JP3648567B2 - Hollow model manufacturing method - Google Patents

Description

【００５８】
多官能ポリオール成分（Ｆ）にポリエーテルを使用すると、ポリエーテル鎖が導入されたことになる。ポリエステルポリオールを使用する時、ポリエーテルのエステルならばポリエーテル鎖が導入されたことになる。多官能ポリイソシアネート成分（Ｇ）がポリエーテルによってジョイントされた末端イソシアネート、言わゆるｑｕａｓｉのプレポリマーならばポリエーテル鎖を導入されたことになる。このポリエーテル鎖はウレタン樹脂のソフト成分であり、特にプロピレンオキサイドから誘導されたポリエーテル鎖は非常にソフトである。非常にソフトであると言うことは、脱ロウ・焼成工程にて高温に加熱された時、熱分解を起こし、熱分解にて液化流出燃焼し易い性質を持っている。本発明では、ポリエーテル鎖を２−２５重量％含有せしめる事によって、この特性を巧みに発揮させるものである。ポリエーテル鎖の含有が２重量％を下るとこの効果は減衰消滅する。ポリエーテル鎖の含有が２０重量％以上になると、ソフト成分があまりにも多くなり、硬化物が柔らかくなって、模型に要求される硬度をキープすることが出来なくなる。より好ましいポリエーテル鎖の含有量は５−２０重量％である。
【００５９】
多官能ポリオール成分（Ｆ）と多官能ポリイソシアネート成分（Ｇ）との配合量は、ＮＣＯ基数とＯＨ基数を計算し、通常、無発泡ウレタンの場合はＮＣＯ基数とＯＨ基数の比率ＮＣＯ／ＯＨが１．０近辺に成るように設計される。発泡ウレタンの場合ＮＣＯ／ＯＨは、１．０〜１．１程度のイソシアネート過剰領域にて設計される。
【００６０】
ＮＣＯ／ＯＨ＝１．０とは、イソシアネート基と水酸基の数が同数であり、反応が完遂する設計である。つまり最高の強度を発現する領域である。本発明では、ＮＣＯ／ＯＨ＝０．７〜１．０とＮＣＯ不足領域にて設定されているものである。通常、このようなＮＣＯ不足領域でウレタンの分子設計は行われない。本発明でこのような異常と言えるＮＣＯ／ＯＨ領域で分子設計を行える理由は、ポリイソシアネート成分の平均官能基数を２．１以上ポリオール成分の平均官能基数を３．０以上と多官能とすることによって、ＮＣＯ／ＯＨが１．０以下の領域において３次元網目構造が取れるからである。ＮＣＯ基不足、ＯＨ基過剰であるが、使用モノマーが多官能なるため、官能基の完全反応なくとも、モノマーの連結が完成し、主鎖を構成できるからである。過剰の反応相手のないＯＨ基は、主鎖にＯＨ基を保有した状態で反応を終結する。これによって、親水性のキープが高まり、疎水性の強い可塑剤を相分離ミクロ分散させるのに有効となるものと考えられる。
【００６１】
以上のことから、ＮＣＯ／ＯＨ＝０．７〜１．０、好ましくは０．８〜０．９であることが望ましい。ＮＣＯ／ＯＨが０．７以下になると、イソシアネート基の大幅不足状態となり、反応硬化後３次元網目構造を取れなくなり、極端に硬度低下を引き起こし、ついには形状保持が難しくなるほど柔らかくなる。一方、ＮＣＯ／ＯＨが１．０以上になると、イソシアネート基が過剰となり、脱型時間が来ても未反応イソシアネート基が残留し、所定硬度が出ないとか、硬化物表面に色むらが発生するという現象が発生し、好ましくない。
【００６２】
多官能ポリオール成分（Ｆ）と多官能ポリイソシアネート成分（Ｇ）の化学反応を促進する触媒としては、金属触媒及びアミン触媒がある。金属触媒としては、オクチル酸亜鉛・オクチル酸鉛やジブチルチンジラウレート、ジブチルチンジアセテート、等が挙げられる。アミン触媒としてはトリエチレンジアミン、ＮＮ−ジメチルピペラジン、Ｎ−メチルモルホリン、等が挙げられる。これらの触媒は通常ポリオール成分中に添加される。通常１〜１０００ｐｐｍが多官能ポリオール成分（Ｆ）に添加され、可使時間が調整される。本発明においては、使用可能時間つまり、可使時間が５分以内となるように多官能ポリオール成分（Ｆ）に触媒が添加され使用されるものである。可使時間が５分以上になると、硬化・脱型時間が２時間以上となり、樹脂模型製作上支障を来すことのなる。可使時間が１分以下の場合には、反応粘度アップが早く、２液混合・注型作業時間が取りづらくなる。よって、可使時間は１〜２分が好ましい。
【００６３】
次いで、本発明に使用される可塑剤（Ｈ）について説明する。本発明に使用する可塑剤（Ｈ）とは、化学反応を起こす官能基を持たない不活性な揮発性が無視できる化合物で室温にて液状である。可塑剤（Ｈ）としては、エステル系可塑剤、エーテル系可塑剤、エステル・エーテル系可塑剤が挙げられる。具体的に、エステル系可塑剤としては、ジオクチルアジペート（ＤＯＡ）、ジオクチルフタレート（ＤＯＰ）、ジブチルフタレート（ＤＢＰ）が代表的である。その他、酢酸ベンジル、安息香酸ブチル、安息香酸オクチル、安息香酸イソペンチル、エチレングリコール安息香酸ジエステル、ポリエチレングリコール安息香酸ジエステル、プロピレングリコール安息香酸ジエステル、ポリプロピレングリコール安息香酸ジエステル、エチレングリコールジオリエート、ポリエチレングリコールジオリエート、プロピレングリコールジオリエート、ポリプロピレングリコールジオリエート等が挙げられる。エーテル系可塑剤としては、エチレングリコールジブチルエーテル、エチレングリコールジフエニルエーテル、ジエチレングリコールジメチルエーテル、ジエチレングリコールメチルエチルエーテル、ジエチレングリコールジエチルエーテル、ジエチレングリコールエチルブチルエーテル、ジエチレングリコールジブチルエーテル、トリエチレングリコールジメチルエーテル、トリエチレングリコールジメチルエーテル、トリエチレングリコールジエチルエーテル、トロエチレングリコールジブチルエーテル，テトラエチレングリコールジメチルエーテル、テトラエチレングリコールジエチルエーテル等が挙げられる。エーテルエステル系としては、エチレングリコールモノブチルエーテルアセテート、ジエチレングリコールモノエチルエーテルアセテート、ジエチレングリコールモノブチルエーテルアセテート、ジエチレングリコールモノフエニルエーテルアセテート等が挙げられる。
【００６４】
前記可塑剤（Ｈ）の使用量は、２液反応硬化型ウレタン樹脂液（Ｄ）に対して２〜２０重量％である。可塑剤（Ｈ）の使用量が２０重量％以上に高含有させると、可塑剤（Ｈ）が樹脂模型の表面へブリードし、ベタツキ・タックが発生する。また、可塑剤（Ｈ）の使用量が２重量％以下になると、脱ロウ・焼成工程で、樹脂を熱分解・溶融・流失燃焼させる時に、流出しにくくなる。なぜなら、可塑剤（Ｈ）は、室温で液体であり、高温では流出しやすい低粘度となるからである。このような効果を強く発揮させるためには、可塑剤（Ｈ）はできるだけ高含有させたいものである。通常、樹脂成分の中に可塑剤が多く含まれると、硬化樹脂の表面へ可塑剤がブリードし、表面にタックやベタツキが発生する。そこで、できるだけ可塑剤（Ｈ）を高含有させるために鋭意研究を行った結果、可使時間５分以内にて急速硬化させて、可塑剤（Ｈ）が硬化樹脂から相分離し、硬化樹脂の３次元網目構造内にミクロ分散状態で閉じこめられる状態と成すことが有効であることを見い出した。
【００６５】
この様な相分離ミクロ分散構造は、言葉で表現するならば、蜂の巣状の硬化樹脂の中に幼虫となる可塑剤（Ｈ）が包含されていると表現できる。蜂の巣状の硬化樹脂は強度物性に優れた構造であり、可塑剤（Ｈ）を蜂の巣内において大切に保存し、外部へ放出しない立体構造である。したがって、可塑剤（Ｈ）は比較的高含有となっても硬化物表面ににじみ出し、タック発生を引き起こすことはない。相分離ミクロ分散構造を取らない時は、可塑剤は硬化樹脂中に溶解することになり、飽和状態以上になると可塑剤が硬化物表面ににじみ出し、タックが発生する。また、にじみ出しが多いとベタツキが発生し易くなる。このような相分離ミクロ分散構造は電子顕微鏡にて確認されている。相分離ミクロ分散構造を助成するには可使時間５分以内で急速硬化せしめることが必要である。好ましくは３分以内である。可使時間が５分以上になると、相分離ミクロ分散が完結しにくくなり、また模型製作時脱型に１日以上必要となり模型製作上迅速性が失われる。
【００６６】
前記可塑剤（Ｈ）は２液反応硬化型樹脂液（Ｄ）として存在する時点では、可塑剤（Ｈ）は均一溶解状態が必要であり、反応硬化する段階で硬化樹脂から相分離ミクロ分散が助成され、反応硬化完結時点ではミクロ分散した可塑剤を包含し表面へのブリードを妨げるものである。こう言った微妙なバランスの上に組成が構成されるものである。つまり、可塑剤（Ｈ）と反応硬化性樹脂の親水性・疎水性のバランスをうまく調整された領域に設計されるものである。親水性セグメントとしては、アルキレンオキサイド鎖が有効であり、疎水性セグメントとしては炭化水素鎖が有効である。これらの親水性セグメント・疎水性セグメントは、使用する原料モノマーの選択にて決定される。これらの親水性と疎水性のバランスはある程度乖離させた設計が必要である。２液反応硬化型ウレタン樹脂液（Ｄ）にエチレンオキサイド鎖を多用すると親水性が強くなるし、プロピレンオキサイド鎖にするとエチレンオキサイド鎖よりは親水性が弱まる。エチレンオキサイド鎖やプロピレンオキサイド鎖を少なくすると疎水性が強い２液反応硬化型ウレタン樹脂液（Ｄ）となり、親水性と疎水性を有る範囲内で調整することができる。また、可塑剤（Ｈ）の種類と使用量を調整することにより、可塑剤（Ｈ）自身の親水性と疎水性を有る範囲内で調整することができる。例えば末端をアルキルエーテルとする場合、メチルエーテル・エチルエーテル・ブチルエーテル・フエニルエーテルと変化するに従って疎水性が大きくなる。このように、可塑剤（Ｈ）の化学構造と使用量、２液反応硬化性ウレタン樹脂液（Ｄ）の化学構造と使用量を変えて相分離ミクロ分散する領域範囲を設定するものである。この様な手段によって、可塑剤（Ｈ）を比較的疎水性強く、樹脂成分を比較的親水性強く設定してやると、相分離ミクロ分散がうまく成立する。
