KR20160066129A - Coating Composition Having Superior Corrosion-Resistance After Bending and Coated Steel Sheet Using the Same - Google Patents

Abstract

The present invention relates to an organic/inorganic composite coating composition comprising, on the solid content basis: 20-60 wt% of an urethane-acrylic resin and nanosilicate-phenoxy resin; and an inorganic anti-erosive agent. The anti-erosive agent comprises: 7-33 wt% of an epoxy-based or amino-based silane (silane A); 24-57 wt% of a vinyl-based or acrylic silane (silane B); 3-11 wt% of vanadium phosphate; 0.1-1.4 wt% of Mg oxide; 2-10 wt% of zinc phosphate; 0.5-3.4 wt% of titanium carbonate; 0.5-4 wt% of zirconium oxide; and 0.4-3 wt% of silica. When the coating composition is used to form a coating layer on a zinc-plated steel sheet, it is possible to significantly improve the erosion-resistance of the planar portion and bending processed portion of a steel sheet.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating composition having excellent corrosion resistance after bending and a coated steel plate using the same.

The present invention relates to a coating composition excellent in corrosion resistance and a coated steel sheet using the coating composition.

In order to impart corrosion resistance and paint adhesion to galvanized steel sheets, zinc-base alloy coated steel sheets, aluminum-plated steel sheets, aluminum-based alloy coated steel sheets, cold-rolled steel sheets and hot-rolled steel sheets used for automobile materials, And a chromate film containing chromium as a main component is coated on the substrate.

The main chromate treatment includes an electrolytic chromate and a coating type chromate. Of these electrolytic chromate treatments, hexavalent chromium is the main component. In addition, a treatment liquid containing various anions such as sulfuric acid, phosphoric acid, boric acid, Is conducted to the cathode. On the other hand, in the coating type chromate treatment, inorganic colloid and inorganic ion are added to a solution in which a part of hexavalent chromium is reduced in advance in advance to prepare a treatment solution, and then a metal plate is immersed in the treatment solution, Method.

When these methods are used, various measures are required in the working environment and drainage treatment due to the toxicity of hexavalent chromium contained in the chromate treatment liquid. In the case of recycling and disposal of automobiles, household appliances, and building materials using the surface- Causing human and environmental pollution problems.

Accordingly, steel makers are focusing on the development of surface-treated steel plates that do not contain hexavalent chromium and have corrosion resistance and other effects. In addition, the price of zinc, which is the main material of the plated steel sheet plating layer, is rapidly increasing. Therefore, researches for replacing zinc with other elements, reducing the content of zinc, or reducing the amount of plating deposit are continuing.

As a typical technique, Zinc Aluminum-Magnesium (ZAM) is a method for using a small amount of zinc as a substitute material and using aluminum or magnesium, which is a common metal, as a main component of the plating layer. In the case of such an alloy-coated steel sheet, although corrosion resistance above a certain level can be secured, there is a problem that heat resistance, surface appearance, high temperature and high humidity resistance and weldability are heated.

As another method, a technique for reducing the amount of plating on the plated steel sheet has been proposed. However, the plating adhesion amount is a factor that greatly affects the corrosion prevention of the metal and the long-term rust-preventive property. As the adhesion amount of the plating increases, the time required for the occurrence of redness increases, that is, the corrosion resistance increases. Therefore, the zinc plating deposit amount can not be reduced due to the problem of corrosion resistance which occurs quickly.

Therefore, research is needed to reduce the amount of zinc plating, and to compensate for corrosion resistance without using chromium-containing solutions.

An inorganic or organic composite coating composition is used to form an inorganic or organic composite coating layer on the surface of a galvanized steel sheet to greatly improve the corrosion resistance of a steel plate and a processed portion after bending.

According to one embodiment of the present invention, there is provided a composition comprising, on a solids basis, 20 to 60% by weight of a urethane-acrylic resin and a nanosilicate-phenoxy resin; Wherein the inorganic anticorrosive agent comprises 7 to 33% by weight of silane A which is an epoxy or amino silane, 24 to 57% by weight of vinyl silane or silane B which is an acrylic silane, 3 to 11% by weight of vanadium phosphate, 0.1 to 1.4% by weight of Mg oxide, 2 to 10% by weight of zinc phosphate, 0.5 to 3.4% by weight of titanium carbonate, 0.5 to 4% by weight of zirconium oxide and 0.4 to 3% by weight of silica.

The inorganic corrosion inhibitor may be 40 to 80% by weight.

The content of the urethane-acrylic resin may be from 12 to 30% by weight, and the content of the nano-silicate-phenoxy resin may be from 8 to 30% by weight based on the solid composition.

The weight average molecular weight (Mw) of the urethane-acrylic resin or the nano-silicate-phenoxy resin may be 40,000 to 90,000.

