The experiments were carried out to obtain the informations of the effects on the adhesive strength of coating films with some factors such as the kinds of pigment, pigment volume concentration and so on. The samples were nitrocellulose lacquer, acrylic lacquer and alkyd resin paint. Paints were prepared in various pigment volume concentrations with rutil titanium dioxide and carbon black pigments. Adhesive strength (Adherometer, ultrasonic wave method and crosshatch test), stress-strain properties and pigment interactions for the respective coating films were determined. Generally, the adhesive strength of the film increase with pigmentation. However, the cause and the factors which dominate the rate of increase of the adhesive strength are not clear. From our experimental results, it was found that as the system in which the interaction between pigment and vehicle was large, that is, the system in which the adhesion of vehicle molecule on the surface of the pigment was good, as the increase tendency of the adhesive strength was remarkable.
The purpose of this paper is to investigate about the discoloration of chrome vermilion in sulfuric acid solution, and also about its prevention method by surface treatment with reagents such as sodium lignin sulfonate, soluble starch, saponin, gum arabic and zein. The measurement of spectral reflectance, the X-ray analysis, the solubility of chrome vermilion composition in sulfuric acid solution and also the adsorption of zein on chrome vermilion in DMF (N, N-dimethylformamide) solution were carried out. The results obtained were as follow; Chrome vermilion is decomposed with sulfuric acid, and the color of chrome vermilion changed from reddish orange to yellow with decreasing pH. Chrome vermilion treated with certain surface treating agents showed no color change with increasing acidity. And the minimum concentrations of the surface treating agents to prevent discoloration were found as follow : 0.08% sodium lignin sulfonate, 0.40% soluble starch, 0.16% saponin, 0.40% gum arabic in aqueous solutions and 0.56% zein in DMF solution. The solubility of the sufficiently surface treated chrome vermilion in sulfuric acid solution became remarkably small. The adsorption of zein on chrome vermilion (at 25°C) followed Langmuir's isotherm. From the results of adsorption isotherm of zein on chrome vermilion and the minimum concentration of zein to prevent discoloration, it is concluded that the prevention of discoloration occurs nearly at the amount of saturated monolayer adsorption
The mixture of inorganic pigments and organic pigments in several weight ratios was ground by a grinder. The changes of the surface properties of the pigment mixtures with grinding time were investigated by specific surface area measurement, X ray diffraction analysis and electronmicrograph. As a conclusion, when the amount of organic pigment was large in proportion to that of the inorganic one, the inorganic pigment was covered by organic one and the grinding of the inorganic pigment was interfered by the lubricating action of the organic one.On the other hand, when the amount of inorganic pigment was large in proportion to the organic one, the lubricating action of the organic pigment was not found.