JPS63206481A - Painted and welded can body - Google Patents

Abstract

PURPOSE:To permit execution of severe drawing without exfoliation of resin coating layers by forming a tin-iron alloy, tin layer and chromium.chromate layer successively on a steel sheet for a can body and coating and forming the resin coating layers on the inside and outside surfaces. CONSTITUTION:The surface-treated steel sheet for forming the can body has at least the tin-iron alloy layer 7, the tin layer 8 and the chromium.chromate layer 9 in this order on the substrate steel sheet 6. The tin layer 8 is formed by assuring >=50mg/m<2> tin remaining without being alloyed and is discontinuously distributed in the range of 10-60% of the steel sheet surface. The layer 9 is 5-40mg/m<2> in terms of metal chromium. Such surface-treated steel sheet is subjected to resin painting 10 on the outside surface and on the inside surface side of the can body from which the weld zone is removed; thereafter, the steel sheet is cut. rounded and welded to form the can body. The weld zone is subjected to resin painting and the can body is drawn until the diameter W1 in the apertures is reduced as shown in the figure. Exfoliation of the resin coating layers 10 does not arise even if the drawing size is 6-15% of the diameter W of the can body.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention comprises a reduced diameter portion on at least one opening side,
This invention relates to a welded can body used for beverage cans etc. whose inner and outer surfaces are coated with a protective resin coating layer.

(Prior Art) In recent years, variations in metal beverage cans and the like have come into widespread use due to the diversification of tastes.

As one type of can, a three-piece so-called neck-in can is known, which has a continuous diameter-reducing portion where the diameter of the can body gradually decreases toward the opening side of the can body. However, this neck-in-three-piece can is designed to reduce costs by downsizing the can lid, and to reduce packaging costs by making the outer surface of the can body and the can lid seam on the same surface. The narrowing dimension of the can body in the axial direction of the can body is also relatively small, less than 6% of the can body diameter,
There is little change in the appearance of the can body.

On the other hand, the opening side of the can body is subjected to a large constriction process in which the constriction dimension of the can body in the axial direction of the can body is 6% or more of the can body diameter to form a characteristic reduced diameter part. It is necessary that even if a large forming process is performed during the drawing process, a predetermined shape can be obtained, there is no problem in terms of the quality of the can, and there is no problem in terms of productivity.

Conventionally, these deformed welded can bodies have been made of steel, tin-free steel, or nickel-plated steel plate provided with a resin coating layer.

However, although the weldability of furiki, which is made by applying tin plating uniformly on the base steel plate, is relatively good, cracks are likely to occur in the welded area, and furthermore, the crank opens during the narrowing process mentioned above, and the welding Cracks may occur in the repair resin coating layer.

Furthermore, when the drawing process is performed in this way, the cohesive force of the tin oxide film layer is small at the place where the drawing process is performed, so the tin oxide film layer is destroyed and the resin coating layer and the resin coating layer are destroyed regardless of the type of resin. The adhesive strength of T-pee1 is usually I Kg/ct.
It is less than or equal to a. As a result, the resin coating layer on the inner surface of the can body can easily peel off or get scratched due to the large drawing process, reducing the shelf life of the contents, or the external resin coating layer or printed surface can peel off or be damaged, resulting in poor appearance. Damage or rust may occur.

On the other hand, tin-free steel or nickel-plated steel sheets have poor weldability because they do not have tin on their surfaces, and compared to tinplate, welding defects are more likely to occur and productivity is lower. Moreover, splashes or voids may occur at the welded portion, which may deteriorate the quality of the can body. Furthermore, when the above-mentioned drawing process is performed, the resin coating layer of these steel sheets is less likely to peel off or be damaged than that of furiki. In order to dissolve the iron into the iron, the inner surface of the can body needs to be coated with resin twice in advance, or repair painting is required after the can body is narrowed, resulting in poor productivity and an increase in costs.

(Problems to be Solved) The present invention eliminates such conventional inconveniences and provides welding that firmly adheres to the can body without causing the resin layer coated on the inner and outer surfaces of the can body to peel off even when subjected to severe drawing processing. The purpose is to provide can bodies.

