JPH0639963A - Laminated steel plate for welded can - Google Patents

Abstract

PURPOSE:To improve the thermal shrinking properties of film and ensure that its adhesive power does not deteriorate even after undergoing processes such as welding and retort treatment by laminating a specific film in a belt form in the line direction of a plated steel strip with a specified width of unvarnished part left. CONSTITUTION:The subject laminated steel plate 8 has plated skin film consisting of a metal chromium layer of 5mg/m<2> min to 50mg/m<2> max and a chemically treated layer 6 of chromium hydroxide of 5mg/m<2> min to 25mg/m<2> max in terms of chromium, which are formed on a tinned layer with a deposit amount of 0.9g/m<2> min to 2.8g/m<2> max. In addition, a belt-like thermally pressure-deposited resin film layer 1 is formed on one surface or both surfaces of a steel plate with a surface roughness PPI (threshold value: 0.5mum) of 5 min and 150 max, in a strip line direction, with a specified width of unvarnished part 4 left. This resin film layer is of a biaxially stretched film consisting of polyethylene terephthalate containing 0.5mol% min and 10mol% max of isophthalic acid as an acid component.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steel plate for a can, which is used for a welding can such as a food can and is preliminarily laminated with a resin.

[0002]

2. Description of the Related Art Can manufacturing methods include a solder can manufacturing method, a welding can manufacturing method, an adhesive can manufacturing method, a drawing ironing can manufacturing method, a drawing can manufacturing method and the like. The welded can manufacturing method has the advantages that the device is simpler than other can manufacturing methods, the equipment cost is low, work can be performed easily and reliably, and the strength of the welded portion is high and it can withstand advanced processing. Therefore, it is a can manufacturing method that has rapidly spread.

A tin-plated steel sheet was initially used as a can material for the solder can manufacturing method and the welding can manufacturing method. However, in the case of welding, the amount of tin deposited is much smaller than that in soldering.
It is used in combination with thin plating and other metals. In this respect as well, the growth of the welding can manufacturing method is expected.

On the other hand, the body and lid of food cans have been painted. Thick film coating to improve corrosion resistance on the inner surface of the can, protective coating on the outer surface, printing, etc. However, when applying these,
The plated steel sheet is cut into a sheet having a predetermined size, and each of these is coated or printed. This process is one of the issues to be rationalized in the can manufacturing process because it requires physical distribution costs and requires measures against environmental pollution due to painting.

Under these circumstances, conventionally, a laminated steel strip for welding cans has been proposed in which a film is laminated in a strip shape on a steel strip while avoiding the welded portion. For example, JP-A-3-236
In 954, there is proposed a can material in which thermoplastic films are laminated in a width corresponding to the height of the can, leaving a non-laminated portion having a width of 2 to 5 mm. The resin species of the thermoplastic film is polyester, It discloses that polypropylene, polyethylene and nylon are good.

[0006]

However, in the above-mentioned proposed can material, a decrease in adhesion between the resin film and the base due to heat influence during welding, repair coating of the welded portion, retort treatment, etc. is taken into consideration. However, there is a problem that the resin film swells or peels off due to the retort treatment.

The present invention has been made to solve this problem. By devising to reduce the heat effect at the time of welding and ensuring an adhesion force that does not decrease even when the heat effect is applied, the retort adhesion resistance is improved. It is intended to provide a good laminated steel plate for a welding can.

[0008]

Means for achieving this object is a steel plate obtained by laminating a resin film in a strip shape along the line direction of the strip leaving a varnish avoiding portion of a predetermined width on the surface of the plated steel plate, The plating film has the following (I)
And (ro), and the resin film has the following (ha),
There are (ni) and (ho), and each resin film is laminated on each plating film, but the resin film of (ha) and (ni) has a surface roughness PPI (threshold value 0.5 μm) of 5 or more. Laminate for welding can, which is directly thermocompression-bonded to the plating film surface of 150 or less, and the resin film of (ho) is adhered to the plating film surface by the following (e) adhesive layer and laminated on one side or both sides of the plated steel sheet, respectively. It is a steel plate.

