JP4288576B2

JP4288576B2 - Method for producing resin-coated metal sheet

Info

Publication number: JP4288576B2
Application number: JP2003173115A
Authority: JP
Inventors: 邦治森; 裕久藤田; ▲煕▼ 永野; 英人大橋
Original assignee: Toyobo Co Ltd
Current assignee: Toyobo Co Ltd
Priority date: 2002-06-21
Filing date: 2003-06-18
Publication date: 2009-07-01
Anticipated expiration: 2023-06-18
Also published as: JP2004074779A

Description

【０００１】
【発明の属する技術分野】
本発明は樹脂被覆金属板の製造方法に関するものである。さらに詳細には、製缶性（例えば、絞り・しごき加工性）とフレーバー性に優れた樹脂被覆金属板の製造方法関するものであって、かつ温水殺菌処理が実施される金属缶に好適な樹脂被覆金属板の製造方法に関するものである。
【０００２】
【従来技術】
従来、金属缶の缶内面および缶外面は腐蝕防止を目的として、エポキシ系，フェノール系等の各種熱硬化性樹脂を溶剤に溶解または分散させたものを塗布し、金属表面を被覆することが広く行われてきた。しかしながら、この熱硬化性樹脂の被覆方法では塗料の乾燥に長時間を要するため生産性が低下したり、多量の有機溶剤による環境汚染など好ましくない問題を発生させることが多いという欠点があった。
【０００３】
かかる欠点を解決するため、金属板に熱可塑性樹脂を溶融押出法で被覆する方法が開示されている（例えば、特許文献１参照）。また、溶融押出した熱可塑性樹脂を一旦冷却固化させた後、加熱された金属板に圧着する方法が開示されている（例えば、特許文献２参照）。また、溶融押出法で作製したポリエチレンテレフタレートおよび／またはポリブチレンテレフタレートの未配向フィルムを加熱された金属板に圧着する方法が開示されている（例えば、特許文献３参照）。しかしながら、これらの熱可塑性樹脂の被覆方法では、Ｔダイから層状に溶融樹脂を押出す際、溶融樹脂膜の巾減少（ネックインと称す）が大きく、被覆に必要な樹脂巾に対して数１０ｃｍ広い巾で製膜する必要があり、経済性の点から満足される方法ではなかった。
【０００４】
かかる欠点を解決するため、三官能以上の多塩基酸または多価アルコール成分を共重合させたポリエステルを配合してなるポリエステルを使用することによりネックインを小さくする方法が開示されている（例えば、特許文献４、特許文献５参照）。しかしながら、これらの被覆方法では、三官能以上の多塩基酸または多価アルコール成分を共重合させたポリエステルが押出機からＴダイに至る溶融工程で熱劣化しやすく、熱安定剤を併用しても得られた溶融樹脂膜に異物（例えば、ゲル状異物または劣化物を核とした異物）が発生しやすく、製缶時に樹脂被覆層に異物を起点とした亀裂が入るため、製缶用の樹脂被覆金属板として満足されるものではなかった。
【０００５】
また、絞り・しごき缶に用いられる樹脂被覆金属板の被覆用樹脂では、製缶（絞り・しごき加工）に追従しうる優れた成形性が要求されるばかりでなく、製缶後に美麗化を目的として実施される外面焼付け塗装の加熱においても耐衝撃性が低下しないことが要求される。しかしながら、前記の樹脂被覆金属板は耐衝撃性が低下することが多く、耐衝撃性の要求を満足するものではなかった。
【０００６】
【特許文献１】
特開昭５７−２０３５４５号公報
【特許文献２】
特開平１０−３０９７７５号公報
【特許文献３】
特開２００１−１４４７号公報
【特許文献４】
特開平１０−８６３０８号公報
【特許文献５】
特開２０００−７１３８８号公報
【０００７】
【発明が解決しようとする課題】
本発明は前記従来技術の問題点を解消することを目的とするものである。即ち、溶融押出時のネックインが小さく、かつ得られた溶融樹脂膜に異物が発生しにくいため、経済性と製缶性に優れ、かつ得られた金属缶のフレーバー性に優れ、かつ内容物を充填後に実施される温水殺菌処理で金属缶外面の外観不良（樹脂膜の白化）が発生しにくい樹脂被覆金属板の製造方法を提供するものである。
【０００８】
【課題を解決するための手段】
本発明の目的は、金属板の片面に融点１８０℃以上の結晶性ポリエステルを主体とする樹脂膜（Ａ）を被覆しもう一方の面に融点１８０℃以上の結晶性ポリエステルよりなる樹脂膜（Ｂ）を被覆する製造方法において、Ｔダイを用いて両端部にオレフィン系ポリマーが合流された状態で得た溶融樹脂膜を冷却固化後に両端部を切断除去して樹脂膜（Ａ）と樹脂膜（Ｂ）を得る方法と樹脂膜（Ａ）および樹脂膜（Ｂ）を加熱された金属板にラミネートする方法よりなる樹脂被服金属板の製造方法であって、かつ樹脂膜（Ａ）はポリトリメチレンテレフタレートを主体とするポリエステルとオレフィン系ポリマーが７０：３０〜１００：０（重量％）よりなるものであり、樹脂膜（Ｂ）はポリトリメチレンテレフタレートを主体とするポリエステルよりなるものであることを特徴とする樹脂被覆金属板の製造方法によって達成される。
【０００９】
【発明の実施の形態】
本発明ではポリトリメチレンテレフタレートの特性を損なわない範囲でテレフタル酸以外のジカルボン酸成分とプロピレングリコール以外のグリコール成分を使用できる。例えば、ジカルボン酸として、イソフタル酸，オルソフタル酸，ナフタレンジカルボン酸，ジフェニルスルホンジカルボン酸，５−ナトリウムスルホイソフタル酸等の芳香族ジカルボン酸、シュウ酸，コハク酸，アジピン酸，セバシン酸，デカンジカルボン酸，マレイン酸，フマル酸，ダイマー酸等の脂肪族ジカルボン酸、ｐ−オキシ安息香酸等のオキシカルボン酸、シクロヘキサンジカルボン酸等の脂環族ジカルボン酸が使用できる。また、プロピレングリコール以外のグリコール成分として、エチレングリコール，ブタンジオール，ペンタンジオール，ヘキサンジオール，ネオペンチルグリコール等の脂肪族グリコール、シクロヘキサンジメタノール等の脂環族グリコール、ビスフェノールＡ，ビスフェノールＳ等の芳香族グリコールが使用できる。
