JP3594699B2 - High efficiency coating method - Google Patents

Description

複合型造粒は、同一容器内に撹拌造粒、転動造粒、流動層造粒の各機能を結合あるいは融合し、造粒物の形状、密度、粒径などの品質を自在に製造する機能や、混合、造粒、乾燥、コーティングなどの単位操作を目的、用途に応じて任意に操作できる機能がある。
【０００４】
次に、各種複合型造粒装置の具体例を挙げると、以下の装置が挙げられる。まず撹拌流動層型では、奈良機械製作所製の「スーパーファインマトリックスＳＭＡ型」や、パウレックス社製の「マルチフレックスグラニュレーターＭＰ型」がある。また、転動流動層型では、岡田精工社製の「スピラコータＳＰ型」が挙げられる。そして、撹拌転動流動層型では、フロイント産業社製の「スパイラフローＳＦＣ型」や不二パウダル社製の「ニューマルメライザーＮＱ型」等である。前記流動層装置は、大半が回分式（バッチ処理方式）であり、流動板や撹拌羽根上部あるいは側面よりスプレーガン（スプレーノズル）により噴霧造粒（コーティング）される。噴霧造粒処理が終了した処理品は、下部側面にある排出弁を介し製品排出口から外部へ排出される。これら装置・方式等については以下に示す提案がなされている。
【０００５】
その代表例の提案としては、特公平２−５６９３５号、特公平３−１０６３号、特公平３−４２０２８号、特公平３−４２０２９号、特公平３−１３５４３０号、特公平５−４１２８号、特公平５−４９９０１号、特公平５−１１５０８号、特公平５−１９２５５５号、特公平６−１８６号等の各公報があり、これら公報は噴霧液滴径について、本発明とは異なり、微粒化制御していないので、粉体粒子衝突時に多くの分裂反跳液滴を発生させ、この液滴が装置内壁面や回転羽根あるいは他の粉体粒子に付着し、凝集体を多く発生させている。また、それと同時に分裂反跳液滴は、噴霧液滴に比べ非常に微粒化されているため、瞬時に固化するものも発生し、固化したコート物質は、乾燥固化状態（コートカス）で粉体表面に付着し、コート品質を悪化させたりしている。
【０００６】
一方、被コーティング物質の表面に滑らかな被膜を形成させることを目的とする浸漬法も紹介されている。この方式は医薬品分野等で錠丸剤をコーティング液中に浸漬させ、これを引き上げ乾燥させる方法であるが、小粒子径の粉粒体のコーティングには不向きであった。小粒径の粉粒体の場合、浸漬後の乾燥工程で粒子同士が付着・凝集を起し最終的には団塊状態となり、一次粒子としての形態が要求される分野では困難であった。
また、コーティング液の溶媒沸点が１００℃以上の溶媒では、前記紹介した各造粒装置内での温度が沸点以下となるケースが多々あるため、乾燥不良品が発生することもある。特にジャケット加熱による乾燥を行なう混合造粒法、ミキサー等では、その傾向は顕著で、コート後の粒子がブロック状の塊になりやすい。また、装置内に残留溶媒のガスが充満しやすく、環境・安全面で問題が残る。
他方、以上紹介した各造粒法はバッチ処理（回分式）であると同時に、スプレー法や浸漬法では１バッチあたりの処理時間が長く生産性も悪い。そのため、生産性を向上させる為に並列に同一機種あるいはスケールの大きな装置を導入して生産性を向上させなければならず、製品のコストアップにもつながっている。
【０００７】
【発明が解決しようとする課題】
従って、本発明の目的は、上記従来のコーティング方法の問題点を解決することによって、粉体粒子を高効率にコーティングでき、且つ容易に高品位のコーティング品が得られる造粒装置によるコーティング方法を提供することにある。
【０００８】
【課題を解決するための手段】
本発明によれば、第一に、被コーティング粉粒体が粉粒体撹拌槽内でコーティング樹脂溶液中に浸った状態でコーティングされるコーティング方法において、該粉粒体撹拌槽内を減圧状態にしてコート・撹拌・乾燥を行なうことを特徴とする高効率コーティング方法が提供される。すなわち、このコーティング方法は、コーティング装置の粉粒体撹拌造粒装置内に、被コーティング物質（粉粒体）を投入し、次にコーティング樹脂溶液を被コーティング物質が完全に浸るまで投入する。その状態で撹拌槽を密閉し２〜５分間撹拌羽根と解砕羽根を回転させ、全粉粒体を浸漬させる。そして、その状態で撹拌槽内の内部圧力を５００ｍｍＨｇ以下になるまで減圧させ、コート・撹拌・乾燥を行なう。槽内含水率が２０％以下になったら、撹拌羽根と解砕羽根の回転数をアップさせ、コーティング粉粒体を得ることを特徴とする方法である。
【０００９】
また、本発明によれば、第二に、被コーティング粉粒体が粉粒体撹拌槽内で転動流動状態に保持された状態で噴霧コーティングされるコーティング方法において、該該粉粒体撹拌槽内を減圧状態にしてコート・撹拌・乾燥を行なうことを特徴とする高効率コーティング方法が提供される。すなわち、このコーティング方法は、粉粒体を粉粒体撹拌造粒装置内で転動流動状態にさせ、その状態の粉粒体にコーティング樹脂溶液を噴霧するコーティング方法で、そのときの撹拌造粒装置内圧力が減圧状態であることを特徴とする方法である。
【００１０】
