KR100671954B1 - Multi-functional photo-curable aqueous coating composition for top coating of mobile phone - Google Patents

Abstract

Provided is a multi-functional photo-curable aqueous coating composition for top coating of a mobile phone, which contains a small amount of volatile organic compounds and has good physical properties such as adhesion, hot water resistance, acid resistance, etc. The multi-functional photo-curable aqueous coating composition for top coating of a mobile phone comprises (A) 55-95wt% of a photo-curable and water-dispersible acrylate resin prepared by undergoing a urethane reaction of hydroxy multi-functional acrylate and urethane oligomer having isocyanate terminals with hydrophilic groups, (B) 1-10wt% of a photo initiator, (C) 0.01-25wt% of photo-curable oligomer, and (D) 3-10wt% of water-miscible organic solvent.

Description

MULTI-FUNCTIONAL PHOTO-CURABLE AQUEOUS COATING COMPOSITION FOR TOP COATING OF MOBILE PHONE}

1 is a structural diagram showing a coating film of a typical mobile phone (in the figure, 1 is a plastic material; 2 is a bottom coating film; and 3 is a top coating film),

2 is an analysis result of high efficiency liquid quantitative chromatography (HPLC) of a monomer having a hydroxyl group and an acryl group prepared in Preparation Example 2 of the present invention,

The present invention relates to a high-functional photocurable aqueous coating composition for coating a mobile phone, including a photocurable water-dispersible acrylate resin, specifically, a urethane oligomer and an hydroxy high-functional acrylate having an isocyanate terminal into which a hydrophilic group is introduced. High functional photocurable water-based coating material for mobile phone topcoat, which is environmentally friendly and has excellent physical properties and workability, including a photocurable water-dispersible acrylate resin, a photoinitiator, a photocurable oligomer and a small amount of water-miscible organic solvent prepared by urethane reaction. It relates to a composition.

Due to the rapid industrialization, the global environment is rapidly deteriorating such as air and water pollution, ozone depletion and global warming. It's going on.

Particularly, in the air pollution part, an aqueous coating paint which minimizes the use of volatile organic compounds (VOCs) is applied to many parts. Such an aqueous coating paint is applied to an ultraviolet curable paint, and research and development of an ultraviolet curable aqueous paint is actively being carried out not only in Korea but also in various countries of the world.

As a representative method of manufacturing a conventional UV-curable aqueous coating, there is disclosed a method of forcibly dispersing a photocurable resin using a dispersant such as polyvinyl pyrrolidone as in EP 0012339. The coating liquid prepared by such a forced dispersion method is incompatible with other types of photocurable aqueous dispersions (for example, urethane dispersions or acrylic emulsions), and even after drying, the dispersant contains a considerable amount of water, thereby allowing photocuring. It has a bad effect on the transparency and hardness of the after coating film.

Further, photocurable polys disclosed in U.S. Patent Nos. 5,135,963, 6,011,078, 6,207,744, 6,335,397, 6,436,540, German Patent Publication No. 4031732, European Patent No. 0753531, 870788, and 0872502. Urethane aqueous products have a relatively large molecular weight for stability in the aqueous phase has a disadvantage of low curing density. That is, the water dispersion has a relatively large molecular weight for water dispersion stability compared to the UV-curable oligomer and the UV-curable monomer, which influences the physical properties of the conventional oil-based photo-curing paint, even if the functional group at the end is simply increased to the UV-curable oil-based paint Compared with conventional oil-based photocurable paints, this product has low curing density after curing, which results in poor transparency and hardness, and requires properties of most coatings for coating coatings for mobile phone coatings such as hydrolysis resistance, acid resistance, cosmetic resistance, hot water resistance, and abrasion resistance. Are largely inadequate.

