JP2001316851A - Tin plating steel sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface treated steel sheet for cans usable for DI can, food can, beverage can and the like, particularly, a tin plated steel sheet excellent in workability, coating adhesion, yellowing resistance and rust prevention. SOLUTION: This surface treated sheet is characterized by having a chemical conversion coating containing P and Sn on the upper layer of tin plated layer formed on the surface of a steel sheet, in which P content in the above chemical conversion coating is 0.5-100 mg/m2 as the coating weight of P, and Sn content in the above coating is in the range of 0.01-60 as the ratio of its coating weight to P, and moreover, having a silane coupling layer on the upper layer of the above chemical conversion coating, in which the coating weight of the above silane coupling layer is in the range of 0.1-250 mg/m2 as the coating weight of Si.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface-treated steel sheet for cans used in DI cans, food cans, beverage cans, and the like, and in particular, has excellent workability, paint adhesion, yellowing resistance and rust resistance. It relates to a tin-plated steel sheet.

[0002]

2. Description of the Related Art Tin-plated steel sheets, called tinplates, have been widely used as surface-treated steel sheets for cans. Such tin-plated steel sheets are usually prepared by applying tin plating to a tinplate base sheet, Chemical conversion treatment is generally performed by immersion in chromic acid solution or electrolysis in this solution, and the chromium oxide film formed on the tin plating layer by this chemical conversion treatment prevents the growth of Sn oxide. At the same time, the tin-plated steel sheet surface turns yellow due to the Sn oxide film,
It has an effect of suppressing so-called yellowing (yellowing resistance) and improving adhesion to paint and rust resistance.

[0003] However, due to recent environmental problems, movements to regulate chromium are progressing in various fields, and the demand for chromium-free surface-treated steel sheets for cans is increasing day by day.

[0004] As a technique relating to chromium-free surface-treated steel sheet for cans, for example, Japanese Patent Publication No. 55-24516 discloses a technique.
A surface treatment method of a tin-plated steel sheet in which a conversion coating containing no Cr is formed on the tin-plated steel sheet by direct current electrolysis using a tin-plated steel sheet as a cathode in a phosphoric acid-based solution is disclosed. Japanese Patent No. 32308 discloses an electroplating tin for a seamless can in which P or P and Al are contained in a chemical conversion film, and a chemical conversion film containing no Cr is applied to the surface of the tin plating layer.

However, when the performances such as paint adhesion, yellowing resistance, and rust resistance are comprehensively viewed, all of the chemical conversion films described in the above-mentioned publications are formed by a conventional chemical conversion using a dichromic acid solution. It cannot be said that the above performance is sufficiently obtained as compared with the film.

[0006] In addition to the above-mentioned chromium-free requirements, there is a demand for a surface-treated steel sheet for cans, as well as cost reduction as a material for cans. Particularly in tin-plated steel sheets, since tin is an expensive metal, reduction in the amount of tin plating has been promoted.

[0007] However, tin is a metal having a very high lubricity, and reducing the amount of tin plating leads to deterioration of workability. Therefore, there is naturally a limit in reducing the amount of tin plating.

Further, in the case of a conventional tin-plated steel sheet in which a chromium oxide film is formed on a tin-plated layer, the chromium oxide film is advantageous in terms of corrosion resistance but is hard. If the amount of tin plating is reduced,
This was not always an optimal coating because "galling" was apt to occur in the can making process, and workability was deteriorated.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to provide a chemical conversion film formed on an upper layer of a tin plating layer, which has a function of improving the film characteristics, but is not desirable due to environmental problems. Processability without containing
An object of the present invention is to provide a tin-plated steel sheet having excellent paint adhesion, yellowing resistance and rust resistance at low cost.

[0010]

The present invention will be described below in more detail. When a chemical conversion film containing no Cr is formed on the tin plating layer using the above conventional technology, it is difficult to satisfy all of the workability, paint adhesion, yellowing resistance and rust resistance. Met.