また、本発明によれば、第三に上記第一又は第二に記載したコーティング方法において、前記粉粒体撹拌槽が、撹拌を目的とする撹拌羽根と解砕を目的とする解砕羽根を備え且つ冷却・加熱が可能なジャケットを有し、コート・撹拌・乾燥時は、ジャケット加熱温度がコーティング樹脂溶液中の溶媒沸点温度と同等若しくはそれ以上の温度であることを特徴とする高効率コーティング方法が提供され、第四に、上記第三に記載したコーティング方法において、前記粉粒体撹拌槽に備えられた撹拌羽根と解砕羽根の回転数が、コート時は乾燥時の回転数の１／２以下の回転数で行なわれ、しかも撹拌羽根回転数と解砕羽根回転数の比が１：２〜１：４の範囲でコーティングされることを特徴とする高効率コーティング方法が提供される。すなわち、第三のコーティング方法は、粉粒体を撹拌させる撹拌羽根と解砕羽根を有する粉粒体撹拌造粒装置において、冷・加熱が可能なジャケット内温度が、コーティング樹脂溶液中の溶媒沸点温度と同等若しくはそれ以上の加熱温度でコート・撹拌・乾燥することを特徴とする方法であり、第四のコーティング方法は、前記粉粒体撹拌槽内に設置される撹拌羽根と解砕羽根の回転数比が１：２〜１：４の範囲で回転し、乾燥時はコート時の２倍以上の回転数であることを特徴とする方法である。
【００１１】
更に、本発明によれば、上記第二に記載したコーティング方法において、前記噴霧コーティングが、粉粒体粒子径の１／５以下の噴霧液滴径で、且つ平均粒径が２〜１５μｍの噴霧液滴で実施されることを特徴とする高効率コーティング方法が提供され、第六に、上記第五に記載したコーティング方法において、前記噴霧液滴径が、レーザー式粒度分布計測器によって計測された値で、体積累積値の１０％値と９０％値の比（９０％値／１０％値）が５．００以下であることを特徴とする高効率コーティング方法が提供され、また第七に、上記第一に記載したコーティング方法において、前記粉粒体撹拌槽内が５００ｍｍＨｇ以下の減圧雰囲気下にあることを特徴とする高効率コーティング方法が提供される。
【００１２】
【作用】
本発明では、コーティング装置として、例えば図１に示されるような撹拌混合造粒装置を用いる。
図１において、１は粉粒体撹拌造粒装置、２は粉粒体解砕羽根、３は粉粒体撹拌羽根、４はスプレーノズル、５は冷・加熱ジャケット、６はバグフィルター、７は減圧用真空ポンプ、８はコーティング樹脂溶液供給ポンプ、９は溶媒トラップ装置、１０は溶媒回収装置、１１は回収溶媒である。造粒工程（コート・撹拌・乾燥）においては、粉粒体撹拌造粒装置１内に粉粒体を供給し、粉粒体撹拌羽根３と粉粒体解砕羽根２を同時に回転させ、粉粒体の転動流動層を形成させる。
【００１３】
本発明の第一のコーティング方法である液浸漬造粒法（図１の右半分側に模式的に表示される）は、粉粒体解砕羽根２が隠れる迄粉粒体を投入し、その後コーティング樹脂溶液１２を粉粒体１３が完全に浸漬するまで投入する。そして、その状態で粉粒体撹拌造粒装置１を密閉し、粉粒体全粒子表面にコーティング樹脂溶液中の樹脂が付着するように、２〜５分粉粒体撹拌羽根３と粉粒体解砕羽根２を同時に回転させる。その後、粉粒体撹拌造粒装置内を減圧用真空ポンプ７で槽内圧力が５００ｍｍＨｇ以下になるように減圧させながら、コーティング・撹拌・乾燥を行なうものである。
【００１４】
一方、本発明の第二のコーティング方法であるスプレー法（図１の左半分側に模式的に表示される）は、粉粒体撹拌羽根３と粉粒体解砕羽根２を回転させ、装置内で粉粒体を転動流動状態にさせる。その状態の粉粒体に、コーティング樹脂溶液供給ポンプ８によりコーティング液を供給し、スプレーノズル４を介して微粒液滴化したコーティング樹脂溶液を噴霧する。そして、その時の装置内圧力は、液浸漬造粒法と同じ条件で行ない、コーティング・撹拌・乾燥を行なうものである。
【００１５】
本発明の減圧雰囲気下におけるコーティング・撹拌・乾燥時に発生する排気溶媒は、溶媒トラップ装置９によって回収され、排気管からは熱風ガスのみが排気される。本発明のコーティングされた粉粒体は、粉粒体撹拌造粒装置内に設置された計測器（水分計又は溶剤ガス濃度計）によって管理され、槽内含水率が２０％以下になったら回収され、次工程に供給される。
【００１６】
本発明のコーティング方法は、コート液を噴霧する方法でも、粉体粒子をコート液中に浸漬させる方法でもよく、スプレー方法、浸漬方法ともにコーティング時・乾燥時は、ジャケット加熱をする。そのときの加熱温度は、コーティング樹脂溶液中の溶媒沸点よりも高い温度に設定する。この温度は装置内の減圧状態で溶媒沸点が下がるので、減圧状態を確認しながらジャケット温度を設定する。また、本発明の装置内における圧力は、５００ｍｍＨｇ以下迄減圧させて、コーティング・乾燥を行なうが、減圧が弱い（５００ｍｍＨｇ〜７６０ｍｍＨｇ）と乾燥操作時の乾燥時間が長くなったり、凝集粒子が多発し生産効率が大幅に低下する。
【００１７】
次に、本発明における各コーティング方法について説明する。
噴霧する方法は、噴霧されるコート液滴径を平均粒径で２〜１５μｍに、且つ体積累積値の１０％値と９０％値の比（９０％値／１０％値）を５．００以下に制御して噴霧コーティングする。噴霧液滴径は、好ましくは３〜１０μｍである。噴霧液滴径が１５μｍを超えると、被コーティング粒子（小粒径粉粒体）表面上に形成された乾燥後の膜が大きな凹凸状として形成される為、不均一なコート被膜となる。また、突起部分では膜内部が乾燥しにくくなる為（膜表面が乾燥しても、内部は未乾燥状態として存在する）、他のコーティング物質（コーティング後の小粒径粉体粒子）との接触時及び衝突時に接合して凝集体となる。また、液滴径が大きいと、所望のコーティング膜厚が得られない問題と、液滴が被コーティング粒子に衝突した際、液滴が分裂し微粒な分裂反跳液滴となり装置内壁部に付着したり、瞬時に乾燥し固形化して層外へ排出され、歩留り低下を招く原因となる。
一方、噴霧液滴径が２μｍ未満となると、噴霧後の液滴中に含まれる溶媒分が瞬時に蒸発（乾燥濃度上昇による）して膜化できなくなる。このため、コート液中の樹脂分が乾燥固形粒子となり、飛散物あるいは樹脂カスとして装置内壁部へ積着したり、排気側へ飛び歩留り低下を生じることもある。
