CARBON NANOTUBE DISPERSION AND UTILIZATION OF SAME

• US 20100330358A1
• Filed: 02/08/2008
• Published: 12/30/2010
• Est. Priority Date: 02/08/2008
• Status: Active Grant

• Current Assignee: Meijo Nano Carbon Co., Ltd.
• Original Assignee: Meijo Nano Carbon Co., Ltd.
• Inventors: Hashimoto, Takeshi
• Granted Patent: US 9,181,090 B2
• Time in Patent Office: Days
• US Class Current: 428/323
• CPC Class Codes: B82Y 30/00 Nanotechnology for materials or surface science, e.g. nanocomposites
• CPC Class Codes: B82Y 40/00 Manufacture or treatment of nanostructures
• CPC Class Codes: C01B 2202/34 Length
• CPC Class Codes: C01B 2202/36 Diameter
• CPC Class Codes: C01B 32/174 Derivatisation; Solubilisation; Dispersion in solvents
• CPC Class Codes: Y10T 428/25 Web or sheet containing structurally defined element or component and including a second component containing structurally defined particles

Abstract

The present invention provides a carbon nanotube dispersion, in which carbon nanotubes are uniformly dispersed and a satisfactory dispersed state is maintained over a long period of time, and also inherent properties of carbon nanotubes can be exhibited. The carbon nanotube dispersion contains an alcohol solvent (preferably a lower alcohol having about 1 to 4 carbon atoms) and a polyvinyl acetal resin.

Claims

1. A carbon nanotube dispersion comprising carbon nanotubes dispersed in a liquid medium, wherein the liquid medium includes an alcohol solvent and a polyvinyl acetal resin, 0.5 mg to 200 mg of the carbon nanotubes are dispersed per 100 mL of the alcohol solvent and a weight ratio of the polyvinyl acetal resin to the carbon nanotubes is between 0.5 and 2.

2. The dispersion according to claim 1, wherein the alcohol solvent is a lower alcohol having 1 to 4 carbon atoms.

3. The dispersion according to claim 1, wherein the carbon nanotubes have a length of at least about 1 μ

m and a diameter of less than about 0.1 μ

m.

5. The dispersion according to claim 1, wherein the polyvinyl acetal resin has an average molecular weight of 1.0×

10⁴ to 2.5×

10⁴.

6. The dispersion according to claim 1, wherein the polyvinyl acetal resin is a polyvinyl butyral resin.

7. The dispersion according to claim 6, wherein the polyvinyl butyral resin has a degree of butyralation of 65 mol % to 80 mol %.

8. The dispersion according to claim 6, wherein the polyvinyl butyral resin, when dissolved at a concentration of 10% by weight in a mixed solvent of ethanol and toluene mixed at a volume ratio of 1:

1 at a temperature of 20°

C., has a solution viscosity of 5 mPa·

s to 30 mPa·

s.

9. The dispersion according to claim 1, wherein the dispersion has the property that the carbon nanotubes maintain a dispersed state for at least 2 weeks when allowed to stand undisturbed at room temperature.

12. A carbon nanotube film obtained by applying the carbon nanotube dispersion according to claim 1 onto a substrate.

15. The dispersion according to claim 2, wherein the polyvinyl acetal resin is a polyvinyl butyral resin having an average molecular weight of 1.0×

10⁴ to 2.5×

10⁴ and a degree of butyralation of 65 mol % to 80 mol % and wherein the carbon nanotubes have a length of at least 1 μ

m and a diameter of less than 0.1 μ

m.

16. The dispersion according to claim 15, wherein the polyvinyl butyral resin, when dissolved at a concentration of 10% by weight in a mixed solvent of ethanol and toluene mixed at a volume ratio of 1:

1 at a temperature of 20°

C., has a solution viscosity of 5 mPa·

s to 30 mPa·

s and wherein the dispersion has the property that the carbon nanotubes remain in a uniformly dispersed state for at least 2 weeks when allowed to stand undisturbed at room temperature.

17. A carbon nanotube film obtained by applying the carbon nanotube dispersion according to claim 16 onto a substrate.

18. A carbon nanotube film obtained by applying the carbon nanotube dispersion according to claim 15 onto a substrate.

4. (canceled)

10. A method for producing a dispersion comprising carbon nanotubes dispersed in a liquid medium, comprising:

preparing a liquid medium containing an alcohol solvent and a polyvinyl acetal resin,

placing carbon nanotubes in a container along with the liquid medium and

carrying out a dispersion treatment on the contents of the container,

wherein 0.5 mg to 200 mg of the carbon nanotubes are dispersed per 100 mL of the alcohol solvent, a weight ratio of the polyvinyl acetal resin to the carbon nanotubes is between 0.5 and 2 and the dispersion treatment includes at least stirring and application of ultrasonic.

11. The method according to claim 10, wherein the dispersion treatment is carried out so that a dispersion is formed that comprises carbon nanotube bundles having a length of at least 1 μ

m and a diameter of less than 0.1 μ

m dispersed in the liquid medium.

13. A carbon nanotube film obtained by applying the dispersion produced according to the method described in claim 10 onto a substrate.

14. A carbon nanotube film obtained by applying the dispersion produced according to the method described in claim 11 onto a substrate.

19. A method according to claim 11, wherein the alcohol solvent at least substantially comprises an alcohol having 1 to 4 carbon atoms, the polyvinyl acetal resin is a polyvinyl butyral resin having an average molecular weight of 1.0×

10⁴ to 2.5×

10⁴ and a degree of butyralation of 65 mol % to 80 mol %, and the ultrasound is applied at a frequency of between about 20 kHz to 40 kHz and a power output of between about 80 W to 200 W.

20. A method according to claim 19, wherein the alcohol is selected from ethanol, methanol and 2-proponal.

21. A liquid dispersion comprising carbon nanotubes suspended in a liquid medium, wherein the liquid medium comprises at least one alcohol and at least one polyvinyl acetal resin, wherein a weight-to-volume ratio of the carbon nanotubes to the alcohol is 0.5-200 milligrams of carbon nanotubes per 100 milliliters of alcohol and wherein a weight ratio of the polyvinyl acetal resin to the carbon nanotubes is between 0.5 and 2.