本発明におけるポリエステルには、必要に応じて酸化防止剤，熱安定剤，紫外線吸収剤，可塑剤，顔料，帯電防止剤，潤滑剤，結晶核剤，無機又は有機粒子よりなる滑剤等を配合させてもよい。
本発明におけるポリエステルの製造方法については特に限定しない。即ち、エステル交換法または直接重合法のいずれの方法で製造されたものであっても使用できる。また、分子量を高めるために固相重合法で製造されたものであってもかまわない。さらに缶に内容物を充填後に実施されるパストライズ処理，レトルト処理等でのポリエステル樹脂からのオリゴマー量を少なくする点より、減圧固相重合法で製造されたオリゴマー含有量が低いポリエステルを使用することは好ましい。但し、樹脂膜（Ａ）と樹脂膜（Ｂ）のポリエステルのポリトリメチレンテレフタレートの比率が同一であることが好ましい。その理由は、樹脂の無駄を省く観点から層状に押出された樹脂を冷却固化後に切断除去して得た両端部を含む樹脂を樹脂膜（Ａ）の中央部で再使用した場合、金属板に被覆された樹脂膜の品質が安定するためである。
【００１０】
本発明で使用されるポリエステルの融点は１８０℃以上であることが製缶性（絞り・しごき加工において、缶内面側の樹脂ではポンチの離型性の確保、缶外面側の樹脂ではかじり抑制［樹脂皮膜での縦方向のキズ］）から必要である。
【００１１】
ポリエステルとブレンドされるオレフィン系ポリマーは特に限定しない。低密度ポリエチレン，中密度ポリエチレン，高密度ポリエチレン，直鎖状低密度ポリエチレン，超高分子量ポリエチレン，ポリプロピレン，エチレン−プロピレン共重合体，エチレン−ブテン共重合体，エチレン−酢酸ビニル共重合体，エチレン−エチルアクリレート共重合体，エチレン−ビニルアルコール共重合体，アイオノマー等が使用できる。但し、Ｔダイから押出された層状の樹脂膜（Ａ）の両端部と中央部で使用するオレフィン系ポリマーおよび樹脂膜（Ｂ）の両端部で使用するオレフィン系ポリマーは同一であることが好ましい。その理由は、樹脂の無駄を省く観点から層状に押出された樹脂を冷却固化後に切断除去して得た両端部を含む樹脂を樹脂膜（Ａ）の中央部で再使用した場合、金属板に被覆された樹脂膜の品質が安定するためである。
本発明ではポリエステル系フィルムのポリエステルとオレフィン系ポリマーの比率は７０：３０〜１００：０（重量％）であることが必要である。オレフィン系ポリマーが３０重量％を超える場合、製缶性（加工ポンチの離型性）が劣り、かつ得られた金属缶のフレーバー性が劣るため好ましくない。
本発明では両端部を含む樹脂を再使用する場合、再使用比率は特に限定しないが、５〜６０（重量％）が好ましい。
【００１２】
本発明ではポリエステルとオレフィン系ポリマーをＴダイから層状に押出す際、両端部（片側が５cm以下の部分）にオレフィン系ポリマーを使用することが必要である。
本発明ではポリエステルとオレフィン系ポリマーをドライブレンドまたは溶融混合して得たポリマーを公知の１軸または２軸押出機内で溶融させた後、エッジラミネーションタイプ等の公知のマルチマニホールドダイを使用して層状の溶融樹脂膜を得る。
【００１３】
本発明では冷却固化方法として、回転させた冷却ロールにＴダイから層状に溶融した樹脂を接触させる公知の方法が使用できる。溶融樹脂を冷却ロールに接触させる際、強制的にエアーを吹き付ける方法又は静電気で密着させる方法を採用することが好ましい。また、強制エアー吹き付け法，静電密着法のいずれにおいても層状樹脂の両端部と中央部を独立させて実施する方法がより好ましい。
本発明では冷却固化させた後、両端部を切断除去して得た樹脂膜を加熱された金属板に直接ラミネートする方法、または冷却固化させた後、両端部を切断除去して得た樹脂膜を一旦巻取った後、別工程で加熱された金属板にラミネートする方法のいずれも使用できる。但し、後者の被覆方法においては、冷却固化物を縦延伸（例えば、ポリエステルのガラス転移点以上で１．３〜６．０倍延伸）を実施し、さらに緊張下で熱処理（例えば、５０℃以上かつポリエステルの融点−２０℃の温度で１〜２０秒間）を実施することが好ましい。その理由は、巻取った樹脂膜ロールを保管した後、この樹脂膜ロールを加熱金属板に被覆する際、巻出し張力による樹脂膜の破断と樹脂膜ロールの保管時における経時収縮に起因したシワ，ブロッキング等を抑制するのに好ましいためである。
本発明では金属板として、ティンフリースティール等の表面処理鋼板あるいはアルミニウム板またはアルミニウム合金板あるいは表面処理を施したアルミニウム板またはアルミニウム合金板が使用できる。これらの金属板をポリエステルの融点−２０℃以上かつ融点＋１５０℃に加熱した後、ラミネートロールを使用して樹脂膜（Ａ）と樹脂膜（Ｂ）を金属板に同時ラミネートまたは逐次ラミネートし、引き続いてこのラミネート金属板をポリエステルの融点＋１０℃以上かつ融点＋６０℃で加熱した後、水冷および／または空冷して樹脂被覆金属板を得る。本発明では金属板上の樹脂膜厚みは特に限定されないが、１０〜５０μｍが被覆効果（防錆性）と経済性の点から好ましい。
【００１４】
【実施例】
以下、実施例をもとに本発明を説明する。
［評価方法］
（１）ポリエステルの融点
ポリエステル組成物を３００℃で５分間加熱溶融した後、液体窒素で急冷して得たサンプル１０ｍｇを用い、窒素気流中、示差走査型熱量計（ＤＳＣ）を用いて１０℃／分の昇温速度で発熱・吸熱曲線（ＤＳＣ曲線）を測定したときの、融解に伴う吸熱ピークの頂点温度を融点Ｔｍ（℃）とした。
【００１５】
（２）ネックイン量
Ｔダイの吐出口巾（６０ｃｍ）とｎ＝３で測定した冷却固化後の樹脂膜巾（両端部を切断除去する前の樹脂膜巾）の平均値（Ａｃｍ）を用い、次式でネックイン量（ｃｍ）を求めた。ネックイン量が５ｃｍ以下を実用性ありと評価した。
ネックイン量（ｃｍ）＝６０−Ａ
【００１６】
（３）樹脂被覆金属板の作製方法
２５０℃に加熱したアルミニウム合金板（厚み：0.２６mmの３００４系合金板）の片面に樹脂膜（Ａ），もう一方の面に樹脂膜（Ｂ）を同時にラミネートした後、２７５℃で加熱した後に水中急冷してラミネートアルミニウム板を作製した。
【００１７】
（４）缶内面樹脂と加工ポンチの離型性
ラミネートアルミニウム板をｎ＝１０で製缶し、成形缶上部に起る座屈程度を目視観察した。評価基準は以下のとおり設定し、○を実用性ありと評価した。
○：缶開口部の座屈未発生
△：缶開口部円周の約１／３に座屈発生
×：缶開口部円周の１／３以上に座屈発生
【００１８】
（５）缶外面の耐かじり性（缶外面樹脂における縦方向のキズ）
