GB2451046A

GB2451046A - Method for the production of multicomponent cellulose fibers

Info

Publication number: GB2451046A
Application number: GB0821012A
Authority: GB
Inventors: Birgit Kosan; Christoph Michels; Frank Meister; Ralf-Uwe Bauer
Original assignee: Thueringisches Institut fuer Textil und Kunststoff Forschung eV
Current assignee: Thueringisches Institut fuer Textil und Kunststoff Forschung eV
Priority date: 2006-05-10
Filing date: 2007-04-26
Publication date: 2009-01-14
Anticipated expiration: 2027-04-26
Also published as: GB0821012D0; RU2008148573A; WO2007128268A2; AT510254B1; WO2007128268A3; RU2431004C2; GB2451046B; DE112007001615A5; DE102006022009B3

Abstract

The aim of the invention is to create a method for producing multicomponent cellulose fibers that have a reduced swelling capacity and an increased wet abrasion resistance. Said aim is achieved by dispersing 75 to 25 percent by volume of cellulose with 25 to 75 percent by volume of at least one additional fiber-forming polymer component in a water-containing ionic liquid and adding stabilizers, eliminating as much of the water as possible by means of shearing, temperature, and a vacuum, shaping the obtained microscopically homogeneous solution to fiber/fiber bundle through at least one spinning nozzle, guiding the same through an air-conditioned gap while drawing the same, precipitating the oriented jets of solution by treating the same with a tempered solution which can be mixed with the ionic liquid while representing a precipitating agent for the cellulose and the additional fiber-forming polymer component so as to subject the same to spinodal decomposition, separating the oriented jets of solution from the precipitation bath, and then finishing the same.

Description

NETHOD FOR THE PRODUCTION OF

MTJLTICONPONENT CELLULOSE FIBERS

(Description]

This invention relates to a process for producing cellulosic multicomponent fibers having reduced swelJ.ability and increased wet abrasion resistance.

(Prior art)

Viscose fibers incorporating secondary components can undergo an appreciable increase in swellability, as expressed by their water retention capacity (WRy) (M. Einzmann et al.; Lenzinger Berichte 84 (2005) 42-49). Examples of a WRV decrease are not known.

The addition of secondary polymers to cellulose solutions in N-methylmorpholirie N-oxide monohydrate (N1MO) makes it possible to produce lyocell fibers with discrete incorporation of the secondary component in the pore system which have increased swellability irrespective of whether the secondary component has hydrophilic or hydrophobic properties (M. Einzmann et al.; Lenzinger Berichte 84 (2005) 42-49; F. Meister et al.; Lenzinger Berichte 78 (1998) 59-64; Ch. Michels; Abschlussberjcht zurn BMWA-Proj ekt "Modelluntersuchungen zuin Lyocell Prozess", Reg. No. 1077/03 (2005) 13-19) WO 98/09009 claims the addition of linear synthetic polymers, for example LD polyethylene, to cellulose-NNMO solutions. Again, although the added polymers are hydrophobic and are liquid at the time of dispersion (working temperatures above the melting temperature of the added polymers), a matrix/island structure develops with the same or increased swellability. p

Studies on lyocell fibers and modified lyocell fibers have shown that there is a log-log correlation between their WRV and their wet abrasion resistance (NSB).

(Ch. Nichels; Abschlussbericht zum BMWA-Projekt "Modelluntersuchungen zuin Lyocell Prozess", Reg. No. 1077/03 (2005) 21) It is only by subsequent derivatization of a cellulose fiber with hydrophobic substituents that one achieves a reduction in swellability and an increase in NSB.

A process for producing lyocell fibers from ionic liquids is claimed in DE 10 2004 031 025 B3, wherein these lyocell fibers have comparable swellability to lyocell fibers produced by the NNNO process.

WO 2005/098546 A2 describes the production of blends of at least two differing polymers or copolymers in at least one ionic liquid. The polymers are dissolved individually directly in the substantially water-free ionic liquids, the polymer solutions are mixed and cast films are obtained from the polymer blend by coagulation with aqueous media and characterized.

