KR20050109171A - Powder coating composition for silver plating and silver plating method of aluminum wheel using the same - Google Patents

Abstract

The present invention relates to a silver film coating method characterized by forming a silver film after coating the powder coating and aluminum wheel capable of forming a silver film.

Powder coating material for silver film formation of the present invention is 70 to 96.6% by weight, at least one resin selected from the group consisting of epoxy resin, polyester resin and acrylic resin, 0.2 to 3% by weight leveling agent, 0.2 to 2% by weight benzoin It is configured to include, when using the powder coating of the present invention can be represented on the metal plating texture on the aluminum wheel.

Description

Powder coating composition for silver film under coating and aluminum film silver film coating method {POWDER COATING COMPOSITION FOR SILVER PLATING AND SILVER PLATING METHOD OF ALUMINUM WHEEL USING THE SAME}

The present invention relates to the invention of a powder coating capable of forming a silver film for the implementation of metal plating texture.

Conventionally, vacuum deposition, electroplating, or electroless plating methods have been used to realize metal plating textures. However, these conventional methods cause a lot of pollutants, and the size of the plated object to be vacuum deposited is limited. There was a problem of economic feasibility and mass production.

Therefore, the demand for an environmentally friendly and economical metal plating texture implementation method is increasing rapidly in recent years.

However, the conventional aluminum wheel coating method has not exhibited the same texture as the metal plating due to the characteristic limitations of the metal plating texture that can be represented by the conventional powder coating and the limitation of the metal texture implementation of the liquid coating.

Therefore, the present invention is to solve the problems of the prior art that the conventional powder coating is not formed for the silver film under the formation of the silver film is not made.

In other words, the object of the present invention is a powder coating which easily forms a silver film and at the same time achieves various coating performances required for aluminum wheels and metal plating without changing the structure of the current aluminum wheel coating line using the powder coating. It is to provide a method for facilitating silver film coating to give a texture.

The present invention provides a powder coating capable of forming a silver film.

The present invention also provides a silver film coating method that satisfies all the physical properties required as a coating material of the aluminum wheel and at the same time expresses a very good metal plating texture.

More specifically, the present invention provides a silver film coating method capable of realizing the same texture as the actual metal plating without significantly changing the structure and properties of the currently available aluminum wheel coating line.

The present invention also provides an environmentally friendly silver film undercoat powder coating and an environmentally friendly and economical silver film coating method using the paint.

The present invention provides a powder coating which is easy to form a silver film while solving the above problems of the prior art, and provides a silver film coating which satisfies the overall film performance required for an aluminum wheel using the powder coating of the present invention. Compared to metal plating, it can be called an innovative metal plating replacement method by lowering coating cost, improving productivity, utilizing an existing coating line, and implementing a beautiful metal plating texture.

The powder coating composition of the present invention comprises 70 to 96.6% by weight of a resin selected from the group consisting of an epoxy resin, a polyester resin and an acrylic resin, 0.2 to 3% by weight of a leveling agent, and 0.2 to 2% by weight of benzoin. .

More detailed embodiments of the powder coating composition of the present invention are represented in detail in Tables 1 to 4 below.

Table 1 is an embodiment of the epoxy resin powder coating.

Ingredient Name Content (wt%) Epoxy Resin ^{* 1)} 87.0 to 96.6 Curing agent ^{* 2)} 3.0-8.0 Leveling agent ^{* 3)} 0.2-3.0 Benzoin 0.2-2.0 Sum 100 * 1) Epoxy equivalent of about 600 ~ 3000 resin is used alone or mixed. * 2) Substituted dicyandiamide type is used as hardener for high gloss epoxy powder coating. * 3) Urea-aldehyde and n It is a coating film smoothing agent of -butyl polyacrylate composition.

Table 2 is an embodiment of the epoxy polyester powder coating.

Ingredient Name Content (wt%) Polyester resin ^{* 1)} 45.0 ~ 70.0 Epoxy resin ^{* 2)} 25.0-54.6 Leveling agent ^{* 3)} 0.2-3.0 Benzoin 0.2-3.0 Sum 100 * 1) Resin with acid value of 20 ~ 90 is used alone or mixed. * 2) Epoxy equivalent is used with alone or mixed resin of about 600 ~ 3000 * 3) Urea- It is a coating film leveling agent of an aldehyde resin and n-butyl polyacrylate composition.

