1978 年 98 巻 6 号 p. 782-788
Sedimentation volume (V2/V1), yield value (F), and differential viscosity (df/dg), obtained from the flow curve, were studied by changing the concentration of sodium chondroitin sulfate (Ch-Na) and/or simple salt in the concentrated system of aqueous kaolinite suspension. The above parameters decreased with increasing concentration of Ch-Na or simple salt by breaking the card-house structure of kaolinite (dispersing effect), but these parameters increased in the region of a high concentration of simple salt, showing aggregation between faces and/or edges of kaolinite by electrostatic shielding effect of the added salt. On the other hand, relative viscosity (ηrel) decreased with the concentration of simple salt or Ch-Na because the hydrodynamic radius of secondary particle became smaller with the concentration of addend, and the structure of secondary particle was more compact than card-hause structure at high concentrations of simple salt. The mean diameter (dm) of secondary particles, measured by the sedimentation balance in a dilute suspension, also decreased with the concentration of addend, as did F, df/dg, and V2/V1. It was concluded that the dispersing effect corresponds to making small particles in dilute suspension and to breaking the card-house structure in the concentrated suspension. The effective dispersing concentration of Ch-Na increased with the concentration of kaolinite because dispersing effect appears owing to its adsorption onto kaolinite but, in the case of simple salt, the concentration dependence was small because the ionic strength of the medium is effective for dispersing kaolinite particles by shielding the electrostatic attractive force between the face and edge of kaolinite particles.