JP3684532B2 - Manufacturing method of resin model and lost wax precision casting method using the resin model - Google Patents

Description

【００２４】
さらにまた、前記２液反応硬化型ウレタン樹脂液（Ａ）に微細なロウ・ワックス成分（ｄ）を５〜４０重量％配合することが望ましい。
【００２５】
また、前記２液反応硬化型ウレタン樹脂液（Ａ）に微量水分（ｅ）を添加し水発泡ウレタンとすることが望ましい。
【００２６】
さらにまた、前記樹脂模型は、その体積の２０〜７０％の範囲内の内部中空空間を有することが望ましい。また、前記内部中空空間は、ロウ・ワックス成分（ｄ）で充填されてもよく、発泡ウレタンで充填されても良いものである。
【００２７】
また、ロストワックス法による精密鋳造法は、上述した樹脂模型を用いることが望ましく、また精密鋳造品は、この精密鋳造法で製造されることが望ましい。
【００２８】
【発明の実施の形態】
図１は本発明の実施の形態に係る樹脂模型１の一例を示した斜視図である。以下、この樹脂模型１を製造する方法について図面により説明する。
【００２９】
第１の実施の形態において、図２に示すように、樹脂模型形成用モールド２（以下、モールド２）は、シリコンゴムによって形成されたシリコンゴム型であり、樹脂模型１と同一形状の内部空間３を有し、またこの内部空間３と外部に開口する注型口４及びエア抜き口５とを有すると共に、注型口４及び内部空間３を連通する注型口通路４１、エア抜き口５と内部空間３を連通する空気抜き通路５１とを有する。
【００３０】
前記内部空間３に注入される下記する２液反応硬化型ウレタン樹脂液（Ａ）は、混合容器６において混合され、第1回目として、前記内部空間３の容積の５〜２０％量が注入される。そして、図３で示すように、前記注型口４及び前記エア抜き口５をシールテープ等のシール部材７，８によって閉鎖する。そして、前記モールド２を、図示しない回転成型機に設置して、１〜３分間多方向に回転させ、２液反応硬化型ウレタン樹脂液（Ａ）をモールド２の内壁に付着固化させ、ウレタン樹脂層１１を形成させる（硬化物層形成工程）。そして、上述した操作を複数回繰り返してウレタン樹脂層１１を積層し（積層工程）、図４で示すように、所定の厚さの樹脂模型１２が得られるものである（樹脂模型形成工程）。この樹脂模型１２は、仕上がりの樹脂模型１となる部分と、注型口通路４１の周囲に形成された注型口通路部分１３と、エア抜き通路５１の周囲に形成されたエア抜き通路部分１４とによって構成され、モールド２から脱型される（脱型工程）。そして、前記樹脂模型１２から前記注型口通路積層体部分１３とエア抜き通路積層体部分１４とを切除し、完成品としての樹脂模型１が得られるものである（仕上げ工程）。
【００３１】
この実施の形態では、上述した操作は、３回行った。これは、積層工程が１回とか２回の場合には、モールド内壁全面を完全に覆い尽くすことが出来ず、結果的に欠損部を包含した模型となるため不都合を生じたからであり、積層工程が７回以上になると、作業回数・作業工程時間がかさみ、迅速な模型製作が損なわれることになるからである。実験により、通常積層工程は３回〜６回にてモールド内壁全面を完全に樹脂で覆い尽くすことが出来ることが明らかとなった。好ましい積層工程は３回〜４回である。
【００３２】
モールド２内へ注入する２液反応硬化型ウレタン樹脂液（Ａ）の量は、樹脂模型１の全体積の何％量とするかで設定することが望ましい。通常１回の注入に使用される２液反応硬化型ウレタン樹脂液（Ａ）の量は、樹脂模型全体積の５〜２０％量が望ましいことが実験により明らかとなった。具体的には、１回の注入に使用される２液反応硬化型ウレタン樹脂液（Ａ）の量が樹脂模型全体積の５％量未満の場合、３〜６回の積層工程でモールド内壁を完全に覆い尽くすことが難しくなるため、７回以上の積層工程が必要となり、迅速な樹脂模型製作を損なうことになる。一方、１回の注入に使用される２液反応硬化型ウレタン樹脂液（Ａ）の量が樹脂模型全体積の２０％量以上の場合、３〜４回の積層工程でモールド２の内壁を完全に覆い尽くすことが出来るが、樹脂模型１の中空は少なくなり４０％以上の内部中空模型を製作することが出来ず、後の脱ロウ・焼成工程に負荷がかかり、鋳型が割れ易くなると言った結果を生じた。
【００３３】
こうして作成された樹脂模型１は、模型体積中２０〜６０％が内部中空となる。これは、後の脱ロウ・焼成工程にかかる負荷を大幅に低減するものであり、鋳型が割れることに対し、大きな有効性を発揮するものである。
【００３４】
脱ロウ・焼成工程にかかる負荷を最大限に低減するには、樹脂模型１の膜厚を極力低減すべきである。それには、本発明にて限定する範囲以上に１回の積層膜厚を薄くし、積層回数を多くすることである。これは前述した通り、樹脂模型製作工程が増加し結果的に製作時間が増大し、短納期・安価製作に合致しない。そこで、第２の実施の形態として、図５で示すように、積層回数を２回程度にしてモールド２の内壁に樹脂層を不完全ながら形成させた後、樹脂模型１２を脱型しない状態で、注型口４より樹脂模型１の中空部位３０に溶融ロウ成分１５を注入し、常温で冷却後、脱型する方法が有効である。つまり、前記中空部位３０に充填されたロウ成分１５は、鋳型製作までの各工程で、樹脂模型１を補強し、模型としての強度を保持せしめるための有効手段となるものである。
【００３５】
同様に、第３の実施の形態では、脱ロウ・焼成工程にかかる負荷を最大限に低減するために、積層回数２回程度にしてモールド２の内壁に樹脂層を不完全ながら形成させた後、樹脂模型１２を脱型しない状態で、注型口４より模型中空部位３０に発泡ウレタン樹脂液１６を注入し、模型中空部位３０を発泡ウレタン樹脂で充填させ、脱型する方法も有効である。つまり、模型中空部位３０に充填された発泡ウレタン樹脂は、鋳型製作までの各工程で、樹脂模型１を補強し、模型としての強度を保持せしめるための有効手段となるものである。
【００３６】
尚、上述した第２及び第３の実施の形態を示す図５及び図６において、同一の個所並びに同様の効果を奏する個所には同一の符号を付してその説明を省略する。
【００３７】
次ぎに、本発明に使用される２液反応硬化型ウレタン樹脂液（Ａ）の成分配合構成について説明する。
【００３８】
２液反応硬化型ウレタン樹脂液（Ａ）の骨格は多官能ポリオール成分（ａ）と多官能ポリイソシアネート成分（ｂ）の２液から構成されるものであり、２液混合により常温で化学反応が開始され、発熱硬化するものである。２液反応硬化型ウレタン樹脂液（Ａ）に含有される可塑剤（ｃ）、ロウ・ワックス成分（ｄ）は、多官能ポリオール成分（ａ）または多官能ポリイソシアネート成分（ｂ）どちらかに配合されても良いし、両方に配合されてもよい。また、水分（ｅ）は、多官能イソシアネート成分（ｂ）と化学反応を起こすものであるがため多官能ポリオール成分（ａ）に前もって配合されるものである。
【００３９】
次いで各成分について説明する。多官能ポリオール成分（ａ）としては、低分子ポリオール、ポリエーテルポリオール、アミンポリオール、ポリエステルポリオール、アクリルポリオール、ポリブタジエンポリオール等 特殊なものとしてはヒマシ油及びその誘導体が使用される。
【００４０】
低分子ポリオールとしては、エチレングリコール・プロピレングリコール・１−４ブタンジオール・グリセリン・トリメチロールプロパン・ペンタエリスリトールなどが挙げられる。
【００４１】
ポリエーテルポリオールとしては、上記低分子ポリオールにエチレンオキサイドやプロピレンオキサイドを付加した各種分子量のポリエーテルポリオール等が挙げられる。ポリエーテルポリオールは、エチレンオキサイド単独付加、プロピレンオキサイド単独付加、混合付加、順次付加など色々な付加方式によって、末端水酸基は１級・２級となる。これによって末端水酸基の反応性が異なり、付加鎖がエチレンオキサイド、プロピレンオキサイドによって親水性・疎水性が異なる各種各様なポリエーテルポリオールとなる。また、ＴＨＦのカチオン重合により得られるポリテトラメチレンエーテルグリコールもあり、通常ＰＴＭＧと言われている。
【００４２】
アミンポリオールとは、アンモニア・エチレンジアミン、ポリエチレンポリアミン等の低分子アミンに、エチレンオキサイドやプロピレンオキサイドを付加せしめたものである。よって、分子内に３級窒素を含有することになり、イソシアネートの反応性を促進させる効果を保有したポリオールである。アンモニアをスターターとしたアミンポリオールは３官能であり、エチレンジアミンをスターターとしたアミンポリオールは４官能であり、ポリエチレンポリアミンをスターターとすれば、４官能以上の多官能となる。これらは急速硬化を行う本発明には欠かせない成分である。
【００４３】
ポリエステルポリオールとしては、二塩基酸と低分子ポリオールをエステル化にて分子末端を水酸基とした縮合型ポリエステルポリオールがある。二塩基酸と低分子ジオール・トリオールの種類を選択調整、分子量の調整、多官能低分子ポリオールの少量使用などによって多種多様なポリエステルポリオールとなる。縮合型ポリエステルポリオールに使用される二塩基酸としては、アジピン酸が多用されている。低分子ジオールとしては、エチレングリコール・プロピレングリコール、１．４ブタンジオール等。トリオールとしては、グリセリン、トリメチロールプロパン、それらのアルキレンオキサイド低付加物等である。また、ε−カプロラクタムの開環重合型ポリエステルポリオールは、開環重合開始剤の種類・使用量を調整することによって官能基数、分子量が調整されるものである。これらにアルキレンオキサイドを付加することによって、ポリエステル鎖とポリエーテル鎖を持ったものもあり、非常に多様性があるものもある。また、エチレンカーボネートの開環によって得られるカーボネートジオールなるものもある。
【００４４】
アクリルポリオールとしては、メチルアクリレートやメチルメタアクリレートに末端水酸基を含有するアクリルモノマーを重合させたものであり、アクリル鎖の中に複数の水酸基を持ったアクリルオリゴマーである。アクリルモノマーの種類を選択し分子量を調整することによって得られる各種のアクリルポリオールが市販されている。造膜するレベルまで重合度を上げ高分子化し有機溶剤に溶解せしめた樹脂液は、脂肪族ポリイソシアネートによってわずかな架橋を行い耐候性に優れた塗料となる。
【００４５】
ポリブタジエンポリオールとしては、末端に水酸基を含有するブタジエンと二重結合を有する化合物との共重合物である。比較的疎水性の強いポリオールである。
【００４６】
これらの多官能ポリオールをポリイソシアネートにてジョイントし、末端水酸基としたウレタン化変性ポリオールとしてもよい。ウレタン化変性によりオリゴマー化され、分子量がやや大きくなるので、粘度が増加する傾向が強い。
【００４７】
これらの多官能ポリオールは単独使用されても良いし、２種以上を混合使用してもよい。一般的には、目的に対して数多い要求項目を満たすために各種の多官能ポリオール成分を必要量混合使用にて分子構造設計が成されるものである。これらの多官能ポリオール成分（ａ）は分子末端に活性な水酸基を持つものであり、分子末端の水酸基の種類によってイソシアネートとの反応性が異なるものである。
【００４８】
特にポリエーテルポリオール、ポリエステルポリオールは水分との親和性が強く、微量の水分を含有するものである。この微量水分は水発泡ウレタンにて使用する場合は何ら不都合はない。しかし、無発泡ウレタンとする場合には微量水分量をしっかりと低減コントロールすることが必要である。そのために多官能ポリオール成分（ａ）は、加熱混合脱水工程を経て生産されるものである。
【００４９】
多官能ポリイソシアネート成分（ｂ）とは、１分子中に２個以上のイソシアネート基を含有する化合物であり、ポリオール成分とは１分子中に２個以上の水酸基を含有するものである。イソシアネート基は非常に反応性に富んだ官能基であり、活性水素を持つ水酸基とか、アミノ基とかチオール基と反応する。アミノ基とかチオール基とは瞬間的に反応するために反応性に乏しいイソシアネート成分と反応性に乏しい芳香族アミンなどに限定適応されるが、それでもあまりにも早く反応するためにその組み合わせは多用されていない。
【００５０】
ポリイソシアネート成分としては、芳香族ポリイソシアネート、脂肪族ポリイソシアネート、脂環族ポリイソシアネートがある。芳香族ポリイソシアネートとしてはトリレンジイソシアネートとジフエニルメタンジイソシアネートが代表的である。トリレンジイソシアネートは、製造時の化学反応上、各種異性体の混合物として得られ、工業的には２，４−体と２，６−体の混合比によりＴＤＩ―１００（２，４−ＴＤＩ １００％）、ＴＤＩ―８０（２，４−ＴＤＩ ８０％ ２，６−ＴＤＩ ２０％）、ＴＤＩ―６５（２，４−ＴＤＩ ６５％ ２，６−ＴＤＩ ３５％）が市販されている。ジフエニルメタンジイソシアネートとしては、これも製造時の化学反応上、各種異性体の混合物として得られ、工業的には純ＭＤＩとポリメリックＭＤＩがある。純ＭＤＩとは２核体であり、ポリメリックＭＤＩとは多核体であり、純ＭＤＩは蒸留にて単離され、釜残としてポリメリックＭＤＩが残る。ポリメリックＭＤＩは製造条件にて多核体数が異なるために、各種のポリメリックＭＤＩが各メーカーより市販されている。また、ナフタリン核にイソシアネート基を持たせたナフタレンジイソシアネートやトリジンジイソシアネート、が挙げられる。脂肪族ポリイソシアネートとしては、ヘキサメチレンジイソシアネート、イソホロンジイソシアネート、キシリレンジイソシアネート、リジンジイソシアネートが挙げられる。脂環族ポリイソシアネートとしては、キシリレンジイソシアネートを水添した水添キシリレンジイソシアネートやＭＤＩを水添した水添ＭＤＩが挙げられる。
