KR20010057540A - A coating type chromate-resin liquids with excellent weldability and anti-finger property and a method for manufacturing anti-finger printed sheets using it - Google Patents

Abstract

PURPOSE: A coating type chromate-resin solution is provided which not only has stability (storage property) of a resin solution for a finger printing resistant steel sheet but also forms a chromium-resin mixed film after coating the solution on the steel sheet, and a method is provided to secure weldability and finger printing resistance of the steel sheet using the resin solution. CONSTITUTION: The coating type chromate-resin solution having superior weldability and finger printing resistance comprises a main solvent resin in which 40 to 50 wt.% of butylacrylate, 40 to 49 wt.% of methylmethacrylate and 1 to 20 wt.% of methacrylic acid are polymerized and an average particle size is 0.05 to 0.1 microns; colloidal silica coated with alumina in which a weight ratio of the main solvent resin to silica is 4:6 to 1.5:8.5; chromium aqueous solution in which a constituent ratio of trivalent chromium in 10 to 30 g/l of chromium constituent is 0.3 to 0.5 based on the total volume of chromium aqueous solution; and 0.5 to 5 g/l of N-β(aminoethyl)γ-aminopropyl trimethoxysilane coupling agent based on the total volume of chromate-resin solution. The method comprises the steps of preparing the coating type chromate-resin solution by adding a main solvent resin to a mixed solution of alumina coated colloidal silica, chromium aqueous solution and silane coupling agent; coating the chromate-resin solution on both sides of a steel sheet to be plated; and forming a chromium-resin mixed film layer comprising 30 to 50 mg/m2 and 400 to 700 mg/m2 on the steel sheet by bake drying the steel sheet at a temperature of 140 to 150 deg.C.

Description

A coating type chromate-resin solution excellent in weldability and fingerprint resistance and a method for producing a fingerprint-resistant steel sheet using the same

The present invention relates to a coated chromate-resin solution excellent in weldability and anti-fingerprint, and a method for producing a steel strip using the same, and more particularly, to a coated chromate-resin mixed solution for producing a chromium-resin mixed film and The present invention relates to a method for producing a steel sheet excellent in surface appearance, corrosion resistance, chemical resistance and water resistance, as well as weldability and fingerprint resistance.

Electro-galvanized steel sheet is widely used for home appliances and various other applications because of securing uniform coating amount, adhesion with base iron and excellent surface appearance. In general, electro-galvanized steel sheet is demanded into the processing process and processed according to the use of the product. However, the demand can easily be contaminated on the surface of the steel sheet due to organic substances or fingerprints in the workplace in the treatment process, the contaminated portion has a problem affecting the corrosion resistance and paintability of the steel sheet.

In order to prevent this in advance, an anti-fingerprint steel plate for treating chromate of a thin film on an electrogalvanized steel sheet, followed by a resin coating process, has been developed and is now commercially available.

Anti-fingerprint steel plate is largely divided into household appliances, special applications (for deep processing used in motors, etc.), and is divided into applications and produced by chromate treatment and resin coating treatment.

However, the anti-fingerprint steel plate is highly leached due to zinc corrosion in a wet environment, and the surface is easily contaminated by organic materials such as fingerprints during processing, so that the colloidal material and an aqueous solution of chromium ion added with an emulsion resin are used. The solution using was apply | coated.

Such steel sheet is excellent in corrosion resistance and rubbing resistance, but when it is used in the parts requiring processing and welding such as copiers or computer shells, a large amount of resin is contained in the coating, so welding using electric resistance such as electric spot and welding In this case, there is a problem that the weld is burned black and the appearance around the weld is poor.

Such proposals include Japanese Patent Publication Nos. 92-8224, 88-96277, and 88-96276, which propose a method of forming a coated chromate coating in which a chromate treatment solution is applied to a steel sheet surface and then immediately dried without washing with water. have. In this method, a solution in which a resin and a silica oxide are added to the chromate solution is used.

Since the film formed as described above contains a resin and a silicon oxide, a thicker film is formed at the same amount of chromium as compared with the conventional reactive chromate film, and thus the plating layer protection effect by the chromate film is improved to improve corrosion resistance and fingerprint resistance.

However, there is a problem in that the appearance of the weld is poor, as well as when the bonding strength is weak between the chromium oxides or between the resin and the chromium oxide or the silica, chemical resistance, chromium or resin components are dissolved in the subsequent degreasing or washing process. There is a problem in that the quality of the steel sheet is not only deteriorated by deteriorating the coating properties, but also has to undergo an additional wastewater treatment process due to the dissolved chromium component.

