JP5498741B2 - Aluminum can lid - Google Patents

Description

  The present invention relates to an aluminum can lid used for sealing beverage cans, food cans and the like, and more particularly to an aluminum can lid used for sealing canned products sterilized by a pasteriser treatment.

Aluminum can lids used in beverage cans and food cans such as alcoholic beverages such as beer, carbonated beverages, fruit juice beverages, and coffee beverages, improved corrosion resistance, appearance and processability for contents, anticorrosion properties, and scratches In order to prevent this, a resin coating is applied on both sides to form a coating layer.
Furthermore, a wax layer is formed on the coating layer as a lubricant during molding of the can lid. However, if the amount of applied wax is too large, the wax adheres to the can lid mold, It may cause molding defects or may come off the mold and adhere to the molded product as foreign matter. As a countermeasure, it is necessary to frequently clean the mold, which causes a decrease in productivity and workability. For this reason, in order to improve the moldability of the can lid by suppressing the amount of applied wax, it is common practice to add wax in advance to the coating layer.
Such an aluminum can lid is manufactured through the following steps. First, a resin paint to which wax is added is applied to both surfaces of the aluminum alloy plate by a roll coater or the like while gradually winding the aluminum alloy plate wound in a coil shape. Then, the aluminum alloy plate coated with the resin paint is heated by a heating device, and the resin paint is baked to form a resin layer. Next, a liquid wax is applied to one side or both sides of an aluminum alloy coated plate for can lids, which is an aluminum alloy plate having this resin layer, and naturally cooled to below the melting point, and the wax liquid is solidified to form a wax. A layer is formed to produce an aluminum alloy plate for can lids. The manufactured aluminum alloy plate for can lids is directly conveyed to the can lid production line, or once taken up again in a coil shape by a winding device and then conveyed to the can lid production line, and pressed in the can lid production process. A can lid is manufactured by performing various processes such as molding.
And the manufactured can lid is wound around one end of a separately manufactured can body part, or the bottomed can body is filled with contents, and then the open end of the can body It is tightened.

JP 2004-160512 A

In the production of the above canned products, the contents are filled, and after the can lid is wound and sealed, sterilization by a pastoriser device may be performed. This is to sterilize by heating by putting hot water of 65 ° C. to 85 ° C. on a canned product (hereinafter referred to as “past riser treatment”). In this pasterizer treatment, warm water is bathed in the canned product, and as shown in FIG. 5, the wax layer on the surface of the can lid is heated to the melting point or higher and melts to become liquid, and then aggregates and cools. When it solidifies, it may form a white spotted pattern (hereinafter referred to as a wax spot). As shown in FIG. 6 (A), such a wax spot may be recognized as foreign matter adhesion or dirt, and it may cause complaints from consumers as defects in the appearance of canned products. A solution was sought.
An object of the present invention is to provide an aluminum can lid having an appearance that is excellent in aesthetics, in view of the problems of the prior art as described above.

In order to solve the above-mentioned problem, in the aluminum can lid of the invention according to claim 1, a coating layer formed by heating and baking on the outer surface of the can lid is formed, and the top of the coating layer is formed. An aluminum can lid manufactured from an aluminum alloy plate for can lids having a wax layer formed thereon, wherein the coating layer is an aluminum can lid containing polyethylene / polytetrafluoroethylene wax and oxidized polyethylene wax as particulate wax. The coating layer contains the particulate wax in a proportion of 1 PHR or more and 10 PHR or less, and the arithmetic average roughness Ra (JIS B0601) on the surface of the coating layer after can lid molding is 0.28 μm to .0. It is characterized by being 52 μm .

