INDUSTRIAL A N D ENGINEERING CHEiMISTRY
822
A great many modifications of the methods described in general in the literature have been tried by the author of this paper, in the effort to discover the best conditions under which viscose could be produced from linters. It is generally recognized by workers in this field that viscose made from wood pulp is more readily dissolved in water than that made from very pure forms of cellulose, such as cotton. It is also generally known that viscose made from wood pulp produces films, or threads, which are not as strong as those produced from the purer forms of cellulose.
ACID CONCENTRATION
IN PRELIMINARY TREATMENT
FIG.%-COMPARATIVE
VISCOSITY OF S O L U T I O N S OF VISCOSE M A D E FROM C O T T O N L I N T E R S TREATED WITH NITRIC ACID
Experiments were conducted in which the conditions of formation of the alkali were tried, and both temperature and time of exposure were varied. The conditions under which the alkali cellulose was ripened were varied and the effects noted. In many of these preparations the alkali reaction was not complete and the resulting xanthogeiiate would not dissolve in water. In others the alkali reaction had gone too far and, while complete solubility of the ester often resulted, the viscosity of the solution was very low. A method suggested by &fits~herling~~ for the production of viscose from cotton was tried out with linters. This method was briefly as follows: One hundred grams of linters were treated with 750 grams of 20 per cent sodium hydroxide for 20 minutes a t 25" C. Alkali was pressed out under pressure and the pressed alkali cellulose weighed 360 grams. This was exposed to air for 44 hours at 25" C. It was then placed in a bottle, 50 grams of carbon disulfide added, and the bottle sealed. The mixture was allowed to stand a t 25" C. for 18 hours.l4 Fifty grams of sodium hydroxide were dissolved in a liter of water and this solution was added to the xanthogenate. The whole was made up to 2000 grams. The solution was practically complete, but the product was thin and watery, and very unsatisfactory for most applications. This very low viscosity of the product just described reminded the author of a series of viscose preparations 1s Paper presented before the Section of Cellulose Chemistry a t the 62nd Meeting of the American Chemical Society, New York, N. Y.. September 6 t o 10, 1921. 1 4 Mitscherling proposed the use a t this point of sodium hydroxide equal t o the weight of the original cellulose.
Vol. 15, No. 8
whiah he had made earlier from partially hydrolyzed linters. These preparatibns were likewise low in viscosity. In a series of experiments in which the method suggested by Mitscherling's paper was modified, it was found that by shortening the time of exposure of the alkali cellulose to air (ripening) the viscosity of the product became much greater. When the time was shortened to 5 hours, a product of high viscosity and other fine qualities was produced. Reference was made earlier in this discussion to the effect on viscose of preliminary treatment of the cellulose. Herein apparently lies the reason for the difference in properties of wood-pulp viscose and cotton viscose. The treatment through which wood pulp goes in order to free the cellulose from lignin, etc., is more drastic than that through which cotton is put. The effect is noticed in the more rapid solution of viscose made from wood pulp than that made from cotton, and at the same time the production of weaker threads or films by the former when compared with those from the latter. This was borne out by a series of experiments performed by the author. Samples of linters were treated for varying lengths of time with hydrochlnric acid and afterwards washed until neutral. Viscose was made from these acid-treated linters, and in every case very thin watery products were formed. The cellulose was rendered much more reactive by the acid treafment, but the products made from the viscose possessed very little strength. The final piece of work in connection with this research consisted in the preparation of viscose from samples of linters which had been treated with increasing concentrations of nitric acid. Thirty-gram samples of linters were treated with nitric acid solutions ranging from 10 to 70 per cent, for 18 hours a t 25' C. After washing thoroughly, until free from acid, these samples were dried at room temperature. Each sample was converted into viscose, using identical conditions for all. A blank (untreated fibers) was run for a comparative test. The blank test gave viscose which possessed the highest viscosity of all the samples, and in the acid-treated samples the viscosity fell with great rapidity. A Stormer viscometer was used to gain some idea of the comparative viscosities. The results of these tests were as follows: Per cent Acid Used for Preliminary Treatment 0 10 20
30
40 50 60
70 Water
Number of Seconds for 100 Revolutions 3300 1500 900 420
178 50 27
7 6
The greatest diminution of viscosity occurred when the Iowest concentration of acid was used. This is readily seen when the figures are plotted, as in Fig. 3.
ACKNOWLEDOME NT The author wishes to express his appreciation to W. A. Hamor, of Mellon Institute, and to Alexander Lowy, of the University of Pittsburgh, for many helpful suggestions during the course of this research. Zanetti Appointed on Committee of League of Nations J. Enrique Zanetti has been appointed t o a committee of the League of Nations which will investigate the whole question of chemical warfare. Associated with Dr. Zanetti, who is now in England on leave of absence from Columbia during the next academic year, will be a group of chemists representing other countries, among whom will be Sir William Jackson Pope, of Cambridge University, England, and Charles Moureu, of the University of Paris.
