Acetylation of lignocellulosic fibres

C - Chemistry – Metallurgy – 08 – H

Patent

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Details

C08H 8/00 (2010.01) B27K 5/00 (2006.01) C08B 3/06 (2006.01)

Patent

CA 2208080

This invention relates to a process for acetylation of lignocellulosic fibres (LF) using an acetylating agent comprising acetic anhydride at a temperature of above 140 °C and a pressure of 100-150 kPa wherein raw or substantially raw LFs are treated with a superheated acetylating agent comprising at least 20 % w/w acetic anhydride for a duration of at least 1.5 minutes in an acetylation reactor (3), the treatment with superheated acetylating agent also ensuring that the acetylated LFs are substantially free from occluded, adsorbed or absorbed acetylating agent, the amounts of which are less than 5 % w/w of the acetylated LFs recovered from the base of a circulation cyclone (5), so as to substantially acetylate the LFs to achieve a weight gain of at least 2 %. The LFs may optionally be pre-treated, prior to being treated with the superheated acetylating agent, with a liquid acetylating agent, preferably by spraying, for a very short period of time.

L'invention porte sur un procédé d'acétylation de fibres lignocellulosiques au moyen d'un agent d'acétylation à teneur d'anhydride acétique (au moins 20 % en poids) porté à une température supérieure à 140 DEG C et à une pression de 100-150 kPa. Le procédé consiste à traiter les fibres (à l'état brut ou semi-brut) pendant au moins 1,5 minute dans un réacteur d'acétylation (3). Le traitement par l'agent d'acétylation surchauffé garantit que les fibres acétylées sont pratiquement exemptes d'agent d'acétylation occlus, absorbé ou adsorbé lequel ne représente que 5 % en poids des fibres acétylées récupérées à la base d'un cyclone à circulation (5). L'acétylation presque complète des fibres permet d'obtenir un gain de poids d'au moins 2 %. Avant l'opération, les fibres peuvent facultativement être prétraitées par un agent d'acétylation liquide de préférence pulvérisé pendant une très courte durée.

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