JP2006007154A - Method for manufacturing bottle can and bottle can manufactured thereby - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a bottle can which can prevent cracking of an outer face coating in the screwing part of a bottle can during necking or screwing process and thereby improve the opening property of a cap and the re-closing property after opening and which can particularly enable a cap to be opened and closed easily even in a sterilization condition including retort treatment and the state of vending at hot. <P>SOLUTION: The method for manufacturing a bottle can involves steps of carrying out the printing of a beverage bottle can made of an aluminum alloy except a screw part after size coat baking of a formed bottomed cylindrical body; applying a coating material containing a silica type or fluorine type blocking resistant agent having an average particle diameter of 3-10 μm in an amount of 0.01-5% by weight to the resin component of an outer face coating material; carrying out necking and screwing process after adjustment of the outer face coating in a curing state of 80-96% gelation; and carrying out after-baking of at least the cap attachment part of the bottle can in a step after the screwing process. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an aluminum alloy bottle can for beverages of alcoholic beverages such as beer and soft drinks sealed with a screw cap, and prevents cracking of the outer surface coating film of the bottle can screw processing portion during processing. In addition, the cap can be opened and reopened after opening, and the cap can be easily opened and closed even under sterilization conditions including retort treatment and hot sales, and the method thereof. It relates to the bottle can manufactured by.

  Aluminum alloy bottle cans used as containers for alcoholic beverages such as beer and soft drinks are molded into bottomed cylinders by drawing and ironing molding (DI molding) of aluminum alloy plates, and then the order is slightly There is also a size coat treatment for improving the adhesion with the coating film on the outer surface and its baking step, an overcoat treatment with printing / clear varnish and its baking step, and further an inner surface coating and its baking step in order. The diameter of the opening side of the bottomed cylinder (can barrel) is reduced, and the necking process for forming the cap attachment part and the screw machining process for forming the screw part for screwing the cap onto the cap attachment part are performed in this order. Usually done.

  In the bottle can manufacturing process, the overcoat paint and the internal paint on the outer surface of the can body are baked and cured in a gas oven or the like before the necking process and the screw process. Therefore, when necking and screwing are performed in this state, there is a problem that the coating is hardened too much and cracking occurs. There was a problem of expanding. When the contents are filled in this state and the cap is screwed, it becomes prominent especially when subjected to heating such as high temperature retort treatment or hot selling, and the cracks are further expanded by moisture entering the cracked part of the coating film. In the end, the outer coating may be peeled off. When the coating film is peeled off, not only the appearance is deteriorated, but also the corrosion resistance of the bottle can is lowered and the torque at the time of opening and closing the cap is concerned.

On the other hand, if the coating is not completely cured in order to prevent cracking of the coating, and the necking is performed in a flexible state, for example, a gel fraction of about 90%, cracking can be prevented. , Blocking between the inner surface of the cap and the outer surface of the can screw part occurs, or the wax in the outer surface coating that is bleed on the surface is washed away in the cleaning process after screw processing, resulting in similar blocking. However, due to the lack of smooth sliding between the cap and screw part, there is a problem that the torque when opening the cap increases, and the torque when the valve is re-closed after opening once, which is called reseal torque. Had occurred.
In particular, adjusting the degree of hardening of the coating film by adjusting the baking condition of the coating film to prevent cracking of the coating film, coupled with the fact that the wax in the paint added as a lubricant is washed away after screw processing, High-temperature retort processing for sterilization performed after filling, high-temperature processing such as hot sale that is heated for a long time, etc., and the coating state (incomplete curing state) in which the curing state of the screw outer surface of the bottle can is adjusted, In order to promote blocking by mutual fusion of the paint on the inner surface of the cap, it was impossible to completely avoid the occurrence of extremely high torque when opening and closing the cap.

