JPH09227252A - Method for coating inorganic board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the adhesiveness, weatherability and water resistance of a coating film on the surface of an inorg. board. SOLUTION: A moisture-curing solvent-base coating material exhibiting good adhesiveness is applied on the surface of an inorg. board 1, and the coating film A of the coating material is coated with a water-base coating material good in weatherability to completely cover and enclose the coating film A by the coating film B of the water-base coating material. As a result, the liberation of the moisture contained in the inorg. board 1 number the coating film A to the outside is prevented, and the curing of the coating film A from its contact face with the inorg. board is promoted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for coating the surface of an inorganic board such as a fiber cement board, a gypsum board, a calcium silicate board, a magnesium carbonate board or the like.

[0002]

BACKGROUND OF THE INVENTION The above-mentioned inorganic board is used as an incombustible building board for interior boards, exterior boards, roofing materials and the like. The surface of such an inorganic plate is coated to reinforce and protect it. A water-based paint is recommended as a paint used for coating the inorganic plate. What is important is that the water-based paint uses a synthetic resin emulsion as a vehicle. In the synthetic resin emulsion, the molecular weight of the synthetic resin can be increased to improve weather resistance and durability. It is suitable for painting building boards exposed to the outside. In addition, the specific gravity of the roof material is generally 1.8.
It has a high specific gravity of ~ 2.2, and there is a demand for lightweight roofing materials from the structural problems of the load on buildings and the working environment of construction workers. However, it has been difficult to apply a paint having excellent adhesion and weather resistance to a lightweight roofing material having a specific gravity of 1.5 or less by using a water-based paint.

[0003]

2. Description of the Related Art Conventionally, there has been provided a method of applying a moisture-curable solvent-based paint on the surface of an inorganic plate and then applying a water-based paint (JP-A-6-345563).

[0004]

In the above-mentioned conventional method, the coating film of the moisture-curable solvent-based paint is cured by contacting with the surrounding moisture, but especially in the contact surface with the inorganic plate, it is contained in the inorganic plate. It cures due to moisture. However, if the coating film is not completely covered with the water-based coating film, the moisture-curing solvent-based coating film is exposed to the outside of the coating film, for example, the moisture-curing at the end face (edge) of the inorganic plate. The coating film of the moisture-curable solvent-based paint is formed on the exposed portion of the moisture-curable solvent-based paint Moisture contained in the inorganic plate escapes from the exposed parts to the outside, and the curing from the surface of the coating film of the moisture-curable solvent-based paint that is in contact with the inorganic plate is uneven or incomplete. As a result of preferential curing from the surface of the coating film that is in contact with moisture in the air, the adhesion of the coating film with the moisture-curable solvent-based coating becomes insufficient and The effect of improving adhesion was not sufficiently exhibited. There was also a problem of blocking due to an incompletely cured coating film.

[0005]

[Means for Solving the Problems] As a means for solving the above-mentioned conventional problems, a moisture-curing solvent-based coating material is applied to the surface of an inorganic plate, wholly or partially, and an aqueous coating material is applied onto the surface. The coating film of the solvent-based paint is applied so as to completely cover and prevent the escape of the moisture contained in the inorganic plate under the coating film of the moisture-curable solvent-based paint to the outside, It is intended to provide a method for coating an inorganic plate that promotes smooth and uniform curing from the surface of the coating film that is in contact with the inorganic plate.

[Inorganic board] The inorganic board targeted by the present invention is a molded product of hydraulic inorganic powder such as fiber cement board, gypsum board, calcium silicate board, magnesium carbonate board and the like. It is a desirable target. As the fiber cement board, mainly Portland cement, silica stone powder, silica sand, silicon dust, silicon-containing powder such as silicon flour is added thereto, if desired, fly ash, blast furnace slag, perlite, zeolite, One or more kinds of aggregates such as vermiculite are added, and if desired, calcium chloride,
A hydraulic inorganic powder mixture containing a hardening accelerator such as magnesium chloride, calcium sulfate, magnesium sulfate, aluminum sulfate, sodium aluminate, etc. is used, in which sepiolite, wollastonite, glass fiber, whiskers, etc. One or more kinds of inorganic fibers, wood fibers such as wood chips, wood wool and pulp, and organic fibers such as polyester fibers, polyamide fibers, acrylic fibers and acetate fibers are mixed. The fiber cement board is manufactured by molding a hydraulic inorganic powder mixture containing the reinforcing fibers into a plate shape by a dry method, a semi-dry method, a wet method, or the like, and curing it by natural curing or autoclave curing.

