JP2007045510A - Laminated steel sheet for two-piece can, and two-piece laminated can - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laminated steel plate suitable for manufacturing a laminated two-piece can processed to a high extent which prevents a laminated resin layer from being peeled off and broken even if the laminated two-piece can is such a can body having a high degree of processing as an aerosol two-piece can, and to provide the laminated two-piece can having a high degree of processing high extent. <P>SOLUTION: The laminated steel plate is used for manufacturing such a two-piece can that a height h, a maximum radius r, and a minimum radius d of a final molded body and a radius R of a disc before molding which has the same weight as the final molded body satisfy inequalities: 0.1≤d/R≤0.25 and 1.5≤h/(R-r)≤4. At least one surface of the steel plate has a coating layer made of a polyolefin resin. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a laminated steel plate suitable for manufacturing a two-piece can having a high degree of processing such as an aerosol can, and a two-piece laminated can having a high degree of processing.

  There are roughly two-piece cans and three-piece cans for aerosol metal containers. The two-piece can has a beautiful appearance due to the absence of a seam portion (welded portion), but generally has a high degree of processing. The three-piece can has a seam portion, and its appearance is inferior to that of the two-piece can. However, the degree of processing is generally low. For this reason, in the market, two-piece cans are often used for small-scale and high-end products, and three-piece cans are often used for large-capacity and low-priced products.

  The metal material in the aerosol two-piece can is generally made of expensive and thick aluminum or the like, and inexpensive and thin steel plate materials such as tinplate and tin-free steel are hardly used. The reason is that the aerosol two-piece can has a high degree of processing, so that it is difficult to apply drawing or DI processing, and aluminum is manufactured by applying impact molding applicable to a soft metal material. Under such circumstances, industrial significance is very large if steel sheets such as tinplate and tin-free steel that are inexpensive and thin but have high strength can be used.

  Conventionally, various methods for drawing and DI processing of laminated steel sheets have been proposed, but a method for producing a can body that performs diameter reduction processing with a high degree of processing after drawing, such as an aerosol two-piece can, has not been studied.

  For example, Patent Documents 1 to 3 disclose a processing method for drawing and drawing ironing of a resin-coated metal plate, but the degree of processing described in Patent Documents 1 to 3 (the drawing ratio in Patent Documents 1 to 3). ) Is in a range lower than that defined in the present invention. This is because Patent Documents 1 to 3 target beverage cans, food cans, and the like, and beverage cans and food cans are can bodies having a processing degree lower than the range of processing degrees defined in the present invention.

Therefore, the inventors manufactured a two-piece can with a high degree of processing by multi-stage forming by drawing ironing and shrinking using a laminated steel sheet, and a problem peculiar to high processing occurred. Specifically, resin There were problems of delamination and breakage of the layers. Therefore, it is necessary to study a new manufacturing method in order to manufacture a can body having a high workability such as an aerosol two-piece can.
Japanese Examined Patent Publication No. 7-106394 Japanese Patent No. 2526725 JP 2004-148324 A

  The object of the present invention is to solve the above-mentioned problems and produce a two-piece laminated can with high workability that can prevent peeling and breaking of the laminate resin layer even in a high-working can such as an aerosol two-piece can. It is to provide a laminated steel sheet suitable for the above and a two-piece laminated can having a high degree of processing.

  Means of the present invention for solving the above-mentioned problems are as follows.

  (1) The height h, maximum radius r, and minimum radius d (including the case where r and d are the same) of the final molded body are compared with the radius R of the circular plate before molding in which the weight is equivalent to the final molded body. A laminated steel plate used for manufacturing a two-piece can satisfying the relationship of 0.1 ≦ d / R ≦ 0.25 and 1.5 ≦ h / (R−r) ≦ 4, A laminated steel plate for a two-piece can having a coating layer of a polyolefin resin on one side (first invention).

  (2) The laminated steel sheet for a two-piece can according to (1), wherein the polyolefin resin is disposed as an upper layer via a steel sheet surface and an adhesive resin layer (second invention).

