JP3259416B2 - Laminated steel sheet for welding cans - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated steel sheet used for welding cans such as food cans and the like, and more particularly to a coating structure for preventing a decrease in adhesion of a resin film previously laminated in a can-making process such as welding.

[0002]

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

[0003] Tin-plated steel sheets were initially used as the material for cans for the soldering can method and the welding canning method, but the welding method requires much less tin adhesion than the soldering method. Therefore, it is used in combination with thin plating and other metals. Also in this respect, the rationalization of the welding can manufacturing method is expected.

[0004] On the other hand, the body and lid of food cans have been painted. Thick film coating to enhance the corrosion resistance of the inner surface of the can, protective coating of the outer surface, printing, etc. However, when applying these,
The plated steel sheet is cut into a sheet of a predetermined size, and each of these sheets is painted, dried or printed. This process is one of the issues to be rationalized in the can manufacturing process, because it requires distribution costs and requires measures against environmental pollution caused by painting.

Under such circumstances, a laminated steel strip for a welding can has been proposed in which a film is laminated in a strip shape on a steel strip while avoiding a welded portion. For example, JP-A-3-236
No. 954 proposes a material for a can in which a thermoplastic film is laminated with a width corresponding to the height of the can, leaving a non-laminated portion having a width of 2 to 5 mm. The resin type 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 the adhesion between the coating film and the substrate due to heat influence during welding, repair coating of a welded portion, retort treatment, or the like is taken into consideration. As a result, there was a problem that retort resistance was insufficient.

The present invention has been made in order to solve this problem, and has a film structure for coping with a cause of a decrease in adhesion in a can-making process, thereby securing an adhesion force which is hardly reduced even when heated, and having a resistance to heat. An object of the present invention is to provide a laminated steel sheet for a welding can having a high retort property.

[0008]

Means for attaining this object is to provide a biaxially stretched resin having a predetermined width continuously in the line direction of the strip while leaving a varnish avoiding portion having a predetermined width on at least one surface of the plated steel sheet. A laminated steel sheet in which a film is closely adhered directly or through an adhesive layer, wherein the plated steel sheet is the next (i) or (b), and the resin film is the next (a), (n) or ( (V), wherein the adhesive layer is the following ((v)), and further, (v) or (v) is adhered on (i), and (v) is over F), and (h) is adhered to the laminated steel sheet for welding cans.

(I) A nickel plating layer having an adhesion amount of 50 mg / m ² or more and 1000 mg / m ² or less is provided on the surface of the steel sheet, and a metal chromium amount of 5 mg / m ² or more and 50 mg is provided on the nickel plating layer.
/ m ² or less, has a chemical conversion coating of 5 mg / m ² or more and 25 mg / m ² or less, and has a surface roughness PPI (threshold value of 0.
5 μm) is 5 or more and 150 or less.

(B) A nickel plating layer having an adhesion amount of 50 mg / m ² or more and 1000 mg / m ² or less on the surface of the steel sheet, and a chromium metal amount of 5 mg / m ² or more and 50 mg
/ m ² or less in plated steel sheet having a hydrated oxide of chromium 5 mg / m ² or more 25 mg / m ² or less of the chemical conversion film.

(G) More than 0.5 mol% of the acid component and 10 mol
% Or less is a biaxially stretched resin film of a polyethylene terephthalate copolymer having isophthalic acid. (2) A biaxially stretched resin film having a two-layer structure in which a polyethylene terephthalate copolymer containing 0.5% by mole or more and 10% by mole or less of an acid component contains isophthalic acid as a lower layer and a polyethylene terephthalate homopolymer as an upper layer.

