JP3735761B2 - Super absorbent composite - Google Patents

Description

【００１７】
【表２】

【００１８】
０．５％分散液での未離解ＢＣと離解ＢＣの粘度上昇効果を比較すると、５倍以上の上昇効果が認められる（表２参照）。
【００１９】
さらに、木材パルプ由来のＳ−ＭＦＣとＢＣのそれぞれの０．５％水分散液についてホモジナイザーまたはミキサーによる離解処理を行った場合の粘度(ｃｐ)の比較は表３に示すとおり、ＢＣはその離解処理効果が大きく、離解後の粘度は大幅に増大し、Ｓ−ＭＦＣの３〜５倍となる。
【００２０】
【表３】

【００２１】
０．５％分散液での未離解ＢＣと離解ＢＣについて行った保水性の比較は表４に示す。
【００２２】
尚、保水性の評価は下記の試験方法に従って行った。
分散液５０ｍＬを遠心分離可能な試験管（内径３０ｍｍ×長さ１００ｍｍ，容量５０ｍＬ）中に計り取り、これを５００Ｇ（１６５０ｒｐｍ）〜３０００Ｇ（４０００ｒｐｍ）で１０分間遠心分離し、沈積量（ｍＬ）を読み取り、次の式に従って抱水量を算出した。
【００２３】
【数１】

【００２４】
【表４】

【００２５】
表４から、２０００Ｇで未離解品が３２ｍＬ／ｇであるのに対して、離解品は１２８ｍＬ／ｇ約４倍量に抱水量が上昇する。
【００２６】
また、ＢＣ水性分散液での分散安定性を２４時間放置後の相分離量で比較すると図１に示すように、未離解品は０．３％付近まで相分離が発生するが、離解品は０．１％前後ですでに相分離が発生しなくなる。尚、図１中、実線はＢＣ未離解品を、点線はＢＣ離解品を示す。
【００２７】
分散安定性試験：
濃度の異なる分散液の一定量を目盛付試験管に入れ、２４時間静置後、相分離した上澄液量と下部の分散液量を読み取り、下部の分散液部分の比率を求めた。
【００２８】
ＢＣ離解品は電子顕微鏡を用いて観察すると平均長さが０．０１〜数１０μｍという極微細繊維状（ミクロフィブリル) であって、その超ミクロ繊維の示す交絡効果と上述した水性分散液（水溶性有機溶媒／水との混合溶媒）の示す高い粘度と保水性と相まって、ＳＡＰに対する結合・分散安定剤として好適である。
【００２９】
ＢＣ離解品の分散液をＳＡＰの結合・分散安定剤として使用するには、ＳＡＰに膨潤を与えず、しかも凝集ガム化等を惹起させない水性分散溶媒が選択される。水溶性有機溶媒の種類と水との混合比率によるＳＡＰの膨潤、凝集現象を表５に示す。
【００３０】
【表５】

