JP3688418B2 - Water-absorbing agent and sanitary material - Google Patents

Description

【０３３７】
表１の結果から、実施例１〜実施例３に示すように、２種類以上の形状の攪拌翼７…を備えた連続押出式混合機１・５４にて吸水性樹脂と架橋剤とを混合、反応させた場合には、実施例４及び実施例５に示すように、１種類（同一形状）の攪拌翼７…を備え、その配設密度を変更することで押し出し推力を調整する連続押出式混合機５５にて混合、反応させた場合と比べて、高加圧下における吸収倍率により優れた吸水剤を得ることができることが判る。従って、連続押出式混合機１・５４にて混合攪拌することにより、高加圧下においてさらに高い吸収倍率を示す吸水剤が得られることが判明した。
【０３３８】
〔実施例６〕
実施例１で得られたＮＯ．１吸水剤に対して、前述の方法により衝撃力（Ａ）を与えてＮＯ．６吸水剤を得た。また、このＮＯ．６吸水剤に対して、衝撃付与前後の高加圧下の吸収倍率の測定を前記方法にて行った。上記測定結果を表２に示す。
【０３３９】
〔実施例７〕
実施例２で得られたＮＯ．２吸水剤に対して、前述の方法により衝撃力（Ａ）を与えてＮＯ．７吸水剤を得た。また、このＮＯ．７吸水剤に対して、衝撃付与前後の高加圧下の吸収倍率の測定を前記方法にて行った。上記測定結果を表２に示す。
【０３４０】
〔実施例８〕
実施例３で得られたＮＯ．３吸水剤に対して、前述の方法により衝撃力（Ａ）与えてＮＯ．８吸水剤を得た。また、このＮＯ．８吸水剤に対して、衝撃付与前後の高加圧下の吸収倍率の測定を前記方法にて行った。上記測定結果を表２に示す。
【０３４１】
【表２】

【０３４２】
表２の結果から、前記実施例１〜実施例３に示す吸水剤に衝撃力（Ａ）を与えた場合には、実施例６〜実施例８に示すように、物性値Ｑ／Ｐが０．９３〜１．００となり、衝撃による高加圧下吸収倍率があまり変化しないこと、即ち、衝撃前の高加圧下吸収倍率を維持できることが判明した。
【０３４３】
〔実施例９〕
実施例１で得られたＮＯ．１吸水剤に対して前述の方法により衝撃力（Ｂ）を与えてＮＯ．９吸水剤を得た。また、このＮＯ．９吸水剤に対して、衝撃付与前後の高加圧下の吸収倍率の測定を前記方法にて行った。上記測定結果を表３に示す。
【０３４４】
〔実施例１０〕
実施例２で得られたＮＯ．２吸水剤に対して前述の方法により衝撃力（Ｂ）を与えてＮＯ．１０吸水剤を得た。また、このＮＯ．１０吸水剤に対して、衝撃付与前後の高加圧下の吸収倍率の測定を前記方法にて行った。上記測定結果を表３に示す。
【０３４５】
〔実施例１１〕
実施例３で得られたＮＯ．３吸水剤に対して前述の方法により衝撃力（Ｂ）を与えてＮＯ．１１吸水剤を得た。また、このＮＯ．１１吸水剤に対して、衝撃付与前後の高加圧下の吸収倍率の測定を前記方法にて行った。上記測定結果を表３に示す。
【０３４６】
〔実施例１２〕
実施例５で得られたＮＯ．５吸水剤に対して前述の方法により衝撃力（Ｂ）を与えてＮＯ．１２吸水剤を得た。また、このＮＯ．１２吸水剤に対して、衝撃付与前後の高加圧下の吸収倍率の測定を前記方法にて行った。上記測定結果を表３に示す。
【０３４７】
【表３】

【０３４８】
表３の結果から、前記実施例１〜実施例３および実施例５に示す吸水剤に衝撃力（Ｂ）を与えた場合には、実施例９〜実施例１２に示すように、物性値Ｙ／Ｘが０．８６〜１．００となり、衝撃による高加圧下吸収倍率があまり変化しないこと、即ち、衝撃前の高加圧下吸収倍率を維持できることが判明した。
【０３４９】
〔実施例１３〕
カルボキシル基を有する吸水性樹脂の製造に際して、単量体成分としてのアクリル酸ナトリウム（中和率７５モル％）の３８重量％水溶液５５００部に、内部架橋剤としてのトリメチロールプロパントリアクリレート２．７部を溶解させて反応液とした。単量体成分に対するトリメチロールプロパントリアクリレートの使用量は、０．０４モル％である。次に、この反応液を窒素ガス雰囲気下で、３０分間脱気した。
【０３５０】
次いで、シグマ型羽根を２本有するジャケット付きステンレス製双碗型ニーダーに蓋を付けた反応器に上記反応液を供給し、反応液を３０℃に保ちながら、上記反応器内を窒素ガス置換した。続いて、反応液を攪拌しながら、重合開始剤としての過硫酸アンモニウム２．８部及び還元剤としてのＬ−アスコルビン酸０．０２部を添加し、実施例１と同様の重合操作を行った。この結果、約０．１ｍｍ〜３ｍｍに細分化された含水ゲル状重合体を得た。
【０３５１】
次いで、上記含水ゲル状重合体を、実施例１と同様に乾燥した後、粉砕に用いられるロール同士が所定の間隔（ロールギャップ約１．６３ｍｍ、約０．４３ｍｍ、約０．１５ｍｍ）を有するように３段に形成されたロールグラニュレター型粉砕機を用いて粉砕し、次いで、目開き８５０μｍのＪＩＳ標準篩で分級することにより、平均粒径が３００μｍの不定型破砕状の吸水性樹脂（Ａ）を得た。さらに、この吸水性樹脂（Ａ）を、目開き１５０μｍのＪＩＳ標準篩で分級することにより、粒径８５０μｍ〜１５０μｍの吸水性樹脂（Ａ₁)８６．３重量％および粒径１５０μｍ未満の吸水性樹脂微粉末（Ａ₂)１３．７重量％を得た。
【０３５２】
次いで、上記の吸水性樹脂微粉末（Ａ₂)を、図１に示す連続押出式混合機１に２ｋｇ／分の割合で投入すると共に、上記連続押出式混合機１に設けられた口径５ｍｍの液供給口４から、イオン交換水を、吸水性樹脂微粉末（Ａ₂)１００重量部に対してイオン交換水１３０重量部の割合で投入することによって、上記吸水性樹脂微粉末（Ａ₂)とイオン交換水とを連続的に混合した。この結果、排出口５から、粒子状の均一な含水ゲル状造粒物が連続的に排出された。得られた粒子状の含水ゲル状造粒物は、個々の粒子の凝集体であり、その大部分が、粒径約１ｍｍ〜５ｍｍの均一な含水ゲル状造粒物であった。また、上記含水ゲル状造粒物の固形分は、４３．６重量％であった。尚、含水ゲル状造粒物の固形分とは、含水ゲル状造粒物中の吸水性樹脂の量（含有量）を示す。
【０３５３】
次に、この含水ゲル状造粒物を、目開き３００μｍのＪＩＳ標準金網上に、約５ｃｍの厚みになるように広げ、１６０℃の熱風循環式乾燥機で乾燥させた。この結果、上記含水ゲル状造粒物は均一かつ固形分９０重量％以上に十分に乾燥され、造粒粒子同士を手でも容易に解砕することが可能な粉体状の乾燥造粒物が得られた。該乾燥造粒物中の１０ｍｍを越える塊は５％に過ぎなかった。
【０３５４】
次いで、この乾燥造粒物を、前記ロールグラニュレター型粉砕機を用いると共に、ロールギャップを広げて粉砕（最終ロールギャップ約０．２７ｍｍ）し、目開き８５０μｍのＪＩＳ標準篩で分級することにより、吸水性樹脂造粒物（１）を得た。
【０３５５】
このようにして得られた上記吸水性樹脂造粒物（１）、吸水性樹脂（Ａ）、吸水性樹脂（Ａ₁)、および吸水性樹脂微粉末（Ａ₂)の粒度分布、無加圧下での吸収倍率および造粒破壊率を測定した。上記粒度分布を表４に示すと共に、吸収倍率および造粒破壊率の測定結果を合わせて表５に示す。また、上記吸水性樹脂微粉末（Ａ₂)の電子顕微鏡写真（５０倍）を図１８に示す。
【０３５６】
さらに、上記吸水性樹脂造粒物（１）１００重量部に対し、エチレングリコールジグリシジルエーテル０．０５重量部、グリセリン０．７５重量部、水３重量部、イソプロピルアルコール０．７５重量部、および乳酸０．５重量部からなる表面架橋剤を混合し、２００℃で４０分間加熱することにより、Ｎｏ．１３吸水剤を得た。上記測定上記ＮＯ．１３吸水剤の無加圧下および高加圧下の吸収倍率、吸収速度、および造粒破壊率を測定した。上記測定結果を表６に示す。
【０３５７】
また、上記吸水性樹脂造粒物（１）の電子顕微鏡写真（５０倍）を図１９に示す。上記吸水性樹脂造粒物（１）は、原料として図１８に示した粒径１５０μｍ未満の吸水性樹脂微粉末（Ａ₂)を用いているにも拘らず、３００μｍ〜８５０μｍの粒径を有する粒子が約８割を占める凝似一次粒子の造粒物（凝集体）となり、結果的に、衝撃力（Ｂ）によって規定される造粒破壊率が２．４重量％という造粒強度の強い造粒物（凝集体）となっていた。
【０３５８】
尚、図示はしないが、本実施例にて得られた乾燥前の含水ゲル状造粒物の光学顕微鏡写真では、該含水ゲル状造粒物が個々の一粒一粒の含水ゲルの凝集体である事実や、架橋剤を含まない水で造粒した場合、吸水膨潤後は造粒前の複数の粒子に分かれて膨潤する事実も別途確認されている。
【０３５９】
〔実施例１４〕
実施例１３において、連続押出式混合機１で含水ゲル状造粒物を得るに際して、吸水性樹脂微粉末（Ａ₂)１００重量部に対して添加するイオン交換水の量を、１３０重量部から１６３重量部に変更する以外は、実施例１３と同様の反応・操作を行って、固形分３８．０重量％の含水ゲル状造粒物を得た。
【０３６０】
その後、上記含水ゲル状造粒物を実施例１３と同様の方法により乾燥した。この結果、上記含水ゲル状造粒物は均一かつ十分に乾燥され、造粒粒子同士を手でも容易に解砕することが可能な粉体状の乾燥造粒物が得られた。該乾燥造粒物中の１０ｍｍを越える塊は５％に過ぎなかった。
【０３６１】
次いで、この乾燥造粒物を、実施例１３と同様に粉砕、分級することにより、吸水性樹脂造粒物（２）を得た。該吸水性樹脂造粒物（２）の粒度分布、無加圧下での吸収倍率および造粒破壊率を測定した。上記粒度分布を表４に示すと共に、吸収倍率および造粒破壊率の測定結果を合わせて表５に示す。
【０３６２】
さらに、上記吸水性樹脂造粒物（２）を用いて、実施例１３と同様の混合・加熱処理を行ってＮｏ．１４吸水剤を得た。上記ＮＯ．１４吸水剤の無加圧下および高加圧下の吸収倍率、吸収速度、および造粒破壊率を測定した。上記測定結果を表６に示す。
【０３６３】
〔実施例１５〕
実施例１３において、連続押出式混合機１で含水ゲル状造粒物を得るに際して、吸水性樹脂微粉末（Ａ₂)１００重量部に対して添加するイオン交換水の量を、１３０重量部から７４重量部に変更する以外は、実施例１３と同様の反応・操作を行って、固形分５７．６重量％の含水ゲル状造粒物を得た。尚、混合は均一であったが、実施例１３・１４と比較すると、その混合の均一性は、若干劣るものであった。
【０３６４】
その後、上記含水ゲル状造粒物を実施例１３と同様の方法により乾燥した。この結果、上記含水ゲル状造粒物は均一かつ十分に乾燥され、造粒粒子同士を手でも容易に解砕することが可能な粉体状の乾燥造粒物が得られた。該乾燥造粒物中の１０ｍｍを越える塊は５％に過ぎなかった。
【０３６５】
次いで、この乾燥造粒物を、実施例１３と同様に粉砕、分級することにより、吸水性樹脂造粒物（３）を得た。該吸水性樹脂造粒物（３）の粒度分布、無加圧下での吸収倍率および造粒破壊率を測定した。上記粒度分布を表４に示すと共に、吸収倍率および造粒破壊率の測定結果を合わせて表５に示す。
【０３６６】
さらに、上記吸水性樹脂造粒物（３）を用いて、実施例１３と同様の混合・加熱処理を行ってＮｏ．１５吸水剤を得た。このＮＯ．１５吸水剤の無加圧下および高加圧下の吸収倍率、吸収速度、および造粒破壊率を測定した。上記測定結果を表６に示す。
【０３６７】
〔実施例１６〕
実施例１３において、連続押出式混合機１で含水ゲル状造粒物を得るに際して、吸水性樹脂微粉末（Ａ₂)１００重量部に対して添加するイオン交換水の量を、２３０重量部から４１重量部に変更する以外は、実施例１３と同様の反応・操作を行って、固形分７０．９重量％の含水ゲル状造粒物を得た。尚、混合は均一であったが、実施例１５よりはやや劣るものであり、また、得られた含水ゲル状造粒物は、連続押出式混合機１のケーシング２の内面への付着や、凝集が起こりやすいものであった。
【０３６８】
その後、上記含水ゲル状造粒物を実施例１３と同様の方法により乾燥した。この結果、上記含水ゲル状造粒物は均一かつ十分に乾燥され、造粒粒子同士を手でも容易に解砕することが可能な粉体状の乾燥造粒物が得られた。該乾燥造粒物中の１０ｍｍを越える塊は５％に過ぎなかった。
【０３６９】
次いで、この乾燥造粒物を、実施例１３と同様に粉砕、分級することにより、吸水性樹脂造粒物（４）を得た。該吸水性樹脂造粒物（４）の粒度分布、無加圧下での吸収倍率および造粒破壊率を測定した。上記粒度分布を表４に示すと共に、吸収倍率および造粒破壊率の測定結果を合わせて表５に示す。
【０３７０】
さらに、上記吸水性樹脂造粒物（４）を用いて、実施例１３と同様の混合・加熱処理を行ってＮｏ．１６吸水剤を得た。このＮＯ．１６吸水剤の無加圧下および高加圧下の吸収倍率、吸収速度、および造粒破壊率を測定した。上記測定結果を表６に示す。
【０３７１】
〔比較例１〕
実施例１３において、吸水性樹脂微粉末（Ａ₂)とイオン交換水とを混合する際に、連続押出式混合機１に代えて、図２１に示す従来の連続押出式混合機１００を用いた以外は、実施例１３と同様の反応・操作を行った。しかしながら、上記従来の連続押出式混合機１００によって得られた混合物は、造粒物ではなく、主に１ｃｍ〜５ｃｍのゲル状の塊であり、この結果、上記連続押出式混合機１００の排出口１０６から連続的に排出することはできなかった。次に、上記ゲル状の塊に対し、実施例１と同様の方法により乾燥を試みたが、乾燥しなかった。しかも、水可溶成分の増加等、物性低下が見られた。
【０３７２】
〔比較例２〕
比較例１において、図１７に示す従来の連続押出式混合機１００で吸水性樹脂微粉末（Ａ₂)とイオン交換水とを混合する際に、吸水性樹脂微粉末（Ａ₂)１００重量部に対して添加するイオン交換水の量を、１３０重量部から１０重量部に変更する以外は、比較例１と同様の反応・操作を行った。しかしながら、上記吸水性樹脂微粉末（Ａ₂)は吸収速度が速く、上記従来の連続押出式混合機１００によって得られた混合物は、含水ゲル状造粒物ではなく、ダマ状の粉末状造粒物を多く含むと共に、水性液が全く行き渡らず、未造粒のままの吸水性樹脂微粉末（Ａ₂)を半分以上含むものであった。
【０３７３】
次に、上記ダマ状の粉末状造粒物を、実施例１３と同様に乾燥、粉砕、分級することにより、比較吸水性樹脂造粒物（１）を得た。該比較吸水性樹脂造粒物（１）の粒度分布、無加圧下での吸収倍率および造粒破壊率を測定した。上記粒度分布を表４に示すと共に、吸収倍率および造粒破壊率の測定結果を合わせて表５に示す。
【０３７４】
また、上記比較吸水性樹脂造粒物（１）の電子顕微鏡写真（５０倍）を図２０に示す。上記比較吸水性樹脂造粒物（１）は、原料として図１８に示した粒径１５０μｍ未満の吸水性樹脂微粉末（Ａ₂)を用いているが、１５０μｍ以上の造粒物が約２４重量％しかなく、かつ、その造粒も個々の微粉末の点接触であり、結果的に、衝撃力（Ｂ）によって規定される造粒破壊率１００重量％という、弱い造粒物（凝集体）となっていた。
【０３７５】
さらに、上記比較吸水性樹脂造粒物（１）を用いて、実施例１３と同様の混合・加熱処理を行ってＮｏ．１比較用吸水剤を得た。上記Ｎｏ．１比較用吸水剤の無加圧下および高加圧下の吸収倍率、吸収速度、および造粒破壊率を測定した。上記測定結果を表６に示す。
【０３７６】
〔比較例３〕
実施例１３において、吸水性樹脂造粒物（１）に代えて、吸水性樹脂（Ａ₁)を８６．３重量％、吸水性樹脂微粉末（Ａ₂)を１３．７重量％の割合で含む吸水性樹脂（Ａ）を用いた以外は、実施例１３と同様の反応・操作を行って、Ｎｏ．２比較用吸水剤を得た。また、このＮＯ．２比較用吸水剤の無加圧下および高加圧下の吸収倍率、吸収速度、および造粒破壊率を測定した。上記測定結果を表６に示す。
【０３７７】
〔実施例１７〕
実施例１において、内部架橋剤としてのポリエチレングリコールジアクリレート（ｎ＝８）の使用量を、２．９部から３．９部に変更した以外は、実施例１と同様の反応・操作を行って、含水ゲル状重合体を得た。
【０３７８】
次いで、上記含水ゲル状重合体を、実施例１と同様に乾燥した後、実施例１３よりもロールギャップが狭くなるように設定（最終ロールギャップ約０．１５ｍｍ）されたロールグラニュレター型粉砕機を用いて粉砕し、目開き８５０μｍのＪＩＳ標準篩で分級することにより、平均粒径が２６０μｍの不定型破砕状の吸水性樹脂（Ｂ）を得た。さらに、この吸水性樹脂（Ｂ）を、目開き１５０μｍのＪＩＳ標準篩で分級することにより、粒径８５０μｍ〜１５０μｍの吸水性樹脂（Ｂ₁)８２．０重量％および粒径１５０μｍ未満の吸水性樹脂微粉末（Ｂ₂)１８．０重量％を得た。
【０３７９】
次いで、上記の吸水性樹脂微粉末（Ｂ₂)を、図１に示す連続押出式混合機１に２ｋｇ／分の割合で投入すると共に、上記連続押出式混合機１に設けられた口径５ｍｍの液供給口４から、グリセリン０．１重量部を溶解させたイオン交換水を、吸水性樹脂微粉末（Ｂ₂)１００重量部に対して１６３重量部の割合で投入することによって、上記吸水性樹脂微粉末（Ｂ₂)と、グリセリンを含むイオン交換水とを連続的に混合した。この結果、排出口５から、粒子状の均一な含水ゲル状造粒物が連続的に排出された。得られた粒子状の含水ゲル状造粒物は、個々の粒子の凝集体であり、その大部分が、粒径約１ｍｍ〜５ｍｍの均一な含水ゲル状造粒物であった。また、得られた上記含水ゲル状造粒物の固形分は、３８．０重量％であった。
【０３８０】
次に、この含水ゲル状造粒物を、目開き３００μｍのＪＩＳ標準金網上に、約５ｃｍの厚みになるように広げ、１６０℃の熱風循環式乾燥機で乾燥させた。この結果、上記含水ゲル状造粒物は均一かつ十分に乾燥され、手でも容易に解砕可能な粉体状の乾燥造粒物が得られた。該乾燥造粒物中の１０ｍｍを越える塊は５％に過ぎなかった。
【０３８１】
次いで、この乾燥造粒物を、実施例１３における乾燥造粒物粉砕時と同じロールギャップ（最終ロールギャップ約０．２７ｍｍ）に設定されたロールグラニュレター型粉砕機を用いて粉砕し、その後、目開き８５０μｍのＪＩＳ標準篩で分級することにより、吸水性樹脂造粒物（５）を得た。
【０３８２】
このようにして得られた上記吸水性樹脂造粒物（５）、吸水性樹脂（Ｂ）、吸水性樹脂（Ｂ₁)、および吸水性樹脂微粉末（Ｂ₂)の粒度分布、無加圧下での吸収倍率および造粒破壊率を測定した。上記粒度分布を表４に示すと共に、吸収倍率および造粒破壊率の測定結果を合わせて表５に示す。
【０３８３】
さらに、上記吸水性樹脂造粒物（５）を用いて、実施例１３と同様の混合・加熱処理を行ってＮｏ．１７吸水剤を得た。また、このＮｏ．１７吸水剤の無加圧下および高加圧下の吸収倍率、吸収速度、および造粒破壊率を測定した。上記測定結果を表６に示す。
【０３８４】
【表４】

【０３８５】
【表５】

【０３８６】
【表６】

【０３８７】
上記実施例１３〜１７および比較例１〜３の結果から、２種類以上の攪拌翼７…を有し、これによって、押し出し推力が異なる領域を有する本願の連続押出式混合機１を用いて造粒することにより、造粒強度に優れた吸水性樹脂造粒物が得られることが判る。また、このように造粒強度に優れた吸水性樹脂造粒物を吸水剤の原料として用いることで、機械的ストレスに強く、しかも、吸水速度の速い吸水剤を得ることができることが判る。これに対し、押し出し推力が一定である従来の連続押出式混合器１００を用いた場合には、吸水性樹脂微粉末に添加する水分量が多ければ造粒物とはならず、逆に水分量が少なければ造粒強度に優れた吸水性樹脂造粒物を得ることができないことが判る。
【０３８８】
〔実施例１８〕
実施例５において、図７に示す連続押出式混合機５５に設けられた攪拌翼７（第一の攪拌翼７ａ）の吸水性樹脂押出面７ａ₁ と回転軸６に垂直な平面とのなす角度（以下、単に吸水性樹脂押出面の角度と記す）を、回転軸の全長を１００％としたときの攪拌翼７…の配設域に応じて種々変更することで、実施例５とは混合条件を変えて吸水性樹脂と表面架橋剤とを混合した。そして、得られた混合物における「ダマ」の割合を測定した。
【０３８９】
次いで、上記混合物を２０メッシュ金網に通過させた後、該混合物を１９５℃で４０分間加熱処理することにより、吸水剤を得た。上記吸水剤の無加圧下および高加圧下での吸収倍率を測定した。上記測定結果を、上記連続押出式混合機５５における混合条件と合わせて表７に示す。
【０３９０】
【表７】