【００１８】
本発明のスプレー法によるコーティングは、噴霧液滴径を微粒化し且つコーティング雰囲気（環境）を減圧状態にしているので、コート液溶媒が溶剤系でも水系でも高固形液でも、均一な膜形成が可能である。特に水系では、水の沸点は、溶剤系よりも高いのでより効果的（効率的）に被膜形成が可能である。
本発明のスプレー法によるコーティングは、噴霧液滴が体積累積値の１０％値と９０％値の比（９０％値／１０％値）が、５．００以下の粒度分布の液滴が噴霧・コーティングされる。しかし、前記比が５．００以上になると、液滴分布における小粒径側液滴でコートされた膜厚及び膜均一性と、大粒径側液滴でコートされた膜厚及び均一性が大きく異なる。その為、同一処理品内での品質ばらつきが大きくなり、サンプリングによっては、所望の品質特性が得られない場合が生じる。
【００１９】
本発明のスプレーコーティング方法は、前記したスプレー法及び条件で噴霧されるが、コーティング装置内において、噴霧される液滴中の溶媒沸騰温度域でコーティングされる。液滴の溶媒沸騰温度域でコーティングされると噴霧直後、粉体粒子表面に液滴が衝突・膜化し、その瞬間に液滴中の溶媒が蒸発するので膜が固化する。しかし、コーティング装置内の温度環境が、液滴中溶媒の沸騰温度域よりも低いと、コーティング後膜化しても膜内部は固化しない状態で存在しやすくなる。その場合、他の粒子と接触あるいは衝突、更に内壁面に接触・衝突したとき、付着・凝集・固着等が発生する。
【００２０】
一方、被コーティング粉粒体をコーティング樹脂粒子中に浸す方法の場合は、乾燥後の被膜厚みが目標厚みになる様にコーティング樹脂溶液を被コーティング粉粒体が投入されてある装置内へ入れる。そして、被コーティング粉粒体が全て浸るまで、撹拌・混合を行なう。撹拌・混合時間としては、２〜５分間行なえば十分である。本発明の粉粒体撹拌混合造粒槽は、内壁部と外壁部の間に冷・温水が流せるジャケットを有し、コーティング・乾燥時は、ジャケット内を加熱する。そのときのジャケット加熱方法・条件は、スプレー法とほぼ同じ方法・条件で行なえばよく、装置内圧力も同じでよい。しかし、〔コーティング時の撹拌羽根回転数と解砕羽根回転数〕と〔乾燥時に於ける撹拌羽根回転数と解砕羽根回転数〕は変える必要がある。コーティング時の撹拌羽根と解砕羽根の回転数は、それぞれ〔２００〜６００ｒｐｍ、７００〜２０００ｒｐｍ〕、乾燥時はコーティング時における各羽根回転数の〔１．５〜３倍〕の回転数で行なう。コーティング時における羽根回転数が前記回転数より低いと、均一な混合撹拌作用が働かず、撹拌されている粉粒体全体へコーティングがされにくくなる。また、反対に羽根回転数が高いと、撹拌混合作用は問題ないが、コーティング樹脂溶液が跳ね上ったりして、樹脂の付着効率が低下したり（コーティング時）、コーティングされた樹脂が剥離したり、粉体粒子自身が破壊（粉砕）されることがある。（乾燥時）
【００２１】
本発明のコーティング方法は、噴霧方法でも液浸漬方法でも、より均一な膜を形成させることにより、前記問題を解決した高効率コーティング方法である。
【００２２】
【実施例】
次に、本発明を実施例により更に詳細に説明する。
各実施例に共通の固定条件は次の通りである。

【００２３】
実施例１〜８
表２に示す条件でフェライトキャリアにコート液をコーティングし、ＰＶＡ被覆キャリアを得た。
【００２４】
【表２】

【００２５】
比較例１
実施例１の装置内圧力を〔５００ｍｍＨｇ〕から〔常圧（７６０ｍｍＨｇ）〕に替えた他は、全て実施例１と同条件でＰＶＡ被覆キャリアを得た。
【００２６】
比較例２
実施例２の〔撹拌羽根回転数〕と〔解砕羽根回転数〕を適正回転数より低く設定した他は、全て実施例２と同条件でＰＶＡ被覆キャリアを得た。
【００２７】
比較例３
実施例５の〔ジャケット加熱温度〕を溶媒沸点温度より低く設定した他は、全て実施例５と同条件でＰＶＡ被覆キャリアを得た。
【００２８】
比較例４
実施例６の〔撹拌羽根回転数〕と〔解砕羽根回転数〕の設定を、適正回転数より高めに設定した他は、全て実施例６と同条件でＰＶＡ被覆キャリアを得た。
【００２９】
比較例５
実施例１の装置内圧力を弱減圧〔７００ｍｍＨｇ〕に替え、〔ジャケット加熱温度〕を溶媒沸点よりも低く設定した他は、全て実施例１と同条件でＰＶＡ被覆キャリアを得た。
【００３０】
比較例６
実施例３の〔装置内圧力〕を〔常圧（７６０ｍｍＨｇ）〕に替えた他は、全て実施例３と同条件でＰＶＡ被覆キャリアを得た。
【００３１】
比較例７
実施例４の〔噴霧液滴径〕と〔体積粒径比〕を大きくした他は、全て実施例４と同条件でＰＶＡ被覆キャリアを得た。
【００３２】
比較例８
実施例４の〔撹拌羽根回転数〕と〔解砕羽根回転数〕を適正回転数より高く設定した他は、全て実施例４と同条件でＰＶＡ被覆キャリアを得た。
【００３３】
比較例９
実施例３の〔撹拌羽根回転数〕と〔解砕羽根回転数〕を適正回転数より低く設定した他は、全て実施例３と同条件でＰＶＡ被覆キャリアを得た。
【００３４】
比較例１０
実施例７の〔噴霧液滴径〕の粒径を適正液滴径より微粒化した他は、全て実施例７と同条件でＰＶＡ被覆キャリアを得た。
【００３５】
比較例１１
実施例８の〔装置内圧力〕を弱減圧〔７００ｍｍＨｇ〕に替え、〔ジャケット加熱温度〕を溶媒沸点よりも低く設定した他は、全て実施例８と同条件でＰＶＡ被覆キャリアを得た。
【００３６】
以上の比較例１〜１１で採用された条件をまとめて表３に示す。
【００３７】
【表３】

【００３８】
以上の得られたＰＶＡ被覆キャリアについて品質評価を行なった。その結果を表４に示す。なお、評価方法等は下記によった。
