KR20110087024A - Aqueous coating composition for painting nonferrous metal substrate, and method of fabricating nonferrous metal case using the same - Google Patents

Abstract

PURPOSE: An aqueous coating composition for painting nonferrous metal substrates is provided to form a coating film which does not generate volatile organic compounds while preventing the lowering of properties. CONSTITUTION: An aqueous coating composition for painting nonferrous metal substrates includes 100 parts by weight of a water-dispersible polyurethane-acryl resin, 0.1~100.0 parts by weight of a cross-linking agent, and 0.1~10 parts by weight of additives. The water-dispersible polyurethane-acryl resin is a negative ion type including a carboxylic acid group. A method for manufacturing the aqueous coating composition for painting nonferrous metal substrates comprises the steps of: forming an undercoating layer(13) on the nonferrous metal substrate using the aqueous coating composition; and forming a top coating layer on the undercoating layer.

Description

Aqueous coating composition for painting nonferrous metal substrate, and method of fabricating nonferrous metal case using the same}

The present invention relates to an aqueous coating composition, and more particularly to an aqueous coating composition for non-ferrous metal coating.

Non-ferrous metal is a metal other than iron, for example, magnesium, aluminum, etc. have been applied in various ways for light and short reduction of the product in the field of electronic products such as portable terminals. Non-ferrous metals are an alternative material that overcomes the limitations of slimmer, lighter weight of existing plastic materials, and the scope of application is increasing. In 2010, the application rate is expected to increase by 50-60%. In addition, in order to protect the material and to realize various colors, a plurality of coating layers are formed on the nonferrous metal, for example, an undercoating color layer and a top coating layer.

Meanwhile, in recent years, as the use of volatile organic compounds (VOCs) is regulated worldwide, researches for converting existing oily coatings into aqueous coatings have been conducted in various industrial fields.

Accordingly, there is a need to form coating layers applied on such nonferrous metals using an aqueous coating agent.

The problem to be solved by the present invention is to provide a non-ferrous metal coating aqueous coating composition and a non-ferrous metal case manufacturing method using the same.

Technical problems of the present invention are not limited to the technical problems mentioned above, and other technical problems not mentioned will be clearly understood by those skilled in the art from the following description.

One aspect of the present invention to achieve the above object provides an aqueous coating composition for non-ferrous metal coating. The composition contains 100 parts by weight of the water-dispersed polyurethane-acryl dispersion, 0.1 to 100 parts by weight of the crosslinking agent, and 0.1 to 10 parts by weight of the additive.

Another aspect of the present invention to achieve the above object provides a method for producing a non-ferrous metal case. First, an undercoat layer is formed on a nonferrous metal substrate by using an aqueous coating composition containing 100 parts by weight of a water-dispersible polyurethane-acrylic resin, 0.1 to 100 parts by weight of a crosslinking agent, 0.1 to 100 parts by weight of a pigment, and 0.1 to 10 parts by weight of an additive. . A top coating layer is formed on the under coating layer.

According to the present invention, in the case of using a coating composition containing an oily resin by using a coating composition containing the water-dispersible polyurethane-acrylic resin as a base resin to form a coating film on a non-ferrous metal substrate, specifically, a magnesium substrate. Compared to the above, a coating film which does not generate volatile organic compounds (VOCs) without any deterioration in physical properties can be obtained.

Technical problems of the present invention are not limited to the technical problems mentioned above, and other technical problems not mentioned will be clearly understood by those skilled in the art from the following description.

1 is a cross-sectional view showing a non-ferrous metal case including a coating film formed using an aqueous coating composition according to an embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in more detail in order to describe the present invention in more detail. However, the present invention is not limited to the embodiments described herein but may be embodied in other forms.

Aqueous coating composition for nonferrous metal coating according to an embodiment of the present invention is 100 parts by weight of water-dispersed polyurethane-acryl dispersion, 0.1 to 100 parts by weight of crosslinking agent, and 0.1 to 10 parts by weight of additive based on solid content It contains.

The water-dispersible polyurethane-acrylic resin is a new material capable of forming a coating film using water as a solvent, and has excellent adhesion to non-ferrous metal substrates, particularly magnesium-based substrates, but also has excellent wear resistance and chemical resistance. Therefore, by using the coating composition containing the water-dispersible polyurethane-acrylic resin as a base resin to form a coating film on the magnesium-based substrate, physical properties are not lowered at all compared to the case of using the coating composition containing an oil-based resin. It is possible to obtain a coating film which does not generate a volatile organic compound (VOC).

