KR20050070496A - Method of preparing urethane acrylic hybrid resin for metal coating - Google Patents

Abstract

Disclosed is a method for producing a water-soluble urethane acryl hybrid resin applied to form a coating film on a metal. The above-described method is prepared by mixing the water-soluble urethane dispersion resin and at least one or more types of acryl monomer and an initiator to prepare an acryl monomer mixture, and then injecting the acryl monomer mixture into the water-soluble urethane dispersion resin, and performs an acryl polymerization reaction. It provides a method for producing a water-soluble urethane acryl hybrid resin. When the urethane acryl hybrid resin formed in this way is used for the metal, the urethane acryl hybrid resin may have both urethane and acryl properties having improved weather resistance and hardness.

Description

Manufacturing method of urethane acryl hybrid resin for metal coating {METHOD OF PREPARING URETHANE ACRYLIC HYBRID RESIN FOR METAL COATING}

The present invention relates to a method for producing a urethane aric hybrid resin applied to the coating of a metal substrate, a method for producing a water-soluble urethane aric hybrid resin coated on a steel sheet having a plating layer consisting of a mixture of zinc, nickel, aluminum, silica or a single configuration. It is about.

The technical field described above and its use are disclosed in Korean Patent Laid-Open Publication No. 10-2003-0058455. However, the contents described in the above patents are related to urethane arics by simple mixing of aric emulsion resins and urethane resins, and have excellent physical properties such as weather resistance solvent resistance, but are poor in storage properties and are excessive surfactants included in emulsion resins. Therefore, it has disadvantageous properties in physical properties such as water resistance and chemical resistance in thin film coating. And the problem due to the absence of physical and chemical bonding between the emulsion and the urethane tends to increase.

In addition, Korean Patent Publication No. 10-2003-0018922 discloses a urethane acrylic resin showing a core cell form using a mixture of an isocyanate terminated premonomer of urethane and an acryl-based unsaturated monomer. Specifically, the urethane acrylic resin is prepared by a method of reacting a prepolymer having an isocyanate remaining in an end group with an acryl monomer and other monomers capable of reacting with a urethane reactor. However, according to the above-described method, since the reaction is difficult to control, the particle size is very likely to appear irregularly, and the urethane prepolymer has a problem of poor water resistance because a hydrophilic polyol must be used in order to have hydrophilicity.

Therefore, in order to improve the problems described above, the present invention is a urethane and acryl resin of the urethane acryl hybrid resin having excellent corrosion resistance, weather resistance, storage and water resistance when coating the metal by physically hybridizing the non-responsive It is an object to provide a manufacturing method.

According to the method for producing a water-soluble urethane acrylic hybrid resin according to an embodiment of the present invention for achieving the above object of the present invention, first, a water-soluble urethane dispersion resin, an acrylic monomer composed of at least one kind and An acryl monomer mixture formed by mixing the initiator is prepared. Subsequently, an acrylic monomer mixture is added to the water-soluble urethane dispersion resin to perform an aric polymerization reaction to prepare a water-soluble urethane acryl hybrid resin.

The water-soluble urethane acryl hybrid resin formed by this method has excellent storage properties, no phase separation when forming a paint, and has excellent properties such as appearance and corrosion resistance, weather resistance, water resistance, heat resistance, chemical resistance, etc. of the coating film.

Hereinafter, the present invention will be described in detail.

According to the method for producing a water-soluble urethane acryl hybrid resin according to an embodiment of the present invention, first, a water-soluble urethane dispersion resin and an acryl monomer mixture are prepared. Subsequently, the acryl monomer mixture is slowly added to the water-soluble urethane dispersion resin to polymerize to form a water-soluble urethane acryl hybrid resin.

The aqueous or water-soluble urethane acrylic hybrid resin prepared by the above-mentioned method largely includes a water-soluble urethane dispersion resin and an acryl monomer.

The water-soluble urethane dispersion resin is a material that is already well known and includes polyols and isocyanate groups. The polymer which occupies most of the water-soluble urethane dispersion resin contains carboxylic acid, and the polyol includes a polyester-based and polyether-based polyol. And the isocyanate group is divided into aliphatic, alicyclic, aromatic. The water-soluble urethane dispersion resin contains a water-soluble solvent in the resin.

