PRODUCTION METHOD

Abstract: Coarse cellulosic material is delivered into a feed hopper (1) having an outlet fitted with a rotary valve (2). The coarse material is blown to a grinder (10) and classifier (11). The grinder (10) has a drive unit with a power load monitor (12) fitted with a controller (13). The classifier (11) is driven by a variable speed drive unit (15) which is also controlled by the controller (13). A fan (20) with a variable speed drive unit (21) draws ground and classified cellulosic material into a receiving bin (23) for separation in a separator screen unit (30). The operating speed of the fan (20) and the operating conditions of the grinder (10) and classifier (11) are controlled to optimise the processing of the cellulosic material.

Description: ■ Production Method- The invention relates to a method for producing cellulose- based excipients such as carboxymethylcellulose and the like. In roduction The specifications for cellulose based excipients, particularly pharmaceutical excipients, are high in order to comply with processing and regulatory requirements. Such cellulose products generally have a high value, however, there is a need to optimise the processing method to minimise losses and to provide a range of such cellulose-based products which meet these requirements. Statements of Invention According to the invention, there is provided a method for producing cellulose-based excipients comprising the steps oft- setting a desired operating load on a grinder; delivering coarse cellulosic material from a feed hopper to the grinder; grinding the coarse cellulosic material; classifying the ground cellulosic material in a grinder having a classifier drive unit; controlling the classifier drive unit in accordance with the operating load on the grinder; drawing the ground and classified cellulosic material into a grinder receiving bin; delivering the ground and classified cellulosic material to a separator; separating the classified cellulosic material into cellulosic material of a desired size and oversize material; delivering the cellulosic material of desired size into a holding bin; and packing the cellulosic material from the holding bin. In one embodiment of the invention, the ground and classified material is drawn into the grinder receiving bin by a fan having a variable speed drive and the method includes the step, prior to delivery of the coarse cellulosic material to the grinder, of setting the speed of the fan drive to a desired speed matched to the coarse cellulosic material. Preferably, the method includes the step of delivering the oversize cellulosic material from the separator to the feed hopper for recycling. In one embodiment of the invention, the operating load on the grinder drive is sensed by sensing the operating power of the grinder drive, the classifier drive unit is a variable speed drive and the classifier drive unit is controlled by varying the drive speed of the classifier in accordance with the operating power of the grinder drive. In a preferred arrangement, a rotary air valve is provided at the feed hopper outlet and the coarse cellulosic material is delivered from the feed hopper to the grinder by a blower unit. Preferably, the method includes the step of de-bagging coarse cellulosic materials into the feed hopper. Detailed Description of the Invention The invention will be more clearly understood from the following description thereof given by way of example only with reference to the accompanying drawing which is a schematic diagram illustrating the method for producing cellulose-based pharmaceutical excipients according to the invention. Referring to the drawing, there is illustrated a method for producing cellulose-based excipients and in this case pharmaceutical excipients such as carboxymethylcellulose and the like. The method is in this case used in the production of three different types of cellulose-based excipients. These may be a blend of different excipients. Equivalent equipment used in processing different cellulosic materials are illustrated in some cases for clarity as separate items but are assigned the same reference numerals. In the method of the invention, coarse cellulosic material is delivered into a feed hopper 1 having an outlet fitted in this case with a fixed speed rotary valve 2. The coarse cellulosic material is blown by a blower unit 3 along a common supply line 4 to a grinder/classifier unit 5. The grinder/classifier unit 5 comprises a grinder 10 and a classifier 11. The grinder 10 has a drive unit with an associated power load, in this case, operating amps monitor 12 fitted with a controller 13. The classifier 11 is driven by a variable speed drive unit 15, the operation of which is controlled by the controller 13. A fan 20 fitted with a variable speed drive unit 21 draws ground and classified cellulosic material along a delivery line 22 to a grinder receiving bin 23. Air is exhausted through a plurality of air filter socks 25. The receiving bin 23 has an outlet fitted with a rotary valve 27 through which the ground and classified cellulosic material is delivered to a separator screen unit 30. The screen unit 30 may have any size of aperture fitted to achieve separation into a desired size fraction and oversize. The desired size fraction is delivered through a rotary valve 31 by a blower unit 32 along an output line 35. The oversize material is recovered and delivered along a recycling line 38 to the feed hopper 1. In some cases, the cellulosic material with the desired size distribution is delivered into a silo 40 and collected in a holding bin 41 available for packaging on demand. In another case, the cellulosic material is blended for improved consistency in a blender unit 45 fitted with a blending screw prior to delivery to a silo 40. In the method of the invention, cellulose-based excipients are produced by first setting, using the variable speed drive unit 21, an operating speed for the fan 20 matched to the cellulosic material being processed. A desired operating load on the grinder 10 is then set using the amp sensing unit 12 linked to the controller 13 for controlling the speed control unit 15 of the classifier 11. The fan 20 and blower unit 3 are operated to release the valve 2, allowing coarse cellulosic material to be delivered along the feed line 4 to the grinder 10. The coarse cellulosic material is ground in the grinder 10 and then classified in the classifier 11. The drive unit 15 of the classifier 11 is controlled in accordance with the operating load on the grinder 10. The fan 20 draws the ground and classified cellulosic material into the grinder receiving bin 23. On operation of the rotary valve 27, the cellulosic material is delivered to the separator unit 30 where the cellulosic material is separated into cellulosic material of a desired size and oversize material which is recycled to the feed hopper 1. The invention provides an optimised process for producing not only one but several different cellulose-based excipients, particularly pharmaceutical excipients. The particle size range of the cellulosic material is consistent and a wider range, particularly fine grades, of particle sizes may be produced. As any oversize material is recycled, the yield is optimised. The throughput of cellulosic material is maximised as the residence time in the grinder/classifier unit is optimised. The invention also provides a method of production of cellulosic material in which the energy requirement is optimised. The invention is not limited to the embodiments hereinbefore described which may be varied in detail.

