JP2000248371A - Laminated steel sheet for non-polished general welded can - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve neutral and acidic content protectivity, thermal deterioration resistance at the time of welding and thermal weldability at the time of printing by including polyester resin coating layers consisting of a plurality of resin layers on a chromate treated film which is the inner surface side of a can. SOLUTION: The resin coating layers to be disposed on the chromate treated film which is the inner surface side of the can of an electrolytic chromate treated steel sheet consists of the plurality of resin layers and the total film thickness thereof is specified to 10 to 30 μm. The resin layer in contact with the chromate treated film surface among the plural resin layers is >=1.5 μm in film thickness and consists of a copolymer polyester resin containing 70 to 95 mol% ethylene terephthalate unit. The resin layer in contact with the contents in the can consists of a polyester resin contg. >=80 mol% ethylene terephthalate unit and having a melting point of >=210 deg.C. In the case such polyester resin having a melting point of >=250 deg.C is used, the film thickness of the resin layer is preferably confined to <=10 μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a neutral or acidic (pH 8 to pH 3) application suitable for a can body or a lid of a general can (especially a large can) such as an 18L can or a pail can. The present invention relates to a laminated steel sheet for non-polishing welded general cans, which has excellent content protection properties, especially excellent corrosion resistance in neutral and surfactant-based contents.

[0002]

2. Description of the Related Art In the field of large cans for general cans, attempts have been made to produce highly corrosion-resistant cans using various laminated steel sheets from the viewpoint of productivity and energy saving. Since heat treatment such as retort treatment is not performed in large cans, film adhesion after retort is not required as in beverage cans.
Conventionally, a large and high corrosion-resistant can using a laminated steel plate has been disclosed in Japanese Patent Publication No. 1-55104, and Japanese Patent Publication No. 64-139.
Japanese Patent Application Publication No. JP-A-2006-13312 discloses a technique relating to a can body lock seam can and an adhesive can. However, rock-sealed cans and glued cans have the disadvantage that the seam strength is weaker than welded cans, and rock-sealed canned cans and glued cans can be stacked wider than welded cans. There is also a disadvantage that the material cost is higher than that of the welding can because the parts are required.

[0003] On the other hand, large-sized inner-layer welded cans for general can use also have the following problems. That is, when a large-sized inner-surface laminated welding can is manufactured using an inexpensive electrolytic chromate-treated steel sheet, polishing welding is generally performed. In this polishing welding, the surface treatment film (chromate treatment film) is removed by polishing. As a result, the corrosion resistance after welding repair of the exposed portion of the base iron becomes a problem, and therefore, there is a problem that it is difficult to manufacture a highly corrosion-resistant can.

Further, when a method of mechanically polishing and removing a surface treatment film in an industrial can-making process is carried out, a large amount of polishing dust (metal powder) is generated, and the polishing dust becomes foreign matter in the can. There is also a problem of mixing. For this reason, even if the inner surface of the can is laminated to improve the corrosion resistance, the content cannot be sufficiently protected due to contamination of the content by foreign matter. Further, in this polishing welding, there is also a problem that a resin layer (laminated film) near a welded portion is thermally deteriorated by heat input during welding.

On the other hand, electrolytic chromate-treated steel sheets for non-polishing welding are disclosed in Japanese Patent Publication No. Hei 6-37714, Japanese Patent Laid-Open Publication No. Hei 2-179895, and Japanese Patent Publication No. Hei 7-947.
Numerous proposals have been made, including the 19th publication. However, these prior arts all relate to steel plates for bare inner cans and painted cans, and there is no disclosure of steel plates for laminated cans.

A technique for repairing a welded portion of a laminated can is also disclosed in Japanese Patent Publication No. 63-50265, etc., but the conventional technique including this proposal is based on the case where a material steel sheet has a tin-based plating film. Repair of non-polishing welds of
Repair of polished welds when the material steel sheet has a chromium plating film. Repair that can ensure high corrosion resistance equivalent to that of laminated steel sheets for unpolished welds of chromium surface treatment films that do not use expensive tin. Nothing discloses the technology.

Conventionally, as a laminated steel sheet for use in general cans, a laminated steel sheet mainly coated with a polyolefin resin film is known. However, this polyolefin resin laminated steel sheet accounts for a large proportion of the contents of general large cans. It has been reported that in the occupied surfactant, there is a tendency for the surface of the film to crack over time in the stress concentration area such as the wound processing area and cause corrosion (iron and steel V
ol. 81 (1995) No. 10 P41). Further, in the case of a conventional polyolefin resin laminated steel sheet for general can use, in the case of a laminated resin having a low melting point, a coating printing (for example, an oil-based printing process, a clear varnish coating process, etc.) on the outer surface of the can performed after continuous coil lamination. In the baking step, there is also a problem that the laminated resin is thermally fused with the conveying means.

