JP2005296998A - Can-manufacturing method for preventing growth of hair crack - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent coating hair and film hair generated when manufacturing a drawn can, a re-drawn can, and a re-drawn and ironed can which are formed of a metallic sheet having an organic coating layer as material. <P>SOLUTION: In a method for manufacturing a metallic container by cup-forming or draw-ironing by using a metallic sheet with at least one side thereof coated with resin film, laser beam irradiation is performed before or after cup-forming, and a part of a surface-coated resin layer is removed to prevent hair growth. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a can manufacturing method for forming a can body from a plate material having an organic coating layer formed on at least one side of a substrate, and more specifically, a plate material having an organic coating layer formed on at least one side of a substrate. The present invention relates to a can-making method for preventing coated hair and film hair generated when a drawn can, redrawn can, and redraw-ironed can are produced as materials.

  Drawing cans used for carbonated beverage cans, juice cans, coffee beverage cans or food cans such as solid food cans such as jelly {for example, Japanese Patent Publication No. 60-11576 (Patent Document 1)} Molded cans {for example, JP-A-3-155419 (Patent Document 2), JP-A-4-324826 (Patent Document 3)}, thinned redraw-ironing can {for example, JP-A-7-275961 When forming a seamless can such as (see Patent Document 4) and a can lid {for example, see Japanese Patent Publication No. 3-58814 (Patent Document 5)} or the like, at least one side (usually both sides) of the metal layer is organic. A blank is punched out of the plate material on which the coating layer has been formed with a punch and die, and immediately after drawing in the same process to form a drawn molded body, a seamless can body and can lid are formed in the next process. The law has been adopted.

  Japanese Patent Application Laid-Open No. 58-16848 discloses an edge of a seamless can or can lid formed in this way (in the case of a seamless can body, the edge of a flange portion, in the case of a can lid, the edge of a curled portion). As described in (Patent Document 6), a large number of hair-like organic coating pieces (hereinafter referred to as organic coating hairs: usually about 10 mm or more in length) are likely to occur. This organic coated hair peels off from the edge, remains attached to the inner surface of the can, is filled and sealed with the contents, and can be found as a foreign object, but in that case the hair itself is harmless However, it is suspected of being unsanitary and is subject to complaints. For this reason, cans with organic coating hair found by 100% inspection are rejected. Therefore, in this case, there arises a problem that the product yield is lowered.

In addition, the organic film hair on the can lid may enter the can during sealing. In addition, it may fall off during the can manufacturing process, get into the space between the tool and the can body, and cause a film defect, resulting in a problem of quality deterioration of the can body and can lid.
The cause of the occurrence of organic film hair is as described in JP-A No. 2000-167625 (Patent Document 7), and is explained in detail by taking as an example the production of a thinned redrawn-ironed can.

  When punching into a blank as a hair prevention method, at least at the time when the plate material and the punch come into contact with each other and start punching, the punching edge of the punch edge face near the edge of the punch is near the punch. There is a disclosure (Patent Document 7) of a tool set so that the angle formed with the tangent line is 3 to 60 degrees. However, when the cutting edge is worn, especially when the organic film is thick or soft, these tools are disclosed. The reality is that the proposal cannot completely prevent hair. Further, as an example in which laser irradiation of a can material is proposed, a proposal for removing an unnecessary resin by irradiating an infrared pulse laser to a resin-free portion of a material for a welding can {Japanese Patent Laid-Open No. 7-290258 (Patent Document) 8)}.

Japanese Patent Publication No. 60-11576 Japanese Patent Laid-Open No. 3-155419 JP-A-4-324826 JP-A-7-275961 Japanese Patent Publication No. 3-58814 JP 58-16848 A JP 2000-167625 A JP 7-290258 A

  The present invention relates to coating film hair and film hair generated when producing a drawing can, a redrawing can, and a redrawing-ironing can using a plate material having an organic coating layer formed on at least one side of a substrate. It is an object of the present invention to provide a method for preventing canning.