The urethane-acrylic resin may be synthesized using 2-hydroxyethyl methacrylate, acrylamide or acrylic monomer which is a compound of these.

The acrylic monomer may have a content of 2 to 5 wt% with respect to the urethane-acrylic resin.

The urethane-acrylic resin may have an equivalent ratio of NCO / OH of 1 to 3.

The nano-silicate-phenoxy resin may be synthesized using one or more alkyl substituted phenol monomers selected from 4-ethyl phenol, 2,6-dimethyl phenol, 2-ethyl phenol and 2-isopropyl phenol.

The nano-silicate-phenoxy resin may include nano-silicate in an amount of 1 to 5 wt% based on 100 wt% of the nano-silicate-phenoxy resin.

The nanosilicate-phenoxy resin may comprise a nanosilicate having a particle size of 20 nm or less.

The nanosilicate-phenoxy resin may comprise one nanosilicate selected from calcium silicate, lithium silicate and ammonium hexafluorosilicate.

The silane A may be at least one selected from an epoxy silane and an amino silane.

The epoxy silane may be gamma glycidoxypropyltriethoxysilane and gamma glycidoxypropyltrimethoxysilane.

The amino-based silane may be gammaaminopropyltriethoxysilane and gammaaminopropyltrimethoxysilane.

The silane B may be at least one selected from vinyl silane and acrylic silane.

The organic-inorganic hybrid coating composition may further include a lubricant in an amount of 0.3 to 2 parts by weight based on 100 parts by weight of solid content.

The lubricant may be at least one wax selected from paraffin wax, olefin wax, carnauba wax, polyester wax, polyethylen wax, polypropylene wax, polyethylene-Teflon modified wax, and polytetrap wax have.

The wax may have a particle size of 0.5 to 5 mu m.

The inorganic corrosion inhibitor may further comprise thio-urea, and the content of thio-urea relative to the inorganic corrosion inhibitor may be 0.5 to 7 wt%.

According to another embodiment of the present invention, A zinc-based plated layer formed on one side or both sides of the base steel sheet; And a coating layer formed on the plating layer, wherein the coating layer is a cured product of the organic / inorganic composite coating composition.

The coating amount of the coating layer may be 0.5 to 2 g / m < 2 > based on one side of the steel sheet.

When the coating layer is formed on the surface of the galvanized steel sheet by using the inorganic or organic composite coating composition, the present invention has the effect of significantly improving the corrosion resistance of the flat plate portion of the steel sheet and the processed portion after bending.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view of a method for securing plate corrosion resistance of a coated steel sheet according to an embodiment of the present invention. FIG.
Fig. 2 is a photo of corrosion resistance evaluation after the bending of the coated steel sheet of Inventive Example 27. Fig.
3 is a photograph showing the corrosion resistance of the coated steel sheet of Comparative Example 23 after bending.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. However, the embodiments of the present invention can be modified into various other forms, and the scope of the present invention is not limited to the embodiments described below.

The inventors of the present invention have conducted extensive studies for securing the corrosion resistance of a coated steel sheet and have found that the use of a binder resin capable of maximizing the barrier effect of an organic system and the effect of an inorganic rust inhibitor and maximizing the acceptance of an inorganic corrosion- The optimal combination was derived. As a result, it has been recognized that the corrosion resistance of the flat plate portion and the bending portion can be secured by reducing the amount of the zinc plating layer adhered to the steel plate and forming the inorganic or organic composite coating layer on one or both surfaces of the steel sheet.

(A) and (b) of FIG. 1 is a schematic view of the plate corrosion resistance ensure Method of coating a steel sheet, the silane A, Silane B, and vanadium force fades (V-PO ₄₎ contained in the coating layer as shown in the schematic diagram Act as barriers to corrosion factors, and inorganic corrosion inhibitors such as silica, titanium-carbonate, zirconium oxide, Mg oxide and zinc phosphate play a role of corrosion inhibition (corrosion retardation).

The silane A and silane B contained in the coating layer are distributed throughout the coating layer and can act to protect the corrosion factor. Further, silane A and silane B can maintain the barrier effect while maintaining the hydrophobicity of the coating layer not only at the uppermost portion of the coating layer but also at the intermediate layer

On the other hand, the corrosion factors penetrate the barrier and reach the final layer, vanadium phosphate. In the case of the vanadium phosphate layer, it reacts with the zinc layer to form a phosphate layer, thereby acting as a final anti-corrosion barrier in the coating layer. However, after a certain period of time, the vanadium phosphate layer may be attacked by corrosive factors and white rust may be generated in the zinc layer.

As a rust inhibitor, silica, titanium-carbonate, zirconium oxide, etc. react with corrosive factors penetrated into the coating layer to form a more stable compound, thereby inhibiting the addition of zinc to the zinc layer.

