GB959375A - Manufacture of hardboards, fibre boards and the like - Google Patents

Abstract

In the production of hardboard or fibreboard from rubber wood (Hevea brasiliensis), the wood is shredded, treated with boiling water or steam until at least 10% but at most 40% by weight of the hemi-cellulose is removed resulting in a fibrous pulp and the pulp is compressed into boards. Under preferred conditions, boiling water containing caustic soda or lime is employed for the treatment, to the resulting pulp there are added prior to its compression 10-40% by weight of sawdust and/or coconut coir dust, 0.5-4% of a condensation resin or vegetable oil binder, and 0.5-4% of a hydrophobic substance (unspecified), and the compressing operation is carried out at a temperature of 140 DEG -220 DEG C. and a pressure of between 170 and 1,422 lbs. per sq. in. for between 8 and 15 minutes. The boards may incorporate sizing, tempering agents, colouring and insect repellents. According to an example, 500 kg. of wood from rubber trees (Hevea brasiliensis) are disintegrated into chips of length about 3 cm. and the wood chips are steamed within a revolving autoclave in the presence of 1%-3% caustic soda for a period of about 5 minutes up to 3 hours, until at least 10% and at most 40% by weight of the hemi-cellulose is removed resulting in a fibrous pulp, the period depending upon the pressure obtaining in the autoclave and on the temperature corresponding to this (e.g. 5-10 minutes at 12 atm. pressure or 3 hours at 1 atm. pressure). Some water can be added during steaming to decrease the proportion of caustic soda in order to obtain a fibrous pulp which will be lighter in colour. The steamed material is crushed or pulverised whereby the hemi-cellulose lignins go into solution and are removed with the water, and the resultant pulp is pressed into slabs.ALSO:In the production of hardboard or fibreboard from rubber wood (Hevea brasiliensis), the wood is shredded, treated with boiling water or steam until at least 10% but at most 40% by weight of the hemi-cellulose is removed resulting in a fibrous pulp and the pulp is compressed into boards. Under preferred conditions, boiling water containing caustic soda or lime is employed for the treatment, to the resulting pulp there are added prior to its compression 10-40% by weight of sawdust and/or coconut coir dust, 0.5-4% of a condensation resin or vegetable oil binder, and 0.5-4% of a hydrophobic substance (unspecified), and the compressing operation is carried out at a temperature of 140 DEG -220 DEG C. and a pressure of between 170 and 1422 lb. per sq. inch for between 8 and 15 minutes. The boards may incorporate sizing, tempering agents, colouring and insect repellents. According to an example, 500 kg. of wood from rubber trees (Hevea brasiliensis) are disintegrated into chips of length about 3 cm. and the wood chips are steamed within a revolving autoclave in the presence of 1%-3% caustic soda for a period of about 5 minutes up to 3 hours, until at least 10% and at most 40% by weight of the hemi-cellulose is removed resulting in a fibrous pulp, the period depending upon the pressure obtaining in the autoclave and on the temperature corresponding to this (e.g. 5-10 minutes at 12 atm. pressure or 3 hours at 1 atm. pressure.) Some water can be added during steaming to decrease the proportion of caustic soda in order to obtain a fibrous pulp which will be lighter in colour. The steamed material is crushed or pulverised whereby the hemicellulose lignins go into solution and are removed with the water, and the resultant pulp is pressed into slabs.