JP2015117402A - Surface-treated steel plate, organic resin-coated metal container, and method for manufacturing surface-treated steel plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface-treated steel plate excellent in adhesiveness to an organic resin layer and in corrosion resistance, an organic resin-coated metal container excellent in adhesiveness to a resin applied on outer or inner surfaces of can and in resistance to fluorine elution, and a method for manufacturing the surface-treated steel plate.SOLUTION: The surface-treated steel plate has a surface treatment layer containing fluorine and essentially comprising zirconium and oxygen on at least one surface of a steel plate; and the surface-treated steel plate contains a group 2 element on a surface side of the surface treatment layer.

Description

  The present invention relates to a surface-treated steel sheet, an organic resin-coated metal container, and a method for producing the surface-treated steel sheet. More specifically, the present invention relates to a surface-treated steel sheet having excellent adhesion and elution resistance to an organic resin coating and its It relates to a manufacturing method.

In the fields of home appliances, building materials, vehicles, aircraft, containers, etc., chromate treatment has been known as a treatment for improving the adhesion between steel sheet and organic coating, and it has been widely used due to its excellent corrosion resistance and adhesion. Has been.
There are two types of chromate treatment, one containing hexavalent chromium and the other containing no hexavalent chromium. However, in recent years, from the viewpoint of environment and occupational health, if hexavalent chromium is used as a starting material, Regardless of the situation, there is an increasing trend to ban the inclusion of hexavalent chromium in the starting material itself.

  Of course, in metal container materials such as cans and can lids, a chromate treatment of the type in which hexavalent chromium does not remain is used in the final product, and usually, coating with an organic resin or the like is further performed thereon. . For example, cathodic electrolysis of a tin-plated steel plate in an aqueous solution of sodium dichromate, cathodic electrolysis treatment of a steel plate in a fluoride-containing chromic anhydride aqueous solution, or treatment of an aluminum alloy with phosphoric acid chromate and an organic resin thereon The one coated with is used.

  Metallic containers such as cans and can lids are often subjected to hot water retort treatment for the purpose of sterilizing the contents. As a result, the material is exposed to a harsh environment, and thus there is a problem that the adhesion between the organic resin coating and the metal surface tends to be lowered, and various studies have been conducted in the past to solve the problem. Currently, tinplate and electrolytic chromic acid-treated steel sheets used as materials for cans are treated by performing hot water washing or hot water washing in the final surface treatment process for the purpose of improving hot water adhesion. A technique is used in which an anion such as sulfate ion or fluorine ion in the coating is controlled to form a metal surface having excellent adhesion to the organic coating (Non-patent Documents 1 and 2).

  In recent years, an immersion treatment using a treatment liquid containing Zr (zirconium) or Ti (titanium) has been proposed as a non-chromium-based surface treatment being studied for steel sheets (Patent Document 1). However, the surface-treated steel sheet by Zr or Ti immersion treatment is inferior in the corrosion resistance of the coating, and the coating deposition rate is slower than the electrolytic chromic acid-treated steel sheet (TFS) conventionally used as a can material. The problem was that the productivity was remarkably inferior. For this reason, Zr and / or Ti treatment and / or Al treatment using cathodic electrolysis have been proposed as high-speed treatment processes instead of immersion treatment, all of which form a metal oxygen compound on the surface of the substrate at high speed. It is known that it can be made (Patent Documents 3, 4, and 5).

Further, as a method for improving the adhesion of the metal oxygen compound film to the organic resin layer, after forming a metal oxygen compound film containing a Zr oxygen compound on the substrate, the surface of the metal oxygen compound film is 80 ° C. or higher. A technology relating to a method for producing a steel plate for containers having a chemical conversion coating having a metal Zr content of 1 to 100 mg / m ² and an F content of 0.1 mg / m ² or less is disclosed (Patent Document 6). ).

International Publication No. 2002/103080 Japanese Patent Laid-Open No. 7-11483 JP 2004-190121 A JP-A-2005-97712 JP 2006-348360 A International Publication No. 2012/036200

"Technology History of Surface-treated Steel Sheets for Cans in Japan" Published by Japan Iron and Steel Institute, published on October 31, 1998, p87 last line to p90

  Aiming to improve the corrosion resistance of the substrate by directly forming a metal oxygen compound film mainly composed of oxygen compounds such as Zr, Al, Ti, etc. on the metal substrate surface without providing a metal plating layer on the metal substrate. In this case, it is necessary to increase the coating thickness (coating amount) as compared with the case where the metal plating layer is provided. Especially in seamless can applications where the degree of processing is large, the underlying iron is likely to be exposed by processing, or the adhesion to the organic resin is likely to decline, so ensuring the corrosion resistance by increasing the coating amount and simultaneously with the organic resin There was a need to improve the adhesion of the.

  In addition to the above-mentioned items related to adhesion, another object to be solved by the present invention is to prevent the components constituting the metal container from eluting into the contents. For metal containers, maintaining the quality of the contents is very important, and special attention must be paid to the dissolution of components from the metal containers into the contents. In general, typical examples of elution of metallic components of containers are iron elution due to corrosion and elution of anions such as sulfate ions and fluorine ions in the coating. In addition to the pH of the contents and sterilization conditions, metal surface treatment It is necessary to pay attention to many things such as the coating amount and surface morphology of the film, or the adhesion strength with organic resin coatings such as films and coatings.

  Patent Document 2 shows an example in which the surface of a metal oxygen compound coating on a metal plating layer is cleaned with hot water to improve adhesion. However, when a large coating amount as described above is required, in order to achieve the desired surface treatment characteristics and elution suppression, it is not possible with the hot water cleaning used in the conventionally used electrolytic chromic acid-treated steel sheets. I found it sufficient. Therefore, when diverting an electrolytic chromic acid treatment line to form a metal oxygen compound film, it requires longer cleaning time than before, so that the operation speed of the surface treatment line is restricted or a treatment for washing. In addition to increasing the number of tanks, it has been found that there are many problems such as increasing the productivity load and energy use load, such as using a large amount of hot water.

  The present invention has been made in view of such a situation, and the object thereof is to provide a surface-treated steel sheet having excellent adhesion and corrosion resistance with an organic resin layer when an organic resin layer is formed on the surface. An object of the present invention is to provide an organic resin coated container excellent in adhesion to an outer surface resin and fluorine elution resistance, and a method for producing the surface-treated steel sheet.

According to the present invention, there is provided a surface-treated steel sheet having a surface treatment layer containing fluorine and mainly composed of zirconium and oxygen on at least one surface of the steel sheet, wherein a group 2 element is provided on the surface side of the surface treatment layer. A surface-treated steel sheet characterized by containing is provided.
In the surface-treated steel sheet of the present invention,
(1) The group 2 element is present as a fluorine compound,
(2) the group 2 element is at least one of calcium and magnesium;
(3) The molar ratio AE / Zr between the group 2 element (AE) and the zircomnium (Zr) in the surface treatment layer is 0.2 or more,
(4) It is preferable that the weight film thickness of zirconium in the surface treatment layer is 100 to 200 mg / m ² .

  According to the present invention, there is also provided an organic resin-coated metal container comprising an organic resin-coated surface-treated steel sheet obtained by forming an organic resin coating on the surface-treated steel sheet.