(F) Biaxially stretched resin film of polyethylene terephthalate homopolymer. (F) 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, wherein the bisphenol A type epoxy resin is contained in an amount of 70% by weight to 90% by weight.
An adhesive layer obtained by curing an adhesive containing:

[0013]

[Function] The varnish avoiding portion is not laminated with resin,
A chemical conversion treatment for improving the adhesion of the paint is applied on the nickel plating. Therefore, by using the varnish avoiding portion as a welding margin, it is not necessary to remove the resin film at the time of welding at the time of can making, even for a steel plate on which a resin film is laminated in advance.

On the other hand, in the resin laminate band, a chemical conversion treatment is applied to the plating layer similarly to the varnish avoiding portion, and the resin is laminated thereon. For this reason, it is not necessary to apply time-consuming painting at the time of can making. The width of the resin laminate band is determined by the diameter of the can, for example, 16 for a 200 ml beverage can.
1 mm.

Since the varnish avoiding portion is welded so as to be in contact with the front and back, it is necessary to be located at a position opposite to both surfaces of the steel plate. However, the resin laminate band only needs to be provided at least on one surface serving as 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 inner surface corresponds to the resin laminate band according to the present invention, the outer surface corresponds to only the plating layer, or the coating film band,
The surface may be treated according to demand such as a white coat resin laminate or a printed resin laminate band.

[0016] Since at least one side which becomes the inner surface after the can-making is preliminarily laminated with a resin, even if it undergoes processes such as welding, baking printing, neck-in processing and flange-forming processing at the time of can-making, no damage or deterioration occurs. In addition, the film must maintain corrosion resistance and the like even when the contents are filled and after filling.

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 propagates also in the circumferential direction of the can body. The effect of the resin layer must not be reduced by this effect. If the width of the varnish avoiding portion is too narrow, the resin is melted or deteriorated, and the corrosion resistance and the adhesion to the plated steel sheet are reduced. The width of the varnish avoiding portion required to avoid the influence of heat during welding differs depending on the welding method.
In the case of electric resistance welding called the pseudoronic method, which is currently frequently used, it is safe to set the predetermined value of the width to 5 mm or more. Further, if a high-speed welding method using high-density energy is used, the width may be small, but about 0.5 mm is necessary because the thickness of the steel sheet for cans is about 0.2 mm.

Next, the resin film must withstand the processing and heating during the above-mentioned steps, and must have high corrosion protection in combination with the plating layer. Further, when a resin film is thermocompression-bonded, it must have good heat sealability. Such resins include:
There are polyolefin, polyester or nylon.
However, during retort treatment, it is exposed to superheated steam,
Polyolefins and nylons, which have relatively low melting points and are unstable at high temperatures, have poor adhesion at this time, leaving problems such as peeling. Polyester resins are known as a well-balanced resin having not only processability but also corrosion resistance. Among them, polyethylene terephthalate and polyethylene naphthalate are excellent in heat resistance. In particular, a polyethylene terephthalate-based resin has corrosion resistance and flexibility to withstand severe processing, and a biaxially stretched film has high performance of shielding corrosive substances.

However, it has been found that when a biaxially stretched film of polyethylene terephthalate resin is laminated by a thermocompression bonding method, the adhesion to the surface of a plated steel sheet (hereinafter, referred to as heat fusion property) is not always sufficient. If the temperature of the plated steel sheet becomes too high during thermocompression bonding, the hydrated oxide in the chemical conversion treatment layer changes, and the adhesive strength with the resin tends to decrease. For this reason, it is inappropriate to heat above 230 ° C.

On the other hand, the above resin film has a melting point of 260 ° C.
As described above, the cause is that in the case of biaxially stretched polyethylene terephthalate resin film, sufficient fluidity is not obtained at the time of thermocompression bonding, it cannot follow the unevenness of the plating surface, and the resin may not fully spread to every corner Probably because there is. Air and moisture remain in areas where resin does not spread,
This acts in the direction of peeling the resin film by heating after the can making step. To prevent these entanglements and residues,
It is preferable that the surface of the plated steel sheet is flat and the resin film has fluidity during thermocompression bonding.

