Resin-coated metal sheet for plastic working, and method for manufacturing metal cylindrical body with bottom using metal sheet

Abstract

To provide a resin-coated metal sheet for plastic working, on which a lubricant is applied so that when plastic working is performed using the resin-coated metal sheet, the resin coating on the metal sheet is not damaged and further, damage to the resin coating during heat treatment for removing the lubricant is effectively suppressed.SOLUTION: There is provided a resin-coated metal sheet 10 in which a coating film layer 5 made of a mixed paraffin of liquid paraffin and solid paraffin is formed on a surface of a resin coating 3 of the resin-coated metal sheet 10.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a resin-coated metal sheet for plastic working, and further to a method for producing a metal cylindrical body with a bottom (such as a metal can or a metal cup) by plastic working using the resin-coated metal sheet. [Background technology]

[0002] Generally, metal cylindrical bodies with a bottom (such as metal cans and metal cups) obtained by plastic processing of metal (such as punching, bending, drawing, and ironing) have their inner and outer surfaces coated with a resin such as polyester, which improves corrosion resistance and printability.

[0003] Incidentally, the resin-coated metal cylindrical body with a bottom as described above is naturally obtained by plastic processing using a metal plate with at least one surface coated with resin. Since such plastic processing involves severe processes such as large bending, squeezing, and ironing, a lubricant is applied to the surface of the resin coating during the processing to prevent damage or peeling of the resin coating during processing and to facilitate the removal of jigs used in the processing (see Patent Documents 1 to 3). This is because the lubricant does not function well if it is applied by a means such as a spray instead of being applied. Any lubricant remaining on the surface of the resin coating is removed by heat treatment after the required processing.

[0004] However, when a conventional resin-coated metal sheet coated with a lubricant is subjected to plastic working, the lubricant falls off during the plastic working, which results in damage or peeling of the resin coating, and furthermore, there is a problem that the lubricant builds up on the jig used in the plastic working, which easily contaminates the jig. In order to reliably avoid such problems, it is conceivable to use a lubricant with a high melting point, but in this case, the resin coating formed on the surface of the processed product is damaged by the heat treatment for removing the lubricant, and an improvement is required. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 2508910 [Patent Document 2] Patent No. 2526725 [Patent Document 3] Patent No. 3794265 Summary of the Invention [Problem to be solved by the invention]

[0006] Therefore, the object of the present invention is to provide a resin-coated metal sheet for plastic processing, which is coated with a lubricant so that when plastic processing is performed using the resin-coated metal sheet, the resin coating on the metal sheet is not damaged, and further, damage to the resin coating during heat treatment to remove the lubricant is effectively suppressed. Another object of the present invention is to provide a method for producing a metal cylindrical body with a bottom using the above resin-coated metal sheet. [Means for solving the problem]

[0007] According to the present invention, in a resin-coated metal sheet for plastic working, There is provided a resin-coated metal sheet for plastic working, characterized in that a coating film made of a paraffin mixture of liquid paraffin and solid paraffin is formed on the resin-coated surface of the metal sheet.

[0008] The resin-coated metal sheet for plastic working according to the present invention preferably employs the following aspects. (1) The melting point of the mixed paraffin is less than 64°C. (2) In the mixed paraffin, the solid paraffin (A) and the liquid paraffin (B) are mixed in a mass ratio of A:B=80:20 to 95:5. (3) The resin coating is made of polyester resin. (4) The resin coating is formed on both sides of the metal plate, and the coating film is formed on each of the resin coatings on both sides. (5) The coating film formed on one side of the metal plate is thicker than the coating film formed on the other side of the metal plate. (6) The thickness of the coating film formed on one side of the metal plate is 20 to 120 mg / m 2 The thickness of the coating film formed on the other side is in the range of 50 to 80% of the thickness of the coating layer on one side. (7) The metal plate is made of pure aluminum or an aluminum alloy.