Claims: £LΛ2M£ 1. A method for producing cellulose-based excipients comprising the steps of:- setting a desired operating load on a grinder; delivering coarse cellulosic material from a feed hopper to the grinder; grinding the coarse cellulosic material; classifying the ground cellulosic material in a grinder having a classifier drive unit; controlling the classifier drive unit in accordance with the operating load on the grinder; drawing the ground and classified cellulosic material into a grinder receiving bin; delivering the ground and classified cellulosic material to a separator; separating the classified cellulosic material into cellulosic material of a desired size and oversize material; delivering the cellulosic material of desired size into a holding bin; and packing the cellulosic material from the holding bin. 2. A method as claimed in claim 1 wherein the ground and classified material is drawn into the grinder receiving bin by a fan having a variable speed drive and the method includes the step, prior to delivery of the coarse cellulosic material to the grinder, of setting the speed of the fan drive to a desired speed matched to the coarse cellulosic material. 3. A method as claimed in claim 1 or 2 including the step of delivering the oversize cellulosic material from the separator to the feed hopper for recycling. 4. A method as claimed in any preceding claim wherein the operating load on the grinder drive is sensed by sensing the operating power of the grinder drive, the classifier drive unit is a variable speed drive and the classifier drive unit is controlled by varying the drive speed of the classifier in accordance with the operating power of the grinder drive. 5. A method as claimed in any preceding claim wherein a rotary air valve is provided at the feed hopper outlet and the coarse cellulosic material is delivered from the feed hopper to the grinder by a blower unit. 6. A method as claimed in any preceding claim including the step of de-bagging one or more coarse cellulosic materials into the feed hopper. 7. A method for producing cellulose-based excipients substantially as hereinbefore described with reference to the accompanying drawing. 8. Cellulose-based excipients whenever produced by a method as claimed in any preceding claim.

Inventors: MURPHY MICHAEL G, O'GRADY DECLAN M, MURPHY, MICHAEL, G., O'GRADY, DECLAN, M.
Applicants: GRADY DECLAN M O, MURPHY MICHAEL G, SHIELDAIG LIMITED, MURPHY, MICHAEL, G., O'GRADY, DECLAN, M.
Application year: 1997
Main classification: D21B1
IPC codes: D21B1