JP4385478B2

JP4385478B2 - Water-absorbing composite and water-absorbing article

Info

Publication number: JP4385478B2
Application number: JP2000073612A
Authority: JP
Inventors: 浩二加藤; 喜一伊藤; 義昭森
Original assignee: Mitsubishi Chemical Corp
Current assignee: Mitsubishi Chemical Corp
Priority date: 1999-03-16
Filing date: 2000-03-16
Publication date: 2009-12-16
Anticipated expiration: 2020-03-16
Also published as: JP2000328456A

Description

【０００１】
【発明の属する技術分野】
本発明は、不織布のような繊維質基材に吸水性樹脂粒子が結着している吸水性複合体を連続的に製造する方法に関するものである。本発明の製造方法で製造された吸水性複合体は、いわゆる紙おむつや生理用ナプキンなどのような吸水性物品の製造に用いるのに好適である。
【０００２】
【従来の技術】
紙、パルプ、不織布、スポンジ状ウレタン樹脂等は吸水性が高いために、従来から保水剤として生理用ナプキン、紙おむつ等を始めとする各種の衛生用品及び農業用資材等に使用されてきた。しかし、これらの吸水性材料はその吸水量が自重の１０〜５０倍程度に過ぎない。このため、多量の水を吸水又は保持させるためには多量の材料が必要とされ、著しく嵩高になるという問題があった。また、吸水した材料を加圧すると、簡単に水分を放出してしまう等の欠点もあった。
【０００３】
この種の吸水材料の上記欠点を改善することを目的として、近年、高吸水性の種々の高分子材料が提案されている。例えば、澱粉のグラフト重合体（特公昭５３−４６１９９号公報等）、セルロ−ス変性体（特開昭５０−８０３７６号公報等）、水溶性ポリマーの架橋物（特公昭４３−２３４６２号公報等）、自己架橋型アクリル酸アルカリ金属塩ポリマ−（特公昭５４−３０７１０号公報等）等が提案されている。
【０００４】
これらの吸水性ポリマーの吸水性能はかなり高いレベルに達しているが、その殆どが粉末状であるために、例えば、生理用ナプキン、紙おむつ等の衛生材料として使用するためにはティッシュ、不織布、綿等の基材上に吸水性樹脂粉末を均一に分散させる必要がある。しかし、公知の方法で分散させた吸水性樹脂粉末は、繊維質基材上に安定性良く固定することが困難であり、均一に分散させた後でも一部局所に集合化することが多く、また、吸水後の膨潤ゲルも安定性良く繊維質基材上に固定されずに繊維質基材から容易に移動してしまうという欠点があった。このような移動を防ぐために吸水性樹脂粉末をフラッフパルプ等に接着剤で接着すると、接着剤により吸水性樹脂粉末が吸水して膨潤が阻害されるので、一般に樹脂粒子本来の吸水性能が発現しなくなってしまう。
【０００５】
更に、上記の様な吸水性樹脂粉末を繊維質基材に均一に分散させて吸収体を得る方法では、繊維質基材上からポリマ−粉末が漏れやすいばかりか、粉末の取り扱いに伴う煩雑さ、並びに、均一な分散を効率良く行う上でのプロセス上の問題等により、コストも極めて割高にならざるを得なかった。
【０００６】
これらの問題を解決する方法として、アクリル酸系重合性モノマー水溶液をレドックス系開始剤で重合開始させた混合液からなる液滴を繊維質基材に担持させて重合させる方法が提供されている（特開平９−６７４０３号公報）。この方法によれば、吸水性及び吸水速度に優れ、高吸水性ポリマー粒子が繊維質基材上に安定性良く固定化された吸水性複合体を製造しうる。しかし、製品用途によっては、この吸収性複合体よりもさらに一段と高性能な吸収材料が求められている。
【０００７】
【発明が解決しようとする課題】
従って本発明は、吸水性樹脂粒子の製造と同時に、吸水性樹脂粒子をその本来の吸水性能および保水性能を発現し得るように繊維質基材に固着させることから成る、効率の良い吸水性複合体の連続製造方法を提供することを課題とする。また本発明は、このような性質を有する吸水性複合体を利用した実用性の高い吸水性物品を提供することも課題とする。
【０００８】
【課題を解決するための手段】
本発明者は上記課題を解決するために鋭意検討を重ねた結果、下記の工程：
（Ａ）カルボキシル基の２０％以上が中和している不飽和カルボン酸を主成分とする重合性モノマー水溶液を液滴状で重合させつつ落下させ、落下点に繊維質基材を送入することにより重合途上の樹脂粒子を繊維質基材に付着させ、付着後に重合を完了させて粒子−基材複合体を形成させる複合化工程
（Ｂ）該複合体に、カルボキシル基および／またはカルボキシート基と反応しうる２個以上の官能基を有する架橋剤を、該複合体中の重合性モノマー由来の樹脂粒子１００重量部につき１〜１００重量部の水の存在下で添加して反応させる表面架橋工程
を含むことを特徴とする、本発明の吸水性複合体の連続製造方法を提供するに至った。
【０００９】
本発明の連続製造方法では、表面架橋工程より前に、粒子−基材複合体を構成する樹脂粒子の含水率を１０〜４０重量％に調整する含水率調整工程を行うことができ、複合化工程より後に、粒子−基材複合体を構成する樹脂粒子に残存する重合性モノマーを処理する残存モノマー処理工程を行うことができる。本発明の連続製造方法では、表面架橋工程に供する粒子−基材複合体を構成する樹脂粒子の含水率は１０〜４０重量％であることが好ましい。また、複合化工程で得られる粒子−基材複合体の樹脂粒子の少なくとも一部は、樹脂粒子が相互に結着した凝集粒状体であり、かつこの凝集粒状体を構成する樹脂粒子の一部は繊維質基材に直接には付着していないことが好ましい。
【００１０】
また本発明は、上記の連続製造方法により製造した吸水性複合体も提供する。本発明の吸水性複合体は、例えば４０ｇ／ｃｍ²の加圧下において１０分間生理食塩水を吸水させたときの吸水量が、該吸水性複合体に担持された吸水性ポリマー１ｇあたり１５ｇ以上であることが好ましい。
さらに本発明は、これらの吸水性複合体を用いることを特徴とする吸水性物品も提供する。
【００１１】
【発明の実施の形態】
以下において、本発明の吸水性複合体の連続製造方法、吸水性複合体、および吸水性物品について詳細に説明する。
本発明の吸水性複合体の製造方法は、上記の複合化工程と表面架橋工程を含むものである。
複合化工程では、重合性モノマー水溶液を液滴状に分散させた状態で、気相中で重合を行わせる。このような重合方法は公知であり、通常は重合室の上部に設けた液分散装置に重合開始剤を含む重合性モノマー水溶液を供給し、液滴として重合室内を落下させる間に重合が行われる。
【００１２】
複合化工程で用いる重合性モノマーとしては、吸水性樹脂を与えるものであれば任意のものを用いることができるが、通常はアクリル酸、メタクリル酸、マレイン酸、イタコン酸などの不飽和カルボン酸が用いられる。所望ならばこれらのいくつかを併用したり、これらに（メタ）アクリルアミド、２−ヒドロキシエチル（メタ）アクリレートなどの他のモノマーを併用してもよい。これらのなかでもアクリル酸又はメタクリル酸を用いるのが好ましい。特に好ましいのはアクリル酸であり、通常はアクリル酸単独、又はアクリル酸が５０モル％以上、特に８０モル％以上を占めるモノマー混合物を用いるのが好ましい。
【００１３】
なお、これらの不飽和カルボン酸は、その少なくとも一部を水溶性塩、例えばアルカリ金属塩やアンモニウム塩として用いるのが好ましく、こうすることにより得られる吸水性樹脂の吸水能を向上させることができる。例えばアクリル酸であれば、２０％以上、好ましくは２０〜９０％をアルカリ金属塩やアンモニウム塩として重合に供することにより、得られる吸水性樹脂の吸水能を著しく向上させることができる。
【００１４】
本発明において重合に供する重合性モノマーの溶液中には、所望ならば少量の架橋剤を含有させることもできる。架橋剤としては、例えば、Ｎ，Ｎ′−メチレンビス（メタ）アクリルアミドや（ポリ）エチレングリコールジグリシジルエーテル等を用いることができ、架橋剤の使用量はモノマーに対して通常０．０１〜１重量％、好ましくは０．０５〜０．５重量％である。架橋剤の量が多過ぎると、生成する樹脂粒子の吸水能が低下する傾向がある。
【００１５】
モノマー溶液中の重合性モノマー濃度は、遊離型及び塩型のそれぞれの重量の合計で、通常２０重量以上、好ましくは２５重量％以上である。モノマー濃度が小さすぎると、適度の粘度の有する液滴の形成が困難であり、樹脂粒子が繊維質基材に付着する際にその形状がくずれ易く、ひいては最終的に得られる吸水性複合体の物性が劣ったものとなり易い。モノマー濃度の上限は、取扱い性などの点から、８０重量％程度である。
【００１６】
重合開始剤としては、酸化性を示すラジカル発生剤と還元剤との組合せから成るレドックス系重合開始剤を用いるのが好ましい。ラジカル発生剤としては、過酸化水素を用いるのが好ましいが、過硫酸アンモニウムや過硫酸カリウム等の過硫酸塩、ｔ−ブチルハイドロパーオキシドやクメンハイドロパーオキシド等のハイドロパーオキシド類、その他、第二セリウム塩、過マンガン酸塩、亜塩素酸塩、次亜塩素酸塩などを用いることができる。これらのラジカル発生剤は、重合性モノマーに対して０．０１〜１０重量％、特に０．１〜２重量％となるように用いるのが好ましい。
【００１７】
還元剤としてはＬ−アスコルビン酸又はそのアルカリ金属塩を用いるのが好ましいが、他にも亜硫酸ナトリウム、亜硫酸水素ナトリウム等の亜硫酸塩、チオ硫酸ナトリウム、酢酸コバルト、硫酸銅、硫酸第一鉄などを用いることもできる。これらの還元剤は、重合性モノマーに対して０．０１〜１０重量％、特に０．１〜２重量％となるように用いるのが好ましい。
【００１８】
重合反応は公知の種々の方式で行うことができるが、特願平１０−３３０２８３号明細書に記載の方式に従い、ラジカル発生剤を含む重合性モノマー水溶液と、還元剤を含む重合性モノマー水溶液とを、重合室の上部に相対向して設置されているそれぞれのノズルから液柱状に噴出させ、空中で両液を衝突させて混合すると共に液滴状に分散させる方式により行うのが好ましい（図２）。例えば、レドックス系重合開始剤を構成する酸化剤と重合性モノマ−水溶液を含む第１液と、レドックス系重合開始剤を構成する還元剤と重合性モノマ−水溶液を含む第２液とを気相中で混合する方法を好ましい方法として例示することができる。液滴の大きさは５〜３０００μｍ、特に５０〜１０００μｍが好ましい。両液が混合すると直ちに重合が開始され、引続き液滴内で重合が進行しつつ重合室内を落下する。重合室の雰囲気は重合反応に支障を来さない限り任意である。通常は雰囲気ガスとしては窒素、ヘリウム、炭酸ガスなどを用いるが、空気や水蒸気を用いることもできる。雰囲気の温度は通常は室温〜１５０℃、好ましくは室温〜１００℃である。なお、雰囲気中に水蒸気を送入する場合には、反応に供するモノマー水溶液の濃度や、生成する樹脂粒子に所望の含水率などに基づき、モノマー水溶液からの水分蒸発をどの程度にするかの点から設定すればよい。
【００１９】
本発明では重合室にシート状の繊維質基材を送入し、これを重合室の床面に平行に移動させつつ、その上に落下してくる重合途上の樹脂粒子を付着させることが好ましい。繊維質基材としては、一定の形状に形成されていて、かつ重合途上の樹脂粒子が付着し易いものであればよく、布、紙、パルプ、不織布などを用いることができる。なかでも、繊維質基材が粗に集積されていて樹脂粒子が内部にまで入り込み易く、かつ樹脂粒子が繊維質基材に強く付着することが可能な、フラッフパルプ又は不織布を用いるのが好ましい。特に好ましいのは湿潤状態でも強度の大きい、ポリエステル、ポリオレフィン、ポリアミド、アセテートなどのような（半）合成繊維からなる不織布である。不織布を構成する繊維質基材の繊維の太さは１０〜５０μｍが好ましく、また不織布の目付量は１０〜１００ｇ／ｍ²、特に２０〜５０ｇ／ｍ²であるのが好ましい。
【００２０】
重合進行中の液滴が気相中或いは基材上に接して凝集粒状体を形成する時点での重合率は、３〜９７％、好ましくは２０〜９７％、さらに好ましくは５０〜９５％であるように諸条件を設定する。この重合率が余り低い場合には、液滴同士が衝突しても凝集粒状体とはならず一体化して大粒子となったり、基材上に液滴が落下した時に液が基材上に広がったり或いは吸収ないし含浸されたりして凝集粒状体の形状で基材に付着させることが不可能になる。また、余り高い場合には、基材との接着力が発現せず、基材と吸水性ポリマーとの固定性が悪くなる。また、複合化工程において、繊維質基材に接した時点における重合性モノマーの重合率は２０〜９７％であることが好ましい。
【００２１】
樹脂粒子は、最終的に得られる吸水性複合体中に５０〜４００ｇ／ｍ²となるように繊維質基材に付着させる。用途にもよるが一般に８０〜３００ｇ／ｍ²となるように付着させるのが好ましい。吸水性複合体の樹脂粒子の含有量が少ないと、当然のことながら吸水能が小さくなる。また含有量が多過ぎることは一般に不経済であり、かつ繊維質基材と結合する部分の割合が減少して、繊維質基材との結合力が弱くなる。
【００２２】
本発明の連続製造方法で製造される吸水性複合体を構成する樹脂粒子は、その少なくとも一部が重合途上の樹脂粒子（一次粒子）が相互に結着して凝集粒状体を構成しており、かつこの凝集粒状体を構成する樹脂粒子（一次粒子）の一部は繊維質基材に直接結合していないものであることが好ましい。このような凝集粒状体は比表面積が大きいので吸水速度が大きく、かつ凝集粒状体を構成する一次粒子の一部でしか繊維質基材に結合していないので、吸水して膨潤するに際し繊維質基材から受ける拘束が小さく、吸水能に優れている。また凝集粒状体を構成する一次粒子同士の接合面は一体化しているので、吸水前は勿論のこと吸水後においても、凝集粒状体が一次粒子に崩壊して繊維質基材から脱落することが少ない。樹脂粒子の３０重量％以上が凝集粒状体であるのが好ましく、５０重量％以上、特に８０重量％以上が凝集粒状体であれば更に好ましい。一般に凝集粒状体の比率が大きいほど吸水材としての性能が優れている。凝集粒状体の粒径は実質的に１００〜３０００μｍの範囲にあるのが好ましい。粒径が１００μｍより小さいと、吸水性能が十分に発現しない傾向がある。また粒径が３０００μｍより大きくなると、シート状基材との接着力が弱くなる傾向がある。凝集粒状体の比率や粒径は、主として気相中における重合途上の粒子の密度や分布状態、流動状態などを適宜調整することにより制御することができる。例えば凝集粒状体の比率を大きくするには、重合途上の粒子が落下の途中において相互に接触する機会が増加するように、重合室の単位横断面積当たりの落下樹脂量を大きくしたり、重合室内に上昇流を発生させて樹脂粒子の落下速度を遅くしたりすればよい。また重合室内に偏流を発生させて、落下する樹脂粒子の分布に片寄りを生じさせるのも一方法である。
【００２３】
上記により得られた繊維質基材に重合途上の樹脂粒子が付着した粒子−基材複合体は、次いで親水性有機溶媒と接触させて樹脂粒子の保有している水分の一部を除去して、後続する表面架橋を行うのに好適な含水率に調整する含水率調整工程に供することが好ましい。本発明では、粒子−基材複合体中の重合性モノマー由来の樹脂粒子１００重量部につき１〜１００重量部の水の存在下で架橋剤を添加して反応させる。特に架橋剤添加時の樹脂粒子の含水率は１０〜４０重量％であることが好ましい。含水率は多過ぎても少な過ぎても吸水性能の優れた樹脂粒子を得にくくなる傾向がある。なお、本明細書における「含水率」は、樹脂粒子に含まれている水分重量を、樹脂粒子の含水状態の重量を１００重量％としたときの重量％で表示したものである。
【００２４】
