Electrochemical heat source

• US 5,538,020 A
• Filed: 06/22/1994
• Issued: 07/23/1996
• Est. Priority Date: 06/28/1991
• Status: Expired due to Term

• Current Assignee: R J Reynolds Tobacco Company (R. J. Reynolds Tobacco)
• Original Assignee: R J Reynolds Tobacco Company (R. J. Reynolds Tobacco)
• Inventors: Sensabaugh, Andrew J. Jr., Ridings, Henry T., Banerjee, Chandra K., Lehman, Richard L., Chiou, Joseph J., Farrier, Ernest G.
• Primary Examiner(s): Seidleck, James J.
• Assistant Examiner(s): Truong, Duc
• Application Number:
  US08/263,618
• Time in Patent Office: 762 Days
• Field of Search: 131/194, 131/359, 131/369
• US Class Current: 131/369
• CPC Class Codes: A24B 15/165 comprising as heat source a carbon fuel or an oxidized or thermally degraded carbonaceous fuel, e.g. carbohydrates, cellulosic material
• CPC Class Codes: A24B 15/24 by extraction; Tobacco extracts
• CPC Class Codes: A24F 42/10 Devices with chemical heating means
• CPC Class Codes: A24F 42/80 Manufacture

Abstract

Electrochemical heat sources, materials used to make electrochemical heat sources and methods of forming electrochemical heat sources are disclosed. The electrochemical heat sources includes at least two metallic agents capable of interacting electrochemically with one another, such as magnesium and iron or nickel. The metallic agents may be provided in a variety of forms, including a frozen melt, a bimetallic foil, wire of a first metal wrapped around strands of a different metal, and a mechanical alloy. The metallic agents may be in the form of a powder filling a straw, or small particles extruded with a binder or pressed to form a rod. The powder filled straw or rod may be placed in a heat chamber surrounded by tobacco in a smoking article. An electrolyte solution contacts the metallic agents in the heat chamber to initiate the electrochemical interaction, generating heat which in turn may be used to volatilize nicotine and flavor materials in the tobacco. The heat sources may also be used to heat foods or beverages, in hand warmers, and to heat equipment or materials.

Claims

1. A method of making a controlled-rate electrochemical heat source comprising the steps of:

a) providing particles comprising an anode material and a cathode material combined in a form useful as an electrochemical heat source;

b) contacting said particles with an aqueous electrolyte solution and allowing the particles to electrochemically react to utilize a limited portion of the anode material;

c) stopping the electrochemical reaction in a partially completed state; and

d) utilizing the partially reacted particles to make the controlled-rate electrochemical heat source.

2. The method of claim 1 wherein the particles of step b) are contacted by a limited amount of the electrolyte solution and wherein the step of stopping the electrochemical reaction comprises allowing the particles to heat up, the heat driving off water in the electrolyte solution.

3. The method of claim 1 wherein the anode material comprises magnesium and the cathode material comprises either nickel or iron.

4. The method of claim 1 wherein the partially reacted particles are mixed with unreacted particles to form the electrochemical heat source.

5. An electrochemical heat source made by the method of claim 4.

6. The method of claim 1 wherein the step b) of utilizing a portion of the anode material increases the electrical resistance of the partially reacted particles and thereby slows the rate of reaction for the partially reacted particles when used in the heat source.

7. The method of claim 1 wherein the particles primarily comprises particles between 50 and 80 U.S. mesh and about 10% to about 20% of the particles have a size between 80 and 140 U.S. mesh.

8. An electrochemical heat source comprising:

a) a heat source body comprising at least two metallic agents capable of interacting electrochemically with one another when contacted by an aqueous electrolyte solution and

b) an absorbent outerwrap placed around the heat source body on which steam generated by the electrochemical reaction can condense.

9. The electrochemical heat source of claim 8 wherein the at least two metallic agents comprise magnesium and either nickel or iron.