(Means for Solving the Problems) In order to achieve the above-mentioned object, the present invention provides at least one opening side of a can body whose side edges are welded, and a can body diameter that is smaller toward the opening. A reduced diameter part is provided by drawing processing, and the maximum reduction dimension of the can body in the axial direction of the can body in this reduced diameter part is 6 to 15% of the can body diameter, The surface-treated steel sheet forming the can body has at least a drinking cup alloy, a tin layer, and a chromium chromate layer on the base steel sheet in this order, and the amount of tin deposited forming the tin layer is 50 mg/bo or more, and the steel sheet The chromium/chromate layer is discontinuously distributed in the range of 10 to 60% of the surface, and the chromium/chromate layer has a concentration of 5 to 60% in terms of metallic chromium.
40 mg/nf, and is characterized by a resin coating layer coated on the inner and outer surfaces of the can body.

First, an example of the welded can body formed by drawing according to the present invention will be described below with reference to FIG.

(1) is a cylindrical can body with welded seams on the side edges and openings (2) at both ends; (3) is the opening (2) of the can body (1);
The illustrated example shows a reduced diameter portion including a plurality of step portions (5) each having a diameter smaller than the body diameter of the adjacent small diameter portion (4) toward the opening (2) provided by drawing processing on the side. In this example, the reduced diameter portions (3) are provided on both openings (2) sides of the can body (1), and the reduced diameter portions (3) are provided at the openings (2) of the can body (1).
The opening diameter W formed in the opening (2) by performing drawing processing on the 2) side is in the range of 6 to 15% as determined by the following formula.

In order to form such a can body, there are a plurality of gaps on one or both ends of the can body from the center of the can body to the opening side, and a plurality of narrowing steps are performed in the order from the opening side. This is done by applying a narrowing process to form a reduced diameter section with a plurality of steps that are successively smaller in diameter than the can body diameters of adjacent small diameter sections from the center side of the can body toward the opening side, and then narrowed down to the final diameter. .

In the illustrated example, the opening (2) side of the can body (1) is formed with a plurality of stepped portions ( 5) with a reduced diameter part (
3), but in the present invention, the diameters are sequentially smaller than the body diameters of the adjacent small diameter portions (4) toward the opening (2) of the can body (1). After a reduced diameter part (3) having a plurality of steps (5) is formed by drawing, a small diameter part (4) is formed on at least one opening (2) side of the can body (1). and a stepped portion (5).
) from the inner and outer surfaces of the can body (1) using rolls to form a smooth continuous diameter-reducing portion in which the can body diameter W gradually decreases toward the opening (2).

The present inventor found that when such a severe drawing process is applied to a welded can body made of a conventional can body material, the coating effect of the resin coating layer is significantly reduced in the drawing process, As a result of studying this problem, the present invention was completed based on the finding that such inconveniences can be overcome by using the above-mentioned can body material of the present invention.

That is, in the present invention, the tin layer of the steel plate, that is, the tin that remains without being alloyed, is secured at 50 mg/% or more, and the tin layer does not cover the entire surface of the steel plate, but is discontinuous in the range of 10 to 60% of the tin layer. The purpose of using a steel plate plated in a pattern (island-like or mottled) distribution and setting the amount of tin to 50 mg/M or more is to improve the protection of the base steel plate and the weldability. Then, the steel plate is covered with a discontinuous tin layer.
When the tin content is less than 0%, the adhesion of the resin coating layer is good when subjected to drawing processing like tin-free steel, but it is difficult to secure a tin content of 50 mg/nr or more, resulting in poor weldability. decrease. In addition, if it exceeds 60%, splashes and cranks are likely to occur during welding, causing peeling and cracking of the resin coating layer at the welded part, as well as leakage during manufacturing of tin-plated steel sheets and baking when providing the resin coating layer. In the process, a brittle tin oxide layer is formed, which is interposed between the resin coating layer and the base steel plate and lowers the adhesive strength below the adhesive strength with the resin coating layer that can withstand the drawing process.

Furthermore, the tin-plated steel sheet used in the present invention has chromium, which is composed of metallic chromium with a deposit of 2 to 20 mg/nf and chromium oxide with a deposit of 3 to 20 mg/m2 in terms of chromium, on the tin layer. It has a chromate layer. This chromium/chromate layer covers the entire tin layer, which is discontinuously distributed in the form of islands or spots, and protects the surface of the steel sheet where no tin layer is present, improving corrosion resistance and strengthening the adhesive strength with the resin coating layer. improve.