含水率調整工程で用いる親水性有機溶媒としては、含水率３０重量％以下、特に１０重量％以下のエタノール、メタノール又はアセトンが好ましい。例えばこのようなエタノール又はメタノールが収容されている脱水槽に粒子−基材複合体を浸漬したのち、樹脂粒子がつぶれない程度に軽く圧搾ロールを通過させたり、風を吹きつけたりして、付着しているエタノールやメタノールを除去する方法を採用することができる。なお、アルコールの除去は、後続する表面架橋剤溶液の付与に支障のない程度に行えばよく、付着しているアルコールを完全に除去する必要はない。浸漬条件は脱水に供する樹脂粒子の含水率及び目標とする樹脂粒子の含水率により異なるが、通常は室温で３０秒〜５分間程度浸漬すればよい。重合室から取り出された粒子−基材複合体は、脱水槽に導入するまでの搬送過程で重合がほぼ完了しており、また温度も通常は室温になっているので、脱水槽に導入する前に強制冷却する必要はない。
【００２５】
なお、複合化工程では重合反応に供するモノマー水溶液の濃度や、重合室雰囲気の温度、湿度などを制御することにより、重合室から取り出される粒子−基材複合体の樹脂粒子の含水率を、表面架橋に好適な１０〜４０重量％とすることも可能であり、この方法によるときは上述の含水率調整工程は不必要である。
【００２６】
含水率調整工程で樹脂粒子の含水率を所望の値にまで低下させた粒子−基材複合体は、次いで表面架橋工程に送られる。吸水性樹脂粒子の表面に架橋剤を付与したのち加熱して表面架橋することにより樹脂粒子の特性を改良することは公知であり、表面に選択的に架橋構造が形成される結果、吸水して膨潤するに際し膨潤を阻害せずにその形状を維持することができるものと考えられている。この工程では先ず粒子−基材複合体の樹脂粒子に表面架橋剤の溶液を付与する。表面架橋剤としては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ビス（メタ）アクリレート等の重合性モノマーと共重合し得る多官能化合物や、（ポリ）エチレングリコールジグリシジルエーテル等のカルボン酸基と反応し得る官能基を複数個有する化合物が用いられる。好ましいのはグリシジル基を有する架橋剤であり、特にポリグリシジルエーテルを用いることが好ましい。これらの表面架橋剤は、通常樹脂粒子（乾燥基準）に対して０．１〜１重量％、好ましくは０．２〜０．５重量％となるように用いられる。なお、これらの表面架橋剤は、樹脂粒子の表面全体に均一に付与されるように、水やアルコール（エタノールやメタノール等）で希釈して０．１〜１重量％、特に０．２〜０．５重量％のアルコール溶液として用いるのが好ましい。架橋剤溶液の付与は通常は噴霧器を用いて架橋剤溶液を樹脂粒子に噴霧したり、粒子−基材複合体を反転させて樹脂粒子付着面が下面になるようにして移動させつつ、これに架橋剤溶液を収容した槽に下部が浸漬しているロールブラシで架橋剤溶液を塗布する方法により行うのが好ましい。なお、架橋剤溶液を過剰に付与したのち、圧搾ロールで樹脂粒子がつぶれない程度に軽く圧搾したり、風を吹きつけたりして、余剰の架橋剤溶液を除去するようにしてもよい。この架橋剤溶液の付与は室温で行えばよい。架橋剤溶液を付与された粒子−基材複合体は、次いで加熱して架橋反応を進行させ、樹脂粒子表面に選択的に架橋構造を形成させる。架橋反応の条件は用いる架橋剤により適宜選択すればよいが、通常は１００℃以上の温度で１０分間以上反応させる。本発明の連続製造方法により製造される吸水性複合体の吸水性能は、この表面架橋工程までで実質的に決定される。
【００２７】
表面架橋工程を経た粒子−基材複合体は残存モノマー処理工程に送られることが好ましい。粒子−基材複合体の樹脂粒子中には、未反応の重合性モノマーが残存しているが、これらの重合性モノマーは人体に有害なので、この残存モノマー処理工程でその残存量を用途により定まる許容範囲にまで低減させる。
【００２８】
例えば重合性モノマーとして部分中和したアクリル酸を用いた場合には、一般に数百ｐｐｍ、多い場合には１０００ｐｐｍ以上ものモノマーが残存しているが、紙おむつや生理用ナプキンなどの用途に供する場合には、一般的には残存量は５００ｐｐｍ以下にするのが好ましく、残存量を３００ｐｐｍ以下、特に１００ｐｐｍ以下にまで低減させるのが最も好ましい。
【００２９】
重合性モノマーの処理はいくつかの方法で行うことができる。その一つの方法では、残存モノマーの重合を進行させることにより処理する方法がある。例えば粒子−基材複合体を１００〜２５０℃の温度で加熱処理し残存モノマーを重合させる方法、樹脂粒子に重合性モノマーの重合を促進する触媒ないしは触媒成分を付与したのち加熱して、重合性モノマーを重合させる方法がある。例えば前述のレドックス系重合開始剤を用いて重合を行った場合には、ラジカル発生剤が残存していることが多いので樹脂粒子に還元剤溶液を付与すればよい。還元剤としてはレドックス系重合開始剤として用いる亜硫酸ナトリウム、亜硫酸水素ナトリウム、Ｌ−アスコルビン酸等を用いればよく、通常はこれらを０．５〜５重量％水溶液として樹脂粒子に付与する。還元剤の付与量は乾燥樹脂１００重量部あたり０．１〜２０重量部でよい。還元剤溶液の付与は、噴霧器を用いてスプレーしたり、還元剤溶液中に浸漬するなど、任意の方法で行うことができる。還元剤を付与した樹脂粒子は次いで加熱して重合性モノマーを重合させる。加熱は例えば１００〜１５０℃で１０〜３０分間程度行えばよい。この加熱により樹脂粒子の含水率は低下するが、含水率がいまだ高い場合には更に乾燥機で乾燥して製品の吸水性複合体とすることができる。また、粒子−基材複合体中の樹脂粒子１００重量部につき０．０１〜１重量部の過酸化物および／またはアゾ化合物を添加した後加熱して、残存モノマー量を低減させることもできる。
【００３０】
さらに残存モノマーの重合を進行させる方法としては、紫外線又は放射線を照射する方法もある。
紫外線を照射する方法では、通常の紫外線ランプを用いればよく、照射強度、照射時間等は用いる繊維質基体の種類、重合性モノマー含浸量等によって決定する。一般的には紫外線ランプの照射強度は１０〜２００Ｗ／ｃｍ、好ましくは３０〜１２０Ｗ／ｃｍであり、照射時間は０．１秒〜３０分であり、ランプ−複合体の間隔は２〜３０ｃｍである。紫外線を照射する時の雰囲気としては、真空下または窒素、アルゴン、ヘリウム等の無機ガス存在下、または空気中のいずれも使用できる。また照射温度は特に制限はなく、室温で充分その目的を達成することができる。用いる紫外線照射装置にも特に制限はなく、静置状態にて一定時間照射する方法、あるいはベルトコンベアーにて連続的に照射する方法等を用いることができる。
【００３１】
また、この時の複合体中の水分量は、一般的には重合体１重量部に対して０．０１〜４０重量部、好ましくは０．１〜１．０重量部とする。０．０１重量部未満又は４０重量部超過の水分量は、未重合モノマーの低減化に影響を及ぼす傾向がある。この水分量は、複合化工程および／または表面架橋工程での水分量を制御することによって実現することもできるし、また表件架橋工程後に水分量を調節することによって実現することもできる。
【００３２】
また放射線を照射する方法では、電磁性放射線や微粒子性イオン化放射線の様な高エネルギー放射線が用いられる。具体的には、加速電子やガンマー線を例示することができる。照射されるべき線量は、前記複合体中の未重合モノマー量や、水分量等により変化するが、一般的には０．０１〜１００メガラド、好ましくは０．１〜５０メガラド、である。１００メガラド超過の線量では吸水量が極めて小さくなり、また０．０１メガラド未満では本発明で目的とする吸水能や、吸水速度が大きく、未重合モノマーが特段に小さいものが得られ難い。
【００３３】
また、この時の複合体中の水分量としては、一般的には繊維質基体１重量部に対して４０重量部以下、好ましくは１０重量部以下、が採用される。４０重量部超過の水分量では吸水速度改良効果が少なく、特に未重合モノマーの低減化に著しい影響を及ぼすので好ましくない。
【００３４】
本発明で複合体に高エネルギー放射線を照射する時の雰囲気としては、真空下または窒素、アルゴン、ヘリウム等の無機ガス存在下、または空気中のいずれであってもよい。好ましい雰囲気は空気であって、空気中で照射を行うと吸水能や吸水速度の大きくかつ未重合モノマーが特段に小さくなる。また照射温度には特に制限はなく、室温で充分にその目的を達成することができる。
【００３５】
未反応の重合性モノマーを処理する他の方法としては、残存モノマーを除去する方法がある。例えば表面架橋工程から取り出された粒子−基材複合体を、冷却したのち、含水有機溶媒中に浸漬して、重合性モノマーを抽出する方法がある。含水有機溶媒としてはエタノール、メタノール、アセトンを用いることができ、その含水率は１０〜９０重量％、特に３０〜６０重量％であるのが好ましい。一般に含水率が高いほど重合性モノマーの除去能が高いが、含水率の高い含水有機溶媒を用いると後続する乾燥工程でのエネルギー消費が多くなる。粒子−基材複合体を含水有機溶媒に浸漬する時間は通常５〜３０分間程度で十分であり、粒子−基材複合体を揺動させるなど重合性モノマーの抽出を促進する手段を採用するのも好ましい。浸漬処理後は乾燥機で処理して乾燥し、製品の吸水性複合体とする。通常は樹脂粒子の含水率が１０％程度となるように乾燥すればよい。
【００３６】
重合性モノマーを除去する更に他の方法としては、粒子−基材複合体を過熱水蒸気又は水蒸気含有ガスで処理する方法がある。例えば１１０℃の飽和水蒸気を１２０〜１５０℃に加熱して過熱水蒸気として粒子−基材複合体に接触させることにより、樹脂粒子中の重合性モノマーを低減させることができる。この方法では樹脂粒子中の水が水蒸気となって蒸発する際に、重合性モノマーも同時に気化して樹脂粒子から抜け出るものと考えられる。この方法によれば重合性モノマーの除去と製品の乾燥とを兼ねることができる。
【００３７】
本発明では、上記の複合化工程、表面架橋工程を必須の工程とし、含水率調整工程、残存モノマー処理工程を好ましい工程として行う。その順序は、複合化工程を最初に行った後は任意の順序で行うことができる。好ましい工程順は、複合化工程、表面架橋工程、残存モノマー処理工程を順次行うもの、複合化工程、残存モノマー処理工程、表面架橋工程を順次行うもの、複合化工程、残存モノマー処理工程、含水率調整工程、表面架橋工程を順次行うもの、複合化工程、含水率調整工程、表面架橋工程、残存モノマー処理工程を順次行うもの、複合化工程、含水率調整工程、残存モノマー処理工程、表面架橋工程を順次行うものである。
【００３８】
本発明の連続製造方法により吸水性複合体を製造する方法の１例を図１に従って説明すると、ロール（１）に巻かれた目付量３５ｇ／ｍ²のポリエステル不織布（２）を巻き戻しつつ、重合室（３）にその床面に平行に３０ｍ／分で送入する。重合室の上部に還元剤を含む重合性モノマー水溶液Ａを噴射するノズルと、酸化剤を含む重合性モノマー水溶液Ｂを噴射するノズルとを下向きに相対向させ、相対向する２本１組のノズルが１ｃｍ間隔で５対設置されている。その条件は、ノズルの内径が０．１８ｍｍ、ノズルの対向角度が３０度、ノズル間の対向間隔が３．５ｍｍ、不織布面からノズル開口端までの高さが３ｍである。
【００３９】
ノズルには、下記の重合性モノマー水溶液を常温で供給し、それぞれのノズルから５．０ｍ／秒で噴出させる。重合室には雰囲気が温度約２０〜６０℃、湿度約３０〜１００％となるように、その下部から水蒸気を含む空気を供給し、上部から排気する。排気は排ガス処理装置に導入する。
重合性モノマー水溶液Ａ：アクリル酸とアクリル酸ナトリウムとの５０重量％水溶液（アクリル酸：アクリル酸ナトリウム＝４：６（モル比））に、過酸化水素をアクリル酸とアクリル酸ナトリウムの合計に対して２．８重量％となるように含有させた水溶液。
重合性モノマー水溶液Ｂ：アクリル酸とアクリル酸ナトリウムとの５０重量％水溶液（アクリル酸：アクリル酸ナトリウム＝４：６（モル比））に、Ｌ−アスコルビン酸ナトリウムをアクリル酸とアクリル酸ナトリウムの合計に対して１．１重量％となるように含有させた水溶液。
【００４０】
ノズルから噴射された重合性モノマー水溶液ＡとＢとは衝突して液滴を形成し、重合しつつ不織布上に落下して、重合率約９５％以上の樹脂粒子として不織布に付着する。樹脂粒子の付着量は乾燥樹脂基準で約２００ｇ／ｍ²である。樹脂粒子の大きさは約２００〜１５００μｍであり、樹脂粒子の約９０％は凝集粒状体である。
【００４１】
樹脂粒子が付着した不織布は、脱水槽（４）に送入される。脱水槽には９６％エタノールが収容されており、不織布はこのエタノール中に５分間滞留して、含水率が含水樹脂基準で約２０％となるように脱水される。脱水槽のエタノールは、含水率が一定に維持されるように、その一部を連続的に抜出して蒸留塔（５）で脱水蒸留したのち、脱水槽に循環する。
【００４２】
脱水槽から取出した樹脂粒子が付着した不織布は、付着しているエタノールを風を吹抜けて除去したのち、表面架橋装置（６）に送入される。ここでは樹脂粒子に先ずエチレングリコールジグリシジルエーテルの０．５重量％エタノール溶液を、樹脂粒子に対し乾燥樹脂基準でエチレングリコールジグリシジルエーテルが０．３５重量％となるように噴霧して付与し、次いで約１１０℃に３０分間加熱して表面架橋させる。
【００４３】
表面架橋装置から引出した不織布は、風を吹付けて冷却したのち未反応の重合性モノマー抽出槽（７）に送入される。抽出槽（７）には常温の５０重量％含水エタノールが収容されており、不織布はこの含水エタノール中に２０分間滞留させる。これにより樹脂粒子の重合性モノマーの含有率は乾燥樹脂基準で約８０ｐｐｍに低下する。抽出槽から取出した不織布は内部に水蒸気が送入されている乾燥用ドラム（８）に接触させて、エタノール及び水を蒸発させて除去する。このようにして製造された吸水性複合体は巻取機（９）で巻取り、製品として出荷する。なお抽出槽（７）の含水エタノールは、モノマーが蓄積しないようにその一部を連続的に抜出し、新しい含水エタノールを補給する。
【００４４】
本発明の連続製造方法により製造した吸水性複合体は、高い吸水性を示す。
吸水性複合体の吸水性は多面的な性質であり、吸水性複合体の使用目的に応じて各種の評価方法で評価される。具体的には、吸収する液体として水、生理食塩水または人工尿等を用いて、吸水能（一定時間が経過する間に吸収することができる液体量を、吸水性ポリマー単位重量当たりの重量として表したもの）、保水能（一度液体を吸収した吸水性複合体を一定条件下で脱水処理した後に保持されている液体量を、吸水性ポリマー単位重量当たりの重量で表したもの）、常圧下吸水速度（短期の特定時間が経過する間に吸収することができる液体量を、吸水性ポリマー単位重量当たりの重量として表したもの）、加圧下吸水速度（一定加圧下で短期の特定時間が経過する間に吸収することができる液体量を、吸水性ポリマー単位重量当たりの重量として表したもの）等を測定することにより評価することができる。
【００４５】
本発明の連続製造方法によれば、例えば、ＪＩＳＫ−７２２４に準じた装置を用いて生理食塩水による加圧下吸水速度を測定したときに次のような吸水性を示す吸水性複合体が提供される。具体的には、４０ｇ／ｃｍ²の加圧下において１０分間生理食塩水を吸水させたときの吸水量が、該吸水性複合体に担持された吸水性ポリマー１ｇあたり１５ｇ以上である吸水性複合体、４０ｇ／ｃｍ²の加圧下において２０分間生理食塩水を吸水させたときの吸水量が、該吸水性複合体に担持された吸水性ポリマー１ｇあたり１８ｇ以上である吸水性複合体、４０ｇ／ｃｍ²の加圧下において６０分間生理食塩水を吸水させたときの吸水量が、該吸水性複合体に担持された吸水性ポリマー１ｇあたり２２ｇ以上である吸水性複合体、６０ｇ／ｃｍ²の加圧下において１０分間生理食塩水を吸水させたときの吸水量が、該吸水性複合体に担持された吸水性ポリマー１ｇあたり１３ｇ以上である吸水性複合体、６０ｇ／ｃｍ²の加圧下において２０分間生理食塩水を吸水させたときの吸水量が、該吸水性複合体に担持された吸水性ポリマー１ｇあたり１５ｇ以上である吸水性複合体、６０ｇ／ｃｍ²の加圧下において６０分間生理食塩水を吸水させたときの吸水量が、該吸水性複合体に担持された吸水性ポリマー１ｇあたり１９ｇ以上である吸水性複合体が好ましく提供される。
