JPS62182041A - High corrosion-resistant easy-open can cover - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to a can lid for canned goods, and is particularly suitable as a can lid for canned containers containing salt-containing and highly corrosive contents such as seafood, agricultural products, and sports drinks. Regarding aluminum easy-open can lids.

(Prior Art) Conventionally, can containers for contents containing relatively high amounts of salt, such as seafood, agricultural products, and sports drinks, have been made using tin cans with lids wrapped around the sides of the tin cans. Can lids were opened with a can opener or easy-open can lids were used. However, in recent years, the use of aluminum easy-open can lids has been considered from the viewpoint of ease of opening, but if a tin can body and an aluminum can lid are used to make a can container, If there is an exposed metal part, the aluminum material and the tin plate form a so-called bimetal battery, with the aluminum material side serving as the anode and the tin plate serving as the cathode, promoting corrosion of the aluminum material. In particular, for easy-open can lids, the outer surface is processed with score lines and rivets for attaching the tension opening piece, so the protective coating on the inner surface of these parts is subject to large processing strains, which can cause cracks and other problems, reducing the protective effect. In addition, the aluminum board in the score line area is thinner by the depth of the score line groove, so this part (the remaining thickness of the board where the score line is processed) is If pitting corrosion occurs on the score residual (called the score residual), it will lead to a hole in a short period of time, and there is a risk that the contents will leak.One possible countermeasure is to make the score residual thicker, but if it is thicker, the tensile opening piece will be pulled. When the can lid is opened, the breaking strength of the score line increases and the opening performance becomes poor.Therefore, a can lid with better corrosion resistance is required, and an aluminum alloy core layer (core material) is used as the can lid base material. JP-A-52-8388 discloses a cladding layer in which a thin layer of an aluminum alloy having a composition different from that of the core layer is formed on top of the cladding layer.
No. 60-219047, etc. have proposed appropriate use as easy-open can lids for canned containers that require excellent opening ability and high corrosion resistance as described above. However, there was a need in the industry for an aluminum easy-open can lid with excellent corrosion resistance and opening properties.

(Object of the Invention) The object of the present invention is to fill a can body with highly corrosive contents in a can body using a steel material such as tin plate as the can body member and an aluminum easy-open can lid as the can lid. To provide an easy-open can lid made of aluminum that has excellent corrosion resistance and excellent opening ability without causing any corrosion that would pose a practical problem on the can lid even under severe corrosive conditions such as when stored for a long period of time. be.

(Structure of the Invention) According to the present invention, an aluminum clad material consisting of an aluminum alloy core layer and a cladding layer is used as the aluminum base material constituting the can lid, and a protective coating is provided on the cladding layer on the inner surface of the can lid. In the easy-open can lid, the outer surface of the can lid has a score line regulating the opening, the core layer of the easy-open can lid has a thickness of 0.2 to 0.4 mm, and the cladding layer has a thickness of 0. .01" is 0.1 mm, and the score ratio (R) of the score line regulating the opening of the easy-open can lid is 0.6 h≧R≧0.IT4+Tz (However, T1 is the thickness of the core layer T2 is An easy-open can lid that achieves the above object can be obtained by using an easy-open can lid that has a thickness (representing the thickness of the cladding layer on the inner surface of the can lid).Next, the present invention will be explained in more detail.

1 to 3 show a fully open type aluminum easy-open can lid showing an example of the embodiment of the present invention. Figure 1 is its plan view, Figure 2 is nn of Figure 1.
Figure 3 shows an enlarged view of the score line processing section. A protective coating 5 is provided on the cladding layer 3 on the inner surface of the can of the aluminum cladding material 4 consisting of the core layer 2 and cladding layer 3 of the can lid 1.
A score line 6 is carved on the outer surface side to regulate the opening, and a tension opening piece 7 is attached by riveting.

