JP3847371B2 - Water-absorbent resin composition, method for producing the same, and hygiene article using the same - Google Patents
Water-absorbent resin composition, method for producing the same, and hygiene article using the same Download PDFInfo
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Description
【０００１】
【発明の属する技術分野】
本発明は、吸水性樹脂組成物の製造法に関する。本発明で得られた吸水性樹脂組成物は、生理用品、おむつ、使い捨て雑巾等の衛生用品や保水剤等の農園芸用品、汚泥の凝固剤、建材の結露防止剤、油類の脱水剤等に利用できる。
【０００２】
【従来の技術】
従来より、吸水性樹脂としては各種のものが知られているが、吸水性能が不十分なもの、保存時に吸水性樹脂粉末が吸湿し凝集して流動性に問題があるもの、加工時に樹脂粉末が発塵して取り扱い性に劣るもの等それぞれに欠点が指摘されている。また、吸水性樹脂が用いられた衛生用品の使用時に粘着感がある等の欠点が指摘されているものもある。
【０００３】
このような欠点を改良するため吸水性樹脂には、種々の改良が施されている。たとえば、吸水性樹脂に表面近傍を架橋剤により架橋する方法や、吸水性樹脂粉末の表面近傍を界面活性剤でコーティング処理する方法等の方法によれば、吸水性能や使用時の粘着感を改良しうる。しかし、かかる方法によって得られる吸水性樹脂も流動性や発塵性の点で十分でない。
【０００４】
また、特開昭６０−１６３９５６号公報には、吸水性樹脂粉末に、無機質粉末の存在下で水と架橋剤を添加し、架橋反応と水の留去を同時に行う方法が開示されている。しかし、この方法では得られる吸水性樹脂組成物の流動性を改良できるが、発塵性を満足できない。また、特開平２−１５３９０３号公報には、吸水性樹脂粉末を架橋剤により架橋させる際に、水およびエーテル化合物を存在させる方法が開示されている。しかし、この方法では得られる吸水性樹脂組成物の流動性を十分満足できない。また、特開平４−１１４７０号公報には、吸水性樹脂粉末に、無機質粉末の存在下で水、架橋剤および分散剤を添加する技術が開示されている。しかし、この方法では、発塵性を満足するものの、使用時の粘着感が残る。
【０００５】
【発明が解決しようとする課題】
本発明は、各種吸水性能を有し、かつ使用時の粘着感を満足するとともに、発塵性、流動性も良好な吸水性樹脂組成物を製造する方法を提供することを目的とする。
【０００６】
【課題を解決するための手段】
本発明者は、前記の如き課題を解決すべく鋭意検討を重ねた結果、吸水性樹脂粉末に、不活性な無機質粉末の存在下で水と架橋剤を添加して、架橋反応と水の留去を行なうに際し、水と架橋剤とともにポリ（メタ）アクリル酸アルカリ金属塩を添加することにより、前記目的を達成しうる吸水性樹脂組成物が得られることを見出した。本発明はかかる新たな知見に基づいて完成されたものである。
【０００７】
【発明の実施の形態】
吸水性樹脂としては、架橋剤と反応する官能基を有する各種公知のものを使用できる。たとえば、カルボキシル基、水酸基、スルホン基、アミノ基等を有する単量体単位を重合体または共重合体の構成成分として含有する各種公知の吸水性樹脂があげられるが、これらの吸水性樹脂中でも、カルボキシル基を有するものが好ましい。
【０００８】
吸水性樹脂の具体例としては、カルボキシメチルセルロース架橋物、ポリオキシエチレン架橋物、（メタ）アクリル酸アルカリ金属塩重合体の架橋物、（メタ）アクリル酸アルカリ金属塩−（メタ）アクリルアミド−スルホン化アクリルアミド３元共重合体の架橋物、多糖類（たとえば澱粉等）−（メタ）アクリル酸グラフト共重合体の架橋物、多糖類−アクリロニトリルグラフト共重合体の加水分解物の架橋物、多糖類−（メタ）アクリル酸アルキルエステルグラフト共重合体のケン化物の架橋物、多糖類−アクリルアミド共重合体のケン化物の架橋物、（メタ）アクリル酸アルキルエステル−酢酸ビニル共重合体のケン化物の架橋物等を例示できる。これら吸水性樹脂のなかでも、本発明では（メタ）アクリル酸アルカリ金属塩重合体の架橋物が好ましい。これら吸水性樹脂は単独で用いてもよく、２種以上混合して用いてもよい。