【００４６】
特に、４０ｇ／ｃｍ²の加圧下において１０分間生理食塩水を吸水させたときの吸水量と、６０ｇ／ｃｍ²の加圧下において１０分間生理食塩水を吸水させたときの吸水量との和が、該吸水性複合体に担持された吸水性ポリマー１ｇあたり２８ｇ以上である吸水性複合体、４０ｇ／ｃｍ²の加圧下において２０分間生理食塩水を吸水させたときの吸水量と、６０ｇ／ｃｍ²の加圧下において２０分間生理食塩水を吸水させたときの吸水量との和が、該吸水性複合体に担持された吸水性ポリマー１ｇあたり３３ｇ以上である吸水性複合体、４０ｇ／ｃｍ²の加圧下において６０分間生理食塩水を吸水させたときの吸水量と、６０ｇ／ｃｍ²の加圧下において６０分間生理食塩水を吸水させたときの吸水量との和が、該吸水性複合体に担持された吸水性ポリマー１ｇあたり４０ｇ以上である吸水性複合体が好ましく提供される。これらの吸水性複合体は、使用目的に合わせて適宜選択して用いることができる。
【００４７】
これらの吸水性複合体は、これまで吸水性樹脂が利用されていた様々な用途に用いることができる。「吸水性ポリマー」８１〜１１１頁（増田房義、共立出版、１９８７）、「高吸水性樹脂の開発動向とその用途展開」（大森英三、テクノフォーラム、１９８７）、田中健治、「工業材料」４２巻４号１８〜２５頁、１９９４、原田信幸、下村忠生、同２６〜３０頁には吸水性樹脂の様々な用途が紹介されており、適宜用いることができる。例えば紙おむつ、生理用品、鮮度保持材、保湿剤、保冷剤、結露防止剤、土壌改良材等が挙げられる。
【００４８】
また更に特開昭６３−２６７３７０号公報、特開昭６３−１０６６７号公報、特開昭６３−２９５２５１号公報、特開昭２７０８０１号公報、特開昭６３−２９４７１６号公報、特開昭６４−６４６０２号公報、特開平１−２３１９４０号公報、特開平１−２４３９２７号公報、特開平２−３０５２２号公報、特開平２−１５３７３１号公報、特開平３−２１３８５号公報、特開平４−１３３７２８号公報、特開平１１−１５６１１８号公報等に提案されているシート状吸水性複合体の用途にも用いることができる。
【００４９】
【実施例】
以下に実施例、参考例、比較例および試験例を挙げて本発明をさらに具体的に説明する。以下の実施例に示す材料、使用量、割合、処理内容、処理手順等は、本発明の趣旨を逸脱しない限り適宜変更することができる。したがって、本発明の範囲は以下に示す具体例に限定されるものではない。
【００５０】
（実施例１）
８０重量％のアクリル酸水溶液１２５重量部に、４８．５重量％の水酸化ナトリウム水溶液５７．３重量部、水６．４重量部、架橋剤（Ｎ，Ｎ′−メチレンビスアクリルアミド）０．１５重量部と更に酸化剤として３０重量％の過酸化水素水溶液５．０重量部を加えて溶液Ａを調製した。溶液Ａのモノマー濃度は６０重量％、中和度は５０モル％であった。
これとは別に８０重量％のアクリル酸水溶液１２５重量部に、４８．５重量％の水酸化ナトリウム水溶液５７．３重量部、水９．９重量部、架橋剤（Ｎ，Ｎ′−メチレンビスアクリルアミド）０．１５重量部と更に還元剤としてＬ−アスコルビン酸１．５重量部を加えて溶液Ｂを調製した。溶液Ｂのモノマー濃度、中和度は溶液Ａと同様であった。
【００５１】
図２に示した構造の内径０．１３ｍｍの２本のノズルが対になり、ノズルから流出する溶液Ａ、Ｂの交差角度が３０度、ノズル先端の距離が４ｍｍに調節した対向２本ノズルが１ｃｍ間隔に５対配置されたノズルに、一方のノズルより前記Ａ液、対向側の一方のノズルより前記Ｂ液をそれぞれ液温４０℃に加温し、それぞれ流速５ｍ／秒となるようにポンプで供給した。
Ａ液及びＢ液はそれぞれのノズル対のノズルから液柱状で放出されたところで合流し、それぞれ約１０ｍｍほど液柱を形成した後、液滴となって重合が進行しながら気相中（空気中、温度５０℃）を落下し、液滴の一部は気相中で衝突し凝集粒状体を形成し、ノズルの先端より下方３ｍに設置したポリエステル製不織布基材（目付量：３０ｇ／ｍ²）上に落下し、該基材上で重合を完了させた。また同時に液滴の一部は該基材上に落下し、基材上で凝集粒状体を形成後、該基材上で重合を完了させた。このような複合化工程を経て、吸水性ポリマーは該基材上に担持された。基材に担持された吸水性ポリマーの含水率は２０重量％であった。
【００５２】
さらに該複合体には０．５重量％エチレングリコールジグリシジルエーテル（ＥＧＤＧＥ）のエタノール溶液をＥＧＤＧＥが担持されたポリマーに対し（乾燥ポリマーベース）、３０００重量ｐｐｍとなる様噴霧した。ＥＧＤＧＥのエタノール溶液を施した複合体はさらに１１０℃温風乾燥機により担持されたポリマーの含水率が５％になるまで乾燥し、ポリマー担持量として２００ｇ／ｍ²が施された吸水性複合体を得た。
【００５３】
（実施例２）
実施例１と同じ方法で複合化工程まで行い、含水率２０重量％の吸水性ポリマーが担持された基材（複合体）を得た。
該複合体には０．５重量％エチレングリコールジグリシジルエーテル（ＥＧＤＧＥ）のエタノール溶液をＥＧＤＧＥが担持されたポリマーに対し（乾燥ポリマーベース）、３０００重量ｐｐｍとなる様噴霧した。ＥＧＤＧＥのエタノール溶液を施した複合体はさらに蒸気供給装置を具備した通気バンド式乾燥機にて、温度が１３０℃で、露点が１２０℃である水蒸気を基材に垂直に吹き付けた。水蒸気と基材との接触時間は２分で、その線速度は０．５ｍ／秒で行った。これにより吸水性複合体を得た。得られた複合体に担持されたポリマーの含水率は５％であり、ポリマー担持量として２００ｇ／ｍ²が施された吸水性複合体を得た。
【００５４】
（実施例３）
８０重量％のアクリル酸水溶液１２５重量部に、４８．５重量％の水酸化ナトリウム水溶液５７．３重量部、水６８．８重量部、架橋剤（Ｎ，Ｎ′−メチレンビスアクリルアミド）０．１５重量部と更に酸化剤として３０重量％の過酸化水素水溶液５．０重量部を加えて溶液Ａを調製した。溶液Ａのモノマー濃度は４５重量％、中和度は５０モル％であった。
これとは別に８０重量％のアクリル酸水溶液１２５重量部に、４８．５重量％の水酸化ナトリウム水溶液５７．３重量部、水７２．５重量部、架橋剤（Ｎ，Ｎ′−メチレンビスアクリルアミド）０．１５重量部と更に還元剤としてＬ−アスコルビン酸１．５重量部を加えて溶液Ｂを調製した。溶液Ｂのモノマー濃度、中和度は溶液Ａと同様であった。
【００５５】
図２に示した構造の内径０．１３ｍｍの２本のノズルが対になり、ノズルから流出する溶液Ａ、Ｂの交差角度が３０度、ノズル先端の距離が４ｍｍに調節した対向２本ノズルが１ｃｍ間隔に５対配置されたノズルに、一方のノズルより前記Ａ液、対向側の一方のノズルより前記Ｂ液をそれぞれ液温５０℃に加温し、それぞれ流速５ｍ／秒となるようにポンプで供給した。
Ａ液及びＢ液はそれぞれのノズル対のノズルを出たところで合流し、それぞれ約１０ｍｍほど液柱を形成した後、液滴となって重合が進行しながら気相中（空気中、温度５０℃）を落下し、液滴の一部は気相中で衝突し凝集粒状体を形成し、ノズルの先端より下方３ｍに設置したポリエステル製不織布基材（目付量：３０ｇ／ｍ²）上に落下し、該基材上で重合を完了させた。また同時に液滴の一部は該基材上に落下し、基材上で凝集粒状体を形成後、該基材上で重合を完了させた。このような複合化工程を経て、吸水性ポリマーは該基材上に担持された。基材に担持された吸水性ポリマーの含水率は４５重量％であった。
【００５６】
続いて該複合体に過硫酸カリウム（ＫＰＳ）の１重量％水溶液を、過硫酸カリウムが担持されたポリマーに対し（乾燥ポリマーベース）２０００重量ｐｐｍとなるよう噴霧した。その後、該複合体は１１０℃温風乾燥機により担持されたポリマーの含水率が２０％になるまで乾燥した。
さらに該複合体には０．５重量％エチレングリコールジグリシジルエーテル（ＥＧＤＧＥ）のエタノール溶液をＥＧＤＧＥが担持されたポリマーに対し（乾燥ポリマーベース）、３０００重量ｐｐｍとなる様噴霧した。ＥＧＤＧＥのエタノール溶液を施した複合体はさらに１１０℃温風乾燥機により担持されたポリマーの含水率が５％になるまで乾燥し、ポリマー担持量として２００ｇ／ｍ²が施された吸水性複合体を得た。
【００５７】
（実施例４）
含水率４５重量％の吸水性ポリマーが担持された基材（複合体）に、亜硫酸水素ナトリウム（ＮａＨＳＯ₃）の０．５重量％水溶液を、亜硫酸水素ナトリウムが担持されたポリマーに対し（乾燥ポリマーベース）１０００重量ｐｐｍとなるよう噴霧した点を除き、実施例３と同じ方法により吸水性複合体を得た。
【００５８】
（実施例５）
実施例１と同じ方法で複合化工程まで行い、含水率２０重量％の吸水性ポリマーが担持された基材（複合体）を得た。
該複合体に１０００ｍＪ／ｃｍ²の紫外線を照射した後、０．５重量％エチレングリコールジグリシジルエーテル（ＥＧＤＧＥ）のエタノール溶液をＥＧＤＧＥが担持されたポリマーに対し（乾燥ポリマーベース）、３０００重量ｐｐｍとなる様噴霧した。ＥＧＤＧＥのエタノール溶液を施した複合体はさらに１１０℃温風乾燥機により、担持されたポリマーの含水率が５％になるまで乾燥し、ポリマー担持量として２００ｇ／ｍ²が施された吸水性複合体を得た。
【００５９】
（実施例６）
実施例１と同じ方法で複合化工程まで行い、含水率２０重量％の吸水性ポリマーが担持された基材（複合体）を得た。
該複合体にダイナミトロン加速器を装備した電子線装置より、空気雰囲気下２０メガラドの線量で電子線を照射して、吸水性複合体を得た。引き続き、０．５重量％エチレングリコールジグリシジルエーテル（ＥＧＤＧＥ）のエタノール溶液をＥＧＤＧＥが担持されたポリマーに対し（乾燥ポリマーベース）、３０００重量ｐｐｍとなる様噴霧した。ＥＧＤＧＥのエタノール溶液を施した複合体はさらに１１０℃温風乾燥機により、担持されたポリマーの含水率が５％になるまで乾燥し、ポリマー担持量として２００ｇ／ｍ²が施された吸水性複合体を得た。
【００６０】
（実施例７）
実施例３と同じ方法で複合化工程まで行い、含水率４５重量％の吸水性ポリマーが担持された基材（複合体）を得た。
該複合体を、担持されたポリマー１重量部（乾燥ポリマーベース）に対し、１０重量部の３０重量％エタノール水溶液に浸漬し、室温下３０分間放置した。その後、該複合体はエタノール水溶液から取り出され、さらに１０重量部のエタノールに浸漬し、室温下３０分間放置した。エタノールから取り出された複合体はさらに、０．５重量％エチレングリコールジグリシジルエーテル（ＥＧＤＧＥ）のエタノール溶液をＥＧＤＧＥが担持されたポリマーに対し（乾燥ポリマーベース）、３０００重量ｐｐｍとなる様噴霧した。ＥＧＤＧＥのエタノール溶液を施した複合体はさらに１１０℃温風乾燥機により、担持されたポリマーの含水率が５％になるまで乾燥し、ポリマー担持量として２００ｇ／ｍ²が施された吸水性複合体を得た。
【００６１】
（参考例１）
実施例１と同じ方法でＡ液およびＢ液を調製した。図２に示した構造の内径０．１３ｍｍの２本のノズルを使用し、ノズル間角度を３０度、ノズルの先端の間の距離を４ｍｍとし、一方のノズルより前記Ａ液、他方のノズルより前記Ｂ液を、それぞれ液温４０℃に加温し、それぞれ流速５ｍ／秒となるようにポンプで供給した。Ａ液及びＢ液はノズルを出たところで合流し、約１０ｍｍほど液柱を形成した後、液滴となって空気（６０℃）の上昇気流中を落下した。この液滴をノズルの先端より下方１００ｃｍに設置したポリエステル製不織布基材（目付量：３０ｇ／ｍ²）上に落下し、該基材上で重合を完了させた。
【００６２】
基材に担持された吸水性ポリマーの含水率は３０重量％であった。さらに該複合体には０．５重量％エチレングリコールジグリシジルエーテル（ＥＧＤＧＥ）のエタノール溶液を、ＥＧＤＧＥが担持されたポリマーに対し（乾燥ポリマーベース）、３０００重量ｐｐｍとなる様噴霧した。ＥＧＤＧＥのエタノール溶液を施した複合体はさらに１１０℃温風乾燥機に担持させた吸水性ポリマーの含水率が５％になるまで乾燥し、ポリマー担持量として２００ｇ／ｃｍ²が施された吸水性複合体を得た。
【００６３】
（参考例２）
実施例３と同じ方法で複合化工程まで行い、含水率４５重量％の吸水性ポリマーが担持された基材（複合体）を得た。該複合体には、０．５重量％エチレングリコールジグリシジルエーテル（ＥＧＤＧＥ）のエタノール溶液をＥＧＤＧＥが担持されたポリマーに対し（乾燥ポリマーベース）、３０００重量ｐｐｍとなる様噴霧した。ＥＧＤＧＥのエタノール溶液を施した複合体はさらに１１０℃温風乾燥機により、担持されたポリマーの含水率が５％になるまで乾燥し、ポリマー担持量として２００ｇ／ｍ²が施された吸水性複合体を得た。
【００６４】
（参考例３）
実施例１と同じ方法で複合化工程まで行い、含水率２５重量％の吸水性ポリマーが担持された基材（複合体）を得た。該複合体を、１１０℃温風乾燥機により、担持されたポリマーの含水率が５％になるまで乾燥し、ポリマー担持量として２００ｇ／ｍ²が施された吸水性複合体を得た。さらに得られた複合体には、０．５重量％エチレングリコールジグリシジルエーテル（ＥＧＤＧＥ）のエタノール溶液をＥＧＤＧＥが担持されたポリマーに対し（乾燥ポリマーベース）、３０００重量ｐｐｍとなる様噴霧した。ポリマー担持量として２００ｇ／ｍ²が施された吸水性複合体を得た。
【００６５】
（比較例１）
実施例１と同じ方法で複合化工程まで行い、含水率２０重量％の吸水性ポリマーが担持された基材（複合体）を得た。
担持されたポリマーの含水率が５％になるまで乾燥し、ポリマー担持量として２００ｇ／ｍ²が施された吸水性複合体を得た。
【００６６】
（比較例２）
１００ｍｌのコニカルフラスコに、水酸化ナトリウム（純度９６重量％）１３．１ｇを採り、氷冷下に純水３９．０ｇで溶解した。これにアクリル酸３０ｇを徐々に加えて中和した。中和度は約７５％、水溶液中のモノマー濃度として約４５重量％となった。
これにラジカル重合開始剤として過硫酸カリウムを０．０５ｇ採って、上記モノマー水溶液中に溶解させ、Ｎ₂にて脱気した。
【００６７】
別にポリエステル不織布（目付量：３０ｇ／ｍ²）を０．５８３ｇ採って、これに上記モノマー水溶液をロールコーターによって不織布全面に塗布して繊維に沿って線条模様に施した。含浸されたモノマー量は、不織布に対して６．８重量倍であった。これを、あらかじめＮ₂で脱気して９０℃にした恒温反応槽内に入れた。重合は直ちに起って、部分中和ポリアクリル酸ナトリウムの自己架橋物からなる高吸水性ポリマーがポリエステル不織布にその繊維に沿って線条模様に安定性良く固定された複合体が得られた。
【００６８】
次いで、この複合体の水分量を約２５重量％（高吸水性ポリマー重量基準であり、以下同様）とし、これにエチレングリコールジグリシジルエーテル０．０１２ｇ（乾燥ポリマー３０００ｐｐｍ）を、０．５重量％エタノール溶液として噴霧してから、１１０℃温風乾燥機を用いて、担持されたポリマーの含水率が５％になるまで乾燥し、ポリマー担持量として２００ｇ／ｍ²が施された吸水性複合体を得た。
【００６９】
（試験例）
実施例１〜７、参考例１〜３および比較例１〜２で得た各吸水性複合体について、以下の測定と試験を行った。
（１）ポリマーが凝集粒状体となっている比率吸水性複合体の複数箇所の走査型顕微鏡写真（ＳＥＭ写真）を撮影後、任意に１００個の粒子を選定して凝集の有無を判定した。凝集粒状体の密度は均一と仮定して、ポリマーが凝集粒状体となっている比率を計算した。
【００７０】
（２）凝集粒状体の平均粒子径
吸水性複合体の複数箇所のＳＥＭ写真を撮影後、任意に１００個の粒子を選定して粒子径を計測し、測定値の平均を求めた。
【００７１】
（３）基材上への落下時の重合率
基材を置く位置にメタノールの液面が位置するように秤量したメタノールの入ったビーカーを設置し、重合を開始させた反応混合物の液滴を気相中で形成し、メタノールの入ったビーカー中へ重合途中の凝集粒状体が落下するようにした。メタノール中のモノマー量を液体クロマトグラフィーで測定した。また、メタノール中のポリマーを１３０℃で３時間減圧乾燥した後、重量を測定した。それぞれの重量から以下の式により重合率を計算した（Ｍｐはポリマー重量、Ｍｍはモノマー重量、単位ｇ）。
【数１】