The roughness PPI of the surface of the plated steel sheet (threshold 0.5 μ
When m)) is 150 or less, air and moisture are less involved and sufficient adhesion can be obtained when a resin film described later is laminated. The surface roughness PPI is the number of peaks (per inch) whose height exceeds a threshold among peaks appearing in the cross section of the surface. The smaller the PPI, the less air and moisture are involved. This is shown in FIG. Figure (a) shows the case where the PPI (threshold 0.5 μm) on the surface is laminated on a large plated steel sheet of about 500, and Figure (b) shows the PPI (threshold 0.5
μm) is about 50 when laminated on a relatively small surface. In FIG. 5A, a space 3 exists between the resin film 1 and the plated steel sheet surface 2, but not in FIG. 5B.

However, the surface of a steel sheet having a PPI (threshold value 0.5 μm) that is too small is liable to be scratched during handling such as printing and printing. That is, the surface roughness PPI (threshold value 0.5 μm) of the plated steel sheet is suitably 5 or more and 150 or less. 1
It is more preferable that the value is 00 or less.

In order to reduce the surface roughness of the plated steel sheet, 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.

There are various methods for lowering the melting point of the resin film to enhance the heat-fusibility. For example, a part of terephthalic acid of polyethylene terephthalate may be replaced with phthalic acid, isophthalic acid, sebacic acid or the like. However, at the same time, the degree of crystallization of the resin film also decreases. The degree of crystallization of the resin film is an important factor, and if the resin film has not been crystallized, it will undergo crystallization at the time of heating after the can making process, ie, welding, printing ink baking, retort treatment, etc. Shrink. In particular, shrinkage often occurs near the varnish avoiding portion during welding, and when shrinkage occurs, stress accumulates inside the resin film, so that adhesion tends to deteriorate during processing. If the melting point is not lowered without losing the characteristics of the homopolymer of polyethylene terephthalate, such as heat resistance, corrosion resistance, and flexibility, the object cannot be achieved.

As a result of various studies on the acid component, the inventors have found that the above object can be achieved by replacing part of terephthalic acid with isophthalic acid. The isophthalic acid substitution is considered to reduce crystallization of the resin during film formation and lower the melting point.

In this case, unless the isophthalic acid content is 0.5 mol% or more of the acid component, the effect of improving the heat-fusibility is not remarkable. On the other hand, if the isophthalic acid content is too large, the resin film shrinks during heating in the can making process, and the adhesion to the plated steel sheet surface is reduced. For this reason, 10 mol% of the acid component
Should be avoided. That is, when a biaxially stretched film of a copolymer of polyethylene terephthalate and polyethylene isophthalate as a main component and the acid component thereof is 0.5 mol% or more and 10 mol% or less of isophthalic acid, heat-fusibility is good and It is also possible to prevent a decrease in adhesion in the can making process. In particular, the isophthalic acid content is 1.
More preferably, it is 0 mol% or more and 8.0 mol% or less.

Since the homopolymer of polyethylene terephthalate and the copolymer of polyethylene isophthalate have the above-mentioned characteristics, respectively, as a two-layer film, 0.5 mol% or more and 10 mol% or less of the acid component are isophthalic. If the acid copolymer is used as the lower layer, a sufficient adhesive force can be obtained even if the upper layer is a homopolymer.

By adopting such a film structure, it is more advantageous in cost than a film in which the whole film is a copolymer. In this case, the thickness of the copolymer layer needs to be at least 0.5 μm or more, and desirably 1 μm or more, for the surface roughness of the plated surface. The thickness of the resin film is not limited, but when it is combined with a plating layer described later, the thickness is suitably 5 μm to 60 μm.