In addition, US Pat. No. 6,521,702 introduces a polyfunctional polyester acrylate in which some hydroxy groups (-OH) and carboxyl groups (-COOH) remain to react two hydroxyl groups with isocyanates and neutralize the carboxyl groups. By the method of dispersing in water to give a UV-curable aqueous coating method. However, the method is advantageous in terms of physical properties, but the production cost of the polyfunctional polyester acrylate is very high and the process is complicated, so it is difficult to reduce the variation of each product, so the industrial productivity is very low.

As described above, conventional UV-curable water-based paints have relatively high molecular weight and low acrylic functional groups, and thus have low crosslinking density, so that physical properties such as gloss, hardness, and water resistance are insufficient or poor in productivity for use in mobile phone top coats. There is a demand for the development of an aqueous coating material for mobile phone coating having excellent physical properties.

Accordingly, the inventors of the present invention can provide a photocurable, photocurable water-dispersible resin prepared by introducing a hydrophilic group, a photoreactor and a highly functional hydroxy acrylate monomer to increase hardness, and a water-miscible organic solvent and ethylene in the resin. Development of a highly functional photocurable aqueous coating composition prepared by adding a small amount of propylene) oxide-added photocurable oligomer, satisfying the physical properties required for coating of a mobile phone, while improving workability and appearance. It is possible to provide a coating coating solution.

Accordingly, an object of the present invention is to provide a highly functional photocurable water-based coating composition for mobile phone coating which is environmentally friendly and has excellent physical properties such as workability and adhesion, hot water resistance, acid resistance, cosmetic resistance, wear resistance, chemical resistance, pencil hardness, and the like. .

In the present invention to achieve the above object,

(A) 55 to 95% by weight of a photocurable water-dispersible acrylate resin prepared by urethane reaction of a urethane oligomer having an isocyanate terminal having a hydrophilic group introduced therein and a hydroxy high functional acrylate, (B) 1 to 10% by weight of a photoinitiator, (C) Provided is a high functional photocurable aqueous coating composition for mobile phone top coat, comprising 0.01 to 25% by weight of a photocurable oligomer as a reactive diluent and 3 to 10% by weight of a water miscible organic solvent.

Hereinafter, the present invention will be described in more detail.

The high functional photocurable aqueous coating composition of the present invention is characterized by the following.

First, in order to increase the degree of curing of the photocurable water-dispersible acrylate resin, a highly functional hydroxy acrylate is introduced at the end of the resin to increase the crosslinking density, and the functional group portion having hydrophilicity inside the molecule and the unsaturated hydrocarbon group capable of ultraviolet photocuring. Coupling by chemical reaction improves the hardness of the coating film surface and the physical properties required for mobile top coating, which is insufficient in the prior art.

Second, unlike the conventional UV-curable aqueous coating composition, it is not a catalyst for initiating a photocuring reaction only in the ultraviolet region of the wavelength range of 200 to 400 nm and light in a specific region wavelength, but in the wavelength range of the region required by the operator in the coating film manufacturing process. At least one photoinitiator capable of initiating a photocuring reaction is added to the composition to achieve good workability and high productivity.

Third, unlike conventional UV-curable aqueous coating compositions, a small amount of water-miscible organic solvents and / or photocured oligomers to which ethylene oxide or propylene oxide is added imparts excellent appearance and workability.

The photocurable water-dispersible acrylate resin used in the coating composition of the present invention is prepared from a polyester polyol, an isocyanate having a hydrophilic group introduced therein, and a material having a functional group capable of reacting with the hydrophilic group and a functional group capable of reacting with the isocyanate. , A urethane oligomer having a hydrophilic functional group may be prepared by urethane reaction with a hydroxy high functional acrylate.

As the polyester polyol in the present invention, preferably, a difunctional polyester diol may be used, and is prepared by ester condensation of an excess of glycol and dicarboxylic acid. At this time, the reaction proceeds until the acid value using the neutralization titration becomes 0.5 mg KOH / g or less, and it is preferable to use glycol: dicarboxylic acid in an equivalent ratio of 2: 1 to 3: 1, and the obtained polyester polyol is inverse It is preferred that the copolymer is a mixture of aliphatic or aromatic structures having an OH value of 56 to 112 mg / KOH g by titration method and a molecular weight of 1,000 to 2,000 calculated using this end group analysis.