According to the first aspect of the present invention, minute irregularities are formed on the surface of the coating layer, the wettability of the coating layer with respect to the wax is improved, and the wax and the coating layer surface are easily adapted to each other. Thus, even when the wax in the wax layer melts and becomes liquid, it is difficult to agglomerate and it is difficult to form wax spots. Furthermore, since minute irregularities are formed on the surface of the coating layer, light is irregularly reflected on the surface of the coating layer, and a whitish color tone with suppressed gloss on the lid surface is obtained. Therefore, even if the aluminum can lid is subjected to a pasteriser process and the wax layer on the surface of the can lid is heated to a temperature higher than the melting point to form a wax spot, the surface of the can lid has a whitish appearance similar to that of the aggregated wax. Present. Therefore, it is possible to prevent the wax spots from being recognized as white spots.
That is, the generation of wax spots can be prevented by a combination of the effect of suppressing the generation of wax spots and the effect of making it difficult to visually recognize when the wax spots are generated. Such an action is generally observed in particulate wax, but as an effect of preventing white spotted pattern generated after the pasteriser treatment, the effect of polyethylene / polytetrafluoroethylene wax and oxidized polyethylene wax Is higher than other particulate waxes. Moreover, even if added alone, the effect is high, but it is preferable to include both polyethylene / polytetrafluoroethylene wax and oxidized polyethylene wax, and due to the synergistic effect of both components, white spots can be effectively formed even with a small addition amount. Generation of a pattern can be prevented. In addition, the polyethylene / polytetrafluoroethylene wax in the present invention may be obtained by coating polyethylene particles with polytetrafluoroethylene resin to form particles, or by coating polytetrafluoroethylene resin particles with polyethylene. You may have done. Preferably, polyethylene particles coated with polytetrafluoroethylene resin to form a particulate wax are preferably used. By coating polyethylene particles with polytetrafluoroethylene resin with a high softening point to form particles, the particle diameter of the particulate wax is kept larger even after baking of the paint, and it is effective on the coating layer surface. Unevenness can be formed.

Further , by containing the content of the particulate wax at a ratio of 1 PHR or more and 10 PHR or less, the wax is effectively prevented from agglomerating, and appropriate irregularities are formed on the surface of the coating film layer. Due to the unevenness, the coating layer on the surface of the can lid has a moderately whitish appearance, and the light is irregularly reflected, so that the gloss is suppressed and the surface becomes a cloudy white tone. Therefore, even if a wax spot is formed, it is difficult to visually recognize the product, and deterioration of the product appearance can be suppressed. When the total addition amount is less than 1 PHR, sufficient unevenness is not formed on the surface of the coating layer, and thus a white cloudy surface cannot be obtained. In addition, since the amount of the wax is small, the affinity between the surface of the coating layer and the wax is small, and the wettability of the coating layer surface to the wax is not improved, so that the wax is likely to aggregate and the occurrence of wax spots can be prevented. Disappear. In addition, if it exceeds 10 PHR, the surface of the coating layer may become too white, or the adhesion between the aluminum alloy plate and the coating layer may be reduced, and the particulate wax dispersed in the paint may aggregate. Therefore, when a paint is applied to the aluminum alloy plate to form a coating film layer, the paint cannot be uniformly applied and unevenness may occur in the coating film.

Moreover , it is set as the surface roughness from which the arithmetic mean roughness Ra of a coating-film layer is set to 0.28 micrometer-0.52 micrometer. By limiting the arithmetic average roughness of the coating layer to this range, moderate irregularities are formed on the surface of the coating layer, and the coating layer on the surface of the can lid has a moderately whitish appearance, and The gloss is suppressed by the irregular reflection of light, resulting in a surface with a white and cloudy tone. Therefore, even if a wax spot is formed, it is difficult to visually recognize the product, and deterioration of the product appearance can be suppressed. When the arithmetic average roughness is less than 0.30 μm, sufficient unevenness is not formed on the surface of the coating layer, and thus a white cloudy surface cannot be obtained. In addition, since the wettability of the coating layer surface to the wax is not improved, the wax tends to aggregate and the generation of wax spots cannot be prevented. On the other hand, if it exceeds 10 PHR, the surface of the coating layer becomes too white and the appearance of the product is deteriorated.

3 is a schematic diagram showing a layer structure in a cross section of an aluminum can lid of Example 1. FIG. 3 is a flowchart showing a process of a method for manufacturing an aluminum can lid of Example 1. It is a figure which shows the roll coater which coats the resin coating material on the aluminum alloy plate of Example 1. FIG. It is a schematic diagram which shows the roll waxer which apply | coats a liquid wax to the aluminum alloy coating plate for can lids in which the coating-film layer of Example 1 was formed. It is a schematic diagram which shows the process in which a wax spot is formed by a pasteriser process. It is the photograph showing the can lid surface after the past riser process of the past (A) and this invention (B).

