WO2017179913A2 - High quality textured composite resin composition and galvanized steel sheet coated with composite resin composition - Google Patents

Abstract

The present invention provides a composite resin composition comprising 30 to 60% by weight of a urethane-modified polyester resin in which a linear type and a crosslinking type are mixed, 3 to 15% by weight of at least one curing agent from among an aziridine curing agent and a melamine curing agent, 0.05 to 1.5% by weight of an acid curing catalyst, 0.05 to 1.5% by weight of an amine curing catalyst, 0.1 to 15% by weight of a colored inorganic pigment, and a remainder of a solvent. Also, the present invention provides a composite resin-coated galvanized steel sheet having a composite resin coating film formed of the above composition.

Description

High quality composite resin composition and galvanized steel sheet coated with the composite resin composition

The present invention relates to a steel sheet excellent in processability and chemical resistance having a high-quality color texture coated with a composite resin of color for application in the field of imaging appliances field and its manufacturing method.

For home appliances such as TVs, the Case Top, Bottom Chassis and Rear Cover parts must have a luxurious texture that induces consumers to buy, and the moldability required for press processing. Corrosion and chemical resistance are required to be used for more than 10 years.

Thus, aluminum metal, plastic injection molding or thick film color coated steel sheet is used for the above components. Among these, aluminum metal has advantages of being light and resistant to corrosion. However, the appearance made of aluminum metal generally has a monotonous texture, and is usually expensive because of the color coating after hair-line processing.

In addition, the plastic injection molding can implement a variety of designs, there is no limit of molding is used as a panel material, but low productivity and environmental friendliness has been pointed out as a problem.

On the other hand, color-coated steel sheets are usually composed of the lower, middle, and top layers, and the coating thickness is usually 30 mm or more. Therefore, high-quality appearance can be realized, but productivity is low and expensive.

The present invention, as an embodiment, a color composite resin composition excellent in the processability and chemical resistance of the high-quality texture, thin film by omitting the intermediate coating in the existing color-coated steel sheet, galvanized steel plate coated with the composite resin composition and a method of manufacturing the same To provide.

In this patent, the thickness of the coating film is thin, but the micron-sized metal and inorganic pigments surface-treated with organic material to make it appear uniformly in the coating film as well as the effect of acid and amine catalysts effectively. It is to form a predetermined pattern of.

In addition, the present invention is not only beautiful in appearance and texture, but also has excellent physical properties such as corrosion resistance, chemical resistance, and press workability, and aims to provide a panel for video appliances.

In one aspect, the present invention provides a composite resin composition. The composite resin composition is, in one aspect, 30 to 60% by weight of a mixture of linear and crosslinked urethane-modified polyester resin, 3 to 15% by weight of at least one of an aziridine curing agent or melamine curing agent, 0.05 to 1.5 acid curing catalyst It provides the composite resin composition which is a weight%, 0.05-1.5 weight% of amine curing catalysts, and 0.1-15 weight% of colored inorganic pigments, and contains a remainder solvent.

The urethane-modified polyester resin is preferably a weight ratio of linear and crosslinking type of 1: 1 to 1: 4.

The melamine curing agent preferably comprises a weight ratio of methylated melamine and imino melamine in a ratio of 1: 1 to 1: 4.

The methylated melamine may be butoxymethyl melamine, hexamethoxy methyl melamine or mixtures thereof.

The imino melamine may be used trimethoxymethyl melamine.

The acid curing catalyst may be at least one sulfonic acid selected from the group consisting of p-toluenesulfonic acid, dodecylbenzenedisulfonic acid, dinonyltoluene disulfonic acid, and dinonylnaphthalenesulfonic acid.

The acid curing catalyst may be sulfonic acid blocked with an amine compound.

The sulfonic acid blocked with the amine compound may be amine neutralized dodecylbenzenesulfonic acid.

The amine curing catalyst may be a primary amine, secondary amine, tertiary amine or a mixture of two or more thereof.

It is preferable that the volatility of the amine curing catalyst is higher than that of the acid curing catalyst.

The colored composite resin composition may further include a metal pigment, and the metal pigment may further include 0.1 to 15% by weight of the total weight of the composition.

The solvent may be included in an amount such that the composite resin composition takes a viscosity of 20 to 200 seconds to be discharged from the DIN cup (DIN, 53211).

Furthermore, the present invention includes a holding steel sheet including a galvanized layer and a composite resin coating film formed on at least one surface of the holding steel sheet, wherein the composite resin coating film is a linear and crosslinked urethane-modified polyester resin 50 to 80% by weight. ; 3 to 20% by weight of at least one of an aziridine curing agent or a melamine curing agent; And it provides a galvanized steel sheet, which is a colored composite resin coating film formed of colored inorganic pigment 3-20% by weight.

The urethane-modified polyester resin is preferably a weight ratio of linear and crosslinking type of 1: 1 to 1: 4.

The colored inorganic pigment may be at least one selected from the group consisting of carbon black, carbon nanotubes, graphite, graphene, ferric oxide (Fe ₂ O ₃ ), and titanium dioxide (TiO ₂ ).

The colored inorganic pigments may have a particle diameter of 0.01 to 20 µm and an oil absorption of 60% or less.

The colored composite resin coating film further comprises a metal pigment, the metal pigment is preferably 0.5 to 20% by weight of the total weight of the colored composite resin coating film.

The metal pigment may be aluminum alone or an aluminum containing alloy.

It is preferable that the said metal pigment is flake shape of 0.1-5 micrometers in thickness.

