JP6832797B2 - Manufacturing method of bottle cans, bottle cans with caps, and bottle cans - Google Patents

Description

The present invention relates to a metal bottle can whose mouth is sealed by a cap, a bottle can with a cap, and a method for manufacturing a bottle can.

As a container filled with contents such as beverages, a bottle can with a cap in which a cap is screwed into a male screw portion formed at the mouth of a bottle-shaped metal can (bottle can) is known. The outer surface of this type of bottle can is printed and painted with various designs indicating the contents and their source. Further, in printing and painting of such a design, for example, after applying a base layer called a white coat layer (base coat layer) or a size coat layer to the outer surface of a bottle can, a print layer and an overcoat layer are sequentially provided. It has a structure. Further, there is also known a structure in which a printing layer and an overcoat layer are sequentially provided without forming a base layer on the bottle can.

Patent Document 1 describes that a size coat layer and an overcoat layer are laminated in this order on the outer surface of a bottle can. Patent Document 1 describes that an overcoat layer is formed on all parts of the outer surface side of the bottle can except the curl portion, and by forming the overcoat layer, a plurality of bottle cans can be formed. Even when the outer surfaces of the bottle cans come into contact with each other during the collective transportation, it is possible to prevent damage such as scratches from occurring on the outer surface of the bottle cans, and at the mouth (mouthpiece). It is described that these machining tools can be operated smoothly when forming a male threaded portion or the like.

Patent Document 2 describes a metal bottle can in which a base coat layer is formed instead of a size coat layer on the surface of a metal can substrate, and a print layer (ink layer) and an overcoat layer are further formed in this order. Have been described. In Patent Document 2, the base coat layer is a material of the size coat layer to which a pigment is added to form a white color, and is subsequently applied by coating the surface of the can substrate with the base coat layer. It is described that the color development of the ink is improved and the appearance design is improved. It is also described in Patent Document 2 that the size coat layer is formed in order to improve the adhesion of the ink applied thereafter. In addition, the print layer is made by printing information, patterns, etc. according to the contents filled in the bottle can with ink, and the overcoat layer protects the printed print layer (ink layer) and also protects the printed print layer (ink layer). It is also described that it improves the sliding of the can surface.

Further, in Patent Document 2, the base coat layer is coated downward from the male threaded portion including at least the male threaded portion (threaded portion) excluding the trimming allowance at the upper end of the opening of the can substrate, and the overcoat layer is the can substrate. It is described that the structure is such that the base coat layer is interposed inside the overcoat layer below the male threaded portion of the can substrate.

Japanese Unexamined Patent Publication No. 2005-178883 Japanese Patent No. 3916957

As described in Patent Document 1 or Patent Document 2, a male screw portion for screwing a cap is formed at the mouth portion of a bottle can. Therefore, if the hardness of the coating film is high, cracks may occur in the coating film during molding of the male screw portion, and the cracks in the coating film may affect the opening property and corrosion resistance of the capped bottle can. On the other hand, if the hardness of the coating film is low, the sliding of the lower part of the bulging portion where the inner surface of the cap is tightly locked and the cap when the cap is wound around the mouth is hindered, and the opening torque May be high.

In Patent Document 2, since the base coat layer formed on the metal bottle can is made of a softer material than the overcoat layer, the overcoat layer has a high hardness when forming the male screw portion and the curl portion at the mouth portion. It is described that the base coat layer can serve as a cushioning material to prevent cracks and the like in the overcoat layer. However, even in this case, when the cap is wound around the mouth portion, sliding with the cap is hindered at the lower portion of the bulging portion, and the opening torque may increase.

The present invention has been made in view of such circumstances, and is a method for manufacturing a bottle can, a bottle can with a cap, and a bottle can that can achieve both the workability of the male screw portion and the slidability of the bulging portion. The purpose is to provide.

In the bottle can of the present invention, a mouth portion is formed on the upper portion of a metal can base, and the mouth portion has a male screw portion and a bulge portion that is connected to the lower side of the male screw portion and bulges outward in the radial direction. The bottle can is provided with a printing layer in which ink is printed on the outer surface of the can substrate so as to form a design, and an overcoat layer coated on the printing layer. The printing layer is formed at least in the bulging portion, and the printing layer formed in the bulging portion contains a curing accelerator that promotes curing of the overcoat layer, and the male screw A printing layer containing the curing accelerator is not formed in the portion.

