KR102310666B1 - Primer coating composition - Google Patents

Abstract

The present invention relates to a base coating composition comprising an acid-modified polyester-based resin, a pigment, and a solvent.

Description

Undercoat composition {PRIMER COATING COMPOSITION}

The present invention relates to an undercoat composition coated on a trivalent chromium-plated surface.

Conventional automobile parts are plated with hexavalent chromium (Cr) to give a beautiful appearance. However, since hexavalent chromium is vulnerable to corrosion due to snow removal salt, parts plated with hexavalent chromium have a problem of discoloration due to snow removal salt. Accordingly, in the automobile parts industry, there is a trend to plating the plastic material using trivalent chromium instead of hexavalent chromium. The trivalent chromium plating is superior to the hexavalent chromium plating in terms of physical properties for snow removal, for example, appearance stability, and can implement a luxurious and dark mirror image in automobile parts. In order to protect the plated surface plated with such trivalent chromium and to further improve its appearance, it is common to apply a paint on the plated surface.

However, the plated surface plated with trivalent chromium has poor adhesion properties and poor physical properties such as water resistance, weather resistance, high pressure car washability, and chipping resistance when applying the conventional undercoat for hexavalent chromium plating surface. . Therefore, there is a demand for the development of an undercoat capable of forming a coating film having excellent physical properties such as adhesion, water resistance, weather resistance, high pressure car wash resistance, and chipping resistance when coated on a trivalent chrome plating surface.

Specifically, Korean Patent Registration No. 1,463,179 (Patent Document 1) includes a polyol resin, a color pigment, an extender pigment, a leveling agent, a reaction accelerator, an ultraviolet absorber, an ultraviolet stabilizer, and a solvent. One-time coating applied to the chrome plating surface Disclosed is a two-component coating composition for solution. However, the coating composition of Patent Document 1 has a limitation in that the prepared coating film has poor water resistance.

Therefore, there is a need for research and development on a base coating composition capable of forming a coating film with excellent various physical properties such as adhesion, water resistance, weather resistance, high pressure car wash resistance and chipping resistance when painting on a plated surface of trivalent chromium.

Korean Patent Registration No. 1,463,179 (published on: April 24, 2014)

Accordingly, the present invention provides a base coating composition capable of forming a coating film having excellent various physical properties, such as adhesion, water resistance, weather resistance, high pressure car wash resistance, and chipping resistance, when painting on a plated surface of trivalent chromium.

The present invention provides a base coating composition comprising an acid-modified polyester-based resin, a pigment, and a solvent.

The surface roughness of the plated surface plated with trivalent chromium was very low, so there was a limitation in that the adhesion of the coating film was remarkably insufficient. On the other hand, when the undercoat composition according to the present invention is applied to the plated surface of trivalent chromium, the acid-modified polyester-based resin in the undercoat composition corrodes the plated surface, thereby increasing the specific surface area of the plated surface and increasing the specific surface area. Due to this, the adhesion between the prepared coating film and the plating surface is increased, and a coating film having excellent various physical properties such as water resistance, weather resistance, high pressure car wash resistance and chipping resistance can be formed. Therefore, the primer coating composition according to the present invention can be usefully used to paint trivalent chromium-plated automobile parts (eg, radiator grille, door handle, handle, center fascia, gearbox, etc.).

Hereinafter, the present invention will be described in detail.

As used herein, “number average molecular weight” is measured by a conventional method known in the art, and may be measured by, for example, a gel permeation chromatograph (GPC) method. Furthermore, the “glass transition temperature” is measured by a conventional method known in the art, and may be measured, for example, by differential scanning calorimetry (DSC). In addition, functional groups such as "acid value" and "hydroxyl value" may be measured by a method well known in the art, for example, may represent a value measured by a method of titration.

In addition, the term "part by weight" as used herein means a weight ratio between raw material components.

undercoat composition

The primer coating composition according to the present invention includes an acid-modified polyester-based resin, a pigment, and a solvent.

Acid-modified polyester resin

The acid-modified polyester-based resin plays a role in enhancing the adhesion, high-pressure car wash, and chipping resistance of the coating film.

