JP3014630B2 - How to paint a synthetic resin hollow body - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for applying a gloss coating to the surface of a hollow body made of synthetic resin, particularly a hollow body made of synthetic resin having high mechanical strength.

[0002]

2. Description of the Related Art Hollow bodies made of synthetic resin blow-molded.
In particular, the surface of a synthetic resin hollow body having high mechanical strength has irregularities of about 0.1 to 1 mm due to air generated between the cavity surface and bathrin at the time of blow molding or a scratch at the time of mold release. For this reason, if the glossy coating is applied to the blow molded synthetic resin hollow body as it is, the irregularities clearly appear on the painted surface, and the outer surface becomes unsightly despite the glossy coating. To solve such a drawback, as disclosed in JP-A-1-94977, the surface of a hollow body blow-molded with a thermoplastic resin,
A method has been developed in which an undercoat containing 20 to 60% by weight of a pigment having a particle size of 0.1 to 10 .mu.m is applied to conceal irregularities on the surface of the hollow body, and then an overcoat is applied. However, in the method disclosed in Japanese Patent Application Laid-Open No. 1-194977, although the undercoat paint adheres strongly to the surface of the hollow body after curing, the adhesion at the time of painting is poor, and the painting operation is efficient. In addition, there is a problem that the coating film is charged after curing and dust and dust adhere to the surface of the hollow body.

[0003]

SUMMARY OF THE INVENTION According to the present invention, it is possible to obtain a beautiful glossy surface by concealing irregularities caused by blow molding of the surface of a hollow body, and at the same time, to improve the efficiency of coating work.
An object of the present invention is to provide a method for coating a synthetic resin hollow body capable of obtaining a coating film having low chargeability.

[0004]

As a result of research conducted by the present inventors, an undercoat containing a specific conductive powder is applied so as to obtain a predetermined electric resistance, and then a gloss coating is performed. It was found that the above problem could be solved.
Therefore, the present invention provides an undercoating material containing conductive powder having a particle size of 0.1 to 10 μm on the surface of a blow-molded synthetic resin hollow body so that the coating film surface resistance becomes 10 ² to 10 ⁷ Ω. A method for coating a synthetic resin hollow body, which is applied and then coated with a gloss paint, wherein the undercoat paint is 5 to 15% by weight of conductive titanium oxide and 3 to 12% by weight of conductive carbon black as the conductive powder. %. Hereinafter, the present invention will be described in detail.

(Hollow Body Made of Synthetic Resin) The method of the present invention relates to a hollow body made of a blow-moldable synthetic resin, in particular, having a mechanical strength with a flexural modulus (ASTMD790) of 10,000 kg / cm ² or more. Suitable for coating hollow bodies composed of large thermoplastics. Examples of the blow-moldable synthetic resin used in the present invention include ABS resin (acrylonitrile-butadiene-styrene), polysulfone resin, polyethersulfone resin, polycarbonate resin, polyphenylene ether resin, polybutylene terephthalate resin, polyacetal resin, polypropylene resin, Examples include polyethylene terephthalate resin and polyphenylene oxide resin. In the present invention, these synthetic resins are used alone or in combination of two or more to coat a blow-molded hollow body. In the blow molding of a hollow body to be coated according to the present invention, after the hollow resin is poured with a straw or the like in a state where the mold is open, the mold is closed and air is simultaneously introduced from the mold (pin). In this case, burrs are formed at a portion where the molds are united. When the resin is not completely flowing, gas is emitted, and when the gas cannot be completely removed, irregularities are generated. Examples of such hollow bodies include air conditioner hoses, pins for boring, plastic bottles, benches, and the like.

(Undercoat paint) The undercoat paint used in the present invention is a liquid paint containing conductive titanium oxide and conductive carbon black as conductive powder. In the present invention, by adding a conductive powder containing conductive titanium oxide and conductive carbon black to the undercoat paint, it is possible to conceal unevenness due to blow molding of the surface of the hollow body and to obtain a clean glossy surface. In addition, there is an effect that the coating efficiency is high and a coating film having low chargeability can be obtained. The conductive titanium oxide of the present invention is usually obtained by subjecting a non-conductive titanium oxide powder to a specific treatment to impart conductivity. For example, a conductive titanium oxide can be obtained by forming a tin oxide-based conductive layer on the surface of a titanium oxide powder, and commercially available products include white conductive powder W-1-P of Mitsubishi Materials Corporation. In the present invention, ordinary conductive carbon black can be used without any particular limitation. Preferred commercial products include conductive carbon blacks # 3050 and # 3250 of Mitsubishi Chemical.

