JP4103974B2 - Polyester resin-coated aluminum seamless can and method for producing the same - Google Patents
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Description
【０００１】
【発明の属する技術分野】
本発明は、樹脂被覆アルミニウムシームレス缶およびその製造方法に関する。
【０００２】
【従来の技術】
アルミニウムやスチールを素材とした金属缶・容器は、その形状からスリーピース缶とツーピース缶とに大別される。スリーピース缶は、地蓋、缶胴、天蓋からなるためスリーピース缶と呼ばれている。一方ツーピース缶は、地蓋と缶胴とが一体となったもので、それに天蓋とからなるためツーピース缶、または、缶胴部に接合部がないことからシームレス缶とも呼ばれている。
【０００３】
金属缶の場合、缶内面には耐食性を確保するため塗装が施されて使用されているが、近年、熱可塑性樹脂フィルムを積層したラミネート缶が開発され、市場に出回っている。ラミネート缶は、金属素材に樹脂フィルムを積層させたものから、缶体成形加工を行うものが主であり、特にツーピース缶を得るには高度な成形加工技術を必要とする。かかる意味においても、ツーピースのラミネート缶に関わる技術は、例えば特開平７−２２４１号公報、特開平７−１９５６１９号公報、特開平８−２４４７５０号公報等、数多く提案され、開示されている。
【０００４】
ラミネート缶のメリットは、消費者側から見た場合、適用する有機樹脂フィルムにもよるが、耐内容物性、特に内容物の味、風味と言ったフレーバー性に優れている点が第一に挙げられている。一方、デメリットとしては、今度は製罐メーカー側からであるが、前述したようにツーピース缶の場合、熱可塑性樹脂フィルム被覆金属板の加工度合（又は、変形度合）が大きいので成形時に内面樹脂フィルムに傷が入ったりして、缶内面の品質確保ができなくなるため、缶体の品質検査を厳重に行う必要があることと、製品歩留りが現行の塗装缶に比べて劣ると言った点が挙げられる。
【０００５】
特に、スチール素材を用いたツーピースラミネート缶の場合、前記の傾向が大きいが、アルミニウム素材のラミネート缶でも同様なことが起こる。こうしたラミネート缶内面の樹脂フィルムの欠陥は、前述したように缶成形加工時に入るものであり、この欠陥を最小限に押さえることは、品質、製品歩留まりの点から重要な技術課題であることは言うまでもない。
【０００６】
一方、トータル缶コストの低減化から、使用金属板の薄板化や缶蓋である開口容易缶蓋（イージーオープンエンド、通称ＥＯＥ）の径を小さくすることが進められている。開口容易缶蓋について言えば、例えば、缶胴が３５０ｍｌのビール缶の場合、通称３１１と呼ばれ、缶胴直径は約９３．７ｍｍ（３×１１／１６インチφ）であり、当然巻き締める缶蓋も３１１であるが、現在は２０６（直径約６０．３ｍｍ即ち２×６／１６インチφ）や２０４（直径約５７．２ｍｍ即ち２×４／１６インチφ）となっており、更に２０２（直径約５４．０ｍｍ即ち２×２／１６インチφ）化が進められている。このことは、必然的に缶胴の開口部をより小さい径に絞る、いわゆる縮径化となり、従って缶胴に用いられている金属は勿論、その表面に被覆されている樹脂フィルムに取っても厳しい加工を受けることになる。
【０００７】
しかし、しごき加工を伴うツーピース缶成形法、特に高加工度の場合の内面の樹脂フィルムに傷その他の欠陥を入れることなく成形する手段や、また高縮径化のためのネック加工やフランジ加工で、樹脂フィルムに傷その他の欠陥を入れることなく成形する適切な方法がないのが現状である。
【０００８】
【発明が解決しようとする課題】
本発明は、こうした実情に鑑みなされたもので、樹脂フィルム欠陥のない高耐食性、高品質な樹脂被覆アルミニウムシームレス缶を歩留まりよく提供することを目的とするものである。
【０００９】
【課題を解決するための手段】
本発明の第一は、皮膜Ｃ量として５〜５０ｍｇ／ｍ ２ のリン酸またはリン酸ジルコニウムと有機樹脂の有機無機複合型化成処理皮膜を有する板厚０．２０〜０．３２ｍｍアルミニウム板の両面に、厚み１０〜５０μｍ、融点（Ｔｍ）２００〜２６０℃、冷結晶化熱（Ｈｃ）８．５〜４５．０Ｊ／ｇ、かつ融解熱（Ｈｍ）１０．５〜５０．０Ｊ／ｇ、密度１．３６ｇ／ｃｍ ３ 未満の熱可塑性ポリエステル樹脂フィルムが積層されているポリエステル樹脂被覆アルミニウム板から得られたものであって、カップへの絞り加工、カップの再絞り加工、再絞りカップのしごき加工を施し、ついでこれを加熱、冷却した後の前記熱可塑性ポリエステル樹脂フィルムの密度が１．３６ｇ／ｃｍ ３ 未満であることを特徴とするポリエステル樹脂被覆アルミニウムシームレス缶に関する。なお、前記密度は第４工程にかける前の段階のものを測定した値である。
【００１０】
前記ポリエステル樹脂フィルムを被覆する前の前記アルミニウム板の表面には、皮膜Ｃ量として５〜５０ｍｇ／ｍ2のリン酸またはリン酸ジルコニウムと有機樹脂の複合型化成処理皮膜を形成しておくことが好ましい。
【００１１】
本発明の第二は、皮膜Ｃ量として５〜５０ｍｇ／ｍ ２ のリン酸またはリン酸ジルコニウムと有機樹脂の有機無機複合型化成処理皮膜を有する板厚０．２０〜０．３２ｍｍアルミニウム板の両面に、厚み１０〜５０μｍ、融点（Ｔｍ）２００〜２６０℃、冷結晶化熱（Ｈｃ）８．５〜４５．０Ｊ／ｇ、かつ融解熱（Ｈｍ）１０．５〜５０．０Ｊ／ｇ、密度１．３６ｇ／ｃｍ ３ 未満の熱可塑性ポリエステル樹脂フィルムが被覆されているポリエステル樹脂被覆アルミニウム板を、カップへの絞り加工（第１工程）、カップの再絞り加工（第２工程）、再絞りカップのしごき加工（第３工程）、次いでネック加工・フランジ加工（第４工程）を行ってシームレス缶を製造する方法において、前記ポリエステル樹脂被覆アルミニウム板を前記の被覆樹脂のガラス転移温度（Ｔｇ）から被覆樹脂の冷結晶化温度（Ｔｃ）の範囲で、ストレッチ加工および／またはしごき加工を付加し、下記式（１）
〔数１〕
加工度＝〔（Ｂｔ−Ｗｔ）／Ｂｔ〕×１００ ・・・（１）
Ｂｔ：缶底部のアルミニウム板の板厚
Ｗｔ：缶壁部のアルミニウム板の最も薄い部位の板厚
から求められる加工度の値が１０％以内になるように絞り加工（第１工程）を行い、次いで第１工程で得られたカップを前記の被覆樹脂のガラス転移温度（Ｔｇ）から被覆樹脂の冷結晶化温度（Ｔｃ）の範囲で、ストレッチ加工および／またはしごき加工を付加し、第１工程の加工度と合せて、前記式（１）から求められる加工度の値が２５％以内になるように再絞り加工（第２工程）を行い、次に、第２工程で得られた再絞りカップの缶体温度を５０℃以下にした後、加工金型の温度を１２０℃以下に保持し、第１工程の絞り加工の加工度及び第２工程の再絞り加工の加工度と合わせて式（１）で与えられる加工度が５０〜７０％になるように第３工程のしごき加工を行い、次いで第３工程で得られた該缶体を加熱・冷却して再度ポリエステル樹脂フィルムの密度を１．３６ｇ／ｃｍ ３ 未満にした後、ネック加工・フランジ加工（第４工程）を行うことを特徴とするポリエステル樹脂被覆アルミニウムシームレス缶の製造方法に関する。
【００１２】
【発明の実施の形態】
以下、本発明の方法の実施形態について詳細に説明する。
まず、本発明におけるアルミニウム板は、アルミニウムまたはアルミニウム合金よりなる板である。
本発明の方法に適用されるアルミニウム板はとくに制限はないが、通常缶容器に用いられる３００４系アルミニウム合金や５０５２系アルミニウム合金、５０８１系アルミニウム合金等種々のアルミニウム合金が適用される。
アルミニウム合金の板厚としては、０．２０〜０．３２ｍｍのものが適用される。
板厚０．２０ｍｍ以下では、炭酸飲料やビール等を充填・密封する内圧缶の場合、耐圧強度が十分でなく缶底部が張り出した状態になる場合があり、好ましくない。
一方、０．３２ｍｍを超えた場合、缶の耐圧強度は十分確保されるが、実質的には品質過剰であり、経済的ではない。
【００１３】
板厚の限定理由は、上述のような缶の耐圧強度から限定したものである。
従って適用するアルミニウム板の機械的特性、特に耐力強度と関わりがある。即ち、耐力強度が高い場合は板厚の薄手化が可能となるが、実際に本発明を実施する際は、板厚は缶全体の強度バランスを考慮し、適宜選択することが望ましい。
【００１４】
次に、本発明のアルミニウム板表面に有する表面処理皮膜について述べる。
表面処理としては、通常アルミニウム板の絞りしごき缶の成形加工後の表面処理として使用されている、リン酸クロム酸処理やリン酸ジルコニウム処理が適用されるが、特に、缶壁部の板厚減少度が最終加工度６０％を超えるような大きい加工度の場合や前述したネック加工が厳しい高縮径の場合は、リン酸またはリン酸ジルコニウムと有機樹脂との有機無機複合型化成処理が有効である。
有機無機複合型化成処理の場合、付着量は皮膜中Ｃ量として５〜５０ｍｇ／ｍ2が良く、５ｍｇ／ｍ2以下では被覆性が劣り、防食作用および密着性が共に不十分となり、缶体成形加工後に樹脂フィルムが局部的に剥離する、いわゆるデラミが起こったり局部的な腐食が起こったり、また、耐デント性も劣り好ましくない。
一方、５０ｍｇ／ｍ2を超えると、被覆性は良好であるが、加工度が大きい缶体成形加工の場合や、特にネック加工が厳しい高縮径の場合は、皮膜が凝集破壊を起こし密着性が低下し、樹脂フィルムが剥離するといった場合があるので好ましくない。
表面処理皮膜量としては、皮膜Ｃ量として１０〜４０ｍｇ／ｍ2が好適である。
【００１５】
このようなアルミニウム板表面処理の具体的方法としては、リン酸またはリン酸とフッ化ジルコニウムと水溶性有機樹脂、例えば水溶性フェノール樹脂、水溶性アクリル樹脂等を含む水溶液に必要に応じて、反応性を促進させるためにフッ酸、ポリリン酸を添加した処理液を、アルミニウム板にロール塗布した後、水洗、乾燥し硬化させる方法や、処理液をアルミニウム板にスプレー塗布した後、水洗、乾燥し硬化させる方法、処理液にアルミニウム板を浸漬した後、水洗、乾燥し硬化させる方法、等が適宜適用できる。乾燥硬化方法としては熱風での乾燥、電気炉での乾燥等の方法が適用でき、温度は１５０〜２５０℃で乾燥時間は１０秒〜２分程度である。
【００１６】
次に、本発明の方法に適用されるポリエステル樹脂フィルムについて説明する。
本発明では樹脂フィルムは、熱可塑性ポリエステル樹脂フィルムが適用される。
本発明において、被覆する樹脂フィルムを熱可塑性ポリエステル樹脂フィルムに限定した理由は、▲１▼耐熱性が良い、▲２▼内容物のフレーバーが確保される、と言った、例えばポリエチレンやポリプロピレンなどのポリオレフィン系樹脂フィルムにない、缶用途に適した特性を有しているからである。
熱可塑性ポリエステル樹脂としては、例えばポリエチレンテレフタレート（ＰＥＴ）、ポリブチレンテレフタレート（ＰＢＴ）、ポリエチレンイソフタレート（ＰＥＩ）のようなホモポリマーや、例えばポリエチレンテレフタレートとポリエチレンイソフタレートとの共重合樹脂であるコーポリマーや、またこうしたホモポリマーやコポリマーのブレンド樹脂等が適用される。
【００１７】
樹脂フィルムの厚みとしては、１０〜５０μｍである。
缶の内面に当たる面に積層されるフィルム厚みは、缶内面の耐食性の点から限定されるものであり、１０μｍ未満では缶の成形加工後に充填する内容物にもよるが、十分な耐食性を確保するのは難しい場合がある。
一方、５０μｍを超えると、内容物に対し耐食性は十分確保されるが、実質的に過剰品質となり、経済的でない。
フィルム厚みとしては、１２〜４０μｍが品質および経済性からは好ましい範囲である。
【００１８】
