JPH0696775B2 - Surface-treated steel sheet with excellent corrosion resistance, adhesion and lubricity - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention has a specific feature that the surface of a steel sheet contains chromate, silica sol and a solid lubricant, and either or both of a silane coupling agent and a titanium coupling agent. The present invention relates to a surface-treated steel sheet having a resin film formed by improving the corrosion resistance and lubricity of the resin film.

(Prior art) Of the surface-treated steel sheets, which have been treated with a water-dispersible or water-soluble resin to form cold-rolled steel sheets or plated steel sheets and have a resin film that imparts paintability and corrosion resistance to them As a material having excellent resistance and corrosion resistance, there is a material in which a chromate film is formed on the surface of a steel sheet, and a resin single film or a resin film containing an inorganic substance is further formed on the chromate film. This surface-treated steel sheet is provided with corrosion resistance by the first layer of chromate film and coatability by the second layer of resin film. For the resin of the resin film, the resin film is water-soluble for convenience. A hydrophilic one having a hydroxyl group in the molecule has been used.

(Problems to be Solved by the Invention) However, in the case of the surface-treated steel sheet as described above, its corrosion resistance depends on the chromate film of the first layer, so even if it is attempted to improve the corrosion resistance, there is a limit to the improvement. there were. Therefore, in order to further improve the corrosion resistance, it is necessary to improve the corrosion resistance of the second layer resin film.

As a method of improving the corrosion resistance of the resin film, a method of adding hexavalent chromium to the colored resin film can be considered. To add hexavalent chromium by this method, treat with a resin film treatment liquid containing hexavalent chromium. There is a need to. However, if chromic anhydride or chromate is added to contain hexavalent chromium in the resin film treatment liquid, the hydroxyl groups of the resin molecules are oxidized, the treatment liquid gels, and it becomes impossible to apply it to the steel sheet.
Hexavalent chromium is also reduced to trivalent chromium so that it no longer exhibits corrosion resistance. Therefore, it has been difficult to include hexavalent chromium in the conventional resin film.

Further, when the conventional resin film is subjected to roll forming or press working on a steel sheet, it is scratched or peeled off, and the molding workability is still insufficient.

(Means for Solving Problems) In the present invention, it has been difficult to form a resin film in such a manner as described above.
The present invention provides a surface-treated steel sheet capable of containing valent chromium and having improved lubricity.

The surface-treated steel sheet of the present invention prevents the resin from being oxidized in the treatment liquid stage by making the resin of the resin film a water-dispersible copolymer having no hydroxyl group, and adjusting the acid value of the copolymer. To improve the water resistance, adhesion and physical properties of the resin film and the adhesion to the coating film when applied, and to add chromate as a hexavalent chromium source in the film of this copolymer, and Silica sol was added to improve the physical properties and corrosion resistance, and a lubricant was added to improve the lubricity during molding.

However, when the remaining treatment liquid after forming the resin film of the composition on the steel sheet was stored, it was observed that the viscosity increased in about 7 weeks, gelation occurred, and coating became impossible by roll coating, etc. The liquid was found to have some problems with long term storage stability. Therefore, in the present invention, as a result of various studies to improve the storage stability of the treatment liquid, it is only necessary that the treatment liquid further contains a silane coupling agent, a titanium coupling agent, or both in the resin film. I found out.

That is, the present invention uses (A) a general color CH as the resin of the resin film.
₂ = CR ₁ -COOR ₂ (wherein R ₁ is H, CH ₃ and R ₂ are alkyl groups in which C is 1-8)
95% by weight, (B) α, β unsaturated carboxylic acid monomer 3 to
Emulsion polymerization of 20% by weight and (C) 0.1 to 50% by weight of a monomer copolymerizable with these monomers [however, the total of (A), (B) and (C) is 100% by weight] With a copolymer resin film having an acid value per solid content of 10 to 200 obtained by, chromate, silica sol and a solid lubricant in the resin film,
A material containing either or both of a silane coupling agent and a titanium coupling agent is formed.

