Study On Dissolution And Regeneration Of Cellulose In The New Solvent System

Cellulose is the most abundant natural polymer on earth,which consists in plenty of resources.It has many virtues,such as environment friendly,and is widely used in textile,clothing,papermaking,medicine,building materials and coatings etc.Due to the high density of hydrogen bonds,it is difficult to be melted or dissolved.Both the traditional solvents such as copper ammonia solution or copper ethylenediamine aqueous solution,NaOH/CS2 and the reported new solvents,including LiCl/DMAc,NMMO,NaOH/H2O,NaOH/urea/H2O,ionic liquid,etc.have some drawbacks.The traditional solvents are being banned due to the bad stability of solution and the pollution.There are still some deficiencies about the reported new solvents,such as low solubility,the high price of the solvent or the limitation of recycling technology.Therefore,it is of great significance to develop a new generation of solvent which can dissolve cellulose conveniently,quickly and efficiently.Guided by the previous work of the research group and the thoughts of dissolving cellulose based on hydrogen bond competition and shielding mechanism,a new room temperature solvent system has been developed,which can directly and efficiently dissolve natural cellulose to obtain stable cellulose solution.The main works are as follows:(1)A new solvent system-TBD was obtained by introducing a cosolvent in TBAH aqueous solution,and the non-derivative dissolution of cellulose in the new solvent system was realized.8 wt%transparent solution of natural wood pulp with polymerization degree of 750 was obtained at room temperature in about 30 min.Increasing the temperature,increasing the content of TBAH,prolonging the time or decreasing the degree of polymerization of cellulose could improve the solubility to a certain extent,and a maximum of 12 wt%cellulose solution could be obtained.The interaction between co-solvent and TBAH as well as solvent and cellulose were analyzed,which revealed that the hydroxyl anions from the TBAH broke down inter-and intra-molecular hydrogen bond,in the same procedure,the co-solvent could stabilize the broken hydrogen bond in the solution,which led to the good dispersion of cellulose molecules in the solution.(2)The cellulose solution has been regenerated to cellulose II crystal directly in water or acid aqueous solution.The polarity of regenerated agent has a significant effect on the crystallinity of regenerated cellulose.When regenerated in water,the crystallinity of regenerated cellulose was as high as 57%,while the amorphous regenerated cellulose was produced in ethanol.The study of the gelation showed that the cellulose solution gelled in the presence of water vapor,air,carbon dioxide or hydrogen chloride.The regeneration of cellulose in water from the gelled cellulose solution was cellulose Ⅲ with TBA+ doping.(3)A new type of cellulose solvent has been developed,which can dissolve nature cellulose rapidly and efficiently at room temperature.Controlling the regeneration procedure,the regenerated cellulose with different crystalline structure can be obtained,including cellulose Ⅱ,cellulose Ⅲ and amorphous cellulose.The excellent solubility and the convenient process make the TBD solvent system have a good prospect in the field of wet spinning and film making.Regenerated cellulose with different crystalline structure has different thermal and mechanical properties,which will expand the application of regenerated cellulose in many fields.