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic view showing a layer structure in a cross section of an embodiment of an aluminum can lid of the present invention. As the aluminum alloy plate used in the aluminum can lid of the present invention, a JIS 5000 series aluminum alloy plate is suitably used for can lid molding, but pure aluminum or other aluminum alloys can also be used. In order to impart corrosion resistance to both surfaces of the aluminum alloy plate, a chemical conversion treatment film is formed by performing a phosphoric acid chromate treatment. A paint layer is formed by applying a paint on the chemical conversion coating. As the paint, a general paint containing known resins such as epoxy resin, epoxy / acrylic resin, polyester resin, vinyl chloride resin, epoxy / uric acid resin, and epoxy / phenolic resin may be used. it can. As the solvent and dispersion medium for these resin coatings, both organic solvent systems and water systems can be suitably used.

  Particulate wax is added to the paint. As the average particle diameter of the particulate wax, those having an average particle diameter of about 1 μm to 20 μm measured using a scattering type particle size distribution measuring apparatus by laser diffraction are suitably used. A particulate wax having a particle size of less than 1 μm is not preferable because the particles are too small to sufficiently roughen the surface of the coating layer. On the other hand, a particulate wax having a particle diameter of more than 20 μm is not preferable because the surface of the lid becomes too white due to excessive surface roughness, or the adhesion of the coating layer may be lowered. More preferably, a particulate wax of about 3 μm to 6 μm is used. As the material for the particulate wax, polyethylene / polytetrafluoroethylene wax and oxidized polyethylene wax are suitable. More preferably, by adding both of them, a large matting effect can be exhibited even with a small addition amount due to the synergistic effect of these components. Further, the softening point of the particulate wax may be higher than the baking temperature of the coating layer or lower than the baking temperature. When the softening point of the particulate wax is higher than the baking temperature of the coating layer, irregularities can be formed on the surface of the coating layer by maintaining the particulate shape of the particulate wax even after baking. Conversely, when the softening point of the particulate wax is lower than the baking temperature of the coating layer, the particulate wax existing on the surface of the coating layer is deformed during the baking process or melted on the surface of the coating layer. By forming a hole in which the coating layer is depressed at the position where the particulate wax originally existed by flowing, irregularities are formed on the surface of the coating layer. Due to the unevenness formed in this way, the surface of the can lid has a whitish and erasable color tone, the wettability of the surface of the coating layer to the wax is improved, and the generation of wax spots can be prevented.

  The coating layer is formed by applying this paint to the outer surface of the aluminum alloy plate, which is then heated in an oven and baked. The formed coating layer has fine irregularities due to the effect of the particulate wax. In addition, the coating layer contains a wax component so that the compatibility between the coating layer and the wax forming the wax layer is increased. By improving the wettability, the wettability of the coating layer surface is improved. This makes it difficult for the wax to agglomerate even when the pasteriser treatment is performed, and the formation of wax spots can be prevented. Moreover, light is irregularly reflected by the unevenness | corrugation on the surface of a coating-film layer, and it becomes the surface of the whitish color tone with which glossiness was suppressed and gloss was suppressed. The thickness of the coating layer can be determined as appropriate depending on the performance required for the can lid, but in the case of a lid used for canned food, it is generally about 2 μm to 5 μm. If necessary, paint is applied to the inner surface of the can lid to form a coating layer. In addition to the particulate wax, a conventionally known wax may be appropriately added.

  A wax layer is formed on the coating layer. The wax layer formed on the coating layer can be formed by applying and solidifying a wax liquid such as paraffin wax, microcrystalline wax, or petrolatum. The wax layer can be provided on the outer surface and the inner surface of the can lid, and the wax layer of the aluminum alloy plate and the wax layer on the inner surface side can be the same type or different types. Can be formed. These may be appropriately selected and used depending on the application.

