JP3822293B2 - Composition for producing sintered compact including extraction and degreasing process and method for producing sintered compact using the same - Google Patents
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Description
【０００１】
【発明の属する技術分野】
本発明は特定の燒結成形体製造方法に使用するための燒結成形体製造用組成物、更にはそれを用いる燒結成形体の製造方法、更には焼結成形体製造用乾燥体に関する。
【０００２】
【従来の技術】
精密な燒結成形体や形状が複雑な燒結成形体は、一般に、燒結可能な粉体を利用して以下の方法により製造される。即ち、まず燒結可能な粉体とバインダーとを加熱混練後冷却し、成形用材料を造粒する。次いでこれを射出成形してグリーン成形体を製造し、該グリーン成形体を脱脂工程に付してバインダー成分を除き、続いてこれを燒結する。
これらの内、脱脂工程はグリーン成形体中からバインダーを除去する目的で行われる。また、ひび割れ、膨れ、変形等の欠陥のない品質の良好な燒結成形体を製造するための最も重要な工程である。
【０００３】
脱脂工程には、グリーン成形体を加熱してバインダーを加熱分解しガス化して除去する加熱脱脂方法や、グリーン成形体を溶媒処理して可溶性バインダー成分を溶出除去した後、残りのバインダーを加熱分解してガス化して除去する方法がある。
【０００４】
この内、加熱脱脂方法は、グリーン成形体の表面からバインダーの分解ガスが発散するかあるいはバインダーが滲み出して気化するのみであり、加熱昇温速度を速くしてグリーン成形体中のバインダーの熱分解及びガス化を短時間に集中して行うと、中心部で加熱分解で生成したガスがスムーズに表面に移行できず、成形体内部に圧がかかり、成形体にひび割れや膨れが生ずることがある。このため、迅速な加熱を避け、このような問題が生じない温度条件下で長時間加熱して脱脂を行なわなければならない。
特に、燒結成形体製造用組成物に含まれる燒結可能な粉体が、粒径が小さく比表面積が大きい粒体の場合には、グリーン成形体を製造する際の成形用材料の加熱流動性が安定するように、バインダーの配合量を多くする必要がある。従ってこのような粒体からなる燒結成形体製造用組成物を使用した場合の脱脂工程は、多量に含まれるバインダーを除去するために、加熱工程を多段階にする等の工夫が必要になる。
また、加熱による脱脂工程においてひび割れや膨れが生ずるおそれがないものであっても、燒結成形体製造用組成物に含まれる燒結可能な粉体が比重の高い金属粉体や球状粉体である場合には、加熱脱脂工程で成形体に変形が生ずることが多い。従ってこの場合にも脱脂の際の昇温速度を遅くする必要がある。
従って、バインダーの除去を容易にするため、バインダーに昇華性物質を添加する方法がある。しかし、昇華性物質を添加したものは、グリーン成形体を製造する際の成形用材料の混練の際やグリーン成形体の射出成形の際に昇華性物質が昇華し、グリーン成形体の製造時のスプルー・ランナー部の再生が困難になる。
【０００５】
一方、グリーン成形体を溶媒処理して溶媒に可溶なバインダー成分を溶出除去した後、残りのバインダー成分を加熱分解しガス化して除去する方法は、溶媒処理によってグリーン成形体中に空隙が生じ、これを通り道として加熱による残りのバインダーの熱分解及びガス化をスムーズに行なうものである。これにより加熱脱脂工程でのグリーン成形体のひび割れ、膨れ、変形等をある程度回避することができる。
しかし、現在使用されているバインダーは、鉱油、脂肪酸系油、天然油等の液体原料を多量に含むため、グリーン成形体中からこれらの油成分が滲み出すことが多い。特に長期間保存したグリーン成形体は油成分の滲み出しがより激しい。従って、グリーン成形体の表面に滲み出した油成分によって溶媒処理による脱脂の際にひび割れや膨れが発生する場合がある。
また、バインダー中の可塑剤や滑剤を沸騰水によって溶出させる方法がある。しかし、グリーン成形体の成形用材料の安定性の維持、成形用材料の射出成形時の加熱流動性の維持、グリーン成形体の強度の維持等の点から、可塑剤や滑剤の配合量を多くするには限度がある。
更に、水溶性熱可塑性有機ポリマーと水に不溶の熱可塑性有機ポリマーとを含む有機バインダーを使用し、成形体と水を接触させて前者を抽出する方法がある（特公平２−１０１１０１号公報）。しかし、ここで記載されているバインダーの組み合わせでは、その後の残りの有機バインダーを加熱除去する脱脂工程において、成形体の変形を十分に防止することが出来ない。
【０００６】
なお、特開平２−１４５７０４号公報、特開平３ー１９９３０２号公報、成形加工シンポジア’９３，ｐ２２５等にはポリアセタール樹脂とポリエチレングリコールを含むバインダー組成物が記載されているが、これらは加熱脱脂を対象としたものであり、溶媒抽出による脱脂工程については、触れられていない。
【０００７】
【発明が解決しようとする課題】
本発明の目的は、グリーン成形体の脱脂工程を短時間で効率的に行え、しかも加熱脱脂工程で成形体にひび割れ、膨れ、変形等を生ずることがなく、また寸法精度が高く、均質な燒結成形体が得られる燒結成形体製造用組成物、それを用いる焼結成形体の製造方法及びそれに係る焼結成形体製造用乾燥体を提供することにある。
【０００８】
【課題を解決するための手段】
即ち、本発明の第１は、焼結可能な粉体、並びにバインダー成分としてポリアセタール樹脂（Ａ）、融点もしくは軟化点が３０℃以上の水溶性又は親水性溶剤可溶性の有機化合物（Ｂ）、及び加熱脱脂可能な樹脂（Ｃ）（ポリアセタール樹脂（Ａ）を除く）を含むことを特徴とする水又は親水性溶剤による抽出脱脂工程、乾燥工程及び加熱脱脂工程を含む燒結成形体製造方法に使用する燒結成形体製造用組成物を提供する。
本発明の第２は、有機化合物（Ｂ）がポリエチレンオキサイド、ポリエチレングリコール、メチルセルロース、カルボキシルメチルセルロース、ポリアクリルアミドの金属塩、ポリアクリル酸の金属塩又はポリメタクリル酸の金属塩である本発明の第１記載の抽出脱脂工程、乾燥工程及び加熱脱脂工程を含む燒結成形体製造方法に使用する燒結成形体製造用組成物を提供する。
本発明の第３は、加熱脱脂可能な樹脂（Ｃ）がポリオレフィン樹脂、変性ポリオレフィン樹脂、ポリスチレン、ポリビニルブチラール、エチレン−酢酸ビニル共重合体又はポリブチルメタクリレートである本発明の第１又は２記載の抽出脱脂工程、乾燥工程及び加熱脱脂工程を含む燒結成形体製造方法に使用する燒結成形体製造用組成物を提供する。
