KR101143212B1 - A Resin Coated Steel Sheet Having Superior Multi Press Formability, A Resin Coating Composition Therefor and An Adhesive Improving Composition Therefor - Google Patents

Abstract

The present invention relates to a resin-coated steel sheet which is excellent in electromagnetic shielding workability, electromagnetic shielding property, coating film adhesion and electric conductivity, resin coating composition which gives excellent multi-pass workability to be used therein, and adhesion improving composition which improves the adhesion between a base steel sheet and a resin coating film . According to one embodiment of the present invention, a base steel sheet; And a resin comprising 100 parts by weight of a polyester resin having a weight of more than 20,000 and 50,000 on at least one of the front and back surfaces of the base steel sheet, 8-20 parts by weight of a melamine curing agent, 5-15 parts by weight of a quencher and 5-15 parts by weight of a pigment A resin coating film formed of a coating composition. Also, the resin coating composition and the composition of the polyurethane resin and melamine curing agent having a number average molecular weight of 10,000 to 25,000, 25 to 40 parts by weight of the composition, 3 to 20 parts by weight of the silicate compound, 0.5 to 10 parts by weight of the silane compound, And 1 to 5 parts by weight of a phosphoric acid ester. The resin-coated steel sheet is excellent in workability, adhesion, electrical conductivity and electromagnetic wave shielding property, and is suitable for use as a panel for electromagnetic devices, particularly, a shell panel.

Resin-coated steel sheet, multi-layering processability, adhesion, electric conductivity, electromagnetic wave shielding, electronic panel outer panel, fingerprint additive

Description

[0001] The present invention relates to a resin-coated steel sheet having excellent multi-layering workability, a resin coating composition used therefor, and a composition for improving adhesion,

The present invention relates to a resin-coated steel sheet excellent in multi-layering workability, a resin coating composition used therefor, and a composition for improving adhesion. More specifically, the present invention relates to a resin-coated steel sheet excellent in electromagnetic shielding, electromagnetic shielding, film adhesion, electrostatic earth and electric conductivity, a resin coating composition for imparting multiple workability to a steel sheet, And an adhesion improving composition for improving adhesion.

The resin-coated steel sheet has excellent corrosion resistance, weatherability, and solvent resistance, and its surface is also beautiful, and thus it is widely used for internal and external plates of household appliances and computers.

On the other hand, as electronic devices have recently become more sophisticated, miniaturized and highly functional, shortening of life span due to electromagnetic waves harmful to the human body and malfunctions of devices caused in electronic parts circuits are problematic. Therefore, the resin-coated steel sheet is required to have excellent surface electrical conductivity. Further, when the steel sheet is used as an outer panel, excellent designability, workability, adhesion, scratch resistance and the like are also required.

Conventional PCM (Pre-coated metal) coated steel sheet used for home appliances has a three-layer coating film formed by pretreatment, undercoating and topcoating, and has a thickness of more than 20 μm. In addition, there is a disadvantage in that productivity is low due to limitations of thick film coating by a roll coating or a curtain coating method, and it is also disadvantageous in terms of cost reduction.

As a method for solving this problem, there has recently been provided a low cost cost steel sheet for home appliance having excellent heat resistance, workability and adhesion to a coating film by minimizing the thickness of the coating film and improving the physical properties of the coating resin. However, such a steel sheet is limited in its application to appliances for deep processing due to thinning of the film thickness.

Therefore, there is a demand for a steel sheet which is excellent in workability, in particular, multi-layer workability, and further requires a resin-coated steel sheet excellent in adhesion to a coating film, productivity, workability, electrical conductivity and electromagnetic wave shielding property.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide a resin-coated steel sheet having excellent processability.

According to another embodiment of the present invention, there is provided a resin-coated steel sheet excellent in not only processability but also electromagnetic shielding property, coating film adhesion property, electrostatic earth property and electric conductivity.

According to another embodiment of the present invention, there is provided a resin coating composition which imparts good workability to a steel sheet.

Further, according to another embodiment of the present invention, there is provided an adhesion improving composition which provides adhesion to a steel sheet, electric conductivity, electrostatic earth property and electromagnetic wave shielding property.

In one aspect of the present invention,

Base steel sheet; And

100 parts by weight of a polyester resin having a weight of more than 20,000 to 50,000 on at least one surface of the front and back surfaces of the above-mentioned base steel sheet, 8 to 20 parts by weight of a melamine curing agent, 5 to 15 parts by weight of a quencher, 5 to 15 parts by weight of a resin-coated steel sheet.

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In another aspect of the present invention,

There is provided a resin coating composition comprising 100 parts by weight of a polyester resin having a number average molecular weight of more than 20,000 to 50,000, 8 to 20 parts by weight of a melamine curing agent, 5 to 15 parts by weight of a quencher and 5 to 15 parts by weight of a pigment.

Furthermore, in another aspect of the present invention,

25 to 40 parts by weight of a composition of a polyurethane resin and a melamine curing agent having a number average molecular weight of 10,000 to 25,000, 3 to 20 parts by weight of a silicate compound, 0.5 to 10 parts by weight of a silane compound, 0.2 to 8 parts by weight of a titanium compound, To 5 parts by weight of an adhesion improving composition (undercoat composition).

The resin-coated steel sheet according to one embodiment of the present invention exhibits excellent stretchability and workability, in particular, multi-layered workability, by a resin coating film comprising a high molecular weight polyester resin formed on the front and / It is suitable for use. The steel sheet according to one embodiment of the present invention also has a beautiful appearance because it has a semi-glossy and beautiful color. Furthermore, the steel sheet exhibits improved processability, adhesion, electrical conductivity, electrostatic earth and electromagnetic wave shielding due to the adhesion improving film (lower coating film) which is further formed on the front and / or rear surface of the base steel sheet.

