JP4783705B2 - Manufacturing method of bottle can and bottle can manufactured by the method - Google Patents

Description

  The present invention relates to a bottle can made of aluminum alloy for beverages such as soft drinks, coffees, beers and the like sealed with a screw cap, and the discoloration of the bottom outer surface does not occur in the sterilization treatment after filling the contents, which is extremely severe Bottle cans using a bottomed cylindrical body for bottle cans that have undergone chemical conversion treatment to produce a paint film that is less damaged even when the curled parts are processed with no risk of leakage or corrosion. The present invention relates to a production method, a bottle can produced by the production method, and a chemical conversion apparatus therefor.

  Aluminum alloy bottles used for beverages are molded into bottomed cylinders by drawing and ironing (DI processing) of aluminum alloy plates, and the lubricating oil adhering to the outer surface of the bottomed cylinder is degreased and washed. In general, a zirconium phosphate chemical conversion solution is sprayed on the entire inner and outer surfaces to form a zirconium phosphate chemical conversion film (hereinafter abbreviated as “chemical conversion film”), followed by washing and drying. Next, although there is some order in order, the outer surface is subjected to a size coat treatment for improving the adhesion with the coating film and a baking process, if necessary, and printing / overcoat treatment (by clear varnish) and its After sequentially performing the baking process, the inner surface coating and the baking process, the diameter of the opening side of the bottomed cylinder is reduced and the cap mounting part is formed, and the cap mounting part is screwed into the cap mounting part. Usually, a screw machining process for forming the threaded portion and a curl machining process (including slot machining) for maintaining the sealing performance with the cap are performed in this order.

Similar to bottle cans, after DI processing, chemical film formation, cleaning and drying, printing / overcoat treatment and baking process, inner surface coating and baking process, usually four steps of necking and flange In the case of conventional aluminum cans that are processed (hereinafter abbreviated as “four-stage neck cans”), if the amount of the chemical conversion film is thin, discoloration (black discoloration) of the outer surface of the bottom will occur due to hot water sterilization after filling the contents. When the amount of chemical coating is thick, peeling of the coating occurs in necking and flange processing. Therefore, the upper and lower limit values of the chemical coating are approximately 8 to 15 mg / m ² (hereinafter, the chemical coating thickness is determined by the fluorescent X-ray method). In general, it is indicated by the measured amount of zirconium. Further, when retort sterilization is performed, discoloration (whitening) of the outer surface of the bottom portion occurs, so it is common to coat the outer surface of the bottom portion or to increase the lower limit of the chemical conversion film to about 12 mg / m ^2. It was.

For bottle cans, the outer surface of the upper end of the cylindrical body is coated with a size paint with good adhesion before curling, and then the exterior paint is applied on top of it. There is almost no. However, on the inner surface of the upper end of the cylindrical body, the amount of deformation of the curl is extremely large, so that the inner surface coating film applied onto the chemical conversion film is peeled even with a film amount of 15 mg / m ² or less, which is the upper limit of the four-stage neck can. However, wrinkles were likely to occur. For this reason, after filling and capping the contents, the contents may leak from the wrinkle-occurring portion.

Proposal that 3-14 mg / m ² is good as the amount of film that does not cause peeling of the neck part (refer to Patent Document 1), and a proposal related to a method of providing a difference in the film amount of the neck part and the bottom part (refer to Patent Document 2) However, these are proposals for a four-stage neck can, not a bottle can with a severe degree of processing, and the details of the evaluation of the coating amount at the upper end of the bottomed cylindrical body and the discoloration of the bottom outer surface are detailed. Evaluation is not performed.
Proposals related to coating to prevent cracking and peeling of the paint film on the bottle can curl part include a proposal that a medium layer or the like is previously formed on the surface on which the screw part is formed (see Patent Document 3) or an internal paint film. In order to repair cracks and the like, a proposal has been made (see Patent Document 4) that a corrected inner surface coating is applied to the top surface of the mouth portion and / or the inner surface of the mouth portion, but the chemical conversion film has not been studied.
Japanese Patent Publication No. 3-53170 JP 11-49170 A JP 2003-181577 A Japanese Patent Laid-Open No. 2003-11979

  In the present invention, by appropriately providing the thickness of the chemical conversion film, discoloration of the bottom outer surface does not occur in the sterilization treatment after filling the contents, and the inner surface side of the upper end of the bottomed cylindrical body for the bottle can (after the bottle can curling) In the method of manufacturing a bottomed cylindrical body for an aluminum alloy bottle can provided with a chemical conversion coating so that the coating film on the curled outer surface and the curled top surface of the bottle mouth portion does not peel off even during curling, It is an object of the present invention to provide a used bottle can, a bottomed cylindrical body for the aluminum alloy bottle can, and a chemical conversion treatment apparatus therefor.

