JPH07112229A - Working method for flange edge part of metallic can - Google Patents

Abstract

PURPOSE:To prevent dropping out of enamel hair and to prevent the outer surface of another metallic can from being marred by a flange edge part by applying paint to the flange edge part of a metallic can. CONSTITUTION:For instance, by paint applied to the flange edge part of a metallic can made of an iron, a stainless steel, a tin plate, etc., enamel hair generated in the flange edge part is fixed, and dropping out of the enamel hair is prevented. Also, since the flange edge part is covered, even when a metallic can comes into contact with the outer surface of the other metallic can, it does not mar up the metallic cans. For paint to be used, cold setting type paint, cold drying type paint or thermosetting type paint may by used. It is acceptable to mix these paint with surface slip accelerator agent, etc., to make the other metallic can hardly flow owing to the coating film formed of a flange edge part or to make enamel hair peel off.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for processing a flange edge portion of a metal can. More specifically, it is possible to prevent the enamel hair of the flange edge portion from falling off when cutting the original plate, and to prevent the flange edge portion from scratching the outer surface of another metal can. Regarding processing method.

[0002]

2. Description of the Related Art In recent years, the amount of canned beverages such as coffee, juice, oolong tea, and metal cans such as food cans has remarkably increased in accordance with changes in consumer life. Of these metal cans, the so-called three-piece can is equivalent to the size of one can after the original plate (sheet plate) is coated in advance in the order of inner surface coating, outer surface undercoating coating, printing, and outer surface finish coating. Cutting into a plate (blank plate), curling,
It is made by welding and flange processing.

When manufacturing a three-piece can, when a sheet plate is cut to obtain a blank plate, paint chips called enamel hair are generated on the contact end face.

The enamel hair thus generated is more likely to fall off by neck processing and stretching processing in the subsequent flange processing, but it must be prevented that such enamel hair is mixed into the contents of the metal can. .

Further, since the obtained metal cans are transferred in a close-packed state on the conveyor in the final process of the can making process or in the filling line of the filling factory, the flange edges of the metal cans are different from those of other metal cans. There were cases where the outer surface was scratched and the coating film was peeled off, and the enamel hair and the peeled coating film got into the metal can.

Conventionally, as a method for reducing the detachment of the enamel hair and the peeling of the coating film, a method of improving the return direction at the time of cutting the sheet plate and the shape of the necking flange, and improving the adhesive strength between the paint and the sheet plate Although some methods have been proposed and have achieved some results, these methods cannot sufficiently prevent detachment of the enamel hair or peeling of the coating film, and further improved prevention. Development of methods is expected.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above prior art, and prevents the enamel hair from falling off and prevents the flange edge portion from scratching the outer surface of another metal can. It is an object of the present invention to provide a method of processing a flange edge portion of a metal can which can be performed.

[0008]

That is, the present invention relates to a method for processing a flange edge portion of a metal can, which is characterized in that a paint is applied to the flange edge portion of the metal can.

[0009]

According to the method of working the flange edge portion of the metal can of the present invention, the enamel hair generated at the flange edge portion is fixed by the coating material applied to the flange edge portion. Since the detachment is prevented and the flange edge portion is covered, even if the flange edge portion comes into contact with the outer surface of another metal can, it is not damaged.

The material of the metal can used in the present invention is not particularly limited, and examples thereof include iron, stainless steel, tin plate, aluminum, copper and tin.

As the coating material applied to the flange edge portion of the metal can, for example, a room temperature curing type coating material, a room temperature drying type coating material, a thermosetting type coating material and the like are used.

Examples of the room temperature-curable coating material include room-temperature-curable epoxy-based coating material containing epoxy resin and aliphatic polyamine or dimer acid-modified polyamidoamine as main components, alkyd and desiccant using unsaturated polyester or drying oil. Oxidation-curable coating consisting of unsaturated polymer such as epoxy ester mainly composed of oil fatty acid and optionally containing metal catalyst such as zinc naphthenate, one-component wet-curing polyurethane-based coating, two-component polyurethane-polyol In addition to urethane resin paints such as type polyurethane paints, chelate type acrylic paints containing aluminum chelating agents, photo-curable paints, water-initiated anion polymerizable paints such as α-methyl cyanoacrylate, etc. However, the present invention is not limited to such examples. Not to. Among these room temperature curable paints, epoxy-polyamide paints, polyamine paints, and unsaturated polyester paints that have been used in food cans and the like are preferable for food hygiene.

