KR20150074898A - UV curable top coating resin composition for coil-coating, the method for preparing the same and coil-coated steel sheet having a coating layer formed thereof - Google Patents

Abstract

The present invention relate to an ultraviolet ray curable top resin composition used for coating an upper part of a color coating layer to improve image clarity, scratch resistance, hardness of coating, processibility, impact resistance and other functions of the color coating formed on the steel plate when manufacturing coil coating steel plates with use of a pre-coated-metal method manner, a manufacturing method thereof and a coil-coating steel plate coated with the resin composition.

Description

TECHNICAL FIELD [0001] The present invention relates to a UV-curable top coat resin composition for coil-coating, a method for producing the composition, and a coil-coated steel sheet coated with the composition sheet having a coating layer formed < RTI ID = 0.0 >

The present invention relates to a method for producing a coil-coated steel sheet by using a PCM (Pre-Coated-Metal) method, wherein the pre-coated steel sheet has excellent ductility, scratch resistance, And a method for producing the same, and a coil-coated steel sheet coated with the resin composition, which can be used for coating an upper portion of a color coating layer, in order to improve transparency and other functions.

In most industrial products, steel plates are first molded and processed to produce products, followed by second coating to protect the appearance of colors and products. As a result, manufacturers of finished products through these processes often operate painting lines separately from product manufacturing lines.

On the other hand, the coil-coated steel sheet is manufactured by Pre-Coated-Metal (PCM) method which is applied before the finished product is finished. When the coil-coated steel sheet is used to manufacture the product, Due to the reduced production cost and time required to produce the finished product, steel plates for many finished products are being replaced by coil-coated steel plates.

However, in the case of coil-coated steel sheets, the physical functions such as workability and impact resistance are very important because they are formed and processed by cutting and pressing methods after being painted, and processing is performed to obtain finished products Thereafter, defects such as cracking and peeling of the coating film should not occur.

In order to secure such workability, studies on the tensile strength, surface characteristics and composition of the steel sheet as the basic material have been continuously carried out, and researches on the coating composition applied on the steel sheet have also been conducted by many organizations and companies at home and abroad.

Conventionally, such a coil-coating paint uses a thermosetting polyester resin, a high polymer polyester resin, an alkyd resin, and an epoxy resin as a resin composition having excellent workability and impact resistance, and melamine formaldehyde resin, urea formaldehyde resin , Phenol formaldehyde resin, etc. However, since most of the paints contain a large amount of organic solvents and paint is applied by mixing a diluent separately during the painting operation, it is a problem in environmental pollution .

Furthermore, conventional coatings for coil coating are mostly thermosetting type coatings, and coatings such as roll coating and flow coating are applied after preheating zone and tunneling through a curing zone The length of tunnel ovens for coil coating ranges from 20m to 100m at coating rates of 40m / min to 150m / min per minute, because of the need for curing drying times ranging from 20 seconds to 90 seconds using a hot air oven or induction oven There is a problem in that the initial facility investment cost is large.

INDUSTRIAL APPLICABILITY The resin composition for coil-coating of the present invention is environmentally friendly because it does not contain an organic solvent, but viscosity can be easily controlled during coating using roll coating without an organic solvent.

Unlike conventional thermosetting resin compositions, the resin composition for coil-coating of the present invention can be cured within a few seconds by using an ultraviolet curable resin composition, thereby improving productivity and simplifying facilities.

However, the resin composition for coil-coating according to the present invention makes it possible to impart external appearance characteristics such as linearity or scratch resistance, extensibility and stable surface hardness to a coating film applied at a level equal to or higher than that of the conventional thermosetting resin composition.

According to one embodiment of the invention, on the basis of the total weight of the composition,

20 to 50 parts by weight of a urethane (meth) acrylate oligomer;

30 to 70 parts by weight of a (meth) acrylic acid ester monomer;

3 to 10 parts by weight of an ultraviolet initiator; And

0.05 to 2 parts by weight of a coating film smoothing agent,

The urethane (meth) acrylate oligomer is formed by reacting a (meth) acrylate containing a diisocyanate compound, a polyol, and a hydroxyl group to provide an ultraviolet curable top resin composition for coil-coating.

The diisocyanate compound may be at least one selected from the group consisting of 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 1,3-xylene diisocyanate, 1,4-xylene diisocyanate, 1,5-naphthalene diisocyanate, Which is composed of phenylene diisocyanate, P-phenylene diisocyanate, 4.4'-bisphenylene diisocyanate, hexamethylene diisocyanate, hexamethylene diisocyanate derivative, isophorone diisocyanate, hydrophenylmethane diisocyanate and cyclohexane diisocyanate May be at least one selected from the group.

The polyol may be at least one selected from the group including alkylene glycols, C ₁ to C ₁₅ aliphatic alcohols, polyester polyols, caprolactone polyols, polycarbonate polyols, poly C ₁ to C ₆ alkylene glycols and polyether polyols have.

The (meth) acrylate containing a hydroxyl group is preferably selected from the group consisting of 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2- (Meth) acrylate, 2-hydroxyalkyl (meth) acryloylphosphate, 4-hydroxycyclohexyl (meth) acrylate, pentaerythritol Triacrylate, and caprolactone (meth) acrylate.

The (meth) acrylic acid ester monomer may be at least one member selected from the group consisting of monofunctional (meth) acrylate monomers and polyfunctional (meth) acrylate monomers.

The monofunctional (meth) acrylate monomer may be selected from the group consisting of acrylamide, dimethylaminoethyl (meth) acrylate, hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, hydroxybutyl (Meth) acrylate, dicyclopentadiene (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, isobornyl (meth) acrylate, (Meth) acrylate, butoxy ethyl (meth) acrylate, polyethylene glycol monoacrylate, and polypropylene glycol monoacrylate.

Wherein the polyfunctional (meth) acrylic acid ester monomer is selected from the group consisting of ethylene glycol (meth) acrylate, dicyclopentenyl di (meth) acrylate, triethylene glycol di (meth) acrylate, tetraethylene glycol di (Meth) acrylate, trimethylolpropane tri (meth) acrylate, trimethylolpropane tri (meth) acrylate, trimethylolpropane trioxypropyltrimethacrylate, trimethylolpropane trioxyethyltrimethacrylate, tripropylene glycol Di (meth) acrylate, ditrimethylol propane, tetra (meth) acrylate, neopentyl glycol di (meth) acrylate, neopentyl glycol propoxylate di (meth) acrylate, bisphenol A diglycidyl ether Di (meth) acrylate, butanediol di (meth) acrylate, hexanediol di (meth) acrylate, hexamethylene diol di (Meth) acrylate, pentaerythritol tetra (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate and dipentaerythritol hexa It may be at least one selected.