In a preferred embodiment of the invention, the dialcohols usable in the preparation of the polyester diols are glycols having from 2 to 15 carbon atoms, for example neopentylglycol, 1,4-butanediol, 1,6- Hexanediol, diethylene glycol, dipropylene glycol, triethylene glycol, tripropylene glycol, and the like, and dicarboxylic acids include monoesters of dicarboxylic acids or their anhydrides such as adipic acid, fumaric acid, maleic acid and maleic acid. Anhydride, phthalic acid, phthalic anhydride, crotonic acid, ataconic acid, isophthalic acid and the like.

In the present invention, the polyester polyol (I) is reacted with an isocyanate having a hydrophilic group introduced therein and a material having a hydrophilic group and a functional group capable of reacting with the isocyanate to prepare a urethane oligomer (N) having an isocyanate end having the hydrophilic group introduced therein. As the isocyanate into which the hydrophilic group is introduced, all diisocyanates (D) can be used, preferably butylene diisocyanate, hexamethylene diisocyanate (HDI), 1-isocyanato-3,3 Aliphatic diisocyanates such as, 5-trimethyl-5-isocyanatomethyl-cyclohexane (IPDI), bis (isocyanatocyclohexyl) -methane, 2,4-diisocyanatotoluene, 2,6-diisosia Aromatic diisocyanates such as nattoluene, 4,4-diisocyanato-diphenylmethane, isomers thereof or It may be a mixture of.

In addition, the material having a functional group capable of reacting with the hydrophilic group and isocyanate, hydrophilic groups such as sulfonium, ammonium, carboxylate, sulfonate are introduced into the oligomer so as to have water dispersibility, so that the amine, hydride can react with the isocyanate. A substance having a functional group such as a hydroxy group and having a hydrophilic group in a cationic form and an anionic form may be used, and examples thereof include bis-hydroxymethyl-propionic acid, glyconic acid and 2-aminoethylaminoethane-sulfonic acid.

In the reaction for preparing the urethane oligomer, a material having an isocyanate having a hydrophilic group introduced therein: (polyester diol + hydrophilic group and a functional group capable of reacting with an isocyanate is preferably used in an equivalent ratio of 2: 1 to 1.8, and a hydrophilic group and The amount of the substance having a functional group capable of reacting with the isocyanate is preferably not more than 5% of the total amount of the urethane oligomer (N) prepared by the reaction, and is also measured by the neutralization reverse titration method of the prepared urethane oligomer. The amount (NCO%) is preferably 2 to 6% of the total amount of the urethane oligomer produced.

The reaction may be accelerated by adding an appropriate amount of a suitable catalyst such as tin octoate, dibutyl tin dilaurate or tertiary amine, which is a tin-based metal compound, in order to prevent difficulty in manufacturing due to an increase in viscosity. Preference is given to carrying out the reaction in an organic solvent which is water miscible and which does not contain a hydroxy group, such as acetone, butanone, tetrahydrofuran, dioxane, acetonitrile, 1-methyl-2-pyrrolidone.

In addition, in the reaction, a photocurable monomer may be used as a reactive diluent for controlling the curing rate and adhesion of the coating film and controlling the viscosity of the reactant in place of the organic solvent, and such photocurable monomer does not contain a hydroxyl group. Non-reactive aliphatic polyhydric polyalcohols and esters of acrylic acid derived from their alkoxy compounds, for example trimethylolethane triacrylate, trimethylolpropane triacrylate, pentaerythritol tetraacrylate, hexanediol di It is preferable to use acrylate, octadiol diacrylate, tripropylene glycol diacrylate, and the like. At this time, if the amount of the photocurable monomer is too large, the curing rate of the coating film is slowed down and the physical properties of the coating film is deteriorated. If the amount is too small, the viscosity of the reactant is increased and the liquid phase of the composition becomes unstable.