(Ii) Adhesion amount is 0.9 g / m ² or more and 2.8 g / m ²
The amount of metallic chromium on the following tin plating layer is 5 mg / m ² or more 50
mg / m ² or less hydrated oxides chromium 5mg of chromium / m ²
Plating film having a chemical conversion treatment layer of 25 mg / m ² or less (filter) Adhesion amount of 0.6 g / m ² or more 2.0 g on a nickel plating layer of 15 mg / m ² or more and 100 mg / m ² or less / m ²
On the following two-layer plated layer plated with tin, further, the amount of metal chromium is 5 mg / m ² or more and 50 mg / m ² or less, and the hydrated oxide chromium is 5 mg / m ² or more and 25 mg / m ² or less as chromium. Biaxially stretched film of polyethylene terephthalate copolymer in which 0.5 mol% to 10 mol% of acid component is isophthalic acid

(Ni) 0.5 mol% or more of the acid component 10 mol
% Bi-axially oriented film of polyethylene terephthalate copolymer with isophthalic acid as lower layer and polyethylene terephthalate homopolymer as upper layer (ho) Biaxially oriented film of polyethylene terephthalate homopolymer An adhesive consisting of a bisphenol A type epoxy resin having an average molecular weight of 15,000 or more and 30,000 or less and a resol type phenol resin based on bisphenol A, which is heat-cured with an adhesive containing 70 wt% or more and 90 wt% or less of the bisphenol A type epoxy resin. Adhesive layer

[0011]

[Function] Resin is not laminated on the varnish avoiding part,
A chemical conversion treatment is applied on the tin plating to improve the adhesion of the paint. FIG. 1 shows the surface of this laminated steel sheet. The strip-shaped varnish avoiding portions 4 and the resin laminate strips 5 are alternately provided in parallel with the rolling direction of the steel sheet. A cross section is shown in FIG. 1 is a resin film, 6 is a chemical conversion treatment layer, 7 is a plating layer, and 8 is a steel plate. The film of the varnish avoiding portion 4 is composed only of the chemical conversion treatment layer 6 and the plating layer 7, and is not covered with the resin film 1. Therefore, by using the varnish avoidance portion as a welding allowance, it is not necessary to remove the resin film at the time of welding at the time of can-making even with a steel sheet on which the resin film 1 is laminated in advance.

On the other hand, in the resin laminate strip 5, the plating layer is subjected to a chemical conversion treatment similarly to the varnish avoiding portion 4, and the resin is laminated thereon. For this reason, it is not necessary to apply troublesome coating at the time of can manufacturing. The width of this resin laminate band is determined by the diameter of the can, and is 161 mm for a 200 ml beverage can, for example.

Since the varnish avoidance portion is welded on the front and back sides, it is necessary on both sides of the steel sheet, but the resin laminate band may be provided on at least one side which is the inner surface of the can. Of course, it may be provided on both sides, and in this case, the treatment is performed in consideration of the inner surface and the outer surface of the can. For example, the surface corresponding to the inner surface has the resin laminate band according to the present invention, and the surface corresponding to the outer surface has only the plating film, the coating film band, the white coat resin laminate or the printed resin laminate band. The processing surface may be adapted accordingly.

At least one side, which is the inner surface after can making, is preliminarily laminated with resin, so that no damage or deterioration occurs even during the steps of welding, outer surface printing, processing, etc. during can making, and at the time of filling the contents. Also, the film must maintain corrosion resistance as well as adhesion of the film after filling.

First, at the time of welding, the width of the varnish avoiding portion has an important meaning. The temperature of the weld exceeds 1000 ° C, and the heat also propagates in the circumferential direction of the can. Adhesion and other properties of the resin film should not be deteriorated by this influence. If the width of the varnish avoiding portion is too narrow, the resin melts or deteriorates to deteriorate the adhesion, workability, and corrosion resistance. If you examine the heat propagation area, welding speed, plate thickness, thermal conductivity, etc. are related,
The effect of welding speed is large. The width of the weld required to avoid the effect of heat during welding varies depending on the welding method,
In the case of the electric resistance narrow lap seam welding method which is widely used at present, it is safe to set it to 5 mm or more. If a high-speed welding method using high-density energy is used, the width may be narrow, but since the thickness of the steel plate for a can is around 0.2 mm, about 0.5 mm is necessary. It goes without saying that when the varnish avoidance portion is located at the edge of the steel plate, the width of half the above is sufficient.