Here, if the acid value of the water-soluble urethane dispersion resin to be applied is less than about 10, it is difficult to accept the urethane dispersion resin, and if the acid value exceeds about 100, there is a problem that the water resistance of the urethane dispersion resin is inferior. Not desirable

Therefore, water-soluble urethane dispersion resins having an acid value in the range of about 10 to 100 are used.

In addition, when the particle size of the water-soluble urethane dispersion resin, that is, the average diameter of the particles is less than about 10 nm, the stability of the acryl monomer is excellent, but the chemical resistance of the urethane is reduced, and the average diameter of the particles is about 1000. If it exceeds nm, a problem of deterioration of the stability of the aric occurs.

Therefore, the water-soluble urethane dispersion resin should be used having a particle size of about 10 to 1000nm, more preferably a urethane dispersion resin having a particle size of about 100 to 500nm.

The water-soluble solvent used to prepare the water-soluble urethane dispersion resin facilitates the reaction of the isocyanate group and the polyol, and controls the phase change of the urethane resin, and includes N-vinylpyrrolidone or acetone.

Here, when the amount of the water-soluble solvent used to prepare the water-soluble urethane dispersion resin is less than about 1% by weight of the total water-soluble urethane dispersion resin, it is difficult to diffuse the acrylic monomer mixture into the urethane dispersion resin, thereby stabilizing the acrylic monomer. A difficult problem occurs, and when about 20% by weight or more of the acryl monomer swells during the reaction, the viscosity rises or a problem occurs that the hybrid between the stable acryl monomer and urethane becomes difficult.

Therefore, the amount of the water-soluble solvent used to prepare the water-soluble urethane dispersion resin is used within about 1 to 20% by weight of the total water-soluble urethane dispersion resin.

In addition, when the molecular weight of the water-soluble urethane dispersion resin is less than about 40000, there is a problem that the chemical resistance and water resistance, which is the basic characteristic of the urethane resin, decreases, and when the molecular weight exceeds about 200000, it does not stabilize the acryl monomer, There is a problem that the synthesis is not easy because it is absorbed and swelled.

Therefore, the present invention uses a water-soluble urethane dispersion resin having a molecular weight in the range of about 40000 to 200000.

When the amount of the water-soluble urethane dispersion resin is less than about 10% by weight relative to the solid content of the entire urethane acrylic hybrid resin component, it is not only difficult to stabilize the mixture of the acrylic monomer, but also has physical properties such as elasticity and chemical resistance of the urethane. There is a problem that is reduced, if more than about 60% by weight, the price is higher, the problem is that the commerciality is lowered.

Therefore, the amount of the water-soluble urethane dispersion resin should be used within about 10 to 70% by weight, and more preferably within about 20 to 60% by weight relative to the solid content of the total urethane acrylic hybrid resin component.

Examples of the material usable as the water-soluble urethane dispersion resin include urethane dispersions prepared by Dipia Co., Ltd. (solid content of 34%, acid value of 20 or less, molecular weight of 70000, N-pinolidon content of 8%), Alberdink-Borey U series manufactured by Alberdink Boley), Takelac W series manufactured by Mitzui Takeda Chemical Co., Ltd., NeoRez series manufactured by Avecia, USA, Hyrex series manufactured by Korean photoluminescent chemistry, and domestic hep Impression produced by scam, etc. may be mentioned, which may be used alone or in combination.

The acrylic monomers used to form the water-soluble urethane acrylic hybrid resin according to the present invention may use a monomer including a separate crosslinkable functional group for crosslinking with a curing agent after the resin is prepared.

 In addition, a small amount of surfactant may be added in order to more stabilize the atric monomer in the water-soluble urethane dispersion resin in the process of forming the water-soluble urethane acrylic hybrid resin.

If the amount of the acrylic monomer is less than about 40% by weight relative to the solid content of the total water-soluble urethane Acrylic hybrid resin, the amount of urethane increases, so that the price is less competitive. When the amount of the acrylic monomer exceeds 80% by weight, the acrylic monomer is the water-soluble urethane dispersion resin. The problem of inferior stability occurs.

Therefore, the Acrylic monomer should be used within about 30 to 90% by weight, more preferably from about 40 to 80% by weight relative to the solids of the water-soluble urethane Acrylic hybrid resin.