According to the present invention, the urethane oligomer (N) having an isocyanate terminal into which the hydrophilic group is introduced is urethane-reacted with a high functional acrylate (A) having a hydroxyl group capable of reacting with an isocyanate functional group to photocurable water-dispersible acrylate resin To prepare.

The hydroxy high functional acrylate (A) used to prepare a photocurable urethane resin has a hydroxyl group in the molecule and contains 2 to 6 acrylic groups, and Korean Patent Publication No. 2003-61357, German Patent Publication It may be prepared according to the method described in 2838691 et al. The hydroxy high functional acrylates include 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 4-hydroxybutyl acrylate, trimethylolpropane di / triacrylate mixture (TMPTA), pentaerythritol tri / Tetraacrylate mixture (PETA), dipentaerythritol penta / hexaacrylate mixture (DiPETA), and the like. The hydroxy high functional acrylate may be a mixture of a substance having one hydroxy group and a substance having no hydroxy group, and a substance having a content of one hydroxy group having a content of 45 to 55%.

The photocurable water-dispersible acrylate resin production reaction proceeds until the characteristic peak of 2,260 cm ^-1 of isocyanate in Fourier Transform Infrared Spectroscopy (FT-IR) disappears completely, and when the reaction is completed, the photocurable oligomer is hydrophilic. Basic compounds are used to neutralize all or part of the acid groups of the resin, which may be organic and inorganic bases such as alkali and alkaline earth metal hydroxides, oxides, carbonates, hydrogen carbonates and ammonia. Or primary, secondary or tertiary amines are preferred, with tertiary amines such as triethylamine, triethanol amine, dimethylethanolamine or diethylethanolamine being more preferred. In the reaction, the amount and neutralization degree of acid groups included in the resin should be sufficient to disperse the resin in water at about 50 to 100% of the base, and the neutralized resin is dispersed at 40 to 60% of the solid content in water. A photocurable water-dispersible acrylate resin having 4 to 10 acrylic groups at the oligomer terminal is prepared.

As described above, the photocurable water-dispersible acrylate resin according to the present invention, a polyester polyol, an isocyanate having a hydrophilic group introduced therein, a hydrophilic group and a material having an organic group capable of reacting with the isocyanate at the same time according to a conventional method and an organic solvent. Or by first stirring and mixing the photocurable monomer as a reactive diluent, and adding a hydroxyl group high functional acrylate to react until the isocyanate is completely extinguished, and adding a basic compound to neutralize the resin. Conventional catalysts, radical inhibitors and the like may be further added during the first stirring mixing.

A photo-initiator, a photocurable oligomer and a water-miscible organic solvent may be added to the photocurable water-dispersible acrylate resin prepared as described above to obtain a high functional photocurable aqueous coating composition for mobile phone coating according to the present invention.

In the present invention, the photocurable water-dispersible acrylate resin is used in an amount of 55 to 95% by weight, preferably 70 to 90% by weight based on the total composition. At this time, when the amount of the photocurable water-dispersible acrylate resin is higher than 95% by weight, the crosslinking density of the cured coating film is too high, so that the coating film is brittle, cracks are generated by heat or impact, and hardness and wear are less than 55% by weight. Mechanical properties such as deterioration

The compositions of the present invention also include conventional photoinitiators that act in the complex wavelength band of 200 to 400 nm to form radicals by light of various wavelengths and to crosslink unsaturated hydrocarbons present in the coating liquid. Examples of photoinitiators include Merck's Tarocure 1173, Ciba's Igacure 500, BASF's TPO, Lambert's KIP 100, and the like, in an amount of 1 to 10% by weight, preferably 2 to 5% by weight, based on the total composition. Can be used.

