JP3147717B2 - Surface-treated steel sheet for painted or film-laminated two-piece can with excellent work adhesion and work corrosion resistance, and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface-treated steel sheet which is a material steel sheet for two-piece cans which is subjected to severe processing after coating or film laminating, and particularly to a coating or film excellent in adhesion and corrosion resistance after processing. Laminate 2
The present invention relates to a surface-treated steel sheet for a piece can and a method for producing the same.

[0002]

2. Description of the Related Art In a conventional can-making process, a tin plate, an electrolytic chromate-treated steel plate (hereinafter, referred to as TFS), a metal plate such as aluminum is coated once or a plurality of times, and then a can-making process is performed. In some cases, painting may be performed after can processing. In the manufacturing process of a can lid and a cap, it is common to apply a coating to a metal plate and then process it.

In recent years, a technique for laminating an organic resin film on a metal plate has been developed and put into practical use. JP-A-57-182428, JP-B-61-3676.
Japanese Patent Application Laid-Open Publication No. H11-133, etc. discloses a method in which a metal plate is heated to a temperature equal to or higher than the melting point of a film and bonded by heat fusion.

[0004] There are various methods for processing after coating or film lamination. Particularly high processing is performed by drawing or squeezing, squeezing, pulling, bending or the like on a metal plate alone or in combination. There is a two-piece can manufacturing method in which a can bottom and a can body are integrally formed by repeatedly performing the process as needed.

On the other hand, in recent years, can manufacturers have been reducing the thickness of can bodies from the viewpoint of material saving.
In the case of piece cans, measures are taken to increase the degree of processing during can making. In the production of can lids and caps, metal plates after painting or film lamination are subjected to processing such as drawing, bending, overhanging, and screw processing.

By the way, severe processing performed after painting or film lamination has a great influence on the form of the plating film on the base surface-treated steel sheet. For example, in the case of TFS, when the coating film or the film is dissolved and removed from the material after the draw bead processing and the plating film is observed, a number of cracks are generated in the metal chromium layer and the hydrated chromium oxide, and the new surface of the metal chromium and iron is formed. It has been found to appear. This is because the outermost resin film has a large ductility, so it shows a healthy appearance even when subjected to quite severe processing, but the electrolytic chromate film is extremely thin and the hydrated chromium oxide layer has low ductility, so it is processed. This is considered to be due to the occurrence of cracks that could not follow the deformation, exposing a new surface of iron and metallic chromium.

[0007] The adhesion between the resin film and the base surface-treated steel sheet after processing depends on the adhesion state after processing of the interface between the resin film and the electrolytic chromate treatment film and the adhesion state between the newly formed surface of iron and metallic chromium and the resin film. Therefore, the adhesiveness after processing (hereinafter referred to as processing adhesion) is caused by the fact that cracks occur in the electrolytic chromate-treated film and the sound adhesive interface decreases, and the adhesive force between the new surface and the resin film interface is weak. )
And the corrosion resistance (hereinafter referred to as processing corrosion resistance) is deteriorated.

As described above, if the degree of processing is increased in order to reduce the wall thickness for the purpose of saving the material, performance such as processing adhesion and processing corrosion resistance is greatly deteriorated. Further, the film adhesion method by the above-mentioned heat fusion also has a large deterioration in processing adhesion and processing corrosion resistance, and is hardly practical.

As a technique for solving such a problem, a method of laminating an organic resin film coated with an adhesive in advance on a metal plate is disclosed in Japanese Patent Publication No. 4-74176.
It is disclosed in Japanese Patent Publication No. 5-71035, Japanese Patent Application Laid-Open No. 2-70430, and the like.

According to the methods disclosed in these publications, the working adhesion and the working corrosion resistance are improved, but it is necessary to evaporate the solvent of the adhesive by heating it, which not only complicates the process but also reduces the amount of solvent discharged. This causes problems such as treatment of wastewater and an increase in energy consumption, which is not preferable from the viewpoint of environmental conservation.

Further, in the case where particularly severe processing is performed in the manufacturing process, further processing adhesion and processing corrosion resistance are required, and when exposed to a high-temperature steam environment during retort processing, the degree of performance deterioration is further increased. Therefore, even with these techniques, the degree of improvement in processing adhesion and processing corrosion resistance is still insufficient, and there is a problem that it cannot be applied to some contents.