In the portion where the printing layer containing the curing accelerator is interposed inside the overcoat layer, the curing accelerator is supplied from the printing layer to the overcoat layer, so that the overcoat layer is more than the portion not interposing the printing layer. Hardness can be increased. Therefore, when opening a bottle can with a cap in which the cap is wrapped around the mouth, the cap locked to the bulging portion can be smoothly slid and the opening torque can be prevented from increasing. .. On the other hand, in the male screw portion, since the printing layer containing the curing accelerator is not interposed inside the overcoat layer, the hardness of the overcoat layer can be maintained lower than that in the bulging portion. Therefore, it is possible to prevent cracks from occurring in the coating film during processing of the male threaded portion. Therefore, both the workability of the male screw portion and the slidability (slipperiness) of the coating film surface of the bulging portion can be achieved at the same time.

In the bottle can of the present invention, the pigment concentration of the printing layer formed on the bulging portion is preferably 60% by mass or less.

The higher the pigment concentration in the print layer, the lower the resin concentration in the print layer. Therefore, when the pigment concentration of the printing layer formed on the bulging portion exceeds 60% by mass, the resin concentration of the printing layer in that portion becomes low, and the adhesion between the surface of the can substrate and the printing layer is lowered. When molding the bulging portion, the coating film easily peels off from the surface of the can substrate. Therefore, by setting the pigment concentration of the printing layer to 60% by mass or less, good adhesion between the surface of the can substrate and the coating film can be maintained.

In the bottle can of the present invention, the printing layer may be formed on a base layer composed of a white coat layer or a size coat layer formed on the outer surface of the can substrate.

When a base layer composed of a white coat layer or a size coat layer is formed, the adhesion between the outer surface of the can substrate and the print layer can be improved. Further, when the base layer composed of the white coat layer is formed, it is possible to further form a painted surface in which the metal base of the can base is hidden.

Further, the bottle can with a cap of the present invention has a cap attached to the mouth of the bottle can.

Further, the bottle can with a cap of the present invention is a bottle can with a cap for retort sterilization, which is heat-treated at 100 ° C. or higher after the cap is attached to the mouth.

The method for producing a bottle can of the present invention includes an outer surface printing coating step of printing and coating the outer surface of a bottomed tubular can substrate, and an inner surface coating of applying coating to the inner surface of the can substrate after the outer surface printing and coating step. A process, a mouth forming step of forming a mouth portion having a diameter smaller than that of the lower portion on the upper part of the can substrate after the inner surface coating step, and a threaded portion forming of forming a male screw portion and a bulging portion on the mouth portion. The outer surface printing and painting step comprises printing ink on the outer surface of the can substrate to form a printing layer, applying the outer surface coating on the printing layer, and then heating the outer surface coating. The pre-overcoat layer is formed without completely baking, and the inner surface coating step is performed after applying the inner surface paint to the inner surface of the can substrate on which the pre-overcoat layer is formed. The inner surface coating is baked at a temperature equal to or higher than the baking temperature of the layer to form the inner surface coating layer, and the pre-overcoat layer is baked to form the overcoat layer. In the painting step, an ink containing a curing accelerator that promotes curing of the overcoat layer is printed on at least the planned formation portion of the bulging portion on the outer surface of the can substrate, and the planned formation portion of the male screw portion is printed. The printing layer is formed without printing the ink containing the curing accelerator.

In this method for manufacturing a bottle can, an ink containing a curing accelerator that promotes curing of the overcoat layer is printed on the planned formation portion of the bulging portion of the can substrate in the outer surface printing coating step. A printing layer containing a curing accelerator that promotes curing of the overcoat layer can be formed inside the overcoat layer. As a result, in the bulging portion, the curing accelerator is supplied from the printing layer to the overcoat layer, so that the hardness of the overcoat layer can be made higher than that of the portion not interposing the printing layer. Therefore, when the cap-equipped bottle can with the cap wrapped around the mouth is opened, the cap can be slid smoothly and the opening torque can be prevented from increasing. On the other hand, in the male screw portion, since the printing layer containing the curing accelerator is not interposed inside the overcoat layer, the hardness of the overcoat layer can be maintained lower than that in the bulging portion. Therefore, it is possible to prevent cracks from occurring in the coating film during processing of the male threaded portion. Therefore, both the workability of the male screw portion and the slidability of the bulging portion can be achieved at the same time.

Further, in the above-mentioned method for manufacturing a bottle can, a pre-overcoat layer is formed in the outer surface printing coating process without completely baking the outer surface coating material, and an inner surface coating layer is formed in the inner surface coating process, and the pre-overcoat layer is formed. Bake to form an overcoat layer. As a result, the outer surface paint can be baked over time by the outer surface printing coating process and the inner surface coating process, the entire overcoat layer can be cured with uniform hardness, and the adhesion between the coating film and the surface of the can substrate can be achieved. An overcoat layer having a desired hardness can be formed. Further, in this method for manufacturing a bottle can, since a pre-overcoat layer to be an overcoat layer is formed in advance in the outer surface printing and coating process, the handleability of the can substrate can be maintained well in the inner surface coating process.

