KR20030007985A - High-lubricant anti finger print steel sheet without chromate that is developed the deep drawing ability, the corrosion resistance in low temperature - Google Patents

Abstract

PURPOSE: A high lubrication chromium-free finger printing resistant steel sheet is provided which improves wettability with resin by treating the phosphate surface with weak acid (a mixture of hydrofluoric acid, nitric acid and hydrochloric acid) after improving corrosion resistance by micronizing the structure of a phosphate film through surface cleaning. CONSTITUTION: The high lubrication chromium-free finger printing resistant steel sheet is characterized in that it is manufactured by refining phosphate structure by adding chelate compound to the phosphate solution in surface treatment process for treating 1.0 to 2.5 g/m¬2 of phosphate solution onto electrogalvanized steel, increasing resin wettability by adding about 1.0 to 3.0 g/L of starch to the phosphate solution, etching the surface of the phosphate solution treated electrogalvanized steel with a weak acidic solution prepared by mixing one or more acids selected from the group consisting of hydrofluoric acid, nitric acid and hydrochloric acid, and baking the high lubrication finger printing resistant resin film to a drying temperature of 75 to 90 deg.C after coating a thin film of urethane modified acryl copolymer resin on the etched phosphate film coated electrogalvanized steel in a resin adherence amount of 800 to 1500 mm/m¬2, wherein the urethane modified acryl copolymer resin is prepared by synthesizing 2 to 40 wt.% of ethylenic unsaturated monomer enabling radical polymerization, 1 to 10 wt.% of urethane prepolymer which is chain extended to a low molecular compound having two or more active hydrogens obtained by reacting polyol with polyisocyanate, 4 to 15 wt.% of polypropylene based wax, 10 to 20 wt.% of silica, 2 to 10 wt.% of ethanol or isopropyl alcohol, 0.1 to 5 wt.% of a polymerization initiator for ethylenic monomer which is capable of radical polymerization and selected from t-butyl perbenzoate, lauryl perbenzoate, benzoyl peroxide, t-butylhydroperoxide, azobisisobutyronitrile and azobis dimethylbutyronitrile, and 2 to 15 wt.% of carbodiimide added to polymer for improving curing reaction.

Description

High-lubricant anti finger print steel sheet without chromate that is developed the deep drawing ability, the corrosion resistance in low temperature}

The present invention relates to a high lubricating chromium-free (Cr-free) steel plate without the chromate treatment step in the galvanized steel sheet, in particular high lubrication chromium-free (excellent workability, corrosion resistance and resin adhesion even without the chromate treatment) Cr-free) to a fingerprint steel plate.

Electro-galvanized steel sheet is widely used in interior and exterior materials of home appliances due to its beautiful surface appearance, and various post-treatment chemical treatments are performed on the galvanized steel sheet due to demand for high performance and high quality.

In the case of anti-fingerprint products, it is a resin treatment product on the surface of thin chromate treated products and phosphate treated products in order to prevent contamination by workers' hands or oil in various workplaces.

In the case of chromate-treated products, not only chromium-treated hexavalent chromium (Cr + 6) is generated as wastewater, but also wastes a lot of money and time for wastewater treatment. It is known to be.

In addition, the simple rubbing treatment on the surface of the phosphate treated product is poor quality in the corrosion resistance and resin adhesion portion, which appears to be deteriorated processability.

In the case of conventionally used resin, polyester wax or fluorine (PTFE) wax is added to the modified acrylic resin, and when epoxy is used as a curing agent, the workability is reduced and the resin film is destroyed. Quality in the market has become a complaint from demanders.

Therefore, the present inventors have conducted a number of studies and experiments to solve the above problems, and as a result it was found that the product produced according to the present invention can be produced superior to the conventional product quality characteristics. The present invention is basically a chromium (Cr) containing process that is subject to internationally regulated use of anti-fingerprint products, that is, away from the conventional method according to the chromate process treatment, instead of a chromate treatment in the lower surface through a surface adjustment process containing a chelating agent The purpose of this study is to improve the corrosion resistance by miniaturizing the phosphate coating structure and then to treat the phosphate surface with weak acid (hydrofluoric acid, nitric acid, hydrochloric acid mixture) in order to improve the adhesion with the resin. In addition, the present invention is a water dispersion in which the average particle diameter of the aqueous resin dispersion is 50 nm or less by dropping the ethylenically unsaturated monomer and urethane which can be radically polymerized with a homer mixer in order to improve the fingerprint processability and the process blackening property. After applying a thin film of a resin containing 2 to 15% by weight of carbodiimide as a curing agent to the urethane-modified acrylic copolymer resin, the temperature of the steel sheet was about 75 to 150 ° C., especially 75 to 90 ° C. It is an object of the present invention to provide a method for producing a high lubrication chromium free (Cr-free) or chromium-free steel sheet steel sheet in the range.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic diagram showing a cross section of a high lubricating chrome-free fingerprint steel plate film according to the present invention.

