FLAME RETARDANT COMPOSITION AND COMPOSITE PANEL

FIELD

[0001] The present disclosure relates to a flame retardant core composition, a composite panel including the core composition, and methods of making the core composition and composite panel.

BACKGROUND

[0002] Composite panels are used in a variety of applications including, for example, buildings, transportation, sign and display, and other structures. In buildings, for example, composite panels have been used as architectural cladding, walls, partitions, and ceilings, and the panels can provide aesthetic functionality and structural integrity. Depending on their composition, composite panels can be weatherproof, sound absorbing, fire resistant or retardant, impact resistant, and substantially maintenance free.

[0003] Composite panels include two or more different layers. Certain commercially available composite panels include a core layer and two outer layers, one outer layer attached to each side of the core layer. The outer layers can comprise aluminum, an aluminum alloy, or some other metallic material, for example. The outer layers can provide a desired appearance and suitable maintenance properties (corrosion resistance, self cleaning properties, etc.), and the core layer can provide rigidity and other desired features.

[0004] Building regulations may specify that composite panels used in certain building applications exhibit limited combustibility. Some regulations may require that construction materials, such as architectural cladding applied on specified surfaces of a building, are substantially non-combustible and achieve an Al or A2 classification under European Standard EN 13501-1. The particular classification achieved for a composite panel under the EN 13501-1 standard depends on the panel’s performance in specific fire, smoke, and flaming droplets and particles testing. An Al classification generally applies to materials that do not smoke or produce flaming droplets or particles when tested under the EN-13501-1 standard. An A2 classification generally applies to materials that produce a small quantity of smoke and do not produce flaming droplets or particles when tested under EN-13501-1. An

1

301825017 A2 classification also requires that the material (for example, a composite panel) has a heat of combustion that does not exceed 3.0 MJ/kg when evaluated under test method EN ISO 1716, “Fire technical testing of building products - determination of calorific potential.”

SUMMARY

[0005] According to one aspect, the present disclosure provides a core composition for a composite panel. The core composition comprises a mixture of materials including 80 to 97 percent by weight inorganic particulate and 0.1 to 10 percent by weight of a binder composition. The inorganic particulate comprises at least one flame retardant hydrated metal oxide and at least one filler. The inorganic particulate has a surface area less than 2 meters squared per gram (m ² /g) and a median particle size in the range of 1 micrometer (pm) to 1000 pm. The core composition has an ultimate tensile strength of at least 0.5 MPa.

[0006] According to another aspect, the present disclosure provides a composite panel that includes two outer layers and a core layer comprising a core composition. The outer layers may comprise, for example, aluminum, aluminum alloy, or another metal or metal alloy. The core composition comprises a mixture of materials including 80 to 97 percent by weight inorganic particulate and 0.1 to 10 percent by weight of a binder composition. The inorganic particulate comprises at least one flame retardant hydrated metal oxide and at least one filler. The inorganic particulate has a surface area less than 2 meters squared per gram (m ² /g) and a median particle size in the range of 1 micrometer (pm) to 1000 pm. The core composition of the core layer has an ultimate tensile strength of at least 0.5 MPa.

[0007] It is understood that the invention disclosed and described in this specification is not limited to the aspects described in this Summary. The reader will appreciate the foregoing details, as well as others, upon considering the following detailed description of various non limiting and non-exhaustive aspects according to this disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] The features and advantages of the examples, and the manner of attaining them, will become more apparent, and the examples will be better understood, by reference to the following description taken in conjunction with the accompanying drawings, wherein:

[0009] FIG. l is a cross-sectional view of a non-limiting embodiment of a composite panel according to the present disclosure including a flame retardant core composition; [0010] FIG. 2 is a graph illustrating a computational model of a relationship between an amount of the binder composition residing in bulk space (by volume percent) and surface area of the inorganic particulate;

[0011] FIG. 3 is a graph plotting surface area of inorganic particulate in core samples A-C versus ultimate tensile strength;

[0012] FIG. 4 is a graph plotting median particle size of inorganic particulate in core samples A-C versus ultimate tensile strength;

[0013] FIG. 5 is a bar chart showing ultimate tensile strength of core samples D-K and M; and

[0014] FIG. 6 is a bar chart showing 4-hour water absorption of core samples D-L.

DETAILED DESCRIPTION OF NON-LIMITING EMBODIMENTS

[0015] Various examples are described and illustrated herein to provide an overall understanding of the structure, function, and use of the disclosed articles and methods. The various examples described and illustrated herein are non-limiting and non-exhaustive. Thus, the invention is not limited by the description of the various non-limiting and non-exhaustive examples disclosed herein. Rather, the invention is defined solely by the claims. The features and characteristics illustrated and/or described in connection with various examples may be combined with the features and characteristics of other examples. Such modifications and variations are intended to be included within the scope of this specification. As such, the claims may be amended to recite any one or more features or characteristics expressly or inherently described in, or otherwise expressly or inherently supported by, this specification. Further, Applicant reserves the right to amend the claims to affirmatively disclaim features or characteristics that may be present in the prior art. The various embodiments disclosed and described in this specification can comprise, consist of, or consist essentially of the features and characteristics as variously described herein.