【００７２】
（４）生理食塩水吸水能
３００ｍｌのビーカー吸水性複合体を約１．０ｇおよび濃度０．９％の生理食塩水約２００ｇをそれぞれ秤量して入れてから、約４時間放置して生理食塩水によってポリマーを充分に膨潤させた。次いで、１００メッシュ篩で水切りをした後、下記式に従って生理食塩水吸水能を算出した。式中の重量の単位はすべてｇである。
【数２】

【００７３】
（５）生理食塩水保水能
複合体に担持された吸水性ポリマーの重量Ｗ₁が１ｇとなるように複合体を切断し、２５０メッシュのナイロン袋（２０ｃｍ×１０ｃｍ）に入れ、室温の生理食塩水（濃度０．９重量％）５００ｍｌ中に３０分間浸漬した。次いでナイロン袋を引上げ、１５分間懸垂して水切りしたのち、遠心分離機を用いて９０Ｇで９０秒間脱水した。脱水後のナイロン袋の重量Ｗ₂を測定した。また吸水性ポリマーを担持していない不織布を生の複合体と同じ大きさに切断し、同様の操作を行い、その重量Ｗ₃を測定した。生理食塩水の保水能は以下の式にしたがって算出した。ここでＷ₁〜Ｗ₃の単位はすべてｇである。
【数３】

【００７４】
（６）常圧下吸水速度
３００ｍｌのビーカーに吸水性複合体を約１．０ｇおよび濃度０．９％の生理食塩水約２００ｇをそれぞれ秤量して入れてから、５分間放置して生理食塩水によってポリマーを膨潤させた。次いで、１００メッシュ篩で水切りをした後、上記式に従って生理食塩水吸水能を算出し、これを吸水速度とした。
【００７５】
（７）加圧下吸水速度
ＪＩＳＫ−７２２４に準じ、図３に示される装置を用いて生理食塩水による加圧下吸水速度を測定した。予め１０ｃｍ×１０ｃｍに切断した複合体を小孔のあいた支持板に敷いた不織布上に担持された吸水性ポリマーが上になる様にのせ、さらにその上に支持板下に敷いたものを同じ不織布をのせた。さらにその上に所定のおもりをのせ、所定の圧力（４０ｇ／ｃｍ²または６０ｇ／ｃｍ²）を複合体にかけた。複合体の下面を０．９％生理食塩水と接触させて複合体が生理食塩水を吸水する量を測定した。開始後１０分間、２０分間および６０分間に吸水した０．９％生理食塩水の量をもって加圧下吸水速度とした。
【００７６】
（８）残留未反応重合性単量体濃度（残存モノマーの濃度）
吸水性複合体０．５ｇを精秤し、これを２リットルビーカー中のイオン交換水１リットルに添加し、約１０時間撹拌下に充分膨潤させた。膨潤後のポリマーゲルを２００メッシュ篩で濾別し、濾過液を高速液体クロマトグラフィーにて分析した。別に既知の濃度を示す単量体標準液を作り、これにより検量線を作って絶対濃度を求めた。
試験結果を以下の表に示す。
【００７７】
【表１】

