Patent Publication Number: US-2021171398-A1

Title: Gypsum panels, systems, and methods

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a National Phase Application pursuant to 35 U.S.C. § 371, of International Application No. PCT/US2019/031267 filed on May 8, 2019, which claims priority benefit of U.S. Provisional Application No. 62/699,288, filed Jul. 17, 2018, the disclosures of which are incorporated by reference herein in their entirety. 
    
    
     BACKGROUND 
     The present invention relates generally to the field of panels for use in building construction, and more particularly to gypsum panels and methods of making gypsum panels. 
     Typical building panels, such as building sheathing or roof panels, include a core material, such as gypsum, and a mat facer, such as a fiberglass mat facer. During manufacturing, the gypsum core material is traditionally applied as a slurry to a surface of the mat facer and allowed to set, such that the mat facer and gypsum core are adhered at the interface. Often, such panels suffer from water intrusion and other performance issues. 
     Accordingly, it would be desirable to provide panels having improved water-resistive properties. 
     SUMMARY 
     In one aspect, methods of making gypsum panels are provided, including forming a first gypsum slurry by combining stucco, water, a siloxane, and a siliconate, and setting the first gypsum slurry to form at least part of a core of the gypsum panel, wherein a ratio of siloxane to siliconate in the first gypsum slurry is from about 1:1 to about 1:50. 
     In another aspect, methods of making gypsum panels are provided, including forming a first gypsum slurry by combining stucco, water, and a siliconate, and setting the first gypsum slurry to form at least part of a core of the gypsum panel, wherein the siliconate is present in the first gypsum slurry in an amount of 3 lb/msf to about 50 lb/msf, for a gypsum panel having a thickness of about ¼ inch to about 1 inch, and wherein the first gypsum slurry contains no siloxane. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Referring now to the drawings, which are meant to be exemplary and not limiting, and wherein like elements are numbered alike. The detailed description is set forth with reference to the accompanying drawings illustrating examples of the disclosure, in which use of the same reference numerals indicates similar or identical items. Certain embodiments of the present disclosure may include elements, components, and/or configurations other than those illustrated in the drawings, and some of the elements, components, and/or configurations illustrated in the drawings may not be present in certain embodiments. 
         FIG. 1  is a cross-sectional view of a gypsum panel. 
         FIG. 2  is a cross-sectional view of a gypsum panel 
         FIG. 3  is a perspective view of a building sheathing system. 
         FIG. 4  is a graph showing the total water absorption (%) for various samples as tested in the Examples. 
         FIG. 5  is a graph showing the total water absorption (%) for various samples as tested in the Examples. 
     
    
    
