Self limiting microwave heaters
First Claim
1. A self-limiting dispersion of a conductive material in a binder where said conductive material consists essentially of a carbon material having a structure selected to have a percolation threshold when dispersed in said binder at a concentration of from about 10 weight percent to about 45 weight percent in said binder, said binder comprising a thermoplastic material selected to go through a first order phase transition or a second order phase transition at a temperature from about 300°
- F. to about 480°
F. and said dispersion being near the percolation threshold so that its electrical conductivity drops at least about 1.5 orders of magnitude when above the binder phase transition temperature wherein said conductive material combined with said binder has a surface resistivity ranging from about 25 ohms per square to about 100,000 ohms per square at room temperature.
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Accused Products
Abstract
A self-limiting dispersion of a conductive material in a binder is disclosed wherein the conductive material consists essentially of a carbon material having a structure selected to undergo percolation when dispersed in the binder at a concentration of from about 10 weight percent to about 45 weight percent. The binder comprises a thermoplastic material selected to go through a first order phase transition or a second order transition at a temperature from about 300° F. to about 480° F. and the dispersion is formulated near the conductance percolation threshold so that its electrical conductivity drops precipitously (e.g., at least about 1.5 orders of magnitude) above the binder transition temperature. The dispersion of the conductive material in the binder is especially suitable for use as a self-limiting microwave heater material which is either a molding composition, or surface coating composition, and especially a composition that can be applied to a substrate by printing.
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Citations
52 Claims
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1. A self-limiting dispersion of a conductive material in a binder where said conductive material consists essentially of a carbon material having a structure selected to have a percolation threshold when dispersed in said binder at a concentration of from about 10 weight percent to about 45 weight percent in said binder, said binder comprising a thermoplastic material selected to go through a first order phase transition or a second order phase transition at a temperature from about 300°
- F. to about 480°
F. and said dispersion being near the percolation threshold so that its electrical conductivity drops at least about 1.5 orders of magnitude when above the binder phase transition temperature wherein said conductive material combined with said binder has a surface resistivity ranging from about 25 ohms per square to about 100,000 ohms per square at room temperature. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 52)
- F. to about 480°
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19. An article of manufacture comprising a self-limiting microwave heater wherein said heater comprises a film of a self-limiting dispersion of a conductive material in a binder, where said conductive material consists essentially of a carbon material having a structure selected to have a percolation threshold when dispersed in said binder at a concentration of from about 10 weight percent to about 45 weight percent in said binder, said dispersion being near the percolation threshold so that its electrical conductivity drops at least about 1.5 orders of magnitude when above the binder phase transition temperature, wherein said conductive material consists essentially of carbon black or graphite having a nitrogen absorption surface area of from about 5 to about 160 m2 /g, a DBP absorption number of from about 30 to about 150 cc/100 gm, and an average particle diameter of from about 15 to about 100 nm, said binder comprising a thermoplastic material selected to go through a first order phase transition or a second order phase transition at a temperature of from about 300°
- F. to about 480°
F. when exposed to microwave radiation, said film being from about 0.1 mils to about 10 mils thick. - View Dependent Claims (20, 21, 22)
- F. to about 480°
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23. An article of manufacture for heating food by microwave energy comprising a self-limiting dispersion of a conductive material in a binder where said conductive material consists essentially of a carbon material having a structure selected to have a percolation threshold when dispersed in said binder at a concentration of from about 10 weight percent to about 45 weight percent in said binder, said binder comprising a thermoplastic material selected to go through a first order phase transition or a second order phase transition at a temperature from about 300°
- F. to about 480°
F., said dispersion being near the percolation threshold so that its electrical conductivity drops at least from about 1.5 to about 2 orders of magnitude when above the binder phase transition temperature, wherein said conductive material combined with said binder has a surface resistivity ranging from about 25 ohms per square to about 100,000 ohms per square at room temperature. - View Dependent Claims (24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41)
- F. to about 480°
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42. A method of heating food comprising applying microwave energy to an article of manufacture where said article of manufacture comprises a self-limiting dispersion of a conductive material in a binder where said conductive material consists essentially of a carbon material having a structure selected to have a percolation threshold when dispersed in said binder at a concentration of from about 10 weight percent to about 45 weight percent in said binder, wherein said conductive material consists essentially of carbon black or graphite having a nitrogen absorption surface area of from about 5 to about 160 m2 /g, a DBP absorption number of from about 30 to about 150 cc/100 gm, and an average particle diameter of from about 15 to about 100 nm, said binder comprising a thermoplastic material selected to go through a first order phase transition or a second order phase transition at a temperature of from about 300°
- F. to about 480°
F. when exposed to microwave radiation, said food being operatively associated with said article of manufacture, said microwave energy being sufficient to raise the temperature of said article of manufacture from about 300°
F. to about 480°
F. - View Dependent Claims (43, 44, 45, 46, 47, 48, 49, 50, 51)
- F. to about 480°
Specification