纤维素非水溶剂体系的研究——纤维素浓溶液的流变性

把纤维素直接溶解于二甲基亚砜(DMSO)和多聚甲醛(PF)混合溶剂中,能制成可纺性良好的纤维素浓溶液。测定溶液的流变性能,直接获得纤维素浓溶液的粘流活化能等物理参数;研究了热力学和动力学条件与原液可纺性之间的关系,确定了可纺性良好的原液的热力学和动力学参数,为纺制纤维素纤维和制备中空纤维膜奠定了基础。     

The effect of solution variables on the solution of cellulose in dimethyl sulfoxide

Through the study of the effects of concentration, temperature, and molar ration (of paraformaldehyde to cellulose) on solution viscosity and per cent transmittance (at 530 nm), it has been demonstrated that cellulose solutions in dimethyl sulfoxide (DMSO) are readily produced. By heating 1, 2, and 50 to 100 parts by weight of cellulose, paraformaldehyde, and DMSO, respectively, extremely viscose cellulose solutions and gels were prepared. Solutions with concentrations as high as 10% were prepared. However, the optimum conditions to effect complete cellulose solution in DMSO at 75°C were found to be 0.5% cellulose and 0.8 and 1.0% paraformaldehyde. This corresponds to a paraformaldehyde-to-cellulose molar ratio of about 10:1.     

Transparent and semi-interpenetrating network P(vinyl alcohol)- P(Acrylic acid) hydrogels: pH responsive and electroactive application

ABSTRACT

In this paper, poly(vinyl alcohol)-poly(acrylic acid) based transparent semi-interpenetrating network (semi-IPN) hydrogels were synthesized by using a solvent mixture of dimethyl sulfoxide and deionized water via free radical polymerization and subsequent freeze-thaw technique. The formation of the semi-IPN hydrogels was conformed from FT-IR spectra. The acrylic acid concentration effect on the hydrogels was investigated in terms of transparency, crystalline structure and thermal stability by using UV-visible spectroscopy, X-ray diffraction and thermogravimetric analysis. Swelling behaviours of the semi-IPNPAP hydrogels were studied in deionized water and different pH solutions. The compression and electroactive behaviour was tested in fully hydrated stage by using compression test and by applying electrical voltage. The hydrogels showed displacements under the applying voltage and detailed experiment is illustrated.     

Thermosensitive poly(n‐isopropylacrylamide) hydrogels bonded on cellulose supports

A two‐step initiation and polymerization process was developed for the preparation of two series of hydrogel–cellulose composites with distinctively different morphologies and swelling behaviors. Hydroentangled cotton cellulose fibers were optimally initiated in 20 mM aqueous ammonium cerium(IV) nitrate for 15 min and then polymerized in aqueous solutions of N‐isopropylacrylamide (NIPAAm) monomer and N,N′‐methylene bisacrylamide (BisA) crosslinker. The extents of hydrogels on the cellulose solids could be controlled by variations in the concentrations of the monomer and crosslinker as well as the NIPAAm/BisA solution‐to‐solid ratios. The two series of hydrogel–cellulose composites formed were hydrogel‐covered/filled cellulose (I) and cellulose‐reinforced hydrogel (II) composites. Series I composites were synthesized with NIPAAm/BisA solutions below the liquid saturation level of the cellulose; this led to pore structures (size and porosity) that depended on both the extent and swelling of the grafted hydrogels. Series II composites were polymerized in the presence of excessive NIPAAm/BisA solutions to produce cellulose solids completely encapsulated in the hydrogels. All the cellulose‐supported hydrogels exhibited lower extents of phase transition over a wider temperature range (28–40°C) than the free poly(N‐isopropylacrylamide) hydrogels (32°C). These findings demonstrate that hydrogels can be used to control the pore structure of cellulose and can be supported with cellulose fibers. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 999–1006, 2003     

Comparative study of homogeneous solvents for the esterification crosslinking of cellulose with 1,2,3,4‐butanetetracarboxylic dianhydride and water absorbency of the reaction products

Superabsorbent hydrogels were prepared via esterification crosslinking of cellulose with 1,2,3,4‐butanetetracarboxylic dianhydride (BTCA) in three solvent systems: lithium chloride (LiCl)/N‐methyl‐2‐pyrrolidinone (NMP), LiCl/N,N‐dimethylacetamide (DMAc), and tetrabutylammonium fluoride/dimethyl sulfoxide (TBAF/DMSO). The absorbency of the hydrogels was strongly dependent on the BTCA feed to cellulose ratio as well as the nature of the solvent system used. The rate of cellulose esterification was enhanced in TBAF/DMSO relative to the other systems, and the highest water absorbency of the hydrogels (987 g g^?1 polymer) was also achieved using this system. The hydrogels obtained in the TBAF/DMSO system had a similar degree of both crosslinking and grafting, indicating that both reactions were promoted to the same extent in this solvent, whereas crosslinking was preferentially enhanced over grafting in the LiCl/NMP and LiCl/DMAc systems. The difference in the composition of the hydrogels was attributed to the difference in the electronegativity of the fluoride and chloride anions in these solvents. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