     DETAILED DESCRIPTION 
     Improved water repelling, or water-resistive, gypsum panels have been developed, along with associated methods for their manufacture. In certain embodiments, the panels contain a relatively high amount of a siliconate in at least a portion (e.g., in at least a layer) of the gypsum panel core. In certain embodiments, the relatively high amount of siliconate is combined with a relatively low amount of siloxane. Such panels have been discovered to display improved water-resistant and moisture migration properties, while maintaining the mechanical properties of gypsum products, such as nail pull and flexural strength, compressive strength and humid bond. Generally, this disclosure is intended to encompass various forms of gypsum panel products, such as sheathing panels, roofing panels, and other glass mat and paper faced gypsum panels. While certain embodiments may be described with reference to the term “sheathing” or “roofing”, it should be understood that the panels described herein are not meant to be limited to these particular uses, and that the features of panels described as sheathing or roofing panels may be encompassed by other types of gypsum panels. 
     As used herein, the term “water-resistive” or similar phrases refers to the ability of a panel or system to resist liquid or bulk water from penetrating, leaking, or seeping past the sheathing and into the surrounding wall components. Such properties may be further defined according to various ASTM test methods, which are described herein. 
     Gypsum panels or boards may contain a set gypsum core sandwiched between two mats, one or both of which may be coated. The mat coating may be a substantially continuous barrier coating. As used herein, the term “substantially continuous barrier coating” refers to a coating material that is substantially uninterrupted over the surface of the mat. 
     During manufacturing, a gypsum slurry may be deposited on the uncoated surface of a facer material, such as a paper sheet or fiberglass mat (which may be pre-coated offline or online), and set to form a gypsum core of the panel. The gypsum slurry may penetrate some portion of the thickness of the fiberglass mat or adhere to a paper facing material, and provide a mechanical bond for the panel. The gypsum slurry may be provided in one or more layers, having the same or different compositions, including one or more slate coat layers. As used herein, the term “slate coat” refers to a gypsum slurry having a higher wet density than the remainder of the gypsum slurry that forms the gypsum core. 
     While this disclosure is generally directed to gypsum panels, it should be understood that other cementitious panel core materials are also intended to fall within the scope of the present disclosure. For example, cementitious panel core materials such as those including magnesium oxide or aluminosilicate may be substituted for the gypsum of the embodiments disclosed herein, to achieve similar results. 
     Moreover, while embodiments of the present disclosure are described generally with reference to fiberglass mats or paper facing materials, it should be understood that other mat materials, including other fibrous mat materials, may also be used in the present panels. In certain embodiments, the nonwoven fibrous mat is formed of fiber material that is capable of forming a strong bond with the material of the building panel core through a mechanical-like interlocking between the interstices of the fibrous mat and portions of the core material. Examples of fiber materials for use in the nonwoven mats include mineral-type materials such as glass fibers, synthetic resin fibers, and mixtures or blends thereof. Both chopped strands and continuous strands may be used. 
     Various embodiments of this disclosure are for purposes of illustration only. Parameters of different steps, components, and features of the embodiments are described separately, but may be combined consistently with this description of claims, to enable other embodiments as well to be understood by those skilled in the art. Various terms used herein are likewise defined in the description, which follows. 
     Methods 
     In certain embodiments, methods of making gypsum panels in accordance with this disclosure include forming a first gypsum slurry by combining stucco, water, and a siliconate, and setting the first gypsum slurry to form at least part of a core of the gypsum panel. The siliconate may be present in the slurry in an amount that is higher than is typical, such as from about 3 lb/msf to about 50 lb/msf, for a gypsum panel having a thickness of about ¼ inch to about 1 inch. As used herein the term “about” is used to refer to is used to refer to plus or minus 2 percent of the relevant numeral that it describes. These methods may be used to produce gypsum panels having any of the features, or combinations of features, described herein. In particular, these methods may be used to product gypsum panels having improved water-resistant characteristics, such as gypsum panels that display a water absorption of less than about 10 percent, such as 5 percent, by weight, after a 2 hour immersion. 
     The panel thickness ranges given herein are meant to be exemplary, and it should be understood that panels in accordance with the present disclosure may have any suitable thickness. Where amounts of materials present within the panel are defined in terms of lb/msf over a certain thickness of panel, it should be understood that the amount of the relevant material described to be present per volume of the panel may be applied to various other panel thicknesses. In certain embodiments, the panels have a thickness from about ¼ inch to about 1 inch. For example, the panels may have a thickness of from about ½ inch to about ⅝ inch, such as from about ½ inch to about ¾, as generally described. 
     In some embodiments, the first gypsum slurry contains siliconate but is free of siloxane, while achieving the water-resistant properties described herein. In other embodiments, the first gypsum slurry contains stucco, water, a siloxane, and a siliconate. In such embodiments, the ratio of siloxane to siliconate in the first gypsum slurry may be from about 1:1 to about 1:50, which represents a relatively high amount of siliconate as compared to traditional panels. As described herein and demonstrated by the Examples, it was discovered that relatively low siloxane and high silconate usage, and even siliconate usage with no siloxane, achieved target water resistant and moisture resistance (e.g., as measured by 2 hours total immersion and surface water absorption standards) without impaired board quality and processing. 
     In certain embodiments, the ratio of siloxane to siliconate in the first gypsum slurry is from about 1:2 to about 1:30, such as from about 1:2 to about 1:20, such as from about 1:2 to about 1:15, such as from about 1:2 to about 1:10, such as from about 1:2 to about 1:5. For example, the siliconate may be present in the first gypsum slurry in an amount of from about 10 lb/msf to about 40 lb/msf, for a gypsum panel having a thickness of about ¼ inch to about 1 inch, such as in an in an amount of from about 10 lb/msf to about 30 lb/msf, such as in an amount of from about 15 lb/msf to about 30 lb/msf. For example, the siloxane may be present in the first gypsum slurry in an amount of from about 0.01 lb/msf to about 20 lb/msf, for a gypsum panel having a thickness of about ¼ inch to about 1 inch, such as in an amount of from about 0.01 lb/msf to about 5 lb/msf, for a gypsum panel having a thickness of about ¼ inch to about 1 inch. 