Table 3 is an embodiment of the polyurethane powder coating.

Ingredient Name Content (wt%) Polyester resin ^{* 1)} 70.0-87.6 Curing agent ^{* 2)} 12-25.0 Leveling agent ^{* 3)} 0.2-3.0 Benzoin 0.2-3.0 Sum 100 * 1) Use the resin with hydroxyl value of 25 ~ 55 alone or in combination. * 2) Use IPDI with Blocked NCO% of 10 ~ 20 alone or in mixture. * 3) Urea -Coating film leveling agent of aldehyde resin and n-butyl polyacrylate composition.

Table 4 is a specific example of the acrylic resin powder coating.

Ingredient Name Content (wt%) Acrylic resin ^{* 1)} 79.6 ~ 86.0 Curing agent ^{* 2)} 9.0-20 Leveling agent ^{* 3)} 0.2-3.0 Benzoin 0.2-3.0 Sum 100 * 1) As a glycidyl methacrylate resin, eew is used alone or in a mixture of 300 to 600. * 2) Used as a dodecanoic acid to cure GMA resin. * 3) Urea-aldehyde resin and It is a coating film smoothing agent of n-butyl polyacrylate composition.

The silver film coating method of the present invention includes a pretreatment process of aluminum wheel material and a coating process of the powder coating for silver film undercoat, silver film coating process, silver film protective transparent coating coating process.

1 is a partially enlarged sectional view of an aluminum wheel coated with a silver film by the method of the present invention, 1 is an aluminum wheel material, 2 is a coating film of silver coating film for silver film coating, 3 is a silver coating film, and 4 is a transparent coating film for silver film coating.

Hereinafter, the present invention will be described in detail.

Epoxy resins, polyester resins and acrylic resins used in the powder coating composition of the present invention are generally used in the field of powder coating compositions, and are not particularly limited as long as the effects of the present invention can be achieved.

Specifically, the epoxy resin used in the present invention is a BPA type and is commercially available from Kukdo Chemical, Kumho P & B, DOW, Vantico, and the like.

Polyester resin is commercially available from SK-Ucb, Alkenz, DSM, Solutia, etc., and acrylic resin is commercially available from DIC, Reichhold, Anderson Development, Clariant, and the like.

The powder coating used in the present invention should be well coated with the silver film activation pretreatment agent, and at the same time, the roughness of the powder coating surface should be good so that the silver film can be smoothly formed.

The powder coating surface which satisfies these conditions is achieved by the leveling agent of the present invention.

This invention is a coating film leveling agent containing two or more components as a leveling agent.

The composition of the coating film smoothing agent used in the present invention simultaneously contains a component having a large polarity and a component having a small polarity.

The present invention not only achieves the smoothness of the coating film required for silver film coating superior to the conventional powder coating by using the coating film smoothing agent of such a composition, but also can be easily etched on the surface of the coating film by an acidic silver film activator. It became possible.

Specific examples of the coating film leveling agent of the present invention include urea-aldehyde resins and n-butyl polyacrylates. The coating film smoothing agent achieves the etching effect by the silver film active liquid and excellent smoothness and roughness of the coating film surface.

Silver film coating method of the aluminum wheel using the powder coating of the present invention is as follows.

Contaminants (dust, antirust oil, processed oil, etc.) on the surface of the aluminum wheel material 1 are removed using a cleaning agent or the like.

The powder coating material of the present invention is coated on the washed aluminum wheel material to form a powder coating film 2 to ease the uneven surface of the aluminum wheel material to facilitate the formation of a silver film.

A silver nitrate (AgNO ₃ ) aqueous solution, a reducing agent and a surface active liquid are sprayed onto the powder coating film 2 to form a silver film, and the residue is washed with pure water to remove the residue.

The reducing agent used in the present invention is not particularly limited, but an aqueous solution of dextranose is preferably used.

The surface active liquid used in the present invention is used to facilitate the formation of the silver film, and is preferably an aqueous tin chloride (SnCl ₂ ) solution.

