IES990683A2 - Fire retardant cladding panels - Google Patents

Abstract

A composite fire retardant wooden cladding panel has a wooden substrate board covered on both faces with veneer sheets. A fire retardant outer coating is sprayed in a controlled manner at high volume and low pressure onto the surface of one or both veneer sheets. The fire retardant coating comprises an inner base coat of two layers of a water based intumescent lacquer and an outer top coat of a solvent based catalysed lacquer. <Figure 1>

Description

The invention relates to the manufacture of fire retardant wooden cladding panels, and in particular to veneered cladding panels.

In many building applications in which wooden panels are used, it is necessary to provide some fire resistance to the panels. To this end, a number of fire resistant paints and varnishes for coating a surface of a cladding panel are available such as those described in Patent Specification Nos. US 5,206,088, US 4,849,298, US 4,099,975 and US 3,915,777, for example, which operate with varying degrees of success. The manner of application of the paint to a substrate can have a significant bearing on the fire resistant properties imbued to the substrate.

It is an object of the present invention to provide a new and improved composite fire retardant wooden cladding panel and a method for manufacturing composite veneered wooden panels with good fire resistance in an efficient and cost effective manner.

Statements of Invention According to the invention, there is provided a composite fire retardant wooden cladding panel comprising a wooden substrate board having a front face and a rear face, a decorative first veneer sheet bonded to the front face of the substrate board covering said front face, a second veneer sheet bonded to the rear face of the substrate board covering said rear face, a fire retardant outer coating covering at least an outer exposed front surface of the decorative first veneer sheet, said fire retardant outer coating comprising an inner base coat of at least two layers to a desired thickness of a water based intumescent lacquer and an outer top coat of a desired thickness of a solvent based catalysed lacquer. If desired, outer surfaces of both veneer sheets can be covered with the fire retardant coating.

In a particularly preferred embodiment, the base coat covers the outer surface of IE990683 -2the or each veneer sheet at a rate of at least 380g/m2 and the top coat covers the outer surface of the or each veneer sheet at a rate of at least 90 g/m2.

In another aspect of the invention, there is provided a method for manufacturing a composite fire retardant wooden cladding panel, comprising the steps:bonding a decorative first veneer sheet to a front face of a wooden substrate board and bonding a second veneer sheet to a rear face of the substrate board to form a composite panel, spraying a fire retardant outer coating onto at least an outer exposed front surface of the decorative veneer sheet in a controlled manner, the fire retardant coating comprising an inner base coat of a water based intumescent lacquer and an outer top coat of a solvent based catalysed lacquer, spraying the base coat onto the front surface of the decorative veneer sheet in at least two layers to build up a desired thickness of base coat on the surface of the decorative veneer sheet, the second and any subsequent layer being applied over the preceding layer whilst said preceding layer is still wet, drying the base coat, sanding the base coat, spraying the top coat over the base coat to provide a top coat of a desired thickness over the base co'at, and drying the top coat In one embodiment of the invention, the base coat and top coat are sprayed onto the panel at a pressure in the range 30-35lbs per square inch.

IE990683 -3In a preferred embodiment, the base coat is applied to the decorative veneer sheet in two layers.

In another embodiment, each layer of the base coat has a wet film thickness of at least 150 microns.

In a further embodiment, the base coat is applied at a rate of at least 380 g/m2.

In another embodiment, the top coat is applied at a rate of at least 90 g/m2.

In a particularly preferred embodiment, the method includes drying the base coat in a drying room, controlling the temperature in the drying room to about 20°C and the relative humidity within the drying room to about 50%.

In a further embodiment, the method includes regulating the moisture content of the veneer sheet such that it does not exceed 15% prior to spraying the fire retardant coating onto the veneer sheet Preferably, the method includes maintaining the moisture content of the veneer sheet within the range 10-12%.

In some cases, if desired, both veneer sheets are coated with the fire retardant coating.

Detailed Description of the Invention The invention will be more clearly understood by reference to the accompanying drawing which is a schematic flowchart illustrating a method and apparatus for manufacturing the fire retardant wooden cladding panels of the invention.

Referring to the drawing, at a veneering station 10, a wooden substrate board, which may conveniently be of medium density fibre board or other composite board, is coated on both sides with veneer sheets which are bonded to front and rear faces of the substrate board with adhesive in conventional fashion to form a IE990683 -4composite panel. A veneer sheet applied to the front face of the substrate board is of a good quality decorative veneer such as American oak for example, as this face of the panel will be exposed to view in use. The veneer sheet applied to the rear face of the substrate board may also be a high quality decorative veneer if said rear face will be exposed in use. More usually, as the rear face will, in use, be hidden from view - facing a wall on which the panel is mounted, for example a lower quality veneer such as Gabon veneer can be used.

