JPS61166998A - Method for coating molded plastic article with paint by electrodeposition - Google Patents

Abstract

PURPOSE:To form a paint film having superior adhesion, insulation and decorativeness on a molded plastic article by subjecting the article to electroless plating, electroplating and composite Ni plating in an Ni plating bath contg. plastic powder and by coating the article with paint by electrodeposition. CONSTITUTION:The surface of a plastic article is washed and roughened by etching. A Cu or Ni film of about 0.3mum thickness is formed on the roughened surface by electroless plating, the surface of the electrically conductive film is electroplated with Cu or Ni, and a composite Ni layer contg. plastic powder is formed in an Ni electroplating bath contg. dispersed plastic powder. The plastic article is then coated with paint by electrodeposition. A paint film having superior adhesion, insulation and decorativeness can be formed.

Description

[Detailed description of the invention]! jiJ: (2 Summer 1 Stand!) The present invention relates to a method of forming a coating film for insulation, corrosion prevention, etc. after plating a plastic molded product.

Current Techniques and Problems There are known methods of plating plastic molded products for the purpose of imparting decorative properties and conductivity. In plastic molded products subjected to such plating treatment, it may be necessary to form an insulating film on the plating film in order to improve the corrosion resistance of the plating film and impart insulation properties.

For example, in recent years, in order to prevent electronic equipment from malfunctioning due to electromagnetic interference, 1! Magnetic shield (
(Hereinafter referred to as EMI shielding), methods for this purpose include making the case of electronic equipment made of metal, applying conductive paint to the plastic case, and applying conductive paint to the plastic case. A method of applying wet plating to the case is known. E like this
For cases that have been given conductivity for MI shielding, a coating film is formed on the conductive film by methods such as dipping or spray painting for purposes such as insulation, corrosion prevention, and decoration on the case surface. ing.

However, with paint films formed by flattening or spray painting, the thickness of the paint film becomes uneven, resulting in poor dimensional stability of the case, poor adhesion of the paint film, and easy peeling. There is a problem.

In addition, if a coating film is formed by spray painting or brushing after plating, it is impossible for manufacturing personnel to work, and the process takes a long time. !
! There are disadvantages such as high cost.

Means for Solving the Problems In view of the problems of the prior art as described above, the inventor of the present invention
As a result of extensive research, we applied electroless plating to plastic molded products to make them conductive, and then electroplated them.
Next, after performing composite nickel plating containing plastic powder, a coating film is formed using electrodeposition coating, which makes it possible to form a plating film and a coating film on a plastic molded product in a one-step process, and is also advantageous. The resulting coating film is uniform and has good adhesion, as well as insulation and
It was also found that it has excellent decorative properties.

That is, the present invention provides a plastic molding characterized in that a plastic molded product is subjected to electroless plating, then electroplated, and then a composite nickel plating film containing plastic powder is formed, and then electrodeposition coating is performed. This relates to the electrodeposition coating method for products.

In the present invention, first, a plastic molded article is cleaned in accordance with a conventional method, and then, depending on the type of plastic molded article, a known etching solution such as H2804-CrO2, hydrochloric acid,
Using an etching solution appropriately selected from NaOH etc.
The surface of the molded article is roughened.

Next, an electroless plating catalyst is attached to the surface of the plastic molded product. The catalyst may be attached using a conventional method, such as a sensitizer-activator method or a catalyst-accelerator method.

After attaching the catalyst, electroless copper plating or electroless nickel plating is applied to the plastic.

- imparts electrical conductivity to the base. The film thickness of electroless copper plating or electroless nickel plating must be 0 to provide conductivity.
．． Approximately 3 μm is sufficient, but plating may be made thicker. The type of plating solution and plating conditions for electroless copper plating and electroless nickel plating are not particularly limited, and may be according to conventional methods.

After imparting conductivity to the plastic molded product through electroless plating, electroplating is performed. The types of electroplating are
Although it may be determined as appropriate depending on the purpose, various platings such as nickel plating, copper plating, zinc plating, tin plating, and various alloy platings can be applied. Moreover, the film thickness of electroplating may be appropriately determined depending on the purpose.

In order to impart an electromagnetic shielding effect to a plastic molded product, copper plating or nickel plating is preferable as electroplating, and copper plating is particularly preferable. There are no particular restrictions on the type of copper plating, and for example, a known copper sulfate plating bath (CuSOt).