【００７８】
本発明の連続製造方法により製造した実施例１〜７および参考例１〜３の吸水性複合体は、いずれも生理食塩水吸水能、保水能、常圧下吸水速度、加圧下吸水速度、残存モノマー濃度が満足しうる範囲内であった。特に実施例１〜７の吸水性複合体は優れた効果を示した。これに対して、比較例１〜２の吸水性複合体は特に加圧下吸水速度が劣っており、満足しうるものではなかった。
【００７９】
【発明の効果】
本発明によれば、吸水能および保水能が高い吸水性複合体を連続的に効率よく製造することができる。
【図面の簡単な説明】
【図１】本発明の方法により吸水性複合体を連続的に製造する際のフローシートの例である。
【図２】本発明の製造方法における混合工程を実施するために用いるノズル構造の一例を示す概略図である。
【図３】試験例で用いた加圧下吸水速度測定装置の概略図である。
【符号の説明】
１不織布のロール
２不織布
３重合室
４脱水槽
５蒸留塔
６表面架橋装置
７重合性モノマー抽出槽
８乾燥機
９吸水性複合体の巻取り機
１１Ａ液用ノズル
１２Ｂ液用ノズル
１３Ａ液
１４Ｂ液
２１ビュレット
２２ゴム栓
２３小穴の開いた支持板
２４不織布
２５樹脂粒子[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for continuously producing a water absorbent composite in which water absorbent resin particles are bound to a fibrous base material such as a nonwoven fabric. The water-absorbent composite produced by the production method of the present invention is suitable for use in the production of water-absorbent articles such as so-called paper diapers and sanitary napkins.
[0002]
[Prior art]
Since paper, pulp, non-woven fabric, sponge-like urethane resin and the like have high water absorption, they have been conventionally used as a water-retaining agent for various sanitary products such as sanitary napkins, paper diapers and the like and agricultural materials. However, these water-absorbing materials have a water absorption amount of only about 10 to 50 times their own weight. For this reason, in order to absorb or retain a large amount of water, a large amount of material is required, and there is a problem that it becomes extremely bulky. In addition, there is a drawback in that moisture is easily released when the absorbed material is pressurized.
[0003]
In recent years, various high-water-absorbing polymer materials have been proposed for the purpose of improving the above disadvantages of this type of water-absorbing material. For example, a starch graft polymer (Japanese Patent Publication No. Sho 53-46199), a cellulose modified product (Japanese Patent Publication No. Sho 50-80376 etc.), a cross-linked product of a water-soluble polymer (Japanese Patent Publication No. Sho 43-23462, etc.) ), Self-crosslinking type alkali metal acrylate polymers (Japanese Patent Publication No. 54-30710, etc.) have been proposed.
[0004]
The water absorption performance of these water absorbent polymers has reached a considerably high level, but since most of them are powdery, for example, tissue, non-woven fabric, cotton for use as sanitary materials such as sanitary napkins and paper diapers. It is necessary to uniformly disperse the water-absorbent resin powder on a substrate such as. However, the water-absorbent resin powder dispersed by a known method is difficult to fix with good stability on the fibrous base material, and is often partly assembled even after being uniformly dispersed, In addition, the swollen gel after water absorption has a drawback that it is easily fixed from the fibrous base material without being fixed on the fibrous base material with good stability. If the water-absorbent resin powder is adhered to fluff pulp or the like with an adhesive to prevent such movement, the water-absorbent resin powder absorbs water and the swelling is inhibited by the adhesive. It will disappear.
[0005]
Furthermore, in the method of obtaining the absorbent by uniformly dispersing the water-absorbent resin powder as described above on the fibrous base material, not only the polymer powder is likely to leak from the fibrous base material, but also the trouble associated with the handling of the powder. In addition, due to process problems in efficiently performing uniform dispersion, the cost has been extremely high.
[0006]
As a method for solving these problems, there is provided a method in which a droplet made of a mixed liquid obtained by initiating polymerization of an acrylic acid-based polymerizable monomer aqueous solution with a redox-based initiator is supported on a fibrous base material and polymerized ( JP-A-9-67403). According to this method, it is possible to produce a water-absorbing composite excellent in water absorption and water absorption speed and having highly water-absorbing polymer particles fixed on a fibrous base material with good stability. However, depending on the application of the product, an absorbent material with higher performance than that of the absorbent composite is required.
[0007]
[Problems to be solved by the invention]
Accordingly, the present invention provides an efficient water-absorbing composite comprising the water-absorbing resin particles fixed to the fibrous base material so that the water-absorbing resin particles can exhibit their original water-absorbing performance and water-retaining performance simultaneously with the production of the water-absorbing resin particles. It is an object of the present invention to provide a method for continuously manufacturing a body. Another object of the present invention is to provide a highly practical water-absorbing article using a water-absorbing composite having such properties.
[0008]
[Means for Solving the Problems]
As a result of intensive studies in order to solve the above problems, the present inventors have conducted the following steps:
(A) A polymerizable monomer aqueous solution mainly composed of an unsaturated carboxylic acid neutralized by 20% or more of carboxyl groups is dropped while being polymerized in the form of droplets, and the fibrous base material is fed to the dropping point. Composite step of attaching resin particles in the process of polymerization to a fibrous base material, completing the polymerization after the attachment to form a particle-base composite
(B) A crosslinking agent having two or more functional groups capable of reacting with a carboxyl group and / or a carboxylate group is added to the composite in an amount of 1 to 100 parts by weight of resin particles derived from the polymerizable monomer in the composite. Surface cross-linking step of adding and reacting in the presence of 100 parts by weight of water
It came to provide the continuous manufacturing method of the water absorptive complex of this invention characterized by including this.
[0009]
In the continuous production method of the present invention, before the surface cross-linking step, a moisture content adjusting step of adjusting the moisture content of the resin particles constituting the particle-substrate composite to 10 to 40% by weight can be performed, and the composite After the step, a residual monomer treatment step for treating the polymerizable monomer remaining in the resin particles constituting the particle-substrate composite can be performed. In the continuous manufacturing method of this invention, it is preferable that the moisture content of the resin particle which comprises the particle-substrate composite used for a surface crosslinking process is 10 to 40 weight%. Further, at least a part of the resin particles of the particle-base composite obtained in the compositing step is an agglomerated granule in which the resin particles are bound to each other, and a part of the resin particle constituting the agglomerated granule Is preferably not directly attached to the fibrous base material.
[0010]
Moreover, this invention also provides the water absorptive composite manufactured by said continuous manufacturing method. The water-absorbing composite of the present invention is, for example, 40 g / cm ² The amount of water absorption when physiological saline is absorbed for 10 minutes under the above pressure is preferably 15 g or more per 1 g of the water-absorbing polymer supported on the water-absorbing composite.
Furthermore, the present invention also provides a water-absorbing article using these water-absorbing composites.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the continuous production method, the water-absorbent composite, and the water-absorbent article according to the present invention will be described in detail.
The method for producing a water-absorbing composite according to the present invention includes the above-described composite process and surface cross-linking process.
In the compounding step, polymerization is performed in the gas phase with the polymerizable monomer aqueous solution dispersed in the form of droplets. Such a polymerization method is publicly known, and the polymerization is usually performed while supplying a polymerizable monomer aqueous solution containing a polymerization initiator to a liquid dispersion apparatus provided at the upper part of the polymerization chamber and dropping it as droplets in the polymerization chamber. .
[0012]
As the polymerizable monomer used in the complexing step, any monomer can be used as long as it gives a water-absorbing resin. Usually, unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid and itaconic acid are used. Used. If desired, some of these may be used in combination, or other monomers such as (meth) acrylamide and 2-hydroxyethyl (meth) acrylate may be used in combination. Among these, it is preferable to use acrylic acid or methacrylic acid. Particularly preferred is acrylic acid, and it is usually preferred to use acrylic acid alone or a monomer mixture in which acrylic acid accounts for 50 mol% or more, particularly 80 mol% or more.
[0013]
In addition, it is preferable to use at least a part of these unsaturated carboxylic acids as a water-soluble salt, for example, an alkali metal salt or an ammonium salt, and the water-absorbing ability of the water-absorbing resin obtained in this way can be improved. . For example, in the case of acrylic acid, the water-absorbing ability of the resulting water-absorbent resin can be remarkably improved by subjecting 20% or more, preferably 20 to 90%, to the polymerization as an alkali metal salt or ammonium salt.
[0014]
In the present invention, a small amount of a crosslinking agent may be contained in the solution of the polymerizable monomer subjected to polymerization, if desired. As the crosslinking agent, for example, N, N′-methylenebis (meth) acrylamide or (poly) ethylene glycol diglycidyl ether can be used, and the amount of the crosslinking agent used is usually 0.01 to 1 weight with respect to the monomer. %, Preferably 0.05 to 0.5% by weight. When there is too much quantity of a crosslinking agent, there exists a tendency for the water absorption ability of the resin particle to produce | generate to fall.
[0015]
The concentration of the polymerizable monomer in the monomer solution is generally 20% or more by weight, preferably 25% by weight or more, as the total weight of each of the free type and salt type. When the monomer concentration is too small, it is difficult to form droplets having an appropriate viscosity, and when the resin particles adhere to the fibrous base material, the shape thereof is liable to break down. It tends to be inferior in physical properties. The upper limit of the monomer concentration is about 80% by weight from the viewpoint of handleability.
[0016]
As the polymerization initiator, it is preferable to use a redox polymerization initiator comprising a combination of an oxidizing radical generator and a reducing agent. Hydrogen peroxide is preferably used as the radical generator, but persulfates such as ammonium persulfate and potassium persulfate, hydroperoxides such as t-butyl hydroperoxide and cumene hydroperoxide, etc. Cerium salts, permanganates, chlorites, hypochlorites and the like can be used. These radical generators are preferably used in an amount of 0.01 to 10% by weight, particularly 0.1 to 2% by weight, based on the polymerizable monomer.
[0017]
As the reducing agent, it is preferable to use L-ascorbic acid or an alkali metal salt thereof. In addition, sulfites such as sodium sulfite and sodium hydrogen sulfite, sodium thiosulfate, cobalt acetate, copper sulfate, ferrous sulfate, etc. It can also be used. These reducing agents are preferably used in an amount of 0.01 to 10% by weight, particularly 0.1 to 2% by weight, based on the polymerizable monomer.
[0018]
The polymerization reaction can be carried out by various known methods. According to the method described in Japanese Patent Application No. 10-330283, a polymerizable monomer aqueous solution containing a radical generator, a polymerizable monomer aqueous solution containing a reducing agent, Is preferably ejected in the form of a liquid column from the respective nozzles installed opposite to each other at the upper part of the polymerization chamber, and the two liquids collide with each other in the air to be mixed and dispersed into droplets (see FIG. 2). For example, a first liquid containing an oxidizing agent and a polymerizable monomer aqueous solution constituting a redox polymerization initiator, and a second liquid containing a reducing agent and a polymerizable monomer aqueous solution constituting a redox polymerization initiator are vapor-phased. The method of mixing in can be illustrated as a preferable method. The size of the droplet is preferably 5 to 3000 μm, particularly preferably 50 to 1000 μm. As soon as the two liquids are mixed, the polymerization starts, and the polymerization proceeds in the droplet and falls in the polymerization chamber. The atmosphere in the polymerization chamber is arbitrary as long as it does not interfere with the polymerization reaction. Usually, nitrogen, helium, carbon dioxide, or the like is used as the atmospheric gas, but air or water vapor can also be used. The temperature of the atmosphere is usually room temperature to 150 ° C, preferably room temperature to 100 ° C. In addition, when water vapor is fed into the atmosphere, the amount of water evaporation from the aqueous monomer solution is determined based on the concentration of the aqueous monomer solution used for the reaction and the desired moisture content of the generated resin particles. Set from.
[0019]
In the present invention, it is preferable to feed the sheet-like fibrous base material into the polymerization chamber, and move the resin parallel to the floor surface of the polymerization chamber while adhering the resin particles that are falling on the polymerization chamber. . As the fibrous base material, any material may be used as long as it is formed in a certain shape and easily adheres to the resin particles during polymerization, and cloth, paper, pulp, nonwoven fabric, or the like can be used. Among them, it is preferable to use fluff pulp or a nonwoven fabric in which the fibrous base material is roughly accumulated, the resin particles can easily enter the inside, and the resin particles can strongly adhere to the fibrous base material. Particularly preferred is a non-woven fabric made of (semi) synthetic fibers such as polyester, polyolefin, polyamide, acetate, etc., which has high strength even in a wet state. The fiber thickness of the fibrous base material constituting the nonwoven fabric is preferably 10 to 50 μm, and the basis weight of the nonwoven fabric is 10 to 100 g / m. ² , Especially 20-50g / m ² Is preferred.
[0020]
The polymerization rate at the time when droplets in the process of polymerization are in contact with the gas phase or on the substrate to form agglomerated particles is 3 to 97%, preferably 20 to 97%, more preferably 50 to 95%. Set various conditions as shown. If this polymerization rate is too low, even if the droplets collide with each other, they do not become agglomerated particles but are integrated into large particles, or when the droplets fall on the substrate, the liquid is deposited on the substrate. It becomes impossible to adhere to the base material in the form of agglomerated particles by spreading or absorbing or impregnating. Moreover, when too high, the adhesive force with a base material will not express but the fixability of a base material and a water absorbing polymer will worsen. Moreover, it is preferable that the polymerization rate of the polymerizable monomer at the time of contact with the fibrous base material is 20 to 97% in the compounding step.
[0021]
The resin particles are 50 to 400 g / m in the water-absorbing composite finally obtained. ² It is made to adhere to a fibrous base material so that it may become. Generally 80 to 300 g / m depending on the application ² It is preferable to adhere so that it becomes. If the content of the resin particles in the water-absorbing composite is small, the water absorption ability is naturally reduced. Moreover, when there is too much content, it is generally uneconomical, the ratio of the part couple | bonded with a fibrous base material reduces, and the bond strength with a fibrous base material becomes weak.
[0022]
At least a part of the resin particles constituting the water-absorbing composite produced by the continuous production method of the present invention is composed of resin particles (primary particles) being polymerized to form an aggregated granular material. And it is preferable that a part of the resin particles (primary particles) constituting the aggregated granular material are not directly bonded to the fibrous base material. Since such agglomerated granular material has a large specific surface area, the water absorption speed is large, and only a part of the primary particles constituting the agglomerated granular material is bonded to the fibrous base material. The restraint received from the substrate is small, and the water absorption capacity is excellent. In addition, since the joint surfaces of the primary particles constituting the aggregated granular material are integrated, the aggregated granular material may collapse into primary particles and drop off from the fibrous base material not only before water absorption but also after water absorption. Few. It is preferable that 30% by weight or more of the resin particles are agglomerated particles, and more preferably 50% by weight or more, particularly 80% by weight or more are agglomerated particles. In general, the larger the ratio of the aggregated granular material, the better the performance as a water absorbing material. The particle diameter of the aggregated granular material is preferably substantially in the range of 100 to 3000 μm. When the particle size is smaller than 100 μm, the water absorption performance tends to be insufficient. On the other hand, when the particle diameter is larger than 3000 μm, the adhesive strength with the sheet-like substrate tends to be weakened. The ratio and the particle size of the aggregated granular material can be controlled mainly by appropriately adjusting the density, distribution state, flow state, etc. of the particles in the gas phase during polymerization. For example, in order to increase the ratio of the agglomerated particles, the amount of dropped resin per unit cross-sectional area of the polymerization chamber is increased or the polymerization chamber is increased so that the number of particles in the polymerization process is in contact with each other during the fall. It is only necessary to generate an upward flow to slow down the falling speed of the resin particles. Another method is to generate a drift in the polymerization chamber to cause a deviation in the distribution of the falling resin particles.
[0023]
The particle-base composite in which resin particles in the process of polymerization are attached to the fibrous base material obtained as described above is then brought into contact with a hydrophilic organic solvent to remove a part of the water held by the resin particles. It is preferable that the water content is adjusted to a water content suitable for subsequent surface cross-linking. In the present invention, a crosslinking agent is added and reacted in the presence of 1 to 100 parts by weight of water per 100 parts by weight of the resin particles derived from the polymerizable monomer in the particle-base composite. In particular, the water content of the resin particles when the crosslinking agent is added is preferably 10 to 40% by weight. If the water content is too high or too low, it tends to be difficult to obtain resin particles having excellent water absorption performance. The “moisture content” in this specification represents the weight of water contained in the resin particles in terms of weight% when the weight of the water content of the resin particles is 100% by weight.