Examples of the above applied acryl monomers include methyl acrylate, ethyl acrylate, ethyl acrylate, isopropyl acrylate, normal butyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, isopropyl Methacrylate, normal butyl methacrylate, normal hexyl methacrylate, etc. can be illustrated. And an acryl monomer containing a functional group for crosslinking. A monomer containing a carboxyl group. Acrylate, metaacrylic acid, and hydroxyl group-containing monomers. 2-Hadihydroxy methacrylate, hydroxypropyl methacrylate, 2-hydroxyethyl acrylate, Roxypropyl acrylate etc. are mentioned. As the amide monomer, for example, acryamide, N-methylol acrylamide, diacetone amide, glycidyl methacrylate and the like can be used.

The method for preparing a urethane acrylic hybrid resin by adding the acryl monomer mixture to a water-soluble urethane dispersion resin is first slowly added to the water-soluble urethane dispersion resin in a water-soluble urethane dispersion resin at room temperature and then sufficiently stabilized in the acryl monomer mixture. By raising the temperature step by step to the polymerization of the acric.

 In another method, the acrylic monomer mixture is separated into several volumes in a constant volume, and then a part of the separated acrylic monomer mixture is added to stabilize the acrylic monomer. And it heats up and makes a polymerization reaction. Subsequently, the reaction was finished, and the temperature was lowered to room temperature again, and the remaining acryl monomer mixture was added to stabilize the acryl monomer. Subsequently, it raises and reacts by heating up. Here, since the process must repeatedly perform cooling, stabilization, and a temperature increase reaction by dividing the number of acryl monomers, a more stabilized urethane acryl hybrid resin can be obtained.

The method of synthesizing the urethane acrylic hybrid resin described above is such that the acryl monomer stabilizes and forms a nucleus between particles of the water-soluble urethane dispersion resin. As the formation and reaction proceeds, a constant cross layer is formed with the nucleus. The so-called core-shell structure has a large amount of acryl in the core and a high proportion of water-soluble urethane dispersion resin in the shell.

Therefore, it is important to add the acryl monomer mixture at about 40 to 60 ° C. in the method for synthesizing the urethane acritic hybrid resin of the present invention. Here, when the acryl monomer compound is added dropwise to the water-soluble urethane dispersion resin at a temperature of less than about 40 ° C., the flow of the acryl monomer and the water-soluble urethane dispersion resin is poor, and thus, a stable phase formation is difficult. When the temperature exceeds about 60 ° C. Before the stable phase is formed, the reaction of acric occurs first and sludge is formed.

Therefore, in order for the acryl monomer to be sufficiently stabilized in the water-soluble urethane dispersion resin, an acryl monomer mixture should be added at about 40 to 60 ° C.

Further, in addition to the above method, when the acrylic monomer mixture is continuously added dropwise to the water-soluble urethane dispersion resin by the well-known Acry's seed emulsion polymerization method at the temperature at which the initiator is reacted, sludge is formed due to the lack of stabilization time of the Acrylic monomer. do.

Thus, this method requires some surfactants to aid stability in the water soluble urethane dispersion resins, and the use of surfactants is preferably used at about 2% by weight or less of the total acryl monomer mixture. This is because when the surfactant is used in excess of about 2% by weight, water resistance and chemical resistance are inferior.

Hereinafter, the present invention will be described in more detail with reference to Examples and Experimental Examples. However, the present invention is not limited by the following examples, and it will be understood that various modifications and applications may be made within the spirit and scope of the present invention based on the detailed description and the claims of the present invention.

Example 1

A 1 LT four-necked glass flask was attached with a thermometer, a condenser, a stirrer, and a temperature raising device. 230 g of deionized water and 350 g of DIFIY's urethane dispersion (solid content 34%, acid value 20 or less, molecular weight 70000, N-pinolidon content 8%) were added and stirred to prepare a water-soluble urethane dispersion resin.

Subsequently, 30 g of methyl methacrylate, 60 g of styrene, 30 g of normal-butyl acetic acid, and 2.4 g of 2-2 'azobis (2-methylpropanenitrile) (AIBN) as an initiator were mixed and dissolved in a separate container to prepare an acryl monomer mixture. Prepared.

Subsequently, the acryl monomer mixture was slowly added to the stirrer and stirred at room temperature for 1 hour, and then 1 hour at 40 ° C, 1 hour at 50 ° C, 1 hour at 60 ° C, 1 hour at 70 ° C, and 1 hour at 80 ° C. The reaction mixture was gradually heated in temperature to obtain a water-soluble urethane acryl hybrid resin having a solid content of 34%.

