Process for the preparation of polymer fibers from polymers dissolved in ionic liquids by means of an air gap spinning process

Abstract

The invention relates to a process for the production of polymer fibers from polymers dissolved in ionic liquids by means of an air gap spinning process, characterized in that a) a spinning solution that contains an ionic liquid and a dissolved polymer is produced; b) said spinning solution is guided through an extruder before it is divided into fibers via a die; and c) the obtained fibers are guided via an air gap through a coagulation bath.

Claims

1. A process for the production of cellulosic fibers from cellulose dissolved in ionic liquids by means of an air gap spinning process, the process comprising: a) preparing a spinning solution by: a1) producing a heterogeneous mixture of cellulose, water as a non-solvent which does not or only partially dissolve the cellulose, and ionic liquid, and a2) distilling off the water in a thin-film evaporator such that the spinning solution contains per 100 parts by weight of ionic liquid, less than 3 parts by weight of water, and 6 to 20 parts by weight of dissolved cellulose which results in pseudo plastic properties of the spinning solution, b) guiding the spinning solution of a2 through an extruder before it is divided into fibers via a die, and c) guiding the fibers via an air gap through a coagulation bath, wherein the fibers are drawn in the air gap.

2. The process according to claim 1, characterized in that the cation of the ionic liquid is an organic, heterocyclic cation having one to three nitrogen atoms as part of a heterocyclic ring system of the organic, heterocyclic cation, and the anion of the ionic liquid is a compound having a carboxylate group.

3. The process according to claim 1, characterized in that the cation of the ionic liquid is an imidazolium cation of the following formula I ##STR00002## wherein R1 represents an organic radical with 1 to 20 carbon atoms, and R2, R3, R4 and R5 represent an H atom or an organic radical having 1 to 20 carbon atoms.

4. The process according to claim 1, characterized in that the cellulose has an average degree of polymerization DP of 200 to 2000.

5. The process according to claim 1, characterized in that the distilling off of the non-solvent is carried out at a temperature of 50 to 150° C. and a pressure of less than 1 bar.

6. The process according to claim 1, characterized in that in process step b) a temperature of the spinning solution in the extruder is 40 to 120° C.

7. The process according to claim 1, characterized in that the fibers are drawn after passage through the die, wherein a degree of drawing is 1.5 to 3.5.

8. The process according to claim 1, characterized in that a contact time in the coagulation bath is 1 second to 60 seconds.

9. The process according to claim 1, characterized in that process steps a) to c) are carried out continuously.

10. The process according to claim 1, characterized in that the fibers are cellulosic fibers with a defibrillation grade of 1 to 2.5.

11. The process according to claim 1, characterized in that the spinning solution of a) contains per 100 parts by weight of ionic liquid, 0.1 to 1 parts by weight of water, and 10 to 14 parts by weight of cellulose.

12. The process according to claim 1, characterized in that the spinning solution of a) with pseudo plastic properties is not a gel.

13. The process according to claim 1, characterized in that the ionic liquid is selected from 1-ethyl-3-methylimidazolium acetate, 1-methyl-3-methylimidazolium acetate, 1-ethyl-3-ethylimidazolium acetate, 1-methyl-3-methylimidazolium octanoate, 1-ethyl-3-ethylimidazolium octanoate, and mixtures thereof.

14. The process according to claim 1, characterized in that the extruder is a core-progressive screw extruder.

15. A process for the production of cellulosic fibers from cellulose dissolved in ionic liquids by means of an air gap spinning process, the process comprising: a) preparing a spinning solution by: a1) producing a heterogeneous mixture of cellulose, water as a non-solvent which does not or only partially dissolve the cellulose, and ionic liquid, and a2) distilling off the water in a thin-film evaporator such that the spinning solution contains per 100 parts by weight of ionic liquid, less than 3 parts by weight of water, and 6 to 20 parts by weight of dissolved cellulose which results in pseudo plastic properties of the spinning solution, b) guiding the spinning solution of a2 through an extruder before it is divided into fibers via a die, and c) guiding the fibers via an air gap through a coagulation bath; and wherein the spinning solution of a) has a crossover at about 16 rad/s at 110° C.