[0008]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a laminate made of an electrolytic chromated steel sheet suitable for a welding can body of a general can (especially a large can) such as an 18L can or a pail can. A steel sheet that is neutral or acidic (pH 8 to pH 3) to protect its contents (characteristics that do not cause contaminants or metal elution) and resistance to heat deterioration during welding (performance that does not cause resin whitening) Another object of the present invention is to provide a laminated steel sheet for non-abrasive welded general cans having excellent heat-fusibility during printing.

[0009]

Means for Solving the Problems In order to solve the above-mentioned problems, the present inventors have developed various laminated steel sheets having different configurations of a surface treatment film and a resin coating layer of a material steel sheet.
Detailed investigations and examinations were carried out from the viewpoints of resistance to heat deterioration, protection of contents, and heat-sealing properties. As a result, the following findings were obtained.

(1) Corrosion resistance and heat deterioration resistance of can body The steel sheet in which a polyolefin resin is laminated on the inner surface of the can is particularly useful when the content of the can is a surfactant. The layer degrades over time, cracks and is prone to corrosion. On the other hand, a steel sheet laminated with a specific polyester resin on the surface serving as the inner surface side of the can as described below does not deteriorate with time in the resin layer of the wound processing portion even in the surfactant, and thus causes a crack. There is no such thing.

Among the resin layers on the inner side of the can, the resin layer in contact with the contents of the can is, among the polyester resins, particularly a polyester resin containing an ethylene terephthalate unit of 80 mol% or more and having a melting point of 210 ° C. or more. By doing so, good corrosion resistance and heat resistance can be obtained. On the other hand, among the resin layers on the inner surface side of the can, the resin layer in contact with the surface treatment film surface, if the content of the ethylene terephthalate unit is excessive, the heat effect at the time of welding and the baking of paint printing on the outer surface of the can. Since spherulites are easily generated, which causes whitening of the film and remarkable deterioration in adhesion at the can body processing portion, it is preferable to use a polyester resin having an ethylene terephthalate unit content of 70 to 95 mol%.

Further, the resin layer in contact with the contents of the can among the resin layers on the inner surface side of the can has a high ethylene terephthalate unit content and a high melting point (melting point: 25).
In the case of using a polyester resin (for example, homopolyethylene terephthalate resin) having a temperature of 0 ° C. or more, the resin is liable to be whitened due to the heat effect at the time of welding or painting. is there.

(2) Corrosion resistance of the welded portion As described above, the corrosion resistance of the can body portion on the inner side of the can is significantly improved by laminating a specific polyester resin as compared with the coating material. In order to ensure the corrosion resistance as described above, it is necessary to secure the same corrosion resistance as that of the canned body in the weld repaired part.

[0014] In this respect, an electrolytic chromate-treated steel sheet (a steel sheet having a portion corresponding to the inner surface of a can body excluding a welded portion) laminated with a polyester resin (particularly, a polyester resin having an ethylene terephthalate unit as a main component) is used. Perform normal abrasive welding, and use a polyester resin (for example, a polyester resin containing ethylene terephthalate unit as a main component and having a melting point of 190 ° C. or less in consideration of a reduction in load when baking the repair resin). ), The corrosion resistance of the weld repaired part repaired to the same film thickness as the laminated part of the can body part (metal elution resistance in acidic contents and corrosion resistance under the film) is remarkably compared to the laminated part of the can body part Inferior results.

On the other hand, non-abrasive welding is performed on a laminated steel sheet (a steel sheet having a portion corresponding to the inner surface of a can body except for a welded portion) made of an electrolytic chromated steel sheet having a specific film structure. The weld repaired part obtained by repairing the welded part in the same manner as described above exhibits substantially the same corrosion resistance as that of the laminated part of the can body (metal resistance in acidic contents and corrosion resistance under the film). This is presumably because the non-polishing welding and the reduction in the input power during welding suppress the destruction of the plating film near the welded portion as compared with the case of polishing welding.

Further, the can body laminating part near the welded part is
In the case of polishing welding, damage to the resin film layer and reduction in film adhesion are observed due to the influence of heat generated during welding. On the other hand, in the case of non-polishing welding, the shape and density of protrusions (protrusions made of chromium metal and / or hydrated chromium oxide) formed on the chromate treated film surface of the electrolytic chromate treated steel sheet, and chromium hydrate oxidation Suppresses excessive heat generation by optimizing the amount of chromium adhering to the material layer, and suppresses damage to the resin film layer near the weld (weld heat affected zone) by applying a specific resin film as a laminate film can do.

In the non-polishing welding, the surface roughness of most part of the base of the weld repaired portion becomes the surface roughness of the material steel plate. For this reason, from the viewpoint of preventing entrapment of air bubbles between the resin layer and the steel plate surface that affect corrosion resistance and ensuring weldability, it is necessary to appropriately select the surface roughness of the material steel plate and the thickness of the adhesive resin layer. .