According to the present invention, there is further provided a method for producing a surface-treated steel sheet having a surface treatment layer mainly containing zirconium and oxygen on at least one surface of the steel sheet, wherein the surface-treated steel sheet comprises an aqueous solution containing Zr ions and F ions. The film formation step by cathodic electrolysis of the steel sheet in the step, followed by one or more of immersion treatment, spray treatment, and cathodic electrolysis treatment using a surface conditioning aqueous solution containing a group 2 element There is provided a method for producing a surface-treated steel sheet, comprising a surface conditioning step.
In the method for producing the surface-treated steel sheet of the present invention,
(1) The group 2 element is at least one of calcium and magnesium,
(2) In the surface conditioning step, the fluorine reduction rate from the film forming step is 30% or less,
Is preferred.

According to the present invention, when an organic resin layer is formed on the surface, it is possible to provide a surface-treated steel sheet having excellent adhesion and corrosion resistance with the organic resin layer, and as a container, fluorine elution resistance and adhesion with organic resin. An organic resin-coated metal container excellent in corrosion resistance can be provided, and a method for producing the surface-treated steel sheet can be provided.
In particular, in the present invention, the presence of a group 2 element, particularly a group 2 element fluorine compound, on the surface side of the surface treatment layer makes it possible to insolubilize fluorine and suppress elution of fluorine and dissolve zirconium. Therefore, it becomes possible to stabilize the structure of the surface treatment layer and to reduce defects in the entire surface treatment layer.
In addition, after the organic resin layer is formed on the surface, it is possible to effectively prevent peeling of the organic resin layer even when processing or heat treatment is performed, and the organic resin layer is cracked, so that the metal surface is exposed in a wet environment. To provide a surface-treated steel sheet that is less prone to corrosion even in an exposed state and can suppress the elution of metal constituent components of the container, an organic resin-coated metal container using the surface-treated steel sheet, and a method for producing the surface-treated steel sheet Can do.

In the method for producing a surface-treated steel sheet according to the present invention, in the surface adjustment step, any one or more of immersion treatment, spray treatment, and cathodic electrolysis treatment is performed using a surface adjustment aqueous solution containing a group 2 element. Therefore, the hot water cleaning used to clean electrolytic chromic acid-treated steel sheets can be changed to warm water or room temperature water, and the processing time is shorter and the energy load is better than when only hot water cleaning is used. Yes.
Moreover, by adopting a surface conditioning process using a surface conditioning aqueous solution containing a group 2 element, instead of removing fluorine in the coating and discharging it to the environment, as in the case of performing only hot water cleaning, Fluorine in the coating can be insolubilized in the coating by reacting with group 2 elements, thereby suppressing the fluorine reduction rate from the surface-treated steel sheet after the coating forming step to 30% or less, and fluorine in the waste water. The manufacturing method of the surface treatment steel plate which can reduce a density | concentration, has a small waste_water | drain load, and was excellent in environmental conservation can be provided.

It is a figure which shows the atomic concentration change of the depth direction calculated | required with the X-ray photoelectron spectrometer about the surface treatment layer of the surface treatment steel plate of this invention. It is a figure which shows the atomic concentration change of the depth direction calculated | required with the X-ray photoelectron spectrometer about the surface treatment layer of the surface treatment steel plate of the comparative example 4. It is a figure which represents typically the cross-section of the surface treatment steel plate of this invention.

The surface-treated steel sheet of the present invention is a surface-treated steel sheet having a surface treatment layer containing fluorine and mainly containing zirconium and oxygen on at least one surface of the steel sheet, and a group 2 element on the surface side of the surface treatment layer It is an important feature to contain.
In the surface-treated steel sheet of the present invention, having a group 2 element on the surface side of the surface treatment layer or having a fluorine compound means that X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), and analytical electrons It can be grasped by various surface analysis and cross-sectional analysis such as a microscope (SEM, TEM).

As described above, the surface-treated steel sheet 1 obtained by the present invention includes a surface-treated layer mainly containing zirconium and oxygen on at least one side (both sides in the figure) of the steel sheet 2 as shown in FIG. 3 and the surface side 3b of the surface treatment layer contains a group 2 element, particularly a fluorine compound of the group 2 element. Usually, an organic resin-coated surface-treated steel sheet having an organic resin layer formed on the surface-treated layer 3 is used, and then used as a metal container member such as a can.
Below, the surface treatment steel plate in this invention, the organic resin coating container using the surface treatment steel plate, and the manufacturing method of a surface treatment steel plate are demonstrated.

(Surface-treated steel sheet)
The surface treatment layer containing fluorine and mainly composed of zirconium and oxygen formed on the surface-treated steel sheet of the present invention is considered to have an amorphous structure such as ZrOx (OH) y-zFz. It is considered that this film is dehydrated by drying or baking, and F is removed to change to an oxide film having a large amount of crystal components, and when heating further proceeds, the film finally becomes close to ZrO2. However, excessive heating that exceeds the thermal history experienced by normal cans induces cracks in the coating due to structural changes, and results in a more ceramic-like coating. This is not preferable because it causes a decrease in adhesion. In addition, if the amount of F in the surface treatment layer is extremely reduced by washing with hot water or the like, it becomes easy to induce structural changes in the coating even with slight heating, leading to a reduction in the cohesive strength of the coating, and the resin-coated metal plate This causes a decrease in corrosion resistance in the cross-cut test, and causes a decrease in corrosion resistance and adhesion when the can body is impacted.
Therefore, the surface treatment layer preferably has a structure such as ZrOx (OH) y-zFz containing F or OH.

For a long period of time, we have investigated the relationship between coating components such as Zr content and F content, cross-cut corrosion resistance after retorting, and adhesion to the coating resin. As a result, it was found that a surface treatment film containing a large amount of zirconium and fluorine is effective for these properties.
However, with regard to fluorine, when surface-treated steel sheets with a very large F content in the coating are used for metal cans, the extra fluorine present in the surface-treated layer during retort sterilization and high-temperature storage of the can It may elute in and impair the flavor of the contents. On the other hand, when fluorine in the film is forcibly excluded by hot water cleaning, etc., as described above, it is likely to induce structural changes in the film, causing deterioration in performance such as corrosion resistance and adhesion. It becomes. Therefore, in the surface-treated steel sheet of the present invention, it is useful to suppress the elution of fluorine in the surface-treated film by performing the surface conditioning treatment, for maintaining the flavor of the contents and maintaining the performance of the metal can. Become.
On the other hand, with respect to zirconium, when the amount of Zr is small, there are many defective portions of the surface-treated film, so that the film is likely to cause elution of iron as a base material. When iron elution occurs, iron elution occurs in the anodic reaction, but alkali is generated at the interface between the coating resin and the metal coating due to the counter reaction, the cathode reaction. The generation of alkali accelerates the elution of fluorine in the surface-treated film and causes interface peeling between the coating resin and the surface-treated layer. Accordingly, a surface-treated film containing a large amount of zirconium is preferable in terms of cross-cut corrosion resistance after retorting and adhesion to the coating resin.

