氨基甲酸酯法再生纤维素膜的结构及性能

利用氨基甲酸酯法制备了再生纤维素膜。采用红外、X射线衍射、扫描电子显微镜等分析方法,对纤维素氨基甲酸酯再生膜（CC再生膜）的性能及结构进行表征。分析了凝固浴浓度和铸膜液浓度分别对CC再生膜的机械性能的影响。结果表明,再生膜为典型的C-II型结晶,结晶度有所降低。CC再生膜表面和断面结构致密、均匀,制备的CC再生膜物理机械性能良好。     

Regenerated cellulose membrane prepared with ionic liquid 1‐butyl‐3‐methylimidazolium chloride as solvent using wheat straw

BACKGROUND: Currently, cellulose membranes are prepared by cellulose acetate hydrolysis or chemical derivatization dissolution and regeneration using cotton pulp or wood pulp. In this study, the concept ‘lignocelluloses biorefinery’ was used, and good quality long fiber was fractionated from wheat straw using clean technologies. The objective of this study is to develop wheat straw cellulose to prepare regenerated cellulose membrane with ionic liquid 1‐butyl‐3‐methylimidazolium chloride ([BMIM]Cl) as solvent. RESULTS: Wheat straw cellulose (WSC) fractionated from wheat straw contained 93.6% α‐cellulose and the degree of polymerization (DP) was 580. WSC was dissolved directly without derivatization in [BMIM]Cl. With increase in dissolving temperature, the DP of the regenerated cellulose dropped, which resulted in a decrease in the intensity of regenerated cellulose membrane. After regeneration in [BMIM]Cl, the WSC transformed from cellulose I to cellulose II, and the crystallinity of the regenerated cellulose was lower than the original cellulose. The regenerated WSC membrane had good mechanical performance and permeability, the tensile strength and breaking elongation were 170 MPa and 6.4%, respectively, the pure water flux was 238.9 L m^?2 h^?1 at 0.3 MPa pressure, and the rejection of BSA was stabilized at about 97%. CONCLUSION: Wheat straw cellulose fractionated from wheat straw satisfied the requirement to prepare regenerated cellulose membrane using ionic liquid [BMIM]Cl as solvent. Copyright © 2012 Society of Chemical Industry     

纤维素氨基甲酸酯溶液的制备及稳定性研究

研究了制备纤维素纤维的新型原料——纤维素氨基甲酸酯(CC)溶液的制备工艺及其稳定性。结果表明:在-5~10℃条件下,用聚合度为350~612的纤维素浆粕(棉浆粕、木浆粕)合成的氮含量(酯化度)为2.34%~3.56%的CC能很好地溶解在质量百分比浓度为8%~11%的NaOH溶液中,形成淡黄色透明溶液,该溶液稳定性良好,可用于纺丝。另外,尿素、AlCl3及ZnCl2在一定范围内对CC有助溶作用。     

戊二醛交联改性再生纤维素纤维的研究

以氯化1-丁基-3-甲基咪唑离子液体为溶剂对木质纤维素进行溶解并纺丝,得到再生纤维素纤维,再使用戊二醛对再生纤维素纤维进行交联改性,研究其交联改性条件对再生纤维素纤维力学性能的影响。结果表明:经戊二醛交联后,再生纤维素纤维的断裂强度有明显的提高;在戊二醛质量分数为4%,反应温度为50℃,反应时间为30 min的交联条件下,所得再生纤维素纤维的断裂强度为3.2 cN/dtex。     

Cellulose Regeneration and Chemical Recycling: Closing the “Cellulose Gap” Using Environmentally Benign Solvents

Strategies to mitigate the expected “cellulose gap” include increased use of wood cellulose, fabric reuse, and recycling. Ionic liquids (ILs) are employed for cellulose physical dissolution and shaping in different forms. This review focuses on the regeneration of dissolved cellulose as nanoparticles, membranes, nonwoven materials, and fibers. The solvents employed in these applications include ILs and alkali solutions without and with additives. Cellulose fibers obtained via the carbonate and carbamate processes are included. Chemical recycling (CR) of polycotton (cellulose plus poly(ethylene terephthalate)) is addressed because depending on the recycling approach employed, this process is akin to regeneration. The strategies investigated in CR include preferential dissolution or depolymerization of one component of the blend, and separation of both components using ILs. It is hoped that this review focuses the attention on the potential applications of regenerated cellulose from its solutions and contributes to the important environmental issue of recycling of used materials.     