Hereinafter, the resin coating composition (topcoat composition) and the adhesion improving composition (bottomcoat composition) which give excellent workability to the resin-coated steel sheet and steel sheet according to the present invention will be described in more detail.

The resin-coated steel sheet according to the present invention is a resin-coated steel sheet in which a resin coating film (top coating film) is formed on at least one surface of the front and back surfaces of a base steel sheet, and the resin coating film has a more improved stretchability and workability, It exhibits a beautiful color and appearance of semi-gloss. The resin coating film which gives the steel sheet excellent workability can be formed of a resin coating composition comprising a polyester resin having a number average molecular weight of more than 20,000 to 50,000, a melamine curing agent, a quencher and a pigment. A resin coating composition which is applied to a base steel sheet to form a resin coating to thereby impart good workability to the steel sheet is also provided by an embodiment of the present invention.

A high molecular weight polyester resin is used as the base resin in the resin coating composition so as to exhibit excellent stretchability and processability. It is preferable that the polyester resin having an aliphatic molecular structure also exhibits a low viscosity and a high elongation. As the polyester resin, a polyester resin having a number average molecular weight of more than 20,000 to 50,000, preferably 21,000 to 50,000, more preferably 21,000 to 35,000 and even more preferably 23,000 to 30,000 Is preferably used. The number average molecular weight of more than 20,000 means any number average molecular weight greater than 20,000 . When the number average molecular weight is 20,000 or less, sufficient workability, specifically, resistance to cracking of the coating film during multiple curing is insufficient, and when the number average molecular weight exceeds 50,000, this is not preferable in view of resin synthesis. In addition, the larger the number average molecular weight of the resin is, the more flexible the molecules are, and the resin is easily stretched during deep drawing, which is advantageous in terms of crack resistance. However, when the number average molecular weight is too large, there is a disadvantage in that the coating film adhesion is poor.

More preferably, the polyester resin is a mixture of two or more kinds of polyester resins having different number average molecular weights. But are not limited to, for example, a number average molecular weight of more than 20,000 to 25,000 A polyester resin and a polyester resin having a number average molecular weight of more than 25,000 to 50,000, preferably a number average molecular weight of more than 25,000 to 35,000, can be mixed and used. More specifically, when the number average molecular weight is more than 20,000 to 25,000 A polyester resin having a number average molecular weight of more than 25,000 to 50,000, more preferably a polyester resin having a number average molecular weight of 23,000 to 25,000 and a polyester resin having a number average molecular weight of 27,000 to 35,000 at a ratio of 3: 7 to 7 : 3 by weight. The number average molecular weight of more than 25,000 means any number average molecular weight greater than 25,000. A polyester resin having a number average molecular weight of more than 20,000 to 25,000 When the content is lower than the lower limit, the coating film cracking resistance is lowered, and when the content of the polyester resin having a number average molecular weight of more than 25,000 to 50,000 is larger than the upper limit value, the coating film adhesion is lowered. If the content of the polyester resin having a number average molecular weight of more than 20,000 to 25,000 exceeds the upper limit value, that is, if the content of the polyester resin having a number average molecular weight of more than 25,000 to 50,000 is less than the lower limit value, Which is undesirable.

As the curing agent for the resin coating composition, a melamine-based curing agent having excellent reactivity is used when induction heating is used and the time (Duration Time) is short. The melamine curing agent is blended in an amount of 8 to 20 parts by weight based on 100 parts by weight of the polyester resin. When the amount of the melamine-based curing agent is less than 8 parts by weight, the curing reaction becomes incomplete and the effect of fixing the respective constituents, that is, the pigment and silica, is low. When the amount exceeds 20 parts by weight, And it is not preferable from the viewpoint of crack resistance of the coating film. As the melamine-based curing agent, one having good reactivity is preferably used. Examples of the melamine-based curing agent include, but are not limited to, melamine, butoxymethylmelamine, hexamethoxymethylmelamine, trimethoxymethylmelamine, and the like. The melamine-based curing agents may be used alone or in combination of two or more thereof.

In the resin coating composition, a quencher is added in order to improve the corrosion resistance and hiding power of the resin film and to lower the core tack. The quencher may be added in an amount of 5 to 15 parts by weight based on 100 parts by weight of the polyester resin. If the content of the quencher is less than 5 parts by weight, the content is too small to have an effect on the corrosion resistance and glossiness, and if it exceeds 15 parts by weight, the coating film adhesion becomes poor. The quenching agent may be selected from the group consisting of, for example, silica, magnesium oxide, zirconia, alumina and titania, alone or in combination. Silica is particularly preferred.

The resin coating composition is also compounded with a pigment. The pigment may be blended in an amount of 5 to 15 parts by weight based on 100 parts by weight of the polyester resin. If the content of the pigment is less than 5 parts by weight, it is difficult to obtain sufficient heat absorbing and / or dissipating properties and a high covering ratio of the base steel sheet, and if it exceeds 15 parts by weight, the coating film adhesion and surface appearance are deteriorated. The average particle diameter of the pigment is not particularly limited, but it is preferable in terms of dispersibility to use an ink having an average particle size of about 10 to 30 nm. As the pigment, any pigment applicable to the resin coating composition can be used in consideration of the heat radiation property and color to be imparted to the steel sheet. Examples of the pigment include, but are not limited to, black pigments such as carbon black and carbon nanotubes, graphite, ceramic pigments, and colored pigments used as coloring agents in PCM steel sheets. The ceramic pigment is not particularly limited and may be selected from common metal oxides known to be applicable in this technical field such as chromium, iron, nickel, cobalt, antimony, tin, silicon lead, aluminum, vanadium, praseodymium, May be used alone or in combination of two or more to exhibit various colors.