According to one embodiment of the present invention, the organic / inorganic composite coating composition comprises, on a solid basis, 20 to 60 wt% of a urethane-acrylic resin and a nanosilicate-phenoxy resin; Wherein the inorganic anticorrosive comprises 7 to 33% by weight of silane A, which is an epoxy silane or amino silane, 24 to 57% by weight of vinyl silane or silane B which is an acrylic silane, 3 to 11% by weight of vanadium phosphate 0.1 to 1.4% by weight of Mg oxide, 2 to 10% by weight of zinc phosphate, 0.5 to 3.4% by weight of titanium carbonate, 0.5 to 4% by weight of zirconium oxide and 0.4 to 3% by weight of silica.

The inorganic anticorrosive agent may be contained in an amount of 40 to 80% by weight based on the total composition. When the content of the inorganic anticorrosive agent is less than 40% by weight, it is difficult to secure the effect of corrosion resistance. When the content of the inorganic anticorrosive agent is more than 80% by weight, the effect of improving the physical properties by injection is insignificant.

The urethane-acrylic resin and the nano-silicate-phenoxy resin as the organic resin serve as a binder resin, and can contain a large amount of an inorganic corrosion inhibitor for securing corrosion resistance. The content of the urethane-acrylic resin and the nano-silicate-phenoxy resin is preferably 20 to 60% by weight with respect to the entire composition based on the solid content. When the content is less than 20% by weight, the corrosion resistance, If it is more than 60% by weight, the effect of improving the physical properties by the addition is insignificant, which is uneconomical.

In order to synthesize the urethane-acrylic resin, an urethane dispersion containing an acrylic monomer in the core can be synthesized by first introducing an acrylic monomer into the urethane resin. Then, an urethane-acrylic resin can be synthesized by adding an initiator of an acrylic monomer and further performing polymerization reaction at a temperature of 75 to 90 캜 for 6 hours.

Since the urethane-acrylic resin serves as a dispersant in which the urethane resin disperses the acrylic resin without the emulsifier, a resin having relatively excellent corrosion resistance can be obtained. The content of the urethane-acrylic resin is preferably 12 to 30% by weight, and if it is less than 12% by weight, it is difficult to ensure corrosion resistance and solvent resistance. If it is more than 36% by weight, the effect of improving the physical properties is insufficient.

The acrylic monomer may be 2-hydroxyethyl methacrylate, acrylamide or a compound thereof. Also, the acrylic monomer is not a urethane-acrylic resin which is mixed simply by reacting with residual isocyanate contained in the urethane resin, but a urethane-acrylic resin is crosslinked with a urethane or urea bond to form a urethane- Can be obtained.

The content of the acrylic monomer is preferably 2 to 5% by weight, and if the content is less than 2% by weight, the amount of the monomer reacting with the residual isocyanate is small and the degree of crosslinking of the urethane- The effect of the urethane reaction of the acrylic monomer and the isocyanate becomes insignificant, which is uneconomical.

In order to secure the hardness of the resin by controlling the composition ratio of the isocyanate constituting the hard segment, the equivalent ratio (NCO / OH equivalent ratio) of the NCO group and the OH group during the polymerization of the urethane-acrylic resin is 1 to 3 . When the value of the equivalence ratio of NCO / OH is less than 1, the process blackening property is weakened. When the value of the equivalence ratio is more than 3, the solution stability and corrosion resistance are poor. Further, in order to secure such an effect, the value of the NCO / OH equivalence ratio is more preferably controlled to 1.3 to 1.9, and most preferably to 1.6.

The nano-silicate-phenoxy resin is a resin prepared by adding a nano-silicate anticorrosion agent in the process of synthesizing a phenoxy resin, and can improve the corrosion resistance, the processing blackness, and the chemical resistance of the coated steel sheet.

The content of the nano-silicate-phenoxy resin is preferably 8 to 30% by weight. When the content is less than 8% by weight, it is difficult to secure corrosion resistance and in-process blackening. If the content is more than 30% by weight, Is not economical.

Unlike general phenoxy resins, the monomers used for the synthesis of the phenoxy resins may be alkyl-substituted phenols for improving the crosslinking of the resin and improving the physical properties. Examples of the alkyl-substituted phenol monomers include 4-ethylphenol, 2,6-dimethylphenol, 2-ethylphenol and 2-isopropylphenol (2 -isopropylphenol). < / RTI >

The crosslinking agent is preferably hexamethylenetetramine, and the silicate is preferably added together with the crosslinking agent in an amount of 10 to 50% by weight based on the crosslinking agent. At this time, the particle size of the nanosilicate is preferably 20 nm or less, more preferably 10 to 20 nm. When the particle size is limited, it is possible to increase the density of the resin coating to improve the adhesion of the coating film during bending or the like.

On the other hand, the nanosilicate may be one selected from calcium silicate, lithium silicate, and ammonium hexafluoro silicate.

