Graftability of beaten pulps and acetylated pulps

Ce(IV)-induced polymerization of acrylonitrile with acetylated bagasse and wood pulps, having different acetyl contents, has been investigated. The graft yield is dependent on the acetyl content as well as the origin of the pulp. Increasing the acetyl content of pulps caused a significant decrease in the polymer loading. However, the rate of polymerization of acetylated wood pulp is much higher than that of acetylated bagasse pulp. The ceric consumption during grafting decreases as the acetyl content of the pulp increases. The effect of beating of the pulps, to various degrees of freeness, on their reactivity toward grafting process has also been studied. Generally, the state of cellulose, as defined by its degree of beating, and the origin of the pulp strongly influenced the graft yield. In creasing the beating degree of bagasse pulp resulted in a decrease in graft yield, while beating of wood pulp, to a definite degree, inhibits the polymerization reaction. The consumption of Ce(IV) by the beaten pulps during oxidation is somewhat greater than that consumed by the unbeaten pulps, whereas the consumption during grafting of acrylonitrile onto beaten pulps depends on the initial concentration of ceric solution. Also, the effect of grafting of acrylonitrile onto acetylated wood and bagasse pulps on their strength properties as well as the effect of grafting onto beaten pulps on their properties has been investigated. Grafting of acrylonitrile onto acetylated bagasse pulp decreased its strength properties, but improved its beatability comparatively to those of original pulp (0 acetyl content). On the other hand, grafting of acrylonitrile onto acetylated wood pulp resulted in a great improvement in its strength properties compared to those of grafted unacetylated pulp. Grafted unbeaten pulps gave thinner and weaker paper than the original pulp (without grafting). Beating of bagasse pulp before grafting gave pulp which possessed a higher strength properties, at low °SR, than those of pulp beaten after grafting. Raising the °SR by rebeating the pulp after reaction up to the original value had an adverse effect on the strength. Beating of bagasse pulp before grafting did not accelerate the reaction rate, but it saved some power consumption, since the time required for beating of grafted pulp to a given °SR was lower than that of ungrafted pulp.     

Graft copolymerization of acrylonitrile onto bagasse and wood pulps

Graft copolymerization of acrylonitrile onto bagasse and wood pulps has been studied using ceric ammonium nitrate as initiator. The effect of order of reactants addition on grafting was examined: three methods were studied. Addition of the pulp to a mixture of initiator and monomer (method A) resulted in more efficient grafting than the other two methods. The reaction produced more grafting at 50°C than at 30°C or at 40°C. The results showed that the monomer and initiator concentrations are the major factors influencing the grafting rate of acrylonitrile. Increasing the acrylonitrile or initiator concentration was accompanied by a substantial increase in graft yields. Increasing the initiator concentration is more effective on polymerization rate than the increase in monomer concentration. The extent of grafting of this monomer can best be controlled by reaction time. Water swelling of pulps significantly affected the grafting rate of acrylonitrile as well as the ceric consumption during grafting. The reactivity of bagasse pulp towards grafting of acrylonitrile is higher than that of wood pulp due to a more open structure of cellulose in bagasse pulp as well as the presence of some lignin which accelerates grafting. Ceric consumption during grafting depends on the nature of the pulp as well as the monomer and initiator concentrations, time, temperature, and the method of grafting. More Ce(IV) is consumed during grafting than during oxidation of the pulps under identical reaction conditions, due to homopolymer formation which accompanied grafting. The ceric consumption by bagasse during grafting or oxidation is somewhat greater than that consumed by wood pulp under similar reaction conditions.     

Radiation grafting of vinyl monomers onto wood pulp cellulose. II

The effect of radiation dose rate and beating time on the mutual radiation grafting of styrene to unbleached and bleached kraft wood pulp was studied. Companion studies on the effect of beating time, peroxidation grafting, and order of monomer addition on the preirradiation graft copolymerization of acrylamide and diethylaminoethyl methacrylate were conducted on bleached wood pulp. The grafting rate of styrene increased with dose rate, but the kinetics suggests a significant diffusional resistance to the observed grafting rate. The per cent graft measured at fixed grafting conditions decreased markedly as pulp beating (effected prior to grafting) was increased. It is suggested that the decrease in grafting with beating is due to an increase in the accessibility and swelling of the beaten fibers. Dimethylaminoethyl methacrylate appeared to inhibit the grafting of acrylamide, and double grafting had to be used to graft both hydrophilic polymers to the pulp. The mechanical properties of high-yield pulp and groundwood were improved by the addition of the grafted pulps. The double grafts appeared to show promise as fibrous beaten additives for dry strength improvement. The styrenegrafted pulps were found not to respond at all to the beating process.     

