KR20070068595A - Preparing method of steel sheet having chrome free coating film, steel sheet prepared thereby and coating composition used therefor - Google Patents

Abstract

A manufacturing method a chromium-free steel sheet, a surface treated chromium-free steel sheet, and a chromium-free surface treatment composition are provided to be particularly excellent in blackening resistance. A method for manufacturing a steel sheet comprises the steps of: coating a galvanized steel sheet with a first coating solution comprising 50 wt.% or more of silicon based on the contents of inorganic components of a first coating solution, and drying the first coating solution at a temperature of 40 to 200 deg.C to form a first coating layer; and drying the second coating solution at a temperature of 120 to 200 deg.C after coating the first coating layer with a second coating solution comprising 10 to 70 wt.% of a vinyl-based binder resin combined with a corrosion resistant inorganic material, 15 to 75 wt.% of an acryl-based binder resin combined with a corrosion resistant inorganic material, 5 to 40 wt.% of an epoxy-based binder resin and a solvent based on the content of solids contained in the second coating solution, wherein the corrosion resistant inorganic material is contained in the second coating solution in an amount of 3 to 25 wt.% of the total solid content of the second coating solution.

Description

Preparing Method of Steel Sheet Having Chrome Free Coating Film, Steel Sheet Prepared Thereby and Coating Composition Used Therefor}

1 is a side cross-sectional view showing a schematic structure of a steel sheet prepared by coating the surface treatment composition of the present invention.

The present invention relates to a method for producing a surface-treated steel sheet, which does not contain chromium, and to a steel sheet and a coating composition prepared according to the present invention, and more particularly, to a method for manufacturing a surface-treated steel sheet that does not contain chromium having particularly good porosity resistance. It relates to a steel sheet and surface treatment composition prepared accordingly.

Recently, with increasing interest in environmental issues around the world, regulations on the use of environmental pollutants such as Cr, Pb, Cd, Hg, PBB, and PBDE are being tightened. In particular, the Restriction of Hazardous Substances (RoHS) implemented by the EU (Restricted of Hazardous Substances, June 06, 2004), Waste from Electrical and Electronic Equipment (WEEE) implemented (06.7.1), and the disposal of waste vehicles ( Typical examples are ELV (End-of-Life Vehicles, 2007.1.1) and REACH (Registration, Evaluation and Authorization of Chemicals). The government needs to actively respond to new environmental management policies such as waste reduction and green procurement.

Conventionally, galvanized steel sheet and zinc-based alloy plated steel sheet, aluminum plated steel sheet, aluminum alloy plated steel sheet, cold rolled steel sheet, hot rolled steel sheet, etc., which are used for automotive materials, home appliances, building materials, etc., are provided with corrosion resistance and paint adhesion. In order to do this, a surface treatment method of coating a chromate coating mainly composed of chromium on the surface is generally performed. The main chromate treatments are electrolytic chromate and coated chromate. Among them, electrolytic chromate treatment is composed of hexavalent chromium as a main component and a metal plate using a treatment solution in which various anions such as sulfuric acid, phosphoric acid, boric acid, and halogen are added. Cathode electrolysis is generally practiced. On the other hand, in the coating type chromate treatment, a method in which an inorganic colloid and an inorganic ion are added to a solution in which a part of hexavalent chromium is reduced to trivalent beforehand is used to deposit a metal plate therein or spray the treatment solution onto the metal plate. It is carried out by.

When using these methods, due to the toxicity of hexavalent chromium contained in the chromate treatment solution, various measures are required in the working environment and drainage treatment, and for recycling and disposal of automobiles, home appliances, building materials, etc. using the surface treatment metal. It also causes human health and environmental pollution.

Therefore, each steel company is focusing on developing a surface-treated steel sheet that does not contain hexavalent chromium and does not contain chromium that can satisfy various requirements such as corrosion resistance, alkali resistance and conductivity. Conventionally, a method of manufacturing a metal salt film mainly composed of phosphate as a main component on the surface of a steel sheet, and then coating a resin-based film mainly composed of acryl and urethane resin as a main component thereon, or the primary film and the secondary coating. Surface-treated metal steel sheets containing no chromium were prepared by forming the coating films into resin coating films.

However, the products are often deteriorated in the electrical conductivity and weldability of the metal sheet due to the metal salt or film thickness, which is not suitable for the use of electromagnetic wave suppression, internal noise suppression and processability of copying machines, printers, VCRs and computers. There is a problem.

Also, in recent years, as most home appliances require surface-treated steel sheets that do not contain chromium having excellent conductivity, a coating steel sheet containing no chromium has been developed by coating only the first resin-based coating. However, unless the composition of the resin-based surface treatment composition is particularly excellent, there is a problem in that quality characteristics such as corrosion resistance are significantly lower than those of conventional chromium-treated or phosphate coated steel sheets. In recent years, however, major domestic and foreign home appliance manufacturers have established their own quality standards for materials and obtained quality certification for the development of environmentally friendly products for surface-treated steel sheets that do not contain chromium. I buy it.

