Compagnie Francaise De Raffinage

K.r.p. Plastiques

Michel Vernon

Guy Lemoine

Robert Lucas

A continuous process for making rigid PVC foam objects by extruding a preform from an initial PVC mixture, optionally cutting the preform into blanks, and expanding the preform or the blanks in water heated to a temperature above 70.degree. C. The initial mixture contains polyvinyl chloride, at least a first blowing agent capable of generating a gas, for example an isocyanate or a polyisocyanate, and at least one organic anhydride (and does not contain any added inert particles finely divided therein). The initial mixture may also contain less than one weight percent of a second blowing agent, for example azobisisobutyronitrile or azodicarbonamide. The objects produced possess heat- and sound-insulating properties.

Process for the production of objects made of a rigid expanded material

An improved process and apparatus for producing rigid cellular materials comprising polyvinyl chloride, wherein the controlled expansion of embryonic blocks obtained by molding, is carried out in a single expansion box closed throughout the whole duration of the expansion treatment, in several stages including pre-heating, pre-expanding and final expansion to the final dimensions of the block, the expansion box containing the block expanded to its final dimensions being then immersed in a bath of cold water for dimensional stabilization. The expansion box comprises at least two plates, with a frame attached to the lower face of each plate, to form, in use, a closed expansion box which is provided with a centering and holding mechanism to maintain the embryonic block in place within the expansion box, a device for opening and closing the expansion box being also provided, as well as a mechanism for transferring a plurality of expansion boxes assembled together from one bath to the other in succession.

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Trilport, France

Michel Vernon