In order to prevent shrinkage of the resin film, it is desirable that the biaxially stretched film in which the polyethylene terephthalate resin has been crystallized is strongly adhered to the surface of the plated steel sheet. As one of the means, there is a method of using an adhesive which is more fluid than a film. However, this adhesive must have sufficient adhesiveness and heat resistance as well as a resin film, and must be sufficiently cured in a short time, such as when a laminated steel sheet is continuously manufactured. If the can is made with insufficient curing, the adhesion of the resin film is reduced during the retort treatment, and a phenomenon called so-called "whitening" in which the uncured resin reacts and the resin film becomes cloudy white appears.

Epoxy resin is 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, there is a disadvantage that curing takes too much time, and in some cases, the resin becomes too hard and deteriorates processability. The present inventors have investigated the relationship between these phenomena and the resin, and found that there is a resin that compensates for the disadvantages of the epoxy resin.
It was also found that an optimum molecular weight range also exists for the epoxy resin.

First, in order to complete the curing in a short time, it is advisable to mix an appropriate amount of a resol type phenol resin having bisphenol A as a base. This resin is selected in consideration of the above-mentioned heat resistance and workability, in addition to the fact that the adhesive is cured in a short time by the addition thereof (hereinafter, referred to as short-time curability). This resole type phenol resin is
It is considered that the reactivity reduces the curing time by reacting with an unreacted functional group of the epoxy resin at the time of heating by bonding 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 higher molecular weight cures in a shorter time.

FIG. 2 shows this state. In the figure, the vertical axis is the short-time reactivity, the horizontal axis is the epoxy resin content in the adhesive,
The rest is the above resole phenolic resin. Number average molecular weight of epoxy resin is about 5000, 10000, 15000, 2000
As a result of investigation on the cases of 0 and 30,000, the curability in a short time decreases as the content of the epoxy resin increases, and especially when the content exceeds 90% by weight, the decrease becomes remarkable. A decrease in short-time curability leads to whitening during retort.
Also, the higher 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 adhesive property of the adhesive mainly depends on the epoxy, and if the epoxy resin content is less than 70% by weight, a sufficient adhesion may not be obtained during processing. Further, the molecular weight of the epoxy resin also has an upper limit. If the molecular weight is large, the adhesive film after heat curing becomes hard. If the number average molecular weight exceeds 30,000, cracking or cracking may occur during processing.

That is, as for the adhesive, the bisphenol A type epoxy resin contains a resol type phenol resin based on bisphenol A, and the content of the bisphenol A type epoxy resin agent is 70 wt% or more.
0 wt% or less and the number average molecular weight is 15000 or more and 30000 or less, even if the resin film is polyethylene terephthalate, strong adhesion can be obtained between the surface of the plated steel sheet and even a short-time heating. Further, defects such as cracking, peeling or whitening of the film can be avoided by heating, processing or retort treatment in the can making process.

As for the amount of the adhesive, an appropriate amount to be applied varies depending on the surface roughness of the plated steel sheet. Since air or moisture must not be involved, an amount sufficient to compensate for the surface roughness is necessary. If the surface roughness is large, an appropriate amount of application is large. However, the plating layer surface roughness of the current plated steel sheet has a center line average roughness Ra of about 0.1 μm to 0.4 μm,
It hardly changes after the chromic acid chemical conversion treatment. Amount of adhesive in such plated steel sheet about 2mg / dm ² ~50mg / dm 2 is appropriate.

The resin film to be laminated using the adhesive is not limited to a homopolymer, but may be an acid component of 10 mol.
A copolymer containing l% or less of isophthalic acid may be used. In laminating, a treatment such as corona discharge may be used in combination.

The purpose of plating is to provide a high degree of corrosion resistance. It is difficult to completely block ion permeation of the resin by using only the resin layer. The taste and aroma of the contents may change in the food can due to elution. In addition, the presence of the plating layer stably maintains the anticorrosion effect even when subjected to a retort treatment exposed to a high temperature.

Nickel is a harmless metal and has excellent corrosion resistance. The nickel plating ensures the above-mentioned corrosion resistance, and performs a chemical conversion treatment so that the nickel plating adheres well to an organic resin such as a paint or a film, and also prevents the generation of iron splash at a high-speed welding at a varnish avoiding portion.