１．スプレー法と液浸漬法は設定樹脂固形分が異なるのでコート・乾燥時間が異なっている。
２．装置内壁面への付着度合いは、目視で付着度合いを判定し、５段階にランク分けした。最も良いものは〔◎〕、最も悪いものを〔×〕としている。
３．凝集度については、投入コーティング前の粉体粒子と、噴霧及び液浸漬後のコート液が乾燥した時の樹脂固形分の合計を総投入量とし、その重量に対する基準メッシュ以上残留した重量比を５段階にランク分けし、付着度合い同様に◎〜×で表わした。
４．〔微細品発生率〕は、コート後の粉体粒子を基準メッシュで篩分けし、通過した量を、コート上がり総重量で割った重量比を表わす。
５．〔コート樹脂カス発生度〕は、コート後の粒子表面を電子顕微鏡写真で観察し、その度合いを５段階に層別し、ほとんどカスのないものを〔◎〕とし、ランク分けは内壁面付着評価と同様な方法で行なった。
６．〔コート膜厚ばらつき〕は、最小膜厚と最大膜厚を計測し、その差に応じてランクを５段階に層別した。評価ランクは他の５段階評価方法と同じ方法で行なった。
７．〔表面性〕は、コート樹脂カス発生度評価時に表面状態に評価し、凹凸の少ないものを〔◎〕とした。
８．〔歩留り〕は、総投入量に対するコート後の回収重量の比（ｗｔ％）。但し、凝集発生した粉体粒子はコート後の出来高からは除いた（凝集品は、製品として使用できない為）。
９．〔帯電特性・電気特性〕は、基準値（目標値）に対するずれ度合いを５段階に層別し、ずれの少ないものを〔◎〕とし、ずれ度合いに応じて評価分けした。
１０．〔総合評価〕は、製品の生産性・品質等を含め、総合的に優れているものを〔◎〕とし、５段階に層別した。
【００３９】
【表４】

【００４０】
【発明の効果】
本発明のコーティング方法は、被コーティング粉粒体が粉粒体撹拌槽内でコーティング樹脂溶液中に浸った状態でコーティングされるか、又は被コーティング粉粒体が粉粒体撹拌槽内で転動流動状態に保持された状態で噴霧コーティングされるコーティング方法において、該粉粒体撹拌槽内を減圧状態にしてコート・撹拌・乾燥を行なうという構成にしたことから、以下のような顕著な効果を奏することができ、高効率の噴霧コーティング及び液浸漬コーティングが可能となり、高品位の製品を得ることができる。
（イ）スプレー法においては、液滴径が小粒径、且つ均一分布をしているので、コーティング後の粒子表面状態が滑らか、且つ均一コート膜となる。そのため、各品質特性値（帯電特性・電気特性等）が安定する。
（ロ）液浸漬法においては、短時間で粒子表面が滑らかなコート膜形成ができ、且つ均一コート膜となる。そのためスプレー法同様に品質特性値が安定する。
（ハ）コーティング装置内壁部への付着物が低減するので、メンテナンスが容易になる。
（ニ）コーティング時及び乾燥時における、粒子の凝集が低減するので、品質特性値が安定、且つ歩留りも向上する。また、生産性の向上、コスト低減も達成できる。
（ホ）装置内圧力を減圧状態にしてコーティングするので、水のように沸点が高く乾燥しにくい溶媒でも、短時間でコーティング・乾燥ができ、生産性が向上する。
【図面の簡単な説明】
【図１】本発明に使用される撹拌混合造粒装置の一例を示す説明図であり、粉粒体撹拌層の右半分側は液浸造粒法時の状態を、左半分側はスプレー造粒法時の状態を、それぞれ模式的に表示している。
【符号の説明】
１ 粉粒体撹拌槽
２ 粉粒体解砕羽根
３ 粉粒体撹拌羽根
４ スプレーノズル
５ 冷・加熱ジャケット
６ バグフィルター
７ 減圧用真空ポンプ
８ コーティング樹脂溶液供給ポンプ
９ 溶媒トラップ装置
１０ 溶媒回収管
１１ 回収溶媒
１２ コーティング樹脂溶液
１３ 粉粒体
１４ 含水率検知装置[0001]
[Industrial applications]
The present invention relates to a method for efficiently coating a resin on the surface of powder particles.
[0002]
[Prior art]
Granulation devices have been actively introduced since around 1970, mainly in the pharmaceutical and food industries, because they can process small-quantity multi-product production, mixing, granulation, and drying processes in the same container. In addition, the social environment required for granulated products is such that, for small-quantity multi-product production, granules with particle size, density, shape, etc. can be obtained arbitrarily, and mixing, granulation, coating and drying are performed by a single facility There has been a demand for a complex operation capable of selecting any process and a multifunctional FA unmanned system capable of arbitrarily obtaining the above-mentioned quality.