The acid-modified polyester-based resin may be a polyester-based resin modified with one or more acids selected from the group consisting of organic acids and inorganic acids. Specifically, the acid-modified polyester-based resin may be a polyester-based resin modified with an inorganic acid.

In addition, the inorganic acid may include, for example, at least one selected from the group consisting of sulfuric acid, nitric acid, phosphoric acid, and carbonic acid. Specifically, the inorganic acid may include, for example, at least one selected from the group consisting of sulfuric acid, nitric acid, and phosphoric acid.

Furthermore, the organic acid may include, for example, at least one selected from the group consisting of formic acid, acetic acid, oxalic acid and fatty acid. Specifically, the organic acid may be formic acid, acetic acid, oxalic acid or fatty acid having 1 to 2 carbon atoms.

In addition, the acid-modified polyester-based resin may be prepared by reacting a polyfunctional alcohol and an acid compound and then modifying it with an acid. For example, the acid-modified polyester-based resin may be prepared by reacting so that the equivalent ratio of the hydroxyl group of the polyfunctional alcohol to the carboxyl group of the acid compound is 1.02:1 to 1.10:1, and then modifying with an acid. At this time, the reaction may be carried out at 200 to 250 °C, or 210 to 230 °C.

The acid content of the acid-modified polyester resin may be 1 to 5 parts by weight, or 1.5 to 3.7 parts by weight, based on 100 parts by weight of the acid-modified polyester resin. When the acid content of the acid-modified polyester resin is out of the above range, the adhesion and water resistance of the coating film are lowered, and the polymerization of the resin does not proceed, so that the overall physical properties of the paint, particularly color discoloration, may occur.

Furthermore, the polyfunctional alcohol may include, for example, 2 to 4 hydroxyl groups. For example, the polyfunctional alcohol is at least one selected from the group consisting of neopentyl glycol, trimethylolpropane, ethylene glycol, pentaerythritol, hexanediol, butylethylpropanediol (BEPD) and cyclohexanedimethanol (CHDM). may include. In addition, the acid compound may include, for example, at least one selected from the group consisting of maleic anhydride, isophthalic acid, terephthalic acid, hexahydrophthalic acid, cyclohexanedicarboxylic acid (CHDA), and adipic acid.

In addition, the acid-modified polyester-based resin may have an acid value (Av) of 5 to 30 mgKOH/g, or 10 to 20 mgKOH/g. When the acid value of the acid-modified polyester-based resin is out of the above range, the curing reaction of the composition may be delayed and the hardness and appearance of the coating film may be deteriorated.

In addition, the acid-modified polyester-based resin may have a number average molecular weight (Mn) of 5,000 to 15,000 g/mol, or 7,000 to 12,000 g/mol. When the number average molecular weight of the acid-modified polyester-based resin is within the above range, the chipping resistance of the prepared coating film is excellent. .

Furthermore, the acid-modified polyester-based resin may have a glass transition temperature (Tg) of 10 to 50 °C, or 20 to 40 °C. When the glass transition temperature of the acid-modified polyester-based resin is within the above range, the workability of the composition and water adhesion resistance of the prepared coating film can be improved, and when the glass transition temperature is outside the above range, the weather resistance of the prepared coating film is reduced can be

In addition, the acid-modified polyester-based resin may have a viscosity at 25° C. of 100 to 3,000 cps, or 500 to 2,500 cps. When the viscosity at 25° C. of the acid-modified polyester-based resin is within the above range, adhesion and chipping resistance of the coating film may be improved, and if the viscosity is outside the above range, chipping resistance may be reduced.

Furthermore, the acid-modified polyester-based resin may be included in the composition in an amount of 40 to 55 parts by weight based on 3 to 25 parts by weight of the pigment. Specifically, the acid-modified polyester-based resin may be included in the composition in an amount of 45 to 53 parts by weight based on 3 to 25 parts by weight of the pigment. When the content of the acid-modified polyester-based resin is within the above range, there is an excellent effect in appearance, water resistance, heat cycle resistance, acid resistance and alkali resistance of the prepared coating film.

pigment

Pigments serve to impart color or increase strength to the prepared coating film.

