Laminate panel

Abstract

The invention relates to a sealed laminate panel (10), such as a framed laminate panel comprising an open-celled substrate layer (12) within the frame and at least one layer of sheetform material (11) provided over each of opposing surfaces of the framed substrate, which may be prepared by a one-shot process. The invention further relates to a method of forming a laminate panel (10) of the present invention. The laminate panels of the present invention are useful, for example, in buildings, trains, boats, and as architectural components, for example architectural mouldings, although the invention has wide application to a broad range of structures. Aspects of the invention described relate to doors, panels in train carriages and boats, and other panels, in particular those used in buildings.

Description

[0001] Laminate Panel

[0002] The invention relates to a sealed laminate panel, such as a framed laminate panel comprising an open-celled substrate layer within the frame and at least one layer of sheetform material provided over each of opposing surfaces of the framed substrate, which may be prepared by a one-shot process. The invention further relates to a method of forming a laminate panel of the present invention. The laminate panels of the present invention are useful, for example, in buildings, trains, boats, and as architectural components, for example architectural mouldings, although the invention has wide application to a broad range of structures. Aspects of the invention described relate to doors, panels in train carriages and boats, and other panels, in particular those used in buildings.

[0003] Background

[0004] Doors, and other panels have traditionally been made from wood. However, unless specially treated, wood can warp if exposed to changes in temperature and / or humidity. This can be disadvantageous aesthetically and can also lead to difficulties in opening and closing the doors and partitions. The latter are particular problems in the light of modern building safety regulations, where warped doors and panels can constitute a fire hazard. Furthermore, wood can be relatively expensive to obtain and there are major environmental concerns in respect of the use of certain types of wood.

[0005] Over the last few decades there has therefore been a trend towards providing artificial doors or panels. One type of artificial door is a moulded door. Moulded doors can be formed by a number of different methods.

[0006] Foam resin laminate panels of the kind comprising a foam resin layer and a skin are being employed increasingly in the building, decorating and furniture industries because of the wide range of useful properties achievable.

[0007] In known systems, the skins may be formed by compression moulding or pressing of a sheet moulding compound (SMC). The SMC includes a thermosetting resin, for example a polyester resin, together with reinforcing fibres, for example glass fibres.

[0008] To make the formed skin, the sheet moulding compound is folded to form a block of charge and placed into a preheated moulding cavity. The mould is closed and pressure is applied to press the moulding compound so that it spreads to all parts of the mould. Heat and pressure is applied until the moulded material has cured. The mould is then opened and the formed skin is removed. The shaped skins can then be secured to opposite sides of a frame, prior to injecting a foam into a cavity located between the skins. The foam acts as a filler and can assist in providing improved rigidity and insulation for the door. The door can then be finished as appropriate.

[0009] However, although this method can be effective, it is not always reliable. This is because the curing of foam and the filling of the cavity is difficult to control accurately. Furthermore, the rheological properties of the curing foam can be adversely affected by wire mesh reinforcements, which are often provided between the skins in order to strengthen the resultant product.

[0010] There are further disadvantages associated with the forming of the SMC skins using such a method. For example, the SMC needs to be folded to form a block in the mould cavity. This is because air trapped in the mould cavity and gases formed during the curing reaction needs to be released during the moulding operation.

[0011] Also, high pressure is required to affect the moulding; pressures of 1000 to 5000 tonnes are not unknown.

[0012] This places constraints on the materials which can be used for the mould itself. In such arrangements, stainless steel moulds are used, but these are expensive, and they are slow to heat, leading to long set-up times before the required mould temperature is reached. For example, heating a stainless steel mould to 180 degrees centigrade needed for compression moulding might take several hours. In addition, stainless steel moulds are heavy, and changing a mould for the forming of a different skin profile might take half a day including the cooling, mould changing and heating-up cycle. Therefore, such compression moulding processes have in the past generally been used to produce high volume products due to investment in making the mould and the downtime in changing moulds.

[0013] Also, another disadvantage with this method is that where the skin is subsequently adhered to a core with adhesive or filled with foam to form a foam laminate structure, structural failure of the bond between the skin and the core can be a problem.

[0014] In known systems, such as that of W02009 / 044169, composite products, such as laminates, are formed by applying a layer of sheet-form material onto a surface of a substrate and pressing the sheet-form material to the substrate, wherein the configuration of the substrate is such that gas and / or vapour can be displaced from the pressing region. This method provides good bonding of sheet-form material together with a substrate, in particular, an open-celled foam. The process of curing the resin present in the sheetform material produces gas, and the open sides of the substrate allow gas bubbles to be released which otherwise might become trapped in the cured sheet-form material and compromise desirable properties such as strength and may also contribute to undesirable warping of the laminate. However, the production of gas and the need for this gas to dissipate has hitherto prevented the possibility of a “one-shot” method, which is a method where a single pressing step is used to press the sheet-form material into a framed substrate to produce a composite product, such as a laminate panel. By way of example, it is known that such prior art processes have suffered from the framed panels exploding during moulding as a result of the build-up of gases during manufacture.

[0015] Other prior art solutions which make use of pressing would typically back fill a part bonded substrate with resin which provides inferior bonding overall and does not represent a true “one shot” process in which the entire panel, including the frame, is formed in a single pressing step.

[0016] Detailed Description of the Invention

[0017] An object of the present invention is to provide an improved method of forming an sealed laminate panel where the substrate layer is able to hold and dissipate gas during compression of, for example a framed sheet-form material, in a single step to provide a “one-shot” process. This is provided by cavities in the form of pressure-equalising voids which are present in the open-celled substrate and / or the frame itself where applicable which can accommodate gas which is produced during the pressing stage and avoid pressure build up before it may be dissipated.

[0018] According to an aspect of this invention, there is provided a method of forming a one-shot sealed laminate panel, the method comprising: providing an open-celled substrate layer; providing at least one layer of sheet-form material over each of opposing surfaces of the substrate and which is in contact with the substrate layer over substantially all of the perimeter edge of the substrate layer; and at least one vent in fluidic communication between the substrate and the atmosphere; pressing the sheet-form material into the open-celled substrate in a single pressing step to form the laminate panel; wherein the open-celled substrate defines one or more cavities; and wherein the cavities provide voids to pressure-equalise the sealed laminate panel during manufacture. Preferably, the method comprises providing a sealed framed laminate panel, the method comprising the steps of providing an open-celled substrate layer within a frame such that the frame is in contact with the substrate layer over substantially all of the perimeter edge of the substrate layer; and at least one vent in fluidic communication between the substrate and the atmosphere; providing at least one layer of sheet-form material over each of opposing surfaces of the framed substrate; pressing the sheet-form material into the open- celled substrate in a single pressing step to form the framed laminate panel; wherein the frame and / or open-celled substrate define one or more cavities; and wherein the cavities provide voids to pressure-equalise the framed laminate panel during manufacture.

[0019] Open-Celled Substrate

[0020] The substrate useful in the present invention is an open-celled substrate, which is a base material that has open cells into which the sheet-form material can flow (or “key into”). Curing of one or more resin present in the sheet-form material within the cells allows for strong bonding of the sheet-form material to the open-celled substrate.

[0021] In examples of the present invention, the open-celled substrate preferably comprises a rigid foam, for example a foam material obtained by causing or allowing a mixture of phenolic resole, acid hardener and finely divided particulate solid to cure under conditions in which foaming for the mixture is caused primarily or solely by volatilisation of small molecules present in the resole or formed as a by-product of the curing reaction. The formation of an example of such foams is described in detail in EP 0010353 and foamed bodies comprising these foams can be obtained as ACELL foam from Acell Holdings Limited, UK. In some examples of the invention, a polyurethane foam is preferred.

[0022] Preferably the open-celled substrate has a density in the range of 75 to 500 kg / m3, such as 100 to 450 kg / m3, more preferably 120 to 400 kg / m3and most preferably 120 to 250 kg / m3. It has been found that such foams can be caused to reproduce on a face thereof the detail of even quite fine and complex press or mould surfaces by the application of a suitable pressure the level of which depends on the nature and density of the foam material but can readily be determined by simple experiment.

[0023] As the open-celled substrate has a substantially open-cell structure, when the layer of sheet-form material is pressed into the cells or pores of the material, the gas or vapour therein can be dissipated through tortuous pathways defined by the open cells of the substrate. While any suitable material may be employed, aspects of the invention are particularly suitable for use with substantially rigid structural materials, for example foams, that is, preferably self-supporting foams which are resistant to deflection under load and do not collapse under moderate pressure. The physical properties of such foams, especially the compressive strength and deflection under load are believed to be related to (amongst other factors) cell wall thickness. In some examples, the cell size for suitable open-celled substrate material is found to be in the range of about 0.5 mm to 5 mm, more preferably 0.5 or 1 mm to 2 or 3 mm.

[0024] It is preferred for the open-celled substrate to include a filler material, for example a finely divided filler material. Foamed phenolic resin reinforced with a finely divided filler is particularly preferred in some arrangements because of the excellent combination of physical properties and fire resistance that can be obtained for laminates formed from it.

[0025] Typically, at least some of the cells or pores of the foamed open-celled substrate are open to the surface of the face on which the layer of sheet-form material is to be applied, and preferably they open out below the surface to a greater width than the opening, thereby providing an undercut which can enhance the keying of the sheet-form material to the open-celled substrate.

[0026] Sheet-form material is applied over each opposing surface of the framed open-celled substrate and optionally all of the perimeter edge. In this way, a laminate panel including a skin on two sides is formed and optionally an encapsulated laminate panel. For example, where the laminate panel comprises a door, both sides of the door are formed in a single step.

[0027] In some examples of the invention, the open-celled substrate comprises a foam having frangible cell walls, such as a foam which undergoes compression, the foam crumbling by brittle fracture of the cell walls e.g. involving a clean fracture of the cell walls. Such a foam can retain a clear and substantially dimensionally accurate imprint in the crushed zone of an object through which the compressive force is applied. In general, it is preferred that the yield strength of the foam, which in this case means the minimum force required to cause the fracture of the cell walls and for the foam to crumble, is in the range of about 100 to 140 KPa (15 to 20 Ibs / sq.in) more preferably at least 200 KPa (30 Ibs / sq.in), since this provides useful impact resistance. In general, for a given foam composition, the greater the density, the greater the yield strength.

[0028] For such a method, it is advantageous to use an open cell foam having frangible walls as pressing into a conventional foamed core such as of polystyrene is in some cases not successfully achieved because the resilience of the foam may cause distortion of the skins when the pressure is released.

[0029] In some examples of the invention, plastics foams are preferred which are substantially open-cell and rigid. However, the foam is advantageously selected to be of a high density relative to the foamed polystyrene conventionally used, e.g. a density of 75 kg / m3or above, since this gives a better feel to the laminate panel and makes it sound and handle more like a conventional wooden panel. However, foams having lower densities may also be selected. Where a higher density is desirable, the foam may contain a filler, more preferably a finely divided inert and preferably inorganic solid. The filler may be selected such that it contributes to the laminate panel’s ability to resist changes in temperature. In a particularly preferred embodiment, the filler is capable of absorbing moisture, e.g. as water of crystallisation.