Conventionally, a method of coating polyaniline on a metal plate as a coating method in consideration of conductivity without containing hexavalent chromium is disclosed in Japanese Patent Laid-Open Nos. 8-92479 and 8-500770. However, since polyaniline having high rigidity and low adhesion exists between the metal and the resin film, the film can be easily peeled off from the polyaniline and the metal interface and the polyaniline and the resin interface. Because of this, there is a problem when painting the upper portion in order to give the design, more corrosion resistance and other functions to the steel sheet. Low adhesion films are generally known to have low corrosion resistance. In addition, the solution stability is low, there is a lot of sediment, and a bad smell occurs, there is also a problem in the workability, such as inhibition of the overall working environment. In addition, the composition of the present invention, the Republic of Korea Applicant No. 2004-111343 also exhibited an excellent effect of improving the characteristics such as conductivity, corrosion resistance, alkali resistance, high temperature and high humidity by using a method of coating only the primary on the galvanized layer, In particular, some products that are used for heavy processing have a problem that the surface of the processing friction portion is slightly blackened due to lack of blackening resistance.

It is an object of the present invention to provide a method for producing a steel sheet which does not contain chromium, in particular, which has improved void blackening resistance.

Another object of the present invention is to provide a surface treated steel sheet which does not contain chromium, in particular, which has improved pore blackening resistance.

It is a further object of the present invention to provide a surface treatment composition which does not contain chromium, which has particularly improved co-blackening resistance.

The object of the present invention is not limited to the above-mentioned objects, and other objects not mentioned will be clearly understood by those skilled in the art from the following description.

In one aspect of the present invention,

Coating a first coating solution containing 50 wt% or more of silicon based on the content of the inorganic component of the first coating solution on a galvanized steel sheet and drying at a temperature of 40-200 ° C. to form a primary coating layer; And

 10-70% by weight of the vinyl-based binder resin compounded with the corrosion-resistant inorganic material, 15-75% by weight of the acrylic binder resin compounded with the corrosion-resistant inorganic material, about 5 to 40% by weight of the epoxy-based binder resin and the solvent, based on the solids content of the second coating solution. To include, wherein the corrosion-resistant inorganic material is 3 to 25% by weight of the total solids of the second coating liquid coating the second coating liquid on the first coating layer and drying at 120-200 ℃;

There is provided a steel sheet manufacturing method comprising a.

In another aspect of the present invention,

galvanized steel;

A first coating layer formed on the steel sheet with a first coating solution containing 50 wt% or more of silicon based on the content of the inorganic component of the first coating solution; And

10-70% by weight of the vinyl-based binder resin compounded with the corrosion-resistant inorganic material, 15-75% by weight of the acrylic binder resin compounded with the corrosion-resistant inorganic material, epoxy binder resin based on the solids content of the second coating solution on the first coating layer It comprises a to 40% by weight and a solvent, the corrosion-resistant inorganic material is provided with a steel sheet comprising; a second coating layer formed of a second coating liquid of 3 to 25% by weight of the total solids of the second coating liquid.

In another aspect of the present invention,

Provided is a first coating layer composition formed on a steel sheet according to the present invention comprising at least 50% by weight of silicon based on the content of the inorganic component of the first coating solution.

Furthermore, in another aspect of the present invention,

10-70% by weight of the vinyl-based binder resin compounded with the corrosion-resistant inorganic material, 15-75% by weight of the acrylic binder resin compounded with the corrosion-resistant inorganic material, about 5 to 40% by weight of the epoxy-based binder resin and the solvent, based on the solids content of the second coating solution. It includes, wherein the corrosion-resistant inorganic material is provided with a second coating layer composition formed on the first coating layer according to the present invention is 3 to 25% by weight of the total solids of the second coating liquid.

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

In the present invention, the silica-based pretreatment solution is first coated on the steel sheet to form a first coating layer, and then the first coating layer is coated with a resin coating with a second coating solution to form a second coating layer, thereby forming the black void resistance of the steel sheet. Is improved. According to the present invention, not only the blackening resistance of the steel sheet is improved, but also shows excellent conductivity, corrosion resistance, alkali resistance and high temperature and high humidity resistance, and it is environmentally friendly because it does not contain chromium.

In the present invention, two coating layers are formed on the steel sheet. The primary coating layer is formed of a silica based pretreatment solution.

The silica-based pretreatment solution (hereinafter referred to as 'first coating solution') comprises a silicon (Si) component, other inorganic components, and a solvent.

The first coating solution contains at least 50% by weight of silicon based on the total inorganic component content of the first coating solution. If the content of silicon in the first coating liquid is less than 50% by weight, the corrosion resistance is insufficient, which is not preferable. Corrosion resistance is improved as the amount of silicon added in the first coating solution is improved, and the inorganic component in the first coating solution may be made of only silicon components.

The silicon component may be added as a salt such as silicate or silica or as a precursor in the form of an oxide or hydride. The precursor may be added in powder form, emulsion form, solution form or colloidal form.

