AU642742B2

AU642742B2 - Improvements in reflective foil insulation

Info

Publication number: AU642742B2
Application number: AU78506/91A
Authority: AU
Inventors: Hilton Edward Renouf
Original assignee: RENOUF IND Pty Ltd
Current assignee: RENOUF INDUSTRIES PTY Ltd
Priority date: 1990-05-25
Filing date: 1991-05-01
Publication date: 1993-10-28
Anticipated expiration: 2011-05-01
Also published as: AU7850691A

Description

IMPROVEMENTS IN REFLECTIVE FOIL INSULATION

This invention relates to thermal insulation and more particularly to reflective foil insulation. It is particularly concerned with an improved reflective foil laminate material, and a method of and apparatus for manufacturing such improved reflective foil laminate material.

Reflective foil insulation has been used in Australia for some 30 years to provide an effective barrier which significantly reduces heat flow into and out of a building, commercial, industrial or domestic, into which it has been incorporated. The use of reflective foil insulation results in a greater effectiveness of heating and cooling appliances thus reducing energy consumption required to produce the same heating or cooling effect when compared to an un-insulated building.

As stated above reflective foil insulation finds application in the insulation of many varied and different structures including the insulation of domestic dwellings and it will be convenient to hereinafter describe the invention with reference to such use.

To gain maximum effect against heat loss during winter and conversely heat gained during the summer months, it is preferable to have insulation applied to the ceiling space, walls and floors of the dwelling. In an existing dwelling it is usually not practicable to insulate the walls and this is preferably done during the actual construction of dwelling.

In the 30 or so years since reflective foil insulation was introduced into the Australian market there have been relatively few changes to its construction. Thermal insulation of this type is a composite structure formed of reflective metal foil, particularly aluminum, and a strengthening material such as paper, particularly kraft paper. The materials are bonded together to form an insulating sheet that is foldable and adapted to be rolled into a compact form. In use the sheet is un-rolled or unfolded and cut to the required length and attached by staples, nails, or the like to the dwelling in a known manner. Whilst laminates comprising a single sheet of aluminum foil bonded to paper are known and used, it is preferred that a second sheet of aluminum foil be bonded to the paper to form a sandwich structure with the paper comprising the middle layer. This double-sided reflective foil laminate is more efficient and is resistant to water and water vapor and therefore has a potentially longer life.

The paper or other material forming the laminate provides rigidity and strength to the aluminum foil which, by itself, is relatively flimsy and fragile and unable to withstand rough treatment experienced in installation and use.

The basic reflective foil insulation material referred to above may be modified by the inclusion of reinforcing mesh or threads, generally fiberglass, between the paper and at least one of the aluminum foil layers. The reinforcing mesh or threads increases tear resistance of the laminate.

It is common practice to provide the external surface of one of the aluminum foil layers with an "anti-glare" coating. This treatment reduces the discomfort often experienced by brick-layers and tilers when reflective foil insulation has been installed. It is also common practice to print the external surface of at least one of the aluminum foil layers with the name of the manufacturer, advertising material, and/or instructions for installation of the material.

In recent times a public and corporate awareness of potentially hazardous building materials has manifested itself. This awareness has included a consideration of the flammability characteristics of building material including insulation.

In reflective foil insulation commercially available in Australia the foil is generally laminated to the paper by means of a hot melt adhesive such as polyethylene. Whilst such a composite has the advantage of being of light weight, waterproof and of satisfactory strength characteristics, the polyethylene adhesive is flammable, thus imparting to the foil composite a flammability index of approximately 17 (AS- 1530:2:1973). Whilst prior to 1989 domestic building regulations in Australia specified a maximum flammability index of 26, new Australian uniform building regulations now state that all sarking type materials must have a flammability index of no greater than 5.

In an attempt to decrease the flammability index, flame-retardant hot melt adhesives, such as the chlorinated paraffins have been proposed. Reflective foil insulation incorporating such adhesives has a flammability index of less than 5 but has two major disadvantages. To bond the foil satisfactorily to paper, and to prevent the paper from burning, substantial quantities of adhesive are required. This results in a product significantly heavier than the polyethylene bonded laminate. The increase in weight, however, does not significantly increase the strength characteristics of the laminate. Further, the fire retardant property of the chlorinated paraffins results in the voluminous evolution of gas on heating. This gas smothers flames preventing the paper layer from burning. Unfortunately, the gas produced may be toxic.

