KR20030059521A - Galvanizing primer polyester coating composition - Google Patents

Abstract

The present invention relates to a polyester coating composition for PM steel sheet, and more particularly to forming a urethane group in a PC steel sheet paint composed of a polyester resin and melamine resin in which an inexpensive aromatic monomer and an expensive aliphatic monomer are appropriately mixed. By mixing the isocyanate resin and the catalyst, the adhesiveness of the material and repainting of various top coatings are excellent, and the low-temperature curing is possible, and the durability of the steel sheet can be achieved simply by going through the process of the continuous news galvanize line without going through the continuous color line. The present invention relates to an improved and improved polyester coating composition for PMC steel sheet that can be coated with various paints.

Description

Galvanizing primer polyester coating composition

The present invention relates to a polyester coating composition for PM steel sheet, and more particularly to forming a urethane group in a PC steel sheet paint composed of a polyester resin and melamine resin in which an inexpensive aromatic monomer and an expensive aliphatic monomer are appropriately mixed. By mixing the isocyanate resin and the catalyst, the adhesiveness of the material and repainting of various top coatings are excellent, and the low-temperature curing is possible, and the durability of the steel sheet can be achieved simply by going through the process of the continuous news galvanize line without going through the continuous color line. The present invention relates to an improved and improved polyester coating composition for PMC steel sheet that can be coated with various paints.

A general coil coating steel sheet is a zinc plated steel sheet produced in a continuous galvanized line (hereinafter referred to as "CGL") and a colored steel plate coated through a continuous color line (hereinafter referred to as "CCL"). Separate by.

The steel sheet produced in the CGL of the coil coating steel sheet is divided into galvalume, galvanyl, galvanize, alstar, etc., depending on the type of plating to be plated, and according to the amount of plating and the plating method, the galvanized steel sheet, galvanized It can be divided into annealing steel sheet and galvanized steel sheet. Each steel plate is classified according to its use and characteristics, and the biggest element of the division is the zinc plating amount and the aluminum content.

Recently, in the United States, Europe, South America, etc., relatively far from Korea, zinc dust is generated during the transfer of steel sheets, making it difficult to paint general paints required by consumers on each steel sheet. The back has been constantly occurring.

In order to solve the above dissatisfaction, some attempted to increase the chromate plating amount plated on the steel sheet or to coat the water-soluble transparent resin.

However, when the plating amount of the chromate is increased as described above, import and export obstacles occur due to the heavy metal crack, and consumer complaints are caused, and when the chromate is plated with the desired color, When coating the paint to be used as a problem that the adhesion between the steel plate and the paint significantly decreased.

In addition, in the case of a steel plate coated with a water-soluble transparent resin, moisture is introduced into the steel sheet when passing through a high temperature and high humidity sea, and a black spot phenomenon occurs in which a part of the resin is changed due to the moisture, which not only damages the appearance of the steel sheet, In the coating, the adhesion between the steel sheet and the paint was poor, and the boiling water resistance and the hot water resistance of the steel plate coated with the paint were deteriorated.

Another problem that may occur when using the water-soluble transparent resin is that when the resin is applied to the steel sheet needs a proper temperature at the time of drying, and should be coated in the CCL, so that the effect of the price increase occurs relatively There is this.

Because of these problems in CGL, it is very rare for ordinary consumers to use steel sheets manufactured in CGL, and the market size is small, and the value added value is provided by supplying only specific lines with perfect precleaning and pretreatment processes. This is a falling reality.

In order to overcome the above problems, the sales of color steel sheets having excellent steel sheet quality, that is, steel sheets that have passed CCL have been continuously made since the beginning, but in the case of color steel sheets that have undergone CCL, they are manufactured through another line. The price has risen more than twice, there has been a problem that can not satisfy all the needs of consumers want a variety of colors and shapes.

Therefore, it is excellent in the adhesiveness with the above-mentioned raw materials, satisfying the customer's desire about color, and supplying a low-cost type steel sheet was urgently needed.

Accordingly, the inventors of the present invention, in a PC steel sheet paint containing a polyester resin and a melamine resin in which an aromatic monomer and an aliphatic monomer are appropriately mixed, when the isocyanate resin forming a urethane group and a catalyst are mixed, the adhesion between the paint and the material The present invention has been completed by knowing that the repainting property of the coating is improved, the coating properties of the coating can be improved at low temperatures, and thus the excellent physical properties of the coating in CGL can be exhibited.