[0009] According to the present invention, the resin-coated metal sheet for plastic working is prepared, The metal plate is subjected to plastic working to obtain a bottomed cylindrical body so that at least the surface on which the mixed paraffin coating film is formed is on an inner surface; Trimming the top of the bottomed cylindrical body; Next, the trimmed bottomed cylindrical body is heated to a temperature of 180°C to 210°C to remove the adhering lubricant, thereby providing a method for producing a resin-coated metal cylindrical body with a bottom. In such a manufacturing method, it is preferable to subject the product to post-processing after removing the lubricant. [Effects of the Invention]

[0010] The resin-coated metal sheet for plastic working of the present invention has a lubricant coated on the resin coating, similar to conventionally known resin-coated metal sheets used for plastic working. However, a major feature of the present invention is that a mixed paraffin of liquid paraffin and solid paraffin is used as the lubricant.

[0011] That is, if a low-melting-point lubricant is used, it exhibits high fluidity during plastic working, making it prone to shedding. As a result, sufficient lubrication is not stably exhibited, and the resin coating is prone to damage and peeling. In some cases, the lubricant may build up on the jig used in plastic working, contaminating the jig with the lubricant. However, such low-melting-point lubricants can be quickly removed by heating at low temperatures (e.g., below 210°C), which is advantageous in terms of avoiding damage to the resin coating during heat treatment for lubricant removal. On the other hand, if a high-melting-point lubricant is used, it does not fall off during plastic working and is firmly retained on the resin coating, thereby exhibiting excellent lubrication and effectively avoiding problems such as damage to the resin coating or buildup of lubricant on the jig during plastic working. However, in this case, heat treatment for lubricant removal must be performed at high temperatures, which makes the resin coating prone to damage and peeling during such heat treatment.

[0012] As described above, whether a low-melting-point lubricant or a high-melting-point lubricant is used, damage or peeling of the resin coating occurs during either plastic working or heat treatment for the lubricant. However, in the present invention, this inconvenience is solved by using a paraffin mixture of liquid paraffin and solid paraffin as the lubricant. The exact reason why the use of such a paraffin mixture solves the above problem is unknown, but the inventors speculate as follows. That is, liquid paraffin is a low-melting-point component, and solid paraffin is a high-melting-point component, but they are miscible and integrated, and due to the drop in melting point, they behave as a low-melting-point component. Therefore, they can be quickly removed by low-temperature heat treatment (for example, below 210°C). Furthermore, such mixed paraffins naturally contain high-molecular-weight components (long-chain components) derived from solid paraffin. Therefore, these high-molecular-weight components prevent the mixed paraffin from falling off the resin coating during plastic processing, stably retaining it and functioning as a lubricant, effectively preventing damage to or falling off of the resin coating.

[0013] In the resin-coated metal sheet for plastic working of the present invention, the mixed paraffin functioning as a lubricant is effectively prevented from falling off, and plastic working can be performed while effectively avoiding damage or peeling of the resin coating. Moreover, the mixed paraffin can be removed by heat treatment at a low temperature that does not cause damage or peeling of the resin coating. Therefore, by plastic working using such a resin-coated metal sheet coated with mixed paraffin, it is possible to efficiently produce resin-coated metal cylindrical bodies with a bottom (e.g., metal cans and metal cups) having a resin coating formed on the inner or outer surface. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a cross-sectional side view showing a resin-coated metal sheet for plastic working according to the present invention. [Figure 2] 2 is a schematic view showing the external shape of a metal cup, which is an example of a metal cylindrical body with a bottom manufactured from the resin-coated metal sheet for plastic working of FIG. 1. FIG. [Figure 3] 2 is a schematic view showing the external shape of a metal can, which is an example of a metal cylindrical body with a bottom produced from the resin-coated metal sheet for plastic working of FIG. 1. FIG. [Figure 4] 4 is a schematic diagram showing a process for producing the metal cylindrical body with a bottom shown in FIG. 2 or FIG. 3 by plastic working using the resin-coated metal plate for plastic working of FIG. 1. DETAILED DESCRIPTION OF THE INVENTION

[0015] <Resin-coated metal sheet> Referring to FIG. 1, the resin-coated metal sheet of the present invention, generally designated 10, is to be subjected to plastic processing and comprises a metal base plate 1, a resin coating 3 formed on this base plate 1, and a lubricant coating film layer 5 formed on the resin coating 3.

[0016] There are no limitations on the type of metal plate 1 as long as it can be plastically processed, but it is generally a known metal plate such as various surface-treated steel plates or aluminum plates such as pure aluminum or aluminum alloys. The thickness of such metal plate 1 varies depending on the material, but is usually about 0.10 to 0.50 mm.