【００３１】
ＳＡＰは水性分散液中で粉末状態で安定に均一分散している必要があるが、本発明によれば、ＢＣ離解分散液はＳＡＰ粒子が凝集する傾向を軽減させる優れた保護効果を有し、しかも良好な結合効果を奏する。
【００３２】
本発明の高吸収性複合体は基本的には、ＳＡＰとこれを被覆するＢＣ離解ミクロフィブリルとの複合体である。ＳＡＰはその極めて大きい吸水性から、取り扱いや保存が容易でないが、本発明に従ってＢＣ離解ミクロフィブリルで被覆することにより、このような問題が解消される。また、ＳＡＰ粒子を相互にＢＣ離解ミクロフィブリルで結合した構造はミクロフィブリルが各ＳＡＰ粒子を所定の位置に拘束すると共に、その周囲に適当な間隔を確保するため、厚さの極めて薄いシート状の吸収体を構成する。
【００３３】
本発明において使用されるＳＡＰは一般にはカルボキシメチルセルロース、ポリアクリル酸及びその塩類、ポリエチレンオキサイド、ポリアクリルアミド等の水膨潤性ポリマーを部分架橋したもの、あるいはイソブチレンとマレイン酸との共重合体等である。また生分解性のあるポリアスパラギン酸のアミノ酸架橋物、あるいはＡｌｃａｌｉｇｅｎｅｓ Ｌａｔｕｓからの培養生成物である微生物起源高吸水性ポリマー等も含まれる。ＳＡＰ製品としては、粒子状、顆粒状、フィルム状そして不織布状の様々な形態を持ったものが開発されているが、これらは全て本発明で使用可能であり、中でも本発明で望ましいものは、分散媒体中で均一に分散可能な粒状、顆粒状、フレーク状、短針状、ペレット状のもので、ここではこれらを総称して粒子状と称することにする。
【００３４】
また本発明において、ＳＡＰ粒子を所定の位置に拘束するネットワーク構造は、ＢＣ離解ミクロフィブリルによって構成される。このＢＣ離解ミクロフィブリルは前述したように平均長さが０．０１〜数１０μｍという極微細繊維で、ＳＡＰが吸水したときにその膨潤によって直ちに構造が崩壊するのを防止することができる耐水性をもち、しかも水の浸透性、ＳＡＰの膨潤性を阻害しないような性質を持つ。ここで特記すべきことは、ＢＣ離解ミクロフィブリルは前述のように高い保水性を持ち、ソルベーション（束縛水）として水と結合する、極めて強固な水和性を有するということで、この水和性により、含水媒体中に分散されると水和して大きな粘性を示し、安定に分散状態を保持する性質を有する。本発明者の研究結果によれば、ＳＡＰスラリーの安定性を粘度からみて必要とされるミクロフィブリルの濃度を求めると、ＳＡＰ３０％では木材パルプ由来のＳ−ＭＦＣ／ＳＡＰ比２％（Ｓ−ＭＦＣ０．６％）に対し、ＢＣ離解分散液濃度を低くすることができる。エタノール／水＝６０／４０分散系では対ＳＡＰ比０．６０％が相当し、Ｓ−ＭＦＣの約１／４とすることができる。
【００３５】
ＢＣ離解ミクロフィブリル分散媒体中にＳＡＰを添加分散すると、高濃度のＳＡＰを安定に分散させることができ、分散媒体が除去される過程では、強固に自己接合してプラスター状になってネットワーク構造を形成し、ＳＡＰ粒子を包み込んで機械的に包囲すると同時に、ミクロフィブリル相互がイオン的な水素結合効果により結合し、ＳＡＰ粒子を確実に保持する。
【００３６】
次に、本発明に係るＢＣ離解ミクロフィブリルおよびＳＡＰからなる高吸収性複合体を製造する方法について説明する。
【００３７】
先ず、水分散系で離解処理を行って比較的高濃度のＢＣ離解ミクロフィブリルの分散液を調製してこれを母液とする。この母液としては、高濃度になる程製造装置はコンパクトになるが、一方、高粘度になるために取り扱いが難しくなるので、５％以下、好ましくは０．５％〜２％の水分散液が用いられる。このミクロフィブリルの母液に水溶性有機溶媒を加えて、所定のミクロフィブリル濃度とそれに伴う粘度を持ったミクロフィブリル分散液を調製する。
【００３８】
水分散系で離解処理を行う代わりに、０．０５〜１．０％希釈ＢＣ水分散系に水溶性有機溶媒を加えてから離解処理を行ってＢＣ離解ミクロフィブリルの分散液を調製してもよい。いずれの場合においても、水／水溶性有機溶媒との混合溶媒を分散溶媒とするＢＣ離解ミクロフィブリル分散液が調製されたならば、引き続きＳＡＰが添加混合される。
【００３９】
本発明に使用される水溶性有機溶媒としては、比誘電率が１８以上(２０℃)であればＳＡＰに凝集ガム化効果を与える傾向が小さく、且つ水との混合系でＳＡＰをあまり膨潤させないものであればよく、例えば、メチルアルコール、エタノール、イソプロピルアルコールなどのアルコール、エチレングリコール、ジエチレングリコール、プロピレングリコール、低分子量ポリエチレングリコール、グリセリン等の多価アルコール類、アセトン、メチルエチルケトン、ジメチルスルホキシド等の代表的な水可溶性有機溶媒が使用可能である。低沸点のアルコール類は溶媒の蒸留回収等の面ではメリットがあるが、揮発性、引火性が高いため、製造装置に防爆構造の必要がある点で難である。グリコール類は溶媒自体の粘度が高いため、その粘度を利用してＳＡＰの分散状態を安定化するためにはメリットがある。環境への安全性、製品への溶媒の一部残留の可能性等を考慮するとエタノールやプロピレングリコールなどの溶媒が特に適正を持っている。また、架橋剤、抗菌剤等の添加のため、一部シクロヘキサン等の非水溶性溶媒等を分散系に影響を与えない範囲で添加することもありうる。
【００４０】
これらの水溶性有機溶媒と水からなる混合溶媒にＢＣ離解ミクロフィブリルおよびＳＡＰを分散させることにより、ミクロフィブリルのネットワーク構造が形成されてＳＡＰ粒子を組み込み、安定分散状態を確保し、その後に混合溶媒が除去されたときは、ミクロフィブリルの持つ物理的な絡合構造と、ミクロフィブリル同士の安定な水素結合により三次元的な構造が形成されると推定される。
【００４１】
水溶性有機溶媒と水との混合比は、ミクロフィブリルのネットワーク構造化を可能にし、かつＳＡＰの吸収をできるだけ抑制する範囲に設定される。有機溶媒の占める濃度が高い程ＳＡＰの吸水率が減少するので、有機溶媒が多い方が扱いやすい。一方、ＢＣ離解ミクロフィブリルを水和させて、安定分散させるためには、混合溶媒中の水の含有量は多い方が有利である。したがって水／水溶性有機溶媒比は、１０／９０〜５０／５０の範囲が適当である。なお、この比率は使用される有機溶媒と用いるＳＡＰの種類により多少変化する。
【００４２】
この混合溶媒中でのＳＡＰとＢＣ離解ミクロフィブリルとの共存分散状態における、ＳＡＰとＢＣ離解ミクロフィブリルの各分散濃度とＳＡＰとＢＣ離解ミクロフィブリルの濃度比について詳しく説明する。ＳＡＰの濃度は、系の搬送方法によっても異なるが、取り扱いの容易さから、６０％以下、好ましくは５０％〜５％の範囲から選択される。ミクロフィブリル濃度は、ＳＡＰの結合力と分散安定性に影響される。良好な分散安定性を保つためには、０．１％以上が必要であり、好ましくは０．３％〜１．０％である。
【００４３】
このような濃度でＢＣ離解ミクロフィブリルを含有する混合溶媒は、前述のように極めて良好な分散安定性を示し、長時間静置した後にも、相分離を起こし難く、０．３％では２４時間経過するまで相分離は起こらず、０．５％では１００時間後にも相分離は認められない。この良好な分散安定性は、塗布時の操作を容易にするばかりではなく、ＳＡＰ粒子を万遍なく包囲して安定に分散できることを実証するものであり、この形状が、本発明の複合体の優れた吸水性の根幹をなすものであると推測される。
【００４４】
ＳＡＰに対するＢＣ離解ミクロフィブリルの割合は、その値が大きくなると強度が上がるが、紙状になって固くなってくるので、１０％以下が望ましい。０．５％以下では十分な結合力が得にくい。この結合力の評価は、表面強度の測定に用いられるセロテープ法を援用して行うことができ、その結果からみると好適な範囲は０．５％〜５％である。
【００４５】
ＳＡＰ、ＢＣ離解ミクロフィブリル共存分散系に対して、他の成分の添加の可否について説明する。本発明の主目的は如何にＳＡＰを高濃度の状態で取り扱うかにある。ＢＣ離解ミクロフィブリルはＳＡＰに対して優れた結合、分散安定性を示すが、従来使用されていたようなＣＭＣ等の増粘剤の添加や過乾燥による硬化を防ぐため可塑剤としてのポリエチレングリコール等も差し支えない。また上記分散系の中に木材パルプスラリーや合成繊維の分散スラリーを添加することも可能であるが、これらの添加は分散の安定性を阻害し、ミクロフィブリルのＳＡＰ粒子の結合効率も低下させることにもなりかねないので、添加のプロセス等に注意が必要である。
【００４６】
つぎに混合溶媒中にＢＣ離解ミクロフィブリルおよびＳＡＰを分散させた分散液から溶媒成分を分離して高吸収性複合体を形成する方法としては、例えば▲１▼上記スラリーから溶媒を分離して得られるブロック状物を乾燥後、粉砕して粒子状にすれば、ＳＡＰ粒子表面がミクロフィブリルで被覆された球状あるいはフレーク状の粒状体が得られ、▲２▼スラリーをネットで作った型に注いで固液分離した後乾燥すれば、用いた型に応じてペレット状、棒状、筒状、波板状等の三次元構造の形状父賦形複合体が得られ、また▲３▼連続的に薄膜を形成し、乾燥すればシート状複合体が得られる。このようにして得られた複合体は水分含有によって可撓性を示すようになるため、シート状の複合体を例えばエアレイド法によって繊維類と共にマット状に成形し、これに水分を与えてプレス、乾燥することにより、シート状に再成形することも可能である。
【００４７】
以下、特に汎用性の高い、分散液から直接シートに成形する方法について詳しく説明する。前述のように、ミクロフィブリルのネットワーク構造は、その内部にＳＡＰを安定かつ強固に保持した状態を保ちながら、極めて薄い層に成形することを可能にする。すなわち、ＢＣ離解ミクロフィブリルおよびＳＡＰを混合溶媒に分散させた分散液を、適当な平面上に塗布し、溶媒を揮散させることによりミクロフィブリルおよびＳＡＰのみからなるシート状の高吸水性複合体を形成することができる。
【００４８】
あるいは、分散液を適当なシート状支持体上に塗布した場合には、分散液の乾燥後にシート状支持体と上記複合体層とからなる高吸水性複合シート材料が得られる。特にシート状支持体として多孔質な不織布を使用した場合には、その多孔質に応じて分散液の一部が不織布の繊維間に入り込み、分散液の乾燥後に、不織布と上記複合体層とが両者の接合面で絡み合った構造の複合構造となる。この不織布の好ましい多孔質度は、見掛比重で示すと０.２ｇ／ｃｍ³以下、さらに好ましくは０.０１〜０．１ｇ／ｃｍ³である。なお、この場合の不織布の構成素材としては、液の浸透性の問題から、コットン、レーヨン、木材パルプ等の親水性素材、あるいはポリエチレン、ポリプロピレン、ポリエステル等の合成繊維を親水性化処理した素材を用いることが好ましい。支持体となる不織布の形状としては、多孔質なカード乾式、スパンボンド等の不織布類に加えて、表面起毛不織布、ボンディングの弱いカードウエブ、あるいは開織トウなどのシート状素材も使用可能である。
【００４９】
次に、本発明の高吸収性複合体を製造するのに適した装置について図面を参照して説明する。
【００５０】
図２において、符合３１はイオン交換水を貯蔵するタンク、３２はＢＣ離解ミクロフィブリル水分散母液を貯蔵するタンク、３３はエタノールを貯蔵するタンク、３４はＳＡＰを貯蔵するタンクを示す。タンク３２から取出されたＢＣ離解ミクロフィブリル水分散母液は攪拌器を備えた混合器３５に導入され、タンク３１から取出された水で混合器３５内で希釈された後、ポンプの作用で、つぎの攪拌器を備えた混合器３６に導入される。この混合器３６には、タンク３３から取出されたエタノールが導入されており、この混合物が、ポンプの作用で、つぎの攪拌器を備えた混合器３７に導入される。混合器３７には、タンク３４から粒状ＳＡＰが導入されており、ここでＢＣ離解ミクロフィブリル、エタノール、水およびＳＡＰの混合分散液が形成される。
【００５１】
一方、不織布のような適当なシート状支持体１３は、ロール３８から巻き出されたのち、成形部４０に導かれる。この成形部４０は、ベルトコンベア４１と、このベルトコンベアのベルト上に位置するノズル４２を備え、このノズル４２に前記の混合器３７から混合分散液がポンプの作用で供給されるようになっている。シート状支持体１３は、ベルトコンベア４１に導かれて所定の速度で走行する間に、その表面上にノズル４２からの混合分散液が塗布される。もちろん、スプレー状に塗布してもよい。ノズル４２としては、シート状支持体１３上に設けるべき複合体層のパターンに応じて適当な形状のものが設けられる。
【００５２】
成形部４０には、さらに１対のローラからなるロールプレス４３が設けられており、混合分散液が塗布されたシート状支持体１３をプレスすることにより、混合分散液に含有されている溶媒がスクイーズし、分離された溶媒は、ポンプの作用で混合器３６に戻される。
【００５３】
シート状支持体１３は、成形部４０を出たのち、次の乾燥部５０に送られる。この乾燥部５０には熱風が供給され、１対の多孔ロール５１，５２を備え、シート状支持体１３およびこれに塗布された混合分散液は、この多孔ロール５１，５２の周面に沿って搬送される間に乾燥される。
【００５４】
図２中、成形部４０において、シート状支持体１３に混合分散液を塗布する別の装置の例を図３に示す。図３において、符合４４は混合分散液を収容する上面開放の槽を示し、この槽４４内に、周囲の一部が混合分散液中に浸漬された状態で、水平な軸を中心として回転可能な浸漬ロール４５が配置されている。また１対のロール４６，４７が、それぞれ浸漬ロール４５と平行な軸を中心として回転可能に設けられている。一方のロール４６は、浸漬ロール４５の周面に圧接されているとともに、たとえば図４に示すように、多数のリング状の溝４６ａを周面に有しており、平坦な表面をもつ他方のロール４７との間のニップに、混合分散を塗布すべきシート状支持体１３が通過するようになされている。
【００５５】
槽４４内に収容されている混合分散液は、その中を移動する浸漬ロール４５の周面に自身の粘性で付着し、ついで溝付のロール４６を介してシート状支持体１３に転写される。したがってシート状支持体１３の表面には、図５に示すように、相互に平行な多数の帯状に混合分散液層４８が形成されることになる。なおロール４６に形成される凹凸のパターンは任意に設定することができ、このパターンに対応したパターンでシート状支持体１３に混合分散液を塗布することが可能である。
【００５６】
本発明で得られる高吸水性複合体を組み入れた吸収体製品の特徴、性能についても要約説明しておく。本発明の高吸水性複合体を吸収体製品に用いると、まず第一に、使用前でも使用時でも、非吸水状態では極めて薄くコンパクトな構造を持ち、ＳＡＰ粒子が強固に固定、安定化されているため、たとえ折れ曲げや伸縮が働いても、ＳＡＰ粒子が移動することなく、ＳＡＰの脱落、構造の破壊も起こりにくい。
【００５７】
第二に、吸水時にはＳＡＰが９０％以上のパルプレス構造にもかかわらず、ミクロフィブリルの親水性とその物性形態の故に、吸収速度が早くしかもブロッキングを起こさないことである。
【００５８】
第三に、吸水後もフィブリルのネットワークによりゆるやかに膨潤ポリマーを把持し、脱落を防ぐことである。
【００５９】
第四に、使用後の廃棄時の特性である。ＢＣ離解ミクロフィブリルはセルラーゼ活性が極めて高く、土中埋没により短時間で構造がバラバラになる。もしＳＡＰとして生分解性のあるアミノ酸系ポリマー、微生物起源高分子吸収体等を組合わせれば、理想的な環境適応型の吸収体の設計が可能である。
【００６０】
【実施例】
以下、実施例により本発明を具体的に説明する。
【００６１】
実施例１
ＢＣの調製：
シュークロース 5ｇ／ｄＬ、酵母エキス（Ｄｉｆｃｏ）０．５ｇ／ｄＬ、硫安０.５ｇ／ｄＬ、ＫＨ₂ＰＯ₄ ０.３ｇ／ｄＬ、ＭｇＳＯ₄・７Ｈ₂Ｏ ０．０５ｇ／ｄＬ(ｐＨ５．０)の組成の培地５０ｄＬを２０ｄＬ三角フラスコに張込み１２０℃、２０分蒸気殺菌し、酵母エキス０.５ｇ／ｄＬ、ペプトン０.３ｇ／ｄＬ、マンニット２.５ｇ／ｄＬ（ｐＨ６.０）の組成の試験管斜面寒天培地で生育させた（３０℃、３日間）アセトバクター・アセチ・サブスビーシス・キシリナムＡＴＣＣ１０８２１を１白金耳ずつ接種し３０℃で培養した。３０日後、培養液の上層に白色のセルローズ性物質の膜が形成された。このゲルを水洗し、遠心分離して固形物濃度１０％のサンプルを得た。
【００６２】
ＢＣ離解ミクロフィブリルのエタノール／水混合溶媒分散液の調製：
上記サンプルに、水を加え、ミキサー(「オースターブレンダー」)を用いて回転１３,０００ｒｐｍ １０分間処理し、２．０％水分散液を調製し、これにエタノールを加えてエタノール／水が６０／４０、ＢＣ濃度がそれぞれ０．１５％、０．２１％、０．４３％、０．８６％の４水準の混合分散液を用意した。
【００６３】
ＢＣ離解ミクロフィブリル／ＳＡＰ共存分散液の調製：
上記水準のＢＣ離解ミクロフィブリル分散液７０ｃｃに、ＳＡＰ(三洋化成(株)製、商品名「ＩＭ−６７００」)の６０〜１００メッシュ区分け品を３０g を添加して、ＢＣ離解ミクロフィブリル／ＳＡＰ共存分散液を調製した。
この分散液の内訳は表６に示すとおりである。
【００６４】
比較のために、Ｓ−ＭＦＣ（特殊製紙(株)製）のゲル状の４．０％の分散液を母液として、これにエタノールと水を加えてエタノール／水が６０／４０、Ｓ−ＭＦＣ濃度がそれぞれ０.２１％、０.４３％、０.８６％、１.７％の４水準の混合分散液を調製し、上記ＢＣ離解ミクロフィブリルと同様にＳ−ＭＦＣ／ＳＡＰの共存分散液を調製した。この分散液の内訳も表６に示す。
【００６５】
【表６】