In response to these demands, various equipment manufacturers have been developing and commercializing composite granulation equipment since around 1980, and commercialized equipment that processes fluidized bed, agitation, and tumbling in the same container. Was done.
[0003]
Many of the combined granulation methods combine fluidized bed granulation, stirring granulation, and tumbling granulation. For example, the combination is shown in Table 1 below.
[Table 1]

Combined granulation combines or fuses the functions of agitation granulation, tumbling granulation, and fluidized bed granulation in the same vessel, and freely manufactures the quality of the granulated material such as shape, density, and particle size. There is a function and a function that can arbitrarily operate unit operations such as mixing, granulation, drying, and coating depending on the purpose and application.
[0004]
Next, specific examples of various composite-type granulation apparatuses include the following apparatuses. First, the stirred fluidized bed type includes "Super Fine Matrix SMA type" manufactured by Nara Machinery Co., Ltd. and "Multiflex Granulator MP type" manufactured by Pourex. As the rolling fluidized bed type, “Spiracoater SP type” manufactured by Okada Seiko Co., Ltd. is exemplified. Examples of the agitated rolling fluidized bed type include "Spiral flow SFC type" manufactured by Freund Corporation and "Nummarmerizer NQ type" manufactured by Fuji Paudal. Most of the fluidized bed apparatus is of a batch type (batch processing type), and is spray-granulated (coated) by a spray gun (spray nozzle) from above or on a side surface of a fluidized plate or a stirring blade. The processed product after the spray granulation process is discharged to the outside from a product discharge port via a discharge valve on a lower side surface. The following proposals have been made for these devices and methods.
[0005]
Typical proposals include Japanese Patent Publication No. 2-56935, Japanese Patent Publication No. 3-10363, Japanese Patent Publication No. 3-42028, Japanese Patent Publication No. 3-42029, Japanese Patent Publication No. 3-135430, Japanese Patent Publication No. 5-4128, There are various publications such as Japanese Patent Publication No. 5-49901, Japanese Patent Publication No. 5-111508, Japanese Patent Publication No. 5-192555, and Japanese Patent Publication No. 6-186. Is not controlled, so many split recoil droplets are generated at the time of powder particle collision, and these droplets adhere to the inner wall of the device, rotating blades or other powder particles, and generate a large amount of aggregates I have. At the same time, the split recoil droplets are very finely divided compared to the spray droplets, and some of them solidify instantaneously. The solidified coating material is dried and solidified (coat residue) on the powder surface. To the coating, which deteriorates the coating quality.
[0006]
On the other hand, an immersion method for forming a smooth film on the surface of a substance to be coated is also introduced. This method is a method in which a tablet pill is immersed in a coating solution in the field of pharmaceuticals and the like, and is pulled up and dried. However, this method is not suitable for coating a powder having a small particle diameter. In the case of a powder having a small particle diameter, particles adhere and aggregate in a drying step after immersion, and finally form a nodule, which is difficult in a field where the form as primary particles is required.
In addition, in the case of a solvent having a solvent boiling point of 100 ° C. or higher in the coating liquid, the temperature in each of the above-described granulating apparatuses often becomes lower than the boiling point, and thus defective drying may occur. In particular, the tendency is remarkable in a mixed granulation method in which drying is performed by heating with a jacket, a mixer, or the like, and the particles after coating are likely to become block-like lumps. Further, the gas of the residual solvent is easily filled in the apparatus, and there remains a problem in terms of environment and safety.
On the other hand, each of the granulation methods introduced above is a batch process (batch type), and at the same time, the spray method or the immersion method has a long processing time per batch and poor productivity. Therefore, in order to improve the productivity, it is necessary to introduce the same model or a large-scale apparatus in parallel to improve the productivity, which leads to an increase in the cost of the product.
[0007]
[Problems to be solved by the invention]
Accordingly, an object of the present invention is to provide a coating method using a granulating apparatus capable of coating powder particles with high efficiency and easily obtaining a high-quality coated product by solving the problems of the conventional coating method. To provide.
[0008]
[Means for Solving the Problems]
According to the present invention, first, in the coating method to be coated in a state in which the coating powder or granular material is immersed in the coating resin solution in granule stirred tank, and the powder particle body stirred tank in a reduced pressure state high efficiency coating method characterized by performing coating and stirring and drying is provided Te. That is, in this coating method, a substance to be coated (powder and granules) is charged into a granular agitation granulator of a coating apparatus, and then a coating resin solution is charged until the substance to be coated is completely immersed. In this state, the stirring tank is closed, and the stirring blade and the crushing blade are rotated for 2 to 5 minutes to immerse all the powders. Then, in this state, the internal pressure in the stirring tank is reduced to 500 mmHg or less, and coating, stirring, and drying are performed. When the water content in the tank is 20% or less, the number of rotations of the stirring blade and the crushing blade is increased to obtain a coating powder.
[0009]
Further, according to the present invention, secondly, in a coating method in which a powder to be coated is spray-coated while being held in a tumbling fluid state in a powder and particle stirring tank, the powder and particle stirring tank is provided. A high-efficiency coating method is characterized in that the coating, stirring, and drying are performed while the inside is in a reduced pressure state. In other words, this coating method is a coating method in which a granule is brought into a tumbling fluid state in a granule agitation granulator, and a coating resin solution is sprayed on the granule in that state. The method is characterized in that the pressure inside the device is in a reduced pressure state.
