JPS6335796A - Production of electrolytically chromated steel sheet for adhered can - Google Patents

Abstract

PURPOSE:To produce the titled steel sheet having superior adhesive properties in a wet stmosphere at high temp. by cathodically electrolyzing a steel sheet in an electrolytic chromating bath contg. a fluorine compound and a compound having a sulfuric acid radical as auxiliary components and a specified amount of iron as an inevitable impurity and by washing the steel sheet at a specified pH. CONSTITUTION:The amount of iron as an inevitable impurity in an electrolytic chromating bath contg. a fluorine compound such as NH4F and a compound having a sulfuric acid radical such as H2SO4 as auxiliary components is restricted to <=1,000ppm. A steel sheet is cathodically electrolyzed in the bath and washed at 7-9 pH. Thus, electrolytically chromated steel sheets of stable quality are continuously produced in large quantities. The steel sheets endure disinfection at high temp. and are suitable for use as stock for adhered cans.

Description

DETAILED DESCRIPTION OF THE INVENTION Industrial Field of Application No. 191 relates to a method for manufacturing an electrolytic chromic acid treated steel sheet for adhesive cans which exhibits excellent adhesive properties in a high temperature and humid atmosphere.

Conventional technology A multi-layer chromium treated steel sheet with metal chromium in the layer and hydrated chromium oxide in the upper layer is tin-free steel (T, F,
Since '19, it has been used with JiiR cangawa wood, and is used in cans of beer, carbonated beer, etc. started.

However, in recent years, TFS beverage cans are heat-sterilized at a temperature of about 80°C, and the contents can be immediately removed. A hot pack method is used to fill the FT, and then sterilizes the FT after filling with pressurized steam at a temperature exceeding 100"C, and sterilizes the FT.
There is a concern that water will enter the interface between the FS and the coating, lowering the paint density, causing the paint film to peel off, and causing damage from the can 1 → contact area, resulting in crystallization and 19 failures. There is.

Since this first warning, improvements have been made to the hydrated chromium oxide of TFS. For example, there is Japanese Patent Application Laid-Open No. 56-25998.

The technology described in this publication is to inactivate the steel plate surface by cathodic treatment in an alkali metal or ammonium solution immediately before electrolytic chromic acid treatment, followed by anodic treatment. The purpose of this method is to minimize the influence of the crystal orientation of precipitated oxides, and to form a uniform TFS film with excellent aqueous properties and one-time retortability even under heat sterilization conditions. This method may be effective for short-term production.

Problems to be Solved by the Invention However, according to experiments conducted by the present inventors, in an electrolytic chromic acid treatment bath that is continuously operated for a long time, "the effect of the steel sheet deactivation treatment immediately before the electrolytic chromic acid wood treatment is lost; We have found one example in which the adhesiveness is weakened.

Therefore, the present inventors investigated the reason for this and found that the deterioration of the adhesion of TFS treated in a multilayer chromic acid bath after a period of 1 2000-300 in chromic acid treatment bath
It was found that this was caused by iG, which accumulates at a high concentration of 0 ppm.

The F-stage ungenerated IgI was constructed based on these findings to solve the problem, and it contains fluorine compounds and sulfuric acid (compound auxiliaries). 100 iron ions
0 pp or less, cathodize the steel plate, and then p)1
With 1i, which is characterized by washing with water from 7 to 9! This is a method for manufacturing electrolytic crotic acid treated steel sheets for 1.

action The present invention will now be described in detail.

Cold-rolled steel sheets made of TFS material are manufactured through normal cold-rolled steel sheet manufacturing processes, and are manufactured through normal pretreatment processes such as electrolytic degreasing, pickling, and water washing. Further, inactivation treatment as described above may be performed. The steel sheet thus produced is subjected to cathodic electrolysis treatment in an electrolytic chromic acid treatment bath.

1 [The dechromic acid treatment bath may have a normal concentration of chromic acid (50 to 100 g/i) or may have a concentration other than this, and may contain a fluorine compound, an acid, (an auxiliary agent for the compound), etc. contains.

Fluorine compounds improve the quality of chromium hydrated chromium oxide,
The purpose is to withstand heat sterilization treatment, and sulfuric acid), (
The compound is included in order to obtain an excellent metallurgical J1 precipitation efficiency, and the fluorine compound is NH4F.
, tIF system (7) AF type, or Na2SiF6, H
Using 7S i F6-based MAF, type, or a combination of these, sulfuric acid (compounds include H7SO4, Na2S
04 etc.) M, SO2 type is used.

