GB684975A - Improvements in and relating to the production of cellulose triesters - Google Patents

Abstract

<PICT:0684975/IV (a)/1> A cellulose triester such as the triacetate is obtained by passing an esterifying liquid comprising a fatty acid anhydride, an esterification catalyst and an inert solvent through a static bed of cellulose under such conditions that the fibrous form of the cellulosic material is maintained, and reversing the direction of flow of the esterifying liquid at least once during the esterification in order to maintain the required rate of flow of liquid through the bed of cellulosic material. The direction of flow may be reversed each time a marked resistance to the flow is observed. The cellulose may be in the form of cotton linters, wood-pulp, or mixtures of these. It may be pretreated with water, or a fatty acid, before being subjected to esterification. Sulphuric or perchloric acid may be used as catalyst. Carbon tetrachloride may be used as inert solvent. As shown, cellulose is packed in reaction vessel 1 which is connected to pump 2 and reservoir 3 by pipes 4, 5. Pump 2 and reservoir 3 are connected by pipe 6. Pipes 4, 5 are connected together by pipes 9, 10. Esterification liquor is passed upwardly through the bed of cellulose by opening valves 7, 8, and keeping valves 11, 12 closed. To reverse the flow valves 7, 8 are closed and valves 11, 12 are opened. In another arrangement, the static bed of cellulose is placed in a reaction vessel which is connected to a reservoir for the esterifying liquid, a heat exchanger, a pump, and a reversing manifold, the apparatus forming a closed liquid circulating system. Specification 402,692 is referred to.