【０００９】
吸水性樹脂粉末の粒径に、特に限定はなく、粉末状または粒子状である限り、その形状、大きさ等も制限はない。通常は１０〜６００メッシュ程度の粒径を有するものが好ましい。
【００１０】
不活性な無機質粉末としては、例えば含水二酸化ケイ素粉末、含水酸化アルミニウム粉末、含水酸化チタン粉末もしくはこれらの無水物、またはこれらを主成分として含有するものの粉末等があげられる。これら不活性な無機質粉末は単独で用いてもよく、２種以上混合して用いてもよい。前記無機質粉末の結晶系には制限はなく、例えば酸化アルミニウム粉末ではα型、β型、γ型のいずれも同様に有効に利用でき、酸化チタン粉末ではＴｉＯ、Ｔｉ2 Ｏ3 、 ＴｉＯ2 のいずれであってもよい。また、これらの含水物粉末の含水量についても特に限定はなく、例えば水酸化アルミニウム粉末ではＡｌ2 Ｏ3 ・ Ｈ2 Ｏ粉末、Ａｌ2 Ｏ3 ・ ２Ｈ2 Ｏ粉末、Ａｌ2 Ｏ3 ・ ３Ｈ2 Ｏ粉末を、酸化チタン粉末ではＴｉＯ2 ・ Ｈ2 Ｏ粉末、ＴｉＯ2 ・ ２Ｈ2 Ｏ粉末等を同様に用いられる。前記含水または無水の無機質を主成分として含有するものの粉末としては、例えばコロイダルシリカ、ホワイトカーボン、超微粒子状シリカ等の含水二酸化ケイ素および（または）無水二酸化ケイ素（以下、微粒子シリカという）を主成分とするものの粉末、板状水和アルミナ、繊維状水和アルミナのように含水および無水の酸化アルミニウムを主成分とするものの粉末、ルチル型またはアナタース型の含水または無水酸化チタンを主成分として含有するものの粉末等を例示することができる。これら不活性な無機質粉末のうちでは、微粒子状シリカ、二酸化チタン粉末またはアルミナ粉末等が好ましい。なお、当該無機質粉末の粒径としては、平均粒径が０．００１〜１０μｍのものが好ましく、０．００５〜１μｍのものがさらに好ましい。
【００１１】
これら不活性な無機質粉末は、吸水性樹脂粉末を架橋剤により架橋反応させるに際して、吸水性樹脂粉末が凝集することを防止して吸水性樹脂粉末の表面近傍を均一に架橋するために用いられる。すなわち、不活性な無機質粉末の使用により、吸水膨潤状態における吸水性樹脂粒子の相互間の分散性を向上させ、流動性を改善することができる。かかる観点から、不活性な無機質粉末の使用量は、吸水性樹脂粉末１００部（重量部、以下同様）に対し、０．１〜３０部程度、好ましくは１〜２０部とされる。
【００１２】
架橋剤とは、前記吸水性樹脂中に存在するカルボキシレート、水酸基、スルホン基、アミノ基等の官能基と反応しうる２個以上の官能基を有する化合物をいい、このようなものであれば特に限定することなく使用することができる。このような架橋剤としては、例えばジグリシジルエーテル系化合物、多価金属塩、ハロエポキシ系化合物、アルデヒド系化合物またはポリイソシアネート系化合物等があげられる。これら架橋剤のなかでも、本発明ではジグリシジルエーテル系化合物が好ましい。
【００１３】
前記ジグリシジルエーテル系化合物の具体例としては、たとえば（ポリ）エチレングリコールジグリシジルエーテル、（ポリ）プロピレングリコールジグリシジルエーテル、（ポリ）グリセリンジグリシジルエーテル等があげられ、特にエチレングリコールシジルエーテルが好ましい。
【００１４】
前記多価金属塩の具体例としては、たとえばマグネシウム、カルシウム、バリウム、亜鉛等の２価金属またはアルミニウム、鉄等の３価金属のハロゲン化物、硫酸塩、硝酸塩等があげられ、より具体的には硫酸マグネシウム、硝酸マグネシウム、塩化第２鉄、塩化カルシウム、塩化マグネシウム、塩化アルミウム、ポリ塩化アルミウム、硝酸鉄、硝酸カルシウム、硝酸アルミウム等があげられる。
【００１５】