In order to prevent the generation of splash, the amount of nickel to be applied must be 50 mg / m ² or more, and if there is such an amount, the coated polyethylene terephthalate resin film or the coating film is not formed in the varnish avoiding portion. Together, they prevent changes in taste and aroma. A plating amount of nickel exceeding 1000 mg / m ² is excessively high and is not a good idea.

After the can body is rounded at the time of can manufacturing, it is subjected to repair painting after seam welding, and then subjected to drawing work 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 that is not sufficiently adhered is peeled off.

The reason why the chemical conversion treatment is performed after the plating is to form a chromate film and thereby improve the adhesion between the surface of the plated steel sheet and the resin film or the coating film. This treated film is made of chromium hydroxide or oxide
Hydrated oxides) and chromium metal. If the amount of chromium metal is 5 mg / m ² or more and the hydrated oxide chromium forms a film of 5 mg / m ² or more as chromium, a stronger adhesive force is obtained. can get. Also the amount of metallic chromium is much greater than the 50mg / m ^2, 25mg / m amount of Matamizu hydrous oxide chromium as chromium
Even if it exceeds ² , the effect on adhesion does not change.
Furthermore, the hydrated oxide of chromium is thicker than the 25 mg / m ^2,
The brown color becomes strong and is not preferable as a printing base.

[0042]

【Example】

Embodiment 1 FIG. A cold-rolled steel sheet having a thickness of 0.20 mm and a width of 842 mm was purified by degreasing and pickling, nickel-plated on both sides, and subjected to a chemical conversion treatment. This treated steel sheet is preheated to 180 to 230 ° C. with an induction heater, and a polyethylene terephthalate copolymer containing isophthalic acid of the present invention or a two-layer resin film having this copolymer as a lower layer and a homopolymer as an upper layer is prepared. After being continuously bonded while being pressed with a roll, post-heating and cooling were performed to obtain a laminated steel sheet. With respect to the obtained laminated steel sheet, weldability, heat fusion property of the laminate film, shrinkage property, work adhesion and retort adhesion resistance were examined.

The nickel plating bath used had the following composition. _{NiSO 4 · 6H 2 O 240g /} l NiCl · 6H 2 O 45g / l H 3 BO 4 30g / l pH 2.6 chemical conversion treatment was performed using chromic anhydride bath containing sodium sulfate.

The laminate has a width of 161 mm and a thickness of 10 to 5
Apply a resin film of 0 μm to
After continuous pressure bonding with a silicone rubber roll maintained at 0 ° C., post-heating was performed at 205 ° C. to 225 ° C., followed by water cooling.

The test and its evaluation were performed as follows. Weldability: 200 ml can bodies were welded at a welding speed of 40 mpm using a pseudoronic type welding machine, and the occurrence of splash was evaluated. Thermal adhesion: 180 ° peeling immediately after lamination, a mark that was not peeled off until the resin film was torn off was marked with 〇, a mark peeled at 200 g / cm or more was marked with △, and 200
Those peeled at g / cm or less were evaluated with x marks.

Shrinkage: The steel sheet immediately after lamination was blanked, heated at 210 ° C. for 30 seconds, rapidly cooled, and the shrinkage ratio was determined from the difference in resin film width before and after heating. Working adhesion: After making a can body by welding with the laminated film surface as the inner surface side, a test piece is cut out from the can body near the welded portion, and a cross cut is cut on the film surface at intervals of 2 mm, and after 4 mm extrusion of Erichsen The adhesive was peeled off with an adhesive tape and evaluated based on the percentage of the peeled area. In addition,
The test results were summarized as: when the peeled area was less than 10%, when it was 10% or more and less than 30%, and when it was 30% or more, x.

