Marianna Vehviläinen

Modification of hardwood dissolving pulp with purifiedTrichoderma reesei cellulases

Hardwood dissolving pulp was treated with purifiedTrichoderma reeseiendoglucanases and cellobiohydrolases. Endoglucanases were more efficient in hydrolysing pulp carbohydrates than were the cellobiohydrolases at the same protein dosage. Endoglucanases also lowered the viscosity and improved the alkaline solubility more dramatically. There was a clear correlation between the alkaline solubility and viscosity, and therefore the solubility could only be improved by lowering the viscosity of the pulp. At the same degree of cellulose degradation, endoglucanase II was found to be most effective in reducing the viscosity and thus improving the solubility. Cellobiohydrolases had a less pronounced effect on the viscosity or solubility.

Fibre porosity development of dissolving pulp during mechanical and enzymatic processing

Dissolving grade pulps are used as raw material for manufacture of regenerated cellulose fibres and their use is constantly growing. Despite intensive research, there is still a need to develop cellulose dissolution-regeneration processes that would be economically viable, fulfil the pre-conditions of sustainability and would be able to meet the strict product quality requirements. The basis for creation of such a process is in deep understanding of the biomass structure and factors affecting the cellulose modification and dissolution. In this paper, the effects of the mechanical and enzymatic pre-treatments on the pore structure and alkaline solubility of dissolving grade pulp are discussed. Formation of micro- and macropores in the pulp fibres during mechanical shredding was found to correlate with the susceptibility of the fibres to enzymatic hydrolysis. The fibre porosity development during the processing was studied by a modified solute exclusion approach, which revealed differences between the effect of mild enzyme or acid hydrolysis on the pore structure of fibres. The dissolution of the modified fibres in NaOH/ZnO was evaluated and found to correlate with overall pore volume and accessible surface area analysed by the modified solute exclusion method.

CELSOL – Biotransformation of cellulose for fibre spinning

The well-known ability of various cellulase enzymes to degrade cellulose has already been applied in order to improve the conventional cellulose xanthate process. The aim of the present CELSOL-research is to develop a method for making cellulose directly soluble in aqueous sodium hydroxide, without chemical substitution of the cellulose. The method is based on a combination of mechanical and biochemical treatments though efficient dissolution of hardwood pulps requires an additional chemical pretreatment. The effect of combined treatments on the supermolecular structure of common pulps was measured by the change in the degree of polymerisation and by the solubility of the cellulose in 9wt% aqueous sodium hydroxide. The celluloses treated by above methods are characterized to be highly soluble and the alkaline solution, containing 3-7 w/w% cellulose, can be regenerated to films and fibres.

Functional hybrid fibers of cellulose/microcrystalline chitosan. I. Manufacture of viscose/microcrystalline chitosan fibers

Blends of microcrystalline chitosan (MCCh) with cellulose xhanthate alkaline solutions were prepared to investigate the effects of aqueous MCCh gel concentration and additives on the spinnability of hybrid cellulose/chitosan fibers and their properties. The properties of the spinning solution were mainly dependent on the concentration of MCCh in the aqueous gel-like dispersion and the amount mixed into the cellulose xhanthate solution. Sodium alginate chemically close to cellulose and chitosan was used as an additive to improve the miscibility of chitosan due to the ionic bonds formed with chitosan 2-amino groups. Using an optimized ratio of 2 : 1 of MCCh to the sodium alginate, a maximum of 6% of MCCh calculated from alpha-cellulose content could be introduced into the sodium xhanthate solution containing originally 9% of alpha-cellulose. The yield of MCCh in the resulting fibers was dependent on the molecular mass, and varied between 73–82%. The strength, elongation, and color of the resulting hybrid fibers were only slightly changed and the WRV remarkably increased compared to standard fibers.

Impact of mechanical and enzymatic pretreatments on softwood pulp fiber wall structure studied with NMR spectroscopy and X-ray scattering

Dissolution of wood pulp can be enhanced by applying certain pretreatments before exposing the fibers to solvents. We have analyzed effect of mechanical and enzymatic pretreatments on softwood fiber wall structure using nuclear magnetic resonance (NMR) spectroscopic methods, small and wide angle X-ray scattering (SAXS, WAXS). NMR diffusometry was used to estimate the effect of pretreatments on average pore sizes at micrometer size scale and for the connectivity of the porous network. A proton NMR experiment was used to quantify the nonfreezing water content inside the fiber wall, and solid state NMR

The effect of the outermost fibre layers on solubility of dissolving grade pulp

^{13}\hbox {C}

EFFECT OF ACID AND ENZYMATIC TREATMENTS OF TCF DISSOLVING PULP ON THE PROPERTIES OF WET SPUN CELLULOSIC FIBRES

13C cross polarization (CP) magic angle spinning (MAS) spectroscopy was used to observe the effect of pretreatments on crystallinity and lateral fibril dimensions of cellulose fibrils, and in combination with fiber saturation point measurement to calculate the average pore size at nanometer size scale. Both WAXS and CP–MAS NMR experiments confirmed that there were no changes in crystallinity nor in fibril lateral dimensions due to pretreatments. The pretreatments caused an increase in the amount of nonfreezing water, suggesting an opening of the pore system. According to diffusion experiments there are only minor changes in micrometer scale pore network due to pretreatments. SAXS results indicated that enzymatic treatment increased the microfibrillar distance, and there was also an increase in cross relaxation rate of magnetization from water to cellulose protons as observed by NMR. These were interpreted to be due to opening of microfibrillar bundles, leading to an increased accessibility of water.

Dissolution of enzyme-treated cellulose using freezing–thawing method and the properties of fibres regenerated from the solution

ABSTRACT Never-dried pine sulphate paper grade pulp was treated with specific enzyme mixture from Trichoderma reesei , which increased the alkaline solubility of pulp from 20% to 69% and decreased the DP W from 1124 to 622. The effect of different viscose process additives and zinc oxide on solubility was studied. The best combination for producing a good spinning dope was chosen. The fibres were spun using a wet spinning machine and titre, tenacity and elongation of the fibres were determined. The strongest fibres obtained have tenacity of 1.2 cN/dtex and elongation of 12-13%, which are comparable to the properties of cotton.