The present invention
[1] An aluminum alloy plate is drawn and ironed to form a bottomed cylindrical body, and after outer surface coating and baking and inner surface coating and baking are performed, necking is performed near the opening of the bottomed cylindrical body. In a bottle can manufacturing method in which a cap attaching portion for attaching a cap for sealing an opening is formed and a screw portion for screwing the cap onto the cap attaching portion is formed, prior to normal chemical conversion treatment, After treating with only a small amount of chemical conversion liquid only on the bottom outer surface of the bottom cylindrical body, the amount of the coating on the bottom outer surface of the bottomed cylindrical body is 8 to 15 mg in terms of zirconium by applying a means for forming a chemical conversion film on the entire inner and outer surfaces. / m ^2, and a method of manufacturing an aluminum alloy bottle cans, wherein the coating amount of the opening tip portion inner surface to 5-7 mg / m ² in terms of zirconium,

[2] Prior to the normal chemical conversion treatment, as a means for treating only the chemical conversion solution with a small amount of chemical conversion solution, spraying a small flow rate so that the chemical conversion solution adheres only to the outer surface of the bottom of the bottomed cylindrical body. The method for producing a bottle can according to [1] above,
[3] The concentration of the chemical conversion liquid having a small flow rate for treating only the bottom outer surface of the bottomed cylindrical body is at least the same as the concentration of the chemical conversion liquid that forms a chemical conversion film on the entire inner and outer surfaces of the bottomed cylindrical body. A method for producing a bottomed cylindrical body for a bottle can according to the above [1] or [2],

[4] The coating amount on the bottom outer surface of the bottomed cylindrical body after the chemical conversion liquid treatment is 8 to 15 mg / m ² in terms of zirconium, and the coating amount on the inner surface of the opening tip is 5 to 7 mg / m ² in terms of zirconium. A bottle can manufactured using the method for manufacturing an aluminum alloy bottle can according to any one of [1] to [3], and

  [5] Means for transferring the bottomed cylindrical body with its opening facing downward, inner and outer surface chemical conversion treatment means comprising a riser with a nozzle for spraying a chemical conversion liquid onto the entire inner and outer surfaces of the bottomed cylindrical body to be transferred, And a chemical conversion treatment for the bottomed cylindrical body for a bottle can comprising a small flow rate spraying means for forming a chemical conversion film only on the outer surface of the bottom of the bottomed cylindrical body in front of the riser with nozzle for the inner and outer surfaces The above problems have been solved by developing a device.

In the present invention, a treatment for forming a chemical conversion film on the outer surface of a bottomed cylindrical body for a bottle can is processed with a small amount of chemical conversion liquid only on the outer surface of the bottom of the bottomed cylindrical body prior to the normal chemical conversion treatment. Applying a means for preliminarily forming a chemical conversion film only on the outer surface of the bottom of the bottomed cylindrical body in the first stage, and performing a normal chemical conversion process on the inner and outer surfaces as the second stage. Thus, even if the chemical solution for the inner and outer surfaces is low in concentration, the amount of the chemical film on the outer surface of the bottom can be secured to 8 mg / m ² or more. As a result, it is possible not only to prevent discoloration of the bottom outer surface in the sterilization process after filling the contents, but also to easily form only the amount of chemical conversion film on the inner surface of the upper end of the bottomed cylindrical body as thin as 5 to 7 mg / m ^2. Further, the occurrence of wrinkles on the inner surface of the curled portion can be prevented by curling the bottle can (including slot processing). Therefore, the outer surface of the bottom of the can can ensure the same chemical film thickness as before, so even if the outer surface of the unpainted bottom is not discolored by heat sterilization after filling the contents, Since the chemical conversion film can be made thin, after the contents are filled and capped, the contents do not leak out along the coating film wrinkles of the curled portion.
Even in the newly proposed bottle can chemical conversion treatment device, by spraying the chemical conversion liquid on the inner and outer surfaces, by spraying a small flow rate with the same liquid as the inner and outer surface spray chemical liquid, By developing a chemical conversion treatment apparatus provided with a means for spraying a small flow rate for forming a chemical conversion film only on the bottom outer surface of the bottomed cylindrical body, the above-mentioned bottomed cylindrical body can be produced efficiently.