[0016] Any patent, publication, or other disclosure material identified herein is incorporated herein by reference in its entirety unless otherwise indicated, but only to the extent that the incorporated material does not conflict with existing definitions, statements, or other disclosure material expressly set forth in this specification. As such, and to the extent necessary, the express disclosure as set forth in this specification supersedes any conflicting material incorporated by reference herein. Any material, or portion thereof, that is said to be incorporated by reference into this specification, but which conflicts with existing definitions, statements, or other disclosure material set forth herein, is only incorporated to the extent that no conflict arises between that incorporated material and the existing disclosure material. Applicant reserves the right to amend this specification to expressly recite any subject matter, or portion thereof, incorporated by reference herein.

[0017] Any references herein to“various examples,”“some examples,”“one example,”“an example”, or like phrases, means that a particular feature, structure, or characteristic described in connection with the example is included in at least one example. Thus, appearances of the phrases“in various examples,”“in some examples,”“in one example”,“in an example”, or like phrases, in the specification do not necessarily refer to the same example. Furthermore, the particular described features, structures, or characteristics may be combined in any suitable manner in one or more examples. Thus, the particular features, structures, or characteristics illustrated or described in connection with one example may be combined, in whole or in part, with the features, structures, or characteristics of one or more other examples without limitation. Such modifications and variations are intended to be included within the scope of the present examples.

[0018] In this specification, unless otherwise indicated, all numerical parameters are to be understood as being prefaced and modified in all instances by the term "about", in which the numerical parameters possess the inherent variability characteristic of the underlying measurement techniques used to determine the numerical value of the parameter. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter described herein should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.

[0019] Also, any numerical range recited herein includes all sub-ranges subsumed within the recited range. For example, a range of "1 to 10" includes all sub-ranges between (and including) the recited minimum value of 1 and the recited maximum value of 10, that is, having a minimum value equal to or greater than 1 and a maximum value equal to or less than 10. Any maximum numerical limitation recited in this specification is intended to include all lower numerical limitations subsumed therein and any minimum numerical limitation recited in this specification is intended to include all higher numerical limitations subsumed therein. Accordingly, Applicant reserves the right to amend this specification, including the claims, to expressly recite any sub-range subsumed within the ranges expressly recited. All such ranges are inherently described in this specification such that amending to expressly recite any such sub-ranges would comply with the applicable specification, description, and enablement requirements.

[0020] The grammatical articles "a", "an", and "the", as used herein, are intended to include "at least one" or "one or more", unless otherwise indicated, even if“at least one” or“one or more” is expressly used in certain instances. Thus, the foregoing grammatical articles are used herein to refer to one or more than one (i.e., to "at least one") of the particular identified elements. Further, the use of a singular noun includes the plural, and the use of a plural noun includes the singular, unless the context of the usage requires otherwise.

[0021] Composite panels may be required to exhibit limited combustibility, which is a measure of how easily a substance bursts into flame, through fire or combustion. As with most construction materials, unit weight and cost also are concerns that should be considered in the design of a composite panel. Composite panels including a core composition with significant organic binder content may have limited flame resistance properties. Increasing the content of inorganic, mineral material in the core of a composite panel can reduce combustibility of the panel. However, a composite panel including a core with a very high inorganic mineral particulate content can be heavy, may lack flexibility to absorb the mechanical stresses caused by thermal expansion, may lack tensile strength, all of which would make a panel unsuitable for construction purposes. To address these various concerns, a core composition is provided herein that can be efficiently manufactured and processed, be cost effective, have a sufficient tensile strength, and provide the flexibility needed to absorb mechanical stresses. More specifically, the core composition includes a mixture of materials including 80 % to 97 % by weight of inorganic particulate and 0.1 to 10 percent by weight of a binder composition. The inorganic particulate comprises at least one of magnesium hydroxide (Mg(OH) ₂ ) and aluminum hydroxide (Al(OH) ₃ ). Additionally, the inorganic particulate comprises at least one of calcium hydroxide (Ca(OH) ₂ ), calcium carbonate (CaC0 ₃ ), aluminum oxide (Al ₂ 0 ₃ ), dolomite, lizardite, vermiculite, boehmite, kaolinite, and silica. The inorganic particulate has a surface area of less than 1 m ² /g and a median particle size in the range of 1 pm to 1000 pm. The core composition has an ultimate tensile strength of at least 0.5 MPa. [0022] As used herein“median particle size” means a diameter value where half of the volume of the particles have a diameter below the value and half of the volume of the particles have a diameter above the value.

[0023] FIG. 1 illustrates the construction of a non-limiting embodiment of a composite panel that includes a plurality of layers. For example, the composite panel 100 in FIG. 1 includes a core layer 104 and at least two outer layers l02a, l02b. One of the outer layers l02a, l02b is attached to each side of the core layer 104. In various embodiments, the outer layers l02a, l02b may be joined to the core by one or more of an adhesive, a bond-promotion agent, a binder composition, or other suitable material. The core layer 104 can have a thickness ti of 1 millimeter (mm) to 6 mm such as, for example 2 mm to 5mm, or 2 mm or 3 mm. The composite panel 100 can have an overall thickness t ₂ of 2 mm to 8 mm.

[0024] Each of the outer layers l02a, l02b can be, for example, a foil, a film, a strip, or a plate. The outer layers l02a, l02b can comprise a material such as, for example, a plastic, a metallic material, or combinations of those materials. Metallic materials that can be used in the outer layers l02a, l02b include, for example, aluminum, iron, steel, zinc, tin, copper, bronze, and alloys based on any one or more of those metals or other metals. In various embodiments, the outer layers l02a, l02b comprise aluminum or an aluminum alloy. In various embodiments, an adhesive layer (not shown) is disposed intermediate the core layer 104 and at least one of the two outer layers l02a, l02b.