前記ハロエポキシ系化合物の具体例としては、たとえばエピクロルヒドリン、エピブロモヒドリン、α−メチルエピクロルヒドリン等があげられ、アルデヒド系化合物の具体例としては、たとえばグルタルアルデヒド、グリオキザール等があげられ、イソシアネート系化合物の具体例としては、たとえば、２，４−トリレンジイソシアネート、ヘキサメチレンジイソシアネート等があげられる。
【００１６】
前記架橋剤は、吸水性樹脂の種類に応じて適宜選定してそれぞれを単独で用いてもよく、また２種以上を混合し用いてもよい。本発明では、架橋剤を使用して吸水性樹脂の表面近傍に再度架橋構造を付与することにより、得られる吸水性樹脂粉末の吸水能、吸水速度等の吸水性能や、発塵等の取り扱い性、製品使用時の粘着感等を向上させる。また、かかる観点から前記架橋剤の使用量は、吸水性樹脂粉末１００部に対し０．００５〜５部程度、好ましくは０．０１〜１部とされる。
【００１７】
ポリ（メタ）アクリル酸アルカリ金属塩としては、各種のものを使用できるが重合度が２０００〜１００００程度のものが好ましい。なお、アルカリ金属塩としてはナトリウム塩またはカリウム塩等を例示できる。ポリ（メタ）アクリル酸アルカリ金属塩は、吸水性樹脂粉末および無機質粉末の相互の固着を高め、これら粉末による発塵を著しく低下させると同時に流動性を向上させるために使用される。かかる観点からその使用量は、吸水性樹脂粉末１００部に対し０．０１〜１０部程度、好ましくは０．１〜５部とされる。
【００１８】
本発明の吸水性樹脂組成物の製造は、まず前記所定量の吸水性樹脂の粉末と不活性な無機質粉末を混合しておき、この混合物に、所定量の水、架橋剤およびポリ（メタ）アクリル酸アルカリ金属塩を加えて、架橋反応を行うとともに、水の留去を行なう。ここで水は、架橋した吸水性樹脂組成物が吸水時に高いゲル強度を示し、かつ衛生用品としての使用時に粘着感がない等の諸性能を満足させるために用いられる。かかる観点から水の使用量は吸水性樹脂粉末１００部に対し５〜５０部程度、好ましくは１０〜４０部とされる。
【００１９】
また、吸水性樹脂粉末および不活性な無機質粉末からなる混合物に、水、架橋剤およびポリアクリル酸ナトリウムを添加する方法は特に限定されず、各種方法が採用できるが、工業的見地からは、シャワリング方式やスプレー方式が好ましい。なお、水、架橋剤およびポリ（メタ）アクリル酸アルカリ金属塩を添加する際または添加した後には、通常、撹拌操作が行われるが、当該撹拌方法は、前記成分が実質的に均一混合される限りいずれの方法も採用でき、例えば各種形状の撹拌羽根をもつ撹拌機、ニーダー、パイプラインミキサー等をそのまま用いることができる。
【００２０】
また、本発明の製造法では、前記工程と同時にまたはその後に、反応系内を加熱することにより、吸水性樹脂粉末を架橋させるとともに水を留去させる。加熱条件は、使用する架橋剤の種類、不活性な無機質粉末の種類や使用量、得られる吸水性樹脂組成物の用途等により異なるため一概には決められないが、通常４０〜１５０℃程度が好ましい。また、反応系内を適宜に減圧して水の留去を促進することもできる。なお、吸水性樹脂粉末および不活性な無機質粉末からなる混合物を予め加熱しておき、ついで水、架橋剤およびポリ（メタ）アクリル酸アルカリ金属塩を添加することもできる。
【００２１】
【実施例】
以下に、本発明を実施例により、更に具体的に説明するのが、本発明はこれら実施例に限定されるものではない。
【００２２】
実施例１
吸水性樹脂の粉末（荒川化学工業（株）製、商品名アラソーブ、ポリアクリル酸カリウム塩架橋物）１００ｇおよび不活性な無機質粉末（日本アエロジル（株）製、商品名アエロジル２００、平均粒子径約０．０１２μｍの微粒子シリカ）３ｇをセパラブルフラスコに入れ、撹拌機で充分撹拌しながら、次いで架橋剤としてエチレングリコールジグリシジルエーテル０．２ｇ、水２５ｇおよびポリアクリル酸ナトリウム０．２ｇ（和光純薬工業（株）製、重合度２７００〜７５００）の混合物を徐々に加え、均一な分散状態にした。その後、加熱し、約１２０℃で水を留去させながら約１時間架橋させることにより、本発明の吸水性樹脂組成物を得た。得られた吸水性樹脂組成物を用いて下記方法により、吸水能、吸水速度、ゲル強度、粘着感、発塵性および流動性を測定した。それらの結果を表２に示す。
【００２３】
（吸水能）