Beyond waste: Transforming wheat straw into oxygen and UV-resistant cellulose films

Regenerated cellulose membrane is a biomaterial obtained by activating, dissolving, solidifying, and regenerating cellulose powder using solvents of different polarities. It has the characteristics of high oxygen resistance and high strength. However, its low water vapor barrier and single function limit its application. In order to improve the water resistance of regenerated cellulose membranes and endow them with UV resistance, lignin was extracted from waste wheat straw using formic acid method. The extracted formic acid lignin (FAL) was added to the cellulose solution to prepare a series of regenerated lignocellulosic membranes (RC-FAL) with different lignin contents. The results indicate that lignin can not only improve the water vapor barrier, tensile strength, and water resistance of the film, but also enhance the oxygen barrier and UV absorption of the film. Compared with pure cellulose film, the contact angle of lignocellulose film can be increased by 66.2%, the UV absorption rate can reach 100%, and the oxygen transmission coefficient has no significant effect. In this paper, a new kind of biological packaging material with high oxygen resistance, strong ultraviolet absorption, and water resistance was prepared by recycling waste wheat straw, it has a broad application prospect in the industrial production of packaging materials.     

离子液体法制备再生细菌纤维素纤维

以离子液体(氯化1-甲基-3-正丁基咪唑)溶解高聚合度细菌纤维素(BC),采用湿法纺丝制备再生细菌纤维素(RBC)初生纤维;通过红外光谱分析(FTIR)、广角X射线衍射(WAXD)分析、热失重(TG)分析、扫描电镜( SEM)、单丝强度拉伸等表征了RBC初生纤维的结构和性能.结果表明:该溶剂体系通过10 h的快速搅拌溶...     

纤维素氨基甲酸酯法制备纤维素海绵

海绵因具有蓬松度好、质地柔软、吸水性好等优点而得以广泛应用。但目前市面上的聚氨酯海绵,不仅原料紧缺,制备过程有污染物产生,而且废弃后难降解,会产生二次污染。为开发可自然降解的纤维素海绵无污染制备工艺,研究了采用纤维素氨基甲酸酯法制备纤维素海绵的工艺。结果表明：由纤维素氨基甲酸酯的氢氧化钠溶液捏合而成的海绵混合体经蒸煮,纤维素再生,成孔剂溶于水中而留下空隙,所得纤维素海绵孔径均一,表面光滑平整,具有较好的柔韧性和黏弹性,完全具有普通聚氨酯海绵的基本特征。     

ZnCl2水溶液制备纤维素膜的研究

以针叶浆为原料,ZnCl2水溶液为溶解溶剂,制备再生纤维素膜。利用单因数实验分析了纤维素膜制各过程中浆浓、反应温度、溶解时间对纤维素膜强度的影响,确定了最佳工艺条件为浆浓3％、反应温度90℃、溶解时间为2h。并通过X-射线衍射（XRD）、傅里叶变换红外光谱（FT-IR）、扫描电镜（SEM）分析,比较经ZnCl2水溶液处理前后纤维的结构和性能变化,发现ZnCl2水溶液是纤维素的非衍生化溶剂,经ZnCl2水溶液处理后的纤维素已由纤维素I转换为纤维素II,制备的再生纤维素膜具有一定的强度,且具有多孔性的特征。     

竹纤维素在NMMO中溶解再生前后的结构研究

以竹浆粕为原料、N-甲基吗啉-N-氧化物(NMMO)为溶剂,利用傅里叶红外光谱、X射线衍射、热重分析等着重研究了竹纤维素在NMMO中溶解前后结构的变化。研究发现:NMMO溶解纤维素过程属于物理过程,未发生衍生化反应,竹纤维素溶解后聚合度较溶解前有所降低,晶型由纤维素Ⅰ变成了纤维素Ⅱ;热重分析表明纤维素再生前后都具有较好的热稳定性。     

再生细菌纤维素薄膜的制备工艺

详细介绍了利用N-甲基吗啉-N-氧化物(NMMO)为溶剂溶解细菌纤维素以及制备再生细菌纤维素薄膜的工艺流程,并对NMMO溶解细菌纤维素机理进行了简要的分析。     

pH可控PVAm-g-PBA/PVA层层自组装 在纤维素膜上的应用

通过酰胺化反应将4-羧基苯硼酸(PBA)接枝到聚乙烯胺(PVAm)高分子链上,制得改性聚乙烯胺(PVAm-g-PBA),利用FTIR和1HNMR对其结构进行了表征。采用硅晶片和聚苯乙烯微球(PS)作为模拟物,将PVAm-g-PBA和聚乙烯醇(PVA)组装到其表面并研究了自组装过程中基材表面电荷的变化规律及自组装膜层厚度的变化。将PVAm-g-PBA与PVA通过pH可控的层层自组装方法处理再生纤维素膜表面。结果表明:PVAm-g-PBA的等电点为pH=7.9;在p H=9.5、与PVA组装上30层高分子膜时,再生纤维素膜的抗张强度与断裂伸长率分别提高了53%和76%。处理后的再生纤维素膜的机械性能得到了明显改善。     