[0011] Therefore, the present inventors have conducted intensive studies to solve the above-mentioned problems in the tin-plated steel sheet, and as a result, formed a chemical conversion film containing two elements of P and Sn on the Sn plating layer. After that, it was found that when the silane treatment with a silane coupling agent was further performed on the upper layer, all of the above performances could be satisfied.

More specifically, by forming a chemical conversion film containing an appropriate amount of P and Sn on the tin plating layer, lubricity is improved, and accordingly, workability is improved. Further, by forming a silane coupling layer further on the chemical conversion film, the reactive groups present in the silane coupling layer are oriented and greatly contribute to the adhesion to the paint on the inner surface of the can. In addition to the chemical conversion film of Sn and Sn acting as an anchor effect for paint adhesion, the silane coupling layer improves compatibility and reactivity with paint, so that these synergistic effects provide excellent paint adhesion. It turned out to show. In addition, they have also found that yellowing resistance and rust resistance are improved by the barrier effect of both the chemical conversion film and the silane coupling layer.

[0013] The tin-plated steel sheet of the present invention has a chemical conversion film containing P and Sn as an upper layer of a tin plating layer formed on the surface of the steel sheet. in the range of 0.5 to 100 mg / m ² Te, the Sn content in the range of 0.01 to 60 in the ratio of P adhering amount of the deposition amount, further, an upper layer of the conversion coating has a silane coupling layer The deposition amount of the silane coupling layer is in the range of 0.1 to 250 mg / m ² in terms of Si deposition amount.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration of the present invention will be described below in detail. The tin-plated steel sheet of the present invention is obtained by applying a Sn plating layer on a normal tinplate and performing a general treatment (reflow treatment) for heating and melting Sn, and the Sn plating layer is more strict. Consists of an Fe-Sn alloy layer and a metal Sn layer. In the present invention, the amount of plating of the Sn plating layer is preferably 0.4 to 3.5 g / m ² per one surface. If the adhesion amount is less than 0.4 g / m ² , the rust resistance is poor, and 3.5 g / m ²
If it exceeds, the cost reduction effect cannot be sufficiently obtained.

The main features of the configuration of the present invention are as follows.
An upper layer of the tin plating layer formed on the surface of the steel sheet has a chemical conversion film containing P and Sn, and the P content in the chemical conversion film is
The deposited amount is in the range of 0.5 to 100 mg / m ² , the Sn content is in the range of 0.01 to 60 in terms of the ratio of the deposited amount to the P deposited amount, and the upper layer of the chemical conversion film is further provided with silane coupling. A silane coupling layer, and the amount of the silane coupling layer to be deposited is in the range of 0.1 to 250 mg / m ² in terms of the amount of Si deposited.

(1) The P content in the chemical conversion film should be in the range of 0.5 to 100 mg / m ² in terms of its adhesion amount. The P content in the chemical conversion film should be 0.5 to 100 mg in terms of its adhesion amount.
/ m ² . If it is less than 0.5mg / m ^2,
This is because processability, paint adhesion and yellowing resistance cannot be sufficiently obtained, and if it exceeds 100 mg / m ² , defects tend to occur in the chemical conversion film, and paint adhesion and workability deteriorate. Note that P
The adhesion amount was measured by surface analysis using fluorescent X-rays.

The chemical conversion film containing P is preferably formed, for example, by a phosphoric acid-based chemical conversion treatment. In this case, the source of P in the chemical conversion treatment solution is not only phosphoric acid but also phosphoric acid. It is more preferable to use metal salts such as sodium phosphate, aluminum phosphate and potassium phosphate, or monohydrogen phosphate.

(2) The Sn content in the chemical conversion coating should be in the range of 0.01 to 60 in terms of the ratio of the coating amount to the P coating amount. The Sn content in the chemical conversion coating should be the most stable tin phosphate coating. In order to form, the ratio of Sn adhesion amount to P adhesion amount is 0.01
It is necessary to be in the range of ~ 60. In particular, within this proper range, it is possible to impart lubricity to the chemical conversion film itself,
Workability can be improved. Incidentally, if the ratio is less than 0.01, unreacted phosphoric acid remains in the chemical conversion film, thereby deteriorating paint adhesion and yellowing resistance.
If it exceeds 60, defects are likely to occur in the chemical conversion film, and rust resistance and paint adhesion deteriorate. In addition, the Sn adhesion amount can be measured by a coulometric method or surface analysis by fluorescent X-ray.