As described above, the reason why the aromatic monomer and the expensive aliphatic monomer should be used together is to consider factors such as ultraviolet rays, temperature, humidity, and wind that may affect the outdoor exposure of the coating film. When only the conventional aliphatic monomer is used, the coating film is excellent in UV resistance, but the glass transition temperature (Tg) and water resistance are relatively low, so it is weak to thermal changes at the time of exposure, causing weather resistance. In order to overcome these disadvantages, a design that enhances water resistance and heat resistance while maintaining UV resistance is required. For this purpose, two monomers are used together.

Therefore, the present invention is excellent in adhesion to the material and repainting of various top coatings, low temperature curing is possible, and can be applied in a variety of colors of paint, and coated in CGL not only improve the durability of the steel sheet but also to be manufactured at a lower cost. It is an object of the present invention to provide a polyester coating composition for PM steel sheet.

In the polyester coating composition for an exterior material, 40 to 80 weight% of hydroxy unsaturated polyester resin, 5 to 50 weight% of melamine resin, 1 to 10 weight% of isocyanate resin which forms a urethane group, 0.5 to 3 weight of hardening accelerator %, 0.01-1% by weight of curing accelerator, 0.1-2% by weight of catalyst, and a polyester coating composition for low-temperature hardening PCM steel sheet comprising a conventional dispersant, leveling agent, Al ₂ (OH) ₃ and a pigment It is done.

As the hydroxy unsaturated polyester resin used in the present invention, unsaturated polyesters, oil modified polyesters and urethane modified unsaturated polyesters or urethane modified oil modified polyesters thereof may be used.

In this invention, it is preferable to use the hydroxy unsaturated polyester resin whose number average molecular weights are 800-15,000, glass transition temperature -15-60 degreeC, and a hydroxyl value is 10-170, More preferably, the number average molecular weights are 1,000- A hydroxy unsaturated polyester resin having a glass transition temperature of -8,000 to 8,000 and a hydroxyl value of 15 to 150 is used.

The oil-modified polyester in the present invention can be prepared from the reaction of a polybasic acid and a polyhydric alcohol.

The polybasic acid may be alicyclic acid, phthalic anhydride, isophthalic acid, terephthalic acid, succinic acid, adipic acid, fumaric acid, maleic anhydride, tetrahydrophthalic anhydride, hexahydro phthalic anhydride and derivatives thereof, such as isophthalic acid. When excessive use of the monomer with a bond is poor in weatherability at the time of forming the coating film, it is preferable to mix and use an acid having a linear structure without a benzene ring such as an alicyclic acid. That is, the mixing ratio of the aromatic monomer and the aliphatic monomer is 1: 3 to 4, when the alpipatic monomer is less than 3, the UV resistance is lowered. When it exceeds 4, the heat resistance and water resistance are lowered, and the weather resistance when exposed to the outdoors. It may cause degradation.

As the polyhydric alcohol, ethylene glycol, propylene glycol, diethylene glycol, butanediol, neopentyl glycol, 3-methylpentanediol, 1,4-hexanediol, 1,6-hexanediol, and the like may be used.

In the present invention, it is preferable to use the hydroxy unsaturated polyester resin in 40 to 80% by weight of the total coating composition, if the content is less than 40% by weight, the flexibility and impact resistance of the coating film is greatly reduced, 80% by weight If it exceeds, the fouling resistance, solvent resistance and hardness of the coating film decreases drastically.

As the melamine resin used in the present invention, a methoxy type melamine resin or a methoxy type melamine resin or a methoxy / butoxy mixed melamine resin having a molecular weight of 300 to 1,000 may be used. The methoxy melamine resin is obtained by polymerization of methanol and formaldehyde, and butoxy melamine is obtained by polymerization of iso-butanol or normal butanol and formaldehyde.

In the present invention, it is preferable to use the melamine resin in an amount of 5 to 50% by weight based on the total coating composition. If the content of the melamine resin is less than 5% by weight, fouling resistance and solvent resistance are drastically reduced, and the content is 50% by weight. When it exceeds%, the flexibility and impact resistance of the coating film are lowered, which is not preferable.