【００６６】
上記のＳＡＰ３０％分散液はＢＣ離解ミクロフィブリルや比較品のＳ−ＭＦＣの濃度が高い程安定であるが、ＢＣでは濃度０．１５％以上では安定であり、攪拌子での攪拌停止後もＳＡＰの沈降は直ぐには見られず０．１０％でも数分間は安定であった。一方、Ｓ−ＭＦＣは濃度０．３％以下では攪拌停止後ＳＡＰの沈降は直ちに始まった。
【００６７】
ＢＣ離解ミクロフィブリル／ＳＡＰ複合シート材料の作成：
上記分散液をエタノール／水＝６０／４０で３倍に希釈して減圧装置に連結したブッフナー漏斗(内径１１ｃｍ)に濾紙、基材不織布（二村化学製ＴＣＦ４０３、見掛比重０.０７ｇ／ｃｍ³）を重ね、その基材不織布上に２０ｃｃの粘稠な分散液を素早く注ぎ、減圧により脱溶媒したのち、熱風乾燥して複合シートとした。
【００６８】
上記複合シート材料の性能評価を、評価法によって示された方法に従って行った結果、表７及び表８に示すとおりであった。
【００６９】
吸水性の評価結果：
上記の複合シート材料の吸水量、保水量及び吸水スピードを調べた。結果は表７に示す。
【００７０】
【表７】

【００７１】
ミクロフィブリルの種類及びＳＡＰに対する配合比率による影響は３種類の評価方法についていずれも差は殆ど見られなかった。
【００７２】
複合シート材料の特性評価結果：
上記複合シート材料の性能評価結果は表８に示す。
【００７３】
【表８】