２００ｍｌのビーカーに０．９％食塩水１５０ｇと吸水性樹脂組成物０．１２ｇとを加え、３０分間放置したのち、２００メッシュの金網で濾過し、遊離してくる水の重量を測定し、下式により算出した。
吸水能＝（添加水の重量−遊離水の重量）／吸水性樹脂組成物の重量
【００２４】
（吸水速度）
１００ｍｌのビーカーに０．９％食塩水５０ｇと撹拌子とを入れ、マグネチックスターラーにて６００ｒｐｍの速度で撹拌しながら、この中に吸水性樹脂組成物２ｇを投入すると、吸水膨潤作用により内容物の流動性が急速に低下し、含水ゲル状となり、撹拌中心の水流渦が消えるという現象が観測される。ここで吸水性樹脂組成物の投入時から水流渦が消えるまでの所要時間を吸水速度とした。
【００２５】
（ゲル強度）
０．９％食塩水５０ｇと吸水性樹脂組成物２ｇを混合してゲル（以下、２５倍ゲルという）を調製し、飯尾電機（株）製のネオカードメーターによりゲルの硬さを測定した。ここでゲルの硬さとはゲルの破断に至るまでの弾性率をいう。
【００２６】
（ゲルの粘着感）
ネオカードメーターにより前記２５倍ゲルの破断力を求め、これらの測定値をもってゲルの粘着感を評価した。ここで破断力とは弾性力の限界に対し、弾性体を破壊させる力をいう。
【００２７】
（流動性）
嵩密度測定装置（ＪＩＳ Ｋ−６７２１）を用い、ダンパーを差し込んだ漏斗に吸水性樹脂組成物を約１２０ｍｌを入れ、所定位置に１００ｍｌのカップをセットした後、速やかにダンパーを開け、吸水性樹脂組成物をカップ内に落下させ、該カップから盛り上がった部分の角度（安息角）を測定した。
【００２８】
（発塵性）
デジタル粉塵計（柴田化学機器（株）製、Ｐ５Ｌ２型）をガラス管で直結した吸引瓶にロートを通して、吸水性樹脂組成物２０ｇを一度に落下させ、生じた粉塵量（ｃｐｍ）を１分間カウントした。
【００２９】
実施例２、比較例１〜３
実施例１において、各成分の使用量を表１に示すように変更した他は、実施例１と同様にして本発明の吸水性樹脂組成物を得た。得られた吸水性樹脂組成物の諸性能を実施例１と同様にして測定した。結果を表２に示す。
【００３０】
【表１】
【表２】
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a water absorbent resin composition. The water-absorbent resin composition obtained in the present invention includes sanitary products such as sanitary products, diapers, disposable rags, agricultural and horticultural products such as water retention agents, sludge coagulants, dew condensation agents for building materials, oil dehydrants, etc. Available to:
[0002]
[Prior art]
Conventionally, various types of water-absorbing resins are known, but those having insufficient water-absorbing performance, water-absorbing resin powders that absorb moisture during storage and have a problem with fluidity, resin powders during processing Have been pointed out in each of those that are dusty and inferior in handleability. In addition, some have pointed out drawbacks such as stickiness when using sanitary goods using a water-absorbing resin.
