JPS5853039B2 - Cleaning solvent for water-based paint color change - Google Patents

Description

[Detailed description of the invention] The present invention relates to a cleaning solvent for changing the color of water-based paint.

Conventionally, 10 to 20 colors of paint are applied in the same paint booth for top-coating automobile exterior panels, and in order to change the colors of these dozens of paints, a color changer is installed in the painting path before the spray gun. Often installed.

The color changer uses a device as shown in the plan view in FIG. 1, and the outline of its configuration is as shown in the figure. A color changer manifold 6 is connected to the switching valve 4 connected to the color changing valve 4 through a cleaning valve 5, and the same number of paint hoses 8 are connected to the manifold 6 through dozens of valves 7. A paint hose 9 is attached to the tip of the manifold 6.
Usually, a spray gun 10 is attached via a.

To change the color of paint using the color changer, a spray gun 10 in which paint A from the previous painting remains, a paint hose 9, and a color changer manifold 6 are required.
The cleaning valve 5 and the valve 1a are opened and the switching valve 4 is switched to introduce compressed air from the air hose 2 into the equipment to discharge the paint A.

After the paint A is discharged from the inside of the device, the switching valve 4 and the switching valve 1b are opened, and a cleaning solvent is introduced from the cleaning solvent hose 3 to wash the inside of the device.

After cleaning, the switching valve 4 is switched again and compressed air is introduced from the air hose 2, and after removing the remaining cleaning solvent from the equipment, the cleaning valve 5 is closed, and the valve 7b is opened to supply paint B from the paint hose 8. This causes the color change.

However, in recent years, laws regulating pollution of water, air, noise, etc. are being enacted to protect the environment, and water-based paints are seen as promising as paints that cause less pollution.
When changing the color of the water-based paint, a color changer as shown in Figure 1 is used, and the cleaning solvent is deionized water. The present inventors have experienced that when a color change is performed, a large amount of paint is discharged immediately after the color change, resulting in many paint defects and sagging.

Note that the water-based paint in the present invention collectively refers to water-soluble paint, water-based emulsion paint, and water-dispersed paint.

Therefore, in order to prevent paint defects and sagging that occur immediately after changing the color of water-based paints, the inventors of the present invention have conducted repeated research on cleaning solvents used in color changes, and as a result, have succeeded in eliminating the occurrence of paint defects and sagging immediately after changing colors. We have developed a cleaning solvent that can be used in this way and propose it here.

The cleaning solvent of the present invention is characterized by using an aqueous solution having a composition of an organic amine concentration of 0.5 to 5% or an ammonia concentration of 0.1 to 2.0%.

When the organic amine concentration of the cleaning solvent used in the present invention is 0.5% or less, there is almost no difference from water and it is not effective, and when the organic amine concentration is 5% or more, the water-based paint is a dispersion type paint. Because the viscosity increases, the amount of paint discharged at the beginning of spraying is small, and defects such as a thin film initially occur.
The organic amine concentration was limited to 0.5-5%.

Note that as the organic amine, DMEA (dimethylethanolamine), triethylamine, morpholine, monoethanolamine, ethylmonoethanolamine, diethylamine, etc. can be used.

Also, the ammonia concentration is 0.1 as well as the organic amine concentration.
% or less, there is no effect, and if it exceeds 2%, if the water-based paint is a dispersion type paint, the viscosity will increase and the amount of paint discharged will change. Therefore, in the present invention, the ammonia concentration is set to 0.1 to 2%.
limited to the range of

One gram equivalent of ammonia is 1/3 to 115, and the concentration of ammonia needs to be lower than that of other organic amines.

EXAMPLES The present invention will be specifically explained below using Examples.

Example 1 Compressed air was supplied at an air pressure of 5 kg/cy4 for 5 seconds to discharge water-based paint A having the composition shown in Table 1 below from the spray gun, paint hose and color changer manifold, and then dimethylethanolamine ( Hereinafter referred to as DMEA.

) was added to 1%, 3%, and 10% of the inside of the equipment with deionized water, and the air pressure was 5 kg/cr.
At A, compressed air was supplied at four levels: 3 seconds, 6 seconds, 9 seconds, and 12 seconds to remove the remaining cleaning solvent.

