Preparation and characterization of methylcelluloses from some annual plant pulps

We used iodomethane to synthesize methylcelluloses from elemental chloride free (ECF) bleached abaca, hemp, flax, jute, and sisal pulps via heterogeneous methylations. The heterogeneous methylation was carried out in isopropanol with iodomethane at 60 °C for 22 h after a pulp was mercerized in excessive 50% NaOH solution for 1 h at ambient temperature. A further methylation was carried out in dimethyl sulfoxide with iodomethane at 30 °C for 48 h using a methylcellulose of low degree of substitution. Fourier transform infrared (FTIR) spectra of the synthesized methylcelluloses showed the existence of methoxyl groups on methylcellulose macromolecules. The degrees of substitution of the synthesized methylcelluloses were measured by 13C nuclear magnetic resonance (NMR) spectroscopy. The molecular weights of the water-soluble methylcelluloses were determined by size exclusion chromatography (SEC). Intrinsic viscosities of the synthesized methylcelluloses were measured in 4% NaOH solution at 20 °C. Methylcelluloses with better properties, such as greater degrees of substitution, molecular weights, viscosities, and intrinsic viscosities, were prepared from the pulps with higher accessibilities and reactivities. The factors influencing the preparation of methylcelluloses from these pulps are discussed.