Heterocoagulation behaviour of polymer latices with spherical silica

Abstract

The heterocoagulation behaviour of amphoteric polymer latices (2 a = 250 nm) on large spherical silica (2 a = 240–1590 nm) was studied as a function of pH, particle size ratio, and of electrolyte and aqueous polymer concentrations in the medium. Under suitable conditions, the adhesion isotherms are all of the high affinity type with well-defined plateaus and the heterocoagulates generated from the mixed suspensions are comprised of uniform composite particles composed of lots of latex particles adhering to the silica particle in the core. Removal experiments show that the adhesion of latex particles is essentially irreversible except for adhesion occurring in a highly alkaline solution. Furthermore, it is found that addition of polymer or electrolyte to the medium is very useful in controlling the contents of organic and inorganic materials in the heterocoagulate particles. These conditions for forming the regular heterocoagulates and the properties of the products have been analysed using the theories of DLVO and heterocoagulation.