JPS61227179A - Surface treated plate having excellent corrosion resistance and lubricity - Google Patents

Abstract

PURPOSE:To obtain a surface treated steel plate having excellent corrosion resistance and lubricity by forming a copolymer resin film having an adequate acid value and contg. chromate, silica sol and solid lubricating agent on the surface of the steel plate. CONSTITUTION:The copolymer resin emulsion having 10-200 acid value per solid content is formed by emulsion-polymerizing 1-95wt% monomer expressed by the general formula CH2=CR1-COOR2 (in which, R1; H, CH3, R2; an alkyl group of 1-8C), 3-20% alpha, beta unsatd. carboxylic acid monomer, 0-50% monomer copolymerizable with these monomers (where 100% the total of the above- mentioned three). The chromate, silica sol and solid lubricating agent such as graphite or MoS2 are added to such emulsion and after the surface of the steel plate is subjected to a chromate treatment, the above-mentioned emulsion is coated thereon and is dried. The resin film which has good adhesiveness and excellent corrosion resistance and lubricity and does not generate the flawing or exfoliation, etc., in the stage of working is thus formed on the surface of the steel plate.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention improves the corrosion resistance and lubricity of the resin film by forming a specific resin film containing chromate, silica sol, and solid lubricant on the surface of a steel plate. The present invention relates to surface-treated steel sheets.

(Prior art) Of the surface-treated steel sheets in which a cold-rolled steel sheet or a galvanized steel sheet is treated with a water-dispersible or water-soluble resin to form a resin film that provides paintability and corrosion resistance on the surface, relatively many Some steel sheets with excellent paintability and corrosion resistance include those in which a chromate film is formed on the surface of a steel plate, and a resin-only film or a resin film containing an inorganic substance is further formed on the chromate film.

This surface-treated steel sheet has one MS layer of chromate film to give it corrosion resistance, and a second layer of resin film to give it paintability. A hydrophilic material having a hydroxyl group was used.

(Problem to be solved by the invention) However, in the case of the above-mentioned surface-treated steel sheet, its corrosion resistance depends on the chromate film of #IJll, so even if an attempt is made to improve the corrosion resistance, there is a limit to the improvement. Ta. Therefore, in order to further improve the corrosion resistance, it was necessary to improve the corrosion resistance of the second layer resin film.

One possible method for improving the corrosion resistance of a resin film is to include hexavalent chromium in the resin film, but in order to incorporate hexavalent chromium using this method, treatment with a resin film treatment solution containing hexavalent chromium is considered. There is a need. However, if chromic anhydride or chromate is added to contain hexavalent chromium in the resin film treatment solution, the hydroxyl groups of the resin molecules will be oxidized, resulting in the treatment J! I! The liquid turns into a delta and cannot be applied to the steel plate, and the hexavalent chromium is reduced to trivalent chromium and no longer exhibits corrosion resistance. For this reason, it has conventionally been difficult to incorporate hexavalent chromium into a resin film.

In addition, conventional resin coatings were scratched or peeled off when a steel plate was subjected to roll 7-ohm processing or press processing, and the forming resistance was still insufficient.

(Means for Solving the Problems) The present invention provides a solution to the problem of infiltration into a resin film, which has been difficult in the past.
The present invention provides a surface-treated steel sheet that allows the inclusion of valent chromium and also has improved lubricity.

The surface-treated steel sheet of the present invention uses a water-dispersible copolymer that does not have hydroxyl groups as the resin of the resin film to prevent the resin from being oxidized at the treatment liquid stage, and also adjusts the acid value of the copolymer. It improves the water resistance, adhesion and physical properties of the resin film, as well as the adhesion to the paint film when painted.

That is, the present invention uses the general formula ell□=cR, -C0OR, (in the formula, R3 is II) as the resin for the colored resin film.
, CII, , R2 is an alkyl group having 1 to 8 carbon atoms) and 1 to 95% of one or more monomers represented by (B) Q, β unsaturated + 1 n-J -Ildh 11
4 jl 蓚n 68 erotic/l/book I bar ---
[
However, the sum of (A), (B) and (C) is io.