[0003]
In order to improve such drawbacks, various improvements have been made to the water absorbent resin. For example, according to methods such as the method of cross-linking the surface of a water-absorbent resin with a crosslinking agent, or the method of coating the surface of a water-absorbent resin powder with a surfactant, the water-absorbing performance and the sticky feeling during use are improved. Yes. However, the water absorbent resin obtained by such a method is not sufficient in terms of fluidity and dust generation.
[0004]
Japanese Patent Application Laid-Open No. 60-163958 discloses a method in which water and a crosslinking agent are added to a water-absorbent resin powder in the presence of an inorganic powder, and a crosslinking reaction and water are distilled off simultaneously. However, although this method can improve the fluidity of the resulting water-absorbent resin composition, it cannot satisfy the dusting property. JP-A-2-153903 discloses a method in which water and an ether compound are present when water-absorbing resin powder is crosslinked with a crosslinking agent. However, this method cannot sufficiently satisfy the fluidity of the water-absorbent resin composition obtained. Japanese Patent Laid-Open No. 4-11470 discloses a technique of adding water, a crosslinking agent, and a dispersant to a water-absorbent resin powder in the presence of an inorganic powder. However, although this method satisfies the dust generation property, the sticky feeling at the time of use remains.
[0005]
[Problems to be solved by the invention]
An object of the present invention is to provide a method for producing a water-absorbing resin composition having various water-absorbing performances and satisfying a sticky feeling during use, and having good dust generation and fluidity.
[0006]
[Means for Solving the Problems]
As a result of intensive studies to solve the above-mentioned problems, the present inventor added water and a crosslinking agent to the water-absorbent resin powder in the presence of an inert inorganic powder, and thereby allowed the crosslinking reaction and water retention. It was found that a water-absorbent resin composition capable of achieving the above-mentioned purpose can be obtained by adding poly (meth) acrylic acid alkali metal salt together with water and a crosslinking agent. The present invention has been completed based on such new findings.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
As the water absorbent resin, various known resins having a functional group that reacts with the crosslinking agent can be used. For example, various known water-absorbing resins containing a monomer unit having a carboxyl group, a hydroxyl group, a sulfone group, an amino group or the like as a constituent component of a polymer or copolymer can be mentioned. Among these water-absorbing resins, Those having a carboxyl group are preferred.
[0008]
Specific examples of the water-absorbing resin include carboxymethylcellulose cross-linked product, polyoxyethylene cross-linked product, (meth) acrylic acid alkali metal salt polymer cross-linked product, (meth) acrylic acid alkali metal salt- (meth) acrylamide-sulfonated Cross-linked product of acrylamide terpolymer, cross-linked product of polysaccharide (eg starch)-(meth) acrylic acid graft copolymer, cross-linked product of hydrolyzate of polysaccharide-acrylonitrile graft copolymer, polysaccharide- Cross-linked product of saponified product of (meth) acrylic acid alkyl ester graft copolymer, cross-linked product of saponified product of polysaccharide-acrylamide copolymer, cross-linked product of saponified product of (meth) acrylic acid alkyl ester-vinyl acetate copolymer Examples can be given. Among these water-absorbing resins, a crosslinked product of a (meth) acrylic acid alkali metal salt polymer is preferred in the present invention. These water-absorbing resins may be used alone or in combination of two or more.
[0009]
There is no particular limitation on the particle diameter of the water-absorbent resin powder, and the shape, size, etc. are not limited as long as it is powdery or particulate. Usually, those having a particle size of about 10 to 600 mesh are preferred.
