(EN) Minced lignocellulose, such as wood, straw, bamboos, bagasse or any other structured vegetal material, is treated in a discontinuous or continuous process. The process consists in boiling this material in an acidified mixture of solvents in an aqueous phase. This mixture of solvents contains water in a proportion of 30 to 70 parts and an organic solvent in a proportion of 70 to 30 parts. The organic solvent consists of either an alcohol of light molecular weight, or a ketone of light molecular weight; it must be easily evaporable and soluble in water. The pH of the medium is adjusted to a pH from 3.5 to 1.7 by adding a catalytic compound selected within the group of the strong acids: hydrochloric, nitric and phosphoric; within the group of these strong acids neutralized by their neutral salts; within the group of the following organic acids: oxalic, maleic, o-phthalic, l-malic, succinic, nicotinic, salicylic and trifluoracetic. The boiling temperatures range between 160 and 210 C, preferably between 180 and 200 C. After three minutes at the minimum, we obtain the separation of the lignin and the hydrolysis of the hemicelluloses dissolved; after that, the fibres are easily dispersible while forming a pulp. By proceeding to a mechanical refining at a high pressure, a high density thermomechanical pulp is obtained after a shorter boiling time. With the neutralized acids, as well as with the organic acids, particularly with the oxalic acid, we can obtain a fibre with a high degree of polymerization. The lignin is obtained as a precipitate which separates from the liquid; the liquid solvent, usually ethanol or acetone, is evaporated; then the drained lignin is redissolved in the minimal quantity of acetone; a new precipitation with an excess of water allows to obtain the lignin in the form of a slightly coloured powder. A prolonged boiling dehydrates and disaggregates the sugars; by the strong acids action, takes place the formation of light molecular weight or microcristalline cellulose, glucose or organic acids, methanol and furfuralic compounds.
(FR) On traite en procede discontinu ou continu de la lignocellulose hachee, telle que bois, paille, bambous, bagasse ou autre materiau vegetal structure. Le procede consiste a cuire ce materiau dans un melange de solvants acidifie en phase aqueuse. Ce melange de solvants contient de l"eau dans une proportion de 30 a 70 parties et un solvant organique de 70 a 30 parties. Le solvant organique consiste soit en un alcool de bas poids moleculaire, soit en une cetone de bas poids moleculaire; il doit etre facilement evaporable et soluble dans l"eau. le pH du milieu est ajuste a une valeur de 3,5 a 1,7 par l"adjonction d"un compose catalytique choisi dans le groupe des acides forts: acide chlorydrique, nitrique et phosphorique; dans le groupe de ces acides forts tamponnes de leurs sels neutres; dans le groupe des acides organiques suivants: acide oxalique, maleique, o-phthalique, l-malique, succinique, nicotinique, salicylique et trifluoracetique. Les temperatures de cuisson se situent entre 160 et 210 C, de preference entre 180 et 200 C. En un temps d"au moins trois minutes l"on obtient la separation de la lignine et l"hydrolise des hemicelluloses dissoutes; apres quoi, les fibres sont aisement dispersibles, tout en formant une pulpe. En procedant a un raffinage mecanique a pression elevee l"on obtient avec un temps de cuisson plus court une pulpe thermomecanique de haute densite. Les acides tamponnes, ainsi que les acides organiques, en particulier l"acide oxalique, permettent d"obtenir une fibre de haut degre de polymerisation. La lignine s"obtient comme precipite qui se separe du liquide; le solvant liquide, habituellement l"ethanol ou l"acetone, est evapore; puis l"on redissout la lignine egouttee dans la quantite minimale d"acetone; une nouvelle precipitation avec un exces d"eau permet d"obtenir la lignine sous forme d"une poudre legerement coloree. Une cuisson prolongee deshydrate et desagrege les sucres; par l"effets des acides forts, il se forme de la cellulose a bas poids moleculaire ou microcristalline, du glucose ou des acides organiques, du methanol et des composes furfuraliques.