また、本発明の方法を実施する際フィルム厚の選定は、後述する缶壁部の薄肉化の加工度との関係があることも選定の際の重要な要素である。
即ち、加工度が高い場合は、当然その加工度に応じフィルム厚みも薄くなるため、その結果として、缶内面の耐食性も低下する。従ってあらかじめ厚手の樹脂フィルムを使用することが望ましいし、一方、加工度が低い場合はそれに応じてあらかじめ薄手のフィルムを適用することが可能となる。
【００１９】
本発明ではポリエステル樹脂は、融点（Ｔｍ）が２００〜２６０℃の樹脂フィルムとする。成形加工時に起こる樹脂フィルムの欠陥は、特にしごき加工時に起こり易いことは、発明者等の研究から明らかになっており、その原因はほぼ次の二点に集約されると考えられる。即ち、成形加工の際に金属の加工熱が発生し、樹脂フィルムの特性を大きく変化させるためで、熱による樹脂フィルムの特性変化は、（１）樹脂フィルムの軟化、（２）樹脂フィルムの結晶化、等がある。
【００２０】
（１）の樹脂フィルムの軟化は、しごき加工時に樹脂フィルムがパンチに付着してしまい、パンチが抜け難くなる、いわゆる離型性不良が起こり、内面の樹脂フィルムに傷を付ける原因となる。
また、離型性不良がひどい場合は、缶体の開口部近傍が座屈し、正規の缶体高さが得られない事態が起こる場合もある。
一方、缶外面側の樹脂フィルムも、しごきダイスによる「かじり」と言われる缶高さ方向への直線的な傷が入り易くなる。外面の「かじり」による傷が入った場合は、その後施される印刷の仕上がり外観を損ねる結果となる。
【００２１】
（２）の樹脂フィルムの結晶化は、しごき加工時の発熱と延伸加工により、樹脂フィルムは配向結晶化が起こり、その結果、高加工に耐えられなくなり樹脂フィルムに亀裂が入る原因となる。
いずれにしても、内面フィルムの欠陥発生に繋がり好ましくない。
【００２２】
前記の樹脂フィルムの熱による軟化の程度は、樹脂の融点（Ｔｍ）と関わっており、融点が下限値の２００℃以下では、たとえ潤滑剤が塗布されていても離型性が劣り、内面樹脂フィルムの欠陥発生原因になったり、正規の缶体高さが得られない場合が起こり好ましくない。
一方、上限値の２６０℃以上では、高融点化に伴う離型性の更なる効果は期待できず飽和する。
樹脂フィルムの融点（Ｔｍ）は前記の離型性や耐かじり性の観点から限定したものであるが、しごき加工時の発熱量は後述する加工度との関係もあり、樹脂フィルムの融点だけで離型性や耐かじり性の良否を決められるものではないが、基本的には融点は高い方が有利であり、好ましくは２１０〜２５５℃、更に好ましくは２２０〜２５５℃が好適である。
【００２３】
本発明では、ポリエステル樹脂フィルムは冷結晶化熱（Ｈｃ）８．５〜４５．０Ｊ／ｇ、かつ融解熱（Ｈｍ）１０．５〜５０．０Ｊ／ｇである。冷結晶化熱（Ｈｃ）や融解熱（Ｈｍ）は、樹脂フィルムの結晶性を示す指標となり、両者とも熱量が大きいほど結晶性の高い樹脂フィルムであることを指す。
高結晶性の樹脂フィルムの場合、前述したようにしごき加工時の発熱と延伸加工により、樹脂フィルムは配向結晶化が起こり、その結果、高加工に耐えられなくなり、樹脂フィルムに亀裂が入る要因となる。また、結晶性ではない、いわゆる非晶質樹脂の場合は、一般的に柔らかい樹脂であり、この場合は前述した離型性不良となる危険性が高い。かかる意味から、本発明の冷結晶化熱（Ｈｃ）や融解熱（Ｈｍ）を限定したものであり、もし冷結晶化熱（Ｈｃ）が８．５Ｊ／ｇ未満であったりまたは融解熱（Ｈｍ）が１０．５Ｊ／ｇ未満であったりした場合には、成形加工時に配向結晶化し難く、樹脂フィルムに亀裂状の欠陥が発生し難いと言った有利な点はあるが、パンチとの離型性に劣り、かえって内面樹脂フィルムの欠陥を発生させ易くなり好ましくない。一方、冷結晶化熱（Ｈｃ）が４５．０Ｊ／ｇ超であったり融解熱（Ｈｍ）が５０．０Ｊ／ｇ超であったりした場合は、パンチとの離型性は全く問題ないが、結晶性が高すぎて成形加工で樹脂フィルムの亀裂欠陥が発生する場合があり好ましくない。
特に、高加工度の成形加工では、亀裂欠陥が発生する危険性が高い。
【００２４】
成形加工における、主にしごき加工時の樹脂フィルムの配向結晶化の程度は、後述する成形時の加工温度条件にも関係あるが、基本的には樹脂固有の結晶性によるところが大きく、かかる意味において、冷結晶化熱（Ｈｃ）および融解熱（Ｈｍ）の最適範囲は、冷結晶化熱（Ｈｃ）は１０．５〜４０．０Ｊ／ｇ、融解熱（Ｈｍ）は１２．５〜４８．０Ｊ／ｇが離型性や耐かじりの点から好ましく最適である。
【００２５】
本発明の方法に適用される熱可塑性ポリエステル樹脂フィルムの密度は１．３６ｇ／ｃｍ ３ 未満である。
密度は樹脂の結晶状態を示す指標となり、例えば、熱や延伸によって結晶化が進み、密度は大きくなる。密度が１．３６ｇ／ｃｍ ３ 未満であるということは、ポリエステル樹脂フィルムの結晶状態としては実質的に非晶質であることを示す。
【００２６】
ラミネート板に被覆した樹脂フィルムを非晶質にする理由は、その後行うカップの絞り加工、カップの再絞り加工、更にしごき加工において、樹脂フィルムの加工性を十分に確保することを目的にしたもので、密度が１．３６ｇ／ｃｍ ３ 以上になると、結晶性の低いポリエステル樹脂フィルムでも成形加工にフィルムが耐えられずフィルムに亀裂欠陥が激しく起こる場合があり好ましくない。
特に、加工度が大きい時は、しごき加工時の発熱と併せて引き延ばし加工により、樹脂フィルムの配向結晶化が一層進み、その結果加工に追随し難くなり、前記の挙動が顕著に現れ、缶体の耐食性が十分に確保できない場合がしばしば起こる。従って、密度が大きい、結晶化した状態からの成形加工は、高加工度に対しては極めて難しく不適である。
【００２７】
更に本発明では、カップの絞り加工、カップの再絞り加工、更にしごき加工の缶成形加工を施した後、得られた缶体を加熱・冷却し再度樹脂フィルムの密度を１．３６ｇ／ｃｍ ３ 未満にした後、ネック加工およびフランジ加工を行う。カップの絞り加工、カップの再絞り加工、更にしごき加工を経て得られる缶体は、この時の加工により、樹脂フィルムの密着性は著しく低下しており、この状態でネック加工およびフランジ加工を行うと、樹脂フィルムは剥離し易い。そこで、本発明では、缶体を加熱・冷却し再度樹脂フィルムの密度を１．３６ｇ／ｃｍ ３ 未満にした後、ネック加工およびフランジ加工に供するものである。樹脂フィルムの密度を１．３６ｇ／ｃｍ ３ 未満にすることで、樹脂フィルムは剥離やクラックが発生することなくネック加工およびフランジ加工を行うことができる。特に、ネック加工率が高い、高縮径化への対応については、樹脂フィルムの高加工密着性が一層必要となり、この場合樹脂フィルムの密度は低い方が非晶質化度が高いため、良好となる。樹脂フィルムの密度を１．３６ｇ／ｃｍ ３ 未満に限定した理由は、前記の理由からで、特に第１工程の絞り加工の前の密度としては、１．３５ｇ／ｃｍ ３ 未満が最適である。
【００２８】
次に、本発明の缶体の成形加工方法について述べる。
本発明の方法では、ポリエステル樹脂フィルムを被覆したラミネートアルミニウム板を、絞り加工にてカップ状に成形する第１工程と、次いで第１工程で得たカップを更に再絞り加工し、第１工程で得たカップより缶径が小さく缶高さの高いカップを成形する第２工程と、次いでこのカップの缶壁部をパンチとしごきダイスの間に通し、缶壁を薄くのばすいわゆるしごき加工を行う第３工程と、第３工程で得た缶体を正規な缶高さに切断するトリミングを行った後、缶開口部を縮径にするネック加工と天蓋を巻き締めるのに必要なフランジ加工を行う第４工程からなっている。
【００２９】
前記の成形加工方法における第１工程の絞り加工、第２工程の再絞り加工、第３工程のしごき加工は、いずれも缶壁部の板厚減少を伴った加工であるが、第４工程のネック・フランジ加工は、事実上板厚減少は伴わない加工である。従って、シームレス缶として成形加工されたものは、第３工程後の缶体が最終缶体となる。
【００３０】
第１工程の絞り加工は、ラミネート板の温度を被覆樹脂フィルムのガラス転移温度（Ｔｇ）から冷結晶化温度（Ｔｃ）の範囲で、ストレッチ加工および／またはしごき加工を付加し、加工度として式（１）から求められる値として１０％以内になるように行う。
【００３１】
また、第２工程の再絞り加工も、第１工程で得たカップの温度を被覆樹脂フィルムのガラス転移温度（Ｔｇ）から冷結晶化温度（Ｔｃ）の範囲で、ストレッチ加工および／またはしごき加工を付加し、加工度として式（１）から求められる値として第１工程の加工度と合わせて２５％以内で行う。
【００３２】
第３工程のしごき加工は、再絞り加工で得たカップの温度を５０℃以下にした後、加工金型の温度を１２０℃以下に保持し、しごき加工後の最終缶体の加工度として式（１）で求められる値として、第１工程および第２工程での加工度と合わせて５０〜７０％の範囲で成形加工を行うものである。
〔数２〕
加工度＝〔（Ｂｔ−Ｗｔ）／Ｂｔ〕×１００ ・・・（１）
Ｂｔ：缶底部のアルミニウム板の板厚
Ｗｔ：缶壁部のアルミニウム板の最も薄い部位の板厚
【００３３】
まず、本発明の缶体成形方法における加工温度について述べる。
本発明の方法における第１工程の絞り加工および第２工程の再絞り加工を、被覆樹脂フィルムのガラス転移温度（Ｔｇ）から冷結晶化温度（Ｔｃ）の範囲に限定した理由は絞り加工によるカップ缶底コーナー部の樹脂フィルムの健全性を確保するためである。
【００３４】
カップ缶底コーナー部の樹脂フィルムは、パンチが最初に当たる個所であり、高い衝撃がかかる。そして、この部位では樹脂フィルムにマイクロクラックが生じやすい。特に、第１工程の絞り加工によるカップ缶底コーナー部は、第２工程の再絞り加工後はカップの缶壁部（側壁部）となり、更に第３工程のしごき加工で延伸されるため、第１工程の絞り加工でカップ缶底コーナー部の樹脂フィルムにマイクロクラックが生じた場合、その後の加工で、激しい樹脂フィルム欠陥となってしまう危険性が高くなり好ましくない。
従って、特に絞り加工によるカップ缶底コーナー部の樹脂フィルムの健全性確保は、缶体の内面品質の点で重要な要素となる。かかる意味において、樹脂フィルムのガラス転移温度（Ｔｇ）以下での絞り加工は、カップの缶底コーナー部の樹脂フィルムにマイクロクラックが生じ易く、好ましくない。
【００３５】
一方、冷結晶化温度（Ｔｃ）以上で絞り加工を行なった場合は、樹脂の熱結晶化が起こり易くなり、樹脂フィルムの衝撃強度が低下し、カップ缶底コーナー部の樹脂フィルムにマイクロクラックが生じ易いこと、更には、前述したように熱結晶化が起こり易くなることはしごき加工で樹脂フィルムの欠陥の発生につながる危険性が高くなること等から、好ましくない。
【００３６】
第１工程の絞り加工および第２工程の再絞り加工を、被覆樹脂フィルムのガラス転移温度（Ｔｇ）から冷結晶化温度（Ｔｃ）の範囲に限定したのは、上記の理由からで、好ましくはガラス転移温度（Ｔｇ）＋５℃から冷結晶化温度（Ｔｃ）−１０℃の範囲が良い。
【００３７】
絞り加工および再絞り加工に供するラミネート板やカップの温度とは、接触式温度計等で測定される表面温度を指し、ラミネート板やカップの温度を、被覆樹脂フィルムのガラス転移温度（Ｔｇ）から冷結晶化温度（Ｔｃ）の範囲に制御する手段としては、ラミネート板やカップを電気炉中で加熱する方法や熱風で加熱する方法など、常用の手段が適用される。
【００３８】
また、絞り加工や再絞り加工を行なう金型の表面温度をガラス転移温度（Ｔｇ）から冷結晶化温度（Ｔｃ）の範囲に加熱して成形加工する加温加工方法も、ラミネート板やカップを加熱した場合と同様な効果が得られるが、この場合は、絞り加工や再絞り加工を行なう前のラミネート板やカップの表面温度により、加工金型の設定温度を決める必要があるが、ラミネート板やカップの表面温度が、例えば常温の場合は、設定温度はガラス転移温度（Ｔｇ）より５〜１０℃高めに設定すると良い。