     The siloxane and siliconate materials may be any suitable siliconate or siloxane chemistries. For example, the siliconate may be an alkaline metal alkylsiliconate or an aromaticsiliconate, including but not limited to, sodium or potassium methylsiliconate, sodium or potassium ethyl siliconate, propylsiliconate, isopropylsiliconate, butylsiliconate, octylsiliconate, phenylsiliconate, or any combination thereof. For example, the siloxane may be polymethylhydrogensiloxane. 
     In certain embodiments, the gypsum core includes multiple layers that are sequentially applied to a facing material, and allowed to set either sequentially or simultaneously, as shown in  FIG. 1 . In such embodiments, the first gypsum slurry may form any one or more of these layers. In other embodiments, the gypsum core includes a single layer formed by the first gypsum slurry. In some embodiments, a second facing material may be deposited onto a surface of the final gypsum slurry layer (or the sole gypsum slurry layer), to form a dual mat-faced gypsum panel, as shown in  FIG. 2 . In certain embodiments, the first gypsum slurry (or each of the outermost gypsum slurry layers) is deposited in an amount of from about 5 percent to about 20 percent, by weight, of the gypsum core. The gypsum slurry or multiple layers thereof may be deposited on the facer material by any suitable means, such as roll coating. 
     In certain embodiments, the first gypsum slurry (or other gypsum slurry layers that form the core) contains one or more additional agents to enhance its performance, such as, but not limited to, wetting agents, fillers, accelerators, set retarders, foaming agents, and dispersing agents. Various example uses of such additives will now be described. 
     In certain embodiments, a wetting agent is selected from a group consisting of surfactants, superplasticisers, dispersants, agents containing surfactants, agents containing superplasticisers, agents containing dispersants, and combinations thereof. For example, the gypsum slurry or layer(s) may include wax, wax emulsions and co-emulsions, silicone, siloxane, or a combination thereof. For example, suitable superplasticisers include Melflux 2651 F and 4930F, commercially available from BASF Corporation. In certain embodiments, the wetting agent is a surfactant having a boiling point of 200° C. or lower. In some embodiments, the surfactant has a boiling point of 150° C. or lower. In some embodiments, the surfactant has a boiling point of 110° C. or lower. For example, the surfactant may be a multifunctional agent based on acetylenic chemistry or an ethoxylated low-foam agent. 
     In certain embodiments, a surfactant is present in the relevant gypsum slurry in an amount of about 0.01 percent to about 1 percent, by weight. In certain embodiments, the surfactant is present in the relevant gypsum slurry in an amount of about 0.01 percent to about 0.5 percent, by weight. In some embodiments, the surfactant is present in the relevant gypsum slurry in an amount of about 0.05 percent to about 0.2 percent, by weight. 
     Suitable surfactants and other wetting agents may be selected from non-ionic, anionic, cationic, or zwitterionic compounds, such as alkyl sulfates, ammonium lauryl sulfate, sodium lauryl sulfate, alkyl-ether sulfates, sodium laureth sulfate, sodium myreth sulfate, docusates, dioctyl sodium sulfosuccinate, perfluorooctanesulfonate, perfluorobutanesulfonate, linear alkylbenzene sulfonates, alkyl-aryl ether phosphates, alkyl ether phosphate, alkyl carboxylates, sodium stearate, sodium lauroyl sarcosinate, carboxylate-based fluorosurfactants, perfluorononanoate, perfluorooctanoate, amines, octenidine dihydrochloride, alkyltrimethylammonium salts, cetyl trimethylammonium bromide, cetyl trimethylammonium chloride, cetylpyridinium chloride, benzalkonium chloride, benzethonium chloride, 5-Bromo-5-nitro-1,3-dioxane, dimethyldioctadecylammonium chloride, cetrimonium bromide, dioctadecyldimethylammonium bromide, sultaines, cocamidopropyl hydroxysultaine, betaines, cocamidopropyl betaine, phospholipids phosphatidylserine, phosphatidylethanolamine, phosphatidylcholine, sphingomyelins, fatty alcohols, cetyl alcohol, stearyl alcohol, cetostearyl alcohol, stearyl alcohols. oleyl alcohol, polyoxyethylene glycol alkyl ethers, octaethylene glycol monododecyl ether, pentaethylene glycol monododecyl ether, polyoxypropylene glycol alkyl ethers, glucoside alkyl ethers, polyoxyethylene glycol octylphenol ethers, polyoxyethylene glycol alkylphenol ethers, glycerol alkyl esters, polyoxyethylene glycol sorbitan alkyl esters, sorbitan alkyl esters, cocamide MEA, cocamide DEA, dodecyldimethylamine oxide, polyethoxylated tallow amine, and block copolymers of polyethylene glycol and polypropylene glycol. For example, suitable surfactants include Surfynol 61, commercially available from Air Products and Chemicals, Inc. (Allentown, Pa.). 
     In certain embodiments, the gypsum slurry (or one or more layers thereof) includes a hydrophobic additive. For example, the gypsum slurry or layer(s) may include wax, wax emulsions and co-emulsions, silicone, siloxane, silanes, or any combination thereof. 
     In certain embodiments, the relevant gypsum slurry includes, alternatively to or in addition to the surfactant, an aqueous polymer or inorganic binder to enhance penetration of the slurry into the mat. In certain embodiments, the gypsum slurry includes the binder in an amount effective to provide from about 0.5 lb/msf to about 50 lb/msf binder in the set gypsum layer. In one embodiment, the gypsum slurry includes the binder in an amount effective to provide from about 0.5 lb/msf to about 15 lb/msf binder in the set gypsum layer. For example, the binder may be a suitable latex binder, such as a hydrophobic modified acrylic latex binder. In one embodiment, the latex binder is one with low surface tension, such as ENCOR 300, commercially available from Arkema (France). For example, the binder may be styrene-butadiene-rubber (SBR), styrene-butadiene-styrene (SBS), ethylene-vinyl-chloride (EVCl), poly-vinylidene-chloride (PVdCl) and poly(vinylidene) copolymers, modified poly-vinyl-chloride (PVC), poly-vinyl-alcohol (PVOH), ethylene-vinyl-acetate (EVA), poly-vinyl-acetate (PVA) and polymers and copolymers containing units of acrylic acid, methacrylic acid, their esters and derivatives thereof (acrylic-type polymers), such as styrene-acrylate copolymers. In one embodiment, the binder is a hydrophobic, UV resistant polymer latex adhesive. For example, the hydrophobic, UV resistant polymer latex binder adhesive may be based on a (meth)acrylate polymer latex, wherein the (meth)acrylate polymer is a lower alkyl ester, such as a methyl, ethyl or butyl ester, of acrylic and/or methacrylic acids, and copolymers of such esters with minor amounts of other ethylenically unsaturated copolymerizable monomers (such as stryrene) which are known to the art to be suitable in the preparation of UV resistant (meth)acrylic polymer latexes. In certain embodiments, the binder coating is free of filler. 
