EP0659219B1 - Cellulose fibres - Google Patents

Abstract

PCT No. PCT/AT94/00087 Sec. 371 Date Jan. 4, 1995 Sec. 102(e) Date Jan. 4, 1995 PCT Filed Jul. 8, 1994 PCT Pub. No. WO95/02082 PCT Pub. Date Jan. 19, 1995Disclosed is a process for producing cellulose fibers having a decreased tendency to fibrillate. The process comprises the steps of extruding a solution of cellulose in a tertiary amine-oxide through spinning holes of a spinneret to form cellulose filaments, conducting the extruded cellulose filaments across an air gap of greater than 30 mm, and introducing the cellulose filaments into a precipitation bath. The process is carried out in a way that the mathematical expression 51.4+0.033xD+1937xM2 -7.18xT-0.094xL-2.50xF+0.045xF2, does not exceed the number 10. In the mathematical expression, D is the spinning hole diameter in mu m, M is the dope output per hole in g/min, T is the titer of the individual filament in dtex, L is the length of the air gap in mm and F is the humidity of the air in the air gap in g of water/kg of air.

Description

The present invention relates to cellulose fibers and to a process for the production of cellulose fibers, a solution of cellulose in a tertiary amine oxide being extruded through spinning holes in a spinneret and the extruded filaments being passed through an air gap with delay into a precipitation bath.

As an alternative to the viscose process, a number of processes have been described in recent years in which cellulose is dissolved in an organic solvent, a combination of an organic solvent with an inorganic salt or in aqueous salt solutions without the formation of a derivative. Cellulose fibers made from such solutions were given the generic name Lyocell by BISFA (The International Bureau for the Standardization of man made Fibers). BISFA defines a cellulose fiber as Lyocell, which is obtained from an organic solvent by a spinning process. BISFA understands "organic solvent" as a mixture of an organic chemical and water. "Solvent spinning" is intended to mean dissolving and spinning without derivatization.

To date, however, only a single process for the production of a cellulose fiber of the Lyocell type has prevailed until industrial implementation. In this process, N-methylmorpholine-N-oxide (NMMO) is used as the solvent. Such a method is described, for example, in US Pat. No. 4,246,221 and provides fibers which are distinguished by a high strength, a high wet modulus and by a high loop strength.

However, the usability of fabrics, e.g. fabrics made from the fibers mentioned, is severely limited by the pronounced tendency of the fibers to fibrillate when wet. Fibrillation is understood to mean breaking open the fiber in the longitudinal direction under mechanical stress in the wet state, as a result of which the fiber is given a hairy, furry appearance. A fabric made and dyed from these fibers loses its color intensity over the course of a few washes. In addition, there are bright stripes on the scuffed and crease edges. The cause of the fibrillation is assumed to be that the fiber consists of fibrils arranged in the direction of the fibers, between which there is only a small amount of cross-connection.

WO 92/14871 describes a method for producing a fiber with a reduced tendency to fibrillation. This is achieved in that all baths with which the fiber comes into contact before the first drying have a pH of maximum 8.5.

WO 92/07124 also describes a method for producing a fiber with a reduced tendency to fibrillation, according to which the undried fiber is treated with a cationic polymer. A polymer with imidazole and azetidine groups is mentioned as such a polymer. In addition, treatment with an emulsifiable polymer, e.g. Polyethylene or polyvinyl acetate, or crosslinking with glyoxal.

In a lecture given by S. Mortimer at the 1993 CELLUCON conference in Lund, Sweden, it was mentioned that the tendency to fibrillation increased with increasing stretching.

It has been shown that the known cellulose fibers of the Lyocell genus still leave something to be desired with regard to the tendency to fibrillation, and the present invention provides the task is to provide a cellulose fiber of the Lyocell genus, which has a further reduced tendency to fibrillation.

worin D der Spinnlochdurchmesser in µm, M der Spinnmasseausstoß pro Loch in g/min, T der Titer des einzelnen Filamentes in dtex, L die Breite des Luftspaltes in mm und F die Feuchte der Luft im Luftspalt in g Wasser/kg Luft ist, maximal die Zahl 10 ergibt, mit der Maßgabe, daß die Breite des Luftspaltes größer als 30 mm vorgesehen wird.This goal is achieved in a method of the type described in the introduction in that methods are carried out in such a way that the mathematical expression $${\text{51.4 + 0.033xD + 1937xM}}^{\text{2nd}}{\text{- 7.18xT - 0.094xL - 2.50xF + 0.045xF}}^{\text{2nd}}$$

where D is the spinning hole diameter in µm, M is the spinning mass output per hole in g / min, T is the titer of the individual filament in dtex, L is the width of the air gap in mm and F is the humidity of the air in the air gap in g of water / kg of air, maximum the number 10 results, with the proviso that the width of the air gap is provided to be greater than 30 mm.