ラミネートアルミニウム板をｎ＝１０で製缶し、成形した缶体胴壁部外面樹脂のキズ発生程度を目視観察した。評価基準は以下のとおり設定し、○を実用性ありと評価した。
○：キズ未発生
△：外面の約１／３にキズ発生
×：外面の１／３以上に激しいキズ発生
【００１９】
（６）フレーバー性
密閉型のガラス容器に充填したｄ−リモネン中に５cm角のラミネートアルミニウム板を浸漬させた後、４０℃の恒温室で１０日間静置し、ｄ−リモネンを吸着させる。表面に付着しているｄ−リモネンをキムワイプで拭き取り重量Ｗ１を測定する。重量Ｗ１測定後のラミネートアルミニウム板を６０℃で２４時間真空乾燥させた後、重量Ｗ２を測定する。さらに、ラミネートアルミニウム板のアルミニウム板を酸溶解後乾燥して得た剥離フィルムの重量Ｗ３を測定する。ｄ−リモネン吸着量を次式により求め重量％で表示する。ｄ−リモネン吸着量が３重量％以下のものを実用性ありと評価する。
ｄ−リモネン吸着量（重量％）＝（Ｗ１−Ｗ２）／Ｗ３×１００
【００２０】
（７）温水処理後の缶外面の白化程度
アルミニウムラミネート板を製缶して得た缶を２７０℃で４０秒間加熱した後水中急冷したものをサンプルとする。このサンプルを８０℃の温水中に１０分間浸漬した後、水中急冷して得た缶外面を目視観察した。評価基準は以下のとおり設定し、○を実用性ありと評価した。
○：白化が目立たない
△：明らかに白化しているが、アルミニウム合金板の色が見える
×：白化によりアルミニウム合金板の色がみえない
【００２１】
［実施例・比較例に用いたポリエステルとオレフィン系ポリマーの略号と内容］
（１）ＰＴＴ：ポリトリメチレンテレフタレート
（２）ＰＥＴ：ポリエチレンテレフタレート
（３）ＣＯ−ＰＥＳ：テレフタル酸とエチレングリコール／シクロヘキサンジメタノール（モル％７０／３０）との共重合ポリエステル
（４）オレフィン：タフマーＡ−４０８５（三井化学社製、商品名）
（５）アイオノマー：ハイミラン１７０６（三井デュポンポリケミカル社製、商品名）
【００２２】
［実施例１］
樹脂膜（Ａ）の中央部の原料としてＰＴＴ８７重量％とオレフィン１３重量％を２８０℃で溶融させ、樹脂膜（Ａ）の両端部の原料としてオレフィン単体を２５０℃で溶融させ、エッジラミネーションタイプのＴダイ（オレフィンの吐出口巾／中央部の吐出口巾／オレフィンの吐出口巾＝２ｃｍ／５６ｃｍ／２ｃｍ、２６０℃に加熱）を用いて、層状に冷却ロール（周速２０ｍ／分）へキャスト（Ｔダイから冷却ロールでの溶融樹脂の接地点までの距離１５cm、中央部と両端部は別々の装置で強制的にエアーを吹付け）した後、両端部（片側５ｃｍ）を切断除去して巻取り、樹脂膜（Ａ）に用いる厚みが２５μｍのロール状の樹脂膜を得た。
また、樹脂膜（Ｂ）の中央部の原料としてＰＴＴを２８０℃で溶融させ、樹脂膜（Ｂ）の両端部の原料としてオレフィン単体を２５０℃で溶融させ、エッジラミネーションタイプのＴダイ（オレフィンの吐出口巾／中央部の吐出口巾／オレフィンの吐出口巾＝２ｃｍ／５６ｃｍ／２ｃｍ、２６０℃に加熱）を用いて、層状に冷却ロール（周速２０ｍ／分）へキャスト（Ｔダイから冷却ロールでの溶融樹脂の接地点までの距離１５cm、中央部と両端部は別々の装置で強制的にエアーを吹付け）した後、両端部（片側５ｃｍ）を切断除去して巻取り、樹脂膜（Ｂ）に用いる厚みが１６μｍのロール状の樹脂膜を得た。
２５０℃に加熱した３００４系アルミニウム合金板（厚み０．２６mm）の片面に樹脂膜（Ａ）を圧着し、もう一方の面に樹脂膜（Ｂ）を圧着し２７５℃に加熱した後、水中急冷してラミネートアルミニウム板を得た。
こうして得られたラミネートアルミニウム板に成形用潤滑剤を塗布した後、加熱して板温７０℃で樹脂膜（Ａ）が缶内面側となるようにして絞り加工を実施した。次いで、得られたカップの温度を４０℃にして金型温度８０℃でしごき加工を実施し、３５０mlサイズのシームレス缶を得た。
ポリエステルの融点，キャスト時のネックイン量，製缶性（缶内面樹脂膜とポンチの離型性と缶外面樹脂膜のキズ発生程度），フレーバー性，温水処理後の缶外面の白化程度を表１に示す。本実施例の方法は、ネックイン量が小さく経済性に優れた樹脂被覆金属板の製造方法であり、製缶性とフレーバー性が優れた樹脂被覆金属板の製造方法であり、さらに外面の耐温水白化性が優れた金属缶が得られる樹脂被覆金属板の製造方法であるといえる。
【００２３】
［実施例２］
樹脂膜（Ａ）の中央部の原料としてＰＴＴ８７重量％とアイオノマー１３重量％とし、樹脂膜（Ａ）の両端部と樹脂膜（Ｂ）の両端部の原料をアイオノマーとした以外は実施例１と同様にして樹脂膜（Ａ）に用いる厚みが２５μｍのロール状樹脂膜と樹脂膜（Ｂ）に用いる厚みが１６μｍのロール状樹脂膜を得た。
ついで、実施例１と同様にラミネートアルミニウム板を作製し、製缶して３５０mlサイズのシームレス缶を得た。
ポリエステルの融点，キャスト時のネックイン量，製缶性（缶内面樹脂膜とポンチの離型性と缶外面樹脂膜のキズ発生程度），フレーバー性，温水処理後の缶外面の白化程度を表１に示す。本実施例の方法は、ネックイン量が小さく経済性に優れた樹脂被覆金属板の製造方法であり、製缶性とフレーバー性が優れた樹脂被覆金属板の製造方法であり、さらに外面の耐温水白化性が優れた金属缶が得られる樹脂被覆金属板の製造方法であるといえる。
【００２４】
［実施例３］
樹脂膜（Ａ）の中央部の原料としてＰＴＴ８７重量％とオレフィン１３重量％を７０重量％と実施例１で樹脂膜（Ａ）を得る前に切断除去した両端部を造粒して得たポリマーを３０重量％とした以外は実施例１と同様にして樹脂膜（Ａ）に用いる厚みが２５μｍのロール状樹脂膜と樹脂膜（Ｂ）に用いる厚みが１６μｍのロール状樹脂膜を得た。ついで、実施例１と同様にラミネートアルミニウム板を作製し、製缶して３５０mlサイズのシームレス缶を得た。
ポリエステルの融点，キャスト時のネックイン量，製缶性（缶内面樹脂膜とポンチの離型性と缶外面樹脂膜のキズ発生程度），フレーバー性，温水処理後の缶外面の白化程度を表１に示す。本実施例の方法は、ネックイン量が小さく経済性に優れた樹脂被覆金属板の製造方法であり、製缶性とフレーバー性が優れた樹脂被覆金属板の製造方法であり、さらに外面の耐温水白化性が優れた金属缶が得られる樹脂被覆金属板の製造方法であるといえる。
【００２５】
［実施例４］