  (3) The polyolefin resin layer is a polypropylene resin, and the adhesive resin layer is a mixture of adhesive polyethylene and adhesive polypropylene, and the adhesive polyethylene is contained in the mixture in an amount of 8 to 20% by mass. The two-piece laminated can according to (2) (third invention),

  (4) Adhesive polyethylene is a homopolymer of ethylene or one or more α selected from ethylene and 1-butene, 1-hexene, 1-heptene, 1-octene, 4-methyl-1-pentene. It is a block or random copolymer with olefin, and adhesive polypropylene is a homopolymer of propylene, or propylene and ethylene, 1-butene, 1-hexene, 1-heptene, 1-octene, 4-methyl-1 -A laminated steel sheet for a two-piece can according to (3), which is a block or random copolymer with at least one α-olefin selected from among pentenes (fourth invention).

  (5) The polypropylene resin is a propylene / ethylene block copolymer, and the ratio of the propylene component of the block copolymer is 50 mol% or more and 98 mol% or less (3) or (4) 2 laminated steel sheet for cans (5th invention).

  (6) A two-piece laminated can manufactured by multi-stage forming the circular plate of the laminated steel sheet according to any one of (1) to (5), wherein the final molded body has a height h and a maximum radius. r, the minimum radius d (including the case where r and d are the same) is 0.1 ≦ d / R ≦ 0.25 with respect to the radius R of the circular plate before molding that is equivalent in weight to the final molded body. And a two-piece laminate can characterized by satisfying a relationship of 1.5 ≦ h / (R−r) ≦ 4 (the sixth invention).

  By producing a two-piece can using the laminated steel sheet of the present invention as a raw material, it is possible to produce a two-piece can having a high workability while preventing the resin layer from peeling and breaking. The two-piece can manufactured by the method of the present invention can be used for applications such as an aerosol two-piece can that requires a high degree of processing.

  The embodiment of the present invention and the reason for limitation will be described.

  FIG. 1 is a diagram for explaining an embodiment of a can manufacturing process according to the present invention, in which a circular blank is formed into a bottomed cylindrical formed body by drawing (including DI processing), and the formed body is further described. The order of steps for manufacturing a two-piece can in which the vicinity of the opening is reduced in diameter and the vicinity of the opening is reduced is shown.

  In FIG. 1, 1 is a disc-shaped blank (blank sheet) before processing, 2 is a base portion and a straight wall portion of the molded body (a straight wall portion not subjected to diameter reduction processing in Step D), 3 is a dome-shaped portion, Reference numeral 4 denotes a straight wall portion that has been reduced in diameter by the neck shape portion, and reference numeral 5 denotes a tapered shape portion that is a tapered wall portion after the diameter reduction processing.

  First, one or a plurality of stages of drawing (including DI processing) is performed on the circular plate blank 1 to form a bottomed cylindrical molded body having a predetermined can diameter (radius r; radius of can outer surface) ( Step A). Next, the bottom of the molded body is formed in a convex shape upward to perform dome processing for forming the dome-shaped portion 3 (step B), and the opening side end of the molded body is trimmed (step C). Next, one or more stages of diameter reduction processing are performed on the opening side portion of the molded body to reduce the diameter of the opening side portion of the molded body to a predetermined can diameter (radius d: radius of the can outer surface). A molded body (2-piece can) is obtained. In the figure, R0 is the radius of the circular blank 1 before molding, h, r, and d are the height of the molded body or final molded body in the middle of molding, the maximum radius, the minimum radius, and R is the final molded body, respectively. And the radius R of the circular plate before molding that is equivalent to the weight R and the radius of the circular plate before molding that is equivalent in weight to the final molded body. In the manufacturing process of the two-piece can, the maximum radius and the minimum radius of the process A are the same, that is, r = d, and the process D is r> d.

  The radius R of the circular plate before molding that is equivalent in weight to the final molded body is determined based on the measured weight of the final molded body. That is, the weight of the final molded body is measured, the dimension (radius) of the circular plate before molding that becomes the same weight as this weight is obtained, and this is the circular shape before molding in which the weight is equivalent to the final molded body. Let it be the radius R of the plate. The can end is trimmed during the manufacturing process of the can body, but the radius R of the circular plate before molding, which is equivalent in weight to the final molded body, is more appropriate because the influence of trim is eliminated. The degree of processing can be evaluated.

