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In this study, ionic liquid treatment for increasing the wet strength of cellulose paper was studied. The effects of treatment conditions with the ionic liquid 1-butyl-3-methylimidazolium chloride ([BMIM]Cl) on the wet strength were investigated. First, the [BMIM]Cl (20 g) was melted at 80-100 °C and the paper was immersed in it for 5-60 s. Next, the paper was immersed in ethanol, and finally, it was washed with distilled water. The paper was dried in a hot press at 110 °C and 1.1 MPa for 5 min. The [BMIM]Cl treatment improved the wet strength of the paper. Disintegration of the papers was investigated by immersing them in distilled water, and the paper treated with [BMIM]Cl did not disintegrate. The minimum treatment time required for improvement of the wet strength of the paper was only 5 s. Excess [BMIM]Cl from the original treatment was recovered by vacuum distillation and dehydration was used to treat new paper. This recovered [BMIM]Cl enhanced the wet strength to a level similar to that obtained with the virgin [BMIM]Cl. Therefore, the [BMIM]Cl can be efficiently re-used in this method. The paper treated with [BMIM]Cl will be composed completely of cellulose. Therefore, this method is a viable alternative to treatment by adding chemical such as a polyamideamine epichlorohydrin (PAE). [ABSTRACT FROM AUTHOR]

The direct dissolution of cellulose offers a pathway to production of regenerated textile fibers. However, fiber production in the Lyocell process requires a high recyclability of the solvent. Some compounds from the class of ionic liquids (IL) may have higher dissolving capacities together with a higher thermal stability than the conventional N‐methylmorpholin‐N‐oxide (NMMO), which makes them more valuable in an industrial process. A promising representative of such an advanced solvent for Lyocell process, 7‐Methyl‐1,5,7‐triazabicyclo[4.4.0]dec‐5‐ene acetate ([MTBDH][AcO]) was investigated in this study. A series of 21 consecutive cellulose dissolving and spinning trials via dry‐jet wet spinning was conducted with the same batch of solvent. In the spinning trials, the cellulose was regenerated into water consisting spinning bath. The solvent was recycled by removing the water from the spin bath via distillation in reduced pressure. Due these drastic changes in the water content of the IL during the whole process, the hydrolytic stability is an important aspect to assess the recyclability of the IL and viability of the whole process. The chemical composition of the IL was monitored by means of NMR spectroscopy. Although there was an increase of hydrolysis level of the solvent, cellulose could be dissolved constantly and spun to obtain staple fibers. The spinning behavior deteriorated slowly along the additional cycles, along with a measured increase in zero‐shear viscosity of the spinning dope. Nevertheless, the physical properties of the obtained fibers were barely influenced by the changes of the ionic liquid. [ABSTRACT FROM AUTHOR]

Cotton fibre dissolution has been investigated using ionic liquids having a functionalized imidazolium cation. Two ionic liquids, 3-butyric acid-1-methyl imidazolium chloride [HOOC4MIM][Cl] (IL-acid) and 3-N,N-diethyl-butyramide-1-methyl imidazolium chloride [(Et)2NOC4MIM][Cl] (IL-amide), were synthesized by passing both through the intermediate 1-(3-Ethoxycarbonyl-propyl)-1-methyl imidazolium bromide. Their chemical structures were then confirmed using NMR and FTIR. 5 wt% cotton fibers have been completely dissolved in both synthesized ionic liquids in 3 h at room temperature. The regenerated cellulose with water, as an anti-solvent, was characterized using XRD, FTIR, TGA, and degree of polymerization (DP) methods. The FTIR and XRD results showed that no other chemical reaction occurred by both synthesized ILs other than the breakage of hydrogen bonds during the dissolution and regeneration processes. In addition, the regenerated cellulose had a reduced crystallinity and a structural transition from cellulose I to cellulose II. TGA results confirmed the low crystallinity of regenerated cellulose by demonstrating its low thermal stability compared to cotton fibers. Furthermore, the DP of cotton fibers was reduced from 805 ± 15 to 737 ± 12 and 765 ± 10 after regeneration from IL-acid and IL-amide, respectively, confirming partial cellulose network degradation. The IL-acid has an oily appearance and a viscosity (44 ± 5 mPa.s at 25 °C), allowing it to dissolve 14.5 wt% cotton fibers at 25 °C, IL-amide can only dissolve 5 wt% in 5 h at 25 °C due to its viscous nature. These results imply that the produced ionic liquids can be considered as competitive solvents for dissolving cellulose. [ABSTRACT FROM AUTHOR]

