JP4865163B2

JP4865163B2 - Steel DI can

Info

Publication number: JP4865163B2
Application number: JP2001253501A
Authority: JP
Inventors: 知彦林; 教雄大森; 幸子太田原; 賢一沖山
Original assignee: Daiwa Can Co Ltd
Current assignee: Daiwa Can Co Ltd
Priority date: 2001-08-23
Filing date: 2001-08-23
Publication date: 2012-02-01
Anticipated expiration: 2021-08-23
Also published as: JP2003063518A

Description

【０００１】
【発明の属する技術分野】
本発明はスチールを素材とした絞り−しごき加工して成形されるＤＩ缶に関するもので、塗膜密着性、耐食性に優れた缶体を提供するものである。
【０００２】
【従来の技術】
金属缶には、筒状の缶胴を製造し、その両端開口部に、天蓋および地蓋を巻締めたスリーピース缶と、缶胴と地蓋が一体となった有底筒状容器に天蓋を巻締めたツーピース缶とがある。
スリーピース缶は、缶胴を電気抵抗溶接や接着剤等で接合するため、素材としてはスチールの薄板が使用される。
一方、ツーピース缶の一種は、缶胴と地蓋が一体となった有底筒状容器が絞り加工や絞り−しごき加工（ＤｒａｗｎａｎｄＩｒｏｎｅｄ）によって得られるため一般にＤＩ缶と呼ばれる。このＤＩ缶は、缶胴の接合を必要とせず、素材としてはアルミニウム合金やスチール等の薄板が使用される。
スチールおよびアルミニウム合金を素材としたＤＩ缶では、缶体成形後、脱脂・化成処理工程を経て、缶の内面側は耐食性確保の観点から塗装が、外面側は商標や装飾のため印刷・塗装が施されて使用されている。
スチール素材のＤＩ缶の内面側の耐食性について言えば、化成処理皮膜だけでは耐食性を向上させることは殆ど難しく、結局は化成処理後に施される塗装に頼っており、しかもその塗布量はスチールを素材としたＤＩ缶の場合はアルミニウム合金を素材としたＤＩ缶に比べて多くしており、それは素材の耐食性がアルミニウム合金に比べてスチールの方が劣ることに起因している。
【０００３】
又、缶の外面側はスチールを素材としたＤＩ缶では印刷デザインにもよるが、印刷外観の点から多くの場合白色塗装が施された後、印刷、クリアーが行われている。しかも、スチールの場合は金属固有の分光反射率がアルミニウム合金に比べて低いことから、黒みを呈する色調（黒みがかった色調）となるため、白色塗料の塗布量はアルミニウム合金を素材とした場合に比べ多くする必要がある。
このように、スチールを素材としたＤＩ缶の場合、内面の塗装および外面の白色塗装の塗布量は、いずれもアルミニウム合金を素材とした場合に比べ、多くする必要があることから、製造コストはむしろ高くなる場合があり、金属素材の価格差はなくなってしまうどころか、トータルコストとしても割高となる場合もある。
また、非常に希なケ−スではあるが、スチールを素材としたＤＩ缶の場合、特に、レトルト加熱殺菌処理を行う内容物を充填した場合に、缶外面側の塗膜が蓋の巻締め部の中から巻締めの外まで達する局部的な浮きが発生することがある。こうした局部浮きは商品価値を著しく低下させることがあるので好ましくない。
こうした缶外面塗膜が局部的に浮くと言った現象は、（１）アルミニウム合金の蓋を巻しめた場合にのみ起こり、（２）胴材がアルミニウム合金を素材としたＤＩ缶では見られないことから、アルミニウム合金蓋とスチール缶胴が接触して起こる「異種金属接触腐食」によるものと考えられている。
【０００４】
また、近年のトータル缶コストの低減化から、使用金属板の板厚の低減化（薄板化）や缶蓋であるアルミニウム合金製の開口容易缶蓋（イージーオープンエンド、通称ＥＯＥ）の径を小さくすることが進み、例えば、缶胴が３５０ｍｌのビール缶の場合、通称２１１径と呼ばれ、缶胴直径は約６６ｍｍであり、当然巻締める缶蓋も２１１径用であったが、現在は２０６径（直径約５８ｍｍ）化、２０４径（直径約５５ｍｍ）化、２０２径（直径約５２ｍｍ）化となっており、更には２００径（直径約４９ｍｍ）化が進められている。
このことは、必然的に缶胴の開口部をネック加工又はネックイン加工により、より小さい径に絞る、いわゆる縮径化となり、従って缶胴に用いられている金属は勿論、その表面に被覆されている有機塗料にとっても厳しい加工をうけることになる。
ＤＩ缶成形後の化成処理はこうした耐食性や縮径化に対応すべく改良検討がなされており、スチ−ルを素材としたＤＩ缶の化成処理は、現在は主にリン酸Ｓｎ系の化成処理が多く適用されている。
しかし、現在適用されているリン酸Ｓｎ系の化成処理では、スチールを素材としたＤＩ缶が持つ多くの問題を解決することは難しい。
【０００５】
スチールを素材としたＤＩ缶の化成処理技術について言えば、例えば特開平１−１７７３７９号公報、特開平２−６０８号公報、特開平１１−２６４０７５号公報等に開示されているが、こうした先行技術では現在要求されている塗膜密着性や耐食性と言った性能面で不十分であり、また前述した希に発生するレトルト加熱殺菌処理時の缶外面側の塗膜浮きを防止できないと言った問題を有している。
スチ−ル素材のＤＩ缶は、アルミニウム合金素材のＤＩ缶に比べ、缶重量が重い、対内容物耐食性が劣る、印刷外観が黒ずむ、と言った欠点があるが、一方缶の流がスムースである、天蓋の巻締性が良く安定していると言った利点もあり、更には素材価格が安価であることから、現状の缶性能が向上できればスチール素材のＤＩ缶を使用したいと言う声は根強くある。
こうした状況から、スチール素材のＤＩ缶の缶体自身の耐食性や缶内外面の塗膜の加工密着性を少しでも向上できる新しい化成処理剤の出現の期待が強くあった。
【０００６】
【発明が解決しようとする課題】
本発明の目的は、スチールを素材としたＤＩ缶の塗料密着性や耐食性を大幅に改善させ、より高品質で生産歩留まりの良い缶を提供する点にある
【０００７】
【課題を解決するための手段】
本発明の第１は、絞りしごき加工によって得られるスチール製ＤＩ缶において、缶の内外面の鋼板表面にリン（Ｐ）−金属（Ｍ）−有機樹脂（Ｒ）からなる化成処理皮膜が形成されており、該化成処理皮膜におけるリン（Ｐ）の付着量が片面で０．０５〜２．０ｍｇ／ｍ^２、金属（Ｍ）の付着量が片面で０．０５〜２．０ｍｇ／ｍ^２、有機樹脂（Ｒ）の付着量が炭素（Ｃ）量として片面で０．５〜２０ｍｇ／ｍ^２、金属（Ｍ）がジルコニウム及び／又はチタニウムであり、かつ炭素（Ｃ）付着量と金属（Ｍ）付着量の比Ｃ／Ｍが１〜１００であることを特徴とするスチール製ＤＩ缶に関する。
