KR102543489B1 - UV Curable Coating Composition - Google Patents

Abstract

The present invention relates to an ultraviolet curable coating composition having excellent processability, hardness and clarity, and a PCM (Pre-Coated Metal) steel sheet to which the same is applied.

Description

UV curable coating composition {UV Curable Coating Composition}

The present invention relates to an ultraviolet curable coating composition having excellent processability, hardness and clarity, and a PCM (Pre-Coated Metal) steel sheet to which the same is applied.

Paint for PCM is also called paint for coil coating, and it is applied using a roll on a steel plate with a uniform surface, so the painting speed is very fast and a uniform coating can be formed, so that products of uniform quality can be produced. suitable for mass production.

Conventionally, polyester-based paint has been widely used as a paint for PCM, but it has a problem in that the hardness and clarity of the coating film are poor. In order to solve this problem, various studies are being conducted, and for example, Patent Publication No. 2009-0072362 discloses a paint for PCM using a urethane-modified polyester resin. However, in the case of the above paint, although workability and hardness were improved to some extent, it did not exhibit excellent clarity while having a sufficient degree of workability and hardness.

SUMMARY OF THE INVENTION The present invention provides an ultraviolet curable paint composition that basically meets physical properties required for paints, such as scratch resistance, chemical resistance, processability, and adhesion, and has excellent hardness and clarity.

In addition, the present invention provides a PCM steel sheet comprising a steel sheet and a coating layer formed on the surface of the steel sheet, wherein the coating layer is a cured product of the UV curable coating composition described above.

The present invention includes a urethane (meth) acrylate oligomer, a reactive monomer and a photoinitiator, wherein the urethane (meth) acrylate oligomer includes a bifunctional urethane (meth) acrylate oligomer and a trifunctional urethane (meth) acrylate oligomer, , The trifunctional urethane (meth) acrylate oligomer provides a UV curable coating composition comprising a trifunctional aliphatic urethane (meth) acrylate oligomer and a trifunctional aromatic urethane (meth) acrylate oligomer.

SUMMARY OF THE INVENTION The present invention provides an ultraviolet curable paint composition that basically satisfies physical properties required for paints, such as scratch resistance, chemical resistance, processability, and adhesion, and has excellent processability, hardness, and clarity.

The "weight average molecular weight" used in the present invention is measured by a conventional method known in the art, and can be measured, for example, by a gel permeation chromatograph (GPC) method. In addition, "viscosity" is measured by a conventional method known in the art, and can be measured using, for example, a Brookfield viscometer.

Hereinafter, the present invention will be described. However, it is not limited only by the following contents, and each component may be variously modified or selectively mixed as needed. Therefore, it should be understood to include all modifications, equivalents or substitutes included in the spirit and scope of the present invention.

<UV-curable coating composition>

The UV-curable coating composition according to the present invention includes a urethane (meth)acrylate oligomer, a reactive monomer and a photoinitiator, and the urethane (meth)acrylate oligomer is a difunctional urethane (meth)acrylate oligomer and a trifunctional urethane (meth) urethane (meth)acrylate oligomer. It includes an acrylate oligomer, and the trifunctional urethane (meth)acrylate oligomer includes a trifunctional aliphatic urethane (meth)acrylate oligomer and a trifunctional aromatic urethane (meth)acrylate oligomer. If necessary, an adhesion promoter, a leveling agent, a slip agent, a solvent, a pigment, and the like may be further included.

Urethane (meth)acrylate oligomer

The UV-curable coating composition according to the present invention includes a urethane (meth)acrylate oligomer as a main resin component forming a coating film. The urethane (meth)acrylate oligomer controls the crosslinking density of the entire coating film to impart workability, hardness and durability to the coating film.

The urethane (meth)acrylate oligomer of the present invention includes two or more types of bifunctional urethane (meth)acrylate oligomers and trifunctional urethane (meth)acrylate oligomers, and the trifunctional urethane (meth)acrylate oligomers are two types The above trifunctional aliphatic urethane (meth)acrylate oligomer and trifunctional aromatic urethane (meth)acrylate oligomer are included. When five or more oligomers are mixed and used as described above, excellent hardness and clarity of the coating film can be secured.

The bifunctional urethane (meth)acrylate oligomer contains two polymerizable functional groups, which are polymerizable unsaturated groups, and serves to impart processability and chemical resistance to paints. As the bifunctional urethane (meth)acrylate oligomer, an aliphatic urethane (meth)acrylate oligomer may be used.

