Refining, mechanical pulp

Semichemical Combination of impure fibers Intermediate pulp refiner mechanical pulp High-yield kraft, high- 6... 

More direct evidence for the formation of o-quinones in light-induced yellowing was presented by Lebo et al. (14). They found that trimethyl phosphite reacts with o-quinones to produce oxyphosphoranes, which in turn, react with water to form cyclic phosphate triesters, as shown in Scheme 3. Treatment of yellowed refiner mechanical pulp with trimethyl phosphite decreased the light absorption at 437 nm, as seen in Table I. Similar decreases in specific absorption were observed at 413 and 320 nm. Solid state 31P nmr analysis of pulp treated with trimethyl phosphite was consistent with the formation of the cyclic phosphate triesters. 

Lebo, S.E., JR., Lonsky, W.F.W., McDonough, T.J., Medveca, PJ. and Dimmel, D.R., "The Occurrence and Light-Induced Formation of ortho-Quinonoid Lignin Structures in White Spruce Refiner Mechanical Pulp", J. Pulp Paper Sci., 1990,16, J139. 

The thermomechanical pulping (TMP) invention in 1939, and the subsequent introduction of this technology from 1968-1973, and refiner mechanical pulping (RMP), permitted the application of mechanical pulping systems to residue sources of wood. Their development spurred the improvement of stone groundwood (SGW) pulping by the introduction of pressurized groundwood (PGW) systems. 

Refiner Mechanical Pulp was developed in 1929 and then used in 1938 for board products. Disk refiners began to be used in 1962 for pulp production. In this case, unlike SGW, small wood pieces or chips are broken down between rotating, grooved, or patterned metal disks at atmospheric pressure. The two methods for mechanically producing pulp are depicted in Fig. 4. One advantage of using refiners is that lowercost wood residues could be used as feedstock. Refiner mechanical pulp production totals about 3.5 x 106 tonnes/year. 

In Fig. 6 all of the methods are divided into purely mechanical pulps and chemically modified pulps. Under purely mechanical pulps the older methods, SGW, RMP, and TMP remain, but three new processes have been added to the list TRMP (thermo-refiner mechanical pulp), PGW (pressure ground wood) and PRMP (pressure refiner mechanical pulp). These purely mechanical methods are all very similar to the older processes. The differences are related to the temperature of either the wood before or during refining. Heat energy or pressure is not applied in the same manner in the different processes. 

There is a dearth of reliable methods available for determining ethylenic groups as components of quinonoid ring systems in lignin. A sensitive and specific method developed by Lebo et al. (1990), based on an addition reaction with trimethyl phosphite, has been used to determine o-quinonoid structures in situ in the lignin component of refiner mechanical pulp. 31P-NMR measurement capability is required for the analysis. 

Fig. 7.7.3. Conductometric titration curve of a refiner mechanical pulp made from sulfonated spruce chips (3.47g). End point A corresponds to titration of the sulfonic acid groups and end point B coresponds to titration of the sulfonic and carboxylic acid groups. (Katz et al. 1984)...

Studies on Pinus species have shown that the nature and amount of extractives depend upon the percentage of heartwood present and thus on tree age. In Piims radiata, heartwood starts forming once the trees are about 12 to 15 years old. Heartwood extractives occur in greatest amount in inner growth rings near the pith (Uprichard, 1971 Lloyd, 1978) especially in the butt log of mature trees (Table 2.5). The high level of resin in the inner zone appears due to a process of enrichment with sapwood extractives via the transverse resin canals (Harris, 1965). Resin acids predominate in heartwood and comprise from 70-80% of total extractives, however in sapwood there are approximately equal amounts of resin acids and fatty acids (Table 2.6). An important feature of the resin constituents of pines is that a mixture of resin acids in turpentine occur in the resin canals, and the fatty acid esters and unsaponifiable materials occur in the ray parenchyma resin. In some processes, for example refiner mechanical pulping some separation of these chemical components can occur. 

Atack D (1972) On the characterization of pressurized refiner mechanical pulps. Svensk Papperstidn, 75(3) 89-94... 

Carbonyl groups of simple aliphatic aldehydes, ortho mdpara quinones, a,P-unsaturated carbonyls and cyclic aromatic anhydrides are known to condense with trimethyl phosphite, producing phosphite esters [62]. Lebo and Lonsky used trimethyl phosphite to determine the light-induced formation of ort/jo-quinonoid functional groups in refiner mechanical pulp [63]. 

Lebo, S. E., and Lonsky, W.F.W., The occurrence and light induced formation of ortho-qninonoid lignin strnctures in white spruce refiner mechanical pulp, J. Pulp Paper Sci. 16(5), J139-J143 (1990). 

GC Myers, GF Leatham, TH Wegner, RA Blanchette. Fungal pretreatment of aspen chips improves strength of refiner mechanical pulp. Tappi / 71(5) 105-108, 1988. 

Refiner mechanical pulp (RMP) is obtained by mechanical defibration of wood-chips in a refiner and is carried out without pre-treatment Defibration takes place under atmospheric pressure. The wood chips are defibrated at temperatures of about 100 °C, mostly in two stages with consistencies of 20 to 30% in the second stage. 

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