JPS63281957A - Container for canned food - Google Patents

Abstract

PURPOSE:To make an aluminum easy-open can whose can opening operation is easy and excellent in long-term storage stability even with respect to boiled fish and shellfishes having high salt concn., by a method wherein at least a tin-iron alloy layer, a discontinuously distributed tin layer and a chromium/chromate layer are formed on the fundamental steel plate of a can body in this order and a resin protective film is provided to the surface becoming the inner surface of the can body of said steel plate while an aluminum base material is used as the material quality of a can lid and two resin protective films are provided thereto on the inner surface side of the can. CONSTITUTION:A surface-treated steel plate has a tin layer 3 containing 50 mg/m<2> or more of tin remaining without being alloyed and discontinuously distributed on the surface of said steel plate within a range of 10-60%. The amount of tin in the steel plate is 1000 mg/m<2> or less, pref., 500 mg/m<2> or less. A chromium/chromate layer 4 consisting of metal chromium whose adhesion amount of 2-20 mg/m<2> and chromium oxide whose adhesion amount of 3-20 mg/m<2> as chromium is provided on the tin layer 3. This layer covers the whole of the tin layer 3 not only to protect the tin layer free surface of the steel plate to enhance the corrosion resistance but also to enhance the bonding strength with a resin film layer. Said chromium/chromate layer is pref. 5-40 mg/m<2> as metal chromium and not pref. when exceeds 40 mg/m<2> since weldability is lowered.

Description

Detailed Description of the Invention (Industrial Application Field) A can container comprising an aluminum easy-open can lid wrapped around a can body made of the surface-treated steel plate of the present invention, which is used for boiled seafood with a high salt concentration. The present invention relates to an edible canning container suitable for canning soup and the like. (Prior art) Boiled seafood, soup, etc. that are canned have a high salt concentration in the liquid (chloride ion concentration of 11,000 pp or more, and a medium pH of 3.5 to 7.0). It is close to sex.

Conventionally, this type of canned seafood container uses a tin-plated steel plate with a protective coating on the inside for the can body, and a can lid made of tin-plated steel with a protective coating on the inside is tightened. The can lid has been used to be opened with a can opener, or to have an easy-open structure in which a score line is provided on the can lid and the lid is opened with a pull-opening piece.

However, in recent years, the use of aluminum easy-open can lids has been considered from the viewpoint of ease of opening the can lid. When used as a canning container for seafood, etc., the concentration of chloride ions inside the canning container is high, so if there is an exposed metal part on the inside of the can body or can lid, even if it is at an extreme level, there will be a problem between the aluminum material and the steel material. A so-called bimetallic battery is formed, with the aluminum side serving as an anode and the steel side serving as a cathode, which accelerates pitting corrosion on the aluminum can lid, and also on the steel side of the can body, where tin on the surface is leached out and corrosion progresses, and then the protective coating is removed. There is a problem in that the coating film peels off and iron elutes.

In other words, easy-open can lids undergo processing such as carving score lines on the outer surface and forming rivets to secure the pull-opening piece, so during these processing, the protective coating film on the inner surface is significantly damaged. Cracks occur due to processing strain, reducing the protective effect and causing pitting corrosion as described above. In addition, if there are poor coatings or cracks in the protective coating on the can body, corrosion will occur in those areas, and the surface of the steel plate will become alkaline, causing the tin between the steel plate and the coating to dissolve, causing the coating to The metal is lifted up, the base metal is eluted, and the horizontally spreading corrosion on the paint film is promoted, resulting in paint peeling and iron elution.

(Problems to be Solved) An object of the present invention is to solve the inconveniences of the conventional art and to provide a container for canning boiled seafood with a high salt concentration using an aluminum easy-open can lid that is easy to open. The object of the present invention is to provide an edible canned container with excellent long-term storage stability.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides an easy-open can lid made of aluminum at at least one opening of a can body made of a surface-treated steel plate with welded side edges. A sealed edible canned container, wherein the can body has at least a tin-iron alloy layer, a tin layer, and a chromium/chromate layer in this order on a base steel plate, and the tin layer has an adhesion amount of 50%. ~100
A surface-treated steel sheet is used in which the chromium/chromate layer is discontinuously distributed in the range of 10 to 60% of the steel sheet surface and has a concentration of 5 to 40 g/rrr in terms of metallic chromium, and is on the inner surface of the can. At least two layers of resin protective coating are provided on the surface, and the easy-open can lid uses a single-layer or multi-layer aluminum base material, and at least two layers of resin protective coating are provided on the inner surface of the can. It is characterized by being provided with.

