JP3575117B2

JP3575117B2 - Two-piece drawn ironing can with excellent corrosion resistance and flavor resistance and method for producing the same

Info

Publication number: JP3575117B2
Application number: JP17265995A
Authority: JP
Inventors: 迪子鶴丸; 和久増田; 正恒渋江; 然朗白根
Original assignee: Toyo Seikan Kaisha Ltd
Current assignee: Toyo Seikan Group Holdings Ltd
Priority date: 1995-06-06
Filing date: 1995-06-06
Publication date: 2004-10-13
Anticipated expiration: 2019-10-13
Also published as: EP0747135B1; DE69616875D1; EP0747135A1; JPH08332527A; DE69616875T2

Description

【０００１】
【産業上の利用分野】
本発明はフランジ部のポリエステル樹脂被覆の密着性を向上した耐食性と耐フレーバー性に優れた絞りしごき缶およびその製造方法に関する。
【０００２】
【従来の技術】
錫メッキ鋼板を用いた２ピース缶は、錫の被覆率が小さく、鋼面が露出する缶が多数発生する重大な欠陥があった。
錫メッキ鋼板自体の錫被覆率は大きく、良好であっても成形時に成形工具に接触すると接触した部分は鋼面が露出し、錫被覆率が低下するのである。
殊に絞り加工としごき加工により成形を行うと加工量が大きいため鋼面の露出が大きくなる問題があった。
そのため絞り、しごき加工後、塗料を缶内面に塗装することが行われているが、このような手段では耐食性と耐フレーバー性が充分でなくこれらの点の欠陥の発生を防止できない。
また、従来のラミネートしたぶりき絞りしごき缶は、絞りしごき加工した後にトリミングし、その後、熱処理し、更にその後ネック・フランジ加工するため、内面フイルムのダメージが比較的大きく、特にネッキング率が大きくなった場合に、フランジ部のポリエステル樹脂内面フイルムが金属から剥離しやすいという問題があった。
【０００３】
化成処理を行うこともあるが効果が充分でなく、作業性も悪い問題がある。
また、ポリエステル樹脂をラミネートした金属板を使用し、しごき率を特定の範囲に規定した、特開昭６０−１７２６３７号と特開平２−３０３６３４号が提案された。
この他、絞り加工温度をＰＥＴフイルムのガラス転移点近傍とした特公平１−５５０５５号や、表面処理被膜の上にメッキ層を設けその上にＰＥＴ被膜を設けてしごき率を特定範囲に規定した特公平３−３３５０６号もある。しかしながらこれ等の先行技術はいずれも錫層とＰＥＴの接着性が不充分であり、また耐フレーバー性が充分でなく、耐衝撃強度も不充分であった。しごき率で特定しても、少い加工量のしごきでもしごき加工を行うとピンホールが発生し鋼面の露出が生じるのでしごき率だけではフレーバー性は向上しない。
これ等の先行技術は錫メッキ層もラミネート樹脂層も被覆量で制御しているがこのような単なる量による制御では被覆層の厚薄を制御出来ないので均一な膜厚の層とはならず、被覆層にピンホールが存在するために充分な性能が発揮されないと考えられる。
【０００４】
【発明が解決しようとする課題】
本発明は金属面とポリエステル樹脂被覆層との密着性に優れた缶と、この缶を高作業性で製造する方法を提供する。
【０００５】
【課題を解決した手段】
本発明は次の手段により全ての課題を解決した。
本発明は、
「１．少なくとも缶内面となる片面に予め熱可塑性樹脂を被覆した錫メッキ鋼板で成形した絞りしごき缶において、熱可塑性樹脂の主成分が結晶性ポリエステル樹脂であり、缶側壁部における該樹脂層の平均厚みは５〜３０μｍであり、錫被膜の平均厚みが０．２〜２．０ｇ／ｍ^２であり、錫の有効被覆率が８５％以上であって、フランジ先端から少なくとも２ｍｍの全周の熱可塑性樹脂の接している金属面が鉄−錫合金で被覆されており、鉄−錫合金の被覆率が０．７以上であることを特徴とする、耐食性とフレーバー性に優れた２ピース絞りしごき缶。
２．被覆樹脂の主成分である結晶性ポリエステル樹脂のＴｇが５５℃以上、固有粘度（ＩＶ）が０．６５以上である、１項に記載された耐食性とフレーバー性に優れた２ピース絞りしごき缶。
３．錫の有効被覆率が、錫被膜の厚みが０．１ｇ／ｍ^２以上の部分の占める割合を示す値である、１項または２項に記載された、耐食性とフレーバー性に優れた２ピース絞りしごき缶。
４．鉄−錫合金の被覆率がフランジ先端から２ｍｍまでの合金錫量Ａと表面錫量ＢからＣ＝Ａ／（Ａ＋Ｂ）の式により求めた値Ｃである、１項ないし３項のいずれか１項に記載された、耐食性とフレーバー性に優れた２ピース絞りしごき缶。
５．錫メッキ厚みが０．４〜６．０ｇ／ｍ^２である錫メッキ鋼板の缶内側となる面に、結晶性ポリエステル樹脂を主成分とする結晶化度が５％以下、厚みが１５〜９０μｍ、破断伸びが１００％以上、Ｔｇが５５℃以上、固有粘度（ＩＶ）が０．６５以上である熱可塑性樹脂被覆を配置して、１回以上の絞り成形によりカップを作り、缶体のフランジ先端から少なくとも２ｍｍとなるべき部分までを加熱処理しその後必要あれば更に再絞り加工して次にパンチと入角度が２〜８度のアイアニングダイにより、しごき加工を行い、最終しごき工程後直ちに冷却することにより、缶側壁部における樹脂層の平均厚みが５〜３０μｍ、錫被膜の平均厚みが０．２〜２．０ｇ／ｍ^２、錫の有効被覆率が８５％以上であって、フランジ先端から少なくとも２ｍｍの全周の熱可塑性樹脂の接している金属面が鉄−錫合金で被覆されており、鉄−錫合金の被覆率が０．７以上である耐食性とフレーバー性に優れた２ピース絞りしごき缶の製造方法。
６．成形時にカップ内面の錫層の温度を２３２℃を越えない温度に維持して成形し、最終しごき成形の後急冷してネッキング部とフランジ部の内面側錫温度を２３２℃以下とした、５項に記載された耐食性とフレーバー性に優れた２ピース絞りしごき缶の製造方法。
７．ポリエステル樹脂を主成分とする熱可塑性樹脂被覆を絞りしごき加工の工程で配向結晶化させる、５項または６項に記載された耐食性とフレーバー性に優れた２ピース絞りしごき缶の製造方法。」
に関する。
【０００６】
【作用】
本発明の第１の特徴は金属とポリエステル樹脂被覆との密着性を向上して耐食性を向上したことである。
前述のように錫メッキ鋼板を絞りしごき加工を施した後ネックフランジ加工するとその加工度が大きい場合錫メッキ層とポリエステル樹脂被覆の剥離が発生する。これは錫メッキ層とポリエステル樹脂被覆の密着性が良好でないためである。ことにフランジ先端から２ｍｍ附近までは、剥離が発生しやすい。
本発明は、剥離の発生する、フランジの先端から少なくとも２ｍｍの全周の金属面を鉄−錫合金で被覆してポリエステル樹脂被覆の剥離を防止した。鉄−錫合金は錫メッキ層よりポリエステル樹脂被覆の接着性が良好で剥離を防止する作用が大きい。
【０００７】
鉄−錫合金被覆はフランジ先端から少なくとも２ｍｍの巾で全周に設けられなければならない。２ｍｍ以内では絞り加工時の剥離を防止できない。
またフランジ先端から少なくとも２ｍｍの全周にわたる鉄−錫合金被覆率は０．７０以上でなければ、充分な剥離効果は奏されない。
鉄−錫合金の被覆率Ｃは、フランジ先端から２ｍｍの錫メッキ鋼板についてＪＩＳＧ３３０３のぶりきの錫付着量試験方法、電解剥離法に準じて合金錫量Ａと表面錫量Ｂを測定し、Ｃ＝Ａ／（Ａ＋Ｂ）により求めた値である。
鉄−錫合金被膜を形成するには、絞り成形により得たカップ状態でカップエッジを約２３０℃以上に加熱することにより錫メッキ層を合金化することができる。
【０００８】
このようにカップエッジ部を合金化してさらに絞り、しごき加工を行うことにより本発明の缶が製造される。また本発明の缶は絞りしごき加工後にフランジとなるべきカップ先端から２ｍｍ以上の部分を２３０℃以上に加熱することによっても得ることができる。
錫の有効被覆率とは錫層の厚さが０．１ｇ／ｍ^２以上の部分の占める割合であり、８５％以下になると錫層があってもフィルム下腐食が発生し耐食性が悪化する。
本発明の前記特徴は、熱可塑性樹脂を錫メッキ面に被覆して絞りしごき加工した缶であって、缶側壁部における樹脂層の厚さを５〜３０μｍとし、錫被膜の平均厚みを０．２〜２．０ｇ／ｍ^２とし、錫の有効被覆率を８５％以上とすることにより、耐食性の著しく向上した缶とする点にある。
【０００９】
何故熱可塑性樹脂を錫メッキ層にラミネートして絞りしごき成形加工を行うと錫層に鋼面の露出が発生しないのかその理由について本発明者は、加工具が錫メッキ層に直接触れないことと、熱可塑性樹脂が緩衝材となって樹脂自身も成形加工されながら錫層に加工の力を伝達するため、錫層に展延の加工力が急激にかからず、展延が無理なく行われるためと考えている。したがってラミネートする熱可塑性樹脂も加工性の良好なものが好ましく結晶性ポリエステル樹脂が適している。
【００１０】
本発明の第２の作用はフレーバー性の良好なことである。
内容物の香気成分が缶内面材料に吸着されると、内容物のフレーバーが変化する。また、缶内面材料が内容物中に溶出しても内容物のフレーバーが変化する。
このようにフレーバー性は錫メッキ層の鋼板の露出だけでなく被覆した樹脂によっても発生する。
本発明者の研究によると缶側壁の錫層の上にラミネート層を形成する熱可塑性樹脂としてＴｇが５５℃以上で固有粘度（ＩＶ）が０．６５以上の結晶性ポリエステル樹脂を使用すると内容物のフレーバー成分の収着量が大きく低下すること、特にイソフタール酸系の共重合ポリエステル樹脂が好ましいことがわかった。
【００１１】
この他、結晶性ポリエステルとしてポリエチレンテレフタレート、ポリブチレンテレフタレート、ポリエチレンナフタレート及びその共重合体、ブレンド物も使用される。
共重合ポリエチレンテレフタレートの共重合成分は酸成分でもアルコール成分でもよい。該酸成分としてはイソフタル酸、フタル酸、ナフタレンジカルボン酸等の芳香族二塩基酸、、アジピン酸、アゼライン酸、セバシン酸、デカンジカルボン酸等の脂肪族ジカルボン酸、シクロヘキサンジカルボン酸の如き脂環族ジカルボン酸等が挙げられ、またアルコール成分としてはブタンジオール、ヘキサンジオール等の脂肪族ジオール、シクロヘキサンジメタノールの如き脂環族ジオール等が挙げられる。これらは単独又は二種以上を使用することが出来る。
【００１２】
これらの結晶性ポリエステルは単層又は２層以上の複層として使用できる。
勿論フレーバー性には錫メッキ層から鋼板が露出することによる影響が大きい。
本発明者は鉄の溶出量を少くするため種々研究した結果、鉄溶出量の少い絞りしごき缶は、錫メッキ鋼板に、錫メッキ厚みが０．４〜６．０ｇ／ｍ^２である錫メッキ鋼板の缶内側となる面に、結晶性ポリエステル樹脂を主成分とする結晶化度が５％以下、厚みが１５〜９０μｍ、破断伸びが１００％以上、Ｔｇが５５℃以上、固有粘度（以下ＩＶと表記する）が０．６５以上である熱可塑性樹脂被覆を配置して、１回以上の絞り成形によりカップを作り、缶体のフランジ先端から少くとも２ｍｍとなるべき部分までを加熱処理し、その後必要あれば再絞り加工して次にパンチと入角度が２〜８度のアイアニングダイにより、しごき加工を行い、最終しごき工程後直ちに冷却し、缶側壁部における樹脂層の平均厚みが５〜３０μｍとなるように成形することにより得ることが出来ることがわかった。
ラミネート樹脂層は、錫メッキ鋼板の両面に設けても良いが缶となった表側の面は耐食、耐フレーバー性に直接関係がなく、印刷を行ったりするので必ずしもラミネート層は必要ではない。
【００１３】
本発明の缶は内面の錫メッキ層に樹脂がラミネートされているので化成処理の必要はない。化成処理を必要としないので作業性を向上させ、使用水を１／２〜１／３に減少することが出来、廃水処理の負担や廃水処理廃棄物を減少することが出来る利点がある。錫層は０．０１μｍ〜０．２５μｍの薄層であるが充分防食性を示し、鉄の溶出を防止して優れた耐フレーバー性を奏する。このような薄層であってしかも有効被覆率が８５％以上の錫層を形成することは従来出来なかった。
【００１４】
缶胴部は大きな加工を受けるのでメッキ層も樹脂層も薄層化する。缶胴部は成形加工による影響が大きく欠陥を生じ易いのである。ラミネートした熱可塑性樹脂層は延伸配向し、強度も大きくなり、バリヤ性も向上する。
そして、成形時の錫温度を２３２℃を越えない温度に保って成形することが好ましい。これは錫の融点が２３１．９℃であるので、錫の融けない温度に保って成形加工することが錫被膜の均一性を保ち、被覆率の変化を防ぐのに有効であるからである。
【００１５】
本発明の第３の特徴は、絞りしごき加工においてパンチ側のラミネート樹脂の温度を粘着温度以下に保って成形加工を行うことである。
成形加工時缶の外面は２５０℃程度まで昇温し、この熱が缶の内面に拡散するので樹脂層の温度も上昇する。温度が上昇しすぎると樹脂層の配向結晶が得られなくなり強度が不足して成形欠陥を生ずる。また粘着温度以上になるとパンチに粘着し成形後のストリップアウト不良を発生する。
【００１６】