Next, there must be an adhesive force between the resin film and the surface of the plated steel sheet to endure neck-in processing and the like. When subjected to the heat associated with welding and external printing, the resin film tends to shrink. At this time, if there is air or water trapped between the resin film and the surface of the plated steel sheet, sufficient adhesion cannot be obtained. Here, if there is a portion with reduced adhesion, peeling occurs during neck-in processing, flange extension processing, or flange winding processing. If the surface of the plated steel sheet has irregularities, the resin film softened to the bottom of the recesses is less likely to enter during lamination, and air and moisture are likely to be entrapped. In order to prevent these inclusions, it is preferable that the unevenness of the surface of the plated steel sheet is gentle and the resin film has fluidity during thermocompression bonding.

Roughness of plated steel surface PPI (Threshold 0.5 μ
When m) is 150 or less, entrapment of air and moisture is small, and sufficient adhesion can be obtained when a resin film described later is laminated. The surface roughness PPI is the number of peaks in the surface cross section whose height exceeds the threshold value per inch. The smaller the PPI, the less entrained air and water. This state is shown in FIG. (a) is the PPI of the surface
(Threshold value 0.5 μm) is laminated to a large plated steel sheet with a value of about 500, and (b) shows a PPI (threshold value 0.5 μm) of 50.
This is the case when it is laminated on a relatively small surface.
In (a), a space 3 exists between the resin film 1 and the plated steel plate surface 2, but it does not exist in (b).

However, a steel plate surface having a PPI (threshold value of 0.5 μm) that is too small is likely to be scratched during handling such as printing and baking. That is, the roughness PPI (threshold value 0.5 μm) of the surface of the plated steel sheet is suitably 5 or more and 150 or less. 100
The following is more preferable.

In order to reduce the roughness of the plated surface, it is effective to reduce the roughness of the base steel sheet. In order to obtain a plated steel sheet surface having a PPI (threshold value 0.5 μm) of 150 or less, a steel sheet having a surface PPI (threshold value 0.5 μm) of 180 or less may be used.

Not only the resin film itself should avoid cracks and breaks during processing, but it is also preferable that it spreads to every corner of the recessed portion on the surface of the plated steel sheet during thermocompression bonding (hereinafter referred to as heat fusion). . Such resin species include polyolefin, polyester, nylon and the like. However, since it is exposed to superheated steam exceeding 100 ° C. during the retort treatment, polyolefin and nylon having a relatively low melting point and unstable at high temperature have a problem in the retort resistance. Among the polyester resins, polyethylene terephthalate and polyethylene naphthalate are excellent in heat resistance. In particular, a polyethylene terephthalate-based resin has corrosion resistance as well as flexibility that can withstand severe processing. Above all, the biaxially stretched film is particularly excellent in the ability to block corrosive substances. However, even with a polyethylene terephthalate type, a homopolymer using 100% terephthalic acid as an acid component has a melting point of more than 260 ° C. and cannot obtain sufficient fluidity during thermocompression bonding. This is because the thermocompression bonding temperature is limited to 230 ° C. or lower in order to avoid alloying of tin in the plating layer.

It is well known that the melting point is lowered by changing the acid component of the polyethylene terephthalate polymer. However, the purpose cannot be achieved unless the melting point is lowered without losing the heat resistance and anticorrosion properties of the homopolymer. As a result of various studies on the acid component, the inventors have found that the above object can be achieved by replacing a part of terephthalic acid with isophthalic acid. Isophthalic acid substitution is considered to reduce the crystallization of the resin during film formation and lower the melting point.

In this case, if the content of isophthalic acid is not less than 0.5 mol% of the acid component, the effect of improving the heat fusion property is not remarkable. On the other hand, if the isophthalic acid content is too high, the resin film shrinks during heating in the can manufacturing process. When heat shrinkage occurs, stress is accumulated in the resin film, and the adhesion with the surface of the plated steel sheet is likely to deteriorate when processed. Therefore, the content of the acid component exceeding 10 mol% should be avoided. That is, it is a biaxially stretched film containing polyethylene terephthalate as a main component and contains 0.5 mol% or more of the acid component of the film.
When 0 mol% or less is isophthalic acid, the heat-sealing property is good, and it is possible to prevent the adhesive force from being lowered in the can manufacturing process. Among them, the isophthalic acid content is 1.0 mol% or more and 8.0 mol%
The following is more preferable.