【０３９１】
上記表７において、「送り」、「戻り」とは、吸水性樹脂の押し出し方向に対する押し出し推力の向きを示す。例えば、図１７に示すように、吸水性樹脂排出方向（つまり、連続押出式混合機５５における材料供給口３側から排出口５側への吸水性樹脂の進行方向）である矢印Ａ方向に対して矢印Ｂ方向に回転軸６が回転したときに、吸水性樹脂の進行方向であるＡ方向と同方向に押し出し推力が生じる場合を「送り」、Ａ方向とは逆方向であるＣ方向に押し出し推力が生じる場合を「戻り」と記す。
【０３９２】
従って、「送り４５°」とは、攪拌翼７の吸水性樹脂押出面７ａ₁ と回転軸６に垂直な平面とのなす角度が４５°であり、吸水性樹脂進行方向に押し出し推力が生じていることを示す。また、「戻り４５°」とは、攪拌翼７の吸水性樹脂押出面７ａ₁ と回転軸６に垂直な平面とのなす角度が４５°であり、吸水性樹脂進行方向とは逆向きに押し出し推力が生じていることを示す。
【０３９３】
また、吸水性樹脂押出面の角度が水平とは、攪拌翼７の翼面が回転軸６の軸方向と平行な状態にあることを示し、上記吸水性樹脂押出面の角度が水平に設定されている場合には、攪拌翼７による押し出し推力は新たには生じない。
【０３９４】
上記表７の結果から、攪拌翼７の吸水性樹脂押出面の角度（攪拌翼７の翼面の向き）を種々変更することにより押し出し推力が小さくなる領域を排出側に設けることで、吸水性樹脂と表面架橋剤等を含む水性液とをより均一に混合することができることが判る。
【０３９５】
以上のように、本発明の吸水剤は、カルボキシル基を有する吸水性樹脂と、このカルボキシル基に反応する架橋剤とを混合、反応させて得られる吸水剤であって、上記吸水剤に所定の荷重を加えることにより衝撃力（Ａ）を与えたとき、その衝撃後の吸水剤における圧力５０ｇ／ｃｍ² での吸収倍率をＱ、衝撃前の吸水剤における同一圧力での吸収倍率をＰとすると、
Ｐ≧２０（ｇ／ｇ）
であり、かつ、
Ｑ／Ｐ≧０．８５
である構成である。
【０３９６】
また、本発明の吸水剤は、以上のように、カルボキシル基を有する吸水性樹脂と、このカルボキシル基に反応する架橋剤とを混合、反応させて得られる吸水剤であって、上記吸水剤に所定の振動を与えることにより衝撃力（Ｂ）を与えたとき、その衝撃後の吸水剤における圧力５０ｇ／ｃｍ² での吸収倍率をＹ、衝撃前の吸水剤における同一圧力での吸収倍率をＸとすると、
Ｘ≧２０（ｇ／ｇ）
であり、かつ、
Ｙ／Ｘ≧０．９０
である構成である。
【０３９７】
上記の構成によれば、本発明の吸水剤は、優れた吸収性能を持ち、かつ機械的ストレスに強いものである。従って、製造プラントにおける搬送や、ユーザにおける加工等で加わる機械的ストレスを受けてもその吸水特性を殆ど低下させず、最終製品中においてその優れた吸収性能を維持する吸水剤を提供することができる。上記各吸水剤は、これらをユーザにおいて最終製品の吸収性物品に加工した後も、その優れた吸収特性を維持できるので、各種の吸収性物品、特に、加圧下における吸収特性を重視される紙オムツや生理用ナプキン、失禁パット等の吸収体を含む衛生材料等の吸収性物品に好適である。
【０３９８】
また、本発明の吸水剤は、以上のように、平均粒径子径２００μｍ〜８００μｍの吸水性樹脂造粒物を表面架橋して得られる吸水剤であって、５０ｇ／ｃｍ ² の加圧下での吸収倍率が２０ｇ／ｇ以上であり、吸収速度が２５秒以下であり、かつ、造粒破壊率が１０重量％以下である構成である。
【０３９９】
上記の構成によれば、従来の造粒方法ではそれぞれ相反する特性であり、同時には満足し得ない物性であった高加圧下での吸収倍率、造粒強度、吸収速度の３つの物性を同時に満足することができる吸水剤を提供することができる。
【０４００】
さらに、本発明の吸水剤の製造方法は、以上のように、カルボキシル基を有する吸水性樹脂を、固定円筒の内部における回転軸の周りに、上記吸水性樹脂に押し出し推力を与える少なくとも一種の攪拌部材を設けた攪拌型の連続押出式混合機における第一領域に供給し、上記吸水性樹脂を、上記第一領域で分散させた後、該第一領域における押し出し推力よりも押し出し推力が小さい第二領域に押し出し、該第二領域で上記吸水性樹脂と水性液とを混合させる構成である。
【０４０１】
本発明の吸水剤の製造方法は、以上のように、上記した各吸水剤の製造方法において、上記第二領域に上記水性液を供給する構成である。
【０４０２】
本発明の吸水剤の製造方法は、以上のように、上記した各吸水剤の製造方法において、上記水性液がカルボキシル基と反応し得る架橋剤を含む構成である。
【０４０３】
上記の構成によれば、吸水性樹脂を上記第一領域で分散させた後、該第一領域における押し出し推力よりも押し出し推力が小さい第二領域に押し出し、該第二領域で上記吸水性樹脂と水性液とを混合させることで、第二領域では、第一領域にて分散された吸水性樹脂の平均速度を低下させ、上記吸水性樹脂と水性液との混合攪拌時間を十分に確保すると共に、上記第一領域にて分散された吸水性樹脂と、水性液とを素早く均一に混合させることができる。この結果、カルボキシル基を有する吸水性樹脂とこのカルボキシル基と反応し得る架橋剤等を含む水性液との混合、反応が効率よく行われ、しかも均一混合を確保することができる。従って、上記の構成によれば、加圧下において高い吸収倍率を示し、かつ製造プラントにおける搬送やユーザにおける最終製品の加工等を行った後にもその優れた吸水性能を維持し、最終製品中において、その使用方法を選ばず、常に優れた特性を発揮することのできる吸水剤を製造することができる吸水剤の製造方法を提供することができる。
【０４０４】
また、本発明の吸水剤の製造方法は、以上のように、平均粒径１０μｍ〜１５０μｍの吸水性樹脂（具体的には、ＪＩＳ標準篩で分級して得られた平均粒径１０μｍ〜１５０μｍの吸水性樹脂）１００重量部に水性液７０重量部〜４００重量部を混合して平均粒径０．３ｍｍ〜１０ｍｍの含水ゲル状造粒物を得た後、該含水ゲル状造粒物を、粉砕しない条件下、１１０℃〜３００℃で収縮乾燥し、分級（具体的には、ＪＩＳ標準篩で分級）して得られた平均粒径２００μｍ〜８００μｍの吸水性樹脂造粒物を表面架橋する構成である。
【０４０５】
上記の構成によれば、従来の造粒方法ではそれぞれ相反する特性であり、同時には満足し得ない物性であった高加圧下での吸収倍率、造粒強度、吸収速度の３つの物性を同時に満足することができる吸水剤を提供することができる。
【０４０６】
本発明の吸水剤の製造装置は、以上のように、カルボキシル基を有する吸水性樹脂と水性液とを混合するための攪拌型の連続押出式混合機を有する吸水剤の製造装置であって、上記連続押出式混合機は、内部に回転軸を有する固定円筒を備え、上記回転軸の周りには、少なくとも一種の攪拌部材が、上記固定円筒内に供給された吸水性樹脂を分散させる第一領域における押し出し推力よりも押し出し推力が小さい第二領域を排出側に形成するように設けられている構成である。
【０４０７】
また、本発明の吸水剤の製造装置は、以上のように、カルボキシル基を有する吸水性樹脂と水性液とを混合するための攪拌型の連続押出式混合機を有する吸水剤の製造装置であって、上記連続押出式混合機は、内部に回転軸を有する固定円筒を備え、上記回転軸の周りには、少なくとも一種の攪拌部材が、上記固定円筒内に供給された吸水性樹脂を分散させる分散領域としての第一領域と、上記第一領域よりも排出側に設けられ、かつ、上記分散領域において分散された吸水性樹脂を上記水性液と混合する混合領域としての第二領域とを形成するように設けられている構成である。
【０４０８】
本発明の吸水剤の製造装置は、以上のように、上記吸水剤の製造装置において、上記連続押出式混合機の固定円筒は、上記吸水性樹脂を供給するための第一供給口と、上記第一供給口よりも排出側に設けられ、上記水性液を供給するための第二供給口とを備え、上記第二供給口は、上記第二領域に設けられている構成である。
【０４０９】
本発明の吸水剤の製造装置は、以上のように、前記した吸水剤の製造装置において、上記連続押出式混合機の固定円筒は、上記吸水性樹脂を供給するための第一供給口と、上記第一供給口よりも排出側に設けられ、上記水性液を供給するための第二供給口とを備え、上記第二供給口は、上記第一領域と第二領域との境界域に設けられている構成である。
【０４１０】
本発明の吸水剤の製造装置は、以上のように、上記各吸水剤の製造装置において、上記回転軸の周りには、上記吸水性樹脂供給側に設けられて押し出し推力を生じる形状に形成された複数の第一の攪拌部材と、これら第一の攪拌部材の排出側に設けられ、かつ、第一の攪拌部材の配設領域における押し出し推力よりも押し出し推力が小さくなる領域を形成する複数の第二の攪拌部材とが順次配されている構成である。
【０４１１】
本発明の吸水剤の製造装置は、以上のように、カルボキシル基を有する吸水性樹脂と水性液とを混合するための攪拌型の連続押出式混合機を有する吸水剤の製造装置であって、上記連続押出式混合機は、内部に回転軸を有する固定円筒を備え、上記回転軸の周りには、形状の異なる２種類以上の攪拌翼が設けられている構成である。
【０４１２】
本発明の吸水剤の製造装置は、以上のように、上記吸水剤の製造装置において、上記第一の攪拌部材は、板状に形成されている構成である。
【０４１３】
本発明の吸水剤の製造装置は、以上のように、上記各吸水剤の製造装置において、上記第二の攪拌部材は、円柱状に形成されている構成である。
【０４１４】
さらに、本発明の吸水剤の製造装置は、以上のように、カルボキシル基を有する吸水性樹脂と水性液とを混合するための攪拌型の連続押出式混合機を有する吸水剤の製造装置であって、上記連続押出式混合機は、内部に回転軸を有する固定円筒を備え、上記回転軸の周りに、同一形状の攪拌部材が配され、その吸水性樹脂押出面と回転軸に垂直な平面とのなす角度および該攪拌部材の配設密度が異なることにより、上記固定円筒内に供給された吸水性樹脂を分散させる第１領域と、該第１領域よりも排出側に、該第１領域における押し出し推力よりも押し出し推力が小さい第２領域とが設けられている構成である。
【０４１５】
本発明の吸水剤の製造装置は、以上のように、上記各吸水剤の製造装置において、上記固定円筒の内径に対する回転軸の直径の比が０．４〜０．６の範囲内である構成である。
【０４１６】
本発明の吸水剤の製造装置は、以上のように、上記各吸水剤の製造装置において、上記連続押出式混合機における固定円筒の内面が、実質的に、水に対する接触角が約６０°以上で約７０℃以上の熱変形温度を有する基材から形成されている構成である。
【０４１７】
上記の構成によれば、上記第一領域では、固定円筒内に供給された吸水性樹脂に、連続押出式混合機の内部へと十分な押し出し推力を与えて分散させ、上記第二領域では、上記第一領域における押し出し推力よりも押し出し推力を小さくすることで、吸水性樹脂の平均速度を低下させ、上記吸水性樹脂と水性液との混合攪拌時間を十分に確保すると共に、上記第一領域にて分散された吸水性樹脂と、水性液とを素早く均一に混合することができる。
【０４１８】
また、上記固定円筒の内面が、実質的に、水に対する接触角が約６０°以上で約７０℃以上の熱変形温度を有する基材から形成されていることで、含水した吸水性樹脂が固定円筒内面に付着することを防止することができると共に、混合期間中に発生する熱に十分耐えることができ、安定した混合を継続することができる。
【０４１９】
さらに、上記固定円筒の内径に対する回転軸の直径の比が０．４〜０．６の範囲内であることで、上記吸水性樹脂と水性液との十分な混合を安定的かつ連続的に行うことができる。
【０４２０】
また、本発明において、上記吸水性樹脂と水性液とを混合させる際には、できるだけ瞬時に両者が全体的に接触する必要がある。このため、上記水性液を供給するための第二供給口が、上記第二領域、より好ましくは第一領域と第二領域との境界域に設けられていることで、上記吸水性樹脂と水性液とを瞬時に接触させ、これにより吸水性樹脂と水性液とを十分均一に、「ダマ」を形成させることなく混合させることができる。
【０４２１】
従って、上記の各構成によれば、連続押出式混合機における攪拌部材の諸構成により、カルボキシル基を有する吸水性樹脂とこのカルボキシル基と反応し得る架橋剤等を含む水性液との混合、反応が効率よく行われ、しかも均一混合を確保することができる。そして、上記の構成によれば、加圧下において高い吸収倍率を示し、かつ製造プラントにおける搬送やユーザにおける最終製品の加工等を行った後にもその優れた吸水性能を維持し、最終製品中において、その使用方法を選ばず、常に優れた特性を発揮することのできる吸水剤を製造することができる吸水剤の製造装置を提供することができる。
【０４２２】
【発明の効果】
請求項１記載の発明の吸水剤は、以上のように、アクリル酸及び／又はその塩を主成分とする親水性単量体を重合・架橋することにより得られ、カルボキシル基を有し、ヒドロゲルを形成する吸水性樹脂粒子と、このカルボキシル基に反応する架橋剤とを混合、反応させて得られる吸水剤であって、上記吸水剤５ｇを７０ｍｍ×１００ｍｍの袋に密封し、その上から重量４ｋｇのローラを１０往復させることにより上記吸水剤に衝撃力（Ａ）を与えたとき、その衝撃後の吸水剤における圧力５０ｇ／ｃｍ² での吸収倍率をＱ、衝撃前の吸水剤における同一圧力での吸収倍率をＰとすると、
Ｐ≧２０（ｇ／ｇ）
であり、かつ、
Ｑ／Ｐ≧０．８５
である構成である。
【０４２３】
請求項２記載の発明の吸水剤は、以上のように、請求項１記載の吸水剤において、Ｐ≧２５（ｇ／ｇ）である構成である。
【０４２４】
請求項３記載の発明の吸水剤は、以上のように、請求項１記載の吸水剤において、Ｑ／Ｐ≧０．９である構成である。
【０４２５】
請求項４記載の発明の吸水剤は、以上のように、請求項１記載の吸水剤において、Ｑ／Ｐ≧０．９５である構成である。
【０４２６】
請求項５記載の発明の吸水剤は、以上のように、アクリル酸及び／又はその塩を主成分とする親水性単量体を重合・架橋することにより得られ、カルボキシル基を有し、ヒドロゲルを形成する吸水性樹脂粒子と、このカルボキシル基に反応する架橋剤とを混合、反応させて得られる吸水剤であって、上記吸水剤３０．０ｇをガラスビーズ１０．０ｇと共に、所定の大きさを有する容器に入れて１００Ｖ／６０Ｈｚで振動速度回転数７５０c.p.m の振動を３０分間与えて上記吸水剤同士を衝突させることにより衝撃力（Ｂ）を与えたとき、その衝撃後の吸水剤における圧力５０ｇ／ｃｍ² での吸収倍率をＹ、衝撃前の吸水剤における同一圧力での吸収倍率をＸとすると、
Ｘ≧２０（ｇ／ｇ）
であり、かつ、
Ｙ／Ｘ≧０．９０
である構成である。
【０４２７】
請求項６記載の発明の吸水剤は、以上のように、請求項５記載の吸水剤において、Ｘ≧２５（ｇ／ｇ）である構成である。
【０４２８】
請求項７記載の発明の吸水剤は、以上のように、請求項５記載の吸水剤において、Ｙ／Ｘ≧０．９２である構成である。
【０４２９】
請求項８記載の発明の吸水剤は、以上のように、請求項５記載の吸水剤において、Ｙ／Ｘ≧０．９５である構成である。
【０４３０】
請求項９記載の発明の吸水剤は、以上のように、請求項１〜８の何れか１項に記載の吸水剤において、上記架橋剤が、多価アルコール化合物、エポキシ化合物、多価アミン化合物およびそれらの塩、アルキレンカーボネート化合物からなる群より選ばれる少なくとも１種の化合物である構成である。
【０４３１】
本発明の吸水剤は、優れた吸収性能を持ち、かつ機械的ストレスに強いものである。従って、製造プラントにおける搬送や、ユーザにおける加工等で加わる機械的ストレスを受けてもその吸水特性を殆ど低下させず、最終製品中においてその優れた吸収性能を維持する吸水剤を提供することができる。上記各吸水剤は、これらをユーザにおいて最終製品の吸収性物品に加工した後も、その優れた吸収特性を維持できるので、各種の吸収性物品、特に、加圧下における吸収特性を重視される紙オムツや生理用ナプキン、失禁パット等の吸収体を含む衛生材料等の吸収性物品に好適であるという効果を奏する。
【０４３２】
請求項１０記載の発明の吸水剤は、以上のように、請求項１〜９の何れか１項に記載の吸水剤において、上記吸水性樹脂粒子を、固定円筒の内部における回転軸の周りに、上記吸水性樹脂粒子に押し出し推力を与える少なくとも一種の攪拌部材を設けた攪拌型の連続押出式混合機における第一領域に供給し、上記吸水性樹脂粒子を、上記第一領域で分散させた後、該第一領域における押し出し推力よりも押し出し推力が小さい第二領域に押し出し、該第二領域で上記吸水性樹脂粒子と、該吸水性樹脂粒子が有するカルボキシル基と反応する架橋剤とを混合させてなる構成である。
【０４３３】
上記の構成によれば、上記吸水性樹脂粒子を、上記第一領域で分散させた後、該第一領域における押し出し推力よりも押し出し推力が小さい第二領域に押し出し、該第二領域で上記吸水性樹脂粒子と架橋剤とを混合させることで、第二領域では、第一領域にて分散された吸水性樹脂の平均速度を低下させ、上記吸水性樹脂粒子と架橋剤との混合攪拌時間を十分に確保すると共に、上記第一領域にて分散された吸水性樹脂粒子と、架橋剤とを素早く均一に混合させることができる。この結果、上記吸水性樹脂粒子と、該吸水性樹脂粒子が有するカルボキシル基と反応する架橋剤との混合、反応が効率よく行われ、しかも均一混合を確保することができる。従って、上記の構成によれば、加圧下において高い吸収倍率を示し、かつ製造プラントにおける搬送やユーザにおける最終製品の加工等を行った後にもその優れた吸水性能を維持し、最終製品中において、その使用方法を選ばず、常に優れた特性を発揮することのできる吸水剤を製造することができるという効果を奏する。
【０４３４】
請求項１１記載の発明の吸水剤は、以上のように、平均粒径子径２００μｍ〜８００μｍの吸水性樹脂造粒物を表面架橋して得られる吸水剤であって、５０ｇ／ｃｍ² の加圧下での吸収倍率が２０ｇ／ｇ以上であり、吸収速度が２５秒以下であり、かつ、造粒破壊率が１０重量％以下である構成である。
【０４３５】
請求項１２記載の発明の吸水剤は、以上のように、請求項１１記載の吸水剤において、上記吸水性樹脂造粒物は、平均粒径１０μｍ〜１５０μｍの吸水性樹脂１００重量部に水性液７０重量部〜４００重量部を混合して平均粒径０．３ｍｍ〜１０ｍｍの含水ゲル状造粒物を得た後、該含水ゲル状造粒物を、粉砕しない条件下、１１０℃〜３００℃で収縮乾燥し、分級してなり、当該吸水剤は、この吸水性樹脂造粒物を表面架橋してなる構成である。
【０４３６】
上記の各構成によれば、従来の造粒方法ではそれぞれ相反する特性であり、同時には満足し得ない物性であった高加圧下での吸収倍率、造粒強度、吸収速度の３つの物性を同時に満足することができる吸水剤を提供することができるという効果を奏する。
【０４３７】
請求項１３記載の発明の衛生材料は、以上のように、請求項１〜１２の何れか１項に記載の吸水剤を含む構成である。
【０４３８】
上記各吸水剤は、衛生材料等の吸収性物品に加工した後も、その優れた吸収特性を維持できるので、特に、加圧下における吸収特性を重視される紙オムツや生理用ナプキン、失禁パット等の吸収体を含む衛生材料に好適である。よって、上記の構成によれば、優れた吸収特性を有する衛生材料を提供することができるという効果を奏する。
【図面の簡単な説明】
【図１】 本発明の一実施の形態に係る吸水剤の製造装置における連続押出式混合機の概略の断面図である。
【図２】 図１に示す連続押出式混合機における攪拌状態を示す説明図であり、（ａ）は、上記連続押出式混合機における第一領域での攪拌状態を示す説明図であり、（ｂ）は、上記連続押出式混合機における第二領域での攪拌状態を示す説明図である。
【図３】 本発明の他の実施の形態に係る吸水剤の製造装置における連続押出式混合機の概略の断面図である。
【図４】 本発明のさらに他の実施の形態に係る吸水剤の製造装置における連続押出式混合機の概略の断面図である。
【図５】 本発明のさらに他の実施の形態に係る吸水剤の製造装置における連続押出式混合機の概略の断面図である。
【図６】 本発明のさらに他の実施の形態に係る吸水剤の製造装置における連続押出式混合機の概略の断面図である。
【図７】 本発明のさらに他の実施の形態に係る吸水剤の製造装置における連続押出式混合機の概略の断面図である。
【図８】 本発明のさらに他の実施の形態に係る吸水剤の製造装置における連続押出式混合機の概略の断面図である。
【図９】 本発明のさらに他の実施の形態に係る吸水剤の製造装置における連続押出式混合機の概略の断面図である。
【図１０】 本発明のさらに他の実施の形態に係る吸水剤の製造装置における連続押出式混合機の概略の断面図である。
【図１１】 上記吸水剤に衝撃力（Ａ）を与えるための装置を示す斜視図である。
【図１２】 上記吸水剤に衝撃力（Ｂ）を与えるために用いられる容器の概略構成図である。
【図１３】 （ａ）は、上記吸水剤に衝撃力（Ｂ）を与える場合の上記容器に対する振動の与え方を説明する説明図であり、（ｂ）は、上記吸水剤に衝撃力（Ｂ）を与える場合の上記容器に対する振動の与え方を（ａ）とは別の角度から説明する説明図である。
【図１４】 上記吸水剤に衝撃力（Ｂ）を与えるための装置の概略構成図である。
【図１５】 上記吸水剤に衝撃力（Ｂ）を与える場合の容器の振動の様子を説明する説明図である。
【図１６】 上記吸水剤の加圧下での吸収倍率を測定するための装置を示す断面図である。
【図１７】 上記連続押出式混合機における攪拌部材の吸水性樹脂押出面の角度と押し出し推力の生じる方向との関係について説明する説明図である。
【図１８】 実施例１３で得られた粒径１５０μｍ未満の吸水性樹脂微粉末（Ａ₂)の構造を電子顕微鏡写真（５０倍）によって示す図面代用写真である。
【図１９】 実施例１３で得られた吸水性樹脂造粒物（１）の構造を電子顕微鏡写真（５０倍）によって示す図面代用写真である。
【図２０】 比較例２で得られた比較吸水性樹脂造粒物（１）の構造を電子顕微鏡写真（５０倍）によって示す図面代用写真である。
【図２１】 従来の吸水剤の製造装置における連続押出式混合機を示す断面図である。
【符号の説明】
１ 連続押出式混合機
２ ケーシング（固定円筒）
３ 材料供給口（第一供給口）
４ 液供給口（第二供給口）
５ 排出口
６ 回転軸
７ 攪拌翼（攪拌部材）
７ａ 第一の攪拌翼（第一の攪拌部材）
７ａ₁ 吸水性樹脂押出面
７ｂ 第二の攪拌翼（第一の攪拌部材）
５１ 連続押出式混合機
５２ 連続押出式混合機
５３ 連続押出式混合機
５４ 連続押出式混合機
５５ 連続押出式混合機
５５’ 連続押出式混合機
５６ 連続押出式混合機
５７ 連続押出式混合機[0001]
BACKGROUND OF THE INVENTION
  The present invention includes, for example, a water-absorbing resin having a carboxyl group and a cross-linking agent capable of reacting with the carboxyl group, which is suitably used for sanitary materials such as paper diapers (disposable diapers), sanitary napkins, and so-called incontinence pads. Water-absorbing agent made by mixing with aqueous liquidAndThe present invention relates to a sanitary material containing the water absorbing agent.
[0002]
[Prior art]
  In recent years, water-absorbing agents containing a water-absorbing resin intended to absorb bodily fluids are widely used as sanitary materials such as paper diapers and sanitary napkins, so-called incontinence pads.
[0003]
  Examples of the water-absorbing resin include a crosslinked polyacrylic acid partially neutralized product, a hydrolyzate of starch-acrylic acid graft polymer, a saponified vinyl acetate-acrylic acid ester copolymer, an acrylonitrile copolymer, or Hydrolysis products of acrylamide copolymers or cross-linked products thereof, and cross-linked products of cationic monomers are known.
[0004]
  The properties that the water absorbent resin should have include excellent water absorption and absorption rate when in contact with aqueous liquids such as body fluids, liquid permeability, gel strength of swollen gels, and water from a substrate containing aqueous liquids. Examples include suction force to be sucked up. However, the relationship between these characteristics does not necessarily show a positive correlation. For example, the higher the absorption ratio, the lower the physical properties such as liquid permeability, gel strength, and absorption rate.
[0005]
  As a method for improving the water absorption characteristics of the water absorbent resin in a well-balanced manner, a technique for crosslinking the vicinity of the surface of the water absorbent resin is known, and various methods have been disclosed so far.
[0006]
  For example, a method using a polyhydric alcohol as a crosslinking agent (Japanese Patent Laid-Open Nos. 58-180233 and 61-16903), a polyvalent glycidyl compound, a polyvalent aziridine compound, a polyvalent amine compound, a polyvalent isocyanate A method using a compound (JP 59-189103), a method using glyoxysar (JP 52-117393), a method using a polyvalent metal (JP 51-136588, JP Sho 61-257235, JP-A 62-7745, and methods using silane coupling agents (JP-A 61-212305, JP-A 61-252212, JP-A 61-264006) Publication), a method using alkylene carbonate (German Patent No. 4020780), and the like are known. In addition, a method in which an inert inorganic powder is present during the crosslinking reaction (Japanese Patent Laid-Open Nos. 60-163356 and 60-255814), and a method in which a dihydric alcohol is present (Japanese Patent Laid-Open No. 1-2292004). Also known are a method in which water and an ether compound are present (JP-A-2-153903), a method in which an alkylene oxide adduct of a monohydric alcohol, an organic acid salt, a lactam, etc. are present (European Patent No. 555692). ing.
[0007]
  In general, the water-absorbent resin is more preferable as the content of powder (fine powder) having a particle size of 150 μm or less is smaller. Such fine powder is clogged in an absorbent article such as a diaper, which causes a decrease in liquid permeability. Further, in addition to the problem of loss as a dust during handling and pneumoconiosis, even if surface crosslinking is performed, there are problems that various physical properties such as absorption capacity under pressure are difficult to improve. For this reason, a water-absorbing resin with less fine powder is desired.
[0008]
  Conventionally, as a method for producing a water-absorbent resin with a small amount of fine powder, (1) a method of adjusting the particle size by adjusting the degree of polymerization and pulverization, and (2) the generated fine powder can be obtained by sieving or air flow. A classification and removal method (US Pat. No. 4,973,632) is known.
[0009]
  However, even in the method (1), a large amount of fine powder such as 10% to several tens% is generated during the production process. Therefore, further discarding of the generated fine powder by the method (2) greatly reduces the yield and is disadvantageous from the viewpoint of disposal cost.
[0010]
  Therefore, a proposal to solve the above problem by granulating or regenerating fine powder that is inevitably generated in the manufacturing process of the water absorbent resin, and further, by granulating, the relative surface area is compared with the primary particles. Various proposals have been made to achieve a high absorption rate by increasing the size.
[0011]
  For example, as a method other than granulation, in European Patent No. 0463388A, US Pat. No. 4,950,692, US Pat. No. 4,970,267, European Patent No. 0477761A, European Patent No. 0496594A, water or a hydrous gel is added to fine powder A method has been proposed in which the fine powder is gelled by mixing, and then the gelled product is pulverized and then regenerated into large particles by drying. In EP 0 644 224, an aqueous liquid containing a water-soluble or water-dispersible polymer compound in a water-absorbing resin in the presence of an insoluble inorganic fine powder has a moisture content of a granulated product of 30% by weight to 70% by weight. The method of granulating by adding so that it becomes is proposed. Further, in US Pat. No. 5,002986, European Patent No. 0318989B, US Pat. No. 5,248,709, US Pat. No. 4,123,397, US Pat. No. 4,734,478, European Patent No. 0629411, and US Pat. No. 5,369,148 Using a fine powder of about 150 μm to several tens of μm as a single or a mixture with large particles, and granulating the powder using an aqueous liquid or the like of about several to about 20% of the powder as a binder Thus, a method for increasing the average particle size of the fine powder to several hundred μm has been proposed.
[0012]
  In general, water or an aqueous liquid is suitable as the binder of the water-absorbent resin from the viewpoints of efficiency, safety, manufacturing cost, and the like. Therefore, in each of the methods described above, most of the methods add an aqueous liquid that plays a role of a binder to the fine powder.
[0013]
  However, the water-absorbing resin, in particular, the finely powdered water-absorbing resin has a large surface area, and therefore has a high absorption rate, and it is difficult to add the aqueous liquid uniformly. In addition, the use of insoluble inorganic fine powder or the like as a mixing aid for an aqueous liquid generally has problems such as not only the problem of cost but also the generation of dust, the granulation strength and various physical properties.
[0014]
  Therefore, as a mixer capable of uniformly adding water when granulating fine powder, for example, a low speed paddle type mixer (European Patent No. 0644224), a high speed stirring type mixer (US Pat. No. 5,0029,861). No. 4,734,478), a specific spray continuous granulator (U.S. Pat. No. 5,360,148), a fluidized bed (European Patent No. 0534899), and the like have been proposed. Further, for methods other than granulation, as a mixer for recirculating fine powder, a Nauta mixer (US Pat. No. 4,950,692), a specific shear mixer (European patent No. 0417761), etc. Has been proposed. Among these mixers, the high-speed agitating mixer is not limited to granulation in the method for producing a water-absorbent resin because of its high productivity. No. gazette) and the like.
[0015]
  For example, the present inventors have already disclosed US Pat. No. 5140076 as a method for producing a water-absorbing agent by efficiently mixing an aqueous liquid such as the cross-linking agent or a treatment liquid containing the cross-linking agent onto the surface of the water-absorbing resin. In Japanese Patent Laid-Open No. 4-214734, a high-speed agitation type mixer having an inner surface made of a specific base material is used to mix the water-absorbing resin and the crosslinking agent, and then the mixture is heated to obtain a surface. A method of reacting the cross-linking agent was proposed. Furthermore, the inventors of the present application have obtained a water-absorbent resin with improved water absorption performance balance, in particular, absorption capacity under pressure, by such a method.
[0016]
  As shown in FIG. 21, the conventional mixer disclosed in the above-mentioned US Pat. No. 5140076 (JP-A-4-214734) has a rotating shaft 102 in a fixed cylinder 101 having an inner surface made of a specific base material. This is a continuous extrusion mixer 100 provided with a plurality of stirring blades 103. The continuous extrusion mixer 100 supplies water-absorbing resin particles from the resin supply port 104, supplies a crosslinking agent from the liquid injection port 105, and discharges the mixture from the discharge port 106 by an extrusion flow caused by the rotation of the stirring blade 103. It comes to take out.
[0017]
[Problems to be solved by the invention]
  However, even if surface crosslinking of the water-absorbent resin particles is performed using the above-described conventional continuous extrusion mixer, the water-absorbent resin transport process and the process of processing the final product such as a diaper on the user side As a result, the surface cross-linked part or the granulated part is lost or destroyed, and the problem that the excellent water absorption characteristics as expected in the final product cannot be maintained has been found. It has also been found that this problem appears more markedly in a water-absorbing resin that exhibits a higher absorption capacity under high pressure.
[0018]
  It has also been found that physical properties such as a decrease in absorption rate, an increase in water-soluble components as impurities, and a decrease in absorption capacity under high pressure may be observed due to granulation and regeneration of fine powder. It was. Further, it has also been found that the problem of deterioration in physical properties due to the granulation is particularly remarkable when the granulation strength is improved by increasing the aqueous liquid as a binder in order to avoid the above-described granulation failure.
[0019]
  And as a factor of said each problem, it is mentioned with the conventional mixer that mixing of a water absorbing resin, a crosslinking agent, and aqueous liquid was not yet satisfactory.
[0020]
  For example, in a fluidized bed (European Patent No. 0534899) and a high-speed agitation type mixer (U.S. Pat. No. 5,142,0076) conventionally used for granulation, the amount of aqueous liquid added is as small as several to no more than 30%. If it exceeds 60%, continuous and stable mixing is extremely difficult.
[0021]
  Further, according to the study by the inventors of the present application, when the amount of the aqueous liquid added exceeds 10%, the mixing of the water-absorbent resin and the aqueous liquid becomes extremely uneven, and as a result, It was found that not only the addition amount of the aqueous liquid for improving the granulation strength was limited, but also that the physical properties were lowered or the granulation was broken by the addition of the non-uniform aqueous liquid. In particular, a high-speed agitation type mixer that has been conventionally used in the production of a water-absorbing resin exhibits high productivity with a small amount of aqueous liquid, but it is almost impossible to add a large amount of aqueous liquid.
[0022]
  Further, according to the study by the inventors of the present application, in a mixer having a large kneading force, such as a shear mixer (European Patent No. 0477761) or a Nauta mixer, which has been used other than granulation, the addition of an aqueous liquid Is relatively easy to carry out, but the mixture after the addition of the aqueous liquid does not become a granular granulated product, but only a large united gel mass is obtained, and because of its shearing force, it absorbs water. It was found that the resin itself deteriorates. Furthermore, when the water-containing resin hydrogel is kneaded or pulverized with a very large force, the hydrogel becomes a gel with a small surface area that is not agglomerated but a crushed surface area. However, it has been found that the absorption rate may decrease. It has also been found that the step of pulverizing an integrated large gel mass by a method other than granulation (US Pat. No. 4,950,692) is likely to cause deterioration of the water absorbent resin itself.
[0023]
  The present invention has been made in view of the above-mentioned conventional problems, and its purpose is to show a high absorption capacity under pressure, and after carrying out transportation in a manufacturing plant or processing of a final product by a user. A water-absorbing agent that maintains excellent water-absorbing performance and can always exhibit excellent characteristics in the final product regardless of the method of use.AndIt is providing the sanitary material containing the said water absorbing agent.
[0024]
[Means for Solving the Problems]
  In order to achieve the above object, the inventors of the present application have made extensive studies on the water-absorbing agent, its production method, its production apparatus, and sanitary materials. As a result, the inventors of the present application manufactured the water-absorbing agent obtained by mixing and reacting a water-absorbing resin having a carboxyl group and a crosslinking agent that reacts with the carboxyl group to satisfy the following configuration. It has been found that a water-absorbing agent that can always exhibit excellent characteristics can be provided, and the present invention has been completed.
[0025]
  That is, the water-absorbing agent of the invention according to claim 1 is obtained by polymerizing and crosslinking a hydrophilic monomer having acrylic acid and / or a salt thereof as a main component in order to solve the above-mentioned problems. A water-absorbing agent obtained by mixing and reacting a water-absorbing resin particle having a group and forming a hydrogel and a cross-linking agent that reacts with the carboxyl group, and sealing the 5 g of the water-absorbing agent in a bag of 70 mm × 100 mm Then, when an impact force (A) is applied to the water absorbent by reciprocating a roller having a weight of 4 kg from above, the pressure in the water absorbent after the impact is 50 g / cm.²If the absorption capacity at Q is Q and the absorption capacity at the same pressure in the water-absorbing agent before impact is P
    P ≧ 20 (g / g)
And
    Q / P ≧ 0.85
It is characterized by being.
[0026]
  In order to solve the above-described problems, the water-absorbing agent of the invention described in claim 2 is characterized in that P ≧ 25 (g / g) in the water-absorbing agent described in claim 1.
[0027]
  The water-absorbing agent of the invention described in claim 3 is characterized in that Q / P ≧ 0.9 in the water-absorbing agent described in claim 1 in order to solve the above problems.
[0028]
  In order to solve the above problems, the water-absorbing agent of the invention described in claim 4 is characterized in that Q / P ≧ 0.95 in the water-absorbing agent described in claim 1.
[0029]
  The water-absorbing agent of the invention according to claim 5 is obtained by polymerizing / crosslinking a hydrophilic monomer mainly composed of acrylic acid and / or a salt thereof in order to solve the above-mentioned problems, and has a carboxyl group. And a water-absorbing agent obtained by mixing and reacting a water-absorbing resin particle forming a hydrogel and a crosslinking agent that reacts with this carboxyl group, and 30.0 g of the water-absorbing agent together with 10.0 g of glass beads, When an impact force (B) is applied by impinging the water-absorbing agent against each other by applying vibration at a vibration speed of 750 c.pm for 30 minutes at 100 V / 60 Hz in a container having a predetermined size, after the impact The pressure in the water-absorbing agent of 50 g / cm²Assuming that the absorption capacity at Y is Y and the absorption capacity at the same pressure in the water absorbent before impact is X,
    X ≧ 20 (g / g)
And
    Y / X ≧ 0.90
It is characterized by being.
[0030]
  In order to solve the above-described problems, the water-absorbing agent of the invention described in claim 6 is characterized in that X ≧ 25 (g / g) in the water-absorbing agent described in claim 5.
[0031]
  The water-absorbing agent of the invention described in claim 7 is characterized in that Y / X ≧ 0.92 in the water-absorbing agent described in claim 5 in order to solve the above-mentioned problems.
[0032]
  The water-absorbing agent of the invention described in claim 8 is characterized in that Y / X ≧ 0.95 in the water-absorbing agent described in claim 5 in order to solve the above problems.
[0033]
  In order to solve the above-described problems, the water-absorbing agent according to claim 9 is the water-absorbing agent according to any one of claims 1 to 8, wherein the cross-linking agent is a polyhydric alcohol compound, an epoxy compound, It is at least one compound selected from the group consisting of polyvalent amine compounds and their salts and alkylene carbonate compounds.
[0034]
  The water-absorbing agent of the present invention has excellent absorption performance and is resistant to mechanical stress. Therefore, it is possible to provide a water-absorbing agent that maintains its excellent absorption performance in the final product without substantially deteriorating its water-absorbing characteristics even when subjected to mechanical stress applied during transportation in a manufacturing plant or processing by a user. . Since each of the above water-absorbing agents can maintain its excellent absorption characteristics even after being processed into an absorbent article as a final product by the user, various absorbent articles, in particular, paper that places importance on absorption characteristics under pressure. It is suitable for absorbent articles such as sanitary materials including absorbent bodies such as diapers, sanitary napkins and incontinence pads.
[0035]
  In order to solve the above-mentioned problems, the water-absorbing agent according to claim 10 is the water-absorbing agent according to any one of claims 1 to 9, wherein the water-absorbing resin particles are rotated inside a fixed cylinder. The shaft is supplied to a first region in a stirring-type continuous extrusion mixer provided with at least one kind of stirring member that gives an extrusion thrust to the water-absorbing resin particles, and the water-absorbing resin particles are supplied to the first region. After being dispersed in the second region, the extrusion thrust is smaller than the extrusion thrust in the first region, and the water-absorbing resin particles in the second region react with the carboxyl groups of the water-absorbent resin particles. It is characterized by being mixed with an agent.
[0036]
  According to said structure, mixing and reaction of the said water absorbent resin particle and the crosslinking agent which reacts with the carboxyl group which this water absorbent resin particle has are performed efficiently, and also uniform mixing can be ensured. Therefore, according to the above configuration, it exhibits high absorption capacity under pressure, and maintains its excellent water absorption performance even after carrying out processing at the production plant or processing of the final product at the user. Regardless of the method of use, it is possible to produce a water-absorbing agent that can always exhibit excellent characteristics.
[0037]
  Claim 11The water-absorbing agent of the described invention is a water-absorbing agent obtained by surface-crosslinking a water-absorbent resin granulated product having an average particle diameter of 200 μm to 800 μm in order to solve the above-mentioned problem, and is 50 g / cm.²The absorption capacity under pressure is 20 g / g or more, the absorption rate is 25 seconds or less, and the granulation failure rate is 10% by weight or less.
[0038]
  In order to solve the above problems, the water-absorbing agent of the invention described in claim 12 is the water-absorbing agent according to claim 11, wherein the water-absorbing resin granulated product has an average particle diameter of 10 μm to 150 μm of 100 wt. 70 parts by weight to 400 parts by weight of an aqueous liquid was mixed to obtain a hydrogel granulated product having an average particle size of 0.3 mm to 10 mm. The water-absorbing agent is characterized by being formed by surface crosslinking of the water-absorbent resin granulated product.
[0039]
  aboveeachAccording to the configuration, the conventional granulation methods have mutually conflicting properties, and simultaneously satisfy the three physical properties of absorption capacity under high pressure, granulation strength, and absorption speed, which were properties that could not be satisfied at the same time. A water-absorbing agent that can be provided can be provided.
[0040]
  Claim 13In order to solve the above problems, the sanitary material of the described inventionClaims 1-12The water-absorbing agent according to any one of the above is included.
[0041]
  Since each of the above water-absorbing agents can maintain its excellent absorption characteristics even after being processed into an absorbent article, in particular, absorbents such as paper diapers, sanitary napkins, incontinence pads, etc. that emphasize absorption characteristics under pressure are used. Suitable for containing sanitary materials.
[0042]
  The present invention is described in detail below.
The inventors of the present application have measured the physical property value Q / P or the physical property value Y / X of various surface-crosslinked water-absorbing agents, so that the physical properties of various water-absorbing agents having an absorption ratio higher than a specific value under pressure can be obtained. It was found that the value Q / P and the physical property value Y / X were different.
[0043]
  As a result of intensive studies, the inventors of the present application have found that the physical property value Q / P and the physical property value Y / X in the surface-crosslinked water-absorbing agent are not affected by the value of the absorption capacity under pressure. It has been found that it varies depending on the density of crosslinking, uniformity of crosslinking, fragility of the surface, and the like. As a result, the inventors of the present invention manufacture the physical property value Q / P or the physical property value Y / X to be equal to or higher than the specific numerical values shown below in the step of crosslinking the vicinity of the surface of the water absorbent resin. Thus, it has been found that a water-absorbing agent having excellent absorption performance and strong against mechanical stress can be obtained.
[0044]
  That is, the water-absorbing agent of the present invention is a water-absorbing agent obtained by mixing and reacting a water-absorbing resin having a carboxyl group and a crosslinking agent that reacts with the carboxyl group, and applies a predetermined load to the water-absorbing agent. When the impact force (A) is applied, the pressure in the water absorbent after the impact is 50 g / cm.²When the absorption ratio at Q is Q and the absorption ratio at the same pressure in the water absorbent before impact is P,
    P ≧ 20 (g / g)
And
    Q / P ≧ 0.85
It is.
[0045]
  The water-absorbing agent of the present invention is a water-absorbing agent obtained by mixing and reacting a water-absorbing resin having a carboxyl group and a crosslinking agent that reacts with the carboxyl group, and the water-absorbing agent is subjected to a predetermined vibration. When the impact force (B) is applied, the pressure in the water absorbent after the impact is 50 g / cm.²When the absorption ratio at Y is Y and the absorption ratio at the same pressure in the water absorbent before impact is X,
    X ≧ 20 (g / g)
And
    Y / X ≧ 0.90
It is.
[0046]
  Here, the quotient Q / P of the absorption capacity under pressure before and after applying the impact force (A) in the present invention is the mechanical property of the water-absorbing agent, that is, the crosslinked surface of the water-absorbing resin subjected to surface crosslinking. It is a physical property value representing the strength against stress. Similarly, the quotient Y / X of the absorption capacity under pressure before and after applying the impact force (B) in the present invention is also applied to the mechanical stress on the crosslinked surface of the water-absorbent resin after surface crosslinking as a water-absorbing agent. It is a physical property value representing strength.
[0047]
  However, the mechanical stress applied to the surface cross-linking of the water-absorbing agent when the impact force (A) is applied and the mechanical stress applied to the surface cross-linking of the water-absorbing agent when the impact force (B) is applied. There is a difference in the degree. That is, the mechanical stress applied to the surface crosslinking of the water absorbing agent when the impact force (A) is applied is stronger than the mechanical stress applied to the surface crosslinking of the water absorbing agent when the impact force (B) is applied.
[0048]
  In the present invention, the impact force (A) applied to the water-absorbing agent is obtained by sealing 5 g of the water-absorbing agent as a reaction product in a 70 mm × 100 mm bag and reciprocating it 10 times with a 4 kg roller from above. Is preferred.
[0049]
  The method for giving the impact force (A) will be specifically described below.
First, as shown in FIG. 11, 5.0 g of a water-absorbing agent (not shown) is placed in a plastic bag 35 with a chuck having a size of 70 mm × 100 mm and a thickness of 0.04 mm. , Chuck. Thereafter, the water-absorbing agent is spread evenly over the entire plastic bag 35 with chuck, and a roller 36 having a diameter of 85 mm, a length of 200 mm, and a weight of 4 kg is rolled 20 times (10 reciprocations) from thereover, The impact force is given to the water absorbent. As described above, by applying a predetermined load to the water absorbing agent, the impact force applied to the water absorbing agent is defined as an impact force (A). As the plastic bag 35 with a chuck, for example, “Unipack (registered trademark) C-4” manufactured by Nippon Shokubai Co., Ltd. is preferably used.
[0050]
  Further, in the present invention, the impact force (B) applied to the water-absorbing agent is such that 30.0 g of the water-absorbing agent as a reaction product is combined with 10.0 g of glass beads having a ball diameter of about 6 mm and a container 41 (FIG. 12 and FIG. 12). 13), as shown in FIG. 13A, the angle formed by the vertical center line of the container 41 and the vertical line is 12.5 ° on each of the left and right sides of the vertical line, and FIG. ), The horizontal movement of the container 41 is 8 mm forward and backward with respect to the stationary position of the container 41, and the elliptical vibration is set so that the vibration speed is 750 c.pm. Is preferably given for a certain period of time.
[0051]
  The method for applying the impact force (B) will be specifically described below.
As shown in FIG. 12, the container 41 used for applying an impact force (B) to the water-absorbing agent is made of a transparent glass having a height of about 10.8 cm, a diameter of about 6.2 cm, and an internal volume of 225 g. A container provided with an inner lid 41b and an outer lid 41a is used for the container body 41c. As such a container, for example, a so-called mayonnaise bottle (trade name: A-29) manufactured by Yamamura Glass Co., Ltd. is preferably used.
[0052]
  Moreover, as the glass beads, glass beads made of soda-lime glass for precision fractional filling with a ball diameter of about 6 mm, which are aligned to a ball diameter of about 5.9 mm to 6.4 mm, are suitable. 10.0 g of the glass beads correspond to 31 to 33 glass beads.
[0053]
  When an impact force (B) is applied to the water absorbing agent, 30.0 g of the water absorbing agent is put into the container main body 41c of the container 41 together with 10.0 g of the glass beads, and the inner lid 41b and the outer lid 41a are closed. Then, the container 41 is fixed to a disperser (No. 488 test disperser manufactured by Toyo Seiki Seisakusyo Co., Ltd.) 42 shown in FIG. 14 by being sandwiched between an upper clamp 43 and a lower clamp 44 provided in the disperser 42. , Vibration at a vibration speed of 750 c.pm at 100 V / 60 Hz is applied for 30 minutes. As a result, the container 41 fixed to the disperser 42 is inclined 12.5 ° (total 25 °) to the left and right with respect to the mounting surface 45 of the upper clamp 43 and the lower clamp 44 in the disperser 42 at the same time. By impacting the front and rear by 8 mm (16 mm in total), an impact force is given to the water-absorbing agent inside the container 41.
[0054]
  The state of vibration of the container 41 in this case will be described below with reference to FIG. The trajectory of the container 41 due to the vibration of the container 41 is easy due to the trajectory of the vertical line at an arbitrary position of the rod 47 fixed to the clamp 46 (upper clamp 43, lower clamp 44) so as to be perpendicular to the gravity. Can be confirmed. The vertical line at an arbitrary position of the bar 47 fixed to the clamp 46 indicates that the bar 47 is tilted 12.5 ° to the left and right from the stationary state, and at the same time moves 8 mm back and forth. Draw an elliptical trajectory as shown. That is, the container 41 receives an elliptical vibration as shown in FIG. Thereby, the water absorbent in the container 41 is stirred by the glass beads enclosed in the container 41 together with the water absorbent, and the water absorbents, the water absorbent and the glass beads, or the water absorbent and the container 41 are mixed. When the inner wall collides with the strength according to the vibration, it receives an impact. As described above, the impact force applied to the water-absorbing agent by giving a predetermined vibration to the water-absorbing agent is referred to as an impact force (B).
[0055]
  The impact forces (A) and (B) are empirically determined forces that represent the impact force received by the water absorbent resin during the manufacturing process. In addition, the measuring method of the absorption magnification under pressure will be described in detail in Examples described later.
[0056]
  As an evaluation of the surface-treated water-absorbing agent, an absorption capacity under pressure is generally evaluated. However, the evaluation of only the absorption capacity under pressure can evaluate the water absorption characteristics of the water-absorbing agent under pressure, but cannot evaluate the depth of surface cross-linking, the uniformity of cross-linking and the fragility of the surface. For this reason, in the evaluation of only the absorption capacity under the above pressure, it occurs in each step after the surface treatment when producing a surface-crosslinked water absorbent or producing an absorbent article using the water absorbent. It is not possible to predict the water absorption characteristics that are reduced by mechanical stress. As a result, conventionally, the expected characteristics may not be obtained in the final product.
[0057]
  However, in the present invention, as an impact resistance test for water-absorbent resin particles, the physical property value Q / P or the physical property value Y / X is measured to evaluate the strength of the surface-crosslinked water-absorbing agent against mechanical stress. , Can now be predicted. Only one of the physical property value Q / P and the physical property value Y / X may be measured according to the sample amount or the like, or both may be measured.
[0058]
  The inventors of the present application have almost no water absorption characteristics even when the water absorbing agent formed so that the physical property value Q / P satisfies the following conditions is subjected to mechanical stress applied during transportation in the manufacturing plant or processing by the user. It has been found that the water-absorbing agent maintains its excellent absorption performance in the final product without lowering.
[0059]
  That is, in the water-absorbing agent of the present invention, the physical property value Q / P is preferably 0.85 or more, more preferably 0.90 or more, and 0.95 or more is excellent in the absorbent article. Most preferred to maintain absorption performance.
[0060]
  In the water absorbing agent of the present invention, the physical property value Y / X is preferably 0.90 or more, more preferably 0.92 or more, and 0.95 or more is excellent in the absorbent article. Most preferred to maintain absorption performance.
[0061]
  In the present invention, 50 g / cm of the absorbent before applying the impact force (A) or impact force (B).²The absorption capacity P or X under pressure in the ink is required to be 20 g / g or more, preferably 25 g / g or more, and most preferably 30 g / g or more.
[0062]
  The absorption rate of the water-absorbent resin before surface crosslinking with respect to physiological saline is preferably 40 g / g or more, and more preferably 45 g / g or more.
[0063]
  Next, the manufacturing method of the said water absorbing agent and its manufacturing apparatus are demonstrated.
[0064]
  The water-absorbing resin used in the production of the water-absorbing agent of the present invention is not particularly limited as long as it has a carboxyl group, but typically contains acrylic acid and / or a salt thereof (neutralized product) as a main component. It is a conventionally known resin that is obtained by polymerizing and crosslinking a hydrophilic monomer that absorbs a large amount of water from 50 to 1000 times in ion-exchanged water to form a hydrogel. Further, as the water-absorbent resin, those having an uncrosslinked water-soluble component in the water-absorbent resin of 25% by weight or less, preferably 15% by weight or less, more preferably 10% by weight or less are used.
[0065]
  Examples of the acrylate include alkali metal salts, ammonium salts and amine salts of acrylic acid. The water-absorbent resin has a constitutional unit in the range of 10 mol% to 40 mol% acrylic acid and 90 mol% to 60 mol% acrylate (however, the total amount of both is 100 mol%). preferable.
[0066]
  In obtaining a water-absorbing resin by polymerizing a hydrophilic monomer mainly composed of acrylic acid and / or a salt thereof, if necessary, it is used in combination with these acrylic acid or a salt thereof and a simple substance other than acrylic acid. It may contain a monomer.
[0067]
  Although it does not specifically limit as monomers other than acrylic acid, Specifically, for example, methacrylic acid, maleic acid, vinylsulfonic acid, styrenesulfonic acid, 2- (meth) acrylamide-2-methyl Anionic unsaturated monomers such as propanesulfonic acid, 2- (meth) acryloylethanesulfonic acid, 2- (meth) acryloylpropanesulfonic acid and salts thereof; acrylamide, methacrylamide, N-ethyl (meth) acrylamide, N -N-propyl (meth) acrylamide, N-isopropyl (meth) acrylamide, N, N-dimethyl (meth) acrylamide, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, methoxypolyethylene glycol (meta ) Acrylate, polyethylene Nonionic hydrophilic group-containing unsaturated monomers such as recall mono (meth) acrylate, vinylpyridine, N-vinylpyrrolidone, N-acryloylpiperidine, N-acryloylpyrrolidine; N, N-dimethylaminoethyl (meth) acrylate, Cationic unsaturated monomers such as N, N-diethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylamide, and quaternary salts thereof Etc. These monomers may be used alone or in combination of two or more as appropriate.
[0068]
  In the present invention, when a monomer other than acrylic acid is used, the monomer other than acrylic acid is 30 mol% or less, preferably 30 mol% or less, based on the total amount of acrylic acid and its salt used as the main component. Is preferably used at a ratio of 10 mol% or less. By using a monomer other than the acrylic acid at the above ratio, the water absorbing property of the obtained water absorbing resin can be further improved, and the water absorbing resin can be obtained at a lower cost.
[0069]
  When polymerizing the hydrophilic monomer mainly composed of the above-mentioned acrylic acid or a salt thereof in order to obtain the water-absorbent resin used in the present invention, bulk polymerization or precipitation polymerization can be performed. From the viewpoint of easy control of the surface and polymerization, it is preferable to perform aqueous solution polymerization or reverse phase suspension polymerization by using the hydrophilic monomer as an aqueous solution.
[0070]
  The concentration of the monomer in the aqueous solution (hereinafter referred to as the monomer aqueous solution) when the hydrophilic monomer is used as an aqueous solution is not particularly limited, but is 10% by weight to 70% by weight. % In the range of 20% by weight to 40% by weight is more preferable. Moreover, when performing the said aqueous solution polymerization or reverse phase suspension polymerization, you may use together solvents other than water as needed, and the kind of solvent used together is not specifically limited.
[0071]
  When starting the above polymerization, for example, potassium persulfate, ammonium persulfate, sodium persulfate, t-butyl hydroperoxide, hydrogen peroxide, 2,2′-azobis (2-aminodipropane) dihydrochloride, etc. These radical polymerization initiators can be used.
[0072]
  Further, a reducing agent that promotes the decomposition of the polymerization initiator can be used in combination, and a redox initiator can be obtained by combining the two. Examples of the reducing agent include (bi) sulfurous acid (salt) such as sodium sulfite and sodium bisulfite, L-ascorbic acid (salt), reducing metal (salt) such as ferrous salt, amines, and the like. Although it is mentioned, it is not particularly limited.
[0073]
  The amount of these polymerization initiators used is usually 0.001 mol% to 2 mol%, preferably 0.01 mol% to 0.05 mol%. When the amount of the polymerization initiator used is less than 0.001 mol%, the amount of unreacted monomer increases, and therefore the amount of residual monomer in the resulting water-absorbent resin increases, which is not preferable. On the other hand, when the usage-amount of these polymerization initiators exceeds 2 mol%, since the amount of water-soluble components in the obtained water-absorbent resin increases, it is not preferable.
[0074]
  Moreover, you may start a polymerization reaction by irradiating active energy rays, such as a radiation, an electron beam, and an ultraviolet-ray, to a reaction system instead of using a polymerization initiator. In addition, the reaction temperature in the said polymerization reaction is although it does not specifically limit, The inside of the range of 20 to 90 degreeC is preferable. Further, the reaction time is not particularly limited, and may be appropriately set according to the kind of the hydrophilic monomer or polymerization initiator, the reaction temperature, and the like.
[0075]
  The water-absorbing resin used in the present invention may be a self-crosslinking type that does not use a crosslinking agent, but two or more polymerizable unsaturated groups or two or more reactive groups in one molecule. Those obtained by copolymerizing or reacting an internal crosslinking agent having a group are more preferred.
[0076]
  Specific examples of these internal crosslinking agents include, for example, N, N-methylenebis (meth) acrylamide, (poly) ethylene glycol (meth) acrylate, (poly) propylene glycol di (meth) acrylate, trimethylolpropane tri (meth). Acrylate, glycerin tri (meth) acrylate, glycerin acrylate methacrylate, ethylene oxide modified trimethylolpropane tri (meth) acrylate, pentaerythritol hexa (meth) acrylate, triallyl cyanurate, triallyl isocyanurate, triallyl phosphate, triallylamine, Poly (meth) allyloxyalkane, (poly) ethylene glycol diglycidyl ether, glycerol diglycidyl ether, ethylene glycol, polyethylene Glycol, propylene glycol, glycerol, pentaerythritol, ethylenediamine, ethylene carbonate, propylene carbonate, polyethylenimine, and glycidyl (meth) acrylate.
[0077]
  These internal cross-linking agents may be used alone or in combination of two or more. These internal cross-linking agents may be added to the reaction system all at once or in divided portions. In the case of using two or more kinds of internal crosslinking agents, it is preferable to essentially use a compound having two or more polymerizable unsaturated groups in consideration of the water absorption characteristics of the resulting water absorbent resin. The amount of these internal crosslinking agents used is preferably in the range of 0.005 mol% to 2 mol%, preferably in the range of 0.01 mol% to 1 mol%, with respect to the hydrophilic monomer. More preferably. When the amount of the internal cross-linking agent used is less than 0.005 mol% and more than 2 mol%, there is a possibility that a water absorbent resin having desired water absorption characteristics cannot be obtained.
[0078]
  When using the internal cross-linking agent to introduce a cross-linked structure into the water-absorbent resin, the internal cross-linking agent is added to the reaction system during or after polymerization of the hydrophilic monomer, or after polymerization and neutralization. You just have to do it.
[0079]
  In the above polymerization, various foaming agents such as carbonic acid (hydrogen) salt, carbon dioxide, azo compound, inert organic solvent, etc .; starch / cellulose, starch / cellulose derivatives, polyvinyl alcohol, polyacrylic acid ( Salt), hydrophilic polymers such as crosslinked polyacrylic acid (salt); various surfactants; chain transfer agents such as hypophosphorous acid (salt) may be added.
[0080]
  When the polymer obtained by the above polymerization reaction is in a gel form, the gel polymer is dried and, if necessary, pulverized to have an average particle size of 10 μm to 1000 μm, preferably 50 μm to 800 μm. When the aqueous liquid contains a crosslinking agent capable of reacting with a carboxyl group, it is preferably adjusted to more than 75 μm and not more than 600 μm, particularly preferably more than 150 μm and not more than 500 μm. The particle shape of the water-absorbent resin thus obtained is not particularly limited, but the effect of the present invention is particularly remarkable when it is an irregularly pulverized shape obtained through a pulverization step. ,preferable.
[0081]
  The water-absorbent resin obtained by the above-described method should have a high absorption rate of 40 g / g or more, more preferably 45 g / g or more with respect to physiological saline. Although the effect of the invention is remarkably expressed, it is preferable, but of course, the above-mentioned absorption ratio is appropriately adjusted according to the purpose. The present invention can be suitably used for a water-absorbing resin that exhibits a high absorption rate of 45 g / g or more, which has heretofore been difficult to uniformly add an aqueous liquid.
[0082]
  In the present invention, the water-absorbing resin having a carboxyl group obtained by the above polymerization and the aqueous liquid are mixed with a specific continuous extrusion mixer. The aqueous liquid may be water; or water in which a water-soluble compound such as a salt, a surfactant, a deodorant, an antibacterial agent, or a water-soluble polymer is dissolved, or a hydrophilic organic solvent. In order to obtain an agent, it is necessary to be a crosslinking agent capable of reacting with a carboxyl group or a treatment liquid containing the crosslinking agent. That is, the water-absorbing agent according to the present invention can be obtained by mixing and reacting a water-absorbing resin having a carboxyl group and a crosslinking agent that reacts with the carboxyl group.
[0083]
  As such a cross-linking agent, a known surface cross-linking agent which can react with a carboxyl group and is usually used for the application is suitable. Examples of the surface cross-linking agent include ethylene glycol, diethylene glycol, propylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, 1,3-propanediol, dipropylene glycol, 2,2,4-trimethyl-1, 3-pentanediol, polypropylene glycol, glycerin, polyglycerin, 2-butene-1,4-diol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,2-cyclohexanedi Methanol, 1,2-cyclohexanol, trimethylolpropane, diethanolamine, triethanolamine, polyoxypropylene, oxyethylene-oxypropylene block copolymer, pentaerythritol, sorbitol Polyhydric alcohol compounds such as ethylene glycol diglycidyl ether, polyethylene diglycidyl ether, glycerol polyglycidyl ether, diglycerol polyglycidyl ether, polyglycerol polyglycidyl ether, propylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, glycidol, etc. Epoxy compounds; polyvalent amine compounds such as ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, polyethyleneimine, and inorganic or organic salts thereof (for example, aditinium salts); 2,4-tri Polyisocyanate compounds such as diisocyanate and hexamethylene diisocyanate; 1,2-ethylenebiso Polyvalent oxazoline compounds such as sazoline; 1,3-dioxolan-2-one, 4-methyl-1,3-dioxolan-2-one, 4,5-dimethyl-1,3-dioxolan-2-one, 4, 4-dimethyl-1,3-dioxolan-2-one, 4-ethyl-1,3-dioxolan-2-one, 4-hydroxymethyl-1,3-dioxolan-2-one, 1,3-dioxane-2 Alkylene carbonate compounds such as -one, 4-methyl-1,3-dioxan-2-one, 4,6-dimethyl-1,3-dioxan-2-one, 1,3-dioxopan-2-one; epichloro Haloepoxy compounds such as hydrin, epibromohydrin, α-methylepichlorohydrin, and polyvalent amine adducts thereof (eg, Hercules Kaimen®); zinc, potassium Siumu, magnesium, aluminum, iron, polyvalent metal compounds such as hydroxides or chlorides such as zirconium and the like. These surface cross-linking agents may be used alone or in combination of two or more. Among these surface cross-linking agents, at least one compound selected from the group consisting of polyhydric alcohol compounds, epoxy compounds, polyvalent amine compounds and salts thereof, and alkylene carbonate compounds is preferred.
[0084]
  In the method for producing a water-absorbing agent, as proposed by the inventors of the present invention in JP-A-6-184320 (US Pat. No. 5,422,405), a crosslinking agent capable of reacting with a carboxyl group has a solubility. In the case where a first surface cross-linking agent and a second surface cross-linking agent having different parameters (SP values) are combined, an absorbent having an even better absorption capacity under pressure can be obtained. The solubility parameter is a value generally used as a factor representing the polarity of a compound. In the present invention, the solubility parameter δ (cal / cm) of the solvent described in Polymer Handbook 3rd edition (published by WILEY INTERSCIENCE) pp. 527 to 539 with respect to the above solubility parameter.^Three)^1/2The value of is applied. As for the solubility parameter of the solvent not described on the above page, the Hoy cohesive energy constant described on page 525 is substituted into the Small formula described on page 524 of the polymer handbook. Apply the derived value.
[0085]
  The first surface cross-linking agent is capable of reacting with a carboxyl group and has a solubility parameter of 12.5 (cal / cm^Three)^1/2The above compounds are preferred, and 13.0 (cal / cm^Three)^1/2The above compounds are more preferable.
[0086]
  In addition, the second surface cross-linking agent has a solubility parameter of 12.5 (cal / cm, which can react with a carboxyl group.^Three)^1/2Less than 9.5 (cal / cm^Three)^1/2~ 12.0 (cal / cm^Three)^1/2A compound within the range is more preferred.
[0087]
  The amount of these crosslinking agents to be used depends on the compounds to be used and combinations thereof, but is preferably within the range of 0.001 to 10 parts by weight with respect to 100 parts by weight of the solid content of the water-absorbent resin. A range of 01 to 5 parts by weight is more preferable.
[0088]
  By using the cross-linking agent, the cross-linking density near the surface of the water-absorbent resin can be made higher than the inside. Moreover, when the usage-amount of a crosslinking agent exceeds 10 weight part, since not only it will become uneconomical but the amount of a crosslinking agent becomes excessive when forming the optimal crosslinked structure in a water absorbing agent, it is unpreferable. Further, when the amount of the crosslinking agent used is less than 0.001 part by weight, it is not preferable because it is difficult to obtain the improvement effect in improving the performance such as the absorption capacity under pressure in the water absorbing agent.
[0089]
  In the present invention, when mixing the water absorbent resin and the crosslinking agent, it is preferable to use water as a solvent. The amount of water used depends on the type, particle size, water content, etc. of the water absorbent resin, but is preferably more than 0 and 20 parts by weight or less with respect to 100 parts by weight of the solid content of the water absorbent resin. More preferably within the range of 10 to 10 parts by weight. Further, when an aqueous liquid is added for purposes other than surface crosslinking, sufficiently uniform mixing is possible if the amount of water is usually about 400 parts by weight or less.
[0090]
  Conventionally, in order to mix a large amount of water of about 70 parts by weight to 400 parts by weight, it is possible to use (1) a powerful mixer with shearing force, or (2) after mixing, by a method other than granulation. In addition, it is necessary to grind the integrated gel mass, and (3) insoluble inorganic fine powder, water-soluble polymer, hydrophilic organic solvent, surfactant, etc. as mixing aids are necessary for granulation. In addition, these methods are accompanied by a decrease in granulation strength and physical properties, and are not preferable in terms of cost. On the other hand, the present invention not only causes these problems, but, unlike the conventional case, the water-absorbent resin particles are directly granulated into a hydrous gel-like granulated product by mixing with an aqueous liquid. There is no need for the addition of a mixing aid or a gel grinding step.
[0091]
  Moreover, when mixing a water absorbing resin and a crosslinking agent, you may use a hydrophilic organic solvent (aqueous liquid) as a solvent as needed. Examples of the hydrophilic organic solvent include lower alcohols such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, and t-butyl alcohol; ketones such as acetone; And ethers such as tetrahydrofuran and methoxy (poly) ethylene glycol; amides such as ε-caprolactam and N, N-dimethylformamide; sulfoxides such as dimethyl sulfoxide and the like. The amount of the hydrophilic organic solvent used is preferably 20 parts by weight or less, based on 100 parts by weight of the solid content of the water-absorbent resin, although it depends on the type, particle size, water content, etc. of the water-absorbent resin. More preferably within the range of 10 to 10 parts by weight. In addition, inorganic acids, organic acids, and polyamino acids disclosed in European Patent No. 0668080 may be present.
[0092]
  In the present invention, the water-absorbent resin and the crosslinking agent are mixed in a specific high-speed agitation type continuous extrusion mixer that constitutes a water-absorbing agent manufacturing apparatus and is used for manufacturing the water-absorbing agent. The structure of the high-speed stirring type continuous extrusion mixer and the mixing of the water absorbent resin and the crosslinking agent using the continuous extrusion mixer will be described in detail later.
[0093]
  And the water-absorbent resin mixed with the cross-linking agent in the high-speed stirring type continuous extrusion mixer is further subjected to heat treatment as necessary, so that the vicinity of the surface is cross-linked. A water-absorbing agent is obtained. In this case, in order to react the crosslinking agent in the vicinity of the surface of the water-absorbent resin, it is preferable to perform heat treatment in consideration of the reactivity of the crosslinking agent, the simplicity of the production apparatus, and the productivity.
[0094]
  The treatment temperature at the time of heat-treating the mixture of the water-absorbent resin and the crosslinking agent is appropriately determined according to the kind of the crosslinking agent to be used and the intended crosslinking density, and is not particularly limited, but preferably It is 80 degreeC or more, More preferably, it exists in the range of 100 degreeC-250 degreeC, Most preferably, it exists in the range of 120 degreeC-210 degreeC. When the treatment temperature is less than 80 ° C., the heat treatment takes time, so that not only the productivity is lowered, but also the uniform surface cross-linking is not achieved and the absorption characteristics of the resulting water-absorbing agent under pressure are lowered. In addition, the remaining of the crosslinking agent tends to be caused.
[0095]
  Said heat processing can be performed using a normal dryer or a heating furnace. Examples of the dryer include, but are not particularly limited to, a groove-type mixing dryer, a rotary dryer, a desk dryer, a fluidized bed dryer, an airflow dryer, and an infrared dryer.
[0096]
  Next, the structure of the high-speed stirring type continuous extrusion mixer used in the present invention will be described below together with the mixing method of the water absorbent resin and the crosslinking agent using the continuous extrusion mixer.
[0097]
  In the continuous extrusion mixer according to the present invention, a water absorbent resin having a carboxyl group and an aqueous liquid containing a crosslinking agent capable of reacting with the carboxyl group are mixed around a rotation axis inside a fixed cylinder. Further, at least one kind of agitation member that gives pushing thrust to the water-absorbent resin is provided. In the continuous extrusion mixer, the stirring member is provided in a first region as a dispersion region for dispersing the water-absorbent resin supplied in the fixed cylinder, on the discharge side from the first region, and It is provided so that the 2nd area | region as a mixing area | region which mixes the water absorbing resin disperse | distributed in the said dispersion | distribution area | region and the said aqueous liquid may be formed.
[0098]
  In the present invention, the stirring member has a pushing thrust smaller than the pushing thrust in the first region in which the water-absorbent resin supplied into the fixed cylinder is dispersed so as to form the dispersion region and the mixing region. Two regions are provided on the discharge side.
[0099]
  That is, the stirring member has a shape, a density, a manner of arrangement, an angle formed by the water-absorbing resin extrusion surface and a plane perpendicular to the rotation axis (or rotation that is the water-absorbing resin extrusion surface and the water-absorbing resin extrusion direction). By adjusting the angle formed by a plane parallel to the axial direction of the shaft, etc., regions in which the pushing thrust force against the water absorbent resin is different are formed inside the fixed cylinder. In addition, the water absorbent resin extrusion surface of the stirring blade refers to a surface that gives the water absorbent resin an extrusion thrust parallel to the rotation axis.
[0100]
  In the continuous extrusion mixer, in the first region, the water-absorbent resin supplied in the fixed cylinder is given a sufficient thrust to the inside of the continuous extrusion mixer to disperse it. And in said 2nd area | region, by making extrusion thrust smaller than the extrusion thrust in said 1st area | region, the average speed of water absorbent resin is reduced, and mixing stirring time of said water absorbent resin and aqueous liquid is enough. In addition to ensuring, the water-absorbent resin dispersed in the first region and the aqueous liquid are mixed quickly and uniformly.
[0101]
  On the other hand, a conventional high-speed stirring type continuous extrusion mixer used for mixing a water-absorbent resin and an aqueous liquid such as a processing liquid containing a cross-linking agent or a cross-linking agent has a plurality of stirring blades of the same shape, with equal intervals and A plurality of blades are arranged around the rotation axis so that the directions of the blade surfaces are the same. That is, the above-described conventional continuous extrusion mixer (US Pat. No. 5140076) has a constant extrusion thrust inside, and cannot uniformly adhere and mix the aqueous liquid to the water absorbent resin. For this reason, the water-absorbing agent obtained by mixing with this conventional continuous extrusion mixer is still insufficient from the viewpoint of non-uniform surface cross-linking by the treatment agent and maintaining its water-absorbing characteristics in the final product. It wasn't.
[0102]
  However, in the continuous extrusion mixer of the present invention, since the stirring member (for example, the stirring blade) is provided so as to have a mixing region on the discharge side of the dispersion region, mixing of the water absorbent resin and the aqueous liquid is performed. It carries out so that it may have 2 or more types of stirring states. As a result, the water-absorbing resin having a carboxyl group and the aqueous liquid containing a crosslinking agent capable of reacting with the carboxyl group are efficiently mixed, and uniform mixing can be performed. In the following description, unless otherwise noted, when simply referred to as a continuous extrusion mixer, the continuous extrusion mixer of the present invention is indicated.
[0103]
  In the present invention, the method for measuring the pushing thrust is not particularly limited, and various methods can be used. Examples of the method for measuring the extrusion thrust include, for example, (1) a method for measuring the wind speed and flow velocity generated by the stirring member in each region, (2) a method for measuring the pressure applied to the cross section of the fixed cylinder, and (3) the above Examples include a method of measuring by calculation from the angle formed by the water absorbent resin extrusion surface of the stirring member and the plane perpendicular to the rotation axis in each region.
[0104]
  As long as the stirring member is provided on the discharge side from the water absorbent resin supply side so as to have a region where the pushing thrust is smaller than that on the water absorbent resin supply side, the shape, arrangement method, etc. There is no particular limitation.
[0105]
  The stirring member may be a continuous screw blade-shaped stirring member (stirring blade) as seen on, for example, a screw conveyor, or a plurality of stirring members (stirring blades) provided independently, for example, )
[0106]
  Further, the plurality of stirring members may be two or more types having different shapes, or may have the same shape.
[0107]
  As a configuration of such a continuous extrusion type mixer, for example, a plurality of first stirring members that give extrusion thrust to the water absorbent resin around the rotating shaft, and these on the discharge side of these first stirring members The structure by which the some 2nd stirring member which forms the area | region where pushing thrust becomes smaller than the pushing thrust in the arrangement | positioning area | region of the 1st stirring member is arranged is mentioned.
[0108]
  In this case, it is preferable that the first stirring member is formed in a plate shape as a shape that gives the thrust to the water absorbent resin. Further, the second stirring member is formed in a columnar shape, for example, so that the pushing thrust in the area where the second stirring member is disposed is smaller than the pushing force in the area where the first stirring member is disposed, and mixing stirring is sufficiently performed. It is preferable as a shape to be secured.
[0109]
  Thus, when the second stirring member is formed in a columnar shape, generally no pushing thrust is generated. For this reason, the pushing thrust received by the water-absorbing resin in the region where the second stirring member is disposed is the pushing thrust generated by the first stirring member (however, in this case, the pushing thrust gradually decreases). . As a result, in the arrangement region of the second stirring member, the pushing thrust becomes smaller than the pushing force in the arrangement region of the first stirring member, and the average speed of the water absorbent resin is reduced. It is efficiently mixed with the aqueous liquid by the stirring member.
[0110]
  However, when the second stirring member is formed in a columnar shape, no pushing thrust is generated by itself. However, if a plurality of the stirring members are arranged and the arrangement interval is sufficiently narrow, depending on the arrangement method. In some cases, the thrust in the direction of discharging the water absorbent resin may be larger than the thrust in the opposite direction. In this case, a thrust thrust in the direction of discharging the water absorbent resin occurs.
[0111]
  In other words, the second agitating member only needs to be formed so that the pushing thrust is smaller in the arrangement area than in the arrangement area of the first agitating member. As, for example, a plurality of first stirring members provided on the water-absorbing resin supply side around the rotating shaft and formed in a shape that generates extrusion thrust, and provided on the discharge side from these first stirring members And a plurality of second stirring members formed in a shape that generates a pushing thrust smaller than that of the first stirring member may be sequentially arranged.
[0112]
  In this case, it is preferable that the first stirring member and the second stirring member are formed in a plate shape as a shape that generates an extrusion thrust. However, the second stirring member is preferably formed in a shape having an area smaller than the area of the first stirring member so that the pushing thrust is smaller than that of the first stirring member.
[0113]
  Moreover, the kind of stirring member provided in each said area | region is not limited to one type. For example, the thrust thrust may be adjusted by mixing the first stirring member and the second stirring member in the second region. Specifically, by mixing a cylindrical stirring member and a plate-like stirring member in the second region, the plate-like stirring member disposed in the second region is mixed in the second region. Extrusion thrust according to the number of arrangement, the manner of arrangement, etc. can be obtained.
[0114]
  Furthermore, it is preferable that the plurality of stirring members in the continuous extrusion mixer are sequentially arranged in a spiral. As a result, a sufficient thrust can be secured and the water-absorbing resin can be smoothly extruded.
[0115]
  On the other hand, in the case where a single screw wing-shaped stirring member is used as the stirring member, the stirring member has, for example, a configuration having a cut or an opening in a portion to be the second region, or a second By adopting a configuration in which the blade width of the portion to be the region is gradually narrowed, regions having different extrusion thrusts can be formed in the fixed cylinder.
[0116]
  Furthermore, as a configuration of the continuous extrusion mixer, for example, at least one kind of stirring member has a plane perpendicular to the water-absorbing resin extrusion surface and the rotation axis so as to form regions having different extrusion thrusts to the water-absorbing resin. The first region and the second region may be provided with different angles (hereinafter also referred to simply as “angle” or “water-absorbent resin extrusion surface angle”).
[0117]
  Specifically, (1) when a stirring blade is used as the stirring member, for example, the direction of the blade surface of the stirring blade is changed between the first region and the second region, or (2) the stirring blade is arranged in a spiral shape When changing the inclination of the spiral between the first region and the second region, or (3) changing the mounting angle of the stirring member with respect to the rotating shaft between the first region and the second region, The angle formed by the resin extrusion surface and the surface perpendicular to the rotation axis can be changed between the first region and the second region.
[0118]
  In this case, in order for the stirring member to generate the pushing thrust, the water absorbent resin extruded surface is inclined with respect to a plane perpendicular to the rotation axis (in other words, the water absorbent resin extruded surface is in the water absorbent resin discharge direction). The stirring member may be disposed so as to be inclined with respect to a plane parallel to the axial direction of the rotation axis.
[0119]
  However, in the present invention, the stirring member may be a single stirring member or a plurality of stirring members that have a stirring function by being arranged, and have a shape and an angle that generate an extrusion thrust in the first region. As long as this is done, it is not necessary for all of the stirring blades disposed in the fixed cylinder to have a shape that generates thrust and further has the above-described angle.
[0120]
  Further, in the second region, it is only necessary that the pushing force in the direction of discharging the water absorbent resin in the entire second region is smaller than that in the first region, and it is only possible to push the water absorbent resin to the discharge side. For example, depending on the magnitude of the pushing thrust in the first area, for example, in the second area, the above-mentioned angle of the stirring member is set to a thrust that does not produce pushing thrust or a thrust opposite to the water-absorbing resin discharge direction. The resulting angle may be set.
[0121]
  Furthermore, as the configuration of the continuous extrusion mixer, for example, at least one kind of agitating member may be arranged at a density different from that of the first region and the second region in order to form regions having different thrusts for the water absorbent resin. It is good also as a structure provided differently.
[0122]
  In this case, for example, the arrangement interval of the stirring members in the second region is made wider than the arrangement interval of the stirring members in the first region, or the number of the stirring members in the second region is set in the first region. By making the number smaller than the number of the stirring members, the pushing thrust in the second region can be made smaller than the pushing thrust in the first region.
[0123]
  The method of changing the thrust thrust by changing the angle formed by the water absorbing resin extrusion surface of the stirring member and the plane perpendicular to the rotation axis or the arrangement density between the first region and the second region is, for example, the first region. This is particularly effective when stirring members having the same shape in the second region are used.
[0124]
  Further, when a single screw blade-shaped stirring blade is used as the stirring member, the mounting angle (the angle formed between the water absorbent resin extrusion surface and the plane perpendicular to the rotation axis) is automatically determined by determining the pitch. ) And arrangement density are determined.
[0125]
  In the present invention, the pushing thrust in the first region and the second region can be variously adjusted by combining the above-described components.
[0126]
  Furthermore, in the present invention, the inner surface of the fixed cylinder in the continuous extrusion mixer is substantially formed of a base material having a contact angle with water of about 60 ° or more and a heat distortion temperature of about 70 ° C. or more. Preferably it is.
[0127]
  If the contact angle of the base material with respect to the water is less than about 60 °, the amount of the water-absorbing water-absorbing resin attached to the inner surface of the fixed cylinder increases, and as a result, the mixing of the water-absorbing resin and the aqueous liquid becomes uneven. There is a case. On the other hand, if the heat distortion temperature of the base material is less than about 70 ° C., the base material may not sufficiently withstand the heat generated during the mixing period, and thus may not be able to continue stable mixing. Because there is, attention is necessary.
[0128]
  Moreover, in this invention, it is preferable that ratio of the diameter of the rotating shaft with respect to the internal diameter of the fixed cylinder in the said continuous extrusion mixer is in the range of 0.4-0.6.
[0129]
  If said ratio is less than 0.4, when mixing a water absorbing resin and aqueous liquid in a 2nd area | region, there exists a possibility that it may become unable to receive sufficient mixing with a stirring blade. On the other hand, if the ratio exceeds 0.6, it is difficult to extrude the water-absorbent resin from the fixed cylinder, and stable mixing may not be continued, so care must be taken.
[0130]
  Further, in the present invention, the continuous extrusion mixer is supplied with the powder of the water-absorbing resin having a carboxyl group in the first region, and the aqueous liquid is in the second region, preferably the first region. It is preferable to be formed so as to be fed into the boundary region between the first region and the second region.
[0131]
  In other words, when mixing the water-absorbent resin and the aqueous liquid, it is necessary to make the entire contact with each other as quickly as possible. Therefore, if this contact is insufficient, agglomerates, so-called “dama”, occur and the uniformity of mixing is impaired. In that respect, the continuous extrusion mixer according to the present invention feeds the water-absorbing resin into the continuous extrusion mixer by the stirring member disposed in the first region, and then the second region, Preferably, by supplying and supplying the aqueous liquid to the boundary area between the first area and the second area, high-speed stirring and mixing of the water absorbent resin and the aqueous liquid is instantaneously performed by the stirring member disposed in the second area. Do. Therefore, the water-absorbing resin and the aqueous liquid can be mixed sufficiently uniformly without forming “dama”.
[0132]
  Further, in the present invention, the pushing thrust received by the water absorbent resin changes as much as possible when changing from the first area to the second area, rather than gently changing according to the distance from the water absorbent resin supply port. Is preferred.
[0133]
  That is, when the aqueous liquid is supplied and fed into the fixed cylinder, the aqueous liquid adheres to the surface of the water absorbent resin dispersed in the first region. However, if the extrusion thrust remains high even after the aqueous liquid is adhered, the water absorbent resin may be extruded without being sufficiently mixed by the stirring member.
[0134]
  Therefore, in order to perform more uniform mixing, it is preferable that (1) the aqueous liquid adhering to the surface of the water absorbent resin is quickly mixed before being absorbed by the water absorbent resin, and (2) The average speed of the water-absorbing resin is reduced, and preferably, the water-absorbing resin is retained on the bottom wall inside the fixed cylinder, so that the mechanical mixing by the stirring member and the inner wall of the cylinder can be efficiently performed, and It is preferable to ensure sufficient mixing and stirring time with the liquid.
[0135]
  Therefore, in the present invention, the stirring member has the largest possible change in pushing thrust between the first region and the second region by combining the above-described components in accordance with the type and amount of the water absorbent resin to be used. It is preferable that it is provided.
[0136]
  Further, in the present invention, by further providing a plurality of first stirring members on the discharge side of the second stirring member described above, it is possible to sufficiently secure the pushing thrust at the time of discharging, and the discharging is suitably performed. There is.
[0137]
  That is, on the further discharge side of the first region as the dispersion region and the second region as the mixing region, the mixture is continuously added to the mixture of the water absorbent resin and the aqueous liquid that are mixed and stirred in the second region. A third region may be provided as a mixture extrusion region that provides an extrusion thrust for extruding out of the extrusion mixer.
[0138]
  In the third region, in order to efficiently extrude the mixture out of the continuous extrusion mixer, a stirring member is provided so as to generate an extrusion thrust in the discharge direction of the water absorbent resin according to the position of the discharge port. Yes.
[0139]
  Furthermore, the continuous extrusion mixer may have a configuration in which the first region and the second region are alternately provided depending on the type of water-absorbing resin used, other conditions, and the like.
[0140]
  In the present invention, the rotational speed of the rotating shaft, that is, the rotational speed of the stirring member depends on the type and amount of the water-absorbent resin and aqueous liquid used, the viscosity of the resulting mixture, etc., but is within the range of 10 rpm to 5000 rpm. Is preferably set in the range of 200 rpm to 4000 rpm, more preferably in the range of 500 rpm to 3000 rpm.
[0141]
  If the rotational speed is too small, the conveyance speed of the water-absorbent resin becomes too slow, and the amount of the water-absorbent resin staying in the fixed cylinder becomes too large, so the water-absorbent resin and the aqueous liquid are mixed sufficiently uniformly. You may not be able to. On the other hand, if the rotational speed is too large, it is difficult to ensure sufficient mixing and stirring time of the water absorbent resin and the aqueous liquid, and the water absorbent resin and the aqueous liquid are discharged before they can be sufficiently mixed. There is a risk of it.
[0142]
  Thus, according to the present invention, since the water-absorbing resin having a carboxyl group and an aqueous liquid containing a crosslinking agent capable of reacting with the carboxyl group can be uniformly mixed, The vicinity can be uniformly crosslinked at an appropriate depth.
[0143]
  For this reason, the water-absorbing agent obtained by the above production method is superior in water-absorbing characteristics, particularly properties such as absorption capacity under pressure, as compared with a water-absorbing agent obtained by a conventional mixer.
[0144]
  Further, as described above, the water-absorbing agent of the present invention has a pressure of 50 g / cm.²P is the absorption capacity at, and an impact force (A) is applied by applying a predetermined load to the water absorbent, and the same pressure (50 g / cm) in the water absorbent after the impact is applied.²) Where Q is the absorption capacity,
    P ≧ 20 (g / g)
And
    Q / P ≧ 0.85
It becomes.
[0145]
  Further, the water-absorbing agent of the present invention has a pressure of 50 g / cm of the water-absorbing agent.²The shock absorption (B) is given by giving a predetermined vibration to the water-absorbing agent, and the same pressure (50 g / cm in the water-absorbing agent after the impact is given.²) Is Y,
    X ≧ 20 (g / g)
And
    Y / X ≧ 0.90
It becomes.
[0146]
  Therefore, according to the present invention, the excellent water absorption performance is maintained even after transporting in the manufacturing plant or processing of the final product by the user, and in the final product, always excellent characteristics are selected regardless of the method of use. The water-absorbing agent to be maintained can be obtained.
[0147]
  Moreover, in this invention, as above-mentioned, manufacture of the said water absorbing agent is performed using the specific continuous extrusion type mixer which has the outstanding mixing property.
[0148]
  For this reason, in the method for producing a water absorbent using a conventional mixer, in order to make the mixing of the water absorbent resin and the aqueous liquid more uniform, the particle size distribution of the water absorbent resin is narrowed or the particle diameter is 150 μm or less. In other words, according to the present invention, it is necessary to control the amount of the water-absorbing resin fine powder (hereinafter sometimes simply referred to as fine powder) within a specific range. Even if the control is not strictly performed, it is possible to always achieve an excellent mixing property. Therefore, according to the present invention, even if the content of fine powder having a particle size of 150 μm or less is large, various characteristics such as absorption capacity under pressure can be improved.
[0149]
