Abstract
In our country, wood, one of the most important raw and construction materials, is rapidly getting scarce.
From the rational utilization of wood, authors have been carried out this study in order to find whether the rejects in paper mills are suitable as raw material for fiberboard or not.
In this report, the rejects in sulfate pulp mill were used as sample material.
1. Preparation of stock. The rejects (so called knots) were disintegrated with Unimax-Refiner (a kind of vertical type refiner), the stock resulted had following characteristics.
freeness (S.R.) 13.5
alcohol-benzol extracts 0.9%
Lignin (72%H2SO4) 24.8%
2. Sheet formation and hot-pressing. The wet fiber sheets were prepared using the laboratory forming box from the suspension of its pulp. Thus obtained wet sheets were pressed holding between wire-gauze and stainless steel plate under next same pressing condition, as the temperature 140°C. the pressure 30 Kg/Cm2 and time 20minutes.
In this experiment, rice straw defibrated after cooking with water, as raw material, was used solely or as blended to above reject.
3. Quality
Qualities of thus obtained hardboard were tested depending upon the specification of JIS-A-5903, the figures measured were as following table. From the above table, it will be known that the characteristics of hardboard prepared with sulfate pulp reject (knot) are the impact strength very high and the flexibility is relatively large in comparing with the density of those boards owing to the partial delignification by cooking process.