【００５１】
ポリイソシアネートは、一般的に反応性に富むため、特に揮発性のあるポリイソシアネートは毒性が強いため、色々な変成を施して使用されている。ウレタン変性、二量化、三量化、ポリカルビジイミド化、ウレア変性、プレポリマー化、ブロック化などがある。これらはイソシアネート基の高反応性を利用して自己縮合させたり、活性成分を介してジョイントせしめ、末端にイソシアネート基を残したものである。
【００５２】
多官能ポリオール成分（ａ）と多官能ポリイソシアネート成分（ｂ）を樹脂成分とする２液反応硬化型ウレタン樹脂液（Ａ）に関する本発明上の特定範囲について説明する。
【００５３】
多官能ポリオール成分（ａ）と多官能ポリイソシアネート成分（ｂ）を樹脂成分とする急速硬化２液反応硬化型ウレタン樹脂液（Ａ）は下記化学構造式によって示されるポリエーテル鎖を２−２０重量％含有するものである。
【００５４】
【化３】

【００５５】
多官能ポリオール成分（ａ）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（ｂ）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。
【００５６】
多官能ポリオール成分（ａ）と多官能ポリイソシアネート成分（ｂ）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おいて設計される。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、きちっと反応が終了する設計である。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不足領域におい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で、ＮＣＯ／ＯＨは１．０以下の領域にて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、主鎖を構成出来る。過剰の反応相手のないＯＨ基は、主鎖にＯＨ基を保有した状態にて反応を終結する。これにて、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に有効打となっているものと考えられる。
【００５７】
ＮＣＯ／ＯＨ＝０．７〜１．０、好ましいくは０．８〜０．９である。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にくくなり、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か、という現象が発生し好ましくない。
【００５８】
多官能ポリオール成分（ａ）と多官能ポリイソシアネート成分（ｂ）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（ａ）に添加され、可使時間が調整される。本発明に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（ａ）に触媒が添加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になる。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。
【００５９】
次いで、本発明に使用される可塑剤（ｃ）について説明する。本発明に使用する可塑剤（ｃ）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出来る化合物で、室温において液状である。可塑剤（ｃ）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、ジエチテ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。
【００６０】
可塑剤（ｃ）の使用量は、２液反応硬化型ウレタン樹脂液（Ａ）に対して２〜２０重量％である。可塑剤（ｃ）の使用量が２０重量％以上に高含有させると可塑剤（ｄ）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。可塑剤（ｃ）の使用量が２重量％以下になると、脱ロウ・焼成工程で樹脂熱分解溶融流失燃焼時、流出しにくくなる。何故ならば可塑剤（ｃ）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。こう言った効果を強く発揮させるためには可塑剤（ｃ）は出来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物表面へ可塑剤がブリードし、表面にタック、やベタツキを発生する。そこで、出来るだけ可塑剤（ｃ）を高含有させるために鋭意検討を行った結果、可使時間５分以内にて急速硬化せしめ、可塑剤（ｃ）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にて閉じこめられる状態と成すことが有効である。
【００６１】
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に相当する可塑剤（ｃ）が包含されていると表現出来る。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（ｃ）を蜂の巣内にて大切に保存し、外部へ放出しない立体構造である。よって、可塑剤（ｃ）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は硬化物表面ににじみ出し、タックが出、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よって確認されている。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。
【００６２】
可塑剤（ｃ）は、２液反応硬化型ウレタン樹脂液（Ａ）として存在する時点では、可塑剤（ｃ）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（ｃ）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。急速硬化２液反応硬化型ウレタン樹脂液（Ａ）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急速硬化２液反応硬化型ウレタン樹脂液（Ａ）となり、親水性と疎水性を有する範囲内で調整することが出来る。また、可塑剤（ｃ）の種類と使用量を調整することにより、可塑剤（ｃ）自身の親水性と疎水性をある範囲内で調整することが出来る。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（ｃ）の化学構造と使用量、急速硬化２液反応硬化性ウレタン樹脂液（Ａ）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。この様な手段にて、可塑剤（ｃ）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。
【００６３】
次いで、本発明に使用されるロウ・ワックス成分（ｄ）について説明する。ロウ・ワックス成分（ｄ）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出来る化合物であり、室温にて結晶性のある固体である。ロウ・ワックス成分（ｄ）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。このロウ・ワックス成分（ｄ）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（ａ）や多官能ポリイソシアネート成分（ｂ）また可塑剤（ｃ）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（Ａ）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。しかる状態にて急速硬化２液反応硬化型ウレタン樹脂液（Ａ）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（ｄ）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。
【００６４】
このロウ・ワックス成分（ｄ）は、２液反応硬化型ウレタン樹脂液（Ａ）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（ｄ）を使用する脱ロウ効果が消滅する。２０重量％以上に成ると、急速硬化２液反応硬化型ウレタン樹脂液（Ａ）の流動性が悪くなり、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。
【００６５】
このロウ・ワックス成分（ｄ）は１ｃｍ^３におさまる粒子状、鱗片状、塊状である。粒子状・塊状とは、玉状・または角砂糖状・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（ｄ）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・ワックス成分（ｄ）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（ｄ）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（ｄ）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・焼成工程において、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。
【００６６】
次いで、本発明に使用される水分（ｅ）について説明する。水分（ｅ）とはＨ₂Ｏである。水分（ｅ）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。本発明の請求項目で言及する水分（ｅ）は、これらを合計したものである。水分（ｅ）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によって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１は、可塑剤（ｃ）とロウ・ワックス成分（ｄ）と気泡を包含した発泡体と成しても良い。発泡を調整した限定範囲内において、発泡体である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。
【００６７】
発泡倍率を決定する主因子は水分（ｅ）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（ｅ）の量は急速硬化２液反応硬化型ウレタン樹脂液（Ａ）に対し、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（ｅ）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スキン層が破壊し、気泡が凹状態にて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。発泡ウレタンに於いては、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。
【００６８】
水分（ｅ）は、通常多官能ポリオール成分（ａ）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される。多官能ポリオール成分（ａ）に配合する場合、水だけでもよいし、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、水ラテックス、水分含有天然高分子等が挙げられる。
【００６９】
界面活性剤水溶液とは、液体洗剤水溶液・固体石鹸・粉末石鹸などであり、ビルダーや香料染料を配合してシャンプー・台所洗剤・工業用洗剤・化粧石鹸として広く市場に出回っている。固体石鹸や粉末石鹸は多量の水分は含有していないが、少量・微量の水分を含有している。水性染料水溶液とは、水に溶解された染料溶液である。水のりとは、メチルセルロースの水溶液・ご飯を水に溶いたのりなどであり、広く文具店で販売されている。水ラテックスとは、酢酸ビニルラテックス・ＥＶＡなどの合成ゴムラテックスであり木工用ボンドとして塗料店・ＤＩＹ・日曜雑貨店にて広く販売されている。水分含有天然高分子の微細片とは、紙類・木材類・繊維類の微細片等である。紙類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。木材類の微細片としては建築用廃木材・土木用廃木材・家具廃材・間伐材・植物の枯れ草、籾殻の微細片等が挙げられる。繊維類としては木綿類・麻類・絹類が挙げられる。
