KR102310381B1 - Primer coating composition for coating of chromium plating - Google Patents

Abstract

The present invention provides a primer coating composition for chrome plating comprising 30 to 60 parts by weight of a linear polyester resin, 10 to 30 parts by weight of a pigment, and 0.5 to 4 parts by weight of a phosphoric acid-based adhesion promoter, and a coating layer formed from the coating composition. It relates to vehicle parts that do.

Description

Undercoat composition for chrome plating coating {PRIMER COATING COMPOSITION FOR COATING OF CHROMIUM PLATING}

The present invention relates to a primer coating composition having excellent adhesion when painting on a chrome-plated surface, and having excellent water resistance, high pressure car wash resistance, chipping resistance and heat resistance.

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, when a conventional base paint for a hexavalent chromium plated surface is applied to a plated surface plated with trivalent chromium, the adhesion between the coating film and the plated surface is insufficient, and the coating film's water resistance, weather resistance, high pressure car wash resistance, chipping resistance, etc. There is also a limit to poor physical properties. 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 primer coating composition for chrome plating coating comprising 30 to 60 parts by weight of a linear polyester resin, 10 to 30 parts by weight of a pigment, and 0.5 to 4 parts by weight of a phosphoric acid-based adhesion promoter.

In addition, the present invention is a chrome-plated vehicle parts; and

Including; a coating layer formed on the chrome plating surface of the vehicle part;

The coating layer is formed from the undercoat composition for the chrome plating coating, and provides a vehicle part.

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 primer coating composition for chrome plating according to the present invention is applied to the trivalent chrome plating surface, the adhesion to the chrome plating surface is excellent, and the water resistance, weather resistance, high pressure car wash resistance, chipping resistance, Various physical properties such as heat resistance are excellent. 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, for example, it can be measured by a GPC (gel permeation chromatograph) method. Furthermore, the "glass transition temperature" is measured by a conventional method known in the art, for example, it can be measured 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 for chrome plating coating

The undercoat composition for chrome plating coating according to the present invention includes a linear polyester resin, a pigment, and a phosphoric acid-based adhesion promoter.

linear polyester resin

The linear polyester resin plays a role in improving the physical properties of the coating film, such as adhesion, high-pressure car washing, and chipping resistance.

The composition according to the present invention includes a linear polyester resin, and has excellent chipping resistance and adhesion and excellent workability than a composition including a branched polyester resin.

The linear polyester resin may be used without any particular limitation as long as it is typically included in the coating composition, and for example, may be prepared by reacting an organic acid with an alcohol compound. In this case, the linear polyester resin may be prepared by reacting so that the equivalent ratio of the hydroxyl group of the alcohol compound and the carboxyl group of the organic acid is 1.02:1 to 1.10:1, and then modifying it with an acid. At this time, the reaction may be carried out at 200 to 250 °C, or 210 to 230 °C.

The alcohol compound may be a compound containing 1 to 4 or 1 to 3 hydroxyl groups, for example, neopentyl glycol, trimethylolpropane, ethylene glycol, pentaerythritol, hexanediol, butylethylpropanediol ( BEPD) and cyclohexanedimethanol (CHDM) may include at least one selected from the group consisting of. 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), phthalic anhydride, and adipic acid. .

In addition, the linear polyester resin has a number average molecular weight (Mn) of 10,000 to 30,000 g/mol, or 15,000 to 20,000 g/mol, and a glass transition temperature (Tg) of 10 to 50 ° C., or 10 to 30 ° C., The viscosity at 25° C. may be 1,000 to 2,800 cps, or 1,300 to 2,300 cps.

When the number average molecular weight of the linear polyester resin is within the above range, the chipping resistance of the prepared coating film is excellent, and when it is out of the above range, the chipping resistance and water adhesion resistance of the prepared coating film may be deteriorated. In addition, when the glass transition temperature of the linear polyester resin is within the above range, the workability of the composition and the 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 lowered. can be In addition, when the viscosity at 25° C. of the linear polyester resin is within the above range, the adhesion and chipping resistance of the coating film may be improved, and if the viscosity is outside the above range, the chipping resistance may be reduced.

The resin of the linear polyester resin may have an acid value (Av) of 1 to 5 mgKOH/g, and a hydroxyl value (OHv) of 1 to 10 mgKOH/g. When the acid value and the hydroxyl value of the acid-modified polyester-based resin are out of the above ranges, adhesion and water resistance of the composition may be reduced.