Accordingly, an object of the present invention is to provide a coated chromate-resin solution which forms a chromium-resin mixed film after coating on a steel sheet together with stability (storability) of the resin solution for anti-finger steel sheet.

Another object of the present invention is to provide a method that can ensure the weldability and fingerprint of the steel sheet using the resin solution.

According to one aspect of the invention,

40-50% by weight of butyl acrylate; Methyl methacrylate 40-49 wt%; And 1 to 20% by weight of methacrylic acid, the main resin having an average particle size of 0.05 to 0.1 mu,

Colloidal silica coated with alumina having a weight ratio of the main resin to silica of 4: 6 to 1.5: 8.5;

An aqueous chromium solution having a component ratio of trivalent chromium in a chromium component of 10 to 30 g / l based on the total volume of the aqueous chromium solution of 0.3 to 0.5; And

A coated chromate-resin solution excellent in weldability and fingerprint resistance is provided, which comprises 0.5 to 5 g / L of N-β (aminoethyl) γ-aminopropyl trimethoxysilane coupling agent based on the total volume of the chromate-resin solution.

According to the second aspect of the present invention,

Preparing a coated chromate-resin solution of the first aspect by adding a main resin to a mixture of alumina-coated colloidal silica, an aqueous solution of chromium and a silane coupling agent;

Applying the chromate-resin solution to both sides of the steel plate to be plated; And

Method for producing a steel sheet comprising the fingerprint, forming a resin mixture coating layer - the steel sheet by baking treatment in 140~150 ℃ on a steel sheet with chromium 30~50mg / m ² and the resin 400~700mg / m ² chromium This is provided.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail.

The resin coating solution of the present invention includes a main resin selected from butyl acrylate resin, methyl methacrylate resin, methacrylic acid; Colloidal silica; Aqueous chromium solution; N-β (aminoethyl) γ-aminopropyl trimethoxysilane coupling agent as a main component, the upper layer of the coated steel sheet having a two-layer structure of the lower layer (metal plating layer)-upper layer (chromate + resin coating layer) on the cold-rolled steel sheet Apply.

Thus, the main resin of the resin coating solution apply | coated to the upper layer is a urethane type resin and acrylic resin which are used normally. The urethane-based resin is used when the processability is required, but the manufacturing cost is not only high, but also has a disadvantage in that the chemical resistance is poor due to the weak bonding strength with the base. Although the acrylic resin is inferior in processability to the urethane resin, it has an advantage of having excellent chemical resistance and excellent gloss since the bonding strength with the object is strong.

Among them, the resin used in the present invention is a water-soluble resin obtained by polymerizing butyl acrylate, methyl methacrylate resin, and methacrylic acid as a main raw material, and has an excellent bonding strength with the base material.

Butyl acrylate in the resin should be polymerized in an amount of 40 to 50% by weight, methyl methacrylate 40 to 49% by weight and methacrylic acid in an amount of 1 to 20% by weight. If the chemical property and surface appearance deteriorate and the above range is exceeded, the workability is extremely reduced, which is not preferable.

In addition, the average particle size of the polymerized resin should be 0.05 ~ 0.1μ, it is not preferable because the gloss and solution stability in the surface appearance is poor if out of this range.

In order to improve the weldability and conductivity of the film prepared in the main resin, colloidal silica is added in a weight ratio of 4: 6 to 1.5: 8.5. In this case, the colloidal silica is unstable in terms of solution stability when the colloidal particles are negatively charged, so that the colloidal particles are coated with alumina in consideration of solution stability so that the particles are positively charged.

When the colloidal silica is less than 6 weight ratio with respect to the resin, the amount of colloidal silica is less, so the surface appearance, in particular glossiness is poor, there is a problem that the burn occurs when welding, and if the weight ratio is more than 8.5 weight, the electrical conductivity and It is not preferable because weldability is improved while gloss resistance and fingerprint resistance deteriorate.

In addition, the chromium ions added to exert the anticorrosive effect of the chromate coating in the resin coating solution are dissolved after dissolving chromic anhydride in water and then used after controlling the ratio of chromium hexavalent ions to trivalent ions using a reducing agent. If the total chromium concentration in the resin coating solution is less than 10g / ℓ because the amount of the chromium compound in the coating applied on the steel sheet is too small, the corrosion resistance is not satisfactory, if the total chromium concentration is 30g / ℓ or more chromium compound in the coating Since this excess is added, the phenomenon of coloring to yellow occurs, which is undesirable in terms of surface appearance.