これを防止するためには加工部を冷却するとともに加工後直ぐに缶体を外面から冷却剤で冷却し、粘着温度以下に保つのが有効である。
また、最終しごき後のパンチ抜け性には、ラミネート樹脂の表面状態が大きく影響している。樹脂表面が細かな凹凸をもっている場合、しごき加工中に樹脂表面の微小凹凸がパンチ表面に圧着し、真空状態になるため、成形後パンチから剥離するのに大きな力を必要とする。このため、カップのストリップアウト時、カップのエッジが折れ曲がり、成形不良となるものである。従ってパンチ抜け性を良化するためには、カップエッジ及びパンチ先端からのエアーが、缶壁とパンチの界面に侵入しやすいように、ラミネート樹脂表面の凹凸が缶高さ方向につながるように筋をいれて、これらの凹凸が孤立しないようにすることが有効である。
【００１７】
加工性を良好にするためラミネート樹脂層の加工温度をＴｇ近傍にすることが好ましい。例えばＰＥＴであれば冷却剤の温度は５０℃程度とすると良い結果が得られる。
カップ成形後、ラミネート樹脂層は一部配向した状態となり成形性が低下するので温度を８０〜２００℃に昇温してアニーリングを行い歪みを除去することが良好な加工を行うのに好ましい。
【００１８】
ラミネート樹脂層がパンチと滑り易いのでしごき加工のアイアニングダイの入り角を低くしパンチの面圧を大きくすることが成形加工上有効である。被覆樹脂層がパンチと滑ると波線状の樹脂欠陥となる。アイアニングダイの入り角度を２〜８°とすることが好ましく、特に６°以下とすることが好適である。絞り加工によりラミネート層の下の金属表面は粗度が多少増加するのでパンチ表面の凹凸や異物の存在により絞り加工時に樹脂欠陥を生じ易い。
したがってパンチ表面を平滑にし、また異物の存在しないようにする必要がある。
さらに本発明によると、錫メッキ鋼板に被覆したポリエステルを主成分とする熱可塑性樹脂層を絞りしごき加工の工程において配向結晶化することが出来るので、耐食性と耐フレーバー性が向上する。
【００１９】
【実施例】
つぎに実施例と比較例を示して具体的に説明する。
実施例、比較例において、絞りしごき条件と製缶条件、錫被膜の被覆係数の測定、鉄−錫合金被覆率の測定、フランジ部剥離の評価、フレーバー性の評価、実缶保存試験の評価は下記のように行った。
【００２０】
１．絞りしごき条件及び製缶条件
実施例１０−１及び実施例１１−１〜１１−４、比較例１１−１〜１１−２以外の実施例・比較例は、下記絞りしごき条件及び製缶条件で行った。
金属板厚０．２４５ｍｍの片面樹脂被覆鋼板を用い、樹脂被覆面が缶内面になるようにして、ブランク径１４２ｍｍにブランキングし、１ｓｔ絞り比１．６でカップを成形後、２ｎｄ絞り比１．３で再絞りし、３工程のしごき成形を行い、缶胴径６５．８ｍｍ、缶胴金属厚み８０μｍ、ネック部金属厚み１３５μｍの絞りしごきカップを成形した。この絞りしごきカップを缶高さが１２３ｍｍになるようにトリミングし、洗浄乾燥した後、外面を印刷し２００℃で３０秒加熱後、缶上部を内径５７．２５ｍｍ（２０６径）に縮径するとともにフランジを成形し絞りしごき缶を得た。再絞りと３工程のアイアニングの成形速度は２００ｃｐｍである。
実施例１０−１は、絞りしごき条件が上記と異なるが、ネック・フランジ条件は同じである。実施例１１−１〜１１−４、比較例１１−１〜１１−２は、絞りしごき条件は上記と同じであるが、ネック・フランジ条件が上記と異なる。個々の実施例・比較例中に異なる点のみ明示する。
【００２１】
２．カップ加熱条件
第１絞りカップを正立におき、カップの上方に高周波誘導加熱コイルを設置し、カップエッジに高周波の磁束がかかるようにする。高周波誘導加熱コイルはカップエッジから３ｍｍの位置に設置した。高周波の出力を調整し、カップエッジの温度を制御した。カップエッジの温度は、カップ内面の樹脂面に、数種の示温塗料を塗布し、変色程度で評価した。実施例・比較例での条件は、注記しない限り、処理時間１．０秒であり、このときのカップエッジの到達温度は約３００℃であった。
【００２２】
３．錫被膜の被覆係数の測定
ネック・フランジ部も含む缶壁内面側の樹脂被膜を除去後、缶内面側壁を円周方向に長さ２．０ｍｍに区切り１０個所につき下記条件で錫のＥＰＭＡ線分析を行い、各場所毎に下記式により錫被膜の被覆係数を求める。こうして求めた各場所の錫被膜の被覆係数の中で最も小さい部分の値をもってこの缶の錫被膜の被覆係数とする。測定法：ＷＤＳ、検出結晶：ＰＥＴ、加速電圧：１０ｋｖ、試料電流：１×１０Ｅ−８Ａ、ビーム径１．０μｍ、検出Ｘ線：ＳｎＬα線、タイムコンスタント：１．０（ｓ）、走査速度：５０μｍ／分、である。
錫被膜被覆係数（％）
＝（錫量が０．１ｇ／ｍ^２以上部の長さ（ｍｍ））×１００／２．０（ｍｍ）
【００２３】
４．鉄−錫合金被覆率の測定
缶体のフランジからネック部の結晶性ポリエステル樹脂を、例えば１，１，１，３，３，３−ヘキサフルオロ−２−プロパノールのような溶剤で溶解し、フランジ先端から２ｍｍまでを切り取り、フランジのエッジと切断面を樹脂でシールし、熱可塑性樹脂に接していた金属面について、ＪＩＳＧ３３０３の“ぶりきの錫付着量試験方法、電解剥離法”に準じた方法で、合金錫量（Ａ）と表面錫量（Ｂ）を測定する。このとき、電流密度は１０ｍＡ／ｃｍ^２で行う。
鉄−錫合金被覆率（Ｃ）を、下記式で定義する。
Ｃ＝Ａ／（Ａ＋Ｂ）
また、熱可塑性樹脂を溶解した後の金属面を走査型電子顕微鏡で、５０００倍以上に拡大した場合、柱状あるいは粒状の鉄−錫合金が観察され、なめらかな金属錫面とは明らかに異なり、識別することができる。
【００２４】
５．フランジ部剥離の評価方法
２０６径あるいは２０２径までネック加工をし、さらにフランジ加工をした後、フランジ部の剥離程度を１０００缶調査し、剥離があった場合を×とし、剥離した缶数で評価した。フランジ部剥離の基準は、缶円周部のいずれの部分においてもフランジエッジから、０．５ｍｍ以上の剥離があった場合を×とした。あるいは缶ハイト方向への線状の剥離が一本以上あった場合を×とし、剥離がなかった場合を○とした。
【００２５】
６．フレーバー性の評価
内容物の香気成分が缶内面材料に収着されると、内容物のフレーバーが変化する。また缶内面材料が内容物中に溶出しても内容物のフレーバーが変化する．フレーバー保持性を、実缶保存試験での内容物フレーバーの官能試験、および香気成分収着率で評価した。
内容物フレーバー官能試験は、コカコーラライト（日本コカコーラ株式会社製炭酸飲料）を充填したのち、室温で３か月間保管し、経時保管なしの液との、官能的な優位差を調べた。危険率５％での優位差なしを○、危険率５％での優位差ありを×、と評価した。
香気成分収着率測定は、日本食品工業学会誌Ｖｏｌ．３４、Ｎｏ．５，１９８７，２６７〜２７３に記載された方法に準じて行った。すなわちモデル液として、柑橘系フレーバー（ミルセン、αテルピネン、ｄリモネン、γテルピネン、ｐシメン、２カレンをそれぞれ１０ｐｐｍになるように混合した）を添加したモデル溶液（クエン酸１％）を試験缶に充填・巻締し、２０℃１０日間保管後、缶内面フイルムから香気成分を回収・濃縮し、ガスクロマトグラフ分析を行い、充填前溶液からの分配比（内面フイルム中の量／内容液中の量）を求めた。香気成分の回収・濃縮・分析方法は前述文献に準じた。ｄ−リモネンの分配比２％未満を○、２％以上を×と評価した。
【００２６】
７．実缶保存試験評価
試験缶数１００缶に定法によりコカコーライト（炭酸飲料）を充填し、蓋を巻締めた後、３７℃で６ヶ月間保存した後、開缶し、缶内面のフイルム下腐食（以下ＵＦＣと略表記する）部の発生面積の測定、及び内容物中に溶出した鉄イオンを原子吸光分光分析法により測定し、平均溶出量を算出した。ＵＦＣは、ＵＦＣ面積が０〜１０ｍｍ^２を○、１０ｍｍ^２を超えるものを×、と評価した。
【００２７】
８．結晶性ポリエステル樹脂の結晶化度の測定
ラミネート樹脂層である結晶性ポリエステル樹脂の結晶化度の測定は、ＳＥＮ−ＩＧＡＫＫＡＩＳＨＩ，Ｖｏｌ．３３、Ｎｏ．１０（１９７７）、７８０〜７８８に記載された方法で行った。すなわちＸ線回折散乱強度分布を結晶及び非晶相からの寄与に分離し、Ｂｒａｇｇ角に関する積分強度比として算出した。
【００２８】
９．加工前樹脂のＴｇ、破断伸び（以下Ｅｌと表記する）、ＩＶの測定
ラミネート板の樹脂層を金属板から剥離したのち、常法でＴｇ、ＥＬ（のび）、を測定した。ＩＶは、ｏ−クロロフェノール中で２５℃で測定した。
【００２９】
１０．缶壁内面平均錫被覆厚みと缶壁内面平均有機樹脂被膜厚みの測定
缶壁内面平均錫被覆厚みは、しごき加工の最も大きい缶壁部（缶底から３０〜８０ｍｍ部）内面の有機樹脂を剥離した後、２０ｍｍφの円形資料を３ケ作製し、蛍光Ｘ線法で測定して得た測定値を算術平均して得た。缶壁内面平均有機樹脂被膜厚みは、同様部位の金属を溶解して有機樹脂を剥離し、任意の点について１０個所マイクロメーターで測定して得られた測定値を算術平均して得た。
【００３０】
実施例１−１
０．２４５ｍｍ厚み、テンパー４、Ｅ２．８／２．８ぶりきの片面に、厚み９０μｍの非晶状態の結晶性ポリエステル樹脂（ポリエチレンテレフタレート／イソフタレート系）を熱被覆し、急冷した。この樹脂の被覆後のＴｇ、ＥＬ、ＩＶ、結晶化度を表１に示す。この片面樹脂被覆錫メッキ鋼板を用い、表１に示す条件で絞りしごき缶を作製した。条件と評価を表１に示す。
【００３１】
実施例１−２、１−３、比較例１−１、１−２
実施例１−２、１−３、比較例１−１は、錫メッキ鋼板に被覆した有機樹脂被膜厚みがそれぞれ３０μｍ、１５μｍ、９μｍであること以外は実施例１−１と同様にして絞りしごき缶を作製した。
比較例１−２は、錫メッキ鋼板に被覆した有機樹脂被膜厚みが１２０μｍであること以外は実施例１−１と同様にして絞りしごき缶を作製した。条件と評価を表１に示す。フランジ成形時にフランジ部が剥離したためフレーバーと実缶の評価は行わなかった。
【００３２】
実施例２−１
０．２４５ｍｍ厚み、テンパー４、Ｅ２．８／２．８ぶりきの片面に、厚み３０μｍの二軸延伸状態の結晶性ポリエステル樹脂（ポリエチレンテレフタレート／イソフタレート系）を熱被覆し、ラミネート板（成形前）のポリエステル樹脂の結晶化度が２％になるように２３０℃での保持時間を調整したのちに、急冷した。この樹脂の被覆後のＴｇ、ＥＬ、ＩＶ、結晶化度を表１に示す。この片面樹脂被覆錫メッキ鋼板を用い、絞りしごき缶を作製した。条件と評価を表１に示す。
【００３３】
実施例２−２、比較例２−１、２−２
実施例２−２、比較例２−１、２−２は、ラミネート板（成形前）のポリエステル樹脂の結晶化度がそれぞれ５％、９％、２４％であること以外は実施例２−１と同様にして絞りしごき缶を作製した。条件と評価を表１に示す。
【００３４】
実施例３−１
０．２４５ｍｍ厚み、テンパー４、Ｅ２．８／２．８ぶりきの片面に、厚み３０μｍの非晶状態の結晶性ポリエステル樹脂（ポリエチレンテレフタレート／イソフタレート系）を熱被覆し、急冷した。このときイソフタル酸の共重合比率を変えることでＴｇを６４℃にしこの鋼板を用い絞りしごき缶を製造した。条件と評価を表１に示す。
【００３５】
実施例３−２、比較例３−１、３−２
実施例３−２、比較例３−１、３−２は、ポリエステル樹脂のＴｇがそれぞれ５８℃（イソフタル酸共重合）、５４℃（セバシン酸共重合）、４８℃（アジピン酸共重合）であること以外は実施例３−１と同様にして絞りしごき缶を作製した。条件と評価を表１に示す。
比較例３−３は、錫メッキ鋼板の片面（内面側）に３μｍ厚さの熱硬化樹脂を塗布したのち乾燥焼付（半硬化状態）し、その上に３０μｍの非晶状態の結晶性ポリエステル樹脂を熱被覆し、急冷すること以外は実施例３−１と同様にして絞りしごき缶を製缶した。条件と評価を表１に示す。
比較例３−４は、熱被覆する樹脂が熱結晶性のないポリエステル樹脂（ポリエチレンテレフタレート／イソフタレート系）であること以外は実施例３−１と同様にして絞りしごき缶を製缶した。条件と評価を表１に示す。
【００３６】
実施例４−１
０．２４５ｍｍ厚み、テンパー４、Ｅ２．８／２．８ぶりきの片面に、厚み３０μｍの非晶状態の結晶性ポリエステル樹脂（ポリエチレンテレフタレート／イソフタレート系）を熱被覆し、急冷した。この樹脂は共重合比率を変えて破断伸びが２８５％になるようにした。この片面樹脂被覆錫メッキ鋼板を用い、絞りしごき缶を作製した。条件と評価を表１に示す。
【００３７】
実施例４−２、比較例４−１
実施例４−２、比較例４−１は、ポリエステル樹脂の破断伸びがそれぞれ１３３％、３％であること以外は実施例４−１と同様にして絞りしごき缶を作製した。条件と評価を表１に示す。
【００３８】
実施例５−１
０．２４５ｍｍ厚み、テンパー４、Ｅ２．８／２．８ぶりきの片面に、厚み３０μｍのＩＶが約１．０の二軸延伸状態の結晶性ポリエステル樹脂（ポリエチレンテレフタレート／イソフタレート系）を熱被覆し、ラミネート板（成形前）のポリエステル樹脂の結晶化度が５％になるように２３０℃に保持したのち、急冷した。この片面樹脂被覆錫メッキ鋼板を用い、絞りしごき缶を作製した。条件と評価を表１に示す。
【００３９】
実施例５−２、比較例５−１、５−２
実施例５−２、比較例５−１、５−２は、ラミネート後のポリエステル樹脂のＩＶがそれぞれ０．６８、０．６３、０．５６であること以外は実施例５−１と同様にして絞りしごき缶を作製した。条件と評価を表１に示す。
【００４０】
【表１】

