Cellulose is an ideal raw material for a large variety of products, because it is biodegradable, renewable, non-toxic and plentiful. The most important cellulose source is wood, which contains about 40% of cellulose from its dry weight. In order to utilise cellulose for high value applications it is separated from the other wood components in the chemical pulping process. The purified cellulose is known as dissolving grade chemical pulp and its cellulose content is from 94% to 97%. The pulp is most commonly used for regenerated cellulosic products such as cellulosic fibres, films, casings and sponges. The production of regenerated items requires the dissolution of cellulose and subsequent regeneration into the desired shape. The dissolution of cellulose is challenging because of strong fibrillar structure of cellulose, which restricts its direct dissolution into cheap and common solvents. Consequently, most of the regenerated cellulosic products are manufactured by the well-known viscose process in which a highly toxic carbon disulphide (CS2) is needed to transform cellulose into a soluble form. However, the enzyme-assisted method offers an ecological way to dissolve and process cellulose, and accordingly to eliminate the environmental load caused by the viscose process. Dissolving grade total chlorine free (TFC) sulphite pulp, a common raw material for the viscose process, was treated with commercial enzyme preparation. The enzymatic treatment decreased the SCAN viscosity of the pulp by 33% and solubilised around 3% of the pulp material. The enzyme-treated pulp was dissolved in aqueous sodium zincate solution and regenerated to cellulosic fibres (Biocelsol) using a wet spinning technique. The spinning dope contained 6wt% of cellulose, 7.8wt% of sodium hydroxide (NaOH) and 0.84wt% of zinc oxide (ZnO). The fibres were spun into 15% sulphuric acid (H2SO4) bath containing 10% of sodium salt (Na2SO4), stretched in a hot water bath, washed, finished and dried. The characteristics of the novel cellulosic Biocelsol fibres were measured and compared with the commercial viscose fibres. The highest tenacity of the obtained fibres was 1.8 cNdtex-1 with elongation of 14% and titre of 1.8 dtex. The crystallinity degree of these fibres was 47% and average size of crystallites 40Å. The tenacity and elongation of the Biocelsol fibres were slightly lower, but the crystallinity degree significantly higher than the comparable values of the commercial viscose fibres (2.1 cNdtex-1, 17% and 28%, respectively). The shape of the Biocelsol fibre cross section was circular and the structure of surface furrowed, whereas the typical cross section of the viscose fibres is serrated and the surface structure striped. The specific flexural rigidity of the Biocelsol fibres was 0.26 mNmm2tex-2 and of the viscose fibres 0.13 mNmm2tex-2. The higher rigidity of the Biocelsol fibres is mainly due to their circular cross section. The internal surface of the fibres as a function of porosity was measured by SAXS. The internal surface of the Biocelsol fibres was more than twofold as compared to the viscose fibres (1008 m2cm-3 and 428 m2cm-3, respectively). This is explained by the fast coagulation rate of the Biocelsol fibres, which favours the development of pores. Consequently, the water swelling of the Biocelsol fibres was 1.5 times higher than that of the viscose fibres, which is an interesting property regarding the hygiene applications, for example. The raw material and fibre forming process of the Biocelsol and the viscose fibres are close to each other. The most significant difference is the absence of carbon disulphide in the Biocelsol process. Even though, the chemical composition of the fibres is alike, the properties differ largely from each other. This is probably due to the rapid solidification of the Biocelsol spinning solution in the acidic bath without any chemical reaction. This leads to the specific properties of the fibres and might restrict the development of higher tenacity fibres at the moment. The advantage of the enzyme-aided pulp treatment method is the total elimination of CS2; it is not needed, because the cellulose dissolves directly after the enzymatic treatment. The enzymes originate from nature, are biodegradable and do not threaten the environment. Their mode of action is catalytic, thus the dosages needed are low and the optimal processing conditions moderate. The regenerated cellulose products manufactured from enzyme-treated pulp are naturally biodegradable. In addition, they do not require bleaching, because no colouring and smell-forming sulphur by-products are formed in the process. Due to the absence of carbon disulphide, the cellulose solution could also be used for application, which does not allow any sulphur traces. The research was carried out in the EU FP6 project Biocelsol - Biotechnological Process for Manufacturing Cellulosic Products with Added Value, with contract number of NMP2-CT-2003-505567. The text reflects only the authors’ views and the Community is not liable for any use that may be made of the information contained therein.
|Publication status||Published - 2008|
|MoE publication type||Not Eligible|
|Event||Fiber Society 2008 Spring Conference - Mulhouse, France|
Duration: 14 May 2008 → 16 May 2008
|Conference||Fiber Society 2008 Spring Conference|
|Period||14/05/08 → 16/05/08|