Two or more kinds of bifunctional aliphatic urethane (meth)acrylate oligomers having different physical properties are mixed as the above bifunctional urethane (meth)acrylate oligomer. For example, the bifunctional urethane (meth)acrylate oligomer includes a first difunctional aliphatic urethane (meth)acrylate oligomer and a second difunctional aliphatic urethane (meth)acrylate oligomer.

The first difunctional aliphatic urethane (meth)acrylate oligomer has a weight average molecular weight of 10,000 to 25,000 g/mol, for example 15,000 to 20,000 g/mol, and a viscosity (60 °C) of 30,000 to 70,000 cps, for example 40,000 to 60,000 cps. When the weight average molecular weight of the first difunctional aliphatic urethane (meth)acrylate oligomer is less than the above-mentioned range, the viscosity is too low, and the adhesion and gloss of the coating film may be deteriorated, and when it exceeds the above-mentioned range, the crosslinking density is greatly This increases the elasticity of the coating film, and as a result, workability, appearance and scratch resistance may be deteriorated. In addition, when the viscosity (60 ° C.) of the first difunctional aliphatic urethane (meth) acrylate oligomer is less than the above-mentioned range, the viscosity is low, and the coating film may be unformed or the adhesion and gloss of the coating film may be reduced. If it is exceeded, paint workability may deteriorate and the appearance of the paint film may deteriorate.

The second difunctional aliphatic urethane (meth)acrylate oligomer has a weight average molecular weight of 500 to 3,000 g/mol, for example, 500 to 1,500 g/mol, and a viscosity (25° C.) of 5,000 to 25,000 cps, for example 10,000 to 15,000 cps. When the weight average molecular weight of the second difunctional aliphatic urethane (meth)acrylate oligomer is less than the above-mentioned range, the viscosity is too low, and the adhesion and chemical resistance of the coating film may be reduced, and when it exceeds the above-mentioned range, the crosslinking density is This greatly increases the elasticity of the coating film, and as a result, chemical resistance, stain resistance, workability and scratch resistance may be deteriorated. In addition, when the viscosity (25 ° C.) of the second difunctional aliphatic urethane (meth)acrylate oligomer is less than the above range, the viscosity is low, so that a coating film may not be formed or the adhesion and chemical resistance of the coating film may be reduced, and the above range If it exceeds, paint workability may be inferior, and the appearance and workability of the coating film may be deteriorated.

The bifunctional urethane (meth)acrylate oligomer may be included in an amount of 3 to 20% by weight, for example, 5 to 15% by weight based on the total weight of the coating composition. In one example, based on the total weight of the coating composition, the first difunctional aliphatic urethane (meth) acrylate oligomer is included in 2 to 12% by weight, for example, 3 to 8% by weight, and the second difunctional aliphatic urethane (meth) ) 1 to 8% by weight of the acrylate oligomer, for example, 2 to 7% by weight. When the content of the first difunctional aliphatic urethane (meth)acrylate oligomer is less than the above-mentioned range, the viscosity is low and the cross-linking density is lowered, and alkali resistance and adhesiveness may be lowered, and when it exceeds the above-mentioned range, the viscosity of the composition is high and workability is poor, which may degrade the appearance and workability of the coating film. In addition, when the content of the second difunctional aliphatic urethane (meth)acrylate oligomer is less than the above-mentioned range, the viscosity is low and the cross-linking density is lowered, so alkali resistance and adhesion may be lowered, and when it exceeds the above-mentioned range, the composition Its viscosity is high and workability is poor, which can lead to deterioration in the appearance and workability of the coating film.

In the present invention, the mixing ratio of the first difunctional aliphatic urethane (meth)acrylate oligomer and the second difunctional aliphatic urethane (meth)acrylate oligomer may be in a weight ratio of 1:0.2 to 2. When the compounding ratio of the second difunctional aliphatic urethane (meth)acrylate oligomer to the first difunctional aliphatic urethane (meth)acrylate oligomer is less than the above range, the crosslinking density and weight average molecular weight increase, thereby increasing the strength and Processability may be deteriorated, and if it exceeds the above range, the weight average molecular weight and viscosity may be reduced, and thus adhesion to the substrate may be deteriorated.

