JP3530869B2 - Coating method of inorganic substrate - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for coating an inorganic substrate. More specifically, the invention of this application relates to a method for coating an inorganic substrate, which can inexpensively prevent a coating film from being checked.

[0002]

2. Description of the Related Art Inorganic boards, mainly composed of cement and fiber components, to which fillers and the like are appropriately added and blended, are widely used for exterior wall materials, building exterior materials such as roof tiles. In the production thereof, a surface of an inorganic substrate which is molded from cement slurry and cured by curing is coated to impart makeup, water resistance, weather resistance and the like. As the paint, an organic water-based paint is mainly used, and it is applied by various methods such as spray coating and flow coater coating so that a thick film-like coating film of 30 μm or more is formed on the surface of the inorganic substrate.

Regarding the coating of the above-mentioned inorganic substrate, it has been pointed out that so-called checking such as cracking often occurs in the coating film due to drying after coating. The occurrence of checking not only impairs the appearance of the product, but also contributes to deterioration of various performances such as water resistance and weather resistance. Therefore, measures have been conventionally considered to prevent checking.

[0004]

For example, one of the proposals is to heat the inorganic substrate before coating. Checking often occurs in winter when the temperature of the inorganic substrate is 30 ° C or lower. Therefore, by heating the inorganic substrate to raise the temperature before coating and drying the coating film from the lower layer side thereof, that is, the inorganic substrate side, the drying from the surface can be suppressed and the checking can be prevented. It is thought to be possible.

However, in this case, since the inorganic substrate has to be heated to 30 ° C. or more before coating, even if a dryer for drying is used as equipment for that purpose, the temperature setting of the dryer is not possible. There is a problem in that it is necessary to raise the cost and increase the ability, which causes cost. Another option is to reduce the wind speed and temperature of the hot air blown onto the coating film surface during drying.

As a method for drying a coating film, a drying method generally known as jet drying is known in which hot air is blown onto the surface of the coating film. In this jet drying, by reducing the wind speed and temperature of the hot air blown onto the coating film surface, drying from the coating film surface is suppressed and checking is prevented, as in the case of the above-mentioned plan in which the inorganic substrate is heated before coating. It is thought that it can be done.

However, the heat energy for drying the coating film is reduced due to the decrease in the wind velocity and temperature of the hot air, and as a result, the drying process requires a long time, the production speed is reduced, and the cost is reduced. reflect. The invention of this application has been made in view of the circumstances as described above, and an object thereof is to provide a method for coating an inorganic substrate that can inexpensively prevent the check of a coating film.

[0008]

Means for Solving the Problems The invention of the present application is, in order to solve the above problems, a method for coating an inorganic substrate in which an organic water-based paint is applied on the surface of the inorganic substrate to a coating film thickness of 30 μm or more and then dried. At a yield value of 50-170
Apply an organic water-based paint in the range of dyn / cm ^{2 to} the surface of the inorganic substrate, and apply a temperature of 100 ° C or more and a wind speed of 7 m /
A method of coating an inorganic substrate (claim 1) is characterized in that hot air of min is blown for 30 seconds or more to perform drying .

The invention of this application is also directed to an inorganic base before coating.
Also intended to provide warming the plate to 20 ° C. or more (claim 2) as a good preferable manner. Hereinafter, the method for coating an inorganic substrate according to the invention of this application will be described in more detail with reference to examples.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION In the method for coating an inorganic substrate according to the invention of this application, the organic water-based coating material is applied to the surface of the inorganic substrate to a coating film thickness of 30 μm or more and then dried, as in the past. In the method for coating an inorganic substrate according to the invention of the application, an organic water-based coating material having a yield value in the range of 50 to 170 dyn / cm ² is coated on the surface of the inorganic substrate.

The inventors of the present application have noticed that the yield value of the organic water-based paint used for coating is in the range of 10 to 40 dyn / cm ² , and the low value of 30 μm
In the above thick coating film, it was thought that the undried internal coating material could easily flow and check after surface drying occurred during drying. Then, when the yield value range of the organic water-based paint in which the occurrence of checking is effectively suppressed is found, and the organic water-based paint having a yield value in the range of 50 to 170 dyn / cm ² is applied to the surface of the inorganic substrate. Obtained the knowledge that the high cost problem pointed out in the above two alternatives could be solved, and completed the invention of this application.

