JP4021713B2 - Manufacturing method of aluminum foil for containers with excellent alkali resistance - Google Patents
Manufacturing method of aluminum foil for containers with excellent alkali resistance Download PDFInfo
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- JP4021713B2 JP4021713B2 JP2002174685A JP2002174685A JP4021713B2 JP 4021713 B2 JP4021713 B2 JP 4021713B2 JP 2002174685 A JP2002174685 A JP 2002174685A JP 2002174685 A JP2002174685 A JP 2002174685A JP 4021713 B2 JP4021713 B2 JP 4021713B2
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- aluminum foil
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Description
【0001】
【発明の属する技術分野】
本発明は、耐アルカリ性に優れた容器用アルミ箔の製造方法に関するものである。
【0002】
【従来の技術】
従来、アルミ箔成形容器は、携帯用容器や食品を盛るために広く使用されており、流動性食品(例えば、カレー、シチュー、ラーメン、グラタン、煮物、スープなど)や、薄肉食品(例えばピザ、ハム、チーズなど)を入れる容器として利用されている。
【0003】
【発明が解決しようとする課題】
近年、このようなアルミ箔成形容器に食品を収容し、冷蔵又は冷凍した状態で流通させ、アルミ箔成形容器ごとコンロやオーブンで加熱して収容された食品を調理する形態のものが知られている。このような食品は、調理した際に酸性やアルカリ性の汁を生じる場合が多く、特にアルミニウムはアルカリに腐食され易いことから、調理により容器がアルカリ腐食を受け変色する場合がある。
特に、ラーメンは麺にかん水と呼ばれるアルカリ成分が添加されているため、アルミ箔成形容器内で麺を茹でた際に、煮汁中にかん水の成分が溶出し、汁が強いアルカリ性となる。そして、このアルカリ性の汁によりアルミ箔成形容器が腐食を受けるとともに、水和酸化皮膜が形成して容器表面が黒色化するという問題がある。
【0004】
本発明は、上記の課題を解決するためになされたものであって、アルカリ性の汁を含む食品の保存及び加熱調理に好適なアルミ箔成形容器に用いられる耐アルカリ性に優れた容器用アルミ箔の製造方法を提供することを目的としている。
【0005】
【課題を解決するための手段】
上記課題を解決するために、本発明に係る耐アルカリ性に優れた容器用アルミ箔の製造方法は、アルミニウム又はアルミニウム合金からなる箔基材の表面に、膜厚30nm以上500nm以下の陽極酸化皮膜を形成するにあたって、pH10.5以上12.5以下のアルカリ性水溶液中で直流電解処理することを特徴としている。
上記製造方法によれば、電解処理により形成される陽極酸化皮膜にアルカリ成分が取り込まれることで、皮膜の耐アルカリ性を向上させることができる。電解液のpHが10.5未満の場合には、皮膜に取り込まれるアルカリ成分が少なく、耐アルカリ性を向上させる効果を得られない。また、pHが12.5に近くなると陽極酸化皮膜の形成効率が低下し、所望の膜厚を得るための処理時間が長くなり、製造効率が低下する。上記から、耐アルカリ性に優れる陽極酸化皮膜を効率よく形成するために、pH10.5〜12.5の範囲とすることが好ましい。