【００６７】
次いで、本発明に使用されるロウ・ワックス成分（Ｉ）について説明する。ロウ・ワックス成分（Ｉ）は、化学反応を起こす官能基を持たない不活性な揮発性が無視できる化合物であり、室温にて結晶性のある固体である。ロウ・ワックス成分（Ｉ）としては、天然に存在する天然ロウ及び合成によって得られる合成ワックスがある。天然ロウとしては、我々の身近に存在するものはロウソクである。天然ロウ成分の化学組成は高級脂肪酸と高級アルコールから成るエステルであり、ロウエステルと言われている。高級脂肪酸・高級アルコールの炭素数は１６以上が主体である。エステル化合物であるから多少酸価が残存する、つまり遊離脂肪酸が残存する。また天然には数多くの飽和・不飽和高級脂肪酸が存在するので、ロウによっては高級不飽和脂肪酸やヒドロキシ酸も含有することになる。これらロウはパラフインに近い化学構造であり、常温で結晶化又は非結晶化した固体でありその融点は一般的に８０℃程度の近辺にある。代表的なロウを挙げると、キャンデリラロウ、カルナバロウ、ライスワックス、密ロウ、鯨ロウ、モンタンロウ、ラノリンロウオーリキュリワックス、アルフアーワックス、コルク繊維ワックス、サトウキビワックス、木ロウ、スーマックロウ、マイクロロリスタリンワックス、地蝋、等が挙げられる。合成ワックスとしてはポリエチレンワックス，Ｆｉｓｈｅｒ−Ｔｔｏｐｓｃｈ合成により得られるワックス、ロウ質共重合体及びそれらのエステル、Ｃ８−Ｃ３２て直鎖状又は分枝状の脂肪鎖を持つ動植物又は食物性油の触媒水素添加によって得られるワックスや、シリコンワックス、フッ素含有ワックス等が挙げられる。これらのロウ・ワックス成分は単独または混合され、また第３成分が添加されたロウ成分、ワックス成分でも良い。
【００６８】
このロウ・ワックス成分（Ｉ）はパラフイン又はオレフインとしての性質が強く、非常に疎水性が強く常温で固体である。よって、多官能ポリオール成分（Ｆ）や多官能ポリイソシアネート成分（Ｇ）また可塑剤（Ｈ）に溶解しにくい性質を持っている。よって、２液反応硬化性型ウレタン樹脂液（Ｄ）に配合されても溶解され難く、液中系内に浮遊している状態にある。しかる状態において、２液反応硬化型ウレタン樹脂液（Ｄ）が急速硬化し、結果的に３次元網目構造の樹脂中に固体として包含されることになる。よって、本発明の樹脂模型はその表面にロウ・ワックス成分が露出するものではないがゆえに、ロウ模型の欠点はことごとく回避されると言った特異性を持っている。このロウ・ワックス成分（Ｉ）は加熱による脱ロウ・焼成工程にて「軟化・熱分解・溶融した樹脂分解物」を流出加速する効果が大きいものである。
【００６９】
このロウ・ワックス成分（Ｉ）は２液反応硬化型ウレタン樹脂液（Ｄ）に対して１〜２０重量％使用されるものである。使用量が１重量％以下だとロウ・ワックス成分（Ｉ）を使用する脱ロウ効果が消滅する。２０重量％以上に成ると、２液反応硬化型樹脂液（Ｄ）の流動性がわるくなり、樹脂模型製作時の作業性が損なわれる。また、樹脂模型自身の強度が低下し、脱型時割れたり折れたりする可能性が高くなる。よって、好ましくは５〜２０重量％である。より好ましくは１０〜１５重量％である。
【００７０】
このロウ・ワックス成分（Ｉ）は１ｃｍ^３の立方体におさまる大きさの粒子状、鱗片状、塊状である。粒子状・塊状とは、玉状または角砂糖状であり、またこれらが多少変形した形状であっても良い。つまり、真玉とか正直角柱などと制限するものではない。大きさも１ｃｍ^３の立方体に収まる大きさである。好ましくは、直径１ｍｍ以下である。１模型の１ｍｍ以下の肉薄部分には、当然このロウ成分は流れ込みにくくなる。よって、模型中のロウ・ワックス成分（Ｉ）の均一分布が損なわれることになるが、模型としての形状保持性、寸法精度、加温時の分解溶融流出性、高温時の燃焼分解残留灰分が少なく、鋳型製作・精密鋳造が実施できれば良い。模型の１ｍｍ以上の肉厚部分には、当然このロウ成分は流れ込みやすい。未硬化樹脂液も流れ込みやすいと言うことになり、結果的に模型が型より脱型出来、模型全体に樹脂成分が行き渡っておれば良い。模型の肉厚部分にロウ・ワックス成分（Ｉ）が多く流れ込むのは、ある意味では好都合である。つまり、肉厚部分は脱ロウ・焼成工程にて溶融流出分解燃焼が遅れがちになる。この部位にロウ・ワックス成分（Ｉ）が比較的多く流れ込み、硬化樹脂にて固定化されていると脱ロウ・焼成工程にて溶融流出分解燃焼をうまく助成してくれる効果が大きく発現されることになる
【００７１】
次いで、本発明に使用される水（Ｊ）について説明する。水分（Ｊ）とはＨ₂Ｏである。水分（Ｊ）は、▲１▼意図的に配合された水分と、▲２▼通常化学品原料に製造工程上混入する微量水分と、▲３▼原料自体が空気中から吸収する水分があると判断されます。本発明で言及する水分（Ｊ）とは、これらを合計したものを水分（Ｊ）としてカウントするものである。水分（Ｊ）を使用する理由は、多官能ポリイソシアネートとの化学反応で発生する炭酸ガスを発泡剤とするものであり、つまり、ウレタンの水発泡技術を導入するものである。その結果、樹脂模型は可塑剤（Ｈ）とロウ・ワックス成分（Ｉ）と気泡を包含した発泡体と成すものである。発泡を調整した限定範囲内において、発泡体であるこの様な樹脂模型自身がしっかりとした形状保持性をキープし、脱ロウ・焼成工程において熱溶融・分解・流出燃焼に大きな有効性を発現するものである。
【００７２】
発泡倍率を決定する主因子は水分（Ｊ）の量であり、副因子は型表面の吸着水・外気の温度・湿度などである。水分（Ｊ）の量は、２液反応硬化型ウレタン樹脂液（Ｄ）に対して０．０１〜１．０重量％含有せしめるものである。好ましくは、０．０３〜０．５重量％である。より好ましくは、０．０８〜０．１５重量％である。水分（Ｊ）が１．０重量％以上になると、気泡が樹脂表面に多量集中し、模型表面のスキン層が薄くなり、脱型時にこのスキン層が破壊し、気泡が凹状態で模型表面に出現することになり、模型表面が不都合となる。つまり、微発泡レベルにコントロールすることが必要である。発泡ウレタンにおいては、気泡の大きさを揃えるために整泡剤が使用される。本発明に於いても当然ながら整泡剤を添加し、気泡の大きさを揃えることが重要である。
【００７３】
前記水分（Ｊ）は通常多官能ポリオール成分（Ｆ）に配合されるものである。水を配合して均一混合し、カールフイッシャー法によって微量水分測定を行うことでコントロールすることができる。多官能ポリオール成分（Ｆ）に配合する場合、水のみでもよいし、水を含有する成分で模型製作上異常を来すものでなければ、特に制限はない。例えば、界面活性剤水溶液、水性染料水溶液、水性のり、樹脂水溶液等が挙げられる。
【００７４】
こうして水発泡せしめる時、気泡の大きさを極力揃えるために整泡剤が使用される。整泡剤とは一種の界面活性剤であり、シリコンにアルキレンオキサイドを付加させたタイプが一般的である。整理泡剤を添加して水発泡せしめることにより、模型の中に比較的均一に同程度の大きさの気泡が点在する発泡体となる。模型の強度は低下するが、脱ロウ工程・焼成工程にて脱ロウ成分・焼成成分が大幅に減少するため、大きな優位性が発現する。模型の強度は厳しいものではなく、模型脱型時スムースに脱型できる強度発現が有ればよい。脱型後の模型は持ち運びに耐えるレベルでよい。常温保管時形状変化が極小さいものなればよい。耐火コーテイング時、コーテイング作業に耐える強度を保持すればよい。よって、高強度を求めるものではないので、可塑剤やロウ・ワックス成分を包含した本発明の樹脂模型で十分なのである。
【００７５】
２液反応硬化型ウレタン樹脂液（Ｄ）には、有機溶剤が使用されても良い。有機溶剤としては、イソシアネートと化学反応をしない不活性な有機溶剤が選択される。不活性な有機溶剤としては芳香族系有機溶剤・エステル系有機溶剤・エーテル系有機溶剤・脂肪族系有機溶剤・塩素系有機溶剤などがある。有機溶剤に要求される性能としては、多官能ポリエーテル成分（Ｆ）や多官能ポリイソシアネート成分（Ｇ）や可塑剤（Ｈ）を溶解し、臭気がマイルドであり、燃焼時有毒ガスを発生しないものであり、経済性が伴うことが要求される。このような要求性能を満たす有機溶剤は、芳香族系有機溶剤から選定されることが望ましい。好ましいのは、トルエン、キシレンである。
【００７６】
２液反応硬化型ウレタン樹脂液（Ｄ）が発熱ゲル化段階において、有機溶剤は気化しやすく、発泡剤的役割を助成する効果がある。また、硬化脱型後の模型内部には有機溶剤が多少とも閉じ込められた状態にある。またどちらかと言えば、燃焼しにくい肉厚１ｍｍ以上の部位には有機溶剤が肉厚部位の内部に残存しており、脱ロウ・焼結工程時燃焼を助成する効果が大きい。また樹脂粘度を低下し、模型製作上の作業性を向上せしめる効果が非常に大きい。
【００７７】