The trifunctional urethane (meth)acrylate oligomer contains three polymerizable functional groups, and serves to impart processability, hardness, chemical resistance, and alkali resistance to paints. The trifunctional urethane (meth)acrylate oligomer includes a trifunctional aliphatic urethane (meth)acrylate oligomer and a trifunctional aromatic urethane (meth)acrylate oligomer.

As the trifunctional aliphatic urethane (meth)acrylate oligomer, two or more types of trifunctional aliphatic urethane (meth)acrylate oligomers having different physical properties are mixed. For example, the first trifunctional aliphatic urethane (meth)acrylate oligomer and the second trifunctional aliphatic urethane (meth)acrylate oligomer are included.

The first trifunctional aliphatic urethane (meth)acrylate oligomer has a weight average molecular weight of 10,000 to 25,000 g/mol, for example 15,000 to 20,000 g/mol, and a viscosity (60 °C) of 500 to 2,500 cps, for example 500 to 1,500 cps. When the weight average molecular weight of the first trifunctional aliphatic urethane (meth)acrylate oligomer is less than the above range, the viscosity and crosslinking density are low, and the hardness and gloss of the coating film may be reduced. When the above range is exceeded, the crosslinking density is It greatly increases the elasticity of the coating film, and as a result, workability, durability, and scratch resistance may be deteriorated. In addition, when the viscosity (60 ℃) of the first trifunctional aliphatic urethane (meth)acrylate oligomer is less than the above-mentioned range, the viscosity is too low, so that a coating film may not be formed or the adhesion and hardness of the coating film may be reduced, and the above-mentioned range If it exceeds, paint workability may be inferior, and the appearance and workability of the coating film may be deteriorated.

The second trifunctional aliphatic urethane (meth)acrylate oligomer has a weight average molecular weight of 500 to 4,000 g/mol, for example, 1,000 to 3,000 g/mol, and a viscosity (25° C.) of 6,000 to 9,000 cps, for example 7,000 to 8,000 cps. When the weight average molecular weight of the second trifunctional aliphatic urethane (meth)acrylate oligomer is less than the above range, the viscosity is too low and the alkali resistance and adhesion of the coating film may be reduced. It greatly increases the elasticity of the coating film, and as a result, the appearance, stain resistance, and scratch resistance may be deteriorated. In addition, when the viscosity (25 ° C.) of the second trifunctional aliphatic urethane (meth) acrylate oligomer is less than the above-mentioned range, the viscosity is too low, and the coating film may be unformed or the adhesion and chemical resistance of the coating film may be lowered, and the above-mentioned If the range is exceeded, paint workability may deteriorate, resulting in deterioration in the appearance and workability of the coating film.

The trifunctional aliphatic urethane (meth)acrylate oligomer may be included in an amount of 3 to 15% by weight, for example, 4 to 10% by weight, based on the total weight of the coating composition. In one example, based on the total weight of the coating composition, the first trifunctional aliphatic urethane (meth) acrylate oligomer is included in 2.9 to 10% by weight, for example, 4 to 7% by weight, and the second trifunctional aliphatic urethane (meth) ) 0.1 to 5% by weight of the acrylate oligomer, for example, 0.3 to 3% by weight. When the content of the first trifunctional aliphatic urethane (meth)acrylate oligomer is less than the above-mentioned range, the viscosity is low and the cross-linking density is lowered, and alkali resistance and adhesiveness may be lowered, and when it exceeds the above-mentioned range, the viscosity of the composition is high, resulting in poor workability and deterioration in the appearance of the coating film. In addition, when the content of the second trifunctional aliphatic urethane (meth)acrylate oligomer is less than the above range, the viscosity is low and the crosslinking density is lowered, and as a result, solvent resistance and adhesion may be lowered, and exceeding the above range In this case, the viscosity of the composition is high and the workability is poor, and the appearance and workability of the coating film may be deteriorated.

In the present invention, the mixing ratio of the first trifunctional aliphatic urethane (meth)acrylate oligomer and the second trifunctional aliphatic urethane (meth)acrylate oligomer may be in a weight ratio of 1:0.01 to 1. When the compounding ratio of the second trifunctional aliphatic urethane (meth)acrylate oligomer to the first trifunctional aliphatic urethane (meth)acrylate oligomer is less than the above range, the crosslinking density and weight average molecular weight increase, thereby increasing the strength and Alkali resistance may be lowered, and if it exceeds the above-mentioned range, the weight average molecular weight and viscosity may be reduced, so that adhesion to the substrate and hardness may be lowered.

