DEFIBRATION TEMPERATURE 



Figure 25-20. — Relationship between wood temperature and energy consumption for 

 defibration of hardwoods and softwoods. (Drawing after Asplund 1939.) 



A pilot plant to investigate the pulping of southern hardwoods by the thermo- 

 mechanical process for paper grades was announced in 1975 (Dillen et al. 1975), 

 but hardwood TMP is little used by southern paper mills. 



CHEMI-MECHANICAL PULP (CCMP) 



Because in many areas of the world hardwood is locally available at lower cost 

 than preferred softwoods, much research is aimed at production of paper-grade 

 hardwood pulp on a disk refiner. No results applying directly to pine-site hard- 

 woods have been published. With certain hardwoods, notably Populus sp., 

 pretreatment of chips with sodium hydroxide and sodium sulfite to produce a 

 chemi-mechanical (CCMP) pulp, can yield a high quality pulp which is used in 

 specialty papers and base stock for coating. Meinecke (1972) found that alkali 

 alone causes a pronounced discoloration of CCMP pulps, but the addition of 

 H2O2 or Na202 yields an extremely bright fibrous hardwood pulp. 



Paper birch {Betula papyrifera Marsh.), a northern hardwood of medium 

 density, has been reported to respond well to chemimechanical pulping (Leask 

 1968). 