The first coating liquid may further include other inorganic components in addition to the silicon component. The other inorganic component is not limited thereto, but may be at least one selected from the group consisting of Ti, Al, Mg, Zr, Mo, P, W, V, Ni, Ag, Au, and Cu. The other inorganic component may be added to the first coating liquid as a precursor containing an inorganic component in the form of a salt, an oxide, or a hydride, similarly to the corrosion resistant inorganic component complexed with the binder resin in the second coating liquid to be described later. These inorganic precursors may be added to the first coating liquid in powder, emulsion, solution or colloidal form. Preferred examples of the precursor may be titania, titanate, alumina, aluminate, zirconia, zirconate, magnesia, molybdate, phosphate, salts or oxides such as tungsten, vanadium, nickel, silver, gold, copper, Hydrides; and the like. Such oxide, hydrogenated or salt precursors may be added alone or in a mixture of two or more thereof. The other inorganic component is preferably used in the same kind and content as the corrosion-resistant inorganic material used in the second coating liquid described later, but may be used in other types and contents.

Other inorganic components may be added to the first coating liquid at 50% by weight or less based on the weight of the total inorganic components of the first coating liquid. This is because the silicon component should be included in more than 50% by weight.

At least one additive, such as a wetting agent, a crosslinking agent, a curing agent, a lubricant, an antifoaming agent, and the like may be added to the first coating solution. The action and kind of these additives are as described for the second coating liquid described later. The amount of these additives is preferably used at 5-15% by weight based on the total solids of the first cotang liquid. If the additive content is less than 5% by weight, the use effect of the additives such as corrosion resistance, alkalinity does not appear, and if the content exceeds 15% by weight, the effect is saturated, and further addition is not meaningful and there is a problem of reducing solution stability.

The same as the additive added to the second coating liquid may be added to the first coating liquid, but other types (for example, a wetting agent in the first coating liquid and a crosslinking agent in the second coating liquid) may be added.

Components except the solids in the first coating solution is a solvent, water or a mixed solvent of water and alcohol may be used as the solvent, in particular, in order to improve the properties such as wettability, dispersibility, etc. of the first coating solution, At least one or more of the acidic or alkaline aqueous solutions may be further added. Ethanol, methanol, propanol, isopropanol, glycerol, and the like may be used as the alcohol solvent. At this time, the alcohol solvent added is preferably used in 1 to 35% by weight based on the first coating liquid. If the alcohol solvent is less than 1% by weight, the stability, dispersibility, wettability, etc. of the solution is lowered, and if it exceeds 35% by weight, the odor and volatility are severe and the operation is bad.

The acidic aqueous solution may be hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, acetic acid, carboxylic acid aqueous solution, or the like, and the alkaline aqueous solution may include sodium hydroxide, potassium hydroxide, sodium carbonate, ammonium hydroxide aqueous solution, and the like. The acidic or alkaline aqueous solution may be used in an amount of 0.2 to 5% by weight based on the first coating solution. In addition, when the acidic or alkaline aqueous solution is less than 0.2% by weight, the coating adhesiveness is lowered. When the acidic or alkaline aqueous solution is more than 5% by weight, corrosion of the base metal may occur or bad smell may occur.

By using the first coating liquid, the void blackening resistance of the steel sheet is improved.

Solids in the first coating solution are 0.5-15% by weight and the balance is a solvent. If the solid content is less than 0.5% by weight, the effect of improving the blackening resistance is insufficient, and if it exceeds 15% by weight, the effect of improving the blackening resistance is saturated and uneconomical.

The first coating solution, prepared as described above, is coated on the steel sheet to form a first coating layer. The coating method is not particularly limited, but may be, for example, roll coating, spray coating, or immersion coating.

The first coating layer is coated so that the dry film thickness is about 10 to 500 mg / m ² . If the thickness of the coating film is less than 10 mg / m ² , there is no effect of improving the blackening resistance, and if it exceeds 500 mg / m ² , the effect on the blackening resistance is saturated, and the economic efficiency due to the price increase is lowered.

After coating the first coating solution, it can be dried at a drying metal temperature (PMT; Pick Metal Temperature) of 40-200 ℃, preferably at 40-100 ℃. For example, it can dry using a conventional hot air dryer. If it is less than 40 ° C., drying is insufficient, and if it is more than 200 ° C., the first coating layer component may burn and discolor.

As described above, a second coating layer, which is a resin layer, is formed on the first coating layer formed on the steel sheet by using the second coating liquid. The second coating liquid is a composition containing no water-soluble or water-dispersible chromium composed of a binder resin, an epoxy resin, an additive, and a solvent having a high corrosion resistance oil and an inorganic compound. As the binder resin, vinyl binder resins and acrylic binder resins are used.

Any solvent can be used as long as it is a water-soluble resin in which a corrosion-resistant inorganic material is compounded as a binder resin in the second coating liquid.

The binder resin in which the corrosion resistant inorganic material is complexed is prepared by adding a corrosion resistant inorganic material to the monomer during the polymerization reaction by polymerization of the monomer so that the corrosion resistant inorganic material reacts with the organic functional group of the polymer to be uniformly introduced into the polymer.