Examples of carbon black pigments include, but are not limited to, Nerox (TM) series, Printex (TM) series, Highblack (TM) series from Ebonics (Germany) These pigments may be used alone or in combination of two or more different pigments.

The resin coating composition may further contain a titanium compound having an effect of increasing adhesion with the steel sheet, if necessary. The titanium compound may be blended at a maximum of 1.0 part by weight with respect to 100 parts by weight of the polyester resin. If the content of the titanium compound exceeds 1.0 part by weight, crack resistance of the coating film deteriorates, which is not preferable. The titanium compound is optionally added and does not limit the lower limit value. However, when a titanium compound is added so that the effect of improving the adhesion, which is an effect of addition of the titanium compound, can be sufficiently exhibited, the titanium compound is added in an amount of not less than 0.3 part by weight to 100 parts by weight of the polyester resin .

Examples of such titanium compounds may include, but are not limited to, titanium carbonate, isopropyldithiethanolaminotitanium, lactic acid titanium chelate, and titanium acetylacetonate. These titanium compounds may be used alone or in combination of two or more.

In order to further improve the physical properties of the steel sheet treated with the resin coating composition as well as the polyester resin, the melamine-based curing agent, the silica and the pigment, the resin coating composition may contain a wax, a curing catalyst, And at least one additive such as a phosphate-based adhesion promoting agent. These optional additives are generally known in the art, and their compounding ratio and the like are not particularly limited, and those skilled in the art can appropriately use these additives as needed.

As the solvent in the resin coating composition, cyclohexanone, toluene, xylene, isopropanol, solvent naphtha, cellosolve, cellosolve acetate and butyl cellosolve can be used. These solvents may be used alone or as a mixture of two or more. After application, cyclohexanone, which is an excellent ketone in spreadability, is the most preferred solvent.

The resin coating composition may be prepared by adding and compounding each of the above components to a solvent. The solid content of the resin coating composition is preferably 30-50 wt%. When the solid content of the resin coating composition is less than 30% by weight, sufficient adhesion amount to the steel sheet can not be secured. When the content of the resin coating composition exceeds 50% by weight, viscosity increases and it is difficult to control the coating amount.

In addition, the viscosity of the resin coating composition is controlled according to the content of the solvent, and the amount of the solvent is not particularly limited, and the content thereof can be appropriately controlled according to the technique commonly used in this technical field. The content of the solvent is not limited thereto, but it is preferable to control the amount of the resin to such an extent that it takes 20 to 80 seconds for the resin coating composition to be discharged from the Din Cup (DIN, 53211), for example.

In one embodiment of the present invention, the resin coating composition may be applied to at least one of the front surface and the rear surface of the base steel sheet. That is, the resin coating composition may be applied to only the front or rear surface of the base steel sheet, or may be applied to both the front surface and the back surface to form a resin coating film (top coat film) having excellent processability. As the base steel sheet, a galvanized steel sheet can be used. Examples of the galvanized steel sheet include, but are not limited to, a hot-dip galvanized steel sheet (GI), a galvannealed galvanized steel sheet (GA), and an electrogalvanized steel sheet (EG).

The resin coating film may be formed to a dry film thickness of 8 to 40 탆, preferably 8 to 30 탆, and more preferably a dry film thickness of 8 to 15 탆. If the dry film thickness of the resin coating film is less than 8 占 퐉, the drawability and adhesion of the coating film are poor and the cracks are likely to occur in the multiple coating. If the thickness exceeds 40 占 퐉, the manufacturing cost is increased and the productivity is lowered.

The resin coating composition may be applied to the front and / or rear surface of the base steel sheet in a manner generally known in the art; For example, a bar-coater, a roll coater or a curtain coater method or the like can be used.

Drying of the coated resin coating composition may also be accomplished by any method generally known in the art. The drying can be performed by a hot air heating method, an infrared heating method, or an induction heating method, though it is not limited thereto.

It is preferable that the resin coating composition is coated on the resin steel sheet and then dried at 180-240 占 폚 with PMT (Peak Metal Temperature). If the PMT is less than 180 DEG C, film formation is difficult, and if the PMT is about 240 DEG C, the PMT is sufficiently dried, so that a drying temperature exceeding this temperature results in unnecessary heat loss.

On the other hand, in order to impart workability, electrical conductivity, electrostatic earth and electromagnetic wave shielding properties to the steel sheet as well as the adhesion between the steel sheet and the resin coating film, the resin-coated steel sheet is coated on the front and / Coating film) may be further included. Improved Adhesion The coating film not only enhances the adhesion between the base steel sheet and the resin coating film but also imparts workability, electrical conductivity, electrostatic earth property and electromagnetic wave shielding property to the steel sheet. / RTI > and / or the back surface.

In one embodiment of the present invention, it is preferable that an adhesion improving coating film is formed on the back surface of the base steel sheet. In another embodiment of the present invention, in the case where the resin coating film is formed only on one side of the base steel sheet, it is preferable to form the adhesion improving coating film on the base steel sheet surface on which the resin coating film is not formed considering the workability, corrosion resistance, Do. According to one embodiment of the present invention, there is provided a resin-coated steel sheet in which an adhesion improving coating film is formed on both sides of a base steel sheet and a resin coating film is formed on one side of the adhesion improving coating film.