[0030] In many examples, rigid foam materials are preferred. For example, a rigid foam could be used to form a panel having a substantially flat (unmoulded) surface which may or may not include surface pattern as described herein.

[0031] Alternatively, or in addition, the surface of the foam may be contoured. The contours could for example be formed on the surface of a foam block, for example by machining or any other suitable method. In such cases, the foam need not for example be a frangible or compressible foam.

[0032] One suitable foam is a rigid filled phenolic foam. One particularly suitable foam is that produced by effecting a curing reaction between:

[0033] (a) a liquid phenolic resole having a reactivity number (as defined below) of at least 1 and

[0034] (b) a strong acid hardener for the resole, in the presence of:

[0035] (c) a finely divided inert and insoluble particulate solid which is present in an amount of at least 5% by weight of the liquid resole and is substantially uniformly dispersed through the mixture containing resole and hardener; the temperature of the mixture containing resole and hardener due to applied heat not exceeding 85°C and the said temperature and the concentration of the acid hardener being such that compounds generated as by-products of the curing reaction are volatilised within the mixture before the mixture sets whereby a foamed phenolic resin product is produced. By a phenolic resole is meant a solution in a suitable solvent of the acid-curable prepolymer composition obtained by condensing, usually in the presence of an alkaline catalyst such as sodium hydroxide, at least one phenolic compound with at least one aldehyde, in well-known manner. Examples of phenols that may be employed are phenol itself and substituted, usually alkyl substituted, derivatives thereof provided that the three positions on the phenolic benzene ring o- and p- to the phenolic hydroxyl group are unsubstituted. Mixtures of such phenols may also be used. Mixtures of one or more than one of such phenols with substituted phenols in which one of the ortho or para positions has been substituted may also be employed where an improvement in the flow characteristics of the resole is required but the cured products will be less highly crosslinked. However, in general, the phenol will be comprised mainly or entirely of phenol itself, for economic reasons.

[0036] The aldehyde will generally be formaldehyde although the use of higher molecular weight aldehydes is not excluded.

[0037] The phenol / aldehyde condensation product component of the resole is suitably formed by reaction of the phenol with at least 1 mole of formaldehyde per mole of the phenol, the formaldehyde being generally provided as a solution in water, e.g. as formalin. It is preferred to use a molar ratio of formaldehyde to phenol of at least 1 .25 to 1 but ratios above 2.5 to 1 are preferably avoided. The most preferred range is 1 .4 to 2.0 to 1 .

[0038] The mixture may also contain a compound having two active H atoms (dihydric compound) that will react with the phenol / aldehyde reaction product of the resole during the curing step to reduce the density of cross-linking. Preferred dihydric compounds are diols, especially alkylene diols or diols in which the chain of atoms between the OH groups contains not only methylene and / or alkyl-substituted methylene groups but also one or more hetero atoms, especially oxygen atoms, e.g. ethylene glycol, propylene glycol, propane-1 , 3-diol, butane-1 ,4-diol and neopentyl glycol. Particularly preferred diols are poly-, especially di-, (alkylene ether) diols e.g. diethylene glycol and, especially, dipropylene glycol. Preferably the dihydric compound is present in an amount of from 0 to 35% by weight, more preferably 0 to 25% by weight, based on the weight of phenol / aldehyde condensation product. Most preferably, the dihydric compound, when used, is present in an amount of from 5 to 15% by weight based on the weight of phenol / aldehyde condensation product. When such resoles containing dihydric compounds are employed in the present process, laminate panels having a particularly good combination of physical properties, especially strength, can be obtained. Suitably, the dihydric compound is added to the formed resole and preferably has 2-6 atoms between OH groups.

[0039] The resole may comprise a solution of the phenol / aldehyde reaction product in water or in any other suitable solvent or in a solvent mixture, which may or may not include water. Where water is used as the sole solvent, it is preferred to be present in an amount of from 15 to 35% by weight of the resole, preferably 20 to 30%. Of course, the water content may be substantially less if it is used in conjunction with a cosolvent, e.g. an alcohol or one of the above-mentioned dihydric compounds where one is used.

[0040] As indicated above, the liquid resole (i.e. the solution of phenol / aldehyde product optionally containing dihydric compound) must have a reactivity number of at least 1 . The reactivity number is 10 / x where x is the time in minutes required to harden the resole using 10% by weight of the resole of a 66-67% aqueous solution of p-toluene sulfonic acid at 60°C. The test involves mixing about 5ml of the resole with the stated amount of the p- toluene sulfonic acid solution in a test tube, immersing the test tube in a water bath heated to 60°C and measuring the time required for the mixture to become hard to the touch. The resole should have a reactivity number of at least 1 for useful foamed products to be produced and preferably the resole has a reactivity number of at least 5, most preferably at least 10.

[0041] The pH of the resole, which is generally alkaline, is preferably adjusted to about 7, if necessary, for use in the process, suitably by the addition of a weak organic acid such as lactic acid.

[0042] Examples of strong acid hardeners are inorganic acids such as hydrochloric acid, sulphuric acid and phosphoric acid, and strong organic acids such as aromatic sulphonic acids, e.g. toluene sulphonic acids, and trichloroacetic acid. Weak acids such as acetic acid and propionic acid are generally not suitable. The preferred hardeners for the process of the invention are the aromatic sulfonic acids, especially toluene sulfonic acids.

[0043] The acid may be used as a solution in a suitable solvent such as water.

[0044] When the mixture of resole, hardener and solid is to be poured, e.g. into a mould and in slush moulding applications, the amount of inert solid that can be added to the resole and hardener is determined by the viscosity of the mixture of resole and hardener in the absence of the solid. For these applications, it is preferred that the hardener is provided in a form, e.g. solution, such that when mixed with the resole in the required amount yields a liquid having an apparent viscosity not exceeding about 50 poises at the temperature at which the mixture is to be used, and the preferred range is 5-20 poises. Below 5 Poises, the amount of solvent present tends to present difficulties during the curing reaction.

[0045] The curing reaction is exothermic and will therefore of itself cause the temperature of the mixture containing resole and acid hardener to be raised. The temperature of the mixture may also be raised by applied heat but the temperature to which said mixture may then be raised (that is, excluding the effect of any exotherm) must not exceed 85 °C.

[0046] If the temperature of the mixture exceeds 85 °C before addition of the hardener, it is difficult or impossible thereafter to properly disperse the hardener through the mixture because of incipient curing. On the other hand, it is difficult, if not impossible, to uniformly heat the mixture above 85 °C after addition of the hardener.

[0047] Increasing the temperature towards 85 °C tends to lead to coarseness and non-uniformity of the texture of the foam but this can be offset at least to some extent at moderate temperatures by reducing the concentration of hardener. However at temperatures much above 75 °C even the minimum amount of hardener required to cause the composition to set is generally too much to avoid these disadvantages. Thus, temperatures above 75 °C are preferably avoided and preferred temperatures for most applications are from ambient temperature to about 75 °C. The preferred temperature range appears to depend to some extent on the nature of the solid (c). For most solids it is from 25 to 65 °C but for some solids, in particular wood flour and grain flour, the preferred range is 25 to 75 °C. The most preferred temperature range is 30 to 50 °C. Temperatures below ambient, e.g. down to 10 °C can be used, if desired, but no advantage is gained thereby. In general, at temperatures up to 75 °C, increase in temperature leads to decrease in the density of the foam and vice versa.

[0048] The amount of hardener present also affects the nature of the laminate panel as well as the rate of hardening. Thus, increasing the amount of hardener not only has the effect of reducing the time required to harden the composition but above a certain level dependant on the temperature and nature of the resole it also tends to produce a less uniform cell structure. It also tends to increase the density of the foam because of the increase in the rate of hardening. In fact, if too high a concentration of hardener is used, the rate of hardening may be so rapid that no foaming occurs at all and under some conditions the reaction can become explosive because of the build up of gas inside a hardened shell of resin. The appropriate amount of hardener will depend primarily on the temperature of the mixture of resole and hardener prior to the commencement of the exothermic curing reaction and the reactivity number of the resole and will vary inversely with the chosen temperature and the reactivity number. The preferred range of hardener concentration is the equivalent of 2 to 20 parts by weight of p-toluene sulfonic acid per 100 parts by weight of phenol / aldehyde reaction product in the resole assuming that the resole has a substantially neutral reaction, i.e. a pH of about 7. By equivalent to p-toluene sulfonic acid, we mean the amount of chosen hardener required to give substantially the same setting time as the stated amount of p-toluene sulfonic acid. The most suitable amount for any given temperature and combination of resole and finely divided solid is readily determinable by simple experiment. Where the preferred temperature range is 25-75 degrees C and the resole has a reactivity number of at least 10, the best results are generally obtained with the use of hardener in amounts equivalent to 3 to 10 parts of p- toluene sulfonic acid per 100 parts by weight of the phenol / aldehyde reaction product. For use with temperatures below 25 degrees C or resoles having a reactivity number below 10, it may be necessary to use more hardener.

[0049] It may be necessary to make some adjustment of the hardener composition in accordance with the nature, especially shape and size, of the press and this can be established by experiment.

[0050] By suitable control of the temperature and of the hardener concentration, the time lapse between adding the hardener to the resole and the composition becoming hard (referred to herein as the setting time) can be varied at will from a few seconds to up to an hour or even more, without substantially affecting the density and cell structure of the product.

[0051] Another factor that controls the amount of hardener required can be the nature of the inert solid. Very few are exactly neutral and if the solid has an alkaline reaction, even if only very slight, more hardener may be required because of the tendency of the filler to neutralize it. It is therefore to be understood that the preferred values for hardener concentration given above do not take into account any such effect of the solid. Any adjustment required because of the nature of the solid will depend on the amount of solid used and can be determined by simple experiment.

[0052] The exothermic curing reaction of the resole and acid hardener leads to the formation of by-products, particularly aldehyde and water, which are at least partially volatilised.

[0053] The curing reaction is affected in the presence of a finely divided inert and insoluble particulate solid which is substantially uniformly dispersed throughout the mixture of resole and hardener. By an inert solid we mean that in the quantity it is used it does not prevent the curing reaction. It is believed that the finely divided particulate solid provides nuclei for the gas bubbles formed by the volatilisation of the small molecules, primarily CH2O and / or H2O, present in the resole and / or generated by the curing action, and provides sites at which bubble formation is promoted, thereby assisting uniformity of pore size. The presence of the finely divided solid may also promote stabilization of the individual bubbles and reduce the tendency of bubbles to agglomerate and eventually cause likelihood of bubble collapse prior to cure. The phenomenon may be similar to that of froth flotation employed in the concentration of low grade ores in metallurgy. In any event, the presence of the solid is essential to the formation of the laminate panel. To achieve the desired effect, the solid should be present in an amount of not less than 5% by weight based on the weight of the resole.

[0054] Any finely divided particulate solid that is insoluble in the reaction mixture is suitable, provided it is inert. The fillers may be organic or inorganic (including metallic), and crystalline or amorphous. Even fibrous solids have been found to be effective, although not preferred. Examples include clays, clay minerals, talc, vermiculite, metal oxides, refractories, solid or hollow glass microspheres, fly ash, coal dust, wood flour, grain flour, nut shell flour, silica, mineral fibres such as finely chopped glass fibre and finely divided asbestos, chopped fibres, finely chopped natural or synthetic fibres, ground plastics and resins whether in the form of powder or fibres, e.g. reclaimed waste plastics and resins, pigments such as powdered paint and carbon black, and starches.