The appropriate amount of adhesion of the wax layer is preferably 10 to 100 mg / m ^{2 although} it varies slightly depending on the type of wax. If the adhesion amount of the wax is less than this range, the moldability at the time of press molding is inferior or the coating layer is scraped, which is not preferable. On the other hand, if the amount of the wax adhering exceeds the above range, it is not preferable because the wax adheres to the mold during press molding and tends to accumulate.

  Next, the manufacturing method of the can lid of this invention is demonstrated with reference to FIG. FIG. 2 is a flowchart showing the steps of the method for manufacturing the aluminum can lid of the first embodiment. As shown in FIG. 2, first, an aluminum alloy plate is unwound from a roll-shaped aluminum coil wound up with an aluminum alloy plate, and a resin paint in which particulate wax is added to both sides of the aluminum alloy plate in the inner and outer surface coating process. Paint (roll coating process). In Example 1, as a coating method, a liquid paint is applied by a roll using a roll coater as shown in FIG. 3, but it is applied by an appropriate method such as spraying the paint on an aluminum alloy plate. can do.

  Next, the metal plate with the coating applied on the surface is conveyed to an oven process, heated for a predetermined time to burn the coating, and then cooled in a cooling zone process to form a coating layer. The formed coating layer has a whitish surface in which minute irregularities are formed and gloss is suppressed by the action of the particulate wax.

  In the Waxer process, a wax that is heated to a temperature equal to or higher than the melting point is applied to the aluminum alloy coated plate on which the coating layer has been formed to form a wax layer. In this embodiment, the wax is applied to the outer surface of the can lid, but may be applied to the inner surface of the can lid as necessary. In Example 1, for wax application, a roll waxer as shown in FIG. 4 is used and applied by a roll, but an appropriate method such as spraying liquid wax from the nozzle onto the surface of the plate is used. Can be applied. The roll waxer includes a gravure roll immersed in a wax melting tank, an applicator roll in contact with an aluminum alloy coated plate for a can lid, a transformer roll in contact with both rolls between the gravure roll and the applicator roll, and a jacket roll in contact with the applicator roll. The wax is uniformly applied to the surface of the aluminum alloy coated plate for can lids.

  Then, the aluminum alloy plate for can lids is manufactured by solidifying the applied wax. The manufactured aluminum alloy plate for can lids is transported to a manufacturing process for manufacturing the can lid, and various processes are performed to manufacture the can lid. In Example 1, the metal plate manufacturing process and the lid making process are directly connected, and the plate-shaped aluminum alloy plate for can lids is directly conveyed. You may convey to a lid making process.

  In the lid making process, in the case of producing a press forming process, a liner applying process for maintaining a sealing property when wound around a can container, and an SOT lid (stain tub lid) for a beverage can The can lid is manufactured through an appropriate process such as a tab attaching process.

  As shown in FIG. 6 (B), the can lid of the present invention has an uneven surface on the surface of the coating layer, so that the surface becomes whitish and the gloss is suppressed. Even if the wax aggregates and a wax spot is formed, it does not stand out and is difficult to visually recognize. Moreover, since the coating layer contains a wax component, the affinity for the wax is good, and the wettability to the wax on the surface of the coating layer is improved by unevenness, so that the wax is less likely to aggregate, The formation of wax spots can be prevented.

(Experimental example)
Hereinafter, experimental examples of the present invention will be shown. First, a chromic acid chromate treatment was applied to a JIS A5182-H19 alloy plate having a thickness of 0.25 mm as an aluminum alloy plate so as to be 20 mg / m ^{2 in} terms of chromium. On the outer surface of this aluminum alloy plate, an epoxy / urea resin is added in varying amounts of particulate wax, and a paint using a mixture of methylisobutyl ketone, xylene, and ethylbenzene as a solvent is prepared using a roll coater. Applied. The coating film thickness after drying was applied to about 4 μm, and baked in a gas oven type drying furnace to form a coating film layer. In this experimental example, 0.5 PHR of lanolin was added as a wax component other than the particulate wax in order to improve the moldability of the can lid.