New fibres prepared from cellulose-aqueous solution of sodium hydroxide systems (review)

The following basic conclusions were drawn from the published data examined; cellulose treated in steamblast conditions can form solutions and gelling pastes in an aqueous solution of sodium hydroxide; the solubility of cellulose in aqueous sodium hydroxide solution is primarily a function of the intramolecular bonds in the cellobiose unit with constant DP; intramolecular bonds are most efficiently broken in steamblast treatment in the cellobiose unit of cellulose I and cellulose III; monofilaments and yarns were obtained from solutions and gelling pastes of cellulose in aqueous sodium hydroxide solution; the physicomechanical properties of the monofilaments and yarns obtained from solutions and gelling pastes of cellulose in aqueous sodium hydroxide solution are still significantly lower than these indexes for viscose textile yarn.All-Russian Scientific-Research Institute of Polymer Fibres. Mytishchi. Translated from Khimicheskie Volokna, No. 2, pp. 11–14, March–April. 1996.     

Dissolution of Ethylenediamine Pretreated Pulp with High Lignin Content in LiCl/DMSO without Milling

Abstract

Various hardwood and softwood chemical pulps, including those with relatively high lignin content (up to ca. 10.5%), were completely dissolved without milling in lithium chloride/dimethyl sulfoxide (LiCl/DMSO) after a pretreatment with ethylenediamine (EDA). Because milling of the sample is not required, degradation of the cell wall components caused by milling does not take place. After the EDA pretreatment, the crystallinity of the pulps remained as high as the original pulps, although the crystal structure changed. This is the first time that transparent solutions of underivatized pulps with high lignin content were obtained in a simple organic solvent system. Interestingly, even in the case of coarse wood meal (40–80 mesh) about 70% could be dissolved after repeating the dissolving procedure two times. The formation of a pulp–EDA or wood–EDA complex seems to be critical for the dissolution in LiCl/DMSO. The nuclear magnetic resonance (NMR) spectrum of the EDA treated pulp solution had good resolution even though the degree of polymerization (DP) of the cellulose in the pulp is very high.     

Studies on syntheses and permeabilities of special polymer membranes. XVI. Permeation and separation characteristics of aqueous polymer solutions for acrylonitrile-styrene copolymer membranes

The permeation and separation characteristics of aqueous polymer solutions using acrylonitrile-styrene copolymer membranes were investigated under various conditions. The membranes obtained from dimethyl sulfoxide solution of acrylonitrile-styrene copolymer have not a sufficient reproducibility and stability of permeation. These lacks were improved by adding ethylene glycol or glycerol to the casting solution and treating the membranes with pressure. The permeation and separation characteristics were influenced significantly by the additional amount of above additives, the heat treatment temperature, and the operating pressure. It was found that the concentration polarization of poly(vinyl alcohol) molecules onto the surface of the acrylonitrile-styrene copolymer membranes is smaller than that onto hydrophilic polymer membranes such as membranes of cellulose acetate, cellulose nitrate, and nylon 12, etc. Moreover, the acrylonitrile-styrene copolymer membranes show better performance for separation and concentrating of aqueous polymer solutions than hydrophilic membranes.     

Studies on syntheses and permeabilities of special polymer membranes, 32. New preparation method of cellulose membranes

The preparation of cellulose membranes from mixtures of cellulose, nonprotonic polar organic solvents, paraformaldehyde, and basic catalyst was studied. When dimethyl sulfoxide was used as casting solvent, the resulting membrane was the densest. An increase of an additional amount of triethyl amine used as basic catalyst gave denser membranes.     

分离有机物水溶液的渗透汽化与汽化渗透膜

该文基于４５篇最新文献，较详细地论述了渗透汽化膜与汽化渗透膜的有机物水溶液分离性能及其影响因素，包括高聚物特征，料液浓度，温度，古游侧压力，膜厚度和操作时间，指出用多数高聚物膜进行渗透汽化操作可以有效地分离多数有机醇，酮，酸，酯，酰胺以及二Ｅ烷，乙腈，吡啶，二甲亚砜和四氢呋喃水溶液；而以壳聚糖及其衍生物膜进行汽化渗透操作则具有更高的分离系数。该文还简要介绍了渗透汽化膜的新应用。为渗透汽化与汽化渗透     

Reentrant conformation transition in poly(N,N-dimethylacrylamide) hydrogels in water-organic solvent mixtures