樹脂膜（Ａ）の中央部の原料としてＰＴＴ８７重量％とオレフィン１３重量％を７０重量％と実施例１で樹脂膜（Ａ）を得る前に切断除去した両端部を造粒して得たポリマーを１５重量％と実施例１で樹脂膜（Ｂ）を得る前に切断除去した両端部を造粒して得たポリマーを１５重量％とした以外は実施例１と同様にして樹脂膜（Ａ）に用いる厚みが２５μｍのロール状樹脂膜と樹脂膜（Ｂ）に用いる厚みが１６μｍのロール状樹脂膜を得た。ついで、実施例１と同様にラミネートアルミニウム板を作製し、製缶して３５０mlサイズのシームレス缶を得た。
ポリエステルの融点，キャスト時のネックイン量，製缶性（缶内面樹脂膜とポンチの離型性と缶外面樹脂膜のキズ発生程度），フレーバー性，温水処理後の缶外面の白化程度を表１に示す。本実施例の方法は、ネックイン量が小さく経済性に優れた樹脂被覆金属板の製造方法であり、製缶性とフレーバー性が優れた樹脂被覆金属板の製造方法であり、さらに外面の耐温水白化性が優れた金属缶が得られる樹脂被覆金属板の製造方法であるといえる。
【００２６】
［実施例５］
樹脂膜（Ａ）の中央部の原料としてＰＴＴ８７重量％とオレフィン１３重量％を７０重量％と実施例１で樹脂膜（Ｂ）を得る前に切断除去した両端部を造粒して得たポリマーを３０重量％とした以外は実施例１と同様にして樹脂膜（Ａ）に用いる厚みが２５μｍのロール状樹脂膜と樹脂膜（Ｂ）に用いる厚みが１６μｍのロール状樹脂膜を得た。ついで、実施例１と同様にラミネートアルミニウム板を作製し、製缶して３５０mlサイズのシームレス缶を得た。
ポリエステルの融点，キャスト時のネックイン量，製缶性（缶内面樹脂膜とポンチの離型性と缶外面樹脂膜のキズ発生程度），フレーバー性，温水処理後の缶外面の白化程度を表１に示す。本実施例の方法は、ネックイン量が小さく経済性に優れた樹脂被覆金属板の製造方法であり、製缶性とフレーバー性が優れた樹脂被覆金属板の製造方法であり、さらに外面の耐温水白化性が優れた金属缶が得られる樹脂被覆金属板の製造方法であるといえる。
【００２７】
［比較例１］
樹脂膜（Ａ）と樹脂膜（Ｂ）の両端部の原料をＰＴＴとした以外は実施例１と同様にしてロール状樹脂膜を得ようとしたが、ネックイン量が大きく，かつ両端部を１８cm切断除去しなければ、厚み分布が一様な中央部が得られないため、経済性に劣る樹脂膜製造方法であった。
【００２８】
［比較例２］
樹脂膜（Ａ）の中央部の原料としてＰＥＴ８７重量％とオレフィン１３重量％とし、樹脂膜（Ｂ）の中央部の原料としてＰＥＴとした以外は実施例１と同様にして樹脂膜（Ａ）に用いる厚みが２５μｍのロール状樹脂膜と樹脂膜（Ｂ）に用いる厚みが１６μｍのロール状樹脂膜を得た。
ついで、実施例１と同様にラミネートアルミニウム板を作製し、製缶して３５０mlサイズのシームレス缶を得た。
ポリエステルの融点，キャスト時のネックイン量，製缶性（缶内面樹脂皮膜とポンチの離型性と缶外面樹脂のキズ発生程度），フレーバー性，温水処理後の缶外面の白化程度を表１に示す。この方法は、ネックイン量が小さく経済性に優れた樹脂被覆金属板の製造方法であり、製缶性とフレーバー性が優れた樹脂被覆金属板の製造方法であったが、外面の耐温水白化性が劣るため、樹脂被覆金属板の製造方法として好ましくない。
【００２９】
［比較例３］
樹脂膜（Ａ）の中央部の原料としてＣＯ−ＰＥＳ８７重量％とオレフィン１３重量％とし、樹脂膜（Ｂ）の中央部の原料としてＣＯ−ＰＥＳ単体とした以外は実施例１と同様にして樹脂膜（Ａ）に用いる厚みが２５μｍのロール状樹脂膜と樹脂膜（Ｂ）に用いる厚みが１６μｍのロール状樹脂膜を得た。
ついで、実施例１と同様にラミネートアルミニウム板を作製し、製缶して３５０mlサイズのシームレス缶を得た。
ポリエステルの融点，キャスト時のネックイン量，製缶性（缶内面樹脂皮膜とポンチの離型性と缶外面樹脂のキズ発生程度），フレーバー性を表１に示す。この方法は、ネックイン量が小さく経済性に優れた樹脂被覆金属板の製造方法であったが、この樹脂膜を被覆した金属板（ラミネートアルミニウム板）を製缶したが、缶内面樹脂と加工ポンチが粘着し缶開口部の全周にわたって座屈が発生し、さらに缶外面樹脂の全周にわたってキズが発生したため製缶性が劣っており、又樹脂被覆金属板（ラミネートアルミニウム板）のフレーバー性も劣っていたため、樹脂被覆金属板の製造方法として好ましくない。
【００３０】
［比較例４］
樹脂膜（Ａ）の中央部の原料としてＰＴＴ５０重量％とオレフィン５０重量％とした以外は実施例１と同様にしてロール状樹脂膜を得た。
ポリエステルの融点，キャスト時のネックイン量，製缶性（缶内面樹脂皮膜とポンチの離型性と缶外面樹脂のキズ発生程度），フレーバー性を表１に示す。この方法は、ネックイン量が小さく経済性に優れた樹脂膜製造方法であったが、得られた樹脂被覆金属板（ラミネートアルミニウム板）のフレーバー性が劣り、さらに加工ポンチの抜けがわるく缶内面開口部の約１／３に座屈が発生したため、樹脂被覆金属板の製造方法として好ましくない。
【００３１】
【表１】

【００３２】
【発明の効果】
本発明の樹脂被覆金属板の製造方法は原料の無駄を省けるため、経済性に優れた製造方法であるばかりでなく、フレーバー性に優れた樹脂被覆金属板が得られる製造方法である。さらに、製缶性（特に、缶内面樹脂膜と加工ポンチの離型性と缶外面樹脂膜の耐キズつき性）に優れた樹脂被覆金属板が得られる製造方法である。さらに、内容物を充填後に実施される温水殺菌処理で金属缶外面の外観不良（樹脂膜の白化）が発生しにくいため、極めて有用な樹脂被覆金属板の製造方法といえる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a resin-coated metal plate. More specifically, it relates to a method for producing a resin-coated metal plate excellent in can manufacturing properties (for example, drawing and ironing workability) and flavor properties, and is suitable for metal cans that are subjected to hot water sterilization treatment. The present invention relates to a method for manufacturing a coated metal plate.