In addition, the linear polyester resin may be included in the composition in an amount of 30 to 60 parts by weight, or 35 to 55 parts by weight based on 10 to 30 parts by weight of the pigment. When the content of the linear polyester resin is less than the above range, the wettability of the composition to the chrome-plated material is insufficient or the stability of the coating film is insufficient. . In addition, when the content of the linear polyester resin exceeds the above range, the drying property of the composition is insufficient or the water resistance of the prepared coating film is insufficient, and the water resistance and chipping resistance of the prepared coating film are insufficient, or the coating workability is insufficient. may occur.

pigment

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

The pigment may be, for example, a hydrophobic pigment including 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 include a black pigment, a white pigment, or a mixture thereof. In addition, the color pigment may include pigments such as blue, red, yellow, and violet.

In addition, the color pigment may be included in the composition in an amount of 3 to 20 parts by weight, or 5 to 15 parts by weight based on 30 to 60 parts by weight of the linear polyester 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 7 parts by weight, or 1 to 4 parts by weight based on 30 to 60 parts by weight of the linear polyester resin. When the content of the black pigment is less than the content range, it may be difficult to impart a required color to the coating film. can be

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 13 parts by weight, or 4 to 11 parts by weight based on 30 to 60 parts by weight of the linear polyester resin. If the content of the white pigment is less than the above range, it may be difficult to impart a required color to the coating film or the water resistance of the coating film may be reduced. have.

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

The extender pigment may be included in the composition in an amount of 1 to 15 parts by weight, or 4 to 11 parts by weight based on 30 to 60 parts by weight of the linear polyester resin. When the content of the extender pigment is less than the above range, the strength of the coating film may be reduced.

In addition, the pigment may be 10 to 30 parts by weight, or 14 to 25 parts by weight based on 30 to 60 parts by weight of the linear polyester resin. When the content of the pigment is less than the above range, the dryness of the composition is insufficient or the water resistance of the prepared coating film is insufficient, so that the water resistance and chipping resistance of the prepared coating film are insufficient. In addition, when the above range of the pigment is exceeded, the wettability of the composition to the chrome-plated material is insufficient or the stability of the coating film is insufficient.

Phosphoric Acid Adhesion Enhancer

The phosphoric acid-based adhesion enhancer serves to enhance the adhesion of the composition.

The phosphoric acid-based adhesion enhancer may include at least one selected from the group consisting of phosphoric acid-based acrylic, phosphoric acid-based polyester, phosphoric acid-based polyether, phosphoric acid-based epoxy, and phosphoric acid. In this case, the phosphoric acid-based acrylic, phosphoric acid-based polyester, phosphoric acid-based polyether, and phosphoric acid-based epoxy mean a phosphoric acid-modified acrylic resin, a phosphoric acid-modified polyester, a phosphoric acid-modified polyether, or an impression-modified epoxy, respectively.

In addition, the phosphoric acid-based adhesion enhancer has a number average molecular weight (Mn) of 300 to 1,000 g/mol, or 600 to 900 g/mol, and the viscosity measured by a Brookfield viscometer at 25° C. is 3,700 to 200,000 cps, The density may be 0.98 to 1.12 g/cm ³ , and the acid value (Av) may be 30 to 80 mgKOH/g, or 35 to 55 mgKOH/g. When the physical properties of the phosphoric acid-based adhesion promoter are within the above range, storage stability and etching effect are improved.

The phosphoric acid-based adhesion promoter may be 0.5 to 4 parts by weight, or 1 to 3 parts by weight based on 30 to 60 parts by weight of the linear polyester resin. When the content of the phosphoric acid-based adhesion enhancer is less than the above range, the surface etching of the chrome-plated base material is insufficient, and thus, there may be a problem of insufficient physical properties such as water resistance, moisture resistance, and high pressure car washability of the prepared coating film. In addition, when the content of the phosphoric acid-based adhesion enhancer exceeds the above range, the curing reaction of the composition is delayed, so that the water resistance, moisture resistance, and chipping resistance of the prepared coating film are insufficient.

solvent

The solvent controls the viscosity and dispersibility of the undercoat composition and serves 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 20 to 50 parts by weight, or 24 to 40 parts by weight based on 30 to 60 parts by weight of the linear polyester resin. When the content of the solvent is within the above range, it is possible to prevent the problems of difficulty in controlling the viscosity of the undercoat composition or of lowering the dispersibility, and the problems of poor appearance of the prepared coating film or a long time being consumed for the formation of the coating film. .

additive

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

The additive may be included in the composition in an amount of 1 to 10 parts by weight, or 3 to 8 parts by weight based on 30 to 60 parts by weight of the linear polyester resin.

