JP3177041B2 - High lubrication chromate treatment solution for plated steel sheets - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0101]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a coating type chromate treatment solution containing a water-dispersible organic resin.

[0092]

2. Description of the Related Art Conventionally, a chromate treatment has been widely used as a temporary rust preventive treatment or a coating base treatment for a hot-dip zinc or zinc-based alloy-plated steel sheet, a hot-dip aluminum or aluminum-based alloy-plated steel sheet, or the like. For the chromate treatment, a reaction type in which a steel sheet is immersed in a chromate treatment solution or spray-treated and then washed with water, or an electrolytic type in which the steel sheet is electrolytically treated in the chromate treatment solution and then washed with water. There is a coating type in which a coating solution and a treatment liquid are applied and dried without washing with water. However, in recent years, a coating type type has become mainstream because an external appearance skin having high corrosion resistance and gloss is required. .

A typical example of the coating type chromate treatment having high corrosion resistance is a treatment solution in which an inorganic colloid or inorganic powder such as silica sol or alumina sol is contained in a chromate film mainly composed of trivalent chromium. The treatment method has remarkably excellent corrosion resistance as compared with other chromate treatments. For this reason, in the fields of household electrical appliances and audio equipment, a large amount of galvanized steel sheet or hot-dip coated steel sheet subjected to the corrosion-resistant chromate treatment is used.

By the way, in the field of home appliances and audio equipment,
In many cases, a steel sheet is pressed to form a member. However, since the chromate film formed by the above-described processing method has poor lubricity, in the case of galvanized steel sheets, etc., high-viscosity press oil is applied and pressed. After processing, it had to be degreased with a chlorine-based organic solvent such as trichloroethane. However, chlorinated solvents are toxic and their use tends to be regulated internationally.

For this reason, the development of a galvanized steel sheet which can be continuously pressed without applying a press oil by forming an organic resin film having excellent workability and lubricity on the chromate film has been studied. ing. However, since the production of this steel sheet is a two-stage process in which a chromate treatment solution is applied and then an organic resin solution is applied, a roll coater, a film drying oven, a cooling device, and the like are required. Each requires two units, which requires large equipment.

As a high corrosion-resistant chromate treatment which has solved the above problems, a water-dispersible organic resin is added to the above-mentioned chromate treatment solution containing an inorganic colloid or an inorganic powder, and chromic acid or an inorganic resin is added. A method is known in which an additive is treated with a treatment liquid dispersed in a resin film (JP-A-2-243).
772). However, when the treatment liquid is continuously applied to the steel sheet by a roll coating method, the treatment liquid is circulated and the treatment liquid is circulated.
Thus, there is a problem that the stability of the processing liquid is lost due to rotation of the nozzle and the processing liquid gels. In addition, when a polymer powder or a pigment of a lubricant is added to the treatment liquid in order to enhance the lubricity and design of the chromate film, the polymer resin powder floats or the pigment is dispersed due to poor dispersibility. There was also the problem of settling. Further, there is a problem that when the die temperature is increased by continuously performing press working without applying oil, the surface of the processed portion is blackened.

007

SUMMARY OF THE INVENTION The present invention relates to a roll-
The treatment liquid does not gel even when applied by the coating method, and the dispersibility of the polymer resin powder and pigment is good. In addition, even if the mold temperature rises during press working, the chromate film turns black. It is intended to provide a highly lubricated chromate treatment liquid for a plated steel sheet that does not have a lubrication.

[0098]

According to the present invention, the chromate treatment liquid is used in an amount of 1 to 20 g / l of total chromium (Cr ³⁺ + Cr ⁶⁺ ).
20 to 500 g / l of a water-dispersible urethane resin, 2 to 10% by mass of a nonionic emulsifier having a hydrophilic-lipophilic ratio of 12 or more,
Silicone-modified polyether-based defoamer containing 0.05 to 3.0% by mass and 2 to 25% by mass of a polymer resin powder lubricant having a melting point of 100 ° C. or more as a lubricant or an average particle size Was added in an amount of 3.0 to 20.0% by mass of a pigment having a particle size of 1.0 μm or less.

[0099]

The present inventors have studied the stability and dispersibility of a chromatized solution containing a water-dispersible organic resin during continuous application and found that a nonionic emulsifier may be added. Further, it has been found that blackening caused by an increase in the temperature of the press mold can be solved by using a urethane resin as the water-dispersible organic resin.