The pigment may be, for example, a color pigment, an extender pigment, or a mixture thereof.

The color pigment serves to secure hiding power and impart color to the coating film. In this case, the color pigment may be a black pigment, a white pigment, or a mixture thereof. The color pigment may include a pigment such as blue, red, yellow, or violet.

In addition, the color pigment may be included in the composition in an amount of 1 to 15 parts by weight, or 4 to 12 parts by weight based on 40 to 55 parts by weight of the acid-modified polyester-based resin. When the content of the color pigment is out of the above range, the hiding power of the prepared coating film may be deteriorated or the economical efficiency of the coating material may be deteriorated.

In this case, the black pigment may be used without any particular limitation as long as it is a commonly known black pigment, for example, carbon black, graphite, iron oxide, or a mixture thereof may be used.

In addition, the black pigment may be included in the composition in an amount of 0.1 to 5 parts by weight, or 0.5 to 3 parts by weight based on 40 to 55 parts by weight of the acid-modified polyester-based resin. When the content of the black pigment is less than 0.1 parts by weight, it may be difficult to impart a required color to the coating film. can be

Furthermore, the white pigment may be used without any particular limitation as long as it is a commonly known white pigment, for example, titanium dioxide and the like may be used.

In addition, the white pigment may be included in the composition in an amount of 1 to 10 parts by weight, or 4 to 9 parts by weight based on 40 to 55 parts by weight of the acid-modified polyester-based resin. If the content of the white pigment is less than 1 part by weight, it may be difficult to give the required color to the coating film or the water resistance of the coating film may be reduced. can

In addition, the extender pigment serves to increase the strength of the prepared coating film. The extender pigment may be used without any particular limitation as long as it is a commonly known component, for example, talc, calcium carbonate, barium sulfate, calcium silicate, silica, or a mixture thereof may be used.

The extender pigment may be included in the composition in an amount of 1 to 10 parts by weight, or 4 to 9 parts by weight based on 40 to 55 parts by weight of the acid-modified polyester-based resin. When the content of the extender pigment is less than 1 part by weight, the strength of the coating film may decrease, and when it exceeds 10 parts by weight, the chipping resistance and high-pressure washing properties of the coating film may decrease.

In addition, the pigment may be 3 to 25 parts by weight, or 9 to 20 parts by weight based on 40 to 55 parts by weight of the acid-modified polyester-based resin. When the content of the pigment is less than 3 parts by weight, the appearance of the coating film may be poor or the strength may be lowered, and when the content of the pigment exceeds 25 parts by weight, the chipping resistance and high-pressure car wash properties of the coating film may be deteriorated.

solvent

The solvent serves to increase the viscosity and dispersibility of the undercoat composition and to secure workability. In this case, the solvent may be, for example, an aromatic hydrocarbon-based solvent or an ether-based solvent.

The aromatic hydrocarbon-based solvent may be, for example, xylene, toluene, or a mixture thereof. Moreover, as a commercial item of the said aromatic hydrocarbon type solvent, Cocosol #100, Cocosol #150, etc. are mentioned.

Further, the ether-based solvent is, for example, di-n-butyl ether, di-isobutyl ether, di-sec-butyl ether, di-n-pentyl ether, diisopentyl ether, di-sec-pentyl ether, Di-tert-amyl ether, di-n-hexyl ether, methyl cyclopentyl ether, methyl cyclohexyl ether, methyl phenyl ether, methyl benzyl ether, ethyl cyclopentyl ether, ethyl cyclohexyl ether, ethyl phenyl ether, ethyl benzyl ether or these may be a mixture of

In addition, the solvent may be included in the composition in an amount of 25 to 40 parts by weight, or 30 to 38 parts by weight based on 40 to 55 parts by weight of the acid-modified polyester-based resin. If the content of the solvent is less than 25 parts by weight, it may be difficult to control the viscosity or the dispersibility of the base coating composition may be lowered. can

additive

The primer coating composition according to the present invention may further include one or more additives selected from the group consisting of a dispersant, a thickener, and a curing accelerator.