As the corrosion resistant inorganic material, Group 1B element, Group 2 element, Group 3B element, Group 4 element, Group 5 element, Group 6A element and Group 8 element may be used, and Si, Ti, Al, Mg, Zr, Mo, P, W, V, Ni, Ag, Au, Cu or a mixture of two or more thereof may be preferably used, and more preferably, Si, Si-P, Si-Ti, or Si-Al is included as a main component. . The binder resin composited with the corrosion resistant inorganic material reacts the corrosion resistant inorganic precursor together with the polymerization reaction of the monomer for preparing the binder resin so that the corrosion resistant inorganic material reacts with the functional group of the binder resin (eg, OCOCH ₃ , Cl, OH, etc.). do. At this time, the reaction may be promoted by adding a reaction catalyst and adding heat.

The corrosion resistant inorganic material may be added to the second coating liquid as a precursor containing the corrosion resistant corrosion resistant inorganic material in the form of salt, oxide or hydride. These inorganic precursors may be added to the monomer for preparing the binder resin in powder, emulsion, solution or colloidal form. Preferred examples of the precursor may be silica, silicate, titania, titanate, alumina, aluminate, zirconia, zirconate, magnesia, molybdate, phosphate, tungsten, vanadium, nickel, silver, gold, copper Salts, oxides, hydrides, and the like. These corrosion-resistant inorganic materials may be used simultaneously or sequentially with a mixture of compounds of inorganic materials alone, or compounds containing two or more of these inorganic materials may be used.

Solid content of the vinyl-based binder resin in which the inorganic material is complexed in the second coating solution is 10 to 70% by weight based on the total solids of the second coating solution. The vinyl-based resin is used to prevent scratches on the surface by painting on industrial paper or cloth, steel plate or aluminum plate, etc., because it has strong water resistance, chemical resistance, acid resistance and salt water resistance, and a strong coating film. It has a soundproofing effect. If the solid content of the vinyl binder resin compounded with the inorganic material is less than 10% by weight, the saline and chemical resistance of the vinyl resin against the penetration of corrosion ions are not exerted, so that the alkali resistance is lowered. There is a fatal problem that the resin film is peeled off when degreasing for 5 minutes. If it exceeds 70% by weight, high temperature and high humidity resistance is reduced, there is a problem that a severe blackening phenomenon occurs. The vinyl binder resin is not limited thereto, but may be one of at least one vinyl monomer selected from the group consisting of vinyl acetate, vinyl alcohol, and vinyl chloride.

In the present invention, in order to reinforce high temperature and moisture resistance and cold resistance, an acrylic binder resin is mixed and used. As the acrylic binder resin, but not limited thereto, for example, one made of at least one acrylic monomer selected from the group consisting of n-butyl acrylate, methyl methacrylate, and n-butyl methacrylate may be used. Can be.

The solids content of the acrylic binder resin in which the corrosion resistant inorganic material is combined is 15 to 75% by weight based on the solids of the entire second coating solution. If the solid content of the acrylic resin compounded with the corrosion resistant inorganic material is less than 15% by weight, there is a problem that high temperature and high humidity resistance is lowered, and when it exceeds 75% by weight, alkali resistance is lowered.

The solids content of the corrosion resistant inorganic substance substituted in the binder resin is 3 to 25% by weight based on the total solids of the second coating liquid. At this time, when the content of the corrosion-resistant inorganic material is less than 3% by weight, the corrosion resistance is low and there is almost no effect of addition, and when the content exceeds 25% by weight, the concentration is saturated, so that a large amount of precipitate is generated, and the solution stability is lowered. There is a problem of decreasing the temperature and humidity.

In the vinyl-based binder resin compounded with the corrosion-resistant inorganic material, the corrosion-resistant inorganic material is preferably combined at 5 to 23 parts by weight based on 100 parts by weight of the vinyl binder resin. In addition, it is preferable that the corrosion resistant inorganic material is combined at 5 to 23 parts by weight based on 100 parts by weight of the acrylic binder resin in the acrylic binder resin in which the corrosion resistant inorganic material is complexed. If the amount of the corrosion-resistant inorganic compound complexed and bonded to the binder resin is less than 5 parts by weight, there is no effect of substitution bonding and the effect of improving corrosion resistance is insufficient. If the amount exceeds 23 parts by weight, the corrosion additive is saturated and solution stability is deteriorated. .

Epoxy-based binder resins are also used in the second coating solution to reinforce porosity blackening, adhesion and processability. Solid content of the epoxy-based binder resin may be added in 5 to 40% by weight based on the total solids of the second coating liquid. If the solid content of the epoxy-based binder resin is less than 5% by weight, there is no effect of improving the blackening resistance, and if it exceeds 40% by weight, solution stability and corrosion resistance may be reduced. It is preferable to use the thing of the molecular weight 8,000-15,000 as said epoxy binder resin. If the molecular weight of the epoxy resin is less than 8,000 there is no effect of improving the blackening resistance, and if it exceeds 15,000, there is a problem that the stability of the solution decreases.

In the surface treatment composition, a component except solids is a solvent, and as the solvent, water or a mixed solvent of water and alcohol may be used. Particularly, in order to improve properties such as wettability and dispersibility of the coating composition, a separate alcohol solvent and acid may be used. At least one or more of the aqueous or alkaline aqueous solution may be further added. Ethanol, methanol, propanol, isopropanol, glycerol, and the like may be used as the alcohol solvent. At this time, the alcohol solvent added is preferably used in 1 to 35% by weight based on the second coating liquid. If the alcohol solvent is less than 1% by weight, the stability, dispersibility, wettability, etc. of the solution is lowered, and if it exceeds 35% by weight, the odor and volatility are severe and the operation is bad.

