GB1002403A - Improvements in the manufacture of regenerated cellulose filaments - Google Patents

Abstract

1,002,403. Viscose spinning. CHIMIOTEX S.A. July 22, 1963 [July 20, 1963]; No. 28981/63. Addition to 910,878. Heading B5B. The process of the parent Specification (wherein filaments of regenerated cellulose are produced by spinning a viscose having a viscosity of at least 150 poises at 15‹ C. and a gamma value of at least 45 and containing a cellulose having a degree of polymerization of at least 400 into an aqueous coagulating bath containing not more than 40 g./1. of. sulphuric acid and substantially free from zinc sulphate, in the presence of formaldehyde) is modified in that the coagulating bath contains 10 to 120 g./1. of sodium sulphate and not more than 1 % by weight of zinc sulphate (calculated as the anhydrous salt) and in that neither the viscose nor the spinning bath contain formaldehyde. Also in that the coagulated viscose filaments formed in the spinning bath are subsequently passed through an aqueous intermediate bath containing a small proportion of a water-soluble aldehyde, and then through a regeneration bath consisting of a hot dilute aqueous solution of sulphuric acid. The proportion of spinning bath liquid carried by the filaments of coagulated viscose from the spinning bath is preferably reduced by hydroextraction, mangling or perforated rollers whose hollow interiors are maintained at subatmospheric pressure. The fall in the gamma value of the filaments during their passage from the spinning bath to the intermediate bath is thereby reduced and the proportion of adelhyde taken up by the filaments in the intermediate bath increased. The viscose used preferably contains at least 3% of cellulose and at least 1À5% of caustic soda and preferably has a gamma value of 55 to 90. The D.P. of the cellulose in the viscose is preferably higher than 500 and its viscosity at the moment of spinning higher than 400 poises at 15‹ C. The spinning bath preferably contains 8 to 40 g./1. of sulphuric acid. The temperature of the first bath is preferably between 5‹ and 40‹ C., especially between 8‹ and 30‹ C. The intermediate bath may be a cold dilute acid bath containing from 1 to 40 grams of a water-soluble aldehyde per litre. The concentration of sulphuric acid and sodium sulphate in the intermediate bath may be similar to that in the coagulating bath. The filaments may be drawn at a draw ratio of at least 2:1 and preferably at least 3:1 in the coagulating bath and/or in the regenerating bath and/or during their passage through the air between these two baths. Specifications 685,631, 711,642 and 720,173 also are referred to.