The weight average molecular weight (Mw) of the trifunctional aromatic urethane (meth)acrylate oligomer may be 500 to 4,000 g/mol, for example, 1,000 to 3,000 g/mol. The trifunctional aromatic urethane (meth)acrylate oligomer may have a viscosity (25° C.) of 7,000 to 13,000 cps, for example, 8,000 to 12,000 cps. When the weight average molecular weight of the trifunctional aromatic urethane (meth)acrylate oligomer is less than the above-mentioned range, the viscosity is too low and the chemical resistance and gloss of the coating film may be deteriorated. The elasticity of the coating film is deteriorated, and as a result, workability, appearance and scratch resistance may be deteriorated. In addition, when the viscosity (25 ° C.) of the trifunctional aromatic urethane (meth) acrylate oligomer is less than the above-mentioned range, the viscosity is low, so that the coating film is not formed or the crosslinking density is lowered, so that the adhesion and chemical resistance of the coating film may be lowered, If the above range is exceeded, the paint workability may be deteriorated and the appearance of the paint film may be deteriorated.

The trifunctional aromatic urethane (meth)acrylate oligomer may be included in an amount of 1 to 10% by weight, for example, 2 to 6% by weight based on the total weight of the coating composition. When the content of the trifunctional aromatic urethane (meth)acrylate oligomer is less than the above range, the viscosity is low and the crosslinking density is lowered, and thus alkali resistance and adhesion may be lowered, and when the content exceeds the above range, the viscosity of the composition is high Workability is poor, and the appearance of the coating film may be deteriorated.

auxiliary resin

The UV-curable coating composition according to the present invention may include, as a resin component, an epoxy resin, a melamine resin, or a mixture thereof as an auxiliary resin. When the auxiliary resin is further included, better chemical resistance may be imparted to the paint.

The epoxy resin is not particularly limited as long as it is a conventional epoxy resin known in the art. For example, a bisphenol A type epoxy resin or a bisphenol F type epoxy resin can be used. The epoxy equivalent of the epoxy resin may be 300 to 700 g/eq, for example 400 to 550 g/eq. The viscosity (25 ℃) of the epoxy resin may be 80 to 170 cps, for example, 100 to 150 cps. When the equivalent weight of the epoxy resin is less than the above range, the chemical resistance and gloss of the coating film may deteriorate due to low crosslinking density, and when the equivalent weight of the epoxy resin exceeds the above range, the crosslinking density greatly increases and the elasticity of the coating film deteriorates, resulting in chemical resistance , stain resistance and scratch resistance may be deteriorated. In addition, when the viscosity (25 ℃) of the epoxy resin is less than the above range, the viscosity is too low, the coating film may not be formed or the adhesion and chemical resistance of the coating film may be reduced, and when the viscosity exceeds the above range, the paint workability is poor The appearance and hardness of the coating film may be deteriorated.

The epoxy resin may be included in an amount of 1 to 10% by weight, for example, 3 to 7% by weight based on the total weight of the coating composition. When the content of the epoxy resin is less than the above range, the crosslinking density is lowered due to low viscosity, and as a result, alkali resistance and adhesion may be lowered. Therefore, the appearance and scratch resistance may be deteriorated.

The weight average molecular weight of the melamine resin may be 5,000 to 9,000 g/mol, for example 6,000 to 8,000 g/mol. The viscosity (25 ℃) of the melamine resin may be 1,000 to 4,000 cps, for example, 2,000 to 3,500 cps. When the weight average molecular weight of the melamine resin is less than the above range, the viscosity is too low and the chemical resistance and gloss of the coating film may be reduced. Chemical resistance, stain resistance and scratch resistance may be deteriorated. In addition, when the viscosity (25 ℃) of the melamine resin is less than the above range, the viscosity is too low, the coating film may not be formed or the adhesion and chemical resistance of the coating film may be lowered, and when it exceeds the above range, the paint workability is poor This may deteriorate the appearance of the coating film.

The melamine resin may be included in an amount of 0.1 to 3% by weight, for example, 0.3 to 1% by weight based on the total weight of the coating composition. When the content of the melamine resin is less than the above range, the viscosity is low and the crosslinking density is lowered, and as a result, alkali resistance and adhesion may be lowered. The appearance and workability of the coating film may be deteriorated.

reactive monomer

The UV curable coating composition according to the present invention includes a reactive monomer. The reactive monomer serves as a crosslinking agent to control the crosslinking density between polymers, and serves to impart hardness, adhesion, processability, and chemical resistance to the coating film.