In the present invention, an aluminum clad material consisting of a core layer and a cladding layer is used as the aluminum can lid base material, but the material constituting the core layer in this aluminum clad material has the drop strength required when used as an easy-open can lid. ,
The material and thickness must be such that it maintains compressive strength, bulge strength, etc. at predetermined levels and also has excellent corrosion resistance. The material may be JTS 3004.3003, which is an aluminum-manganese alloy. Particularly suitable.

In addition, the thickness of the core layer is 0.2~Q, 4mm.
9. If it is thinner than 0.2 mm, it will not be able to maintain its strength as a can lid.
If it is thicker than 4 mm, the workability when tightening the curled portion of the can lid to the can body will be reduced, and it will also be disadvantageous from an economical point of view.

Next, when used as an easy-open can lid, the material constituting the aluminum clad layer has a high level of protection against the contents that have penetrated through the resin protective coating provided on the upper layer due to the combination effect with the core layer. It must be a material that exhibits corrosion resistance and does not adversely affect openness. Basically, the kraft material must be a material that becomes an anode when combined with the core material in terms of electrochemical properties related to corrosion. However, if the degree of becoming an anode increases significantly, corrosion of the cladding layer structure will progress too much and the protective film will peel off, so it is desirable to set it appropriately, and the degree of anode is 20 ~
130 millivolt is suitable. By using corrosive materials, even if corrosion progresses from defects in the protective coating, the corrosion will spread in the direction of the construction method rather than in the direction that causes pitting corrosion in the can stock, resulting in perforation corrosion that leads to holes. It can be prevented. Furthermore, in terms of material strength, it is preferable to use a material with lower breaking strength than the core material from the viewpoint of opening property.If the score residual is the same thickness, the opening property can be improved by using a can lid base material made only of the core material. You'll get something better than if you had. Specifically, such clad materials are those close to pure aluminum materials, such as J.
I 31070 etc. can be cited as a suitable example.

The suitable thickness of the cladding layer is 0.01 to 0.1 mm; if it is thinner than 0.01 mm, it will act as an anode for the core layer, and the effect of preventing pitting corrosion will not last, and the core layer will be damaged. Corrosion may progress and lead to pitting. Also,
When it is thicker than 0.1 mm, the thickness of the core layer becomes relatively thin, and the strength of the can lid, which depends on the core layer, decreases.

When using an aluminum clad material with such a configuration, prior to forming the protective film, it is recommended to perform a known chemical conversion treatment on the surface of the cladding layer, such as phosphoric acid chromate treatment or alumite treatment, to increase corrosion resistance and improve the adhesion of the protective film. It is preferable to increase the Although the cladding layer must be provided on the inner surface of the can, it may also be provided on the outer surface of the can if desired.

Next, as a method for manufacturing an aluminum easy-open can lid using such aluminum clad material, a known method is used, for example, by painting or film laminating the surface of a flat aluminum clad material that has been subjected to chemical conversion treatment. A protective film is provided, a can lid is punched out using this, a sealing compound is applied to the curled edge of the can, a score line is carved on the can lid to restrict the opening, and a pull opening piece is attached by processing. The resin protective coating according to the present invention that can be produced may be a single protective coating, but in order to obtain a can lid with higher corrosion resistance,
A protective coating 5b (second protective coating) is further applied by painting on the protective coating 5a (first protective coating) of the can lid manufactured by the above method to repair defects in the first protective coating on the inner surface of the can lid. Delicious. The first protective film is preferably a protective film made of a thermosetting epoxy resin paint such as an epoxyphenol resin paint, or a protective film laminated with a resin film such as a polyester film.

Further, as the second protective film, it is preferable to use a thermosetting or thermoplastic type epoxy resin paint, vinyl resin paint, or the like, and spray coat it to form a protective film.