また、本発明に係る製造方法では、陽極酸化皮膜を直流電解処理により形成する。これは、交流電解処理により形成された皮膜は、膜厚を厚くし難く、特に、アルカリ水溶液中での電解処理ではその傾向が顕著なものとなる。また、形成された皮膜が多孔質化し易く、皮膜の一部にアルカリ溶解を強く受けた皮膜欠陥が生じやすくなるため好ましくない。
さらに、交流の特性上、基材表面の陽極酸化と溶解が交互に生じるため、緻密な皮膜が形成し難く、変色を生じやすくなる。
上記製造方法によれば、アルカリ腐食に対する耐性に優れ、ラーメンなどの強アルカリ性の汁を含む食品を加熱調理する容器に用いても変色することのない耐アルカリ性に優れた容器用アルミ箔を提供することができる。以下、本発明に係る容器用アルミ箔の構成要件について説明する。
【0006】
膜厚(30〜500nm):膜厚が30nm未満では、陽極酸化皮膜の耐食性が不足してアルカリ性の汁により変色を生じる場合がある。この耐変色性の点からは膜厚は50nm以上とすることが好ましい。
一方、膜厚が500nmを越えると、容器への成形加工時に陽極酸化皮膜にクラックを生じやすくなり、電解工程の処理時間が長くなりコスト高となる。
【0007】
有孔率(5%以下):本発明に係る容器用アルミ箔では、有孔率5%以下のいわゆる無孔質の陽極酸化皮膜が用いられる。無孔質陽極酸化皮膜とは、皮膜成長時に電解液による局所溶解が起こらず、緻密で微細孔のない陽極酸化皮膜を指す。本発明に係る容器用アルミ箔では、この無孔質陽極酸化皮膜の緻密性による優れた耐食性を利用し、効果的にアルカリ腐食を防止することができる。尚、皮膜の有孔率は、電子顕微鏡観察における所定視野内の微細孔の総面積を皮膜の面積で除して導出することができ、本件ではこの有孔率をパーセントで表示している。
【0008】
また、pH10.5以上12.5以下のアルカリ性水溶液中で直流電解処理して形成された陽極酸化皮膜を備えることで、強アルカリに対する耐食性に優れた容器用アルミ箔とされている。
【0009】
次に、本発明に係る容器用アルミ箔においては、前記陽極酸化皮膜の膜厚が、100nm以上300nm以下とされることが好ましい。陽極酸化皮膜の膜厚が300nmを越えると皮膜が白色を帯びるため、容器外観及び電解処理のコストの点から膜厚を300nm以下とすることが好ましい。また、110nm以下の膜厚では陽極酸化皮膜に干渉色が生じ、このような干渉色を呈する陽極酸化皮膜に直火が当接すると、その部分の変色が強調される場合がある。このような変色の強調が実用上生じない範囲としては、膜厚110nm以上とするのがよい。
但し、本発明に係る容器用アルミ箔により構成したアルミ箔成形容器は、上記のような直火に当てて加熱する用途のみに適用するものではないため、膜厚110nm以下の陽極酸化皮膜が呈する干渉色を美観の向上を目的として意図的にアルミ箔に導入し、デザイン性を向上させることにより商品価値の向上を図ることもできる。
【0010】
次に、本発明に係る容器用アルミ箔においては、前記陽極酸化皮膜の膜厚が、100nm以上150nm以下とされることがより好ましい。
本発明に係る陽極酸化皮膜は、薄くとも十分な耐食性を確保し、変色を防止することができるので、電解処理コストを低減するためには可能な限り薄くすることが好ましい。そこで、陽極酸化皮膜の膜厚を100nm以上150nm以下とすれば、膜厚の再現性や電解処理の安定性を損なうことなく処理コストの増加を抑えることが可能である。
【0011】
次に、本発明に係る容器用アルミ箔においては、前記陽極酸化皮膜の膜厚が、110nm以上150nm以下とされることがさらに望ましい。上述したように薄い陽極酸化皮膜は干渉色を呈するので、このような干渉色がほとんどない容器を製造するには、陽極酸化皮膜の膜厚を110nm以上とするのがよい。
【0013】
次に、本発明に係るアルミ箔成形容器は、先のいずれかに記載の容器用アルミ箔を器状に成形したことを特徴とする。
次に、本発明に係るしわ付きのアルミ箔成形容器は、先のいずれかに記載の容器用アルミ箔を成形することにより底壁と、該底壁の周縁から立ち上がる周壁とが形成され、前記周壁にしわが付与されたことを特徴とする。