【００７４】
複合シート材料はほぼ仕様通りで、厚さ、重さ、付着ＳＡＰ＋ＭＣ、見掛け比重にサンプル間の差は見られず、ほぼ同様のものが作成出来たことが分かる。
【００７５】
ＢＣ離解処理品は比較品のＳ−ＭＦＣに対してセロテープによる１８０°ピリングテストでは同一配合比ならば約２級の差が見られ、ＳＡＰの剥離は１／５〜１／１０以下となっている。即ち、ＢＣ離解処理品は同一のＳＡＰの耐剥離性を得るのに比較品のＳ−ＭＦＣの１／３〜１／４の配合で十分その性能を出していると言うこともできる。例えば、ＭＣ／ＳＡＰ比(％)でＢＣ離解処理品が０．３％のピリングテスト結果は３級で、Ｓ−ＭＦＣで３級を得るにはＭＣ／ＳＡＰ比（％）は１．０％が必要であった。同様に４級を得るには０．５％に対し２．０％、５級を得ようとすれば、１．０％に対し４．０％の高配合が必要であった。
【００７６】
又、剛軟度はＳ−ＭＦＣの配合が多くなると剛くなる程度がＢＣ離解処理品と比較して大きいことから、ＢＣ離解処理品を使用することにより柔らかい風合のものとなる。
【００７７】
以上のことから、ＢＣ離解処理品は比較品のＳ−ＭＦＣに対してＳＡＰに対する配合比を大幅に下げることが可能であると共に風合の向上も併せて図ることが可能であることが分かった。
【００７８】
以下に、上表の評価項目の評価方法を示す。
厚さ（ｍｍ）：厚さ計（ＪＩＳ）で測定
重さ（ｇ）：電子上皿天秤で１１０ｍｍφの基材と共に測定し、付着させたＳＡＰ＋ＭＣ(バインダー）量は基材の重量を差し引いて算出し、ｍ²当りの量で表示した。
見掛比重(ｇ／ｃｍ³）：厚さ及び基材面積と付着させたＳＡＰ＋ＭＣの重量から算出した。
剛軟性（ｍｍ）：１１０ｍｍ×２０ｍｍのサンプルを図６、図７に示す方法で測定した。
【００７９】
サンプルＳの一端をステンレス製のメジャーＭの先端を直角に置き、自重で垂れ下がった位置（αｍｍ) のメジャーの目盛を読み取って剛軟性とした。
【００８０】
［ＳＡＰの結合安定性の評価 (セロテープによる１８０°ピリングテスト）］
サンプルに１５ｍｍ幅のニチバン製のセロテープをはり接着面を１５ｍｍ×１０ｍｍとし、上から軽くフランネルで押さえた後、１ｋｇ／ｃｍ² の荷重を１０分間かける。除重後手でサンプルから１８０°ピリングの状態でセロテープをはがし、セロテープに付着しているＳＡＰの付着状態をＳＡＰの付着面積（％）を測定してＭＣ（ミクロファイバー）の結合安定性を評価した。判定の基準を図８に示す。
【００８１】
［複合体の吸水量、保水量、吸水スピードの評価］
上記複合体について、充分な量の生理食塩水に３０分間浸漬後、ＪＩＳ Ｋ−７２２３に準じて吸水量、保水量を測定した。吸水スピードはＳＡＰ塗布面を上にした１１ｃｍφの複合シートの中心上にビューレットにより生理食塩水を２０ｍＬ滴下し、その初期吸水時間を測定した。
実施例２：連続塗布実験
図３に示した塗布装置を備えた、図２に示す製造装置を用いて、高吸水性複合体を製造した。使用材料は次のとおりである。
【００８２】
(１) ミクロフィブリル／ＳＡＰ共存分散液：実施例１サンプルＮｏ．３又は比較例サンプルＮｏ．Ｂ

(３) シート状支持体：２層構成スルエアーマルボンドウエブ４０ｇ／ｍ²、見掛比重０.０６ｇ／ｃｍ³の不織布で下記の構成を持ったものを用いた。

【００８３】
上記シート状支持体１３を１０ｍ／ｍｉｎの速度で走行させながら、その上層表面上に上記(２)成分の混合分散液を巾５ｍｍの間隔をおきながら約１０ｍｍ巾で連続塗布した。その後、ロールで圧縮して溶媒を除去した後、熱風乾燥した。
【００８４】
得られたシート状高吸水性複合体は下記のような特性を持っていた。

【００８５】
なお、得られた高吸水体の保水量をＪＩＳ Ｋ−７２２３に基づいて測定した。その結果ＳＡＰ１ｇ当たり４２ｇ（実施例２）、４０ｇ（比較例）の保水量を示し、ブランクとほぼ同等な数値を示した。
【００８６】
【発明の効果】
以上説明したようにＢＣの解繊、離解処理分散液は木材パルプ由来のＳ−ＭＦＣでは見られない大幅な粘度上昇、保水性向上効果を奏し、ＳＡＰに対する結合、分散安定剤として好適である。然して、高濃度のＳＡＰスラリーを安定化させることができ、形態安定性、柔軟性、吸水速度、風合等において優れた、ＳＡＰが９０％以上含有するような典型的なパルプレスの高吸水性複合体を提供することができる。
【図面の簡単な説明】
【図１】 ＢＣ未離解分散液、ＢＣ離解分散液についてのＢＣ濃度とＢＣ分散安定性との関係を示す図面
【図２】 本発明に係る高吸水性複合体を製造する装置を例示したブロック略線図
【図３】 図２に示した装置に使用される他の塗布装置を例示したブロック略線図
【図４】 図３の装置に使用された溝付きロールの平面図
【図５】 図４に示した装置で混合溶媒分散液が塗布されたシート状支持体の横断面図
【図６】 剛軟性（ｍｍ）を測定する方法を示す説明図
【図７】 図６のＡ−Ａに沿った断面図
【図８】 ＳＡＰの結合安定性の判定基準を示すチャート図
【符号の説明】
３１〜３４ タンク
３５〜３７ 混合器
４０ 成形部
４１ ベルトコンベア
４２ ノズル
４３ ロールプレス
４４ 槽
４５ 浸漬ロール
４６，４７ ロール
４８ 混合分散液層
５０ 乾燥部
５１，５２ 加熱ロール
６０ 圧縮部
６１，６２ プレスロール[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a high-absorbency composite having improved morphological stability, flexibility, water absorption rate, texture, etc., comprising fibrillated bacterial cellulose defibrated, disaggregated, and particulate high water-absorbent resin. The present invention relates to a highly water-absorbing composite having an absorbent composite as a main water-absorbing body. This superabsorbent composite can be widely used in absorbent products such as blood absorbent bodies for infants and adults, sanitary products for women or medical use as well as ordinary superabsorbents. It is useful as a thin composite of Palpress using a polymer.
[0002]
[Prior art]
The main component of the absorber that absorbs moisture and body fluid used in the absorbent product is a conventional combination of fluffy wood pulp and a so-called polymer absorber (abbreviated as “SAP”). . However, in recent years, there has been a large social demand for thinner and more compact absorbent products compared to conventional relatively bulky absorbent products in order to improve logistics efficiency, improve shelf efficiency at retail stores, and save resources. It has become.
[0003]
As a means of compacting and thinning, in the combination of SAP and pulp, if the ratio of SAP having a water absorption capacity 2 to 10 times higher than that of pulp is increased and the ratio of pulp is decreased, it becomes thin and compact. Ultimately, if the structure of SAP 100% is adopted, it should be possible to pursue a thin layer and compactness to the maximum.
[0004]
On the other hand, the higher the SAP ratio, the more so-called “gel blocking phenomenon” based on the properties of SAP occurs during water absorption, and the absorbent product does not function with the calculated efficiency. The configuration around 1/1 is considered the limit, and SAP / pulp = 3 or more, or further increasing the SAP ratio to form a Palpress structure close to 100% SAP is a very difficult technical problem. . Here, the term “Palpress” is used as a generic term for those in which the ratio of pulp to SAP is less than around 1, in accordance with concepts commonly applied in this field.
[0005]
Of course, various challenges have been made with respect to the Palpress structure. For example, a method of making a fibrous or web-like SAP sheet by direct spinning or partial hydrolysis of acrylic acid fibers, or impregnating a monomer such as acrylic on the web and polymerizing it with ultraviolet rays or electron beams. Various attempts have been made such as making a web-like water-absorbing polymer, or carboxymethylating a non-woven fabric such as cellulose and then partially crosslinking to make a sheet-like water-absorbing polymer.
[0006]
However, there have been no reports of industrially and economically successful examples due to material cost problems and significant capital investment.
[0007]
[Problems to be solved by the invention]
In order to achieve the secondary structure of SAP as a main component, firstly, it is necessary to have a binder that is stable to moisture and does not inhibit the absorption of SAP. The presence of a substrate that provides a physical support and diffusion medium is required, and thirdly, how the binder and SAP are distributed on the substrate.
[0008]
From the above viewpoint, the present inventor has conducted intensive research on the optimization of the binder, the base material, and the distribution state thereof, and pulverized microfibrils having wettability obtained from cellulose or cellulose derivatives, that is, wood pulp. And so-called MFC (microfibrillated cellulose) obtained by high-level beating, S-MFC with more microfibrillation, bacterial cellulose (hereinafter abbreviated as “BC”) obtained by metabolism of microorganisms and SAP Such a water-swellable solid as a main component is dispersed in a mixed solvent of a water-compatible organic solvent that stably hydrates and disperses water, and the microfibrils and SAP are separated from the dispersion, and then removed. After the solvent is dried, the SAPs mutually become intertwined with the microfibrils. Thus, a composite composition having a structure constrained by bonding and hydrogen bonding is obtained. The composite composition can be made into an arbitrary shape by itself or formed on a sheet-like support such as a non-woven fabric. A thin Palpress superabsorbent composite containing 90% or more of SAP was developed and a patent application was filed (Japanese Patent Application No. 8-333520).
[0009]
Therefore, when preparing a superabsorbent composite composed of microfibrils and SAP, in order to stabilize the SAP slurry by generating a high-concentration SAP slurry without SAP being agglomerated or swollen by the dispersion medium. Therefore, it is important to maximize the viscosity of the microfibril dispersion, and the present invention has been made to achieve these problems.
[0010]
[Means for Solving the Problems]
As a result of continuous studies to achieve the above-mentioned problems, the present inventors have found that, among microfibrils having hydration properties obtained from cellulose or cellulose derivatives, BC defibration and disaggregation treatment dispersions have a significant increase in viscosity and water retention. It has been found that not only the improvement of (water repellency) but also the coagulation gum tendency of SAP is reduced in the coexistence with SAP, the dispersion stability of SAP is enhanced, and a softer superabsorbent complex is provided. The present invention has been completed.
[0011]
That is, in the invention of claim 1, the BC disaggregation product, SAP is agglomerated, or
At a concentration that does not swell Dielectric constant is 18 or more (20 ° C.), and water-soluble at least one of methanol, ethanol, isopropyl alcohol, ethylene glycol, diethylene glycol, propylene glycol, low molecular weight polyethylene glycol, glycerin, acetone, methyl ethyl ketone and dimethyl sulfoxide In a mixed solvent of water-soluble organic solvent and water A high-absorbency composite characterized in that a SAP dispersoid and a SAP co-dispersion liquid are prepared by dispersing and mixing the SAP, and a solvent component is separated from the co-dispersion liquid and dried. Yes, the invention of claim 2 The superabsorbent composite according to claim 1, wherein the water / water-soluble organic solvent ratio is 10/90 to 50/50. In the invention of claim 3, the dispersion concentration of BC in a mixed solvent of a water-soluble organic solvent and water is 0.05 to 1.0% by weight, and the dispersion concentration of SAP is 5 to 60% by weight. The superabsorbent composite according to claim 4, wherein the invention of claim 4 According to claim 1 The co-dispersed liquid is applied to a sheet-like support, desolvated, and then dried. The superabsorbent sheet material is characterized in that the sheet-like support has a hydrophilic porous property. The superabsorbent sheet material according to claim 4, which is a nonwoven fabric.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail.
[0013]
BC used in the present invention is generally obtained as an extracellular metabolic product of bacteria when acetic acid bacteria are cultured. The crude BC after the culture contains residual culture components and bacterial cells, which are purified BC through, for example, alkali washing and water washing operations. Purified BC is a state in which one or one ultrafine fiber of various sizes is entangled and assembled. In this state, the properties are unstable, and it is not uniform to be used as a dispersant, a viscosity modifier or the like. Therefore, defibration and disaggregation processing is performed under a high share (see Japanese Patent Publication No. 4-64521 etc.). Furthermore, it can be hydrolyzed with an acid of 1N or more and disaggregated under a high share (see Japanese Patent Publication No. 5-80484).
[0014]
As an example, defibration and disaggregation treatment is a defibration that can give a high share of mixers, homogenizers (nanomizers), super grinders, desc refiners, etc. in a slurry state in water or a mixed solvent of water and water-soluble organic solvent It is performed using a disaggregation device.
[0015]
The viscosity of the BC dispersion liquid is greatly increased by the disaggregation treatment, and water retention (water retention) and dispersion stability are improved. In order to smoothly perform the disaggregation process, an appropriate BC slurry concentration range is set according to the disaggregation apparatus to be used. For example, in a homogenizer (“High Flex Disperser”), the BC concentration at the time of disaggregation is set to 0.5% or less. If it exceeds 0.5%, it is not preferable since it becomes creamy due to the disaggregation of BC, and the viscosity of the liquid becomes high and may not circulate. Further, in the mixer (“Oaster Pender”), it is 1.0% or less that the cutter rotates stably and the dispersion circulates. Table 1 shows the state of disaggregation performed by a mixer performed by changing the BC concentration to 0.1 to 2.0%, and Table 2 shows the concentration of BC dispersion and the viscosity change during disaggregation.
[0016]
[Table 1]