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 4 parts by weight, or 1 to 3 parts by weight based on 30 to 60 parts by weight of the linear polyester resin. When the content of the dispersant is within the above range, problems in which the dispersibility of the undercoat composition is lowered and the high-pressure carwashing properties and chipping resistance of the coating film are lowered can be prevented.

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 4 parts by weight, or 1 to 3 parts by weight based on 30 to 60 parts by weight of the linear polyester resin. When the content of the thickener is within the above range, it is difficult to control the viscosity of the undercoat composition, and the problem of poor coating workability or poor appearance of the prepared coating film due to the high viscosity of the undercoat composition can be prevented.

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.

In addition, the curing accelerator may be included in the composition in an amount of 0.1 to 3 parts by weight, or 0.5 to 2.5 parts by weight based on 30 to 60 parts by weight of the linear polyester resin. When the content of the curing accelerator is out of the above range, it may be difficult to obtain an effect of increasing curing reactivity, and it may be difficult to secure painting workability and pot life because curing reactivity is excessively increased.

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 undercoat composition may include the main base part and the base hardener part in a weight ratio of 10 to 25:1, or 15 to 22:1 by weight.

The undercoat composition according to the present invention as described above can form a coating film having excellent various physical properties, such as adhesion, water resistance, weather resistance, high pressure car washing and chipping resistance, when coating on a plated surface of trivalent chromium or hexavalent chromium. . Therefore, the undercoat composition according to the present invention can be usefully used to paint automotive parts (eg, radiator grille, door handle, handle, center fascia, gearbox, etc.) plated with trivalent chromium or hexavalent chromium. .

vehicle parts

A vehicle component according to the present invention includes a chrome-plated vehicle component; and a coating layer formed on the chrome plating surface of the vehicle part.

The vehicle part may be one selected from the group consisting of a radiator grille, a door handle, a handle, a center fascia, a gearbox, a skid plate, a logo, a front molding, and a rear molding.

The chromium plating may be trivalent chromium. That is, the chromium-plated vehicle part may be a vehicle part plated with trivalent chromium.

The coating layer is formed from the undercoat composition for chrome plating coating, and for example, may have an average thickness of 14 μm or less, or 10 to 14 μm. When the coating layer is within the thickness range, it may exhibit proper adhesion to chrome-plated vehicle parts.

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]

Examples 1 to 11 and Comparative Examples 1 to 5. Preparation of coating composition

Using the content of each component shown in Tables 1 and 2, the polyester resin, white pigment, black pigment, extender, adhesion enhancer, dispersant and thickener were placed in a container and mixed 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.

Ingredients (parts by weight) Example One 2 3 4 5 6 7 8 9 10 11 Linear Polyester-1 40 - 21 - 40 20 - 35 50 55 40 Linear Polyester-2 - 40 21 - - - 25 - - - - Linear Polyester-3 - - - 41 - 20 15 - - - - black pigment 2.5 2.5 2.5 2.5 2.5 2.5 2.5 3.5 2.8 1.96 2.5 white pigment 7.5 7.5 7.5 7.5 7.5 7.5 7.5 10.5 8.4 5.88 7.5 extender pigment 7.5 7.5 7.5 7.5 7.5 7.5 7.5 11 8.8 6.16 7.5 dispersant 2 2 2 2 2 2 2 1.5 1.5 1.5 2 thickener 2 2 2 2 2 2 2 1.5 1.5 1.5 2 hardening accelerator 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 2.5 1.5 Adhesion enhancer-1 2 2 2 One - 3 3 One One One - Adhesion enhancer-2 - - - - - - - - - - 2 Adhesion enhancer-3 - - - - 3 - - - - - - Solvent-1 28.5 28.5 28.5 28.5 28.5 28.5 28.5 28 18.5 20 28.5 Solvent-2 6.5 6.5 4.5 6.5 5.5 5.5 5.5 6.5 6 4.5 6.5 total 100 100 100 100 100 100 100 100 100 100 100