[0010]
According to the present invention, thirdly, in the coating method described in the first or second aspect, the powdery and granular stirring tank includes a stirring blade for stirring and a crushing blade for crushing. A high-efficiency coating characterized by having a jacket that can be cooled and heated, and in which coating, stirring, and drying, the jacket heating temperature is equal to or higher than the boiling point of the solvent in the coating resin solution. method is provided, the fourth, in the coating method described above third, the number of revolutions of the stirring blade and the solution砕羽roots provided in the powder or granular material agitation tank, when coat of dry燥時rotational speed of the A high-efficiency coating method is provided, wherein the coating is performed at a rotation speed of 1/2 or less, and the ratio of the rotation speed of the stirring blade to the rotation speed of the crushing blade is in the range of 1: 2 to 1: 4. You. That is, in the third coating method, in a granule stirring and granulating apparatus having a stirring blade for stirring the granules and a crushing blade, the temperature in the jacket that can be cooled and heated, the boiling point of the solvent in the coating resin solution. Coating, stirring and drying at a heating temperature equal to or higher than the temperature, wherein a fourth coating method is a method of stirring blades and crushing blades installed in the powdery particle stirring tank. The method is characterized in that the number of rotations is in the range of 1: 2 to 1: 4, and the number of rotations during drying is twice or more that of coating .
[0011]
Furthermore, according to the present invention, in the coating method described in the second aspect, the spray coating has a spray droplet diameter of 1/5 or less of a granular material particle diameter and an average particle diameter of 2 to 15 μm. A high-efficiency coating method characterized by being performed with droplets is provided. Sixth, in the coating method according to the fifth aspect, the spray droplet diameter is measured by a laser-type particle size distribution measuring device. A high-efficiency coating method characterized in that the ratio (90% / 10%) of the 10% value to the 90% value of the volume cumulative value is 5.00 or less. In the coating method described in the first aspect, there is provided a high-efficiency coating method, wherein the inside of the agitation tank is under a reduced pressure atmosphere of 500 mmHg or less.
[0012]
[Action]
In the present invention, for example, a stirring and mixing granulating apparatus as shown in FIG. 1 is used as the coating apparatus.
In FIG. 1, 1 is a granule stirring granulator, 2 is a granule crushing blade, 3 is a granule stirring blade, 4 is a spray nozzle, 5 is a cooling / heating jacket, 6 is a bag filter, and 7 is a bag filter. A decompression vacuum pump, 8 is a coating resin solution supply pump, 9 is a solvent trap device, 10 is a solvent recovery device, and 11 is a recovered solvent. In the granulation step (coating / stirring / drying), the granules are supplied into the granule stirring / granulating apparatus 1 and the granule stirring blades 3 and the granule crushing blades 2 are simultaneously rotated to obtain the powder. A tumbling fluidized bed of granules is formed.
[0013]
In the first coating method of the present invention, the liquid immersion granulation method (schematically displayed on the right half side in FIG. 1), the powder is charged until the powder crushing blade 2 is hidden, and then The coating resin solution 12 is introduced until the powder 13 is completely immersed. Then, in this state, the granule stirring and granulating apparatus 1 is closed, and the granule stirring blade 3 and the granule are mixed for 2 to 5 minutes so that the resin in the coating resin solution adheres to the entire surface of the granules. The crushing blades 2 are simultaneously rotated. Thereafter, coating, stirring and drying are performed while reducing the pressure inside the powder agitation granulator by the vacuum pump 7 for reducing the pressure so that the pressure in the tank becomes 500 mmHg or less.
[0014]
On the other hand, the spraying method (schematically displayed on the left half side of FIG. 1), which is the second coating method of the present invention, rotates the powder / granular stirring blade 3 and the powder / granulation blade 2 to rotate the apparatus. Inside, the powder is brought into a tumbling state. A coating liquid is supplied to the powdery granules in this state by a coating resin solution supply pump 8, and the coating resin solution formed into fine droplets is sprayed through a spray nozzle 4. The pressure in the apparatus at that time is set under the same conditions as in the liquid immersion granulation method, and coating, stirring and drying are performed.
[0015]
The exhaust solvent generated during coating, stirring, and drying under the reduced-pressure atmosphere of the present invention is collected by the solvent trap device 9, and only the hot air gas is exhausted from the exhaust pipe. The coated granular material of the present invention is controlled by a measuring instrument (a moisture meter or a solvent gas concentration meter) installed in the granular material stirring and granulating apparatus, and when the water content in the tank becomes 20% or less. Collected and supplied to the next process.
[0016]
The coating method of the present invention may be a method of spraying a coating liquid or a method of immersing powder particles in the coating liquid. In both the spraying method and the immersion method, jacket heating is performed during coating and drying. The heating temperature at that time is set to a temperature higher than the boiling point of the solvent in the coating resin solution. At this temperature, the boiling point of the solvent is lowered under reduced pressure in the apparatus, so the jacket temperature is set while checking the reduced pressure. In addition, the pressure in the apparatus of the present invention is reduced to 500 mmHg or less to perform coating and drying. However, if the reduced pressure is weak (500 mmHg to 760 mmHg), the drying time during the drying operation becomes longer or agglomerated particles frequently occur. Production efficiency is greatly reduced.
[0017]
Next, each coating method in the present invention will be described.
The method of spraying is such that the coated droplet diameter is 2 to 15 μm in average particle diameter, and the ratio of the 10% value to the 90% value (90% value / 10% value) of the volume cumulative value is 5.00 or less. And spray coating. The diameter of the spray droplet is preferably 3 to 10 μm. If the sprayed droplet diameter exceeds 15 μm, the dried film formed on the surface of the particles to be coated (small particle size particles) is formed as large irregularities, resulting in an uneven coating film. In addition, since the inside of the film becomes difficult to dry at the protruding portion (even if the film surface is dried, the inside remains in an undried state), it may come into contact with other coating substances (small particle size powder particles after coating). Agglomerates at the time and at the time of collision. In addition, if the droplet diameter is large, the desired coating film thickness cannot be obtained, and when the droplet collides with the particles to be coated, the droplet splits and becomes a fine splitting recoil droplet, which adheres to the inner wall of the apparatus. Or it instantaneously dries and solidifies and is discharged out of the layer, causing a reduction in yield.
On the other hand, if the diameter of the sprayed droplets is less than 2 μm, the solvent contained in the sprayed droplets instantaneously evaporates (due to an increase in dry concentration) and cannot be formed into a film. For this reason, the resin component in the coating liquid becomes dry solid particles, which may be deposited on the inner wall portion of the apparatus as scattered matter or resin scum, or the yield may be reduced toward the exhaust side.