本発明の第４は、バインダー成分の構成割合が、ポリアセタール樹脂（Ａ）５〜４０容量％、有機化合物（Ｂ）２０〜８０容量％、加熱脱脂可能な樹脂（Ｃ）１０〜５０容量％（三者の合計は１００容量％）の各範囲にある本発明の第１ないし３のいずれかに記載の抽出脱脂工程、乾燥工程及び加熱脱脂工程を含む燒結成形体製造方法に使用する燒結成形体製造用組成物を提供する。
本発明の第５は、バインダー成分の合計が２０〜７０容量％、焼結可能な粉体が３０〜８０容量％の割合（両者の合計１００容量％）にある本発明の第４記載の抽出脱脂工程、乾燥工程及び加熱脱脂工程を含む燒結成形体製造方法に使用する焼結成形体製造用組成物を提供する。
本発明の第６は、本発明の第１〜５のいずれかに記載の燒結成形体製造用組成物を成形し、得られたグリーン成形体と水又は親水性溶剤を接触させて前記グリーン成形体から水溶性又は親水性溶剤可溶性の有機化合物（Ｂ）を抽出脱脂し、乾燥して燒結成形体製造用乾燥体を形成して、次いで焼結可能な粉体以外の残余の成分を加熱脱脂により除去し、更に焼結可能な粉体を焼結させることを特徴とする焼結成形体の製造方法を提供する。
本発明の第７は、本発明の第１〜５のいずれかに記載の燒結成形体製造用組成物を成形し、得られたグリーン成形体と水又は親水性溶剤を接触させて前記グリーン成形体から水溶性又は親水性溶剤可溶性の有機化合物（Ｂ）を抽出脱脂した後、乾燥してなる燒結成形体製造用乾燥体を提供する。
以下、本発明を詳しく説明する。
【０００９】
【発明の実施の形態】
（燒結成形体製造用組成物）
本発明に係る燒結成形体製造用組成物は、水又は親水性溶剤のための抽出脱脂工程、乾燥工程及び加熱脱脂工程を含む方法のための焼結成形体の製造用として用いられるものであり、焼結可能な粉体並びにバインダー成分としてポリアセタール樹脂（Ａ）、融点もしくは軟化点が３０℃以上の水溶性又は親水性溶剤可溶性の有機化合物（Ｂ）及び加熱脱脂可能な樹脂（Ｃ）（ポリアセタール樹脂（Ａ）を除く）を含むことを特徴とする。ここで親水性溶剤とは、水と実質的に任意の割合で溶解しうる溶剤を意味し、例えばメタノール、エタノール等のアルコール類、アセトン等のケトン類が挙げられる。
【００１０】
前記燒結成形体製造用組成物のバインダー成分を構成するポリアセタール樹脂（Ａ）としては、オキシメチレン基（−ＣＨ2Ｏ−）を主たる構成単位とする高分子化合物であればよく、ポリオキシメチレンホモポリマー、オキシメチレン以外に他の構成単位を含有するコポリマー、ターポリマー、ブロックコポリマーの何れも使用することができる。また分子が線状のみならず、分岐、架橋構造を有するものであってもよい。前記他の構成単位となるコモノマーとしては、エチレンオキシド、１，２−プロピレンオキシド、１，２−ブチレンオキシド、１，３−ブチレンオキシド、１，３−ジオキサン、１，３−ジオキソラン、ジオキセパン等が例示できる。
本発明において、バインダー成分としてポリアセタール樹脂（Ａ）を用いることにより、グリーン成形体の変形、水又は親水性溶剤による抽出脱脂時の変形、更にはこれに続く加熱脱脂時の成形体の熱変形を小さくすることができると共に、カーボン等の残渣が残らない優れた焼結成形体を得ることができる。
【００１１】
前記焼結成形体製造用組成物のバインダー成分を構成する融点もしくは軟化点が３０℃以上の水溶性又は親水性溶剤可溶性の有機化合物（Ｂ）としては、好ましくは融点もしくは軟化点が４０℃以上、更に好ましくは融点もしくは軟化点が５０℃以上のものであり、例えばポリエチレンオキサイド、ポリエチレングリコール、メチルセルロース、カルボキシルメチルセルロース、ポリアクリルアミドの金属塩、ポリアクリル酸の金属塩又はポリメタクリル酸の金属塩が挙げられ、好ましくはポリエチレングリコールであり、中でも重合度が１８００以上、特に重合度が２０００〜５０００のポリエチレングリコールが好ましい。なお、前記金属塩を構成する金属としてはカリウム、ナトリウム等のアルカリ金属、カルシウム、バリウム等のアルカリ土類金属、亜鉛等が挙げられる。
【００１２】
前記加熱脱脂可能な樹脂（Ｃ）は、後記のように焼結成形体製造用組成物から得られるグリーン成形体と水又は親水性溶剤を接触させ、前記グリーン成形体から水溶性又は親水性溶剤可溶性の有機化合物（Ｂ）を抽出したのち、加熱によりポリアセタール樹脂（Ａ）及び残余している場合は水溶性又は親水性溶剤可溶性の有機化合物（Ｂ）成分と共に、成形体から除くことができる樹脂である。
【００１３】
このような加熱脱脂可能な樹脂（Ｃ）は、ポリアセタール樹脂（Ａ）と水溶性又は親水性溶剤可溶性の有機化合物（Ｂ）の双方と親和性を有するものから選ばれる。ここで、親和性を有するとは、(1)溶融混練によりポリアセタール樹脂（Ａ）、水溶性又は親水性溶剤可溶性の有機化合物（Ｂ）及び加熱脱脂可能な樹脂（Ｃ）から前段階のバインダー組成物を製造する際、あるいは(2)前記バインダー組成物と焼結可能な粉体とを配合し溶融混練して本発明の焼結成形体製造用組成物を製造する際、あるいは(3)焼結可能な粉体及びバインダーの各成分を一括して配合し、本発明の焼結成形体製造用組成物を製造する際、ポリアセタール樹脂（Ａ）及び水溶性又は親水性溶剤可溶性の有機化合物（Ｂ）から加熱脱脂可能な樹脂（Ｃ）が実質的に相分離しないことを指す。相分離を起こす樹脂を用いると、グリーン成形体の成形性が悪く、また均一な焼結成形体が得られない。
【００１４】
前記加熱脱脂可能な樹脂（Ｃ）としては、例えばポリエチレン、ポリプロピレン、エチレン−プロピレン共重合体等のポリオレフィン樹脂、変性ポリオレフィン樹脂、ポリスチレン、ポリビニルブチラール、エチレン−酢酸ビニル共重合体、ポリメチルメタクリレート又はポリブチルメタクリレート等を挙げることができる。
【００１５】
前記変性ポリオレフィン樹脂は広い概念を有し、芳香族基又は極性基の導入によって変性させたオレフィン系重合体であって、例えば以下に説明するような共重合、グラフト共重合等によって得られる種々の重合体が例示できる。
(1)オレフィン（及びこれを共重合可能なモノマー）とグリシジル基を具備する不飽和化合物、例えばグリシジルメタクリレート等のα，β−不飽和酸のグリシジルエステルとの共重合体で、例えばエチレン−グリシジルメタクリレート共重合体、
(2)ポリエチレン、ポリプロピレン、エチレン−プロピレン共重合体等のオレフィン重合体に、ビニル系重合体、例えばポリメチルメタクリレート、ポリスチレン又はポリスチレンを主体とする共重合体等を、分岐又は架橋構造的に化学結合させた共重合体、
