-swellable clay mineral that can be uniformly dispersed in water, and (C) water. And (B) a method for producing an organic / inorganic composite hydrogel in which a monomer (A ′), which is a constituent component of a water-soluble organic polymer, is polymerized in the presence of water.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
The (A) water-soluble organic polymer referred to in the present invention includes an organic polymer having a property of swelling in water, in addition to those soluble in water. Such water solubility and water swellability may be achieved under specific polymer concentration, temperature, pressure conditions, and coexistence of other additive components. The water-soluble organic polymer may be a polymer from a single monomer or a copolymer obtained by polymerizing a plurality of types of monomers.
[0013]
The (A) water-soluble organic polymer used in the present invention preferably has an interaction with (B) a water-swellable clay mineral that can be uniformly dispersed in water, for example, (B) with hydrogen bonds, ionic bonds, and coordination. Those having a functional group capable of forming a bond, a covalent bond and the like are preferable.
[0014]
Specific examples of the organic polymer having these functional groups include organic polymers having an amide group, amino group, hydroxyl group, tetramethylammonium group, silanol group, epoxy group, and the like. Further, as the water-soluble organic polymer used in the present invention, those having functionality are particularly preferable. For example, polymer properties (for example, hydrophilicity and hydrophobicity) in an aqueous solution are LCST (lower critical eutectic temperature, Lower Critical Solution Temperature) Organic polymers with characteristics that change greatly with slight temperature changes before and after.
[0015]
(A) Specific examples of water-soluble organic polymers are selected from acrylamide, N-substituted acrylamide derivatives, N, N-disubstituted acrylamide derivatives, N-substituted methacrylamide derivatives, and N, N-disubstituted methacrylamide derivatives. Water-soluble organic polymer obtained by polymerizing one or more of the above. It is also possible to use the above monomers in combination with other organic monomers as long as a uniform organic / inorganic composite hydrogel is formed.
[0016]
Such water-soluble organic polymers include poly (acrylamide), poly (N-methylacrylamide), poly (N-ethylacrylamide), poly (N-cyclopropylacrylamide), poly (N-isopropylacrylamide), poly (methacrylic). Amide), poly (N-methylmethacrylamide), poly (N-cyclopropylmethacrylamide), poly (N-isopropylmethacrylamide),
[0017]
Poly (N, N-dimethylacrylamide), poly (N, N-dimethylaminopropylacrylamide), poly (N-methyl-N-ethylacrylamide), poly (N-methyl-N-isopropylacrylamide), poly (N- Methyl-Nn-propylacrylamide), poly (N, N-diethylacrylamide), poly (N-acryloylpyrrolidin), poly (N-acryloylpiperidine), poly (N-acryloylmethylhomopiperazine), Examples thereof include poly (N-acryloylmethylpiperazine).
[0018]
The water-soluble organic polymer (A) used in the present invention may be one that dissolves or swells in a mixed solvent of water and an organic solvent miscible with water, in addition to those that dissolve and swell in water. . As a mixed solvent of water and an organic solvent miscible with water, a mixture of water and one or more organic solvents miscible with water (forming a homogeneous phase) is used. Examples of these organic solvents include polar solvents such as methanol, acetone, methyl ethyl ketone, and tetrahydrofuran. The mixing ratio of water and these organic solvents can be arbitrarily selected as long as the water-swellable clay (B) can be uniformly dispersed.
[0019]
The (B) water-swellable clay mineral that can be uniformly dispersed in water in the present invention is a clay mineral that can swell and uniformly disperse in water, and is particularly preferably molecular (single layer) or in water. It is a layered clay mineral that can be uniformly dispersed at a close level. For example, water-swellable smectite or water-swellable mica is used. Specifically, water-swellable hectorite containing sodium as an interlayer ion, water-swellable montmorillonite, water-swellable saponite, water-swellable synthetic mica, etc. Can be mentioned.
[0020]
In the present invention, the water-swellable clay mineral needs to be finely and uniformly dispersed in the aqueous solution before the water-soluble organic polymer monomer is polymerized, and is particularly dissolved in the aqueous solution. Is desirable. Here, dissolution means a state in which there is no large clay mineral aggregate that causes precipitation of a clay mineral or a cloudy aqueous solution. More preferably, the material is dispersed with a thickness of about 1 to 10 nanometers, and particularly preferably the material is dispersed with a thickness of about 1 or 2 layers.
[0021]
As the component (C) water of the present invention, water or a mixed solvent of water and an organic solvent miscible with water may be used, and a water-swellable clay mineral and organic monomer that are uniformly dispersed are used. . In the case of using a mixed solvent, the gel contains an organic solvent in addition to water, but here, for convenience, these are all referred to as a hydrogel.
[0022]
The organic-inorganic composite hydrogel of the present invention comprises (C) a three-dimensional network formed by combining (A) a water-soluble organic polymer and (B) a water-swellable clay mineral that can be uniformly dispersed in water. ) Organic / inorganic composite hydrogel containing water. That is, (A) and (B) were combined at the molecular level in water, so that (A) was bridged by (B) or (B) was bridged by (A). A three-dimensional crosslinked product comprising A) and (B) is formed including water.
[0023]
That is, the organic / inorganic composite hydrogel in the present invention is a hydrogel that can be formed without an organic crosslinking agent, and is an organic polymer crosslinked product obtained by polymerizing an organic crosslinking agent added to a conventionally known organic monomer. It has excellent properties different from hydrogel (hereinafter referred to as organic crosslinked hydrogel).
[0024]
Also, the dried organic / inorganic composite hydrogel in the present invention needs to once form such an organic / inorganic composite hydrogel, and the dried organic / inorganic composite hydrogel can be obtained by drying them.
[0025]
For example, as shown in Comparative Examples 5 to 8, when each aqueous solution of (A) and (B) is prepared and then simply mixed, even if it is composed of the same component composition as the present invention, The organic / inorganic composite hydrogel of the invention cannot be obtained.
[0026]
The ratio of (A) water-soluble organic polymer and (B) water-swellable clay mineral that can be uniformly dispersed in water in the organic / inorganic composite hydrogel of the present invention is a three-dimensional network comprising (A) and (B). It is sufficient that the organic / inorganic hydrogel having the above is prepared, and it is not necessarily limited depending on the types of (A) and (B) to be used, but from the viewpoint of the ease and uniformity of hydrogel synthesis, it is preferably B / A The weight ratio is 0.01 to 10, more preferably 0.03 to 2.0, and particularly preferably 0.1 to 1.0.
[0027]
When the weight ratio of B / A is less than 0.01, the gel characteristics referred to in the present invention are often insufficient, and when it exceeds 10, the resulting hydrogel becomes brittle or uses a large amount of water. Problem arises. On the other hand, the ratio of (C) water to (A + B) can be arbitrarily set in a wide range from 0 to a very large value depending on the purpose by adjusting the amount of water in the polymerization process or by subsequent swelling or drying.
[0028]
The maximum amount of water contained in the organic / inorganic composite hydrogel obtained in the present invention, that is, the maximum water absorption amount (Cmax) at equilibrium swelling is the type and ratio of the components A and B, and environmental conditions such as temperature and pH. The organic / inorganic composite hydrogel of the present invention is characterized in that Cmax is larger than that of a conventional organic crosslinked hydrogel, although it varies depending on the above.
[0029]
Generally, Cmax decreases as B / A increases. The maximum amount of (C) under a certain condition (equilibrium swelling water absorption Cmax) is measured by holding the organic / inorganic composite hydrogel in excess water for a long time under the condition. For example, when an organic / inorganic composite hydrogel synthesized at a certain water content is kept in excess water at a temperature of 20 ° C., further water is taken into the hydrogel and finally an equilibrium swelling (maximum swelling) at 20 ° C. To reach.
