GB884435A - Improvements in or relating to tobacco web material - Google Patents

Abstract

After the extraction of water-soluble constituents therefrom, natural tobacco is chemically digested to form a fibrous pulp from which a web is made, the web being thereafter impregnated with at least a portion of the extract. The extraction is effected by hot water in a closed tank, followed by draining, pressing and/or centrifuging. If the extract or insoluble portion are not to be immediately further treated they may be refrigerated or the latter formed into a dry pulp lap. Chemical digestion of the insoluble portion is effected by a caustic under pressure or by nitric acid, the digestion liquor being then removed by draining and pressing. Caustic digestion is controlled to leave the resultant pulp neutral, but nitric acid digestion leaves an acid pulp which is waterrinsed, neutralized with sodium hydroxide or carbonate, and again rinsed. The pulp is then formed into a water slurry and refined in a paper-making beater having a roll which effects a brushing action, fillers such as titanium dioxide, clay, calcium carbonate or activated alumina being added, after which the slurry is further refined in a Jordan machine, disc refiner or both, and is made into a web on a Foudrinier machine or other paper-making machine such as that of U.S.A. Specification 2,045,095, to the headbox of which an aqueous solution of cationic starch is fed simultaneously with the slurry, which may also have added thereto in the headbox a minor proportion of a slurry of manila hemp fibres of 5 ... 8 mm. fibre length. The formed and dried web is saturated by spraying or bathing with a solution of aldehyde and a protein or polymeric alcohol cross-linking agent and, optionally, humectant, ethyl or isopropyl alcohol and phosphoric acid, and is again dried. The polymeric alcohol may be polyvinyl alcohol and the protein may be soybean protein, casein or gelatin, and the aldehyde may be formaldehyde, acetaldehyde or glyoxal. Some or all of the aqueous component of the solution may be neutralized extract as described below. The water-soluble constituent extract is concentrated by evaporation and then acidified by a mixture of phosphoric and citric acids, the resulting protein precipitate being separated off if desired. The extract is then neutralized by potassium carbonate, and humectant, vegetable dye and, optionally, polyvinyl alcohol are added. The humectant may be glycerol, sorbitol or propylene glycol. The extract is added to the web by spraying or bathing, and the web is then dried and impregnated by running it through an emulsion of water and a vegetable wax or polyvinyl alcohol. Finally, the web is calendered and/or embossed to simulate tobacco leaf. The extract and insoluble portion may be bleached with hydrogen peroxide immediately after separation, even sufficiently to give a white final web for use as cigarette wrappers. The final web may also be used for cigarette fillers and cigar wrappers and binders. Quantitative process examples are given.