As described above, the homopolymer of polyethylene terephthalate does not shrink due to heating and has an excellent shielding effect, and the copolymer containing isophthalic acid has a good heat fusion property. Therefore, if the film has a two-layer structure and the copolymer having 0.5 mol% to 10 mol% of the acid component is isophthalic acid as the lower layer and the upper layer as the homopolymer of polyethylene terephthalate, the advantages of both can be utilized. Therefore, it is possible to obtain a laminate layer which has a very small heat shrinkage and a good heat fusion property and a large shielding effect. Such a film structure is more cost effective than a film in which the entire film is a copolymer. In this case, the thickness of the copolymer layer needs to be at least a threshold value of the surface roughness of the plated surface of 0.5 μm or more, and is preferably 1 μm or more.

There is a method of using an adhesive as another means for compensating for the drawback of the polyethylene terephthalate homopolymer which is inferior in heat fusion property. This adhesive must have sufficient adhesiveness as well as heat resistance like a resin film, and must be sufficiently hardened in a short time when continuously producing laminated steel sheets. If a can is made with insufficient curing, the adhesiveness of the resin film may decrease during retort treatment, or a phenomenon called so-called whitening may appear in which the resin film becomes cloudy white.

Epoxy resin is a resin often used as an adhesive. Among them, bisphenol A type epoxy is chemically stable and has heat resistance. However, depending on the molecular weight of the adhesive resin, it may take too long to cure, or in some cases it may become too hard to reduce the workability of the adhesive layer. The inventors have made a thorough investigation into the relationship between these phenomena and the resin and found that there are resins that make up the drawbacks of epoxy resins and that epoxy resins also have an optimum molecular weight range.

First, in order to complete the curing in a short time, it is advisable to mix an appropriate amount of bisphenol A-based resol type phenol resin. This resin is selected in consideration of the heat resistance and the workability described above, in addition to the fact that the adhesive cures in a short time by the addition thereof (hereinafter referred to as short-time curability). Due to its reactivity, this resol type phenol resin reduces the curing time by reacting with the unreacted functional groups of the epoxy resin during adhesive heating to crosslink the epoxy.

On the other hand, the short-time curability is related to the molecular weight of the epoxy resin itself, and the resin having a larger molecular weight cures in a shorter time. This state is shown in FIG. In the figure, the vertical axis is the short-time curability, the horizontal axis is the content of the epoxy resin in the adhesive, and the rest is the resol-type phenol resin. The number average molecular weight of epoxy resin is about 5000, 10000, 15000, 20000, 3
It is the result of examining about the case of 0000, the short-time curability decreases as the epoxy resin content increases,
Especially, when it exceeds 90 wt%, the decrease becomes remarkable. A decrease in short-time curability leads to whitening during retort. Also, the larger the number average molecular weight of the epoxy resin, the better the short-time curability, and the effect is clear at 15,000 or more.

However, the adhesiveness of the adhesive mainly depends on the epoxy resin, and if the epoxy resin content is less than 70 wt%, sufficient adhesion may not be obtained during processing. Also, the molecular weight of the epoxy resin has an upper limit, and if the molecular weight is large, the adhesive film after heat curing becomes hard. If the number average molecule exceeds 30,000, it may crack or break during processing.

That is, the adhesive is a bisphenol A type epoxy resin containing a bisphenol A based resol type phenol resin, and the content of the bisphenol A type epoxy resin agent is 70 wt% or more 9
When the number average molecular weight is 0 wt% or less and the number average molecular weight is 15,000 or more and 30,000 or less, even if the resin film is polyethylene terephthalate, strong adhesion can be obtained between the surface of the plated steel sheet and the surface of the plated steel sheet even for a short time. In addition, it is possible to avoid defects such as cracks, peeling or whitening of the film by heating, processing or retort treatment in the can making process.