(3)α−オレフィンと不飽和化合物、例えばα，β−不飽和酸のグリシジルエステルとの共重合体に対して、該重合体と共重合可能な他のモノマー、例えばアクリロニトリル、スチレン、メタクリル酸メチル、アクリル酸メチル、メタクリル酸等のモノマーの１種以上、又はこれらのモノマーからなるビニル系（共）重合体、例えばポリメタクリル酸メチル、ポリスチレン、ポリアクリロニトリル、アクリロニトリル−スチレン共重合体等をグラフト重合等により共重合したもの、例えば、エチレン−グリシジルメタクリレート共重合体にアクリロニトリル−スチレン共重合体、ポリメタクリル酸メチル、ポリスチレン等をグラフト重合させたもの、
(4)オレフィンの単独重合体、オレフィンの共重合体、オレフィンと他のビニル系モノマー例えばジエン化合物、α，β−不飽和酸又はそのエステル等の誘導体、又はビニル化合物等とを共重合したオレフィンを主体とする共重合体等からなるオレフィン系重合体に対して、水酸基を具備する不飽和化合物を反応させて得られる水酸基変性オレフィン重合体、
(5)オレフィンの単独重合体、オレフィンの共重合体、オレフィンと他のビニル系モノマー、例えばジエン化合物、α，β−不飽和酸又はそのエステル等の誘導体等とを共重合したオレフィンを主体とする共重合体、等からなるオレフィン系重合体に、不飽和カルボン酸又はその誘導体、例えばマレイン酸、フマル酸等の不飽和ジカルボン酸又はそれらの無水物、アクリル酸、又はメタクリル酸等の不飽和カルボン酸又はそれらのエステルをグラフト重合等により共重合させたもの、
(6)オレフィン系重合体と、エーテル系重合体、例えばポリエチレンオキシド、ポリプロピレンオキシド等とを、分岐又は架橋構造的に化学結合させた共重合体、
(7)オレフィン系重合体とエポキシ基含有モノマー、例えばグリシジルメタクリレート、グリシジルアクリレート等を、ラジカル開始剤の存在下で加熱して得られるエポキシ変性オレフィン系重合体、
(8)イソシアネート基含有モノマーで変性したオレフィン系重合体等である。
【００１６】
前記加熱脱脂可能な樹脂（Ｃ）のうち、成形性、親和性等の点でエチレン−酢酸ビニル共重合体、ポリブチルメタクリレート、ポリビニルブチラール、変性ポリオレフィン樹脂を用いることが好ましい。
【００１７】
本発明に係る燒結成形体製造用組成物において、前記バインダー成分の構成割合は、ポリアセタール樹脂（Ａ）５〜４０容量％、水溶性又は親水性溶剤可溶性の有機化合物（Ｂ）２０〜８０容量％、加熱脱脂可能な樹脂（Ｃ）１０〜５０容量％（三者の合計は１００容量％）の各範囲であることが好ましく、特に好ましくはポリアセタール樹脂（Ａ）の割合が１０〜３０容量％、水溶性又は親水性溶剤可溶性の有機化合物（Ｂ）の割合が３０〜７０容量％、加熱脱脂可能な樹脂（Ｃ）の割合が１５〜４０容量％の各範囲である。
【００１８】
加熱脱脂可能な樹脂（Ｃ）が１０容量％未満になると、ポリアセタール樹脂（Ａ）と水溶性又は親水性溶剤可溶性の有機化合物（Ｂ）が均一に混合しにくくなり、良好なグリーン成形体を得ることが困難になり、加熱脱脂工程における割れや膨れの原因となることがある。また、加熱脱脂可能な樹脂（Ｃ）が５０容量％を越えると、必然的にポリアセタール樹脂（Ａ）の配合量が制約され、グリーン成形体の熱変形温度の低下に伴う加熱脱脂工程での成形体の変形、及び脱脂後の残カーボン量の増大の原因となる場合がある。
また、水溶性又は親水性溶剤可溶性の有機化合物（Ｂ）が８０容量％を超えると、ポリアセタール樹脂（Ａ）と加熱脱脂可能な樹脂（Ｃ）との合計量が少なくなるため、加熱による脱脂工程で成形体が変形し易くなり、また２０容量％未満では組成物の流動性が低下し、グリーン成形体を成形する際の射出成形を円滑に行なえなくなる場合がある。
【００１９】
本発明の燒結成形体製造用組成物は、主として前記バインダー成分と燒結可能な粉体とからなる。
本発明の燒結成形体製造用組成物に使用できる燒結可能な粉体としては、セラミックス、金属、サーメット等がある。
【００２０】
本発明の燒結成形体製造用組成物は、焼結可能な粉体と前記バインダーの合計量を１００容量％としたとき、その中に前記バインダー成分を合計量として２０〜７０容量％、好ましくは２５〜６５容量％、特に好ましくは３０〜６０容量％含有する。バインダーの配合割合は、使用するセラミックス、金属、サーメット等の燒結可能な粉体の種類や加えられる他のバインダーの種類によっても適宜選択することができる。
【００２１】
本発明の燒結成形体製造用組成物には、前記バインダーの各成分以外で、かつ前記バインダーの各成分の前記配合割合に含まれないものとして、熱可塑性樹脂、ワックス類、可塑剤又は滑剤などの有機物を使用することができる。
前記ワックス類としては、例えばパラフィンワックス、ポリエチレンワックス、カルバナワックス、ポリエチレングリコール、蜜ロウ、木ロウ、合成ワッスク等が挙げられる。可塑剤としては、例えばジオクチルフタレート、ジブチルフタレート、ジエチルフタレート等のフタル酸系化合物が挙げられる。更にまた、滑剤としては、例えばステアリン酸エステル等の脂肪酸系エステル及びその誘導体が挙げられる。これらの配合割合は、これらをも含む焼結成形体製造用組成物の全体に対して２０容量％以下、好ましくは１０容量％以下の範囲である。
【００２２】
本発明の燒結成形体製造用組成物の調製は、各配合成分の配合順序に特に限定されないが、例えばポリアセタール樹脂（Ａ）、水溶性又は親水性溶剤可溶性の有機化合物（Ｂ）及び加熱脱脂可能な樹脂（Ｃ）の各バインダー成分を予め混合し、溶融混練して冷却固化させ、粉砕するかペレット状としたバインダー組成物を一旦製造し、これに焼結可能な粉体を混合してもよく、あるいは焼結可能な粉体及びバインダーの各成分等の全ての成分を一括して配合し、溶融混練してもよい。
【００２３】
本発明の燒結成形体製造用組成物は、燒結成形体の予備成形体であるグリーン成形体を成形する際の成形用材料となる。通常、前記のように燒結成形体製造用組成物を加熱混練した後冷却して造粒し、グリーン成形体用の成形用材料とする。この成形用材料を成形してグリーン成形体を製造する。成形方法としては、通常、射出成形方法が採用される。次いで、得られたグリーン成形体と水又は親水性溶剤とを接触させてグリーン成形体から水溶性又は親水性溶剤可溶性の有機化合物（Ｂ）を抽出し、次いで加熱による脱脂工程に付し焼結可能な粉体以外の残余の成分を除去し、更に脱脂後の成形体を燒結することによって、目的の燒結成形体を得る。
なお、燒結成形体製造用組成物は前記のように一旦造粒することなく、射出成形機の前段の溶融混練押出機で製造し、そのままグリーン成形体を射出成形してもよい。
【００２４】
前記グリーン成形体と水又は親水性溶剤との接触方法は、水溶性又は親水性溶剤可溶性の有機化合物（Ｂ）が除去される方法であれば特に限定されないが、水中又は親水性溶剤中にグリーン成形体を浸漬することにより簡単に達成することができる。その際の液温及び浸漬時間は水溶性又は親水性溶剤可溶性の有機化合物（Ｂ）の種類やグリーン成形体中のその含量により異なるが、通常２０〜８０℃で０．５〜２０時間である。