The reactive monomer may be a (meth)acrylate monomer containing a hydroxyl group. Non-limiting examples of the reactive monomer include 2-hydroxyethyl acrylate, 2-hydroxymethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, hydroxybutyl acrylate, hydroxybutyl methacrylate rate, 3-chloro-2-hydroxypropyl methacrylate, 2-hydroxy-3-phenoxypropyl acrylate, hydroxy pivalic acid neopentyl glycol diacrylate (HPNDA), tris (2-hydroxyethyl) isocyanurate triacrylate (THEICTA: Tri(2-hydroxyethyl)isocyanurate triacrylate), pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, ethoxylated pentaerythritol tetra (meth)acrylate, dipentaerythritol polyacrylate, and the like, and these may be used alone or in combination of two or more.

For example, the reactive monomer may include a difunctional reactive monomer, a trifunctional reactive monomer, or a mixture thereof.

The molecular weight of the bifunctional reactive monomer may be 150 to 450 g/mol, for example, 250 to 350 g/mol, and the viscosity (25° C.) may be 10 to 40 cps, for example 15 to 30 cps. . When the molecular weight of the bifunctional reactive monomer is less than the above range, the crosslinking efficiency may be lowered and hardness and chemical resistance may be lowered. Appearance, adhesion and chemical resistance may deteriorate. In addition, when the viscosity (25 ° C.) of the bifunctional reactive monomer is less than the above range, the viscosity is too low, and the weather resistance of the coating film may be reduced. It can be.

The trifunctional reactive monomer may have a molecular weight of 200 to 700 g/mol, for example, 350 to 550 g/mol, and a viscosity (25° C.) of 700 to 1,800 cps, for example, 900 to 1,600 cps. . When the molecular weight of the trifunctional reactive monomer is less than the above range, crosslinking efficiency and intermolecular bonding strength may be lowered, and thus chemical resistance and weather resistance may be lowered. there is. In addition, when the viscosity (25 ℃) of the trifunctional reactive monomer is less than the above range, the viscosity is too low, so that a coating film may not be formed or the adhesion and alkali resistance of the coating film may be reduced. The appearance and processability may be deteriorated due to poor performance.

The reactive monomer may be included in an amount of 2 to 20% by weight, for example, 4 to 10% by weight based on the total weight of the coating composition. For example, based on the total weight of the coating composition, the bifunctional reactive monomer is included in 1 to 10% by weight, for example, 2 to 5% by weight, and the trifunctional reactive monomer is included in 1 to 10% by weight, for example It may contain 2 to 5% by weight. When the content of the bifunctional reactive monomer is less than the above range, the viscosity of the coating composition increases and flowability and leveling properties may be reduced, and when it exceeds the above range, the viscosity of the composition is very low and curability is lowered, As a result, workability and adhesion may deteriorate. In addition, when the content of the trifunctional reactive monomer is less than the above range, the viscosity is low and the crosslinking density is lowered, and as a result, the degree of crosslinking, adhesion and painting workability may be lowered, and when the content exceeds the above range, the viscosity is If it is too high, the flexibility of the coating film may be lowered and the gloss may be lowered.

photoinitiator

The UV curable coating composition according to the present invention includes a photoinitiator. The photoinitiator is a component that serves to initiate photopolymerization by being excited by ultraviolet (UV) light, and a conventional photoinitiator in the art may be used without limitation.

Non-limiting examples of usable photoinitiators include Irgacure 184, Irgacure 369, Irgacure 651, Irgacure 819, Irgacure 907, benzionalkylether, benzophenone, benzyldimethylkatal, hydroxyl Hydroxycyclohexyl phenylacetone, Chloroacetophenone, 1,1-Dichloro acetophenone, Diethoxy acetophenone, Hydroxy Acetophenone , 2-Choro thioxanthone, 2-ETAQ (2-EthylAnthraquinone), 1-hydroxy-cyclohexyl-phenyl-ketone, 2-hydroxy -2-methyl-1-phenyl-1-propanone (2-Hydroxy-2-methyl-1-phenyl-1-propanone), 2-hydroxy-1-[4-(2-hydroxyethoxy)phenyl ]-2-methyl-1-propanone (2-Hydroxy-1-[4-(2-hydroxyethoxy)phenyl]-2-methyl-1-propanone), bis(2,4,6-trimethylbenzoyl)phenylphos There are pine oxide (Bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide), methylbenzoylformate, and the like, and these may be used alone or in combination of two or more.