Our earlier Australian Patent Application No. 73334/87 proposed the use of a flame-rctardant lamina sandwiched between two laminae of aluminum foil in an improved reflective foil laminate insulation material. The use of a flame-retardant lamina reduced the amount of non-flammable adhesive required to bond the paper lamina to the aluminum foil, but it was still necessary to use a heavy hot-melt non-flammable adhesive to bond at least one of the aluminum foil laminae to the paper lamina in order to achieve a flammability index of less than 5.

The use of lighter water-based adhesives in the manufacture of reflective foil laminate material is known, but only to bond one side of the strengthening paper to one of the reflective foil laminae. Hitherto, it has not been possible to use water-based adhesives to bond both sides of the strengthening paper lamina to the reflective foil laminae owing to the impermeable nature of the reflective foil which prevents removal of the moisture from the water-based adhesive trapped in the reflective foil laminate material.

It is desirable to provide an improved reflective foil laminate insulation material which alleviates or ameliorates at least some of the problems associated with prior art reflective foil laminates.

It is particularly desirable to provide a lightweight, reflective foil laminate insulating material having a low flammability index, preferably less than 5, whilst maintaining satisfactory strength and durability characteristics.

It is also desirable to provide an effective method of manufacturing a lightweight, low flammability index foil laminate insulation material.

According to one aspect of the present invention there is provided a reflective foil laminate material comprising a lamina of strengthening material sandwiched between two laminae of reflective foil material wherein each side of the strengthening lamina is bonded to a respective one of said reflective foil laminae by a non-flammable water-based adhesive.

According to another aspect of the present invention there is provided a method of manufacturing a reflective foil laminate material wherein said method comprises the steps of: bonding a first reflective foil lamina to one side of a strengthening lamina with a water-based adhesive layer; pre-drying the strengthening lamina with the first reflective foil lamina bonded to it; and bonding a second reflective foil lamina to the other side of the strengthening lamina with another layer of water-based adhesive.

In the present invention the strengthening lamina may comprise a flame-retardant paper or absorbent fabric material, eg. as described in our earlier Australian patent application No. 73334/87, but preferably it comprises ordinary kraft paper and at least one, preferably each of the water-based adhesive layers comprises a waterproof, non-flammable synthetic rubber water-based adhesive.

The water-based adhesive layer penetrates the pre-dried paper and replaces moisture removed from the paper during the drying step in the method of the present invention without raising the moisture content of the laminate material to an unacceptable level. The present invention preferably uses a water-based adhesive having a solid content appreciably higher than that of conventional water-based adhesives in current use for bonding aluminum foil to one side only of kraft paper.

In a preferred embodiment the water-based adhesive has from 50-60% solids and 40-50% water content, conveniently 55% solid content. This is at least three times the solid content of conventional water-based laminating adhesives.

Conventional methods of making reflective foil laminate insulating material use a thin coating of about 5 g/m² of water-based adhesive and a large amount, a minimum of 200 g m², of flame-retardant hot melt adhesive to achieve a flammability index of below 5. The present invention, envisages the use of about three times the amount of water-based adhesive on each side of the paper (i.e. about 15 g m² on each side) to achieve the required flammability index of less than 5. Thus a much lower quantity of water-based adhesive is required in total compared with the total weight of adhesive, water-based and hot melt, used in conventional methods of manufacturing reflective foil laminates. This enables the use of thicker paper in the present invention to produce a product which is approximately half the weight of conventional reflective foil laminate but which is stiffer and stronger both in burst strength and tensile strength than conventional reflective foil laminates.

It has however, been found that the conventional method of applying adhesive to the sides of the strengthening layer, i.e. using rollers to apply the adhesive, is not very suitable for the larger quantity of water-based adhesive having a higher solid content, since the adhesive would tend to stick to the rollers. In a preferred embodiment, the method of the present invention includes the steps of applying the adhesive to the sides of the paper with a spreading blade.

According to a further aspect of the present invention there is provided apparatus for performing the method of the present invention comprising a first bonding station for bonding a lamina of reflective foil to a lamina of strengthening material, means for supplying said lamina of strengthening material and said lamina of reflective foil to the first bonding station, means at the first bonding station for applying a non¬ flammable water-based adhesive to one side of the strengthening lamina, a second bonding station for bonding a second lamina of reflective foil to the opposite side of the strengthening lamina, means for feeding the strengthening lamina with the first reflective lamina bonded thereto from the first bonding station to the second bonding station, means for supplying said second lamina of reflective foil to the second bonding station, heating means for heating the strengthening lamina with the first reflective lamina bonded thereto between the first and second bonding stations, and means at said second bonding station for applying a further layer of non-flammable water-based adhesive to said opposite side of said strengthening lamina.

The apparatus may also include means for supplying a reinforcing mesh to the second bonding station to be bonded between the strengthening lamina and said second reflective foil lamina. In a preferred embodiment, at least one and preferably both of the means for applying the layers of non-flammable adhesive comprise a spreading blade.