It is suitable to add 5 to 15% by weight, preferably 8 to 13% by weight, of conductive titanium oxide to the undercoat paint. The reason for defining the addition amount in this manner is that if the amount is less than 5% by weight, the coating film becomes black, and no color is formed when an overcoating material having a low concealing property is applied.
If it is larger than this, the cost increases and it becomes impractical. The conductive carbon black is 3 to 12
%, Preferably 5 to 10% by weight. The reason for defining the amount of addition in this manner is that if the amount is less than 3% by weight, the conductivity is lost and the electrostatic coating of the top coat becomes difficult. If the amount is more than 12% by weight, the thixotropy of the paint is reduced. This is because the workability becomes worse due to the size increase.

It is appropriate to add 20 to 60% by weight, preferably 30 to 50% by weight, of a pigment including these conductive powders to the undercoat paint. As the pigment of the present invention, in addition to the conductive powder, conductive powder such as zinc white, talc,
Pigments such as kaolin, clay, titanium oxide and carbon black can be used. In particular, when a precipitated barium sulfate is added together with the conductive carbon black and the conductive titanium oxide, a conductive gray coating film can be obtained. The amount of the precipitated barium sulfate added is 12 to 33% by weight, preferably 15 to 27% by weight, based on the weight of the undercoat paint. The reason why the amount of the precipitated barium sulfate to be added is specified is that if the amount is less than 12% by weight, the coating film becomes thinner when dried and the unevenness of the base cannot be covered, and if it is more than 33% by weight. This is because the spray workability deteriorates and the adhesion decreases.
Also, conductive carbon black used for undercoat paint,
0.1 to 10 μm particle size of conductive titanium oxide and other pigments,
Preferably, the thickness is 0.1 to 5 μm. The reason why the particle size of the pigment is defined in this way is that if the particle size is smaller than 0.1 μm, the irregularities of the blow molded hollow body cannot be sufficiently shielded. This is because the appearance is impaired.

The undercoat paint of the present invention has a coating surface resistance.
Anti 10^Two~Ten⁷Ω, preferably 10^Three~Ten^FiveΩ
Appropriate. The surface resistance of the paint film is defined in this way.
Is 10 ^Two If it is smaller than Ω, there will be too much conductive powder,
Spray workability of undercoat paint deteriorates and uniform coating film is obtained.
10⁷If it is larger than Ω, it will be due to electrostatic painting
It is difficult to apply the top coat and it is not possible to obtain a constant film thickness
Because it becomes. Primer paint is made of poly as binder
Ester resin, alkyd resin, isocyanate resin,
Use acrylic resin, etc., and add silicone
And a surface conditioner. In this case, the pigment
The whole amount, a part of the resin and the solvent are milled over 24 hours.
Knead, and then stir with a disper, including the rest.
It is made by adding additives and the like. In this paint, the main agent
, Hardener and diluted thinner at the specified ratio, and air
Apply with a spray gun and bake at 80 ° C for 30 minutes
Perform After the undercoat has cured, the topcoat is
Paint and bake at 80 ° C for 30 minutes. In addition, overcoat
The paint is sufficient to satisfy the physical properties of coatings for outer panels of automobiles.
Paint film and color
There is no particular limitation as long as it is chilled.

[0010]

According to the method of the present invention, the coating operation can be carried out efficiently, and the unevenness of the hollow body surface by blow molding can be concealed, and a coating film having a clean glossy surface and low chargeability can be obtained. I got it.

[0011]

Next, the present invention will be described in more detail with reference to Examples and Comparative Examples. In the examples, “parts” and “%” are based on weight. (Example 1) 7 g of conductive carbon black, 10 g of conductive titanium oxide, 22 g of precipitated barium sulfate, 35 g of polyester resin, 10 g of ester solvent and 5 g of aromatic solvent were mixed and kneaded with a ball mill for 24 hours. Thereafter, 0.5 g of a surface conditioner, 5.5 g of an aromatic solvent and 5 g of an ester solvent were added, and the mixture was sufficiently stirred with a disper to prepare a conductive paint of Example 1. (Example 2, Comparative Examples 1-4) Example 2 and Comparative Examples 1-4
Was prepared in the same manner as in Example 1 using the components shown in Table 1.