Commercialized methoxy melamine resins having properties that can be used in the present invention are CYMEL-303, CYMEL-325, CYMEL-327, CYMEL-350, CYMEL-370 (from CYTEC), RESIMINE-7550, RESIMINE-717 , RESIMINE-730, RESIMINE-747, RESIMINE-797 (manufactured by SOLUTIA), BE-3717, BE-370, BE-3747 (manufactured by BIP) and the like. , BE-692 (available from BIP), RESIMINE-7512, and RESIMINE-750 (available from SOLUTIA).

Examples of butoxy / methoxy mixed resins include RESIMINE-755, RESIMINE-757, RESIMINE-751 (manufactured by SOLUTIA), CYMEL-1168, CYMEL-1170, and CYMEL-232 (manufactured by CYTEC). .

When the butoxy melamine resin is used alone, or each melamine resin is simply mixed with each other, instead of the methoxy melamine and butoxy melamine resin mixed type melamine resin, compatibility with the polyester resin is drastically deteriorated, and melamine is used as a coating material. It is transferred to the upper layer, which not only lowers the weather resistance of the coating but also degrades the gloss of the coating.

The isocyanate resin used in the present invention should be masked to prevent room temperature curing. Products satisfying the above properties are typically isophorone diisocyanate (IPDI), toluene diisocyanate (TDI), Hexamethylene diisocyanate (HMDI), trimer hexamethylene diisocyanate (Trimer HMDI), and the like.

To be suitable for thermosetting resins, isocyanate resins without double bonds should be used in order to suppress yellowing. Products satisfying these properties include Desmodure BL 3575, BL1203 (available from Bayer), R6711, R6730, R6720. , R6710 (manufactured by KCC Co., Ltd.) and the like, and masking agents used in these products include phenol, m-nitrophenol, p-chlorophenol, catechol, hydrogen cyanide, ethylmalonate, acetylacetone, and ethyl acetoacetate. , Caprolactam, β-thionaphthalene, isooctylphenol, 4-hydroxybiphenol, α-pyrrolidone, and the like, when using an oxime masking agent. As a result, severe yellowing may occur in the coating film. Therefore, it is most preferable to use isocyanate masked with malonate such as ethylmalonate. .

The amount of isocyanate resin used in the composition of the present invention is preferably used 1 to 10% by weight, even more preferably 3 to 7% by weight, when the amount is less than 1% by weight of the coating film The effect of improving the acid resistance is low, and when used in excess of 10% by weight, there is a problem in that the raw material cost of the paint increases.

The curing accelerator used in the present invention is a raw material used to improve the density of the coating film by promoting the curing of the polyester resin, which is the main component of the present invention, and the melamine resin, which is a curing agent. It is characterized by using weight%.

As the sulfonic acid, p-toluenesulfonic acid, dodecylbenzenedisulfonic acid, dinonylnaphthalenedisulfonic acid, dinonylnaphthalenesulfonic acid, and the like may be used, and among these, p-toluenesulfonic acid or dinonylnaphthalenesulfonic acid is preferably used.

In this case, the sulfonic acid is preferably shielded with a material that can be dissociated by heat, and as the shielding material, an amine may be generally used. As the amine, secondary amine is preferable, and specific examples thereof include diethylamine, diisopropylamine, diisopropanolamine, di-n-propylamine, di-n-butylamine, diisobutylamine, di-secondary-butyl Amines, diallylamines, diamylamines, N-ethyl-1,2-dimethylpropylamine, N-methylhexylamine, di-n-octylamine, piperidine, 2-pipecoline, 3-piecoline, 4-piecoline, morpholine, and the like, and an effective amount thereof of 15 to 45% by weight was added to the composition, thereby greatly increasing the stain resistance of the coating film.

In the present invention, the curing accelerator is used in the total coating composition of 0.3 to 3% by weight, preferably 0.5 to 2% by weight. At this time, when the amount of the curing accelerator is less than 0.3% by weight, curing of the coating film is insufficient depending on the working conditions, so that it is impossible to maintain proper fouling resistance. When it exceeds 3% by weight, curing of the coating film occurs too rapidly, Popping occurs in the coating film or shrinkage of the coating film.