(3) Protection of contents Non-polishing welding to a laminated steel sheet made of electrolytic chromate-treated steel sheet having a specific film structure (a steel sheet that has been laminated on the inner surface of the can body except for the welded portion) Is repaired with a film or powder of polyester resin (for example, a polyester resin containing ethylene terephthalate unit as a main component) at the same thickness as the can body, and the metal parts such as polished metal powder are compared with polished welding cans. And the amount of metal eluted in the contents of the can is significantly smaller than that of the inner-coated can.

(4) Heat-resistant fusing characteristics with the transfer equipment at the time of can outer surface coating printing The resin layer on the inner surface side of the can is baked in the paint printing process (oil-based printing process, outer surface clear varnish coating process) on the outer surface of the can. In order to prevent heat fusion to the transport equipment at the time, the melting point of the resin usually needs to be about 210 ° C. or higher, although it depends on the baking temperature according to the ink or paint used for painting and printing. is there. Although no polyolefin resin satisfies this condition, a polyester resin, particularly a specific polyester resin containing an ethylene terephthalate unit as a main component, can satisfy such a melting point.

The present invention has been made based on the above findings.
The characteristic configuration is as follows. [1] The amount of metal chromium deposited on the steel plate surface was 60 mg /
m²Super 150mg / m ²The following metal chrome layer and above
The amount of adhesion of the layer in terms of metallic chromium is 3 to 9 mg per side.
/ M²Treatment with chromium hydrated oxide layer
Metallic chromium on the surface of the chromate-treated film
And / or massive projections of chromium hydrated oxide
The surface of the chromate-treated film formed has a surface roughness Ra:
0.15-0.40 μm, 25 μ per inch of surface
Number of protrusions exceeding inches: 10 to 120 PPI
Laminated steel sheet made from dechromated steel sheet
The protrusion is the maximum when the steel sheet is observed in a plan view.
The length of the diameter part is 100 nm or less and the steel plate is flat.
The length of the largest diameter part is 10 nm or more 1
The number of protrusions of 00 nm or less is 1 × 10¹²Pieces / m²Less than
Which is at least the inner side of the can.
Has a total thickness of 10 to 30 composed of multiple resin layers
a polyester resin coating layer of
Of the multiple resin layers that make up the resin coating layer,
The thickness of the resin layer in contact with the treated film surface is 1.5 μm or more.
And 70-95 mol% of ethylene terephthalate
Made of copolyester resin containing
The resin layer in contact with the object is 80% by mole or more of ethylene
Polyester containing phthalate units and having a melting point of 210 ° C or higher
For non-polishing welded general cans characterized by being made of tellurium resin
Laminated steel sheet.

[2] In the laminated steel sheet of the above [1],
A laminated steel sheet for non-polishing welded general cans, wherein the resin layer in contact with the contents of the can is made of a polyester resin having a melting point of 250 ° C. or more, and the thickness of the resin layer is 10 μm or less.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the details of the present invention will be described in detail.
I will explain with the reason. Material steel of laminated steel sheet of the present invention
Electrolytic chromate-treated steel sheet
60mg / m per side²Super 150mg / m
²The following metal chrome layer and the upper metal chrome equivalent
3-9mg / m per side ²Chromium hydrated acid
Having a chromate treatment film composed of
Chromium metal and / or
Electrolytic chromium with lumps of hydrated oxide
Mate treated steel plate, the protrusions are observed on the steel plate in plan view
Length of the largest diameter part when it is
In addition, the length of the maximum diameter part is 10
There is no protrusion exceeding 0 nm).
The length of the largest diameter part when observed in a plane is 10 nm or more
The number of protrusions of 100 nm or less is 1 × 10¹²Pieces / m²Not yet
It must be full.

When the amount of chromium metal on the chromium metal layer constituting the chromate-treated film is 60 mg / m ² or less per one side, the corrosion resistance (film peeling property) under the laminated resin film is poor, and the bare corrosion resistance during plate storage is also poor. Inferior. On the other hand, even if the amount of deposited chromium exceeds 150 mg / m ² per surface, the effect of improving corrosion resistance and weldability corresponding to the amount of deposited chromium cannot be obtained, and the economy is rather deteriorated.

If the chromium hydrated oxide layer has a coating amount of less than 3 mg / m ² per one side of the chromium metal oxide layer, large-lumped projections (maximum of metal chromium and / or chromium hydrated oxide) Diameter length is 100n
In the steel sheet of the present invention in which no protrusions exceeding m) are present, the film adhesion is poor, and corrosion under the laminated film tends to occur. On the other hand, in order to perform non-polishing high-speed welding at 15 m / min or more, the amount of chromium hydrated oxide layer to be deposited must be 9 mg / m ² or less per one surface in terms of metal chromium. ^If it exceeds ² , the weldability in non-polishing high-speed welding is inferior.

On the surface of the chromate treatment film, massive projections made of chromium metal and / or chromium hydrated oxide are present in a dispersed manner. The effects of such massive projections are as follows: (1) When the chromium hydrated oxide layer is broken by the projections when contacting a steel plate or an electrode, the contact resistance is reduced and the high-speed weldability is improved. ) The adhesion of the laminate film is improved by the anchor effect of the projection, (3) light absorption by the projection,
Scattering improves the surface color of the steel sheet.

