Composite material containing microwave susceptor material

Claim 2

A composite flexible packaging film material for controlled generation of heat by absorption of microwave energy so as to generate additional heat for food packaged by said film during transmission of said microwave energy by said film material during microwave cooking of said food, comprising (a) a dielectric substrate substantially transparent to microwave radiation, and (b) a coating on at least one surface of the substrate comprising (i) about 5 to 80% by weight of metal or metal alloy susceptor in flake form, and (ii) about 95 to 20% by weight of a thermoplastic dielectric matrix, said flakes being dispersed in said dielectric matrix so that they are substantially insulated from each other, wherein the surface weight of said coating on the substrate is in the range of about 2.5 to 100 g/m 2 D.C. surface resistance of the resulting composite material is at least 1×10 6 ohms per square.

Claim 3

A composite of claim 1 where the coating contains about 25 to 80% by weight of metal or metal alloy susceptor and about 75 to 20% by weight of a thermoplastic dielectric matrix.

Claim 4

A composite of claim 1 or 2 where the dielectric substrate is a polyester copolymer selected from the group consisting of copolymers of ethylene glycol, terephthalic acid and azelaic acid, copolymers of ethylene glycol, terephthalic acid and isophthalic acid, or mixtures of said copolymers.

Claim 5

A composite of claim 1 or 2 where the susceptor is aluminum.

Claim 6

A composite of claim 1 where the dielectric substrate is polyethylene terephthalate film, and the coating on at least one surface thereof comprises 30 to 60% by weight aluminum flake and 70 to 40% by weight of a copolymer of ethylene glycol with terephthalic acid and either isophthalic acid or azelaic acid or mixture of such copolymers.

Claim 7

A packaging material comprising a composite of claim 1 or 2 laminated to a second dielectric substrate substantially transparent to microwave radiation.

Claim 8

A packaging material of claim 6 where the second dielectric substrate is a polyester film or paper.

Claim 9

A composite of claim 1 or 2 capable of heating to a temperature of about 150° C. or higher when subjected to microwave energy of 550 watts at 2450 megahertz for a period of 120 seconds.

Claim 10

A composite of claim 1 or 2 capable of heating to a temperature of about 190° C. or higher when subjected to microwave energy of 550 watts at 2450 megahertz for a period of 120 seconds.

Claim 11

A composite of claim 1 where the susceptor comprises a circular flake having an ellipticity in the range of about 1:1 to 1:2.

Claim 12

A composite of claim 10 where the susceptor comprises an aluminum flake.

Claim 13

A composite of claim 11 where the susceptor comprises about 40 to 70 % by weight of the coating.

Claim 14

A composite of claim 1 where the susceptor comprises an oblong flake having an ellipticity greater than 1:2.

Claim 15

A composite of claim 13 where the susceptor comprises an aluminum flake.

Claim 16

A composite of claim 14 where the susceptor comprises about 20 to 60 % by weight of the coating.

Claim 17

A composite of claim 1 where the coating comprises at least two layers and the direction of alignment of susceptor flakes in at least one of said layers is oriented at about ninety degrees to the direction of alignment of susceptor flakes in at least one other of said layers.

Claim 18

A composite of claim 16 where the susceptor is an oblong flake having an ellipticity greater than 1:2.

Claim 19

A composite of claim 1, samples of which when exposed to a microwave electric field of 243 V/cm for four minutes, said electric field parallel to the longitudinal direction of the composite in half of said samples and said electric field parallel to the cross direction of the composite in half of said samples, meet the following requirements: (1) MD and TD are each within Temp±5%; (2) Each MD Temperature is within MD±10%, and (3) Each TD Temperature is within TD±10%, where MD Temperature is the temperature for any sample exposed with said electric field direction parallel to the longitudinal direction of the composite and MD is the mean temperature of all of such samples; TD Temperature is the temperature for any sample exposed with said electric field direction parallel to the cross direction of the composite and TD is the mean temperature of all of such samples; and Temp is the mean of all MD Temperatures and TD Temperatures, all temperatures being in Centigrade and measured after four minutes exposure to the microwave electric field.

Claim 20

A method for making a composite of claim 1 comprising applying a plurality of thin, dilute coats of a dispersion of susceptor and thermoplastic matrix in a suitable solvent to the dielectric substrate.

Claim 21

The method of claim 19 in which said thin, dilute coats are applied in a manner so that the direction of alignment of susceptor flakes in at least one said coat is oriented at about ninety degrees to the direction of alignment of susceptor flakes in at least one other of said coats.

