Unbleached Cellulose Research Articles

IR SPECTRA AND HEATS OF HYDRATION OF THE OZONATED PULP

Reduce the consumption of chlorine dioxide in the bleaching of pulp is one of the main problems of technology of production of bleached pulp at Russian enterprises. We have developed a modified method of bleaching of sulphate hardwood pulp with a degree of ozonization. The new in work is the identification of the mechanism of ozonation on the structure of cellulose at different stages of the pulp bleaching. To assess structural changes of cellulose in the process of bleaching was used technique for IR spectroscopy. To characterize the hydrophilic properties of the cellulose used a calorimetric method and the method equilibrium sorption.Shown an advantage of using both chlorine dioxide and ozone in the bleaching of sulphate hardwood pulp. The obtained results of physical and chemical research associated with physico-mechanical properties of bleached and unbleached cellulose at different stages of bleaching. Shows the effect of ozonation on the mechanism of interaction of cellulose with bleaching agents. Effective delignification in the joint use of ozone and chlorine dioxide, can reduce the cost of bleaching chemicals. The brightness level corresponds to the world standards. and the content of organochlorine compounds (AOH) decreased by 30%. Reduce the consumption of chlorine dioxide helps to reduce contamination of waste water, reducing the content of organochlorine compounds (AOH).

Grinding process for the production of nanofibrillated cellulose based on unbleached and bleached bamboo organosolv pulp

Nanofibrillated cellulose (NFC) is a type of nanomaterial based on renewable resources and produced by mechanical disintegration without chemicals. NFC is a potential reinforcing material with a high surface area and high aspect ratio, both of which increase reinforcement on the nanoscale. The raw materials used were unbleached and bleached bamboo organosolv pulp. Organosolv pulping is a cleaner process than other industrial methods (i.e. Kraft process), as it uses organic solvents during cooking and provides easy solvent recovery at the end of the process. The NFC was produced by treating unbleached and bleached bamboo organosolv pulps for 5, 10, 15 and 20 nanofibrillation cycles using the grinding method. Chemical, physical and mechanical tests were performed to determine the optimal condition for nanofibrillation. The delamination of the S2 layer of the fibers during nanofibrillation contributed to the partial removal of amorphous components (mainly lignin), which have low polarity and improved the adhesion of the fibers, particularly the unbleached cellulose. The transverse modulus of elasticity of the unbleached NFC was highest after 10 nanofibrillation cycles. Further treatment cycles decreased the modulus due to the mechanical degradation of the fibers. The unbleached NFC produced by 10 cycles have a greater transverse modulus of elasticity, the crystallite size showed increase with the nanofibrillation, and after 5 nanofibrillation cycles, no differences are observed in the morphology of the fibers.

Bark derived submicron-sized and nano-sized cellulose fibers: From industrial waste to high performance materials

In this study, the use of bark as a natural source for the production of cellulose nanofibers has been explored for the first time. The fibrillation using bleached and unbleached cellulose fibers from the bark yielded sub-micron scale (<1μm) and nanoscale fibers (<100nm). Previous attempts to break the cross-linked lignin barrier to produce fibrillated submicron sized or nano sized cellulose fibers with high lignin content (>20%) have never been possible from any other sources. The maximum elastic modulus value of 15.6GPa and tensile strength value of 76MPa were obtained for the films made from fibrillated bark cellulose fibers. The water vapour barrier efficiency for these films is comparable to nanocellulose films from other studies.

Sound Absorption Properties of Unbleached Cellulose Loose-Fill Insulation Material

Recyclable cellulose loose-fill insulation has been commonly used in heavy timber construction for treating attic areas, under floors, and wall cavities. Through the kraft process, the unbleached cellulose adopts a texture characterized by small crumbs, forming a porous medium. In this work, different samples of a single layer of loose-fill cellulose insulation with different thicknesses were tested to measure their sound absorption properties, the airflow resistivity, and porosity for both dry and moist samples. The regression coefficients for an empirical model were calculated using a numerical optimization method. It is concluded that the model predicts the acoustical performance of this material well and that the sound absorption properties of the material are similar to those of mineral fiber-based materials.