Conformational changes in poly(N,N-dimethylacrylamide) (PDMA) networks swollen in aqueous solutions of organic solvents are studied both experimentally and theoretically. PDMA hydrogels of various charge densities were prepared by free-radical crosslinking copolymerization. Swelling behavior of the hydrogels was investigated in aqueous organic solvent mixtures as functions of solvent species and the concentration. With increasing volume fraction ? of acetone, tetrahydrofuran, or 1,4-dioxane in the aqueous solution, PDMA hydrogels exhibit reentrant conformation transition. During this transition, the gel first deswells in the range of ? between 0.4 and 0.9, and then rapidly reswells if ? is monotonically increased. The reswelling of the collapsed PDMA gel occurs in a narrow of ? above ?=0.97. It was shown that the reentrant transition in PDMA gels requires moderate hydrogen bonding organic solvents, so that the hydrophobic interactions between PDMA and the organic solvent dominate the swelling process. The results were interpreted using the theory of equilibrium swelling. The interaction parameters in the gel system as well as the partition parameter of the organic solvent between the gel and the solution phases were calculated.     

Separation of aqueous organic liquid solutions through polymer membranes

Characteristics of permeation and separation for aqueous dimethyl sulfoxide, acetic acid and ethanol solutions through some polymer membranes such as chitosan, poly(vinyl chloride) and poly(dimethyl siloxane) membrane were studied by evapomeation. In temperature difference controlling evapomeation (TDEV), when the temperature of the feed solution was kept constant and the temperature of the membrane surroundings was changed, permselectivity for water increased in the chitosan and poly(vinyl chloride) membranes; in the poly(dimethyl siloxane) membrane the perm-selectivity for ethanol increased while decreasing the temperature of the membrane surroundings. Permeation and separation mechanisms for aqueous organic liquid solutions through the above polymer membranes by the TDEV method are discussed.     

改性纤维素微球的制备及其对Pb2＋吸附性能的研究

利用绿色环保的碱／尿素／水溶剂体系直接制备纤维素溶液共混聚乙烯亚胺（PEI）,然后通过高压静电法制备再生纤维素微球,并与戊二醛交联固定化,制备了复合型吸附材料。借助吸附动力学和吸附等温方程研究了改性纤维素微球对Pb2＋的吸附性能,结果表明改性纤维素微球对Pb2＋具有较好的吸附容量达到9．46mg／g,相比空白微球提高50％以上,并且吸附过程符合准二级动力学方程和Freundlich等温方程。     

Regenerated cellulose aerogel: Morphology control and the application as the template for functional cellulose nanoparticles

This article focuses on controlling the morphology of regenerated cellulose aerogel (RCA) and its application as a template for the preparation of functional cellulose nanoparticles (FCNPs). RCA is prepared by lyophilizing cellulose hydrogel which is fabricated through a sol–gel method in sodium hydroxide (NaOH)/urea aqueous solution. The morphology of RCA is adjusted by varying the gelation temperature and time. With the gelation temperature and time increasing, lamellar RCA transforms into strings of cellulose nanoparticles. Subsequently, RCA with the morphology of "strings of nanoparticles" is modified through the bulk condensation of l -lactic acid and RCA. Eventually, the prepared functionalized RCA (FRCA) is dispersed in an organic solvent to obtain purified FCNPs. The results demonstrate that single FCNP can be obtained by dispersing FRCA in dimethyl sulfoxide. Moreover, the prepared FCNPs have uniform size, good thermal-stability, and increasing hydrophobicity, which are ideal candidates for polymer composites in terms of fillers.     

一种新型球形纤维素吸附剂的研究

棉花经碱化、老化和磺化得黏胶液 ,再用热溶胶转相法制得球形纤维素珠体。对纤维素珠体进行交联、接枝 ,研制出球形羧基纤维素吸附剂。在黏胶的制备过程中 ,棉与碱的最佳质量比为 1∶1,老化时间 6 0h ,磺化温度 2 3℃、磺化时间 3 0h ,CS2 用量为碱纤维素中纤维素质量的35 6 %。在成球过程中 ,V (黏胶 )∶V(变压器油 ) =(1 0∶3 5 )～ (1 0∶2 0 )。交联的最佳条件为 :交联温度 75℃ ,环氧氯丙烷用量 14mL ,碱液质量分数为 10 %。接枝的主要因素包括丙烯腈浓度 2 95mol/L、Ce4 + 盐浓度 0 0 0 72mol/L、接枝反应时间 1 0h以及接枝反应温度 2 5℃。这种球形纤维素吸附剂在不同溶液 /溶剂中的膨胀系数为 1 0 0～ 1 36 ,能经受 1 2mol/L的HCl和 1 0mol/L的NaOH水溶液 15次的反复处理 ,而且对Cr3 + 、Al3 + 、Cu2 + 、Zn2 + 金属离子的吸附容量分别为 2 8 1、14 6、49 2和 37 3mg/g。     

亚砜基改性纤维素膜的SO2气体渗透性能研究

分别使用二甲基亚砜浸泡的物理方法及苯基乙烯基亚砜加成的化学方法对纤维素膜进行了改性,并对改性膜的性能进行了测试.结果表明改性后纤维素膜仍为致密结构,SO2的渗透性能及其对N2的分离性能明显提高,其中改性液中添加二甲基亚砜的均相化学加成反应所得的改性膜具有较好的SO2渗透稳定性.     

