JP3533262B2 - Coating method of inorganic plate - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for coating a surface of an inorganic plate such as a fiber cement plate, a gypsum plate, a calcium silicate plate and a magnesium carbonate plate. BACKGROUND OF THE INVENTION The above-mentioned inorganic boards are used as non-combustible building boards for interior boards, exterior boards, roofing materials and the like. The surface of such an inorganic plate is coated to reinforce and protect the surface. A water-based paint is recommended as a paint used for coating the inorganic plate. Water-based paints use synthetic resin emulsions as vehicles. In synthetic resin emulsions, the weather resistance and durability can be improved by increasing the molecular weight of the synthetic resin. It is suitable for painting building boards exposed to the outside such as. The specific gravity of the roofing material is generally 1.8.
There is a demand for a lightweight roofing material having a high specific gravity of about 2.2 and a structural problem of a load applied to a building and a work environment of a construction worker. However, it was difficult to apply a coating having excellent adhesion and weather resistance to a lightweight roof material having a specific gravity of 1.5 or less. Therefore, there has been provided a method in which a water-based paint is undercoated on the surface of an uncured inorganic plate, cured and cured, and then the water-based paint is overcoated (JP-A-3-232782). . However, the synthetic resin emulsion, which is a vehicle of the water-based paint, is a dispersion of synthetic resin particles having a large particle diameter. When the paint is applied to the surface of the inorganic plate, the paint does not easily penetrate into the inorganic plate. There is a problem that the adhesion of the film is poor. In particular, in the case of a light inorganic plate having a low specific gravity and a good workability, the density of the inorganic plate is low and the internal structural strength is small. It becomes easy to peel off together with the surface layer of the plate, and the problem of adhesion becomes extremely serious. Therefore, as a means for solving the above-mentioned problem of adhesion, when coating the surface of the inorganic plate with a water-based paint, a moisture-curable solvent-based paint containing a urethane resin having an isocyanate group is applied prior to the coating of the water-based paint. A method of coating an inorganic plate is provided. The urethane resin having an isocyanate group is cured by moisture, but requires a large amount of moisture to be cured. Therefore, a coating film containing a urethane resin having an isocyanate group hardens on the surface where moisture is easily contacted, but the inside hardens slowly. The adhesion of the applied water-based paint film is reduced. Therefore, after the moisture-curable urethane resin paint is applied, it must be left for a long period of time to sufficiently cure the coating, resulting in inefficient coating. In particular, when the above-mentioned moisture-curable urethane resin paint is applied thickly, it takes a very long time to completely cure the coating film. Further, the urethane resin generates a toxic gas when burned, and thus is not desirable as a paint for an inorganic plate used for a building material of a house. According to the present invention, as a means for solving the above-mentioned problems, when a surface of an inorganic plate is coated with an aqueous paint, a moisture-curing method containing a synthetic resin having a hydrolyzable silyl group is used. An object of the present invention is to provide a method for coating an inorganic plate in which a solvent-based paint is applied prior to the application of the water-based paint. [Inorganic plate] The inorganic plate to be used in the present invention is a molded product of a hydraulic inorganic powder such as a fiber cement plate, a gypsum plate, a calcium silicate plate and a magnesium carbonate plate. It is recommended as a target. As the fiber cement board, mainly Portland cement, silica powder, silica sand, silicon dust, silicic acid-containing powder such as silicon flour is added,
If desired, one or more aggregates such as fly ash, blast furnace slag, pearlite, zeolite, vermiculite, etc. are added, and calcium chloride, if desired,
Use a hydraulic inorganic powder mixture to which a hardening accelerator such as magnesium chloride, calcium sulfate, magnesium sulfate, aluminum sulfate, sodium aluminate, etc. is added, and use as a reinforcing fiber sepiolite, wollastonite, glass fiber, whisker, etc. One or two or more kinds of organic fibers such as inorganic fibers, wood chips, wood wool, pulp, and other wood fibers, polyester fibers, polyamide fibers, acrylic fibers, and acetate fibers are mixed. The fiber cement board is manufactured by molding a hydraulic inorganic powder mixture obtained by mixing the reinforcing fibers into a plate shape by a dry method, a semi-dry method, a wet method, or the like, and curing by natural curing or autoclave curing. [Water-based paint] The water-based paint used in the present invention is a pigment or filler such as calcium carbonate, titanium oxide, carbon black, chrome yellow, red iron oxide or the like, if desired, using a synthetic resin emulsion as a vehicle. Further, if desired, a plasticizer such as dibutyl phthalate or dioctyl phthalate, a thickener or protective colloid such as polyvinyl alcohol, methylcellulose, carboxymethylcellulose or the like, an ultraviolet absorber, an antioxidant 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. Acrylic resin emulsions are desirable synthetic resin emulsions for the present invention. The acrylic resin emulsion is an acrylic ester alone or a copolymer emulsion of an acrylic ester and another copolymerizable monomer such as methacrylic ester, styrene, and vinyl acetate. The preferred composition for the water-based paint of the present invention is 15 to 20% by weight of the solid content of the synthetic resin, preferably 16.5 to 18%.