  In the conventional necking processing and screw processing of bottle cans and the like, in order to prevent cracking of the outer coating film, a proposal to form a medium layer or the like in advance on the surface on which the screw portion is formed (see, for example, Patent Document 1) In order to repair cracks and the like of the inner surface coating film, a proposal to apply a corrected inner surface coating to the top surface of the mouth portion and / or the inner surface of the mouth portion (see, for example, Patent Document 2), or the surface of the can base of a bottle can A coating film of the first layer formed below the screw portion and the screw portion on the surface of the formed can base, and a plurality of layers of the second layer and the third layer formed in a predetermined range below the screw portion. There are proposals to prevent the cracking of the coating film by making the Young's modulus of the coating film of the first layer lower than that of the third layer (for example, see Patent Document 3). Consider to improve the torque when opening and closing That is not.

JP 2003-181577 A JP 2003-011979 A JP 2003-205945 A

  The present invention prevents the occurrence of coating film cracking of the outer coating film in necking and screw processing by adjusting the hardening state of the outer coating film prior to necking and screw processing in the manufacture of aluminum alloy bottle cans. In addition, by adding an anti-blocking agent to the outer coating film, blocking of the outer coating film whose curing state is adjusted and the coating film on the inner surface side of the cap is prevented, the slipperiness is improved, and the cap is easy to open and close. It aims at development of the manufacturing method of the aluminum alloy bottle can for drinks, and the bottle can manufactured by this method.

The present invention
[1] In the manufacturing process for beverage aluminum alloy bottle cans, the molded bottomed cylindrical body is size-coated and baked, then printed without the threaded portion, and then painted with a paint with an antiblocking agent added. Then, the outer surface coating film is adjusted to a cured state with a gel fraction of 80 to 96% and subjected to necking and screw processing, and at least the cap mounting portion of the bottle can is after-baked at a stage after the screw processing. A method for producing a bottle can characterized by

    [2] As the anti-blocking agent, a paint in which 0.01 to 5% by weight of a silica-based or fluorine-based anti-blocking agent having an average particle diameter of 3 to 10 μm is used with respect to the resin content of the outer surface paint is used. The method for producing a bottle can according to [1] above,

[3] The method for producing a bottle can according to [1] or [2], wherein the after baking is performed at a stage after completion of a cleaning process performed after screw processing,
[4] The method for producing a bottle can according to any one of [1] to [3], wherein the after baking is applied only to a local part of a cap attachment portion of the bottle can,
[5] The bottle can manufacturing method according to any one of [1] to [4], wherein the after baking is performed using a near infrared lamp,

[6] A bottle can in which the outer surface paint to which the anti-blocking agent of the cap attachment portion is added after being baked is in a cured state with a gel fraction of 97% or more,
[7] The above [6], wherein the anti-blocking agent is uniformly dispersed at least in the outer surface coating film of the screw portion, and a lubricating component such as wax in the outer surface coating is bleed on the surface of the cap mounting portion. Bottle cans,
By solving this problem, the above problems were solved.

  The present invention adjusts the state of hardening of the coating film of the outer surface coating material to which an antiblocking agent has been added prior to the necking process and screw processing performed after painting and baking in the aluminum alloy bottle can manufacturing process for beverages. Hot sale where high temperature retort treatment and long-time heating are performed while necking and screwing are applied in a cured state where the gel fraction of the film is 80 to 96% to prevent cracking of the outer coating film during diameter reduction processing Etc., it is possible to prevent blocking between the outer surface coating film and the cap inner surface coating film in which the cured state is adjusted.

Furthermore, at the stage after screw processing, the outer surface coating film can be almost completely cured (gel fraction is 97% or more) by post-baking at least the cap mounting part of the bottle can. The torque can be lowered and the cap opening performance can be improved.
In this case, heating by after-baking is applied not only to the entire bottle can but only to the local area of the cap mounting part, thereby preventing deterioration of the inner surface paint due to excessive heating and preventing thermal deterioration of the aluminum material. Strength deterioration can be prevented. In particular, when after-baking is performed using a near-infrared lamp, it is effective as a means for locally heating the cap mounting portion. Thereby, the cap opening property and the re-opening and closing property by external coating after printing can also be improved.

Hereinafter, an example of the can manufacturing process of the bottle can according to the present invention will be described with reference to FIG. 1, but the method of the present invention can also be applied to other can manufacturing processes.
For bottle cans, a round blank is punched out of an aluminum alloy plate coated with lubricating oil wound in a coil shape, and a cup is formed using a press, etc., and a bottomed cylindrical body is formed by drawing and ironing (DI processing). And After trimming the opening of the cylinder, the lubricating oil on the inner and outer surfaces of the can body is removed by degreasing and cleaning, and after the chemical conversion film treatment is performed, the cylinder is dried.