In addition, the nano-silicate-phenoxy resin preferably contains 1 to 5% by weight of nano-silicate in 100% by weight of the resin. If the content of the nano-silicate is less than 1% by weight, the effect of the corrosion-resistant agent is difficult to exhibit. If the content of the nano-silicate is more than 5% by weight, the improvement of the effect is small.

The lower the weight-average molecular weight (Mw) of the urethane-acrylic resin or the nano-silicate-phenoxy resin is, the lower the viscosity of the liquid. When additives such as external additives and solvents are added, the solution stability is poor. It can fall. On the other hand, as the weight average molecular weight increases, physical properties such as adhesion and corrosion resistance are excellent, and even when bending or stretching, the coating film is less likely to fall off and exhibits excellent physical properties. Therefore, weight average molecular weight control of the resin is important.

Accordingly, the weight average molecular weight (Mw) of the urethane-acrylic resin or the nano-silicate-phenoxy resin is preferably 40,000 to 90,000. If the weight average molecular weight is less than 40,000, the inorganic corrosion resistance may be precipitated. If the weight average molecular weight exceeds 90000, the corrosion resistance may be deteriorated.

The silane compounds are generally vinyl, epoxy, chloro, amino, acrylic, and the like. The silane A in the present invention is preferably at least one selected from epoxy-based and amino-based silane. The epoxy-based silane may be gamma glycidoxypropyl triethoxysilane and gamma glycidoxypropyl trimethoxysilane. Meanwhile,

The amino-based silane may be gamma aminopropyl triethoxysilane, gamma aminopropyl trimethoxysilane, or the like.

The content of the silane A is preferably 7 to 33% by weight. When the content is less than 7% by weight, the solvent resistance and the water repellency of the coating layer are poor and it is difficult to effectively block corrosive factors by securing sufficient hydrophobic groups. , The solution stability may be deteriorated and the effect of improving the corrosion resistance due to the increase of the content is insignificant, which is uneconomical.

The silane B may be at least one selected from vinyl silane and acrylic silane, and the corrosion resistance of the steel sheet after processing can be maximized by including it in the coating solution composition. The content of the silane B is preferably 24 to 57% by weight. When the content is less than 24% by weight, the effect of corrosion resistance is poor. When the content is more than 57% by weight, the solution stability is lowered. to be. On the other hand, the silane B may be at least one selected from vinyl silane and acrylic silane.

The vanadium phosphate has an effect of improving corrosion resistance, and the content of vanadium phosphate is preferably 3 to 11 wt%. When the content is less than 3% by weight, the corrosion resistance is poor. When the content is more than 11% by weight, the appearance of the steel sheet may be blackened in a high temperature and high humidity atmosphere.

The Mg oxide can be used by dissolving it in an aqueous solution of vanadium phosphate, and thus the effect of improving the corrosion resistance can be exhibited. The content of the Mg oxide is preferably 0.1 to 1.4% by weight. If the content is less than 0.1% by weight, it is difficult to secure the corrosion resistance effect. If the content is more than 1.4% by weight, the stability of the solution may be deteriorated.

The zinc phosphate is included as an auxiliary additive for improving the corrosion resistance, and the content of zinc phosphate is preferably 2 to 10% by weight. When the content is less than 2% by weight, it is difficult to secure the corrosion resistance effect. When the content is more than 10% by weight, the solution stability is lowered and the effect of improving the physical properties with respect to the amount of injection is not significant.

The titanium carbonate is included for the stability of the coating solution and the reactivity of the base steel sheet and the coating solution, and can serve as a coupling agent between the resin and the inorganic material. The content of the titanium carbonate is preferably 0.5 to 3.4% by weight. If the content is less than 0.5% by weight, it is difficult to secure corrosion resistance. If the content is more than 3.4% by weight, the effect of improving the corrosion resistance is small.

The content of zirconium oxide to improve the corrosion resistance is preferably 0.5 to 4% by weight. When the content of zirconium oxide is less than 0.5 wt%, it is difficult to ensure corrosion resistance. When the content of zirconium oxide is more than 4 wt%, the effect of improving the corrosion resistance is small.

The silica is included to improve the corrosion resistance, and mainly colloidal silica can be used. The content of the silica is preferably in the range of 0.4 to 3% by weight, and if it is less than 0.4% by weight, it is difficult to secure the corrosion resistance. If the amount is more than 3% by weight, the stability of the solution may be deteriorated.

The coating solution composition may further include a lubricant which improves the workability of the coated steel sheet to improve corrosion resistance after processing. The type of the lubricant is not particularly limited and may be selected from the group consisting of paraffin wax, olefin wax, carnauba wax, polyester wax, polyethylen wax, polypropylene wax, polyethylene-Teflon modified wax and polytephen wax One or more selected waxes may be used.