% By weight, 12 to 16% by weight of the pigment or filler, preferably 13.5 to 14.5% by weight, 65 to 75% by weight of water, preferably 67.5 to 70% by weight. When a water-based paint is applied to the top coat, as the undercoat water-based paint before applying the intermediate solvent-based paint, a synthetic resin having a low molecular weight and having slightly poor weather resistance may be used. [Solvent-based paint] The solvent-based paint used in the present invention is an organic solvent solution of a synthetic resin having a hydrolyzable silyl group as a vehicle. The hydrolyzable silyl group is an alkoxysilyl group such as methoxysilane and ethoxysilane, a halogenated silyl group such as chlorosilane and bromosilane, and the like. A hydrolyzable silyl group in which groups condense to form a siloxane bond. As the solvent-based paint, an organic solvent solution of the synthetic resin is used as it is as a so-called clear lacquer. If desired, a curing agent or a pigment or filler similar to that used for the water-based paint, a plasticizer, an ultraviolet ray An absorbent, an antioxidant and the like may be added. As the synthetic resin having a hydrolyzable silyl group, an acrylic resin, a styrene resin, a vinyl acetate resin or the like having the above hydrolyzable silyl group is used. It is desirable that a low molecular weight resin is mixed with the synthetic resin having a hydrolyzable silyl group. Since the low-molecular synthetic resin easily penetrates from the surface of the inorganic plate into the inside, the adhesion of the coating film of the synthetic resin is improved. As the organic solvent used in the solvent-based paint, ethyl acetate, butyl acetate, toluene, xylene,
Examples include cellosolve acetate, ethyl cellosolve, butyl cellosolve, methanol, ethanol, butanol, acetone, methyl ethyl ketone, methyl isobutyl ketone, and the like. [Painting] In the coating, a solvent-based paint is applied to the surface of the inorganic plate and dried, and then an aqueous paint is applied and dried. The coating with the solvent-based paint may be performed in two stages of undercoating and intermediate coating, or the undercoating with the solvent-based paint may be performed with a water-based paint. The coating is performed using a general coating machine such as a roll coater, a spray, a flow coater, and a shower coater. However, the type of the coating machine may be changed in each stage of undercoating, intermediate coating, and topcoating. The coating amount of the above-mentioned paint is about 80 to 140 g / m ² as the total resin content of each layer regardless of whether the three-stage coating of undercoating, intermediate coating, and topcoating is performed, or the two-stage coating of undercoating and topcoating. Just fine. Drying after coating may be performed by natural drying, when the inorganic plate is autoclaved, or by using preheating, or by heating at 90 to 110 ° C. for about 5 to 15 minutes. In the present invention, a solvent-based coating containing a synthetic resin having a hydrolyzable silyl group is applied to the surface of the inorganic plate prior to coating with the aqueous coating. In the solvent-based paint, the synthetic resin is dissolved in an organic solvent at a substantially molecular level. Therefore, when the solvent-based paint is applied, the solvent-based paint permeates from the surface of the inorganic plate to the inside. As described above, the synthetic resin of the solvent-based paint penetrates into the inside of the inorganic plate and coats the surface of the inorganic plate, and even when a small amount of water comes into contact with the inorganic plate or the moisture in the atmosphere, the sodium contained in the inorganic plate is reduced. The hydrolyzable silyl group of the synthetic resin is rapidly decomposed by the catalytic action of an alkali metal such as potassium or an alkaline earth metal such as magnesium or calcium to generate a silanol group, and a siloxane bond is further formed between the silanol groups. Thus, the synthetic resin is quickly cured not only on the surface but also inside the coating film. Then, the internal structure near the surface of the inorganic plate is reinforced, and the coating film firmly adheres to the surface of the inorganic plate due to the anchoring effect and the internal structure reinforcing effect. In particular, when a low-molecular synthetic resin is mixed, the low-molecular synthetic resin exhibits extremely high permeability to the inorganic plate, and the anchoring effect and the internal structure reinforcing effect are increased. When the water-based paint is applied on the coated film of the solvent-based paint formed in the cured state, good adhesion between the solvent-based paint and the water-based paint is obtained. Is shown. [Examples and Comparative Examples] A slurry containing 42.5% by weight of cement, 42.5% by weight of silica sand powder, 10% by weight of fly ash, and 5% by weight of pulp usually contains 10% by weight of a slurry. After the paper was pressed and cured at 60 ° C. for 10 hours, it was cured at room temperature for one week to obtain a specific gravity of 1.