The metal pigments are cetyl sulfate sodium salt, cetyl sulfate ammonium salt, stearyl sulfate sodium salt, stearyl sulfate ammonium salt, glycerin fatty acid ester, polyglycerol fatty acid ester, glyceryl ricinoleate, glyceryl stearate, glyceryl rosinate, Lanes-5, lanes-10, lanes-15, lanolin, lautrimonium chloride, cetrimonium bromide, cetrimonium chloride, sodium isostearoyl lactate, sorbitan laurate, sorbitan stearate, It may be surface treated with at least one organic compound selected from the group consisting of sorbitan oleate and the organic compounds of Formulas 1 to 5.

[Formula 1]

(In Formula 1, R is a C5-C15 chain alkyl compound.)

[Formula 2]

(In Formula 2, R is a C1-C10 chain alkyl compound, n is an integer from 1 to 10.)

[Formula 3]

(In Formula 3, R is a C1-C10 chain alkyl compound, n is an integer of 1 to 10)

[Formula 4]

(In Formula 4, R is a C1-C10 chain alkyl compound, n is an integer of 1-10.

[Formula 5]

(In Formula 5, R is a C1-C10 chain alkyl compound, and n is an integer of 1-10.)

The composite resin film preferably has a thickness of 3 to 30㎛.

The composite resin coating film may have a pattern.

A transparent resin coating film may be further included on the composite resin coating film. The transparent resin coating film may be formed of 65 to 95% by weight of the urethane-modified polyester resin mixed with linear and crosslinking type and 5 to 35% by weight of at least one curing agent of aziridine curing agent or melamine curing agent.

The transparent resin coating film may have a thickness of 0.1 to 3㎛.

Zinc-coated steel sheet coated with a colored composite resin according to an embodiment of the present invention has a high-quality texture of excellent appearance having a metallic texture on the surface and a predetermined pattern on the surface of the coating film.

In addition, the colored composite resin coated steel sheet according to an embodiment of the present invention can be obtained by coating the surface of the coating film with a thin coating by the roll coating or spray coating to obtain a beautiful colored coating coating.

In addition, the colored composite resin coated steel sheet according to an embodiment of the present invention is improved in press workability and chemical resistance, and thus can be suitably used as a panel for imaging appliances.

1 is a graph of the composition ratio of colored metal and inorganic pigments.

2 is a cross-sectional view schematically showing a layer structure of a composite resin coated galvanized steel sheet having a composite resin coating film according to one embodiment of the present invention.

Figure 3 is a schematic diagram schematically showing a process for producing a coated galvanized steel sheet by applying a composite resin composition according to an embodiment of the present invention.

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

The colored composite resin composition of the present invention is a predetermined inorganic pigment in a transparent resin composition consisting of a urethane-modified polyester polymer and aziridine or melamine curing agent, an acid catalyst, an amine catalyst and a solvent in which linear and crosslinking types are mixed in a predetermined ratio. It provides a colored composite resin composition comprising a metal pigment. With such a resin composition, a predetermined pattern can be continuously formed on the surface of the coating film due to the difference in curing rate between the inside of the coating film and the surface of the coating film during curing of the binder resin.

To this end, the composite resin composition of the present invention is 30 to 60% by weight of the urethane-modified polyester resin relative to the total resin composition weight; 3 to 15% by weight of iriridine curing agent or melamine curing agent; 0.05 to 1.5 weight percent acid catalyst; 0.05 to 1.5% by weight of the amine curing catalyst, 0.1 to 15% by weight of the colored inorganic pigment and the remainder of the solvent, the resin composition may further comprise a metal pigment.

Hereinafter, the resin composition of this invention is demonstrated in detail.

<Binder Resin>

The present invention uses a urethane-modified polyester resin as a binder resin. Urethane-modified polyester resin used in the present invention can form a fine pattern on the surface of the coating film during curing, it is excellent in workability and chemical resistance.

As the urethane-modified polyester resin, a weight average molecular weight (Mw) of 2000 to 40000 may be used. For example, the weight average molecular weight may be 2000 to 30000, 2000 to 25000, 3000 to 40000, 5000 to 40000, 3000 to 30000, 5000 to 30000 or 5000 to 25000. If the molecular weight is less than 2,000, the chemical resistance and processability of the coating film are insufficient, and if the molecular weight exceeds 40,000, the storage stability and workability of the solution may deteriorate.

As said binder resin, it is more preferable to use the urethane modified polyester resin which mixed linear and crosslinking type especially. In the case where the linear and crosslinked urethane-modified polyester resin is used as the binder resin, workability can be further improved, and a predetermined pattern is more easily obtained by the nature of the functional group when reacting with an acid catalyst and an amine catalyst. Contribute to the formation. More preferably, the urethane-modified polyester resin may be a glass transition temperature of 0 to 70.

The urethane-modified polyester composition may be blended in a weight ratio of linear structure and crosslinked structure of 1: 1 to 1: 4, preferably 1: 1 to 1: 3. It is preferable to mix | blend a crosslinked structure and resin of a linear structure with the said compounding ratio from the viewpoint of the processability of a coating film, and the physical property of a coating film hardness, and can form a hard and dense hardened film.

In addition, the urethane-modified polyester resin is preferably 10 to 500, more preferably those having a hydroxyl group (-OH) of 20 to 400. When hydroxyl value exceeds 500, the chemical resistance of a coating film falls, and when it is less than 10, crosslinking property of a coating film falls.

In addition, the urethane-modified polyester resin may have an acid value of 5 to 30 mgKOH / g, preferably an acid value of 10 to 25 mgKOH / g. When the acid value exceeds 30 mgKOH / g, the chemical resistance of the coating film is lowered, and when the acid value is less than 10 mgKOH / g, the crosslinkability of the coating film is lowered.

