Study on the dissolution process of different kinds of cellulose into ionic liquids

Abstract

Dissolution conditions of cotton, linter pulp, avicel, and nadelholz sulfur pulp (NSP) into 1-butyl-3-methylimidazolium chloride (BmimCl), 1-allyl-3-methylimidazolium chloride (AmimCl), and 1-ethyl-3-methylimidazolium acetate (EmimAc) are examined to obtain colorless and high viscosity uniform solutions. The tested dissolution conditions are inadequate for EmimAc. Degradation of cellulose was suppressed by choosing adequate dissolution temperatures for BmimCl (130 °C) and AmimCl (110 °C) solutions at depressed conditions without mechanical stirring, though it was difficult to obtain colorless uniform solutions for avicel and linter. Dynamic viscoelastic properties of uniform solutions of cotton and NSP in BmimCl and AmimCl showed typical terminal region behavior. Lowering the bubble burst speed in the early stage of dissolution by keeping at 0.1 atm was effective compared to high vacuum. Moreover, preheating at lower temperature resulted in more mild bubble burst and the higher relative viscosity, denoting that the molecular weight of cellulose change with the swelling condition and bubble burst speed by changing the temperature and pressure.