[0055] Solids having more than a slightly alkaline reaction, e.g. silicates and carbonates of alkali metals, are preferably avoided because of their tendency to react with the acid hardener. Solids such as talc, however, which have a very mild alkaline reaction, in some cases because of contamination with more strongly alkaline materials such as magnesite, are acceptable.

[0056] Some materials, especially fibrous materials such as wood flour, can be absorbent and it may therefore be necessary to use generally larger amounts of these materials than non- fibrous materials, to achieve valuable foamed products.

[0057] The solids preferably have a particle size in the range 0.5 to 800 microns. If the particle size is too great, the cell structure of the foam tends to become undesirably coarse. On the other hand, at very small particle sizes, the foams obtained tend to be rather dense. The preferred range is 1 to 100 microns, most preferably 2 to 40 microns. Uniformity of cell structure appears to be encouraged by uniformity of particle size. Mixtures of solids may be used if desired. If desired, solids such as finely divided metal powders may be included which contribute to the volume of gas or vapour generated during the process. If used alone, however, it be understood that the residues they leave after the gas by decomposition or chemical reaction satisfy the requirements of the inert and insoluble finely divided particulate solid required by the process of the invention.

[0058] Preferably, the finely divided solid has a density that is not greatly different from that of the resole, so as to reduce the possibility of the finely divided solid tending to accumulate towards the bottom of the mixture after mixing.

[0059] One preferred class of solids is the hydraulic cements, e.g. gypsum and plaster, but not Portland cement because of its alkalinity. These solids will tend to react with water present in the reaction mixture to produce a hardened skeletal structure within the cured resin. Moreover, the reaction with the water is also exothermic and assists in the foaming and curing reaction. Foamed products obtained using these materials have particularly valuable physical properties. Moreover, when exposed to flame even for long periods of time they tend to char to a brick-like consistency that is still strong and capable of supporting loads. The laminate panels also have excellent thermal insulation and energy absorption properties. The preferred amount of inert particulate solid is from 20 to 200 parts by weight per 100 parts by weight of resole.

[0060] Another class of solids that is preferred because its use yields products having properties similar to those obtained using hydraulic cements comprises talc and fly ash. The preferred amounts of these solids are also 20 to 200 parts by weight per 100 parts by weight of resole.

[0061] For the above classes of solid, the most preferred range is 50 to 150 parts per 100 parts of resole.

[0062] Thixotropic foam-forming mixtures can be obtained if a very finely divided solid such as Aerosil (finely divided silica) is included.

[0063] If a finely divided metal powder is included, electrically conducting properties can be obtained. The metal powder is preferably used in amounts of from 50 to 250 parts per 100 parts by weight of resole.

[0064] In general, the maximum amount of solid that can be employed is controlled only by the physical problem of incorporating it into the mixture and handling the mixture. In general it is desired that the mixture is pourable but even at quite high solids concentrations, when the mixture is like a dough or paste and cannot be poured, foamed products with valuable properties can be obtained.

[0065] In general, it is preferred to use the fibrous solids only in conjunction with a non-fibrous solid since otherwise the foam texture tends to be poorer.

[0066] Other additives may be included in the foam-forming mixture; e.g. surfactants, such as anionic materials e.g. sodium salts of long chain alkyl benzene sulfonic acids, non-ionic materials such as those based on polyethylene oxide) or copolymers thereof, and cationic materials such as long chain quaternary ammonium compounds or those based on polyacrylamides; viscosity modifiers such as alkyl cellulose especially methyl cellulose, and colorants such as dyes or pigments. Plasticisers for phenolic resins may also be included provided the curing and foaming reactions are not suppressed thereby, and polyfunctional compounds other than the dihydric compounds referred to above may be included which take part in the cross-linking reaction which occurs in curing; e.g. di- or poly-amines, di- or poly-isocyanates, di- or poly-carboxylic acids and aminoalcohols.

[0067] Polymerisable unsaturated compounds may also be included possibly together with free- radical polymerisation initiators that are activated during the curing action e.g. acrylic monomers, so-called urethane acrylates, styrene, maleic acid and derivatives thereof, and mixtures thereof.

[0068] Other resins may be included e.g. as prepolymers which are cured during the foaming and curing reaction or as powders, emulsions or dispersions. Examples are polyacetals such as polyvinyl acetals, vinyl polymers, olefin polymers, polyesters, acrylic polymers and styrene polymers, polyurethanes and prepolymers thereof and polyester prepolymers, as well as melamine resins, phenolic novolaks, etc.

[0069] Conventional blowing agents may also be included to enhance the foaming reaction, e.g. low boiling organic compounds or compounds which decompose or react to produce gases.

[0070] The foam-forming compositions may also contain dehydrators, if desired.

[0071] A preferred method of forming the foam-forming composition comprises first mixing the resole and inert filler to obtain a substantially uniform dispersion of the filler in the resole, and thereafter adding the hardener. Uniform distribution of both the filler and the hardener throughout the composition is essential for the production of uniformly textured foam products and therefore thorough mixing is required.

[0072] If it is desired that the composition is at elevated temperature prior to commencement of the exothermic reaction, this can be achieved by heating the resole or first mixing the resole and the solid and then heating the mixture. Preferably the solid is added to the resole just before the addition of the hardener. Alternatively, the mixture of resole, solid and hardener may be prepared and the whole mixture then heated, e.g. by short wave irradiation, preferably after it has been charged to a press. A conventional radiant heat oven may also be used, if desired, but it is difficult to achieve uniform heating of the mixture by this means.

[0073] Preferably, the foam has a density in the range 75 to 500 kg / m3, such as 100 to 450 kg / m3, more preferably 120 to 400 kg / m3and most preferably 100 to 250 kg / m3. Foam cell size is also important because up to a limit the larger the size of the cell for a given density, the thicker will be the walls and hence the greater the physical strength of the foam. However if the cell size is too large, the strength begins to suffer. Preferably, the cell size is in the range of 1 to 3mm.

[0074] It will also be appreciated that the cell size can also be used, at least in part, to help absorb the build-up of pressure during pressing of the laminate structure.

[0075] Frame

[0076] Where present, the frame is a rigid structure which is present over substantially all of the perimeter edge of the open-celled substrate. The frame provides structure and strength to the panel and also defines the shape of the end product, such as a door. For example, a square or rectangular frame may be used to produce a laminate panel useful as a door. Other shapes of frame are envisioned, such as circular or triangular frames, which would provide for a circular or a triangular laminate panel. Historically, the integration of a frame into a laminate has necessitated a process typically including at least two pressing steps, in order to avoid pressure spikes that lead to process failures (e.g. blow-outs) and product flaws. However, the present invention provides a process in which a framed laminate panel is obtainable in a one-shot process, without loss of product quality such as blowouts and / or facial imperfections. This offers substantial efficiency improvements in comparison to conventional processes and can substantially increase production outputs.

[0077] The frame is in contact with the open-celled substrate layer over substantially all of the perimeter edge of the substrate layer and the frame preferably includes at least one vent in fluidic communication between the open-celled substrate and the atmosphere.

[0078] The frame may be prepared from any suitable material that is rigid enough to not buckle or break during the pressing of the sheet-form material into the open-celled substrate and to withstand the temperatures of processing. For example, the frame may be made from stone, metal, wood, polymeric materials, or combinations thereof. Preparation of a suitably rigid frame in a desired shape and configuration would be within the capabilities of the skilled person.

[0079] The corners of the frame may be held together using known methods such as butt joints, mitred butt joints, dowel joints, biscuit joints or any other suitable type of joint.

[0080] Depending on the materials used, suitable materials for securing the joints include adhesives, welds, nails, screws, staples, brackets, connectors or other suitable means.

[0081] The vent

[0082] The vent forms a channel or port to allow gas and / or vapour to escape. The vent allows the movement of gas from the inside environment of the panel to the outside atmosphere. The vent (be it in the sheet-form material and / or in the frame) does not necessitate any particular configuration in the substrate in the region of the vent. Gas is freely able to move through the open-celled substrate and the vent allows fluidic communication between the open-celled substrate and the outside of the panel. This allows for gas within the open-celled substrate to pass through the sheet-form material and / or frame and be vented out of the open-celled substrate (e.g. when a pressure differential is developed between the internal panel environment and outside of the panel).

[0083] In some examples, a single vent may be incorporated on one side of the panel and / or frame to be discrete or reduce additional post-manufacture aesthetic modifications (e.g. to plug or disguise the vent). In other examples, multiple vents may be included, for instance, on opposing sides of the frame, so as to provide additional vent sites to facilitate escape of gas when a pressure differential is established during processing.

[0084] The vent may also comprise a one-way valve which allows gas and / or vapour only to escape. A benefit of the use of such a value is that it can also be used to provide a vacuum within the laminate panel.

[0085] It will be appreciated that the vent may be integrally formed in the panel and / or the frame; or may be added to and / or inserted into the panel and / or frame. By way of example, at its simplest, the vent may comprise a hole drilled from the outside of an end of the panel and / or frame into an inner end of the panel and / or frame (and thus in fluid communication with the open-celled substrate. The vent may also take the form of a gap in the frame, for example, between parts forming the frame. In one example, the vent may be formed between vertical and horizontal parts forming the frame, for example in a corner of the frame. It will also be appreciated that such a vent could be formed in other of the corners or elsewhere depending on the structure of the frame.

[0086] The vent channel may be of any suitable shape and / or cross-section so long as it allows vapour to escape. By way of example, the channel may be tubular in length, tapered in a particular direction along its length, serpentine or corrugated.

[0087] The movement of gas itself may be smooth or tortuous, and a person of skill in the art is capable of selecting according to need.

[0088] It will also be appreciated that ideally, the vent is sized so as to reduce the potential for ingress of moisture into the internal cavity of the panel and / or frame. Further, the positioning and sizes of the vents must be such so as to allow for the attachment of other fixings and fixtures such as hinges and handles, for example where the framed panel is a door.

[0089] Sheet-Form Material

[0090] The sheet-form material preferably includes a thermoset. The material may include further components, for example components to enable the material to be handled in sheet-form.

[0091] The sheet-form material of aspects of the invention, may include any appropriate matrix composition. For example, the matrix may include one or more of a thermosetting polymer, for example an epoxy resin, a phenolic resin, a polyester resin, a polyvinylester resin, a bismaleimide or polyimide, and / or any other suitable material. The material may include melamine, which is useful as a fire retardant. The matrix materials may further include hardeners, accelerators, fillers, pigments, and / or any other components as required. The matrix may include a thermoplastic material.