Example 2

A thermometer, a condenser, a stirrer, and a temperature raising device were attached to a 1 LT four-necked glass flask. A water-soluble urethane dispersion resin was prepared by adding 180 g of deionized water and 180 g of U910 (solid content of 30%, acid value of 8 or less, and N-pinolidon content of 12%) of Alberdink Boley, Germany. .

Subsequently, 30 g of methyl methacrylate, 60 g of styrene, 30 g of normal-butyl acetic acid, and 2.4 g of 2-2'azobis (2-methylpropanenitrile) (AIBN) as an initiator were mixed and dissolved in a separate container to prepare an acryl monomer mixture. Prepared.

Subsequently, the acrylic monomer mixture was slowly added to the stirrer and stirred at room temperature for 1 hour, followed by 1 hour at 40 ° C, 1 hour at 50 ° C, 1 hour at 60 ° C, 1 hour at 70 ° C, and 1 hour at 80 ° C. It heated up in stages and obtained the water-soluble urethane aric hybrid resin of 34% of solid content.

Example 3

A thermometer, a condenser, a stirrer, and a temperature raising device were attached to a 1 LT four-necked glass flask. 210 g of deionized water and 180 g of Takelac W605 (30% solids, 8 or less acetone, 1% or less acetone) of Mitzui Takeda Chemical Co., Ltd. were added thereto, followed by stirring to prepare a water-soluble urethane dispersion resin.

Subsequently, 30 g of methyl methacrylate, 60 g of styrene, 30 g of normal-butyl acetic acid, and 2.4 g of 2-2'azobis (2-methylpropanenitrile) (AIBN) as an initiator were mixed and dissolved in a separate container to prepare an acryl monomer mixture. Prepared.

Subsequently, the acrylic monomer mixture was slowly added to the stirrer and stirred at room temperature for 1 hour, followed by 1 hour at 40 ° C, 1 hour at 50 ° C, 1 hour at 60 ° C, 1 hour at 70 ° C, and 1 hour at 80 ° C. It heated up by the reaction and obtained the water-soluble urethane acrylic hybrid resin of 34% of solid content.

Example 4

A thermometer, a condenser, a stirrer, and a temperature raising device were attached to a 1 LT four-necked glass flask. 230 g of deionized water and 350 g of DIFIY's urethane dispersion (solid content 34%, acid value 20 or less, molecular weight 70000, N-pinolidon content 8%) were added and stirred to prepare a water-soluble urethane dispersion resin.

Subsequently, 30 g of methyl methacrylate, 60 g of styrene, 30 g of normal-butyl acetic acid, and 2.4 g of 2-2'azobis (2-methylpropanenitrile) (AIBN) as an initiator were mixed and dissolved in a separate container to prepare an acryl monomer mixture. Prepared.

Subsequently, 1/4 weight% of the acryl monomer mixture was slowly added to the stirrer, stirred at room temperature for 30 minutes, and then maintained at 50 ° C. for 1 hour and 80 ° C. for 1 hour, followed by cooling to 50 ° C. or lower. The monomer mixture was divided and charged to give a water-soluble urethane acrylic hybrid resin having a solid content of 34%.

Example 5

A thermometer, a condenser, a stirrer, and a temperature raising device were attached to a 1 LT four-necked glass flask. Here, 210 g of deionized water and 175 g of DIFIY's urethane dispersion (solid content 34%, acid value 20 or less, molecular weight 70000, N-pinolidon content 8%) and domestic photocatalytic urethane dispersion Hyrex RS-161M (solid content) 30%, acid value 8 or less, acetone content 1% or less) 200 g was added thereto, and stirred to prepare a water-soluble urethane dispersion resin.

Subsequently, 30 g of methyl methacrylate, 60 g of styrene, 30 g of normal-butyl acetic acid, and 2.4 g of 2-2 'azobis (2-methylpropanenitrile) (AIBN) as an initiator were mixed and dissolved in a separate container to form an acryl monomer mixture. Prepared.

Subsequently, 1/4 weight% of the acryl monomer mixture was slowly added to the stirrer, stirred at room temperature for 30 minutes, and then maintained at 50 ° C. for 1 hour and 80 ° C. for 1 hour, followed by cooling to 50 ° C. or lower. The monomer mixture was divided and charged to give a water-soluble urethane acrylic hybrid resin having a solid content of 34%.