Production of fibers is not described, nor are there any indications of the swellability of the polymer blends obtained.

[Object] The present invention has for its object to provide a simple process for producing cellulosic multicomponent fibers having reduced swellability and increased wet abrasion resistance.

We have found that this object is achieved in relation to the process of the present invention when 75 -25 % by volume of cellulose and 25 -75 % by volume of at least one further fiber-forming polymeric component are dispersed in a water-containing ionic liquid in the presence of stabilizers, the water is very substantially removed by shearing, heating and reduced pressure, the resulting microscopically homogeneous solution is formed through at least one spinneret die into fiber, drawn down through a conditioned gap, the oriented jets of solution are coagulated by treatment with a temperature-controlled solution which is miscible with the ionic liquid but constitutes a coagulant for the cellulose and the further fiber-forming polymeric component by spinodal separation, separated from the coagulation bath and subsequently aftertreated.

We found that, surprisingly, ionic liquids which contain cellulose and certain fiber-forming polymers, for example polyacrylonitrile (PAN) or poly-acrylonitrile copolyxners, in certain concentration ranges are capable of forming, not a matrix/island structure, but a matrix/matrix structure, i.e., two separate continuous phases, which survive coagulation by spinodal separation. Dissolving the cellulose out by cuoxain leaves a fibrous structure of PAN (cf. figure 1). This obviously results in a distinct decrease in swellability but an increase in NSB. As evident from example 2 (figure 2), there is again a log-log relationship which in the range 0 -75 % by volume of PAN conforms to the equation in NSB = 39.772 -8.686 (in WRV) where R = 0.998. The plot of breaking strength, dry and wet, against composition in % by volume (figure 3) suggests that the phase inversion takes place on admixture of 50 % by volume of PAN. The ratio Cdry/Gwet is = 1 for fractions > 50 % by volume of cellulose, changing to = 1 at fractions > 50 % by volume of PAN.

It has further emerged as beneficial when the secondary polymer alone forms a low-viscosity solution with the ionic liquid and accordingly is easier to disperse. The ratio of the zero shear viscosities for cellulose/secondary polymer should be distinctly above 1, preferably above 10.

Chemical puips from wood, cotton and other annual plants, produced by the sulfite, sulfate or prehydrolysis sulfate process, will prove useful as cellulosic component. The bleaching process for the chemical puips is of minor significance.

Polyacrylonitrile (PAN) and polyacrylonitrile copolymers with, for example, 6 % by mass of methyl acrylate will prove optimal as secondary polymers. The secondary component can have pulverulent or fibrous form (Dolanit , Dolan , Dralon , Orion , Woipryla fiber, etc.) and should preferably have hydrophobic properties.

The ionic liquids tested were imidazolium descendants, such as l-butyl-3--methylimidazolium chloride (BMIMC1), l-.ethyl-3-methylimidazolium chloride (EMIMC1), 1-butyl-3-inethylimidazolium acetate (BMINAc) and 1-ethyl3-methylimidazolium acetate (BMIMAc).

The polymer solutions were stabilized by adjusting their hydrogen ion concentrations (pH value) with a nonvolatile base, for example sodium hydroxide or polyethyleneimine with or without propyl gallate or similar stabilizers such as tarinins, p-phenylene-diamine, quinone.

Useful coagulation media include water and/or water-miscible alcohols which may include up to 50% of the ionic liquids used as solvents.

The invention will now be elucidated by reference to the following examples:

[Examples]

Example 1

The production of cellulose-secondary polymer solutions in ionic liquids and their characterization and spinning into fibers were carried out according to the following general procedure: The requisite amount of chemical pulp and secondary polymer fiber were mixed in accordance with the stated mixing ratio, beaten up in water by means of an Ultra-Turrax in a liquor ratio of 20:1, and dewatered to about 35 % by mass by pressing of f. The amount of the press-moist polymeric mixture needed in accordance with the targeted solids content, for the polymer solution was introduced into ionic liquid containing 20 % by mass of water and stabilizers, and dispersed, and the aqueous suspension was adjusted to a pH > 8 by addition of a 0.1 molar aqueous NaOH solution.