The urethane-modified polyester resin may be included in the range of 30 to 60% by weight based on the total weight of the composite resin composition. If it is out of the above range, the drying property may be degraded when the coating film is cured, and other deterioration of physical properties occurs.

<Hardener>

The composite resin composition of the present invention includes a curing agent for curing the binder resin, and examples of the curing agent include the aziridine-based curing agent and the melamine-based curing agent. Although these hardening | curing agents are excellent in reactivity, it does not specifically limit, For example, the aziridine hardening | curing agent or melamine hardening | curing agent of the following structural formula is mentioned.

Formula (a) is an aziridine curing agent, wherein R is -H, -CH ₃ , -CH ₂ CH ₃ , -CH ₂ CH ₂ CH ₃ , -CH ₂ OH or -CH ₂ CH ₂ OH, these aziri A dine hardener can be used individually by 1 type, of course, and can also be used in mixture of 2 or more type.

In addition, as said melamine hardening | curing agent, although it is not limited to this, the imino melamine of Formula (b) and the methylated melamine of Formula (c) can be used. Compared with methylated melamine, imino melamine has a fast curing reaction rate, which is advantageous for high-speed curing, and as the content thereof increases, the degree of curing increases and the hardness of the coating film increases. On the other hand, fully substituted methylated melamine provides a good surface quality due to the slow cure rate and the smoothness of the coating film. Therefore, while improving the surface quality of a coating film using methylated melamine, the reaction rate can be improved by adding imino melamine which is fast in reaction rate. Preferably, the imino melamine of formula (b) and the methylated melamine of formula (c) may be mixed in a weight ratio of 1: 1 to 1: 4.

The methylated melamine may include butoxymethyl melamine and hexamethoxy methyl melamine, and the imino melamine may include trimethoxymethyl melamine. Examples of melamine products usable in the present invention include CYMEL-303, CYMEL-325, CYMEL-327, CYMEL-350, CYMEL-370 from CYTEC, and RESIMINE-7550, RESIMINE-717, RESIMINE-730, RESIMINE from SOLUTIA. -747, RESIMINE-797 and BIP's BE-3717, BE-370, BE-3747, etc. are mentioned.

The melamine curing agent may be included in an amount of 3 to 15% by weight based on the composite resin composition. It is preferable that the resin and the melamine-based curing agent are blended in the blending ratio in terms of physical properties of the coating film, and may be formed into a dense cured film.

<Acid catalyst and amine catalyst>

The composite resin composition of the present invention includes an acid catalyst and an amine catalyst as a curing reaction accelerator to promote the curing reaction of the urethane-modified polyester resin as a binder and the aziridine or melamine molecules as a curing agent to improve the hardness of the coating film.

In this case, it is appropriate to use the amine catalyst having a higher volatility than the acid catalyst. These catalysts cause a difference in curing rate between the inside and the surface of the coating film when the curing reaction is performed at a high temperature. By using the difference in curing rates, irregularities on the surface of the coating film are formed to form a predetermined pattern in the coating film. When the pattern is formed on the surface of the coating film as described above, the surface texture can be improved by the matting effect.

The acid catalyst is not limited thereto, and sulfonic acid may be used. Examples of the sulfonic acid include p-toluenesulfonic acid, dodecylbenzenedisulfonic acid, dinonyltoluene disulfonic acid, dinonylnaphthalenesulfonic acid, and the like, and of course, these may be used alone or in combination of two or more thereof. .

More preferably, the sulfonic acid catalyst is one that is blocked with an organic chain that can be dissociated by heat. Examples of such blocking materials include amine compounds. Examples of the sulfonic acid blocked with such an organic chain include, but are not limited to, amine neutralized dodecylbenzenesulfonic acid.

The acid catalyst may be used from 0.05 to 1.5 parts by weight based on 100 parts by weight of the resin composition. When the amount of the acid catalyst used is too small, the curing temperature of the coating film becomes high, and the physical properties of the coating film cannot be maintained, and when too much, the curing of the coating film occurs too rapidly or the stability of the solution with time deteriorates.

In addition, the amine catalyst is a hydrocarbon-substituted primary amine (NH ₂ -R ₁ ), secondary amine (NH-R ₁ , -R ₂ ), tertiary amine (NR ₁ , -R ₂ , -R ₃ ) Can be used. In this case, the hydrocarbon (R ₁ , R ₂ , R ₃ ) may be an aliphatic or aromatic chain. Specific examples of the amine catalyst that can be used in the present invention include, but are not limited to, diethylamine, diisopropylamine, diisopropanolamine, di-n-propylamine, di-n-butylamine, diisobutylamine , Di-tert-butylamine, diallylamine, diamylamine, N-ethyl-1,2-dimethylpropylamine, N-methylhexylamine, di-n-octylamine, piperidine, 2-pipecoline , 3-piecoline, 4-piecoline, morpholine, and the like, and these may be used alone, or two or more may be mixed and used.

The amine catalyst may also be used in the amount of 0.05 to 1.5% by weight based on the composite resin composition. If the amount of the amine catalyst is too small, the curing temperature of the coating film becomes high and the physical properties of the coating film cannot be maintained. If too much, the curing of the coating film occurs too rapidly or the stability of the solution with time deteriorates.

Colored inorganic pigments

In the present invention, color may be imparted by adding an inorganic pigment to the composite resin composition. The inorganic pigment may be suitably used in the present invention as long as it has an inherent color. However, as shown in FIG. 1, a combination of a pigment having an intrinsic color of black and red and white may be used. By using the pigment at a predetermined blending ratio of various colors can be implemented is preferred.

The inorganic pigment is preferably included in an amount of 0.1 to 15% by weight. If the inorganic pigment content is less than 0.1% by weight, it is difficult to realize a high concealment rate and beautiful color on the steel sheet, and when the content exceeds 15% by weight, the viscosity of the solution is increased, and workability is lowered and a beautiful surface appearance is difficult to obtain.