上記本発明に係るアルミ箔成形容器によれば、耐アルカリ性に優れる食品容器を提供することができる。特に、強アルカリの汁を含み、係る容器を用いて加熱調理されるラーメンの容器として好適である。
【0014】
【発明の実施の形態】
以下、本発明に係る容器用アルミ箔の製造方法の実施の形態について説明するが、本発明は以下の実施の形態に限定されるものではない。
まず、アルミニウム又はアルミニウム合金からなる箔基材を用意する。本発明に係る容器用アルミ箔に適用する箔基材としては、特に限定されず、容器用アルミ箔として従来から用いられているA3004やA3105のアルミニウム合金を問題なく用いることができる。また、基材の厚さも通常用いられている30〜150μm程度、あるいはそれ以上の厚さのものであっても良い。
【0015】
また、上記の基材上に無孔質陽極酸化皮膜を形成するにあたっては、前記基材の表面に前処理を行うことが好ましい。この前処理としては、特に限定されず、要は素材の表面に付着した油脂分を除去し、素材表面の不均質な酸化物皮膜が除去できるものであればよい。例えば、弱アルカリ性の脱脂液による脱脂処理を施したのち、水酸化ナトリウム水溶液でアルカリエッチングをしたのち、硝酸水溶液中でデスマット処理を行う方法や脱脂処理後に酸洗浄を行う方法などが適宜選択して用いられる。
【0016】
次に、上記箔基材の表面に陽極酸化皮膜を電解処理により形成する。本発明に係る製造方法では、電解液としてpH9以上のアルカリ性水溶液を用い、直流電解処理することで有孔率5%以下の陽極酸化皮膜を箔基材の表面に形成する。
上記電解液としては、生成する陽極酸化皮膜を溶解しにくく、かつ無孔質の陽極酸化皮膜を生成する電解質である炭酸塩、アルカリ金属の水酸化物、珪酸塩、ホウ酸、ホウ酸塩、リン酸塩、アジピン酸塩、フタル酸塩、安息香酸塩、酒石酸塩、クエン酸塩などの群から選ばれる1種または2種以上を溶解した水溶液が用いられる。これらの電解質のなかでも炭酸塩、珪酸塩、リン酸塩が酸化皮膜の性状、コストなどの点で好ましい。電解液のpH調整は、例えば電解液に適量のNaOHを添加することにより容易に調整することが可能である。また、陽極酸化皮膜の膜厚の調整は電解時間により調整することができる。
尚、電解液中の電解質濃度は2重量%からその電解質の飽和濃度の範囲で選ばれる。電解浴の浴温は15〜70℃の範囲で十分であり、浴温を70℃を越える高温とする必要はない。
直流電解処理にあたっては、箔基材を陽極とし、陰極には電解液に不溶性の導電材料が用いられ、例えば炭素電極が陰極とされる。
そして、電解処理後の箔基材表面を水洗して、本発明に係る容器用アルミ箔を得ることができる。
【0017】
(アルミ箔成形容器)
図1は、本発明に係る容器用アルミ箔を形成して作製できるアルミ箔成形容器の斜視構成図であり、このアルミ箔成形容器10は、比較的底浅の底壁11とその周縁から立ち上がる周壁12と、周壁12の上端部から外周側へ延出されたフランジ部13とから概略構成されており、周壁12にはその立設方向に多数のしわ14が形成されている。係るアルミ箔成形容器は、底壁11形成後に絞り加工してしわ14を付与しながら周壁12を形成し、その後フランジ部13を形成し、その外周を縁巻き加工することで作製することができる。
【0018】
図1に示すアルミ箔成形容器10は、耐アルカリ性に優れる本発明の容器用アルミ箔により構成されていることで、ラーメンなどの強アルカリの汁を含む食品を調理しても、汁によるアルカリ腐食で変色することがなく、アルカリ性の食品の調理や保存に好適なアルミ箔成形容器である。
【0019】
【実施例】
以下、実施例により本発明を更に詳細に説明するが、以下の実施例は本発明の技術範囲を限定するものではない。
本例では、上記実施の形態の製造方法により容器用アルミ箔を作製し、得られたアルミ箔を成形して図1に示すアルミ箔成形容器を作製して、アルミ箔容器の耐変色性を検証した。
【0020】
