JP3792330B2 - Method for modifying water absorbent resin and method for producing water absorbent resin - Google Patents

Description

【００２１】
本発明にかかる変性方法によって変性（以下、処理と称する）することができる吸水性樹脂は、特に限定されるものではなく、反応性基を有し、固体状またはゲル状であればよい。上記の反応性基としては、カルボキシル基が特に好ましい。また、吸水性樹脂は、内部に架橋構造を有することが好ましい。該吸水性樹脂としては、具体的には、内部に架橋構造を有し、かつ、部分的に中和されたポリ（メタ）アクリル酸が挙げられる。
【００２２】
上記の吸水性樹脂は、例えば、アクリル酸またはその塩（以下、アクリル酸（塩）と記す）を主成分とする単量体組成物を重合することにより得られる。該吸水性樹脂としては、具体的には、例えば、ポリアクリル酸部分中和物架橋体、デンプン−アクリロニトリルグラフト重合体の加水分解物、デンプン−アクリル酸グラフト重合体の中和物、酢酸ビニル−アクリル酸エステル共重合体のケン化物、アクリロニトリル共重合体若しくはアクリルアミド共重合体の加水分解物またはこれらの架橋体、カルボキシメチルセルロースの架橋体、カチオン性モノマーの架橋体、イソブチレン−無水マレイン酸共重合架橋体、２−アクリルアミド−２−メチルプロパンスルホン酸とアクリル酸との共重合架橋体、ポリエチレンオキシド架橋体、メトキシポリエチレングリコールとアクリル酸との共重合架橋体等が挙げられる。これら例示の吸水性樹脂のうち、ポリアクリル酸（塩）の架橋体がより好ましい。ポリアクリル酸（塩）の架橋体は、該架橋体が有する酸基が５０モル％〜９０モル％の範囲内で中和されていることが好ましい。また、塩としては、アルカリ金属塩、アルカリ土類金属塩、アンモニウム塩、ヒドロキシアンモニウム塩、アミン塩、アルキルアミン塩等が好ましい。
【００２３】
単量体組成物は、アクリル酸（塩）の他に、必要に応じて、該アクリル酸（塩）と共重合可能な親水性単量体を含んでいてもよい。上記親水性単量体としては、具体的には、例えば、メタクリル酸、クロトン酸、（無水）マレイン酸、フマル酸、イタコン酸、ケイ皮酸、ソルビン酸、β−アクリロイルオキシプロピオン酸、２−（メタ）アクリロイルエタンスルホン酸、２−（メタ）アクリロイルプロパンスルホン酸、２−（メタ）アクリルアミド−２−メチルプロパンスルホン酸、ビニルスルホン酸、スチレンスルホン酸、アリルスルホン酸、ビニルホスホン酸、２−（メタ）アクリロイルオキシエチルリン酸等のアニオン性不飽和単量体、および、これらのアルカリ金属塩やアルカリ土類金属塩、アンモニウム塩、アルキルアミン塩；
アクリルアミド、メタクリルアミド、Ｎ−エチル（メタ）アクリルアミド、Ｎ−ｎ−プロピル（メタ）アクリルアミド、Ｎ−イソプロピル（メタ）アクリルアミド、Ｎ，Ｎ−ジメチル（メタ）アクリルアミド、２−ヒドロキシエチル（メタ）アクリレート、２−ヒドロキシプロピル（メタ）アクリレート、メトキシポリエチレングリコール（メタ）アクリレート、ポリエチレングリコールモノ（メタ）アクリレート、ビニルピリジン、Ｎ−ビニルピロリドン、Ｎ−アクリロイルピペリジン、Ｎ−アクリロイルピロリジン等のノニオン性不飽和単量体；
Ｎ，Ｎ−ジメチルアミノエチル（メタ）アクリレート、Ｎ，Ｎ−ジエチルアミノエチル（メタ）アクリレート、Ｎ，Ｎ−ジメチルアミノプロピル（メタ）アクリレート、Ｎ，Ｎ−ジメチルアミノプロピル（メタ）アクリルアミド等のカチオン性不飽和単量体、および、これらの四級化物（例えば、アルキルハライドとの反応物、ジアルキル硫酸との反応物等）；等が挙げられる。これら親水性単量体は、単独で用いてもよく、また、二種類以上を併用してもよい。
【００２４】
単量体組成物がアクリル酸（塩）を主成分として含む場合において、該アクリル酸（塩）以外の親水性単量体の使用量は、単量体組成物全体の３０モル％以下がより好ましく、１０モル％以下がさらに好ましい。
【００２５】
上記の単量体組成物を（共）重合してなる吸水性樹脂は、内部に架橋構造（一次架橋構造）を有することが好ましい。上記の架橋構造は、単量体組成物を（共）重合させる際に内部架橋剤を用い、該単量体組成物と内部架橋剤とを共重合若しくは反応させることにより、容易に導入することができる。尚、吸水性樹脂は、内部架橋剤を必要としない自己架橋型であってもよい。
【００２６】
上記の内部架橋剤としては、例えば、分子内にビニル基（重合性不飽和基）を複数有する化合物；分子内にビニル基を少なくとも１つ有すると共に、単量体組成物の反応性基と反応し得る官能基を少なくとも１つ有する化合物；分子内に該反応性基と反応し得る官能基を複数有する化合物；が挙げられる。これら内部架橋剤は、単独で用いてもよく、また、二種類以上を併用してもよい。
【００２７】
分子内にビニル基を複数有する化合物としては、具体的には、例えば、Ｎ，Ｎ’−メチレンビス（メタ）アクリルアミド、（ポリ）エチレングリコールジ（メタ）アクリレート、（ポリ）プロピレングリコールジ（メタ）アクリレート、トリメチロールプロパントリ（メタ）アクリレート、トリメチロールプロパンジ（メタ）アクリレート、グリセリントリ（メタ）アクリレート、グリセリンアクリレートメタクリレート、エチレンオキサイド変性トリメチロールプロパントリ（メタ）アクリレート、ペンタエリスリトールテトラ（メタ）アクリレート、ジペンタエリスリトールヘキサ（メタ）アクリレート、Ｎ，Ｎ−ジアリルアクリルアミド、トリアリルシアヌレート、トリアリルイソシアヌレート、トリアリルホスフェート、トリアリルアミン、ジアリルオキシ酢酸、Ｎ−メチル−Ｎ−ビニルアクリルアミド、ビス（Ｎ−ビニルカルボン酸アミド）、テトラアリロキシエタン等のポリ（メタ）アリロキシアルカン等が挙げられる。
【００２８】
分子内にビニル基を少なくとも１つ有すると共に、反応性基と反応し得る官能基を少なくとも１つ有する化合物としては、例えば、ヒドロキシル基やエポキシ基、カチオン性基等を少なくとも１つ有するエチレン性不飽和化合物が挙げられる。該化合物としては、具体的には、例えば、グリシジル（メタ）アクリレート、Ｎ−メチロールアクリルアミド、（メタ）アクリル酸ジメチルアミノエチル等が挙げられる。
【００２９】
分子内に反応性基と反応し得る官能基を複数有する化合物としては、例えば、ヒドロキシル基やエポキシ基、カチオン性基、イソシアネート基等を少なくとも２つ有する化合物が挙げられる。該化合物としては、具体的には、例えば、（ポリ）エチレングリコールジグリシジルエーテル、グリセロールジグリシジルエーテル、エチレングリコール、ポリエチレングリコール、プロピレングリコール、グリセリン、ペンタエリスリトール、エチレンジアミン、エチレンカーボネート、ポリエチレンイミン、硫酸アルミニウム等が挙げられる。
【００３０】
上記例示の内部架橋剤のうち、分子内にビニル基を複数有する化合物を用いることがより好ましい。分子内にビニル基を複数有する化合物を用いることにより、得られる吸水性樹脂の諸特性、例えば吸水特性等がより一層向上する。親水性単量体に対する内部架橋剤の使用量は、親水性単量体および内部架橋剤の組み合わせ等にもよるが、親水性単量体に対して０．００５モル％〜３モル％の範囲内が好ましく、０．０１モル％〜１．５モル％の範囲内がより好ましい。
【００３１】
また、単量体組成物を（共）重合させる際には、デンプンおよびその誘導体、セルロースおよびその誘導体、ポリビニルアルコール、ポリアクリル酸（塩）およびその架橋体等の親水性高分子や、次亜リン酸およびその塩等の連鎖移動剤を反応系に添加してもよい。
【００３２】
単量体組成物を（共）重合させる重合法としては、例えば、水溶液重合、逆相懸濁重合、バルク重合、沈澱重合等の公知の種々の重合形態が採用でき、特に限定されるものではない。このうち、単量体組成物を水溶液の状態で重合させる水溶液重合、逆相懸濁重合が、重合反応を容易に制御できると共に、得られる吸水性樹脂の諸特性がより一層向上するのでより好ましい。
【００３３】
また、単量体組成物を（共）重合させる際には、ラジカル重合開始剤や、紫外線、電子線等の活性エネルギー線等を用いることができる。上記のラジカル重合開始剤としては、具体的には、例えば、過硫酸カリウム、過硫酸ナトリウム、過硫酸アンモニウム、ｔ−ブチルヒドロパーオキサイド、過酸化水素、２，２’−アゾビス（２−アミジノプロパン）二塩酸塩、２，２’−アゾビスイソブチロニトリル、過酸化ベンゾイル、クメンヒドロパーオキサイド、ジ−ｔ−ブチルパーオキサイド等の過酸化物が挙げられる。これらラジカル重合開始剤は、単独で用いてもよく、また、二種類以上を併用してもよい。さらに、酸化性ラジカル重合開始剤を用いる場合には、該酸化性ラジカル重合開始剤と、亜硫酸ナトリウム、亜硫酸水素ナトリウム等の亜硫酸塩、重亜硫酸塩、チオ硫酸塩、ホルムアミジンスルフィン酸、硫酸第一鉄、Ｌ−アスコルビン酸等の還元剤と組み合わせることにより、レドックス開始剤としてもよい。親水性単量体に対する上記重合開始剤の使用量は、親水性単量体および重合開始剤の組み合わせ等にもよるが、親水性単量体に対して０．００１モル％〜２モル％の範囲内が好ましく、０．０１モル％〜０．５モル％の範囲内がより好ましい。
【００３４】
吸水性樹脂の形状は、特に限定されるものではなく、例えば、球状、顆粒状、鱗片状、扁平状等の粒子状；繊維状；シート状、フィルム状、板状、ブロック状、不定形状；等のあらゆる形状を採用することができる。また、吸水性樹脂は、多孔質であってもよく、連続気泡を有するいわゆるスポンジ状であってもよい。さらに、吸水性樹脂の大きさは、特に限定されるものではなく、いわゆる微粉末状であってもよい。つまり、吸水性樹脂は、変性剤で処理される際に所定の形状並びに大きさを有している必要はなく、その用途等に応じた形状並びに大きさを有していればよい。即ち、本発明にかかる変性方法は、処理すべき吸水性樹脂の形状並びに大きさを問わない。
【００３５】
吸水性樹脂を変性剤で処理する際の処理条件は、変性剤がガス状で存在し得る条件であればよく、特に限定されるものではない。例えば、処理圧力は、減圧、常圧、加圧の何れであってもよい。尚、吸水性樹脂の処理の度合い、例えば、架橋密度や架橋深度を比較的大きくする際には、減圧下での処理よりも常圧下での処理の方が好ましい場合があり、また、常圧下での処理よりも加圧下での処理の方が好ましい場合がある。つまり、処理圧力は、所望する処理の度合いに応じて、適宜設定すればよい。該処理圧力を操作することにより、吸水性樹脂の処理の度合いを簡単に制御することができる。
【００３６】
処理温度は、処理圧力、或いは、吸水性樹脂と変性剤との反応性等にもよるが、室温〜３００℃の範囲が好ましく、１００℃〜２５０℃の範囲がより好ましく、１３０℃〜２３０℃の範囲がさらに好ましい。反応時間は、処理温度、処理圧力、或いは、吸水性樹脂と変性剤との反応性等に応じて設定すればよく、特に限定されるものではないが、数秒〜２時間程度、好ましくは数分〜１時間程度とすれば充分である。尚、吸水性樹脂と変性剤との反応は、水が無い反応系、つまり、いわゆる無水状態であっても進行する。即ち、本発明にかかる変性方法は、処理系に水分が存在しているか否かによる影響を受けない。
【００３７】
処理装置は、吸水性樹脂（以下、重合体と称する）と、ガス状の変性剤（以下、単にガスと称する）とを充分に接触させることができる構成、つまり、固体−気体系の反応を実施することができる構成を備えていればよく、特に限定されるものではない。該処理装置としては、公知の各種反応装置を採用することができ、例えば、（１）重合体を緩やかに移動させながらガスと接触反応させる移動層型反応装置；（２）重合体をガス中に浮遊懸濁させながら、該ガスと接触反応させる流動層型反応装置；（３）重合体を固定層とし、ガスを単相流や、向流、平行流の形式で流動させて接触反応させる固定層型反応装置；（４）槽内の重合体とガスとを攪拌翼によって攪拌しながら接触反応させる攪拌槽型反応装置；（５）重合体をガスの気流によって吹き飛ばしながら、該ガスとの接触反応を進行させる気流型反応装置；等が挙げられる。
【００３８】
移動層型反応装置としては、具体的には、例えば、図１または図２に示すように、重合体を下向きに移動させると共に、ガスを上向きに流動させる向流立型反応装置；図３に示すように、重合体を下向きに移動させると共に、ガスを横向きに流動させる十字流型反応装置；図４または図５に示すように、重合体をベルトコンベアで水平に移動させると共に、ガスを上向きに流動させる移動グレート型反応装置；図６に示すように、装置を回転させることによって重合体とガスとを同方向に移動させるロータリーキルン（回転炉）型反応装置；図７に示すように、装置内に複数の段を設け、重合体を上の段から下の段へ順次移動させると共に、ガスを上向きに流動させる多段炉型反応装置；等が挙げられる。尚、図５に示す移動グレート型反応装置は、重合体がシート状等の場合に特に好適である。
【００３９】
流動層型反応装置としては、具体的には、例えば、図８または図９に示すように、多孔板や金網、パイプ等の内挿物を備えた装置内で、ガスを上向きに流動させることによって重合体を浮遊懸濁させる気固流動層型反応装置；図１０に示すように、ガスを上向きに高速で流動させることによって重合体を浮遊懸濁させる高速流動層型反応装置；図１１に示すように、ガスを上向きに噴射し、該噴流によって重合体を浮遊懸濁させる噴流層型反応装置；等が挙げられる。
【００４０】
攪拌槽型反応装置としては、具体的には、例えば、図１２に示すように、槽内の重合体とガスとを攪拌翼によって攪拌する気固攪拌槽型反応装置；図１３に示すように、槽内に複数の仕切板を設け、攪拌翼によって攪拌しながら重合体およびガスを下の段から上の段へ順次移動させる多段翼槽型反応装置；等が挙げられる。
【００４１】
気流型反応装置としては、具体的には、例えば、図１４に示すように、重合体をガスの気流によって吹き飛ばす気固気流型反応装置；等が挙げられる。
【００４２】
処理装置、つまり、反応装置の構成は、上記例示の構成にのみ限定されるものではない。また、処理装置は、バッチ式（回分式）、連続式の何れの方式を採用していてもよい。例えば、オートクレーブ等の密閉系の反応装置も、処理装置として好適に用いることができる。即ち、本発明にかかる変性方法は、バッチ式、連続式の何れの方式でも好適に実施することができる。そして、吸水性樹脂と、ガス状の変性剤とを処理装置を用いて所定の処理条件下で充分に接触させることにより、該吸水性樹脂を均一に処理することができる。本発明にかかる変性方法は、ガスを用いるので、変性を比較的短時間で充分にかつ確実に行うことができる。
【００４３】
以上のように、本発明にかかる吸水性樹脂の変性方法は、吸水性樹脂をガス状の変性剤で変性する方法である。また、本発明にかかる吸水性樹脂の変性方法は、上記変性剤が架橋剤である方法である。
【００４４】
上記の方法によれば、従来の方法では必要であった溶媒や分散媒が不用となる。従って、従来の方法と比較して、変性の作業工程が簡単化され、かつ、コストが掛からない。また、変性後の吸水性樹脂に変性剤、並びに、溶媒や分散媒が残留することがないので、安全性に優れる。さらに、吸水性樹脂と変性剤とを効率的に反応させることができると共に、変性後、過剰の変性剤を極めて簡単かつ容易に除去・回収することができ、また、回収した変性剤の再利用を容易に図ることができる。
【００４５】
その上、吸水性樹脂の大きさ、形状に関わらず、均一に変性することができる。従って、従来の方法では対応できない形状の吸水性樹脂や、多孔質の吸水性樹脂であっても変性することができる。また、例えば、いわゆる微粉末状の吸水性樹脂であっても変性することができる。即ち、変性すべき吸水性樹脂の形状並びに大きさを問わない。さらに、変性後の表面が破壊される等の物理的ダメージを吸水性樹脂が受けることもない。
【００４６】