Such a water-dispersible polyurethane-acrylic resin may be an anion type having a carboxylic acid group. The number average molecular weight (Mn) of the water-dispersed polyurethane-acrylic resin may be 100,000 to 1,000,000.

The water dispersion type polyurethane-acrylic resin may have an acid number of 10 to 20 mgKOH / g to exhibit excellent adhesion on a nonferrous metal substrate. In addition, the water-dispersed polyurethane-acrylic resin may have a tensile strength of 100 ~ 200% and a tensile strength of 3500 ~ 4500 N / ㎡ to have a suitable hardness in the state coated on a non-ferrous metal substrate.

The crosslinking agent may be polyaziridine, melamine resin, or a combination thereof. The polyaziridine or the melamine resin may crosslink the polyurethane-acrylic resin while forming an amino ester by reacting with a terminal carboxyl group of the water-dispersible polyurethane-acrylic resin. As a result, the hardness and the solvent resistance of the coating film can be improved.

In the case where the crosslinking agent is polyaziridine, considering the proper chemical resistance and hardness of the coating film, the polyaziridine may be contained in an amount of 0.1 to 10 parts by weight based on 100 parts by weight of the polyurethane-acrylic resin based on solid content. The polyaziridine may be pentaerythritol-tris- (β- (N-aziridinylpropionate) (Pentaerythritol-tris- (β- (N-aziridinyl) Propionate).

Preferably, the crosslinking agent may be a melamine resin having an excellent effect of improving hardness and solvent resistance of the coating film. In consideration of appropriate chemical resistance and hardness of the coating film, the melamine resin may be contained in an amount of 10 to 100 parts by weight, preferably 10 to 60 parts by weight, based on 100 parts by weight of the polyurethane-acrylic resin, based on solid content. The melamine resin is excellent in compatibility with the water-dispersed polyurethane-acrylic resin, it may be a methoxymethyl melamine resin that can lower the drying temperature and shorten the drying time.

In the case of using the melamine resin as a crosslinking agent, an acid catalyst may be further added. In this case, the drying temperature of the coating film of the polymer composition in which the melamine resin is added as a crosslinking agent can be lowered, and the drying time can be shortened. The acid catalyst may be a blocked organic acid, for example a blocked p-toluene sulfonic acid. The acid catalyst may be used in an amount of 0.2 to 5 parts by weight based on 100 parts by weight of the crosslinking agent.

The additive may be at least one selected from the group consisting of leveling agents, slip agents, defoamers, and neutralizing agents.

The smoothing agent is used to reduce the surface tension of the composition to improve the spreadability and appearance during painting, it may be a silicone-based or acetylene diol-based surfactant. In the case of the aqueous coating solution, since the surface tension of water is higher than that of the organic solvent, the wettability of the substrate to be coated may be poor. By adding the leveling agent, the wettability may be improved. Preferably the leveling agent is acetylene diol type 2,4,7,9-tetramethyl-5 dekin-4,7-diol (2,4,7,9-tetramethyl-5 decyne-4,7-diol) yl Can be. The leveling agent may be contained in 0.5 to 5 parts by weight based on 100 parts by weight of the polyurethane-acrylic resin solid content. If the content of the leveling agent is less than 0.5 parts by weight, there is a problem in that the coating solution is poorly adhered to the material because the wetting effect of the coating solution is lowered. have.

The slip agent is an additive for improving slip property of the coating film, and may be polyethylene wax. The slip agent may be contained in an amount of 0.5 to 5 parts by weight based on 100 parts by weight of the polyurethane-acrylic resin solid content.

The antifoaming agent is to improve workability by removing bubbles during preparation or coating of the composition, and may be an acetylene diolge material such as 2,4,7,9-tetramethyl-5 dekin-4,7-diol. The antifoaming agent may be contained in an amount of 0.1 to 5 parts by weight based on 100 parts by weight of the polyurethane-acrylic resin solid content.

The aqueous coating composition for nonferrous metal coating may further contain a pigment. The pigment may be contained in an amount of 0.1 to 100 parts by weight based on 100 parts by weight of the water-dispersible polyurethane-acrylic resin based on solid content. Such pigments may be used in paste form, i.e., materials in which the pigments are dispersed in a stable state on a solution. Specifically, the pigment may be an inorganic pigment such as titanium oxide, carbon black or iron oxide, or an organic pigment such as phthalocyanine blue, phthalocyanine green, or perylene red.

1 is a cross-sectional view showing a non-ferrous metal case including a coating film formed using an aqueous coating composition according to an embodiment of the present invention.