【００４１】
（註）表中のＡ〜Ｓは次の意味の略号である。
Ａ：イソフタル酸共重合ＰＥＴ
Ｂ：セバシン酸共重合ＰＥＴ
Ｃ：アジピン酸共重合ＰＥＴ
Ｄ：熱硬化樹脂（接着層）＋イソフタル酸共重合ＰＥＴ
Ｅ：熱結晶性のないイソフタル酸共重合ＰＥＴ
Ｆ：缶内面平均有機樹脂被膜（μｍ）
Ｇ：缶内面平均錫被覆厚み（ｇ／ｍ^２）
Ｈ：缶内面錫有効被覆率（０．１ｇ／ｍ^２以上の部分の割合）
Ｊ：加工前樹脂のＴｇ（℃）
Ｋ：加工前樹脂のＩＶ（ｄｌ／ｇ）
Ｌ：加工前樹脂のＥＬ（％）
Ｍ：加工前樹脂の結晶化度（％）
Ｎ：最終しごき直前の冷却
Ｏ：アイアニングダイ入角度（度）
Ｐ：腐食性評価
Ｑ：フレーバー性評価
Ｒ：香気成分収着
Ｓ：フレーバー官能試験
ＵＦＣ：膜下腐蝕
径：ネック後缶口部径呼称
率：鉄−錫合金被覆率
評：フランジ部剥離評価
なお比較例１−２は成形、製缶状態が不良でフランジが剥離した。またパンチ抜け性が悪く連続成形不能であった。
【００４２】
比較例６−１、６−２
比較例６−１、６−２は、０．２４５ｍｍ厚み、テンパー４、Ｄ６．０／２．８ぶりき、Ｅ２．８／２．８ぶりきを、２．８側を外面側にして、有機樹脂被覆のない状態で絞りしごき加工し、洗浄・乾燥したのちに、ビニルオルガノゾル系の樹脂をスプレー塗装し、焼付硬化を行い、絞りしごき缶を製缶し、缶壁内面平均錫被覆厚みの測定、錫被膜の被覆係数の測定、フランジ部剥離評価、フレーバー性の評価、実缶保存試験評価を行った。鉄−錫合金の被覆率の測定は行わなかった。その結果、缶壁内面平均錫被覆厚みはそれぞれ２．０ｇ／ｍ^２、０．９ｇ／ｍ^２であり、缶壁内面錫被覆率はそれぞれ８１％、７７％であり、フランジ部剥離缶数は０であり、実缶保存試験でのＦｅ溶出量はそれぞれ２．７ｐｐｍ、６．５ｐｐｍであり、ＵＦＣ評価はそれぞれ×、×であり、フレーバー官能試験評価はそれぞれ×、×であった。また実缶保管試験ではそれぞれ１００缶中、５缶、９缶に蓋巻締部からの穿孔漏洩があった。
【００４３】
実施例７−１
０．２４５ｍｍ厚み、テンパー４、Ｄ６．０／２．８のぶりきの６．０側（内面側）に、厚み３０μｍの非晶状態の結晶性ポリエステル樹脂（ポリエチレンテレフタレート／イソフタレート系）を熱被覆し、急冷した。この片面樹脂被覆錫メッキ鋼板を用い、絞りしごき缶を作製した。条件と評価を表２に示す。
【００４４】
実施例７−２、７−３、比較例７−１、７−２
実施例７−２はＤ４．５／２．８ぶりき（４．５が内面側）、実施例７−３、比較例７−１、７−２は、軟鋼板片面（内面側）の錫メッキ量がそれぞれ０．６ｇ／ｍ^２、０．３ｇ／ｍ^２、０．０ｇ／ｍ^２であり他面（外面側）の錫メッキ量がいずれも２．８となるように錫メッキを行い、それ以外は実施例７−１と同様にして絞りしごき缶を作製した。条件と評価を表２に示す。
【００４５】
比較例８
比較例８は、最終しごき後の冷却を行わないこと以外は実施例１−２と同様にして絞りしごき缶を作製した。しごき成形後のパンチ抜けが悪く、成形カップが得られなかった。
【００４６】
実施例９−１
１ｓｔ、２ｎｄ、３ｒｄとも入角２°のアイアニングダイ（以下ＩＤと略）を用いた以外は実施例１−２と同様にして、絞りしごき缶を作製した。条件と評価を表２に示す。
【００４７】
実施例９−２、９−３、比較例９−１、９−２
実施例９−２、９−３、比較例９−１、９−２は、ＩＤ入角がそれぞれ６°、８°、１０°、１２°であること以外は実施例９−１と同様にして絞りしごき缶を作製した。条件と評価を表２に示す。
【００４８】
実施例１０−１
０．２４５ｍｍ厚み、テンパー１、Ｅ２．８／２．８ぶりきの片面に、厚み３０μｍの非晶状態の結晶性ポリエステル樹脂（ポリエチレンテレフタレート／イソフタレート系）を熱被覆し、急冷した。この樹脂の被覆後のＴｇ、Ｅｌ、ＩＶ、結晶化度を表１に示す。この片面樹脂被覆錫メッキ鋼板を用い、樹脂被覆面が缶内面になるようにして、ブランク径１４２ｍｍにブランキングし、絞り比２．１でカップを成形後、３工程のしごき成形を行い、缶胴径６５．８ｍｍ、缶胴金属厚み８０μｍ、ネック部金属厚み１３５μｍの絞りしごきカップを成形した。このとき第１絞りカップのカップエッジを高周波誘導加熱処理した。この絞りしごきカップを、缶高さが１２３ｍｍになるようにトリミングし、洗浄乾燥した後、外面を印刷し２００℃で３０秒加熱後、缶上部を内径５７．２５ｍｍに縮径するとともにフランジを成形し絞りしごき缶を得た。成形の条件を表２に示す。
このようにして得た絞りしごき缶について、平均錫被覆厚み、有機樹脂被膜厚み、錫被膜の被覆係数の測定、鉄−錫合金の被覆率の測定、製缶状態の肉眼観察、フレーバー性の評価、実缶保存試験評価を行った。その結果を表２に示す。
【００４９】
実施例１１−１
第１絞りカップを、カップエッジ到達温度約３００℃で１．０秒間高周波誘導加熱処理したことと、缶上部を内径５２．４０ｍｍ（２０２径）まで縮径したこと以外は、実施例１−２と同様にして絞りしごき缶を作成した。条件及び評価結果を表２に示す。
【００５０】
実施例１１−２
第１絞りカップを、カップエッジ到達温度約３２０℃で１．０秒間高周波誘導加熱処理したこと以外は、実施例１１−１と同様にして絞りしごき缶を作成した。条件及び評価結果を表２に示す。
【００５１】
実施例１１−３
缶内面になるべきぶりきの錫メッキ量が、６．０ｇ／ｍ^２であること以外は、実施例１１−１と同様にして絞りしごき缶を作成した。条件及び評価結果を表２に示す。
【００５２】
実施例１１−４
缶内面になるべきぶりきの錫メッキ量が、０．６ｇ／ｍ^２であること以外は、実施例１１−１と同様にして絞りしごき缶を作成した。条件及び評価結果を表２に示す。
【００５３】
比較例１１−１
第１絞りカップを、カップエッジ到達温度約２４０℃で１．０秒間高周波誘導加熱処理したこと以外は、実施例１１−１と同様にして絞りしごき缶を作成した。条件及び評価結果を表２に示す。
【００５４】
比較例１１−２
カップでの加熱処理がないこと以外は、実施例１１−１と同様にして絞りしごき缶を作成した。条件及び評価結果を表２に示す。
【００５５】
実施例１−１〜１−３、３−１、３−２、７−１〜７−３、１０−１、１１−１〜１１−４から、絞りしごき缶が缶内面となる面に予め熱可塑性樹脂を熱被覆した錫メッキ鋼板から成形されており、缶胴内面の熱可塑性樹脂の主成分が結晶性ポリエステル樹脂であり、缶側壁部における熱可塑性樹脂層の平均厚みが５〜３０μｍであり、缶壁内面平均錫被覆厚みが０．２〜２．０ｇ／ｍ^２であり、錫の有効被覆率が８５％以上であり、フランジ先端から少くとも２ｍｍの全周の熱可塑性樹脂の接している金属面が鉄−錫合金で被覆されており、鉄−錫合金の被覆率が０．７以上である場合、耐食性（Ｆｅ溶出、ＵＦＣ、穿孔腐食性）とフレーバー性（耐香気成分収着性、耐異臭成分溶出性）に優れることが分かる。
【００５６】
比較例６−１、６−２から、絞りしごき缶が有機被膜のない錫メッキ鋼板から成形されたのち、スプレー塗装されることにより有機被膜を形成された場合、錫の有効被覆率が８５％を下回り、耐食性とフレーバー性が劣ることが分かる。
【００５７】
比較例３−３から、絞りしごき缶が、缶内面となる面に予め熱硬化性樹脂を被覆しその上に熱可塑性樹脂を被覆した錫メッキ鋼板から成形された場合、錫の有効被覆率が８５％を下回り、耐食性とフレーバー性が劣ることが分かる。
【００５８】
比較例３−４から、缶胴内面の熱可塑性樹脂の主成分が非晶性（熱結晶性のない）ポリエステル樹脂の場合、錫の有効被覆率が８５％を下回り、耐食性とフレーバー性が劣ることが分かる。
【００５９】
比較例１−１から、缶側壁部における熱可塑性樹脂の平均厚みが５μｍを下回る場合、錫の有効被覆率が８５％を下回り、耐食性とフレーバー性が劣ることが分かる。
【００６０】
比較例１−２から、缶側壁部における熱可塑性樹脂の平均厚みが３０μｍを上回る場合、フランジ部に有機樹脂と金属の間で剥離が起こり、製缶出来ないことが分かる。
【００６１】
比較例７−１、７−２から、缶壁内面平均錫被覆厚みが０．２ｇ／ｍ^２を下回る場合、錫の有効被覆率が８５％を下回り、耐食性とフレーバー性が劣ることが分かる。
【００６２】
比較例１−１、２−１、２−２、３−１〜３−４、４−１、５−１、５−２、６−１、６−２、７−１、７−２、９−１、９−２、１１−１、１１−２から、錫の有効被覆率が８５％を下回ると、耐食性とフレーバー性が劣ることが分かる。
比較例１１−１から、カップエッジの高周波誘導加熱処理温度が低い場合、鉄−錫合金の被覆率が０．７を下回り、フランジ剥離となりパックテストに供するに値する缶は製缶できないことが分かる。
比較例１１−２から、カップでの加熱処理がない場合、鉄−錫合金の被覆率が０．７を下回り、フランジ剥離となりパックテストに供するに値する缶は製缶できないことが分かる。
比較例１１−１、１１−２から、鉄−錫合金の被覆率が０．７を下回ると、フランジ剥離となり、製缶できないことが分かる。
【００６３】
比較例８から、最終しごき後に冷却しない場合、パンチ抜け性が劣り、連続成形できないことが分かる。
【００６４】
実施例２−１、２−２、３−１、３−２、４−１、４−２、５−１、５−２、９−１〜９−３、１１−１〜１１−４、比較例２−１、２−２、３−１、３−２、４−１、５−１、５−２、８、９−１、９−２、１１−１、１１−２から、缶胴内面の熱可塑性樹脂の主成分である結晶性ポリエステル樹脂のＴｇが５５℃以上、ＩＶが０．６５以上で、成形加工前樹脂の結晶化度が５％以下であり、Ｅｌが１００％以上であり、１回以上の絞り成形によりカップを作り、缶体のフランジ先端より少くとも２ｍｍとなるべき部分までを加熱処理しその後必要あれば更に再絞り加工し、アイアニングダイの入角度が２〜８度であり、最終しごき工程後直ちに冷却して製造することにより、絞りしごき缶が缶内面となる面に予め熱可塑性樹脂を熱被覆した錫メッキ鋼板から成形されており、缶胴内面の熱可塑性樹脂の主成分が結晶性ポリエステル樹脂であり、缶側壁部における熱可塑性樹脂層の平均厚みが５〜３０μｍであり、缶壁内面平均錫被覆厚みが０．２〜２．０ｇ／ｍ^２であり、錫の有効被覆率が８５％を以上であって、フランジ先端から少なくとも２ｍｍの全周の、熱可塑性樹脂に接している金属面が鉄−錫合金で被覆されている、耐食性とフレーバー性に優れた絞りしごき缶を製造することが分かる。
【００６５】
【表２】