10. An electrochemical heat source comprising:

a) at least two metallic agents capable of interacting electrochemically with one another when contacted by an aqueous electrolyte solution and

b) a boiling modifier which does not react with the metallic agents and which is capable of preventing water in the solution from boiling at temperatures produced by the heat source.

11. The electrochemical heat source of claim 10 wherein the boiling modifier is selected from the group consisting of glycerin, triethylene glycol, 1-3-propane diol and mixtures thereof.

12. The electrochemical heat source of claim 10 wherein the at least two metallic agents comprise magnesium and either nickel or iron.

13. An electrochemical heat source comprising:

a) at least two metallic agents capable of interacting electrochemically with one another to produce hydrogen when contacted by an aqueous electrolyte solution; and

b) an oxidizing agent suitable for oxidizing said hydrogen at temperatures produced by the heat source.

14. The electrochemical heat source of claim 13 wherein the oxidizing agent is selected from the group consisting of calcium nitrate, sodium nitrate, sodium nitrite and mixtures thereof.

15. The electrochemical heat source of claim 13 wherein the oxidizing agent is encapsulated to minimize its contact with the metallic agents prior to reaction of the metallic agents with the electrolyte solution.

16. The electrochemical heat source of claim 13 wherein the at least two metallic agents comprise magnesium and either nickel or iron.

17. An electrochemical heat source comprising:

a) at least two metallic agents capable of interacting electrochemically with one another when contacted by an aqueous electrolyte solution and

b) a phase change material mixed with said metallic agents in said heat source and capable of absorbing heat produced by the electrochemical reaction by changing phases and releasing said heat later by change back to its original phase.

18. The electrochemical heat source of claim 17 wherein the phase change material is selected from the group consisting of sugars, waxes and mixtures thereof.

19. The electrochemical heat source of claim 17 wherein the at least two metallic agents comprise magnesium and either nickel or iron.

20. An electrochemical heat source comprising:

a) at least two metallic agents capable of interacting electrochemically with one another when contacted by an aqueous electrolyte solution and

b) an acid capable of maintaining the pH of the electrolyte solution below a point where the electrochemical reaction is impeded.

21. The electrochemical heat source of claim 20 wherein the at least two metallic agents comprise magnesium and the acid is effective to maintain the pH of the electrolyte below a pH of about 11.5.

22. The electrochemical heat source of claim 20 wherein the acid is selected from the group consisting of malic acid, citric acid, lactic acid and mixtures thereof.

23. The electrochemical heat source of claim 20 wherein the acid is provided in a solution with the electrolyte.

24. The electrochemical heat source of claim 20 wherein the acid is provided on a solid support to provide a controlled source of hydrogen ions.

25. The electrochemical heat source of claim 20 wherein the acid is in the form of a solid mixed with the electrolyte solution to form a slurry.

26. The electrochemical heat source of claim 20 wherein the at least two metallic agents comprise magnesium and either nickel or iron.

27. An electrochemical heat source comprising:

a) at least two metallic agents capable of interacting electrochemically with one another when contacted by an aqueous electrolyte solution, the at least two metallic agents being formed into an elongated shape with side portions of substantially greater surface area than the end portions, and

b) a porous wick disposed around the periphery of the electrochemical heat source so as to contact all of said side portions, the wick being capable of distributing the electrolyte solution from a source of said solution to portions of the heat source distant from said solution source.

28. The electrochemical heat source of claim 27 wherein the porous wick comprises an absorbent paper.

29. The electrochemical heat source of claim 27 wherein the elongated shape comprises a cylinder and the side portions comprise rounded surfaces of the cylinder.

30. The electrochemical heat source of claim 27 wherein the at least two metallic agents comprise magnesium and either nickel or iron.

31. A method of operating an electrochemical heat source wherein the heat source comprises at least two metallic agents capable of interacting electromechanically with one another, the method comprising the steps of:

a) contacting the metallic agents with an aqueous electrolyte;

b) vaporizing water from the electrolyte by heat generated by the electrochemical reaction; and

c) condensing at least a portion of the water vapor so produced on an absorbent material which also acts as a wick to return said condensed water vapor to the electrolyte.