WO2002018682A1 - Method for producing cellulose fibers and cellulose filament yarns - Google Patents

Abstract

The invention relates to a method for producing cellulose fibers and cellulose filament yarns with improved properties on the basis of cellulose according to a dry-wet spinning method using aqueous aminoxides, especially N-methyl-morpholino-N-oxide as a solvent. The inventive method comprises the following steps: a) dispersing the cellulose and the aqueous aminoxide at an elevated temperature in a reactor, removing the water and subjecting the dispersion to shearing, thereby converting it to a homogeneous solution with a relaxation time in the range of from 0.5 to 80 seconds at 85 DEG C, b) feeding the solution to at least one spinning nozzle and shaping it, c) transporting the jet of solution through a non-precipitating medium while further shaping it, and d) precipitating the cellulose yarn or bunch of yarns, separating it from the precipitation bath via a deflection element and washing, treating to give softness and suppleness, drying and optionally cross-linking the product(s) in a multi-step post-dischargement treatment. In step a), a solution with a cuoxam degree of polymerization (DP) of the cellulose of >/= 450 is produced, said solution is shaped in steps b) and c) with a strain rate of (I). The reviving batch in step d) optionally also contains a cross-linking agent.

Description

Process for the production of cellulose fibers and cellulose filament yarns

[Description]

The invention relates to a process for the production of cellulose fibers or cellulose filament yarns with improved properties from cellulose by the dry-wet extrusion process with aqueous amine oxides, in particular N-methyl-morpholine-N-oxide, as solvent, in which a) pulp and aqueous amine oxide are added dispersed at elevated temperature in a reactor, with removal of water and shear in 0 a homogeneous solution with a zero shear viscosity in the range of 1000-8000 Pas and a relaxation time in the range of 0.5-80 seconds at 85 ° C, b) the solution at least one Spinning nozzle feeds and deforms, c) the solution jet is transported through a non-precipitating medium with further deformation, and d) the cellulose thread or the yarn filament precipitates in a precipitation bath, separates it from the precipitation bath via a deflecting element and washes in a multi-stage aftertreatment , dries and crosslinked if necessary.

0 [state of the art]

From US Pat. Nos. 4,246,221 and 4,416,698, the dissolving of cellulose in water-containing amine oxides, the shaping in spinning capillaries with low shear, the drawing of the solution jets in a large air gap, the precipitation of the 5 cellulose by an aqueous amine oxide-containing Spinning bath and the removal of the cellulose thread using a godet known.

US Pat. No. 5,417,909 describes a process which deforms the solution in the spinning capillaries under medium to high shear, the solution jets in a short manner

The air gap warps, the cellulose precipitates and the threads or thread group are grasped over a spinning funnel and transported in direct current. EP 0 430 926, EP 0 494 852, EP 0 756 025 and WO 94/28 210 describe certain nozzles with different spinning capillary geometry and arrangement. WO 96/20 300 deals with the distance between two spinning capillaries and the path between spinning capillary and deflection element in the precipitation bath.

EP 0 584 318, EP 0 671 492, EP 0 795 052, WO 94/28 218 and WO 96/21 758 describe the different forms of treating the thread family in the gap between the spinneret and the precipitation bath with air having different water contents.

EP 0 659 219 describes the production of a cellulose fiber with a lower tendency to fibrillation, in that an empirical formula of spinneret hole diameter, spinning mass flow, titer, width of the air gap and moisture content of the blown air should not exceed a value of 10. In EP 0731 856 a lower tendency to fibrillation is to be achieved by the fact that the blowing air contains aliphatic alcohols and in EP 0 853 146 by the precipitation taking place in two or more stages. It is also known to change the fiber structure and properties by means of certain aftertreatment processes, such as treatment with crosslinking agents EP 0 783 602, EP 0 796 358, with 10-18% sodium hydroxide solution WO 97/45 574 or with alkanol, diol or triol in at least a wash bath WO 97/25 462. The chemical crosslinking in the aftertreatment leads, in addition to the desired increase in the wet scrub resistance, to a significant embrittlement of the fibers, ie loop tearing strength and elongation at break of the fibers decrease significantly. All of the methods mentioned do not consider the thread formation in the Lyocell process as a unit, predominantly static and try to influence the fiber structure and the fiber properties by modifying individual steps such as the spinneret geometry, the atmosphere in the air gap, the precipitation bath design and / or the aftertreatment. OBJECT OF THE INVENTION

The object of the present invention is to create a method with an improved thread-forming process which captures all the relevant variables for thread-forming in a relationship and thus allows a targeted adjustment of fiber / filament properties based on a solution with a defined cellulose concentration, molecular weight and molecular weight distribution. The fibers spun according to the invention are intended to allow subsequent crosslinking without significant embrittlement.