The chromium/chromate layer is 5 to 40 in terms of metallic chromium.
■/nf is suitable; if it exceeds 40■/nf, weldability deteriorates, which is not preferable. In particular, when forming this layer, the metal chromium layer and the chromium oxide layer each have an adhesion amount of metal chromium of 2 to 20 ■/Cll1, and a suitable amount of chromium oxide adhesion is 3 to 20 ■/ci in terms of metal chromium. .

In addition, the tin-plated steel sheet used in the present invention forms a dense alloy layer on the base steel sheet to improve corrosion resistance.
As a base layer, a layer containing 5 to 200 mg/% of nickel can be provided if desired. This nickel-containing layer includes a nickel plating layer provided on a base steel plate,
There are a nickel-containing layer formed by subjecting the nickel plating layer to annealing diffusion treatment and diffusing part or all of it into the base steel sheet, and a nickel-iron alloy plating layer provided on the base steel sheet.

The above-mentioned tin-plated steel sheet of the present invention is coated with resin on the inner surface of the can body except for the area that will become the welding part, and then cut to the size of a can body blank, rolled up, and the end edges on both sides are overlapped. , and seam weld that part to form the can body. Next, a resin coating is applied to the welded part, the drawing process is performed, and a flange process is applied to the end of the can body, a can lid is seamed to one end of the can body, and a correction coating is applied to the inner surface of the can body as necessary.

As long as the can body is made of the tin-plated steel plate, the resin coating layer applied to the inner surface of the can body may be made of thermoplastic or thermosetting resin paint, which is normally used as can inner surface paint. Although the above-mentioned severe drawing process does not affect the adhesive strength, it is necessary to consider the corrosion resistance, discoloration and flavor of the contents, etc. when selecting a thermosetting resin. Paints are suitable, specifically epoxy resin paints, vinyl resin paints, vinyl organosol paints, polyester paints, polyamide paints, acrylic resin paints, aminoplast paints, oil-based paints, etc. Thermosetting paints containing one type or a combination of two or more types are suitable.

Further, specific preferred examples include a thermosetting epoxy phenol resin, particularly a phenol resin containing 65% by weight or more of a resol type phenol resin formed from bisphenol 8, and bisphenol A having a number average molecular weight of 1,400 to 7,000. It is preferable to form a resin coating film with a thickness of 2 to 10 μm using a thermosetting epoxy phenol resin paint containing a type epoxy resin in a weight ratio of 50,150 to 5,795 μm.

In addition, as thermosetting oil-based paints, oil-based paints similar to those conventionally used as vehicle components of C enamel,
That is, a drying oil such as tung oil, linseed oil, and dehydrated castor oil is heated and reacted with an oil-soluble resin such as a rosin-modified phenol resin, an alkylphenol resin, and a xylene resin, using a small amount of glycerin or pentaerythritol as necessary, and then, Examples include paints obtained by adding an appropriate amount of naphthenic acid or lylunate of iron, manganese, cobalt, etc. as a drying agent and diluting with a solvent.

Such paints may contain organic and inorganic additives and modifiers, if desired.

Further, in the welded can body of the present invention, the outer surface of the can body is also coated prior to welding, at the stage of the can body raw material, or after welding and prior to the above-mentioned drawing process.

When the tin-plated steel sheet of the present invention is used, the resin coating layer on the outer surface of the can body does not peel off from the outer surface of the can body even when subjected to the above-mentioned severe drawing process like the inner surface of the can body. No cracks or cracks will occur.

The paint applied to the outside of the can body must have stain resistance, slip resistance, scratch resistance, hot water resistance, etc., so acrylic resin paint, polyester paint, epoxy resin paint, alkyd resin paint, etc. Thermosetting paints made of one type or a combination of two or more of aminoplast resin type paints and aminoplast resin type paints are suitable.

As mentioned above, the tin-plated steel sheet of the present invention has excellent adhesive properties, so when painting the outside of the can body, the undercoat size coat, which was indispensable when painting conventional tin wood, is not necessary.
In the present invention, good adhesion is obtained even when the above-mentioned severe drawing process is applied, and the resin coating layer does not peel off or the like.

