KR20030059481A - An enhanced flexibility modified-epoxy compound and the preparing method thereof - Google Patents

Abstract

The present invention relates to a modified epoxy resin composition for powder coating with improved bendability and a method for manufacturing the same, and more specifically, to a cored rubber-modified epoxy resin by dispersing a corel rubber in a bisphenol-type epoxy resin to improve flexibility. The modified epoxy resin composition for powder coating which increased the adhesion of the base material and the glass transition temperature of the cured coating film by applying an isocyanate compound to form an oxazolidone ring and then adding a polyfunctional amine compound to increase the crosslinking density. And to a method of manufacturing the same.

Description

Modified epoxy resin composition for powder coating with improved flexibility and manufacturing method thereof {An enhanced flexibility modified-epoxy compound and the preparing method

The present invention relates to a modified epoxy resin composition for powder coating with improved bendability and a method of manufacturing the same, and more particularly, to a cored rubber-modified epoxy resin by dispersing a corel rubber in a bisphenol-type epoxy resin to improve flexibility. The modified epoxy resin composition for powder coating which increased the adhesion of the base material and the glass transition temperature of the cured coating film by applying an isocyanate compound to form an oxazolidone ring and then adding a polyfunctional amine compound to increase the crosslinking density. And to a method of manufacturing the same.

As the primer powder coating applied to the inner surface of a pipe for transporting a fluid, a primer powder coating for polyethylene and a primer powder coating for polypropylene are used.

The conventional primer powder coating for polyethylene was used when the temperature of the contents was 80 ° C. or less, and thus the glass transition temperature of the powder coating was about 110 ° C. There was a limitation in use, and when the temperature of the contents rises to about 110 ℃ or more like crude oil, a metal pipe, which is a transport pipe, was used as a polypropylene instead of polyethylene.

However, when the temperature of the contents becomes higher, a powder coating having a higher glass transition temperature than the primer powder coating for polypropylene is required.

Therefore, the research to develop a powder coating having a higher glass transition temperature characteristics is ongoing, the research using the epoxy resin has been made in various ways.

The research results on powder coatings using epoxy resins are as follows.

U.S. Patent No. 5,407,978 discloses a method of using an aliphatic polyol-modified epoxy resin and a phenol hardener, but the epoxy resin prepared by the above method has excellent flexibility, but poor adhesion and negative electrode peelability, and glass transition of the cured coating film. There is a problem that the use is limited because the temperature is low.

U.S. Patent No. 3,882,064 discloses a method of using dicyandiamide as a bisphenol-A type epoxy resin and a curing agent, but in the case of using dicyandiamide alone as a curing agent according to the method described above, It is sensitive to moisture and unsuitable for application for pipe coating.

U.S. Patent No. 3,819,564 discloses a method of using a bisphenol-A type epoxy resin and a curing agent of an acid anhydride or hydroxypyridine, but in this case, the flexibility of the coating film is lowered, so that impact and bending properties after coating are reduced. There is a bad problem.

In addition, US Patent No. 5,717,011 is a method for increasing the glass transition temperature of the coating film using a small amount of a curing catalyst of imidazoles or amines, or adducting a bisphenol-A type epoxy resin with an imidazole or amine catalyst. In the above case, in the case of dispersing the paint in the early stage of the gel (gel) becomes impossible to work, the powder coating that caused the early gel has a problem of poor corrosion resistance, poor impact and bendability of the painted coating .

Japanese Patent No. 92-20605 proposes a method in which a bisphenol-A type epoxy resin and a noblock type epoxy resin are mixed and a diphenol derivative is used as a curing agent, but in this case, the degree of crosslinking of the noblock type epoxy resin is The high and hard has a disadvantage that the low-temperature impact and flexibility after coating is lowered.

U.S. Pat.Nos. 5,686,185 and 5,077,355 disclose a method of using diphenol as a derivative as a bisphenol-A type epoxy resin and a curing agent, but the powder coating prepared according to the above method has a low glass transition temperature of the coating film. There is an unsuitable disadvantage in using fluids.

U.S. Patent Nos. 3,655,818, 4,708,996 and 4,789,712 disclose methods of using rubber-modified acrylonitrile butadiene copolymers, carboxy-terminated butadiene acrylonitrile as methods for imparting flexibility. According to the present invention, since the glass transition temperature of the modified material itself is too low, it is not suitable as a coating material for high temperature fluid.

