JP5257192B2 - Method for producing surface-treated steel sheet and resin-coated steel sheet - Google Patents

Description

  The present invention relates to a surface-treated steel sheet mainly used for containers such as cans after being coated with a resin by laminating a plastic film or the like on the surface or by applying a paint containing resin, particularly in a high-temperature and humid environment. The present invention relates to a method for producing a surface-treated steel sheet and a method for producing a resin-coated steel sheet, which are excellent in adhesion with the resin coated in (hereinafter referred to as wet resin adhesion).

  Various metal cans such as beverage cans, food cans, pail cans and 18 liter cans use metal plates such as electrolytic chromic acid treated steel plates called tin-plated steel plates or tin-free steel plates. Among these, tin-free steel sheets are manufactured by electrolytically treating steel sheets in a plating bath containing hexavalent Cr, and are characterized by excellent wet resin adhesion to resins such as paints.

  In recent years, due to the increasing awareness of the environment, the use of hexavalent Cr has been regulated worldwide, and there is an alternative material for tin-free steel plates manufactured using a hexavalent Cr plating bath. It has been demanded. For example, Patent Document 1 discloses a steel plate for containers that has been subjected to electrolytic treatment in a tungstic acid solution. Patent Document 2 discloses a surface-treated steel sheet for containers having a phosphate layer formed on the surface. Furthermore, Patent Document 3 has a phenol structure containing one or more of tannic acid or acetic acid and one or more of Ti or Zr or a compound thereof on a surface treatment layer containing one or more of Sn and Ni. A steel plate for containers in which a resin film is formed has been proposed. Furthermore, Patent Document 4 proposes a surface-treated metal material that does not contain phosphate ions and has an inorganic surface treatment layer and an organic surface treatment layer mainly composed of Ti, O, and F.

  On the other hand, various types of metal cans have been manufactured by processing metal cans such as tin-free steel sheets and then processing them into cans. Instead of this, a method of processing a resin-coated metal plate coated with a resin such as a plastic film into a can body is frequently used. In this resin-coated metal plate, it is necessary that the resin is strongly adhered to the metal plate. In particular, the resin-coated metal plate used as a beverage can or a food can is subjected to a retort sterilization process after filling the contents. In some cases, strong wet resin adhesion is required so that the resin does not peel even in a high temperature wet environment.

JP 2004-285380 A Japanese Patent Laid-Open No. 2001-220685 JP 2002-355921 A JP 2006-009046 A

  However, a resin-coated steel sheet using a container steel plate subjected to electrolytic treatment in a tungstic acid solution described in Patent Document 1, and a container surface-treated steel sheet having a phosphate layer formed on the surface described in Patent Document 2 The steel sheet for containers in which the resin film having a phenol structure described in Patent Document 3 is formed, and the inorganic surface treatment layer and the organic surface treatment layer mainly composed of Ti, O, and F described in Patent Document 4 are formed. In any of the surface-treated metal materials, the wet resin adhesion in the retort atmosphere is insufficient.

  An object of the present invention is to provide a method for stably producing a surface-treated steel plate that does not use Cr, has excellent wet resin adhesion, and can be used as a substitute for a tin-free steel plate, and a method for producing a resin-coated steel plate.

  As a result of intensive research on a method for producing a surface-treated steel sheet that does not use Cr, is excellent in wet resin adhesion, and can be used as a substitute for a tin-free steel sheet, ions containing Ti, Fe, Co, Extremely good wet resin by installing an anion exchange membrane between the anode and the steel sheet and subjecting the steel sheet to cathodic electrolysis in an aqueous solution containing ions including metals such as Ni, V, Cu, Mn and Zn It discovered that the surface-treated steel plate which has adhesiveness can be manufactured stably.

  The present invention has been made based on such knowledge, and at least one surface of a steel plate has at least one selected from among ions containing Ti and Fe, Co, Ni, V, Cu, Mn and Zn. A method for producing a surface-treated steel sheet, characterized in that, in an aqueous solution containing ions containing metal, an anion exchange membrane is installed between the anode and the steel sheet, and the steel sheet is subjected to cathodic electrolytic treatment to form an adhesive film. I will provide a.

  In the method for producing a surface-treated steel sheet according to the present invention, Ti is 0.008 to 0.07 mol / L (L: liter), and at least one selected from Fe, Co, Ni, V, Cu, Mn, and Zn. It is preferable to perform the cathodic electrolysis treatment in an aqueous solution containing 0.01 to 10 metals in a total molar ratio to Ti.