In the surface-treated steel sheet of the present invention, fluorine in the surface-treated film reacts with a group 2 element in the aqueous solution for surface conditioning, and is formed on the surface side as a fluorine compound in which fluorine is insolubilized. In addition, the effect of reducing the defects in the surface treatment layer as described later is also produced. As a result, the surface-treated steel sheet according to the present invention can maintain corrosion resistance and adhesion even with a smaller amount of Zr than in the past.
As the coating amount in the surface treatment layer in the surface-treated steel sheet of the present invention, the Zr amount is preferably in the range of 10 to 350 mg / m ² . If the amount of Zr is less than 10 mg / m ² , the cross-cut corrosion resistance after the organic resin coating and the resin adhesion on the inner and outer surfaces of the can after the retort become insufficient. On the other hand, if the amount of Zr exceeds 350 mg / m ² , not only is it uneconomical but also the work adhesion is gradually lowered, which is not preferable.
Moreover, as F amount, it is preferable that it is 0.3-30 mg / m < ² >. When the amount of F exceeds 30 mg / m ² , it becomes difficult to suppress elution of fluorine even when a compound layer of a group 2 element is formed on the surface side. On the other hand, when the amount of F is less than 0.3 mg / m ² , It is not preferable because the cohesive force of the film is reduced due to the structural change due to the sum, and the adhesion and corrosion resistance are reduced.

In the present invention, group 2 elements contained on the surface of the surface treatment layer by the surface conditioning treatment include beryllium, magnesium, calcium, strontium, barium, radium, etc., but react with fluorine to form a hardly soluble compound. In addition, Ca and Mg are preferable from the viewpoint of safety, hygiene, availability, and cost, and Ca is most preferable from the viewpoint of reactivity and poor solubility.
In particular, when the amount of Zr is large, the coating film contains more fluorine, so fluorine elution resistance becomes more important. The molar ratio of the group 2 element AE such as calcium and zirconium Zr in the surface treatment layer, AE / Zr is preferably 0.2 or more, and the weight film thickness of the group 2 element AE such as calcium is preferably in the range of 7 to 150 mg / m ² . If it is less than 7 mg / m ² , the contribution to suppression of fluorine elution and reduction of surface defects is small. If it exceeds 150 mg / m ² , the cohesive force of the coating is lowered, and the workability and adhesiveness are lowered. In addition, when two or more group 2 elements are included, AE shows the total amount.

The surface-treated steel sheet of the present invention is a surface-treated steel sheet having a surface treatment layer containing fluorine and mainly composed of zirconium and oxygen, and having a group 2 element compound layer on the surface side of the surface treatment layer. This is an important feature.
FIG. 1 shows that a surface-treated steel sheet containing a surface treatment layer containing fluorine and containing zirconium and oxygen as a main component is treated with a calcium-containing aqueous solution by a surface conditioning step, and calcium and fluorine are mainly present on the surface side of the surface treatment layer. Using the surface-treated steel sheet of the present invention in which a compound layer to be formed was formed, the change in atomic concentration in the depth direction was shown.
In the example of FIG. 1, an X-ray photoelectron spectrometer (hereinafter referred to as XPS)
By using the peaks of C1s, O 1 s, F1s, Fe2p3, Zr3d, and Ca2p3, the total of these elements is 100%, the horizontal axis is the Ar sputtering depth (SiO2 equivalent value) from the surface, and each atomic concentration Showed changes. For reference, FIG. 2 shows the results of examining the atomic concentration distribution in the depth direction using the surface-treated steel sheet before being treated with the calcium-containing aqueous solution in the surface conditioning step. 1 corresponds to the analysis result of the surface-treated steel sheet prepared in Example 11 described later and FIG. 2 represents the comparative example 4 described later.

FIG. 1 shows that Ca is present on the surface side of the surface treatment layer in the surface-treated steel sheet of the present invention. Further, in FIG. 1, the F concentration on the surface side of the surface treatment layer is increased and the Zr concentration and the O concentration are decreased compared to FIG. 2 that has not undergone the surface adjustment step. This is considered to be because fluorine and calcium reacted to form an insoluble compound on the surface by treatment with a calcium-containing aqueous solution. Further, in FIG. 1, it can be seen that, compared to FIG. 2, even when sputtering from the surface to a deep part, the atomic concentration of Fe is difficult to increase and the defect portion of the surface treatment layer is difficult to be exposed. .
In addition, the same tendency is shown also in Examples 1 to 15 and Comparative Examples 1 to 5 which will be described later. Compared to the comparative example represented by FIG. While existing on the surface side, an increase in F concentration on the surface side is observed.

(Method for producing surface-treated steel sheet)
<Film formation process>
In the method for producing a surface-treated steel sheet of the present invention, first, in the film forming step, the steel sheet is subjected to cathodic electrolysis in an aqueous solution containing Zr ions and F ions, so that fluorine is contained on at least one surface of the steel sheet. Zr compound coating mainly composed of zirconium and oxygen has a Zr amount of 10 to 350 mg / m ² , more preferably 10 to 200 mg / m ² , and an F amount of 0.3 to 30 mg / m ² . Form to range. In particular, inhibition of the fluorine reduction rate in the surface conditioning step described below, since the effect the greater the coating amount is large, Zr weight 100 mg / ^{m 2} or more, and particularly preferably in the range especially 100 to 200 mg / ^{m 2.}
The steel sheet after forming the surface treatment layer is squeezed with an electrolytic treatment solution with a roll, washed with water, and further squeezed with rinsing water with a roll, and then sent to the next surface adjustment step.

The Zr concentration in the electrolytic treatment solution used in the film forming step is preferably 1,000 to 10,000 ppm, the F concentration is preferably 600 to 13,000 ppm, and the electrolytic treatment solution pH is preferably 2 to 5, more preferably 2.5. It is more preferable that it is -4, and it is preferable that the electrolytic treatment liquid temperature is 30-60 degreeC.
Various compounds can be added to the electrolytic treatment solution used in the film forming step as described later. In addition to Zr ions and F ions, nitrate ions and ammonium ions used for pH adjustment are included in the aqueous electrolytic solution. Basically, ions and Fe ions, which are components eluted from the substrate, are included.

The agent for forming the Zr ions constituting the electrolytic treatment solution is not particularly limited, for _{example, K 2 ZrF 6, (NH} 4) 2 ZrF 6, (NH 4) 2 ZrO (CO 3) 2, H ₂ ZrF ₆ , ZrO (NO ₃ ) ₂ , ZrO (CH ₃ COO) _{2 and the} like can be used. In the present invention, the above-mentioned drugs may be used alone or in combination of two or more.

When forming a Zr compound film by cathodic electrolysis, it is usually desirable to use a treatment liquid containing F ions in addition to the Zr ions described above as the electrolytic treatment liquid. By containing F ions in the electrolytic treatment liquid, the F ions act as a complexing agent for enhancing the solubility of Zr ions in the electrolytic treatment liquid. The Zr compound can be precipitated, and therefore the adhesion between the coating and the organic resin layer can be further improved.
When there are few F ions in the electrolytic treatment solution, Zr causes local precipitation, and a thick portion and a thin portion where Zr is present in the coating are mixed, resulting in a coating with poor film thickness uniformity. The film is inferior in adhesion and corrosion resistance after processing. Therefore, in the film forming step, it is necessary to manage the molar ratio F / Zr in the film so that the molar ratio F / Zr of F atoms to Zr atoms in the film is 0.6 or more.