When the secondary polymer was in pulverulent form, the cellulose alone was beaten up in water and pressed off.

The pulverulent secondary polymer was directly dispersed in the ionic liquid containing 30 % by mass of water and stabilizers, then the press-moist cellulose was introduced and dispersed, and the aqueous suspension was adjusted to a pH of > 8 by addition of a 0.1 molar aqueous NaOH solution.

After the suspension had been transferred into a vertical kneader, a homogeneous polymer solution was produced by vigorous shearing, slowly rising temperature from 90 to 130 C and decreasing pressure from 850 to 5 mbar by complete removal of water. The dissolving times amounted to a consistent 90 mm. The solutions were assessed with regard to their microimage in polarized light and rheologically characterized. The results are shown in table 1.

Table 1

No. Secondary polymer -Solvent Solids (ri085 C polymer ratio of content [%J cellulose/secondary (Pas] ____ polymer [% by mass) ____________ ____________ 1.1 PAN homopolymer -80/20 BMIMC1 13.9 41760 1. 2 PAN comopolymer -80/20 BMIMC1 14.1 39800 1.3 PAN homopolymer -80/20 BMIMc PAN does not dissolve 1.4 PAN homopolymer -60/40 EMIMC1 20.3 28167 1.5 Secondary cellulose BMIMC1 13.1 33460 ____ acetate 80/20 ______________ 1.6 Chitin -80/20 BMIMc]. chitin does not dissolve 1.7 Chitin -80/20 BNIMAc chitin does not dissolve 1.8 Chitosan -80/20 BMIMC1 chitosan does not dissolve 1.9 Chitosan -80/20 BMIMAc chitosan does not dissolve 1.10 Polyamide 1465 -80/20 BMIMC1 14.3 (39380 1.11 PLA -80/20 BMIMC1 PLA does not dissolve 1.12 PLA -80/20 BMIMAc 13.8 325 1.13 PLA -80/20 ENIMAc 14.0 650 1.14 Wool -80/20 BMIMC1 12.9 8413 1.15 PMMA -80/20 BMIMC1 PZ'IMA does not dissolve 1.16 PMMA -60/40 BMIMAc 16.8 21540' 1.17 1PNMA -90/10 BMIMAc,1]..0 3606 1 zero shear viscosity at 110 C -__,i., . -BMIMC1: l-butyl-3-methylimidazolium chloride EMINC1: l-ethyl-3-methylimjdazoljum chloride BMIMAc: l-butyl-3--niethyljmjdazoljum acetate ENIMAc: l-ethyl-3--rnethylimidazolium aceate PAN homopolyrner: Dolanit 10 polyacrylonitrile fiber PAN copolyrner: copolyrner with 6 % of methyl acrylate PLA: polylactide PMMA: polymethyl methacrylate The polymer solutions were spun in accordance with the procedure described hereinbelow. The spinning solution was fed at the requisite rate at 85 C bulk temperature via a plunger-type spinning apparatus to the spin pack, filtered, heated in a heat exchanger to the spinning temperature S, relaxed in an inflow chamber and forced through dies containing 30 spinning capillaries having an L/DA ratio of 1 and an exit diameter IDA of 90 jrn. The jets of solution pass through the conditioned air gap of length a and are additionally quenched with air at 25 C and moisture content and air rate as per table 2.

The oriented sheet of yarn passes through the spin bath at a temperature of 20 C while the polymer network is simultaneously coagulated, is separated from the coagulation bath at a takeoff speed of Va = 30 In/mm at an angle of 3 40 0, withdrawn via godet rolls and subjected to a discontinuous, tensionless aftertreatment by washing and drying. The spinning conditions for some of the polymer mixtures described in table 1 are recited in table 2 under the same number.