The curing accelerator used in the present invention is a sulfonic acid shielded with tertiary amine as a raw material used for the purpose of making the surface of the coating film dense and preventing the metal marks generated when metals collide with each other while using a small amount of melamine. Can be used.

The sulfonic acid may be the same kind as the sulfonic acid used in the curing accelerator, but is characterized by using a tertiary amine as a shielding material.

0.01 to 1% by weight of the curing accelerator is used, and when used less than 0.01% by weight, the effect of promoting the surface film hardening and the effect of preventing the metal mark is inhibited, when used in excess of 1% by weight, the coating film The surface shrinks and the effect disappears.

A catalyst used for promoting the curing of the isocyanate resin used in the coating composition of the present invention is preferably a tin catalyst, and a product that can be used is DBTDL Stan BL (Japan catalyst product). The amount of the catalyst used is 0.1 to 2% by weight, preferably 0.5 to 1% by weight. At this time, when the amount of the catalyst used is less than 0.1% by weight, the effect of the catalyst is lowered, and the effect of improving acid resistance is lowered. When used in excess of 2% by weight, a yellowing phenomenon occurs and the cost of the raw material of the paint is increased.

The polyester coating composition of this invention can be used also as a transparent coating which does not use a pigment, and can also form a coating film using an organic or inorganic pigment.

As a pigment used as a colored paint, it is preferable to use a pigment which can impart heat resistance and chemical resistance suitable for PCM paint. In addition, the basic particles of the pigment should also be sufficiently considered. Examples of such pigments include cyanine blue, titanium oxide white, iron oxide red, carbon black, chrome yellow, carbon black, and the like. , Aluminum hydroxide compounds and the like can be used.

In addition to the components exemplified above, conventionally applied dispersants, leveling agents, Al ₂ (OH) _3, and the like may be added.

As a coating steel material that can be used for the coating of the present invention, cold rolled steel, zinc hot dipping steel, electro-zinc steel, alloy-plate steel, copper sheet and tin-plate steel, etc. may be used, and among these, mainly Materials used include cold rolled steel (CR), electro zinc steel sheet (EGI), zinc hot dipping steel sheet (GI), galvanic annealing steel sheet (GA), and the like.

In addition, as a pretreatment of the material used, phosphate, chromate or similar materials may be used, and even without pretreatment if necessary.

As the coating method of the paint according to the present invention, curtain coating, roll coating, immersion coating and spray coating can be used, and the coating thickness used for coating is preferably 5 to 15 µm.

The baking time can be changed according to the baking conditions, and due to the limitation of baking conditions in the CGL line, it should be possible to cure even baking at a short time at low temperature. Such baking conditions are 6-8 seconds at 200-300 ℃. However, the shipbuilding can be adjusted.

If the present invention will be described in detail based on the embodiment as follows, the present invention is not limited by the embodiment.

Production Example

Manufacture of M / B (Mill Base)

100 g of each resin (70% solids, solvent is a 1/1 (v / v) mixture of cyclohexane (Kodak) / KOCOSOL # 100 (porous product)), TiO ₂ 200 g (Japan Ishihara or DuPont), Each dispersant and viscoelastic modifier were placed in a 1 L tin container, and then 200 g of 1-2 mm glass beads were mixed with the solution, followed by dispersion for 1 hour 30 minutes with a shake type disperser (KCC, product name; RED DEVIL). The particle size after dispersion was adjusted to 5 μm or less.

Manufacture of L / D (Let Down)

Resin / melamine / isocyanate resin / curing agent / curing accelerator were added to the prepared M / B to make the ratio of pigment and resin to 1.2 / 1, and the leveling agent ( Product Name: R5900, KCC Co., Ltd., 0.5 weight ratio is added. The viscosity of the prepared paint was adjusted to 100 SEC / Ford Cup # 4, 25 ° C.

Examples 1-8 and Comparative Examples 1-3

Using the method prepared according to the preparation example, a paint including the components shown in Table 1 below was prepared in the same manner.

The composition of Table 1 was prepared based on the solid content, and the solvent used in the paint was excluded. Solvents used in paints were used to control the fluidity and viscosity required to prepare the paints.