  Although it does not specifically limit as a chemical | medical agent for forming F ion contained in an electrolytic processing liquid, For example, zirconium ammonium fluoride, aluminum fluoride, titanium fluoride, sodium fluoride, ammonium fluoride, hydrofluoric acid , Calcium fluoride, hexafluorosilicic acid, sodium hexafluorosilicate, and the like can be used. Among them, a drug having high solubility in water is preferable.

In addition, an electrolyte such as nitrate ion or ammonium ion is added to the electrolytic treatment liquid within a range not impeding the formation of the Zr compound film for the purpose of improving the conductivity in the treatment liquid and adjusting the pH of the treatment liquid. Also good.
Furthermore, one or more additives among organic acids such as citric acid, lactic acid, tartaric acid and glycolic acid, and polymer compounds such as polyacrylic acid, polyitaconic acid and phenol resin are added to the electrolytic treatment solution. It may be. In the present invention, by adding an additive such as an organic acid or a phenol resin to the electrolytic treatment solution, the formed Zr compound film can contain an additive such as an organic acid or a phenol resin. In addition to imparting flexibility of the metal oxygen compound film, adhesion to the organic resin layer can be further improved.

Although it does not specifically limit as a current density in the case of performing a cathodic electrolysis process to a base material, Preferably it is 1-30 A / dm < ² >.
In addition, when performing the cathodic electrolysis treatment on the base material, it is preferable to use an intermittent electrolysis method in which a cycle of energization and deenergization is repeated. In this case, the total energization time for the base material (cycle of energization and deenergization) Is preferably 0.3 to 30 seconds.
In addition, when the cathode electrolytic treatment is performed on the base material, the counter electrode installed on the base material may be anything as long as it does not dissolve in the electrolytic processing solution during the cathode electrolytic treatment. A titanium plate coated with iridium oxide is preferred because it has a low overvoltage and is difficult to dissolve in the electrolytic treatment solution.

<Surface adjustment process>
In the present invention, it is an important feature that a surface conditioning process using a group 2 element is performed after the film forming process.
That is, the surface-treated steel sheet containing a fluorine-containing, surface-treated layer mainly composed of zirconium and oxygen obtained by the above-described film forming step is immersed using a surface conditioning aqueous solution containing a group 2 element. Any one or more of treatment, spray treatment, and cathodic electrolysis is performed. By this treatment, the Group 2 element is present on the surface side of the surface treatment layer. As described above, it is particularly preferable that the Group 2 element is present as a fluorine compound in which the fluorine reacts with fluorine and the fluorine is insolubilized.
After the treatment such as the immersion treatment, the surface conditioning aqueous solution is squeezed from the steel sheet with a roll, washed with water, and further washed with squeezed water with a roll, and then dried with hot air or the like.

When the surface adjustment process is not performed, as described above, the container formed from the organic resin-coated surface-treated steel sheet coated with the organic resin has a fluorine content present in the film in the hot water sterilization process such as retort. It elutes into the contents and as a result induces a structural change of the film, causing performance degradation such as corrosion resistance and adhesion.
Therefore, before the resin coating is applied as the material for the can, in the surface conditioning step, fluorine that contains fluorine and diffuses to the surface side in the surface treatment layer mainly composed of zirconium and oxygen is added to the group 2 element and the compound. It is important to form a layer and make it insoluble.

Examples of group 2 elements used in the aqueous solution for surface conditioning include beryllium, magnesium, calcium, strontium, barium, radium, etc., but there are water-soluble drugs when used in the aqueous solution for surface conditioning. In addition, it is necessary to consider such points as being easy to bond with fluorine, forming a poorly soluble fluorine compound, being readily available, having excellent safety and hygiene, and being inexpensive. For this reason, it is more preferable to use calcium or magnesium which forms hardly soluble CaF ₂ or MgF ₂ after reaction with fluorine.
Here, the surface conditioning aqueous solution may contain either calcium ions or magnesium ions, or both. When only one ion is contained, an aqueous solution for surface conditioning containing calcium can be most suitably used.

  As an aqueous solution for surface adjustment, the drug in the case of using calcium is not particularly limited as long as it is dissolved in water, but calcium lactate, calcium hydroxide, calcium gluconate, calcium chloride, calcium nitrate, calcium sulfate, calcium citrate, carbonate There are calcium, calcium hydrogen hydrogen phosphate and the like, and among these, those having high water solubility are more preferable. In addition, the drug using magnesium is not particularly limited as long as it dissolves in water, but there are magnesium chloride, magnesium nitrate, magnesium sulfate, magnesium citrate, magnesium acetate, magnesium gluconate, etc., and when the aqueous solution is alkaline Magnesium gluconate is particularly preferred.

  As apparent from the fact that the surface conditioning aqueous solution itself has a role of insolubilizing the fluorine of the surface treatment film, the water during the preparation of the chemical contains fluorine or contains fluorine dissolved in the surface conditioning process. However, there is no intentional addition or inclusion of fluorine.

Further, in the surface conditioning step, the liquidity of the aqueous solution for surface conditioning itself is preferably in the range of pH 2 to 13, particularly pH 5 to 11, more preferably pH 5.5 to 7, and thereby in the surface treatment layer. Fluorine in the form of free F ions, not complex ions, can be more efficiently combined with group 2 elements, and can be stably group 2 element fluorine compounds on the surface side of the surface treatment layer. Can improve the fluorine elution resistance and reduce the fluorine concentration in the waste water.
In addition, if pH is less than 2, it will have a bad influence also on the corrosion resistance of the steel plate itself which is a peripheral device or a base material, and on the other hand, if pH is more than 11, it will stabilize a fluorine compound on the surface side of a surface treatment layer. When the ability to form decreases and the pH exceeds 13, in particular, the proportion of fluorine dissolved in the aqueous solution for surface adjustment increases, and eventually the fluorine concentration in the waste water increases, which is not preferable.

As an alkaline agent used for adjusting the pH of the aqueous solution for surface adjustment, a hydroxylated compound of a group 2 element that exhibits water-solubility and alkalinity, such as Ca (OH) ₂ or Mg (OH) ₂ is used. Is the simplest. However, since the solubility of these chemicals in water is relatively small, it is necessary to replenish the chemicals frequently when the surface conditioning process is continuously performed by immersion or cathodic electrolysis or when cathodic electrolysis is performed. In some cases, labor may be required to maintain the aqueous solution. In such a case, it is preferable from the viewpoint of easy processing that a spray method in which a new surface conditioning aqueous solution is always sprayed onto the steel sheet is employed. Even if a Group 2 chemical agent is water-soluble and does not show alkalinity, it can be used as an aqueous solution for alkaline surface conditioning by adding a chemical containing one or more of sodium, ammonium and potassium to adjust the pH. it can.
In addition, as a chemical other than the Group 2 element used for adjusting the pH of the aqueous solution for surface conditioning, ammonia, zirconium zirconium carbonate, sodium hydroxide, sodium carbonate, sodium bicarbonate, sodium phosphate, sodium hydrogen phosphate, water Examples thereof include potassium oxide, potassium carbonate, sodium borate, sodium silicate and the like, and two or more kinds of chemicals may be added.
In addition, various surfactants and chelating agents can be added to the surface conditioning aqueous solution as necessary.