The water-dispersible organic resin is added to the chromatization treatment liquid in the form of an emulsion. The present inventors have found that the emulsifier contained in this emulsion has a high stability during continuous application of the chromatization treatment liquid. It was found that it affected the dispersibility. That is, since the water-dispersible organic resin emulsion is produced by an emulsion polymerization method in which an emulsifier, a monomer and a polymerization initiator are added to distilled water and polymerized while heating under stirring, the emulsion contains an emulsifier. . For this reason, when the emulsion is blended with the chromatizing solution, the emulsifier used during the production of the emulsion is inevitably mixed into the chromating solution.

However, cationic emulsifiers in emulsion polymerization tend to suppress the polymerization reaction.
Anionic or nonionic type is used, and when polymerization is not possible only with nonionic type, anionic type is mixed and used.However, when the emulsion is blended with a chromate treatment solution, the emulsifier in the emulsion is diluted. It was found that the type of the emulsifier and the type of the emulsifier made the chromate treatment liquid unstable, and also caused gelation and reduced dispersibility during continuous coating.

That is, when chromic acid is added to an aqueous solution of an anionic or nonionic emulsifier-containing water-dispersible organic resin, in the case of an aqueous solution containing an anionic emulsifier, the resin gradually starts to gel and separates and precipitates. In the case of an aqueous solution, it is stable even when chromic acid is added, and there is no problem in dispersibility even when a polymer resin powder or a pigment is added.

However, the addition of this nonionic emulsifier is
If the amount is less than 10% by mass, gelling of the treatment liquid occurs, and if the amount is more than 10% by mass, a large amount of an emulsifier is present in the applied film, so that the film is hardly cured even when dried. For this reason, the addition amount needs to be 2 to 10% by mass. If it is necessary to use an emulsion containing only an anionic emulsifier, it is necessary to add a nonionic emulsion to prevent gelation of the treatment liquid. It is necessary to make the ratio of the nonionic emulsifier to 0.7 or more. When the nonionic emulsifier has a hydrophilic-lipophilic ratio (HLB value) of less than 12, gelation cannot be prevented by addition of 2 to 10% by mass, and therefore, the nonionic emulsifier has a hydrophilic-lipophilic ratio of 12 or more. You need to use

Examples of the nonionic emulsifier include commercially available nonionic surfactants such as polyoxyethylene alkyl ether, polyoxyethylene alkylphenyl ether, polyoxyethylene alkyl ester, sorbital alkyl ester, and the like. Polyoxyethylene sorbital alkyl ester, polyoxyethylene-polyoxypropylene block polymer, etc.
What has a lipophilicity ratio of 12 or more may be used.

[0152] The chromate treatment liquid was prepared by increasing the amount of the emulsifier.
Foam is likely to be generated by the circulation and stirring of the processing liquid, and the foam is transferred to the coating film, and the film at that part is locally thinned. It is necessary to add an antifoaming agent to suppress the generation of foam. There is. As the defoaming agent, a silicone-modified polyether-based one, for example, a polyether obtained by polymerizing polyethylene oxide and polypropylene oxide as a main skeleton and a part of which is modified with silicone is used. There is a need to. Alcohols, organic phosphoric acids, unmodified polyethers, glycols, etc. have no sustained defoaming effect, while silicones and fluorines have excellent defoaming. Despite the effect, repelling occurs during coating, and the film is not uniform. The addition of this defoamer must be 0.05 to 3.0% by mass. If it is less than 0.05% by mass,
When the defoaming effect is insufficient, bubbles are involved, and when the content exceeds 3.0% by mass, repelling occurs.

When the type and concentration of the emulsifier are adjusted as described above, floating or sedimentation does not occur even when the polymer resin powder or pigment is added. However, the polymer resin powder was continuously pressed without oil coating. If the mold temperature rises to 100 ° C
In some cases, the temperature must not be melted at this temperature. When the polymer resin powder is melted, the lubricating performance and the blackening suppressing effect are significantly reduced, and the effect of addition is reduced. As the polymer resin powder, polyethylene, polypropylene, polystyrene, polyvinylidene fluoride, polytetrafluoroethylene, and the like can be used. If the addition amount is less than 2% by mass, not much lubricity is obtained,
If the content exceeds 25% by mass, repelling occurs at the time of application to the hot-dip coated steel sheet, or the adhesion of the coating film is reduced by coating after press working. Therefore, the addition amount is set to 2 to 25% by mass. The reason why the polymer resin powder is added as the lubricant is that the organic lubricant has better dispersibility than the inorganic lubricant.