In the present invention, the content of the photoinitiator may be 1 to 10% by weight based on the total weight of the UV curable coating composition. If the content of the photoinitiator is less than 1% by weight, strength and adhesion of the coating film may be reduced due to deterioration of curability or uncuring, and wrinkles may occur due to uncuring of the coating film. On the other hand, when the content of the photoinitiator exceeds 10% by weight, contamination due to the unreacted photoinitiator or deterioration in adhesion due to low polymerization degree may be caused.

additive

In addition to the components described above, the UV-curable coating composition of the present invention may use additives known in the art without limitation within a range that does not impair the effects of the present invention.

Additives that can be used include adhesion promoters (eg, acid esters, silicones), leveling agents (eg, non-silicone surfactants), slip agents (eg, polyalphaolefins), and the like. These may be used alone or in combination of two or more. In the present invention, the content of the additive may be appropriately adjusted within a range known in the art. For example, the amount of each of the additives may be 0.1 to 5% by weight based on the total weight of the UV curable coating composition.

In addition, the UV curable coating composition of the present invention may contain a solvent. The solvent serves to improve workability by adjusting the viscosity of the paint, has excellent solvency and stability, and can be used without particular limitation as long as it does not interfere with the main reaction. For example, an aromatic hydrocarbon-based solvent, an ester-based solvent, an ether-based solvent, an alcohol-based solvent, or a mixture thereof may be used. Non-limiting examples of usable solvents include cyclohexanone, xylene, toluene, cellosolve acetate, methyl ethyl ketone, methyl isobutyl ketone, dibasic ester, propylene glycol methyl ether acetate, n-butyl acetate, propylene glycol Monomethyl acetate, 3-methoxy butyl acetate, ethylene glycol butyl ether, diethylene glycol methyl ether, diethylene glycol ethyl ether, diethylene glycol butyl ether, ethylene glycol monohexyl ether, ethanol, isopropanol, n-butanol, amyl alcohol , butyl carbitol, paraffin oil, or a mixed solvent thereof.

In the present invention, the content of the solvent may be the remaining amount satisfying the total weight (100% by weight) of the coating composition, for example, 10 to 60% by weight based on the total weight of the coating composition. When the content of the solvent is within the above range, workability is improved and excellent physical properties of the coating film can be exhibited. When the content of the solvent is less than 10% by weight, the viscosity of the composition is high and workability may be deteriorated, and when the content of the solvent is less than 60% by weight, the viscosity of the composition is low, and the problem of flowing down during application occurs and dimensional stability and adhesion are deteriorated. may occur.

In addition, the UV curable coating composition of the present invention may include a pigment. Pigments can be used to express a desired color (color) in a paint or to increase the strength or gloss of a paint film. As the pigment, organic pigments, inorganic pigments, metallic pigments, aluminum-paste, pearls, etc. may be used without limitation, and these may be used alone or in combination of two or more. Non-limiting examples of usable pigments include azo-based, phthalocyanine-based, iron oxide-based, cobalt-based, carbonate-based, sulfate-based, silicate-based, and chromate-based pigments, such as titanium dioxide, zinc oxide, and bismuth vanadate. , cyanine green, carbon black, red iron oxide, iron oxide sulfur, navy blue, cyanine blue, and mixtures of two or more thereof.

The content of the pigment is not particularly limited, and may be 0.1 to 20% by weight, for example, 0.5 to 15% by weight based on the total weight of the coating composition. When the content of the pigment is less than the above range, the hiding power of the prepared film may be insufficient, and when it exceeds the above range, stability, mechanical properties and adhesion of the composition may be deteriorated.

<PCM steel plate>

The present invention provides a PCM steel sheet having a coating layer formed using the UV curable coating composition described above. The PCM steel sheet includes a steel sheet and one or more coating layers formed on the surface of the steel sheet, and at least one of the one or more coating layers includes a coating layer formed by applying the above-described ultraviolet curable coating composition and then curing the coating layer. .