     In certain embodiments, the relevant gypsum slurry may also include additional additives meant to improve the water-resistant properties of the core. Such additives may include, for example, poly(vinyl alcohol), optionally including a minor amount of poly(vinyl acetate); metallic resinates; wax, asphalt, or mixtures thereof, for example as an emulsion; a mixture of wax and/or asphalt and cornflower and potassium permanganate; water insoluble thermoplastic organic materials such as petroleum and natural asphalt, coal tar, and thermoplastic synthetic resins such as poly(vinyl acetate), poly(vinyl chloride), and a copolymer of vinyl acetate and vinyl chloride, and acrylic resins; a mixture of metal rosin soap, a water soluble alkaline earth metal salt, and residual fuel oil; a mixture of petroleum wax in the form of an emulsion and either residual fuel oil, pine tar, or coal tar; a mixture of residual fuel oil and rosin; aromatic isocyanates and diisocyanates; wax emulsions, including paraffin, microcrystalline, polyethylene, and various co-emulsified wax emulsions; wax asphalt emulsion, each optionally with potassium sulfate, alkali, or alkaline earth aluminates, and Portland cement; a wax-asphalt emulsion prepared by adding to a blend of molten wax and asphalt, an oil-soluble, water-dispersing emulsifying agent, and admixing the aforementioned with a solution of case including, as a dispersing agent, an alkali sulfonate of a polyarylmethylene condensation product. Mixtures of these water-resistance additives, in addition to the siliconate and optional siloxane in the first gypsum slurry, may also be employed. 
     In certain embodiments, the gypsum slurry (or one or more layers thereof) is substantially free of foam, honeycomb, excess water, and micelle formations. As used herein, the term “substantially free” refers to the slurry containing lower than an amount of these materials that would materially affect the performance of the panel. That is, these materials are not present in the slurry in an amount that would result in the formation of pathways for liquid water in the glass mat of a set panel, when under pressure. 
     In certain embodiments, the panel core slurry (or layers thereof) may be deposited on a horizontally oriented moving web of facer material, such as pre-coated fibrous mat. A second coated or uncoated mat may be deposited onto the surface of the panel core slurry opposite the mat, e.g., a non-coated surface of the second mat contacts the panel core slurry. In some embodiments, a moving web of a mat may be placed on the upper free surface of the aqueous panel core slurry. Thus, the panel core material may be sandwiched between two facer mats, one or both having a mat coating. In certain embodiments, allowing the panel core material and/or mat coating to set includes curing, drying, such as in an oven or by another suitable drying mechanism, or allowing the material(s) to set at room temperature (i.e., to self-harden). 
     A barrier coating may be applied to one or both (in embodiments having two) mat surfaces, prior to or after drying of the mat. In some embodiments, the mats are pre-coated when they are associated with the panel core slurry. In some embodiments, depositing a barrier coating onto the second surface of the first coated mat occurs after setting the first gypsum slurry to form at least a portion of a gypsum core. In some embodiments, the gypsum core coated with the barrier coating is cured, dried, such as in an oven or by another suitable drying mechanism, or the materials are allowed to set at room temperature. In some embodiment, infrared heating is used to flash off water and dry the barrier coating. 
     Methods of constructing a building sheathing system, as shown in  FIG. 3 , are also provided herein, including installing at least two gypsum panels  300  having an interface therebetween, and applying a seaming component  320  at the interface between the at least two of the gypsum panels  300 . Gypsum panels used in these methods may have any of the features, properties, or combinations of features and/or properties, described herein. Sheathing systems constructed by these methods may have any of the features, properties, or combinations or features and/or properties, described herein. The seaming component may be any suitable seaming component as described herein. 
     Panels and Systems 
     Gypsum panels having improved water absorption resistance may be made by any of the methods described herein. Such panels may beneficially display one or more of the following water absorption resistance characteristics: an average water absorption of not more than 5 percent by weight, after 2 hours of immersion, according to ASTM C1396/C1396M-14a (2014), an average water absorption of not more than 10 percent by weight, after 2 hours of immersion, according to ASTM C1396/C1396M-14a (2014), an average water absorption of not more than 10 percent by weight, after 2 hours of immersion, according to ASTM C1177/C117M-13 (2013), an average water absorption of not more than 5 percent by weight, after 2 hours of immersion, according to ASTM C1178/C1188M-13 (2013), and/or an average surface water absorption of a face side of the gypsum panel of not more than 0.5 g, after 2 hours, according to ASTM C1178/C1188M-13 (2013). 
     In certain embodiments, as shown in  FIG. 1 , a gypsum panel  100  includes a gypsum core  101  having a first surface and a second opposed surface, and a first facer material  104  (shown here as a fibrous mat, though paper facing materials may also be used, as discussed herein) associated with the first surface of the gypsum core  101 , such that gypsum of the gypsum core penetrates at least a portion of the first mat  104 . The various layers are illustrated as separate layers in the figures for ease of illustration; however, it should be understood that overlap of these materials may occur at their interfaces. 
     In certain embodiments, the gypsum panel  100  includes a set gypsum core  101  associated with a first surface of first fibrous mat  104  and an optional mat coating  106  applied to a second surface of the first fibrous mat  104 . For example, the mat coating may have a dry weight of from about 1 pound to about 25 pounds per thousand square feet (lb/msf) of board surface, such as less than 15 pounds per thousand square feet. For example, the mat coating may be substantially continuous, such that it covers at least 99 percent of the board surface, or at least 99.9 percent of the mat surface. 
     Suitable coating materials (i.e., the precursor to the dried mat coating) contain at least one suitable polymer binder. Suitable polymer binders may be selected from polymeric emulsions and resins, e.g. acrylics, siloxane, silicone, styrene-butadiene copolymers, polyethylene-vinyl acetate, polyvinyl alcohol, polyvinyl chloride (PVC), polyurethane, urea-formaldehyde resin, phenolics resin, polyvinyl butyryl, styrene-acrylic copolymers, styrene-vinyl-acrylic copolymers, styrene-maleic anhydride copolymers. In some embodiments, the polymer binder is an acrylic latex or a polystyrene latex. In some embodiments, the polymer binder is hydrophobic. In certain embodiments, the binder includes UV curable monomers and/or polymers (e.g. epoxy acrylate, urethane acrylate, polyester acrylate). In certain embodiments, the mat coating contains the polymer binder in an amount of from about 5 percent to about 75 percent, by weight, on a dry basis. 
