Pine sulfite

Figure 2A compares a cotton linter pulp with a bleached pine sulfite pulp, BPS, and two different bleached pine kraft pulps, BPC and BRK. It is immediately apparent that the initial weight loss from the cotton linters pulp occurs at a higher temperature than for the three wood pulps, and in fact, this was true for all the other wood pulps as well. In addition, the residue at the conclusion of pyrolysis was lowest for the cotton linter pulp. Figure 2 also shows that although the early pyrolytic behavior of the three wood pulps is similar, the later behavior and the residues are differentiated. In fact, the two pine kraft pulps, BRK and BPC, are more dissimilar than are the BPS and BPC pulps, which are bleached pine sulfite and bleached pine kraft pulps, respectively. In the latter two pulps, the species of pine is the same whereas the pine kraft, BRK, is from a different pine species grown in the southern hemisphere. 

Figure 2B shows a group of sulfite pulps with the cotton linters pulp shown again for comparison. The USS and BSS pulps, unbleached and bleached spruce sulfite, respectively, are quite similar and fall between the cotton linters pulp and the bleached pine sulfite pulp with respect to both initial decomposition and final residue. 

The structure of the mannan, or mannans, in wood cannot be described with certainty. Hess and Liidtke isolated a mannan from pine sulfite pulp identical with ivory-nut mannan-A in optical rotation and x-ray diagram. Husemann prepared, from spruce hemicellulose, fractions having rotational values in agreement with those for the mannan from pine sulfite... 

Sulfite pulps have properties that are desirable for tissues and top quaHty, fine papers. Because sulfite pulping is not as versatile as kraft pulping, various options have been developed, and the choice of a specific process is dependent on individual mill situations. The unbleached pulp has high (60+) brightness compared to kraft pulp and is easily bleached. However, it is limited to select wood species. The heartwood of pine, Douglas fir, and cedars are not easily pulped. Additionally, pulps produced from hardwood have limited economic value because of low strength. 

Figure 10. Fractionation of spruce spent sulfite liquor and pine kraft black liquor.

The resin in the parenchyma cells is mainly composed of fatty acid esters (fats and waxes) and sterols. When wood is pulped, this resin usually remains encapsulated inside the parenchyma cells, while the oleoresin becomes dispersed in the liquor. This is particularly the case with spruce parenchyma cells, which have minute pores and rigid cell walls. Pine parenchyma cells have larger pores and release their resin more readily (Table 5-1). The resin content of acid sulfite spruce pulps can be effectively lowered by fiber fractionation. The situation is different for pine pulps in which the proportion of parenchyma cells is lower. 

During acid sulfite pulping, lignin may also condense with reactive phenolic extractives. Pinosylvin and its monomethyl ether, present in pine heartwood, are examples of phenolic extractives of this type. Dual condensation of pinosylvin with lignin generates harmful cross-links. Consequently, pine heartwood cannot be delignified by the conventional acid sulfite method. 

Fig. 8-17. Yield in oxygen bleaching. Full line, inhibitor added dotted line, no inhibitor addition, (a) Spruce sulfite (b and c) pine kraft (d) spruce sulfite pulps (reducing end groups have been eliminated by NaBH4 reduction).

During acid sulfite pulping a-pinene and some monocyclic terpenes are partially converted to p-cymene (Fig. 7-18). Crude cymene can be separated from the digester gas relief condensates and purified by distillation. With spruce and fir the distilled product is 99% p-cymene and only minor quantities of other products, such as borneol and sesquiterpenes, are present. Pine wood contains 3-carene, which affords appreciable quantities of m-cymene besides p-cymene. The crude cymene can be used within the mill as a resin-cleaning solvent. The distilled p-cymene finds use in the paint and varnish industry. 

Although preliminary studies suggest that face-laminations can be obtained using adhesives made from condensed tannins that pass the standards of the American Institute of Timber Construction (< ), less is known about how to formulate adhesives using these materials for end-jointing of wood. This study, funded by the USDA Small Business Innovation Research Program, was undertaken to develop adhesive formulations containing 50% of sulfite extracts obtained from the bark of southern pine trees and demonstrate their use in... 

Extracts from southern pine bark obtained by extracting finely ground bark with 4.0% sodium sulfite and 0.4% sodium carbonate at 100 °C can be used to replace 50% of the PRF resin in a honeymoon system forbonding exterior quality structural end-joints in lodgepole pine or Douglas-fir. 

Four types of condensed tannins were studied in the adhesive dips 1) extracts from pecan nut pith obtained by digestion with aqueous sodium sulfite-sodium carbonate solutions, 2) purified tannins from southern pine bark, 3) extracts from southern pine bark obtained by digestion with aqueous sodium sulfite-sodium carbonate solutions, and 4) tannins extracted with acetone-water solutions from peanut skins. 

The sulfite extract performed nearly as well as the peanut skin tannin in bonding to nylon. Use of a tannin sulfonate derivative does not seem to hinder the development of strong bonds (compare peanut skin and sulfite extracts from pine bark). Likewise, the presence of carbohydrates in the tannin extracts does... 

Figure 2. Pullout forces of polyester cords for various tannin-containing adhesive dips as a function of percent resorcinol. 1, pecan pith sulfite extract 2, purified pine bark tannin 3, pine bark sulfite extract 4, peanut skin tannin.

Figure 6. Comparison of the pullout forces of polyester and nylon cords for dips containing pine bark sulfite extract.

Table II. Elemental Composition and Carbohydrate Content of Sulfite Extracts from Pecan Nut Pith and Southern Pine Bark...

Materials. All test papers were obtained from a single roll or were made from pulp. The following test papers were used (1) Foldur kraft paper, a bleached kraft paper made from 90% southern pine and 10% hardwood pulps, with 0.5% rosin size and 3% titanium filler (2) newsprint paper made from 80% groundwood and 20% unbleached sulfite pulp and (3) handsheets prepared from a 1 1 furnish of Weyerhaeuser New Bern softwood (NBS) and New Bern hardwood (NBH) bleached kraft pulps. 

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. 

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