Patent GB-355382-A (GB)
Title: Manufacture of cellulose derivatives
IPC: C08B17/02
Filed: 1930-05-29
Abstract: <PICT:0355382/III/1> In the manufacture of organic esters and ethers of cellulose, the reaction temperature is controlled by the regulated vaporization of a volatile liquid constituent of the reaction mixture, the temperature being kept at a constant level for a period of time and then changed, at least once, to a new level, at which it is again kept constant for a period of time.  Suitably, the reaction mixture including the volatile liquid, e.g. liquid sulphur dioxide, is contained in a closed vessel, and when the reaction temperature tends to rise above the desired point, sufficient vapour is removed from the vessel, or the pressure on the system is sufficiently reduced, to cause further vaporization and so reduce the temperature to the desired point ; the removal of vapour may be effected by condensing vapour within the vessel, or by releasing vapour from the vessel and returning the condensate, or an equivalent amount of liquid, to the vessel.  Means for heating the reaction mixture may be provided, and the supply of heat may be regulated conjointly with the removal of the vapour. The regulation may be automatic.  One form of apparatus is described, Fig. 1 (not shown), comprising a pressure-tight reaction vessel fitted with a stirrer and communicating with a condenser closed at the top.  A cooling coil in the condenser is fed with cold brine through a pipe line which includes a valve that is automatically operated in accordance with the reaction temperature.  If the temperature rises above the desired point, the valve is opened, or opened further, with the result that vapour in the condenser is condensed.  The pressure in the reaction vessel in thus reduced, and more liquid is vaporized from the reaction mixture, the temperature of which falls accordingly. As the temperature of the mixture falls, the valve tends to close. By adjusting the automatic control device, the reaction temperature may be varied as desired.  Another form of apparatus comprises a closed reaction vessel 2 connected to a condenser 3a, which has tubes 13 supported in plates 11 and surrounded by liquid sulphur dioxide.  The space 12 containing the liquid sulphur dioxide is connected to a condenser 16 having a pipe 17 to return condensate to the space 12. The condenser 16 is cooled by a coil 18 fed with cold brine from a tank 21 by a pump 35.  A temperature-sensitive device 7, having a terminal 9 subject to the temperature of the reaction mixture, controls a valve in a pipe 22 supplying compressed air to pipes 23, 24.  The pipe 23 terminates in a pressure-actuated device 25 which operates a valve 27 in a pipe 30 supplying steam to a coil 31 in the reaction vessel.  A similar pressure-actuated device at the end of the pipe 24 operates a valve 28 in a branch of the pipe 30 through which steam is supplied to the pump 35.  The valve 27 has a spring 33 which tends to open it, and the valve 28 has a spring 36 which tends to close it.  In operation, an undesired rise in the reaction temperature causes a flow of air through the pipes 23, 24, which shuts valve 27 and opens valve 28.  The supply of steam to the coil 31 is thus shut off, and the circulation of cold brine through the coil 18 is effected.  This causes condensation of vapour in the condenser 16, with consequent evaporation of liquid from the space 12, cooling of the tubes 13, condensation of vapour within the tubes 13, and evaporation of liquid in the reaction vessel 2.  If the temperature falls below the desired point, the control 7 operates so that steam is supplied to the coil 31, and the supply of steam to the pump 35 is reduced to shut off.  The temperature that is automatically maintained may be varied by setting the control 7 in different positions by means of a device 37.  Specification 306,531, [Class 2 (ii), Cellulose &c], is referred to.ALSO:<PICT:0355382/IV/1> In the manufacture of organic esters and ethers of cellulose, the reaction temperature is controlled by the regulated vaporization of a volatile liquid constituent of the reaction mixture, the temperature being kept at a constant level for a period of time and then changed, at least once, to a new level, at which it is again kept constant for a period of time.  Suitably, the reaction mixture including the volatile liquid, e.g. liquid sulphur dioxide, is contained in a closed vessel, and when the reaction temperature tends to rise above the desired point, sufficient vapour is removed from the vessel, or the pressure on the system is sufficiently reduced, to cause further vaporization and so reduce the temperature to the desired point; the removal of vapour may be effected by condensing vapour within the vessel, or by releasing vapour from the vessel and returning the condensate, or an equivalent amount of liquid, to the vessel.  Means for heating the reaction mixture may be provided, and the supply of heat may be regulated conjointly with the removal of the vapour.  The regulation may be automatic.  One form of apparatus is described (Fig. 1, not shown), comprising a pressure-tight reaction vessel fitted with a stirrer and communicating with a condenser closed at the top.  A cooling coil in the condenser is fed with cold brine through a pipe line which includes a valve that is automatically operated in accordance with the reaction temperature.  If the temperature rises above the desired point, the valve is opened, or opened further, with the result that vapour in the condenser is condensed.  The pressure in the reaction vessel is thus reduced, and more liquid is vaporized from the reaction mixture, the temperature of which falls accordingly. As the temperature of the mixture falls, the valve tends to close.  By adjusting the automatic control device, the reaction temperature may be varied as desired.  Another form of apparatus comprises a closed reaction vessel 2 connected to a condenser 3a, p  which has tubes 13 supported in plates 11 and surrounded by liquid sulphur dioxide.  The space 12 containing the liquid sulphur dioxide is connected to a condenser 16 having a pipe 17 to return condensate to the space 12.  The condenser 16 is cooled by a coil 18 fed with cold brine from a tank 21 by a pump 35.  A temperature-sensitive device 7, having a terminal 9 subject to the temperature of the reaction mixture, controls a valve in a pipe 22 supplying compressed air to pipes 23, 24.  The pipe 23 terminates in a pressure-actuated device 25 which operates a valve 27 in a pipe 30 supplying steam to a coil 31 in the reaction vessel.  A similar pressure-actuated device at the end of the pipe 24 operates a valve 28 in a branch of the pipe 30 through which steam is supplied to the pump 35.  The valve 27 has a spring 33 which tends to open it, and the valve 28 has a spring 36 which tends to close it.  In operation, an undesired rise in the reaction temperature causes a flow of air through the pipes 23. 24, which shuts valve 27 and opens valve 28. The supply of steam to the coil 31 is thus shut off, and the circulation of cold brine through the coil 18 is effected.  This causes condensation of vapour in the condenser 16, with consequent evaporation of liquid from the space 12, cooling of the tubes 13, condensation of vapour within the tubes 13, and evaporation of liquid in the reaction vessel 2.  If the temperature falls below the desired point, the control 7 operates so that steam is supplied to the coil 31, and the supply of steam to the pump 35 is reduced or shut off. The temperature that is automatically maintained may be varied by setting the control 7 in different positions by means of a device 37. Specification 306,531, [Class 2 (ii), Cellulose &c.], is referred to.