  First, as Experimental Example 1, a lid on which a coating layer was formed by adding particulate waxes of both polyethylene / polytetrafluoroethylene wax (PE / PTFE) and oxidized polyethylene wax (oxidized PE) was prepared. In addition, as a comparative example, a paint containing no particulate wax and adding 10 PHR of lanolin and a paint containing no wax component were prepared, and a lid formed with a coating layer was prepared in the same manner as described above. Then, as Experimental Example 2, polyethylene / polytetrafluoroethylene wax was added, and a lid formed with a coating layer without adding oxidized polyethylene wax was prepared. As Experimental Example 3, an oxidized polyethylene wax was added, and a lid in which a coating layer was formed without adding polyethylene / polytetrafluoroethylene wax was prepared. The average particle diameter of the particulate wax used in this experimental example was 5 μm. In addition, as a scattering type particle size distribution measuring apparatus by laser diffraction used for measuring the average particle diameter, LA 920 manufactured by Horiba Seisakusho was used.

Thereafter, in order to form a wax layer on the coating film on the outer surface after molding the can lid, a paraffin wax that was melted and turned into a liquid was applied by a roll coater to produce an aluminum alloy plate for a can lid. The amount of wax applied was 50 mg / m ² .

And the aluminum alloy plate for can lids was conveyed to the lid making process, and the press molding etc. by the metal mold | die were performed, and the SOT lid | cover for drink cans was manufactured. The manufactured SOT lid was wound around an aluminum can filled with water and subjected to a pasteriser treatment. In the pasterizer treatment, water at about 80 ° C. was bathed in an aluminum can for 20 minutes, and then the can was dried to remove water droplets on the surface of the can. The outer surface of the SOT lid after the pasterizer treatment was visually observed to determine whether or not a white spotted pattern in which wax was aggregated could be visually recognized. Moreover, arithmetic mean roughness Ra (JISB0601) of the coating-film layer surface was measured about the sample before wax application | coating of the aluminum alloy plate used for manufacture of each can lid. Furthermore, as a state of whitening on the lid surface, the color tone of the lid surface was visually determined to determine whether the whiteness of the lid surface was appropriate. Table 1 shows the amount of wax added to the resin layer, the arithmetic average roughness Ra, and the visual evaluation results for each sample of Experimental Example 1.
[Visual Evaluation Criteria for Wax Group]
X: The pattern can be clearly confirmed.
Δ: The pattern is inconspicuous.
○: The pattern is hardly visible.
◎ ・ ・ ・ The pattern is not visible at all.

  The addition amount of the wax component shown in Table 1 is the ratio of the particulate wax to the solid content excluding the solvent content in the paint, that is, the ratio of the particulate wax to the resin component in the coating layer is based on PHR (100 parts by weight of the resin component). (Weight of added wax). Among the evaluation results in Table 1, Sample Nos. 1-1 to 1-18 are examples of the present invention, and Samples No. 1-19 and No. 1-20 are comparative examples.

  As the visual evaluation, the case where the pattern could be clearly confirmed was evaluated as x, the case where the pattern was inconspicuous, Δ, the case where the pattern was almost invisible, and the case where the pattern was not visible at all were evaluated as ◎. In addition, the whitening state of the lid surface was evaluated as ◯ for the case where the lid surface was moderately white and the appearance of the lid was not inferior, and the case where the lid surface was not whitened or was too white was evaluated as x. .

  In Experimental Example 1, Samples No. 1-1 to No. 1-5, No. 1-7 to No. 1-9, No. 1 in which the total amount of particulate wax added is 5 PHR or more. No. 12, No. 1-13, No. 1-15, and No. 1-16 are in a state where the wax spots cannot be seen at all. However, with regard to the whitening state of the lid surface, the appearance of the can lid surface is white in the samples No. 1-1, No. 1-7, No. 1-12, and No. 1-15 in which the total addition amount exceeds 10. Thus, the appearance performance was inferior as compared with the total addition amount of 10 or less. In Nos. 1-19 and 1-20, the lid surface was not whitened at all.

  In samples No. 1-6, No. 1-10, and No. 1-11 in which the total addition amount is in the range of 2.5 PHR to 4.5 PHR, the wax spots were hardly visible. Further, in the samples No. 1-14, No. 1-17, and No. 1-18 in which the total addition amount is in the range of 1.0 to 1.5 PHR, the wax spots became inconspicuous.