【００７０】
天然高分子の微細片は、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、天然高分子の微細片を多官能ポリオール成分（ａ）中に混合分散させると、天然高分子の微細片に含有した水分を系内持ち込むことになり、多官能ポリオール成分（ａ）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（Ｈ）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（ａ）の水分量をコントロールすることになる。
【００７１】
このような水分含有物質添加にて発泡させる場合、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出来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。
【００７２】
また、本発明には有機溶剤が使用されても良い。使用可能な有機溶剤としては、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。この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（ａ）や多官能ポリイソシアネート（ｂ）や可塑剤（ｃ）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、経済性が伴わねば成らない。このような要求性能を満たす有機溶剤としては、芳香族系有機溶剤から選定される。好ましいのは、トルエン、キシレンである。
【００７３】
２液反応硬化型ウレタン樹脂液（Ａ）が発熱ゲル化段階において、有機溶剤は気体になりやすく、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。
【００７４】
２液反応硬化ウレタン型樹脂液（Ａ）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せしめることは、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（Ａ）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。
【００７５】
一方、硬化した樹脂が非常に硬い場合には、加温加熱時に溶融分解流失燃焼が遅れ、樹脂の膨張にて鋳型が割れて破損を引き起こす。よって、硬化した樹脂模型全体が早く軟化し、樹脂の膨張応力が、湯口や空気抜き口へ応力分散せしめることが必要である。このためには、硬化物である焼失樹脂模型の８０℃の硬度がショアーＤ硬度で２０−５５が最適であることを見い出した。より好ましくは３０−５０である。８０℃の硬度がショアーＤ硬度で５５以上になると、硬化樹脂の膨張応力緩和が悪く、湯口や空気抜き口へ応力分散が出来ず一方的に膨張し、ついには鋳型をその膨張力で破損せしめることになる。８０℃の硬度がショアーＤ硬度で２０以下の場合、夏場温度での樹脂模型硬度がショアーＤで４０以下となり、樹脂模型製作時の脱型工程で硬度不足を引き起こし、無理な脱型応力にて樹脂模型が変形することがある。
【００７６】
このように、焼失模型用樹脂組成の設定には、樹脂の量と骨格・硬化の速さ・可塑剤成分やロウ・ワックス成分の溶融流出燃焼成分・硬化物の硬さ・発泡制御・等が相互に関与するものであり、そのバランスが取れた最適適応範囲を見い出し本発明に到達した。
【００７７】
こうして設計された２液反応硬化ウレタン樹脂液体（Ａ）を成形した樹脂模型の形状を最も焼失し易い形態に成形することも重要な要素である。そこで、肉厚部位が中空に成形出来る回転成形を各種検討した結果、模型形状・回転成形条件によっては中空樹脂模型となることを見い出し、ロストワックス精密鋳造に適応させ、脱ロウ・焼成時に鋳型が割れず、精密鋳造品を製作することが出来た。
【００７８】
２液反応硬化型ウレタン樹脂液（Ａ）の実施例は下記の通りである。
【００７９】
３ツ口コルベンにクルードＭＤＩ（ＮＣＯ＝３２％）３２．０重量部、可塑剤として２−エチルヘキシルアジペートを５．０重量部、キシレンを８．０重量部、を仕込み、均一攪拌溶解後、室温にてロウ・ワックス成分を３．０重量部添加し、攪拌混合した。ＮＣＯ＝２０．５％であった。これを多官能ポリイソシアネート成分▲１▼とした。次いで、４ツ口コルベンにエチレンジアミン・プロピレンオキサイド付加物（ＭＷ＝３００）７．０重量部、エチレンジアミン・プロピレンオキサイド付加物（ＭＷ＝４００）８．０重量部及びトリメチロールプロパン・プロピレンオキサイド付加物（ＭＷ＝４００）１６．０重量部、可塑剤として２−エチルヘキシルアジペート５．０重量部を仕込み、キャピラリーより窒素ガスを吸引させながら、真空にて１００℃１時間攪拌混合脱水した。カールフイッシャーにて水分を測定したところ水分は０．０２％であった。次いで、キシレンを９．０重量部添加混合希釈し、整泡剤を０．０１重量部、オクチル酸亜鉛／キシレン溶液（１０％溶液）を微量添加し可使時間を９０秒に調整した。更に天然高分子系廃棄物の微細片として新聞紙シユレータカット細片（約０．５ｃｍ×約１ｃｍのサイズ、水分含有量１０％調整品）１．０重量部、整泡剤０．０１重量部、ロウ・ワックス成分を５．０重量部添加し、これを多官能ポリオール成分▲１▼とした。
【００８０】
多官能ポリオール成分▲１▼と多官能ポリイソシアネート成分▲１▼の配合比は１：１（重量）である。計算値は、ＮＣＯ／ＯＨは０．８３、可塑剤含有量は１０．０重量％ ポリエーテル鎖含有量は２１．０重量％ ロウ・ワックス成分含有量は８．０重量％、多官能ポリオール成分の平均官能基数は３．３２、多官能ポリイソシアネート成分の平均官能基数は２．３０である。
【００８１】
多官能ポリオール成分▲１▼と多官能ポリイソシアネート成分▲１▼の配合比＝１：１（重量）から成る２液反応硬化型ウレタン樹脂液（Ａ）の特性値は次の通りである。
【００８２】
可使時間＝９０秒、混合粘度＝１２ｍＰａｓ、脱型可能時間＝２０分、硬化物外観は薄黄褐色微発泡であった。
【００８３】
【発明の効果】
近年、精密鋳造部品への精度に対する要求・複雑形状に対する要求レベルが強くなって来た。溶融金属をチタン合金としたチタン合金精密鋳造品は、軽量・高強度・高耐熱・耐腐食性に優れた特性を生かして特殊な産業分野において、急激に需要が増大しており、特に自動車部品・ジェットエンジン部品・原子力関係・熱交換機部品・宇宙開発ロケット部品分野の特殊部品は複雑形状化・高寸法精度化した部品設計が進展しており、従来よりも高度な技術開発が要求されている。
【００８４】
また、高度な部品設計が進展しても、設計に忠実なる精密鋳造品が出来なければ意味がない。複雑形状・高寸法精度を有する精密鋳造技術を高めることが非常に重要なのである。さらに、ロストワックス精密鋳造のキー技術の１つはやはり模型なのである。従来のロウ模型を用いたロストワックス精密鋳造では、これらの高度な要求に応えることが技術的に困難に成って来た。つまり、強度的に脆いロウ成分で複雑・高精度な模型を製作することは、自ずと技術的に限界にあるものである。
【００８５】
したがって、本発明によれば、精密鋳造に用いられる模型を樹脂で成形すると共に、その樹脂模型が中空部分を有することから、精密鋳造用模型における焼失性を向上させることができると共に、回転成形を用いたことから、その中空部分を有する樹脂模型を簡易な方法で形成することができるため、市場で要求される複雑形状・高精度な精密鋳造品が生産出来ることになる。具体的には、肉厚１ｍ／ｍ以下の薄肉部位・肉厚１０ｍ／ｍ程度の厚肉部位・シヤープエッジ部位・これらが３次元曲面で絡み合った複雑な形状を有する精密鋳造品が生産出来ることになる。
【００８６】
本発明による技術を実用化することにて、自動車産業・航空機産業・宇宙開発産業の進展に大きく貢献出来るものと確信する。
【図面の簡単な説明】
【図１】本願発明の実施の形態に係る樹脂模型の一例を示した斜視図である。
【図２】本願発明の第１の実施の形態に係る樹脂模型の製造方法において、２液反応硬化型ウレタン樹脂液をモールドに注入する工程の例を示した断面図である。
【図３】本願発明の第１の実施の形態に係る樹脂模型の製造方法において、第１回目の硬化物積層工程を説明するための断面図である。
【図４】本願発明の第１の実施の形態に係る樹脂模型の製造方法において、樹脂模型形成工程を説明するための断面図である。
【図５】本願発明の第２の実施の形態に係る樹脂模型の製造方法において、樹脂模型形成工程を説明するための断面図である。
【図６】本願発明の第３の実施の形態に係る樹脂模型の製造方法において、樹脂模型形成工程を説明するための断面図である。
【符号の説明】
１ 樹脂模型
２ 樹脂模型形成用モールド（モールド）
３ 内部空間
４ 注型口
５ エア抜き口
６ 混合容器
７，８ シール部材
１２ 樹脂模型
１３ 注型口通路積層体
１４ エア抜き通路積層体
Ａ ２液反応硬化型ウレタン樹脂液[0001]
[Technical field to which the invention belongs]
The present invention relates to a method for producing a resin model used for precision casting by, for example, the lost wax method.
[0002]
[Prior art]
As a prior art, first, the entire precision casting method by the lost wax method will be described. In the lost wax method, a molten wax component is injected into a mold for mass production of a wax model, and after cooling, it is demolded to produce a wax model having the same shape as the cast product, and the surface of the wax model is fireproof. After solidifying with objects, heat to melt out the wax model, and then make a mold that is completely burned out by high-temperature firing, and then cast the molten alloy into the mold and cool and solidify it It goes through a manufacturing process in which the mold is crushed and the cast is taken out.
[0003]
In the process of producing a wax model by injection molding a wax component into a mold, the injection temperature, injection pressure, injection pressure holding time, and cooling demolding temperature are controlled, and a wax model of a constant quality is produced. The wax model produced in this way is stored in a constant temperature room at a constant temperature, and sufficient care is taken to maintain dimensional accuracy. The wax model is assembled by brazing the wax model to a separately created gate model. The entire assembled model is called a tree. Since the shape of the tree is directly used as a gate system, many factors such as the properties of the molten metal, the size and shape of the casting, the casting conditions, and the ability to cut from the tree are taken into consideration in the design.
[0004]
