Method of producing cellulose carbamate filaments or fibres

Abstract

According to an example aspect of the present invention, there is provided a method of producing cellulose carbamate filaments or fibres. The method comprising the steps of providing a cellulose carbamate dope, feeding the cellulose carbamate dope into a spinning unit exhibiting an aqueous spin bath containing sulphuric acid and a dissolved aluminium compound, coagulating the cellulose carbamate to form cellulose carbamate filaments and subjecting the cellulose carbamate filaments to stretching, optional cutting to form fibres, and optional washing. Further, the method comprises chemical recycling by withdrawing a portion of the spin bath to regeneration by removing at least a part of the sodium, water and zinc ions, and recycling at least part of the regenerated aqueous spin bath to the spinning unit, wherein the withdrawn aqueous spin bath preferably contains, at a temperature of at least 10 ℃, before regeneration dissolved ammonium nitrogen in the form of ammonium sulphate in an amount of less than 20 g / l of the spin bath.