Further, it is preferable that the particle size of the solid wax is limited to 0.5 to 5 占 퐉 so that the lubricant can be easily liquefied at a set curing temperature. If the particle size is less than 0.5 탆, the lubricating effect by the wax particles is deteriorated. If the particle size exceeds 5 탆, lubrication of the lubricant during curing of the coating layer becomes difficult.

The amount of the lubricant may be 0.3 to 2 parts by weight based on 100 parts by weight of the solid composition. If the content is less than 0.3 parts by weight, the slip property may be insufficient, resulting in breakage of the surface treatment layer and the material during press working, resulting in deterioration in corrosion resistance after processing. If the content exceeds 2 parts by weight, stability of the solution itself is deteriorated, The corrosion resistance may be deteriorated due to the distribution of the particles.

The inorganic anticorrosive may further contain thio-urea. In the case of thio-urea, it may be used as a hardening accelerator in the present invention as an organic compound used for preparing resins, medicines and the like. The content of the thio-urea may be 0.5 to 7% by weight based on the inorganic corrosion inhibitor. If the content of the thio-urea is less than 0.5% by weight, the effect of promoting hardening is hardly exhibited. If the content is more than 7% by weight, There is an effect of shortening the time, but the solution stability is reduced.

Since the coating layer is formed on one side or both sides of the steel sheet to be described later by using the coating solution having the above composition, the corrosion resistance after the flat plate portion and the bending process of the steel sheet can be maximized.

According to another embodiment of the present invention, the organic-inorganic composite coated steel sheet includes a base steel sheet, a zinc-based plating layer formed on one side or both sides of the base steel sheet, and a coating layer formed on the zinc-based plating layer, And may be a cured product of the composite coating solution composition.

The coated steel sheet may include a coating layer formed on the zinc plated layer, and may be coated on one side or both sides of the zinc plated steel sheet using the coating solution described above. At this time, it is preferable to control the deposition amount of the coating layer to 0.5 to 2 g / m < 2 >. If the adhesion amount is less than 0.5 g / m 2, it is difficult to ensure corrosion resistance. If it exceeds 2 g / m 2, the conductivity of the coating layer is deteriorated.

[Example 1]

Coated on the surface of a hot-dip galvanized steel sheet having a zinc adhesion amount of 40 g / m < 2 > on the surface of the hot-dip galvanized steel sheet by the roll coating method and controlling the adhesion amount to 0.8 g / And heated to 140 캜 to form a coating layer.

The solution stability of each coating solution prepared in the composition shown in the following Table 1 was evaluated, and the corrosion resistance and black weathering of the coated steel sheet coated with the coating solution were evaluated.

≪ Evaluation of solution stability &

The stability of the solution was judged to be defective (X) when the viscosity of the coating solution increased by 20% or more from the initial stage or when the solution was precipitated, decomposed and gelated as a result of visual observation.

≪ Evaluation of plate corrosion resistance &

The plate corrosion resistance was evaluated by measuring the time required for 5% of white rust to occur in the condition of salt concentration 5%, temperature 35 ℃, and spray pressure 1 kg / cm ² . The evaluation criteria of the plate corrosion resistance were evaluated as follows based on 120 hours.

○: 120 hours or more X: 120 hours or less

≪ Evaluation of Dark Metamorphism &

The chromaticity evaluation was carried out by measuring the color difference (delta E) before and after holding the coated steel sheet for 120 hours in a thermo-hygrostat at a temperature of 50 ° C and a relative humidity of 95%, and based on the required chromium-free coated steel sheet of 2.0 And evaluated as follows.

O: 2.0 or less X: exceed 2.0

division Coating solution (% by weight) Quality characteristics V-PO ₄ MgO Silane
A Urethane-acrylic resin and nano-silicate-phenoxy resin Zinc phosphate TiCO ₃ ZrO Silly
Car Silane
B solution
stability Plate corrosion resistance Black degeneration Comparative Example 1 2.5 0.7 12 30 3 0.7 1.5 0.8 41 ○ X ○ Inventory 1 3.0 ○ ○ ○ Inventory 2 5 ○ ○ ○ Inventory 3 11 ○ ○ ○ Comparative Example 2 12 ○ ○ X Comparative Example 3 5 0.05 ○ X ○ Honorable 4 0.1 ○ ○ ○ Inventory 5 1.4 ○ ○ ○ Comparative Example 4 2.0 X ○ ○ Comparative Example 5 0.7 5 ○ X ○ Inventory 6 7 ○ ○ ○ Honorable 7 33 ○ ○ ○ Comparative Example 6 35 X ○ ○ Comparative Example 7 12 15 ○ ○ X Honors 8 20 ○ ○ ○ Proposition 9 60 ○ ○ ○ Comparative Example 8 70 ○ X ○ Comparative Example 9 30 1.5 ○ X ○ Inventory 10 2 ○ ○ ○ Exhibit 11 10 ○ ○ ○ Comparative Example 10 12 X ○ ○ Comparative Example 11 3 0.3 ○ X ○ Inventory 12 0.5 ○ ○ ○ Inventory 13 3.4 ○ ○ ○ Comparative Example 12 4.0 X ○ ○ Comparative Example 13 0.7 0.3 ○ X ○ Inventory 14 0.5 ○ ○ ○ Honorable Mention 15 4.0 ○ ○ ○ Comparative Example 14 4.5 X ○ ○ Comparative Example 15 1.5 0.2 ○ X ○ Inventory 16 0.4 ○ ○ ○ Inventory 17 3.0 ○ ○ ○ Comparative Example 16 3.5 X ○ ○ Comparative Example 17 0.8 20 ○ X ○ Inventory 18 24 ○ ○ ○ Evidence 19 57 ○ ○ ○ Comparative Example 18 60 X ○ ○