In the case of a steel sheet including a resin coating film (top coating film), the adhesion improving coating film (undercoating film) is located between the base steel sheet and the resin coating film (top coating film). FIG. 1 is a side cross-sectional view of a resin-coated steel sheet on which an adhesion-improving coating film and a resin coating film are formed on one side of a base steel sheet according to an embodiment of the present invention. FIG. 2 is a side cross-sectional view of a resin-coated steel sheet on which an adhesion improving coating film is formed on the front and rear surfaces of a base steel sheet according to an embodiment of the present invention, and a resin coating film is formed on the adhesion improving coating film on the front side. 3 is a side cross-sectional view of a resin-coated steel sheet on which an adhesion improving film (undercoating film) and a resin coating film (top coat film) are formed on both the front and rear surfaces of the base steel sheet.

In one embodiment of the present invention, the adhesion improving coating film formed on the front and / or rear surface of the base steel sheet may be formed of the following adhesion improving composition. The adhesion improving composition described later is also provided by an embodiment of the present invention.

The composition for improving the adhesion includes a composition of a polyurethane resin and a melamine curing agent having a number average molecular weight of 10,000 to 25,000, a silicate compound, a silane compound, a titanium compound and a phosphate ester.

In general, the inorganic component is good in adhesion between the steel sheet and the resin layer, but the ductility is deteriorated, so that cracking of the steel sheet is liable to occur when the steel sheet is processed such as in the case of shrinkage. On the other hand, the organic resin is excellent in ductility, but has a disadvantage of weak adhesion with the steel sheet, so that it is preferable to use an organic resin mixed with an inorganic component. The adhesion improving composition according to one embodiment of the present invention is an organic component and an inorganic component blended in consideration of the above interaction.

The polyurethane resin-melamine curing agent composition blended in the adhesion improving composition has an action of imparting excellent adhesion, workability and ductility to the steel sheet. The polyurethane resin-melamine-based curing agent composition is excellent in adhesion to a base steel sheet and a resin coating film which is a top coat, so that cracking of a coating film occurring during processing of a household electrical component can be prevented. In addition, the polyurethane resin-melamine-based curing agent exhibits excellent miscibility and solution stability with other components of the adhesion-improving composition as an alkaline resin such as an inorganic compound compounded in the adhesion improving composition.

The polyurethane resin-melamine curing agent composition may be used as a mixture of a polyurethane resin and a melamine curing agent in combination with a polyurethane resin: melamine curing agent at a weight ratio of 10: 1 to 5: 1. The polyurethane resin-melamine-based curing agent composition having the above composition ratio is preferable in terms of corrosion resistance and solvent resistance of the coating film.

The polyurethane resin preferably has a number average molecular weight of 10,000 to 25,000. If the number average molecular weight is less than 10,000, the solvent resistance of the coating film is insufficient, and if the number average molecular weight exceeds 25,000, the storage stability of the solution is insufficient. Examples of the melamine-based curing agent include, but are not limited to, melamine, butoxymethylmelamine, hexamethoxymethylmelamine, trimethoxymethylmelamine, and the like. The melamine-based curing agents may be used alone or in combination of two or more thereof.

The polyurethane resin-melamine-based curing agent composition may be blended in an amount of 25 to 40 parts by weight with the above-mentioned blending amount of the other components of the adhesion improving composition. If the blending amount is less than 25 parts by weight, the adhesion with the top coat film is insufficient. If the blending amount exceeds 40 parts by weight, it is not preferable from the viewpoint of corrosion resistance due to an increase in the organic matter content.

In the adhesion improving composition, the silicate compound is coated on a steel sheet to form a three-dimensional network structure, thereby imparting corrosion resistance and adhesion to the steel sheet. Such silicate compounds are widely used not only for corrosion resistance but also for zinc plating due to their excellent bonding strength with the zinc plated layer and serve as a bridge for bonding the plating layer and the top resin coating layer. The silicate compound may be blended in an amount of 3 to 20 parts by weight with the amount of other components constituting the adhesion improving composition. If the content of the silicate compound is less than 3 parts by weight, adhesion with the steel sheet is weak and it can not exhibit excellent corrosion resistance. If the content of the silicate compound exceeds 20 parts by weight, bonding force with the upper resin layer becomes weak, which is not preferable. Examples of silicate compounds include, but are not limited to, those selected from the group consisting of lithium polysilicate, sodium polysilicate, potassium polysilicate, and colloidal silica, either singly or in combination.

The silane compound in the adhesion-improving composition forms a three-dimensional inorganic polymer chain structure with various organic and inorganic materials to improve the corrosion resistance. The silane compound may be compounded in an amount of 0.5 to 10 parts by weight with respect to the amount of other components constituting the adhesion improving composition. When the content of the silane compound is less than 0.5 parts by weight, adhesion with the steel sheet is weak, and excellent corrosion resistance can not be exhibited. Even if the content of the silane compound exceeds 10 parts by weight, it does not exhibit any further improvement in physical properties. Therefore, there is a problem that the quality is deteriorated due to problems such as stability of the solution. Examples of the silane compound include, but are not particularly limited to, 3-aminopropyltriepoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, N- ( -Aminoethyl) -? - aminopropyltrimethoxysilane,? -Glycidoxypropyltriethoxysilane,? -Glycidoxytrimethyldimethoxysilane, and the like. The silane compounds may be used alone or in combination of two or more.

