JP3544542B1 - Cosmetic elastic cell structure and manufacturing method thereof - Google Patents
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Abstract
【課 題】ずっときめが細かく、風合いが良好で、弾性セル構造体として最適な弾性セル構造体の提供。
【解決手段】ゴムラテックスのようなゴム系水分散体に空気及び珪フッ化ソーダを加えて高速撹拌して微細セル製造用原液とし、これを離型性を有する器材に注入し、直ちにマイクロ波を照射して速やかに凝固させ、乾燥後、加硫を行うことによって、０．１５０ｇ／ｃｍ３以下の見掛け密度、断面のセル数が８個／ｍｍ２以上、５０％圧縮応力が１．０Ｎ／ｃｍ２以下のゴム系弾性セル構造体を製造する。
【選択図面】なし[Problem] To provide an elastic cell structure which is much finer and has a better texture and is optimal as an elastic cell structure.
SOLUTION: Air and sodium silicate are added to a rubber-based aqueous dispersion such as rubber latex and stirred at a high speed to obtain a stock solution for producing fine cells. To solidify quickly, and after drying, vulcanization to give an apparent density of 0.150 g / cm 3 or less, a number of cells in a cross section of 8 cells / mm 2 or more, and a 50% compressive stress of 1.0 N. / Cm 2 or less is produced.
[Selected drawing] None
Description
【０００１】
【産業上の利用分野】
本発明は、微細な気泡構造を有して極めて柔軟であり、肌に対する感触及び塗布性に優れ、化粧用塗布基材として最適に使用される弾性セル構造体、拭き取り性に優れるワイパーなどの洗浄用具、耐久性に優れるクッション材料、ろ過用シートなどの雑貨・工業用基材として最適に使用される弾性セル構造体に関する。
さらに、本発明は、弾性セル構造体製造用原液にマイクロ波の照射により速やかに凝固させることにより、従来のダンロップ法では得られない０．１５０ｇ／ｃｍ３以下の見掛け密度を有し、断面のセル数が８個／ｍｍ２以上の微細気泡のセル構造を持ち、５０％圧縮応力が１．０Ｎ／ｃｍ２以下という極めて柔軟な弾性セル構造体を製造する方法に関する。
上記微細気泡の数は、スライスした断面における、セル壁によって区画された気泡の数を意味する。
また、本発明の弾性セル構造体とは、セル構造体製造用の天然又は合成ゴム系の水分散液からなる原液を使用して、これを速やかに凝固、加熱硬化することによって得られるもので、多数のセル又は気泡が分散した弾性の異形セル構造のものも含むことを意味する。
【０００２】
一般にゴムラテックスから弾性のあるゴムスポンジのような弾性セル構造体を製造するには、ダンロップ法が慣用されている。ダンロップ法は、ゴムラテックスを原料とするものであるが、発泡剤を使用することなく、空気を吹き込んでセル構造体を製造するもので、アルカリ性から酸性に変えることによってゴムラテックスの安定状態を崩し、凝固させる方法である。
すなわち、ダンロップ法では、ゴムラテックスに加硫剤やその他の助剤を添加・混合した液に、多量の空気を吹き込み、珪フッ化ソーダ液を添加してＰＨを酸性にしながら、オークスミキサーなどの撹拌機で高速撹拌して均一微細な気泡を含有させた気泡液とし、これを７０〜２１０秒間で凝固せしめた後、凝固体を加熱、加硫して気泡の安定したセル構造体としている。
このようなダンロップ法では、吹き込み空気量の調整が容易なことから、小さな気泡形成に適する技術とされているが、得られる気泡の小ささと柔軟性に限界があって微細な気泡で柔軟なスポンジを得ることはできなかった。弾性セル構造体の製造には、そのほかの方法としてタラレー法（凍結凝固法）や感熱ゲル化法も知られているが、いずれも微細気泡を有する柔軟なスポンジを得ることはできなかった。
【０００３】
一方、マイクロ波照射加熱により合成樹脂材料やゴム材料を加熱、加硫する方法は公知である。
例えば、特開平５−０４２５５４号公報では、ゴム成型品を製造するのにゴム材料をセラミックス金型に注入して、マイクロ波を照射して瞬時に加熱する方法、特開平６−３１５９６９号公報では、マイクロ波によって瞬間的に加熱・凝固させてゴム製品を成型する方法がある。特開平７‐１１０２５３号公報では、かまぼこ、ちくわ、ソーセージ、ゴム、セラミック等の多岐にわたる練り製品を加熱、製造するのに、口金より連続的に押し出した原料を導波管内でマイクロ波によって瞬時に加熱凝固させる方法、特開平９−１９４６２０号公報では、熱可塑性樹脂（ＰＥ、ＰＰ、塩ビ、ナイロン）と水を含有する物質（結晶水を持つ無機材料）に、適宜の発泡剤を添加した混合物にマイクロ波を照射して発泡させる方法が知られている。