The room temperature curable coating composition is made of petrolatum, wax or the like in order to prevent the formed coating film from being easily scratched by the flange edge portion or being hard to peel off.
A surface lubricant such as silicone type or fluorocarbon type may be blended.

Examples of the room temperature dry type paint include a lacquer type paint which does not undergo a curing reaction. The lacquer type paint is a synthetic resin dissolved in a thinner, and among these, those having a track record of use in food cans, beverage cans and the like are preferable. Specific examples of such lacquer-type paints include vinyl-based paints such as vinyl chloride-vinyl acetate copolymer-based paints composed of vinyl chloride and vinyl acetate, epoxy-based paints such as epoxy-soluble paints composed of epoxy resin, and the like. However, the present invention is not limited to such an example. Examples of the solvent that can be used for such paints include toluene, xylene and other aromatic organic solvents, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone and other ketone organic solvents, methyl alcohol, ethyl alcohol, propyl alcohol, butyl alcohol. Examples include alcohol-based organic solvents such as, ester-based organic solvents such as ethyl acetate and butyl acetate, and aliphatic-based organic solvents such as ethylene glycol, propylene glycol, and normal hexane. Among these, dry at room temperature. Considering the above, low boiling point solvents such as toluene, methyl ethyl ketone, ethyl acetate, methyl alcohol, ethyl alcohol, and normal hexane are preferable.

The room-temperature-drying type coating material has the same effect as that of the room-temperature-curing type coating material so that the formed coating film is less likely to be scratched by the flange edge portion and is hard to peel off. Alternatively, a surface lubricant such as silicone type or fluorocarbon type may be blended.

Further, when the room temperature dry type coating material is used, a low boiling point solvent may be used in order to reduce the amount of residual solvent contained in the formed coating film as much as possible. It is preferable to blow hot air onto the flange edge portion after coating. If the temperature of the hot air is too low, the effect of removing the solvent will be small, and if it is too high, the coating film will deteriorate due to heat,
Since the color may change, it is preferably 100 to 300 ° C., more preferably 150 to 200 ° C., although it varies depending on the type of the room temperature dry type coating material. Further, if the time for blowing the hot air is too short, the effect of removing the solvent will be small, and if it is too long, the productivity will be reduced, so that it is 2 to 20 seconds, especially 5 to 10 seconds. It is preferably about the same.

Examples of the thermosetting paints include thermosetting vinyl paints, melamine resin-modified polyester paints, vinyl organosol paints, epoxy-amino resin paints, phenol resin-modified epoxy resin paints, and polyester-amino. Examples thereof include urea-based paints, urea resin-modified epoxy resin-based paints, acryl-amino-based paints, and the like, but the present invention is not limited to these examples. As the solvent that can be used for the thermosetting coating material, the same solvent as that that can be used for the room temperature drying coating material can be exemplified. Such thermosetting paint is
Since it is forcibly dried by baking after painting, it is not necessary to be particular about the type of solvent.

In addition, the thermosetting coating composition is similar to the room temperature curing coating composition and the room temperature drying coating composition in order to prevent the formed coating film from being easily scratched by the flange edge portion and being difficult to peel off. In addition, petrolatum, wax, surface lubricants such as silicone type and fluorocarbon type may be added.

Generally, the baking paint has a baking temperature of 150 to 2
It is baked at a temperature of 00 ° C. for a baking time of about 5 to 15 minutes, but in the present invention, only the flange edge portion is coated, and the flange edge portion is incorporated into the structure of the can by winding the lid after filling. Therefore, since it is not particularly related to food hygiene, the baking temperature is usually 100 to 300 ° C, especially 200 to 250 ° C. When the baking temperature is lower than the above range, the solvent tends to remain in the formed coating film, and when the baking temperature is higher than the above range, the formed coating film is deteriorated and discolored. Etc. tend to occur. If the baking time is too short, the solvent tends to remain, and if it is too long, the productivity tends to decrease.
It is preferably 0 seconds, especially 5 to 15 seconds.

