Composition of methyl methacrylate-grafted cellulose

Graft copolymerization of methyl methacrylate on cellulose samples was carried out using various initiator systems, and extraction treatment was performed on the copolymers with 50% to 300% grafting by weight. Adding of ceric ion to a suspension of cellulose and methyl methacrylate in water resulted in more efficient grafting than other methods. That is, amount of extracted cellulose from graft copolymers obtained by the conventional ceric ion method was approximately 20%, whereas those obtained either by the hydrogen peroxide method or by the adsorbed ceric ion method amounted to 70% to 80%. However, the amount of extracted homopolymer was approximately proportional to that of extracted cellulose. The composition of refined samples ranged 20% to 30% of cellulose content and 70% to 80% of poly(methyl methacrylate) content throughout all samples, and it was recognized that the proportion of poly(methyl methacrylate) tended to increase slightly with higher per cent grafting. When the structure of refined graft copolymer was derived from these values, it was recognized that the extent of the grafted chain was at most 1 mole per 1 mole of cellulose molecule in the conventional ceric ion method and amounted to only 1/10 mole in the hydrogen peroxide and adsorbed ceric ion methods.     

A study of the low temperature nitration of cellulose in mixed acids

The low temperature surface and bulk nitration of cellulose has been investigated by electron spectroscopy for chemical analysis (ESCA), ¹³C-NMR and X-ray diffraction. Acid mix composition has been probed at room temperature and at low temperatures (0–20°C) by Raman spectroscopy. This multitechnique approach has been employed to elucidate the behavior of surface degree of substitution (DOS) with acid mix composition over a 40°C temperature range. The data obtained have prompted a reinterpretation of previously reported work. Surface “equilibrium DOS” is shown to be established within 1 s at all temperatures investigated. but, at lower temperatures (> 5°C) the surface DOS as monitored by ESCA is observed to “dip” after immersion times of t < 5 s. This change in DOS is correlated with major structural changes in the fiber as observed by SEM. At low temperatures, e.g., ?15°C, nitration is shown to be complete throughout the cellulose fiber after 10 h nitration. Solution state ¹³C-NMR is used to compare the nitrate ester substitution distribution in cellulose nitrates prepared from acid mixes of the same composition at different temperatures.     

Graft copolymerizations of modified cellulose,grafting of acrylonitrile,and methyl methacrylate on carboxy methyl cellulose

Graft copolymers of acrylonitrile (ACN), methyl methacrylate (MMA), and their mixtures on carboxy methyl cellulose (d.S 0.4–0.5) were prepared by the use of ceric ion initiator in aqueous medium. The graft copolymers were characterized by IR spectroscopy. The extent of graft copolymerization of ACN and MMA was measured in terms of graft level, molecular weight of grafted polymer chains, and the frequency of grafting as functions of ceric ion concentration. It was found that at comparable reaction conditions, the molecular weight of the grafted polymer chains and the frequency of grafting were not of the same order of magnitude. For the monomer mixtures, the copolymer compositions obtained from the total nitrogen contents of the copolymer samples showed that a disproportionately low amount of ACN monomeric units were incorporated into the graft copolymer, even at high ACN content of the feed. © 1996 John Wiley & Sons, Inc.     

The synthesis of methyl lactate and other methyl oxygenates from cellulose

Light oxygenates, such as methyl lactate (MLA), methyl levulinate (MLE), methyl formate (MFO), methyl acetate (MAC), dimethoxymethane (DMM), and methoxyacetaldehyde dimethyl acetal (MADA) were synthesized from cellulose in the presence of promoted SnX₂ (X = Cl⁻, Br⁻, and I⁻) salt catalysts in methanol. The presence of halides in SnX₂-ML_n (ML_n is metal salt) catalysts was found crucial for methyl lactate formation from sugar. The investigation shows that ZnCl₂ is an efficient promoter for SnX₂ catalyst in converting cellulose to light oxygenates. Up to 52.2% of total one-pass oxygenate yield was obtained in the presence of SnCl₂–ZnCl₂ catalyst.     

Alkaline hydrolysis of methyl acrylate grafted cellulose fibers

In this work, methyl acrylate grafted cellulose fibers were hydrolyzed in an aqueous NaOH solution to obtain a superabsorbent hydrogel. The effect of process variables, such as the hydrolysis reaction time, temperature, and NaOH concentration, during alkaline hydrolysis were carefully determined and optimized. The degree of hydrolysis was estimated on the basis of the determination of the carboxylate group contents. The material loss during hydrolysis followed a first‐order reaction mechanism. The differences in the behavior of the grafted fibers during hydrolysis could be explained by their structural differences. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Electric birefringence of aqueous solutions of methyl cellulose

Electric birefringence studies have been conducted on six samples of methyl cellulose in the molecular weight range 3 × 10⁴ to 1.5 × 10⁵. Using pulsed electric fields, both the amplitudes and rates of the transient birefringence induced in these solutions have been analysed. For molecular weights below 2 × 10³, the molecules are represented by rigid rods. Above this value increasing flexibility is evident. This can conveniently be seen through reduced electrical parameters, defined herein, which are obtained from a combination of the electrical and geometrical properties of the molecules. These parameters are apparently very sensitive to flexibility in the near-rod regime. It demonstrates the utility of electro-optic experiments in which both the electrical and geometrical data are obtained simultaneously. The persistence length concept does not appear to be adequate when rotary relaxation times are interpreted through it using current equations.     