Retort adhesion resistance: After a can body was made by welding with the laminated film surface as the inner surface side, a test piece was cut out from the can body near the welded portion, a cross cut was made on the film surface, and Erichsen 4 mm extrusion was performed. The test specimen was placed in an aqueous solution at 125 ° C. containing 1.5% NaCl for 30 minutes.
After immersion for a minute, it was forcibly peeled off with an adhesive tape, and the state of peeling was evaluated. The evaluation was as follows: No peeling was observed at all, Δ was observed when slight peeling was observed around the cross cut, and X was observed when almost all surfaces were peeled.

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 detailed conditions and test results of the test pieces subjected to the investigation.

[0049]

[Table 1]

In the examples of Test Nos. 1 to 6, in all the test materials, the weldability was 40 mp without splash.
m, a good heat fusion rate, a small heat shrinkage rate, and satisfactory results in processing adhesion and retort resistance.

On the other hand, the following results were obtained in the comparative example. Test No. 7: Due to insufficient coating weight, iron splash occurred, high-speed welding was not possible, and weldability was poor. Test No. 8: The amount of metallic chromium in the chemical conversion treatment layer was small, the processing adhesion was reduced, and the retort resistance was poor. Test No. 9: The surface of the plated steel sheet was rough, and the heat fusion property was reduced, resulting in poor workability and retort resistance. In the process adhesion and retort tests, the film was found to have swelled.

Test No. 10: Since the content of isophthalic acid in the acid component was small, the heat-fusing property was reduced, and therefore, the processing adhesion and retort adhesion were poor. Test No. 11: Since the content of isophthalic acid in the acid component was large, the shrinkage of the resin film was large, and the retort adhesion was poor. Test No. 12: Since the content of isophthalic acid in the lower layer of the two-layer structure film was small, the heat-fusing property was reduced and the processing adhesion was reduced.
Poor retort adhesion.

In Test No. 13, the surface of the plating layer was rough, and the heat-fusing property, working adhesion, and retort resistance were poor. In Test Nos. 14 and 15, the resin film was inadequate, so the shrinkage was large, the processing adhesion was poor, and the resin film could not withstand retort treatment.

Embodiment 2 FIG. An adhesive is applied to the adhesive surface of the polyethylene terephthalate homopolymer resin film of the present invention in an amount of about 30 mg / dm ² (dry weight), and the coated steel sheet is subjected to a chemical conversion treatment after nickel plating in the same manner as in Example 1. After continuous bonding while being pressed, post-heating was performed to obtain a laminated steel sheet. With respect to the obtained laminated steel sheet, working adhesion and retort adhesion resistance were examined, and occurrence of whitening was observed.

The processing adhesion and retort resistance were measured and evaluated in the same manner as in Example 1. The occurrence of whitening was evaluated as 〇 when no whitening was observed, ら れ る when slight whitening was observed, and × when white and cloudy and clearly whitened. Table 2 shows detailed conditions and test results of the test pieces subjected to the investigation.

[0056]

[Table 2]

In Examples of Test Nos. 21 to 28, all the test materials were excellent in processing adhesion, retort adhesion and whitening resistance, and satisfactory results were obtained.

On the other hand, the following results were obtained in the comparative example. Test No. 29: The molecular weight of the epoxy resin of the adhesive was small, uncured components remained, the processing adhesion and the retort adhesion were reduced, and the whitening resistance was poor. Test No. 30: The molecular weight of the epoxy resin of the adhesive was large, and the processing adhesion and retort resistance were poor.

Test No. 31: The epoxy resin content in the adhesive was small, and the processing adhesion and retort resistance were poor. Test No. 32: Since the epoxy resin content in the adhesive was large and the curing was insufficient, the processing adhesion and the retort adhesion were reduced, and the whitening resistance was poor.