[0010]
Examples of the inert inorganic powder include hydrous silicon dioxide powder, hydrous aluminum oxide powder, hydrous titanium oxide powder or their anhydrides, or powders containing these as a main component. These inert inorganic powders may be used alone or in combination of two or more. There is no limitation on the crystal system of the inorganic powder. For example, any of α-type, β-type, and γ-type can be used effectively for aluminum oxide powder, and any of TiO, Ti 2 O 3 , and TiO 2 can be used for titanium oxide powder. It may be. There is no particular limitation on the water content of these hydrated powder, for example, Al 2 O 3 · H 2 O powder is aluminum hydroxide powder, Al 2 O 3 · 2H 2 O powder, Al 2 O 3 · 3H 2 the O powder, used similarly TiO 2 · H 2 O powder, the TiO 2 · 2H 2 O powder like titanium oxide powder. Examples of the powder containing water-containing or anhydrous inorganic as a main component include water-containing silicon dioxide such as colloidal silica, white carbon, ultrafine silica and / or anhydrous silicon dioxide (hereinafter referred to as fine particle silica) as a main component. Such as powder, plate-like hydrated alumina, fibrous hydrated alumina, powder containing water and anhydrous aluminum oxide as the main component, rutile or anatase type water containing or containing anhydrous titanium oxide as the main component The powder of things etc. can be illustrated. Of these inert inorganic powders, particulate silica, titanium dioxide powder or alumina powder is preferred. In addition, as a particle size of the said inorganic powder, a thing with an average particle diameter of 0.001-10 micrometers is preferable, and a 0.005-1 micrometer thing is still more preferable.
[0011]
These inert inorganic powders are used to uniformly crosslink the vicinity of the surface of the water-absorbent resin powder by preventing the water-absorbent resin powder from aggregating when the water-absorbent resin powder is subjected to a crosslinking reaction. That is, by using an inert inorganic powder, the dispersibility between the water-absorbing resin particles in the water-absorbing swollen state can be improved and the fluidity can be improved. From this viewpoint, the amount of the inert inorganic powder used is about 0.1 to 30 parts, preferably 1 to 20 parts, with respect to 100 parts (parts by weight, hereinafter the same) of the water absorbent resin powder.
[0012]
The crosslinking agent refers to a compound having two or more functional groups capable of reacting with a functional group such as carboxylate, hydroxyl group, sulfone group, amino group and the like present in the water absorbent resin. It can be used without any particular limitation. Examples of such a crosslinking agent include diglycidyl ether compounds, polyvalent metal salts, haloepoxy compounds, aldehyde compounds, and polyisocyanate compounds. Among these crosslinking agents, diglycidyl ether compounds are preferred in the present invention.
[0013]
Specific examples of the diglycidyl ether compound include (poly) ethylene glycol diglycidyl ether, (poly) propylene glycol diglycidyl ether, and (poly) glycerin diglycidyl ether, and ethylene glycol cidyl ether is particularly preferable. .
[0014]
Specific examples of the polyvalent metal salt include divalent metals such as magnesium, calcium, barium and zinc, or halides of trivalent metals such as aluminum and iron, sulfates and nitrates, and more specifically. Examples include magnesium sulfate, magnesium nitrate, ferric chloride, calcium chloride, magnesium chloride, aluminum chloride, polyaluminum chloride, iron nitrate, calcium nitrate, and aluminum nitrate.
[0015]
Specific examples of the haloepoxy compound include, for example, epichlorohydrin, epibromohydrin, α-methylepichlorohydrin, and the like. Specific examples of the aldehyde compound include, for example, glutaraldehyde, glyoxal, and the like. Specific examples include 2,4-tolylene diisocyanate and hexamethylene diisocyanate.
[0016]
The cross-linking agent may be appropriately selected according to the type of the water-absorbing resin and used alone or in combination of two or more. In the present invention, by using a cross-linking agent to give a cross-linked structure again in the vicinity of the surface of the water-absorbent resin, the water-absorbing performance, water-absorbing speed, etc. of the resulting water-absorbent resin powder, and handleability such as dust generation Improves the feeling of adhesion when using the product. Moreover, the usage-amount of the said crosslinking agent shall be about 0.005-5 parts with respect to 100 parts of water absorbing resin powder from this viewpoint, Preferably it is 0.01-1 part.
