JPH06134388A - Using method for recovered coating material - Google Patents

Abstract

PURPOSE:To use a recovered coating material for under coating without affecting coating color even in the case of a thin top coating film. CONSTITUTION:The recovered coating material is used by applying a recovered coating material mixed with plural colors as an intermediate coating or under coating of a top coating. In this case, the recovered coating material is controlled so as to be <+ or -5% difference between the average reflectivity of coating film of the recovered coating material and that of upper coating film. As the under coating film (or intermediate coating film) of the recovered coating material is reduced in affecting the coating color of the top coating film, even when the top coating film is thin the under coating film is thield with top coating film.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of using recovered paint recovered in a paint booth or the like.

[0002]

2. Description of the Related Art When paint is spray-painted in a paint booth, a large amount of paint dust that does not adhere to the object to be painted is generated, but this paint dust is dissolved or dispersed in the wash water in the paint booth and collected. Has been done. The amount of paint dust collected in this wash water is large, and if this is to be discarded, a large amount of money will be required for disposal such as wastewater treatment, and even if it is discarded, the method of burying it in the soil is the mainstream. There is a risk that environmental pollution will occur, and the useful paint will be lost.

Therefore, as for the water-based paint, it has been conventionally studied to collect and reuse the paint collected in the washing water. For example, a recovery method as disclosed in JP-A-49-51324 has been proposed. That is, the paint dilution water obtained by collecting the sprayed paint in water is passed through a reverse osmosis filtration membrane or an ultrafiltration membrane to ultrafilter the water to return the concentration to the same level as the original paint. In this way, it can be reused.

The paint thus collected in the washing water can be reused by being concentrated and recovered by ultrafiltration. However, this method is effective if the paint used in the paint booth has only one color, but in practice, paints of various colors are generally used depending on the object to be painted and the purpose of painting. In many cases, paints of various colors are applied in the same paint booth. In such a case, the plurality of paints collected in the wash water in the paint booth are mixed and become gray, and the recovered paint has a color different from the original color. Therefore, the recovered paint cannot be used in the same way as the original color paint.

For this reason, the usage of the recovered paint is as follows.
It is suitable for use in an undercoat paint (or an intermediate paint) in which the color is not a problem because it is hidden by the overcoat film.

[0006]

However, since the recovered paint has a color different from that of the overcoat paint, when the recovered paint is used as the undercoat paint, the color of the undercoat paint film does not affect the coating color of the overcoat paint. In order to completely conceal with the top coat, the top coat is generally 25 to 30 μm.
It is necessary to apply a thick coating so that the film thickness will be m or more, and a large amount of topcoat paint is required. When the topcoat film thickness is limited, the recovered paint is used as the undercoat paint. There was a problem that I could not do it.

The present invention has been made in view of the above points, and it is possible to use the recovered paint for undercoating and intermediate coating without affecting the coating color even if the thickness of the topcoating film is reduced. It is an object of the present invention to provide a method of using a recovered paint capable of achieving the above.

[0008]

The method of using the recovered paint according to the present invention is to recover the recovered paint by using the recovered paint in which a plurality of colors are mixed as an undercoat or an intermediate coat of a top coat. It is characterized in that the recovered paint is adjusted so that the difference between the average reflectance of the paint film and the average reflectance of the topcoat film is within ± 5%.

In the present invention, the average reflectance of the coating film of the recovered paint can be adjusted by adding white paint or black paint to the recovered paint. Further, in the present invention, after the electrodeposition coating is carried out as an undercoat and heated and dried, the recovered coating can be used as an intermediate coating. Hereinafter, the present invention will be described in detail.

In the present invention, as the recovered paint, paint dust generated during spray painting in the paint booth is dissolved or dispersed in the wash water in the paint booth and collected, and the paint dust is collected in water. It is possible to use the recovered water by diluting the obtained paint dilution water through a reverse osmosis filtration membrane or ultrafiltration membrane so that the water concentration is restored to the same level as the original paint. It is a thing.
Since a plurality of kinds of paints having different colors are often used in the paint booth, the paint collected by collecting in the wash water in the paint booth is generally gray because a plurality of colors are mixed.

In the present invention, this recovered coating material is used as an undercoat (or an intermediate coating). Needless to say, it is used as an undercoat coating in the case of two coats of an overcoat coating and an undercoat coating. In the case of 3 coats of undercoating, it can be used as an intermediate coating besides the undercoating. That is, as in the automobile coating process, it is possible to coat the electrodeposition coating as the undercoat, dry and bake, then use the recovered coating as the intermediate coating and then coat the top coating. In short, in the present invention, the undercoat (or intermediate coat) using the recovered paint is defined to include all those which are applied on the lower side of the overcoat paint. The difference between the average reflectance of the coating film of the recovered paint and the average reflectance of the top coating film is ±
If it is within 5%, the recovered paint can be used as it is as an undercoat (or an intermediate coat).

