Solid polymer solution binders for shaping of finely-divided inert

Abstract

A new class of binders for binding finely divided inert inorganic molding particles when shaped into objects by known mechanical shaping techniques such as injection molding. The novel binders are solid polymer solutions containing a major fraction of a low molecular weight solid relatively non-volatile chemical as solvent in which is substantially dissolved a minor fraction of at least one high molecular weight solid polymer. The solid polymer solution binders when molten are homogeneous solutions and can be readily uniformly mixed with the usual inorganic molding particles into a readily flowable mixture which can be shaped and solidified. When solidified, the polymer and solid chemical remain a substantially homogeneous solution without appreciable phase separation. The solid chemical fraction can be eliminated from the solid object by selective solvent extraction, leaving the solidified polymer fraction essentially undisturbed as a porous matrix for the molding particles so that the shape of the object is faithfully preserved. The resultant porous body can be used as is or have the remaining polymer fraction eliminated, if desired, e.g. by thermal decomposition of the polymer, to obtain a shaped part of the inert inorganic material ready, if desired, for sintering. A coupling agent, such as a plastic or other additive, may be included to improve binder-particle adhesion.