The ultraviolet initiator may be selected from the group consisting of 1-hydroxycyclohexyl phenyl ketone, 2,2-dimethoxy-2-phenylacetone phenone, 2-hydroxy- Phenyl) -2-hydroxy-2-methylpropan-1-one, 1,1-dimethoxydioxybenzoin, 3,3'-dimethyl- 4- methoxybenzophenone, 1- Methyl-1- [4- (methylthio) phenyl] -2-morpholino-propan-1-one, 2,4,6-trimethyl Benzoyldiphenylphosphine oxide, ethyl-2,4,6-trimethylbenzoylphenylphosphinate, bis- (2,6-dimethoxybenzoyl) -2,4,4-trimethylpentylphosphine oxide, bisacylphosphine Benzyl-4'-methyldiphenylsulfide, benzyldimethylketal, furorenone, fluorene, benzaldehyde, benzoin ethyl ether, joining propyl ether, 2-benzyl- 1- (4-morpholinophenyl) -butan-1-one, Acetophenone, 3-methylacetophenone, benzophenone, 4,4'-dimethoxybenzophenone, 4,4'-diaminobenzophenone, 3,3 ', 4,4'-tetra (t- 2-isopropylthioxanthone, 4-isopropylthioxanthone, 4-isopropylthioxanthone, 4-isopropylthioxanthone, Ton, 2-crothioxanthone and 1-cro-4-propoxyoctanoic acid.

Wherein the ultraviolet curable top resin composition for coil-coating further comprises at least one additive selected from the group consisting of an antioxidant, a light stabilizer, an ultraviolet absorber, a dispersant and a defoaming agent,

The additive may be included in an amount of 0.1 to 15 parts by weight based on the total weight of the composition.

The viscosity of the UV-curable top coat resin composition for coil-coating may be 35 to 45 seconds at DIN-CUP (25 캜).

According to another embodiment of the present invention, there is provided a process for preparing a urethane (meth) acrylate oligomer by reacting a (meth) acrylate containing a diisocyanate compound, a polyol and a hydroxyl group; And

(Meth) acrylic acid ester monomer, an ultraviolet initiator and a film-form smoothing agent to the urethane (meth) acrylate oligomer to prepare an ultraviolet-curable top resin composition,

The urethane (meth) acrylate oligomer, the (meth) acrylic acid ester monomer, the ultraviolet initiator, and the coating film smoothing agent are contained in the ultraviolet curable top resin composition at a ratio of urethane (meth) acrylate oligomer 20 To 50 parts by weight; 30 to 70 parts by weight of a (meth) acrylic acid ester monomer; 3 to 10 parts by weight of an ultraviolet initiator; And 0.05 to 2 parts by weight of a coating film smoothing agent, based on the total weight of the composition.

The step of preparing the urethane (meth) acrylate oligomer comprises:

Reacting a diisocyanate compound with a polyol to prepare a polyurethane prepolymer having isocyanate groups at both terminals; And

And reacting the polyurethane prepolymer with (meth) acrylate containing a hydroxyl group to prepare a urethane (meth) acrylate oligomer.

The step of preparing the urethane (meth) acrylate oligomer comprises:

Reacting a (meth) acrylate containing a hydroxyl group with a diisocyanate compound to prepare a polyurethane prepolymer having an isocyanate group at one end; And

And reacting the polyurethane prepolymer with the polyol to prepare a urethane (meth) acrylate oligomer.

According to another embodiment of the present invention,

A color coating layer formed on the base steel sheet; And

And a top coating layer formed on the color coating layer,

Wherein the top coat layer is formed of the resin composition of the ultraviolet curing type for the coil-coating.

The dry film thickness of the top coat layer may be 5 to 10 mu m.

The UV-curable top coat resin composition for a coil-coating according to the present invention is environmentally friendly because it does not contain a volatile organic solvent, and viscosity control can be easily performed in a coating operation using a roll coating without an organic solvent.

In addition, the ultraviolet-curable top resin composition for coil-coating provided in the present invention can reduce the drying speed to 3 seconds or less by using the ultraviolet curing system, and therefore, the length of the tunnel type curing drying zone can be remarkably reduced It is possible to reduce the initial facility investment cost, and at the same time, the curing drying speed becomes faster, and economical efficiency can be secured due to excellent production workability.

In addition, the ultraviolet-curable top resin composition for coil-coating provided in the present invention can be applied on a color coating film at a level equal to or higher than that of a conventional resin without containing a thermosetting resin conventionally used, Line spirit and scratch resistance to give excellent appearance, and to ensure excellent stretchability and stable surface hardness.

Hereinafter, preferred embodiments of the present invention will be described. However, the embodiments of the present invention can be modified into various other forms, and the scope of the present invention is not limited to the embodiments described below. Further, the embodiments of the present invention are provided to more fully explain the present invention to those skilled in the art.

Generally, since the coil-coated steel sheet is formed and processed by cutting and pressing after coating, defects such as cracking and peeling of the coating film formed on the steel sheet are generated.

Therefore, in order to solve such a problem, conventionally, a coil-coating resin composition excellent in mechanical properties such as workability and impact resistance is applied on a color coating layer of a coil-coated steel sheet to be formed.

However, the conventional resin composition for coil-coating conventionally used contains a large amount of an organic solvent in order to facilitate workability during roll coating, thereby causing environmental pollution problems, and it takes a long time for curing in heat curing, The length of the oven required for curing is increased, resulting in a problem in that the productivity is lowered and the equipment becomes larger, which is economical.

Thus, the top coat resin composition for coil-coating provided in the present invention can be cured within a few seconds by ultraviolet curing type, thereby improving productivity and dramatically simplifying facilities. However, since the resin composition for coil-coating of the present invention contains a large amount of unsaturated groups, it is possible to easily form a coating film by the ultraviolet curing reaction, to form a coating film having flexibility and toughness, To impart a good appearance, workability, impact resistance and stable surface hardness to the surface of the applied coating.

Further, the resin composition for coil-coating of the present invention is easy to control the viscosity during coating operation using roll coating without an organic solvent, and is environment-friendly because it does not contain volatile organic solvent.

Specifically, the UV-curable top coat resin composition for coil-coating of the present invention comprises 20 to 50 parts by weight of a urethane (meth) acrylate oligomer based on the total weight of the composition; 30 to 70 parts by weight of a (meth) acrylic acid ester monomer; 3 to 10 parts by weight of an ultraviolet initiator; And 0.05 to 2 parts by weight of a film smoothing agent.

However, the urethane (meth) acrylate oligomer contained in the resin composition of the present invention is formed by reacting a (meth) acrylate containing a diisocyanate compound, a polyol and a hydroxyl group, It is possible to prevent the problems such as cracking and peeling of the coating film even if the post-coating processing and the molding process are carried out by imparting physical properties such as excellent workability, impact resistance and scratch resistance to the coated film.

On the other hand, the diisocyanate compound used in the synthesis of the urethane (meth) acrylate oligomer includes two or more free isocyanate groups in one molecule. Examples thereof include 2,4-toluene diisocyanate, 2,6- Diisocyanate, 1,3-xylene diisocyanate, 1,4-xylene diisocyanate, 1,5-naphthalene diisocyanate, m-phenylene diisocyanate, P-phenylene diisocyanate, At least one selected from the group consisting of diisocyanate, hexamethylene diisocyanate, hexamethylene diisocyanate derivative, isophorone diisocyanate, hydrophenylmethane diisocyanate and cyclohexane diisocyanate can be used.

The polyol used in the synthesis of the urethane (meth) acrylate oligomer may be a polyol commonly used in the art. The polyol may be, for example, an alkylene glycol, At least one selected from the group consisting of aliphatic alcohols, polyester polyols, caprolactone polyols, polycarbonate polyols, poly C ₁ -C ₆ alkylene glycols and polyether polyols can be used, and preferably C ₁ to C ₁₅ Aliphatic alcohols, more preferably C ₂ to C ₁₂ aliphatic alcohols can be used.

