Hardwood pulp

Kokta, B.V., Lo, R.C. and Daneault, C. (1982). The xanthate method of grafting IX. Grafting of acrylonitrile onto high yield hardwood pulp. In Graft Copolymerization of Lignocellulosic Fibers, Hon, D.N.S. (Ed.). ACS Symposium Series, 187, pp. 269-283. 

In the NS SC process sodium sulfite is buffered with sodium carbonate, bicarbonate, and hydroxide to maintain a slightly alkaline pH during the cook. NSSC hardwood pulp is the premier pulp for corrugating medium and cannot be matched by any other process. 

This research was undertaken to study aqueous alkaline reactions of monomeric structures, similar to polymeric wood constituents, from which color would be formed. Since hardwood pulps were of the greatest immediate interest, the reaction of syringyl alcohol, representing the hardwood lignin structure, in aqueous alkaline solution at room temperature has been studied extensively up to the present time, but the reactions of vanillyl alcohol and a-methylvanillyl alcohol, representing the softwood lignin structure, have also been studied to some extent under the same reaction conditions. 

Industrial scale continuous fermentations on rotoevaporated spent sulfite liquor (hardwood pulping, y softwood pulping). 

One of today s fastest growing segments of the wood composition board industry is production of medium density fiberboard (MDF) using a dry process similar to that used for particleboard. First mention of the possibility of utilizing bark for MDF came in a presentation by Brooks in 1971 (43). He described a process in which a homogenous board with superior properties could be made from such raw materials as mixed, unbarked hardwood pulp chips unbarked pine chips, if bark content was less than 30% forest thinnings, branches, and so on and hardwood bark. Furnish was prepared by double-disk pressurized refiners. Brooks concluded a plant could be built to operate on 100% hardwood bark. 

Some classes of pulp such as the sulfites or bisulfites are relatively easy to bleach. These pulps can be bleached with as few as three to five steps (e.g., CEH, CEHEH). Kraft softwood pulps are difficult to bleach to high brightness. From five to seven steps may be required (e.g., CEHEH, CEHDEDP). Kraft hardwood pulps generally are regarded as intermediate in difficulty. 

Part IX Grafting of Acrylonitrile onto High-Yield Hardwood Pulp... 

It was shown that, in general, the paper properties could be improved by the grafting of acrylamide onto low strength pulps (like high yield and mechanical pulps) (8). It is well known that hardwood pulp fibers are considerably shorter (about 1 milli-... 

The objective of this work was to optimize grafting parameters for hardwood pulp in general and aspen in particular. The monomer used was acrylonitrile. 

Fig. 8-24. Response of various pulp types to peroxide bleaching. 1, Semichemical (cold alkali) hardwood 2, acid sulfite softwood 3, mechanical spruce 4, semichemical (neutral sulfite) hardwood pulps (Rydholm, 1965).

Log kappa number = 0 958 + 0 0253 permanganate number Hardwood pulps... 

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. 

In summary, Tetraselmis sp.Tt-1 could be used as a partial substitute of kenaf pulps and an agent for surface improvement of kenaf pulp paper as in the case of hardwood pulp paper. 

Figure.5. Physical properties of microalga-added paper. Symbols ,kenaf pulp ,hardwood pulp...

In the study described above, strong evidence was shown that for the case of James River conductive base paper, a pressure of 13.8 Mfa applied to stainless steel electrodes was sufficient to effectively reduce contact resistance to negligibly small proportions. In the study described below the question as to whether the in situ pressure conductivity method would also be appropriate for different types of nonconductive papers which exhibit varied surface morphology is addressed. Consequently, paper samples were prepared, with basis weights of 60, 115, and 190 g/m2, all with a 1 1 ratio by weight of softwood-hardwood pulp, in a centrifugal dynamic vertical sheet former. Each of... 

In Fig. 15, it is seen that the sheet made of cotton linters is more conductive than the other sheets. The sheet made with "Seagull W" hardwood pulp is the least conductive while the three other pulps have intermediate conductivity values. This behaviour seems to be related to the size of the different types of fibers used to make the sheets. As mentioned previously, hardwood fibers are shorter than softwood fibers, and consequently, there are more interfiber contacts in the sheets made of hardwood fiber. The surface area of a contact is very important to the conductivity. There may be a constrictive effect due to smaller surface at these contacts which results in a restricted flow of ions through the paper, and therefore a lower conductivity. Cotton linters are chemically different and longer than wood fibers and the sheet made of these fibers is more conductive. The difference between the three softwood pulps is probably related to a different chemical composition of its fibers. 

FIydroxybutanoic acid is a major organic component of kraft black liquors from hardwood pulping, but is formed only in trace quantities from the degradation of glucose polymers. It seems likely that it arises from the xylan by a process along the lines of that illustrated in Figure 6.13. 

Analysis of reprecipitated xylan on fibres from kraft pulping of hardwoods by modern methods indicated that the model system of 20 years earlier had been very perceptive both hexeneuronic acid residues and p-L-iduronyl residues were found (The finding caused a stir in the pulp industry, since a KMn04 titre ( kappa number ) had been used traditionally as measure of the residual lignin in the pulp, but in hardwood pulps these titres were too high, by factors of <2, because of the reaction of permanganate with the hexeneuronic acids" ). 

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