Referring to FIG. 1, an undercoat layer 13 is formed by applying an aqueous coating composition on a nonferrous metal substrate 10. The nonferrous metal substrate 10 may be a magnesium substrate. The magnesium substrate may be a substrate suitable for an electronic case, in particular a mobile phone case.

The aqueous coating composition for forming the undercoat 13 is 100 parts by weight of water-dispersed polyurethane-acryl dispersion, 0.1 to 100 parts by weight of crosslinking agent, 0.1 to 100 parts by weight of pigment, and based on solid content It may contain 0.1 to 10 parts by weight of the additive. Detailed description of each component will be referred to the above description.

The undercoat 13 may be formed using a spray coating technique. The undercoat 13 may be hot air dried. This drying process takes 15 to 30 minutes, considering the throughput. To this end, the undercoat 13 may be dried at 150 ℃ or more.

The undercoat 13 may have a thickness of 5 μm or more in consideration of reliability. In addition, the undercoat 13 may have a thickness of 5 ~ 15㎛. When the undercoat 13 has a thickness of more than 15 μm, it is not preferable because the drying time may be increased to reduce the throughput.

The top coating layer 15 is formed on the under coating layer 13. The top coating layer 15 may be formed using a top coating solution. The top coating solution may be a composition excluding a pigment in the aqueous coating composition forming the undercoat 13, and may be a composition in which a silica-based quencher is further added to control gloss. The matting agent may be contained in an amount of 0.1 to 10 parts by weight based on 100 parts by weight of the water-dispersible polyurethane-acrylic resin based on solid content. The top coating layer 15 may also be formed using a spray coating method, the thickness after drying may be 20 ~ 25 ㎛.

Hereinafter, preferred examples are provided to aid the understanding of the present invention. However, the following experimental examples are only for helping understanding of the present invention, and the present invention is not limited to the following experimental examples.

Experimental Examples; examples>

Under Of coating film Adhesion  evaluation

<Manufacture example 1>

As the base resin, 5 g of a water-dispersible polyurethane-acrylic copolymer resin, 0.5 g of a silver paste as a pigment, and 0.05 g of polyaziridine were placed in 10 ml of distilled water and sonicated for several minutes to prepare an undercoating solution. The undercoating solution was coated on a magnesium substrate injection molding using a spray coating method to form an undercoating film. The undercoating film was hot air dried at 150 ° C. for 30 minutes. The thickness of the coating film after drying was about 7 μm.

Comparative Example 1

A coating film was formed under the same conditions as Preparation Example 1, except that an aliphatic polyester type water dispersible polyurethane resin was used as the base resin.

Comparative Example 2

A coating film was formed under the same conditions as in Preparation Example 1, except that an acrylic emulsion was used as the base resin.

Comparative Example 3

A coating film was formed under the same conditions as in Preparation Example 1, except that a polyurethane resin of water-dispersible aliphatic poly (carbonate-diol) system was used as the base resin.

After forming 100 checkered cells by cross-cutting at intervals of 1 mm on the coating films formed through Preparation Examples 1 and 2 and Comparative Examples 1 and 2, the adhesive films were separated from the substrate. The number of cells to be investigated.

The results according to the adhesion evaluation examples are shown in Table 1 below.

Preparation Example 1 Comparative Example 1 Comparative Example 2 Comparative Example 3 Base resin Water Dispersible Polyurethane-Acrylic Copolymer Water Dispersed Polyurethane Resin Acrylic emulsion Water Dispersed Polyurethane Resin type - Aliphatic polyester - Aliphatic poly (carbonate-diol) Particle charge state Negative ion Negative ion - Negative ion Particle size - - - Colloid Solid content (%) 40 36 42 35 PH (25 ℃) 8.0 8.0 8.0 8.0 Viscosity (25 ° C, mPa.s) 150 350 200 100 MFFT (℃) - - 55 - Tensile Strength (N / ㎡) 4,000 6400 - 4,500 kidney(%) 120 250 - 160 Acid value (mg, @ KOH, 1g) 12 - - - Adhesion
(The number of US departures / 100) 80/100 70/100 20/100 50/100 Minimum Film Forming Temperature (MFFT) = Minimum Temperature

Referring to Table 1, 20 cells were separated in Preparation Example 1. On the other hand, 30 cells were separated in Comparative Example 1 using a polyurethane resin, and 80 cells were removed in Comparative Example 2 using an acrylic copolymer emulsion, and an aliphatic poly (carbonate-diol) -based polyurethane resin was used. In Comparative Example 3, 50 cells were separated. As such, the coating film containing the water-dispersible acrylic-urethane copolymer resin as the base resin is shown to be very excellent in adhesion with the nonferrous metal substrate, specifically, the magnesium substrate.