The length of the maximum diameter portion (the maximum diameter portion when the steel sheet is observed in a plane) is 100 n on the chromate-treated film surface.
If there are large projections (protrusions made of chromium metal and / or chromium hydrated oxide) exceeding m, the color of the steel sheet surface becomes brownish, and welding is caused by the influence of these large projections. Since the current value increases, the heat affected range near the welded portion increases, and the laminated resin layer is significantly damaged. In addition, the resistance at the steel plate / steel plate interface that requires preferential heat generation is smaller than the resistance at the electrode / steel plate interface,
Since the heat generation becomes unstable, the non-polishing weldability is also poor.

In addition, the maximum diameter portion (obtained by observing the steel plate in a plan view)
Large lump with a length exceeding 100 nm)
Even when there are no projections, when the steel sheet is observed two-dimensionally
Projection with a maximum diameter of 10 nm or more and 100 nm or less
1 × 10¹²Pieces / m ²Above, the color of the steel plate
The change in tone is small, but the heat affected area near the weld is large
And the laminating fill near the weld due to thermal effects
The deterioration of the system becomes remarkable. Also, for the same reasons as above, steel
Non-polishing weldability due to unstable heat generation at the plate / steel interface
Inferior.

On the other hand, if the density of the projections in the specific form described above is too low, the adhesion of the laminate film is reduced and the chromium hydrated oxide layer is less likely to be broken by the projections. Therefore, it is preferable that the number of protrusions having a maximum diameter of 10 nm or more and 100 nm or less when the steel sheet is observed in a plane is 1 × 10 ⁷ / m ² or more.

The surface of the electrolytic chromate-treated steel sheet has a surface roughness Ra of 0.15 to 0.40 μm and a number of projections exceeding 25 μ inch per inch of 10 to 120.
It is preferably in the range of PPI. When the surface roughness Ra of the electrolytic chromate-treated steel sheet is less than 0.15 μm or the number of projections exceeding 25 μinch per inch is less than 10 PPI, the chromium hydrated oxide layer is likely to be insufficiently broken during non-polishing welding, The stability of welding is easily hindered. On the other hand, when the surface roughness Ra exceeds 0.40 μm or the number of projections exceeding 25 μinch per inch exceeds 120 PPI, bubbles and the like are easily entangled between the laminated film and the steel sheet, and the corrosion resistance is apt to deteriorate.

The laminated steel sheet of the present invention has a resin coating layer composed of multiple resin layers on at least the chromate-treated film on the inner surface side of the can of the electrolytic chromate-treated steel sheet having the above-mentioned film configuration. As a resin coating layer composed of a plurality of resin layers on the inner surface side of the can, the heat-resistant fusing property of the resin at the time of coating printing on the outer surface side of the can, in the can contents required for general cans, particularly in a surfactant A polyester resin is used in consideration of corrosion resistance, heat resistance during welding, and the like. Among them, a polyester resin containing an ethylene terephthalate unit as a main component is preferable.

Of the multiple resin layers constituting the polyester resin coating layer, the resin layer in contact with the contents of the can is 8
Polyester resin containing ethylene terephthalate unit of 0 mol% or more (ethylene terephthalate unit having 100
If not mol%, the balance preferably comprises other ester units). If the ethylene terephthalate unit in this resin layer is less than 80 mol%, the ratio of the copolymer component is too high, so that sufficient corrosion resistance and heat resistance cannot be obtained.

The melting point of the polyester resin containing the ethylene terephthalate unit of 80 mol% or more is 210 ° C. or more from the viewpoint of heat-resistant fusing property. If the melting point of this resin is less than 210 ° C., the resin layer will be thermally fused to the transport equipment during baking in the coating printing process on the outer surface of the can. Further, even if the melting point of the resin is 210 ° C. or more, if the melting point is lower than the melting point of the resin layer in contact with the chromate treatment film, the resin layer in contact with the can contents at the time of lamination is melted, and the properties of the resin layer deteriorate. Because of the possibility, it is necessary that the melting point of the resin constituting the resin layer in contact with the contents of the can be higher than the melting point of the resin constituting the resin layer in contact with the chromate treatment film.

Further, a polyester resin having an ethylene terephthalate unit close to 100 mol% and a melting point of 250 ° C. or more (for example,
When using a homopolyethylene terephthalate resin), the thickness of the resin layer is preferably 10 μm or less from the viewpoint of preventing whitening of the resin due to heat influence during welding or painting. In addition, the resin layer excluding the adhesive layer is preferably a resin layer having a draw ratio of 3.2 × 3.2 or less in order to reduce the shrinkage stress during heating.