そして、変性剤が架橋剤である場合には、吸水性樹脂に架橋処理を施すことができる。また、吸水性樹脂の吸水特性等の諸特性を変性によって向上させることができる。
【００４７】
また、以上のように、本発明にかかる吸水性樹脂の製造方法は、吸水性樹脂とガス状の変性剤とを反応させる方法である。上記の方法によれば、吸水性樹脂とガス状の変性剤とを反応させるので、従来の方法では必要であった溶媒や分散媒が不用となる。従って、従来の方法と比較して、除去工程や乾燥工程等の後処理工程を必要としないので、上記反応の作業工程が簡単化され、かつ、コストが掛からない。また、反応生成物として得られる吸水性樹脂に変性剤、並びに、溶媒や分散媒が残留することがないので、安全性に優れる。さらに、ガス状の変性剤と反応させるので、吸水性樹脂と変性剤とを効率的に反応させることができると共に、反応後、過剰の変性剤を極めて簡単かつ容易に除去・回収することができ、また、回収した変性剤の再利用を容易に図ることができる。これにより、吸水性樹脂を簡単かつ容易に製造することができる。
【００４８】
【実施例】
以下、実施例および比較例により、本発明をさらに詳細に説明するが、本発明はこれらにより何ら限定されるものではない。変性すべき吸水性樹脂（４種類）は、以下の製造方法により製造した。また、変性後の吸水性樹脂の保水量および加圧下の吸水量は、以下の方法で測定した。尚、以下の説明においては、特に断りの無い限り、「部」は「重量部」を示す。
【００４９】
（１）変性すべき吸水性樹脂の製造方法
以下の（ａ）〜（ｄ）に示す製造方法によって、４種類の変性すべき吸水性樹脂を製造した。
【００５０】
（ａ） いわゆる窒素シール並びに除熱・加熱を行うことが可能な反応容器に、中和率が７０モル％であるアクリル酸ナトリウム３０重量％水溶液５，０００部を仕込んだ。つまり、反応容器に、アクリル酸３７１部、アクリル酸ナトリウム１，１２９部、および水３，５００部からなる水溶液を仕込んだ。
【００５１】
次に、該水溶液に、内部架橋剤であるポリエチレングリコールジアクリレート６．７６部を溶解し、水溶液中に窒素ガスを３０分間吹き込む（バブリング）ことにより、溶存酸素を追い出した。次いで、攪拌しながら、上記水溶液に、ラジカル重合開始剤である過硫酸カリウム１．８部、並びに、還元剤であるＬ−アスコルビン酸０．０９部を添加した。その後、該水溶液を窒素気流下、重合開始温度３０℃で重合させた。
【００５２】
重合を開始してから約５分後に、反応系内は７０℃に達した。その後、加熱して反応系内の温度を約７０℃に維持しながら２時間攪拌し、重合反応を完結させた。これにより、ポリアクリル酸ナトリウムからなる含水ゲル状架橋重合体を得た。
【００５３】
得られた含水ゲル状架橋重合体を取り出し、ミートチョッパーを用いて細分した後、細分化物を６０メッシュの金網上に広げ、熱風乾燥機を用いて１５０℃で１３５分間、熱風乾燥した。次いで、乾燥物をコーヒーミルを用いて粉砕し、さらに２０メッシュ（目の大きさ８４０μｍ）の金網で分級することにより、平均粒子径が約４００μｍの粒子状の架橋重合体、即ち、吸水性樹脂（以下、吸水性樹脂（ａ）と記す）を得た。上記の吸水性樹脂（ａ）は、湿気や粘り気がなく、いわゆる「さらさら」の状態であった。
【００５４】
（ｂ） いわゆる窒素シール並びに除熱・加熱を行うことが可能な反応容器に、アクリル酸１，０００部、内部架橋剤であるテトラアリロキシエタン５部、および水３，５００部を仕込み、混合・溶解させて水溶液とした。次に、該水溶液中に窒素ガスを３０分間吹き込む（バブリング）ことにより、溶存酸素を追い出した。次いで、攪拌しながら、上記水溶液に、ラジカル重合開始剤である過酸化水素６部、および２，２’−アゾビス（２−アミジノプロパン）二塩酸塩１部、並びに、Ｌ−アスコルビン酸０．３部を添加した。その後、該水溶液を窒素気流下、重合開始温度２５℃で重合させた。そして、反応系内の温度をほぼ一定に維持しながら約２時間攪拌し、重合反応を完結させた。これにより、ポリアクリル酸からなる含水ゲル状架橋重合体を得た。
【００５５】
次に、得られた含水ゲル状架橋重合体を取り出し、細分した後、細分化物に水酸化ナトリウム４８重量％水溶液８６８部を加えて均一に混練することにより、該重合体中のカルボキシル基のうちの約７５モル％を中和した。つまり、該重合体中のカルボキシル基のうちの約７５モル％をナトリウム塩にした。
【００５６】
中和後の含水ゲル状架橋重合体を取り出し、ドラムドライヤーを用いて１５０℃で乾燥した。次いで、乾燥物をコーヒーミルを用いて粉砕し、さらに２０メッシュの金網で分級することにより、平均粒子径が約４１０μｍの粒子状の架橋重合体、即ち、吸水性樹脂（以下、吸水性樹脂（ｂ）と記す）を得た。上記の吸水性樹脂（ｂ）は、湿気や粘り気がなく、いわゆる「さらさら」の状態であった。
【００５７】
（ｃ） いわゆる窒素シール並びに除熱・加熱を行うことが可能な反応容器に、中和率が８０モル％であるアクリル酸ナトリウム３５重量％水溶液５，０００部を仕込んだ。つまり、反応容器に、アクリル酸２８１部、アクリル酸ナトリウム１，４６９部、および水３，２５０部からなる水溶液を仕込んだ。
【００５８】
次に、該水溶液に、内部架橋剤であるＮ，Ｎ’−メチレンビスアクリルアミド２．２部を溶解し、水溶液中に窒素ガスを３０分間吹き込む（バブリング）ことにより、溶存酸素を追い出した。次いで、攪拌しながら、上記水溶液に、２，２’−アゾビス（２−アミジノプロパン）二塩酸塩４部を添加した。添加してから５分間攪拌を行ったところ、水溶液は白濁し、反応系内に２，２’−アゾビス（２−アミジノプロパン）二アクリル酸塩の白色微粒子の生成が認められた。
【００５９】
その後、直ちに、攪拌しながら、上記水溶液に、過硫酸カリウム１．８部およびＬ−アスコルビン酸０．０９部を添加した。その後、該水溶液を窒素気流下、重合開始温度２５℃で重合させた。
【００６０】
重合を開始してから約５分後に、反応系内は８０℃に達した。その後、加熱して反応系内の温度を約７５℃に維持しながら２時間攪拌し、重合反応を完結させた。これにより、ポリアクリル酸ナトリウムからなる含水ゲル状架橋重合体を得た。
【００６１】
得られた含水ゲル状架橋重合体を取り出し、ミートチョッパーを用いて細分した後、細分化物を６０メッシュの金網上に広げ、熱風乾燥機を用いて１５０℃で１２５分間、熱風乾燥した。次いで、乾燥物をコーヒーミルを用いて粉砕し、さらに２０メッシュの金網で分級することにより、平均粒子径が約４００μｍの粒子状の架橋重合体、即ち、吸水性樹脂（以下、吸水性樹脂（ｃ）と記す）を得た。尚、２，２’−アゾビス（２−アミジノプロパン）二アクリル酸塩は発泡剤としての性質を備えているので、上記の吸水性樹脂（ｃ）は多孔質となっており、その平均孔径は５０μｍであった。また、吸水性樹脂（ｃ）は、湿気や粘り気がなく、いわゆる「さらさら」の状態であった。
【００６２】
（ｄ） 上記（ｂ）の製造方法によって得られた吸水性樹脂（ｂ）を、１００メッシュ（目の大きさ１５０μｍ）の金網でさらに分級することにより、９３メッシュ通過物を分取した。これにより、吸水性樹脂（以下、吸水性樹脂（ｄ）と記す）を得た。上記の吸水性樹脂（ｄ）は、湿気や粘り気がなく、いわゆる「さらさら」の状態であった。
【００６３】
（２）保水量
吸水性樹脂０．２ｇを不織布製のティーバッグ式袋（６ｃｍ×６ｃｍ）に均一に入れ、開口部をヒートシールした後、０．９重量％塩化ナトリウム水溶液（生理食塩水）中に浸漬した。３０分経過後にティーバッグ式袋を引き上げ、遠心分離機を用いて２５０Ｇで３分間水切りを行った後、該袋の重量Ｗ₁ （ｇ）を測定した。また、同様の操作を吸水性樹脂を用いないで行い、そのときの重量Ｗ₀ （ｇ）を測定した。そして、これら重量Ｗ₁ ・Ｗ₀ から、次式、
保水量(g/g) ＝（重量Ｗ₁ (g)−重量Ｗ₀ (g)）／吸水性樹脂の重量(g)
に従って保水量（ｇ／ｇ）を算出した。
【００６４】
（３）加圧下の吸水量
先ず、加圧下の吸水量の測定に用いる測定装置について、図１５を参照しながら、以下に簡単に説明する。
【００６５】
図１５に示すように、測定装置は、天秤１と、この天秤１上に載置された所定容量の容器２と、外気吸入パイプ３と、シリコーン樹脂からなる導管４と、ガラスフィルタ６と、このガラスフィルタ６上に載置された測定部５とからなっている。上記の容器２は、その頂部に開口部２ａを、その側面部に開口部２ｂをそれぞれ有しており、開口部２ａに外気吸入パイプ３が嵌入される一方、開口部２ｂに導管４が取り付けられている。また、容器２には、所定量の生理食塩水（０．９重量％塩化ナトリウム水溶液）１２が入っている。外気吸入パイプ３の下端部は、生理食塩水１２中に没している。外気吸入パイプ３は、容器２内の圧力をほぼ大気圧に保つために設けられている。上記のガラスフィルタ６は、直径５５ｍｍに形成されている。そして、容器２およびガラスフィルタ６は、導管４によって互いに連通している。また、ガラスフィルタ６は、容器２に対する位置および高さが固定されている。
【００６６】
上記の測定部５は、濾紙７と、支持円筒９と、この支持円筒９の底部に貼着された金網１０と、重り１１とを有している。そして、測定部５は、ガラスフィルタ６上に、濾紙７、支持円筒９（つまり金網１０）がこの順に載置されると共に、支持円筒９内部、即ち、金網１０上に重り１１が載置されてなっている。金網１０は、ステンレスからなり、４００メッシュ（目の大きさ３８μｍ）に形成されている。そして、測定時には、金網１０上に、所定量および所定粒子径の吸水性樹脂１５が均一に撒布されるようになっている。また、金網１０の上面、つまり、金網１０と吸水性樹脂１５との接触面の高さは、外気吸入パイプ３の下端面３ａの高さと等しくなるように設定されている。重り１１は、金網１０、即ち、吸水性樹脂１５に対して、５０ｇ／ｃｍ² の荷重を均一に加えることができるように、その重量が調整されている。
【００６７】
上記構成の測定装置を用いて加圧下の吸水量を測定した。測定方法について以下に説明する。
【００６８】
先ず、容器２に所定量の生理食塩水１２を入れる；容器２に外気吸入パイプ３を嵌入する；等の所定の準備動作を行った。次に、ガラスフィルタ６上に濾紙７を載置した。また、この載置動作に並行して、支持円筒９内部、即ち、金網１０上に、吸水性樹脂０．９ｇを均一に撒布し、この吸水性樹脂１５上に重り１１を載置した。
【００６９】
次いで、濾紙７上に、金網１０、つまり、吸水性樹脂１５および重り１１を載置した上記支持円筒９を、その中心部がガラスフィルタ６の中心部に一致するように載置した。
【００７０】
そして、濾紙７上に支持円筒９を載置した時点から、６０分間にわたって経時的に、該吸水性樹脂１５が吸収した生理食塩水１２の重量Ｗ₂ （ｇ）を、天秤１を用いて測定した。また、同様の操作を吸水性樹脂１５を用いないで行い、そのときの重量、つまり、吸水性樹脂１５以外の例えば濾紙７等が吸収した生理食塩水１２の重量を、天秤１を用いて測定し、ブランク重量Ｗ₃ （ｇ）とした。そして、これら重量Ｗ₂ ・Ｗ₃ から、次式、
加圧下の吸水量(g/g) ＝（重量Ｗ₂ (g)−重量Ｗ₃ (g)）／吸水性樹脂の重量(g)
に従って加圧下の吸水量（ｇ／ｇ）を算出した。
【００７１】
〔実施例１〕
攪拌翼を備えた容量１Ｌのオートクレーブ（処理装置）に、吸水性樹脂（ａ）１００部を仕込み、窒素置換した後、窒素ガスで反応系内の圧力を５Ｋｇｆ／ｃｍ² に設定した。次に、攪拌しながら反応系内を１８０℃に昇温し、温度が１８０℃となった時点で、架橋剤（変性剤）としてのエチレンオキサイド３部を反応系内に導入した。このとき、反応系内の圧力は７Ｋｇｆ／ｃｍ² 〜８Ｋｇｆ／ｃｍ² であり、エチレンオキサイドはガス状となっていた。次いで、反応系内の温度を１８０℃に維持しながら１０分間攪拌することにより、架橋処理（変性）を行った。
【００７２】
処理終了後、オートクレーブを開放し、架橋処理が施された吸水性樹脂（以下、架橋吸水性樹脂と記す）を取り出した。該架橋吸水性樹脂は、粒子状であり、湿気や粘り気がなく、いわゆる「さらさら」の状態であった。また、ダマの生成も認められなかった。
【００７３】
上記吸水性樹脂（ａ）表面、並びに、架橋吸水性樹脂表面の赤外吸収スペクトルを、ＦＴ−ＩＲ（フーリエ変換赤外分光法）で測定した。測定装置として、「日本バイオラット株式会社（Nippon Bio-Rad Laboratories K.K.）製 ＦＴＳ−４５」を用いた。また、測定方法（サンプリング法）として、拡散反射（ＤＲ）分光法を採用した。吸水性樹脂（ａ）表面の赤外吸収スペクトルのチャートを図１６に示す。また、架橋吸水性樹脂表面の赤外吸収スペクトルのチャートを図１７に示す。
【００７４】
図１６のチャートにおいては、吸水性樹脂（ａ）表面に存在するカルボキシル基の吸収ピークが、１７２８．３ｃｍ^-1に現れている。これに対し、図１７のチャートにおいては、上記の吸収ピークが、１７５３．８ｃｍ^-1にシフトした状態で現れている。このことから、架橋処理が施されることによって、吸水性樹脂（ａ）表面に存在するカルボキシル基がエチレンオキサイドとエステルを形成したことが判る。つまり、吸水性樹脂（ａ）表面がエチレンオキサイドで変性されたことが判る。
【００７５】
得られた架橋吸水性樹脂の保水量および加圧下の吸水量を上記の方法により測定した。その結果、架橋吸水性樹脂の保水量は３４ｇ／ｇ、加圧下の吸水量は２１ｇ／ｇであった。また、吸水性樹脂（ａ）の保水量および加圧下の吸水量を上記の方法に準じて測定した。その結果、吸水性樹脂（ａ）の保水量は４３ｇ／ｇ、加圧下の吸水量は７ｇ／ｇであった。上記の結果を表２に示す。
【００７６】
〔実施例２〕
攪拌翼を備えた容量１Ｌのオートクレーブに、吸水性樹脂（ｂ）１００部を仕込み、窒素置換した後、窒素ガスで反応系内の圧力を５Ｋｇｆ／ｃｍ² に設定した。次に、攪拌しながら反応系内を１８０℃に昇温し、温度が１８０℃となった時点で、エチレンオキサイド３部を反応系内に導入した。このとき、反応系内の圧力は７Ｋｇｆ／ｃｍ² 〜８Ｋｇｆ／ｃｍ² であり、エチレンオキサイドはガス状となっていた。次いで、反応系内の温度を１８０℃に維持しながら３０分間攪拌することにより、架橋処理を行った。
【００７７】
処理終了後、オートクレーブを開放し、架橋処理が施された吸水性樹脂（以下、架橋吸水性樹脂と記す）を取り出した。該架橋吸水性樹脂は、粒子状であり、湿気や粘り気がなく、いわゆる「さらさら」の状態であった。また、ダマの生成も認められなかった。
【００７８】
得られた架橋吸水性樹脂の保水量は２８ｇ／ｇ、加圧下の吸水量は２１ｇ／ｇであった。また、吸水性樹脂（ｂ）の保水量および加圧下の吸水量を上記の方法に準じて測定した。その結果、吸水性樹脂（ｂ）の保水量は３２ｇ／ｇ、加圧下の吸水量は８ｇ／ｇであった。上記の結果を表２に示す。
【００７９】
〔実施例３〕
攪拌翼を備えた容量１Ｌのオートクレーブに、吸水性樹脂（ｃ）１００部を仕込み、窒素置換した後、窒素ガスで反応系内の圧力を５Ｋｇｆ／ｃｍ² に設定した。次に、攪拌しながら反応系内を１８０℃に昇温し、温度が１８０℃となった時点で、エチレンオキサイド３部を反応系内に導入した。このとき、反応系内の圧力は７Ｋｇｆ／ｃｍ² 〜８Ｋｇｆ／ｃｍ² であり、エチレンオキサイドはガス状となっていた。次いで、反応系内の温度を１８０℃に維持しながら６０分間攪拌することにより、架橋処理を行った。
【００８０】
処理終了後、オートクレーブを開放し、架橋処理が施された吸水性樹脂（以下、架橋吸水性樹脂と記す）を取り出した。該架橋吸水性樹脂は、粒子状であり、湿気や粘り気がなく、いわゆる「さらさら」の状態であった。また、ダマの生成も認められなかった。
【００８１】
得られた架橋吸水性樹脂の保水量は２９ｇ／ｇ、加圧下の吸水量は２２ｇ／ｇであった。また、吸水性樹脂（ｃ）の保水量および加圧下の吸水量を上記の方法に準じて測定した。その結果、吸水性樹脂（ｃ）の保水量は３３ｇ／ｇ、加圧下の吸水量は８ｇ／ｇであった。上記の結果を表２に示す。
【００８２】
〔実施例４〕