【０００８】
本発明における缶体は、スチールを素材とした絞り−しごき加工によって得られる、有底のツーピース缶（ドロー・アイアニング缶、ＤＩ缶）である。
スチール素材としては特に限定するものではないが、現在ＤＩ缶として適用されている薄鋼板にＳｎめっきが施されたブリキが使用される。好ましい具体例としては、板厚が０．１５ｍｍ〜０．３０ｍｍの薄鋼板に片面の付着量として１．０〜６．０ｇ／ｍ^２の錫めっき鋼板があげられる。
板厚は、主に缶強度、特に缶底の耐圧強度（通称ボトム耐圧）によって決められ、内容物を充填した後の内圧によって板厚は選定され、内圧が高い例えば、炭酸飲料やビール等を充填・密封する内圧缶の場合は、板厚が０．１５ｍｍ以下では、いわゆるバックリングと呼ばれる、缶底部が外方へ張り出した状態になる場合があり好ましくない。
一方、スチール素材の場合は、０．３０ｍｍ以上の板厚は耐圧強度は十分に確保されるが、実質的に過剰品質であり、経済的でない。
前記のバックリングといった現象は、同一板厚でも金属素材の機械的強度によって発生するか否かが分かれるため、機械的強度が高い場合は板厚の薄手化は可能となることから、板厚は、缶全体の強度バランスを考慮し、適宜選択することが望ましい。
【０００９】
次に、本発明で適用される化成処理皮膜について述べる。
本発明に適用されるスチール素材のＤＩ缶の化成処理皮膜は、リン（Ｐ）−金属（Ｍ）−有機樹脂（Ｒ）から成る有機無機複合型化成処理皮膜である。リン（Ｐ）の付着量は、片面で０．０５〜２．０ｍｇ／ｍ^２、金属（Ｍ）の付着量は片面で０．０５〜２．０ｍｇ／ｍ^２、有機樹脂（Ｒ）の付着量は炭素（Ｃ）量として片面で０．５〜２０ｍｇ／ｍ^２、金属（Ｍ）がジルコニウム及び／又はチタニウムであり、かつ炭素（Ｃ）付着量と金属（Ｍ）付着量の比Ｃ／Ｍは１〜１００である。
こうした化成処理によって析出する皮膜は、通常交換皮膜と呼ばれ、鋼板やアルミニウムの局部溶解によって起こる水素イオンの還元によりその部位では局部的にｐＨが上昇し、有機樹脂や金属イオンが溶解出来なくなり、析出するもので、析出箇所は鉄の露出部と考えられている。
リン（Ｐ）−金属（Ｍ）−有機樹脂（Ｒ）からなる化成処理皮膜は、対内容物耐食性の向上や缶内外面の塗膜密着性の向上だけでなく、前述したレトルト加熱殺菌処理を行う内容物を充填した場合に発生する、缶外面側の局部的塗膜浮き防止に特に効果がある。
【００１０】
リン（Ｐ）は鋼板やアルミニウムの局部溶解を促すための物質ではあるが、有機樹脂や金属イオンと同時に析出される。
従って、リン（Ｐ）の付着量が直接缶体の耐食性や塗膜密着性に関与するものではないが、皮膜の品質管理面からはリン（Ｐ）の付着量は重要である。
リン（Ｐ）の付着量の下限値である０．０５ｍｇ／ｍ^２未満では有機樹脂（Ｒ）や金属（Ｍ）の析出が不十分で、対内容物耐食性や缶内外面の塗膜密着性が共に劣り好ましくない。
一方、リン（Ｐ）の付着量の上限値である２．０ｍｇ／ｍ^２を超えても、有機樹脂（Ｒ）や金属（Ｍ）の析出による対内容物耐食性や缶内外面の塗膜密着性の向上効果は飽和し経済的でない。
化成処理後に施される缶の内外面塗膜との密着性や、缶内面の耐食性向上からは、基本的には有機樹脂（Ｒ）の付着量が重要である。
有機樹脂（Ｒ）は直接測定ができないため、付着炭素（Ｃ）量として測定され、片面の付着炭素（Ｃ）として０．５〜２０ｍｇ／ｍ^２である。
炭素（Ｃ）量の下限値である０．５ｍｇ／ｍ^２未満では有機樹脂（Ｒ）の析出が不十分で、鉄露出部を十分に覆うことができず、対内容物耐食性や缶内外面の塗膜密着性が共に劣り好ましくない。
特に、密着性については、前述したネック加工の高縮径化に対し、特にレトルト殺菌処理を行う場合に塗膜剥離を起こすことがあるので重要な要件となる。
また、缶内面の耐食性についても、実用上問題ない量とは言え、鉄溶出量が多めになることがあり、好ましくない。
一方、炭素（Ｃ）量の上限値である２０ｍｇ／ｍ２を超えても、有機樹脂（Ｒ）の析出による対内容物耐食性や缶内外面の塗膜密着性の向上効果は飽和し経済的でない。
【００１１】
前述したように、レトルト加熱殺菌処理で発生する外面塗膜の局部浮きは、蓋であるアルミニウムと胴であるスチールとの接触によって起こる「異種金属接触腐食」によるもので、蓋であるアルミニウムが陽極反応として溶解し、胴であるスチール面で陰極反応である酸素の還元反応が起こっている。従って、局部浮きは陰極アルカリピールと判断される。
従って、外面塗膜の局部浮きを防止するには、（１）陰極反応である酸素の還元反応を抑制する表面にすること、（２）もし腐食が起こってもアルカリピールが起こり難い密着力を有する表面にすることが考えられる。
本発明のリン（Ｐ）−金属（Ｍ）−有機樹脂（Ｒ）からなる化成処理皮膜の金属（Ｍ）は、前述した陰極反応である酸素の還元反応を抑制しており、更に有機樹脂（Ｒ）と共存させることで、化成処理皮膜の上層に存在する塗膜がアルカリピールが起こり難い密着力を有する化成処理皮膜となっているものと推定される。
従って、本発明のように有機樹脂（Ｒ）と金属（Ｍ）を共析させることで、前述した缶外面側の塗膜浮き防止に効果が顕著にみられる。
【００１２】
金属（Ｍ）の付着量は片面で０．０５〜２．０ｍｇ／ｍ^２である。
金属（Ｍ）の付着量が下限値を下回る０．０５ｍｇ／ｍ^２未満でも、リン（Ｐ）付着量や有機樹脂（Ｒ）の付着量が本発明の範囲内であれば、対内容物耐食性や缶内外面の塗膜密着性は確保されるが、金属（Ｍ）の付着量が下限値を下回る０．０５ｍｇ／ｍ^２未満では、前述した酸素の還元反応を抑制する効果は劣り、レトルト加熱殺菌処理で発生する外面塗膜の局部浮きを防止することができず好ましくない。
一方、金属（Ｍ）の付着量が上限値である２．０ｍｇ／ｍ^２を超えても、レトルト加熱殺菌処理で発生する外面塗膜の局部浮きの防止効果は飽和し経済的でない。
リン（Ｐ）−金属（Ｍ）−有機樹脂（Ｒ）からなる化成処理皮膜の場合、缶性能や化成処理の安定性からリン（Ｐ）の付着量は、片面で０．１〜１．５ｍｇ／ｍ^２、金属（Ｍ）の付着量は片面で０．１〜１．８ｍｇ／ｍ^２、有機樹脂（Ｒ）の付着量は炭素（Ｃ）量として片面で１．０〜１５ｍｇ／ｍ^２が、特に好ましい範囲である。