As described above, there are various difficulties in developing a resin having both flexibility and high glass transition temperature characteristics.

Therefore, in order to solve the above problems, in order to transfer the high temperature fluid, the cured coating film has a high glass transition temperature, excellent adhesion to the substrate, negative electrode peelability, excellent low temperature impact resistance and bendability, and an epoxy resin resistant to mechanical impact. Development of the composition is urgently needed.

Accordingly, the inventors of the present invention improve the flexibility of the resin when the corel rubber-modified epoxy resin is dispersed by dispersing the corel rubber in a bisphenol-type epoxy resin, and adding an isocyanate compound to the corel rubber-modified epoxy resin. By forming the oxazolidone ring, the adhesion of the base and the glass transition temperature of the cured coating film are increased, and a polyfunctional amine resin is applied thereto to form an isocyanate-coasel rubber-modified epoxy resin to form branches in the main chain to achieve high crosslinking degree. The present invention has been completed by knowing that an epoxy resin having a diameter can be prepared.

Therefore, the present invention reacts the bisphenol-type epoxy resin with corel rubber, isocyanate compound and polyfunctional amines at an appropriate ratio, so that the glass transition temperature of the cured coating film after curing is high, so that a high temperature fluid can be used, and at the same time, it has excellent flexibility and low temperature. It is an object of the present invention to provide a method for producing a modified epoxy resin for powder coating and excellent powder coating composition having excellent mechanical strength, such as impact resistance and bending.

1 is an infrared absorption spectrum of oxazolidone ring.

2 is an infrared absorption spectrum of isocyanate.

In the epoxy resin for powder coating, the number average molecular weight 500-2000 which the polyfunctional amine compound added to the isocyanate-coasel rubber-modified epoxy resin in which the oxazolidone ring was formed in the corel rubber-modified epoxy resin main chain was formed. It is characterized by the isocyanate-corel rubber-modified polyfunctional epoxy resin composition having an epoxy equivalent of 250 to 1000 g / eq, a softening point of 80 to 140 ° C, and a viscosity of 7 to 40 poise (175 ° C).

In addition, the present invention provides a method for producing an epoxy resin for powder coating, comprising the steps of: 1) preparing a corel rubber-modified epoxy resin by dispersing the corel rubber in a bisphenol-type epoxy resin; 2) preparing an isocyanate-coasel rubber-modified epoxy resin in which an oxazolidon ring is formed in the main chain by adding an isocyanate compound to the corel rubber-modified epoxy resin prepared in the first step; And 3) an isocyanate-coacel rubber-modified polyfunctional epoxy compound in which a polyfunctional amine compound is added to the isocyanate-coasel rubber-modified epoxy resin prepared in the second step to produce a branch in the corel rubber-modified epoxy resin main chain. Characterized by a method for producing a modified epoxy resin composition for powder coating comprising the step of preparing a resin.

The present invention is prepared by dispersing a corel rubber in a bisphenol-type epoxy resin to prepare a corel rubber-modified epoxy resin to improve the bendability, by applying a compound having an isocyanate group to the sock end of the molecule to form an oxazolidone ring After the addition of a polyfunctional amine compound to form a branch on the backbone skeleton of the epoxy resin molecule to increase the crosslinking density by increasing the adhesion of the base material and the glass transition temperature of the cured coating film, a method for producing a modified epoxy resin for powder coating It is possible to prepare a powder coating composition having excellent flexibility and high glass transition temperature.

Hereinafter, the method for producing the modified epoxy resin of the present invention will be described in detail step by step.

The first step is to prepare a corel rubber-modified epoxy resin by dispersing corel rubber in a low molecular weight epoxy resin compound.

First, it is preferable to use a low molecular weight (300-400 M.W.) epoxy resin compound obtained from the reaction of polyhydric phenol and epichlorohydrin in the presence of excess caustic soda in terms of dispersion effect.

As described above, the corel rubber is dispersed in a low molecular weight epoxy resin compound obtained by the reaction of polyhydric phenol and epichlorohydrin in the presence of excess caustic soda.

