Patent GB-308348-A (GB)
Title: Improvements in the preparation of cellulose esters and ethers
IPC: C08B1/00
Filed: 1929-03-12
Abstract: 308,348. British Celanese, Ltd., (Assignees of Miles, G. W.). March 22, 1928, [Convention date]. Preparatory treatment of cellulose.-Cellulose esters or ethers, for example cellulose nitrate, formate, acetate, propionate, or butyrate or ethyl, methyl, or benzyl celluloses, are prepared by a process in which cellulosic materials, such as cotton or wood pulp, are subjected to a treatment with hydrofluoric acid and with an aliphatic acid and are then converted into the required cellulose derivative in absence of hydrofluoric acid. The hydrofluoric acid may be applied in a suitable solvent but must be removed, for example by neutralizing or washing, before the materials are converted into the cellulose derivatives. The pre-treatment with aliphatic acids, for example formic, acetic, propionic, or other aliphatic acid, mav be applied by any suitable method, for example the materials may be treated with dilute or concentrated acids, for instance by passing hot liquid acid repeatedly through the materials, or alternatively the vapours of the acids may be applied as described in Specification 263,938 and may be permitted to condense within the cellulosic materials. The treatment may be employed in conjunction with any other form of pre-treatment of cellulosic materials tending to render them more reactive towards or more suitable for esterification or etherification. Any sand or other silicious material is removed or partly removed by the treatment with hydrofluoric acid, whilst the aliphatic acid treatment tends to remove oils, wax. and the like. Other impurities may be removed by suitable processes thus, lignin, wax, oil, or resin may he further removed by boiling with alkali; compounds of iron by warming or otherwise treating with dilute sulphuric, hydrochloric, or other mineral acid and colouring matters by a suitable bleaching treatment, for instance by means of chlorine or bleaching powder. Alternatively, oils, waxes, and similar substances may further be extracted by means of solvents, such as carbon tetrachloride and naphtha. The esterification or etherification may be carried out by any desired method. In an example, cotton linters are moistened with a dilute solution of hydrofluoric acid and are allowed to remain in contact therewith for a time, which varies with the temperature of the treatment and the concentration of the acid, until the sand or other silicious material is dissolved. 7 to 10 days may be required at room temperature. The material is then washed with water and may subsequently be boiled with alkali, subjected to a chlorine or other bleaching treatment followed ;by washing with water to remove the bleaching agent and finally after pressing or drying, treated with hot aliphatic acids. If only excess water has been removed, glacial acetic acid or even acetic anhydride, to form acetic acid with the remaining water, may be employed, while if the materials have been dried, a more or less aqueous acetic acid may be used. The acetic acid may be employed in the form of vapour or the liquid may be passed repeatedly through the material, preferably so that fresh acid comes into contact with the already treated linters and fresh untreated linters with already used acid. The linters containing the acetic acid from the above treatment may, for example, be acetylated by the addition of the appropriate amounts of acetic acid, acetic anhydride and sulphuric acid or other catalyst. Cellulose derivatives prepared from cellulosic materials treated in accordance with the present, process may be used for the manufacture of lacquers, dopes, films, artificial silks, plastic masses. &c. The Specification as open to inspection under Sect. 91 (3) (a) refers broadly to the treatment of cellulosic materials with hydrofluoric acid and to the esterification or etherification of the pretreated materials by any process. This subjectmatter does not appear in the Specification as accepted.