Comparison of cellulose and chitin nanocrystals for reinforcing regenerated cellulose fibers

In this study, regenerated cellulose fibers reinforced by cellulose nanocrystals (CENC) and chitin nanocrystals (CHNC) were prepared by blending the nanocrystals suspensions with the cellulose solution in NaOH/urea/water solvent at room temperature. The effect of nanocrystals' addition on the properties of spinning dopes and regenerated fibers were investigated and compared. Results showed that the obtained CENC and CHNC had different dimensions, and both of them increased the viscosity and decreased the transparency of the spinning dopes. However, the dissolution state of cellulose was not changed. CHNC had a greater influence on the properties of spinning dopes, while CENC had more obvious effect on the performance of regenerated fibers. The CENC reinforced fibers showed a higher crystallinity index as compared to the CHNC reinforced fibers. The tensile strength of the regenerated fibers was evidently improved when 3 wt % CENC or 2 wt % CHNC were added, while the elongation at break of the fibers was slightly decreased with the increase of nanocrystals content. The morphology and thermal stability of the regenerated fibers was not affected by the addition of nanocrystals. This study suggested that the dimension, group and content of nanocrystals were important factors for the reinforcement of regenerated cellulose fibers. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44880.     

蔗渣纤维素氨基甲酸酯的合成

使用平均聚合度为548的蔗渣浆粕和尿素为原料,在二甲苯溶剂中,探讨各种工艺条件对产物氮含量的影响,制备了溶解性和稳定性较好的蔗渣纤维素氨基甲酸酯。产物用红外光谱和热重曲线进行结构和热性质分析,结果表明,蔗渣纤维素在羟基上发生了衍生化反应,引入了"-CONH2"基团;与原料蔗渣浆粕相比,在热裂解前蔗渣纤维素氨基甲酸酯存在更明显的小分子的热分解现象。     

High‐strength regenerated cellulose fibers spun from 1‐butyl‐3‐methylimidazolium chloride solutions

High‐performance regenerated cellulose fibers were prepared from cellulose/1‐butyl‐3‐methylimidazolium chloride (BMIMCl) solutions via dry‐jet wet spinning. The spinnability of the solution was initially evaluated using the maximum winding speed of the solution spinning line under various ambient temperatures and relative humidities in the air gap. The subsequent spinning trials were conducted under various air gap conditions in a water coagulation bath. It was found that low temperature and low relative humidity in the air gap were important to obtain fibers with high tensile strength at a high draw ratio. From a 10 wt % cellulose/BMIMCl solution, regenerated fibers with tensile strength up to 886 MPa were prepared below 22 °C and relative humidity of 50%. High strengthening was also strongly linked with the fixation effect on fibers during washing and drying processes. Furthermore, an effective attempt to prepare higher performance fibers was conducted from a higher polymer concentration solution using a high molecular weight dissolving pulp. Eventually, fibers with a tensile strength of ～1 GPa and Young's modulus over 35 GPa were prepared. These tensile properties were ranked at the highest level for regenerated cellulose fibers prepared by an ionic liquid–based process. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45551.     

Preparation and properties of chemical cellulose from ascidian tunic and their regenerated cellulose fibers

Chemical cellulose (dissolving pulp) was prepared from ascidian tunic by modified paper‐pulp process (prehydrolysis with acidic aqueous solution of H₂SO₄, digestion with alkali aqueous solution of NaOH/Na₂S, bleaching with aqueous NaOCl solution, and washing with acetone/water). The α‐ cellulose content and the degree of polymerization (DPw) of the chemical cellulose was about 98 wt % and 918, respectively. The Japanese Industrial Standard (JIS) whiteness of the chemical cellulose was about 98%. From the X‐ray diffraction patterns and ¹³C‐NMR spectrum, it was found that the chemical cellulose obtained here has cellulose Iβ crystal structure. A new regenerated cellulose fiber was prepared from the chemical cellulose by dry–wet spinning using N‐methylmorpholine‐ N‐oxide (NMMO)/water (87/13 wt %) as solvent. The new regenerated cellulose fiber prepared in this study has a higher ratio of wet‐to‐dry strength (<0.97) than commercially regenerated cellulose fibers. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 1634–1643, 2002.     