The concentration of the auxiliary agent shall be appropriately determined based on the precipitation efficiency of metallic chromium and the precipitation j11 of hydrated chromium butyride. In this case, if only a fluorine compound is contained, the metal chromium precipitation efficiency is sufficient, but the adhesion of hydrated chromium oxide becomes insufficient, and if only a sulfuric acid compound is contained, the adhesion is insufficient. Become.

Electrolytic treatment is carried out in a multilayer chromic acid bath as described in -1-, using a steel plate as a cathode. The present invention reduces iron ions eluted from steel sheets to 11,000pp in such electrolytic treatment.
It is necessary to suppress it to below -. Iron ions increase during continuous plating operations and are impurities (magnetic impurities) that interfere with the long-term stable production of TFS with excellent adhesive properties.

Due to the increase in iron ion concentration, the precipitation effect of metallic chromium - (4
The uniform precipitation of metallic chromium is hindered. As a result, a non-uniform layer (uneven thickness) of hydrated chromium oxide is generated, resulting in an extremely thin hydrated chromium oxide layer, resulting in a low contact n force.

Figure 1 shows the results of one test of contact (high temperature 111 in the + part), which shows that the iron ion concentration was 11000p.
It is clear that the adhesive strength is stable at 11I and below. Iron ions, which are unavoidable impurities, can be easily removed using, for example, a commercially available ion exchange resin.

The TFS thus obtained is further washed with water at pH 7-9. The water washing treatment is so, '-1 in hydrated chromium oxide.
If the pH is less than 7, the anion removal effect will not be as long as 1 minute, and if the pH is higher than 10, the hydrated chromium oxide will dissolve and the necessary adhesive strength will not be obtained. 11 is required to be carried out at pH 7-9.

Electrolytic chromic acid-treated steel sheets manufactured under the following treatment conditions can withstand high-temperature sterilization. As a material of the fi river,
This is something that can guarantee stable quality on Mars.

Example Next, examples of the present invention will be described.

After two stages of normal cold-rolled steel sheet production! A-built steel plate,
Electrolytic chromic acid treatment was carried out under conditions similar to those in the Examples and Comparative Examples described below.

Example 1 (1) Electrolytic chromic acid treatment bath concentration Fe: 500 ppm Cry: 80 g/9j H2SO4: 100 pp Layer N1 (4F: Ig/u) (2) Electrolytic conditions Cathode electrolysis: 60 A/dm2X l sec temperature: 40
(3) Post-treatment (Water Washing Conditions) Immersion at pH 7, 5, and 90° C. for 3 sec Example 2 The same procedure as in Example 1 was performed except that Fe was changed to 11000 pp.

Example 3 The same procedure as in Example 1 was conducted except that Fe: 200 ppm.

Comparative Example 1 The same procedure as in Example 1 was conducted except that Fe: 1 LOOppm was used.

Comparative Example 2 The same procedure as in Example 1 was conducted except that Fe: 1500 ppm was used in Example 1.

The adhesive strength was evaluated by applying epoxy-phenol paint to the sample, baking it, and then hot-pressing a 5-mall test piece with nylon adhesive in a 0.4% citric acid solution for 11 hours.
The adhesive strength was measured by heat sterilization at 0° C. for 18 hours and a T-peel test at 90° bending.

As shown in FIG. 1, the results showed good adhesion when the Fe ion concentration in the electrolytic chromic acid treatment bath was 100 OPP■ or less.

Effects of the Invention According to the present invention, a semi-decomposed chromic acid treated steel sheet which can withstand high temperature sterilization treatment and is suitable as a material for adhesive cans can be continuously obtained in large quantities and with stable quality.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the relationship between the concentration of each Fe ion contained in the electrolytic chromic acid treatment bath and the adhesive strength after high temperature sterilization treatment.

Claims (1)

[Claims] The unavoidable impurity iron ions in the electrolytic chromic acid treatment bath containing auxiliary agents consisting of fluorine compounds and sulfuric acid compounds are reduced by 100%.
The steel plate is subjected to cathodic electrolytic treatment with p
A method for manufacturing an electrolytic chromic acid treated steel sheet for adhesive cans, which comprises performing a water washing treatment in H7-9.