  In addition, before the cathode electrolytic treatment is performed to form the adhesive film, the Ni layer, the Sn layer, the Fe—Ni alloy layer, the Fe—Sn alloy layer, and the Fe—Ni— It is preferable to form at least one type of corrosion resistant film selected from Sn alloy layers.

  The present invention also provides a method for producing a resin-coated steel sheet, wherein the surface of the adhesive film of the surface-treated steel sheet produced by the production method of the present invention is coated with a resin.

  According to the present invention, a surface-treated steel sheet that does not use Cr, has excellent wet resin adhesion, and can be used as a substitute for a tin-free steel sheet can be stably produced. In the surface-treated steel sheet produced by the production method of the present invention, even if the resin is coated to form a resin-coated steel sheet, processed into a can or can lid and exposed to a retort atmosphere, the resin does not peel at all. In addition, surface-treated steel sheets with corrosion-resistant coatings such as Ni layers, Sn layers, Fe-Ni alloy layers, Fe-Sn alloy layers, and Fe-Ni-Sn alloy layers before cathodic electrolysis are treated with resin such as scratches. Even in the missing part, the elution of Fe as a base material is remarkably small and the corrosion resistance is extremely excellent.

It is a figure which shows the relationship between pH fluctuation | variation and Ti amount reduction | decrease rate of an adhesive film. It is a figure explaining a 180 degree peel test.

1) Cathodic electrolytic treatment In an aqueous solution containing ions containing Ti on the steel sheet surface, and further containing ions containing at least one metal selected from Fe, Co, Ni, V, Cu, Mn and Zn When a cathodic electrolytic treatment is performed to form an adhesive film, a surface-treated steel sheet having extremely excellent wet resin adhesion can be produced. The reason for this is not clear at present, but it is dense and the surface irregularities are uniform by incorporating metal elements such as Fe, Co, Ni, V, Cu, Mn, Zn into the film containing Ti. This is probably because a distributed adhesive film is formed.

  At this time, Ti is 0.008 to 0.07 mol / L, preferably 0.02 to 0.05 mol / L, and at least one metal selected from Fe, Co, Ni, V, Cu, Mn and Zn with respect to Ti Using an aqueous solution containing a total molar ratio of 0.01 to 10, preferably 0.1 to 2.5 forms a denser and more evenly distributed adhesive film with surface unevenness, and has better wet resin adhesion. It is preferable in obtaining.

  When a surface-treated steel sheet is continuously manufactured by forming an adhesive film by applying a cathodic electrolysis treatment in such an aqueous solution, the Ti content of the film gradually decreases with the lapse of processing time, leading to a decrease in wet resin adhesion. There is a case. The mechanism of adhesion film formation by cathodic electrolysis in aqueous solution described above is that the solubility of Ti oxide in the aqueous solution decreases as the interfacial pH increases due to hydrogen generation on the cathode side. The Ti oxide that can no longer be dissolved precipitates on the surface of the steel plate (cathode) and forms an adhesive film. Accordingly, in order to secure a stable adhesion amount (Ti amount) of the adhesive film, it is desirable that the pH variation of the aqueous solution itself is small.

  As a result of investigations to suppress the time-dependent change in the Ti amount of the adhesive film, as shown in FIG. 1, if the pH variation of the aqueous solution is 0.2 or less, the decrease in the Ti amount of the adhesive film is 20% or less. It was clarified that it can be suppressed and hardly causes a decrease in wet resin adhesion. In order to reduce the pH fluctuation to 0.2 or less in this way, it is effective to install an anion exchange membrane that does not allow cation permeation between the anode and the steel plate, and to perform cathodic electrolysis with the anode isolated. The surface-treated steel sheet having excellent wet resin adhesion can be stably produced without substantially reducing the Ti content of the adhesive film over at least 7 days. This pH fluctuation is caused by the fact that metal ions such as Fe, Co, Ni, V, Cu, Mn, and Zn are electrolytically oxidized on the anode side, and the number of ions with increased valence increases rapidly. This is thought to be due to changes in the coordination state of metal ions such as metal ions, fluoride ions, Fe, Co, Ni, V, Cu, Mn, and Zn.

The amount of Ti in the adhesive film is preferably 3 to 200 mg / m ² per side. This is because when the Ti content is 3 mg / m ² or more and 200 mg / m ² or less, the effect of improving wet resin adhesion is sufficiently obtained, and when it exceeds 200 mg / m ² , further improvement in wet resin adhesion cannot be expected, resulting in high costs. It is because it becomes. Here, the measurement of the Ti amount of the adhesive film can be performed by surface analysis using fluorescent X-rays.