[0030]
Therefore, by taking out the hydrogel soaked in excess water from time to time and measuring the weight, it is possible to know the time dependency of the swelling of the hydrogel and the water content during equilibrium swelling. The water content [{Cmax / (A + B)} × 100] at the time of equilibrium swelling varies depending on the component type and composition of A and B as described above, and also on environmental conditions such as temperature, pH, or salt concentration. It is possible to vary from a low value of 100% by weight or less to a high value of 100000% by weight or more.
[0031]
The organic / inorganic composite hydrogel in the present invention is characterized in that Cmax is larger than that of a conventional organic crosslinked hydrogel. When the organic / inorganic composite hydrogel of the present invention is equilibrated and swollen at 20 ° C., for example, {Cmax / (A + B)} × 100] is usually 2000% by weight or more, more preferably 3000% by weight or more, and particularly preferably 4000% by weight or more.
[0032]
In addition, the organic / inorganic composite hydrogel in the present invention has a characteristic that the swelling (water absorption) speed is larger than that of the conventional organic crosslinked hydrogel. It is estimated that this is because the three-dimensional cross-linking between (A) and (B) does not inhibit the water absorption characteristics of (A) and is formed uniformly. In addition, when (A) has a property of swelling and shrinking due to a temperature change as described below, it has a feature that not only the swelling but also the shrinking speed is large.
[0033]
The organic / inorganic composite hydrogel of the present invention has a critical temperature (Tc) that is transparent and / or swollen on the low temperature side, and opaque and / or volume contracted on the high temperature side, with Tc as the boundary. Those having the characteristics that the transparency and volume can be reversibly changed by the temperature change up and down are included.
[0034]
Such an organic / inorganic composite hydrogel can be prepared using an organic polymer exhibiting LCST (lower critical solution temperature) in an aqueous solution as the organic polymer. The Tc of the organic / inorganic composite hydrogel may change at the same temperature as the LCST of the organic polymer.
[0035]
The organic / inorganic composite hydrogel of the present invention has a high water absorption as compared with the conventional organic cross-linked hydrogel, high transparency, high volume ratio and change in transparency at the time of expansion and contraction before and after Tc, Those having some or all of the characteristics such as large swelling and / or shrinking speed, excellent mechanical properties and mechanical properties are included.
[0036]
For example, in an organic cross-linked hydrogel, when the cross-linking agent concentration is increased and the cross-linking density is increased, cross-linking becomes non-uniform and transparency may be lost (Comparative Example 4 and T. Tanaka, Scientific American, Vol. 244, 110-123 (1981), the organic / inorganic composite hydrogel of the present invention using the same organic polymer does not lose uniformity and exhibits high transparency.
[0037]
Specifically, the organic / inorganic composite hydrogel of the present invention includes (A) 10-fold amount (weight ratio) of water-soluble organic polymer (C) water and an organic / inorganic composite hydrogel having a thickness of 25 mm. , The light transmittance of visible light is 80% or more, more preferably 85% or more, particularly preferably 90% or more. Also, a dried product obtained by drying the organic / inorganic composite hydrogel can have transparency because the water-swellable clay mineral is finely dispersed.
[0038]
In addition, since the organic / inorganic composite hydrogel of the present invention maintains a clear transition characteristic at Tc, as shown in FIG. 1, the organic crosslinked hydrogel having a relatively high crosslinking density (Comparative Example 4) changes in transparency before and after Tc. In contrast, there is almost no mechanical property, and it has reversible reversibility with high mechanical properties and high transparency before and after Tc (Example 1).
[0039]
Further, with respect to the swelling and shrinkage of the hydrogel before and after Tc, as shown in FIG. 2, the organic-inorganic composite hydrogel (Example 1) was compared with the organic crosslinked hydrogel (Comparative Example 4) at the time of swelling and shrinkage. The volume ratio is high. The volume ratio of the organic / inorganic composite hydrogel of the present invention during swelling and shrinkage can be set according to the purpose, and generally the volume of swelling / shrinking is higher than that of the organic crosslinked hydrogel using the same water-soluble organic polymer. The ratio is large, usually 10 or more, preferably 20 or more, more preferably 30 or more.
[0040]
The organic / inorganic composite hydrogel of the present invention includes those having excellent mechanical properties such as strength, elongation and toughness. In particular, it is characterized in that those having excellent mechanical properties in addition to the above-mentioned high water absorbability, transparency, and various properties such as transparency change and volume change are included. The mechanical and physical properties of the organic / inorganic composite hydrogel vary depending on the water content of the hydrogel. Therefore, the mechanical and mechanical properties of the organic / inorganic composite hydrogel of the present invention were tested using a hydrogel having a water content within a certain range. It is expressed by the result.
[0041]
Specifically, {C / (A + B)} × 100 is 600 to 1000, that is, (C) a hydrogel containing 600 to 1000% by weight of water with respect to the organic + inorganic component (A + B) is used, or (A) It is expressed as a result of testing using a water-soluble organic polymer containing 10 times the amount (weight ratio) of (C) water.
[0042]
Furthermore, since the organic / inorganic composite hydrogel in the present invention has a large elongation at break and the cross-sectional area changes during the test, the cross-sectional area (initial cross-sectional area) of the hydrogel at the start of the test is 0.237 cm.²(Equivalent to a circle having a radius of 0.275 cm) was used as a test material.
[0043]
The organic / inorganic composite hydrogel of the present invention has the above water content and initial cross-sectional area, that is, the water content defined by {C / (A + B)} × 100 is 600 to 1000% by weight, and the initial cross-sectional area is 0. .237cm²And those having a tensile breaking load of 0.1 N or more, preferably 0.5 N or more, more preferably 1 N or more, and particularly preferably 2 N or more, measured using a hydrogel.
[0044]
The organic / inorganic composite hydrogel of the present invention has a tensile elongation at break of 100% or more, more preferably 200% or more, more preferably 300% or more, measured using the hydrogel having the above water content and initial cross-sectional area. Particularly preferably, it is 500% or more, and the load at a tensile elongation of 100% is 0.01N or more, more preferably 0.05N or more, particularly preferably 0.1N or more. It is.
[0045]
On the other hand, the organic crosslinked hydrogels shown in Comparative Example 3, Comparative Example 4 and Comparative Examples 9 to 12 are extremely weak compared to the organic / inorganic composite hydrogel of the present invention, and are weakly attached to the chuck in the tensile test. In most cases, the physical property values could not be measured due to destruction immediately after the test, even if they were devised.
[0046]
Further, the organic / inorganic composite hydrogel of the present invention exhibits good mechanical properties even at the time of water absorption, and has toughness that can withstand, for example, compression, tension, or bending deformation.
Specifically, (A) an organic-inorganic composite hydrogel having a diameter of 5.5 mm and a length of 30 mm containing water (C) containing 10 times the amount (weight ratio) of the water-soluble organic polymer is 1 in the thickness direction. Compressive deformation to a thickness of / 3 or less, preferably 1/5 or less, and / or stretch deformation to a length of 2 times or more, preferably 4 times or more in the length direction. And / or a material whose shape is not destroyed by bending deformation at an angle of 100 degrees or more, preferably 150 degrees or more at the center point of the length.
