JP2004018928A - Aluminum foil for container, and container formed from aluminum foil - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an aluminum foil for a container superior in corrosion resistance, which effectively prevents pitting by salts, and to provide the container formed from the aluminum foil superior in corrosion resistance, which is suitable for preserving foods containing the salts for a long time. <P>SOLUTION: The aluminum foil for the container has an anodic oxide film with a thickness of 20 nm or thicker but 800 nm or thinner formed on the surface of a foil substrate consisting of aluminum or an aluminum alloy, wherein the anodic oxide film has an external layer with a porosity of 60% or less, and a nonporous layer with a porosity of 20% or less having a thickness of 20 nm or more but 600 nm or less. <P>COPYRIGHT: (C)2004,JPO

Description

【００２６】
【発明の効果】
以上、詳細に説明したように、本発明に係る容器用アルミ箔は、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２０ｎｍ以上８００ｎｍ以下の陽極酸化皮膜が形成されており、前記陽極酸化皮膜が、有孔率２０％以下の無孔質層を有するとともに、皮膜外面における有孔率が６０％以下とされており、前記無孔質層の厚さが２０ｎｍ以上６００ｎｍ以下とされたことで、耐食性に優れるアルミ箔成形容器を構成することができるアルミ箔とされている。
【００２７】
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、耐食性に優れ、特に、塩分を含む食品の保存や調理に用いる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しわ付き容器の斜視構成図である。
【図２】図２は、本発明に係るアルミ箔形成容器の一実施の形態であるしわ無し容器の斜視構成図である。
【符号の説明】
１０　しわ付き容器（アルミ箔成形容器）
１５　しわ無し容器（アルミ箔成形容器）
１１　底壁
１２　周壁
１３　フランジ部
１４　しわ[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an aluminum foil for a container and an aluminum foil molded container.
[0002]
[Prior art]
Conventionally, aluminum foil molded containers are widely used for serving portable containers and foodstuffs, and include liquid foods (for example, curry, stew, ramen, gratin, boiled dishes, soups, etc.) and thin-walled foods (for example, pizza, Ham, cheese, etc.).
[0003]
[Problems to be solved by the invention]
In recent years, a form in which food is housed in such an aluminum foil molded container, distributed in a refrigerated or frozen state, and the aluminum foil molded container is heated by a stove or oven to cook the stored food is known. I have. As an aluminum foil molded container used for this purpose, there is a wrinkled aluminum foil molded container having increased strength by forming wrinkles on the container side wall. This wrinkled container is used as a food container with a larger capacity because of its excellent strength, and after punching out aluminum foil, it is drawn into a wrinkled container and then pressed into a die without extending the wrinkles. After the uniform wrinkles are generated in the above, the wrapping is performed.
Such wrinkled containers are often used for long-term storage and cooking of food, but when they come into contact with food containing salt for a long period of time, juice or juice is added to the narrow gaps in the wrinkles of the container. The salt contained therein may enter, causing crevice corrosion and perforation to occur, and the juice of the food inside may leak.
[0004]
The present invention has been made in order to solve the above-mentioned problems, and an object of the present invention is to provide an aluminum foil for a container having excellent corrosion resistance and capable of effectively preventing perforation due to salt.
Another object of the present invention is to provide an aluminum foil molded container having excellent corrosion resistance which is suitable for storage and cooking of food containing salt.
[0005]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, an aluminum foil for a container according to the present invention has an anodized film having a film thickness of not less than 20 nm and not more than 800 nm formed on a surface of a foil substrate made of aluminum or an aluminum alloy. The film has a non-porous layer having a porosity of 20% or less, the porosity on the outer surface of the film is 60% or less, and the thickness of the non-porous layer is 20 nm or more and 600 nm or less. It is characterized by.
According to the above configuration, it is possible to provide an aluminum foil for a container which has excellent resistance to salt corrosion and does not cause puncturing even when used for storage or cooking of food containing salt when used as an aluminum foil molded container. it can. Hereinafter, the components of the aluminum foil for a container according to the present invention will be described.
[0006]
Film thickness (20 to 800 nm): If the film thickness is less than 20 nm, the corrosion resistance of the anodic oxide film may be insufficient, and holes may be formed due to salt content. The thickness of the anodic oxide film is preferably 50 nm or more. By increasing the thickness, coil processing of the aluminum foil can be performed at a high speed, and the production efficiency can be increased.
