Method for manufacture of and a foil for enclosing or wrapping a product to be heated in an oven

Abstract

A method of manufacturing a foil for enclosing or wrapping a product configured to be heated in an oven includes: providing an aluminium layer, applying a first ink material at a surface of the aluminium layer to form a first ink layer, and applying a second ink material at a surface of the first ink layer to form a second ink layer. The first ink layer is positioned between the aluminium layer and the second ink layer, and is configured to absorb radiant energy. The second ink layer is configured to allow radiant energy to pass through to reach the first ink layer. A binder system of the first ink material or the second ink material is based at least in part on polyvinyl butyral (PVB).

Claims

1. A method of manufacturing a foil for enclosing or wrapping a product configured to be heated in an oven, comprising: providing an aluminium layer; applying a first ink material at a surface of the aluminium layer to form a first ink layer; applying a second ink material at a surface of the first ink layer to form a second ink laver, the first ink layer being positioned between the aluminium layer and the second ink layer, wherein the first ink layer is configured to absorb radiant energy, and the second ink layer is configured to allow the radiant energy to pass through to the first ink layer, wherein the second ink layer is an outermost ink layer of the foil, and wherein a binder system of the first ink material and the second ink material is based at least in part on polyvinyl butyral (PVB); and applying a hardener to the second ink layer, wherein the hardener migrates from the second ink layer to the first ink layer based at least in part on the first ink layer including PVB.

2. The method according to claim 1, wherein the first ink layer or the second ink layer is applied with a respective dry areal density or grammage of 1.5-5 grams per square meter (g/m.sup.2), or a respective dry thickness of the first or the second ink layer is less than 5.9 microns (μ).

3. The method according to claim 1, wherein flow time, measured according to International Organization for Standardization (ISO) 2431:2011, of the first or the second ink material before or during application is 35-100 seconds (s) measured with flow cup no. 3 or 30-45 (s) measured with flow cup no. 4, or the kinematic viscosity of the first or the second ink material before or during application is 10-55 square millimeter per second (mm.sup.2/s).

4. The method according to claim 1, wherein the first ink material or the second ink material is diluted with ethyl acetate or propyl acetate or another acetate.

5. The method according to claim 1, wherein the first ink material comprises carbon black.

6. The method according to claim 1, wherein the second ink layer comprises titanium dioxide.

7. The method of claim 1, further comprising: providing the oven configured to transmit radiant energy, at least partly enclosing an object with the foil, and positioning the object within the oven.

8. The method of claim 1, further comprising: applying a third ink material at an opposite surface of the aluminium layer to form a third ink layer, wherein the opposite surface of the aluminium layer is opposite the surface of the aluminium layer where the first ink layer is applied; and applying a fourth ink material at a surface of the third ink layer to form a fourth ink layer, the third ink layer positioned between the aluminium layer and the fourth ink layer, wherein the first ink layer and the third ink layer are configured to absorb radiant energy, and the second ink layer and the fourth ink layer are configured to allow the radiant energy to pass through them.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In the enclosed schematic drawings, which show non-binding examples of embodiments of the present disclosure,

(2) FIG. 1 is an enlarged side view or cross sectional view of a first embodiment of a foil according to the present disclosure,

(3) FIG. 2 is a view similar to that of FIG. 1 illustrating movement of heat energy within the foil,

(4) FIG. 3 is an view similar to that of FIG. 1 of a second embodiment of a foil according to the present disclosure, and

(5) FIG. 4 is a cross sectional view of an embodiment of a packaging according to the disclosure comprising the foil illustrated in FIG. 3.

DETAILED DESCRIPTION

(6) FIGS. 1 and 2 show a first embodiment of a foil according to the present disclosure, the foil 1 being suitable for enclosing or wrapping a product to be heated in an oven.

(7) The foil 1 has been manufactured by an embodiment of the method according to the disclosure comprising the steps of: providing an aluminium layer 2 comprising aluminium, applying a first ink material at a surface of the aluminium layer 2 to form a first ink layer 3, and applying a second ink material at a surface of the first ink layer 3 to form a second ink layer 4, the first ink layer 3 thereby being positioned between the aluminium layer 2 and the second ink layer 4, the first ink layer 3 being adapted for absorbing radiant energy, the second ink layer 4 being adapted for allowing radiant energy to pass through it so as to reach the first ink layer, wherein a binder system of the first and/or second ink material is based on PVB (polyvinyl butyral).

(8) The aluminium layer 2 is in contact with the first ink layer 3, and the first ink layer 3 is in contact with the second ink layer 4.