[0017] 1, the resin coating 3 is provided on both sides of the base plate 1, but depending on the application of the formed product obtained by plastic working, the resin coating 3 may be provided on only one surface. Such a resin coating 3 improves corrosion resistance, scratch resistance, etc.

[0018] The resin coating 3 is not particularly limited and may be formed from a paint made of a thermosetting resin or a thermoplastic resin, a thermoplastic resin film, or the like. However, when used to form bottomed cylindrical bodies such as cups and cans, which will be described later, it is preferable that the resin coating 3 be formed from a thermoplastic resin film from the viewpoint of bendability, etc.

[0019] Examples of such thermoplastic resin films include olefin-based resin films such as polyethylene, polypropylene, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer, ethylene-acrylic ester copolymer, and ionomer; polyester films such as polyethylene terephthalate, polybutylene terephthalate (PET), and ethylene terephthalate / isophthalate copolymer; polyamide films such as nylon 6, nylon 6,6, nylon 11, and nylon 12; and chlorine-containing resin films such as polyvinyl chloride and polyvinylidene chloride. In the present invention, polyester films, particularly PET films, are preferred from the viewpoint of flexibility and heat resistance.

[0020] Furthermore, the thermoplastic resin film used has an appropriate molecular weight depending on the material of the metal plate 1. For example, if the metal plate 1 is made of steel such as a surface-treated steel plate, frictional heat is high during plastic processing, so a film made of a thermoplastic resin with a relatively high molecular weight and a high melting point (e.g., 220°C or higher) is used, whereas if the metal material 1 is made of aluminum such as pure aluminum or an aluminum alloy, great flexibility is required due to the large amount of bending that will be performed, so a film with a relatively low molecular weight and a low melting point (e.g., below 220°C) is preferably used. Of course, such a thermoplastic resin film may contain appropriate amounts of various pigments or fillers to conceal the metal plate 1 or to prevent wrinkles from occurring.

[0021] The above-mentioned thermoplastic resin film (resin coating 3) can be coated on the metal base plate 1 by a heat fusion method, dry lamination, extrusion coating, etc. Furthermore, if the adhesion or heat fusion properties to the metal base plate 1 are poor, a known adhesive, such as a urethane adhesive, epoxy adhesive, acid-modified olefin resin adhesive, copolyamide adhesive, or copolyester adhesive, can be interposed between the thermoplastic resin film (resin coating 3) and the metal base plate 1.

[0022] Such a thermoplastic resin film may be stretched or unstretched. When the resin film is applied to the metal base plate 1 by heat fusion bonding, the resin coating 3 is formed in an unstretched state.

[0023] When the resin coating 3 is formed using a paint made of a thermosetting resin or a thermoplastic resin, the following are typical examples of such paint. Modified epoxy paints such as phenol-epoxy paints and amino-epoxy paints; vinyl or modified vinyl paints such as vinyl chloride-vinyl acetate copolymer, partially saponified vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-maleic anhydride copolymer, epoxy-modified, epoxyamino-modified or epoxyphenol-modified vinyl resin paints; Acrylic resin paints; Synthetic rubber-based paints such as styrene-butadiene copolymers;

[0024] The above-mentioned paints can be applied to the metal plate 1 in the form of an organic solvent solution such as enamel or lacquer, or in the form of an aqueous dispersion or solution, by roller coating, spray coating, dip coating, electrostatic coating, electrophoretic coating, or the like, and if the paint is thermosetting, it can be baked as necessary. The thickness of the resin coating formed from such a paint is usually about 2 to 30 μm.

[0025] A lubricant coating film layer 5 is provided on the resin coating 3 described above, which effectively prevents damage and peeling of the resin coating 3 during severe plastic working. In other words, if such a lubricant coating film layer 5 is not provided, a lubricant liquid would be supplied by spraying or the like during plastic working, but this method makes it difficult to maintain a stable lubricant liquid between the jig used in working and the resin-coated metal sheet 10, which inevitably makes the resin coating 3 more susceptible to damage. To avoid this inconvenience, a lubricant coating film layer 5 is provided on the resin coating 3, so that a lubricant is always present between the jig and the working surface during plastic working.