The acidic aqueous solution may be hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, acetic acid, carboxylic acid aqueous solution, or the like, and the alkaline aqueous solution may include sodium hydroxide, potassium hydroxide, sodium carbonate, ammonium hydroxide aqueous solution, and the like. The acidic or alkaline aqueous solution may be used in an amount of 0.2 to 5% by weight based on the second coating solution. In addition, when the acidic or alkaline aqueous solution is less than 0.2% by weight, the coating adhesiveness is lowered. When the acidic or alkaline aqueous solution is more than 5% by weight, corrosion of the base metal may occur or bad smell may occur.

Furthermore, the resin which does not complex the corrosion-resistant inorganic substance, such as acryl, urethane, epoxy, alkyd, styrene / butadiene, polyethylene, polypropylene, polyester, which are used in the surface treatment liquid conventionally used for the water-soluble resin compounded with the said corrosion-resistant inorganic substance alone Or it can add and mix in 2 or more types of mixtures. In the case where the resin which is not complexed with the above corrosion resistant inorganic material is further used, the amount used is preferably 50% by weight or less, more preferably 5 to 40% by weight, based on the solids content of the second coating solution. Even more preferred is use at 25% by weight. When the binder resin is used in excess of 50% by weight, there is a problem that one or more quality characteristics deteriorate in properties such as corrosion resistance, solution stability, alkali resistance, high temperature and humidity resistance, conductivity, heat resistance, streaks, and point marks of the composition. have.

In addition, the corrosion resistant inorganic material complexed to the binder resin may be added to the second coating liquid as a separate corrosion resistant inorganic material. Similar to the corrosion resistant inorganic material compounded in the binder resin, the corrosion resistant inorganic additive may be added as an inorganic precursor, that is, a salt, an oxide or a hydride, and may also be added in the form of powder, emulsion or solution. Examples of the precursor may be selected from the same as the inorganic precursor in the corrosion-resistant inorganic material complexed with the binder resin. In the case where the corrosion-resistant inorganic material is added separately, the added amount is preferably 10% by weight or less, more preferably 1 to 4% by weight based on the solids content of the second coating liquid. If the amount of the corrosion resistant inorganic material exceeds 10% by weight, it is not preferable because the solution stability is inhibited.

In addition, the surface treatment composition of the present invention may further include one or more additives such as a wetting agent, a crosslinking agent, a curing agent, a lubricant, an antifoaming agent, and the like. The wetting agent is effective in streaking and adhesion, the crosslinking agent and the curing agent in corrosion resistance and alkali resistance, the lubricant in friction coefficient and processability, and the antifoaming agent in improving workability. These additives are preferably used in an amount of 5 to 15% by weight based on the solids content of the second coating liquid. If the content of the additive is less than 5% by weight, the use of additives such as corrosion resistance, alkali resistance does not appear, and if the content exceeds 15% by weight, the effect is saturated, and further addition is not meaningful, and there is a problem of reducing solution stability.

The wetting agent includes a deagglomerated wet dispersant, a polymer wet dispersant, and the like, and preferable examples thereof include a wet dispersant sold by EFCA and Tego, etc., and EFCA 3580 (EFCA) and BW-W500 (Bumwoo Chemical). Or WET 500 (EFCA). As the crosslinking agent, vinylsilane, acrylsilane, epoxysilane, chlorosilane, alkoxysilane, silazane or silylating agent and the like can be used. The lubricant includes silicone wax, polyethylene wax, polypropylene wax, amide wax, polytetrafluoroethylene (PTFE) wax, paraffin wax, and the like. The curing agent may be a polyamine-based, polyamide-based or acid anhydride-based curing agent. The antifoaming agent may be an oil type, a modified type, a solution type, a powder type, or an emulsion type silicone antifoaming agent.

In the second coating solution, the binder resin is excellent in the stability of the solution of the second coating solution because the particles of the corrosion resistant inorganic material are uniformly substituted and dispersed in the organic functional group of the binder resin, and the corrosion resistance, conductivity, alkali resistance, and high temperature and humidity resistance of the anticorrosive coating layer. Etc., the effect is further improved.

In the second coating liquid for forming the resin layer, since the corrosion resistant inorganic particles are uniformly substituted and dispersed in the organic functional groups of the acrylic binder resin and the vinyl binder resin, the corrosion resistant inorganic material is uniformly distributed between the dense resin structures when forming the film. Therefore, the coating layer made of the composition exhibits improved corrosion resistance, conductivity, alkali resistance, high temperature and high humidity resistance, and the stability of the solution itself is also excellent. In addition, by using an epoxy resin, physical properties such as adhesion, processability and coating properties are further improved.

The second coating solution is coated on the first coating layer to form a second coating layer. The second coating liquid may be applied by any coating method generally used in the art, but is not limited thereto, and may be applied by, for example, a roll coating, a spray coating, or a dip coating.