The tin-plated steel plate of the welded can body of the present invention and its painted resin coating layer are schematically shown in FIGS. 2 and 3. FIG. 2 shows an example in which no nickel-containing layer is provided, and FIG. 3 shows an example in which a nickel-containing layer is provided.

(6) is a base steel plate, (7) is a tin-iron alloy layer, (8) is a tin layer, (9) is a chromium chromate layer, 0ω is a resin coating layer, and (11) is a nickel-containing layer.

(Example) Using a steel plate with a thickness of 0.22 mm and having the amount of nickel plating, the amount of tin plating, the amount of metallic chromium, and the amount of chromium oxide (chromium equivalent) shown in Table 1 in the structure shown in Figure 2, A resin-coated base plate was prepared by applying resin coating to the inside and outside of the can body as shown in the figure.

In Table 1, in Example 6 and Comparative Example 2, when forming the resin coating layer on the outer surface of the can body, two resin coating layers were provided using a size coat made of polyester resin as a base coat. .

Next, this resin-coated original sheet is cut into the size of a tanzaku-shaped can body blank, rolled, and the edges of the blanks overlapped, and welded using a known electric resistance welding machine at a welding speed of 60 m/min to form a cylindrical welded can. Created the torso.

Next, the opening of the can body is subjected to drawing processing in several stages using a known roll forming method, and the drawing processing is performed in the shape shown in Figure 1 with the diameter reduction rate of the maximum diameter reduction part as shown in Table 1. We created a can body with

After flanging both opening ends of this can body, an aluminum easy-open can lid was double-sealed to one end of the opening to produce an empty can. Furthermore, the contents of the can were filled with milk coffee, sealed with a tin can lid, subjected to retort treatment for 20 minutes at 125'CX, and then stored for 37'CXa.

In the above-mentioned process, the T-peel peel strength of the resin coating layer was measured in the state of the resin-coated original plate, the weldability was measured during the manufacture of welded can bodies, and the multi-stage diameter reduction was conducted under the test conditions shown in Table 1. After the narrowing process, the adhesion of the resin coating layer on each reduced diameter part was evaluated, as well as the contents of the can after storage and the appearance of the resin coating layer on the outer surface of the can.

In addition, in Comparative Examples 1 to 3, the tin distribution ratio of the tin plating layer of the present invention is outside the range of the present invention, Comparative Example 4 is a conventional tin-free steel, and Comparative Example 5 is a nickel-plated steel plate. It uses In addition, Comparative Example 6.7 was performed with a smaller diameter reduction ratio than the maximum diameter reduction ratio of the present invention, and Comparative Example 8.9 was performed with a larger diameter reduction ratio.

As is clear from the results in Table 1, Examples 1 to 1 of the present invention
6 has excellent adhesion of the resin coating layer on the inner and outer surfaces of the can body even after being subjected to a severe squeezing process of 13%, and also has excellent adhesion in iron elution, flavor, peeling of printed and painted surfaces, and induction of external problems. The raw condition was also good. In Comparative Examples 1 to 3 using conventional tin-plated steel sheets, the adhesion of the resin coating layer at the reduced diameter part on the inner surface of the can body was poor, and in Comparative Example 1 without a size coat, the printing and printing on the outer surface of the can body were poor. Peeling of the painted surface was noticeable, and Comparative Example 2, which was coated with a size coat, was also not good.

Examples 1 to 5, which were not subjected to size coating, were not significantly different from Example 6, which was subjected to size coating, in terms of can appearance.

In addition, in Comparative Example 4 using tin-free steel and Comparative Example 5 using nickel-plated steel plate, the adhesion of the resin coating layer at the reduced diameter part was not necessarily poor, but there was a lot of iron leaching and rust on the outer surface. This caused storage problems.

Comparative Example 6 using the original plate of Comparative Example 1 with a maximum diameter reduction rate of 4%.
7 was good in all respects because the diameter reduction process was small, but from comparison with Comparative Example 1, it was found that 13%
It turned out that it could not withstand such harsh drawing process.

Furthermore, in Comparative Example 8.9 in which the maximum diameter reduction rate was 17% using Example 1, a sufficiently high quality of the can could not necessarily be obtained.