[0017]
As the poly (meth) acrylic acid alkali metal salt, various types can be used, but those having a degree of polymerization of about 2000 to 10000 are preferred. Examples of alkali metal salts include sodium salts and potassium salts. The alkali metal salt of poly (meth) acrylic acid is used to enhance mutual sticking of the water-absorbent resin powder and the inorganic powder, remarkably reduce dusting caused by these powders, and at the same time improve fluidity. From this viewpoint, the amount used is about 0.01 to 10 parts, preferably 0.1 to 5 parts, per 100 parts of the water-absorbent resin powder.
[0018]
In the production of the water absorbent resin composition of the present invention, first, the predetermined amount of the water absorbent resin powder and an inert inorganic powder are mixed, and this mixture is mixed with a predetermined amount of water, a crosslinking agent and poly (meth). An alkali metal acrylate is added to carry out a crosslinking reaction, and water is distilled off. Here, water is used in order to satisfy various performances such that the crosslinked water-absorbent resin composition exhibits high gel strength upon water absorption and has no stickiness when used as a sanitary product. From this viewpoint, the amount of water used is about 5 to 50 parts, preferably 10 to 40 parts, per 100 parts of the water absorbent resin powder.
[0019]
Further, the method of adding water, a crosslinking agent and sodium polyacrylate to a mixture comprising a water absorbent resin powder and an inert inorganic powder is not particularly limited, and various methods can be adopted. A ring method or a spray method is preferable. In addition, when adding water or a crosslinking agent and a poly (meth) acrylic acid alkali metal salt, or after the addition, a stirring operation is usually performed. In the stirring method, the components are substantially uniformly mixed. Any method can be adopted as long as it is used, and for example, a stirrer having various shapes of stirring blades, a kneader, a pipeline mixer and the like can be used as they are.
[0020]
In the production method of the present invention, the water in the water-absorbent resin powder is crosslinked and water is distilled off by heating the reaction system simultaneously with or after the process. The heating conditions vary depending on the type of cross-linking agent used, the type and amount of inert inorganic powder used, the intended use of the resulting water-absorbent resin composition, etc. preferable. Further, the inside of the reaction system can be appropriately depressurized to promote the distillation of water. It is also possible to heat a mixture comprising the water-absorbent resin powder and the inert inorganic powder in advance, and then add water, a crosslinking agent and a poly (meth) acrylic acid alkali metal salt.
[0021]
【Example】
EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples.
[0022]
Example 1
100 g of water-absorbent resin powder (Arakawa Chemical Industries, trade name Arassorb, polyacrylic acid potassium salt cross-linked product) and inert inorganic powder (Nihon Aerosil Co., Ltd., trade name Aerosil 200, average particle size approx. 3 g of 0.012 μm fine particle silica) was placed in a separable flask and stirred well with a stirrer, then 0.2 g of ethylene glycol diglycidyl ether, 25 g of water and 0.2 g of sodium polyacrylate (Wako Pure Chemicals) as a cross-linking agent. A mixture having a degree of polymerization of 2700 to 7500 manufactured by Kogyo Co., Ltd. was gradually added to obtain a uniform dispersion state. Then, it heated, and it bridge | crosslinked for about 1 hour, distilling water off at about 120 degreeC, and obtained the water absorbing resin composition of this invention. Using the resulting water-absorbent resin composition, water absorption capacity, water absorption speed, gel strength, stickiness, dust generation and fluidity were measured by the following methods. The results are shown in Table 2.
[0023]
(Water absorption capacity)
In a 200 ml beaker, add 150 g of 0.9% saline and 0.12 g of the water-absorbent resin composition, leave it for 30 minutes, filter through a 200-mesh wire mesh, measure the weight of the released water, Calculated by the formula.