On the other hand, if the film thickness exceeds 800 nm, cracks are likely to occur in the anodic oxide film during molding into a container, and holes may be formed due to the cracks. In addition, the processing time of the electrolysis process is lengthened and the cost is increased.
[0007]
Porosity: The porosity of the anodic oxide film in the aluminum foil for a container according to the present invention includes the porosity of the outer surface of the anodic oxide film formed on the substrate and the cross-section in the thickness direction of the anodic oxide film. There are two types of porosity. In each case, the porosity is derived from the occupied area ratio of the holes in the field of view of the electron microscope. This is because the porosity in the thickness direction of the anodic oxide film changes according to the film thickness.
The porosity on the outer surface of the anodic oxide film according to the present invention is 60% or less, and belongs to a so-called nonporous or microporous anodic oxide film. If the porosity on the outer surface of this film exceeds 60%, the anodic oxide film becomes porous and brittle, and cracks are likely to occur during processing. In addition, the corrosive substance easily permeates the film and easily reaches the base material, so that the corrosion resistance is lowered and holes are easily formed.
Next, the nonporous layer contained in the anodic oxide film according to the present invention is a layer having a porosity of 20% or less and having a structure corresponding to a so-called nonporous anodic oxide film. The porosity in this case is defined as the area ratio of holes in the cross section in the thickness direction of the anodic oxide film. The nonporous anodic oxide film refers to a dense, nonporous anodic oxide film in which local dissolution by an electrolytic solution does not occur during film growth.
In the aluminum foil for a container according to the present invention, the excellent corrosion resistance due to the denseness of the non-porous layer can be used to effectively prevent perforation due to corrosion. Therefore, the porosity of the non-porous layer according to the present invention is preferably as low as possible.
[0008]
Film thickness of non-porous layer (20 to 600 nm): The film thickness of the non-porous layer corresponds to the thickness of a portion having a porosity of 20% or less in the thickness direction cross section of the anodic oxide film. In the anodic oxide film according to the present invention, it is mainly the non-porous layer that prevents the corrosive substance from entering the substrate, and when the thickness of the non-porous layer is smaller than 20 nm, the corrosive substance is prevented. Can not be sufficiently shut off, thereby deteriorating the corrosion resistance and causing perforation.
On the other hand, if the thickness of the non-porous layer exceeds 600 nm, cracks may occur in the non-porous layer at the time of processing, which may cause perforation.
[0009]
Next, in the aluminum foil for a container according to the present invention, it is preferable that the thickness of the anodic oxide film is 50 nm or more and 500 nm or less. With such a range, excellent corrosion resistance can be obtained, the coil processing can be performed at high speed, and the production efficiency can be increased.
[0010]
Next, in the aluminum foil for a container according to the present invention, it is preferable that the film thickness of the non-porous layer is 50 nm or more and 500 nm or less. With such a range, excellent corrosion resistance can be obtained, the coil processing can be performed at high speed, and the production efficiency can be increased.
[0011]
In the aluminum foil for a container according to the present invention, it is preferable that the porosity on the outer surface of the anodized film is 20% or less. By setting the content in such a range, the whole becomes a nonporous anodic oxide film, more excellent corrosion resistance can be obtained, and an aluminum foil that can effectively prevent perforation can be obtained.
[0012]
Next, an aluminum foil molded container according to the present invention is characterized in that the container aluminum foil described in any of the above is molded into a container shape.
Next, the wrinkled aluminum foil molded container according to the present invention includes a bottom wall formed by molding the aluminum foil for a container described above, and a peripheral wall rising from a peripheral edge of the bottom wall. It is characterized by having been given.
According to the aluminum foil molded container according to the present invention, a food container excellent in corrosion resistance can be provided. In particular, it is suitable as a food container for storing and cooking food containing salt.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of a method for manufacturing an aluminum foil for a container according to the present invention will be described, but the present invention is not limited to the following embodiment.
