Patent GB-743230-A (GB)
Title: Improvements in a method of making a cuprammonium cellulose solution
Inventor: COURTNEY EDWARD JOSEPH
IPC: C08B1/00
Filed: 1953-07-27
Abstract: Cuprammonium cellulose solutions are prepared by mixing together cellulose, an alkali metal hydroxide, a copper compound, water and ammonia in a container, by rotating an agitator in the mixture at such a speed as to produce a zone of violent agitation within the body of the mixture while bringing all parts of the mixture rapidly and repeatedly into and out of the zone of violent agitation, whereby a substantially <PICT:0743230/IV(a)/1> fibre-free solution is formed. The agitator speed may be about 1200-3500 revolutions per minute and the period of agitation may be 2-20 minutes.  The copper compound may be cupric chloride, copper sulphate, boric copper sulphate or cupric hydrate.  The ammonia may be used in the form of an aqueous solution or may be anhydrous.  Hydrated copper sulphate, sodium hydroxide and aqueous ammonium hydroxide are the preferred components of the solvent mixture, about 0.6 part, of sodium hydroxide, 1.9-2.0 parts of hydrated copper sulphate, 1.3-1.5 parts of ammonia and about 15-19 parts of water being used per part of cellulose. Chemically equivalent proportions of other alkali metal hydroxides and other copper compounds may also be used.  In an example 30 grams of comminuted alpha-cellulose pulp is charged into a cylindrical vessel 10 of about 6 inches diameter and 7 inches depth and an agitator or beater 28 is rotated at about 2000 r.p.m. in order to shred and fluff the cellulose.  The vessel 10 is rotated in the contrary direction at about 24 r.p.m.  The beater comprises an uppermost propeller-shaped blade 30 so pitched as to force any liquid in the vessel 10 downwards and seven lower blades which are pitched to force the liquid upwardly.  The shaft 29 of the beater 28 is eccentrically mounted with respect to the axis of the vessel 10 so that the longer blades of the beater nearly touch the wall of the vessel on one side and the beater blades are of such length as to extend a little beyond the axis of rotation of the vessel.  The beater 28 is driven by belt 22 and motor 20.  The vessel 10 is rotated in the contrary direction by the belt 16 and motor 17.  The inner surface of the vessel is scraped by the flexible scraper blade 27 mounted on a fixed vertical spindle 26. The scraper blade 27 is located with respect to the beater 28 so that it is just beyond the beater 28 with respect to the direction of rotation of the vessel 10.  After the addition of the cellulose a solution of 65 grams of hydrated copper sulphate in 187 cc. of water is added to the vessel 10, followed immediately by a solution of 20 grams of sodium hydroxide dissolved in 187 cc. of water, which in turn is followed immediately by 250 cc. of 26 DEG  B<\>ae aqueous ammonia.  The rotation of the beater 28 and vessel 10 is continued for about 2 minutes after the addition of the ammonia, the total running time of the beater being about 3 minutes.  At the end of this period a solution free from cellulose fibres is obtained.  In another example a cellulose solution is similarly prepared in a larger apparatus, using 1.5 pounds of alpha-cellulose pulp and a total agitation time of about 4.5 minutes.  Other forms of beaters which may be used are described. The invention avoids the refrigeration and filtration hitherto commonly used in the preparation of cuprammonium cellulose solutions.