Thermal behavior of ungrafted and grafted bagasse and wood pulps

The effect of grafting of methyl methacrylate (MMA) and acrylonitrile (AN) on the thermal behavior of the pulp of sugar cane loaded with CaCO₃ and the pulp of a broad-leaved tree has been studied by thermal methods. Different experimental conditions of grafting AN onto the eucalyptus pulp have been used, including both water and organic solvent systems as the medium of reaction. To optimize the grafting of MMA onto wood pulp, the effect of pulp swelling and the contact time of the monomer with the pulp have been examined. Ungrafted as well as grafted cellulose samples with different levels of grafting were characterized by differential scanning calorimetry (DSC) and the thermogravimetric analysis (TGA). The CaCO₃ filler makes the pulp of bagasse thermally more stable. The grafting of MMA onto the bagasse or the wood pulps improves their thermal stability. This is not the case for wood grafted with poly(AN). The thermal stability of the grafted and ungrafted samples varies after a few weight percent has been lost. The glass transition temperature (T_g) of the copolymers have been measured and they are in good agreement with the calculated data. © 1993 John Wiley & Sons, Inc.     

Effect of Some Physical Treatments On the Reactivity of Cotton Stalk Pulp Toward Grafting

The effect of different physical treatments-for example, grinding, beating, and swelling with ethylene diamine-on the reactivity of bleached cotton stalk pulp toward grafting with methylmethacrylate monomer using ceric ion redox system is studied. the effect of monomer concentration and liquor ratio of grafting system on the graftability is also demonstrated. the graftability of treated samples is improved by using a liquor ratio of 50:1 instead of 40:1 for the untreated sample. Optimum graft yield for the beaten samples is obtained at 37°SR. Increasing the °SR of the beaten samples decreases the graft yield till it reaches a value lower than that of the untreated sample at 61°SR. Swelling of cotton stalk pulp with ethylene diamine has a high effect on the reactivity toward grafting. the physically treated pulps are characterized by infrared spectra to clarify the effect of these treatments on the crystallinity index (Cr I) of cotton stalk pulp.     

The xanthate method of grafting. III. Effect of lignin content on the graftability of wood pulp

Several commercial wood pulps of different chemical origin and with various lignin content were copolymerized with acrylonitrile using the xanthate grafting process. A number of experiments were carried out to evaluate the effects exerted by the residual lignin and by other wood components on the grafting reaction. The results obtained show that graft copolymers can be prepared in good yields with pulps containing as much as 23% lignin. With the aim to investigate the effect of lignin in more detail, two series of pulps were prepared by delignification of a crude sulfite pulp and a crude Kraft pulp to different levels of lignin content. Sodium chlorite was used as a bleaching agent. Copolymerization results obtained with these pulps indicate some fundamental differences in behavior between sulfite and Kraft pulps. In both cases, the copolymerization is afflicted by a short inhibition period whose duration, however, does not depend on the lignin content in the pulp.     

Alkaline sulfite/anthraquinone pulping of pine wood chips biotreated with Ceriporiopsis subvermispora

Pine wood chips were treated for 30 days with Cemporiopsis subvermispora in 20 dm³ bioreactors. A typical selective biodelignification was observed. The biotreated wood chips and undecayed controls were subjected to modified alkaline sulfite/anthraquinone (ASA) cooking at 170 °C or 175 °C applying varying cooking times ranging from 30 to 270 min. In all cases, the residual lignin content of the pulps prepared from biologically pretreated wood chips was lower than that of the control pulp. With increasing cooking time, however, the differences in kappa number became smaller. Wood chips cooked for a short time required mechanical refining for fiber liberation. A disk‐refining step resulted in pulps with low reject content (0.4%) and high screened yield (56–60%). In this case, the use of biotreated wood chips provided pulps with significantly lower kappa numbers than for the control pulp (71 and 83, respectively). The pulp from biologically pretreated wood fibrillated rapidly, reaching 20° SR in only 38 min beating time in a Jokro mill, while the control pulp required 56 min to reach the same beating degree. Although easier to beat, the biopretreated pulps showed tensile and burst indices similar to those of the control samples. However, their tear indices were always lower. Easier delignification after wood biotreatment was not observed for the reactions performed at long cooking times. Oxygen delignification of biotreated and conventional ASA pulps with low kappa numbers reduced kappa number and improved brightness considerably with the biotreated pulps being favored by a better preservation of viscosity. Copyright © 2004 Society of Chemical Industry     

