JP2000334376A - Metal can and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a metal can free from wrinkles in a neck part and buckling of a can body, or black spots in the neck and flange parts during neck-in processing. SOLUTION: A metal can 2 is provided with a cylindrically formed body part 3, and a bottom part 4 formed integrally with the body part 3 in a state where one of its opening ends 5 is closed, and a thin-film shaped coating film 10 consisting of a thermosetting synthetic resin is formed on a cut section 6 of a part, on which neck-in processing in the opening end of the body part 3 is applied, in a state covering the whole of the cut section 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal can having a bottom and a body integrally formed, and a method for manufacturing the same.

[0002]

2. Description of the Related Art At present, a two-piece can having a structure in which a bottom and a body are integrally formed by drawing or redrawing or drawing and ironing a circular material of a tin-plated steel plate or an aluminum alloy plate is used for beer. It is widely used for beverage cans such as and carbonated beverages. The two-piece can is manufactured by the following procedure as an example.

That is, the opening end of a can body made by punching drawing, redraw forming, drawing ironing, or the like is cut, followed by degreasing and chemical conversion treatment, and then the desired characters, figures, patterns, etc. In order to provide a design on the outer surface of the can body, print coating is applied to the can body, or a printed film is heat-bonded to the can body, and then the inner surface is further applied, and then the opening end is reduced in diameter. After performing neck-in processing (drawing processing), flange processing (edge processing) is performed on the opening end. The neck-in processing and the flange processing are preparation steps for closing the lid around the can body.

[0004] In recent years, metal cans used for beer and carbonated beverages have employed lids having a smaller diameter than the can body in order to save lid material. A plurality of stages of neck-in processing are applied to the open end of the can body. As the can body of such a beverage can, a so-called canister body having a nominal diameter of 211 (about 66 mm) is generally used. Those with a reduced diameter are used. In the future, there is a tendency that the diameter is made smaller than the nominal diameter 206 in order to further reduce the lid material.

[0005] However, in the neck-in processing, wrinkles and bucklings are liable to occur in a portion to be processed which is reduced in diameter stepwise and instantaneously. Causing
It is known that it can easily lead to the cause of poor sealing. Japanese Patent Application Laid-Open No. 50-74563 discloses a state in which a large amount of spray paint adheres to the opening end as one of the factors.
It also describes a state where the opening end has no lubricity.

On the other hand, JP-A-9-29367 discloses that
As means for preventing the occurrence of wrinkles in the portion where neck-in processing is performed, the thickness of the print coating at the open end of the can body is set to be thinner than the print coating applied to other portions,
Alternatively, it is described that a metal substrate is left exposed without applying a print coating film to an opening end.

[0007] Japanese Patent Application Laid-Open No. 9-29842 discloses that
In order to prevent the printed synthetic resin film attached to the outer surface of the can body from being damaged by post-processing such as neck-in processing, the cut end face of the open end of the can body and the upper edge of the synthetic resin film A film-adhered can having a configuration in which the protective film is covered with a protective coating is described.

Further, Japanese Patent Publication No. 63-44026 discloses that a metal can is spray-coated on the inner surface while rotating the metal can around a central axis of the can body in a coating machine, and the metal can is coated with the inner surface. It describes a method for producing a metal can, which is taken out of a coating machine, transported to a drying and baking furnace, and dried and baked there.

[0009]

However, when the can described in Japanese Patent Application Laid-Open No. 9-29367 is subjected to neck-in processing, the metal is exposed at the open end and the open end surface due to friction with the neck-in forming tool. Aluminum powder is generated in the portion, and the aluminum powder adheres and deposits on the forming tool surface. Then, during the continuous production, the adhered material peels off from the forming tool, and mixes with the clear coat provided on the outer surface of the can body to become dark, and streak-like black dirt adheres to the formed neck-in portion to impair the appearance. There was a problem. In addition, the problem of black stains also occurs during flange processing, and furthermore, aluminum powder deposits on the surface of the forming tool, which damages the flange and causes flange cracking. As a result, the lid is tightened. At the time of leakage.

On the other hand, according to the can described in Japanese Patent Application Laid-Open No. 9-29842, the entire cut end face and the outer peripheral edge thereof are directly covered with the neck-in forming tool because they are covered with the protective coating. Although it does not contact, the inner edge of the cut end surface is exposed, so this part slides against the part arranged on the inner peripheral side of the open end of the neck-in forming tool and metal powder Probably, it was generated.

As described above, the number of steps of neck-in molding is increased for the purpose of saving the material of the can body, and this is done by increasing the number of neck molding steps or increasing the neck drawing ratio. However, increasing the number of steps is not economically advantageous, and the actual situation is that the amount of diameter reduction per stage must be increased.

[0012] However, when the diameter reduction per one step is increased, the wall thickness of the neck portion of the two-piece can is smaller than that of the three-piece can by about 0.160 mm.
0.195 mm, can body wall thickness about 0.100 mm-0.
115mm, for steel can, neck wall thickness about 0.12
5mm to 0.160mm, can body wall thickness about 0.065mm
Buckling is likely to occur at the can body or neck forming portion or the can bottom, and the crushing of the can inside the molding machine in this manner may cause the machine to buckle. Shutdowns are forced, resulting in significantly lower production efficiencies.

The present invention has been made in view of the above circumstances, and provides a metal can that does not cause buckling and black stains during neck-in processing, and a method for easily and reliably manufacturing the metal can. The purpose is to do so.