Examples of the black pigment include carbon black, carbon nanotubes, graphite, and graphene, and among these, carbon black is more preferable. Examples of the carbon black pigments include, but are not limited to, the Nerox ™ series, the Printex ™ series, the Highblack ™ series, etc., from Ebonics, Germany. The carbon black black pigment is preferably used in terms of dispersibility of the pigment to use an average particle size of about 10 ~ 100nm, preferably 10-30nm.

Ferrous oxide (Fe ₂ O ₃ ) may be mentioned as the red inorganic pigment. Iron oxide is non-toxic, chemically stable, and has the advantage of producing a variety of colors. In addition, the yellow inorganic pigments include antimony, and examples of the white inorganic pigments include titanium dioxide (TiO ₂ ) and zinc oxide (ZnO).

It is preferable to use the said inorganic pigment which is low in oil absorption. The oil absorption of the pigment may be up to 60%, preferably in the range of 5 to 50%. If the oil absorption amount is too high, the workability is bad and it is difficult to obtain a predetermined pattern, so it is preferable to have the oil absorption amount in the above range.

In addition, the average particle size (particle diameter) of the colored inorganic pigment is appropriately small depending on the thickness of the coating film, for example, may be in the range of 0.1 to 20㎛. In particular, when the pigment particles are continuously arranged on a predetermined pattern formed on the surface of the coating film, it is possible to increase the hardness of the coating film and to improve the texture, thereby providing better design. Therefore, it is preferable that the average size of the inorganic pigment particles has a dry coating thickness of ± 5㎛ of the colored coating composite resin composition. For example, it may be in the range of 5 to 15 μm.

<Metal Pigment>

The composite resin composition may further include a metal pigment, it may implement a metal texture by using a metal pigment. At this time, the metal pigment is preferably further included in an amount of 0.1 to 20.0 parts by weight based on the total weight of the composite resin composition.

As the metal pigment used in the present invention, any metal on the periodic table can be used as long as it has a micron size. For example, Ag, Al, Co, Cu, Fe, Mg, Mn, Mo, Ni, Pd, Pt, Sn, W, Zn metal or the metal comprised by the alloy containing these metals is mentioned.

The metal pigments used in the present invention may be in the form of granules, plates, blocks, or flakes. However, when used as paints, the flakes are more preferably flakes in order to impart excellent metallic feeling and brightness. desirable. Although the pigment on the said flake is not specifically limited, It is preferable to use what has a thickness of 0.1-5 micrometers in order to make the appearance of a coating film excellent.

Among these metallic pigments, aluminum pigments are most preferred because they have excellent gloss and have a low specific gravity and are well floated in the coating film. At this time, the aluminum pigment may be comprised only with aluminum, and may be comprised with the alloy of aluminum and another metal. When using an aluminum alloy pigment, the purity of aluminum is not specifically limited.

And although the aluminum pigment used for this invention is not specifically limited, What has an average particle size of 30 micrometers or less can be used. When the average particle diameter is 30 µm or more, the surface of the coating film becomes rough and excellent texture cannot be obtained. If the average particle diameter is one having a particle size of the above range or less, it can be suitably used in the present invention. At this time, the lower limit is not particularly limited, but is preferably 0.1 µm or more from the viewpoint of ease of production and economical efficiency, and furthermore, in view of the aggregation and dispersibility of the metal pigment, it is more preferable to use an aluminum pigment having a mean particle size of 1 µm or more. Do.

Moreover, ceramic pigments, such as glass, mica, alumina, or titania, can also be used for the resin composition of this invention. Such ceramic pigments may be made to exhibit a metallic metallic texture by plating a surface with a metal to form a metallic coating.

The metal pigment is more preferably surface treated with an organic compound. When surface treatment of the metal pigment with an organic compound, it improves chemical stability to suppress the generation of gas, to prevent the aggregation of solids in the production and storage of the resin composition of the present invention, and in the coating film during the production of coated steel sheet and The dispersion can be further improved.

In this case, as the organic compound suitable for the surface treatment of the metal pigment, the following may be used.

Higher fatty acid alkali salts or ammonium salts represented by the following formula (1) and mixtures thereof may be used.

[Formula 1]

(Wherein R is a C5 to C15 chain alkyl compound)

Examples of the compound include sodium stearate or ammonium salt and sodium oleate or ammonium salt.

Alkyl sulfate salts can also be used. As a compound corresponding to this, sodium salt or ammonium salt of cetyl sulfate and stearyl sulfate is mentioned, for example.

In addition, alkyl ether sulfate salts of the following Chemical Formula 2 may be used.

[Formula 2]

(Wherein R is a C ₁ to C ₁₀ chain alkyl compound and n is an integer from 1 to 10).

Next, the sodium salt or ammonium salt of the alkyl phenol ethoxylate of the following formula (3) can be used.

[Formula 3]

(Wherein R is a chain-like alkyl compound of C ₁ ~ C _10, n is an integer from 1 to 10)

Furthermore, the polyoxyethylene fatty acid ester of the following formula (4) can be used.

[Formula 4]

(Wherein R is a C ₁ to C ₁₀ chain alkyl compound and n is an integer of 1 to 10).

Furthermore, polyoxyethylene sorbitan fatty acid esters of formula 5 can be used.

[Formula 5]

(Wherein R is a C ₁ to C ₁₀ chain alkyl compound and n is an integer from 1 to 10).