更に、リン（Ｐ）−金属（Ｍ）−有機樹脂（Ｒ）からなる化成処理皮膜の場合、特にレトルト加熱殺菌処理で発生する缶外面塗膜の局部浮きの防止の点からは、炭素（Ｃ）付着量と金属（Ｍ）付着量の比であるＣ／Ｍ比が重要で、本発明では１〜１００である。
【００１３】
炭素（Ｃ）量と金属（Ｍ）付着量の比であるＣ／Ｍ比は内外面に施される塗膜の密着性とレトルト加熱殺菌処理で発生する缶外面塗膜の局部浮きの防止との兼備と言った観点から重要で、Ｃ／Ｍ比が下限値である１未満では、塗膜との密着性が不十分で、缶外面塗膜の局部浮きが起こる危険性があり好ましくはない。
一方、上限値である１００を超えても、缶外面塗膜の局部浮き防止効果は飽和する。炭素（Ｃ）量と金属（Ｍ）付着量の比であるＣ／Ｍ比は、５〜５０の範囲が、缶外面塗膜の局部浮き防止効果と化成処理の安定性を考慮すると最適である。
また、リン（Ｐ）−金属（Ｍ）−有機樹脂（Ｒ）からなる化成処理皮膜の金属（Ｍ）としては、ジルコニウム及び／又はチタニウムを用いるが、特にジルコニウムが缶特性の安定性や化成処理の安定性等から最適である。
本発明を実施する方法は特別なものでなく、現在アルミニウム合金やスチールを素材として製造されているＤＩ缶の脱脂・化成処理方法が適用できる。
具体的には、ＤＩ加工後の缶体をアルカリ脱脂した後、例えばリン酸または縮合リン酸とフルオロジルコニウム酸のようなフッ化ジルコニウムやフルオロチタン酸のようなフッ化チタニウム、リン酸スズの一種と水溶性有機樹脂、例えば水溶性フェノール樹脂、水溶性アクリル樹脂等を含む水溶液に必要に応じて、反応性を促進させるためにフッ化水素酸またはフッ化化合物を添加した処理液を、缶体にスプレー塗布した後、水洗、乾燥し硬化させる方法や缶体を処理液に浸漬した後、水洗、乾燥し硬化させる方法等が適宜適用できる。
乾燥硬化方法としては熱風での乾燥、電気炉での乾燥等の方法が適用でき、温度は１５０℃〜２５０℃で乾燥時間は１０秒〜２分程度である。
【００１４】
本発明の有機無機複合化成処理皮膜は、化成処理後の加熱乾燥により有機樹脂の重合反応が起こり、高分子的な皮膜を形成する性質を有している。
しかも、有機樹脂が処理皮膜の表層に富化して存在するため、塗料との密着力が強固なものとなり、前述した、胴部径２１１径の缶体開口部の２０４径（直径約５４ｍｍ）化や２０２径（直径約５２ｍｍ）化、更には２００径（直径約４９ｍｍ）化へのネック加工にも耐えるだけでなく高腐食性の内容物に対しても高耐食性を有する優れた缶体が得られる。
従って、高縮径となるネック加工ほど有機無機複合化成処理皮膜は有利である。
本発明のスチ−ルを素材としたＤＩ缶は、従来のリン酸スズ系化成処理に比べ、缶体の品質特性は著しく向上し、対内容物耐食性、缶内外面の塗膜密着性が大幅に改善されるだけでなく、希に発生するレトルト加熱殺菌処理での缶外面塗膜の局部浮きも抑えることができる。また、塗膜密着性が大幅に改善されるので、缶外面に直接装飾印刷を施す代わりに、接着剤層を備えた印刷フィルムを貼着する方法も採用することができる。
【００１５】
【実施例】
以下、実施例にて、本発明の方法の効果を具体的に説明するが、本発明はこれにより何ら限定されるものではない。尚、本実施例で行った評価方法は以下の通りである。
（１）化成処理皮膜の有機樹脂付着量を示す炭素（Ｃ）量は、島津製作所（株）製の全有機体炭素計（ＴＯＣ−５０００／ＳＳＭ−５０００Ａ固体試料ＴＯＣ測定システム）にて測定した。
（２）化成処理皮膜のリン（Ｐ）および金属（Ｍ）付着量は、理学電機工業株式会社製の蛍光Ｘ線（Ｘ−ＲＡＹＳＰＥＣＴＲＯ−ＭＥＴＥＲ）にて測定した。
（３）塗膜のデュポン衝撃密着性評価は、内外面塗装缶のネック加工部を切り出し、３００ｇ−３０ｃｍの条件でデュポン衝撃試験をおこない、セロファンテープ剥離試験で塗膜の剥離状態を観察した。
◎：塗膜剥離なし ○：微小塗膜剥離僅かに発生
△：塗膜剥離中程度に発生 ×：塗膜剥離大きく発生
（４）塗膜の碁盤目密着性評価は、内外面塗装缶の缶胴部を切り出し、１ｍｍ間隔にＮＴカッター（商品名；折り取りタイプのカッター）で塗膜面に下地金属に達する傷を碁盤目状に１００の升目を入れ、１２５℃で３０分間のレトルト加熱処理を行った後セロファンテ−プ剥離試験を行い塗膜の剥離状態を観察した。
◎：塗膜剥離なし ○：塗膜剥離１〜５％発生
△：塗膜剥離６〜１５％発生 ×：塗膜剥離１６％以上発生
（５）外面塗膜浮き評価は、缶体に水を満注状態で充填し、アルミニウム合金製のＥＯＥ缶蓋で巻締めた後、１３０℃で３０分間のレトルト加熱処理を行い、外面塗膜の浮きの発生状況を評価した。
◎：塗膜浮きなし ○：塗膜浮き０．０１〜０．１％発生
△：塗膜浮き０．２〜２％発生 ×：塗膜剥離２％以上発生
（６）耐食性評価は、市販のペットボトルに充填されていたお茶またはコ−ラを缶体内に所定量充填し、アルミニウム合金製のＥＯＥ缶蓋で巻締めた後、３８℃で６ヶ月貯蔵し腐食状況を観察した。
◎：腐食なし ○：僅かに変色程度の表面腐食発生
△：表面腐食発生 ×：塗膜浮き、または鋼板の孔食を伴う腐食発生
【００１６】
実験例１
板厚０．２２ｍｍの薄鋼板にＳｎめっきを片面付着量として２．８ｇ／ｍ^２を両面に施したブリキを用いてＤＩ成形を行い、缶胴外径２１１径（約６６ｍｍ）で内容物充填量が３５０ｍｌの缶になるように開口端面側をトリミングしてスチール製ＤＩ缶を作成し、直ちに現行のスチ−ルＤＩ缶用のアルカリ脱脂剤でスプレー脱脂・水洗処理した後、リン酸−フッ化ジルコニウム−水溶性フェノール樹脂−フッ化水素酸からなるリン（Ｐ）−金属（Ｍ）−有機樹脂（Ｒ）系で濃度、処理時間等の処理条件を変化させ、スプレーで化成処理を行ったのち水洗、純水水洗処理を行い、２１０℃で４０秒間乾燥した。得られた缶の化成処理皮膜量は、それぞれ次の通りである。
リン付着量０．０３ｍｇ／ｍ^２、Ｚｒ付着量０．０２ｍｇ／ｍ^２、Ｃ付着量０．３１ｍｇ／ｍ^２、Ｃ／Ｍが１５．５０の化成処理（テスト１）、リン付着量０．０７ｍｇ／ｍ^２、Ｚｒ付着量０．０７ｍｇ／ｍ^２、Ｃ付着量０．８５ｍｇ／ｍ^２、Ｃ／Ｍが１２．１４の化成処理（テスト２）、リン付着量０．１１ｍｇ／ｍ^２、Ｚｒ付着量０．１８ｍｇ／ｍ^２、Ｃ付着量２．３２ｍｇ／ｍ^２、Ｃ／Ｍが１２．８９の化成処理（テスト３）、リン付着量０．３２ｍｇ／ｍ^２、Ｚｒ付着量０．３１ｍｇ／ｍ^２、Ｃ付着量３．５４ｍｇ／ｍ^２、Ｃ／Ｍが１１．４２の化成処理（テスト４）、リン付着量０．５６ｍｇ／ｍ^２、Ｚｒ付着量０．４５ｍｇ／ｍ^２、Ｃ付着量７．０６ｍｇ／ｍ^２、Ｃ／Ｍが１５．６９の化成処理（テスト５）、リン付着量１．０７ｍｇ／ｍ^２、Ｚｒ付着量０．８６ｍｇ／ｍ^２、Ｃ付着量１３．１２ｍｇ／ｍ^２、Ｃ／Ｍが１５．２６の化成処理（テスト６）、リン付着量１．７０ｍｇ／ｍ^２、Ｚｒ付着量１．７８ｍｇ／ｍ^２、Ｃ付着量１９．７５ｍｇ／ｍ^２、Ｃ／Ｍが１１．１０の化成処理（テスト７）、リン付着量０．９５ｍｇ／ｍ^２、Ｚｒ付着量０．６５ｍｇ／ｍ^２、Ｃ付着量０．５８ｍｇ／ｍ^２、Ｃ／Ｍが０．８９の化成処理（テスト８）。
