Attapulgite as a Suspension Control Agent and Rheology Modifier in Flowables

摘要

Attapulgite, a naturally occurring mineral known also as palygorskite, is a 2:1 clay mineral (hydrous phyllosilicates). Attapulgite has a crystal lattice with a net negative charge causing the mineral to absorb cations in water or organic molecules to balance the charge deficit. The ability to bind organic and inorganic cations gives this mineral some of its special features, which led to commercial applications such as thickeners and organic sorbents. Attapulgite gel grades are processed in a different manner than the attapulgite sorptive grades to produce very different properties from the same mineral making these products valuable in very different applications. The gel products are characterized for imparting thixotropic viscosity to liquid systems, both solvent- based and water- based. Attapulgite as a mineral is a very hydrophilic material and, therefore, able to be dispersed easily in water systems. High shear is usually desirable to obtain the best performance. For solvent-based systems, the addition of a cationic surfactant becomes necessary in order to assure proper gel development. The ratio of attapulgite to surfactant is also critical and the optimum ratio should be detemined for any particular system. Gel products have found application as suspending agents and rheology modifiers for coatings, inks, adhesives, caulking compounds; animal feed supplements, wet flowable pesticides, etc. Attapulgite thickeners were compared to xantham gums in a water-based system and showed higher viscosity development efficiency and lower cost. The sorptive grades are characterized for their capability of absorbing organic liquids and come in either granular grades or powder grades. They have infinite applications including but not limited to carrier for pesticides, wettable powders, dry flowables or water dispersible granules and filtration products.