Among them, the corrosion resistance varies according to the ratio of chromium trivalent ions and hexavalent ions among the total chromium ions. The ratio of trivalent chromium to the total chromium constituents is 0.3 to 0.5, that is, 30 to 50% of the total chromium. The lower surface is preferable because it can satisfy both surface appearance and corrosion resistance. In this case, it is preferable to use ethylene glycol which can easily reduce chromium hexavalent ions even though a small amount is used as the reducing agent.

A silane coupling agent is added here in order to provide the bonding force of resin and a steel plate. In particular, it is more preferable to use N-β (aminoethyl) γ-aminopropyl trimethoxysilane coupling agent having solution stability and chemical resistance. The amount of use thereof is not preferable because the chemical resistance is lowered below 0.5g / ℓ, the improvement effect is insignificant above 5g / ℓ, while the manufacturing cost increases, which is not preferable.

Furthermore, 10-24 mL / l 2-propanol and / or polyethylene glycol- based on the total volume of the coated chromate-resin solution in order to improve the wettability and leveling with the base metal when coating the chromate coating solution. Co-polypropylene glycol (PEG-co-PPG) may optionally be added at 3-5 mL / L.

The coated chromate solution is preferably prepared by mixing alumina-coated colloidal silica, chromium solution and silane coupling agent and then adding a main resin, wherein 2-propanol and / or polyethylene glycol-co-polypropylene glycol It is preferable to add the silver main resin followed by addition.

The coated chromate solution prepared as described above is coated on both sides of the steel sheet to be plated, followed by baking at MT (steel sheet temperature) of 140 to 150 ° C. to prepare a steel sheet on which a chromium-resin mixed coating layer is formed.

At this time, the film hardening effect is less than 140 ℃ is not preferable, and in 150 ℃ or more chromium hexavalent ions are reduced in excess of chromium trivalent is not preferable in terms of corrosion resistance.

Also together chromium coating weight on the steel sheet is preferably in the ^{30~50mg / m 2, 30mg / m} 2 , so the lack of the amount of chromium poor corrosion resistance and, 50mg / m ² the corrosion resistance is further improved but the yellowness of the exterior surface is too There is a problem that must be painted in the future because it becomes large. The resin coating weight is 400~700mg / m ² together should preferably, 400mg / m ² or less in the undesirable and can not be secured to expertise in the film, the surface roughness large, in the 700mg / m ² or more adverse effect on the weldability due to irregularities It is not desirable because

According to the above, not only conductivity can be imparted by adding colloidal silica as the conductive material in the resin, but also corrosion resistance of the zinc steel sheet can be secured by forming a coating layer in which chromium and resin are mixed. The corrosion resistance, conductivity, and fingerprint resistance are improved because the anti-fingerprint is not secured, and the surface appearance is also improved. Therefore, a steel sheet having excellent weldability and surface appearance as well as general properties to be obtained as a fingerprint-finish steel sheet is obtained. You can get it.

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

<Example>

When 223 g of chromic anhydride is dissolved in 500 g of water, and 15 to 28 g of ethylene glycol is gradually added as a reducing agent, an exothermic reaction occurs to increase the temperature of the solution. The solution was cooled to obtain a chromium solution having a ratio of chromium trivalent to total chromium of 30 to 50%.

The high concentration chromium solution, N-β (aminoethyl) γ-aminopropyl trimethoxysilane coupling agent and 30% colloidal silica thus prepared were mixed in a 1 kg beaker at the amount shown in Table 1a, followed by butyl acrylate. , Water-soluble resins polymerized with methyl methacrylate and methacrylic acid were added in the particle sizes described in Table 1b.

Thereafter, polyethylene glycol-co-polypropylene glycol (PEG-co-PPG) and 2-propanol were added in the amounts shown in Table 1a, and the balance was filled with water to prepare a chromate-resin mixture coating solution.

division Butyl acrylate (% by weight) Methyl methacrylate (% by weight) Methacrylic acid (% by weight) Colloidal silica coated with alumina (g) Chromium solution (g / ℓ) Trivalent Chromium (%) N-β (aminoethyl) γ-aminopropyl trimethoxysilane (g / L) 2-propanol (ml / l) PEG-co-PPG (ml / l) Comparative Example 1 40 40 20 (O ₂ ^-, OH ^-) 220 86 30 3 15 4 Comparative Example 2 40 45 15 NH ₄ ⁺ 256 60 40 3 15 4 Comparative Example 3 50 40 10 Cl ^- 276 120 30 3 15 4 Comparative Example 4 40 50 10 Cl ^- 294 80 40 3 15 4 Comparative Example 5 45 45 10 Cl ^- 270 86 40 3 15 4 Comparative Example 6 48 48 4 Cl ^- 220 86 40 3 15 4 Comparative Example 7 45 45 10 Cl ^- 276 86 40 3 8 5 Comparative Example 8 43 43 14 Cl ^- 294 86 40 3 25 4 Comparative Example 9 43 43 14 Cl ^- 250 86 40 3 20 2 Comparative Example 10 43 43 14 Cl ^- 295 86 40 3 10 6 Inventive Example 1 40 40 20 Cl ^- 220 70 30 0.5 10 3 Inventive Example 2 50 48 One Cl ^- 300 80 40 One 24 5 Inventive Example 3 49 40 11 Cl ^- 256 86 50 3 17 4 Inventive Example 4 40 40 20 Cl ^- 294 90 30 5 13 5 Inventive Example 5 45 45 10 Cl ^- 276 75 40 3 20 3