In this case, the dispersant serves to increase the dispersibility of the undercoat composition. The dispersant may be used without particular limitation as long as it is a commonly known component, for example, modified polyurethane, polycarboxylic acid polyester, alkylammonium salt compound, acrylic compound, polyester compound, or their mixtures and the like may be used.

In addition, the dispersant may be included in the composition in an amount of 0.1 to 2 parts by weight, or 1 to 2 parts by weight based on 40 to 55 parts by weight of the acid-modified polyester-based resin. When the content of the dispersant is less than 0.1 parts by weight, the dispersibility of the undercoat composition may decrease, and when the content of the dispersant exceeds 2 parts by weight, the high-pressure car wash and chipping resistance of the coating film may be deteriorated.

Furthermore, the thickener serves to control the viscosity of the undercoat composition. The thickener may be used without any particular limitation as long as it is a commonly known component, for example, fumed silica, organo clay, silica, wax, urea, or a mixture thereof may be used.

In addition, the thickener may be included in the composition in an amount of 0.1 to 2 parts by weight, or 1 to 2 parts by weight based on 40 to 55 parts by weight of the acid-modified polyester-based resin. When the content of the thickener is less than 0.1 parts by weight, it may be difficult to control the viscosity of the undercoat composition, and when it exceeds 2 parts by weight, the coating workability is deteriorated or the appearance of the prepared coating film becomes poor due to the high viscosity of the undercoat composition. can

In addition, the curing accelerator serves to increase the curing reactivity of the undercoat composition. The curing accelerator may be used without particular limitation as long as it is a commonly known component, for example, dibutyltin dilaurate, dioctyltin dilaurate, dibutyltin bis(acetylacetonate), dibutyltin oxide, Dibutyltin maleate, dibutyltin octoate, dibutyltin dimaleate or mixtures thereof may be used.

Further, the curing accelerator may be included in the composition in an amount of 0.1 to 5 parts by weight, or 1 to 3 parts by weight based on 40 to 55 parts by weight of the acid-modified polyester-based resin. When the content of the curing accelerator is less than 0.1 parts by weight, it may be difficult to obtain the effect of increasing curing reactivity, and when it exceeds 5 parts by weight, curing reactivity becomes excessively high, and it may be difficult to secure paint workability and pot life.

hardener part

The undercoat composition according to the present invention may include the undercoat main part and the undercoat hardener part as described above.

The undercoat curing agent part may include an isocyanate resin. In this case, the curing agent part serves to cure the primer coating composition by cross-linking reaction with the components in the base coating main part. Specifically, the undercoat curing agent may cure the undercoat composition by forming a urethane bond by reacting the isocyanate group of the isocyanate resin with the hydroxyl groups of the components in the undercoat main part.

In addition, as the isocyanate resin, any conventional isocyanate resin that can be used as a curing agent for paints may be used without any particular limitation. For example, the isocyanate resin may be a hexamethylene diisocyanate (HMDI) type having excellent yellowing resistance and weather resistance, for example, an HMDI biuret type.

The undercoating composition may include the undercoat main part and the undercoat hardener part in a weight ratio of 10 to 25:1, or 15 to 20:1 by weight.

As described above, the undercoat composition according to the present invention can form a coating film excellent in various physical properties, such as adhesion, water resistance, weather resistance, high pressure car wash resistance, and chipping resistance, when coated on a plated surface of trivalent chromium. Therefore, the primer coating composition according to the present invention can be usefully used to paint trivalent chromium-plated automobile parts (eg, radiator grille, door handle, handle, center fascia, gearbox, etc.).

Hereinafter, the present invention will be described in more detail through examples. However, these examples are only for helping the understanding of the present invention, and the scope of the present invention is not limited to these examples in any sense.

[Example]

Preparation Examples 1 to 7. Preparation of acid-modified polyester-based resin

The first-stage monomers shown in Table 1 were put into a four-necked round flask, and a nitrogen gas tube, a packed column, an H-type separation tube, a stirrer, a thermometer, and a heater were installed. Thereafter, the temperature was raised to 230°C at a rate of 20°C per hour and maintained for 3 hours to obtain an intermediate reactant. Thereafter, a reflux solvent xylene (XL) was added to the intermediate reactant and refluxed at 230° C. to increase the molecular weight. During the reaction, the second-step monomer was added and reacted, cooled to room temperature, toluene and cyclohexanone were added in a weight ratio of 50:50, and diluted so that the viscosity at 25° C. was 900cps to obtain a polyester resin.