  As the aqueous solution containing ions containing Ti, an aqueous solution containing fluorotitanate ions or an aqueous solution containing fluorotitanate ions and a fluorine salt is suitable. As the compound that gives fluorotitanate ions, fluorinated titanate, ammonium fluoride titanate, potassium fluoride titanate, and the like can be used. As the fluorine salt, sodium fluoride, potassium fluoride, silver fluoride, tin fluoride, or the like can be used. In particular, the method of subjecting the steel sheet to cathodic electrolysis in an aqueous solution containing potassium fluorinated titanate or an aqueous solution containing potassium fluorinated titanate and sodium fluoride efficiently forms a uniform adhesive film. Is possible and preferred.

  The compounds that give ions containing Fe, Co, Ni, V, Cu, Mn and Zn include iron sulfate, iron chloride, cobalt sulfate, cobalt chloride, nickel sulfate, copper sulfate, vanadium oxide sulfate, zinc sulfate, sulfuric acid. Manganese or the like can be used.

  Ti is 0.008 to 0.07 mol / L, preferably 0.02 to 0.05 mol / L, and the total amount of at least one metal selected from Co, Fe, Ni, V, Cu, Mn and Zn is Ti. On the other hand, in order to adjust the molar ratio to 0.01 to 10, preferably 0.1 to 2.5, the mass ratio of Ti and metal in the aqueous solution may be adjusted.

In the cathodic electrolysis treatment, the current density is preferably 5 to 20 A / dm ² .

2) Formation of corrosion-resistant film Corrosion-resistant film such as Ni layer, Sn layer, Fe-Ni alloy layer, Fe-Sn alloy layer, Fe-Ni-Sn alloy layer in advance on the steel sheet surface on which the adhesion film is formed by cathodic electrolysis treatment Since the corrosion-resistant film is firmly bonded to the base steel sheet, even if the resin is partially lost due to scratching or the like after being formed into a resin-coated steel sheet, excellent corrosion resistance can be imparted to the steel sheet. This corrosion-resistant film may be a single layer of Ni layer, Sn layer, Fe-Ni alloy layer, Fe-Sn alloy layer, Fe-Ni-Sn alloy layer, or a multilayer of these layers. Well, it can be formed by a known method according to the constituent metal element.

3) Production method of resin-coated steel plate (laminated steel plate) A resin-coated steel plate can be produced by coating a resin on the surface of the adhesive film of the surface-treated steel plate produced by the method for producing a surface-treated steel sheet of the present invention.

  There is no limitation in particular as resin coat | covered on the surface-treated steel plate manufactured by this invention, Various thermoplastic resins and thermosetting resins can be mentioned. For example, polyethylene, polypropylene, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer, ethylene-acrylic ester copolymer, olefin resin film such as ionomer, or polyester film such as polybutylene terephthalate, or nylon 6 It may be a non-stretched or biaxially stretched thermoplastic resin film such as a polyamide film such as nylon 6,6, nylon 11, or nylon 12, a polyvinyl chloride film, or a polyvinylidene chloride film. When using an adhesive during lamination, urethane adhesive, epoxy adhesive, acid-modified olefin resin adhesive, copolyamide adhesive, copolyester adhesive (thickness: 0.1 to 5.0 μm), etc. Is preferably used. Furthermore, a thermosetting paint may be applied to the surface-treated steel plate side or film side in a thickness range of 0.05 to 2 μm, and this may be used as an adhesive.

  Furthermore, modified epoxy paint such as phenol epoxy, amino-epoxy, vinyl chloride-vinyl acetate copolymer, saponified vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-maleic anhydride copolymer, epoxy-modified- , Epoxyamino-modified, Epoxyphenol-modified Vinyl paint or Modified vinyl paint, Acrylic paint, Synthetic rubber paint such as styrene-butadiene copolymer, etc., or a combination of two or more thermoplastic or thermosetting paints It may be.

  The thickness of the resin coating layer is desirably 3 to 50 μm, particularly 5 to 40 μm. This is because if the thickness is below the above range, the corrosion resistance becomes insufficient, and if the thickness exceeds the above range, problems are likely to occur in terms of workability.