In addition, in the present invention, a photocurable oligomer is used as a reactive diluent for viscosity control, and as the oligomer, ethylene or propylene oxide is added to improve the appearance and workability of the aqueous coating due to its excellent compatibility with the aqueous coating. Photocurable oligomers, preferably polyethylene oxide diacrylate, polypropylene oxide diacrylate, pentaerythritol triacrylate with ethylene oxide added, glycerol triacrylate, trimethylolpropane triacrylate, and the like can be used. The photocurable oligomer is used in an amount of 0.01 to 25% by weight based on the total composition. When the ratio of the oligomer is higher than 10% by weight, the curing rate is lowered and the mechanical and chemical properties are lowered. (levelling) is lowered, and the compatibility is poor due to the dilution power.

As water-miscible organic solvents usable in the composition of the present invention, ethyl cellussolve, butyl cellussolve, texanol, isopropyl alcohol, methanol, ethanol, ethylene glycol, propylene glycol, etc., which are compatible with water, can be used. It can be used in an amount of 3 to 10% by weight based on the composition. In this case, when the ratio of the organic solvent used is higher than 10% by weight, it is in violation of the regulation of volatile organic compounds, and when the ratio is less than 3% by weight, compatibility is poor due to insufficient dilution force, and a phenomenon of silking occurs.

Further, in the present invention, in order to improve the slip and gloss of the coating film, a leveling agent suitable for an aqueous paint, preferably a silicone leveling agent, for example, BYK-345, BYK-347, BYK- 348, TEGO rad 2200N, TEGO 435, etc. of TEGO company can be used in an amount of 0.1 to 3% by weight based on the total composition, and as a radical polymerization inhibitor, hydroquinone, p -methoxyphenol, nitrobenzene, BHT etc. can be used in the quantity of 0.1-1 weight%.

The composition according to the present invention may be prepared by first stirring and mixing the photocurable water-dispersible acrylate resin, the photoinitiator, the photocurable oligomer and the organic solvent in a specified amount according to a conventional method, and include leveling agents, radical polymerization inhibitors and other additives. Etc. can also be added further.

The photocurable aqueous coating composition of the present invention is an acrylic resin, vinyl resin, acrylic emulsion resin, which is commonly used to give a beautiful appearance to the plastic material such as polycarbonate, polyacrylate, polyethylene terephthalate, polymethyl methacrylate, Coating solution for top coat that meets various reliability standards of mobile phone because it has excellent adhesion and high curing density for color coating composition for undercoat prepared by adding aluminum paste, pearl, pigment, etc. to binder such as water-dispersed urethane resin It can be usefully used.

Hereinafter, the present invention will be described in more detail based on the following examples. However, the following examples are not intended to limit the invention only.

Preparation Example 1 : Preparation of Polyester Diol

In a four-necked 3-liter round bottom flask, an electric stirrer and an H tube capable of receiving dehydrated water, a cooler, a thermometer and a heating mantle were installed. 1,074 g of neopentyl glycol as a diol, 1,227 g of adipic acid as a dicarboxylic acid, and 0.2 g of dibutyltin oxide as a reaction catalyst were added thereto, and the temperature was raised to 150 ° C. under nitrogen atmosphere for 1 hour. When water began to emerge from the reaction, the temperature was slowly raised to 210 ° C. at 10 ° C. per 30 minutes to prevent glycol from escaping with water. The reaction was reacted at 210 ° C. for at least 5 hours to obtain 145 g of dehydrated product, wherein the acid value using neutralization titration was 15 mg / KOH g. 500 g of toluene was slowly added to the reaction product and subjected to azeotropy distillation to remove additional dehydrated product to the outside, inducing a positive reaction to lower the acid value to 0.5 mg / KOH g or less, and removing the remaining toluene in a vacuum state. A polyester diol having a hydroxyl value of 74.1 mg KOH / g by the neutralization reverse titration method and a molecular weight of 1,500 g / mol measured by this end group analysis was prepared.

