Insect proof boards
The object of the present invention is to impart lasting excellent insect proof property to boards. According to the present invention, an insecticidal treatment liquid which contains an insecticide in an aqueous dispersion of colloidal silica is applied to the surface of a coat on a substrate applied with coating. Namely, according to the present invention, since a coating composition is not used to fix the insecticide to the surface of the coat, the insecticide is not diluted with a resin in the coating composition.
1. An insect proof board obtained by applying, to the surface of a coat on a substrate applied with coating, an insecticidal treatment liquid which contains an insecticide in an aqueous dispersion of colloidal silica;
wherein the insecticide is a pyrethroid compound;
wherein the colloidal silica comprises about 10 primary fine particles each having a particle diameter of 5 to 10 nm; and
wherein the insecticidal treatment liquid comprises the insecticide, 0.1 to 2.0% by mass of the colloidal silica, 2 to 10% by mass of an alcohol, 0.01 to 0.25% by mass of a surfactant, and a balance amount of water.
2. The insect proof board according to claim 1 , wherein the insecticidal treatment liquid is prepared by adding the insecticide to a dispersion of colloidal silica in a mixed solvent of water and an alcohol.
3. The insect proof board according to claim 2 , wherein the dispersion of colloidal silica in the mixed solvent of water and an alcohol is incorporated with a surfactant as a dispersant.
4. The insect proof board according to claim 1 , wherein the substrate is a cement board, a cement extrusion-molded board, or a calcium silicate board.
5. The insect proof board according to claim 1 , wherein an applied layer of the insecticidal treatment liquid has a thickness of 30 to 80 nm.