Experimental Example

The coating composition prepared according to the above Examples and Comparative Examples was applied to the steel sheet, but the baking conditions were applied for 15 seconds at 280 ℃, a wind speed of 2m, the maximum temperature of the material is adjusted to 150 ~ 170 ℃ temperature It was.

Comparative Example Because of the high curing temperature, the automatic batch oven was used at 280 ℃ for 28 seconds at a wind speed of 2m / s, and the maximum temperature at firing was 232 ℃ (However, the low temperature curing test is a comparative test at a constant temperature. Since it was tested based on the holding temperature based on 150 ℃, 170 ℃, 200 ℃, 230 ℃.

At this time, the coating method was performed by the bar coating method, bar # 14 was used.

The material used for the coating was pretreated by applying 0.45mm GI material manufactured by POSCO Gwangyang Bay to NRC (Non Rinse Chromate; manufactured by Parkerizing Co., Ltd.) at 20 to 40 mg / m2. The content was 87 mg / m 2, and the coating composition was bar-coated and then baked in an auto-discharge oven manufactured by Nippon Frost Thermography at 280 ° C. for 15 seconds to prepare a coating film. Each physical property was measured by the following method, and the results are shown in Table 2 below.

Glossiness (GLOSS 60 °)

60 ° gloss was measured using a BYK or SHEEN polisher.

2. Hardness

-The scratches of the coating film were evaluated using Mitubishi Uni Pensil in Japan. The degree of scratching was H for soft and 2H for hard.

3. Processability

Two materials of the same thickness as the material were inserted at room temperature and processed 180 °, and the processed part was wound with Scotch tape to evaluate peeling and cracking conditions. Evaluated.

4. Solvent resistance

The number of times the methyl ethyl ketone (MEK) was buried in the gauze and reciprocated with a load of 1 Kg was measured.

5. Acid resistance

5% hydrochloric acid solution was applied to the coating film, the surface was covered, and the surrounding was shielded with petrolatum, and it was left at 25 ° C for 24 hours to evaluate the condition of the coating film. The case where the whole surface of a coating film peeled by was evaluated by one point.

6. Base resistance

5% sodium hydroxide solution was applied to the coating film, and the surface was covered with petrolatum, and then it was left at 25 ° C for 24 hours to evaluate the condition of the coating film. The case where the whole surface of a coating film peeled was evaluated by 1 point.

7.Q.U.V-B 500 hours gloss retention rate evaluation

This item is for evaluating the weather resistance / ultraviolet resistance of the coating film. Using a QUV-se device manufactured by Q-PANEL, adjust the UV wavelength to B Type (313 nm), and cycle for 60 hours. The retention was evaluated by comparing the gloss after the test to the initial glossiness of the coating film by irradiation and 40 ° C. for 4 hours. ?? E indicates the degree of discoloration. The higher the value, the worse the weather resistance / ultraviolet resistance.

8. Corrosion resistance evaluation

Using a Q-FOG device manufactured by Q-PANEL in the United States, leaving NaCl dissolved in distilled water for 5 hours under a condition that a solution made of 5% solution was sprayed in an atmosphere of 35 ° C. The rating was given according to the corrosion distance and the size of the blisters. The score was evaluated as 5 points when there was no trace of blisters and 1 point when blisters appeared on the entire surface of the coating film.

9. Urethane top coat repaintability

After repainting 20-40 U of KCC's UT2578, it is naturally dried for 14 days, and the dried coating is left for 3 hours after hot water resistance, and 30 days for hot water resistance, followed by 1 mm cross cut taping. The degree of peeling was evaluated, and when the peeling degree was low, 5 points were evaluated.

10. Low Temperature Curability

Each paint is painted to have a holding temperature of 150 ° C., 170 ° C., 200 ° C. and 230 ° C., and the solvent resistance test of item 4 is carried out.