According to the present invention, the hardness of the overcoat layer can be increased in the bulging portion, and the hardness of the overcoat layer can be maintained lower in the male threaded portion than in the bulging portion. Both slidability can be achieved at the same time.

It is sectional drawing of the main part near the mouth part of the bottle can with a cap which attached the cap to the mouth part of the bottle can of the embodiment of this invention. It is a flow chart of the manufacturing method of the bottle can of the embodiment of this invention. It is a side view explaining the manufacturing method of a bottle can, and describes the molding process of a can base. It is sectional drawing of the main part near the mouth part explaining the manufacturing method of a bottle can, and describes the mouth part molding process, and the thread part molding process which forms a bulge part and a male thread part in a mouth part. It is a cross-sectional view of the main part which enlarged the surface of the can base which explains the manufacturing method of a bottle can, and describes the outer surface printing coating process and the inner surface coating process. It is a side view which made each half of the bottle can of the embodiment of this invention and the cap attached to this bottle can in the cross section.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 6 is a side view showing the bottle can 101 of the embodiment of the present invention and the cap 201 attached to the bottle can 101 with half a cross section. FIG. 1 is a cross-sectional view of a main part of a bottle can 301 with a cap in which a cap 201 is wrapped around the mouth 14 of the bottle can 101, and is an enlarged view of the vicinity of the mouth 14 of the bottle can 101. FIG. 2 is a flow chart of a method for manufacturing a bottle can according to an embodiment of the present invention. 3 to 5 are explanatory views showing each step of the method for manufacturing a bottle can. Of these, FIG. 3 is an external view for explaining the molding process of the can substrate, FIG. 4 is an enlarged view of a main part near the mouth of the can base, and FIG. 5 is an enlarged cross section of the main part on the surface of the can base. The figure is shown. In the following description, the vertical direction shall be determined in the direction shown in FIG.

As shown in FIG. 1, the capped bottle can 301 includes a bottle-shaped metal bottle can 101 and a cap 201, and caps the mouth 14 of the bottle can 101 filled with contents such as beverages. The structure is such that 201 is screwed together.

The bottle can 101 is formed by forming a coating film on the surface of a metal can base 10 such as aluminum or an aluminum alloy. In the bottle can 101 shown in FIG. 1, the coating films 20 and 30 are formed on the outer surface 10o and the inner surface 10i of the can base 10.

As shown in FIG. 6, the can base 10 has a bottomed cylindrical body portion 11, a shoulder portion 12 whose diameter is reduced so as to bend inward in the radial direction at the upper end of the body portion 11, and a shoulder portion 12. A tapered cylinder portion 13 whose diameter is gradually reduced upward in the can axis direction and a mouth portion 14 continuous with the upper end of the tapered cylinder portion 13 are provided, and the body portion 11, the shoulder portion 12, the tapered cylinder portion 13 and the taper cylinder portion 13 are provided. The mouth portion 14 is integrally formed. Further, as shown in FIG. 1, the mouth portion 14 has a bulging portion 15 continuous with the upper end of the tapered cylinder portion 13, a male screw portion 16 continuous with the upper end of the bulging portion 15, and an upper portion above the upper end of the male screw portion 16. A diameter-reduced portion 17 whose diameter is gradually reduced toward the direction of the diameter portion 17 and a curl portion 18 formed at the upper end of the diameter-reduced portion 17 in a state where the opening end portion is folded outward in the radial direction are provided.

As shown in FIG. 1, the coating film 20 formed on the outer surface 10o of the can base 10 is formed on the base layer 21 formed on the outer surface 10o of the can base 10 and the ink formed on the base layer 21. It includes a print layer 22 that is printed to form a design, and an overcoat layer 23 that is coated on the print layer 22. The base layer 21 is composed of a white coat layer or a size coat layer. Further, the printing layer 22 is formed at least on the outer surface of the bulging portion 15, and in FIG. 1, a portion below the bulging portion 15 of the outer surface 10o of the can substrate 10 (bulging portion 15, taper cylinder). The print layer 22 is formed on the portion 13, the shoulder portion 12, and the side surface of the body portion 11, and the print layer 22 is not formed on the portion above the bulging portion 15. The printing layer 22 contains a curing accelerator that accelerates the curing of the overcoat layer 23.

The base layer 21 composed of the white coat layer or the size coat layer is composed of, for example, a polymer polyester-amino resin-based paint. Of these, in the base layer 21 composed of the white coat layer, a white pigment such as titanium oxide or aluminum is blended with the paint.

The overcoat layer 23 is made of a clear outer surface paint having excellent transparency, and is formed by covering substantially the entire outer surface 10o of the can substrate 10. The outer surface paint constituting the overcoat layer 23 is made of, for example, a paint such as a polyester resin or an epoxy resin. Further, the outer surface coating material contains wax in order to improve the slipperiness when the can substrate 10 is conveyed.