First, a foil substrate made of aluminum or an aluminum alloy is prepared. The foil substrate applied to the aluminum foil for a container according to the present invention is not particularly limited, and a 3000 series aluminum alloy such as 3004 conventionally used as an aluminum foil for a container can be used without any problem. Further, the thickness of the substrate may be about 30 to 150 μm, which is usually used, or more.
[0014]
In forming the nonporous anodized film on the substrate, it is preferable to perform a pretreatment on the surface of the substrate. The pre-treatment is not particularly limited, and it is essential that the pre-treatment remove oils and fats adhering to the surface of the material and remove a 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 an aqueous sodium hydroxide solution, a method of performing a desmut treatment in a nitric acid aqueous solution or a method of performing acid cleaning after the degreasing treatment is appropriately selected. Used.
[0015]
Next, an anodic oxide film is formed on the surface of the foil substrate by electrolytic treatment. In the production method according to the present invention, an anodic oxidation having a nonporous layer having a porosity of 60% or less and a porosity of 20% or less is performed by electrolytic treatment using an acidic or alkaline aqueous solution as an electrolytic solution. A film is formed on the surface of the foil substrate.
As the electrolyte, it is difficult to dissolve the anodic oxide film to be generated, and sulfuric acid, silicate, boric acid, borate, phosphate, adipate, which is an electrolyte that generates a nonporous anodic oxide film, An aqueous solution in which one or more selected from the group of phthalate, benzoate, tartrate, citrate, oxalic acid and the like are used. Among these electrolytes, sulfuric acid, silicate, and phosphate are preferred in view of properties of the oxide film, cost, and the like. The thickness of the anodic oxide film can be adjusted by the electrolysis time.
The concentration of the electrolyte in the electrolyte is selected from the range of 2% by weight to the saturation concentration of the electrolyte. The bath temperature of the electrolytic bath is sufficient in the range of 15 to 50 ° C, and it is not necessary to set the bath temperature to a high temperature exceeding 50 ° C. Further, the electrolytic treatment may be performed in two or more stages using two or more kinds of electrolytic solutions.
In the electrolytic 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. Then, the aluminum foil for a container according to the present invention can be obtained by washing the surface of the foil substrate after the electrolytic treatment with water.
[0016]
(Aluminum foil container)
1 and 2 are perspective structural views of an aluminum foil molded container which can be produced by forming an aluminum foil for a container according to the present invention. The aluminum foil molded container 10 shown in FIG. 1 has a relatively shallow bottom wall. 11, a peripheral wall 12 rising from the peripheral edge thereof, and a flange 13 extending from the upper end of the peripheral wall 12 to the outer peripheral side. The peripheral wall 12 has a large number of wrinkles 14 formed in its standing direction. ing. Such an aluminum foil molded container can be manufactured by forming the peripheral wall 12 while forming a wrinkle 14 by drawing after forming the bottom wall 11, forming a flange portion 13 thereafter, and curling the outer periphery thereof. .
The aluminum foil molded container 15 shown in FIG. 2 is a container with no wrinkles formed on the peripheral wall 12.
[0017]
The aluminum foil molded container 10 shown in FIGS. 1 and 2 is made of the aluminum foil for a container of the present invention, which has excellent corrosion resistance. It is an aluminum foil molded container suitable for cooking and preserving food containing salt without causing pitting due to corrosion. In particular, in the container with a wrinkle shown in FIG. 1, there has been a problem of perforation due to crevice corrosion occurring in a crevice of a wrinkle. However, discoloration is caused by using an aluminum foil excellent in corrosion resistance according to the present invention. It realizes an excellent food container with no holes or holes.
[0018]
【Example】
Hereinafter, the present invention will be described in more detail with reference to Examples, but the following Examples do not limit the technical scope of the present invention.
In this example, an aluminum foil for a container was produced by the production method of the above-described embodiment, and the obtained aluminum foil was molded to produce a container with a wrinkle as shown in FIG. 1. ).
[0019]
First, an A3004 O-material foil base material having a thickness of 80 μm is 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 processes were performed by a spray process.
Next, various electrolytic solutions having the constitutions shown in Table 1 were prepared, and an electrolytic treatment was performed using the foil substrate after the above treatment as an anode and a carbon plate as a cathode to form an anodic oxide film on the surface of the foil substrate. did. After the foil substrate after the electrolytic treatment was washed with water for 10 seconds, it was dried at 120 ° C. for 20 seconds to obtain an aluminum foil.