  Thus, in a two-piece can created by applying drawing (including DI processing) and diameter reduction processing to a circular plate blank, the resin layer is stretched in the height direction and contracted in the circumferential direction. . When the degree of processing is high, the amount of deformation of the resin increases, leading to the breakage of the resin layer. In the present invention, not only the parameter d / R indicating the degree of shrinkage but also the parameter h / (R−r) related to the elongation in the can height direction is used as an index of the degree of processing. This is because, in the high workability region, it is necessary to consider the elongation amount in addition to the drawing ratio in order to express the workability. That is, by defining the degree of processing by the degree of shrinkage and the degree of elongation, the degree of deformation of the resin layer is quantified. Since the resin layer extends in the height direction and shrinks in the circumferential direction, it becomes easy to peel off. In addition to the degree of shrinkage, the amount of elongation in the height direction is an important factor.

  In the present invention, regarding the degree of processing of the finally manufactured can body (final molded body), the height h, the maximum radius r, and the minimum radius d of the final molded body are set so that the weight is equivalent to that of the final molded body. Is defined in a range satisfying the can diameter of 0.1 ≦ d / R ≦ 0.25 and 1.5 ≦ h / (R−r) ≦ 4.

  As described above, an object of the present invention is to make it possible to manufacture a can body having a high workability, which has been difficult with the prior art, by using a laminated steel plate. In the prior art, using a laminated steel sheet, the parameter d / R that defines the degree of shrinkage satisfies 0.25 or less, and the parameter h / (R−r) that defines the degree of elongation is 1.5 or more. At the same time, it was difficult to produce a can with a high degree of processing that was satisfactory. Therefore, in the present invention, the working degree d / R of the can body to be manufactured is regulated to 0.25 or less, and h / (R−r) is regulated to 1.5 or more.

  Molding is possible when the parameter d / R that defines the degree of shrinkage is 0.1 or less, or the parameter h / (R−r) that defines the degree of elongation is a high degree of processing exceeding 4. This is because the number of forming steps increases unnecessarily, or the elongation limit of the plate is reached with work hardening, and the plate breaks. Therefore, in the present invention, the degree of processing of the can body to be manufactured is defined as 0.1 ≦ d / R and h / (R−r) ≦ 4.

  Note that the multi-stage forming that is the subject of the present invention is any one of drawing, drawing / ironing, diameter reduction, or a combination of these. When the diameter reduction process is included, the dimension d of the final molded body is r> d. When the diameter reduction processing is not included, the size of the final molded body is r = d (r and d are can diameters of the final molded body).

  In general, the resin type of laminated steel plates used in beverage cans and food cans is polyester represented by polyethylene terephthalate, but according to the results of investigations by the inventors, in the above-mentioned high workability molding, polyolefin Was found to be suitable. In general, a polyolefin resin is cheaper and more deformable than a polyester resin, but is inferior in heat resistance and strength. However, ease of deformation is particularly important in molding with a high degree of processing, and for this reason, polyolefin resins are more suitable than polyester resins. In other words, the polyester-based resin easily breaks at the processing limit, while the polyolefin has a high processing limit, and easily follows the processing for molding with a high processing degree.

  In the drawing process, when forming with such a degree of processing, usually, several to tens of processing steps are required, and the processing degree for each step is relatively small. As a result, the calorific value due to processing becomes smaller, and there is no problem even if a polyolefin resin having poor heat resistance is applied.

  The ease of deformation of the resin layer is related to the accumulation of internal stress as well as the process following ability. That is, for the same amount of deformation, the polyolefin resin-based material that is easily deformed has a smaller internal stress generated than the polyester-based material that is difficult to deform. As a result, the polyolefin system is advantageous for the deterioration of adhesion due to deformation. Based on such a reason, the 1st invention limited the resin layer of the laminated steel plate to the olefin.

  Although the film thickness of a resin layer is not specifically limited, 10 micrometers or more and 50 micrometers or less are preferable. In the case of film lamination, the film cost of less than 10 μm is generally expensive, and the thicker the film thickness, the better the workability, but the higher the cost. When it exceeds 50 μm, the contribution to processability is saturated. This is because it becomes expensive.

  The laminated steel sheet defined by the present invention only needs to cover at least one surface of the steel sheet with the resin layer defined by the present invention.