(1) After shearing a metal plate coated with a resin film on at least one side, and then performing draw forming and draw ironing to manufacture a metal container, laser irradiation treatment is performed before or after draw forming, and in the vicinity of the shearing portion. A can-making method in which hair generation is prevented, wherein at least part of the resin layer is removed.
(2) When laser irradiation is performed before drawing, at least a part of the area between the shear line at the time of drawing and the line inside the thickness of the metal plate from the shear line is at least on one side of the metal plate. Laser irradiation is performed in a ring shape having a width of 0.1 to 10 mm including the circumference, and at least a part of the resin layer on the metal plate surface is removed, and the resin film thickness remaining on the portion subjected to shearing is 0 to 10 μm. A can-making method in which hair generation is prevented as described in (1) above.

(3) In the case of laser irradiation after drawing, the metal cup surface resin layer includes a cup upper end on at least one side of the drawn metal cup and laser irradiation is performed at a width of 0.1 to 10 mm from the upper end. The can-making method according to (1), wherein at least a part of the resin film is removed and the thickness of the resin film remaining on the upper end of the cup is 0 to 10 μm or less.
(4) The can manufacturing method as described in (1) to (3) above, wherein the laser beam is a CO ₂ laser beam that oscillates at a wavelength indicating absorption in the infrared region of the resin.

(5), wherein the laser light is TEA, or Q-switched CO ₂ laser or a continuous wave CO ₂ laser pulse modulation oscillation mode, or a continuous wave CO ₂ laser oscillates at a wavelength showing an absorption in the infrared region of the resin The can manufacturing method which prevented hair generation | occurrence | production as described in said (1)-(4).
(6) The laser light, wherein the laser fluence is not less than the evaporation threshold value of the resin and not more than the threshold value of the surface damage of the base material of the resin-coated metal plate. (5) The can-making method which prevented generation | occurrence | production of the hair.
(7) The method for producing a can preventing hair generation according to the above (1) to (6), wherein the coating resin is a polyester-based resin, a polypropylene-based or a polyethylene-based polymer material.

  According to the present invention, it becomes possible to carry out can making without generation of hair in the can-making process of the resin-coated metal plate, and the can-making operation can be carried out without causing a problem of reduction in product yield and quality of can bodies and can lids. Became.

The present invention relates to a method for producing a metal container by drawing and drawing and ironing using a metal plate coated on at least one side with a resin film. It is a can-making method for preventing hair generation, characterized in that a part of a coated resin layer is removed.
As a means for preventing the hair in the process of making a resin-coated metal plate, the inventors have found in advance that it is very effective to remove the resin film of the part that becomes the hair. The inventors have also found that it is efficient to irradiate a laser, and have completed the present invention.

Furthermore, the inventors have also found that removal of the resin film on the upper end of the cup in the cup state, which is a stage before redrawing and ironing, is also very effective as a measure for preventing hair, and laser is used as a means for removing it. It has been found that it is efficient to irradiate.
Since the hair is generated from the portion corresponding to the end face when the resin-coated metal plate is sheared, the hair is removed by removing the resin film corresponding to the end face in the state of the resin-coated metal plate or the cup. Can be prevented.

  When irradiating a laser in a resin-coated metal plate state, irradiation is performed in a ring shape having a width of 0.1 to 10 mm along a shear line at the time of drawing. A width of 2 to 7 mm is preferable. A position including at least a part of a region between the shear line at the time of drawing and a line inside the metal plate by the thickness of the shear line is preferable. Even when only the inner part of the sheet thickness is irradiated from the shear line, the resin on the shear line adheres to the skeleton (remaining part where the metal plate is sheared) due to deformation of the metal plate during shearing. It may be demonstrated. It is preferable to include the shear line over the entire circumference. (Refer FIG. 8) When irradiating a laser to an end surface in the state of a cup, irradiation with a width of 0.1-10 mm is performed over the perimeter of the end surface of a cup.

  In both the metal plate state and the cup state, the upper limit of the width of the resin film to be removed by irradiating a laser affects the trim length of the final can body. If it exceeds 10 mm, the effect of preventing hair is completely saturated, the trim length becomes too long, and the loss of the material to the can becomes too large, which is not preferable. If the lower limit is 0.1 mm or less, the effect of preventing hair is incomplete, which is not preferable. Preferably it is 2-7 mm.