Next, at least two air or airless coating apparatuses installed to vary and control the injection angle, the injection amount, the injection time, and the distance to the wheel surface according to the size and structure of the aluminum wheel to be coated with the silver film. A silver nitrate aqueous solution and a silver nitrate reducing agent are simultaneously sprayed on the powder coating film surface formed by using a silver film.

At this time, the silver film formed by spraying pure water is prevented from discoloring.

In this process, in order to form a silver film on the surface of the aluminum wheel uniformly, the wheel is rotated in one direction or rotated in both directions, or the back and forth, left and right reciprocating motion around the wheel to be coated by the injector or Do the silver film coating process while performing the circular motion.

When the silver film formation is completed, remove the water and paint the transparent paint. Due to the coating of the transparent paint it is possible to ensure the weather resistance and light resistance, adhesion and corrosion resistance required for the coating material of the wheel.

Specific embodiments of the powder coating of the present invention are shown in Tables 1 to 4 described above.

The composition of Tables 1 to 4 does not include the pigment component representing the color, but when it is desired to display the color, the amount of the resin and the curing agent is added as much as the amount of the organic or inorganic pigment added at the same time as the amount of the pigment is added. Adjust the volume by lowering it to the same ratio.

Hereinafter will be described a process for producing a powder coating of the present invention.

The raw material of the powder coating is weighed according to the purpose, and then put into a pre-mixer, and finely pulverized raw materials of relatively large components such as resins and hardeners, and then other relatively powdery raw materials (e.g., Benzoin, leveling agent, pigment, and the like).

This uniformly mixed starch product is melt-dispersed using a melt kneader (Extruder or ko-kneader, etc.) while applying heat at 80 to 120 ° C, and the chips are passed through a compression roller while cooling the resulting dispersion again. To manufacture).

The chip thus prepared is pulverized into particles having a size of 5 to 105 μm by a mill (mill, grinder, etc.). If the average particle distribution is distributed between 20 ~ 75㎛, it can be applied by electrostatic powder coating machine or triboelectric powder coating machine.

After pre-treatment (alkaline degreasing, etc.) of the powder coating prepared in the above composition on the aluminum wheel to be suitable for powder coating, after coating the powder coating to 40 ~ 180㎛ thickness, 10 ~ at a temperature of 140 ~ 200 ℃ Dry for 50 minutes to cure. The surface active liquid is applied and washed with water so that the silver film is easily formed on the cured powder coating film.

Then, in accordance with the size and structure of the aluminum wheel to be coated with the silver film using an air or airless injector, the spray angle of each injector (or spray gun) is determined in consideration of the rotational speed of the wheel. The amount of silver nitrate solution and reducing agent is sprayed 50 ~ 200ml per wheel for 5 ~ 25 seconds irrespective of the quantity of injector so that the thickness of silver film is 0.1 ~ 0.3㎛. do. At this time, the distance between the wheel surface and the injector is maintained to be about 15 ~ 40cm.

At the same time as the formation of the silver film, the color of the silver film formed by spraying pure water is prevented from being changed, and any remaining water is removed. To ensure this is secured.

Hereinafter, the present invention will be described in detail with reference to Examples, but the Examples are merely illustrative of one form of the present invention, and the scope of protection of the present invention is not limited by the Examples.

Example 1

An epoxy resin powder coating material was prepared as shown in Table 5 below.

Ingredient Name Content (wt%) Epoxy Resin YD-013 93.5 Curing agent CASAMID 710 5.0 Carbon Black C-975 0.5 Leveling agent 0.6 Benzoin 0.4 Sum 100

Epoxy resin was supplied by Kukdo Chemical as BPA type, curing agent was supplied by Thomas Swan as substituted DICY type, and carbon black was supplied by Columbia Chemical.

 Put the ingredients of Table 5 into a premixer, and break down relatively large raw materials such as resins and hardeners into 2 ~ 3mm, and make other small powders of several micrometers to several tens of micrometers. Eg benzoin, leveling agent, pigment, etc.).

The mixed starch product was melt-dispersed while applying a melt kneader (Extruder or Ko-kneader, etc.) at a temperature of 80 to 120 ° C., and then cooled to prepare a chip using a compression roller. . .