(parts by weight) manufacturing example One 2 3 4 5 6 7 Step 1 ethylene glycol 70 - 70 71 44 44 70 neopentyl glycol 210 110 210 112 - 62 230 methyl propanediol - 160 - - 96 97 - pentaerythritol - 20 - 5 - - - Butylethylpropanol - 50 - - - - - hexanediol 20 - 20 - 70 - 20 isophthalic acid - - - 144 148 75 - terephthalic acid 160 - 160 108 74 150 160 phthalic anhydride 140 360 140 - - 133 140 adipic acid 190 40 190 95 130 - 190 sebacic acid - 60 - - - - - tin catalyst 0.5 0.5 0.5 0.5 0.5 0.5 0.5 Step 2 phosphoric acid 20 20 20 20 13 sulfuric acid - - 20 - - - - nitric acid - - - 20 - - - Properties Acid value (mgKOH/g) 15 15 15 15 10 20 11 Number average molecular weight (g/mol) 8,000 8,500 8,500 8,000 7,000 12,000 7,500 Glass transition temperature (℃) 20 25 25 20 20 40 20

Preparation 8. Unmodified polyester-based resin

As raw materials, ethylene glycol (35g), neopentyl glycol (30g), butylethylpropanediol (290g), hexanediol (35g), terephthalic acid (140g), isophthalic acid (90g), phthalic anhydride (40g), adipic acid (160g) , and a tin catalyst (0.5 g) was used, and except that phosphoric acid was not added during the reaction, an unmodified polyester-based resin ester was obtained in the same manner as in Example 1.

The prepared polyester resin had an acid value (Av) of 5 mgKOH/g, a number average molecular weight (Mn) of 8,500 g/mol, and a glass transition temperature (Tg) of 25°C.

Examples 1 to 11 and Comparative Examples 1 to 4. Preparation of undercoat main part

Using the content of each component shown in Tables 2 and 3, the polyester resin, white pigment, black pigment, extender, dispersant and thickener were placed in a container and mixed at low speed using a stirrer. Then, it was dispersed using a ring mill disperser until the dispersed particle size became 20 μm. After that, when the dispersed particle size reached 20 μm, it was transferred to another container, and a curing accelerator, solvent 1 and solvent 2 were added and stirred for 30 minutes to prepare a base coating main part.

ingredient
(parts by weight) Example One 2 3 4 5 6 7 8 9 10 11 Preparation Example 1 48 - 52.5 - 24 42 - - - - Preparation Example 2 - 48 - 43.5 24 - - - - - - Preparation 3 - - - - - - 48 - - - - Preparation 4 - - - - - - - 48 - - - Production Example 5 - - - - - - - - 48 - - Preparation 6 - - - - - - - - - 48 - Preparation 7 48 black pigment 1.5 1.5 One 2 1.5 2.5 1.5 1.5 1.5 1.5 1.5 white pigment 6.5 6.5 4.5 8.5 6.5 8.5 6.5 6.5 6.5 6.5 6.5 extender pigment 6.5 6.5 4.5 8.5 6.5 6.5 6.5 6.5 6.5 6.5 6.5 dispersant 1.5 1.5 1.5 1.5 1.5 2 1.5 1.5 1.5 1.5 1.5 thickener 1.5 1.5 1.5 1.5 1.5 2 1.5 1.5 1.5 1.5 1.5 hardening accelerator 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 Solvent 1 28.5 28.5 28.5 28.5 28.5 28.5 28.5 28.5 28.5 28.5 28.5 Solvent 2 4.5 4.5 4.5 4.5 4.5 6.5 4.5 4.5 4.5 4.5 4.5 total 100 100 100 100 100 100 100 100 100 100 100