【０００４】
また、マイクロ波を利用してゴムや合成樹脂の発泡体の製造に利用する技術も知られている。
例えば、スポンジゴム表面をマイクロ波加熱して表面の平滑性を改善する方法（特開昭５７−１１３０４８号公報、特開昭５８−１６３６３７号公報、特開昭５９−１８７８３５号公報、特開昭６０−２６６６７４号公報）、未加硫ゴムをローラ搬送炉でマイクロ波加熱して膨張倍率を一定にする方法（特開平２−９８４１号公報）、スポンジゴム部の表面を予め熱媒体に接触させて表面前加硫後にマイクロ波を照射する技術（特開平２−１９６６０８号公報）、押出し成形品の電子線照射前にマイクロ波加硫槽で予備加硫して、表面を微発泡させて表面の耐摩耗性を改善した自動車用ウエザーストリップ体の製造方法（特開平４−２２４８３号公報、特開平４−３０１４２７号公報）、未加硫押出し物にマイクロ波エネルギーと熱風エネルギーを与えて寸法の微調整を図る方法（特開平８−１０８４３４号公報）、熱可塑性樹脂にマイクロ波吸収剤を混合して、マイクロ波照射による発泡樹脂製品の製造方法（特開２００１−０４７４５７号公報）が知られているが、ゴム系ラテックスを用いて弾性セル構造体の製造時に、変化し易い弾性セル構造体製造用原液のゲル構造を短時間で固定するために、マイクロ波を用いる技術は知られていない。
【０００５】
【特許文献】
１．特開昭５７−１１３０４８号公報
２．特開昭５８−１６３６３７号公報
３．特開昭５９−１８７８３５号公報
４．特開昭６０−２６６６７４号公報
５．特開平２−９８４１号公報
６．特開平２−１９６６０８号公報
７．特開平４−２２４８３号公報
８．特開平４−３０１４２７号公報
９．特開平５−０４２５５４号公報
１０ 特開平６−３１５９６９号公報
１１．特開平８−１０８４３４号公報
１２．特開平９−１９４６２０号公報
１３．特開２００１−０４７４５７号公報
【０００６】
【発明が解決しようとする課題】
上記ダンロップ法では、ゴムラテックスを原料とする弾性セル構造体の製造用の原液に、空気を吹き込むとともに珪フッ化ソーダを添加しながら撹拌してセル製造用原液として使用する。ゴムラテックス自体は、アルカリ性で安定であるので、珪フッ化ソーダの添加により原液のＰＨは酸性になり、不安定な状態となって凝固が開始するので、７０〜２１０秒という短時間内に離型性を有する成型トレーや容器などにラテックス原液を注入して凝固を完了させことが必要である。
この７０〜２１０秒という凝固完了までの間に、凝固の開始当初は微細な気泡構造であっても、凝固完了までの間に気泡の形状は微細なものが割れて大きな気泡に成長して大きな空隙となり、凝固開始直後の微細気泡構造のままに固定することができなかった。
そこで、本発明では、従来、ゴムラテックスを原料とするスポンジの製造法において、不可能とされていた弾性セル製造用原液の微細気泡を速やかに固定して微細な気泡を多数含む弾性セル構造体とし、極めて柔軟なスポンジを提供することを課題とする。
【０００７】
【課題を解決するための手段】
本発明では、後述するような天然ゴムや合成ゴムラテックス等の水分散液を原料として、これに珪フッ化ソーダを加え、さらに空気を吹き込み高速撹拌によって微細セル製造用原液とし、この微細セル製造用原液を離型性を有する器材に注入した後、マイクロ波を短時間照射して速やかに凝固させ、乾燥し、加硫することによって断面のセル数が８個／ｍｍ２以上、５０％圧縮応力が１．０Ｎ／ｃｍ２以下で、かつ見掛け密度が、０．１５０ｇ／ｃｍ３以下の弾性セル構造体を製造することができる。
本発明における弾性セル構造体製造用原液としては、天然ゴムや合成ゴムラテックス等の水分散液を主体とするもので、例えば天然ゴム（ＮＲ）ラテックス、合成イソプレンゴム（ＩＲ）ラテックス、アクリロニトリル・ブタジエンゴム（ＮＢＲ）ラテックス、スチレン・ブタジエンゴム（ＳＢＲ）ラテックス、ブタジエンゴム（ＢＲ）ラテックス、ウレタン樹脂水分散液、シリコーン樹脂分散液等の単独又は併用によるものが挙げられる。
本発明において得られる微細気泡を多数有する弾性セル構造体は、極めて柔軟で、きめが細かく、肌に対する感触及び塗布機能に優れ、化粧用塗布基材として使用するのが効果的であるが、それ以外に洗浄用具、クッション材料、ろ過材など雑貨・工業用基材としても利用性が高い。
【０００８】
【発明の実施の形態】
すなわち、本発明は、基本的に下記の構成を有するものである。
（１）ゴムラテックス由来弾性セル構造体からなる化粧用塗布具であって、微細径の球形気泡が多数存在し、その一部は微細気泡が集合した異形セル構造を形成してなる、セル数が８個/mm2以上の多数の微細気泡を含有し、見掛け比重が0.150g/cm3以下、50％圧縮応力が1.0N/cm2以下であるゴムラテックス由来の弾性セル構造体から形成されたことを特徴とする化粧用塗布具。
