Heat reflective laminate Field of the invention

The invention relates generally to heat reflective laminates and panels that incorporate a metal foil layer, and to methods for manufacturing such laminates and panels.

Background of the invention

Reconstituted wood panels are used as flooring, roof, wall and door panels whether or not further enhanced with an industrial or decorative coating. The wood based panel may be a low density, medium density or high density fibreboard or particleboard or oriented strand board or a plywood panel or may be a combination of these. Panels are also constructed in sandwich format with a light weight core.

Another substrate suitable for these applications is a substrate made from gypsum, also known as plasterboard. Gypsum has a paper outer layer. Still another suitable panel is a compact laminate. A plurality of impregnated kraft papers may also be used as a substrate for panels.

To reduce the rate of thermal radiation through a substrate applied as a flooring, roof, wall or door panel, a surface layer containing a homogeneous metal layer such as aluminium can be applied to the substrate. The aluminium layer is usually a laminate of an aluminium foil and a backing material to provide resistance to tearing. The aluminium laminate is usually glued to the substrate. The term glued is intended to mean that a glue is applied to either the inside laminate face or to the substrate to which the laminate is to be glued to and is usually an inexpensive PVA or UF glue.

An example of an aluminium layer applied to a particleboard is the R-flor ™ product from Carter Holt Harvey. The aluminium foil laminate is glued to the particleboard flooring, however with little effort can easily be peeled away.

Another example of an aluminium foil laminate is available from the Spantex division of Munksjδ. The laminate is an aluminium foil with an adhesive layer and a pre-

impregnated paper backing. The Spantex aluminium foil laminate is designed to be glued to a substrate.

It is an object of the invention to provide an improved constructional laminate that is preferably less susceptible to delamination than at least some existing panels containing a metal foil layer.

In the manufacture of low pressure melamine (LPM) , also known as direct pressure melamine (DPL) and thermo-fused melamine (TFM), an overlaying paper or papers impregnated with resin and partially cured are pressed onto a substrate in a hot press where the resin flows and bonds the carrier materials to the substrate and is cured to its final state to form the laminate.

In the manufacture of high pressure laminates (HPL) several resin impregnated kraft papers are assembled to form the substrate or core material and a resin impregnated decor paper is placed above the kraft papers. In some cases, for instance when a printed decor paper is used, a resin impregnated clear overlay paper is placed above the decor paper to provide wear protection for the print. Furthermore, in some cases the decorative paper is not impregnated and the clear overlay provides sufficient resin and the high pressure press sufficient pressure to form a uniformly impregnated HPL, this process being known as dry pressing.

In another process known as continuous pressure laminate (CPL), the impregnated decorative paper and impregnated kraft paper or papers and optionally an impregnated clear overlay paper are fed from rolls into a double band hot press. The pressure and heat bonds the impregnated papers into a continuous laminate. Alternatively the impregnated papers may be applied directly and simultaneously onto a wood based panel substrate within the continuous press.

Summary of the invention

It has been realised, in accordance with the invention, that techniques employed in manufacturing LPM, HPL and CPL products can be advantageously adapted to the production of heat reflective laminates incorporating a metal layer. More preferably, the

invention entails providing a partially cured, so-called "b-stage" thermosetting resin between the assembly containing the metal layer and the substrate board, more preferably as an impregnated layer of paper or non-woven fabric. The thermosetting resin provides improved bonding to the substrate and improved impact resistance.

In a first aspect of the invention, there is provided a heat reflective laminate comprising a substrate board, an intermediate carrier layer comprising paper or non-woven fabric overlaying the substrate board, and a metal layer on and adhered to the intermediate carrier layer, wherein the intermediate carrier layer and the substrate board are bonded by a thermosetting resin at least partially impregnating the intermediate layer and an adjacent surface portion of the board.

The invention further provides, in a second aspect, a method of manufacturing a heat reflective laminate comprising combining in a hot press a substrate board, a metal layer on and adhered to an intermediate carrier layer comprising paper or non-woven fabric, and uncured or partially cured thermosetting resin at least partially impregnating the intermediate carrier layer or applied to a surface of the board or introduced between the intermediate carrier layer and the board as a separate layer, wherein the thermosetting resin is further cured by the hot press to bond together the intermediate carrier layer and the substrate board.

The heat reflective laminate may be a constructional laminate, and/or a heat reflective laminated panel.

The substrate board may be a wood-based board, preferably a reconstituted wood board. Such boards include particleboard, fibreboard, oriented strand board and plywood.

Alternatively, the substrate board may be plasterboard.

The thermosetting resin is preferably an amino resin, e.g. a melamine or urea resin or combination of these. The usual such resins employed would typically include melamine and urea formaldehyde resins. Thermosetting resins also include acrylic lacquers.