[0012]

[Table 1] Table 1 ───────────────────────────────── Example Comparative Example 1 2 1 2 3 4 Polyester resin Note 1 35.0 35.0 35.0 35.0 35.0 35.0 Conductive carbon black Note 2 7.0 10.0 7.0 7.0 3.0 7.0 Conductive titanium oxide Note 3 10.0 10.0 1.0 20.0 10.0 ── Non-conductive titanium oxide Note 4 ── ── ── ─ ─ ── 10.0 Precipitable barium sulfate Note 5 22.0 22.0 31.0 22.0 22.0 22.0 Surface modifier 0.5 0.5 0.5 0.5 0.5 0.5 Aromatic solvent Note 6 10.5 7.5 10.5 10.5 14.5 7.5 Ester solvent Note 7 15.0 15.0 15.0 15.0 15.0 15.0 Total 100.0 100.0 100.0 100.0 100.0 100.0

Note 1: Burnock J517 (trade name, manufactured by Dainippon Ink and Chemicals, Inc.) Note 2: Ketchen Black (trade name, manufactured by Nippon EC) Note 3: White conductive powder WP (trade name, manufactured by Mitsubishi Materials Corporation) Note 4; Taipaque R930 (trade name, manufactured by Ishihara Sangyo) Note 5: Brand name, manufactured by Nippon Chemical Industry Co., Ltd. Note 6: Solvesso 100 Note 7: butyl acetate

[0014]

[Table 2] Table 2 ─────────────────────────────────── Example Comparative Example 1 2 1 2 3 4 Hiding of irregularities ○ ○ ○ ○ ○ ○ Non-resistance of coating film surface ○ ○ △ ○ × × Electrostatic paintability 10 ³ 10 ² 10 ⁶ 10 ² 10 ⁸ 10 ⁸ to 10 ⁴ to 10 ³ to 10 ⁷ to 10 ³ to 10 ⁹ to 10 ⁹ Smooth color overcoating ○ ○ × ○ ○ ○ Coating workability ○ ○ ○ × ○ ○ Cost ○ ○ ○ × ○ ○

(Test Method) 1) Convexity of unevenness The blended paint was applied to a thickness of 50 to 70 μm, dried, and then the top coat was dried to determine the state of the surface of the paint film. 2) Non-resistance electrostatic coating property of coating film surface The resistance was measured using a tester capable of measuring the resistance value of the coating film surface in the range of 10 ¹ to 10 ¹⁶ 3) Scratch-resistant overcoating property When the target color did not develop due to the effect of the base when a topcoat having poor concealing properties (50 μm or more) was applied, it was determined that the overcoating resistance was poor. 4) Coating workability The state of the coating film surface when sprayed on the surface of the object to be coated was visually evaluated with an air spray gun (4 Kg of atomizing pressure, discharge rate of 150 cc / min) of Wider 71. 5) Cost The cost of Example 1 was used as a standard and compared with other compounding costs.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor: Yutaka Oshikubo 18-1 Kobuki, Mabiki, Yamato-cho, Ichinomiya-shi, Aichi (56) References JP-A-54-10343 (JP, A) JP-A-6-165966 ( JP, A) JP-A-4-166271 (JP, A) JP-A-58-176224 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B05D 1/00-7/26

Claims (2)

(57) [Claims] An undercoat containing conductive powder having a particle size of 0.1 to 10 μm is coated on the surface of a blow-molded synthetic resin hollow body so that the surface resistance of the coating film becomes 10 ² to 10 ⁷ Ω. painted, then a method of coating a synthetic resin hollow body for applying the gloss paint, the primer coating is as the conductive powder, conductive titanium oxide 5-15 wt% of conductive carbon black 3 ~ 12% by weight , and precipitated barium sulfate
A coating method comprising 12 to 33% by weight of a coating solution. 2. The hollow body has a flexural modulus of 10,000.
Claim 1 comprising a thermoplastic resin of kg / cm ² or more.
Painting method described in.