     Examples of suitable polymer binders that may be used in the continuous barrier coatings described herein include SNAP 720, commercially available from Arkema Coating Resins, which is a structured nano-particle acrylic polymer containing 100% acrylic latex and 49% solids by weight, with a 0.08 micron particle size; SNAP 728, commercially available from Arkema Coating Resins, which is a structured nano-acrylic polymer containing 100% acrylic latex and 49% solids by weight, with a 0.1 micron particle size; and NEOCAR 820, commercially available from Arkema Coating Reins, which is a hydrophobic modified acrylic latex containing 45% solids by weight, with a 0.07 micron particle size. 
     In certain embodiments, the mat coating also contains one or more inorganic fillers. For example, the inorganic filler may be calcium carbonate or another suitable filler known in the industry. In certain embodiments, the filler is an inorganic mineral filler, such as ground limestone (calcium carbonate), clay, mica, gypsum (calcium sulfate dihydrate), aluminum trihydrate (ATH), antimony oxide, sodium-potassium alumina silicates, pyrophyllite, microcrystalline silica, and talc (magnesium silicate). In certain embodiments, the filler may inherently contain a naturally occurring inorganic adhesive binder. For example, the filler may be limestone containing quicklime (CaO), clay containing calcium silicate, sand containing calcium silicate, aluminum trihydrate containing aluminum hydroxide, cementitious fly ash, or magnesium oxide containing either the sulfate or chloride of magnesium, or both. In certain embodiments, the filler may include an inorganic adhesive binder as a constituent, cure by hydration, and act as a flame suppressant. For example, the filler may be aluminum trihydrate (ATH), calcium sulfate (gypsum), and the oxychloride and oxysulfate of magnesium. For example, fillers may include MINEX 7, commercially available from the Cary Company (Addison, Ill.); IMSIL A-10, commercially available from the Cary Company; and TALCRON MP 44-26, commercially available from Specialty Minerals Inc. (Dillon, Mont.). The filler may be in a particulate form. For example, the filler may have a particle size such that at least 95% of the particles pass through a 100 mesh wire screen. 
     In certain embodiments, the precursor material that forms the mat coating also contains water. For example, the coating material may contain the polymer binder in an amount of from about 35 percent to about 80 percent, by weight, and water in an amount of from about 20 percent to about 30 percent, by weight. In embodiments containing the filler, the continuous barrier coating material may also contain an inorganic filler in an amount of from about 35 percent to about 80 percent, by weight. In some embodiments, the polymer binder and the inorganic filler are present in amounts of within 5 percent, by weight, of each other. For example, the polymer binder and filler may be present in a ratio of approximately 1:1. 
     In some embodiments, the mat coating also includes water and/or other optional ingredients such as colorants (e.g., dyes or pigments), transfer agents, thickeners or rheological control agents, surfactants, ammonia compositions, defoamers, dispersants, biocides, UV absorbers, and preservatives. Thickeners may include hydroxyethyl cellulose; hydrophobically modified ethylene oxide urethane; processed attapulgite, a hydrated magnesium aluminosilicate; and other thickeners known to those of ordinary skill in the art. For example, thickeners may include CELLOSIZE QP-09-L and ACRYSOL RM-2020NPR, commercially available from Dow Chemical Company (Philadelphia, Pa.); and ATTAGEL 50, commercially available from BASF Corporation (Florham Park, N.J.). Surfactants may include sodium polyacrylate dispersants, ethoxylated nonionic compounds, and other surfactants known to those of ordinary skill in the art. For example, surfactants may include HYDROPALAT 44, commercially available from BASF Corporation; and DYNOL 607, commercially available from Air Products (Allentown, Pa.). Defoamers may include multi-hydrophobe blend defoamers and other defoamers known to those of ordinary skill in the art. For example, defoamers may include FOAMASTER SA-3, commercially available from BASF Corporation. Ammonia compositions may include ammonium hydroxide, for example, AQUA AMMONIA 26 BE, commercially available from Tanner Industries, Inc. (Southampton, Pa.). Biocides may include broad-spectrum microbicides that prohibit bacteria and fungi growth, antimicrobials such as those based on the active diiodomethyl-ptolylsulfone, and other compounds known to those of ordinary skill in the art. For example, biocides may include KATHON LX 1.5%, commercially available from Dow Chemical Company, POLYPHASE 663, commercially available from Troy Corporation (Newark, N.J.), and AMICAL Flowable, commercially available from Dow Chemical Company. Biocides may also act as preservatives. UV absorbers may include encapsulated hydroxyphenyl-triazine compositions and other compounds known to those of ordinary skill in the art, for example, TINUVIN 477DW, commercially available from BASF Corporation. Transfer agents such as polyvinyl alcohol (PVA) and other compounds known to those of ordinary skill in the art may also be included in the coating composition. 
     In some embodiments, as shown in  FIG. 1 , the gypsum of the gypsum core  101  penetrates a remaining portion of the first fibrous mat  104  such that voids in the mat  104  are substantially eliminated and the water resistance of the panel  100  is further enhanced. For example, in one embodiment, the first mat  104  has a mat coating  106  on a surface opposite the gypsum core  101 , the mat coating  106  penetrating a portion of the first mat  104 , to define the remaining portion of the first mat  104 . That is, gypsum of the gypsum core  101  may penetrate a remaining fibrous portion of the first fibrous mat  104  such that voids in the first mat  104  are substantially eliminated. 
     As used herein the phrase “such that voids in the mat are substantially eliminated” and similar phrases, refer to the gypsum slurry, and thus the set gypsum, of the gypsum core filling all or nearly all of the interstitial volume of the fibrous mat that is not filled by the coating material. In certain embodiments, the gypsum of the gypsum core fills at least 95 percent of the available interstitial volume of the mat. In some embodiments, the gypsum core fills at least 98 percent of the available interstitial volume of the mat. In further embodiments, the gypsum core fills at least 99 percent of the available interstitial volume of the mat. 
     By maximizing gypsum slurry penetration into the side of the mat receiving gypsum, the movement of water under the mat coating within the glass mat of the finished panel when exposed to bulk water head pressures may be substantially and adequately reduced, without significantly altering the water vapor transmission rate (i.e., the ability to dry) of the finished panel. Thus, the gypsum panels disclosed herein may further display one or more improved water-resistive barrier properties. 
     In certain embodiments, the mat  104  is a nonwoven fiberglass mat. For example, the glass fibers may have an average diameter of from about 10 to about 17 microns and an average length of from about ¼ inch to about 1 inch. For example, the glass fibers may have an average diameter of 13 microns (i.e., K fibers) and an average length of ¾ inch. In certain embodiments, the nonwoven fiberglass mats have a basis weight of from about 1.5 pounds to about 3.5 pounds per 100 square feet of the mat. The mats may each have a thickness of from about 20 mils to about 35 mils. The fibers may be bonded together to form a unitary mat structure by a suitable adhesive. For example, the adhesive may be a urea-formaldehyde resin adhesive, optionally modified with a thermoplastic extender or cross-linker, such as an acrylic cross-linker, or an acrylate adhesive resin. 