The tree produced in this way is coated in a layer by repeating the dipping and drying steps in the coating slurry. Binders used in the coating slurry are colloidal silica, ethyl silicate, hybrid and the like. These binders are blended with refractory fine powder as a filler to form a slurry. Specifically, the tree is dipped in the slurry thus produced and pulled up, and then stucco grains are sprinkled and dried. As stucco grains, zircoside and morokite grains are used. The coating operation is completed by repeating these operations several times.
[0005]
Next, the wax model is eluted from the mold at 120-150 ° C. in an autoclave. This is called dewaxing. After the dewaxing, the shell mold is baked by raising the temperature in each stage in a 700-1000 ° C. high-temperature firing furnace in order to remove adhering wax and incompletely burned carbon powder and increase the strength of the mold. The molten alloy is cast into the mold thus manufactured, and after cooling, the mold is collapsed with a knock-at machine, the cast is taken out, and the runners and coughs are cut and removed, and then the attached residual refractory is removed by blasting. . Parts that can be repaired are repaired by welding, finished with a grinder, and then heat treated to produce a cast alloy product.
[0006]
In addition, the model used for lost wax precision casting is required to be heated, melted, decomposed and burned off during the mold manufacturing process. In the prior art, wax is widely used as a model material as a material that can be easily melted, decomposed, and removed by combustion. On the other hand, although it is inferior to wax and wax in properties that are heated, melted, decomposed, and removed by combustion, it is a hollow model made of a synthetic resin with excellent model strength, and it has been adapted to adapt to a form that is easy to be heated, melted, decomposed, and removed Explain the technology.
[0007]
First, various methods have been devised in the past for forming a shape having a hollow portion. The ancients made a hollow cocoon-shaped object by laminating string-like clays in the shape of a snake's skull to create a cocoon, and then making the snake's skulls large and small. At present, a cage having a hollow portion is manufactured by pulling up clay with a certain thickness on a rotating plate. This method is applicable to a simple circular shape that is symmetrical.
[0008]
In glass crafts, molten glass adheres to the tip of the blowing rod under high temperature conditions that maintain fluidity, and air is blown into the molten glass from the tip of the blowing rod to inflate the balloon. Hollow glass crafts are produced by three-dimensional modeling of the appearance of molten glass while rotating. Industrially, molten glass adheres to the tip of the blowing rod under high-temperature conditions that maintain fluidity, is trapped in the split mold, and air is blown into the molten glass from the tip of the blowing rod to expand it into a balloon shape. In this method, the molten glass is pressed against the side surface by air pressure to promote the temperature drop of the molten glass, and the liquid mold is divided and the hollow shaped article is taken out under the condition that the solidified shape is lost. Hyundai performs this method with fully automatic continuous production, and the same shape of hollow glass products is mass-produced.
[0009]
In the plastics field, air is injected into a thermoplastic sheet cylinder softened by heat to make it adhere to the inner wall of the split mold, and after cooling and solidifying, the split mold is divided and a hollow molding product is taken out. It is said.
[0010]
Also, the thermoplastic resin powder is put into the mold through the opening of the heating mold, the mold temperature is raised, the thermoplastic resin powder is melted at the inner surface of the mold, and a thermoplastic resin melt layer is formed, and the mold With cooling, the molten thermoplastic resin adhering to the inner surface of the mold is cooled and solidified and held in shape, and the unmelted thermoplastic resin powder at the center of the mold is removed from the opening of the mold, and finally the heat adhering to the inner surface of the mold By pulling out the plastic resin sheet from the mold opening and inflating the drawn resin sheet with air pressure, an integral hollow molding body is completed. If this is painted neatly, the character mask can be manufactured seamlessly, which is said to be 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.
[0011]
In addition, a small amount of two-component reactive resin is poured into the mold, and while rotating, it adheres and hardens over the entire inner wall part of the mold, forms a turtle shell, and then demolds to form a hollow center part. There is also a rotational molding method to take out. The present invention has found a great effect by using this rotational molding method to create a hollow model with a special resin composition and adapting it to a limited use as a lost wax precision casting model.
[0012]
In addition, stereolithography is a method of irradiating a photocurable resin with light and curing and laminating it into a donut board shape. By controlling the light with a computer, the shape of the donut board is sequentially deformed to obtain a three-dimensional shape object. It is. The central part of this donut board is to give a hollow part to the three-dimensional shape model, and this is also a wonderful hollow-shaped integrated molding manufacturing method. However, 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 production and mass production. You can say that. The above is for integrally molding a hollow model, but there are advantages and disadvantages in the shape that can be molded, the material of the molded product, mass production, and economy.