この抽出脱脂工程により、グリーン成形体中に空隙が生じ、これを通路として、後述する加熱脱脂における残余バインダー成分の熱分解及びガス化をスムーズに行うことができる。
【００２５】
水又は親水性溶剤とグリーン成形体の接触後、加熱脱脂工程の前に乾燥することが好ましい。乾燥して得られたものを燒結成形体製造用乾燥体という。乾燥には３０〜８０℃、−７５５〜−２００ｍｍＨｇの真空乾燥器を用いて１５〜６０分間乾燥することが好ましい。
次いで２５０〜５５０℃で２〜２０時間加熱脱脂することにより、残余バインダー成分を除去する。この場合の昇温速度は、好ましくは２０〜１００℃／時間であり、公知の方法で行われる。本発明の燒結成形体製造用組成物は、バインダー成分としてポリアセタール樹脂（Ａ）を含むため、この加熱脱脂を極めて効率的に行うことができ、加熱脱脂後、残渣が残ることもない。また抽出脱脂工程及び加熱脱脂工程を通して、グリーン成形体の変形も極めて小さい。
脱脂後の燒結成形体製造用乾燥体は、減圧下で通常の方法により焼結工程に付される。
【００２６】
本発明の燒結成形体製造用組成物を用いれば、時計部品、産業用機械部品、医療用器具、自動車部品等の精密な燒結成形体や形状が複雑な燒結成形体を製造することができる。
【００２７】
【実施例】
以下、前記の構成による本発明の燒結成形体製造用組成物のより具体的な成分組成を実施例に基づいて説明するが、本発明はこれらに限定されるものではない。
【００２８】
（実施例１〜６、比較例１〜３）
＜燒結成形体製造用組成物の調製＞
燒結可能な粉体としてＳＵＳ３１６Ｌ（平均粒径約１０μｍ）の粉体を用い、表−１−１及び表−１−２に示すポリアセタール樹脂（Ａ）、有機化合物（Ｂ）としてポリエチレングリコール又はメチルセルロース及び加熱脱脂可能な樹脂（Ｃ）からなるバインダー成分と共に表−１−１及び表−１−２に示す割合で配合し、加圧ニーダーによって１６０℃、６０分間混練した後、この混練物を冷却、破砕して燒結成形体製造用組成物を調製した。
なお、比較例においては、ポリアセタール樹脂（Ａ）の代りにポリエチレン、ポリプロピレン、エチレン−酢酸ビニル共重合体を用いた。
【００２９】
＜グリーン成形体の成形＞
前記で得た燒結成形体製造用組成物を、成形温度１４０〜１８０℃にて射出成形し、図１に示すダンベル試験片形状のグリーン成形体を得た。
【００３０】
＜水抽出工程＞
得られたグリーン成形体を温度２５及び５０℃の水中に０．５〜１８時間浸漬し、抽出処理を行った。抽出後のグリーン成形体を、それぞれ−７５５ｍｍＨｇの真空乾燥機にて５０℃で３０分間乾燥した。
【００３１】
＜加熱脱脂工程＞
水抽出後の各グリーン成形体を大気中で２時間かけて５０℃に昇温した後、３０℃／時間の昇温速度で３２０℃まで昇温し、更に３２０℃に２時間保持する加熱条件による脱脂工程に付した。
【００３２】
＜燒結工程＞
脱脂工程を完了した成形体を、１３００℃にて２時間の燒結条件で燒結し、燒結成形体を得た。
【００３３】
＜評価＞
（１）成形性：グリーン成形体の成形における成形の容易さ、得られたグリーン成形体の性状（特に成形体の均一性）を優＞良＞可で相対的に評価した。
（２）水抽出後のグリーン成形体の状態：目視で膨れの有無を評価し、膨れのないものを良好とした。なお、抽出率は抽出前後の重量変化により算出した。
（３）水抽出した成形体の加熱脱脂による脱脂率を重量変化により算出し、脱脂後の成形体を目視で膨れの有無を評価し、膨れのないものを良好とした。
（４）ダンベル試験片形状のグリーン成形体を図２にように保持して加熱脱脂した後の、ダンベル試験片中央部の変形を目視観察した。
（５）焼結体の性状：焼結後の割れ、膨れの発生状況を観察し、評価した。
【００３４】
＜結果＞
成形性の結果を表−１−１、表−１−２に示す。また各抽出温度における水抽出結果を表−２−１、表−２−２、表−３−１、表−３−２に示す。２５℃におけるポリエチレングリコールの水抽出では、何れも抽出後の成形体の状態は良好であるが、５０℃では、抽出率が上がるに従い、高重合度のポリエチレングリコールを用いた実施例５及びポリアセタール樹脂を用いない比較例において膨れが認められた。
水抽出後の加熱脱脂の結果を表−４−１、表−４−２、表−５−１、表−５−２に示す。本発明の燒結成形体製造用組成物を用いた成形体では、抽出率がほぼ同程度であるにもかかわらず、比較例の組成物から得られる成形体に比べ、一定の脱脂条件で脱脂率が高いことから短時間で脱脂できること、及び脱脂後の成形体の状態がより優れていることが分かる。
なお、加熱脱脂後、膨れがなく、良好な形状を保持していた成形体は、これを焼結処理したとき、膨れ、変形等が極めて小さい良好な焼結成形体を得ることができた。
【００３５】
（実施例７）
実施例１における水抽出に代えて、エタノール（９５重量％）、エタノール（９５重量％）と水の重量による１：１の混合液、エタノール（９５重量％）と水の重量による１：３の混合液で各々抽出を行い、以下の操作は実施例１に準じて行った。この場合、エタノール濃度が高くなるに伴い、若干の膨れが生じたが、何れも良好な焼結成形体が得られた。
【００３６】
【表１】
【表２】
【表３】
【表４】
【表５】
【発明の効果】
本発明の燒結成形体製造用組成物は、バインダー成分としてポリアセタール樹脂（Ａ）及び水溶性又は親水性溶剤可溶性の有機化合物（Ｂ）を含有することが特徴であり、これから得られたグリーン成形体と水又は親水性溶剤を接触させることにより、水溶性又は親水性溶剤可溶性の有機化合物（Ｂ）を効率的に除去でき、それに続く加熱脱脂を比較的短時間に行うことができる。また水又は親水性溶剤による抽出後及び加熱脱脂後の成形体、更には焼結成形体の状態にも優れている。
【図面の簡単な説明】
【図１】グリーン成形体を成形したダンベル試験片形状を示す。
【図２】ダンベル試験片形状のグリーン成形体の、加熱脱脂後の変形量の目視観察方法を示す。[0001]
BACKGROUND OF THE INVENTION
The present inventionFor use in specific sintered compact manufacturing methodsComposition for producing a sintered compact, and further a method for producing a sintered compact using the compositionFurthermore, a dried body for producing a sintered molded bodyAbout.