Ingredient Example (g) Comparative Example (g) One 2 3 4 5 6 One 2 3 Polyester resin CRF33100 ¹⁾ 70 70 CRF00167 ²⁾ 70 80 CRF35503 ³⁾ 70 CRF33114 ⁴⁾ 80 CRF00055 ⁵⁾ 75 70 80 Melamine resin CYMEL303 ⁶⁾ 25 20 25 20 20 20 CYMEL325 ⁷⁾ 25 15 25 Isocyanate Resin BL3175 ⁸⁾ 5 10 R6710 ⁹⁾ 5 5 5 R6730 ¹⁰⁾ 5 5 Curing accelerator Nacure1953 ¹¹⁾ 3 3 3 3 3 3 TaycacureAC931 ¹²⁾ 3 3 3 Curing accelerator Nacure2107 ¹³⁾ 0.1 0.1 0.1 0.1 0.1 0.1 0.1 Leveling agent DISPALON 1980 ¹⁷⁾ 0.5 POLYFLOW90-50 ¹⁸⁾ 0.5 0.5 0.5 0.5 URAD DD-27 ¹⁹⁾ 0.7 0.4 0.8 catalyst DBTDL ²⁰⁾ 0.1 0.2 0.1 0.2 0.15 0.2 0.15 Pigment MINUSIL 5U ²¹⁾ 40 40 40 40 40 CYANINE BLUE 2 2 2 2 2 2 2 2 2 Etc TiO ₂ 50 50 50 50 50 50 50 50 50 Al ₂ (OH) ₃ 40 40 40 40

1.CRF33100: average molecular weight 3,500, glass transition temperature 10 ??, hydroxyl group 35, aliphatic monomer alone, KCC G. 2.CRF00167: number average molecular weight 4,500, glass transition temperature 20 ??, hydroxyl group 35, aromatic monomer: aliphatic Monomer = 1: 4, KCC G.3.CRF35503: Number average molecular weight 4,500, Glass transition temperature 25 ??, hydroxyl group 30, Aromatic monomer: Aliphatic monomer = 1: 3, KCC G.4.CRF33114: Number average molecular weight 3,500 , Glass transition temperature 15 ??, hydroxyl group 35, aromatic monomer: aliphatic monomer = 1: 2, KCC. 5.CRF00055: number average molecular weight 3,500, glass transition temperature 15 ??, hydroxyl group 35, aromatic monomer: aliphatic monomer = 1: 0.5, KCC. 6.CYMEL 303: FULL methoxy melamine, solid content of 1000 or less, 98%, CYTEC company. 7.CYMEL 325: hyimino type methoxy melamine, solid content 80%. CYTEC Corp. 8.BL3175: trimer-type HMDI resin shielded with MEK OXIME, BAYER Corp. 9.R6710: HMDI resin shielded with ethyl malonate, KCC Corp. 10.R6730: trimer-type HMDI resin shielded with MEK oxime KCC G.11.Nacure 1953: Dinonylsulfonic acid shielded with secondary amines, dissociation temperature 140 ° or higher, KING G.12.Taycacure AC931: Dinonylsulfonic acid shielded with secondary amines, dissociation temperature 140 ° C or higher 13.2 Nacure 2107: P-toluene sulfonic acid shielded with tertiary amine, dissociation temperature above 115 ??, BYK P104: BYK-Cheme company 15.EFCA-4050: EFCA company 16.NUOSPERSE 657: BYK Corp. 17.DISPALON 1980: KUSUMOTO CHEMICALS Corp. 18.POLYFLOW 90-50: Public Service Corp. 19.URAD DD-27: ICI Corp. 20.DBTDL: Japan Catalyst Inc. 21.MINUSIL 5U: USA SILICA Corp ,

Example Comparative Example One 2 3 4 5 6 One 2 3 Gloss (GLOSS 60 °) 64 62 60 65 66 64 61 65 62 Hardness 2H 2H H 2H H 2H H H H Machinability 4 4 4 4 4 4 4 4 5 Acid resistance 5 5 5 5 5 5 5 5 5 Solvent resistance 50 ↑ 50 ↑ 50 ↑ 50 ↑ 50 ↑ 50 ↑ 50 ↑ 50 ↑ 50 ↑ Basic resistance 5 5 5 5 5 5 5 5 5 Q.U.V-B 500 Hours Mineral retention rate (%) 52 93 80 91 80 95 50 50 50 ΔE 3.2 0.7 3.2 0.8 2.8 0.9 4.4 7.1 0.7 Corrosion resistance 4 4 3 4 3 4 3 4 2 Urethane Top Coat Repaintability 5 5 5 5 5 5 2 2 One Low temperature curability 50 ↑ 50 ↑ 50 ↑ 50 ↑ 50 ↑ 50 ↑ 5 5 5 50 ↑ 50 ↑ 50 ↑ 50 ↑ 50 ↑ 50 ↑ 10 10 10 50 ↑ 50 ↑ 50 ↑ 50 ↑ 50 ↑ 50 ↑ 20 20 20 50 ↑ 50 ↑ 50 ↑ 50 ↑ 50 ↑ 50 ↑ 50 ↑ 50 ↑ 50 ↑