[0092] The sheet-form material may have a thickness of from 0.3mm to (for example 1mm to 50 mm) to 50mm. In some particularly preferred embodiments, a super thin sheet-form material may be used, for example 0.5mm to 4mm, preferably 1 mm to 3mm, more preferably 1.5mm to 2mm. Such super thin sheets of SMC have traditionally not been suitable for use in the present applications. More specifically, the thinness of such layers has hitherto not been suitable due to the internal pressure build up within the panel and / or frame which can easily cause the thin layers to be deformed. It will be appreciated that as a result of their thinness such layers tend to possess less dimensional stability and are more easily deformed by internal pressure. However, by absorbing the internal pressures, their use is now possible, allowing the production of thinner and lighter surfaces on the panel and / or frame, as well as lighter final products such as doors.

[0093] In addition, the use of such thin layers also facilitates the use of lower pressing pressures.

[0094] A further benefit of the use of such thin layers is that less resin is being used, which provides both a cost benefit and a material benefit. As it is now feasible to use such a super thin layer, less resin is being used, which helps to reduce the amount of gas and / or vapour being produced, which in turn helps with the pressure absorption of the cavities in the panel.

[0095] Alternatively the SMC sheets may have thickness such as from 2mm to 30mm, or even 3mm to 20mm. Sheet-form material having a thickness of 4mm to 15 mm and 5 to 10mm are also envisaged, as are sheets of 6mm to 8mm.

[0096] With regard to the use of phenolic resins, the prior art (see for example US3,005,798, US3,663,503 and US4,369,259) teaches that in order to produce a phenolic resin with limited or reduced colour change, both a colour-stabilising agent and an acid catalyst must be present. Clearly, the requirement of both reactants will increase the costs of producing lighter coloured resins.

[0097] Furthermore, as shown in some of the above-mentioned documents, the colour stabilising agent may be required to be added at a specific point in the reaction process (i.e. whilst the phenol resin is still in water-soluble form) in order to achieve the colour-stabilising effect throughout the resin formed. This creates a more complex reaction process, which will inevitably affect time efficiency and therefore, once again, cost efficiency of producing such resins.

[0098] In addition, many of the methods available for producing lighter coloured phenolic resins require the presence of strong acids or bases to catalyse the reaction process. It is known that the use of such chemicals causes corrosion of equipment which will therefore need to be replaced more frequently.

[0099] Where a phenolic resin is used, it is preferable for wherein the thermosetting material to comprise uncured phenolic resin; filler; a catalyst in an amount of less than 2wt.% relative to the content of phenolic resin; and wherein the filler is present in a ratio of filler to uncured phenolic resin in an amount of 2.5:1 and greater, and further wherein the filler comprises a transition metal hydroxide and / or aluminium hydroxide in a ratio of metal hydroxide to uncured phenolic resin in an amount of 1 :1 .5 to 3:1 .

[0100] The addition of a metal hydroxide compound within the filler allows for the amount of catalyst present to be significantly reduced, and even possibly avoided altogether. Without wishing to be bound by any particular theory, it is believed that the addition of the metal hydroxide compound allows for the uncured phenolic material to reach an equivalent of B-stage curing without the need for a catalyst to be present in any significant quantity, or even at all. As would be fully understood by persons of skill in the art, the B-stage refers to partially cured state which allows for increased processability of such phenolic resins, for example, allowing them to be formed into sheets which may then be applied to the open-celled substrate. The stability is such that the formed sheets can be formed into rolls for storage and later use. Such materials can then be fully cured by the application of heat and pressure.

[0101] Preferably, the amount of catalyst that is present may be less than 1 wt.% relative to the content of the phenolic resin, more preferably less than 0.5 wt.% relative to the content of the phenolic resin, such as less than 0.2 wt.%.

[0102] The uncured material may be substantially free of catalyst. By substantially free, it is meant that the amount of any catalyst present is negligible in terms of the overall effect that it has on uncured material, and its ability to reach a B-stage equivalent of curing.

[0103] For the avoidance of any doubt, the term catalyst is intended to refer to additives which are known to catalyse the curing of such phenolic resins, and are known to aid B-stage curing. Traditionally, such catalysts fall into two main categories, namely acidic and basic. Examples of acidic catalysts include, but are not limited to, one or more of hydrochloric acid, sulphuric acid and oxalic acid. Examples of basic catalysts include, but are not limited to, one or more of ammonia, sodium hydroxide, potassium hydroxide, lithium hydroxide, rubidium hydroxide, caesium hydroxide, barium hydroxide, calcium hydroxide and ethylamine.

[0104] Phenolic resin materials such as described herein have significant advantages over more traditional materials such as SMC. It has been found that the phenolic resin material disclosed herein generally has the following advantages over SMC: better temperature performance and thermal shock resilience, excellent resistance to chemicals, corrosives / solvents, oil and water / salt water (including acid rain), improved fire, smoke and toxicity performance, improved anti-microbial properties, harder, stronger, excellent dimensional stability, electrical resistance, good thermal insulation, superior workability, low temperature processing. Preferably, the sheet-form material is applied as a substantially single thickness. Preferably, the sheet-form material comprises sheet moulding compound (SMC). The SMC comprises a thermosetting resin, preferably a polyester resin, together with reinforcing fibres, preferably glass fibres. There are benefits in using SMC. For example, SMC has low density and favourable mechanical properties compared with other materials (for example thermoplastics), and also exhibits good thermal properties. Of particular importance for some applications, for example building applications, resistance to fire is good. SMC also shows good noise reduction qualities, also important where used as a building material and good chemical resistance.

[0105] Preferably the material, for example the SMC is applied to the mould in unfolded form. This leads to ease of manufacture, and also can reduce the pressure required for the pressing step. As discussed further herein, a plurality of single thickness layers may be provided, the layers preferably overlapping at the edges to reduce the risk of gaps being formed in the skin.

[0106] Preferably the sheet-form material is applied to substantially a whole surface of the press used in the pressing step. Having the sheet-form material extend substantially across the full area of a press face has a number of advantages. For example, in some arrangements, the pressure required to complete the pressing step can be reduced by reducing the amount of lateral flow required of the material in the press. Also, by reducing the amount of flow of material across the press surface, abrasion and / or wear of the surface of the press can be reduced. In this way, the material used for the press can be selected from a wider range of candidate materials as discussed in more detail below.

[0107] The sheet-form material may comprise reinforcement, for example reinforcing fibres. The sheet-form curable material may include carbon fibres, glass fibres or aramid fibres. The amounts of the fibres used are carefully controlled so as to ensure that the SMC resins are able to freely flow into the open-celled substrate during pressing to provide strong bonding between the SMC skins and the open-celled substrate. The SMC is also capable of bonding to the frame, where present, so as to provide improved bonding between the frame and the SMC. The SMC may comprise two main components: a matrix and a reinforcement.

[0108] The matrix preferably comprises a resin which preferably includes polyester, but may include vinyl ester, epoxy, phenolic, or a polyimide. Preferably the matrix comprises a thermosetting resin.

[0109] The matrix may further comprise additives, for example minerals, inert fillers, pigments, stabilizers, inhibitors, release agents, catalysts, thickeners, hydrating additives and / or other suitable materials.

[0110] Alternatively or in addition to the presence of fibres in the sheet-form curable material, reinforcement may be provided as a separate layer of fibres, for example arranged between the sheet-form curable material and the substrate.

[0111] Where the separate layer of reinforcement is provided, it may be located across the whole of the substrate, or may for example be provided in only parts. For example, if there is a particular section of the product which is more susceptible to damage or attack, additional reinforcement can be provided in that region. For example, where the product is to be used in a door, additional reinforcement may be provided at regions of the door which are thinner than others for due to decorative moulding or other features and / or at regions of the door which are more susceptible to damage. Thus, reinforcement may be provided as one or more layers separate from the sheet-form curable material. The additional layer of reinforcement may include short and / or long fibres, for example of materials mentioned above. For example, when the super thin SMC layers are used, long fibres may be preferable.

[0112] The reinforcement preferably comprises glass fibres. The fibres may be cut, for example into lengths of 5 cm or less, or may be continuous. Other reinforcement materials could be used, for example carbon fibres or aramid fibres. In the art, long fibres may be 25mm to 50mm whereas short fibres tend to be less than 25mm.

[0113] There are benefits in using SMC. For example, SMC has low density but favourable mechanical properties compared with other materials for example thermoplastics and also exhibits good thermal properties. Of particular importance for some applications, for example building applications, resistance to fire is good. SMC also shows good noise reduction qualities, also important where used as a building material and good chemical resistance. The fibres may be short fibres, or may be longer fibres. The fibres may be loose, for example, the fibres may be arranged in a uni- or multi-directional manner. The fibres may be part of a network, for example woven or knitted together in any appropriate manner. The arrangement of the fibres may be random or regular, and may comprise a fabric, mat, felt or woven or other arrangement. The material may include short fibres, the fibres may of a length of 5cm or less. Fibres may provide a continuous filament winding. More than one layer of fibres may be provided. The fibres may be in the form of a layer. Where the fibres are in the form of a layer, they may be in the form a fabric, mat, felt or woven or other arrangement.

[0114] The fibres may be selected from one or more of mineral fibres (such as finely chopped glass fibre and finely divided asbestos), chopped fibres, finely chopped natural or synthetic fibres, and ground plastics and resins in the form of fibres. The fibres may include one or more materials. For example, the fibres may include one or more of carbon fibres, glass fibres, aramid fibres and / or polyethylene fibres, such as ultra-high molecular weight polyethylene (UHMWPE). Kevlar (RTM) fibres may be used. Laminate panels including such fibres could be used for protective devices and building products. For example, some laminate panels of the present invention may find application as armoured or bulletproof products. For example, protective panels may be formed having Kevlar (RTM) fibre reinforcement.

[0115] The sheet-form material may comprise an impregnated fibre composite material.

[0116] Sheet-form materials including long fibres can be used in the methods of the present invention, and also sheet-form materials including fibres which are woven together can be used. Without wishing to be bound by theory, it is thought that such materials having relatively long fibre reinforcements and / or including fibre mats or other networks or structures can be used because the movement of material in the press in a direction along the press surface is relatively low.

[0117] Alternatively or in addition to reinforcement being provided as an integral part of the sheetform material, reinforcement may be provided as a separate layer, for example arranged between the sheet-form material and the open-celled substrate.

[0118] Where the separate layer of reinforcement is provided, it may be located across the whole of the open-celled substrate, or may for example be provided in only parts. For example, if there is a particular section of the laminate panel which is more susceptible to damage or attack, additional reinforcement can be provided in that region. For example, where the laminate panel is to be used in a door, additional reinforcement may be provided at regions of the door which are thinner than others due to decorative moulding or other features and / or at regions of the door which are more susceptible to damage.

[0119] Thus the arrangement may include sheet-form material having integral reinforcement, for example short fibres and / or longer fibres which may be arranged as fabrics or mats, for example. In addition, or alternatively, reinforcement may be provided as one or more layers separate from the sheet-form material. The additional layer of reinforcement may include short and / or long fibres, for example of materials mentioned above.

[0120] During the pressing of the sheet-form material into the open-celled substrate in a single pressing step to form the laminate panel (for example a framed laminate panel), preferably the matrix material, for example resin, flows into the structure of the substrate to form a bond.

[0121] Preferably the layer of sheet-form material comprises a curable composition. In some examples of the invention, the sheet-form material might be settable other than by curing.

[0122] Preferably the pressure and heat are chosen such that the sheet-form material is pressed and then sets in the press. Preferably the viscosity of the sheet-form material is reduced during the pressing step.