Dry coating amount of the second coating solution of the present invention is 500 to 1,500 g / m ² . At this time, if the adhesion amount is less than 500 mg / m ² , there is no effect of improving corrosion resistance. If the adhesion amount is more than 1,500 mg / m ^2, the conductivity is low.

After coating the two coating liquids, it is dried at a drying temperature (PMT, Pick Metal Temperature) of about 120-200 ℃. The higher the drying temperature shows a tendency to improve the corrosion resistance of the resin film, but if it is less than 120 ℃ is not unreasonable to meet the customer's requirements quality, if it exceeds 200 ℃ uneconomical, there is a fear of discoloration of the resin layer.

Further, the applicable metal sheet of the present invention may be a galvanized steel sheet, a zinc nickel plated steel sheet, a galvanized steel sheet, a zinc titanium plated steel sheet, a zinc magnesium plated steel sheet, a zinc manganese plated steel sheet, or a zinc-based electroplated steel sheet, such as a zinc aluminum plated steel sheet. Plated steel sheets, aluminum plated steel sheets, and also those plating layers containing, for example, cobalt, molybdenum, tungsten, nickel, titanium, aluminum, manganese, iron, magnesium, tin, copper or mixtures thereof as dissimilar metals or impurities. Steel plate or plated steel sheet in which inorganic materials such as silica and alumina are dispersed in these plating layers, or an aluminum alloy sheet containing silicon, copper, magnesium, iron, manganese, titanium, zinc or a mixture thereof, or cold rolled steel sheet, hot rolled steel sheet, or the like. to be. Moreover, it is applicable also to the multilayer plating board which processed two or more types sequentially among the above platings.

Hereinafter, the present invention will be described in detail through examples. The following examples are intended to illustrate the invention and do not limit the invention.

 EXAMPLE

1. Preparation of the first coating solution

The first coating solution of Comparative Examples 1 to 10 and Examples 1 to 16 was prepared by adding silica to the first coating solution such that the Si component of the inorganic component became an amount shown in Table 1 below. When the Si component was not 100% by weight, titanate was added to provide Ti as another inorganic component so that the inorganic component was 100% by weight.

Other additives include 0.5% by weight of carboxy watch wetting agent BW-W500 (Bumwoo Chemical), 1.2% by weight of silane crosslinking agent BW-C500 (Bumwoo Chemical) based on the total solids of the first coating solution, and amine-based curing agent BW-H500 (Bumwoo) Chemical) 2.5% by weight and polyethylene-based lubricant BW-L500 (Bumwoo Chemical) 1.5% by weight were respectively added in bulk.

About 5% by weight of ethanol as an alcohol solvent and about 0.5% by weight of acetic acid as an acidic aqueous solution were added based on the total amount of the first coating solution, and water was used in the first coating solution using water as the remaining components except the solids in the first coating solution. Solid content concentration was made to be 5 weight%.

2. Preparation of resin coating layer forming composition (second coating liquid)

Vinyl acetate and vinyl alcohol were used together as the vinyl monomer in the same weight ratio to prepare a vinyl binder resin. In preparing the vinyl binder resin, a vinyl binder resin in which a corrosion resistant inorganic material was combined by adding a Si-Ti-Al-P compound as a corrosion resistant inorganic precursor was prepared.

As the acrylic monomer, n-butyl acrylate was used to prepare an acrylic binder resin. When preparing the acrylic binder resin, an acrylic binder resin in which a corrosion resistant inorganic compound was prepared by adding a Si-Ti-Al-P compound to the acrylic monomer as a corrosion resistant inorganic precursor.

Corrosion-resistant inorganic material complexed with the vinyl binder resin and the acrylic binder resin was provided using a mixture in which a silicate: titanate: aluminate: phosphate was mixed in an 8: 1: 0.5: 0.5 weight ratio.

Meanwhile, in preparing the vinyl binder resin and the acrylic binder resin in which the corrosion resistant inorganic material was combined, the precursor was used so that the corrosion resistant inorganic material was compounded in the amount of 10 parts by weight, respectively, per 100 parts by weight of each resin.

In the preparation of the second coating solution, the acrylic resin in which the corrosion resistant inorganic material was combined based on the solid content of the second coating solution was added in an amount of 30% by weight, and the epoxy resin was added in the amount shown in Table 1 below. In consideration of solids, the solids content was added to 100% by weight. On the other hand, in Example 11 and Comparative Example 7, it was the same as in the other cases, except that the acrylic resin in which the corrosion-resistant inorganic compound is used at 15% by weight. Epoxy binder resin (Bumwoo Chemical Co., Ltd.) having a molecular weight of 10,000 was used as the epoxy binder resin.

As other additives, 0.5 wt% of the carboxy watch wetting agent BW-W500 (Bumwoo Chemical), 1.2 wt% of the silane crosslinking agent BW-C500 (Bumwoo Chemical) based on the total solids of the second coating solution, BW-H500 (Bumwoo Chemical) 2.5% by weight and 1.5% by weight of polyethylene lubricant BW-L500 (Bumwoo Chemical) were added in bulk.