Claim 22

A composite of claim 10, 13, 16 or 18 capable of heating to a temperature of about 150 degrees C. or higher when subjected to microwave energy of 550 watts at 2450 Mhz for a period of 120 seconds.

Claim 23

A composite of claim 10, 13, 16 or 18 capable of heating to a temperature of about 190 degrees C. or higher when subjected to microwave energy of 550 watts at 2450 Mhz for a period of 120 seconds.

Claim 24

In combination with food for microwave cooking, a flexible film packaging for said food incorporating composite film material for controlled generation of heat by absorption of microwave energy so as to generate additional heat for said food during transmission of said microwave energy by said composite film material for microwave cooking of said food, said composite film material comprising (a) a dielectric substrate substantially transparent to microwave radiation, and (b) a coating on at least one surface of the substrate comprising (i) about 5 to 80% by weight of metal or metal alloy susceptor in flake form, and (ii) about 95 to 20% by weight of a thermoplastic dielectric matrix, said flakes being dispersed in said dielectric matrix so that they are substantially insulated from each other, wherein the surface weight of said coating on the substrate is in the range of about 2.5 to 100 g/m 2 .

Claim 25

In combination with food for microwave cooking, a flexible film packaging for said food incorporating composite film material for controlled generation of heat by absorption of microwave energy so as to generate additional heat for said food during transmission of said microwave energy by said composite film material for microwave cooking of said food, said composite film material comprising (a) a dielectric substrate substantially transparent to microwave radiation, and (b) a coating on at least one surface of the substrate comprising (i) about 5 to 80% by weight of metal or metal alloy susceptor in flake form, and (ii) about 95 to 20% by weight of a thermoplastic dielectric matrix, said flakes being dispersed in said dielectric matrix so that they are substantially insulated from each other, wherein the surface weight of said coating on the substrate is in the range of about 2.5 to 100 g/m 2 .

Claim 26

In combination with food for microwave cooking, a composite flexible packaging film material for controlled generation of heat by absorption of microwave energy so as to generate additional heat for food packaged by said film during transmission of said microwave energy by said film material during microwave cooking of said food, comprising (a) a dielectric substrate substantially transparent to microwave radiation, and (b) a coating on at least one surface of the substrate comprising (i) about 5 to 80% by weight of metal or metal alloy susceptor in flake form, and (ii) about 95 to 20% by weight of a dielectric matrix, said flakes being dispersed in said dielectric matrix so that they are substantially insulated from each other, wherein the surface weight of said coating on the substrate is in the range of about 2.5 to 100 g/m 2 .

Claim 27

In combination with food for microwave cooking, a composite flexible packaging film material for controlled generation of heat by absorption of microwave energy so as to generate additional heat for food packaged by said film during transmission of said microwave energy by said film material during microwave cooking of said food, comprising (a) a dielectric substrate substantially transparent to microwave radiation, and (b) a coating on at least one surface of the substrate comprising (i) about 5 to 80% by weight of metal or metal alloy susceptor in flake form, and (ii) about 95 to 20% by weight of a dielectric matrix, said flakes being dispersed in said dielectric matrix so that they are substantially insulated from each other, wherein the surface weight of said coating on the substrate is in the range of about 2.5 to 100 g/m 2 .

Claim 28

A composite material for controlled generation of heat by absorption of microwave energy during transmission of said microwave energy, comprising (a) a dielectric substrate substantially transparent to microwave radiation, and (b) a coating on at least one surface of the substrate comprising (i) about 25 to 80% by weight of metal or metal alloy susceptor in flake form, and (ii) about 75 to 20% by weight of a dielectric matrix, said flakes being dispersed in said dielectric matrix so that they are substantially insulated from one another, wherein the surface weight of said coating on the substrate is in the range of about 2.5 to 100 g/m 2 .

Claim 29

A composite material for controlled generation of heat by absorption of microwave energy during transmission of said microwave energy, comprising (a) a dielectric substrate substantially transparent to microwave radiation, and (b) a coating on at least one surface of the substrate comprising (i) about 25 to 80% by weight of metal or metal alloy susceptor in flake form, and (ii) about 75 to 20% by weight of a dielectric matrix, said flakes being dispersed in said dielectric matrix so that they are substantially insulated from one another, wherein the surface weight of said coating on the substrate is in the range of about 2.5 to 100 g/m 2 .

Claim 30

A composite of claim wherein said dielectric substrate is paper.

Claim 31

In the combination of claim 23 wherein said dielectric substrate is paper.

Claim 32

In the combination of claim 24 wherein said dielectric substrate is paper.

Claim 33

The composite of claim 25 wherein said dielectric substrate is paper.