[0018]
In the coating by the spray method of the present invention, since the spray droplet diameter is atomized and the coating atmosphere (environment) is reduced, a uniform film can be formed regardless of whether the coating liquid solvent is a solvent-based solvent, an aqueous solvent, or a high solids liquid. It is. In particular, in a water system, the boiling point of water is higher than that in a solvent system, so that a film can be formed more effectively (efficiently).
In the coating by the spray method of the present invention, the droplets having a particle size distribution in which the ratio of the sprayed droplets to the 10% value and the 90% value (90% value / 10% value) of the volume accumulation value is 5.00 or less are sprayed. Coated. However, when the ratio is 5.00 or more, the film thickness and the film uniformity coated with the small particle size droplets in the droplet distribution and the film thickness and the uniformity coated with the large particle size droplets are reduced. to differ greatly. Therefore, quality variation within the same processed product becomes large, and depending on sampling, a desired quality characteristic may not be obtained.
[0019]
The spray coating method of the present invention is sprayed under the above-mentioned spray method and conditions, and the coating is performed in a coating apparatus in a temperature range of the boiling point of the solvent in the sprayed droplets. When the droplets are coated in the solvent boiling temperature range, the droplets collide with the surface of the powder particles and form a film immediately after spraying, and the solvent in the droplet evaporates at that moment, so that the film solidifies. However, if the temperature environment in the coating apparatus is lower than the boiling temperature range of the solvent in the droplets, the inside of the film is likely to exist without being solidified even if the film is formed after coating. In this case, when the particles come into contact with or collide with other particles and further contact with or collide with the inner wall surface, adhesion, agglomeration, sticking, etc. occur.
[0020]
On the other hand, in the case of the method of immersing the powder to be coated in the coating resin particles, the coating resin solution is introduced into an apparatus into which the powder to be coated is charged so that the film thickness after drying becomes a target thickness. Then, stirring and mixing are performed until all of the particles to be coated are immersed. It is sufficient to perform the stirring and mixing for 2 to 5 minutes. The agitation / mixing granulation tank of the present invention has a jacket through which cold and hot water can flow between the inner wall and the outer wall, and heats the inside of the jacket during coating and drying. At this time, the jacket heating method and conditions may be substantially the same as those of the spray method, and the pressure in the apparatus may be the same. However, it is necessary to change [the rotation speed of the stirring blade and the rotation speed of the crushing blade during coating] and [the rotation speed of the stirring blade and the rotation speed of the crushing blade during drying]. The rotation speeds of the stirring blade and the crushing blade during coating are [200-600 rpm, 700-2000 rpm], and the drying speed is [1.5-3 times] the rotation speed of each blade during coating. If the number of revolutions of the blade during coating is lower than the above-mentioned number of revolutions, the uniform mixing and stirring action does not work, and it is difficult to coat the whole of the stirred powder and granules. On the other hand, if the blade rotation speed is high, the stirring and mixing action is not a problem, but the coating resin solution jumps up, reducing the adhesion efficiency of the resin (at the time of coating), or the coated resin peels off. Or the powder particles themselves may be broken (crushed). (When dry)
[0021]
The coating method of the present invention is a high-efficiency coating method that solves the above-mentioned problem by forming a more uniform film regardless of the spray method or the liquid immersion method.
[0022]
【Example】
Next, the present invention will be described in more detail with reference to examples.
The fixed conditions common to each embodiment are as follows.

[0023]
Examples 1 to 8
A ferrite carrier was coated with a coating solution under the conditions shown in Table 2 to obtain a PVA-coated carrier.
[0024]
[Table 2]

[0025]
Comparative Example 1
A PVA-coated carrier was obtained under the same conditions as in Example 1 except that the internal pressure of the apparatus in Example 1 was changed from [500 mmHg] to [normal pressure (760 mmHg)].
[0026]
Comparative Example 2
A PVA-coated carrier was obtained under the same conditions as in Example 2 except that [Rotation speed of stirring blade] and [Rotation speed of crushing blade] in Example 2 were set lower than appropriate rotation speed.
[0027]
Comparative Example 3
A PVA-coated carrier was obtained under the same conditions as in Example 5 except that the [jacket heating temperature] in Example 5 was set lower than the boiling point of the solvent.
[0028]
Comparative Example 4
A PVA-coated carrier was obtained under the same conditions as in Example 6, except that the setting of [Rotation speed of stirring blade] and [Rotation speed of crushing blade] in Example 6 were set higher than the appropriate rotation speed.
[0029]
Comparative Example 5
A PVA-coated carrier was obtained under the same conditions as in Example 1 except that the internal pressure of the apparatus in Example 1 was changed to slightly reduced pressure [700 mmHg] and the [jacket heating temperature] was set lower than the boiling point of the solvent.
[0030]
Comparative Example 6
A PVA-coated carrier was obtained under the same conditions as in Example 3 except that [in-apparatus pressure] in Example 3 was changed to [normal pressure (760 mmHg)].
[0031]
Comparative Example 7
A PVA-coated carrier was obtained under the same conditions as in Example 4 except that the [spray droplet diameter] and the [volume particle size ratio] of Example 4 were increased.
[0032]
Comparative Example 8
A PVA-coated carrier was obtained under the same conditions as in Example 4 except that [Rotation speed of the stirring blade] and [Rotation speed of the crushing blade] in Example 4 were set higher than the appropriate rotation speed.
[0033]
Comparative Example 9
A PVA-coated carrier was obtained under the same conditions as in Example 3 except that [Rotation speed of the stirring blade] and [Rotation speed of the crushing blade] in Example 3 were set lower than the appropriate rotation speed.
[0034]
Comparative Example 10
A PVA-coated carrier was obtained under the same conditions as in Example 7 except that the particle diameter of [spray droplet diameter] in Example 7 was made finer than the appropriate droplet diameter.
