KR100953432B1 - Metal coating method for plastic material and modeling plastic material thereof - Google Patents

Abstract

PURPOSE: A method for plating a plastic extruded product and moldings thereof are provided to improve workability, to reduce a nickel plating process by shortening whole paltering process, and to obtain adhesion of a metal planting film. CONSTITUTION: A method for plating a plastic extruded product comprises the following steps: a step(S1) etching the plastic extruded product after degreasing the plastic extruded product; a step(S2) performing a first activation process and a second activation process; a step(S3) converting the surface of the plastic extruded product into a conductive material by plating the surface to form a conductive film; a step(S4) electrically plating the plastic extruded product after washing the product with acid; a step(S5) coating the plastic extruded product with chromic acid after washing the plastic extruded product; and a step(S6) coating the surface of the plastic extruded product with urethane-based transparent paint.

Description

Plating method of plastic injection molding and molding manufactured therefrom {METAL COATING METHOD FOR PLASTIC MATERIAL AND MODELING PLASTIC MATERIAL THEREOF}

The present invention relates to a method for plating plastic injection moldings and moldings made therefrom.

In general, metal plating of plastics is known to be of significant commercial importance because the desirable properties of both plastics and metals combine to provide the respective technical and aesthetic advantages.

Therefore, plating plastics with a shiny metallic surface treatment is more economical in terms of cost and weight than replacing molded plastics with metals, and additionally, the plated surface treatments may be applied between the plastic substrate and the plated metal. It does not undergo pitting and corrosion because no pavanic reaction occurs.

In order to improve the adhesion of metal plating to plastics during the plating of plastic injection moldings, many methods have been developed, and as a method of forming metal plating on plastic injection molding, electroplating is mainly applied. Etching-Neutralization-Pre-Dip-First and Second Activity-Chemical Nickel-Copper Lactic Acid Coating-Triple Nickel Plating (Semi-Gloss Nickel-Gloss Nickel-Multinickel)-Chromium-Activation-Chromium Plating-Product Finishing.

Metal plating of the plastic injection molding as described above is made of a multi-step process requiring a large amount of chemicals, and there is a problem such as using a large amount of nickel due to the nickel plating process performed in multiple for corrosion resistance.

In the plating of the plastic injection molding, it is necessary to improve the adhesion and corrosion resistance of the metal and the metal plating, and to improve the metal plating method of smooth coating of the surface of the plastic injection molding.

An object of the present invention is to provide a plating method of a plastic injection molding that can reduce the amount of chemicals and heavy metals, and can improve the adhesion between the plastic surface and the metal and the corrosion resistance of the plated metal.

As an example for achieving the above object, the plating method of the plastic injection molding of the present invention comprises the steps of: degreasing and etching the plastic injection molding; After neutralizing the etched plastic injection molding, a first activation (Catalyst) process of activating a surface using a tin-palladium catalyst, and the plastic injection molding product having undergone the first activation process are carried out in a sulfuric acid (H ₂ SO ₄ ) solution 50 to 50. A second activator process made by immersion for 1 to 2 minutes at 60 ° C; A chemical nickel plating process of plating the activated plastic injection-molded product so that a conductive film is formed to convert the surface into a conductor; A bright nickel plating process of pickling, then washing and electroplating the plastic injection molded product whose surface is converted into a conductor; A chromium plating process of washing the bright nickel-coated plastic injection molding, activating chromium, and then coating it with chromic acid; And a clear coating process for coating the surface of the chromium-plated plastic injection molding with a urethane-based transparent paint.

According to the present invention described above, it can be expected that the effect of excellent adhesion of the metal plated film on the surface of the plastic injection molding even if copper lactate plating is not performed.

In addition, according to the present invention, even if the nickel plating process is not repeated several times, the effect that the corrosion resistance and wear resistance of the metal plated film is excellent can be expected.

In addition, according to the present invention, the overall plating process may be shortened due to the omission of the copper lactate plating process and the shortening of the nickel plating process, which may be performed in multiple, so that the workability and productivity may be improved.

In addition, according to the present invention, since the use of heavy metals is reduced, it is possible to expect an effect of improving the working environment and reducing the harmful effects on workers.

In addition, according to the present invention, since the amount of chemicals used is reduced, the effect of cost reduction and environmental pollution can be expected.

Hereinafter, the plating method of the plastic injection molded product of the present invention will be described in detail with reference to Examples and Drawings. However, the present invention is not limited by the following Examples and Drawings. Figure 1 shows a flow chart of the plating method of the plastic injection molding of the present invention.

