Abstract: The invention is directed to a process for increasing the filling capacity of tobacco under moderate conditions of temperature and pressure. Tobacco is impregnanted with a low boiling impregnant and thereafter subjected to a pre-expansion treatment. The pre-expansion treatment includes a pre-expansion temperature which is above the atmospheric boiling point of the impregnant and which is at least ten degrees below the critical temperature of the impregnant; and a pressure which is at least five atmospheres above the boiling point pressure of the impregnant at the pre-expansion temperature. Under these conditions, the impregnant is maintained primarily in the liquid phase throughout the pre-expansion treatment. Following the pre-expansion treatment, the pressure of the treated tobacco is rapidly reduced to a pressure below the boiling point pressure of the impregnant to thereby effect tobacco expansion without the need for a separate heating step.

Abstract: Cigarette rods and filter rods are provided by manufacturing rods from tobacco cut filler and a circumscribing paper wrap, and then subjecting the rods to conditions such that the cut filler undergoes volume expansion while within the paper wrap. For example, the tobacco rods can be exposed to propane under supercritical conditions within a pressure chamber followed by a venting of the gaseous fluid to expand the tobacco cut filler. The resulting rods are very firm, have good integrity, and frequently do not undergo any noticeable visible change. The resulting rods which contain the volume expanded tobacco can be used as smokable rods for cigarettes or as cigarette filters.