[0047]
In contrast, (B) the organic cross-linked gel having the same composition except that an organic cross-linking agent was used instead of the water-swellable clay mineral, the crack was generated and the shape was destroyed by any or all of the above deformation operations. Or loss occurs.
[0048]
The organic / inorganic composite hydrogel of the present invention needs to form a three-dimensional network composed of an organic polymer and a clay mineral, and can be produced by the following method. Coexistence of (B) after preparing a uniform solution containing (A ′) a monomer of the water-soluble organic polymer (A), (B) a water-swellable clay mineral that can be uniformly dispersed in water, and (C) water. The polymerization of (A ′) is performed below. As a result, fine complexation of (A) and (B) at the molecular level is achieved, and an organic / inorganic composite hydrogel gelled by three-dimensional network formation is obtained.
[0049]
Specifically, organic / inorganic that radically polymerizes (A ′) in the presence of (B) finely dispersed in water using a solution having a composition containing (A ′), (B), and (C) as essential components A method for producing a composite hydrogel, wherein a clay mineral uniformly dispersed at a nanometer level of preferably 1 to 10 layers, more preferably 1 or 2 layers, functions as a crosslinking agent (A ′), A) and (B) are combined in (C) to form a three-dimensional network.
[0050]
The radical polymerization reaction can be performed by a known method such as the presence of peroxide and / or ultraviolet irradiation in the absence of molecular oxygen. Furthermore, this polymerization reaction can be accelerated by heating or ultraviolet irradiation. As the radical polymerization initiator and the catalyst, known and commonly used radical polymerization initiators and catalysts can be appropriately selected and used. Preferably, those having water dispersibility and uniformly contained in the entire system are used.
[0051]
Specifically, as a polymerization initiator, a water-soluble peroxide such as potassium peroxodisulfate or ammonium peroxodisulfate, a water-soluble azo compound such as VA-044, V-50, V-501 (all of which are Wako Pure Chemical Industries, Ltd.) In addition to Yaku Kogyo Co., Ltd.), water-soluble radical initiators having a polyethylene oxide chain are exemplified. On the other hand, as the catalyst, N, N, N ′, N′-tetramethylethylenediamine which is a tertiary amine compound, β-dimethylaminopropionitrile, or the like is preferably used.
[0052]
The polymerization temperature can be set in the range of 0 ° C. to 100 ° C. according to the type of polymerization catalyst and initiator. The polymerization time varies depending on the polymerization conditions such as the catalyst, initiator, polymerization temperature, and amount (thickness) of the polymerization solution, and can generally be carried out for several tens of seconds to several hours. In order to perform polymerization uniformly throughout the system, for example, (A ′) and a polymerization initiator dissolved in water are added to a mixture obtained by uniformly mixing (B) and water in advance. It is effective to devise methods such as adding a polymerization catalyst dissolved in the solution.
[0053]
It is also possible to produce an organic / inorganic composite hydrogel in the form of fine particles by coexisting a known surfactant in the radical polymerization reaction.
In the polymerization of the organic / inorganic composite hydrogel of the present invention, the polymerization yield of (A ′) is high, and the water-soluble organic polymer obtained by polymerization is taken together with the clay mineral into the hydrogel and eluted as a water-soluble component. The amount is small. This is confirmed by the high polymerization yield after washing with water. This result is presumed to be due to the fact that the finely dispersed clay layer acts as an effective cross-linking agent for the water-soluble organic polymer in the polymerization of (A ′) in the presence of (B).
[0054]
Furthermore, in the present invention, for the purpose of improving the properties of the organic / inorganic composite hydrogel, an organic crosslinking agent may be included in the aqueous solution together with the essential components (A ′) and (B) as necessary. The concentration of the organic crosslinking agent contained is not particularly limited and can be selected according to the purpose.
[0055]
Examples of the organic crosslinking agent that can be included as required include conventionally known N, N′-methylenebisacrylamide, N, N′-propylenebisacrylamide, di (acrylamidomethyl) ether, 1,2-di (). Bifunctional compounds such as acrylamide ethylene glycol, 1,3-diacryloyl ethylene urea, ethylene diacrylate, N, N′-diallyl tartaramide, N, N′-bisacrylyl cystamine, triallyl cyanurate, Examples are trifunctional compounds such as triallyl isocyanurate.
[0056]
In the production of the organic / inorganic composite hydrogel of the present invention, hydrogels having various shapes can be prepared by changing the shape of the container. For example, an organic / inorganic composite hydrogel having an arbitrary shape such as a fibrous shape, a rod shape, a flat plate shape, a cylindrical shape, a spiral shape, or a spherical shape can be prepared.
[0057]
In addition to (A), (B), and (C), the organic / inorganic composite hydrogel in the present invention and the dried product thereof, if necessary, for example, an anionic activator, an organic molecule such as an organic dye or an organic pigment, It is possible to include an organic polymer such as a water-soluble polymer or a fibrous substance that does not dissolve in water, inorganic fine particle components such as carbon, silica, and titania at any stage of production. Furthermore, it can be combined (dispersed, laminated, etc.) with other materials according to the purpose.
[0058]
The present invention includes a dried product of the organic / inorganic composite hydrogel obtained by removing water from the organic / inorganic composite hydrogel of the present invention. The method for removing moisture is not particularly limited, but can be performed by appropriately changing conditions such as temperature, airflow, and reduced pressure. Specifically, a hot air circulating dryer or a vacuum dryer is used. The amount of water removed from the hydrogel is not particularly limited, and it can be arbitrarily prepared from a product from which water has been completely removed to a product in which water remains as required.
[0059]
The dried body of the organic / inorganic composite hydrogel of the present invention contains a clay mineral, but can be transparent because the clay mineral is finely dispersed. Therefore, in the case of absorbing a colored aqueous solution or the like in the hydrogel or its dried product, the absorption state can be detected by light transmission or light reflection. Also, when other organic components and inorganic components are dispersed in the hydrogel in advance, there is an advantage that the dispersion state can be clearly grasped.
[0060]
The organic / inorganic composite hydrogel can be crushed, classified, molded, etc. after being hydrogel or in the course of drying or as a dried gel, and can take a form suitable for the purpose of transportation, processing and use. Specific examples include a spherical shape, a scale shape, a powder shape, a film shape, a fiber shape, and a pellet shape. Regarding the size, for example, in the case of powder, those having an average particle size of usually 10 to 1000 μm are used, but are not particularly limited.
[0061]
The dried organic / inorganic composite hydrogel can be reversibly returned to the hydrogel by contact with water such as water, aqueous solution, or moisture. The novel organic / inorganic composite hydrogel of the present invention and a dried product thereof are useful in a wide range of fields such as daily necessities, medicine / medicine, agriculture, civil engineering, and industrial fields.
[0062]
【Example】
EXAMPLES Next, although an Example demonstrates this invention more concretely, this invention is not limited only to the Example shown below from the first.
[0063]
Example 1
As a clay mineral, [Mg_5.34Li_0.66Si₈O₂₀(OH)₄] Na⁺ _0.66A water-swellable synthetic hectorite (trademark Laponite XLG, manufactured by Nippon Silica Co., Ltd.) having the following composition was vacuum-dried at 100 ° C. for 2 hours and used. As the organic monomer, N-isopropylacrylamide (IPAA: manufactured by Kojin Co., Ltd.) was recrystallized using a mixed solvent of toluene and hexane (1/10 weight ratio) and purified into colorless needle crystals before use.
