New microbial products; CF2399 and CF2403, were discovered in a culture broth of fungi. In this study, the interaction between CF2399 and CF2403 and colloid particles and the dispersion stability were examined using Silica (SiO₂) and latex dispersions. CF2399 and CF2403 increased the negative surface charge on colloid particles and enhanced the dispersion stability due to their adsorption on the hydrophobic surface of colloid particles. Moreover, the dispersion stability of concentrated pigments (Titanium dioxide; TiO₂, and kaolin slurry) in the presence of CF2399 and CF2403 was examined. It was found that CF2399 and CF2403 have a high dispersion efficiency especially with a small dosage and that they should be useful as a dispersant for industrial applications.

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We investigated the influence of particle shape on classified size ranges when particles were sieved by a screen with square apertures, and proposed a sieving model for ellipsoidal particles with the diameter of three dimensions, L, B and T. The ranges of B, T and Heywood diameter D_H of the ellipsoidal particles graded by a pair of sieves were calculated based on the ranges of shape indices μ(=T/B) and λ(=B/L). In order to examine the validity of the sieving model, ranges of sizes and shapes of the sieved particles were measured using materials with various sizes and shapes. As a result, it was confirmed that the sieving model proposed in this paper can be applied to predict the range of size for sieved particles with a given range of shape.

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This study was undertaken to investigate the effect of initial slurry concentration on the particle shape and particle size distribution of precipitated calcium carbonate by a carbonation process in which CO₂ was blown into aqueous slurries of Ca(OH)₂. The present carbonation process was formulated on the basis of the concept that the rate of Ca(OH)₂ dissolution is balanced with the rate of CO₂ absorption by carbonation reaction in aqueous slurries containing Ca(OH)₂ fine particles. The relationship between reaction completion time and operational conditions was obtained.
The synthesized calcium carbonate powder was pure white calcite crystal and had cubical shape with a median diameter of 0.4-0.6μm. The reaction completion time was directly proportional to the initial concentration of Ca(OH)₂ in slurry. When the initial slurry concentration was increased to above 5.0wt%, the median diameter x₅₀ increased and the size distribution became narrow. The observed dependence of reaction completion time on the initial slurry concentration and the CO₂ sparging rate could be qualitatively interpreted in terms of the proposed formulation for the carbonation process.

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We developed a new apparatus to measure adhesive forces between fine particles and those of fine particles on a substrate with flat surface by a direct separation method. The apparatus monitored the behavior of individual particles by a microscope with image analyzer when particles were separated from each other, and was able to measure the adhesive force with a high resolution (approximately 2nN). Among the organic particles studied in the present work (corn starch, potato starch and lactose), potato starch showed the highest adhesive force, while lactose showed the lowest adhesive force on a substrates with flat surface. It was clarified that the particle diameter and the size distribution affect the adhesive force of fine particles.

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The effects of surface polarity of particles and the properties of solvent and dispersant (nonionic surfactant) on the dispersion stability of alumina, zeolite and surface-treated silica particles were examined in nonaqueous solvents. The degree of stability was evaluated by a coagulation rate method, which was newly proposed in addition to the sedimentation and rheological methods. As a result, it was found that the solubility parameter of solvent required to provide the maximum stability decreased with increasing surface polarity of particles. This tendency was explained in terms of the van der Waals' interaction between particles, assuming that the electrostatic interaction was neglected in a nonpolar solvent. Maximum stability was achieved at the maximum adsorbed amount of dispersant, as estimated by the adsorption model of dispersant on a particle surface.

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The simulation of flow behavior of two-component developer in electro-photographic equipment is performed to obtain knowledge about the optimum design of a development system. Particle element method taking into account the magnetic interaction between developing particles is used, and the validity of the simulation method is experimentally confirmed. The spike of magnetic brush on a magnetic roll and the shape change of magnetic brush due to changes in magnetic field are well expressed by the simulation. The effects of parameters of development equipment on the flow behavior of developer, such as shape of doctor blade and location of magnetic pole ete., are discussed. The flow behavior of developer changes with these parameters. There are optimum values in these parameters in order to avoid the fusion of toner particles and they are determined by the simulation. The proposed simulation gives very useful information for the design of two-component development system.

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