According to yet another aspect of the present invention there is provided a reflective foil laminate material comprising a lamina of paper bonded on one side to a first reflective lamina of aluminum foil by a first non-flammable water-based adhesive layer, and a fiberglass reinforcing mesh bonded between the other side of said paper lamina and a second reflective lamina of aluminum foil by a second non-flammable water-based adhesive layer.

The present invention will now be described, by way of example only, with reference to the accompanying drawings in which:-

Figure 1 shows a reflective foil laminate insulating material in accordance with the invention; and

Figures 2 and 3 show apparatus for manufacturing reflective foil laminate insulating material in accordance with a further aspect of the present invention. The reflective foil laminate insulating material 1 shown in Figure 1 comprises a first lamina of aluminum reflective foil 2 bonded to one side of a strengthening lamina 3 of absorbent paper or fabric material, such as kraft paper, by a layer 4 of a waterproof non-flammable synthetic rubber water-based adhesive. A reinforcing mesh 5 of fiberglass is bonded between the opposite sides of the strengthening lamina 3 and a second reflective lamina of aluminum foil 7 by a further layer 6 of waterproof non-flammable synthetic rubber water-based adhesive.

It will be appreciated that the second layer 6 of adhesive may be applied on either side of the reinforcing mesh 5 since it will pass through the mesh to bond the strengthening lamina 3 to the reflective foil lamina 7.

Hitherto, it has not been possible using conventional methods and conventional apparams to manufacture effectively the reflective foil insulation material of Figure 1 with water-based adhesive layers 4 and 6 on both sides of the strengthening lamina 3,- because the resultant laminate material would have an excessive moisture content between the outer laminae 2 and 7 of impermeable reflective foil. Novel apparatus for manufacturing the reflective foil laminate material of Figure 1 is illustrated in Figures 2 and 3.

The apparams of Figures 2 and 3 comprises a first bonding station 10, a printing station 20, a heating oven 25 and a second bonding station 30 (see Figure 3). The method of manufacturing reflective foil laminate insulation material in accordance with the invention involves a two stage process utilizing the apparams of Figures 2 and 3.

As shown in Figure 2, kraft paper is fed by feed rollers 12 and 13 from a roll of paper 14 to the bonding station 10. A lamina of reflective aluminum foil is supplied from a roll of foil 16 via a foil feed roller 18 to the bonding station 10 where the foil is bonded to one side of the paper lamina. The paper leaves the bonding station 10 with the foil bonded to it on one side and is fed by a further roller 21 to the printing station 20. At the printing station 20 the external surface of the aluminum foil may be printed with the name of the manufacturer, advertising matter, and/or instructions relating to use of the reflective foil laminate material. Also, an "anti-glare" coating may be applied to the external surface of the aluminum foil lamina by the printing roller 22 of the printing station 20. The printed paper/foil laminate then passes around a heated roller 23 within the heating oven 25 before it is fed via an exit roller 24 to a collecting roller 26. The process continues until the roll of paper 14 and the roll of aluminum foil 16 have been fed completely through the apparatus shown in Figure 2 to produce a roll 28 of bonded paper/foil laminate on the collecting roller 26.

The roll of bonded paper/foil laminate 28 is then taken to the start of the apparams shown in Figure 3 which may comprise, or at least utilize, several parts of the apparams of Figure 2. As shown in Figure 3, the bonded paper/foil laminate is fed from roll 28 directly to the heating oven 25, bypassing the first bonding station 10 and the printing station 20. The bonded paper/foil laminate is fed around an oven entry roller 29 and passes around the heated roller 23 in the heating oven 25 before being fed to the second bonding station 30 by feed roller 32. A second lamina of aluminum foil is fed from a roll 36 via a foil feed roller 38 to the second bonding station 30, and fiberglass mesh fed to the second bonding station 30 from roll 34 is bonded between the second lamina of reflective foil and the surface of the kraft paper opposite from the surface to which the first lamina of foil is bonded. The bonded foil/paper/foil laminate emerging from the bonding station 30 is fed around the exit roller 24 to the collecting roller 26 where it is collected as a finished product in the form of a roll 40 of reflective foil laminate insulation material.

It is common practice in the manufacture of conventional reflective foil insulation to apply adhesives by means of rollers. In the apparatus of the present invention, however, at each bonding station 10; 30 the non-flammable water-based adhesive is applied to the respective surfaces of the strengthening paper by blade spreaders 15; 35 immediately before the paper lamina and the respective foil lamina (and the fiberglass mesh if required) are fed through bonding rollers 11; 31 of the bonding station. The non-flammable water-based adhesive is preferably applied to the strengthening paper lamina from adhesive supply containers 17; 37 through supply nozzles 9; 39 which supply the adhesive at a controlled rate. The blade spreaders 15; 35 then distribute the non-flammable water-based adhesive evenly over the surface of the paper.