【００３９】
また、前記の常用の手段でラミネート板やカップの加熱をガラス転移温度（Ｔｇ）から冷結晶化温度（Ｔｃ）の範囲にして成形加工する方法と、加工を行なう金型の表面温度をガラス転移温度（Ｔｇ）から冷結晶化温度（Ｔｃ）の範囲に加熱して成形加工する加温加工方法の併用も可能であり、設備にあった手段が採用できる。
【００４０】
第１工程の絞り加工、第２工程の再絞り加工に次いで行なう第３工程のしごき加工は、再絞り加工で得たカップの温度を５０℃以下にした後、加工金型の温度を１２０℃以下に保持して行なう。
なお、ここでも再絞り加工で得たカップの温度とは、カップの表面温度を指し、加工金型の温度とは、金型の表面温度を指す。
【００４１】
前述したように、樹脂フィルムの欠陥は、内外面とも、しごき加工で最も起こり易い。
しごき加工は前述したように、缶壁部のみをパンチとしごきダイスの間のクリアランスを瞬時に通し薄肉化する加工であるため、加工の際には金属の激しい加工熱が発生し、樹脂フィルムの特性を大きく変化させる。
熱による樹脂フィルムの特性変化は、（１）樹脂フィルムの軟化、（２）樹脂フィルムの結晶化等があるが、いずれの特性変化も成形加工による樹脂フィルムの欠陥の発生原因となることは前述した通りである。
【００４２】
従って、しごき加工の温度制御は樹脂フィルムの欠陥発生防止の点から重要な要素で、本発明の方法では第２工程の再絞り加工で得たカップの缶体温度を５０℃以下にして、しごき加工を行なう。
カップの缶体温度が５０℃を超えると、内面側の樹脂フィルムは加工パンチとの離型性が劣り、又外面側の樹脂フィルムはかじりが起こり易くなり、内外面とも、樹脂フィルムを傷付ける原因となる。
また、加工金型の温度は、１２０℃以下でしごき加工を行なうが、１２０℃を超える温度では、樹脂フィルムと成形加工金型との離型性が悪く、樹脂フィルムの傷つきが激しくなって、缶内面側は耐食性確保が難しいと共に、場合によっては樹脂フィルムと成形加工金型との離型の際に缶胴部が座屈し、正常な缶体が得られないと言った事態が発生することがある。更に、しごき加工における加工金型が１２０℃を超える温度では、ポリエステル樹脂フィルムの、配向結晶化が急激に進み、その結果、樹脂フィルムの亀裂欠陥が発生し易くなる危険性が高くなる。また、外面側の樹脂フィルムはかじりが激しく起こり、その後行なわれる印刷での外観性が劣るだけでなく、場合によってはかじり部を起点とする缶胴破断が起こる。
従って、しごき加工における加工温度は、缶体の内外面の品質確保の点から極めて重要で、本発明のような樹脂フィルムを被覆したラミネートアルミニウム板から、良好な品質を有する缶体を得るには加工金型の温度を、１２０℃以下に保持することが必要である。
【００４３】
なお、しごき加工の際、加工金型全体の温度を１２０℃以下に保持して行なうのが好ましいが、特に加工度が低い場合は加工パンチの温度を１２０℃以下に保持するだけでも、樹脂フィルムの欠陥防止効果は得られる。しごき加工の際の加工金型の温度、また加工パンチの温度は、基本的には低い方が良く、好適な温度としては１００℃以下にするのが好ましい。
【００４４】
しごき加工はしごきダイス１枚で行なう１段しごき加工や、２枚乃至３枚で行なう多段しごき加工などが適用できる。
【００４５】
再絞り加工で得たカップの缶体温度を５０℃以下にする手段としては、絞り加工で得たカップが５０℃を超えている場合は冷風を当てる等の手法が採用でき、また、加工金型の温度を１２０℃以下にする手段としては、金型に冷却水を通す方法、水、または潤滑成分を水に溶解または分散させたものを吹きかけて冷却する方法、更にはこれらの併用と言った方法が採用できる。どの手法を採用するかは、設備との関係で適宜選択することが好ましい。
【００４６】
次に、本発明の缶体成形方法における加工度について述べる。
前述したように、第１工程の絞り加工の加工度は、下記の式（１）から求められる値として１０％以内になるように行ない、第２工程の再絞り加工の加工度は、式（１）から求められる値として第１工程での加工度と合わせて２５％以内になるように成形加工を行ない、第３工程のしごき加工の加工度は、式（１）から求められる加工度として第１工程および第２工程での加工度と合わせて５０〜７０％の範囲で成形加工を行なうものである。
〔数３〕
加工度＝〔（Ｂｔ−Ｗｔ）／Ｂｔ〕×１００ ・・・（１）
Ｂｔ：缶底部のアルミニウム板の板厚
Ｗｔ：缶壁部のアルミニウム板の最も薄い部位の板厚
【００４７】
式（１）から求められる値として、第１工程の絞り加工の加工度が１０％以内になるように、第２工程の再絞り加工後の加工度が第１工程での加工度と合わせて２５％以内になるように行なう理由は、一度の加工で高加工度の成形を行なうと、加工時の熱と伸ばし加工により、樹脂フィルムが配向結晶化し、成形に耐えられずフィルムに亀裂が発生する場合があるからで、それを避けるためには、上記のように順次加工度を上げた加工を行ない、最終のしごき加工の加工度をなるべく低く抑える方が良い。かかる意味から本発明の方法によれば、缶内外面の樹脂フィルムの健全性が確保される成形加工が可能となる。
【００４８】
特に、第２工程の再絞りカップの段階で、缶壁部の樹脂フィルムが完全に結晶化していない状態にしておくことが、第３工程のしごき加工後の缶体内面の樹脂フィルムの健全性を確保する上で重要であり、再絞り加工後の加工度として２５％以内であれば、しごき加工後の内外面の樹脂フィルムの健全性は確保される。
【００４９】
なお、本発明の方法では、前記の第１工程および第２工程で行なう、ストレッチ加工および／またはしごき加工を付加した絞り加工および再絞り加工は、ストレッチ加工のみを付加した方法でも、あるいはしごき加工のみを付加した方法でも、又はストレッチ加工としごき加工の両方を付加した方法でも、いずれの方法でも良く、適宜適用される。
【００５０】
また、本発明のポリエステル樹脂被覆アルミニウム板では、熱可塑性樹脂フィルムが被覆されていない、アルミニウム板やＳｎメッキ鋼板（ブリキ）等の金属の絞りしごき加工方法として現在行なわれている絞り加工によりカップ状にする第１工程と、次いで第１工程で得たカップを更に再絞り加工し、第１工程で得たカップより缶径が小さく缶高さの高いカップを成形すると同時に、このカップの缶壁部をパンチとしごきダイスの間に通し、缶壁を薄くするしごき加工を同一成形加工機にて行なう第２工程と、第２工程で得た缶体を適当な缶高さに切断するトリミングを行なった後、缶開口部を縮径にするネック加工と天蓋を巻き締めるのに必要なフランジ加工を行なう第３工程から成る方法でも適用可能であるが、この成形方法においても上記の絞り加工は被覆されたポリエステル樹脂のガラス転移温度（Ｔｇ）から冷結晶化温度（Ｔｃ）の範囲にして行ない、再絞り加工およびしごき加工は、加工金型全体の温度を１２０℃以下、もしくは加工度が低い場合は加工パンチの温度を１２０℃以下で行なう事が望ましい。
【００５１】
ポリエステル樹脂フィルム被覆ラミネートアルミニウム板の製造方法としては、加熱されたアルミニウム板の表面に樹脂フィルム供給してロール間で熱圧着し積層させた後、直ちに急冷して、非晶質にする方法や、溶融した樹脂を押し出し、アルミニウム板に供給し積層させ、直ちに急冷して、非晶質にする方法や、一度積層したポリエステル樹脂を、必要に応じ更に樹脂の融点以上に加熱した後直ちに急冷して、非晶質にする方法等が適用できる。
【００５２】
アルミニウム板の加熱方法としては、電気炉中で加熱する方法、熱風による加熱方法、加熱ロールに接触させて加熱する方法等の加熱方法が採用できる。
【００５３】
【実施例】
以下に実施例を挙げて本発明を説明するが、本発明はこれにより何ら限定されるものではない。尚、本実施例等で行った評価方法は以下のとおりである。
【００５４】
（１）樹脂フィルムの密度は、密度勾配管法にて測定した。
（２）樹脂フィルムの融点、冷結晶化熱および融解熱の測定は、示差走査熱量計（ＤＳＣ）で、１０℃／分の昇温速度で測定し、融点はピークをその温度とし、冷結晶化熱および融解熱はそれぞれの山の積分値を冷結晶化熱、融解熱とした。
（３）カップの絞り加工後の缶底コーナー部樹脂フィルムの健全性については、マイクロクラックを、光学顕微鏡で観察しその程度を評価した。
評価は次のように評価基準を設定して行った。
〇：クラックなく良好 □：軽微なクラック発生
△：明確なクラック発生 ×：激しいクラック発生
（４）フィルムと加工パンチの離型性は、成形缶上部に起こる缶体の座屈程度を観察し評価した。
離型性の評価は、次のように評価基準を設定し行った。
〇：缶開口部の座屈なく良好 □：軽微な缶開口部の座屈あり
△：開口部円周の１／３程度座屈 ×：開口部円周の１／３以上座屈（５）缶外面の耐かじり性は、成形した缶体胴壁部外面のかじり発生程度を観察し評価した。
〇：かじりなく良好 □：軽微なかじり発生
△：外面の１／３未満にかじり発生 ×：外面の１／３以上に激しいかじり発生（６）ネック加工およびフランジ加工での樹脂フィルムの状態については、剥離状況やクラック発生状況を肉眼観察や光学顕微鏡で観察し評価した。
剥離状況やクラック発生状況の評価は、次のように評価基準を設定し行った。
〇：剥離やクラックなく良好 □：軽微なクラック発生
△：一部剥離やクラック発生 ×：剥離発生
（７）缶内面の樹脂フィルムの傷付き程度については、１．０ｗｔ％食塩水に界面活性剤０．１ｗｔ％を添加した電解液で、缶体を陽極、陰極を銅線とし、印加電圧６Ｖで３秒後の電流値を測定し、樹脂フィルムの皮膜の健全性の評価とした（以降、この評価法をＱＴＶ試験と称する）。なお本発明においてこの数値の上限は２〜３ｍＡ／缶である。
（８）耐デント性の評価については、３５０ｍｌ缶に水を充填し、１２５℃で３０分レトルト処理を行なった後、５℃で１日冷やし、高さ８０ｃｍの位置から角度６０°で缶底部を下に落下させ、開缶乾燥した後、衝撃変形部以外を絶縁塗料でシールし、衝撃変形部の樹脂フィルムの欠陥発生程度をＱＴＶ試験に用いる電解液で、サンプルを陽極、陰極を銅線とし印加電圧６Ｖで３秒後の電流値を測定し、樹脂フィルムの皮膜の健全性の評価とした（以降、デント性はこの手法による評価結果を示す）。
＊1：第１工程
＊2：第２工程
＊3：第３工程
＊4：第４工程
＊5：比＝比較例
＊6：実＝実施例
【００５５】
実験例１
表面に皮膜Ｃ量として１５ｍｇ／ｍ２のリン酸−フェノール樹脂の複合化成処理皮膜を有する、板厚０．２６ｍｍのアルミニウム板（３００４系合金）の両面に、ガラス転移温度が６７℃、冷結晶化温度が１２３℃、冷結晶化熱が１７．８Ｊ／ｇ、融点が２３８℃、融解熱が１８．０Ｊ／ｇに二軸延伸ポリエステル樹脂フィルムの厚みが８μｍ（テスト１）、１５μｍ（テスト２）、２０μｍ（テスト３）、３０μｍ（テスト４）、４０μｍ（テスト５）、５０μｍ（テスト６）を熱圧着で被覆した後、加熱・急冷し非晶質化ポリエステル樹脂フィルムラミネート板を作成した。各テスト板の樹脂フィルムの密度（ｇ／ｃｍ ３ ）は、表１〜２に示した。
【００５６】
こうして得られたラミネート板に成形用潤滑剤を塗油した後、加熱し板温７０℃でストレッチ加工およびしごき加工を付加した加工度が７％の絞り加工を行った。この時得られたカップの、缶底コーナー部の樹脂フィルムのマイクロクラック発生状況について調べた。次いで、得られたカップを板温７０℃に加熱し、ストレッチ加工およびしごき加工を付加した加工度（この加工度は、第１工程の絞り加工の加工度と合わせた加工度を指し、以下同様とする）が１５％の再絞り加工を行った後、再絞り加工で得られたカップの温度を４０℃にして、金型温度８０℃で最終加工度（この加工度は、第１工程の絞り加工の加工度及び第２工程の再絞り加工の加工度と合わせた加工度を指し、以下同様とする）が６０％のしごき加工を行い、３５０ｍｌビール缶サイズのシームレス缶を作成した。
