PROCESS FOR FORMING SHAPED ARTICLES COMPRISING CARBON NANOTUBES

Abstract

A process for manufacturing shaped articles containing carbon nanotubes including the steps of supplying carbon nanotubes in an acidic liquid containing at least one acid, the at least one acid having a Hammett acidity function less than that of 100% sulfuric acid, the at least one acid having a Hammett acidity function equal or more than that of 90% sulfuric acid, and shaping the acidic liquid comprising carbon nanotubes into a shaped article.

Claims

1. A process for manufacturing shaped article(s) comprising carbon nanotubes, comprising the steps of supplying carbon nanotubes in an acidic liquid comprising at least one acid, the at least one acid having a Hammett acidity function less than that of 100% sulfuric acid, the at least one acid having a Hammett acidity function equal or more than that of 90% sulfuric acid, and shaping the carbon nanotubes in the acidic liquid into a shaped article.

2. The process for manufacturing shaped article(s) comprising carbon nanotubes according to claim 1 wherein a dispersion of carbon nanotubes in an acidic liquid is supplied.

3. The process for manufacturing shaped article(s) comprising carbon nanotubes according to claim 2, wherein at least a part of the carbon nanotubes comprised in the acidic liquid is dissolved in the acidic liquid, the dissolved carbon nanotubes in the acidic liquid constituting at least 0.1 vol. % of the total volume of the dispersion.

4. The process for manufacturing shaped article(s) comprising carbon nanotubes according to claim 3 wherein the dispersion comprises carbon nanotubes comprised in native ropes.

5. The process for manufacturing shaped article(s) comprising carbon nanotubes according to claim 4 wherein the carbon nanotubes dissolved in the acidic liquid are distributed between the native ropes comprised in the dispersion.

6. The process for manufacturing shaped article(s) comprising carbon nanotubes according to claim 1 wherein the at least one acid is sulfuric acid having a Hammett acidity function equal or more than that of 90% sulfuric acid.

7. The process for manufacturing shaped article(s) comprising carbon nanotubes according to claim 1 wherein the acidic liquid comprises one or more further acids, each of the one or more further acids having a Hammett acidity function less than that of 100% sulfuric acid.

8. The process for manufacturing shaped article(s) comprising carbon nanotubes according to claim 7 wherein the acidic liquid comprises polyphosphoric acid as a further acid.

9. The process for manufacturing shaped article(s) comprising carbon nanotubes according to claim 1 wherein less than 80 wt. % of the carbon nanotubes comprised in the dispersion is dissolved into individual carbon nanotubes.

10. The process for manufacturing shaped article(s) comprising carbon nanotubes according to claim 1 wherein the shaped article(s) is/are carbon nanotubes fiber(s), wherein the dispersion is shaped into carbon nanotubes fiber(s) by extruding the dispersion through at least one spinning hole, preferably in a spinneret, to form carbon nanotubes fiber(s).

11. The process for manufacturing shaped article(s) comprising carbon nanotubes according to claim 1 wherein the shaped article is a carbon nanotubes paper, wherein the dispersion is shaped into carbon nanotubes paper by removing the acidic liquid from the dispersion through a porous collecting surface to form a carbon nanotubes paper.

12. The process for manufacturing shaped article(s) comprising carbon nanotubes according to claim 1, wherein the shaped article(s) is/are carbon nanotubes tape(s), wherein the dispersion is shaped into carbon nanotubes tape(s) by casting the dispersion onto a surface.

13. The process for manufacturing shaped article(s) comprising carbon nanotubes according to claim 1, wherein the shaped article is a coaxial wire comprising a shield comprising carbon nanotubes, the shield surrounding a central conductive core and an insulation layer surrounding the central conductive core, wherein the dispersion is shaped into a shield by pultrusion of the central conductive core and the insulation layer surrounding the central conductive core through the dispersion to form a coaxial wire comprising a shield comprising carbon nanotubes.

14. The process according to claim 1 wherein the dispersion comprises carbon nanotubes having a length of at least 5 μm.

15. The process according to claim 4 wherein at least 50 wt. % of the carbon nanotubes comprised in a native rope have the same chirality.

