Claims
- 1. A paper bag food container which can be placed in a microwave oven to heat the food therein comprising a greaseproof inner bag to hold said food, a paper outer beg surrounding and adhesively attached to said inner bag, and a heating element comprising a coating of a microwave reactive composition of a finely divided microwave reactive metal, carbon black, powdered inert solid material and a dielectric binder applied directly to the inner surface of the outer beg and adhesively attached to the outer surface of the inner bag.
- 2. A paper food container as defined in claim 1 wherein the inner bag comprises a polyester film.
- 3. A paper food container as defined in claim 1 wherein the inner bag is formed of a polyester film.
- 4. A paper food container as defined in claim 1 wherein the inner bag is formed of greaseproof paper.
- 5. A food container according to claim 1 wherein the metal is aluminum.
- 6. A food container according to claim 1 wherein the dielectric binder is a water based latex emulsion.
- 7. A food container according to claim 1 wherein the powdered inert solid material is clay.
- 8. A food container according to claim 1 wherein the powdered inert solid material is silica.
- 9. A food container according to claim 1 wherein the heating element on the inner surface of the outer bag is applied in the form of a grid pattern wherein the area covered by the microwave reactive coating composition forming the pattern is within the range of 35 to 80 percent of the total area of the heating element.
- 10. A food container according to claim 9 wherein the area covered by the microwave reactive coating composition of the grid pattern is approximately equal to the uncoated area contained within the grid pattern.
Parent Case Info
This is a continuation of application Ser. No. 07/368,568, filed June 20, 1989 now abandoned.
This invention relates to a package for foods in which the contents may be heated by microwave radiation. In one of its more specific aspects, this invention relates to a food package for raw, cooked, or partially cooked foods and shortening, e.g. butter or oil, hydrogenated oil, normally solid vegetable oil, animal fat, and the like. In another of its more specific aspects, this invention relates to a package for corn kernels and oil or shortening which includes a microwave responsive heating element. A preferred embodiment comprises a composite package or bag comprising an inner liner or and a paper outer container or bag having a microwave responsive heating element on an outer surface of the inner liner or on the outer or inner surface of the outer container.
Numerous containers, including paper or plastic boxes and bags, have been devised for use as packages for foods which are suitable also as utensils for heating or cooking the food in a microwave oven. Many such containers are referred to in European Patent Application Publication Number 256,791, incorporated herein by reference. Some of the prior art containers comprise a heating element which is highly responsive to microwave radiation to produce a more highly elevated temperature in one or more selected areas of the container than that in the rest of the container. One type of heating element comprises metal particles, usually aluminum, vacuum deposited on a polyester film; the metallized film is then laminated onto paper or paperboard. The thus metallized paper or paperboard can then be used in a microwave oven to heat, brown or sear food items placed on the metallized paperboard or in packages comprising metallized paperboard. While such structures can be very effective as heaters, the vacuum deposition process does not readily lend itself to coating selected areas of the film or the application of varying amounts of metal particles or metallized coating to selected areas of the finished carton or structure.
Other methods of forming microwave responsive heating elements involve dispersing particles which are microwave energy absorbers, e.g. carbon, metals, and metal alloys, in a binder and forming a sheet or laminate comprising the dispersed particles. Turpin, U.S. Pat. No. 4,190,757 discloses heaters which comprise a layer of particulate lossy materials, e.g. carbon, iron and various metal oxides, or alloys, in an inorganic binder, e.g. sodium silicate. U.S. Pat. No. 4,264,668 to Balla discloses a heating element made up of a layer of carbon black in an acrylate binder laminated between a carrier layer, e.g. paper, cardboard or plastic material, and an outer layer of thermoplastic material. European Patent Application Publication No. 242,952 discloses a heating element made up of a metal or metal alloy in flake form in a thermoplastic dielectric matrix on a dielectric substrate.
The present invention provides an improved food package comprising a microwave interactive composition coated or printed on paper, polyester or paperboard forming a part of the package.
One preferred embodiment of the present invention includes a multi-layered bag comprising an inner bag or liner of greaseproof paper or polyester film and an outer bag of paper with an integral microwave heating element on the outer surface of the inner bag or on the outer or inner surface of the outer bag. The microwave heating element is made up of a microwave reactive coating applied directly, suitably by a conventional coating or printing process, on a selected surface of the bag or on a suitable substrate. In a preferred embodiment of the invention the microwave reactive coating is applied to the inner surface of the outer bag or container. Alternatively, the microwave reactive coating may be applied directly to the outer surface of the inner or outer bag or container. A preferred microwave interactive coating composition is that disclosed in the commonly assigned copending U.S. patent application of Kenneth A. Pollart et al, Ser. No. 07/239,544, incorporated herein by reference. A preferred coating composition comprises carbon black, at least one finely divided metal or metal oxide, clay, and a dielectric solid organic binder in a carrier liquid.
US Referenced Citations (15)
Foreign Referenced Citations (2)
| Number |
Date |
Country |
| 0242952 |
Oct 1987 |
EPX |
| 0256791 |
Feb 1988 |
EPX |
Continuations (1)
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Number |
Date |
Country |
| Parent |
368568 |
Jun 1989 |
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Patent Grant
4982064