[0123] Preferably the sheet-form material is one that reduces in viscosity and or at least partially liquefies on the application of heat and / or pressure. In this way, some flow of the material in the press can be achieved. This can lead to improved pressing of the material, more uniform thickness and / or reduction of pressing defects. Preferably, the material at least partly flows into cells of the open-celled substrate material during the pressing step. Preferably the material and open-celled substrate are such that the material only partly flows into the open-celled substrate during the pressing step so that good bonding between the skin and the open-celled substrate is obtained while retaining a suitable skin thickness for the required mechanical and other properties of the laminate.

[0124] Preferably the sheet-form material is applied to the open-celled substrate in uniform thickness.

[0125] Preferably the material, for example the SMC is applied to the press in unfolded form. This leads to ease of manufacture, and also can reduce the pressure required for the pressing step. As discussed further herein, a plurality of single thickness layers may be provided, the layers preferably overlapping at the edges to reduce the risk of gaps being formed in the skin.

[0126] Preferably the sheet-form material is applied to substantially a whole press surface.

[0127] The present invention includes a step of pressing the sheet-form material into the open- celled substrate in a single pressing step to form the framed laminate panel. Preferably the pressure applied is less than 200 tonnes per m2, preferably less than about 100 tonnes per m2. In many examples, the pressure applied will be equivalent to less than about 50, 25, 10 or even less than about 5 kg / cm2.

[0128] Optionally, pressing and heating occur simultaneously. In embodiments where the substrate is applied to a press, i.e. a press plate, the press may be a heated press.

[0129] Optionally, the open-celled substrate is heated prior to contact with the sheet form curable material. In which case, the method includes a step of heating the open-celled substrate. The open-celled substrate may be heated to a temperature greater than 100 °C, preferably to a temperature greater than 120 °C, and then contacted with the sheet-form curable material whereby the sheet-form curable material is heated. The open-celled substrate may be heated via induction heating, or by irradiation with an electromagnetic radiation. Heating may improve the flow of the sheet-form curable material. Optionally, pressing and heating occur simultaneously.

[0130] Preferably the electromagnetic radiation comprises radiation with a frequency of from 300 MHz to 300 GHz, preferably from 300 MHz to 30 GHz, more preferably from 300 MHz to 3 GHz. The electromagnetic radiation may comprise radiation with a frequency of from 800 MHz to 1000 MHz, preferably from 902 MHz to 928 MHz. The electromagnetic radiation may comprise radiation with a frequency of from 2.2 GHz to 2.7 GHz, preferably from 2.4 GHz to 2.5 GHz.

[0131] Preferably the open-celled substrate is irradiated with electromagnetic radiation with a power of at least 500 W, more preferably at least 700 W, for example at least 800 W. Any suitable power may be used for the irradiation and it will be understood that industrial irradiation systems with much higher power output may be used depending on the specific application. For example the power of the irradiation system may be at least 100 kW or at least 1 MW. The irradiation may be conducted by any method known in the art. The electromagnetic radiation may include microwave radiation, the irradiation may be conducted by means of a microwave oven, although other methods of emitting electromagnetic radiation may also be used.

[0132] Preferably, the open-celled substrate is conducted for a time period of from 30 seconds to 6 minutes. Irradiation of the open-celled substrate with electromagnetic radiation allows the open-celled substrate to be heated rapidly throughout its structure. Therefore, curing of the sheet-form curable material may be conducted more rapidly than with the traditional heated press, increasing productivity and minimising damage to sensitive components.

[0133] The open-celled substrate may be heated to any suitable temperature such that the curing of the sheet-form material is commenced. Preferably, the open-celled substrate is heated to a temperature of from 100 °C to 250 °C, preferably from 120 °C to 200 °C.

[0134] After irradiation and resultant heating of the open-celled substrate to a temperature such that the curing of the sheet-form curable material is commenced, the open-celled substrate may cool slowly to the extent that the curing of the sheet-form material continues after the period of time in which the open-celled substrate is irradiated. Preferably, the sheet-form curable material is allowed to cure for at least 3 minutes after the irradiation of the open- celled substrate is completed.

[0135] Providing heating by irradiation of the open-celled substrate and not of the sheet-form curable material is advantageous for at least the following reasons. Firstly, as the sheetform curable material forms a skin with an exposed surface, including magnetic susceptor materials in the sheet-form curable material will change the appearance of the sheet-form material and produce an inferior product. Secondly, volatile compounds will be produced in both the manufacture of the open-celled substrate and from the curing of the sheet-form material. Such volatile compounds are undesirable in the final product as they may have associated health risks and such compounds are also likely to be flammable. Heating the open-celled substrate has the advantage of removing such impurities from the open-celled substrate, wherein the volatile compounds may be vaporised and pass out of the open- celled substrate through its open-cells, rather than collecting in the cells.

[0136] Preferably, the open-celled substrate comprises one or more electromagnetic susceptor materials. The open-celled substrate may comprise more than one electromagnetic susceptor materials. For the purposes of the present invention, an electromagnetic susceptor material is considered to be a material which is increased in temperature upon irradiation with electromagnetic radiation. Preferably, the electromagnetic susceptor material is a microwave susceptor material, wherein the term microwave is considered to include electromagnetic radiation with a frequency of from 300 MHz to 300 GHz.

[0137] The one or more electromagnetic susceptor materials will preferably be added as a filler to the open-celled substrate.

[0138] Electromagnetic or microwave susceptor materials may comprise any such materials commonly known in the art. Preferably, the electromagnetic or microwave susceptor material comprises one or more of graphite, carbon black, metals, metal oxides, hydrated inorganic salts or compounds, hydrated organic salts or compounds, water, or ceramic materials. The hydrated inorganic salts or compounds may comprise one or more of hydrated sulphates, hydrated phosphates, hydrated zeolites, or hydrated silicates. The hydrated inorganic salt or compound preferably comprises gypsum or clay minerals. Preferably, the electromagnetic or microwave susceptor material comprises graphite or gypsum.

[0139] The properties of the substrate may be tailored by adjusting the ratio of the different electromagnetic susceptor materials present in the open-celled substrate or the overall amount of electromagnetic susceptor materials in the open-celled substrate. For example the precise rate and magnitude of the heating of the open-celled substrate may be adjusted in this way.

[0140] Irradiation may occur during or prior to pressing the sheet-form material into the open- celled substrate in a single pressing step to form the framed laminate panel.

[0141] Having the SMC extend substantially across the full area of a press face has a number of advantages. For example, in some arrangements, the pressure required to complete the pressing step can be reduced by reducing the amount of lateral flow required of the material in the press. Also, by reducing the amount of flow of material across the press surface, abrasion and / or wear of the surface of the press can be reduced. In this way, the material used for the press can be selected from a wider range of candidate materials as discussed in more detail below.

[0142] The sheet-form material can be applied to the press as a single piece of material.

[0143] Preferably a plurality of sheets of sheet-form material is applied to a press surface. In some arrangements, for example because the press surface is large, or to improve the ease of handling the sheet-form material, several pieces of sheet-form material can be applied to the press and / or the open-celled substrate. Preferably an edge of one sheet overlaps with an edge of an adjacent sheet. In this way, the risk of gaps being formed in the skin on the open-celled substrate is reduced. The additional material at the overlapping region has been found not to lead to reduced quality of the finished laminate panel: any excess material in that region can, in some examples, into the open-celled substrate and / or laterally within the press.

[0144] Thus in some examples, in particular where complex shapes are to be formed, several pieces of sheet-form material can be provided.

[0145] This feature is further advantageous because it can lead to a reduction in the amount of potentially waste sheet-form material. Smaller pieces of material, for example off cuts from larger pieces or cut outs (for example if a panel is to include a glazed section) need not be disposed of but can be used.

[0146] As discussed above, traditional SMC manufacturing processes may generate enormous pressure during the formation of the SMC product. By locating the open-celled substrate behind the SMC skin prior to pressing, air can escape though the cellular structure of the foam reducing greatly the abrasion on the tool surface. Also considerably lower pressures are required. Preferably the pressure is less than 500 tonnes, preferably less than 200 tonnes, preferably less than about 100 tonnes. However, in the present invention the presence of a frame around the substrate, as in the present case, can prevent adequate dissipation or escape of air, leading to build up of pressure ultimately leading to process failures or product flaws, particularly in the case of a “one shot” panel. The present invention overcomes these issues, as described herein, making possible the provision of a “one shot” panel, which benefits from functional advantages (e.g. superior bonding) as well as design advantages associated with the use of sheet-form material and an open celled substrate, that have not been accessed historically.

[0147] Preferably the sheet-form material is applied to a mould or press surface comprising aluminium or aluminium alloy.

[0148] Where lower pressures are used, aluminium tools can be used. This can give rise to low cost tooling, flexible production and less downtime due to tool change over in view of the reduced weight of an aluminium press and speed of heating or cooling an aluminium press compared with a stainless steel press. For example, the volume of an aluminium tool could be significantly smaller than that of a corresponding tool of steel, and this combined with the lower density of aluminium leads to considerable weight advantages when using aluminium presses.

[0149] Where reference is made herein to components being made of or comprising aluminium, preferably the relevant component includes aluminium or an appropriate aluminium alloy or other material including aluminium.

[0150] Preferably the sheet-form material is applied to a press surface having a surface pattern.

[0151] As indicated above, the press surface is preferably shaped for example to provide a profiled surface to the skin of the laminate. Alternatively, or in addition, a surface pattern may be provided on the press to give a surface pattern or texture on the surface of the skin of the laminate.

[0152] For example, a pattern relating to the pattern of a woodgrain may be provided on the surface of the mould or press so as to form a pattern on the surface of the laminate skin resembling woodgrain. Other patterns might be provided to give an alternative finish to the skin.

[0153] Preferably the sheet-form material is such that matrix material, for example the prepolymer resin, extends into the surface of the open-celled substrate during the pressing. This can improve the bond between the skin and the open-celled substrate. Preferably the distance the matrix material extends into the surface is more than 10%, 20% 30% or even 50% of the thickness of the skin on the open-celled substrate. For example, more than 5%, more than 10% or more than 20% of the resin in the sheet-form material may flow into the open-celled substrate.

[0154] The formulation of the sheet-form material may be such that there is sufficient matrixmaterial in the composition to allow for there to be the desired volume of flow of the polymer into the surface of the open-celled substrate. This may require that the sheetform material includes additional resin compared with that of a conventional sheet-form material.

[0155] The method may include the step of providing further components between the two layers of sheet-form curable material. Other components may also be sandwiched between the skins during the pressing process. For example, where the laminate panel is a door, the door frame components, glazing panels and other components might be arranged in the press so that they can be formed into the laminate panel in a single pressing step.

[0156] Preferably the method includes the step of applying the layer of sheet-form material to a press, prior to the step of pressing the sheet-form material into the open-celled substrate in a single pressing step to form the laminate panel (for example framed laminate panel).

[0157] By providing the matrix in the form of a sheet, the use of liquid resin can be avoided. This can give considerable time savings in the manufacture of the laminate panel, as well as benefits regarding the ease of use of the matrix material and a reduction in the manpower and equipment required to apply the matrix material or pre-polymer to the press.