[0060]

As described above, the laminated steel sheet according to the present invention has good corrosion resistance and workability and does not have shrinkage on the surface of a plated steel sheet having excellent weldability and corrosion resistance, but is unsuitable for thermocompression bonding. A resin film is a resin film having an adhesive layer, and a resin film having improved heat-sealing property is a resin film having a shrinkage-suppressing property, leaving a varnish avoiding portion, and being tightly and continuously bonded. . Therefore, the adhesion between the resin film and the plating layer does not decrease in the can making process and the filling process. In addition, since the adhesive layer has excellent curability in a short time, the uncured resin does not remain and does not whiten during the retort treatment. As described above, the effect of the present invention to provide a high-performance can material while sufficiently extracting the characteristics of the material and saving labor is great.

[Brief description of the drawings]

FIG. 1 is a partial cross-sectional view of a laminated steel sheet for explaining one principle of the present invention.

FIG. 2 is a diagram illustrating a relationship between an epoxy resin content of an adhesive and short-time curability for explaining one principle of the present invention.

[Explanation of symbols]

 1 Resin film 2 Plated steel sheet surface 3 Space

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI C09J 163/00 C09J 163/00 C23C 22/00 C23C 22/00 Z 28/00 28/00 C // B29K 67:00 B29K 67 : 00 B29L 9:00 B29L 9:00 (56) References JP-A-4-344231 (JP, A) JP-A-2-57339 (JP, A) JP-A-58-183248 (JP, A) JP JP-A-5-185557 (JP, A) JP-A-2-24738 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B32B 15/08

Claims (3)

(57) [Claims] Claims: 1. An adhesion amount of 50 mg / m ² or more and 1000 mg / m ²
5mg of metallic chrome on the following nickel plating layer
/ m ² or more 50 mg / m ² or less hydrated oxides of chromium 5 mg / m ² or more 25 mg / m ² have the following chemical conversion layer surface roughness PP
A biaxially stretched resin film of a polyethylene terephthalate copolymer in which 0.5 mol% or more and 10 mol% or less of an acid component is isophthalic acid is coated on at least one surface of a plated steel sheet having an I (threshold value 0.5 μm) of 5 or more and 150 or less. A laminated steel sheet for a welding can, characterized in that the varnish avoiding portion having a predetermined width is left and closely attached in a strip shape in the line direction of the strip. 2. A coating amount of 50 mg / m ² or more and 1000 mg / m ^2.
5mg of metallic chrome on the following nickel plating layer
/ m ² or more 50 mg / m ² or less hydrated oxides of chromium 5 mg / m ² or more 25 mg / m ² have the following chemical conversion layer surface roughness PP
A polyethylene terephthalate copolymer containing polyethylene terephthalate as a main component and 0.5 mol% to 10 mol% of an acid component being isophthalic acid is coated on at least one surface of a plated steel sheet having an I (threshold value 0.5 μm) of 5 or more and 150 or less. A biaxially stretched resin film having a two-layer structure in which a lower layer is made of polyethylene terephthalate homopolymer and an upper layer is provided in close contact with a strip in the line direction of the strip except for a varnish avoiding portion having a predetermined width. Laminated steel sheet for welding cans. 3. A coating amount of 50 mg / m ² or more and 1000 mg / m ^2.
5mg of metallic chrome on the following nickel plating layer
on at least one surface of the plated steel sheet having a hydrated oxide of chromium 5 mg / m ² or more 25 mg / m ² or less of the chemical conversion layer with / m ² or more 50 mg / m ² or less, a biaxially stretched resin film of polyethylene terephthalate homopolymer Having a number average molecular weight of 1500
A varnish having a predetermined width is passed through an adhesive layer obtained by curing an adhesive which is a resol type phenol resin containing 70% by weight or less and 90% by weight or less of bisphenol A type epoxy resin of 0 or more and 30,000 or less and containing bisphenol A as a base. A laminated steel sheet for a welding can, characterized in that it is provided in tight contact with the strip in the line direction of the strip except for the avoiding portion.