In a preferred use of the polyol, the alkylene glycol is selected from the group consisting of neopentyl glycol, 3-methyl-1,5-pentanediol, ethylene glycol, propylene glycol, 1,4-butanediol and 1,6- It may be more than one kind. The aliphatic alcohol may be at least one selected from the group consisting of trimethylolpropane, pentaerythritol, tricyclodecane methylol and bis- (hydroxymethyl) -cyclohexane. The polybasic acid which can be reacted with the aliphatic alcohol may be selected from the group consisting of succinic acid, phthalic acid, hexahydrophthalic anhydride, terephthalic acid, adipic acid, azelaic acid and Tetrahydrophthalic anhydride, and tetrahydrophthalic anhydride. Further, the caprolactone polyol may be formed by the reaction of the aliphatic alcohol and? -Caprolactone described above. In addition, the polycarbonate polyol may be formed by the reaction of the aliphatic alcohol described above, for example, 1,6-hexanediol with diphenyl carbonate. The poly (C ₁ -C ₆₎ alkylene glycol may be at least one selected from the group consisting of polyethylene glycol, polypropylene glycol and polytetramethylene glycol. The polyether polyol may include, for example, ethylene oxide-modified bisphenols and the like.

The (meth) acrylate containing the hydroxyl group used in the synthesis of the urethane (meth) acrylate oligomer is preferably at least one selected from the group consisting of 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) Hydroxypropyl (meth) acrylate, 4-butanediol mono (meth) acrylate, 2-hydroxyalkyl (meth) acryloylphosphate, 4 -Hydroxycyclohexyl (meth) acrylate, pentaerythritol triacrylate, and caprolactone (meth) acrylate can be used.

The urethane (meth) acrylate oligomer is preferably contained in the resin composition of the present invention in an amount of 20 to 50 parts by weight based on the total weight of the composition. When the content is less than 20 parts by weight, sufficient workability, impact resistance and scratch resistance can not be imparted to the coating film, cracks may occur in the coating film during processing and molding after coating, and the coating film may peel off from the steel sheet. On the other hand, when the content exceeds 50 parts by weight, the workability and impact resistance may be lowered.

The UV-curable top resin composition for coil-coating of the present invention may contain (meth) acrylate monomer as well as the urethane (meth) acrylate oligomer described above. The (meth) acrylic acid ester monomer functions as a reactive diluent in the resin composition, and maintains a proper viscosity during the roll-coating operation, and undergoes a polymerization reaction upon irradiation with ultraviolet rays to form a coating film.

The kind of the (meth) acrylic acid ester monomer that can be used in the present invention is not particularly limited, but monofunctional (meth) acrylate monomer, polyfunctional (meth) acrylate monomer or a mixture thereof may be used.

Examples of the monofunctional (meth) acrylate monomer include acrylamide, dimethylaminoethyl (meth) acrylate, hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, hydroxybutyl (Meth) acrylate, dicyclopentadiene (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, isobornyl (meth) acrylate, At least one selected from the group consisting of (meth) acrylate, phenoxyethyl (meth) acrylate, butoxyethyl (meth) acrylate, polyethylene glycol monoacrylate and polypropylene glycol monoacrylate.

Examples of the polyfunctional (meth) acrylate monomer include ethylene glycol (meth) acrylate, dicyclopentenyl di (meth) acrylate, triethylene glycol di (meth) acrylate, tetraethylene glycol di Acrylate, trimethylolpropane di (meth) acrylate, trimethylolpropane tri (meth) acrylate, trimethylolpropane trioxypropyl tri (meth) acrylate, trimethylolpropane trioxyethyl tri (meth) Acrylate, neopentyl glycol di (meth) acrylate, neopentyl glycol propoxylate di (meth) acrylate, ditrimethylol propane, tetra (meth) acrylate, neopentyl glycol di (Meth) acrylate, butanediol di (meth) acrylate, hexanediol di (meth) acrylate, hexamethylene (Meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol penta One or more selected from the group can be used.

The (meth) acrylic acid ester monomer is preferably contained in the resin composition of the present invention in an amount of 30 to 70 parts by weight based on the total weight of the composition. When the content is less than 30 parts by weight, the flex workability may decrease and the viscosity may become excessively high, which may result in difficulty in work performance in roll coating. When the content exceeds 70 parts by weight, There is a possibility that the property may decrease.

The UV-curable top coat resin composition for coil-coating according to the present invention can be prepared by coating a topcoat composition of a liquid phase on a coated surface to form a coating film, and then irradiating ultraviolet rays with an ultraviolet initiator .

The ultraviolet ray initiator is not particularly limited as long as it can be commonly used in the art, and a radical polymerization initiator or an ion polymerization initiator can be used. However, the use of a radical polymerization initiator can increase the curing rate Do.

Examples of the radical polymerization initiator include, but are not limited to, 1-hydroxycyclohexyl phenyl ketone, 2,2-dimethoxy-2-phenylacetone phenone, 2- Phenylpropan-1-one, 1- (4-isopropylphenyl) -2-hydroxy-2-methylpropan-1-one, 1,1-dimethoxydeoxybenzoin, 3,3'- -Methoxybenzophenone, 1- (4-dodecylphenyl-2-hydroxy-2-methylpropan-1- -Propane-1-one, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, ethyl-2,4,6-trimethylbenzoylphenylphosphinate, bis- (2,6- dimethoxybenzoyl) 4-benzoyl-4'-methyldiphenylsulfide, benzyldimethylketal, furorenone, fluorene, benzaldehyde, benzoin ethyl ether , Join propyl ether, 2- (4-morpholinophenyl) -butan-1-one, acetophenone, 3-methylacetophenone, benzophenone, 4,4'-dimethoxybenzophenone, 4,4 ' -Diaminobenzophenone, 3,3 ', 4,4'-tetra (t-butylperoxycarbonyl) benzophenone, acetophenone benzyl ketal, triphenylamine, carbazole, 4-chlorobenzophenone, anthraquinone Selected from the group consisting of xanthone, diethylthioxanthone, 2-isopropylthioxanthone, 4-isopropylthioxanthone, 2-crothioxanthone and 1-chromo- One or more species can be used.

Further, in the present invention, by using a dye sensitizer in addition to the radical polymerization initiator, the curing performance can be improved. At this time, the content of the dye sensitizer is not particularly limited, but is preferably about 5 to 15 parts by weight based on 100 parts by weight of the radical polymerization initiator. Examples of the dye sensitizer include kissanite, thioxanthene, coumarin, ketoxalin, benzyldimethylketone, benzophenone, 1-hydroxycyclohexylphenylketone, 2,4,6-trimethylbenzoyldiphenylphosphorus Trimethylbenzoylphenylphosphate, bis- (2,6-dimethoxybenzoyl) -2,4,4-trimethylpentylphosphine oxide, 2-methyl-1- [4-methyl 1-one and 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butan-1-one Can be used.

Further, in the present invention, as the ultraviolet polymerization initiator, Irgacure 184, 651, 500, 907, 369, 784, 2959, Ubecryl P36 (BASF), Lucirin TPO, LR8893 (BIAST) Darocur 1116, 1173, MBF (manufactured by Merck), ESCACURE KIP150, or ESCACURE KIP100F.