In the present invention, the average reflectance is defined as follows. That is, the average reflectance of the recovered paint is
20 nm in the reflection region with a wavelength of 420 to 680 nm
It is defined as the average value of the reflectance at every other interval. The average reflectance of the overcoat paint is defined as the average value of the reflectance every 20 nm in the reflection region where the reflectance / wavelength gradient is smaller than 1 (<1).

However, in general, the difference between the average reflectance of the coating film of the recovered coating material and the average reflectance of the coating film of the top coating is ±
It is usually over 5%. Therefore, in this case, it is necessary to adjust the collected paint so that the average reflectance of the coating film of the recovered paint is close to the average reflectance of the top coated film. The average reflectance can be adjusted by adding a white paint or a black paint to the recovered paint and mixing them. When the average reflectance of the coating film of the recovered paint is lower than the average reflectance of the top coating film, white paint is added and mixed to the recovered paint to increase the average reflectance. When the average reflectance of the coating film of the recovered coating material is higher than the average reflectance of the top coating film, the black coating material is added and mixed with the recovered coating material to lower the average reflectance. In this way, the average reflectance of the recovered paint is adjusted so that the difference between the average reflectance of the coating film of the recovered paint and the average reflectance of the coating film of the topcoat is ± 5%.

Then, the recovered coating material whose average reflectance is adjusted in this way is applied as an undercoat (or an intermediate coating) and dried, and then a topcoat paint prepared by coloring with a pigment is applied. It is possible to paint by drying by drying. In this way, when the recovered paint is applied as the undercoat, the difference between the average reflectance of the coating film of the recovered paint and the average reflectance of the coating film of the topcoat is set to be ± 5% or less. The effect of the undercoat coating film on the coating color of the topcoat film is reduced, and the film thickness of the topcoat film is 20 μm.
The undercoating film can be completely concealed even at a level below
It is no longer necessary to apply a topcoat paint to a thickness of 25 to 30 μm or more as in the conventional case. If the color difference between the surface coating color when the undercoating and the topcoating are performed with the same color paint and the surface coating color when the recovered coating is used for the undercoating is 1.0 or less, the recovered coating is used. The coating system used for the undercoating can be judged to be acceptable, but in order to make the color difference 1.0 or less, the average reflectance of the coating film of the recovered coating and the average reflectance of the coating film of the topcoat are Is required to be ± 5% or less. Therefore, in the present invention, the difference in average reflectance is limited to ± 5% or less. The adjustment of the average reflectance of the recovered paint can be easily done by adding a white paint or a black paint to the recovered paint, so this adjustment is also easily performed within the painting line. Is something that can be done.

When performing undercoating with the recovered paint, it is preferable to set the film thickness of the overcoat film to be the same as or thicker than the film thickness of the undercoat film. Also, it is preferable that the time between the undercoating and the overcoating is longer, and the undercoating film should be completely dried using an auxiliary drying device such as a far infrared heating device before the overcoating. Is preferred. Then, in the above example, the collected paint is used that is collected from the cleaning water of the coating booth, but the collected paint is not limited to this, and is, for example, a target of disposal due to a color mixing error or the like. The following defective paint can be used as the recovered paint.

[0016]

The invention will now be illustrated by the examples. (Examples 1, 2 and Comparative Examples 1, 2, 3) Cream color paint,
Four colors of Bayuge color paint, light blue color paint, and brown color paint are spray-painted, and the wash water in the paint booth is ultra-filtered to a non-volatile content of 55% by weight, and then gray paint is applied. Was recovered. Table 1 shows the reflectance of the coating film of the recovered paint with respect to the wavelength of light.

[0017]

[Table 1]

From Table 1, the average reflectance of every 20 nm in the wavelength range of 420 to 680 nm is 29.4%.
The average reflectance of the coating film of the recovered paint is 29.4%.
Met. Next, an adjusted white paint containing 40% by weight of a titanium pigment was added and mixed in an amount shown in Table 2 with respect to 100 parts by weight of the recovered paint to prepare an adjusted recovered paint 1 and an adjusted recovered paint 2. The adjusted recovered paint 3 and the adjusted recovered paint 4 were prepared. The average reflectance of each adjusted recovered coating material is shown in Table 2.

[0019]

[Table 2]

On the other hand, an orange paint was used as the top coat paint. The reflectance of the coating film of this orange paint at each wavelength is as shown in FIG. 1, and is 640 to 700 nm.
Table 3 shows the reflectance at every 20 nm in the wavelength region of. The average reflectance of the orange paint calculated from the reflectance of Table 3 was 50.7%.