まず、80μm厚のA3004のO材箔基材を用意し、50℃の10%NaOHで10秒間エッチングした後、10秒間水洗し、次いで、25%の10%硝酸で10秒間の中和処理を行い、10秒間水洗した。上記いずれの処理もスプレー処理により行った。
次に、表1に示す構成の各種電解液を用意し、上記の処理が終了した箔基材を陽極とし、炭素板を陰極として電解処理を行い、箔基材の表面に陽極酸化皮膜を形成した。表1に示す電解液のpHは、NaOHを適宜添加することにより調整した。そして、電解処理後の箔基材を10秒間水洗した後、120℃で20秒間乾燥させ、アルミ箔を得た。尚、NO.12については、陽極酸化皮膜の形成に際して交流電解処理を行った。
次に、得られたアルミ箔を、ブランキング、ドローイング、ワイプダウン、カーリングの成形工程に供することで、図1に示す縁の付いたアルミ箔容器を作製した。
【0021】
(評価)
上記にて得られた各アルミ箔容器について、変色性の評価、及び膜厚と有孔率の測定を行った。これらの評価及び測定結果を表1に併記する。また、評価方法、及び測定方法を以下に示す。
【0022】
<変色性>各アルミ箔容器に水道水を入れてガスコンロで加熱して沸騰させ、加熱を維持した状態で乾燥麺を入れ、6分間麺を茹でた。その後、麺と湯を取り出し、アルミ箔容器を水洗、乾燥させて、アルミ箔容器の変色の程度を目視観察した。評価基準は、アルミ箔容器全体に明らかな黒色の変色が観察された場合を×、直火の当たる部分のみに黒色の変色が観察された場合を△、直火の当たる部位のみに黒色ではない僅かな変色が観察された場合を○、変色が全く観察されない場合を◎とした。
【0023】
<膜厚の測定>膜厚は、表1に示す各試料を切断し、その断面を透過電子顕微鏡で観察し、顕微鏡像中の任意の10点の膜厚の平均値から求めた。
【0024】
<有孔率の測定>有孔率は、箔基材表面に形成した陽極酸化皮膜の表面を10万倍の電子顕微鏡で観察し、任意の10箇所について、全観察面積に対する孔部の面積比(パーセント)により求めた。但し、試料内に存在する金属化合物周辺の膜質の不均一な部位は除外した。
【0025】
表1に示すように、NO.1〜9のアルミ箔成形容器は、強アルカリの汁とともに麺を茹でても表面に変色を生じることがなく、耐食性に優れる容器であることが確認された。特に、本発明の要件を満たすアルミ箔を用いて作製されたNO.2〜6のアルミ箔成形容器では、直火が当たった部分においても変色が生じず、極めて優れた耐熱性をも具備することが確認された。このことから、本発明に係るアルミ箔成形容器は、仮に容器が空焚きされた場合にも、容器の破損が生じ難いものであることが示唆される。
これに対して、本発明の要件を満たさないNO.10〜13では、いずれも容器表面に黒色の変色が生じた。
【0026】
【表1】
【0027】
【発明の効果】
以上、詳細に説明したように、本発明に係る耐アルカリ性に優れた容器用アルミ箔の製造方法は、アルミニウム又はアルミニウム合金からなる箔基材の表面に、膜厚30nm以上500nm以下の陽極酸化皮膜を形成するにあたって、pH10.5以上12.5以下のアルカリ性水溶液中で直流電解処理することで、アルカリ腐食に対する耐性に優れ、ラーメンなどの強アルカリ性の汁を含む食品を加熱調理する容器に用いても変色することのない耐アルカリ性に優れた容器用アルミ箔を提供することができる。
【0028】
本発明に係るアルミ箔成形容器は、上記本発明のアルミ箔により構成されるので、耐アルカリ性に優れ、特に、強アルカリの汁を含み、係る容器を用いて加熱調理されるラーメンの容器として好適である。
【図面の簡単な説明】
【図1】 図1は、本発明に係るアルミ箔成形容器の一実施の形態であるラーメン容器の斜視構成図である。
【符号の説明】
10 ラーメン容器(アルミ箔成形容器)
11 底壁
12 周壁
13 フランジ部
14 しわ[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing an aluminum foil for containers excellent in alkali resistance .