After that, size coat (10-30 mg / dm ² ) and its baking process, printing / overcoat (45-100 mg / dm ² ) and its baking process, inner surface coating and baking process, necking process (trimming process, skirt molding) ) And threading process (including curl / slot forming), and then washing and drying, which is usually a bottle can product. In the present invention, the hardening state of the outer coating film is adjusted to 80% as a gel fraction by adding an anti-blocking agent to the paint used for the outer coating film (overcoat) in the can making process and adjusting the baking process. It is characterized in that it is set to ˜96%, and the outer surface coating film is cured to a gel fraction of 97% by post-baking in the stage after threading. Preferably, after-baking is performed after cleaning and drying performed after threading.

Thermosetting resin made of polyester resin, epoxy acrylate resin (also referred to as vinyl ester resin), epoxy resin, acrylic resin, amino resin, phenol resin, etc. is used for the outer surface of the bottle can. Is done.
For these exterior paints, for example, paints to which lubricants such as lanolin and carnauba wax, minerals such as paraffin, mineral wax such as paraffin, synthetic wax such as polyethylene wax, or silicone resin are added are used. The coating film hardness, slipperiness and flexibility change depending on the heat history to be cured. In the present invention, together with these lubricants, a particulate or powdery anti-blocking agent such as silica or fluorine is added.

In order not to generate cracks in the outer surface coating film, the hardening state of the outer surface coating film during necking and screw processing after coating and baking is important, and the gel fraction of the outer surface coating film is 80 to 96%, especially 85 to 92% is preferable, and the processing should be performed in a cured state within this range.
When the gel fraction is less than 80%, the coating film is too soft, and the coating film may be damaged during necking and screw processing. Conversely, if it exceeds 96%, the coating film may be cracked or peeled off during processing. Examples of the method for adjusting the outer surface coating film to the above-described range of the gel fraction include a method for adjusting baking conditions (temperature and time) using a gas oven or the like after the outer surface coating and after the inner surface coating. Generally, the baking condition of the outer coating is 190 ° C. or more × about 20 seconds, and the baking condition of the inner coating is 200 ° C. or more × 60 seconds, but it is necessary to perform under slightly lower conditions than these baking conditions. . Another method for adjusting the gel fraction is a method of blending a small amount of a curing agent such as an amino resin contained in the outer coating.

  However, the bottle can manufactured under these conditions does not have sufficient coating film hardness, so in the retort sterilization process after filling the contents, the outer surface paint of the bottle can and the inner surface of the cap are blocked, and the cap is opened. There is a concern of causing a problem that the torque becomes higher. However, the anti-blocking agent such as silica or fluorine is added to the exterior paint in advance to improve the slipperiness of the exterior paint surface, and the torque when opening the cap even after sterilization conditions including retort treatment. And the torque at the time of re-opening / closing plug can be greatly reduced, and the problem of blocking can be solved.

  As for the anti-blocking agent, preferably a silica-based or fluorine-based anti-blocking agent is added in an amount of 0.01 to 5% by weight, preferably 0.05% to 0.5% by weight, based on the resin content of the outer coating. is there. The antiblocking agent preferably has an average particle size of 3 to 10 μm, particularly 4 to 5 μm. When the addition amount is less than 0.01% by weight, the effect of blocking resistance is diminished, and when the addition amount is more than 5% by weight, the coating film itself may be turbid. Further, when the average particle size is less than 3 μm, the effect of blocking resistance is reduced, and when the average particle size is more than 10 μm, the particles are excessively projected from the coating film, and the smoothness of the coating film surface In addition, there is a risk that coating film scraps may adhere to the guide of the conveyance system of the bottle can production line.