攪拌翼を備えた容量１Ｌのオートクレーブに、吸水性樹脂（ａ）１００部を仕込み、窒素置換した後、窒素ガスで反応系内の圧力を４Ｋｇｆ／ｃｍ² に設定した。次に、攪拌しながら反応系内を１５０℃に昇温し、温度が１５０℃となった時点で、エチレンオキサイド４．８部を反応系内に導入した。このとき、反応系内の圧力は５Ｋｇｆ／ｃｍ² であり、エチレンオキサイドはガス状となっていた。次いで、反応系内の温度を１５０℃に維持しながら４５分間攪拌することにより、架橋処理を行った。
【００８３】
処理終了後、オートクレーブを開放し、架橋処理が施された吸水性樹脂（以下、架橋吸水性樹脂と記す）を取り出した。該架橋吸水性樹脂は、粒子状であり、湿気や粘り気がなく、いわゆる「さらさら」の状態であった。また、ダマの生成も認められなかった。得られた架橋吸水性樹脂の保水量は３０ｇ／ｇ、加圧下の吸水量は１８ｇ／ｇであった。上記の結果を表２に示す。
【００８４】
〔実施例５〕
実施例３における吸水性樹脂（ｃ）１００部の代わりに、１８０℃で所定時間、予め加熱乾燥処理を施した吸水性樹脂（ａ）１００部を用いた以外は、実施例３と同様の架橋処理を行った。
【００８５】
処理終了後、オートクレーブを開放し、架橋処理が施された吸水性樹脂（以下、架橋吸水性樹脂と記す）を取り出した。該架橋吸水性樹脂は、粒子状であり、湿気や粘り気がなく、いわゆる「さらさら」の状態であった。また、ダマの生成も認められなかった。得られた架橋吸水性樹脂の保水量は２９ｇ／ｇ、加圧下の吸水量は２２ｇ／ｇであった。上記の結果を表２に示す。
【００８６】
上記の結果から明らかなように、本発明にかかる変性方法は、変性前の吸水性樹脂に水分が含まれているか否かによる影響を受けないことが判る。つまり、変性すべき吸水性樹脂が水分を含んでいても含んでいなくても、変性の結果に影響を与えないことが判る。
【００８７】
〔実施例６〕
実施例３における吸水性樹脂（ｃ）１００部の代わりに、吸水性樹脂（ｄ）１００部を用いた以外は、実施例３と同様の架橋処理を行った。
【００８８】
処理終了後、オートクレーブを開放し、架橋処理が施された吸水性樹脂（以下、架橋吸水性樹脂と記す）を取り出した。該架橋吸水性樹脂は、粒子状であり、湿気や粘り気がなく、いわゆる「さらさら」の状態であった。また、ダマの生成も認められなかった。
【００８９】
得られた架橋吸水性樹脂の保水量は２３ｇ／ｇ、加圧下の吸水量は１１ｇ／ｇであった。また、吸水性樹脂（ｄ）の保水量および加圧下の吸水量を上記の方法に準じて測定した。その結果、吸水性樹脂（ｄ）の保水量は２７ｇ／ｇ、加圧下の吸水量は６ｇ／ｇであった。上記の結果を表２に示す。
【００９０】
〔実施例７〕
攪拌翼を備えた容量１Ｌのオートクレーブに、吸水性樹脂（ａ）１００部を仕込み、窒素置換した後、窒素ガスで反応系内の圧力を５Ｋｇｆ／ｃｍ² に設定した。次に、攪拌しながら反応系内を２００℃に昇温し、温度が２００℃となった時点で、エチレンオキサイド３部を反応系内に導入した。このとき、反応系内の圧力は７Ｋｇｆ／ｃｍ² 〜８Ｋｇｆ／ｃｍ² であり、エチレンオキサイドはガス状となっていた。次いで、反応系内の温度を２００℃に維持しながら１０分間攪拌することにより、架橋処理を行った。
【００９１】
処理終了後、オートクレーブを開放し、架橋処理が施された吸水性樹脂（以下、架橋吸水性樹脂と記す）を取り出した。該架橋吸水性樹脂は、粒子状であり、湿気や粘り気がなく、いわゆる「さらさら」の状態であった。また、ダマの生成も認められなかった。得られた架橋吸水性樹脂の保水量は３５ｇ／ｇ、加圧下の吸水量は１９ｇ／ｇであった。上記の結果を表２に示す。
【００９２】
〔実施例８〕
攪拌翼を備えた容量１Ｌのオートクレーブに、１８０℃で所定時間、予め加熱乾燥処理を施した吸水性樹脂（ａ）１００部を仕込み、窒素置換した後、窒素ガスで反応系内の圧力を５Ｋｇｆ／ｃｍ² に設定した。次に、攪拌しながら反応系内を２００℃に昇温し、温度が２００℃となった時点で、エチレンオキサイド３部を反応系内に導入した。このとき、反応系内の圧力は７Ｋｇｆ／ｃｍ² 〜８Ｋｇｆ／ｃｍ² であり、エチレンオキサイドはガス状となっていた。次いで、反応系内の温度を２００℃に維持しながら６０分間攪拌することにより、架橋処理を行った。
【００９３】
処理終了後、オートクレーブを開放し、架橋処理が施された吸水性樹脂（以下、架橋吸水性樹脂と記す）を取り出した。該架橋吸水性樹脂は、粒子状であり、湿気や粘り気がなく、いわゆる「さらさら」の状態であった。また、ダマの生成も認められなかった。得られた架橋吸水性樹脂の保水量は３３ｇ／ｇ、加圧下の吸水量は２２ｇ／ｇであった。上記の結果を表２に示す。
【００９４】
〔実施例９〕
攪拌翼を備えた容量１Ｌのオートクレーブに、吸水性樹脂（ａ）１００部を仕込み、窒素置換した後、窒素ガスで反応系内の圧力を５Ｋｇｆ／ｃｍ² に設定した。次に、攪拌しながら反応系内を２２０℃に昇温し、温度が２２０℃となった時点で、架橋剤（変性剤）としてのプロピレンオキサイド３部を反応系内に導入した。このとき、反応系内の圧力は７Ｋｇｆ／ｃｍ² 〜８Ｋｇｆ／ｃｍ² であり、プロピレンオキサイドはガス状となっていた。次いで、反応系内の温度を２２０℃に維持しながら６０分間攪拌することにより、架橋処理（変性）を行った。
【００９５】
処理終了後、オートクレーブを開放し、架橋処理が施された吸水性樹脂（以下、架橋吸水性樹脂と記す）を取り出した。該架橋吸水性樹脂は、粒子状であり、湿気や粘り気がなく、いわゆる「さらさら」の状態であった。また、ダマの生成も認められなかった。得られた吸水性樹脂の保水量は２９ｇ／ｇ、加圧下の吸水量は１９ｇ／ｇであった。上記の結果を表２に示す。
【００９６】
〔実施例１０〕
攪拌翼を備えた容量１Ｌのオートクレーブに、１８０℃で所定時間、予め加熱乾燥処理を施した吸水性樹脂（ａ）１００部を仕込み、窒素置換した後、窒素ガスで反応系内の圧力を５Ｋｇｆ／ｃｍ² に設定した。次に、攪拌しながら反応系内を２４０℃に昇温し、温度が２４０℃となった時点で、エチレンオキサイド３部を反応系内に導入した。このとき、反応系内の圧力は８Ｋｇｆ／ｃｍ² 〜９Ｋｇｆ／ｃｍ² であり、エチレンオキサイドはガス状となっていた。次いで、反応系内の温度を２４０℃に維持しながら３分間攪拌することにより、架橋処理を行った。
【００９７】
処理終了後、オートクレーブを開放し、架橋処理が施された吸水性樹脂（以下、架橋吸水性樹脂と記す）を取り出した。該架橋吸水性樹脂は、粒子状であり、湿気や粘り気がなく、いわゆる「さらさら」の状態であった。また、ダマの生成も認められなかった。得られた架橋吸水性樹脂の保水量は３０ｇ／ｇ、加圧下の吸水量は２２ｇ／ｇであった。上記の結果を表２に示す。
【００９８】
〔実施例１１〕
架橋剤（変性剤）としてのエチレングリコールジグリシジルエーテル１００部をステンレス製の容器に仕込んだ後、該容器の上部開口部を２００メッシュのステンレス製の金網で覆った。次に、該金網上に吸水性樹脂（ａ）５０部を均一に撒布した。
【００９９】
その後、容器を加熱することによってエチレングリコールジグリシジルエーテルを気化させ、ガス状のエチレングリコールジグリシジルエーテルを吸水性樹脂（ａ）に１０分間、接触させることにより、架橋処理（変性）を行った。
【０１００】
処理終了後、架橋処理が施された吸水性樹脂（以下、架橋吸水性樹脂と記す）を回収した。該架橋吸水性樹脂は、粒子状であり、湿気や粘り気がなく、いわゆる「さらさら」の状態であった。また、ダマの生成も認められなかった。得られた架橋吸水性樹脂の保水量は３６ｇ／ｇ、加圧下の吸水量は１１ｇ／ｇであった。上記の結果を表２に示す。
【０１０１】
〔比較例１〕
攪拌翼を備えた容量１Ｌのオートクレーブに、吸水性樹脂（ａ）１００部を仕込み、窒素置換した後、窒素ガスで反応系内の圧力を７Ｋｇｆ／ｃｍ² 〜８Ｋｇｆ／ｃｍ² に設定した。次に、攪拌しながら反応系内を１８０℃に昇温し、温度を１８０℃に維持しながら６０分間攪拌した。つまり、架橋剤としてのエチレンオキサイドを用いないで処理を行った。
【０１０２】
処理終了後、オートクレーブを開放し、処理が施された吸水性樹脂（以下、架橋吸水性樹脂と記す）としての比較用架橋吸水性樹脂を取り出した。該比較用架橋吸水性樹脂の保水量は４０ｇ／ｇ、加圧下の吸水量は８ｇ／ｇであり、加圧下の吸水量は向上されていなかった。上記の結果を表２に示す。
【０１０３】
〔比較例２〕
攪拌翼を備えた容量１Ｌのオートクレーブに、吸水性樹脂（ａ）１００部を仕込んだ後、攪拌しながら反応系内を１８０℃に昇温し、温度を１８０℃に維持しながら６０分間攪拌した。つまり、架橋剤としてのエチレンオキサイドを用いず、かつ、窒素ガスで反応系内を置換並びに加圧しないで処理を行った。
【０１０４】
処理終了後、オートクレーブを開放し、処理が施された吸水性樹脂（以下、架橋吸水性樹脂と記す）としての比較用架橋吸水性樹脂を取り出した。該比較用架橋吸水性樹脂の保水量は４２ｇ／ｇ、加圧下の吸水量は７ｇ／ｇであり、加圧下の吸水量は向上されていなかった。上記の結果を表２に示す。
【０１０５】
〔比較例３〕
流動乾燥型装置を用いて吸水性樹脂（ｄ）１００部を流動させながら、該吸水性樹脂（ｄ）に、加圧式スプレーノズルを用いて架橋剤としてのエチレングリコール３重量％水溶液１０部を断続的に噴霧することにより、両者を混合した。しかしながら、上記の混合は不均一となってしまい、多量のダマが生成した。
【０１０６】
上記の混合物を１８０℃に昇温し、温度を１８０℃に維持しながら６０分間加熱することにより、処理を行った。処理終了後、該混合物を２０メッシュの金網で分級することにより、通過物を分取した。これにより、処理が施された吸水性樹脂（以下、架橋吸水性樹脂と記す）としての比較用架橋吸水性樹脂を得た。
【０１０７】
上記の比較用架橋吸水性樹脂には、多量のダマの生成が認められた。得られた比較用架橋吸水性樹脂の保水量は２６ｇ／ｇ、加圧下の吸水量は６ｇ／ｇであり、吸水性樹脂（ｄ）とエチレングリコール３重量％水溶液との混合が不均一であったため、加圧下の吸水量は向上されていなかった。つまり、実施例６の結果と比較して、加圧下の吸水量が著しく劣ることが判った。上記の結果を表２に示す。
【０１０８】
【表２】

【０１０９】
上記実施例１〜１１の結果から明らかなように、吸水性樹脂に架橋処理を施すことにより、加圧下の吸水量が向上されることが判る。また、比較例１〜３の結果との比較から明らかなように、本発明にかかる変性方法は、吸水性樹脂と架橋剤（変性剤）とを効率的に反応させることができることが判る。さらに、本発明にかかる製造方法により、吸水性樹脂を簡単かつ容易に製造することができることが判る。
【０１１０】
【発明の効果】
本発明の請求項１記載の吸水性樹脂の変性方法は、以上のように、アクリル酸またはその塩を主成分とする単量体組成物を重合することにより得られる内部に架橋構造を有する吸水性樹脂を、ガス状の変性剤と接触させることにより変性する方法である。本発明の請求項２記載の吸水性樹脂の変性方法は、以上のように、上記変性剤は、減圧、常圧または加圧下で、変性剤の沸点以上の温度で吸水性樹脂と接触する方法である。本発明の請求項３記載の吸水性樹脂の変性方法は、以上のように、上記変性剤は、吸水性樹脂が有する反応性基と反応する架橋剤である方法である。本発明の請求項４記載の吸水性樹脂の変性方法は、以上のように、上記吸水性樹脂は、内部架橋剤の存在下で、単量体組成物を重合することにより得られ、上記単量体組成物は、親水性単量体を含み、上記内部架橋剤は、上記親水性単量体に対して０．００５〜３モル％の範囲内である方法である。本発明の請求項５記載の吸水性樹脂の変性方法は、以上のように、吸水性樹脂を変性剤と接触させる温度が、１００℃〜２５０℃の範囲である方法である。本発明の請求項６記載の吸水性樹脂の変性方法は、以上のように、吸水性樹脂と接触した後、変性剤は液化または固化する方法である。
【０１１１】
これにより、従来の方法では必要であった溶媒や分散媒が不用となる。従って、従来の方法と比較して、変性の作業工程が簡単化され、かつ、コストが掛からない。また、変性後の吸水性樹脂に変性剤、並びに、溶媒や分散媒が残留することがないので、安全性に優れる。さらに、吸水性樹脂と変性剤とを効率的に反応させることができると共に、変性後、過剰の変性剤を極めて簡単かつ容易に除去・回収することができ、また、回収した変性剤の再利用を容易に図ることができるという種々の効果を奏する。
【０１１２】
その上、吸水性樹脂の大きさ、形状に関わらず、均一に変性することができる。従って、従来の方法では対応できない形状の吸水性樹脂や、多孔質の吸水性樹脂であっても変性することができる。また、例えば、いわゆる微粉末状の吸水性樹脂であっても変性することができる。即ち、変性すべき吸水性樹脂の形状並びに大きさを問わない。さらに、変性後の表面が破壊される等の物理的ダメージを吸水性樹脂が受けることもないという種々の効果も併せて奏する。
【０１１３】
そして、変性剤が架橋剤である場合には、吸水性樹脂に架橋処理を施すことができる。また、吸水性樹脂の吸水特性等の諸特性を変性によって向上させることができるという効果を奏する。
【０１１４】
本発明の請求項７記載の吸水性樹脂の製造方法は、以上のように、上記本発明にかかる変性方法により、吸水性樹脂とガス状の変性剤とを反応させる方法である。上記の方法によれば、吸水性樹脂とガス状の変性剤とを反応させるので、従来の方法では必要であった溶媒や分散媒が不用となる。従って、従来の方法と比較して、除去工程や乾燥工程等の後処理工程を必要としないので、上記反応の作業工程が簡単化され、かつ、コストが掛からない。また、反応生成物として得られる吸水性樹脂に変性剤、並びに、溶媒や分散媒が残留することがないので、安全性に優れる。さらに、ガス状の変性剤と反応させるので、吸水性樹脂と変性剤とを効率的に反応させることができると共に、反応後、過剰の変性剤を極めて簡単かつ容易に除去・回収することができ、また、回収した変性剤の再利用を容易に図ることができる。これにより、吸水性樹脂を簡単かつ容易に製造することができるという効果を奏する。
【図面の簡単な説明】
【図１】 本発明にかかる変性方法に好適に用いられる反応装置の概略の構成を示す説明図である。
【図２】 本発明にかかる変性方法に好適に用いられる他の反応装置の概略の構成を示す説明図である。
【図３】 本発明にかかる変性方法に好適に用いられるさらに他の反応装置の概略の構成を示す説明図である。
【図４】 本発明にかかる変性方法に好適に用いられるさらに他の反応装置の概略の構成を示す説明図である。
【図５】 本発明にかかる変性方法に好適に用いられるさらに他の反応装置の概略の構成を示す説明図である。
【図６】 本発明にかかる変性方法に好適に用いられるさらに他の反応装置の概略の構成を示す説明図である。
【図７】 本発明にかかる変性方法に好適に用いられるさらに他の反応装置の概略の構成を示す説明図である。
【図８】 本発明にかかる変性方法に好適に用いられるさらに他の反応装置の概略の構成を示す説明図である。
【図９】 本発明にかかる変性方法に好適に用いられるさらに他の反応装置の概略の構成を示す説明図である。
【図１０】 本発明にかかる変性方法に好適に用いられるさらに他の反応装置の概略の構成を示す説明図である。
【図１１】 本発明にかかる変性方法に好適に用いられるさらに他の反応装置の概略の構成を示す説明図である。
【図１２】 本発明にかかる変性方法に好適に用いられるさらに他の反応装置の概略の構成を示す説明図である。
【図１３】 本発明にかかる変性方法に好適に用いられるさらに他の反応装置の概略の構成を示す説明図である。
【図１４】 本発明にかかる変性方法に好適に用いられるさらに他の反応装置の概略の構成を示す説明図である。
【図１５】 本発明にかかる変性方法によって変性された吸水性樹脂が示す性能の一つである加圧下の吸水量の測定に用いる測定装置の概略の断面図である。
【図１６】 本発明の一実施例において用いた吸水性樹脂（ａ）表面の赤外吸収スペクトルのチャートである。
