the inventive process is described in more detail below with reference to examples . for this , first the term “ pressure time ” will be defined as the total of the pressure - buildup time up to the time the final pressure is first reached , and the optimum holding time after reaching the final pressure up to the start of the decompression operation . an inventive sufficiently long pressure time can be achieved by the following variants of the process procedure : i . slow pressure buildup until the directly following decompression ii . rapid pressure buildup with subsequent holding time , that is to say allowing the vessel to stand under pressure without feed or removal of treatment gas iii . rapid pressure buildup with subsequent holding time , before start of decompression there is a further feed of treatment gas to again reach the final pressure . since the pressure in the vessel decreases during the holding time owing to cooling , a process procedure as under variant iii ., makes it possible to re - establish the final pressure before the decompression . surprisingly , this procedure , compared with variant ii ., leads to a further , although small , increase in filling capacity . the following examples 1 and 2 describe first the effect of various pressure times and process variants at a filling density of tobacco in the pressure vessel of 0 . 15 kg / dm 3 according to the prior art : the high - pressure treatment was carried out in a laboratory autoclave using a contents volume of 2 dm 3 . jacketing for circulating liquid media served for setting the desired working temperatures . the pressure buildup proceeded from below , and the pressure reduction from above . a plurality of valves made the intended connection diagrams possible . a compressor served for setting the final pressure . the laboratory apparatus for thermal post - treatment consisted of a permeable wire mesh serving as conveyor belt , guide plates for forming the tobacco web in the desired width , a steam nozzle having a slotted exit orifice and a steam extractor disposed beneath the belt . the post - treatment with saturated steam was performed at a belt velocity of 5 cm / s and a steam output of 10 kg / h . the tobacco samples were spread out in flat plastic dishes and conditioned under standardized climatic conditions at 21 ° c . and 62 % relative humidity . the filling capacities were determined using a borgwaldt densimeter , and the specific volume , in cm 3 / g , was converted to a nominal moisture of 12 % by weight and a nominal temperature of 22 ° c . from the data of the untreated control or base samples and the expanded samples , the relative filling capacity increase , also termed degree of expansion , is calculated from the following formula , where f b is the filling capacity of the base sample and f e is the filling capacity of the expanded tobacco : the experiments were carried out at a tobacco moisture of 18 % by weight and initial tobacco weights of 300 g . the working temperature was set by thermostating to 40 ° c . the final pressure was 700 bar , and the decompression was performed in the course of about 0 . 5 min . all experiments were based on a uniform mixture of virginia tobaccos and the described post - treatment method using saturated steam . variations were made in the pressure buildup time , the holding time after reaching the final pressure , and also the option of further feed at the end of the holding time . table 1 contains a compilation of the experimental parameters and the relative increases in filling capacity , or degrees of expansion , achieved . the experiments were carried out in a similar manner to example 1 , but at a tobacco moisture of 12 % and a working temperature of 60 ° c . table 2 contains the experimental parameters and also the relative increases in filling capacity or degrees of expansion achieved . the results of examples 1 and 2 clearly show that in the range of conventional filling densities , the pressure time has only a small effect on the increase in filling capacity . the following examples 3 and 4 show the effect of different pressure times and process variants at a tobacco filling density in accordance with the invention in the pressure vessel of greater than 0 . 2 kg / dm 3 : the experiments were carried out in a similar manner to example 1 , but using an initial tobacco weight of 500 g . the tobacco was compressed by manual pressing during filling of the pressure vessel . table 3 contains the compilation of the experimental parameters and the relative increases in filling capacity , or degrees of expansion , achieved . the experiments were carried out in a similar manner to example 2 , but using an initial tobacco weight of 450 g . the tobacco was heated to approximately 50 ° c . using a microwave oven before the pressure vessel was filled and was compressed by manual pressing during filling . table 4 contains the compilation of the experimental parameters and the relative increases in filling capacity or degrees of expansion achieved . examples 3 and 4 illustrate the effect of pressure time on the increase in filling capacity at inventive filling densities greater than 0 . 2 kg / dm 3 . a good expansion effect can only be achieved under these conditions if the pressure time exceeds a value of approximately 300 sec . furthermore , it is clear that at comparable pressure times , process variant iii . gives the best results . another embodiment of the present invention concerns a process for enhancing the filling capacity of tobacco material or tobacco additional material , wherein the material is mechanically compressed before , during or after the pressure vessel is filled .
the invention relates to a process for enhancing the filling capacity of tobacco , such as cut tobacco leaf or tobacco midribs , or tobacco additional material , by treating the tobacco material having an initial moisture of 10 - 30 % with a treatment gas consisting of nitrogen and / or argon at pressures of 400 to 1 , 000 bar followed by a continuous decompression and subsequent thermal post - treatment of the discharged tobacco material . the filling density of the tobacco charge in the autoclave is greater than 0 . 2 kg / dm 3 .