２液反応硬化型ウレタン樹脂液（Ｄ）に天然高分子系廃棄物の微細片が配合使用されてもよい。天然高分子系廃棄物の微細片とは、紙類の廃棄物・木材類の廃棄物・繊維衣類の廃棄物の微細片等である。紙類の廃棄物の微細片としては新聞紙・広告紙・事務コピー用紙・包装用紙・段ボール等の微細片が挙げられる。木材類の廃棄物の微細片としては、建築用廃木材、土木用廃木材、家具廃材、間木材、植物の枯れ草、籾殻の微細片等が挙げられる。繊維衣類の廃棄物としては、木綿衣類、麻衣類、羊毛衣類の微細片が挙げられる。詳細に例を挙げれば、紙類ならば使い捨てられた事務用紙をシユレーターにてカットし微細化されたもの、木材類ならば解体・粉砕・切断にて派生するおがくず、繊維衣類ならば単繊維状に破砕切断された繊維くずである。長さ１ｍｍ以下の各種形状物まで微細化されたものが好ましい。
【００７８】
これら天然高分子系廃棄物の微細片は、多官能ポリオール成分（Ｆ）に配合されるのが好ましい。天然高分子系廃棄物の微細片の比重は多官能ポリオール成分（Ｆ）の比重に近似するため、沈降・浮上が少なく天然高分子系廃棄物の微細片の液中に浮遊することになり、混合することにより比較的均一分散させることが容易である。天然高分子系廃棄物の微細片を多官能ポリオール成分（Ｆ）の液中に混合する場合、天然高分子系廃棄物の微細片の中に包含されている空気によって混合分散しがたく浮上する場合には、減圧状態において脱気すれば、空気は除去され、混合分散がやりやすくなる。
【００７９】
前記天然高分子系廃棄物の微細片は、一般的に親水性があるため大なり小なり湿気を含有している。よって、天然高分子系廃棄物の微細片を多官能ポリオール成分（Ｆ）中に混合分散させると、天然高分子系廃棄物の微細片に含有した水分を持ち込むことになり、多官能ポリオール成分（Ｆ）中の水分量が増加することになる。よって、天然高分子系廃棄物の微細片の混合量によって持ち込まれた水分量を加味して、多官能ポリオール成分（Ｆ）の水分量をコントロールすることになる。
【００８０】
２液反応硬化型樹脂液（Ｄ）には各成分の調整剤・安定剤・着色剤・可燃性フイラー・希釈溶剤が添加される。安定剤としては、ヒンダードフエノール系・ヒンダードアミン系酸化防止剤が使用される。着色剤としては有機染料・カーボン粉が有効である。顔料は焼成工程において灰分として残留するため好ましくない。難燃剤の添加は避けるべきである。可燃性フイラーとしては、中空バルーン又は及び炭素粉を１〜１０％含有せしめることが有効である。中空樹脂バルーンとは、真比重０．１５〜０．５０ｇ／ｃｃ、粒子経１５〜１００μｍの軽量微分末であり、ＵＣＡＲ Ｐｈｅｎｏｌｉｃ Ｍｉｃｒｏｂａｌｌｏｏｎ（ユニオンカーバイド社製）とか、マツモトマイクロスフエアー（松本油脂製薬（株）製）にて市販されているものである。こういった中空樹脂バルーンを含有させることは、樹脂模型に空気を埋め込むことになり、脱ロウ工程・焼成工程において、分解・流出・燃焼を促進し、残留灰分を少なくすると言った効果が発現する。中空樹脂バルーンの含有量は樹脂模型に対し０．１〜１０重量％である。１０重量％以上になると、２液反応硬化型ウレタン樹脂液（Ｄ）ががさつき、スムースな流動性が得られにくくなる。よって好ましくは３〜８重量％である。
【００８１】
【発明の効果】
以上説明したように、本願発明よれば、自動車・航空機・原子力・宇宙開発に多用されるように成って来た高強度・耐熱性・耐腐食性に優れたチタン合金から成る精密鋳造部品を多量に且つ経済的に製造することが可能となる。中でも、航空機や宇宙開発において要求されるさらなる軽量化に対して有効な製造方法であり、部品間の接合を極力省略した一体成型鋳造部品の製造を可能にするものである。
【００８２】
このように、本発明は、従来技術ではなし得なかった中空部位を有する薄肉複雑形状模型を一体成型し、この模型を焼失模型として鋳型を製造し、チタン合金精密鋳造部品の量産を可能とするものである。
【００８３】
さらに、従来の分割模型接合方法と比較して、本発明は中空部位を有する薄肉複雑形状模型を一体成型するため、中子形成用モールドを作成し、中子を生産せねば成らない工程が増加すると言ったデメリットも発生するが、模型の接合工程が省略されると言ったメリットが生まれる。その結果、生産される模型は接合部位がないため、設計意図を忠実に反映した寸法精度の高い模型となる点に大きな有効性がある。この模型にて製造される鋳型・精密鋳造品が寸法精度の高いものとなることは言うまでもない。
【図面の簡単な説明】
【図１】本願発明の実施の形態に係る中空模型の一例を示す斜視図である。
【図２】図１に示す中空模型の断面図である。
【図３】本願発明の実施の形態に係る中子の一例を示す斜視図である。
【図４】図２に示す中子の断面図である。
【図５】中子の製造工程の一部を示す断面図である。
【図６】中子の製造工程の一部の他の実施の形態を示す断面図である。
【図７】中空模型の製造工程の一部を示す断面図である。
【図８】中子を含む中空模型を示した断面図である。
【図９】中子心材を除去する工程を示した断面図である。
【図１０】中子の皮膜を除去する工程を示した断面図である。
【符号の説明】
１ 中空模型
２ 開口部
３ 中空部分
４ 隔壁
５ 中子
６ 中子心材
７ 皮膜[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a hollow model manufacturing method for manufacturing a hollow model having a hollow portion having at least one opening communicating with the outside.
[0002]
[Prior art]
Various methods have been devised in the past for modeling a shape having a hollow shape. In order to create a spear, the ancients made a hollow spider-like structure by laminating string-like clays joined together in a snake's skull shape, and making the snake's skulls large and small. On the other hand, the cage | basket which has a hollow part is manufactured now by raising the clay put on the rotating plate with a fixed thickness. These methods are applied to a symmetric simple circular shape.
[0003]
In glass crafts, molten glass is attached to the tip of the blowing rod under high-temperature conditions that maintain fluidity, and air is injected from the tip of the blowing rod into the molten glass to inflate the balloon. A hollow glass craft is produced by three-dimensional modeling of the appearance of molten glass while rotating. Industrially, the molten glass is attached to the tip of the blowing rod under high temperature conditions that maintain fluidity, confined in the split mold, air is injected into the molten glass from the tip of the blowing rod, and inflated into a balloon shape, The molten glass is pressed against the side of the split mold with air pressure, the temperature of the molten glass is accelerated, the fluidity is lost, the condition is such that the shape can be retained by solidification, and the hollow mold is taken out by dividing the split mold. . Hyundai performs this method by fully automatic continuous production, producing large quantities of hollow glass products of the same shape.
[0004]
In the plastics field, there is also a method in which air is injected into a thermoplastic sheet cylinder softened by heat to adhere to the inner wall of the split mold, and after cooling and solidifying, the split mold is divided to take out a hollow shaped article. It is said.