  The second invention prescribes that the polyolefin resin is disposed as an upper layer via a steel plate surface and an adhesive resin layer, that is, a resin layer made of an adhesive resin is provided between the steel plate and the steel plate. This is because the adhesive strength with the steel sheet is enhanced by disposing the adhesive resin layer. Polyolefin resins are more advantageous than polyester resins in terms of increasing internal stress due to processing, but initial adhesion before processing is generally inferior to polyester. For this reason, it is preferable to use an adhesive resin for processing that particularly requires adhesion, and for application of an olefin resin having poor adhesion. The adhesive layer may be a layer that strongly bonds the upper layer and the steel plate.

  The third invention discloses a suitable combination of an adhesive resin layer and an upper polyolefin resin. The reason why the upper layer is limited to polyolefin resin is that olefin is excellent in elongation. The lower resin layer in contact with the steel plate surface is composed of adhesive (thermal adhesive) polypropylene and adhesive (thermal adhesive) polyethylene as main components, and these two resins are used in combination. The adhesive resin layer is made of a mixture of adhesive polyethylene and adhesive polypropylene. This adhesive resin layer is an adhesive layer in which a polyethylene resin is mixed rather than using a polypropylene-based thermal adhesive resin alone. This is because it is more advantageous for adhesion after processing.

  The adhesive polyethylene content is defined as 8 to 20% because the adhesion is inferior when the content is less than 8%, and the adhesion with the upper layer is reduced when the ratio of the polyethylene resin is increased, and the processing is performed when the content exceeds 20%. This is because there is a risk that delamination may occur.

  The adhesive polypropylene is a propylene homopolymer, or a block or random copolymer of propylene and α-olefin. Examples of the α-olefin in the latter case include ethylene, 1-butene, 1-hexene, 1-heptene, 1-octene, 4-methyl-1-pentene, etc., and use one or more of these. Can do. The melt flow rate (MFR JIS K6758) of the adhesive polypropylene is preferably 0.5 to 20 g / 10 min.

  The adhesive polypropylene preferably has an adhesive property (thermal adhesive property) by introducing an unsaturated carboxylic acid and / or a derivative thereof into a polypropylene resin. As the unsaturated carboxylic acid or derivative thereof used for this acid modification, unsaturated carboxylic acid or derivative thereof such as maleic acid, acrylic acid, fumaric acid, tetrahydrophthalic acid, itaconic acid, citraconic acid, crotonic acid, nadic acid, For example, amides, imides, anhydrides, esters, acid halides and the like can be used, and one or more of these can be used, but maleic anhydride is generally used. Graft polymerization is common as a method for introducing these unsaturated carboxylic acids and / or derivatives thereof into polypropylene. In particular, graft polymerization in which maleic anhydride is 0.01 to 5% by mass is preferable.

  The adhesive polyethylene to be mixed with the adhesive polypropylene-based resin is an ethylene homopolymer, or a block or random copolymer of ethylene and α-olefin, but the latter is required to ensure adhesion with the upper layer. These copolymers are preferred. When the polyethylene resin is a block or random copolymer of ethylene and α-olefin, the amount of α-olefin that gives a side chain is preferably 1 to 25 mol%. If the amount of α-olefin is less than 1 mol%, the adhesiveness with the upper polypropylene resin layer is lowered. On the other hand, if it exceeds 25 mol%, the adhesiveness at room temperature increases and film formation becomes difficult. Examples of the α-olefin include propylene, 1-butene, 1-hexene, 1-heptene, 1-octene, and 4-methyl-1-pentene, and one or more of these can be used. A particularly preferable copolymer of the polyethylene resin is a random copolymer.

  The melt flow rate (MFR ASTM D1238) of the adhesive polyethylene is preferably 0.5 to 50 g / 10 min from the viewpoint of film forming properties.

  The adhesive polyethylene preferably has an adhesive property (thermal adhesive property) by introducing an unsaturated carboxylic acid and / or a derivative thereof into a polyethylene resin. As the unsaturated carboxylic acid or derivative thereof used for this acid modification, unsaturated carboxylic acid or derivative thereof such as maleic acid, acrylic acid, fumaric acid, tetrahydrophthalic acid, itaconic acid, citraconic acid, crotonic acid, nadic acid, For example, amides, imides, anhydrides, esters, acid halides and the like can be used, and one or more of these can be used. Maleic anhydride, methyl acrylate, methyl methacrylate, etc. are generally used. Is. Among these, from the viewpoint of corrosion resistance, it is preferable to use maleic anhydride alone or a mixture of maleic anhydride and one or more of other unsaturated carboxylic acids.