[0017]
[Table 2]

[0018]
When the viscosity increasing effect of undissolved BC and disaggregated BC in the 0.5% dispersion is compared, an increasing effect of 5 times or more is observed (see Table 2).
[0019]
Furthermore, as shown in Table 3, a comparison of the viscosity (cp) when 0.5% aqueous dispersions of S-MFC and BC derived from wood pulp are subjected to a disaggregation treatment by a homogenizer or a mixer is shown in Table 3. The treatment effect is large, and the viscosity after disaggregation is greatly increased to 3 to 5 times that of S-MFC.
[0020]
[Table 3]

[0021]
Table 4 shows a comparison of water retention carried out for undissolved BC and disaggregated BC with 0.5% dispersion.
[0022]
The water retention was evaluated according to the following test method.
50 mL of the dispersion is weighed into a centrifugeable test tube (inner diameter 30 mm × length 100 mm, capacity 50 mL), centrifuged at 500 G (1650 rpm) to 3000 G (4000 rpm) for 10 minutes, and the amount of deposition (mL) is determined. The water content was calculated according to the following equation.
[0023]
[Expression 1]

[0024]
[Table 4]

[0025]
From Table 4, the undissolved product at 2000G is 32 mL / g, whereas the disaggregated product has a water holding amount of about 4 times 128 mL / g.
[0026]
Moreover, when the dispersion stability in the BC aqueous dispersion is compared with the amount of phase separation after standing for 24 hours, as shown in FIG. 1, phase separation occurs up to about 0.3% in the undisaggregated product, Phase separation no longer occurs at around 0.1%. In FIG. 1, a solid line indicates a BC undissolved product, and a dotted line indicates a BC disaggregated product.
[0027]
Dispersion stability test :
A certain amount of dispersion having different concentrations was placed in a graduated test tube, allowed to stand for 24 hours, and then the amount of the supernatant liquid separated from the phase and the amount of the lower dispersion were read to determine the ratio of the lower dispersion.
[0028]
The BC disaggregated product is an ultrafine fiber (microfibril) having an average length of 0.01 to several tens of μm when observed with an electron microscope. The entanglement effect exhibited by the ultramicrofiber and the above-described aqueous dispersion (water-soluble) In combination with the high viscosity of the organic organic solvent / water mixed solvent) and water retention, it is suitable as a binding / dispersion stabilizer for SAP.
[0029]
In order to use the dispersion of the BC disaggregated product as an SAP binding / dispersion stabilizer, an aqueous dispersion solvent that does not swell the SAP and does not cause agglomeration or the like is selected. Table 5 shows the SAP swelling and aggregation phenomena depending on the mixing ratio of the water-soluble organic solvent and water.
[0030]
[Table 5]