Here, the general formula CH ₂ ═CR ₁ —COOR ₂ constituting the copolymer resin is used.
Examples of the monomer include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate,
Butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, and the like, and examples of α, β unsaturated carboxylic acid monomers include acrylic acid, methacrylic acid, itaconic acid, maleic acid, and the like. Examples of the monomer copolymerizable with the above monomer include styrene, α-methylstyrene, vinyl acetate, vinyl chloride, vinylidene chloride and the like.

The reason why the copolymer resin as described above is used in the present invention is that a film having the desired physical properties can be obtained, and the industrial production of the copolymer resin is easy.

The reason why the acid value of the copolymer resin is 10 to 200 per solid content is that if it is less than 10, the water resistance is good but the adhesion to the steel sheet is poor, and if it exceeds 200, the water resistance is poor. This is because the corrosion resistance decreases. With respect to this acid value, if the acid value is in the range of 15 to 100, the water resistance and adhesiveness of the film will be good, so it is preferable to set it in this range.

The chromate contained in the resin film is water-soluble,
Inexpensive ones are preferable, such as ammonium chromate,
Suitable are magnesium chromate, potassium dichromate, calcium chromate, zinc chromate, manganese chromate, nickel chromate, cobalt chromate, strontium chromate and the like.

Similarly, it is preferable that the solid lubricant also has good water dispersibility, is inexpensive, and does not deteriorate the corrosion resistance, adhesion, weather resistance and the like of the film even when contained in the film. As such a material, an inorganic solid lubricant is preferable to an organic solid lubricant, and for example, molybdenum disulfide, tungsten disulfide, boron nitride, graphite, graphite fluoride and the like are preferable, and particularly molybdenum disulfide and graphite are contained in the film. It is inexpensive and preferable because it has no reactivity with the additive. These solid lubricants may be mixed and used. Liquid lubricants (such as synthetic lubricants) and semi-solid lubricants (such as wax) can be used as solid lubricants, but these are effective for lubricating effect, long-term stability, and treatment liquid. This is because the dispersibility and stability are inferior to those of the solid lubricant.

The amount of these chromate, silica sol and solid lubricant contained in the resin film is 0.1 to 50 parts by weight for chromate per 100 parts by weight of copolymer resin, 0.5 to 100 parts by weight for silica sol, and solid. In the case of lubricant, it is preferable to use 3 to 15 parts by weight.

Regarding the fixed lubricant content, as shown in Fig. 1, the dynamic friction coefficient decreases as the content increases and the lubricity at the time of processing improves, but the content is 3 parts by weight relative to 100 parts by weight of resin. If it is less than 10 parts by weight, the effect of addition is not recognized so much, and if it exceeds 15 parts by weight, the adhesion of the film to the steel sheet decreases,
In addition, the dispersibility in the treatment liquid deteriorates, the solid lubricant precipitates, and the treatment liquid gels. Therefore, it is preferable that the content of the solid lubricant be within the above range.

The average particle size of the solid lubricant is preferably 0.3 to 1.0 μ. When the average particle size is less than 0.3μ, the solid lubricant does not protrude much from the surface of the resin film, so the lubricating effect is small, and when it exceeds 1.0μ, the smoothness of the film is impaired and the treatment liquid It is also difficult to disperse it inside.

Even if one or both of the silane coupling agent and the titanate coupling agent are contained, they are preferably contained in 0.05 to 1.0 parts by weight with respect to 100 parts by weight of the copolymer resin. If it is less than 0.05 parts by weight, almost no addition effect is observed, and if it exceeds 1.0 parts by weight, in the case of the silane coupling agent, the storage stability becomes more and more favorable as the content increases, The water-repellent effect peculiar to silicon causes cissing during application of the treatment liquid, resulting in non-uniform coating thickness and composition. On the other hand, in the case of the titanium coupling agent, on the contrary, gelation of the treatment liquid is significantly promoted, which causes a problem in storage stability.

There are various types of silane coupling agents, but if they are water-dispersible or water-soluble, the monomer type [eg vinyl-tri (β-methoxyethoxy) silane, γ-glycidyltrimethoxysilane] , Oligomer type (for example, glycid type), resin deformation type (for example, acrylic modification, epoxy modification), cation type, etc. can be used. Further, a titanate coupling agent can be used as long as it is water-dispersible or water-soluble, and preferable examples thereof include tetra (2,2-diallyloxymethyl-1-).
Butyl) bis (di-tridecyl) phosphite titanate, bis (dioctyl pyrophosphate) oxyacetate titanate, bis (dioctyl pyrophosphate) ethylene titanate and the like.