Hereinafter, an example of the can manufacturing process of the aluminum alloy bottle can according to the present invention will be described with reference to FIG. 1, but the method of the present invention can also be applied to other can manufacturing processes.
A bottle can is made by punching a circular blank from an aluminum alloy plate coated with lubricating oil wound in a coil, forming a cup with a press, etc., and then drawing and ironing (DI processing) to form a bottomed cylindrical body. To do.
The lubricating oil on the outer surface of the bottomed cylindrical body is removed by degreasing and washing, the degreasing chemical solution is washed away, and then a chemical conversion treatment is performed to form a chemical conversion film on the inner and outer surfaces of the bottomed cylindrical body, and the chemical conversion liquid is washed with water (including pure water washing). And then dry. After that, size coat and baking process, printing / overcoat and baking process, inner surface coating and baking process, necking process (including trimming process), screw process (including skirt process), curl process (slot) Washing and drying after processing) to make a bottle can product.

  In this case, the bottle can is subjected to severe necking processing, screw processing, curling processing, etc., compared to the 4-stage neck can, so the coating surface of the inner surface coating performed before these processing has undergone great deformation, Easy to take damage. And the site | part where this inner surface coating film was damaged has a danger that it will corrode or a metal will elute because a metal part contacts the content.

  Metal cans (including bottle cans) are mainly coated with water-based paint on the inner surface to prevent metal corrosion and elution due to contact with the contents. The water-based paint is composed of a dispersion medium composed of water and an organic solvent and a resin component. The organic solvent usually includes n-butanol, isobutanol, butyl cellosolve, dimethylethanolamine and the like. Moreover, as a resin component, an epoxy resin, an acrylic resin, and a phenol resin are usually contained in many things.

  The zirconium phosphate based chemical conversion liquid used in the present invention contains, as main components, hexafluorozirconic acid, hydrogen fluoride and its water-soluble salt, phosphoric acid and the like. After DI processing, the lubricating oil adhering to the bottomed cylindrical body is degreased, and in the chemical conversion treatment process, the zirconium phosphate-based chemical conversion liquid is sprayed on the inner and outer surfaces of the bottomed cylindrical body, so that the surface of the bottomed cylindrical body is insoluble. Form a film.

  Conventionally, degreasing treatment is carried out by spraying with a riser with an upper nozzle and a riser with a lower nozzle, while the bottomed cylindrical body is inverted (with the opening facing downward) and conveyed by a net conveyor, and the chemical conversion treatment process is also the same The chemical conversion liquid is sprayed onto the bottomed cylindrical body (inner and outer surface spray) to form a chemical conversion film. Thereafter, the bottom chemical conversion liquid is blown with air using a blow-off fan, and washed with water in the next cleaning rinse tank of the chemical conversion tank.

In the present invention, prior to the normal chemical conversion treatment, a method of treating only the bottom outer surface of the bottomed cylindrical body with a small amount of chemical conversion liquid is adopted. The means for forming a thin chemical conversion film only on the bottom outer surface of the bottomed cylindrical body for bottle cans is not particularly limited. For example, mist spraying can be performed using a mist spray nozzle.
The chemical conversion process flow when the mist spray is performed with a thicker chemical solution than the inner and outer surface sprays is improved as shown in FIG. 2, and the chemical process flow when the mist spray is performed with the same chemical liquid as the inner and outer surface sprays is shown in FIG. It improved like 3.
The bottomed cylindrical body (1) formed from the aluminum alloy plate, degreased and washed passes through the inner and outer surface formation line (3) while being placed on the net conveyor (2) with the opening facing downward. The inner and outer surface chemical conversion line (3) may be the same as a normal chemical conversion line, and a plurality of upper nozzle risers (4-1) for spraying chemical conversion liquid on the outer surface of the bottomed cylindrical body (1). (4-3) and a riser with a lower nozzle (4-4) for spraying the chemical conversion liquid on the inner surface (in FIGS. 2 and 3, the upper three and the lower one) Shows riser with nozzle). In addition, the number of the upper and lower risers with nozzles can be appropriately selected depending on the amount of the chemical conversion coating on the inner and outer surfaces.