【００６６】
（註）表中のＡ〜Ｓは次の意味の略号である。
Ａ：イソフタル酸共重合ＰＥＴ
Ｂ：セバシン酸共重合ＰＥＴ
Ｃ：アジピン酸共重合ＰＥＴ
Ｄ：熱硬化樹脂（接着層）＋イソフタル酸共重合ＰＥＴ
Ｅ：熱結晶性のないイソフタル酸共重合ＰＥＴ
Ｆ：缶内面平均有機樹脂被膜（μｍ）
Ｇ：缶内面平均錫被覆厚み（ｇ／ｍ^２）
Ｈ：缶内面錫有効被覆率（０．１ｇ／ｍ^２以上の部分の割合）
Ｊ：加工前樹脂のＴｇ（℃）
Ｋ：加工前樹脂のＩＶ（ｄｌ／ｇ）
Ｌ：加工前樹脂のＥＬ（％）
Ｍ：加工前樹脂の結晶化度（％）
Ｎ：最終しごき直前の冷却
Ｏ：アイアニングダイ入角度（度）
Ｐ：腐食性評価
Ｑ：フレーバー性評価
Ｒ：香気成分収着
Ｓ：フレーバー官能試験
ＵＦＣ：膜下腐蝕
径：ネック後缶口部径呼称
率：鉄−錫合金被覆率
評：フランジ部剥離評価
なお、比較例１１−１、１１−２は成形、製缶状態が不良でフランジが剥離した。比較例８はネックフランジ部が剥離した。パンチ抜け性が悪く連続成形不能であった。
【００６７】
【発明の効果】
本発明は従来知られていない、錫メッキ層が０．２ｇ／ｍ^２〜２．０ｇ／ｍ^２の薄層であって、その表面に熱可塑性樹脂の５〜３０μｍの同時加工されたラミネート層を設けた錫の有効被覆率が８５％以上であって、フランジ先端から少くとも２ｍｍの全周の熱可塑性樹脂の接している金属面が鉄−錫合金で被覆されており、鉄−錫合金の被覆率が０．７以上の絞りしごき缶であって耐食性と耐フレーバー性に非常に優れた効果を奏する。[0001]
[Industrial applications]
TECHNICAL FIELD The present invention relates to a drawn and ironed can with improved adhesion of a polyester resin coating of a flange portion and excellent corrosion resistance and flavor resistance, and a method for producing the same.
[0002]
[Prior art]
The two-piece can using the tin-plated steel sheet had a serious defect that the tin coverage was low and a large number of cans with exposed steel surfaces occurred.
The tin coverage of the tin-plated steel sheet itself is large, and even if it is good, when it comes into contact with the forming tool at the time of molding, the contacted portion exposes the steel surface and the tin coverage decreases.
In particular, when forming by drawing and ironing, there is a problem in that the exposed surface of the steel is increased due to a large amount of processing.
For this reason, paint is applied to the inner surface of the can after drawing and ironing, but such means do not have sufficient corrosion resistance and flavor resistance, and cannot prevent the occurrence of defects at these points.
In addition, conventional laminated tinned and drawn iron cans are drawn and ironed, trimmed, then heat-treated, and then neck-flanged, resulting in relatively large damage to the inner surface film, especially the necking rate. In such a case, there is a problem that the polyester resin inner film of the flange portion is easily peeled off from the metal.
[0003]
Although a chemical conversion treatment may be performed, the effect is not sufficient and there is a problem that workability is poor.
JP-A-60-172637 and JP-A-2-303634 have been proposed in which a metal plate laminated with a polyester resin is used and the ironing rate is specified in a specific range.
In addition, Japanese Patent Publication No. 1-55055, in which the drawing temperature is set near the glass transition point of PET film, and a plating layer provided on a surface treatment film, a PET film is provided thereon, and the ironing rate is specified in a specific range. There is also Japanese Patent Publication No. 3-33506. However, in these prior arts, the adhesion between the tin layer and PET is insufficient, the flavor resistance is not sufficient, and the impact strength is also insufficient. Even if it is specified by the ironing rate, if ironing is performed with a small amount of ironing, pinholes are generated and the steel surface is exposed. Therefore, flavoring cannot be improved only by the ironing rate.
In these prior arts, both the tin plating layer and the laminate resin layer are controlled by the coating amount, but the control by such a simple amount cannot control the thickness of the coating layer. It is considered that sufficient performance is not exhibited due to the presence of pinholes in the coating layer.
[0004]
[Problems to be solved by the invention]
The present invention provides a can having excellent adhesion between a metal surface and a polyester resin coating layer, and a method for producing the can with high workability.
[0005]
[Means for solving the problem]
The present invention has solved all the problems by the following means.
The present invention
"1. In a drawn and ironed can molded from a tin-plated steel sheet in which at least one side serving as an inner surface of a can is coated with a thermoplastic resin in advance, a main component of the thermoplastic resin is a crystalline polyester resin, and the resin layer on the side wall of the can is The average thickness is 5 to 30 μm, and the average thickness of the tin film is 0.2 to 2.0 g / m ² The effective surface coverage of tin is 85% or more, and the metal surface in contact with the thermoplastic resin around the entire circumference of at least 2 mm from the tip of the flange is coated with an iron-tin alloy. A two-piece drawn and ironed can excellent in corrosion resistance and flavor, having a coverage of 0.7 or more.
2. 2. The two-piece drawn and ironed can according to item 1, wherein the crystalline polyester resin as a main component of the coating resin has a Tg of 55 ° C. or more and an intrinsic viscosity (IV) of 0.65 or more, which is excellent in corrosion resistance and flavor.
3. The effective coverage of tin is 0.1 g / m. ² 2. A two-piece drawn and ironed can excellent in corrosion resistance and flavor as described in item 1 or 2, which is a value indicating the ratio of the above portions.
4. Any one of items 1 to 3, wherein the iron-tin alloy coverage is a value C obtained from the amount of alloy tin A and the amount of surface tin B up to 2 mm from the end of the flange by the formula C = A / (A + B) 2. A two-piece drawn and ironed can excellent in corrosion resistance and flavor as described in the item.
5. Tin plating thickness is 0.4 to 6.0 g / m ² The surface of the tin-plated steel sheet, which is the inside of the can, is made of a crystalline polyester resin as a main component, has a crystallinity of 5% or less, a thickness of 15 to 90 μm, a breaking elongation of 100% or more, a Tg of 55 ° C. or more, A thermoplastic resin coating having a viscosity (IV) of 0.65 or more is arranged, and a cup is made by drawing at least once, and a heat treatment is performed until at least 2 mm from the tip of the flange of the can body, and then necessary. If it is, it is redrawn and then it is ironed by an punching die with an insertion angle of 2 to 8 degrees. By cooling immediately after the final ironing process, the average thickness of the resin layer on the side wall of the can is reduced. 5 to 30 μm, average thickness of tin film is 0.2 to 2.0 g / m ² , The effective coverage of tin is 85% or more, and the metal surface in contact with the thermoplastic resin of at least 2 mm from the tip of the flange is covered with the iron-tin alloy, and the coverage of the iron-tin alloy The method for producing a two-piece drawn and ironed can excellent in corrosion resistance and flavor properties, which is 0.7 or more.
6. Item 5. Molding while maintaining the temperature of the tin layer on the inner surface of the cup at a temperature not exceeding 232 ° C. at the time of molding, and quenching after the final ironing to reduce the inner surface tin temperature of the necking portion and the flange portion to 232 ° C. or less. 2. A method for producing a two-piece drawn and ironed can excellent in corrosion resistance and flavor as described in 1).
7. Item 5. The method for producing a two-piece drawn ironed can excellent in corrosion resistance and flavor described in Item 5 or 6, wherein a thermoplastic resin coating mainly composed of a polyester resin is drawn and oriented and crystallized in a step of ironing. "
About.
[0006]
[Action]
A first feature of the present invention is that corrosion resistance is improved by improving adhesion between a metal and a polyester resin coating.
As described above, when the tin-plated steel sheet is drawn and ironed, and neck flange processing is performed, if the degree of processing is large, the tin-plated layer and the polyester resin coating are separated. This is because the adhesion between the tin plating layer and the polyester resin coating is not good. In particular, peeling is likely to occur up to about 2 mm from the tip of the flange.
In the present invention, the metal surface around the entire circumference of at least 2 mm from the tip of the flange where peeling occurs is coated with an iron-tin alloy to prevent peeling of the polyester resin coating. The iron-tin alloy has better adhesion of the polyester resin coating than the tin plating layer, and has a greater effect of preventing peeling.
[0007]
The iron-tin alloy coating must be provided over the entire circumference with a width of at least 2 mm from the flange tip. If it is less than 2 mm, peeling during drawing cannot be prevented.
If the iron-tin alloy coverage over the entire circumference of at least 2 mm from the tip of the flange is not 0.70 or more, a sufficient peeling effect is not exhibited.
The coating ratio C of the iron-tin alloy is determined by measuring the amount of tin alloy A and the amount of surface tin B of a tin-plated steel plate 2 mm from the end of the flange according to the tin adhesion test method for tinplate and the electrolytic peeling method according to JIS G3303. , C = A / (A + B).
In order to form an iron-tin alloy coating, the tin plating layer can be alloyed by heating the cup edge to about 230 ° C. or higher in the cup state obtained by drawing.
[0008]
In this way, the can of the present invention is manufactured by alloying the cup edge portion, further drawing and ironing. The can of the present invention can also be obtained by heating a portion 2 mm or more from the tip of the cup which should become a flange after drawing and ironing to 230 ° C. or more.
The effective coverage of tin means that the thickness of the tin layer is 0.1 g / m ² This is the proportion occupied by the above-mentioned portions. If the content is less than 85%, even if there is a tin layer, corrosion under the film occurs and the corrosion resistance deteriorates.
The feature of the present invention is a can which is drawn and ironed by coating a thermoplastic resin on a tin-plated surface, wherein the thickness of the resin layer on the side wall of the can is 5 to 30 μm and the average thickness of the tin film is 0.1 μm. 2 to 2.0 g / m ² By setting the effective coverage of tin to 85% or more, a can having significantly improved corrosion resistance can be obtained.
[0009]
The inventor of the reason why the steel surface is not exposed to the tin layer when the thermoplastic resin is laminated on the tin plating layer and squeezing and ironing is performed, the processing tool does not directly touch the tin plating layer. Since the thermoplastic resin acts as a cushioning material and transmits the processing force to the tin layer while the resin itself is being formed, the processing force of the spread is not suddenly applied to the tin layer, and the spread is performed without difficulty. I think it's because. Therefore, the thermoplastic resin to be laminated is preferably one having good processability, and a crystalline polyester resin is suitable.
[0010]
The second effect of the present invention is that the flavor is good.
When the aroma component of the content is adsorbed on the inner material of the can, the flavor of the content changes. Further, even if the inner material of the can is eluted into the contents, the flavor of the contents changes.
As described above, the flavor property is generated not only by the exposure of the steel sheet of the tin plating layer but also by the resin coated.
According to the study of the present inventor, when a crystalline polyester resin having a Tg of 55 ° C. or more and an intrinsic viscosity (IV) of 0.65 or more is used as a thermoplastic resin for forming a laminate layer on a tin layer on the side wall of a can. It was found that the sorbed amount of the flavor component was significantly reduced, and that an isophthalic acid-based copolymerized polyester resin was particularly preferable.
[0011]
In addition, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate and copolymers and blends thereof are also used as crystalline polyesters.
The copolymer component of the copolymerized polyethylene terephthalate may be an acid component or an alcohol component. Examples of the acid component include aromatic dibasic acids such as isophthalic acid, phthalic acid, and naphthalenedicarboxylic acid, adipic acid, azelaic acid, sebacic acid, aliphatic dicarboxylic acids such as decanedicarboxylic acid, and alicyclics such as cyclohexanedicarboxylic acid. Examples of the alcohol component include aliphatic diols such as butanediol and hexanediol, and alicyclic diols such as cyclohexanedimethanol. These can be used alone or in combination of two or more.
[0012]
These crystalline polyesters can be used as a single layer or as two or more layers.
Of course, the flavor is greatly affected by the steel sheet being exposed from the tin plating layer.
As a result of various studies conducted by the present inventor to reduce the amount of iron eluted, a drawn ironing can with a small amount of iron eluted was coated on a tin-plated steel sheet with a tin plating thickness of 0.4 to 6.0 g / m. ² The surface of the tin-plated steel sheet, which is the inside of the can, is made of a crystalline polyester resin as a main component, has a crystallinity of 5% or less, a thickness of 15 to 90 μm, a breaking elongation of 100% or more, a Tg of 55 ° C. or more, A thermoplastic resin coating having a viscosity (hereinafter referred to as IV) of 0.65 or more is arranged, a cup is formed by one or more drawing operations, and a portion from the flange tip of the can body to a portion to be at least 2 mm is formed. Heating, then re-drawing if necessary, then ironing with an punch and an ironing die with an insertion angle of 2 to 8 degrees, cooling immediately after the final ironing step, and removing the resin layer on the side wall of the can. It was found that it can be obtained by molding so that the average thickness is 5 to 30 μm.
The laminate resin layer may be provided on both sides of the tin-plated steel sheet, but the front side surface of the can is not directly related to corrosion resistance and flavor resistance, and printing is performed, so the laminate layer is not necessarily required.
[0013]
The can of the present invention does not require a chemical conversion treatment because the resin is laminated on the tin plating layer on the inner surface. Since no chemical treatment is required, the workability is improved, the amount of water used can be reduced to １／ to ３, and the burden of wastewater treatment and wastewater treatment waste can be reduced. Although the tin layer is a thin layer having a thickness of 0.01 μm to 0.25 μm, it exhibits a sufficient anticorrosion property, prevents elution of iron, and exhibits excellent flavor resistance. Conventionally, it has not been possible to form such a thin tin layer having an effective coverage of 85% or more.
[0014]
Since the can body undergoes large processing, both the plating layer and the resin layer are thinned. The body of the can is greatly affected by the forming process and is liable to cause defects. The laminated thermoplastic resin layer is stretched and oriented, the strength is increased, and the barrier property is improved.
It is preferable to maintain the tin temperature during molding at a temperature not exceeding 232 ° C. This is because, since the melting point of tin is 231.9 ° C., molding at a temperature at which tin does not melt is effective in maintaining the uniformity of the tin coating and preventing a change in the coating rate.
[0015]
A third feature of the present invention is that in the drawing and ironing process, the forming process is performed while maintaining the temperature of the laminated resin on the punch side at or below the adhesive temperature.
During molding, the temperature of the outer surface of the can rises to about 250 ° C., and since this heat diffuses to the inner surface of the can, the temperature of the resin layer also increases. If the temperature is too high, oriented crystals of the resin layer cannot be obtained, resulting in insufficient strength and molding defects. If the temperature is higher than the adhesive temperature, the adhesive sticks to the punch and causes strip-out failure after molding.
[0016]
In order to prevent this, it is effective to cool the processing portion and immediately cool the can body with a coolant from the outer surface immediately after the processing to keep the temperature below the adhesive temperature.
