Preparation Of Sodium Carboxymethyl Cellulose With High Degree Of Substitution From Moso Bamboo Shoot Shell

Sodium carboxymethyl cellulose (CMC) is an important kind of cellulose derivates and has been widely used as the thickener, emulsifier, flow controller, or stabilizer in a broad range of products including food, pharmaceuticals, oil drilling mud, detergents, paper, paint, and the textile industry. The properties of CMC are greatly influenced by the degree of substitution (DS). The DS value of CMC is defined as the average number of carboxymethyl groups per repeating unit. The properties of CMC water solution such as fungus resistance, salt tolerance, acid and alkali resistance increase with the increasing of the DS.China has the largest production amount of bamboo shoot in the world. The bamboo shoot shell can be used as an important source of the cellulose materials. In this paper, the moso bamboo shoot shell from Fujian province was chosen as the raw material for the source of cellulose. Firstly, the chemical components of moso bamboo shoot shell were quantitatively analysised to confirm the relative content of cellulose. The analysis results showed that the relative content of cellulose in the moso bamboo shoot shell was above 1/3. Moreover the lignin content of the moso bamboo shoot shell was low that may be good for the removing of the impurities. The moso bamboo shoot shell has a great exploitation and utilization value. The refined cellulose was extracted from the moso bamboo shoot shell by the chemical degumming method and the a-cellulose content was above 90% which could be applied to produce high quality CMC. The refined cellulose was characterized by scanning electron microscope (SEM) and x-ray diffraction (XRD). The obtained results demonstrated that most of the impurities were removed from the moso bamboo shoot shell and the obtained cellulose bundle became significantly soft and bend which may be good for carboxymethylation.The refined cellulose was then used for the mercerization and etherification modification. A new feed method was firstly proposed in etherifying stage that was sodium monochloracetate with monochloracetate (MCA) co-participate in the etherification reaction. This new method was called the mixed alkali etherification process in this work. The etherification efficiency and DS for CMC product were studied. This new mixed alkali etherification process was compared with the conventional process which applied monochloracetate as the etherifying agent directly. By experimental research, theoretical prediction and FTIR, SEM, XRD characterizations, it was speculated that the utilization efficiency of etherifying reagents were improved and more etherifying reagents could permeate into the cellulose. This lead to the destroying of the hydrogen bonds interactions between cellulose molecular chains and the decrease of the crystallinity of cellulose, therefore the uniformity of reaction and the DS of CMC were increased with the new method. The CMC with DS of 1.432 was achieved that belongs to high DS. The advantages and a certain generalizability were verified by the bamboo celllulose of the mixed alkali etherification process.Finally, the influences of the sodium hydroxide dose in the mercerization, monochloroacetic acid dose in mixed etherifying reagents, sodium hydroxide dose in mixed etherifying reagents, etherifying temperature and etherifying duration on the DS of CMC were investigated based on the mixed alkali etherification process from moso bamboo shoot shell. Moreover, the response surface methodology was applied to confirm the optimized technological conditions for new process and the CMC with DS of 1.457 was achieved under the optimum conditions.