The titanium compound acts to accelerate the crosslinking and curing of the adhesion improving composition and to improve the corrosion resistance of the coating film. The crosslinking and curing properties by the titanium compound and the corrosion resistance can be optimally exhibited. The composition may be blended in an amount of 0.2 to 8 parts by weight with respect to the amount of other components constituting the composition for improving adhesion. If the content of the titanium compound is less than 0.2 parts by weight, the corrosion resistance effect is poor. If the content of the titanium compound exceeds 8 parts by weight, further improvement in physical properties is not exhibited. Examples of the titanium compound include, but are not limited to, titanium carbonate, isopropyltriethanolaminotitanium, lactic acid titanium chelate, and titanium acetylacetonate. The titanium compounds may be used alone or in combination of two or more.

A phosphate ester for enhancing the adhesion of the composition to the steel sheet is further blended with the composition for improving adhesion. The phosphoric acid ester may be compounded in an amount of 1.0 to 5.0 parts by weight with respect to the amount of other components constituting the adhesion improving composition. If the phosphoric ester content is less than 1.0 part by weight, the adhesion between the steel sheet and the upper resin coating film is insufficient, and even if it exceeds 5.0 parts by weight, there is no effect of increasing the physical properties to increase the content and it is uneconomical.

The adhesion improving composition may further contain a low molecular weight urethane resin having excellent adhesion with a steel sheet as a binder resin that acts to bind the above inorganic components. The low-molecular-weight urethane resin used as the binder resin has a low molecular weight when the molecular weight is high, so that the low-molecular-weight urethane resin having a number average molecular weight of 1,000 or less is used. The smaller the number average molecular weight is, the more preferable the urethane resin is, and the lower limit value of the number average molecular weight is not particularly limited. The larger the number average molecular weight of the urethane resin is, the larger the chain of molecules is, and the flexibility of the resin itself is deteriorated. The low-molecular-weight urethane resin can be blended to a maximum of 60 parts by weight relative to the amount of the other components constituting the adhesion improving composition. If the amount of the low molecular weight urethane resin is more than 60 parts by weight, the resin content is too high and the corrosion resistance is deteriorated. The lower molecular weight urethane resin is not limited to the lower limit of the content as an optional component, but it is more preferable that the low molecular weight urethane resin is added in an amount of 20 parts by weight or more to the adhesion improving composition so that sufficient action can be exhibited by the addition of the urethane resin.

If necessary, an additive such as a defoaming agent or a wetting agent may be added to the adhesion improving composition to improve the coating property. Such additives are common to those skilled in the art, and those skilled in the art can select and use them appropriately as needed. The adhesion-improving composition can be prepared by adding the above-mentioned respective components in pure water to the above-mentioned amount, and blending them.

The adhesion improving composition is preferably adjusted to have a solid content of 8 to 20% by weight, preferably 10 to 16% by weight. When the solid content of the composition for improving adhesion is less than 8% by weight, an appropriate undercoating amount can not be obtained. When the content is more than 20% by weight, solution storage and workability are poor. The adhesion improving composition preferably has a viscosity of 4-10 cps because it exhibits excellent roll coating workability in this viscosity range. When the viscosity of the composition for improving adhesion is less than 4 cps, an appropriate undercoating amount can not be obtained. When the viscosity exceeds 10 cps, solution storage and workability are poor. The solid content and viscosity of the adhesive resin composition can be adjusted by adjusting the amount of pure water.

The adhesion improving composition is applied to the front and / or rear surface of the base steel sheet to form an adhesion improving coating film, and the resin-coated steel sheet having the adhesion improving coating film exhibits not only excellent workability but also adhesion, electric conductivity, electrostatic earth and electromagnetic shielding properties.

If necessary, the adhesion improving composition may be coated on the front and / or rear surfaces of the base steel sheet and dried to further improve the adhesion improving coating film.

The adhesion improving composition may be formed on the entire surface and / or the rear surface of the base steel sheet to have a dry film thickness of 0.8 to 3.0 μm, preferably a dry film thickness of 0.8 to 2.0 μm, more preferably 0.8 to 1.5 μm have. If the dry film thickness of the coating film is less than 0.8 mu m, the adhesion and corrosion resistance are insufficient, and if it exceeds 3.0 mu m, the electrical conductivity is insufficient. On the other hand, the dry film thickness of 0.8 to 3.0 mu m corresponds to an adhesion amount of 800 to 3,000 mg / m < 2 >.

The adhesion improving composition may be coated on a base steel sheet by a method generally known in the art, such as the application of the resin coating composition described above, but is not limited thereto. For example, a bar coater, a roll coater, A curtain coater method can be used. Drying of the coated adhesion improving composition may also be performed by any method generally known in the art, as in the case of the resin coating composition described above. The drying can be performed by a hot air heating method, an infrared heating method, or an induction heating method, though it is not limited thereto. The coating of the adhesion-improving composition is preferably dried at 150 to 180 ° C in PMT (Peak Metal Temperature) in terms of drying efficiency. If the PMT is less than 150 ° C, it is insufficient for curing the resin, and if it exceeds 180 ° C, it is not preferable from the viewpoint of adhesion.

