Birch pulps

FIGURE 10.5 Contribution from lignin, hexenuronic acid, and non lignin structures to the kappa number in various unbleached alkaline pine and birch pulps. (Li, J. and Gellerstedt, G., Nordic Pulp Pap Res J, 13(2),153-158, 1998.)... 

Isolated cellulose I and xylan extracted finm bleached birch pulp was mixed in order to study the process opposite to the removal of hemicelluloses fiom bleached kraft pulp by acid hydrolysis (16). The spectrum of hydrated tylan is shown in Figure 6. 

Clermont L P 1961 The fatty acids of aspen poplar, basswood, yellow birch and white birch. Pulp Pap Mag Can 62T511-514... 

The pulp and paper industries use three types of raw materials, namely, hard wood, soft wood, and nonwood fiber sources (straw, bagasse, bamboo, kenaf, and so on). Hard woods (oaks, maples, and birches) are derived from deciduous trees. Soft woods (spruces, firs, hemlocks, pines, cedar) are obtained from evergreen coniferous trees. 

Triterpenoids occur in hardwood parenchyma resin, and closely related sterols are also present in softwoods (Fig. 5-6). Sterols typefied by the abundant /3-sitosterol, mostly have a hydroxyl group in the C-3 position. They also appear as the alcohol component in fatty acid esters (waxes). Triterpenoids and sterols are sparingly soluble substances contributing to pitch problems in pulping and paper making. Some trees contain polyterpenes and their derivatives known as polyprenols. Betulaprenols, present in birch wood, belong to this category of substances (Fig. 5-7). 

Fig. 7-23. Removal of lignin during kraft pulping of pine (---) and birch (—) as a function of...

Hansson, J.-A. (1970). Sorption of hemicelluloses on cellulose fibres, Part 3. The temperature dependence on sorption of birch xylan and pine glucomannan at kraft pulping conditions. Sven. Papperstidn. 73,49-53. 

Simonson, R. (1965). The hemicellulose in the sulfate pulping process, Part 3, The isolation of hemicellulose fractions from birch sulfate cooking liquors. Sven. Papperstidn. 68, 275-280. 

Figure 2C compares three kraft pulps. Two bleached pine kraft pulps, SKA and BPC, show a relative crossover in their degradation curves and a bleached birch kraft pulp, BBC, shows an initial loss of weight at a lower temperature but has about the same residue as the other two pulps. 

Figure 2D compares a number of sulfite pulps. Two of them, an unbleached spruce sulfite, USS, and an unbleached mixed hardwood sulfite, HS, have remarkably similar degradation curves but show different final residues. A bleached neutral sulfite semichemical pulp, FB, and an unbleached semichemical birch sulfite, SBS, have similar and much steeper initial degradation curves than the other two pulps. The semichemical birch sulfite pulp, SBS, has a degradation curve which crosses over those of the other three pulps shown in Figure 2D. 

Pulps 50% maple, 35% birch, 15% poplar beaten to 400 Canadian Standard Freeness. 

Janson J, Sjostrom E (1966) Sulphur content in relation to the degree of sulphonation in birch and spruce sulphite pulps Sven Papperstidn 69 107-110 Katz S, Beatson RP, Scallan AM (1984) The determination of strong and weak acidic groups in sulfite pulps Sven Papperstidn 87 R48-R53... 

Studies carried out with the aim of developing models to estimate migration include a study by Aurela and Ketoja (2002). They estimated the diffusion rate of model compounds (butanol, ethanol, butyl acetate and tetrahydrofuran) in air at room temperature. They then measured the diffusion of these substances through papers with different grammages (and hence, porosities) produced from birch Kraft pulp. The model compounds were not in contact with the test papers and hence transferred via the gas phase. They concluded that the diffusion constants determined in air could be used in random walk simulation to predict migration in a fibre network. Random walk simulations are a mathematical means of modelling processes based on probability distribution and are often applied to investigate diffusion processes. 

On the other hand, when the hardwoods, birch and aspen, are pulped by either the sulfate process or the sulfite process, a substantial proportion of the xylan remaining in the pulp is of the acidic type. ... 

On comparing data on the carbohydrate composition of wood with those on sulfate pulps, Sundman and coworkers concluded that the galactans and arabans of wood are almost completely dissolved during the sulfate cook. About 70% of the mannan is dissolved from pine wood, as is about 60% of the mannan from birch. From pine, about 50 to 70% of the... 

The pre-hydrolyzed pine and birch sulfate pulps (see Table XVII) war-... 

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