<Production of hydroxy high functional acrylate>

Preparation Example 2

A four-necked, 3-liter round bottom flask was equipped with an electric stirrer and an H tube capable of receiving dehydrated water, a cooler, a thermometer, a heating mantle, and the like. About 90 ° C., which is a temperature at which azeotropic distillation is carried out by adding 50.9 g of pentaerythritol, 109.2 g of acrylic acid, 163 g of toluene, 0.2 g of hydroquinone and 0.1 g of nitrobenzene as a radical polymerization inhibitor, and 2.5 g of sulfuric acid as a catalyst. It heated up to. As the reaction proceeded, water and toluene were simultaneously released into the H tube, and the reaction was terminated when the amount of dehydrated water was 71 g. The reactant is present in the form of a mixture of a trifunctional monomer having one hydroxy group and a tetrafunctional monomer having no hydroxy group, and there is also unreacted acrylic acid. Thus, an acid-base reaction is performed by washing unreacted acrylic acid with an aqueous sodium hydroxide solution. Unreacted acrylic acid was removed using. Finally, toluene was removed under vacuum to prepare a hydroxyl group high functional acrylate having a ratio of trifunctional and tetrafunctional 1.2: 1 by high efficiency liquid quantitative chromatography (HPLC) (see FIG. 2). At this time, about 10% of high molecular weight substances suspected as side reactions due to cationic polymerization by sulfuric acid were detected, but there was no significant problem in the subsequent reaction.

Preparation Example 3

A hydroxyl group high functional acrylate having a ratio of 5: 6 to 5 and 6 functional by HPLC was prepared in the same manner as in Preparation Example 2, except that dipentaerythritol was used instead of pentaerythritol.

<Production of Photocurable Water Dispersible Acrylate Resin>

Example 1

An electric stirrer, a cooler, a thermometer, a heating mantle and the like were installed in a four-necked 3L round bottom flask. 460.4 g of polyester diol prepared in Preparation Example 1 as a polyester polyol, 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethyl-cyclohexane as an isocyanate having a hydrophilic group introduced therein (IPDI) 136.3 g, bis-hydroxymethyl-propionic acid (DMPA) 32.9 g as a material having a functional group capable of reacting with a hydrophilic group and an isocyanate, 250 g of hexanediol diacrylate (HDDA) as a photocurable monomer, as a catalyst 0.4 g of dibutyltin dilaurate (DBTDL) and 1 g of methoxyhydroquinone were added and stirred as a radical polymerization inhibitor. When the reactant was slowly exothermic and the exotherm was terminated at about 60 ° C., the reaction temperature was forced up to 80 ° C. using a heating mantle. The measured value (%) of isocyanate calculated by excluding the amount of HDDA after the reaction at 80 ° C. for 8 hours was 4.1%.

After the temperature of the reactant was lowered to 40 ° C. and 96 g of the hydroxy high functional acrylate prepared in Preparation Example 2 was added, 2,260 cm ^{−1, which} is an isocyanate characteristic peak on Fourier Transform Ultraviolet Spectroscopy (FT-IR), was completely The reaction was carried out at 100 ° C. until disappeared. Upon completion of the reaction, the temperature was lowered to 60 ° C. and the acid group of the resin was neutralized by slowly dropping 24 g of triethylamine as a basic compound using a dropping funnel. After neutralization for 1 hour or more and completely neutralized, 1,500 g of distilled water was added while stirring at high speed to prepare a photocurable water-dispersible acrylate resin having 6 acrylic functional groups at the end of the resin.

Example 2

Photocuring type having 10 acrylic functional groups at the end of the resin in the same manner as in Example 1 except that the hydroxy high functional acrylate prepared in Preparation Example 3 was used instead of the hydroxy high functional acrylate prepared in Preparation Example 2. A water-dispersible acrylate resin was prepared.