Examples of the method of applying the coating material to the flange edge portion of the metal can include a spray coating method, a roll coating method, a method of immersing only the flange edge portion in the coating material, and the present invention is only such an example. It is not limited to. Note that among these methods, the roll coating method is preferable in that only the flange edge portion can be applied accurately.

Examples of rolls that can be used in the roll coating method include metal rolls, felt rolls, and rubber rolls. Among these, considering the ease of painting and the durability of the roll,
Metal rolls and felt rolls are preferred.

Further, although it is usually preferable to apply the coating material to the flange edge portion after the flanging, it is also possible to apply the coating material when cutting the blank plate.

If the thickness of the coating film (after drying) is too thin, it may not be possible to sufficiently prevent the enamel hair from falling off, or the flange edge may scratch the outer surface of another metal can. If it is too thick, and if it is too thick, the internal stress of the paint will be large and cracks will easily occur in the coating film, which will rather lead to the mixing of the coating film. Is preferably about 1 to 20 mg, especially about 2 to 10 mg.

Thus, when the flange edge portion of the metal can is processed by the processing method of the present invention, detachment of the enamel hair and peeling of the coating film can be prevented, and the flange edge portion is coated with the coating film. As it is covered, it does not scratch the outer surface of other metal cans.

Next, the method of processing the flange edge portion of the metal can of the present invention will be described in more detail based on examples, but the present invention is not limited to these examples.

Examples 1 to 22 Flange edges of 250 g cans made from Canlite materials (manufactured by Shin Nippon Steel Co., Ltd.) by the roll coating method using metal rolls using the paints shown in Table 1 After coating the parts, warm air was blown to the coating film under the conditions shown in Table 1.

As the physical properties of the formed coating film, the film thickness (when dried), the amount of enamel hair, the scratch resistance and the amount of residual solvent were examined according to the following methods. The results are shown in Table 2.

(B) Film thickness The amount of coating when dried was determined by measuring with a precision balance.

(B) Amount of enamel hair The flange portion of the metal can on which the paint has been applied is immersed in water of a 1000 ml beaker filled with water, the flange portion is rubbed with a commercially available toothbrush, and the enamel hair is dropped into water. It was This was carried out for 100 cans, and the enamel hair that had fallen into the water was filtered and then thoroughly dried to obtain the weight of the enamel hair.

(C) Scratch resistance 20 strokes per minute (1 stroke: 100 mm)
The metal can on which the paint has been applied is fixed to a rubbing tester that reciprocates at a ratio of 0, and the flange of the metal can is attached to a metal plate coated with an outer surface for a can so that the thickness of the coating becomes 7 μm. The number of times of rubbing until the base of the metal plate was visible was counted by pressing and rubbing with a pressure of 0.5 kg / cm ² .

(D) Amount of residual solvent Cut off the flange of the metal can on which the coating has been applied,
It was put in a 190 ml metal can filled with nitrogen gas, sealed, heated at 150 ° C. for 10 minutes, and the amount of the vaporized solvent was measured by gas chromatography.

Comparative Example 1 In Examples 1 to 22, the amount of enamel hair and scratch resistance were examined in the same manner as in Examples 1 to 22 using a metal can in which the coating was not applied to the flange edge portion. The results are shown in Table 2.

[0033]

[Table 1]

[0034]

[Table 2]

As is clear from the results shown in Table 2,
When the flange edge portion of the metal can is coated as in Examples 1 to 22, the loss of the enamel hair is reduced,
It is also understood that the scratches due to the flange edge can be extremely reduced.

[0036]

According to the method for processing the flange edge portion of a metal can of the present invention, it is possible to prevent the enamel hair from falling off and prevent the flange edge portion from scratching the outer surface of another metal can. Is played.

Claims (2)

[Claims] 1. A method of processing a flange edge portion of a metal can, which comprises coating the flange edge portion of the metal can with a coating material. 2. The method for processing a flange edge portion of a metal can according to claim 1, wherein the coating material is a room temperature curing type coating material, a room temperature drying type coating material, or a thermosetting type coating material.