Experimental Examples 1 to 5

The water-soluble urethane acryl hybrid resin obtained in Examples 1 to 5 was used to obtain a urethane acryl hybrid paint having a composition as shown in Table 1 below. In Table 1 below, the components represent weight percent.

           Experimental Example ＼ Raw Materials Experimental Example 1 Experimental Example 2 Experimental Example 3 Experimental Example 4 Experimental Example 5 Suzy Example 170 Example 270 Example370 Example 470 Example 570 Antifoam 0.1 0.1 0.1 0.1 0.1 Humectant 0.2 0.2 0.2 0.2 0.2 Rust preventive 1.5 1.5 1.5 1.5 1.5 Thickener 0.3 0.3 0.3 0.3 0.3 water 27.9 27.9 27.9 27.9 27.9 Sum 100 100 100 100 100

Comparative Experimental Examples 1 and 2

For comparison, a paint having a composition of Table 2 was obtained by applying a commercially available mixed solution of an acryl emulsion and a urethane dispersion resin and a reactive urethane acryl hybrid system. In Table 2 below, the components represent weight percent.

               Experimental Example Comparative Example 1 Comparative Example 2 Comparative Example 3 Resin 1 (Note 1) 40 0 0 Resin 2 (Note 2) 35 0 0 Resin 3 (Note 3) 0 58 0 Resin 4 (Note 4) 0 0 58 Antifoam 0.1 0.1 0.1 Humectant 0.2 0.2 0.2 Rust preventive 1.5 1.5 1.5 Thickener 0.3 0.3 0.3 water 22.9 34.9 34.9 Sum 100.0 100.0 100.0

^{Note 1)} Resin 1 in Table 2 is a water-soluble urethane dispersion resin Hyrex RS-161M (30% solids)

^{Note 2)} ACPI emulsion resin (Solid content 34%)

^{Note 3)} Hydridur 570 (41% solids ^{) of} Air Products, USA

^{Note 4)} Hydridur 580 (41% solids ^{) of} Air Products, USA

How to Make a Specimen

Each coating formed in Experimental Examples 1 to 5 and Comparative Experimental Examples 1 to 3 was coated on a galvanized steel sheet having a thickness of 70 × 150 and degreased to a thickness of 2 μm, followed by baking at a steel plate temperature of 100 ° C. To prepare a surface-treated steel sheet respectively. And, in order to find out the characteristics of each of the experimental examples and comparative examples shown in Table 1 and Table 2 was tested by the experimental method mentioned below. At this time, the results of the physical property test of the obtained coating film is shown in Table 3 below.

       Experimental Example Experimental Example 1 Experimental Example 2 Experimental Example 3 Experimental Example 4 Experimental Example 5 Comparative Experiment 1 Comparative Experimental Example 2 Comparative Experiment 3 varnish Zhejiang ◎ ◎ ◎ ◎ ◎ △ ◎ ◎ Exterior ◎ ◎ ◎ ◎ ◎ △ ◎ ◎ Coating Exterior ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ Corrosion resistance ◎ ◎ ◎ ◎ ◎ ◎ △ △ Weather resistance ◎ ◎ ◎ ◎ ◎ ◎ △ △ Water resistance ◎ ◎ ◎ ◎ ◎ ◎ × × Heat resistance ◎ ◎ ◎ ◎ ◎ ◎ × × Chemical resistance ◎ ◎ ◎ ◎ ○ △ × ×

Paint storage test

Appearance test

The paints formed in Examples 1 to 5 and Comparative Examples 1 to 3, respectively, were sealed and evaluated by measuring a change in solution state after storage for 30 days.

(◎: no abnormality, ×: layer separation)

Hypotonic test

The coated examples and comparative examples were sealed and stored at 50 ° C. for 10 days and then evaluated by measuring the change in viscosity at 25 ° C. with Ford Cup # 4.

(◎: No abnormality, (circle): viscosity rises for 5 seconds, (triangle | delta): viscosity rises for 10 seconds, x: measurement is impossible)

Coating film property test

Appearance test

Evaluate the appearance of the painted specimens, with no foreign matter and no unpainted area.

(◎: No abnormality, ○: Tee slightly, △: Cratering, ×: Unpainted)

Corrosion resistance test

The painted specimens were sprayed continuously with 5% saline solution at 35 ° C and 95% humidity to evaluate the initial degree of rust.