The ink constituting the print layer 22 is formed by blending a general thermosetting resin and a pigment as a main element for forming a coating film, and the pigment concentration of the print layer 22 is 60% by mass or less. Is preferable. In addition, a transparent ink containing no pigment can be used for the print layer 22.

For example, the thermosetting resin of the ink is an alkyd resin, and organic or inorganic (titanium oxide, aluminum, etc.) is used as the white pigment. Further, the ink contains an organic solvent and additives such as a foaming agent and silicon. In addition to the white pigment, a colored pigment is used as the ink of the printing layer 22, and printing is performed in a pattern according to the design. In addition, the ink contains a curing accelerator that accelerates the curing of the overcoat layer 23. The curing accelerator contained in the ink is not particularly limited, but examples of the curing accelerator for accelerating the curing of the polyester resin and the epoxy resin constituting the overcoat layer 23 are shown in Table 1 below. The indicated substances can be used.

Further, as shown in FIG. 1, the coating film 30 formed on the inner surface 10i of the can substrate 10 includes an inner surface coating layer 31 formed on the inner surface 10i of the can substrate 10. The inner surface coat layer 31 is formed by covering substantially the entire inner surface 10i of the can substrate 10. The inner surface paint constituting the inner surface coat layer 31 is selected according to the contents to be filled inside the bottle can 101, and is composed of, for example, a paint such as an epoxy resin or an acrylic diameter resin.

The cap 201 includes a cup-shaped cap main body 210 and a liner 220 arranged inside the cap main body 210. Although not shown, the cap body 210 is formed by forming a coating film on the inner and outer surfaces of a metal cap substrate such as aluminum or an aluminum alloy. Before being attached to the mouth portion 14 of the bottle can 101, the cap body 210 has a cylindrical shape that substantially hangs from the disc-shaped top surface portion 211 and the peripheral edge of the top surface portion 211, as shown in FIG. It has a skirt portion 212. As shown in FIG. 6, the skirt portion 212 of the cap body 210 has a knurl recess 213 and a vent hole 214, a female screw forming portion 215, a slit 216, and the like, in order from the base end side to the tip end side on the top surface portion 211 side. A bridge 217 and a hem 218 are formed.

The knurl recess 213 formed at a position close to the top surface portion 211 on the upper portion of the skirt portion 212 applies a frictional force to the hand when the cap is opened. Further, the vent hole 214 is for releasing the internal pressure at the time of opening, and a plurality of the knurl recesses 213 and the vent hole 214 are formed in the circumferential direction of the skirt portion 212. Further, since the upper piece 214a of the vent hole 214 is formed in a state of being pushed inward in the radial direction, the liner 220 is arranged between the upper piece 214a and the top surface portion 211 to prevent the vent hole 214 from coming off.

A plurality of slits 216 are intermittently formed in the lower portion of the skirt portion 212 in the circumferential direction, and a bridge 217 is formed between the adjacent slits 216, and the skirt portion 212 is formed through the slits 216. The upper part 212a and the lower part 212b are separated from each other, and the upper part 212a and the lower part 212b are connected by a plurality of bridges 217 formed between the slits 216.

The liner 220 is rotatably installed with respect to the cap body 210. In this case, the liner 220 has a laminated structure of the sliding layer 221 and the sealing layer 222. Of these, the sliding layer 221 is arranged on the inner surface side of the top surface portion 211 of the cap body 210, is formed in a disk shape by polypropylene or the like, and is slidably formed on the inner surface of the top surface portion 211. Further, the sealing layer 222 is formed of an elastomer resin or the like softer than the sliding layer 221 and comes into contact with the curl portion 18 of the bottle can 101 when the cap 201 is closed so that the inside of the bottle can 101 can be sealed. It is configured. Further, in FIG. 1, the sealing layer 222 is formed of an annular and thick sealing portion 223 that is in close contact with the curl portion 18 and a thin portion 224 that is thinner than the sealing portion 223 and is formed inside the sealing portion 223. Has been done.

Then, the bottle can 301 with a cap is capped by covering the mouth 14 of the bottle can 101 with the cap 201 and pressing the liner 220 on the inner surface of the top surface 211 of the cap body 210 against the curl portion 18. , The cap 201 is attached to the mouth 14 of the bottle can 101 and manufactured. Specifically, after filling the inside of the bottle can 101 with the contents, the female screw forming portion 215 of the cylindrical skirt portion 212 of the cap body 210 is screwed along the male screw portion 16 to form the female screw portion 219. At the same time, the cap 201 is attached to the mouth portion 14 by winding the hem portion 218 of the skirt portion 212 around the lower portion of the bulging portion 15 and locking the skirt portion 212. As a result, the bottle can 301 with a cap in which the mouth 14 of the bottle can 101 is sealed by the cap 201 is manufactured.