  Further, it is most desirable that the resin film thickness remaining after laser irradiation is 0 μm, that is, it is completely removed, but even if it is not completely 0 μm, it is effective in preventing hair generation. Although it is desirable that the thickness is 0 to 5 μm, the effect appears even when 5 to 10 μm, which is a fairly incomplete removal. This is because a thin resin film usually has a thickness of about 12 μm, but if it is thinned to 10 μm or less by a laser, if the edge is squeezed with a tool, the resin will be a metal edge. This is thought to be because it is difficult to be cut.

Next, the principle of resin film removal by laser will be described. The resin film is removed by melting and evaporating the resin by the energy of the laser beam. Therefore, the laser energy density needs to exceed a certain intensity. That is, it is necessary that the energy density per unit area of the laser beam exceeds the resin evaporation / melting threshold. This energy density is called laser fluence. When a pulse laser is used, assuming that the pulse energy is E [J] and the area of the focused laser beam is S [cm ² ], the fluence F is defined by the following equation. A diagram showing the definition is shown in FIG.
F = E / S [J / cm ² ]
The threshold laser fluence for general resin evaporation / melting is 1 J / cm ² or less.
Furthermore, it is efficient to use laser light having an absorption wavelength of the resin film.

FIG. 2 shows light transmittance characteristics in the infrared wavelength region of 900 to 1200 cm ⁻¹ of a PET film 30 μm thick, which is a representative thermoplastic resin used for the resin-coated metal plate. In FIG. 2, the horizontal axis represents the wave number [cm ⁻¹ ] which is the reciprocal of the wavelength, and the vertical axis represents the light transmittance. As is apparent from FIG. 2, the PET resin has wavelengths (A) to (F) with high absorption at which the transmittance is significantly reduced. This is due to resonance absorption between vibration modes such as C—H and C—O bonds in the PET molecule and infrared light of a specific wavelength. Therefore, by irradiating laser light with wavelengths (A) to (F) having relatively high absorptance, energy can be efficiently supplied to the PET molecules in a resonant manner, and vibrational excitation can be performed.

  Here, if a pulse laser beam having a short pulse time width and a large energy and a high peak output is used as the incident laser beam, the molecule absorbs a large number of photons (photons) in an instant and dissociates in multiple stages. Vibrationally excited to a high energy state. As a result, the chemical bond having the weakest binding force in the molecule is broken, and the molecule is decomposed and evaporated. Such a molecular excitation / dissociation phenomenon by infrared pulsed laser light is called infrared multiphoton dissociation. The phenomenon in which decomposed resin is evaporated and scattered and removed is called laser ablation. By using infrared pulse laser light, it is possible to remove the resin film more efficiently.

Next, the laser fluence [J / cm ² ] required for laser ablation will be specifically described. FIG. 3 shows the relationship between the laser fluence and the removal depth per unit pulse when the PET resin-laminated steel sheet is irradiated with a TEACO ₂ laser pulse described later to remove the PET resin. Here, a laser wavelength of 9.2715 μm belonging to the wavelength region (B) having a relatively large absorption rate in FIG. 2 was used. From FIG. 3, it can be seen that the laser ablation ability is increased by the increase of the laser fluence, and it is possible to remove 10 μm or more per unit laser pulse with a laser fluence of about 5 J / cm ² . Since the resin thickness of the resin-coated metal plate is generally about 12 to 100 μm, the resin film can be completely removed by laser irradiation of about 10 pulses.

In order to induce laser ablation, it is necessary to supply a minimum molecular dissociation energy. Therefore, there is a laser fluence threshold for laser ablation depending on the type of resin and the laser wavelength. It is predicted from FIG. 3 that the threshold value when a laser beam having a wavelength of 9.2715 μm is used for PET resin is about 1 J / cm ² or less.
Next, the laser used in the present invention will be described. The infrared wavelength region described above matches the oscillation wavelength region of the CO ₂ laser. Therefore, laser ablation can be induced by using a pulsed CO ₂ laser. In addition, the CO ₂ laser is one of the most well-established lasers at present, and is optimal for the industrial use purpose of the present invention.