こうして得られた缶体について、樹脂フィルムと金型との離型性、外面樹脂フィルムの耐かじり性の程度を調べた。
更に、前記で得られたシームレス缶を再度加熱・急冷し樹脂フィルムを非晶質にした後、缶径呼称２０２（直径約５４．０ｍｍ）ネック加工およびフランジ加工を行った。ネック加工およびフランジ加工を行なう第４工程にかける前の樹脂フィルムの密度（ｇ／ｃｍ ３ ）は表１〜２に示した。
こうして得た缶体について、ネック加工およびフランジ加工部の樹脂フィルムの剥離やクラック発生状況を調べると共に、ＱＴＶ試験およびデント性で缶内面の品質を調べた。その評価結果は表３〜４に示した。
【００５７】
【表１】
【表２】
【表３】
【表４】
（考察）
表１〜４から、本発明の実施例は比較例のテスト１に比べ、ＱＴＶ値は低い値を示し良好な樹脂フィルムの健全性を有していることが分かる。また、デント性についても、本発明の実施例は比較例に比べ、良好であることが分かる。一方、離型性、耐かじり性およびフランジ加工部およびネック加工部の状況については、本発明の実施例および比較例共に良好であった。
【００６２】
実験例２
実験例１で用いた複合化成処理皮膜を有するアルミニウム板の両面に、樹脂フィルムの融点１９３℃、冷結晶化熱６．３Ｊ／ｇ、融解熱８．４Ｊ／ｇのフィルム（テスト７）、融点２０５℃、冷結晶化熱８．９Ｊ／ｇ、融解熱１３．０Ｊ／ｇのフィルム（テスト８）、融点２１８℃、冷結晶化熱１４．８Ｊ／ｇ、融解熱１５．３Ｊ／ｇのフィルム（テスト９）、融点２３０℃、冷結晶化熱１８．７Ｊ／ｇ、融解熱２０．７Ｊ／ｇのフィルム（テスト１０）融点２４２℃、冷結晶化熱１９．６Ｊ／ｇ、融解熱２３．２Ｊ／ｇのフィルム（テスト１１）、融点２５２℃、冷結晶化熱２４．４Ｊ／ｇ、融解熱２９．３Ｊ／ｇのフィルム（テスト１２）、融点２５７℃、冷結晶化熱４１．５Ｊ／ｇ、融解熱４６．１Ｊ／ｇのフィルム（テスト１３）、融点２６１℃、冷結晶化熱４６．０Ｊ／ｇ、融解熱５３．５Ｊ／ｇのフィルム（テスト１４）の、それぞれの厚みが２０μｍの二軸延伸ポリエステル樹脂フィルムを熱圧着で被覆した後、加熱・急冷し非晶質化ポリエステル樹脂フィルムラミネート板を作成した。各テスト板の樹脂フィルムの密度（ｇ／ｃｍ ３ ）は、表５〜６に示した。
【００６３】
こうして得られたラミネート板に成形用潤滑剤を塗油した後、加熱し板温７５℃でしごき加工を付加した加工度が５％の絞り加工を行った。この時得られたカップの、缶底コーナー部の樹脂フィルムのマイクロクラック発生状況について調べた。
次いで、得られたカップを温度７５℃に加熱し、ストレッチ加工およびしごき加工を付加した加工度が２２％の再絞り加工を行った後、再絞り加工で得られたカップの温度を２５℃にして、金型温度８０℃で最終加工度が６０％のしごき加工を行い、３５０ｍｌビール缶サイズのシームレス缶を作成した。
こうして得られた缶体について、樹脂フィルムと金型との離型性、外面樹脂フィルムの耐かじり性の程度を調べた。
更に、前記で得られたシームレス缶を再度加熱・急冷し樹脂フィルムを非晶質にした後、缶径呼称２０２（直径約５４．０ｍｍ）のネック加工およびフランジ加工を行った。ネック加工およびフランジ加工にかける前の樹脂フィルムの密度（ｇ／ｃｍ ３ ）は表５〜６に示した。
こうして得た缶体について、ネック加工部およびフランジ加工部の樹脂フィルムの剥離やクラック発生状況を調べると共にＱＴＶ試験およびデント性で缶内面の品質を調べた。その評価結果を表７〜８に示した。
【００６４】
【表５】
【表６】
【表７】
【表８】
（考察）
表７〜８から、比較例のテスト７は金型離型性や耐かじり性が劣り、比較例のテスト１４はＱＴＶ値が高く、デント性も劣る。それに対し本発明の実施例のテスト８〜１３は金型離型性や耐かじり性が良好で、またＱＴＶ値、デント性も低い値を示し、良好な樹脂フィルムの健全性を有していることが分かる。
【００６９】
実験例３
表面に皮膜Ｃ量として１５ｍｇ／ｍ２のリン酸−フェノール樹脂の複合化成処理皮膜を有する、板厚０．２８ｍｍのアルミニウム板（３００４系合金）の両面に、実験例２のテスト１１で用いたフィルムを熱圧着条件を変えて被覆した後、必要に応じ加熱冷却し、密度の異なるポリエステル樹脂フィルムラミネート板を作成した。得られたラミネート板の樹脂フィルムの密度（ｇ／ｃｍ ３ ）は１．３４６（テスト１５）、１．３５１（テスト１６）、１．３６４（テスト１７）、１．３７５（テスト１８）であった。こうして得られたラミネート板に成形用潤滑剤を塗油した後、加熱し板温７０℃でストレッチ加工を付加した加工度が５％の絞り加工を行った。
【００７０】
この時得られたカップの、缶底コーナー部の樹脂フィルムのマイクロクラック発生状況について調べた。
次いで、得られたカップを温度７０℃に加熱し、ストレッチ加工およびしごき加工を付加した加工度が２２％の再絞り加工を行った後、再絞り加工で得られたカップの温度を４０℃にして、金型温度１００℃で最終加工度が６３％のしごき加工を行い、３５０ｍｌビール缶サイズのシームレス缶を作成した。
ラミネート樹脂フィルムの物性は表９に示した。こうして得られた缶体について、樹脂フィルムと金型との離型性、外面樹脂フィルムの耐かじり性およびＱＴＶ試験で内面樹脂フィルムの健全性を調べた。その評価結果は表１０に示した。
【００７１】
【表９】
【表１０】
（考察）
表１０から、本発明の実施例は比較例のテスト１７、１８に比べ、ＱＴＶ値は低い値を示し、良好な樹脂フィルムの健全性を有していることが分かる。離型性については本発明の実施例も比較例も良好であった。
【００７４】
実験例４
実験例２のテスト１１で得られたラミネート板に、成形用潤滑剤を塗油した後加熱し、板温５０℃（テスト１９）、７０℃（テスト２０）、９０℃（テスト２１）、１１０℃（テスト２２）、１２０℃（テスト２３）、１３０℃（テスト２４）にて、ストレッチ加工およびしごき加工を付加した加工度が７％の絞り加工を行った。この時得られたカップの、缶底部コーナーの樹脂フィルムのマイクロクラック発生状況について観察した。
次いで、得られたカップを板温７０℃に加熱し、ストレッチ加工およびしごき加工を付加した加工度が２２％の再絞り加工を行った後、再絞り加工で得られたカップの温度を４０℃にして、金型温度８０℃で最終加工度が６０％のしごき加工を行い、３５０ｍｌビール缶サイズのシームレス缶を作成した。
また、前記のテスト２０で得られた再絞り加工のカップについて、温度を３０℃（テスト２５）、４０℃（テスト２６）、５０℃（テスト２７）、６０℃（テスト２８）にした後、金型温度８０℃で最終加工度が６０％のしごき加工を行い、３５０ｍｌビール缶サイズのシームレス缶を作成した。尚、比較のため前記テスト２４で得た絞りカップの温度を７０℃にし、ストレッチ加工およびしごき加工を付加した加工度が２２％の再絞り加工を行った後、カップ温度を４０℃（テスト２９）、６０℃（テスト３０）にし、金型温度８０℃で最終加工度が６０％のしごき加工を行い、３５０ｍｌビール缶サイズのシームレス缶を作成した。樹脂フィルムの物性、成形条件は表１１〜１３に示した。
こうして得られた缶体について、樹脂フィルムと金型との離型性、外面樹脂フィルムの耐かじり性およびＱＴＶ試験で内面樹脂フィルムの健全性を調べた。その評価結果を表１４〜１６に示した。
【００７５】
【表１１】
【表１２】
【表１３】
【表１４】
【表１５】
【表１６】
（考察）
表１１〜１６から、本発明の実施例は比較例のテスト１９、２４、２８、２９、３０に比べ、カップ缶底コーナー部のクラック発生、金型離型性、耐かじり性が全て良好で、ＱＴＶ値も低く良好な樹脂フィルムの健全性を有していることが分かる。
【００８２】
実験例５
実験例２のテスト１１から得られた最終加工度が６０％のシームレス缶を、再度加熱・急冷した後、缶径呼称２０２（直径約５４．０ｍｍ）のネック加工、フランジ加工を行い、樹脂フィルムの剥離状況およびクラックの発生状況を観察すると共に、缶内面の品質について、ＱＴＶ試験およびデント性を調べた。ネック加工およびフランジ加工にかける前の樹脂フィルムの密度（ｇ／ｃｍ ３ ）は１．３４０（テスト３１）、１．３５３（テスト３２）、１．３６９（テスト３３）、１．３８６（テスト３４）である。樹脂フィルム物性と成形条件は表１７に、その評価結果は表１８に示した。
【００８３】
【表１７】
【表１８】
（考察）
表１８から、本発明の実施例は比較例のテスト３３、３４に比べ、ネック加工およびフランジ加工時に発生する樹脂フィルムの剥離やクラックが発生し難いことが分かる。また得られる缶体内面のＱＴＶ試験およびデント性値は小さく、優れた樹脂フィルムの健全性を有していることが分かる。
【００８６】
実験例６
皮膜Ｃ量として３ｍｇ／ｍ２（テスト３５）、８ｍｇ／ｍ２（テスト３６）、１５ｍｇ／ｍ２（テスト３７）、３２ｍｇ／ｍ２（テスト３８）、４６ｍｇ／ｍ２（テスト３９）、５８ｍｇ／ｍ２（テスト４０）の複合化成処理皮膜を有する、板厚０．２８ｍｍのアルミニウム板（３００４系合金）の両面に、実験例２のテスト１１で用いた二軸延伸ポリエステル樹脂フィルムを熱圧着で被覆した後、加熱・急冷し非晶質化ポリエステル樹脂フィルムラミネート板を作成した。各テスト板の樹脂フィルムの密度（ｇ／ｃｍ ３ ）は、表１９〜２０に示した。
こうして得たラミネート板に成形用潤滑剤を塗油した後加熱し、板温７０℃でストレッチ加工およびしごき加工を付加した加工度が７％の絞り加工を行った。
この時得られたカップの、缶底コーナー部の樹脂フィルムのマイクロクラック発生状況について調べた。
次いで、得られたカップを温度７０℃に加熱し、ストレッチ加工およびしごき加工を付加した加工度が２２％の再絞り加工を行った後、再絞り加工で得られたカップの温度を４０℃にして、金型温度８０℃で最終加工度が６３％のしごき加工を行い、３５０ｍｌビール缶サイズのシームレス缶を作成した。
更に、前記で得られたシームレス缶を再度加熱・急冷し樹脂フィルムを非晶質にした後、缶径呼称２０６及び２０２のネック加工およびフランジ加工を行なった。ネック加工およびフランジ加工にかける前の樹脂フィルムの密度は、表１９〜２０に示した。
【００８７】
こうして得た缶体について、ネック加工およびフランジ加工部の樹脂フィルムの剥離やクラック発生状況を調べると共に、ＱＴＶ試験および耐デント性で缶内面の品質を調べた。その評価結果は缶径呼称２０６のネック加工およびフランジ加工を行った缶体については、ネック加工およびフランジ加工部の樹脂フィルムの剥離は認められなかった。
そこで、缶径呼称２０２のネック加工およびフランジ加工を行った缶体の評価結果を表２１〜２２に示した。
【００８８】
【表１９】
【表２０】
【表２１】
【表２２】
（考察）
表２１〜２２から、本発明例は比較例のテスト３５、４０に比べ、カップ缶底部のクラックは発生し難く、耐デント性も良好で、得られる缶体のＱＴＶ値は小さく、優れた樹脂フィルムの健全性を有していることが分かる。
また、高縮径のネック加工およびフランジ加工時に発生する樹脂フィルムの剥離やクラックが発生し難いことが分かる。
【００９３】
【発明の効果】
以上、説明したように、本発明を実施することで、得られる缶体内面のポリエステル樹脂フィルムは優れた樹脂フィルムの健全性を有していることから、高耐食性のアルミニウムシームレス缶が得られる。
従って、種々の内容物を充填することが可能であることから、品種の統一化に安心して対応出来るので、経済的に有利となり、その社会的意義は大きいものである。[0001]
BACKGROUND OF THE INVENTION
The present invention is a resin-coated aluminum seamless canAnd soIt relates to the manufacturing method.