[0005]
In addition, the thermoplastic resin powder is put into the mold through the opening of the heating mold, the mold temperature is raised, and the thermoplastic resin powder in surface contact with the mold is melted to form a thermoplastic resin layer. Along with mold cooling, the molten thermoplastic resin adhering to the inner surface of the mold is cooled and held in shape, and unmelted thermoplastic resin powder at the center of the mold is removed from the mold opening, and finally on the inner surface of the mold The adhered thermoplastic resin sheet is pulled out from the mold opening, and the pulled-out resin sheet is expanded by air pressure to form an integral hollow shaped body. If you paint it beautifully, you can seamlessly create a mask of popular characters. This is slush molding. This is a method that takes advantage of the property that the molded thermoplastic resin has rubber elasticity, and is elastically restored to its original shape after being folded out of the mold opening.
[0006]
These shaped objects produced by blow molding or slush molding have a hollow portion that is substantially similar to the outer shape, and it is difficult to form a shaped product in which the outer shape and the hollow portion have completely different shapes.
[0007]
In the casting field, a core is installed in the mold, molten metal is poured into the space formed between the mold and the core, and then cooled, and the mold and core are crushed and removed to produce a hollow casting. doing. This can be a modeled object in which the outer shape and the hollow part have completely different shapes, and it is a long-standing and complicated hollow-shaped one-piece modeled manufacturing method.
[0008]
In this way, basically, a hollow model is formed by inserting a core into a mold, holding the shape with a modeling material in between, and then erasing the core. The core material is air, sand connected by a binder, resin powder with poor thermal conductivity, or foamed resin that liquefies and flows out due to volume contraction due to heat. Or a wax that is easily liquefied by heat and flows out, or polyethylene glycol that is washed away with water. That is, the core is subjected to collapse removal, outflow removal, volume shrinkage removal, combustion gasification removal, and dissolution cleaning removal.
[0009]
At present, a method for integrally forming a hollow complex shape model having completely different properties from the basic hollow body manufacturing method described above has been developed. It is a stereolithography method in which a photocurable resin is irradiated with light to be cured and laminated into a donut board shape, and the shape of the donut board is sequentially deformed by computer-controlled light to obtain a three-dimensional shape object. The central part of the board is to give the three-dimensional shape model a hollow part, which is also a wonderful hollow-shaped monolithic structure manufacturing method. This method is a very powerful method for producing one model, but it takes a long time to produce many identical models, and it is not suitable for multiple to mass production. I can say that. The above is for integrally molding a hollow model, but it is natural that there are advantages and disadvantages in the shape that can be molded, the material of the molded product, mass production, and economy.
[0010]
Here, the hollow complex shape model proposed by us is used for precision casting by the lost wax method, and the hollow complex shape model is burned down by outflow, decomposition, and combustion in the dewaxing / firing process. As a method of approximating this, the following can be mentioned.
[0011]
Japanese Patent Application Laid-Open No. 2002-66689 manufactures a model mainly composed of a synthetic resin that can be dissolved in a solvent, embeds the model in a mold by an investment method or a ceramic mold method, and immerses the mold in a solvent. A method is disclosed in which a part is dissolved or softened to form a gap at the interface between the model and the mold, and the mold and the model are baked at a high temperature to disappear the model.
[0012]
Japanese Patent Laid-Open No. 2001-121244 discloses a method of manufacturing a cylindrical hollow precision casting product by dividing a hollow model, manufacturing a hollow wax model by joining the divided wax model, and precision casting by the lost wax method. Yes.
[0013]
In JP-A-11-123723, a core is formed from a foam of a polymer compound, an unvulcanized rubber container is formed around the core, and then the rubber container is heated and vulcanized to form a core. A method is disclosed in which the polymer foam is melted to reduce the volume, or the core is dissolved and removed with an organic solvent.
[0014]
JP-B-8-300333 prepares a core made of a foam material that shrinks and disappears by heating, and injects a molding material in which the core is placed in a mold and a powder and a binder are mixed. Disclosed is a method for producing a powder molded product, comprising: a step of obtaining a molded body; and a step of eliminating the core by heating the molded body integrated with the core. .
[0015]
[Problems to be solved by the invention]
In recent years, as the technology has advanced dramatically, the technical demand has become increasingly complex. Even in the precision casting field, light alloys with excellent strength, heat resistance, and corrosion resistance have been developed, and precision casting parts have been dramatically reduced in weight, strength, heat resistance, and corrosion resistance. . As a result, industrial precision casting parts are also used in automobile engine parts, aircraft parts, space development rocket parts, space stationery parts, etc., and titanium alloys are attracting the most attention as materials. The shape is not a simple shape like a bottle or bottle, but a complicated shape that has multiple 3D curved surfaces and multiple complex hollow parts, such as a manifold around the engine, a hollow rotor blade of a turbine, and a fuel supply engine part of a rocket. is there. Moreover, since it is necessary to reduce the weight, it has been demanded that a large number of complicated shapes having a thin portion with a thickness of 1 mm or less can be produced.
[0016]
These precision castings are generally manufactured by precision casting by the lost wax method, and one precision casting requires one mold. Furthermore, one model is required for one mold. However, industrial production of precision cast parts is not sufficient with current technology.
[0017]
First, there is a big problem in integrally forming a complex hollow model. It is common to divide and produce complex hollow models, and then join them to form complex hollow shapes. However, the thinner the complex shape, the easier it is to cause misalignment and better dimensional accuracy. It is difficult to make a model. Therefore, it is necessary to establish a mass production type manufacturing method capable of integrally molding a complex shape model having a hollow portion.
[0018]
Next, since the conventional wax model is fragile in strength and it is difficult to produce a thin model having a thickness of 1 mm or less, the problem is how to use the material of the model. For this reason, a lost wax in which melamine resin powder is dispersed and dissolved in the wax component to modify the wax component has been developed. However, the material is insufficient in strength and toughness, and cannot be applied to a thin model having a thickness of 1 mm or less. . In particular, it is known that the phenomenon that thin-walled parts “break, crack, and deform” occurs frequently during demolding. As described above, it is difficult to manufacture the model itself, and the present situation is that the mold and casting have not been achieved.
[0019]
As a result of intensive studies on such problems, the present inventors have found a method for comprehensively solving the problems and have reached the present invention.
[0020]
[Means for Solving the Problems]
Therefore, the method for manufacturing a hollow model according to the present invention is a method for manufacturing a hollow model having a hollow part having at least one opening communicating with the outside, and is made of foam (B) and can be accommodated in the hollow part. A core core material forming step for forming a core core material of a large size, and a film forming step for coating the core core material with a film forming component (A) to form a film having the same outer shape as the hollow portion. The core formed in the core forming step and the core forming step is placed in a mold (C) that forms the outer shape of the hollow model, and a two-component reaction rapid-curing urethane resin liquid (D) in the gap A hollow model forming step for forming a hollow model in which the core is contained by demolding and injecting the organic solvent (E) into the film made of the film forming component (A), Dissolving the core material comprising (B) The core core material removing step for removing the core core material, and the coating film removing step for extracting and removing the film from which the core core material has been removed from the opening.
[0021]
The film-forming component (A) is preferably a reaction-curing urethane having a Schier hardness of A50-95 having flexibility, and the foam (B) is preferably expanded polystyrene.
[0022]
Furthermore, the urethane resin liquid (D) for two-component reaction rapid curing casting is composed of a polyfunctional polyol component (F), a polyfunctional polyisocyanate component (G), and a plasticizer (H). It is desirable that the plasticizer (H) is micro-dispersed in phase separation within 5 minutes.
[0023]
Furthermore, the urethane resin liquid (D) for two-component reaction rapid curing type casting has fine wax-component (I) and a minute amount of moisture (J) in a predetermined ratio, and contains wax-wax fine particles. Desirably, the urethane foam is dispersed and included.
[0024]
The hollow model manufactured by the hollow model manufacturing method is preferably used for precision casting by the lost wax method, and the precision cast product is preferably manufactured by this hollow model.
[0025]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the invention will be described.
[0026]
When the final product is a precision casting by the lost wax method, the model disappears in the dewaxing and firing process when the mold is manufactured, so one model is required for each product. It is easy to manufacture one complex shape model having a hollow portion. This can process three-dimensional data into CAM data in CAD, send it to an optical modeling machine, and perform optical modeling to integrally model a complex shape model having a hollow portion. If a plurality of models with the same shape are produced, the production speed will be too slow for the stereolithography. In this case, a complex shape model having a plurality of hollow portions must be manufactured by duplicating the complex shape model having a hollow portion obtained by stereolithography as a master model. In this case, a large number of complex shape models having hollow portions are manufactured, and it is desired to make a seamless integral molding; there are parts having a thickness of 1 mm or less in various places; at the time of mold production by the lost wax method, by a dewaxing process and a firing process. The model is required to melt, flow, burn, gasify and disappear.
[0027]
Based on the above, a description will be given of a complex shape model having a hollow portion using the special shape core of the present invention. 1 and 2 show an example of a hollow model having a hollow portion. This hollow model 1 is a 1 mm thick shaped object having hollow portions 3 partitioned by a partition wall 4 connected to an opening 2.
[0028]
Next, the core necessary for forming the hollow model 1 shown in FIGS. 1 and 2 is shown in FIG. The core 5 is formed by a hollow space forming portion 5 a for forming the hollow portion 3 and an opening forming portion 5 b for forming the opening 2. Further, the core 5 according to the embodiment of the present invention is constituted by a core core material 6 made of a foam (B) and a film 7 made of a film-forming component (A) coated on the core core material 6. Is done.
[0029]
Here, the process of manufacturing the core 5 will be described. The core material 6 is formed by cutting out from a foam board. When the core itself has a curved surface, it is formed into a predetermined shape by NC processing based on CAD data. This core material 6 becomes a shape having a slightly smaller dimension than the core and will eventually disappear, so that strict dimensional accuracy is not required.