[0002]
[Prior art]
Conventionally, the inner and outer surfaces of metal cans have been widely coated with various thermosetting resins such as epoxies and phenols dissolved or dispersed in solvents to prevent corrosion. Has been done. However, this thermosetting resin coating method has a drawback in that it takes a long time to dry the paint, so that productivity is lowered and undesired problems such as environmental pollution due to a large amount of organic solvent often occur.
[0003]
In order to solve such a drawback, a method of coating a metal plate with a thermoplastic resin by a melt extrusion method is disclosed (for example, see Patent Document 1). Further, a method is disclosed in which a melt-extruded thermoplastic resin is once cooled and solidified, and then crimped to a heated metal plate (see, for example, Patent Document 2). Also disclosed is a method of pressure-bonding an unoriented film of polyethylene terephthalate and / or polybutylene terephthalate produced by a melt extrusion method to a heated metal plate (see, for example, Patent Document 3). However, in these thermoplastic resin coating methods, when the molten resin is extruded in layers from the T-die, the width of the molten resin film is greatly reduced (called neck-in), and several tens of centimeters relative to the resin width required for coating. It was necessary to form a film with a wide width, which was not a satisfactory method from the viewpoint of economy.
[0004]
In order to solve such drawbacks, a method for reducing neck-in by using a polyester obtained by blending a polyester obtained by copolymerizing a tribasic or higher polybasic acid or polyhydric alcohol component has been disclosed (for example, (See Patent Document 4 and Patent Document 5). However, in these coating methods, a polyester obtained by copolymerizing a tribasic or higher polybasic acid or polyhydric alcohol component is likely to be thermally deteriorated in a melting process from an extruder to a T die, and a heat stabilizer may be used in combination. Resin for can manufacturing because foreign matter (for example, foreign matter having gel-like foreign matter or deteriorated product as a core) is likely to occur in the obtained molten resin film, and cracks are generated in the resin coating layer at the time of can making. It was not satisfactory as a coated metal plate.
[0005]
Resin-coated metal sheet coating resins used for squeezing and ironing cans not only require excellent moldability to follow canning (drawing and ironing), but also for the purpose of beautification after making the cans It is required that the impact resistance is not lowered even in the heating of the outer surface baking coating performed as described above. However, the resin-coated metal plate often has a reduced impact resistance, and does not satisfy the demand for impact resistance.
[0006]
[Patent Document 1]
JP-A-57-203545 [Patent Document 2]
JP-A-10-309775 [Patent Document 3]
JP 2001-1447 A [Patent Document 4]
JP-A-10-86308 [Patent Document 5]
Japanese Unexamined Patent Publication No. 2000-71388
[Problems to be solved by the invention]
The object of the present invention is to solve the problems of the prior art. That is, since the neck-in at the time of melt extrusion is small and foreign matter is hardly generated in the obtained molten resin film, it is excellent in economy and can-making property, and excellent in the flavor property of the obtained metal can, and the contents The present invention provides a method for producing a resin-coated metal plate in which appearance defects (whitening of the resin film) of the outer surface of a metal can are unlikely to occur by hot water sterilization performed after filling the metal.
[0008]
[Means for Solving the Problems]
An object of the present invention is to coat a resin film (A) mainly composed of crystalline polyester having a melting point of 180 ° C. or higher on one side of a metal plate and to form a resin film (B) made of crystalline polyester having a melting point of 180 ° C. or higher on the other side. ), The molten resin film obtained in a state where the olefinic polymer is joined to both ends using a T die is cooled and solidified, and then both ends are cut and removed to obtain a resin film (A) and a resin film ( B) and a resin film (A) and a method for producing a resin-coated metal plate comprising laminating a resin film (B) on a heated metal plate, and the resin film (A) is polytrimethylene A polyester mainly composed of terephthalate and an olefin polymer are composed of 70:30 to 100: 0 (% by weight), and the resin film (B) is a polyester mainly composed of polytrimethylene terephthalate. Is achieved by the method for producing a resin-coated metal sheet, characterized in that those of the additional level.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
In the present invention, a dicarboxylic acid component other than terephthalic acid and a glycol component other than propylene glycol can be used as long as the properties of polytrimethylene terephthalate are not impaired. For example, as dicarboxylic acid, aromatic dicarboxylic acid such as isophthalic acid, orthophthalic acid, naphthalenedicarboxylic acid, diphenylsulfone dicarboxylic acid, 5-sodium sulfoisophthalic acid, oxalic acid, succinic acid, adipic acid, sebacic acid, decanedicarboxylic acid, Aliphatic dicarboxylic acids such as maleic acid, fumaric acid and dimer acid, oxycarboxylic acids such as p-oxybenzoic acid, and alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid can be used. As glycol components other than propylene glycol, aliphatic glycols such as ethylene glycol, butanediol, pentanediol, hexanediol and neopentylglycol, alicyclic glycols such as cyclohexanedimethanol, and aromatics such as bisphenol A and bisphenol S Glycol can be used.
In the polyester of the present invention, an antioxidant, a heat stabilizer, an ultraviolet absorber, a plasticizer, a pigment, an antistatic agent, a lubricant, a crystal nucleating agent, a lubricant composed of inorganic or organic particles, and the like are blended as necessary. May be.
