Patent GB-531283-A (GB)
Title: Improvements in the oxidation of cellulose
IPC: C08B15/04
Filed: 1939-07-17
Abstract: 531,283. Photographic stripping and backing layers. KODAK, Ltd. July 17, 1939, No. 20683. Convention date, July 15, 1938. [Class 98 (ii)] [Also in Group IV] Cellulose material is submitted to an oxidation treatment at a temperature not exceeding about 20‹C. with at least 0.6 parts of gaseous nitrogen dioxide to 1 part of cellulose until the cellulose becomes substantially completely soluble in alkali. The nitrogen dioxide may be passed through the cellulose in a continuous stream. The treatment results in the production of a cellulose compound in which carboxyl groups are attached to the terminal carbon atoms of the glucose units of the cellulose molecules. The compound may be treated with alkalies to form alkali-metal salts. The compound may be regarded as a polyanhydro glucuronic acid. Products may be obtained which have a CO<SP>2</SP> equivalency of at least 13 per cent. may be obtained. The product may be used for making transparent films or sheets by dissolving it in an aqueous solution of a base such as an alkali metal hydrate, ammonia, pyridine, or triethanolamine, spreading the solution and drying. The water-soluble film thus produced may be rendered insoluble by treating it with dilute acid and drying. Glycerine may be incorporated in the film-forming solution to impart flexibility to the film. Salts of the oxidized cellulose may be prepared by acting thereon with a base or salt of a weak acid. The salt may be separated from solution by pouring the solution into alcohol, acetone, or like water-miscible non- solvent. The salts may be used as interlayers in photographic stripping film or as backings for photographic films. The oxidized cellulose is one in which the cellulose molecule is undegraded. As produced it retains the original fibrous structure of the cellulose. In the production of the oxidized cellulose the time of treatment with nitrogen dioxide may be 50 hours or more, or it may be 7 hours or less. As shown in Fig. 1, cotton is placed in flask E which may be agitated by hand or mechanically. The flask may be provided with cooling means to prevent the temperature from rising above 20‹C. The cooling device may be a moist cloth upon which water constantly drops. Liquid NO<SP>2</SP> is placed in flask F with P<SP>2</SP> O<SP>5</SP> to absorb moisture. Flask F is gently warmed and gaseous NO<SP>2</SP> passes into flask E. Water and a lower oxide of nitrogen formed during the reaction leave the flask by tube B. Air is mixed with this gas at C so as to re-convert it to NO<SP>2</SP> which then passes to flask F. If desired, the process may be carried out at elevated pressure. The autoclave used may be evacuated and either gaseous NO<SP>2</SP> may be forced therein or the NO <SP>2</SP> may be present in liquid form apart from the cellulose and may be vaporized by heating. As shown in Fig. 2, the cellulose is placed in flask G. The apparatus is evacuated by connecting tube M to a water-pump or other device. Liquid NO<SP>2</SP> is placed in funnel K and allowed to fall into tube J and then it is vaporized into the flask. Instead of cotton cellulose, refined bagasse, refined wood-pulp, or regenerated cellulose may be subjected to the treatment.