Process for the production of shaped cellulose articles

Abstract

A method of manufacturing a cellulose-based shaped article. The method comprises subjecting a solution of lignocellulosic material, dissolved in a distillable ionic liquid, to a spinning method, wherein the ionic liquid is a diazabicyclononene (DBN)-based ionic liquid. DBN-based ionic liquids have good dissolution power, high thermal and chemical stability, lack runaway reactions and exhibit low energy consumption, due to low spinning temperatures. The shaped cellulose articles can be used as textile fibers, high-end non-woven fibers, technical fibers, films for packaging, and barriers films in batteries, as membranes and as carbon-fiber precursors.

Claims

1. A method of manufacturing of a cellulose-based shaped article by subjecting a solution comprising a lignocellulosic material dissolved in a distillable ionic liquid to a spinning method, wherein the ionic liquid is a diazabicyclononene (DBN) based ionic liquid.

2. The method according to claim 1, wherein the DBN-based ionic liquid comprises a DBN-based cation and an anion that imparts a high basicity, in terms of the Kamlet-Taft beta (?) parameter, said DBN-based cation having a residue R, which is selected from linear and branched alkyl, typically C.sub.1-C.sub.6 alkyl, alkoxy, alkoxyalkyl and aryl groups, and hydrogen.

3. The method according to claim 1, wherein the DBN-based ionic liquid comprises a 1,5-diazabicyclo[4.3.0]non-5-enium cation of the formula (I) ##STR00002## R.sub.1 is selected from the group of hydrogen, linear and branched C.sub.1-C.sub.6 alkyl, C.sub.1-C.sub.6 alkoxy, C.sub.1-C.sub.10 alkoxyalkyl and C.sub.6-18 aryl groups, an anion selected from halides; pseudohalides; a carboxylate; an alkyl sulphite, an alkyl sulphate, a dialkyl phosphite, a dialkyl phosphate, a dialkyl phosphonites, and a dialkyl phosphonate.

4. The method according to claim 1, wherein the DBN-based ionic liquid has a 1,5-diazabicyclo[4.3.0]non-5-enium cation of Formula (I) in claim 3, where R.sub.1 is H, and a carboxylate anion.

5. The method according to claim 1, wherein the DBN-based ionic liquid is [DBNH][CO.sub.2Et] or[DBNH][OAc].

6. The method according to claim 1, wherein the lignocellulosic material is a chemical, mechanical or chemimechanical pulp produced from wood or a non-wood source, or where the lignocellulosic material is a waste material.

7. The method according to claim 1, wherein the solution additionally comprises a lignin.

8. The method according to claim 1, wherein the lignin is derived from a lignin-containing pulp.

9. The method according to claim 1, wherein a solution comprising a lignocellulosic material dissolved in a distillable DBN-based ionic liquid is extruded through a spinning nozzle, shaped as filament or film by stretching the film or filament while still in solution to orient the molecules, and after passing through the air-gap, the fibres or film are drawn through a water-containing spin bath, where the cellulose is regenerated.

10. The method according to claim 1, where any type of unbleached and bleached chemical pulp is used as raw material.

11. The method according to claim 1, wherein spinning is carried out by air-gap spinning, wet spinning, or dry-jet wet spinning.

12. The method according to claim 1, where the spinning solution has a zero shear viscosity between 5,000 and 70,000 Pas at spinning conditions.

13. The method according to claim 1, where the solvent is purified by vacuum distillation.

14. The method according to claim 1, wherein the cellulose fibre produced has a dry tenacity of >35 cN/tex and a wet-to-dry tenacity of >0.80.

15. The method according to claim 1, wherein the polysaccharides present in the lignocellulosic pulp undergo negligible degradation, if any, during the process.

16. The method according to claim 1, wherein the process causes negligible water pollution due to degradation products.

17. The method according to claim 1, wherein the fibres produced are suitable for use in woven or non-woven textiles, for technical purposes, or for use as carbon-fibre precursors.