【図１７】 本発明の一実施例において得られた架橋吸水性樹脂表面の赤外吸収スペクトルのチャートである。
【符号の説明】
１ 天秤
２ 容器
３ 外気吸入パイプ
４ 導管
５ 測定部
６ ガラスフィルタ
７ 濾紙
９ 支持円筒
１０ 金網
１１ 重り
１２ 生理食塩水
１５ 吸水性樹脂[0001]
BACKGROUND OF THE INVENTION
In the present invention, for example, a water-absorbent resin is subjected to a crosslinking treatment, etc. Water absorbent resin A denaturing method to denature, and Water absorbent resin It is related with the manufacturing method.
[0002]
[Prior art]
Conventionally, in a water absorbent resin which is a kind of hydrophilic polymer, in order to improve various characteristics such as water absorption characteristics, a crosslinking treatment (secondary crosslinking) is performed using a crosslinking agent (modifier) on the water absorbent resin. Processing) is performed. As a method for introducing a secondary cross-linked structure into the water absorbent resin, a crosslinking agent or a swelling liquid in which the water absorbent resin is swollen using a solvent, or a dispersion liquid in which the water absorbent resin is dispersed using a dispersion medium are used. A method of reacting the water absorbent resin and the crosslinking agent in a so-called solid-liquid system by adding and mixing the solution is employed. In addition, as said solvent and a dispersion medium, hydrophilic compounds, such as water and alcohol, are used, for example.
[0003]
[Problems to be solved by the invention]
However, the conventional method has various problems as described below. That is, since a solvent or a dispersion medium is used when the water-absorbing resin and the crosslinking agent are reacted, after the reaction, a post-treatment process such as a removal process or a drying process for removing the solvent or the dispersion medium is necessary. For this reason, the work process of introducing the secondary cross-linked structure into the water-absorbent resin is complicated. Moreover, since there exists a possibility that a crosslinking agent, a solvent, and a dispersion medium may remain in the water-absorbent resin after the reaction, it may be inferior in safety. Furthermore, it is difficult to remove and recover the excess crosslinking agent after the reaction.
[0004]
In addition, for example, when the water-absorbing resin is in a so-called fine powder form, mixing the water-absorbing resin with a solvent or a dispersion medium generates lumps, and the water-absorbing resin swells or disperses sufficiently and uniformly. I can't. Therefore, depending on the size and shape of the water absorbent resin, it is not possible to uniformly introduce the secondary cross-linked structure into the water absorbent resin. In addition, in order to swell or disperse the water-absorbent resin sufficiently and uniformly, the swelling liquid or the dispersion liquid must be stirred relatively vigorously, so that physical damage such as destruction of the surface after the reaction is absorbed. Resin is easy to receive. Note that “dama” indicates a state in which particles are aggregated to form a lump.
[0005]
Further, when the degree of cross-linking treatment of the water-absorbent resin, for example, the cross-linking density and the cross-linking depth is relatively large, a relatively large amount of solvent or dispersion medium must be used. It cannot be reacted efficiently. Further, when a relatively large amount of solvent or dispersion medium is used, lumps are easily generated and the energy cost of the post-treatment process increases.
[0006]
Therefore, in the above conventional method, In the reaction between the water absorbent resin and the crosslinking agent, The various problems described above are invited. Therefore, a novel that can solve the above various problems Water absorbent resin The denaturation method is envy. That is, the present invention has been made in view of the above-described conventional problems, and the object thereof is a novel that does not cause the above various problems. Water absorbent resin It is to provide a modification method. Another object of the present invention is to Water absorbent resin It is in providing the manufacturing method of.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, the inventors of the present application Water absorbent resin An extensive study was made on the modification method. As a result, the modifier is made gaseous and the gaseous modifier is used. Water absorbent resin Without inviting the various problems described above, Water absorbent resin Has been found to be easily and easily denatured, and the present invention has been completed. Also, Water absorbent resin By reacting with a gaseous modifier, Water absorbent resin It has been found that can be easily and easily manufactured.
[0008]
That is, in order to solve the above-mentioned problems, the method for modifying a water-absorbent resin according to the first aspect of the present invention has an internal structure obtained by polymerizing a monomer composition mainly composed of acrylic acid or a salt thereof. The water-absorbent resin having a crosslinked structure is modified by bringing it into contact with a gaseous modifier. In order to solve the above-described problems, the water-absorbing resin modification method of the invention described in claim 2 is the water-absorbing resin modification method according to claim 1, wherein the denaturing agent is under reduced pressure, normal pressure or increased pressure. It is characterized by contacting with the water-absorbent resin at a temperature equal to or higher than the boiling point of the modifier. In order to solve the above problems, the method for modifying a water absorbent resin according to claim 3 is the method for modifying a water absorbent resin according to claim 1 or 2, wherein the modifier is a reaction possessed by the water absorbent resin. It is characterized by being a crosslinking agent that reacts with a functional group. In order to solve the above-described problems, the water-absorbing resin modification method according to any one of claims 1 to 3, The water absorbent resin is obtained by polymerizing the monomer composition in the presence of an internal crosslinking agent, The monomer composition includes a hydrophilic monomer, and the internal cross-linking agent is based on the hydrophilic monomer. 0.005 to 3 mol% It is characterized by being within the range. In order to solve the above-mentioned problem, the water-absorbing resin modifying method according to any one of claims 1 to 4 is characterized in that the water-absorbing resin is modified with a modifier. The temperature to be brought into contact with is in the range of 100 ° C to 250 ° C. In order to solve the above-mentioned problem, the water-absorbing resin modification method according to claim 6 is in contact with the water-absorbent resin in the water-absorbing resin modification method according to any one of claims 1 to 5. Thereafter, the modifying agent is characterized by liquefaction or solidification.