[0002]
[Prior art]
Conventionally, aluminum foil molded containers are widely used for serving portable containers and foods, such as liquid foods (for example, curry, stew, ramen, gratin, boiled food, soup, etc.) and thin-walled foods (for example, pizza, Ham, cheese, etc.).
[0003]
[Problems to be solved by the invention]
In recent years, foods are stored in such aluminum foil molded containers, distributed in a refrigerated or frozen state, and cooked in food that is stored in a stove or oven together with the aluminum foil molded containers. Yes. Such foods often produce acidic or alkaline juices when cooked. In particular, since aluminum is easily corroded by alkali, the container may be subjected to alkali corrosion and discoloration by cooking.
In particular, ramen has an alkali component called irrigation water added to the noodles, so when the noodles are boiled in an aluminum foil molded container, the irrigation water components are eluted in the broth and the juice becomes strongly alkaline. And there is a problem that the aluminum foil molded container is corroded by this alkaline juice, and a hydrated oxide film is formed to blacken the surface of the container.
[0004]
The present invention was made to solve the above problems, the superior container aluminum foil alkali resistance to be used in the preferred aluminum foil molded containers for storage and cooking of foods containing alkaline juice The object is to provide a manufacturing method.
[0005]
[Means for Solving the Problems]
In order to solve the above problems, a manufacturing method excellent container aluminum foil alkali resistance of the present invention, the surface of the aluminum or foil base made of aluminum alloy, the 500nm following the anodized film above the thickness 30nm In forming, direct current electrolytic treatment is performed in an alkaline aqueous solution having a pH of 10.5 or more and 12.5 or less.
According to the said manufacturing method, the alkali resistance of a film | membrane can be improved by an alkali component being taken in into the anodic oxide film formed by electrolytic treatment. When the pH of the electrolytic solution is less than 10.5, there are few alkali components taken into the film, and the effect of improving alkali resistance cannot be obtained. Moreover, when pH becomes close to 12.5, the formation efficiency of an anodized film will fall, the processing time for obtaining a desired film thickness will become long, and manufacturing efficiency will fall. From the above, in order to efficiently form an anodized film excellent in alkali resistance, it is preferable to set the pH in the range of 10.5 to 12.5.
In the manufacturing method according to the present invention, the anodized film is formed by direct current electrolytic treatment. This is because it is difficult to increase the film thickness of the film formed by alternating current electrolytic treatment, and the tendency is particularly remarkable in electrolytic treatment in an alkaline aqueous solution. In addition, the formed film is easily made porous, and a film defect that is strongly subjected to alkali dissolution is easily generated in a part of the film, which is not preferable.
Furthermore, due to alternating current characteristics, anodic oxidation and dissolution on the surface of the base material occur alternately, so that it is difficult to form a dense film, and discoloration is likely to occur.
According to the above production method, there is provided an aluminum foil for a container that is excellent in alkali corrosion resistance and has excellent alkali resistance that is not discolored even when used in a container for cooking food containing a strong alkaline juice such as ramen. be able to. Hereinafter, the constituent requirements of the aluminum foil for containers according to the present invention will be described.
[0006]
Film thickness (30 to 500 nm): If the film thickness is less than 30 nm, the corrosion resistance of the anodic oxide film may be insufficient and discoloration may occur due to alkaline juice. From the viewpoint of discoloration resistance, the film thickness is preferably 50 nm or more.
