JP2990397B2 - How to apply water-based paint - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for applying a water-based paint.

[0002]

2. Description of the Related Art Conventionally, it is known that the coating conditions of water-based paints in which most of the resin dissolving agent and most of the diluent at the time of coating are water are very narrow. That is, in a water-based paint in which the diluent is water, paint dripping is likely to occur due to slow evaporation of water.
It is said that it is necessary to apply the paint while maintaining the relative humidity at a relatively low humidity of 40 to 70% under a temperature condition of 30 ° C.

[0003] However, maintaining the relative humidity at a low value of 40 to 70% not only requires enormous equipment and maintenance costs for dehumidification, but also causes defective coating films due to dust charging. There is a fear. Therefore, for example,
In the technology disclosed in Japanese Patent Application Laid-Open No. 2-86429, 30 to 65 is used.
A water-based paint is applied to a preheated object at a relative humidity of 75 to 95% in a high humidity state.
30-60 ° C. in the technique disclosed in US Pat.
The pre-heated object is coated with the water-based paint in a high humidity state of 70% or more relative humidity to reduce equipment costs and maintenance costs and to obtain good coating performance.

[0004]

However, according to the experimental results of the present inventor, the relative humidity of 40 to 70 was obtained under conventional general coating conditions, that is, at a temperature of 25 to 30 ° C.
%, It is possible to apply a water-based paint, and it is possible to secure the required coating thickness without causing paint dripping, but due to the low humidity, the coating surface It was found that there was a problem in that the dryness was too fast, and the texture was rough.

In the prior art disclosed in Japanese Patent Application Laid-Open Nos. 52-86429 and 52-87434, even if equipment for keeping the coating environment at low humidity is unnecessary, it is necessary to preheat the equipment. Not only does this require equipment and energy, but also because the object to be coated is preheated, the surface of the coating film dries too quickly and the roughness of the coating film cannot be eliminated.

The present invention has been made in view of the above circumstances, and provides a method for coating a water-based paint which can obtain good paintability without requiring extra equipment and energy for adjusting the coating conditions. The purpose is to:

[0007]

To achieve the above object, according to the first aspect of the present invention, temperature (° C.) is set on an X-axis and relative humidity (%) is set on an XY coordinate with a Y-axis. And (20, 70), (20, 80), (32, 80)
And a range defined by the four coordinate points (32, 95) as a coating environment condition, the water-based paint being atomized and applied to the object.
The water-based paint has a viscosity immediately after atomization of 3
0-100 centipoise, viscosity at the time of application is 700-12
It has thixotropic properties of 00 centipoise.

[0008]

EXAMPLES As aqueous paints having thixotropic properties, silver metallic paint A (WT-330, manufactured by Kansai Paint Co.) and blue metallic paint B (WT-330, manufactured by Kansai Paint Co.) were used. Comparative coating experiments were carried out using silver metallic paint C and blue metallic paint D, which are water-based paints, with different temperatures and relative humidity.

[0009] Here, the viscosity of the coatings A to D is
Table 1 shows the results measured at rest, during circulation, after air atomization, at the time of application to the object to be coated, and at each measurement time of 3 minutes after application.

[0010]

[Table 1]

In Table 1 above, each viscosity is a value measured by a B-type viscometer, and each paint A, B, C,
For when the circulation of D uses the conduits 30 mm? × 150 meters under a pressure of 10~12kg / cm ^2, for air atomization, 5 kg / cm ² using a REA gun of 1 mm in diameter (manufactured by Ransburg-Gema Co.) Atomized by the pressure of

As is apparent from Table 1, paints C and D are:
While there was no change in viscosity at each measurement time, paint A,
B has a remarkable increase in viscosity at the time of application compared to immediately after atomization, and has thixotropic properties.

The spray gun, coating thickness and baking temperature used in the coating experiments are as follows.