The UV initiator is preferably included in an amount of 3 to 10 parts by weight based on the total weight of the composition. If the content is less than 3 parts by weight, curing defects may occur. If the content is more than 10 parts by weight, adherence may be decreased upon formation of a coating film due to overcuring.

In addition, the resin composition of the present invention may further include a photosensitizer together with the ultraviolet initiator to improve the photoinitiator efficiency. At this time, it is most preferable that the photosensitizer is included in an amount of 5 to 15 parts by weight based on 100 parts by weight of the ultraviolet initiator in order to increase the photoinitiator efficiency. Examples of the photosensitizer include, but are not limited to, benzophenone, 10-butyl-2-chloroacridone, 2-isopropylthio 2-Isopropyl Thioxanthone or 2,4-Diethyl Thioxanthone may be used.

The ultraviolet curable top resin composition for coil-coating of the present invention may include a leveling agent to smooth the composition smoothness. The coating film smoothing agent can be generally used in the art, and the kind is not particularly limited. For example, ordinary coating agent smoothing agents such as BYK's product can be used.

The coating film smoothing agent is preferably included in an amount of 0.05 to 2 parts by weight based on the total weight of the composition. When the content is less than 0.05 part by weight, the leveling and slipping properties of the dry coating layer may be lowered. When the content exceeds 2 parts by weight, bubble stabilization may occur during coating, which may adversely affect the workability .

The ultraviolet-curable top resin composition for coil-coating of the present invention may further comprise at least one additive selected from the group consisting of antioxidants, light stabilizers, ultraviolet absorbers, dispersants and defoamers, if necessary. Examples of the antioxidant include Irganox 1010, Irganox 1035, Irganox 1076, Irganox 1222 (BASF, Japan). Examples of the antioxidant include Tinuvin 292, Tinuvin 144, Tinuvin 144 Sanol LS-770, sanol LS-765, sanol LS-292 or sanol LS-744 (Sankyo, Japan) can be used. The ultraviolet absorber may be Tinuvin P, Tinuvin 234, Tinuvin 320, Tinuvin 328 (BASF, Japan), Sumisorb 110, Sumisorb 130, Sumisorb 140, Sumisorb 220, Sumisorb 250, Sumisorb 320 or Sumisorb 400 And dispersant and antifoaming agent, respectively, can be used as a conventional additive agent for paints such as TEGO and EFKA.

The additive may be contained in an amount not lowering the physical properties required for the resin composition of the present invention, for example, 0.1 to 15 parts by weight based on the total weight of the composition.

The UV-curable top coat resin composition for coil-coating according to the present invention can be used at a level of 35 to 45 seconds at 25 ° C and DIN CUP # 4 using a stopwatch, An easy level of viscosity can be ensured for the work.

(Meth) acrylate containing a diisocyanate compound, a polyol and a hydroxyl group to react with a urethane (meth) acrylate to produce a UV-curable top coat resin composition for a coil-coating according to another embodiment of the present invention. Preparing a liquid oligomer; And (meth) acrylic acid ester monomer, ultraviolet ray initiator and film-form smoothing agent to the urethane (meth) acrylate oligomer to prepare an ultraviolet curable top resin composition.

The urethane (meth) acrylate oligomer, the (meth) acrylic acid ester monomer, the ultraviolet initiator and the coating film smoothing agent may be urethane (meth) acrylate based on the total weight of the composition in the step of preparing the ultraviolet- 20 to 50 parts by weight of an oligomer; 30 to 70 parts by weight of a (meth) acrylic acid ester monomer; 3 to 10 parts by weight of an ultraviolet initiator; And 0.05 to 2 parts by weight of a film smoothing agent.

However, in the present invention, the step of preparing the urethane (meth) acrylate oligomer comprises reacting a diisocyanate compound with a polyol to prepare a polyurethane prepolymer having isocyanate groups at both terminals thereof; And reacting the polyurethane prepolymer with (meth) acrylate containing a hydroxyl group to prepare a urethane (meth) acrylate oligomer.

Alternatively, the step of preparing the urethane (meth) acrylate oligomer in the present invention comprises reacting a (meth) acrylate containing a hydroxyl group with a diisocyanate compound to prepare a polyurethane prepolymer having isocyanate groups at one terminal ; And reacting the polyurethane prepolymer with a polyol to prepare a urethane (meth) acrylate oligomer.

In the present invention, the diisocyanate compound used in the synthesis of the urethane (meth) acrylate oligomer of the present invention includes two or more free isocyanate groups in one molecule, and examples thereof include 2,4-toluene diisocyanate, 1,4-xylene diisocyanate, 1,5-naphthalene diisocyanate, m-phenylene diisocyanate, P-phenylene diisocyanate, 4.4'-xylene diisocyanate, At least one selected from the group consisting of bisphenylene diisocyanate, hexamethylene diisocyanate, hexamethylene diisocyanate derivative, isophorone diisocyanate, hydrophenylmethane diisocyanate and cyclohexane diisocyanate can be used.

The polyol used in the synthesis of the urethane (meth) acrylate oligomer may be a polyol commonly used in the art. The polyol may be, for example, an alkylene glycol, At least one selected from the group consisting of aliphatic alcohols, polyester polyols, caprolactone polyols, polycarbonate polyols, poly C ₁ -C ₆ alkylene glycols and polyether polyols can be used, and preferably C ₁ to C ₁₅ Aliphatic alcohols, more preferably C ₂ to C ₁₂ aliphatic alcohols can be used.

In a preferred use of the polyol, the alkylene glycol is selected from the group consisting of neopentyl glycol, 3-methyl-1,5-pentanediol, ethylene glycol, propylene glycol, 1,4-butanediol and 1,6- It may be more than one kind. The aliphatic alcohol may be at least one selected from the group consisting of trimethylolpropane, pentaerythritol, tricyclodecane methylol and bis- (hydroxymethyl) -cyclohexane. The polybasic acid which can be reacted with the aliphatic alcohol may be selected from the group consisting of succinic acid, phthalic acid, hexahydrophthalic anhydride, terephthalic acid, adipic acid, azelaic acid and Tetrahydrophthalic anhydride, and tetrahydrophthalic anhydride. Further, the caprolactone polyol may be formed by the reaction of the aliphatic alcohol and? -Caprolactone described above. In addition, the polycarbonate polyol may be formed by the reaction of the aliphatic alcohol described above, for example, 1,6-hexanediol with diphenyl carbonate. The poly (C ₁ -C ₆₎ alkylene glycol may be at least one selected from the group consisting of polyethylene glycol, polypropylene glycol and polytetramethylene glycol. The polyether polyol may include, for example, ethylene oxide-modified bisphenols and the like.

The (meth) acrylate containing the hydroxyl group used in the synthesis of the urethane (meth) acrylate oligomer is preferably at least one selected from the group consisting of 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) Hydroxypropyl (meth) acrylate, 4-butanediol mono (meth) acrylate, 2-hydroxyalkyl (meth) acryloylphosphate, 4 -Hydroxycyclohexyl (meth) acrylate, pentaerythritol triacrylate, and caprolactone (meth) acrylate can be used.

The urethane (meth) acrylate oligomer is preferably contained in the resin composition of the present invention in an amount of 20 to 50 parts by weight based on the total weight of the composition. When the content is less than 20 parts by weight, sufficient workability, impact resistance and scratch resistance can not be imparted to the coating film, cracks may occur in the coating film during processing and molding after coating, and the coating film may peel off from the steel sheet. On the other hand, when the content exceeds 50 parts by weight, the workability and impact resistance may be lowered.