Having regard to the foregoing, it will be appreciated that the present invention provides an effective process for manufacturing reflective foil laminate insulation material in which a non-flammable water-based adhesive can be used to bond reflective foil laminae to both sides of an absorbent strengthening lamina of, for instance, kraft paper. Preferably the adhesive used is a waterproof non-flammable synthetic rubber water-based adhesive which is able to penetrate the paper to provide a very effective bond of foil to paper. The use of a waterproof synthetic rubber water- based adhesive provides a further advantage in that the reflective foil laminate insulating material will not delaminate when exposed to wet or humid conditions, or to extreme heat or cold. The laminate material in accordance with the invention will withstand complete immersion in water for 24 hours, whereas conventional reflective foil insulation including a thin layer of conventional water-based adhesive will delaminate when exposed to such a severe test

It will be appreciated that various modifications may be made to the reflective foil laminate insulating material and to the apparams and process for manufacturing the material described above without departing from the scope of the present invention. For instance, in some cases it is not essential to include a reinforcing mesh of fiberglass or similar material. Also, it may not be desirable in some cases for the reflective foil laminate to incorporate printed matter and/or an "anti-glare" coating on its external surfaces. In this case, the printing station 20 in Figure 2 may be bypassed with the paper/foil laminate being fed directly to the heating station 25 via roller 29, as illustrated in broken lines in Figure 2.

Claims

1. A.reflective foil laminate material comprising a lamina of strengthening material sandwiched between two laminae of reflective foil material wherein each side of the strengthening lamina is bonded to a respective one of said reflective foil laminae by a non-flammable water-based adhesive.

2. The reflective foil laminate material of claim 1 wherein the strengthening lamina comprises a flame-retardant paper or absorbent fabric material.

3. The reflective foil laminate material of claim 1 wherein the strengthening lamina comprises kraft paper.

4. The reflective foil laminate material of claim 1 wherein at least one of the water-based adhesive layers comprising a waterproof, non-flammable synthetic rubber water-based adhesive.

5. The reflective foil laminate material of any one of claims 1 to 4 wherein the water-based adhesive has from 50-60% solids and 40-50% water content.

6. A method of manufacturing a reflective foil laminate material wherein said method comprises the steps of: bonding a first reflective foil lamina to one side of a strengthening lamina with a water-based adhesive layer; pre-drying the strengthening lamina with the first reflective foil lamina bonded to it; and bonding a second reflective foil lamina to the other side of the strengthening lamina with another layer of water-based adhesive.

7. The method of claim 6 wherein the strengthening lamina comprises a flame-retardant paper or absorbent fabric material.

8. The method of claim 6 wherein the strengthening lamina comprises kraft paper.

9. The method of claim 6 wherein at least one of the water-based adhesive layers comprising a waterproof, non-flammable synthetic rubber water-based adhesive.

10. The method of any one of claims 6 to 9 wherein the water-based adhesive has from 50-60% solids and 40-50% water content.

11. Apparatus for performing the method of claim 6, comprising a first bonding station for bonding a lamina of reflective foil to a lamina of strengthening material, means for supplying said lamina of strengthening material and said lamina of reflective foil to the first bonding station, means at the first bonding station for applying a non-flammable water-based adhesive to one side of the strengthening lamina, a second bonding station for bonding a second lamina of reflective foil to the opposite side of the strengthening lamina, means for feeding the strengthening lamina with the first reflective lamina bonded thereto from the first bonding station to the second bonding station, means for supplying said second lamina of reflective foil to the second bonding station, heating means for heating the strengthening lamina with the first reflective lamina bonded thereto between the first and second bonding stations, and means at said second bonding station for applying a further layer of non-flammable water-based adhesive to said opposite side of said strengthening lamina.

12. The apparatus of claim 11 further including means for supplying a reinforcing mesh to the second bonding station to be bonded between the strengthening lamina and said second reflective foil lamina.

13. The apparatus of claim 11 or 12 wherein the means for applying the layers of non-flammable adhesive comprise a spreading blade.

14. A reflective foil laminate material comprising a lamina of paper bonded on one side to a first reflective lamina of aluminum foil by a first non-flammable water-based adhesive layer, and a fiberglass reinforcing mesh bonded between the other side of said paper lamina and a second reflective lamina of aluminum foil by a second non-flammable water-based adhesive layer.