Next, the obtained aluminum foil was subjected to blanking, drawing, wipe-down, and curling forming steps to produce a wrinkled container with an edge shown in FIG.
[0020]
(Evaluation)
About each aluminum foil container obtained above, the discoloration property, evaluation of perforation, and measurement of film thickness and porosity were performed. These evaluation and measurement results are also shown in Table 1. The evaluation method and the measurement method are shown below.
[0021]
<Perforability> Each aluminum foil container was charged with 5% diluted soy sauce, kept at 25 ° C. for 7 days, and the perforated state of the container was visually observed. In particular, wrinkles where holes easily occur were also observed in detail. The evaluation criterion was evaluated as ○ when no perforation occurred, and x when perforation occurred.
[0022]
<Measurement of film thickness> The film thickness was determined by cutting each sample shown in Table 1, observing the cross section with a transmission electron microscope, and calculating the average value of the film thickness at arbitrary 10 points in the microscope image. Further, a portion having a porosity of 20% or less was measured by observing a cross section of the sample, and the thickness was determined as a nonporous layer thickness. However, sites where the film quality was uneven around the metal compound existing in the sample were excluded.
[0023]
<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 a 100,000-magnification electron microscope, and measuring the area ratio of the hole to the total observation area at any 10 locations. Determined by However, sites where the film quality was uneven around the metal compound existing in the sample were excluded.
[0024]
As shown in Table 1, the aluminum foil molded containers of Examples 1 to 8 produced using the aluminum foil satisfying the requirements of the present invention have no corrosion in any of them and have excellent corrosion resistance. Was confirmed.
In contrast, in Comparative Examples 1 to 5, which did not satisfy the requirements of the present invention, perforations were observed in the containers.
[0025]
[Table 1]

[0026]
【The invention's effect】
As described above in detail, the aluminum foil for a container according to the present invention has an anodic oxide film having a thickness of 20 nm or more and 800 nm or less formed on the surface of a foil base material made of aluminum or an aluminum alloy. The oxide film has a nonporous layer having a porosity of 20% or less, the porosity on the outer surface of the film is 60% or less, and the thickness of the nonporous layer is 20 nm or more and 600 nm or less. Thus, the aluminum foil can be used to form an aluminum foil molded container having excellent corrosion resistance.
[0027]
Since the aluminum foil molded container according to the present invention is constituted by the aluminum foil of the present invention, it has excellent corrosion resistance, and is particularly suitable as a container used for storage and cooking of foods containing salt.
[Brief description of the drawings]
FIG. 1 is a perspective view of a wrinkled container as an embodiment of an aluminum foil molded container according to the present invention.
FIG. 2 is a perspective view of a wrinkle-free container, which is an embodiment of the aluminum foil forming container according to the present invention.
[Explanation of symbols]
10 Wrinkled container (aluminum foil molded container)
15 Wrinkle-free container (aluminum foil molded container)
11 bottom wall 12 peripheral wall 13 flange 14 wrinkle

Claims (6)

An anodized film having a film thickness of not less than 20 nm and not more than 800 nm is formed on the surface of the foil base material made of aluminum or an aluminum alloy,
The anodic oxide film has a nonporous layer having a porosity of 20% or less, and a porosity on the outer surface of the film is 60% or less;
An aluminum foil for a container, wherein the thickness of the nonporous layer is 20 nm or more and 600 nm or less. 2. The aluminum foil for a container according to claim 1, wherein the thickness of the anodized film is 50 nm or more and 500 nm or less. 3. The aluminum foil for a container according to claim 1 or 2, wherein the thickness of the nonporous layer of the anodic oxide film is 50 nm or more and 500 nm or less. The aluminum foil for a container according to any one of claims 1 to 3, wherein a porosity on an outer surface of the anodized film is set to 20% or less. An aluminum foil molded container obtained by molding the aluminum foil for a container according to any one of claims 1 to 4 into a container shape. A bottom wall and a peripheral wall rising from a peripheral edge of the bottom wall are formed by molding the aluminum foil for a container according to any one of claims 1 to 4, and wrinkles are applied to the peripheral wall. Wrinkled aluminum foil molded container.

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