[0025] The core layer 104 is comprised of a core composition that includes a binder composition binding the core layer’s other ingredients into the layer 104. Limiting the concentration of binder in the core composition of the core layer 104 can increase the flame resistance (i.e., reduce the combustibility) of the core layer 104 and the composite panel 100. For example, the concentration of binder composition within the core composition (and core layer) can be less than 15% by weight based on total weight of the core composition, such as, for example, less than 10% by weight of the core composition, 1% to 10% by weight of the core composition, or 3% to 6% by weight of the core composition. In various embodiments, the core composition forming the core layer can comprise less than 10% by weight of a binder composition (based on total weight of the core composition) and a balance of inorganic particulate, wherein the inorganic particulate is bound into the core layer by the binder composition. Limiting the concentration of binder composition in the core

composition and, therefore, core layer 104 also can lower the heat of combustion of the core layer 104. In order to provide significant flame resistance to the core layer 104 and the composite panel 100, the core layer 104 can have a heat of combustion ( e.g ., fuel content) less than 3.0 MJ/kg (as measured according to EN ISO 1716) such as, for example, less than 2.5 MJ/kg, less than 2.0 MJ/kg, or 1.0 MJ/kg to 3.0 MJ/kg.

[0026] In various embodiments, the binder composition can comprise an organic binder composition. In various embodiments, the organic binder composition comprises a latex binder. The latex binder can comprise a water-suspended thermoplastic and/or thermoset polymer resin particles resulting from an emulsion-polymerization process. The waterborne latex can enable uniform distribution of the inorganic particulate within the core layer. For example, when water is removed from the latex binder, organic particles with the latex binder coalesce to form a uniform film of binder on and/or between the inorganic particulate. Once the water is removed, the tensile strength of the core layer can be generated through an interconnected network of binder film within the core layer.

[0027] The particle size of the binder composition can affect the amount of binder composition that will be present in the space between particles in the core layer (e.g., bulk space). For example, decreasing a particle size of the binder composition can increase the amount of binder composition in the bulk space and as a result the ultimate tensile strength of the core can increase. In certain embodiments, the binder composition can have a particle size of 1 nanometer (nm) to 2000 nm such as, for example, less than 1000 nm, less than 400 nm, less than 200 nm, or 100 to 400 nm.

[0028] In various embodiments, the binder composition can include a polymer. The polymer can be any one or more polymer suitable for use in a composite panel. In various

embodiments, the polymer can hold inorganic particulate in the core layer 104 together and also may adhere the core 104 to the outer layers l02a, l02b of the composite panel 100. The binder composition can include, for example, vinyl acetate (VA), vinyl acetate ethylene co polymer (EVA), acrylic, acrylic co-polymer, vinyl acrylic, vinyl alcohol, ethylene glycol, ethylene vinyl alcohol co-polymer, polystyrene, polypropylene, polyethylene,

polyisobutylene, a plasticizer, or combinations of any one or more of those materials or other suitable material. In various embodiments, the binder composition includes or consists of polyvinyl alcohol stabilized ethylene-vinyl acetate co-polymer latex with a glass transition temperature of -13 °C. [0029] In various embodiments, the binder composition can comprise an inorganic binder composition. For example, the inorganic binder composition can comprise a geopolymer, a cement, or combinations of those materials. In various embodiments, the binder composition can comprise both inorganic and organic compounds that contribute to the binding functionality of the binder composition.

[0030] The glass transition temperature (T _g ) of the binder composition can affect the flexibility, brittleness, and/or tensile strength of the core layer. For example, a decrease in the glass transition temperature of the binder composition can result in an increase in flexibility and a decrease in ultimate tensile strength of the core layer. Correspondingly, an increase in the glass transition temperature of the binder composition can increase brittleness and increase ultimate tensile strength. Blending at least two polymers having different glass transition temperatures can optimally balance flexibility, brittleness, and tensile strength of the core layer. For example, the binder composition can comprise a first polymer with a first glass transition temperature and a second polymer with a second glass transition temperature to provide a core layer having a combination of ultimate tensile strength and flexibility that could not be achieved using the first polymer or the second polymer alone. In various embodiments, the glass transition temperature (T _g ) of the binder composition is in a range of - 40 °C to 35 °C such as, for example, -20 °C to 20 °C.

[0031] The core composition can comprise an inorganic particulate. The amount of inorganic particulate within the core composition (and core layer) can be less than 97% by weight of the core composition such as, for example, 80% to 97% by weight of the core composition, or 85% to 97% by weight of the core composition. In various embodiments, the core composition and (core layer) can comprise an inorganic particulate content less than 97% by weight of the core composition (and core layer), with the binder composition constituting the balance of the core composition. In various embodiments, the core composition can comprise an inorganic particulate content of at least 90% by weight of the core composition.