[0024]
The hydrophilic organic solvent used in the water content adjusting step is preferably ethanol, methanol or acetone having a water content of 30% by weight or less, particularly 10% by weight or less. For example, after immersing the particle-base composite in a dehydration tank containing such ethanol or methanol, the particles are adhered by passing through a squeeze roll or blowing wind to such an extent that the resin particles do not collapse. A method of removing ethanol and methanol can be employed. The alcohol may be removed to an extent that does not hinder the subsequent application of the surface cross-linking agent solution, and it is not necessary to completely remove the adhering alcohol. The immersion conditions vary depending on the water content of the resin particles to be dehydrated and the water content of the target resin particles, but it is usually sufficient to immerse at room temperature for about 30 seconds to 5 minutes. The particle-substrate composite taken out from the polymerization chamber is almost completely polymerized in the conveying process until it is introduced into the dehydration tank, and the temperature is usually at room temperature. There is no need for forced cooling.
[0025]
In the compounding step, the water content of the resin particles of the particle-substrate composite taken out from the polymerization chamber is controlled by controlling the concentration of the aqueous monomer solution used for the polymerization reaction, the temperature and humidity of the polymerization chamber atmosphere, and the like. It is also possible to make it 10 to 40 weight% suitable for bridge | crosslinking, and when using this method, the above-mentioned moisture content adjustment process is unnecessary.
[0026]
The particle-base composite in which the moisture content of the resin particles is reduced to a desired value in the moisture content adjusting step is then sent to the surface crosslinking step. It is known to improve the properties of the resin particles by applying a crosslinking agent to the surface of the water-absorbent resin particles, followed by heating to cross-link the surface of the water-absorbent resin particles. It is considered that the shape can be maintained without inhibiting the swelling during swelling. In this step, first, a solution of a surface cross-linking agent is applied to the resin particles of the particle-base composite. As the surface cross-linking agent, polyfunctional compounds that can be copolymerized with polymerizable monomers such as N, N'-methylenebis (meth) acrylamide, (poly) ethylene glycol bis (meth) acrylate, (poly) ethylene glycol diglycidyl ether, etc. A compound having a plurality of functional groups capable of reacting with the carboxylic acid group is used. A cross-linking agent having a glycidyl group is preferred, and polyglycidyl ether is particularly preferred. These surface cross-linking agents are usually used in an amount of 0.1 to 1% by weight, preferably 0.2 to 0.5% by weight, based on the resin particles (dry basis). These surface cross-linking agents are diluted with water or alcohol (ethanol, methanol, etc.) so as to be uniformly applied to the entire surface of the resin particles, and 0.1 to 1% by weight, particularly 0.2 to 0%. It is preferably used as a 5% by weight alcohol solution. The application of the cross-linking agent solution is usually performed by spraying the cross-linking agent solution onto the resin particles using a sprayer or inverting the particle-base composite so that the resin particle adhering surface is on the lower surface while moving it. It is preferable to carry out by a method of applying the crosslinking agent solution with a roll brush whose lower part is immersed in a tank containing the crosslinking agent solution. In addition, after giving a crosslinking agent solution excessively, you may make it remove excessive surplus crosslinking agent solution by squeezing lightly so that a resin particle may not be crushed with a pressing roll, or blowing a wind. The application of the crosslinking agent solution may be performed at room temperature. The particle-substrate composite to which the cross-linking agent solution has been applied is then heated to cause a cross-linking reaction to selectively form a cross-linked structure on the resin particle surface. The conditions for the cross-linking reaction may be appropriately selected depending on the cross-linking agent to be used. Usually, the reaction is performed at a temperature of 100 ° C. or higher for 10 minutes or longer. The water absorption performance of the water-absorbing composite produced by the continuous production method of the present invention is substantially determined up to this surface crosslinking step.
[0027]
It is preferable that the particle-substrate composite that has undergone the surface cross-linking step is sent to the residual monomer treatment step. Unreacted polymerizable monomers remain in the resin particles of the particle-base composite, but these polymerizable monomers are harmful to the human body, so the residual amount is determined by the use in the residual monomer treatment step. Reduce to an acceptable range.
[0028]
For example, when partially neutralized acrylic acid is used as the polymerizable monomer, the monomer is generally several hundred ppm, and in the case of a large amount, 1000 ppm or more of the monomer remains, but it is used for applications such as paper diapers and sanitary napkins. In general, the residual amount is preferably 500 ppm or less, and most preferably reduced to 300 ppm or less, particularly 100 ppm or less.
[0029]
The treatment of the polymerizable monomer can be performed in several ways. One of the methods is a method in which the treatment is performed by advancing polymerization of the residual monomer. For example, a method in which the particle-base composite is heat-treated at a temperature of 100 to 250 ° C. to polymerize the remaining monomer, a catalyst or a catalyst component that promotes polymerization of the polymerizable monomer is added to the resin particle, and then heated to polymerize. There is a method of polymerizing monomers. For example, when the polymerization is carried out using the above-described redox polymerization initiator, the radical generator often remains, so a reducing agent solution may be applied to the resin particles. As the reducing agent, sodium sulfite, sodium bisulfite, L-ascorbic acid or the like used as a redox polymerization initiator may be used, and these are usually applied to the resin particles as a 0.5 to 5% by weight aqueous solution. The amount of the reducing agent applied may be 0.1 to 20 parts by weight per 100 parts by weight of the dry resin. Application | coating of a reducing agent solution can be performed by arbitrary methods, such as spraying using an atomizer and immersing in a reducing agent solution. The resin particles provided with the reducing agent are then heated to polymerize the polymerizable monomer. Heating may be performed, for example, at 100 to 150 ° C. for about 10 to 30 minutes. Although the moisture content of the resin particles is reduced by this heating, if the moisture content is still high, it can be further dried with a dryer to obtain a water-absorbing composite of the product. Further, 0.01 to 1 part by weight of peroxide and / or azo compound is added to 100 parts by weight of the resin particles in the particle-base composite, followed by heating to reduce the residual monomer amount.
[0030]
Further, as a method of proceeding the polymerization of the residual monomer, there is a method of irradiating with ultraviolet rays or radiation.
In the method of irradiating with ultraviolet rays, an ordinary ultraviolet lamp may be used, and the irradiation intensity, irradiation time, etc. are determined by the type of fibrous substrate used, the amount of polymerizable monomer impregnation, and the like. Generally, the irradiation intensity of the ultraviolet lamp is 10 to 200 W / cm, preferably 30 to 120 W / cm, the irradiation time is 0.1 second to 30 minutes, and the lamp-complex interval is 2 to 30 cm. is there. As an atmosphere when irradiating with ultraviolet rays, any of vacuum, presence of an inorganic gas such as nitrogen, argon, helium, or air can be used. The irradiation temperature is not particularly limited, and the object can be sufficiently achieved at room temperature. There is no restriction | limiting in particular also in the ultraviolet irradiation apparatus to be used, The method of irradiating for a fixed time for a fixed time, the method of irradiating continuously with a belt conveyor, etc. can be used.
[0031]
The water content in the composite at this time is generally 0.01 to 40 parts by weight, preferably 0.1 to 1.0 parts by weight, relative to 1 part by weight of the polymer. A water content of less than 0.01 parts by weight or more than 40 parts by weight tends to affect the reduction of unpolymerized monomers. This amount of water can be realized by controlling the amount of water in the complexing step and / or the surface cross-linking step, or can be realized by adjusting the amount of water after the surface cross-linking step.
[0032]
In the method of irradiating with radiation, high energy radiation such as electromagnetic radiation or fine particle ionizing radiation is used. Specifically, acceleration electrons and gamma rays can be exemplified. The dose to be irradiated varies depending on the amount of unpolymerized monomer in the complex, the amount of water, and the like, but is generally 0.01 to 100 megarads, preferably 0.1 to 50 megarads. When the dose exceeds 100 megarads, the amount of water absorption becomes extremely small. When the dose is less than 0.01 megarad, the water absorption capacity and the water absorption speed intended in the present invention are large, and it is difficult to obtain a particularly small unpolymerized monomer.
[0033]
Further, the water content in the composite at this time is generally 40 parts by weight or less, preferably 10 parts by weight or less, based on 1 part by weight of the fibrous substrate. An amount of water exceeding 40 parts by weight is not preferable because the effect of improving the water absorption rate is small and particularly has a significant effect on the reduction of unpolymerized monomers.
[0034]
In the present invention, the atmosphere when irradiating the composite with high energy radiation may be in a vacuum, in the presence of an inorganic gas such as nitrogen, argon or helium, or in the air. A preferable atmosphere is air. When irradiation is performed in the air, the water absorption capacity and the water absorption speed are large and the unpolymerized monomer is particularly small. Moreover, there is no restriction | limiting in particular in irradiation temperature, The objective can fully be achieved at room temperature.
[0035]
As another method for treating the unreacted polymerizable monomer, there is a method for removing the residual monomer. For example, there is a method of extracting the polymerizable monomer by cooling the particle-substrate composite taken out from the surface crosslinking step and then immersing it in a water-containing organic solvent. As the water-containing organic solvent, ethanol, methanol, and acetone can be used, and the water content is preferably 10 to 90% by weight, particularly preferably 30 to 60% by weight. In general, the higher the water content is, the higher the ability to remove the polymerizable monomer is. However, when a water-containing organic solvent having a high water content is used, the energy consumption in the subsequent drying step increases. The time for immersing the particle-base composite in the water-containing organic solvent is usually about 5 to 30 minutes, and means for promoting extraction of the polymerizable monomer such as rocking the particle-base composite is adopted. Is also preferable. After the immersion treatment, it is treated with a dryer and dried to obtain a water absorbent composite of the product. Usually, the resin particles may be dried so that the moisture content of the resin particles is about 10%.
[0036]
Yet another method for removing the polymerizable monomer is to treat the particle-substrate composite with superheated steam or a steam-containing gas. For example, the polymerizable monomer in the resin particles can be reduced by heating saturated steam at 110 ° C. to 120 to 150 ° C. and bringing it into contact with the particle-base composite as superheated steam. In this method, it is considered that when the water in the resin particles evaporates as water vapor, the polymerizable monomer also vaporizes and escapes from the resin particles. According to this method, both removal of the polymerizable monomer and drying of the product can be performed.
[0037]
In the present invention, the above-mentioned compounding step and surface cross-linking step are essential steps, and the moisture content adjusting step and the residual monomer treatment step are carried out as preferable steps. The order can be performed in any order after the compounding step is first performed. The preferred order of the process is the compounding process, the surface crosslinking process, the residual monomer treatment process sequentially, the compounding process, the residual monomer treatment process, the surface crosslinking process sequentially performed, the compounding process, the residual monomer treatment process, the water content. What performs adjustment process, surface cross-linking process sequentially, composite process, water content adjustment process, surface cross-linking process, residual monomer treatment process, composite process, water content adjustment process, residual monomer treatment process, surface cross-linking process Are sequentially performed.
[0038]
An example of a method for producing a water-absorbent composite according to the continuous production method of the present invention will be described with reference to FIG. 1. A basis weight of 35 g / m wound on a roll (1) ² The polyester nonwoven fabric (2) is rewound and fed into the polymerization chamber (3) at 30 m / min parallel to the floor surface. A nozzle for injecting a polymerizable monomer aqueous solution A containing a reducing agent on the upper part of the polymerization chamber and a nozzle for injecting a polymerizable monomer aqueous solution B containing an oxidizing agent face each other downward, and a set of two nozzles facing each other Are installed in 5 pairs at intervals of 1 cm. The conditions are that the inner diameter of the nozzle is 0.18 mm, the facing angle of the nozzle is 30 degrees, the facing distance between the nozzles is 3.5 mm, and the height from the nonwoven fabric surface to the nozzle opening end is 3 m.
[0039]
The following polymerizable monomer aqueous solution is supplied to the nozzles at room temperature, and is ejected from each nozzle at 5.0 m / second. The polymerization chamber is supplied with air containing water vapor from the lower part and exhausted from the upper part so that the atmosphere is about 20 to 60 ° C. and the humidity is about 30 to 100%. Exhaust gas is introduced into the exhaust gas treatment device.
Polymeric monomer aqueous solution A: 50% by weight aqueous solution of acrylic acid and sodium acrylate (acrylic acid: sodium acrylate = 4: 6 (molar ratio)), hydrogen peroxide to the total of acrylic acid and sodium acrylate An aqueous solution containing 2.8% by weight.
Polymerizable monomer aqueous solution B: 50% by weight aqueous solution of acrylic acid and sodium acrylate (acrylic acid: sodium acrylate = 4: 6 (molar ratio)), L-sodium ascorbate was added to acrylic acid and sodium acrylate An aqueous solution containing 1.1% by weight based on the weight.
[0040]
The polymerizable monomer aqueous solutions A and B ejected from the nozzle collide to form droplets, drop onto the nonwoven fabric while polymerizing, and adhere to the nonwoven fabric as resin particles having a polymerization rate of about 95% or more. The amount of resin particles attached is about 200 g / m on a dry resin basis. ² It is. The size of the resin particles is about 200 to 1500 μm, and about 90% of the resin particles are agglomerated granules.
[0041]
The nonwoven fabric to which the resin particles are adhered is fed into the dehydration tank (4). 96% ethanol is accommodated in the dehydration tank, and the nonwoven fabric stays in this ethanol for 5 minutes and is dehydrated so that the water content is about 20% based on the water-containing resin. A portion of the ethanol in the dehydration tank is continuously withdrawn and dehydrated and distilled in the distillation column (5) so that the water content is kept constant, and then circulated to the dehydration tank.
[0042]
The nonwoven fabric to which the resin particles taken out from the dehydration tank are attached is removed by blowing off the attached ethanol and then fed into the surface cross-linking device (6). Here, a 0.5 wt% ethanol solution of ethylene glycol diglycidyl ether is first applied to the resin particles by spraying the resin particles so that ethylene glycol diglycidyl ether is 0.35 wt% on a dry resin basis, Subsequently, it is surface-crosslinked by heating to about 110 ° C. for 30 minutes.
[0043]
The nonwoven fabric drawn out from the surface cross-linking device is cooled by blowing air and then fed into an unreacted polymerizable monomer extraction tank (7). The extraction tank (7) contains 50 wt% aqueous ethanol at room temperature, and the nonwoven fabric is retained in the aqueous ethanol for 20 minutes. As a result, the content of the polymerizable monomer in the resin particles is reduced to about 80 ppm on a dry resin basis. The non-woven fabric taken out from the extraction tank is brought into contact with a drying drum (8) into which water vapor has been introduced to evaporate and remove ethanol and water. The water-absorbing composite thus produced is wound up by a winder (9) and shipped as a product. In addition, a part of the water-containing ethanol in the extraction tank (7) is continuously withdrawn so as not to accumulate monomers, and fresh water-containing ethanol is supplied.
[0044]
The water-absorbing composite produced by the continuous production method of the present invention exhibits high water absorption.
The water absorption of the water-absorbing composite is a multifaceted property and is evaluated by various evaluation methods depending on the intended use of the water-absorbing composite. Specifically, using water, physiological saline, artificial urine or the like as the liquid to be absorbed, the water absorption capacity (the amount of liquid that can be absorbed over a certain period of time is expressed as the weight per unit weight of the water absorbent polymer. Water retention capacity (represented by the weight per unit weight of the water-absorbent polymer after the water-absorbing composite once absorbed the liquid is dehydrated under certain conditions), under normal pressure Water absorption rate (the amount of liquid that can be absorbed while a short period of time passes is expressed as the weight per unit weight of the water-absorbing polymer), water absorption rate under pressure (a short period of time passes under constant pressure) The amount of liquid that can be absorbed during the measurement can be evaluated by measuring the weight per unit weight of the water-absorbing polymer.
[0045]