The coasel rubber to be used has a particle size of 300 to 20,000 mm 3 of coasel particles, and preferably has an average particle size of 900 to 2,000 mm 3.

At this time, if the core cell rubber particle size used is less than 300 kPa, the dispersion is poor, and if it exceeds 20,000 kPa, the mechanical properties decrease.

The structure of corel rubber is mainly composed of the core of graft rubber particles. The core of elastic or rubbery core is composed of conjugated diene rubber, acrylic rubber, silicone rubber or copolymers thereof. Some of the components are a non-polar component that has a characteristic that the particles are melted well in the epoxy resin and graft bonded to the core, and some are composed of a polar component that can react with the epoxy group or phenol group.

The average molecular weight of the cell is generally 10,000 to 250,000 and consists of a polymer that can be melted well in an epoxy resin, which is an ethylenically unsaturated compound, specifically styrene, acrylate, methacrylate, acrylonitrile, acrylic acid, Vinyl monomer components such as methacrylic acid, hydroxypropyl acrylate, hydroxyethyl acrylate, glycidyl acrylate and glycidyl methacrylate are polymerized in combination.

In particular, the cell polymer having a reactive group is easily reacted with the epoxy resin to easily disperse. For example, styrene / acrylonitrile / glycidyl methacrylate, styrene / acrylonitrile / acrylic acid, ethyl acryl Acrylate / methacrylic acid, styrene / methyl methacrylate / methacrylic acid, styrene / methyl methacrylate / glycidyl methacrylate, styrene / acrylonitrile / methyl methacrylate-glycidyl methacrylate, etc. Preference is given to cells composed of constituent polymers.

In the present invention, poly (butyl acrylate) core / poly (methyl methacrylate) cells satisfying the above conditions are KM series products (Rom & Haas Co., Ltd.), MBS (Styrene-) such as KM-334 and KM-355P. Butadiene-methyl methacrylate) When the EXL series (Cureha Co., Ltd.), C-type (Misubishi Rayon Co., Ltd.), etc. are used as the coacell, excellent physical properties can be obtained. Type (manufactured by Mississippi Rayon), EXL-8866, 2611,2655 (Rom & Haas Co., Ltd.) for coacell products with carboxy polar group, and EXL-2314 (QL) for coacell products with glycidyl group. Lehha company) and the like can be used.

The amount of coasel rubber used for the modification of the epoxy resin is 1 to 20 parts by weight based on 100 parts by weight of epoxy resin, and when the amount is less than 1 part by weight, the flexibility may deteriorate. And it may adversely affect the negative electrode peelability and the glass transition temperature of the cured coating film may be lowered.

In the second step, an isocyanate compound is added to the corel rubber-modified epoxy resin prepared in the first step to form an oxazolidone ring in the corel skeleton-modified epoxy resin backbone, thereby obtaining the isocyanate-corel rubber-modified epoxy resin. To prepare a step.

After the reaction is performed by adding an isocyanate compound having an isocyanate functional group in the sock end to the corel rubber-modified epoxy resin prepared in the first step, an epoxy resin in which an oxazolidone ring is formed in the main chain is obtained as in the following Formula 1.

Compounds having an isocyanate functional group at the sock end include methane diisocyanate, butane-1,1-diisocyanate, ethane-1,2-diisocyanate, butane-1,2-diisocyanate, transvinyline diisocyanate, propane-1, 3-diisocyanate, butane-1,4-diisocyanate, 2-butane-1,4-diisocyanate, 2-methylbutane-1,4-diisocyanate, pentane-1,5-diisocyanate, 2,2- Dimethyl-pentane-1,5-diisocyanate, hexane-1,6-diisocyanate, heptane-1,7-diisocyanate, octane-1,8-diisocyanate, nonane-1,9-diisocyanate, decan-1 , 10-diisocyanate, dimethylsilane diisocyanatediphenylsilane diisocyanate, w, w'-1,3-dimethylbenzene diisocyanate, w, w'-1,3-dimethylchlorohexane diisocyanate, w, w'- 1,4-dimethylchlorohexane diisocyanate, w, w'-1,4-dimethylnaphthalene diisocyanate, w, w'-1,5-dimethylnaphthalene diisocyanate, cyclohexane-1,3-diisocyanate, cyclohexane-1,4-diisocyanate, dicyclohexylmethane-4,4-diisocyanate, 1 , 3-phenyline diisocyanate, 1,4-phenyline diisocyanate, 1-methylbenzene-1,4-diisocyanate, 1-methylbenzene-2,5-diisocyanate, 1-methylbenzene-2,6- Diisocyanate, 1-methylbenzene-3,5-diisocyanate, diphenylether-4,4-diisocyanate, diphenylether-2,4-diisocyanate can be used selectively.