  Further, glycidyl methacrylate, vinyl acetate, methyl acrylate, and ionomer may be used alone or in admixture of two or more. Examples of methods for introducing these unsaturated carboxylic acids and / or derivatives thereof into polyethylene include graft polymerization, random polymerization, and block polymerization. In particular, graft polymerization in which maleic anhydride is 0.01 to 5% by mass is preferable.

  It was determined that the adhesive layer resin composed of the above adhesive polypropylene and adhesive polyethylene was mixed so as to be 8 to 20 mol% of adhesive polyethylene. When the proportion of the adhesive polyethylene is less than 8 mol%, the adhesion with the base steel plate is poor. On the other hand, if the proportion of the adhesive polyethylene exceeds 20 mol%, it becomes unsuitable because peeling from the main layer (upper layer) tends to occur.

  In addition, an appropriate amount of a compound other than the above can be blended with the adhesive resin as long as the effects of the present invention are not impaired.

  The thickness of the adhesive layer composed of the adhesive polypropylene and adhesive polyethylene is not particularly limited, but is preferably 2 to 10 μm. When the thickness of the adhesive layer is less than 2 μm, a portion where the adhesive resin is locally thin is likely to be formed, and there is a risk that the coating of the steel plate is locally degraded and the adhesion is impaired. On the other hand, the adhesive resin is generally expensive, and when the thickness of the adhesive layer is greater than 10 μm, there is no problem in terms of performance, but it is not practical because it is economically inferior.

  The propylene / ethylene block copolymer shown in the fifth invention is known to have a sea-island structure in which a polyethylene component is dispersed in a granular form in a polypropylene resin. Polypropylene in the matrix (sea part) is characterized by higher strength compared to polyethylene, which is advantageous in terms of handling (such as wrinkle resistance), and the polyethylene component (island part) compared to polypropylene. It has the characteristic of being flexible.

  During high processing, the resin layer has a tendency that molecules are aligned (orientated) in the processing direction. As a result, internal stress increases and peeling tends to occur. However, in such a resin system having a sea-island structure, the internal stress is relieved by the presence of the island portion. This is considered that the internal stress is relieved by the deformation of the flexible polyethylene part. The reason why the ratio of the polypropylene component is defined as 50 mol% or more and 98 mol% or less is set from this viewpoint. If the ratio exceeds 98 mol%, the advantages of the sea-island structure described above cannot be utilized. If it is less than mol%, the above-mentioned sea-island structure cannot be maintained, so that a special effect cannot be obtained.

  The laminated steel sheet of the present invention may be used by adding additives such as pigments, lubricants, stabilizers, etc. in the resin layer, or in addition to the resin layer defined in the present invention, an upper layer or a resin layer having other functions may be used. When there is a base steel plate or an adhesive resin layer, it may be arranged in an intermediate layer with the adhesive resin layer.

  The method of laminating to the steel plate is not particularly limited, and it may be appropriately selected, such as a thermocompression bonding method in which a biaxially stretched film or an unstretched film is thermocompression bonded, or an extrusion method in which a resin layer is directly formed on a steel plate using a T die. In all cases, it has been confirmed that sufficient effects can be obtained.

This is because the laminated steel sheet defined in the present invention is cheaper and more economical than aluminum or the like because the base metal sheet is a steel sheet. As the steel plate, it is preferable to use general tin-free steel or tinplate. Tin-free steel, for example, a metal layer of chromium coating weight 50-200 mg / ^{m 2} on the surface, the adhesion amount of metal chromium conversion preferably has an chromium oxide layer of 3 to 30 mg / ^{m 2.} The tinplate preferably has a plating amount of 0.5 to 15 g / m ² . Although plate | board thickness is not specifically limited, For example, the thing of the range of 0.15-0.30 mm is applicable. Moreover, this technology can be simply applied to an aluminum material if economic efficiency is not taken into consideration.

  When producing a two-piece can by multi-stage forming using the laminated steel sheet of the present invention, in order to prevent the peeling of the resin layer, the molded product is not less than the glass transition point of the polyolefin resin in the middle of processing or in the final step. The orientation caused by the processing may be appropriately eliminated by performing a heat treatment that is heated to a temperature.