The surface-treated steel sheet used in the present invention has a tin layer, that is, a residual unalloyed tin of 50 μ/rr1 or more, and the tin layer does not uniformly cover the entire surface, but accounts for 10 to 60% of the tin layer.
Discontinuously (i.e., islands or patches) within a range of
Use distributed ones.

By using a surface-treated steel sheet in which tin is discontinuously distributed in this way, the horizontal spreading corrosion under the coating film will not progress even if a bimetal is formed, unlike conventional products, and the above-mentioned problems will be greatly reduced. Ru.

The amount of tin in the steel sheet of the present invention is suitably 1000 mg/m2 or less, more preferably 500 μg/rrf or less. That is, if the amount is more than this, the distribution of tin will substantially approach the conventional uniform distribution, which is unsuitable. However, if the tin content is less than 50 mg/m2, the weldability will be poor when welding the side edges of the can body when forming the can body, which is not preferable. In addition, the distribution of tin should not cover the entire surface of the steel plate (a discontinuous distribution in the range of 10 to 60% is suitable; if the distribution on the surface is less than 10%, corrosion resistance is good, but the amount of tin should be reduced to 50%/ It is difficult to maintain the weldability above rrf, which reduces weldability.Also, when it exceeds 60%, it approaches the conventional type, and as mentioned above, horizontal spreading corrosion due to easy elution tends to progress, and furthermore, the can body side Splash and cranks are likely to occur when welding edges, causing peeling and cracking of the resin coating layer at the welded area, as well as formation of a brittle tin oxide layer during tin plating flow and the baking process when installing the resin coating layer. However, this is interposed between the resin coating layer and the base steel plate and reduces the adhesive strength of the resin coating layer.

Furthermore, the surface-treated steel sheet used in the present invention has a chromium/chromate layer on the tin layer consisting of metallic chromium with a deposit of 2 to 20 g/nf and chromium oxide with a deposit of 13 to 20 g/nl in terms of chromium. have This chromium/chromate layer covers the entire tin layer, which is discontinuously distributed in the form of islands or spots, and protects the surface of the steel sheet where no tin layer is present, improving corrosion resistance and strengthening the adhesive strength with the resin coating layer. improve.

The chromium/chromate layer has a thickness of 5 to 40 cm in terms of metallic chromium.
/rd is suitable, and if it exceeds 40 mg/m2, weldability deteriorates, so it is not preferable. In particular, when forming this layer, the metal chromium layer and the chromium oxide layer each have an adhesion amount of metal chromium of 2 to 20 ■/c++1, and a suitable amount of chromium oxide adhesion of 3 to 20 ■/d in terms of metal chromium. .

In addition, the surface-treated plate used in the present invention forms a dense alloy layer on the base steel plate and improves corrosion resistance.
As a base layer, a nickel-containing layer of 5 to 200 .mu./i can be provided if desired. This nickel-containing layer may be a nickel-plated layer provided on a base steel sheet, or a nickel-containing layer formed by subjecting the nickel plating layer to annealing diffusion treatment and diffusing part or all of it into the base steel sheet. Furthermore, there is a nickel-iron alloy plating layer provided on a base steel plate.

The above-mentioned surface-treated steel sheet of the present invention is coated with a protective resin on the inner surface of the can body, except for the area that will be the welded part, and then cut into the size of a can body blank, and then rolled up and edged on both sides. The sections are overlapped and the sections are seam welded to form the can body. Next, the welded part is coated with resin, the opening end is narrowed if desired, the end of the can body is flanged, and an aluminum easy-open can lid is seamed to one end of the can. Apply correction paint to the inside of the body.

The resin protective coating provided on the inner surface of the can body can be selected from thermoplastic or thermosetting resin coatings, which are usually used as can interior coatings, to provide corrosion resistance, discoloration, and flavor resistance of the contents. It should be selected appropriately by considering the following factors, and thermosetting resin paints are suitable in this respect.
Specifically, epoxy resin paint, vinyl resin paint,
Thermosetting paints consisting of one or a combination of two or more of vinyl organosol paints, polyester paints, polyamide paints, acrylic resin paints, aminoplast paints, and oil-based paints are suitable.

Furthermore, specific preferred examples include thermosetting epoxy phenol resins, particularly phenol resins containing 65% by weight or more of resol type phenol resins formed from bisphenol A, and those having a number average molecular weight of 1,400 to 7,000. It is preferable to form a resin coating film with a thickness of 2 to 10 μm using a thermosetting epoxy phenol resin paint containing bisphenol A type epoxy resin in a weight ratio of 50150 to 5/95.