[0014]

SUMMARY OF THE INVENTION In order to achieve the above-mentioned object, a first aspect of the present invention is to provide a cylindrical body and a state in which one open end of the body is closed. In a metal can having the body and a bottom integrally formed, a coating layer made of a thermosetting synthetic resin is provided on a cut end surface of a portion where neck-in processing is performed at an opening end of the body. It is characterized in that it is formed so as to cover the entire cut end surface.

Therefore, according to the first aspect of the present invention, the smoothness of the can as a can with respect to the forming tool during the neck-in processing is improved, so that no wrinkles are generated at the opening end, and the neck is formed. Since the force is reduced, buckling of the trunk can be suppressed. Furthermore, in the invention of claim 1, since the above-mentioned forming tool and the metal base material of the cut end face do not directly contact each other, aluminum powder is not generated even in the case of a so-called aluminum can made of an aluminum alloy. The neck-in molding does not become black due to adhesion of aluminum powder.

According to a second aspect of the present invention, in addition to the first aspect, the width of the coating layer is set to a width protruding on the inner peripheral side and the outer peripheral side of the cut end face. It is characterized by the following.

According to the second aspect of the present invention, since the coating layer protrudes to the inner and outer peripheral sides of the cut end face, the metal base material at the inner and outer peripheral edges of the cut end face during neck-in molding is neck-in molded. No direct contact with the tool
Therefore, generation of metal powder is more reliably suppressed.

According to a third aspect of the present invention, in addition to the first or second aspect, the thickness of the coating layer is 1.0
It is characterized in that it is set within the range of μm to 1.5 μm.

Therefore, according to the third aspect of the present invention, the coating layer can sufficiently withstand a plurality of neck-in processes, and wrinkles and buckling due to an excessively large film thickness do not occur.

Further, according to the present invention, there is provided a metal can having a cylindrical body, and a bottom integrally formed with the body with one opening end of the body closed. Applying an inner surface paint to the inner surface of the metal can while rotating about the center axis of the body, then taking out the applied metal can from the coating machine, and continuously adjusting the center axis of the body. A baking oven is performed in a state where the inner paint is pre-dried by blowing warm air into the inside of the metal can while rotating the metal can to the center, and further, the rotation of the metal can around the central axis of the body is stopped. In the method for manufacturing a metal can to form an inner surface coating by drying and baking the pre-dried inner surface paint, the step of applying the inner surface paint to the inner surface of the metal can,
A repair paint made of a thermosetting synthetic resin is applied to the cut end face of the opening end of the body in the rotating state, and further, in the step of pre-drying the inner surface paint, the center axis of the body is On the other hand, an air flow is supplied to the repair paint from the outside in the radial direction of the opening end to the inside of the repair paint, and the repair paint is pre-dried while suppressing the flow of the repair paint to the outer surface side of the body portion. In the step of drying and baking the paint for the inner surface, the repair paint in a pre-dried state is bake-dried to form a coating layer on the cut end face.

According to the fourth aspect of the present invention, in performing the preliminary drying of the repair paint, the repair paint tends to flow from the cut end face to the outer peripheral side of the body due to centrifugal force caused by the rotation of the metal can. Since the air flow to be suppressed is continuously supplied to the repair paint, the repair paint flows non-uniformly to the outer peripheral side of the body, without being dried as it is biased to the outer peripheral surface of the body, In other words, the repair paint can be pre-dried to the desired state. In addition, the occurrence of neck wrinkles due to uneven drying of the repair paint is prevented.

Further, in the invention of claim 4, the formation of the inner coating film and the formation of the coating film on the cut end face of the can body are substantially performed, and the can body in the inner coating film forming step is rotated. During this state, the inner coating film forming step and the repair coating film forming step are performed substantially in parallel. In other words, the equipment for rotating and stopping the can in the two different types of coating film forming processes is simplified, and therefore, no special can rotating means is required for forming the repair coating film. A metal can having a configuration in which a coating layer is provided on the cut end surface of the open end can be efficiently manufactured.

According to a fifth aspect of the present invention, in addition to the fourth aspect, the air flow is supplied obliquely from the bottom side of the metal can to the opening end side. Is what you do.

Therefore, according to the fifth aspect of the present invention, there is no possibility that the pressure of the air flow on the repair paint is excessively increased, so that not only the flow to the outer surface of the can body but also the inner surface of the can body is reduced. Since the inflow can also be suppressed, it is possible to reliably form a coating layer having a uniform thickness, for example, even if the repair paint is small.

[0025]

Next, an embodiment of the present invention will be described with reference to the drawings. In the present invention, both the print-painted can and the film-sticking can are targeted, but here, only the print-painting can is illustrated and described, and the film-sticking can is referred to as the print-painting can without being particularly illustrated. The following description focuses on the differences.

FIGS. 1 and 2 are cross-sectional views showing a print-painted can 1 before neck-in processing is performed. As shown in these figures, the can body 2 has a lengthwise direction. A cylindrical can body 3 having a constant diameter, and formed integrally with the can body 3 in a state where one open end of the can body 3 is closed, and recessed in a dome shape toward the open end 5. And a can bottom 4. That is, the can body 2 is a bottomed can body in which a can bottom 4 and a can body such as a drawn can, a redrawn can, a stretch can, a drawn ironed can, and an impact can are integrally formed, that is, a two-piece can. . The cut end face 6 of the open end 5 is linear and orthogonal to the central axis of the can body 3.

