the aqueous vehicle content which is typically water can vary depending on the type of materials to impart optimum handling properties and compatibility with other components in the mixture the vehicle content is less than it would be if the supercritical fluid were not used for example with water as a vehicle and co 2 as the supercritical fluid the amount of water can be reduced by as much as 15 as a typical example and it is to be understood that the present invention is not limited to these values a water content of typically about 29 to about 32 by weight without the co 2 addition would be reduced to about 27 to 28 by weight or lower if feasible the dry powder mixture components are first blended the liquid components are then added with further mixing to form a granular wet batch this batch is introduced into an extruder where it is further homogenized and de aired the extruder must be one in which the mixture components can be uniformly blended with the supercritical fluid thus two stage de airing single auger extruder or a twin screw mixer with a die assembly attached to the discharge end are suitable in the latter the proper screw elements are chosen according to material and other process conditions in order to build up sufficient pressure to force the batch material through the die extrusion temperatures typically range from room temperature to no higher than about 60 u00b0 c the supercritical fluid can be introduced into the extruder in any form that is easy to handle for example if supercritical carbon dioxide is used dry ice can be introduced into the extruder however the mixture in.