     In certain embodiments, as shown in  FIG. 1 , the gypsum core  101  includes two or more gypsum layers  102 ,  108 . For example, the gypsum core may include various gypsum layers having different compositions. In some embodiments, the first gypsum layer  102  that is in contact with the mat  104  (i.e., the layer that forms an interface with the coating material  106  and at least partially penetrates the first mat) is a slate coat layer. In some embodiments, the first gypsum layer  102  is present in an amount from about 5 percent to about 20 percent, by weight, of the gypsum core  101 . In certain embodiments, the slate coat layer is formed from the first gypsum slurry described herein (i.e., the slurry having the high siliconate content, with or without siloxane). In other embodiments, the entire panel core is formed from the first gypsum slurry. The first gypsum slurry (i.e., the slurry containing a relatively high amount of siliconate, with or without a relatively low amount of siloxane) may form one or more of these layers. 
     In certain embodiments, as shown in  FIG. 2 , a gypsum panel  200  includes two fibrous mats  204 ,  212  (which could alternatively be paper facers) that are associated with the gypsum core  201 . The second mat  212  is present on a face of the gypsum core  201  opposite the first mat  204 . In some embodiments, only the first mat  204  has a mat coating  206  on a surface thereof. In other embodiments, both mats  204 ,  212  have a coating  206 ,  214  on a surface thereof opposite the gypsum core  201 . In some embodiments, the gypsum core  201  includes three gypsum layers  202 ,  208 ,  210 . One or both of the gypsum layers  202 ,  210  that are in contact with the mats  204 ,  212  may be a slate coat layer. In certain embodiments, one or both of the gypsum layers  202 ,  210  that are in contact with the mats  204 ,  212  may be a slate coat layer with hydrophobic characteristics and/or a wet density of from about 88 pcf to about 98 pcf, or of from about 93 pcf to about 96 pcf. 
     The layers of the gypsum core may generally be similar to gypsum cores used in other gypsum products, such as gypsum wallboard, dry wall, gypsum board, gypsum lath, and gypsum sheathing. For example, the gypsum core may be formed by mixing water with powdered anhydrous calcium sulfate or calcium sulfate hemihydrate, also known as calcined gypsum or stucco, to form the aqueous gypsum slurry, and thereafter allowing the slurry mixture to hydrate or set into calcium sulfate dihydrate, a relatively hard material. In certain embodiments, the gypsum core includes about 80 weight percent or above of set gypsum (i.e., fully hydrated calcium sulfate). For example, the gypsum core may include about 85 weight percent set gypsum. In some embodiments, the gypsum core includes about 95 weight percent set gypsum. The gypsum core may also include a variety of additives, such as accelerators, set retarders, foaming agents, and dispersing agents, in addition to the siliconate/siloxane, as discussed herein. 
     In certain embodiments, one or more layers of the gypsum core also includes reinforcing fibers, such as chopped glass fibers. For example, the gypsum core, or any layer(s) thereof, may include up to about 0.6 pounds of reinforcing fibers per 100 square feet of panel. For example, the gypsum core, or a layer thereof, may include about 0.3 pounds of reinforcing fibers per 100 square feet of panel. The reinforcing fibers may have a diameter between about 10 and about 17 microns and have a length between about 6.35 and about 12.7 millimeters. 
     The gypsum core, or one or more layers thereof, may also include one or more additives that enhance the inherent fire resistance of the gypsum core. Such additives may include chopped glass fibers, other inorganic fibers, vermiculite, clay, Portland cement, and other silicates, among others. 
     In certain embodiments, as discussed above, the building panels described herein may display one or more improved performance characteristics such as water repellence, moisture migration, and other weather related properties. 
     Building sheathing systems are also provided herein, and include at least two of the improved water-resistive gypsum panels described herein, including any features, or combinations of features, of the panels described herein. 
     In certain embodiments, as shown in  FIG. 3 , a building sheathing system includes at least two gypsum panels  300  and a seaming component  320  configured to provide a seam at an interface between at least two of the gypsum panels  300 . In certain embodiments, the seaming component comprises tape or a bonding material. For example, the seaming component may be a tape including solvent acrylic adhesives, a tape having a polyethylene top layer with butyl rubber adhesive, a tape having an aluminum foil top layer with butyl rubber adhesive, a tape having an EPDM top layer with butyl rubber adhesive, a tape having a polyethylene top layer with rubberized asphalt adhesive, or a tape having an aluminum foil top layer with rubberized asphalt adhesive or rubberized asphalt adhesives modified with styrene butadiene styrene. For example, the seaming component may be a bonding material containing silyl terminated polyether, silyl modified polymers, silicones, synthetic stucco plasters and/or cement plasters, synthetic acrylics, sand filled acrylics, and/or joint sealing chemistries comprising solvent based acrylics, solvent based butyls, latex (water-based, including EVA, acrylic), polysulfides polyurethanes, and latexes (water-based, including EVA, acrylic). 
     Thus, the above-described enhanced panels may be installed with either a tape, liquid polymer, or other suitable material, to effectively treat areas of potential water and air intrusion, such as seams, door/window openings, penetrations, roof/wall interfaces, and wall/foundation interfaces. As such, the building sheathing panels, when used in combination with a suitable seaming component, create an effective water-resistive barrier envelope. 
     EXAMPLES 
     Embodiments of the water-resistive panels disclosed herein were constructed and tested, as described below. 
     First, roof board-type sample gypsum panels were made using various amounts and ratios of siloxane and siliconate in the gypsum core slurry. Specifically, the gypsum core slurry was made by combining stucco, water, dispersant, and foam water in consistent amounts, with varying amounts of siliconate, with or without siloxane, according to the sample parameters shown below in Table 1. A 2 hour water absorption test was performed in which the sample panels were immersed for 2 hours and then the percent weight gain was measured. Additionally, surface Cobb, normalized nail pull, humid bond (on face and back), and slump tests were performed to assess the impact on mechanical board properties. Comparative samples containing no siloxane or siliconate and containing an inverse ratio of siloxane to siliconate were also tested. The results are shown in Table 1 and the water absorption test results are shown in  FIG. 4 . 
     
