Carbon nanotube dispersion and utilization of same

• US 9,181,090 B2
• Filed: 02/08/2008
• Issued: 11/10/2015
• 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
• Primary Examiner(s): Wu, David W
• Assistant Examiner(s): REDDICK, MARIE L
• Application Number:
  US12/866,548
• Publication Number:
  US 20100330358A1
• Time in Patent Office: 2,832 Days
• Field of Search: 524/379, 524/557
• US Class Current: 1/1
• 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 butyral resin, 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 butyral resin to the carbon nanotubes is between 0.5 and 2 and

the polyvinyl butyral resin exhibits a solution viscosity of 5 mPa·

s to 30 mPa·

s at 20°

C. when dissolved at a concentration of 10% by weight in a mixed solvent consisting of ethanol and toluene at a volume ration of 1;

1.

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 2, wherein the polyvinyl butyral resin has a degree of polymerization of 150 to 600 and a degree of butyralization 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.

4. The dispersion according to claim 3, 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.

5. A carbon nanotube film obtained by applying the carbon nanotube dispersion according to claim 4 onto a substrate.

6. 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.

7. The dispersion according to claim 1, wherein:

the polyvinyl butyral resin also satisfies at least one of the following conditions (iii)-(v);

(iii) it has 20 mol% to 35 mol% of hydroxyl groups;

(iv) it has a degree of butyralization of 65 mol% to 80 mol%;

(v) it has 5 mol% or less of acetyl groups.

8. The dispersion according to claim 7, wherein the polyvinyl butyral resin satisfies all three conditions (iii)-(v).

9. The dispersion according to claim 1, wherein the polyvinyl butyral resin has a degree of butyralization of 65 mol% to 80 mol%.

10. The dispersion according to claim 1, wherein:

the polyvinyl butyral resin exhibits a solution viscosity of 9 mPa·

s to 15 mPa·

s at 20°

C. when dissolved at a concentration of 10% by weight in a mixed solvent consisting of ethanol and toluene at a volume ratio of 1;

1; and

the polyvinyl butyral resin also satisfies the following conditions (vi)-(viii);

(vi) it has 20 mol% to 35 mol% of hydroxyl groups;

(vii) it has a degree of butyralization of 71±

3 mol%; and

(viii) it has 2 mol% to 5 mol% of acetyl groups.

11. The dispersion according to claim 10, wherein the weight-to-volume ratio of the carbon nanotubes to the alcohol is 1-10 milligrams of carbon nanotubes per 100 milliliters of alcohol.

12. The dispersion according to claim 11, wherein the liquid medium consists of ethanol and polyvinyl butyral resin.

13. 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.

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

15. 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 butyral 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 butyral resin to the carbon nanotubes is between 0.5 and 2 and the dispersion treatment includes at least stirring and application of ultrasound; and

the polyvinyl butyral resin exhibits a solution viscosity of 5 mPa·

s to 30 mPa·

s at 20°

C. when dissolved at a concentration of 10% by weight in a mixed solvent consisting of ethanol and toluene at a volume ratio of 1;

1.

16. The method according to claim 15, 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.

17. A method according to claim 16, wherein the alcohol solvent at least substantially comprises an alcohol having 1 to 4 carbon atoms, the polyvinyl butyral resin has a degree of polymerization of 150 to 600 and a degree of butyralization 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.

18. A method according to claim 17, wherein the alcohol is selected from ethanol, methanol and 2-proponal.

19. A carbon nanotube film obtained by applying the dispersion produced according to the method described in claim 15 onto a substrate.

20. A liquid dispersion comprising carbon nanotubes dispersed in a liquid medium, wherein the liquid medium comprises at least one alcohol and at least one polyvinyl butyral resin, 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 a weight ratio of the polyvinyl butyral resin to the carbon nanotubes is between 0.5 and 2 and

the polyvinyl butyral resin exhibits a solution viscosity of 5 mPa·

s to 30 mPa·

s at 20°

C. when dissolved at a concentration of 10% by weight in a mixed solvent consisting of ethanol and toluene at a volume ratio of 1;

1.