Further, the surface condition of the laminated resin greatly affects the punch-out property after the final ironing. When the resin surface has fine irregularities, the fine irregularities on the resin surface are pressed against the punch surface during the ironing process, and a vacuum is created. Therefore, a large force is required to peel off the punch after molding. Therefore, when the cup is stripped out, the edge of the cup is bent, resulting in molding failure. Therefore, in order to improve the punch-out property, the air from the cup edge and the tip of the punch can easily enter the interface between the can wall and the punch, and the streaks must be formed so that the unevenness of the laminate resin surface is connected to the can height direction. Therefore, it is effective to prevent these irregularities from being isolated.
[0017]
In order to improve the processability, it is preferable that the processing temperature of the laminated resin layer is close to Tg. For example, in the case of PET, a good result can be obtained by setting the temperature of the coolant to about 50 ° C.
After the cup molding, the laminate resin layer is partially oriented and the moldability is reduced. Therefore, it is preferable to increase the temperature to 80 to 200 ° C. and perform annealing to remove distortion, in order to perform favorable processing.
[0018]
Since the laminated resin layer is slippery with the punch, it is effective in molding to reduce the entry angle of the ironing die and increase the surface pressure of the punch. If the coating resin layer slides with the punch, a wavy resin defect occurs. The entry angle of the ironing die is preferably 2 to 8 °, and particularly preferably 6 ° or less. Since the metal surface under the laminate layer is slightly increased in roughness by drawing, resin defects are likely to occur at the time of drawing due to unevenness of the punch surface and the presence of foreign matter.
Therefore, it is necessary to make the punch surface smooth and free of foreign matter.
Further, according to the present invention, the thermoplastic resin layer mainly composed of polyester coated on the tin-plated steel sheet can be oriented and crystallized in the step of drawing and ironing, so that the corrosion resistance and the flavor resistance are improved.
[0019]
【Example】
Next, an example and a comparative example will be described specifically.
In Examples and Comparative Examples, drawing ironing conditions and can-making conditions, measurement of the coating coefficient of tin coating, measurement of iron-tin alloy coating rate, evaluation of flange portion peeling, evaluation of flavor properties, evaluation of the actual can storage test are as follows. The procedure was as follows.
[0020]
1. Drawing and ironing conditions and can making conditions
Examples and Comparative Examples other than Example 10-1 and Examples 11-1 to 11-4 and Comparative Examples 11-1 to 11-2 were performed under the following drawing and ironing conditions and can making conditions.
Using a single-sided resin-coated steel plate having a metal plate thickness of 0.245 mm, blanking was performed to a blank diameter of 142 mm so that the resin-coated surface was the inner surface of the can, and a cup was formed at the first draw ratio of 1.6, and then the second draw ratio was 1 Then, iron drawing was performed in three steps, and a drawn ironing cup having a can body diameter of 65.8 mm, a metal thickness of the can body of 80 μm, and a metal thickness of the neck portion of 135 μm was formed. This squeezed ironing cup was trimmed to a can height of 123 mm, washed and dried, printed on the outer surface, heated at 200 ° C. for 30 seconds, and then the upper part of the can was reduced to an inner diameter of 57.25 mm (206 diameter). A flange was formed and a drawn iron can was obtained. The forming speed of redrawing and three steps of ironing is 200 cpm.
In Example 10-1, the drawing and ironing conditions are different from the above, but the neck and flange conditions are the same. In Examples 11-1 to 11-4 and Comparative examples 11-1 to 11-2, the drawing and ironing conditions were the same as above, but the neck and flange conditions were different from those described above. Only different points will be clearly shown in each of the examples and comparative examples.
[0021]
2. Cup heating conditions
Place the first iris cup upright and place a high frequency wave above the cup Induction heating A coil is installed so that high-frequency magnetic flux is applied to the cup edge. high frequency Induction heating The coil was set at a position 3 mm from the cup edge. The high frequency output was adjusted to control the cup edge temperature. The temperature of the cup edge was evaluated based on the degree of discoloration by applying several types of temperature-indicating paints to the resin surface inside the cup. The conditions in the Examples and Comparative Examples were a processing time of 1.0 second unless otherwise noted, and the temperature reached by the cup edge at this time was about 300 ° C.
[0022]
3. Measurement of tin coating factor
After removing the resin coating on the inner surface of the can wall including the neck and flange, the inner side wall of the can was divided into 2.0 mm lengths in the circumferential direction, and the EPMA line analysis of tin was performed for each of the 10 locations under the following conditions. The coating coefficient of the tin coating is determined by the following equation. The value of the smallest part of the tin coating coefficient of each location thus obtained is defined as the tin coating coefficient of this can. Measurement method: WDS, detection crystal: PET, acceleration voltage: 10 kv, sample current: 1 × 10E-8A, beam diameter 1.0 μm, detection X-ray: SnLα ray, time constant: 1.0 (s), scanning speed: 50 μm / min.
Tin coating coefficient (%)
= (Tin amount 0.1 g / m ² Length of above part (mm)) x 100 / 2.0 (mm)
[0023]
4. Measurement of iron-tin alloy coverage
The crystalline polyester resin of the neck portion is dissolved from the flange of the can body with a solvent such as 1,1,1,3,3,3-hexafluoro-2-propanol, and a portion up to 2 mm from the flange tip is cut off. The edge and the cut surface are sealed with a resin, and the metal surface which has been in contact with the thermoplastic resin is subjected to a method according to JIS G3303, “Testing method for tin adhesion on tinplate, electrolytic peeling method” to determine the amount of tin alloy (A). ) And the amount of surface tin (B) are measured. At this time, the current density was 10 mA / cm ² Do with.
The iron-tin alloy coverage (C) is defined by the following equation.
C = A / (A + B)
Also, when the metal surface after dissolving the thermoplastic resin is magnified 5000 times or more with a scanning electron microscope, a columnar or granular iron-tin alloy is observed, which is clearly different from the smooth metal tin surface, Can be identified.
[0024]
5. Flange peeling evaluation method
After necking was performed to a diameter of 206 or 202, and further flange processing was performed, the degree of peeling of the flange portion was examined for 1,000 cans. The criterion of the peeling of the flange portion was x when there was peeling of 0.5 mm or more from the flange edge in any part of the circumferential portion of the can. Alternatively, the case where one or more linear peelings in the direction of the can height were found was evaluated as x, and the case where there was no peeling was evaluated as ○.
[0025]
6. Evaluation of flavor properties
When the fragrance component of the content is sorbed on the inner material of the can, the flavor of the content changes. Also, the flavor of the contents changes even if the inner material of the can elutes into the contents. Flavor retention was evaluated by a sensory test of the flavor of the contents in a real can preservation test, and a sorption ratio of aroma components.
In the content flavor sensory test, after filling with Coca-Cola Light (carbonated beverage made by Nippon Coca-Cola Co., Ltd.), it was stored at room temperature for 3 months, and the sensory superiority difference with the liquid without storage over time was examined. The case where there was no superiority difference at the risk rate of 5% was evaluated as 、, and the case where there was a superiority difference at the risk rate of 5% was evaluated as ×.
Measurement of the odor component sorption rate is described in Journal of the Japan Food Industry Association, Vol. 34, no. 5,1987, 267-273. That is, a model solution (1% citric acid) containing a citrus flavor (mixed with 10 ppm each of myrcene, α-terpinene, d-limonene, γ-terpinene, p-cymene, and 2 carene) was added to the test can. After filling and winding, storing at 20 ° C for 10 days, collecting and concentrating the fragrance components from the inner film of the can, performing gas chromatography analysis, and determining the distribution ratio from the solution before filling (the amount in the inner film / the amount in the content liquid) ). The method of collecting, concentrating, and analyzing the odor components was in accordance with the aforementioned literature. A distribution ratio of d-limonene of less than 2% was evaluated as ○, and a distribution ratio of 2% or more was evaluated as x.
[0026]
7. Actual can storage test evaluation
100 cans are filled with coca-colite (carbonated drink) by a standard method, and after closing the lid, storing at 37 ° C. for 6 months, opening the cans, opening the inner surface of the cans under film (hereinafter abbreviated as UFC). Area), and the amount of iron ion eluted in the contents was measured by atomic absorption spectroscopy, and the average elution amount was calculated. UFC has a UFC area of 0 to 10 mm ² ○, 10mm ² Those that exceeded × were evaluated as ×.
[0027]
8. Measurement of crystallinity of crystalline polyester resin
The measurement of the crystallinity of the crystalline polyester resin which is the laminate resin layer is performed by the method described in SEN-IGAKKAISHI, Vol. 33, no. 10 (1977), 780-788. That is, the X-ray diffraction scattering intensity distribution was separated into contributions from a crystal phase and an amorphous phase, and calculated as an integrated intensity ratio with respect to the Bragg angle.
[0028]
9. Measurement of Tg, elongation at break (hereinafter referred to as El) and IV of resin before processing
After peeling the resin layer of the laminate plate from the metal plate, Tg and EL (growth) were measured by a conventional method. IV was measured at 25 ° C. in o-chlorophenol.
[0029]
10. Measurement of the average tin coating thickness on the can wall inner surface and the average organic resin coating thickness on the can wall inner surface
The average tin coating thickness on the inner surface of the can wall was determined by peeling the organic resin from the inner surface of the can wall (30-80 mm from the bottom of the can), which was the largest in ironing, and then preparing three 20 mmφ circular materials. The measured values obtained by the measurement were obtained by arithmetic averaging. The average thickness of the organic resin film on the inner surface of the can wall was obtained by dissolving the metal at the same site and peeling the organic resin, and arithmetically averaging the measured values obtained by measuring at 10 points with a micrometer at arbitrary points.
[0030]
Example 1-1
One side of a 0.245 mm thick, Temper 4, E2.8 / 2.8 tinplate was heat-coated with an amorphous crystalline polyester resin (polyethylene terephthalate / isophthalate system) having a thickness of 90 μm and quenched. Table 1 shows the Tg, EL, IV, and crystallinity of this resin after coating. Using this single-sided resin-coated tin-plated steel sheet, a drawn iron can was produced under the conditions shown in Table 1. Table 1 shows the conditions and evaluation.
[0031]
Examples 1-2 and 1-3, Comparative Examples 1-1 and 1-2
Examples 1-2, 1-3 and Comparative Example 1-1 were drawn and ironed in the same manner as in Example 1-1, except that the thickness of the organic resin film coated on the tin-plated steel sheet was 30 μm, 15 μm, and 9 μm, respectively. A can was made.
In Comparative Example 1-2, a drawn and ironed can was produced in the same manner as in Example 1-1, except that the thickness of the organic resin film coated on the tin-plated steel sheet was 120 µm. Table 1 shows the conditions and evaluation. The flavor and the actual can were not evaluated because the flange portion peeled off during the flange forming.
[0032]
Example 2-1
One side of a 0.245 mm thick, Temper 4, E2.8 / 2.8 tinplate is thermally coated with a 30 μm thick biaxially stretched crystalline polyester resin (polyethylene terephthalate / isophthalate system), and a laminated plate (formed) After the holding time at 230 ° C. was adjusted so that the crystallinity of the polyester resin in the preceding paragraph was 2%, the polyester resin was quenched. Table 1 shows the Tg, EL, IV, and crystallinity of this resin after coating. Using this one-side resin-coated tin-plated steel sheet, a drawn and ironed can was produced. Table 1 shows the conditions and evaluation.
[0033]
Example 2-2, Comparative Examples 2-1 and 2-2
Example 2-2 and Comparative Examples 2-1 and 2-2 are the same as those in Example 2-1 except that the crystallinity of the polyester resin of the laminated plate (before molding) is 5%, 9% and 24%, respectively. In the same manner as described above, a drawn and ironed can was prepared. Table 1 shows the conditions and evaluation.
[0034]
Example 3-1
An amorphous crystalline polyester resin (polyethylene terephthalate / isophthalate) having a thickness of 30 μm was heat-coated on one side of a 0.245 mm thick, Temper 4, E2.8 / 2.8 tinplate, and quenched. At this time, the Tg was adjusted to 64 ° C. by changing the copolymerization ratio of isophthalic acid, and the steel sheet was used to produce a drawn iron can. Table 1 shows the conditions and evaluation.
[0035]
Example 3-2, Comparative Examples 3-1 and 3-2
In Example 3-2 and Comparative Examples 3-1 and 3-2, the Tg of the polyester resin was 58 ° C (isophthalic acid copolymerization), 54 ° C (sebacic acid copolymerization), and 48 ° C (adipic acid copolymerization). Except for this, a drawn and ironed can was produced in the same manner as in Example 3-1. Table 1 shows the conditions and evaluation.
In Comparative Example 3-3, a thermosetting resin having a thickness of 3 μm was applied to one side (inner side) of a tin-plated steel sheet, followed by drying and baking (semi-cured state), and a 30 μm amorphous crystalline polyester resin thereon. Was heated and quenched in the same manner as in Example 3-1 except for quenching. Table 1 shows the conditions and evaluation.
In Comparative Example 3-4, a drawn and ironed can was produced in the same manner as in Example 3-1 except that the resin to be thermally coated was a polyester resin having no thermal crystallinity (polyethylene terephthalate / isophthalate). Table 1 shows the conditions and evaluation.
[0036]
Example 4-1
An amorphous crystalline polyester resin (polyethylene terephthalate / isophthalate) having a thickness of 30 μm was heat-coated on one side of a 0.245 mm thick, Temper 4, E2.8 / 2.8 tinplate, and quenched. This resin was changed in copolymerization ratio so that the elongation at break was 285%. Using this one-side resin-coated tin-plated steel sheet, a drawn and ironed can was produced. Table 1 shows the conditions and evaluation.
[0037]
Example 4-2, Comparative example 4-1
In Example 4-2 and Comparative Example 4-1, drawn and ironed cans were produced in the same manner as in Example 4-1 except that the breaking elongation of the polyester resin was 133% and 3%, respectively. Table 1 shows the conditions and evaluation.
[0038]
Example 5-1
On one side of a 0.245 mm thick, Temper 4, E2.8 / 2.8 tinplate, a 30 μm thick biaxially stretched crystalline polyester resin (polyethylene terephthalate / isophthalate system) having an IV of about 1.0 was heated. After being coated and kept at 230 ° C. so that the crystallinity of the polyester resin of the laminated plate (before molding) becomes 5%, it was quenched. Using this one-side resin-coated tin-plated steel sheet, a drawn and ironed can was produced. Table 1 shows the conditions and evaluation.
[0039]
Example 5-2, Comparative Examples 5-1 and 5-2
Example 5-2 and Comparative Examples 5-1 and 5-2 are the same as Example 5-1 except that the IV of the polyester resin after lamination is 0.68, 0.63, and 0.56, respectively. A squeezed and ironed can was made. Table 1 shows the conditions and evaluation.
[0040]
[Table 1]