It was found that the formation of threads from the extremely viscoelastic cellulose solutions in the Lyocell process can be interpreted as a two-stage stretching deformation, in which the stretching deformation takes place in the first stage under the influence of the pressure in the nozzle duct and in the second stage under that of the axial tensile stress in the air gap (see Fig. 1). This gives the pressure ΔP

und die Dehnspannung σ_D zu.DELTA.P

and the tensile stress σ _D too

σ - _D = η _-, _D - ε _a m mi 't- ε Λ _a = 11Q9.11 - m10-5 10' ^V - - e ln SK-1 _L - ^c c _ett . - D _A - a

Herein η _{D is} the expansion viscosity in Pas, s the expansion speed in s ^"1 , T ₁₀ the fineness of the material to be spun

Fiber in dtex, v _a the withdrawal speed in m / min, p _L the density of the solution in g / cm ³ , c _Ce ιι. the cellulose concentration of the spinning solution in%, D _E inlet diameter and D _A outlet diameter of the spinning capillary in cm, 1 length of the spinning capillary in cm, a length of the air gap in cm and SV spinning in the air gap, ie the ratio of take-off and spraying speed.

The expansion viscosity for a spinning solution is determined by the cellulose concentration, the molar mass and molar mass distribution and only changes with the temperature and elongation speed. The rate of expansion of the overall process follows

and contains all process-relevant variables that particularly capture the kinetics of thread formation.

Zero shear and zero stretch viscosities are directly related and according to Trouton __ (_-. O) ⁼ 3 ° _{→ 0} The zero shear viscosity of the cellulose solutions at 85 ° C is preferably 1000 - 8000 Pas when spinning to filaments and preferably 5000 when spinning to staple fibers - 40000 Pas. The breadth of the viscosity range results from the fact that the experimentally accessible zero shear viscosity of the cellulose solutions, in addition to the molecular weight and

Concentration also depends on its degree of solvation or state of solution and only after complete solvation, i.e. long release time reaches a minimum final value. Practical spinning solutions are often incompletely solvated for spinning and thus simulate a higher value for the zero shear viscosity or the molar mass. [Cf. Michels Ch. U. Meister F. "Das Papier" 51 (1997) 4 pp. 161-165 and Michels Ch. And Kosan B. "Chemical Fibers Intern." 50 (2000) 12 pp. 556-561].

It has now been found that between the elongation speed and the "quality of the fiber structure" expressed by the Loop tensile strength and elongation at break of the fibers or filaments are functionally related. In Figure 2, the loop tear force and in Fig. 3 the elongation at break is plotted against the elongation speed of fiber samples, which is the result of spinning 3 cellulose solutions with 11.2% cellulose

(Cuoxam DP in the range 507 - 527, molecular inconsistency U _η = 5.9) were obtained. The tensile strength of the 25 fiber samples was relatively constant at 41.1 ± 1.9 cN / tex, the range of fluctuation of the birefringence was small. This means that the orientation of the fiber samples was of the same order of magnitude, although the spinning delay varied considerably with values between 7 and 32. This also explains that there is a dependency between the working capacity of the fibers (product of tensile strength and elongation at break in J / g) and the stretching speed, but this is much lower.

In a preferred embodiment of the process according to the invention, fibers are spun at a stretching speed in the range between 15 and 40 [1 / s] and the fibers are treated in the last stage before drying with a solution which simultaneously contains softening agent, a crosslinking agent and a crosslinking catalyst. After drying and crosslinking, a fiber with a significantly increased wet scrub resistance is obtained with only a slight change in the other fiber parameters. In another embodiment of the process according to the invention, filament yarns are spun at a stretching speed in the range 60-100 [l / s], the amine oxide is removed by washing in several stages, dried to a water content> 80% by means of a first heated roller duo and carried by piston diaphragm pumps driven by compressed air motors and spray nozzles onto the thread sheet a defined amount of a mixture of finishing agent and crosslinking agent, dries and crosslinks via a second heated roller duo. A filament yarn with significantly increased wet scrub resistance is obtained. The method for determining wet scrub resistance has been described in the literature [Mieck KP; Langner H.; Nechwatal A. "Melliand Textile Reports" 74 (1993) p. 945; "Lenzinger Reports" 74 (1994) pp. 61-68; and Mieck KP; Nicolai A; Nechwatal A.; "Lenzinger reports" 76 (1997) p. 103] described in detail. The measure of wet abrasion resistance is the required number of revolutions of a roller of a certain geometry covered with a cellulose fabric, which leads to the breakage of a moistened fiber under defined tension. The lyocell fibers have in Depending on their molar mass and orientation, a wet scrub resistance in the range between 10 and 50 scrubbing cycles. From the literature mentioned it also appears that there is sufficient wet scrub resistance if the fiber test results in> 340 scrubbing cycles.