FIG. 2 shows the effect of preventing thickening of the treatment liquid by the silane coupling agent. Even when the treatment liquid is a two-component solution of the copolymer resin and the chromate, even after 6 months have elapsed. It does not thicken or gel and has good long-term storage stability. However, when silica sol or a solid lubricant is added to this two-component treatment liquid, thickening and gelation are rapidly promoted. However, when a silane coupling agent is further added, long-term storage stability becomes good again. The reason for this is not clear, but it is presumed that the silane coupling agent acts as a dispersant to stably disperse the chromate, silica sol, and solid lubricant individually in water as a medium.

When a silane coupling agent or a titanium coupling agent is added, the resin film firmly adheres to the base (steel plate surface or chromate film) to improve the adhesion. This is because the resin film and the base are -Si-O- and -Ti-O- as mediums.
It is thought to be due to chemical bonding. Further, since it is dehydrated and condensed with the functional group of the copolymer resin, the coating film adhesion and the corrosion resistance are extremely improved when the top coat is applied.

Since the resin film contains chromate, it exhibits corrosion resistance even if it is formed directly on the steel plate, but for further corrosion resistance, a chromate film is formed on the steel plate and a resin film is formed on it. To do. In this case, the chromate film may be of any type such as a reaction type or a coating type, but it is preferable that the total amount of chromium is 5 to 200 mg / m ² . The film thickness of the resin film is preferably 0.2-10 μm.

The steel sheet is a cold rolled steel sheet, a plated steel sheet (for example, a hot dip plated steel sheet,
(Electroplated steel sheet, vapor deposition plated steel sheet, alloyed hot dip plated steel sheet, hot-dip or electroalloy plated steel sheet, etc.).

Next, the present invention will be described with reference to examples.

(Example) Acrylic emulsion obtained by emulsion polymerization of 50 wt% methyl methacrylate, 40 wt% butyl acrylate, and 10 wt% acrylic acid [resin content 40 wt%, PH2.
3. Add various chromates and silica sol (Snowtex O, Nissan Chemicals) to a viscosity of 25 cps (25 ° C, B-type viscometer), acid value per solid content of about 78], and add this aqueous solution as X. did.

On the other hand, an acrylic emulsion obtained by emulsion polymerization of 55% by weight of methyl acrylate, 40% by weight of butyl acrylate, and 5% by weight of acrylic acid [resin content 40% by weight, PH2.
6, various chromates and silica sol (Snowtex O, Nissan Chemical Co., Ltd.) were added in the same manner as above to a viscosity of 150 cps (same as above) and an acid value per solid content of 40], and this aqueous solution was designated as Y.

Cold-rolled steel sheets and hot-dip galvanized steel sheets were prepared by using the aqueous solutions X and Y prepared as described above, and eight different aqueous solutions prepared by adding different solid lubricants to them.
0.6 mm) was processed to produce a surface-treated steel plate.

Aqueous solutions X-1 and Y-1 0.05% by weight of vinyl-tri (β-methoxy) silane and tetra (2,2-diallyloxyether-1-butyl) per 100 parts by weight of resin in the aqueous solutions X and Y, respectively. Add 0.05 parts by weight of bis (didodecyl) phosphite titanate, and add to each solution 100 parts of resin in the same solution.
Per part by weight molybdenum disulfide [Product name: Moly Colloid CF62
6, manufactured by Nippon Graphite Industry Co., Ltd.] was added in an amount of 1 to 15 parts by weight to prepare aqueous solutions X-1 and Y-1, respectively.

Aqueous solution X-2 and Y-2 0.5 parts by weight of an aqueous solution of glycidsilane oligomer dissolved in aqueous solutions X and Y was added to 0.5 parts by weight per 100 parts by weight of resin in the solution of X and Y. 1 to 15 parts by weight of a mixture of molybdenum disulfide (same as above) and graphite [trade name: Oil Height G307, manufactured by Nippon Graphite Industry Co., Ltd.] per 100 parts by weight of each resin of X-2 and Y, respectively. -2.