[0002]
[Prior art]
A precise sintered compact or a sintered compact having a complicated shape is generally produced by the following method using a powder that can be sintered. That is, first, a powder that can be sintered and a binder are heated and kneaded and then cooled to granulate the molding material. Next, this is injection molded to produce a green molded body. The green molded body is subjected to a degreasing process to remove the binder component, which is subsequently sintered.
Among these, the degreasing step is performed for the purpose of removing the binder from the green molded body. Further, it is the most important process for producing a sintered compact having a good quality free from defects such as cracks, swelling and deformation.
[0003]
In the degreasing process, the green molded body is heated to thermally decompose and gasify and remove the binder, or the green molded body is treated with a solvent to elute and remove soluble binder components, and then the remaining binder is thermally decomposed. Then, there is a method of removing it by gasification.
[0004]
Among these, the heat degreasing method is such that the decomposition gas of the binder is emitted from the surface of the green molded body or only the binder oozes and vaporizes, and the heating temperature of the binder in the green molded body is increased by increasing the heating rate. If decomposition and gasification are concentrated in a short time, the gas generated by heat decomposition at the center cannot smoothly move to the surface, pressure is applied to the inside of the molded body, and cracks and swelling may occur in the molded body. is there. For this reason, it is necessary to avoid rapid heating and degrease by heating for a long time under temperature conditions where such problems do not occur.
In particular, when the sinterable powder contained in the composition for producing a sintered compact is a granule having a small particle size and a large specific surface area, the heat fluidity of the molding material when producing the green compact is high. In order to stabilize, it is necessary to increase the compounding quantity of a binder. Therefore, the degreasing process in the case of using a composition for producing a sintered compact comprising such granules requires a device such as a multi-step heating process in order to remove a large amount of binder.
In addition, even if there is no risk of cracking or swelling in the degreasing process by heating, the powder that can be sintered contained in the composition for producing a sintered compact is a metal powder or spherical powder having a high specific gravity. In many cases, the molded body is deformed in the heat degreasing step. Therefore, also in this case, it is necessary to slow down the temperature rising rate during degreasing.
Therefore, there is a method of adding a sublimable substance to the binder in order to facilitate the removal of the binder. However, when the sublimation substance is added, the sublimation substance sublimates when the molding material is kneaded when the green molded body is manufactured or when the green molded body is injection molded. It becomes difficult to regenerate the sprue runner.
[0005]
On the other hand, the method in which the green molded body is treated with a solvent to dissolve and remove the binder component soluble in the solvent, and then the remaining binder component is thermally decomposed and removed by gasification. The remaining binder is thermally decomposed and gasified smoothly by heating through this path. As a result, cracking, swelling, deformation, etc. of the green molded body in the heat degreasing step can be avoided to some extent.
However, since the binder currently used contains a large amount of liquid raw materials such as mineral oil, fatty acid oil, and natural oil, these oil components often ooze out from the green molded body. In particular, a green molded body stored for a long period of time has a more oozing oil component. Therefore, cracks and blisters may occur during degreasing by solvent treatment due to the oil component that has oozed out on the surface of the green molded body.
There is also a method of eluting the plasticizer and lubricant in the binder with boiling water. However, in order to maintain the stability of the molding material of the green molded body, maintain the heat fluidity during injection molding of the molding material, maintain the strength of the green molded body, etc. There is a limit to it.
Furthermore, there is a method of using an organic binder containing a water-soluble thermoplastic organic polymer and a thermoplastic organic polymer insoluble in water, and extracting the former by bringing the molded body into contact with water (Japanese Patent Publication No. 2-101101). . However, the combination of binders described here cannot sufficiently prevent deformation of the molded body in the degreasing step in which the remaining organic binder is removed by heating.
[0006]
In addition, in JP-A-2-145704, JP-A-3-199302, molding symposia '93, p225 and the like, a binder composition containing a polyacetal resin and polyethylene glycol is described. It is intended, and the degreasing process by solvent extraction is not mentioned.
[0007]
[Problems to be solved by the invention]
The object of the present invention is to perform the degreasing process of the green molded body in a short time and efficiently, and the molded body does not crack, swell or deform in the heat degreasing process. Composition for producing a sintered compact from which a sintered compact is obtained,Method for producing sintered compact using the sameAnd dry body for producing sintered compact according to the sameIs to provide.
[0008]
[Means for Solving the Problems]
That is, the first of the present invention is a sinterable powder, a polyacetal resin (A) as a binder component, a water-soluble or hydrophilic solvent-soluble organic compound (B) having a melting point or softening point of 30 ° C. or higher, and It is used in a method for producing a sintered molded article including an extraction and degreasing step using water or a hydrophilic solvent, a drying step, and a heating and degreasing step, including a heat degreasing resin (C) (excluding a polyacetal resin (A)). Provide a composition for producing a sintered compact.
In the second aspect of the present invention, the organic compound (B) is polyethylene oxide, polyethylene glycol, methyl cellulose, carboxymethyl cellulose, polyacrylamide metal salt, polyacrylic acid metal salt or polymethacrylic acid metal salt. Provided is a composition for producing a sintered compact for use in the method for producing a sintered compact including the extraction degreasing step, the drying step and the heating degreasing step described above..
According to a third aspect of the present invention, the heat-degreasing resin (C) is a polyolefin resin, a modified polyolefin resin, polystyrene, polyvinyl butyral, an ethylene-vinyl acetate copolymer or polybutyl methacrylate. Provided is a composition for producing a sintered compact for use in a method for producing a sintered compact including an extraction degreasing step, a drying step and a heating degreasing step..
According to the fourth aspect of the present invention, the constituent ratio of the binder component is 5 to 40% by volume of the polyacetal resin (A), 20 to 80% by volume of the organic compound (B), and 10 to 50% by volume of the heat-degreasing resin (C) ( The sintered compact used for the sintered compact manufacturing method including the extraction degreasing step, the drying step and the heat degreasing step according to any one of the first to third aspects of the present invention, in which the total of the three is 100% by volume) Providing a manufacturing composition.