  Next, the cap mounting part where the outer coating film is incompletely cured due to necking and screw processing is post-baked in the process after screw processing, so that the performance of the paint can be fully exhibited. . By this after-baking treatment, the coating film hardness increases to a cured state with a gel fraction of 97% or more (pencil hardness of about 4H), and a lubricant such as wax contained in the coating bleeds to the surface. As a result, it was found that the problem that the torque at the time of opening the cap becomes high can be solved. In particular, when an after baking process is performed after the cleaning process performed after screw machining, the lubricant that bleeds on the coating film surface by baking remains particularly preferable. Further, when afterbaking is performed only on the cap mounting portion of the bottle can, it is preferable because side effects such as a decrease in buckling strength of the bottle can do not occur. However, the entire bottle can can be afterbaked.

  At the time of after-baking, as shown in FIG. 2 (showing only heating of the cap mounting portion), a method of heating the bottle can 1 while rotating it with the rotating machine 2 in the circumferential direction of the can is preferable, but the whole is heated. The method is also possible. When using near-infrared lamp 3 (with a peak wavelength of about 0.8 to 2.5 μm) as a heating means, unlike the gas oven, baking with near-infrared is a part where the near-infrared is rotating at a pin point. Since it is irradiated, the heating of the can body is suppressed by not applying heat to the entire can, and there is also an advantage of suppressing the decrease in the buckling strength of the side wall. However, the heating means is not limited to near infrared rays, and other heating means such as far infrared heating and general gas oven heating are also possible.

[Measuring method]
(Torque measurement method)
1st torque: Torque from the beginning of turning the cap to the point where the torque rises and drops when the bottle can is tightened, treated at 123 ° C for 23 minutes and then opened at 60 ° C.
2nd torque: Torque after the 1st torque until the bridge of the skirt is cut.
Reseal torque: Maximum torque when the cap is re-opened after opening (however, the torque until the cap before the opening origin is turned in the closing direction, and the torque near the opening origin) Is different)

(Gel fraction of coating film)
A sample is cut into 5 cm × 5 cm, extracted with a toluene solution (100 ° C.) for 30 minutes and then left in a desiccator for 1 hour to measure.
The weight of the coated plate before extraction (= A) and the weight of the coated plate after extraction and drying (= B) are defined as the difference (A−B = C).
The paint film is peeled off from the painted plate after extraction and drying (scraped with a sugar cube soaked with acetone), and the weight of the plate is measured (= D). The gel fraction is determined by the following formula.
Gel fraction (%) = 100− [100 × C / (AD)]

(Examples 1-3)
Size coating treatment and baking (190 ° C x 20 seconds) is applied to the outer surface of a bottomed cylindrical body manufactured by a normal can-making process, and predetermined printing is performed thereon. An overcoat (outer surface coating) with a paint containing a polyester resin to which a blocking agent was added in the ratio shown in Table 1 was performed, and baked in a gas oven at 190 ° C. for 15 seconds. Next, the inner surface was coated with an epoxy-acrylic resin, and was baked at 200 ° C. for 50 seconds in a gas oven.
When the gel fraction of the outer surface coating film was measured in carrying out the necking process, the curing degree as shown in Table 2 was shown.
Necking processing and screw processing were performed on the cylindrical body that had been subjected to painting and baking treatment, and then washed and dried.

Then, only the cap attachment part of the bottle can body was subjected to an after baking process of 230 ° C. or more × 20 seconds using near infrared rays (peak wavelength: 1.2 μm). For the after baking process, the near infrared irradiation conditions were a distance of 50 mm from the near infrared lamp (manufactured by HIBEC, model: HYP100-28, 1960 watts), rotation of the can 40 rpm, and angle of the can 90 degrees with respect to the lamp light.
When the surface state of the outer surface coating film of the cap mounting portion of these bottle cans was observed with the naked eye, no defects such as cracks in the coating film were found.
These bottle cans were capped after filling with water on a trial basis, subjected to a retort treatment at 123 ° C for 23 minutes, and then opened and reopened at 60 ° C. The results are shown in Table 2.