Aqueous solution X-3 and Y-3 Aqueous solutions X and Y were respectively added with 1 part by weight of vinyl-tri (β-methoxy) silane and tetra (2,2-diallyloxyether-1-butyl) per 100 parts by weight of resin in the same solution. 1 part by weight of bis (didodecyl) phosphite titanate was added, and 1 to 15 parts by weight of graphite [trade name: Aldais F33G, manufactured by Nippon Graphite Industry Co., Ltd.] was added to each solution per 100 parts by weight of resin in the solution. Were added to make them aqueous solutions X-3 and Y-3, respectively.

Aqueous solution X-4 and Y-4 0.5% by weight of vinyl-tri (β-methoxy) silane and tetra (2,2-diallyloxyether-1-butyl) were added to 100% by weight of resin in the aqueous solution X and Y-4, respectively. 0.5 parts by weight of bis (didodecyl) phosphite titanate was added, and 100 parts of resin in the same solution was added to each solution.
1 to 15 parts by weight of graphite [trade name: Aldais F33G, manufactured by Nippon Graphite Industry Co., Ltd.] was added per part by weight, and they were used as aqueous solutions X-4 and Y-4, respectively.

The manufacturing process and formation of the chromate film were as follows.

(A) Manufacturing process Steel sheet → Degreasing → Chromate treatment → Resin coating treatment Aqueous solution coating → Drying (150 ° C, 10 seconds) (B) Chromate coating formation Chromic anhydride 20g /, Na ₂ SiF ₆ 1g /, 40 ° C treatment After being immersed in the liquid for 5 seconds, the excessively adhered aqueous solution was removed by roll squeeze.

Table 1 shows the relationship between the base steel sheet, the aqueous solution used and the formed resin film of the surface-treated steel sheet thus produced, and Table 2 shows the adhesion and corrosion resistance of the resin film of the surface-treated steel sheet and the coefficient of dynamic friction. And the lubricity during processing (roll forming, hat bendability by Erichsen tester).

The adhesiveness of the resin film was investigated by the DuPont impact test and evaluated according to the following criteria.

◎ No peeling of film ○ Slight peeling of film △ Significant peeling of film × Significant peeling of film Corrosion resistance was measured by salt water atmosphere fog test (JIS Z
2371) and a wetting test (temperature 50 ° C, humidity 98%). In both tests, make a notch that reaches the surface of the steel sheet in a flat plate state, the one before processing is subjected to the test as it is, the one after processing is subjected to the test after roll forming, and the cellophane tape is once attached to the notch after the test Then, the peeling state of the film was evaluated by the following criteria. In the case of the salt spray test, the test was carried out for 24 hours for the cold rolled steel sheet as the base steel sheet and 500 hours for the hot rolled galvanized steel sheet. On the other hand, the wet test was performed for 500 hours regardless of the base steel sheet.

◎ No peeling ○ Peeling width or rust generation width is 1 mm or less from the notch △ Peeling width or rust generation width is more than 1 mm from the notch and 3 mm or less × Peeling width or rust generation width is more than 3 mm from the notch The roll forming property and hat bendability were evaluated according to the following criteria.

◎ The film is not damaged at all ○ Slightly damaged film △ Very damaged film × Significantly damaged film As is clear from Table 2, the surface-treated steel sheet of the present invention has excellent corrosion resistance, and the dynamic friction coefficient decreases as the content of the solid lubricant in the resin film increases, and the degree of resin film damage during processing decreases. Become. However, if the lubricant content is resin
If it exceeds 15 parts by weight with respect to 100 parts by weight, the adhesion of the resin film will deteriorate.