Resin adhesion amount (mg / m ² ) Average particle size of the resin (μ) Comparative Example 1 500 0.1 Comparative Example 2 400 0.1 Comparative Example 3 700 0.1 Comparative Example 4 600 0.2 Comparative Example 5 900 0.05 Comparative Example 6 380 0.05 Comparative Example 7 700 0.05 Comparative Example 8 400 0.1 Comparative Example 9 450 0.05 Comparative Example 10 550 0.1 Inventive Example 1 400 0.05 Inventive Example 2 200 0.1 Inventive Example 3 500 0.1 Inventive Example 4 600 0.05 Inventive Example 5 450 0.1

The chromate-resin mixed coating solution thus prepared is coated on both sides of the galvanized steel sheet by a roll coating method, followed by baking to attach the resin with the resin adhesion amount shown in Table 1b. , Conductivity and surface appearance, and further evaluated the solution stability of the prepared solution and the results are shown in Table 2 below.

Corrosion resistance, anti-fingerprint, weldability, conductivity, surface appearance and solution stability were evaluated as follows.

(1) corrosion resistance

The prepared specimens were measured at 35 ° C. under a salt spray environment of 5% NaCl using ASTM G170 to measure the white rust development time of the planar site and the Ericsson 6 mm extrusion site.

(2) anti-fingerprint

Color difference values before and after applying white wasserine to the prepared specimens were measured.

(Circle): Fingerprint attachment is not visually recognized.

(Triangle | delta): Fingerprint attachment is visually discernible.

X: A fingerprint is distinguished clearly.

(3) weldability

Under the welding conditions of the pressing force of 250kgf and the energization time of 16 cycles, it was confirmed whether there was a burn trace around the nugget according to the welding current in the spot welder.

○: No trace of burnt around the nugget is observed by the naked eye.

(Triangle | delta): The trace of the burnt around a nugget is observed visually.

X: Spattering occurs during welding, and traces of burnt around the nugget are clearly observed.

(4) conductivity

Conductivity was measured using a surface resistor.

○: The electrical resistance of the coating is 1.5Ω or less

(Triangle | delta): The electrical resistance of a film is 1.5-5 ohms

X: The electrical resistance of the film is more than 5Ω

(5) Surface appearance (color and glossiness)

The surface appearance was evaluated using a color difference meter and gloss meter.

(Circle): It is bright and beautiful yellow.

(Triangle | delta): The light color was severely colored yellow, or there is no coloring of yellow at all.

X: Pinhole of a water droplet pattern generate | occur | produces or yellowness is severe.

(6) solution stability

The chromate coating solution was prepared and then left at 35 ° C. for 45 days and then evaluated by measuring the appearance and viscosity of the solution.

(Circle): When stored for 45 days, a viscosity and a solution state do not change.

X: When stored for 45 days, not only the viscosity changes but also the gelation of the solution is observed.

division Anti-fingerprint Surface appearance Corrosion Resistance (hours) conductivity Weldability Solution stability Comparative Example 1 ○ ○ 72 ○ ○ × Comparative Example 2 ○ △ 48 ○ ○ × Comparative Example 3 ○ △ 150 ○ ○ ○ Comparative Example 4 ○ △ 60 ○ ○ ○ Comparative Example 5 ○ ○ 100 △ × ○ Comparative Example 6 △ ○ 120 ○ ○ ○ Comparative Example 7 ○ × 78 ○ ○ ○ Comparative Example 8 ○ × 150 × × ○ Comparative Example 9 ○ × 72 ○ ○ ○ Comparative Example 10 ○ × 140 △ △ ○ Inventive Example 1 ○ ○ 110 ○ ○ ○ Inventive Example 2 ○ ○ 124 ○ ○ ○ Inventive Example 3 ○ ○ 144 ○ ○ ○ Inventive Example 4 ○ ○ 150 ○ ○ ○ Inventive Example 5 ○ ○ 144 ○ ○ ○

○: excellent, △: good, ×: defective

As shown in Tables 1 and 2, in Comparative Example 1, as a result of using a chromate coating liquid prepared using colloidal silica in which the counter ions of the colloidal silica were anions (O ^{2 −} , OH ⁻ ) in the solution component, In terms of stability, the chromium layer and the resin layer were separated with time, and gelling of the particles of the solution was observed.