18. The method according to claim 1, wherein the shaped article is a film or a fibre.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows a comparison of rheological key parameters of NMMO and [DBNH][OAc] cellulose solutions;

(2) FIG. 2 shows the properties of [DBNH][OAc] spun fibres as function of draw for a 13 wt-% solution of Bahia pulp in [DBNH][OAc];

(3) FIG. 3 shows the tenacity for [DBNH][OAc] spun fibres as function of elongation for a 13 wt-% solution of Bahia pulp in [DBNH][OAc];

(4) FIG. 4 shows the properties of [DBNH][OAc] spun fibres and NMMOxH.sub.2O spun fibres as function of draw for a 13 wt-% solution of Bahia pulp in [DBNH][OAc] or NMMOxH.sub.2O;

(5) FIG. 5 shows the tenacity for [DBNH][OAc] spun fibres or NMMOxH.sub.2O spun fibres as function of elongation for a 13 wt-% solution of Bahia pulp in [DBNH][OAc] or NMMOxH.sub.2O;

(6) FIG. 6 shows the tenacity for [DBNH][OAc] spun fibres and commercial cellulose fibres as function of elongation;

(7) FIG. 7 shows the molar mass distribution (SEC-MALLS) for the pulp, the dope and the fibre;

(8) FIG. 8 shows the molar mass distribution for Kraft lignin, eucalyptus pre-hydrolysis kraft (Euca-PHK) and a blend of 15 wt-% soda-AQ lignin with 85 wt-% Euca-PHK;

(9) FIG. 9 shows the fibre tenacity as function of fibre fineness for pure cellulose, and blends of 15 wt-% resp. 20 wt-% soda AQ lignin with Euca-PHK pulp;

(10) FIGS. 10a and 10b show draw ratio vs. fibre properties for the fibres according to the present invention (AALTO fibre) and NMMO fibres;

(11) FIG. 11 shows stress-starin curves of regenerated cellulose fibres; and

(12) FIGS. 12a and 12b show the effect of pulp source on fibre properties.

DESCRIPTION OF EMBODIMENTS

(13) The use of DBN-based ionic liquids as solvents for lignocellulosic material for spinning dopes has not been described earlier. These solvents are characterized by their ability to dissolve the wood pulp rapidly. The resulting solutions are solid or have high viscosity at low temperatures but relatively low viscosity at moderately elevated temperatures (?100? C.) and, thus, perform very well in fibre spinning.

(14) According to a preferred embodiment, the DBN-based ionic liquid comprises a DBN-based cation with a residue R, which is selected from the group consisting of linear or branched alkyl, typically C.sub.1-C.sub.6 alkyl, alkoxy, alkoxyalkyl, aryl and hydrogen, and an anion that imparts a high basicity, in terms of the Kamlet-Taft beta (13) parameter.

(15) Preferably, the DBN-based ionic liquid comprises a 1,5-diazabicyclo[4.3.0]non-5-enium cation of the formula (I)

(16) ##STR00001##
wherein

(17) R.sub.1 is selected from the group consisting of hydrogen, linear and branched C.sub.1-C.sub.6 alkyl, C.sub.1-C.sub.6 alkoxy, C.sub.1-C.sub.10 alkoxyalkyl and C.sub.6-18 aryl groups, which optionally are substituted with one or more substituents selected from hydroxy and halogen, and

(18) an anion selected from halides, such as fluoride, chloride, bromide and iodide; pseudohalides, such as cyanide, thiocyanide, and cyanate; a carboxylate, preferably formate, acetate, propionate, or butyrate; an alkyl sulphite, an alkyl sulphate, a dialkyl phosphite, a dialkyl phosphate, a dialkyl phosphonites, and a dialkyl phosphonate.

(19) More preferably, the DBN-based ionic liquid has a 1,5-diazabicyclo[4.3.0]non-5-enium cation of formula (I) above, where R.sub.1 is H, and the anion is a carboxylate anion, preferably formate, acetate, propionate or butyrate.