Acid value per solid content obtained by weight %1 emulsion polymerization: 10~
By using a copolymer resin of No. 200 and containing a solid lubricant in the resin film, the molding resistance was improved.

Here, the general formula CH,=CR constituting the copolymer resin.

-COOR2 monomers include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, etc. , Examples of β-unsaturated carboxylic acid monomers include acrylic acid, methacrylic acid, itaconic acid, maleic acid, etc. Furthermore, examples of monomers copolymerizable with these monomers include styrene, a- The list ends with methylstyrene, vinyl acetate, vinyl chloride, vinylidene chloride, etc.

The reason for using the above-mentioned copolymer resin 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 set to 10 to 200 per solid content is because if it is less than 10, the water resistance is good but the adhesion to the steel plate is poor, and if it exceeds 200, the water resistance is poor. This is because corrosion resistance decreases. The acid value is preferably set within the range of 15 to 100 because the film will have good water resistance and adhesion.

In the present invention, the resin film is formed as described above, and 6
Chromate is contained as a chromium source, silica sol is contained to improve the physical properties and corrosion resistance of the film, and a lubricant is contained to improve lubricity during molding. The chromate to be contained here is preferably water-soluble and inexpensive, such as ammonium chromate, magnesium chromate, potassium dichromate, calcium chromate, zinc chromate, manganese chromate, nickel chromate, chromium Cobalt acid, strontium chromate, etc. are suitable.

Similarly, as a solid lubricant, it is preferable to use one that has good water dispersibility, is inexpensive, and does not reduce the corrosion resistance, adhesion, weather resistance, etc. of the film even if it is included in the film. As such, inorganic solid lubricants are preferable to organic solid lubricants, such as molybdenum disulfide, tungsten disulfide, boron nitride, graphite, graphite heptafluoride, etc., especially molybdenum disulfide and graphite. is preferable because it has no reactivity with additives in the film and is inexpensive. These solid lubricants may be used in combination. Note that solid lubricants can also be used in liquid form (e.g. synthetic lubricating oil) or semi-solid lubricant (e.g. wax), but these differ in terms of lubricating effect, long-term stability, and susceptibility in processing liquids. This is because they are inferior to solid lubricants in terms of dispersibility and stability.

The amount of these chromate, silica sol and solid lubricant to be contained in the resin film is 0.1 to 50 parts by weight for chromate and 0.5 to 100 parts by weight for silica sol per 100 parts by weight of copolymer resin. Parts by weight, 3 for solid lubricants
It is preferable to adjust the amount to 10 parts by weight.

Regarding the solid lubricant content, as shown in the attached drawings,
As the content increases, the coefficient of dynamic friction decreases, and the lubricity during processing becomes better.
If the amount is less than 10 parts by weight, the addition effect will not be noticeable, and if the amount is 10 parts by weight, the adhesion of the film to the steel plate will decrease, and the dispersibility in the processing liquid will deteriorate, causing the solid lubricant to settle. or the processing liquid may become sluggish. Therefore, it is preferable that the content of the solid lubricant is within the above range.

The average particle size of the solid lubricant is preferably 0.3 to 1.0μ, which means that if the average particle size is less than 0.3μ,
This is because the solid lubricant does not protrude much from the surface of the resin film, so it has little lubricating effect.On the other hand, if it exceeds 1.0μ, the smoothness of the film will be impaired and it will be difficult to disperse it into the processing liquid.

The thickness of the resin film is preferably 0.2 to 10 μm.