The UV-curable top resin composition for coil-coating of the present invention may contain (meth) acrylate monomer as well as the urethane (meth) acrylate oligomer described above. The (meth) acrylic acid ester monomer functions as a reactive diluent in the resin composition, and maintains a proper viscosity during the roll-coating operation, and undergoes a polymerization reaction upon irradiation with ultraviolet rays to form a coating film.

The kind of the (meth) acrylic acid ester monomer that can be used in the present invention is not particularly limited, but monofunctional (meth) acrylate monomer, polyfunctional (meth) acrylate monomer or a mixture thereof may be used.

Examples of the monofunctional (meth) acrylate monomer include acrylamide, dimethylaminoethyl (meth) acrylate, hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, hydroxybutyl (Meth) acrylate, dicyclopentadiene (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, isobornyl (meth) acrylate, At least one selected from the group consisting of (meth) acrylate, phenoxyethyl (meth) acrylate, butoxyethyl (meth) acrylate, polyethylene glycol monoacrylate and polypropylene glycol monoacrylate.

Examples of the polyfunctional (meth) acrylate monomer include ethylene glycol (meth) acrylate, dicyclopentenyl di (meth) acrylate, triethylene glycol di (meth) acrylate, tetraethylene glycol di Acrylate, trimethylolpropane di (meth) acrylate, trimethylolpropane tri (meth) acrylate, trimethylolpropane trioxypropyl tri (meth) acrylate, trimethylolpropane trioxyethyl tri (meth) Acrylate, neopentyl glycol di (meth) acrylate, neopentyl glycol propoxylate di (meth) acrylate, ditrimethylol propane, tetra (meth) acrylate, neopentyl glycol di (Meth) acrylate, butanediol di (meth) acrylate, hexanediol di (meth) acrylate, hexamethylene (Meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol penta One or more selected from the group can be used.

The (meth) acrylic acid ester monomer is preferably contained in the resin composition of the present invention in an amount of 30 to 70 parts by weight based on the total weight of the composition. When the content is less than 30 parts by weight, the flex workability may decrease and the viscosity may become excessively high, which may result in difficulty in work performance in roll coating. When the content exceeds 70 parts by weight, There is a possibility that the property may decrease.

The UV-curable top coat resin composition for coil-coating according to the present invention can be prepared by coating a topcoat composition of a liquid phase on a coated surface to form a coating film, and then irradiating ultraviolet rays with an ultraviolet initiator .

The ultraviolet ray initiator is not particularly limited as long as it can be commonly used in the art, and a radical polymerization initiator or an ion polymerization initiator can be used. However, the use of a radical polymerization initiator can increase the curing rate Do.

Examples of the radical polymerization initiator include, but are not limited to, 1-hydroxycyclohexyl phenyl ketone, 2,2-dimethoxy-2-phenylacetone phenone, 2- Phenylpropan-1-one, 1- (4-isopropylphenyl) -2-hydroxy-2-methylpropan-1-one, 1,1-dimethoxydeoxybenzoin, 3,3'- -Methoxybenzophenone, 1- (4-dodecylphenyl-2-hydroxy-2-methylpropan-1- -Propane-1-one, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, ethyl-2,4,6-trimethylbenzoylphenylphosphinate, bis- (2,6- dimethoxybenzoyl) 4-benzoyl-4'-methyldiphenylsulfide, benzyldimethylketal, furorenone, fluorene, benzaldehyde, benzoin ethyl ether , Join propyl ether, 2- (4-morpholinophenyl) -butan-1-one, acetophenone, 3-methylacetophenone, benzophenone, 4,4'-dimethoxybenzophenone, 4,4 ' -Diaminobenzophenone, 3,3 ', 4,4'-tetra (t-butylperoxycarbonyl) benzophenone, acetophenone benzyl ketal, triphenylamine, carbazole, 4-chlorobenzophenone, anthraquinone Selected from the group consisting of xanthone, diethylthioxanthone, 2-isopropylthioxanthone, 4-isopropylthioxanthone, 2-crothioxanthone and 1-chromo- One or more species can be used.

Further, in the present invention, by using a dye sensitizer in addition to the radical polymerization initiator, the curing performance can be improved. At this time, the content of the dye sensitizer is not particularly limited, but is preferably about 5 to 15 parts by weight based on 100 parts by weight of the radical polymerization initiator. Examples of the dye sensitizer include kissanite, thioxanthene, coumarin, ketoxalin, benzyldimethylketone, benzophenone, 1-hydroxycyclohexylphenylketone, 2,4,6-trimethylbenzoyldiphenylphosphorus Trimethylbenzoylphenylphosphate, bis- (2,6-dimethoxybenzoyl) -2,4,4-trimethylpentylphosphine oxide, 2-methyl-1- [4-methyl 1-one and 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butan-1-one Can be used.

Further, in the present invention, as the ultraviolet polymerization initiator, Irgacure 184, 651, 500, 907, 369, 784, 2959, Ubecryl P36 (BASF), Lucirin TPO, LR8893 (BIAST) Darocur 1116, 1173, MBF (manufactured by Merck), ESCACURE KIP150, or ESCACURE KIP100F.

The UV initiator is preferably included in an amount of 3 to 10 parts by weight based on the total weight of the composition. If the content is less than 3 parts by weight, curing defects may occur. If the content is more than 10 parts by weight, adherence may be decreased upon formation of a coating film due to overcuring.

In addition, the resin composition of the present invention may further include a photosensitizer together with the ultraviolet initiator to improve the photoinitiator efficiency. At this time, it is most preferable that the photosensitizer is included in an amount of 5 to 15 parts by weight based on 100 parts by weight of the ultraviolet initiator in order to increase the photoinitiator efficiency. Examples of the photosensitizer include, but are not limited to, benzophenone, 10-butyl-2-chloroacridone, 2-isopropylthio 2-Isopropyl Thioxanthone or 2,4-Diethyl Thioxanthone may be used.

The ultraviolet curable top resin composition for coil-coating of the present invention may include a leveling agent to smooth the composition smoothness. The coating film smoothing agent can be generally used in the art, and the kind is not particularly limited. For example, ordinary coating agent smoothing agents such as BYK's product can be used.

The coating film smoothing agent is preferably included in an amount of 0.05 to 2 parts by weight based on the total weight of the composition. When the content is less than 0.05 part by weight, the leveling and slipping properties of the dry coating layer may be lowered. When the content exceeds 2 parts by weight, bubble stabilization may occur during coating, which may adversely affect the workability .

The ultraviolet-curable top resin composition for coil-coating of the present invention may further comprise at least one additive selected from the group consisting of antioxidants, light stabilizers, ultraviolet absorbers, dispersants and defoamers, if necessary. Examples of the antioxidant include Irganox 1010, Irganox 1035, Irganox 1076, Irganox 1222 (BASF, Japan). Examples of the antioxidant include Tinuvin 292, Tinuvin 144, Tinuvin 144 Sanol LS-770, sanol LS-765, sanol LS-292 or sanol LS-744 (Sankyo, Japan) can be used. The ultraviolet absorber may be Tinuvin P, Tinuvin 234, Tinuvin 320, Tinuvin 328 (BASF, Japan), Sumisorb 110, Sumisorb 130, Sumisorb 140, Sumisorb 220, Sumisorb 250, Sumisorb 320 or Sumisorb 400 And dispersant and antifoaming agent, respectively, can be used as a conventional additive agent for paints such as TEGO and EFKA.