*1) Each plating layer of the original plate was measured using the following method.

(a) The amount of nickel plating and the amount of tin plating were measured by fluorescent X-ray method.

(For the chromate treatment, the total amount of chromium was measured using a fluorescent X-ray method, and the amount of metallic chromium was further measured using a constant current electrolysis method in a 0.IM NaJPOa solution, and the difference was taken as the amount of chromium oxide. .

*2) Unalloyed tin amount, JIS G33
It was measured by the electrolytic peeling method described in 03.

*3) Area ratio of unalloyed tin layer to original plate area.

*4) Only the main component resin is listed.

*5) 'T-pee1 strength is measured by providing a resin coating layer on the original plate a as shown in Fig. 3, pasting the resin coating layers together with adhesive C, and pulling them in the 90' direction from the top and bottom, until the resin coating layer is The stress at the time of peeling was measured. In addition,
In the table, <1 kg/cm indicates that the adhesive strength between the original plate and the resin coating layer is smaller than the bending stress of the original plate and is determined to be 1 kg/cm or less, and > 2 kg/all indicates that the adhesive strength between the original plate and the resin coating layer is lower than the bending stress of the original plate. and adhesive strength (approximately 2 kg/c
m).

*6) Weldability was measured using electric resistance seam welding (55011z sine wave) on original plates with a thickness of 0.22 m5+ at a welding speed of 60 m/min with an overlap width of 0.40 mm, and the effective range of welding current and welding The condition of the surface was observed and determined.

◎ The welding suitability range is extremely wide and good welding can be achieved stably.

O is within a practical range.

Δ There are many splash cracks and it is difficult to repair and cover the welded surface with paint.

*7) Defects such as peeling or wrinkles in the resin coating layer of the can body after the diameter reduction process were visually determined.

O Shows good condition with no abnormality.

Δ　Although within the practical range, the quality is unstable.

× Not practical *8) Canned food was evaluated using the following test method.

(b) Iron elution and flavor were determined by filling an empty can with milk coffee, retorting it at 125°C for 20 minutes, storing it at 37°C for 3 months, and measuring the iron elution amount after opening the can and determining the flavor. I did it.

(b) The peeling state of the printed and painted surfaces was visually observed by visually observing the peeling state of the resin coating layer on the outer surface of the processed part of the can body including the welded part or the printed surface.

(c) External student condition: 45°C, humidity 85%RH
The state of rust was determined after storage for 10 days.

O Shows good condition with no abnormality.

Δ　Although within the practical range, the quality is unstable.

× Not practical (effect) As is clear from the above explanation, when the present invention is applied,
The tin-plated steel plate that forms the welded can body has a predetermined amount of tin layer discontinuously distributed on the base steel plate and a predetermined amount of chromium/chromate layer covering the tin layer, so it is necessary to paint the inside and outside of the can body. Because the adhesiveness with the resin coating layer is strong, the effectiveness of the protective coating on the inner and outer surfaces of the can body does not deteriorate even when subjected to severe drawing processing with a maximum diameter reduction rate of 6 to 15%. Excellent deformation of excellent quality. It has the effect of providing a welded can body.

[Brief explanation of the drawing]

FIG. 1 is a diagram for explaining the reduced diameter part of the can body of the present invention, FIGS. 2 and 3 are schematic diagrams of the can body structure of the present invention, and FIG. 4 is a diagram showing the T-pee1 strength. It is an explanatory diagram of a test.

Claims (1)

[Claims] 1. At least one opening side of the can body whose side edges are welded is provided with a reduced-diameter part where the diameter of the can body decreases toward this opening, and the can body in this reduced-diameter part is The maximum narrowing dimension of the can body in the axial direction of the can body is set to 6 to 15% of the can body diameter, and the surface-treated steel plate forming the can body is coated with at least a tin-iron alloy on the base steel plate. It has a tin layer and a chromium/chromate layer in this order, and the amount of tin deposited forming the tin layer is 50 mg/m^2 or more and 10 to 60% of the surface of the steel plate.
The chromium/chromate layer is discontinuously distributed in the range of 5 to 40 mg/m^2 in terms of metallic chromium,
A painted welded can body, characterized in that a resin coating layer is applied and formed on the inner and outer surfaces of the can body.