  In contrast, Sample No. 1-19 to which 10 PHR of lanolin was added without adding particulate wax and Sample No. 1-20 to which no wax component was added were in a state where the pattern could be clearly confirmed, The effect of preventing the occurrence of was not observed.

  Therefore, when the particulate waxes of both polyethylene / polytetrafluoroethylene wax and oxidized polyethylene wax were added, the effect of preventing the occurrence of wax spots was recognized when the total addition amount was 1.0 to 10.0 PHR. Further, as a more preferable range, an effect of making the wax spots almost inconspicuous at a total addition amount of 2.5 to 10.0 PHR was recognized. Further, as a preferable range, when the total addition amount is 5.0 to 10.0 PHR, the effect of preventing the generation of wax spots to the extent that the wax spots cannot be seen at all is recognized. In Experimental Example 1, the can lid of Sample No. 1-5 was the one with the highest outer surface quality as judged from the degree of occurrence of wax spots and the color tone of the outer surface of the can lid. Further, from the results of Experimental Example 1, when the surface roughness of the coating layer is 0.28 μm or more, the effect of preventing the formation of wax spots is recognized, and when the surface roughness is 0.34 μm or more, the effect of making the wax spots almost inconspicuous is recognized. The effect of preventing the generation of wax spots was recognized to the extent that the wax spots could not be seen at all at 42 μm or more. Further, up to 0.51 μm, the lid surface color was moderately whitened, but at 0.53 μm or more, it was too whitened, resulting in an unfavorable color tone for the can lid. Therefore, from the result of Experimental Example 1, the surface roughness of the coating layer is preferably 0.28 μm to 0.51 μm, more preferably 0.34 μm to 0.51 μm, and most preferably 0.42 μm to 0.51 μm. Met.

In Experimental Example 2, a polyethylene / polytetrafluoroethylene wax having an average particle diameter of about 5 μm was added, and a coating layer was formed without adding an oxidized polyethylene wax. As in Experimental Example 1, the outer surface of the SOT lid after the pasterizer treatment was visually observed to determine whether or not a white spotted pattern in which wax was aggregated could be visually recognized. Moreover, arithmetic mean roughness Ra (JISB0601) of the coating-film layer surface was measured about the sample before wax application | coating of the aluminum alloy plate used for manufacture of each can lid. Table 2 shows the amount of wax added to the resin layer, the arithmetic average roughness Ra, and the visual evaluation results for each sample of Experimental Example 2.

  In Experimental Example 2, no wax spots were visible at all for Samples No. 2-1 to No. 2-4 in which the total amount of particulate wax added was 7.0 PHR or more. However, when the total addition amount exceeded 10, in Sample No. 2-1, the outer ring on the surface of the can lid was too white, and the appearance was inferior compared to the total addition amount of 10 or less.

  Therefore, when polyethylene / polytetrafluoroethylene wax was added as a particulate wax, a total addition amount of 1.0 to 10.0 PHR was found to be effective in preventing the formation of wax spots. Further, as a more preferable range, an effect that the total addition amount is 3.0 to 10.0 PHR and at least the wax spots are hardly noticeable was recognized. Further, as a preferable range, when the total addition amount is 7.0 to 10.0 PHR, an effect of preventing the generation of the wax spots to the extent that the wax spots cannot be recognized at all is recognized. Further, from the results of Experimental Example 2, the effect of preventing the formation of wax spots was observed when the surface roughness of the coating layer was 0.28 μm or more, and the effect of making the wax spots almost inconspicuous when 0.32 μm or more was observed. An effect of preventing the formation of wax spots was recognized so that the wax spots could not be seen at all at 44 μm or more. Moreover, although the color tone of the lid surface was moderately whitened up to 0.52 μm, it was too whitened at 0.54 μm, resulting in an unfavorable color tone as the outer ring of the can lid. Therefore, from the results of Experimental Example 2, the surface roughness of the coating layer is preferably 0.28 μm to 0.52 μm, more preferably 0.32 μm to 0.52 μm, and most preferably 0.44 μm to 0.52 μm. Met.