The resin-coated steel sheet provided in one embodiment of the present invention comprises (1) a resinous coating formed on at least one of the front and back surfaces of (1) a base steel sheet and (2) a base steel sheet; (2) ① Adhesive steel sheet, ② Adhesion improving coating formed on at least one of the front and back side of the backing sheet (undercoat); And (3) a resin coating film (top coating film) formed on the front or back side backing steel sheet on which the adhesion improving film is not formed, or on the front and / or rear adhesion improving coating film. In the resin-coated steel sheet according to an embodiment of the present invention, the lower sheet, the upper sheet and the steel sheet may be, for example, but not limited to, the following laminated form; Rear Top Coat / Steel Plate, Rear Top Coat / Rear Coating / Steel Plate, Rear Top Coat / Rear Coating / Steel Coating / Front Coating / Rear Coating / Rear Coating / Steel Coating / Front Coating, Rear Coating / Steel Coating / Front Coating, Rear Coating / Front top,

Rear plate / Steel plate / Front top plate, Rear plate plate / Steel plate / Front plate plate / Front plate plate (Fig. 1), Steel plates / Front plate plate, Steel plates / Front plate plate / Front plate plate, Rear plate plate, Rear plate plate 2).

The resin-coated steel sheet according to one embodiment of the present invention exhibits excellent stretchability and processability, specifically, multi-roll workability. Specifically, the physical properties of the resin-coated steel sheet according to one embodiment of the present invention are attained by improving the adhesiveness of multiple cigarettes, and exhibit excellent press workability in multiple cigarettes, specifically, crack resistance of the coating film. In addition, the steel sheet according to an embodiment of the present invention exhibits excellent electrostatic earth resistance with a surface electric resistance value of 0.1 m? Or less. Furthermore, the resin-coated steel sheet is excellent in electric conductivity and electromagnetic shielding property, has semi-gloss and beautiful color and appearance, and has a thin resin film thickness than conventional black PCM steel sheet, , And is suitable for use as an advanced panel in the field of video appliances in which demand is rapidly increasing recently.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, the present invention is not limited to the following examples.

Example 1: Property evaluation according to the compositional change of the adhesion improving composition (undercoat composition)

A mixture of a urethane resin having a number average molecular weight of 18,000 and a melamine curing agent in a weight ratio of 10: 3, a silicate compound, a silane compound, a titanium compound and a phosphoric ester were added to purified water in the amounts shown in Table 1 below, A composition for improving the adhesiveness of ashes and comparative materials was prepared. On the other hand, the amount of pure water was adjusted so that the solid content of each adhesion improving composition was 10 to 15% by weight. The viscosity of the adhesion improving composition is adjusted to a range of about 4-10 cps.

As the melamine-based curing agent, butoxymethylmelamine was used. As the silicate compound, lithium polysilicate was used. As the silane compound, 3-aminopropyltriepoxysilane was used. As the titanium compound, titanium carbonate was used. A low molecular weight polyurethane having a molecular weight of 900 was used when low molecular weight polyurethane was used.

Thereafter, the adhesion improving composition of each of the inventive material and the comparative material prepared in the following Table 1 was applied to both sides of an electro galvanized steel (electro galvanized steel (EG) coated on both sides with a single side coated amount of 20 g / m ² Coated to a dry film thickness of 1 mu m, baked at PMT-165 DEG C, and then cooled to form an adhesion improving film (undercoat film).

Then, the corrosion resistance of the steel sheet having the adhesion improving coating film was measured and shown in Table 1 below. The corrosion resistance was measured as described in the following physical property evaluation items.

On the other hand, the resin coating composition was roll-coated on a coating film having a dry film thickness of 10 mu m on the coating film having improved adhesion to the front surface of the steel sheet having the adhesion improving coating film shown in Table 1, followed by baking at PMT-210 DEG C and cooling to form a resin coating film After that, the adhesion of the resin coating film was evaluated and shown in Table 1. The adhesion was measured as described in the following physical property evaluation items.

The resin coating composition (top coat composition) was prepared by adding 100 parts by weight of a cyclohexanone polyester resin having a number average molecular weight of 27,000, 15 parts by weight of a melamine curing agent, 10 parts by weight of a quencher and 10 parts by weight of a pigment. The cyclohexanone solvent is used so that the total solid content of the resin coating composition is 35 to 45% by weight. In addition, the resin coating composition was formulated so as to have a time-consuming viscosity of about 30 to 60 seconds upon discharge from the Dean cup (DIN 53211). Hereinafter, the resin coating composition having such a composition will be referred to as "base resin coating composition" hereinafter. To the to a melamine-based curing agents and the trimethoxy methyl melamine pigment having an average particle diameter of about 15-25㎚ Printex (Printex) ^TM (Cod Inc. (Degussa), Germany), matting agent, the mean particle size of about Synthetic silica of DONGYANG CHEMICAL CHEMICAL CO., LTD. Was used.

[Table 1] Evaluation of physical properties according to composition of undercoat composition

As can be seen from the above Table 1, the adhesion improving composition and the low molecular weight urethane resin containing the polyurethane resin-melamine curing agent composition, the silicate compound, the silane compound, the titanium compound and the phosphoric acid ester in the content of the present invention were further added (Undercoating film) formed of the adhesion improving composition containing the above-mentioned resin composition exhibits excellent corrosion resistance and adhesion.

On the other hand, the comparative material 1-4 in which a large amount of silane is added, the comparative material 1-6 in which a titanium compound is added in a large amount, and the comparative material 1-10 in which a large amount of phosphoric acid ester is added show good physical properties, but are used in large amounts and are uneconomical.