[0035]
Comparative Example 11
A PVA-coated carrier was obtained under the same conditions as in Example 8 except that [in-apparatus pressure] was changed to slightly reduced pressure [700 mmHg] and [jacket heating temperature] was set lower than the solvent boiling point.
[0036]
Table 3 summarizes the conditions employed in Comparative Examples 1 to 11 described above.
[0037]
[Table 3]

[0038]
Quality evaluation was performed on the PVA-coated carrier obtained above. Table 4 shows the results. In addition, the evaluation method etc. were based on the following.
1. The coating method and the drying time are different between the spray method and the liquid immersion method because the set resin solid content is different.
2. Regarding the degree of adhesion to the inner wall surface of the apparatus, the degree of adhesion was visually determined and classified into five levels. The best one is [◎] and the worst one is [x].
3. Regarding the degree of agglomeration, the total amount of the resin particles when the powder particles before input coating and the coating liquid after spraying and liquid immersion were dried was taken as the total input amount, and the weight ratio remaining over the reference mesh to the weight was 5%. The results were ranked according to the stage, and represented by ◎ to × similarly to the degree of adhesion.
4. The [fine article generation rate] represents a weight ratio obtained by sieving the coated powder particles through a standard mesh, and dividing the amount of the particles passed by the total weight of the finished coat.
5. [Coating resin residue generation degree] was evaluated by observing the particle surface after coating with an electron microscope photograph and stratifying the degree into five stages. Those with almost no residue were marked with [◎]. Was performed in the same manner as described above.
6. [Coating film thickness variation] was obtained by measuring the minimum film thickness and the maximum film thickness, and classified into five ranks according to the difference. The evaluation rank was performed in the same manner as the other five-step evaluation methods.
7. [Surface property] was evaluated as a surface state at the time of evaluation of the degree of occurrence of coat resin residue.
8. [Yield] is the ratio (wt%) of the recovered weight after coating to the total input amount. However, the agglomerated powder particles were excluded from the volume after coating (since the agglomerated product cannot be used as a product).
9. [Charging characteristics / Electrical characteristics] were classified into five stages with respect to the deviation from the reference value (target value).
10. [Comprehensive evaluation] was evaluated as [◎] if it was comprehensively excellent, including the productivity and quality of the product, and classified into five stages.
[0039]
[Table 4]

[0040]
【The invention's effect】
According to the coating method of the present invention, the powder to be coated is coated in a state where the powder to be coated is immersed in the coating resin solution in the powder / particle stirring tank, or the powder to be coated rolls in the powder / particle stirring tank. In the coating method of spray coating in a state of being kept in a fluid state, the coating / stirring / drying is performed with the inside of the granular stirring tank under reduced pressure. Therefore, spray coating and liquid immersion coating can be performed with high efficiency, and a high-quality product can be obtained.
(A) In the spray method, since the droplet diameter is small and has a uniform distribution, the particle surface state after coating is smooth and uniform. Therefore, each quality characteristic value (charging characteristic, electric characteristic, etc.) is stabilized.
(B) In the liquid immersion method, a coat film having a smooth particle surface can be formed in a short time, and a uniform coat film can be obtained. Therefore, the quality characteristic value is stabilized similarly to the spray method.
(C) Since the amount of deposits on the inner wall of the coating apparatus is reduced, maintenance is facilitated.
(D) Since the aggregation of particles during coating and drying is reduced, the quality characteristic value is stable and the yield is improved. In addition, improvement in productivity and reduction in cost can be achieved.
(E) Since the coating is performed with the pressure in the apparatus reduced, the solvent can be coated and dried in a short time even with a solvent having a high boiling point and difficult to dry, such as water, and the productivity is improved.
[Brief description of the drawings]
FIG. 1 is an explanatory view showing one example of a stirring and mixing granulation apparatus used in the present invention, wherein the right half side of a powdered granulation layer shows a state during immersion granulation, and the left half side shows a spray granulation apparatus. The state at the time of the grain method is schematically displayed.
[Explanation of symbols]
REFERENCE SIGNS LIST 1 powder / particle stirring tank 2 powder / particle crushing blade 3 powder / particle stirring blade 4 spray nozzle 5 cooling / heating jacket 6 bag filter 7 decompression vacuum pump 8 coating resin solution supply pump 9 solvent trap device 10 solvent recovery pipe 11 Recovered solvent 12 Coating resin solution 13 Powder 14 Water content detector

Claims (7)

In a coating method in which a powder to be coated is coated in a state where the powder to be coated is immersed in a coating resin solution in a powder / particle stirring tank, the coating, stirring, and drying are performed while the pressure in the powder / particle stirring tank is reduced. Highly efficient coating method. In a coating method of spray-coating a coating resin solution in a state where the powder to be coated is held in a tumbling fluidized state in a powder and particle stirring tank, the inside of the powder and particle stirring tank is reduced in pressure to perform coating, stirring, A highly efficient coating method characterized by performing drying. The granular material stirring tank has a stirring blade for stirring and a crushing blade for crushing, and has a jacket that can be cooled and heated. Is a temperature equal to or higher than the boiling point of the solvent in the coating resin solution. Rotational speed of the stirring blade and the solution砕羽roots provided in the powder or granular material agitation tank, when coating is performed at below half the rotational speed rotational speed of the dry燥時, moreover stirring blade rotation speed and crushing 4. The high-efficiency coating method according to claim 3, wherein the coating is performed in a ratio of a blade rotation number of 1: 2 to 1: 4. 3. The high efficiency according to claim 2, wherein the spray coating is performed with a spray droplet having a diameter of 1/5 or less of the particle diameter of the granular material and an average particle diameter of 2 to 15 m. Coating method. The spray droplet diameter is a value measured by a laser-type particle size distribution measuring instrument, and a ratio (90% value / 10% value) of a 10% value to a 90% value of the volume cumulative value is 5.00 or less. The highly efficient coating method according to claim 5, wherein: 2. The high-efficiency coating method according to claim 1, wherein the inside of the granular stirring tank is under a reduced pressure atmosphere of 500 mmHg or less.

Images