Of the multiple resin layers constituting the polyester resin coating layer, the resin layer in contact with the chromate-treated film surface has a resin adhesiveness in the can processed portion after undergoing heat history such as painting printing on the outer surface of the can. From the viewpoint of securing
% Of an ethylene terephthalate unit (70-95 mol% of the ethylene terephthalate unit is the other ester unit). When the amount of the ethylene terephthalate unit is less than 70 mol%, the effect of suppressing spherulite formation is saturated, and the film cost is also increased. On the other hand, if the ethylene terephthalate unit is 95
If the amount exceeds mol%, spherulites are liable to be generated during baking in the coating printing process on the outer surface of the can, thereby significantly deteriorating the adhesion at the can body processed portion. The thickness of the resin layer in contact with the surface of the chromate treatment film is 1.5 μm or more. When the thickness of the resin layer is less than 1.5 μm, the adhesiveness of the film decreases.

As a specific example of the polyester resin copolymer used in the present invention, a linear copolymer polyester such as a non-crystalline copolymer of ethylene terephthalate and ethylene isophthalate is suitable. Further, a copolymerized polyester of ethylene glycol or cyclohexanedimethanol and terephthalic acid is also suitable. When a homopolyethylene terephthalate resin is used as the polyester resin constituting the resin layer in contact with the contents of the can, a polyester resin having a melting point of 260 ° C. or more, a crystallinity of 2.0 or more, and a draw ratio of 6 or less is preferable. . Further, the resin layer may contain a white pigment such as TiO _{2 of} less than about 20 wt%.

The number of resin layers constituting the polyester resin coating layer is two or more. If the resin layer is a single layer, it is not preferable because it is necessary to control the orientation so that the resin layer in contact with the chromate treatment film has a predetermined orientation during lamination.
The number of resin layers is arbitrary, but a polyester resin coating layer composed of four or more films is not preferable because the cost is significantly increased.

The thickness of the polyester resin coating layer formed on the inner surface of the can has a great effect on corrosion resistance such as resistance to metal elution.
0 μm. If the film thickness is less than 10 μm, only corrosion resistance equal to or less than that of the coated steel sheet is obtained, and a film thickness of 10 μm or more is required to obtain stable corrosion resistance more than twice of the coated steel sheet. on the other hand,
When the film thickness exceeds 30 μm, the effect of improving corrosion resistance such as resistance to metal elution is saturated, and on the contrary, economic efficiency is impaired.

As described above, the electrolytic chromate-treated steel sheet serving as the base steel sheet of the laminated steel sheet of the present invention has a block-like projection with a specific form and density on the surface of the chromate-treated film. As a method for producing an electrolytic chromate treated steel sheet having a chromate treatment film, for example, a steel sheet is made of 80ASD in a plating bath containing chromic acid as a main component and containing F ions at a concentration of 2.0 g / l or less.
Electrolytic chromate treatment at the above current density (current density at the part where the steel sheet faces the electrode), and also at the part where the steel sheet does not face the electrode, except for the contact part between the roll and the steel sheet,
The treatment is performed such that the current is supplied at a current density of 0.5 ASD or more (to prevent the chromium hydrated oxide layer from being destroyed, which causes abnormal growth of the projections).
By appropriately selecting the ion concentration and the current density, it is possible to form massive projections in a desired form and density on the chromate-treated film surface.

There is no particular limitation on the method of laminating the electrolytic chromate-treated steel sheet. A method of continuously laminating a resin film produced in advance on the electrolytic chromate-treated steel sheet (film coil laminating method), and a method of laminating a molten resin by a T-die Resin coating by any method, such as a method of hot extrusion directly onto the surface of an electrolytic chromate-treated steel sheet (melt hot extrusion lamination method), a method of laminating a resin film produced in advance for each cut plate (film sheet lamination method), etc. Can be applied.

[0040]

EXAMPLE A cold-rolled steel sheet having a thickness of 0.32 mm was formed by a usual method.
After electrolytic degreasing and pickling, bath temperature 45 ° C, chromic acid: 100
-200 g / l, F ion: 0.5-2.0 g / l, S
O ₄Ions: containing 0.5 to 2.0 g / l;
Medium in plating bath with weight ratio of SO4 ion less than 0.3
With electrolytic chromate treatment at a current density of 80 ASD or more
Then, an electrolytic chromate-treated steel sheet was obtained. Note that this electrolytic
In the romate process, the steel plate is immersed in
The non-energized section other than the contact section was not provided.

The form and density of massive projections (projections made of chromium metal and / or hydrated chromium oxide) formed on the surface of the chromate-treated film of the electrolytic chromate-treated steel sheet depend on the F ion concentration in the plating bath and the current. The density was controlled by selecting the density (the current density at the portion where the steel plate and the electrode face each other and the current density at the portion where the steel plate and the electrode did not face each other). The morphology and formation density of the protrusions on the chromate-treated film surface of the obtained electrolytic chromate-treated steel sheet were measured by observing the chromate-treated film surface with a transmission electron microscope.