As the steel sheet, a metal sheet used in the art may be used without limitation. Non-limiting examples include zinc hot-dipped steel (GI), electro-zinc steel (EGI), hot-dip galvanized steel, alloyed hot-dip galvanized steel, electro-galvanized steel, hot-dip aluminum-zinc alloyed steel, aluminum sheet, and the like. there is.

The PCM steel sheet according to the present invention may be manufactured according to a conventional method in the art, and may be composed of, for example, a step of coating the above-described UV curable coating composition on a metal sheet as a substrate and then drying it. As the coating method of the PCM paint composition, a conventional coating method known in the art can be applied, and for example, curtain coating, roll coating, immersion coating, bar coating, spray coating, and the like can be applied. Baking conditions may be appropriately changed according to conditions such as the width and thickness of the baking metal plate, line speed, and the like. For example, it may be performed for 35 to 40 seconds at a peak metal temperature (PMT) of 190 to 230 °C. If necessary, the metal sheet may be pretreated with a non-chromate-based compound before painting.

Hereinafter, the present invention will be described in more detail through examples. However, the following examples are only for facilitating the understanding of the present invention, and the scope of the present invention is not limited to the examples in any sense.

[Example 1-11]

According to the composition shown in Table 1 below, UV curable coating compositions of Examples 1-11 were prepared.

[Comparative Example 1-13]

According to the composition shown in Table 2 below, UV curable coating compositions of Comparative Examples 1-13 were prepared.

Oligomer 1: first difunctional aliphatic urethane acrylate oligomer (weight average molecular weight 18,000 g/mol, viscosity (60 ° C) 48,000 cps)

Oligomer 2: second difunctional aliphatic urethane acrylate oligomer (weight average molecular weight 1,000 g/mol, viscosity (25 ° C) 12,700 cps)

Oligomer 3: first trifunctional aliphatic urethane acrylate oligomer (weight average molecular weight 18,000 g/mol, viscosity (60 ° C) 1,000 cps)

Oligomer 4: Second trifunctional aliphatic urethane acrylate oligomer (weight average molecular weight 1,900 g/mol, viscosity (25° C.) 7,800 cps)

Oligomer 5: trifunctional aromatic urethane acrylate oligomer (weight average molecular weight 2,500 g/mol, viscosity (25 ° C) 10,500 cps)

Epoxy resin: EEW 450-500 g/eq, viscosity (25 ℃) 130 cps)

Melamine resin: weight average molecular weight 6,800 g/mol, viscosity (25 ℃) 2,900 cps)

Monomer 1: bifunctional reactive monomer (hydroxypivalic acid neopentyl glycol diacrylate, molecular weight 325 g/mol, viscosity (25 ° C) 25 cps)

Monomer 2: Trifunctional reactive monomer (tris (2-hydroxyethyl) isocyanurate triacrylate, molecular weight 453 g / mol, viscosity (25 ℃) 1,300 cps)

Adhesion promoter 1: methacrylic acid ester (acid value 150 mgKOH/g, specific gravity 1.18, viscosity (25 ° C) 250 cps)

Adhesion promoter 2: 3-Methacryloxypropyl Trimethoxysilane (molecular weight 249, specific gravity 1.04, NV 60%)

Leveling agent: nonionic organic surfactant (density 1.03 g/cm ³ )

Slip agent: Polyalphaolefin (specific gravity 0.85, viscosity (25 ℃) 147 cps)

Photoinitiator: 1-Hydroxy-Cyclohexylphenyl-ketone

Toner 1: Black (SSAP BLACK B-780, Ilsam)

Colorant 2: Blue (SSAP BLUE 280, Ilsam)

Toner 3: Violet (SSAP Violet 190, Ilsam)

Solvent: Methyl Iso Butyl Ketone, Propylene glycol methyl ether acetate mixed solvent

[Experimental Example-Evaluation of physical properties]

The UV-curable coating composition prepared in each Example and Comparative Example was air spray coated on a transparent polycarbonate specimen (PC) to a thickness of 12 μm (top layer, based on dry film thickness), and then dried for 300 seconds at a temperature of 80 ° C. After removing the solvent, it was cured by irradiating with an energy of 3,500 mJ/cm 2 at a position of 20 cm in the air with a high-pressure mercury lamp of 180 mW/cm 2 to prepare a specimen for physical property test. The physical properties of the prepared specimens were evaluated according to Table 3 below, and the results are shown in Tables 4 and 5 below.