[0030]
The core material 6 is disposed in the core forming mold 8. In the embodiment shown in FIG. 5, it is suspended in the core forming mold 8 by a support device 11 comprising a support arm 9 and a weight 10 and is held in a hollow state. In the embodiment shown in FIG. 6, the core is made by the same material as the film-forming component (B) coated on the core core material 6, in this embodiment the support member 13 made of a reactive curable urethane resin liquid. The mold 8 is held. The core forming mold 8 determines the shape of the core 5 and requires a certain degree of dimensional accuracy.
[0031]
5 and 6, a reaction curable urethane resin liquid is injected into the gap 12 between the core core material 6 and the core forming mold 8 coated with the release agent, so that the film 7 is formed. . In this case, normal pressure casting or vacuum casting may be used. Vacuum casting is preferable. Then, after casting and curing of the reactive curable urethane resin liquid, the core forming mold 8 is divided, and the core 5 in which the core core material 6 is coated with the film 7 made of the film forming component (A) is demolded. Then, the core 5 is obtained.
[0032]
Next, the process of installing the core 5 in the mold 20 and injecting and curing the two-component reaction rapid-curing urethane resin liquid (D) as a model material will be described. As shown in FIG. 7, two cores 5 are mounted on a model mold 20 and supported by a support unit 21 (not shown) or a support portion 21 made of the same material as a two-component reaction rapid-curing urethane resin solution (D). It is held hollow in the model mold 20. The model mold 20 determines the shape of the model and requires a certain degree of dimensional accuracy.
[0033]
Then, a reaction curable casting urethane resin liquid (D) serving as a model material is injected into the gap 22 between the core 5 and the model mold 20 coated with the release agent. Normal pressure casting or vacuum casting may be used. Vacuum casting is preferable. After casting and curing, the model mold 20 is divided, and the hollow model 1 including the core 5 as shown in FIG. 8 is removed.
[0034]
Then, as shown in FIG. 9, the coating 7 of the core 5 is broken through, and the organic solvent (E) is injected into the foam (B) as the core core material 5 to be dissolved and removed. In this embodiment, the organic solvent (E) is injected into the foam (B), which is the core core material 5 included in the hollow model 1, by the syringe 40. Thereby, the foam (B) is dissolved and liquefied by the organic solvent (E). The foam (B) is completely dissolved in the organic solvent (E) in the bag of the film 7, so that the model material is not violated. Then, the organic solvent (E) in which the foam (B) is dissolved is sucked into the syringe and removed. In this way, the foam (B) disappears and is removed in a very short time without application of heat or physical stress.
[0035]
Finally, as shown in FIG. 10, the film 7 made of the film-forming component (A) is drawn out from the opening 2 of the hollow model 1 and removed. In this embodiment, a necessary portion of the film 7 included in the model is cut by scissors and pulled out by tweezers. This method is not applicable when the opening 2 of the model is about the size of a needle hole, but this process is sufficient if the opening is large enough to accommodate tweezers and surgical scissors. is there. If consideration is given at the shape design stage, the opening of the model can be kept constant. Even if this process is not performed carefully, the film 7 can be easily pulled out, and if the model has a certain level of physical properties, it will not cause damage. On the other hand, the conventional lost wax model has a high risk of damage due to insufficient strength.
[0036]
As described above, the hollow model 1 having the hollow portion 3 can be manufactured. In order to add further details, the material components used in each step will be described.
[0037]
Moreover, it can be said that the core 5 of this invention is a two-layer structure which consists of a foam (B) coat | covered with the film-forming component (A). Examples of the foam (B) used as the core material 6 for the core 5 include foams of various polymers such as foamed styrene, foamed urethane, and foamed phenol. Since it is dissolved and removed with an organic solvent in the subsequent step, the most advantageous is that it is required to be easily dissolved in the organic solvent. Therefore, as a preferable foam (B), there is no crosslinked structure peculiar to a thermosetting resin, that is, a foam of a thermoplastic resin is most easily dissolved in a solvent. For that reason, foamed styrene is most preferred as the foam (B). A foam made of a reactive cross-linking and curing type resin such as foamed urethane or foamed phenol cannot be easily dissolved in an organic solvent, and must be pierced.
[0038]
The film-forming component (A) that forms the film 7 on the surface of the core 6 is a cured product of a casting resin liquid. As resin for casting, 2 liquid reaction curable urethane resin liquid, 2 liquid reaction curable epoxy resin liquid, catalyst addition curable unsaturated polyester resin liquid, catalyst addition curable acrylic resin liquid, catalyst addition RTV silicone resin liquid Etc. As the casting core resin liquid for core core material coating, it is finally pulled out from the opening 2 of the model, so it has flexibility, can be cut with scissors and a knife, and when pulled out with tweezers, Tensile strength that is not easily cut is required. Further, since it is injected and cured in the gap between the core forming mold 8 and the core core material 6, characteristics such as a viscosity that can be mixed and injected and a certain curing speed at room temperature are required. As such a resin liquid, a two-component reaction curable solventless urethane resin liquid, and a urethane elastomer type having a Shore A hardness of 45 to 95 is most effective.
[0039]
The core forming mold 8 is a mold, a simple mold, a resin mold, or a gypsum mold. Molds are used for mass production, simple molds for medium production, and resin molds and gypsum molds for small production. A silicon rubber mold as a prototype is effective for a shape having a poor draft, but the production of 20 to 30 is the limit. It is effective to use a plurality of silicon molds for producing about 100 prototype models.
[0040]
Examples of the organic solvent (E) for dissolving the foamed styrene which is the core core material 6 include styrene, alkyl styrene, styrene derivatives, chlorinated solvents, and ester / ketone based organic solvents. These are low-boiling solvents and require attention to odor and fire. Alkyl styrene is a medium-boiling solvent, and odor and fire are most preferred because they are mildly dangerous.
[0041]
The two-component reaction rapid-curing urethane resin liquid (D), which serves as a model component, is one of the key points in the present invention and will be described in detail. The two-component reaction rapid-curing urethane resin liquid (D) used as a model material for the present invention comprises a polyfunctional polyol component (F), a polyfunctional polyisocyanate component (G), and a plasticizer (H). It is a unique material characterized in that phase-separated micro-dispersion during rapid curing. Further, when the wax component (I) and water (J) are added to this composition, the performance as a burnout model is further improved.
[0042]
The polyfunctional polyol component (F) used here is a low molecular polyol, a polyether polyol, an amine polyol, a polyester polyol, an acrylic polyol, a polybutadiene polyol or the like, and as a special one, castor oil and its derivatives are used. .
[0043]
Examples of the low molecular polyol component include ethylene glycol, propylene glycol, 1-4 butanediol, glycerin, trimethylolpropane, and pentaerythritol.
[0044]
Examples of the polyether polyol include polyether polyols of various molecular weights obtained by adding ethylene oxide or propylene oxide to the low molecular weight polyol. The polyether polyol has a primary hydroxyl group and a secondary hydroxyl group by various addition methods such as ethylene oxide single addition, propylene oxide single addition, mixed addition, and sequential addition. Accordingly, the reactivity of the terminal hydroxyl group is different, and various polyether polyols having different hydrophilicity / hydrophobicity due to the addition chain of ethylene oxide or propylene oxide are obtained. There is also polytetramethylene ether glycol obtained by cationic polymerization of THF, which is usually referred to as PTMG.
[0045]
The amine polyol is obtained by adding ethylene oxide or propylene oxide to a low molecular amine such as ammonia / ethylenediamine or polyethylene polyamine. Therefore, it is a polyol that has tertiary nitrogen in the molecule and has the effect of promoting the reactivity of isocyanate. The amine polyol using ammonia as a starter is trifunctional, the amine polyol using ethylenediamine as a starter is tetrafunctional, and if a polyethylene polyamine is used as a starter, it becomes a polyfunctional polyfunctional or higher. These are indispensable components for the present invention that performs rapid curing.
[0046]
Examples of the polyester polyol include a condensed polyester polyol having a molecular terminal as a hydroxyl group by esterification of a dibasic acid and a low molecular polyol. By selecting and adjusting the types of dibasic acid and low molecular diol / triol, adjusting the molecular weight, and using a small amount of polyfunctional low molecular polyol, various polyester polyols can be obtained. Adipic acid is frequently used as the dibasic acid used in the condensed polyester polyol. Low molecular diols include ethylene glycol and propylene glycol. Examples of triols such as 1.4 butanediol include glycerin, trimethylolpropane, and their low alkylene oxide adducts. Moreover, as the ring-opening polymerization type polyester polyol of ε-caprolactam, the number of functional groups and the molecular weight are adjusted by adjusting the type and amount of the ring-opening polymerization initiator. By adding alkylene oxides to these, some have a polyester chain and a polyether chain, and some are very diverse. There is also a carbonate diol obtained by ring opening of ethylene carbonate.
[0047]
The acrylic polyol is obtained by polymerizing an acrylic monomer containing a terminal hydroxyl group with methyl acrylate or methyl methacrylate, and is an acrylic oligomer having a plurality of hydroxyl groups in an acrylic chain. Various acrylic polyols are commercially available by selecting the type of acrylic monomer and adjusting the molecular weight. The resin liquid whose degree of polymerization has been increased to a film-forming level and has been polymerized and dissolved in an organic solvent is a paint having excellent weather resistance by slightly crosslinking with an aliphatic polyisocyanate.
[0048]
The polybutadiene polyol is a copolymer of a butadiene containing a hydroxyl group at a terminal and a compound having a double bond. It is a polyol with relatively strong hydrophobicity.