[0026] In the present invention, a mixed paraffin of liquid paraffin and solid paraffin is used as the lubricant to form the coating film layer 5. The use of such a mixed paraffin effectively prevents damage and peeling of the resin coating 3 during plastic working, and also makes it possible to remove the lubricant (mixed paraffin) remaining on the surface of the molded product by heat treatment after plastic working without causing damage or peeling of the resin coating 3.

[0027] Solid paraffin (also called solid paraffin) and liquid paraffin are both hydrocarbons obtained by distillation of petroleum, and are mutually compatible. Solid paraffin has a melting point higher than room temperature (25°C) and a carbon number distribution of about 20 to 40, and is commonly called paraffin wax. On the other hand, liquid paraffin is liquid at room temperature and generally has a carbon number distribution of about 15 to 35.

[0028] In the present invention, the coating film layer 5 made of mixed paraffin is stably retained on the resin coating 3 without falling off due to heat generated by friction with the jig during plastic working, thereby providing good lubrication, suppressing damage to the resin coating 3, and enabling smooth jig removal and effectively preventing lubricant buildup on the jig. For example, if the coating film layer 5 were formed solely from liquid paraffin, the coating film layer 5 would fall off during plastic working, making the resin coating 3 more susceptible to damage and lubricant buildup on the jig, hindering jig removal and reducing production efficiency. On the other hand, if the coating film layer 5 were formed solely from solid paraffin, the coating film layer 5 would effectively be prevented from falling off during plastic working and preventing peeling of the resin coating 3, but a high-temperature heat treatment would be required to remove the coating film layer 5 after plastic working, which would result in peeling of the resin coating and buildup of lubricant on the surface of the processed product during this heat treatment stage.

[0029] Thus, in the present invention, by forming the coating film layer 5 from mixed paraffin, problems caused by peeling or damage of the resin coating 3 can be effectively prevented.

[0030] In the present invention, the mixing ratio of liquid paraffin and solid paraffin in the paraffin mixture can be determined based on their melting points, since they are compatible with each other. For example, the mixing ratio is determined so that the melting point (peak-top temperature) measured by thermal analysis such as DSC is less than 64°C, and particularly preferably in the range of 50 to 62°C. If the melting point is too high, the amount of solid paraffin will be excessive. As a result, the heating temperature for removing the coating film layer 5 will be too high, which will likely cause problems such as peeling of the resin coating 3 when removing the coating film layer 5 by heat treatment after plastic working. Furthermore, the fluidity of the coating film layer 5 will be poor during plastic working, and sufficient lubrication will not be achieved, which will also likely cause peeling or damage to the resin coating 3. On the other hand, if the melting point is too low, the amount of liquid paraffin will be excessive, which will cause the coating film layer 5 to fall off during plastic working, which will likely cause problems such as peeling of the resin coating 3.

[0031] The blending ratio for setting the melting point within the above range cannot be determined in general because it depends on the carbon numbers of the liquid paraffin and solid paraffin used. However, the larger the carbon number of the solid paraffin used, the more liquid paraffin should be blended. Generally, the solid paraffin (A) and the liquid paraffin (B) are blended in a mass ratio of A:B = 80:20 to 95:5, particularly 90:10 to 95:5. The two are blended by heating above the melting point of the solid paraffin. The molten mixed paraffin is applied to the resin coating 3 and then cooled to form the coating film layer 5.

[0032] Some solid paraffins have melting points within the above range. Therefore, such solid paraffins exhibit the above melting points without being mixed with liquid paraffin. However, in this case, since they do not contain liquid paraffin with a low molecular weight and a small carbon number, they have poor fluidity and poor lubricity during plastic working, which makes the resin coating 3 prone to peeling or damage.

[0033] Furthermore, in the present invention, the fact that the coating film layer 5 is formed from a paraffin mixture of liquid paraffin and solid paraffin can be confirmed by measuring the molecular weight distribution using a known method such as GPC. Specifically, the molecular weight distribution curve of the paraffin mixture is either very broad across the low molecular weight range in the liquid state to the high molecular weight range in the solid state, or it exhibits sharp peaks in both the high molecular weight range in the solid state and the low molecular weight range in the liquid state. On the other hand, solid paraffin or liquid paraffin alone, even if it has the same melting point as the paraffin mixture, exhibits a molecular weight peak only in the high molecular weight range in the solid state or the low molecular weight range in the liquid state. Therefore, the use of a paraffin mixture can be confirmed from these differences.