In Experimental Example 3, an oxidized polyethylene wax having an average particle size of about 5 μm was added, and a coating film was formed without adding polyethylene / polytetrafluoroethylene wax. As in Experimental Example 1, the outer surface of the SOT lid after the pasterizer treatment was visually observed to determine whether or not a white spotted pattern in which wax was aggregated could be visually recognized. Moreover, arithmetic mean roughness Ra (JISB0601) of the coating-film layer surface was measured about the sample before the wax application | coating of the aluminum alloy plate used for manufacture of each can lid. Table 3 shows the amount of wax added to the resin layer, the arithmetic average roughness Ra, and the visual evaluation results for each sample of Experimental Example 3.

In Experimental Example 3, in Sample No. 3-1 to No. 3-3 in which the total amount of particulate wax added was 8.0 PHR or more, the wax spots were not visible at all. However, in Sample No. 3-1, in which the total addition amount exceeded 10, the appearance of the can lid surface was too white, and the appearance was inferior compared to the total addition amount of 10 or less.
In samples No. 3-4 to No. 3-7 in which the total addition amount is in the range of 3.0 PHR to 7.0 PHR, the wax spots were hardly visible. In addition, in the sample No. 3-8 having a total addition amount of 1.0 PHR, the wax spots became inconspicuous.

  Therefore, when the oxidized polyethylene wax was added as a particulate wax, the effect of preventing the occurrence of wax spots was recognized when the total addition amount was 1.0 to 10.0 PHR. Further, as a more preferable range, an effect that the total addition amount is 3.0 to 10.0 PHR and at least the wax spots are hardly noticeable was recognized. As a more preferable range, when the total addition amount is 8.0 to 10.0 PHR, the effect of preventing the generation of the wax spots was recognized to the extent that the wax spots could not be seen at all. Further, from the results of Experimental Example 3, when the surface roughness of the coating layer is 0.30 μm or more, the effect of preventing the formation of wax spots is recognized, and when the surface roughness is 0.33 μm or more, the effect of making the wax spots almost inconspicuous is recognized. The effect of preventing the formation of wax spots was recognized so that the wax spots could not be seen at all at 47 μm or more. Moreover, although the color tone of the lid surface was moderately whitened up to 0.49 μm, it was too whitened at 0.53 μm, resulting in an unfavorable color tone for the appearance of the can lid. Therefore, from the results of Experimental Example 3, the surface roughness of the coating layer is preferably 0.30 μm to 0.49 μm, more preferably 0.33 μm to 0.49 μm, and most preferably 0.47 μm to 0.49 μm. Met.

  Therefore, from the results of Experimental Examples 1 to 3, the effect of preventing the formation of wax spots was recognized when the total amount of particulate wax added was in the range of 1.0 PHR to 10.0 PHR, and the total added amount was 3.0 to 10.0 PHR. At least, the effect of making the wax spots almost inconspicuous is recognized, and as a more preferable range, when the total addition amount is 8.0 to 10.0 PHR, the effect of preventing the generation of the wax spots is recognized to the extent that the wax spots cannot be seen at all. I understood. Moreover, as the surface roughness of the coating layer, the effect of preventing the generation of wax spots was observed when the surface roughness of the coating layer was 0.28 μm to 0.52 μm, and most of the wax spots were 0.32 μm to 0.52 μm. An inconspicuous effect was observed, and the effect of preventing the formation of wax spots was recognized to the extent that the wax spots were completely invisible at 0.42 μm to 0.52 μm.

  The present invention has been described with reference to the preferred embodiments. However, the present invention is not limited to these embodiments, and various modifications can be made within the scope of the present invention.

Claims (1)

An aluminum can manufactured from an aluminum alloy plate for a can lid in which a coating layer is formed by heating and baking on the outer surface of the can lid, and a wax layer is formed on the coating layer. In the lid,
The coating layer is an aluminum can lid containing polyethylene / polytetrafluoroethylene wax and oxidized polyethylene wax as particulate wax ,
The coating layer contains the particulate wax in a ratio of 1 PHR to 10 PHR,
An aluminum can lid, characterized in that an arithmetic average roughness Ra (JIS B0601) on the surface of the coating layer after molding the can lid is 0.28 μm to 0.52 μm .