Method and device for the production of cellulose fibers and cellulose filament yarns

#1. Field of Technology

#The main application relates to a method for the production of cellulose fibers or -filaments from cellulose according to the dry-wet-extrusion process with aqueous amine oxides, especially N-methyl-morpholine-N-oxide as solvent, where a) cellulose or a cellulose mixture is dispersed with a Cuoxam-DP in the range of 250 to 3,000 in aqueous amine oxide, b) the dispersion obtained in this manner is transferred at an increased temperature under dehydration and shearing into a homogenous solution with a zero shear viscosity in a range of 600 to 6,000 PAs and a relaxation time in a range of 0.3 to 50 s at 85° C. respectively; c) the solution is supplied to at least one spinning nozzle and first guided through an impaction chamber shared by one nozzle or a plurality of nozzles where its dwelling time is at least equal to its relaxation time at the spinning temperature, d) the solution is formed in each spinning nozzle into at least one capillary and the capillary (or capillaries) of each nozzle are guided under drawing through a non-precipitative medium and then through a spinning bath under precipitation of the cellulose threads, and e) the cellulose threads are separated at the end of the spinning bath drawing frame by diversion from the spinning bath flows and the threads are pulled off. The main application furthermore relates to a device for the production of cellulose fibers or -filaments from cellulose according to the dry-wet-extrusion process with aqueous amine oxides as solvents with a spinning package having a spinning nozzle plate, spinning nozzles and a shared impaction chamber arranged above the spinning nozzle plate and the spinning nozzles arranged in a row, with the volume of the shared impacting chamber satisfying the equation V≧vL*λm, wherein V represents the volume of the impaction chamber in cm3, vL represents the flow of the volume of the cellulose solution in cm3/s and λm represents the relaxation time at the frequency maximum of the relaxation spectrum of the spinning solution, furthermore with a spinning bath in two containers connected by a spinning bath pump, a gap between the spinning nozzles and the spinning bath surface in the upper of the two containers, and a drawing off godet.

#2. Description of Related Art

#The invention is explained in greater detail by means of the illustration and the example. Shown are:

#FIG. 1 the relaxation time spectrum of a spinning solution with 12 percent-by-mass cellulose (Cuoxam-DP 480) at a spinning temperature of 85° C.;

#FIG. 2 the schematic representation of a device for the production of cellulose fibers and -filaments, and

#The FIGS. 2 and 3 show the upper spinning bath container 1 of a spinning device in accordance with the invention. The spinning nozzles 6, of which only one is shown in FIG. 2, have impaction chambers as shown and described in greater detail in the main application. The outflow sides of the spinning nozzles 6 have a distance from the spinning bath surface 7 that forms the air gap a. The floor 10 of the spinning bath container 1 is equipped with several thread guide elements 11 according to the arrangement of the nozzles 6, and the thread bundles 12 exit the container 1 together with the spinning bath liquid flows 14 through said thread guide elements. The thread bundles 12 of all thread guide elements 11 are deflected by the spinning bath flows 14 under an angle and rolled up with appropriate tensile stress. The spinning bath flows 14 reach the lower spinning bath container (not shown) and are pumped back into the upper spinning bath container 1 through the line 16 by means of a pump (not shown). The thread bundles 12 pass the spinning bath drawing frame w, which reaches from the surface of the bath to the point below the thread guide elements 11 where the thread bundles 12 separate from the spinning bath liquid flows 14. The line 16 runs into a settling chamber 18 that is partially filled with filler bodies (not shown) and the spinning bath liquid flows from said settling chamber 18 through the openings 19 into the actual container 1. FIG. 3 shows that the thread guide elements 11 are arranged in the floor 10 in a row and the thread bundles 12 run next to one another parallel to the drawing-off godet (not shown).

#The spinning bath container 1 has two overflows 9 that can be adjusted vertically and thus determine the level of the spinning bath and the width of the gap a. At the overflows 9, a nozzle tube 20 with a slot 21 that reaches across the row of the nozzles 6 and/or the row of the capillary assemblages 26 is attached by means of the holders 23. The nozzle tube 20 is loaded on both sides with a weak flow of air through the line 24, and said flow of air can be adjusted through a needle valve (not shown). The flow of air 25 leaves the slot 21 (150 mm×1 mm outlet opening) in the shape of a line across the entire width and slants towards the bath surface 7 so that the capillary assemblages come into contact with the flow of air immediately prior to their entry into the spinning bath. The slotted nozzle is located approximately 10 mm above the surface of the spinning bath.

#It was found that when using the device according to the FIGS. 2 and 3, but at first without any air blow of the capillary assemblages by means of the arrangement 20, 21 in the direction of the immersion point of the capillaries into the spinning bath, and when using four monofil nozzles, i.e., four thimble nozzles (12.5 mm diameter) with only one respective 200 μm diameter boring, the width of the gap a can be changed continuously between 10 and 300 mm during spinning without any noticeable spinning failures. The spinning apparatus did not allow a gap width a>300 mm. The experiments were performed with a 12 percent-by-mass cellulose solution in aqueous N-methyl morpholine-N-oxide (NMMO) which had the relaxation time spectrum shown in FIG. 1 and an λm of 3.0 s. To determine the relaxation time from the rheological data of the cellulose solution, reference is made to Ch. Michels, Das Papier, (1998), pages 3 to 8. The drawing-off speed was 100 meters per minute. Increasing the drawing-off speed to 300 meters per minute led to the same results. When replacing the thimble nozzles with nozzles having 30 140-μm diameter borings each, the maximum failure-free gap a drops to approximately 40 to 60 μm.