[0013]
There is also a production method in which a hollow part is created by embedding an erasable core and manufacturing a molded body and then dissolving the core in an organic solvent or water.
[0014]
Here, a conventional technique in which a hollow resin model is applied to a lost wax precision casting resin model and precision casting is performed is as follows. Examples of the photo-curing resin made into a hollow resin model by stereolithography and adapted to lost wax precision casting are disclosed in JP-A-9-52145, JP-A-7-47443, JP-A-2001-18033, JP-A-2000-5843, and JP-A-20005843. 11-57943 and many others are disclosed. Japanese Patent Laid-Open No. 2000-210755 is disclosed as an example of applying a foamed urethane resin model that can be regarded as a kind of hollow body to lost wax precision casting. This is a reaction injection molding thermosetting polyurethane foam model, a shell mold is formed around the model, the model is sintered and removed in the heating process, the shell mold is cured, and a molten metal or molten alloy is cast. To do.
[0015]
The present invention is a precision casting method using the lost wax method, by rotationally molding a special urethane resin liquid containing a plasticizer and a wax component as essential components, and using a hollow foamed / non-foamed urethane resin model as an alternative to a wax model. It is proposed and is basically different from the above prior art example.
[0016]
[Problems to be solved by the invention]
When producing a precision casting by the lost wax method, the model is generally a wax model made of a wax component. This makes use of the characteristics that the wax component is easily melted away at a high temperature and is excellent in the ability to burn in the mold high-temperature firing step. However, in recent years, precision castings have a complicated structure, and strict dimensional accuracy has been required. Along with this, various problems have occurred, and there are many situations that cannot be handled by the wax model.
[0017]
In other words, the problems with these wax models are that the edges are hard to come out, the thin ribs are difficult to stand up, the thin ribs are easy to break, and the thin parts must be removed with great care when releasing. A wax model with a too thin part of 1 mm or less has a technical limit in production. Furthermore, the produced wax model has the problems of being easily damaged due to its low surface hardness, dimensional accuracy is poor, and being damaged by a drop impact when carried. Furthermore, the created wax model undergoes a shape change under summer conditions. Because it is easy, there was a problem that it must be stored in a constant temperature room. In particular, great care must be taken when moving wax models in summer. The wax component is a relatively low molecular organic substance and softens at about 80 ° C. Thus, the problem of the wax model is concentrated on the problem caused by the wax component. In order to improve the problems caused by such a wax component, improvement research has been made by changing the composition of the wax component, but the wax component is a low melting point organic substance at a temperature slightly higher than room temperature, and is crystallized at room temperature. Since it is solidified, it has not yet solved the fundamental problem.
[0018]
The wax component of the wax model used in the lost wax precision casting method is generally a blend of paraffin, rosin, carnauba wax and terephthalic acid. Details of the wax component are described in the casting manual (edited by the Japan Foundry Association). In order to improve this wax component, Japanese Patent Laid-Open No. 5-38549 discloses that effectiveness is increased by adding melamine powder to the wax component. However, as long as the wax component melts at a high temperature and retains the property of being easily dewaxed, there is a limit in improving the mechanical strength properties of the wax model even if an organic polymer melamine powder is added. When it comes to complex shape models with a wall thickness of 1 mm or less, there is still a problem that the problems caused by the basic properties of the wax, such as the model being broken, cracked, and distorted when the wax model is removed, cannot be avoided. It remains.
[0019]
Therefore, the subject of this invention is providing the manufacturing method of the lost wax precision casting resin model and the lost wax precision casting method for solving the above-mentioned various problems resulting from a wax model.
[0020]
[Means for Solving the Problems]
Therefore, the present invention is a method for producing a resin model used for precision casting by the lost wax method and adaptation to the lost wax precision casting: a two-component reaction-curing urethane resin liquid (1 to 3 minutes of pot life) A) Volume amount corresponding to 5% to 20% of the internal space volume through the casting port of the resin model forming mold that defines the internal space having the same shape as the manufactured product A cured product layer forming step of forming a cured product layer of a two-component reaction curable urethane resin on the inner wall of the resin model forming mold by sealing the casting port and rotating the resin model forming mold; And the cured product layer forming step is repeated 3 to 6 times every 3 to 5 minutes to laminate the cured product layer, thereby forming a resin model having a space in the central portion; the resin model; Mold for forming La the resin model having at least a demolding step of demolding.
[0021]
The two-component reaction curable urethane resin liquid (A) is composed of a polyfunctional polyol component (a), a polyfunctional polyisocyanate component (b), and a plasticizer component (c). The average functional group number is 2.8 or more, the polyfunctional polyisocyanate component (b) has an average functional group number of 2.0 or more, NCO / OH is 0.7 to 1.0, and the reaction curing agent plasticizer component (c) It is desirable that the phase separation microdisperse.
[0022]
Furthermore, the two-component reaction curable urethane resin solution (A) preferably contains 2 to 25% by weight of a polyether chain represented by the following chemical formula.
[0023]
[Chemical formula 2]

[0024]
Furthermore, it is desirable to blend 5 to 40% by weight of the fine wax component (d) with the two-component reaction curable urethane resin solution (A).
[0025]
Moreover, it is desirable to add a trace amount of water (e) to the two-component reaction curable urethane resin liquid (A) to form water-foamed urethane.
[0026]
Furthermore, it is desirable that the resin model has an internal hollow space in the range of 20 to 70% of its volume. The internal hollow space may be filled with a wax wax component (d) or with urethane foam.
[0027]
The precision casting method using the lost wax method desirably uses the above-described resin model, and the precision casting product is desirably manufactured by this precision casting method.
[0028]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a perspective view showing an example of a resin model 1 according to an embodiment of the present invention. Hereinafter, a method for manufacturing the resin model 1 will be described with reference to the drawings.
[0029]
In the first embodiment, as shown in FIG. 2, the resin model forming mold 2 (hereinafter referred to as mold 2) is a silicon rubber mold formed of silicon rubber, and has the same shape as the resin model 1. 3, and has a casting port 4 and an air vent port 5 that open to the outside, and a casting port passage 41 and an air vent port 5 that communicate with the casting port 4 and the internal space 3. And an air vent passage 51 communicating with the internal space 3.
[0030]
The following two-component reaction curable urethane resin liquid (A) to be injected into the internal space 3 is mixed in the mixing container 6 and, as the first time, 5 to 20% of the volume of the internal space 3 is injected. The Then, as shown in FIG. 3, the casting port 4 and the air vent port 5 are closed by seal members 7 and 8 such as a seal tape. And the said mold 2 is installed in the rotary molding machine which is not shown in figure, rotates for 1 to 3 minutes in multiple directions, 2 liquid reaction hardening type urethane resin liquid (A) adheres and solidifies on the inner wall of the mold 2, and urethane resin Layer 11 is formed (cured product layer forming step). And the operation mentioned above is repeated several times, the urethane resin layer 11 is laminated | stacked (lamination process), and as shown in FIG. 4, the resin model 12 of predetermined thickness is obtained (resin model formation process). The resin model 12 includes a portion that becomes the finished resin model 1, a casting port passage portion 13 formed around the casting port passage 41, and an air vent passage portion 14 formed around the air vent passage 51. And demolded from the mold 2 (demolding step). Then, the casting port passage laminate portion 13 and the air vent passage laminate portion 14 are cut out from the resin model 12 to obtain the resin model 1 as a finished product (finishing step).
[0031]
In this embodiment, the above-described operation was performed three times. This is because when the laminating process is performed once or twice, the entire inner wall of the mold cannot be completely covered, resulting in inconvenience because the model includes a defect portion. This is because the number of operations and the work process time increase, and rapid model production is impaired. Experiments revealed that the entire inner wall of the mold can be completely covered with the resin in the normal lamination process 3 to 6 times. The preferred lamination process is 3 to 4 times.
[0032]
The amount of the two-component reaction curable urethane resin liquid (A) injected into the mold 2 is desirably set according to what percentage of the total volume of the resin model 1. Experiments have revealed that the amount of the two-component reaction curable urethane resin liquid (A) that is usually used for one injection is desirably 5 to 20% of the total volume of the resin model. Specifically, when the amount of the two-component reaction curable urethane resin liquid (A) used for one injection is less than 5% of the total volume of the resin model, the inner wall of the mold is removed by three to six lamination steps. Since it becomes difficult to cover completely, seven or more lamination steps are required, which impairs rapid resin model production. On the other hand, when the amount of the two-component reaction curable urethane resin liquid (A) used for one injection is 20% or more of the total volume of the resin model, the inner wall of the mold 2 is completely completed in three to four lamination steps. However, the resin model 1 is less hollow, making it impossible to produce more than 40% of the internal hollow model, which puts a load on the subsequent dewaxing and firing process, and makes the mold easy to break. Produced a result.