1) Process of degreasing and etching plastic injection molding [S1].

The plating method of the present invention is a method for plating plastic injection moldings, that is, injection moldings made of synthetic resin as a raw material, and is not limited by the type of plastic, injection method, or use of injection molding plastics. Although the present invention has been described using an automobile wheel cap as an example, it is apparent that the present invention is not limited thereto, and may be widely applied to a mass-produced plastic injection molding by a conventional method.

In this case, as shown in FIG. 2, when the plastic injection molded product is injected in a method of improving and minimizing the injection stress, cracking of the plastic injection molded product may be reduced, thereby significantly reducing the plating defect rate.

The plastic injection molding is first degreased before metal plating is performed, and degreasing is performed by dipping the plastic injection molding into a surfactant or the like. The surfactant may be appropriately selected. This is done to clean the surface of the molded article by removing the molding powder, the mold release agent applied to the mold, and unnecessary fingerprint marks, etc., and to provide hydrophilicity to the surface of the plastic injection molding.

The injection-molded injection product is etched. Etching is performed to destroy and remove butadiene and the like contained in the plastic injection molding, and as shown in FIG. 3, to form irregularities on the surface of the plastic injection molding to improve adhesion between the components to be plated later. chromic acid) and sulfuric acid (sulfuric acid) in a 1: 1 weight ratio of the immersion for 5 minutes to 15 minutes, preferably 5 minutes to 10 minutes at 60 to 75 ℃, preferably 68 to 72 ℃ conditions It is done by

If the etching conditions are formed as described above, even the ABS-PC product can obtain the advantage that the corrosion surface is well etched. If the ratio of chromic acid in the etching solution is less than the above range, acrylonitrile (Acrylonitril) tends to be hydrolyzed in the plastic injection molding, and if it exceeds the above range, the oxidizing action tends to be difficult even if the chromic acid is saturated. The ratio of heavy chromic acid and sulfuric acid may be maintained in the above range.

2) neutralizing the etched plastic injection molding with alkali, and then activating the surface by using a tin-palladium catalyst and immersing the plastic injection molding after the first activation in a sulfuric acid (H ₂ SO ₄ ) solution. 2nd activation process [S2].

Etched plastic injection molding is sufficiently washed with water to remove and neutralize the etching solution. The neutralization treatment is for reducing the Cr ⁺⁶ of the etching solution to Cr ⁺³ , for example, a solution of sodium bisulphide. By dipping at least 1 min at room temperature using hydrogen peroxide (H ₂ O ₂ ) solution. This is done to neutralize the etchant to prevent the unplated phenomenon in the later electroless plating.

The neutralized plastic injection molding is pre-dip for the anti-aging effect of washing with water into the active catalyzed liquid. Pre-dip is carried out in a pre-dip tank, which is immersed in an aqueous solution of hydrochloric acid (HCl) 20 to 30% by weight at room temperature for 30 seconds to 1 minute. The pre-dip is performed to make the activation process well.

First and second activator processes are performed to activate the surface of the plastic injection molded product, which has undergone pre-dip, as a conductor.

The first and second activation processes adsorb and penetrate the pre-dip plastic injection product into the palladium chloride (platinum group) colloidal catalyst, which is a catalyst for chemical plating, in order to deposit a conductive film of metal ions (Ni ++) during the subsequent electroplating. The process of making it solidify after making it.

The first activation process, also called catalysis, is a process that gives a seed to be plated on the plastic surface, which is a non-conductor, and is required for the plating process, and removes the thin oxide layer formed during the previous treatment. Makes it active.

In the first activation process, the neutralized plastic injection product was immersed for 5 to 10 minutes in an aqueous hydrochloric acid solution containing 25 to 35% of hydrochloric acid in a colloidal tin-palladium catalyst at a concentration of 80 to 100 ppm. Is washed with water to form a catalyst layer on the surface of the plastic injection molding. The schematic diagram of the tin-palladium cluster catalyst used at this time is simply shown in FIG. 4.

As for the stock-palladium catalyst, it is preferable to use a tin (Sn) and palladium (Pd) in a weight ratio of 2: 1 in terms of the solidification of the catalyst layer. This is a process of adsorbing and penetrating strong metal ions onto the surface of a hydrophilic plastic injection product quenched in an etching process to impart a catalytic metal nucleus. That is, since the surface of the plastic injection molded product itself is not catalytic, it is difficult to reduce the reaction even if it is deposited in the chemical nickel plating solution.