[0049]
These polyfunctional polyols may be jointed with polyisocyanate to form a urethanized modified polyol having terminal hydroxyl groups. Since it is oligomerized by urethanization modification and the molecular weight is slightly increased, the viscosity tends to increase. Therefore, it is preferable that a part of the polyfunctional polyol is a urethanized modified polyol.
[0050]
Moreover, these polyfunctional polyols may be used alone or in combination of two or more. In general, in order to satisfy many requirements for the purpose, the molecular structure is designed by mixing and using various polyfunctional polyol components in necessary amounts. These polyfunctional polyol components (F) have an active hydroxyl group at the molecular end, and have different reactivity with isocyanate depending on the type of hydroxyl group at the molecular end.
[0051]
In particular, polyether polyols and polyester polyols have a strong affinity for moisture and contain a very small amount of moisture. This trace amount of water is not inconvenient when used with water-foamed urethane. However, in the case of non-foamed urethane, it is necessary to control the amount of trace moisture to be reduced. Therefore, the polyfunctional polyol component (F) is produced through a heating and mixing dehydration step.
[0052]
The polyfunctional polyisocyanate component (G) is a compound containing two or more isocyanate groups in one molecule, and the polyol component is one containing two or more hydroxyl groups in one molecule. Isocyanate groups are highly reactive functional groups and react with hydroxyl groups with active hydrogen, amino groups, and thiol groups. The amino group or thiol group reacts instantaneously, so it is limited to isocyanate components with poor reactivity and aromatic amines with poor reactivity, but the combination is still frequently used because it reacts too quickly. Absent.
[0053]
Examples of the polyisocyanate component (G) include aromatic polyisocyanates, aliphatic polyisocyanates, and alicyclic polyisocyanates. Typical aromatic polyisocyanates are tolylene diisocyanate and diphenylmethane diisocyanate. Tolylene diisocyanate is obtained as a mixture of various isomers due to the chemical reaction during production. Industrially, TDI-100 (2,4-TDI 100% is obtained depending on the mixing ratio of 2,4-isomer and 2,6-isomer. ), TDI-80 (2,4-TDI 80% 2,6-TDI 20%) and TDI-65 (2,4-TDI 65% 2,6-TDI 35%) are commercially available. Diphenylmethane diisocyanate is also obtained as a mixture of various isomers due to chemical reaction during production, and industrially includes pure MDI and polymeric MDI. Pure MDI is binuclear, polymeric MDI is polynuclear, and pure MDI is isolated by distillation, leaving polymeric MDI as the residue. Since polymeric MDI has different numbers of polynuclear bodies depending on production conditions, various polymeric MDIs are commercially available from various manufacturers. Further, naphthalene diisocyanate and tolidine diisocyanate having an isocyanate group in the naphthalene nucleus can be mentioned. Examples of the aliphatic polyisocyanate include hexamethylene diisocyanate, isophorone diisocyanate xylylene diisocyanate, and lysine diisocyanate. Examples of the alicyclic polyisocyanate include hydrogenated xylylene diisocyanate hydrogenated with xylylene diisocyanate and hydrogenated MDI hydrogenated with MDI.
[0054]
The polyisocyanate is generally rich in reactivity, and particularly volatile polyisocyanate is highly toxic and is used after various modifications. Examples include urethane modification, dimerization, trimerization, polycarbidiimide conversion, urea modification, prepolymerization, and blocking. These are self-condensed utilizing the high reactivity of isocyanate groups, or are joined via active ingredients, leaving isocyanate groups at the ends.
[0055]
A specific range on the present invention relating to the two-component reaction curable urethane resin liquid (D) having the polyfunctional polyol component (F) and the polyfunctional polyisocyanate component (G) as resin components will be described.
[0056]
The two-component reaction curable urethane resin liquid (D) containing the polyfunctional polyol component (F) and the polyfunctional polyisocyanate component (G) as resin components has a polyether chain represented by the following chemical structural formula. It is contained by weight.
[0057]
[Chemical 1]

[0058]
When polyether is used for the polyfunctional polyol component (F), a polyether chain is introduced. When polyester polyol is used, if it is an ester of polyether, a polyether chain is introduced. If the polyfunctional polyisocyanate component (G) is a terminal isocyanate jointed by a polyether, so-called quasi prepolymer, a polyether chain is introduced. This polyether chain is a soft component of a urethane resin, and in particular, a polyether chain derived from propylene oxide is very soft. The fact that it is very soft has the property of causing thermal decomposition when heated to a high temperature in the dewaxing / firing process, and being liable to liquefy outflow combustion by thermal decomposition. In the present invention, 2-25% by weight of a polyether chain is included to skillfully exhibit this characteristic. This effect is attenuated and extinguished when the polyether chain content falls below 2% by weight. When the content of the polyether chain is 20% by weight or more, the soft component becomes too much, the cured product becomes soft, and the hardness required for the model cannot be maintained. A more preferable polyether chain content is 5 to 20% by weight.
[0059]
The blending amount of the polyfunctional polyol component (F) and the polyfunctional polyisocyanate component (G) is calculated by calculating the number of NCO groups and the number of OH groups. Usually, in the case of non-foamed urethane, the ratio NCO / OH number is NCO / OH. Designed to be around 1.0. In the case of urethane foam, NCO / OH is designed in an isocyanate excess region of about 1.0 to 1.1.
[0060]
NCO / OH = 1.0 is a design in which the number of isocyanate groups and hydroxyl groups is the same, and the reaction is completed. In other words, it is a region that exhibits the highest strength. In the present invention, NCO / OH = 0.7 to 1.0 and the NCO shortage region is set. Usually, molecular design of urethane is not performed in such an NCO-deficient region. The reason why molecular design can be performed in the NCO / OH region that can be said to be abnormal in the present invention is that the average number of functional groups of the polyisocyanate component is 2.1 or more and the average number of functional groups of the polyol component is 3.0 or more. This is because a three-dimensional network structure can be obtained in a region where NCO / OH is 1.0 or less. This is because the NCO group is deficient and the OH group is excessive, but the monomer used is polyfunctional, so that the monomer connection can be completed and the main chain can be constructed without the complete reaction of the functional group. An OH group having no excessive reaction partner terminates the reaction with the OH group held in the main chain. As a result, the hydrophilicity is increased, and it is considered that this is effective for micro-dispersion of a strongly hydrophobic plasticizer.
[0061]
From the above, it is desirable that NCO / OH = 0.7 to 1.0, preferably 0.8 to 0.9. When NCO / OH is 0.7 or less, the isocyanate group becomes significantly insufficient, and a three-dimensional network structure cannot be obtained after reaction hardening, causing an extremely low hardness and finally becoming so soft that it is difficult to maintain the shape. On the other hand, when NCO / OH is 1.0 or more, the isocyanate groups become excessive and unreacted isocyanate groups remain even when the demolding time comes, and the predetermined hardness does not come out, or color unevenness occurs on the surface of the cured product. This phenomenon is not preferable.
[0062]
As a catalyst which accelerates | stimulates the chemical reaction of a polyfunctional polyol component (F) and a polyfunctional polyisocyanate component (G), there exist a metal catalyst and an amine catalyst. Examples of the metal catalyst include zinc octylate / lead octylate, dibutyltin dilaurate, and dibutyltin diacetate. Examples of the amine catalyst include triethylenediamine, NN-dimethylpiperazine, N-methylmorpholine, and the like. These catalysts are usually added to the polyol component. Usually, 1-1000 ppm is added to the polyfunctional polyol component (F), and the pot life is adjusted. In the present invention, the catalyst is added to the polyfunctional polyol component (F) so that the usable time, that is, the usable time is within 5 minutes. If the pot life is 5 minutes or more, the curing / demolding time is 2 hours or more, which may hinder the production of the resin model. When the pot life is 1 minute or less, the reaction viscosity is increased rapidly, and the time required for mixing and casting the two liquids becomes difficult. Therefore, the pot life is preferably 1 to 2 minutes.
[0063]
Next, the plasticizer (H) used in the present invention will be described. The plasticizer (H) used in the present invention is a compound having no functional group that causes a chemical reaction and having negligible inert volatility, and is liquid at room temperature. Examples of the plasticizer (H) include ester plasticizers, ether plasticizers, and ester / ether plasticizers. Specifically, as the ester plasticizer, dioctyl adipate (DOA), dioctyl phthalate (DOP), and dibutyl phthalate (DBP) are representative. Others: benzyl acetate, butyl benzoate, octyl benzoate, isopentyl benzoate, ethylene glycol benzoate diester, polyethylene glycol benzoate diester, propylene glycol benzoate diester, polypropylene glycol benzoate diester, ethylene glycol dioleate, polyethylene glycol dioleate , Propylene glycol dioleate, polypropylene glycol dioleate and the like. Ether plasticizers include ethylene glycol dibutyl ether, ethylene glycol diphenyl ether, diethylene glycol dimethyl ether, diethylene glycol methyl ethyl ether, diethylene glycol diethyl ether, diethylene glycol ethyl butyl ether, diethylene glycol dibutyl ether, triethylene glycol dimethyl ether, triethylene glycol dimethyl ether, triethylene Examples include glycol diethyl ether, troethylene glycol dibutyl ether, tetraethylene glycol dimethyl ether, and tetraethylene glycol diethyl ether. Examples of ether esters include ethylene glycol monobutyl ether acetate, diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate, and diethylene glycol monophenyl ether acetate.