The additive may be contained in an amount not lowering the physical properties required for the resin composition of the present invention, for example, 0.1 to 15 parts by weight based on the total weight of the composition.

The production method of the present invention is characterized in that the urethane (meth) acrylate oligomer prepared as described above is used in the production of a resin composition, whereby the coating film formed on the steel sheet for coil-coating has excellent properties such as workability, impact resistance and scratch resistance Thus, even if the post-painting processing and the molding step are performed, problems such as cracking and peeling of the coating film can be prevented.

According to another embodiment of the present invention, A color coating layer formed on the base steel sheet; And a top coating layer formed on the color coating layer. The top coating layer may be formed of a resin composition for an ultraviolet curable top coat for coil-coating according to the present invention.

However, the base steel sheet usable in the present invention is not particularly limited and a hot-dip coated steel sheet, an electroplated steel sheet or a dry-coated steel sheet can be used. The kind of metal constituting the base steel sheet is not particularly limited, Alloy steel, stainless steel, copper and the like.

The coil-coated steel sheet of the present invention may further include at least one coating layer between the color coating layer and the base steel sheet, depending on the purpose or process of the steel sheet to be produced. For example, .

In addition, in the present invention, the color coating layer formed on the base steel sheet corresponds to a color coating layer for coil coating, and its composition may include, for example, but not limited to, a polyester resin, A variety of colors can be displayed in consideration of the purpose of the printer, the needs of the consumer, and the like, and may include various printing layers as required.

As described above, the coil-coated steel sheet of the present invention can form an upper coat layer on the color coat layer using the ultraviolet curable top resin composition for coil-coating provided in the present invention, The curing drying time can be reduced by the ultraviolet ray curing method, and it is possible to reduce the investment cost of the initial painting equipment and to provide excellent productivity. Furthermore, since the top coat layer is formed on a color coat layer capable of exhibiting various colors, it is possible to produce an excellent gloss performance and an appearance performance, and it is also possible to provide a top coat composition having a processability comparable to that of the conventional thermosetting resin composition, So that it is possible to manufacture a desired industrial product by processing steel sheets in various forms desired by a consumer without problems such as cracking and peeling of the coating film

At this time, the dry film thickness of the top coat layer is preferably 5 to 10 mu m. When the thickness of the dried coating film is less than 5 占 퐉, it is difficult to ensure mechanical properties such as sufficient workability, impact resistance and scratch resistance, cracks are formed in the color coating layer and the top coating film layer during processing, have. On the other hand, when the thickness exceeds 10 mu m, the thickness of the top coat layer becomes too thick, and cracks may occur.

Example

Hereinafter, the present invention will be described more specifically by way of specific examples. The following examples are provided to aid understanding of the present invention, and the scope of the present invention is not limited thereto.

[Production Example 1]

A four-necked flask equipped with a thermometer, a condenser, a dropping funnel and a stirrer was charged with 2 equivalents of isophorone diisocyanate, and 500 ppm of hydroquinone as a polymerization inhibitor was added. The temperature was raised to 70 占 폚, 2 equivalents of caprolactone acrylate was added dropwise for 2 hours, and the reaction was maintained for 1 hour. After adding 100 ppm of dibutyl tin dilaurate, the temperature was raised to 80 DEG C and the reaction was maintained for 4 hours. After confirming that there was no NCO peak by infrared spectroscopy (IR), the resultant was cooled to 60 DEG C to prepare a urethane acrylate oligomer composition <A>.

[Production Example 2]

A urethane acrylate oligomer composition <B> was prepared in the same manner as in Preparation Example 1, except that instead of isophorone diisocyanate, succinimidyl diisocyanate was used in the same amount.

[Production Example 3]

A urethane acrylate oligomer composition < C > was prepared by using the same method as in Preparation Example 1, except that caprolactone methacrylate was used in the same amount instead of caprolactone acrylate.

[Production Example 4]

A four-necked flask equipped with a thermometer, a condenser, a dropping funnel and a stirrer was charged with 4 equivalents of hexamethylene diisocyanate, and 500 ppm of hydroquinone as a polymerization inhibitor was added. The temperature was raised to 70 占 폚 and 2 equivalents of polytetramethylene glycol (molecular weight 1000) was added dropwise for 2 hours, and the reaction was maintained for 1 hour. When the theoretical NCO% was reached, 2 equivalents of pentaerythritol triacrylate was added dropwise over 1 hour, then 100 ppm of dibutyltin dilaurate was added, the temperature was raised to 80 캜 and the reaction was maintained for 4 hours. After confirming that there is no NCO peak by infrared spectroscopy (IR), it was cooled to 60 캜 to obtain a hard type urethane acrylate oligomer Composition < D >

[Production Example 5]

A urethane acrylate oligomer composition < E > was prepared by using the same method as in Production Example 4, except that isophorone diisocyanate was used in the same equivalent amount as that of hexamethylene diisocyanate.

[Production Example 6]

A urethane acrylate oligomer composition <F> was prepared by using the same method as in Production Example 4 except that instead of polytetramethylene glycol, polyester polyol (neopentyl glycol and adipic acid condensation product, molecular weight 2000) was used in the same amount .

[Experimental Example 1]

1. Preparation of UV curable top coat composition for coil coating

(IBOA), hydroxypropyl acrylate (HPA) and tetrahydrofurfuryl acrylate (THFA) were charged into a 1 L vessel in the same amounts as shown in Table 1, and then UV ray initiator IRGACURE 184 (manufactured by BASF) Were added in the same amounts as shown in Table 1, followed by stirring to dissolve uniformly. Thereafter, oligomers or PU-340 (manufactured by Mitsubishi Chemical Co., Ltd., polyfunctional oligomer) and A-8560TL (manufactured by HS Chemtron, Inc.) prepared in Production Examples 1 to 6 were mixed with a urethane (meth) (BYK 377 manufactured by BYK Co., Ltd.) as a coating film smoothing agent in the amounts shown in Table 1, and then uniformly stirred again to obtain a coating solution for coil coating An ultraviolet curable top coat composition was prepared.

2. Preparation of Test Specimens

(1) EGI (electrogalvanized steel sheet, 0.8 T, 7 cm x 15 cm) was surface-cleaned with XYLENE to remove dust and foreign matter on the surface, and then dried in a hot air oven at 80 ° C for 10 minutes, Respectively. Finish coat of 9800 UV WHITE BASE (manufactured by SAMHWA PAINT CO., LTD.) Was coated on the pretreated material using BAR COAT # 20, dried by heating in PMT (PEAT METAL TEMPERATURE) at 230 ° C in an induction oven, 12 ㎛ base coat coating specimens were prepared. Thereafter, the prepared UV-curable top coat composition for coating was coated on BASE COAT coated specimens using BAR COAT # 6, then cured and dried in a tunnel type UV drying furnace (1500 mJ / cm 2) ) Ultraviolet (UV) curing type top coat coating composition for coil-coating was prepared.