In addition, as thermosetting oil-based paints, conventionally used oil-based paints, such as dry oils such as tung oil, linseed oil, and dehydrated castor oil, and oil-soluble resins such as rosin-modified phenolic resins, alkylphenol resins, and xylene resins are used. Paint obtained by heating reaction using a small amount of glycerin or pentaerythritol depending on the situation, then adding an appropriate amount of naphthenic acid or lylunate of iron, manganese, cobalt, etc. as a drying agent and diluting with a solvent. can be mentioned.

Such paints may contain organic and inorganic additives and modifiers, if desired.

Further, in the welded can body of the present invention, the outer surface of the can body is also painted or printed at the stage of the can body raw material prior to welding.

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

The paint applied to the outside of the can body must have stain resistance, slip resistance, scratch resistance, hot water resistance, etc., so acrylic resin paint, polyester paint, epoxy resin paint, alkyd resin paint, etc. Thermosetting paints made of one type or a combination of two or more of aminoblast resin type paints and aminoblast resin type paints are suitable.

As mentioned above, the surface-treated steel sheet of the present invention has excellent adhesive properties, so when painting the outer surface of the can body, the undercoat size coat, which was indispensable for conventional tin wood, is not necessary.
In the present invention, good adhesion can be obtained even without using it, and the resin coating layer does not peel off even when subjected to the severe squeezing process described above.

The surface-treated steel sheet of the welded can body of the present invention and its painted resin coating layer are schematically shown in FIGS. 1 and 2. FIG. 1 shows an example in which no nickel-containing layer is provided, and FIG. 2 shows 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 in the canned containers of the present invention, conventional aluminum materials can be used without any problems as long as the resin protective coating is securely applied and there are no exposed metal parts. However, as mentioned above, the structure of the canned container that is the object of the present invention is extremely susceptible to corrosion, so even if a slight coating defect occurs during the can lid manufacturing process or subsequent handling process, pitting corrosion will further increase. It is desirable that the material is a material that does not easily cause corrosion that can lead to ) A thin layer of an aluminum alloy having a composition different from that of the core layer is formed as a cladding layer on top of the core layer, and a cladding material with enhanced corrosion resistance or prevention of pitting corrosion by using two types of metals is more suitable.

A method for manufacturing an aluminum easy-open can lid coated with a resin protective coating using such can lid material is preferably to carry out a chemical conversion treatment in order to obtain a can lid with a higher degree of corrosion resistance. A first resin protective coating is applied to the surface of a flat aluminum can lid material by painting, then punched into a circular can lid shape, a sealing compound is applied to the curled peripheral portion, and a score line is formed on the panel surface to regulate the opening. After engraving and attaching the tension opening piece, a second resin protective coating is applied to the inner surface of the can by painting, and defects in the first protective coating on the inner surface of the can lid are repaired. method is suitable. In this case, the first resin protective film is preferably a protective film made of a thermosetting epoxy resin paint such as an epoxyphenol resin paint, and the second resin protective film is a thermosetting or thermoplastic epoxy resin. It is suitable to use a paint based on paint, a vinyl resin paint, or the like, which is spray-coated to form a protective film.

(Example) (Creation of canning container body) Using a 0.22 m thick steel plate with the amount of nickel plating, amount of tin plating, amount of metallic chromium, amount of chromium oxide (chromium equivalent) and tin distribution shown in Table 1, A resin-coated base plate was prepared by applying the resin coating layer shown in Table 1 to the surface corresponding to the inner surface of the can body, except for the welded joint area, and painting it. Next, this resin-coated original plate was cut into a tanza (shaped can body blank size), rolled, and the edges of the blank corresponding to the welding joints were overlapped and welded at a welding speed of 60 m/min using a known electric resistance welding machine. A can body was formed. Furthermore, an epoxy phenol resin paint was applied and baked on the welded joint on the inner surface side to correct the coating of the welded area. After that, flanging was performed on the openings at both ends of the can body, and one end was coated with a coating as described below. The fully open aluminum can lid is double-sealed, and the size is 301 diameter and size 3 for canning seafood, and 301 is for agricultural products.
A container body having a diameter of No. 4 and the configuration shown in Table 2 was prepared.