[0064]
The amount of the plasticizer (H) used is 2 to 20% by weight based on the two-component reaction curable urethane resin solution (D). When the plasticizer (H) is used in an amount of 20% by weight or more, the plasticizer (H) bleeds to the surface of the resin model, causing stickiness and tackiness. Further, when the amount of the plasticizer (H) used is 2% by weight or less, it becomes difficult to flow out when the resin is thermally decomposed, melted, and washed away in the dewaxing / firing process. This is because the plasticizer (H) is liquid at room temperature and has a low viscosity that easily flows out at high temperatures. In order to exert such an effect strongly, the plasticizer (H) is desired to be contained as high as possible. In general, when a large amount of plasticizer is contained in the resin component, the plasticizer bleeds on the surface of the cured resin, and tack and stickiness are generated on the surface. Therefore, as a result of intensive research to make the plasticizer (H) as high as possible, it was rapidly cured within 5 minutes of pot life, and the plasticizer (H) was phase-separated from the cured resin. It has been found that it is effective to form a three-dimensional network structure that is confined in a micro-dispersed state.
[0065]
Such a phase-separated micro-dispersed structure can be expressed by words that a plasticizer (H) that becomes a larva is included in a honeycomb-shaped cured resin. The honeycomb-shaped cured resin has a structure with excellent strength properties and a three-dimensional structure in which the plasticizer (H) is carefully stored in the honeycomb and is not released to the outside. Therefore, even if the plasticizer (H) becomes relatively high, the plasticizer (H) oozes out on the surface of the cured product and does not cause tackiness. When the phase-separated micro-dispersed structure is not taken, the plasticizer is dissolved in the cured resin, and when the saturated or higher state is reached, the plasticizer oozes out on the surface of the cured product to cause tackiness. In addition, when there is a lot of bleeding, stickiness is likely to occur. Such a phase-separated micro-dispersed structure has been confirmed with an electron microscope. In order to support the phase-separated micro-dispersed structure, it is necessary to rapidly cure within 5 minutes of pot life. Preferably it is within 3 minutes. If the pot life is 5 minutes or more, the phase separation micro-dispersion becomes difficult to complete, and it takes 1 day or more for demolding at the time of making the model, and the speed of manufacturing the model is lost.
[0066]
At the time when the plasticizer (H) exists as a two-component reaction curable resin liquid (D), the plasticizer (H) needs to be in a uniformly dissolved state, and phase separation microdispersion from the cured resin occurs at the stage of reaction curing. It is subsidized and includes a micro-dispersed plasticizer at the time of completion of reaction curing to prevent bleeding to the surface. The composition is based on this delicate balance. That is, it is designed in a region in which the balance between the hydrophilicity and hydrophobicity of the plasticizer (H) and the reactive curable resin is well adjusted. An alkylene oxide chain is effective as the hydrophilic segment, and a hydrocarbon chain is effective as the hydrophobic segment. These hydrophilic segments / hydrophobic segments are determined by selection of raw material monomers to be used. A design in which the balance between the hydrophilicity and the hydrophobicity is somewhat deviated is necessary. When the ethylene oxide chain is frequently used in the two-component reaction curable urethane resin liquid (D), the hydrophilicity becomes stronger, and when the propylene oxide chain is used, the hydrophilicity becomes weaker than the ethylene oxide chain. If the ethylene oxide chain and the propylene oxide chain are reduced, a two-component reaction curable urethane resin liquid (D) having strong hydrophobicity can be obtained, and can be adjusted within a range having hydrophilicity and hydrophobicity. Moreover, it can adjust within the range which has hydrophilic property and hydrophobicity of plasticizer (H) itself by adjusting the kind and usage-amount of a plasticizer (H). For example, when the terminal is an alkyl ether, the hydrophobicity increases as it changes to methyl ether, ethyl ether, butyl ether, phenyl ether. As described above, the region of the phase-separated micro-dispersion is set by changing the chemical structure and amount of the plasticizer (H) and the chemical structure and amount of the two-component reaction curable urethane resin liquid (D). When the plasticizer (H) is set to be relatively hydrophobic and the resin component is set to be relatively hydrophilic by such means, phase-separated micro-dispersion is successfully established.
[0067]
Next, the wax component (I) used in the present invention will be described. The wax component (I) is a compound having no functional group that causes a chemical reaction and having negligible inert volatility, and is a solid that is crystalline at room temperature. The wax wax component (I) includes naturally occurring waxes and synthetic waxes obtained by synthesis. As natural wax, candles are the ones that are close to us. The chemical composition of the natural wax component is an ester composed of a higher fatty acid and a higher alcohol, which is called a wax ester. Higher fatty acids and higher alcohols are mainly composed of 16 or more carbon atoms. Since it is an ester compound, some acid value remains, that is, free fatty acid remains. In addition, since many saturated and unsaturated higher fatty acids exist in nature, some waxes also contain higher unsaturated fatty acids and hydroxy acids. These waxes have a chemical structure close to that of paraffin and are solids crystallized or non-crystallized at room temperature, and their melting points are generally around 80 ° C. Typical waxes include candelilla wax, carnauba wax, rice wax, beeswax, whale wax, montan wax, lanolin wax olicuric wax, alpha wax, cork fiber wax, sugarcane wax, wood wax, sumac wax, micro lollies. Stalin wax, ground wax, and the like. Synthetic waxes include polyethylene waxes, waxes obtained by Fisher-Ttopsch synthesis, waxy copolymers and their esters, C8-C32 animal or plant oils having linear or branched fatty chains, or catalytic hydrogen of food oil Examples thereof include wax obtained by addition, silicon wax, and fluorine-containing wax. These wax components may be used alone or mixed, and may be a wax component and a wax component to which a third component is added.
[0068]
This wax component (I) has strong properties as paraffin or olefin and is very hydrophobic and solid at room temperature. Therefore, the polyfunctional polyol component (F), the polyfunctional polyisocyanate component (G), and the plasticizer (H) are difficult to dissolve. Therefore, even if it mix | blends with 2 liquid reaction curable urethane resin liquid (D), it is hard to melt | dissolve and it exists in the state which floats in the liquid system. In an appropriate state, the two-component reaction-curable urethane resin liquid (D) is rapidly cured, and as a result, is contained as a solid in the resin having a three-dimensional network structure. Therefore, since the resin model of the present invention does not expose the wax component on its surface, it has a specificity that all the defects of the wax model are avoided. This wax component (I) has a great effect of accelerating the outflow of the “softened, thermally decomposed and melted resin decomposed product” in the dewaxing and firing process by heating.
[0069]
This wax component (I) is used in an amount of 1 to 20% by weight based on the two-component reaction curable urethane resin solution (D). When the amount used is 1% by weight or less, the dewaxing effect using the wax component (I) disappears. If it is 20% by weight or more, the fluidity of the two-component reaction curable resin liquid (D) becomes poor, and the workability at the time of manufacturing the resin model is impaired. In addition, the strength of the resin model itself decreases, and the possibility of cracking or breaking during mold removal increases. Therefore, it is preferably 5 to 20% by weight. More preferably, it is 10 to 15% by weight.
[0070]
This wax component (I) is 1cm ³ It is in the form of particles, scales, and lumps that fit in the cube. The particulate or lump shape is a ball shape or a sugar cube shape, and may be a shape in which these are slightly deformed. In other words, it is not limited to true or honest prisms. 1cm in size ³ The size fits in the cube. Preferably, the diameter is 1 mm or less. Of course, this wax component does not easily flow into a thin part of one model of 1 mm or less. Therefore, although the uniform distribution of the wax component (I) in the model is impaired, the shape retention property as a model, dimensional accuracy, decomposition / melting outflow property at heating, combustion decomposition residual ash at high temperature are reduced. It is only necessary to perform mold manufacturing and precision casting. Of course, this wax component tends to flow into a thick part of the model of 1 mm or more. This means that the uncured resin liquid can easily flow, and as a result, the model can be removed from the mold, and the resin component should be spread throughout the model. In a sense, it is advantageous that a large amount of wax component (I) flows into the thick part of the model. That is, melt outflow decomposition combustion tends to be delayed in the dewaxing / firing process. A relatively large amount of wax component (I) flows into this part, and if it is fixed with a cured resin, the effect of successfully assisting melt outflow decomposition combustion in the dewaxing / firing process is greatly expressed. become
[0071]
Next, water (J) used in the present invention will be described. What is moisture (J)? ₂ O. Moisture (J) consists of (1) intentionally mixed water, (2) a trace amount of water that is usually mixed in chemical raw materials in the manufacturing process, and (3) moisture that the raw materials themselves absorb from the air. Will be judged. The moisture (J) referred to in the present invention is the sum of these counted as moisture (J). The reason for using moisture (J) is to use carbon dioxide gas generated by a chemical reaction with polyfunctional polyisocyanate as a foaming agent, that is, to introduce urethane water foaming technology. As a result, the resin model consists of a plasticizer (H), a wax component (I), and a foam containing bubbles. Within the limited range where foaming is adjusted, such a resin model that is a foam keeps its solid shape retention, and exhibits great effectiveness in thermal melting, decomposition, and outflow combustion in the dewaxing and firing processes. Is.
[0072]
The main factor that determines the expansion ratio is the amount of moisture (J), and the subfactors are adsorbed water on the mold surface, temperature and humidity of the outside air, and the like. The amount of moisture (J) is 0.01 to 1.0% by weight based on the two-component reaction curable urethane resin solution (D). Preferably, it is 0.03 to 0.5 weight%. More preferably, it is 0.08 to 0.15% by weight. When the moisture (J) is 1.0% by weight or more, a large amount of bubbles are concentrated on the resin surface, the skin layer on the model surface becomes thin, the skin layer is destroyed at the time of demolding, and the bubbles are in a concave state on the model surface. It will appear and the model surface will be inconvenient. In other words, it is necessary to control the fine foaming level. In foamed urethane, a foam stabilizer is used to make the size of the bubbles uniform. In the present invention, of course, it is important to add a foam stabilizer to make the size of the bubbles uniform.