  The resin can be coated by any means. For example, it can be performed by an extrusion coating method, a cast film thermal bonding method, a biaxially stretched film thermal bonding method, or the like. In the case of the extrusion coating method, it can be produced by extrusion coating a resin on a surface-treated steel sheet in a molten state and thermally bonding the resin. That is, after melt-kneading the resin with an extruder, the resin is extruded from a T-die into a thin film, and the extruded molten resin film is pressed and integrated with a surface-treated steel sheet between a pair of laminate rolls, and then rapidly cooled. To do. When extrusion coating a multi-layer resin coating layer, use multiple extruders for each layer, merge the resin streams from each extruder in a multi-layer die, and then extrude as in the case of a single layer resin. Just coat it. Further, by passing a surface-treated steel sheet vertically between a pair of laminate rolls and supplying a molten resin web on both sides thereof, both surfaces of the surface-treated steel sheet can be coated with resin.

  Such a resin-coated steel sheet can be applied to three-piece cans and seamless cans (two-piece cans) having side seams. The present invention can also be applied to a stay-on-tab type easy open can lid and a full open type easy open can lid.

Using plating baths a and b shown in Table 1 on both sides of cold-rolled cold-rolled steel sheets (thickness 0.2 mm) as cold-rolled steel used for the production of tin-free steel sheets (TFS), A metal layer is formed by the methods A to D.
A: After annealing the cold-rolled steel sheet at about 700 ° C and performing temper rolling with an elongation of 1.5%, alkaline electrolytic degreasing and sulfuric acid pickling were performed, and then Ni plating treatment was performed using the plating bath a. Form a corrosion-resistant film consisting of the applied Ni layer.
B: Cold-rolled steel sheet is alkaline electrolytically degreased and Ni-plated using plating bath a, then annealed at about 700 ° C in a 10 vol% H ₂ +90 vol% N ₂ atmosphere, and then Ni-plated After diffusing and infiltrating, temper rolling with an elongation of 1.5% is performed to form a corrosion-resistant film composed of an Fe—Ni alloy layer.
C: Alkaline electrolytic degreasing of cold-rolled steel sheet, Ni plating using plating bath a, and then annealing at 700 ° C in 10 vol% H ₂ +90 vol% N ₂ atmosphere After diffusing and penetrating and temper rolling with an elongation of 1.5%, degreasing, pickling, Sn plating using the plating bath b, and heating and melting treatment for heating and holding above the melting point of tin are performed. By this treatment, a corrosion-resistant film composed of an Fe—Ni—Sn alloy layer and an upper Sn layer is formed.
D: Alkaline electrolytic degreasing of the cold-rolled steel sheet, annealing and temper rolling in the same manner as in Condition A, and then Sn plating using the plating bath b, followed by a heat-melting process that heats and maintains the melting point of tin or higher . By this treatment, a corrosion-resistant film composed of the Fe—Sn alloy layer and the upper Sn layer is formed.

  In the treatment of C and D, a part of Sn plating is alloyed by heat melting treatment. The amount of pure Sn remaining without alloying is shown in Table 3 together with the amount of Ni and the amount of Sn in the corrosion-resistant film.

  On the corrosion-resistant film formed on both surfaces of the steel sheet, it was subjected to cathodic electrolysis under the conditions of cathodic electrolysis shown in Tables 2 and 3, and dried to form an adhesive film. Make 1-18. In the surface-treated steel plates No. 1 and 12, the adhesive film does not contain Co, Fe, Ni, V, Cu, Mn, and Zn. In the surface-treated steel plate No. 18, a corrosion-resistant film is not formed. In the surface-treated steel plates Nos. 5, 8, 14, and 17, the cathode electrolytic treatment was performed without installing an anion exchange membrane. As an anion exchange membrane, Neotomta series C1 ion type AMX manufactured by Astom Co., Ltd. is used.

  The Ti amount of the adhesive film is obtained by fluorescent X-ray analysis in comparison with a calibration plate obtained by chemical analysis of the adhesion amount in advance. In addition, for the amount of Fe, Co, Ni, V, Cu, Mn, and Zn deposited, select the appropriate measurement method from the same fluorescent X-ray analysis method as Ti, chemical analysis, Auger electron spectroscopy, and secondary ion mass spectrometry. Thus, the mass ratio of Co, Fe, Ni, V, Cu, Mn and Zn to Ti contained in the adhesive film is evaluated.

  In addition, we will investigate the stability of the production by determining the pH fluctuation and the Ti content reduction rate of the adhesive film when cathodic electrolytic treatment is continued for 7 days.

