New Solvents for Cellulose. II. Ethylenediamine/Thiocyanate Salt System

Abstract

ABSTRACT:The ethylenediamine/thiocyanate salt system was found to be a new solvent for cellulose. The solubility, dissolution behavior, solution properties, and cellulose recovered from the solutions were investigated. The dissolution took place at room temperature, and the maximum solubility achieved was 16 % (w/w) for cellulose of DP210 in the ethylenediamine/sodium thiocyanate 54/46 (w/w). The dependence of cellulose solubility on DP is also described. Tracing the dissolution behavior of the cellulose by CP/MAS 13 C NMR measurements revealed the polymorphic conversion of cellulose I to III to amorphous structure during the dissolution process. The cellulose dissolved was stable for 30 days storage at room temperature. Microscopic observations and steady-shear viscosity measurements of the solutions indicated mesophase formation of cellulose in the ethylenediamine/sodium thiocyanate system. This anisotrpoic phase appeared from ca. 10 % (w/w) cellulose with DP210 and greatly depended on the cellulose concentrations. Coagulation studies disclosed that cellulose II and amorphous cellulose were recovered from the cellulose/ethylenediamine/thiocyanate salt solutions when water and alcohol were used as a coagulant, respectively. It was suggested that this solvent system has high potential for cellulosic fiber and film formations.KEY WORDS Cellulose / Cellulose Solvent / Cellulose Solution / Amine / Thiocyanate / Dissolution Mechanism / Regenerated Cellulose / Cellulose is a linear and high molecular weight polymer as well as a natural, renewable, and biodegradable material. However, due to its considerable inter-and intramolecular hydrogen bonds, cellulose neither melts nor dissolves readily in common solvents. The complicated crystalline and amorphous morphology has also been preventing cellulose from being exploited to its fullest potential. Any process which simplifies or hastens the dissolution of cellulose represents a significant step forward in the development of cellulose as a viable, ecologically favorable polymer source. Furthermore, the ability of cellulose and cellulose derivatives to form mesophase in certain solvents has resulted in attempts to develop high-performance cellulosic fibers and membrane. At present, there are a few solvents that can directly dissolve cellulose without heavy metal complexation and any chemical derivatization, which are lithium chloride/dimethyl acetamide (LiCl/DMAc), 3 N-methylmorpholine-N-oxide/water (NMMO/H 2 O), 4 calcium thiocyanate/water (Ca(SCN) 2 /H 2 O), 5 etc. Quite recently, ionic liquids containing 1-butyl-3-methylimidazolium cations were discovered to dissolve high M w pulp (DP % 1000) with 10 % (w/w) at elevated temperatures. 6 However, almost known solvents still have some undesirable points, for example, chemical safety, environmental concern, degradation of cellulose, requirements of high temperatures and/or pretreatment of cellulose, poor mechanical properties of the cellulose recovered, and high cost for commercial use.We have been studied new solvent for ...

Ionic Liquids for the Production of Man-Made Cellulosic Fibers: Opportunities and Challenges

“…By dissolving cellulose in non-derivatizing solvents, this problem can be by-passed. Of the several direct cellulose solvents, such as Cuen (cupriethylene diamine) [10], Cuoxam (cuprammonium hydroxide) [10], Cadoxen (CdO/ethylenediamine) [10], DMAc/LiCl [11], DMSO/TBAF [12,13], ammonia or amine/thiocyante [14][15][16][17], and phosphoric acid [18,19], only Nmethylmorpholine N-oxide (NMMO) monohydrate has been developed to a commercial level. The latter is used for the production of so-called Lyocell fibers [20].…”

Preparation and characterization of sodium carboxymethyl cellulose from cotton stalk using microwave heating

“…1 Cellulose is a linear and high molecular weight polymer that does not solubilize in common solvents because of inter-and intra-molecular hydrogen bonding. 2,3 The commercial form of cellulose available is sometimes used in the form of original fibres, and sometimes is used in a derivative form such as sodium carboxymethyl cellulose (CMC).…”

Dissolution of cellulose in ethylene diamine/salt solvent systems

“…Dissolution of cellulose in ammonia/ammonium thiocyanate (NH 3 /NH 4 SCN) (Cuculo et al 2000) and analogous solvent systems including hydrazine/salt, hydrazine hydrate/salt and ethylene diamine/salt solvent systems (Hattori et al 2002(Hattori et al , 2004 have been achieved by cycling the cellulose/ solvent mixture through repeated freezing, thawing and mixing steps. Cuculo et al (1994a, b) determined that the freeze thaw cycling process disrupted hydrogen bonding between and within cellulose chains.…”

“…The EDA/KSCN system and other systems analogous to the NH 3 /NH 4 SCN system including EDA/salt and hydrazine/salt systems have been shown to successfully dissolve cellulose without degradation (Hattori et al 2002(Hattori et al , 2004. Although the cellulose solutions formed in these solvents behave similarly to the extensively studied NH 3 /NH 4 SCN system, EDA/salt solvents in particular hold promise as easy to handle and flexible solvents for cellulose processing.…”