  In the present invention, it is not always necessary to strictly control the particle size. However, for the purpose of improving handleability and further improving physical properties, fine powder obtained in the water-absorbent resin manufacturing process, specifically, fine powder having a particle size of 150 μm or less, particularly 75 μm or less is classified and removed. By doing so, a water-absorbent resin with a reduced particle size and a narrow particle size distribution may be used as a raw material for the water-absorbing agent.
[0150]
  The fine powder removed in the present invention can be recovered by granulating using the continuous extrusion mixer without being discarded, and used again as a raw material for the water-absorbing agent. That is, the continuous extrusion mixer can be used not only for surface crosslinking but also for granulating a water-absorbing resin in the production of an absorbent.
[0151]
  By using a water absorbent resin having a large surface area (water absorbent resin granulated product) obtained by granulation as a raw material for the water absorbent, a granulated product having a large surface area obtained by crosslinking the water absorbent resin granulated product. A water-absorbing agent containing (cross-linked granulated product) can be obtained. In the present invention, the fine powder used in the granulation may be removed by the water-absorbing agent production process, but for the purpose of improving the absorption rate, the pulverization or polymerization conditions are adjusted intentionally. It may be manufactured. Furthermore, in the present invention, the water-absorbing agent containing the fine powder obtained may be further granulated after the surface-crosslinking of the water-absorbing resin containing the fine powder without removing the fine powder.
[0152]
  That is, when the water-absorbing agent used in the present invention contains a crosslinked granulated product having a large surface area, a water-absorbing agent having a higher absorption rate can be obtained.
[0153]
  Below, the granulation method of a water absorbing resin and the manufacturing method of the water absorbing agent using this granulation method are demonstrated. In the present invention, the water-absorbent resin used for granulation as a raw material for the water-absorbing agent may be only a fine powder (for example, a particle size of 150 μm or less) or a water-absorbent resin containing such a fine powder. Moreover, you may granulate the water absorbing agent containing fine powder as it is. Furthermore, as described above, the fine powder is classified from a mixture of the fine powder and a water absorbent resin having a particle diameter larger than that of the fine powder (that is, the water absorbent resin after polymerization) in the manufacturing process of the water absorbent. It may also be one that has been intentionally produced by adjusting grinding or polymerization conditions for the purpose of improving the absorption rate. Further, the water-absorbing resin used for granulation may or may not be subjected to surface cross-linking.
[0154]
  When granulating the water-absorbent resin or its fine powder, it is preferable to use an aqueous liquid, particularly water, as a binder. When granulating the water-absorbent resin, the amount of aqueous liquid used as the binder depends on the type, particle size, water content, etc. of the water-absorbent resin, but with respect to 100 parts by weight of the water-absorbent resin, It may be in the range of more than 0 and 400 parts by weight or less. By using a water absorbent resin granulated product or a water absorbent resin containing a water absorbent resin granulated product as a raw material for the water absorbent, a water absorbent having a high absorption rate can be obtained.
[0155]
  And according to the study by the inventors of the present application, in the final product, a water-absorbing agent excellent in granulation strength is obtained so that it has high physical properties and does not choose the method of use and can always exhibit excellent characteristics. Therefore, the amount of the aqueous liquid used as the binder is preferably 70 parts by weight or more, that is, in the range of 70 parts by weight to 400 parts by weight with respect to 100 parts by weight of the water absorbent resin, It was found that the content is particularly preferably in the range of from 200 parts by weight to 200 parts by weight, and most preferably in the range of from 100 parts by weight to 180 parts by weight from the viewpoint of physical properties, granulation strength, mixing property and the like.
[0156]
  If the amount of the aqueous liquid used exceeds 400 parts by weight, the effect of improving the granulation strength commensurate with the increase in the amount of aqueous liquid added cannot be obtained, which is disadvantageous in terms of drying costs. Further, when the amount of the aqueous liquid used exceeds 400 parts by weight, even if the continuous extrusion mixer of the present invention is used, the physical properties are lowered and the water-absorbent resin and the aqueous liquid (binder) are sufficiently uniformly mixed. There is a risk that it will not be possible. The aqueous liquid is preferably 90% by weight or more, preferably 99% by weight or more, more preferably 99% to 100% by weight from the viewpoint of physical properties and granulation strength. It is particularly preferable that it consists only of water.
[0157]
  On the other hand, when the amount of the aqueous liquid used is less than 70 parts by weight, the granulation strength is insufficient, and in the final product, it may not be possible to always exhibit excellent characteristics regardless of the method of use. There is. In particular, when the amount of the aqueous liquid used is too small, not only the granulation strength tends to be insufficient, but also the adhesive strength of the resulting hydrogel granulated product becomes strong. For example, the amount of water added is 30 parts by weight to 65 parts by weight. Within the range of parts by weight, there arises a problem that the hydrated gel-like granulated product adheres to the inner surface of the fixed cylinder of the mixer or the like and easily aggregates with each other. As a result, it may be disadvantageous for drying despite the reduction in the amount of aqueous liquid used, so care must be taken.
[0158]
  That is, in order to improve the granulation strength, it is necessary to add a predetermined amount or more of an aqueous liquid to the water absorbent resin.
[0159]
  However, in the past, due to the problem of the mixer, as a mixer of an aqueous liquid for granulation, the above-described high-speed stirring mixer (US Pat. No. 5,002986, US Pat. No. 4,734,478) or a specific spray is used. Even if a continuous granulator (US Pat. No. 5,360,148), fluidized bed (European Patent 0534899) or the like is used, the amount of aqueous liquid that can be added uniformly and stably to 100 parts by weight of the water-absorbing resin is: About 30 parts by weight was the limit.
[0160]
  Further, as a technique other than granulation, when a shear mixer (European Patent No. 0477761) or a Nauta mixer (U.S. Pat. No. 4,950,692) is used for mixing the fine powder and the aqueous liquid, it is strong. Due to the shearing force, it is possible to add and mix over 100 parts by weight of an aqueous liquid, but the resulting mixture is integrated and does not become a granulated product. There is a problem that the water absorbent resin deteriorates.
[0161]
  Generally, when the addition amount of the aqueous liquid with respect to the water-absorbent resin exceeds 60 parts by weight, the water-absorbent resin is gelled to become a hydrous gel. In this case, since the shear mixer kneads the water-absorbent resin and the aqueous liquid by the shearing force, the resulting hydrogel does not become a granular granulated product (aggregate) but is continuous and integrated. It becomes a huge gel. For this reason, the water-containing gel has a small surface area and cannot be dried as it is, and generally requires separate grinding of the gel by shearing (US Pat. No. 4,950,692). For this reason, there is also a problem that the water-absorbent resin granulated product is deteriorated also by a decrease in the water absorption rate and the pulverization step.
[0162]
  Further, in the method of using a mixing aid such as insoluble inorganic powder or water-soluble polymer for improving the water mixing property (European Patent No. 0644224), the mixing is still non-uniform and the granulation strength is increased. And cause deterioration of physical properties.
[0163]
  Therefore, in order to improve the granulation strength and various physical properties, the amount of the aqueous liquid added to the water absorbent resin is set within a predetermined range, and the water absorbent resin and the aqueous liquid are uniformly mixed without being kneaded (sheared). It is important to mix and obtain a granulated product (aggregate) directly. According to the present invention, by using a specific continuous extrusion type mixer, conventionally, for the first time, without performing the mixing aid used for granulation or pulverization of the gel used for other than granulation, A hydrogel granulated product can be obtained from water and fine powder.
[0164]
  In this invention, said conditions were cleared by using the above-mentioned continuous extrusion type mixer. That is, in the present invention, by using the continuous extrusion mixer, a mixing aid that causes a decrease in physical properties without kneading the water absorbent resin and the aqueous liquid even when the amount of the aqueous liquid is large is provided. Even if not used, it is possible to mix uniformly. Moreover, the hydrated gel obtained using the continuous extrusion mixer is in the form of particles, and can usually be dried as it is as a discontinuous granular granulated product in which individual hydrated gels are aggregated. In addition, the fact that each hydrogel is a discontinuous granular granule (aggregate) is based on the fact that a plurality of individual particles are gathered and aggregated while maintaining the shape according to the optical micrograph. It can be confirmed by the fact that it swells as discontinuous particles upon water absorption. Therefore, in the present invention for obtaining a water-containing gel-like granulated product directly from water and fine powder, it is not necessary to pulverize the gel by mixing aid or shearing as in the prior art. Can be prevented.
[0165]
  In the present invention, examples of the aqueous liquid used for the granulation include water and the aforementioned hydrophilic organic solvent. Among them, the aqueous liquid is preferably water alone or water containing a small amount of a crosslinking agent. In this case, as the crosslinking agent, for example, the above-described types and amounts of surface crosslinking agents can be used. Thus, by using a crosslinking agent in combination with the aqueous liquid, it is possible to reduce water-soluble components and further improve the granulation strength.
[0166]
  Moreover, as mentioned above, the continuous extrusion mixer of the present invention is extremely excellent in mixing properties. Thereby, while being able to mix a lot of aqueous liquids stably, continuous granulation ability and productivity can be improved. In addition, the mixing method of the water-absorbing resin and the aqueous liquid in the continuous extrusion mixer is as described in the method for producing the water-absorbing agent.
[0167]
  In the present invention, when only fine powder is granulated as the water-absorbent resin, the average particle diameter of the fine powder is preferably in the range of 150 μm to 10 μm, and particles having a particle diameter of substantially 150 μm or less are 70 It is preferably contained in an amount of not less than wt%, more preferably not less than 90 wt%. In addition, the shape of the fine powder is preferably an indeterminate shape obtained by aqueous solution polymerization rather than a spherical shape obtained by reverse phase suspension polymerization in terms of granulation strength. Furthermore, the fine powder is more preferably a fine powder before surface cross-linking.
[0168]
  In the present invention, the average particle diameter of the resulting hydrogel granulated product is preferably in the range of 0.3 mm to 10 mm, more preferably in the range of 0.5 mm to 8 mm. It is particularly preferable that it is in the range of ˜5 mm. If the particle size of the hydrated gel granule is smaller than 0.3 mm, the ratio of granulation is low and the granulation strength of the dry granulated product obtained by drying the hydrated gel granulate is not good. There is a risk of becoming sufficient. Moreover, when the particle size of the hydrated gel granulated product exceeds 10 mm, the physical properties may decrease or the fine powder may increase.
[0169]
  That is, in order to obtain a water-absorbing agent that is further superior in granulation strength and excellent in properties such as absorption capacity and absorption rate under pressure, a particulate hydrogel granulate having an appropriate particle size is used. After obtaining, it is preferable to dry and shrink the hydrogel granulated product.
[0170]
  Thus, in the granulation method of the present invention, the granulation strength can be further improved by adding an aqueous liquid, particularly water, and preferably drying.
[0171]
  When the amount of the aqueous liquid added is less than 10%, drying may not be performed. However, when 70 parts by weight or more of the aqueous liquid is added, the resulting hydrogel granule is shrunk by drying. It is necessary to make it.
[0172]
  The above water-absorbing resin is firmly integrated by adding a large amount of aqueous liquid and then drying, and as shown in the electron micrograph of FIG. A collection). Thus, it is 20 to 100 times, preferably 30 to 50 times that the water-absorbent resin fine powder is almost agglomerated primary particles (agglomerated fine powder) by granulation. This can be easily determined by comparing the particles before granulation with the particles after granulation in the enlarged electron micrograph. In addition, the fact that the particles are granulated (aggregate of fine powder) is an optical micrograph of the hydrogel granule or an electron micrograph taken without crushing the dried hydrogel granulate. Thus, it can be seen from the fact that aggregation of individual particles can be confirmed, and in a large excess of water, the particles are divided into a plurality of particles before granulation and swell discontinuously.
[0173]
  In the present invention, when the hydrated gel granulated product is dried, it is desirable to dry the hydrated gel granulated product as it is without substantially pulverizing or kneading. In other words, the hydrated gel granule is dried under conditions where the hydrated gel granule directly obtained from the water-absorbent resin powder (fine powder) is not pulverized or kneaded.
[0174]
  In the present invention, the drying method is not particularly limited, and for example, the above-described dryer or heating furnace is preferably used. Further, the drying temperature is not particularly limited, but drying at a relatively high temperature is preferable from the viewpoint of granulation strength. Specifically, the drying temperature is in the range of 110 ° C to 300 ° C, preferably in the range of 120 ° C to 200 ° C, and more preferably in the range of 150 ° C to 180 ° C. When the hydrated gel granule is dried at the above drying temperature, the particulate hydrated gel granule shrinks more during drying, and as a result, a strong water absorbent resin granulate can be obtained. Therefore, it is preferable. In addition, when drying the hydrated gel-like granulated product, the hydrated gel-like granulated product may be dried alone or before drying, which is obtained by the aqueous solution polymerization or reverse phase suspension polymerization described above. It may be mixed with a gel polymer and dried together. In this case, the above-described normal dryer or heating furnace is used for drying.
[0175]
  The particulate dry granulated product thus obtained is shrunk by drying into a strong dry granulated product, but may be further pulverized to adjust the particle size as necessary. The method for pulverizing the dried granulated product is not particularly limited, and for example, a vibration mill or a roll granulator type pulverizer is preferably used.
[0176]
  As described above, the water absorbent resin granulated product of the present invention is obtained after mixing 70 parts by weight to 400 parts by weight of an aqueous liquid with a specific continuous extrusion mixer with respect to 100 parts by weight of the water absorbent resin. The particulate hydrogel granulated product can be easily obtained by drying under conditions that do not pulverize the hydrogel granulated product.
[0177]
  In the present invention, the average particle diameter of the water absorbent resin granulated product obtained by the above method is preferably in the range of 200 μm to 800 μm, and more preferably in the range of 200 μm to 500 μm. That is, in the present invention, it is preferable to granulate particles having a mean particle size of 200 μm to 800 μm with a particle size of 150 μm or less (average particle size is, for example, 100 μm or less).
[0178]
  Unlike the conventional water-absorbent resin granulated product, the water-absorbent resin granulated product has a far superior granulation strength and does not have a decrease in physical properties. Moreover, as shown in the electron micrograph shown in FIG. 19, the water-absorbent resin granulated product is surprisingly granulated into porous primary particles and exhibits a high absorption rate.
[0179]
  Therefore, as described above, the water-absorbing resin granulated product obtained through the above granulation step is further subjected to the above-mentioned surface cross-linking so that it exhibits excellent absorption capacity under high pressure, granulation strength, and high absorption rate. An agent can be obtained. The absorption capacity of the water-absorbing agent under no pressure is 20 g / g or more, preferably 25 g / g or more, more preferably 30 g / g or more.
[0180]
  That is, as a method for producing a water-absorbing agent in the present invention, particles having an average particle diameter of 0.3 mm to 10 mm are prepared by mixing 70 parts by weight to 400 parts by weight of an aqueous liquid with 100 parts by weight of a water absorbent resin having an average particle diameter of 10 μm to 150 μm. After obtaining a water-containing gel-like granulated product, it is shrink-dried at 110 ° C. to 300 ° C. under non-pulverized conditions, and the resulting water-absorbent resin granulated product having an average particle size of 200 μm to 800 μm is further subjected to surface crosslinking The method is most preferable.
[0181]
  Using the above production method, the absorption capacity under high pressure is 20 g / g or more, preferably 25 g / g or more, the absorption rate is 25 seconds or less, preferably 20 seconds or less, and the granulation failure rate. Is 10% by weight or less, preferably 5% by weight or less, more preferably 2% by weight or less, and particularly preferably 1% by weight or less.
[0182]
  As described above, according to the present invention, the conventional granulation methods have mutually contradicting properties, and at the same time, the physical properties that cannot be satisfied are the absorption capacity under high pressure, granulation strength, and absorption speed. It is possible to obtain a water-absorbing agent that can simultaneously satisfy the physical properties for the first time.
[0183]
  That is, in the conventional granulation method, as described above, in the case of granulating after surface crosslinking, in the case of performing surface crosslinking after granulation, or in the case of surface crosslinking simultaneously with granulation, as described above, granulation It was difficult to obtain a water-absorbing agent that could easily satisfy the three physical properties of absorption capacity, absorption rate, and granulation strength under high pressure. In particular, the use of a mixing aid has a problem that it tends to cause a decrease in physical properties and granulation strength of the resulting water-absorbent resin granulated product. On the other hand, according to the present invention, the above physical properties are obtained by cross-linking the surface of the porous granulated particles (aggregates) granulated into the condensed primary particles through the particulate hydrogel granulate. A water-absorbing agent that can be satisfied at the same time can be obtained. In the present invention, the above granulation does not use a mixing aid, but water substantially containing water alone or a small amount of a crosslinking agent is preferably used.
[0184]
  In the present invention, the granulation method may be applied to granulate a relatively small amount of fine powder contained in the surface-crosslinked water-absorbing agent or to compounding with other water-soluble compounds. it can. However, in this case, the amount of the aqueous liquid used as the binder or solution is preferably in the range of 0.1 to 30 parts by weight with respect to 100 parts by weight of the absorbent. More preferably, it is within the range of 10 to 10 parts by weight, and particularly preferably within the range of 1 to 5 parts by weight.
[0185]
  If the amount of the aqueous liquid is too large, surface cross-linking may be destroyed even if the continuous extrusion mixer according to the present invention is used. On the other hand, if the amount of the aqueous liquid is too small, a sufficient granulation strength cannot be obtained, which is not preferable.
[0186]
  In the present invention, even when granulating the already surface-crosslinked fine powder contained in the water-absorbing agent as described above, as in the case of producing the water-absorbent resin granulated product, Thus, a water-absorbing agent having excellent granulation strength can be obtained without the resulting crosslinked granulated product being deteriorated. Further, since the water-absorbing agent (crosslinked granulated product) has a larger surface area than the primary particles by granulation, the water-absorbing agent (crosslinked granulated product) is particularly excellent in properties such as absorption capacity and absorption rate under pressure.
[0187]
  In addition, according to the present application, as the granulated strength of the crosslinked granulated product, an impact force (B) is given by giving a predetermined vibration to the crosslinked granulated product, and the fracture rate of the crosslinked granulated product after the impact is determined. By measuring, the strength against mechanical stress of the crosslinked granulated product can be evaluated and predicted. For this reason, according to the present application, by measuring the fracture rate of the crosslinked granulated product, it is possible to maintain its excellent water absorption performance even after carrying out processing at the manufacturing plant or processing of the final product at the user, Among them, it is possible to obtain a water-absorbing agent that always maintains excellent characteristics regardless of the method of use.
[0188]
  In the present invention, the impact force (B) applied to the water absorbing agent is as described above. The fracture rate of the crosslinked granulated product (hereinafter referred to as granulation failure rate) is determined by applying the aforementioned impact force (B) to the crosslinked granulated product for 30 minutes and then vibrating with glass beads. The weight of the crosslinked granulated particles in the container 41 is measured, and the weight of the crosslinked granulated particles after vibration is divided by the weight of the granulated particles before vibration.
[0189]
  When measuring the granulation failure rate of the crosslinked granulated product, 30.00 g of the crosslinked granulated product is used as the granulated product. That is, when the granulation failure rate is granulated particles of a certain particle size, impact strength (B) is applied to 30.00 g of a crosslinked granulated product having a particle size equal to or larger than the particle size before granulation, and is destroyed, The weight of the generated particles having a constant particle size can be measured by measuring by low tap classification using a JIS standard sieve.
[0190]
  In the above measurement, by using a water-absorbent resin granulated product or a water-absorbing resin instead of the crosslinked granulated product, the granulation failure rate of the granulated product before surface crosslinking can be measured, and the water absorption As one of the impact resistance test methods for water-soluble resin particles, it is possible to measure the destruction rate of a water-absorbent resin that has not been crosslinked or granulated.
[0191]
  Thus, in the present invention, by measuring the granulation failure rate, the physical property value Q / P, and the physical property value Y / X, the water absorption when the water absorbing agent includes a granulated product (crosslinked granulated product). The strength of the agent against mechanical stress can be evaluated and predicted. In other words, until now, when the water-absorbing agent contains a granulated product (cross-linked granulated product), a large amount of water is actually absorbed during transportation in the manufacturing plant that is trying to evaluate granulation failure in the final product or processing of the final product by the user. Unless it was carried out using an agent, it was impossible to evaluate the physical property deterioration and the granulation failure rate. However, according to the above method, it is possible to provide a simple impact resistance test method for a water-absorbing agent at a laboratory level corresponding to transportation in a production plant, processing of a final product by a user, and the like.
[0192]
  Therefore, according to the present invention, the strength of the water-absorbing agent against mechanical stress can be evaluated in advance by a simple method. Therefore, the strength of the water-absorbing agent is excellent even after transport in a manufacturing plant or processing of a final product by a user. Thus, it is possible to obtain a water-absorbing agent that maintains excellent water absorption performance and always maintains excellent characteristics in the final product regardless of the method of use.
[0193]
  In the present invention, each of the above water-absorbing agents further includes a disinfectant, a deodorant, an antibacterial agent, a fragrance, various inorganic powders, a foaming agent, a pigment, a dye, a hydrophilic short fiber, a fertilizer, an oxidizing agent, a reducing agent, Water, salts, and the like can be added to thereby impart various functions to the water absorbing agent. Of course, the mixer of the present invention can also be suitably used for the addition of such compounds.
[0194]
  Furthermore, as described above, since each of the above water-absorbing agents can maintain its excellent absorption characteristics even after being processed into an absorbent article as a final product by the user, various absorbent articles, particularly under pressure It is suitable for absorbent articles such as sanitary materials including absorbents such as paper diapers, sanitary napkins, incontinence pads and the like where absorption characteristics are important.
[0195]
  In JP-A-8-84927 and Canadian Patent Publication No. 2154425, the content of fine powder worn by a mechanical load is reduced by coating a water-absorbing polymer with a non-reactive water-soluble film-forming polymer. Is described. However, according to the present application, by using a specific continuous extrusion mixer, there is no need for a process such as coating the surface portion of the resin particles with a non-reactive water-soluble film-forming polymer as in the above publication. In addition, there is no deterioration in physical properties due to film coating, and a water-absorbing agent that is resistant to mechanical stress and has excellent absorption performance can be provided by a normal process.
[0196]
DETAILED DESCRIPTION OF THE INVENTION
  [Embodiment 1]
  An embodiment of the present invention will be described below with reference to FIGS.
[0197]
  As shown in FIG. 1, a high-speed stirring type continuous extrusion mixer 1 constituting a part of the water-absorbing agent production apparatus of the present embodiment has a casing 2 as a fixed cylinder fixed horizontally, for example. ing.
[0198]
  In the casing 2, as shown on the right side in the figure, a material supply port (first supply port) 3 for supplying and supplying powder water-absorbing resin is formed. In this position, a liquid supply port (second supply port) 4 through which an aqueous liquid such as a crosslinking agent is introduced is provided. Moreover, the discharge port 5 is formed in the left end side in the same figure.
[0199]
  Note that, as disclosed in JP-A-4-214734, a base material having a contact angle with water of 60 ° and a thermal deformation temperature of 70 ° C. or more is provided on the inner surface of the casing 2 as an inner tube. It is preferable.
[0200]
  That is, if the contact angle of the base material with respect to water is less than about 60 °, mixing of the water absorbent resin and the aqueous liquid may be non-uniform. Also, if the heat distortion temperature is less than about 70 ° C., the substrate cannot sufficiently withstand the heat generated during the mixing period. For this reason, when the said base material is not satisfy | filling the said conditions, since stable mixing may be unable to be continued, attention is required.
[0201]
  Examples of the base material on the inner surface of the casing 2 include, for example, polyethylene, polypropylene, polyester, polyamide, fluororesin, polyvinyl chloride, epoxy resin and silicone resin, or synthetic resin such as glass, Examples thereof include composites of the above-mentioned synthetic resins that are augmented with inorganic fillers such as graphite, bronze and molybdenum disulfide, or organic fillers such as polyimide.
[0202]
  Among the above substances, polyethylene tetrafluoride, polyethylene trifluoride, polyethylene trifluorochloride, ethylene tetrafluoride-ethylene copolymer, ethylene trifluorochloride-ethylene copolymer, propylene pentafluoride-ethylene tetrafluoride copolymer, perfluoro Fluorine resins such as alkyl vinyl ether-ethylene tetrafluoride copolymers and polyvinyl fluoride are particularly desirable.
[0203]
  On the other hand, a rotating shaft 6 that is rotationally driven by a drive motor 8 is provided inside the casing 2, and a plurality of stirring blades 7 are provided around the rotating shaft 6 as stirring members. .
[0204]
  The plurality of stirring blades 7 are provided in a first region as a dispersion region for dispersing the water-absorbing resin supplied in the casing 2, and on the outlet 5 side of the first region, and the dispersion In order to form a second region as a mixing region for mixing the water-absorbent resin dispersed in the region and the aqueous liquid, a second region having a smaller pushing thrust than the pushing force in the first region is provided on the discharge port 5 side. It is provided to have.
[0205]
  In the present embodiment, each of the plurality of stirring blades 7 is sequentially arranged in a spiral around the rotation shaft 6, and the first stirring blades 7a and the second having different shapes are arranged. It consists of stirring blades 7b. In the present embodiment, first stirring blades 7a ... are arranged in the first region. In the second region, the second stirring blades 7b are arranged, and the first stirring blades 7a are partially arranged.
[0206]
  The shape of the first stirring blade 7a is, for example, a plate shape such as a rectangle and the like, thereby generating an extrusion thrust. The first stirring blade 7a is not necessarily limited to a plate shape such as a rectangle, but may be a paddle plate shape such as a fin or a butterfly, and has a curved surface instead of a flat plate. It may be plate-shaped. Further, as shown in FIG. 1, the first agitating blade 7a does not need to have a straight tip edge, and may be formed in, for example, an arc shape, and has a blade edge such as a flea. It may be what you did.
[0207]
  In addition, the shape of the first agitating blades 7a can be variously changed as long as it has a shape that generates pushing thrust, such as a circular shape, an elliptical shape, a triangular plate shape, and a prism shape.
[0208]
  That is, the shape and size of the first stirring blades 7a, the arrangement density, the arrangement method, the water absorbent resin extrusion surface 7a.₁In the first region, the angle formed between the rotary shaft 6 and the plane perpendicular to the rotary shaft 6 gives the water-absorbent resin supplied into the casing 2 a sufficient extrusion thrust into the continuous extrusion mixer 1 to disperse it. There is no particular limitation as long as it is set so that it can be set.
[0209]
  In the present embodiment, the continuous extrusion mixer 1 has a balance with other conditions. For example, by partially changing the size of the first stirring blades 7a, We are trying to make adjustments. Further, the first stirring blade 7a ... is perpendicular to the rotary shaft 6 and has a water absorbent resin extrusion surface 7a.₁Is arranged around the rotation axis 6 so as to be inclined with respect to a plane perpendicular to the rotation axis 6.
[0210]
  On the other hand, the shape of the second stirring blade 7b is, for example, a cylindrical shape. Further, the second stirring blade 7 b is fixed so as to be perpendicular to the rotating shaft 6. In this case, in the second region, the pushing thrust is not generated by the second stirring blades 7b, but the pushing thrust is generated only by the first stirring blades 7a. In addition, although slightly, the second agitating blades 7b ... receive resistance to reduce the pushing thrust.
[0211]
  Therefore, in the second region, the pushing thrust of the water absorbent resin is smaller than that in the first region, and the average speed of the water absorbent resin is reduced. As a result, in the continuous extrusion mixer 1, as shown in FIGS. 2 (a) and 2 (b), stirring is performed in two types of stirring states. As shown in FIG. 2 (a), in the first region, the water-absorbing resin 37 receives the pushing thrust force toward the discharge port 5 by the first stirring blades 7a, and the first stirring blades 7a. Receives centrifugal force by rotation. Therefore, the water-absorbing resin 37 is not mixed by the first stirring blades 7a in the first region, and is pushed out to the second region while being rotated along the outer wall of the casing 2 in a dispersed state. .
[0212]
  On the other hand, as shown in FIG. 2B, in the second region, the pushing thrust is smaller than that in the first region, and the average speed of the water absorbent resin 37 is decreased. For this reason, the water-absorbing resin 37 stays on the bottom wall of the casing 2 and is supplied from the liquid supply port 4 by the first stirring blades 7a ... and the second stirring blades 7b ... and adheres to the surface of the water-absorbing resin 37. While being mixed with an aqueous liquid (not shown), it is pushed out toward the discharge port 5 by the pushing thrust transmitted from the first region and the pushing thrust generated by the first stirring blades 7a disposed in the second region. .
[0213]
  In the present embodiment, in the continuous extrusion mixer 1, the shape of the second stirring blade 7b is cylindrical, but the shape of the second stirring blade 7b is not limited to this. . The shape of the second agitating blade 7b only needs to be formed such that the pushing thrust is smaller in the arrangement region than in the arrangement region of the first stirring blades 7a.
[0214]
  Accordingly, the shape of the second stirring blade 7b may be, for example, a shape that does not generate an extrusion thrust, or a shape that generates an extrusion thrust smaller than that of the first stirring blade 7a.
[0215]
  Here, specific examples of the shape that does not generate the pushing thrust include a columnar shape, a rod shape thinner than the columnar shape, or a pin shape. Further, the shape that generates the pushing thrust smaller than that of the first stirring blade 7a is a shape that generates the pushing thrust, although it depends on the shape of the first stirring blade 7a, and the shape of the first stirring blade 7a. Area (water absorbent resin extruded surface 7a₁Any area may be used as long as the area is smaller than the area. Therefore, the shape of the second stirring blade 7b may be, for example, a plate shape having a narrower width or a smaller size than the first stirring blade 7a. The shape provided with the opening part may be sufficient.
[0216]
  Further, the tip shape of the second stirring blade 7b is not necessarily a flat surface as shown in FIG. 1, but may be a spherical surface such as a hemispherical surface.
[0217]
  Further, the first stirring blades 7a ... and the second stirring blades 7b ... may be provided with attachment nuts or the like at the lower part. Further, in order to prevent the mixture from adhering to the stirring blades 7 and the rotating shaft 6, the surface of the stirring blades 7 and the rotating shaft 6 is coated with a film made of Teflon resin or the like, coated with a plating process or a Teflon resin tube or the like. It is preferable to have applied.
[0218]
  In the continuous extrusion mixer 1, the first stirring blades 7 a... Are partially mixed in the arrangement region (second region) of the cylindrical second stirring blades 7 b. As a result, the continuous extrusion mixer 1 can adjust the extrusion thrust in the region where the second stirring blades 7b are disposed.
[0219]
  That is, the pushing thrust is, for example, the shape of the stirring blade 7, the density of the stirring blades 7 in each region, or the manner of arrangement of the stirring blades 7, the water absorbent resin extruded surface 7 a.₁Can be adjusted by adjusting the angle between the plane parallel to the rotation axis 6 and the like.
[0220]
  The distance between the outer periphery of the rotary shaft 6 and the inner wall of the casing 2 is preferably set in consideration of the stirring efficiency.
[0221]
  As shown in FIG. 1, the plate-like first stirring blades 7 a... Are formed from the end of the material supply port 3 in the rotary shaft 6 when the total length of the rotary shaft 6 existing in the casing 2 is 100%. On the other hand, the cylindrical second stirring blades 7b... Are provided in a portion having a length of about 65% from the end on the discharge port 5 side.
[0222]
  Thereby, said 1st stirring blade 7a ... is the inside of the continuous extrusion mixer 1 with respect to the water absorbing resin which has a carboxyl group, and the aqueous liquid containing the crosslinking agent etc. which can react with this carboxyl group. Give enough thrust. And by making the thrust thrust smaller than the thrust thrust in the arrangement region of the first stirring blades 7a ... by the second stirring blades 7b ..., the mixing stirring time can be sufficiently secured and sufficiently mixed. it can.
[0223]
  In addition, it is preferable to set the attachment pitch of each said stirring blade 7 ... according to the target uniform mixing state.
[0224]
  In the continuous extrusion mixer 1, the material supply port 3 for introducing the powdery water-absorbing resin is formed in a region where the first stirring blades 7 a. The liquid supply port 4 for introducing the liquid is formed in the vicinity of the boundary with the first area in the arrangement area of the second stirring blades 7b.
[0225]
  That is, when mixing the water-absorbent resin and the aqueous liquid, it is necessary to make the entire contact as soon as possible. If this is insufficient, so-called “dama” occurs and the uniformity of mixing is impaired. In that respect, the continuous extrusion mixer 1 feeds water-absorbing resin into the continuous extrusion mixer 1 by the first stirring blades 7a, and instantaneously absorbs water by the second stirring blades 7b. Since the resin and the aqueous liquid are stirred and mixed at a high speed, the water absorbent resin and the aqueous liquid can be sufficiently uniformly mixed.
[0226]
  When the water-absorbing resin having a carboxyl group and the aqueous liquid containing a crosslinking agent capable of reacting with the carboxyl group are mixed in the continuous extrusion mixer 1 having the above-described configuration, the mixture is rotated by the drive motor 8. The shaft 6 is rotated at a high speed of, for example, about 500 to 3000 rpm.
[0227]
  In this state, a water-absorbing resin having a carboxyl group is supplied from the material supply port 3. Then, the water absorbent resin is transferred into the continuous extrusion mixer 1 by the pushing thrust of the plate-shaped first stirring blades 7a formed in a spiral shape.
[0228]
  Next, by injecting an aqueous liquid containing a cross-linking agent from the liquid supply port 4, the water-absorbing resin and the aqueous liquid containing the cross-linking agent and the like are disposed in the arrangement region of the second stirring blades 7 b. Mix well. As a result, the water-absorbent resin and the aqueous liquid containing the crosslinking agent are uniformly mixed, and eventually the mixture is automatically discharged from the discharge port 5.
[0229]
  Next, this mixture becomes a water-absorbing agent having excellent strength characteristics by further cross-linking the surface, for example, by a heating device (not shown) in the water-absorbing agent manufacturing apparatus.
[0230]
  Thus, the continuous extrusion mixer 1 in the present embodiment is a fixed casing for uniformly mixing a water-absorbing resin having a carboxyl group and an aqueous liquid containing a crosslinking agent capable of reacting with the carboxyl group. 2 has a structure in which a plurality of stirring blades 7 are provided around the rotation shaft 6, and these stirring blades 7 are made of two or more types having different shapes.
[0231]
  In other words, the conventional agitating blades of the continuous extrusion mixer are composed of a plurality of agitating blades of the same shape, which are arranged around the rotating shaft so that the directions of the blade surfaces are the same and the intervals are the same. The stirring was not uniform and the mixing was not sufficient.
[0232]
  However, in the present embodiment, the stirring blades 7 are made of two or more types having different shapes, so that the mixing is performed by two or more types of stirring states. As a result, the water-absorbing resin having a carboxyl group and the aqueous liquid containing a crosslinking agent capable of reacting with the carboxyl group are efficiently mixed, and uniform mixing can be performed without generating “dama”. it can. For this reason, in the final product, it is possible to provide a water-absorbing agent that can always exhibit excellent characteristics and a manufacturing apparatus thereof, regardless of the method of use.
[0233]
  Further, since the plurality of stirring blades 7 are sequentially arranged in a spiral manner, a sufficient thrust can be secured and the water-absorbing resin or the like can be smoothly pushed out.
[0234]
  Further, around the rotating shaft 6 in the continuous extrusion mixer 1 in the present embodiment, there are a plurality of first stirring blades 7a that give extrusion thrust to the water absorbent resin, and these first stirring blades 7a. On the discharge side, there are arranged second stirring blades 7b, which form a region in which the pushing thrust is smaller than the pushing thrust in the region where the first stirring blades 7a are disposed.
[0235]
  Therefore, the continuous extrusion mixer 1 is a continuous extrusion type with respect to the water-absorbing resin having a carboxyl group and an aqueous liquid containing a crosslinking agent capable of reacting with the carboxyl group by the first stirring blade 7a. By providing a sufficient pushing thrust to the inside of the mixer 1, and then making the pushing thrust smaller than the pushing thrust in the arrangement region of the first stirring blade 7a ... by the second stirring blade 7b ... The mixing and stirring time can be sufficiently ensured and sufficiently mixed. Therefore, the reaction can be performed in a state where the water absorbent resin and the aqueous liquid are sufficiently uniformly mixed.
[0236]
  Moreover, since the first stirring blades 7a are formed in a plate shape, the first stirring blades 7a are preferable as a shape that generates an extrusion thrust. Further, since the second agitating blades 7b are formed in a columnar shape, the pushing thrust force in the second region, which is the disposing region of the second agitating blades 7b, is used as the disposing region of the first stirring blades 7a. This is preferable as a shape that is smaller than the pushing thrust force in the first region and sufficiently ensures mixing and stirring.
[0237]
  Furthermore, the inner surface of the casing 2 in the continuous extrusion mixer 1 is substantially formed from a base material having a contact angle with water of about 60 ° or more and a heat deformation temperature of about 70 ° C. or more.
[0238]
  That is, if the contact angle of the base material with respect to water is less than about 60 °, mixing of the water-absorbent resin and the aqueous liquid may be non-uniform, and if the heat distortion temperature is less than about 70 ° C., May not be able to sufficiently withstand the heat generated during the mixing period, and thus stable mixing may not be continued, but this embodiment can avoid this.
[0239]
  Further, the continuous extrusion mixer 1 is supplied with a water-absorbing resin powder having a carboxyl group in an arrangement region of the first stirring blades 7a, and an aqueous liquid containing a crosslinking agent capable of reacting with the carboxyl group. It is formed so as to be fed into the arrangement area of the second stirring blades 7b.
[0240]
  Therefore, the continuous extrusion mixer 1 feeds the water-absorbing resin into the continuous extrusion mixer 1 by the first stirring blades 7a, and then the arrangement region of the second stirring blades 7b. When the aqueous liquid is supplied and supplied, the high-speed stirring and mixing of the water-absorbent resin and the aqueous liquid is instantaneously performed by the second stirring blades 7b. Thereby, the continuous extrusion mixer 1 can sufficiently mix the water-absorbent resin and the aqueous liquid.
[0241]
  Note that the stirring blades 7 in the present embodiment are two types of first stirring blades 7a and second stirring blades 7b, but are not necessarily limited to this, for example, different types. It is possible to provide the agitating blades 7 of the shape, and this can further improve the agitation efficiency.
[0242]
  Further, the continuous extrusion mixer 1 is configured such that an aqueous liquid containing a crosslinking agent capable of reacting with a carboxyl group is supplied and fed into the arrangement region of the second stirring blades 7b. More preferably, the supply of the aqueous liquid is performed at the boundary between the first region and the second region. For this purpose, as shown in the continuous extrusion mixer 51 in FIG. 3, the liquid supply port 4 includes an arrangement area of the first stirring blades 7 a and an arrangement area of the second stirring blades 7 b. The configuration may be provided in the boundary area.
[0243]
  The liquid supply port 4 is provided in the boundary region between the arrangement region of the first stirring blades 7a ... and the arrangement region of the second stirring blades 7b ... so that the first stirring blades 7a ... Aqueous liquid is uniformly attached to the dispersed water-absorbing resin, and the water-absorbing resin and the aqueous liquid are mixed more quickly and uniformly before the aqueous liquid adhering to the water-absorbing resin is absorbed by the water-absorbing resin. be able to. Therefore, the water-absorbing resin having a carboxyl group and the aqueous liquid containing a crosslinking agent capable of reacting with the carboxyl group are more efficiently mixed, and uniform mixing can be performed without generating “dama”. For this reason, the liquid supply port 4 is provided in the boundary region between the arrangement region of the first stirring blades 7a ... and the arrangement region of the second stirring blades 7b ... Regardless of the method of use, a water-absorbing agent that can always exhibit excellent properties can be produced more stably.
[0244]
  In the continuous extrusion mixer 1, the discharge port 5 is formed on the bottom wall of the casing 2. However, the formation position of the discharge port 5 is not necessarily limited to the bottom wall of the casing 2. Instead, for example, as shown in the continuous extrusion mixer 51 of FIG.
[0245]
  Further, the shape of the casing 2, that is, the shape of the continuous extrusion mixer is not particularly limited, and may be various shapes as shown in FIGS. 4 and 5. For example, the continuous extrusion mixer 52 shown in FIG. 4 has a configuration in which the material supply port 3 is provided on the top wall of the casing 2 provided at an inclination and the discharge port 5 is provided on the bottom wall. Therefore, the continuous extrusion mixer 52 is configured such that gravity is added to the pushing thrust. On the other hand, the continuous extrusion mixer 53 shown in FIG. 5 is configured to push out the water absorbent resin supplied from the material supply port 3 shown on the right side in the drawing while pushing it up against gravity. Further, since the continuous extrusion mixer 52 and the continuous extrusion mixer 53 are both provided with the casing 2 inclined, the length of the stirring path (the length of the casing 2) in a narrow space. Can be secured. Alternatively, the stirring path can be set longer in the same space. Thus, in the present invention, the shape of the continuous extrusion mixer is not particularly limited. What is necessary is just to select the thing of an optimal shape as said continuous extrusion type mixer, for example according to the kind, usage-amount, use, etc. of the water absorbing resin to be used.
[0246]
  As described above, according to the present invention, a water-absorbing resin having a carboxyl group and an aqueous liquid containing a crosslinking agent capable of reacting with the carboxyl group can be uniformly mixed. Therefore, according to the present invention, it is possible to uniformly crosslink the vicinity of the surface of the water-absorbent resin at an appropriate depth, and to obtain a water-absorbing agent having excellent absorption performance and strong against mechanical stress.
[0247]
  Furthermore, according to the invention, there is provided a water-absorbing agent that maintains its excellent absorption performance in the final product without substantially deteriorating its water-absorbing characteristics even when subjected to mechanical stress applied by transportation in a manufacturing plant or processing by a user. There is an effect that it can be provided.
[0248]
  Moreover, if the manufacturing method and the manufacturing apparatus of a water absorbing agent of this invention are used, it can react with the water absorbing resin which has a carboxyl group, and this carboxyl group with various structures of the several stirring blade in a continuous extrusion mixer. The mixing reaction with an aqueous liquid containing a cross-linking agent or the like is efficiently performed, and there is an effect that uniform mixing can be ensured.
[0249]
  [Embodiment 2]
  An embodiment of the present invention will be described below with reference to FIG. In the present embodiment, differences from the first embodiment will be mainly described. For convenience of explanation, components having the same functions as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.
[0250]
  As shown in FIG. 6, the high-speed agitation type continuous extrusion mixer 54 constituting a part of the water-absorbing agent manufacturing apparatus of the present embodiment has a casing 2 as a fixed cylinder fixed horizontally, for example. ing.
[0251]
  As shown on the right side of the figure, the casing 2 is provided with a material supply port 3 for supplying and supplying powder water-absorbing resin. A cross-linking agent is provided at a position on the discharge side of the material supply port 3. A liquid supply port 4 for introducing an aqueous liquid such as the above is provided. Moreover, the discharge port 5 is formed in the left end side in the same figure.
[0252]
  Then, the continuous extrusion mixer 54 in the present embodiment is provided inside the casing 2 so as to uniformly mix the water-absorbing resin having a carboxyl group and an aqueous liquid containing a crosslinking agent capable of reacting with the carboxyl group. Around the rotating shaft 6, it has the structure which provided the some stirring blade 7 ... as a stirring member, These stirring blades 7 ... consist of two or more types from which a shape differs.
[0253]
  In the present embodiment, when the total length of the rotary shaft 6 existing in the casing 2 is 100%, the continuous extrusion mixer 54 has about 25% from the end of the material supply port 3 of the rotary shaft 6. Paddle-shaped first stirring blades 7a are provided in the length portion and a portion having a length of about 25% from the end on the discharge port 5 side, and the tip is hemispherical in the central portion other than the above. Cylindrical second stirring blades 7b are provided.
[0254]
  In the continuous extrusion mixer 54, the first agitating blade 7a, the second agitating blade 7b, the first agitating blade 7a, and so on are arranged in this order from the material supply port 3 side. By being arranged in a spiral around 6, a first region, a second region, and a third region as a mixture extrusion region are formed in this order from the material supply port 3 side.
[0255]
  Further, in the continuous extrusion mixer 54, the discharge port 5 is provided on the bottom wall of the casing 2 on the side opposite to the material supply port 3 formation side.
[0256]
  Further, in the continuous extrusion mixer 54, the first stirring blades 7a ... and the second stirring blades 7b ... are provided with attachment nuts in the lower part and fixed to the rotary shaft 6 by the attachment nuts. .
[0257]
  And said 1st stirring blade 7a ... is perpendicular | vertical with respect to the rotating shaft 6, and is a water absorbing resin extrusion surface 7a.₁Is fixed around the rotation shaft 6 so as to be inclined with respect to a plane perpendicular to the rotation shaft 6, thereby giving an extrusion thrust to the water absorbent resin.
[0258]
  In the continuous extrusion mixer 51, for example, there is a balance with other conditions. For example, the water absorbent resin extruded surface 7a of the first stirring blade 7a.₁The thrust force is adjusted by partially changing the angle between the surface and the surface perpendicular to the rotating shaft 6 and the density of the arrangement.
[0259]
  In the continuous extrusion mixer 54, the shape of the second stirring blades 7b is formed in a columnar shape, and the second stirring blades 7b are perpendicular to the rotating shaft 6. It is fixed to. Accordingly, in the second region, no pushing thrust is generated by the second stirring blades 7b, so that the water absorbent resin is pushed out only by the pushing thrust of the first stirring blades 7a arranged in the first region. It is. Further, although slightly, the thrust is reduced by receiving resistance by the second stirring blades 7b. For this reason, in the second region, the pushing thrust becomes smaller toward the discharge port 5 side.
[0260]
  In this way, the second stirring blades 7b ... are pushed out to the discharge side of the first stirring blades 7a ... more than the thrust thrust in the first region where the first stirring blades 7a ... are arranged. A second region where the thrust is reduced is formed.
[0261]
  Therefore, even in the continuous extrusion mixer 51, in the arrangement region (second region) of the second stirring blades 7b ..., the thrust thrust in the arrangement region (first region) of the first stirring blades 7b ... Extrusion thrust becomes smaller than that, and the average speed of the water-absorbent resin decreases. As a result, the water-absorbing resin stays in the arrangement region of the second stirring blades 7b, and the water-absorbing resin and the aqueous liquid are uniformly mixed by the second stirring blades 7b.
[0262]
  Also in the continuous extrusion mixer 54, the material supply port 3 for charging the powdered water-absorbing resin is formed in the arrangement region of the first stirring blades 7a, which is the first region, and the cross-linking agent is used. The liquid supply port 4 for introducing the aqueous liquid to be contained is formed in an arrangement region of the second stirring blades 7b. Thereby, also in the continuous extrusion mixer 54, the water-absorbing resin and the aqueous liquid are instantaneously brought into contact with each other instantaneously, and a mixture free from “dama” can be obtained.
[0263]
  The continuous extrusion mixer 54 is further provided with a plurality of first stirring blades 7a ... on the discharge side of the second stirring blades 7b ... as a mixture extrusion region (third region). . Thereby, the continuous extrusion mixer 54 efficiently extrudes the water absorbent resin (mixture) uniformly mixed with the aqueous liquid out of the continuous extrusion mixer 54.
[0264]
  In the continuous extrusion mixer 54, the first agitating blades 7a having the same shape are used in the first region and the third region. However, in the said 3rd area | region, the 1st stirring blade 7a is arrange | positioned so that the direction of the blade surface may differ from the direction of the blade surface of the 1st stirring blade 7a arrange | positioned in the 1st area | region. . In other words, the first stirring blades 7 a... Arranged in the respective regions adjust the direction of the pushing thrust according to the position of the discharge port 5.
[0265]
  Accordingly, in the continuous extrusion mixer 54, since the discharge port 5 is provided on the bottom wall of the casing 2, the direction of the blade surface of the first stirring blade 7a is divided between the first region and the third region. However, for example, when the discharge port 5 is provided at the end surface of the water absorbent resin discharge direction in the casing 2, the direction of the pushing thrust is set to be the same in the first region and the third region. do it.
[0266]
  As described above, in the continuous extrusion mixer 54, by providing the paddle-shaped first stirring blades 7a on the discharge side of the second stirring blades 7b, the pushing thrust in the vicinity of the discharge port 5 is increased. The mixture is preferably discharged.
[0267]
  [Embodiment 3]
  One embodiment of the present invention will be described below with reference to FIGS. In the present embodiment, differences from the first and second embodiments will be mainly described. For convenience of explanation, components having the same functions as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.
[0268]
  As shown in FIG. 7, a high-speed stirring type continuous extrusion mixer 55 constituting a part of the water-absorbing agent manufacturing apparatus of the present embodiment has a casing 2 as a fixed cylinder fixed horizontally, for example. ing.
[0269]
  As shown on the right side of the figure, the casing 2 is provided with a material supply port 3 for supplying and supplying powder water-absorbing resin. A cross-linking agent is provided at a position on the discharge side of the material supply port 3. A liquid supply port 4 for introducing an aqueous liquid such as the above is provided. Moreover, the discharge port 5 is formed in the left end side in the same figure.
[0270]
  And the continuous extrusion mixer 55 in this Embodiment is the inside of the casing 2 in order to mix uniformly the water absorbing resin which has a carboxyl group, and the aqueous liquid containing the crosslinking agent etc. which can react with this carboxyl group. Around the rotating shaft 6, it has the structure which provided the some stirring blade 7 ... as a stirring member, and these stirring blades 7 ... consist of one type which has the same shape.
[0271]
  In the present embodiment, the continuous extrusion mixer 55 includes paddle-shaped first stirring blades 7a around the rotating shaft 6 provided in the casing 2 with partially different arrangement densities. Is provided.
[0272]
  That is, in the continuous extrusion mixer 55, the first agitating blades 7a... Are, for example, the end of the material supply port 3 of the rotating shaft 6 when the total length of the rotating shaft 6 existing in the casing 2 is 100%. The portion having a length of about 25% from the end and the portion having a length of about 25% from the end on the discharge port 5 side is provided with a high arrangement density, and is provided so that the arrangement density is low in the central portion other than the above. Yes.
[0273]
  In the continuous extrusion mixer 55, the first agitating blades 7a are sequentially arranged from the material supply port 3 side so that the arrangement density thereof becomes dense, coarse, and dense. By being arranged in a spiral around, a first region, a second region, and a third region as a mixture extrusion region are formed in this order from the material supply port 3 side.
[0274]
  Further, in the continuous extrusion mixer 55, the discharge port 5 is provided on the bottom wall of the casing 2 on the side opposite to the material supply port 3 formation side.
[0275]
  In the continuous extrusion mixer 55, the first stirring blades 7a are provided with a mounting nut at the lower portion, and are fixed to the rotary shaft 6 by the mounting nut.
[0276]
  And the 1st stirring blade 7a ... arrange | positioned by the said 1st area | region and the 2nd area | region is perpendicular | vertical with respect to the rotating shaft 6, and is a water absorbing resin extrusion surface 7a.₁Is fixed around the rotation shaft 6 so as to be inclined with respect to a plane perpendicular to the rotation shaft 6, thereby giving an extrusion thrust to the water absorbent resin.
[0277]
  In the present embodiment, the continuous extrusion mixer 55 uses the stirring blade 7 having the same shape in the first region and the second region, and the direction of the blade surface (for example, the water absorbent resin extrusion surface 7a).₁The direction is also the same. In the continuous extrusion mixer 55 according to the present embodiment, the water absorbent resin extruded surface 7a of each first stirring blade 7a disposed in the first region and the second region.₁And the plane perpendicular to the rotation axis 6 are equally set to 45 °.
[0278]
  However, in the continuous extrusion mixer 55, the arrangement density of the first stirring blades 7a in the second region (the central portion) is set so that the first region (of the material supply port 3 in the rotating shaft 6). Therefore, the pushing thrust in the second region is smaller than the pushing thrust in the first region.
[0279]
  Therefore, also in this embodiment, the average speed of the water absorbent resin in the second region is lower than the average speed of the water absorbent resin in the first region. As a result, in the second region, the water absorbent resin and the water Mixing with the liquid is performed.
[0280]
  However, in the present embodiment, in the continuous extrusion mixer 55, the pushing thrust in the first region and the second region is adjusted only by the arrangement density of the first stirring blades 7a. For this reason, the change in the pushing thrust when moving from the first area to the second area and the difference in the magnitude of the pushing thrust between the first area and the second area are the same as those in the first and second embodiments. Smaller than that.
[0281]
  In the present invention, in order to perform more uniform mixing, it is preferable to change the pushing thrust force as much as possible when changing from the first region to the second region, rather than gently changing it.
[0282]
  Therefore, in order to perform more uniform mixing, for example, in the first region and the second region, the water absorbent resin extruded surface 7a of the first stirring blade 7a.₁It is preferable to further increase the difference in the thrust thrust by changing the angle formed between the axis and the plane perpendicular to the rotation shaft 6.
[0283]
  In this case, for example, as shown in the continuous extrusion mixer 55 ′ of FIG. 8, the stirring blade 7 is disposed in the second region so that the blade surface is parallel to the axial direction of the rotary shaft 6. For example, water-absorbing resin extrusion surface 7a₁By disposing it so that it faces in the opposite direction to the first region, the difference in the pushing thrust can be further increased.
[0284]
  That is, when the agitating blade 7 is arranged so that its blade surface is parallel to the axial direction of the rotating shaft 6, no pushing thrust is generated by the agitating blade 7 (first agitating blade 7a). The stirring blade 7 is, for example, a water absorbent resin extruded surface 7a.₁Is arranged so as to face the direction opposite to the first region, the stirring blade 7 (first stirring blade 7a) generates a thrust in the opposite direction to the first region.
[0285]
  In addition, the direction of the blade surface of the stirring blade 7 in each of the above regions, particularly the direction of the blade surface in the above-mentioned second region is not necessarily the same. For example, the direction of the blade surfaces of the stirring blades 7 in the second region (the water absorbent resin extruded surface 7a₁... and an angle formed by a plane perpendicular to the rotary shaft 6), as shown in the continuous extrusion mixer 55 'in FIG. Each of the thrusts can be set separately within a range in which the pushing thrust acts so that the water-absorbing resin is discharged in the direction of the discharge port 5 as the thrust is reduced.
[0286]
  Also in the continuous extrusion mixers 55 and 55 ′, as shown in FIGS. 7 and 8, on the discharge side of the second region, in the region where the arrangement density of the first stirring blades 7a is high. By forming a certain third region (mixture extrusion region), the pushing thrust in the vicinity of the discharge port 5 is increased, and the mixture is suitably discharged.
[0287]
  [Embodiment 4]
  The following will describe an embodiment of the present invention with reference to FIG. In the present embodiment, differences from the first embodiment will be mainly described. For convenience of explanation, components having the same functions as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.
[0288]
  As shown in FIG. 9, a high-speed stirring type continuous extrusion mixer 56 constituting a part of the water-absorbing agent manufacturing apparatus of the present embodiment has a casing 2 as a fixed cylinder fixed horizontally, for example. ing.
[0289]
  As shown on the right side of the figure, the casing 2 is provided with a material supply port 3 for supplying and supplying powder water-absorbing resin. A cross-linking agent is provided at a position on the discharge side of the material supply port 3. A liquid supply port 4 for introducing an aqueous liquid such as the above is provided. Moreover, the discharge port 5 is formed in the left end side in the same figure.
[0290]
  Then, the continuous extrusion mixer 56 in the present embodiment is provided inside the casing 2 in order to uniformly mix the water-absorbing resin having a carboxyl group and an aqueous liquid containing a crosslinking agent capable of reacting with the carboxyl group. The rotating shaft 6 has a structure in which a plurality of stirring blades 7 are provided as stirring blades. The stirring blades 7 are made of two or more types having different shapes.
[0291]
  In the present embodiment, the continuous extrusion mixer 56 is provided with a rectangular plate-shaped first stirring blade 7a... Around the rotating shaft 6 provided in the casing 2 and partially arranged in density. Are arranged in a double spiral shape with different shapes (sizes).
[0292]
  In the continuous extrusion mixer 56, for example, a portion (first region) having a length of about 35% from the end of the material supply port 3 in the rotating shaft 6 is the same as the first stirring blade in the first embodiment. 7a... Are arranged in a state where the lead is twice the pitch and the arrangement density is high like a double thread. On the other hand, in the portion (second region) having a length of about 65% from the end of the rotary shaft 6 on the outlet 5 side, the first stirring blades 7a formed in a rectangular thin plate shape are provided with the first It arrange | positions so that the arrangement | positioning density may become lower than an area | region.
[0293]
  In the continuous extrusion mixer 56, the average speed of the first stirring blades 7a in the first region is higher than the average speed of the first stirring blades 7a in the first region of the continuous extrusion mixer 1. It is set to be faster. That is, in the continuous extrusion mixer 56, the first agitating blades 7a are arranged so that the lead is twice the pitch. For example, in FIG. When the rotating shaft 6 makes one rotation, it moves to point B.
[0294]
  And the 1st stirring blade 7a ... distribute | arranged to the said 1st area | region and the 2nd area | region is perpendicular | vertical with respect to the rotating shaft 6, and is a water absorbing resin extrusion surface 7a.₁Is fixed around the rotation shaft 6 so as to be inclined with respect to a plane perpendicular to the rotation shaft 6, thereby giving an extrusion thrust to the water absorbent resin. However, the water absorbent resin extruded surface 7a of each first stirring blade 7a disposed in the first region and the second region.₁And the plane perpendicular to the rotation axis are equal to each other.
[0295]
  In the present embodiment, as in the third embodiment, the pushing thrust is generated both in the first region and in the second region. However, in the continuous extrusion mixer 56, due to the difference in the arrangement density and shape of the first stirring blades 7a in the first region and the second region, the pushing thrust force between the first region and the second region. Is larger than that of the continuous extrusion mixer 55 in the third embodiment.
[0296]
  Also in the present embodiment, in the second region, the pushing thrust is smaller than the pushing thrust in the first region, and the average speed of the water absorbent resin is lowered. As a result, the water-absorbing resin stays in the second region, and the water-absorbing resin and the aqueous liquid are uniformly mixed by the first stirring blades 7a disposed in the second region.
[0297]
  [Embodiment 5]
  The following will describe an embodiment of the present invention with reference to FIG. In the present embodiment, differences from the first embodiment and the second embodiment will be mainly described. For convenience of explanation, components having the same functions as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.
[0298]
  As shown in FIG. 10, a high-speed stirring type continuous extrusion mixer 57 that constitutes a part of the water-absorbing agent manufacturing apparatus of the present embodiment has a casing 2 as a fixed cylinder fixed horizontally, for example. ing.
[0299]
  As shown on the right side of the figure, the casing 2 is provided with a material supply port 3 for supplying and supplying powder water-absorbing resin. A cross-linking agent is provided at a position on the discharge side of the material supply port 3. A liquid supply port 4 for introducing an aqueous liquid such as the above is provided. Moreover, the discharge port 5 is formed in the left end side in the same figure.
[0300]
  Then, the continuous extrusion mixer 57 in the present embodiment is provided inside the casing 2 in order to uniformly mix the water-absorbing resin having a carboxyl group and an aqueous liquid containing a crosslinking agent capable of reacting with the carboxyl group. Around the rotating shaft 6, a single screw wing-like stirring blade 7 is provided as a stirring member.
[0301]
  In the present embodiment, openings 9 are provided in the blade surface of the portion that becomes the second region in the stirring blade 7. In the present embodiment, for example, when the total length of the rotating shaft 6 existing in the casing 2 is 100%, a portion having a length of about 25% from the end of the material supply port 3 of the rotating shaft 6 is defined as the first region. A portion having a length of about 25% from the end of the rotating shaft 6 on the discharge port 5 side is defined as a third region, and a central portion between the first region and the second region is defined as a second region.
[0302]
  In the continuous extrusion mixer 57, there is a balance with other conditions. For example, the extrusion thrust is adjusted by providing the stirring blade 7 with openings 9. That is, in the continuous extrusion mixer 57, the stirring blade 7 is formed in the second region so as to generate an extrusion thrust smaller than the extrusion thrust generated in the first region.
[0303]
  Therefore, also in the continuous extrusion mixer 57, in the second region, the pushing thrust is smaller than the pushing force in the first region, and the average speed of the water-absorbing resin is lowered. As a result, the water absorbent resin stays in the second region, and the water absorbent resin and the aqueous liquid are uniformly mixed by the stirring blade 7 in the second region.
[0304]
  And the said stirring blade 7 is provided with the part without an opening part in the discharge side of said 2nd area | region as a mixture extrusion area | region (3rd area | region). Thereby, in the said continuous extrusion mixer 57, the extrusion thrust of the discharge port 5 vicinity becomes large, and discharge | emission of a mixture is performed suitably.
[0305]
【Example】
  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further in detail, this invention is not limited at all by these. Various performances of the water absorbing agent were measured by the following methods.
[0306]
  (A) Absorption capacity without pressure
  0.2 g of the water-absorbing agent was uniformly placed in a non-woven bag (60 mm × 60 mm) and immersed in a 0.9 wt% sodium chloride aqueous solution (physiological saline). After 60 minutes, the bag was pulled up, drained at 250 G for 3 minutes using a centrifuge, and then the weight W of the bag₁(G) was measured. In addition, the same operation is performed without using a water absorbent, and the weight W at that time₀(G) was measured. And these W₁・ W₀From the following formula,
  Absorption capacity under no pressure (g / g)
          = (Weight W₁(G)-Weight W₀(G)) / weight of water-absorbing agent (g)
Thus, the absorption capacity (g / g) under no pressure was calculated.
[0307]
  For the water-absorbing resin, the water-absorbing resin mixture, and the water-absorbing resin granulated product, the absorption capacity (g / g) under no pressure was calculated by the same method as in the case of using the water absorbing agent.
[0308]
  (B) Absorption capacity under high pressure
  First, for the measuring device used to measure the absorption capacity under pressure,FIG.Based on
[0309]
  FIG.As shown in FIG. 1, the measuring device includes a balance 21, a container 22 having a predetermined capacity placed on the balance 21, an outside air suction pipe sheet 23, a conduit 24, a glass filter 26, and the glass filter 26. And the measurement unit 25 placed on the surface.
[0310]
  The container 22 has an opening 22a on the top and an opening 22b on the side. An outside air suction pipe 23 is fitted into the opening 22a of the container 22, and a conduit 24 is attached to the opening 22b.
[0311]
  The container 22 contains a predetermined amount of physiological saline 32. The lower end portion of the outside air suction pipe 23 is immersed in the physiological saline 32. The outside air suction pipe 23 is provided to keep the pressure inside the container 22 at almost atmospheric pressure. The glass filter 26 is formed with a diameter of 55 mm. And the container 22 and the glass filter 26 are mutually connected by the conduit | pipe 24 which consists of silicone resins. Further, the position and height of the glass filter 26 with respect to the container 22 are fixed.
[0312]
  The measurement unit 25 includes a filter paper 27, a support cylinder 28, a wire mesh 29 attached to the bottom of the support cylinder 28, and a weight 30. In the measuring unit 25, a support cylinder 28 having a filter paper 27 on the glass filter 26 and a wire mesh 29 on the bottom is placed in this order, and a weight 30 is placed inside the support cylinder 9, that is, on the wire mesh 10. It has become. The metal mesh 29 is made of stainless steel and is formed to 400 mesh (aperture 38 μm). Further, the height of the upper surface of the wire mesh 29, that is, the contact surface between the wire mesh 29 and the water absorbing agent 31 is set to be equal to the height of the lower end surface 23 a of the outside air suction pipe 23. And the predetermined amount and the water absorbing agent of a predetermined particle diameter are uniformly spread | dispersed on the metal-mesh 29. FIG. The weight 30 is 50 g / cm with respect to the water absorbent 31 on the wire mesh 29.²The weight is adjusted so that the load can be uniformly applied.
[0313]
  Using the measuring device having the above configuration, the absorption capacity of the water-absorbing agent 31 under high pressure was measured. The measurement method will be described below.
[0314]
  First, a predetermined preparatory operation such as inserting a predetermined amount of physiological saline 32 into the container 22 and inserting the outside air suction pipe 23 is performed. Next, the filter paper 27 is placed on the glass filter 26, and 0.9 g of the water absorbing agent is uniformly sprayed on the inside of the support cylinder 28, that is, on the wire mesh 29, in parallel with this placing operation. A weight 30 is placed on 31.
[0315]
  Next, the wire mesh 29 of the support cylinder 28 on which the water absorbing agent 31 and the weight 30 are placed is placed on the filter paper 27 so that the center portion thereof coincides with the center portion of the glass filter 26.
[0316]
  Then, from the time when the support cylinder 28 is placed on the filter paper 27, the weight of the physiological saline 32 absorbed by the water-absorbing agent 31 over time is obtained from the measured value of the balance 21 over 60 minutes.
[0317]
  Further, the same operation is performed without using the water absorbing agent 31, and the blank weight, that is, the weight of the physiological saline 32 absorbed by, for example, the filter paper 27 other than the water absorbing agent 31, is obtained from the measured value of the balance 21, and the blank value is obtained. It was. Next, correction is performed by subtracting the blank value, and the weight of the physiological saline 32 actually absorbed by the water-absorbing agent 31 is divided by the weight of the water-absorbing agent 31 (0.9 g). g / g) was calculated.
(C) Absorption rate
  1.000 g of a water absorbing agent was sprayed on a glass petri dish having an inner diameter of about 60 mm. Next, 20.00 g of 0.4 wt% saline set at a temperature of 25 ° C. is intravenously injected into the petri dish from the center until the water absorbing agent absorbs all the saline (visual observation). The number of seconds was measured. In addition, it shows that it is a high absorption rate, so that this time is short.
[0318]
  [Example 1]
  In the production of a water-absorbing resin having a carboxyl group, polyethylene glycol diacrylate (n = 8) was added to 5500 parts of a 33% by weight aqueous solution of sodium acrylate as a monomer component (neutralization rate 75 mol%). ) 2.9 parts was dissolved to prepare a reaction solution. Next, the reaction solution was degassed for 30 minutes in a nitrogen gas atmosphere.
[0319]
  Subsequently, the reaction solution was supplied to a reactor having a lid on a jacketed stainless steel double kneader with two sigma-shaped blades, and the inside of the reactor was replaced with nitrogen gas while keeping the reaction solution at 30 ° C. Subsequently, while stirring the reaction solution, 2.4 parts of ammonium persulfate as a polymerization initiator and 0.12 part of L-ascorbic acid as a reducing agent for promoting the decomposition of the polymerization initiator were added. Polymerization started after minutes. And it superposed | polymerized at 30 to 80 degreeC, and the water-containing gel-like polymer was taken out 60 minutes after superposition | polymerization started.
[0320]
  The obtained hydrogel polymer was spread on a 50 mesh (mesh opening 300 μm) wire net and dried with hot air at 150 ° C. for 90 minutes. Next, the dried product is pulverized using a vibration mill, and further classified with a 20-mesh wire mesh (mesh size: 850 μm), whereby the average particle size is 400 μm and the proportion of particles having a particle size of less than 150 μm is 12% by weight. A regularly crushed water-absorbing resin was obtained.
[0321]
  Next, a colored surface cross-linking agent composed of 0.1 part by weight of ethylene glycol diglycidyl ether, 4 parts by weight of water, and 1 part by weight of isopropyl alcohol with respect to 100 parts by weight of the above water-absorbing resin is shown in FIG. When the total length of the rotary shaft 6 existing in the extruder 1, that is, the casing 2 is 100%, the rotary shaft 6 is provided at a portion of about 35% from the end of the material supply port 3. A plate-shaped first stirring blade 7a ... and a high-speed stirring mixer having a cylindrical second stirring blade 7b ... provided at a length of about 65% from the end on the discharge port 5 side are charged. The mixture reaction was continuously performed.
[0322]
  The resulting mixture was uniformly colored, and when this mixture was passed through a 20-mesh wire mesh, the mass that did not pass was 0.2%.
[0323]
  Thereafter, the mixture was heat-treated at 195 ° C. for 40 minutes to obtain NO. 1 water-absorbing agent was obtained. No. above. The absorption capacity of one water-absorbing agent under no pressure and high pressure was measured. The measurement results are shown in Table 1.
[0324]
  [Example 2]
  For 100 parts by weight of the same water-absorbent resin as in Example 1, 0.5 part by weight of glycerin as the first surface cross-linked part, 0.1 part by weight of ethylene glycol diglycidyl ether as the second surface cross-linked part, and 3 parts by weight of water The colored surface cross-linking agent consisting of 1 part by weight and 1 part by weight of ethyl alcohol was continuously mixed using the same continuous extrusion mixer 1 as used in Example 1 above.
[0325]
  The resulting mixture was uniformly colored, and when this mixture was passed through a 20 mesh wire mesh, the mass that did not pass was 0%.
[0326]
  Thereafter, the mixture was heat-treated at 195 ° C. for 40 minutes to obtain NO. Two water-absorbing agents were obtained. No. above. 2 Absorption capacity of the water-absorbing agent under no pressure and high pressure was measured. The measurement results are shown in Table 1.
[0327]
  Example 3
  For 100 parts by weight of the same water-absorbing resin as in Example 1 and Example 2, 0.5 parts by weight of glycerin as the first surface cross-linked part and 0.1 parts by weight of ethylene glycol diglycidyl ether as the second surface cross-linked part When the colored surface cross-linking agent composed of 3 parts by weight of water and 1 part by weight of ethyl alcohol is used as the continuous extrusion mixer 54 shown in FIG. In which a paddle-shaped first agitating blade 7a is provided in a portion having a length of about 25% from the end of the material supply port 3 and a portion having a length of about 25% from the end on the discharge port 5 side. In the central part other than the above, the mixture was continuously mixed using a high-speed stirring mixer having a cylindrical second stirring blade 7b.
[0328]
  The resulting mixture was uniformly colored, and when this mixture was passed through a 20-mesh wire mesh, the mass that did not pass was 0.5%.
[0329]
  Thereafter, the mixture was heat-treated at 195 ° C. for 40 minutes to obtain NO. Three water-absorbing agents were obtained. No. above. The absorption capacity of the three water-absorbing agents under no pressure and high pressure was measured. The measurement results are shown in Table 1.
[0330]
  Example 4
  With respect to 100 parts by weight of the same water-absorbing resin as in Examples 1 to 3, a colored surface cross-linking agent comprising 0.1 part by weight of ethylene glycol diglycidyl ether, 4 parts by weight of water and 1 part by weight of isopropyl alcohol The mixture was continuously stirred at high speed using a continuous extrusion mixer 55 shown in FIG.
[0331]
  The resulting mixture was unevenly colored, and “dama” having a high degree of coloring was visually observed. Moreover, when this mixture was passed through a 20-mesh wire mesh, there was 7.3% of mass that did not pass.
[0332]
  Thereafter, the mixture was heat-treated at 195 ° C. for 40 minutes in the same manner as in Examples 1 to 3 to obtain NO. 4 water-absorbing agents were obtained. The above NO. The absorption capacity of the four water-absorbing agents under no pressure and high pressure was measured. The measurement results are shown in Table 1.
[0333]
  Example 5
  100 parts by weight of the same water-absorbing resin as in Examples 1 to 3 above, 0.5 parts by weight of glycerin as the first surface cross-linked part, 0.1 parts by weight of ethylene glycol diglycidyl ether as the second surface cross-linked part A colored surface cross-linking agent composed of 3 parts by weight of water and 1 part by weight of ethyl alcohol was continuously mixed using a continuous extrusion mixer 55 shown in FIG.
[0334]
  The resulting mixture was unevenly colored, and “dama” having a high degree of coloring was visually observed. Moreover, when this mixture was passed through a 20-mesh wire mesh, 5.4% of lumps that did not pass were present.
[0335]
  Thereafter, the mixture was heat-treated at 195 ° C. for 40 minutes to obtain NO. 5 water-absorbing agents were obtained. The above NO. The absorption capacity of the 5 water-absorbing agent under no pressure and high pressure was measured. The measurement results are shown in Table 1.
[0336]
[Table 1]