In Comparative Example 1, since the content of vanadium phosphide is lower than the range controlled by the present invention, the zinc phosphate layer which inhibits permeation of corrosion factor is insufficient and the corrosion resistance is lowered.

In Comparative Example 2, since the content of vanadium phosphide was higher than the range controlled by the present invention, excessive etching occurred and the black discoloration was lowered.

In Comparative Example 3, since the content of Mg oxide was lower than the range controlled by the present invention, the corrosion inhibition was insufficient due to insufficient corrosion inhibiting effect through Mg hydrate formation.

In Comparative Example 4, since the content of Mg oxide was higher than the range controlled by the present invention, it was more than necessary in the solution and reacted with other corrosion-resistant additives, and the solution stability was lowered.

In Comparative Example 5, since the content of silane A was lower than the range controlled by the present invention, the crosslinking effect between the resin of the silane and the inorganic material was insufficient and the corrosion resistance was degraded.

In Comparative Example 6, since the content of silane A was higher than the range controlled by the present invention, solution stability was lowered due to exceeding the silane content stably dispersed in the solution.

In Comparative Example 7, since the content of the urethane-acrylic resin and the nano-silicate-phenoxy resin was lower than the range controlled by the present invention, the role of the binder resin was insufficient and penetration of moisture was easy in high temperature and high humidity atmosphere, .

In Comparative Example 8, the content of the urethane-acrylic resin and the nano-silicate-phenoxy resin was higher than the range controlled by the present invention, so that the content of the inorganic anticorrosive agent was decreased and the corrosion resistance was lowered.

In Comparative Example 9, since the content of zinc phosphate was lower than the range controlled by the present invention, the corrosion resistance of the steel sheet deteriorated due to the lack of a corrosion assistant role.

In Comparative Example 10, because the content of zinc phosphate was higher than the range controlled by the present invention, proper mixing and dispersion with other corrosion inhibitors were not achieved in the solution, and the solution stability was degraded.

In Comparative Example 11, since the content of the titanium carbonate was lower than the range controlled by the present invention, the crosslinking function with the resin was insufficient and the corrosion resistance was lowered.

In Comparative Example 12, since the content of titanium carbonate was higher than the range controlled by the present invention, proper mixing and dispersion with other corrosion inhibitors were not achieved in the solution, and the solution stability was degraded.

In Comparative Example 13, since the content of zirconium oxide was lower than the range controlled by the present invention, the corrosion resistance of the steel sheet was deteriorated due to insufficient anti-corrosive role.

In Comparative Example 14, since the content of zirconium oxide was higher than the range controlled by the present invention, proper mixing and dispersion with other corrosion inhibitors were not achieved and the solution stability was degraded.

In Comparative Example 15, since the content of silica was lower than the range controlled by the present invention, the bonding strength with the resin layer was decreased and the corrosion resistance was lowered.

In Comparative Example 16, since the content of silica was higher than the range controlled by the present invention, proper mixing and dispersion with other corrosion inhibitors were not achieved and the solution stability was degraded.

In Comparative Example 17, since the content of silane B was lower than the range controlled by the present invention, the bond with the organic and inorganic additives and the role of increasing the corrosion resistance were weakened, and the corrosion resistance of the steel sheet was lowered.

In Comparative Example 18, since the content of silane B was higher than the range controlled by the present invention, the solution stability was lowered and the corrosion resistance was decreased.

On the other hand, Examples 1 to 19, which satisfy the composition of the coating solution to be controlled according to the present invention, can be confirmed to be excellent in solution stability, corrosion resistance, solvent resistance and weathering resistance.

[Example 2]

The lubricant (PE-PTFE wax) contained in the coating solution of Example 18 was limited to the content or particle size listed in Tables 2 and 3. Thereafter, the coating solution was coated on a hot-dip galvanized steel sheet having a plating adhesion amount of 40 g / m 2 by a bar coating method, and then the hot-dip galvanized steel sheet was heated to a temperature of 140 ° C using an induction heater to form a coating layer Respectively.

