Spruce, alkaline pulping

Immergut and R8.nby have resolved a mixture of a xylan and a gluco-mannan from a spruce sulfite pulp by a series of alkaline extractions and... 

Coniferaldehyde structures are the major leucochromophore present in spruce lignin. These end groups are also present to a large extent in unbleached mechanical pulps and are responsible for a major portion of the absorption of UV-radiation above 350 nm. Mild sulfite treatment leads to a considerable reduction in the content of coniferaldehyde structures. After bleaching of mechanical and chemimechanical pulps with alkaline hydrogen peroxide, coniferaldehyde structures are to a large extent eliminated and they cannot be considered to be major contributor to the photo-... 

The recent studies of the Finnish group further emphasize the complexity of the xylan in wood cellulose. These workers have shown that the properties of the xylan in wood pulps depend not only on the method of pulping but also on the type of raw material. It was observed that, when pulps are prepared by the (acidic) sulfite process from the softwoods, pine and spruce, a substantial part of the xylan is of the acidic type (see Fig. 2, p. 303). Even when these sulfite pulps are refined further with hot alkali, some acidic xylan remains. However, when pulps are prepared from pine and spruce by the (alkaline) sulfate process, the acidic xylan is removed and only neutral xylan remains. 

Figure IL The SEC molar mass distribution curves for arabino-4-O-methyl-glucuronoxylan (from spruce holocellulose), arabinohexenuronoxylan (kraft pulp) and two different 4 0-methylglucuronoxylans (sulfite and dissolving pulp) obtained by the SEC/MALDI-MS procedure. Each xylan was analyzed separately employing the alkaline (pH 13) buffer SEC system and subsequently graphed on the same MALDI-MS calibrated absolute molar mass scale.

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