5 is a schematic diagram of the surface of the plastic injection molded product activated by the first activation process.

In order to activate the catalytic metal adsorbed on the surface of the plastic on which the first activation process is completed, a second activation process is performed.

In the second activation process, the plastic injection molded product is subjected to the first activation process in a sulfuric acid (H ₂ SO ₄ ) solution (concentration of 10-20% sulfuric acid solution) for 1 to 2 minutes, preferably for 1 minute. To immersion for 1 minute 30 seconds.

The second activation process is applied after adjusting the conditions according to the degree of adsorption of the catalytic metal after the first activation process, and if the second activation process is excessive, the nucleus of palladium may be dropped from the surface of the plastic injection molding. Do it.

Meanwhile, when the sulfuric acid (H ₂ SO ₄ ) solution used in the second activation process is contaminated to cause stardust, it is necessary to periodically renew the sulfuric acid (H ₂ SO ₄ ) solution so that the sulfuric acid (H ₂ SO ₄ ) solution is not contaminated.

Figure 6 shows a schematic surface of the plastic injection molding activated by the second activator process. As described above, the plastic injection molding that has undergone the second activator process has a surface with tin removed and palladium fixed, unlike in FIG. 5, to facilitate nickel plating (electroless plating) later.

In other words, the surface of the plastic injection molded product, which is electroless plated through the etching process and the first and second activator processes, is conductive and enables electroplating, which is essential for conventional metal plating. The lactic acid copper plating process can be omitted.

As described above, the fixing surface of the palladium formed on the surface of the plastic injection molded product which has undergone the first activation and the second activation process has a thickness in the range of 0.3 μm to 0.5 μm, so that nickel is well adhered during electroplating.

3) A chemical nickel plating process [S3] to convert the surface of the activated plastic injection molding into a conductor.

After the activation process, the water is sufficiently washed and then a chemical nickel plating process is performed to form a conductive film with nickel metal ions so that the deposition of nickel plating is performed firmly.

The chemical nickel plating process maintains an alkaline state of pH 8.5 to 9.5 at room temperature and is immersed in a chemical nickel plating solution containing 4 to 6 g / L of nickel (Ni ++) metal ions for 3 to 5 minutes and washed with water. Thereby converting into a conductor having a conductive coating formed on the surface of the plastic injection molding.

Figure 7 shows the surface schematic of the plastic injection molding chemical chemical plating process was performed.

If the surface of the plastic injection molding is not sufficiently activated by the activation process, chemical nickel plating is not faithfully performed. In other words, the site where the chemical nickel plating is not made means that the palladium activity is not performed, and there is a problem of cracking or peeling the plating later. When the plating is peeled off, nickel is eluted, which may cause side effects such as skin allergy or heavy metal contamination caused by the use of nickel. Therefore, the activation process must be faithfully performed.

It is preferable that the thickness of the chemical nickel plating layer is in the range of 0.3 to 0.5 μm in view of balance of thickness thinning and corrosion resistance.

4) Pickling, flushing and bright nickel plating processes of plastic injection-molded parts whose surfaces are converted to conductors [S4].

In the present invention, by washing the chemical nickel plating solution by washing the surface of the plastic injection-molded product with the conductive film formed by the chemical nickel plating treatment, it is pickled without plating copper lactate. Pickling is performed using an acid solution maintained at pH 3 or less, for example, an acid solution containing 0.5 to 2% by weight of an inorganic acid, and washed with water after washing to wash the used acid solution.

Washed plastic injection moldings undergo a bright nickel plating process. Glossy nickel plating is performed to secure decorative properties, and the thickness of the glossy nickel plating layer may be in a range of 4 to 12 μm, which may be preferable for securing decorative properties. Such polished nickel plating is 25 to 35% by weight of nickel sulfate (NiSO ₄ ), 3 to 5% by weight of nickel chloride (NiCl ₂ ), 4 to 6% by weight of boric acid (H ₃ BO ₃ ) at a working temperature of 50 to 60 ℃ and It consists of the process of immersing for 10 to 20 minutes in the conditions which made the current density into 300-500 A / dm <^2> and constant voltage 6-8V in the bright nickel plating liquid containing a suitable quantity of polish and residual amount of water, and wash | cleaning.

