| In traditional process of reconstituted tobacco sheet by papermaking method, tobacco stem and scrap are mixed and refined at a high concentration. However, because tobacco stem and scrap are very difference in fiber properities and morphology, this process has many drawbacks, such as non-uniform tobacco pulp, much more small components, the declining of retention and drainage and the decreasing of the bulk. At the same time, the loss of aromatic composition in tobacco raw materials can not maintain the original natural flavor of the tobacco and affects the cigarette flavor. Because the tobacco pulp is made of tobacco stem and scrap which are mainly composed of the hybrid cells, epidermal cells and other non-fibrous components, the fiber content in tobacco pulp is less and the bonding strength of tobacco pulp is low, which can not meet the operating requirements of paper machine. Due to the critical requirements of the safety indicators, the selection and application of paper strengthening agent and other additives are greatly restricted. In order to ensure the stable operation of paper machine, the process of traditional papermaking tobacco sheet have solved these problems by adding wood fiber. However, although adding wood fiber can improve the physical strength of the tobacco sheet, and ensure the paper machine stable running, it inevitably brings about some negative impact on the intrinsic quality of reconstituted tobacco sheet. For example, it increases the wood gas and irritation feel of cigarette products, and brings about bad mouth feel. All these have restricted the use of reconstituted tobacco sheet in the cigarette manufacturing industry.Facing with these issues, we developed a new process for pulping of tobacco scrap, and the effect of different pulping processes of tobacco stem on the physical properties of reconstituted tobacco sheet was also investigated. Lastly, the fine prepared by beating of bleached soft wood kraft pulp (BSKP) was used as a strengthening agent in this study,and the effect of the fine on the physical properties of reconstituted tobacco sheet and the vacuum drainage of tobacco pulp was researched.Firstly, tobacco scrap was pulverized by Wiley mill and screened into different mesh scrap with 40-60mesh,60-80mesh,80-120mesh,120-200mesh,200-300mesh and>300mesh. Then, the different mesh tobacco scraps were extracted by water under a specific conditions. After separating solid from liquid, the solid, namely tobacco scrap pulp, was mixed with tobacco stem pulp, wood fiber and PCC to make reconstituted tobacco sheets. The physical properties (tensile strength, bulk and softness) of reconstituted tobacco sheets and the retention and drainage of the tobacco pulp were studied to optimize the suitable mesh of pulverized tobacco scrap. The results showed that with the increasing of the mesh number (the reduction of particle size) of pulverized tobacco scrap, the tensile strength of reconstituted tobacco sheet gradually increased, but bulk, softness and first pass retention decreased gradually, and permeance and drainage rate increased firstly and then decreased. With adding 60-120mesh tobacco scrap, the reconstituted tobacco sheet had better physical properties. Compared with the traditional processes,i.e. the tobacco scrap was refined at a low concentration or the tobacco stem and scrap were mixed and refined at a high concentration, the new process,i.e. the tobacco scrap was pulverized and extracted, had many advantages. The physical properties of reconstituted tobacco were improved, the bulk increased by 0.02cm3/g to 0.04cm3/g respectively, and the softness was improved greatly.Then the effects of different pulping processes of tobacco stem on the physical properties and hazardous substances of reconstituted tobacco sheet were investigated. The results showed that compared with the high consistency refining of tobacco stem, the low consistency refining of tobacco stem could improve the quality of reconstituted tobacco sheet. The bulk and softness of the reconstituted tobacco sheet were improved by 3.2%and 21.9%respectively, which could contribute to the full combustion of tobacco, as a result of reducing the harmful substances.Finally, the fines with different lengthes were prepared from BSKP and their effects on the physical properties (tensile strength, bulk and softness) of reconstituted tobacco sheets and the vacuum drainage of tobacco pulp were studied to optimize the suitable length and dosage of the fines added as a strengthening agent. The results showed that with the decrease in length and the increase in dosage of the fines, the tensile strength increase significantly, but the bulk, softness and vacuum drainage were affected negatively. This new process was compared with the traditional process. When the dosages of wood pulp and fines were 12% and 1% respectively, the bulk and softness were improved effectively in the case of a slight decrease of tensile strength, and the dosage of wood pulp reduced by 35%, which could contribute to the decrease of wood gas and the increase of the natural aroma components for the cigarettes. |