（２）ゴムスポンジシートをスライスし、スライス面を外側にして貼り合わされた接合されたものであることを特徴とする（１）の化粧用塗布具。
（３）ゴム系ラテックス配合液に、空気及び珪フッ化ソーダを加えて撹拌して弾性セル製造用原液とし、離型性を有する器材に注入してマイクロ波の照射により速やかに凝固させて、乾燥、加硫を行うことによって、微細径の球形気泡が多数存在し、その一部は微細気泡が集合した異形セル構造を形成し、セル数が８個/mm2以上の多数の微細気泡を含有し、見掛け比重が0.150g/cm3以下、50％圧縮応力が1.0N/cm2以下以下であることを特徴とするゴムラテックス由来弾性セル構造体の製造方法。
【０００９】
【発明の実施の形態】
本発明において得られるゴム系弾性セル構造体の見掛け密度は０．１５０ｇ／ｃｍ３以下、特に０．１２〜０．１３ｇ／ｃｍ３のものであり、化粧用塗布具として風合いが良好で、ファンシーであり、従来きめの細かさで知られる湿式ウレタンスポンジをはるかに凌ぐものである。
また、従来技術によって得られたゴム系セル構造体の断面のセル数は、５．０〜５．７個／ｍｍ２程度であるが、本発明で得られる弾性セル構造体の断面のセル数は、８／ｍｍ２個以上、特に１２個／ｍｍ２以上のものである。また、物性的には、従来法によって得られたゴム系セル構造体は、５０％圧縮応力が１．５〜１．６Ｎ／ｃｍ２であるのに対して、本発明のゴム系弾性セル構造体では、５０％圧縮応力が１．０Ｎ／ｃｍ２以下、特に０．４１〜０．６０Ｎ／ｃｍ２ であり、従来品に比べて極めて柔軟性が改善されている。
【００１０】
従来のダンロップ法によりゴム系ラテックスを原液として得られたセル構造体の断面と本発明で得られるゴム系弾性セル構造体の断面を顕微鏡で観察すると、従来法のものは気泡が粗大気泡構造を形成しているのに対して、本発明のものは微細径の球形気泡が多数存在し、その一部は微細気泡が集合した異形セル構造を形成している。
すなわち、従来法では原液に吹き込まれた空気でフォーミングされた微細な気泡が、凝固完了までの間に経時的に粗大気泡に成長するが、本発明では原液を注入後直ちにマイクロ波を照射して短時間の間に凝固させるため、微細な気泡の状態で弾性セル構造体を形成していることが確認できる。
本発明の弾性セル構造体は、結果的に上述するように従来品よりずっときめが細かく、風合いが良好で、化粧用塗布具等に最適なものである。
【００１１】
ゴム系弾性セル構造体の物性を、ゴム系ラテックスとして代表的なＮＢＲラテックスを原料として本発明法によって得られた弾性セル構造体と従来のダンロップ法によって得られたものを対比すると、表１のとおりである。
なお、配合処方及び加工方法は実施例１に準ずる。
微細セル製造用原液注入からマイクロ波照射までの時間を１０秒、３０秒、５０秒、７０秒とし、それぞれの条件で得た弾性セル構造体の見掛け密度（Ｎ／ｃｍ２）、断面のセル数（個数／ｍｍ２）及び５０％圧縮応力（Ｎ／ｃｍ２ ）をそれぞれ測定する。
【００１２】
【表１】
（２）セル数の測定は、デジタルＨＤマイクロスコープ ＶＨ−７０００による。
（３）マイクロ波の周波数は、２４５０ＭＨＺものを用いる。
【００１３】
表１からみて、本発明法によれば、マイクロ波照射までが、７０秒以下であれば、いずれの場合であっても従来のダンロップ法で得られたスポンジよりはきめの細かい気泡の柔軟なものが得られることが確認できた。
【００１４】
本発明の弾性セル構造体の製造方法を具体的に説明すると、先ずゴム系ラテックスに加硫剤やその他の助剤を添加・混合した配合液に、空気を吹き込み、珪フッ化ソーダを加えてオークスミキサーなどにより強撹拌をして弾性セル構造体製造原液とする。このセル構造体製造原液の重量と容積の関係は、２５０ｇから１２０ｇの重量で１０００ｃｃ程度の容積（すなわち、４〜８倍程度）を占めるようにする。セル構造体製造原液を離型性を有する器材に注入し、マイクロ波を照射するが、注入後からマイクロ波の照射までの時間は、極力短いことが望ましいが、７０秒以内であれば充分である。マイクロ波の周波数は、周波数２４５０ＭＨＺのものを使用したが、格別限定されるものではない。
また、マイクロ波の照射時間そのものは、数十秒程度の照射時間であればよく、好ましくは２０秒以下、特に１０〜１５秒の照射時間でもよい。照射時間が３０秒を越えると、過加熱によってセル構造体が局部的に膨張するので好ましくない。
【００１５】
ダンロップ法のような弾性セル構造体を製造する従来技術ではマイクロ波を使用することのない凝固であるから、配合液の凝固に６０〜２１０秒を要し、その間に経時的に気泡径が大きくなり、最終的にはシャボン玉が割れるように各気泡が破裂し、各気泡がつながり、気泡径が拡大するので、これを防ぐために温度、時間などの凝固条件の制御がきわめて大きな要件となっていたが、本発明によれば、マイクロ波で速やかに加熱凝固するので、従来技術に求められていた温度、時間などの凝固条件の制御が不必要となるが、得られた発泡体の気泡は凝固の初期段階の微細のままで固定することができるので、結果的に得られたセル構造体はきめ細かく肌に優しい弾性セル構造体として有用である。
【００１６】
本発明で使用するゴムラテックスの固形分濃度は６０重量％以上、望ましくは６５重量％以上の高濃度のものが好ましい。