(Effect) As described above, since the resin of the resin film of the surface-treated steel sheet of the present invention does not have a hydroxyl group, even if chromate is contained in the treatment liquid during production, the resin is not oxidized and gels. In addition, since a silane coupling agent and a titanium coupling agent are added to the treatment liquid, long-term storage stability is excellent. Further, since the resin film contains chromate, silica sol and a silane coupling agent or a titanium coupling agent, the resin film is superior in corrosion resistance and adhesion to those not containing them. Further, since the resin film contains a solid lubricant, it has excellent lubricity, so that the resin film is not scratched or peeled off even when roll forming or pressing is performed.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the solid lubricant content of the resin coating and the dynamic friction coefficient in the surface-treated steel sheet of the present invention.
FIG. 2 is a graph showing the long-term storage stability of the treatment liquid when a silane coupling agent is added to the treatment liquid used when producing the surface-treated steel sheet of the present invention.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI technical display location B32B 15/08 Q 101 7148-4F C09D 5/08 PNF 6904-4J

Claims (12)

[Claims] 1. A surface of a steel sheet having (A) the general formula CH ₂ = CR ₁ -COOR
₁ (or more than 1) of the monomer represented by ₂ (wherein R ₁ is H, CH ₃ , R ₂ is an alkyl group in which C is 1 to 8) and 1 to 95% by weight,
(B) α, β unsaturated carboxylic acid monomer 3 to 20% by weight,
(C) 0 to 50% by weight of a monomer copolymerizable with these monomers [provided that the total of (A), (B) and (C) is 100
% By weight] Acid value per solid content obtained by emulsion polymerization 10 to 20
A copolymer resin film of 0, in which the resin film contains chromate, silica sol and a solid lubricant and either or both of a silane coupling agent and a titanium coupling agent are formed. A surface-treated steel sheet excellent in corrosion resistance, adhesion and lubricity, which is characterized in that 2. A surface excellent in corrosion resistance, adhesion and lubricity according to claim 1, wherein the resin film contains 3 to 15 parts by weight of a solid lubricant per 100 parts by weight of the resin. Treated steel plate. 3. The surface-treated steel sheet excellent in corrosion resistance, adhesion and lubricity according to claim 1, wherein the solid lubricant is graphite. 4. The surface-treated steel sheet excellent in corrosion resistance, adhesion and lubricity according to claim 1, wherein the solid lubricant is molybdenum disulfide. 5. The surface-treated steel sheet excellent in corrosion resistance, adhesion and lubricity according to claim 1, wherein the solid lubricant is a mixture of graphite and molybdenum disulfide. 6. A surface-treated steel sheet excellent in corrosion resistance, adhesion and lubricity according to claim 1, characterized in that the solid lubricant has an average particle diameter of 0.3 to 1.0 μm. 7. A chromate film is formed on the surface of a steel plate,
On the chromate film, (A) _one of the monomers represented by the general formula CH ₂ = CR ₁ -COOR ₂ (wherein R ₁ is H, CH ₃ and R ₂ are alkyl groups in which C is 1 to 8). Seed or 2 or more 1
~ 95% by weight, (B) α, β unsaturated carboxylic acid monomer 3
To 20% by weight and (C) 0 to 50% by weight of a monomer copolymerizable with these monomers [however, the total of (A), (B) and (C) is 100% by weight] Copolymer resin film having an acid value per solid content of 10 to 200 obtained by polymerization, chromate in the resin film, silica sol and a solid lubricant,
A surface-treated steel sheet excellent in corrosion resistance, adhesion and lubricity, characterized in that a material containing one or both of a silane coupling agent and a titanium coupling agent is formed. 8. A surface excellent in corrosion resistance, adhesion and lubricity according to claim 7, wherein the resin coating contains 3 to 15 parts by weight of a solid lubricant per 100 parts by weight of the resin. Treated steel plate. 9. A surface-treated steel sheet excellent in corrosion resistance, adhesion and lubricity according to claim 7, wherein the solid lubricant is graphite. 10. The corrosion resistance according to claim 7, wherein the solid lubricant is molybdenum disulfide.
Surface-treated steel sheet with excellent adhesion and lubricity. 11. A surface-treated steel sheet excellent in corrosion resistance, adhesion and lubricity according to claim 7, wherein the solid lubricant is a mixture of graphite and molybdenum disulfide. 12. A surface-treated steel sheet excellent in corrosion resistance, adhesion and lubricity according to claim 7, characterized in that the solid lubricant has an average particle diameter of 0.3 to 1.0 μm.