(2) However, in order to compare the physical properties of the coating composition with the conventional thermosetting resin composition, Fine Coat SL4000 CLEAR (manufactured by Samhwa Paints Co., Ltd.) was painted using BAR COAT # 28 on a base coat paint prepared by the same process as described above Thereafter, the film was cured and dried in PMT (PEAT METAL TEMPERATURE) at 230 ° C. in a hot-air drying furnace to prepare a transparent coating sample (Comparative Example 4) on a thermosetting top coat for coil-coating with a dry film thickness (DFT) of 8 μm.

3. Test and Evaluation Methods

The test specimens thus prepared were evaluated for viscosity, gloss, adhesion, workability, impact resistance, pencil hardness, scratch resistance, abrasion resistance and flame retardancy by the following methods, and the results are shown in Table 2 .

(1) Viscosity

The viscosity was 80% of the solution filled in a 500 g vessel, and then calibrated to 25 ° C using a thermostatic bath and a barrel thermometer. After that, using JAHN CUP # 4 and stopwatch, Were measured and evaluated.

(2) gloss

The gloss meter was calibrated by SHEEN's Tri-Glossmeter according to the equipment manual, and 60 ° gloss of the coated sample was measured.

(3) Adhesion

The adhesive strength was determined by drawing one line horizontally and vertically with a gap of 1 mm on the specimen according to the adhesion test method of the paint of ISO 2409, attaching a cellophane adhesive tape thereon, and peeling off 100 pieces of the separated coated surface The number of remaining pieces was measured.

(4) Processability

T-Bend tester was used to test from 0T to 4T. After bending, it was observed with naked eyes to determine whether or not it was peeled off. In the absence of exfoliation, the grade was applied to the specimen. (Target level: 0T ~ 3T)

(5) Impact resistance

DUPONT method Impact tester was used. A weight of 500g was dropped on the front and back of the specimen, and then a cellophane adhesive tape was attached to the test area and peeled off. The peeling and cracking of the coating were judged as follows.

○: No crack occurred

C: Crack occurred

×: Peeling of the coating film

(6) Pencil Hardness

The pencil hardness was measured by a pencil hardness tester according to JIS K-5400. The pencil hardness was measured at a 45 ° angle with respect to the pencil type (B, HB, F, H, 2H, I evaluated the degree with eyes (target level: H or higher).

(7) scratch resistance

The cured coating layer was reciprocated 20 times in the same direction as the coating direction with the nail and in the direction perpendicular to the coating direction, and scratch marks remained on the coating layer were observed and evaluated by the following methods.

○: No marks appear

△: Mark slightly visible

X: Mark appears clearly

(8) Abrasion resistance

The specimen with the coating layer was cut into 10 cm width and 10 cm length. Then, a line was drawn diagonally from each corner, and the corners were cut by 1 cm. Then, a hole having a diameter of 1 cm was drilled at the point where the diagonal line intersected to complete the specimen applicable to ABRATION TESTER. The finished specimens were subjected to abrasion resistance test 1000 times with CS-1 (# 10) 250g * 2EA, and the difference in weight before and after test of the specimens was recorded.

○: Weight reduction is less than 5g and there is no part where the original plate is loaded.

△: The weight reduction is 5g or less, but there is a part where the disk is loaded.

X: The weight loss is more than 5g, and the part containing the disc is obvious.

(9) Salt water silent

The specimens were left to stand for 500 hours in a salt sprayer according to the ASTM B-117 standard, and the blisters and rusts of the coatings after the sample washing and 1 hour of natural drying were evaluated according to ASTM D-610 as follows .

○: Less than 0.03% of blister and rust

Δ: Blister and rust generation less than 0.1%

X: Less than 0.3% of blister and rust

division Example
One Example
2 Example
3 Example
4 Example
5 Example
6 Example
7 Example
8 Example
9 Comparative Example
One Comparative Example
2 Comparative Example
3 Comparative Example
4 I.B.O.A 40 40 40 40 40 40 40 40 40 10 55 40 Fine coat SL4000 CLEAR H.P.A. 5 5 5 5 5 5 5 5 5 5 5 5 T.H.F.A. 8 8 8 8 8 8 8 8 8 8 8 8 IRGACURE 184 5 5 5 5 5 5 5 5 5 5 5 5 Oligomer
<A> 25 25 25 - - - - - - - - - Oligomer
<B> - - - 25 25 25 - - - - - - Oligomer
<C> - - - - - - 25 25 25 45 15 - Oligomer
<D> 16.5 - - 16.5 - - 16.5 - - - - - Oligomer
<E> - 16.5 - - 16.5 - - 16.5 - 26.5 11.5 - Oligomer
<F> - - 16.5 - - 16.5 - - 16.5 - - - PU-340 25 A-8560TL 16.5 BYK 377 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 Sum 100 100 100 100 100 100 100 100 100 100 100 100

(Note that the unit of each component content described in Table 1 means weight% based on the total weight of the composition).

division Viscosity (sec) Polish(%) Adhesion Processability Impact resistance Pencil hardness Scratch resistance Abrasion resistance Salt water silent Example 1 40 95 100 1T ○ H ○ ○ ○ Example 2 43 96 100 1T ○ H ○ ○ ○ Example 3 37 94 100 1T ○ F ○ ○ ○ Example 4 42 95 100 1T ○ H ○ ○ ○ Example 5 44 94 100 1T ○ H ○ ○ ○ Example 6 39 95 100 1T ○ F ○ ○ ○ Example 7 38 93 100 1T ○ H ○ ○ ○ Example 8 41 95 100 1T ○ H ○ ○ ○ Example 9 35 95 100 1T ○ F ○ ○ ○ Comparative Example 1 120 95 100 2T △ H ○ ○ ○ Comparative Example 2 25 93 90 1T ○ B × × × Comparative Example 3 45 91 80 3T × F △ △ × Comparative Example 4 60 87 100 1T ○ HB △ △ ○

As shown in Table 2, the specimens of Examples 1 to 8 showed generally good results in terms of appearance, adhesiveness, workability, impact resistance, surface hardness and the like.

On the other hand, Comparative Example 1, in which the content of the monomer was less than the range of the present invention, was too large to be easily predicted to have difficulty in roll coating, and in addition, both impact resistance and pencil hardness showed poor results.

In addition, Comparative Example 2, in which the monomer content exceeded the range of the present invention, showed a very thin viscosity, but showed both pencil hardness, scratch resistance, abrasion resistance, and salt water repellency.

In addition, Comparative Example 3, which contained different oligomers, but not the urethane (meth) acrylate oligomer of the present invention, also showed the results for both impact resistance, pencil hardness, scratch resistance, abrasion resistance and salt spray resistance.

In the case of Comparative Example 4 using the conventional thermosetting resin composition, the overall physical properties were good, but it was found that the ultraviolet curing type of Examples 1 to 9 had lower gloss and hardness than the coated specimen.

As a result, it can be seen that the reliability of the specimens of Comparative Examples 1 to 4 was lowered, and the specimens of Examples 1 to 9 belonging to the scope of the present invention had gloss and hardness higher than those of the conventional thermosetting type, And scratch resistance and abrasion resistance. Since the organic solvent in the composition is not contained and the rapid curing can be performed by the ultraviolet ray method, it is more environmentally friendly than the conventional thermosetting type coating material, and is easier to mass-produce Able to know.