With respect to the amount of the adhesive, the appropriate amount of application varies depending on the surface roughness of the plated steel sheet. Since air and water must not be entrained, an amount to supplement the surface roughness is necessary, and when the surface roughness is large, the appropriate coating amount increases. However, the surface roughness of the current chromate-treated tin-plated steel sheet or nickel-tin-plated steel sheet is PPI (threshold value 0.
5 μm) 20 to 200 or so. Adhesive layer weight in such plated steel sheet about 2mg / dm ² ~50mg / dm 2 is appropriate.

The resin film to be laminated with the adhesive is not limited to a homopolymer, but 10 mol as an acid component.
A copolymer containing 1% or less of isophthalic acid may be used. In addition, a treatment such as corona discharge may be used together during lamination.

The purpose of plating is to impart a high degree of corrosion resistance, and it is difficult to completely prevent the permeation of ions when only the resin layer is used, and even if a large amount of corrosion does not occur, a slight amount of iron elutes. Depending on the food can, the taste and aroma of the contents may change. Also, due to the presence of the plating film,
Even if a small defect occurs in the organic resin layer such as the resin film and the weld repair coating, the anticorrosion effect can be maintained by the retort treatment exposed to high temperature.

In the case of a tin-plated single layer, if the amount of adhesion is 0.9 g / m ² or more, it is of course possible to prevent a change in taste and aroma in combination with the coating film in the resin film to be laminated or the varnish avoiding portion. Retort resistance is also significantly improved. 2.8 g / m ²
If the amount of tin plating exceeds 1, the quality will be excessive. When nickel plating is performed, tin plating is further performed. This is to ensure the above-mentioned corrosion resistance and to obtain a varnish avoiding portion that facilitates high-speed welding.

Since tin is a soft metal and has a low melting point, a large contact area can be easily obtained with the electrode due to the softening of tin during seam welding. Therefore, a current necessary for welding flows uniformly at a relatively low voltage, and a reliable welding surface can be obtained. In seam welding, if an excessive current locally flows, a splash of a part of the metal is generated, which may stain the welded part or may result in insufficient joining of the insufficient current part. This phenomenon becomes more remarkable as the welding speed increases. When tin plating is applied on the thin nickel plating layer, the effect is recognized even if the amount of tin is small, and if it is 0.6 g / m ² or more, it can sufficiently withstand high speed welding. The maximum amount of tin is 2.0 g /
m ² is sufficient, and an amount exceeding this is not economically disadvantageous because there is no further improvement in quality.

Like tin, nickel is a harmless metal and has excellent corrosion resistance. If a nickel layer is interposed between the tin layer and the steel sheet, the formation of tin-iron alloy is suppressed. For this reason,
When the plating layer is a two-layer plating of nickel and tin, by depositing 15 mg / m ² or more of nickel as the lower layer, the adhesion amount of tin plating can be reduced to 100 mg / m 2.
^No more than ² is required.

Since all of these plating layers satisfy both corrosion resistance and weldability, they can be used both on the inner surface and the outer surface. That is, the plating layer may be tin-plated or nickel-tin two-layer plating on both sides, or either one surface may be tin-plated and the other surface may be nickel-tin-two-layer plating. Further, in these plated layers, the plated metal may be distributed in the form of particles or islands as long as the range of the surface roughness of the plated steel sheet of the present invention is maintained.

At the time of can making, the can body is bent into a round shape, seam-welded, and then repair-painted, and then subjected to a drawing process called neck-in. That is, the upper part of the body of the can is narrowed down to form the neck portion. Further, the opening is flanged to attach the can lid. When subjected to such processing, the film or coating film is peeled off when the heat fusion property is good but the adhesion is small.

The reason why the chemical conversion treatment is carried out after plating is to form a chromate film and thereby enhance the adhesion between the surface of the plated steel sheet and the resin film or coating film.
This treated film consists of chromium hydroxide or oxide (referred to as hydrated oxide) and metallic chromium. When the amount of metallic chromium is 5 mg / m ² or more, the hydrated chromium oxide is 5 mg / m as chromium.
By forming ^two or more films, stronger adhesion can be obtained. Even if the amount of metallic chromium exceeds 50 mg / m ² and the amount of hydrated oxide chromium exceeds 25 mg / m ² , the effect on the adhesion is unchanged. Furthermore, when the hydrated chromium oxide is thicker than 25 mg / m ² as chromium, the brown color becomes strong, which is not preferable as a printing substrate.