Ingredients (parts by weight) comparative example One 2 3 4 Preparation Example 1 37 - - - Preparation 3 - 57.5 - - Preparation 4 - - 37 - Preparation 8 - - - 48 black pigment 1.5 0.5 1.5 1.5 white pigment 7 2 7 6.5 extender pigment 17 2.5 17 6.5 dispersant 1.5 1.5 1.5 1.5 thickener 1.5 1.5 1.5 1.5 hardening accelerator 1.5 1.5 1.5 1.5 Solvent 1 28.5 28.5 28.5 28.5 Solvent 2 4.5 4.5 4.5 4.5 total 100 100 100 100

Hereinafter, manufacturers and product names, or component names, etc. of each component used in Comparative Examples and Examples are shown below.

- Black pigment: carbon black

- White pigment: titanium dioxide

- extender pigment: aluminum silicate

- Dispersant: BYK-170 (product name), BYK-Chemie GmbH (manufacturer)

- Thickener: Synthetic Silica (Product Name: AEROSIL R972, Manufacturer: EVONIK)

- Curing accelerator: dibutyltin dilaurate (DBTDL)

- Solvent 1: Toluene

- Solvent 2: Xylene

experimental example. Characteristics evaluation of the coating film

The undercoating main part prepared in Examples 1 to 11 and Comparative Examples 1 to 4 and a polyisocyanate-based curing agent (HDI Buiret type, manufacturer: COVESTRO, product name: ACU35541) were mixed in a weight ratio of 20:1, and diluted with a diluted thinner. A primer coating composition having a viscosity of Podcup #4 at 25° C. of 13 to 14 seconds was prepared.

Thereafter, the undercoat composition was coated on the plated surface plated with trivalent chromium (plating object: radiator grill) (dry film thickness: 10-14 μm) and dried at room temperature for 9 minutes to form a base coat.

Then, a base paint (product name: UT5721(F)-1999, manufacturer: KCC) was coated on the undercoat (dry film thickness: 20-30 μm) and dried at room temperature for 9 minutes to obtain a final coating film.

Thereafter, the physical properties of the undercoat film or the final coating film as described above were evaluated in the following manner, and the results are shown in Table 4 below. In this case, excellent is indicated by ◎, good is indicated by ○, normal is indicated by △, and bad is indicated by X.

(1) Appearance

After the undercoat composition was applied and dried at 70° C. for 30 minutes, the degree of bubbles, foreign substances, spots, grooves, and orange peel on the surface was visually evaluated. The test was repeated 6 times, and when passed 6 times, it was evaluated as excellent, when it passed 5 times, it was evaluated as good, when it passed 3 and 4 times, it was evaluated as normal, and when it passed 3 times or less, it was evaluated as bad. At this time, the pass condition is that there are no bubbles, foreign substances, spots and grooves, and there is no orange peel visually.

(2) Adhesiveness

The adhesion of the final coating film was evaluated based on the ASTM D3359 tape adhesion test method, the number of peeled parts among 100 scales of 1 mm X 1 mm (width X length) size. The test was repeated 6 times, and when passed 6 times, it was evaluated as excellent, when it passed 5 times, it was evaluated as good, when it passed 3 and 4 times, it was evaluated as normal, and when it passed 3 times or less, it was evaluated as bad. At this time, the pass condition was that the adhesion was M2.5 or more based on the standards described in ISO 2409.

(3) water resistance

After immersing the final coating film in a 40 ℃ constant temperature bath for 10 days, the adhesion and appearance evaluation of the above item (2) was performed, and the test was repeated 6 times, excellent if passed 6 times, good if passed 5 times In the case of passing 3 times and 4 times, it was evaluated as normal, and when it passed 3 times or less, it was evaluated as poor. At this time, as for the passing conditions, it was determined visually that adhesion was M2.5 or more and there was no swelling, cracking, and discoloration of the coating film.