Acetylation behaviour of cotton and bagasse celluloses. II. Effect of hot alkali refining

The alkali pretreatments of cotton linters, bagasse dissolving pulp, and bagasse kraft pulp increased the accessibility of the cellulose hydroxy groups to acetylating molecules. The pretreatment with hot alkali resulted in a higher degree of esterification than with cold alkali. The filterabilities of cellulose acetates obtained from alkali pretreated samples of cotton linters, dissolving pulp, and kraft pulp were better than in case of the untreated samples. Hot refining resulted in better filterability than cold refining, but resulted in stronger degradation and lower thermal stability than cold refining. The presence of hemicelluloses in the untreated pulp lowered the reactivity towards acetylation but favoured the reactivity towards xanthation. In case of cotton linters both reactivities were improved by the alkaline pretreatments. The increase in reactivity resulting from the depolymerization of the cellulose overcame the increase in inaccessibility resulting from drying after the alkaline treatment. The removal of hemicelluloses from the dissolving and kraft pulps by alkaline extraction deteriorated the reactivities towards xanthation, but had a favourable effect on the reactivity towards acetylation.     

Radiation grafting of vinyl monomers onto wood pulp cellulose. Part I

The effect of dose, dose rate, monomer type, and monomer concentration on the water transport behavior in grafted cellulose pulp and hand sheets was studied. At low dose rates, grafting rates of styrene onto wood pulp were less with hand sheets than with the pulp itself. Grafting was also found to be decreased by increasing the dose rate. Grafting mixtures of styrene and acrylonitrile gave better yields than styrene alone. Excellent grafting yields were obtained by treating the pulp or hand sheets with water before adding vinyl monomers. In this way, solvents such as dioxane could be eliminated from the grafting mixture. The hand sheets, grafted with mixtures of acrylonitrile and styrene, had good mechanical properties although less than the corresponding ungrafted sheets. Grafting decreased the moisture regain in pulp and hand sheets. Gamma irradiation of wood pulp under ambient conditions without additives reduced the water sorption considerably.     

The xanthate method of grafting. V. Graftability of mechanical pulp

Softwood mechanical pulp was copolymerized with acrylonitrile using the xanthate redox grafting process. Experiments carried out under different reaction conditions (temperature, H₂O₂, concentration, pH, reaction time) showed that mechanical pulp is less apt to form graft copolymers than chemical pulps. In most cases, long inhibition periods were observed, and the product formed thereafter contained large quantities of homopolymer. It was not possible to raise grafting efficiency by increasing the concentration of hydrogen peroxide. A series of experiments with pulps having different particle size showed a moderate increase in total conversation to polymer with decreasing mean fiber length. The latter, however, produced little influence on the copolymer/homopolymer ratio.     

Effect of accelerated aging on the properties of some writing paper sheets

Writing papers made from kraft softwood pulp and bagasse dissolving pulp were subjected to thermal aging for different time intervals (24, 48, 72, 96 and 120h) and the resulting changes in their chemical, physical and submicroscopic properties were investigated. The crystallinity changes in these pulps during thermal aging were studied by X-ray diffractograms. The carboxyl content of the kraft softwood pulp increased with time of thermal aging up to 96h and then decreased with increasing aging time, while the carboxyl content of bagasse dissolving pulp increased during thermal aging up to 72h and then decreased after this time. The crystallinity of kraft softwood pulp increased gradually during thermal aging. However, in the case of bagasse dissolving pulp the crystallinity increased up to 72h and then decreased. All pulps were characterized by a reduction in the degree of whiteness and chain depolymerization during the time of thermal aging.     