After removing the cleaning solvent, water-based paint B having the composition shown in Table 1 below was supplied, and changes over time in the amount of paint discharged using compressed air supply time as a parameter for each concentration of DMEA in deionized water were measured.

To measure the amount of paint discharged, as shown in Figure 2, the spray gun 10 is fixed at a height of 1 m and the paint is discharged horizontally, and the amount of paint discharged in a minute time is calculated by determining how many meters the paint flies. We investigated changes in

In addition, for the measurement, we investigated in advance how many meters the paint would travel and how many cc/sec the discharge amount would be, and the calculations were made by comparing this.

The measurement results are shown in FIGS. 3 to 5.

Figure 3 shows the discharge amount of water-based paint B after cleaning the equipment with deionized water with a DMEA concentration of 1%, and Figure 4 G'! DM
Water-based paint B when using deionized water with an EA concentration of 3%
FIG. 5 shows the discharge amount of water-based paint B when using deionized water with a DMEA concentration of 10%.

In the diagram, 1 is 3 seconds, ■ is 6 seconds, ■ is 9 seconds, and ■ is 12 seconds.
The amount of water-based paint B discharged when the remaining cleaning solvent is removed by supplying compressed air per second is shown.

Said symbols are referenced in the drawings below.

In Figures 3 and 4, even if the organic amine concentration of the present invention (DMEA 1%, 3%) is within a limited range and the cleaning solvent remaining in the equipment mixes with the water-based paint, early paint discharge occurs. The quantity is stable.

On the other hand, in FIG. 5, it was found that the organic amine concentration was outside the limited range of the present invention (DMEA concentration 10%), and the water-based paint thickened and the paint discharge amount changed.

Reference Example 1 All examples were the same as in Example 1 except that the DMEA-containing deionized water used in Example 1 was replaced with conventional deionized water.
In the same manner as above, the change in the amount of paint discharged over time was measured using the compressed air supply time as a parameter.

The measurement results are shown in FIG.

From FIG. 6, it can be seen that when the inside of the equipment is cleaned with deionized water, the amount of paint discharged from the spray gun immediately after the paint is discharged is extremely large, and the amount of paint discharged does not become stable until about 3 to 4 seconds later.

That is, it is clear that immediately after cleaning with deionized water, paint defects and sagging are likely to occur because the amount of paint discharged is large.

Example 2 The water-based paint B used in Example 1 was diluted with deionized water with DMEA concentrations of 1%, 3%, and 10%, and conventional deionized water, and the viscosity of the paint relative to the dilution rate was measured. , its viscosity curve is shown in FIG.

In the figure, X is the DMEA concentration of 1%, Y is the DMEA concentration of 3%, z is the dilution rate viscosity curve with deionized water when the DMEA concentration is 10%, and W is the dilution rate with deionized water. Hail viscosity curve.

From FIG. 7, it was found that the DMEA-containing deionized water had less viscosity change (and was superior as a cleaning solvent) than the deionized water.

In this example, deionized water containing DMEA was used, but any amine applicable to water-based paints may be used.

As described above, the cleaning solvent for water-based paint color change of the present invention can ensure a stable paint discharge rate even immediately after cleaning with water-based paints whose paint discharge rate tends to change, and can prevent the occurrence of defects. Therefore, the present invention is of great industrial value.

[Brief explanation of the drawing]

Fig. 1 is a plan view of a color changer used for color change, Fig. 2 is an explanatory diagram of a device for measuring changes in paint discharge amount over time, and Figs. 3 to 5 are aqueous paints immediately after washing in Example 1. A graph of the change over time in the amount of paint discharged, FIG. 6 is a graph of the economic change in the amount of water-based paint discharged immediately after washing in Reference Example 1, and FIG. 7 is a graph of the dilution rate viscosity curve of the water-based paint in Example 2. It is. In the figure, 1, 7... Valve, 2... Air hose, 3... Cleaning solvent hose, 4...
...Switching valve, 5...Washing valve, 6.
...Color changer manifold, 8,9.
・・・・・・Paint horse, Arawa.

Claims (1)

[Claims] 1. A cleaning solvent for changing the color of water-based paint, characterized by using an aqueous solution having an organic amine concentration of 0.5 to 5% or an ammonia concentration of 0.1 to 2.0%.