Solubility parameters, hydrophilicity, hydrophobicity, acidity, and basicity of pigments, resins, and solvents were evaluated, and these values were used to apply affinity concepts to pigment dispereion. The results of these studies show that careful adjustment of the interactions or affinities among pigments, resins, and solvents is essential in designing the ideal pigment dispersions for organic coatings, and some important factors for the adjustment of the interactions, shown above were found.
Surface character of phthalocyanine blue pigments cotreated with acidic and basic derivatives has been studied in the respect of electrical phenomena in two kinds of different alkyd resin solutions. In short-oil-modified alkyd solution, surface potential increased proportionally as the basic treatment ratio increased; while in long-oil-modified alkyd solution, the increase of the surface potential was not proportional. In order to clarify the effect of the cotreatment on the surface potential, the elctrical conductivity of the dispersion in each resin solution was measured. The electrical conductivity increased as the basic treatment ratio increased, but the increasing rate was not proportional. The study of electrical phenomena suggested that acid and basic groups on the surface of cotreated pigment affect each other to be activated, and the treated surface interact with the resins.
Surface modification of maghemite magnetic particles by titanate coupling agents was performed. Good reactivity of titanate coupling agents to the surface of maghemite was confirmed. The magnetic paints of maghemite particles treated with titanate coupling agents showed excellent dispersibility. The magnetic recording tapes manufactured with these magnetic paints also showed excellent magnetic characteristics. The dispersibility of the paints was evaluated by observing the dependence of the orientation of magnetic particles on the alternating magnetic field. We have proven this novel evaluation method to be a useful method in evaluating the dispersibility of magnetic particles in these paints. This detailed analysis indicated that magnetic particles responded to the outer magnetic field in the primary particle unit.