(20) The most preferred DBN-based ionic liquids are [DBNH][CO.sub.2Et] and [DBNH][OAc].

(21) The lignocellulosic material is typically a chemical, mechanical or chemimechanical pulp produced from wood or a non-wood source, preferably a bleached or unbleached chemical pulp, produced by a known pulping process, such as kraft, pre-hydrolysis kraft, soda anthraquinone (AQ), sulphite, organosolv, alkaline sulfite anthraquinone methanol (ASAM), alkaline sulfite anthraquinone (ASA), and monoethanolamine (MEA), most preferably a bleached dissolving pulp.

(22) In one preferred embodiment, the solution additionally comprised of a lignin or of lignin-containing pulp.

(23) The lignin is derived from a pulping process, preferably alkali lignin, kraft lignin, soda-AQ lignin, lignosulphonate, thiolignin, organosolv-lignin, ASAM-lignin or ionic liquid-extracted lignin (ILL).

(24) The solution of the lignocellulosic material, optionally in combination with lignin, dissolved in the distillable DBN-based ionic liquid, is preferably shaped into a fibre or film by extruding the solution through a spinning nozzle, for example a spinneret into an air-gap, shaping it as a filament or film by stretching the film or filament while still in solution to orient the molecules, and after passing through the air-gap, the fibres or film are drawn through a water-containing spin bath, where the cellulose is regenerated.

(25) Preferably, the spinning solution has a zero shear viscosity between 5,000 and 70,000 Pas, preferentially 30,000 Pas, at spinning conditions.

(26) The solvent withdrawn from the solution is preferably purified by vacuum distillation.

(27) The cellulose fibre produced by this method has a dry tenacity of >35 cN/tex and a wet-to-dry tenacity of >0.80, preferably a dry tenacity of ?40 cN/tex or even ?45 cN/tex, and a wet-to-dry tenacity of ?0.90.

(28) The polysaccharides present in the lignocellulosic pulp used as raw material undergo no or negligible degradation during the process.

(29) The process causes negligible water pollution due to degradation products, especially negligible COD.

(30) DBN-based ionic liquids, in particular [DBNH] carboxylates show superior solubility and spinnability properties. The pulp is dissolved extremely fast at moderate temperatures with only gentle stirring. In contrast to NMMO, no water has to be evaporated from a solvent-water mixture but the pulp is dissolved directly in the ionic liquid. This accelerates the preparation step substantially. The resulting solution shows similar viscoelastic properties as NMMO solutions, but already at lower temperatures and is, thus, less energy consuming when processed (FIG. 1). The filament stability in the fibre spinning process is excellent. High draw ratios of >10 can be accomplished. The resulting fibres are similar or slightly superior to commercial fibres in terms of strength properties (Table 1).

(31) TABLE-US-00001 TABLE 1 Properties of commercial textile fibres (2) and fibres spun from [DBNH][OAc] NMMO Viscose Modal Tencell [DBNH][OAc] Titre [dtex] 1.4 1.3 1.3 1.9 Tenacity cond. [cN/dtex] 23.9 33.1 40.2 45.7 Elongation cond. [%] 20.1 13.5 13.0 9.2 Tenacity wet [cN/dtex] 12.5 18.4 37.5 41.9 Elongation wet [%] 22.0 14.1 18.4 11.3

(32) Table 1 shows that the fibres spun from [DBNH][OAc] show even better strength properties than the commercial fibres.

(33) The following non-limiting examples illustrate the invention.

Example 1: Preparation of the Spinning Dope

(34) 5-20 wt-% pulp (preferentially 10-15 wt-%) are mixed in the neat DBN-based distillable ionic liquid [DBNH][OAc] and the suspension is transferred to a vertical kneader system (or a stirrer at smaller scale). Dissolution proceeds fast (within time periods of 0.5-3 h) at low revolution (10 rpm) and moderate temperature (60? C.-100? C.). The resulting solution can be filtrated by means of a pressure filtration, equipped with a metal fleece filter (fineness 5 ?m absolute) and is degassed in a heated vacuum environment. However, those two steps are not necessarily required.

