JP2527330B2 - Edible canned container - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Use) A canned container in which an aluminum easy-open can lid is wound around a can body made of the surface-treated steel sheet of the present invention, and boiled seafood having a high salt concentration, The present invention relates to an edible canned container suitable for canning soup and the like.

(Prior art) Canned boiled seafood, soup, etc. have a high salt concentration in the sap and a chloride ion concentration of 1000 ppm or more,
It has a pH of 3.5-7.0 and is close to neutral.

Conventionally, a canned container of this type of seafood uses a tin-plated steel plate with a protective coating on the inner surface of the can body, and a tin-coated steel plate with a protective coating on the inner surface of the can lid. As the can lid, those which are opened by a can opener and those which have an easy open structure in which a score line is provided on the can lid and the lid is opened by a pulling opening piece have been used.

However, in recent years, it has been considered to use an aluminum easy-open can lid because of the ease of opening the can lid. When used as a container and used for the seafood, etc., the chloride ion concentration in the canned container is high, so if there is a slight metal exposed part on the inner surface of the can body and the can lid, a so-called bimetal is formed between the aluminum material and the steel material. When the battery is formed, the aluminum material side becomes the anode and the steel material side becomes the cathode, pitting corrosion of the aluminum can lid is promoted, and tin on the surface of the steel material side of the can body elutes and corrosion progresses, then the protective coating film There is a problem that peeling occurs and iron is eluted.

That is, since the easy-open can lid undergoes processing such as forming score lines on the outer surface side and forming rivets for fixing the pulling opening pieces, the protective coating film on the inner surface is large during these processing. Cracking occurs due to work strain, the protective effect is reduced, and pitting corrosion as described above occurs. Also,
In the can body, if there are coating defects such as coating defects or cracks in the protective coating film, corrosion occurs at that part, the surface of the steel sheet becomes alkaline, tin between the steel sheet and the coating film elutes, and the coating film rises. The base metal elutes, lateral corrosion under the coating film is promoted, and coating film peeling and iron elution occur.

(Problems to be Solved) An object of the present invention is to solve a conventional inconvenience and to provide a canned container such as a boiled seafood having a high salt concentration using an aluminum easy-open can lid that is easy to open. And to provide a canned food container having excellent long-term storability.

(Means for Solving the Problems) In order to achieve such an object, the present invention provides an aluminum easy-open can lid in at least one opening of a can body made of a surface-treated steel plate having side edges welded. A canned edible canned container, wherein the can body has at least a tin-iron alloy layer, a tin layer, and a chromium-chromate layer on a base steel sheet in this order, and the tin adhesion amount forming the tin layer is 50. ~ 1000 mg
/ m ² and discontinuously distributed in the range of 10 to 60% of the steel plate surface, and the chromium / chromate layer is 5 in terms of metallic chromium.
A surface-treated steel sheet of ˜40 mg / m ² is used, and at least two layers of resin protective coating are provided on the inner surface of the can. The easy-open can lid is a single-layer or multi-layer aluminum base material. And a resin protective coating of at least two layers is provided on the inner surface of the can.

The surface-treated steel sheet used in the present invention secures a tin layer, that is, tin not alloyed and remaining at 50 mg / m ² or more, and the tin layer does not uniformly cover the entire surface but 10 to 60% thereof. Discontinuously distributed (and island-shaped or mottled) is used.

When the surface-treated steel sheet in which tin is discontinuously distributed in this way is used, unlike the conventional one, even if a bimetal is formed, the lateral spread corrosion under the coating film does not proceed, and the above-mentioned problems are greatly reduced. It

It is suitable that the steel sheet of the present invention has a tin content of 1000 mg / m ² or less, more preferably 500 mg / m ² or less. That is, if the amount is larger than this, the tin distribution is not suitable because it is substantially close to the conventional uniform distribution. However, if the tin content is less than 50 mg / m ² , the weldability is poor when the can body side edge portion is welded and joined when forming the can body, which is not preferable. It is suitable that the distribution of tin does not cover the entire surface of the steel sheet but is distributed discontinuously in the range of 10 to 60%. If the distribution of the surface is less than 10%, the corrosion resistance is good but the tin content is
It is difficult to secure more than 50 mg / m ² and it reduces the weldability. Further, if it exceeds 60%, it approaches the conventional one, and as described above, lateral spread corrosion due to tin elution is likely to proceed,
Furthermore, splashing and cracks are likely to occur during welding of the side edge of the can body, causing peeling and cracking of the resin coating layer at the welded portion, and reflow during tin plating and brittle tin during the baking process when the resin coating layer is provided. An oxide layer is formed, which intervenes between the resin coating layer and the base steel sheet and reduces the adhesive strength of the resin coating layer.