Compared with the metal plating process of the conventional plastic injection molding, the lactic acid copper plating process is omitted in the present invention, and the polished nickel plating process is reduced by reducing the triple nickel plating process such as semi-gloss nickel plating, polished nickel plating, and multi-nickel plating. To perform.

Copper lactate plating has been widely applied as a first layer of electroplating to plastic materials, and has excellent physical properties, namely, ductility and good adhesiveness, compared to copper and copper pyrophosphate copper plating. Copper lactic acid plating is performed to prevent the adhesion of the plating film from deterioration due to shrinkage due to thermal expansion coefficient aberration of the plastic and the metal plated on the surface thereof, and copper lactic acid plating absorbs shrinkage due to thermal expansion due to copper ductility, and thus the adhesion of the finished product. It was necessary for.

The present invention provides a plating method excellent in adhesion between the plastic injection-molded product and the metal film even without such copper lactate plating. The copper lactate plating could be omitted because the palladium is well adhered to the surface of the plastic injection-molded product by the etching process and the activation process as described above to facilitate the fixing of nickel.

On the other hand, in order to improve the corrosion resistance, nickel plating tended to apply double or triple nickel plating or increase the thickness of the plating. In the present invention, it is excellent in the adhesion of nickel and can satisfy sufficient corrosion resistance even with one-time plating, and can reduce the thickness of the nickel plating, so that the thickness of the finished product can be reduced, and the advantages of reducing the amount of nickel used You can expect the effect to get.

5) Chrome plating process of the plastic injection coating the bright nickel [S5].

When the nickel base plating is completed as described above, chromium plating is performed. That is, the glossy nickel-coated plastic injection molding is first subjected to a chromium activation process in order to increase the adhesion of sufficiently washed chromium. The chromium activation process consists of immersion in an aqueous solution containing 0.2 to 0.5% by weight of chromic acid (CrO ₃ ) at room temperature for 30 seconds to 1 minute. This is done to prevent the solution used in the nickel coating or the like from flowing into the chromium coating and to impart hydrophilicity to the surface of the plastic injection-molded product on which the nickel layer is formed.

The chromium plating process is performed after the chromium activation process is performed. The chromium plating process has a current density of 800 to 1,000 A in a chromium plating solution consisting of 20 to 30 wt% of chromic acid (CrO ₃ ), 0.04 to 0.14 wt% of sulfuric acid (H ₂ SO ₄ ) and a residual amount of water at a working temperature of 35 to 45 ° C. / dm ² , a constant voltage of 5 to 6 V in a condition of immersion for 3 to 5 minutes. By the chromium plating process described above, wear resistance is imparted to the surface of the plastic injection molded product, and the gloss characteristic of the chromium metal can be imparted.

6) Clear coating process of the chromium-plated plastic injection molding [S6].

In the present invention, the plating of the plastic injection molding is not carried out a copper lactate plating process, the conventional triple plating nickel plating is performed in a single process. Therefore, in the present invention, after the entire plating process is performed, a clear coating process of coating the plastic injection molded chrome plated using a urethane-based transparent paint is performed.

The transparent paint used for the clear coating is a urethane-based transparent paint, and isocyanate-based curing agents are mixed and used therein. The use of a urethane paint and an isocyanate hardener in a weight ratio of 1: 0.3 to 1, preferably in a weight ratio of 1: 0.5, is preferable in view of transparency and curing of the urethane paint.

By performing the clear coating as described above, the corrosion resistance of the chromium-plated plastic injection molding can be further reinforced, the stability of the chromium plating can be improved, and the thickness of the plating layer is advantageously formed.

The plastic injection molding produced by the above method did not cause any exposure, swelling, peeling, cracking, etc. after plating, roughness, spots, cloudiness, wrinkle irregularities, abrasive patterns, deformation by polishing, scratches, bruise grooves, No stains, pinholes, etc. were formed, which resulted in an excellent appearance.

The test for adhesion, abrasion resistance and corrosion resistance to the plating film of the plastic injection molded product completed by the above process is performed as follows.

Experimental Example 1. Adhesion Test

[Heat Cycle Test ]

Using the specimen of the plastic injection molding (100mm × 80mm × 5mm) which has been plated by the above-described process, the heat cycle test was carried out by the method of two cycles with 70 ° C 1Hr → room temperature 0.5Hr → -30 ° C 1Hr → room temperature 0.5Hr as one cycle. (MS-191-53) was carried out. As a result, good results were obtained without swelling or cracking.