Structure and properties of novel regenerated cellulose films prepared from cornhusk cellulose in room temperature ionic liquids

Cornhusk cellulose was regenerated using the ionic liquids viz., 1‐allyl‐3‐methylimidazolium chloride (AmimCl) and 1‐ethyl‐3‐methylimidazolium acetate (EmimAc). The cast cellulose films were characterized by FTIR, WAXD and SEM techniques. Their mechanical properties were also studied. These studies indicated that AmimCl and EmimAc are good solvents for the regeneration of cornhusk cellulose. The regenerated cornhusk cellulose (RCC) was found to be cellulose (II) with dense structure. The films cast from AmimCl exhibited good mechanical properties; the tensile modulus and strength were as high as 6 GPa and 120 MPa respectively, whereas these values for those films cast using EmimAc were found to be 4.1 GPa and 47 MPa respectively. Further, it was observed that after regeneration, the solvents could be effectively recycled. Thus a novel nonpolluting process of forming RCC films from agricultural waste was developed. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

蔗渣纤维素在离子液体中的溶解与再生

以蔗渣纤维素为原料,在1-烯丙基-3-甲基咪唑氯盐([Amim]Cl)离子液体中,制备出蔗渣纤维素再生膜。通过偏光显微镜观察了蔗渣纤维素的溶解过程,采用红外光谱、扫描电镜、X射线衍射、热重及力学性能等分析测试手段,对蔗渣纤维素及再生膜进行表征,结果表明:未经活化的蔗渣纤维素可快速、直接溶解在离子液体中,再生前后蔗渣纤维素发生了从纤维素Ⅰ到纤维素Ⅱ的晶型转变,蔗渣纤维素再生膜具有致密的结构,热力学稳定性达到292℃,拉伸强度高达144MPa。     

功能性再生纤维素复合膜的制备及性能研究进展

纤维素是自然界中储量最大的天然高分子化合物,被认为是未来能源和化工的主要原料。然而,天然纤维素聚合度高、结晶度高的特性,使其难以溶于常规溶剂,极大限制了纤维素的应用。近年来,人们发现了多种新型纤维素溶剂体系,本文简要介绍了基于新型纤维素溶剂体系制备而来的再生纤维素膜以及一系列功能性再生纤维素基有机/无机复合膜材料。通过新型纤维素溶剂体系溶解再生得到的再生纤维素基复合膜在多孔性、热稳定性、强度等性能方面得到一定程度的改善,有望应用于包装、污水处理、传感器、生物医学等领域。本文基于再生纤维素膜及其复合膜材料的最新研究进展,对今后发展的热点方向进行了展望,旨在为纤维素溶解和功能性再生纤维素新材料的开发提供参考。     

Impact of non‐solvent on regeneration of cellulose dissolved in 1‐(carboxymethyl)pyridinium chloride ionic liquid

Cellulose dissolved in ionic liquid (1‐(carboxymethyl)pyridinium chloride)/water (60/40 w/w) mixture is regenerated in various non‐solvents, namely water, ethanol, methanol and acetone, to gain more insight into the contribution of non‐solvent medium to the morphology of regenerated cellulose. To this end, the initial and regenerated celluloses were characterized with respect to crystallinity, thermal stability, chemical structure and surface morphology using wide‐angle X‐ray diffraction, thermogravimetric analysis, Fourier transform infrared spectroscopy and scanning electron microscopy. According to the results, regardless of non‐solvent type, all regenerated samples have the same chemical structure and lower crystallinity in comparison to the initial cellulose, making them a promising candidate for efficient biofuel production based on enzymatic hydrolysis of cellulose. The reduction in crystallinity of regenerated samples is explained based on the potential of the non‐solvent to break the hydrogen bonds between cellulose chains and ionic liquid molecules as well as the affinity of water and non‐solvent which can be evaluated based on Hansen solubility parameter. The latter also determines the phase‐separation mechanism during the regeneration process, which in turn affects surface morphology of the regenerated cellulose. The pivotal effect of regenerated cellulose crystallinity on its thermal stability is also demonstrated. Regenerated cellulose with lower crystallinity is more susceptible to molecular rearrangement during heating and hence exhibits enhanced thermal stability. © 2019 Society of Chemical Industry