<Production of High Functional Waterborne Coating Composition for Photocuring>

Example 3

80% by weight of the photocurable water-dispersible acrylate resin prepared in Example 1, 7% by weight of butyl cellulsolve as an organic solvent, 10% by weight of polyethylene glycol diacrylate (molecular weight 500) as a photocurable oligomer, Igacure 500 as a photoinitiator 1.5 wt% and 0.5 wt% of TPO, and 1 wt% of BYK 345 as a leveling agent were sequentially added and stirred to prepare a highly functional photocurable aqueous coating material.

Example 4

A highly functional photocurable aqueous coating was prepared in the same manner as in Example 3 except that the resin prepared in Example 2 was used.

Comparative Example 1

An ultraviolet curable paint was prepared in the same manner as in Example 3 except that BASF's Laromer LR8949 bifunctional urethane acrylate dispersion was used as the acrylate resin.

<Production of Coating Film>

Examples 6 and 7

Silver-based oil paint (SSCP) and a mixed diluent were mixed in a ratio of 1: 1.33 to a mobile phone-shaped injection molded product made of polycarbonate resin (Cheil Industries) and sprayed to the same thickness of 3 to 4 μm. After carrying out, it dried for 10 minutes at 60 degreeC, and completed the undercoat. Subsequently, the paints prepared in Examples 3 and 4 were spray-coated to the injection molding, each having the same thickness of 20 to 30 μm, dried at 70 ° C. for 5 minutes, and then 80 W / in an ultraviolet curing machine in which a metal lamp and a mercury lamp were simultaneously present. The coating film was prepared by fully curing at a rate of 10 m / min at cm intensity (see FIG. 1).

Comparative Examples 2 and 3

UV #PSL 8700 (SSCP Co., Ltd.) and Comparative Example 1, which is widely used for coating top coats and is widely used in mobile top coats as a top coat paint for oily mobile phones, and contains 50% of mixed solvents such as toluene, ethyl acetate, and methyl ethyl ketone. A coating film was prepared in the same manner as in Examples 6 and 7, except that each of paints was used.

Property evaluation

Physical and chemical properties of the coating films obtained in Examples 6 and 7, and Comparative Examples 2 and 3, respectively, were measured, and measurement methods and evaluation criteria of physical properties were as follows:

(1) adhesion

Using a razor sharp razor, draw 11 horizontal and vertical lines on the cured coating film at intervals of 1 cm, attach 3M transparent tape, and peel off sharply to an angle of 180 ㅀ. This is repeated three times at the same position to check the peeling phenomenon of the coating film.

(2) hot water resistance

After the coating film is left in 100 ° C. boiling water for 1 hour and cooled at room temperature, the coating film is checked for swelling, peeling, and cracking and adhesion is measured.

(3) acid resistance

After leaving the coating film in a buffer solution of pH 4.5 for 72 hours, the coating film is checked for swelling, peeling, and cracking and adhesion is measured.

(4) cosmetic resistance

After evenly applying the sunscreen of the UV protection index 20 to the coating film, it is allowed to stand for 24 hours in a constant temperature and humidity chamber of 80 ℃, 80% relative humidity, and then check the coating film swelling, peeling, cracking, and measure the adhesion.

(5) wear resistance

Using a Norman Tul RCA measuring instrument, the number of round trips until the material is exposed (loading 50 or more) at a load of 175 g is measured.

(6) chemical resistance

Reciprocating Eraser Wear 99.5% of methyl alcohol in the industrial eraser of the tester so as not to dry and measure the number of round trips until the material is exposed (more than 100 times).

(7) pencil hardness

Three times with a Mitsubishi pencil of various strengths with a load of 1 kg to measure the strength of the pencil without scratches coating coating (H or more).

As shown in Table 1, the aqueous coating composition comprising a photocurable water-dispersible acrylate resin according to the present invention can provide a coating film of environmentally friendly and equivalent physical properties compared to the oil-based coating composition of Comparative Example 2, of the present invention Compared with other aqueous coating compositions which do not use a photocurable water-dispersible acrylate resin, a coating film having excellent physical properties such as hot water resistance, acid resistance, cosmetic resistance, abrasion resistance, chemical resistance, and pencil hardness can be provided.

