Preparation Of Modified Cellulose Acetate Fibers And Studies On Its Application In Filtration Of Cigarette Smoke

Carcinogens of many kinds in the cigarette smoke, such as TSNAs,PAHs and free radical, can be harmful to health. Lots of domestic and foreign researchers have accomplished much long-term work, among which adopting multiple cigarette filters instead of conventional filters is the main method. The multiple cigarette filters can dramatically improve the filtration ability and taste of the smoke, but they also have many disadvantages. The uniformity of additive in multiple filters may be poor. The process of manufacturing multiple cigarette filters is complex. The pollution of the air during the manufacturing process is grievous. And the cost of multiple cigarette filters is much higher. The disadvantages have limited the popularization of multiple filters.In order to solve the disadvantages of multiple filters, we plan to prepare modified cellulose acetate tow based on conventional process of cellulose acetate tow. The methods by using nanotechnology in spinning dope and surface modification of conventional cellulose acetate fibers haven't been reported in public.In this paper, the mechanism of filtration of particulate materials and vapour materials through cigarette filter and the filtration efficiency have been investigated. The test methods of tar,nicotine,carbon monoxide, TSNAs and free radicals have been established. The modifying process and filtration mechanism of harmful materials in the smoke have been investigated. The main contents are as following:1 Selection of additivesPorous materials, chemical materials, Chinese traditional medicine, biological materials and nano particles used in multiple filters have been reported. But there are few materials can be used in this paper. The additives used in spinning oil should be achromatous and flavourless, and be soluble in water.The pH value of additive solution should be 6～8. The additives used in spinning dope should be achromatous and flavourless, and be insoluble in acetone. The particle size of additives should be less than 1 um and easy to be dispersed in acetone. All of the additives selected in this paper can be heated to 120°C.Chitosan, polyvinyl alcohol, sodium pyroglutamic acid, zinc gluconate, sorbitol and starch were used as additives in spinning oil. The modified cellulose acetate fibers were prepared when we confirmed the adding sequence and quantity of additives.The results showed that sodium pyroglutamic acid was suitable to be added in spinning oil, and the modified cellulose acetate fibers could selectively eliminate tar and TSNAs in the smoke.Nano-silica, citric acid, nano-phosphate and zeolite particles were used as additives in spinning dope. The results showed that nano-silica had notable effection on tar in the smoke.2 Modification of additivesBased on selection of additives, chitosan was modifed in order to get better performance. We prepared chitosan-g-β- dextrine as additive in spinning dope. The results show that chitosan-g-β- dextrine has notable effection on tar and PAHs in the smoke. Compared with conventional cellulose acetate fibers, the modified ones containing chitosan-g-β- dextrine had better effection, and the reduction in PAHs in the smoke after filtration with the modified fibers was 48.1%.Besides, porous starch was used as carrier for biological enzyme by interconnection and adsorption. The porous starch with enzyme was used as additive in spinning dope. The results showed that the porous starch with enzyme had good and stable biological activity.3 Preparation of modified cellulose fibers towTwo methods of preparing modified cellulose fibers tow by spinning oil and dope were studied in this paper. We chose sodium pyroglutamic acid and chitosan-g- β- dextrine as additives in spinning oil, nano-silica and porous starch with enzyme as additives in spinning dope. We prepared cellulose acetate/nano-silica composite fibers and other modified cellulose acetate fibers on the industrial equipment successfully.The results showed that reduction in tar and TSNA in the smoke after filtration with the modified fibers containing sodium pyroglutamic acid was 16.4% and 25.7%. Among TSNA in the smoke , the reduction of the content of NNN was 67.6%.Nano-silica particles were easy to be dispersed in acetone after the surface modification with silane. Cellulose acetate/nano-SiO2 composites were prepared and spun into fibers. The results showed that the composite fibers had an optimal filtration effect on the tar in cigarette smoke. Compared with conventional cellulose acetate fibers, the composite ones had greater specific surface area, and the reduction in tar in the smoke after filtration with the composite fibers was 31.7%.Chitosan-g-β- dextrine had evident effection on tar and PAHs in the smoke. The reduction of PAHs was 46.6% which meaned that the modification of chitosan was effective.Porous starch was used as carrier for biological enzyme by interconnection and adsorption. The porous starch with enzyme was used as additive in spinning dope. The results showed that the reduction of free radicals in particulate phase and vapor phase were 21.34% and 25.07% by using the modified cellulose fibers.4 Mechanisms of effections on harmful componentsThe mechanisms of filtration of cellulose fibers in cigarette filters contain direct interception, inertial impaction,and diffusional deposition. A new mechanism was proposed in this paper was electric charge adsoption. Besides, much hydroxy and unsaturated bond exist on the surface of nano-silica and chitosan-g-β- dextrine. Thus many components in the smoke are easy to form hydrogen bond with the additives.BET method was used to characterize the adsorption ability of modified cellulose fibers. It is apparent that composite fibers have a greater specific surface area than pure CA fibers because of the gigantic specific area of the nano-silica particles on the surface. The increase of specific surface area was 104% ,and there existed lots of pores of 20～100nm on the surface of modified cellulose fibers. The filtration of harmful components in particulate phase was improved dramatically because of the change of surface morphology.The effection mechanism of filtration of TSNA is showed as following:The mechanism shows that sodium pyroglutamic acid has strong effection on TSNA with plane structure. But sodium pyroglutamic acid has the same electric charge with nicotine in the smoke, the modified cellulose fibers don't adsorpt nicotine. Thus the modified cellulose fibers can hold the taste of cigarette smoke. They eliminate harmful components such as tar and TSNA selectively.The effection mechanism of elimination of free radiclas is showed as following:5 Innovation points in the paperInnovation points in this paper are listed as following:(1) Modified cellulose acetate tow based on conventional process of cellulose acetate tow were prepared successfully. The methods by using nanotechnology in spinning dope and surface modification of conventional cellulose acetate fibers haven't been reported in public .(2) A series of modified cellulose fibers with different function have been prepared successfully. They can eliminate harmful components such as tar, TSNA, free radicals and PAHs selectively. Such products haven't been reported yet in the world.(3) Very single filament among the modified cellulose fibers contains additives. Thus modified cellulose fibers solve the disadvantage of poor uniformity of additive in multiple filters(4) Compared with conventioanl cellulose fibers, the cost of modified cellulose fibers only increases about 2%, and the cost of multiple filters will increase about 30%. The modified cellulose fibers have obvious cost advantage.(5) The mechanism of effections on harmful components were investigated deeply in this paper. And BET method was used to characterize adsorption ability of modified cellulose fibers for the first time.We invited experts to taste cigarette using modified cellulose acetate fibers. The results showed that the taste of cigarette using modified fibers became softer and lighter. And it matchs the demand of customers and the trend of "Chinese style cigarette". The modifed cellulose fibers in this paper has a great prospect of popularization in cigarette industry.