Example 2: Evaluation of physical properties of a steel sheet according to conditions for forming a coating film (undercoating film)

35 parts by weight of a mixture of a urethane resin having a number average molecular weight of 17,000 and a melamine resin in a weight ratio of 10: 3, 10 parts by weight of a silicate compound, 3 parts by weight of a silane compound, 3 parts by weight of a titanium compound, 2 parts by weight of a phosphoric ester, (Hereinafter referred to as a " basic adhesion improving composition ") was prepared by blending the above components. The pure water was adjusted so that the solids content of the adhesion improving composition was about 12-15% by weight. The viscosity of the adhesion improving composition is adjusted to the range of about 4-10 cps.

As the melamine-based curing agent, butoxymethylmelamine was used. As the silicate compound, sodium polysilicate was used. As the silane compound, 3-aminopropyltriepoxysilane was used. As the titanium compound, titanium carbonate was used.

Thereafter, the basic adhesion improving composition was applied to both sides of an electro galvanized steel sheet (electro galvanized steel (EG) having a single side coated amount of 20 g / m < ² > Coated and dried by baking at the firing temperature (PMT) shown in Table 2 below, followed by cooling to form an undercoating film. The corrosion resistance of the inventive material and the comparative steel sheet was measured, and the results are shown in Table 2. The corrosion resistance ≪ / RTI >

On the other hand, the standard resin coating composition of Example 1 was roll-coated to a dry film thickness of 10 탆 on the coating film having improved adhesion on the front surface of the steel sheet having the adhesion improving coating film shown in Table 2 and dried at PMT-210 캜 to obtain a resin coating film . After that, the adhesiveness of the inventive material having the resin coating film and the comparative steel sheet was evaluated and shown in Table 2 below. The adhesion was measured as described in the following physical property evaluation items.

[Table 2] Properties according to undercoating conditions

As can be seen from the above Table 2, the resin steel sheet having the adhesion improving coating film formed with the baking temperature and the coating amount (dry film thickness) falling within the range according to one embodiment of the present invention shows excellent corrosion resistance and adhesion.

Example 3 Evaluation of Properties of Resin Coating Composition (Phase Composition)

The basic adhesion improving composition of Example 2 was coated on both sides of an electro galvanized steel sheet (electro galvanized steel (EG) galvanized on both sides with a single-sided coating amount of 20 g / m < ² > Coated, PMT baked at 165 ° C, and then cooled to form an adhesion improving film (undercoating film).

Then, the resin coating composition of the composition as shown in Table 3 below was roll-coated on the coated surface of the steel sheet having the adhesion improving coating film so as to have a dry film thickness of 10 탆, Dried and cooled to form a resin coating film (top coat film). The resin coating compositions of the following Table 3 were prepared by adding cyclohexanone in the contents shown in Table 3, respectively. The cyclohexanone solvent is used so that the total solid content of each resin coating composition is 35 to 45% by weight. The resin coating composition is formulated to have a time-consuming viscosity of about 30 to 60 seconds upon discharge from the Dean Cup (DIN 53211). In the resin coating composition, trimethoxymethyl melamine was used as a melamine-based curing agent, silica having a particle diameter of 3 탆 as a light quenching agent, and Printex ^TM (manufactured by Daegu Silica Co., Ltd.) having a particle diameter of about 15-25 nm Degussa, Germany) was used. And titanium carbonate is used when a titanium compound is further added.

Then, the solvent resistance, the film cracking resistance and the corrosion resistance of the inventive material having the resin coating film and the comparative steel sheet were evaluated and are shown in Table 3 below. The solvent resistance, the coating film crack resistance and the corrosion resistance were measured as described in the following physical property evaluation items.

[Table 3] Property evaluation according to composition change of top coat film

(Invention Reagent 3-10, the resin coating composition is applied on both sides of the adhesion improving coating)

As can be seen from the above Table 3, a resin coating composition comprising a polyester resin, a melamine curing agent, a quencher and a pigment in an amount according to an embodiment of the present invention, and a resin coating film formed of a resin coating composition further comprising a titanium compound A top coat film) exhibits excellent solvent resistance, coating film crack resistance and corrosion resistance.

Example 4: Evaluation of physical properties of steel sheet according to resin coating (top coat) formation conditions

The basic adhesion improving composition of Example 2 was coated on both sides of an electro galvanized steel sheet (electro galvanized steel (EG) galvanized on both sides with a single-sided coating amount of 20 g / m < ² > Coated, PMT baked at 165 ° C, and then cooled to form an adhesion improving film (undercoating film).

Then, the base resin coating composition of Example 1 was roll-coated so as to have a dry film thickness of the following Table 4 on the coating film having improved adhesion to the front surface of the steel sheet on which the adhesion improving coating film was formed, and baked And cooled to form an aqueous coating film. Then, the solvent resistance, crack resistance and corrosion resistance of each of the inventive material and comparative steel sheet in Table 4 were evaluated and shown in Table 4 below. The solvent resistance, the coating film crack resistance and the corrosion resistance were measured as described in the following physical property evaluation items.

[Table 4] Evaluation of physical properties according to coating conditions

As can be seen from Table 4, the black resin steel sheet having an aqueous coating film formed at a baking temperature and a dry film thickness falling within the range according to one embodiment of the present invention has excellent solvent resistance, film crack resistance and corrosion resistance. A signboard of the comparative material 4-4 having a thickness of more than 40 mu m exhibits excellent physical properties, but the production cost is increased, which is not preferable from the viewpoint of productivity.

(Property evaluation method)

(1) Bending part crack workability (coating film crack resistance)

Stretch the resin-coated steel sheet to 25%, bend the surface of the steel sheet by 180 °, and tighten it until it becomes flat (0T-bending). Insert a scotch tape on the curved coating and peel off the coating The bending portion crackability (coating film crack resistance) was evaluated by the presence or absence of cracks on the tape peeled off.