In the laminate of the invention, there may further be an underlay layer of paper or non- woven fabric between the immediate carrier layer and the substrate board, the cured thermosetting resin impregnating this underlay layer and thereby bonding it to the intermediate carrier layer and the substrate board.

In the method of the invention, the thermosetting resin is preferably introduced to the hot press as a partially cured thermosetting resin impregnating said intermediate carrier layer or impregnating an underlay of paper or non-woven fabric between the intermediate carrier layer and the substrate board. In this case, the partially cured thermosetting resin has preferably been partially cured by near infrared irradiation.

There may be an overlay of thermosetting resin or lacquer over the metal layer.

In an embodiment, the metal and an adhesive layer are combined with a paper or non- woven after the latter has been impregnated with the thermosetting resin. In all cases the paper or non-woven and the thermosetting resin are laminated under heat and pressure to the substrate board to provide a permanent bonding to the substrate.

The lamination may be effected in a static hot press, or a continuous hot press. There may be a metal layer on one or both sides of the substrate. The metal layer may be on one side of the substrate with an alternative coating applied to the other side. The alternative coating may be a decorative coating such as a decorative laminate. The alternative coating may be the wear side of the laminate product where it is to be applied as laminate flooring or a table top. The decorative coating may be applied to the substrate simultaneously with the metal layer, as would be the case in a low pressure laminate (LPL) hot press, or may be a high pressure laminate (HPL) glued to the substrate. In another alternative construction, a HPL may be glued to the metal side of the laminate product.

The metal may be covered by a thermosetting resin applied as a paper impregnated with the resin and bonded to the metal layer in a hot press. The impregnated paper may be a clear overlay paper or may be a decorative paper whether uni-coloured or printed.

The metal layer itself may be lacquered before or after the hot pressing step.

The constructional laminate may be further decorated or coated for application as, for example but not limited to, wooden parquet, laminate flooring, carpet, linoleum, pvc tiles, cork tiles, wall paper or painting.

The choice of metal employed in the laminate product or in the method will be dependent on the desired end properties. Examples of suitable metal foils are aluminium and stainless steel. Aluminium is preferred.

The metal layer may be a metal foil or may include a metallised paper, non-woven or plastic.

Where the metal layer includes a metal foil, the foil may be a homogeneous foil, or it may be perforated or otherwise have a surface modification. The foil may have its surface modified by using a pressplate with the required relief in mirror image, or be perforated, e.g. by having the surface of a pressplate etched to a depth so that needle- like structures will penetrate the metal foil in the pressing process.

The invention also extends to a panel that comprises or includes a heat reflective laminate product according to the invention, or manufactured by the method of the invention.

Detailed description of the drawings

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

Fig. 1 is a simple not-to-scale schematic diagram of a heat reflective laminate according to an embodiment of the invention;

Fig. 2 depicts the substrate board and metal foil layer assembly before they are laminated together in a hot press to obtain the product of Figure 1 ;

Fig. 3 is a diagram similar to Figure 2 that shows an alternative embodiment of heat reflective laminate according to the invention;

Figures 4 to 9 are diagrams similar to Figure 1 of other alternative heat reflective laminate embodiments within the scope of the invention; and

Figures 10 to 16 are diagrams of alternative pre-laminated assemblies for use in embodiments of heat reflective laminate.

In the drawings, the double line 50 between the substrate and metal foil assembly denotes where the thermosetting resin creates a substantially permanent bond.

Embodiments of the invention

In the embodiment of Figures 1 and 2, the constructional laminate 10 is formed in a hot press by combining the two components of Figure 2, i.e. substrate board 12 and a prelaminated assembly 20 comprising an intermediate carrier layer 22 of paper and a metal foil layer 24 on and adhered to intermediate carrier layer 22 by an interposed coating of suitable adhesive 26. Paper carrier layer 22 is impregnated with a partially cured thermosetting resin, conveniently melamine or urea formaldehyde resin for this application. In the hot press, the resin is fully cured by the necessary heat, and, under pressure, at least partially impregnates the intermediate carrier layer 22 and a surface portion 13 of the substrate board 12, whereby the resin bonds them together.

In the embodiment depicted in Figure 3, intermediate carrier layer 322 for metal foil 324 is not pre-impregnated with resin, but instead the thermosetting resin is introduced partially cured to the hot press per an impregnated underlay 30 between layer 322 and substrate 312.