[0039]

【Example】

Example 1. A cold-rolled steel sheet having a thickness of 0.20 mm and a width of 842 mm was purified by degreasing and pickling, and then plated on both sides and subjected to chemical conversion treatment. However, when tin plating was applied, chemical conversion treatment was applied after reflow treatment. The treated steel sheet was preheated to 180 to 230 ° C. with an induction heater, and the resin film was continuously adhered while being pressure-bonded with a roll, followed by post-heating and cooling to obtain a laminated steel sheet. The obtained laminated steel sheet was examined for weldability, heat-sealing property of laminate film, shrinkability, processing adhesion and retort adhesion resistance.

Ferrostan bath was used for tin plating, and Watt bath was used for nickel plating. The chemical conversion treatment was performed using a chromic anhydride bath containing sodium sulfate. In the lamination, a resin film having a width of 161 mm and a thickness of 10 to 50 μm was continuously pressure-bonded while providing a varnish avoiding portion, and then heated at 205 ° C. to 225 ° C. for 5 seconds to 10 minutes and cooled with water.

The resin film was a monolayer film of polyethylene terephthalate copolymer containing isophthalic acid (test
Nos. 1 to 10) and a two-layer structure film (Test Nos. 11 and 17) having the copolymer as the lower layer and the polyethylene terephthalate homopolymer as the upper layer. In the two-layer structure film, the lower layer had a thickness of 4 μm and the upper layer had a thickness of 25 μm.

The test and its evaluation were carried out as follows. Weldability: Welding speed 40m using a Sudronic welder
A 200 ml can body was welded at pm and the presence or absence of splash was evaluated.

Thermal adhesiveness: 180 ° peeling was performed immediately after lamination, and those which were not peeled off until the resin film was torn were marked with ◯, those peeled with 200 g / cm or more were marked with Δ, and 200 g / cm or less. What was peeled off with was evaluated by X mark. Shrinkability: Blanking the steel plate immediately after lamination, 21
After being heated at 0 ° C. for 30 seconds and then rapidly cooled, the shrinkage rate was obtained from the difference in the width of the resin film before and after heating.

Processing adhesion: After making a can body by welding with the laminated film surface as the inner surface side, a test piece was cut out from the can body in the vicinity of the welded portion, and cross cuts were cut on the film surface at 2 mm intervals. After extruding 4 mm of Erichsen, it was forcibly peeled off with an adhesive tape and evaluated based on the percentage of the peeled area. The test results are summarized as ◯ when the peeled area is less than 10%, Δ when the peeled area is 10% or more and less than 30%, and x when the peeled area is 30% or more.

Retort adhesion resistance: After the can barrel is made by welding with the laminated film surface as the inner surface side, a test piece is cut out from the can barrel near the welded portion, a cross cut is put on the film surface, and Erichsen 4 mm extrusion is performed. The test piece was placed in an aqueous solution containing 1.5% NaCl at 125 ° C.
After soaking for a minute, the adhesive tape was forcibly peeled off, and the state of peeling was evaluated. The evaluation was that no peeling occurred at all ◯,
Slight peeling was observed around the cross-cut area, Δ, and peeling was observed on almost the entire surface, x.

The characteristics were also investigated for comparative examples outside the scope of the present invention and compared with the examples of the present invention.
Table 1 shows the detailed conditions of the test pieces used for the investigation and the test results.
Shown in.

[0047]

[Table 1]

In the examples of Test Nos. 1 to 11, the welding speed of 40 pmp was achieved without the occurrence of splash, the heat fusion property was good, the heat shrinkage rate was small, and the processing adhesion and the retort adhesion resistance were satisfactory. Results were obtained.

On the other hand, in the comparative example, the following results were obtained. Test No. 12: Since the tin plating amount was insufficient, splash occurred, high-speed welding was not possible, and the weldability was poor. Test No. 13: The amount of metal chromium in the chemical conversion treatment was small, the work adhesion was lowered, and the retort resistance was poor. Test No. 14: The surface of the plated steel sheet was rough and the work adhesion and retort resistance were poor. Blisters were also found in the film in these tests.