The method for producing the polyester in the present invention is not particularly limited. That is, it can be used even if it is produced by either the transesterification method or the direct polymerization method. Further, it may be produced by a solid phase polymerization method in order to increase the molecular weight. Furthermore, use a polyester with a low oligomer content produced by the low-pressure solid-state polymerization method from the viewpoint of reducing the amount of oligomers from the polyester resin in pastry treatment, retort treatment, etc. that are carried out after filling the contents in the can. Is preferred. However, it is preferable that the ratio of the polyester polytrimethylene terephthalate of the resin film (A) and the resin film (B) is the same. The reason is that when the resin including both ends obtained by cutting and removing the resin extruded in a layer form after cooling and solidification is reused in the central part of the resin film (A) from the viewpoint of eliminating waste of the resin, This is because the quality of the coated resin film is stabilized.
[0010]
Polyester used in the present invention has a melting point of 180 ° C. or higher. Can manufacturing ability (in drawing and ironing process, the inner surface of the can ensures punch releasability, the outer surface of the can suppresses galling [ It is necessary from vertical scratches in the resin film]).
[0011]
The olefin polymer blended with the polyester is not particularly limited. Low density polyethylene, medium density polyethylene, high density polyethylene, linear low density polyethylene, ultra high molecular weight polyethylene, polypropylene, ethylene-propylene copolymer, ethylene-butene copolymer, ethylene-vinyl acetate copolymer, ethylene- An ethyl acrylate copolymer, an ethylene-vinyl alcohol copolymer, an ionomer, or the like can be used. However, the olefin polymer used at both ends and the center of the layered resin film (A) extruded from the T die is preferably the same as the olefin polymer used at both ends of the resin film (B). The reason is that when the resin including both ends obtained by cutting and removing the resin extruded in a layer form after cooling and solidification is reused in the central part of the resin film (A) from the viewpoint of eliminating waste of the resin, This is because the quality of the coated resin film is stabilized.
In the present invention, the ratio of the polyester to the olefin polymer in the polyester film needs to be 70:30 to 100: 0 (% by weight). If the olefin-based polymer exceeds 30% by weight, it is not preferable because the can-making ability (releasability of processed punch) is inferior and the flavor of the resulting metal can is inferior.
In the present invention, when the resin including both ends is reused, the reuse ratio is not particularly limited, but is preferably 5 to 60 (% by weight).
[0012]
In the present invention, when the polyester and the olefin polymer are extruded in a layer form from the T die, it is necessary to use the olefin polymer at both end portions (portions where one side is 5 cm or less).
In the present invention, a polymer obtained by dry blending or melt-mixing a polyester and an olefin polymer is melted in a known single-screw or twin-screw extruder, and then layered using a known multi-manifold die such as an edge lamination type. A molten resin film is obtained.
[0013]
In the present invention, as a cooling and solidification method, a known method in which a resin melted in a layer form from a T die is brought into contact with a rotated cooling roll can be used. When the molten resin is brought into contact with the cooling roll, it is preferable to employ a method of forcibly blowing air or a method of closely contacting with static electricity. Moreover, both the forced air spraying method and the electrostatic contact method are more preferable to carry out the method in which both end portions and the central portion of the layered resin are made independent.
In the present invention, after cooling and solidifying, a method of directly laminating a resin film obtained by cutting and removing both ends on a heated metal plate, or a resin film obtained by cutting and removing both ends after cooling and solidifying Any of the methods of once winding the film and laminating it on a metal plate heated in a separate process can be used. However, in the latter coating method, the cooled and solidified product is longitudinally stretched (for example, stretched 1.3 to 6.0 times above the glass transition point of the polyester), and further heat-treated (for example, 50 ° C or higher) under tension. And the melting point of the polyester is preferably -20 ° C for 1 to 20 seconds). The reason for this is that, after storing the wound resin film roll, when the resin film roll is coated on a heated metal plate, the resin film roll is wrinkled due to breakage of the resin film due to unwinding tension and shrinkage with time during storage of the resin film roll. This is because it is preferable to suppress blocking and the like.
In the present invention, a surface-treated steel plate such as tin-free steel, an aluminum plate, an aluminum alloy plate, a surface-treated aluminum plate or an aluminum alloy plate can be used as the metal plate. After heating these metal plates to a melting point of -20 ° C. or higher and a melting point of + 150 ° C. of polyester, the resin film (A) and the resin film (B) are simultaneously laminated or sequentially laminated on the metal plate using a laminating roll. The laminated metal plate is heated at a melting point of polyester of + 10 ° C. or higher and a melting point of + 60 ° C., and then cooled with water and / or air to obtain a resin-coated metal plate. Although the resin film thickness on a metal plate is not specifically limited in this invention, 10-50 micrometers is preferable from the point of a coating effect (rust prevention property) and economical efficiency.
[0014]
【Example】
Hereinafter, the present invention will be described based on examples.
[Evaluation methods]
(1) Melting point of polyester After heating and melting a polyester composition at 300 ° C. for 5 minutes, 10 mg of a sample obtained by quenching with liquid nitrogen and 10 ° C. using a differential scanning calorimeter (DSC) in a nitrogen stream. The peak temperature of the endothermic peak accompanying melting when the exothermic / endothermic curve (DSC curve) was measured at a rate of temperature rise per minute was defined as melting point Tm (° C.).
[0015]
(2) Use the average value (Acm) of the discharge port width (60 cm) of the neck-in amount T-die and the resin film width after cooling and solidification (resin film width before cutting and removing both ends) measured at n = 3. The neck-in amount (cm) was determined by the following formula. A neck-in amount of 5 cm or less was evaluated as practical.
Neck-in amount (cm) = 60-A
[0016]
(3) Preparation method of resin-coated metal plate Resin film (A) on one side of aluminum alloy plate (3004 series alloy plate with a thickness of 0.26 mm) heated to 250 ° C and resin film (B) on the other side After laminating at the same time, the laminate was heated at 275 ° C. and then quenched in water to produce a laminated aluminum plate.
[0017]
(4) The inner surface resin of the can and the mold release laminate aluminum plate of the processing punch were made with n = 10, and the degree of buckling occurring at the upper part of the formed can was visually observed. Evaluation criteria were set as follows, and ○ was evaluated as practical.
○: Buckling has not occurred in the can opening Δ: Buckling has occurred in about 1/3 of the circumference of the can opening ×: Buckling has occurred in more than 1/3 of the circumference of the can opening [0018]
(5) Scratch resistance of the outer surface of the can (longitudinal scratch on the outer surface of the can)
A laminated aluminum plate was canned at n = 10, and the degree of generation of scratches on the outer surface of the molded can body wall portion was visually observed. Evaluation criteria were set as follows, and ○ was evaluated as practical.