また、比較のため、前記の缶高さと同一の高さになるようにトリミングしたスチ−ル製ＤＩ缶を、脱脂処理は本発明例と同様に行い、化成処理を現行のリン酸Ｓｎ系の処理（テスト９）を行ったリン付着量が１．０３ｍｇ／ｍ^２の缶も併せて作成した。
次いで、缶の外面には酸化チタンを含有する市販のアクリル・アミノ系白色塗料をロール塗装で１５０〜１６０ｍｇ／ｄｍ^２塗装し、乾燥・焼き付けを行い、更に印刷を施し、その上に市販のポリエステル・エポキシ・アミノ系クリヤー塗料をロール塗装で６０ｍｇ／ｄｍ^２塗装してから乾燥・焼き付けを行った後、缶の内面には市販のエポキシ・フェノール系内面用塗料をスプレー塗装で７０〜８０ｍｇ／ｄｍ^２塗装し、乾燥・焼き付けを行った後、内外面塗装缶の開口部に、ネック加工とフランジ加工とを行い、開口部径が２０２径の缶を作成した。
こうして得た、内外面塗装缶の塗膜密着性を調べるため、デュポン衝撃密着性評価および碁盤目密着性評価を行った。
また、外面のレトルト加熱殺菌処理での塗膜浮きを調べるため、缶体に水を満注状態で充填し、開口部にアルミニウム合金製のＥＯＥ缶蓋を巻締めた後、１３０℃で３０分間レトルト加熱殺菌処理を行い、外面塗膜の浮き発生率を評価した。
耐食性を調べるため、市販のペットボトルに充填されていたお茶またはコーラを、缶体内に所定量充填し、開口部にアルミニウム合金製のＥＯＥ缶蓋を巻締めた後、３８℃で６ヶ月間貯蔵し腐食状況を観察した。
実験例１で行った、本発明のスチール製ＤＩ缶の化成処理皮膜および比較例の化成処理皮膜の明細、そして各種の評価結果を表１に示した。
【００１７】
【表１】

【００１８】
表１から判るように、本発明の化成処理を施したテスト２〜テスト７（本発明例１〜６）のスチール製ＤＩ缶は、内外面の塗膜密着性に優れ、また、外面塗膜の浮き発生率に対しても良好な性能を示し、内容物耐食性にも優れていることが判る。
それに反し、テスト１（比較例１）のＺｒ付着量およびＣ付着量が共に本発明の下限値未満の場合は、内外面の塗膜密着性は劣り、外面塗膜の浮き発生率も高く、内容物耐食性も劣る。また、テスト８（比較例２）のＣ／Ｍが１以下の場合も、やはり内外面の塗膜密着性は劣り、外面塗膜の浮き発生率も高い。
また、現行のリン酸Ｓｎ系化成処理を施したテスト９（比較例３）の場合、内外面の塗膜密着性は本発明の化成処理皮膜を有する缶と遜色ないが、外面塗膜の浮き発生率は高いことがわかる。
【００１９】
実験例２
板厚０．２２ｍｍの薄鋼板に、缶の内面に当たる面にはＳｎめっきを片面付着量として２．８ｇ／ｍ^２、缶の外面に当たる面にはＳｎめっきを片面付着量として５．６ｇ／ｍ^２のブリキを用いて実験例１と同一径のＤＩ成形を行い、実験例１の手順に従いトリミングした後、直ちに現行のスチール製ＤＩ缶用のアルカリ脱脂剤でスプレー脱脂・水洗処理した後、リン酸−フッ化チタニウム−水溶性フェノール樹脂−フッ化水素酸からなるリン（Ｐ）−金属（Ｍ）−有機樹脂（Ｒ）系で濃度、処理時間等の処理条件を変化させ、スプレーで化成処理を行ったのち水洗、純水水洗処理を行い、２１０℃で４０秒間乾燥した。得られた缶の化成処理皮膜量は、それぞれ次の通りである。
リン付着量０．１２ｍｇ／ｍ^２、Ｔｉ付着量０．０７ｍｇ／ｍ^２、Ｃ付着量１．５１ｍｇ／ｍ^２、Ｃ／Ｍが２１．５７の化成処理（テスト１０）、リン付着量０．３５ｍｇ／ｍ^２、Ｔｉ付着量０．２３ｍｇ／ｍ^２、Ｃ付着量３．２４ｍｇ／ｍ^２、Ｃ／Ｍが１４．０９の化成処理（テスト１１）、リン付着量０．８３ｍｇ／ｍ^２、Ｔｉ付着量０．７４ｍｇ／ｍ^２、Ｃ付着量１０．３５ｍｇ／ｍ^２、Ｃ／Ｍが１３．９９の化成処理（テスト１２）、リン付着量１．２６ｍｇ／ｍ^２、Ｔｉ付着量１．３６ｍｇ／ｍ^２、Ｃ付着量１４．７２ｍｇ／ｍ^２、Ｃ／Ｍが１０．８２の化成処理（テスト１３）。
また、比較のため、前記の缶高さにトリミングしたスチール製ＤＩ缶に脱脂処理は本発明例と同様に行い、化成処理を現行のリン酸Ｓｎ系の処理（テスト１４）を行ったリン付着量が０．８７ｍｇ／ｍ^２の缶も併せて作成した。その後、缶の外面及び内面に、実験例１と同一の塗装及び印刷を施し、更に、内外面塗装缶の開口部に、ネックイン加工とフランジ加工とを行って、開口部径が２０２径の缶を作成した。
こうして得た、内外面塗装缶を、実験例１の手順に従って、缶の内外面の塗膜密着性、外面塗膜の塗膜浮き発生率および缶内面の耐食性を調べた。
実験２で行った、本発明のスチール製ＤＩ缶の化成処理皮膜および比較例の化成処理皮膜の明細、そして各種の評価結果を表２に示した。
【００２０】
【表２】

【００２１】
表２から判るように、本発明の化成処理を施したテスト１０〜テスト１３（本発明例７〜１０）のスチール製ＤＩ缶は、内外面の塗膜密着性に優れ、また、外面塗膜の浮き発生率に対しても良好な性能を示し、内容物耐食性にも優れていることが判る。
一方、比較例である現行のリン酸Ｓｎ系化成処理を施したテスト１４（比較例４）は、内外面の塗膜密着性は本発明の化成処理皮膜を有する缶と遜色ないが、外面塗膜の浮き発生率は高いことがわかる。
【００２２】
【発明の効果】
以上説明したように、本発明の化成処理を施したスチール製ＤＩ缶は、缶の内外面に塗装される塗膜の密着性に優れ、また内面の対内容物耐食性にも優れていることから、品質の安定性が向上できる。更に、特に、内容物を充填後にレトルト加熱殺菌処理を行う用途に対しても、希に外面の塗膜浮きが発生することがあるトラブルがほぼ完全に解消できる。こうした優れた特性を有していることから、単に品質が向上できるだけではなく、製造面でも安心して生産できるため、生産性が大幅に向上でき、経済的効果も大きいものがある。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a DI can formed by drawing-ironing using steel as a raw material, and provides a can body excellent in coating film adhesion and corrosion resistance.