The CO ₂ laser has 100 or more oscillation lines over a wavelength range of 9 to 11 μm (wave number 900 to 1090 cm ⁻¹ ), and the oscillation wavelength can be selected by using a wavelength selection element such as a diffraction grating. FIG. 2 also shows a schematic diagram of the oscillation line of the CO ₂ laser. Here, since the interval between the adjacent oscillation lines is about ¹ to 2 cm ⁻¹ , subtle wavelength selection is possible in accordance with the wavelength that is highly absorbed by the resin.

The main methods for obtaining pulsed light in a CO ₂ laser include a TEA (Transversally Excited at Atmospheric Pressure Lateral Excitation Atmospheric Pressure Operation) method and a Q-switch method. Although the former has a limit in pulse repetition capability at a practical level, it is possible to obtain a pulse energy of 10 J / pulse or more and a peak output of 50 MW or more, so a high laser fluence over a relatively large area with a unit laser pulse. It is possible to obtain a region.

  On the other hand, as apparent from FIG. 3, the film thickness of the resin to be removed increases as the laser fluence increases. Therefore, the TEA laser is suitable for removing the resin at a specific point on the metal plate in a short time. On the other hand, in the Q switch method, the pulse energy is generally 1 J / pulse or less, and in order to obtain a laser fluence sufficient for laser ablation, it is necessary to narrow the laser beam cross-sectional area with a lens or the like. The laser ablation area becomes smaller. However, the pulse repetition frequency can be 10 kHz or higher, and can be used for high-speed can manufacturing.

By the way, as another method for obtaining a pulse laser in a CO ₂ laser, there is a pulse oscillation mode obtained by pulse-modulating an excitation discharge of a continuous wave laser. In this case, the peak output of the obtained pulsed light is generally 20 kW or less, and the pulse time width becomes a long pulse exceeding 10 μs. Therefore, it was usually considered unsuitable for laser ablation removal.

However, if the absorption coefficient of the laser beam of the resin material that is symmetrical to be removed is sufficiently large, sufficient energy is supplied to the resin for evaporation removal even at a low peak output, and the heat transfer coefficient of the resin is sufficiently small. It was found that even a long pulse laser beam can be removed with a sharp cross section without affecting the periphery. For example, a polyethylene-based polymer material containing a PET resin or some additives therein has a very large absorption with respect to a CO ₂ laser as shown in FIG. 2, and a thermal conductivity of about 0.37 W / m · K. And small. As a result, removal processing with a clean removal cross section is possible even in the pulse modulation mode of a continuous wave laser.

Furthermore, a continuous wave laser is also applicable if a certain fluence or more can be obtained. The definition of the fluence F [J / mm ² ] in the case of a continuous wave laser is as follows: the average power of the continuous wave laser is P [W] = [J / s], and the scanning speed of the laser beam is V [cm / s]. When the beam shape is d ₁ , d ₂ [cm] and the beam area is S = π / 4 (d ₁ × d ₂ ) (← the area of the ellipse), it is defined by the following equation. An explanatory diagram is shown in FIG.
F = (P / S) × (d ₂ / V)

Next, a laser irradiation method will be described. FIG. 5 is an explanatory view of an example of laser irradiation to the resin-coated metal plate of the present invention. The annular laser irradiation is realized by (for example) circumferential scanning irradiation of a laser beam. A laser beam output from a CO ₂ laser device (not shown) is reflected by two scanning mirrors. The reflected beam is focused on the laminated steel plate by the fθ lens. Here, the two scanning mirrors vibrate in directions orthogonal to each other by a galvano motor (not shown), and the vibration angle is electrically controlled, so that the laser beam can be scanned in an annular shape on the irradiation plane.

FIG. 6 is an explanatory view of an example of laser irradiation to the upper part of the cup after the cup molding of the present invention. It is an example which scans the laser beam side similarly to FIG. The laser beam is incident at an oblique angle due to incidence on the inner wall of the can, and the irradiation power density is reduced by that amount, but removal similar to that on a flat plate is possible by increasing the incident power and reducing the scanning speed. . Apart from this example, it is also possible to scan (rotate) the cup with the laser irradiation position fixed.
In either method, when a pulse laser is used, the resin having a desired thickness can be removed by appropriately adjusting the beam scanning speed and the pulse repetition frequency. Also, when using a continuous wave laser, the desired removal is performed by controlling the fluence by appropriately adjusting the power, the scanning speed, and the condensing shape according to the above formula.