[0033]
In the resin model 1 thus created, 20 to 60% of the model volume is hollow inside. This greatly reduces the load applied to the subsequent dewaxing and firing steps, and exhibits great effectiveness against cracking of the mold.
[0034]
In order to reduce the load applied to the dewaxing / firing process to the maximum, the film thickness of the resin model 1 should be reduced as much as possible. For this purpose, the thickness of the laminated film is reduced once and the number of laminated times is increased more than the range limited in the present invention. As described above, this increases the resin model manufacturing process, resulting in an increase in manufacturing time, and does not match short delivery and low cost manufacturing. Therefore, as a second embodiment, as shown in FIG. 5, after forming the resin layer incompletely on the inner wall of the mold 2 with the number of times of lamination being about 2, the resin model 12 is not demolded. An effective method is to inject the molten wax component 15 into the hollow portion 30 of the resin model 1 from the casting port 4 and to demold after cooling at room temperature. That is, the wax component 15 filled in the hollow portion 30 is an effective means for reinforcing the resin model 1 and maintaining the strength as a model in each process up to mold production.
[0035]
Similarly, in the third embodiment, after the resin layer is formed on the inner wall of the mold 2 incompletely, the number of times of lamination is about twice in order to reduce the load applied to the dewaxing / firing process to the maximum. It is also effective to inject the urethane foam resin liquid 16 into the model hollow portion 30 from the casting port 4 without filling the resin model 12 and fill the model hollow portion 30 with the foamed urethane resin to remove the mold. . That is, the foamed urethane resin filled in the model hollow portion 30 is an effective means for reinforcing the resin model 1 and maintaining the strength as a model in each process up to the mold production.
[0036]
In FIGS. 5 and 6 showing the second and third embodiments described above, the same portions and portions having similar effects are denoted by the same reference numerals, and description thereof is omitted.
[0037]
Next, the component composition of the two-component reaction curable urethane resin liquid (A) used in the present invention will be described.
[0038]
The skeleton of the two-component reaction curable urethane resin liquid (A) is composed of two liquids of a polyfunctional polyol component (a) and a polyfunctional polyisocyanate component (b). It is initiated and is exothermic. The plasticizer (c) and wax / wax component (d) contained in the two-component reaction curable urethane resin solution (A) are blended with either the polyfunctional polyol component (a) or the polyfunctional polyisocyanate component (b). Or may be blended in both. Moreover, since water | moisture content (e) raise | generates a chemical reaction with a polyfunctional isocyanate component (b), it is previously mix | blended with a polyfunctional polyol component (a).
[0039]
Next, each component will be described. As the polyfunctional polyol component (a), castor oil and its derivatives are used as special ones such as a low molecular polyol, polyether polyol, amine polyol, polyester polyol, acrylic polyol, polybutadiene polyol and the like.
[0040]
Examples of the low molecular polyol include ethylene glycol, propylene glycol, 1-4 butanediol, glycerin, trimethylolpropane, and pentaerythritol.
[0041]
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. By this, the reactivity of the terminal hydroxyl group is different, and various polyether polyols having different hydrophilicity / hydrophobicity depending on ethylene oxide and propylene oxide are added to the added chain. There is also polytetramethylene ether glycol obtained by cationic polymerization of THF, which is usually referred to as PTMG.
[0042]
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, the polyol contains tertiary nitrogen in the molecule and possesses 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.
[0043]
As the polyester polyol, there is a condensed polyester polyol in which a molecular terminal is a hydroxyl group by esterification of a dibasic acid and a low molecular polyol. A variety of polyester polyols can be obtained by selectively 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. Adipic acid is frequently used as the dibasic acid used in the condensed polyester polyol. Examples of the low molecular diol include ethylene glycol / propylene glycol and 1.4 butanediol. Examples of triols include glycerin, trimethylolpropane, and their low alkylene oxide adducts. Further, the ring-opening polymerization type polyester polyol of ε-caprolactam is one in which 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.
[0044]
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 obtained by selecting the type of acrylic monomer and adjusting the molecular weight are commercially available. 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 subjected to slight cross-linking with an aliphatic polyisocyanate and becomes a paint having excellent weather resistance.
[0045]
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.
[0046]
These polyfunctional polyols may be jointed with polyisocyanate to form a urethanized modified polyol having terminal hydroxyl groups. Since it is oligomerized by urethane modification and the molecular weight is slightly increased, the viscosity tends to increase.
[0047]
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 (a) have an active hydroxyl group at the molecular end, and the reactivity with isocyanate differs depending on the type of hydroxyl group at the molecular end.
[0048]
In particular, polyether polyol and polyester polyol 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 (a) is produced through a heating and mixing dehydration step.
[0049]
The polyfunctional polyisocyanate component (b) 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.
[0050]
Examples of the polyisocyanate component include aromatic polyisocyanate, aliphatic polyisocyanate, and alicyclic polyisocyanate. Typical aromatic polyisocyanates are tolylene diisocyanate and diphenylmethane diisocyanate. Tolylene diisocyanate is obtained as a mixture of various isomers due to chemical reaction during production, and 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%), 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.
[0051]
Since polyisocyanates are generally rich in reactivity, volatile polyisocyanates are particularly toxic and are 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.
[0052]
The specific range on the present invention regarding the two-component reaction curable urethane resin liquid (A) having the polyfunctional polyol component (a) and the polyfunctional polyisocyanate component (b) as resin components will be described.
[0053]
The rapid-curing two-component reaction-curable urethane resin liquid (A) having the polyfunctional polyol component (a) and the polyfunctional polyisocyanate component (b) as resin components has 2 to 20 weights of a polyether chain represented by the following chemical structural formula. % Content.
[0054]
[Chemical 3]

[0055]
When a polyether is used for the polyfunctional polyol component (a), 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 (b) is a terminal isocyanate joined by a polyether, that is, a 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 and 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.
[0056]
The blending amount of the polyfunctional polyol component (a) and the polyfunctional polyisocyanate component (b) 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 of NCO / OH groups is 1 Designed to be around 0.0. In the case of urethane foam, NCO / OH is designed in an isocyanate excess region of about 1.0 to 1.1. 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 properly. In other words, it is a region that exhibits the highest strength. In the present invention, NCO / OH = 0.7 to 1.0, which is set in the NCO shortage region. 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 NCO / OH can take a three-dimensional network structure in an area of 1.0 or less. Although the NCO group is insufficient and the OH group is excessive, the monomers used are polyfunctional, so that the monomer connection can be completed and the main chain can be constructed without complete reaction of the functional groups. An OH group having no excessive reaction partner terminates the reaction with the OH group held in the main chain. Thus, it is considered that the hydrophilic keep is increased and it is effective to disperse the strongly hydrophobic plasticizer in the phase separation micro-dispersion.
[0057]
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 it becomes difficult to obtain a three-dimensional network structure after reaction hardening, extremely lowers the hardness, and finally becomes so soft that it is difficult to maintain the shape. On the other hand, when NCO / OH is 1.0 or more, isocyanate groups become excessive, unreacted isocyanate groups remain even when the demolding time comes, and a predetermined hardness does not appear, or color unevenness occurs on the surface of the cured product. Is not preferable.
[0058]
As a catalyst for promoting the chemical reaction between the polyfunctional polyol component (a) and the polyfunctional polyisocyanate component (b), there are 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 (a), and the pot life is adjusted. In the present invention, the catalyst is added to the polyfunctional polyol component (a) 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 and demolding time is 2 hours or more, which will hinder the production of the resin model. When the pot life is 1 minute or less, the reaction viscosity increases rapidly, making it difficult to take the time for mixing and casting the two liquids. Therefore, the pot life is preferably 1 to 2 minutes.
[0059]
Next, the plasticizer (c) used in the present invention will be described. The plasticizer (c) used in the present invention is a compound having no functional group that causes a chemical reaction and having negligible inert volatility, and is a liquid at room temperature. Examples of the plasticizer (c) 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 diethene glycol monophenyl ether acetate.
[0060]
The usage-amount of a plasticizer (c) is 2 to 20 weight% with respect to a 2 liquid reaction hardening type urethane resin liquid (A). When the plasticizer (c) is used in an amount of 20% by weight or more, the plasticizer (d) bleeds to the surface of the resin model, causing stickiness and tackiness. When the amount of the plasticizer (c) used is 2% by weight or less, it becomes difficult to flow out during the resin decomposing / melting and burning combustion in the dewaxing / firing process. This is because the plasticizer (c) is a liquid at room temperature and has a low viscosity that easily flows out at a high temperature. In order to exert such an effect strongly, the plasticizer (c) is desired to be contained as high as possible. Usually, when a large amount of plasticizer is contained in the resin component, the plasticizer bleeds to the surface of the cured product, causing tackiness or stickiness on the surface. Therefore, as a result of diligent studies to make the plasticizer (c) as high as possible, it was quickly cured within 5 minutes of pot life, and the plasticizer (c) phase separated from the cured resin. It is effective to form a state of being confined in a micro-dispersed state within a three-dimensional network structure.