Based on the total amount of the second coating solution, about 5% by weight of ethanol as an alcohol solvent and about 0.5% by weight of acetic acid as an acidic aqueous solution were added, and water was used as the remaining ingredient except the solids in the second coating solution. Solid content concentration was made to be 15 weight%.

3. Manufacturing of coated steel sheet

1) Specimen: An electro galvanized steel sheet (EG) having a plating adhesion amount of 20 g / m 2 was used as a material steel sheet for applying the surface treatment composition.

2) Coating method: The specimen was immersed in the first coating solution for 3 seconds, coated with a dry coating film adhesion amount of Table 1 and dried under PMT conditions of Table 1 to form a first coating layer.

Thereafter, the second coating liquid was applied to the dry coating film amount shown in Table 1 below on the first coating layer by using a continuous roll coating simulator, and dried under PMT conditions as shown in Table 1 to form a second coating layer.

4. Performance Evaluation Method

(1) Refractory blackening: after the friction coefficient was measured using a draw bead friction tester (load 1,000kgf, speed 1,000mm / min, distance 100mm), the resin film of the specimen was damaged by scratching the bead surface of the friction tester. Was evaluated according to the following criteria.

○: less than 1% damage area

△: damage area 1% or more but less than 5%

X: Damage area over 5%

(2) Corrosion resistance: The specimens were subjected to a salt spray test according to JISZ2371 for 120 hours, and the degree of corrosion was evaluated by the following criteria.

○: less than 5% of white and blue

△: more than 5% of white rust less than 20%

X: 20% or more of white blue

(3) Solution stability: 100 g of the second coating solution is 50? After 10 days in the oven, the degree of precipitation, gelation and separation of the solution was evaluated according to the following criteria.

○: No precipitation, gelation or separation

△: One of fine precipitation, gelation and separation

X: One or more of precipitation, gelation, and separation occur to some extent

5. Evaluation Results

Table 1 shows the properties of the steel sheet having a coating layer formed of the first and second coating solutions prepared above and the solution stability of the second coating solution under the above conditions.

TABLE 1

division Primary pretreatment condition Secondary resin treatment condition Quality characteristic Economic / Saturation Silica (wt%) Amount of adhesion (mg / ㎡) PMT (℃) Epoxy (wt%) Amount of adhesion (mg / ㎡) PMT (℃) Black and white Corrosion resistance Solution stability Comparative Example 1 0 100 60 20 1,000 180 X ○ ○ Comparative Example 2 20 100 60 20 1,000 180 X ○ ○ Comparative Example 3 40 100 60 20 1,000 180 X ○ ○ Example 1 50 100 60 20 1,000 180 △ ○ ○ Example 2 65 100 60 20 1,000 180 ○ ○ ○ Example 3 75 100 60 20 1,000 180 ○ ○ ○ Example 4 100 100 60 20 1,000 180 ○ ○ ○ Comparative Example 4 75 5 60 20 1,000 180 X ○ ○ Example 5 75 10 60 20 1,000 180 △ ○ ○ Example 6 75 250 60 20 1,000 180 ○ ○ ○ Example 7 75 500 60 20 1,000 180 ○ ○ ○ △ Comparative Example 5 75 100 30 20 1,000 180 X △ ○ Example 8 75 100 40 20 1,000 180 △ ○ ○ Example 9 75 100 100 20 1,000 180 ○ ○ ○ △ Comparative Example 6 75 100 One 0 1,000 180 X ○ ○ Example 10 75 100 60 5 1,000 180 ○ ○ ○ Example 11 75 100 60 40 1,000 180 ○ ○ △ Comparative Example 7 75 100 60 50 1,000 180 ○ X X Comparative Example 8 75 100 60 20 400 180 ○ X ○ Example 12 75 100 60 20 500 180 ○ △ ○ Example 13 75 100 60 20 800 180 ○ ○ ○ Example 14 75 100 60 20 1,500 180 ○ ○ ○ △ Comparative Example 9 75 100 60 20 1,600 180 ○ ○ ○ X Comparative Example 10 75 100 60 20 1,000 110 ○ X ○ Example 15 75 100 60 20 1,000 120 ○ △ ○ Example 16 75 100 60 20 1,000 150 ○ ○ ○

As described in Table 1, the steel sheet having the method of Examples 1 to 16 and the coating layers formed of the first and second coating liquids in the composition range of the present invention showed excellent quality characteristics.

The steel sheet produced by the method of the present invention and the surface treatment composition used therein are not only excellent in blackening resistance, but also exhibit excellent corrosion resistance, alkali resistance, corrosion resistance and solution stability. Therefore, it can be easily used as a material for deep processing by the customer. It is also environmentally friendly because it does not contain chromium.