Test No. 15: Since the content of isophthalic acid in the acid component was small, the heat-welding property was deteriorated, and therefore the process adhesion and retort resistance were poor. Test No. 16: Since the content of isophthalic acid in the acid component was large, the shrinkage rate of the resin film was large and the retort resistance and adhesion were poor. Test No. 17: Since the content of isophthalic acid in the lower layer was small, the heat-sealing property was deteriorated, and the processing adhesion and retort adhesion resistance were poor.

In Test No. 18, the surface of the plating film was rough, so the work adhesion and retort resistance were poor. Test No. 19
Then, since the resin film was improper, the resin film was softened and peeled off by the heat during the retort treatment.
In Test No. 20, the resin film was improper and was softened and peeled by the retort treatment.

Example 2. Example 1. Similarly, after pre-treating the plated steel sheet used for the above, it is preheated to 180 to 230 ° C. and the adhesive is applied to the surface of the film in contact with the plating surface.
About 0 mg / dm ² (dry weight) was applied, the resin film was pressure-bonded with a roll and continuously bonded, and then post-heating was performed to obtain a laminated steel sheet. The resulting laminated steel sheet was examined for weldability, shrinkage of the laminate film, processing adhesion, retort adhesion resistance, and whitening resistance.

The laminate has a width of 161 mm and a thickness of 10
A resin film of 50 μm polyethylene terephthalate homopolymer was continuously pressure-bonded while providing a varnish avoiding portion. The pressure roll is made of silicone rubber and the surface temperature is 19
Maintained at 5 ° C. Immediately after pressure bonding, the steel plate temperature is set to 205 ° C to 22 ° C.
It was kept at 5 ° C for 5 seconds to 30 seconds for post-heating and immediately cooled with water.

The test and its evaluation were carried out in the same manner as in Example 1 for the weldability, shrinkability, work adhesion and retort adhesion resistance.
Is the same as. Regarding whitening resistance, 125 ° C. 1.
Perform retort treatment by immersing in 5% NaCl aqueous solution for 30 minutes and observe the degree of whitening. If no whitening is observed, ◯; if slight whitening is observed, △; cloudy white, clear whitening occurs. It was evaluated as x.

The characteristics were also investigated for comparative examples outside the scope of the present invention and compared with the examples of the present invention.
Table 1 shows the detailed conditions of the test pieces used for the investigation and the test results.
Shown in.

[0056]

[Table 2]

In Examples of Test Nos. 1 to 9, satisfactory results were obtained in all the tests. On the other hand, in the comparative example, the following results were obtained. Test No. 10: Since the amount of tin plating was insufficient, splash occurred, high-speed welding was not possible, and the weldability was poor. Test No. 11: The amount of metal chromium in the chemical conversion treatment was small and the processing adhesion and retort resistance were poor. Test No. 12: The epoxy resin of the adhesive had a small molecular weight, and uncured components remained, resulting in poor processing adhesion and retort adhesion resistance and poor whitening resistance.

Test No. 13: The epoxy resin of the adhesive had a large molecular weight, the processing adhesion was lowered, and the retort resistance was poor. Test No. 14: The content of epoxy resin in the adhesive was small, and the processing adhesion and retort adhesion resistance were poor. Test No. 15: The content of the epoxy resin in the adhesive was large, the heating time of 30 seconds was insufficient for curing, the retort adhesion resistance was decreased, and the whitening resistance was poor.

[0059]

As described above, the laminated steel sheet according to the present invention has good workability and is shielded on the surface of the plated steel sheet excellent in weldability, corrosion resistance and resin film adhesion except for the varnish avoiding portion. A polyethylene terephthalate-based biaxially stretched resin film, which is highly effective, is laminated. In particular, polyethylene terephthalate homopolymer, which has a very small heat shrinkability, had a problem with the heat fusion property, but it was solved as a copolymer containing isophthalic acid within a range not impairing the heat fusion shrinkage, or This has been solved by using a resin film having a two-layer structure having this copolymer as a lower layer, or by using an adhesive having good heat resistance, processability, and short-time curability in addition to adhesiveness.