The dissolution of cellulose is a critical step for the efficient utilization of this renewable resource as a starting material for high value-added chemical and biofuel production. In this study, three aprotic solvents were chosen to couple with three ionic liquids (ILs) as binary solvent systems for cellulose dissolution. The percentage of dissolved cellulose of each IL/co-solvent was evaluated and the crystallinity index (CrI) of the undissolved cellulose residues after dissolution were investigated by XRD. Dimethyl sulfoxide exhibited the most effective synergistic interaction with the ILs among three co-solvents for cellulose dissolution. In general, the higher percentage of dissolved cellulose of the IL/co-solvent binary system, the lower CrI value of the undissolved cellulose residue after dissolution. In addition, the dissolution of cellulosic materials with different crystallinity and degree of polymerization indicated that the crystallinity of a cellulosic material played a more dominating role than degree of polymerization in its dissolution process. The hydrogen bond basicity (β value) of selected IL/co-solvent binary system was also calculated. The results showed that the β value of a binary IL/co-solvent system exhibited different trend than neat IL in terms of the cellulose dissolution ability, which should be attributed to the co-solvent effect. [ABSTRACT FROM AUTHOR]

Cellulose, as the most abundant sustainable resource on earth, can be chemically transformed into a variety of biodegradable materials, which have been proposed as the ideal substitutes for plastic products. The first challenge for the fabrication of cellulose-based functional materials is the successful dissolution of cellulose by solvents. However, most existing cellulose solvents have environmental, economic, and other drawbacks that limit their further industrial applications. Research on developing novel solvent systems with "greener" and "cheaper" properties is needed to meet the challenges. [ABSTRACT FROM AUTHOR]

Lyocell fibers have received increased attention during the recent years. This is due to their high potential to satisfy the rising market demand for cellulose-based textiles in a sustainable way. Typically, this technology adopts a dry-jet wet spinning process, which offers regenerated cellulose fibers of excellent mechanical properties. Compared to the widely exploited viscose process, the lyocell technology fosters an eco-friendly process employing green direct solvents that can be fully recovered with low environmental impact. N-methylmorpholine N-oxide (NMMO) is a widely known direct solvent that has proven its success in commercializing the lyocell process. Its regenerated cellulose fibers exhibit higher tenacities and chain orientation compared to viscose fibers. Recently, protic superbase-based ionic liquids (ILs) have also been found to be suitable solvents for lyocell-type fiber spinning. Similar to NMMO, fibers of high mechanical properties can be spun from the cellulose-IL solutions at lower spinning temperatures. In this article, we study the different aspects of producing regenerated cellulose fibers using NMMO and relevant superbase-based ILs. The selected ILs are 1,5-diazabicyclo[4.3.0]non-5-ene-1-ium acetate ([DBNH]OAc), 7-methyl-1,5,7-triazabicyclo[4.4.0] dec-5-enium acetate ([mTBDH]OAc) and 1,8-diazabicyclo[5.4.0]undec-7-enium acetate ([DBUH]OAc). All ILs were used to dissolve a 13 wt% (PHK) cellulose pulp. The study covers the fiber spinning process, including the rheological characterization of the various cellulose solutions. Moreover, we discuss the properties of the produced fibers such as mechanical performance, macromolecular properties and morphology. [ABSTRACT FROM AUTHOR]

In this work, several kinds of quaternary ammonium-based room-temperature ionic liquids (QA RTILs) are synthesized by alkylation and ion-exchange reactions for the rapid dissolution of cellulose. The applications of cellulose materials have been limited due to their poor solubility in conventional organic solvents, because of a high degree of structural regularity and a large number of hydrogen bonds. The prepared ionic liquids were identified by nuclear magnetic resonance, elemental analysis, and liquid chromatography-mass spectrometry. The results indicated that N,N,N-triethylhexan-1-aminium acetate (N6222OAc), tetrahexylammonium acetate (N6666OAc), and N,N,N,N′,N′,N′-hexaethyldecane-1,10-diaminium acetate (C10(N222OAc)2) exhibited good cellulose-dissolution without any pretreatment. The regenerated cellulose films with a low degree of crystallization of the cellulose II phase were also prepared easily in this process using N6222OAc due to its polar and small cation. These QA RTILs can be used as non-derivatizing solvents for cellulose and can also be easily recycled because of their thermostable and nonvolatile properties. [ABSTRACT FROM AUTHOR]