(4) moisture resistance

After leaving the final coating film under conditions of 50±2° C. and 95±2% relative humidity for 10 days, moisture was removed from the final coating film by air blow. After leaving it at room temperature for 1 hour, the appearance and adhesion were evaluated and confirmed, and the adhesion was performed in the same manner as in the above item (2). The test was repeated 6 times, and when passed 6 times, it was evaluated as excellent, when it passed 5 times, it was evaluated as good, when it passed 3 and 4 times, it was evaluated as normal, and when it passed 3 times or less, it was evaluated as bad. At this time, as for the passing conditions, it was determined visually that adhesion was M2.5 or more and there was no swelling, cracking, and discoloration of the coating film.

(5) heat resistance

After leaving the final coating film in an oven at 80° C. for 300 hours, adhesion and appearance were evaluated, and the adhesion was performed in the same manner as in item (2). The test was repeated 6 times, and when passed 6 times, it was evaluated as excellent, when it passed 5 times, it was evaluated as good, when it passed 3 and 4 times, it was evaluated as normal, and when it passed 3 times or less, it was evaluated as bad. At this time, as for the passing conditions, it was determined visually that adhesion was M2.5 or more and there was no swelling, cracking, and discoloration of the coating film.

(6) Heat resistance cycle test

The final coating film was treated at 80±2℃ for 3 hours, at room temperature for 1 hour, at -40±2℃ for 3 hours, at room temperature for 1 hour, at 50±2℃ and 95±2% relative humidity for 7 hours, And after 1 hour treatment at room temperature, repeated heat treatment for a total of 5 times, and then left at room temperature for 1 hour, the appearance and adhesion of the final coating film were evaluated. The adhesion was performed in the same manner as in item (2), and the test was repeated 6 times. As for the evaluation criteria, if it passed 6 times, it was evaluated as excellent, if it passed 5 times, it was good, if it passed 3 times and 4 times, it was evaluated as average, and if it passed 3 times or less, it was evaluated as bad. At this time, as for the passing conditions, it was determined visually that adhesion was M2.5 or more and there was no swelling, cracking, and discoloration of the coating film.

(7) Salt spray resistance

The final coating was sprayed for 240 hours according to the spray conditions (35±2℃ and 95% relative humidity, spray amount: 0.5~3.0ml/h, saline solution concentration: 5±1w/v%, brine solution pH: 6.5~7.2). After that, it was washed with water to remove moisture. After leaving it at room temperature for 1 hour, the appearance and adhesion of the coating film were evaluated. The adhesion was performed in the same manner as in item (2), and the test was repeated 6 times. As for the evaluation criteria, if it passed 6 times, it was evaluated as excellent, if it passed 5 times, it was good, if it passed 3 times and 4 times, it was evaluated as average, and if it passed 3 times or less, it was evaluated as bad. At this time, as for the passing conditions, it was determined visually that adhesion was M2.5 or more and there was no swelling, cracking, and discoloration of the coating film.

(8) acid resistance

After dropping 0.2 ㎖ of 0.1N aqueous sulfuric acid solution on the surface of the final coating film, leave it at room temperature for 24 hours, wash with water, remove moisture from the surface by air blow, and then leave it at room temperature for 1 hour, and then check the appearance of the final coating film. It was observed to evaluate the acid resistance. The test was repeated 6 times, and when passed 6 times, it was evaluated as excellent, when it passed 5 times, it was evaluated as good, when it passed 3 and 4 times, it was evaluated as normal, and when it passed 3 times or less, it was evaluated as bad. In this case, the pass condition was determined to be grade 3 or higher on a gray scale (KSK 0910). At this time, as for the gray scale, grade 5 was judged as no contamination, grade 3 as normal, and grade 2 as contamination.

(9) alkali resistance

Alkali resistance was evaluated in the same manner as in item (8), except that 0.1N sodium hydroxide aqueous solution was used instead of sulfuric acid aqueous solution.

(10) Weather resistance

Appearance and adhesion of the coating film were evaluated after exposure to an energy of 2500 kJ in a xenon weatherometer tester environment, and the adhesion was performed in the same manner as in item (2), and the test was repeated 6 times. As for the evaluation criteria, if it passed 6 times, it was evaluated as excellent, if it passed 5 times, it was good, if it passed 3 times and 4 times, it was evaluated as average, and if it passed 3 times or less, it was evaluated as bad. At this time, as for the passing conditions, it was determined visually that adhesion was M2.5 or more and there was no swelling, cracking, and discoloration of the coating film.