The amount of isocyanate compound is 1 to 30 parts by weight based on 100 parts by weight of the corel rubber-modified epoxy resin prepared in the first step, and if the amount is less than 1 part by weight, the glass transition temperature of the cured coating film is low. If it exceeds 30 parts by weight, manufacturing problems may occur, and flexibility is reduced.

When the isocyanate addition reaction proceeds, an oxazolidone ring is formed, and when the absorption wavelength is compared by using an infrared spectroscopy, the absorption wavelength of the isocyanate functional group is 2274 cm ⁻ as shown in FIGS. 1 and 2. ^It can be seen that the peak disappears and the peak of 1750 cm ⁻¹ , the absorption wavelength of the oxazolidone ring, is formed.

N is an integer of 1 or more, R 'is diepoxide, diglycidyl ether bisphenol-A, diglycidyl ether diphenol, diglycidyl ether glycol, diglycidyl ether dicarboxylic acid, Vinyl cyclohexanedioxide, dicyclopentadiene dioxide, 3,4-epoxy cyclohexanecarboxylate, and the like, wherein R ″ is diisocyanate, toluene diisocyanate, diphenylmethane diisocyanate, phenylene diisocyanate, naphthalene di Isocyanate, dianisidene diisocyanate, toluidine diisocyanate, hexamethylene diisocyanate, styrene diisocyanate, vinylene diisocyanate and the like.

There are several types of catalysts used for the smooth progress of the reaction. Bases and amines (Lewis base) are sodium hydroxide, sodium hydrogen sulfate, pyridine, lithium chloride, lithium oxide, tin chloride, zinc chloride, BF3-ether compound, BF3. -Complex compounds and quaternary ammonium salts. Hydrogen compounds include phenyltrimethylammonium chloride, tetramethylammonium salt, benzyltrimethylammonium salt, dodecyltrimethylammonium chloride salt, tetraalkylammonium halide, and the like. Midazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-undecylimidazole, 2-phenylimidazole, 2-isopropylimidazole, 2,4-dimethyl Midazole, 2-phenyl-4-methylimidazole, and phosphonium salts and derivatives thereof include butyltriphenylphosphonium bromide, tri-allylphosphine, butyl allyl phosphine butyltriphenyl phosphate-formate, butyl Lee phenyl phosphate oxalate, ethyl triphenyl phosphate may be used such as succinate, ethyl triphenyl phosphonium salt compound.

The addition amount of the catalyst is used in an amount of 0.03 to 1.0 parts by weight based on 100 parts by weight of the isocyanate compound used in the second step reaction, and used by dissolving in an additive solvent.

The third step is to prepare a resin in which branching is formed in the epoxy main chain skeleton by adding a polyfunctional amine resin to the isocyanate-coasel rubber-modified epoxy resin prepared in the second step.

The polyfunctional amine resins used are diethylenetriamine, triethylene tetramine, diethylaminopropylamine, n-aminoethyl piperazine, benzyl dimethylamine, tolisphenol, 2-ethylhexate, metaphenylenediamine, dia Minodiphenylmethane, diaminodiphenylsulfone, dicyanamide, methanediamine, xylylenediamine, bisaminopropyltetraoxa spiroundecan adduct and the like can be used.

The amount of polyfunctional amine resin added is 1 to 30 parts by weight based on 100 parts by weight of isocyanate-coasel rubber-modified epoxy resin, but when used less than 1 part by weight, the glass transition temperature of the cured coating film is low, and 30 parts by weight. If exceeded, the flexibility decreases, and problems may occur in manufacturing.

In other words, excessive use of coasel rubber for the purpose of improving the bendability tends to reduce the glass transition temperature and decrease the dispersion effect of the coacell rubber, whereas resins having isocyanate groups for high glass transition temperature Increasing the amount of modification of the functional amines has a problem of gelation in the modification process, in order to produce a composition having a high flexibility and a high glass transition temperature at the same time, the content of the components and the manufacturing process should be made in harmony.