(9) In the method of manufacture of the foil 1 the aluminium layer 2 is first provided as an aluminium foil that is rolled off of a roll. The aluminium layer substantially consists of aluminium. The first ink layer 3 is then applied on the surface of the aluminium layer 2 after which the second ink layer 4 is applied on the surface of the first ink layer 3.

(10) After application of the ink layers 3, 4, the ink layers 3, 4 are allowed to dry and/or harden for about 48 hours.

(11) FIG. 2 illustrates an “internal reflection” effect that occurs or may occur inside the foil 1. It is noted that this explanation is a theory and the applicant does not intend to be bound by this theory. The straight arrow in FIG. 2 illustrates a first portion of radiant heat radiating on the second ink layer 4 from an outside on an outer surface thereof from an inner oven surface. As shown, this first portion passes through the second ink layer 4, another portion being reflected on and yet another portion being absorbed in the second layer 4. As also shown, this first portion reaches and is at least partly absorbed as heat energy in the first ink layer 3, the first ink layer conducting at least part of this heat energy to the aluminium layer 2 (not illustrated). Additionally, the first ink layer 3 allows a second portion of the radiant energy to pass through the first ink layer 3 so as to reach the aluminium layer 3. A (relatively small) portion of this second portion is absorbed as heat energy in the aluminium layer, and a third portion is reflected by the aluminium layer 2, the latter being shown as the first half of the bent arrows in FIG. 2. A portion of this third portion may again be absorbed as heat energy in the first ink layer 3, a portion of which again being conducted to the aluminium layer 2 as heat energy. A fourth portion of the radiant energy continues through the first ink layer 3 to reach an inner surface of the second ink layer 4 where a fifth portion is reflected by the second ink layer 4, this being illustrated by the second half of the bent arrows. A portion of this fifth portion is then again absorbed in the first ink layer 3, and a sixth portion of the radiant heat continues to reach the aluminium layer 2, which again may absorb a portion and reflect a portion, and the process may continue again as described above. From the first ink layer 3 the heat energy absorbed in the first ink layer 3 is conducted to the aluminium layer 2, this conduction being illustrated by the waves in the aluminium layer 2 in FIG. 2. Hereby, a comparably large portion of the radiant energy radiating on the second ink layer 4 is absorbed as heat energy in the foil 1, specifically in the aluminium layer 2 thereof, and the aluminium layer 2 may transfer this heat energy via conduction and/or radiation and/or convection to an object wrapped in or positioned within the foil 1. The object to be heated will be positioned at a surface of the aluminium layer 2 facing oppositely from the surface on which the first ink layer 3 is applied.

(12) The first and second ink materials are diluted into ethyl acetate.

(13) The first ink material is pigmented with ripened carbon black. The second ink material is pigmented with titanium dioxide, TiO2.

(14) The first ink layer 3 is printed on the aluminium layer 2. The second ink layer 4 is subsequently printed on the first ink layer 3. The printing is done by rotogravure printing. The first ink layer 3 is applied using a U5 raster gravure roller, applying about 6.5 g/m2 wet weight of the first ink material on the aluminium layer 2. The gravure roller is 142 lines per cm, a channel width of 17μ, a cell depth of 31μ and a stylus (the angle in the bottom of the cell) of approximately 130 degrees. The second ink layer is applied using a U7 raster gravure roller, applying approximately 5 g/m2 wet weight of the second ink material on the first ink layer 3. The gravure roller is with 144 lines per cm, a channel width of about 20.8μ, a cell depth of 20 about 41μ and a stylus (the angle in the bottom of the cell) of approximately 120 degrees. The aluminium layer thickness is about 13μ.

(15) The aluminium layer 2 is a base or substrate or carrier layer that forms the basis for the application of the ink layers 3 and 4.

(16) In other embodiments one or more further layers may be provided between the first and second ink layers 3, 4 and/or between the first ink layer 3 and the aluminium layer 2 and/or on a surface of the aluminium layer 3 facing away from the first ink layer 3 and/or on a surface of the second ink layer 4 facing away from the first ink layer 3. Such layers may include one or more further ink layers.

(17) The first and second ink materials comprise an isocyanate-based hardener or cross-linker. The hardener or cross-linker may migrate during manufacture to affect both ink layers 3, 4. The amount of hardener applied to the initial ink materials is about 10% wet weight, i.e. weight percentage of the ink material(s) in the wet condition, i.e. before being applied.

(18) Flow time of the hardener before addition to the initial ink materials measured according to ISO 2431:2011 is approximately 45 seconds measured with flow cup no 5.

(19) The first ink layer 3 is applied with an areal density or grammage of about 2.3 g/m2 (dry weight). Similarly, the second ink layer 4 is applied with an areal density or grammage of about 2.6 g/m2 (dry weight). A thickness of each of the first and second ink layers 3, 4 is about 2.2μ, an accumulated thickness of the first and second ink layers 3, 4 being about 4.4μ. Thicknesses in this context are measured in a dry condition of the ink layers 3, 4.