As described above, the resin film at an arbitrary position of the resin-coated metal plate can be removed in a short time by using laser light.
In the present invention, since the resin removed by laser irradiation evaporates, there is no problem of generation of resin cutting waste that has been a problem in mechanical scraping. Furthermore, since the scattered resin can be quickly removed from the laser beam path by spraying the assist gas near the laser irradiated part, problems such as absorption of the laser beam by the scattered resin and other removed resin are also easy. Can be solved.

Also, the laser ablation threshold laser fluence of the resin is 1 J / cm ² or less, and several J / cm ² is sufficient for laser ablation. However, such low laser fluence is a surface treatment such as plating. Below the damage threshold. Therefore, in the present invention, by appropriately selecting the laser fluence, only the surface resin can be selectively removed without damaging the base surface treatment.

The metal plate is not particularly defined as long as it can adhere to the resin and ensure ironing performance, but as a technique widely applied to metal strips for containers, It is desirable to perform surface treatment with chromic acid, dichromic acid, phosphoric acid, organic acid or the like in advance. Application examples include aluminum, aluminum alloys, tin-free, chromium-plated steel sheets, nickel-plated steel sheets, phosphoric acid-treated steel sheets, organophosphoric acid resin-treated steel sheets, tin-plated steel sheets, and tin-nickel plated steel sheets.
Here, the removal of the PET resin has been described as an example, but the PP resin also has absorption in the infrared wavelength region as shown in FIG. Therefore, the resin used for PP and other resin-coated metal plates can be used to remove a resin having absorption in the infrared wavelength region. It can also be applied to painted metal plates.

Hereinafter, the effects of the method of the present invention will be specifically described with reference to Examples, but the present invention is not limited thereto. The molding method / evaluation method performed in this example is as follows. (1) For drawing and ironing can molding, blank drawing is performed with a blank diameter of 142mm, a cup is molded with a first drawing ratio of 1.6, then redrawing with a 2nd drawing ratio of 1.3, and ironing is performed in three steps. A drawn and ironed can with a body diameter of 65.8 mm was formed. The forming speed of redrawing and three-step ironing is 100 cpm. The total ironing rate was three conditions of 30, 45, and 66.7%.
(2) The can lid was formed by blanking draw with a blank diameter of 85 mm to form a can lid of φ200.
(3) The hair evaluation method evaluated the presence or absence of hair by visually observing the end face of the can body after the ironing forming in three steps.
(4) The resin film thickness was obtained by dissolving a metal plate with hydrochloric acid and measuring the thickness of the isolated film with a micrometer.

(Example 1)
Example 1 will be described with reference to FIG.
For the resin-coated metal plate 1, an electrolytic chromic acid-treated steel plate having a thickness of 0.23 mm was used as a base material. The adhesion amount of metallic chromium is 110 mg / m ² , and the adhesion amount of hydrated chromium oxide is 15 mg / m ² in terms of metallic chromium. A 25 μm PET film was laminated on one side of the steel plate and a 15 μm PET film was laminated on the other side by a thermal lamination method. Both surfaces of this resin-coated metal plate were irradiated with an infrared pulse laser in an annular shape having an inner diameter of φ137 mm and an outer diameter of φ146 mm so that the front and back centers coincided. A TEACO ₂ laser was used as the infrared pulse laser device 2. The pulse energy is 2.5 J / pulse and the peak power is about 20 MW. In this laser apparatus, the total reflection mirror of the laser resonator is replaced with a diffraction grating as a wavelength selection element, and the laser oscillation wavelength can be selected.