[0041]
(Note) A to S in the table are abbreviations with the following meanings.
A: Isophthalic acid copolymerized PET
B: Sebacic acid copolymerized PET
C: Adipic acid copolymerized PET
D: Thermosetting resin (adhesive layer) + isophthalic acid copolymerized PET
E: Isophthalic acid copolymerized PET without thermal crystallinity
F: average organic resin coating on the inner surface of the can (μm)
G: average tin coating thickness on the inner surface of the can (g / m ² )
H: Tin internal effective coverage (0.1 g / m ² Proportion of the above parts)
J: Tg of resin before processing (℃)
K: IV of resin before processing (dl / g)
L: EL of resin before processing (%)
M: Crystallinity of resin before processing (%)
N: Cooling immediately before final ironing
O: Ironing die insertion angle (degree)
P: Corrosion evaluation
Q: Flavor evaluation
R: Aroma component sorption
S: Flavor sensory test
UFC: Sub-film corrosion
Diameter: Can neck diameter after neck
Rate: Iron-tin alloy coverage
Comment: Flange peeling evaluation
In Comparative Example 1-2, the flange was peeled off due to poor molding and canning conditions. In addition, punching was poor and continuous molding was impossible.
[0042]
Comparative Examples 6-1 and 6-2
In Comparative Examples 6-1 and 6-2, 0.245 mm thickness, temper 4, D6.0 / 2.8 tinting, and E2.8 / 2.8 tinting, with the 2.8 side as the outer surface side, After squeezing and ironing without organic resin coating, washing and drying, spray coating with a vinyl organosol resin, baking and hardening, making a squeezing and ironing can, inner tin surface average tin coating thickness , Measurement of the coating coefficient of the tin film, evaluation of the peeling of the flange portion, evaluation of the flavor property, and evaluation of the actual can storage test. The coverage of the iron-tin alloy was not measured. As a result, the average tin coating thickness on the inner surface of the can wall was 2.0 g / m2, respectively. ² , 0.9 g / m ² The tin coverage on the inner wall of the can wall is 81% and 77%, respectively, the number of flange peeled cans is 0, and the Fe elution amount in the actual can storage test is 2.7 ppm and 6.5 ppm, respectively. The UFC evaluation was x and x, respectively, and the flavor sensory test evaluation was x and x, respectively. Further, in the actual can storage test, out of 100 cans, 5 cans and 9 cans had perforation leakage from the lid winding portion.
[0043]
Example 7-1
A 30 μm-thick amorphous crystalline polyester resin (polyethylene terephthalate / isophthalate) was heated to the side (inner side) of the tinplate having a thickness of 0.245 mm, temper 4 and D 6.0 / 2.8. Coated and quenched. Using this one-side resin-coated tin-plated steel sheet, a drawn and ironed can was produced. Table 2 shows the conditions and evaluation.
[0044]
Examples 7-2 and 7-3, Comparative examples 7-1 and 7-2
Example 7-2 was tinned with D4.5 / 2.8 (4.5 is the inner side), Example 7-3, Comparative Examples 7-1 and 7-2 were tin on one side of the mild steel plate (the inner side). Each plating amount is 0.6g / m ² 0.3g / m ² , 0.0 g / m ² Then, tin plating was performed so that the amount of tin plating on the other surface (outer surface side) was 2.8 in each case, and the other steps were the same as in Example 7-1 to produce a drawn and ironed can. Table 2 shows the conditions and evaluation.
[0045]
Comparative Example 8
In Comparative Example 8, a drawn and ironed can was produced in the same manner as in Example 1-2 except that cooling after the final ironing was not performed. The punch was poor after ironing and the molded cup was not obtained.
[0046]
Example 9-1
A drawn and ironed can was manufactured in the same manner as in Example 1-2, except that an ironing die (hereinafter abbreviated as ID) having an angle of incidence of 2 ° was used for all of the first, second and third rds. Table 2 shows the conditions and evaluation.
[0047]
Examples 9-2 and 9-3, Comparative examples 9-1 and 9-2
Examples 9-2 and 9-3 and Comparative Examples 9-1 and 9-2 are the same as Example 9-1 except that the ID angles are 6 °, 8 °, 10 °, and 12 °, respectively. A squeezed and ironed can was made. Table 2 shows the conditions and evaluation.
[0048]
Example 10-1
An amorphous crystalline polyester resin (polyethylene terephthalate / isophthalate) having a thickness of 30 μm was heat-coated on one side of a 0.245 mm thick, Temper 1, E2.8 / 2.8 tinplate, and quenched. Table 1 shows Tg, El, IV, and crystallinity after coating with this resin. Using this one-sided resin-coated tin-plated steel sheet, blanking was performed to a blank diameter of 142 mm so that the resin-coated surface was the inner surface of the can, and a cup was formed at a drawing ratio of 2.1. A drawn ironing cup having a body diameter of 65.8 mm, a metal thickness of the can body of 80 μm, and a metal thickness of the neck portion of 135 μm was formed. At this time, the cup edge of the first drawing cup is Guidance Heat treated. This squeezed ironing cup is trimmed so that the can height becomes 123 mm, washed and dried, printed on the outer surface, heated at 200 ° C. for 30 seconds, then reduced in diameter at the upper part of the can to 57.25 mm and formed a flange. A squeezed and ironed can was obtained. Table 2 shows the molding conditions.
With respect to the drawn ironing can thus obtained, the average tin coating thickness, the thickness of the organic resin coating, the measurement of the coating coefficient of the tin coating, the measurement of the iron-tin alloy coating ratio, the visual observation of the can-making state, and the evaluation of the flavor property , A can storage test evaluation. Table 2 shows the results.
[0049]
Example 11-1
The first squeeze cup is heated at a cup edge reaching temperature of about 300 ° C. for 1.0 second. Guidance Except for performing the heat treatment and reducing the inner diameter of the can upper part to 52.40 mm (202 diameter), a drawn ironing can was prepared in the same manner as in Example 1-2. Table 2 shows the conditions and evaluation results.
[0050]
Example 11-2
The first squeeze cup is heated at a cup edge reaching temperature of about 320 ° C. for 1.0 second. Guidance A squeezed and ironed can was prepared in the same manner as in Example 11-1, except for performing the heat treatment. Table 2 shows the conditions and evaluation results.
[0051]
Example 11-3
Tin plating amount of tinplate to be on the inner surface of the can is 6.0 g / m ² A wrung and ironed can was made in the same manner as in Example 11-1, except that Table 2 shows the conditions and evaluation results.
[0052]
Example 11-4
Tin plating amount of tinplate to be the inner surface of the can is 0.6 g / m ² A wrung and ironed can was made in the same manner as in Example 11-1, except that Table 2 shows the conditions and evaluation results.
[0053]
Comparative Example 11-1
The first squeeze cup is heated at a cup edge reaching temperature of about 240 ° C. for 1.0 second. Guidance A squeezed and ironed can was prepared in the same manner as in Example 11-1, except for performing the heat treatment. Table 2 shows the conditions and evaluation results.
[0054]
Comparative Example 11-2
A squeezed and ironed can was prepared in the same manner as in Example 11-1, except that there was no heat treatment in the cup. Table 2 shows the conditions and evaluation results.
[0055]
From Examples 1-1 to 1-3, 3-1 and 3-2, 7-1 to 7-3, and 10-1 and 11-1 to 11-4, the drawn and ironed can was previously placed on the inner surface of the can. Molded from a tin-plated steel sheet heat-coated with a thermoplastic resin, the main component of the thermoplastic resin on the inner surface of the can body is a crystalline polyester resin, and the average thickness of the thermoplastic resin layer on the side wall of the can is 5 to 30 μm. Yes, the average tin coating thickness on the inner surface of the can wall is 0.2 to 2.0 g / m ² The effective surface area of tin is 85% or more, and the metal surface in contact with the thermoplastic resin of at least 2 mm from the tip of the flange is covered with the iron-tin alloy. It can be seen that when the coverage is 0.7 or more, excellent corrosion resistance (Fe elution, UFC, perforation corrosion resistance) and flavor properties (anti-odor component sorption resistance, anti-odor component elution resistance) are excellent.
[0056]
From Comparative Examples 6-1 and 6-2, when the drawn and ironed can was formed from a tin-plated steel sheet without an organic coating and then an organic coating was formed by spray coating, the effective tin coverage was 85%. It can be seen that the corrosion resistance and flavor were inferior.
[0057]
From Comparative Example 3-3, when the drawn and ironed can was formed from a tin-plated steel sheet in which a surface to be an inner surface of the can was previously coated with a thermosetting resin and a thermoplastic resin was coated thereon, the effective tin coverage was Below 85%, it can be seen that the corrosion resistance and flavor are inferior.
[0058]
From Comparative Example 3-4, when the main component of the thermoplastic resin on the inner surface of the can body is an amorphous (no thermocrystalline) polyester resin, the effective coverage of tin is less than 85%, and the corrosion resistance and flavor properties are poor. You can see that.
[0059]
From Comparative Example 1-1, when the average thickness of the thermoplastic resin in the side wall portion of the can is less than 5 µm, the effective coverage of tin is less than 85%, and the corrosion resistance and flavor properties are poor.
[0060]
From Comparative Example 1-2, it can be seen that when the average thickness of the thermoplastic resin in the side wall portion of the can exceeds 30 μm, peeling occurs between the organic resin and the metal in the flange portion, and the can cannot be made.
[0061]
From Comparative Examples 7-1 and 7-2, the average tin coating thickness on the inner surface of the can wall was 0.2 g / m. ² When the ratio is less than, the effective coverage of tin is less than 85%, which indicates that the corrosion resistance and the flavor are inferior.
[0062]
Comparative Examples 1-1, 2-1 2-2, 3-1 to 3-4, 4-1 5-1 5-2, 6-1, 6-2, 7-1, 7-2, From 9-1, 9-2, 11-1, and 11-2, it can be seen that when the effective coverage of tin is less than 85%, the corrosion resistance and flavor properties are inferior.
From Comparative Example 11-1, high frequency of cup edge Induction heating When the treatment temperature is low, the coverage of the iron-tin alloy falls below 0.7, the flange peels off, and it can be seen that cans worthy of being subjected to the pack test cannot be made.
From Comparative Example 11-2, it can be seen that when there was no heat treatment in the cup, the coverage of the iron-tin alloy was less than 0.7, the flange peeled off, and a can worthy of being subjected to the pack test could not be made.
From Comparative Examples 11-1 and 11-2, it can be seen that when the iron-tin alloy coverage is less than 0.7, flange peeling occurs and the can cannot be made.
[0063]
From Comparative Example 8, it can be seen that when not cooled after the final ironing, punch removability is poor and continuous molding cannot be performed.
[0064]
Examples 2-1, 2-2, 3-1, 3-2, 4-1, 4-2, 5-1, 5-2, 9-1 to 9-3, 11-1 to 11-4, From Comparative Examples 2-1, 2-2, 3-1, 3-2, 4-1, 5-1, 5-2, 8, 9-1, 9-2, 11-1, and 11-2, cans The crystalline polyester resin, which is the main component of the thermoplastic resin on the inner surface of the body, has a Tg of 55 ° C. or more, an IV of 0.65 or more, a crystallinity of the resin before molding of 5% or less, and an El of 100% or more. A cup is formed by one or more drawing operations, a heat treatment is performed on at least a portion that should be at least 2 mm from the end of the flange of the can body, and then, if necessary, a redrawing process is performed. ８8 ° C. By cooling immediately after the final ironing process and manufacturing, the drawn ironing can is coated with a thermoplastic resin beforehand on the inner surface of the can. The main component of the thermoplastic resin on the inner surface of the can body is a crystalline polyester resin, and the average thickness of the thermoplastic resin layer on the side wall of the can is 5 to 30 μm. The coating thickness is 0.2 to 2.0 g / m ² The effective metal coverage of tin is 85% or more, and the metal surface in contact with the thermoplastic resin over the entire circumference of at least 2 mm from the end of the flange is coated with an iron-tin alloy, and the corrosion resistance and flavor are high. It can be seen that a drawn ironing can with excellent properties is manufactured.
[0065]
[Table 2]