[0002]
[Prior art]
For metal cans, a cylindrical can body is manufactured, and a canopy is attached to a bottomed cylindrical container in which the can body and the ground are integrated, and a three-piece can in which the canopy and the ground are tightened at both end openings. There are two-piece cans that are tightened.
The three-piece can is made of a thin steel plate because the can body is joined by electric resistance welding or an adhesive.
On the other hand, a kind of two-piece can is generally called a DI can because a bottomed cylindrical container in which a can body and a ground cover are integrated is obtained by drawing or drawing and ironing (Drawn and Ironed). The DI can does not require joining of the can body, and a thin plate such as an aluminum alloy or steel is used as a material.
For DI cans made of steel and aluminum alloys, after the can body is formed, the inner surface of the can is painted from the viewpoint of ensuring corrosion resistance, and the outer surface is printed and painted for trademark and decoration purposes. It has been used.
Speaking of the corrosion resistance of the inner surface of steel DI cans, it is almost difficult to improve the corrosion resistance with the chemical conversion coating alone, and ultimately it depends on the coating applied after chemical conversion treatment, and the coating amount is made of steel. In the case of DI cans, the number of DI cans is higher than that of DI cans made of aluminum alloy, which is due to the fact that the corrosion resistance of the material is inferior to that of aluminum alloy.
[0003]
In addition, the outer surface of the can is a DI can made of steel, depending on the print design. However, in many cases, printing and clearing are performed after a white coating is applied from the viewpoint of printing appearance. Moreover, in the case of steel, the spectral reflectance inherent to metal is lower than that of aluminum alloy, so the color tone is black (blackish color), so the amount of white paint applied is when aluminum alloy is used as the material. It is necessary to increase more.
Thus, in the case of DI cans made of steel, the amount of coating on the inner surface and the white coating on the outer surface needs to be increased compared to the case of using aluminum alloy as the material. In some cases, the price may be higher, and the price difference of the metal material may be eliminated, and the total cost may be higher.
Although it is a very rare case, in the case of DI cans made of steel, the coating on the outer surface of the can is tightened on the lid, especially when the contents to be subjected to retort heat sterilization are filled. There may be a local float that extends from inside the part to outside the winding. Such local float is not preferable because it may significantly reduce the commercial value.
The phenomenon that the outer surface paint film of this can floats locally occurs only when (1) the aluminum alloy lid is wound, and (2) the body is not seen in DI cans made of aluminum alloy. For this reason, it is thought to be due to “foreign metal contact corrosion” that occurs when the aluminum alloy lid and the steel can body contact.
[0004]
In addition, due to the recent reduction in total can cost, the thickness of the metal plate used (thin plate) has been reduced, and the diameter of the easy-open can lid (easy open end, commonly known as EOE) made of aluminum alloy, which is a can lid, has been reduced. For example, when the can body is a 350 ml beer can, it is commonly called the 211 diameter, the diameter of the can body is about 66 mm, and naturally the can lid to be tightened is also for the 211 diameter, but now it is 206 The diameter (diameter of about 58 mm), the diameter of 204 (diameter of about 55 mm), the diameter of 202 (diameter of about 52 mm), and the diameter of 200 (diameter of about 49 mm) are being promoted.
This inevitably results in a so-called diameter reduction by narrowing the opening of the can body to a smaller diameter by necking or neck-in processing, so that the metal used in the can body is of course coated on its surface. Even organic paints that have been subjected to severe processing.
The chemical conversion treatment after DI can molding has been studied to cope with such corrosion resistance and diameter reduction. Currently, the chemical conversion treatment of DI cans using steel as a raw material is mainly a phosphoric acid-based chemical conversion treatment. Many have been applied.
However, it is difficult to solve many problems of DI cans made of steel by the phosphoric acid Sn chemical conversion treatment currently applied.
[0005]
Speaking of chemical conversion treatment technology for DI cans made of steel, for example, they are disclosed in JP-A-1-177379, JP-A-2-608, JP-A-11-264075 and the like. However, it is not sufficient in terms of performance, such as coating adhesion and corrosion resistance, which are currently required, and the problem that the paint float on the outer surface of the can during the retort heat sterilization treatment mentioned above cannot be prevented. have.
Steel DI cans have the following disadvantages: the can weight is heavier than the aluminum alloy DI cans, the corrosion resistance to the contents is inferior, and the printing appearance is darkened, but the can flow is smooth. There is also an advantage that the canopy's tightness is good and stable, and furthermore, the material price is cheap, so if the current can performance can be improved, the voice that wants to use the steel DI can Persistent.
Under such circumstances, there was a strong expectation for the appearance of a new chemical conversion treatment agent that could improve the corrosion resistance of the steel DI can body itself and the processing adhesion of the coating film on the inner and outer surfaces of the can.
[0006]
[Problems to be solved by the invention]
An object of the present invention is to significantly improve the paint adhesion and corrosion resistance of DI cans made of steel, and to provide cans with higher quality and better production yield.
[0007]
[Means for Solving the Problems]
In the first aspect of the present invention, in a steel DI can obtained by squeezing and ironing, a chemical conversion film made of phosphorus (P) -metal (M) -organic resin (R) is formed on the inner and outer surface of the steel plate. The chemical conversion coating In Adhesion amount of phosphorus (P) But One side so 0.05-2.0 mg / m ² , Metal (M) The amount of adhesion is One side so 0.05-2.0 mg / m ² , Organic resin (R) adhesion amount as carbon (C) piece In terms of 0.5-20mg / m ² , The metal (M) is zirconium and / or titanium, And carbon (C) Adhesion The present invention relates to a steel DI can characterized in that the ratio C / M of the amount and the metal (M) adhesion amount is 1 to 100.
[0008]
The can body in the present invention is a bottomed two-piece can (draw / ironing can, DI can) obtained by drawing-ironing processing using steel as a raw material.
Although it does not specifically limit as a steel material, The tinplate by which Sn plating was given to the thin steel plate currently applied as DI can is used. As a preferable specific example, the adhesion amount of one side to a thin steel plate having a thickness of 0.15 mm to 0.30 mm is 1.0 to 6.0 g / m. ² These are tin-plated steel sheets.