The can 2 has a thickness of 0.10 m as an example.
It is made of a 3004 series aluminum alloy plate of about m to 0.30 mm, and an organic chemical conversion film (not shown) is provided on the surface thereof. Other examples of the can body material include a surface-treated steel plate such as an aluminum plate and tin-free steel, a tin plate, a chromium-plated steel plate, an aluminum-plated steel plate, a nickel-plated steel plate, and various other alloy-plated steel plates.

An inner coating 7 for protecting the contents is formed on the inner surfaces of the can body 3 and the can bottom 4. The inner coating film 7 is provided up to near the edge of the opening end 5. That is, the can body 2 has a structure in which the metal base near the edge on the inner surface side of the opening end 5 is exposed. On the other hand, an ink layer 8 is formed on the outer surface of the can body 3 by printing characters, figures, patterns, and the like in order to enhance the design. Further, a clear coat (overcoat) 9 is provided on the outer surface of the ink layer 8 to protect the printing surface. The clear coat 9 is provided up to near the edge of the opening end 5. That is, the can body 2 has a structure in which the metal substrate of only the chemical conversion film near the edge on the outer surface side of the opening end 5 is exposed.

The ink used for printing is preferably an alkyd resin type ink from the viewpoint of adhesion to a metal substrate, and other examples include aqueous inks and ultraviolet curable inks. On the other hand, as the clear coat 9, for example, an acrylic-based
Polyester-based, epoxy-based thermosetting synthetic resin paints are used, and synthetic resins containing lubricants such as silicone and wax in curable synthetic resins such as ultraviolet curable synthetic resin and electron beam curable synthetic resin Can also be adopted.

Further, a repair coating layer 10 is provided on the cut end face 6 of the open end portion 5 over the entire circumference, in other words, the cut end face 6 is covered with the repair coat layer 10. Thus, the cut end face 6 has a structure in which the metal substrate having no chemical conversion film is not exposed. The repair coating layer 10 protrudes from the cut end face 6 to the left and right sides in FIG.
And the edge of the opening end 5 is covered over the entire circumference. Also. The thickness of the repair coating layer 10 is, for example, 0.
It is set within the range of 5 μm to 5.0 μm, particularly 1.0 μm.
It is more preferable to set a uniform thickness in the range of m to 1.5 μm in order to prevent occurrence of neck wrinkles. In addition,
The repair coating layer 10 includes the inner coating film 7 and the clear coat 9
It is also possible to adopt a structure partially overlapping with.

Further, the repair coating layer 10 is made of a thermosetting synthetic resin such as an acrylic, polyester, epoxy, or phenol resin. A lubricant such as wax or wax may be added. The curable synthetic resin preferably has both impact resistance and abrasion resistance, and is preferably a resin of the same type as the clear coat 9 and the inner coating film 7.

On the other hand, the film-sticking can has substantially the same structure as that of the print-coated can 1 shown in FIGS. 1 and 2 in terms of the structure itself of the can body 2, ie, the can of this film-sticking can. A printed thermoplastic resin film instead of the ink layer 8 and the clear coat 9 in the printing can 1 is thermally bonded to the outer surface of the cylinder.

Specific examples of the thermoplastic resin film include polyester resins such as polyethylene terephthalate resin and polybutylene terephthalate resin, copolymer polyester resins comprising a copolymer of polyethylene terephthalate and isophthalic acid, and polypropylene resins. A transparent polymer resin alone selected from a polycarbonate resin, a polystyrene resin, a polyolefin resin, a vinyl chloride resin, a polyvinylidene chloride copolymer or the like, or a thermoplastic resin film made of a composite of the above resins is used. The thickness of the film is 10μ
Those having a range of m to 20 μm are used.

As a printing method for the above-mentioned film,
It is carried out using gravure printing or flexographic printing, but from the viewpoint of design, gravure printing with clear image quality and high quality is preferable. As an ink used for printing, polyurethane, a copolymer of vinyl chloride-vinyl acetate or the like is used, and isocyanate or the like is added as a curing agent.

The adhesive applied to the printing surface of the film or the film surface opposite to the printing surface, in other words, the surface facing the outer surface of the can body 3 is made of polyester, polyurethane, epoxy or the like. The thermosetting synthetic resin is preferably used in combination of two or more kinds in consideration of adhesion to a metal material. The thickness of the adhesive is
The range is preferably from 1 μm to 8 μm, and particularly preferably from 5 μm to 7 μm from the viewpoint of appearance design.

Further, a clear coat is provided on the surface of the thermoplastic resin film opposite to the surface on which the adhesive is applied. As the clear coat, specifically, a curing agent such as an amino resin is used for a polyester resin, an epoxy resin, an epoxy-modified polyester resin, an acrylic resin, and the like, and a well-known lubricant is contained in these curing materials. Things can be exemplified.

A repair coating layer is also provided on the cut end face of the open end of the film sticking can. This repair coating layer is the repair coating layer 1 provided on the printing paint can 1 shown in FIG.
0, and therefore may partially overlap with the thermoplastic resin film. If the entire cut end face is covered with the repair coating layer, the metal base is exposed on the inner and outer surfaces of the open end. Even if it does, when the can lid is wound up, there is no particular problem in the corrosion resistance since it is covered with the sealant.

Next, FIG. 3 is a schematic diagram showing a production line 11 used in a series of steps, and FIG. 3 is a schematic view showing a production line 11 used in a series of steps. A coating machine 12 for performing a step of applying a paint to the inner surface of the can body 2 and a step of applying a repair paint 24 to the cut end surface 6, a conveyor 13 for performing a preliminary drying step, and a drying and baking furnace 14 for performing a baking step. And an elevator 15 for supplying the can 2 to the drying and baking furnace.

