Development of Xanthated Cellulose Nanofiber

Abstract

Cellulose nanofiber（CNF） is produced by fibrillating pulps to the nano-sized fibrils either through chemical or mechanical processes. It possesses interesting properties, such as high strength, high elastic modules, low thermal expansion, and thixotropy of the suspension. For these properties, it can be used for various applications, and is drawing great attention in recent years as a promising next-generation material. It is well known that CNF with a particular microfibril unit fineness and high aspect ratio can be obtained by firstly introducing either carboxylate or phosphate groups into cellulose, followed by gentle mechanical fibrillation with the help of the electrostatic repulsion and/or osmotic effects caused by those introduced anions.

Our company, Rengo, has been manufacturing cellophane from pulps for many years. Since cellulose xanthate, an intermediate product in the production process, is also an anionic cellulose derivative, we put our effort on this intermediate to make CNF. We found that xanthated cellulose nanofiber（XCNF） with a diameter of about 3-10 nm can be generated efficiently by maintaining the crystallinity of cellulose type I and controlling the degree of substitution to prevent the formed cellulose xanthate from dissolving in the solution through the fibrillation process. Such obtained XCNF can be easily converted（r egenerated） to a non-substituted cellulose nanofiber（RCNF） form by treating XCNF with either heat or acid. Although some agglomerates were observed, the diameter of RCNF is still in the range of a few nanometers. As a non-substituted CNF, our product is extremely small in diameter and with high transparency. Moreover, since it is cellulose, its heat resistance is close to that of pulps. Based on these characteristics, various applications are under development.