On the other hand, if the film thickness exceeds 500 nm, cracks are likely to occur in the anodized film during molding into a container, and the treatment time of the electrolysis process becomes longer and the cost increases.
[0007]
Porosity (5% or less): In the aluminum foil for containers according to the present invention, a so-called nonporous anodic oxide film having a porosity of 5% or less is used. The nonporous anodic oxide film refers to an anodic oxide film that is dense and free of micropores, and does not cause local dissolution by an electrolyte during film growth. The aluminum foil for containers according to the present invention can effectively prevent alkali corrosion by utilizing the excellent corrosion resistance due to the denseness of the nonporous anodic oxide film. The porosity of the film can be derived by dividing the total area of the micropores within a predetermined field of view in electron microscope observation by the area of the film, and in this case, the porosity is displayed as a percentage.
[0008]
Moreover, it is set as the aluminum foil for containers excellent in the corrosion resistance with respect to a strong alkali by providing the anodic oxide film formed by direct-current electrolysis treatment in alkaline aqueous solution of pH 10.5 or more and 12.5 or less .
[0009]
Next, in the aluminum foil for containers which concerns on this invention, it is preferable that the film thickness of the said anodized film shall be 100 nm or more and 300 nm or less. When the film thickness of the anodized film exceeds 300 nm, the film is white. Therefore, the film thickness is preferably 300 nm or less from the viewpoint of the container appearance and the cost of electrolytic treatment. Further, when the film thickness is 110 nm or less, an interference color is generated in the anodized film, and when a direct fire comes into contact with the anodized film exhibiting such an interference color, the discoloration of the part may be emphasized. The range in which such discoloration enhancement does not occur in practice is preferably a film thickness of 110 nm or more.
However, since the aluminum foil molded container constituted by the aluminum foil for containers according to the present invention is not applied only to the application of heating to the direct flame as described above, an anodized film having a film thickness of 110 nm or less is exhibited. It is possible to improve the product value by intentionally introducing the interference color into the aluminum foil for the purpose of improving aesthetics and improving the design.
[0010]
Next, in the aluminum foil for containers which concerns on this invention, it is more preferable that the film thickness of the said anodized film shall be 100 nm or more and 150 nm or less.
Even if the anodic oxide film according to the present invention is thin, it can secure sufficient corrosion resistance and prevent discoloration. Therefore, it is preferable to make it as thin as possible in order to reduce the cost of electrolytic treatment. Therefore, if the film thickness of the anodized film is 100 nm or more and 150 nm or less, it is possible to suppress an increase in processing cost without impairing the reproducibility of the film thickness and the stability of the electrolytic treatment.
[0011]
Next, in the aluminum foil for containers according to the present invention, it is more desirable that the thickness of the anodic oxide film be 110 nm or more and 150 nm or less. As described above, the thin anodic oxide film exhibits an interference color. Therefore, in order to manufacture a container having almost no such interference color, the film thickness of the anodic oxide film is preferably 110 nm or more.
[0013]
Next, an aluminum foil molded container according to the present invention is characterized in that the container aluminum foil described above is molded into a container shape.
Next, a wrinkled aluminum foil molded container according to the present invention is formed by forming the container aluminum foil according to any one of the above, and a peripheral wall rising from a peripheral edge of the bottom wall is formed, It is characterized by wrinkles on the peripheral wall.
According to the aluminum foil molded container according to the present invention, a food container having excellent alkali resistance can be provided. In particular, it is suitable as a container for ramen that contains strong alkali juice and is cooked using such a container.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, although embodiment of the manufacturing method of the aluminum foil for containers which concerns on this invention is described, this invention is not limited to the following embodiment.
First, a foil base material made of aluminum or an aluminum alloy is prepared. It does not specifically limit as a foil base material applied to the aluminum foil for containers which concerns on this invention, The aluminum alloy of A3004 and A3105 conventionally used as an aluminum foil for containers can be used without a problem. Further, the thickness of the base material may be about 30 to 150 μm, which is usually used, or more.