[0031]
SAP needs to be stably and uniformly dispersed in a powder state in an aqueous dispersion, but according to the present invention, the BC disaggregation dispersion has an excellent protective effect to reduce the tendency of SAP particles to aggregate, In addition, a good bonding effect is achieved.
[0032]
The superabsorbent composite of the present invention is basically a composite of SAP and BC disaggregated microfibrils covering the same. SAP is not easy to handle and store due to its extremely high water absorption, but such problems are solved by coating with BC disaggregated microfibrils according to the present invention. In addition, the structure in which SAP particles are bonded to each other by BC disaggregated microfibrils is formed by a very thin sheet-like structure so that the microfibrils constrain each SAP particle to a predetermined position and secure an appropriate interval around it. Configure the absorber.
[0033]
The SAP used in the present invention is generally a partially crosslinked water-swelling polymer such as carboxymethylcellulose, polyacrylic acid and salts thereof, polyethylene oxide, polyacrylamide, or a copolymer of isobutylene and maleic acid. . Also included are biodegradable polyaspartic acid amino acid cross-linked products or microorganism-derived superabsorbent polymers that are cultured products from Alcaligenes Latus. As SAP products, those having various forms of particles, granules, films and nonwovens have been developed, all of which can be used in the present invention. The particles, granules, flakes, short needles, and pellets that can be uniformly dispersed in the dispersion medium are collectively referred to as particles.
[0034]
Moreover, in this invention, the network structure which restrains SAP particle | grains to a predetermined position is comprised by BC disaggregation microfibril. This BC disaggregated microfibril is an ultrafine fiber having an average length of 0.01 to several tens of μm as described above, and has water resistance capable of preventing the structure from being immediately collapsed due to swelling when the SAP absorbs water. In addition, it has the property of not inhibiting water permeability and SAP swelling. It should be noted that BC disaggregated microfibrils have high water retention as described above and have extremely strong hydration properties that bind to water as a solvation (bound water). Due to the nature, when dispersed in a water-containing medium, it has a property of hydrating and exhibiting a large viscosity and stably maintaining a dispersed state. According to the research result of the present inventor, when the concentration of microfibrils required for the stability of the SAP slurry from the viewpoint of the viscosity is determined, the S-MFC / SAP ratio 2% derived from wood pulp (S-MFCO .6%), the BC disaggregation dispersion concentration can be lowered. The ethanol / water = 60/40 dispersion system corresponds to a SAP ratio of 0.60%, which can be about 1/4 of S-MFC.
[0035]
When SAP is added and dispersed in the BC disaggregated microfibril dispersion medium, high-concentration SAP can be stably dispersed, and in the process of removing the dispersion medium, it is strongly self-bonded to form a plaster network structure. At the same time as forming and enclosing and mechanically enclosing the SAP particles, the microfibrils are bonded together by ionic hydrogen bonding effects, ensuring the retention of the SAP particles.
[0036]
Next, a method for producing a superabsorbent composite comprising BC disaggregated microfibrils and SAP according to the present invention will be described.
[0037]
First, a disaggregation process is performed in an aqueous dispersion to prepare a dispersion of a relatively high concentration of BC disaggregated microfibrils, which is used as a mother liquor. As the mother liquor, the higher the concentration, the more compact the manufacturing apparatus. On the other hand, since it becomes difficult to handle due to the high viscosity, an aqueous dispersion of 5% or less, preferably 0.5% to 2% is used. Used. A water-soluble organic solvent is added to the microfibril mother liquor to prepare a microfibril dispersion having a predetermined microfibril concentration and a viscosity associated therewith.
[0038]
Instead of performing a disaggregation treatment in an aqueous dispersion, a water-soluble organic solvent is added to a 0.05 to 1.0% diluted BC aqueous dispersion and then a disaggregation treatment is performed to prepare a dispersion of BC disaggregation microfibrils. Good. In any case, if a BC disaggregated microfibril dispersion using a mixed solvent of water / water-soluble organic solvent as a dispersion solvent is prepared, SAP is subsequently added and mixed.
[0039]
As the water-soluble organic solvent used in the present invention, if the relative dielectric constant is 18 or more (20 ° C.), the tendency to give the SAP an agglomerated gum is small, and the SAP does not swell so much in a mixed system with water. It may be anything, for example, alcohols such as methyl alcohol, ethanol, isopropyl alcohol, polyhydric alcohols such as ethylene glycol, diethylene glycol, propylene glycol, low molecular weight polyethylene glycol, glycerin, acetone, methyl ethyl ketone, dimethyl sulfoxide, etc. Any water-soluble organic solvent can be used. Low-boiling alcohols have advantages in terms of solvent distillation recovery and the like, but are difficult in that they require an explosion-proof structure in the production equipment because of their high volatility and flammability. Since glycols have a high viscosity of the solvent itself, there is an advantage in stabilizing the dispersed state of SAP using the viscosity. Considering the safety to the environment and the possibility of some residual solvent in the product, solvents such as ethanol and propylene glycol are particularly suitable. In addition, due to the addition of a crosslinking agent, an antibacterial agent, etc., a water-insoluble solvent such as cyclohexane may be added in a range that does not affect the dispersion system.
[0040]
By dispersing BC disaggregated microfibrils and SAP in a mixed solvent composed of these water-soluble organic solvent and water, a network structure of microfibrils is formed, SAP particles are incorporated, and a stable dispersion state is secured. When is removed, it is presumed that a three-dimensional structure is formed by the physical entanglement structure of the microfibril and the stable hydrogen bond between the microfibrils.
[0041]
The mixing ratio of the water-soluble organic solvent and water is set within a range that enables network formation of microfibrils and suppresses SAP absorption as much as possible. The higher the concentration of the organic solvent, the lower the water absorption rate of the SAP. On the other hand, in order to hydrate and stably disperse BC disaggregated microfibrils, it is advantageous that the content of water in the mixed solvent is large. Accordingly, the water / water-soluble organic solvent ratio is suitably in the range of 10/90 to 50/50. This ratio varies slightly depending on the organic solvent used and the type of SAP used.
[0042]
The dispersion concentration of SAP and BC disaggregated microfibrils and the concentration ratio of SAP and BC disaggregated microfibrils in the coexistence dispersion state of SAP and BC disaggregated microfibrils in this mixed solvent will be described in detail. The SAP concentration varies depending on the transport method of the system, but is selected from the range of 60% or less, preferably from 50% to 5%, for ease of handling. Microfibril concentration is affected by SAP binding strength and dispersion stability. In order to maintain good dispersion stability, 0.1% or more is necessary, and preferably 0.3% to 1.0%.
[0043]
The mixed solvent containing BC disaggregated microfibrils at such a concentration exhibits extremely good dispersion stability as described above, and does not easily cause phase separation even after standing for a long time. Phase separation does not occur until the time has elapsed, and at 0.5%, phase separation is not observed even after 100 hours. This good dispersion stability not only facilitates the operation at the time of application, but also demonstrates that the SAP particles can be uniformly surrounded and stably dispersed, and this shape of the composite of the present invention is demonstrated. It is presumed to form the basis of excellent water absorption.
[0044]
The ratio of BC disaggregated microfibrils to SAP increases as the value increases, but the strength increases, but it becomes hard and becomes paper-like, so 10% or less is desirable. If it is 0.5% or less, it is difficult to obtain a sufficient bonding force. The evaluation of the binding force can be performed with the aid of the cello tape method used for measuring the surface strength, and the preferable range is 0.5% to 5% in view of the result.
[0045]
Whether or not other components can be added to the SAP / BC disaggregated microfibril coexisting dispersion system will be described. The main object of the present invention is how to handle SAP in a high concentration state. BC disaggregated microfibrils show excellent binding and dispersion stability to SAP, but polyethylene glycol as a plasticizer to prevent hardening due to the addition of thickeners such as CMC and over-drying that have been used in the past There is no problem. It is also possible to add a wood pulp slurry or a synthetic fiber dispersion slurry to the above dispersion, but these additions inhibit the dispersion stability and reduce the binding efficiency of microfibril SAP particles. Therefore, attention should be paid to the addition process.
[0046]
Next, as a method for separating a solvent component from a dispersion in which BC disaggregated microfibrils and SAP are dispersed in a mixed solvent to form a superabsorbent composite, for example, (1) obtained by separating the solvent from the slurry. If the block-like product is dried and then pulverized to form particles, spherical or flaky granules with the SAP particle surface coated with microfibrils can be obtained. (2) Pour the slurry into a mold made of net If solid-liquid separation is performed and then dried, a three-dimensional shape-molded composite such as pellets, rods, cylinders, and corrugated plates can be obtained according to the mold used, and (3) continuously If a thin film is formed and dried, a sheet-like composite is obtained. Since the composite obtained in this way becomes flexible when it contains moisture, the sheet-like composite is formed into a mat shape together with fibers by, for example, the airlaid method, and water is given to the composite to be pressed. By drying, it can be reshaped into a sheet.
[0047]
Hereinafter, a method for forming a sheet directly from a dispersion, which is particularly versatile, will be described in detail. As described above, the network structure of the microfibril makes it possible to form a very thin layer while keeping the SAP in a stable and strong state. That is, a dispersion in which BC disaggregated microfibrils and SAP are dispersed in a mixed solvent is applied on a suitable plane, and the solvent is stripped to form a sheet-like superabsorbent composite composed only of microfibrils and SAP. can do.
[0048]
Or when a dispersion liquid is apply | coated on a suitable sheet-like support body, the superabsorbent composite sheet material which consists of a sheet-like support body and the said composite layer is obtained after drying of a dispersion liquid. In particular, when a porous non-woven fabric is used as the sheet-like support, a part of the dispersion enters between the fibers of the non-woven fabric depending on the porosity, and after the dispersion is dried, the non-woven fabric and the composite layer are It becomes a composite structure in which the joint surfaces of the two are intertwined. The preferred porosity of this nonwoven fabric is 0.2 g / cm in terms of apparent specific gravity. ^Three Or less, more preferably 0.01 to 0.1 g / cm ^Three It is. In addition, as a constituent material of the nonwoven fabric in this case, from the problem of liquid permeability, hydrophilic materials such as cotton, rayon and wood pulp, or materials obtained by hydrophilizing synthetic fibers such as polyethylene, polypropylene and polyester are used. It is preferable to use it. As the shape of the nonwoven fabric used as a support, in addition to porous card dry type, non-woven fabrics such as spunbond, sheet-like materials such as surface-raised nonwoven fabrics, card webs with weak bonding, or woven tows can be used. .
[0049]
Next, an apparatus suitable for producing the superabsorbent composite of the present invention will be described with reference to the drawings.
[0050]
In FIG. 2, reference numeral 31 is a tank for storing ion exchange water, 32 is a tank for storing BC disaggregated microfibril water dispersion mother liquor, 33 is a tank for storing ethanol, and 34 is a tank for storing SAP. The BC disaggregated microfibril water dispersion mother liquor taken out from the tank 32 is introduced into a mixer 35 equipped with a stirrer, diluted with water taken out from the tank 31 in the mixer 35, and then subjected to the pump operation. Are introduced into a mixer 36 equipped with a stirrer. Ethanol taken out from the tank 33 is introduced into the mixer 36, and this mixture is introduced into a mixer 37 equipped with a next stirrer by the action of a pump. Granular SAP is introduced into the mixer 37 from the tank 34, where a mixed dispersion of BC disaggregated microfibrils, ethanol, water and SAP is formed.
[0051]
On the other hand, an appropriate sheet-like support 13 such as a nonwoven fabric is unwound from the roll 38 and then guided to the forming unit 40. The molding unit 40 includes a belt conveyor 41 and a nozzle 42 located on the belt of the belt conveyor, and the mixed dispersion liquid is supplied to the nozzle 42 from the mixer 37 by the action of a pump. Yes. While the sheet-like support 13 is guided to the belt conveyor 41 and travels at a predetermined speed, the mixed dispersion from the nozzle 42 is applied on the surface thereof. Of course, it may be applied in the form of a spray. As the nozzle 42, a nozzle having an appropriate shape is provided according to the pattern of the composite layer to be provided on the sheet-like support 13.
[0052]
The forming unit 40 is further provided with a roll press 43 composed of a pair of rollers. By pressing the sheet-like support 13 on which the mixed dispersion is applied, the solvent contained in the mixed dispersion is reduced. The squeezed and separated solvent is returned to the mixer 36 by the action of the pump.
[0053]
The sheet-like support 13 exits the forming unit 40 and is then sent to the next drying unit 50. Hot air is supplied to the drying unit 50 and includes a pair of porous rolls 51 and 52, and the sheet-like support 13 and the mixed dispersion applied thereto are arranged along the peripheral surfaces of the porous rolls 51 and 52. It is dried while being transported.
[0054]
In FIG. 2, an example of another apparatus for applying the mixed dispersion liquid to the sheet-like support 13 in the molding unit 40 is shown in FIG. In FIG. 3, reference numeral 44 denotes an open top tank for storing the mixed dispersion, which can be rotated around a horizontal axis while being partially immersed in the mixed dispersion in the tank 44. A dipping roll 45 is arranged. A pair of rolls 46 and 47 are provided so as to be rotatable about an axis parallel to the immersion roll 45. One roll 46 is in pressure contact with the peripheral surface of the immersion roll 45, and has a large number of ring-shaped grooves 46a on the peripheral surface, for example, as shown in FIG. The sheet-like support 13 to which the mixed dispersion is to be applied passes through the nip between the roll 47 and the roll 47.
[0055]
The mixed dispersion accommodated in the tank 44 adheres to the peripheral surface of the immersion roll 45 moving in the tank 44 by its own viscosity, and then transferred to the sheet-like support 13 via the grooved roll 46. . Therefore, as shown in FIG. 5, a mixed dispersion layer 48 is formed in a number of strips parallel to each other on the surface of the sheet-like support 13. In addition, the uneven | corrugated pattern formed in the roll 46 can be set arbitrarily, and it is possible to apply | coat the mixed dispersion liquid to the sheet-like support body 13 with the pattern corresponding to this pattern.
[0056]
The characteristics and performance of the absorbent product incorporating the superabsorbent composite obtained by the present invention will also be summarized. When the highly water-absorbent composite of the present invention is used in an absorbent product, first of all, it has a very thin and compact structure in a non-water-absorbing state before and during use, and SAP particles are firmly fixed and stabilized. Therefore, even if bending or expansion / contraction works, the SAP particles do not move and the SAP is not easily dropped and the structure is not easily broken.
[0057]
Second, at the time of water absorption, despite the Palpress structure with SAP of 90% or more, the absorption rate is fast and no blocking occurs because of the hydrophilicity of the microfibril and its physical form.
[0058]
Thirdly, the swollen polymer is gently gripped by the network of fibrils even after water absorption to prevent dropping.
[0059]
Fourth, it is a characteristic at the time of disposal after use. BC disaggregated microfibrils have an extremely high cellulase activity, and the structure becomes disintegrated in a short time by being buried in the soil. If a biodegradable amino acid polymer or a microbial polymer absorber is combined as SAP, an ideal environment-adaptive absorber can be designed.
[0060]
【Example】
Hereinafter, the present invention will be described specifically by way of examples.
[0061]
Example 1
Preparation of BC :
Sucrose 5 g / dL, yeast extract (Difco) 0.5 g / dL, ammonium sulfate 0.5 g / dL, KH ₂ PO _Four 0.3 g / dL, MgSO _Four ・ 7H ₂ O 50 gL of a medium having a composition of 0.05 g / dL (pH 5.0) was placed in a 20 dL Erlenmeyer flask and steam-sterilized at 120 ° C. for 20 minutes. A platinum loop of Acetobacter aceti subsibisis xylinum ATCC 10821 grown on a test tube slope agar medium having a composition of 0.5 g / dL (pH 6.0) (30 ° C., 3 days) was inoculated one by one and cultured at 30 ° C. After 30 days, a white cellulose substance film was formed on the upper layer of the culture solution. The gel was washed with water and centrifuged to obtain a sample having a solid concentration of 10%.
[0062]
Preparation of ethanol / water mixed solvent dispersion of BC disaggregated microfibrils :
Water is added to the sample, and the mixture is processed at 13,000 rpm for 10 minutes using a mixer (“Oaster blender”) to prepare a 2.0% aqueous dispersion. Ethanol is added to this to add 60% ethanol / water. / 40, 4 levels of mixed dispersions with BC concentrations of 0.15%, 0.21%, 0.43% and 0.86% were prepared.
[0063]
Preparation of BC disaggregated microfibril / SAP coexisting dispersion :
30g of 60-100 mesh section of SAP (trade name “IM-6700”, manufactured by Sanyo Chemical Co., Ltd.) is added to 70cc of BC disaggregated microfibril dispersion of the above level, and BC disaggregated microfibril / SAP coexistence A dispersion was prepared.
The breakdown of this dispersion is as shown in Table 6.
[0064]
For comparison, a gelatinous 4.0% dispersion of S-MFC (manufactured by Tokushu Paper Co., Ltd.) was used as a mother liquor, and ethanol and water were added thereto to make ethanol / water 60/40, S-MFC. Four levels of mixed dispersions with concentrations of 0.21%, 0.43%, 0.86%, and 1.7% were prepared, respectively, and S-MFC / SAP coexisting dispersions as with the BC disaggregated microfibrils. Was prepared. The breakdown of this dispersion is also shown in Table 6.
[0065]
[Table 6]