(35) The spinning dope is then transformed in hot, liquid state to the cylinder of the piston-spinning unit. The spinning conditions are summarized in Example 2 below. The fibres were washed and dried online by means of a washing bath and drying channel, respectively.

(36) Naturally, it is also possible to transfer the spinning dope as solid pieces at room temperature to the cylinder of the piston-spinning unit.

Example 2: Spinning of DBN-Based Dopes

(37) Spinning dope (13 wt-% pre-hydrolysis eucalyptus kraft pulp in [DBNH][OAc]) prepared as described in Example 1 is spun through a multi-filament spinneret (18 holes, 100 ?m capillary diameter) at 80? C. with an extrusion velocity of 0.8 ml/min. The take-up velocity was varied systematically to set different draw-ratios. Temperature of the coagualtion bath: 14-18? C.; the washing bath 50? C., and the drying channel 80? C. Further parameter and the properties of the resulting fibres are given in Table 2 and FIG. 2. The filaments depicted excellent spinning stability over the whole range investigated.

(38) TABLE-US-00002 TABLE 2 Spinning parameter and fiber properties (godet 1: filament up-take after coagulation bath, godet 2: after washing bath, godets 3 + 4: after drying channel). Tensile test Conditionned Spinning conditions Titer Force Ten, godet 1 godet 2 godet 3 godet 4 draw dtex +/? cN +/? Elong. % +/? cN/tex +/? 7 8 8.2 8.2 1.45 13.85 1.61 40.86 2.64 6.58 1.00 29.70 2.32 10.9 11.7 12 12 2.12 9.02 0.70 34.64 2.30 8.37 1.00 38.57 3.12 15 15.7 16 16 2.83 7.60 0.96 28.38 2.64 10.03 1.19 37.49 2.01 20.7 21.6 22 22 3.89 5.75 0.72 21.25 2.10 7.14 1.05 37.10 1.54 25.4 26.5 27 27 4.77 4.31 0.47 17.34 1.96 7.01 1.37 40.33 2.53 31 31.8 32 32 5.65 4.28 0.75 17.20 2.00 8.54 0.69 40.76 3.96 37.1 37.8 38 38 6.72 3.59 0.36 14.41 1.11 8.40 1.02 40.37 2.96 43.3 43.8 44 44 7.78 2.64 0.30 11.49 1.23 7.67 1.36 43.56 1.75 60 10.60 1.91 0.32 9.02 1.71 9.46 1.08 47.14 4.17 Tensile test Wet Spinning conditions Titer Force Ten, godet 1 godet 2 godet 3 godet 4 draw dtex +/? cN +/? Elong. % +/? cN/tex +/? 7 8 8.2 8.2 1.45 13.53 0.99 29.45 2.61 10.81 2.05 21.91 2.82 10.9 11.7 12 12 2.12 8.88 0.87 23.47 2.49 10.64 1.49 26.46 1.81 15 15.7 16 16 2.83 9.09 1.37 22.45 2.49 13.47 1.50 24.92 2.18 20.7 21.6 22 22 3.89 5.40 0.55 16.56 1.61 11.00 1.08 30.78 2.66 25.4 26.5 27 27 4.77 4.14 0.44 12.46 1.58 8.13 1.53 30.21 3.40 31 31.8 32 32 5.65 4.00 0.48 12.53 1.93 10.86 2.04 31.38 3.17 37.1 37.8 38 38 6.72 3.09 0.39 10.26 1.31 10.90 1.26 33.49 4.06 43.3 43.8 44 44 7.78 3.09 0.52 10.00 1.98 11.10 1.82 32.26 2.31 60 10.60 1.94 0.20 7.97 0.78 12.09 0.53 41.26 4.24

Example 3: Fibres from Lignin and Cellulose Blends

(39) Lignin from commercial sources (Kraft Lignin) was mixed with commercial Eucalyptus (pre-hydrolysis kraft, PHK) pulp in ratios up to 20:80 and dissolved in [DBNH][OAc] to yield a concentration of 13 wt-%. The spinning temperature was adjusted such that the zero shear viscosity was between 20000 and 30000 Pas. The fibre regeneration was accomplished in water at a temperature of 10-20? C., preferably below 15? C. through an air gap with a fixed length of 10 mm.