[0337]
  From the results of Table 1, as shown in Examples 1 to 3, the water-absorbing resin and the crosslinking agent were mixed in a continuous extrusion mixer 1/54 equipped with two or more types of stirring blades 7. In the case of reaction, as shown in Example 4 and Example 5, continuous extrusion is provided that includes one type (same shape) of stirring blades 7 and adjusts the thrust thrust by changing the arrangement density. It can be seen that an excellent water-absorbing agent can be obtained by the absorption capacity under high pressure as compared with the case of mixing and reacting in the type mixer 55. Accordingly, it has been found that a water-absorbing agent exhibiting a higher absorption capacity under high pressure can be obtained by mixing and stirring with the continuous extrusion mixer 1/54.
[0338]
  Example 6
  The NO. The impact force (A) is applied to one water-absorbing agent by the method described above, and NO. 6 water-absorbing agents were obtained. In addition, this NO. With respect to 6 water-absorbing agents, the measurement of the absorption capacity under high pressure before and after applying the impact was performed by the above method. The measurement results are shown in Table 2.
[0339]
  Example 7
  The NO. No. 2 is applied to the water-absorbing agent by applying the impact force (A) by the aforementioned method. 7 water-absorbing agent was obtained. In addition, this NO. For the 7 water-absorbing agent, the absorption capacity under high pressure before and after the impact was applied was measured by the above method. The measurement results are shown in Table 2.
[0340]
  Example 8
  The NO. No. 3 is applied to the water-absorbing agent by applying the impact force (A) by the method described above. 8 water-absorbing agents were obtained. In addition, this NO. For the 8 water-absorbing agent, the absorption capacity under high pressure before and after the impact was applied was measured by the above method. The measurement results are shown in Table 2.
[0341]
[Table 2]