◎: excellent, ○: good, X: poor

◎: excellent, ○: good, X: poor

As confirmed from the results of Table 4, in the case of the paint compositions of Examples 1-11 according to the present invention, adhesion, processability, curability, appearance characteristics, alkali resistance and solvent resistance were all excellent.

On the other hand, as confirmed from the results of Table 5, in the case of the paint compositions of Comparative Examples 1-13 that deviate from the composition according to the present invention, most of the measured items showed poor physical properties. Specifically, Comparative Examples 1 and 2 are examples in which the first difunctional aliphatic urethane (meth)acrylate oligomer is used in an amount outside the scope of the present invention, and Comparative Example 3 is the first difunctional aliphatic urethane (meth)acrylate oligomer This is an example without using . Comparative Examples 4 and 5 are examples in which the second difunctional aliphatic urethane (meth)acrylate oligomer is used in an amount outside the scope of the present invention, and Comparative Example 6 does not use the second difunctional aliphatic urethane (meth)acrylate oligomer example is not Comparative Examples 7 and 8 are examples in which the first trifunctional aliphatic urethane (meth)acrylate oligomer is used in an amount outside the scope of the present invention, and Comparative Example 9 does not use the first trifunctional aliphatic urethane (meth)acrylate oligomer example is not Comparative Example 10 is an example in which the second trifunctional aliphatic urethane (meth)acrylate oligomer is not used, and Comparative Example 11 is an example in which the second trifunctional aliphatic urethane (meth)acrylate oligomer is used in an amount outside the scope of the present invention am. Comparative Example 12 is an example in which the trifunctional aromatic urethane (meth)acrylate oligomer is not used, and Comparative Example 13 is an example in which the trifunctional aromatic urethane (meth)acrylate oligomer is used in an amount outside the scope of the present invention.

Claims (7)

An ultraviolet curable coating composition comprising a urethane (meth)acrylate oligomer, a reactive monomer and a photoinitiator,
The urethane (meth)acrylate oligomer is 2 to 12% by weight of the first difunctional aliphatic urethane (meth)acrylate oligomer, based on the total weight of the ultraviolet curable coating composition, the first difunctional aliphatic urethane (meth)acrylate 1 to 8% by weight of the second difunctional aliphatic urethane (meth)acrylate oligomer having different physical properties from those of the oligomer, 2.9 to 10% by weight of the first trifunctional aliphatic urethane (meth)acrylate oligomer, the first trifunctional aliphatic urethane (metha) acrylate oligomer ) 0.1 to 5% by weight of a second trifunctional aliphatic urethane (meth)acrylate oligomer having different physical properties from the acrylate oligomer and 1 to 10% by weight of a trifunctional aromatic urethane (meth)acrylate oligomer,
The first difunctional aliphatic urethane (meth)acrylate oligomer has a weight average molecular weight of 10,000 to 25,000 g/mol and a viscosity (60 °C) of 30,000 to 70,000 cps,
The second difunctional aliphatic urethane (meth)acrylate oligomer has a weight average molecular weight of 500 to 3,000 g/mol and a viscosity (25 °C) of 5,000 to 25,000 cps,
The first trifunctional aliphatic urethane (meth)acrylate oligomer has a weight average molecular weight of 10,000 to 25,000 g/mol, and a viscosity (60 °C) of 500 to 2,500 cps,
The second trifunctional aliphatic urethane (meth) acrylate oligomer has a weight average molecular weight of 500 to 4,000 g / mol, and a viscosity (25 ℃) of 6,000 to 9,000 cps UV curable coating composition. delete delete The UV curable coating composition according to claim 1, wherein the trifunctional aromatic urethane (meth)acrylate oligomer has a weight average molecular weight of 500 to 4,000 g/mol and a viscosity (25 °C) of 7,000 to 13,000 cps. The UV curable coating composition according to claim 1, further comprising an epoxy resin, a melamine resin, or a mixture thereof. The UV curable coating composition according to claim 1, comprising 2 to 20% by weight of the reactive monomer and 1 to 10% by weight of the photoinitiator based on the total weight of the UV curable coating composition. A steel sheet and one or more coating layers formed on the surface of the steel sheet, wherein at least one of the coating layers is formed from the ultraviolet curable coating composition according to any one of claims 1 and 4 to 6. PCM (Pre-Coated Metal) steel sheet.