(Creation of can lid) JIS3 aluminum-manganese alloy as core material
003. Using JIS 3004, an aluminum-manganese-magnesium alloy, and JIS 5052, an aluminum-magnesium alloy, and using pure aluminum JISIO 70 as the cladding material, a cladding layer is clad on the surface of the core layer that will become the inner surface of the can using a hot rolling method. The aluminum clad material as shown in Table 2 obtained by Roll coat the paint and bake at 205℃ for 10 minutes to achieve an average film thickness of 4μ.
A protective film (first protective film) was formed.

Next, punch out this painted aluminum clad material into the shape of a can lid.
After applying a sealing compound to the curled portion, a score line process and a tension opening piece attachment process were performed to obtain a fully open can lid shape with a score ratio as shown in Table 2.

Next, epoxy phenol resin paint, epoxy ester resin paint, or thermosetting vinyl resin paint was spray coated on the protective coating on the inner surface of the can lid, and 2 coats of each were applied.
10℃×3.5 minutes, 210℃×3.5 minutes, 200℃×
Baking was carried out for 1.5 minutes to form a protective film (second protective film) with an average thickness of 4 μm, and a fully open aluminum can lid having a diameter of 301 and having the can lid number shown in Table 2 was prepared.

In addition, only JIS5052 and JIS3 can be used as can lid base materials.
The first step was carried out in the same manner as above using only the 003 aluminum material. A can lid provided with the second protective coating and a can lid provided with only the first protective coating were created. In addition, using the can lid base material used for can lid number 2 and can lid number 9, an epoxy phenolic resin brimer with an epoxy resin/phenol resin ratio of 6/4 was applied to the inner surface of the can lid to a dry thickness. It was coated to a thickness of 1μ and dried with air, and then a 25μ thick polyethylene terephthalate resin film was thermocompressed at 200 to 230°C, and further heat treated at 200°C for 10 minutes to form a polyethylene terephthalate resin film laminate can. A lid base material was created, and then a full open can lid was created using this material in the same manner as described above.

(Creation and evaluation of canned products) ■Creation of canned seafood Salmon fillet soaked in saline solution with a salinity concentration of 13% for 15 minutes and stuffed with 1.0% saline solution in the canning container body with the can body number shown in Table 1. Then, using a bottom lid made of tin-free steel and double-coated with a coating film of epoxy phenol resin paint, the can was double-sealed using a seamer so that the canned vacuum level was 65 oaHg. 1 in °C
Test cans were prepared by heat sterilization for 10 minutes. The pH of the liquid content of this canned product was 6.3, and the chloride ion concentration was 6300 pps+.

■ Creation of canned agricultural products Granular sweet corn and saline solution with a salt concentration of 1.5% are stuffed into the canning container body using the can body number in Table 1, and the vacuum level of the canned product is 65 cmHg in the same manner as above. The bottom lid was double-sealed, and then heat sterilized at 116°C for about 80 minutes to prepare test cans.

The pH of the liquid content of the canned product was 6.2, and the chloride ion concentration was 3700 pp.

Using the obtained cans, a real can storage test was conducted at 37° C. for 6 months, after which the cans were opened and the can bodies and lids were evaluated. As a result, as shown in Table 3, the can body and can lid of the present invention have good quality, with no corrosion that would cause practical problems in both the can body and can lid. However, when can lids with only one layer of protective coating and insufficient protection are used (test can numbers 3, 6, 10, 16, and 18), and can bodies with can body numbers different from those of the present invention are used. When No. 6.7 was used (test can numbers 15, 16, 17, and 18), corrosion occurred on the can body or can lid.

(Effects of the present invention) As is clear from the above description, the present invention is effective for long-term storage even when boiled seafood with a high salt concentration is canned using an aluminum easy-open can lid that is easy to open. This has the effect of providing an edible canning container that does not cause any problems.

[Brief explanation of the drawing]

1 and 2 are schematic diagrams 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... Chrome/chromate layer

Claims (1)

[Claims] 1. An edible can container comprising a can body made of a surface-treated steel plate with welded side edges and an aluminum easy-open can lid wrapped around at least one opening, the can body having at least a tin base plate on a base steel plate. It has an iron alloy layer, a tin layer, and a chromium chromate layer in this order, and the amount of tin deposited forming the tin layer is 50 to 1000 mg/m^2, and
A surface-treated steel plate with a discontinuous distribution of chromium and chromate in the range of ~60% and a concentration of 5 to 40 mg/m^2 in terms of metallic chromium was used, and a resin protective coating was applied to the inner surface of the can. The easy-open can lid is made of a single-layer or multi-layer aluminum base material, and the inner surface of the can is provided with at least two layers of resin protective coating. canning container.