Thereafter, the electrolytic chromate-treated steel sheet was heated to a temperature equal to or higher than the melting point of the resin film (adhesive layer) to perform lamination on one side or both sides, and quenched with water within 2 seconds from the temperature range from the melting point of the film to 250 ° C. . At this time, for a steel plate corresponding to the can body, about 10 m
An m-width lamination avoiding portion was provided.

After lamination of one side of the steel sheet, after lamination, a surface corresponding to the outer surface of the can was subjected to clear coating and baking at a temperature lower than the melting point of the film. After the above-mentioned laminated steel sheet was canned by non-polishing welding (polishing welding for a part), the welded portion and the laminated avoidance portion were repaired using a polyester resin having a melting point of 180 ° C. The following performance evaluation was performed on the obtained laminated steel sheet and the can body obtained by canning the laminated steel sheet.

(1) Adhesion of Film on Can Body Laminate Part After forming into a can body part for an 18L can, a tape peeling test was performed on the resin film layer (including the heat affected zone) of the processed part, and the following processing was performed. The film adhesion was evaluated. ：: No peeling of film ×: Peeling of film

(2) Corrosion Resistance of Surfactant in Can Body Laminate in Surfactant After forming into a can body for an 18L can, a sample was cut out from the can body. This sample was subjected to a DuPont impact test to examine the presence or absence of corrosion after immersion in a neutral detergent (trade name: Rypon F) at 38 ° C. for 4 weeks, and the corrosion resistance after processing was evaluated as follows. ○: No discoloration due to corrosion ×: Discoloration due to corrosion

(3) Acid-Resistant Content Properties of the Can Body Laminated Portion After forming into a can body for an 18 L can, a sample was cut out from the can body. This sample was treated with 1.5% citric acid + 1.
The state of corrosion and the amount of iron elution after immersion in a 5% salt solution at 38 ° C. for 4 weeks were examined.
Acid-resistant physical properties were evaluated as follows by comparing with the test results for the coated cans that had been repeatedly coated. For the comparison material, a sample was cut out from the body of the can in which the inner surface of the can was coated twice (paint: epoxy phenol paint), immersed in the test solution under the same conditions as above, The elution amount was examined. ：: Better than twice-painted material ×: Equal to or less than twice-painted material

(4) Corrosion resistance of heat-affected zone of welding A laminated portion near the welded portion is 1 cm along the canned body welded portion.
The sheet was cut into a size of × 2 cm, and subjected to electrolytic peeling at −1.2 V vs. SCE in a 2% NaOH aqueous solution, and the presence or absence of peeling of the laminate film was evaluated as follows. ○: No peeling of laminated film ×: Peeling of laminated film

(5) Corrosion Resistance of Weld Repaired Part A sample was cut out so that the weld repaired part was located at the center of a size of 7 cm × 7 cm, and this sample was placed in a 1.5% citric acid + 1.5% saline solution at 38 ° C. for 4 hours. The amount of iron eluted after immersion for a week was examined, and the corrosion resistance was evaluated as follows. ○: Iron elution amount equal to or less than the non-welded repair part of the can body laminate part ×: Iron elution amount exceeding the non-weld repair part of the can body laminate part

(6) Weldability Using an 18L can body welding machine (VWS manufactured by Fuji Kogyo Co., Ltd.), continuous can making of the can body was performed at a wire speed of 21 m / min while changing the can making opportunity three times. The weldability was evaluated as follows based on the ACR at that time. ：: ACR is always 5 points or more in the tap range Δ: Tap range is not stable ×: ACR is always less than 5 points

(7) Surface color tone Based on the K value (% / 1000 nm), the color tone of the steel sheet surface was evaluated as follows. This K value is 480 nm to 70 wavelength.
The reflectance-wavelength gradient is determined at intervals of 10 nm between 0 nm,
It is a numerical value obtained by further correcting the obtained average value to a reflectance difference per 1000 nm. At a value of -20 or less, a good metallic tone is obtained. ：: K value is -20 or less ×: K value is more than -20

(8) Heat resistance A laminated steel sheet of 20 cm × 20 cm is held in a wicket, and subjected to baking at 200 ° C. for 10 minutes assuming coating heating, and then the presence or absence of indentation of the wicket on the laminated surface is examined. Was evaluated as follows. ○: No indentation ×: Indentation

(9) Heat discoloration resistance The laminated plate is heated to 300 ° C. in consideration of the heating state of the welded portion and the like.
After heating for 10 seconds, the film after heating was examined for the presence of discoloration (whitening) and evaluated as follows. ○: No whitening ×: Whitening

Example 1 A laminated steel sheet was manufactured using an electrolytic chromate-treated steel sheet having a different surface roughness and an attached amount of a chromate-treated film as a material steel sheet. In the present embodiment, the resin film layer laminated on the inner surface side of the can has a two-layer structure, and a resin layer (adhesion layer: film thickness: 4 μm) in contact with the chromate treatment film is a copolymerized polyester resin having a melting point of 198 ° C. (ethylene terephthalate unit). : 82 mol%), and a homopolyethylene terephthalate resin having a melting point of 260 ° C was used for the resin layer (base layer: 8 µm in thickness) in contact with the contents of the can. On the outer surface of the can, a polyester-based thermosetting resin paint was applied and baked (baking temperature 140 ° C.) to form a coating film having a thickness of 5 μm.