(40) The properties of fibres made from lignin cellulose blends are shown in FIGS. 8 and 9.

(41) The spinning of these dopes, according to the present invention, shows important advantages over NMMO and [EMIM][OAc]-based dopes. This can be seen in Table 3 below.

(42) Table 3 shows shear rheology of the spinning dope according to this invention, compared with known NMMO- and [EMIM][OAc]-based spinning dopes

(43) TABLE-US-00003 Temperature Viscosity ? G [? C.] ?.sub.0 [Pa s] [1/s] [Pa] [DBNH][OAc] 80 21306 1.5 4100 13 wt-% NMMO 100 20000 3.0 4955 13 wt-% [EMIM][OAc] 95 20262 1.9 5000 20 wt-%

(44) The spinning temperature was chosen according to the visco-elastic properties of the dopes. [DBNH][OAc], even though solid at room temperature, shows much lower viscosity than the corresponding NMMO dopes. Thus, the spinning temperature can be lowered by 20? C. or more.

(45) FIGS. 3-6 show that fibres spun from [DBNH][OAc] show even better strength properties than commercial fibres.

(46) Table 4 shows the fiber properties spun from different concentrations of the present spinning dope at different draw ratios.

(47) TABLE-US-00004 TABLE 4 Fiber properties spun from different concentrations at different draw ratios. Pulp conditioned wet con- Titer Force Elong. Tenacity Titer Force Elong. Tenacity Draw centration (dtex) (cN) (%) (cN/tex) (dtex) (cN) (%) (cN/tex) 5.3 13% 3.44 ? 0.29 13.73 ? 1.18 8.83 ? 0.91 40.03 ? 2.86 3.48 ? 0.34 11.38 ? 1.02 11.70 ? 0.78 32.81 ? 3.04 15% 4.27 ? 0.31 19.51 ? 2.26 10.05 ? 1.37 45.62 ? 3.07 3.64 ? 0.20 16.43 ? 1.39 13.53 ? 0.97 45.21 ? 3.01 17% 4.15 ? 0.46 22.34 ? 2.98 10.38 ? 1.02 53.83 ? 2.94 3.85 ? 0.50 17.27 ? 2.35 12.20 ? 0.76 44.99 ? 3.75 10.6 13% 1.91 ? 0.32 9.02 ? 1.71 9.46 ? 1.08 47.14 ? 4.17 1.94 ? 0.20 7.97 ? 0.78 12.09 ? 0.53 41.26 ? 4.24 15% 2.25 ? 0.13 12.21 ? 0.68 10.68 ? 0.65 54.36 ? 2.09 1.89 ? 0.11 9.66 ? 0.79 15.45 ? 1.16 51.15 ? 3.85 17% 2.11 ? 0.35 11.64 ? 2.05 11.08 ? 1.69 55.22 ? 3.29 2.08 ? 0.27 10.81 ? 1.07 12.43 ? 1.13 52.23 ? 3.86 14 17% 1.73 ? 0.20 9.53 ? 0.82 9.72 ? 1.24 55.45 ? 3.44 1.49 ? 0.17 7.22 ? 0.71 11.56 ? 0.92 48.50 ? 3.28 17.7 13% 1.21 ? 0.14 6.08 ? 0.80 8.50 ? 0.83 50.45 ? 4.75 1.18 ? 0.18 5.42 ? 0.84 9.60 ? 1.13 46.35 ? 5.20 15% 1.35 ? 0.19 7.72 ? 0.65 9.6 ? 1.24 57.60 ? 3.37 1.09 ? 0.21 6.11 ? 1.01 10.69 ? 1.13 56.65 ? 3.71

(48) From FIG. 7, which shows the molar mass distribution (SEC-MALLS) for the pulp, the dope and the fibre, one can conclude that basically no depolymerization has occurred during the dissolution and fibre processing steps. The deviations shown are likely caused by variations in the measurement. The very little degradation (see Table 4 below) could further be reduced by reduced dissolution temperature (85? C.). Spinning temperature was 72? C.