・5H20200~250Q/Q 1H2Som40~
60Q/Q, appropriate amount of brightener), copper birophosphate plating bath (copper birophosphate 70-90 J/Q1 potassium birophosphate 3
40-380g/Q, ammonia water 1-3112/Q,
An appropriate amount of brightener) can be used, and plating can be carried out according to a conventional method. In order to provide electromagnetic shielding effect,
The thickness of the plating film is usually preferably about 5 to 25 μm.

Next, on top of the plating film formed by electroplating,
A composite nickel film is formed using an electrolytic nickel plating solution in which plastic powder is dispersed. This composite nickel plating film is in the form of eutectoid plastic powder, and the subsequent electrodeposited coating strongly bonds with the eutectoid plastic powder, resulting in a coating film with excellent adhesion. . As the plastic powder, epoxy, acrylic, polycarbonate, nylon, polyester, styrene, etc. can be used, and in order to increase the number of eutectoids, one having a particle size of 1 to 50 μm, preferably 1 to 10 μm is used. As a plating solution for dispersing plastic powder, a normal nickel plating solution can be used, such as Watt bath (nickel sulfate 230
~250g/Q, nickel chloride 40-50J/Q, boric acid 30-40Q/(i), nickel sulfamate plating bath (nickel sulfamate 400-500Q/Q
, 硼I! 30-40Q/Q, sodium chloride 5-10
g/+1) etc. can be used. The dispersion range of the plastic powder into the nickel plating bath is preferably about 5 to 100 Q/Q. The temperature of the plating bath may be the same as that of a normal nickel plating bath, and the plating bath may be sufficiently stirred to perform wi flow heavy density plating of about 2 to 5 A/ds2. The thickness of the plating film is about 2 to 50 μm, preferably about 3 to 7 μm. If the film thickness is too thin, the amount of eutectoid plastic powder will decrease, which is not preferable.

Next, a coating film is formed on the composite nickel plating film by an electrodeposition coating method. There are no particular restrictions on the paint for electrodeposition, and examples include known water-soluble paints for electrodeposition that are mainly composed of thermosetting acrylic resins, epoxy amine resins, and other resins, with pigments added as necessary. can be used.

Conditions for electrodeposition coating vary depending on the paint used, but 7j1 deposition is usually carried out at about 80 to 150 V for about 0.5 to 3 minutes. 211 coating may be carried out using either the cathode or the anode depending on the type of the 'R coating paint used, or both may be used in combination. The thickness of the coating film is usually 5-25μ
It may be about m.

After electrodeposition coating, the electrodeposited resin is cured by baking.

Baking conditions are determined by the type of resin; for example, for thermosetting acrylic resin, baking conditions are 150 to 190°C.
It is sufficient to bake for about 5 to 30 minutes, and in the case of epoxy amine resin, it is sufficient to bake for about 15 to 30 minutes at a temperature of about 150 to 170°C.

Materials for plastic molded products to which the present invention can be applied may be resins with a heat distortion temperature of 110° C. or higher or reinforced resins containing various fillers, and any plating-grade engineering plastics can be used. Specific examples include Noryl, polycarbonate, polyester,
Examples include thermoplastic resins such as nylon, thermosetting resins such as epoxy and phenol, and particularly preferred are heat-resistant resins with a softening point of 150° C. or higher.

Effects of the invention ■ Electrodeposition coating can use the same mounting equipment as used for plating, so there is no need to separate the plating process and the painting process, and the process can be performed continuously in one line. It is possible to improve productivity and reduce processing costs.

■ The coating film produced by Wi@painting has excellent throwing power and can easily cover areas that were previously difficult to apply by brushing or spray painting.

■・I! Electrodeposition coating has no buildup or dripping of paint, the thickness of the coating film is uniform, and it has excellent dimensional stability of the treated product.

■ The electrodeposited coating on the composite nickel plating film exhibits strong adhesion, so even if the treated product is used for a long period of time, the coating will not peel off, and it has properties such as insulation, anti-corrosion, and anti-oxidation. It can last for a long time.

■ Electrodeposition coatings have a uniform and smooth surface, and especially those containing pigments, depending on the type of pigment, the surface condition is uniform and smooth.
A highly decorative paint film colored in the color of each ridge can be obtained.

■ Copper plating or nickel plating as electroplating has excellent EM (shielding effect).

Examples Example 1 A plating film and a 12M paint film were formed on a polyethylene terephthalate resin molded product containing 20% glass filler and 25% wollastonite according to the following method, and only the drying temperature of the paint film was different. 31!1! A similar sample was prepared.

o Alkaline resin: NaO8200g/Q aqueous solution at 60℃
Soak for 10 minutes.