Spray gun; Bell type coating device (manufactured by Bear Co., Ltd.) as a rotary atomizing type Rotating speed 3 to 3.5 × 10 ⁴ rpm Discharge rate 100 to 160 cc / min REA gun as an air atomizing type (Randsburg)・ Gema Co.) Atomizing air pressure 2.5-3.5 kg / cm ² Discharge rate 200-300 cc / min Coating thickness: 15-20 μm (dry), 50-60 μm (wet) Baking temperature: 140 ° C. × 20 min . Under these conditions, for temperature and relative humidity, X
Under various coating conditions (points P _{1 to} P ₉ ) indicated by XY coordinates in FIG. 1 where the axis is temperature and the Y axis is relative humidity, each paint A,
Table 2 shows the results of coating tests performed on B, C, and D, respectively. In Table 2 Thus, the symbol ○ is without paint sagging occurs, moreover shown that feel also good painting result is obtained, the symbol × ₁
Indicates that the paint sagging occurs and the symbol × ₂ shows a rough that feeling is expressed in texture.

[0015]

[Table 2]

From these experimental results, it can be seen that when paints A and B are used, that is, when an aqueous paint having thixotropic properties is used, excellent paintability can be obtained within the range shown by the oblique lines in FIG. Was. That is, the temperature (° C.)
(20, 70), (20, 80), (32, 8) on the XY coordinate with the relative humidity (%) as the Y axis.
When coating is performed using a thixotropic water-based paint with the range defined by the four coordinate points (0) and (32,95) as the coating environment condition, it is possible to prevent paint dripping and to make the feel rough. Is prevented, and excellent coating properties are obtained.

Furthermore, the thixotropic properties are as follows:
To maintain the atomizable viscosity, the viscosity immediately after atomization should be 30 ~
100 centipoise, it is desirable that the viscosity at the time of application is 700 to 1200 centipoise to prevent paint dripping, by using such an aqueous paint having thixotropic properties, excellent coatability. It is possible to obtain it reliably.

In applying such a water-based paint, the temperature and the relative humidity may be controlled by adjusting the circulating air to the paint booth by a general method. For the temperature, for example, a gas burner and a cooler may be used. For the relative humidity, for example, a water contact type humidifier or the like can be used, and there is no need for extra equipment and energy for adjusting the coating conditions.

[0019]

As described above, according to the present invention, (20, 70), (20, 80) are obtained on the XY coordinates with temperature (° C.) as the X axis and relative humidity (%) as the Y axis. ),
Since the aqueous paint having thixotropic properties is atomized and applied to the object by setting the range defined by the four coordinate points (32, 80) and (32, 95) as the coating environment condition, the thixotropic properties of the aqueous paint are paint sag I by the rapid viscosity increase <br/> after the coating deposition by can be effectively prevented. I
In addition, the relative humidity is relatively high under the above-mentioned specific coating environment conditions, and it is not necessary to preheat the object.
No special equipment / energy required for preheating
While, to be moderately gentle evaporation of water and
Prevents roughening (roughness) of the coating film and prevents dust from adhering to the surface to obtain a good coating film, which greatly contributes to the improvement of coating quality as a whole
can do.

In particular, the water-based paint has a viscosity immediately after atomization of 30 to 100 centipoise, and a viscosity at the time of application of 700 to 700 centipoise.
Since it has a thixotropic property of 1200 centipoise, it is possible to surely atomize with a coating gun and to reliably prevent paint dripping after coating, thereby obtaining more excellent coating properties.

[Brief description of the drawings]

FIG. 1 is a graph showing a coating environment determined by temperature and relative humidity.

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Claims (1)

(57) [Claims] 1. On an XY coordinate having temperature (° C.) as an X axis and relative humidity (%) as a Y axis, (20, 70),
(20,80), (32,80) and (32,95)
A coating method in which a water paint is atomized and applied to an object to be coated by setting a range defined by four coordinate points as coating environment conditions , wherein the water paint has a viscosity of 30 to 100 cm immediately after atomization.
Poise, viscosity at the time of coating 700-1200 centipoise
Characterized by having a thixotropic property ,
How to apply water-based paint .