If the particle size is larger than 1.0 μm, the dispersion in the treatment liquid is insufficient even if a nonionic emulsifier is added, so that the pigment having a particle size of 1.0 μm or less is used. Is 3.0 to 20.0% by mass. If the amount is less than 3.0% by mass, a predetermined color tone cannot be obtained.
There is no dispersion stability, and it is easy to gel.

The chromate treatment solution was composed of all chromium (Cr ³⁺ + C
r ⁶⁺ ) concentration of 1 to 20 g / l. Total chromium concentration is 1
When the amount is less than g / l, the corrosion resistance of the chromate film is insufficient, and when it exceeds 20 g / l, the treatment liquid is liable to gel and becomes unstable. As a chromate supply source, chromate, chromate (for example, ammonium chromate, zinc chromate, sodium chromate, barium chromate, etc.), and dichromate (for example, ammonium dichromate, etc.) may be used. Good.

The chromate treatment solution contains Cr ³⁺ / Cr
Organic reducing agents in order to adjust the ratio of ⁶⁺ (e.g., sugars,
Alcohols and the like) and inorganic reducing agents may be added. In addition, inorganic colloids such as silica sol and alumina sol may be added to increase corrosion resistance, and sulfuric acid, phosphoric acid, A small amount of an inorganic acid such as nitric acid or hydrofluoric acid may be added.

As the water-dispersible organic resin of the chromate treatment liquid, there are acrylic resin, epoxy resin, urethane resin, polyester resin, polyolefin resin and the like. Urethane resin is the most flexible, high ductility, Use this because it is the most effective in controlling the change. The concentration is 20-5
Make up to 00 g / l. If it is less than 20 g / l, the amount of the resin required for improving the lubricity cannot be obtained, and if it exceeds 500 g / l, the treatment liquid is easily gelled irrespective of the addition of an emulsifier described later, and becomes unstable. Become.

The application of the chromate treatment solution to the plated steel sheet is as follows:
A roll coating method is preferred, but other coating methods, for example,
It may be applied by an electrostatic atomization method or a spray method. After application, it is dried without washing.

[0222]

【Example】

Example 1 A urethane resin emulsion, an emulsifier, and a silicone-modified polyethylene oxide (silicon-modified polyether-based defoamer) were added to a chromic acid aqueous solution in which chromic anhydride was reduced to Cr ³⁺ / Cr ⁶⁺ = 0.25. And high molecular weight polyethylene resin powder (average particle size 1.5 μm, melting point 132 ° C.) 1 as a lubricant
0% by mass was added to prepare a chromate treatment solution having the composition shown in Table 1, and the stability of this treatment solution during continuous application with a roll coater and the dispersion stability of the lubricant. And the uniform applicability was investigated. Table 2 shows the results.

(1) Stability test of processing solution at the time of continuous coating with a roll coater A processing solution at a temperature of 40 ° C. was set on a roll coater, and 2
After running for 4 hours, the stability of the processing solution was evaluated according to the following criteria. : No gelling or sedimentation of the resin was observed in the treatment liquid. ×: Gelation or sedimentation of the resin was observed in the treatment liquid.

(2) Dispersion Stability Test of Lubricant The treatment liquid at 40 ° C. was stirred and allowed to stand, and the state of dispersion of the lubricant one hour after standing was evaluated according to the following criteria. ○: No concentration of lubricant was observed at the upper part of the processing liquid ×: Lubricant was observed at the upper part of the processing liquid

(3) Uniform applicability test The treatment liquid was applied to an electrogalvanized steel sheet by a roll coater, and the appearance of the application was evaluated according to the following criteria. ；: Uniform application and good appearance ×; Appearance during application and gelation of treatment liquid prevent application

[0262]

[Table 1] (Note 1) The lubricant is the same in both the examples and comparative examples. (Note 2) A in the nonionic emulsifier is a polyoxyethylene alkyl ether, and B is a polyoxyethylene alkyl phenyl ether. (Note 3) C in the anionic emulsifier is sodium alkyl sulfate. (Note 4) A / C of Example No. 5 = 0.7, A / C of No. 7
C = 0.56.

[0279]

[Table 2]

The chromate-treated electrogalvanized steel sheet prepared in the uniform coating test was subjected to the following tests for wettability, corrosion resistance in the processed portion, and paintability to examine the performance. Table 3 shows the results.