The concentration of group II element ions contained in the aqueous solution for surface conditioning is preferably in the range of 0.002 to 0.5 mol / l. If it is less than 0.002 mol / l, the reaction efficiency when forming the fluorine compound of the group 2 element on the surface side of the surface treatment layer is poor, and if it exceeds 0.5 mol / l, the precipitation of the group 2 element tends to be excessive. This is not preferable because the cohesive strength of the coating is reduced.
As described above, the surface conditioning step can be performed by dipping, spraying or cathodic electrolysis using a surface conditioning aqueous solution containing a Group 2 element, but from the viewpoint of rapid processing, the surface conditioning aqueous solution. Among them, it is preferable to add a cathodic electrolysis treatment, while spray treatment and immersion treatment are suitable as simple means. The liquid property of the aqueous solution for surface adjustment to be used is desirably in the pH range as described above. In particular, in order to reduce the dissolution of fluorine in the aqueous solution for surface adjustment and to reduce the drainage load, the pH is 5.5. It is suitable to be in the range of ~ 7.
In addition, when performing a cathodic electrolysis process, it is preferable from the surface of process efficiency that the electrical conductivity of the aqueous solution for surface adjustment containing a group 2 element is 2 mS / cm or more.

As described above, the surface conditioning step allows a group 2 element, particularly a group 2 element compound to be present on the surface side of the surface treatment layer. Here, the group 2 element compound formed on the surface side of the surface treatment layer is preferably a fluorine compound, and more preferably hardly soluble. The group 2 element forming the hardly soluble compound is preferably a calcium and / or magnesium compound, and may be a single compound of calcium and magnesium, or a compound containing both calcium and magnesium. There may be. Among these, in the case of a single compound, a calcium fluorine compound which forms a hardly soluble compound can be most suitably used.
The molar ratio of group 2 element AE to zirconium Zr in the surface treatment layer, AE / Zr is preferably 0.2 or more, particularly preferably in the range of 0.4 to 1.8, and the weight of group 2 element It is more effective that the film thickness is 7 mg / m ² or more.

In the surface conditioning step, the temperature of the aqueous solution for surface conditioning does not need to be specified in particular, but from the point of reactivity and temperature management, it may be in the range of 30 to 80 ° C, particularly 30 to 60 ° C. More preferred. In addition, the total treatment time of the immersion treatment, the spray treatment, the cathodic electrolysis treatment and the like using the surface conditioning aqueous solution is preferably 0.1 to 5 seconds, and is preferably in the range of 0.5 to 3 seconds. Further preferred.
Further, in the surface adjustment step, after the treatment with the aqueous solution for surface adjustment, a washing treatment by warm water or hot water of about 40 ° C. to 95 ° C. or spraying may be additionally performed.

(Steel substrate)
Examples of the steel sheet used for the surface-treated steel sheet of the present invention include a hot-rolled steel sheet based on an aluminum killed steel continuous cast material, a cold-rolled steel sheet obtained by cold rolling these hot-rolled steel sheets, and these hot-rolled steel sheets and cold-rolled steel sheets. A steel plate provided with a metal plating layer containing Zn, Sn, Ni, Cu, Al, or the like on the steel plate can be used.
Further, a steel plate in which an alloy layer such as a Sn—Ni—Fe alloy, a Sn—Fe alloy, or a Ni—Fe alloy is present on a part of the surface or the entire surface can also be used. It is also possible to use a steel plate having a metal plating layer. Among these, from the viewpoint of cost, a steel plate that does not have a metal plating layer or has an iron exposed portion dispersed on the surface even if it has a plating layer is the basis. Most preferably used as a material.
The thickness of the substrate is not particularly limited and may be appropriately selected depending on the intended use, but is preferably 0.07 to 0.4 mm.

(Organic resin coating)
As described above, the surface-treated steel sheet obtained by the present invention is excellent in the adhesion of the organic resin layer when the organic resin coating layer is formed on the surface treatment layer, and is particularly organic even when the retort treatment is performed. In addition to preventing peeling of the resin layer, the organic resin layer is cracked, and even when the metal surface is exposed in a wet environment, the progress of corrosion is effectively prevented, and the elution of the metal component components of the container is suppressed. Yes.
The resin constituting such an organic resin layer is not particularly limited, and may be appropriately selected according to the use of the surface-treated steel sheet of the present invention (for example, a can container filled with a specific content). However, mention may be made of resin coatings made of various thermoplastic resins and coatings made of thermosetting paints or thermoplastic paints. Examples of resin coatings made of thermoplastic resins include polyethylene, polypropylene, ethylene-propylene copolymers, ethylene-vinyl acetate copolymers, ethylene-acrylic ester copolymers, olefin resin films such as ionomers, polyethylene terephthalate, poly Polyethylene film such as butylene terephthalate, or non-stretched or biaxially stretched thermoplastic film such as nylon 6, nylon 6,6, nylon 11, nylon 12 or other polyamide film, polyvinyl chloride film, polyvinylidene chloride film, etc. It may be. Among these, non-oriented polyethylene terephthalate obtained by copolymerizing isophthalic acid is particularly preferable. Moreover, the resin for constituting such an organic resin layer may be used alone, or may be used by blending different resins.

When the thermoplastic resin is coated as the organic resin coating, it may be a single resin layer or a multilayer resin layer formed by coextrusion or the like. When a multilayer polyester resin layer is used, a polyester resin having a composition with excellent adhesion is selected for the base layer, that is, the surface-treated steel sheet, and the surface layer is excellent in content resistance, that is, extraction resistance and non-adsorption of flavor components. This is advantageous because polyester resins having different compositions can be selected.
Examples of multilayer polyester resin layers are shown as surface layer / lower layer, polyethylene terephthalate / polyethylene terephthalate / isophthalate, polyethylene terephthalate / polyethylene / cyclohexylene dimethylene / terephthalate, polyethylene terephthalate / isolated with low isophthalate content. Polyethylene terephthalate / isophthalate having a high phthalate / isophthalate content, polyethylene terephthalate / isophthalate / [blend of polyethylene terephthalate / isophthalate and polybutylene terephthalate / adipate] and the like are of course not limited thereto. The thickness ratio of the surface layer to the lower layer is preferably in the range of 5:95 to 95: 5.

In the organic coating, known compounding agents for resins, such as anti-blocking agents such as amorphous silica, inorganic fillers, various antistatic agents, lubricants, antioxidants, ultraviolet absorbers, etc. are blended according to known formulations. can do.
Of these, tocopherol (vitamin E) is preferably used. Tocopherol has been conventionally known as an antioxidant to prevent a decrease in molecular weight due to oxidative decomposition during heat treatment of a polyester resin and to improve dent resistance. When this tocopherol is blended with a polyester composition blended as a modified resin component, not only the dent resistance, but also when the film is cracked due to severe conditions such as retort sterilization and hot bender, It is possible to prevent the corrosion from proceeding from the crack and to obtain the effect that the corrosion resistance is remarkably improved.
Tocopherol is preferably blended in an amount of 0.05 to 3% by weight, particularly 0.1 to 2% by weight.

  The thickness of the organic resin coating applied to the surface-treated steel sheet obtained by the present invention is desirably 3 to 50 μm, particularly 5 to 40 μm in general with a thermoplastic resin coating. Is preferably in the range of 1 to 50 μm, particularly 3 to 30 μm. When the thickness is less than the above range, the corrosion resistance becomes insufficient, and when the thickness exceeds the above range, a problem is likely to occur in terms of workability.