[0032] The inorganic particulate can include a flame retardant hydrated metal oxide which is a water producing, flame retardant, and/or non-combustible material. For example, the flame retardant hydrated metal oxide can include such as, for example, magnesium oxide

(Mg(OH) ₂ ), aluminum hydroxide (Al(OH) ₃ ), calcium hydroxide (Ca(OH) ₂ ), hydrotalcite, hydrocalumite, and hydromagnesite, or combinations of any one or more of those materials. Additionally, the inorganic particulate can comprise a filler such as, for example, calcium carbonate (CaC0 ₃ ), aluminum oxide (AI2O3), magnesium oxide (MgO), calcium oxide (CaO), dolomite, lizardite, vermiculite, boehmite, kaolinite (Al ₂ Si205(0H) ₄ ), silica, dolomitic lime, huntite, nesquehonite, gypsum, a clay, a mica, a montmorillonite, or combinations of any one or more of those materials or other suitable material.

[0033] The inorganic particulate can be held together by the binder composition within the core layer. However, reducing the binder composition content can limit adhesion between particles of the inorganic particulate and reduce the ultimate tensile strength of the core layer. Increasing the binder composition concentration in the core composition can decrease the flame resistance of the core layer and composite panel. Thus, the binder composition should be used efficiently in the core, including no more than is needed to suitably bind the inorganic particulate within the core layer and achieve sufficient ultimate tensile strength within the core layer. In various embodiments, the tensile strength of the core composition and core layer is greater than 0.5 megapascals (MPa) such as, for example, greater than 1.5 MPa, greater than 2.0 MPa, greater than 3.0 MPa, or greater than 10 MPa.

[0034] Particle size and surface area of the inorganic particulate can be selected to improve adhesion within the core layer with a reduced concentration of binder composition. The surface area of the inorganic particulate can affect the amount of binder composition that resides in the pores of the inorganic particulate and the amount of binder composition that can be adsorbed to the surface of the inorganic particulate. The present inventors have observed that minimizing the surface area of the inorganic particulate, as generally described herein, can limit the area on the particulates’ surfaces available for binding with the binder composition, thereby allowing more of the binder composition to reside in the bulk space of the core layer and bind the layer together. An increase in the binder composition in the bulk space can increase the tensile strength of the core. In certain embodiments, the surface area of the inorganic particulate is less than 2 m ² /g such as, for example, less than 1 m ² /g, less than 0.8 m ² /g, less than 0.75 m ² /g, less than 0.65m ² /g, or less than 0.5 m ² /g.

[0035] Additionally, the particle size of the inorganic particulate in the core composition can affect the porosity of the core layer produced from the composition. For example, efficiently packing the inorganic particulate within the core by optimizing the particle size of the inorganic particulate can limit the porosity of the core and/or the available bulk space. In turn, the binder composition content within the core can be reduced with a minimal, if any, reduction in adhesive strength and/or ultimate tensile strength of the core. In certain embodiments, the median particle size of the inorganic particulate in the core compositions is less than 1000 pm such as, for example, 1 pm to 1000 pm or 10 pm to 500 pm.

[0036] Additionally, in various embodiments, the core layer can include a mixture of various sizes of inorganic particulate to increase packing efficiency of the particulate. The increased packing efficiency can decrease porosity, decrease bulk space, and/or limit cavity formation with the core layer. For example, the inorganic particulate in a core composition can include at least two fractions with different median particle size. The difference between the median particle sizes can vary by a factor of 4 to 15 such as, for example, 6 to 10, or 7 to 8. For example, a first particulate fraction in the inorganic particulate can have a median particle size of 10 pm to 50 pm, and a second particulate fraction can have a median particle size of 210 pm to 250 pm. The use of fractions having the first and second median particle sizes can enable a denser packing of the materials in the core layer which can create a thin, flexible, water resistant, and strong composite panel including a reduced concentration of binder composition. In various embodiments, the core layer has an elongation at room temperature (e.g, 20°C) of greater than 2% such as, for example, 2% to 3%, or 3 % to 5 %. In various embodiments, the core layer has an elongation at room temperature of less than 10%.

[0037] The median particle size of the inorganic particulate also can affect the flame retardant properties of the core layer. For example, some inorganic particulate can decompose and generate water in order to limit and/or delay combustion of the core layer and the composite panel. A rate of decomposition of such inorganic particulate can be affected by median particle size within the core composition due to differences in the surface area to volume ratio. An inorganic particulate having a relatively large median particle size can take longer to decompose than an inorganic particulate having a smaller particle size. The present inventors have observed that providing inorganic particulate of varying size in a core composition, as generally described herein, can improve the fire suppression properties of the core layer and the composite panel.

[0038] Additionally, the porosity of the core layer can affect dewatering of the core layer during manufacture of the core layer. In various embodiments, the core composition can be formed into a sheet having a thickness of 1 mm to 6 mm such as, for example, 2 mm to 5 mm, or 2mm to 3 mm. For example, a mixture of the binder composition, inorganic particulate, and in some embodiments an additional material can be initially formed into a layer having a thickness of 6 mm that is subsequently compressed in a continuous press to a sheet having a thickness of 3 mm. During compression to form the 3 mm sheet, water may be removed from the core composition. A larger porosity ( e.g greater than 15 % by volume) can enable efficient dewatering of the core composition during production of the core layer.

In various embodiments, the core layer comprises water in a range of 0 to 70% by weight of the core layer such as, for example, 0.1% to 50% by weight of the core layer, or 1% to 20% by weight of the core layer. The water can be provided in the core composition as a visco- elastic modifier to achieve a synergy between the properties of the materials within the core composition and the method used to produce the core layer.