This was found to be the same level or higher than the result obtained by testing in the same method using a plastic injection molding is completed by the conventional copper lactate plating and multi-nickel plating method.

That is, even when the plating is completed by the process of the present invention it can be confirmed that the adhesion of the plated film is excellent.

Experimental Example 2. Corrosion Resistance Test

Using the same specimen as used in Experimental Example 1 NaCl 50g / l, PH 6.5 ~ 7.2, spray amount 1.5 ± 0.5ml / 80 ㎠ / H, Tank temperature 35 ℃ ± 2, Air saturator temperature 47 ℃ ± 2, Corrosion resistance was tested under conditions of 240 Hr salt spray (MS-600-35) at an air pressure of 70 to 167 kPa, which resulted in good results without corrosion being found.

This was found to be better than the existing level compared with the results obtained by testing in the same manner using the plastic injection molding is completed by the conventional copper lactate plating and multi-nickel plating method.

That is, even when the plating is completed by the process of the present invention it can be confirmed that the plating film excellent corrosion resistance.

Experimental Example 3. Wear Resistance Test

Using the same specimen used in Experimental Example 1, the test load 0.5 kg, test speed 15 ± 5 m / min, the friction body is the material of parallel ship # 10, WET condition is a tester immersed in kerosine for 30 seconds The wear resistance was tested under the conditions of dry 500 times and wet 50 times when the conditions were met. As a result, there was no free exposure, swelling and cracking.

This was found to be more than the same level as compared with the results obtained by testing in the same method using a plastic injection molding is completed by the conventional copper lactate plating and multi-nickel plating method.

That is, even when the plating is completed by the process of the present invention it can be confirmed that the wear resistance of the plated film is excellent.

Figure 1 shows a flow chart of the plating process of the plastic injection molding of the present invention.

2 is a photograph showing an example of stress improvement for reducing crack formation of a plastic injection molding.

Figure 3 is a schematic diagram showing the surface of the plastic injection molding made of the etching step of the plating process of the plastic injection molding of the present invention.

4 shows a schematic diagram of a tin-palladium catalyst.

5 is a schematic view showing the surface of the plastic injection molded product made of the first activation step of the plating process of the plastic injection molded product of the present invention.

6 is a schematic view showing the surface of the plastic injection molded product made of the second activation process of the plating process of the plastic injection molded product of the present invention.

Figure 7 is a schematic diagram showing the appearance of the electroless plating film formed on the surface of the plastic injection molded product of the present invention.

Figure 8 is a photograph showing the appearance of a wheel cap for a vehicle coated with a metal film by the plating process of the plastic injection molding of the present invention.

Claims (6)

Degreasing and etching the plastic injection molding; After neutralizing the etched plastic injection molding, the first activation (Catalyst) for activating the surface by using a tin-palladium catalyst, and the plastic injection molding product after the first activation process are carried out in a sulfuric acid (H ₂ SO ₄ ) solution in 50 to 60 A second activator process made by immersing for 1 to 2 minutes under the condition of ℃; A chemical nickel plating process of plating the activated plastic injection-molded product so that a conductive film is formed to convert the surface into a conductor; A bright nickel plating process of pickling, then washing and electroplating the plastic injection molded product whose surface is converted into a conductor; A chromium plating process of washing the bright nickel-coated plastic injection molding, activating chromium, and then coating it with chromic acid; And, Clear coating process for coating with urethane-based transparent paint on the surface of the chromium-plated plastic injection molding Plating method of plastic injection molding, characterized in that comprises a. The method according to claim 1, The etching is a plating method of a plastic injection molding, characterized in that chromic acid (sulfuric acid) and sulfuric acid (sulfuric acid) is immersed in a mixed solution in a weight ratio of 1: 1 to 5 to 15 minutes at 60 to 75 ℃ conditions. In claim 1, The first activation process is a method of immersing the neutralized plastic injection product in an aqueous hydrochloric acid solution (25-35 wt% hydrochloric acid) containing a colloidal tin-palladium catalyst at a concentration of 80 to 100 ppm for 5 to 10 minutes. Plating method of plastic injection molding, characterized in that made. The method according to claim 3, The tin-palladium catalyst is a plating method of a plastic injection molding, characterized in that the tin: palladium is 2: 1 by weight ratio. delete The method according to claim 1, The urethane-based paint is a plating method of a plastic injection molding, characterized in that the urethane-based paint and isocyanate-based curing agent is mixed in a ratio of 1: 0.3 to 1 by weight.

Images