JPS58909B2 - Defoaming method for slurry paint - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to defoaming of a slurry paint, that is, a paint in which water is used as a medium and resin powder with an average particle size of approximately 5 to 50 μm is dispersed in the solid content in an amount of approximately 20 to 60% by weight. It is about the method.

In recent years, in the paint industry, efforts have been made to make paints pollution-free and resource-saving, and the use of water-dilutable paints and powder paints has been increasing in place of conventional organic solvent-based paints.

However, these non-polluting and resource-saving paints have had problems in customization and use.

For example, among water-diluted paints, water-soluble paints cannot have a high solid content concentration, so thick films cannot be painted at once, and emulsion paints use a large amount of surfactant, so the water resistance and chemical resistance of the paint film are affected. The problem was that it was bad.

Furthermore, since powder coatings require special coating equipment, they cannot be applied as widely as conventional organic solvent-based coatings, and have the disadvantage that their uses are severely limited.

Recently, slurry paints have been developed as pollution-free and resource-saving paints that solve the above-mentioned drawbacks.

Generally speaking, slurry paints have a high solid content concentration, so they can be coated in thick layers at one time, and can use the same coating equipment as conventional organic solvent-based paints, and they contain less amount of surfactants, etc. Therefore, it has the advantage that a coating film with excellent water resistance and chemical resistance can be formed.

However, although slurry paints have the above-mentioned advantages, a large amount of bubbles are generated in the paint because the resin powder is dispersed in water using a dispersing machine and a kneading machine during paint production.
If the foam is used without defoaming, it will change over time during storage, and the resin powder will tend to aggregate with each other. If the foam is applied as it is, the paint film will become bumpy, making it impossible to obtain a smooth painted surface. Ta.

Conventionally known methods for defoaming paints include a method of adding an antifoaming agent, a photographic defoaming method, and the like.

However, the former method causes a decrease in the corrosion resistance of the coating film, and the latter method requires a batch-type device, and degassing increases the volume, so the equipment needs to be larger. It had the disadvantage of poor work efficiency.

The present invention relates to a new method that overcomes the drawbacks of the defoaming methods described above.

More specifically, the present invention relates to a method for defoaming slurry paint that can be defoamed continuously and without deteriorating the quality of the paint.

That is, the present invention provides a slurry-like paint, which is characterized in that a slurry-like paint containing air bubbles is strongly jetted from a spray gun so as not to dry, and collides with a wall or a baffle plate, and then the collided sprayed liquid particles are collected. Concerning a defoaming method.

The present invention will be described below with reference to the drawings.

FIGS. 1, 2, and 3 show typical defoaming equipment for slurry paint used in the present invention.

1 to 3, a slurry-like paint containing air bubbles is injected into a chamber 2 by a spray gun 1 having an air atomization type two-fluid nozzle, and is caused to collide with a baffle plate 3 or a side wall or bottom wall of the chamber 2, This is a defoaming device in which defoamed slurry paint flows down and is collected in a container 4.

FIG. 1 shows a method in which the sprayed slurry paint collides with a baffle plate 3, and FIGS. 2 and 3 show a method in which the sprayed slurry paint collides with the bottom wall and side wall of the chamber 2, respectively.

In FIGS. 1 to 3, an air vent is provided at the bottom of the chamber 2, but a cyclone may be used as the air vent in some cases.

In addition, in Figures 1 to 3, the process is carried out in the chamber 2 in order to increase the collection efficiency of the sprayed paint and to prevent changes in the solid content concentration of the slurry paint due to volatilization of water.
It is not necessarily necessary to carry out the process in a chamber as shown in FIG.

In Figure 4, a slurry-like paint tank 5 containing air bubbles is supplied to the spray gun by a pump (in some cases, the tank 5 may be placed at a higher position than the spray gun and fed to the spray gun by gravity). Air bubbles are removed by atomizing air. In the present invention, the slurry paint is atomized at the tip of the spray gun 1 and sprayed onto the baffle plate 3. In the present invention, the conditions for spraying the slurry paint are as follows: Diameter of about 0.5 to 4.0 mm, particularly preferably 0.8 to 3
mm; atomization air pressure approximately 1 to 7 kg/cm2, particularly preferably 2 to 4 kg/cm2; paint ejection amount approximately 60 to 10,100
O/min; (atomizing air capacity)/(paint ejection capacity) ratio approximately 1
00 to 2,000, particularly preferably 500 to 1,500. Under such conditions, the average spray particle diameter of the slurry paint is 20 to 1,000 microns, which improves defoaming efficiency.

If the diameter of the paint nozzle is larger than the above range, the sprayed particles of the slurry paint will be large and the defoaming efficiency will be poor, and if it is smaller, the amount of the slurry paint discharged will be reduced, which is unfavorable in terms of work efficiency.

In addition, if the atomization air pressure is higher than the above range, spray dust is likely to be formed, and the dust becomes lumpy in the collected paint, which has a negative effect on the paint film.On the other hand, if the atomization air pressure is lower than the above range, the atomization of the slurry paint becomes worse. , which is also undesirable because the defoaming efficiency deteriorates.

