Patent GB-1323200-A (GB)
Title: Plant for continuous production of cellulose triacetate in a  heterogeneous phase
IPC: C08B17/02
Filed: 1971-07-02
Abstract: 1323200 Solid/liquid and liquid/liquid contact; moving belt filters and extrusion presses PROEKTNO-KONSTRUKTORSKOE BJURO PO PROEKTIRO-VANIJU OBORUDOVANIA DLYA PROIZVODSTVA PLASTICHESKIKH MASS I SINTETICHESKIKH SMOL AND NAUCHNO-PROIZVODSTVENNOE OBIEDINENIE "PLASTPOLIMER" 2 July 1971 31092/71 Headings BID and B1F [Also in Division C3] A plant for continuous production of cellulose triacetate in a heterogeneous phase, comprises consecutively arranged apparatus for activating 1, acetylation and benzene washings 2, benzene stripping 3, partial saponification 4, water washings 5, and final product drying (not shown), units 1 to 4 being interconnected by connecting adapters 15 serving for conveying the fibrous reaction mass from one apparatus to another and provided with means for creating therein a sealing plug from the conveyed reaction mass, said means comprising a screw conveyer 16 with a valve 19 arranged at its discharge orifice 18, spring-loaded by spring 20 in the direction opposite to the direction of travel of the conveyed fibrous reaction mass. The screw conveyer also serves to squeeze out excess liquid component when the reaction mass is transferred from one apparatus unit to another, and for this purpose is provided in its lower part with a longitudinal groove 27 closed from the inside by a perforated plate 28 extending over the wall of the adaptor 15. As shown, the activation apparatus 1 in which the cellulose is treated with acetic acid is made as an air-tight chumber 6 fitted with a perforated belt 7, and provided with sprayers 8, a screw 9 distributing the cellulose over the width of the conveyer 7, loosening means 10 and a screw collector 11. Acetylation and benzene washing unit 2, partial saponification apparatus 4 and water washing apparatus 5 are of similar design, and are fitted with an articulated placing conveyer 13 designed for levelling the cellulose layer from above and controlling its thickness, but the acetylation and benzene washing unit 2 is also fitted with pumps 12 for circulation of benzene. In each of these units, under the conveyer 7 are arranged baths 14 for removing the liquid drained off. Benzene stripping apparatus 3 is made as a screw arranged in an elliptical chamber. In operation, cellulose is loaded via adapter 15 into the activating unit 1 and distributed by screw 9 over the width of perforated belt 7. Acetic acid is supplied through sprayers 8, and the activated cellulose is loosened by loosener 10, is collected by screw collector 11 and passes to the connecting adaptor 15, in which the screw conveyer 16 feeds the fibrous reaction mass into the compacting chamber near the discharge orifice 18. In this chamber the mass is compacted creating a plug which seals the activation apparatus 1, separating it from the acetylation and benzene washings apparatus 2. As the sealing plug overcomes the action of the spring 20, it urges the valve 19 open and creates a clearance at the discharge orifice 18 for the continuous exit of the compacted reaction mass, while the liquid component is squeezed out and drained through perforated plate 28, collector 33 and nozzle 34, and also through perforated dish 29 and nozzle 30. The reaction mass then passes to apparatus 2, where it is distributed by screw 9 over conveyer 7, levelled by conveyer 13, sprayed with an acetylating mixture of acetic anhydride, benzene and acetic acid together with chlorinated lime as catalyst, and the resulting fibrous cellulose triacetate is washed with benzene, circulated by pumps 12, to neutralize the remaining catalyst. The resulting cellulose triacetate containing liquid benzene is loosened by loosener 10, and passes via screw 11 to adapter 15 which links apparatus 2 with benzene stripping apparatus 3. In the adapter a sealing plug is created and benzene is partially squeezed out, and in apparatus 3 the cellulose triacetate is sprayed with hot water, treated with steam and squeezed out with the formation of a sealing plug in the adapter 15 which connects apparatus 3 with the apparatus 4 for partial saponification. In apparatus 4 the cellulose triacetate layer is treated with 10-12% aqueous nitric acid, and the partially saponified product is removed from belt 7 by loosener 10 and passes via screw 11 to adapter 15, where it it is squeezed out, and is then fed by a pneumatic conveyer through conduit 36 to the apparatus 5 for a series of water washings. After further squeezing in adapter 15, arranged after apparatus 5, the product is delivered by pneumatic conveyer through conduit 37 to a conventional drying apparatus.