Thermomechanical pulp -

The printing of newspapers is conducted at very high speeds, often reaching 3000 feet per miaute. AH three printing processes utilize similar quaHty newsptint which, essentiaHy, is made of groundwood or thermomechanical pulp. Presses are fed a continuous web of newsptint that unwiads from a feed roUer. Inks dry by absorption of Hquid iato the porosity of the substrate. Some evaporation of water ia a flexo pubHcation ink can accelerate the dryiag process. 

The TMP process is similar to the RMP process except that after chip washing, a steaming vessel is inserted to achieve the thermoplasticization of the lignin in the wood. The production of thermomechanical pulps increased dramatically after the introduction of this method in the early 1970s. Because these pulps can be substituted for conventional groundwood pulps in newsprint blends to give a stronger paper, lower quantities of the more expensive, lower yield chemical pulps are required. 

This study was supported by UK. Ministry of Agriculture, Fisheries and Food for the LINK Collaborative Programme(Multi-use Approach to Cereal Straw Fractionation Using Thermomechanical Pulping) in Crops for Industrial Use under Agreement CSA 2054. 

Figure 1.2. Bleaching of a sprace thermomechanical pulp (TMP) in the presence of a Ru-THP species 100°C, 340 psi H2, 3 h, 1.5% consistency.

Figure 1.5. Relative bleaching powers of BBHPE and THP for a thermomechanical pulp.

Commercial Masonite and Asplund boards and the asphalt-impregnated insulation board were sampled before any commercial heat treatment. The corresponding "thermomechanical" pulps had been produced by pressurized refining of steamed chips. The higher pre-steaming temperature used in the Masonite process resulted In a yield of about 85% as compared to a fiber yield of about 94% of the Asplund pulps, the remainder being dissolved. 

Figure 13 presents the Arrhenius plots for all boards of density between 850 and 1 100 kg/m. Here the hardboard line is the mean of both Asplund and Masonite type commercial hardboards, presented in more detail in Figure 14. There was no significant difference between hardboards from 2.3 to 6 mm thick made of the two related types of coarse thermomechanical pulp. Semi-hardboards...

Between the lignin containing hardboards some differences occur. The groundwood hardboard with largely carbohydrate fiber surfaces has a much larger initial heat release, and chemical activation by temperature, than the commercial hardboards of coarse thermomechanical pulp which are made up of fiber bundles separated in the middle lamella, and surrounded by a rather smooth layer of partly condensed lignin. 

Figure 1.1 Scanning electron photomicrograph of a cross section of a national newspaper comprising 90% spruce and 10% pine thermomechanical pulp (TMP) fibres (45gm 2 and 8fibres thick). Scale bar = 25 fiin.

Figure 9.2 Comparison of the effect of repeated recycling of Kraft and thermomechanical pulp (TMP) fibres on tensile strength and fibre swelling. 

Thermomechanical Pulp (TMP), CTMP, and Semichemical Pulping Liquors... 

McCarthy et al. Role of resin acids in the anaerobic toxicity of chemi-thermomechanical pulp wastewaters. Water. Res. 1990, 24, 1401-1405. 

Kantardjieff, A. Jones, J.P. Practical experiences with aerobic biofilters in TMP (thermomechanical pulping) sulfite and fine paper mills in Canada. Water Set Technol. 1997, 35 (2-3), 227-234. 

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