The invention is based on the knowledge that the structure of the cellulose fiber can be influenced so favorably by setting the spinning parameters that a less fibrillating fiber is formed.

A preferred embodiment of the method according to the invention is that the method is carried out in such a way that the mathematical expression results in a maximum of 5.

The overall parameters titer, spinning mass emissions per nozzle hole, air gap width and moisture in the air gap are related in terms of their effect on the fibrillation behavior of the fibers via the above mathematical expression, that is, a change in a parameter which has a negative effect on fibrillation can be achieved by appropriate adaptation one or more other parameters can be compensated. This naturally results Limits due to economic or technical circumstances, for example a spinning mass throughput of 0.01 g / hole / min offers excellent conditions for spinning a low-fibrillation fiber, but is unfavorable for economic reasons. A spinning mass throughput of 0.025 to 0.05 g / hole / min is therefore preferred.

It has also been shown that large air gap widths have a positive effect on the fibrillation behavior, but that this leads to the occurrence of spinning defects relatively quickly in the small hole / hole spacings used in staple fiber nozzles. An air gap width of less than 100 mm is therefore preferred.

With regard to the humidity of the air in the air gap, the humidity of the normal indoor climate is sufficient for nozzles with a small diameter of the spinning holes or the lowest spinning mass throughput, while for higher throughputs or for the more easily spinnable nozzles an air humidity between 20 and 30 g is sufficient Water / kg air is preferred. The temperature in the air gap is chosen so that on the one hand the dew point is not fallen below, i.e. that no water condenses in the air gap and on the other hand that there are no difficulties in spinning due to the temperature being too high. Values between 10 and 60 ° C can be set, with temperatures between 20 and 40 ° C being preferred.

All known cellulosic spinning materials can be processed by the process according to the invention. So these spinning masses can contain between 5 and 25% cellulose. However, cellulose contents between 10 and 18% are preferred. Hard or softwood can be used as the raw material for pulp production, and the degrees of polymerization of the pulp (s) can be in the range of commercially available products. However, it has been shown that the spinning behavior is better with a higher molecular weight of the pulp is. Depending on the degree of polymerization of the pulp or solution concentration, the spinning temperature can be between 75 and 140 ° C. and can be optimized in a simple manner for each pulp or for each concentration. The warping in the air gap depends on the diameter of the nozzle hole and the concentration of cellulose in the solution when the titer of the fibers is fixed. In the range of the preferred cellulose concentration, however, no influence of this on the fibrillation obsolescence could be determined as long as one is in the area of the optimal spinning temperature.

The test methods and preferred embodiments of the invention are described in more detail below.

Fibrillation assessment

The friction of the fibers against one another during washing processes or during finishing processes in the wet state was simulated by the following test: 8 fibers were placed in a 20 ml sample vial with 4 ml water and in a laboratory shaker type RO-10 from Gerhardt for 3 hours, Bonn (FRG) shaken at level 12. The fibrillation behavior of the fibers was then assessed under the microscope by counting the number of fibrils per 0.276 mm fiber length.

Textile data

Strength and elongation were tested according to the BISFA regulation "Internationally agreed methods for testing viscose, modal, cupro, lyocell, acetate and triacetate staple fibers and tows", edition 1993.

Examples 1-29

It became a 12% spinning solution of sulfite and sulfate pulp (12% water, 76% NNMO) spun at a temperature of 115 ° C. A melt index device from Davenport used in plastics processing was used as the spinning apparatus. This device consists of a heated, temperature-controlled cylinder into which the spinning mass is poured. The spinning mass is extruded through the spinneret attached to the underside of the cylinder by means of a piston which is loaded with a weight. This process is called dry / wet spinning because the extruded filament is immersed in a spinning bath after passing through an air gap.

A total of 29 extrusion tests were carried out, the nozzle diameter, the spinning mass output, the titer of the extruded filament, the width of the air gap and the moisture being varied. The results are shown in Table 1. The column "Fibrils" shows the average number of fibrils over a fiber length of 276 µm.