[0064]
As the polymerization initiator, potassium peroxodisulfate (PPS: manufactured by Kanto Chemical Co., Inc.) was diluted with pure water at a ratio of PPS / water = 0.384 / 20 (g / g) and used as an aqueous solution. As the catalyst, N, N, N ′, N′-tetramethylethylenediamine (TMEDA: manufactured by Kanto Chemical Co., Inc.) was used by diluting at a ratio of TMEDA / water = 160 μl / 20 g. As the water, pure water obtained by distilling ion-exchanged water was used. All water was used after bubbling high-purity nitrogen in advance for 3 hours or more to remove oxygen.
[0065]
In a constant temperature room at 20 ° C., 16.96 g of pure water and a Teflon stirrer were placed in a flat bottom glass container having an inner diameter of 25 mm and a length of 80 mm, the inside of which had been replaced with nitrogen, and 0.662 g of Laponite XLG was bubbled into the container while stirring. A small and clear solution was prepared by adding little by little with care.
[0066]
To this, 2.0 g of IPAA was added and stirred for 5 minutes to obtain a colorless transparent solution. Next, 1.06 g of PPS aqueous solution and 2.0 g of TMEDA aqueous solution were added with stirring, and further stirred for about 15 seconds to obtain a colorless transparent solution (D). A portion (3 ml × 3) of (D) was transferred to three glass tube containers having a closed inner diameter of 5.5 mm and a length of 150 mm so as not to come into contact with oxygen, and then sealed at the top, at 20 ° C. And allowed to stand for 15 hours for polymerization.
[0067]
The remaining solution (D) was also allowed to stand in a flat bottom glass container at 20 ° C. for 15 hours for polymerization. The operations from preparation of the solution to polymerization were all performed in a nitrogen atmosphere in which oxygen was blocked. After 15 hours, elastic, tough, colorless, transparent, uniform columnar and rod-like gels were formed in the flat bottom glass container and the glass tube container, and were carefully taken out from both containers.
[0068]
No heterogeneous or opaque aggregation due to clay minerals or the like was observed in the gel. It was found that the gel was a hydrogel containing {C / (A + B)} × 100 = 750% by weight of water by drying the gel with a vacuum dryer at 100 ° C. until the weight became constant. The following purification operation was repeated 3 times on the removed hydrogel to obtain a purified hydrogel.
[0069]
The purification was repeated (taken out by being immersed in 2 L of water for 2 days and then taken out by being immersed in 1 L of 70 ° C. water for 2 hours). The purified hydrogel was dried at 100 ° C. under reduced pressure to obtain a dried hydrogel from which moisture was removed. It was confirmed that the dried gel body was immersed in water at 20 ° C. to return to an elastic hydrogel having the same shape as before drying.
[0070]
The dried gel is subjected to Fourier transform infrared absorption spectrum (FT-IR) measurement by KBr method (using a Fourier transform infrared spectrophotometer FT / IR-550 manufactured by JASCO Corporation), and poly (N-isopropylacrylamide). Inherent infrared absorption (eg 1460cm^-1, 1550cm^-1, 1650cm^-12920cm^-12970cm^-1) And infrared absorption inherent in Laponite XLG (eg 460 cm)^-1650cm^-1, 1005cm^-1) Was observed.
[0071]
Further, thermogravimetric analysis (TG-DTA220 manufactured by Seiko Denshi Kogyo Co., Ltd .: raised to 600 ° C. at 10 ° C./min) under air flow, and B / A = 0.333 (weight ratio) was performed. Obtained.
[0072]
From the above, the gel obtained in this example is a hydrogel composed of an organic polymer (poly (N-isopropylacrylamide)), a clay mineral, and water having a component ratio according to the charged composition, and the organic polymer. Despite the absence of the addition of a crosslinking agent in the synthesis of the above, it becomes a colorless, transparent and uniform hydrogel, and the dried gel (solid) obtained by removing water from the hydrogel is immersed again in water. It was concluded that a three-dimensional network in which organic polymer and clay mineral were combined at the molecular level was formed in water. The organic polymer synthesized under the same conditions except that no clay mineral coexists became a polymer aqueous solution and did not become a hydrogel.
[0073]
Unrefined rod-like organic / inorganic composite hydrogel (cross-sectional area = 0.237 cm²) Is attached to a tensile testing device (manufactured by Shimadzu Corporation, desktop type universal testing machine AGS-H) so that there is no slippage at the chuck part, and the distance between grades is 20 mm, and the pulling speed is 100 mm / min. As a result of the test, the breaking load was 1.1 N, the breaking elongation was 550%, and the load at a tensile elongation of 100% was 0.09 N.
[0074]
After refining a rod-like organic / inorganic composite hydrogel cut to a length of 10 mm, it is immersed in water at six temperatures ranging from 20 ° C. to 50 ° C., left to stand for 1 day, and the volume is measured. The change in contraction was measured. The results are shown in FIG. 1 together with the results of Comparative Example 4 (organic crosslinked hydrogel).
[0075]
The organic / inorganic composite hydrogel obtained in this example had the toughness as described above, had a critical temperature (Tc), swelled at a temperature below Tc, and contracted at a temperature below Tc. The volume ratio during swelling and shrinking at 20 ° C. and 50 ° C. showed a high value of 24.
[0076]
After purifying the columnar organic / inorganic composite hydrogel taken out from the flat-bottomed glass container, the one immersed in water at five temperatures of 20 ° C. to 50 ° C. is cut out with a thickness of 2 mm, and NDH manufactured by Nippon Denshoku Industries Co., Ltd. The light transmittance was measured using -300A. The results are shown in FIG. 2 together with the results of Comparative Example 4. The organic / inorganic composite hydrogel obtained in this example showed a clear change in transparency at the boundary of Tc, and became highly transparent at a temperature below Tc, and became opaque (white turbid) at a temperature below Tc.
[0077]
(Examples 2 to 4)
Polymerization was conducted in the same manner as in Example 1 except that the amount of clay mineral (Laponite XLG) was changed to 0.132 g (Example 2), 0.264 g (Example 3), and 1.322 g (Example 4). The organic-inorganic composite hydrogel was prepared. In Examples 2 to 4, a colorless and transparent uniform hydrogel was obtained at room temperature.
[0078]
The hydrogel evaluation results measured in the same manner as in Example 1 are shown below. {C / (A + B)} × 100 is 940 wt% (Example 2), 880 wt% (Example 3), 600 wt% (Example 4), and the B / A ratio is 0.065 (Example 2). ), 0.135 (Example 3), and 0.66 (Example 4).
[0079]
When the temperature of the obtained hydrogel was raised, all had a critical temperature (Tc) around 35 ° C., and were colorless and transparent below Tc, and became opaque and contracted below Tc. The volume ratio during swelling and shrinking in water at 20 ° C. and 50 ° C. was 31 (Example 2) and 13 (Example 4). In addition, shrinkage occurred in a short time within 1 minute due to temperature change, and swelling occurred in a shorter time than Comparative Example 3.
[0080]
The results of the tensile test measurement were as follows: breaking load: 0.65 N (Example 3), 7.0 N (Example 4), breaking elongation: 430% (Example 3), 650% (Example 4), elongation: 100 % Load was 0.033 N (Example 3) and 0.40 N (Example 4). Moreover, the water content {Cmax / (A + B)} × 100 contained in the hydrogel obtained by equilibrium-swelling in 20 ° C. water after cutting the obtained hydrogel into 5 mm squares was 11300 wt% (Example 2), 7200 wt. % (Example 3) and 5000% by weight (Example 4).
[0081]
(Examples 5-7)
As an organic monomer, the IPAA described above was used in Example 5, N, N-dimethylacrylamide (DMAA: Wako Pure Chemical Industries, Ltd.) in Example 6, and N, N-diethylacrylamide (DEAA: Wako Pure) in Example 7. Yakuhin Kogyo Co., Ltd.) was used. DMAA and DEAA were used after removing a polymerization inhibitor by using a silica gel column (manufactured by Merck) in a volume of 80 ml with respect to 100 ml of the organic monomer.
[0082]
In a constant temperature room at 20 ° C., 18.96 g of pure water and a Teflon stirrer were placed in a flat bottom glass container having an inner diameter of 25 mm and a length of 80 mm, the inside of which had been purged with nitrogen. A small and clear solution was prepared by adding little by little with care. To this, 2.0 g of IPAA (Example 5), 2.0 g of DMAA (Example 6) or 2.0 g of DEAA (Example 7) was added and stirred until a colorless transparent solution was obtained.