  The heat treatment method is not particularly limited, and it has been confirmed that the same effect can be obtained with an electric furnace, a gas oven, an infrared furnace, an induction heater, or the like. The heating rate, heating time, and cooling rate may be appropriately selected according to the effect, but the higher the heating rate, the more efficient, and the approximate heating time is about 15 seconds to 60 seconds. The cooling rate is not limited, and it is preferable that the cooling rate is fast. However, the cooling rate may be appropriately selected according to the effect.

  Examples of the present invention will be described below.

"Production of laminated steel sheet"
T4CA and TFS (metal Cr layer: 120 mg / m ² , Cr oxide layer: 10 mg / m ^{2 in} terms of metal Cr) having a thickness of 0.20 mm were used as the base metal plate. Various resin layers were formed using a film thermocompression bonding method) or a direct laminating method (direct extrusion method). In addition, about the film lamination, two types, what used the biaxially stretched film and what used the unstretched film, were implemented. A film having an upper layer thickness of 45 μm and a lower layer (adhesive resin layer) thickness of 5 μm was laminated on both surfaces of the metal plate.

  Table 1 shows the production method of the laminated steel sheet and the contents of the produced laminated steel sheet.

The laminating method is as follows.
Film thermocompression bonding method 1: A film prepared by the biaxial stretching method was subjected to thermocompression bonding with a nip roll in a state where the steel sheet was heated to the melting point of the resin + 10 ° C., and then cooled by water cooling within 7 seconds.
Film thermocompression bonding method 2: An unstretched film was thermocompression bonded with a nip roll while the steel sheet was heated to the melting point of the resin + 10 ° C., and then cooled by water cooling within 7 seconds.
Direct extrusion method: resin pellets are kneaded and melted with an extruder, coated on a running steel plate from a T-die, and then the resin-coated steel plate is nip-cooled with an 80 ° C. cooling roll, and further water-cooled Cooled by.
The adhesive resin layer is extruded together with the upper layer from an extruder and a T die by a co-extrusion method to form a film or directly on a steel plate.
The coated steel sheet of the comparative example was coated with an epoxy thermosetting resin and heated at 220 ° C. for 10 minutes to form a coating film having a thickness of 8 μm.

"Can body molding"
Using the produced test steel plate, a can body (final formed body) was produced according to the following procedure in accordance with the production process shown in FIG. Table 2 shows the shapes of the intermediate molded body (process C) and the final molded body (process D). The drawing process of the process A was performed in 5 stages, and the diameter reduction process of the process D was performed in 7 stages.

  In Table 2, h, r, d, ha, hc, and R of the final molded body (step D) are the height to the open end of the final molded body, the diameter of the base portion 2, and the diameter of the neck shape portion 3, respectively. The height of the base body 2, the height of the neck-shaped portion 3, and the radius of the circular plate blank before molding that is equivalent in weight to the final molded body (see FIG. 1). The radius R of the circular plate blank was determined as follows. Measure the weight of the blank sheet before molding and the weight of the final molded body after the trimming process. Based on the measurement results, determine the radius of the blank sheet before molding that is equivalent to the weight of the final molded body. It was set as the radius R of the circular plate blank before shaping | molding in which a body and a weight became equivalent.

1) Blanking (71-94mmφ)
2) Drawing and ironing (process A)
Can with radius r and height h of d / R: 0.24 to 0.32, h / (R−r): 1.84 to 2.75 in five stages of drawing. A body (intermediate can body) was produced. Moreover, in order to produce a desired can body, the ironing process was also used together suitably.
3) Dome shape processing of can bottom (process B)
A hemispherical overhanging process having a depth of 6 mm was performed on the bottom of the can.
4) Trim processing (Process C)
The upper end of the can was trimmed by about 2 mm.
5) Diameter reduction of the upper part of the cylinder (Process D)
The diameter of the cylinder is reduced, specifically, the die neck method in which the opening end is pressed against the inner tapered die to reduce the diameter, and the final can body shape shown in Table 2 is obtained. A can body was produced.

  The adhesion, workability, and appearance of the film layer of the can body produced by the above procedure were evaluated as follows. The evaluation results are also shown in Table 3.