羧甲基纤维素的生产与应用

综述了羧甲基纤维素的生产工艺及技术关键。重点介绍了羧甲基纤维素在洗涤剂，石油，建筑，食品 ，纺织，日用化工等行业的作用及用途，并提出了发展方向。     

Hexavalent-chromium-initiated graft copolymerization of methyl methacrylate onto cellulose

Graft copolymerization of methyl methacrylate (MMA) onto cotton–cellulose has been carried out using hexavalent chromium Cr(VI) as initiator. Aqueous-methanolic solution of perchloric acid has been chosen as the reaction medium. The effect of monomer, initiator, acid, reaction medium, and temperature on the graft percentage has been found out. The reactions have also been carried out in the presence of polymerization, inhibitors, and retarders, such as hydroquinone and transition metal salts like CuSO₄, FeCl₃, etc. The grafted samples, after exhaustive separation of homopolymers and purification, were subjected to various chemical, mechanical, and thermal testings. The results of various analyses have been compared with the reference, and the improvement in the graft has been evaluated. A suitable mechanism for the grafting processes has been suggested, in accordance with the experimental results.     

NMR study of water adsorbed on methyl methacrylate-grafted cellulose

Graft cellulose samples were prepared by three different initiation methods, and the widths of the NMR absorption spectra of samples were measured at various water contents. Samples prepared by both hydrogen peroxide and adsorbed ceric ion methods exhibited maximum widths of NMR absorption spectra at about 10% grafting, whereas the corresponding values for the sample prepared by the conventional ceric ion method were about 30%. Even a minimum value was found on the sample prepared by the latter method. The reason for such different water-binding behaviors of samples is discussed from the viewpoint of difference in the composition of graft celluloses.     

硝酸铁与水杨酸甲酯绿色硝化的选择性及其副产物组成的研究

研究了硝酸铁与水杨酸甲酯的绿色硝化反应。主要产物为3-硝基水杨酸甲酯(O)和5-硝基水杨酸甲酯(P),其选择性与工业化生产比得到了提高,最大比值为P/O=5.3。副产物的组成通过红外光谱、元素分析、差热热重和固体漫反射光谱确定为Fe(NO3)a(MNS)bOc1.8 H2O,其中a+b+2 c=3,随着反应物浓度的增加,a减小b增大。并回收了硝酸铁,其回收率为73.4%(以铁含量为基准)。     

Direct voltammetry and catalysis of hemoenzymes in methyl cellulose film

Horseradish peroxidase (HRP) and catalase (Cat) immobilized on edge-plane pyrolytic graphite (EPG) electrodes by methyl cellulose (MC). Both the hemoenzymes entrapped in the MC film undergo fast direct electron-transfer reaction, corresponding to hemeFe(III)+e→hemeFe(II). The formal potential (E⁰′), the apparent coverage (Γ), the electron transfer coefficient (α) and the apparent electron transfer rate constant (k_s) were calculated by performing nonlinear regression analysis of square wave voltammetry (SWV) experimental data. E⁰′ are linearly dependent on pH, indicating the electron transfer of Fe(III)/Fe(II) redox couple companied with the transfer of proton. The processes of catalytically reducing oxygen, hydrogen peroxide and nitric oxide by HRP and Cat entrapped in MC film are also explored.     

Pentavalent vanadium ion-induced grafting of methyl methacrylate onto cotton cellulose

Graft polymerization of methyl methacrylate (MMA) onto cotton cellulose using vanadium pentanitrate as initiator was studied under a variety of conditions. The graft yield increased with increasing initiator concentration up to 8 mmole/l. and then decreased upon further increase in initiator concentration. Increasing MMA concentration from 1 to 5% was accompanied by a significant increase in the degree of grafting. The latter was also affected by the kind and concentration of the acid incorporated in the polymerization medium. Based on graft yields, the efficiency of the acids follows the order H₂SO₄ > HNO₃ > HClO₄. Replacement of the acid with isopropyl alcohol was also examined. An isopropyl alcohol concentration of 10% constitutes the optimal concentration for grafting. Maximum graft yield depends upon the polymerization temperature; it follows the order 50°C ≥ 60°C > 40°C > 30°C > 70°C. Reaction mechanisms for grafting in the presence of acid as well as in the presence of isopropyl alcohol are proposed.     