In addition, glycerin fatty acid and polyglycerin fatty acid esters, glyceryl ricinoleate, glyceryl stearate, glyceryl rosinate, lanes-5, lanes-10, lanes-15, lanolin, lautrimonium chloride, Certrimonium bromide, cetrimonium chloride, sodium isostearoyl lactate, sorbitan laurate, sorbitan stearate, sorbitan oleate and mixtures thereof may also be used.

The composite resin composition of the present invention is mixed with an iriridine curing agent or melamine curing agent, an acid catalyst and an amine catalyst in a urethane-modified ester resin containing a linear and cross-linking type in a predetermined ratio as a binder resin in a solvent to disperse the composite resin composition After manufacture, it can manufacture by adding and mixing a colored inorganic pigment, or it can manufacture by mixing and dispersing the colored inorganic pigment in a solvent. In addition, it is possible to further mix the metal pigment to implement the color of the metal texture.

In order to further improve the physical properties of the coating film as described above, the resin composition of the present invention may be further blended with additives such as waxes, curing catalysts, pigment aggregation inhibitors, antifoaming agents, and leveling agents, if necessary. . These arbitrary additives can be suitably used also in this invention as long as they are generally used, and can be applied according to a normal compounding ratio.

In the resin composition, the balance other than the components to be blended is a solvent, and as the solvent, toluene, xylene, isopropanol, solvent naphtha, cellosolve, cellosolve acetate, butyl cellosolve, and the like may be used. The solvent may be used in one kind or a mixture of two or more kinds.

Although the viscosity of the composite resin composition may vary depending on the content of the solvent, the content of the solvent added to the composition may be appropriately adjusted as necessary, and is not particularly limited herein. For example, in consideration of the coating amount and adhesion of the resin composition, for example, it may be adjusted to an amount that becomes a viscosity of 20 to 200 seconds to be discharged from the DIN cup (DIN, 53211).

The resin composition according to the present invention is to provide a coating film having excellent processability and chemical resistance, and each of the components forms a composite network structure by forming a coating film by mixing an inorganic pigment and a metal with a linear and crosslinked urethane-modified polyester resin. To provide excellent press formability and hardness.

It provides the steel plate containing the coating film formed by the said composite resin composition of this invention. The steel sheet may be provided by applying the colored resin composition described above to at least one of the first and second surfaces of the base steel sheet. That is, the composite resin composition may be applied only to the first surface or the second surface of the steel sheet, or may be applied to both the first and second surfaces to form a colored composite resin coating film. It may include a transparent resin coating film formed on the composite resin coating film.

Galvanized steel sheet may be used as the base steel sheet. Examples of galvanized steel sheets are not limited thereto, but for example, hot dip galvanized steel (GI), alloyed hot dip galvanized steel (GA), electrogalvanized steel (EG), aluminum plated steel or zinc-aluminum-magnesium Alloy plated steel sheet or the like can be used.

The colored composite resin coating film on the base steel sheet is formed by the colored resin composition provided above, and at least one curing agent and colored inorganic pigment of a urethane-modified polyester resin, aziridine curing agent, or melamine curing agent mixed with linear and crosslinking type. It includes. According to the present invention, the coating film composition is 50 to 80% by weight of the linear and crosslinking type urethane-modified polyester resin, 3 to 20% by weight of at least one of aziridine curing agent or melamine curing agent and colored inorganic pigment 3-20 Contains weight percent.

The solvent contained in the composition does not remain in the steel sheet by drying. In addition, the acid curing catalyst and the amine curing catalyst may also be volatilized, but may remain in a trace amount.

Furthermore, when the composition for forming the coating film further comprises a metal pigment, the pigment is included in the coating film, the pigment may be present in an amount of 0.5 to 20% by weight of the total weight of the coating film.

The colored composite resin coating film is formed to have a dry coating thickness of 3 to 30 µm, preferably 5 to 25 µm, and more preferably 5 to 20 µm. When the dry coating thickness of the colored composite resin film is less than 3 μm, the color and hiding power, processability, and solvent resistance of the composite resin film are low, and when it exceeds 30 μm, manufacturing cost increases and productivity is low, which is not preferable.

A transparent resin coating film may be formed on the colored composite resin coating film. The transparent resin coating film may be formed using the same composition except that inorganic pigments and metal pigments that provide color are not included in the composition for forming the colored composite resin coating film. The transparent resin coating film thus formed may be formed of 65 to 95% by weight of a urethane-modified polyester resin mixed with linear and crosslinked forms and 5 to 35% by weight of at least one curing agent of an aziridine curing agent or melamine curing agent.

The transparent resin coating film may be formed to have a dry coating thickness of 0.1 to 3㎛, preferably 0.3 to 2㎛, more preferably 0.5 to 1.5㎛. If the dry coating thickness of the transparent resin film is less than 0.3㎛ does not improve the additional color and texture, if the thickness exceeds 3㎛ the effect is not significant improvement in color and texture compared to the increase in thickness.

The colored composite resin composition and the transparent resin composition may be coated on the first side and / or the second side of the base steel sheet by a conventional resin coating method, for example, a bar coater, a roll coater, a slot die (Slot). Die coating or curtain coater method may be used. Furthermore, the colored composite resin composition may be applied by any one of the above methods, and the transparent resin composition may be applied by a method different from the method of applying the composite resin composition of the above methods, and further, by spray coating A transparent resin coating film can also be formed.

Drying of the coated colored composite resin composition and the transparent resin composition may also be carried out by any method generally known in the art. Although drying is not limited to this, it can carry out by a hot air heating system, an infrared heating system, or an induction heating system.