Further surface-treated steel sheet used in the present invention, on the tin layer, a chromium chromate consisting of chromium oxide coating weight 3 to 20 mg / m ² in coating weight 2 to 20 mg / m ² of metallic black and terms of chromium With layers. This chromium / chromate layer covers the entire tin layer that is discontinuously distributed in islands or mottles as described above, protects the steel sheet surface where no tin layer exists, improves corrosion resistance, and at the same time bonds with the resin coating layer. Improve.

The chromium / chromate layer is 5-40 mg in terms of metallic chromium
/ m ² is suitable, and if it exceeds 40 mg / m ² , the weldability is deteriorated, which is not preferable. In particular, when the layer is formed, the metallic chromium layer and the chromium oxide layer each have a metallic chromium adhesion amount of 2 to 20.
It is mg / cm ² and the adhesion amount of chromium oxide is 3 in terms of metallic chromium.
~ 20 mg / cm ² is suitable.

Further, the surface-treated steel sheet used in the present invention, in order to form a dense alloy layer on the base steel sheet to improve the corrosion resistance,
As a base layer, a nickel-containing layer of 5 to 200 mg / m ² can be provided if desired. As the nickel-containing layer, a nickel-plated layer provided on a base steel sheet, a nickel-containing layer formed by annealing and diffusing the nickel-plated layer and diffusing a part or all of the nickel-plated layer into the base steel sheet, Further, nickel provided on the base plate
There is an iron alloy plating layer.

The surface-treated steel sheet of the present invention described above, except for the area to be the welded portion, is resin-protected on the surface that is the inner surface of the can body, and then, after being cut to a can body blank size, it is rounded to both side edges. The parts are overlapped and the parts are seam welded to form a can body. Next, the welded part is coated with resin, the opening end is narrowed down if desired, and the body end of the can is flanged, and an aluminum easy-open can lid is wound around one end of the can end, and the can can be Apply correction coating to the inside of the body.

As a resin protective coating provided on the inner surface of such a can body, corrosion resistance and discoloration or flavor of contents can be selected from thermoplastic type or thermosetting type resin coatings that are usually used for the inner surface of a can. The thermosetting resin paint is suitable in this respect. Specifically, epoxy resin paint, vinyl resin paint, vinyl organosol paint, polyester paint are suitable. ,
Thermosetting paints that are a combination of one or two or more of polyamide paints, acrylic resin paints, aminoplast paints, oil-based paints and the like are suitable.

Furthermore, a specific example is given of a thermosetting epoxy phenolic resin, particularly a phenolic resin containing 65 wt% or more of a resol type phenolic resin formed from bisphenol A and a bisphenol A having a number average molecular weight of 1400 to 7000. 2 to 10μ film thickness using thermosetting epoxy phenolic resin paint containing 50/50 to 5/95 weight ratio of epoxy resin
It is preferable to form the resin coating film.

Also, oil-based paints that have been conventionally used as thermosetting oil-based paints, that is, dry oils such as tung oil, linseed oil, and dehydrated castor oil, and oil-soluble resins such as rosin-modified phenol resin, alkylphenol resin, and xylene resin are required. A paint obtained by reacting with a small amount of glycerin / pentaerythritol according to the above, and then adding an appropriate amount of naphthenic acid such as iron, manganese, cobalt or linolenate as a desiccant, and diluting with a solvent Can be mentioned.

If desired, such paints may be used in combination with organic and inorganic additives and modifiers.

Furthermore, the welded can body of the present invention is also coated or printed on the outer surface of the can body at the stage of the material of the can body prior to welding.

When the surface-treated steel sheet of the present invention is used, it has good adhesiveness to the resin coating layer and does not peel off from the outer surface of the can body or crack.

Since the paint applied to the outer surface of the can body is required to have stain resistance, slip resistance, scratch resistance, hot water resistance, etc., acrylic resin paints, polyester paints, epoxy resin paints, alkyd resins. A thermosetting coating material in which one type or a combination of two or more types of the system coating material and the aminoplast resin coating material is suitable.