[0066]
(Note) A to S in the table are abbreviations with the following meanings.
A: Isophthalic acid copolymerized PET
B: Sebacic acid copolymerized PET
C: Adipic acid copolymerized PET
D: Thermosetting resin (adhesive layer) + isophthalic acid copolymerized PET
E: Isophthalic acid copolymerized PET without thermal crystallinity
F: average organic resin coating on the inner surface of the can (μm)
G: average tin coating thickness on the inner surface of the can (g / m ² )
H: Tin internal effective coverage (0.1 g / m ² Proportion of the above parts)
J: Tg of resin before processing (℃)
K: IV of resin before processing (dl / g)
L: EL of resin before processing (%)
M: Crystallinity of resin before processing (%)
N: Cooling immediately before final ironing
O: Ironing die insertion angle (degree)
P: Corrosion evaluation
Q: Flavor evaluation
R: Aroma component sorption
S: Flavor sensory test
UFC: Sub-film corrosion
Diameter: Can neck diameter after neck
Rate: Iron-tin alloy coverage
Comment: Flange peeling evaluation
In addition, in Comparative Examples 11-1 and 11-2, the molding and can-making state were poor, and the flange was peeled off. In Comparative Example 8, the neck flange portion peeled off. Poor punch punching properties prevented continuous molding.
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【The invention's effect】
The present invention has a conventionally unknown tin plating layer of 0.2 g / m2. ² ~ 2.0g / m ² Having a laminated layer of 5-30 μm of thermoplastic resin on the surface of which the effective coverage of tin is 85% or more, and the entire circumference of at least 2 mm from the tip of the flange. The metal surface in contact with the thermoplastic resin is coated with an iron-tin alloy, and the iron-tin alloy has a coating rate of 0.7 or more, which is an extremely excellent effect on corrosion resistance and flavor resistance. To play.