In the capped bottle can 301 configured in this way, when the upper portion 212a of the cap 201 above the bridge 217 of the cap 201 is rotated around the can axis with respect to the bottle can 101, the upper portion 212a is along the male screw portion 16. The cap 201 moves upward in the circumferential direction and the axial direction, but since the lower portion 212b below the bridge 217 is locked to the bulging portion 15, the bridge 217 is broken and the upper portion of the skirt portion 212 is formed. The 212a and the lower 212b are separated from each other. Then, the upper portion of the cap 201 (the upper portion 212a of the skirt portion 212) is removed from the mouth portion 14, and the lower portion of the cap 201 (the lower portion 212b of the skirt portion 212) is left in the mouth portion 14.

Next, an embodiment to which the method for producing a bottle can of the present invention is applied will be described by taking the case of producing the bottle can 101 configured as described above as an example.

As shown in the flow chart of FIG. 2, the method for manufacturing a bottle can of the present embodiment includes a drawing / ironing process (DI processing) S11 for forming a bottomed tubular can base 10A (FIG. 3A). After the outer surface printing coating step S12 for coating the outer surface of the bottomed tubular can base 10A, the inner surface coating step S13 for coating the inner surface of the can substrate 10A after the outer surface printing coating step S12, and the inner surface coating step S13. A mouth molding step S14 for molding a mouth portion 14A whose diameter is reduced from the lower portion on the upper portion of the can base 10A, and a male screw portion 16 and a bulging portion 15 are molded on the mouth portion 14A of the can base 10A to form a bottle can. The configuration includes a threaded portion forming step S15 for forming 101.

In the drawing / ironing process S11, a thin metal plate is punched out and drawn to form a relatively large-diameter, shallow cup (not shown), and then the cup is again drawn and ironed (DI processing). In addition, as shown in FIG. 3A, a bottomed tubular can base 10A is formed, and the upper end portion of the can base 10A is trimmed and aligned.

In the outer surface printing coating step S12, as shown in FIGS. 5A to 5C, the base layer 21, the printing layer 22, and the pre-overcoat layer 24 are laminated in this order on the outer surface 10o of the can substrate 10A. A film 20A is formed. 5 (a) to 5 (d) show a cross-sectional view of a main part of the can base 10A at the boundary between the planned formation portion of the bulging portion 15 and the planned formation portion of the male screw portion 16. First, as shown in FIG. 5A, the base layer 21 is formed by applying the paint constituting the base layer 21 on the outer surface 10o of the can base 10A, and then transporting the paint to an oven and drying the base layer 21. In this case, the base layer 21 is formed on substantially the entire surface of the outer surface 10o of the can base 10A.

Then, ink is printed on the base layer 21 as shown in FIG. 5B to form the print layer 22. As the ink, an ink containing a curing accelerator that promotes curing of the overcoat layer 23 (pre-overcoat layer 24) is used. Then, as shown in FIGS. 3 (b) and 5 (b), this ink contains a planned formation portion of the bulging portion 15 of the outer surface 10o of the can substrate 10A, and the planned forming portion of the bulging portion 15. Print in the area 41 below. That is, the ink is printed except for the region 42 including the curl portion 18, the reduced diameter portion 17, and the male screw portion 16 to be formed at intervals from the upper end of the outer surface 10o of the can substrate 10A, and the male screw portion 16 is scheduled to be formed. The printing layer 22 is formed on the outer surface 10o of the can substrate 10A without printing the ink containing the curing accelerator on the portion. Reference numeral 22t shown in FIGS. 3 and 5 indicates the upper end of the print layer 22.

For example, the ink constituting the printing layer 22 is, for example, 15% by mass to 55% by mass of an alkyd resin, 15% by mass to 60% by mass of organic and inorganic pigments, 15% by mass to 30% by mass of an organic solvent, and foaming. 0.3% by mass to 1.0% by mass (addition to the entire ink) of a curing accelerator that accelerates the curing of the polyester resin constituting the overcoat layer 23 is mixed with an additive such as an agent in an amount of several mass%. (Amount). The pigment is preferably contained in the ink in an amount of 60% by mass or less.

Then, as shown in FIG. 5C, the outer surface paint constituting the overcoat layer 23 is applied onto the print layer 22 formed on the outer surface 10o of the can substrate 10A in this way. The outer surface paint is applied to almost the entire surface of the outer surface o of the can substrate 10A, and is formed by covering the printing layer 22 and the base layer 21. For the outer surface paint, for example, a polyester resin (solvent type paint) is used. In addition, the outer surface coating material contains wax in order to improve slipperiness.