Each veneered panel is delivered to a spraying station 12 at which a fire retardant outer coating is sprayed onto at least the outer exposed front surface of the decorative veneer sheet in a controlled manner. If, as mentioned previously, the rear face of the panel will also be exposed in use, it will also be covered with the fire retardant coating.

The fire retardant coating comprises an inner base coat of a water based intumescent lacquer and an outer coat of a solvent based catalysed lacquer.

The base coat is sprayed onto the panel in two layers, each layer of the base coat having a wet film thickness of at least 150 microns. It will be noted that after the first layer has been applied to the panel, it is only allowed to partially dry and then the second layer is applied over the first layer whilst the first layer is still wet.

The base coat has two components which are mixed together immediately before application. The first component comprises melamine formaldehyde resin urea formaldehyde and the second component is phosphoric acid ester solution. It will be noted that with some veneers such as cherry, for example, a primer will be applied to the panel before the base coat. Overall, the base coat is applied at a rate of about 380 g/m2.

A number of the panels to which both layers of the base coat have been applied are mounted spaced-apart on a rack which is delivered into a drying room 14. The panels are dried for about two hours within the drying room 14, the temperature being controlled to about 20°C and the relative humidity to about 50% within the drying room.

IE990683 -5Downstream of the drying room 14, the panels are delivered to a sanding station 16 at which each panel has a surface of the base coat lightly abraded. After cleaning 18 the abraded surface, the panels are returned to the spraying station 12 for spraying the top coat over the base coat on each panel. The top coat is applied by spraying to about 95 microns wet film thickness at a rate of about 90g/m2 and is then left to dry 18 in ambient air.

The top coat is a two component lacquer, the components being mixed 10 immediately prior to application. The first component is a composition of amino acids and alkalyd resins and vinyl polymers, and the second component is a dilute solution of sulphuric acid.

It will be noted that for optimum results, it is desirable to carefully control the 15 spraying of both the base coat and the top coat onto the panel. In this regard, spray equipment which provides a high volume low pressure (in the order of 3035lbs per square inch) spray gives best results.

It is also desirable to regulate the moisture content of each veneer sheet to which 20 the protective coating is to be applied such that it does not exceed 15%, and most preferably the moisture content is within the range 10-12%.

The invention is not limited to the embodiments hereinbefore described which may be varied in both construction and detail within the scope of the appended claims.

Claims (5)

1. A composite fire retardant wooden cladding panel comprising a wooden substrate board having a front face and a rear face, a decorative first veneer sheet bonded to the front face of the substrate board covering said front face, a second veneer sheet bonded to the rear face of the substrate board covering said rear face, a fire retardant outer coating covering at least an outer exposed front surface of the decorative first veneer sheet, said fire retardant outer coating comprising an inner base coat of at least two layers to a desired thickness of a water based intumescent lacquer and an outer top coat of a desired thickness of a solvent based catalysed lacquer, the base coat covering the outer surface of the or each veneer sheet at a rate of at least 380 g/m 2 and the top coat covering the outer surface of the or each veneer sheet at a rate of at least 90 g/m 2

2. A method for manufacturing a composite fire retardant wooden cladding panel of the type claimed in claim 1, comprising the steps:bonding a decorative first veneer sheet to a front face of a wooden substrate board and bonding a second veneer sheet to a rear face of the substrate board to form a composite panel, spraying a fire retardant outer coating onto at least an outer exposed front surface of the decorative veneer sheet in a controlled manner, the fire retardant coating comprising an inner base coat of a water based intumescent lacquer and an outer top coat of a solvent based catalysed lacquer, spraying the base coat onto the front surface of the decorative veneer sheet in at least two layers to build up a desired thickness of base coat on the surface of the decorative veneer sheet, the second and any subsequent layer being applied over the preceding layer whilst said preceding layer is still wet, - - ----------------IE990683 -7drying the base coat, sanding the base coat, spraying the top coat over the base coat to provide a top coat of a desired thickness over the base coat, and drying the top coat.

3. A method as claimed in claim 2 wherein the base coat and top coat are sprayed onto the panel at a pressure in the range 30-35lbs per square inch (206-242kPa), the base coat being applied to the decorative veneer sheet in two layers, each layer of the base coat having a wet film thickness of at least 150 microns, the base coat being applied at a rate of at least 380 g/m 2 , the top coat being applied at a rate of at least 90 g/m 2 , including drying the base coat in a drying room, controlling the temperature in the drying room to about 20°C and the relative humidity within the drying room to about 50%, including regulating the moisture content of the veneer sheet such that it does not exceed 15% prior to spraying the fire retardant coating onto the veneer sheet, and preferably maintaining the moisture content of the veneer sheet within the range 10-12%.

4. A method for manufacturing a composite fire retardant wooden cladding panel substantially as hereinbefore described with reference to the accompany drawing.

5. A composite fire retardant wooden cladding panel whenever produced by the method as claimed in any of claims 2 to 4.