Claims (22)

Coating a first coating solution containing 50 wt% or more of silicon based on the content of the inorganic component of the first coating solution on a galvanized steel sheet and drying at a temperature of 40-200 ° C. to form a primary coating layer; And  10-70% by weight of the vinyl-based binder resin compounded with the corrosion-resistant inorganic material, 15-75% by weight of the acrylic binder resin compounded with the corrosion-resistant inorganic material, about 5 to 40% by weight of the epoxy-based binder resin and the solvent, based on the solids content of the second coating solution. To include, wherein the corrosion-resistant inorganic material is 3 to 25% by weight of the total solids of the second coating liquid coating the second coating liquid on the first coating layer and drying at 120-200 ℃; Steel sheet manufacturing method comprising a. The method of claim 1, wherein the first coating solution is characterized in that the coating on the steel sheet with a dry film adhesion amount of 10-500mg / ㎡. The method of claim 1, wherein the second coating liquid is coated on the first coating layer with a dry coating amount of 100-1,500 mg / ㎡. The method of claim 1, wherein the first coating liquid comprises at least one inorganic component selected from the group consisting of Ti, Al, Mg, Zr, Mo, P, W, V, Ni, Ag, Au, Cu and mixtures thereof. Further comprising. The method according to claim 1, wherein the vinyl binder resin in which the corrosion resistant inorganic material is combined comprises 5 to 23 parts by weight of the corrosion resistant inorganic material based on 100 parts by weight of the vinyl binder resin. The method according to claim 1, wherein the acrylic binder resin in which the corrosion resistant inorganic material is complexed comprises 5 to 23 parts by weight of the corrosion resistant inorganic material based on 100 parts by weight of the acrylic binder resin. The method of claim 1, 5 or 6, wherein the corrosion resistant inorganic material is at least one selected from the group consisting of Si, Ti, Al, Mg, Zr, Mo, P, W, V, Ni, Ag, Au and Cu Characterized in that it is selected from corrosion resistant minerals. The method of claim 1, wherein the second coating liquid has at least one corrosion resistance selected from the group consisting of acrylic, urethane, epoxy, alkyd, styrene / butadiene, polyethylene, polypropylene, polyester and mixtures thereof, which are not compounded with a corrosion resistant inorganic material. And further comprising a resin in which the inorganic material is not complexed. The method of claim 6, wherein the resin having no corrosion resistant inorganic material is contained at 50 wt% or less based on the solids content of the second coating solution. The method of claim 1, wherein the second coating liquid further comprises up to 10% by weight of the corrosion-resistant inorganic material based on the solids content of the first coating liquid. galvanized steel; A first coating layer formed on the steel sheet with a first coating solution containing 50 wt% or more of silicon based on the content of the inorganic component of the first coating solution; And 10-70% by weight of a vinyl-based binder resin compounded with a corrosion-resistant inorganic material, 15-75% by weight of an acrylic-based binder resin compounded with a corrosion-resistant inorganic material based on the solids content of the second coating solution on the first coating layer, about an epoxy-based binder resin 5 to 40% by weight and a solvent, wherein the corrosion-resistant inorganic material is a second coating layer formed of a second coating liquid of 3 to 25% by weight of the total solid content of the second coating liquid; excellent steelwork comprising black steel. The steel sheet according to claim 11, wherein the first coating liquid is coated on the steel sheet with a dry coating amount of 10-500 mg / m 2. 12. The steel sheet according to claim 11, wherein the second coating liquid is coated on the first coating layer with a dry coating weight of 100-1,500 mg / m 2. A first coating layer composition applied to the steel sheet of claim 11 comprising at least 50% by weight of silicon based on the content of the inorganic component of the first coating solution. The method of claim 14, wherein the first coating liquid further comprises at least one inorganic component selected from the group consisting of Ti, Al, Mg, Zr, Mo, P, W, V, Ni, Ag, Au and Cu. Composition characterized in that. 10-70% by weight of the vinyl-based binder resin compounded with the corrosion-resistant inorganic material, 15-75% by weight of the acrylic binder resin compounded with the corrosion-resistant inorganic material, about 5 to 40% by weight of the epoxy-based binder resin and the solvent, based on the solids content of the second coating solution. To include, wherein the corrosion-resistant inorganic material is applied to the first coating layer of claim 12 which is 3 to 25% by weight of the total solids of the second coating solution. 17. The composition of claim 16, wherein the vinyl binder resin including the corrosion resistant inorganic material comprises 5 to 23 parts by weight of the corrosion resistant inorganic material based on 100 parts by weight of the vinyl binder resin. The composition of claim 16, wherein the acrylic binder resin in which the corrosion resistant inorganic material is complexed comprises 5 to 23 parts by weight of the corrosion resistant inorganic material based on 100 parts by weight of the acrylic binder resin. 19. The at least one corrosion resistant inorganic material according to any one of claims 16 to 18, wherein the corrosion resistant inorganic material is selected from the group consisting of Si, Ti, Al, Mg, Zr, Mo, P, W, V, Ni, Ag, Au and Cu. The composition of claim 1, wherein the composition is selected from. The method of claim 16, wherein the second coating liquid is at least one corrosion resistance selected from the group consisting of acryl, urethane, epoxy, alkyd, styrene / butadiene, polyethylene, polypropylene, polyester and mixtures thereof having no complex of corrosion resistant inorganic material The composition is characterized in that it further comprises a resin which is not complexed with an inorganic material. The composition of claim 16, wherein the resin having no corrosion resistant inorganic material is contained at 50 wt% or less based on the solids content of the second coating solution. The composition of claim 16, wherein the second coating liquid further comprises 10% by weight or less of the corrosion resistant inorganic material based on the solids content of the first coating liquid.

Images