[0342]
  From the results shown in Table 2, when impact force (A) was applied to the water-absorbing agent shown in Examples 1 to 3, the physical property value Q / P was 0 as shown in Examples 6 to 8. It was found that the absorption capacity under high pressurization due to impact did not change much, that is, the absorption capacity under high pressurization before impact could be maintained.
[0343]
  Example 9
  The NO. The impact force (B) is applied to one water-absorbing agent by the method described above and NO. Nine water-absorbing agents were obtained. In addition, this NO. For the 9 water-absorbing agent, the absorption capacity under high pressure before and after applying the impact was measured by the above method. The measurement results are shown in Table 3.
[0344]
  Example 10
  The NO. 2 Impact force (B) is applied to the water-absorbing agent by the method described above, and NO. Ten water-absorbing agents were obtained. In addition, this NO. For 10 water-absorbing agents, the absorption capacity under high pressure before and after the impact was applied was measured by the above method. The measurement results are shown in Table 3.
[0345]
  Example 11
  The NO. No. 3 by applying impact force (B) to the water-absorbing agent by the method described above. 11 water-absorbing agent was obtained. In addition, this NO. For 11 water-absorbing agent, the absorption capacity under high pressure before and after the impact was applied was measured by the above method. The measurement results are shown in Table 3.
[0346]
  Example 12
  The NO. 5 Impact force (B) is applied to the water-absorbing agent by the method described above, and NO. 12 water-absorbing agents were obtained. In addition, this NO. With respect to 12 water-absorbing agents, the above-described method was used to measure the absorption capacity under high pressure before and after impact application. The measurement results are shown in Table 3.
[0347]
[Table 3]