3 to 1.5 inorganic plate blanks were produced. As shown in Table 1, a solvent-based paint and then a water-based paint were applied to the surface of the inorganic plate by spraying. For drying the coating film, heat drying was applied at 100 ° C. for 5 minutes after the application of the solvent-based coating, and 105 ° C. for 10 minutes after the application of the aqueous coating.
The coating amount 15 to 30 g / m ² of solvent-based paints and water-based paints and 80 to 120 / m ^2. The solvent-based paint used in this example was a mixed synthetic resin obtained by mixing a methoxysilyl group-containing acrylic resin with a methoxysilyl group-containing low molecular weight acrylic resin at 30% by weight, and toluene: ethyl acetate = 6.
A clear lacquer dissolved at a concentration of 30% by weight in a mixed solvent of 0: 40% by weight. The aqueous paint is 40 parts by weight of an acrylic resin emulsion (solid content 50% by weight), 2 parts by weight of a coloring pigment, 7 parts by weight of titanium oxide. , 11 parts by weight of calcium carbonate and 60 parts by weight of water. As a comparison, a solvent-based paint, which is a clear lacquer obtained by dissolving a urethane resin having an isocyanate group in a mixed solvent of methyl ethyl ketone: ethyl acetate = 60: 40 by weight at a concentration of 30% by weight, was used. Prepared a test piece of a coated inorganic plate in the same manner as in the example. The coating film performance tests described below were performed on the test pieces of the inorganic plates of the examples and the comparative examples coated as described above. Coating adhesion: After immersion in water for 24 hours to absorb water, excess water is wiped off, and then a peeling test is performed with an adhesive tape to check the adhesion of the coating. Adhesive strength with water-based paint film: After applying the water-based paint and drying and cooling, a steel block is adhered to the surface of the paint film, and after the adhesive is solidified, immersed in water for 24 hours, a tensile test is performed using an attachment. Do. Complete curing time of the coating film: After applying the solvent-based paint and drying under the above conditions, the coating film layer of the test piece is subjected to a peeling test with an adhesive tape under a normal temperature environment, and the number of days until the substrate is peeled is examined. . Table 1 shows the results of the coating film performance test. [Table 1] Referring to Table 1, the coating film of the present invention has excellent performance in both adhesion and adhesion strength as compared with the coating film of the comparative example. And, in the present invention, the coating film of the solvent-based paint is already almost completely cured after heating and drying, but the coating film of the comparative example has a surface layer portion in a cured state, but the interior is still uncured. Since it remains, it takes a long time until the solvent-based paint is completely cured, and a curing period of the product is required. According to the present invention, since a solvent-based paint containing a synthetic resin having a hydrolyzable silyl group which does not generate toxic gas and has a high curing rate even with a small amount of moisture is used, the coating process is also controlled. A coated inorganic plate which is easy and has excellent adhesion of the coating film can be obtained.

────────────────────────────────────────────────── ─── Continued on the front page (51) Int.Cl. ⁷ Identification code FI C04B 41/71 C04B 41/71 (56) References JP-A-7-109187 (JP, A) JP-A-7-108218 (JP) JP-A-6-345563 (JP, A) JP-A-8-301674 (JP, A) JP-A-9-227252 (JP, A) JP-A-11-236283 (JP, A) 9-278562 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C04B 41/00-41/72

Claims (1)

(57) [Claim 1] When coating the surface of an inorganic plate with a water-based paint, a moisture-curable solvent-based paint containing a synthetic resin having a hydrolyzable silyl group is applied before the water-based paint is applied. Coating method for inorganic plate characterized by coating