加硫剤としては活性硫黄が一般的である。加硫促進剤としてはチアゾール系、チオ尿素系、チウラム系、ジチオカルバメート系などの加硫促進剤の内から任意のものが使用出来る。その他、酸化防止剤、抗菌・防黴剤、着色剤などを配合しても差し支えない。
ただし、配合剤が粉体の場合はボールミルなどを使用して水と混練し、水分散液の状態で使用することが好ましい。
ゴムラテックス配合液に珪フッ化ソーダを配合し、空気を吹き込み、オークスミキサーなどで攪拌して得られるセル構造製造原液としては、該原液２５０ｇで１０００ｃｃ（４倍容積）のものから、配合液１２０ｇが１０００ｃｃ（８倍容積）を呈するものまでを用いるのが適当である。
上記のセル構造体製造原液は、離型性を有する器材に注入してマイクロ波を照射して速やかに凝固し、次いでこれを乾燥、加硫することによってセル構造を固定する。加硫工程は、乾熱による加硫又は蒸熱による湿熱加硫等の慣用の手段を採用することができる。
【００１７】
【実施例】
以下、本発明を実施例によってさらに詳しく説明する。
なお、本発明は実施例の記載に限定されることなく、明細書記載の構成において同等の効果を発揮する。
【実施例１】
下記の配合処方により配合液を調製する。但し、各成分の数値は固型分換算した値であり、その単位は全て重量部である。
得られたセル構造体製造原液を４００ｍｍ×４００ｍｍの方形の成形型に注入した。
成形型では厚さ２５ｍｍのシート状として、注入後からマイクロ液の照射までの時間を５０秒とした。マイクロ波の照射時間は、１５秒間として原液を凝固させた。次いで、１００℃で４５分間乾燥して、厚さ２４ｍｍのＮＢＲセル構造体シートを得た。
得られた弾性セル構造体を１２ｍｍの厚さにスライスして面膜同士を貼り合わせて、直径６０ｍｍの円形に打ち抜いた。打ち抜きの後に、１１０℃で３０分の加熱加硫して後、縁を研磨して化粧用スポンジパフを得た。
得られたスポンジパフの見掛け密度は、０．１２０ｇ／ｃｍ３、５０％圧縮応力は、０．４８Ｎ／ｃｍ２であり（但し、試料の大きさは２ｃｍ角）、スライス面のセル数は１１．５個／ｍｍ２であった。極めて微細な発泡を有する柔軟なセル構造を有していた。
得られた化粧用スポンジパフは、肌の感触がソフトで優れており、化粧用具テストモニターの実用試験でも評価の高い塗布具であることが確認できた。
【００１８】
【実施例２】
実施例１の配合により得た配合液１００部に、珪フッ化ソーダ１．５部を混合しながら、空気を吹き込み、オークスミキサーで６倍発泡のセル構造体製造原液を調製して離型性ベルト上に、厚さ５０ｍｍのシート状として２．２ｍ／分の速度で移動しながら注入した。注入後、マイクロ波の照射までの時間を５０秒とした。
マイクロ波の照射時間を１２秒間として原液を凝固させた。次いで１００℃で４５分間乾燥し、１１０℃で３０分の蒸気加硫を行い、ＮＢＲセル構造体シートを得た。
得られた弾性セル構造体の見掛け密度は、０．１３０ｇ／ｃｍ３であり、５０％圧縮応力は０．４１Ｎ／ｃｍ２であった。このシートを５ｍｍ厚さにスライスしたが、スライス面のセル数は１１．７個／ｍｍ２で、工業用基材としてワイバー等に最適であった。
【００１９】
【発明の効果】
本発明において得られる弾性セル構造体の見掛け密度は０．１５０ｇ／ｃｍ３以下のもので、化粧用塗布具として風合いが良好で、ファンシーであり、従来きめの細かさで知られる湿式ウレタン樹脂を原料として得られるウレタンスポンジをはるかに凌ぐものである。
また、本発明で得られる弾性セル構造体の断面のセル数は、８／ｍｍ２個以上のものであり、５０％圧縮応力が１．０Ｎ／ｃｍ２以下、特に０．４１〜０．５０Ｎ／ｃｍ２ であり、極めて柔軟なスポンジとなっている。
このように本発明で得られる弾性セル構造体は、上述するように従来品よりずっときめが細かく、風合いが良好で、弾性セル構造体として最適である。[0001]
[Industrial applications]
INDUSTRIAL APPLICABILITY The present invention has an extremely flexible structure having a fine cell structure, is excellent in texture and applicability to the skin, and is used for cleaning an elastic cell structure optimally used as a base material for cosmetic application and a wiper having excellent wiping properties. The present invention relates to an elastic cell structure optimally used as a miscellaneous / industrial base material such as a tool, a cushion material having excellent durability, and a sheet for filtration.