The isocyanate-coasel rubber-modified polyfunctional epoxy resin produced by the method of the present invention as described above has a number average molecular weight of 500 to 2000, an epoxy equivalent of 250 to 1000 g / eq, a softening point of 80 to 140 ° C, and a viscosity of 7 to 40 poise ( 175 ° C).

Since the resin of the present invention prepared by the above method has a high softening point of 80 to 140 ° C., the glass transition temperature of the cured coating film is also higher than 130 ° C., so that high-temperature fluid transfer is possible, and denatured core rubber is dispersed. Since it is made of resin, the low temperature impact property and the flexibility are improved, so that the physical properties of the powder coating applied to the pipe for transporting the high temperature fluid can be sufficiently satisfied.

In addition, the present invention is a powder coating composition consisting of an hydroxy resin, a curing agent, a reaction catalyst, and a curing accelerator, and using an isocyanate-coacel rubber-modified polyfunctional epoxy resin prepared according to the method of the present invention. To prepare a powder coating composition.

Referring to the specific composition of the powder coating composition is prepared in accordance with the present invention in detail.

100 parts by weight of isocyanate-coasel rubber-modified polyfunctional epoxy resin of the present invention, 3 to 10 parts by weight of dicyandiamide curing agent having an equivalent weight of 50 to 400 g / eq, and 5 to 30 parts by weight of a curing accelerator, 0.1 to 0.6 It manufactures using a weight part and 1-5 weight part of normal additives.

As the curing agent, a dicyandiamide curing agent (C783: manufactured by Thomas Swan) was used. The amount of the curing agent was adjusted according to the equivalent ratio of the epoxy resin and the curing agent. At this time, when the equivalent of the curing agent was less than 50, the flexibility was poor. There is a problem in controlling the reactivity, the hardness is lowered if the amount of the hardener is added less than 3 parts by weight, the flexibility is poor if it exceeds 10 parts by weight.

As a pigment, 5 to 30 parts by weight of titanium dioxide (TiO ₂ ) and other small amounts of organic pigments are used as a white pigment.When the amount is less than 5 parts by weight, the concealment is poor and the coating film is reduced in hardness, and it is more than 30 parts by weight. If it is, the coating film will be hard and the flexibility will decrease.

As the curing accelerator, 0.1 to 0.6 parts by weight of organotin compounds such as imidazoles, phosphonium-based compounds, and butyl tin dilaurate were used. If it exceeds 0.6 parts by weight, the storage stability may be drastically deteriorated and gelation may occur during dispersion.

As the filler, barium sulfate (BaS0 ₄ ), calcium carbonate (CaC0 ₃ ), silica (SiO ₂ ), aluminum hydroxide (Al ₂ (OH) ₃ ), or the like may be used. As a flow improving agent, 0.5-1.5 weight part of acryl-type (Modaflow, Monsanto make; fib-5, PI-201, Wally's make; Acronal-4F; BASF make), a silicone type, etc. can be used.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the scope of the present invention is not limited by the following Examples.

Example 1

100 parts by weight of a bisphenol-type epoxy resin and 3 parts by weight of corel rubber were added thereto, followed by dispersion reaction at 80 to 120 ° C. for about 2 hours to prepare a corel rubber-modified epoxy resin. 15 parts by weight of an isocyanate monomer was added dropwise to the corel rubber-modified epoxy resin and reacted at 150 to 180 ° C. for 2 to 4 hours, and then 3 parts by weight of a polyfunctional amine resin (diaminophenylmethane) were added thereto at about 150 to 180 ° C. By reacting for 2-3 hours, the isocyanate-corel rubber-modified polyfunctional epoxy resin of the present invention was prepared. Physical properties of the prepared resin are shown in Table 1 below.

Examples 2-5

Isocyanate-coasel rubber-modified polyfunctional epoxy resin of the present invention was prepared in the same manner as in Example 1, and the type and content of components used and the physical properties of the prepared resin are shown in Table 1 below.

Comparative Examples 1 to 4

Conventional epoxy resins were prepared under the same conditions as in Example without applying corel rubber and polyfunctional amine resins, and the types and amounts of components used and measured physical properties are shown in Table 1 below.