A mist spray nozzle (5-1) is provided on the upstream side of the riser with nozzle for outer surface (4-1) as means (5) for forming a chemical conversion film only on the outer surface of the bottom of the bottomed cylindrical body as the first stage. Since this mist spray only requires that the chemical conversion liquid adheres only to the bottom outer surface of the bottomed cylindrical body (1), the flow rate of the mist spray is such that the chemical conversion liquid is applied to the outer surface of the body of the bottomed cylindrical body (1). Even if it adheres, it should just be a flow rate that does not flow down to the tip. That is, by the mist spray, a small amount of chemical conversion liquid is accumulated in the concave portion of the bottom outer surface of the bottomed cylindrical body (1), but the chemical liquid accumulated in the concave portion overflows on the outer surface of the body of the bottomed cylindrical body (1). The flow rate is good enough not to give out, and the lower limit is different from about 1 to 3 ml / can depending on the concentration, but the upper limit is preferably about 9 ml / can.
When the chemical conversion liquid overflows on the outer surface of the body portion of the bottomed cylindrical body (1), the chemical conversion liquid adheres to the net conveyor (2). Since the tip of the bottomed cylindrical body (1) is in contact with the net conveyor (2), the chemical liquid adhering to the net conveyor (2) wraps around the inner surface of the tip of the bottomed cylindrical body (1), and the coating on the part Since the amount becomes thick, it is not preferable.

The bottomed cylindrical body (1) The outer surface of the bottom may not be painted. To prevent blackening of aluminum during sterilization with hot water, the whitening of aluminum during retort sterilization is prevented to a minimum of about 8 mg / m ^2. For that purpose, a minimum of about 12 mg / m ² is required. Therefore, in order to obtain a necessary amount of chemical conversion film on the bottom outer surface of the bottomed cylindrical body (1), it is advantageous that the chemical conversion reaction time is long. Therefore, the mist spray nozzle (5-1) should be as far away as possible from the inner / outer surface spray (4) in the upstream direction to obtain the chemical reaction time. However, if it is assumed that there is a chemical liquid that has fallen without contacting the bottomed cylindrical body (1) among the chemical liquid sprayed by mist spray, in order to collect and recirculate the dropped chemical liquid, The position where the formed chemical solution returns into the chemical conversion tank (6) or the position where the means is taken is preferable.
On the other hand, since the inner surface of the bottomed cylindrical body (1) is painted, there is no problem of discoloration during sterilization even if the chemical film is thin, and means for forming a chemical film only on the bottom outer surface of the bottomed cylindrical body (5) The same means is not required on the inner surface side. On the contrary, when the chemical conversion film on the inner surface of the bottomed cylindrical body (1) is thick, there is a risk of causing wrinkles on the curled part, so that it is 7 mg / m ² or less, preferably 5.5 to 6.6 mg / m. It is good to process so that it may become the range of ² .
When the chemical conversion film is not formed, when the washing water after the chemical conversion treatment is dried, the washing water and aluminum react with each other to form aluminum hydroxide, so that a so-called brown spot is generated in which the portion looks brown. Therefore, it is necessary to form a chemical conversion film also on the inner surface side.

After the inner and outer surface chemical conversion line (3), the chemical conversion liquid accumulated at the bottom of the bottomed cylindrical body (1) is blown off (7) and returned to the chemical conversion liquid tank (6). Subsequently, the bottomed cylindrical body (1) The inner and outer surfaces are washed with water by a washing machine (8) (only one first riser with a nozzle is shown in FIGS. 2 and 3) to completely wash away the chemical conversion liquid. Subsequently, it is dried and sent to the next size coating process. As a result, the amount of the chemical conversion coating on the outer surface of the bottom can be set to 8 to 15 mg / m ² because a sufficient chemical conversion treatment time can be secured even when the inner and outer surface sprays have a low concentration of chemical liquid, and the inner and outer surface sprays are low. Since it is a chemical liquid having a concentration (20 ppm as zirconium), the amount of chemical film on the inner surface of the upper end of the bottomed cylindrical body opening can be reduced to 7 mg / m ² or less.
When using a chemical conversion solution that is thicker than the inner and outer surface sprays, the concentration is uncertain because it affects the amount of spray, processing temperature, processing time, etc., but is generally 100 to 500 ppm as the zirconium concentration, which is preferable from the viewpoint of ease of handling. Is about 150 to 300 ppm.
The invention will be specifically described below with reference to examples.