As described above, since the surface-treated steel sheet of the present invention has excellent adhesiveness, the undercoat size coat, which is almost indispensable for the conventional tinplate material, is used for coating the outer surface of the can body. Even if it is not used, good adhesiveness is obtained, and peeling or the like does not occur in the resin coating layer even if the above-mentioned severe narrowing processing is performed.

The surface-treated steel plate of the welding can of the present invention and the coated resin coating layer thereof are schematically shown in FIGS. 1 and 2. FIG. 1 is an example in which a nickel-containing layer is not provided, and FIG. 2 is an example in which a nickel-containing layer is provided. (1) is a base steel plate, (2) is a tin-iron alloy layer, (3)
Is a tin layer, (4) is a chromium / chromate layer, (5) is a resin coating layer, and (6) is a nickel-containing layer.

Next, as the aluminum easy-open can lid material used for the canned container of the present invention, the conventional aluminum material can be used without any problem as long as the resin protective coating is surely applied and no metal exposed portion is applied. However, as described above, since the structure of the canned container which is the object of the present invention is extremely prone to corrosion, even if a slight coating film defect occurs in the manufacturing process of the can lid and the subsequent handling process, pitting corrosion is further caused. A material that is unlikely to cause corrosive corrosion is desirable, for example, an aluminum clad material disclosed in JP-A-52-8388 and JP-A-60-219047, that is, a core layer of aluminum alloy (a layer serving as a core material). ), A thin layer of an aluminum alloy having a different composition from the core layer is formed as a clad layer, and
A clad material in which corrosion resistance is enhanced by a kind of metal or pitting corrosion is prevented is more suitable.

As a method for producing an aluminum easy-open can lid having a resin protective coating using such a can lid material, in order to obtain a can lid having a higher degree of corrosion resistance, it is preferable to perform a chemical conversion treatment on a flat plate. A first resin protective coating is applied to the surface of the aluminum can lid material by painting, then punched into a circular can lid shape, a sealing compound is applied to the peripheral curl portion, and a score line is formed on the panel surface to regulate the opening. In addition, a method of repairing the defective portion of the first protective coating on the inner surface of the can lid by applying a second resin protective coating on the surface that will be the inner surface of the can after the attachment processing of the tension opening piece is performed Is suitable. In this case, the first resin protective coating is preferably a protective coating made of a thermosetting epoxy resin coating such as an epoxyphenol resin coating, and the second resin protective coating is a thermosetting or thermoplastic epoxy resin. It is suitable to use a paint such as a vinyl-based paint or a vinyl resin-based paint and spray-coat it to form a protective film.

(Example) (Preparation of main body of canned container) A nickel-plated amount, a tin-plated amount, a chromium metal amount, a chromium oxide (chromium equivalent) amount and a tin-distributed steel plate having a thickness of 0.22 mm shown in Table 1 were used. The resin coating layer shown in -1 was formed on the surface corresponding to the inner surface side of the can body by excluding the portion corresponding to the welded joint portion to prepare a resin coated original plate. Then, this resin-coated original plate is cut into a can-shaped can body blank size, rounded, and the blank edge portions corresponding to the welding joint are overlapped and welded at a welding speed of 60 m / min using a known electric resistance welding machine. Formed a torso. Further, epoxy phenolic resin-based paint was applied to the welded joint on the inner surface side and baked to correct the coating of the welded portion. After that, both ends of the can body are flanged, and the aluminum full-open can lid described later is double wound at one end, and it is 301 diameter flat No. 3 size as a canning container for seafood, and for agricultural products. For example, a container body of 301 diameter flat No. 4 size and the constitution shown in Table 2 was prepared.

(Creation of can lid) JIS300 of aluminum-manganese alloy as core material
3, JIS 300 of aluminum-manganese-magnesium alloy
Using JIS5052 of 4 and aluminum-magnesium alloy, and using JIS1070 of pure aluminum as a clad material, obtained by clad a clad layer by a hot rolling method on the surface which becomes the inner surface side of the core layer can Using such an aluminum clad material, and using the aluminum clad material whose surface is clad with phosphoric acid chromate as the can lid base material, roll-coat epoxy epoxy resin based paint on the inner surface of the can lid. The film was baked at 205 ° C. for 10 minutes to form a protective film (first protective film) having an average film thickness of 4 μm.