(49) TABLE-US-00005 TABLE 4 kDa PULP DOPE FIBER Mw 240.4 216.0 207.5 Mn 72.2 76.8 74.6 PDI 3.3 2.8 2.8

(50) FIGS. 10a and 10b show draw ratio vs. fiber properties for the fibres according to the present invention (AALTO fiber) and NMMO fibres.

(51) FIG. 11 shows stress-strain curves of regenerated cellulose fibres.

(52) FIGS. 12a and 12b show the effect of pulp source on fibre properties. These matters are also shown in Table 5 below.

(53) TABLE-US-00006 TABLE 5 Dope Pulp wt % Titer ?.sub.c ?.sub.c ?.sub.w ?.sub.c E Wood Process Hemi pulp dtex DR cN/tex % cN/tex % GPa Euca PHK 2.6 13 1.2 17.7 50.5 8.5 46.4 11.5 26.5 Birch PHK 5.6 13 1.6 12.4 52.6 10.1 46.0 11.4 19.7 Spruce AS 3.3 13 1.6 12.4 48.5 10.0 45.7 11.8 21.7 Pine Kraft 15.1 13 1.7 10.6 48.4 11.0 41.3 11.2 25.1

(54) No or negligible water pollution from pulp degradation products was observed. The measurements could not identify any measurable COD (chemical oxygen demand) caused by carbohydrate degradation. Thus, it is assumed that the COD caused by carbohydrate degradation is less than 5 kg COD/t of pulp. When using the same pulp (Eucalyptus PHK pulp), the pulp specific emissions during the viscose process (dissolution and degradation of alkali-soluble fraction) is about 40 kg/t of pulp.

INDUSTRIAL APPLICABILITY

(55) The shaped cellulose-based articles produced by the method of this invention can be used as textile fibres, high-end non-woven fibres, technical fibres, films for packaging with superior properties than cellophane but comparable to polyethylene films, barriers films in batteries, membranes etc. The fibres can also be used as carbon fibre precursors.

CITATION LIST

Patent Literature

(56) WO 03/029329 A2 DE 102005017715 A1 WO 2006/108861 A2 WO 2011/161326 A2 WO 2007/101812 A1 DE 102004031025 B3 WO 2007/128268 A2 WO 2009/118262 A1

Non Patent Literature

(57) 1. Bywater, N. (2011) The global viscose fibre industry in the 21st centurythe first 10 years. Lenzinger Ber. 89:22-29. 2. R?der, T., Moosbauer, J., Kliba, G., Schlader, S., Zuckerst?tter, G., Sixta, H. (2009) Comparative characterisation of man-made regenerated cellulose fibres. Lenzinger Ber. 87:98-105. 3. Buijtenhuijs, F. A., Abbas, M., Witteveen, A. J. (1986). The degradation and stabilization of cellulose dissolved in N-methylmorpholine N-oxide (NMMO). Papier (Darmstadt) 40:615-619. 4. Rosenau, Thomas; Potthast, Antje; Sixta, Herbert; Kosma, Paul (2001) The chemistry of side reactions and byproduct formation in the system NMMO/cellulose (Lyocell process). Progress in Polymer Science 26(9):1763-1837. 5. Swatloski, R. P., Spear, S. K., Holbrey, J. D., Rogers, R. D. (2002) Dissolution of Cellose with Ionic Liquids. J. Am. Chem. Soc. 124:4974-4975.