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

Claims (16)

Based on the total weight of the composition,
20 to 50 parts by weight of a urethane (meth) acrylate oligomer;
30 to 70 parts by weight of a (meth) acrylic acid ester monomer;
3 to 10 parts by weight of an ultraviolet initiator; And
0.05 to 2 parts by weight of a coating film smoothing agent,
The urethane (meth) acrylate oligomer is formed by reacting a (meth) acrylate containing a diisocyanate compound, a polyol and a hydroxyl group.
The process of claim 1, wherein the diisocyanate compound is selected from the group consisting of 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 1,3-xylene diisocyanate, 1,4-xylene diisocyanate, 1,5- Naphthalene diisocyanate, m-phenylene diisocyanate, P-phenylene diisocyanate, 4.4'-bisphenylene diisocyanate, hexamethylene diisocyanate, hexamethylene diisocyanate derivative, isophorone diisocyanate, And at least one member selected from the group consisting of cyclohexane diisocyanate and cyclohexane diisocyanate.
The composition of claim 1 wherein said polyol is selected from the group consisting of alkylene glycols, C ₁ to C ₁₅ aliphatic alcohols, polyester polyols, caprolactone polyols, polycarbonate polyols, poly C ₁ to C ₆ alkylene glycols and polyether polyols Wherein at least one of the thermosetting resin and the thermosetting resin is a thermosetting resin.
The positive resist composition according to claim 1, wherein the (meth) acrylate containing a hydroxyl group is selected from the group consisting of 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2- (Meth) acrylate, 4-hydroxycyclohexyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, Acrylate, pentaerythritol triacrylate, and caprolactone (meth) acrylate. The resin composition according to claim 1,
The resin composition according to claim 1, wherein the (meth) acrylic acid ester monomer is at least one selected from the group consisting of a monofunctional (meth) acrylate monomer and a polyfunctional (meth) acrylate monomer.
6. The composition of claim 5 wherein the monofunctional (meth) acrylate monomer is selected from the group consisting of acrylamide, dimethylaminoethyl (meth) acrylate, hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, Acrylate, isobornyl (meth) acrylate, lauryl (meth) acrylate, dicyclopentadiene (meth) acrylate, tetra Coil-coatings which are at least one selected from the group consisting of hydroxypropyl (meth) acrylate, hydroxyethyl (meth) acrylate, hydroxyethyl (meth) acrylate, Based ultraviolet curable resin composition.
6. The polyfunctional (meth) acrylate monomer according to claim 5, wherein the polyfunctional (meth) acrylate monomer is selected from the group consisting of ethylene glycol (meth) acrylate, dicyclopentenyl di (meth) acrylate, triethylene glycol di Trimethylolpropane tri (meth) acrylate, trimethylolpropane di (meth) acrylate, trimethylolpropane tri (meth) acrylate, trimethylolpropane trioxypropyl tri (meth) Acrylate, neopentyl glycol di (meth) acrylate, tripropylene glycol di (meth) acrylate, ditrimethylol propane, tetra (meth) acrylate, neopentyl glycol di (Meth) acrylate, butanediol di (meth) acrylate, hexanediol di (meth) acrylate, hexanediol di (Meth) acrylates such as methylene diol di (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol penta Wherein at least one selected from the group consisting of a fluorine-containing resin and a fluorine-containing resin is used.
2. The composition of claim 1 wherein the UV initiator is selected from the group consisting of 1-hydroxycyclohexyl phenyl ketone, 2,2-dimethoxy-2-phenylacetone phenone, 2-hydroxy- - (4-isopropylphenyl) -2-hydroxy-2-methylpropan-1-one, 1,1-dimethoxydioxybenzoin, 3,3'- (2-methyl-1- [4- (methylthio) phenyl] -2-morpholino-propan-1-one, 2 , 4,6-trimethylbenzoyldiphenylphosphine oxide, ethyl 2,4,6-trimethylbenzoylphenylphosphinate, bis- (2,6-dimethoxybenzoyl) -2,4,4-trimethylpentylphosphine Benzoyl-4'-methyldiphenylsulfide, benzyldimethylketal, furorenone, fluorene, benzaldehyde, benzoin ethyl ether, joining propyl ether, 2-benzyl -2-dimethylamino-1- (4-morpholinophenyl ) -Butan-1-one, acetophenone, 3-methylacetophenone, benzophenone, 4,4'-dimethoxybenzophenone, 4,4'- diaminobenzophenone, 3,3 ' Tetra (t-butylperoxycarbonyl) benzophenone, acetophenone benzylketal, triphenylamine, carbazole, 4-crobenzhenephenone, anthraquinone, xanthone, diethylthioxanthone, Ton, 4-isopropylthioxanthone, 2-crothioxanthone, and 1-crolo-4-propoxythioxanthone.
The ultraviolet curable top resin composition for a coil-coating according to claim 1, further comprising a photosensitizer,
Wherein the photosensitizer is contained in an amount of 5 to 15 parts by weight based on 100 parts by weight of the ultraviolet initiator.
The ultraviolet curable top resin composition for coil-coating according to claim 1, further comprising at least one additive selected from the group consisting of an antioxidant, a light stabilizer, an ultraviolet absorber, a dispersing agent and a defoaming agent,
Wherein the additive is contained in an amount of 0.1 to 15 parts by weight based on the total weight of the composition.
The ultraviolet-curable top resin composition according to claim 1, wherein the viscosity of the ultraviolet curable top coat resin for coil-coating is DIN-CUP (25 占 폚) 35 to 45 seconds.
Reacting a (meth) acrylate containing a diisocyanate compound, a polyol and a hydroxyl group to prepare a urethane (meth) acrylate oligomer; And
(Meth) acrylic acid ester monomer, an ultraviolet initiator, and a coating film smoother to the urethane (meth) acrylate oligomer to prepare an ultraviolet curable top resin composition,
The urethane (meth) acrylate oligomer, the (meth) acrylate monomer, the ultraviolet initiator and the coating film smoothing agent are contained in the ultraviolet curable top resin composition in an amount of from 20 to 100 parts by weight, 50 parts by weight; 30 to 70 parts by weight of a (meth) acrylic acid ester monomer; 3 to 10 parts by weight of an ultraviolet initiator; And 0.05 to 2 parts by weight of a coating film smoothing agent.
13. The method of claim 12, wherein the step of preparing the urethane (meth)
Reacting a diisocyanate compound with a polyol to prepare a polyurethane prepolymer having isocyanate groups at both terminals; And
(Meth) acrylate oligomer by reacting the polyurethane prepolymer with (meth) acrylate containing a hydroxyl group to prepare a urethane (meth) acrylate oligomer.
13. The method of claim 12, wherein the step of preparing the urethane (meth)
Reacting a (meth) acrylate containing a hydroxyl group with a diisocyanate compound to prepare a polyurethane prepolymer having an isocyanate group at one end; And
And reacting the polyurethane prepolymer with a polyol to prepare a urethane (meth) acrylate oligomer.
Base steel sheet;
A color coating layer formed on the base steel sheet; And
And a top coating layer formed on the color coating layer,
Wherein the top coat layer is formed from the ultraviolet curable top resin composition for coil-coating according to any one of claims 1 to 11.
16. The coil-coated steel sheet according to claim 15, wherein the top coat layer has a dry film thickness of 5 to 10 mu m.