Research On Preparation And Characterization Of Mulberry Bark Sodium Carboxymethyl Cellulose

Mulberry bark is a great potential of natural renewable resources. In this work, the mulberry bark fibers whereα-cellulose content is 96.14% was extracted from mulberry barks by an secondary alkali cooking degumming at 100°C and bleaching process at atmospheric pressure. Hemicellulose, pectin and lignin and other impurities have been very low in mulberry fibers after chemical degumming, and the FT-IR and XRD results also indicated that these impurities were removed extensively in retting process. Then sodium carboxymethyl cellulose (CMC) was prepared from mulberry cellulose by alkalization and etherification, and the best preparation was got though orthogonal test. The mulberry bark CMC products with substitution degrees rangging from 0.5 to 1.0 was prepared by adjusting etherification temperature. Based on the industry standards QB/T 2318-2007 " toothpaste with sodium carboxymethyl cellulose," the chemical and physical indexes of CMC products were detected. The FT-IR spectras showed that the hydroxyl groups of cellulose molecules have had the chemical reaction with chloroacetic acid, and a part of the hydroxyl hydrogen in macrmolecular chain have been replaced by carboxymethyl. Therefore, the crystal structure of CMC and cellulose are also different. The thermal decomposition temperature of CMC is 320°C, which is lower than 380°C of cellulose, but was still higher than 300°C. So it has good heat-stable performance. From this, we think that mulberry bark fiber can be used as a raw material rich in cellulose.The viscosity is one of CMC product most important technical specifications. Its value is affected with the degree of substitution, concentration, time, shear rate and other factors. But changes in these parameters will also have the influence to the stability in its application process. Moreover, the effects of degree of substitution, concentration, time, pH, salt concentration, ect. on the viscosity of CMC solution were analyzed in this article. The results showed that the CMC aqueous solution exhibited the pseudoplastic fluid flow feature. The viscosity of CMC aqueous solution increased with the increase of degree of substitution and concentration. The solution could keep stable for a long period at high viscosity. The viscosity was maximum at pH = 8. And the salt viscosity ratio(SVR) decreased with NaCl content increased, but increased a little when concentration was higher than 6%. Because of more uniform distribution of substitution groups in molecular chain of high degree of substitution, the viscosity drop degree was small in the salt solution, and its anti-salinity was good. In addition, the acid viscosity ratio of high degree of substitution CMC (DS = 0.97) increased with the NaCl content and then decreased. Furthermore the AVR value was maximum when NaCl concentration was about 4%. All of the results suggested that the CMC products prepared from the mulberry bark could achieve the requirements for the application in the household chemical industry, such as detergent, toothpaste and textile, so that the mulberry bark could be used as the raw material for the preparation of CMC instead of cotton linter.In the paper industry, CMC can be added to the paper pulp to improve the physical strength of the paper. Because the fibers with a negative charge, CMC can be adsorbed to the fiber surface though other cationic auxiliary. The cationic polyacrylamide (CPAM) and the mulberry bark CMC with degree of substitution 0.97 and 0.52 were used together in this experiment. The results showed that, the enhancement effect of the mulberry bark CMC with degree of substitution 0.97 was better than the degree of substitution 0.52. And when the addition amount was 0.8 (w/w)% , the tensile index of the paper was the largest 51 N ? m / g. Furthemore when the intrant CMC with DS 0.97 was 0.4 (w/w)% of dry pulp, the elongation of paper was from 2.35% of pure pulp increased to 2.74%. The CMC with high degree of substitution used with CPAM, when the intrant CMC with DS 0.97 was 0.8 (w/w)% of dry pulp, the bursting strength of paper enhanced most. Moreover 0.4 (w/w)% of CMC added, the tearing and folding wndurance increase in a big way. The enhancement effect of CMC sample with low degree of subsitution was less than the higher one.