The fifth aspect of the present invention is the extraction according to the fourth aspect of the present invention, wherein the total of the binder components is 20 to 70% by volume and the sinterable powder is in a ratio of 30 to 80% by volume (the total of both is 100% by volume). Provided is a composition for producing a sintered compact for use in a method for producing a sintered compact including a degreasing step, a drying step and a heat degreasing step..
6th of this invention shape | molds the sintered compact manufacturing composition in any one of 1-5 of this invention, makes the obtained green molded object contact water or a hydrophilic solvent, and said green molding Extracting and degreasing the water-soluble or hydrophilic solvent-soluble organic compound (B) from the body, drying to form a dried body for producing a sintered molded body, and then heating and degreasing the remaining components other than the sinterable powder And a method for producing a sintered compact characterized by sintering a powder that can be further sinterd..
7th of this invention shape | molds the sintered compact manufacturing composition in any one of 1-5 of this invention, and makes the obtained green molded object and water or a hydrophilic solvent contact, and said green molding Provided is a dried body for producing a sintered molded body, which is obtained by extracting and degreasing a water-soluble or hydrophilic solvent-soluble organic compound (B) from a body and then drying.
The present invention will be described in detail below.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
(Composition for the production of sintered compacts)
The present inventionPertaining toThe composition for producing a sintered compact is an extraction degreasing process for water or a hydrophilic solvent., Drying process and heating degreasing processIs used for the production of a sintered compact for a process comprising a sinterable powder and a polyacetal resin (A) as a binder component,Water-soluble or hydrophilic solvent-soluble organic compound (B) having a melting point or softening point of 30 ° C. or higherHeat degreasing resin (C) (excluding polyacetal resin (A))It is characterized by including. Here, the hydrophilic solvent means a solvent that can be dissolved in water at a substantially arbitrary ratio, and examples thereof include alcohols such as methanol and ethanol, and ketones such as acetone.
[0010]
As the polyacetal resin (A) constituting the binder component of the composition for producing a sintered molded body, an oxymethylene group (-CH2Any high molecular compound having O-) as a main structural unit may be used, and any of a polyoxymethylene homopolymer, a copolymer containing other structural units in addition to oxymethylene, a terpolymer, and a block copolymer can be used. Further, the molecule may have not only a linear shape but also a branched or crosslinked structure. Examples of the comonomer as the other structural unit include ethylene oxide, 1,2-propylene oxide, 1,2-butylene oxide, 1,3-butylene oxide, 1,3-dioxane, 1,3-dioxolane, dioxepane and the like. it can.
In the present invention, by using the polyacetal resin (A) as a binder component, deformation of the green molded body, deformation during extraction and degreasing with water or a hydrophilic solvent, and subsequent thermal deformation of the molded body during heating and degreasing While being able to make it small, the outstanding sintered compact which does not remain residues, such as carbon, can be obtained.
[0011]
As the water-soluble or hydrophilic solvent-soluble organic compound (B) having a melting point or softening point of 30 ° C. or higher, constituting the binder component of the composition for producing a sintered compact, preferably the melting point or softening point is 40 ° C. or higher, More preferably, the melting point or softening point is 50 ° C. or higher, and examples include polyethylene oxide, polyethylene glycol, methyl cellulose, carboxymethyl cellulose, polyacrylamide metal salt, polyacrylic acid metal salt, and polymethacrylic acid metal salt. In particular, polyethylene glycol is preferable, and polyethylene glycol having a polymerization degree of 1800 or more, and particularly a polymerization degree of 2000 to 5000 is preferable. Examples of the metal constituting the metal salt include alkali metals such as potassium and sodium, alkaline earth metals such as calcium and barium, and zinc.
[0012]
The heat degreasable resin (C) is obtained by bringing a green molded body obtained from the composition for producing a sintered molded body into contact with water or a hydrophilic solvent, as described later, and water-soluble or hydrophilic solvent-soluble from the green molded body. After extraction of the organic compound (B), a resin that can be removed from the molded body together with the polyacetal resin (A) by heating and the organic compound (B) component soluble in a water-soluble or hydrophilic solvent if remaining is there.
[0013]
Such a heat-degreasing resin (C) is selected from those having affinity with both the polyacetal resin (A) and the water-soluble or hydrophilic solvent-soluble organic compound (B). Here, having affinity means (1) a binder composition in the previous stage from polyacetal resin (A), water-soluble or hydrophilic solvent-soluble organic compound (B) and heat-degreasing resin (C) by melt kneading. Or (2) when the binder composition and sinterable powder are blended and melt-kneaded to produce the composition for producing a sintered compact of the present invention, or (3) sintering When the components of possible powders and binders are blended together to produce the composition for producing a sintered compact of the present invention, the polyacetal resin (A) and the water-soluble or hydrophilic solvent-soluble organic compound (B) The resin (C) that can be heated and degreased does not substantially phase-separate. If a resin that causes phase separation is used, the green molded article has poor moldability, and a uniform sintered molded article cannot be obtained.
[0014]
Examples of the heat-degreasing resin (C) include polyolefin resins such as polyethylene, polypropylene, and ethylene-propylene copolymer, modified polyolefin resins, polystyrene, polyvinyl butyral, ethylene-vinyl acetate copolymer, polymethyl methacrylate, and poly Examples thereof include butyl methacrylate.
[0015]
The modified polyolefin resin has a broad concept and is an olefin polymer modified by introduction of an aromatic group or a polar group. For example, various types of polymers obtained by copolymerization, graft copolymerization, etc. described below can be used. A polymer can be illustrated.
(1) A copolymer of an olefin (and a monomer copolymerizable therewith) and an unsaturated compound having a glycidyl group, for example, a glycidyl ester of an α, β-unsaturated acid such as glycidyl methacrylate, such as ethylene-glycidyl. Methacrylate copolymers,
(2) Branched or cross-linked structurally chemistry of olefin polymers such as polyethylene, polypropylene, and ethylene-propylene copolymers, vinyl polymers such as polymethyl methacrylate, polystyrene or copolymers based on polystyrene. Bonded copolymers,
(3) For a copolymer of an α-olefin and an unsaturated compound, such as a glycidyl ester of an α, β-unsaturated acid, other monomers copolymerizable with the polymer, such as acrylonitrile, styrene, methacrylic acid Grafting one or more monomers such as methyl, methyl acrylate, methacrylic acid, or vinyl (co) polymers composed of these monomers, such as polymethyl methacrylate, polystyrene, polyacrylonitrile, acrylonitrile-styrene copolymer, etc. Copolymerized by polymerization, for example, ethylene-glycidyl methacrylate copolymer graft polymerized with acrylonitrile-styrene copolymer, polymethyl methacrylate, polystyrene,
(4) Olefin homopolymers, olefin copolymers, olefins and other vinyl monomers such as diene compounds, derivatives of α, β-unsaturated acids or esters thereof, or olefins copolymerized with vinyl compounds, etc. A hydroxyl group-modified olefin polymer obtained by reacting an unsaturated compound having a hydroxyl group with an olefin polymer comprising a copolymer mainly comprising
(5) Olefin homopolymers, olefin copolymers, olefins and other vinyl monomers such as diene compounds, α, β-unsaturated acids or their derivatives, etc. An olefin polymer comprising a copolymer, etc., an unsaturated carboxylic acid or a derivative thereof, for example, an unsaturated dicarboxylic acid such as maleic acid or fumaric acid, or an anhydride thereof, an acrylic acid or methacrylic acid or the like. Copolymerized carboxylic acids or their esters by graft polymerization,
(6) a copolymer obtained by chemically bonding an olefin polymer and an ether polymer such as polyethylene oxide, polypropylene oxide and the like in a branched or cross-linked structure,
(7) An epoxy-modified olefin polymer obtained by heating an olefin polymer and an epoxy group-containing monomer such as glycidyl methacrylate, glycidyl acrylate, etc. in the presence of a radical initiator,
(8) An olefin polymer modified with an isocyanate group-containing monomer.