[0083]
To this, 160 μl of TMEDA was added, and then 1.06 g of an aqueous PPS solution was added with stirring, followed by stirring for 5 minutes to obtain a colorless transparent solution (D ′). (D ') The stirring bar was removed from the solution, and the mixture was sealed and allowed to stand at 20 ° C. to gel the entire system (the contents did not move even when the container was placed on its side). All the above operations were performed in a nitrogen atmosphere in which oxygen was blocked. Then N₂While maintaining the atmosphere, the mixture was allowed to stand in a 70 ° C. water bath for 2 hours for polymerization. After 2 hours, the cylindrical gel produced in the flat bottom glass container was carefully removed from the container.
[0084]
In Examples 5 and 7, uniform cloudy gels having elasticity and toughness were obtained, and in Example 6, transparent gels having elasticity and toughness were obtained. None of the non-uniform or opaque aggregation due to clay minerals or the like was observed in the cloudy gel.
[0085]
The {C / (A + B)} × 100 measured in the same manner as in Example 1 was 750% by weight, and B / A was 0.33, which was a uniform organic material composed of an organic polymer, clay mineral, and water. / It was found to be an inorganic composite hydrogel. The cloudy hydrogels of Example 5 and Example 7 did not change to transparent even when the temperature was lowered. Moreover, even if the transparent hydrogel of Example 6 changed temperature at 0-70 degreeC, it remained transparent without becoming cloudy.
[0086]
(Examples 8 to 12)
As the organic monomer, N-isopropylacrylamide (IPAA) is used in Example 8, N, N-dimethylacrylamide (DMAA) is used in Example 9, and N, N-diethylacrylamide (DEAA) is used in Example 10. In Example 11, acryloylmorpholine (ACMO; manufactured by Kojin Co., Ltd.) was used, and in Example 12, N, N-dimethylaminopropylacrylamide (DMAPA; manufactured by Kojin Co., Ltd.) was used.
[0087]
For IPAA (Example 8), 0.75 times (weight ratio) of toluene was added to IPAA, dissolved at 40 ° C., returned to room temperature, and then added 7.5 times (weight ratio) of hexane. Stirring gave needle-like colorless crystals. Finally, IPAA obtained by removing the solvent by filtration and vacuum drying at room temperature was used. DMAA (Example 9), DEAA (Example 10) and ACMO (Example 11) were used in the same manner as in Examples 6 and 7, except that the polymerization inhibitor was removed.
[0088]
DMAPA (Example 12) was used by adding 20% by volume of acetone to DMAPA to lower the viscosity, removing the polymerization inhibitor with an activated alumina column (80 cc / 100 ml monomer), and then removing the acetone with a rotary evaporator. .
[0089]
All the water used was used after pure oxygen obtained by distilling ion-exchanged water was bubbled with high-purity nitrogen gas for 3 hours or more in advance to remove the contained oxygen. In this example, all operations before polymerization (all operations from the preparation of the solution to the removal of the hydrogel) were performed in a nitrogen atmosphere or a nitrogen stream from which oxygen was removed. In addition, the catalyst and the initiator aqueous solution were prepared in a nitrogen atmosphere in which oxygen was blocked in the same manner as the above operation.
[0090]
Into a two-necked flask which was purged with nitrogen inside the water bath at 20 ° C., 85.3 g of pure water from which dissolved oxygen was removed and a Teflon stirrer were placed, and 2.98 g of Laponite XLG was bubbled into the mixture while stirring. A small and clear solution was prepared by adding little by little with care. To this, 9.0 g of IPAA (Example 8), 9.0 g of DMAA (Example 9), 9.0 g of DEAA (Example 10), 9.0 g of ACMO (Example 11), or 9.0 g of DMAPA (Example 12) And stirred until a homogeneous transparent solution was obtained.
[0091]
The weight ratio of XLG / monomer is 0.331. Next, after the flask was cooled in an ice bath, 72 μl of TMEDA that had been cooled separately in an ice bath was added and stirred for 30 seconds, and then similarly cooled in an ice bath. 4.77 g of the same PPS aqueous solution was added with stirring and stirred for 30 seconds to obtain a uniform transparent solution. The solution was allowed to stand in a 15 ° C. water bath for 20 hours to complete the polymerization.
[0092]
In any of Examples 8 to 12, an elastic hydrogel in which the entire system was gelled (the contents did not move even when the container was placed sideways) was obtained in the flask. No aggregation due to non-uniform or opaque clay mineral or polymer was observed in the hydrogel. As a result of examining the transparency of the hydrogel obtained by polymerization at an ice bath temperature (about 1 ° C.), Examples 8, 9, 11 and 12 were uniformly transparent, and Example 10 was uniformly translucent. .
[0093]
As a result of measuring the visible light transmittance of the hydrogel cut to a thickness of 25 mm using NDH-300A manufactured by Nippon Denshoku Industries Co., Ltd., the total transmittance was 95% (Example 8) and 81% (Example 9). ), 40% (Example 10), 85% (Example 11), and 90% (Example 12).
[0094]
Next, the ice bath was changed to a 50 ° C. warm water bath to examine the change in transparency. In Examples 9, 11 and 12, the transparency hardly changed, but in both Examples 8 and 10, the total transmittance changed to opaque with 10% or less.
[0095]
On the other hand, the hydrogel obtained by polymerization was cut into a rod shape having a diameter of 5.5 mm and a length of 30 mm, and compressed to 1/3 and 1/5 in the thickness direction, and doubled and quadrupled in the length direction. And a test of bending deformation at angles of 100 degrees, 150 degrees and more at the center point of the length. As a result, in any of the samples of Examples 9 to 12, in the above test, the shape was not broken, cracked, or lost, and the original state was restored.
[0096]
Further, in the bending deformation test, any deformation of 180 ° or more returned to the original state after the test without causing destruction or cracking. Further, the obtained hydrogel had a diameter of 5.5 mm (cross-sectional area of 0.237 cm).²), Cut out to a length of 50 mm, sandwiched by round sandpaper so that the top and bottom 10 mm are not damaged and do not slide, using the same tensile test apparatus as in Example 1, distance between gauge points = 30 mm, pulling speed = 100 mm A tensile test was conducted at 1 min.
[0097]
As a result, in Example 8, the breaking load was 2.9 N, the breaking elongation was 1001%, the load at a tensile elongation of 100% was 0.103 N, and in Example 9, the breaking load was 2.4 N and the breaking elongation was 1112%. The load at a tensile elongation of 100% was 0.089N. In Example 10, the breaking load was 4.8N, the breaking elongation was 892%, and the load at a tensile elongation of 100% was 0.173N.
[0098]
Moreover, the water content {Cmax / (A + B)} × 100 contained in the hydrogel obtained by equilibrium swelling in 20 ° C. water after cutting the obtained hydrogel into 5 mm square was 6200 wt% (Example 8), 5000 wt. % (Example 9), 3700% by weight (Example 10), and 4700% by weight (Example 11). In addition, by measuring the weight of the dried product obtained by purification in the same manner as in Example 1, the polymerization yield of the monomers was 99% or more in all of Examples 8 to 11, indicating a high yield. It was done.
[0099]
(Example 13) Using 3.15 g of acrylamide (AAM: manufactured by Kanto Chemical Co., Inc.) purified using ethanol and toluene as organic monomers, and using 2.8 g of water-swellable layered clay mineral XLG (XLG / monomer) = 0.89 weight ratio), 50 g in total as water, 0.05 g potassium peroxodisulfate as initiatorAndPolymerization experiments and evaluation tests were conducted in the same manner as in Example 8 except that the polymerization temperature was 23 ° C.
[0100]
As a result, a transparent and uniform organic / inorganic composite hydrogel having a transparency (total transmittance) at a measurement temperature of 1 ° C. of 85% at a thickness of 25 mm and having toughness was obtained. Further, even when the measurement temperature of transparency was 50 ° C., the total transmittance hardly changed.
[0101]
(Example 14)
1.788 g of XLG is used as a clay mineral, and at the same time, an organic crosslinking agent (N, N′-methylenebisacrylamide: BIS: manufactured by Kanto Chemical Co., Inc.) is used at 0.5 mol% of the organic monomer, and the polymerization temperature is set. A polymerization solution was prepared and a polymerization experiment and an evaluation test were performed in the same manner as in Example 9 except that the temperature was 30 ° C.
