• Nousiainen, Pertti
• Vehviläinen, Marianna
• Grönqvist, Stina
• Janicki, Jaroslaw
• Kamppuri, Taina
• Rom, Monika
• Christoffersson, Kristina Elg
• Ciechanska, Danuta
• Siika-Aho, Matti

Abstract

Cellulose is an ideal raw material for a large variety of products,because it is biodegradable, renewable, non-toxic and plentiful. The mostimportant cellulose source is wood, which contains about 40% of cellulose fromits dry weight. In order to utilise cellulose for high value applications itis separated from the other wood components in the chemical pulping process.The purified cellulose is known as dissolving grade chemical pulp and itscellulose content is from 94% to 97%. The pulp is most commonly used forregenerated cellulosic products such as cellulosic fibres, films, casings andsponges.The production of regenerated items requires the dissolution of cellulose andsubsequent regeneration into the desired shape. The dissolution of celluloseis challenging because of strong fibrillar structure of cellulose, whichrestricts its direct dissolution into cheap and common solvents.Consequently, most of the regenerated cellulosic products are manufactured bythe well-known viscose process in which a highly toxic carbon disulphide (CS2)is needed to transform cellulose into a soluble form. However, theenzyme-assisted method offers an ecological way to dissolve and processcellulose, and accordingly to eliminate the environmental load caused by theviscose process.Dissolving grade total chlorine free (TFC) sulphite pulp, a common rawmaterial for the viscose process, was treated with commercial enzymepreparation. The enzymatic treatment decreased the SCAN viscosity of the pulpby 33% and solubilised around 3% of the pulp material. The enzyme-treated pulpwas dissolved in aqueous sodium zincate solution and regenerated tocellulosic fibres (Biocelsol) using a wet spinning technique. The spinningdope contained 6wt% of cellulose, 7.8wt% of sodium hydroxide (NaOH) and0.84wt% of zinc oxide (ZnO). The fibres were spun into 15% sulphuric acid(H2SO4) bath containing 10% of sodium salt (Na2SO4), stretched in a hot waterbath, washed, finished and dried. The characteristics of the novel cellulosicBiocelsol fibres were measured and compared with thecommercial viscosefibres.The highest tenacity of the obtained fibres was 1.8 cNdtex-1 with elongationof 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 theBiocelsol fibres were slightly lower, but the crystallinity degreesignificantly higher than the comparable values of the commercial viscosefibres (2.1 cNdtex-1, 17% and 28%, respectively).The shape of the Biocelsol fibre cross section was circular and the structureof surface furrowed, whereas the typical cross section of the viscose fibresis serrated and the surface structure striped. The specific flexural rigidityof the Biocelsol fibres was 0.26 mNmm2tex-2 and of the viscose fibres 0.13mNmm2tex-2. The higher rigidity of the Biocelsol fibres is mainly due to theircircularcross section. The internal surface of the fibres as a function ofporosity was measured by SAXS. The internal surface of the Biocelsol fibreswas more than twofold as compared to the viscose fibres (1008 m2cm-3 and 428m2cm-3, respectively). This is explained by the fast coagulation rate of theBiocelsol fibres, which favours the development of pores. Consequently, thewater swelling of the Biocelsol fibres was 1.5 times higher than that of theviscose fibres, which is an interesting property regarding the hygieneapplications, for example.The raw material and fibre forming process of the Biocelsol and the viscosefibres are close to each other. The most significant difference is the absenceof carbon disulphide in the Biocelsol process. Even though, the chemicalcomposition of the fibres is alike, the properties differ largely from eachother. This is probably due to the rapid solidification of the Biocelsolspinning solution in the acidic bath without any chemical reaction. This leadsto the specific properties of the fibres and might restrict the developmentof higher tenacity fibres at the moment.The advantage of the enzyme-aided pulp treatment method is the totalelimination of CS2; it is not needed, because the cellulose dissolves directlyafter the enzymatic treatment. The enzymes originate from nature, arebiodegradable and do not threaten the environment. Their mode of action iscatalytic, thus the dosages needed are low and the optimal processingconditions moderate.The regenerated cellulose products manufactured from enzyme-treated pulp arenaturally biodegradable. In addition, they do not require bleaching, becauseno colouring and smell-forming sulphur by-products are formed in the process.Due to the absence of carbon disulphide, the cellulose solution could also beused for application, which does not allow any sulphur traces.The research was carried out in the EU FP6 project Biocelsol -Biotechnological Process for Manufacturing Cel...

Topics

• impedance spectroscopy
• pore
• surface
• Carbon
• zinc
• Sodium
• viscosity
• wood
• cellulose
• crystallinity
• small angle x-ray scattering
• dissolving
• Sulphur
• wet spinning
• rapid solidification