Svensk Papperstidning-nordisk Cellulosa 

About: Svensk Papperstidning-nordisk Cellulosa is an academic journal. The journal publishes majorly in the area(s): Lignin & Pulp (paper). Over the lifetime, 91 publications have been published receiving 2484 citations.

Studies on finely divided wood. Part 1. Extraction of lignin with neutral solvents

Abstract: Previous work on extraction of lignin and cellulose from wood, ground in various ways, and other attempts to isolate 'native lignins' are reviewed. Present opinions about the state of lignin in wood are summarized. Possible methods of disintegration and suitable neutral solvents for extraction of lignin are discussed in connection with experience gathered in the present investigation. It was found that by grinding wood, dispersed in a non-swelling liquid, in a vibrational ball mill it is possible to extract 50per thousand or more of the lignin from spruce ( Picea excelsa ), providing the charge to the mill is small enough. A 'standard method' is presented: Wood is reduced to pass a 20 mesh screen, pre-extracted to remove resins etc., ground 48 hrs. in a Lampen mill (12 g. charge) and 48 hrs. in a vibrational ball mill (6 g. charge), using toluene for dispersion, and extracted with aqueous dioxane. After evaporation of the solvent, the lignin is dissolved in aqueous acetic acid, precipitated into water, dried, dissolved in C 2 H 4 Cl 2 -EtOH (2 + 1 by volume), precipitated into ethyl ether, washed, and dried. A faintly cream-colored, ash-free powder, 'milled wood lignin' (M.W.L.), is obtained. The molecular weight of M.W.L. from spruce is about 11000 (weight average) or about 60 phenyl-propane units. Lignincarbohydrate complexes, extractable from milled wood with dimethylformamide, are slightly soluble in dioxane and contaminate M. W.L., which contains a small amount of sugars. These sugars are the same as in hemicellulose and occur in the same proportions. Determinations of the contents of phenolic hydroxyl groups and ultraviolet light absorption studies indicate similar structures of M.W.L., and lignin derivatives isolated under mild conditions. Determination of p -hydroxy-benzyl alcohol groups gave a value half of that of Brauns' native lignin but double that of wood, and it is concluded that the value of M.W.L. is equal, or close to, that of proto-lignin. It is suggested that M.W.L. is a very useful material for lignin chemists.

The determination of strong and weak acidic groups in sulfite pulps

Abstract: Two methods are presented for the determinations of the sulfonate and carboxylate groups in sulfite pulps. One method involves the initial conversion of the groups to their magnesium salts. A differentiation of the two groups is then made based upon the liberation of magnesium from the carboxylate groups by 0.01 M acetic acid followed by the elution of magnesium from the sulfonate groups by 0.1 M hydrochloric acid. The elution by acetic acid is, however, not completely specific for the carboxylate groups and a small correction must be made. In the second method, the groups are converted to hydrogen form and are then titrated conductometrically with sodium hydroxide in the presence of 0.001 M sodium chloride. Inflexion points mark the end of titration of the strong acids and the total acids. Good agreement was obtained between the two methods but conductometric titration is preferred for its directness and simplicity.

The effect of cations on pulp and paper properties

Abstract: The trace metals within pulps appear to exist largely as the counterions of the acid groups present. If the mixture of cations normally present in a pulp is removed and replaced by a single species, it is found that the paper made from the pulp is increasingly stronger in the order of Al+++?6H+?6Mg++?6Ca++?6Li+?6Na+. It is believed that the more advantageous the cationic form, the greater is the total number of free ions generated within the cell wall. This causes the entry of additional water into the wall by osmosis and the accompanying swelling and plasticization increases the ability of the fibers to bond extensively. The effect of changing an unbeaten pulp from its calcium form (which is that existing in conventional pulps) to its sodium form confers the same beneficial effects of an appreciable amount of beating of the calcium form. The treatment, however, is without the usually undesirable side effects of fiber shortening and fines generation which accompany beating. As a result the cationic treatment shows better retention of certain properties of the unbeaten pulp notably freeness and optical properties.

The reactions of lignins with oxygen and hydrogen peroxide in alkaline media

Abstract: The reactions of lignins upon treatment with oxygen and hydrogen peroxide in alkaline media are summarized on the basis of the results from studies with appropriate model compounds. Two types of initial oxidation reactions may be distinguished: (1) Electrophilic attack on carbanions by molecular oxygen (oxygenations) (2) Nucleophilic addition of hydroperoxide anions to carbonyl and conjugated carbonyl structures. These two oxidants attack in phenolic and enolic lignin structures centres having alternately high (oxygen) and low (hydrogen peroxide) electron density. Both the reactions with oxygen and those with hydrogen peroxide result in the formation of intermediates of the hydroperoxide type. Subsequently, the intermediates undergo rearrangements, resulting in the cleavage of carbon-carbon bonds or in the formation of epoxide intermediates, or alternatively are converted into ortho-or para-quinoid structures. The products of the cleavage of carbon-carbon bonds and the quinoid and epoxide intermediates undergo alkaline-oxidative degradation ultimately yielding simple acids and hydrophilic polymerization products. The two types of initial oxidation (1 and 2) may take place simultaneously or sequentially, both during treatment with oxygen in alkali (oxygen pulping and bleaching). In the former process, hydrogen peroxide is generated by the autoxidation of enediol structures while, in the latter process, oxygen is originally present in the atmosphere and/or is formed by the decomposition of hydrogen peroxide. Although intimately connected with each other during both processes, these two types of oxidation reactions should be considered separately. By doing so, known observations from technical treatments of wood, pulps and lignins with oxygen or hydrogen peroxide can be interpreted in chemical terms.