According to the continuous production method of the present invention, for example, there is provided a water-absorbing composite that exhibits the following water absorption when the water absorption rate under pressure with physiological saline is measured using an apparatus according to JIS K-7224. Is done. Specifically, 40 g / cm ² A water-absorbing composite having a water absorption amount of 15 g or more per 1 g of the water-absorbing polymer supported by the water-absorbing composite, 40 g / cm ² A water-absorbing composite having a water absorption amount of 18 g or more per 1 g of the water-absorbing polymer supported by the water-absorbing composite, 40 g / cm ² A water-absorbing composite having a water absorption amount of 22 g or more per 1 g of the water-absorbing polymer supported by the water-absorbing composite, 60 g / cm ² A water-absorbing composite having a water absorption amount of 13 g or more per 1 g of the water-absorbing polymer supported by the water-absorbing composite, 60 g / cm ² A water-absorbing composite having a water absorption amount of 15 g or more per 1 g of the water-absorbing polymer supported by the water-absorbing composite, 60 g / cm ² A water-absorbing composite having a water absorption amount of 19 g or more per 1 g of the water-absorbing polymer supported on the water-absorbing composite is preferably provided when physiological saline is absorbed for 60 minutes under the pressure of.
[0046]
In particular, 40 g / cm ² The amount of water absorption when physiological saline was absorbed for 10 minutes under the pressure of 60 g / cm ² A water-absorbing composite with a water absorption amount of 28 g or more per 1 g of the water-absorbing polymer supported by the water-absorbing composite, 40 g / cm ² The amount of water absorbed when physiological saline was absorbed for 20 minutes under the pressure of 60 g / cm ² A water-absorbing composite having a sum of water absorption of 20 g of physiological saline under pressure of 20 g / cm, per g of water-absorbing polymer supported on the water-absorbing composite, 40 g / cm ² The amount of water absorbed when physiological saline was absorbed for 60 minutes under pressure of 60 g / cm ² A water-absorbing composite having a sum of water absorption when water of physiological saline is absorbed for 60 minutes under a pressure of 40 g or more per 1 g of water-absorbing polymer supported on the water-absorbing composite is preferably provided. These water-absorbing composites can be appropriately selected and used according to the purpose of use.
[0047]
These water-absorbing composites can be used in various applications where water-absorbing resins have been used. "Water-absorbing polymer", pages 81 to 111 (Fusayoshi Masuda, Kyoritsu Shuppan, 1987), "Development trend of superabsorbent resin and its application development" (Eizo Omori, Techno Forum, 1987), Kenji Tanaka, "Industrial Materials" 42, No. 4, pp. 18-25, 1994, Nobuyuki Harada, Tadao Shimomura, pp. 26-30, various uses of the water-absorbing resin are introduced and can be used as appropriate. For example, paper diapers, sanitary products, freshness-keeping materials, moisturizing agents, cold-retaining agents, anti-condensation agents, soil improvement materials and the like can be mentioned.
[0048]
Furthermore, JP-A-63-267370, JP-A-63-10667, JP-A-63-295251, JP-A-270801, JP-A-63-294716, JP-A-64- No. 64602, JP-A-1-231940, JP-A-1-243927, JP-A-2-30522, JP-A-2-153373, JP-A-3-21385, JP-A-4-133728 It can also be used for applications of sheet-like water-absorbing composites proposed in Japanese Patent Laid-Open No. 11-156118.
[0049]
【Example】
Examples below Reference examples, The present invention will be described more specifically with reference to comparative examples and test examples. The materials, amounts used, ratios, processing details, processing procedures, and the like shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention is not limited to the specific examples shown below.
[0050]
Example 1
125 parts by weight of 80% by weight aqueous acrylic acid solution, 57.3 parts by weight of 48.5% by weight aqueous sodium hydroxide solution, 6.4 parts by weight of water, 0.15 cross-linking agent (N, N′-methylenebisacrylamide) Solution A was prepared by adding 5.0 parts by weight of a 30% by weight aqueous hydrogen peroxide solution as an oxidizing agent. The monomer concentration of Solution A was 60% by weight, and the degree of neutralization was 50 mol%.
Separately, 125 parts by weight of 80% by weight acrylic acid aqueous solution, 57.3 parts by weight of 48.5% by weight sodium hydroxide aqueous solution, 9.9 parts by weight of water, and a crosslinking agent (N, N′-methylenebisacrylamide) ) 0.15 parts by weight and 1.5 parts by weight of L-ascorbic acid as a reducing agent were added to prepare a solution B. The monomer concentration and neutralization degree of Solution B were the same as Solution A.
[0051]
Two nozzles having an inner diameter of 0.13 mm in the structure shown in FIG. 2 are paired, and the opposing two nozzles in which the crossing angle of the solutions A and B flowing out from the nozzles are adjusted to 30 degrees and the distance between the nozzle tips is adjusted to 4 mm Pump the A liquid from one nozzle and the B liquid from one nozzle on the opposite side to a liquid temperature of 40 ° C., and pump them to a flow rate of 5 m / sec. Supplied with.
Liquid A and liquid B merge when they are discharged in the form of liquid columns from the nozzles of the respective nozzle pairs, and form liquid columns of about 10 mm each, and then form liquid droplets in the gas phase (in the air as polymerization proceeds) , Temperature 50 ° C.), a part of the droplet collides in the gas phase to form an agglomerated granular material, and is a polyester nonwoven fabric base material (weight per unit: 30 g / m) placed 3 m below the tip of the nozzle ² ) To complete the polymerization on the substrate. At the same time, some of the droplets dropped on the substrate, formed aggregated granular materials on the substrate, and then completed the polymerization on the substrate. Through such a compounding step, the water-absorbing polymer was supported on the substrate. The water content of the water-absorbing polymer supported on the substrate was 20% by weight.
[0052]
Further, 0.5 wt% ethylene glycol diglycidyl ether (EGDGE) in ethanol was sprayed on the composite to a polymer on which EGDGE was supported (dry polymer base) to 3000 ppm by weight. The composite to which the ethanol solution of EGDGE was applied was further dried by a hot air dryer at 110 ° C. until the water content of the polymer reached 5%, and the amount of polymer supported was 200 g / m. ² Thus, a water-absorbing composite with the above was obtained.
[0053]
(Example 2)
The composite process was performed in the same manner as in Example 1 to obtain a base material (composite) carrying a water-absorbing polymer having a water content of 20% by weight.
The composite was sprayed with an ethanol solution of 0.5 wt% ethylene glycol diglycidyl ether (EGDGE) to the polymer on which EGDGE was supported (dry polymer base) to 3000 ppm by weight. The composite to which the ethanol solution of EGDGE was applied was further sprayed vertically with water vapor having a temperature of 130 ° C. and a dew point of 120 ° C. in a vent band dryer equipped with a steam supply device. The contact time between water vapor and the substrate was 2 minutes, and the linear velocity was 0.5 m / second. This obtained the water absorptive composite. The water content of the polymer supported on the obtained composite was 5%, and the amount of polymer supported was 200 g / m. ² Thus, a water-absorbing composite with the above was obtained.
[0054]
(Example 3)
125 parts by weight of 80% by weight aqueous acrylic acid solution, 57.3 parts by weight of 48.5% by weight aqueous sodium hydroxide solution, 68.8 parts by weight of water, 0.15 cross-linking agent (N, N′-methylenebisacrylamide) Solution A was prepared by adding 5.0 parts by weight of a 30% by weight aqueous hydrogen peroxide solution as an oxidizing agent. The monomer concentration of Solution A was 45% by weight, and the degree of neutralization was 50 mol%.
Separately, 125 parts by weight of 80% by weight acrylic acid aqueous solution, 57.3 parts by weight of 48.5% by weight sodium hydroxide aqueous solution, 72.5 parts by weight of water, and a crosslinking agent (N, N′-methylenebisacrylamide) ) 0.15 parts by weight and 1.5 parts by weight of L-ascorbic acid as a reducing agent were added to prepare a solution B. The monomer concentration and neutralization degree of Solution B were the same as Solution A.
[0055]
Two nozzles having an inner diameter of 0.13 mm in the structure shown in FIG. 2 are paired, and the opposing two nozzles in which the crossing angle of the solutions A and B flowing out from the nozzles are adjusted to 30 degrees and the distance between the nozzle tips is adjusted to 4 mm Pump the A liquid from one nozzle and the B liquid from one nozzle on the opposite side to the liquid temperature of 50 ° C., and pump each so that the flow rate becomes 5 m / sec. Supplied with.
The liquid A and liquid B merge at the exit of the nozzles of the respective nozzle pairs, and after forming a liquid column of about 10 mm, the liquid droplets are formed into droplets in the gas phase (in air, at a temperature of 50 ° C.). ), A part of the droplet collides in the gas phase to form an aggregated granular material, and is a polyester nonwoven fabric substrate (weight per unit: 30 g / m) placed 3 m below the tip of the nozzle ² ) To complete the polymerization on the substrate. At the same time, some of the droplets dropped on the substrate, formed aggregated granular materials on the substrate, and then completed the polymerization on the substrate. Through such a compounding step, the water-absorbing polymer was supported on the substrate. The water content of the water-absorbing polymer supported on the substrate was 45% by weight.
[0056]
Subsequently, a 1% by weight aqueous solution of potassium persulfate (KPS) was sprayed onto the complex so that the polymer on which potassium persulfate was supported (dry polymer base) was 2000 ppm by weight. Thereafter, the composite was dried by a 110 ° C. hot air dryer until the water content of the polymer supported was 20%.
Further, 0.5 wt% ethylene glycol diglycidyl ether (EGDGE) in ethanol was sprayed on the composite to a polymer on which EGDGE was supported (dry polymer base) to 3000 ppm by weight. The composite to which the ethanol solution of EGDGE was applied was further dried by a hot air dryer at 110 ° C. until the water content of the polymer reached 5%, and the amount of polymer supported was 200 g / m. ² Thus, a water-absorbing composite with the above was obtained.
[0057]
(Example 4)
Sodium bisulfite (NaHSO) was applied to a substrate (composite) on which a water-absorbing polymer having a water content of 45% by weight was supported. _Three A water-absorbing composite was obtained in the same manner as in Example 3, except that a 0.5 wt% aqueous solution of) was sprayed to a polymer carrying sodium bisulfite (dry polymer base) to 1000 ppm by weight. It was.
[0058]
(Example 5)
The composite process was performed in the same manner as in Example 1 to obtain a base material (composite) carrying a water-absorbing polymer having a water content of 20% by weight.
1000 mJ / cm on the composite ² Then, an ethanol solution of 0.5 wt% ethylene glycol diglycidyl ether (EGDGE) was sprayed on the EGDGE-supported polymer (dry polymer base) to 3000 ppm by weight. The composite subjected to the ethanol solution of EGDGE was further dried with a hot air dryer at 110 ° C. until the water content of the supported polymer became 5%, and the amount of polymer supported was 200 g / m. ² Thus, a water-absorbing composite with the above was obtained.
[0059]
(Example 6)
The composite process was performed in the same manner as in Example 1 to obtain a base material (composite) carrying a water-absorbing polymer having a water content of 20% by weight.
The composite was irradiated with an electron beam at a dose of 20 megarads in an air atmosphere from an electron beam apparatus equipped with a dynamitron accelerator to obtain a water-absorbing composite. Subsequently, an ethanol solution of 0.5 wt% ethylene glycol diglycidyl ether (EGDGE) was sprayed on the EGDGE-supported polymer (dry polymer base) to 3000 ppm by weight. The composite subjected to the ethanol solution of EGDGE was further dried with a hot air dryer at 110 ° C. until the water content of the supported polymer became 5%, and the amount of polymer supported was 200 g / m. ² Thus, a water-absorbing composite with the above was obtained.
[0060]
(Example 7)
The composite process was performed in the same manner as in Example 3 to obtain a base material (composite) carrying a water-absorbing polymer having a water content of 45% by weight.
The composite was immersed in 10 parts by weight of a 30% by weight aqueous ethanol solution with respect to 1 part by weight of the supported polymer (dry polymer base) and allowed to stand at room temperature for 30 minutes. Thereafter, the complex was taken out from the aqueous ethanol solution, further immersed in 10 parts by weight of ethanol, and allowed to stand at room temperature for 30 minutes. The complex taken out from ethanol was further sprayed with an ethanol solution of 0.5 wt% ethylene glycol diglycidyl ether (EGDGE) on the polymer on which EGDGE was supported (dry polymer base) to 3000 ppm by weight. The composite subjected to the ethanol solution of EGDGE was further dried with a hot air dryer at 110 ° C. until the water content of the supported polymer became 5%, and the amount of polymer supported was 200 g / m. ² Thus, a water-absorbing composite with the above was obtained.
[0061]
( Reference example 1 )
Liquid A and liquid B were prepared in the same manner as in Example 1. Two nozzles having an inner diameter of 0.13 mm having the structure shown in FIG. 2 are used, the angle between the nozzles is 30 degrees, the distance between the nozzle tips is 4 mm, the liquid A from one nozzle, and the other nozzle The liquids B were each heated to a liquid temperature of 40 ° C. and supplied with a pump at a flow rate of 5 m / second. The liquid A and the liquid B merged at the exit of the nozzle, formed a liquid column of about 10 mm, and then dropped into a rising air stream of air (60 ° C.) as droplets. A polyester nonwoven fabric base material (weight per unit area: 30 g / m) in which this droplet is placed 100 cm below the tip of the nozzle ² ) To complete the polymerization on the substrate.
[0062]
The water content of the water-absorbing polymer supported on the substrate was 30% by weight. Further, an ethanol solution of 0.5 wt% ethylene glycol diglycidyl ether (EGDGE) was sprayed on the composite so as to give 3000 ppm by weight with respect to the polymer on which EGDGE was supported (dry polymer base). The composite to which the ethanol solution of EGDGE was applied was further dried until the water content of the water-absorbing polymer supported on a 110 ° C. hot air dryer reached 5%, and the amount of polymer supported was 200 g / cm. ² Thus, a water-absorbing composite with the above was obtained.
[0063]
( Reference example 2 )
The composite process was performed in the same manner as in Example 3 to obtain a base material (composite) carrying a water-absorbing polymer having a water content of 45% by weight. The composite was sprayed with an ethanol solution of 0.5 wt% ethylene glycol diglycidyl ether (EGDGE) to a polymer on which EGDGE was supported (dry polymer base) to 3000 ppm by weight. The composite subjected to the ethanol solution of EGDGE was further dried with a hot air dryer at 110 ° C. until the water content of the supported polymer became 5%, and the amount of polymer supported was 200 g / m. ² Thus, a water-absorbing composite with the above was obtained.
[0064]
( Reference example 3 )
The composite process was performed in the same manner as in Example 1 to obtain a base material (composite) carrying a water-absorbing polymer having a water content of 25% by weight. The composite was dried with a hot air dryer at 110 ° C. until the water content of the supported polymer became 5%, and the amount of polymer supported was 200 g / m. ² Thus, a water-absorbing composite with the above was obtained. Further, the obtained composite was sprayed with an ethanol solution of 0.5 wt% ethylene glycol diglycidyl ether (EGDGE) to a polymer on which EGDGE was supported (dry polymer base) to 3000 ppm by weight. 200 g / m as the polymer loading ² Thus, a water-absorbing composite with the above was obtained.
[0065]
(Comparative Example 1)
The composite process was performed in the same manner as in Example 1 to obtain a base material (composite) carrying a water-absorbing polymer having a water content of 20% by weight.
Dry until the water content of the supported polymer is 5%, and the amount of polymer supported is 200 g / m. ² Thus, a water-absorbing composite with the above was obtained.
[0066]
(Comparative Example 2)
In a 100 ml conical flask, 13.1 g of sodium hydroxide (purity 96% by weight) was taken and dissolved in 39.0 g of pure water under ice cooling. To this, 30 g of acrylic acid was gradually added for neutralization. The degree of neutralization was about 75%, and the monomer concentration in the aqueous solution was about 45% by weight.
To this, 0.05 g of potassium persulfate as a radical polymerization initiator was taken and dissolved in the monomer aqueous solution. ₂ Degassed at.
[0067]
Separately polyester non-woven fabric (weight per unit: 30 g / m ² ) Was applied to the entire surface of the nonwoven fabric by a roll coater and applied in a linear pattern along the fibers. The amount of monomer impregnated was 6.8 times the weight of the nonwoven fabric. This in advance ₂ Was put in a constant temperature reaction tank which was deaerated at 90 ° C. Polymerization occurred immediately, and a composite was obtained in which a superabsorbent polymer composed of a self-crosslinked product of partially neutralized sodium polyacrylate was fixed to a non-woven polyester fabric along the fibers with good stability.
[0068]
Next, the water content of this composite was about 25% by weight (based on the weight of the superabsorbent polymer, the same shall apply hereinafter), and 0.012 g of ethylene glycol diglycidyl ether (3000 ppm of dry polymer) was added to 0.5% by weight. After spraying as an ethanol solution, it is dried using a 110 ° C. hot air dryer until the water content of the supported polymer becomes 5%, and the amount of polymer supported is 200 g / m 2. ² Thus, a water-absorbing composite with the above was obtained.
[0069]
(Test example)
Example 1 7, Reference Examples 1-3 The following measurements and tests were performed on the water-absorbing composites obtained in Comparative Examples 1 and 2.
(1) After taking a scanning micrograph (SEM photograph) of a plurality of locations of the ratio water-absorbing composite in which the polymer is an aggregated granular body, 100 particles were arbitrarily selected to determine the presence or absence of aggregation. Assuming that the density of the agglomerated particles is uniform, the ratio of the polymer to agglomerated particles was calculated.
[0070]
(2) Average particle diameter of aggregated granular material
After taking SEM photographs of a plurality of locations of the water-absorbing composite, 100 particles were arbitrarily selected, the particle diameter was measured, and the average of the measured values was obtained.
[0071]
(3) Polymerization rate when dropped on the substrate
A beaker containing methanol weighed so that the liquid level of methanol is located at the position where the substrate is placed, droplets of the reaction mixture that started polymerization were formed in the gas phase, and the beaker containing methanol The agglomerated particles during polymerization were allowed to fall. The amount of monomer in methanol was measured by liquid chromatography. Further, the polymer in methanol was dried under reduced pressure at 130 ° C. for 3 hours, and then the weight was measured. The polymerization rate was calculated from the respective weights according to the following formula (Mp is polymer weight, Mm is monomer weight, unit g).
[Expression 1]