[0039] After the core layer is compressed and cured, the core layer can have a low porosity which can enhance ultimate tensile strength and/or water resistance of the core. In certain embodiments, the core layer porosity can be less than 15% by volume of the core layer, such as, for example 5% to 10% by volume of the core layer, or less than 10% by volume of the core layer. Low porosity in the core layer can improve the durability of the composite panel since a core layer may delaminate from the outer layers of a composite panel if the core layer absorbs an excess of water. In certain embodiments, the core layer gains less than 10% by weight over 4 hours in 90°C water such as, for example, less than 8% by weight, less than 6% by weight, less than 5% by weight, or 2% to 6% by weight.

[0040] The inorganic particulate within the core composition and core layer can comprise a flame retardant hydrated metal oxide such as, for example, Mg(OH) ₂ , Al(OH) ₃ , Ca(OH) ₂ , boehmite, kaolinite, hydrotalcite, hydrocalumite, hydromagnesite, or combinations of any one or more of those materials or other suitable material. The flame retardant hydrated metal oxide content within the core layer can be in a range of 0% to 97% by weight of the core layer such as, for example, 10% to 50% by weight of the core layer, or 10% to 30% by weight of the core layer. In certain embodiments, the median particle size of the flame retardant hydrated metal oxide can be in a range of 1 pm to 1000 pm such as, for example, 5 pm to 100 pm, or 5 pm to 50 pm.

[0041] Mg(OH) ₂ can decompose to form magnesium oxide (MgO) and water upon heating. The decomposition of Mg(OH) ₂ is an endothermic process that can absorb heat and inhibit and/or delay combustion of the core layer. Additionally, the water generated by the decomposition, usually in vapor form, can lower the temperature of the core layer and inhibit combustion of the core layer. The decomposition of Mg(OH) ₂ to produce water occurs at 300°C. In various embodiments according to the present disclosure, the Mg(OH) ₂ content in the core composition is in a range of 0% to 97% by weight of the core composition such as, for example, 10% to 50% by weight of the core composition, or 10% to 30% by weight of the core composition. The median particle size of the Mg(OH) ₂ can be in a range of 1 pm to 1000 pm such as, for example, 5 pm to 100 pm or 5 pm to 50 pm.

[0042] Al(OH) ₃ also can endothermically decompose to form aluminum oxide (Al ₂ 0 ₃ ) and water. Al(OH) ₃ generally has a lower decomposition temperature than Mg(OH) ₂ of l80°C. However, the higher decomposition temperature of Mg(OH) ₂ can enhance the

manufacturability of a composite panel because a core layer including Mg(OH) ₂ is less likely to prematurely decompose and form water than a core layer including Al(OH) ₃ during high temperature ( e.g greater than 200 °C) production steps. Given the difference in

decomposition temperature between Mg(OH) ₂ and Al(OH) ₃ , the temperature activating the generation of water within the core layer can be adjusted by varying the concentrations of Mg(OH) ₂ and Al(OH) ₃ within the core composition. In various embodiments according to the present disclosure, the Al(OH) ₃ content within the core composition is in a range of 0% to 97% by weight of the core composition such as, for example, 10% to 50% by weight of the core composition, or 10% to 30% by weight of the core composition. In various

embodiments including Al(OH) ₃ the median particle size of the Al(OH) ₃ can be in a range of 1 pm to 1000 pm such as, for example, 5 pm to 100 pm, or 5 pm to 50 pm.

[0043] Ca(OH) ₂ also can endothermically decompose to form calcium oxide (CaO) and water. Ca(OH) ₂ has a decomposition temperature of 500°C. In various embodiments herein, the Ca(OH) ₂ content within the core composition can be in a range of 0% to 97% by weight of the core composition such as, for example, 10% to 50% by weight of the core composition, or 10% to 30% by weight of the core composition. In various embodiments including Ca(OH) ₂ , the median particle size of the Ca(OH) ₂ can be in a range of 1 pm to 1000 pm such as, for example, 5 pm to 100 pm, or 5 pm to 50 pm.

[0044] The inorganic particulate can also comprise a filler which is a substantially non combustible material such as, for example, CaC0 ₃ , Al ₂ 0 ₃ , MgO, CaO, dolomite, lizardite, vermiculite, boehmite, kaolinite, silica, dolomitic lime, huntite, nesquehonite, gypsum, a clay, a mica, a montmorillonite, or combinations of any one or more of those materials or other suitable material. The filler typically has a low surface area which can reduce the overall surface area of the inorganic particulate within the core composition. This can reduce the concentration of the binder composition needed to achieve a desired ultimate tensile strength in the core layer. Additionally, filler typically has a relatively low unit cost and including some concentration of filler in the core composition can reduce the cost to produce composite panel. In various embodiments, the core composition can comprise a filler concentration in a range of 0% to 97% by weight of the core composition, such as, for example, 0.1% to 70% by weight of the core composition, or 40% to 70% by weight of the core composition. In various embodiments, the median particle size of the filler can be in a range of 1 pm to 1000 pm such as, for example, 100 pm to 600 pm, or 210 pm to 250 pm.

[0045] Adjusting the mass ratios of components in the core layer can provide a cost effective, thin, flexible, water resistant, strong, and/or non-combustible composite panel. For example, adjusting the mass ratio of the flame retardant hydrated metal oxide to filler in a range from 5:5 to 9: 1, such as, for example 6:4 to 8:2, or 7:3, can optimize properties of the core layer and composite panel. Additionally, in certain advantageous embodiments the filler can have a median particle size of 230 pm, the flame retardant hydrated metal oxide can have a median particle size of 30 pm, and the inorganic particulate overall can have a surface area less than 0.75 m ² /g such as, for example, less than 0.5 m ² /g.