[0009]
According to the above method, with a gaseous modifier Water absorbent resin Therefore, a solvent and a dispersion medium necessary in the conventional method are not necessary. Therefore, as compared with the conventional method, no post-treatment process such as a removal process or a drying process is required, so that the above-described modification work process is simplified and costs are not increased. In addition, after denaturation Water absorbent resin In addition, since the modifier, the solvent and the dispersion medium do not remain, the safety is excellent. Furthermore, because it is modified with a gaseous modifier, Water absorbent resin Can be efficiently reacted with each other, and after denaturation, excess denaturant can be removed and recovered very easily and easily, and the recovered denaturant can be easily reused. Can do.
[0010]
In addition, since it is modified with a gaseous modifier, Water absorbent resin It can be uniformly modified regardless of the size and shape. Therefore, for example, sheet-shaped, film-shaped, plate-shaped, block-shaped, etc. Water absorbent resin Or porous Water absorbent resin Even it can be modified. Also, for example, so-called fine powder Water absorbent resin Even it can be modified. That is, it should be denatured Water absorbent resin Regardless of the shape and size. In addition, physical damage such as destruction of the modified surface Water absorbent resin Will not receive.
[0011]
And when the modifier is a crosslinking agent, Water absorbent resin Can be subjected to a crosslinking treatment. Also, Water absorption characteristics of water absorbent resin These properties can be improved by modification.
[0012]
Claim 7 Of the described invention Water absorbent resin In order to solve the above problems, the manufacturing method of By the modification method according to the present invention, a water absorbent resin is obtained. And a gaseous modifier are reacted.
[0013]
Claim 7 According to the method described, Water absorbent resin And the gaseous modifier are reacted with each other, so that a solvent and a dispersion medium that are necessary in the conventional method are unnecessary. Therefore, as compared with the conventional method, since a post-treatment process such as a removal process or a drying process is not required, the work process of the reaction is simplified and the cost is not increased. Also obtained as a reaction product Water absorbent resin In addition, since the modifier, the solvent and the dispersion medium do not remain, the safety is excellent. Furthermore, because it reacts with the gaseous modifier, Water absorbent resin Can be efficiently reacted with each other, and after the reaction, excess denaturant can be removed and recovered very easily and easily, and the recovered denaturant can be easily reused. Can do. This Water absorbent resin Can be manufactured easily and easily.
[0014]
The present invention is described in detail below.
[0015]
In the modification method according to the present invention, Water absorbent resin By contacting the gaseous modifier with Water absorbent resin Is denatured. In the manufacturing method according to the present invention, Water absorbent resin By reacting with a gaseous modifier as a reaction product Water absorbent resin Get. The modification specifically indicates, for example, a crosslinking treatment (secondary crosslinking treatment) or the like. Also, Water absorbent resin Specific examples of the reaction between the olefin and the gaseous modifier include a crosslinking reaction, an addition reaction, a substitution reaction, an esterification reaction, and the like.
[0016]
The denaturant is Water absorbent resin What is necessary is just to be gaseous (gaseous) when making it contact. That is, the modifier becomes gaseous under gasification conditions above its boiling point, and in the gaseous state, Water absorbent resin There is no particular limitation as long as it is a compound that can react with the reactive group possessed by the compound, that is, a compound that can react in a so-called solid-gas system. Alternatively, the modifier becomes gaseous under gasification conditions above its boiling point, and Water absorbent resin Liquefaction after contact with, in the liquid state, Water absorbent resin May be a compound capable of reacting with the reactive group possessed by, or Water absorbent resin Solidified after contact with, in the solid state, Water absorbent resin It may be a compound that can react with the reactive group possessed by. In short, the modifier is Water absorbent resin When it is in contact with the gas, it just needs to be gaseous, Water absorbent resin There is no limitation on the state (gaseous, liquid, or solid) of the modifier when it reacts with the reactive group.
[0017]
As the modifier, a so-called cross-linking agent is suitable. Specific examples of the crosslinking agent include alkylene oxide compounds such as ethylene oxide (boiling point: 10.7 ° C./760 mmHg) and propylene oxide (boiling point: 34.2 ° C./760 mmHg);
Alkyleneimine compounds such as ethyleneimine (boiling point: 56 ° C./760 mmHg), propyleneimine (boiling point: 67 ° C./760 mmHg);
Polyglycidyl ether compounds such as ethylene glycol diglycidyl ether (boiling point: 125 ° C./5 mmHg), neopentyl glycol diglycidyl ether (boiling point: 125 ° C./1 mm Hg), glycerol triglycidyl ether (boiling point: 195 ° C./1.5 mm Hg);
Alkylene carbonate compounds such as ethylene carbonate (boiling point: 100 ° C./5 mmHg) and propylene carbonate (boiling point: 242 ° C./760 mmHg);
Polyhydric alcohol compounds such as ethylene glycol (boiling point: 70 ° C./3 mmHg), diethylene glycol (boiling point: 244 ° C./760 mmHg), triethylene glycol (boiling point: 287 ° C./760 mmHg), glycerin (boiling point: 290 ° C./760 mmHg);
Ethylenediamine (boiling point: 116 ° C./760 mmHg), hexamethylenediamine (boiling point: 196 ° C./760 mmHg), diethylenetriamine (boiling point: 207 ° C./760 mmHg), triethylenetetramine (boiling point: 287 ° C./760 mmHg), tetramethylethylenediamine (boiling point: A polyamine compound such as 120 ° C./760 mmHg);
Haloepoxy compounds such as epichlorohydrin (boiling point: 62 ° C./100 mmHg);
Polyaldehyde compounds such as glutaraldehyde (boiling point: 72 ° C./10 mmHg), glyoxal (boiling point: 51 ° C./776 mmHg);
And alkylene sulfide compounds such as ethylene sulfide (boiling point: 53 ° C./760 mmHg) and propylene sulfide (boiling point: 70 ° C./760 mmHg). These modifiers may be used alone or in combination of two or more. By mixing two or more modifiers, Water absorbent resin Several types of denaturation can be carried out simultaneously, ie in one step.
[0018]
In order to bring the above-exemplified compounds into a gas state, the vapor pressure may exceed the pressure in the denaturing system (hereinafter referred to as the processing system). That is, if necessary, the inside of the treatment system may be heated to a temperature equal to or higher than the boiling point of the modifier, or the inside of the treatment system may be transformed so that the pressure in the treatment system is lower than the vapor pressure of the modifier. Moreover, a modifier can also be made into a gas state by implementing both simultaneously.
[0019]
Specifically, when ethylene oxide is described as an example, ethylene oxide is, for example, about 5 Kgf / cm, as is apparent from the temperature-vapor pressure relationship shown in Table 1. ² Under the pressurized condition, gasification is performed at a temperature of 50 ° C. or higher. Therefore, a so-called solid-gas reaction can be carried out by appropriately setting the gasification conditions according to the compound used as the modifier.
[0020]
[Table 1]

[0021]
It can be modified (hereinafter referred to as treatment) by the modification method according to the present invention. Water absorbent resin Is not particularly limited as long as it has a reactive group and is solid or gelled. As the reactive group, a carboxyl group is particularly preferable. Also, Water absorbent resin Preferably has a crosslinked structure inside. The Water absorbent resin Specific examples include poly (meth) acrylic acid having a crosslinked structure inside and partially neutralized.
[0022]
above Water absorbent resin Is obtained, for example, by polymerizing a monomer composition containing acrylic acid or a salt thereof (hereinafter referred to as acrylic acid (salt)) as a main component. The Water absorbent resin Specifically, for example, crosslinked polyacrylic acid partially neutralized product, hydrolyzate of starch-acrylonitrile graft polymer, neutralized product of starch-acrylic acid graft polymer, vinyl acetate-acrylic acid ester copolymer Saponified polymer, hydrolyzate of acrylonitrile copolymer or acrylamide copolymer or cross-linked product thereof, cross-linked product of carboxymethyl cellulose, cross-linked product of cationic monomer, cross-linked product of isobutylene-maleic anhydride copolymer, 2- Examples thereof include a crosslinked copolymer of acrylamide-2-methylpropanesulfonic acid and acrylic acid, a crosslinked polyethylene oxide, and a crosslinked copolymer of methoxypolyethylene glycol and acrylic acid. These examples Water absorbent resin Of these, a crosslinked product of polyacrylic acid (salt) is more preferable. In the crosslinked product of polyacrylic acid (salt), the acid group of the crosslinked product is preferably neutralized within a range of 50 mol% to 90 mol%. As the salt, alkali metal salts, alkaline earth metal salts, ammonium salts, hydroxyammonium salts, amine salts, alkylamine salts and the like are preferable.
[0023]
In addition to acrylic acid (salt), the monomer composition may contain a hydrophilic monomer copolymerizable with the acrylic acid (salt), if necessary. Specific examples of the hydrophilic monomer include methacrylic acid, crotonic acid, (anhydrous) maleic acid, fumaric acid, itaconic acid, cinnamic acid, sorbic acid, β-acryloyloxypropionic acid, 2- (Meth) acryloylethanesulfonic acid, 2- (meth) acryloylpropanesulfonic acid, 2- (meth) acrylamido-2-methylpropanesulfonic acid, vinylsulfonic acid, styrenesulfonic acid, allylsulfonic acid, vinylphosphonic acid, 2- Anionic unsaturated monomers such as (meth) acryloyloxyethyl phosphoric acid, and alkali metal salts, alkaline earth metal salts, ammonium salts, alkylamine salts thereof;
Acrylamide, methacrylamide, N-ethyl (meth) acrylamide, Nn-propyl (meth) acrylamide, N-isopropyl (meth) acrylamide, N, N-dimethyl (meth) acrylamide, 2-hydroxyethyl (meth) acrylate, Nonionic unsaturated monomers such as 2-hydroxypropyl (meth) acrylate, methoxypolyethylene glycol (meth) acrylate, polyethylene glycol mono (meth) acrylate, vinylpyridine, N-vinylpyrrolidone, N-acryloylpiperidine, N-acryloylpyrrolidine body;
Cationic properties such as N, N-dimethylaminoethyl (meth) acrylate, N, N-diethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylamide, etc. And unsaturated monomers, and quaternized products thereof (for example, a reaction product with an alkyl halide, a reaction product with a dialkyl sulfuric acid, etc.); These hydrophilic monomers may be used alone or in combination of two or more.
[0024]
In the case where the monomer composition contains acrylic acid (salt) as a main component, the amount of the hydrophilic monomer other than the acrylic acid (salt) used is less than 30 mol% of the whole monomer composition. Preferably, 10 mol% or less is more preferable.
[0025]
(Co) polymerization of the above monomer composition Water absorbent resin Preferably has a crosslinked structure (primary crosslinked structure) inside. The above crosslinked structure can be easily introduced by using an internal crosslinking agent when (co) polymerizing the monomer composition and copolymerizing or reacting the monomer composition and the internal crosslinking agent. Can do. still, Water absorbent resin May be self-cross-linking without the need for an internal cross-linking agent.
[0026]
Examples of the internal cross-linking agent include a compound having a plurality of vinyl groups (polymerizable unsaturated groups) in the molecule; at least one vinyl group in the molecule and reacting with the reactive group of the monomer composition. And a compound having a plurality of functional groups capable of reacting with the reactive group in the molecule. These internal crosslinking agents may be used alone or in combination of two or more.
[0027]
Specific examples of the compound having a plurality of vinyl groups in the molecule include N, N′-methylenebis (meth) acrylamide, (poly) ethylene glycol di (meth) acrylate, and (poly) propylene glycol di (meth). Acrylate, trimethylolpropane tri (meth) acrylate, trimethylolpropane di (meth) acrylate, glycerin tri (meth) acrylate, glycerin acrylate methacrylate, ethylene oxide modified trimethylolpropane tri (meth) acrylate, pentaerythritol tetra (meth) acrylate , Dipentaerythritol hexa (meth) acrylate, N, N-diallylacrylamide, triallyl cyanurate, triallyl isocyanurate, triallyl phosphate, triallyl And poly (meth) allyloxyalkanes such as amine, diallyloxyacetic acid, N-methyl-N-vinylacrylamide, bis (N-vinylcarboxylic acid amide), and tetraallyloxyethane.
[0028]
Examples of the compound having at least one vinyl group in the molecule and at least one functional group capable of reacting with a reactive group include, for example, an ethylenic group having at least one hydroxyl group, epoxy group, cationic group or the like. Saturated compounds are mentioned. Specific examples of the compound include glycidyl (meth) acrylate, N-methylolacrylamide, dimethylaminoethyl (meth) acrylate, and the like.
[0029]
Examples of the compound having a plurality of functional groups capable of reacting with a reactive group in the molecule include compounds having at least two hydroxyl groups, epoxy groups, cationic groups, isocyanate groups, and the like. Specific examples of the compound include (poly) ethylene glycol diglycidyl ether, glycerol diglycidyl ether, ethylene glycol, polyethylene glycol, propylene glycol, glycerin, pentaerythritol, ethylenediamine, ethylene carbonate, polyethyleneimine, and aluminum sulfate. Etc.
[0030]
Of the internal crosslinking agents exemplified above, it is more preferable to use a compound having a plurality of vinyl groups in the molecule. Obtained by using a compound having multiple vinyl groups in the molecule Water absorbent resin Characteristics of the For example Water absorption characteristics and the like are further improved. The amount of the internal crosslinking agent used relative to the hydrophilic monomer depends on the combination of the hydrophilic monomer and the internal crosslinking agent, but ranges from 0.005 mol% to 3 mol% with respect to the hydrophilic monomer. The inside is preferable and the inside of the range of 0.01 mol%-1.5 mol% is more preferable.
[0031]
In addition, when (co) polymerizing the monomer composition, hydrophilic polymers such as starch and derivatives thereof, cellulose and derivatives thereof, polyvinyl alcohol, polyacrylic acid (salt) and cross-linked products thereof, hypoxia Chain transfer agents such as phosphoric acid and salts thereof may be added to the reaction system.
[0032]
As the polymerization method for (co) polymerizing the monomer composition, for example, various known polymerization forms such as aqueous solution polymerization, reverse phase suspension polymerization, bulk polymerization, and precipitation polymerization can be adopted, and the polymerization method is not particularly limited. Absent. Among these, aqueous solution polymerization and reverse phase suspension polymerization in which the monomer composition is polymerized in an aqueous solution state can be obtained while the polymerization reaction can be easily controlled. Water absorbent resin These characteristics are more preferable because they are further improved.