The colored composite resin composition and the transparent resin composition are preferably dried at 180 to 260 at PMT (Peak Metal Temperature). Although not limited thereto, in particular, for example, in the case of a hot air heating method, the composition may be dried by hot air treatment for 10 to 50 seconds at a temperature of 200 to 340 atmosphere. In the case of the induction heating method, the composition may be dried for 5 to 20 seconds in a frequency range of 5 to 50 MHz and power of 3 to 15 KW.

In another embodiment of the present invention, when the composite resin film is formed on only one surface of the steel sheet, it is preferable that a resin coating film is formed on the surface of the steel sheet on which the composite resin film is not formed in consideration of the processability and corrosion resistance of the steel sheet.

According to one embodiment of the present invention, a steel coating film is formed on both sides of the base steel sheet, and a steel sheet having improved workability is formed in which a colored composite resin coating film provided as one embodiment of the present invention is formed on one surface of the coating film. On the other hand, in the case of a steel plate including a colored composite resin coating film (top coat), the undercoat can be located between the base steel sheet and the composite resin coating film (top coat).

Figure 2 is a side cross-sectional view of a colored composite resin sheet formed of a colored composite resin composition. As can be seen from a of FIG. 2, a composite resin coating film made of a composite resin composition according to the present invention may be formed on a surface of a galvanized steel sheet. In this case, the composite resin composition may be coated on a chromium-free undercoat on a galvanized steel sheet as shown in b of FIG. 2 to form the composite resin film. Meanwhile, as shown in FIG. 2C, a transparent resin film may be formed on the composite resin film. Furthermore, as shown in FIG. 2D, the composite resin composition may be applied onto the undercoat to form a composite resin film, and a transparent resin coating film may be formed thereon.

In one embodiment of the present invention, the undercoat is further formed on the first and / or second surface of the holding steel sheet is not particularly limited, increase the adhesion between the holding steel sheet and the colored composite resin coating film, It may be any coating film known to be applied between the base steel sheet and the colored composite resin coating film (top coat) by imparting to the steel sheet properties required for other steel sheets such as paintability, corrosion resistance, and the like.

Thus, by forming the composite resin coating film on the Cr-free undercoat film or by forming the transparent resin coating film on the composite resin coating film layer, the concealment effect of the steel sheet is increased due to the increase in the coating thickness by the undercoat and the transparent resin. It is more preferable because the diffuse reflection of light can be reduced to give a more beautiful color.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, the following examples are examples of specific embodiments of the present invention, and the present invention is not limited thereto.

Example  1 to 12 and Comparative example  1 to 11

As shown in Table 1 below, a urethane-modified polyester resin, a curing agent, an acid catalyst and an amine catalyst were mixed and added to a solvent to prepare 100 parts by weight of a transparent resin composition. In the said transparent resin composition, remainder is a solvent.

Subsequently, urethane-modified polyester resins, curing agents, acid catalysts and amine catalysts, inorganic pigments, and metal pigments were further added and mixed in the contents as shown in Examples 1 to 12 and Comparative Examples 1 to 11 of Table 1 below, and these were mixed. Into the solvent was dispersed using a high speed bead mill disperser. This produced the colored composite resin composition.

As the urethane-modified polyester resin, a weight ratio of a crosslinking type resin having a weight average molecular weight of 16000 (manufactured by KCC, Tg = 10) and a linear resin (manufactured by KCC (manufactured by KCC, Tg = 60)) of 20000 is 2: 1. It was used by mixing.

The curing agent was used by mixing hexamethoxymethylmelamine as imino melamine and butoxymethylmelamine as methylated melamine in a weight ratio of 1: 3. Further, the aziridine curing agent used in Example 1 was used having the structural formula (R = -CH ₃₎ of the formula (a).

As the acid catalyst, amine neutralized dodecylbenzenesulfonic acid (pH = 6-7, activity = 25%, manufactured by King, USA) was used.

The amine catalyst was used dinonyl naphlenylene sulfonic acid (DNNSA).

The solvent used cellosolve acetate.

Colored pigments were used as black pigments (carbon black, Printex ™ series from Evonix), red pigments (ferric oxide) and white pigments (titanium dioxide).

The prepared solution is an electrogalvanized steel sheet (Inventive Examples 1, 4, 5, 6, 9, 10 and 14 to 22) or an electrogalvanized steel sheet having an electrogalvanized layer having a surface coating weight of 20 g / m 2 as shown in Table 2. Composite resin compositions of Examples 1 to 12 and Comparative Examples 1 to 11 on steel sheets (Inventive Examples 2, 3, 7, 8, 12, and 13) having a chromium-free undercoat layer having a dry coating film thickness of 1 µm on the substrate. Roll-coated to a dry film thickness of 5 to 15 µm, cured and dried at PMT (peak metal temperature) 230, and then cooled to cool the composite resin coating having the composite resin coating layers of Inventive Materials 1 to 22 and Comparative Materials 1 to 11. Steel sheet was prepared.

In the case of the invention materials 3, 8, and 13, the transparent resin coating film (1 micrometer of dry coating film thickness) was formed on the said composite resin coating layer. In this case, the transparent resin composition used was the same as the composite resin composition of Example 2 except that the inorganic pigment and the metal pigment were not included, and the transparent resin composition was sprayed on the composite resin coating layer.

3 schematically illustrates a process of forming a transparent resin coating layer of a roll-coating composite resin coating and spraying method to form a composite resin steel sheet coating layer.

The surface properties of the composite resin coated steel sheet having the composite resin coating layer thus obtained were evaluated, and the results are shown in Table 2. Surface properties and their evaluation shown in Table 2 was performed by the following method.

< Film thickness >

The thickness of the coating film was measured with a non-destructive portable coating film thickness gauge.

<Appearance>

The design and texture of the color of the coating film, in particular, whether the pattern formed on the surface was formed, the size, uniformity and continuity of the formed pattern, and the like were evaluated.