Here, the yield value generally refers to the force at which the generated deformation cannot be restored when a sufficiently large force (stress) is applied to an object (solid and liquid). The value means the limit of flow. Therefore, the greater the yield value of the paint, the less likely it is that movement such as sagging or shrinkage will occur. When the yield value of the organic water-based paint is 50 dyn / cm ² or more, the inorganic substrate is not particularly heated before coating,
Even if the velocity and temperature of the hot air during jet drying are not reduced, the coating applied in the form of a thick film having a thickness of 30 μm or more does not cause the check due to the drying. However, when the yield value of the organic water-based paint exceeds 170 dyn / cm ² , although the checking can be prevented, the surface of the paint film will become discolored, causing a new appearance defect and making it unsuitable for spray painting. Therefore, it is pointed out that the production speed is lowered and the cost is increased. Therefore, in the method for coating an inorganic substrate according to the invention of this application, the yield value of the organic water-based coating material for coating the surface of the inorganic substrate is set in the range of 50 to 170 dyn / cm ² . The yield value of the organic water-based paint can be adjusted, for example, by changing the addition amount and type of the thickener, and the adjustment to the above range is easy.

In consideration of weather resistance, the organic water-based paint preferably has a solid content concentration of 45% or more. If the solid content concentration is less than 45%, the weather resistance of the coating film will deteriorate. Thus, the coating method of the inorganic substrate of the invention of this application, the yield value was 50-170 dyn / cm ² by coating the surface of the inorganic substrate with an organic water-based coating, it was likely to occur by drying. Checking of the coating film is prevented, and this can be realized at low cost. For this reason, when so-called jet drying is performed after painting , hot air with a temperature of 100 ° C or more and a wind speed of 7 m / min can be blown on the surface of the coated film for 30 seconds or more to dry it, maintaining a high production rate. It is also possible to do.

In the method for coating an inorganic substrate according to the invention of this application, the inorganic substrate before coating can be heated to 20 ° C. or higher. As described above, when the temperature of the inorganic substrate becomes 30 ° C. or lower in the winter, etc., the coating film was likely to be checked due to drying.However, in the coating method for the inorganic substrate of the invention of this application, the yield of the organic water-based paint was Values 50-170 dyn / cm
^Since it is in the range of ² , even if the temperature of the inorganic substrate before coating is 30 ° C. or less, the check does not occur in the coating film. However, if the temperature of the inorganic substrate before coating falls below 20 ° C, it will take a long time to dry, and the production rate will be affected to a considerable extent. Therefore, in the method for coating an inorganic substrate of the invention of this application, the inorganic substrate can be heated to 20 ° C. or higher before coating to shorten the drying time. The heating temperature is 20 ℃
Since it is reduced as described above, for example, the load on the dryer is small, the jet drying described above is easily realized, and the cost is hardly affected.

[0015]

[Example] On the surface of an inorganic substrate for roof tiles, an organic water-based paint having a solid content concentration of 45% adjusted to the yield value shown in Table 1 was spray-coated, and then the coating film was heated at a temperature of 100 ° C and a wind speed of 7 m / min. It was dried by blowing hot air for 30 seconds (jet drying).
The presence or absence of checking due to drying, the appearance of the coating film, and the spray coatability were evaluated. The results are as shown in Table 1.

[0016]

[Table 1]

As shown in Table 1, when the yield value of the organic water-based paint for coating the surface of the inorganic substrate is in the range of 50 to 170 dyn / cm ² , jet drying is performed at a sufficiently high temperature with high speed hot air. Even if you go, the coating will not be checked,
A good appearance is obtained. Also, spray painting is possible, and the production rate is kept high. If the yield value of the organic water-based paint is less than 50 dyn / cm ² , the coating will be checked due to drying, and if the yield value exceeds 170 dyn / cm ² , a new appearance defect will occur and the spray coatability will be impaired. It

Of course, the invention of this application is not limited to the above-described embodiments and examples. It goes without saying that various aspects are possible in terms of details such as the type of organic water-based paint, solid content concentration, and drying conditions.

[0019]

As described above in detail, according to the invention of the present application, it is possible to inexpensively prevent the check of the coating film when coating the surface of the inorganic substrate in the production of the exterior wall material, the roof tile and other building exterior materials. It

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-5-96233 (JP, A) JP-A-49-99530 (JP, A) JP-A-9-188578 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) B05D 7/00 B05D 3/02 B05D 7/24 301

Claims (2)

(57) [Claims] 1. A method for coating an inorganic substrate, which comprises applying an organic water-based coating on the surface of an inorganic substrate so as to have a coating film thickness of 30 μm or more, and then drying the coating, wherein the yield value is in the range of 50 to 170 dyn / cm ^2. It was coated on the surface of the inorganic substrate, coating
When hot air with a temperature of 100 ° C or more and a wind speed of 7 m / min is applied to the surface of the subsequent coating film.
A method for coating an inorganic substrate, characterized by spraying and drying for at least 30 seconds . 2. The inorganic substrate before coating is heated to 20 ° C. or higher.
The method for coating an inorganic substrate according to claim 1, wherein