| abstract |
Primary polymer particles having a size at least 90 % below 10νm and which contain water-soluble and water-insoluble polymer are made by reverse phase polymerisation of a water-soluble ethylenically unsaturated monomer or monomer blend with cross-linking agent, and the emulsion is then spray-dried to form spray-dried granules which disintegrate upon addition to water, thereby forming an aqueous composition of the insoluble particles having activity similar to the starting emulsion. This aqueous composition of insoluble particles is particularly useful for flocculation, for instance, flocculation of sewage sludge followed by centrifugation or belt pressing, or for viscosification. |