  Formation of the organic coating on the surface-treated steel sheet obtained by the present invention can be performed by any means. For example, in the case of thermoplastic resin coating, extrusion coating, cast film thermal bonding, biaxially stretched film thermal bonding This can be done by law. In the case of the extrusion coating method, it can be manufactured by extrusion coating a polyester resin in a molten state on a surface-treated metal material and thermally bonding it. That is, after melt-kneading the polyester resin with an extruder, it is extruded from a T-die into a thin film, and the extruded molten resin film is passed through a pair of laminating rolls together with a surface-treated metal material and is pressed and integrated under cooling. Then quench rapidly. When extrusion coating a multilayer polyester resin layer, an extruder for surface layer resin and an extruder for lower layer resin are used, and the resin flow from each extruder is merged in a multiple multilayer die, and thereafter a single layer Extrusion coating may be performed as in the case of resin. Further, by passing a surface-treated metal material vertically between a pair of laminate rolls and supplying a molten resin web on both sides thereof, a polyester resin coating layer can be formed on both sides of the substrate.

  The production of the organic coated surface-treated steel sheet having an organic coating made of polyester resin by the extrusion coating method is specifically performed as follows. If necessary, the surface-treated steel sheet is preheated by a heating device and supplied to a nip position between a pair of laminate rolls. On the other hand, the polyester resin is extruded in the form of a thin film through a die head of an extruder, supplied between the laminate roll and the surface-treated steel sheet, and pressed onto the surface-treated steel sheet by the laminate roll. The laminating roll is maintained at a constant temperature, and a thin film made of a thermoplastic resin such as polyester is pressure-bonded to the surface-treated steel sheet to thermally bond them together and cooled from both sides to obtain an organic-coated surface-treated steel sheet. In general, the formed organic-coated surface-treated steel sheet is further cooled in order to guide it to a cooling water tank or the like to prevent thermal crystallization.

  In this extrusion coating method, the polyester resin layer has a low crystallinity level and the difference from the amorphous density is suppressed to 0.05 g / cm 3 or less by selection of the resin composition and rapid cooling by a roll or a cooling bath. Therefore, sufficient workability with respect to subsequent can manufacturing, lid processing, etc. is guaranteed. Of course, the rapid cooling operation is not limited to the above example, and the laminate sheet can be rapidly cooled by spraying cooling water on the formed organic-coated surface-treated steel sheet.

The thermal adhesion of the polyester resin to the surface-treated steel sheet is performed by the amount of heat that the molten resin layer has and the amount of heat that the surface-treated steel sheet has. The heating temperature (T1) of the surface-treated steel sheet is generally 90 ° C. to 290 ° C., particularly 100 ° C. to 280 ° C., while the laminating roll temperature is suitably 10 ° C. to 150 ° C.
Moreover, the organic resin coating of the surface-treated steel sheet obtained by the production method of the present invention is also produced by thermally bonding a polyester resin film previously formed by a T-die method or an inflation film-forming method to the surface-treated steel sheet. be able to. As the film, an unstretched film formed by a cast molding method in which the extruded film is rapidly cooled can be used, and this film is biaxially stretched sequentially or simultaneously at the stretching temperature, and the stretched film is heat-set. It is also possible to use a biaxially stretched film produced by the above method.

(Metal container)
As described above, the metal container (can) formed using the surface-treated steel sheet of the present invention is formed from an organic-coated surface-treated steel sheet in which an organic resin coating is formed on the surface of the surface-treated steel sheet. Is preferable, and can be formed by any can manufacturing method. Specifically, it can be a three-piece can (welded can) having a side seam or a seamless can (two-piece can), but as described above, a surface treatment with a large amount of Zr from the viewpoint of adhesion to an organic resin. Considering the point of using a steel plate, application to a seamless can is most preferable.
Seamless cans are drawn, drawn and re-squeezed, bent and stretched by drawing and redrawing (stretching), and drawn and redrawed by drawing and redrawing, or drawn or drawn so that the organic coating is on the inner surface of the can. It is manufactured by attaching to a conventionally known means such as ironing.
In addition, for seamless cans that are subjected to advanced processing such as bending / stretching (stretching) by drawing / redrawing, bending / stretching / ironing by drawing / redrawing, the organic coating is coated with thermoplastic resin by the extrusion coating method. It is particularly preferred that Such an organic-coated surface-treated steel sheet is excellent in work adhesion, and therefore can provide a seamless can having excellent corrosion resistance and excellent coating adhesion even when subjected to severe processing. .

(lid)
The can lid formed using the surface-treated steel sheet of the present invention is preferably formed from an organic-coated surface-treated steel sheet as in the metal container described above, and can be formed by any conventionally known lid-making method. . Specifically, the present invention can be applied to a flat lid, a stay-on-tab type easy open can lid, and a full open type easy open can lid.
In the can lid of the present invention, the lid can be formed using any of the various embodiments of the organic-coated surface-treated steel sheet of the present invention without limitation.

Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples. In addition, the to-be-treated material, degreasing agent, and organic coating used in the examples are arbitrarily selected from commercially available materials, and do not limit the method for manufacturing the steel sheet for surface treatment according to the present invention. .
In addition, the preparation method of a surface treatment board and the evaluation method of each characteristic are as follows.

(Film formation process)
A low carbon steel plate having a thickness of 0.225 mm and a width of 200 mm was used as an original plate, and then alkaline electrolytic degreasing and sulfuric acid immersion pickling were performed as pretreatment. Thereafter, the steel sheet was immersed in an electrolytic treatment solution and subjected to cathodic electrolysis, whereby a compound film containing F on the surface of the steel sheet and mainly composed of Zr was formed on both surfaces. Next, the steel sheet was squeezed with a roll, washed with water, and further washed water was squeezed with a roll to form a film.
Electrolytic treatment solution: Zirconium ammonium fluoride is dissolved as a Zr compound, and an aqueous solution having a Zr concentration of 6,000 ppm and an F concentration of 7,500 ppm. PH of the electrolytic treatment solution: 3.0 (pH adjustment with nitric acid and / or ammonia) Implementation)
Electrolytic solution temperature: 40 ° C
Counter electrode: iridium oxide-coated titanium plate Method of energization during cathodic electrolysis: Energization for 0.15 seconds at a current density of 3 A / dm ² was performed once or a plurality of times (hereinafter referred to as the number of cycles).

(Surface adjustment process)
The steel sheet after completion of the film forming step was treated with an aqueous solution for surface conditioning for a predetermined time, and then the steel sheet was squeezed with a roll, washed with water, further squeezed with a roll, and then dried with hot air to obtain a surface-treated steel sheet.
In the present invention, as the surface adjustment step, using an aqueous solution for surface adjustment containing a group 2 element, any one or more of immersion treatment, spray treatment, and cathodic electrolysis treatment can be used. A surface treatment aqueous solution containing calcium or magnesium was used for immersion treatment, spray treatment, or cathodic electrolysis treatment. In the cathode electrolysis in the surface adjustment step, an iridium oxide-coated titanium plate was used as the counter electrode, and a cycle of energizing 0.15 seconds and stopping energization for 0.1 seconds was performed a plurality of times.