Description

EXAMPLES

(1) Compounds and Raw Materials Used in the Examples:

(2) EMIM octanoate: 1-ethyl-3-methylimidazolium octanoate (R1 in formula I is ethyl and R3 in formula I is methyl), EMIM octanoate is an ionic liquid, hereinafter also referred to as IL for ionic liquid)

(3) Cellulose: Eucalyptus sulfide pulp (Examples 1 to 5) and cotton linters in Examples 6 to 11.

Examples 1 to 5

(4) In these examples cellulosic fibers were prepared as described below:

(5) Production of the Spinning Solution

(6) First, a heterogeneous mixture of the following ingredients was produced.

(7) 11 weight percent cellulose, eucalyptus pulp

(8) 8.1 weight percent of water, and

(9) 80.9 weight percent octanoate

(10) For this purpose, EMIM octanoate was treated with ice, since warming occurs when water is added. Then, the cellulose was added. The mixture was mixed for about 45 minutes in an “AMK kneader” at 40 rpm and room temperature.

(11) The water was then distilled off in a thin-film evaporator (type: VD 83-6-RRS-11 from VTA):

(12) Rotation speed: 400 rpm

(13) Jacket temperature 120° C.

(14) Temperature discharge pump: 110° C.

(15) Vacuum: 60 mbar

(16) After the distillation, a spinning solution with 12 wt % of dissolved cellulose was obtained.

(17) Characterization of the Spinning Solution:

(18) The characterization of the spinning solution is carried out by means of a rheometer. Rheological assessments serve primarily to check the spinnability of a textile pulp. Important parameters here are the zero-shear viscosity, i.e., the theoretical viscosity at no load and the crossover, i.e. the point at which the loss and storage modulus are the same. Frequez sweep tests are performed to obtain these quantities. In addition, the spinning solution should have pseudoplastic properties and should not be a gel. Since spun over an air gap, the solution must have sufficiently large elastic properties to form stable filaments, but these filaments must also be drawn. Therefore, it should have sufficiently viscous properties.

(19) In this case, depending on the temperature, the spinning solution had a zero shear viscosity of 1000 Pas at 110° C., or 20000 Pas at 50° C., and a crossover at about 16 rad/s at 110° C.) or about 0.8 rad/s at 50° C. It also had pseudoplastic properties up to 50° C. These values were determined with a Rheometrics “Dynamic Stress Rheometer SR 500”. The measuring head was a 25 mm diameter plate. A force-controlled frequency sweep was measured. The frequency ranged from 100 rad/s to 0.1 rad/s at a force of 100 Pas. This measurement was carried out in each case at 110° C. to 40° C. descending in 10 K steps. The measuring gap was 1 mm.

(20) Processing of the Spinning Solution

(21) The spinning solution was transferred to a “pressure filtration tank 10 liter” from Karl Kurt Juchheim. The filter used was a metal mesh made of austenitic stainless steel, material number 1.4401 with a mesh size of 0.043 mm and a wire thickness of 0.035 mm.

(22) The filtration unit was positioned on a rack over the extruder. The pressure filter tank was connected to the intake at the extruder by means of a heatable transfer line.

(23) The extruder was an extruder called Haake Polylab Rheocord. The screw of the extruder was core progressive with a ratio of channel depths of 2 to 1, i.e., the channel depth is twice as large at the inlet than at the outlet. The diameter of the screw was 19 mm, the length 25×diameter, i.e. 475 mm.

(24) The textile pulp was guided into the extruder through the filter by means of a pressure of 2 bar. In the extruder, the textile pulp was transported by a screw to the spinning pump. The spinning pump used was a Feinprüf gear pump with a displacement of 0.6 cm.sup.3/rev.

(25) The spinning solution was guided through the spinning head, where it was evenly distributed on the die by means of another filter and a distribution block. The die used here has a hole diameter of 60 μm with an L/D ratio of 2/1, has 168 holes and is from Enka Technika. This complete setup from the pressure filtration to the die was heated to the spinning temperature.