Crosslinking agent  Under with or without Coating film  Property evaluation

<Manufacture example 2>

A coating film was formed under the same conditions as in Preparation Example 1, except that 0.4 g (solid content of 80 wt%) of methoxymethyl melamine (L073, BASF, Germany) was added instead of 0.05 g of polyaziridine as a crosslinking agent.

<Comparative Example 4>

Except not using a crosslinking agent, a coating film was formed under the same conditions as Preparation Example 1.

<Hot resistance test>

Substrates having the coating films formed through Preparation Examples 1 and 2, and Comparative Example 4 were immersed in warm water at 80 ° C. for 60 minutes and then taken out, and then tested to see if the coating film was released from the substrate using an adhesive tape.

<RCA Abrasion Test>

After rubbing 500 times of 275 g of paper on the coating films formed through Preparation Examples 1 and 2, and Comparative Example 4 using the RCA wear tester, the state of the coating films was examined.

Resistant Cosmetic Test

After applying ultraviolet cream on the coating films formed through Preparation Examples 1 and 2, and Comparative Example 4, and left for 24 hours in a chamber maintained at 60 ℃, 90% humidity and then taken out, using an adhesive tape It was tested whether the coating film deviated from the substrate.

Table 3 shows the peeling of the coating film according to the hot water resistance test, RCA abrasion test, and the cosmetic test for the coating film according to Preparation Examples 1 and 2, and Comparative Example 4.

Preparation Example 1 Production Example 2 Comparative Example 4 Crosslinker conditions Polyaziridine  Methoxymethyl melamine none Hot water resistance test ○ X ○ RCA Abrasion Test ○ X ○ Resistant Cosmetic Test ○ X ○ ○: coating film peeling occurs, X: coating film peeling does not occur

Referring to Table 2, coating films formed using a coating solution containing polyaziridine as a crosslinking agent (Preparation Example 1) and coating films formed using a coating solution not containing a crosslinking agent (Comparative Example 4) The coating film was completely peeled off by the hot water test, the RCA abrasion test and the cosmetic test. On the other hand, in the coating film formed using methoxymethyl melamine as in Preparation Example 2, neither peeling of RCA wear resistance, hot water resistance and cosmetics occurred. From these results, it can be seen that when methoxymethyl melamine is used as the curing agent, the hot water resistance, the RCA wear resistance and the cosmetic properties of the coating film formed on the magnesium substrate are satisfactory.

Under Coating film  According to the thickness after drying Coating film  Property evaluation

<Manufacture example 3>

A coating film was formed under the same conditions as Preparation Example 2, except that the thickness of the coating film after drying was 3 μm.

&Lt; Preparation Example 4 &

A coating film was formed under the same conditions as Preparation Example 2, except that the thickness of the coating film after drying was 15 μm.

Table 3 shows the peeling of the coating film according to the hot water resistance test, the RCA abrasion test, and the cosmetic test according to Preparation Examples 2, 3, and 4, respectively.

Production Example 3 Production Example 2 Preparation Example 4 Thickness after drying of undercoat 3 μm 7 μm 15 μm Hot water resistance test ○ X X RCA Abrasion Test ○ X X Resistant Cosmetic Test ○ X X ○: coating film peeling occurs, X: coating film peeling does not occur

Referring to Table 3 above, when the undercoating film had a thickness of 3 μm after drying (Production Example 3), the coating film was peeled off by a hot water resistance test, an RCA wear test, and a cosmetic test. However, when the undercoating film had a thickness of 7 µm or more after the drying (Manufacture Example 2, Preparation Example 4), the coating film was not peeled off by the hot water resistance test, the RCA abrasion test, and the cosmetic test. From these results, it can be seen that when the thickness of the coating film after drying is 7 µm or more, the hot water resistance, the RCA wear resistance, and the cosmetic properties of the coating film formed on the magnesium substrate are satisfactory.

Under drying temperature Coating film  Property evaluation

Production Example 5

A coating film was formed under the same conditions as Preparation Example 2 except that the coating film was hot-air dried at 130 ° C. for 15 minutes.

<Manufacture example 6>

A coating film was formed under the same conditions as Preparation Example 2 except that the coating film was hot-air dried at 130 ° C. for 30 minutes.

<Manufacture example 7>

A coating film was formed under the same conditions as Preparation Example 2 except that the coating film was hot-air dried at 150 ° C. for 10 minutes.