[0033]
Further, when (co) polymerizing the monomer composition, a radical polymerization initiator, active energy rays such as ultraviolet rays and electron beams, and the like can be used. Specific examples of the radical polymerization initiator include potassium persulfate, sodium persulfate, ammonium persulfate, t-butyl hydroperoxide, hydrogen peroxide, and 2,2′-azobis (2-amidinopropane). Examples thereof include peroxides such as dihydrochloride, 2,2′-azobisisobutyronitrile, benzoyl peroxide, cumene hydroperoxide, and di-t-butyl peroxide. These radical polymerization initiators may be used alone or in combination of two or more. Further, when an oxidizing radical polymerization initiator is used, the oxidizing radical polymerization initiator and a sulfite such as sodium sulfite and sodium bisulfite, bisulfite, thiosulfate, formamidinesulfinic acid, sulfuric acid first It is good also as a redox initiator by combining with reducing agents, such as iron and L-ascorbic acid. The amount of the polymerization initiator used for the hydrophilic monomer depends on the combination of the hydrophilic monomer and the polymerization initiator, but is 0.001 mol% to 2 mol% with respect to the hydrophilic monomer. Within the range is preferable, and within the range of 0.01 mol% to 0.5 mol% is more preferable.
[0034]
Water absorbent resin The shape of is not particularly limited, for example, particles such as sphere, granule, scale, flat, etc .; fiber; sheet, film, plate, block, irregular, etc. Shape can be adopted. Also, Water absorbent resin May be porous or so-called sponge having open cells. further, Water absorbent resin The size of is not particularly limited, and may be a so-called fine powder. That means Water absorbent resin Need not have a predetermined shape and size when treated with a denaturing agent, but may have a shape and size according to the application. That is, the modification method according to the present invention should be processed. Water absorbent resin Regardless of the shape and size.
[0035]
Water absorbent resin The treatment conditions for treating with a modifier are not particularly limited as long as the modifier can exist in a gaseous state. For example, the processing pressure may be any of reduced pressure, normal pressure, and increased pressure. still, Water absorbent resin When the degree of the treatment, for example, the crosslinking density and the crosslinking depth is relatively large, the treatment under normal pressure may be preferable to the treatment under reduced pressure, and the treatment under normal pressure may be preferable. Treatment under pressure may be preferable. That is, the processing pressure may be appropriately set according to the desired degree of processing. By manipulating the processing pressure, Water absorbent resin The degree of processing can be easily controlled.
[0036]
The processing temperature is the processing pressure or Water absorbent resin Although it depends on the reactivity of the compound with the modifier, the range of room temperature to 300 ° C is preferable, the range of 100 ° C to 250 ° C is more preferable, and the range of 130 ° C to 230 ° C is more preferable. The reaction time is the processing temperature, processing pressure, or Water absorbent resin It may be set in accordance with the reactivity between the compound and the denaturing agent, and is not particularly limited. However, it is sufficient that the time is about several seconds to 2 hours, preferably about several minutes to 1 hour. still, Water absorbent resin The reaction with the modifier proceeds even in a reaction system without water, that is, in a so-called anhydrous state. That is, the modification method according to the present invention is not affected by whether water is present in the treatment system.
[0037]
The processing equipment Water absorbent resin (Hereinafter referred to as a polymer) and a gaseous modifier (hereinafter simply referred to as gas) can be sufficiently brought into contact with each other, that is, a structure capable of carrying out a solid-gas reaction. There is no particular limitation as long as it is provided. As the processing apparatus, various known reaction apparatuses can be employed. For example, (1) a moving bed type reaction apparatus in which a polymer is brought into contact with a gas while gently moving the polymer; (2) the polymer is contained in the gas. (3) A polymer is used as a fixed bed, and the gas is flowed in a single-phase flow, a counter-current flow, or a parallel flow to cause a contact reaction. Fixed bed type reactor; (4) Stirred tank reactor for contacting and reacting the polymer and gas in the tank with stirring blades; (5) While blowing the polymer by a gas stream, And an air flow type reaction apparatus for advancing the contact reaction.
[0038]
Specifically, as the moving bed type reaction apparatus, for example, as shown in FIG. 1 or FIG. 2, a countercurrent standing type reaction apparatus that moves the polymer downward and flows the gas upward; As shown in FIG. 4 or FIG. 5, the polymer is moved horizontally on the belt conveyor and the gas is directed upwards, as shown in FIG. 4 or 5. A moving great type reactor that flows into a rotary kiln (rotary furnace) type reactor that moves a polymer and a gas in the same direction by rotating the apparatus as shown in FIG. 6; an apparatus as shown in FIG. A multi-stage reactor type reactor in which a plurality of stages are provided therein, the polymer is sequentially moved from the upper stage to the lower stage, and the gas is allowed to flow upwards. 5 is particularly suitable when the polymer is in the form of a sheet or the like.
[0039]
Specifically, as the fluidized bed type reaction apparatus, for example, as shown in FIG. 8 or FIG. 9, the gas is allowed to flow upward in an apparatus equipped with an insert such as a perforated plate, a wire mesh, and a pipe. A gas-solid fluidized bed type reaction apparatus that suspends and suspends a polymer by a high-speed fluidized bed type reaction apparatus that suspends and suspends a polymer by flowing a gas upward at a high speed as shown in FIG. As shown, a spouted bed type reactor in which a gas is jetted upward and the polymer is suspended and suspended by the jet flow.
[0040]
Specifically, as the stirred tank reactor, for example, as shown in FIG. 12, a gas-solid stirred tank reactor in which the polymer and gas in the tank are stirred by a stirring blade; as shown in FIG. And a multistage blade tank reactor in which a plurality of partition plates are provided in the tank and the polymer and gas are sequentially moved from the lower stage to the upper stage while stirring with a stirring blade.
[0041]
Specific examples of the gas flow type reaction apparatus include a gas-solid gas flow type reaction apparatus that blows off a polymer by a gas flow as shown in FIG.
[0042]
The configuration of the processing apparatus, that is, the reaction apparatus is not limited to the configuration illustrated above. Further, the processing apparatus may employ either a batch type (batch type) or a continuous type. For example, a closed reaction apparatus such as an autoclave can also be suitably used as the processing apparatus. That is, the modification method according to the present invention can be preferably carried out by either a batch system or a continuous system. And Water absorbent resin And a gaseous modifier are sufficiently brought into contact with each other under a predetermined processing condition using a processing apparatus. Water absorbent resin Can be processed uniformly. Since the modification method according to the present invention uses a gas, the modification can be carried out sufficiently and reliably in a relatively short time.
[0043]
As described above, the present invention is applied. Water absorbent resin The modification method of Water absorbent resin Is modified with a gaseous modifier. Also according to the present invention Water absorbent resin The modification method is a method in which the modifying agent is a crosslinking agent.
[0044]
According to said method, the solvent and dispersion medium which were required by the conventional method become unnecessary. Therefore, as compared with the conventional method, the modification work process is simplified and the cost is not increased. In addition, after denaturation Water absorbent resin In addition, since the modifier, the solvent and the dispersion medium do not remain, the safety is excellent. further, Water absorbent resin Can be efficiently reacted with each other, and after denaturation, excess denaturant can be removed and recovered very easily and easily, and the recovered denaturant can be easily reused. Can do.
[0045]
Moreover, Water absorbent resin It can be uniformly modified regardless of the size and shape. Therefore, shapes that cannot be handled by conventional methods Water absorbent resin Or porous Water absorbent resin Even it can be modified. Also, for example, so-called fine powder Water absorbent resin Even it can be modified. That is, it should be denatured Water absorbent resin Regardless of the shape and size. In addition, physical damage such as destruction of the modified surface Water absorbent resin Will not receive.
[0046]
And when the modifier is a crosslinking agent, Water absorbent resin Can be subjected to a crosslinking treatment. Also, Of water absorbent resin Various characteristics such as water absorption characteristics can be improved by modification.
[0047]
In addition, as described above, according to the present invention. Water absorbent resin The manufacturing method of Water absorbent resin And a gaseous modifier. According to the above method, Water absorbent resin And the gaseous modifier are reacted with each other, so that a solvent and a dispersion medium that are necessary in the conventional method are unnecessary. Therefore, as compared with the conventional method, since a post-treatment process such as a removal process or a drying process is not required, the work process of the reaction is simplified and the cost is not increased. Also obtained as a reaction product Water absorbent resin In addition, since the modifier, the solvent and the dispersion medium do not remain, the safety is excellent. Furthermore, because it reacts with the gaseous modifier, Water absorbent resin Can be efficiently reacted with each other, and after the reaction, excess denaturant can be removed and recovered very easily and easily, and the recovered denaturant can be easily reused. Can do. This Water absorbent resin Can be manufactured easily and easily.
[0048]
【Example】
EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further in detail, this invention is not limited at all by these. Should be denatured Water absorbent resin (4 types) were manufactured by the following manufacturing method. In addition, after denaturation Water absorbent resin The amount of water retained and the amount of water absorbed under pressure were measured by the following methods. In the following description, “parts” means “parts by weight” unless otherwise specified.
[0049]
(1) Water-absorbing resin to be modified Manufacturing method
According to the production methods shown in the following (a) to (d), four types of Water-absorbing resin to be modified Manufactured.
[0050]
(A) A reaction vessel capable of performing so-called nitrogen sealing and heat removal / heating was charged with 5,000 parts of a 30 wt% aqueous solution of sodium acrylate having a neutralization rate of 70 mol%. That is, an aqueous solution consisting of 371 parts of acrylic acid, 1,129 parts of sodium acrylate, and 3,500 parts of water was charged into the reaction vessel.
[0051]
Next, 6.76 parts of polyethylene glycol diacrylate as an internal cross-linking agent was dissolved in the aqueous solution, and nitrogen gas was blown into the aqueous solution for 30 minutes (bubbling) to drive out dissolved oxygen. Next, 1.8 parts of potassium persulfate as a radical polymerization initiator and 0.09 part of L-ascorbic acid as a reducing agent were added to the aqueous solution while stirring. Thereafter, the aqueous solution was polymerized at a polymerization initiation temperature of 30 ° C. under a nitrogen stream.
[0052]
About 5 minutes after the start of polymerization, the temperature in the reaction system reached 70 ° C. Then, it heated and stirred for 2 hours, maintaining the temperature in a reaction system at about 70 degreeC, and the polymerization reaction was completed. As a result, a hydrogel crosslinked polymer composed of sodium polyacrylate was obtained.
[0053]
The obtained water-containing gel-like crosslinked polymer was taken out and subdivided using a meat chopper, and then the subdivided product was spread on a 60-mesh wire mesh and hot-air dried at 150 ° C. for 135 minutes using a hot-air dryer. Next, the dried product is pulverized using a coffee mill, and further classified with a 20 mesh (mesh size 840 μm) wire mesh, whereby a particulate crosslinked polymer having an average particle size of about 400 μm, that is, Water absorbent resin (Less than, Water absorbent resin (Denoted as (a)). above Water absorbent resin (A) had no moisture or stickiness and was in a so-called “smooth” state.
[0054]
(B) A reaction vessel capable of performing so-called nitrogen sealing and heat removal / heating is charged with 1,000 parts of acrylic acid, 5 parts of tetraallyloxyethane as an internal cross-linking agent, and 3,500 parts of water and mixed. -It was dissolved to make an aqueous solution. Next, nitrogen gas was blown into the aqueous solution for 30 minutes (bubbling) to drive out dissolved oxygen. Next, with stirring, the aqueous solution was mixed with 6 parts of hydrogen peroxide as a radical polymerization initiator, 1 part of 2,2′-azobis (2-amidinopropane) dihydrochloride, and 0.3 parts of L-ascorbic acid. Parts were added. Thereafter, the aqueous solution was polymerized at a polymerization initiation temperature of 25 ° C. under a nitrogen stream. The mixture was stirred for about 2 hours while maintaining the temperature in the reaction system almost constant, thereby completing the polymerization reaction. Thereby, a hydrogel crosslinked polymer made of polyacrylic acid was obtained.
[0055]
Next, the obtained water-containing gel-like crosslinked polymer is taken out and subdivided, and then 868 parts of a 48% by weight aqueous solution of sodium hydroxide is added to the subdivided product and uniformly kneaded, so that among the carboxyl groups in the polymer. About 75 mol% of the product was neutralized. That is, about 75 mol% of the carboxyl groups in the polymer were converted to sodium salts.
[0056]
The neutralized hydrogel crosslinked polymer was taken out and dried at 150 ° C. using a drum dryer. Next, the dried product is pulverized using a coffee mill, and further classified with a 20 mesh wire netting to obtain a particulate crosslinked polymer having an average particle size of about 410 μm, ie, Water absorbent resin (Less than, Water absorbent resin (Denoted as (b)). above Water absorbent resin (B) was in a so-called “smooth” state without moisture or stickiness.
[0057]
(C) A reaction vessel capable of performing so-called nitrogen sealing and heat removal / heating was charged with 5,000 parts of a 35 wt% sodium acrylate aqueous solution having a neutralization rate of 80 mol%. That is, an aqueous solution consisting of 281 parts of acrylic acid, 1,469 parts of sodium acrylate, and 3,250 parts of water was charged into the reaction vessel.
[0058]
Next, 2.2 parts of N, N′-methylenebisacrylamide as an internal cross-linking agent was dissolved in the aqueous solution, and nitrogen gas was blown into the aqueous solution for 30 minutes (bubbling) to drive out dissolved oxygen. Next, 4 parts of 2,2′-azobis (2-amidinopropane) dihydrochloride was added to the aqueous solution while stirring. When the mixture was stirred for 5 minutes after the addition, the aqueous solution became cloudy, and formation of white fine particles of 2,2′-azobis (2-amidinopropane) diacrylate was observed in the reaction system.
[0059]
Immediately thereafter, 1.8 parts of potassium persulfate and 0.09 part of L-ascorbic acid were added to the aqueous solution while stirring. Thereafter, the aqueous solution was polymerized at a polymerization initiation temperature of 25 ° C. under a nitrogen stream.
[0060]
About 5 minutes after the start of polymerization, the temperature in the reaction system reached 80 ° C. Then, it heated and stirred for 2 hours, maintaining the temperature in a reaction system at about 75 degreeC, and the polymerization reaction was completed. As a result, a hydrogel crosslinked polymer composed of sodium polyacrylate was obtained.
[0061]
The obtained water-containing gel-like crosslinked polymer was taken out and subdivided using a meat chopper, and then the subdivided product was spread on a 60-mesh wire mesh and hot-air dried at 150 ° C. for 125 minutes using a hot-air dryer. Next, the dried product is pulverized using a coffee mill, and further classified with a 20-mesh wire mesh, whereby a particulate crosslinked polymer having an average particle diameter of about 400 μm, ie, Water absorbent resin (Less than, Water absorbent resin (Denoted as (c)). In addition, since 2,2′-azobis (2-amidinopropane) diacrylate has properties as a foaming agent, Water absorbent resin (C) was porous, and the average pore diameter was 50 μm. Also, Water absorbent resin (C) was a so-called “smooth” state without moisture or stickiness.
