Pulp Fibres

The paper making process, in very simplistic terms, involves the use of pulp, additives and water to make a final paper sheet. The type of paper being made will influence the levels of all of these components, for example high quality paper will utilise high levels of pulp fibre and additives, whereas tissue paper will use very little. Diagram 1 below illustrates the process. 

Hemicelluloses Pulp fibres 1% Acid methanolysis with HC1, followed GC FID n.r. n.r. 38... 

The end group which is produced contains a carboxylic acid functionality which has an influence on the anionicity of pulp fibres (Chapter 6) but, in this form, it is resistant to further alkaline degradation. The hemicelluloses are also able to undergo the same type of peeling reaction but at different rates from each other and from cellulose. The /3-1,4-xylans, for example, are more stable to alkaline degradation than the glucomannans. 

Once the pulp fibres have been refined to the necessary degree, they are then formed into a sheet of paper on the paper machine. The paper formation process itself is essentially a fast filtration process and involves the delivery of a dilute fibre suspension in water on to a woven endless plastic wire belt, through which it drains to form a wet fibre network. The Fourdrinier paper machine is the most well-established system for forming the wet web, but there are now many variations of this basic principle. A schematic diagram of the Fourdrinier formation process is shown in Figure 5.15. 

Figure 9.2 shows that, during recycling of chemically delignified (Kraft) pulp fibres, irreversible pore closure within the cell wall takes place which leads to a reduction in their cell wall water content as measured by the fibre saturation point (see Chapter 5). The net effect of this is a loss in fibre flexibility which, in turn, leads to less effective inter-fibre bonding. 

The use of ceric ion initiation to graft polymers on to the surface of wood pulp fibres requires pre-bleaching of the fibres to remove most of the lignin (Mansour etal., 1982). The reaction requires acidic conditions, with a typical system utilizing ceric ammonium... 

Figure 4. The treatment of photochemically yellowed, bleached TMP reduces the yellow chromophores to colourless groups as seen by the decrease in Ak to zero at wavelengths above 400 nm. Reduction of the carbonyl groups produced by near-uv irradiation plus those native to the pulp fibre decreases Ak at 330 nm to a negative value (Adapted from ref. 15 and 33).

Methoxylation of TMP samples was achieved by heating pulp fibres together with appropriate amounts of dimethyl sulphate in an equivolume solvent of water, ethanol and dimethoxyethane(74), methoxyl content of the pulp fibres being controlled by the amount of dimethyl sulphate added (Schmidt, J.A. Heitner, C. J. Wood Chem. Chem. Technol., In Press). Samples were analysed for methoxyl content by Scharwzkopf Microanalytical Laboratories, Woodside, New York. Analysis of the TMP samples for phenolic hydroxyl content was according to the method of Gellerstedt and Lindfors(76). 

Manufacturing and Foam fractionation, Polishes, asphalt (paving) Ink, gel, paints, pulp fibre... 

An alternative to sedimentation for removing suspended solids is flotation. This tends to be used for low-density particles that tend to float anyway during conventional sedimentation processes. Drinking water examples include algae and floes of humic and fulvic acids that result from the treatment of coloured waters [549]. Wastewater examples include fatty materials, pulp fibres, and oils that can be floated... 

J. F. Kennedy, G. O. Phillips, and P. A. Williams (eds.), Cellulosics Pulp, Fibre and Environmental Aspects, Ellis Horwood, Chichester, 1993. 

Figure 1 Schematic presentation of a pulp fibre in an aqueous electrolyte solution...

Pulping deseribes the processes by whieh wood is redueed to fibre, or strictly to a mixture of fibre and fibre debris. Papermaking, although teehnieally complex is simple in prineiple. Paper is made by spreading a layer of pulp fibres in suspension on the surfaee of a moving wire (mesh) sereen so as to form a wet paper web whieh, after pressing to remove water and eonsolidate the fibre mat, is dried to form paper. 

Some ehemieal pulp fibres respond very quickly. Thin-walled fibres rapidly become flexible on beating and may collapse while being beaten. Thieker walled cells require heavier beating to achieve the same degree of flexibility. Latewood tracheids of Douglas fir respond only slowly while their earlywood fibres are beaten very easily indeed. 

Y Liu, R Gustafson, and J Callis. Microspectroscopic Analysis and Kappa Determination of Single Pulp Fibres Stained with Acridine Orange. J. Pulp Paper Set 25 351-355,... 

Pulp represents the major raw material basis for the two main applications a) about 95% for paper and board production, where the pulp fibres are additionally modified to give a coherent paper sheet and b) about 5% for chemical... 

The C -factor represents the capacity of the refiner to impose impacts upon pulp fibres passing through. The C-factor finks the power input, P, and pulp mass flow rate, F, through a refiner to the average number, N, and intensity, /, of impacts imposed on fibres. N and I are derived Ifom the relationships shown in Equations (13.11). 

Figure 7.5. Advancing contact angles versus immersion distance along a bleached and an unbleached thermomechanical pulp fibre using equations 7.2 and 7.3 and assuming that the receding contact angle is zero...

ATR-FTIR was used to determine the concentration of a chemical additive (cationic polyacrylamide resin) within a pulp fibre. The depth distribution of the additive was determined by sputter etching the fibre surface. The obtained profile was compared qualitatively with that obtained by the variable-angle ATR-FTIR depth profiling method. Most of the additive was located at the surface, with some distributed within the fibre (137). 

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