[0034] In the resin-coated metal sheet 10 of the present invention described above, the coating film layer 5 is formed on the resin coating 3. As shown in FIG. 1, when the resin coating 3 is formed on both sides of the metal sheet 1, the coating film layer 5 is formed on each of the resin coatings 3. However, when the resin coating 3 is formed on only one side of the metal sheet 1, the coating film layer 5 is formed only on one of the resin coatings 3.

[0035] Furthermore, the thickness of the coating film layer 5 is set within an appropriate range depending on the material of the metal plate and the degree of plastic working. For example, when the metal plate 1 is made of a material that is difficult to deform, such as steel, the thickness of the coating film layer 5 is relatively large, 40 to 120 mg / m 2 However, if the metal plate 5 is made of pure aluminum or an aluminum alloy, which is relatively easy to deform, the thickness of the coating film layer 5 may be thinner.

[0036] Furthermore, the resin-coated metal sheet 10 of the present invention is suitable for use in the manufacture of a metal cylinder with a bottom. However, depending on the shape of the metal cylinder with a bottom, the degree of plastic working may differ significantly between one surface and the other. That is, the load applied during plastic working may differ between the inner and outer surfaces of the formed metal cylinder with a bottom. In such cases, it is preferable to form a thick coating film layer 5 on the surface of the resin-coated metal sheet 10 that is subjected to a large load (for example, the surface that will become the inner surface). The thickness of the thick coating film layer 5 should be 20 to 120 mg / m 2 , especially 20-100 mg / m 2 , 40-90 mg / m 2 For example, it is preferable to set the thickness of the coating film layer 5 on one side to which a large load is applied in the range of 20 to 120 mg / m 2 When the thickness of the coating film layer 5 on the opposite surface is set to about 50 to 80%, and more preferably 50 to 60%, of the thickness of the coating film layer 5 on one side, it is preferable to set the thickness of the coating film layer 5 on the opposite surface to 50 to 80%, and particularly 50 to 60% of the thickness of the coating film layer 5 on one side. In particular, when a metal plate 1 made of aluminum (pure aluminum or aluminum alloy) is used, it is optimal to vary the thickness of the coating layer 5 as described above.

[0037] <Metal bottomed cylindrical body> The resin-coated metal sheet 10 of the present invention described above can be suitably used to manufacture a metal cylindrical body with a bottom by subjecting it to plastic working. Typical examples of such a metal cylindrical body with a bottom are a metal cup 20 shown in FIG. 2 and a metal can 30 shown in FIG.

[0038] The metal cup 20 in Fig. 2 has a body 21 and a bottom 23, and a curled portion 25 is formed at the top end. Metal cups 20 of this type are usually sold empty without a lid, and general consumers fill them with beverages and use them to drink the beverage. For this reason, the curled portion 25 is formed at the top end of the body 21, making it easy to drink from. Furthermore, to allow multiple metal cups 20 to be stacked and stored, the opening diameter d1 at the top end of the body 21 is larger than the outer diameter d2 of the bottom 23, and the body 21 has an inclined wall that tapers toward the bottom, making it easy to stack and store.

[0039] A metal cup 20 of this type is usually formed using a resin-coated metal plate 10 having a resin coating 3 on both sides, but because the bottom 23 side is reduced in diameter (repeated drawing is performed), a greater load is applied to the inner side than to the outer side during plastic processing, and as a result, the coating film layer 5 on the inner side of the aforementioned resin-coated metal plate 10 is formed thicker than on the outer side.

[0040] 3 has a body 31 and a bottom 33, but the body 31 is substantially straight, and a neck-in 35 and a flange 37 are formed at the top of the body 31, which are reduced in diameter. After being filled with the liquid content, such a metal can 30 is usually fitted with a lid (not shown) at the top before being sold, and after the contents are removed, the can is discarded and appropriately collected. Therefore, the flange 37 is formed to allow the lid to be attached, and the neck-in 35 is formed during the process of forming the flange 37.

