| 摘要 |
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. |