       
         
           
               
             
               
                 TABLE 1 
               
               
                   
               
               
                 Sample Board Parameters and Test Results 
               
               
                 Low Siloxane/High Siliconate Usage Trial Results (1/2″ Sheathing) 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
               
               
            
               
                 Component 
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
               
               
                 Siloxane 
                 0 
                 10 
                 5 
                 5 
                 3 
                 3 
                 0 
                 0 
                 0 
                 0 
               
               
                 (lbs/msf) 
               
               
                 Siliconate 
                 0 
                 5 
                 10 
                 15 
                 10 
                 15 
                 10 
                 15 
                 30 
                 40 
               
               
                 (lbs/msf) 
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
               
               
                 Total: 
                 0 
                 15 
                 15 
                 20 
                 13 
                 18 
                 10 
                 15 
                 30 
                 40 
               
               
                 (lbs/msf) 
               
               
                 Siloxane/ 
                 0/0 
                 2/1 
                 1/2 
                 1/3 
                 2/7 
                 1/5 
                 0/10 
                 0/15 
                 0/30 
                 0/40 
               
               
                 Siliconate 
               
               
                 ratio 
               
               
                 Stucco 
                 2000 
                 2000 
                 2000 
                 2000 
                 2000 
                 2000 
                 2000 
                 2000 
                 2000 
                 2000 
               
               
                 (lbs/msf) 
               
               
                 Water 
                 1640 
                 1640 
                 1640 
                 1640 
                 1640 
                 1640 
                 1640 
                 1640 
                 1640 
                 1640 
               
               
                 Dispersant 
                 3.5 
                 3.5 
                 3.5 
                 3.5 
                 3.5 
                 3.5 
                 3.5 
                 3.5 
                 3.5 
                 3.5 
               
               
                 (lbs/msf) 
               
               
                 Foam water 
                 3.2% 
                 3.2% 
                 3.2% 
                 3.2% 
                 3.2% 
                 3.2% 
                 3.2% 
                 3.2% 
                 3.2% 
                 3.2% 
               
               
                 Physical 
               
               
                 Test 
               
               
                 Results 
               
               
                 2-hr Water 
                 52.00 
                 1.90 
                 2.30 
                 1.90 
                 2.10 
                 2.50 
                 15.00 
                 4.90 
                 2.40 
                 1.90 
               
               
                 absorption 
               
               
                 (%) 
               
               
                 Surface 
                 105.42 
                 0.92 
                 0.82 
                 0.81 
                 0.88 
                 0.34 
                 0.87 
                 1.36 
                 0.78 
                 0.79 
               
               
                 Cobb (g) 
               
               
                 Normalized 
                 76.28 
                 70.34 
                 75.03 
                 74.79 
                 72.05 
                 73.08 
                 78.83 
                 75.3 
                 81.4 
                 77.73 
               
               
                 Nail Pull 
               
               
                 (lbf) 
               
               
                 Humid 
               
               
                 Bond (lbf): 
               
               
                 Face 
                 29.7 
                 29.8 
                 28.4 
                 30.0 
                 28.2 
                 33.2 
                 24.6 
                 19.7 
                 17.8 
                 13.7 
               
               
                 Back 
                 30.1 
                 31.2 
                 33.3 
                 28.0 
                 29.4 
                 27.0 
                 22.0 
                 24.0 
                 14.4 
                 15.4 
               
               
                 Slump (in) 
                 7.25 
                 7.25 
                 7.25 
                 7.25 
                 7.25 
                 7.00 
                 7.37 
                 7.25 
                 7.50 
                 7.67 
               
               
                   
               
            
           
         
       
     
     Next, sheathing-type sample gypsum panels were made using various amounts and ratios of siloxane and siliconate in the gypsum core slurry. Specifically, the gypsum core slurry was made by combining stucco, water, dispersant, and foam water in consistent amounts, with varying amounts of siliconate, with or without siloxane, according to the sample parameters shown below in Table 2. A 2 hour water absorption test was performed in which the sample panels were immersed for 2 hours and then the percent weight gain was measured. Additionally, surface Cobb, normalized nail pull, humid bond (on face and back), pH, and slump tests were performed to assess the impact on mechanical board properties. Comparative samples containing no siloxane or siliconate and containing an inverse ratio of siloxane to siliconate were also tested. The results are shown in Table 2 and the water absorption test results are shown in  FIG. 5 . 
     