[0012]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has excellent processing adhesion and processing corrosion resistance even when severe processing is performed after painting or film lamination. It is an object of the present invention to provide a surface-treated steel sheet for painted or film-laminated two-piece cans and a method for producing the same, which can be applied to all contents, including contents that require the following.

[0013]

In order to solve the above-mentioned problems, the present inventors have developed a TFS which is a surface-treated steel sheet having relatively good adhesion to an organic resin layer such as a painted or laminated film. Using as a base, the bonding mechanism at the bonding interface between the resin film and TFS was examined in detail. In addition, a detailed investigation was conducted on the bonding interface when subjected to severe processing after bonding with paint or a laminate film, and processing adhesion and processing corrosion resistance in an aqueous environment of the inner surface after filling the contents or in a high-temperature steam environment during retort processing. The mechanism by which the metal deteriorates was investigated in detail.

As a result, in order to suppress the deterioration of the work adhesion and the work corrosion resistance, the hydrogen bonding force which is dominant in the adhesion between the hydrated chromium oxide layer present on the uppermost layer of TFS and the paint or laminate film is required. It has been found that it is important to increase the content, and it is effective to provide an organic substance having a specific polar group. In addition, for the part where a new metal surface appears at the bonding interface due to deformation due to processing, re-adhesion occurs after processing, and furthermore, it is possible to suppress degradation of characteristics by collecting eluted metal ions. They have found that it is possible to use the above-described method of providing an organic substance having a polar group in this mechanism.

The present invention has nothing to do with the conventional method of applying an adhesive to a film at the time of laminating, and thus, by applying a specific organic substance to the hydrated chromium oxide layer of TFS, it is possible to paint or coat the film. The inventors have found that the work adhesion and work corrosion resistance after severe processing of the steel sheet after lamination are remarkably improved and completed.

That is, according to the present invention, first, the lower layer is formed on at least one surface of the base steel sheet in an amount of 30 to 300 per side.
mg / m ² of metal chromium layer, and the upper layer has an electrolytic chromate-treated film composed of 5 to 30 mg / m ² of hydrated chromium oxide layer in terms of metal chromium per side, wherein the hydrated chromium oxide layer is Process adhesion and corrosion resistance, characterized by containing an organic substance containing at least one organic resin having a molecular weight of 1,000 or more having an acid group in the molecule and having an average adhesion amount of 1 to 1000 mg / m ² as a solid concentration. Provided is a surface-treated steel sheet for painted or film-laminated two-piece cans that is excellent in quality.

Second, the organic substance contained in the hydrated chromium oxide layer has excellent processing adhesion and processing corrosion resistance, characterized in that the total weight of the phosphate groups with respect to the total organic substance weight is 3% or more. Provide a surface-treated steel sheet for painted or film-laminated two-piece cans.

Third, by subjecting the steel sheet to electrolytic chromate treatment directly or after chromium plating, a metal chromium layer of 30 to 300 mg / m ² per side on at least one side of the steel sheet and a metal chromium layer Two layers of a hydrated chromium oxide layer of 5 to 30 mg / m ^{2 in} terms of conversion are formed, and at least one layer containing a phosphate group in the molecule is subsequently formed.
Applying an aqueous solution containing an organic substance containing a kind of polymer at a concentration of 0.3 g / l or more, or performing electrolytic treatment in the aqueous solution;
A method for producing a coated or film-laminated two-piece can surface-treated steel sheet having excellent work adhesion and work corrosion resistance, which is characterized by then drying.

According to the present invention having such a configuration,
Suppresses the deterioration of processing adhesion and corrosion resistance due to the increase in workability due to the thinning of can bodies, which has been promoted from the viewpoint of resource saving, and can be applied to contents that require retort treatment, etc., which is a high-temperature steam environment. Painting or film lamination 2
The surface-treated steel sheet for a piece can can be provided without increasing the cost.