[0066]
The above SAP 30% dispersion is more stable as the concentration of BC disaggregated microfibrils and the comparative S-MFC is higher. However, with BC, the concentration is stable at 0.15% or more, and even after stirring is stopped with a stirrer, SAP Sedimentation was not observed immediately and was stable for several minutes even at 0.10%. On the other hand, when S-MFC had a concentration of 0.3% or less, SAP sedimentation started immediately after stirring was stopped.
[0067]
Preparation of BC disaggregation microfibril / SAP composite sheet material :
The dispersion was diluted 3-fold with ethanol / water = 60/40 and connected to a Buchner funnel (inner diameter: 11 cm) connected to a decompression device. Filter paper, base nonwoven fabric (TCF403 manufactured by Nimura Chemical, apparent specific gravity of 0.07 g / cm) ^Three ), A 20 cc viscous dispersion was quickly poured onto the base nonwoven fabric, and the solvent was removed by decompression, followed by drying with hot air to obtain a composite sheet.
[0068]
As a result of performing the performance evaluation of the composite sheet material according to the method shown by the evaluation method, it was as shown in Table 7 and Table 8.
[0069]
Evaluation results of water absorption :
The water absorption amount, water retention amount and water absorption speed of the composite sheet material were examined. The results are shown in Table 7.
[0070]
[Table 7]