[Evaluation standard]

◎: (very good), ○: (excellent), △: (inferior), ×: (very inferior)

<Glossy>

60 ° mirror reflection value was measured and evaluated using the SHEEN company.

<Pencil hardness>

A 10 cm line was drawn at a 45 ° angle with a 1000 ± 10 g load with a Mitsubishi Corporation pencil (HB-4H) and evaluated for scratches.

Corrosion Resistance Evaluation

Corrosion resistance was evaluated by the Cyclic Corrosion Test (CCT). Brine spray (concentration 5%, spray pressure of 35 to 1kg / cm 2) for 5 hours at 95% relative humidity, dry at 2% at 30% RH, temperature 70, then 95% RH 50 The treatment was repeated for 1 cycle for 3 hours at 100 cycles, and then the area of red rust generated on the surface of the steel sheet was evaluated.

[Evaluation standard]

◎: corrosion area 0% ○: corrosion area 5% or less

(Triangle | delta): 5-30% of corrosion area X: 30% or more of corrosion area

< Bending  Processability Evaluation>

After 10% tensile processing on the colored coated steel sheet, the surface of the steel sheet is placed in a vise, bent 180 ° at a pressure of 1 kgf, and tightened until it becomes flat (0T-bending). When the scotch tape was attached to the bent coating film and then the coating film was peeled off, the crack was generated on the surface peeled off the tape and the presence or absence of the film peeling was evaluated.

[Evaluation standard]

(Double-circle): No crack generation and peeling of a coating film in a coating film

(Circle): Fine cracks are seen in a coating film, but there is no peeling of a coating film.

(Triangle | delta): Crack generation is severe in a coating film, and there is no coating film peeling

X: A crack generate | occur | produces severely in a coating film, and a coating film peels

<Chemical Resistance>

When gauze wetted with MEK (Methyl Ethyl Ketone) at 1 Kg load was rubbed reciprocally with a force of 1 Kgf, the number of times until the coating film was peeled off was determined.

[Evaluation standard]

◎: 100 times or more

○: more than 70 times less than 100 times

△: more than 40 times less than 70 times

×: less than 40 times

In the invention, the colored composite resin composition has excellent appearance design due to its beautiful exterior color when coated with a dry coating thickness of 10 μm, but includes a undercoat layer by Cr-free undercoat treatment at the bottom of the composite resin coating layer. (Inventive material 1, 4, 5, 6, 9, 10, 14 and 15) or in the case of including a transparent resin film by further treating the transparent resin on top of the composite resin coating layer (Inventive material 2, 3, 7, 8 , 12 and 13), it can be seen that more beautiful colors. This effect is considered to be the result of the increase in the hiding effect of the steel sheet with the increase in the thickness of the coating film by the bottom coat and the transparent resin, and the increase in the clarity of the color due to the pigment due to the reduced reflection of light.

From the comparative materials 1 and 2, the urethane-modified polyester resin has a higher degree of curing than the linear structure, and the comparative material 2 using the urethane-modified polyester resin having a crosslinked structure has a high hardness and excellent chemical resistance. On the other hand, in terms of processability, there was a poor effect such as cracking of the coating film. On the other hand, the comparative material 1 using the urethane modified polyester resin which has a linear structure showed the result opposite to the comparative material 2.

In addition, Comparative Materials 6 and 7 using the compositions of Comparative Examples 6 and 7, in which the weight ratio of the linear urethane-modified polyester resin and the crosslinked urethane-modified polyester resin do not satisfy the preferred range of the present invention, are in terms of processability and chemical resistance. Resulted in inferior results.

On the other hand, inventive materials 1 to 3 using the composition of Example 1 containing an aziridine curing agent is somewhat lower than the case of using a melamine curing agent composed of an alkyl group of a chain structure and containing an aromatic ring, and chemical resistance Although the results were relatively low, it was found that they had good overall film properties.

In addition, compared to methyl melamine, imino melamine has a fast curing reaction rate, which is advantageous for high-speed curing, and when its content is increased, the degree of curing increases and the hardness of the coating film increases. For this reason, the comparative material 4 which used the imino melamine hardening | curing agent independently showed the poor workability of a coating film. On the other hand, in the case of Comparative Material 3 using a methylated melamine curing agent alone, the workability was evaluated as excellent, but the chemical resistance was low.

In addition, Comparative materials 8 and 9 using the compositions of Comparative Examples 8 and 9, which is a case where the mixing ratio of the melamine curing agent is outside the preferred range of the present invention, showed a result of further reduced processability and chemical resistance, in particular, the content of imino melamine In the case of Comparative Example 9 contained in this excess, it was evaluated that the appearance design was deteriorated.

Furthermore, when an acid catalyst and an amine catalyst are added, irregularities on the surface of the coating film are formed when the coating film is dried, thereby forming a predetermined pattern, thereby obtaining a coating film having an improved surface texture by the matting effect. However, in the case of Comparative Material 5 using the composition of Comparative Example 5, which does not contain an acid catalyst and an amine catalyst, a pattern was not formed, and the hardness was low and the corrosion resistance was poor. On the other hand, it was found that the comparative properties 10 and 11, in which the amount of the catalyst used was small or excessive, deteriorated in appearance characteristics.