Synthesis and Identification of Graft Copolymers of Wood Pulp and 4-Methyl-2-oxy-3-oxopent-4-ene

A set of graft copolymers of wood pulp and 4-methyl-2-oxy-3-oxopent-4-ene has been synthesized. The graft reaction is a free radical polymerization coinitiated by calcium chloride, hydrogen peroxide on wood pulp in dimethylsulfoxide at 30°C. The wood pulps used in this research are unbleached products produced by chemical, thermal and mechanical pulping. All of them contain 25 to 29 weight percent lignin. Separation of the grafted wood pulp from homopoly(1-methyl-1-(2-oxy-1-oxopropyl)ethylene) formed during the reaction was done by benzene extraction. The results show that after the reaction, virtually all the wood pulps have a weight increase and, for very high yield sodium bisulfite pulp, a weight increase of up to 92.7% of the original weight of pulp was obtained. The Fourier transform infrared spectra of the benzene unextr-actable fractions provide strong proof of grafting.

The grafted wood pulp is a surface-modified pulp. Grafting has changed the surface properties of the starting wood pulp from hydrophilic to hydrophobic. The importance of this change is that the grafted wood pulp has potential use as a reinforcing material without use of coupling agents in many hydrophobic polymer matrixes.

The reaction products contain homopoly(1-methyl-1-(2-oxy-1-oxopropyl)ethylene) and uniformly dispersed grafted wood pulp. Under ordinary thermal compression conditions, thermoplastic composite objects can be made directly from the reaction products which contain up to 56 weight percent wood pulp.     

Cold alkali refining of cellulosic pulps derived from Egyptian cotton and bagasse

A cotton linter pulp, a bagasse dissolving pulp and a bagasse paper pulp were subjected to cold sodium hydroxide refining and the resulting changes in their chemical, physical and submicroscopic characteristics were investigated. In the case of cotton linters the main change took place in the physical and submicroscopic properties and the refining resulted in better reactivity towards xanthation. The α-cellulose content of the paper and viscose pulps increased with alkali concentration until it reached a constant value which depends on the type of pulp and the concentration of alkali. The refining of the paper and viscose pulps impaired their reactivity towards xanthation. The presence of the more hydrophilic hemicellulose increased the swelling ability of the fibres and made them more reactive towards xanthation. The undesirable effects of drying after refining with high alkali concentration could be overcome if the DP is sufficiently lowered. In this case the resulting shorter chain macromolecules dissolve more readily during xanthation.     

Graft copolymers of wood pulp and 1-phenylethene. I. Generality of synthesis and proof of copolymerization

A method of grafting lignin-containing materials is now known that allows 1-phenylethylene (styrene, [100-42-5]) graft copolymers of a lignin source to be quantitatively made. The grafting reaction is a solution polymerization often run in aprotic, polar, organic solvents. Grafting changes solubility and surface properties of the lignin-containing material. The lignin-containing materials grafted are unbleached wood pulps produced by chemical, thermal, and mechanical pulping. Grafting wood pulp produces a wood-reinforced, thermoplastic composite. © 1993 John Wiley & Sons, Inc.     

蔗渣浆制造黏液纤维的研究

<正>在黏液纤维制造中,用蔗渣浆代替木浆作原料,常被人怀疑甚至否定其可能性,其主要根据为草类纤维的形态结构不同於木材纤维,而以天然纤维的形态结构作为对原料适合与否的判断标准。我们认为:黏液丝浆的良好制备条件均应最大限度地破坏了天然纤维的形态结构,主要是细胞壁的组织。後者的存在影响丝光化与黄酸化的反应     

Preparation,characterization, and properties of unbleached,bleached, and grafted pulps from JRC‐321 variety jute fiber

Graft copolymerization onto jute pulps opened the door to new concepts in pulp and paper research. Jute pulp from the JRC‐321 variety white jute fiber was prepared by the alkaline sulfite pulping process. The pulp obtained was bleached by the chlorination, extraction, and hypochlorite sequence technique to remove excess lignin for making bright and good quality paper. Special attention was focused on the graft copolymerization of acrylamide monomer onto the unbleached and bleached pulps by the use of a complex initiating system: Cu(II)/glycine/KHSO₅ in aqueous solution. It was found that percentage grafting was high in the case of bleached pulp. The grafted pulps so obtained were characterized by FTIR and their thermal behavior was characterized by TGA. Their mechanical properties such as tensile strength, percentage elongation, and tenacity were measured and compared. The physical properties such as rot‐resistance and water‐retention capacity of the grafted and the ungrafted pulps were determined. The effect of the percentage grafting variation on the above mentioned properties was examined. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1963–1969, 2002     

