Polynosefasern und Verfahren zu ihrer Herstellung

摘要

1,167,555. Polynosic fibres. MITSUBISHI RAYON CO. Ltd. 19 Sept., 1967 [22 Sept., 1966; 12 Oct., 1966], No. 42530/67. Heading B5B. Improved polynosic fibres are prepared by extruding viscose having aγ-value of at least 50 into a coagulation bath containing formaldehyde, stretching the resulting filaments in a second bath, treating the stretched filaments in a third aqueous bath containing a salt selected from, an alkali metal salt of a mineral acid, an alkaline earth metal salt of a mineral acid, an ammonium salt of a mineral acid, or their mixture, the pH of the third bath being kept between 2 and 10À5, and its temperature between 30‹ and 90‹ C., and then subjecting the treated fibres to regeneration. The third bath may also contain up to 0À5 g./l. of a zinc salt of a mineral acid or a cadmium salt of a mineral acid and up to 1 g./l. of sulphuric acid. The second bath is desirably a low concentration sulphuric acid bath. In one embodiment viscose having a total alkali concentration of 2 to 8% and a salt point of at least 16 is extruded into a co-agulating bath containing 4 to 15 g./l. of formaldehyde, 20 to 250 g./l. of sodium sulphate, and sulphuric acid at a concentration defined by the equations: Minimum concentration of sulphuric acid (g./l.)=3A+8. Maximum concentration of sulphuric acid (g./l.)=8A+16. A being the alkali concentration (%) in the viscose, the filaments then being withdrawn from the coagulation bath and stretched under a tension of up to 0À3 g./d. in a second bath kept at 45‹ to 75‹ C., and are then treated with an aqueous solution of a salt as above, the treating temperature being in the range 30‹ to 70‹ C. In another embodiment viscose is extruded into a coagulation bath containing 1 to 15 g./l. of formaldehyde, the filaments withdrawn from the coagulation bath then being highly stretched in a second bath under a tension of at least 0À3 g./d., the temperature of the second bath being at least 60‹ C., and the stretched filaments then being treated in the relaxed state with an aqueous solution of the aforesaid salt, the treating temperature being within the range 40‹ to 90‹ C. If relatively strong swelling conditions are adopted in the above salt treatment the cross-section of the resulting fibres can be varied, and even hollow filaments can be obtained.