Patent GB-1096509-A (GB)
Title: Polynosic fibers and a process for producing the same
IPC: D01F2/06
Filed: 1966-07-21
Abstract: 1,096,509. Polynosic viscose fibres. MITSUBISHI RAYON CO. Ltd. July 21, 1966 [Aug. 3, 1965; Aug. 23, 1965; Nov. 5, 1965], No. 32786/66. Heading B5B. A process for producing polynosic fibres is characterized by extruding a viscose having a gamma value of above 55 into a coagulating bath containing from 8 to 25 g./l. of sulphuric acid, from 0À05 to 1À5 g./l. of anhydrous zinc sulphate and from 10 to 150 g./l. of anhydrous sodium sulphate and kept at a temperature of below 35‹ C., withdrawing the filaments thus formed from the coagulating bath in a state where the gamma value of the filaments is above 40, introducing the resulting filaments into a second bath containing sulphuric acid, zinc sulphate and sodium sulphate, the concentration of said sulphuric acid being less than 3 g./l. that of anhydrous zinc sulphate being from 0À05 to 3 g./l. and the sum of the concentrations of the zinc sulphate and the sodium sulphate, expressed as the anhydrous salts, being from 0À5 to 60 g./l., in a state where the gamma value of the filaments is above 30, and then introducing the filaments withdrawn from the second bath into a third bath to complete regeneration. Preferably, the viscosity of the viscose on spinning is from 100 to 1000 poises at 20‹ C., more preferably from 200 to 600 poises. The concentration of cellulose in the viscose is suitably from 4 to 8%, the alkali concentration in the viscose preferably from 2 to 5%, and the gamma value of the viscose above 55, desirably above 65. The viscose may contain a surface-active agent soluble in viscose but insoluble in the coagulating bath. General formulae of suitable surface-active agents are given. Filaments may be withdrawn from the coagulation bath and stretched in air and the resulting stretched filaments in a state where their gamma value is over 30 may be introduced into the second bath in which the concentration of sulphuric acid is less than 2 g./l. that of anhydrous zinc sulphate is from 0À2 to 3 g./l. and the sum of the concentrations of the zinc sulphate and the sodium sulphate expressed as the anhydrous salts from 5 to 60 g./l. The temperature of the second bath is normally above 50‹ C., preferably above 80‹ C., and especially when formaldehyde is contained in the coagulating bath. Alternatively, filaments withdrawn from the coagulating bath may be introduced, in a state where the gamma value of the filaments is above 40, into the second bath in which the concentration of sulphuric acid is less than 3 g./l. that of anhydrous zinc sulphate is from 0.05 to 3 g./l. and the sum of the concentrations of the zinc sulphate and the sodium sulphate expressed as the anhydrous salts is from 0À5 to 50 g./l. and stretched in the second bath. In such a process, filaments withdrawn from the coagulation bath may be introduced, in a state where the gamma value of the filaments is above 45, into the second bath in which the concentration of sulphuric acid is less than 2 g./l. that of anhydrous zinc sulphate is from 0À1 to 0À6 g./l. and the sum of the concentrations of the zinc sulphate and the sodium sulphate expressed as the anhydrous salts is from 1 to 30 g./l., the second bath being at a temperature above 60‹ C. Alternatively, where formaldehyde is added to the coagulating bath, viscose may be extruded into a coagulating bath containing from 10 to 25 g./l. of sulphuric acid, from 0À05 to 0À9 g./l. of anhydrous zinc sulphate, from 10 to 150 g./l. of anhydrous sodium sulphate and from 1 to 6 g./l. of formaldehyde. Filaments withdrawn from the coagulating bath may be treated with a diluted aqueous solution of a heavy metal salt and then introduced into the second bath. Specified heavy metal salts include cadmium sulphate and nickel sulphate, suitably present in concentrations of from 0À2 to 1 g./l., expressed as the anhydrous salt. The filaments withdrawn from the second bath, if necessary after cutting, are introduced into the third or regeneration bath, in which they are completely regenerated. As the third bath, an aqueous bath containing from 2 to 15 g./l. of sulphuric acid and kept at a temperature above 80‹ C. is preferably employed. Polynosic fibres so made have a wet tenacy of 3À4 to 5À0 g./d., wet modulus of 1À0 to 2À0 g./d. at 5% elongation, loop tenacity of 2À0 to 4À0 g./d., fibrillation degree of below 20 and solubility of below 70% in 2N sodium hydroxide solution at 20‹ C. after ethanolysis. Such fibres may be made when formaldehyde is not added to the coagulation bath. When aldehyde is added to the coagulation bath, it is possible to produce polynosic fibres having a wet tenacity of 4À5 to 6À0 g./d., a dry knot tenacity of 2À0 to 3À8 g./d., a wet modulous of 2À0 to 4À0 g./d. at 5% elongation, a fibrillation degree of below 50, a solubility of below 65% in 2N sodium hydroxide solution at 20‹ C. after ethanolysis and a dye absorption of above 45%.