The table shows the diameter of the spinning hole in µm, the output in g of spinning mass / hole / min, the titer in dtex, the air gap in mm and the moisture in g H₂O / kg of air. The number given under "Fibrils" is an average of several results. Examples 4, 12, 13, 14, 20, 22, 25, 27 and 29 are comparative examples. All other examples are according to the invention and, when the corresponding parameters are inserted in the empirically found mathematical expression, give a number less than 10. The table shows that the cellulose fibers according to the invention have remarkably fewer fibrils than the comparison fibers in the test.

Examples 30-41

The procedure was analogous to the conditions of Examples 1-29, the parameters being changed as indicated. In the The "Fibrils" column shows the average number of fibrils over a fiber length of 276 µm. Table 2 Example No. Hole diameter Output Titer gap Humidity Fibrils 30 (V) 130 0.045 1.8 12th 5.3 27 31 (V) 130 0.045 1.8 12th 4.0 43 32 100 0.026 1.7 60 23.5 2.8 33 (V) 100 0.025 1.7 45 13.4 16 34 100 0.025 1.7 60 25.4 3.2 35 (V) 100 0.025 1.7 30th 13.3 15.1 36 (V) 100 0.025 1.7 30th 12.7 19th 37 100 0.025 1.7 60 24.4 1.9 38 (V) 100 0.049 1.7 90 0.5 34 39 100 0.049 3.2 90 19.0 0 40 100 0.041 1.8 90 29.0 0.9 41 130 0.025 1.3 90 30.0 3.2

The spinning parameters are given in the units shown in Table 1.

Examples 30, 31, 33, 35, 36 and 38 do not meet the mathematical expression used according to the invention and represent comparative examples. The table shows that these fibers have an increased number of fibrils (more than 10 fibrils per 276 μm fiber length).

Table 3 shows characteristic fiber data for the fibers shown in Table 2. Table 3 Example No. Fiber strength cond. cN / tex Fiber elongation cond. % Fiber strength wet cN / tex Fiber stretch wet% 30 (V) 46.1 10.5 33.8 14.2 31 (V) 50 11.3 41.4 14 32 31.9 17.7 27.5 24.5 33 (V) 34.3 15.2 29.1 23.5 34 28.8 16.5 24.5 21.8 35 (V) 34.1 14.8 29.3 19.8 36 (V) 33.3 16.3 30.5 18.8 37 29.4 17.2 23.9 21.3 38 (V) 30.4 11.8 22.5 14.3 39 25.6 15.6 19.5 22.5 40 24.6 14.8 18.2 21.4 41 28.5 15.8 24.2 20.9

Examples 42 to 54

The procedure was analogous to the conditions of Examples 1-29, the parameters being changed as indicated. The column "Fibrils" in Table 4 below shows the average number of fibrils over a fiber length of 276 μm.

The spinning parameters are given in the units shown in Table 1.

Table 4 shows a significant reduction in the number of fibrils as soon as an air gap of about 25-30 mm is exceeded.

Claims (6)

1. Process for the preparation of cellulose fibres in which a solution of cellulose in a tertiary amine-oxide is extruded through orifices in a spinneret and the extruded filaments are led under tension across an air gap into a precipitation bath, with the proviso that the width of the air gap is greater than 30 mm, characterised in that the process is carried out in such a way that the mathematical expression $${\text{51.4 + 0.033xD + 1937xM}}^{\text{2}}{\text{- 7.18xT - 0.094xL - 2.50xF + 0.045xF}}^{\text{2}}$$

   

   wherein D is the diameter of the spinning orifice in µm, M is the output of spinning material per orifice in g/min, T is the titre of the individual filaments in dtex, L is the width of the air gap in mm, and F is the humidity of the air in the air gap in g water/kg air
   has a maximum value of 10.
2. Process in accordance with Claim 1, characterised in that the process is carried out in such a way that the mathematical expression has a maximum value of 5.
3. Process in accordance with one of Claims 1 or 2, characterised in that the output of spinning material per orifice is between 0.025 and 0.05 g/min.
4. Process in accordance with one or more of Claims 1 to 3, characterised in that the width of the air gap is less than 100 mm.
5. Process in accordance with Claims 1 or 2, characterised in that when using a spinneret with orifices whose diameter is between 70 and 130 µm, the humidity of the air in the air gap is maintained between 20 and 30 g water/kg air.
6. Cellulose fibres of the Lyocell type with reduced tendency to fibrillation obtained in accordance with a process as claimed in Claims 1 to 5.