Study On The Solubility And Application Properties Of Pulp Fiber In Alkali Urea Solution

In recent years, as people increasingly concerns the oil resources shortage question, the research of renewable biomass resources to replace petrochemical products have been the concern of scientists. Cellulose is considered to be the most abundant natural polymer on the earth, and it has the characteristics of easy biodegradation, is reproducible and can be derived. Due to the influence of the intramolecular and intermolecular hydrogen bonding, the cellulose molecules has the characteristic of super molecular structure of the coexistence of crystalline region and non-crystalline region, a lot of hydroxyl (-OH) was closed in the crystalline structure, leading to the low cellulose reactivity. Simultaneously, with the influence of paperless office and low carbon and environmental protection idea of people habits, the development of traditional paper industry has been an unprecedented challenge. The utilization of pulp fiber in the traditional paper industry has to face seriously affected. So the research on of the material utilization in the field of non paper pulp fiber will become an important subject in the future.In the experiment, the soft-wood pulp fiber was used as the raw material, and the NaOH/urea and NaOH/thiourea/urea aqueous solution were used as the solvent of the pulp fiber to study the dissolution characteristics of the pulp fiber. In the course of the study, the dissolution rate and relative water retention value were the evaluation indexes. And the effects of solvent ratio, solution temperature, stirring speed and the quality of raw materials on the solubility of pulp fiber were studied. The structure and properties of the pulp fiber were analyzed by means of FQA, FT-IR, XRD, SEM and TG before and after dissolution. Studies have shown that the best dissolving effect on pulp fibers of two types of alkali urea system was at -10℃. The best ratio of NaOH/urea solvent was 7:12 (Wt%), and the maximum dissolution rate was 50.04%, the best ratio of NaOH/thiourea/urea was 7:7:7 (Wt%), and the maximum dissolution rate was 63.95%. The water retention value of NaOH/urea solvent treated fiber can reach the optimum value 562.3%. The water retention value of the NaOH/thiourea/urea solvent treated fiber can reach the best value 645.3%. The fiber morphology changed obviously after alkali urea solution treatment:the fiber length became shorter, and the surface and interior were damaged by different degree. But the cellulose macromolecule chemical structure was not changed. The crystallinity of cellulose was obviously decreased, and the crystal structure of cellulose I was transformed into cellulose II crystal structure.Beating and cellulase hydrolysis treatment of pulp fiber in alkali urea system impact on solubility studies showed that the beating and cellulase pretreatment had certain activation on pulp fibers. The experiment determined the best pulping degree was 50° SR, the best enzyme treatment time was 2h. The dissolution of fiber in alkali urea system rate increased about 10%.The dissolution of fiber in alkali urea system rate increased about 20% and the relative water retention value showed the same change rule after pretreatment.It showed that the activation effect of cellulase pretreatment on fiber was good than beating pretreatment effect.The cellulose based hydrogels were prepared by crosslinking reaction with N-N’ methylene bis acrylamide (MBA) at room temperature. A series of controllable properties of cellulose hydrogel were prepared by controlling the amount of crosslinking agent. The results showed that the cellulose hydrogel prepared by pulp fiber had a three-dimensional network structure, which had a strong ability of water absorption and dye adsorption. The maximum water absorption of the hydrogel was 180.4g·g-1, and the adsorption rate of methylene blue dye was 2.440mg·g-1.