(a) roll-coater, (b) solution pan, (c) back-up roll, (d) spray coater, (e) oven

Claims (26)

1. 30 to 60 wt% of a urethane-modified polyester resin mixed with linear and crosslinking type;

   3 to 15 weight percent of at least one curing agent of an aziridine curing agent or a melamine curing agent;

   0.05 to 1.5% by weight acid curing catalyst;

   0.05 to 1.5 weight percent of an amine curing catalyst;

   0.1-15% by weight of colored inorganic pigments; And

   Residual Solvent

   Composite resin composition comprising a.
2. The composite resin composition of claim 1, wherein the urethane-modified polyester resin has a weight ratio of linear and crosslinked in a range of 1: 1 to 1: 4.
3. The composite resin composition of claim 1, wherein the melamine curing agent comprises a weight ratio of methylated melamine and imino melamine in a ratio of 1: 1 to 1: 4.
4. The composite resin composition of claim 3, wherein the methylated melamine is butoxymethyl melamine, hexamethoxy methyl melamine or a mixture thereof.
5. The composite resin composition of claim 3, wherein the imino melamine is trimethoxymethyl melamine.
6. The composite resin composition of claim 1, wherein the acid curing catalyst is at least one sulfonic acid selected from the group consisting of p-toluenesulfonic acid, dodecylbenzenedisulfonic acid, dinonyltoluenedisulfonic acid, and dinonylnaphthalenesulfonic acid.
7. The composite resin composition of claim 1, wherein the acid curing catalyst is sulfonic acid blocked with an amine compound.
8. The composite resin composition of claim 7, wherein the sulfonic acid blocked with the amine compound is an amine neutralized dodecylbenzenesulfonic acid.
9. The composite resin composition of claim 1, wherein the amine curing catalyst is a primary amine, a secondary amine, a tertiary amine, or a mixture of two or more thereof.
10. The composite resin composition of claim 1, wherein the volatility of the amine curing catalyst is higher than that of the acid curing catalyst.
11. The composite resin composition of claim 1, wherein the composite resin composition further comprises a metal pigment, and the metal pigment is 0.1 to 15% by weight of the total weight of the composition.
12. The composite resin composition of claim 1, wherein the solvent is at least one selected from the group consisting of toluene, xylene, isopropanol, solvent naphtha, cellosolve, cellosolve acetate, and butyl cellosolve.
13. The composite resin composition of claim 1, wherein the solvent comprises the composite resin composition in an amount such that the composite resin composition requires a viscosity of 20 to 200 seconds to be discharged from a DIN cup (531).
14. A steel sheet including a galvanized layer and a composite resin film formed on at least one surface of the steel sheet,

    The composite resin coating film is 50 to 80% by weight of a urethane-modified polyester resin mixed linear and crosslinking type; 3 to 20% by weight of at least one of an aziridine curing agent or a melamine curing agent; And a colored composite resin film formed of 3 to 20% by weight of the colored inorganic pigment, galvanized steel sheet.
15. The galvanized steel sheet according to claim 14, wherein the urethane-modified polyester resin has a weight ratio of linear and crosslinked in a range of 1: 1 to 1: 4.
16. The galvanized steel sheet according to claim 14, wherein the colored inorganic pigment is at least one selected from the group consisting of carbon black, carbon nanotubes, graphite, graphene, ferric oxide (Fe ₂ O ₃ ), and titanium dioxide (TiO ₂ ). .
17. The galvanized steel sheet according to claim 14, wherein the colored inorganic pigment has a particle diameter of 0.01 to 20 µm and an oil absorption amount of 60% or less.
18. The galvanized steel sheet according to claim 14, wherein the colored composite resin coating film further comprises a metal pigment, wherein the metal pigment is 0.5 to 20% by weight of the total weight of the colored composite resin coating film.
19. The galvanized steel sheet according to claim 18, wherein the metal pigment is aluminum alone or an aluminum containing alloy.
20. 19. The galvanized steel sheet according to claim 18, wherein the metal pigment has a flake shape of 0.1 to 5 mu m in thickness.
21. The method of claim 18, wherein the metal pigment is cetyl sulfate sodium salt, cetyl sulfate ammonium salt, stearyl sulfate sodium salt, stearyl sulfate ammonium salt, glycerin fatty acid ester, polyglycerol fatty acid ester, glyceryl ricinoleate, glyceryl stearate , Glyceryl Rosinate, Lanes-5, Lanes-10, Lanes-15, Lanolin, Lautrimonium Chloride, Cetrimonium Bromide, Cetrimonium Chloride, Sodium Isostearoyl Lactate, Sorbitan Laurate Galvanized steel sheet surface-treated with at least one organic compound selected from the group consisting of sorbitan stearate, sorbitan oleate and the organic compounds of Formulas 1 to 5.

    [Formula 1]

    

    (In Formula 1, R is a C5-C15 chain alkyl compound.)

    [Formula 2]

    

    (In Formula 2, R is a C1-C10 chain alkyl compound, n is an integer from 1 to 10.)

    [Formula 3]

    

    (In Formula 3, R is a C1-C10 chain alkyl compound, n is an integer of 1 to 10)

    [Formula 4]

    

    (In Formula 4, R is a C1-C10 chain alkyl compound, n is an integer of 1-10.

    [Formula 5]

    

    (In Formula 5, R is a C1-C10 chain alkyl compound, and n is an integer of 1-10.)
22. The galvanized steel sheet according to claim 14, wherein the composite resin film has a thickness of 3 to 30 µm.
23. The galvanized steel sheet according to claim 14, wherein the composite resin coating film has a pattern.
24. The galvanized steel sheet according to any one of claims 14 to 23, further comprising a transparent resin coating film on the composite resin coating film.
25. The method of claim 24, wherein the transparent resin coating film

    A galvanized steel sheet formed of 65 to 95 wt% of a urethane-modified polyester resin mixed with linear and crosslinked forms and 5 to 35 wt% of at least one of an aziridine hardener or a melamine hardener.
26. The galvanized steel sheet according to claim 24, wherein the transparent resin coating film has a thickness of 0.1 to 3 µm.

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