More specifically, the coating machine 12 holds the plurality of cans 2 with the center axis of the can 3 oriented horizontally.
In addition, an intermittent transition path 16 having a circular shape that rotates in the counterclockwise direction in FIG. 3, a pair of rotatable support rolls 17 that support the can bodies 3 of the respective can bodies 2, and a support that sandwiches the intermittent transition path 16. A can rotation belt 18 is provided at a position facing the roll 17 and contacts the can body 3 to rotate the can body 2 along the central axis. The belt 18 for rotating the can
A belt 20 is wound around each of the pulleys 19, and one of the pulleys 19 is driven to rotate by a motor (not shown).

Further, the coating machine 12 is provided with the opening end 5 of the can 2.
Inner coating means 2 which is disposed on the side and sprays a coating material 50 (hereinafter referred to as an inner coating material 50) on the inner surface of the can body 2.
1 and a repair paint applying means 22 for applying a repair paint 24 to the cut end face 6 of the can body 2. That is, the coating machine 12 is configured to apply the paint to the inner surface while rotating the plurality of can bodies 2 around the central axis of the can body 3 and simultaneously apply the repair paint 24 to the cut end surface 6. It has become.

Examples of the repair paint applying means 22 are as shown in FIGS. The repair paint application means 22 shown in FIG. 4 has a repair paint spray nozzle 23 disposed at a position facing the lowermost part in the drawing of the cut end surface 6 of the opening end 5, and the center axis of the can body 3. The repair paint 24 is sprayed on the cut end face 6 in a direction parallel to the above.

The repair paint applying means 22 shown in FIG.
The repair paint spray nozzle 23 is disposed below the open end 5 of the can body 2, and repair paint 24 is repaired on the open end 5 in a direction substantially orthogonal to the central axis of the can body 3. The paint 24 is sprayed.

Further, the repair paint applying means 22 shown in FIG.
Has a configuration in which the repair paint 24 is dropped and supplied to the cut end surface 6. Specifically, a paint reservoir 25 arranged at a position above the opening end 5 in the drawing, a felt holding jig 26 facing the opening end 5 and freely contacting / separating from the cutting end surface 6 are provided. Is provided. The felt holding jig 26 holds a felt material 27 having an annular structure tapered so as to have a large diameter toward the can bottom 4. That is, the felt material 27 is arranged in a state of being in light contact with the cut end surface 6, the repair paint 24 is dropped from the paint reservoir 25 toward the felt material 27, and the repair paint 24 is cut through the felt material 27. It is configured to be applied to the end face 6.

The repair paint applying means 22 shown in FIG. 7 has a paint tank 28 containing a predetermined amount of repair paint 24 arranged below the can body 3. 2 is supplied. Specifically, the paint tank 28 is formed of a container having an open upper side (the can body 3 side), and the paint tank 28 is rotatably supported inside the paint tank 28 in a direction along the center axis of the can body 3. Two rollers 29
(29a, 29b) are provided with their positions shifted in the vertical direction. Each roller 29 is in a state where a part of the outer peripheral surface is in contact with each other. In addition, each roller 29
Are respectively covered with a felt material (not shown).

A part of the outer peripheral surface of the roller 29a disposed on the lower side is immersed in the repair paint 24, whereas the outer peripheral surface of the roller 29b disposed on the upper side is The state is in contact with the end 5. In addition, near the outer peripheral surface of the upper roller 29b, a tip end of a liquid draining spatula 30 attached to the paint tank 28 is arranged. That is,
By rotating the lower roller 29a clockwise in the figure, the upper roller 29b rotates counterclockwise, and the repair paint 24 adhered to the lower roller 29a.
Is supplied to the outer peripheral surface of the upper roller 29b, and after the repair paint 24 is adjusted to an appropriate amount through the spatula 30,
It is configured to be applied to the cut end face 6 and the open end 5.

On the other hand, the intermittent transition path 16 in the coating machine 12
The transport conveyor 13 is disposed on the lower left side in FIG. The transport conveyor 13 includes a frame 31 installed in a posture oriented in the horizontal direction in FIG. 3, and an endless belt including a large number of suction plates 32 movably mounted along the frame 31. . As shown in FIGS. 8 and 9, each suction plate 32 is formed with three small holes 33 penetrating in the thickness direction of the suction plate 32. The bottom 2 of the body 2 is sucked and held by the suction plate 32, and is transported as it is.

On the suction surface side of the suction plate 32,
A pair of can rotation belts 34 are arranged in a position along the frame 31 at a position closer to the can bottom 4 than the center of the can body 3.
These can-rotating belts 34 have substantially the same configuration as the can-rotating belt 18 provided in the coating machine 12, and all of them rotate clockwise. The interval between the can rotation belts 34 is set to be substantially the same as the outer diameter of the can body 3 of the target can body 2. In other words, by rotating the can body 3 of the can body 2 between the pair of rotating belts 34 in the vertical direction in FIG. 9, the can body 3 continues to rotate in a fixed direction about the central axis of the can body 3. It is configured to be transported.

A discharge section 36 of a blower 35 for main blow is arranged on the front side of the conveyor 13 in FIG. 3, that is, at a portion facing each suction plate 32. The blower 35 blows hot air 37 substantially parallel to the central axis of the can body 3 toward the inner surface of the can body 3 of the can body 2 conveyed by the conveyor 13 (hereinafter referred to as a main blow for convenience). The discharge section 36 has a certain length in the direction along the conveyor 13 and has a large number of discharge ports (not shown) arranged at predetermined intervals.
, And pre-drys the inner paint while transporting.