[0102]
As a result, a transparent and tough organic / inorganic composite hydrogel gel was obtained. The total transmittance at a thickness of 25 mm (measurement temperature: 1 ° C.) was 90%, and the transparency was hardly changed even when the measurement temperature was 50 ° C. A rod-shaped hydrogel cut to a diameter of 5.5 mm and a length of 30 mm is subjected to a compression deformation test up to 1/5 in the thickness direction, a stretch deformation test of 4 times in the length direction, and a bending deformation test up to 180 degrees at the center of the length. In any case, the shape was not destroyed and returned to the original shape after the test.
[0103]
(Examples 15 to 17)
A mixed solvent of water and methanol is used instead of water, and the mixed solvent ratio (weight ratio) of water: methanol is 80:20 (Example 15), 60:40 (Example 16), 40:60 (Example) 17) and the polymerization experiment was conducted in the same manner as in Example 2 except that the polymerization temperature was 15 ° C.
[0104]
As a result, in any of Examples 15 to 17, a uniform and tough organic / inorganic composite hydrogel composed of poly (N-isopropylacrylamide), XLG, water, and methanol was obtained. The transparency of the hydrogel after polymerization (ice bath temperature: measured at about 1 ° C.) was transparent in Example 15 and opaque in Examples 16 and 17. In particular, Example 17 was completely white.
[0105]
Then, it refine | purified using the pure water by the method similar to Example 1. FIG. After purification, Tc was measured by changing the water temperature using an organic / inorganic composite hydrogel swollen in 20 ° C. water. As a result, the organic / inorganic composite hydrogels obtained in Examples 15 to 17 all show a critical temperature (Tc) at 33 ° C., and are colorless and transparent and swell at temperatures below that, and are white and opaque above Tc. To cause volume contraction.
[0106]
From the above results, it was shown that the organic / inorganic composite hydrogel in the present invention can be obtained even using a mixed solvent of water and an organic solvent miscible with water. As a result of thermogravimetric analysis of the dried product, B / A (weight ratio) was 0.066 in all cases.
[0107]
(Examples 18 to 21)
Polymerization was carried out in the same manner as in Example 8 in Example 18, Example 9 in Example 19, Example 10 in Example 20, and Example 11 in Example 21 except that the polymerization temperature was 50 ° C. In all cases, a tough uniform organic-inorganic composite hydrogel was obtained.
[0108]
The transparency at the polymerization temperature immediately after polymerization was transparent in Examples 19 and 21, and white and opaque in Examples 18 and 20. Then, when it cooled to 1 degreeC, it was transparent in Example 18, Example 19, and Example 21, and was opaque-translucent in Example 20. The resulting hydrogel was cut to a thickness of 25 mm and the total visible light transmittance measured at 1 ° C. was 84% (Example 18), 93% (Example 19), 30% (Example 20), 88%. (Example 21).
[0109]
(Example 22)
As an organic monomer, water (85.3 g), XLG (2) were used in the same manner as in Example 8, except that 4.5 g of N-isopropylacrylamide (IPAA) and 3.94 g of N, N-dimethylacrylamide (DMAA) were used. .98 g), TMEDA (72 μl) and PPS (4.77 g in aqueous solution) were prepared and polymerized at 15 ° C. An elastic and uniform translucent hydrogel was obtained.
[0110]
No aggregation due to non-uniform or opaque clay mineral or polymer was observed in the hydrogel. The hydrogel obtained by polymerization was cut to a width of 25 mm, and the transparency was measured while changing the temperature. As a result, the translucency (total transmittance of about 40 to 35%) was changed to opaque (total transmittance of 5% or less). Change (LCST) occurred at about 40-50 ° C. In Example 8 using IPAA alone, compared with the rapid change from transparent (total transmittance of 90%) to opaque (total transmittance of 6%) at 32 ° C. to 34 ° C., the change is shifted to the high temperature side. It became wide.
[0111]
On the other hand, the hydrogel obtained by polymerization is cut into a rod shape having a diameter of 5.5 mm and a length of 30 mm and compressed to 1/3 and 1/5 in the thickness direction, and up to 2 times and 4 times in the length direction. A test for stretching and a test for bending deformation at angles of 100 degrees, 150 degrees and more at the center point of the length were performed. As a result, in any of the tests, the shape was not broken, cracks, or defects were not caused, and the original state was restored. Further, in the bending deformation test, any deformations of 180 degrees or more did not cause destruction or cracks, and returned to the original state after the test.
[0112]
(Examples 23 and 24)
The amounts of the water-swellable clay mineral XLG and the organic monomer IPAA are as follows: in Example 23, XLG = 2.98 g, IPAA = 0.45 g, XLG / IPAA = 6.62 weight ratio; in Example 24, XLG = 0 Experiments were conducted in the same manner as in Example 8, except that 0596 g, IPAA = 4.5 g, and XLG / IPAA = 0.003. As a result, in both Example 23 and Example 24, uniform solutions could be prepared, and uniform transparent gels were obtained as a result of polymerization. The total transmittance of the gel cut to a thickness of 25 mm was 95.1% (Example 23) and 98.2% (Example 24).
[0113]
(Examples 25 and 26)
As a water-swellable clay mineral, instead of XLG, in Example 25, XLS (6% by weight of sodium pyrophosphate in XLS and peptizer: Nippon Silica Kogyo Co., Ltd.), in Example 26, synthetic smectite SWN The experiment was conducted in the same manner as in Example 8 except that (Coop Chemical Co., Ltd.) was used. As a result, in both Example 25 and Example 26, uniform solutions could be prepared, and uniform transparent gels were obtained as a result of polymerization. The total transmittance of the gel cut to a thickness of 25 mm was 90.4% (Example 25) and 83.8% (Example 26).
[0114]
(Comparative Example 1)
Polymerization was carried out at 20 ° C. for 15 hours in the same manner as in Example 1 except that no clay mineral was added. In both the flat bottom glass container and the glass tube container, only a colorless transparent solution in which poly (N-isopropylacrylamide) was dissolved in water was obtained, and no gel was formed. Further, when the temperature of the solution was raised, a polymer gel that became cloudy at about 32 ° C. or more was obtained in a state separated from water, and then when the temperature was lowered to 20 ° C., it returned to the aqueous solution again.
[0115]
In addition, the polymer in the obtained solution was confirmed by diluting in 5 L of water, holding it in a 50 ° C. water tank, causing the lysate to flocculate, and centrifuging (20 ° C., 10,000 rpm, 60 minutes). The sample was separated and further subjected to reprecipitation purification using water, acetone, and hexane, and then the sample was analyzed (infrared absorption spectrum measurement, nuclear magnetic resonance spectrum measurement).
[0116]
(Comparative Example 2)
Polymerization was carried out in the same manner as in Comparative Example 1 except that NaOH was adjusted to pH 11. As a result, a colorless and transparent solution of poly (N-isopropylacrylamide) was obtained as in Comparative Example 1, and no gel was produced. . From this, it was confirmed that there was no influence of the pH increase accompanying the clay mineral addition of Example 1.
[0117]
(Comparative Examples 3 and 4)
The same procedure as in Example 1 was carried out except that the IPAA monomer was added without using the clay mineral, and then an organic cross-linking agent was added at 1 mol% (Comparative Example 3) and 5 mol% (Comparative Example 4) of IPAA. Then, polymerization was carried out at 20 ° C. for 15 hours. As the organic crosslinking agent, N, N′-methylenebisacrylamide (BIS) (manufactured by Kanto Chemical Co., Inc.) was used as it was. In Comparative Example 3, a colorless and transparent gel was obtained, and in Comparative Example 4, a cloudy gel was obtained. As a result of measurement in the same manner as in Example 1, {C / (A)} × 100 was 990% by weight (Comparative Example 3) and 935% by weight (Comparative Example 4), and was confirmed to be an organic crosslinked hydrogel. It was.
[0118]