In order to achieve the above object, the present invention performs a phosphate treatment of a thin film of about 1.8 to 2.2 g / ㎡ on the surface of the galvanized steel sheet, and surface etching for about 1 to 3 seconds using a weak acid (hydrofluoric acid, nitric acid, hydrochloric acid mixture) After the polymerization, the ethylenically unsaturated monomer and urethane capable of radical polymerization were finely added dropwise with a Homer mixer, and the carbodiimide was used as a curing agent in the water-dispersed urethane-modified acrylic copolymer resin having an average particle diameter of 50 nm or less. Highly lubricated chromium with excellent processability and corrosion resistance by applying the resin to which 2 ~ 15% by weight of (Carbodiimide) is applied in a thin film, followed by baking in a temperature range of about 75 ~ 150 ℃, especially 75 ~ 90 ℃. It is possible to provide a free (Cr-free) to the steel sheet.

That is, the present invention promotes densification of phosphate tissue by adding a chelating compound to the surface treatment process in order to treat phosphate of 1.0 to 2.5 g / m 2 on the galvanized steel sheet, and to prepare starch component in the phosphate solution of 1.0 to 3.0. Ethylene unsaturated monomers capable of radical polymerization after adding about 1 g / l to increase resin adhesiveness and etching the surface for 1 to 3 seconds with a weakly acidic solution made by mixing two or more kinds of hydrofluoric acid, nitric acid and hydrochloric acid. 40 wt%, 1-10 wt% of urethane prepolymer chain-extended with low molecular weight compound having at least two active hydrogens obtained by reacting polyol and polyisocyanate, 4-15 wt% of polypropylene wax, 10 silica 20 wt%, 2-10 wt% ethanol or isopropyl alcohol, t-butylperbenzoate, lauryl perbenzoate, benzoyl peroxide, t-butylhydroperoxide, azobisisoisobutyrate as polymerization initiator 0.1-5% by weight relative to the ethylenic monomer capable of radical polymerization in thyronitrile and azobisdimethylbutyronitrile, and carbodiimide was synthesized by adding 2 to 15% by weight of carbodiimide to the polymer to improve the curing reaction. It relates to a high lubricating chromium-free to steel plate, characterized in that the resin coating amount coated with a urethane-modified acrylic copolymer resin thin film baking at a drying temperature range of 75 ~ 90 ℃.

Hereinafter, the present invention will be described in more detail.

First, the phosphate coating process will be described first. The surface adjustment is performed using a titanium colloidal component before the phosphate coating treatment in the present invention. Each component composition and working conditions are as shown in Tables 1 and 2 below.

Through the treatment process as shown in Table 1 and Table 2, a thin phosphate film of about 1.8 to 2.2 g / m 2 was formed on the surface of the galvanized steel sheet, resulting in a whiteness (L value) of 72 to 76 and chroma. Secure a value between -2.0 and 3.2 and b value between -1.0 and 2.3. In particular, horizontal spray nozzle method using special nozzle and bar to maximize counter flow effect in order to secure uniform surface appearance and to make film structure finer and uniform. phosphate treatment by a nozzle type).

The higher the phosphate coating amount, the lower the processability due to the destruction of the phosphate layer during processing after resin application, and thus, about 1500 to 2500 ppm of starch, an organic additive, is added to ensure a uniform coating amount regardless of the reaction time. Could. If the amount of starch exceeds the existing amount, the paintability is improved, but it is important to add an appropriate amount because it shows poor performance in corrosion resistance.

On the other hand, by adding a chelating agent in the surface treatment step before the phosphate treatment step to improve the corrosion resistance through the densification of the phosphate tissue. After performing the above phosphate coating process, the etching process is performed to replace the existing Cr coating process in order to secure the resin adhesion as the anti-fingerprint treatment.The liquid composition method and working method are shown in (Table 3) and same.

Same as Table 3 Etching process is replaced by Cr coating process, and then the ethylenically unsaturated monomer and urethane which can be radically polymerized are added dropwise with a homer mixer to make the average particle diameter of the aqueous resin dispersion less than 50 nm. High lubricity with excellent workability and corrosion resistance when the resin is added to the urethane-modified acrylic copolymer resin with a thin film of resin containing 2 to 15% by weight of carbodiimide as a curing agent. High-lubrication chromium-free (Cr-free) with excellent processability, corrosion resistance, and resin adhesion by chrome-free resin coating and thin film coating about 800 ~ 1500mg / ㎡ and baking at 75 ~ 90 ℃. Fingerprint steel plate was produced.

In the case of anti-fingerprint resins, main resin and lubricating additives were tested to improve workability, blackening and corrosion resistance. Corrosion resistance is affected by the content of silica sol, and when it is lowered below the A range (some differences occur depending on the resin), the corrosion resistance is greatly decreased, and the corrosion resistance is gradually decreased above the range. The smaller the particle size of silica sol, the better the corrosion resistance.

