New Zealand Journal of Forestry (1976) 21(1): 95–104
©New Zealand Institute of Forestry
Pulping of New Zealand beeches (Nothofagus species) and associated forest species
The prospects for pulping the beeches (Nothofagus spp.) by mechanical, semichemical and chemical pulping procedures are reviewed. The response of the associated species quintinia (Quintinia acutifolia), kamahi (Weinmannia racemosa), rata (Metrosideros robusta), and rimu (Dacrydium cupressinum) to kraft pulping is also described.
Beech refiner pulps are dark in colour and have very poor papermaking quality. Cold soda pulps have only moderate strength and would generally require bleaching prior to paper production. Beech neutral sulphite semichemical pulps have strength properties which are about two-thirds of those of corresponding kraft pulps, but are suitable for corrugating media.
Although bisulphite pulps (50% yield) are obtainable from beech, the pulps have lower strength than kraft pulps. Nitric acid pulps of the same yield have similar strength properties.
Chemical pulps are best prepared by alkaline pulping methods. Kraft pulps from the beeches are obtained in yields of between 42 and 52%, and the average yield for all species is about 49%). Associated species also give pulps within this yield range. Pulps beaten for 4000 rev. in the PFI mill had tear index of 10, and tensile index of about 80. Beech kraft pulps can be bleached to high brightness. The use of a prehydrolysis stage prior to kraft pulping gives pulps rich in cellulose, of 38%> yield, which after bleaching are comparable to rayon-grade commercial pulps.
Soda pulps are obtained from beech in 41% yield. Pulps of similar yield can be obtained from the beeches using soda-oxygen pulping. The papermaking properties of these pulps are similar to those of normal kraft pulps.
Of the various alternatives available, the manufacture of bleached kraft pulps holds most promise.