Table 2 Spinning conditiofls No. Spin dope temp. Air gap Air rate Air humidity SpinnabilitY Sp [ C) a [mm] (1/mirj__ (gun3] ________________ 1.1 103.5 90 35 3.0 1.7/1.3 dtex ____________ very good 1.2 102.0 80 35 3.8 1.7/1.3 dtex very good 1.4 109.4 110 none 9.6 1.7 dtex ___________ very good 1.5 100.0 80 70 3.2 1.7 dtex ___________ spinnable 1.10 104.1 90 50 3.0 1.7/1.3 dtex ___________ very good 1.14 83.9 50 60 3.2 1.7 dtex ___________ spinnable 1.16 100 -130 ________ ___________ not spinnable 1.17 88.8 40 70 3.0 1.7 dtex ___________ spinnabi e

Example 2

A eucalyptus pulp (Cuoxam IJP: 556) and a polyacrylo-nitrile homopolynher fiber (Dolanit 10) were mixed in various mixing ratios, beaten up in water by means of an tiltra-TurraX at a liquor ratio of 20:1 and dewatered to 35 % by mass by pressing off. The amount of the press-moist polymer mixture needed in accordance with the desired solids content for the polymer solution was introduced into BMIMC1 containing 20 % by mass of water and 0.03 % by mass of propyl gallate, and dispersed and a homogeneous polymer solution was obtained by the procedure described in example 2. The results are shown

in table 3.

The microimages examined after solution production showed homogeneous solutions which did not contain any fiber fragments of cellulose or PAN residues whatsoever. With increasing PAN content, however, the microimages showed the occurrence of a Tyndall effect.

The solutions were rheologically characterized before spinning.

Fiber DP was determined similarly to the determination on purely cellulose fibers by allowing for the cellulose starting weight in accordance with the mixing ratio used. The cellulose is selectively dissolved out of the fiber by cuoxam, whereas polyacrylonitrile (PAN) is insoluble in cuoxam. So the selective process of dissolving in cuoxam leaves the fibrous structure of the remaining PAN intact (see figure 1).

Table 3 Cellulose-PAN solutions of differing mixing ratios Mo. Polymer ratio Solids content C Fiber DP cellulose/PAN polymer solution _____ [% by mass) (%] [PasJ __________ 2.1 100 / 0 (comparison) 11.2 14530 509 2.2 90 / 10 12.1 14770 484 2.3 80 / 20 13.9 41760 465 2.4 70 / 30 15. 2 29860 441 2.5 65 / 35 16.5 45574 447 2.6 60 / 40 17.2 39307 474 [2.7 50 / 50 19.2 29500 430 The polymer solutions were spun with the aid of a plunger-type spinning apparatus by following a dry-wet spinning process in accordance with the procedure described under example 3. to form cellulosic multicomponent fibers. The spinning conditions and physical properties of the fibers obtained are recited below and in table 4.

General spinning conditions: -10 -die exit diameter: 90 jrrt number of capillaries of die: 30 takeoff speed: 30 rn/mm spinning bath temperature: 20 C Table 4: Spinning conditions and fiber values Example 2.1 2.2 2.3 2.4 2.5 2.6 2.7 (compa-rison) _______ _______ ________ Cellulose/PAN 90/10 80/20 70/30 65/35 60/40 50/50 ratio 100/0 87.4/ 75.4/ 64.1/ 58.7/ 53.5/ 43.4/ % by mass 100/0 14.6 24.6 35.9 41.3 46.5 56.6 % by volume _______ ______ Spinning conditionS: ______ Flow rate 1.25 1.11 0. 98 0.89 0.82 0.78 0.73 Eg/min per die) _______ ______ Spinning 93.5 90.0 103.5 104.7 103.3 103.9 114.2 temperature SSp E C) _______ ______ ______ Air gap a (mm) 80 -80 90 90_ 90 125 90 Air rate 60 35 35 20 25 20 5 (1/mini ________ _______ Air humidity 2.7 2.2 3.0 5.0 4.3 2.6 3 [g/rn3] _________ ________ Fiber properties: Fineness (dtexJ 1.73_ 1.66 1.68 1.69 1.67 1.73 1.72 Breaking 50.3 44.6 35.1 30.4 27.3 23.9 19.4 strength, cond.