As a method for forming a chemical conversion film containing Sn, for example, tin phosphate, tin (II) chloride, tin (II) chloride, tin (II) chloride, tin (II) chloride and tin (II) chloride having tin ions are added to the above-mentioned phosphoric acid-based chemical conversion treatment solution. It is preferable to form insoluble and most stable tin phosphate on the tin plating layer.

(3) A silane coupling layer is provided on the chemical conversion film, and the amount of the silane coupling layer deposited is
In the present invention, it is important to form a silane coupling layer with an appropriate amount of adhesion on the above-mentioned chemical conversion film in terms of the amount of Si to be in the range of 0.1 to 250 mg / m ² . The silane coupling layer can be formed by, for example, a silane treatment using a silane coupling agent. The general chemical formula of the silane coupling agent is X-
Si-OR _2or3 (OR: alkoxy group).

The silane coupling agent hydrolyzes an alkoxysilyl group (Si-OR) with water to form a silanol group, and adheres to the steel sheet surface by a dehydration condensation reaction with -OH. In the upper layer of the steel sheet, a reactive group corresponding to X in the general chemical formula is oriented and is compatible with or bonded to a resin such as paint.

As the silane coupling agent, γ-
Methacryloxypropyltrimethoxysilane, β-
(3,4-epoxycyclohexyl) ethyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, N-2- (aminoethyl) 3-aminopropyltrimethoxysilane, N-2 (aminoethyl) 3- Aminopropylmethyldimethoxysilane, γ-aminopropyltriethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, γ-mercaptopropylmethoxysilane, γ-chloropropyltrimethoxysilane, vinyltriethoxysilane, vinyltris (2- _{Methoxyethoxy} ) silane and the like can be used. In particular, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane in which an epoxy group is present at X of X—Si—OR _2or3 in the general chemical formula of the silane coupling agent, and γ-glycidoxypropyltrimethoxysi Orchid, amino group, N
-2 (aminoethyl) 3-aminopropyltrimethoxysilane, N-2- (aminoethyl) 3-aminopropylmethyldimethoxysilane, and γ-aminopropyltriethoxysilane are preferred. This is because of excellent compatibility and reactivity with the epoxy paint used for the inner surface of the can.

To further explain the above-mentioned improvement in adhesion, it is more preferable to form a silane coupling layer after forming a P and Sn-containing chemical conversion film than to form a silane coupling layer directly on a Sn plating layer. Forming on a Sn plating layer has a greater effect of improving paint adhesion. That is, it is considered that the adhesion of the paint is improved by the synergistic effect of the anchor effect of the chemical conversion film containing P and Sn and the excellent compatibility and reactivity with the coating film of the silane coupling layer.

In the present invention, the adhesion amount of the silane coupling layer is defined as a range in which the effect of improving the adhesion is remarkably exhibited.
The Si adhesion amount is in the range of 0.1 to 250 mg / m ² . 0.1mg /
If it is less than m ^2, is because coverage reduced adhesion improving effect of the silane coupling layer is not sufficiently obtained,
If it exceeds 250 mg / m ² , the unreacted silane coupling agent is self-condensed, and the effect of improving the adhesion is reduced.

The silane coupling agent treatment can be performed by applying a solution obtained by diluting the silane coupling agent in water, but if repelling occurs,
Solutions diluted with alcohol can be used. For example, it can be uniformly applied to a steel plate with a solution containing 50% by mass or more of ethanol, 0.5 to 20% by mass of a silane coupling agent, and the remaining water.

The temperature of the silane coupling agent treatment is from 50 to
The range of 130 ° C is preferable, and below 50 ° C, the -O
This is because a dehydration-condensation reaction between H and the alkoxy group of the silane coupling agent does not occur, and there is a possibility that a sound silane coupling layer is not formed. This does not occur, but the discoloration of the Sn plating is likely to occur.