[0158] The method may include the step of applying the layer of sheet-form material directly to a surface of a press.

[0159] In other examples, one or more further layers might be applied between the sheet-from material and the tool surface itself. In some examples, materials might be applied to the tool surface, for example to assist pressing and / or release of the laminate panel from the press. A coating composition may be applied to the press which forms a coating on the laminate panel after pressing. The composition may be coloured. The composition may be applied to the press in the form of a powder, for example using an electrostatic method.

[0160] Preferably the method further includes the step of providing a veil between the sheet-form pressing material and a surface of the press.

[0161] Preferably the veil comprises a sheet of material which is provided between the sheetform pressing material and the press surface before pressing. The provision of the veil preferably gives rise to improvements or changes in the surface finish of the pressed article compared with an arrangement in which the veil is not present.

[0162] For example, where the sheet-form material comprises a reinforcing component, preferably the veil acts to prevent or reduce the amount of the reinforcing component at the surface of the resulting laminate panel. For example, where the sheet-form material comprises SMC including short glass fibres, it has been found in some situations that the glass fibres on pressing can project from the surface of the laminate panel giving a disadvantageous surface finish. By using a veil, it can be possible to provide a barrier to certain components of the sheet-form material, for example so as to improve surface finish.

[0163] In some examples, it is thought that the use of a veil has the effect of reducing movement of the matrix material in the plane of the sheet-form material. It is a preferred feature of the aspects of the present invention that the movement in the plane of the sheet-form material is reduced; it is thought that this gives better finish to the laminate panels in some arrangements.

[0164] The veil is preferably substantially pervious to a component of the sheet-form material during the pressing.

[0165] In this way, a component, for example a resin component, of the sheet-form material can pass through the veil during pressing so that a resin finish at the surface of the laminate panel can be formed.

[0166] Therefore, the material for the veil is preferably chosen so that it is sufficiently pervious to certain components of the sheet-form material (in particular the resin), while providing a barrier function for certain other components for example glass fibres or other reinforcements.

[0167] In some arrangements the veil can be placed directly adjacent to the sheet-form material and there will be sufficient penetration by the resin components for a satisfactory surface finish to be produced. However, it is envisaged that a further layer may be provided between the veil and the sheet-form material to improve the surface finish. For example, a layer of resin material may be provided on the surface of the press. This may be applied by any appropriate method.

[0168] Alternatively, or in addition, the veil layer may comprise additional components, for example resin material to improve surface finish.

[0169] The veil may comprise a non-woven material. In particular where the veil is applied directly to the press, it may be desired for the veil material not to have a particular texture or finish, which might form a perceptible surface structure at the surface of the laminate panel. However, in other arrangements, such a surface structure or pattern at the surface may be an advantageous feature.

[0170] Where such a structure is not desired, preferably the veil comprises a non-woven material. For example, preferably the veil does not comprise a knitted or woven surface, although in some cases such a material could be used, in particular if a surface treatment had been provided to reduce the surface structure of the veil material. For example, in some arrangements, the veil might comprise a fleece or brushed surface. However, for most applications, preferably at least one surface of the veil material has substantially no surface structure or pattern.

[0171] The veil may comprise a felt cloth. For example the veil may comprise a polyester material. Alternative materials could be used, for example comprising wool, polyethylene, polypropylene or PET. The veil might comprise a fleece material, or might comprise a foam material. As indicated above, a suitable material preferably is pervious to the resin to be used, and has a suitable surface texture.

[0172] The veil may comprise a polyester material having a weight of about 120 to about 150 g / m2.

[0173] By applying a sheet-form material to a substrate comprising an open-celled structure, several advantages can be achieved in examples of this aspect of the invention.

[0174] In particular, by using an open-celled substrate, air in the press and gases produced during the pressing process can pass into and through the open cell structure of the foam so that the risk of the air and gases leading to flaws and other deformities in the skin are reduced.

[0175] In some examples, it will be arranged that the formulation of the sheet-form material is such that there is the desired flow of the pressing material into the surface of the open- celled substrate. In some examples, this will be achieved by there being excess prepolymer material in the composition, for example compared with corresponding compositions for other applications.

[0176] Thus the thickness of the skin formed may be self-regulating in that the pressing operation will compress the sheet-form material to a predetermined thickness, and the excess resin will flow into the open-celled substrate. This also aids in the use of the super thin SMC sheets as described above. Also, less accuracy in the formulation of the sheet-form material is required, since any excess prepolymer in the composition will be removed into the open-celled substrate on the pressing step.

[0177] In preferred examples, the material of the sheet-form material passes into the cells or other formations of the open-celled substrate material during the pressing process and provides a mechanical bond between the open-celled substrate and the pressed skin. This can reduce the risk of delamination of the skin from the open-celled substrate core, provide a stable laminate panel when exposed to heating / cooling cycles and provides a monolithic composite structure without the need for an adhesive to be applied or the assembly of parts.

[0178] In preferred examples, the sheet-form material forms an outer skin on the open-celled substrate, which is mechanically keyed into the open-celled substrate giving a good bond between the skin and the open-celled substrate. In some cases it has been found that the bond achieved at the interface of the skin and the open-celled substrate is in fact stronger then the material of the open-celled substrate itself. A laminate panel made by this method may fail within the open-celled substrate layer, and not at the interface.

[0179] Preferably the method includes applying heat and pressure to the open-celled substrate and the sheet-form material. Preferably the sheet-form material is cured directly onto the open-celled substrate. This important feature may be provided independently. A broad aspect of the invention provides, curing a sheet of curable material directly onto the surface of the open-celled substrate (as well as the frame where present), preferably the open-celled substrate configured to displace gas or vapour from the interface region, preferably the open-celled substrate comprising an open-cell foam.

[0180] Preferably the sheet-form material comprises a thermosetting material, the method including the step of causing or allowing the material to cure.

[0181] Preferably the method comprises a method of compression moulding. Preferably the pressure and temperature and cycle time are chosen so that the sheet-form material sets in the mould. Preferably the mould is profiled to produce the desired shape of skin.

[0182] A contoured surface of the laminate panel can be obtained. For example the surface of the laminate panel may include depressions formed during the pressing step as the components are pressed onto the mould. Thus moulded composite laminate panel can be formed.

[0183] It is envisaged that the methods of the present invention can be used to form a laminate panel having no surface mouldings, for example flat laminate panel. In this case, the open-celled substrate may comprise any suitable material. Preferably the open-celled substrate comprises a rigid material so that the pressing step can be carried out most successfully and the open-celled substrate can provide desired mechanical properties to the laminate panel. In some examples, where a contoured surface is required, the required contours or mouldings can be formed on the surface of the open-celled substrate. For example, the required shape may be formed in the open-celled substrate by machining, for example, an open-celled substrate block comprising polyurethane foam. The shape of the mould is matched to the contours of the open-celled substrate so that when the components are pressed onto the mould surface, the resulting panel has the skin having the required contours bonded to the shaped substrate. However, preferably the open-celled substrate comprises a crushable material such that, during the application of pressure step, a surface of the open-celled substrate is moulded.

[0184] The open-celled substrate may comprise a frangible material. Such a material may be rigid and non-crushable in the normal use of the resulting laminate panel, but during the pressing step, the open-celled substrate material can be crushed to mould the open-celled substrate. Where a mould surface is used, the open-celled substrate material can be crushed so that its surfaces facing the mould conform to the contours of the mould surface.

[0185] The open-celled substrate contributes to the ability to manufacture the laminate panel through a one-shot process, although it has been found by the inventors that it is necessary for the frame and / or open-celled substrate of the panel to define one or more cavities, as described herein, in order for a panel to be made reproducibly by a “one-shot” process. These cavities provide voids to pressure-equalise the laminate panel during manufacture (i.e. they provide internal free volume to accommodate gas). The voids have been found to prevent pressure spikes during the one-shot manufacturing process and facilitate dissipation of gas through the substrate to escape through the vent provided (such as in the frame) where there is a pressure differential between the internal panel environment and outside of the panel.

[0186] Cavities

[0187] The one or more cavities defined by the frame and / or open-celled substrate provide voids to pressure-equalise the laminate panel during manufacture. This means that during pressing of the sheet-form material onto each of opposing surfaces of the substrate, gas contained within the open-cell substrate and / or any gas which is produced during curing of any resins present in the sheet-form material may be accommodated in the cavities so as to avoid pressure spikes that otherwise lead to process failures. In the context of the present invention, a “void” is preferably not in contact with the sheetform material (although this is possible where the voids are present on a bottom face of a laminate panel or even at the edges), and sheet-form material will not fill the voids during the pressing stage, thereby retaining volume within the internal panel environment which may accommodate gas. The free volume provided by the voids within the internal panel environment confers desirable pressure-equalising properties that enable the one-shot process to be used whilst avoiding process failures or product flaws resulting from pressure spikes. Typically, where present in the substrate, a void may be encapsulated entirely by the open-celled substrate, a combination of the open-celled substrate and the frame (where present), or a combination of the open-celled substrate and overlying sheetform material. The open-celled substrate may additionally have other surface hollows or channels, which are accessible to the sheet-form material and into which the sheet-form material flows during the pressing stage. However, such hollows or channels do not form voids in the laminate.

[0188] In some embodiments, the method further comprises the pre-step of introducing the one or more cavities into the frame and / or open-celled substrate. Cavities in the frame may be in fluidic communication with cavities formed in the open-celled substrate. The pattern of the cavities may be of any form whether regular or random, and the cavities may be distributed across all the frame and / or open-celled substrate or only occupy one or more regions of the frame (e.g. one side of a rectangular or square frame) and / or open-celled substrate (e.g. a central area, or the area around the periphery of the open-celled substrate).

[0189] Cavities may be formed in the frame and / or open-celled substrate by any suitable means, for example mechanically or chemically. Cavities in the frame and / or open-celled substrate may be formed by any method known in the art, such as machining, cutting, drilling, boring (such as by the insertion of a pipe), lasers, waterjet drilling, or melting. It is also possible to incorporate cavities into the open-celled substrate at the time of preparation of the substrate by using a mould with projections which, for example, may generate channels in the resulting substrate. As will be appreciated, methods of forming cavities in the frame and / or open-celled substrate, which may depend on the particular form or composition of the frame or open-celled substrate, would be apparent to the skilled person.

[0190] Preferably, introduction of the one or more cavities is undertaken before integration of the open-celled substrate within the frame where present. It may be more convenient to introduce cavities into the open-celled substrate and the frame separately, for example, if a different method is better suited to the specific material or dimensions of the open-celled substrate and the frame, or for example if cavities of differing dimensions are desired in the open-celled substrate and the frame.

[0191] Preferably, at least one of the one or more cavities is integrated within the internal structure of the open-celled substrate as a void over the thickness of the open-celled substrate.

[0192] Preferably, the open-celled substrate includes a plurality of cavities on each of its opposing surfaces over which the sheet-form material is provided. The presence of cavities on each of its opposing surfaces over which the sheet-form material is provided allows for more uniform pressure equalising across the internal panel environment, by providing an even distribution of free volume capable of accommodating gas.