In this embodiment, the laser oscillation wavelength is selected at a wavelength of 9.2715 μm (wave number 1078.57 cm ⁻¹ ) belonging to the wavelength region (B) having a relatively high light absorption coefficient in the infrared light transmittance characteristics of PET in FIG. did. As shown in FIG. 5, the laser beam was irradiated with a circumferential scan. A beam output from a CO ₂ laser device (not shown) is reflected by two scanning mirrors, and the reflected beam is focused on a resin-coated metal plate by an fθ lens. By oscillating in directions orthogonal to each other and electrically controlling the oscillation angle, the laser beam was scanned in an annular shape on the irradiation plane. The laser fluence was adjusted to 3.6 J / cm ^{2 at} which laser ablation can occur sufficiently. The resin film on the irradiated part was almost completely removed by evaporation. When 100 cans were molded under the molding conditions described above and the occurrence of hair was evaluated, no generation was observed.

(Example 2) An example of laser irradiation to a cup is shown. The used cup was plated with Ni of 500 mg / m ^{2 on} both sides, then coated with aluminum pigment on one side of the surface-treated steel sheet that had been subjected to electrolytic chromic acid treatment, and 25 μm thick on the other side. It produced from the steel plate which laminated | stacked this PET resin film. In addition, the diameter of the cup was 85 mm, and the PET resin film lamination surface was used as the inner surface of the cup. FIG. 6 shows an example of a configuration apparatus, in which a Q-switched CO ₂ laser is used as laser light, and the upper end portion of the cup inner surface is continuously irradiated with a constant width laser. The pulse energy is 100 mJ / pulse and the peak output is 350 kW. The laser wavelength was selected to be a wavelength of 9.2715 μm (wave number 1078.57 cm ⁻¹ ) as in Example 1.

  A laser fluence exceeding the laser ablation threshold at the irradiation position is obtained by adjusting the laser beam to an elliptical diameter of 5 mm in the cup height direction and 0.8 mm in the circumferential direction. Further, the repetition frequency of the laser pulse was adjusted to 6.25 kHz, and the laser beam of 10 pulses or more was irradiated to the same position at the irradiation speed of 30 m / min. While rotating the cup so that the irradiation speed was 30 m / min, the 4.5 mm portion was irradiated from the upper end of the cup. The resin film on the irradiated part was almost completely removed by evaporation. 100 cans after cup molding were molded under the molding conditions described above, and the occurrence of hair was evaluated, and no generation was observed.

(Example 3)
Using the pulse modulation oscillation mode of the continuous wave CO ₂ laser, after applying Ni plating with an adhesion amount of 500 mg / m ² on both sides with the same irradiation device as in FIG. 5, on one side of the surface-treated steel sheet subjected to electrolytic chromic acid treatment Laser irradiation was performed on the PET resin film surface of a steel sheet in which a 3 μm thick coating was applied with an aluminum pigment and a 25 μm thick PET resin film was laminated on the other side. The peak output of the used pulse laser is 6.4 kW, the pulse energy is 100 mJ, the pulse time width is 25 μs, and the pulse repetition frequency is 5 kHz. The laser wavelength and laser beam were adjusted to an elliptical diameter of 0.4 mm in the laser traveling direction and 0.2 mm in the perpendicular direction. The irradiation speed is 30 m / min, and the number of incident pulses to the same point is about 10 pulses. Irradiation was performed in a ring shape having an outer diameter of 141.9 mm and an inner diameter of 141.5 mm. The resin film on the irradiated part was almost completely removed by evaporation. The cup is molded so that the PET resin film surface becomes the inner surface of the can under the molding conditions described above, and the cup shear line assumed at the time of laser irradiation coincides when the cup is molded. When a can body was molded and the occurrence of hair was evaluated, no occurrence was observed.

Example 4
Using pulse modulation oscillation mode of a continuous wave CO ₂ laser, with the same irradiation apparatus and FIG. 6, an aluminum plate (plate coated with a resin film of polypropylene of 25μm thick the PET resin film of 12μ thickness on one side to the other single-sided Laser irradiation was performed on both sides of a cup formed by molding a thickness of 0.32). The peak output of the used pulse laser is 6.4 kW, the pulse energy is 100 mJ, the pulse time width is 25 μs, and the pulse repetition frequency is 5 kHz. The laser beam is adjusted to an elliptical diameter of 10 mm in the cup height direction and 0.8 mm in the circumferential direction, the irradiation speed is 30 m / min, and the number of incident pulses to the same point is about 10 pulses. .