In Comparative Example 3, Tc was around 33 ° C., transparent and swollen on the lower temperature side than Tc, and white turbid and contracted on the higher temperature side than Tc. The volume ratio during swelling and shrinking at 20 ° C. and 50 ° C. was about 8. On the other hand, in Comparative Example 4, all remained cloudy even when the temperature was changed. Although it swelled on the low temperature side at about 33 ° C. and contracted on the high temperature side, the volume ratio during swelling and contraction at 20 ° C. and 50 ° C. was about 5. Changes in volume and total transmittance due to temperature changes in Comparative Example 4 are shown in FIGS. 1 and 2 together with the results of Example 1. FIG.
[0119]
(Comparative Examples 5 and 6)
In an aqueous solution obtained by dissolving 1 g of poly (N-isopropylacrylamide) obtained in Comparative Example 1 in 10 g of water, 0.331 g (Comparative Example 5) or 0.066 g (Comparative Example 6) of clay mineral (Laponite XLG) was stirred. However, in each case, a hydrogel having uniform toughness could not be obtained, although an attempt was made to prepare a composite composed of an organic polymer having the same composition as Example 1 and Example 2, a clay mineral, and water. It was.
[0120]
(Comparative Example 7)
Except for using DEAA monomer, 0.15 g of poly (N, N-diethylacrylamide) obtained in the same manner as in Comparative Example 1 was added to a transparent aqueous solution obtained by dissolving 14.85 g of water in 0.2 g of clay mineral (Laponite XLG). A clear solution of 9.8 g in water was added while gradually stirring to prepare a mixture. When the XLG aqueous solution was added to 0.88 g (B / A = 0.117), a white floating substance was precipitated in the solution according to the amount of added XLG, and changed to a cloudy solution. Further addition was continued, and the mixture remained a cloudy solution even when the addition amount was 3.88 g (B / A = 0.517), for example.
[0121]
These cloudy mixed solutions were heterogeneous solutions in which white aggregates floated in water, and when this was heated, it was observed that the cloudiness further increased at a temperature higher than about 28 ° C. However, in any case, a uniform hydrogel was not obtained. Furthermore, even when the amount of clay added was increased or the initial polymer solution concentration was increased, a uniform and tough hydrogel as obtained in the examples could not be obtained.
[0122]
(Comparative Example 8)
A mixture containing an organic polymer, a clay mineral, and water was prepared in the same manner as in Comparative Example 7, except that a poly (N, N-diethylacrylamide) aqueous solution was gradually added to 10 g of the XLG aqueous solution. By adding and mixing, a white turbid solution was obtained. By heating to Tc or higher, the turbidity was further increased, and a hydrogel with uniform toughness could not be obtained in any case.
[0123]
(Comparative Examples 9-12)
After adding DEAA (Comparative Examples 9 and 10) or ACMO (Comparative Examples 11 and 12) without using clay minerals, the organic cross-linking agent N, N′-methylenebisacrylamide (BIS) was added to 1 mol of DEAA or ACMO. % (Comparative Examples 9 and 11) and 5 mol% (Comparative Examples 10 and 12), except that they are used in the same manner as in Example 10 or Example 11, and left in a water bath at 15 ° C. for 20 hours for polymerization. Completed.
[0124]
In any of Comparative Examples 9 to 12, a hydrogel in which the entire system was gelled (the contents did not move even when the container was placed on the side) was obtained in the flask. None of the non-uniform aggregation was observed in the hydrogel. As a result of examining the transparency of the hydrogel obtained by polymerization at an ice bath temperature (about 1 ° C.), Comparative Examples 9 and 11 were uniformly transparent, and Comparative Examples 10 and 12 were opaque. As a result of measuring the visible light transmittance of the hydrogel cut to a thickness of 25 mm using NDH-300A manufactured by Nippon Denshoku Industries Co., Ltd., the total transmittance was 98% (Comparative Example 9) and 24% (Comparative Example 10). ), 98% (Comparative Example 11), and 22% (Comparative Example 12).
[0125]
On the other hand, in Comparative Examples 9 to 12, polymerization was carried out under the above conditions using a glass tube having an inner diameter of 5.5 mm and a length of 150 mm as a polymerization vessel to obtain a rod-like organic crosslinked hydrogel. The obtained hydrogel was cut into a rod shape with a length of 30 mm, compressed to 1/3 in the thickness direction, tested to stretch twice in the length direction, and bent at an angle of 100 degrees at the center of the length. A test was conducted.
[0126]
As a result, in all the samples of Comparative Examples 9 to 12, cracks occurred in the above test, and the shapes were broken or lost. Furthermore, the hydrogel obtained in Comparative Examples 9-12 was 5.5 mm in diameter (cross-sectional area 0.237 cm).²), Carefully cut out to a length of 50 mm, sandwiched by round sandpaper so as not to damage 10 mm above and below, and using the same tensile test apparatus as in Example 1, distance between gauge points = 30 mm, pulling speed = An attempt was made to perform a tensile test at 100 mm / min, but the sample was brittle and most of the sample was broken before being attached to the chuck. Moreover, even those lightly attached to the chuck were broken immediately after the test, and no physical property values were obtained.
[0127]
(Comparative Examples 13 and 14)
Except for using a glass tube container having an inner diameter of 5.5 mm and a length of 150 mm, Comparative Example 13 was compared with Comparative Example 3 and Comparative Example 14 was a bar-shaped organic bridge having an outer diameter of 5.5 mm by the same method as Comparative Example 4. A hydrogel was obtained by polymerization. The obtained hydrogel was cut out to a length of 30 mm, compressed to 1/3 in the thickness direction, tested to extend twice in the length direction, and tested to bend and deform at an angle of 100 degrees at the center point of the length. went.
[0128]
As a result, in all the samples of Comparative Examples 13 and 14, cracks occurred in the above test, and the shapes were broken or lost. Further, it was cut out to a length of 50 mm, sandwiched between round sand papers so as not to damage and slip 10 mm above and below, and using the same tensile test apparatus as in Example 1, the distance between gauge points = 30 mm, the pulling speed = 100 mm / Attempts were made to perform a tensile test in minutes, but the samples were brittle and any sample broke before being mounted on the chuck, and no physical property values were obtained.
[0129]
Further, the obtained organic cross-linked hydrogel was cut into approximately 5 mm square, and then the water content {Cmax / (A)} × 100 contained in the organic cross-linked hydrogel obtained by equilibrium swelling in 20 ° C. water was 1500% by weight (comparative example) 13) and 800% by weight (Comparative Example 14).
[0130]
【The invention's effect】
The present invention is a novel organic / inorganic composite hydrogel having excellent functionality such as uniformity, transparency, mechanical properties, mechanical properties, water absorption, swelling / shrinkage properties, a method for producing the same, and removing water from the hydrogel Thus, a dried body of the organic / inorganic composite hydrogel obtained can be provided.
[0131]
The organic / inorganic composite hydrogel obtained by the present invention includes a tough and tough hydrogel, a transparent or uniform white hydrogel, a transparent and / or volume-swelled state on the low temperature side, and opaque and / or volume on the high temperature side. Those having a critical temperature (Tc) that reversibly changes to a contracted state are included, and the dried gel of the organic-inorganic composite hydrogel can be reversibly returned to the hydrogel by immersion in water. It is useful in a wide range of fields such as daily necessities, medicine / medical care, agriculture, civil engineering, and industrial fields.
[Brief description of the drawings]
1 is a diagram showing volume changes during swelling and shrinkage of the organic / inorganic composite hydrogel obtained in Example 1 and the organic crosslinked hydrogel obtained in Comparative Example 4 with temperature in water. FIG. The vertical axis represents the hydrogel volume (mm³) Represents the temperature (° C.) on the horizontal axis.
2 is a graph showing changes in transparency of the organic / inorganic composite hydrogel obtained in Example 1 and the organic crosslinked hydrogel obtained in Comparative Example 4 depending on the temperature. FIG. The vertical axis represents total transmittance (%), and the horizontal axis represents temperature (° C.).