(cN/tex] ________ _______ Breaking 43.7 37.5 34.2 28.0 27.7 26.7 19.5 strength, wet (cN/tex) ________ _______ Extension, 11.7 10.6 9.2 15. 5 10.7 10.3 12.9 cond. [%] _______ ______ -11 -Extension, wet 12.8 12.2 12. 9 18.2 19.3 16.9 28.9 1%) ________ _______ _______ ________ Loop breaking 22.2 19.5 18.6 16.6 15.5 11.0 13.1 strength [cN/tex) ________ Wet abrasion' 28 36 59 114 221 618 4466 [cycles) ________ ______ Water retention 65.9 64.4 61.3 57.3 53.2 45.3 37.5 capacity [%) _______ Dye uptake2 50 54 54 54 52 [mg / g I ________ _______ _______ ________ the method of determining wet abrasion resistance is described by K.-P. Mieck, H. Langner; A. Nechwatal; Lenzinger Berichte 74 (1994) 61-68.

2 dye uptake was determined on 6 % solutions of the dye Direct Red 81 (reaction conditionS: 3 hours at 80 C, 14.2 gIl of sodium sulfate). The cellulose-PAN fibers exhibited a slightly increased dye uptake compared with the purely cellulose fiber, while the Dolanit 10 PAN fiber used had no uptake for this dye (dye uptake: 0 mg/g).

The log-log relationship between NSB and WRy found for lyocell fibers from solutions of cellulose/secondary component in NNNO is beautifully confirmed by this example for lyocell fibers from cellulose/PAN in ionic liquids (cf. figure 2).

The plot of breaking strength, dry and wet, against compositiOn in % by volume with inclusion of the fiber values for the mixture of 24.7 % by volume of cellulose / 75.5 % by volume of PAN (example 4, not included in table 4) in figure 3 shows the phase conversion at a volume ratio of 50:50 very clearly.

-12 -Example 3 Cellulose/PAN mass ratio 60:40 A cotton linters pulp (Cuoxam DP: 454) was beaten up with PAN fibers (Dolanit 10) by means of an Ultra-Turrax in water at a liquor ratio of 20:1 as far as the individual fiber and pressed off to a solids content of %. 174 g of the press-moist fiber mixture were introduced into 341.6 g of l-ethyl-3-methylimidazoljum chloride (EMIMC1) containing 30 % by mass of water and 0.2 g of propyl gallate and dispersed to obtain a homogeneous suspension which was adjusted to pH > 8 by means of 0.1 molar aqueous sodium hydroxide solution.

The suspension was transferred into a vertical kneader, and a homogeneous polymer solution was produced under vigorous shearing, slowly rising temperature from 90 to C and decreasing pressure from 850 to 5 mbar with distillative removal of the water. The dissolving time was 90 mm.

Analytical characterization of the polymer solution gave the following data: solids content: 20.3 % zero shear viscosity: (85 C) : 28167 Pas The polymer solution was spun into fibers by means of the dry-wet spinning process. The spinning conditions and fiber values are shown below in table 5.

-13 -Table 5 Spinning conditions and fiber values

Example I 3

Spinning conditions: ____________ Mass flow [g/min and die) 0.73 Spinning temperature Sg 1 C) 109.4 Air gap a [mm] 110 Air rate [1/mm] none Air humidity [gun3] 9.6 Fiber properties: Fineness [dtexJ 1.84 Breaking strength, cond. [cN/tex) 25.4 Breaking strength, wet [cN/tex) 21.8 Extension, cond. [%J 34.3 Extension, wet [%) 39.3 Loop breaking strength [cN/tex] 21.7 Wet abrasion' (cycles) 250 -Fiber DP 422 Example 4 Cellulose/PAN mass ratio (30:70) 12.0 g of a eucalyptus chemical pulp (dry content: %, Cuoxarn DP: 892) and 26.8 g of PAN fibers (Dolanit 10, dry content 99.25 %) were conjointly beaten up in water by means of an Ultra-Turrax in a liquor ratio of 20:1 to the point of the individual fiber and pressed off to a solids content of 25 %. The press-moist fiber mixture was introduced into 265 g of 1-butyl-3 -methylimidazoliulfl chloride (BMIMC1) containing 20 % by mass of water and 0.1 g of propyl gallate and dispersed to obtain a homogeneous suspension which was adjusted to pH > 8 by means of a nonvolatile base. The suspension was transferred into a vertical kneader, and a homogenous polymer solution was produced under vigorous shearing, slowly rising -14 -temperature from 90 to 135 C and decreasing pressure from 850 to 3 nibar with distillative removal of the water. The dissolving time was 90 mm.