Table 1 shows the results of the above-mentioned tests (the film adhesion of the can body, the corrosion resistance in a surfactant, and the non-polishing weldability) on these laminated steel sheets, together with the structure of the laminated steel sheets. In Table 1, No. Comparative Example No. 4 is inferior in film adhesion and corrosion resistance in a surfactant because the amount of chromium hydrated oxide layer deposited (in terms of chromium metal) is small. No. Comparative Example No. 5 is inferior in non-polishing weldability because the amount of chromium hydrated oxide layer attached (in terms of metallic chromium) is too large.

No. Comparative Example No. 6 was inferior in corrosion resistance in a surfactant because the amount of chromium deposited on the chromium metal layer was small. No. Comparative Example 7 is inferior in non-polishing weldability because the surface roughness of the base steel sheet is too small. No. In Comparative Example No. 8, since the surface roughness of the base steel sheet was too large, air bubbles were easily entrapped between the steel sheet surface and the film, and thus the corrosion resistance in the surfactant was poor.

[0056]

[Table 1]

Example 2 A laminated steel sheet was manufactured using electrolytic chromate-treated steel sheets having different shapes and densities of projections on the surface of the chromate-treated film. In the present embodiment, the resin film layer laminated on the inner surface side of the can has a two-layer structure, and a resin layer (adhesion layer: film thickness: 4 μm) in contact with the chromate treatment film is a copolymerized polyester resin having a melting point of 198 ° C. (ethylene terephthalate unit). : 82 mol
%) And a resin layer (base layer: film thickness 8) in contact with the contents of the can.
For μm), a homopolyethylene terephthalate resin having a melting point of 260 ° C. was used. On the outer surface of the can, a polyester-based thermosetting resin paint was applied and baked (baking temperature 140 ° C.) to form a coating film having a thickness of 5 μm.

Results of the above test on these laminated steel sheets (color tone, non-polishing weldability, corrosion resistance of weld heat affected zone)
Are shown in Table 2 together with the configuration of the laminated steel sheet. In Table 2, no. Comparative Example 2 had no protrusions having a maximum diameter of more than 100 nm on the surface of the chromate-treated film, but had no protrusions with a maximum diameter of 10 to 100 nm because the formation density of the protrusions was 1 × 10 ¹² / m ² or more. Poor polishing weldability. No. Comparative Example 3 has a protrusion having a maximum diameter of more than 100 nm on the chromate-treated film surface,
Further, since the formation density of protrusions having a maximum diameter portion of 10 to 100 nm is 1 × 10 ¹² / m ² or more, the color tone and the non-polishing weldability are inferior.

[0059]

[Table 2]

Example 3 Laminated steel sheets having different configurations of the resin film layer laminated on the inner side of the can were manufactured. In the present embodiment, the material steel plate has a surface roughness Ra of 0.1.
An electrolytic chromate-treated steel sheet having a protrusion of 35 μm and a projection number exceeding 25 μ inch per inch on the steel sheet surface of 100 PPI was used. Chromium deposition amount of electrolytic chromate-treated steel plate, the metal chromium layer is 100 mg / m ^2, hydrated chromium oxide layer is 5 mg / m ² reckoned as metal chromium The configuration of the protrusions formed on the chromate conversion coating surface Is
When the steel plate is observed in a plane, the maximum diameter is 100
nm, and the number of projections having a maximum diameter of 10 nm or more and 100 nm or less when the steel sheet was observed in a plane was 1 × 10 ¹¹ / m ² .

For the resin film layer laminated on the inner surface of the can, the resin films shown in Table 3 were used. A polyester-based thermosetting resin coating was applied to the outer surface of the can, and baked at a temperature equal to or lower than the thermal fusion temperature of the resin film on the inner surface of the can to form a coating film having a thickness of 5 μm.

Tables 4 and 5 show the results of the above tests (film adhesion, corrosion resistance in surfactants, and acid content resistance) on these laminated steel sheets together with the structure of the resin film layer laminated on the inner surface of the can. . In Tables 4 and 5, Comparative Example 6 is inferior in film adhesion because the thickness of the resin layer in contact with the chromate-treated film surface is small. No. In Comparative Example 10, the resin layer was a single layer, and the heat resistance was poor because the melting point of the resin layer in contact with the contents of the can was low. In addition, No. 6, no. In Comparative Example 9, although the resin layer in contact with the contents of the can was composed of a polyester resin (homopolyethylene terephthalate resin) having a melting point of 250 ° C. or higher, the thickness of this resin layer exceeded 10 μm. Whitening of the resin layer occurs during heating. In addition, No. In No. 9, since the total thickness of the resin film layer exceeds 30 μm, the effect of improving corrosion resistance is saturated.

