GB366963A - Improvements in the manufacture of solutions of fibroin - Google Patents

Abstract

Copper-ammonium solutions for dissolving fibroin contain more than 4 molecules of ammonia to 1 atom of copper. If copper salts are used for the preparation of the solutions, sufficient alkali must be used to convert all the copper into hydroxide, but excess of alkali should be avoided. In examples (1) a copper hydroxide paste is dissolved in 10 per cent ammonia, the solution being cooled to -- 5 DEG C.; (2) copper sulphate is dissolved in ammonia solution, and caustic soda solution is added, the solution being cooled to -- 15 DEG C. and filtered to remove sodium sulphate.ALSO:Fibroin is dissolved in a cuprammonia solution containing more than 4 molecules of ammonia to one atom of copper at a temperature below 0 DEG C., preferably 0 to --15 DEG C., and the solution is maintained at such temperature during any further steps in its preparation where practicable, and during its storage if any. A solution is thus obtained of high viscosity, suitable for the production of artificial silk. To prevent degradation of the fibroin it is advisable to treat the solution for the removal of some of the ammonia. This may be effected by suction or by passing through the solution a current of an inert gas, preferably until the solution contains not more than two molecules of ammonia to one atom of copper, in which operation it may be necessary to raise the temperature to 25 DEG C; or the fibroin complex may be precipitated from the solution by addition of salt solutions such as ammonium sulphate, sodium sulphate or sodium chloride, or organic liquids soluble in water such as methyl or ethyl alcohol or acetone, the precipitate being then redissolved in water. The quantity of copper hydroxide should be not more than 30 parts copper to 100 parts air-dry degummed fibroin. This avoidance of an excess of copper allows of filtering the solution through a cellulose filter such as wadding without causing the filter mass to swell. If copper salts are used for the preparation of the solution, there must be used sufficient alkali to convert all the copper into hydroxide, but excess of alkali should be avoided. In examples (1) a copper hydroxide paste is dissolved in 10 per cent ammonia, the solution being cooled to -5 DEG C.; degummed natural silk is added, and the whole is filtered and maintained at the same temperature; (2) copper sulphate is dissolved in ammonia solution, and caustic soda is added, the solution being cooled to -15 DEG C. and filtered to remove sodium sulphate; degummed "frison" is added and dissolved with stirring, and a current of nitrogen is introduced while heating to 15-20 DEG C.; the solution is filtered and led to the spinning machine; (3) the solution of "frison" made as described in the preceding example is treated with acetone instead of nitrogen; the precipitated mass is kneaded with acetone and then dissolved in water and filtered. Specification 366,987 is referred to.