<Manufacture example 8>

A coating film was formed under the same conditions as Preparation Example 2 except that the coating film was hot-air dried at 150 ° C. for 15 minutes.

<Manufacture example 9>

A coating film was formed under the same conditions as Preparation Example 2 except that the coating film was dried at hot air at 170 ° C. for 15 minutes.

Preparation Example 2, and whether the coating film peeling according to the hot water resistance test, RCA abrasion test, the cosmetic test for the coating film according to Preparation Examples 5 to 9 are shown in Table 4 below.

Preparation Example 5 Preparation Example 6 Preparation Example 7 Preparation Example 8 Production Example 2 Preparation Example 9 Dry condition 130 ° C., 15 minutes 130 ℃, 30 minutes 150 ℃, 10 minutes 150 ° C., 15 minutes 150 ℃, 30 minutes 170 ° C., 15 minutes Hot water resistance test ○ ○ ○ X X X RCA Abrasion Test ○ X X X X X Resistant Cosmetic Test ○ ○ ○ X X X ○: coating film peeling occurs, X: coating film peeling does not occur

Referring to Table 5, when the coating film drying conditions are 130 ℃, 15 minutes (Preparation Example 5), the coating film was peeled off by the hot water resistance test, RCA wear test and cosmetics test, the coating film drying conditions 130 ℃, 30 In the case of powder (manufacturing example 6) and 150 degreeC and 10 minutes (manufacturing example 7), the coating film was peeled off by the hot water resistance test and the cosmetic test except the RCA abrasion resistance test. On the other hand, when the coating film drying conditions are 150 ℃, 15 minutes (Preparation Example 8); 150 degreeC and 30 minutes (production example 2); And in the case of 170 degreeC and 15 minutes (production example 9), the coating film did not peel at all by the hot water resistance test, the RCA abrasion test, and the cosmetics test. From these results, it can be seen that the drying time of the coating film is preferably at least 15 minutes at 150 ℃ or more.

In the above, the present invention has been described in detail with reference to preferred embodiments, but the present invention is not limited to the above embodiments, and various modifications and changes by those skilled in the art within the spirit and scope of the present invention. This is possible.

10: nonferrous metal substrate 13: undercoating film
15: top coating film

Claims (10)

An aqueous coating composition for non-ferrous metal coating containing 100 parts by weight of a water-dispersed polyurethane-acryl dispersion, 0.1 to 100 parts by weight of a crosslinking agent, and 0.1 to 10 parts by weight of an additive. The method of claim 1,
The water-dispersed polyurethane-acrylic resin is an anionic type non-ferrous metal coating aqueous coating composition having a carboxylic acid group (carboxylic acid group). The method of claim 1,
The water dispersion type polyurethane-acrylic resin is an aqueous coating composition for non-ferrous metal coating having an acid number (Acid Number) of 10 ~ 20 mgKOH / g. The method according to claim 1 or 3,
The water-dispersed polyurethane-acrylic resin is a non-ferrous metal coating aqueous coating composition having a tensile rate of 100 to 200%, and a tensile strength of 3500 ~ 4500 N / ㎡. The method of claim 1,
The crosslinking agent is a polyaziridine, melamine resin, or a composite thereof, an aqueous coating composition for nonferrous metal coating. The method of claim 1,
The crosslinking agent is a methoxymethyl melamine resin non-ferrous metal coating coating composition. The method of claim 6,
An aqueous coating composition for non-ferrous metal coating, which further contains 0.2 to 5 parts by weight of an acid catalyst based on 100 parts by weight of the crosslinking agent. The method of claim 1,
The additive is at least one selected from the group consisting of a leveling agent (slip agent), a slip agent (slip agent), a defoamer, and a neutralizing agent. Using an aqueous coating composition containing 100 parts by weight of a water-dispersed polyurethane-acryl dispersion, 0.1 to 100 parts by weight of a crosslinking agent, 0.1 to 100 parts by weight of a pigment, and 0.1 to 10 parts by weight of an additive on a nonferrous metal substrate. Forming an undercoat layer; And
Non-ferrous metal case manufacturing method comprising the step of forming a top coating layer on the undercoat layer. 10. The method of claim 9,
The top coating layer is an aqueous coating composition containing 100 parts by weight of a water-dispersible polyurethane-acryl dispersion, 0.1 to 100 parts by weight of a crosslinking agent, 0.1 to 10 parts by weight of a matting agent, and 0.1 to 10 parts by weight of an additive. Method for manufacturing a non-ferrous metal case formed by.

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