Further, a blower 38 for side blowing is provided below the conveyor 13 in FIG. A large number of discharge ports (not shown) arranged at predetermined intervals in the discharge section 39 of the blower 38 are inclined by about 30 to 60 degrees with respect to the center axis of the can body 3 and open from the bottom 4 of the can. It is arranged in a posture facing the end 5. That is, the hot air 40 is blown to the vicinity of the opening end 5 of the can 2 conveyed by the conveyor 13 (hereinafter, referred to as a side blow for convenience).

The discharge section 39 of the blower 38 may be arranged in a position substantially perpendicular to the central axis of the can body 3 instead of the above arrangement, that is, the hot air 40 is supplied in parallel with the cut end face 6. Can be provided. In addition, warm air 3
The temperature of 7,40 is set in the range of 30C to 80C, more preferably in the range of 40C to 60C. The wind speed is in the range of 0.2 m / sec to 5 m / sec, more preferably 1.0 m / sec.
m / sec to 2.0 m / sec. This pressure is such that the repair paint 24 does not flow into the inner surface of the opening end 5.

At the left end of the transport conveyor 13 in FIG. 3, an elevator 15 is installed which rotates from below to above and from the near side to the far side. The basic structure of the elevator 15 is similar to that of the transport conveyor 13, that is, the elevator 15 includes an endless belt including a frame forming a negative pressure chamber as a whole, and a number of suction plates movable along the frame. In addition, the suction bottom plate 4 of the can body 2 is sucked and held by the suction plate by generating a suction negative pressure in the space on the frame side, and is transported as it is.

One opening end of the twister 42 is disposed from the middle position to the upper position in the elevator 15, while the other opening end is connected to the entrance of the drying and baking furnace 14. The twister 42 is a guide for forcibly changing the attitude of the can body 2. In this specific example, the center axis of the can body 3 is oriented horizontally, and the open end 5 is located on the near side in FIG. 3. The can body 2 in the turned posture is changed to a posture in which the opening end 5 is directed upward and the center axis of the can body 3 is directed vertically.

That is, when the can 2 raised by the elevator 15 in the horizontal position moves in the twister 42, the position is forcibly changed to a state in which the opening end is directed upward, and the drying and baking furnace 14 is moved in that position. Supplied within. Inside the drying and baking oven 14, a conveyor 43 rotating counterclockwise in FIG. 3 is provided. That is, the drying and baking furnace 14 performs the drying and baking while transporting the plurality of can bodies 2 leftward in FIG.

Therefore, in manufacturing the can 2 having the structure shown in FIGS. 1 and 2,
First, it is supplied to an intermittent transition path 16 (for example, an intermittent rotating turret or the like) of the coating machine 12 to perform inner coating for protecting contents. Specifically, the can body 2 is held by the support roller 17 in a state where the running belt 20 is in contact with the outer surface of the can body 3, so that the can body 2 is turned around the center axis of the can body 3 in FIG. Forced to rotate clockwise. The inner surface paint 50 made of a thermosetting synthetic resin is spray-coated on the inner surface of the rotating can body 2.
At the same time as this inner surface coating step, the repair paint 24 is applied to the cut end surface 6 of the opening end 5. As the means, any of the repair paint applying means 22 shown in FIGS. 4 to 7 described above is employed.

Here, a small amount of the repair paint 24 is applied to the cut end face 6.
After applying the repair paint 24 in order to apply the repair paint 24 uniformly over the entire circumference of the work, uniform work such as removing excess repair paint 24 using a felt or the like or leveling it along the cut end surface 6. May be performed.

The coated can body 2 is separated from the support roll 17 of the coating machine 12 and the can rotating belt to separate the conveyor 1.
3, the can bottom 4 is adsorbed by the adsorption plate 32, and the can body 3 is conveyed while being sandwiched between a pair of can rotation belts 34. That is, while being transported, the can body 2 slides the can bottom 4 against the suction plate 32 while the can body 3
Rotation about the central axis of is continued. The rotation speed of the can body 3 is set, for example, in a range of 5 to 60 rpm, and more preferably, about 30 rpm.

Further, main blow is performed on the can 2 being conveyed, and as a result, the inner coating 50 is dried to form the inner coating 7. In addition, the temperature of the hot air 37 for the main blow is set to 20 to 60 ° C. as an example. Further, at the same time as the main blow, a side blow is performed on each can 2 for about 1 to 5 seconds. The temperature of the hot air 40 for side blow is also set to 20 to 60 ° C. as an example. Thereby, the flow of the repair paint 24 to the outer peripheral surface side of the can body 3 due to the centrifugal force caused by the rotation of the can body 2 is suppressed, and as a result, the repair paint 24 is thinly and uniformly coated on the cut end surface 6. dry. That is, the conveyor 1
While the can 2 is conveyed by 3, the preliminary drying of the inner coating 50 by the main blow is performed, and at the same time, the preliminary drying of the repair paint 24 by the side blow.

Next, the can body 2 is provided with a drying and baking oven 14 for completely baking the inner paint 50 and the repair paint 24 respectively.
Sent to Specifically, the pre-dried can body 2 is transferred from the conveyor 13 to the elevator 15 and transported upward by the elevator 15 in FIG. 3 while being rotated about the central axis of the can body 3. After being unwound, it is supplied to the opening of the twister 42.