[0041] In a metal can 30 of this type, the body 31 is significantly thinned, and in particular, in the case of an aluminum can, the wall is extremely thinned (repeated ironing is performed), resulting in a high height H. In such a metal can 30, a large load is applied to the inner surface during plastic working (ironing), and as a result, the coating film layer 5 on the inner surface of the resin-coated metal sheet 10 described above is formed thicker than on the outer surface. As mentioned above, in particular in the case of an aluminum can, the can height H is set high due to the extremely thinned wall caused by the severe ironing process, and therefore the coating film layer 5 on the inner surface is set thicker.

[0042] <Production of metal cylindrical body with bottom> The production of a metal cylindrical body with a bottom using the resin-coated metal sheet 10 of the present invention is carried out by the process shown in FIG. 4, taking the metal cup 20 of FIG. 2 or the metal can 30 of FIG. 3 as an example.

[0043] 4, the resin-coated metal sheet 10 of the present invention is first subjected to a punching process. That is, the resin-coated metal sheet 10 is punched out using a punch 51 and a punching die 53 to obtain a disk 55 and a punching residue 57 (see FIG. 4(a)).

[0044] 4(b), a drawn cup (bottomed cylindrical body) 60 is obtained by drawing from the disk 55. That is, the disk 55 is held on a drawing die 63 by a presser 61, and in this state, a drawing punch 65 is passed through the disk 55, thereby obtaining the drawn cup (bottomed cylindrical body) 60.

[0045] 4(c), the drawn cup (bottomed cylindrical body) 60 obtained in this manner is subjected to redrawing and ironing processes to obtain a bottomed cylindrical intermediate body 70 that will be the precursor of the metal cup 20 or metal can 30. That is, the drawn cup 60 obtained above is pushed downward using an ironing punch 75 while held in a redraw die 73 by a presser 71, and is then passed through a plurality of ironing dies 77 (77-1 to 77-3) held by a predetermined frame 76 to perform ironing, thereby obtaining the bottomed cylindrical intermediate body 70.

[0046] The bottomed cylindrical intermediate body 70 is suitably extruded onto a hold-down ring (annular holding mold) 79, where the bottom is shaped so as to be able to stably contact the ground.

[0047] The bottomed cylindrical intermediate 70 obtained in this manner is in a straight body state, but when manufacturing the metal cup 20 shown in Figure 2, it is repeatedly drawn without thinning, and is shaped into a cup shape with an upper diameter larger than the diameter at the bottom.

[0048] The bottomed tubular intermediate body 70 obtained as described above is subjected to trimming, and the upper end is cut off, as shown in Fig. 4(d). As a result, the upper end is trimmed evenly, and the resin coating 3 can be present up to the upper end.

[0049] After trimming, as shown in FIG. 4( e), a heat treatment is performed to remove the residue (mixed paraffin) of the coating film layer 5. This heat treatment is performed by introducing the trimmed bottomed tubular intermediate 70 into a heating oven. The intermediate 70 is usually transported into the heating oven in an upright position with the open end facing upward, but if welding at the bottom of the bottomed tubular intermediate 70 becomes a problem, the bottomed tubular intermediate 70 can also be transported in an inverted position and introduced into the heating oven.

[0050] In the present invention, it is important that the heating temperature in the heating oven be 180°C to 210°C, particularly 195°C to 205°C. Conventionally, this heating has been performed at temperatures higher than 210°C. However, in the present invention, the coating film layer 5 is formed from a mixed paraffin containing liquid paraffin. This effectively prevents the resin coating 3 from falling off or being damaged during the plastic processing up to the formation of the trimmed bottomed tubular intermediate 70, while also enabling the remaining mixed paraffin to be removed at a temperature lower than 210°C. This reliably prevents peeling or damage to the resin coating 3 formed on the inner and outer surfaces of the bottomed tubular intermediate 70, such as the recession of the resin coating 3 from the trimmed end, exposing the metal, or melting and dripping of the resin to the bottom.

