Flexible packaging sheets

A flexible laminate including at least three layers suited for wrapping, packaging and shipping food articles that are to be heated in a microwave oven comprising a base sheet composed of microwave transparent flexible sheet material coated on at least one surface thereof with a layer of microwave interactive coupling material which becomes hot when exposed to microwave energy and being susceptible to melting, shrinking, warping and/or sriveling when exposed to microwave energy, said base sheet being positioned on a selected portion of the laminate to achieve heating of said food product through conduction of heat from the layer of microwave interactive coupling material to the food product in a selected area where the coupling material is located while other portion of the laminate remain unheated when exposed to microwave energy, and two layers of dimensionally stable flexible backing sheet material, one such backing sheet being bonded to each side of the base sheet to form a sandwich structure in which the base sheet is encapsulated and dimensionally stabilized by the enclosing flexible backing sheets on each side thereof, said backing sheets being composed of non-thermoplastic fibers that assist in preserving the integrity, dimensions and shape of the base sheet when the base sheet is exposed to microwave energy and heat being transferred from the base sheet through one of the dimensionally stable fibrous backing sheets to the food product by thermal conduction without disturbing the fibrous structure thereof.

A flexible laminate to be used in a packaging container for food articles that are to be heated in a microwave oven, said laminate comprising,

• (1) an enclosed layer of microwave interactive coupling material comprising a lossy composition which becomes hot anmd is itself susceptible to scorching or shriveling when exposed to microwave energy in a microwave oven,
• (2) said interactive layer being positioned within a selected part of the laminate to achieve heating of the food product through conduction of heat from the layer of microwave interactive coupling material to the food product in a selected area where the coupling material is located while other portions of the laminate remain unheated when exposed to microwave energy,
• (3) said laminate being formed into a container having a top and a bottom and side walls and said and said interactive layer being incorporated into one wall of the container adapted to support the food product during heating whereby the food product rests upon the laminate above the interactive layer in a heat conductive relationshop therewith,
• (4) a backing layer of flexible sheet material bonded to each side of the microwave interactive layer to form a sandwich structure in which the microwave interactive layer is encapsulated and dimensionally stabilized by the enclosing flexible backing sheets on each side thereof,
• (5) said backing sheets being composed of microwave transparent sheet material wherein at least one of the backing sheets is composed of nonthermoplastic fibers that assist in preserving the integrity, dimensions and shape of the microwave interactive layer when the laminate is exposed to microwave energy and
• (6) whereby during heating in a microwave oven, heat is transferred from the microwave interactive layer through one of the backing sheets to the food product by thermal conduction to thereby carry heat into the surface of the food from the interactive layer without damaging portions of the sheet material remote from the food.