The can body 2 further changes its posture from the posture in which the central axis of the can body 3 is directed horizontally to the posture in which the opening end 5 is arranged on the upper side while sliding down the inside of the twister 42 by its own weight. In this state, it is placed on the conveyor 43 of the drying and baking oven 14 and moves inside the drying and baking oven 14 at, for example, 200 ° C. to 260 ° C. and 1 ° C.
It is baked under heating conditions of about 3 minutes. That is, the baking hardening of the repair paint 24 for one can 2 and the inner paint 5
And bake hardening of 0 are performed simultaneously. As a result, a repair coating layer 10 as shown in FIGS. 1 and 2 is formed.
As described above, the repair coating layer 10 covers the entire circumference of the cut end face 6 with a uniform thickness, and protrudes to the inner and outer peripheral sides of the cut end face 6 (the inner peripheral face and the outer peripheral face of the cut end face 6). (Projecting inward and outward, respectively, from the surface). The protruding amount α (see FIG. 2) is formed to be at most about the metal wall thick portion t at the opening end. If the protrusion is formed beyond that range, it will cause milling in the repair coating film during drying, which is not preferable.

After the baking process, the can 2 is sent to the neck-in process. Here, conventionally known neck-in forming tools and methods can be employed. As shown in FIG. 10, the neck-in forming tool 44 is slidable with a deformed cylindrical necking die 45 having different inner diameters in the length direction and a center axis aligned with the inner peripheral side of the necking die 45. And a fitted knockout 46. The inside diameter of the one opening end of the necking die 45 is set to be the same as the outside diameter of the target can body 2. Further, a portion from this portion toward the other open end of the necking die 45 has a structure in which the diameter is reduced while forming a smooth curved surface.

Then, the opening end of the can body 2 is fitted to the inner peripheral portion of the necking die 45,
The can body 2 is pushed toward a gap between the inner peripheral surface of the knockout 46 and the outer peripheral surface of the knockout 46. Then, the opening end 5 is deformed while moving along the inner surface of the necking die 45, and as a result,
The opening end 5 is reduced in diameter, and the neck-in molding of the can 2 is completed. When pushing the can body 2 toward the neck-in forming tool 44, the necking die 45 does not directly rub against the cutting end face 6 and the outer peripheral edge thereof (the outer peripheral edge of the opening end 5). 6 and the inner peripheral edge thereof (the inner peripheral edge of the opening end 5) and the knockout 46 do not directly rub against each other, so that a so-called black stain caused by the generation of metal powder does not occur in the processed portion. Further, since the sliding resistance of the can body 2 with respect to the neck-in forming tool 44 is small, the occurrence of buckling particularly in the can body 3 is prevented.

Next, in order to confirm the effects of this embodiment, cans of the examples having predetermined characteristics and cans of the comparative example were prepared, and the results of various experiments are shown.

(Example 1) The can 2 used for the experiment was the same as that shown in FIG.
And a printed painted can having the structure shown in FIG. That is, an ink layer 8 is formed on the outer surface of the can body, and a clear coat 9 made of a thermosetting synthetic resin containing a lubricant such as wax or silicon is applied on the upper surface of the ink layer 8. Have been. On the other hand, an inner coating film 7 is formed on the inner surface of the can body 3. The inner coating film 7 and the clear coat 9 are both provided so as to be shifted from the cut end face 6 by about 1.0 mm, that is, the exposed portion of the metal base is formed inside and outside the opening end portion 5. A repair coating was applied to the cut end surface 6 of the opening end 5 of the can body 2 by using a repair paint applying means 22 having a configuration shown in FIG. 4 (spray coating). Then, the can body 2 and the unpainted can body were combined with each other using a necking die 45 having a radius of curvature R of 3.0 mm as shown in FIG. The rate was tested. The results are shown in Table 1 (Test No. 1 and Test No. 5).

The reason for setting the radius of curvature R of the necking die 45 to the above value is 4.0 mm ≦ R ≦ 5.0 mm.
In the case of (1), neck-in molding is performed without any particular problem even when the metal base is exposed on the cut end face 6. On the other hand, in order to increase the diameter reduction, R <4.0 mm, particularly 3.0 mm.
It is experimentally known that, in the case of the following, the resistance at the time of processing increases and the forming force increases, so that the can body 3 has a strong tendency to buckle.

(Example 2) After printing on the outer surface of the can body 3 and applying clear coating, repair coating was performed using the repair paint applying means 22 configured as shown in FIG. 6 (felt coating). The repair paint 24 was dropped on the felt material 27 once every three seconds. Then, as in the first embodiment,
The can body 2 having been subjected to the repair coating and the can body having not been subjected to the repair coating were tested for the neck forming force and the buckling occurrence rate for aluminum cans. The results are shown in Table 1 (Test No. 2 and Test No. 6).

(Example 3) A repair can be applied by using a film sticking can in place of the print coating can 1 and using the same means as in Example 1, that is, the repair paint applying means 22 having the structure shown in FIG. (Spray coating). Note that this film sticking can has a configuration in which a thermoplastic resin film is thermocompression-bonded to a position shifted from the cut end face 6 by about 0.5 mm to 1.0 mm,
The metal body of the can 2 is configured to be partially exposed. This is because if the film jumps out of the cut end face 6 of the opening end 5, film hair is likely to occur during neck-in processing and may adhere to the inner surface of the can 2.
Then, in the same manner as in Example 1, the can 2
And the can body without the repair coating were tested for neck forming force and buckling occurrence rate for steel cans. The results are shown in Table 1 (Test No. 3 and Test No.
7).