[0193] Preferably, the size differential between length, width and depth dimensions of respective cavities on the surfaces of the open-celled substrate is less than 20%.

[0194] Preferably, the plurality of cavities on the surfaces of the open-celled substrate is distributed evenly across the length and / or width of the open-celled substrate surface. A more even distribution of cavities on the surfaces of the open-celled substrate allows for more uniform pressure equalising across the internal panel environment as it is formed in the one-shot process and more efficient venting of gas, preventing any localised bubbling or rupture of the open-celled substrate where gas is not vented due to a local dearth of ventilation.

[0195] Preferably, the depth of any of the one or more cavities provided at the surface of the open-celled substrate does not exceed 30% of the total thickness of the open-celled substrate. Cavities at the open-celled substrate of the substrate not exceeding 30% of the total thickness of the open-celled substrate provides a good compromise to allow for good ventilation of gas within voids of the open-celled substrate whilst not excessively weakening the structure of the open-celled substrate due to presence of cavities of excessive volume or depth. Preferably, the depth of any of the one or more cavities provided at the surface of the open-celled substrate does not exceed 20%, 15%, 10%, or 5% of the total thickness of the open-celled substrate. For example, the depth of any of the one or more cavities provided at the surface of the open-celled substrate may be from 1 % to 30%, 5% to 30%, 10% to 30%, 15% to 30%, 20% to 30%, 1 % to 20%, 5% to 20%, 10% to 20%, or 1 % to 10% of the total thickness of the open-celled substrate. Preferably, the size differential between length, width and depth dimensions of respective cavities of the plurality on the surfaces of the open-celled substrate is less than 20%, more preferably less than 15%, even more preferably less than 10 %.

[0196] Preferably, the plurality of cavities on the surfaces of the open-celled substrate is distributed evenly across the length and / or width of the open-celled substrate surface.

[0197] The cavities may take any shape suitable for providing voids to pressure-equalise the laminate panel during manufacture. For example, the cavities may be prisms, such as square or circular prisms, or the cavities may be substantially spherical or hemispherical. Combinations of different shaped are also envisioned. The exact shape and dimensions of the cavities may vary depending on the method used to prepare them.

[0198] In the case of cavities defined by the frame, the cavities may take the form of one or more indentations, depressions, grooves, etc on the inner face of the frame. Cavities of this type defined by the inner surface of the frame will be in fluidic communication with the open-celled substrate. Where cavities are defined in the inner surface of the frame, any gas which exits the open-celled substrate may enter these cavities during the “one-shot” process to provide pressure equalisation.

[0199] The cavities may also be formed between the frame and the open-celled substrate. Such cavities can form during manufacture of the laminate panel. By way of example, mechanical give in the frame and / or joints of the frame, during pressing can form cavities suitable for absorbing pressure (e.g. in situ formation of a cavity).

[0200] Cavities defined by the frame may, or may not, be in fluidic communication with one or more vent in the frame, and / or may provide one or more vent in the frame. A cavity in fluidic communication with one or more vent will allow for venting of any accumulated gas that enters the cavity. Any cavity in the frame which is in fluidic communication with the environment outside of the frame and with the open-celled substrate, i.e. a cavity which passes through the whole width of the frame, can be considered to also provide a vent.

[0201] Grooves in the inner face of the frame, such as horizontal or vertical grooves, with reference to the width plane of the laminate panel, are a useful form of cavity. Grooves provide a large surface area of contact between the cavity and the open-celled substrate which allows for rapid transfer of gas from the open-celled substrate to the cavity which allows for rapid pressure equalisation. Additionally, grooves may extend to an outer edge of the frame and be in fluidic communication with the environment outside of the frame, and thus also provide a vent.

[0202] Where the panel is moulded during pressing, crushing of the open-celled substrate may reduce the amount of space available for absorbing pressure. In such instances, extra cavities and / or channels may be added within the foam so as to improve the ability to absorb the internal pressure produced during curing. In such instances, the positioning of the vents may also be of importance.

[0203] Laminate Panel

[0204] According to an aspect of this invention, there is provided a one-shot laminate panel obtained, or obtainable, from a method according to any one of the preceding claims. Preferably, the one-shot laminate panel is a framed laminate panel.

[0205] According to an aspect of the invention, there is provided a one-shot sealed laminate panel comprising: an open-celled substrate layer; at least one layer of sheet-form material over each of opposing surfaces of the substrate and which is in contact with the substrate layer over substantially all of the perimeter edge of the substrate layer; and at least one vent in fluidic communication between the substrate and the atmosphere; wherein the open- celled substrate defines one or more cavities; and wherein the cavities provide voids to pressure-equalise the framed laminate panel during manufacture.

[0206] Preferably, according to another aspect of this invention, there is provided a sealed framed laminate panel comprising: an open-celled substrate layer provided within a frame, such that the frame is in contact with the substrate layer over substantially all of the perimeter edge of the substrate layer and wherein the frame includes at least one vent in fluidic communication with the substrate; at least one layer of sheet-form material provided over each of opposing surfaces of the framed substrate; wherein the frame and / or open-celled substrate define one or more cavities, said cavities forming voids for pressure-equalising the framed laminate panel during manufacture. In such an embodiment, the framed laminate panel comprises a core sandwiched between two sheet-form material skins.

[0207] In some embodiments of the invention, the sheet-form material is applied directly to the open-celled substrate. A benefit of the present invention is that the one-shot process obviates the need for separate adhesives layers to enhance adhesion. Preferably, at least one of the one or more cavities is integrated within the internal structure of the open-celled substrate as a void over the thickness of the open-celled substrate. Preferably, the open-celled substrate includes a plurality of cavities on each of its opposing surfaces over which the sheet form material is provided. Preferably, the size differential between length, width and depth dimensions of respective cavities of the plurality on the surfaces of the open-celled substrate is less than 20%, more preferably less than 15%, even more preferably less than 10 %.

[0208] Preferably, the plurality of cavities on the surfaces of the open-celled substrate is distributed evenly across the length and / or width of the open-celled substrate surface. Preferably, the depth of the one or more cavities provided at the surface of the open-celled substrate does not exceed 30% of the total thickness of the open-celled substrate. Preferably, the depth of any of the one or more cavities provided at the surface of the open-celled substrate does not exceed 20%, 15%, 10%, or 5% of the total thickness of the open-celled substrate. For example, the depth of any of the one or more cavities provided at the surface of the open-celled substrate may be from 1 % to 30%, 5% to 30%, 10% to 30%, 15% to 30%, 20% to 30%, 1 % to 20%, 5% to 20%, 10% to 20%, or 1 % to 10% of the total thickness of the open-celled substrate.

[0209] Any feature in one aspect of the invention may be applied to other aspects of the invention, in any appropriate combination. In particular, method aspects may be applied to product aspects, and vice versa.

[0210] Figures

[0211] The invention will now be further described with reference to the figures in which:

[0212] Figure 1 depicts an embodiment of the laminate panel with the open celled substrate, sheet-form material, and cavities depicted;

[0213] Figure 2 depicts an exploded diagram of the laminate panel with the open celled substrate, sheet-form material, cavities, and frame depicted;

[0214] Figure 3 depicts an alternative embodiment of the laminate panel with the open celled substrate, sheet-form material, and cavities depicted;

[0215] Figure 4 depicts the “one-shot” process of pressing the sheet-form material into the open- celled substrate in a single pressing step to form the framed laminate panel; and Figure 5 depicts an embodiment of a laminate panel with particular emphasis on the cavities.

[0216] Figure 1 depicts an example of a laminate panel (10) prepared or preparable by the method of the present invention. In this example, the open celled substrate (12) has a substantially square shaped perimeter edge. The frame is not shown in this figure. The top and bottom faces of the open-celled substrate layer are covered by a layer of sheetform material (11) which is pressed over each of the opposing surfaces of the open-celled substrate layer (12) during manufacture of the laminate panel (10). Also depicted in Figure 1 are cavities (13) defined by the open celled substrate (12)wherein the cavities provide voids to pressure-equalise the framed laminate panel during manufacture. Cavities may also be defined by the frame (i.e. on the inward facing surfaces thereof) although the frame is not depicted in Figure 1 . In this example, the cavities (13) are depicted as circular holes in the open celled substrate (12), although the cavities (13) may take any suitable shape. The cavities (13) in Figure 1 are not necessarily shown to scale and are depicted with these dimensions and positioning purely for illustration and emphasis. The cavities (13) are depicted as having a diameter of approximately half the height of the open celled substrate layer (12), although the cavities (13) may be any appropriate size suitable to provide voids to pressure-equalise the framed laminate panel during manufacture.

[0217] Figure 2 depicts an exploded diagram of a laminate panel (20) prepared or preparable by the method of the present invention. The laminate panel (20) of Figure 2 is similar to that of Figure 1 albeit with differences depicted in the layer of sheet-form material (21) and the cavities (23) in addition to the frame (24) being depicted (in exploded form). The frame (24) is in contact with the substrate layer over substantially all of the perimeter edge of the substrate layer (22) (although it is depicted separately in this figure for illustration purposes). The frame (24) has a substantially square shaped perimeter to match that of the open-celled substrate (22). The frame (24) includes at least one vent (25) in fluidic communication with the substrate. In Figure 2, vent (25) is depicted as two semicircles in a corner of the frame (24). It would be appreciated that when the frame (24) is positioned over the perimeter edge of the substrate layer (22), the two semicircular vents (25) would form one circular vent (25) in a corner of the frame (24). The vent (25) is depicted as circular in Figure 2, and is not necessarily shown to scale, the vent (25) may be any appropriate size suitable for gas to pass from the open-celled substrate (22) through the vent (25). Similarly, the vent (25) may take any appropriate positioning on the frame (24), although positioning a vent (25) in one or more corners of the frame (24) is preferred. In Figure 2 a single vent (25) is depicted, although one or more vents (25) may be present in the frame (24), for example, in one or more corners of the frame, or in each corner of the frame.

[0218] The frame (24) is shown with a given thickness in this figure for illustration purposes, although any suitable thickness could be used. Also depicted in this figure are exemplary cavities defined by the frame (24). In this figure, the cavities take the form of grooves (26a and 26b) disposed in the inner face of the frame (24). Both vertical grooves (26a) and a horizontal groove (26b), with reference to the width plane of the laminate panel, are depicted in Figure 2. Grooves (26a and 26b) are a particularly suitable form of cavity disposed within the inner face of the frame (24) and are well suited to allowing pressure equalisation during the pressing step. The shape, size, position, and number of the grooves (26a and 26b) are shown for illustration purposes, cavities, such as grooves, of any suitable dimensions, positioning, and number may be defined by the frame. Cavities such as grooves may be defined by only one inner face of the frame, or by one or more of, or all of the inner faces of the frame. In Figure 2 both vertical grooves (26a) and a horizontal groove (26b) are depicted, however in some embodiments only one or more vertical grooves (26a) are present, and in other embodiments only one or more horizontal grooves (26b) are present. Alternatively, any combination of vertical grooves (26a) and horizontal grooves (26b), and / or any other form of cavities may be present in the frame (24).