Water absorption capacity = (weight of added water−weight of free water) / weight of water absorbent resin composition
(Water absorption speed)
In a 100 ml beaker, 50 g of 0.9% saline solution and a stirrer were placed. While stirring at a speed of 600 rpm with a magnetic stirrer, 2 g of the water-absorbent resin composition was added thereto, and the contents were absorbed by the water-absorbing swelling action. A phenomenon is observed in which the fluidity of the water drops rapidly and becomes a hydrous gel, and the water vortex at the center of stirring disappears. Here, the time required from when the water-absorbing resin composition was introduced until the water flow vortex disappeared was defined as the water absorption speed.
[0025]
(Gel strength)
A gel (hereinafter referred to as a 25-fold gel) was prepared by mixing 50 g of 0.9% saline and 2 g of the water-absorbent resin composition, and the hardness of the gel was measured with a Neocard meter manufactured by Iio Electric Co., Ltd. Here, the hardness of the gel refers to the elastic modulus until the gel breaks.
[0026]
(Gel adhesion)
The breaking strength of the 25-fold gel was determined with a neo-card meter, and the tackiness of the gel was evaluated using these measured values. Here, the breaking force means a force for breaking the elastic body with respect to the limit of the elastic force.
[0027]
(Liquidity)
Using a bulk density measuring device (JIS K-6721), about 120 ml of the water-absorbent resin composition is put into a funnel into which a damper is inserted, and after setting a 100 ml cup at a predetermined position, the damper is quickly opened and the water-absorbent resin is placed. The composition was dropped into the cup, and the angle (rest angle) of the portion raised from the cup was measured.
[0028]
(Dust generation)
Pass the funnel through a funnel directly connected with a digital dust meter (Shibata Chemical Equipment Co., Ltd., P5L2 type) through a glass tube, drop 20 g of water-absorbent resin composition at once, and count the amount of dust (cpm) generated for 1 minute. did.
[0029]
Example 2, Comparative Examples 1-3
A water-absorbent resin composition of the present invention was obtained in the same manner as in Example 1 except that the amount of each component used in Example 1 was changed as shown in Table 1. Various performances of the obtained water absorbent resin composition were measured in the same manner as in Example 1. The results are shown in Table 2.
[0030]
[Table 1]
[Table 2]
Claims (4)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP07945796A JP3847371B2 (en) | 1996-03-06 | 1996-03-06 | Water-absorbent resin composition, method for producing the same, and hygiene article using the same |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP07945796A JP3847371B2 (en) | 1996-03-06 | 1996-03-06 | Water-absorbent resin composition, method for producing the same, and hygiene article using the same |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH09241322A JPH09241322A (en) | 1997-09-16 |
| JP3847371B2 true JP3847371B2 (en) | 2006-11-22 |
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| JP07945796A Expired - Fee Related JP3847371B2 (en) | 1996-03-06 | 1996-03-06 | Water-absorbent resin composition, method for producing the same, and hygiene article using the same |
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| US7173086B2 (en) * | 2003-10-31 | 2007-02-06 | Stockhausen, Inc. | Superabsorbent polymer with high permeability |
| TW200720347A (en) * | 2005-09-30 | 2007-06-01 | Nippon Catalytic Chem Ind | Water-absorbent agent composition and method for manufacturing the same |
| CN102898662B (en) | 2006-03-27 | 2015-06-03 | 株式会社日本触媒 | Production method for water-absorbing resin composition |
| EP2980128B1 (en) | 2013-03-27 | 2018-04-18 | Sumitomo Seika Chemicals CO. LTD. | Water-absorbent resin composition production method |
| KR101772658B1 (en) | 2014-12-18 | 2017-08-29 | 주식회사 엘지화학 | Superabsorbent Polymers for Blood and Viscous Liquids And Method Of Preparing The Same |
| KR101805088B1 (en) * | 2014-12-18 | 2017-12-05 | 주식회사 엘지화학 | Superabsorbent Polymers By Surface-Modification And Method Of Preparing The Same |
| KR20240008694A (en) * | 2022-07-12 | 2024-01-19 | 주식회사 엘지화학 | Method for preparing super absorbent polymer composite |
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