Furthermore, the present invention has an apparent density of 0.150 g / cm 3 or less, which cannot be obtained by the conventional Dunlop method, by rapidly coagulating the stock solution for producing an elastic cell structure by irradiation of microwaves. The present invention relates to a method for producing an extremely flexible elastic cell structure having a cell structure of fine cells having a cell number of 8 / mm 2 or more and having a 50% compressive stress of 1.0 N / cm 2 or less.
The number of the fine bubbles means the number of bubbles partitioned by the cell walls in the sliced cross section.
The elastic cell structure of the present invention is obtained by using an undiluted solution composed of a natural or synthetic rubber-based aqueous dispersion for producing a cell structure, and quickly solidifying and heat-curing this. , Or a cell having an elastic deformed cell structure in which a large number of cells or air bubbles are dispersed.
[0002]
Generally, the Dunlop method is commonly used to produce an elastic cell structure such as an elastic rubber sponge from rubber latex. The Dunlop method uses rubber latex as a raw material.However, without using a foaming agent, the air is blown into the cell structure to produce a cell structure. Is a method of coagulating.
That is, in the Dunlop method, a large amount of air is blown into a liquid obtained by adding and mixing a vulcanizing agent and other auxiliaries to a rubber latex, and a sodium silicofluoride solution is added to make the PH acidic while using an Oaks mixer or the like. A high-speed stirring is performed by a stirrer to form a bubble liquid containing uniform and fine bubbles, which is coagulated for 70 to 210 seconds, and then the coagulated body is heated and vulcanized to form a cell structure with stable bubbles.
Such a Dunlop method is considered to be a technique suitable for forming small bubbles because the amount of blown air can be easily adjusted. I couldn't get a sponge. As other methods for producing the elastic cell structure, a Tallay method (freezing and coagulation method) and a heat-sensitive gelling method are also known, but none of them could obtain a soft sponge having fine bubbles.
[0003]
On the other hand, a method of heating and vulcanizing a synthetic resin material or a rubber material by microwave irradiation heating is known.
For example, JP-A-5-042554 discloses a method in which a rubber material is injected into a ceramic mold to produce a rubber molded product, and is irradiated with microwaves to instantaneously heat it. There is a method in which a rubber product is molded by heating and solidifying instantaneously by microwaves. In Japanese Patent Application Laid-Open No. Hei 7-110253, in order to heat and manufacture a wide variety of kneaded products such as kamaboko, chikuwa, sausage, rubber, ceramic, etc., the raw material continuously extruded from a die is instantaneously heated by microwaves in a waveguide. According to the coagulation method, Japanese Patent Application Laid-Open No. 9-194620, a mixture of a thermoplastic resin (PE, PP, polyvinyl chloride, nylon) and a substance containing water (an inorganic material having water of crystallization) and an appropriate foaming agent is added. There is known a method of irradiating microwaves to foam.
[0004]
There is also known a technique of utilizing a microwave to produce a foam of rubber or a synthetic resin.
For example, a method for improving the smoothness of the surface of a sponge rubber by microwave heating (Japanese Patent Application Laid-Open Nos. 57-113048, 58-163637, 59-187835, and 59-187835; No. 60-266677), a method in which unvulcanized rubber is microwave-heated in a roller transfer furnace to make the expansion ratio constant (Japanese Patent Laid-Open No. 2-9841), and the surface of a sponge rubber portion is brought into contact with a heat medium in advance. (Japanese Unexamined Patent Publication (Kokai) No. 196608/1990), pre-vulcanization in a microwave vulcanizing bath before electron beam irradiation of extruded products to finely foam the surface (Japanese Patent Application Laid-Open Nos. Hei 4-22483 and Hei 4-301427) for producing a weatherstrip body for automobiles having improved abrasion resistance, by applying microwave energy and hot air energy to an unvulcanized extrudate. (Japanese Unexamined Patent Application Publication No. 8-108434), a method of manufacturing a foamed resin product by mixing a thermoplastic resin with a microwave absorbent and irradiating the microwave (Japanese Patent Application Laid-Open No. 2001-47457). However, when a rubber-based latex is used to manufacture an elastic cell structure, microwaves are used to fix the gel structure of the stock solution for manufacturing the elastic cell structure in a short time. The technology is unknown.