[0219] The layer of sheet-form material (21) is shown with a different surface pattern which may represent the use of a different sheet form material and / or a surface pattern applied to the layer of sheet-form material (21). In the laminate panel (20) of Figure 2 the cavities (23) are depicted as substantially square and are positioned in an alternating height within the open celled substrate (22). The cavities (23) are not necessarily shown to scale and are depicted with these dimensions and positioning purely for illustration and emphasis. The cavities (23) in Figure 2 show that alternative shapes may be used and that any suitable positioning within the open-celled substrate (22)may be used. In Figure 2, the sheet-form material (21) is not shown to cover the top face of the frame (24), this is for illustration purposes, and due to the illustrative width of the frame (24). However, in practice, the sheet-form material (21) may cover all of, part of, or none of the top and bottom faces of the frame (24) as is desired.

[0220] Figure 3 depicts an alternative example of a laminate panel (30) prepared or preparable by the method of the present invention. The laminate panel (30) of Figure 3 is similar to that of Figure 1 albeit with differences depicted in the layer of sheet-form material (31), the cavities (33), and the open-celled substrate (32). The layer of sheet-form material (31) is shown with a different surface pattern which may represent the use of a multiple layers of sheet-form material or further treatment applied to the outermost layer of sheet-form material (31). In the laminate panel (30) of Figure 3 the cavities (33) are depicted as substantially rectangular. The cavities (33) are not necessarily shown to scale and are depicted with these dimensions and positioning purely for clarity and emphasis. The cavities (33) in Figure 3 further show that alternative shapes may be used and that any suitable positioning on the frame may be used. The open-celled substrate (32) of the laminate panel (30) of Figure 3 is depicted as substantially circular to show that any suitable shape of open-celled substrate (32) may be used so long as the frame (not shown) is in contact with the open-celled substrate layer (32) over substantially all of the perimeter edge of the substrate layer.

[0221] Figure 4 depicts a “one-shot” pressing step comprising pressing the sheet-form material into the open-celled substrate in a single pressing step to form a framed laminate panel, for example, the laminate of Figure 1 (frame not shown in Figure 4). The vertical arrows represent pressing the sheet-form material into the open-celled substrate. The diagonal arrows represent the potential movement of gas, such as gas formed during curing of the sheet-form material, towards the frame (not shown). Although the diagonal arrows point outwardly, gas is accommodated within the cavities is free to move inwardly through the tortuous paths defined by the open celled substrate. Generally, the direction of flow is dictated by the location of the vent in the frame (not shown), which allows fluidic communication between the inner panel environment and outside of the panel. . The cavities help the system to pressure equalise during the pressing step which allows for the entire pressing step to proceed in a single step (I ,e, as a “one-shot” process as defined herein). The cavities provide inner volume to accommodate gas whilst it is dissipated through the vent in the frame in a controlled manner, thereby preventing localised pressure spikes which lead to product flaws and process failures.

[0222] Figure 5 depicts a laminate panel (50), such as that of Figure 1. Also depicted in Figure 5 is the upper layer of sheet-form material (51), the open-celled substrate (52) and the cavities (53a and 53b). Cavities 53a are depicted as being defined within the open-celled substrate (52) and extending towards the outer edge of the open-celled substrate (52) which provides the possibility of defining part of the cavity (53a) within the frame (not shown) and allowing the cavity (53a)to, optionally, be coindent with one or more vents in the frame (not shown). Cavities 53b are depicted as being defined entirely within the open-celled substrate (52). The cavities (53a and 53b) of Figure 5 are not necessarily shown to scale and are depicted with these dimensions and positioning purely for clarity and emphasis. The cavities (53a and 53b) of Figure 5 are depicted as circular prisms although they may be defined by any suitable dimensions. The cavities (53a and 53b) therefore allow for gas, such as gas formed during curing of the sheet-form material to pass through the open-celled substrate (52) and to exit the laminate panel (50) through one or more vents in the frame (not shown).

[0223] Example Preparation of Laminate Panel

[0224] A vent is drilled into one corner of a wooden frame, which has a substantially square shape. The frame is placed around a foam open-celled substrate having a substantially square shape, with dimensions such that the square frame is in contact with the substrate layer over substantially all of its perimeter edge. The open-celled foam is machined to introduce cavities across its thickness and distributed evenly over its cross section.

[0225] The sheet-form material comprises a SMC comprising a curable matrix and reinforcement.

[0226] To prepare the SMC, the matrix is prepared by mixing, for example a curable phenolic resin with minerals and additives, for example including calcium carbonate and titanium dioxide together with appropriate pigments.

[0227] The matrix in the form of the resin paste is then applied to a bottom film carrier. Glass fibres as the reinforcement are then applied to the upper surface of the resin paste on the film carrier. A further layer of the resin paste is applied to sandwich the fibres between the layers of matrix. A top film is applied to the upper layer of the matrix. The resulting layered composition is subsequently compressed using a series of rollers to form a sheet of the sheet moulding compound between the film carriers. The material is rolled onto rollers and kept for at least 3 days at a regulated temperature of for example 23 to 27 ° C.

[0228] The resulting SMC is provided over the top and bottom faces of the framed open-celled substrate, the SMC sheets extended across the whole of the top surface and of the bottom surface of the framed open-celled substrate. The SMC material is pressed over each of opposing surfaces of the framed substrate as described herein in a single step, at 140 °C. The “one-shot” method provides a framed laminate panel comprising an open-celled substrate layer provided within a frame with a layer of sheet-form material provided over each of opposing surfaces of the framed substrate.

[0229] In an alternative example, the same procedure is followed to prepare the SMC and the framed open-celled substrate. The SMC is provided over the top and bottom faces of the framed open-celled substrate, the SMC sheets extended across the whole of the top surface and of the bottom surface of the framed open-celled substrate. The SMC material is pressed over each of opposing surfaces of the framed open-celled substrate and the framed open-celled substrate is irradiated with electromagnetic radiation with a frequency of 2.45 GHz and a power of 800 W or 1000 W, for a time period of 1 minute in a microwave oven.

[0230] The irradiation raises the temperature of the open-celled substrate to approximately 200 °C, at which time the sheet-form curable material begins to cure. After the irradiation, the materials are allowed to stand for around 3 minutes such that the sheet-form material becomes fully cured.

Claims

Claims1 . A method of forming a one-shot sealed laminate panel, the method comprising: providing a an open-celled substrate layer; providing at least one layer of sheet-form material over each of opposing surfaces of the substrate and which is in contact with the substrate layer over substantially all of the perimeter edge of the substrate layer; and at least one vent in fluidic communication between the substrate and the atmosphere; pressing the sheet-form material into the open-celled substrate in a single pressing step to form the laminate panel; wherein the open-celled substrate defines one or more cavities; and wherein the cavities provide voids to pressure-equalise the sealed laminate panel during manufacture.

2. A method according to Claim 1 , the method comprising: providing an open-celled substrate layer within a frame such that the frame is in contact with the substrate layer over substantially all of the perimeter edge of the substrate layer; and wherein the frame includes at least one vent in fluidic communication with the substrate and the atmosphere; providing at least one layer of sheet-form material over each of opposing surfaces of the framed substrate; pressing the sheet-form material into the open-celled substrate in a single pressing step to form the framed laminate panel; wherein the frame and / or open-celled substrate define one or more cavities; and wherein the cavities provide voids to pressure-equalise the framed laminate panel during manufacture.

3. A method according to Claim 1 or Claim 2, further comprising the pre-step of introducing the one or more cavities into the frame and / or open-celled substrate.

4. A method according to Claim 3, wherein introduction of the one or more cavities is undertaken before integration of the substrate within the frame.

5. A method according to any one of the preceding claims, wherein at least one of the one or more cavities is integrated within the internal structure of the substrate as a void over the thickness of the substrate.

6. A method according to any one of the preceding claims, wherein the substrate includes a plurality of cavities on each of its opposing surfaces over which the sheet-form material is provided.

7. A method according to Claim 6, wherein the size differential between length, width and depth dimensions of respective cavities on the surfaces of the substrate is less than 20%.

8. A method according to Claim 6 and Claim 7, wherein the plurality of cavities on the surfaces of the substrate is distributed evenly across the length and / or width of the substrate surface.

9. A method according to any one of the preceding claims, wherein the depth of any of the one or more cavities provided at the surface of the substrate does not exceed 30% of the total thickness of the substrate.

10. A method according to any one of the preceding claims, wherein the sheetform material is applied as a substantially single thickness.11 . A method according to any one of the preceding claims, wherein the substrate comprises a foam.

12. A method according to any one of the preceding claims, wherein the sheetform material comprises sheet moulding compound (SMC).

13. A method according to any one of the preceding claims, wherein the frame comprises a material impermeable to gas or vapour.

14. A method according to any one of the preceding claims, further comprising the step of curing the sheet-form material, for example by heating.

15. A method according to any one of the preceding claims, wherein the pressing step includes contacting the sheet-form material with a mould surface having a surface pattern.

16. A one-shot sealedlaminate panel obtained, or obtainable, from a method according to any one of the preceding claims.

17. A one-shot sealed laminate panel according to Claim 16, wherein the sealed laminate panel is a framed laminate panel.

18. A sealed laminate panel comprising: an open-celled substrate layer; at least one layer of sheet-form material over each of opposing surfaces of the substrate and which is in contact with the substrate layer over substantially all of the perimeter edge of the substrate layer; and at least one vent in fluidic communication between the substrate and the atmosphere; wherein the open-celled substrate defines one or more cavities; and wherein the cavities provide voids to pressure-equalise the framed laminate panel during manufacture.

19. A sealed laminate panel according to Claim 18 comprising: an open-celled substrate layer provided within a frame, such that the frame is in contact with the substrate layer over substantially all of the perimeter edge of the substrate layer and wherein the frame includes at least one vent in fluidic communication with the substrate; at least one layer of sheet-form material provided over each of opposing surfaces of the framed substrate; wherein the frame and / or open-celled substrate define one or more cavities, said cavities forming voids for pressure-equalising the framed laminate panel during manufacture.

20. A panel according to Claim 18 or 19, wherein at least one of the one or more cavities is integrated within the internal structure of the substrate as a void over the thickness of the substrate.

21. A panel according to any one of Claims 18 to 20, wherein the substrate includes a plurality of cavities on each of its opposing surfaces over which the sheet form material is provided.

22. A panel according to Claim 21 , wherein the size differential between length, width and depth dimensions of respective cavities of the plurality on the surfaces of the substrate is less than 20%.

23. A panel according to Claim 21 or Claim 22, wherein the plurality of cavities on the surfaces of the substrate is distributed evenly across the length and / or width of the substrate surface.

24. A panel according to any one of Claims 18 to 23, wherein the depth of the one or more cavities provided at the surface of the substrate does not exceed 30% of the total thickness of the substrate.

25. A panel according to any one of Claims 18 to 24, wherein the sheet-form material comprises sheet moulding compound (SMC).

26. A panel according to any one of Claims 18 to 25, wherein the substrate comprises a foam.

27. A panel according to any one of Claims 18 to 26, wherein the sheet-form material is cured.

28. A panel according to any one of Claims 19 to 27, wherein the frame comprises a material impermeable to gas or vapour.

29. A panel according to any one of Claims 18 to 28, wherein the sheet-form material includes a surface pattern.

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