As described above, according to the present invention, a chemical conversion film containing P and Sn in the above-described appropriate range and a silane coupling layer having an appropriate adhesion amount are sequentially formed on the tin plating layer formed on the surface of the steel sheet. By doing so, they succeeded in satisfying all the performances of workability, paint adhesion, yellowing resistance and rust resistance.

Next, an example of a specific manufacturing method according to the present invention will be described. After Sn plating is applied to a normal tinplate, heat melting (reflow) treatment is performed at a temperature equal to or higher than the melting point of tin (231.9 ° C.). Subsequently, after a cathodic treatment of 1 C / dm ^{2 in} a 15 g / l aqueous solution of sodium carbonate, a chemical conversion treatment is performed by a known method such as immersion, electrolysis, spraying, or roll coating.

As the chemical conversion treatment liquid, a metal salt such as phosphoric acid, sodium phosphate, aluminum phosphate, potassium phosphate or the like, and / or monohydrogen phosphate at 1 to 80 g / l in terms of phosphate ion is used. , With stannous chloride 0.001 to 10 g / l stannous chloride, stannic chloride, and / or stannous sulfate,
Use a solution dissolved in water. At this time, an oxidizing agent such as sodium chlorate may be appropriately added as a promoter.

The conditions of the chemical conversion treatment are preferably such that the temperature is 40 to 60 ° C. and the treatment (immersion) time is 1 to 5 seconds. The tin-plated steel sheet after the chemical conversion treatment is dried with warm air at 35 to 120 ° C.

The silane coupling agent treatment for forming the silane coupling layer may be performed, for example, by adding ethanol to 50 mA.
More than ss%, the silane coupling agent is 0.5 to 20 mass%, and the remainder is water, and can be uniformly applied to the steel plate. Drying is performed so that the steel sheet surface temperature reaches 50 to 130 ° C.

The above description is merely an example of the embodiment of the present invention, and various changes can be made within the scope of the claims.

[0033]

Next, embodiments of the present invention will be described in detail below.
Will be described.・ Examples 1 to 21 On a T4 original plate having a thickness of 0.3 mm, 0.4 to 2.8 g / m per side^TwoAdhesion amount
After applying a tin plating layer, perform reflow treatment and continue
1 C / dm in 15 g / l aqueous sodium carbonate solution ^TwoCondition
After performing the cathode treatment in
After the film was formed, the film was further formed under the forming conditions shown in Table 1.
A run coupling layer was formed. The chemical formed at this time
Table 2 shows the composition of the coating and the silane coupling layer.
Show.

Comparative Examples 1 to 9 For comparison, tin-plated steel sheets in which at least one of the conditions for the chemical conversion coating and the conditions for forming the silane coupling layer were out of the proper range of the present invention were also manufactured.

[0035]

【table 1】

[0036]

[Table 2]

(Evaluation of Performance) Examples 1 to 21 and Comparative Examples 1 to
The performance of each tin-plated steel sheet No. 9 was evaluated for workability, paint adhesion, yellowing resistance and rust resistance.

(1) Workability The workability was evaluated by observing the appearance after drawing and ironing, and by the presence or absence of defects such as wrinkles and galling. Table 2 shows the evaluation results. In Table 2, the case where no defect such as wrinkles or galling is observed is indicated by “○”, and the case where the defect is observed is indicated by “×”. Drawing and ironing were performed under the following conditions.

