GB260650A - Manufacture of cellulose formate and of materials therefrom - Google Patents

Abstract

260,650. Fabriek van Chemische Producten, and Ter Horst, A. June 30, 1925. Cellulose formates and processes for making filaments therefrom.-Derivatives of cellulose and formic acid are made by treating cellulose, hydrocellulose, regenerated or mercerized cellulose, a pattly esterified cellulose formate, acetate or nitrate, &c. with formic acid of high percentage strength and a catalyst at a temperature, not higher than 50‹ C., and preferably at 0‹ C. or lower. Suitable catalysts are vater-binding substances such as phosphorus chlorides and oxychloride, sulphuryl chloride, chlorsulphonic acid. hydrochloric and sulphuric acids, chlorides of zinc, aluminium and antimony, and mixtures of hydrochloric acid with the chlorides of zinc, calcium, magnesium, aluminium, and antimony. Mixed esters can be prepared by dissolving another cellulose ester, such as an acetate, in the solution of cellulose formate prepared as above. or the cellulose formate may be treated with acetic anhydride or acetyl chloride and a catalyst. Alternatively, a nitrated cellulose of very low nitrogen content may be treated by the formylating process above described. The derivatives obtained may be employed in the manufacture of artificial silk, artificial straw, ribbons, &c. The formate may be first isolated, preferably after the catalyst has been rendered inactive, and then redissolved, or the primary solutions may be spun directly; the solution may be either coagulated in a suitable coagulating bath, or the formic acid may be evaporated. The primary solutions are stabilized by rendering the catalyst inactive, for example, by neutralization with a base or a salt of a weak acid, such as a formate, or, in the case of hydrochloric acid, by evaporation. When a base or salt is employed for neutralisation, there remain in many cases finelydivided salts suspended in the solution; these have a beneficial effect, especially when spinning the finer grades of silk, and it is therefore of advantage to employ an excess of the salt. As the coagulating bath when spinning artificial silk &c., there may be used an organic liquid, such as alcohol, ether, or acetone, and in general liquids which dissolve formic acid but do not dissolve cellulose formate; or water or an aqueous salt solution, particularly a solution of a formate, the bath being maintained neutral or of the desired acidity by the addition of soda or lime. The freshly-spun silk may be collected on bobbins or in centrifugal boxes, and may be treated in a similar manner to viscose silk. The percentage of formic acid in the finished silk may be modified by saponification with an alkali or alkaline salt; in this way silks showing different permeabilities as regards water and different behaviour in dye baths, may be obtained. Specification 2511/07, [Class 2, Acids and salts, Organic &c.], is referred to. In one of the Provisional Specifications it is stated that the silk may be saponified by treatment according to the processes of Specifications 20672/10, 125,153, 150,989, [Class 15 (ii), Dyeing, Processes &c. for], 169,741, 175,485, 175,486, and 176,034, or according to a process in which the silk is first treated with a bath of stannous chloride or other stannous salt, then washed, and then introduced into a bath of a salt having an alkaline reaction, such as a phosphate barate, carbonate, or silicate. It is stated also that the cellulose may be dyed before or during formylation, and further that salts such as calcium sulphocyanide may be added to the solution to be spun. Finally, it is stated that the finished silk mav be swollen bv treatment with solutions of formic or acetic acids or of stannous, chloride, zinc chloride, magnesium chloride, ammonium chloride, and other water-soluble chlorides, sulpho-cyanides, resin or soap, or by treatment with alcohol or glycerol.