Since the resin film contains chromate, it exhibits corrosion resistance even if it is formed directly on the steel plate, but in order to exhibit even more corrosion resistance, it is necessary to apply a chromate film to the steel plate.

is formed, and a resin film is formed thereon. In this case, the type of chromate film generally does not matter, such as reactive type or coating type, but the total amount of chromate film is 5 to 200 IIIg/l1
It is preferable to set it to 12. The steel plate may be a cold-rolled steel plate or a plated steel plate (for example, a hot-dip plated steel plate, an electroplated steel plate, a vapor-deposited plated steel plate, an alloyed hot-dip plated steel plate, a hot-dipped or electroalloy plated steel plate, etc.). Next, the present invention will be explained with reference to Examples.

(Example) Acrylic emulsion 1 obtained by emulsion polymerization of 50% by weight of methyl methacrylate, 40% by weight of butyl acrylate, and 10% by weight of acrylic acid [Resin content: 40% by weight]
, PH2.3, viscosity 25 cps (25"C, B type viscometer), acid value per solid content 781, various chromates and silica sol (In/-Tex 01 Nissan Chemical Products) were added, This aqueous solution was designated as X.

On the other hand, an acrylic emulsion resin obtained by emulsion polymerization of 55% by weight of methyl acrylate, 40% by weight of butyl 7-acrylate, and 5% by weight of acrylic acid [resin content: 40% by weight,
4 (2,6, viscosity 150 cps (same as above), acid value per solid content 40), various chromates and silica sol (Snowtex O1 Nissan Chemical Products) were added in the same manner as above,
This aqueous solution was designated as Y.

Cold-rolled steel sheets and hot-dip galvanized steel sheets (both with thickness 0, 6I) to produce a surface-treated steel sheet.

Aqueous solution , they were designated as water-soluble 1x-i and Y-1, respectively.

Aqueous solutions
1 to 15 parts by weight of the mixture with Product 1 were added, and these were designated as X-2 and Y-2, respectively.

Aqueous solutions X-3 and Y-3 Graphite [trade name Arguis F33G, Nippon Graphite Industries, Ltd.
1 to 15 parts by weight of each of
-3 and Y-3.

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

(B) Manufacturing process Steel plate → Degreasing → Chromate treatment → Resin film treatment Aqueous solution application → Drying (150°C, 10 seconds) (B) Form of chromate film, formation Chromic anhydride 209 /e, NazS + Fg 1
9/e After being immersed in a 140° C. treatment solution for 5 seconds, excess adhesion of the aqueous solution was removed with a roll squeeze.

Table 1 shows the relationship between the base steel sheet, the aqueous solution used, and the resin film formed in the surface-treated steel sheet manufactured in this manner, and Table 12 shows the adhesion and corrosion resistance of the resin film of the surface-treated steel sheet, as well as the coefficient of dynamic friction and It shows the lubricity during processing (roll 7 ohming property, hat bending property by Erichsen testing machine).

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

◎ The film does not peel off at all O The film slightly peels Δ The film peels off considerably
Z 2371) and a wet test (temperature 50° C., humidity 98%). In both tests, a cut was made to reach the surface of the steel plate in a flat state, and the unprocessed one was used as is for the test, and the processed one was subjected to the test after roll 7 ohm forming. The film was pasted and then rapidly peeled off, and the state of peeling of the film was evaluated using the following criteria. In the case of the salt spray test, the test is conducted for 24 hours on cold-rolled steel sheets, and for 50 hours on hot-dip galvanized steel sheets.
I went for 0 hours. On the other hand, the wet test was conducted for 500 hours, regardless of the base steel plate.

◎ No peeling○ Width of peeling or rust occurrence is 1mm or less from the notch Δ Width of peeling or rust is more than 1mm from the notch and 3m or less× Width of peeling or rust is 3II11 from the notch
Furthermore, roll 7 ohming properties and hat bending properties were evaluated according to the following criteria.

O The film is not damaged at all O The film is slightly damaged Δ The film is severely damaged X The film is severely damaged As is clear from Table 2, the surface-treated steel sheet of the present invention has excellent corrosion resistance. Furthermore, as the solid lubricant content in the resin film increases, the coefficient of dynamic friction decreases, and the degree of damage to the resin film during processing decreases.