[0005]
[Patent Document]
1. JP-A-57-113048; JP-A-58-163637. JP-A-59-1878354. Japanese Patent Application Laid-Open No. Sho 60-2666775. Japanese Patent Application Laid-Open No. 2-9841 6. JP-A-2-1966087. JP-A-4-22483 8. JP-A-4-301427 9. JP-A-5-042554 10 JP-A-6-315969 11. JP-A-8-108434. JP-A-9-194620 13. Japanese Patent Application Laid-Open No. 2001-047457
[Problems to be solved by the invention]
In the above-mentioned Dunlop method, air is blown into a stock solution for producing an elastic cell structure using rubber latex as a raw material and stirred while adding sodium silicate to use as a stock solution for cell production. Since the rubber latex itself is alkaline and stable, the pH of the undiluted solution becomes acidic by the addition of sodium silicate, and the coagulation starts in an unstable state, so that it is separated within a short time of 70 to 210 seconds. It is necessary to inject the latex stock solution into a molding tray or container having moldability to complete coagulation.
Until the completion of the solidification of 70 to 210 seconds, even if the solidification has a fine bubble structure at the beginning of the solidification, the shape of the fine bubbles is broken until the solidification is completed, and the bubbles grow into large bubbles. It became voids and could not be fixed with the fine bubble structure immediately after the start of solidification.
Therefore, in the present invention, an elastic cell structure containing a large number of fine bubbles by rapidly fixing fine bubbles of a stock solution for producing an elastic cell, which was previously considered impossible in a method of producing a sponge using rubber latex as a raw material. It is an object to provide an extremely flexible sponge.
[0007]
[Means for Solving the Problems]
In the present invention, an aqueous dispersion such as a natural rubber or a synthetic rubber latex as described below is used as a raw material, sodium silicate is added thereto, and air is further blown into the stock solution for fine cell production by high-speed stirring. After injecting the stock solution into equipment having releasability, it is irradiated with microwaves for a short period of time, quickly solidified, dried, and vulcanized, so that the number of cells in the cross section is 8 cells / mm 2 or more, 50% compression. An elastic cell structure having a stress of 1.0 N / cm 2 or less and an apparent density of 0.150 g / cm 3 or less can be manufactured.
The stock solution for producing the elastic cell structure in the present invention is mainly composed of an aqueous dispersion such as natural rubber or synthetic rubber latex, and includes, for example, natural rubber (NR) latex, synthetic isoprene rubber (IR) latex, acrylonitrile butadiene. Rubber (NBR) latex, styrene / butadiene rubber (SBR) latex, butadiene rubber (BR) latex, urethane resin aqueous dispersion, silicone resin dispersion and the like, alone or in combination.
The elastic cell structure having a large number of microbubbles obtained in the present invention is extremely flexible, fine-grained, excellent in feel and application function to skin, and is effective to be used as a cosmetic application base material. In addition, it is highly applicable as a cleaning tool, cushioning material, filter material, and other miscellaneous / industrial base materials.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
That is, the present invention basically has the following configuration.
(1) A cosmetic applicator comprising an elastic cell structure derived from rubber latex, in which a large number of fine-sized spherical bubbles are present, and a part of which forms a deformed cell structure in which fine bubbles are aggregated. Is formed from an elastic cell structure derived from rubber latex containing a large number of microbubbles of 8 / mm 2 or more, an apparent specific gravity of 0.150 g / cm 3 or less, and a 50% compressive stress of 1.0 N / cm 2 or less. A cosmetic applicator, characterized in that:
(2) The cosmetic applicator according to (1), wherein the rubber sponge sheet is sliced and bonded with the sliced surface facing outward.
(3) Air and sodium silicate are added to the rubber-based latex compound liquid and stirred to form an undiluted solution for producing an elastic cell, which is poured into a mold-releasing device and rapidly solidified by microwave irradiation. By performing drying and vulcanization, a large number of fine-sized spherical bubbles exist, some of which form a deformed cell structure in which the fine bubbles are aggregated, and a large number of fine bubbles with a cell number of 8 cells / mm 2 or more are formed. A method for producing an elastic cell structure derived from rubber latex, comprising: an apparent specific gravity of 0.150 g / cm 3 or less and a 50% compressive stress of 1.0 N / cm 2 or less.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
The apparent density of the rubber-based elastic cell structure obtained in the present invention is 0.150 g / cm 3 or less, particularly 0.12 to 0.13 g / cm 3 , and has a good texture as a cosmetic applicator, This is far superior to the wet urethane sponge conventionally known for its fineness.
The number of cells in the cross section of the rubber-based cell structure obtained by the conventional technique is about 5.0 to 5.7 cells / mm 2 , but the number of cells in the cross section of the elastic cell structure obtained by the present invention is Is 8 / mm 2 or more, especially 12 / mm 2 or more. In terms of physical properties, the rubber-based cell structure obtained by the conventional method has a 50% compressive stress of 1.5 to 1.6 N / cm 2 , whereas the rubber-based elastic cell structure of the present invention has a 50% compressive stress of 1.5 to 1.6 N / cm 2. In the body, the 50% compressive stress is 1.0 N / cm 2 or less, particularly 0.41 to 0.60 N / cm 2 , and the flexibility is extremely improved as compared with the conventional product.