The plate thickness is mainly determined by the strength of the can, especially the pressure resistance of the bottom of the can (commonly called the bottom pressure resistance). The plate thickness is selected according to the internal pressure after filling the contents. In the case of an internal pressure can that is filled and sealed, when the plate thickness is 0.15 mm or less, the so-called buckling, which is a state where the bottom of the can protrudes outward, is not preferable.
On the other hand, in the case of a steel material, a plate thickness of 0.30 mm or more can provide sufficient pressure resistance, but is substantially excessive quality and is not economical.
Since the phenomenon such as buckling occurs depending on the mechanical strength of the metal material even if the plate thickness is the same, if the mechanical strength is high, the plate thickness can be reduced. It is desirable to select appropriately considering the strength balance of the entire can.
[0009]
Next, the chemical conversion film applied in the present invention will be described.
The steel material DI can chemical conversion coating applied to the present invention is an organic-inorganic composite chemical conversion coating consisting of phosphorus (P) -metal (M) -organic resin (R). Adhesion of phosphorus (P) Amount , Piece In terms of 0.05-2.0 mg / m ² , Metal (M) adhesion amount is one piece In terms of 0.05-2.0 mg / m ² The amount of organic resin (R) attached is the amount of carbon (C) On one side 0.5-20mg / m ² , The metal (M) is zirconium and / or titanium, And carbon (C) Adhesion Ratio of metal and metal (M) adhesion C / M Is 1-100.
The film deposited by such a chemical conversion treatment is usually called an exchange film, and the pH rises locally at the site due to the reduction of hydrogen ions caused by local dissolution of the steel sheet and aluminum, and the organic resin and metal ions cannot be dissolved. The deposit is considered to be an exposed portion of iron.
The chemical conversion coating consisting of phosphorus (P) -metal (M) -organic resin (R) not only improves the corrosion resistance to contents and the coating adhesion on the inner and outer surfaces of the can, but also performs the aforementioned retort heat sterilization treatment. This is particularly effective for preventing local paint film floating on the outer surface of the can, which occurs when the contents to be performed are filled.
[0010]
Phosphorus (P) is a substance that promotes local dissolution of steel plates and aluminum, but is deposited simultaneously with organic resins and metal ions.
Therefore, the adhesion amount of phosphorus (P) is not directly related to the corrosion resistance and coating film adhesion of the can, but the adhesion amount of phosphorus (P) is important from the viewpoint of coating quality control.
0.05 mg / m, which is the lower limit of the amount of phosphorus (P) deposited ² If it is less than 1, the precipitation of the organic resin (R) and the metal (M) is insufficient, and the corrosion resistance to the contents and the adhesion between the inner and outer surfaces of the can are inferior.
On the other hand, 2.0 mg / m, which is the upper limit of the amount of phosphorus (P) attached ² Even if it exceeds the range, the effect of improving the corrosion resistance to contents and the adhesion between the inner and outer surfaces of the can due to the precipitation of the organic resin (R) and metal (M) is saturated and not economical.
The adhesion amount of the organic resin (R) is fundamentally important in terms of adhesion to the inner and outer coating films of the can applied after the chemical conversion treatment and improvement of the corrosion resistance of the inner surface of the can.
Since organic resin (R) cannot be measured directly, it is measured as the amount of attached carbon (C), and is 0.5 to 20 mg / m as attached carbon (C) on one side. ² It is.
0.5 mg / m, which is the lower limit of the amount of carbon (C) ² If it is less than 1, the precipitation of the organic resin (R) is insufficient, the iron exposed portion cannot be sufficiently covered, and the corrosion resistance to the contents and the coating adhesion on the inner and outer surfaces of the can are both inferior.
In particular, the adhesiveness is an important requirement because the coating film may be peeled off particularly when the retort sterilization treatment is performed in order to increase the diameter of the neck processing described above.
Further, the corrosion resistance of the inner surface of the can is not preferable because it may cause a large amount of iron elution, although it is an amount that causes no problem in practice.
On the other hand, even if it exceeds 20 mg / m2 which is the upper limit of the amount of carbon (C), the effect of improving the corrosion resistance to contents and the adhesion between the inner and outer surfaces of the can due to the precipitation of the organic resin (R) is saturated and not economical. .
[0011]
As described above, the local float of the outer coating film generated by the retort heat sterilization treatment is due to “foreign metal contact corrosion” caused by the contact between the lid aluminum and the barrel steel, and the lid aluminum is the anode. It dissolves as a reaction, and a reduction reaction of oxygen, which is a cathode reaction, takes place on the steel surface which is the cylinder. Therefore, the local float is determined as a cathodic alkali peel.
Therefore, in order to prevent local lifting of the outer coating, (1) a surface that suppresses the reduction reaction of oxygen, which is a cathodic reaction, and (2) an adhesion that hardly causes alkali peel even if corrosion occurs. It is conceivable that the surface has a surface.
The metal (M) of the chemical conversion film comprising phosphorus (P) -metal (M) -organic resin (R) of the present invention suppresses the oxygen reduction reaction, which is the cathode reaction described above, and further contains an organic resin ( By coexisting with R), it is presumed that the coating film existing in the upper layer of the chemical conversion film is a chemical conversion film having an adhesive force that hardly causes an alkali peel.
Accordingly, by co-depositing the organic resin (R) and the metal (M) as in the present invention, the effect is remarkably seen in preventing the above-described coating film from floating on the outer surface side of the can.
[0012]
The amount of metal (M) deposited on one side so 0.05-2.0 mg / m ² It is.
Amount of metal (M) attached But Below the lower limit 0 . 05mg / m ² If the amount of phosphorus (P) or the amount of organic resin (R) is within the range of the present invention, the corrosion resistance to the contents and the coating adhesion between the inner and outer surfaces of the can can be ensured. ) Adhesion amount But Below the lower limit 0 . 05mg / m ² If it is less than the above, the effect of suppressing the oxygen reduction reaction described above is inferior, and it is not preferable because local float of the outer surface coating film generated by the retort heat sterilization treatment cannot be prevented.
On the other hand, the amount of metal (M) attached But The upper limit is 2.0 mg / m ² Even if it exceeds 1, the effect of preventing local float of the outer surface coating film generated by retort heat sterilization is saturated and not economical.
In the case of a chemical conversion treatment film composed of phosphorus (P) -metal (M) -organic resin (R), adhesion of phosphorus (P) due to can performance and stability of chemical conversion treatment Amount , One side so 0.1-1.5 mg / m ² , Metal (M) is attached on one side so 0.1-1.8 mg / m ² The amount of organic resin (R) attached is the amount of carbon (C) On one side 1.0-15mg / m ² Is a particularly preferred range.
Furthermore, in the case of a chemical conversion treatment film comprising phosphorus (P) -metal (M) -organic resin (R), carbon (C ) Adhesion The C / M ratio, which is the ratio between the amount and the metal (M) deposition amount, is important, and is 1 to 100 in the present invention.
[0013]
The C / M ratio, which is the ratio of carbon (C) and metal (M) adhesion, is the adhesion of the coating applied to the inner and outer surfaces and the prevention of local floatation of the can outer coating that occurs during retort heat sterilization. If the C / M ratio is less than 1, which is the lower limit, the adhesion to the coating film is insufficient, and there is a risk of local floating of the outer coating film on the can, which is not preferable. .