The invention will be explained using examples:

[Examples] Example 1

465 g of activated and stabilized spruce sulfite cellulose (water content 55 mass%; stabilizer 0.05 mass%; Cuoxam DP 490; molecular inconsistency U _η = 5.7) are dissolved in 2530 g N-methylmorpholine-N-oxide (NMMO) with a water content of 40% by mass dispersed and transferred with heating, shearing and evaporating 995 g of water into a homogeneous solution with a zero shear viscosity of 5950 Pas, a relaxation time of 4.2 s and a filter value of 56. The solution consists of 12.8 mass% cellulose, 75.9 mass% NMMO and 11.3 mass% water.

A small-scale test facility was used for spinning, which was used to manufacture both staple fibers and Filament yarns allowed. In the present example, fibers were produced with the following settings: fiber fineness 1.10 dtex

- Flow rate 1.11 ml solution / min (density 1.18 g / cm ³ ) spinning temperature 85 ° C

Spinneret (56 spinning capillaries; D _E = 228 μm; D _A = 150 μm 1 = 0.05 cm)

- Air gap (a = 7.0 cm; line-shaped blowing with air - approx. 10 1 / min 1.0 cm above the entry of the filament into the precipitation bath at an angle of ~ 80 ° to the direction of the thread.)

Spray speed 1.12 m / min

- take-off speed 30.2 m / min calculated stretching speed 6.02 s ^"1

The filament sheet was washed, cut into stacks of 50 mm, finished and dried. The test revealed the following fiber parameters:

Parameter / trial (A)

Fineness dtex 1.10

Tensile strength cond. cN / tex 45.6

Tensile strength wet cNtex 38.2 rel. Tear strength ratio 3% 83.8

Elongation at break cond. 17.1

Elongation at break wet% 14.8

Loop tensile strength cN / tex 26.1 rel. Schlingenreißkraftverh. % 57.3

Wet scrub resistance T 31

Example 2

265 g of a cellulose mixture of 98% eucalyptus and 2%

Cotton-Linters-Zeil-fabric was pretreated enzymatically, pressed to a water content of 50% by mass, dispersed in 2593 g of NMMO with a water content of 25% and with heating, shearing and evaporation of 623 g of water in a homogeneous solution with a zero shear viscosity of 4108 Pas and a relaxation time of 4.9 s transferred at 85 ° C. The particle analysis gave a filter value of 90. The composition of the solution was 10.6 mass% cellulose, 77.8 mass% NMMO and 11.6 mass% water. The cellulose mixture of the solution had a Cuoxam DP of 543 and a non-uniformity of 6.05.

The solution was spun (density 1.16 g / cm ³ ) at a melt temperature of 80 ° C through a nozzle with 30 spinning capillaries (D _E = 221 μm; D _A = 140 μm; 1 = 0.05 cm) through a Air gap (a = 5 cm) with a spinning delay of 16.4, and a take-off speed of 72.8 m / min to one

Fineness 1.12 dtex. The resulting elongation rate was 19.2 s ^"1. The fiber was washed, finished and dried at 125 ° C. (A). In parallel, in a second series of experiments, the finishing liquor simultaneously contained 5 g / 1 glyoxal and 0.5 g / 1 magnesium chloride (pH 6.7)

The application was carried out once by spraying the fiber (B) predried to> 80% water and on the other hand by dipping and pressing using a roller duo (C). The fiber test gave the following values:

Beispiel 3

Example 3

300 g eucalyptus pulp, enzymatically pretreated, pressed to a water content of 45 mass%, are dispersed in 2726 g NMMO with a water content of 30 mass% and with heating, shearing and evaporation of 772 g water in a homogeneous solution (density 1.178 g / cm ³ ) transferred with a zero shear viscosity of 5 081 Pas and a relaxation time of 6.0 s at 85 ° C. The particle analysis showed a filter value of 76. The composition of the solution was 12.0 mass% cellulose (Cuoxam DP 508, non-uniformity 5.9), 76.3 mass% NMMO and 11.7 mass% water.

The solution was spun at a melt temperature of 85 ° C. through a nozzle with 330 spinning capillaries (D _E = 225 μm; D _A = 90 μm; 1 = 0.05 cm) through an air gap (a = 2.0 cm) a spin delay of 10.3 and a take-off speed of 32.2 m / min to a fiber with a fineness of 1.09 dtex. The calculated elongation rate was 21.8 s ^"1. The fiber was washed, finished and dried at 125 ° C. (A). In parallel, in a second series of tests the

Aviva liquor simultaneously 7.5 g / 1 of an adduct of glyoxal and sodium bisulfite (B).