However, the lubricant content is 10 parts by weight per 100 parts by weight of resin.
If the amount exceeds parts by weight, the adhesion of the resin film will deteriorate.

(Effects) As described above, the resin in the resin coating of the surface-treated steel sheet of the present invention does not have hydroxyl groups, so even if chromate is included in the treatment solution during manufacturing, the resin will not be oxidized and will not gel. .

Furthermore, since the resin film contains chromate and silica sol, it has better corrosion resistance than one that does not contain them. Furthermore, since the resin film contains a solid lubricant, it has excellent lubricity, and even when subjected to roll ohming or press working, the resin film will not be damaged or peeled off.

[Brief explanation of the drawing]

The attached drawing is a graph showing the relationship between the solid lubricant content of the resin film and the coefficient of dynamic friction in the surface-treated steel sheet of the present invention.

Claims (12)

[Claims] (1) On the surface of the steel plate (A) General formula CH_2=CR_1-
COOR_2 (in the formula, R_1 is H, CH_3, R_2 is C
1 to 95% by weight of one or more monomers represented by 1 to 8 alkyl groups), 3 to 20% by weight of (B) α,β unsaturated carboxylic acid monomer, and (C ) 0 to 50% by weight of a monomer copolymerizable with these monomers [However, (A),
The total of (B) and (C) is 100% by weight] A copolymer resin film with an acid value of 10 to 200 per solid content obtained by emulsion polymerization, with chromate, silica sol and solid lubricant in the resin film. A surface-treated steel sheet with excellent corrosion resistance and lubricity, characterized in that it contains a chemical agent. (2) The resin film contains 3 parts of solid lubricant per 100 parts by weight of resin.
The surface-treated steel sheet with excellent corrosion resistance and lubricity according to claim 1, characterized in that the content is 10 parts by weight. (3) The surface-treated steel sheet with excellent corrosion resistance and lubricity according to claim 1, wherein the solid lubricant is graphite. (4) The surface-treated steel sheet with excellent corrosion resistance and lubricity according to claim 1, wherein the solid lubricant is molybdenum disulfide. (5) The surface-treated steel sheet with excellent corrosion resistance and lubricity according to claim 1, wherein the solid lubricant is a mixture of graphite and molybdenum disulfide. (6) The surface-treated steel sheet with excellent corrosion resistance and lubricity according to claim 1, wherein the solid lubricant has an average particle size of 0.3 to 1.0 μm. (7) A chromate film is formed on the surface of the steel plate, and on the chromate film (A) general formula CH_2=CR_1-COOR_2 (in the formula, R_1 is H,
CH_3, R_2 is an alkyl group having 1 to 8 carbon atoms) and 1 to 95% by weight of one or more monomers represented by (B
) 3 to 20% by weight of α, β unsaturated carboxylic acid monomer, (
C) 0 to 50% by weight of a monomer copolymerizable with these monomers [however, the total of (A), (B) and (C) is 10% by weight]
0% by weight] Acid value per solid content obtained by emulsion polymerization: 10
A surface-treated steel sheet having excellent corrosion resistance and lubricity, characterized in that a copolymer resin film containing chromate, silica sol, and a solid lubricant is formed in the resin film. (8) The resin film absorbs solid lubricant at 3 parts by weight per 100 parts by weight of resin.
The surface-treated steel sheet with excellent corrosion resistance and lubricity according to claim 7, characterized in that the content is 10 parts by weight. (9) The surface-treated steel sheet with excellent corrosion resistance and lubricity according to claim 7, wherein the solid lubricant is graphite. (10) The surface-treated steel sheet with excellent corrosion resistance and lubricity according to claim 7, wherein the solid lubricant is molybdenum disulfide. (11) The surface-treated steel sheet with excellent corrosion resistance and lubricity according to claim 7, wherein the solid lubricant is a mixture of graphite and molybdenum disulfide. (12) The surface-treated steel sheet with excellent corrosion resistance and lubricity according to claim 7, wherein the solid lubricant has an average particle size of 0.3 to 1.0 μm.