Analytical characterization of the polymer solution gave the following data: solids content: 15.2 % zero shear viscosity: (95 C) : 927 Pas The polymer solution was spun into fibers by means of the dry-wet spinning process. The spinning conditions and fiber values are shown below in table 6.

Table 6 Spinning conditions and fiber values

Example 4

Spinning conditions: Flow rate g/min per die] 0.91 Spinning temperature &Sp ( C] 98.8 Air gap a [mm] 90 Air rate [1/mm) 17 Air humidity [g/m3J 7.8 Fiber properties: ___________ Fineness [dtexj 1.82 Breaking strength, cond. 1 cN/texj 12.2 Breaking strength, wet [cN/tex) 12.7 Extension, cond. [%) 13 Extension, wet [%) 32 Loop breaking strength [cN/tex] 9.2 Wet abrasion [cycles] > 10 000 Water retention capacity [%J 17.6 1 the wet abrasion test is discontinued after 000 cycles, so that larger values cannot be determined.

Claims

-15 -(Claims] 1. A process for producing cellulosic multicornponent

fibers having reduced swellability from ionic liquids characterized in that 75 -25 % by volume of cellulose and 25 -75 % by volume of at least one further fiber- forming polymeric component are dispersed in a water-containing ionic liquid in the presence of stabilizers, the water is very substantially removed by shearing, heating and reduced pressure, the resulting microscopically homogeneous solution is formed through at least one spinrieret die into fiber, drawn down through a conditioned gap, the oriented jets of solution are coagulated by treatment with a temperature-controlled solution which is miscible with the ionic liquid but constitutes a coagulant for the cellulose and the further fiber-forming polymeric component by spinodal separation, separated from the coagulation bath and subsequently aftertreated.
2. The process for producing cellulosic multicomponent fibers according to claim 1 characterized in that the cellulosic component used comprises chemical puips having a cuoxarn DP in the range 300 -2000, produced from wood, cotton linters or other annual plants by the sulfite or sulfate/prehydrolysis sulfate process.
3. The process for producing cellulosic multicoinponent fibers according to claim 1 characterized in that the further fiber-forming component used comprises polyacrylonitrile.
4. The process for producing cellulosic rnulticornponent fibers according to claim 1 characterized in that the further fiber-forming -16 -component used comprises copolyrners of polyacrylonitrile.
5. The process for producing cellulosic multicomponent fibers according to claim 1 characterized in that the ratio of the zero shear viscosities of the solutions of cellulose and secondary polymer in the ionic liquid alone is above 1.
6. The process for producing cellulosic multicomponent fibers according to claim 1 characterized in that the ionic liquids used comprise l-butyl-3-methylimidazolium chloride (BMIMC1) and/or 1-ethyl-3-rnethylimidazolium chloride (EMIMC1) and/or l-butyl-3-methylimidazolium acetate (BMIMAc) and/or 1-ethyl-3-methylimidazoljum acetate (EMIMAc).
7. The process for producing cellulosic multicomponent fibers according to claim 1 characterized in that the stabilizers used comprise nonvolatile bases alone or in combination with propyl gallate, tannins, p-phenylenediamine or quinone.
8. The process for producing cellulosic multicomponent fibers according to claim 1 characterized in that the nonvolatile bases used comprise alkali metal hydroxides or polyethyleneimine.
9. The process for producing cellulosic multicomponent fibers according to claim 1 characterized in that the coagulation medium used comprises water and/or water-miscible alcohols which may include up to 50% of the ionic liquids used as solvents.
10. Cellulosic niulticomponent. fibers having reduced -17 -swellability, obtained by following a process of claims 1 to 9.