(11) High pressure car washability

Using a high-pressure car wash tester, high-pressure water was sprayed on the final coating film from a distance of 10 cm at a pressure of 70 kgf, and the degree of peeling of the coating film was evaluated. The test was repeated 6 times, and when passed 6 times, it was evaluated as excellent, when it passed 5 times, it was evaluated as good, when it passed 3 and 4 times, it was evaluated as normal, and when it passed 3 times or less, it was evaluated as bad. At this time, the pass condition was based on the adhesiveness of M2.5 or more.

(12) Chipping resistance

After firing 50 g of zeolite at an angle of 45°, a pressure of 4.0 kgf and a distance of 100 mm from the final coating at room temperature, the degree of indentation on the surface of the final coating was evaluated. The test was repeated 6 times, and when passed 6 times, it was evaluated as excellent, when it passed 5 times, it was evaluated as good, when it passed 3 and 4 times, it was evaluated as normal, and when it passed 3 times or less, it was evaluated as bad. At this time, the pass condition was based on the occurrence of two or less marks of 2 mm or more on the surface of the final coating film.

ingredient Example comparative example One 2 3 4 5 6 7 8 9 10 11 One 2 3 4 Exterior ◎ ◎ ◎ ◎ ◎ ○ ○ ○ ◎ ◎ ◎ △ △ X ○ adherence ◎ ◎ ◎ ◎ ◎ ○ ○ ◎ ◎ ◎ ○ ○ ○ △ X water resistance ◎ ◎ ◎ ○ ◎ ◎ ◎ ○ ◎ ◎ ○ △ △ X X moisture resistance ◎ ◎ ◎ ◎ ◎ ○ ○ ◎ ◎ ◎ ○ ○ ○ △ X heat resistance ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ○ ○ △ X heat cycle resistance ◎ ◎ ◎ ○ ◎ ◎ ○ ○ ◎ ◎ ○ △ △ X X Salt spray resistance ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ○ ○ ○ △ X acid resistance ◎ ◎ ◎ ○ ◎ ◎ ○ ○ ◎ ◎ ◎ △ △ X ○ alkali resistance ◎ ◎ ◎ ○ ◎ ◎ ○ ○ ◎ ◎ ◎ △ △ X ○ weather resistance ◎ ◎ ◎ ◎ ◎ ○ ○ ◎ ◎ ◎ ◎ ○ ○ △ X high pressure car wash ◎ ◎ ◎ ○ ◎ ◎ ◎ ○ ◎ ◎ ◎ ○ ○ △ X Chipping resistance ◎ ◎ ◎ ◎ ◎ ○ ○ ○ ◎ ◎ ◎ ○ ○ △ ○

As shown in Table 4, the final coating film prepared from the compositions of Examples 1 to 11 had adhesion, moisture resistance, heat resistance, heat cycle resistance, salt spray resistance, acid resistance, alkali resistance, weather resistance, high pressure car wash resistance and chipping resistance. It was found that all of the physical properties were excellent.

Claims (4)

40 to 55 parts by weight of an acid-modified polyester-based resin, 3 to 25 parts by weight of a pigment, and 25 to 40 parts by weight of a solvent,
The acid-modified polyester-based resin is a polyester-based resin modified with an inorganic acid containing at least one selected from the group consisting of sulfuric acid, nitric acid, phosphoric acid and carbonic acid,
The acid content of the acid-modified polyester-based resin is 1 to 5 parts by weight based on 100 parts by weight of the acid-modified polyester-based resin. The method according to claim 1,
The acid-modified polyester-based resin is a polyester-based resin prepared by reacting the polyfunctional alcohol so that the equivalent ratio of the hydroxyl value of the polyfunctional alcohol to the carboxyl group of the acid compound is 1.02:1 to 1.10:1 and then modifying it with an acid. The method according to claim 1,
The acid-modified polyester-based resin has an acid value of 5 to 30 mgKOH/g, a number average molecular weight of 5,000 to 15,000 g/mol, and a glass transition temperature of 10 to 50° C., a base coating composition. delete