[0002]
[Prior art]
Metal cans / containers made of aluminum or steel are roughly classified into three-piece cans and two-piece cans based on their shapes. A three-piece can is called a three-piece can because it consists of a ground, a can body, and a canopy. On the other hand, the two-piece can is an integrated unit of a ground cover and a can body, and since it is composed of a canopy, it is also called a two-piece can or a seamless can because there is no joint in the can body.
[0003]
In the case of metal cans, the inner surface of the can is coated and used to ensure corrosion resistance. In recent years, laminated cans laminated with a thermoplastic resin film have been developed and are on the market. Laminate cans are mainly formed by laminating a resin film on a metal material, and performing can body forming processing. In particular, in order to obtain a two-piece can, advanced forming processing technology is required. In this sense as well, many techniques relating to the two-piece laminate can have been proposed and disclosed, for example, in JP-A-7-2241, JP-A-7-195619, and JP-A-8-244750.
[0004]
The merit of laminated cans depends on the organic resin film to be applied when viewed from the consumer side, but the first point is that they are excellent in content resistance, especially the flavor and taste of the contents. It has been. On the other hand, as a demerit, this time is from the steelmaking manufacturer side, but as described above, in the case of a two-piece can, the processing degree (or degree of deformation) of the thermoplastic resin film-coated metal plate is large, so the inner resin film at the time of molding The quality of the inner surface of the can cannot be ensured due to scratches on the surface of the can, so it is necessary to strictly inspect the quality of the can body, and the product yield is inferior to the current paint can It is done.
[0005]
In particular, in the case of a two-piece laminate can using a steel material, the above-mentioned tendency is large, but the same thing occurs in a laminate can made of an aluminum material. As described above, defects in the resin film on the inner surface of the laminated can are introduced during can molding, and it goes without saying that minimizing these defects is an important technical issue in terms of quality and product yield. Yes.
[0006]
On the other hand, in order to reduce the total can cost, efforts are being made to reduce the diameter of the metal plate used and the diameter of an easy-to-open can lid (easy open end, commonly known as EOE) which is a can lid. Speaking of easy-to-open can lids, for example, if the can body is a 350 ml beer can, it is commonly called 311 and the can body diameter is about 93.7 mm (3 × 11/16 inch φ). Although the lid is also 311, it is now 206 (diameter about 60.3 mm or 2 × 6/16 inch φ) or 204 (diameter about 57.2 mm or 2 × 4/16 inch φ), and further 202 ( The diameter is about 54.0 mm, that is, 2 × 2/16 inch φ). This inevitably results in a so-called diameter reduction by narrowing the opening of the can body to a smaller diameter. Therefore, the metal used in the can body, as well as the resin film coated on the surface thereof, can be taken. It will undergo severe processing.
[0007]
However, it is a two-piece can molding method with ironing, especially by means of molding without causing scratches or other defects in the resin film on the inner surface in the case of a high degree of processing, as well as neck processing and flange processing for high diameter reduction. However, the present situation is that there is no appropriate method for forming the resin film without causing scratches or other defects.
[0008]
[Problems to be solved by the invention]
This invention is made | formed in view of such a situation, and it aims at providing the high corrosion resistance and high quality resin-coated aluminum seamless can without a resin film defect with a sufficient yield.
[0009]
[Means for Solving the Problems]
The first of the present invention is5-50 mg / m as coating C amount 2 Having an organic-inorganic composite chemical conversion coating of phosphoric acid or zirconium phosphate and organic resinPlate thickness 0.20-0.32 mm On both sides of an aluminum plate, thickness 10-50 μm, melting point (Tm) 200-260 ° C., cold crystallization heat (Hc) 8.5-45.0 J / g, and heat of fusion ( Hm) 10.5-50.0 J / g, density 1.36g / cm 3 Less than thermoplastic polyester resin filmStackedPolyester resin coated aluminumIt was obtained from a plate and subjected to drawing to a cup, redrawing of the cup, and ironing of the redrawn cup, and then the density of the thermoplastic polyester resin film after heating and cooling was 1 .36g / cm 3 Is less thanThe present invention relates to a polyester resin-coated aluminum seamless can. In addition, the said density is the value which measured the thing of the step before applying to a 4th process.
[0010]
The surface of the aluminum plate before the polyester resin film is coated is 5 to 50 mg / m as the amount of coating C.2It is preferable to form a composite chemical conversion treatment film of phosphoric acid or zirconium phosphate and an organic resin.
[0011]
The second of the present invention is5-50 mg / m as coating C amount 2 A thickness of 0.20 to 0.32 mm of an aluminum plate having an organic-inorganic composite chemical conversion treatment film of phosphoric acid or zirconium phosphate and an organic resin, a thickness of 10 to 50 μm, a melting point (Tm) of 200 to 260 ° C., and cooling Heat of crystallization (Hc) 8.5-45.0 J / g, heat of fusion (Hm) 10.5-50.0 J / g, density 1.36 g / cm 3 A polyester resin-coated aluminum plate coated with less than a thermoplastic polyester resin film is drawn into a cup (first step), cup redrawn (second step), and redrawn cup ironed (third). Step), followed by neck processing / flange processing (fourth step) to produce a seamless can, wherein the polyester resin-coated aluminum plate is subjected to cold crystallization of the coating resin from the glass transition temperature (Tg) of the coating resin. Within the temperature (Tc) range, stretch processing and / or ironing processing is added, and the following formula (1)
〔number1]
Degree of processing = [(Bt−Wt) / Bt] × 100 (1)
Bt: Thickness of the aluminum plate at the bottom of the can
Wt: the thickness of the thinnest part of the aluminum plate on the can wall
Then, the drawing process (first step) is performed so that the value of the degree of processing obtained from is within 10%, and then the cup obtained in the first step is taken from the glass transition temperature (Tg) of the coating resin. In the range of the cold crystallization temperature (Tc), stretch processing and / or ironing processing is added, and together with the processing degree of the first step, the processing degree value obtained from the formula (1) is within 25%. Then, after the redrawing process (second step) was performed, the can body temperature of the redrawing cup obtained in the second step was reduced to 50 ° C or lower, and then the temperature of the processing mold was maintained at 120 ° C or lower. The ironing process of the third step is performed so that the degree of processing given by the formula (1) is 50 to 70% in combination with the degree of processing of the drawing process of the first step and the degree of processing of the redrawing process of the second step. Then, the can obtained in the third step is heated and cooled, and then again The density of the Le resin film 1.36 g / cm 3 The method of manufacturing a polyester resin-coated aluminum seamless can characterized by performing neck processing and flange processing (fourth step)About.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the method of the present invention will be described in detail.
First, the aluminum plate in the present invention is a plate made of aluminum or an aluminum alloy.
The aluminum plate applied to the method of the present invention is not particularly limited, but various aluminum alloys such as a 3004 series aluminum alloy, a 5052 series aluminum alloy, and a 5081 series aluminum alloy which are usually used for can containers are applied.
The thickness of the aluminum alloy is 0.20 to 0.32 mm.
When the plate thickness is 0.20 mm or less, in the case of an internal pressure can that is filled and sealed with carbonated beverages or beer, the pressure strength is not sufficient and the bottom of the can may be overhanging, which is not preferable.
On the other hand, when the thickness exceeds 0.32 mm, the pressure resistance of the can is sufficiently ensured, but the quality is practically excessive and not economical.
[0013]
The reason for limiting the plate thickness is limited by the pressure resistance of the can as described above.
Therefore, it relates to the mechanical properties of the aluminum plate to be applied, particularly the proof strength. That is, when the proof strength is high, the plate thickness can be reduced. However, when actually carrying out the present invention, the plate thickness is preferably selected in consideration of the strength balance of the entire can.
[0014]
Next, the surface treatment film on the surface of the aluminum plate of the present invention will be described.
As the surface treatment, chromic phosphate treatment or zirconium phosphate treatment, which is usually used as the surface treatment after molding of aluminum plate drawn iron cans, is applied. When the degree of processing exceeds a final processing degree of 60%, or when the necking mentioned above is severely reduced in diameter, an organic / inorganic composite conversion treatment of phosphoric acid or zirconium phosphate and an organic resin is effective. is there.
In the case of organic-inorganic composite type chemical conversion treatment, the adhesion amount is 5 to 50 mg / m as the amount of C in the film.25mg / m2Below, the coatability is inferior, both the anticorrosive action and the adhesiveness are insufficient, the resin film is locally peeled after the can molding process, so-called delamination or local corrosion occurs, and dent resistance Is also inferior and undesirable.
On the other hand, 50 mg / m2The coating property is good, but in the case of can molding with a high degree of processing, especially when the neck processing is severely high diameter reduction, the film causes cohesive failure and adhesion decreases, and the resin film Is not preferred because it may peel off.
The surface treatment film amount is 10 to 40 mg / m as the film C amount.2Is preferred.
[0015]
As a specific method of such an aluminum plate surface treatment, phosphoric acid or phosphoric acid, zirconium fluoride, and a water-soluble organic resin such as a water-soluble phenol resin, a water-soluble acrylic resin, etc. In order to promote the properties, the treatment liquid to which hydrofluoric acid and polyphosphoric acid have been added is roll-coated on an aluminum plate, then washed with water, dried and cured, and after the treatment liquid is spray-coated on the aluminum plate, washed with water and dried. A method of curing, a method of immersing an aluminum plate in a treatment solution, washing with water, drying and curing, and the like can be appropriately applied. As a drying and curing method, a method such as drying with hot air or drying in an electric furnace can be applied, the temperature is 150 to 250 ° C., and the drying time is about 10 seconds to 2 minutes.
[0016]
Next, the polyester resin film applied to the method of the present invention will be described.
In the present invention, a thermoplastic polyester resin film is applied as the resin film.
In the present invention, the reason why the resin film to be coated is limited to the thermoplastic polyester resin film is that (1) heat resistance is good, and (2) the flavor of the contents is ensured, such as polyethylene or polypropylene. This is because it has characteristics suitable for cans that are not found in polyolefin resin films.
Examples of the thermoplastic polyester resin include homopolymers such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and polyethylene isophthalate (PEI), and copolymers such as a copolymer resin of polyethylene terephthalate and polyethylene isophthalate. In addition, blend resins of such homopolymers and copolymers are applied.
[0017]
The thickness of the resin film is 10 to 50 μm.
The thickness of the film laminated on the inner surface of the can is limited from the point of corrosion resistance of the inner surface of the can, and if it is less than 10 μm, depending on the contents to be filled after the can molding process, sufficient corrosion resistance is ensured. It can be difficult.
On the other hand, if it exceeds 50 μm, the corrosion resistance is sufficiently ensured for the contents, but it becomes substantially excessive quality and is not economical.
As film thickness, 12-40 micrometers is a preferable range from quality and economical efficiency.
[0018]
In addition, when the method of the present invention is carried out, the selection of the film thickness is also an important factor in the selection because it has a relationship with the degree of processing for reducing the wall thickness of the can wall described later.
That is, when the degree of processing is high, the film thickness is naturally reduced according to the degree of processing, and as a result, the corrosion resistance of the inner surface of the can is also reduced. Accordingly, it is desirable to use a thick resin film in advance. On the other hand, when the degree of processing is low, it is possible to apply a thin film in advance accordingly.
[0019]
In the present invention, the polyester resin is a resin film having a melting point (Tm) of 200 to 260 ° C. It is clear from researches by the inventors that defects in the resin film that occur during the molding process are particularly likely to occur during the ironing process, and the causes are considered to be summarized in the following two points. That is, metal processing heat is generated during the molding process, and the characteristics of the resin film are greatly changed. The characteristic changes of the resin film due to heat are (1) softening of the resin film and (2) crystal of the resin film. There is a change.
[0020]
The softening of the resin film of (1) causes the resin film to adhere to the punch during the ironing process, causing a so-called releasability failure that makes it difficult to remove the punch, and causes damage to the resin film on the inner surface.
In addition, when the releasability is severe, the vicinity of the opening of the can body may buckle, and there may be a situation in which the normal can body height cannot be obtained.
On the other hand, the resin film on the outer surface side of the can also easily undergoes linear scratches in the height direction of the can called “galling” due to the ironing die. In the case where scratches are caused by “galling” on the outer surface, the finished appearance of the subsequent printing is impaired.
[0021]
The crystallization of the resin film of (2) causes orientational crystallization of the resin film due to heat generation during the ironing process and stretching process, and as a result, the resin film cannot withstand high processing and causes cracks in the resin film.