[0348]
  From the results shown in Table 3, when impact force (B) was applied to the water-absorbing agents shown in Examples 1 to 3 and Example 5, as shown in Examples 9 to 12, the physical property value Y / X was 0.86 to 1.00, and it was found that the absorption capacity under high pressure by impact did not change much, that is, the absorption capacity under high pressure before impact could be maintained.
[0349]
  Example 13
  In the production of a water-absorbing resin having a carboxyl group, 2.7 parts of trimethylolpropane triacrylate as an internal cross-linking agent was added to 5500 parts of a 38 wt% aqueous solution of sodium acrylate (neutralization rate: 75 mol%) as a monomer component. Part was dissolved to prepare a reaction solution. The usage-amount of the trimethylol propane triacrylate with respect to a monomer component is 0.04 mol%. Next, the reaction solution was degassed for 30 minutes in a nitrogen gas atmosphere.
[0350]
  Next, the reaction solution was supplied to a reactor having a lid on a jacketed stainless steel double kneader with two sigma blades, and the inside of the reactor was replaced with nitrogen gas while keeping the reaction solution at 30 ° C. . Subsequently, while stirring the reaction solution, 2.8 parts of ammonium persulfate as a polymerization initiator and 0.02 part of L-ascorbic acid as a reducing agent were added, and the same polymerization operation as in Example 1 was performed. As a result, a hydrogel polymer fragmented into about 0.1 mm to 3 mm was obtained.
[0351]
  Next, after the water-containing gel-like polymer is dried in the same manner as in Example 1, the rolls used for pulverization have predetermined intervals (roll gaps of about 1.63 mm, about 0.43 mm, and about 0.15 mm). In this way, it is pulverized using a roll granulator type pulverizer formed in three stages, and then classified with a JIS standard sieve having an aperture of 850 μm, whereby an irregularly pulverized water-absorbing resin having an average particle size of 300 μm ( A) was obtained. Furthermore, this water-absorbing resin (A) is classified by a JIS standard sieve having an opening of 150 μm, whereby a water-absorbing resin having a particle diameter of 850 μm to 150 μm (A₁) Water absorbent resin fine powder (A₂) 13.7 wt% was obtained.
[0352]
  Next, the above water absorbent resin fine powder (A₂) In the continuous extrusion mixer 1 shown in FIG. 1 at a rate of 2 kg / min, and ion-exchanged water is absorbed from the liquid supply port 4 having a diameter of 5 mm provided in the continuous extrusion mixer 1. Resin fine powder (A₂) The water-absorbent resin fine powder (A) was added at a ratio of 130 parts by weight of ion-exchanged water to 100 parts by weight.₂) And ion-exchanged water were continuously mixed. As a result, a particulate uniform hydrogel granulated product was continuously discharged from the discharge port 5. The obtained particulate hydrogel granules were aggregates of individual particles, most of which were uniform hydrogel granules having a particle size of about 1 mm to 5 mm. The solid content of the hydrated gel granulated product was 43.6% by weight. In addition, solid content of a water-containing gel-like granulated material shows the quantity (content) of the water absorbing resin in a water-containing gel-like granulated material.
[0353]
  Next, the hydrated gel-like granulated product was spread on a JIS standard wire mesh with an opening of 300 μm so as to have a thickness of about 5 cm, and dried with a hot air circulation dryer at 160 ° C. As a result, the hydrated gel-like granulated product is uniformly and sufficiently dried to a solid content of 90% by weight or more, and a powder-like dry granulated product that can be easily crushed by granulated particles is obtained. Obtained. The mass exceeding 10 mm in the dry granulated product was only 5%.
[0354]
  Next, the dry granulated product is pulverized with the roll granule type pulverizer and the roll gap widened (final roll gap is about 0.27 mm), and classified by a JIS standard sieve having an opening of 850 μm. A water-absorbent resin granulated product (1) was obtained.
[0355]
  The water absorbent resin granulated product (1), water absorbent resin (A), water absorbent resin (A₁), And water absorbent resin fine powder (A₂) Particle size distribution, absorption capacity under no pressure and granulation failure rate were measured. The particle size distribution is shown in Table 4, and the measurement results of absorption ratio and granulation failure rate are shown in Table 5. Further, the water absorbent resin fine powder (A₂) Is an electron micrograph (50 ×) shown in FIG.
[0356]
  Furthermore, with respect to 100 parts by weight of the water absorbent resin granulated product (1), 0.05 part by weight of ethylene glycol diglycidyl ether, 0.75 part by weight of glycerin, 3 parts by weight of water, 0.75 part by weight of isopropyl alcohol, and By mixing a surface cross-linking agent composed of 0.5 part by weight of lactic acid and heating at 200 ° C. for 40 minutes, No. 13 water-absorbing agents were obtained. The above measurement NO. The absorption capacity, absorption rate, and granulation failure rate of 13 water-absorbing agents under no pressure and high pressure were measured. The measurement results are shown in Table 6.
[0357]
  Moreover, the electron micrograph (50 times) of the said water absorbent resin granulated material (1) is shown in FIG. The water absorbent resin granulated product (1) is a water absorbent resin fine powder (A) having a particle size of less than 150 μm shown in FIG.₂) Is used, but particles having a particle size of 300 μm to 850 μm become agglomerated aggregates (aggregates) of approximately primary particles that account for about 80%, and as a result, defined by impact force (B) The granulated product (aggregate) having a high granulation strength with a granulation failure rate of 2.4% by weight was obtained.
[0358]
  Although not shown, in the optical micrograph of the water-containing gel-like granule before drying obtained in this example, the water-containing gel-like granule is an agglomerate of each individual water-containing gel. It has also been confirmed separately that the fact that when granulated with water containing no cross-linking agent, it swells by being divided into a plurality of particles before granulation after water absorption swelling.
[0359]
  Example 14
  In Example 13, the water-absorbing resin fine powder (A₂) The same reaction and operation as in Example 13 was carried out except that the amount of ion-exchanged water added to 100 parts by weight was changed from 130 parts by weight to 163 parts by weight, and the solid content was 38.0% by weight. A hydrogel granulated product was obtained.
[0360]
  Thereafter, the hydrogel granulated product was dried by the same method as in Example 13. As a result, the water-containing gel-like granulated product was uniformly and sufficiently dried, and a powdery dry granulated product capable of easily crushing the granulated particles by hand was obtained. The mass exceeding 10 mm in the dry granulated product was only 5%.
[0361]
  Next, the dried granulated product was pulverized and classified in the same manner as in Example 13 to obtain a water absorbent resin granulated product (2). The water-absorbent resin granulated product (2) was measured for particle size distribution, absorption capacity under no pressure and granulation failure rate. The particle size distribution is shown in Table 4, and the measurement results of absorption ratio and granulation failure rate are shown in Table 5.
[0362]
  Further, using the water-absorbent resin granulated product (2), the same mixing and heating treatment as in Example 13 was performed, and No. 1 was obtained. 14 water-absorbing agents were obtained. The above NO. The absorption capacity, absorption rate, and granulation failure rate of 14 water-absorbing agents under no pressure and high pressure were measured. The measurement results are shown in Table 6.
[0363]
  Example 15
  In Example 13, the water-absorbing resin fine powder (A₂) The same reaction and operation as in Example 13 was performed except that the amount of ion-exchanged water added to 100 parts by weight was changed from 130 parts by weight to 74 parts by weight, and the solid content was 57.6% by weight. A hydrogel granulated product was obtained. Although the mixing was uniform, the uniformity of the mixing was slightly inferior to Examples 13 and 14.
[0364]
  Thereafter, the hydrogel granulated product was dried by the same method as in Example 13. As a result, the water-containing gel-like granulated product was uniformly and sufficiently dried, and a powdery dry granulated product capable of easily crushing the granulated particles by hand was obtained. The mass exceeding 10 mm in the dry granulated product was only 5%.
[0365]
  Next, the dried granulated product was pulverized and classified in the same manner as in Example 13 to obtain a water absorbent resin granulated product (3). The water-absorbent resin granulated product (3) was measured for particle size distribution, absorption capacity under no pressure, and granulation failure rate. The particle size distribution is shown in Table 4, and the measurement results of absorption ratio and granulation failure rate are shown in Table 5.
[0366]
  Further, using the water-absorbent resin granulated product (3), the same mixing and heating treatment as in Example 13 was carried out to obtain No.1. 15 water-absorbing agents were obtained. This NO. The absorption capacity, absorption rate, and granulation failure rate of 15 water-absorbing agents under no pressure and high pressure were measured. The measurement results are shown in Table 6.
[0367]
  Example 16
  In Example 13, the water-absorbing resin fine powder (A₂) The same reaction and operation as in Example 13 was carried out except that the amount of ion-exchanged water added to 100 parts by weight was changed from 230 parts by weight to 41 parts by weight, and the solid content was 70.9% by weight. A hydrogel granulated product was obtained. In addition, although mixing was uniform, it was slightly inferior to Example 15, and the obtained hydrogel granule was adhered to the inner surface of the casing 2 of the continuous extrusion mixer 1, Aggregation was likely to occur.
[0368]
  Thereafter, the hydrogel granulated product was dried by the same method as in Example 13. As a result, the water-containing gel-like granulated product was uniformly and sufficiently dried, and a powdery dry granulated product capable of easily crushing the granulated particles by hand was obtained. The mass exceeding 10 mm in the dry granulated product was only 5%.
[0369]
  Next, the dried granulated product was pulverized and classified in the same manner as in Example 13 to obtain a water absorbent resin granulated product (4). The water-absorbent resin granulated product (4) was measured for particle size distribution, absorption capacity under no pressure and granulation failure rate. The particle size distribution is shown in Table 4, and the measurement results of absorption ratio and granulation failure rate are shown in Table 5.
[0370]
  Further, using the water-absorbent resin granulated product (4), the same mixing and heating treatment as in Example 13 was carried out to obtain No.1. 16 water-absorbing agents were obtained. This NO. The absorption capacity, absorption rate, and granulation failure rate of 16 water-absorbing agents under no pressure and high pressure were measured. The measurement results are shown in Table 6.
[0371]
  [Comparative Example 1]
  In Example 13, a water absorbent resin fine powder (A₂) And ion-exchanged water are mixed in the same reaction and operation as in Example 13 except that the conventional continuous extrusion mixer 100 shown in FIG. 21 is used instead of the continuous extrusion mixer 1. went. However, the mixture obtained by the conventional continuous extrusion mixer 100 is not a granulated product but mainly a gel-like lump of 1 cm to 5 cm. As a result, the outlet of the continuous extrusion mixer 100 106 could not be continuously discharged. Next, although it tried to dry with respect to the said gel-like lump by the method similar to Example 1, it did not dry. Moreover, physical properties such as an increase in water-soluble components were observed.
[0372]
  [Comparative Example 2]
  In Comparative Example 1, the water-absorbent resin fine powder (A₂) And ion-exchanged water are mixed with water absorbent resin fine powder (A₂) The same reaction and operation as in Comparative Example 1 was performed except that the amount of ion-exchanged water added to 100 parts by weight was changed from 130 parts by weight to 10 parts by weight. However, the water absorbent resin fine powder (A₂) Has a high absorption rate, and the mixture obtained by the conventional continuous extrusion mixer 100 contains not a hydrogel granulated product but a large amount of lumpy powdered granulated product, and the aqueous liquid is completely distributed. The water-absorbent resin fine powder (A₂).
[0373]
  Next, the dama-like powdered granulated product was dried, ground and classified in the same manner as in Example 13 to obtain a comparative water absorbent resin granulated product (1). The comparative water absorbent resin granulated product (1) was measured for particle size distribution, absorption capacity under no pressure, and granulation failure rate. The particle size distribution is shown in Table 4, and the measurement results of absorption ratio and granulation failure rate are shown in Table 5.
[0374]
  Moreover, the electron micrograph (50 times) of the said comparative water absorbent resin granulated material (1) is shown in FIG. The comparative water absorbent resin granulated product (1) is a water absorbent resin fine powder (A) having a particle size of less than 150 μm shown in FIG.₂), But there are only about 24% by weight of granulated material of 150 μm or more, and the granulation is also point contact of individual fine powder, and as a result, is defined by impact force (B). It was a weak granulated product (aggregate) with a granulation failure rate of 100% by weight.
[0375]
  Further, using the comparative water-absorbent resin granulated product (1), the same mixing and heating treatment as in Example 13 was carried out to obtain No.1. 1 A water absorbing agent for comparison was obtained. No. above. 1 The absorption capacity, absorption rate, and granulation failure rate of the comparative water-absorbing agent under no pressure and high pressure were measured. The measurement results are shown in Table 6.
[0376]
  [Comparative Example 3]
  In Example 13, instead of the water absorbent resin granulated product (1), the water absorbent resin (A₁) 86.3% by weight, water absorbent resin fine powder (A₂) Was used in the same manner as in Example 13 except that the water-absorbent resin (A) containing 13.7 wt% was used. 2 A water-absorbing agent for comparison was obtained. In addition, this NO. 2 The absorption capacity, absorption rate, and granulation failure rate of the comparative water-absorbing agent under no pressure and high pressure were measured. The measurement results are shown in Table 6.
[0377]
  Example 17
  In Example 1, the same reaction and operation as in Example 1 were performed, except that the amount of polyethylene glycol diacrylate (n = 8) used as the internal crosslinking agent was changed from 2.9 parts to 3.9 parts. Thus, a hydrogel polymer was obtained.
[0378]
  Next, after the above hydrogel polymer was dried in the same manner as in Example 1, a roll granulator type pulverizer was set so that the roll gap was narrower than that in Example 13 (final roll gap was about 0.15 mm). And pulverizing with a JIS standard sieve having an opening of 850 μm, an irregularly crushed water-absorbing resin (B) having an average particle size of 260 μm was obtained. Furthermore, this water-absorbing resin (B) is classified with a JIS standard sieve having an opening of 150 μm, whereby a water-absorbing resin (B) having a particle size of 850 μm to 150 μm.₁) Water-absorbing resin fine powder (B₂) 18.0 wt% was obtained.
[0379]
  Next, the water absorbent resin fine powder (B₂) At a rate of 2 kg / min into the continuous extrusion mixer 1 shown in FIG. 1 and 0.1 part by weight of glycerin from the liquid supply port 4 having a diameter of 5 mm provided in the continuous extrusion mixer 1. Ion-exchanged water dissolved in water-absorbent resin fine powder (B₂) The above water absorbent resin fine powder (B₂) And ion-exchanged water containing glycerin were continuously mixed. As a result, a particulate uniform hydrogel granulated product was continuously discharged from the discharge port 5. The obtained particulate hydrogel granules were aggregates of individual particles, most of which were uniform hydrogel granules having a particle size of about 1 mm to 5 mm. Further, the solid content of the obtained hydrogel granule was 38.0% by weight.
[0380]
  Next, the hydrated gel-like granulated product was spread on a JIS standard wire mesh with an opening of 300 μm so as to have a thickness of about 5 cm, and dried with a hot air circulation dryer at 160 ° C. As a result, the hydrated gel-like granulated product was uniformly and sufficiently dried, and a powdery dry granulated product that could be easily crushed by hand was obtained. The mass exceeding 10 mm in the dry granulated product was only 5%.
[0381]
  Then, this dried granulated product was pulverized using a roll granulator type pulverizer set to the same roll gap (final roll gap of about 0.27 mm) as in the dried granulated product in Example 13, and then By classifying with a JIS standard sieve having an opening of 850 μm, a water absorbent resin granulated product (5) was obtained.
[0382]
  The water-absorbent resin granules (5), water-absorbent resin (B), water-absorbent resin (B) thus obtained are obtained.₁), And water absorbent resin fine powder (B₂) Particle size distribution, absorption capacity under no pressure and granulation failure rate were measured. The particle size distribution is shown in Table 4, and the measurement results of absorption ratio and granulation failure rate are shown in Table 5.
[0383]
  Further, using the water-absorbent resin granulated product (5), the same mixing and heating treatment as in Example 13 was carried out to obtain No.1. 17 water-absorbing agents were obtained. In addition, this No. The absorption capacity, absorption speed, and granulation failure rate of 17 water-absorbing agent under no pressure and high pressure were measured. The measurement results are shown in Table 6.
[0384]
[Table 4]