Ingredients (parts by weight) comparative example One 2 3 4 5 Linear Polyester-1 27.5 65 40 40 - branched polyester - - - - 40 black pigment 3 One 2.5 2.5 2.5 white pigment 10 5 7.5 7.5 7.5 extender pigment 10 5 7.5 7.5 8.5 dispersant 3 One 2 2 2 thickener 3 One 2 2 2 hardening accelerator 1.5 One 1.5 1.5 2.5 Adhesion enhancer 1 2 3 - - - Adhesion enhancer 4 - - - 5 - Solvent-1 33.5 13.5 30.5 27.5 30.5 Solvent-2 6.5 4.5 6.5 4.5 4.5 total 100 100 100 100 100

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

Linear Polyester-1: Mn 15,000g/mol, Tg 11.5℃, viscosity 2,300cps at 25℃, acid value 5mgKOH/g, hydroxyl value 10mgKOH/g

Linear Polyester-2: Mn 17,000g/mol, Tg 22℃, viscosity at 25℃ 1,900cps, acid value 1mgKOH/g, hydroxyl value 3mgKOH/g

Linear Polyester-3: Mn 20,000g/mol, Tg 27.8℃, viscosity at 25℃ 1,400cps, acid value 3mgKOH/g, hydroxyl value 7mgKOH/g

Branched polyester: Mn 18,500g/mol, Tg 23℃, viscosity 2,000cps at 25℃, acid value 10mgKOH/g

Black Pigment: Carbon Black

White Pigment: Titanium Dioxide

Extender pigment: BASF, ALIMINIUM SILICATE ASP-200 Cube

Dispersant: BYK, BYK 170

Thickener: EVONIC, AEROSIL R-972 Cube

Hardening accelerator: FTC-KOREA, DBTDL (Dibutyltin dilaurate)

Adhesion Enhancer-1: Phosphoric acid-modified epoxy (NV: 65% by weight, viscosity at 25°C: 11,200cps, Av: 55mgKOH/g, flash point: 38°C, density at 25°C: 1.08 g/cm ³ )

Adhesion Enhancer-2: Phosphoric acid-modified polyester (NV: 55.3% by weight, viscosity at 25°C: 3,700cps, Av: 50mgKOH/g, flash point: 58°C, density at 25°C: 1.10 g/cm ³ )

Adhesion Enhancer-3: Phosphoric acid-modified polyester (NV: 65% by weight, viscosity at 25°C: 15,500 cps, AV: 38 mgKOH/g, flash point: 32°C, density at 25°C: 0.99 g/cm ³ )

Adhesion enhancer-4: Shin-Etsu Silicone, KBM-403

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 5 and a polyisocyanate-based curing agent (HM DI Buiret type, manufacturer: COVESTRO, product name: ACU35541) were mixed in a weight ratio of 20:1, and diluted with a diluted thinner Thus, a primer coating composition having a viscosity of Pod Cup #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: 25-35 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 Tables 3 and 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 if it passed 6 times, it was evaluated as excellent, if it passed 5 times, it was evaluated as good, if it passed 3 or 4 times, it was evaluated as normal, and if it passed less than 3 times, 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 mmX1 mm (width X length) size. The test was repeated 6 times, and if it passed 6 times, it was evaluated as excellent, if it passed 5 times, it was evaluated as good, if it passed 3 or 4 times, it was evaluated as normal, and if it passed less than 3 times, 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 or 4 times, it was evaluated as normal, and if it passed less than 3 times, 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 if it passed 6 times, it was evaluated as excellent, if it passed 5 times, it was evaluated as good, if it passed 3 or 4 times, it was evaluated as normal, and if it passed less than 3 times, 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 if it passed 6 times, it was evaluated as excellent, if it passed 5 times, it was evaluated as good, if it passed 3 or 4 times, it was evaluated as normal, and if it passed less than 3 times, 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 resistant cycle

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 or 4 times, it was evaluated as normal, and if it passed less than 3 times, 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

