Showing papers on "N-Methylmorpholine N-oxide published in 2007"

Lyocell fibres based on direct dissolution of cellulose in N-methylmorpholine N-oxide: Development and prospects

Abstract: The scientific principles of direct dissolution of cellulose in the NMMO—water system demonstrate the major possibility of obtaining concentrated spinning solutions and spinning hydrated cellulose fibres from them. The specific features of the properties of NMMO (high boiling point and insufficient thermal stability) that dissolves the NMMO—water system (narrow concentration range, optimum for dissolution of cellulose) makes it necessary to recycle the washing water by evaporating it, which causes high power consumption for this process. It is expedient to examine the possibilities of membrane technologies, including electrodialysis, for solving problems of recycling the solvent and cutting power consumption. However, this path only allows partially concentrating used washing water, since there is the danger of crystallization of NMMO di-and monohydrate. Spinning through an air gap from highly viscous solutions with long relaxation times at high spinneret draw ratios results in highly oriented fibres with high tensile rigidity (high deformation modulus). Fabrication of fibres whose properties correspond to ordinary viscose fibres will perhaps require “going away” from highly viscous solutions to a lower concentration and spinning by the ordinary wet method, but the volume of solvent used increases significantly, recycling it is more difficult, and power consumption increases. For the same reason of high orientation, the fibres exhibit important fibrillation when wet, and a “peach skin” effect is formed in the finished textiles. To reduce fibrillation, special treatments of the fabrics must be used, biofinishing, for example. During use of the articles, fibrillation can reappear, in laundering, for example. The technology for fabricating fibres of the Lyocell type requires solving many problems. Developing research on selecting alternative solvents and dissolving systems for direct dissolution of cellulose to obtain concentrated spinning solutions is simultaneously useful.

New solvent for polyrotaxane. III. Dissolution of a poly(ethylene glycol)/cyclodextrin polyrotaxane in a calcium thiocyanate aqueous solution or N-methylmorpholine-N-oxide monohydrate

Abstract: Calcium thiocyanate [Ca(SCN)2] aqueous solutions above 40 wt % and N-methylmorpholine N-oxide (NMMO) monohydrate, which are known to dissolve cellulose, were found to be good solvents for a polyrotaxane comprising α-cyclodextrin and poly(ethylene glycol). The polyrotaxane could be dissolved up to 12 and 10 wt % in a 40 wt % Ca(SCN)2 aqueous solution and NMMO, respectively. These are the first instances of a neutral aqueous solution and a cyclic amine oxide, respectively, that readily dissolve the polyrotaxane. These new good solvents, as well as other solvents of the polyrotaxane, except for dimethyl sulfoxide, are identical to those of cellulose, indicating that the dissolution mechanism of the polyrotaxane is dominated by intra- and intermolecular hydrogen bonding of the molecule similar to that of cellulose dissolution. The concentrated polyrotaxane solution in a 40 wt % Ca(SCN)2 aqueous solution showed apparent thixotropy and spontaneous gelation of the solution caused by a gradual increase in its viscosity. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007

Rheological behavior of chitosan derivative/cellulose polyblends from N-methylmorpholine N-oxide/H2O solution

Abstract: O-carboxymethylated chitosan (O-CMCh) aqueous solution (I) and Ethyletheramine Chitosan (EACS) aqueous solution (II) were blended with cellulose N-methylmorpholine N-oxide solution, and corresponding polyblends (Polyblend I and II) were obtained. The rheology of this three liquids, (cellulose solution, Polyblend I and II), was investigated in this study. Then the influence on rheology, because of the addition of chitosan derivative, was discussed.

Degradation processes in the cellulose/ N -methylmorpholine- N -oxide system studied by HPLC and ESR. Radical formation/recombination kinetics under UV photolysis at 77 K

Abstract: Degradation processes of N-methylmorpholine-N-oxide monohydrate (NMMO), cellulose and cellulose/NMMO solutions were studied by high performance liquid chromatography (HPLC) and electron spin resonance (ESR) spectroscopy. Kinetics of radical accumulation processes under UV (λ = 248 nm) excimer laser flash photolysis was investigated by ESR at 77 K. Beside radical products of cellulose generated and stabilized at low temperature, radicals in NMMO and cellulose/NMMO solutions were studied for the first time in those systems and attributed to nitroxide type radicals ∼CH2–NO•–CH2∼ and/or ∼CH2–NO•–CH3∼ at the first and methyl •CH3 and formyl •CHO radicals at the second step of the photo-induced reaction. Kinetic study of radicals revealed that formation and recombination rates of radical reaction depend on cellulose concentration in cellulose/NMMO solutions and additional ingredients, e.g., Fe(II) and propyl gallate. HPLC measurements showed that the concentrations of ring degradation products, e.g., aminoethanol and acetaldehyde, are determined by the composition of the cellulose/NMMO solution. Results based on HPLC are mainly maintained by ESR that supports the assumption concerning a radical initiated ring-opening of NMMO.

Degradation processes in the cellulose/N-methylmorpholine-N-oxide system studied by HPLC and ESR. Radical formation/recombination kinetics under UV photolysis at 77 K

Abstract: Degradation processes of N-methylmorpholine-N-oxide monohydrate (NMMO), cellulose and cellulose/NMMO solutions were studied by high performance liquid chromatography (HPLC) and electron spin resonance (ESR) spectroscopy. Kinetics of radical accumulation processes under UV (λ = 248 nm) excimer laser flash photolysis was investigated by ESR at 77 K. Beside radical products of cellulose generated and stabilized at low temperature, radicals in NMMO and cellulose/NMMO solutions were studied for the first time in those systems and attributed to nitroxide type radicals ∼CH2–NO•–CH2∼ and/or ∼CH2–NO•–CH3∼ at the first and methyl •CH3 and formyl •CHO radicals at the second step of the photo-induced reaction. Kinetic study of radicals revealed that formation and recombination rates of radical reaction depend on cellulose concentration in cellulose/NMMO solutions and additional ingredients, e.g., Fe(II) and propyl gallate. HPLC measurements showed that the concentrations of ring degradation products, e.g., aminoethanol and acetaldehyde, are determined by the composition of the cellulose/NMMO solution. Results based on HPLC are mainly maintained by ESR that supports the assumption concerning a radical initiated ring-opening of NMMO.