<Adhesion test>
The can body was sheared into a substantially rectangular shape in the can height direction so as to have a width of 15 mm in the circumferential direction, and only the steel plate was sheared linearly in the circumferential direction at a position 10 mm from the bottom surface in the can height direction. As a result, a test piece composed of a 10 mm portion and the remaining portion on the bottom side in the can height direction with the shearing position as a boundary was created. A steel plate having a width of 15 mm and a length of 60 mm is connected to the 10 mm portion (welding), and the 60 mm steel plate portion is held, and the remaining portion of the film is peeled off by about 10 mm from the breaking position. A peel test was carried out in the direction of 180 ° with the part from which the film was peeled off and the 60 mm steel plate part being held. The minimum value of the observed peel strength was used as an index of adhesion.
"Peel strength"
Less than 3N / 15mm: ×
3N / 15mm or more, less than 5N / 15mm: ○
5N / 15mm or more: ◎

"Film processability evaluation"
A seal with a small window of 15 mmφ centered at a position 10 mm from the upper end of the can so that the measurement area was 15 mmφ. Next, the small window portion was immersed in an electrolytic solution (KCl: 5% solution, temperature is room temperature), and a voltage of 6.2 V was applied between the steel plate and the electrolytic solution. Evaluation was made as follows according to the current value measured at this time.
"Current value"
1.0 mA or less: ○
Over 1.0 mA: ×

"Evaluation results"
Can bodies C1 to C7 are examples of the present invention, and showed good values for film adhesion and workability.

  Can bodies C8 to 13 and C15 and 16 are examples of the present invention, and a polypropylene-polyethylene block copolymer is provided in the main layer, and both processability and adhesion are good. In particular, the adhesion was ◎.

  Can body C14 is an example of the present invention, and the main layer is a polypropylene-polyethylene block copolymer, but the polyethylene concentration is lower than the lower limit. Both workability and adhesion were good, but the adhesion was only good.

  The can body 15 is a comparative example of the present invention. The resin layer was coated with a thermosetting paint, and the processability and adhesion were both x.

  The laminated steel sheet of the present invention can be used to produce a two-piece can with a high workability that can prevent peeling and breaking of the laminated resin layer. The two-piece laminate can of the present invention can be used for applications such as aerosol cans that require a high degree of processing.

It is a figure explaining one Embodiment of the manufacturing process of the can of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Blank sheet 2 Base | substrate part 3 Dome shape part 4 Neck shape part 5 Tapered shape part

Claims (6)

The height h, the maximum radius r, and the minimum radius d (including the case where r and d are the same) of the final molded body are 0 with respect to the radius R of the circular plate before molding in which the weight is equivalent to the final molded body. 1 ≦ d / R ≦ 0.25 and 1.5 ≦ h / (R−r) ≦ 4, a laminated steel sheet used for the production of a two-piece can, wherein at least one side of the steel sheet, A laminated steel sheet for a two-piece can, comprising a coating layer of a polyolefin resin. 2. The laminated steel sheet for a two-piece can according to claim 1, wherein the polyolefin resin is disposed as an upper layer through a steel sheet surface and an adhesive resin layer. The polyolefin resin layer is a polypropylene resin, and the adhesive resin layer is a mixture of adhesive polyethylene and adhesive polypropylene, and the adhesive polyethylene is contained in the mixture in an amount of 8 to 20% by mass. The laminated steel sheet for a two-piece can according to claim 2. Adhesive polyethylene is a homopolymer of ethylene, or ethylene and one or more α-olefins selected from 1-butene, 1-hexene, 1-heptene, 1-octene and 4-methyl-1-pentene. Block or random copolymer, adhesive polypropylene is propylene homopolymer or propylene and ethylene, 1-butene, 1-hexene, 1-heptene, 1-octene, 4-methyl-1-pentene The laminated steel plate for a two-piece can according to claim 3, which is a block or random copolymer with one or more α-olefins selected from the group consisting of: 5. The two-piece according to claim 3, wherein the polypropylene resin is a propylene / ethylene block copolymer, and a ratio of a propylene component of the block copolymer is 50 mol% or more and 98 mol% or less. Laminated steel sheet for cans. A two-piece laminated can manufactured by multi-stage forming the circular plate of the laminated steel sheet according to any one of claims 1 to 5, wherein the final molded body has a height h, a maximum radius r, and a minimum radius d. (Including the case where r and d are the same), but 0.1 ≦ d / R ≦ 0.25 and 1.5 with respect to the radius R of the circular plate before molding that is equivalent in weight to the final molded body ≦ h / (R−r) ≦ 4 The two-piece laminate can characterized by satisfying the relationship.

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