(Comparative Example 1)
The chemical conversion treatment obtained was carried out in the same manner as in the example without using a means for forming a chemical conversion film on the outer surface of the bottom of the bottomed cylindrical body with the same chemical conversion liquid concentration as in the example (inner / outer surface spray). A bottle can body was molded from the finished bottomed cylindrical body in the same manner as in the Examples, and various tests were conducted in the same manner. The results are shown in Table 1.

(Examples 1-7, Comparative Examples 2-3)
50 degreased and washed 310 ml bottomed cylinders were prepared for each. The mist spray was used as a means for reducing the chemical concentration and forming only the bottom outer surface of the bottomed cylindrical body, and the chemical conversion treatment was performed using the bottomed cylindrical body forming apparatus shown in FIG. 2 or FIG. .
Alsurf 450 manufactured by Nippon Paint Co., Ltd. was used as the chemical conversion solution, and the concentration of the chemical conversion solution was diluted so that the inner and outer surface spray liquid had a zirconium concentration of 20 ppm and the concentrated chemical liquid had a zirconium concentration of 240 ppm, and the temperature was 45 ° C. Here, the concentration and temperature of the chemical conversion solution and the number of risers with nozzles were determined by the amount of chemical conversion film on the outer surface of the bottom.

The concentration of the mist spray was the concentrated chemical liquid in Examples 1 to 4, and the same chemical liquid as the inner and outer surface sprays in Examples 5 to 7.
The flow rate of the mist spray was 1 to 9 ml / can in Examples 1 to 4, 1 to 11 ml / can for Comparative Example 2, Examples 5 to 7 and Comparative Example 3.
As coating conditions, size coating (10-30 mg / dm ² after baking) and baking were performed, and printing, overcoat (45 to 100 mg / dm ² after baking) and baking were performed.
The bottomed cylindrical body that has been subjected to chemical conversion treatment is manufactured using a normal bottle can body production line, the boiling water blackening test on the outer surface of the bottle can body, the retort treatment test, the wrinkle occurrence rate of the inner surface coating film on the curled part, The incidence of leakage in the content preservation test was tested. The results are shown in Table 1.

[Measuring method]
A. Zr conversion coating amount; Amount measured by fluorescent X-ray method.
B. Boiling water blackening; Immerse in boiling water for 30 minutes and evaluate from 0 (best) to 5 (worst).
C. Retort whitening; evaluated at 0 (best) to 5 (worst) at 125 ° C. for 30 minutes in a high-pressure steam sterilizer.
D. Occurrence rate of coating film wrinkle: Visual observation of the coating film wrinkle of the curled part after molding into a bottle can. Evaluation is based on the number of generated cans in 50 cans.
E. Leakage occurrence rate: Observe leakage of contents when filled with sports drink and stored for 2 months at 50 ° C. Evaluation is based on the number of generated cans in 50 cans.

In Comparative Example 1, since the coating amount on the bottom outer surface of the bottomed cylindrical body was less than 8 mg / m ² , blackening occurred.
In Example 1, since the chemical liquid concentration of the mist spray was high, the coating amount on the bottom outer surface of the bottomed cylindrical body was larger than in Comparative Example 2, and the blackening level was improved. In Example 2, the coating amount on the outer surface of the bottom portion was further increased to a level corresponding to whitening during retort processing. In Example 3, further whitening was not observed. In Example 4, because the flow rate of the mist spray was too high and the chemical conversion solution flowed through the bottomed cylindrical wall surface and circulated around the inner surface of the tip portion, the amount of coating on the inner surface of the tip portion increased, However, the contents were not leaked.