[0021]

[Table 3]

Then, the recovered paint was applied as a one-stage paint (undercoating paint) to a dry film thickness shown in Table 4, baked at 140 ° C. for 20 minutes, and then an orange paint was used as a two-stage paint (topcoating paint). As a result, a two-coat coating was carried out by applying as above and baking in the same manner. Here, the adjusted recovered paint 2 and the adjusted recovered paint 3 in which the difference between the average reflectances of the coating films of the recovered paint and the orange paint is within 5% are Examples 1 and 2, respectively, and the recovered paint and the orange color are Unadjusted recovered paint and adjusted recovered paint 1 in which the difference in the average reflectance of the paint coating exceeds 5%,
The adjusted recovered paint 4 was used as Comparative Examples 1, 2, and 3, respectively. For comparison, orange paint was used as both the first-stage paint and the second-stage paint, and the two-coat paint was applied by applying the paint so that the dry film thickness shown in Table 4 was obtained and baking it in the same manner. It was set to 1.

The color difference between the color of the coated surface in Examples 1 and 2 and Comparative Examples 1, 2 and 3 and the color of the coated surface in Control 1 was measured. The results are shown in Table 4.

[0024]

[Table 4]

(Example 3, Comparative Examples 4 and 5) A red coating material was used as the top coating material. The reflectance of the coating film of this red paint at each wavelength is as shown in FIG.
The reflectance at every 20 nm in the wavelength region of 00 nm was as shown in Table 3 above. The average reflectance of the orange paint calculated from the reflectance of Table 3 was 35.6%.

The above-mentioned unadjusted recovered paint, adjusted recovered paint 1 and adjusted recovered paint 2 were used as the recovered paint, and the recovered paint was applied as a one-stage paint (undercoating paint) so that the dry film thickness shown in Table 5 was obtained. Then, after baking at 140 ° C for 20 minutes, the red paint is a two-stage paint (top paint).
As a result, a two-coat coating was carried out by applying as above and baking in the same manner. Here, the adjusted recovered paint 1 in which the difference in the average reflectance between the recovered paint and the red paint is 5% or less is shown as Example 3, and the difference in the average reflectance between the recovered paint and the red paint. The unadjusted recovered paint and the adjusted recovered paint 2 having a ratio of more than 5% were used as Comparative Examples 4 and 5, respectively. For comparison, red paint was used as both the first-stage paint and the second-stage paint, and the two-coat paint was applied by applying the paint so that the dry film thickness shown in Table 5 was obtained and baking it in the same manner. And

The color difference between the color of the coated surface in Example 3 and Comparative Examples 4 and 5 and the color of the coated surface in Control 2 was measured. The results are shown in Table 5.

[0028]

[Table 5]

As can be seen from Tables 4 and 5, those of Examples 1, 2 and 3 in which the difference in average reflectance between the coating films of the recovered paint and the topcoat paint is 5% or less are the coating films of the topcoat paint. Thickness 14
Even if the thickness was as thin as -15 μm, the color difference from the control was 1.0 or less, and the coating appearance was acceptable. (Example 4) A cationic electrodeposition paint ("Power Top U2600" manufactured by Nippon Paint Co., Ltd.) was used as an undercoat paint, which was electrodeposited on a steel sheet, washed with water, and then heat-cured at 170 ° C for 20 minutes. . After this, the recovered coating material used in Example 3 was applied as an intermediate coating material in the same manner as in Example 3, and the top coating material used in Example 3 was coated in the same manner.
The color difference between the top coating and the bottom coating was 0.4, which was as good as in Example 3.

[0030]

As described above, according to the present invention, when the recovered paint in which a plurality of colors are mixed is applied as the undercoat or the middle coat of the top coat, the recovered paint is used.
Since the recovered paint was adjusted so that the difference between the average reflectance of the coating film of the recovered paint and the average reflectance of the top coating film was within ± 5%, the undercoat film (or intermediate coating film) with the recovered paint
Has a smaller effect on the coating color of the top coating film, and even if the thickness of the top coating film is thin, the undercoat coating film (intermediate coating film) can be hidden, and the coating film thickness of the top coating film can be reduced. However, the recovered paint can be used for undercoating and intermediate coating without affecting the coating color.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the light wavelength and reflectance of an orange topcoat and a red topcoat.

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Toshihiro Okai 19-17 Ikedanaka-cho, Neyagawa-shi, Osaka Japan Paint Co., Ltd. (72) Inventor Tetsuro Fusano 19-17 Ikedanaka-cho, Neyagawa-shi, Osaka Japan Into Inc.

Claims (3)

[Claims] 1. When the recovered paint is used by applying the recovered paint in which a plurality of colors are mixed as an undercoat or an intermediate coat of an overcoat, the average reflectance of the coating film of the recovered paint and the average reflection of the overcoat film are used. A method of using the recovered paint, which comprises adjusting the recovered paint so that the difference in the ratio is within ± 5%. 2. The method of using the recovered paint according to claim 1, wherein the average reflectance of the coating film of the recovered paint is adjusted by adding a white paint or a black paint to the recovered paint. 3. The method of using the recovered coating material according to claim 1, wherein the recovered coating material is used as an intermediate coating after the electrodeposition coating is carried out as an undercoat and dried by heating.