(26) The filaments emerging from the die were guided through an air gap of 10 mm into a coagulation bath. The coagulant contained water as a non-solvent. The temperature of the coagulation bath was 21° C.

(27) The fiber was deflected after an immersion depth of 300 mm and withdrawn from the coagulation bath via a godet duo with a defined speed, and transported away. Depending on the desired drawing and exit speed, the line speed varied according to the table.

(28) A wet-spinning machine from Fourne was used. It comprises a total of 9 godet duos.

(29) Between the first five of these godet duos there were 3 washing baths each 1200 mm in length. They contained water at a temperature of 88° C. The end of this wash unit was a washing godet duo. Here, the fiber was rinsed one last time continuously with water at room temperature. The washing process took place directly on the godet.

(30) After the washing godet duo, there were two more godet duos for the preparation for use. Between these two drives was an aqueous immersion bath through which the fiber was guided. Through the preparation, that is, by the additives in the immersion bath, the fiber received a non-sticky finishing in the usual way, so as to prevent sticking of the individual filaments during drying.

(31) The drying step was carried out on a heated godet duo at 80° C.

(32) The fiber was then guided through a hot air duct at (1200 mm, 120° C.) and wound after the last godet duo with a tension controlled Oeriklon Barmag winder type WUFF 6E.

(33) The above described production of the cellulosic fibers was repeated under different conditions. The table contains the necessary information on the production and properties of the obtained cellulosic fiber.

(34) The textile-mechanical properties were measured with a “Favimat” from Textechno. In each case, the means were determined from 20 individual fiber measurements.

(35) TABLE-US-00001 Exam- Exam- Exam- Exam- Exam- ple 1 ple 2 ple 3 ple 4 ple 5 Solution [%] 12 12 12 12 12 concentration Spinning [° C.] 54 60 60 90 90 temperature Exiting speed [m/min] 5.9 5.9 12.8 12.8 27.8 Line speed [m/min] 10.7 10.7 22.5 15 39.0 Drawing [%] 80 80 90 120 40 Drives 1-9 [m/min] 10.7 10.7 22.5 28 39 Textile- mechanical properties Elongation [%] 6 9 6 6 6 at break Max. tensile [cN/tex] 37 34 41 51 31 force Single fiber [dtex] 1.8 2.0 1.8 1.7 2.4 fineness Modulus of [cN/tex] 1900 1600 1900 1900 1600 elasticity

Example 6-8

(36) Execution as in example 1-5. The pulp used was cotton linters. The alpha cellulose content leads to much improved fiber properties

(37) TABLE-US-00002 Exam- Exam- Exam- ple 6 ple 7 ple 8 Solution concentration [%] 12 12 12 Spinning temperature [° C.] 54 60 60 Exiting speed [m/min] 5.9 5.9 12.8 Line speed [m/min] 13.6 14.1 22.5 Drawing [%] 130 140 90 Drives 1-9 [m/min] 13.6 14.1 22.5 Textile-mechanical properties Elongation at break [%] 5 6 6 Max. tensile force [cN/tex] 56 57 46 Single fiber fineness [dtex] 1.2 1.3 1.8 Modulus of elasticity [cN/tex] 2400 2300 2200

Example 9-11 (Comparative Examples)

(38) Execution was as in Example 6-8, but without screw extruder:

(39) The drawing could not be achieved. A summary of the fiber properties at max. drawing compared to Example 6-8 is shown in the following table:

(40) TABLE-US-00003 Exam- Exam- Exam- ple 9 ple 10 ple 11 Solution concentration [%] 12 12 12 Spinning temperature [° C.] 54 60 60 Exiting speed [m/min] 5.9 5.9 12.8 Line speed [m/min] 8.5 10.2 17.9 Drawing [%] 45 70 40 Drives 1-9 [m/min] 8.5 10.2 17.9 Textile-mechanical properties Elongation at break [%] 14 16 15 Max. tensile force [cN/tex] 23 29 21 Single fiber fineness [dtex] 2.6 2.5 3.2 Modulus of elasticity [cN/tex] 800 900 600