Abstract: A method is provided for producing dense, free-flowing and non-caking alkali metal silicate-based particles which are heat expandable into lightweight particles of a spumiform character. Pursuant to the invention, one provides at a selected temperature a dilatant aqueous gel comprising an alkali metal silicate as the majority non-aqueous component, the silicate being present in the gel in a dissolved state; and the non-aqueous content of the gel being in the range of from about 38 to 65% (w/w). Shearing forces are imposed upon the gel which exceed the flow response characteristics of the gel, whereby the viscosity of the gel becomes sufficiently high to cause a discontinuity in the gel, resulting in disruption into discrete particles. The discrete particles are conditioned while being maintained as separate entities to thereby form a skin on the particles so that they will not agglomerate or coalesce with one another.

Abstract: Methods and additives for purging thermoplastic extruders and associated apparatus are included which involve the addition of a purging additive to a follower thermoplastic resin which additive when heated causes the follower resin to froth as it passes through the unit, the passage of frothed resin thereby causing the removal of the contents of the unit, which contents includes resident resin along with resident additives, degraded materials and any other undesired materials which may be present in the unit.

Abstract: A method of producing dense, free-flowing alkali metal silicate-based particles which, when sufficiently heated, will form lightweight particles of a spumiform nature which may be employed as thermal or acoustical insulation or as a lightweight filler for gypsum or cement or for numerous other purposes. The method comprises premixing a liquid alkali metal silicate with selected fillers and/or insolubilizers, adjusting the temperature and solids content of the mixture until it passes into a dilatant gel state which will fracture when extended at a rate of between about 3 and 95 cm/minute, and subsequently extruding or pelletizing the gel at this temperature to form particles which are conditioned in an air stream for at least one second and then dried to a moisture level of between about 5 and 30%. These particles or pellets serve as a stable intermediate which can be expanded to form lightweight spumiform particles by further heating at a later time or at a remote location.