[0061]
If such a phase-separated micro-dispersed structure is expressed in words, it can be expressed that a plasticizer (c) corresponding to a larva is included in a honeycomb-shaped cured resin. The honeycomb-shaped cured resin has a structure with excellent strength properties, and has a three-dimensional structure in which the plasticizer (c) is carefully stored in the honeycomb and is not released to the outside. Therefore, even if the plasticizer (c) becomes relatively high, it does not ooze out on the surface of the cured product and cause tackiness. When the phase-separated micro-dispersion structure is not taken, the plasticizer will be dissolved in the cured resin, and when the saturation level or higher is reached, the plasticizer will ooze out on the surface of the cured product, causing tackiness, and sticking if there is much oozing. It tends to occur. Such a phase-separated micro-dispersed structure has been confirmed by 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.
[0062]
At the time when the plasticizer (c) exists as a two-component reaction curable urethane resin liquid (A), the plasticizer (c) needs to be in a uniformly dissolved state and is phase-separated from the cured resin at the stage of reaction curing. Is included and includes a micro-dispersed plasticizer at the time of completion of the reaction curing to prevent bleeding to the surface. The composition is based on this delicate balance. That is, it is designed in a region where the balance between hydrophilicity and hydrophobicity of the plasticizer (c) 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 an ethylene oxide chain is frequently used in the rapid curing two-component reaction curable urethane resin liquid (A), 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 rapid curing two-component reaction-curing urethane resin solution (A) having strong hydrophobicity can be obtained and adjusted within a range having hydrophilicity and hydrophobicity. Moreover, the hydrophilicity and hydrophobicity of plasticizer (c) itself can be adjusted within a certain range by adjusting the kind and amount of the plasticizer (c). For example, when the terminal is an alkyl ether, the hydrophobicity increases as it changes to methyl ether, ethyl ether, butyl ether, phenyl ether. In this way, the chemical structure and amount of the plasticizer (c) and the chemical structure and amount of the rapid curing two-component reaction curable urethane resin liquid (A) are changed to set the region range in which the phase separation micro-dispersion is performed. is there. When the plasticizer (c) is set to be relatively hydrophobic and the resin component is set to be relatively hydrophilic by such means, phase separation micro-dispersion is successfully established.
[0063]
Next, the wax component (d) used in the present invention will be described. The wax component (d) 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 component (d) 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. This wax component (d) has strong properties as paraffin or olefin and is very hydrophobic and solid at room temperature. Therefore, the polyfunctional polyol component (a), the polyfunctional polyisocyanate component (b), and the plasticizer (c) are difficult to dissolve. Therefore, even if it mix | blends with 2 liquid reaction curable urethane resin liquid (A), it is hard to melt | dissolve and it exists in the state which floats in the liquid system. In this state, the rapid curing two-component reaction curing type urethane resin liquid (A) is rapidly cured, and as a result, it is included 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 (d) 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.
[0064]
This wax component (d) is used in an amount of 1 to 20% by weight based on the two-component reaction curable urethane resin liquid (A). When the amount used is 1% by weight or less, the dewaxing effect using the wax component (d) disappears. When it becomes 20% by weight or more, the fluidity of the rapid curing two-component reaction curing type urethane resin liquid (A) is deteriorated, 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.
[0065]
This wax component (d) is 1cm ³ It is in the form of particles, scales, or lumps that fit. The particle shape or lump shape may be a ball shape, a sugar cube shape, or a slightly deformed shape. In other words, it is not limited to true or honest prisms. 1cm in size ³ The size fits in. 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 (d) in the model is impaired, the shape retention as a model, dimensional accuracy, decomposition / melt outflow property during heating, and combustion decomposition residual ash at high temperature are reduced. It is only necessary to perform mold manufacturing and precision casting. Of course, the wax component (d) is likely 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 (d) 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 and wax component (d) flows into this part, and when fixed with a cured resin, the effect of successfully supporting melting, outflow, decomposition, and combustion is greatly manifested in the dewaxing and firing processes. Will be.
[0066]
Next, the moisture (e) used in the present invention will be described. Moisture (e) is H ₂ O. Moisture (e) is determined to have (1) intentionally blended water, (2) trace amounts of water mixed into the chemical raw materials in the manufacturing process, and (3) moisture absorbed from the air itself. . The moisture (e) referred to in the claims of the present invention is the sum of these. The reason for using moisture (e) is that carbon dioxide gas generated by a chemical reaction with polyfunctional polyisocyanate is used as a foaming agent, that is, a water foaming technique for urethane is introduced. As a result, the resin model 1 may be formed as a foam containing a plasticizer (c), a wax component (d), and bubbles. Within the limited range where foaming is adjusted, the resin model itself, which is a foam, maintains solid shape retention, and exhibits great effectiveness in hot melting, decomposition, outflow, and combustion in the dewaxing and firing processes. is there.
[0067]
The main factor that determines the expansion ratio is the amount of moisture (e), and the subfactors are adsorbed water on the mold surface, temperature / humidity of the outside air, and the like. The amount of moisture (e) is 0.01 to 1.0% by weight with respect to the rapid curing two-component reaction curing type urethane resin liquid (A). Preferably, it is 0.03 to 0.5 weight%. More preferably, it is 0.08 to 0.15% by weight. When the moisture (e) 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 during demolding, and the bubbles appear on the model surface in a concave state. As a result, the model surface becomes 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.
[0068]
The moisture (e) is usually blended with the polyfunctional polyol component (a). It is controlled by mixing water and mixing uniformly, and measuring trace moisture by the Karl Fischer method. When blended with the polyfunctional polyol component (a), water alone is sufficient, and there is no particular limitation as long as the component containing water does not cause abnormalities in model production. For example, surfactant aqueous solution, aqueous dye aqueous solution, aqueous paste, resin aqueous solution, water latex, water-containing natural polymer, and the like can be mentioned.
[0069]
Surfactant aqueous solutions are liquid detergent aqueous solutions, solid soaps, powdered soaps, etc., and are widely marketed as shampoos, kitchen detergents, industrial detergents, and cosmetic soaps by blending builders and perfume dyes. Solid soap and powdered soap do not contain a large amount of water, but they contain a small amount of water. An aqueous dye aqueous solution is a dye solution dissolved in water. A water paste is a solution obtained by dissolving an aqueous solution of methyl cellulose or rice in water, and is widely sold in stationery stores. Water latex is a synthetic rubber latex such as vinyl acetate latex and EVA, and is widely sold as a woodworking bond at paint stores, DIY stores, and sunday general stores. The fine piece of moisture-containing natural polymer is a fine piece of paper, wood, or fiber. Examples of the fine pieces of paper include fine pieces such as newspaper, advertising paper, office copy paper, packaging paper, and cardboard. Examples of the fine pieces of wood include waste wood for construction, waste wood for civil engineering, waste furniture, thinned wood, dead grass of plants, fine pieces of rice husks, and the like. Examples of fibers include cotton, hemp and silk.
[0070]
Natural polymer fine pieces generally contain more or less moisture due to hydrophilicity. Therefore, when the fine pieces of the natural polymer are mixed and dispersed in the polyfunctional polyol component (a), the moisture contained in the fine pieces of the natural polymer is brought into the system, and the polyfunctional polyol component (a) The amount of moisture will increase. Therefore, the water content of the polyfunctional polyol component (a) is controlled by taking into consideration the water content brought in by the amount of fine particles (H) mixed in the natural polymer waste.
[0071]
In the case of foaming by adding such a moisture-containing substance, 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 smoothly removed 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.
[0072]
In the present invention, an organic solvent may be used. As an organic solvent that can be used, 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 this organic solvent is that it dissolves polyfunctional polyether (a), polyfunctional polyisocyanate (b) and plasticizer (c), has a mild odor, and does not generate toxic gas during combustion. And it must be economical. The organic solvent satisfying such required performance is selected from aromatic organic solvents. Preference is given to toluene and xylene.
[0073]
In the exothermic gelation stage of the two-component reaction curable urethane resin liquid (A), the organic solvent tends to become a gas and has an effect of assisting 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.
[0074]
To the two-component reaction-curing urethane type resin liquid (A), a regulator, a stabilizer, a colorant, a flammable 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 preferable 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 particle size of 15 to 100 μm, such as UCAR Phenolic Microballon (manufactured by Union Carbide) or Matsumoto Microsphere (Matsumoto Yushi Seiyaku Co., Ltd.) ))). Inclusion of such hollow resin balloons embeds air in the resin model, which promotes decomposition, outflow and combustion in the dewaxing process and firing process, and produces the effect of reducing residual ash content. . 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 curable urethane resin solution (A) will be loosened and smooth fluidity will be difficult to obtain. Therefore, it is preferably 3 to 8% by weight.