After applying the outer surface paint, the can substrate 10A is heated in an oven to dry the outer surface paint without completely baking it to form the pre-overcoat layer 24. As the baking conditions, for example, the baking temperature is 180 ° C. to 200 ° C. × 20 seconds to 40 seconds (about 180 ° C. × 30 seconds). The pre-overcoat layer 24 is formed with a hardness that does not peel off when the can substrate 10A is handled in the subsequent step.

In the inner surface coating step S13, the inner surface paint is sprayed onto the inner surface 10i of the can substrate 10A on which the pre-overcoat layer 24 is formed by spraying or the like. Then, the inner surface paint is baked at a temperature equal to or higher than the baking temperature of the pre-overcoat layer 24 in the outer surface printing coating step S12, and as shown in FIG. 5D, the inner surface 10i of the can substrate 10A is baked. The inner coat layer 31 is formed to form the coating film 30, and the pre-overcoat layer 24 is baked to form the overcoat layer 23 on the outer surface 10o of the can substrate 10A to form the coating film 20. As the baking conditions, for example, the baking temperature is set to 190 ° C. to 220 ° C. × 50 seconds to 70 seconds (about 200 ° C. × 60 seconds), which is longer than the baking time of the precoat layer 24 in the outer surface printing coating step S12. Since the pre-overcoat layer 24 is formed in advance on the outer surface 10o of the can substrate 10A in the outer surface printing coating step S12, the handleability of the can substrate 10A can be well maintained in the inner surface coating step S13.

As described above, since the print layer 22 contains a curing accelerator that promotes the curing of the overcoat layer 23, the portion of the overcoat layer 23 where the print layer 22 is interposed is from the print layer 22. By supplying the curing accelerator to the overcoat layer 23, the hardness of the overcoat layer 23 can be increased as compared with the portion where the print layer 22 is not interposed inside. That is, since the print layer 22 is formed in the planned formation portion (region 41) of the bulging portion 15, the hardness of the overcoat layer 23 becomes high. On the other hand, since the print layer 22 is not formed in the planned formation portion (region 42) of the male screw portion 16, the hardness of the overcoat layer 23 is maintained low.

Further, in the outer surface printing coating step S12, which is a pre-process of the inner surface coating step S13, the pre-overcoat layer 24 is formed without completely baking the outer surface paint, and the pre-overcoat layer 24 is baked in the inner surface coating step S13 to overcoat. It forms a layer 23. As described above, by baking the overcoat layer 24 (coating film 20) over time by the outer surface coating step S12 and the inner surface coating step S13, the entire overcoat layer 24 can be cured with uniform hardness and coated. The adhesion between the film 20 and the surface of the can substrate 10A can be improved. Then, in the inner surface coating step S13, the inner surface coat layer 31 can be formed and the overcoat layer 23 having a desired hardness can be formed.

If the baking temperature is too high, the aluminum of the can base 10A may soften and the strength of the bottle can 101 to be manufactured may decrease. Therefore, the upper limit of the baking temperature in the inner surface coating step S13 is a temperature that does not cause softening of aluminum.

Next, in the mouth forming step S14, a neck-in process is performed in which the upper portion of the can substrate 10A on which the coating films 20 and 30 are formed is subjected to neck-in processing on the inner surface 10i and the outer surface 10o, and FIG. 3C or FIG. As shown in 4 (a), a can base 10B having a shoulder portion 12, a tapered cylinder portion 13, and a straight mouth portion 14A is formed on the upper portion. Further, after molding the mouth portion 14A, the upper end of the can base 10B is cut and trimmed to make the height of the upper end of the mouth portion 14A uniform.

In the threaded portion forming step S15, the diameter of the mouth portion 14A is expanded again, leaving the lower end portion of the straight mouth portion 14A, and then the diameter of the upper portion of the mouth portion 14A is reduced again except for the lower portion of the enlarged diameter portion. As a result, as shown in FIG. 4B, the mouth portion 14B formed by forming the bulging portion 15 bulging outward in the radial direction is formed. Further, by threading the upper portion of the mouth portion 14B, as shown in FIG. 4C, a bottle can 101 having the mouth portion 14 in which the male screw portion 16 is formed is formed. At the time of processing the male threaded portion 16, the printed layer 22 is formed in the portion to be formed of the male threaded portion 16, and as described above, the hardness of the overcoat layer 23 is maintained low. Therefore, it is possible to prevent the coating film 20 from being cracked. In the threaded portion forming step S15, when the male threaded portion 16 is formed, the diameter-reduced portion 17 that gradually reduces in diameter toward the upper side and the opening portion 14B connected to the reduced-diameter portion 17 are formed on the male-threaded portion 16. The curl portion 18 is formed by winding the upper end outward and bending it, and the mouth portion 14 is formed.