(4) Wetting test A stainless steel plate (SUS304,
The coefficient of kinetic friction with respect to (BA finish) was measured at a load of 200 gf and a moving speed of 60 mm / min, and evaluated according to the following criteria. ◎ Less than 0.2 ○ 0.2 or more, less than 0.3 △ 0.3 or more, less than 0.4 × 0.4 or more

(5) Corrosion resistance test of processed part A test for a bead (sliding deformation) was performed under a pressure of 200 kgf.
After the drawing speed was set at 500 mm / min, a salt spray test (JIS Z 2371) was performed for 100 hours, and the rate of occurrence of red rust was evaluated according to the following criteria. ○ Red rust occurrence rate 0% △ Red rust occurrence rate less than 20% × Red rust occurrence rate 20% or more

(6) Paintability test A solvent-based acrylic resin paint was applied so as to have a dry coating thickness of 20 μm, and was baked and dried.
m) An Erichsen overhang (3 mm) test was performed, and after the test, the processed portion was forcibly peeled off with a cellophane tape, and the coating film remaining rate was evaluated according to the following criteria. ○ Residual rate 90% or more △ Residual rate 60% or more, less than 90% × Residual rate less than 60%

[0332]

[Table 3] (Note) Those having no uniform coating property in Table 2 could not carry out the above tests.

Example 2 Chromic anhydride was reduced to Cr ³⁺ / Cr ⁶⁺ = 0.40. A chromic acid aqueous solution having a total chromium concentration of 8 g / l and a urethane resin emulsion having a resin concentration of 200 g / l were used as a nonionic emulsifier. 5% by mass of a polyoxyethylene alkyl ether having an HLB value of 14 and 0.1% of a silicone-modified polyethylene oxide as a silicone-modified polyether defoaming agent.
5% by mass, a polypropylene resin powder (average particle size: 2 μm, melting point: 145 ° C.) and a pigment were further added as a lubricant to prepare a chromate treatment solution having the composition shown in Table 4.
Stability of the treatment liquid during continuous coating with a roll coater,
The dispersion stability and uniform applicability of the lubricant were investigated in the same manner as in Example 1. Table 5 shows the results.

[0324]

[Table 4]

[0351]

[Table 5]

Further, each test of wettability, corrosion resistance of the processed part, and paintability was performed on the chromated electrogalvanized steel sheet prepared in the uniform coating test in the same manner as in Example 1, and the target color tone Was investigated. The results are shown in Table 6. The evaluation of the color tone was evaluated by ○ when a predetermined color tone was obtained, and by X when the predetermined color tone was not sufficiently obtained.

[037]

[Table 6]

[0386]

As described above, the chromate treatment liquid of the present invention does not gelate even if it is continuously applied to a plated steel sheet by a roll coating method. Good dispersibility of powder and pigment. Furthermore, the chromate film does not turn black even if the mold temperature rises during the press working.

Continuation of the front page (56) References JP-A-6-192849 (JP, A) JP-A-4-247883 (JP, A) JP-A-3-219086 (JP, A) JP-A-60-197882 (JP) , A) JP-A-62-182283 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C23C 22/00-22/86

Claims (4)

(57) [Claims] 1. Total chromium (Cr ³⁺ + Cr ⁶⁺ ) 1 to 20
g / l, 20 to 500 g / l of a water-dispersible urethane resin, 2 to 10% by mass of a nonionic emulsifier having a hydrophilic-lipophilic ratio of 12 or more, and a silicone-modified polyether-based antifoaming agent of 0.05 to 5 g / l.
A highly lubricating chromate treatment liquid for plated steel sheets, comprising 3.0% by mass and 2 to 25% by mass of a polymer resin powder having a melting point of 100 ° C. or higher. 2. The highly lubricating chromate treatment solution for a plated steel sheet according to claim 1, wherein the ratio of the nonionic emulsifier to all emulsifiers is 0.7 or more. 3. The processing liquid according to claim 1, which has an average particle size of 1.0.
A highly lubricated chromate treatment solution for plated steel sheets, wherein a pigment having a size of not more than μm is added in an amount of 3.0 to 20.0% by mass. 4. The highly lubricating chromate treatment liquid for a plated steel sheet according to claim 3, wherein the ratio of the nonionic emulsifier to all emulsifiers is 0.7 or more.