Anyway, it leads to the generation | occurrence | production of the defect of an inner surface film, and is unpreferable.
[0022]
The degree of softening of the resin film by heat is related to the melting point (Tm) of the resin. When the melting point is 200 ° C. or lower, the releasability is poor even if a lubricant is applied, and the inner surface resin It may cause film defects or a case where the normal can height cannot be obtained.
On the other hand, at an upper limit of 260 ° C. or higher, a further effect of releasability accompanying the increase in the melting point cannot be expected and is saturated.
The melting point (Tm) of the resin film is limited from the viewpoints of mold release and galling resistance, but the calorific value at the time of ironing is also related to the degree of processing described later, and only the melting point of the resin film. The quality of releasability and galling resistance is not determined, but basically a higher melting point is advantageous, preferably 210 to 255 ° C, more preferably 220 to 255 ° C.
[0023]
In the present invention, the polyester resin film has a cold crystallization heat (Hc) of 8.5 to 45.0 J / g and a heat of fusion (Hm) of 10.5 to 50.0 J / g. The heat of cold crystallization (Hc) and the heat of fusion (Hm) serve as an index indicating the crystallinity of the resin film, and both indicate that the higher the amount of heat, the higher the crystallinity of the resin film.
In the case of a highly crystalline resin film, as described above, due to the heat generated during the ironing process and the stretching process, the resin film undergoes orientational crystallization, and as a result, the resin film cannot withstand high processing, causing cracks in the resin film. Become. In addition, in the case of a so-called amorphous resin that is not crystalline, it is generally a soft resin, and in this case, there is a high risk of the above-mentioned releasability failure. In this sense, the heat of cold crystallization (Hc) and heat of fusion (Hm) of the present invention are limited. If the heat of cold crystallization (Hc) is less than 8.5 J / g or the heat of fusion (Hm ) Is less than 10.5 J / g, there is an advantage that it is difficult to cause orientational crystallization at the time of molding, and crack-like defects are hardly generated in the resin film. It is inferior in property, and on the contrary, it is easy to generate defects on the inner surface resin film, which is not preferable. On the other hand, when the heat of cold crystallization (Hc) is more than 45.0 J / g or the heat of fusion (Hm) is more than 50.0 J / g, there is no problem with the releasability from the punch. Since the crystallinity is too high, cracking of the resin film may occur in the molding process, which is not preferable.
In particular, there is a high risk that crack defects will occur in a forming process with a high degree of processing.
[0024]
In the molding process, the degree of orientation crystallization of the resin film during the ironing process is mainly related to the processing temperature conditions during molding, which will be described later. The optimum ranges of the heat of cold crystallization (Hc) and the heat of fusion (Hm) are 10.5 to 40.0 J / g for the heat of cold crystallization (Hc) and 12.5 to 48.0 J for the heat of fusion (Hm). / G is preferable and optimal from the viewpoint of releasability and galling resistance.
[0025]
The density of the thermoplastic polyester resin film applied to the method of the present invention is 1.36.g / cm 3 Is less than.
The density is an index indicating the crystalline state of the resin. For example, the crystallization proceeds by heat or stretching, and the density increases. Density is 1.36g / cm 3 That it is less than shows that it is substantially amorphous as a crystalline state of a polyester resin film.
[0026]
The reason for making the resin film coated on the laminate plate amorphous is to ensure sufficient processability of the resin film in subsequent cup drawing, cup redrawing, and ironing. And the density is 1.36g / cm 3 If it becomes above, even if it is a polyester resin film with low crystallinity, a film cannot endure a forming process, and a crack defect may occur violently in a film, and is unpreferable.
In particular, when the degree of processing is large, the orientation crystallization of the resin film further progresses due to stretching processing in combination with heat generation during ironing processing, and as a result, it becomes difficult to follow processing, and the above behavior appears remarkably, and the can body Often, corrosion resistance cannot be sufficiently secured. Therefore, forming from a crystallized state having a high density is extremely difficult and unsuitable for a high degree of processing.
[0027]
Further, in the present invention, after the cup drawing process, the cup redrawing process, and the ironing can forming process are performed, the resulting can body is heated and cooled, and the density of the resin film is adjusted to 1.36 again.g / cm 3 After making it less, neck processing and flange processing are performed. The can obtained by drawing the cup, redrawing the cup, and further squeezing has significantly reduced the adhesion of the resin film due to the processing at this time. In this state, the neck processing and the flange processing are performed. And a resin film is easy to peel. Accordingly, in the present invention, the density of the resin film is adjusted to 1.36 again by heating and cooling the can body.g / cm 3 After making it less than, it is used for neck processing and flange processing. Resin film density 1.36g / cm 3 By making it less than this, the resin film can be subjected to neck processing and flange processing without causing peeling or cracking. In particular, in order to cope with a high neck processing rate and high diameter reduction, it is necessary to have a high processing adhesion of the resin film. In this case, the lower the density of the resin film, the higher the degree of amorphization. It becomes. Resin film density 1.36g / cm 3 The reason for limiting to less than the above is because of the above-mentioned reason, and particularly as the density before the drawing process in the first step, 1.35.g / cm 3 Less than is optimal.
[0028]
Next, a method for forming a can body according to the present invention will be described.
In the method of the present invention, a laminated aluminum plate coated with a polyester resin film is first drawn into a cup shape by drawing, and then the cup obtained in the first step is further drawn again. A second step of forming a cup having a smaller can diameter and a higher can height than the obtained cup, and then performing a so-called ironing process in which the can wall portion of the cup is passed through a punching and dies and the can wall is thinned. After performing trimming to cut the can body obtained in the third step and the third step into a regular can height, neck processing for reducing the diameter of the can opening and flange processing necessary for tightening the canopy are performed. It consists of the 4th process.
[0029]
The drawing process in the first step, the redrawing process in the second process, and the ironing process in the third process are all processes accompanied by a reduction in the plate thickness of the can wall. Neck / flange machining is practically free of any reduction in plate thickness. Therefore, in the case where the seamless can is molded, the can after the third step becomes the final can.
[0030]
In the first drawing process, the temperature of the laminate is in the range of the glass transition temperature (Tg) to the cold crystallization temperature (Tc) of the coated resin film, and stretch processing and / or ironing processing is added, and the degree of processing is expressed as a degree of processing. The value obtained from (1) is set to be within 10%.
[0031]
Also, the redrawing process in the second step is a stretch process and / or an ironing process in which the temperature of the cup obtained in the first step is in the range of the glass transition temperature (Tg) to the cold crystallization temperature (Tc) of the coated resin film. Is added within 25% as the value obtained from the expression (1) as the degree of work together with the degree of work in the first step.
[0032]
In the ironing process of the third step, the temperature of the cup obtained by redrawing is set to 50 ° C. or lower, the temperature of the processing mold is held to 120 ° C. or lower, and the degree of processing of the final can body after ironing is expressed as an expression As the value obtained in (1), the molding process is performed in the range of 50 to 70% in combination with the degree of processing in the first step and the second step.
〔number2]
Degree of processing = [(Bt−Wt) / Bt] × 100 (1)
Bt: Thickness of the aluminum plate at the bottom of the can
Wt: the thickness of the thinnest part of the aluminum plate on the can wall
[0033]
First, the processing temperature in the can forming method of the present invention will be described.
The reason why the drawing process in the first step and the redrawing process in the second step in the method of the present invention are limited to the range of the glass transition temperature (Tg) to the cold crystallization temperature (Tc) of the coated resin film is the cup by drawing. This is to ensure the soundness of the resin film at the corner of the can bottom.
[0034]
The resin film at the corner of the bottom of the cup can is where the punch hits first, and a high impact is applied. And in this part, a microcrack tends to arise in a resin film. Particularly, the cup can bottom corner portion by the drawing process in the first step becomes the can wall portion (side wall portion) of the cup after the redrawing process in the second step, and is further stretched by the ironing processing in the third step. If a microcrack is generated in the resin film at the corner of the cup can bottom in one step of drawing, the risk of severe resin film defects in the subsequent processing increases, which is not preferable.
Therefore, securing the soundness of the resin film at the corner of the cup can bottom by drawing is an important factor in terms of the quality of the inner surface of the can body. In this sense, drawing at a temperature lower than the glass transition temperature (Tg) of the resin film is not preferable because microcracks are likely to occur in the resin film at the corner of the can bottom of the cup.
[0035]
On the other hand, when drawing is performed at a temperature equal to or higher than the cold crystallization temperature (Tc), thermal crystallization of the resin is likely to occur, the impact strength of the resin film is reduced, and micro cracks are formed in the resin film at the corner of the cup can bottom. Further, it is not preferable that the thermal crystallization is likely to occur as described above because the risk of causing defects in the resin film by the ironing process is increased.
[0036]
The reason why the drawing process in the first step and the redrawing process in the second step are limited to the range of the glass transition temperature (Tg) to the cold crystallization temperature (Tc) of the coated resin film is as described above. A range from the glass transition temperature (Tg) + 5 ° C. to the cold crystallization temperature (Tc) −10 ° C. is preferable.
[0037]
The temperature of the laminate and cup used for drawing and redrawing refers to the surface temperature measured with a contact thermometer, etc., and the temperature of the laminate and cup is determined from the glass transition temperature (Tg) of the coated resin film. Conventional means such as a method of heating a laminate plate or cup in an electric furnace or a method of heating with hot air is applied as the means for controlling the cold crystallization temperature (Tc).
[0038]
In addition, a heating process method in which the surface temperature of a mold for drawing or redrawing is heated from the glass transition temperature (Tg) to the cold crystallization temperature (Tc) for forming is also used. The same effect as when heated can be obtained, but in this case, it is necessary to determine the set temperature of the processing mold depending on the surface temperature of the laminate plate and cup before drawing or redrawing. When the surface temperature of the cup is at room temperature, for example, the set temperature is preferably set 5 to 10 ° C. higher than the glass transition temperature (Tg).
[0039]
In addition, the method of forming the laminated plate or cup by heating from the glass transition temperature (Tg) to the cold crystallization temperature (Tc) by the conventional means, and the surface temperature of the mold for processing the glass transition It is possible to use a warming processing method in which molding is performed by heating in the range of the temperature (Tg) to the cold crystallization temperature (Tc), and means suitable for the equipment can be adopted.
[0040]
In the ironing process in the third step, which is performed after the drawing process in the first process and the redrawing process in the second process, after the temperature of the cup obtained by the redrawing process is set to 50 ° C. or less, the temperature of the working mold is set to 120 ° C. Keep it below.
In this case, the temperature of the cup obtained by redrawing also refers to the surface temperature of the cup, and the temperature of the processing mold refers to the surface temperature of the mold.
[0041]
As described above, the defect of the resin film is most likely to occur in the ironing process on both the inner and outer surfaces.
As described above, the ironing process is a process in which only the can wall is punched and the clearance between the ironing dies is instantaneously reduced in thickness, and during the process, intense metal processing heat is generated and the resin film Change characteristics significantly.
There are (1) softening of the resin film, (2) crystallization of the resin film, etc. as the characteristic change of the resin film due to heat, but it is mentioned above that any characteristic change causes a defect of the resin film due to molding processing. That's right.
[0042]
Therefore, the temperature control of the ironing process is an important element from the viewpoint of preventing the occurrence of defects in the resin film. In the method of the present invention, the temperature of the cup body obtained by the redrawing process in the second step is set to 50 ° C. or less. Processing.
When the cup body temperature exceeds 50 ° C, the resin film on the inner surface side is inferior in releasability from the processing punch, and the resin film on the outer surface side tends to be galling, causing damage to the resin film on both the inner and outer surfaces It becomes.
Further, the temperature of the processing mold is ironing at 120 ° C. or less, but at a temperature exceeding 120 ° C., the releasability between the resin film and the molding processing mold is poor, and the resin film is severely damaged, It is difficult to ensure corrosion resistance on the inner surface of the can, and in some cases, the can body may buckle when releasing the resin film and the molding die, and a normal can body cannot be obtained. There is. Furthermore, when the working mold in the ironing process exceeds 120 ° C., the orientation crystallization of the polyester resin film proceeds rapidly, and as a result, there is a high risk that crack defects of the resin film are likely to occur. In addition, the resin film on the outer surface side is severely galvanized, resulting in not only inferior appearance in printing performed thereafter, but also breakage of the can body starting from the galling portion.
Therefore, the processing temperature in the ironing process is extremely important from the viewpoint of ensuring the quality of the inner and outer surfaces of the can body, and in order to obtain a can body having good quality from the laminated aluminum plate coated with the resin film as in the present invention. It is necessary to keep the temperature of the working mold at 120 ° C. or lower.
[0043]
In the ironing process, it is preferable to keep the temperature of the entire processing mold at 120 ° C. or less. However, when the degree of processing is low, the resin film can be obtained even by maintaining the temperature of the processing punch at 120 ° C. or less. The defect prevention effect can be obtained. Basically, the temperature of the working die during the ironing process and the temperature of the working punch should be low, and the preferred temperature is preferably 100 ° C. or lower.