[0046] In certain embodiments according to the present disclosure, the inorganic particulate content within the core composition can be in a range of 80% to 97% by weight based on the total weight of the core composition, and the core composition can comprise a filler including CaC0 ₃ and a flame retardant hydrated metal oxide including Al(OH) _3. In certain

embodiments, a mass ratio of the CaC0 ₃ to the Al(OH) ₃ in the core composition can be in a range of from 5:5 to 9: 1, such as, for example 6:4 to 8:2, or 7:3. Also, in certain

embodiments, the CaC0 ₃ can have a median particle size of 230 microns, the Al(OH) ₃ can have a median particle size of 30 microns, and the overall surface area of the inorganic particulate can be less than 0.75 m ² /g, such as, for example, less than 0.5 m ² /g. The present inventors have observed that utilizing inorganic particulate comprising CaC0 ₃ and Al(OH) ₃ with varying particle sizes in a core composition, as generally described herein, can improve the fire suppression properties within a core layer of a composite panel.

[0047] The core composition may comprise additional materials. For example, the core composition may include one or more of a surfactant, a smoke reducer, a glass foam, a fiber mesh (inorganic, organic, or combinations thereof), a tackifier, an antioxidant, an additive, and a lubricant. In various embodiments, the core composition can comprise a surfactant content of 0% to 5% by weight based on the weight of the core composition such as, for example, 0.1% to 3% by weight of the core composition. In various embodiments, the surfactant comprises at least one of polycarboxilic acid, a salt of carboxylic acid, an acrylic emulsion, and a polyethyleneimine. In various embodiments, the core composition can comprise a fiber mesh content of 0 to 10% based on the weight of the core composition such as, for example, 0.1 % to 10% by weight of the core composition.

[0048] The core layer can be manufactured by a variety of methods which can include mixing, forming, heating, and compacting. The core composition can be produced by mixing ingredient materials. Mixing can be accomplished using, for example, a twin screw extruder, a single screw extruder, a high intensity rotary mixer, a high shear mixer, a planetary mixer, a ribbon mixer, and/or or other suitable device. After the core composition has been provided, the composition can be formed into a sheet, strip, or layer using one or more of various forming methods that include, for example, extrusion, roll compaction, high shear roll- compaction, belt compaction, and/or other suitable method. In certain method embodiments, the sheet, strip, or layer can be heated by techniques employing, for example, a direct fired tunnel/belt/pusher furnace, an indirect gas fired tunnel/belt/pusher furnace, an industrial waste heat conversion tunnel/belt/pusher furnace, a static furnace, and/or other suitable heating device. In certain method embodiments, the sheet, strip, or layer can be compacted using, for example, uniaxial pneumatic compaction, mechanical compaction, hydraulic compaction, belt pressing, roll compaction, higher shear roll compaction, and/or other suitable compaction method. Those having ordinary skill in the production of core layers for composite panels used in, for example, architectural cladding, will be familiar with methods for producing core layer of such panels.

[0049] In various embodiments, the core layer can be rolled into a coiled form having an internal bend radius of at least 400 mm such as, for example, 400mm. In various

embodiments, the core can be rolled into the coiled form without the outer layers and then utilized to produce a composite panel at a later time.

[0050] A composite panel can be created from the core composition utilizing various fabrication methods known in the art. In various embodiments, a fabrication method may include distributing the core composition onto a conveyor belt utilizing a scattering unit. Subsequently, the distributed core composition may be compressed to form a core layer of a predetermined thickness utilizing a continuous press. The core mixture can be heated during the compression. The core layer can be bonded with two outer layers utilizing a press having a pair of laminating rolls. The outer layers may comprise, for example, at least one of aluminum, iron, steel, stainless steel, zinc, tin, copper, bronze, and alloys based on any one or more of those metals or other suitable metal. For example, the core layer can be introduced into a gap between the pair of laminating rolls utilizing a conveyor and thereafter pressed between the two outer layers. During the transport of the core layer from the continuous press to the laminating rolls, the core layer can be heated, so as to melt the bonding agents and/or binder composition within the core layer to facilitate adhesion to the outer layers. In various embodiments, an adhesive layer may be disposed between the core and at least one of the two outer layers prior to introducing the core layer to the laminating rolls.

[0051] EXAMPLES

[0052] The present inventors observed that incorporating an inorganic particulate having a small median particle size and a high surface area in a core composition can decrease the ultimate tensile strength of a core layer in a composite panel as a result of incomplete surface coverage of the inorganic particulate by the binder composition and/or a low concentration of binder composition in the space between inorganic particulate ( e.g ., bulk space). Referring to FIG. 2, the relationship between (i) the binder composition residing in the bulk space by volume percent of the bulk space and (ii) the surface area of the inorganic particulate was computationally modeled by mass-volume, assuming a spherical latex particles close pack array, and the available surface area of the powders. As illustrated, the binder composition residing in the bulk space by volume percent of the bulk space decreases with increasing surface area of the inorganic particulate and eventually leads to incomplete surface coverage of the inorganic particulate by the binder composition (e.g., a negative value on the y-axis in FIG. 2). Incomplete surface coverage by binder composition can result in low ultimate tensile strength in the core layer and/or a core with unbound inorganic particulate.