利用甲基纤维素辅助合成介孔二氧化硅微球

通过调节硅酸四乙酯（TEOS）和嵌段聚合物F127（EO₁₀₆PO₇₀EO₁₀₆）体系的pH值调控TEOS水解的速度,并利用甲基纤维素（MC）在水热条件下形成网格状液晶微滴结构的特点,一步诱导硅胶初级粒子聚沉制备微米级介孔氧化硅微球。研究了溶胶 凝胶的温度、pH值对成球性和孔结构的影响,通过氮吸附（BET）,X射线衍射（XRD）、透射电子显微镜（TEM）、扫描电子显微镜（SEM）、马尔文激光粒度分析（Malven）等手段分析表征了介孔氧化硅微球的形貌和孔结构,实验结果表明通过向TEOS和F127体系中加入MC,在pH＝1、80℃条件下一步水热晶化可以合成直径在4～6 μm、比表面积为450 m²·g^-1、孔径为4.2 nm的介孔氧化硅微球。     

芳烃衍生物硝化产品的分离研究

本文通过在硝化过程中后制取二甲苯麝香为例，提出了芳烃衍生物经硝化反应后选用合适的有机溶剂作萃取剂，将溶解在过量酸中的硝化产物萃取出来这一新方法。研究结果表明：选用适宜蹬萃取剂可从反应混合物中萃取出硝化产物，萃取后得到的溶液经中和、过滤、蒸馏，结晶等分离过程，最终得到芳烃衍生物的硝化产物，过量的酸可保持在较高的浓度，有利于过量酸的再循环使用，萃取剂经蒸馏后亦可再利用，因此，该方法可降低成本，并减少环境污染。     

β-苯乙醇对位硝化工艺研究

β-苯乙醇在浓硫酸催化下与乙酸酐发生酯化反应,然后与硝酸和硫酸组成的混酸发生对位硝化反应,再用氢氧化钠水解合成对硝基-β-苯乙醇,讨论了反应温度、反应时间、硝酸用量对硝化反应收率的影响,在优化条件下平行实验结果表明,对硝基-β-苯乙醇的总收率和纯度分别达到71 7%、98 3%。经IR、元素分析证实了其结构。     

Ceric salt-initiated graft copolymerization of methyl methacrylate on preoxidized cellulose samples

The effects of preoxidation of cellulose samples on graft copolymerization in the presence of ceric salt (Ce⁴⁺) as an initiator were investigated. The use of Ce⁴⁺ as oxidizing agent inhibited the formation of grafts, and the number of grafts decreased as the concentration of Ce⁴⁺ in the pretreatment rose. In contrast, the samples oxidized with periodic acid (HIO)₄ or hydrogen peroxide (H₂O₂) tended to show improved initiation characteristics and gave a larger number of grafts than the unoxidized samples. The reactivity of oxidized samples toward Ce⁴⁺ was examined and the following results were obtained: The part of easy reactivity decreased in the Ce⁴⁺-oxidized samples but it increased in the HIO₄-oxidized samples; on the other hand, it did not vary greatly in the H₂O₂-oxidized samples. Cellulose is probably oxidized to different states by different oxidizing agents, and the reactivity of Ce⁴⁺ toward these oxidized samples, as one index, seems to be reflected in the graft copolymerization. It was consequently recognized that the graft copolymerization characteristics of cellulose samples could be improved significantly by proper selection of oxidiation conditions.     

Grafting of methyl methacrylate onto cellulose nitrate initiated by benzoyl peroxide

It has been observed that grafting of vinyl monomers onto cellulose nitrate in solution takes place using benzoyl peroxode. The graft copolymer was isolated from the unreacted backbone and homopolymer by selective solvent extraction. The effect of variables, such as the initiator concentration, the monomer concentration and the reaction time on the percent grafting and the grafting efficiency, were discussed. A probable mechanism for grafting of vinyl monomers to cellulose nitrate in solution has been proposed.     

硅胶负载磷钼钒杂多酸选择性催化硝化合成5-硝基水杨酸甲酯

制备了硅胶负载Keggin型H6PMo9V3O40,并用于催化水杨酸甲酯的硝化反应;考察了反应时间、反应温度、催化剂用量、硝酸用量及催化剂重复使用次数对硝化反应的影响。结果表明,该催化剂对硝化反应具有很高的催化活性和对位选择性,在优化的反应条件下,硝基水杨酸甲酯的产率为94%,p/o为6.58,5-硝基水杨酸甲酯的产率达到81.6%;催化剂回收容易,重复使用5次后,仍有很好的催化活性。     

对二氯苯硝化过程中抑制副产物的研究

分析对二氯苯硝化后物料不易快速分层的原因,结合2,5-二氯硝基苯的生产情况提出解决方案.