[0044]
For the ironing process, a one-stage ironing process performed with one ironing die or a multi-stage ironing process performed with two to three sheets can be applied.
[0045]
As a means for lowering the can body temperature of the cup obtained by redrawing to 50 ° C. or lower, a technique such as applying cold air when the cup obtained by drawing is over 50 ° C. can be adopted. Means for lowering the mold temperature to 120 ° C. or less include a method of passing cooling water through a mold, a method of cooling by spraying water or a solution obtained by dissolving or dispersing a lubricating component in water, and a combination thereof. Can be adopted. It is preferable to select an appropriate method in accordance with the facility.
[0046]
Next, the degree of processing in the can forming method of the present invention will be described.
As described above, the working degree of the drawing process in the first step is set to be within 10% as a value obtained from the following formula (1), and the working degree of the redrawing process in the second step is expressed by the formula ( The forming process is performed so that the value obtained from 1) is 25% or less in combination with the work degree in the first step, and the work degree of the ironing process in the third step is the work degree obtained from the equation (1). In combination with the degree of processing in the first step and the second step, the forming is performed in the range of 50 to 70%.
〔number3]
Degree of processing = [(Bt−Wt) / Bt] × 100 (1)
Bt: Thickness of the aluminum plate at the bottom of the can
Wt: the thickness of the thinnest part of the aluminum plate on the can wall
[0047]
As the value obtained from equation (1), the degree of processing after redrawing in the second step is combined with the degree of processing in the first step so that the degree of drawing in the first step is within 10%. The reason why it is within 25% is that if a high degree of processing is performed at one time, the resin film is oriented and crystallized due to heat and stretching during processing, and the film cannot withstand forming and cracks occur. Therefore, in order to avoid this, it is better to perform the processing with increasing the processing degree sequentially as described above and keep the processing degree of the final ironing processing as low as possible. In this sense, according to the method of the present invention, it is possible to perform a molding process that ensures the soundness of the resin film on the inner and outer surfaces of the can.
[0048]
In particular, the state of the resin film on the inner surface of the can body after the ironing process in the third step should be such that the resin film on the can wall portion is not completely crystallized at the stage of the redrawing cup in the second step. When the degree of processing after redrawing is within 25%, the soundness of the resin film on the inner and outer surfaces after ironing is ensured.
[0049]
In the method of the present invention, the drawing process and the redrawing process to which the stretching process and / or the ironing process are performed in the first step and the second process described above may be performed by the method having only the stretch process or the ironing process. Either of these methods may be used, as long as it is a method in which only the process is added, or a method in which both the stretching process and the ironing process are added.
[0050]
Further, in the polyester resin-coated aluminum plate of the present invention, a cup shape is formed by a drawing process currently performed as a drawing and ironing method of a metal such as an aluminum plate or a Sn-plated steel plate (tinplate) that is not coated with a thermoplastic resin film. The cup obtained in the first step and then the cup obtained in the first step are further redrawn to form a cup having a smaller can diameter and a higher can height than the cup obtained in the first step. The second step in which the part is punched and passed between the ironing dies, and the ironing process to thin the can wall is performed with the same molding machine, and the trimming to cut the can body obtained in the second step to an appropriate can height In this molding method, it is also possible to apply a method comprising a third step of performing a neck processing for reducing the diameter of the can opening and a flange processing necessary for winding up the canopy after being performed. The above drawing is performed in the range of the glass transition temperature (Tg) to the cold crystallization temperature (Tc) of the coated polyester resin, and the redrawing and ironing are performed at a temperature of the processing die as a whole at 120 ° C. or less. Alternatively, when the degree of processing is low, it is desirable that the processing punch temperature be 120 ° C. or less.
[0051]
As a method of manufacturing a polyester resin film-coated laminated aluminum plate, a method of supplying a resin film to the surface of a heated aluminum plate and laminating it by thermocompression bonding between rolls, immediately quenching and making it amorphous, Extrude the molten resin, supply it to the aluminum plate, laminate it, immediately cool it down to make it amorphous, or heat up the polyester resin once laminated to more than the melting point of the resin, if necessary A method of making it amorphous can be applied.
[0052]
As a method for heating the aluminum plate, a heating method such as a method of heating in an electric furnace, a method of heating with hot air, or a method of heating in contact with a heating roll can be employed.
[0053]
【Example】
Hereinafter, the present invention will be described with reference to examples, but the present invention is not limited thereto. In addition, the evaluation method performed by the present Example etc. is as follows.
[0054]
(1) The density of the resin film was measured by a density gradient tube method.
(2) The melting point, cold crystallization heat, and heat of fusion of the resin film were measured with a differential scanning calorimeter (DSC) at a rate of temperature increase of 10 ° C./min. For the heat of crystallization and the heat of fusion, the integrated value of each peak was taken as the heat of cold crystallization and the heat of fusion.
(3) About the soundness of the can bottom corner part resin film after the drawing of the cup, microcracks were observed with an optical microscope and the degree thereof was evaluated.
Evaluation was performed by setting evaluation criteria as follows.
◯: Good without cracks □: Minor cracks generated
Δ: Clear cracking ×: Severe cracking
(4) The releasability of the film and the processing punch was evaluated by observing the degree of buckling of the can body occurring at the upper part of the can.
Evaluation of releasability was performed by setting evaluation criteria as follows.
◯: Good without buckling of can opening □: With slight buckling of can opening
Δ: Buckling about 1/3 of the circumference of the opening ×: Buckling more than 1/3 of the circumference of the opening (5) The galling resistance of the outer surface of the can is determined by the degree of occurrence of galling of the outer surface of the molded can body wall Observed and evaluated.
○: Good without galling □: Minor galling occurred
△: Scratching occurs in less than 1/3 of the outer surface ×: Severe galling occurs in 1/3 or more of the outer surface (6) Regarding the state of the resin film in the neck processing and the flange processing, It was observed and evaluated with an optical microscope.
Evaluation of the peeling situation and crack occurrence situation was performed by setting evaluation criteria as follows.
○: Good without peeling or cracking □: Minor cracking
Δ: Partial peeling or cracking ×: Peeling occurred
(7) About the degree of damage to the resin film on the inner surface of the can, an electrolytic solution obtained by adding 0.1 wt% of a surfactant to 1.0 wt% saline, the can body as an anode, the cathode as a copper wire, and an applied voltage of 6 V The current value after 3 seconds was measured to evaluate the soundness of the film of the resin film (hereinafter, this evaluation method is referred to as a QTV test). In the present invention, the upper limit of this numerical value is 2 to 3 mA / can.
(8) For the evaluation of dent resistance, a 350 ml can was filled with water, subjected to retort treatment at 125 ° C. for 30 minutes, cooled at 5 ° C. for 1 day, and then at the bottom of the can at an angle of 60 ° from a position of 80 cm in height. After dropping the container and drying the can, seal the parts other than the impact deformation part with insulating paint, and use the electrolyte solution used for the QTV test to determine the degree of defect occurrence of the resin film in the impact deformation part. Then, the current value after 3 seconds was measured at an applied voltage of 6 V, and the soundness of the film of the resin film was evaluated (hereinafter, the dent property indicates the evaluation result by this method).
*1: First step
*2: Second step
*Three: Third step
*Four: Fourth step
*Five: Ratio = comparative example
*6: Actual = Example
[0055]
Experimental example 1
15 mg / m as the amount of film C on the surface2A glass transition temperature of 67 ° C., a cold crystallization temperature of 123 ° C., and a cold crystallization heat on both surfaces of a 0.26 mm thick aluminum plate (3004 series alloy) having a composite chemical conversion treatment film of phosphoric acid-phenol resin Is 17.8 J / g, melting point is 238 ° C., heat of fusion is 18.0 J / g, and the thickness of the biaxially stretched polyester resin film is 8 μm (Test 1), 15 μm (Test 2), 20 μm (Test 3), 30 μm ( Test 4), 40 μm (Test 5), and 50 μm (Test 6) were coated by thermocompression bonding, and then heated and quenched to prepare an amorphized polyester resin film laminate. Density of resin film on each test plate(G / cm 3 )Are shown in Tables 1-2.
[0056]
After applying a molding lubricant to the laminate plate thus obtained, it was heated and drawn at a plate temperature of 70 ° C. and subjected to stretch processing and ironing to a degree of processing of 7%. The occurrence of microcracks in the resin film at the corner of the can bottom of the cup obtained at this time was examined. Subsequently, the obtained cup was heated to a plate temperature of 70 ° C., and the degree of processing obtained by adding stretch processing and ironing processing (this degree of processing indicates the degree of processing combined with the degree of processing of the drawing process in the first step, and so on. After the redrawing process of 15%, the temperature of the cup obtained by the redrawing process is set to 40 ° C., and the final processing degree at the mold temperature of 80 ° C. (this processing degree is the same as that of the first step). The degree of processing combined with the degree of processing of drawing and the degree of processing of redrawing in the second step, the same shall apply hereinafter) was 60% ironed to create a 350 ml beer can-sized seamless can.
The can thus obtained was examined for the releasability between the resin film and the mold and the degree of galling resistance of the outer surface resin film.
Furthermore, after heating and quenching the seamless can obtained above again to make the resin film amorphous, the can diameter designation 202 (diameter of about 54.0 mm) was subjected to neck processing and flange processing. Density of the resin film before the fourth process for necking and flange processing(G / cm 3 )Are shown in Tables 1-2.
Regarding the can body thus obtained, the state of peeling and cracking of the resin film at the neck processing and flange processing portion was examined, and the quality of the inner surface of the can was examined by QTV test and dent property. The evaluation results are shown in Tables 3-4.
[0057]
[Table 1]
[Table 2]
[Table 3]
[Table 4]
(Discussion)
From Tables 1 to 4, it can be seen that the example of the present invention has a low QTV value and a good resin film soundness as compared with test 1 of the comparative example. Moreover, it turns out that the Example of this invention is favorable also about a dent property compared with a comparative example. On the other hand, as for the releasability, galling resistance, and the situation of the flange processed portion and the neck processed portion, both the examples of the present invention and the comparative examples were good.
[0062]
Experimental example 2
A resin film having a melting point of 193 ° C., a cold crystallization heat of 6.3 J / g, a heat of fusion of 8.4 J / g (test 7), a melting point on both surfaces of the aluminum plate having the composite chemical conversion film used in Experimental Example 1 Film with 205 ° C, cold crystallization heat 8.9 J / g, heat of fusion 13.0 J / g (test 8), melting point 218 ° C, heat of cold crystallization 14.8 J / g, heat of fusion 15.3 J / g (Test 9), melting point 230 ° C., cold crystallization heat 18.7 J / g, melting heat 20.7 J / g film (test 10) melting point 242 ° C., cold crystallization heat 19.6 J / g, melting heat 23. 2 J / g film (test 11), melting point 252 ° C., cold crystallization heat 24.4 J / g, heat of fusion 29.3 J / g film (test 12), melting point 257 ° C., cold crystallization heat 41.5 J / g g, film of heat of fusion 46.1 J / g (test 13), A biaxially stretched polyester resin film having a point of 261 ° C., a cold crystallization heat of 46.0 J / g and a heat of fusion of 53.5 J / g (test 14), each having a thickness of 20 μm, was coated by thermocompression and then heated. -Quenched to prepare an amorphous polyester resin film laminate. Density of resin film on each test plate(G / cm 3 )Are shown in Tables 5-6.
[0063]
After applying a molding lubricant to the laminate plate thus obtained, it was heated and drawn at a plate temperature of 75 ° C. and subjected to ironing to a working degree of 5%. The occurrence of microcracks in the resin film at the corner of the can bottom of the cup obtained at this time was examined.
Next, the obtained cup was heated to a temperature of 75 ° C., subjected to a redrawing process with a degree of processing of 22% after adding a stretch process and an ironing process, and then the temperature of the cup obtained by the redraw process was set to 25 ° C. Then, ironing was performed at a mold temperature of 80 ° C. and a final processing degree of 60%, to produce a 350 ml beer can-sized seamless can.
The can thus obtained was examined for the releasability between the resin film and the mold and the degree of galling resistance of the outer surface resin film.
Further, the seamless can obtained above was heated and quenched again to make the resin film amorphous, and then neck processing and flange processing of a can diameter designation 202 (diameter of about 54.0 mm) were performed. Density of resin film before necking and flange processing(G / cm 3 )Are shown in Tables 5-6.
The can body thus obtained was examined for the state of peeling and cracking of the resin film at the neck processing portion and the flange processing portion, and at the same time the quality of the inner surface of the can was examined by QTV test and dent property. The evaluation results are shown in Tables 7-8.
[0064]
[Table 5]
[Table 6]
[Table 7]
[Table 8]
(Discussion)
From Tables 7-8, the test 7 of a comparative example is inferior to mold release property and galling resistance, and the test 14 of a comparative example has a high QTV value and indented property. On the other hand, Tests 8 to 13 of the examples of the present invention have good mold releasability and galling resistance, low QTV values and low dent properties, and have good resin film soundness. I understand that.