(20) The flow time measured according to ISO 2431:2011 of the first and second ink materials before and during application thereof is approximately 80 seconds measured with flow cup no. 3.

(21) The resultant foil 1 shown in FIGS. 1 and 2 comprises the aluminium layer 2, the first ink layer 3 positioned between the aluminium layer 2 and the second ink layer 4.

(22) The foil 1 of FIGS. 1 and 2 may be used in an embodiment of the method according to the disclosure for heating an object. This method comprises the steps of: providing an oven (not shown) transmitting radiant energy, providing the foil 1, positioning an object to be heated (not shown), such as a potato to be baked, within the foil 1, and positioning of the object within the oven.

(23) The oven comprises an internal enamel coating which in use transmits heat energy in the form of radiant heat and convection to an oven spacing in which the object is positioned.

(24) The oven is heated and the “internal reflection” effect explained above with reference to FIG. 2 may occur within the foil 1.

(25) In FIGS. 3 and 4 elements of the drawings which are identical to or have the same function as elements in FIGS. 1 and 2 are provided with identical reference numbers.

(26) FIG. 3 shows a second embodiment of the foil according to the disclosure. This foil 1 is identical to and is manufactured in an identical manner as the foil 1 shown in FIGS. 1 and 2 except for the differences explained in the following.

(27) Thus, according to the disclosure the foil 1 of FIG. 3 is manufactured by the method explained above with reference to FIGS. 1 and 2. The method comprises the further steps of: applying a third ink material on an opposite surface of the aluminium layer to form a third ink layer 5, the opposite surface being opposite to the surface of the aluminium layer 2 on which the first ink layer 3 is applied, and applying a fourth ink material on a surface of the third ink layer 5 to form a fourth ink layer 6, the third ink layer 5 thereby being positioned between the aluminium layer 2 and the fourth ink layer 6, the first 3 and third 5 ink layers being adapted for absorbing radiant energy, the second 4 and fourth 6 ink layers being adapted for allowing radiant energy to pass through them so as to reach the first 3 and third 5 ink layers, respectively.

(28) The third ink layer 5 is identical to the first layer 3, and the fourth ink layer 6 is identical to the second ink layer 3.

(29) Accordingly, the resultant foil 1 of FIG. 3 comprises the aluminium layer 2, the first ink layer 3 positioned between the aluminium layer 2 and the second ink layer 4, the first ink layer 3 being adapted for absorbing radiant energy, the second ink layer 4 being adapted for allowing radiant energy to pass through it. Furthermore, the third ink layer 5 is positioned between the aluminium layer 2 and the fourth ink layer 6, the third ink layer 5 being positioned oppositely from the first ink layer 3 with respect to the aluminium layer 2, the third ink layer 5 being adapted for absorbing radiant energy, the fourth ink layer 6 being adapted for allowing radiant energy to pass through it.

(30) The foil 1 shown in FIG. 3 is not only suitable for absorbing heat energy in the aluminium layer 2 and transmit the energy to an object (not shown) wrapped in the foil 1 via heat conduction; the provision of the additional third 5 and fourth 6 ink layers allows for heat energy to be efficiently transmitted to the object also via radiation and/or convection, especially since the third ink layer 5 has a high emissivity and radiant heat may to some extent pass through the fourth ink layer. Therefore, the foil 1 need not be in contact with the object, but may be provided at a distance. This allows for using the foil 1 as a lid of a tray with the object or product to be heated therein and to be used as the tray material where there is a distance between the object and the foil 1 at least in some areas.

(31) Accordingly, FIG. 4 shows an embodiment of the packaging according to the disclosure in the form of a lidded food tray 7. The food tray 7 comprises a tray 8 and a lid 9 for enclosing an object 10 to be heated in an oven (not shown). The object may be a ready meal, a TV dinner or the like. Both the tray 8 and the lid 9 are cut from a sheet of the foil 1 of FIG. 3. Since the foil 1 of FIG. 3 is symmetrical about a centre plane of the aluminium layer 3, it does not matter how the foil 1 is positioned.

(32) The tray 8 has in a conventional manner in a cold form process been shaped into a tray shape. The aluminium layer 2 of the tray foil 1 may advantageously have been modified to have a thickness of about 100μ so as to provide greater stiffness.

(33) As can be seen in FIG. 4 there is a distance between the object 10 and the lid 9. As mentioned, oven heat absorbed in the lid 9 may efficiently be transferred to the object 10 via convection and radiation from the lid 9.