Claims

In a drawn ironing can molded from a tin-plated steel sheet coated with a thermoplastic resin in advance on at least one inner surface of the can, the main component of the thermoplastic resin is a crystalline polyester resin, and the average thickness of the resin layer on the side wall of the can is 5 to 30 μm, the average thickness of the tin film is 0.2 to 2.0 g / m ² , the effective coverage of tin is 85% or more, and the thermoplastic resin is at least 2 mm from the tip of the flange. A two-piece drawn ironing can excellent in corrosion resistance and flavor, characterized in that the metal surface in contact with the iron-tin alloy is coated with an iron-tin alloy, and the coating ratio of the iron-tin alloy is 0.7 or more.

The two-piece drawn ironing can according to claim 1, wherein the crystalline polyester resin as a main component of the coating resin has a Tg of 55 ° C or more and an intrinsic viscosity (IV) of 0.65 or more, which is excellent in corrosion resistance and flavor. .

The two-piece drawer according to claim 1 or 2, wherein the effective coverage of tin is a value indicating a ratio of a portion where the thickness of the tin film is 0.1 g / m ² or more. Ironing can.

4. The method according to claim 1, wherein the coating ratio of the iron-tin alloy is a value C obtained from the amount of alloy tin A and the amount of surface tin B up to 2 mm from the end of the flange by the formula C = A / (A + B). 2. A two-piece drawn and ironed can excellent in corrosion resistance and flavor as described in the item.

A tin-plated steel sheet having a tin-plated thickness of 0.4 to 6.0 g / m ² has a crystallinity of 5% or less and a thickness of 15 to 90 μm mainly composed of a crystalline polyester resin, A thermoplastic resin coating having a breaking elongation of 100% or more, a Tg of 55 ° C. or more, and an intrinsic viscosity (IV) of 0.65 or more is arranged, and a cup is made by drawing at least once, and a flange tip of the can body is formed. From 2 to at least 2 mm, then re-drawing if necessary, then ironing with a punch and an ironing die with an insertion angle of 2 to 8 degrees, and cooling immediately after the final ironing process By doing so, the average thickness of the resin layer in the side wall of the can is 5 to 30 μm, the average thickness of the tin film is 0.2 to 2.0 g / m ² , the effective tin coverage is 85% or more, and the flange tip At least 2 The metal surface in contact with the thermoplastic resin on the entire circumference of mm is coated with an iron-tin alloy, and the iron-tin alloy coating rate is 0.7 or more. 2-piece drawing and ironing with excellent corrosion resistance and flavor. How to make cans.

The molding is performed while maintaining the temperature of the tin layer on the inner surface of the cup at a temperature not exceeding 232 ° C. at the time of molding, and quenching is performed after the final ironing to reduce the inner surface tin temperature of the necking portion and the flange portion to 232 ° C. or less. 5. The method for producing a two-piece drawn and ironed can described in 5 which is excellent in corrosion resistance and flavor.

The method for producing a two-piece drawn ironed can excellent in corrosion resistance and flavor according to claim 5 or 6, wherein the thermoplastic resin coating mainly composed of a polyester resin is oriented and crystallized in a step of drawing and ironing.