[0069]
Experimental example 3
15 mg / m as the amount of film C on the surface2The film used in Test 11 of Experimental Example 2 was coated on both surfaces of an aluminum plate (3004 series alloy) having a thickness of 0.28 mm having a composite chemical conversion treatment film of phosphoric acid-phenol resin under different thermocompression bonding conditions. Then, it heat-cooled as needed and created the polyester resin film laminated board from which a density differs. Density of resin film of the obtained laminate(G / cm 3 )Were 1.346 (test 15), 1.351 (test 16), 1.364 (test 17), and 1.375 (test 18). After applying a molding lubricant to the laminate plate thus obtained, it was heated and drawn at a plate temperature of 70 ° C. and stretched to a degree of processing of 5%.
[0070]
The occurrence of microcracks in the resin film at the corner of the can bottom of the cup obtained at this time was examined.
Next, the obtained cup was heated to a temperature of 70 ° C., and after performing redrawing with a degree of processing of 22% with the addition of stretch processing and ironing, the temperature of the cup obtained by redrawing was set to 40 ° C. Thus, ironing was performed at a mold temperature of 100 ° C. with a final processing degree of 63%, and a 350 ml beer can-sized seamless can was produced.
The physical properties of the laminated resin film are shown in Table 9. For the can thus obtained, the releasability between the resin film and the mold, the anti-galling resistance of the outer resin film, and the soundness of the inner resin film were examined by a QTV test. The evaluation results are shown in Table 10.
[0071]
[Table 9]
[Table 10]
(Discussion)
From Table 10, it can be seen that the examples of the present invention have lower QTV values than the tests 17 and 18 of the comparative examples, and have good resin film soundness. Regarding the releasability, both the examples of the present invention and the comparative examples were good.
[0074]
Experimental Example 4
The laminate plate obtained in Test 11 of Experimental Example 2 was coated with a molding lubricant and then heated, and the plate temperature was 50 ° C. (Test 19), 70 ° C. (Test 20), 90 ° C. (Test 21), 110 Drawing was performed at 7 ° C. with stretch and ironing applied at ℃ (Test 22), 120 ℃ (Test 23), and 130 ℃ (Test 24). The occurrence of microcracks in the resin film at the corner of the bottom of the can of the cup obtained at this time was observed.
Next, the obtained cup was heated to a plate temperature of 70 ° C., and after performing redrawing with a degree of processing of 22% with the addition of stretch processing and ironing, the temperature of the cup obtained by redrawing was set to 40 ° C. Then, ironing was performed at a mold temperature of 80 ° C. and a final processing degree of 60%, to produce a 350 ml beer can-sized seamless can.
In addition, for the redrawn cup obtained in Test 20, the temperature was set to 30 ° C. (Test 25), 40 ° C. (Test 26), 50 ° C. (Test 27), 60 ° C. (Test 28), Ironing was performed at a mold temperature of 80 ° C. and a final processing degree of 60%, to produce a 350 ml beer can-sized seamless can. For comparison, the temperature of the drawn cup obtained in the test 24 was set to 70 ° C., and after performing the redrawing with a degree of processing of 22% with the addition of stretch processing and ironing, the cup temperature was set to 40 ° C. (test 29 ) And 60 ° C. (test 30), and a ironing process with a final processing degree of 60% was performed at a mold temperature of 80 ° C. to produce a 350 ml beer can-sized seamless can. The physical properties and molding conditions of the resin film are shown in Tables 11-13.
For the can thus obtained, the releasability between the resin film and the mold, the anti-galling resistance of the outer resin film, and the soundness of the inner resin film were examined by a QTV test. The evaluation results are shown in Tables 14-16.
[0075]
[Table 11]
[Table 12]
[Table 13]
[Table 14]
[Table 15]
[Table 16]
(Discussion)
From Tables 11-16, the Example of this invention has all the crack generation | occurrence | production of a cup can bottom corner part, mold releasability, and galling resistance compared with the tests 19, 24, 28, 29, and 30 of a comparative example. It can be seen that the QTV value is low and the resin film has good soundness.
[0082]
Experimental Example 5
A seamless can obtained from Test 11 of Experimental Example 2 having a final processing degree of 60% is heated and quenched again, and then neck processing and flange processing of a can diameter designation 202 (diameter of about 54.0 mm) are performed to obtain a resin film. In addition to observing the peeling state and the occurrence of cracks, the quality of the inner surface of the can was examined by QTV test and dent property. Density of resin film before necking and flange processing(G / cm 3 )Are 1.340 (test 31), 1.353 (test 32), 1.369 (test 33), and 1.386 (test 34). The resin film properties and molding conditions are shown in Table 17, and the evaluation results are shown in Table 18.
[0083]
[Table 17]
[Table 18]
(Discussion)
From Table 18, it can be seen that the example of the present invention is less likely to cause peeling or cracking of the resin film that occurs during neck processing and flange processing than the tests 33 and 34 of the comparative example. Moreover, the QTV test and dent property value of the inner surface of the obtained can body are small, and it can be seen that the resin film has excellent soundness.
[0086]
Experimental Example 6
The amount of film C is 3 mg / m2(Test 35), 8 mg / m2(Test 36), 15 mg / m2(Test 37), 32 mg / m2(Test 38), 46 mg / m2(Test 39), 58 mg / m2The biaxially stretched polyester resin film used in Test 11 of Experimental Example 2 was coated by thermocompression bonding on both surfaces of a 0.28 mm thick aluminum plate (3004 alloy) having the composite chemical conversion coating of (Test 40). Thereafter, heating and rapid cooling were performed to prepare an amorphized polyester resin film laminate. Density of resin film on each test plate(G / cm 3 )Are shown in Tables 19-20.
The laminated board thus obtained was coated with a molding lubricant and then heated, and the sheet was subjected to a drawing process at a sheet temperature of 70 ° C. with a degree of processing of 7% by adding a stretch process and an ironing process.
The occurrence of microcracks in the resin film at the corner of the can bottom of the cup obtained at this time was examined.
Next, the obtained cup was heated to a temperature of 70 ° C., and after performing redrawing with a degree of processing of 22% after adding stretch processing and ironing, the temperature of the cup obtained by redrawing was set to 40 ° C. Then, ironing was performed at a mold temperature of 80 ° C. with a final processing degree of 63%, and a 350 ml beer can-sized seamless can was produced.
Further, the seamless can obtained above was heated and quenched again to make the resin film amorphous, and then neck processing and flange processing of can diameter designations 206 and 202 were performed. The density of the resin film before being subjected to neck processing and flange processing is shown in Tables 19-20.
[0087]
The can body thus obtained was examined for the state of peeling and cracking of the resin film in the necked and flanged portions, and the quality of the inner surface of the can was examined by QTV test and dent resistance. As a result of the evaluation, no peeling of the resin film at the necked portion and the flanged portion was observed with respect to the can body that was subjected to the necking and flanged processing of the can diameter designation 206.
Therefore, Tables 21 to 22 show the evaluation results of the can body that has been subjected to the neck processing and flange processing of the can diameter designation 202.
[0088]
[Table 19]
[Table 20]
[Table 21]
[Table 22]
(Discussion)
From Tables 21 to 22, the inventive example is less susceptible to cracking at the bottom of the cup can than the tests 35 and 40 of the comparative example, the dent resistance is good, and the resulting can body has a small QTV value and an excellent resin. It turns out that it has the soundness of a film.
Moreover, it turns out that the peeling of a resin film and a crack which generate | occur | produce at the time of a high diameter reduction neck process and a flange process do not generate | occur | produce easily.
[0093]
【The invention's effect】
As described above, by implementing the present invention, the polyester resin film on the inner surface of the resulting can body has excellent soundness of the resin film, so that a highly corrosion-resistant aluminum seamless can is obtained.
Therefore, since various contents can be filled, it is possible to deal with unification of varieties with peace of mind, which is economically advantageous and has great social significance.
Claims (2)
〔数１〕
加工度＝〔（Ｂｔ−Ｗｔ）／Ｂｔ〕×１００ ・・・（１）
Ｂｔ：缶底部のアルミニウム板の板厚
Ｗｔ：缶壁部のアルミニウム板の最も薄い部位の板厚
から求められる加工度の値が１０％以内になるように絞り加工（第１工程）を行い、次いで第１工程で得られたカップを前記の被覆樹脂のガラス転移温度（Ｔｇ）から被覆樹脂の冷結晶化温度（Ｔｃ）の範囲で、ストレッチ加工および／またはしごき加工を付加し、第１工程の加工度と合せて、前記式（１）から求められる加工度の値が２５％以内になるように再絞り加工（第２工程）を行い、次に、第２工程で得られた再絞りカップの缶体温度を５０℃以下にした後、加工金型の温度を１２０℃以下に保持し、第１工程の絞り加工の加工度及び第２工程の再絞り加工の加工度と合わせて式（１）で与えられる加工度が５０〜７０％になるように第３工程のしごき加工を行い、次いで第３工程で得られた該缶体を加熱・冷却して再度ポリエステル樹脂フィルムの密度を１．３６ｇ／ｃｍ ３ 未満にした後、ネック加工・フランジ加工（第４工程）を行うことを特徴とするポリエステル樹脂被覆アルミニウムシームレス缶の製造方法。 A thickness of 10 to 50 μm on both sides of a 0.20 to 0.32 mm aluminum plate having an organic-inorganic composite chemical conversion coating of 5 to 50 mg / m 2 of phosphoric acid or zirconium phosphate and an organic resin as the amount of coating C ; Melting point (Tm) 200-260 ° C., heat of cold crystallization (Hc) 8.5-45.0 J / g, heat of fusion (Hm) 10.5-50.0 J / g, density less than 1.36 g / cm 3 A polyester resin-coated aluminum plate coated with a thermoplastic polyester resin film is drawn into a cup (first step), cup redrawn (second step), and redrawn cup ironing (third step). Then, in the method of manufacturing a seamless can by performing neck processing and flange processing (fourth step), the polyester resin-coated aluminum plate is subjected to the glass transition temperature of the coating resin. Stretch processing and / or ironing processing is added within the range from the degree (Tg) to the cold crystallization temperature (Tc) of the coating resin, and the following formula (1)
[Equation 1 ]
Degree of processing = [(Bt−Wt) / Bt] × 100 (1)
Bt: Thickness of the aluminum plate at the bottom of the can
Wt: the thickness of the thinnest part of the aluminum plate on the can wall
Then, the drawing process (first step) is performed so that the value of the degree of processing obtained from is within 10%, and then the cup obtained in the first step is taken from the glass transition temperature (Tg) of the coating resin. In the range of the cold crystallization temperature (Tc), stretch processing and / or ironing processing is added, and together with the processing degree of the first step, the processing degree value obtained from the formula (1) is within 25%. Then, after the redrawing process (second step) was performed, the can body temperature of the redrawing cup obtained in the second step was reduced to 50 ° C or lower, and then the temperature of the processing mold was maintained at 120 ° C or lower. The ironing process of the third step is performed so that the degree of processing given by the formula (1) is 50 to 70% in combination with the degree of processing of the drawing process of the first step and the degree of processing of the redrawing process of the second step. Then, the can obtained in the third step is heated and cooled, and then again After the density Le resin film to less than 1.36 g / cm 3, a manufacturing method of a polyester resin coated aluminum seamless can which is characterized in that the neck processing and flanging (fourth step).
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP19666598A JP4103974B2 (en) | 1998-06-26 | 1998-06-26 | Polyester resin-coated aluminum seamless can and method for producing the same |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP19666598A JP4103974B2 (en) | 1998-06-26 | 1998-06-26 | Polyester resin-coated aluminum seamless can and method for producing the same |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JP2000006967A JP2000006967A (en) | 2000-01-11 |
| JP4103974B2 true JP4103974B2 (en) | 2008-06-18 |
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Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP19666598A Expired - Fee Related JP4103974B2 (en) | 1998-06-26 | 1998-06-26 | Polyester resin-coated aluminum seamless can and method for producing the same |
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| Country | Link |
|---|---|
| JP (1) | JP4103974B2 (en) |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2007029755A1 (en) | 2005-09-09 | 2007-03-15 | Toyo Seikan Kaisha, Ltd. | Resin-coated seamless aluminum can and resin-coated aluminum alloy lid |
| JP5125044B2 (en) * | 2006-09-25 | 2013-01-23 | 東洋製罐株式会社 | Method for producing resin-coated can |
| US9506152B2 (en) * | 2011-08-31 | 2016-11-29 | Jfe Steel Corporation | Resin coated metal sheet |
| JP6019823B2 (en) * | 2012-07-02 | 2016-11-02 | Ｊｆｅスチール株式会社 | Resin coated metal plate |
| JP5867422B2 (en) * | 2013-01-29 | 2016-02-24 | Ｊｆｅスチール株式会社 | Resin coated metal plate |
-
1998
- 1998-06-26 JP JP19666598A patent/JP4103974B2/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| JP2000006967A (en) | 2000-01-11 |
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