In Comparative Example 2, as a result of using a chromate coating solution in which colloidal silica was stabilized with NH ₄ ⁺ ions, NH ₄ ⁺ ions were subsequently decomposed into NH ₃ and reacted with other components to stabilize the colloidal silica with cations. It was confirmed that the solution stability exhibited the same tendency as that of Comparative Example 1, but also the corrosion resistance was deteriorated because the adhesion amount of chromium in the rubbing film was 20 mg / m ² .

In Comparative Example 3, as a result of evaluating the to-coating film to which the chromium adhesion amount was attached at 60 mg / m ² , the yellowness value was too large and the surface appearance was not satisfactory.

In the comparative example 4, when the chromate coating liquid using the particle | grains whose average particle size of resin is 0.2-0.25 micrometer was used, the glossiness after a rubbing process was 10-15, and surface appearance was not satisfactory.

In Comparative Example 5, as a result of evaluating the anti-fingerprint film having the adhesion amount of the anti-fingerprint resin at 800 to 1000 mg / m ² , the electrical resistance of the film was low as 2 to 5 Ω, so that the conductivity was low. Could.

In Comparative Example 6, as a result of evaluating an anti-fingerprint film having a resin adhesion amount of 380 mg / m ² , the anti-fingerprint was poor enough that the fingerprint adhesion was visually discernible.

In Comparative Examples 7 to 10, 2-propanol or polyethylene glycol-co-polypropylene glycol was added, respectively. In Comparative Example 7, 2-propanol was used as 8 ml / L and Comparative Example 9 was used in polyethylene glycol-co- By adding polypropylene glycol in a small amount of 2 ml / L, it was observed that the wettability of the to-coating film was deteriorated and polka dot pinhole defects occurred.

Comparative Example 8 also added 2-propanol to 25 ml / l and Comparative Example 10 added an excess of polyethylene glycol-co-polypropylene glycol to 6 ml / l, resulting in thickening of the anti-fingerprint solution, resulting in a total viscosity of 20 cps. Since the coating solution is attracted to both edges during the fingerprint coating, it can be observed that it causes the color difference with the center.

In contrast, Inventive Examples 1 to 5, which were tested by the method of the present invention, were excellent in solution stability, anti-fingerprint, corrosion resistance, conductivity, and weldability, and a bright and beautiful surface appearance could be observed.

According to the above, by treating the chromium-resin mixed film on the steel sheet within the proper composition and conditions, it is possible to produce a steel plate excellent in solution stability, conductivity and surface appearance as well as weldability and fingerprinting.

Claims (4)

40-50% by weight of butyl acrylate; Methyl methacrylate 40-49 wt%; And 1 to 20% by weight of methacrylic acid, the main resin having an average particle size of 0.05 to 0.1 mu, Colloidal silica coated with alumina having a weight ratio of the main resin to silica of 4: 6 to 1.5: 8.5; An aqueous chromium solution having a component ratio of trivalent chromium in a chromium component of 10 to 30 g / l based on the total volume of the aqueous chromium solution of 0.3 to 0.5; And Applicable chromate-resin solution having excellent weldability and fingerprint resistance, comprising 0.5-5 g / l of N-β (aminoethyl) γ-aminopropyl trimethoxysilane coupling agent based on the total volume of the chromate-resin solution The solution of claim 1, wherein 10 to 24 mL / L 2-propanol and / or 3 to 5 mL / L polyethylene glycol-co-polypropylene glycol are added to the solution based on the total volume of the solution. Solution Preparing a coated chromate-resin solution of claim 1 by adding a main resin to a mixture of alumina-coated colloidal silica, an aqueous solution of chromium and a silane coupling agent; Applying the chromate-resin solution to both sides of the steel plate to be plated; And Anti-fingerprint steel sheet production process comprising the, forming a resin mixture coating layer - the steel sheet by baking treatment in 140~150 ℃ on a steel sheet with chromium 30~50mg / m ² and the resin 400~700mg / m ² chromium The method of claim 3, wherein the coated chromate-resin solution is prepared and then 10 to 24 ml / l 2-propanol and / or 3 to 5 ml / l polyethylene glycol-co-polypropylene glycol based on the total volume of the solution. Method for characterized in that the addition of