Patent GB-516672-A (GB)
Title: Improvements in or relating to the production of cellulose derivatives
IPC: C08B15/06
Filed: 1938-07-01
Abstract: 516,672. Cellulose derivatives and their applications. DU PONT DE NEMOURS & CO., E. I. July 1, 1938, No. 19611. Convention date, Aug. 30, 1937. [Class 2 (ii)] Nitrogen-containing cellulose derivatives are obtained by bringing cellulose and urea or a urea derivative into intimate admixture in an aqueous medium either free from metallic compounds, and if desired in presence of organic bases, or in presence of a basic alkali metal or alkaline earth metal compound, and subjecting the-mixture to a raised temperature and for a period of time such that the cellulose derivative produced is soluble in dilute aqueous caustic soda and contains combined nitrogen to an extent less than 5, preferably from 1-2.5 per cent. by weight. The cellulose may be impregnated with the urea in solution or suspension in a liquid, excess of urea and liquid being then removed. The cellulose is. then subjected to heating. Instead of urea, there may be used a urea derivative in which one or both hydrogen atoms of one of the amino groups is replaced by a monovalent hydrocarbon radicle containing less than 5 carbon atoms, or a monovalent organic radicle containing less than 5 atoms and consisting of carbon, hydrogen, and oxygen only, or a derivative in which the oxygen of the CO group is replaced by sulphur. Methyl urea,' n-propyl urea, unsymmetrical diethyl urea, and thiourea may be used. Wood pulp or cotton linters may be steeped in a solution containing urea, caustic soda, and a wetting agent. The material is pressed, dried, and then baked at a temperature of 120-300‹C., or drying and baking may be carried out simultaneously. The products may be dissolved in dilute caustic soda by stirring and cooling. For obtaining products of reduced viscosity the reaction may be conducted in the presence of hydrogen peroxide or ferric chloride, or the products may be digested with hydrogen peroxide, oxalic acid or sodium hypochlorite. When using ferric chloride, precipitation of hydroxide is prevented by adding potassium tartrate. The solutions of the products in. dilute aqueous caustic soda solutions may be rendered more stable by incorporating small proportions of zinc oxide or beryllium oxide in the caustic soda solutions before dissolving the urea-cellulose. The process may be carried out continuously or as a batch process. Cellulose of all kinds including natural or artificial fibres, yarns, fabrics, or films, may be subjected to the treatment. Instead of caustic soda there may be used sodium carbonate, acetate, sulphide, borate, or phosphate, calcium hydroxide, or quinoline. Mixtures of alcohol with water may be used in the steeping baths. Cellulose may be used in sheet form or in the form of a suspension. The solutions of the urea-celluloses in alkalies may be coagulated by acids. They may be used for the production of filaments, films, bottlecaps, sponges, coating or sizing compositions for textiles, wood, stone, or metals. The products may be used in admixture with other cellulose derivatives, resins, oils, waxes, or pigments. The products may be used as raw materials for the production of cellulose esters or ethers. Specification 486,527 is referred to. The'Specification as open to inspection under Sect. 91 describes also the treatment of cellulosic material with urea alone or in an organic solvent, such as pyridine, or in presence of alkali and in. an alcoholic medium such as methyl or isobutyl alcohol. This subjectmatter does not appear in the-Specification as accepted.