Therefore, this laminated steel sheet has excellent resistance even in the retort treatment that is exposed to a harsh environment without the adhesive strength being lowered even after the steps of processing and heating during can making. By providing such an excellent can material, the effect of the present invention that contributes to the rationalization of the can manufacturing process and products is great.

[Brief description of drawings]

FIG. 1 is a plan view of a laminated steel plate for a welding can of the present invention.

FIG. 2 is a sectional view of a laminated steel plate for a welding can of the present invention.

FIG. 3 is a partial cross-sectional view of a laminated steel plate for explaining one principle of the present invention.

FIG. 4 is a diagram illustrating a relationship between a short-time curability and an epoxy resin content in the adhesive, which explains one performance of the adhesive.

[Explanation of symbols] 1 resin film 2 surface of plated steel sheet 3 space 4 varnish avoidance portion 5 resin laminate band 6 chemical conversion treatment layer 7 plating layer 8 steel sheet

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI Technical display location B65D 25/14 A 6540-3E 25/34 B 6540-3E C09J 163/00 JFP 8830-4J C23C 22 / 00 Z 28/02 // B29K 67:00 B29L 7:00 4F (72) Inventor Naoyuki Oba 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nihon Steel Pipe Co., Ltd.

Claims (6)

[Claims] 1. A plated steel sheet having the following (ii) plating film, wherein the plated steel sheet has a surface roughness PPI (threshold value 0.5 μm) of 5 or more and 150 or less on one side or both sides, A laminated steel sheet for a welding can, which has the following resin film which is thermocompressed in a strip shape along the line direction of the strip leaving a varnish avoiding portion of a predetermined width. (Ii) When the amount of metal chromium is 5 mg / m ² or more and 50 mg / m ² or less and the hydrated oxide chromium is 5 mg as chromium on the tin-plated layer with an adhesion amount of 0.9 g / m ² or more and 2.8 g / m ² or less / m ² or more 25 mg / m
Biaxially stretched film of polyethylene terephthalate copolymer in which 0.5 mol% or more and 10 mol% or less of the acid component is isophthalic acid having a chemical conversion treatment layer of ² or less 2. The laminated steel sheet for a welding can according to claim 1, wherein the laminated steel sheet for a welding can has a resin film in () instead of the resin film in (). (2) Biaxially stretched film having a two-layer structure in which a polyethylene terephthalate copolymer in which 0.5 mol% to 10 mol% of an acid component is isophthalic acid is a lower layer and a polyethylene terephthalate homopolymer is an upper layer 3. A strip-shaped strip (a) is formed along the strip line direction on at least one surface of the plated steel sheet having the (ii) plating film on the surface of the steel sheet, leaving a varnish avoiding portion of a predetermined width. The next (ho) glued by a certain glue layer
Laminated steel sheet for welding cans, which has the resin film of. (H) Biaxially stretched film of polyethylene terephthalate homopolymer (H) An adhesive comprising a bisphenol A type epoxy resin having a number average molecular weight of 15,000 or more and 30,000 or less and a resol type phenol resin based on bisphenol A. Adhesive layer obtained by heating and curing an adhesive containing 70 wt% or more and 90 wt% or less of epoxy resin 4. The laminated steel plate for a welding can according to claim 1, which has the following (b) plating film in place of the (i) plating film. (Filtrate) weight deposited on the deposition amount 15 mg / m ² or more 100 mg / m ² of nickel plated layer is 0.6 g / m ² or more 2.0 g / m ²
On the following two-layer plating plated with tin, further, the amount of metal chromium is 5 mg / m ² or more and 50 mg / m ² or less, and the hydrated oxide chromium is 5 mg / m ² or more and 25 mg / m ² or less as chromium. Plating film with chemical conversion layer 5. The laminated steel sheet for a welding can according to claim 2, wherein the laminated steel sheet for a welding can has a plating film of (b) instead of the plating film of (i). 6. The laminated steel sheet for a welding can according to claim 3, wherein the laminated steel sheet for a welding can has a plating film of (b) instead of the plating film of (a).