Furthermore, the easy-open can lid must have excellent opening properties along the score line when the pull-opening piece is pulled. In general, if the groove 6 of the score line is made shallower and the score residual 7 is made larger, the opening property will be lowered, and if the groove 6 of the score line is made deeper and the score residual 7 is made smaller, the opening property will be improved. As corrosion progresses, pitting becomes more likely to occur. In the present invention, the thickness of the core layer 2 is 0.2 to 0.4fl, and the thickness of the cladding layer 3 is 0.01fl.
~0,1fII aluminum clad material, in order to maintain corrosion resistance and excellent opening property, the score ratio 7 thickness (R) should be 0.6Tt ≥ R2O, ITt + T2 (however, TL is the core It has been found that the layer thickness T2 needs to be set within the range of cladding layer thickness.

In other words, the score ratio 8 is the thickness of the core layer 6 (TI)
By keeping 60% or less of the thickness of the core layer 6, leaving 10% or more of the thickness of the core layer 6, and making the cladding layer deep enough so that the groove of the score line does not cover it, both the opening property and the corrosion resistance are good as described above. It can be used as an easy-open can lid, and if this condition is not met, the opening property or corrosion resistance will be poor.

In the present invention, the combination of the cladding layer and the core layer has a material composition that is difficult to cause corrosion, especially drilling corrosion, and the cladding layer is made of aluminum material, which has a lower breaking strength than the core layer. From this point, it is possible to make the score residual thicker than can lids made of conventional single materials, and this, combined with the electrochemical properties, is synergistically advantageous against perforation due to perforation corrosion in the relevant part. It can be done.

The can body to which the aluminum easy-open can lid of the present invention is fastened may be a two-piece can body made of steel or aluminum such as tin plated steel plate, thin tinned steel plate, or tin-free steel. One example is a 3-piece can body, which is particularly suitable as a can lid that requires a high degree of corrosion resistance, such as a can lid made of steel that forms a bimetallic battery.

(Example) Next, an example of the present invention will be described. Can lid configurations of Examples (using can lid numbers L3, 5, 6, 7.8) and comparative examples (using can lid numbers 2, 4.9), which will be described later,
The evaluation results are shown in the table.

(Creation of can lid) J f of aluminum-manganese alloy as core material
Using S 3003, J I S 3004 and aluminum-magnesium alloy J I S 5052,
Pure aluminum JIS 10 as cladding material
70 and cladding layers on both sides of the core layer using a hot rolling method, as shown in the table, is used, and the surface of the cladding layer is subjected to phosphoric acid chromate chemical conversion treatment. Using this as a can lid base material, roll coat an epoxy phenol resin paint on the inner surface of the can lid, bake at 205°C for 10 minutes,
A protective film (first protective film) having an average thickness of 4 μm 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, score line processing and tension opening piece removal processing were performed to obtain a fully open can lid shape with the score ratio shown in the table.

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 film thickness of 4 μm, and the can lid numbers 1, 2.3, 4.
6,7.8. A fully open aluminum can lid was created and evaluated as described below.

In addition, can lids with can lid number 9 using only JIS 5052 aluminum material as the can lid base material and can lids with can lid number 5 without the second protective coating were also created and evaluated as described below.

(Creation of test cans for actual can storage test and evaluation of can lids) Plate thickness 0.
20++m (7) tin plate (!! Area weight: 2.8g/side)
Using the can body material with an epoxyphenol resin paint coating on the inside surface of the can, weld the side joints together to create a 3-piece can body, and attach one end of the opening to the can body material. A welded can container body was created by double seaming a furiki can lid coated with an epoxyphenol resin coating. In addition, a can body of a 3-piece can was created by using the same tin plate as above with a coating of zinc-dispersed oil-based paint on the inside surface of the can, and soldering the side seams. A solder can container body was prepared by double-sealing a furiki can lid with a coating made of zinc-dispersed oil-based paint on one end of the opening.