[0071]
There was almost no difference in the effect of the blending ratio on the type of microfibril and the SAP in all three evaluation methods.
[0072]
Result of characterization of composite sheet material :
The performance evaluation results of the composite sheet material are shown in Table 8.
[0073]
[Table 8]

[0074]
It can be seen that the composite sheet material was almost as specified, and there was no difference between the samples in thickness, weight, adhesion SAP + MC, and apparent specific gravity, and it was found that almost the same thing could be made.
[0075]
With the 180 ° pilling test using cello tape, the BC disaggregation processed product shows a difference of about 2nd grade with the same compounding ratio in the 180 ° pilling test using cello tape, and the SAP peeling is 1/5 to 1/10 or less. Yes. In other words, it can be said that the BC disaggregation-treated product exhibits its performance sufficiently by the blending of 1/3 to 1/4 of the comparative S-MFC in order to obtain the same SAP peel resistance. For example, with a MC / SAP ratio (%) of a BC disaggregation product of 0.3%, the pilling test result is grade 3, and to obtain grade 3 with S-MFC, the MC / SAP ratio (%) is 1.0% Was necessary. Similarly, in order to obtain the fourth grade, it was necessary to obtain a high blending of 2.0% for 0.5% and 4.0% for 1.0% if obtaining the fifth grade.
[0076]
Further, since the degree of bending becomes greater when the blending of S-MFC is larger than that of the BC disaggregation processed product, the soft softness is obtained by using the BC disaggregation processed product.
[0077]
From the above, it was found that the BC disaggregation-treated product can greatly reduce the blending ratio with respect to the S-MFC of the comparative product and can improve the texture as well. .
[0078]
The evaluation methods for the evaluation items in the above table are shown below.
Thickness (mm): measured with a thickness gauge (JIS)
Weight (g): Measured with a 110 mmφ substrate with an electronic pan balance, and the amount of attached SAP + MC (binder) is calculated by subtracting the weight of the substrate, m ² The amount per unit is displayed.
Apparent specific gravity (g / cm ^Three ): It was calculated from the thickness of the base material and the attached SAP + MC.
Bending / softening (mm): A sample of 110 mm × 20 mm was measured by the method shown in FIGS.
[0079]
One end of the sample S was placed at a right angle with the tip of a stainless steel measure M, and the scale of the measure at the position (αmm) depending on its own weight was read to make it flexible.
[0080]
[Evaluation of SAP binding stability (180 ° pilling test using cello tape)]
Apply a 15mm wide Nichiban cello tape to the sample, make the adhesive surface 15mm x 10mm, and lightly press it with flannel from the top, then 1kg / cm ² Apply a load of 10 minutes. The cellophane was peeled off from the sample in a 180 ° pilling state after the weight removal, and the adhesion state of the SAP adhering to the cellophane was measured for the adhesion area (%) of the SAP to evaluate the binding stability of MC (microfiber). . The criteria for determination are shown in FIG.
[0081]
[Evaluation of water absorption, water retention, water absorption speed of the composite]
About the said composite_body | complex, after 30-minute immersion in the sufficient amount of physiological saline, the water absorption amount and the water retention amount were measured according to JISK-7223. As for the water absorption speed, 20 mL of physiological saline was dropped by a burette on the center of an 11 cmφ composite sheet with the SAP application surface up, and the initial water absorption time was measured.
Example 2: Continuous application experiment
A superabsorbent composite was produced using the production apparatus shown in FIG. 2 equipped with the coating apparatus shown in FIG. The materials used are as follows.
[0082]
(1) Microfibril / SAP coexisting dispersion: Example 1 Sample No. 3 or Comparative Sample No. B

(3) Sheet-like support: Two-layer sulairmal bond web 40 g / m ² , Apparent specific gravity 0.06g / cm ^Three A non-woven fabric having the following constitution was used.

[0083]
While running the sheet-like support 13 at a speed of 10 m / min, the mixed dispersion of the component (2) was continuously applied on the surface of the upper layer at a width of about 10 mm with an interval of 5 mm. Then, after compressing with a roll and removing a solvent, it dried with hot air.
[0084]
The obtained sheet-like superabsorbent composite had the following characteristics.

[0085]
In addition, the water retention amount of the obtained superabsorbent was measured based on JIS K-7223. As a result, the water retention amount was 42 g (Example 2) and 40 g (Comparative Example) per 1 g of SAP, and the numerical value was almost the same as that of the blank.
[0086]
【The invention's effect】
As described above, BC defibration and disaggregation treatment dispersions exhibit a significant increase in viscosity and water retention that are not observed in wood pulp-derived S-MFC, and are suitable as a binding agent and dispersion stabilizer for SAP. However, it is possible to stabilize a high concentration SAP slurry, excellent in form stability, flexibility, water absorption speed, texture, etc., and a typical Palpress high water absorption composite containing 90% or more of SAP. The body can be provided.
[Brief description of the drawings]
FIG. 1 is a drawing showing the relationship between BC concentration and BC dispersion stability for BC undissolved dispersion and BC disaggregated dispersion.
FIG. 2 is a schematic block diagram illustrating an apparatus for producing a superabsorbent composite according to the present invention.
3 is a schematic block diagram illustrating another coating apparatus used in the apparatus shown in FIG.
4 is a plan view of a grooved roll used in the apparatus of FIG.
5 is a cross-sectional view of a sheet-like support coated with a mixed solvent dispersion liquid using the apparatus shown in FIG.
FIG. 6 is an explanatory diagram showing a method for measuring bending resistance (mm).
7 is a cross-sectional view taken along line AA in FIG.
FIG. 8 is a chart showing criteria for determining the binding stability of SAP.
[Explanation of symbols]
31-34 tanks
35-37 mixer
40 Molding part
41 Belt conveyor
42 nozzles
43 Roll press
44 tanks
45 Immersion roll
46, 47 rolls
48 Mixed dispersion layer
50 Drying section
51,52 Heating roll
60 compression section
61, 62 Press roll

Claims (5)

Bacterial cellulose disaggregation is a concentration that does not flocculate or swell particulate superabsorbent resin and has a relative dielectric constant of 18 or more (20 ° C.), methanol, ethanol, isopropyl alcohol, ethylene glycol, diethylene glycol, propylene Disperse in a mixed solvent of water and at least one water-soluble organic solvent of glycol, low molecular weight polyethylene glycol, glycerin, acetone, methyl ethyl ketone, and dimethyl sulfoxide, and add and mix the particulate superabsorbent resin into this. Preparing a co-dispersion solution of the bacterial cellulose disaggregation product and the particulate superabsorbent resin, separating a solvent component from the co-dispersion solution, and drying the mixture. The superabsorbent composite according to claim 1, wherein the water / water-soluble organic solvent ratio is 10/90 to 50/50.   2. The dispersion concentration of bacterial cellulose in a mixed solvent of a water-soluble organic solvent and water is 0.05 to 1.0% by weight, and the dispersion concentration of the particulate superabsorbent resin is 5 to 60% by weight. Super absorbent composite A superabsorbent sheet material, wherein the co-dispersing liquid according to claim 1 is applied to a sheet-like support, desolvated, and dried.   The superabsorbent sheet material according to claim 4, wherein the sheet-like support is a hydrophilic porous nonwoven fabric.

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