On the other hand, even if the upper limit of 100 is exceeded, the local float prevention effect of the can outer surface coating film is saturated. The C / M ratio, which is the ratio between the carbon (C) amount and the metal (M) adhesion amount, is in the range of 5 to 50, considering the local float prevention effect of the can outer surface coating film and the stability of the chemical conversion treatment. .
In addition, as the metal (M) of the chemical conversion film made of phosphorus (P) -metal (M) -organic resin (R), zirconium And / or Titanium Use However, zirconium is particularly optimal from the viewpoint of stability of can characteristics, stability of chemical conversion treatment, and the like.
The method for carrying out the present invention is not special, and a degreasing / chemical conversion treatment method for DI cans currently produced using aluminum alloy or steel as a raw material can be applied.
Specifically, after the DI processed can body is degreased with alkali, for example, phosphoric acid or condensed phosphoric acid and zirconium fluoride such as fluorozirconic acid, titanium fluoride such as fluorotitanic acid, or a kind of tin phosphate And a treatment liquid in which hydrofluoric acid or a fluorinated compound is added as necessary to an aqueous solution containing water-soluble organic resin, for example, water-soluble phenol resin, water-soluble acrylic resin, etc. After spray coating, a method of washing with water, drying and curing, a method of immersing the can body in the treatment liquid, washing with water, drying and curing, etc. can be applied as appropriate.
As a drying and curing method, a method such as drying with hot air or drying in an electric furnace can be applied, the temperature is 150 ° C. to 250 ° C., and the drying time is about 10 seconds to 2 minutes.
[0014]
The organic-inorganic composite chemical conversion coating of the present invention has a property that a polymerization reaction of the organic resin occurs by heat drying after the chemical conversion treatment to form a polymer coating.
Moreover, since the organic resin is enriched in the surface layer of the treatment film, the adhesion to the coating becomes strong, and the diameter of the can body opening with the diameter of the barrel portion of 211 is made 204 (diameter: about 54 mm). No. 202 diameter (diameter: about 52 mm), and can withstand high-corrosive contents as well as withstands neck processing to 200 diameter (diameter: about 49 mm). It is done.
Therefore, the organic-inorganic composite chemical conversion coating film is more advantageous as the neck processing has a higher diameter reduction.
The DI can made from the steel of the present invention has significantly improved quality characteristics of the can body compared to the conventional tin phosphate chemical conversion treatment, and greatly improved the corrosion resistance to the contents and the coating adhesion between the inner and outer surfaces of the can. In addition to being improved, it is possible to suppress the local float of the outer surface coating film of the can in the retort heat sterilization treatment that occurs rarely. Moreover, since the coating film adhesion is greatly improved, a method of sticking a printing film provided with an adhesive layer can be employed instead of directly performing decorative printing on the outer surface of the can.
[0015]
【Example】
Hereinafter, the effects of the method of the present invention will be specifically described with reference to Examples, but the present invention is not limited thereto. The evaluation method performed in this example is as follows.
(1) The carbon (C) amount indicating the organic resin adhesion amount of the chemical conversion coating was measured with a total organic carbon meter (TOC-5000 / SSM-5000A solid sample TOC measurement system) manufactured by Shimadzu Corporation. .
(2) The phosphorus (P) and metal (M) adhesion amount of the chemical conversion film was measured with a fluorescent X-ray (X-RAY SPECTRO-METER) manufactured by Rigaku Corporation.
(3) The DuPont impact adhesion evaluation of the coating film cut out the neck processing part of the inner and outer surface coating cans, performed a DuPont impact test under the condition of 300 g-30 cm, and observed the peeling state of the coating film by the cellophane tape peeling test.
◎: No coating film peeling ○: Small coating film peeling occurred slightly
Δ: Occurred during coating film peeling ×: Large coating film peeling occurred
(4) The cross-cut adhesion evaluation of the paint film is made by cutting out the can body of the inner and outer surface coated cans, and scratching the paint film surface with a NT cutter (trade name; take-off type cutter) at 1 mm intervals. 100 grids were put in a grid pattern, and after 30 minutes of retort heat treatment at 125 ° C., a cellophane tape peel test was conducted to observe the peeled state of the coating film.
◎: No peeling of coating film ○: 1-5% of coating film peeling
Δ: Occurrence of coating film peeling 6-15% x: Occurrence of coating film peeling 16% or more
(5) External surface coating float evaluation was performed by filling the can body with water in a fully-filled state, winding it with an aluminum alloy EOE can lid, and performing a retort heat treatment at 130 ° C. for 30 minutes. The state of occurrence of floating was evaluated.
◎: No paint float ○: Paint paint lift 0.01-0.1%
Δ: Occurrence of paint film 0.2 to 2% x: Occurrence of paint film peeling 2% or more
(6) Corrosion resistance is evaluated by filling a can with a predetermined amount of tea or roll filled in a commercially available plastic bottle, tightening it with an aluminum alloy EOE can lid, and storing at 38 ° C. for 6 months. The corrosion situation was observed.
◎: No corrosion ○: Surface corrosion slightly discolored
Δ: Surface corrosion occurred ×: Corrosion occurred with paint film floating or steel plate pitting corrosion
[0016]
Experimental example 1
2.8 g / m with Sn plating on one side of thin steel plate with a thickness of 0.22 mm ² DI is made using tinplate coated on both sides, and the steel DI can is made by trimming the open end face side so that the can fills 350 ml with a can body outer diameter of 211 (about 66 mm). Immediately after spray degreasing and water-washing with the current alkaline degreasing agent for steel DI cans, phosphorus (P) -metal (M) consisting of phosphoric acid-zirconium fluoride-water-soluble phenolic resin-hydrofluoric acid ) -Organic resin (R) system was subjected to chemical conversion treatment by changing the treatment conditions such as concentration and treatment time, followed by washing with water and pure water, followed by drying at 210 ° C. for 40 seconds. The amount of the chemical conversion film of the obtained can is as follows.
Phosphorous adhesion amount 0.03mg / m ² , Zr adhesion amount 0.02mg / m ² , C adhesion amount 0.31mg / m ² , C / M is 15.50 chemical conversion treatment (test 1), phosphorus adhesion amount 0.07 mg / m ² , Zr adhesion amount 0.07mg / m ² , C adhesion amount 0.85mg / m ² , C / M = 12.14 chemical conversion treatment (test 2), phosphorus adhesion 0.11 mg / m ² , Zr adhesion amount 0.18mg / m ² , C adhesion amount 2.32 mg / m ² , Chemical conversion treatment with C / M of 12.89 (test 3), phosphorus adhesion amount 0.32 mg / m ² Zr adhesion amount 0.31 mg / m ² , C adhesion amount 3.54mg / m ² , Chemical conversion treatment with C / M of 11.42 (Test 4), Phosphorous adhesion amount 0.56 mg / m ² Zr adhesion amount 0.45 mg / m ² , C adhesion amount 7.06mg / m ² , C / M = 15.69 chemical conversion treatment (test 5), phosphorus adhesion 1.07 mg / m ² , Zr adhesion amount 0.86mg / m ² , C adhesion amount 13.12mg / m ² , C / M 15.26 conversion test (test 6), phosphorus adhesion 1.70 mg / m ² Zr adhesion amount 1.78 mg / m ² , C adhesion amount 19.75 mg / m ² , Chemical conversion treatment with C / M of 11.10 (test 7), phosphorus adhesion amount 0.95 mg / m ² , Zr adhesion amount 0.65 mg / m ² , C adhesion amount 0.58mg / m ² , C / M is 0.89 (test 8).