Hereinafter, the present invention will be described in detail. The conventional mechanism of adhesion between a TFS having a hydrated chromium oxide layer on the surface and a resin film such as a film or paint is as follows.
It is considered that the dominant one is caused by a hydrogen bond acting between the hydroxyl group of the hydrated chromium oxide layer and the polar group of the resin film. Therefore, there is no other way to increase the adhesion between the hydrated chromium oxide layer and the resin film except to change the resin film itself or the quality of the hydrated chromium oxide layer. However, even if the quality of the hydrated chromium oxide layer is changed, there is no other way but to reduce the mixing ratio of other anions contained in the electrolytic chromate treatment or to change the anion species. Since it does not change, there is naturally a limit in improving the adhesion.

On the other hand, in the present invention, the hydrated chromium oxide layer contains an organic resin having a phosphoric acid group in the molecule and having a molecular weight of 1000 or more, so that the bonding mechanism itself is greatly different from the conventional one. That is, an organic resin having a phosphate group and a molecular weight of 1000 or more forms a hydrogen bond stronger than the hydrogen bonding force between the hydrated chromium oxide and the resin film,
By using such an organic resin, the adhesive strength is remarkably improved.

The present invention can provide not only the effect of improving the primary adhesion to the above-mentioned resin film but also the following effects. When processing after bonding the resin film to TFS, the resin film can be deformed according to the processing, but the metal chromium layer and the hydrated chromium oxide layer are cracked and become island-like. New chromium and iron surfaces. In the conventional TFS, the portion that bears the adhesion after processing is dominated by the adhesion between the hydrated chromium oxide layer and the resin film remaining after processing, and the adhesion between the newly formed surface of iron and metallic chromium and the resin film. Because the force is extremely low, the overall adhesion is significantly reduced.
However, the surface-treated steel sheet according to the present invention has an organic resin having a phosphate group between the newly formed surface of iron and metal chromium that appears after processing and the resin film, and has excellent adhesion after processing because it has an adhesive force. That is, since the organic resin having a phosphate group is disposed in the hydrated chromium oxide layer, this mixed layer is cracked by the processing in the metal chromium layer and the hydrated chromium oxide layer containing the organic resin. Even if it becomes island-shaped, the organic resin contained in the hydrated chromium oxide layer keeps the bonding interface with the upper resin film and the bonding interface with the island-shaped metal chromium sound. In addition, since the organic resin in the hydrated chromium oxide follows the elongation during processing to some extent, it may be attached to the resin film or create a crack between islands that have formed islands, and after processing, The above-mentioned organic resin containing a phosphate group can also exist between the emerging surface of the emerging iron and chromium metal and the resin film. The newly formed surface of iron and metallic chromium is rapidly oxidized in a processing environment to form a surface having a hydroxyl group. Therefore, the bond between the newly formed surface of iron and metal chromium and the interface between the organic resin and the interface between the organic resin and the resin film can be provided with an adhesive force due to hydrogen bonding, thereby significantly improving the processing adhesion as compared with the conventional TFS. You can do it.
In addition, due to such a mechanism, it is considered that such a polymer is more excellent when it is not linear but three-dimensional.

Further, the phosphate group can be esterified by causing a dehydration reaction with the metal hydroxide, and when the reaction occurs under high temperature conditions at the time of adhesion to the resin film and at the time of processing,
Since the bond that controls adhesion changes from a hydrogen bond to a covalent bond, the bonding force increases dramatically.

Further, the surface-treated steel sheet of the present invention has excellent adhesion in a high temperature aqueous environment or a steam environment. Generally, in the environment described above, the adhesiveness is deteriorated because, when water enters the interface between the resin film and the steel sheet, because of the polarity of the water, the water replaces the hydrogen bond that supports the adhesiveness. It seems to be because. However, in the present invention, the organic resin having a phosphate group has a strong hydrogen bond even in the conventional TFS elution, so that it is difficult to be replaced by water, and therefore, the adhesiveness is excellent even in a high-temperature aqueous environment or a steam environment. .

In addition, the fact that hydrogen bonds are not replaced by water molecules also has the effect of preventing expansion leakage, so that corrosion resistance after processing is also excellent. Furthermore,
The phosphate groups have the ability to trap cations as used in ion exchange resins. Thus, the phosphate groups capture the eluted iron ions. In a system in which a new surface of iron is exposed after processing, such a mechanism for trapping iron ions does not exist in the conventional TFS. Therefore, the conventional TFS
The surface treated steel sheet of the present invention has a remarkably improved work corrosion resistance as compared with the above.

