GB217168A - Process for the production of cellulose conversion products - Google Patents

Abstract

Cellulose conversion products in the form of solutions, pastes or doughs are obtained by treating cellulosic bodies with strong sulphuric acid at a temperature not below \sw9 DEG C. and not above 4 DEG C., preferably between \sw5 DEG C. and 5 DEG C., for example, between \sw2 DEG C. and 9 DEG C.; the proportions of acid particularly suitable are not more than 6 parts and not less than 1.5 parts of sulpuric acid monohydrate, for example, not more than 4 parts and not less than 2 parts, for each part of air-dried cellulosic material. To separate the products, the solution, dough or paste is mixed with a precipitating-agent such as snow, ground ice, ice-water, dilute acid preferably intensely cooled, a cooled salt solution, a solution of acetic acid or benzenesulphonic acid or phenolsulphonic acid or other organic acid, or a solution of an alcohol; the product is washed and if desired, dried, and is brought into a form for technical use by solution in caustic alkali, such solution being conducted according to the character of the initial cellulose material and the conditions of the preceding treatment, either at room temperatures or at lower temperatures, for example, at \sw5 DEG C. to \sw12 DEG C., such lower temperatures being useful in effecting solution in cases where the action of the sulphuric acid has not proceeded to a great extent. The solutions in caustic alkali may be used in the manufacture of artificial silk, &c., artificial hair, films, plastic masses, coatings, finishings, sizes, artificial leather, &c. As the initial material there may be used, bleached or unbleached cellulose of any kind, products obtained by the mechanical comminution of cellulose in the presence of water, products obtained by treating cellulose with reducing or oxidizing agents, products obtained by heating cellulose alone or with water, glycerine, or salts; products resulting from the treatment of cellulose with hot or cold alkalies with or without subsequent treatment with dilute acids and with or without previous or subsequent treatment with oxidizing or reducing agents; the cellulose hydrates obtained by precipitating solutions of cellulose in cuprammonia or zinc chloride solutions; artificial silk, &c., hydrocellulose, oxycelluloses, and the products obtained by treating cellulose with strong acids, cuprammonia or zinc chloride solutions, to a point short of dissolution. In examples, sulphuric acid of 60 DEG B<\>ae is employed, and the acid is precooled before the addition of the cellulose to a temperature lower than that at which the reaction is conducted; the cellulose may be dried and cooled before addition to the acid. Specification 212,864 is referred to. The Specification as open to inspection under Sect. 91 (3) (a) includes the employment of temperatures up to but not above 6 DEG C. This subject-matter does not appear in the Specification as accepted.