In the case of processability, when PE-based wax is added as a lubricant for polyethylene-based resins, powdering resistance and LDH (Blank diameter / Punch diameter) values are excellent. ) In the case of main resin, PTFE modified PE wax as a lubricant showed excellent performance.

Melting point Tm (melting point) of the lubricant was higher than the mold temperature appeared to be good workability. Therefore, in the case of the high lubrication-fingerprint resin-added lubricant applied in the present invention, the friction coefficient at room temperature was selected as well as the friction coefficient at the processing temperature was small and the variation was small according to the temperature.

The choice of these lubricant additives affects the surface unevenness and surface gloss and the surface tension of the coating. In the case of the main resin used in the present invention, the surface tension during the addition of the lubricant was limited to 45 dyne / cm or less.

Hereinafter, the present invention will be described in more detail with reference to the following examples.

(Example)

The resin composition prepared by the method according to the present invention described above was prepared in a highly lubricated chromium-free to steel plate without chromate treatment on the galvanized steel sheet. Test values for the products are given in Table 4.

In the case of corrosion resistance evaluation, the area of white rust was investigated by the salt spray laboratory of 80mm ~ 150mm plate. The salt spray test conditions were 35 ℃, sodium chloride (NaCl) concentration 5%, saturated air temperature 47 ℃. Spray pressure was 1 kgf / cm 2.

In the case of the present invention, all of the values were less than the allowable lower limit of less than 5% in the corrosion resistance evaluation when viewed in 120 hours.

For workability (LDH), a die 120φ, a pressing force of 2.0 tons, and a drawing speed of 1.3 mm / sec were used by using a universal testing machine. The processability of the present invention also showed a very good value without chromate treatment.

The surface color difference was measured using a color difference meter of a tristimulus direct reading method. As shown in the above example, in the case of workability (LDH, mm), the resin itself was shown to be affected by the resin itself rather than by the anti-fingerprint treatment, and the main resin component was acrylic epoxy resin, PE wax and PTFE wax. When urethane and carbodiimide were added to ethylenically unsaturated monomers than those included The resin showed good results, and the corrosion resistance and other physical properties showed that the high lubrication chromium-free steel plate was equivalent or superior to that of the Cr-base treated product.

In the case of the surface appearance, urethane and carbodiimide were added to the ethylenically unsaturated monomer rather than the epoxy emulsion, PE wax and PTFE wax. The resin showed good results.

Therefore, in the present invention, the addition of a chelating compound in the surface adjustment process to improve the corrosion resistance through the refinement of the phosphate structure and to improve the resin adhesion through the etching process (urethane and carbodiimide is added to the ethylenically unsaturated monomer) Added By applying a resin, it is possible to develop a high lubrication chromium-free fingerprint steel sheet.

According to the method of the present invention as described above, after performing a phosphate treatment of a thin film of about 1.8 ~ 2.2g / ㎡ on the surface of the galvanized steel sheet, the surface using a weak acid (hydrofluoric acid, nitric acid, hydrochloric acid mixture) for about 1 to 3 seconds After etching, it is finely added dropwise with an ethylenically unsaturated monomer capable of radical polymerization and urethane and a home mixer, and the carbodiamide as a curing agent to the water-dispersed urethane-modified acrylic copolymer resin so that the average particle diameter of the aqueous resin dispersion is 50 nm or less. (Carbodiimide) 2-15% by weight of the resin was applied in a thin film, then the steel sheet temperature is baked at about 75 ~ 150 ℃ to obtain a high lubricating chromium-free steel plate excellent in workability and corrosion resistance Can be.

Claims (1)

A chelating compound is added to the surface treatment process for the phosphate treatment of 1.0-2.5 g / m 2 on the galvanized steel sheet to promote the densification of phosphate tissue, and 1.0-3.0 g / l of starch is added to the phosphate solution. To increase resin adhesion, and to etch the surface with a weak acid solution made by mixing one or two or more of hydrofluoric acid, nitric acid, and hydrochloric acid, and then 2 to 40 wt% of an ethylenically unsaturated monomer capable of radical polymerization, polyol and polyisocyanate. 1 to 10% by weight of a urethane prepolymer chain-extended with a low molecular weight compound having two or more active hydrogens obtained by the reaction, 4 to 15% by weight of polypropylene wax, 10 to 20% by weight of silica, ethanol or isopropyl 2-10 weights of alcohol, As a polymerization initiator, t-butylperbenzoate, lauryl perbenzoate, benzoyl peroxide, t-butyl hydroperoxide, azobisisobutyronitrile, azobisdi 0.1-5% by weight relative to the ethylenic monomer capable of radical polymerization in methylbutyronitrile, urethane-modified acrylic copolymer synthesized by adding 2-15% by weight of carbodiimide to the polymer to improve the curing reaction High lubricity chromium-free to steel plate, characterized in that the resin is applied by baking at a drying temperature range of 800 ~ 1500mg / ㎡, 75 ~ 90 ℃ coated with a resin thin film.