Next, on both surfaces of these surface-treated steel sheets No. 1 to 18, using an isophthalic acid copolymer polyethylene terephthalate film having a draw ratio of 3.1 × 3.1, a thickness of 25 μm, a copolymerization ratio of 12 mol%, and a melting point of 224 ° C. Laminating conditions such that the biaxial orientation degree (BO value) of the steel sheet is 150, that is, the steel sheet feed speed: 40 m / min, the rubber roll nip length: 17 mm, and the time from pressure bonding to water cooling: 1 sec. Is made. Here, the nip length is the length in the transport direction of the portion where the rubber roll and the steel plate are in contact. And about the produced laminated steel plate, the following wet resin adhesiveness and corrosion resistance are evaluated.
Wet resin adhesion: After maintaining in a retort atmosphere at a temperature of 130 ° C. and a relative humidity of 100% for 25 minutes, wet resin adhesion is evaluated by a 180 ° peel test in this atmosphere. The 180 ° peel test is a test piece (size: 30 mm x 100 mm, with both sides of the front and back sides set to n = 1, leaving a film 2 as shown in Fig. 2 (a) and cutting out part 3 of the steel plate 1. 2 for each laminated steel sheet), and as shown in Fig. 2 (b), attach a weight 4 (100g) to one end of the test piece and turn it 180 ° to the film 2 side and leave it for 30 min. This is a film peeling test. Then, the peel length 5 shown in (c) of FIG. 2 is measured and evaluated, and the average of the peel lengths (n = 2) on the front and back surfaces of each laminated steel sheet is obtained. It can be said that the smaller the peeling length 5 is, the better the wet resin adhesion is. However, if the peeling length 5 is less than 10 mm, it is evaluated that the excellent wet resin adhesion intended by the present invention is obtained.
Corrosion resistance: Cut the laminate surface of the laminated steel plate to reach the steel plate substrate using a cutter knife, and immerse it in 80 ml of a test solution in which 1.5% by mass NaCl aqueous solution and 1.5% by mass citric acid aqueous solution are mixed in equal amounts, 55 ° C And left for 9 days to evaluate the corrosion resistance of the cut part (where both the front and back surfaces are n = 1 and n = 2 for each laminated steel sheet) as follows. And
○: No corrosion at n = 2 ×: Corrosion at 1 or more of n = 2 Table 4 shows the results. The surface-treated steel sheets No. 2 to 4, 6, 7, 9 to 11, 13, 15, and 16 that are examples of the present invention have a pH variation of 0.2 when cathodic electrolysis is performed in an aqueous solution having the composition of the present invention. Because of the following, the rate of decrease in the Ti amount of the adhesive film is small, the production stability is excellent, and the wet resin adhesion and corrosion resistance are also excellent. In contrast, the surface-treated steel sheets No. 5, 8, 14, and 15, which are comparative examples, have a large Ti content reduction rate because the pH fluctuation during cathodic electrolysis exceeds 0.2, and the production stability It is inferior to. Further, the surface-treated steel sheets No. 1 and 12 as comparative examples are inferior in wet resin adhesion because the composition of the aqueous solution at the time of cathodic electrolysis is outside the present invention. The surface-treated steel sheet No. 18, which is an example of the present invention, has no problem in manufacturing stability and wet resin adhesion, but is inferior in corrosion resistance because there is no corrosion-resistant film. In addition, the control of the pH fluctuation by the anion exchange membrane in the present invention is particularly effective when the aqueous solution contains Fe.

1 Steel plate
2 film
3 Parts cut from steel plate
4 weights
5 Peel length

Claims (4)

  In an aqueous solution containing ions containing Ti and ions containing at least one metal selected from Fe, Co, Ni, V, Cu, Mn and Zn on at least one side of the steel plate, the anode and the steel plate A method for producing a surface-treated steel sheet, wherein an anion exchange membrane is installed between the two and a steel sheet is subjected to cathodic electrolytic treatment to form an adhesive film.   In an aqueous solution containing Ti of 0.008 to 0.07 mol / L and containing at least one metal selected from Fe, Co, Ni, V, Cu, Mn and Zn in a total molar ratio of 0.01 to 10 with respect to Ti 2. The method for producing a surface-treated steel sheet according to claim 1, wherein a cathodic electrolysis treatment is performed.   Before forming the adhesive film by performing cathodic electrolysis, the Ni layer, Sn layer, Fe-Ni alloy layer, Fe-Sn alloy layer and Fe-Ni-Sn alloy are formed on the steel sheet surface on which the adhesive film is formed. 3. The method for producing a surface-treated steel sheet according to claim 1, wherein at least one type of corrosion-resistant film selected from the layers is formed.   4. A method for producing a resin-coated steel sheet, comprising coating a resin on the surface of an adhesive film of the surface-treated steel sheet produced by the method for producing a surface-treated steel sheet according to claim 1.

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