The bottle can 101 manufactured in this manner is subjected to capping processing in a state where the cap 201 is put on the mouth portion 14 and the liner 220 is pressed against the curl portion 18 after filling the contents inside. A cap 201 is attached to the mouth portion 14, and a bottle can 301 with a cap is manufactured.

Specifically, the female screw forming portion 215 of the cylindrical skirt portion 212 of the cap body 210 is threaded along the male screw portion 16 of the mouth portion 14 to form the female screw portion 219, and the hem of the skirt portion 212 is formed. The cap 201 is attached to the mouth portion 14 by winding the portion 218 under the bulging portion 15 and locking the portion 218. As a result, the state in which the liner is pressed against the mouth portion 14 of the bottle can 101 is maintained, and the mouth portion 14 is sealed.

Further, in the bottle can 301 with a cap for retort sterilization, after the cap 201 is attached to the mouth portion 14, a retort sterilization treatment accompanied by a heat treatment of 100 ° C. or higher is performed.

In the bottle can 101 configured as described above, the print layer 22 is cured to the overcoat layer 23 at the portion where the print layer 22 containing the curing accelerator of the overcoat layer 23 is interposed inside the overcoat layer 23. By supplying the accelerator, the hardness of the overcoat layer 23 can be made higher than that of the portion not interposing the print layer 22. As described above, since the print layer 22 is formed on the bulging portion 15, the hardness of the overcoat layer 23 in that portion can be increased, and the slidability (slipperiness) of the surface of the coating film 20 can be improved. .. Therefore, when opening the capped bottle can 301 in which the cap 201 is wound around the mouth portion 14 of the bottle can 101, the cap 201 locked to the bulging portion 15 can be smoothly slid and the cap 201 can be opened. It is possible to prevent the torque from increasing.

On the other hand, in the male screw portion 16 of the bottle can 101, as described above, since the printing layer 22 containing the curing accelerator is not interposed inside the overcoat layer 23, the overcoat layer 23 is compared with the bulging portion 15. Hardness can be kept low. Therefore, it is possible to prevent the coating film 20 from being cracked during the processing of the male screw portion 16.

As described above, in the bottle can 101, the hardness of the overcoat layer 23 can be increased in the bulging portion 15, and the hardness of the overcoat layer 23 can be maintained lower in the male screw portion 16 than in the bulging portion 15. Both the workability of the portion 16 and the slidability of the surface of the coating film 20 of the bulging portion 15 can be achieved at the same time.

If the amount of the curing accelerator added to the entire ink of the printing layer 22 is less than 0.3% by mass, the curing promoting effect of the overcoat layer 23 due to the addition of the curing accelerator cannot be sufficiently obtained. Further, if the amount of the curing accelerator added to the entire ink exceeds 1.0% by mass, the hardness of the overcoat layer 23 (coating film 20) becomes too high and becomes brittle. In this case, the coating film 20 on the bulging portion 15 (bottle can with cap 301) may be peeled off by particularly processing the bulging portion 15 and performing a retort sterilization treatment accompanied by a heat treatment at 100 ° C. or higher. is there.

Further, the higher the pigment concentration of the print layer 22, the lower the resin concentration of the print layer 22. Therefore, when the pigment concentration of the printing layer 22 formed on the bulging portion 15 exceeds 60% by mass, the resin concentration of the printing layer 22 in that portion becomes low, and the adhesion between the surface of the can substrate 10A and the printing layer 22 becomes low. Is reduced, and the coating film 20 is easily peeled off from the can substrate 10 (10A to 10C) during molding of the bulging portion 15 and the like. Therefore, the pigment concentration of the printing layer 22 on the bulging portion 15 is preferably 60% by mass or less. As a result, the adhesion between the surface of the can substrate 10 and the printing layer 22 can be maintained well.

Further, in the bottle can 101 of the above embodiment, the printing layer 22 is formed on the base layer 21 composed of the white coat layer or the size coat layer formed on the outer surface 10o of the can base 10, but below. It is also possible to form the printing layer 22 directly on the outer surface 10o of the can substrate 10 without forming the stratum 21. When the base layer 21 is formed as in the bottle can 101 of the present embodiment, the adhesion between the outer surface 10o of the can base 10 and the printing layer 22 can be improved. Further, when the base layer 21 made of the white coat layer is formed, it is possible to further form a painted surface in which the metal base of the can base 10 is hidden.

Further, the configuration of the present invention is not limited to the configuration in which the inner surface coating layer 31 is provided on the inner surface 10i of the can base 10, but the inner surface 10i of the can base 10 is like the bottle can 101 of the present embodiment. When the inner surface coating layer 31 (coating film 30) is formed on the surface, the inner surface coating layer 31 can protect the inner surface 10i of the bottle can 101 (can base 10), so that when the male screw portion 16 and the bulging portion 15 are processed. It is possible to prevent damage such as scratches from occurring on the inner surface 10i.