[0051] In particular, when manufacturing a metal can 30 made of aluminum or an aluminum alloy with an extremely thin body, polyester, particularly polyethylene terephthalate, which has a low melting point (for example, 220°C or lower), is used as the polymer forming the resin coating 3, and peeling or damage to the resin coating 3 is more likely to occur during this heating step. However, in the present invention, the heating temperature in this heat treatment step can be set to a temperature lower than 200°C, particularly 195°C or lower, so that peeling or damage to the resin coating 3 can be reliably prevented even in such cases.

[0052] In the present invention, the heating time in the heating oven in the heat treatment step varies depending on the size of the bottomed cylindrical intermediate body 70 to be subjected to the heat treatment, but is generally about 30 to 60 seconds.

[0053] After removing the residue (mixed paraffin) of the coating film layer 5 remaining on the inner and outer surfaces of the bottomed cylindrical intermediate body 70 trimmed by the heat treatment as described above, the intermediate body is subjected to post-processing known per se (FIG. 4(f)), thereby obtaining the metal cup 20 shown in FIG. 2 or the metal can 30 shown in FIG. 3.

[0054] For example, when obtaining a metal cup 20, the upper part of the intermediate body 70 is curled to form the curled portion 25, and then the heat treatment process is carried out, and printing or the like is applied to the outer surface before the cup is put up for sale.

[0055] Furthermore, when obtaining the metal can 30, necking and flange processing are carried out to form the necking 35 and flange 37, and then exterior printing and the like are carried out. After such post-processing has been carried out, the metal can 30 is filled with the contents, and a lid is attached by seaming using the flange 37, and the can is then sold.

[0056] According to the present invention, the lubricant (mixed paraffin) is removed without damaging the resin coating 3 present on the inner and outer surfaces of the metal cup 20 or the metal can 30, so that the above-mentioned post-processing can be carried out quickly and efficiently. [Explanation of symbols]

[0057] 1: Metal plate 3: Resin coating 5: Lubricant coating film layer 10: Resin-coated metal plate 20: Metal cup 21: Torso 23: Bottom 25: Curl section 30: Metal can 31: Torso 33: Bottom 35: Neck-in 37: Flange 55:Disc 57: Punching residue 60: Squeezing cup 70: Bottomed cylindrical intermediate

Claims

1. In a resin-coated metal sheet for plastic working, A resin-coated metal sheet for plastic working, characterized in that a coating film made of a mixed paraffin of liquid paraffin and solid paraffin is formed on the resin-coated surface of the metal sheet.

2. 2. The resin-coated metal sheet for plastic working according to claim 1, wherein the melting point of the mixed paraffin is lower than 64°C.

3. 2. The resin-coated metal sheet for plastic working according to claim 1, wherein in the mixed paraffin, the solid paraffin (A) and the liquid paraffin (B) are mixed in a mass ratio of A:B = 80:20 to 95:

5.

4. 2. The resin-coated metal sheet for plastic working according to claim 1, wherein the resin coating comprises a polyester resin.

5. 2. The resin-coated metal sheet for plastic working according to claim 1, wherein the resin coating is formed on both sides of the metal sheet, and the coating film is formed on each of the resin coatings on both sides.

6. 6. The resin-coated metal sheet for plastic working according to claim 5, wherein the coating film formed on one side of the metal sheet is thicker than the coating film formed on the other side of the metal sheet.

7. The thickness of the coating film formed on one side of the metal plate is 20 to 120 mg / m ２ 7. The resin-coated metal sheet for plastic working according to claim 6, wherein the thickness of the coating film formed on the other side is in the range of 50 to 80% of the thickness of the coating layer on one side.

8. 2. The resin-coated metal sheet for plastic working according to claim 1, wherein the metal sheet is made of pure aluminum or an aluminum alloy.

9. A resin-coated metal sheet for plastic working according to any one of claims 1 to 8 is prepared, The metal plate is subjected to plastic working to obtain a bottomed cylindrical body so that at least the surface on which the mixed paraffin coating film is formed is on an inner surface; Trimming the top of the bottomed cylindrical body; Next, the trimmed bottomed cylindrical body is heated to a temperature of 180°C to 210°C to remove the adhering lubricant, thereby producing a resin-coated metal cylindrical body.

10. The method for producing a resin-coated metal cylindrical body with a bottom according to claim 9, wherein the body is subjected to post-processing after the removal of the lubricant.

Images