Claims

(C) Water is contained in a three-dimensional network formed by combining (A) a water-soluble organic polymer and (B) a water-swellable layered clay mineral that can be uniformly dispersed in water. An inorganic composite hydrogel comprising :
The component monomer (A ′) of the water-soluble organic polymer (A) is an acrylamide derivative and / or a methacrylamide derivative,
(B) The organic / inorganic composite hydrogel, wherein the water-swellable layered clay mineral that can be uniformly dispersed in water is water-swellable smectite or water-swellable mica.

(B) The water-swellable layered clay mineral that can be uniformly dispersed in water is uniformly dispersed in a thickness of 1 to 10 layers, and is combined to act as a crosslinking agent for the (A) water-soluble organic polymer. The organic-inorganic composite hydrogel according to claim 1.

The organic / inorganic composite hydrogel according to claim 1 or 2, wherein (A) the water-soluble organic polymer and (B) the water-swellable layered clay mineral that can be uniformly dispersed in water are complexed at a molecular level.

The organic-inorganic composite hydrogel according to claim 1, wherein the three-dimensional network is formed without using an organic crosslinking agent.

(C) Water is contained in a three-dimensional network formed by combining (A) a water-soluble organic polymer and (B) a water-swellable layered clay mineral that can be uniformly dispersed in water. It inorganic composite hydrogel der,
The component monomer (A ′) of the water-soluble organic polymer (A) is an acrylamide derivative and / or a methacrylamide derivative,
(B) The water-swellable layered clay mineral that can be uniformly dispersed in water is water-swellable smectite or water-swellable mica,
Further, (B) an organic / inorganic composite hydrogel in which the water-swellable layered clay mineral that can be uniformly dispersed in water forms a three-dimensional network as a main crosslinking agent.

(B) A water-swellable layered clay mineral that can be uniformly dispersed in water is dissolved in water, and (B) in the presence of water-swellable layered clay mineral that can be uniformly dispersed in water and (C) water, The organic-inorganic composite hydrogel according to any one of claims 1 to 5, which is obtained by polymerizing a constituent monomer (A ') of A) a water-soluble organic polymer.

The organic / inorganic composite hydrogel according to claim 1, wherein the (B) water-swellable layered clay mineral is water-swellable hectorite.

The organic / inorganic composite hydrogel according to any one of claims 1 to 7 , wherein a weight ratio of (B) water-swellable layered clay mineral / (A) water-soluble organic polymer is 0.01 to 10.

9. A critical temperature (Tc) that is transparent and / or volume swelled on the low temperature side and reversibly changes to opaque and / or volume contracted on the high temperature side. Organic / inorganic composite hydrogel.

The water content defined by {C / (A + B)} × 100 is 600 to 1000% by weight, and the tensile breaking load is 0.1 N or more measured using a hydrogel having an initial cross-sectional area of 0.237 cm ² . The organic-inorganic composite hydrogel according to any one of claims 1 to 9, wherein a tensile breaking elongation is 100% or more and a load at a tensile elongation of 100% is 0.01 N or more.

The organic-inorganic composite gel according to any one of claims 1 to 10, wherein a water content {Cmax / (A + B)} × 100 at equilibrium swelling in water at 20 ° C. is 2000% by weight or more.

A dried product of an organic / inorganic composite hydrogel obtained by removing water from the organic / inorganic composite hydrogel according to any one of claims 1 to 11 .

A method for producing an organic-inorganic composite hydrogel according to claim 1 or 5,
(A) A monomer (A ′) that is a constituent of a water-soluble organic polymer and (B) a water-swellable layered clay mineral that can be uniformly dispersed in water are dissolved in (C) water, and the (B) water Water-swellable layered clay mineral that can be uniformly dispersed in (C) monomer (A ′) that is a constituent of water-soluble organic polymer in the presence of water in the absence of molecular oxygen and A method for producing an organic / inorganic composite hydrogel that is polymerized by ultraviolet irradiation .

Were uniformly dispersed in the thickness of 1 to 10 layers (B) be present as a crosslinking agent uniformly dispersible water-swellable layered clay mineral in water, the polymerization of the monomer (A '), according to claim 13, wherein A method for producing an organic / inorganic composite hydrogel.

The weight ratio of the monomer of (B) water-swellable layered clay mineral that can be uniformly dispersed in water / (A ′) water-soluble organic polymer (A) is 0.01 to 10, according to claim 13 or 14 . A method for producing an organic / inorganic composite hydrogel.

Tensile strength of the resulting organic / inorganic composite hydrogel was measured using a hydrogel having a water content defined by {C / (A + B)} × 100 of 600 to 1000 wt% and an initial cross-sectional area of 0.237 cm ^2. The organic-inorganic composite according to any one of claims 13 to 15 , wherein the breaking load is 0.1N or more, the tensile breaking elongation is 100% or more, and the load at a tensile elongation of 100% is 0.01N or more. A method for producing a hydrogel.

The resulting organic-inorganic composite hydrogel, water content at equilibrium swelling in water at 20 ℃ {Cmax / (A + B)} × 100 is 2000% by weight or more, according to any one of claims 13 to 16 Manufacturing method of organic / inorganic composite gel.