       
         
           
               
             
               
                 TABLE 2 
               
             
            
               
                   
               
               
                 Sample Board Parameters and Test Results 
               
               
                 Low Siloxane/High Siliconate Usage Trial Results (1/2″ Sheathing) 
               
            
           
           
               
               
               
               
               
               
               
               
               
               
               
            
               
                   
                 Control 
                 T1 
                 T2 
                 T3 
                 T4 
                 T5 
                 T6 
                 T7 
                 T8 
                 C2 
               
               
                   
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
               
               
            
               
                 Component 
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
               
               
                 Siloxane 
                 7.5 
                 4 
                 4 
                 3 
                 2 
                 0 
                 0 
                 0 
                 0 
                 7.5 
               
               
                 (lbs/msf) 
               
               
                 Siliconate 
                 4 
                 7.5 
                 10 
                 12.5 
                 15 
                 15 
                 18.5 
                 0 
                 18.5 
                 4 
               
               
                 (lbs/msf) 
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
               
               
                 Total: 
                 11.5 
                 11.5 
                 14 
                 15.5 
                 17 
                 15 
                 18.5 
                 0 
                 18.5 
                 11.5 
               
               
                 (lbs/msf) 
               
               
                 Siloxane/ 
                 1 7/8 
                 1/2 
                 2/5 
                 1/4 
                 1/7 
                 0/15 
                 0/18.5 
                 0/0 
                 0/18.5 
                 7/8 
               
               
                 Siliconate 
               
               
                 ratio 
               
               
                 Stucco 
                 1667.8 
                 1667.8 
                 1667.8 
                 1667.8 
                 1667.8 
                 1667.8 
                 1667.8 
                 1667.8 
                 1667.8 
                 1667.8 
               
               
                 (lbs/msf) 
               
               
                 Water 
                 0 
                 0 
                 0 
                 20 
                 20 
                 20 
                 20 
                 20 
                 20 
                 0 
               
               
                 reduction 
               
               
                 Dispersant 
                 3.5 
                 3.5 
                 3.5 
                 3.5 
                 3.5 
                 3.5 
                 3.5 
                 3.5 
                 3.5 
                 3.5 
               
               
                 (lbs/msf) 
               
               
                 Foam 
                 4.50% 
                 4.50% 
                 4.50% 
                 4.50% 
                 4.50% 
                 4.50% 
                 4.50% 
                 4.50% 
                 4.50% 
                 4.50% 
               
               
                 water 
               
               
                 Physical 
               
               
                 Test 
               
               
                 Results 
               
               
                 2-hr Water 
                 2.54 
                 3.98 
                 5.84 
                 5.03 
                 9.44 
                 27.63 
                 19.95 
                 51.88 
                 21.60 
               
               
                 absorption 
               
               
                 (%) 
               
               
                 Surface 
                 0.6 
                 0.45 
                 0.73 
                 0.67 
                 0.93 
                 187 
                 1.53 
                 30.2 
                 1.55 
                 0.8 
               
               
                 Cobb (g) 
               
               
                 Humid 
               
               
                 Bond 
               
               
                 (lbf): 
               
               
                 Face 
                 31.9 
                 25.5 
                 23.1 
                 27.6 
                 25.1 
                 26.2 
                 26.0 
                 33.1 
                 26.3 
                 31.6 
               
               
                 Back 
                 19.8 
                 19.1 
                 15.5 
                 16.2 
                 18.5 
                 18.3 
                 17.6 
                 18.6 
                 18.7 
                 19.4 
               
               
                 pH 
                 8.4 
                 9.3 
                 9.7 
                 9.9 
                 10.0 
                 10.0 
                 10.2 
                 6.6 
                 10.1 
                 8.6 
               
               
                 Slump (in) 
                 7.25 
                 8.00 
                 8.75 
                 8.50 
                 8.50 
                 8.50 
                 8.75 
                 7.25 
                 9.00 
                 7.75 
               
               
                   
               
            
           
         
       
     
     As can be seen from the results in Tables 1 and 2 and  FIGS. 4 and 5 , samples containing relatively high amounts of siliconate without siloxane (e.g., above about 10 lb/msf siliconate in the absences of siloxane) and samples containing a ratio of siloxane to siliconate of 1:2 (or higher amounts of siliconate) displayed results similar to traditional high siloxane usage samples. In particular, the described samples showed 2 hour water absorption results of less than 5 percent for the roofing type panels, and less than 20 percent, with many less than 10 percent, for sheathing type panels. 
     Moreover, both examples demonstrate that the sample panels displayed similar mechanical properties to the traditional high siloxane samples, as evidenced by the surface Cobb, normalized nail pull, humid bond, and slump test results. 
     Typically, lower amounts of siliconate are used in such panels to achieve ageing resistance properties. Without intending to be bound by a particular theory, it is believed that instead of its traditional usage, increasing the amount of siliconate present in the gypsum slurry provides a cross-linking reaction to provide the noted water-resistant performance in the gypsum panel. Thus, it was discovered that instead of traditional water resistance additives, which may be costly, relatively high amounts of siliconate can be used to achieve improved water resistance properties, without sacrificing mechanical properties of the boards. 
     While the disclosure has been described with reference to a number of embodiments, it will be understood by those skilled in the art that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions, or equivalent arrangements not described herein, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.