Optimizing the binder composition and inorganic particulate to achieve complete surface coverage and to increase the amount of binder in the bulk space can increase the ultimate tensile strength of the core layer.

[0053] The surface area and particle size of the inorganic particulate was measured prior to addition to the core composition. The surface area was measured using nitrogen adsorption and Brunauer-Emmett-Teller (BET) theory. Additionally, the particle size of the inorganic particulate was determined according to ASTM E2651.4078 utilizing laser diffraction wet analysis with agitation/circulation in water and alcohol (and surfactant, if needed) and calculated via Mie Theory.

[0054] Core samples A-M listed in Tables 1 and 2 were prepared. The core compositions initially included 4% by weight water to aid in mixing the compositions and to provide a wet molding compound. Portions of the wet molding compounds were uniaxially compacted at 100 pounds per square inch (psi) in a 50 mm diameter die set. The compacts were dried at l20°C for 60 minutes in an ambient atmosphere laboratory oven. Thereafter, the dried samples were compacted at l20°C in a 50 mm diameter die set at 3200 psi. The compacted core samples were cooled and evaluated.

[0055] Core samples A-C were prepared using a mixture including an inorganic particulate comprising CaC0 ₃ filler and Al(OH) ₃ fire retardant hydrated metal oxide, and an organic binder composition including vinyl acetate ethylene co-polymer (EVA) having a glass transition temperature of -13 °C. The glass transition temperature (T _g ) was measured utilizing differential scanning calorimetry (DSC) with a temperature range of -30 °C to 600 °C and a ramp rate of 5 °C per minute. Core samples A-C had an inorganic particulate content of 90% by weight and an EVA content of 10% by weight. The median particle size of the CaC0 ₃ used in core samples A-C differed. Table 1 lists the composition and various measured properties for dried and compacted core samples A-C, including combined inorganic particle surface area, combined inorganic median particle size, median Al(OH) ₃ particle size, median CaC0 ₃ particle size, and porosity.

Table 1

[0056] Core samples A-M were prepared having dimensions of 0.5 inch wide, 2 inches long, and 3 mm thick. An Intron® Universal Testing System Model No. 4486 was used to test the specimens for ultimate tensile strength. The ultimate tensile strength of each of core samples A-C was tested, and the maximum and average ultimate tensile are shown in Table 1. FIG. 3 plots ultimate tensile strength versus combined inorganic surface area for core samples A-C. As illustrated in FIG. 3, decreasing the surface area of the inorganic particulate while maintaining the same concentration (10%) of organic binder composition within the core sample resulted in an increase in the ultimate tensile strength of the core sample.

[0057] FIG. 4 plots ultimate tensile strength as a function of inorganic median particle size for core samples A-C. As illustrated, increasing the median particle size of the inorganic particulate while maintaining the same concentration (10%) of organic binder composition within the core sample resulted in an increase in the ultimate tensile strength of the core sample.

[0058] Core samples D-M were prepared in a similar manner to core samples A-C using a wet mixture including an inorganic particulate including CaC0 ₃ filler and Al(OH) ₃ or Mg(OH) ₂ fire retardant hydrated metal oxide, and one of several different binder

compositions listed in Table 2. Core samples D-M included an inorganic particulate content of 90% by weight and an organic binder composition content of 10% by weight. For core samples D-M, the surface area of the Al(OH) ₃ was 2 m ² /g, the surface area of the Mg(OH) ₂ was 3 m ² /g, and the surface area of the CaC0 ₃ was 0.4m ² /g. Additionally, for core samples D-M, the median particle size of the Al(OH) ₃ was 11 pm, the median particle size of the Mg(OH) ₂ was 23 pm, and the median particle size of the CaC0 ₃ was 230 pm.

Table 2

[0059] The ultimate tensile strength of core samples D-K and M was tested and the results are illustrated in the bar chart shown in in FIG. 5.

[0060] The 4 hour water absorption of core samples D-L was tested. The initial weight of a specimen of the respective core sample was measured prior to submersion of the specimen into water. Then, the specimen was submersed into water at a temperature of 90 °C for 4 hours. Thereafter, the specimen was removed from the water, the surface of the specimen was dried, and the final weight of the specimen was measured. The percent weight gain of the specimen after the 4 hour submersion based on the initial weight is illustrated in the bar chart shown in FIG. 6.

ASPECTS OF THE INVENTION

[0061] Various aspects of the invention include, but are not limited to, the aspects listed in the following numbered clauses. A core composition for a core composite panel, the core composition including a mixture of materials comprising:

80 to 97 percent by weight of inorganic particulate comprising:

at least one flame retardant hydrated metal oxide, and

at least one filler,

wherein the inorganic particulate has a surface area less than 2 m ² /g and a median particle size in the range of 1 pm to 1000 pm; and