UASB performance for bleached and unbleached kraft pulp synthetic wastewater treatment

This paper presents the performance of two bench scale Upflow Anaerobic Sludge Blanket reactors (UASB) used for the treatment of synthetic substrates that simulate bleached and unbleached cellulose pulp plant wastewaters. The control reactor was fed with diluted black liquor and the treatment reactor with the same substrate plus a mixture of chlorinated organics. The total concentration of the chlorinated compounds was gradually increased from 2.5 mg l −1 to 15.0 mg l −1. The average COD removal efficiency during the last phase of the experiment was 81% in the control reactor and 76% in the treatment reactor. These results indicate the capability of UASB reactors to treat this kind of wastewater and the low impact of the chlorinated organics on COD removal efficiency. The minimum overall chlorinated organics removal efficiency was 71% and the maximum was 99.7%. The experiment indicates that under the conditions used in this research the presence of chlorinated organics does not negatively impact the treatment process.

Cellulose from Softwood via Prehydrolysis and Soda/Anthraquinone Pulping

A two stage process based on a hydrolytic pretreatment and a soda/anthraquinone pulping stage has been studied to produce bleachable-grade cellulose from residual softwood sawdust, concretely a mixture of ground spruce (Abies alba) and pine (Pinus insignis). The hydrolytic pretreatment, which is carried out in an isothermal plug-flow reactor, solubilizes the hemicelluloses and substances of low molecular weight, and partially depolymerizes the lignin which can then be more easily extracted during the pulping stage. Soda/AQ pulping was performed on the pretreated fiber in a stirred batch reactor. The resulting cellulose pulps have low contents of residual hemicelluloses and ash, and a low enough amount of residual lignin which means that a chlorine-free bleaching procedure may be used. The effect of the process variables on the chemical characteristics and yields of the unbleached cellulose are presented. The combination of an autohydrolytic pretreatment at 231 °C for 5.5 min and a pulping stage at 170 °C for 150 min using 0.1% of anthraquinone, results in a cellulose yield of 64% of the potential. Because of the pretreatment the cellulose is partially depolymerized. This cellulose has a kappa number of 16.6, a non detectable content of hemicelluloses by HPLC analysis, an ash content of 0.60%(w/w) and an average degree of polymerization of 300.

Degradation of lignin with monomethylamine

AbstractWood chips were treated with gaseous mixtures of monomethylamine and water vapour at temperatures between 160 and 120°C and pressurs ranging between 1.5 and 7.0 MPa. The degradation products were subsequently extracted with different solvents at ambient pressure. First, The degradation products of lignin were extracted with highly selective organic solvents such as diethyl ether or 2‐butanone. Then, the remaining decomposition products were extracted with water or an aqueous solution of monomethylamine. The latter extract contains the degradation products of the hemicelluloses in a relatively high concentration. After a three hour digestion, the residue obtained from spruce had a lignin content of 3.1 wt‐% (pine: 3.7 wt‐%; birch 0.3 wt‐%). The total yield of unbleached cellulose was approximately 60 wt‐%.

Effects of water and bleaching on the mechanical properties of cellulose fibre cements

The mechanical properties of bleached and unbleached cellulose fibre—cement composites are studied in both dry and wet conditionS. Bleaching the fibres increases both the elastic modulus and flexural strength but reduces the specific work of fracture. Water has a dramatic adverse effect on the elastic modulus and flexural strength of the composites irrespective of whether the fibres are bleached or not. However, water increases remarkably the fracture resistance. A failure mechanism is proposed to explain these experimental results and this is supported by evidence obtained from scanning electron micrographs of fracture surfaces.

Study of the Kinetics of the Adsorption of Dialdehyde Starch on Cellulose

AbstractThe kinetics of adsorption of dialdehyde starch water solution on sulphite unbleached and bleached coniferous cellulose were studied. The kinetics of adsorption is described by an exponential kinetic equation applied for energetically uniform heterogeneous surfaces. The energy of activation for unbleached cellulose was in the limits from 10.6–27.6, while those of bleached cellulose were from 12.6–20.0 kJ/mol and were not dependent on the initial concentration of the DAS solution but linearly grow with the increase of the adsorbed DAS amount. The studied process was effected by the entropy factors exerting a defining influence on the initial rate, while the energy ones defined the changing of the rate.