Novel biodegradable superabsorbent hydrogels derived from cotton cellulose and succinic anhydride: Synthesis and characterization

The synthesis of novel superabsorbent hydrogels was investigated with the reaction of cotton cellulose and succinic anhydride (SA) in the presence of 4‐dimethylaminopyridine as an esterification catalyst in a mixture of lithium chloride (LiCl) and N‐methyl‐2‐pyrrolidinone (NMP) or in a mixture of tetrabutylammonium fluoride (TBAF) and dimethyl sulfoxide (DMSO), followed by NaOH neutralization. Interestingly, a hydrogel was obtained without any crosslinking agent, and this indicated the partial formation of a diester between the cellulosic hydroxyl group and SA. The products obtained in LiCl/NMP exhibited superior absorbency to these obtained in TBAF/DMSO. The former absorbed an amount of water about 400 times its dry weight, and this was comparable to a conventional sodium polyacrylate superabsorbent hydrogel. Furthermore, in an aqueous NaCl solution, the absorbency of the product hydrogels was higher than that of the sodium polyacrylate superabsorbent hydrogel. The formed hydrogels biologically degraded almost completely after 25 days, and this showed their excellent biodegradability. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 99: 3251–3256, 2006     

EXTRACTION OF METAL IONS WITH DZEHPA FROM MIXED AQUEOUS-ORGANIC MEDIA

Extraction of metal ions from the aqueous-organic solution containing dimethyl formamide(DMF), dimethyl sulfoxide(DMSO) and acetonitrile(AN) was investigated by using di-2-ethylhexyl-phosphoric acid(D2EHPA) as an extractant. The organic phase was a binary solution of D2EHPA and n-hexane, or D2EHPA and toluene, while the polar phase was a three component solution of metal salt, non-aqueous solvent and water. The extracted metal ions were Cr(III), Fe(III), Al, Cu, Ni, Co(II), Mg and Ag.

The extraction behaviors may be explained by the solvation ability of non-aqueous solvents, the decrease in distribution of the extractant and extract into the organic phase, and the interaction between the extractant and non-aqueous solvents due to the dissolution of non-aqueous solvents in the organic phase.     

Esterification of viscose fibres with orthophosphoric acid and study of their physicochemical and mechanical properties

Esterification of viscose fibres with aqueous solutions of orthophosphoric acid and urea at different ratios of components was investigated. It was shown that in phosphorylation of cellulose with these solutions, one-substituted cellulose phosphates are formed and a side process of formation of cellulose carbamates takes place together with accumulation of phosphate groups. A decrease was found in the mechanical strength of the phosphorylated cellulose preparations and the degree was a function of the concentration of orthophosphoric acid and urea as the phosphorylating solution. Phosphorus-containing viscose fibres (up to 0.5 mmole/g of phosphate groups) obtained in solutions of orthophosphoric acid and urea with a 0.25–0.63 and 3.33–4.17 M concentration have the most satisfactory mechanical properties and stability in phosphate buffer with pH 7.5. __________ Translated from Khimicheskie Volokna, No. 1, pp. 26–30, January—February, 2007.     

Properties of cellulose xanthate solutions prepared in an organic solvent

Conclusions 1. To compare the properties of cellulose xanthates made by xanthation of alkali cellulose in an organic solvent medium, in a quasi-liquid state and in carbon disulphide vapour, the change in the properties of xanthate solutions with time was studied.2. Solutions of quasi-liquid xanthate differ by increased viscosity and decreased ripeness, which involves increased structure-formation in the solution, because of the higher degree of polymerisation of the cellulose and the lower degree of esterification of the cellulose xanthate.3. The decomposition rate of quasi-liquid xanthate in the initial ripening period of the viscose is higher than the decomposition rate of standard xanthate because of the increased degree of esterification of the secondary hydroxyl groups of the cellulose macromolecules, and the complication of secondary esterification of cellulose xanthate in solution.All-Union Scientific Research Institute for Man-Made Fibres. Translated from Khimicheskie Volokna, No. 2, pp. 33–35, March–April, 1969.