0 etching: 98%H2S Ot 5011Q/Q
and acidic ammonium fluoride (NH,F-HF) 20Q
/Q for 10 minutes at 40°C.

0 catalyst provision: Catalyst (trademark “Catalyst C11
Okuno Pharmaceutical Co., Ltd.) for 4 minutes at 25°C, washed with water, and then soaked in 98% H2S Oa 50 Q/Q aqueous solution for 4 minutes.
Soak for 3 minutes at 0°C.

0 Electroless steel plating: Electroless copper plating solution (trademark “Top Chemical Copper Plating 500” Okuno Pharmaceutical Co., Ltd. WJ) at 25°C.
Soak for 5 minutes.

0 activation: immersed in 98% H2S Ot 50 wd/Q aqueous solution at 50°C for 1 minute.

O electrolytic copper plating: CUSOA ・5H20200Q
/Q, 98% 1ii1150 to I/12 and light tl
J (Trademark “Top Lucina 81M” manufactured by Okuno Pharmaceutical Co., Ltd.)
3A/ using a sulfuric acid steel plating bath consisting of 51111/Q.
Plating with d■2 for 20 minutes.

0 composite nickel plating: N15Ot ・6H20240
Q/Q, N5CQ2 ・6H2045 (J/Q, H
Using a composite nickel plating solution consisting of 3BO330Q/Q, saccharin 0.5 (J/Q, and 20 a/Q of epoxy powder with a particle size of 2 to 10 μm, 1 at 3A/d■2
Plating for 0 minutes.

0 electrodeposition coating: thermosetting water-soluble acrylic resin electrodeposition paint (
Electrodeposition was performed using Commercial A ["Honey Prite" manufactured by Honey Kasei ■] using the sample as an anode at a voltage of 100 V and a bath temperature of 20° C. for 30 seconds.

0 Drying: Heating in an oven at 150°C, 165°C, and 180°C for 20 minutes.

Each sample of molded articles made of polyethylene terephthalate resin subjected to the above-described treatment had a uniform and smooth appearance, and the thickness of the coating film was approximately 10 μm. The pencil hardness of this coating film was measured according to the method of JIS 0 0202, and the hardness of the film cured at 150°C was H~2H, 1
Those cured at 65°C took 2H to 3H, and those cured at 180°C took 3H to 4 days, indicating sufficient surface hardness.

In addition, the resistance value of the electrocoated film was measured using a tester (M
When measured using an ODEL3400, n')7-II) and Hi-Sheet resistance measuring device (K-705RD, manufactured by Kyowa Kaikou Co., Ltd.), each sample had no conductivity and was found to be a good insulating film.

Also, on the coating film, using a knife, 1+u/
After making 100 squares of 1 square on each side in a lattice pattern by inserting the perpendicular cuts of the il spacings until they reach the composite nickel plating film, we applied adhesive tape and removed it instantly without leaving any residue. When the adhesion of the coating film was measured by calculating the number of squares, there was no peeling in any of the samples, and the adhesion was good.

In addition, the EMI shielding effect of the plastic molded product subjected to the above-mentioned tightening treatment and electrodeposition coating treatment was evaluated using the shield box method at a frequency of 0.1. The results of measurements of electric and magnetic field waves of ~100,100 O are shown in FIG. The results for each sample were similar to those shown in FIG. As is clear from Fig. 1, the plastic molded product treated by the method of the present invention has a good EM resistance of 115 to 120 dB or more against electric field waves and 5 to 120 dB against magnetic field waves.
It showed an I-shielding effect.

Comparative Example 1 - Except for using a nickel plating solution obtained by removing the epoxy powder from the composite nickel plating solution used in Example 1,
A plating film and a coating film by electrodeposition were formed on a plastic molded article in the same manner as in Example 1 at a coating film heating temperature of 165°C.

The adhesion of this coating film was measured in the same manner as in Example 1, and as a result, out of 100 squares, 55 squares remained without being peeled off.

Comparative Example 2 A bond with a composite nickel film formed in the same manner as in Example 1 was spray-painted (using trademark "Door Akron H" made by Tsukuba Paint) and heated at 120"C for 30 minutes to form a film of about 15 μm. A coating film was formed.

As a result of measuring adhesion using the same method as in Example 1,
The number of squares of 1ooa that remained without peeling was 30.
It was.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the results of measuring the EMI shielding effect of plastic molded products treated by the method of the present invention. (or more) ′−1・

Claims (1)

[Claims] (1) After applying electroless plating to the plastic molded product,
A method for electrocoating plastic molded products, which comprises electroplating, forming a composite nickel plating film containing plastic powder, and then applying electrocoating.