Green synthesis of room temperature ionic liquids (RTILs), are presented as friendly and challenging solvents for the effective dissolution of oil palm-lignocellulosic biomass. A series of Bronsted acidic-ionic liquids were prepared by the direct neutralization of diethyl dimethyl ammonium hydroxide with several (economical and environmental friendly) Bronsted acids as RTILs. The structural and physicochemical characterization was performed by applying various techniques as Fourier transform infrared (FT-IR), nuclear magnetic resonance (NMR), thermo gravimetric analysis (TGA), differential scanning calorimetry (DSC), zeta-nanosizer and dynamic light scattering (DLS) respectively, to state the effect of anion on the extended cellulose dissolution capabilities of the synthesized RTILs under mild conditions. As a polysaccharide solvent, diethyl dimethyl ammonium phosphate (A1P) showed the extreme capability to extract 65 % of cellulose from biomass without any pretreatment for 30 min. The present study could be a significant step toward the synthesis of efficient RTILs and generating upgraded cellulose for Hi-tech engineered composites and energy concerns. [ABSTRACT FROM AUTHOR]

We have found that the dissolution of cellulose in the binary mixed solvent tetrabutylammonium acetate/dimethyl sulfoxide follows a previously overlooked near-stoichiometric relationship such that one dissolved acetate ion is able to dissolve an amount of cellulose corresponding to about one glucose residue. The structure and dynamics of the resulting cellulose solutions were investigated using small-angle X-ray scattering (SAXS) and nuclear magnetic resonance techniques as well as molecular dynamics simulation. This yielded a detailed picture of the dissolution mechanism in which acetate ions form hydrogen bonds to cellulose and causes a diffuse solvation sheath of bulky tetrabutylammonium counterions to form. In turn, this leads to a steric repulsion that helps to keep the cellulose chains apart. Structural similarities to previously investigated cellulose solutions in aqueous tetrabutylammonium hydroxide were revealed by SAXS measurement. To what extent this corresponds to similarities in dissolution mechanism is discussed. [ABSTRACT FROM AUTHOR]

Chitosan is a widely used biopolymer with very attractive properties. However, to compensate for the deficiencies in the application of this bio-macromolecule, many studies have been performed on the preparation of chitosan blends with various polymers, such as cellulose, which is abundant and unique with a tough bio-structure. Because of the different dissolution conditions of chitosan and cellulose, an acceptable industrial and environmentally friendly process to prepare a monotonous cellulose-chitosan composite film has not been achieved yet. Therefore, as an alternative approach, nanochitosan (Nano-CS) particles were synthesized and blended with a cellulose matrix, which was dissolved using ionic liquid. Atomic force microscope and field emission scanning electron microscope (FESEM) images demonstrated that the most frequent size of Nano-CS particles was in the 10-60 nm range. FESEM nano-graphs evidenced monotonous distribution of Nano-CS particles through the produced nano-biocomposite films. X-ray diffractograms indicated that following the dissolution process of cellulose a less ordered cellulose matrix or one with less crystallite sizes was formed. Meanwhile, following the addition of certain amounts of Nano-CS, the mechanical properties were improved. Also, optical analysis exhibited proper transparency of the biocomposite films (≈80 %) in the range of visible wavelengths (400-700 nm). [ABSTRACT FROM AUTHOR]

Ionic liquids (ILs) and deep eutectic solvents (DESs) are the two most widely used neoteric solvents. Recently, our group described how the simple addition of acetic acid (AcOH) to 1-Ethyl-3-methylimidazolium chloride (EMIMCl) could promote the transition from the original IL to an eutectic mixture of EMIMCl and AcOH. Herein, we studied how cellulose regeneration and EMIMCl recovery from EMIMCl solutions of cellulose could be benefited by the significant differences existing between EMIMCl- and EMIMCl·AcOH-based mixtures and the easy switching from one to the other. Finally, we also demonstrated that the transition could also be accomplished by addition of acetic anhydride and water so that the process could be eventually useful for the achievement of highly acetylated cellulose. [ABSTRACT FROM AUTHOR]

The ionic liquid (IL) 1-ethyl-3-methylimidazolium acetate ([emim][OAc]) readily dissolves high concentrations of cellulose. However, the high viscosity of [emim][OAc] (162 cP at 20 °C) could limit its use as a solvent for cellulose. Dissolved CO has been shown to decrease the viscosity of ILs. In this study, a 50 psi CO environment was applied for the dissolution of cellulose in [emim][OAc] to determine if the cellulose dissolution could be enhanced. Dissolution profiles of 4 wt% cellulose dissolved in [emim][OAc] were obtained over a 24 h period. A 75% increase in the amount of dissolved cellulose was observed with the application of a 50 psi CO environment. [ABSTRACT FROM AUTHOR]