The prepared chip was pulverized into particles having a size of 5 to 105 μm by a pulverizer (mill, grinder, etc.) to prepare a powder coating of the present invention. Thereafter, the average particle size of the powder coating of the present invention was adjusted to 42 µm.

The powder coating of this example was coated with an average film thickness of 90 μm on a pretreated aluminum wheel using a corona electrostatic powder coating apparatus, and then maintained in a hot air circulating electric oven set at 180 ° C. for 45 minutes to cure the coating. Due to the size, thickness, and weight of the wheel, the actual temperature and time that the wheel material receives even after heating under these conditions is about 10 minutes at about 180 ° C, so that suitable film curing is possible.

After coating the aluminum wheel coated with the powder coating of the present embodiment using a silver film coating system so that the thickness of the silver film is 0.2 μm, it was put in a hot air oven set at 70 ° C. and dried for 45 minutes, and then about 25 ° C. After cooling to room temperature, an acrylic type top coat was coated so as to have a dry coating thickness of about 20 μm, and cured at 140 ° C. for 30 minutes.

After the obtained aluminum wheel was left for 24 hours, the gloss and mechanical properties of the coating film were tested. The test methods and results are shown in Table 6 below.

Test Items Test Methods standard Coating Film Performance Gloss of Powder Coating ASTM D523 80% or more 98% Silver film luster ASTM D523 None (undecided) Too high to measure Gloss after Top Clearness ASTM D523 None (undecided) Too high, not measurable Impact resistance ASTM D2794 500g / 50cm or more 500g / 50cm Flexibility Machinability Flexural Testing Machine 1/8 "φ no crack No crack Stretch resistance ISO 1520 5 mm or more 7 mm Pencil hardness Mitsubishi Uni-pencil H or more H ⁺ Adhesion ASTM D3359 100/100 100/100 Salt water spray resistance ASTM B117 480 hours, one side peeling width within 3mm 1 mm Appearance (color) Visual judgment None (undecided) Similar to plating appearance

Example 2

To prepare an epoxy polyester powder coating as shown in Table 7.

Ingredient Name Content (wt%) Polyester resin CC2428 47.0 Epoxy Resin YD-013 32.0 Titanium Oxide (TiO ₂ ) R-706 20.0 Leveling agent 0.6 Benzoin 0.4 Sum 100

The polyester resin is supplied from SK-Ucb, the epoxy resin is supplied from Kukdo Chemical as BPA type, and the titanium oxide is supplied from DuPont.

Powder coating of the present invention was prepared in the same manner as in Example 1, the components of Table 7.

The powder coating thus prepared was coated on a pre-treated aluminum wheel using a corona electrostatic powder coating apparatus with an average film thickness of 90 μm and maintained for 45 minutes in a hot air circulating electric oven set at 180 ° C. to cure the coating film. Thereafter, silver film coating was performed in the same manner as in Example 1. The obtained coating film performance is as Table 8 below.

Test Items Test Methods standard Coating Film Performance Gloss of Powder Coating ASTM D523 80% or more 99% Silver film luster ASTM D523 None (undecided) Too high to measure Gloss after Top Clearness ASTM D523 None (undecided) Too high to measure Impact resistance ASTM D2794 500g / 50cm or more 1000g / 50cm Flexibility Machinability Flexural Testing Machine 1/8 "φ no crack No crack Stretch resistance ISO 1520 5 mm or more 7 mm Pencil hardness Mitsubishi Uni-pencil H or more H ⁺ Adhesion ASTM D3359 100/100 100/100 Salt water spray resistance ASTM B117 480 hours, one side peeling width within 3mm 1.5mm Appearance (color) Visual judgment None (undecided) Similar to plating appearance

Example 3

A polyurethane powder coating was prepared as shown in Table 9 below.

Raw material name Content (wt%) Polyester Resin CC-283 79.0 Curing Agent B-1530 19.5 Carbon Black C-975 0.5 Leveling agent 0.6 Benzoin 0.4 Sum 100

The polyester resin was supplied from SK-Ucb, the curing agent was supplied from Huls, and the carbon black was supplied from Columbia Chemical.

Powder coating of the present invention was prepared in the same manner as in Example 1, the components of Table 9.