Production and Characterization of Cellulose Nanofibrils from Different Chemical and Mechanical Pulps

In this study, mechanical fibrillation for the production of cellulose nanofibrils (CNF) from chemical and mechanical pulps with different chemical compositions was studied. To investigate the effect of nanofibrillation on wood pulps by the grinder, the nanofibrils obtained from grinded pulp were characterized with morphology, particle size distribution, apparent viscosity in aqueous solution, degree of crystallinity, and water retention capacity. The results showed that the low lignin-containing unbleached kraft pulp (UKP) exhibited good performance for fibrillation, resulting in CNF with high viscosity, high water retention value, and small particle size. However, the fibrillation of high lignin-containing chemi-thermomechanical pulp was the most inefficient which resulted in heterogeneous materials with relatively low viscosity, low water retention value, and large particle size compared to chemical pulps. Furthermore, bleached softwood pulp from radiata pine was found to be much faster and for easier fibrillation compared to the bleached hardwood pulp from acacia due to the more rigid structure of hardwood fibers.     

Grafted wood pulp containing quaternary ammonium group and its application in the removal of different anions from aqueous solution

Network wood pulp based on acrylonitrile (AN) has been chemically modified through different reactions to obtain group capable of anion exchange. Graft copolymerization of AN onto wood pulp was carried out by using γ‐radiation ⁶⁰Co. Factors affecting the grafting process, e.g., radiation dose and monomer concentration, was investigated. The chemical modification of cyano groups were carried out by reaction with ethanolamine producing oxazoline group followed by quaternization of tertiary amine by reaction with benzyl chloride producing quaternary ammonium salt. The grafted and modified wood pulp were characterized by FTIR, SEM, and TGA. Qualitative adsorption experiments were conducted to evaluate the ability of modified wood pulp to fix sulfate, phosphate, nitrate, and dichromate from aqueous solution using batch extractions. Based on the results obtained, it may be concluded that it is possible to modify chemically wood pulp containing cyano groups by different routes to use it as anion exchanger for different anions. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3120–3128, 2007     

Impregnation of Hardboard with Poly(methyl methacrylate)

The increasing deficiency of natural woods has led to the use of agricultural residues in the preparation of pulp and boards. The important agricultural residues are bagasse, straws, and cotton stalks, which accumulate in vast amounts. Some studies concerning the use of bagasse (Lumen et al., 1963), rice straw (Mobarak et al., 1975; Fadl et al., 1984), cotton stalks (Mobarak and Nada, 1975), and other agricultural residues (Lathrop and Naffziger, 1949; Aronosky and Lathrop, 1949) for producing hardboards are available. Actually, resins are added to pulp before board formation to give a final board of high strength and water resistance. The common resins are phenol-formaldehyde, urea-formaldehyde, and melamine- formaldehyde. Also, in one of our previous works, whole black liquor (Nada et al., 1982), produced from rice straw pulping process or its separated components (lignin, hemicellulose, and silica) (El-Saied et al., 1982) in the presence or absence of phenol-formaldehyde resin during hardboard preparation, was used to improve the strength properties of board. Other treatments are used to modify the hardboard or paper sheet properties, by impregnation of the sheets in resin solution (Plomely and Cottstein, 1968; Nada et al., 1981) or by polymer solution (Calleton et al., 1970; Youssef et al., in press). In addition, chemical modifica-tions such as acetylation, grafting (Smraishi et al., 1982). and cyanoethylation are carried out on wood and hardboard to improve their dimensional stability.     

国产棉浆粕的性能表征及制备二醋酸纤维素的研究

为了探索制造烟用二醋酸纤维素片的浆粕原料国产化,采用扫描电子显微镜、X-射线衍射、热重分析、红外光谱、半纤维素分析等方法表征了国产醋化级棉浆粕的物化特性,并评价了国产棉浆粕的醋化反应性能。结果表明,与进口木浆粕相比,国产棉浆粕具有α-纤维素含量高、结晶度高、半纤维素含量低的特点。国产棉浆粕的醋化反应活性低于木浆,采用国产棉浆粕制备的醋片白度和丙酮浊度优于以木浆为原料制备的醋片。