As described above, the photocurable water-based coating composition according to the present invention includes a high-functional photocurable water-dispersible acrylate resin and a small amount of water-miscible organic solvent, while meeting the volatile organic compound (VOC) environmental standards, It has excellent physical properties such as acid resistance, cosmetic resistance, abrasion resistance, chemical resistance, pencil hardness, etc., which satisfies the reliability required by mobile coating agents when coating on mobile phones, and has excellent adhesion and high cure density in colored coating compositions for undercoat coatings. Since it can be usefully used as a coating composition for a top coat that meets various reliability standards of the mobile phone.

Claims (13)

(A) 55 to 95% by weight of a photocurable water-dispersible acrylate resin prepared by urethane reaction of a urethane oligomer having an isocyanate terminal having a hydrophilic group introduced therein and a hydroxy high functional acrylate, (B) 1 to 10% by weight of a photoinitiator, (C) 0.01-25 weight% of photocurable oligomers, and (D) 3-10 weight% of water-miscible organic solvents, The high functional photocurable aqueous coating composition for mobile phone top coats. The method of claim 1, The photocurable water-dispersible acrylate resin is a composition characterized in that it has 4 to 10 acrylic groups at the terminals. The method of claim 1, The urethane oligomer is prepared by reacting a polyester polyol with an isocyanate having a hydrophilic group introduced therein and a material having a hydrophilic group and a functional group capable of reacting with the isocyanate. The method of claim 3, wherein The polyester polyol is a composition characterized in that the copolymer is a mixture of aliphatic or aromatic structures having an OH value of 56 to 112 mg / KOH g by the reverse titration method and a molecular weight of 1,000 to 2,000 calculated using the same. The method of claim 3, wherein Isocyanates introduced with hydrophilic groups include butylene diisocyanate, hexamethylene diisocyanate (HDI), 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethyl-cyclohexane (IPDI), bis ( Aliphatic diisocyanate selected from isocyanatocyclohexyl) -methane, aromatic diisocyanate selected from 2,4-diisocyanatotoluene, 2,6-diisocyanatotoluene, 4,4-diisocyanato-diphenylmethane, these Composition is selected from the group consisting of isomers and mixtures thereof. The method of claim 3, wherein A material having a functional group capable of reacting with a hydrophilic group and an isocyanate is bis-hydroxymethyl-propionic acid, glyconic acid or 2-aminoethylaminoethane-sulfonic acid. The method of claim 3, wherein At the time of reaction, the composition characterized by using an isocyanate to which a hydrophilic group is introduced: (a material having a polyester polyol + hydrophilic group and a functional group capable of reacting with an isocyanate) in an equivalent ratio of 2: 1 to 1.8. The method of claim 1, The hydroxy high functional acrylate is characterized in that it comprises one hydroxy group and 2 to 6 acrylic groups in the molecule. The method of claim 8, Hydroxy high functional acrylates include 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 4-hydroxybutyl acrylate, trimethylolpropane di / triacrylate mixture (TMPTA), pentaerythritol tri / tetra At least one selected from the group consisting of an acrylate mixture (PETA) and a dipentaerythritol penta / hexaacrylate mixture (DiPETA). The method of claim 1, The photocurable oligomer is a composition characterized in that the addition of ethylene or propylene oxide. The method of claim 10, The photocurable oligomer is selected from the group consisting of polyethylene oxide diacrylate, polypropylene oxide diacrylate, pentaerythritol triacrylate with ethylene oxide added, glycerol triacrylate and trimethylolpropane triacrylate. Composition. The method of claim 1, The water miscible organic solvent is ethyl cellulose solution, butyl cellulose solution, texanol, isopropyl alcohol, methanol, ethanol, ethylene glycol and propylene glycol. Mobile phone coated with a coating composition according to any one of claims 1 to 12.

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