0.1 to 10 percent by weight of a binder composition,

wherein the core composition exhibits tensile strength of at least 0.5 MPa. The core composition of clause 1, wherein the filler comprises at least one of CaC0 ₃ , MgC0 ₃ , Al ₂ 0 ₃ , MgO, CaO, dolomite, lizardite, vermiculite, boehmite, kaolinite, silica, dolomitic lime, huntite, nesquehonite, gypsum, a clay, a mica, and a

montmorillonite. The core composition of clause 1 and/or 2, wherein the flame retardant hydrated metal oxide is at least one of Mg(OH)2, Al(OH)3, Ca(OH)2, hydrotalcite, hydrocalumite, and hydromagnesite. The core composition of clause 1, 2, and/or 3, wherein the flame retardant hydrated metal oxide comprises 10 to 50 percent by weight Mg(OH) ₂ based on total weight of the core. The core composition of clause 1, 2, 3, and/or 4, wherein flame retardant hydrated metal oxide comprises 10 to 50 percent by weight Al(OH) ₃ based on total weight of the core. The core composition of clause 1, 2, 3, 4, and/or 5, wherein the flame retardant hydrated metal oxide comprises 10 to 30 percent by weight Al(OH) ₃ based on total weight of the core. The core composition of clause 1, 2, 3, 4, 5, and/or 6, wherein the mixture comprises 40 to 70 percent by weight of filler based on total weight of the core. The core composition of clause 1, 2, 3, 4, 5, 6, and/or 7, wherein the mixture comprises 40 to 70 percent by weight CaC0 ₃ based on total weight of the core. The core composition of clause 1, 2, 3, 4, 5, 6, 7, and/or 8, wherein the mixture comprises Al(OH) ₃ and CaC0 _3. The core composition of clause 1, 2, 3, 4, 5, 6, 7, 8, and/or 9, wherein a mass ratio of the CaC0 ₃ to the Al(OH) ₃ is in a range of 6:4 to 8:2. The core composition of clause 1, 2, 3, 4, 5, 6, 7, 8, 9, and/or 10, wherein the CaC0 ₃ has a median particle size in a range of 210 pm to 250 pm, and the Al(OH) ₃ has a median particle size in a range of 10 pm to 50 pm. The core composition of clause 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, and/or 11, wherein the binder composition comprises at least one of a thermoplastic and a thermoset plastic. The core composition of clause 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 and/or 12, wherein the binder composition comprises at least one of vinyl acetate, vinyl acetate ethylene co- polymer, acrylic, acrylic co-polymer, vinyl acrylic, vinyl alcohol, ethylene glycol, ethylene vinyl alcohol co-polymer, polystyrene, polypropylene, polyethylene, polyisobutylene, a plasticizer, a cement, and a geopolymer. The core composition of clause 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, and/or 13, further comprising 0.1 to 3 percent by weight a surfactant based on total weight of the core. 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, and/or 14, wherein the surfactant comprises at least one of polycarboxilic acid, a salt of carboxylic acid, an acrylic emulsion, and a polyethyleneimine. The core composition of clause 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, and/or 15, wherein the binder composition binds the inorganic particulate in the core composition. The core composition of clause 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, and/or 16, wherein the binder composition has a glass transition temperature of -40 °C to 35 °C. The core composition of clause 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, and/or 17, wherein the surface area of the inorganic particulate is less than 1 m ² /g. The core composition of clause 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, and/or 18, further comprising less than 15 percent porosity. The core composition of clause 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, and/or 19, wherein the core composition exhibits tensile strength of at least 2 MPa. The core composition of clause 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, and/or 20, further comprising a fuel content less than 3 MJ/kg. The composite panel of clause 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, and/or 21, wherein the binder composition has a particle size of less than 1000 nm. The core composition of clausel, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, and/or 22, further comprising 0.1 to 10 percent by weight a fiber mesh based on total weight of the core composition. A composite panel comprising two outer layers and a core layer intermediate and attached to the two outer layers, the core layer comprising the core composition of clause 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, and/or 23. The composite panel of clause 24, wherein the outer layers comprise at least one of aluminum, iron, steel, stainless steel, zinc, tin, copper, bronze, and alloys based on any one or more of those metals. 26. The composite panel of clause 24 and/or 25, wherein the core layer has a thickness of 1 mm to 6 mm.

27. The composite panel of clause 24, 25, and/or 26, having an overall thickness of 2 mm to 8 mm.

28. The composite panel of clause 24, 25, 26, and/or 27, further comprising an adhesive interlayer intermediate the core and at least one of the two outer layers.

29. The composite panel of clause 24, 25, 26, 27, and/or 28, wherein the filler comprises at least one of CaC0 ₃ , MgC0 ₃ , Al ₂ 0 ₃ , MgO, CaO, dolomite, lizardite, vermiculite, boehmite, kaolinite, silica, dolomitic lime, huntite, nesquehonite, gypsum, a clay, a mica, and a montmorillonite.

30. The composite panel of clause 24, 25, 36, 27, 28, and/or 19, wherein the flame

retardant metal hydroxide is at least one of Mg(OH) ₂ , Al(OH) ₃ , Ca(OH) ₂ , hydrotalcite, hydrocalumite, and hydromagnesite.

[0062] One skilled in the art will recognize that the herein described components, devices, operations/actions, and objects, and the discussion accompanying them are used as examples for the sake of conceptual clarity and that various configuration modifications are contemplated. Consequently, as used herein, the specific examples/embodiments set forth and the accompanying discussion are intended to be representative of their more general classes. In general, use of any specific exemplar is intended to be representative of its class, and the non-inclusion of specific components, devices, operations/actions, and objects should not be taken limiting.

[0063] While the present disclosure provides descriptions of various specific aspects for the purpose of illustrating various aspects of the present disclosure and/or its potential applications, it is understood that variations and modifications will occur to those skilled in the art. Accordingly, the invention or inventions described herein should be understood to be at least as broad as they are claimed, and not as more narrowly defined by particular illustrative aspects provided herein.