[0385]
[Table 5]

[0386]
[Table 6]

[0387]
  From the results of Examples 13 to 17 and Comparative Examples 1 to 3, the continuous extrusion mixer 1 of the present application having two or more types of stirring blades 7. It turns out that the water-absorbing-resin granulated material excellent in granulation strength is obtained by granulating. In addition, it can be seen that a water-absorbing agent that is strong against mechanical stress and has a high water-absorbing speed can be obtained by using a water-absorbent resin granulated product having excellent granulation strength as a raw material for the water-absorbing agent. On the other hand, when the conventional continuous extrusion mixer 100 having a constant extrusion thrust is used, if there is a large amount of water added to the water absorbent resin fine powder, it will not become a granulated product, and conversely If the amount is small, it is understood that a water-absorbent resin granulated product having excellent granulation strength cannot be obtained.
[0388]
  Example 18
  In Example 5, the water absorbent resin extruded surface 7a of the stirring blade 7 (first stirring blade 7a) provided in the continuous extrusion mixer 55 shown in FIG.₁And the plane perpendicular to the rotating shaft 6 (hereinafter simply referred to as the angle of the water-absorbing resin extrusion surface), depending on the arrangement area of the stirring blades 7 when the total length of the rotating shaft is 100%. By changing variously, the water-absorbent resin and the surface cross-linking agent were mixed under different mixing conditions from Example 5. And the ratio of "dama" in the obtained mixture was measured.
[0389]
  Subsequently, after passing the said mixture through a 20 mesh metal-mesh, the water absorbing agent was obtained by heat-processing this mixture for 40 minutes at 195 degreeC. The absorption capacity of the water-absorbing agent under no pressure and high pressure was measured. The measurement results are shown in Table 7 together with the mixing conditions in the continuous extrusion mixer 55.
[0390]
[Table 7]