[Aqueous paint] The aqueous paint used in the present invention is a synthetic resin emulsion as a vehicle, and if desired, pigments or fillers such as calcium carbonate, titanium oxide, carbon black, chrome yellow, red iron oxide and the like. Further, if desired, a plasticizer such as dibutyl phthalate or dioctyl phthalate, a thickener or protective colloid such as polyvinyl alcohol, methyl cellulose or carboxymethyl cellulose, an ultraviolet absorber, an antiaging agent and the like are added. It is desirable to add the above-mentioned pigment or filler to the above-mentioned synthetic resin emulsion in order to improve the ultraviolet resistance of the paint. Examples of the synthetic resin emulsion include acrylic resin emulsions, vinyl acetate resin emulsions, styrene resin emulsions, urethane resin emulsions, and styrene-butadiene copolymer emulsions, which are commonly used as paint vehicles. An acrylic resin emulsion is a desirable synthetic resin emulsion for the present invention in terms of properties. The acrylic resin emulsion is an acrylic ester alone or a copolymer emulsion of an acrylic ester and another copolymerizable monomer such as methacryl ester, styrene, and vinyl acetate. The preferred composition for the water-based paint of the present invention is 15 to 20% by weight of synthetic resin solid content, preferably 16.5 to 18%.
% By weight, 12-16% by weight of the pigment or filler, preferably 13.5-14.5% by weight, 65-75% by weight of water, preferably 67.5-70% by weight. When a water-based paint is applied to the top coat, a synthetic resin having a low molecular weight and slightly inferior weather resistance may be used as the undercoat water-based paint before the medium-type solvent-based paint is applied.

[Moisture-Curable Solvent-Based Paint] The moisture-curable solvent-based paint used in the present invention uses an organic solvent solution of a moisture-curable synthetic resin as a vehicle. The above-mentioned moisture-curable solvent-based paint uses the organic solvent solution of the above-mentioned moisture-curable synthetic resin as a so-called clear lacquer, but if desired, a curing agent, or a pigment or filler similar to that used in the water-based paint. Materials, plasticizers, UV absorbers, antioxidants, etc. may be added. As the moisture-curable synthetic resin, an acrylic resin having a free isocyanate group or a hydrolyzable silyl group, a styrene resin, a urethane resin, a vinyl acetate resin or the like is used. Examples of the organic solvent used in the moisture-curable solvent-based paint include ethyl acetate, butyl acetate, toluene, xylene, cellosolve acetate, ethyl cellosolve, butyl cellosolve, methanol, ethanol, butanol, acetone, methyl ethyl ketone, and methyl isobutyl ketone. It

[Coating] For the coating of the present invention, a moisture-curable solvent-based paint is applied to the surface of the above-mentioned inorganic plate, the coating film is dried at least until the fluidity is substantially lost, and then an aqueous paint is applied and dried. Done by. The coating with the moisture-curable solvent-based paint may be performed in two steps, an undercoat and an intermediate coating, and a coating process with an aqueous paint may be added as an undercoat for the moisture-curable solvent-based paint. The coating is performed by using a general coating machine such as a roll coater, a spray, a flow coater, and a shower coater, but the type of the coating machine may be changed in each stage of undercoating, intermediate coating, and topcoating. The coating amount of the above paint is about 8 to 12 g / scale ² as the total resin content of each layer when three-step coating of undercoating, intermediate coating and topcoating is performed, and each layer when two-step coating of undercoating and topcoating is performed. The total resin content is about 13 to 17 g / scale ² . Drying after painting can be done naturally, or if the inorganic plate is aged in an autoclave, it can be dried using its preheat, or 90-
Heat drying at 110 ° C. for about 5 to 15 minutes is applied.

In the present invention, the moisture-curable solvent-based paint is applied to the surface of the inorganic plate prior to coating with the water-based paint. In the moisture-curable solvent-based paint, the moisture-curable synthetic resin is dissolved in an organic solvent at a molecular level,
When the moisture-curable solvent-based paint is applied, the moisture-curable solvent-based paint penetrates from the surface of the inorganic plate to the inside to reinforce the internal structure near the surface of the inorganic plate, thus anchoring effect and internal structure reinforcement. Due to the effect, the coating film A of the moisture-curable solvent-based paint firmly adheres to the surface of the inorganic plate. When a water-based paint is applied as a base coat, there are gaps formed between synthetic resin particles in the coating film formed by the water-based paint. The solvent-based paint penetrates into the inorganic plate through the gaps in the coating film of the water-based paint. Therefore, the internal structure in the vicinity of the surface of the inorganic plate is reinforced, and the coating film A of the moisture-curable solvent-based paint is anchored through the gaps between the coating films of the water-based paint, so that the coating film of the water-based paint is removed from above. Fix A on the surface of the inorganic plate. In particular, the roofing material as a base material has a high specific gravity to increase the strength and to improve the adhesion and weather resistance of the coating film A. However, the coating method of the present invention uses a moisture-curing type even if the base material has a low specific gravity. By applying the solvent-based paint prior to the water-based paint, the adhesion and weather resistance are improved by the above-mentioned action. In this way, the moisture-curable solvent-based coating composition is applied, and the aqueous coating composition is applied onto the coating film A formed by drying the coating film at least until the fluidity almost disappears. When the coating film A made of the paint is completely covered with the coating film B made of the water-based paint, the moisture contained in the inorganic plate below the coating film A does not escape to the outside and the coating film A is effectively removed. It acts substantially uniformly on the contact surface side with the inorganic plate to promote the curing of the coating film A from the contact surface with the inorganic plate. As a result, the coating film A adheres well to the inorganic plate, and is cured almost completely in a short time to lose the blocking property, and the coating film B of the water-based paint also exhibits good adhesion.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION

[Examples and Comparative Examples] A slurry containing 10 wt% of a mixture of 65 wt% cement, 20 wt% silica sand powder, 10 wt% fly ash, and 5 wt% pulp was made into paper by a usual method, and the paper product was pressed. After heating and curing at 60 ° C. for 10 hours, autoclave curing was performed at a saturated vapor pressure of 0.7 MPa for 10 hours, and an inorganic plate having a specific gravity of 1.3 to 1.5 and a considerably low specific gravity was manufactured.

As shown in FIG. 1, FIG. 2 and FIG. 3, the surface of the inorganic plate (1) is coated with an acrylic aqueous undercoat paint by spraying and dried to form an undercoat film C, on which a moisture curing type is applied. A solvent-based paint was applied and dried to form a coating film A. In the embodiment shown in FIG. 1, an aqueous top coating composition is applied onto the coating composition A by spraying, and the coating composition B is completely covered with the coating composition B of the aqueous coating composition. Comparative Example 1 shown in FIG.
In Comparative Example 2, the coating film B was formed only on the upper surface of the coating film A, and in Comparative Example 2 shown in FIG.
The film is dried at 105 ° C for moisture-curing solvent-based paint,
For 5 minutes, in the case of a water-based paint, heat drying was applied at 105 ° C. for 10 minutes. The coating amount was 10 g / square ² for each layer. The moisture-curable solvent-based paints used in this example and the comparative example were made of a non-yellowing moisture-curable urethane resin having a free isocyanate group at the terminal, methyl ethyl ketone: ethyl acetate = 6.
It is a clear lacquer dissolved in a mixed solvent of 0:40 weight ratio at a concentration of 30% by weight, and the aqueous paint is 40 parts by weight of acrylic resin emulsion (solid content 50% by weight), 2 parts by weight of color pigment, 7 parts by weight of titanium oxide. , 11 parts by weight of calcium carbonate and 60 parts by weight of water.

The following coating film performance tests were conducted on the test pieces of the three types of inorganic plates thus coated. Coating adhesion: 50 hours after immersion in water for 24 hours to absorb water
After conditioning for 2 hours at 70 ° C. and a relative humidity of 70%, a peeling test is performed with an adhesive tape to check the adhesion of the coating film. Table 1 shows the results of the coating film performance test.

[Table 1]

As shown in Table 1, in the test piece of the present invention, the coating film B prevents the moisture contained in the inorganic plate below the coating film A from escaping to the outside. The curing of A from the contact surface of the inorganic plate proceeds substantially uniformly and smoothly, and the coating film C, the coating film B and the coating film A exhibit excellent adhesion to each other. In the test piece of Comparative Example 1, since the moisture in the inorganic plate escapes from the end surface of the coating film B, the curing of the coating film A from the contact surface of the inorganic plate becomes incomplete and the in-layer destruction occurs, Further, the adhesion between the coating film B and the coating film A is considerably deteriorated. In the test piece of Comparative Example 2, the coating film A
As a result of the moisture in the air coming into contact with the surface of the film and the curing from the surface preferentially progressing, the curing from the contact surface of the inorganic plate of the coating film A becomes more incomplete, and the in-layer destruction of the coating film A becomes more remarkable. Become.

[0015]

Thus, according to the present invention, a coated inorganic plate having excellent adhesion, weather resistance and water resistance of a coating film can be obtained.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of an embodiment.

FIG. 2 is an explanatory diagram of Comparative Example 1.

FIG. 3 is an explanatory diagram of Comparative Example 2.

[Explanation of symbols]

 1 Inorganic board A Moisture-curing solvent-based paint film B B Water-based topcoat film

Claims (1)

[Claims] 1. A surface coating of a moisture-curable solvent-based paint on the surface of an inorganic plate, wholly or partially, and a water-based coating so as to completely cover and seal the coating film of the moisture-curable solvent-based paint. Method for coating an inorganic plate characterized by