[Evaluation standard]

?: No cracks,?: Micro cracks, X: Cracks.

(2) Solvent resistance

The resin-coated steel sheet was prepared as a test piece of 50x100 mm in size, and judged by the number of times until the coating film was peeled off when rubbed with a force of 1 kgf with a gum soaked with methyl ethyl ketone (MEK).

[Evaluation standard]

?: More than 50 times,?: 20 to 50 times, X: less than 20 times

(3) Corrosion resistance

The corrosion resistance was evaluated by using a salt spraying apparatus (JIS E2731, Japan Industrial Standard Test Method JIS E2731) to evaluate the corrosion resistance of the steel plate specimen by spraying 5% brine at a spraying pressure of 1 Kg / m ² on a steel sheet at a rust generation area%. In the case of the undercoat which improves the adhesion, it was evaluated as rust occurrence area% after 72 hours after the saline spray. In the case of the top coat of the resin coating film, the rust occurrence area after 120 hours after the spraying was evaluated as%.

O: area of corrosion 0 area,?: Area of corrosion 5 to 10 area, X: area of corrosion 10 area

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a side cross-sectional view of a resin-coated steel sheet on which an adhesion improving coating film and a resin coating film are formed on one surface of a base steel sheet,

FIG. 2 is a side cross-sectional view of a resin-coated steel sheet on which an adhesion improving film is formed on the front and back surfaces of a base steel sheet, and a resin coating film is formed on the adhesion improving film,

Fig. 3 is a side cross-sectional view of a resin-coated steel sheet on both the front and back surfaces of a base steel sheet, in which an adhesion improving coating film and a resin coating film are formed.

Claims (21)

Base steel sheet; And Wherein at least one of the front and back surfaces of the backing steel sheet has a number average molecular weight of more than 20,000 to 25,000 100 parts by weight of a polyester resin obtained by mixing a polyester resin and a polyester resin having a number average molecular weight of more than 25,000 to 50,000 in a weight ratio of 3: 7 to 7: 3, 8 to 20 parts by weight of a melamine curing agent, And 5 to 15 parts by weight of a pigment. The composition of claim 1, wherein at least one of a front surface and a back surface of the base steel sheet has a number average molecular weight of 10,000 to 25,000, 25 to 40 parts by weight of a composition of a polyurethane resin and a melamine curing agent, 3 to 20 parts by weight of a silicate compound, 0.5 to 10 parts by weight of a titanium compound, 0.2 to 8 parts by weight of a titanium compound, and 1 to 5 parts by weight of a phosphoric acid ester, wherein the undercoating composition comprises, when a resin coating film is formed on the base steel sheet, And is formed on the base steel sheet when the resin coating film is not formed between the steel sheet and the resin coating film and on the base steel sheet Resin coated steel sheet. The resin-coated steel sheet according to claim 1, wherein the base steel sheet is a galvanized steel sheet. delete delete delete The melamine-based curing agent according to claim 1 or 2, wherein the melamine-based curing agent is at least one melamine-based curing agent selected from the group consisting of melamine, butoxymethylmelamine, hexamethoxymethylmelamine and trimethoxymethylmelamine. Steel plate. The resin-coated steel sheet according to claim 1, wherein the resin coating composition further comprises a titanium compound at a maximum of 1.0 part by weight. The resin-coated steel sheet according to claim 2 or 9, wherein the titanium compound is at least one selected from the group consisting of titanium carbonate, isopropylditriethanolaminotitanium, lactic acid titanium chelate and titanium acetylacetonate. . The resin-coated steel sheet according to claim 1, wherein the resin coating film has a dry film thickness of 8 to 40 탆. The resin-coated steel sheet according to claim 1, wherein the resin coating film is formed by drying the resin coating composition with a PMT (Peak Metal Temperature) of 180-240 ° C. The resin-coated steel sheet according to claim 2, wherein the undercoating film is formed on both sides of the base steel sheet, and the resin coating film is formed on one side of the undercoating film. The resin-coated steel sheet according to claim 2, wherein the silicate compound is at least one selected from the group consisting of lithium polysilicate, sodium polysilicate, potassium polysilicate, and colloidal silica. 3. The composition of claim 2 wherein said silane compound is selected from the group consisting of 3-aminopropyltriepoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, N- (? -Aminopropyltrimethoxysilane,? -Glycidoxypropyltriethoxysilane, and? -Glycidoxytrimethyldimethoxysilane. The resin-coated steel sheet according to claim 1, The resin-coated steel sheet according to claim 2, wherein the undercoating composition further comprises up to 60 parts by weight of a urethane resin having a number average molecular weight of 1,000 or less. The resin-coated steel sheet according to claim 2, wherein the undercoating film has a dry film thickness of 0.8 to 3.0 占 퐉. The resin-coated steel sheet according to claim 2, wherein the undercoating film is formed by drying the undercoating composition with PMT at 150 to 180 ° C. When the number average molecular weight exceeds 20,000 to 25,000 100 parts by weight of a polyester resin obtained by mixing a polyester resin and a polyester resin having a number average molecular weight of more than 25,000 to 50,000 in a weight ratio of 3: 7 to 7: 3, 8 to 20 parts by weight of a melamine curing agent, And 5 to 15 parts by weight of a pigment. 19. The resin coating composition of claim 18, wherein the resin coating composition further comprises up to 1.0 part by weight of the titanium compound. delete delete

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