16. A shaped article comprising carbon nanotubes, comprising carbon nanotubes obtainable by the process according to claim 1.

17. The shaped article according to claim 16 wherein the shaped article comprises less than 10000 ppm of chlorine.

18. The shaped article according to claim 16 wherein the shaped article is a carbon nanotubes fiber having a resistivity of less than 1000 μΩ.Math.cm.

19. A composite article comprising one or more shaped article(s) comprising carbon nanotubes according to claim 16.

Description

EXAMPLES

[0129] Carbon nanotubes fibers were spun from a dispersion comprising carbon nanotubes as listed in Table 1. The carbon nanotubes were dried overnight in a vacuum oven at 160° C. before forming the dispersion.

[0130] Resistivity has been determined using a 4-point probe method. A fiber is placed on a hard underground and at enough tension applied to keep the fiber straight. The two outer contacts for applying current and two inner contacts for measuring electrical voltage are applied by pressuring probes on the fiber surface. A Hewlett Packard multimeter 34401A is used. Tests with different distances between the contacts, different fiber thickness and resistance values showed good reproducibility of the results. Resistivity has been calculated from resistance using fibers fiber density of 1.3 g/cm.sup.3.

TABLE-US-00001 TABLE 1 Carbon nanotubes (CNT) used in preparing CNT fibers Diameter Length CNT No. of walls [nm] [μm] G/D ratio A Single wall 1.8 5 224 (at 488 nm) B Single wall 1.6 5 161 (at 532 nm) C Single wall 1.6 5 80 (at 532 nm) D Double wall 2 6 70

Examples 1-5

[0131] A dispersion of carbon nanotubes in an acidic liquid was provided by mixing carbon nanotubes with an acidic liquid. In a glovebox the acidic liquid and the carbon nanotubes were brought together in a container to a concentration of 1 wt. % of the CNT material. The container was then placed in a Speedmixer type DAC 150.1 FVZ-K and mixed during 60 minutes at 3000 rpm. The appearance of the dispersion was judged under the microscope. CNT fibers were extruded by extruding the dispersion through a syringe into a coagulation bath. The coagulation bath consisted of water, or acetone where specifically mentioned (example 3). The fibers were formed in the coagulation bath by moving the syringe through the bath.

TABLE-US-00002 TABLE 2 Examples 1-4 Example CNT Acidic liquid Microscopy 1 A 96% sulfuric acid Coarse fibrous Some fiber material breakage 2 A 99.8% sulfuric acid Fine fibrous Fiber material sufficiently strong 3 A 100 parts 96% sulfuric Fibrous flocks Weak fiber acid and 33.3 parts polyphosphoric acid 4 A 102.5 parts 99.8% Strings of Fiber sulfuric acid and 8.2 CNT's sufficiently parts polyphosphoric strong acid

Examples 5-6

[0132] A dispersion of carbon nanotubes in an acidic liquid consisting of 100 parts of 99.8% sulfuric acid and 8 parts of polyphosphoric acid (Merck) was provided. In a glovebox the acidic liquid and the carbon nanotubes were brought together in a container to a predetermined concentration of CNT material, as listed in Table 3. The container was then placed in a Speedmixer type DAC 800.1 FVZ and mixed during 60 minutes at 1950 rpm. Fibers were extruded by extruding the dispersion through a syringe into a coagulation bath consisting of water. The fibers were formed in the coagulation bath by moving the syringe through the bath.

TABLE-US-00003 TABLE 3 Examples 5-6 Concentration Linear density of CNT's in of fiber Resistivity Example CNT dispersion [dtex] [μΩ .Math. cm] 5 A 1 wt. % 93 177 6 A 2.5 wt. % 238 249

Examples 7-10

[0133] A dispersion of carbon nanotubes in an acidic liquid was provided. In a glovebox the acidic liquid and the carbon nanotubes were brought together in a container to a concentration of 3.5 wt. % of CNT material. Different acidic liquids were used, as listed in Table 4. The container was then placed in a Speedmixer type DAC 150.1 FVZ-K and mixed during 60 minutes at 3500 rpm. CNT fibers were extruded by extruding the dispersion through a syringe (examples 7-9) or by extruding the dispersion using a plunger type of spinning machine (example 10) into a coagulation bath consisting of water with or without air gap.