Hereinafter, the reasons for limiting the invention will be described.
In the present invention, at least one surface of the base steel sheet has a two-layer electrolytic chromate treatment film in which the lower layer is a metal chromium layer and the upper layer is a hydrated chromium oxide layer.

Here, the amount of deposited metal chromium in the lower layer is 30 to 300 mg / m ² per one side. The amount of adhesion is 30
If the amount is less than mg / m ² , there is a problem in corrosion resistance, and 300
If it exceeds mg / m ² , the processability is inferior.
In any case, there is no problem as long as the amount is used for a normal electrolytic chromate treated steel sheet.

The adhesion amount of the hydrated chromium oxide in the upper layer is 5 to 30 mg / m ^{2 in} terms of chromium metal on one side. If the adhesion amount is less than 5 mg / m ² , the metal chromium layer is not uniformly covered with the hydrated chromium oxide, the exposed area of the metal layer becomes large, and the corrosion resistance, the aging deterioration resistance, and the processing adhesion are inferior. On the other hand, if it exceeds 30 mg / m ² , the hydrated chromium oxide is too thick, which results in deterioration of appearance and deterioration of adhesion, which is not preferable.

The hydrated chromium oxide layer in the upper layer of the electrolytic chromate-treated film contains at least one organic resin having a phosphoric acid group in the molecule and having a molecular weight of 1,000 or more, and has an average adhesion amount of 1 to 1000 mg / solid as a solid concentration. m ² is contained. Here, in the organic layer containing a resin having a phosphoric acid group in the molecule, it is preferable that the total weight of the phosphoric acid group with respect to the total organic substance weight is 3% or more. This is because a phosphate group can function effectively at a concentration higher than this, and can exert an effect of remarkably improving adhesion.

In the present invention, examples of the organic resin having a phosphoric acid group in the molecule include polyvinyl alcohol phosphate, itaconic acid phosphate, and a copolymer containing the same. Or two or more are contained. Further, the organic substance may contain other organic substances such as polyethylene glycol in addition to the organic resin having a phosphoric acid group in the molecule.

It is necessary that the molecular weight of the organic resin having a phosphoric acid group in the molecule is at a high molecular level of 1,000 or more. The reason why the molecular weight is specified to be 1000 or more is that if the molecular weight is low, it cannot be stretched at the time of processing as described above, and the processing adhesion cannot be sufficiently improved. The upper limit of the molecular weight of the organic resin is not particularly limited, but is preferably 5,000,000 or less.

The average amount of organic matter deposited is 1 to 1000 mg /
m ² . 1mg to effectively improve adhesion
/ M ² is the minimum required, and even if it exceeds 1000 mg / m ² , the effect of improving the adhesion is saturated, and the proportion of the organic matter portion in the hydrated chromium oxide layer becomes too high, so that aggregation in the polymer occurs. This is because breakage is likely to occur and adversely affect adhesion. In addition, the average adhesion amount is 100 mg / m
^In order to make it ² or more, it is necessary to have appropriate equipment that can uniformly attach organic substances so as not to impair the surface appearance, and it takes time to dry. It is uneconomical because it becomes difficult. Therefore, the average amount of adhesion was 100 mg /
It is preferably less than m ² .

In the present invention, by subjecting the steel sheet to electrolytic chromate treatment directly or after chromium plating, at least one side of the steel sheet has a thickness of 30 to 300 m per side.
g / m ² metal chromium layer and two layers of a chromium hydrate oxide layer of 5 to 30 mg / m ^{2 in} terms of metal chromium per side formed on the upper layer, and at least one layer containing a phosphoric acid group in the molecule An aqueous solution containing an organic substance containing the polymer of 0.3 g / l or more is applied or electrolytically treated in the aqueous solution, and then dried to produce a surface-treated steel sheet having the above-described structure.

Here, the electrolytic chromating method is a one-liquid method in which chromium metal and hydrated chromium oxide are simultaneously precipitated.
And a two-liquid method in which a hydrated chromium oxide is deposited after the formation of the metal chromium layer.