○: Scratch not occurred Δ: Scratch occurred in about 1/3 of the outer surface ×: Severe scratch generated more than 1/3 of the outer surface [0019]
(6) After immersing a 5 cm square laminated aluminum plate in d-limonene filled in a sealed glass container of flavor, d-limonene is adsorbed by standing in a constant temperature room at 40 ° C. for 10 days. The d-limonene adhering to the surface is wiped off with Kimwipe and the weight W1 is measured. The laminated aluminum plate after the weight W1 measurement is vacuum-dried at 60 ° C. for 24 hours, and then the weight W2 is measured. Further, the weight W3 of the release film obtained by dissolving the aluminum plate of the laminated aluminum plate after acid dissolution and drying is measured. The adsorbed amount of d-limonene is obtained by the following formula and expressed in weight%. Those having an adsorbed amount of d-limonene of 3% by weight or less are evaluated as practical.
d-Limonene adsorption amount (% by weight) = (W1-W2) / W3 × 100
[0020]
(7) About the degree of whitening of the outer surface of the can after hot water treatment A can obtained by making an aluminum laminate plate can be heated at 270 ° C. for 40 seconds and then rapidly cooled in water. After immersing this sample in warm water at 80 ° C. for 10 minutes, the outer surface of the can obtained by quenching in water was visually observed. Evaluation criteria were set as follows, and ○ was evaluated as practical.
○: Whitening is inconspicuous △: Whitening is apparent, but the color of the aluminum alloy plate is visible ×: The color of the aluminum alloy plate is not visible due to whitening [0021]
[Abbreviations and contents of polyester and olefin polymer used in Examples and Comparative Examples]
(1) PTT: Polytrimethylene terephthalate (2) PET: Polyethylene terephthalate (3) CO-PES: Copolyester of terephthalic acid and ethylene glycol / cyclohexanedimethanol (mol% 70/30) (4) Olefin: Tafmer A-4085 (trade name, manufactured by Mitsui Chemicals, Inc.)
(5) Ionomer: High Milan 1706 (trade name, manufactured by Mitsui DuPont Polychemical Co., Ltd.)
[0022]
[Example 1]
As a raw material for the central part of the resin film (A), 87% by weight of PTT and 13% by weight of olefin are melted at 280 ° C., and as a raw material for both ends of the resin film (A), a single olefin is melted at 250 ° C. Cast into layered cooling rolls (peripheral speed 20 m / min) using T die (olefin outlet width / central outlet width / olefin outlet width = 2 cm / 56 cm / 2 cm, heated to 260 ° C.) (The distance from the T die to the ground point of the molten resin on the cooling roll is 15 cm, and the center and both ends are forcibly blown with separate devices), then both ends (5 cm on one side) are cut off and removed. Winding and the roll-shaped resin film whose thickness used for a resin film (A) is 25 micrometers were obtained.
Further, PTT is melted at 280 ° C. as a raw material for the central portion of the resin film (B), olefin simple substance is melted at 250 ° C. as a raw material for both ends of the resin film (B), and an edge lamination type T die (olefin Use a discharge port width / discharge port width in the center / discharge port width of olefin = 2 cm / 56 cm / 2 cm, heated to 260 ° C.) and cast into a cooling roll (circumferential speed 20 m / min) in layers (cooled from the T die) The distance to the contact point of the molten resin with the roll is 15cm, the center and both ends are forcibly blown with a separate device), then both ends (5cm on one side) are cut off and wound up to form a resin film A roll-shaped resin film having a thickness of 16 μm used in (B) was obtained.
A resin film (A) is pressure-bonded to one side of a 3004 series aluminum alloy plate (thickness 0.26 mm) heated to 250 ° C., a resin film (B) is pressure-bonded to the other side, heated to 275 ° C., and then rapidly cooled in water. Thus, a laminated aluminum plate was obtained.
A lubricant for molding was applied to the laminated aluminum plate thus obtained, and then heated and drawn at a plate temperature of 70 ° C. so that the resin film (A) was on the inner surface side of the can. Next, the temperature of the obtained cup was set to 40 ° C., and ironing was performed at a mold temperature of 80 ° C. to obtain a 350 ml size seamless can.
Shows the melting point of polyester, neck-in amount during casting, can-making ability (releasability between can inner surface resin film and punch and degree of scratch on outer resin surface of can), flavor, and whitening degree of outer surface of can after hot water treatment. It is shown in 1. The method of this example is a method for producing a resin-coated metal plate having a small neck-in amount and excellent in economic efficiency, and is a method for producing a resin-coated metal plate having excellent can-making properties and flavor properties. It can be said that this is a method for producing a resin-coated metal plate from which a metal can excellent in warm water whitening property can be obtained.
[0023]
[Example 2]
Example 1 except that PTT 87% by weight and ionomer 13% by weight are used as the raw material for the central portion of the resin film (A), and the ionomer is used as the raw material for both ends of the resin film (A) and both ends of the resin film (B). Similarly, a roll-shaped resin film having a thickness of 25 μm used for the resin film (A) and a roll-shaped resin film having a thickness of 16 μm used for the resin film (B) were obtained.
Next, a laminated aluminum plate was produced in the same manner as in Example 1, and canned to obtain a 350 ml size seamless can.
Shows the melting point of polyester, neck-in amount during casting, can-making ability (releasability between can inner surface resin film and punch and degree of scratch on outer resin surface of can), flavor, and whitening degree of outer surface of can after hot water treatment. It is shown in 1. The method of this example is a method for producing a resin-coated metal plate having a small neck-in amount and excellent in economic efficiency, and is a method for producing a resin-coated metal plate having excellent can-making properties and flavor properties. It can be said that this is a method for producing a resin-coated metal plate from which a metal can excellent in warm water whitening property can be obtained.
[0024]
[Example 3]
Polymer obtained by granulating both ends cut and removed before obtaining the resin film (A) in Example 1 as 87% by weight of PTT and 70% by weight of olefin as the raw material of the central part of the resin film (A) A roll-shaped resin film having a thickness of 25 μm used for the resin film (A) and a roll-shaped resin film having a thickness of 16 μm used for the resin film (B) were obtained in the same manner as in Example 1 except that the amount was 30% by weight. Next, a laminated aluminum plate was produced in the same manner as in Example 1, and canned to obtain a 350 ml size seamless can.
Shows the melting point of polyester, neck-in amount during casting, can-making ability (releasability between can inner surface resin film and punch and degree of scratch on outer resin surface of can), flavor, and whitening degree of outer surface of can after hot water treatment. It is shown in 1. The method of this example is a method for producing a resin-coated metal plate having a small neck-in amount and excellent in economic efficiency, and is a method for producing a resin-coated metal plate having excellent can-making properties and flavor properties. It can be said that this is a method for producing a resin-coated metal plate from which a metal can excellent in warm water whitening property can be obtained.
[0025]
[Example 4]
Polymer obtained by granulating both ends cut and removed before obtaining the resin film (A) in Example 1 as 87% by weight of PTT and 70% by weight of olefin as the raw material of the central part of the resin film (A) 15% by weight and the resin film (A) in the same manner as in Example 1 except that the polymer obtained by granulating both ends cut and removed before obtaining the resin film (B) in Example 1 was changed to 15% by weight. ) Used to obtain a roll-shaped resin film having a thickness of 25 μm and a roll-shaped resin film having a thickness of 16 μm used for the resin film (B). Next, a laminated aluminum plate was produced in the same manner as in Example 1, and canned to obtain a 350 ml size seamless can.