[0015]
Moreover, when forming a nonporous anodic oxide film on said base material, it is preferable to pre-process the surface of the said base material. The pretreatment is not particularly limited, and may be any material as long as it can remove the oil and fat adhering to the surface of the material and remove the heterogeneous oxide film on the surface of the material. For example, after performing a degreasing treatment with a weak alkaline degreasing solution, after performing alkali etching with a sodium hydroxide aqueous solution, a method of performing a desmut treatment in a nitric acid aqueous solution or a method of performing acid cleaning after a degreasing treatment is appropriately selected. Used.
[0016]
Next, an anodized film is formed on the surface of the foil base material by electrolytic treatment. In the production method according to the present invention, an alkaline aqueous solution having a pH of 9 or more is used as the electrolytic solution, and an anodic oxide film having a porosity of 5% or less is formed on the surface of the foil base material by direct current electrolytic treatment.
As the electrolytic solution, carbonate, alkali metal hydroxide, silicate, boric acid, borate, which is an electrolyte that hardly dissolves the produced anodized film and produces a nonporous anodized film, An aqueous solution in which one or more selected from the group of phosphate, adipate, phthalate, benzoate, tartrate, citrate and the like is dissolved is used. Among these electrolytes, carbonates, silicates, and phosphates are preferable in terms of properties of the oxide film, cost, and the like. The pH of the electrolytic solution can be easily adjusted, for example, by adding an appropriate amount of NaOH to the electrolytic solution. The film thickness of the anodized film can be adjusted by the electrolysis time.
The electrolyte concentration in the electrolytic solution is selected from the range of 2% by weight to the saturated concentration of the electrolyte. The bath temperature of the electrolytic bath is sufficient in the range of 15 to 70 ° C, and the bath temperature does not need to be higher than 70 ° C.
In the direct current electrolysis treatment, a foil base material is used as an anode, and a conductive material insoluble in an electrolytic solution is used as a cathode. For example, a carbon electrode is used as a cathode.
And the foil base material surface after electrolytic treatment can be washed with water, and the aluminum foil for containers which concerns on this invention can be obtained.
[0017]
(Aluminum foil molding container)
FIG. 1 is a perspective configuration diagram of an aluminum foil molded container that can be manufactured by forming an aluminum foil for containers according to the present invention, and this aluminum foil molded
[0018]
The aluminum foil molded
[0019]
【Example】
EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, a following example does not limit the technical scope of this invention.
In this example, an aluminum foil for a container is produced by the manufacturing method of the above embodiment, and the obtained aluminum foil is molded to produce the aluminum foil molded container shown in FIG. Verified.
[0020]
First, an 80 μm thick A3004 O material foil base material was prepared, etched with 10% NaOH at 50 ° C. for 10 seconds, washed with water for 10 seconds, and then neutralized with 25% 10% nitric acid for 10 seconds. And washed with water for 10 seconds. All of the above treatments were performed by spray treatment.
Next, various electrolyte solutions having the configurations shown in Table 1 are prepared, and the electrolytic treatment is performed using the foil base material after the above treatment as an anode and the carbon plate as a cathode, and an anodic oxide film is formed on the surface of the foil base material. did. The pH of the electrolytic solution shown in Table 1 was adjusted by appropriately adding NaOH. The foil base material after the electrolytic treatment was washed with water for 10 seconds and then dried at 120 ° C. for 20 seconds to obtain an aluminum foil. In addition, NO. For No. 12 , AC electrolytic treatment was performed during the formation of the anodized film.
Next, the obtained aluminum foil was subjected to blanking, drawing, wiping down, and curling forming steps, thereby producing an aluminum foil container with an edge shown in FIG.
[0021]
(Evaluation)
About each aluminum foil container obtained above, evaluation of discoloration and the measurement of the film thickness and the porosity were performed. These evaluation and measurement results are also shown in Table 1. Moreover, the evaluation method and the measuring method are shown below.