When introducing an organic substance, the aqueous solution to be applied on the electrolytic chromate-treated film is 0.3% of the organic substance.
Preferably, the content is at least g / l. If the concentration is lower than this, the effective amount does not adhere to the steel sheet surface, and it is difficult to sufficiently increase the adhesion. In the present invention, after the electrolytic chromate treatment,
It is important to apply an aqueous solution containing an organic substance before the hydrated chromium oxide layer is completely dried, and to introduce the organic substance into the hydrated chromium oxide layer. That is, the hydrated chromium oxide layer that has not been dried immediately after the treatment is in a gel state, adsorbs water molecules, and contains anions present in the electrolytic chromate treatment solution. Are easily bonded, and a hydrated chromium oxide layer containing an organic resin can be easily formed. Furthermore, applying an aqueous solution containing an organic substance without drying after the electrolytic chromate treatment, or performing an electrolytic treatment in the aqueous solution, can be performed in-line without a major equipment modification in a conventional TFS production line. It is possible and the cost increase is very small and economically advantageous.

The base steel sheet is not particularly limited, and any steel sheet usually used for this type of surface-treated steel sheet can be used. For example, a low carbon Al-killed steel sheet can be used.

[0037]

Next, specific examples of the present invention will be described. [Test materials] (1) Surface-treated steel sheet All examples and comparative examples are low carbon Al-killed continuous cast steel, a T4CA material having a thickness of 0.20 mm as an original steel strip.
It was manufactured using a vertical TFS line.

Then, after an electrolytic chromate treatment shown in Table 1, an aqueous solution of an organic substance or an aqueous solution in which an organic substance emulsion was dispersed was applied under the same conditions as shown in Table 1, and dried to form an organic substance layer. The amount of the organic layer deposited was controlled by adjusting the pressing pressure of the squeezing roll or setting the coating roll. Table 2 shows the substances used for the organic layer.

(2) Coating The surface-treated steel sheets described in Examples and Comparative Examples were 200 × 3
A cut plate having a thickness of 00 mm was coated with an epoxy resin paint on both sides under the following conditions and baked.

Epoxy resin paint adhesion amount: 60 mg / dm ² (after drying) Baking temperature: 210 ° C. Baking time: 10 minutes (3) Film lamination The surface-treated steel sheet described in Examples and Comparative Examples was 200 × 3
A cut sheet of 00 mm was formed, and a commercially available polyester film was laminated on both sides under the following conditions.

Film: Biaxially oriented polyester film (copolymer of polyethylene glycol and terephthalic acid / isophthalic acid) Film thickness: 25 μm Crystal melting temperature of film: 229 ° C. Steel sheet temperature immediately before lamination: 235 ° C. Laminating speed: 2 m / Sec Cooling after laminating: water cooling (quenching) [Evaluation] (1) Drawing workability A painted or laminated surface-treated steel plate was punched into a disk having a diameter of 158 mm, and a cylindrical cup was drawn at a drawing ratio of 2.92. Thereafter, the peeling state of the film or coating on the inner surface of the cup was observed with a loupe. At that time, five points were set to a good state without delamination, and the evaluation was made in five stages so that the degree of delamination increased as the number of points decreased to four points, three points, two points, and one point.

Further, a retort treatment was performed for 90 minutes in an aqueous solution of 1.5% NaCl + 1.5% citric acid, washed with water and dried. Similarly, the peel strength of the inner surface of the cup was evaluated in five steps based on the same standard.

(2) Bending work Painted or laminated surface-treated steel sheet is 30 × 300 mm
Using a tool with a tip R of 0.25 mm, a draw bead test is performed at a holding pressure of 1000 kgf, and a 15% compression process is performed by a rolling mill, and a loupe is formed on the opposite side of the draw bead tool contact surface. Was observed. At this time, the degree of peeling was evaluated in five steps as in the evaluation of the drawability.

A retort treatment was performed for 90 minutes in an aqueous solution of 1.5% NaCl + 1.5% citric acid. Similarly, the opposite side of the contact surface of the draw bead tool was observed with a loupe, and evaluated on a 5-point scale based on the same standard.

(3) Repack test A laminated surface steel plate is punched into a disk having a diameter of 110 mm.
First, a cylindrical cup is drawn with a draw ratio of 1.51,
Next, redrawing was performed at a drawing ratio of 1.20, and a cylindrical cup (total drawing ratio of 1.81) was prepared. The state of peeling of the film on the inner surface of the cup was observed with a loupe, and evaluated on a 5-point scale based on the same criteria as above.