(◎: No more than 72 hours, ○: Initial call after 48 hours △: Initial call after 24 hours, ×: Initial call before 24 hours)

Weather resistance test

Painted specimens are tested for weather discoloration or loss after 500 hours of weather resistance testing.

(◎: No abnormality, ○: Less than 50% of discoloration, △: Complete discoloration, ×: Completely eliminated)

Water resistance test

The coated specimen is immersed in warm water at 40 ° C. for 5 days and then evaluated for discoloration or loss of the coating.

(◎: No abnormality, ○: Less than 50% of discoloration, △: Complete discoloration, ×: Completely eliminated)

Heat resistance test

The coated specimen is left at 250 ° C. for 5 minutes to evaluate the discoloration or loss of the coating.

(◎: No abnormality, ○: Color change within 50%, △: Full color change, ×: Full deterioration)

Chemical Resistance Test

1 ml of 0.5 N caustic soda solution was added to the coated specimen to evaluate the discoloration of the material after 8 minutes.

(◎: No abnormality, ○: Color change within 50%, △: Full color change, ×: Full deterioration)

As described above, the water-soluble urethane acryl hybrid resin, which is formed by injecting the acryl monomer mixture into the water-soluble urethane dispersion resin, is formed by the acryl polymerization reaction, is excellent in drying property of the coating film, excellent chemical resistance of urethane, weather resistance and hardness is improved. It can have the physical properties of Acrik at the same time.

In addition, the water-soluble urethane acrylic hybrid resin formed by the above-described method is excellent in storage properties, there is no phase separation when forming the paint, and has excellent properties in terms of appearance and corrosion resistance, weather resistance, water resistance, heat resistance, chemical resistance, etc. of the coating film.

In addition, since the solvent uses water as the main component, it has the advantage of reducing energy saving problems, environmental pollution problems, work hygiene stability problems and fire risk.

Claims (9)

(a) preparing a water soluble urethane dispersion resin; (b) preparing an acryl monomer mixture by mixing an acryl monomer composed of at least one kind with an initiator; And (c) injecting the acryl monomer mixture into the water-soluble urethane dispersion resin, and performing an acropolymerization reaction to form a water-soluble urethane acryl hybrid resin. The method of claim 1, wherein the water-soluble urethane dispersion resin has an acid value of 10 to 100 and an average size of particles of 10 to 1000 nm. According to claim 1, wherein the water-soluble urethane dispersion resin contains N-vinylpyrrolidone or acetone which is a water-soluble solvent, the amount of the water-soluble solvent is 1 to 20% by weight of the total water-soluble urethane dispersion resin, The molecular weight of a urethane dispersion resin is 40000-200000, The manufacturing method of the water-soluble urethane acrylic hybrid resin characterized by the above-mentioned. The method of claim 1, wherein the water-soluble urethane dispersion resin is used in an amount of 10 to 70 wt% based on the solids content of the water-soluble urethane acrylic hybrid resin component. The method of claim 1, wherein the acrylic monomer is 30 to 90% by weight relative to the solids of the total water-soluble urethane acrylic hybrid resin. According to claim 1, wherein the acryl monomer is methyl acrylate, ethyl acrylate, ethyl acrylate, isopropyl acrylate, normal butyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, iso A method for producing a water-soluble urethane acryl hybrid resin, characterized in that it comprises at least one selected from the group consisting of propyl methacrylate, normal butyl methacrylate and normal hexyl methacrylate. The method of claim 1, wherein step (c) Reacting the water-soluble urethane dispersion resin with the acryl monomer mixture at a temperature of 30 to 60 ° C. to stabilize the atric monomer included in the acryl monomer mixture; And And raising the temperature to polymerize the water-soluble urethane dispersion resin and the acryl monomer mixture. The method of claim 1, wherein step (c) comprises: (I) adding 1 / n (n is a natural water of 2 or more) of the acryl monomer mixture to the water-soluble urethane dispersion resin and reacting at a temperature of 30 to 60 ° C; (II) polymerizing the water-soluble urethane dispersion resin with the 1 / n acryl monomer mixture by raising the temperature; (III) adding 1 / n of the acryl monomer mixture to the resultant of step (II) and reacting at a temperature of 30 to 60 ° C .; And And (IV) repeating steps (II) and (III) n-1 times until the acryl monomer mixture is exhausted. The method of claim 1, wherein in the step (c), a polymerization reaction is performed by further mixing 0.1 to 2% by weight of the acryl monomer mixture.