Further, in the above embodiment, the print layer 22 is formed by using the ink containing the curing accelerator of the overcoat layer 23, but the printing layer is composed of the ink containing the curing accelerator of the overcoat layer 23 and the ink thereof. Ink that does not contain a curing accelerator can be partially applied separately on the outer surface of the can substrate 10. Further, the printing layer can be formed by applying an ink containing no curing accelerator of the overcoat layer 23 to the planned formation portion of the male screw portion 16.

In this case, since the ink applied to the portion to be formed of the male screw portion 16 is an ink that does not contain the curing accelerator of the overcoat layer 23, even if the overcoat layer 23 is formed in an overlapping manner, it is interposed inside the ink. The printing layer does not accelerate the curing of the overcoat layer 23. Therefore, the hardness of the overcoat layer 23 on the male threaded portion 16 can be kept low. Further, since the hardness of the overcoat layer 23 can be partially changed only by separately coating the printing layer without separately coating the outer surface paint constituting the overcoat layer 23, the workability of the male screw portion and the swelling can be changed. It is possible to easily manufacture a bottle can that has both the robustness of the coating film on the lower part of the portion.

The present invention is not limited to the configuration of the above embodiment, and various changes can be made to the detailed configuration without departing from the spirit of the present invention.
For example, in the above embodiment, an example of a bottle can made of aluminum or an aluminum alloy is shown as a metal bottle can, but the present invention is not limited thereto. For example, when a bottle can is manufactured from another metal such as a tin-plated steel plate having excellent workability, the same effect as that of the present embodiment can be obtained.

10, 10A, 10B Can base 10i Inner surface 10o Outer surface 11 Body 12 Shoulder 13 Tapered cylinder 14, 14A, 14B Mouth 15 Protrusion 16 Male thread 17 Reduced diameter 18 Curl 20, 20A, 30 Membrane 21 Base layer 22 Printing layer 23 Overcoat layer 24 Pre-overcoat layer 31 Inner surface coat layer 41, 42 Area 101 Bottle can 201 Cap 210 Cap body 215 Female screw formation planned part 218 Hem part 219 Female thread 220 Liner 301 Capped bottle can

Claims (6)

A bottle can in which a mouth portion is formed on the upper part of a metal can base, and a male screw portion and a bulging portion that is connected to the lower side of the male screw portion and bulges outward in the radial direction are formed in the mouth portion. There,
It is provided with a print layer in which ink is printed on the outer surface of the can substrate so as to form a design, and an overcoat layer in which the ink is coated on the print layer.
The printing layer is formed at least on the bulging portion.
The printing layer formed on the bulging portion contains a curing accelerator that promotes curing of the overcoat layer.
A bottle can characterized in that a printing layer containing the curing accelerator is not formed on the male threaded portion. The bottle can according to claim 1, wherein the pigment concentration of the printing layer formed on the bulging portion is 60% by mass or less. The bottle can according to claim 1 or 2, wherein the printing layer is formed on a base layer composed of a white coat layer or a size coat layer formed on the outer surface of the can substrate. A bottle can with a cap, wherein a cap is attached to the mouth of the bottle can according to any one of claims 1 to 3. The capped bottle according to claim 4, wherein the capped bottle can is a capped bottle can for retort sterilization that is heat-treated at 100 ° C. or higher after the cap is attached to the mouth. can. An outer surface printing process that paints the outer surface of a bottomed tubular can substrate, and
After the outer surface printing and painting step, an inner surface coating step of applying a coating to the inner surface of the can substrate and
A mouth molding step of molding a mouth portion having a diameter smaller than that of the lower portion on the upper portion of the can substrate after the inner surface coating step,
The mouth portion is provided with a threaded portion molding step for forming a male threaded portion and a bulging portion.
In the outer surface printing coating step, ink is printed on the outer surface of the can substrate to form a printing layer, and the outer surface coating material is applied onto the printing layer and then heated to completely burn the outer surface coating material. It is said to be the process of forming the pre-overcoat layer.
In the inner surface coating step, after applying the inner surface paint to the inner surface of the can substrate on which the pre-overcoat layer is formed, the inner surface paint is at a temperature equal to or higher than the baking temperature of the pre-overcoat layer. Is baked to form the inner surface coat layer, and the pre-overcoat layer is baked to form the overcoat layer.
In the outer surface printing coating step, an ink containing a curing accelerator that promotes curing of the overcoat layer is printed on at least the planned formation portion of the bulging portion on the outer surface of the can substrate, and the male screw portion is scheduled to be formed. A method for producing a bottle can, which comprises forming the printing layer without printing the ink containing the curing accelerator on the portion.

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