[0022]
<Discoloration> Tap water was put into each aluminum foil container, heated by a gas stove and boiled, dried noodles were put in a state where the heating was maintained, and the noodles were boiled for 6 minutes. Thereafter, the noodles and hot water were taken out, the aluminum foil container was washed with water and dried, and the degree of discoloration of the aluminum foil container was visually observed. Evaluation criteria are x when a clear black discoloration is observed in the entire aluminum foil container, △ when a black discoloration is observed only in a portion exposed to direct fire, and not black only in a portion subjected to direct fire The case where slight discoloration was observed was marked as ○, and the case where no discoloration was observed at all was marked as ◎.
[0023]
<Measurement of Film Thickness> The film thickness was determined from the average value of film thicknesses at arbitrary 10 points in the microscope image by cutting each sample shown in Table 1 and observing the cross section with a transmission electron microscope.
[0024]
<Measurement of Porosity> The porosity is measured by observing the surface of the anodic oxide film formed on the surface of the foil base material with an electron microscope of 100,000 times, and the area ratio of the hole portion to the total observation area for any 10 locations. (Percent). However, the uneven part of the film quality around the metal compound present in the sample was excluded.
[0025]
As shown in Table 1, NO. It was confirmed that the aluminum foil molded containers 1 to 9 were excellent in corrosion resistance without causing discoloration on the surface even when boiled noodles together with strong alkali juice. In particular, NO. Manufactured using an aluminum foil that satisfies the requirements of the present invention. In the aluminum foil molded containers of 2 to 6, it was confirmed that no discoloration occurred even in the portion where the direct fire was applied, and the heat resistance was extremely excellent. From this, it is suggested that the aluminum foil molded container according to the present invention hardly breaks the container even when the container is emptied.
On the other hand, NO. Which does not satisfy the requirements of the present invention . In 10 to 13 , black discoloration occurred on the container surface.
[0026]
[Table 1]
[0027]
【The invention's effect】
As described above in detail, the method for producing an aluminum foil for containers according to the present invention, which is excellent in alkali resistance, is an anodic oxide film having a film thickness of 30 nm or more and 500 nm or less on the surface of a foil substrate made of aluminum or an aluminum alloy. In forming a food, it is excellent in resistance to alkaline corrosion by direct current electrolytic treatment in an alkaline aqueous solution having a pH of 10.5 or more and 12.5 or less, and is used in a container for cooking food containing a strong alkaline juice such as ramen. In addition, it is possible to provide an aluminum foil for containers having excellent alkali resistance without causing discoloration.
[0028]
Since the aluminum foil molded container according to the present invention is composed of the aluminum foil of the present invention, it is excellent in alkali resistance, and particularly suitable as a ramen container that contains a strong alkali soup and is cooked using such a container. It is.
[Brief description of the drawings]
FIG. 1 is a perspective configuration diagram of a ramen container which is an embodiment of an aluminum foil molded container according to the present invention.
[Explanation of symbols]
10 Ramen container (aluminum foil molding container)
11
Claims (1)
前記箔基材の表面に陽極酸化皮膜を形成するにあたって、pH10.5以上12.5以下のアルカリ性水溶液中で直流電解処理することを特徴とする耐アルカリ性に優れた容器用アルミ箔の製造方法。 An aluminum foil molded container in which an anodized film having a film thickness of 30 nm or more and 500 nm or less is formed on the surface of a foil base material made of aluminum or an aluminum alloy, and is used for storage and cooking of food containing alkaline juice. A method for producing an aluminum foil for containers having excellent alkalinity ,
In forming an anodic oxide film on the surface of the foil base material, a method for producing an aluminum foil for containers excellent in alkali resistance , wherein direct current electrolytic treatment is performed in an alkaline aqueous solution having a pH of 10.5 or more and 12.5 or less.
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JP2002174685A JP4021713B2 (en) | 2002-06-14 | 2002-06-14 | Manufacturing method of aluminum foil for containers with excellent alkali resistance |
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JP4021713B2 true JP4021713B2 (en) | 2007-12-12 |
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