Shows the melting point of polyester, neck-in amount during casting, can-making ability (releasability between can inner surface resin film and punch and degree of scratch on outer resin surface of can), flavor, and whitening degree of outer surface of can after hot water treatment. It is shown in 1. The method of this example is a method for producing a resin-coated metal plate having a small neck-in amount and excellent in economic efficiency, and is a method for producing a resin-coated metal plate having excellent can-making properties and flavor properties. It can be said that this is a method for producing a resin-coated metal plate from which a metal can excellent in warm water whitening property can be obtained.
[0026]
[Example 5]
Polymer obtained by granulating both end parts cut and removed before obtaining the resin film (B) in Example 1 as 87% by weight of PTT and 70% by weight of olefin as the raw material of the central part of the resin film (A) A roll-shaped resin film having a thickness of 25 μm used for the resin film (A) and a roll-shaped resin film having a thickness of 16 μm used for the resin film (B) were obtained in the same manner as in Example 1 except that the amount was 30% by weight. Next, a laminated aluminum plate was produced in the same manner as in Example 1, and canned to obtain a 350 ml size seamless can.
Shows the melting point of polyester, neck-in amount during casting, can-making ability (releasability between can inner surface resin film and punch and degree of scratch on outer resin surface of can), flavor, and whitening degree of outer surface of can after hot water treatment. It is shown in 1. The method of this example is a method for producing a resin-coated metal plate having a small neck-in amount and excellent in economic efficiency, and is a method for producing a resin-coated metal plate having excellent can-making properties and flavor properties. It can be said that this is a method for producing a resin-coated metal plate from which a metal can excellent in warm water whitening property can be obtained.
[0027]
[Comparative Example 1]
A roll-shaped resin film was obtained in the same manner as in Example 1 except that the raw material at both ends of the resin film (A) and the resin film (B) was changed to PTT. If the 18 cm portion is not cut and removed, a central portion having a uniform thickness distribution cannot be obtained, and thus the resin film manufacturing method is inferior in economic efficiency.
[0028]
[Comparative Example 2]
The resin film (A) was made into the resin film (A) in the same manner as in Example 1 except that PET was 87% by weight and 13% by weight of olefin as the raw material for the central part of the resin film (A) and PET was used as the raw material for the central part of the resin film (B). A roll resin film having a thickness of 25 μm and a roll resin film having a thickness of 16 μm used for the resin film (B) were obtained.
Next, a laminated aluminum plate was produced in the same manner as in Example 1, and canned to obtain a 350 ml size seamless can.
Table 1 shows the melting point of polyester, the amount of neck-in when casting, the can-making ability (removability of the resin film and punch inside the can and the degree of scratches on the outer resin of the can), flavor, and the degree of whitening of the outer surface of the can after hot water treatment. Shown in This method is a method for producing a resin-coated metal plate having a small neck-in amount and excellent in economic efficiency, and was a method for producing a resin-coated metal plate having excellent can-making properties and flavor properties. Since it is inferior in property, it is not preferable as a method for producing a resin-coated metal plate.
[0029]
[Comparative Example 3]
Resin in the same manner as in Example 1, except that 87% by weight of CO-PES and 13% by weight of olefin were used as the raw material for the central part of the resin film (A), and CO-PES was used alone as the raw material for the central part of the resin film (B). A roll-shaped resin film having a thickness of 25 μm used for the film (A) and a roll-shaped resin film having a thickness of 16 μm used for the resin film (B) were obtained.
Next, a laminated aluminum plate was produced in the same manner as in Example 1, and canned to obtain a 350 ml size seamless can.
Table 1 shows the melting point of polyester, the amount of neck-in at the time of casting, can-making properties (removability of can inner surface resin film and punch and degree of scratches on outer surface of can), and flavor properties. This method was a method of manufacturing a resin-coated metal plate with a small neck-in amount and excellent economy, but a metal plate (laminated aluminum plate) coated with this resin film was made, but the inner surface resin and processing The punch sticks, buckling occurs all around the can opening, and scratches are generated all around the outer surface of the can, resulting in inferior can-making performance, and flavor of resin-coated metal plate (laminated aluminum plate) Since it was also inferior, it was not preferable as a manufacturing method of a resin-coated metal plate.
[0030]
[Comparative Example 4]
A roll-shaped resin film was obtained in the same manner as in Example 1 except that 50% by weight of PTT and 50% by weight of olefin were used as raw materials for the central part of the resin film (A).
Table 1 shows the melting point of polyester, the amount of neck-in at the time of casting, can-making properties (removability of can inner surface resin film and punch and degree of scratches on outer surface of can), and flavor properties. This method was a resin film manufacturing method with a small neck-in amount and excellent economic efficiency, but the obtained resin-coated metal plate (laminated aluminum plate) was inferior in flavor, and further, the punched-out punching was difficult. Since buckling occurs in about 1/3 of the opening, it is not preferable as a method for producing a resin-coated metal plate.
[0031]
[Table 1]

[0032]
【The invention's effect】
The method for producing a resin-coated metal sheet according to the present invention is not only an economical production method but also a method for producing a resin-coated metal sheet having excellent flavor properties because waste of raw materials can be eliminated. Furthermore, it is a manufacturing method that can provide a resin-coated metal plate excellent in can-making properties (particularly, releasability of the can inner surface resin film and processing punch and scratch resistance of the outer surface resin film of the can). Furthermore, since the appearance defect (whitening of the resin film) of the outer surface of the metal can hardly occurs in the hot water sterilization process performed after filling the contents, it can be said to be a very useful method for producing a resin-coated metal plate.

Claims

One surface to the melting point 180 ° C. or higher of the crystalline polyester resin coated film (A) composed mainly of other surface consisting of a melting point 180 ° C. or more crystalline polyester resin film of a metal plate (B) a resin which is coated A method for producing a coated metal plate, comprising:
The resin film (A) is composed of a polyester mainly composed of polytrimethylene terephthalate and an olefin polymer of 70:30 to 100: 0 (% by weight).
The resin film (B) is all SANYO made of polyester mainly composed of polytrimethylene terephthalate,
A step of obtaining a resin film (A) and a resin film (B) by cutting and removing both ends after cooling and solidifying the molten resin film obtained in a state in which the olefin polymer is merged at both ends using a T die ;
The resin film (A) and method for producing a resin-coated metal sheet characterized by comprising the step of laminating a resin film (B) to the heated metal plate.

A polyester film coating characterized in that the olefin polymer used at both ends and the center of the resin film (A) according to claim 1 and the olefin polymer used at both ends of the resin film (B) are the same. A method for producing a metal plate.