(Example 4) Repair coating was performed using a film sticking can made of aluminum as the material of the can body and using the repair paint applying means 22 shown in FIG. 4 (spray coating). In the same manner as in Example 1, the can body 2 having been subjected to the repair painting and the can body having not been subjected to the repair painting were tested for the neck forming force and the buckling occurrence rate for steel cans. The results are shown in Table 1 (Test No. 4 and Test No. 8).

[Table 1]

* Material Specifications The steel can was made of an electrolytic tin-plated steel plate having a thickness of 0.24 mm as a material of the can body, and a clear coat of a polyester-amino resin and a repair paint made of a phenol resin. On the other hand, an aluminum can has a thickness of 0.
A 30 mm 3004 series aluminum alloy was used, and the same material as that of the steel can was used for both the clear coat and the repair paint.

* Occurrence rate of buckled cans As shown in FIGS. 12 and 13, with the can bottom 2 arranged vertically with the can bottom 4 arranged on the lower side, an air pressure of 5 kgf / cm ^{2 is applied} inside the can ^2. And a load tester 47 is assembled to the open end 5 to apply a load from above the can 2, and a value (F1) at which the can 2 buckles is measured. The buckling of the can body 3 is determined by visually confirming that the can body 3 has been crushed into a belt shape, and measuring the buckling strength measurement value (F1).

Next, the neck-in forming tool 44 is attached to the load tester 47, and the opening end 5 is attached to the neck-in forming tool 44 (not shown). The peak value (F2) when neck 5 is formed is measured by the load tester 47. Neck processing force peak value (F2) and buckling strength measurement value (F1)
Buckling tends to occur when F2> F1. In order to confirm the tendency, 100,000 units of each of the above-described Examples and Comparative Examples were manufactured, and the occurrence of buckled cans was calculated by confirming the presence or absence of buckling.

* Evaluation of Wax Stain In aluminum cans, the outer surface side of the neck-in forming part was visually checked for black stains, and the same wax-stained substance after starting the forming using the same neck-in forming tool 44 was used. It was investigated whether or not it occurred from the eyes.

* Repair Coating Layer Thickness of Cut End Surface The thickness of the repair coating layer 10 was measured by taking cross-sectional photographs of a plurality of portions of the opening end 6 and enlarging them to measure the film thickness.

* Consideration Test No. 1 to Test No. 4 provided with the repair coating layer 10
Are test Nos. 5 to 5 having no repair coating layer 10.
8, the buckling occurrence rate is reduced. Note that the test
In No. 3, although the buckling occurrence rate is 0.001%, this value is in a negligible range, that is, a range in which neck molding can be performed.

In the case of aluminum cans, a test of a film-sticking can
Comparing No.4 with Test No.8, Test No.4 has a neck processing force (F2) of 20k compared to Test No.8
gf to 40 kgf. On the other hand, when the test No. 2 and the test No. 6 of the printed painted can 1 are compared, the test No.
2 is the neck processing force (F2) compared to Test No. 6.
Is reduced by 10 kgf to 30 kgf.

In the case of a steel can, a comparison between Test No. 3 and Test No. 7 of the film-sticking can shows that in Test No. 3, the neck forming force is reduced by about 30 kgf as compared with Test No. 7. You can see that. Test N for Printed Paint Can 1
Comparing o.1 with test No.5, test No.1 has a neck processing force (F2) of 20 to 3 as compared with test No.5.
It turns out that it has decreased by 0 kgf.

The repaired coating on the cut end face as a whole has a neck forming force (F2) reduced by 10 to 15%, which indicates that forming is easy. That is, an effect of suppressing buckling was observed. In addition, the cutting end face 6
No difference was found between spray coating and felt coating as the repair coating means.

Although not shown in Table 1, when the thickness of the repair coating layer 10 is more than 2.0 μm, especially in the case of a film-attached aluminum can, even if the thickness is uniform over the entire circumference, neck-in A phenomenon that wrinkles occurred in the processed portion occurred. Also,
When the thickness is less than 1.0 μm, the repair coating layer 10 is worn away by contact with the neck-in forming tool 44 during the first-stage neck-in processing, so that the effect of reducing the resistance in the second-stage neck-in processing is remarkable. I can no longer see it. Repair coating layer 1
In the test using the aqueous solution of acetone copper sulfate containing 35% of hydrogen chloride, it was found that the damage of 0 was scattered around the entire circumference.

Further, although not shown in Table 1, those without side blow were compared with the case of side blow with the repair paint 24 attached to the cut end surface 6.
However, even with the same thickness of 1.5 μm, the occurrence of wrinkles during neck-in processing is reduced by about 15
% Increased. In addition, the wax stain was confirmed only in the case of the aluminum can. However, in the case without the repair coating layer 10, the wax stain began to be noticeable from the 30,000th can in the case of the printed painted can, and in the case of the film pasted can, it was 7,000. While the wax stain starts to stand out from the can, the repair coating layer 1
It was found that those having 0 had no wax stains even in a large number of cans, and thus the repair coating layer 10 was effective.

[0079]

As described above, according to the first aspect of the present invention, a coating layer made of a thermosetting synthetic resin is formed on the entire cut end face of the opening end where the neck-in processing is performed. It has good slipperiness with the forming tool used for neck-in processing, so it is possible to suppress the occurrence of wrinkles at the opening end and the occurrence of buckling of the trunk during neck-in processing, enabling efficient continuous production. Become. Further, even if the metal base is exposed from the opening end of the can having the film bonded to the outer surface of the body, buckling of the body is reduced, and the production efficiency can be improved. Furthermore, in the body part made of aluminum can with a film attached, falling off of aluminum powder at the time of neck-in processing is reduced, and accordingly, wax and the like are not contaminated,
In addition, since aluminum powder does not adhere to the tool at the time of flange processing, continuous production of stable quality metal cans becomes possible.

