Reversibly swellable hydrophilic lamellar mineral - with unidirectional shrinkage on drying, useful as carrier, refractory binder and release agent

摘要

Mineral is based on a reversibly swellable 3-layer mineral of large-faced crystalline type, with disconnected crystal layer. This is produced from fine-grained vermiculite, hydro-mica or even nonswellable mineral with these minerals deposited within the crystals with >50 (>75)wt. % tabular crystals with extremely thin, uniformly planae tubular crystals with a thickness of 0.5-10(0.5-5) mu m and face dimensions corresponding to an equiv. dia. of 10-200 mu m and a ratio of thickness/equiv. dia. =1.10, (=1.20). The particles have hydrophilic properties at the planar faces, which rapidly take up or yield polar liquids, such as water, and strong adhesion or cohesion, which leads to shrinkage only in one direction, i.e. perpendicular to the tabular plane, on drying the particles from a dispersion in a polar liquid (water) or moistening the dray material. The particles lie over one another in layers and gave a plasticity of 35-65 wt. % dry material w.r.t. the moist material. Mineral is used partic. as refractory binder for the prodn. of mouldings and films and as release agent. It is also useful as carrier for various materials, e.g. plant protection agents.