Other embodiments are illustrated in Figures 4 to 9: in each case like elements are indicated by like reference numerals preceded by the figure number. Figure 4 is a modification of the embodiment of Figures 1 and 2, in which the resin has been introduced as a coating on the substrate board 412 rather than by impregnating carrier layer 422. The arrangement of Figure 5, depicts an additional overlay 40, impregnated in thermosetting resin, on the metal foil 524. The alternative of lacquering the metal foil 40' is shown in Figure 6.

Figure 7 represents a double-sided product in which the assembly of Figure 4 is laminated to both sides of a common substrate board 712. Figures 8 and 9 depict a decorative laminate 60,60' applied to the opposite side of the substrate 812,912. Where this is a decorative laminate, it may be a flooring laminate and/or may comprise or include a clear overlay. The decorative laminate may include hard particles to improve abrasion resistance. The decorative laminate may be a continuous or high pressure laminate glued to the substrate.

In an economically advantageous embodiment of the method of the invention, the resin is cured to b-stage using electromagnetic radiation, preferably near infrared (NIR) radiation. Where the substrate board is coated with the resin, this partial curing may be affected in situ on the board. In other cases where a carrier layer, underlay or overlay is impregnated, partial curing to b-stage may be effected prior to introduction to the hot press.

In an economically advantageous embodiment of the method of the invention, a carrier material such as paper is impregnated with a thermosetting resin such as melamine or urea formaldehyde in a multi-dip bath, and the impregnated paper is partially cured to the so-called b-stage, preferably using near infra-red (NIR) irradiation. This may be done by the well known paper impregnation method using impregnation equipment readily available from the company Vits Langenfeld Germany. In the impregnation process it is usual to cool the web after impregnation and chilled rolls may be provided for this purpose. The chilled rolls are advantageously used to provide cooling for the web as an adhesive layer and metal foil are laminated to the impregnated paper. This produces the prelaminated assembly 20 of Figure 2, ready to be combined in a hot press with a substrate board 12.

The thickness of the metal foil can vary and is selected to achieve different degrees of thermal radiation resistance. The metal layer can alternatively be applied in the form of a metallised paper, metallised non-woven or metallised plastic film. Metallised paper is a well known product, usually used for decorative or barrier properties, made by vapour deposition in a vacuum usually in very thin layers. For example, the metallised paper from the firm Glatfelter is claimed to be 150 Angstrom +/- 3 Angstrom. Figures 10 to 12

depict alternative forms of prelaminated assemblies containing a metallised paper, metallised non-woven or metallised plastic film that may be employed in embodiments of the invention in place of the prelaminated assemblies 20 of Figures 1 to 9. In these cases, the metallised layer is indicated at 1024,1124 and 1224, and the substrate (paper, non-woven or plastic film) on which the metal is deposited is indicated at 70. In the case of Figure 10, this is also the intermediate carrier layer 1022. Figure 12 includes a lacquer overlay 1240'.

The metallised paper or non-woven may be impregnated with the thermosetting resin either after or before metallisation, i.e. metal deposition.

Advantageously, the metal layer may include deposited melamine powder. Melamine powder provides a flame retardant effect. The deposition of melamine may be effective before or after deposition of the aluminium layer, however for economic reasons it would be logical, and preferable, to apply the melamine and aluminium simultaneously. Simultaneous application of the melamine and aluminium would require two or more vapour streams in the one vacuum chamber. Application of melamine and an oxide is disclosed in the applicant's pending International patent application PCT/AU2006/000774. In an alternative arrangement, the aluminium, or aluminium and melamine, may be applied by vapour deposition to a paper or non-woven already impregnated with uncured or partially cured thermosetting resin.

Figures 13 to 16 depict examples of prelaminated assemblies containing vapour deposited melamine that may be employed in embodiments of the invention in place of the prelaminated assemblies 20 of Figures 1 to 9. The vapour deposited melamine layer is shown at 80 in each diagram. It will be seen that the assemblies of Figures 13 to 15 are modifications of those of Figures 10 to 12 respectively, with the melamine layer 80 vapour deposited on substrate paper, non-woven or plastic film 70. In each case, the metallised layer, e.g. 1224, and the melamine layer 80 may be interspersed co-deposits.

The paper side of the metallised paper may be impregnated with a thermosetting resin while the metal side of the metallised paper may be coated with a thermosetting resin.

Alternatively an overlay or non-woven may be impregnated with a thermosetting resin and used on one or both sides of the metallised paper.

Examples of suitable thermosetting resins for the purpose of this invention are urea formaldehyde, melamine formaldehyde and mixtures of two or more of these resins. Other thermosetting resins may be used to fulfill the requirements of the invention.

As used herein, except where the context requires otherwise the term "comprise" and variations of the term, such as "comprising", "comprises" and "comprised", are not intended to exclude other additives, components, integers or steps.