Spray on the final film 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±1 w/v%, brine solution pH: 6.5~7.2) After that, it was washed with water and moisture was removed. 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 or 4 times, it was evaluated as normal, and if it passed less than 3 times, 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 if it passed 6 times, it was evaluated as excellent, if it passed 5 times, it was evaluated as good, if it passed 3 or 4 times, it was evaluated as normal, and if it passed less than 3 times, 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 at 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 if it passed 6 times, it was evaluated as excellent, if it passed 5 times, it was evaluated as good, if it passed 3 or 4 times, it was evaluated as normal, and if it passed less than 3 times, 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 if it passed 6 times, it was evaluated as excellent, if it passed 5 times, it was evaluated as good, if it passed 3 or 4 times, it was evaluated as normal, and if it passed less than 3 times, 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 One 2 3 4 5 6 7 8 9 10 11 Exterior ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ○ ○ ◎ adherence ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ water resistance ◎ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ moisture resistance ◎ ◎ ◎ ◎ ◎ ○ ○ ○ ○ ○ ○ heat resistance ◎ ◎ ◎ ◎ ◎ ◎ ○ ◎ ○ ◎ ◎ heat cycle resistance ◎ ◎ ◎ ○ ◎ ◎ ◎ ○ ○ ◎ ○ Salt spray resistance ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ acid resistance ◎ ◎ ◎ ◎ ◎ ◎ ○ ○ ◎ ◎ ○ alkali resistance ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ weather resistance ◎ ◎ ◎ ◎ ◎ ○ ○ ○ ○ ○ ○ high pressure car wash ◎ ◎ ◎ ○ ◎ ◎ ○ ◎ ○ ○ ○ Chipping resistance ◎ ◎ ◎ ◎ ○ ○ ○ ○ ○ ○ ○ note pass pass pass pass pass pass pass pass pass pass pass

ingredient comparative example One 2 3 4 5 Exterior △ ◎ ○ ◎ ○ adherence ○ △ ○ ○ ○ water resistance X X X X X moisture resistance ○ △ X △ △ heat resistance ○ ○ △ ○ ○ heat cycle resistance △ △ ○ ○ △ Salt spray resistance ○ ○ ○ ○ ○ acid resistance △ △ △ △ ◎ alkali resistance ○ △ ○ X ◎ weather resistance ○ △ △ △ ○ high pressure car wash △ △ △ X ○ Chipping resistance ○ △ ○ △ △ note fail fail fail fail fail

As shown in Table 3, the final coating film prepared from the compositions of Examples 1 to 11 had adhesion, water resistance, moisture resistance, heat resistance, heat cycle resistance, salt spray resistance, acid resistance, alkali resistance, weather resistance, high pressure car wash resistance and It was found that all physical properties such as chipping resistance were excellent.

On the other hand, as shown in Table 4, Comparative Examples 1 and 2 containing a small amount or an excessive amount of the linear polyester resin lacked water resistance, heat cycle resistance, acid resistance and high pressure car wash resistance. In addition, Comparative Example 3, which does not include a phosphoric acid-based adhesion promoter, lacked water resistance, moisture resistance, heat resistance, acid resistance, weather resistance, and high-pressure car washing properties. Furthermore, Comparative Example 4 including a silane-based adhesion enhancer not including a phosphoric acid group lacked water resistance, moisture resistance, acid resistance, alkali resistance, weather resistance, high pressure car wash resistance and chipping resistance. In addition, Comparative Example 5 including the branched polyester resin and not including the adhesion promoter was insufficient in water resistance, moisture resistance, heat cycle resistance and chipping resistance.

Claims (7)

30 to 60 parts by weight of a linear polyester resin, 10 to 30 parts by weight of a pigment, and 0.5 to 4 parts by weight of a phosphoric acid-based adhesion promoter,
The phosphoric acid-based adhesion enhancer includes at least one selected from the group consisting of phosphoric acid-based acrylic, phosphoric acid-based polyester, phosphoric acid-based polyether, phosphoric acid-based epoxy, and phosphoric acid,
The phosphoric acid-based adhesion enhancer has a number average molecular weight of 300 to 1,000 g/mol and an acid value of 30 to 80 mgKOH/g, a base coating composition for chrome plating coating. The method according to claim 1,
The linear polyester resin has a number average molecular weight of 10,000 to 30,000 g/mol, a glass transition temperature of 10 to 50 °C, and a viscosity at 25 °C of 1,000 to 2,800 cps, a base coat composition for chrome plating coating. delete delete chrome plated vehicle parts; and
Including; a coating layer formed on the chrome plating surface of the vehicle part;
The coating layer is formed from the primer coating composition for a chrome plating coating of claim 1 or 2, a vehicle part. 6. The method of claim 5,
The chromium plating is trivalent chromium plating. 6. The method of claim 5,
The vehicle part is one selected from the group consisting of a radiator grille, a door handle, a handle, a center fascia, a gearbox, a skid plate, a logo, a front molding, and a rear molding.