The steel sheet thus prepared was evaluated for plate corrosion resistance, corrosion resistance after bending, and weather resistance, and the evaluation results are shown in FIGS. 2 and 3. The plate corrosion resistance and the black weatherability evaluation method are the same as those in Example 1, and the corrosion resistance evaluation method after bending is as follows.

≪ Evaluation of corrosion resistance after bending >

After the bending process, the specimens were pressed in the form of L-shaped and pressed at 90 kPa to a specimen size of 70 * 80 mm with a force of 30 kN. The evaluation criteria of the corrosion resistance after the bending process were evaluated as follows based on 24 hours.

○: 24 hours or more X: 24 hours or less

division Weight portion Plate corrosion resistance Corrosion resistance after bending Black degeneration Comparative Example 19 0.1 ○ X ○ Inventory 20 0.3 ○ ○ ○ Inventory 21 0.5 ○ ○ ○ Inventory 22 One ○ ○ ○ Comparative Example 20 3 ○ ○ X Comparative Example 21 5 X X X

division Particle size (탆) Plate corrosion resistance Corrosion resistance after bending Black degeneration Inventory 23 0.5 ○ ○ ○ Honors 24 One ○ ○ ○ Honors 25 3 ○ ○ ○ Evidence 26 5 ○ ○ ○ Comparative Example 22 10 X X ○

In Comparative Example 19, the plate corrosion resistance was good, but the weight enough to exhibit the lubricant property could not be introduced, resulting in poor corrosion resistance after bending.

In Comparative Examples 20 and 21, the wax particles were excessively distributed in the coating layer due to the excessive inclusion of the lubricant component, resulting in nonuniformity in the coating layer itself, and the corrosion resistance after the flat portion and bending was decreased.

In Comparative Example 22, as the size of the solid wax particles became larger, the coating solution hardly melted at a curing temperature of 140 ° C. and was likely to remain in the coating layer. Therefore, the resin component of the coating layer and cross- -linking), thereby promoting corrosion and reducing corrosion resistance.

[Example 3]

The coating solution described in the present invention was applied to a hot-dip galvanized steel sheet having a coating amount of 40 g / m 2 by a bar coating method, and then the hot-dip galvanized steel sheet was heated to 140 ° C. using an induction heater to form a coating layer . The measurement result of the wet adhesion amount of Example 27 was 800 mg / m 2, and the photograph of the evaluation of the corrosion resistance of the bending test was shown in Fig.

After applying the existing organic-inorganic hybrid solution (Application No.: 10-2012-0085369) to the hot-dip galvanized steel sheet having the plating adhesion amount of 40 g / m 2 by bar coating method, the hot-dip galvanized steel sheet was coated with PMT 140 Lt; 0 > C to prepare a coating layer (Comparative Example 23). The wet adhesion amount measurement result of Comparative Example 23 was 800 mg / m < 2 >, and a photograph evaluating the corrosion resistance of the bending work was shown in Fig.

The corrosion resistance, the solvent resistance and the black weather resistance of the inventive example 27 and the comparative example 23 were evaluated after bending, and the evaluation results are shown in Table 4.

≪ Evaluation of corrosion resistance after bending >

The corrosion resistance evaluation after bending was carried out in a salt spray test under the conditions of a salt concentration of 5%, a temperature of 35 ° C and a spray pressure of 1 kg / cm ² , and the time of 5% of white rust was measured. The bending process was performed by pressing the specimen at a force of 30 kN for a specimen size of 70 * 80 mm and then bending the specimen 90 ° in the Lame shape.

<Evaluation of solvent resistance>

The solvent resistance evaluation was a test to confirm whether the coating film was sufficiently cured. A gauze cotton sufficiently impregnated with MEK (methyl ethyl ketone) solvent was pressed on the coated surface and rubbed by reciprocating 20 times with a machine. At this time, (Delta E) were measured.

&Lt; Evaluation of Dark Metamorphism &

In the evaluation of the weathering resistance, the color difference (delta E) before and after holding the coated steel sheet was measured in a constant temperature and humidity chamber at a temperature of 50 ° C and a relative humidity of 95%.

division Corrosion resistance after bending
(time) Solvent resistance
(Delta E) Black degeneration
(Delta E) Comparative Example 23 24 0.3 1.8 Honors 27 72 0.4 1.5

In Comparative Example 23, more than 5% of white rust was formed within 24 hours, and the solvent resistance was measured to be 0.3, and the black color resistance was 1.8.

On the other hand, in the case of the invention 27, no white rust was observed even after 72 hours, and the results of the solvent resistance test and the weathering resistance evaluation showed color differences of 0.4 and 1.5, respectively.

