GB200834A - Improvements in and relating to a process of preparing cellulose derivatives - Google Patents

Abstract

Cellulose ethers of a high degree of etherification are obtained by a multistage process with small amounts of alkalies and alkylating agents by the further alkylation or aralkylation of alkyl or aralkyl derivatives of cellulose prepared by treating cellulose or a conversion product or derivative thereof with alkylating or aralkylating agent in the presence of less than 2 mols (preferably less than 1.5 mols) of caustic alkali to 1 mol of C6H10O5, the water content being less than 0.5 part to 1 part of air-dried raw material, or the material being substantially free from water. When the quantity of water is not too small the product is at least partly soluble in aqueous alkalies, while if the water content is very small they are at least partly soluble in cold water and may be soluble in glacial or strong acetic acid, and also in hydrochloric acid. The product of the first stage of etherification is treated as it is for the next stage, or may be first isolated from the reaction mixture. By suitably choosing the conditions of the further etherification, products may be obtained which are soluble in or swell in very cold water which are advantageous when the product (say threads) is required to absorb water-soluble substance such as dyes. For this purpose the conditions are large quantity of water, small quantity of alkali and low reaction temperature. Or hard brittle ethers suitable for instance for lacquers and varnishes, may be obtained by using small quantities of water, large quantities of alkali and higher temperatures. Examples describe the production of the alkali cellulose containing the requisite proportions of alkali and water for the initial material the cellulose being mixed in a disintegrator edge runner machine &c. with the alkali solution or with solid and dissolved alkali or with solid alkali with or without water and excess being removed by for instance hydraulic presses, or the excess water may be removed to the necessary degree by drying. The alkyl or aralkyl esters of inorganic acids are preferably used for the etherification, such as ethyl or methyl chloride, ethyl bromide, dialkyl sulphates, benzyl chloride and ethyl iodide those agents with low boiling points requiring autoclaves while the others may be used in open vessels with or without reflux condensers. Examples describe the use of ethyl chloride. If it is desired to separate the product of the first etherification, the reaction mixture may be washed with hot water and dried, the ether being almost insoluble in hot water. Those of the intermediates (first products of etherification) which dissolve in alkalies may be converted into films or threads by treatment of the solution with acids or other precipitants known in the viscose art. The intermediates may be treated for further etherification in one or more stages so as to produce ethers of different degrees of etherification by using different quantities of alkalies and etherifying agents; products which dissolve or swell in cold water are obtained by using smaller quantities of these agents and products insoluble in and unaffected by water by using larger quantities. The ethers produced when ethyl chloride is used for the final etherification, are soluble in volatile solvents such as alcohol, benzol, alcohol-benzol mixtures, glacial acetic acid, chloroform, chloroform-alcohol mixture, and methyl-acetate-methyl-alcohol mixture and yield flexible films. The ether produced, in an example in which the final etherification is effected with di-ethyl sulphate is soluble in volatile solvents such as glacial acetic acid, benzol-alcohol mixture, chloroform-methyl-alcohol mixture, methyl-acetate-methyl-alcohol mixture. Specifications 177,089, 177,810, 200,816, 203,346, and 203,347 are referred to. The Specification, as open to inspection under Sect. 91 (3) (a) includes also the preparation of the intermediate products by treating a cellulose having a low water content or substantially free from water and a low alkali content with an etherifying-agent. This subject-mater does not appear in the Specification as accepted.