In addition, Coca-Cola (trade name) is contained in the cup.
Were repacked and subjected to a storage test at 38 ° C. for 3 months.
After this storage test, the peeling state of the film and the metal plate on the inner surface of the cup was observed with a loupe, and evaluated on a 5-point scale based on the same criteria as above. At the same time, iron ions eluted in Coca-Cola were determined by atomic absorption method.

The evaluation results are shown in Table 1.
As shown in Table 1, the surface-treated steel sheets of Examples that are within the scope of the present invention have not only excellent primary adhesion after painting or film lamination, but also adhesion after processing, and further after retorting. It was confirmed that the adhesiveness was excellent. Further, the amount of iron eluted when the contents were stored for a long time was extremely small, and it was confirmed that the processing corrosion resistance was remarkably improved.

On the other hand, the comparative examples out of the range of the present invention were particularly inferior in processing adhesion after retort treatment and corrosion resistance during storage of contents. As described above, it was confirmed that by using the surface-treated steel sheet according to the present invention, excellent processing adhesion and processing corrosion resistance can be obtained regardless of the electrolytic chromating method. It should be noted that the present invention is not limited to the above-described embodiment, and can be carried out in other various modes without departing from the gist of the present invention.

[0049]

[Table 1]

[0050]

[Table 2]

[0051]

As described above, according to the present invention,
It is excellent in processing adhesion and processing corrosion resistance even when subjected to severe processing after painting or film lamination, and can respond to increase in processing degree due to thinning of can body, requiring retort treatment Provided are a surface-treated steel sheet for a painted or film-laminated two-piece can and a method for producing the same, which can be applied to all kinds of contents such as the following contents. As described above, according to the present invention, since excellent processing adhesion and processing corrosion resistance can be obtained without going through complicated steps, its economic value is extremely high.

──────────────────────────────────────────────────続 き Continuation of front page (51) Int.Cl. ⁷ Identification symbol FI C23C 28/00 C23C 28/00 C C25D 11/38 301 C25D 11/38 301A 303 303 (56) References JP-A-4-308092 (JP, A) JP-A-2-70430 (JP, A) JP-A-67-19398 (JP, A) JP-B-4-74176 (JP, B2) JP-B-51-44094 (JP, B1) ( 58) Field surveyed (Int.Cl. ⁷ , DB name) B05D 1/00-7/26 B32B 15/08 104 C23C 22/24 C23C 28/00 C25D 11/38 301 C25D 11/38 303

Claims (3)

(57) [Claims] 1. A metal chromium layer having a lower layer of 30 to 300 mg / m ² per side on at least one surface of a base steel sheet,
The upper layer is 5 to 30 mg / m ^{2 in} terms of metal chromium per side.
Wherein the chromium oxide layer comprises at least one organic resin having a phosphate group in the molecule and having a molecular weight of 1000 or more.
Seed-containing average deposition amount is 1 to 1000 mg as solid concentration
/ M ² , a surface-treated steel sheet for painted or film-laminated two-piece cans, which is excellent in work adhesion and work corrosion resistance, characterized by containing an organic substance having a thickness of / m ² . 2. The processing adhesion and processing corrosion resistance according to claim 1, wherein the organic substance contained in the hydrated chromium oxide has a total weight of phosphate groups of 3% or more based on the total weight of the organic substance. Surface-treated steel sheet for painted or film-laminated two-piece cans that excels in quality. 3. The steel sheet is subjected to electrolytic chromate treatment directly or after chromium plating, so that at least one side of the steel sheet has a metal chromium layer of 30 to 300 mg / m ² per side and a metal chromium layer on the upper side in terms of metal chromium per side. 5
Forming a second layer of hydration to 30 mg / m ² of chromium oxide layer, subsequently an aqueous solution containing organics 0.3 g / l or more concentrations that include at least one polymer containing a phosphate group in the molecule A method for producing a coated or film-laminated two-piece surface-treated steel sheet having excellent work adhesion and work corrosion resistance, which is applied or electrolytically treated in the aqueous solution and then dried.