Preparation Example: Preparation of Paint Composition

The powder coating compositions were each blended using the epoxy resins prepared according to Examples 1 to 5 and Comparative Examples 1 to 4 of the present invention, and then uniformly mixed using a container mixer. The mixture was melt-mixed at 90 to 120 ° C. through an extruder of Nieder or Extruder (PLK 46, BUSS), and then a powder mill having an average particle size of 30 to 60 microns was prepared using a grinder.

The components used in the composition of the powder coating and the amount used are shown in Table 2 below.

Test Example

Using the resins of Examples and Comparative Examples, the composition is formulated as shown in Table 2 below, and powder coating is prepared using the coating method described above, and then coated on a preheated specimen and bar at 230 ° C. for 1 hour, followed by curing. After preparing a coating film specimen having a thickness of 300 ± 50 ㎛ was shown in Table 3 by evaluating the physical properties as follows.

Flexibility According to CAN / CSA I 245.20 Clause 12.11 test method.

Impact According to CAN / CSA I 245.20 Clause 12.12 Test Method.

<Boiling number> According to CAN / CSA I 245.20 test method.

<Cathode peelability> According to CAN / CSA I 245.20 test method.

<Storage stability> Blocking phenomenon after storing the prepared paint in 40 ℃ oven for 7 days

<Glass Transition Temperature> According to AN / CSA I 245.20 Test Method.

As shown in Table 3, the powder coating according to the present invention was excellent in both the flexibility measured at -35 ℃ and 25 ℃, exhibited good characteristics against the impact applied at 1.5 J at -30 ℃, 95 ℃ Even when measured by heating for 24 hours in hot water, it showed a lower value than the conventional comparative example showed excellent properties.

In addition, the negative electrode peelability measured by applying a voltage of 1.5 V at 65 ° C. for 48 hours was lower than that of the comparative example, indicating that the negative electrode peelability was excellent. The result was also excellent in storage stability performed at 40 ° C. for 4 weeks. The storage stability was better than that of the comparative example.

The coating film glass ion was 95 to 110 ° C. in the comparative example, while the embodiment of the present invention was shown to be 145 to 157 ° C., indicating that the glass transition temperature of the coating film was improved to 50 to 62 ° C. or more.

As described above, the isocyanate-coasel rubber-modified polyfunctional epoxy resin according to the present invention has improved bendability and impact resistance by adding isocyanate, and polyfunctional amine resin is added to increase the crosslinking density, so that the glass transition temperature is 50 ° C. or more. There is an increasing effect. Therefore, when the isocyanate-corel rubber-modified polyfunctional epoxy resin of the present invention is applied to a powder coating, the glass transition temperature of the coating film becomes high when used on a metal surface, especially a pipe, etc. Applicable as At the same time, mechanical properties such as bendability and impact properties, cathodic peeling properties, and adhesiveness after boiling water treatment exhibit excellent properties, so that not only the field of conventional polyethylene or polypropylene primer paint is used, but also a fluid transport having a wider temperature range. It can be applied to the case, etc., which has the effect of extending the range of powder coating.

Claims (6)