The powder coating was coated on a pre-treated aluminum wheel using a corona electrostatic powder coating apparatus with an average film thickness of 70 μm, and maintained in a hot air circulation type electric oven set at 200 ° C. for 45 minutes to cure the coating. Thereafter, silver film coating was performed in the same manner as in Example 1. The obtained coating film performance is shown in Table 10 below.

Test Items Test Methods standard Coating Film Performance Gloss of Powder Coating ASTM D523 80% or more 93% Silver film luster ASTM D523 None (undecided) Too high to measure Gloss after Top Clearness ASTM D523 None (undecided) Too high to measure Impact resistance ASTM D2794 500g / 50cm or more 1000g / 50cm Flexibility Machinability Flexural Testing Machine 1/8 "φ no crack No crack Stretch resistance ISO 1520 5 mm or more 7 mm Pencil hardness Mitsubishi Uni-pencil H or more H ⁺ Adhesion ASTM D3359 100/100 100/100 Salt water spray resistance ASTM B117 480 hours, one side peeling width within 3mm 1.5mm Appearance (color) Visual judgment None (undecided) Similar to plating appearance

Example 4

As shown in Table 11, an acrylic resin powder coating of the present invention was prepared.

Raw material name Content (wt%) Acrylic resin FINE DIC A257 79.5 Hardener DDDA 19.0 Carbon Black C-975 0.5 Leveling agent 0.6 Benzoin 0.4 Sum 100

The acrylic resin was supplied by DIC, the curing agent was supplied by Dupont, and the carbon black was supplied by Columbia Chemical.

Powder coating of the present invention was prepared in the same manner as in Example 1, the components of Table 11.

The prepared powder coating was coated with an average thickness of 70 μm on a pretreated aluminum wheel using a corona electrostatic powder coating apparatus, and then maintained in a hot air circulating electric oven set at 150 ° C. for 45 minutes to cure the coating. Thereafter, silver film coating was performed in the same manner as in Example 1. The obtained film performance is shown in Table 12 below.

Test Items Test Methods standard Coating Film Performance Gloss of Powder Coating ASTM D523 80% or more 99% Silver film luster ASTM D523 None (undecided) Too high to measure Gloss after Top Clearness ASTM D523 None (undecided) Too high to measure Impact resistance ASTM D2794 500g / 50cm or more 500g / 50cm or more Flexibility Machinability Flexural Testing Machine 1/8 "φ no crack No crack Stretch resistance ISO 1520 5 mm or more 6 mm or more Pencil hardness Mitsubishi Uni-pencil H or more 2H Adhesion ASTM D3359 100/100 100/100 Salt water spray resistance ASTM B117 480 hours, one side peeling width within 3mm 1.5mm Appearance (color) Visual judgment None (undecided) Similar to plating appearance

Comparative example

The performance of the coating film was compared with the aluminum wheel coated with the powder coating of Examples 1 to 4 by using the epoxy polyester resin powder coating material commercially available as a powder coating.

As a conventional epoxy polyester resin powder coating, white powder coatings commercially available from three companies such as Construction Chemical, KCC, and Akzo Nobel were employed as Comparative Examples 1 to 3, and tested. Conventional powder coating products of the company can not know the exact composition and ratio, but contains a polyester resin, epoxy resin, titanium oxide, antioxidant and the like. As Comparative Example 1, Parkmel PP # 4420 of Construction Chemistry, Powdermel EX8816 of KCC (Korea Chemical) as Comparative Example 2, and Interpon 700 of Alzo Nobel were used as Comparative Example 3, respectively.

The powder coatings of Comparative Examples 1 to 3 were coated with an average film thickness of 90 μm on an aluminum wheel pretreated using a corona electrostatic powder coating apparatus in the same manner as in Example 2, and then set to 180 ° C. in a hot air circulating electric oven set at 180 ° C. It was kept for a minute to cure the coating film.

Thereafter, after performing the silver film coating process in the same manner as in Example 1, the acrylic type top coat was coated so as to have a dry film thickness of about 20 μm and cured at 140 ° C. for 30 minutes.

In comparison with the coated aluminum wheels of Examples 1 to 4 and Comparative Examples 1 to 3 of the present invention are shown in Table 13.