(Comparative Examples 1-3)
The outer surface of the bottomed cylindrical body manufactured in the same manner as in the example was subjected to size coating and baking in the same manner as in the example, and predetermined printing was performed thereon, and a silica-based or fluorine-based anti-blocking agent was listed in Table 1. External coating and baking were performed with the external coating added at the ratio shown in FIG. 1, and internal coating and baking were performed in the same manner as in the examples. When the gel fraction of the outer surface coating film was measured in carrying out the necking process, the curing degree as shown in Table 2 was shown.
The cylinder subjected to the coating and baking treatment was subjected to necking processing, screw processing, cleaning and drying, and was not subjected to after baking.
When the surface state of the outer coating film on the cap mounting portion of this bottle can was observed with the naked eye, no defects such as cracks in the coating film were found.
A filling test was performed on these bottle cans in the same manner as in the example, and changes in the opening torque and the reopening torque were measured. The results are shown in Table 2.

(Comparative Example 4)
A size coat treatment / baking was performed in the same manner as in Comparative Example 1 except that no anti-blocking agent was added to the outer coating, and predetermined printing was performed thereon, followed by outer coating / baking, and inner coating / baking. When the gel fraction of the outer surface coating film was measured in carrying out the necking process, the curing degree as shown in Table 2 was shown.
The cylinder subjected to the coating / baking treatment was subjected to necking processing, screw processing, cleaning and drying, and afterbaked in the same manner as in the example.
When the surface state of the outer coating film on the cap mounting portion of this bottle can was observed with the naked eye, no defects such as cracks in the coating film were found.
A filling test was performed on these bottle cans in the same manner as in the example, and changes in the opening torque and the reopening torque were measured. The results are shown in Table 2.

From the above results, it is possible to prevent cracking of the outer coating film by adjusting the gel fraction, and in Table 2, by adding an anti-blocking agent to the outer coating material and after baking, the first torque · 2nd compared to the comparative example. Both torque and reseal torque decreased.
As a result, the adjustment of the gel fraction was effective in preventing cracking of the outer coating film, and the addition of an anti-blocking agent and after-baking were effective in reducing the opening torque and the replugging torque. .

  In the production of beverage aluminum bottle cans, the present invention prevents the occurrence of coating film cracking and peeling of the outer coating film during necking and screw processing, and at the same time, the outer coating film of the screw portion and the cap inner surface side. Improves slipperiness with the coating film, prevents blocking, improves lubricity by bleeding of lubricants such as wax, improves slipperiness, makes the cap easy to open and close, sterilization treatment including retort treatment and hot sale Even under such circumstances, it was possible to provide a method for producing a beverage aluminum alloy bottle can that can be easily opened and closed, and a bottle can produced by the method.

An example of a bottle can manufacturing process Heating method for bottle can screw

Explanation of symbols

1 Bottle can 2 Rotating machine 3 Infrared lamp

Claims (7)

In the aluminum alloy bottle can manufacturing process for beverages, after the size-bottomed cylindrical molded body is size-coated and baked, it is printed except for the threaded portion, and then coated with a paint added with an anti-blocking agent. The outer surface coating film is adjusted to a cured state with a gel fraction of 80 to 96%, and is subjected to necking processing and screw processing, and at least the cap mounting portion of the bottle can is after-baked at the stage after the screw processing. To make bottle cans. The coating material which mix | blended 0.01 weight%-5weight% of silica type or fluorine type antiblocking agents with an average particle diameter of 3-10 micrometers as an antiblocking agent with respect to the resin content of an outer surface coating is used. The manufacturing method of the bottle can of description. The method for manufacturing a bottle can according to claim 1 or 2, wherein the after-baking is performed at a stage after completion of a cleaning process performed after screw processing. The manufacturing method of the bottle can of any one of Claims 1-3 WHEREIN: The said after baking is given only to the local part of the cap attachment part of a bottle can, The manufacturing method of the bottle can characterized by the above-mentioned. 5. The bottle can manufacturing method according to claim 1, wherein the after baking is performed using a near infrared lamp. 6. A bottle can in which the outer surface paint added with a blocking-resistant agent in the cap mounting portion is in a cured state with a gel fraction of 97% or more by after-baking. The bottle can according to claim 6, wherein the anti-blocking agent is uniformly dispersed in at least the outer surface coating film of the screw portion, and a lubricating component such as wax in the outer surface coating is bleed on the surface of the cap mounting portion.

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