Patent GB-442635-A (GB)
Title: Process for the manufacture of cellulose derivatives
IPC: C08B3/28
Filed: 1935-04-03
Abstract: <PICT:0442635/IV/1> In the manufacture of cellulose derivatives and particularly organic derivatives a solution of the cellulose derivative, for example the esterification solution is atomized by means of a stream of gas or vapour and the atomized solution is subjected to the action of a liquid precipitant for the cellulose derivative. The product is then obtained in the form of puffed and enlarged porous particles.  The precipitating bath is preferably compatible with the atomizing gas and may be water for example if the solution is atomized with steam.  Examples of suitable solvents for the solution are chloroform, acetic acid, acetone with or without alcohol, or ethylene dichloride, with or without alcohol.  Suitable atomizing vapours or gases are steam, especially dry steam, compressed air, carbon dioxide or nitrogen. Vapours of benzene or kerosene may be employed the precipitating liquid being such that it will dissolve them and being cooled.  A cellulose derivative solution is fed, e.g. direct from a ripening plant to a receptacle 11 by a conduit 12 and valve 13.  Pressure supplied through a pipe 14 forces the solution out at 15 via a suitable flow control valve 16 to an ejector nozzle 21.  A steam line 17 connects with a pipe 19 having a steam ejector orifice 22 which directs the steam across the gap in the mixing chamber 23 and out through the discharge orifice 24 to pipe 25 which conveys the atomized solution to a receiver 26 containing a liquid precipitant for the cellulose derivative.  The receiver has a drain 27 connected with a point above the point of entry 28 of the pipe 25 and provided with a cylindrical gauge filter 29.  A pipe 31 with valve 32 can supply fresh precipitating liquid either continually or intermittently.  The pipe 19 has an extension 35 with valve 36 for cleaning purposes.  The ejector nozzle should be warned to a temperature approximately that of the steam before starting.  The size of the particles of the atomized solution may be varied by controlling the pressure of the steam and the rate of flow of the solution.  The precipitated material removed from the receiver 26 may be washed, steamed or chemically stabilized and redissolved to form working solutions.  All parts of the apparatus which contact with the cellulose derivative may be of stainless steel or chromium plated or coated with a protective insoluble coating material.  In an example cellulose is reacted with acetic anhydride in the presence of sulphuric acid as catalyst and acetic acid as solvent diluent.  Water is added to the solution and the cellulose acetate ripened until soluble in acetone.  The resulting solution comprises 500 parts by weight of cellulose acetate and 1600 parts of acetic acid of about 93 per cent strength.  Aqueous sodium carbonate or acetate is thoroughly mixed into the solution to "kill" the catalyst.  The solution is allowed to flow from the receptacle 11 to the ejector nozzle under a gauge pressure of 10 lbs. per sq. inch. at a rate between 10 and 70 gallons per hour.  Dry steam is supplied for atomization at a pressure of 125 lbs. per sq. inch.  The precipitating bath is water at 30 DEG  C.