TABLE-US-00004 TABLE 4 Examples 7-10 Linear density of fiber Resistivity Example CNT Acidic liquid [dtex] [μΩ .Math. cm] 7a (air gap) A 99.8% sulfuric acid 230 149 7b (no air gap) A 99.8% sulfuric acid 241 170 8a (air gap) A 99.9% sulfuric acid 227 135 8b (no air gap) A 99.9% sulfuric acid 228 136 9a (air gap) A 100 parts 99.8% 242 124 sulfuric acid and 8 parts of polyphosphoric acid 9b (no air gap) A 100 parts 99.8% 244 124 sulfuric acid and 8 parts of polyphosphoric acid 10 (no air gap) A 99.9% sulfuric acid 252 150

Examples 11-14

[0134] A dispersion of carbon nanotubes in an acidic liquid consisting of 99.9% sulfuric acid was provided. In a glovebox the acidic liquid and the carbon nanotubes were brought together in a container to a concentration of 1 wt. % of CNT material.

[0135] The container was then placed in a Speedmixer type DAC 150.1 FVZ-K and mixed at 3500 rpm during 40 minutes (example 11-13) or during 50 minutes (example 14). CNT fibers were extruded by extruding the dispersion through one capillary of 510 μm (example 11-13) or three capillaries of 500 μm (example 14) using a plunger type spinning machine into a coagulation bath without air gap. The coagulation bath consisted of water. The CNT fibers were drawn through the coagulation bath and wound on a drum. The extrusion speed and winding speed were varied, as listed in Table 5.

TABLE-US-00005 TABLE 5 Examples 11-14 Linear Extrusion Winding density speed speed of fiber Resistivity Example CNT [m/min] [m/mi] [dtex] [μΩ .Math. cm] 11 B 2 2 54 47 12 B 2 3 37 41 13 B 4 4 65 47 14 B 2 2.2 125 47

Examples 15-16

[0136] A dispersion of carbon nanotubes in an acidic liquid consisting of 99.9% sulfuric acid was provided. In a glovebox the acidic liquid and the carbon nanotubes were brought together in a container to a concentration of 1 wt. % of CNT material.

[0137] The container was then placed in a Speedmixer type DAC 150.1 FVZ-K and mixed at 3500 rpm during 50 minutes. CNT fibers were extruded by extruding the dispersion through one capillary (example 15) or three capillaries (example 16) using a plunger type spinning machine into a coagulation bath without air gap. The coagulation bath consisted of water. The CNT fibers were drawn through the coagulation bath and wound on a drum. The extrusion speed and winding speed were varied, as listed in Table 6.

TABLE-US-00006 TABLE 6 Examples 15-16 Linear Extrusion Winding density speed speed of fiber Resistivity Example CNT [m/min] [m/mi] [dtex] [μΩ .Math. cm] 15 D 2 4 15 29 16 D 2 2.2 79 29

Examples 17-19

[0138] A dispersion of carbon nanotubes in an acidic liquid consisting of 99.9% sulfuric acid was provided. In a glovebox the acidic liquid and the carbon nanotubes were brought together in a container to a concentration of 1 wt. % of CNT material. The container was then placed in a Speedmixer type DAC 800.1 FVZ and mixed at 1950 rpm during 10 minutes. This acidic liquid comprising carbon nanotubes could not be extruded using a syringe. The acidic liquid comprising carbon nanotubes was additionally mixed using a Theysohn 20 mm twin screw extruder and collected. The collected acidic liquid comprising carbon nanotubes from the twin screw extruder was subsequently extruded through a single capillary using a syringe into a coagulation bath without air gap (example 17). The coagulation bath consisted of water. In examples 18 and 19, the acidic liquid comprising carbon nanotubes additionally mixed with the twin screw extruder was extruded in-line through one capillary (example 18) or through 7 capillaries (example 19).

TABLE-US-00007 TABLE 7 Examples 17-19 Linear density of fiber Resistivity Example CNT [dtex] [μΩ .Math. cm] 17 A 49 80 18 A 80 168 19 A n.a. n.a.