Next, after punching this painted aluminum clad material into a can lid shape and providing a sealing compound in the curl part,
Score line processing and tensile opening piece mounting processing are performed.
The score-resistive full-open can lid shape described in 1 above was used.

Next, spray coat an epoxy phenol resin-based paint, an epoxy ester resin-based paint, or a thermosetting vinyl resin-based paint on the protective coating on the inner surface of the can lid.
210 ° C x 3.5 minutes, 210 ° C x 3.5 minutes, 200 ° C x 1.5 minutes baking was performed to form a protective film (second protective film) with an average film thickness of 4μ. A full open can lid made of aluminum was created.

In addition, using a JIS5052 only and JIS3003 only aluminum material as a can lid base material, a can lid provided with the first and second protective coatings and a can lid provided with only the first protective coating were prepared in the same manner as above. . Further, using the can lid base material used for the can lid number 2 and the can lid number 9, an epoxy phenol resin-based primer with an epoxy resin / phenol resin ratio of 6/4 is dried on the surface which becomes the inner side of the can lid to have a dry thickness of Apply it to 1μ and blow dry.
A 25 μm thick polyethylene terephthalate resin film is thermocompression-bonded thereto at 200 to 230 ° C., and further heat treated at 200 ° C. for 10 minutes to prepare a polyethylene terephthalate resin film laminated can lid base material, which is then used. A full open can lid was prepared in the same manner as described above.

(Preparation and evaluation of canned fish) Preparation of canned fish and shellfish 1. Salmon fillet immersed in salt solution with 13% salt concentration for 15 minutes 1.
Canned with a 0% saline solution in the body of a canned container with the can body number shown in Table-1, and then canned using a bottom lid provided with a double coat of a tin-free steel material and an epoxyphenol resin-based paint. Was double-wound with a seamer so that the degree of vacuum was 65 cmHg, and then heat sterilized at 115 ° C. for 110 minutes to prepare a test canned product. The pH of the juice of the canned contents was 6.3 and the chloride ion concentration was 6300 ppm.

Preparation of Canned Agricultural Products Granular sweet corn and saline solution with a salt concentration of 1.5% are packed in a canned container body using the can body number shown in Table-1 and the bottom lid is made in the same manner as described above so that the vacuum degree of the canned food is 65 cmHg. Was double-wound and then heat-sterilized at 116 ° C. for about 80 minutes to give a test can. The liquid pH of the contents of this canned food was 6.2 and the chloride ion concentration was 3700 ppm.

Using the obtained canned product, an actual can storage test was conducted at 37 ° C. for 6 months, after which the cans were opened and the can body and the can lid were evaluated. As a result, as shown in Table 3, the canned container comprising the can body and the can lid of the present invention had good can quality without causing corrosion which would cause a practical problem in both the can body and the can lid. When a can lid having only one layer of protective coating on the can lid and insufficient protection of the coating (test can number 3,6,10,16,18) and a can barrel number 6 different from the present invention for the can barrel When using 7 and 7 (test can number 15,16,17,18)
The can body or the can lid was corroded.

(Effect of the present invention) As is apparent from the above description, the present invention uses an aluminum easy-open can lid that is easy to open and long-term preservation even when boiled seafood having a high salt concentration is canned. It is effective to provide an edible canned container that does not hinder the operation.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 and FIG. 2 are schematic views showing the structure of a can body used in the present invention. 1 ... Base steel plate, 2 ... Tin-iron alloy layer 3 ... Tin layer 4 ... Chromium / chromate layer

Claims (1)

(57) [Claims] 1. An edible canning container in which an aluminum easy-open can lid is wound around at least one opening of a can body made of a surface-treated steel plate having side edges welded, the can body being on a base steel plate. At least a tin-iron alloy layer, a tin layer, and a chromium / chromate layer in this order, and the amount of tin deposited to form the tin layer is 50 to 1000 mg / m ² and 10 to 60% of the steel plate surface.
Range using a surface-treated steel sheet wherein chromium chromate layer is 5 to 40 mg / m ² reckoned as metal chromium as well as distribution in discrete, the surface to be the the can inner surface side is provided with a resin protective film The easy-open can lid uses a single-layer or multi-layer aluminum base material, and at least two layers of a resin protective coating are provided on the inner surface of the can, which is an edible can container.