Item Examples 1-4 Comparative Examples 1 to 3 Coating performance Corrosion resistance ◎ HB-2H ○ ◎◎ × HB ○ ×× Competitiveness Product Value Added ◎◎ ◎ × ◎: Very good, ○: Good, △: Normal, ×: Poor

In this comparison, the appearance measurement indicates the degree to which the plating texture is realized, and the adhesion means the adhesion between the powder coating and the silver film, and the corrosion resistance indicates the corrosion resistance between the formed silver film, the powder coating and the silver film. .

On the other hand, value added is a comparative evaluation of the finished products when the wheels of Examples 1 to 4 and the powder coating of Comparative Examples 1 to 3 in which the silver film is normally formed.

From this, it can be seen that the powder coating of the present invention achieves an excellent plating quality unlike the conventional powder coating, and at the same time, the productivity is equal to or higher than that of the conventional powder coating. In addition, the powder coating of the present invention shows that it is remarkably excellent in adhesion and corrosion resistance, while having a shock resistance than the conventional powder coating.

The present invention implements a metal plating texture on the aluminum wheel, which cannot be realized by the conventional powder coating method, as a technique of applying a silver film to an aluminum wheel.

The silver film coating method of the present invention is environmentally friendly because no generation of pollutants and harmful substances occurs like the conventional processes such as electroplating, vacuum deposition, and electroless plating. In addition, in the conventional process, the polishing process of the material is essential, and a lot of time and effort is required in the polishing process, while in the process of the present invention, the powder coating is performed using the powder coating of the present invention, such as polishing and preplating processes. Since it does not go through, it can expect economic savings and resource saving effect by saving time and effort.

In addition, the method of the present invention can be applied without modification by only partially supplementing the conventional aluminum wheel coating system, so it is easy to be introduced in a conventional coating company, and the mass production system through automatic coating is possible, thereby securing economic feasibility. .

1 is a partially enlarged cross-sectional view of an aluminum wheel coated with a silver film according to the present invention in which an aluminum wheel material 1, a powder coating film 2, a silver film 3 and a transparent film 4 are sequentially stacked.

2 is a conceptual diagram illustrating a method of coating a silver film through a silver film coating device spraying device.

Claims (9)

A powder coating film for forming a silver film comprising 70 to 96.6 wt% of a resin selected from the group consisting of an epoxy resin, a polyester resin and an acrylic resin, 0.2 to 3 wt% of a leveling agent, and 0.2 to 2 wt% of benzoin. The powder coating material for forming a silver film according to claim 1, further comprising 3 to 8% by weight of a curing agent. Powder coating film for silver film formation comprising 87 to 96.6% by weight of epoxy resin, 3 to 8% by weight of curing agent, 0.2 to 3% by weight of leveling agent, and 0.2 to 2% by weight of benzoin. Powder coating material for silver film formation containing 45 to 70 weight% of polyester resin, 25 to 54.6 weight% of epoxy resin, 0.2 to 3 weight% of leveling agents, and 0.2 to 3 weight% of benzoin. A powder coating film for forming a silver film comprising 70 to 87.6% by weight of polyester resin, 12 to 25% by weight of curing agent, 0.2 to 3% by weight of leveling agent, and 0.2 to 3% by weight of benzoin. Powder coating film for silver film formation comprising 79.6 to 86.0% by weight of acrylic resin, 9 to 20% by weight of curing agent, 0.2 to 3% by weight of leveling agent, and 0.2 to 2% by weight of benzoin. The powder coating material for silver film formation as described in any one of Claims 1-6 whose leveling agent is a coating film leveling agent of urea-aldehyde resin and n-butyl polyacrylate composition. 1 step of coating the powder coating or liquid coating on the aluminum wheel; Depending on the size and structure of the aluminum wheel, the silver nitrate is formed on the surface of the coating film formed by two or more air or airless coating devices installed to vary the angle of injection, amount of injection, injection time, and distance from the wheel surface. The aluminum wheel silver film coating method comprising two steps of spraying the aqueous solution and the silver nitrate reducing agent at the same time. The method of claim 8, wherein the wheel is rotated in one direction or in both directions, or the front and rear left and right reciprocating motions or circular motions are performed around the wheel to be coated so that the silver film is uniformly formed on the aluminum wheel surface. Aluminum wheel silver film coating method comprising.