Blank diameter: 170 mmφ Drawing conditions: 1-step drawing ratio 1.8, 2-step drawing ratio 1.3 Drawing ironing diameter: 3-step ironing 60 mmφ

(2) Paint Adhesion The paint adhesion was evaluated by the following test method. After applying an epoxyphenol-based paint having an adhesion amount of 50 mg / dm ² to the surface of each of the tin-plated steel sheets, baking was performed at 210 ° C. for 10 minutes. Next, after laminating the two coated and baked tin-plated steel sheets so that the coated surfaces face each other with the nylon adhesive film interposed therebetween, the pressure is 2.94 × 10 ⁵ Pa, the temperature is 190 ° C., and the pressing time is 30 minutes. After bonding, the test piece was divided into test pieces having a width of 5 mm, and the test pieces were subjected to strength measurement using a tensile tester.
Next, the paint adhesion was evaluated. Another test piece is
Immersed in 1.5 mass% NaCl + 1.5 mass% citric acid solution for 7 days,
Thereafter, the secondary paint adhesion was evaluated from the results of the strength measurement similarly performed using a tensile tester. Table 2 shows the evaluation results.
Shown in In Table 2, "◎" indicates that the measured strength per 5 mm width of the test piece was 68.6 [N] or more, and 49.0 [N] or more
"○" when the value is less than 8.6 [N], 49.0 [N] or more 49.0
The case of less than [N] is indicated by "△" and the case of less than 29.4 [N] is indicated by "x".

(3) Yellowing resistance Each of the above tin-plated steel sheets is left in a constant temperature and constant temperature bath at a temperature of 40 ° C. and a relative humidity of 85% for 60 days, and thereafter, the discoloration of the surface is observed to evaluate the yellowing resistance. did. Table 2 shows the evaluation results.
In Table 2, the case where no discoloration is observed is indicated by “○”, and the case where discoloration is observed is indicated by “×”.

(4) Rust resistance Each of the tin-plated steel sheets was subjected to a high humidity state at a temperature of 50 ° C. and a relative humidity of 98% and a dry state at a temperature of 25 ° C. and a relative humidity of 60%.
It was exposed to an environment that alternated every minute, and the number of days until rust was generated on the surface was examined, thereby evaluating rust resistance. Table 2 shows the evaluation results. In Table 2, “○” indicates that no rust was observed for 30 days or more,
"△", if it is recognized for 15 days or more and less than 30 days,
The case where the generation of rust was observed for less than 15 days is indicated by "x".

As is clear from the results in Table 2, Examples 1 to
All of No. 21 were excellent in all of workability, paint adhesion, yellowing resistance and rust resistance. On the other hand, Comparative Examples 1 to 9 in which at least one of the chemical conversion film condition and the silane coupling layer formation condition is out of the proper range of the present invention are those of any of workability, paint adhesion, yellowing resistance and rust resistance. It turns out that the performance is poor and not at a practical level.

[0044]

According to the present invention, there is provided a chemical conversion film and a silane coupling layer formed on an upper layer of a tin plating layer, which contain Cr, which has an effect of improving the film characteristics, but is not desirable due to environmental problems. Without being contained, a remarkable effect that a tin-plated steel sheet excellent in workability, paint adhesion, yellowing resistance and rust resistance can be provided. In addition, the tin-plated steel sheet of the present invention has a chemical conversion film that can maintain excellent workability as an upper layer of the tin-plated layer even when the amount of the tin-plated layer is reduced as compared with the conventional tin-plated steel sheet. Also, there is an effect that cost can be reduced.

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Kazuo Mochizuki 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba F-term in Technical Research Institute, Kawasaki Steel Co., Ltd. 4K026 AA02 AA10 AA11 BA03 BB06 BB08 BB09 CA16 CA18 CA23 CA24 CA26 DA02 DA03 DA06 DA13 EB07 4K044 AA02 BA10 BA17 BA21 BB04 BC02 BC04 BC05 CA11 CA16 CA18 CA53

Claims (1)

[Claims] 1. A chemical conversion film containing P and Sn is provided on a tin plating layer formed on the surface of a steel sheet, and the P content in the chemical conversion film is 0.5 to 100 mg / m2 in terms of the adhesion amount. ² , the Sn content is in the range of 0.01 to 60 in terms of the ratio of the amount of P deposited to the amount of P deposited, and further, a silane coupling layer is provided on the chemical conversion film, and the silane coupling layer A tin-coated steel sheet, wherein the amount of Si is in the range of 0.1 to 250 mg / m ² in terms of Si amount.