According to the second aspect of the present invention, the width of the cut end surface coating layer is set to a width protruding toward the inner and outer peripheral sides of the cut end surface, and the inner and outer peripheral edges of the cut end surface are formed. Since the metal base does not come into direct contact with the neck-in forming tool, the generation of metal powder can be more reliably prevented, and the productivity of metal cans can be further improved.

According to the third aspect of the present invention, the thickness of the cut end surface coating layer is set in the range of 1.0 μm to 1.5 μm, so that the coating film can be formed by a plurality of steps of neck-in processing. Since there is no possibility that the layer is completely worn away and wrinkles do not occur in the processed part due to the excessively thick coating layer, the productivity of the metal can can be further improved.

Further, according to the invention of claim 4, in parallel with the step of applying the paint to the inner surface of the metal can, the thermosetting synthetic resin is applied to the cut end surface of the opening end of the rotating body. In the process of applying a repair paint consisting of, and pre-drying the paint for the inner surface, the repair paint uses an air flow that is substantially orthogonal to the center axis of the body and is directed from the outside to the inside in the radial direction of the body. In the process of supplying and pre-drying, and drying and baking the paint for the inner surface, the repair paint in the pre-dried state is dried and baked to form a coating layer, so that the repair paint protrudes to the outside of the trunk and is bumpy. Thus, a metal can having a configuration in which a coating layer is provided on the cut end surface of the open end can be easily and reliably manufactured without drying.

Further, according to the fifth aspect of the present invention, since the air flow is supplied obliquely from the bottom side toward the opening end side, the pressure of the air flow against the repair paint does not become excessively large. In addition, since the flow to the outer surface side of the can body is suppressed and the flow to the inner surface side of the can body is also suppressed, the desired coating film layer can be more easily formed.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a printing paint can having a repair coating layer on a cut end surface.

FIG. 2 is an enlarged sectional view showing an open end of the printing painted can.

FIG. 3 is a schematic view showing a production line according to the inventions of claims 4 and 5;

FIG. 4 is a schematic view showing an example of a repair paint applying means.

FIG. 5 is a schematic view showing another example of the repair paint applying means.

FIG. 6 is a schematic view showing still another example of the repair paint applying means.

FIG. 7 is a schematic view showing another example of the repair paint applying means.

FIG. 8 is a schematic view showing a transport conveyor and a can body in a state of being transported by the transport conveyor.

FIG. 9 is a cross-sectional view schematically showing an arrangement relationship between each member and a can body in the conveyor.

FIG. 10 is a sectional view schematically showing a neck-in forming tool.

FIG. 11 is a cross-sectional view showing an assembled state of the opening end and the neck-in forming tool during neck-in processing.

FIG. 12 is a schematic diagram showing a state in which air is press-fitted into a can body and a load tester is assembled.

FIG. 13 is a schematic view showing a state where a load is further applied.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Printing can, 2 ... Can body, 3 ... Can body, 4 ... Can bottom, 5 ... Open end, 6 ... Cutting end face, 10 ... Repair coating layer, 12 ... Coating machine, 14 ... Dry baking furnace, 22: repair paint application means, 24: repair paint, 38: blower,
40 ... Side blow.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification FI theme coat ゛ (reference) // B21D 51/26 B21D 51/26 PF term (reference) 3E061 AA15 AB04 AC01 BB18 4D075 AA01 AA67 AA82 AA85 BB24Y BB29Z CA47 CA50 DA15 DB01 DC42 EA19

Claims (5)

[Claims] 1. A metal can having a cylindrical body and a bottom integrally formed with the body with one open end of the body closed, wherein the open end of the body is provided. A metal can, characterized in that a coating layer made of a thermosetting synthetic resin is formed on a cut end face of a portion where neck-in processing is performed in a portion so as to cover the entire cut end face. 2. The metal can according to claim 1, wherein the width of the coating layer is set to a width protruding on an inner peripheral side and an outer peripheral side of the cut end surface. 3. The metal can according to claim 1, wherein the thickness of the coating layer is set in a range of 1.0 μm to 1.5 μm. 4. A metal can having a cylindrical body, and a bottom integrally formed with the body with one open end of the body closed, and a central axis of the body. Applying an inner surface paint to the inner surface of the metal can while rotating around the center,
The coated metal can is taken out of the coating machine, and the inside of the metal can is blown with hot air while rotating about the center axis of the body to dry the paint for the inner surface. In a method of manufacturing a metal can, the can is housed in a drying baking furnace with the rotation about the center axis of the body stopped, and the pre-dried inner coating is dried and baked to form an inner coating film. In the step of applying an inner surface paint to the inner surface of the metal can, a repair paint made of a thermosetting synthetic resin is applied to a cut end surface of the opening end of the body in a rotating state, and further, the inner surface In the step of pre-drying the paint,
Supplying an air flow to the repair paint from the outside in the radial direction of the opening end to the inside axis with respect to the center axis of the body to suppress the flow of the repair paint to the outer surface side of the body. A metal can, wherein, in the step of drying and baking the paint for the inner surface, the repair paint in a pre-dried state is bake-dried to form a coating layer on the cut end face. Manufacturing method. 5. The method for manufacturing a metal can according to claim 4, wherein the air flow is supplied obliquely from the bottom side of the metal can toward the opening end side.