[0062]
(D) Obtained by the production method of (b) above Water absorbent resin By further classifying (b) with a 100-mesh (mesh size 150 μm) wire mesh, 93-mesh passed material was collected. This Water absorbent resin (Less than, Water absorbent resin (Denoted as (d)). above Water absorbent resin (D) was a so-called “smooth” state without moisture or stickiness.
[0063]
(2) Water retention amount
0.2 g of the water-absorbent resin was uniformly placed in a non-woven tea bag bag (6 cm × 6 cm), the opening was heat-sealed, and then immersed in a 0.9 wt% sodium chloride aqueous solution (physiological saline). After 30 minutes, the tea bag type bag is pulled up, drained at 250 G for 3 minutes using a centrifuge, and the weight W of the bag ₁ (G) was measured. In addition, the same operation is performed without using a water absorbent resin, and the weight W at that time is ₀ (G) was measured. And these weights W ₁ ・ W ₀ From the following formula,
Water retention (g / g) = (Weight W ₁ (g)-Weight W ₀ (g)) / weight of water absorbent resin (g)
The water retention amount (g / g) was calculated according to
[0064]
(3) Water absorption under pressure
First, a measurement apparatus used for measuring the amount of water absorption under pressure will be briefly described below with reference to FIG.
[0065]
As shown in FIG. 15, the measuring device includes a balance 1, a container 2 having a predetermined capacity placed on the balance 1, an outside air suction pipe 3, a conduit 4 made of silicone resin, a glass filter 6, The measuring unit 5 is placed on the glass filter 6. The container 2 has an opening 2a at the top and an opening 2b at the side, and the outside air intake pipe 3 is fitted into the opening 2a, while the conduit 4 is attached to the opening 2b. It has been. The container 2 contains a predetermined amount of physiological saline (0.9 wt% sodium chloride aqueous solution) 12. The lower end portion of the outside air intake pipe 3 is immersed in the physiological saline 12. The outside air suction pipe 3 is provided in order to keep the pressure in the container 2 at almost atmospheric pressure. The glass filter 6 is formed with a diameter of 55 mm. The container 2 and the glass filter 6 are communicated with each other by a conduit 4. Moreover, the position and height of the glass filter 6 with respect to the container 2 are fixed.
[0066]
The measurement unit 5 includes a filter paper 7, a support cylinder 9, a wire mesh 10 attached to the bottom of the support cylinder 9, and a weight 11. In the measuring unit 5, the filter paper 7 and the support cylinder 9 (that is, the wire mesh 10) are placed on the glass filter 6 in this order, and the weight 11 is placed inside the support cylinder 9, that is, on the wire mesh 10. It has become. The metal mesh 10 is made of stainless steel and has a mesh size of 400 (mesh size 38 μm). At the time of measurement, a predetermined amount and a predetermined particle diameter of the water-absorbing resin 15 are uniformly distributed on the wire mesh 10. Further, the height of the upper surface of the wire mesh 10, that is, the contact surface between the wire mesh 10 and the water absorbent resin 15 is set to be equal to the height of the lower end surface 3 a of the outside air intake pipe 3. The weight 11 is 50 g / cm with respect to the wire mesh 10, that is, the water absorbent resin 15. ² The weight is adjusted so that the load can be uniformly applied.
[0067]
The amount of water absorption under pressure was measured using the measuring apparatus having the above configuration. The measurement method will be described below.
[0068]
First, a predetermined preparatory operation such as putting a predetermined amount of physiological saline 12 into the container 2; fitting the outside air suction pipe 3 into the container 2; Next, the filter paper 7 was placed on the glass filter 6. In parallel with this placing operation, 0.9 g of water-absorbing resin was uniformly distributed inside the support cylinder 9, that is, on the wire net 10, and the weight 11 was placed on the water-absorbing resin 15.
[0069]
Next, the metal mesh 10, that is, the support cylinder 9 on which the water absorbent resin 15 and the weight 11 were placed was placed on the filter paper 7 so that the center portion thereof coincided with the center portion of the glass filter 6.
[0070]
Then, the weight W of the physiological saline 12 absorbed by the water absorbent resin 15 over time from the time when the support cylinder 9 is placed on the filter paper 7 over 60 minutes. ₂ (G) was measured using the balance 1. Further, the same operation is performed without using the water absorbent resin 15, and the weight at that time, that is, the weight of the physiological saline 12 absorbed by, for example, the filter paper 7 other than the water absorbent resin 15 is measured using the balance 1. Blank weight W _Three (G). And these weights W ₂ ・ W _Three From the following formula,
Water absorption under pressure (g / g) = (weight W ₂ (g)-Weight W _Three (g)) / weight of water absorbent resin (g)
The water absorption amount under pressure (g / g) was calculated.
[0071]
[Example 1]
To a 1 L autoclave (processing device) equipped with a stirring blade, Water absorbent resin (A) After charging 100 parts and replacing with nitrogen, the pressure in the reaction system was changed to 5 kgf / cm with nitrogen gas. ² Set to. Next, the temperature in the reaction system was raised to 180 ° C. while stirring, and when the temperature reached 180 ° C., 3 parts of ethylene oxide as a crosslinking agent (modifier) was introduced into the reaction system. At this time, the pressure in the reaction system is 7 kgf / cm. ² ~ 8Kgf / cm ² The ethylene oxide was gaseous. Next, the mixture was stirred for 10 minutes while maintaining the temperature in the reaction system at 180 ° C. to carry out a crosslinking treatment (modification).
[0072]
After the treatment, the autoclave was opened and the cross-linking treatment was performed Water absorbent resin (hereinafter referred to as crosslinked water absorbent resin) Was taken out. The Cross-linked water absorbent resin Was particulate, free of moisture and stickiness, and was in a so-called “smooth” state. In addition, no lumps were observed.
[0073]
the above Water absorbent resin (A) the surface, and Cross-linked water absorbent resin The infrared absorption spectrum of the surface was measured by FT-IR (Fourier transform infrared spectroscopy). As a measuring apparatus, “Nippon Bio-Rad Laboratories KK FTS-45” was used. Further, diffuse reflection (DR) spectroscopy was adopted as a measurement method (sampling method). Water absorbent resin (A) A chart of the infrared absorption spectrum of the surface is shown in FIG. Also, Cross-linked water absorbent resin A chart of the infrared absorption spectrum of the surface is shown in FIG.
[0074]
In the chart of FIG. Water absorbent resin (A) The absorption peak of the carboxyl group present on the surface is 1728.3 cm ^-1 It is appearing in. In contrast, in the chart of FIG. 17, the above absorption peak is 1753.8 cm. ^-1 Appears in a shifted state. From this, by performing a crosslinking treatment, Water absorbent resin (A) It turns out that the carboxyl group which exists in the surface formed ethylene oxide and ester. That means Water absorbent resin (A) It turns out that the surface was modified with ethylene oxide.
[0075]
Obtained Cross-linked water absorbent resin The amount of water retained and the amount of water absorbed under pressure were measured by the above methods. as a result, Cross-linked water absorbent resin The water retention amount was 34 g / g, and the water absorption under pressure was 21 g / g. Also, Water absorbent resin The water retention amount of (a) and the water absorption amount under pressure were measured according to the above method. as a result, Water absorbent resin The water retention amount of (a) was 43 g / g, and the water absorption amount under pressure was 7 g / g. The results are shown in Table 2.
[0076]
[Example 2]
To a 1 liter autoclave equipped with a stirring blade, Water absorbent resin (B) After charging 100 parts and replacing with nitrogen, the pressure in the reaction system was changed to 5 kgf / cm with nitrogen gas. ² Set to. Next, the temperature in the reaction system was raised to 180 ° C. while stirring, and when the temperature reached 180 ° C., 3 parts of ethylene oxide was introduced into the reaction system. At this time, the pressure in the reaction system is 7 kgf / cm. ² ~ 8Kgf / cm ² The ethylene oxide was gaseous. Subsequently, the crosslinking treatment was performed by stirring for 30 minutes while maintaining the temperature in the reaction system at 180 ° C.
[0077]
After the treatment, the autoclave was opened and the cross-linking treatment was performed Water absorbent resin (hereinafter referred to as crosslinked water absorbent resin) Was taken out. The Cross-linked water absorbent resin Was particulate, free of moisture and stickiness, and was in a so-called “smooth” state. In addition, no lumps were observed.
[0078]
Obtained Cross-linked water absorbent resin The water retention amount was 28 g / g, and the water absorption under pressure was 21 g / g. Also, Water absorbent resin The water retention amount and the water absorption amount under pressure in (b) were measured according to the above method. as a result, Water absorbent resin The water retention amount of (b) was 32 g / g, and the water absorption amount under pressure was 8 g / g. The results are shown in Table 2.
[0079]
Example 3
To a 1 liter autoclave equipped with a stirring blade, Water absorbent resin (C) After 100 parts were charged and purged with nitrogen, the pressure in the reaction system was changed to 5 kgf / cm with nitrogen gas. ² Set to. Next, the temperature in the reaction system was raised to 180 ° C. while stirring, and when the temperature reached 180 ° C., 3 parts of ethylene oxide was introduced into the reaction system. At this time, the pressure in the reaction system is 7 kgf / cm. ² ~ 8Kgf / cm ² The ethylene oxide was gaseous. Next, crosslinking was performed by stirring for 60 minutes while maintaining the temperature in the reaction system at 180 ° C.
[0080]
After the treatment, the autoclave was opened and the cross-linking treatment was performed Water absorbent resin (hereinafter referred to as crosslinked water absorbent resin) Was taken out. The Cross-linked water absorbent resin Was particulate, free of moisture and stickiness, and was in a so-called “smooth” state. In addition, no lumps were observed.
[0081]
Obtained Cross-linked water absorbent resin The water retention amount was 29 g / g, and the water absorption under pressure was 22 g / g. Also, Water absorbent resin The water retention amount and the water absorption amount under pressure in (c) were measured according to the above method. as a result, Water absorbent resin The water retention amount of (c) was 33 g / g, and the water absorption amount under pressure was 8 g / g. The results are shown in Table 2.
[0082]
Example 4
To a 1 liter autoclave equipped with a stirring blade, Water absorbent resin (A) After charging 100 parts and substituting with nitrogen, the pressure in the reaction system was 4 kgf / cm 2 with nitrogen gas ² Set to. Next, the temperature inside the reaction system was raised to 150 ° C. while stirring, and when the temperature reached 150 ° C., 4.8 parts of ethylene oxide was introduced into the reaction system. At this time, the pressure in the reaction system is 5 kgf / cm. ² The ethylene oxide was gaseous. Subsequently, the crosslinking treatment was performed by stirring for 45 minutes while maintaining the temperature in the reaction system at 150 ° C.
[0083]
After the treatment, the autoclave was opened and the cross-linking treatment was performed Water absorbent resin (hereinafter referred to as crosslinked water absorbent resin) Was taken out. The Cross-linked water absorbent resin Was particulate, free of moisture and stickiness, and was in a so-called “smooth” state. In addition, no lumps were observed. Obtained Cross-linked water absorbent resin The water retention amount was 30 g / g, and the water absorption amount under pressure was 18 g / g. The results are shown in Table 2.
[0084]
Example 5
In Example 3 Water absorbent resin (C) Instead of 100 parts, a heat drying treatment was performed in advance at 180 ° C. for a predetermined time. Water absorbent resin (A) The same crosslinking treatment as in Example 3 was performed except that 100 parts were used.
[0085]
After the treatment, the autoclave was opened and the cross-linking treatment was performed Water absorbent resin (hereinafter referred to as crosslinked water absorbent resin) Was taken out. The Cross-linked water absorbent resin Was particulate, free of moisture and stickiness, and was in a so-called “smooth” state. In addition, no lumps were observed. Obtained Cross-linked water absorbent resin The water retention amount was 29 g / g, and the water absorption under pressure was 22 g / g. The results are shown in Table 2.
[0086]
As is clear from the above results, the modification method according to the present invention is: Water-absorbent resin before modification It can be seen that it is not affected by whether moisture is contained in or not. In other words, it should be denatured Water absorbent resin It can be seen that whether or not contains moisture does not affect the result of denaturation.
[0087]
Example 6
In Example 3 Water absorbent resin (C) Instead of 100 parts, Water absorbent resin (D) The same crosslinking treatment as in Example 3 was performed except that 100 parts were used.
[0088]
After the treatment, the autoclave was opened and the cross-linking treatment was performed Water absorbent resin (hereinafter referred to as crosslinked water absorbent resin) Was taken out. The Cross-linked water absorbent resin Was particulate, free of moisture and stickiness, and was in a so-called “smooth” state. In addition, no lumps were observed.
[0089]
Obtained Cross-linked water absorbent resin The water retention amount was 23 g / g, and the water absorption under pressure was 11 g / g. Also, Water absorbent resin The water retention amount of (d) and the water absorption amount under pressure were measured according to the above method. as a result, Water absorbent resin The water retention amount of (d) was 27 g / g, and the water absorption amount under pressure was 6 g / g. The results are shown in Table 2.
[0090]
Example 7
To a 1 liter autoclave equipped with a stirring blade, Water absorbent resin (A) After charging 100 parts and replacing with nitrogen, the pressure in the reaction system was changed to 5 kgf / cm with nitrogen gas. ² Set to. Next, the temperature in the reaction system was raised to 200 ° C. while stirring, and when the temperature reached 200 ° C., 3 parts of ethylene oxide was introduced into the reaction system. At this time, the pressure in the reaction system is 7 kgf / cm. ² ~ 8Kgf / cm ² The ethylene oxide was gaseous. Then, the crosslinking treatment was performed by stirring for 10 minutes while maintaining the temperature in the reaction system at 200 ° C.
[0091]
After the treatment, the autoclave was opened and the cross-linking treatment was performed Water absorbent resin (hereinafter referred to as crosslinked water absorbent resin) Was taken out. The Cross-linked water absorbent resin Was particulate, free of moisture and stickiness, and was in a so-called “smooth” state. In addition, no lumps were observed. Obtained Cross-linked water absorbent resin The water retention amount was 35 g / g, and the water absorption under pressure was 19 g / g. The results are shown in Table 2.
[0092]
Example 8
A 1 L autoclave equipped with a stirring blade was preliminarily heated and dried at 180 ° C. for a predetermined time. Water absorbent resin (A) After charging 100 parts and replacing with nitrogen, the pressure in the reaction system was changed to 5 kgf / cm with nitrogen gas. ² Set to. Next, the temperature in the reaction system was raised to 200 ° C. while stirring, and when the temperature reached 200 ° C., 3 parts of ethylene oxide was introduced into the reaction system. At this time, the pressure in the reaction system is 7 kgf / cm. ² ~ 8Kgf / cm ² The ethylene oxide was gaseous. Next, crosslinking was performed by stirring for 60 minutes while maintaining the temperature in the reaction system at 200 ° C.