For comparison, a steel DI can trimmed so as to have the same height as the above-mentioned can was degreased in the same manner as in the present invention example, and the chemical conversion treatment was performed using the current Sn phosphate system. The phosphorus adhesion amount after the treatment (test 9) was 1.03 mg / m ² The cans were also made.
Next, a commercially available acrylic / amino-based white paint containing titanium oxide is applied to the outer surface of the can by roll coating at 150 to 160 mg / dm. ² After coating, drying and baking, printing is performed, and a commercially available polyester / epoxy / amino-based clear paint is applied to the roll by 60 mg / dm. ² After painting and drying / baking, the inner surface of the can is sprayed with a commercially available epoxy / phenolic inner surface paint at 70-80 mg / dm ² After coating, drying and baking, necking and flange processing were performed on the opening of the inner and outer surface coated cans, and a can with a diameter of 202 was created.
In order to examine the coating film adhesion of the inner and outer surface coated cans thus obtained, DuPont impact adhesion evaluation and cross-cut adhesion evaluation were performed.
In addition, in order to examine the float of the coating film in the retort heat sterilization treatment on the outer surface, the can body was filled with water in a fully-filled state, and an aluminum alloy EOE can lid was wrapped around the opening, and then at 130 ° C. for 30 minutes A retort heat sterilization treatment was performed, and the floating occurrence rate of the outer surface coating film was evaluated.
In order to check the corrosion resistance, tea or cola filled in a commercially available plastic bottle is filled into a can, and an aluminum alloy EOE can lid is wrapped around the opening, and then stored at 38 ° C for 6 months. The corrosion situation was observed.
Table 1 shows the details of the chemical conversion treatment film of the steel DI can of the present invention and the chemical conversion treatment film of the comparative example and various evaluation results performed in Experimental Example 1.
[0017]
[Table 1]

[0018]
As can be seen from Table 1, the steel DI cans of Test 2 to Test 7 (Invention Examples 1 to 6) subjected to the chemical conversion treatment of the present invention have excellent coating adhesion on the inner and outer surfaces, and the outer coating film. It shows good performance with respect to the rate of occurrence of buoyancy and is excellent in the corrosion resistance of the contents.
On the other hand, when both the Zr adhesion amount and the C adhesion amount of Test 1 (Comparative Example 1) are less than the lower limit of the present invention, the coating adhesion between the inner and outer surfaces is inferior, and the float occurrence rate of the outer coating film is high. The content corrosion resistance is also poor. Moreover, when C / M of Test 8 (Comparative Example 2) is 1 or less, the coating adhesion between the inner and outer surfaces is also inferior, and the occurrence rate of the floating coating on the outer surface is high.
In addition, in the case of Test 9 (Comparative Example 3) subjected to the current phosphoric acid Sn-based chemical conversion treatment, the adhesion of the coating film on the inner and outer surfaces is not inferior to that of the can having the chemical conversion treatment film of the present invention. It can be seen that the incidence is high.
[0019]
Experimental example 2
A thin steel plate having a thickness of 0.22 mm and a surface that contacts the inner surface of the can with Sn plating of 2.8 g / m on one side. ² The surface that contacts the outer surface of the can is 5.6 g / m with Sn plating on one side. ² After performing DI molding with the same diameter as that of Experimental Example 1 using the tinplate of the steel sheet and trimming according to the procedure of Experimental Example 1, it was immediately spray degreased and washed with an alkaline degreasing agent for steel DI cans, and then phosphoric acid. -Titanium fluoride-Water-soluble phenolic resin-Phosphorus (P)-Metal (M)-Organic resin (R) system consisting of hydrofluoric acid. After the washing, washing with pure water and washing with pure water were performed, followed by drying at 210 ° C. for 40 seconds. The amount of the chemical conversion film of the obtained can is as follows.
Phosphorous adhesion amount 0.12mg / m ² Ti adhesion amount 0.07mg / m ² , C adhesion amount 1.51mg / m ² , Chemical conversion treatment with C / M 21.57 (test 10), phosphorus adhesion amount 0.35 mg / m ² Ti adhesion amount 0.23mg / m ² , C adhesion amount 3.24mg / m ² , C / M is 14.09 chemical conversion treatment (test 11), phosphorus adhesion amount 0.83 mg / m ² Ti adhesion amount 0.74mg / m ² , C adhesion amount 10.35mg / m ² , Chemical conversion treatment with C / M of 13.99 (test 12), phosphorus adhesion amount of 1.26 mg / m ² Ti adhesion amount 1.36mg / m ² , C adhesion amount 14.72mg / m ² , Chemical conversion treatment with C / M of 10.82 (test 13).
For comparison, the steel DI can trimmed to the height of the can was degreased in the same manner as in the present invention example, and the phosphorous adhesion was performed by performing the current phosphoric acid Sn-based treatment (test 14). Amount 0.87mg / m ² The cans were also made. Thereafter, the same coating and printing as in Experimental Example 1 are performed on the outer surface and inner surface of the can, and further, neck-in processing and flange processing are performed on the opening of the inner and outer surface coating can, and the opening diameter is 202 diameter. I made a can.
According to the procedure of Experimental Example 1, the inner and outer surface coated cans thus obtained were examined for coating adhesion on the inner and outer surfaces of the can, the rate of occurrence of coating film floating on the outer surface coating, and the corrosion resistance of the inner surface of the can.
Table 2 shows the details of the chemical conversion coating of the steel DI can of the present invention and the chemical conversion coating of the comparative example, and various evaluation results, performed in Experiment 2.
[0020]
[Table 2]

[0021]
As can be seen from Table 2, the steel DI cans of Test 10 to Test 13 (Invention Examples 7 to 10) subjected to the chemical conversion treatment of the present invention have excellent coating adhesion on the inner and outer surfaces, and the outer coating film. It shows good performance with respect to the rate of occurrence of buoyancy and is excellent in the corrosion resistance of the contents.
On the other hand, the test 14 (Comparative Example 4) subjected to the current phosphoric acid Sn-based chemical conversion treatment as a comparative example is similar to the can having the chemical conversion coating of the present invention in terms of coating adhesion on the inner and outer surfaces. It can be seen that the incidence of film float is high.
[0022]
【Effect of the invention】
As described above, the steel DI can subjected to the chemical conversion treatment of the present invention is excellent in the adhesion of the coating film coated on the inner and outer surfaces of the can, and also excellent in the corrosion resistance to the contents on the inner surface. , Quality stability can be improved. In addition, particularly for applications in which retort heat sterilization is performed after filling the contents, troubles in which the coating film floats rarely can be almost completely eliminated. Because of these excellent characteristics, not only the quality can be improved, but also production can be performed with peace of mind, so that productivity can be greatly improved and there are significant economic effects.

Claims

In a steel DI can obtained by squeezing and ironing, a chemical conversion film made of phosphorus (P) -metal (M) -organic resin (R) is formed on the inner and outer steel plate surfaces of the can, and the chemical conversion film The adhesion amount of phosphorus (P) in the surface is 0.05 to 2.0 mg / m ^{2 on} one side , the adhesion amount of metal (M) is 0.05 to 2.0 mg / m ^{2 on} one side , and the adhesion of organic resin (R) amount 0.5-20 ^{/ m} 2 in single plane as a carbon (C) content, metal (M) is zirconium and / or titanium, and carbon (C) ratio of coating weight and the metal (M) attached amount C Steel DI can characterized by / M being 1-100.