Beispiel 4

Example 4

The solution preparation (10.6% cellulose; density 1.16 g / cm ³ at 85 ° C) is carried out analogously to Example 2, the spinning at 84 ° C

Melt temperature with the following parameters: - Spinneret D _E = 221 μm; D _A = 140 µm; 1 = 0.05 cm; 58 spinning capillaries

Air gap 6.0 cm (line-shaped blowing of the filament coulter with 11.5 1 / min air perpendicular to the filament running direction approx. 1 cm before entering the precipitation bath) - spraying speed 18.5 m / min

- take-off speed 302 m / min

- Expansion speed 83.7 s ^"1

After washing, predrying, finishing and drying, the filaments were wound up as yarn with a fineness of 75 dtex f (58) (A). The finish was applied using a precision pump and "fingers". In a parallel test, the finish contained 10 g / 1 Arkofix (commercial product from Höchst AG) and 1 g / 1 magnesium sulfate (B) at the same time. The test was carried out using the standard methods as filament yarn ( a, b) as well as after cutting into stacks as fiber A, B.

^1> Differences due to test method (filament bundle test with 100 cm clamping length; fiber single fiber test with 1 cm clamping length).

Claims

[Claims] 1. Process for the production of cellulose fibers or cellulose filaments by the dry-wet extrusion process with aqueous amine oxides, in particular N-methylmorpholine-N-oxide, in which a) pulp and aqueous amine oxide are dispersed at elevated temperature in a mixing / kneading reactor and transferred with dehydration and shear into a homogeneous solution with a relaxation time in the range of 0.5 - 80 seconds, b) the solution is fed to at least one spinneret and deformed in the spinning capillary (s) with the stretching rate έ _D , c) the deformed one Solution is transported through a non-precipitating medium with simultaneous further deformation at the stretching speed s _a , d) the cellulose thread or the thread bundle fails in a precipitation bath, separates it from the precipitation bath by deflection via a godet, in a multi-stage aftertreatment device in fiber or filament form washes, bleaches, softened, dried if necessary, crosslinked if necessary and then the filaments are wound up individually as yarn or combined to form a cable and cut into stacks, characterized in that a solution with a Cuoxam DP of cellulose> 450 is prepared in stage a), this solution in stages b) and c) with a stretching speed

deformed and that the finish liquor in step d) optionally contains a crosslinking agent at the same time. 2. The method according to claim 1, characterized in that the expansion speed in the nozzle channel of the relationship i ² PL ^'C Cell. ^{, lJ} E ^'L is sufficient, in which Tι ₀ the fineness of the fiber / filament in dtex, v _a the withdrawal speed in m / min, p the density of the spinning solution in g / cm ³ , c _Ce ιι. the cellulose concentration of the solution in%, 1 the length of the nozzle channel in cm and D _E or D _A corresponds to the diameter of the spinning capillary entry or exit. 3. The method according to claim 1, characterized in that the expansion speed between the spinning capillary outlet and the precipitation bath entry of the relationship s _a = 19, M0-5 ^{Tw 'Va} . e ^{lasr ~ x} PL - ^C Cell. - ^D A - a is sufficient, where a corresponds to the length of the draft in cm and SV corresponds to the spinning draft, ie the ratio of the withdrawal speed and spraying speed. 4. The method according to claim 1-3, characterized in that when spinning fibers the stretching speed έ _{D a is} preferably in the range 4 - 40 s ^"1 . 5. The method according to claim 1-3, characterized in that when spinning filament yarns the stretching speed ε _{D is} preferably in the range 40-120 s ^"1 . 6. The method according to claim 1-5, characterized in that the Avivageflotte simultaneously contains a bi- or polyfunctional crosslinking agent of the dialdehyde type, preferably glyoxal and / or its derivatives and the pH of the Avivageflotte has a value <9. 7. The method according to claim 1-5, characterized in that the crosslinking agent is an adduct of glyoxal and sodium bisulfite. 8. The method according to claims 1-6, characterized in that the after-treatment liquors are applied via metering units, consisting of nozzles and membrane piston pumps running at high frequency, as a finely divided mist to the thread sheet and, if necessary, a defined excess is squeezed out via a roller mill , 9. The method according to claims 1-6, characterized in that the crosslinking agent or the crosslinking agent-containing finish is applied via a unit consisting of precision pump (s) and metering pen (s).