[0010]
When the cross section of the cell structure obtained by using the rubber latex as a stock solution by the conventional Dunlop method and the cross section of the rubber elastic cell structure obtained by the present invention are observed with a microscope, the conventional method has a coarse cell structure. On the other hand, in the case of the present invention, a large number of spherical bubbles having a fine diameter exist in the present invention, and a part thereof forms a deformed cell structure in which the fine bubbles are aggregated.
That is, in the conventional method, fine bubbles formed by air blown into the stock solution grow into coarse bubbles with time until the completion of solidification, but in the present invention, the microwave is irradiated immediately after the stock solution is injected. Since it is solidified in a short time, it can be confirmed that the elastic cell structure is formed in the state of fine bubbles.
As a result, the elastic cell structure of the present invention has much finer texture than the conventional product, and has a good texture, as described above, and is most suitable for a cosmetic applicator and the like.
[0011]
The physical properties of the rubber-based elastic cell structure were compared between the elastic cell structure obtained by the method of the present invention using a typical NBR latex as a rubber-based latex as a raw material and that obtained by the conventional Dunlop method. It is as follows.
Note that the compounding formulation and the processing method are the same as in Example 1.
The time from injection of the undiluted solution for microcell production to microwave irradiation was set to 10 seconds, 30 seconds, 50 seconds, and 70 seconds, and the apparent density (N / cm 2 ) of the elastic cell structure obtained under each condition and the cell of the cross section The number (number / mm 2 ) and the 50% compressive stress (N / cm 2 ) are measured, respectively.
[0012]
[Table 1]
(2) The number of cells is measured with a digital HD microscope VH-7000.
(3) A microwave frequency of 2450 MHz is used.
[0013]
As can be seen from Table 1, according to the method of the present invention, if the time until the microwave irradiation is 70 seconds or less, in any case, the fine bubbles are more flexible than the sponge obtained by the conventional Dunlop method. It was confirmed that something was obtained.
[0014]
The method for producing the elastic cell structure of the present invention will be specifically described. First, air is blown into a compounded liquid obtained by adding and mixing a vulcanizing agent and other auxiliaries to a rubber-based latex, and sodium silicate is added. Vigorous stirring is performed with an Oaks mixer or the like to obtain an elastic cell structure manufacturing stock solution. The relationship between the weight and the volume of the cell structure manufacturing stock solution is such that a weight of 250 g to 120 g occupies a volume of about 1000 cc (that is, about 4 to 8 times). The cell structure manufacturing stock solution is injected into a device having mold release properties, and microwave irradiation is performed. The time from injection to microwave irradiation is preferably as short as possible, but is sufficient if it is within 70 seconds. is there. The microwave frequency of 2450 MHZ was used, but is not particularly limited.
Further, the irradiation time of the microwave itself may be an irradiation time of about several tens of seconds, preferably 20 seconds or less, and more preferably 10 to 15 seconds. If the irradiation time exceeds 30 seconds, the cell structure locally expands due to overheating, which is not preferable.
[0015]
In the conventional technology for producing an elastic cell structure such as the Dunlop method, since coagulation is performed without using microwaves, coagulation of the blended liquid requires 60 to 210 seconds, during which time the bubble diameter increases with time. In the end, each bubble bursts so that the soap bubble breaks, the bubbles are connected, and the bubble diameter expands.To prevent this, control of solidification conditions such as temperature and time is an extremely important requirement. However, according to the present invention, since the solidification is rapidly performed by heating with microwaves, it is unnecessary to control the coagulation conditions such as the temperature and time required in the related art, but the bubbles of the obtained foam are not required. Since the cell structure can be fixed as it is in the fine stage in the early stage of solidification, the resulting cell structure is useful as a fine and skin-friendly elastic cell structure.
[0016]
The rubber latex used in the present invention preferably has a high solids content of 60% by weight or more, preferably 65% by weight or more.
Active sulfur is generally used as a vulcanizing agent. As the vulcanization accelerator, any of thiazole, thiourea, thiuram and dithiocarbamate vulcanization accelerators can be used. In addition, an antioxidant, an antibacterial / antifungal agent, a coloring agent and the like may be blended.
However, when the compounding agent is a powder, it is preferable to knead it with water using a ball mill or the like and use it in the form of an aqueous dispersion.
Sodium fluorinated sodium is blended into the rubber latex blended liquid, air is blown in, and the mixture is stirred with an Oak mixer or the like. However, it is appropriate to use one having a capacity of 1000 cc (8 times the volume).
The above-mentioned stock solution for producing a cell structure is injected into a device having releasability, irradiated with microwaves, rapidly solidified, and then dried and vulcanized to fix the cell structure. In the vulcanization step, conventional means such as vulcanization by dry heat or wet heat vulcanization by steam heat can be employed.
[0017]
【Example】
Hereinafter, the present invention will be described in more detail with reference to Examples.
The present invention is not limited to the description of the embodiment, but exerts the same effect in the configuration described in the specification.