[0073]
The moisture (J) is usually added to the polyfunctional polyol component (F). It can be controlled by mixing water and mixing uniformly, and measuring trace moisture by the Karl Fischer method. When blended with the polyfunctional polyol component (F), water alone may be used, and there is no particular limitation as long as the component containing water does not cause abnormalities in model production. For example, a surfactant aqueous solution, an aqueous dye aqueous solution, an aqueous paste, an aqueous resin solution and the like can be mentioned.
[0074]
In this way, when foaming with water, a foam stabilizer is used in order to make the size of bubbles as much as possible. The foam stabilizer is a kind of surfactant and is generally a type in which alkylene oxide is added to silicon. By adding an ordering foaming agent and foaming with water, it becomes a foam in which bubbles of the same size are scattered relatively uniformly in the model. Although the strength of the model is lowered, the dewaxing component / fired component is greatly reduced in the dewaxing process / baking process, and thus a great advantage is expressed. The strength of the model is not severe, and it is only necessary to have strength that can be removed smoothly when the model is removed. The model after demolding may be at a level that can withstand carrying. It is sufficient that the shape change during storage at room temperature is extremely small. What is necessary is just to hold | maintain the intensity | strength which can endure coating work at the time of fireproof coating. Therefore, since the high strength is not required, the resin model of the present invention including the plasticizer and the wax component is sufficient.
[0075]
An organic solvent may be used for the two-component reaction curable urethane resin solution (D). As the organic solvent, an inert organic solvent that does not chemically react with isocyanate is selected. Examples of the inert organic solvent include aromatic organic solvents, ester organic solvents, ether organic solvents, aliphatic organic solvents, and chlorine organic solvents. The performance required for organic solvents is that it dissolves the polyfunctional polyether component (F), polyfunctional polyisocyanate component (G), and plasticizer (H), has a mild odor, and does not generate toxic gases during combustion. It is required to be economical. The organic solvent satisfying such required performance is desirably selected from aromatic organic solvents. Preference is given to toluene and xylene.
[0076]
In the exothermic gelation stage of the two-component reaction curable urethane resin liquid (D), the organic solvent is easily vaporized and has an effect of supporting the role of a foaming agent. In addition, the organic solvent is somewhat confined inside the model after the demolding. If anything, the organic solvent remains in the thick portion where the thickness is 1 mm or more, which is difficult to burn, and the effect of assisting combustion during the dewaxing / sintering process is great. In addition, the effect of reducing the resin viscosity and improving the workability in manufacturing the model is very large.
[0077]
Fine pieces of natural polymer waste may be blended and used in the two-component reaction curable urethane resin solution (D). The fine piece of natural polymer waste is a fine piece of paper waste, wood waste, textile clothing waste, or the like. Examples of the fine pieces of paper waste include fine pieces of newspaper, advertising paper, office copy paper, packaging paper, cardboard, and the like. Examples of the fine pieces of wood waste include building waste wood, civil engineering waste wood, furniture waste, inter-wood, plant dead grass, rice hull fine pieces, and the like. Examples of the waste of textile clothing include fine pieces of cotton clothing, hemp clothing, and wool clothing. For example, in the case of paper, disposable office paper is cut and refined by a oscillator, in the case of wood, sawdust derived from dismantling, crushing and cutting, and in the case of textile clothing, it is a single fiber. It is the fiber waste which was crushed and cut into pieces. What was refined | miniaturized to the various shapes below 1 mm in length is preferable.
[0078]
These fine pieces of natural polymer waste are preferably blended with the polyfunctional polyol component (F). Since the specific gravity of the fine fragments of the natural polymer waste approximates the specific gravity of the polyfunctional polyol component (F), there will be less sedimentation and levitation, and it will float in the liquid of the fine fragments of the natural polymer waste, It is easy to disperse relatively uniformly by mixing. When the fine pieces of natural polymer waste are mixed in the liquid of the polyfunctional polyol component (F), the fine particles of the natural polymer waste are easily mixed and dispersed by the air contained in the fine pieces of the natural polymer waste. In some cases, if deaeration is performed in a reduced pressure state, air is removed and mixing and dispersion are facilitated.
[0079]
The fine pieces of the natural polymer waste generally contain moisture to a greater or lesser extent due to hydrophilicity. Therefore, when the fine pieces of natural polymer waste are mixed and dispersed in the polyfunctional polyol component (F), the moisture contained in the fine pieces of natural polymer waste is brought into the polyfunctional polyol component (F). The water content in F) will increase. Therefore, the water content of the polyfunctional polyol component (F) is controlled in consideration of the amount of water brought in depending on the amount of the fine fragments of the natural polymer waste.
[0080]
To the two-component reaction curable resin liquid (D), a regulator, a stabilizer, a colorant, a combustible filler, and a diluent solvent are added. As the stabilizer, a hindered phenol-based or hindered amine-based antioxidant is used. Organic dyes and carbon powder are effective as the colorant. The pigment is not preferred because it remains as ash in the firing step. The addition of flame retardants should be avoided. As the flammable filler, it is effective to contain 1 to 10% of a hollow balloon or carbon powder. The hollow resin balloon is a lightweight differential powder having a true specific gravity of 0.15 to 0.50 g / cc and a particle size of 15 to 100 μm. The product is commercially available. Inclusion of such hollow resin balloons embeds air in the resin model, and in the dewaxing process and firing process, promotes decomposition, outflow and combustion, and the effect of reducing residual ash content is manifested. . The content of the hollow resin balloon is 0.1 to 10% by weight with respect to the resin model. If it is 10% by weight or more, the two-component reaction-curing urethane resin liquid (D) will be loosened and it will be difficult to obtain smooth fluidity. Therefore, it is preferably 3 to 8% by weight.
[0081]
【The invention's effect】
As explained above, according to the present invention, a large amount of precision cast parts made of titanium alloy with high strength, heat resistance and corrosion resistance, which have been widely used in automobiles, aircraft, nuclear power and space development. And can be manufactured economically. Above all, it is an effective manufacturing method for further weight reduction required in aircraft and space development, and enables the manufacture of an integrally molded casting part in which joining between parts is omitted as much as possible.
[0082]
As described above, the present invention integrally molds a thin-walled complex shape model having a hollow portion that could not be achieved by the prior art, and manufactures a mold using this model as a burned-out model, enabling mass production of titanium alloy precision cast parts. Is.
[0083]
Furthermore, in comparison with the conventional split model joining method, the present invention integrally molds a thin complex shape model having a hollow portion, so that an increased number of steps are required to create a core forming mold and produce the core. Then, the demerit mentioned above occurs, but the merit that the joining process of the model is omitted is born. As a result, since the model to be produced has no joint part, it has a great effect in that it becomes a model with high dimensional accuracy that faithfully reflects the design intention. It goes without saying that molds and precision castings manufactured with this model have high dimensional accuracy.
[Brief description of the drawings]
FIG. 1 is a perspective view showing an example of a hollow model according to an embodiment of the present invention.
FIG. 2 is a cross-sectional view of the hollow model shown in FIG.
FIG. 3 is a perspective view showing an example of a core according to an embodiment of the present invention.
4 is a cross-sectional view of the core shown in FIG.
FIG. 5 is a cross-sectional view showing a part of the manufacturing process of the core.
FIG. 6 is a cross-sectional view showing another embodiment of a part of the manufacturing process of the core.
FIG. 7 is a cross-sectional view showing a part of the manufacturing process of the hollow model.
FIG. 8 is a cross-sectional view showing a hollow model including a core.
FIG. 9 is a cross-sectional view showing a step of removing the core core material.
FIG. 10 is a cross-sectional view showing a step of removing the core film.
[Explanation of symbols]
1 Hollow model
2 opening
3 hollow parts
4 Bulkhead
5 core
6 Core material
7 Film

Claims (3)

A core core material forming step for forming a core material made of a foam (B) having a size that can be accommodated in a hollow portion of a hollow model having at least one opening communicating with the outside, and a film forming component on the core material A core forming step comprising a coating forming step of coating (A) to form a coating having the same outer shape as the hollow portion, and forming the outer shape of the hollow model by forming the core formed in the core forming step A hollow that is placed in the mold (C), and injects the urethane resin liquid (D) for two-component reaction rapid-curing mold into the void, cures it, and removes the mold to form a hollow model in which the core is contained A core forming process, a core forming process for injecting an organic solvent (E) into the film made of the film forming component (A), and melting and removing the core made of the foam (B); The core film from which the core material has been removed is pulled from the opening. In the hollow model production method comprising a film removal step of removing by,
The method for producing a hollow model, wherein the film-forming component (A) is a reaction-curable casting urethane having a shore hardness of A50-95 having flexibility, and the foam (B) is foamed polystyrene .   The two-component rapid curing urethane resin liquid (D) is composed of a polyfunctional polyol component (F), a polyfunctional polyisocyanate component (G), and a plasticizer (H). The method for producing a hollow model according to claim 1, wherein the plasticizer (H) is micro-dispersed in phase separation within minutes. The two-component reaction curable urethane resin liquid for casting (D) is a foamed urethane having fine wax and wax components (I) and water (J) in a predetermined ratio and including wax wax fine particles in a dispersed manner. The hollow model manufacturing method according to claim 1, wherein:

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