(Production of organic resin-coated surface-treated steel sheet)
The obtained surface-treated steel sheet is a 19 μm-thick stretched film having a polyethylene terephthalate / isophthalate copolymer composition containing 11 mol% of an isophthalic acid component on one side of a metal plate on the inner surface side of the can. A stretched film having a thickness of 13 μm, having a polyethylene terephthalate / isophthalate copolymer composition containing 12 mol% of an isophthalic acid component and colored in white containing titanium oxide, on the other surface on the side, After thermocompression bonding via a laminate roll, water-cooling was immediately performed to obtain an organic resin-coated surface-treated steel sheet while paying attention to an appropriate orientation state remaining in the film. The produced organic resin-coated surface-treated steel sheet was used for the production of metal cans, except that a part was used for cross-cut corrosion resistance evaluation.

(Production of metal cans)
Paraffin wax was electrostatically applied to both surfaces of the obtained organic resin-coated surface-treated steel sheet, and then punched into a circle having a diameter of 143 mm, and a drawn cup having a diameter of 91 mm and a height of 36 mm was produced according to a conventional method. Subsequently, the drawn cup was simultaneously drawn and ironed twice to form a cup having a small diameter and a large height. Various characteristics of the cup thus obtained were as follows.
Cup diameter 52.0mm
Cup height 111.7mm
30% reduction in the thickness of the can wall relative to the original thickness
This cup is heat-treated at 220 ° C. for 60 seconds after doming molding, followed by trimming of the end of the opening, curved printing, neck-in processing and flange processing to a diameter of 50.8 mm And a 200 ml seamless can was produced.

(Measurement of Zr amount, AE amount (Group 2 element amount))
About the obtained surface-treated steel sheet, the amount of Zr and the amount of AE (Ca amount or Mg amount in the examples) contained in the metal compound film are measured using a fluorescent X-ray analyzer (manufactured by Rigaku Corporation, model number: ZSX100e). did. The molar ratio AE / Zr was determined by the following formula.
AE / Zr = (AE amount / AE atomic weight) / (Zr amount / Zr atomic weight)

(Measurement of F amount)
With respect to the obtained surface-treated steel sheet, in the fluorescent X-ray analysis, the trace amount analysis of F has a limit in terms of quantitative accuracy, and in particular, it is not possible to directly quantify F from a surface-treated steel sheet with an F amount of 1.5 mg / m ² or less. Have difficulty. As a result of various studies, we quantified the following measurements. That is, a retort treatment at 130 ° C. for 30 minutes was performed using a special cell that can hold 160 cm ² on one side of the surface-treated steel sheet in contact with 183 g of ultrapure water. Then, the fluorine ion extracted in the ultrapure water was measured by the ion chromatograph (DX-320 made from DIONEX). From the obtained F concentration, the F weight present in the ultrapure water was determined, and this was converted to the F weight present per unit area of the surface-treated steel sheet to obtain the F amount in the coating.
In addition, about the surface treatment steel plate which passed through the surface adjustment process shown in an Example, even if it performs the above-mentioned retort process, since F hardly elutes, it cannot know F amount of a surface treatment steel plate. Therefore, the measured value by fluorescent X-ray was used about the surface treatment steel plate which passed through the surface adjustment process. However, when the F amount is less than 1.5 mg / m ² , the peak of the fluorescent X-ray is not clear, and therefore the surface treatment coating shavings in an amount corresponding to 10 times or more of the area normally measured with the fluorescent X-ray Were collected, and after measuring F with fluorescent X-rays, it was calculated by converting to F amount per unit surface area.

(Measurement of F decrease rate)
It was determined how much the F amount of the surface-treated steel sheet that had undergone the surface adjustment step was reduced from the F amount of the surface-treated steel plate that was formed only in the film forming step. This evaluation is an index of the fluorine load effect in the waste water in the surface adjustment step, and is preferably 30% or less.

(Cross cut corrosion resistance evaluation)
A test piece in which a cross-cut wound reaching a 4 cm-long substrate is made in a portion corresponding to the inner surface side of the obtained surface-treated steel sheet with a cutter is placed in a bottle, and commercially available coffee (trade name Blendy bottle coffee) The bottle was degassed by dipping in low sugar, Ajinomoto General Foods Co., Ltd., and the corrosive state was evaluated after aging at 37 ° C. for 4 weeks. During this period, coffee was periodically replaced to minimize mold generation. For the evaluation of the corrosion state, the test piece was taken out from the coffee, and the cross-cut portion and its surroundings were evaluated by visually observing the state of discoloration due to the peeling of the organic resin layer or the generation of the corrosion product.
In the periphery of the crosscut portion, 1 point has a maximum width of discoloration or film peeling of 3 mm or more, 2 points are 2 mm or more and less than 3 mm, 3 points are 1 mm or more and less than 2 mm, and 0.5 mm or more and less than 1 mm The thing was evaluated as 4 points, and less than 0.5 mm as 5 points, and those of 3 points or more were judged to be acceptable.

(Can inner surface resin adhesion evaluation)
Using the obtained seamless can, after filling with distilled water, the can and the lid were double-rolled and subjected to a retort treatment at 125 ° C. for 30 minutes. Then, after removing the lid from the can body and removing the contents, the surface-treated plate was cut in half at the 45-degree rolling direction. Next, the can cut into halves was immersed in a solution of 0.02% by weight of a surfactant added to a 1% by weight sodium chloride aqueous solution for 1 hour, and further on the bottom side of the can at the 135 degree direction of rolling. Further, it was cut into half with scissors, and the peeled state of the last cut surface of the inner surface of the bottom surface of the can was observed to evaluate the resin adhesion. 1 point with 10 mm or more peeling near the cut surface, 2 points with less than 10 mm and 5 mm or more, 3 points with less than 5 mm and 2 mm or more, 4 points with peeling but less than 2 mm, None were evaluated as 5 points, and 3 or more points were accepted.

(F elution resistance evaluation)
The obtained seamless can was filled with 183 g of ultrapure water, double-clamped, subjected to a retort treatment at 130 ° C. for 30 minutes, and then the fluorine ions extracted into the ultrapure water were ion chromatographed ( It measured by DIONEX DX-320). The case where F was 0.1 ppm or more was rated as x, and the case where F was less than 0.1 ppm was rated as ◯.

(Evaluation of drainage load)
Drainage loadability was evaluated from the F decrease rate described above. The case where the decrease rate of the F amount was 30% or less was marked as ◯, and the case where it exceeded 30% was marked as Δ. ○ is more preferable than Δ.

Example 1
First, in the coating formation step, an iridium oxide-coated titanium plate was used as the counter electrode in the electrolytic treatment solution, and the current was applied once for 0.15 seconds at a current density of 3 A / dm ² using the steel plate as a cathode. After squeezing with a roll, it was washed with normal temperature water, and further the rinsing water was squeezed with a roll. Subsequently, a surface adjustment step by cathodic electrolysis was performed. As the surface conditioning aqueous solution, a 0.1 mol / l calcium lactate aqueous solution was used, and the electrical conductivity of the solution was 6.57 mS / cm and the pH was 6.96. In the aqueous solution for surface conditioning at a liquid temperature of 30 ° C., the surface conditioning step was carried out by repeating the cycle of 0.15 second energization and 0.1 second energization twice at a current density of 4 A / dm ² . The steel sheet after the surface conditioning step was squeezed with an aqueous solution after being squeezed with a roll, and further squeezed rinsing water with a roll and then dried to obtain a surface-treated steel sheet.