[0072]
(4) Saline water absorption capacity
About 1.0 g of a 300 ml beaker water-absorbing complex and about 200 g of 0.9% concentration physiological saline were weighed and left for about 4 hours to sufficiently swell the polymer with physiological saline. . Subsequently, after draining with a 100 mesh sieve, the physiological saline water absorption capacity was calculated according to the following formula. All units of weight in the formula are g.
[Expression 2]

[0073]
(5) Saline retention capacity
Weight of water-absorbing polymer supported on the composite W ₁ The composite was cut to 1 g, placed in a 250 mesh nylon bag (20 cm × 10 cm), and immersed in 500 ml of room temperature physiological saline (concentration 0.9 wt%) for 30 minutes. The nylon bag was then pulled up, suspended for 15 minutes and drained, and then dehydrated at 90 G for 90 seconds using a centrifuge. Weight of nylon bag after dehydration W ₂ Was measured. In addition, a non-woven fabric that does not carry a water-absorbing polymer is cut into the same size as the raw composite, and the same operation is performed. _Three Was measured. The water retention capacity of physiological saline was calculated according to the following formula. Where W ₁ ~ W _Three The unit of is all g.
[Equation 3]

[0074]
(6) Absorption speed under normal pressure
In a 300 ml beaker, about 1.0 g of the water-absorbing complex and about 200 g of 0.9% strength physiological saline were weighed and placed, and allowed to stand for 5 minutes to swell the polymer with the physiological saline. Next, after draining with a 100 mesh sieve, the physiological saline water absorption capacity was calculated according to the above formula, and this was taken as the water absorption speed.
[0075]
(7) Water absorption speed under pressure
In accordance with JIS K-7224, the water absorption rate under pressure with physiological saline was measured using the apparatus shown in FIG. Place the composite that has been cut into 10cm x 10cm in advance on the nonwoven fabric that has been laid on a support plate with a small hole so that the water-absorbing polymer is placed on top, and then lay the layer under the support plate on the same nonwoven fabric. I put it on. Furthermore, a predetermined weight is put on the pressure, and a predetermined pressure (40 g / cm ² Or 60 g / cm ² ) Was applied to the composite. The lower surface of the complex was brought into contact with 0.9% physiological saline, and the amount of the complex that absorbed physiological saline was measured. The water absorption rate under pressure was defined as the amount of 0.9% physiological saline that was absorbed for 10 minutes, 20 minutes, and 60 minutes after the start.
[0076]
(8) Residual unreacted polymerizable monomer concentration (residual monomer concentration)
0.5 g of the water-absorbing complex was precisely weighed and added to 1 liter of ion-exchanged water in a 2 liter beaker, and sufficiently swollen with stirring for about 10 hours. The swollen polymer gel was filtered off with a 200 mesh sieve, and the filtrate was analyzed by high performance liquid chromatography. Separately, a monomer standard solution having a known concentration was prepared, and thereby a calibration curve was prepared to obtain an absolute concentration.
The test results are shown in the following table.
[0077]
[Table 1]

[0078]
Examples 1 to 1 produced by the continuous production method of the present invention 7 and Reference Examples 1-3 All of the water-absorbing composites were within the ranges in which the physiological saline water absorption capacity, water retention capacity, water absorption speed under normal pressure, water absorption speed under pressure, and residual monomer concentration were satisfactory. In particular, the water-absorbing composites of Examples 1 to 7 showed excellent effects. On the other hand, the water-absorbing composites of Comparative Examples 1 and 2 were particularly unsatisfactory because of their poor water absorption rate under pressure.
[0079]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, the water absorptive composite_body | complex with high water absorption ability and water retention ability can be manufactured continuously and efficiently.
[Brief description of the drawings]
FIG. 1 is an example of a flow sheet when a water-absorbing composite is continuously produced by the method of the present invention.
FIG. 2 is a schematic view showing an example of a nozzle structure used for carrying out a mixing step in the production method of the present invention.
FIG. 3 is a schematic diagram of a water absorption rate measuring device under pressure used in a test example.
[Explanation of symbols]
1 Nonwoven roll
2 Nonwoven fabric
3 Polymerization chamber
4 Dehydration tank
5 Distillation tower
6 Surface cross-linking equipment
7 Polymerizable monomer extraction tank
8 Dryer
9 Winder of water absorbent composite
11 Nozzle for liquid A
12 B liquid nozzle
13 A liquid
14 B liquid
21 Bullet
22 Rubber stopper
23 Support plate with small holes
24 Nonwoven fabric
25 Resin particles

Claims

The following steps:
(A) Polymerization mainly composed of unsaturated carboxylic acid in which 20% or more of carboxyl groups are neutralized
Liquid columnar first containing an aqueous monomer solution and an oxidizing agent constituting a redox polymerization initiator
Liquid and unsaturated carboxylic acid in which 20% or more of carboxyl groups are neutralized
A liquid column containing an aqueous polymerizable monomer solution and a reducing agent constituting a redox polymerization initiator
A droplet is formed by collision mixing with the second liquid in the gas phase,
The polymer is dropped while polymerizing and the fibrous base material is fed into the dropping point.
Resin particles in the polymerization process with a polymerization rate of 20-97% are adhered to the fibrous base material.
And a particle-base composite having a water content of 10 to 40% by weight after completion of polymerization after adhesion
Compounding process to form
(B) Two or more that can react with the carboxyl group and / or carboxylate group in the complex
The crosslinking agent having the above functional group is used as a resin particle 100 derived from a polymerizable monomer in the composite.
Surface cross-linking step in which 1 to 100 parts by weight of water is added and reacted in the presence of water
Produced by the process comprising, a water-absorbing composite comprising water-absorbing polymer and the fibrous base material, the following (1) to (3) water absorbent composites that meet at least one condition.
(1) The amount of water absorbed when physiological saline is absorbed for 10 minutes under a pressure of 40 g / cm ² is 15 g or more per 1 g of the water-absorbing polymer supported on the water-absorbing composite.
(2) The amount of water absorption when physiological saline is absorbed for 20 minutes under a pressure of 40 g / cm ² is 18 g or more per 1 g of the water-absorbing polymer supported on the water-absorbing composite.
(3) The amount of water absorption when physiological saline is absorbed for 60 minutes under a pressure of 40 g / cm ² is 22 g or more per 1 g of the water-absorbing polymer supported on the water-absorbing composite.

The following steps:
(A) Polymerization mainly composed of unsaturated carboxylic acid in which 20% or more of carboxyl groups are neutralized
Liquid columnar first containing an aqueous monomer solution and an oxidizing agent constituting a redox polymerization initiator
Liquid and unsaturated carboxylic acid in which 20% or more of carboxyl groups are neutralized
A liquid column containing an aqueous polymerizable monomer solution and a reducing agent constituting a redox polymerization initiator
A droplet is formed by collision mixing with the second liquid in the gas phase,
The polymer is dropped while polymerizing and the fibrous base material is fed into the dropping point.
Resin particles in the polymerization process with a polymerization rate of 20-97% are adhered to the fibrous base material.
And a particle-base composite having a water content of 10 to 40% by weight after completion of polymerization after adhesion
Compounding process to form
(B) Two or more that can react with the carboxyl group and / or carboxylate group in the complex
The crosslinking agent having the above functional group is used as a resin particle 100 derived from a polymerizable monomer in the composite.
Surface cross-linking step in which 1 to 100 parts by weight of water is added and reacted in the presence of water
Produced by the process comprising, a water-absorbing composite comprising water-absorbing polymer and the fibrous base material, the following (1) to (3) water absorbent composites that meet at least one condition.
(1) The amount of water absorbed when physiological saline is absorbed for 10 minutes under a pressure of 60 g / cm ² is 13 g or more per 1 g of the water-absorbing polymer supported on the water-absorbing composite.
(2) The amount of water absorbed when physiological saline is absorbed for 20 minutes under a pressure of 60 g / cm ² is 15 g or more per 1 g of the water-absorbing polymer supported on the water-absorbing composite.
(3) The water absorption when the physiological saline is absorbed for 60 minutes under a pressure of 60 g / cm ² is 19 g or more per 1 g of the water-absorbing polymer supported on the water-absorbing composite.

The following steps:
(A) Polymerization mainly composed of unsaturated carboxylic acid in which 20% or more of carboxyl groups are neutralized
Liquid columnar first containing an aqueous monomer solution and an oxidizing agent constituting a redox polymerization initiator
Liquid and unsaturated carboxylic acid in which 20% or more of carboxyl groups are neutralized
A liquid column containing a polymerizable monomer aqueous solution and a reducing agent constituting a redox polymerization initiator
A droplet is formed by collision mixing with the second liquid in the gas phase,
The polymer is dropped while polymerizing and the fibrous base material is fed into the dropping point.
Resin particles in the polymerization process with a polymerization rate of 20-97% are adhered to the fibrous base material.
And a particle-base composite having a water content of 10 to 40% by weight after completion of polymerization after adhesion
Compounding process to form
(B) Two or more that can react with the carboxyl group and / or carboxylate group in the complex
The crosslinking agent having the above functional group is used as a resin particle 100 derived from a polymerizable monomer in the composite.
Surface cross-linking step in which 1 to 100 parts by weight of water is added and reacted in the presence of water
Produced by the process comprising, a water-absorbing composite comprising water-absorbing polymer and the fibrous base material, the following (1) to (3) water absorbent composites that meet at least one condition.
(1) The sum of the amount of water absorbed when physiological saline is absorbed for 10 minutes under a pressure of 40 g / cm ² and the amount of water absorbed when physiological saline is absorbed for 10 minutes under a pressure of 60 g / cm ^2. Is 28 g or more per 1 g of the water-absorbing polymer supported on the water-absorbing composite.
(2) the sum of the water absorption amount when allowed to absorb water for 20 minutes saline under pressure of 40 g / cm ^2, and the water absorption amount when allowed to absorb water for 20 minutes saline under pressure of 60 g / cm ² Is 33 g or more per 1 g of the water-absorbing polymer supported on the water-absorbing composite.
(3) Water-absorbing complex, water absorption amount when physiological saline is absorbed for 60 minutes under a pressure of 40 g / cm ² , and water absorption amount when physiological saline is absorbed for 60 minutes under a pressure of 60 g / cm ² The sum of the water absorption amount is 40 g or more per 1 g of the water-absorbing polymer supported on the water-absorbing composite.

A water-absorbent article using the water-absorbent composite according to any one of claims 1 to 3.