[0093]
After the treatment, the autoclave was opened and the cross-linking treatment was performed Water absorbent resin (hereinafter referred to as crosslinked water absorbent resin) Was taken out. The Cross-linked water absorbent resin Was particulate, free of moisture and stickiness, and was in a so-called “smooth” state. In addition, no lumps were observed. Obtained Cross-linked water absorbent resin The water retention amount was 33 g / g, and the water absorption amount under pressure was 22 g / g. The results are shown in Table 2.
[0094]
Example 9
To a 1 liter autoclave equipped with a stirring blade, Water absorbent resin (A) After charging 100 parts and replacing with nitrogen, the pressure in the reaction system was changed to 5 kgf / cm with nitrogen gas. ² Set to. Next, the temperature in the reaction system was raised to 220 ° C. while stirring, and when the temperature reached 220 ° C., 3 parts of propylene oxide as a crosslinking agent (modifier) was introduced into the reaction system. At this time, the pressure in the reaction system is 7 kgf / cm. ² ~ 8Kgf / cm ² And propylene oxide was gaseous. Subsequently, the mixture was stirred for 60 minutes while maintaining the temperature in the reaction system at 220 ° C. to carry out a crosslinking treatment (modification).
[0095]
After the treatment, the autoclave was opened and the cross-linking treatment was performed Water absorbent resin (hereinafter referred to as crosslinked water absorbent resin) Was taken out. The Cross-linked water absorbent resin Was particulate, free of moisture and stickiness, and was in a so-called “smooth” state. In addition, no lumps were observed. The obtained water-absorbent resin had a water retention amount of 29 g / g, and the water absorption amount under pressure was 19 g / g. The results are shown in Table 2.
[0096]
Example 10
A 1 L autoclave equipped with a stirring blade was preliminarily heated and dried at 180 ° C. for a predetermined time. Water absorbent resin (A) After charging 100 parts and replacing with nitrogen, the pressure in the reaction system was changed to 5 kgf / cm with nitrogen gas. ² Set to. Next, the temperature in the reaction system was raised to 240 ° C. while stirring, and when the temperature reached 240 ° C., 3 parts of ethylene oxide was introduced into the reaction system. At this time, the pressure in the reaction system is 8 kgf / cm. ² ~ 9Kgf / cm ² The ethylene oxide was gaseous. Subsequently, the crosslinking process was performed by stirring for 3 minutes, maintaining the temperature in a reaction system at 240 degreeC.
[0097]
After the treatment, the autoclave was opened and the cross-linking treatment was performed Water absorbent resin (hereinafter referred to as crosslinked water absorbent resin) Was taken out. The Cross-linked water absorbent resin Was particulate, free of moisture and stickiness, and was in a so-called “smooth” state. In addition, no lumps were observed. Obtained Cross-linked water absorbent resin The water retention amount was 30 g / g, and the water absorption amount under pressure was 22 g / g. The results are shown in Table 2.
[0098]
Example 11
After 100 parts of ethylene glycol diglycidyl ether as a crosslinking agent (modifier) was charged into a stainless steel container, the upper opening of the container was covered with a 200-mesh stainless steel wire mesh. Next, on the wire mesh Water absorbent resin (A) 50 parts were uniformly distributed.
[0099]
Thereafter, the vessel is heated to vaporize ethylene glycol diglycidyl ether, and gaseous ethylene glycol diglycidyl ether is Water absorbent resin Crosslinking treatment (denaturation) was performed by contacting (a) for 10 minutes.
[0100]
After finishing the treatment, it was cross-linked Water absorbent resin (hereinafter referred to as crosslinked water absorbent resin) Was recovered. The Cross-linked water absorbent resin Was particulate, free of moisture and stickiness, and was in a so-called “smooth” state. In addition, no lumps were observed. Obtained Cross-linked water absorbent resin The water retention amount was 36 g / g, and the water absorption under pressure was 11 g / g. The results are shown in Table 2.
[0101]
[Comparative Example 1]
To a 1 liter autoclave equipped with a stirring blade, Water absorbent resin (A) After charging 100 parts and substituting with nitrogen, the pressure in the reaction system was set to 7 kgf / cm with nitrogen gas. ² ~ 8Kgf / cm ² Set to. Next, the temperature in the reaction system was raised to 180 ° C. while stirring, and the mixture was stirred for 60 minutes while maintaining the temperature at 180 ° C. That is, the treatment was performed without using ethylene oxide as a cross-linking agent.
[0102]
After the treatment, the autoclave was opened and the treatment was performed Water absorbent resin (hereinafter referred to as crosslinked water absorbent resin) For comparison as Cross-linked water absorbent resin Was taken out. For comparison Cross-linked water absorbent resin The water retention amount was 40 g / g, the water absorption under pressure was 8 g / g, and the water absorption under pressure was not improved. The results are shown in Table 2.
[0103]
[Comparative Example 2]
To a 1 liter autoclave equipped with a stirring blade, Water absorbent resin (A) After charging 100 parts, the reaction system was heated to 180 ° C. while stirring and stirred for 60 minutes while maintaining the temperature at 180 ° C. That is, the treatment was carried out without using ethylene oxide as a cross-linking agent and replacing and pressurizing the inside of the reaction system with nitrogen gas.
[0104]
After the treatment, the autoclave was opened and the treatment was performed Water absorbent resin (hereinafter referred to as crosslinked water absorbent resin) For comparison as Cross-linked water absorbent resin Was taken out. For comparison Cross-linked water absorbent resin The water retention amount was 42 g / g, the water absorption amount under pressure was 7 g / g, and the water absorption amount under pressure was not improved. The results are shown in Table 2.
[0105]
[Comparative Example 3]
Using fluid drying type equipment Water absorbent resin (D) While flowing 100 parts, Water absorbent resin In (d), both parts were mixed by spraying 10 parts of ethylene glycol 3weight% aqueous solution as a crosslinking agent intermittently using a pressure type spray nozzle. However, the above mixing became non-uniform and a large amount of lumps was generated.
[0106]
The above mixture was heated to 180 ° C. and heated for 60 minutes while maintaining the temperature at 180 ° C. to carry out the treatment. After completion of the treatment, the mixture was classified with a 20-mesh wire mesh to collect the passing material. As a result, processing was performed Water absorbent resin (hereinafter referred to as crosslinked water absorbent resin) For comparison as Cross-linked water absorbent resin Got.
[0107]
For comparison Cross-linked water absorbent resin Produced large amounts of lumps. Obtained for comparison Cross-linked water absorbent resin The water retention amount is 26 g / g, the water absorption under pressure is 6 g / g, Water absorbent resin Since the mixing of (d) with the 3% by weight aqueous solution of ethylene glycol was uneven, the water absorption under pressure was not improved. That is, it was found that the amount of water absorption under pressure was significantly inferior to the result of Example 6. The results are shown in Table 2.
[0108]
[Table 2]

[0109]
As is clear from the results of Examples 1 to 11 above, Water absorbent resin It can be seen that the amount of water absorption under pressure is improved by subjecting to a crosslinking treatment. Moreover, as is clear from the comparison with the results of Comparative Examples 1 to 3, the modification method according to the present invention is: Water absorbent resin It can be seen that it can be efficiently reacted with the crosslinking agent (modifier). Furthermore, by the production method according to the present invention, Water absorbent resin It can be seen that can be manufactured easily and easily.
[0110]
【The invention's effect】
As described above, the method for modifying a water-absorbent resin according to claim 1 of the present invention is a water-absorbing resin having a crosslinked structure inside obtained by polymerizing a monomer composition mainly composed of acrylic acid or a salt thereof. In this method, the functional resin is modified by bringing it into contact with a gaseous modifier. In the method for modifying a water absorbent resin according to claim 2 of the present invention, as described above, the modifier is brought into contact with the water absorbent resin at a temperature equal to or higher than the boiling point of the modifier under reduced pressure, normal pressure or increased pressure. It is. As described above, the method for modifying a water-absorbent resin according to claim 3 of the present invention is a method in which the modifier is a crosslinking agent that reacts with a reactive group of the water-absorbent resin. The method for modifying a water absorbent resin according to claim 4 of the present invention is as described above. The water absorbent resin is obtained by polymerizing the monomer composition in the presence of an internal crosslinking agent, The monomer composition includes a hydrophilic monomer, and the internal cross-linking agent is based on the hydrophilic monomer. Within the range of 0.005 to 3 mol% It is a method. As described above, the method for modifying a water absorbent resin according to claim 5 of the present invention is a method in which the temperature at which the water absorbent resin is brought into contact with the modifier is in the range of 100 ° C to 250 ° C. The method for modifying a water absorbent resin according to claim 6 of the present invention is a method in which the modifier is liquefied or solidified after contact with the water absorbent resin as described above.
[0111]
This eliminates the need for solvents and dispersion media that were necessary in conventional methods. Therefore, as compared with the conventional method, the modification work process is simplified and the cost is not increased. In addition, after denaturation Water absorbent resin In addition, since the modifier, the solvent and the dispersion medium do not remain, the safety is excellent. further, Water absorbent resin Can efficiently react with the denaturant, and after denaturation, the excess denaturant can be removed and recovered very easily and easily, and the recovered denaturant can be easily reused. There are various effects that can be achieved.
[0112]
Moreover, Water absorbent resin It can be uniformly modified regardless of the size and shape. Therefore, shapes that cannot be handled by conventional methods Water absorbent resin Or porous Water absorbent resin Even it can be modified. Also, for example, so-called fine powder Water absorbent resin Even it can be modified. That is, it should be denatured Water absorbent resin Regardless of the shape and size. In addition, physical damage such as destruction of the modified surface Water absorbent resin There are also various effects that are not received.
[0113]
And when the modifier is a crosslinking agent, Water absorbent resin Can be subjected to a crosslinking treatment. Also, Of water absorbent resin There is an effect that various characteristics such as water absorption characteristics can be improved by modification.
[0114]
Of the present invention Claim 7 Described Water absorbent resin As described above, the manufacturing method of By the modification method according to the present invention, the water absorbent resin and the gaseous modifier are reacted. Is the method. According to the above method, Water absorbent resin And the gaseous modifier are reacted with each other, so that a solvent and a dispersion medium that are necessary in the conventional method are unnecessary. Therefore, as compared with the conventional method, since a post-treatment process such as a removal process or a drying process is not required, the work process of the reaction is simplified and the cost is not increased. Also obtained as a reaction product Water absorbent resin In addition, since the modifier, the solvent and the dispersion medium do not remain, the safety is excellent. Furthermore, because it reacts with the gaseous modifier, Water absorbent resin Can be efficiently reacted with each other, and after the reaction, excess denaturant can be removed and recovered very easily and easily, and the recovered denaturant can be easily reused. Can do. This Water absorbent resin The effect that it can manufacture easily and easily is produced.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram showing a schematic configuration of a reaction apparatus suitably used in a modification method according to the present invention.
FIG. 2 is an explanatory diagram showing a schematic configuration of another reaction apparatus suitably used in the modification method according to the present invention.
FIG. 3 is an explanatory diagram showing a schematic configuration of still another reaction apparatus suitably used in the modification method according to the present invention.
FIG. 4 is an explanatory diagram showing a schematic configuration of still another reaction apparatus suitably used in the modification method according to the present invention.
FIG. 5 is an explanatory diagram showing a schematic configuration of still another reaction apparatus suitably used in the modification method according to the present invention.
FIG. 6 is an explanatory diagram showing a schematic configuration of still another reaction apparatus suitably used in the modification method according to the present invention.
FIG. 7 is an explanatory diagram showing a schematic configuration of still another reaction apparatus suitably used in the modification method according to the present invention.
FIG. 8 is an explanatory diagram showing a schematic configuration of still another reaction apparatus suitably used in the modification method according to the present invention.
FIG. 9 is an explanatory diagram showing a schematic configuration of still another reaction apparatus suitably used in the modification method according to the present invention.
FIG. 10 is an explanatory diagram showing a schematic configuration of still another reaction apparatus suitably used in the modification method according to the present invention.
FIG. 11 is an explanatory diagram showing a schematic configuration of still another reaction apparatus suitably used in the modification method according to the present invention.
FIG. 12 is an explanatory diagram showing a schematic configuration of still another reaction apparatus preferably used in the modification method according to the present invention.
FIG. 13 is an explanatory diagram showing a schematic configuration of still another reaction apparatus suitably used in the modification method according to the present invention.
FIG. 14 is an explanatory diagram showing a schematic configuration of still another reaction apparatus suitably used in the modification method according to the present invention.
FIG. 15 is modified by the modification method according to the present invention. Water absorbent resin It is general | schematic sectional drawing of the measuring apparatus used for the measurement of the amount of water absorption under pressure which is one of the performance which shows.
FIG. 16 is used in one embodiment of the present invention. Water absorbent resin (A) It is the chart of the infrared absorption spectrum of the surface.
FIG. 17 obtained in one embodiment of the present invention Cross-linking It is a chart of the infrared absorption spectrum of the water-absorbent resin surface.
[Explanation of symbols]
1 Balance
2 containers
3 Outside air intake pipe
4 conduit
5 Measurement section
6 Glass filter
7 Filter paper
9 Support cylinder
10 Wire mesh
11 Weight
12 Saline
15 Water-absorbing resin

Claims (7)

  A water-absorbing resin having a crosslinked structure inside obtained by polymerizing a monomer composition mainly composed of acrylic acid or a salt thereof is modified by bringing it into contact with a gaseous modifier. A method for modifying a water-absorbent resin.   The method for modifying a water absorbent resin according to claim 1, wherein the modifier is brought into contact with the water absorbent resin at a temperature equal to or higher than the boiling point of the modifier under reduced pressure, normal pressure, or increased pressure.   3. The method for modifying a water absorbent resin according to claim 1, wherein the modifier is a crosslinking agent that reacts with a reactive group of the water absorbent resin. The water absorbent resin is obtained by polymerizing the monomer composition in the presence of an internal crosslinking agent,
The monomer composition includes a hydrophilic monomer,
The said internal crosslinking agent exists in the range of 0.005-3 mol% with respect to the said hydrophilic monomer, The modification | denaturation of the water absorbing resin of any one of Claims 1-3 characterized by the above-mentioned. Method.   The method for modifying a water-absorbent resin according to any one of claims 1 to 4, wherein the temperature at which the water-absorbent resin is brought into contact with the modifier is in the range of 100C to 250C.   The method for modifying a water absorbent resin according to any one of claims 1 to 5, wherein the modifier is liquefied or solidified after contact with the water absorbent resin.   A method for producing a water-absorbent resin, comprising reacting the water-absorbent resin with a gaseous modifier by the modifying method according to any one of claims 1 to 6.

Images