  About the obtained surface-treated steel sheet, according to the method mentioned above, Zr amount, AE amount, and F amount were measured. The coating amount measurement results are shown in Table 1. Table 1 also shows the value of AE / Zr indicating the molar ratio of the Group 2 element (AE) and Zr calculated from the coating amount, and the F reduction rate described above. In the table, “-” means not implemented.

Example 2
The same operation as in Example 1 was performed except that the current density in the film forming step was 10 A / dm ² and the number of cycles was 2 and the current density in the surface adjustment step was 1 A / dm ² .

Example 3
The same operation as in Example 2 was performed except that the current density in the surface adjustment step was set to 6.5 A / dm ² .

Example 4
The treatment in the surface adjustment step was performed in the same manner as in Example 2 except that the immersion treatment was performed at 60 ° C. for 3 seconds.

Example 5
The same operation as in Example 3 was performed except that the current density in the film forming step was 10 A / dm ² and the number of cycles was four.

Example 6
Ammonia was added to a 0.1 mol / l calcium lactate aqueous solution to prepare a surface conditioning aqueous solution having a pH of 11.0 and a liquid conductivity of 7.13 mS / cm, and a current density of 2 A / dm ² at a liquid temperature of 40 ° C., a cycle. It carried out like Example 5 except having implemented the surface adjustment process by several times of cathodic electrolysis.

Example 7
The same operation as in Example 6 was performed except that the cathode electrolysis current density in the surface adjustment step was set to 7 A / dm ² .

Example 8
The same procedure as in Example 6 was performed except that the treatment in the surface adjustment step was a spray treatment for 3 seconds.

Example 9
The same procedure as in Example 2 was performed except that the number of cycles in the film forming step was eight.

Example 10
The same operation as in Example 9 was performed except that the current density in the surface adjustment step was 4 A / dm ² and the number of cycles was four.

Example 11
The same operation as in Example 10 was performed except that the current density in the surface adjustment step was set to 6.5 A / dm ² .

Example 12
Using 0.1 mol / l of magnesium nitrate hexahydrate, an aqueous solution for surface adjustment having a liquid electrical conductivity of 15.1 mS / cm and pH of 5.61 was prepared, and the current density was 4 A / dm ² at a liquid temperature of 40 ° C. This was carried out in the same manner as in Example 11 except that the surface adjustment step by cathodic electrolysis was performed twice.

Example 13
It implemented similarly to Example 10 except having made the cycle number in a film formation process into 12 times.

Example 14
It implemented similarly to Example 11 except having made the cycle number in a film formation process into 12 times.

Example 15
In the surface adjustment step, a 0.1 mol / l calcium nitrate aqueous solution with a pH of 5.6 was used as the surface adjustment aqueous solution, and the cathode temperature was 40 ° C., the current density was 4 A / dm ² , and the number of cycles was twice. This was carried out in the same manner as in Example 13.

<< Comparative Example 1 >>
It implemented like Example 1 except not having implemented the surface adjustment process.

<< Comparative Example 2 >>
It implemented similarly to Example 2 except not having implemented the surface adjustment process.

<< Comparative Example 3 >>
It implemented like Example 5 except not having implemented the surface adjustment process.

<< Comparative Example 4 >>
It implemented like Example 9 except not having implemented the surface adjustment process.

<< Comparative Example 5 >>
It implemented like Example 13 except not having implemented the surface adjustment process.

(Discussion)
As is clear from Table 1, in Examples 1 to 15, the amount of Zr in the coating was 12 to 182 mg / m ^2, and in the surface adjustment step, the coating was performed with an aqueous solution containing a Group 2 element. Plates having an F content of 0.4 to 19.8 mg / m ² were prepared. In Comparative Examples 1 to 3 in which the surface adjustment step is not performed, F elution resistance is satisfied, but it is inferior in terms of cross-cut corrosion resistance and adhesion, and these performances improve as the Zr amount increases. On the contrary, it became a material inferior to F elution resistance. The organic resin-coated metal plate prepared from the material subjected to the surface adjustment process in Examples 1 to 15 is excellent in cross-cut corrosion resistance, and is also excellent in inner surface adhesion of metal cans and F elution resistance. The layer has high adhesion, and even when the organic resin layer is cracked after being subjected to molding and retort treatment, the container should maintain the adhesion of the organic resin layer and maintain the quality of the contents. Was confirmed.
Moreover, in Examples 1-15, F reduction rate was so small that Zr amount in a film was large, and 30% or less F reduction rate was shown especially in Zr amount 100 mg / m < ² > or more. That is, it was found that even if the F decrease rate is small, it is possible to create a material excellent in corrosion resistance, adhesion, and F elution resistance.
Further, as apparent from Table 1, the AE amount in Examples 1 to 15 was 7.7 to 141 mg / m ² , while the comparative example showed a value of 1.4 to 5.1 mg / m ^2. It was. The comparative example does not pass through the surface conditioning process, and no intentional group 2 element is added to the aqueous solution and washing water in the film forming process. These are the aqueous solution and washing water in the film forming process. It is considered that it is derived from Ca and Mg which are contained as inevitable impurities. Looking at the AE / Zr ratio in Table 1, all the materials of Examples 1 to 15 showing good performance showed 0.2 or more, and Comparative Examples 1 to 5 not satisfying the performance were less than 0.2. It was. Therefore, it is possible to distinguish Ca and Mg contained as inevitable impurities by using the AE / Zr ratio.

Claims (9)

  A surface-treated steel sheet having a surface treatment layer mainly containing zirconium and oxygen on at least one surface of the steel sheet, wherein the surface treatment layer contains a group 2 element. Surface treated steel sheet.   The surface-treated steel sheet according to claim 1, wherein the group 2 element is present as a fluorine compound.   The surface-treated steel sheet according to claim 1 or 2, wherein the group 2 element is at least one of calcium and magnesium.   The surface-treated steel sheet according to any one of claims 1 to 3, wherein a molar ratio AE / Zr between the group 2 element (AE) and the zirconium (Zr) in the surface treatment layer is 0.2 or more. . The surface-treated steel sheet according to claim 1, wherein the zirconium has a weight film thickness of 100 to 200 mg / m ² .   An organic resin-coated metal container comprising an organic resin-coated surface-treated steel sheet obtained by forming an organic resin coating on the surface-treated steel sheet according to any one of claims 1 to 5.   A method for producing a surface-treated steel sheet having a surface treatment layer containing fluorine and mainly composed of zirconium and oxygen on at least one surface of the steel sheet, and cathodically electrolyzing the steel sheet in an aqueous solution containing Zr ions and F ions A film forming step by the step, and subsequently a surface adjustment step by performing any one or more of a dipping treatment, a spray treatment, and a cathodic electrolysis treatment using the aqueous solution for surface adjustment containing a group 2 element; and A method for producing a surface-treated steel sheet, comprising:   The method for producing a surface-treated steel sheet according to claim 7, wherein the Group 2 element is at least one of calcium and magnesium.   The method for producing a surface-treated steel sheet according to claim 7 or 8, wherein, in the surface adjustment step, the rate of fluorine reduction from the film formation step is 30% or less.

Images