Next, the canned contents include seafood, agricultural products, etc. as listed on the table.
Beverages were taken up, seafood and beverages were filled into welded can containers, and agricultural products were filled into soldered can containers, and the aluminum full-open can lids were double-sealed to create actual can storage test cans, and accelerated tests were conducted. After being stored at 37°C for 6 months, the can was opened and the corrosion status of the can lid was evaluated. Additionally, the openability of the can lid was also evaluated separately. The results are shown in the table. From this result, test can numbers 1, 3, 5, and 6, which are examples of the present invention.
,7゜8 (Canned food number 1, 3, 5, 6.7.8 >
It had excellent opening properties and corrosion resistance without any practical problems. Among these, test can number 5 (can lid number 5), which has a single layer of protective coating on the can lid, has no practical problems, but compared to other cans with two layers of protective coating, there is a problem with the construction method in the defective parts of the coating. Corrosion was observed, and the corrosion resistance was at a slightly low level. - Test can number 2 (can lid number 2) with a large score random, which is a comparative example of the strength-grip invention, had poor openability of the can lid, and test can number 4 (can lid number 4) with a small score random Although the opening ability was good, pitting corrosion occurred at the score line area, and some cans were observed to have perforations. In addition, test can number 9 using a conventional product without a cladding layer as the aluminum can lid base material
(Can lid number 9) was found to be defective, as some of the cans with corrosion, which is a practical problem, were observed in all the canned contents after storage.

(Effects of the Invention) According to the present invention, the aluminum base material constituting the can lid of a can container is an aluminum clad material consisting of a core layer and a clad layer, and a protective coating is provided on the clad layer on the inner surface of the can lid. The easy-open can lid has a score line for regulating the opening on the outer surface of the can lid, and the core layer of the easy-open can lid has a thickness of 0.2 to 0.4 m. , the cladding layer has a thickness of 0.01 to 0.1 fins, and the score relation (R) of the score line regulating the opening of the easy-open can lid is 0.6 T (≧R≧0.1 tt + T31. (However, Ti is the thickness of the core layer, T2 is the thickness of the cladding layer on the inner side of the can lid.) Since the structure is an easy-open can lid, the can lid has excellent opening properties, and When used as can lids for can containers that use steel as the can body, even under harsh conditions such as storing highly corrosive contents for long periods of time, corrosion that can lead to perforation in the can lid is a practical problem. It has the effect of providing excellent quality can lids that do not occur.

[Brief explanation of drawings]

1 to 3 show a full oven type aluminum easy-open can lid showing an example of the embodiment of the present invention. Figure 1 is its plan view, Figure 2 is nn of Figure 1.
Figure 3 shows an enlarged view of a portion of the score line processing section. 2--core layer 3--1... cladding layer 5--
---Protective coating 6--Score line 8 ---Score Residual Patent Applicant Hokkai Seikan Co., Ltd. i4 Procedural Amendment (Method) 1985 5ri! 2nd 1. Display of the case 1986 Patent Application No. 19978 2. Name of the invention Highly corrosion resistant easy-open can lid 3. Person making the amendment Relationship to the case Patent applicant

Claims (1)

[Claims] 1. An aluminum clad material consisting of an aluminum alloy core layer and a cladding layer is used as the aluminum base material constituting the can lid, and a protective coating is provided on the cladding layer on the inner surface of the can lid, and the outer surface of the can lid is coated with a protective coating. In the easy-open can lid provided with a score line for regulating the opening, the core layer of the aluminum clad material has a thickness of 0.2 to 0.4 mm, and the clad layer has a thickness of 0.01 to 0.4 mm. 1 mm, and the score ratio of the score line that regulates the opening of the easy-open can lid (
R) is 0.6T_1≧R≧0.1T_1+T_2 (however, T_1
is the thickness of the core layer, and T_2 is the thickness of the cladding layer on the inner surface of the can lid. 2. The protective film is composed of two layers, a first protective film and a second protective film, and the first protective film is formed on the cladding layer on the inner surface of the can, and then an easy-open can lid forming process with a score line is performed. 2. The easy-open can lid according to item 1 above, wherein a second protective film is formed on the first protective film.