  The resin film of the irradiated portion was almost completely evaporated and removed on the PET film surface side, but the resin film remained on the polypropylene resin film side on the average of 10 points by about 8 μm. The cup is molded so that the PET resin film surface is the outer surface of the can under the molding conditions described above, and the cup shear line assumed at the time of laser irradiation coincides when the cup is molded. , 100 cans were molded, and the occurrence of hair was evaluated, and no occurrence was observed.

(Example 5)
For the resin-coated metal plate, an electrolytic chromate-treated steel plate having a thickness of 0.19 mm was used as a base material. The adhesion amount of metallic chromium is 110 mg / m ² , and the adhesion amount of hydrated chromium oxide is 15 mg / m ² in terms of metallic chromium. After coating 5 μmm on one side of the steel plate, a 12 μm PET film was laminated on the other side by a thermal lamination method. In the same manner as in Example 1, the resin-coated metal plate was irradiated with an infrared pulse laser in a ring shape having an inner diameter of φ83 mm and an outer diameter of φ86 mm. The resin film on the irradiated part was almost completely removed by evaporation.
The can lid is molded so that the PET resin film surface becomes the inner surface of the can under the molding conditions described above, and the shear line of the can lid blank, which was assumed at the time of laser irradiation, coincides when the can lid is molded. When 100 cans were molded and the occurrence of hair was evaluated, no occurrence was observed.

It is fluence explanatory drawing in the case of a pulse laser. It is a figure which shows the infrared-light transmission characteristic of PET resin. It is a diagram showing the relationship between the PET resin film removal depth of the laser ablation by TEACO ₂ laser according to at laser fluence and the single pulse of the PET resin film. It is fluence explanatory drawing in the case of a continuous wave laser. It is a block diagram of the apparatus used for the can manufacturing method which irradiates a laser to the resin coating metal plate of this invention. It is a block diagram of the apparatus used for the can manufacturing method which irradiates a laser to the upper end of the cup which consists of a resin coating metal plate of this invention. It is a figure which shows the infrared-light transmission characteristic of PP resin. It is a figure which shows the example of the laser irradiation position of this invention.

Claims (7)

Resin layer near the sheared part is subjected to laser irradiation treatment before or after drawing, when producing a metal container by shearing a metal plate coated with a resin coating on at least one side and then drawing and drawing and ironing. A can-making method in which hair generation is prevented, wherein at least a part of the hair is removed. When laser irradiation is performed before drawing, at least a part of the area between the shear line at the time of drawing and the line inside the thickness of the metal plate from the shear line is spread over the entire circumference on at least one side of the metal plate. In this case, laser irradiation is performed in a ring shape having a width of 0.1 to 10 mm to remove at least a part of the resin layer on the metal plate surface, and the thickness of the resin film remaining on the portion subjected to shearing is set to 0 to 10 μm. The can manufacturing method which prevented hair generation | occurrence | production of Claim 1 characterized by the above-mentioned. When the laser irradiation is performed after the drawing, at least one of the resin layers on the metal cup surface is formed by performing laser irradiation at least on one side of the drawn metal cup including a cup upper end and a width of 0.1 to 10 mm from the upper end. The can manufacturing method according to claim 1, wherein the thickness of the resin film remaining on the upper end of the cup is 0 to 10 μm or less. The can manufacturing method according to claim 1, wherein the laser beam is a CO ₂ laser beam that oscillates at a wavelength indicating absorption in the infrared region of the resin. Claims, characterized in that the laser light is TEA, or Q-switched CO ₂ laser or a continuous wave CO ₂ laser pulse modulation oscillation mode, or a continuous wave CO ₂ laser oscillates at a wavelength showing an absorption in the infrared region of the resin Item 5. A can-making method in which hair generation is prevented. 6. The hair according to claim 1, wherein the laser light has a laser fluence that is not less than a threshold value for vaporization of the resin and not more than a threshold value for surface damage of the base material of the resin-coated metal plate. A can-making method that prevents generation. The can-making method according to claim 1, wherein the coating resin is a polyester-based resin, a polypropylene-based or a polyethylene-based polymer material.

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