In the epoxy resin manufacturing method for powder coating, 1) preparing a corel rubber-modified epoxy resin by dispersing the corel rubber in a bisphenol-type epoxy resin; 2) preparing an isocyanate-coasel rubber-modified epoxy resin in which an oxazolidone ring is formed in an epoxy resin backbone by adding an isocyanate compound to the corel rubber-modified epoxy resin prepared in the first step; And 3) The number average is characterized by comprising the addition of the polyfunctional amine compound to the isocyanate-coasel rubber-modified epoxy resin prepared in the second step to produce a branch in the corel rubber-modified epoxy resin backbone It is molecular weight 500-2000, epoxy equivalent 250-1000g / eq, softening point 80-140 degreeC, and viscosity 7-40 poise (175 degreeC), The manufacturing method of the isocyanate-coasel rubber-modified polyfunctional epoxy resin characterized by the above-mentioned. The method of claim 1, wherein the corel rubber is an ethylene unsaturated compound styrene, acrylate, methacrylate, acrylonitrile, acrylic acid, methacrylic acid, hydroxypropyl acrylate, hydroxyethyl acrylate, glycy One or two or more selected from dimethyl acrylate and glycidyl methacrylate are polymerized, and modified epoxy for flexibility of powder coating, characterized in that it is used in an amount of 1 to 20 parts by weight based on 100 parts by weight of the bisphenol-type epoxy resin. Method for producing a resin composition. The isocyanate compound of claim 1, wherein the isocyanate compound of the second stage is methane diisocyanate, butane-1,1-diisocyanate, ethane-1,2-diisocyanate, butane-1,2-diisocyanate, transvinyline diisocyanate, Propane-1,3-diisocyanate, butane-1,4-diisocyanate, 2-butane-1,4-diisocyanate, 2-methylbutane-1,4-diisocyanate, pentane-1,5-diisocyanate, 2,2-dimethyl-pentane-1,5-diisocyanate, hexane-1,6-diisocyanate, heptane-1,7-diisocyanate, octane-1,8-diisocyanate, nonane-1,9-diisocyanate , Decane-1,10-diisocyanate, dimethylsilane diisocyanatediphenylsilane diisocyanate, w, w'-1,3-dimethylbenzene diisocyanate, w, w'-1,3-dimethylchlorohexane diisocyanate, w , w'-1,4-dimethylchlorohexane diisocyanate, w, w'-1,4-dimethylnaphthalene diisocyane Y, w, w'-1,5-dimethylnaphthalene diisocyanate, cyclohexane-1,3-diisocyanate, cyclohexane-1,4-diisocyanate, dicyclohexylmethane-4,4-diisocyanate , 1,3-phenyline diisocyanate, 1,4-phenyline diisocyanate, 1-methylbenzene-1,4-diisocyanate, 1-methylbenzene-2,5-diisocyanate, 1-methylbenzene-2, Coacell prepared in the first step, selected from 6-diisocyanate, 1-methylbenzene-3,5-diisocyanate, diphenylether-4,4-diisocyanate, diphenylether-2,4-diisocyanate A method for producing a modified epoxy resin composition for powder coating having improved flexibility, characterized in that it is used in an amount of 1 to 30 parts by weight based on 100 parts by weight of the rubber-modified epoxy resin. The polyfunctional amine resin used in the third step is diethylenetriamine, triethylene tetramine, diethylaminopropylamine, n-aminoethyl piperazine, benzyl dimethylamine, tolisphenol, 2- Ethyl hexate, metaphenylenediamine, diaminodiphenylmethane, dianodiphenylsulfone, dicyandiamide, methanediamine, xylylenediamine, bisaminopropyltetraoxa spiroundecan adducts are used, 1 to 30 parts by weight based on 100 parts by weight of the isocyanate-corel rubber-modified epoxy resin prepared in the second step, wherein the modified epoxy resin composition for powder coating having improved flexibility. The reaction catalyst used in the second step is sodium hydroxide, sodium hydrogen sulfate, lithium chloride, pyridine, lithium oxide, tin chloride, zinc chloride, BF3-ether compound, BF3-composite compound, quaternary ammonium salt , Phenyltrimethylammonium chloride, tetramethylammonium salt, benzyltrimethylammonium chloride, dodecyltrimethylammonium chloride salt, tetraalkylammonium halogen, 2-methylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole , 2-undecylimidazole, 2-phenylimidazole, 2-isopropylimidazole, 2,4-dimethylimidazole, 2-phenyl-4-methylimidazole, butyl triphenyl phosphonium bromide , Tri-allylphosphine, butyl allyl phosphine butyltriphenyl phosphate-formate, butyltriphenyl phosphate oxalate, ethyltriphenyl phosphate succinate, ethyltriphenyl phosphonium salt compound, The isocyanate compound to 100 parts by weight of 0.03 ~ 1.0 that features a method for producing a bending-modified epoxy resin composition for improved powder coating material used as part by weight based on the. In the powder coating composition containing the epoxy resin as a main component and containing the usual powder coating additive, 100 parts by weight of the epoxy resin prepared according to claim 1, 3 to 10 parts by weight of dicyanide hardener, pigments 5 to 30 A powder coating composition having improved flexibility, characterized in that the composition is comprised by parts by weight, 0.1 to 0.6 parts by weight of a curing accelerator, and 1 to 5 parts by weight of conventional additives.