[0390]
  In Table 7 above, “feed” and “return” indicate the direction of the pushing thrust with respect to the pushing direction of the water absorbent resin. For example, as shown in FIG. 17, with respect to the direction of arrow A, which is the water absorbent resin discharge direction (that is, the direction of water absorbent resin traveling from the material supply port 3 side to the discharge port 5 side in the continuous extrusion mixer 55). When the rotary shaft 6 rotates in the direction of arrow B, “feed” occurs when the thrust is generated in the same direction as the direction A of the water absorbent resin, and pushes in the direction C opposite to the direction A. A case where thrust is generated is referred to as “return”.
[0392]
  Therefore, “feed 45 °” means the water absorbent resin extruded surface 7 a of the stirring blade 7.₁And a plane perpendicular to the rotating shaft 6 is 45 °, which indicates that a thrust thrust is generated in the direction of travel of the water absorbent resin. Further, “return 45 °” means the water absorbent resin extruded surface 7 a of the stirring blade 7.₁And a plane perpendicular to the rotating shaft 6 is 45 °, which indicates that a pushing thrust is generated in the direction opposite to the water absorbent resin traveling direction.
[0393]
  Further, the horizontal angle of the water-absorbing resin extrusion surface means that the blade surface of the stirring blade 7 is in a state parallel to the axial direction of the rotary shaft 6, and the angle of the water-absorbing resin extrusion surface is set to be horizontal. If this is the case, the pushing thrust by the stirring blade 7 is not newly generated.
[0394]
  From the results of Table 7 above, by providing the discharge side with a region where the thrust thrust is reduced by variously changing the angle of the water absorbent resin extrusion surface of the stirring blade 7 (direction of the blade surface of the stirring blade 7), It can be seen that the resin and the aqueous liquid containing the surface cross-linking agent can be more uniformly mixed.
[0395]
  As described above, the water-absorbing agent of the present invention is a water-absorbing agent obtained by mixing and reacting a water-absorbing resin having a carboxyl group and a crosslinking agent that reacts with the carboxyl group. When an impact force (A) is applied by applying a load, the pressure in the water absorbent after the impact is 50 g / cm.²If the absorption capacity at Q is Q and the absorption capacity at the same pressure in the water-absorbing agent before impact is P
    P ≧ 20 (g / g)
And
    Q / P ≧ 0.85
It is the composition which is.
[0396]
  Further, as described above, the water absorbing agent of the present invention is a water absorbing agent obtained by mixing and reacting a water-absorbing resin having a carboxyl group and a crosslinking agent that reacts with the carboxyl group. When an impact force (B) is applied by applying a predetermined vibration, the pressure in the water absorbent after the impact is 50 g / cm.²Assuming that the absorption capacity at Y is Y and the absorption capacity at the same pressure in the water absorbent before impact is X,
    X ≧ 20 (g / g)
And
    Y / X ≧ 0.90
It is the composition which is.
[0397]
  According to said structure, the water absorbing agent of this invention has the outstanding absorption performance, and is strong to mechanical stress. Therefore, it is possible to provide a water-absorbing agent that maintains its excellent absorption performance in the final product without substantially deteriorating its water-absorbing characteristics even when subjected to mechanical stress applied during transportation in a manufacturing plant or processing by a user. . Since each of the above water-absorbing agents can maintain its excellent absorption characteristics even after being processed into an absorbent article as a final product by the user, various absorbent articles, in particular, paper that places importance on absorption characteristics under pressure. It is suitable for absorbent articles such as sanitary materials including absorbent bodies such as diapers, sanitary napkins and incontinence pads.
[0398]
  Further, the water-absorbing agent of the present invention is a water-absorbing agent obtained by surface-crosslinking a water-absorbing resin granulated product having an average particle diameter of 200 μm to 800 μm as described above, and is 50 g / cm. ² The absorption capacity under pressure is 20 g / g or more, the absorption rate is 25 seconds or less, and the granulation failure rate is 10% by weight or less.
[0399]
  According to the above configuration, the conventional granulation methods have mutually conflicting properties, and at the same time, the three physical properties of absorption capacity under high pressure, granulation strength, and absorption speed, which were unsatisfactory properties at the same time, are simultaneously obtained. A water-absorbing agent that can be satisfied can be provided.
[0400]
  Furthermore, as described above, the method for producing a water-absorbing agent of the present invention includes at least one kind of stirring that imparts thrust to the water-absorbing resin by pushing the water-absorbing resin having a carboxyl group around the rotation axis inside the fixed cylinder. After supplying the first region in the stirring-type continuous extrusion mixer provided with the members and dispersing the water-absorbent resin in the first region, the extrusion thrust is smaller than the extrusion thrust in the first region. It is the structure which extrudes into two area | regions and mixes the said water absorbing resin and aqueous liquid in this 2nd area | region.
[0401]
  As described above, the method for producing a water-absorbing agent of the present invention is configured to supply the aqueous liquid to the second region in the method for producing each water-absorbing agent described above.
[0402]
  As described above, the method for producing a water-absorbing agent of the present invention is a configuration in which the aqueous liquid contains a crosslinking agent capable of reacting with a carboxyl group in each of the methods for producing each water-absorbing agent.
[0403]
  According to the above configuration, after the water-absorbing resin is dispersed in the first region, the water-absorbing resin is extruded into the second region having a smaller pushing thrust than the pushing force in the first region, By mixing the aqueous liquid, in the second region, the average speed of the water absorbent resin dispersed in the first region is reduced, and sufficient mixing and stirring time for the water absorbent resin and the aqueous liquid is ensured. The water-absorbing resin dispersed in the first region and the aqueous liquid can be quickly and uniformly mixed. As a result, the mixing and reaction of the water-absorbing resin having a carboxyl group and an aqueous liquid containing a crosslinking agent capable of reacting with the carboxyl group is efficiently performed, and uniform mixing can be ensured. Therefore, according to the above configuration, it exhibits high absorption capacity under pressure, and maintains its excellent water absorption performance even after carrying out transportation in a manufacturing plant or processing of the final product by a user, in the final product, Regardless of the method of use, it is possible to provide a method for producing a water-absorbing agent that can produce a water-absorbing agent that can always exhibit excellent characteristics.
[0404]
  In addition, as described above, the method for producing the water-absorbing agent of the present invention is a water-absorbing resin having an average particle diameter of 10 μm to 150 μm (specifically, an average particle diameter of 10 μm to 150 μm obtained by classification with a JIS standard sieve). (Water-absorbent resin) After mixing 70 parts by weight to 400 parts by weight of an aqueous liquid with 100 parts by weight to obtain a hydrated gel-like granule having an average particle size of 0.3 mm to 10 mm, Surface cross-linking of a water-absorbent resin granulated product having an average particle size of 200 μm to 800 μm obtained by shrink drying at 110 ° C. to 300 ° C. and classification (specifically, classification with a JIS standard sieve) under non-pulverizing conditions. It is a configuration.
[0405]
  According to the above configuration, the conventional granulation methods have mutually conflicting properties, and at the same time, the three physical properties of absorption capacity under high pressure, granulation strength, and absorption speed, which were unsatisfactory properties at the same time, are simultaneously obtained. A water-absorbing agent that can be satisfied can be provided.
[0406]
  The water absorbing agent manufacturing apparatus of the present invention is a water absorbing agent manufacturing apparatus having a stirring type continuous extrusion mixer for mixing a water absorbing resin having a carboxyl group and an aqueous liquid as described above, The continuous extrusion mixer includes a fixed cylinder having a rotating shaft therein, and at least one kind of stirring member is disposed around the rotating shaft to disperse the water-absorbing resin supplied in the fixed cylinder. It is the structure provided so that the 2nd area | region where extrusion thrust is smaller than the extrusion thrust in an area | region may be formed in the discharge | emission side.
[0407]
  In addition, the water absorbing agent manufacturing apparatus of the present invention is a water absorbing agent manufacturing apparatus having a stirring type continuous extrusion mixer for mixing a water absorbing resin having a carboxyl group and an aqueous liquid as described above. The continuous extrusion mixer includes a fixed cylinder having a rotating shaft therein, and at least one kind of stirring member disperses the water-absorbing resin supplied in the fixed cylinder around the rotating shaft. A first region as a dispersion region and a second region as a mixing region that is provided on the discharge side from the first region and that mixes the water absorbent resin dispersed in the dispersion region with the aqueous liquid are formed. It is the structure provided to do.
[0408]
  As described above, the water absorbing agent manufacturing apparatus of the present invention is the water absorbing agent manufacturing apparatus, wherein the fixed cylinder of the continuous extrusion mixer is a first supply port for supplying the water absorbing resin, and A second supply port for supplying the aqueous liquid, the second supply port being provided in the second region.
[0409]
  As described above, the water absorbing agent manufacturing apparatus of the present invention is the above-described water absorbing agent manufacturing apparatus, wherein the fixed cylinder of the continuous extrusion mixer is a first supply port for supplying the water absorbing resin; A second supply port for supplying the aqueous liquid, the second supply port being provided at a boundary region between the first region and the second region. It is the composition which is done.
[0410]
  As described above, the water-absorbing agent manufacturing apparatus of the present invention is formed in the shape of each of the water-absorbing-agent manufacturing apparatuses, which is provided on the water-absorbing resin supply side and generates an extrusion thrust around the rotating shaft. A plurality of first agitating members, and a plurality of first agitating members that are provided on the discharge side of the first agitating members and that form a region where the pushing thrust is smaller than the pushing thrust in the region where the first agitating members are disposed. The second stirring member is sequentially arranged.
[0411]
  The water absorbing agent manufacturing apparatus of the present invention is a water absorbing agent manufacturing apparatus having a stirring type continuous extrusion mixer for mixing a water absorbing resin having a carboxyl group and an aqueous liquid as described above, The continuous extrusion mixer includes a fixed cylinder having a rotation shaft therein, and two or more types of stirring blades having different shapes are provided around the rotation shaft.
[0412]
  As described above, the water-absorbing agent manufacturing apparatus of the present invention is configured such that, in the water-absorbing agent manufacturing apparatus, the first stirring member is formed in a plate shape.
[0413]
  As described above, the water absorbing agent manufacturing apparatus of the present invention is configured such that, in each of the water absorbing agent manufacturing apparatuses, the second stirring member is formed in a columnar shape.
[0414]
  Furthermore, as described above, the water absorbent production apparatus of the present invention is a water absorbent production apparatus having a stirring type continuous extrusion mixer for mixing a water absorbent resin having a carboxyl group and an aqueous liquid. The continuous extrusion mixer includes a fixed cylinder having a rotating shaft inside, a stirring member having the same shape is arranged around the rotating shaft, and a plane perpendicular to the water absorbent resin extrusion surface and the rotating shaft. The first region for dispersing the water-absorbing resin supplied into the fixed cylinder, and the first region closer to the discharge side than the first region. And a second region having a smaller pushing thrust than the pushing thrust.
[0415]
  As described above, the water absorbing agent manufacturing apparatus of the present invention has a configuration in which the ratio of the diameter of the rotating shaft to the inner diameter of the fixed cylinder is in the range of 0.4 to 0.6 in each of the water absorbing agent manufacturing apparatuses. It is.
[0416]
  As described above, the water-absorbing agent production apparatus of the present invention is such that in each of the water-absorbing agent production apparatuses, the inner surface of the fixed cylinder in the continuous extrusion mixer is substantially at a contact angle with water of about 60 ° or more. And a base material having a heat distortion temperature of about 70 ° C. or higher.
[0417]
  According to the above configuration, in the first region, the water-absorbent resin supplied in the fixed cylinder is dispersed by giving sufficient thrust to the inside of the continuous extrusion mixer, and in the second region, The extrusion thrust is made smaller than the extrusion thrust in the first region, thereby reducing the average speed of the water-absorbent resin, ensuring sufficient mixing and stirring time for the water-absorbent resin and the aqueous liquid, and the first region. The water-absorbing resin dispersed in (1) and the aqueous liquid can be quickly and uniformly mixed.
[0418]
  Further, the inner surface of the fixed cylinder is substantially formed of a base material having a contact angle with water of about 60 ° or more and a heat deformation temperature of about 70 ° C. or more, so that the water-absorbing water-absorbing resin is fixed. Adhering to the inner surface of the cylinder can be prevented, and the heat generated during the mixing period can be sufficiently tolerated, and stable mixing can be continued.
[0419]
  Furthermore, when the ratio of the diameter of the rotating shaft to the inner diameter of the fixed cylinder is within the range of 0.4 to 0.6, sufficient mixing of the water absorbent resin and the aqueous liquid is performed stably and continuously. be able to.
[0420]
  Further, in the present invention, when the water-absorbent resin and the aqueous liquid are mixed, it is necessary that they both come into total contact as quickly as possible. For this reason, the 2nd supply port for supplying the said aqueous liquid is provided in the said 2nd area | region, More preferably in the boundary area of a 1st area | region and a 2nd area | region, The said water absorbing resin and aqueous | water-based The liquid can be brought into contact with each other instantaneously, so that the water-absorbent resin and the aqueous liquid can be mixed sufficiently uniformly without forming “dama”.
[0421]
  Therefore, the aboveeachAccording to the configuration, the mixing and reaction of the water-absorbing resin having a carboxyl group and an aqueous liquid containing a crosslinking agent capable of reacting with the carboxyl group is efficiently performed by various configurations of the stirring member in the continuous extrusion mixer. In addition, uniform mixing can be ensured. And according to the above configuration, it shows a high absorption capacity under pressure, and maintains its excellent water absorption performance even after carrying out processing in the manufacturing plant or the final product in the user, in the final product, It is possible to provide a water-absorbing agent production apparatus capable of producing a water-absorbing agent that can always exhibit excellent characteristics regardless of its usage.
[0422]
【The invention's effect】
  As described above, the water-absorbing agent according to the first aspect of the present invention is obtained by polymerizing / crosslinking a hydrophilic monomer mainly composed of acrylic acid and / or a salt thereof, has a carboxyl group, and is a hydrogel. A water-absorbing agent obtained by mixing and reacting the water-absorbing resin particles forming the carboxyl group and a cross-linking agent that reacts with the carboxyl group, wherein the water-absorbing agent 5 g is sealed in a bag of 70 mm × 100 mm, and the weight from above When an impact force (A) is applied to the water absorbent by reciprocating a 4 kg roller 10 times, the pressure in the water absorbent after the impact is 50 g / cm.²If the absorption capacity at Q is Q and the absorption capacity at the same pressure in the water-absorbing agent before impact is P
    P ≧ 20 (g / g)
And
    Q / P ≧ 0.85
It is the composition which is.
[0423]
  As described above, the water-absorbing agent according to the second aspect of the present invention has a configuration in which P ≧ 25 (g / g) in the water-absorbing agent according to the first aspect.
[0424]
  As described above, the water-absorbing agent according to the third aspect of the present invention is configured such that Q / P ≧ 0.9 in the water-absorbing agent according to the first aspect.
[0425]
  As described above, the water-absorbing agent according to the fourth aspect of the present invention is configured such that Q / P ≧ 0.95 in the water-absorbing agent according to the first aspect.
[0426]
  The water-absorbing agent of the invention according to claim 5 is obtained by polymerizing and crosslinking a hydrophilic monomer mainly composed of acrylic acid and / or a salt thereof, and has a carboxyl group, and is a hydrogel. A water-absorbing agent obtained by mixing and reacting the water-absorbing resin particles forming the carboxyl group and a cross-linking agent that reacts with the carboxyl group, and 30.0 g of the water-absorbing agent together with 10.0 g of glass beads and having a predetermined size. When the impact force (B) is applied by applying vibrations at a vibration speed of 750 c.pm for 30 minutes at 100 V / 60 Hz and causing the water-absorbing agents to collide with each other in the water-absorbing agent after the impact. Pressure 50g / cm²Assuming that the absorption capacity at Y is Y and the absorption capacity at the same pressure in the water absorbent before impact is X,
    X ≧ 20 (g / g)
And
    Y / X ≧ 0.90
It is the composition which is.
[0427]
  As described above, the water-absorbing agent according to the sixth aspect of the present invention is configured such that X ≧ 25 (g / g) in the water-absorbing agent according to the fifth aspect.
[0428]
  As described above, the water-absorbing agent according to the seventh aspect of the present invention is configured such that Y / X ≧ 0.92 in the water-absorbing agent according to the fifth aspect.
[0429]
  As described above, the water-absorbing agent according to the eighth aspect of the present invention is configured so that Y / X ≧ 0.95 in the water-absorbing agent according to the fifth aspect.
[0430]
  The water-absorbing agent according to claim 9 is the water-absorbing agent according to any one of claims 1 to 8, wherein the crosslinking agent is a polyhydric alcohol compound, an epoxy compound, or a polyvalent amine compound. And a salt thereof and at least one compound selected from the group consisting of alkylene carbonate compounds.
[0431]
  The water-absorbing agent of the present invention has excellent absorption performance and is resistant to mechanical stress. Therefore, it is possible to provide a water-absorbing agent that maintains its excellent absorption performance in the final product without substantially deteriorating its water-absorbing characteristics even when subjected to mechanical stress applied during transportation in a manufacturing plant or processing by a user. . Since each of the above water-absorbing agents can maintain its excellent absorption characteristics even after being processed into an absorbent article as a final product by the user, various absorbent articles, in particular, paper that places importance on absorption characteristics under pressure. There exists an effect that it is suitable for absorbent articles, such as sanitary materials containing absorbers, such as a diaper, a sanitary napkin, and an incontinence pad.
[0432]
  The water-absorbing agent of the invention according to claim 10 is the water-absorbing agent according to any one of claims 1 to 9, as described above, in which the water-absorbing resin particles are placed around the rotation axis inside the fixed cylinder. The water-absorbing resin particles are dispersed in the first region by supplying the water-absorbing resin particles to the first region in a stirring-type continuous extrusion mixer provided with at least one stirring member that gives thrust to the water-absorbing resin particles. Thereafter, the water-absorbing resin particles are extruded into a second region having a smaller pushing thrust than the pushing force in the first region, and the water-absorbing resin particles and the cross-linking agent that reacts with the carboxyl groups of the water-absorbing resin particles are mixed in the second region. It is the composition made to do.
[0433]
  According to the above configuration, after the water-absorbing resin particles are dispersed in the first region, the water-absorbing resin particles are extruded to a second region having a smaller pushing thrust than the pushing force in the first region. In the second region, the average speed of the water-absorbing resin dispersed in the first region is decreased, and the mixing and stirring time of the water-absorbing resin particles and the cross-linking agent is reduced by mixing the water-soluble resin particles and the crosslinking agent. While ensuring sufficiently, the water-absorbent resin particles dispersed in the first region and the crosslinking agent can be quickly and uniformly mixed. As a result, the mixing and reaction of the water-absorbing resin particles and the crosslinking agent that reacts with the carboxyl groups of the water-absorbing resin particles are efficiently performed, and uniform mixing can be ensured. Therefore, according to the above configuration, it exhibits high absorption capacity under pressure, and maintains its excellent water absorption performance even after carrying out transportation in a manufacturing plant or processing of the final product by a user, in the final product, There is an effect that it is possible to produce a water-absorbing agent that can always exhibit excellent characteristics regardless of its usage.
[0434]
  Claim 11The water-absorbing agent of the described invention is a water-absorbing agent obtained by surface-crosslinking a water-absorbent resin granulated product having an average particle diameter of 200 μm to 800 μm as described above, and is 50 g / cm.²The absorption capacity under pressure is 20 g / g or more, the absorption rate is 25 seconds or less, and the granulation failure rate is 10% by weight or less.
[0435]
  The water-absorbing agent of the invention according to claim 12 is the water-absorbing agent according to claim 11, as described above, wherein the water-absorbent resin granulated product is added to 100 parts by weight of the water-absorbing resin having an average particle size of 10 μm to 150 μm. After mixing 70 parts by weight to 400 parts by weight to obtain a hydrated gel-like granulated product having an average particle size of 0.3 mm to 10 mm, the hydrated gel-like granulated product is subjected to 110 ° C. to 300 ° C. under the condition that it is not pulverized. The water-absorbing agent has a structure obtained by cross-linking the surface of this water-absorbent resin granulated product.
[0436]
  aboveeachAccording to the configuration, the conventional granulation methods have mutually conflicting properties, and simultaneously satisfy the three physical properties of absorption capacity under high pressure, granulation strength, and absorption speed, which were properties that could not be satisfied at the same time. The water absorbing agent that can be provided is provided.
[0437]
  Claim 13The sanitary material of the described invention is as described above.Claims 1-12It is the structure containing the water absorbing agent of any one of these.
[0438]
  Each of the above water-absorbing agents can maintain its excellent absorption characteristics even after being processed into an absorbent article such as sanitary materials. It is suitable for a sanitary material containing an absorbent body. Therefore, according to said structure, there exists an effect that the sanitary material which has the outstanding absorption characteristic can be provided..
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view of a continuous extrusion mixer in a water absorbent manufacturing apparatus according to an embodiment of the present invention.
FIG. 2 is an explanatory diagram showing a stirring state in the continuous extrusion mixer shown in FIG. 1, and (a) is an explanatory diagram showing a stirring state in a first region in the continuous extrusion mixer; b) It is explanatory drawing which shows the stirring state in the 2nd area | region in the said continuous extrusion mixer.
FIG. 3 is a schematic cross-sectional view of a continuous extrusion mixer in a water absorbent manufacturing apparatus according to another embodiment of the present invention.
FIG. 4 is a schematic cross-sectional view of a continuous extrusion mixer in a water absorbing agent manufacturing apparatus according to still another embodiment of the present invention.
FIG. 5 is a schematic cross-sectional view of a continuous extrusion mixer in a water-absorbing agent manufacturing apparatus according to still another embodiment of the present invention.
FIG. 6 is a schematic cross-sectional view of a continuous extrusion mixer in a water-absorbing agent manufacturing apparatus according to still another embodiment of the present invention.
FIG. 7 is a schematic cross-sectional view of a continuous extrusion mixer in a water-absorbing agent manufacturing apparatus according to still another embodiment of the present invention.
FIG. 8 is a schematic cross-sectional view of a continuous extrusion mixer in a water absorbing agent production apparatus according to still another embodiment of the present invention.
FIG. 9 is a schematic cross-sectional view of a continuous extrusion mixer in a water-absorbing agent manufacturing apparatus according to still another embodiment of the present invention.
FIG. 10 is a schematic cross-sectional view of a continuous extrusion mixer in a water-absorbing agent manufacturing apparatus according to still another embodiment of the present invention.
FIG. 11 is a perspective view showing an apparatus for applying an impact force (A) to the water absorbing agent.
FIG. 12 is a schematic configuration diagram of a container used for applying an impact force (B) to the water absorbing agent.
FIG. 13A is an explanatory view for explaining how to apply vibration to the container when an impact force (B) is applied to the water absorbent, and FIG. 13B is an impact force (B It is explanatory drawing explaining how to give the vibration with respect to the said container in the case of giving ()) from an angle different from (a).
FIG. 14 is a schematic configuration diagram of an apparatus for applying an impact force (B) to the water absorbing agent.
FIG. 15 is an explanatory diagram for explaining the vibration of the container when an impact force (B) is applied to the water-absorbing agent.
FIG. 16 is a cross-sectional view showing an apparatus for measuring the absorption capacity of the water-absorbing agent under pressure.
FIG. 17 is an explanatory diagram for explaining a relationship between an angle of a water absorbent resin extrusion surface of a stirring member and a direction in which an extrusion thrust is generated in the continuous extrusion mixer.
18 is a water absorbent resin fine powder (A) obtained in Example 13 and having a particle size of less than 150 μm. FIG.₂) Is a drawing substitute photograph showing an electron micrograph (50 ×).
FIG. 19 is a drawing-substituting photograph showing the structure of the water-absorbent resin granulated product (1) obtained in Example 13 with an electron micrograph (50 ×).
FIG. 20 is a drawing-substituting photograph showing the structure of the comparative water-absorbent resin granulated product (1) obtained in Comparative Example 2 with an electron micrograph (50 ×).
FIG. 21 is a cross-sectional view showing a continuous extrusion mixer in a conventional water-absorbing agent manufacturing apparatus.
[Explanation of symbols]
  1 Continuous extrusion mixer
  2 Casing (fixed cylinder)
  3 Material supply port (first supply port)
  4 Liquid supply port (second supply port)
  5 outlet
  6 Rotating shaft
  7 Stirring blade (stirring member)
  7a First stirring blade (first stirring member)
  7a₁Water-absorbent resin extrusion surface
  7b Second stirring blade (first stirring member)
51 Continuous extrusion mixer
52 Continuous extrusion mixer
53 Continuous extrusion mixer
54 Continuous extrusion mixer
55 Continuous extrusion mixer
55 'continuous extrusion mixer
56 Continuous extrusion mixer
57 Continuous extrusion mixer

Claims (13)

A water-absorbing resin particle having a carboxyl group and forming a hydrogel obtained by polymerizing / crosslinking a hydrophilic monomer mainly composed of acrylic acid and / or a salt thereof, and a cross-linking that reacts with the carboxyl group A water absorbing agent obtained by mixing and reacting with an agent,
When 5 g of the water-absorbing agent is sealed in a bag of 70 mm × 100 mm, and an impact force (A) is applied to the water-absorbing agent by reciprocating a 4 kg weight roller 10 times, the pressure in the water-absorbing agent after the impact is 50 g. When the absorption capacity at / cm ² is Q and the absorption capacity at the same pressure in the water-absorbing agent before impact is P,
P ≧ 20 (g / g)
And
Q / P ≧ 0.85
A water-absorbing agent characterized by   The water-absorbing agent according to claim 1, wherein P ≧ 25 (g / g).   The water-absorbing agent according to claim 1, wherein Q / P ≧ 0.9.   The water-absorbing agent according to claim 1, wherein Q / P ≧ 0.95. A water-absorbing resin particle having a carboxyl group and forming a hydrogel obtained by polymerizing / crosslinking a hydrophilic monomer mainly composed of acrylic acid and / or a salt thereof, and a cross-linking that reacts with the carboxyl group A water absorbing agent obtained by mixing and reacting with an agent,
Put 30.0 g of the above water-absorbing agent together with 10.0 g of glass beads in a container having a predetermined size, and apply vibration at a vibration speed of 750 c.pm at 100 V / 60 Hz for 30 minutes to cause the water-absorbing agents to collide with each other. When the impact force (B) is given by the above equation, Y is the absorption capacity at a pressure of 50 g / cm ² in the water absorbent after the impact, and X is the absorption capacity at the same pressure in the water absorbent before the impact.
X ≧ 20 (g / g)
And
Y / X ≧ 0.90
A water-absorbing agent characterized by   6. The water absorbing agent according to claim 5, wherein X ≧ 25 (g / g).   6. The water absorbing agent according to claim 5, wherein Y / X ≧ 0.92.   The water absorbing agent according to claim 5, wherein Y / X ≧ 0.95.   The cross-linking agent is at least one compound selected from the group consisting of polyhydric alcohol compounds, epoxy compounds, polyvalent amine compounds and salts thereof, and alkylene carbonate compounds. The water-absorbing agent according to claim 1. Supplying the water-absorbing resin particles to the first region in a stirring-type continuous extrusion mixer provided with at least one stirring member that gives thrust to the water-absorbing resin particles around the rotation axis inside the fixed cylinder Then, after the water-absorbing resin particles are dispersed in the first region, the water-absorbing resin particles are extruded in the second region having a smaller pushing thrust than the pushing force in the first region, A crosslinking agent that reacts with a carboxyl group of the water-absorbent resin particles; The water-absorbing agent according to claim 1, wherein the water-absorbing agent is mixed. A water-absorbing agent obtained by surface cross-linking a water-absorbent resin granulated product having an average particle diameter of 200 μm to 800 μm,
50 g / cm ² A water-absorbing agent characterized in that the absorption capacity under pressure is 20 g / g or more, the absorption rate is 25 seconds or less, and the granulation failure rate is 10% by weight or less. The water-absorbent resin granulated product is a hydrogel granulated product having an average particle size of 0.3 mm to 10 mm by mixing 100 parts by weight of a water absorbent resin having an average particle size of 10 μm to 150 μm with 70 parts by weight to 400 parts by weight of an aqueous liquid. After obtaining the product, the water-containing gel granule is subjected to shrinkage drying at 110 ° C. to 300 ° C. under classification without pulverization and classification. The water-absorbing agent according to claim 11, wherein A hygiene material comprising the water-absorbing agent according to any one of claims 1 to 12.

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