Development of a staining preventive coating for architecture

Along with the improvement in weathering resistance of architectural coatings, staining has become a focus of interest among people working on urban buildings. Basic studies of staining have been carried out by the Public Works Research Institute Ministry of Construction to develop coatings which are largely free of objectionable stains in the form of mottles and streaks. Through this study, it has been shown that there is a correlation between the degree of staining of a surface when evaluated visually and Delta L*, used as a numerical scale, lightness difference. The staining is noticeable for everybody when Delta L* exceeds -10. The staining substances can be classified into two types, urban type and rural type. It was found that the urban type usually contains more lipophilic substances and is more lipophilic than the rural type. Taking into account the finding that the urban type staining is more intensive than the rural type, a group of urban type staining preventive coatings has been designed, which makes it easier for rain to rinse off the lipophilic stain. A technology has been developed which keep the surface of the coatings hydrophilic for an extended period of time without detracting from the weathering resistance. The staining preventive coating has been examined by newly developed accelerated tests. Its excellent staining preventive performance and weathering resistance have been proved. Subsequent field applications on condominiums and road constructions also demonstrate the excellent results.