[0016]
Of the heat degreasing resin (C), ethylene-vinyl acetate copolymer, polybutyl methacrylate, polyvinyl butyral, and modified polyolefin resin are preferably used in terms of moldability and affinity.
[0017]
The present inventionPertaining toIn the composition for producing a sintered molded body, the constituent ratio of the binder component is 5 to 40% by volume of the polyacetal resin (A), 20 to 80% by volume of the water-soluble or hydrophilic solvent-soluble organic compound (B), and heat degreasing is possible. The resin (C) is preferably in a range of 10 to 50% by volume (the total of the three is 100% by volume), and particularly preferably, the proportion of the polyacetal resin (A) is 10 to 30% by volume, water-soluble or hydrophilic The ratio of the organic compound (B) soluble in the soluble solvent is 30 to 70% by volume, and the ratio of the heat-degreasing resin (C) is 15 to 40% by volume.
[0018]
When the heat degreasable resin (C) is less than 10% by volume, it becomes difficult to uniformly mix the polyacetal resin (A) and the water-soluble or hydrophilic solvent-soluble organic compound (B), thereby obtaining a good green molded body. It may be difficult to cause cracking and swelling in the heat degreasing process. Further, if the heat degreasing resin (C) exceeds 50% by volume, the amount of the polyacetal resin (A) is inevitably restricted, and molding in the heat degreasing process accompanying a decrease in the heat distortion temperature of the green molded body. It may cause deformation of the body and an increase in the amount of residual carbon after degreasing.
In addition, when the amount of the water-soluble or hydrophilic solvent-soluble organic compound (B) exceeds 80% by volume, the total amount of the polyacetal resin (A) and the heat degreasable resin (C) decreases, so that the degreasing step by heating In the case where the green body is less than 20% by volume, the fluidity of the composition is lowered, and injection molding may not be performed smoothly when the green molded body is formed.
[0019]
The composition for producing a sintered compact of the present invention mainly comprises a powder that can be sintered with the binder component.
Sinterable powders that can be used in the composition for producing a sintered compact of the present invention include ceramics, metals, cermets, and the like.
[0020]
The composition for producing a sintered compact of the present invention has a total amount of sinterable powder and the binder of 100% by volume, and the binder component in the total amount is 20 to 70% by volume, preferably It is contained in an amount of 25 to 65% by volume, particularly preferably 30 to 60% by volume. The blending ratio of the binder can be appropriately selected depending on the type of powder that can be sintered, such as ceramics, metal, and cermet to be used, and the type of other binder added.
[0021]
In the composition for producing a sintered molded body of the present invention, a thermoplastic resin, a wax, a plasticizer, a lubricant, or the like other than each component of the binder and not included in the blending ratio of each component of the binder Organic materials can be used.
Examples of the waxes include paraffin wax, polyethylene wax, carbana wax, polyethylene glycol, beeswax, wood wax, and synthetic washes. Examples of the plasticizer include phthalic acid compounds such as dioctyl phthalate, dibutyl phthalate, and diethyl phthalate. Furthermore, examples of the lubricant include fatty acid esters such as stearates and derivatives thereof. These blending ratios are in the range of 20% by volume or less, preferably 10% by volume or less, based on the entire composition for producing a sintered compact including these.
[0022]
Preparation of the composition for producing a sintered molded body of the present invention is not particularly limited to the blending order of each blending component. For example, polyacetal resin (A), water-soluble or hydrophilic solvent-soluble organic compound (B), and heat degreasing are possible. The binder component of each resin (C) is mixed in advance, melt-kneaded, cooled and solidified, and once pulverized or pelletized, the binder composition is once manufactured and mixed with a sinterable powder. Alternatively, all components such as sinterable powder and each component of the binder may be blended together and melt-kneaded.
[0023]
The composition for producing a sintered compact of the present invention is a molding material for molding a green molded body, which is a preform of the sintered compact. Usually, the composition for producing a sintered compact is heated and kneaded as described above, and then cooled and granulated to obtain a molding material for a green compact. A green molded body is manufactured by molding this molding material. As a molding method, an injection molding method is usually employed. Next, the obtained green molded body is contacted with water or a hydrophilic solvent to extract a water-soluble or hydrophilic solvent-soluble organic compound (B) from the green molded body, and then subjected to a degreasing step by heating and sintering. By removing the remaining components other than the possible powder and further sintering the molded product after degreasing, the desired sintered molded product is obtained.
The composition for producing a sintered compact may be produced by a melt-kneading extruder at the front stage of an injection molding machine without granulating as described above, and the green molded article may be injection molded as it is.
[0024]
The method for contacting the green molded body with water or a hydrophilic solvent is not particularly limited as long as it is a method for removing the water-soluble or hydrophilic solvent-soluble organic compound (B). This can be easily achieved by immersing the molded body. The liquid temperature and immersion time at that time vary depending on the type of the water-soluble or hydrophilic solvent-soluble organic compound (B) and its content in the green molded body, but are usually 0.5 to 20 hours at 20 to 80 ° C. .
By this extraction and degreasing process, voids are generated in the green molded body, and the thermal decomposition and gasification of the residual binder component in the heat degreasing described later can be performed smoothly using this as a passage.
[0025]
It is preferable to dry after the contact between water or a hydrophilic solvent and the green molded body and before the heat degreasing step.The product obtained by drying is called a dried product for producing a sintered compact.For drying, it is preferable to dry for 15 to 60 minutes using a vacuum dryer of 30 to 80 ° C. and −755 to −200 mmHg.
Subsequently, the residual binder component is removed by heating and degreasing at 250 to 550 ° C. for 2 to 20 hours. The temperature increase rate in this case is preferably 20 to 100 ° C./hour, and is performed by a known method. Since the composition for producing a sintered compact of the present invention contains the polyacetal resin (A) as a binder component, this heat degreasing can be performed very efficiently, and no residue remains after the heat degreasing. Further, the deformation of the green molded body is extremely small through the extraction degreasing step and the heat degreasing step.
After degreasingDry body for the production of sintered compactsIs subjected to the sintering step by a conventional method under reduced pressure.