Therefore, the hot-dip galvanized steel sheet using the coating solution described in the present invention was evaluated for corrosion resistance after bending, and it was found that the corrosion resistance after machining was slower than that of the conventional inorganic / organic composite coated steel sheet, .

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, But will be obvious to those of ordinary skill in the art.

Claims (21)

20 to 60% by weight, based on solids, of a urethane-acrylic resin and a nano-silicate-phenoxy resin; Wherein the inorganic anticorrosive agent comprises 7 to 33% by weight of silane A which is an epoxy or amino silane, 24 to 57% by weight of vinyl silane or silane B which is an acrylic silane, 3 to 11% by weight of vanadium phosphate, 0.1 to 1.4% by weight of Mg oxide, 2 to 10% by weight of zinc phosphate, 0.5 to 3.4% by weight of titanium carbonate, 0.5 to 4% by weight of zirconium oxide and 0.4 to 3% by weight of silica.
The organic-inorganic hybrid coating composition according to claim 1, wherein the inorganic anticorrosive agent is 40 to 80% by weight based on solids.
The organic-inorganic hybrid coating composition according to claim 1, wherein the content of the urethane-acrylic resin is 12 to 30% by weight and the content of the nano-silicate-phenoxy resin is 8 to 30% by weight based on the total solid content .
The organic-inorganic hybrid coating composition according to claim 1, wherein the urethane-acrylic resin or the nano-silicate-phenoxy resin has a weight average molecular weight (Mw) of 40,000 to 90,000.
The organic / inorganic hybrid coating composition according to claim 1, wherein the urethane-acrylic resin is synthesized using 2-hydroxyethyl methacrylate, acrylamide or an acrylic monomer which is a compound thereof.
6. The organic-inorganic hybrid coating composition according to claim 5, wherein the content of the acrylic monomer is 2 to 5% by weight based on the urethane-acrylic resin.
The organic-inorganic hybrid coating composition according to claim 1, wherein the urethane-acrylic resin has an equivalent ratio of NCO / OH of 1 to 3.
The method of claim 1 wherein the nanosilicate-phenoxy resin is synthesized using at least one alkyl substituted phenol monomer selected from 4-ethylphenol, 2,6-dimethylphenol, 2-ethylphenol, and 2-isopropylphenol. Based composite coating composition.
The organic-inorganic hybrid coating composition according to claim 1, wherein the nanosilicate-phenoxy resin comprises a nanosilicate in an amount of 1 to 5 wt% based on 100 wt% of the nanosilicate-phenoxy resin.
The organic-inorganic hybrid coating composition according to claim 1, wherein the nanosilicate-phenoxy resin comprises a nanosilicate having a particle size of 20 nm or less.
The organic / inorganic hybrid coating composition of claim 1, wherein the nanosilicate-phenoxy resin comprises one nanosilicate selected from calcium silicate, lithium silicate, and ammonium hexafluorosilicate.
The organic-inorganic composite coating composition according to claim 1, wherein the silane A is at least one selected from an epoxy-based silane and an amino-based silane.
13. The composition according to claim 12, wherein the epoxy silane is gamma glycidoxypropyltriethoxysilane and gamma glycidoxypropyltrimethoxysilane.
13. The composition according to claim 12, wherein the amino-based silane is gammaaminopropyltriethoxysilane and gammaaminopropyltrimethoxysilane.
The organic-inorganic hybrid coating composition according to claim 1, wherein the silane B is at least one selected from vinyl silane and acrylic silane.
The inorganic or organic composite coating composition according to claim 1, wherein the organic / inorganic composite coating composition further comprises a lubricant in an amount of 0.3 to 2 parts by weight based on 100 parts by weight of solid content.
17. The lubricating composition according to claim 16, wherein the lubricant is at least one selected from the group consisting of paraffin wax, olefin wax, carnauba wax, polyester wax, polyethylen wax, polypropylene wax, polyethylene-Teflon modified wax, Wherein the at least one wax is selected from the group consisting of polyvinyl alcohol and polyvinyl alcohol.
The organic-inorganic hybrid coating composition according to claim 17, wherein the wax has a particle size of 0.5 to 5 탆.
The inorganic / organic composite coating composition according to claim 1, wherein the inorganic corrosion inhibitor further comprises thio-urea, and the content of thio-urea relative to the inorganic corrosion inhibitor is 0.5 to 7 wt%.
Base steel sheet;
A zinc-based plated layer formed on one side or both sides of the base steel sheet; And
And a coating layer formed on the plating layer, wherein the coating layer is a cured product of the organic-inorganic hybrid coating composition of any one of claims 1 to 19.
The organic-inorganic composite coated steel sheet according to claim 20, wherein the coating amount of the coating layer is 0.5 to 2 g / m 2 based on one side of the steel sheet.

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