As shown in Table 2, the coating composition according to the present invention exhibited the physical properties of the appearance and the chemical resistance and processability represented by the acid resistance, base resistance and solvent resistance equivalent or more than the conventional comparative example, It can be seen that hardness and corrosion resistance are superior to the conventional comparative example.

In addition, the optical retention measured by exposure to ultraviolet rays was 80-95%, which is superior to that of the conventional comparative example of 50%, and the urethane phase repaintability was poorly shown as the comparative examples of 1 to 2, while the present invention All of the examples show the best score of 5, indicating that the repainting is excellent.

As described above, the polyester resin composition according to the present invention is excellent in adhesion to the material and repainting of various top coats, and has excellent corrosion resistance, so that a blister is formed less, and thus may have a beautiful appearance.

In addition, it can be cured within 15-17 seconds at 280 ° C ambient temperature, wind speed 2m / s, which is shorter than conventional polyester resins, and can be coated on the continuous news galvanize line without going through the continuous color line. to be.

Therefore, when the polyester resin is applied to a paint applied to a steel sheet used as an exterior material, it is possible to satisfy a consumer's desire for color, and because it is economical, there is a desirable effect of expanding a consumer layer.

Claims (10)

Polyester coating composition for exterior materials WHEREIN: 40-80 weight% of hydroxy unsaturated polyester resins, 5-50 weight% of melamine resins, 1-10 weight% of urethane resins, 0.5-3 weight% of hardening accelerators, and 0.01 to hardening accelerators A polyester coating composition for low temperature hardening type PCM steel sheet, comprising 1 wt% and 0.1 to 2 wt% of a catalyst. The low temperature hardening type PCM sheet according to claim 1, wherein the hydroxy unsaturated polyester resin has a number average molecular weight of 800 to 15,000, a glass transition temperature of -15 to 60 ° C, and a hydroxyl value of 15 to 180. Polyester coating composition. The polyester coating composition for low temperature hardening type PCM steel sheet according to claim 1, wherein the hydroxy polyester resin has a ratio of 1: 3 to 4 of an aromatic monomer and an aliphatic monomer. The polyester coating composition of claim 1, wherein the melamine resin uses a methoxy melamine resin having a molecular weight of 300 to 1,000 or a methoxy / butoxy mixed melamine resin. The polyester coating composition of claim 1, wherein the urethane resin is composed of a structure without a double bond in the molecule. The method of claim 1, wherein the urethane resin is a phenol, m-nitrophenol, p-chlorophenol, catechol, prologlucinol (Phloroglucinol), hydrogen cyanide, ethyl malonate, acetylacetone, ethyl acetoacetate, caprolactam, A polyester coating composition for a low temperature hardening type PCM steel sheet characterized by using isocyanate masked with one selected from β-thionaphthalene, isooctylphenol, 4-hydroxybiphenol and α-pyrrolidone. According to claim 1, wherein the curing accelerator polyester coating composition for low-temperature curing type PCM steel sheet, characterized in that using the forest phosphonic acid shielded with amine, epoxy or alkyl resin. The polyester coating composition of claim 1, wherein the curing accelerator is a p-toluenesulfonic acid shielded with a tertiary amine. The polyester coating composition of claim 1, wherein the catalyst is a tin-based catalyst. 40 to 80 wt% of hydroxy unsaturated polyester resin, 5 to 50 wt% of melamine resin, 1 to 10 wt% of urethane resin, 0.5 to 3 wt% of curing accelerator, 0.01 to 1 wt% of curing accelerator, 0.1 to 2 wt% of catalyst PCM steel sheet coated with the polyester coating composition for low-temperature hardening type PC steel sheet, comprising a%, a dispersant, a leveling agent, Al ₂ (OH) ₃ and a pigment.