A systematic study of variables that affect the fiber welding process is presented. Cotton cloth samples are treated with controlled amounts of 1-ethyl-3-methylimidazolium acetate for a series of times and temperatures. Diluting the ionic liquid with a volatile molecular co-solvent allows temporal and spatial control of the welding process not possible with neat ionic liquids. Materials are characterized by scanning electron microscopy, infrared spectroscopy, X-ray diffraction, and mechanical (tensile) testing. Results suggest careful management of process variables permits controlled, reproducible manipulation of chemical and physical properties. [ABSTRACT FROM AUTHOR]

The thermal degradation products of 1-alkyl-3-methyl-imidazolium-type ionic liquids (e.g., BMIM, EMIM), which are commonly used in cellulose chemistry, were identified. Imidazole ( 5), N-methylimidazole ( 6), and N-alkylimidazoles ( 7, 8) are the main products. Moreover, dimeric substituted imidazoles ( 9– 11) were found carrying a methylene bridge formed from the N-methyl structure. The former 1-alkyl group (butyl or ethyl) was not present in any of the dimeric compounds. The N-methylene intermediate (12) acts as a precursor for the substituted imidazoles linked by a methylene group. All thermal degradation products are bases and catalyze the previously described reaction between the reducing end of celluloses and 1-alkyl-3-imidazolium cations. To minimize this side reaction, ionic liquids have to be liberated from such basic compounds prior to application as cellulose solvents. In this regard, the usage of “recycled” (and unpurified) ionic liquids has to be treated with caution. [ABSTRACT FROM AUTHOR]

Forestry industries in Chile are facing an important challenge—diversifying their products using green technologies. In this study, the potential use of Ionic Liquids (ILs) to dissolve and hydrolyze eucalyptus wood (mix of Eucalyptusnitens and Eucalyptusglobulus) kraft pulp was studied. The Bleached Hardwood Kraft Pulp (BHKP) from a Chilean pulp mill was used together with five different ILs: 1-butyl-3-methylimidazolium chloride [bmim][Cl], 1-butyl-3-methylimidazolium acetate [bmim][Ac], 1-butyl-3-methylimidazolium hydrogen sulfate [bmim][HSO4], 1-ethyl-3-methylimidazolium chloride [emim][Cl], 1-ethyl-3-methylimidazolium acetate [emim][Ac]. Experimentally, one vacuum reactor was designed to study the dissolution/hydrolysis process for each ILs; particularly, the cellulose dissolution process using [bmim][Cl] was studied proposing one molecular dynamic model. Experimental characterization using Atomic Force Microscopy, conductometric titration, among other techniques suggest that all ILs are capable of cellulose dissolution at different levels; in some cases, the dissolution evolved to partial hydrolysis appearing cellulose nanocrystals (CNC) in the form of spherical aggregates with a diameter of 40–120 nm. Molecular dynamics simulations showed that the [bmim][Cl] anions tend to interact actively with cellulose sites and water molecules in the dissolution process. The results showed the potential of some ILs to dissolve/hydrolyze the cellulose from Chilean Eucalyptus, maintaining reactive forms. [ABSTRACT FROM AUTHOR]

Abstract: In this work, the 1-allyl-3-alkylimidazolium chloride ionic liquids were synthesized and characterized by increasing carbon atoms (n ≤6) of alkyl chains on a cationic 3-imidazole ring. The results indicated that 1-allyl-3-alkylimidazolium chloride with asymmetrical structure on the two sides of a cationic 3-imidazole ring (i.e., n =1, 2, 6) exhibited alkalinity and lower thermal stabilities, and showed better solubility to the cellulose samples at 60–120°C than those with symmetrical structures (n =3, 4). The cellulose samples treated by 20% (w/w) ethylenediamine solution showed better solubility in 1-allyl-3-ethyl, hexyl-imidazolium chloride ionic liquids than that treated with 20% (w/w) NaOH solution at 5°C for 72h. XRD and TG analysis indicated that 002 plane apparent crystallite size as well as thermal stability of the regenerated cellulose samples from the ionic liquids decreased significantly compared with the untreated cellulose samples. [Copyright &y& Elsevier]