  In Comparative Example 2, the concentration of the chemical conversion solution is low, and the flow rate does not reach the amount necessary to form the required film thickness, so that the effect of the mist spray cannot be obtained, and the film amount on the bottom surface of the bottomed cylindrical body is almost not increased. There is no change. In Example 5, the coating amount of the bottom outer surface of the bottomed cylindrical body was increased and the blackening level was improved, but the retort resistance was slightly insufficient. In addition, since the change was not looked at by the front-end | tip part inner surface, there was no generation | occurrence | production of a coating film wrinkle. In Example 6, further blackening was not observed. In Example 7, in addition to blackening resistance, retort resistance was also obtained. In Comparative Example 3, since the amount of mist spray was too large, the chemical conversion solution turned inward, the coating amount on the inner surface of the tip portion increased, and wrinkles and leakage of the contents occurred on the inner coating film.

The present invention, by applying a means for forming a film formed by the chemical conversion liquid only on the bottom outer surface of the bottomed cylindrical body, the amount of the chemical conversion film on the bottom outer surface is maintained at 8 mg / m ² or more even with a low concentration chemical liquid. Discoloration in the sterilization treatment after filling the contents can be prevented, and the amount of chemical conversion film on the inner surface of the upper end of the bottomed cylindrical body can be formed as thin as 5-7 mg / m ² . Bottomed cylindrical body for bottle cans that does not generate inner surface coating wrinkles and the contents do not leak along the inner surface coated wrinkles, a bottle can using the same, a manufacturing method of the bottomed cylindrical body, and therefore A chemical conversion apparatus is provided.

Flow chart of bottle can production line Flow diagram of the bottomed cylindrical body forming apparatus used in the present invention (when the mist spray is a concentrated chemical liquid) Flow chart of the entire bottomed cylindrical body forming apparatus used in the present invention (when the mist spray is the same conversion liquid as the inner and outer surface sprays)

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Bottomed cylindrical body 2 Net conveyor 3 Inner / outer surface formation line 4 Inner / outer surface spray chemical liquid riser nozzle 4-1 to 4-3 Riser with nozzle for outer surface 4-4 Riser with nozzle for inner surface 5 Only bottom outer surface of bottomed cylindrical body Chemical film forming means 5-1 Mist spray nozzle 6 Chemical conversion bath 7 Blow-off device 8 Washing machine

Claims (5)

An aluminum alloy plate is drawn and ironed to form a bottomed cylinder, and after the outer surface coating and baking and the inner surface coating and baking, the opening is formed by necking in the vicinity of the opening of the bottomed cylindrical body. In a manufacturing method of a bottle can in which a cap attaching portion for attaching a cap for sealing is formed and a screw portion for screwing the cap onto the cap attaching portion is formed, prior to normal chemical conversion treatment, a bottomed cylindrical body By treating the bottom outer surface only with a small amount of chemical conversion solution and applying a means for forming a chemical coating on the entire inner and outer surfaces, the coating amount on the bottom outer surface of the bottomed cylindrical body is 8 to 15 mg / m ^{2 in} terms of zirconium. And the amount of coating on the inner surface of the opening tip is 5 to 7 mg / m ^{2 in} terms of zirconium.   Prior to the normal chemical conversion treatment, as a means for treating only the chemical conversion liquid with a small amount of chemical conversion liquid, spraying at a small flow rate so as to adhere the chemical conversion liquid only to the outer surface of the bottom of the bottomed cylindrical body. The manufacturing method of the bottle can of description.   The concentration of the chemical conversion liquid having a small flow rate for treating only the bottom outer surface of the bottomed cylindrical body is at least the same as the concentration of the chemical conversion liquid for forming a chemical conversion film on the entire inner and outer surfaces of the bottomed cylindrical body. The manufacturing method of the bottomed cylindrical body for bottle cans of Claim 1 or 2. The coating amount on the bottom outer surface of the bottomed cylindrical body after the chemical conversion liquid treatment is 8 to 15 mg / m ² in terms of zirconium, and the coating amount on the inner surface of the opening tip is 5 to 7 mg / m ² in terms of zirconium. The bottle can manufactured using the manufacturing method of the aluminum alloy bottle can of any one of -3.   Means for transferring the bottomed cylindrical body downward, chemical conversion treatment means for inner and outer surfaces comprising a riser with a nozzle for spraying a chemical conversion liquid onto the entire inner and outer surfaces of the bottomed cylindrical body to be transferred, and the inner A chemical conversion treatment apparatus for a bottomed cylindrical body for a bottle can, comprising means for forming a chemical conversion film only on the bottom outer surface of a bottomed cylindrical body in front of a riser with a nozzle for an external surface.

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