Moreover, if the amount of paint ejected exceeds the above range, the defoaming efficiency will deteriorate, and if it decreases, it will be unfavorable in terms of work efficiency.

When the ratio of (air capacity for atomization)/(paint ejection capacity) is larger than the above range, spray dust is likely to be formed, and conversely, when it is smaller, the atomization of the slurry paint becomes difficult and the spray particles become large, and the defoaming efficiency is increased. becomes worse, which is not desirable.

Also, the distance between the nozzle of the spray gun and the baffle plate or chamber wall is 50 to 1000 mm, particularly preferably 10 mm.
0 to 300 mm is suitable.

If the distance is shorter than the above range, the splashed paint will accumulate on the nozzle, and when it dries, it will mix with the collected paint and cause spots. On the other hand, if the distance is longer, the water will scatter like a dry spray and cause dust. This is not preferable because there is a problem that it gets mixed into the collection paint and the defoaming efficiency is also poor.

As described above, the method for defoaming slurry paint of the present invention allows defoaming to be carried out continuously and efficiently without deteriorating the quality of the paint.

Hereinafter, the present invention will be explained in more detail with reference to Examples.

Leprosy Examples 1 to 3 and Comparative Examples 1 to 3 40 parts by weight of thermosetting acrylic resin powder coating (Vpet4000 White - Part name manufactured by Dainippon Toyo Co., Ltd.), 0.1 part by weight of activator, and 40 parts by weight of water. was dispersed in a colloid mill to prepare a slurry paint containing many bubbles.

The average particle diameter of the resulting slurry paint was 15 μm (measured with a Coulter counter).

This slurry paint was defoamed under the conditions shown in Table 1 using a two-fluid nozzle spray gun with a paint nozzle diameter of 15 mm in the apparatus shown in FIG.

The results for the defoamed paint are shown in the lower part of Table 1.

Actual strength examples 4 to 7 and comparative examples 4 to 5 Thermosetting acrylic resin powder coating (V pet 1370
White: manufactured by Dainippon Toyo C Co., Ltd. (part name) 40 parts by weight, 0.1 parts by weight of an activator, and 40 parts by weight of water were dispersed in a ball mill to prepare a slurry-like paint containing many bubbles.

The average particle diameter of the obtained slurry paint was 40μ.

This slurry-like paint was applied using the apparatus shown in FIG. 1 with a paint nozzle diameter of 2.5 mmΦ (only Comparative Example 5 was used with a paint nozzle diameter of 0.5 mmΦ).

Degassing was carried out under the conditions shown in Table 1 using a two-fluid nozzle spray gun.

The results for the defoamed paint are shown in the lower part of Table 1.

As is clear from the results in Table 1, in Examples 1 to 7, which were rolled according to the method of the present invention, good defoaming treatment was achieved; Comparative Example 1, which had a small ratio, had a poor defoaming rate and poor storage stability of the paint after defoaming treatment, while Comparative Example 4, which had a high ratio, produced a lot of bubbles in the paint after defoaming treatment. Ta.

Furthermore, in Comparative Example 2, in which the distance to the baffle plate was long, the paint storage stability after degassing was poor, and on the contrary, in Comparative Example 3, in which the distance to the baffle plate was short, many particles appeared in the paint after degassing. I got the result.

Furthermore, in Comparative Example 5, in which a spray gun with a large paint nozzle diameter was used, the paint storage stability after defoaming treatment was poor.

A defoaming rate of 90% or more does not adversely affect the coating film.

Note 2) Occurrence of particles in the collected paint immediately after defoaming treatment◎:
No lumps occur, ○: Very few lumps occur, △: A few lumps occur, × A large number of lumps occur Note 3) Defoaming treated and collected paint is left at 35℃ for 1 week ◎: No abnormality , ○: Very slight seeding, △: Slight seeding, × Large amount of seeding

[Brief explanation of drawings]

1, 2, 3, and 4 are schematic diagrams of a typical slurry paint defoaming device used in the present invention. 1... Spray gun, 2... Chamber, 3... Baffle plate, 4... Collection container,
5... Slurry paint tank.

Claims (1)

[Claims] 1. A slurry-like paint containing air bubbles is strongly jetted from a spray gun so as not to dry, collides with a wall or a baffle plate, and then the collided sprayed liquid particles are collected. A method for defoaming slurry paint. 2 The paint nozzle diameter of the spray gun is 0.5 to 4.0.
2. The method for defoaming a slurry paint according to claim 1, wherein the diameter is 1 mm. 3 The atomizing air pressure of the spray gun is approximately 1 to 7 kg/cm.
2. The method for defoaming a slurry paint according to claim 1 or 2, wherein the amount of paint ejected is about 60 to 1,000 m1/min. 4 The jetting is controlled so that the ratio of atomizing air volume/paint jetting volume is approximately 1.
Claim 1 under the conditions of 00 to 2,000
A method for defoaming a slurry paint according to items 3 to 3. 5 The distance between the spray gun and the wall or baffle plate is approximately 50 mm.
5. A method for defoaming a slurry paint according to claims 1 to 4, characterized in that the thickness is 1,000 mm.