[0075]
On the other hand, when the cured resin is very hard, melting, decomposition and loss combustion is delayed during heating and heating, and the mold is broken by the expansion of the resin, causing damage. Therefore, it is necessary to soften the entire cured resin model quickly and to disperse the expansion stress of the resin to the gate and the air vent. For this purpose, it has been found that the hardness of 80 ° C. of the burned-out resin model, which is a cured product, is optimal with a Shore D hardness of 20-55. More preferably, it is 30-50. When the hardness at 80 ° C becomes 55 or more in Shore D hardness, the cured resin does not relieve the expansion stress, the stress cannot be distributed to the pouring gate and the air vent, and it unilaterally expands, and finally the mold is damaged by the expansion force. become. If the hardness at 80 ° C is 20 or less in Shore D hardness, the resin model hardness at summer temperature will be 40 or less in Shore D, causing insufficient hardness in the demolding process at the time of resin model manufacture, and due to excessive demolding stress The resin model may be deformed.
[0076]
As described above, the setting of the resin composition for the burnout model includes the amount of the resin, the skeleton, the speed of curing, the plasticizer component, the wax and wax component, the molten spill combustion component, the hardness of the cured product, the foam control, etc. The present inventors have reached the present invention by finding an optimum adaptive range that is mutually related and balanced.
[0077]
It is also an important factor to mold the shape of the resin model formed with the two-component reaction-cured urethane resin liquid (A) designed in this way into a form that is most easily burned off. Therefore, as a result of various investigations of rotational molding that can form the thick part hollow, it was found that it became a hollow resin model depending on the model shape and rotational molding conditions, and it was adapted to lost wax precision casting, and the mold was used during dewaxing and firing. We were able to produce precision castings without cracking.
[0078]
Examples of the two-component reaction curable urethane resin liquid (A) are as follows.
[0079]
Charge 32.0 parts by weight of Crude MDI (NCO = 32%), 5.0 parts by weight of 2-ethylhexyl adipate and 8.0 parts by weight of xylene as a plasticizer in a three-necked Kolben. The wax component was added at 3.0 parts by weight and mixed with stirring. NCO = 20.5%. This was designated as polyfunctional polyisocyanate component (1). Next, 7.0 parts by weight of ethylenediamine / propylene oxide adduct (MW = 300), 8.0 parts by weight of ethylenediamine / propylene oxide adduct (MW = 400) and trimethylolpropane / propylene oxide adduct ( (MW = 400) 16.0 parts by weight, and 5.0 parts by weight of 2-ethylhexyl adipate as a plasticizer were charged, and the mixture was stirred and dehydrated in vacuum at 100 ° C. for 1 hour while sucking nitrogen gas from the capillary. When the water content was measured with a Karl Fischer, the water content was 0.02%. Subsequently, 9.0 parts by weight of xylene was added, mixed and diluted, 0.01 parts by weight of a foam stabilizer and a small amount of zinc octylate / xylene solution (10% solution) were added, and the pot life was adjusted to 90 seconds. Furthermore, as a fine piece of natural polymer-based waste, 1.0 parts by weight of a newspaper-cut oscillator-cut piece (approx. 0.5 cm × about 1 cm in size, adjusted to 10% water content), 0.01 parts by weight of a foam stabilizer The wax component was added in an amount of 5.0 parts by weight, and this was designated as polyfunctional polyol component (1).
[0080]
The blending ratio of the polyfunctional polyol component (1) and the polyfunctional polyisocyanate component (1) is 1: 1 (weight). Calculated values are 0.83 for NCO / OH, 10.0% for plasticizer content, 21.0% for polyether chain content, 8.0% for wax component content, polyfunctional polyol component The average functional group number is 3.32, and the polyfunctional polyisocyanate component has an average functional group number of 2.30.
[0081]
The characteristic values of the two-component reaction curable urethane resin liquid (A) comprising the blending ratio of the polyfunctional polyol component (1) and the polyfunctional polyisocyanate component (1) = 1: 1 (weight) are as follows.
[0082]
Pot life = 90 seconds, mixing viscosity = 12 mPas, demoldable time = 20 minutes, the appearance of the cured product was light yellowish brown fine foaming.
[0083]
【The invention's effect】
In recent years, there has been a growing demand for precision and complex shapes for precision cast parts. Titanium alloy precision castings made of molten metal with titanium alloys are rapidly increasing in demand in special industrial fields, taking advantage of their excellent characteristics of light weight, high strength, high heat resistance, and corrosion resistance.・ Jet engine parts, nuclear power related parts, heat exchanger parts, space development rocket parts, special parts in the field of complex shapes and high dimensional accuracy are progressing, and advanced technical development is required. .
[0084]
Even if advanced parts design progresses, it is meaningless unless a precision casting that is faithful to the design is produced. It is very important to improve precision casting technology with complex shapes and high dimensional accuracy. Furthermore, one of the key technologies for lost wax precision casting is still a model. In conventional lost wax precision casting using a wax model, it has become technically difficult to meet these high requirements. In other words, manufacturing a complex and high-accuracy model with a weakly brittle solder component is naturally at the technical limit.
[0085]
Therefore, according to the present invention, the model used for precision casting is molded with resin, and since the resin model has a hollow portion, it is possible to improve the burnout property of the model for precision casting, and to perform rotational molding. Since it used, the resin model which has the hollow part can be formed by a simple method, Therefore The complicated shape and the highly accurate precision casting product which are requested | required in a market can be produced. Specifically, it is possible to produce precision castings with a thin part with a thickness of 1 m / m or less, a thick part with a thickness of about 10 m / m, a sheared edge part, and a complex shape in which these are intertwined with a three-dimensional curved surface. become.
[0086]
I am convinced that the practical application of the technology according to the present invention can greatly contribute to the progress of the automobile industry, aircraft industry, and space development industry.
[Brief description of the drawings]
FIG. 1 is a perspective view showing an example of a resin model according to an embodiment of the present invention.
FIG. 2 is a cross-sectional view showing an example of a process of injecting a two-component reaction curable urethane resin liquid into a mold in the method for manufacturing a resin model according to the first embodiment of the present invention.
FIG. 3 is a cross-sectional view for explaining a first cured product laminating step in the resin model manufacturing method according to the first embodiment of the present invention;
FIG. 4 is a cross-sectional view for explaining a resin model forming step in the resin model manufacturing method according to the first embodiment of the present invention;
FIG. 5 is a cross-sectional view for explaining a resin model forming step in the method for manufacturing a resin model according to the second embodiment of the present invention.
FIG. 6 is a cross-sectional view for explaining a resin model forming step in the method for manufacturing a resin model according to the third embodiment of the present invention.
[Explanation of symbols]
1 Resin model
2 Mold for resin model formation (mold)
3 interior space
4 Casting port
5 Air vent
6 Mixing container
7, 8 Seal member
12 Resin model
13 Cast port passage laminate
14 Air vent passage laminate
A 2 liquid reaction hardening type urethane resin liquid

Claims (8)

A method of manufacturing a resin model used for precision casting by the lost wax method, which includes:
The two-component reaction-curable urethane resin liquid (A) having a pot life of 1 minute to 3 minutes is passed through the casting port of the resin model forming mold that defines the internal space having the same shape as the manufactured product. A volume corresponding to 5% to 20% of the internal space volume is injected into the internal space, the casting port is sealed, the resin model forming mold is rotated, and two liquids are applied to the inner wall of the resin model forming mold. A cured product layer forming step of forming a cured product layer of a reaction-curable urethane resin;
A resin model forming step of laminating the cured product layer by repeating the cured product layer forming step 3 to 6 times every 3 to 5 minutes to form a resin model having a space at a central portion; and the resin model A method for producing a resin model, comprising: a demolding step of demolding the resin model from a forming mold. The two-component reaction curable urethane resin liquid (A) is composed of a polyfunctional polyol component (a), a polyfunctional polyisocyanate component (b), and a plasticizer component (c). The number of groups is 2.8 or more, the average number of functional groups of the polyfunctional polyisocyanate component (b) is 2.0 or more, NCO / OH is 0.7 to 1.0, and the plasticizer component (c) at the time of reaction hardening is a phase. 2. The method for producing a resin model according to claim 1, wherein the resin is dispersed microscopically. The two-component reaction curable urethane resin liquid (A) is

The method for producing a resin model according to claim 1 or 2, comprising 2 to 25% by weight of a polyether chain represented by formula (1). The method for producing a resin model according to claim 1, wherein 5 to 40% by weight of a fine wax component (d) is blended in the two-component reaction curable urethane resin solution (A). The said resin model has an internal hollow space in the range of 20 to 70% of the volume, The manufacturing method of the resin model as described in any one of Claims 1-4 characterized by the above-mentioned. 6. The method for producing a resin model according to claim 5, wherein the internal hollow space is filled with a wax wax component (d). 6. The method for manufacturing a resin model according to claim 5, wherein the internal hollow space is filled with foamed urethane. Lost wax precision casting method which comprises using a resin model produced by the production method of the resin model according to any one of claims 1 to 7.

Images