[0026]
By using the composition for producing a sintered compact of the present invention, it is possible to produce a precise sintered compact such as a watch part, an industrial machine part, a medical instrument, an automobile part or the like, or a sintered compact having a complicated shape.
[0027]
【Example】
Hereinafter, although the more specific component composition of the composition for the sintered compact manufacture of this invention by the said structure is demonstrated based on an Example, this invention is not limited to these.
[0028]
(Examples 1-6, Comparative Examples 1-3)
<Preparation of composition for producing sintered compact>
A powder of SUS316L (average particle diameter of about 10 μm) is used as a powder that can be sintered, polyacetal resin (A) shown in Tables 1-1 and 1-2, polyethylene glycol or methylcellulose as the organic compound (B), and It mix | blends with the ratio shown to Table-1-1 and Table-1-2 with the binder component which consists of resin (C) which can be heated and degreased, knead | mixes for 160 minutes at 160 degreeC with a pressure kneader, Then, this kneaded material is cooled, A composition for producing a sintered compact was prepared by crushing.
In the comparative example, polyethylene, polypropylene, and ethylene-vinyl acetate copolymer were used in place of the polyacetal resin (A).
[0029]
<Green molded body molding>
The composition for producing a sintered molded body obtained above was injection molded at a molding temperature of 140 to 180 ° C. to obtain a dumbbell test piece-shaped green molded body shown in FIG.
[0030]
<Water extraction process>
The obtained green molded body was immersed in water at a temperature of 25 and 50 ° C. for 0.5 to 18 hours, and an extraction treatment was performed. The green molded bodies after extraction were each dried at 50 ° C. for 30 minutes with a vacuum dryer of −755 mmHg.
[0031]
<Heat degreasing process>
Each green molded body after water extraction was heated to 50 ° C. in the air over 2 hours, then heated to 320 ° C. at a rate of 30 ° C./hour, and further maintained at 320 ° C. for 2 hours. To the degreasing step.
[0032]
<Sintering process>
The compact after completing the degreasing process was sintered under sintering conditions at 1300 ° C. for 2 hours to obtain a sintered compact.
[0033]
<Evaluation>
(1) Moldability: Ease of molding in the molding of a green molded body and properties of the obtained green molded body (particularly uniformity of the molded body) were relatively evaluated as excellent> good> good.
(2) State of green molded body after water extraction: The presence or absence of blistering was evaluated visually, and the one without blistering was evaluated as good. The extraction rate was calculated from the change in weight before and after extraction.
(3) The degreasing rate by heat degreasing of the molded body extracted with water was calculated from the change in weight, and the molded body after degreasing was visually evaluated for the presence or absence of swelling, and those without swelling were evaluated as good.
(4) After the dumbbell test piece-shaped green molded body was held as shown in FIG. 2 and heated and degreased, the deformation of the center part of the dumbbell test piece was visually observed.
(5) Properties of sintered body: The occurrence of cracks and blisters after sintering was observed and evaluated.
[0034]
<Result>
The results of moldability are shown in Tables 1-1 and 1-2. The results of water extraction at each extraction temperature are shown in Table-2-1, Table-2-2, Table-3-1 and Table-3-2. In the case of water extraction of polyethylene glycol at 25 ° C., the state of the molded product after extraction is good, but at 50 ° C., Example 5 and polyacetal resin using polyethylene glycol having a high polymerization degree as the extraction rate increases. Swelling was observed in a comparative example in which no was used.
The results of heat degreasing after water extraction are shown in Table-4-1, Table-4-2, Table-5-1 and Table-5-2. The molded body using the composition for producing a sintered molded body of the present invention has a degreasing rate under a constant degreasing condition as compared with the molded body obtained from the composition of the comparative example, although the extraction rate is almost the same. From the fact that it is high, it can be seen that it can be degreased in a short time and the state of the molded body after degreasing is more excellent.
In addition, the molded body which did not swell after heat degreasing and maintained a good shape could be obtained as a good sintered molded body with very little swelling, deformation, etc. when sintered.
[0035]
(Example 7)
Instead of water extraction in Example 1, ethanol (95 wt%), 1: 1 mixture by weight of ethanol (95 wt%) and water, 1: 3 by weight of ethanol (95 wt%) and water Extraction was performed with each of the mixed solutions, and the following operations were performed according to Example 1. In this case, as the ethanol concentration increased, some swelling occurred, but in any case, a good sintered compact was obtained.
[0036]
[Table 1]
[Table 2]
[Table 3]
[Table 4]
[Table 5]
【The invention's effect】
The composition for producing a sintered molded body of the present invention is characterized by containing a polyacetal resin (A) and a water-soluble or hydrophilic solvent-soluble organic compound (B) as a binder component, and a green molded body obtained therefrom By bringing water and a hydrophilic solvent into contact with each other, the water-soluble or hydrophilic solvent-soluble organic compound (B) can be efficiently removed, and the subsequent heating and degreasing can be performed in a relatively short time. Moreover, it is excellent also in the state of a molded body after extraction with water or a hydrophilic solvent and after heat degreasing, and further a sintered molded body.
[Brief description of the drawings]
FIG. 1 shows the shape of a dumbbell test piece formed from a green molded body.
FIG. 2 shows a visual observation method of a deformation amount after heat degreasing of a green molded body having a dumbbell specimen shape.
Claims (7)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP30707696A JP3822293B2 (en) | 1996-11-01 | 1996-11-01 | Composition for producing sintered compact including extraction and degreasing process and method for producing sintered compact using the same |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP30707696A JP3822293B2 (en) | 1996-11-01 | 1996-11-01 | Composition for producing sintered compact including extraction and degreasing process and method for producing sintered compact using the same |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH10140208A JPH10140208A (en) | 1998-05-26 |
| JP3822293B2 true JP3822293B2 (en) | 2006-09-13 |
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| JP30707696A Expired - Fee Related JP3822293B2 (en) | 1996-11-01 | 1996-11-01 | Composition for producing sintered compact including extraction and degreasing process and method for producing sintered compact using the same |
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| JP (1) | JP3822293B2 (en) |
Families Citing this family (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2002104879A (en) | 2000-07-27 | 2002-04-10 | Ngk Insulators Ltd | Method of degreasing powder compact |
| DE60333058D1 (en) | 2002-07-15 | 2010-08-05 | Hitachi Metals Ltd | Process for producing porous, sintered metals for filters |
| JP4330086B1 (en) * | 2009-02-09 | 2009-09-09 | 株式会社テクネス | Method for producing non-oxide ceramic products |
| DK2709967T3 (en) * | 2011-05-18 | 2019-07-29 | Basf Se | PROCEDURE FOR MANUFACTURING ELEMENTS IN POWDER INJECTION PROCEDURE |
| KR20210049700A (en) * | 2019-10-25 | 2021-05-06 | 윤태식 | Binder composition for manufacturing sintered body and debinding method for the same |
| JP7341446B1 (en) * | 2022-02-16 | 2023-09-11 | 旭化成株式会社 | Composition for sintered compacts, green compacts and sintered compacts |
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1996
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| JPH10140208A (en) | 1998-05-26 |
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