Embodiment 1
A mixture is prepared according to the following formulation. However, the numerical value of each component is a value converted into solid components, and the unit thereof is all parts by weight.
The obtained cell structure manufacturing stock solution was poured into a 400 mm × 400 mm square mold.
The mold was a sheet having a thickness of 25 mm, and the time from injection to irradiation of the micro solution was 50 seconds. The microwave irradiation time was set to 15 seconds to coagulate the stock solution. Next, it was dried at 100 ° C. for 45 minutes to obtain a 24 mm-thick NBR cell structure sheet.
The obtained elastic cell structure was sliced to a thickness of 12 mm, the surface films were bonded together, and punched into a circular shape having a diameter of 60 mm. After punching, the composition was heated and vulcanized at 110 ° C. for 30 minutes, and then the edge was polished to obtain a cosmetic sponge puff.
The apparent density of the obtained sponge puff is 0.120 g / cm 3 , the 50% compressive stress is 0.48 N / cm 2 (however, the sample size is 2 cm square), and the number of cells on the slice surface is 11 It was 0.5 pieces / mm 2 . It had a flexible cell structure with very fine foam.
The obtained cosmetic sponge puff had a soft touch on the skin and was excellent, and it was confirmed that the cosmetic sponge puff was a highly evaluated applicator even in a practical test of a cosmetic tool test monitor.
[0018]
Embodiment 2
Air was blown into 100 parts of the mixture obtained in Example 1 while mixing 1.5 parts of sodium silicofluoride, and a 6-fold foamed cell structure manufacturing stock solution was prepared with an Oaks mixer to release the mold. A 50 mm thick sheet was injected onto the belt while moving at a speed of 2.2 m / min. After the injection, the time until microwave irradiation was set to 50 seconds.
The undiluted solution was coagulated with a microwave irradiation time of 12 seconds. Next, drying was performed at 100 ° C. for 45 minutes, and steam vulcanization was performed at 110 ° C. for 30 minutes to obtain an NBR cell structure sheet.
The apparent density of the obtained elastic cell structure was 0.130 g / cm 3 , and the 50% compressive stress was 0.41 N / cm 2 . This sheet was sliced to a thickness of 5 mm, and the number of cells on the sliced surface was 11.7 cells / mm 2 , which was optimal for a wiper or the like as an industrial substrate.
[0019]
【The invention's effect】
The apparent density of the elastic cell structure obtained in the present invention is 0.150 g / cm 3 or less, and the wet urethane resin which has a good texture as a cosmetic applicator, is fancy, and is conventionally known for fineness is used. It far exceeds the urethane sponge obtained as a raw material.
The number of cells in the cross section of the elastic cell structure obtained by the present invention is 8 / mm 2 or more, and the 50% compressive stress is 1.0 N / cm 2 or less, particularly 0.41 to 0.50 N. / Cm 2, which is an extremely flexible sponge.
As described above, the elastic cell structure obtained by the present invention has much finer texture than the conventional product, has a good texture, and is most suitable as the elastic cell structure.
Claims (2)
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| JP2003044852A JP3544542B1 (en) | 2003-02-21 | 2003-02-21 | Cosmetic elastic cell structure and manufacturing method thereof |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2015105113A1 (en) | 2014-01-09 | 2015-07-16 | 株式会社タイキ | Rubber latex elastic foam body |
| JP2018502199A (en) * | 2014-12-22 | 2018-01-25 | エス アンド ピー ワールド リミテッドＳ＆Ｐ Ｗｏｒｌｄ Ｌｔｄ． | NBR sponge for impregnating gel cosmetic composition and method for producing the same |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP3945583B2 (en) | 2004-01-15 | 2007-07-18 | 憲司 中村 | Method for producing cosmetic applicator |
| JP2010001406A (en) * | 2008-06-20 | 2010-01-07 | Sekisui Chem Co Ltd | Foaming rubber sheet |
| KR20230164051A (en) * | 2021-03-31 | 2023-12-01 | 닛토덴코 가부시키가이샤 | resin foam |
| JP7288994B2 (en) * | 2021-03-31 | 2023-06-08 | 日東電工株式会社 | resin foam |
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2003
- 2003-02-21 JP JP2003044852A patent/JP3544542B1/en not_active Expired - Lifetime
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2015105113A1 (en) | 2014-01-09 | 2015-07-16 | 株式会社タイキ | Rubber latex elastic foam body |
| JPWO2015105113A1 (en) * | 2014-01-09 | 2017-03-23 | 株式会社タイキ | Rubber latex elastic foam |
| US10487187B2 (en) | 2014-01-09 | 2019-11-26 | Taiki Corp., Ltd. | Rubber latex elastic foamed body |
| JP2018502199A (en) * | 2014-12-22 | 2018-01-25 | エス アンド ピー ワールド リミテッドＳ＆Ｐ Ｗｏｒｌｄ Ｌｔｄ． | NBR sponge for impregnating gel cosmetic composition and method for producing the same |
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| JP2004250640A (en) | 2004-09-09 |
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