No. Comparative Example 7 is inferior in corrosion resistance and acid resistance in a surfactant because the total thickness of the resin film layer on the inner surface side of the can is small. No. Comparative Example 8 has an olefin-based resin film layer having a low melting point, so that the resin film layer in the vicinity of welding and the like is thermally degraded, and cracks occur in a surfactant, resulting in poor corrosion resistance. I have.

No. 15, No. In Comparative Example 16, the melting point of the resin film layer in contact with the contents of the can was lower than the thermal fusion temperature of the resin film layer in contact with the chromate treatment film.
At the time of lamination, the resin film layer in contact with the contents of the can melts, and a resin layer satisfying adhesion and corrosion resistance has not been obtained. In addition, No. No. 15 has poor heat resistance because the melting point of the resin constituting the resin layer in contact with the contents of the can is low. N
o. In Comparative Example 17, the resin constituting the resin film layer in contact with the contents of the can had an ethylene terephthalate unit of 80 mol.
Since it is less than 1%, the corrosion resistance in the surfactant is inferior.

[0065]

[Table 3]

[0066]

[Table 4]

[0067]

[Table 5]

Example 4 A laminated steel sheet was manufactured by using an electrolytic chromate-treated steel sheet having a different surface roughness and an attached amount of a chromate-treated film as a material steel sheet, and a can body was manufactured by using the laminated steel sheet without polishing or polishing and welding. After the can, the weld was repaired.

In this embodiment, the resin film layer laminated on the inner surface side of the can has a two-layer structure, and the resin layer (adhesion layer: 4 μm in thickness) in contact with the chromate treatment film has a melting point of 198.
A homopolyethylene terephthalate resin having a melting point of 260 ° C. was used for a copolyester resin at 82 ° C. (ethylene terephthalate unit: 82 mol%), and for a resin layer (mother layer: film thickness 8 μm) in contact with the contents of the can. Also,
On the outer surface of the can, a polyester-based thermosetting resin paint was applied and baked (baking temperature 140 ° C.) to form a coating film having a thickness of 5 μm.

Table 6 shows the corrosion resistance of the weld repaired portion of these laminated steel sheets together with the structure of the laminated steel sheets.
According to Table 6, the composition of the laminated steel sheet does not satisfy the conditions of the present invention. 3-No. All of the comparative examples 8 are inferior in corrosion resistance at the weld repaired portion.

[0071]

[Table 6]

[0072]

As described above, the laminated steel sheet for non-polishing welded general cans of the present invention has excellent suitability for use from neutral to acidic when applied to large cans such as 18L cans and pail cans. It is also excellent in the protection of contents, and can be manufactured at low cost using an electrolytic chromate-treated steel sheet as a raw material.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Naoyuki Oba 1-1-2 Marunouchi, Chiyoda-ku, Tokyo Nihon Kokan Co., Ltd. (72) Inventor Toyofumi Watanabe 1-1-2 Marunouchi, Chiyoda-ku, Tokyo Sun F-term (Reference) 4F100 AA22C AB03A AB13B AK42D AK42E AK42K BA05 BA07 BA10A BA10E DD07C EH71B EJ69C GB16 JA04E JB02 JJ03 JK15C JL00 YY00B YY00C YY00D YY00E 4K06A08

Claims (2)

[Claims] 1. A metal chromium deposition amount per side 60 mg / ^{m 2} Ultra 150 mg / ^{m 2} or less of the metallic chromium layer on the steel sheet surface, the adhesion amount is per side at its upper metal chromium conversion 3~9mg / ^{m 2} And a chromium hydrated oxide layer having a chromate-treated film, and a block-like projection made of metallic chromium and / or chromium hydrated oxide is formed on the surface of the chromate-treated film; Roughness Ra: 0.15 to 0.40 μm, number of projections exceeding 25 μ inch per inch of surface: 10 to 120 PP
A laminated steel sheet using an electrolytic chromate-treated steel sheet as a material steel sheet, wherein the protrusion has a maximum diameter of 100 nm or less when the steel sheet is observed two-dimensionally, and observes the steel sheet two-dimensionally. When the maximum diameter part length is 10
The number of protrusions having a thickness of not less than 1 nm and not more than 100 nm is less than 1 × 10 ¹² / m ^2. Having a resin coating layer, of the multilayer resin layer constituting the polyester resin coating layer,
The resin layer in contact with the chromate treatment film surface has a thickness of 1.5μ
m or more and a copolymer polyester resin containing 70 to 95 mol% of ethylene terephthalate units, wherein the resin layer in contact with the can contents contains 80 mol% or more of ethylene terephthalate units and has a melting point of 210 ° C. or more. Laminated steel sheet for non-abrasive welded general cans, characterized by being made of resin. 2. The resin layer in contact with the contents of the can has a melting point of 250.
The laminated steel sheet for non-abrasive welded general cans according to claim 1, wherein the laminated steel sheet is made of a polyester resin having a temperature of at least 10 ° C and having a thickness of 10 µm or less.