Additive for reducing defoaming in gypsum panels

Abstract

Gypsum panels exhibiting decreased defoaming are disclosed. The gypsum panels comprise a gypsum core layer, the gypsum core layer comprising a calcium sulfate material, a defoaming agent, and a propylene glycol alginate additive.

Description

ADDITIVE FOR REDUCING DEFOAMING IN GYPSUM PANELSBACKGROUND

[0001] 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.

[0002] Typical building panels, such as interior building panels, building sheathing, or roof panels, include a core material, such as calcium sulfate dihydrate (referred to as gypsum), and a face layer, such as a paper facer or fiberglass mat facer. Manufacturing of gypsum panels may lead to the production of gypsum waste. For instance, gypsum waste may be produced from gypsum board plant operations, such as plant line start-ups, product changes, or quality issues. Additionally, in some instances, gypsum waste may be produced from normal construction waste streams.

[0003] Sulfates from gypsum waste may be converted into hydrogen sulfide by bacteria that exist in moist environments, such as environments found in landfills. Hydrogen sulfide is a known irritant and toxin in sufficiently high concentrations. Consequently, due to hydrogen sulfide emissions, disposal of gypsum waste at landfills may lead to increased costs for consumers and manufacturers of gypsum panels.

[0004] Accordingly, it would be desirable to reduce a quantity of gypsum waste by producing gypsum panels with recycled gypsum without compromising other properties of the gypsum panels.BRIEF SUMMARY

[0005] Gypsum panels exhibiting decreased defoaming, are provided. Methods of producing such gypsum panels are also provided.

[0006] One embodiment is a gypsum panel, the gypsum panel comprising:

[0007] a gypsum core layer, the gypsum core layer comprising a calcium sulfate material, a defoaming agent, and a propylene glycol alginate additive.

[0008] Another embodiment is a method of making a gypsum panel, comprising:

[0009] i) providing a gypsum core slurry comprising water, a calcium sulfate material, a defoaming agent, and a propylene glycol alginate additive;

[0010] ii) providing a first face layer; and

[0011] iii) setting the gypsum core slurry on the first face layer to form a gypsum core layer of the gypsum panel.BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)

[0012] Having thus described the subject matter in general terms, reference will now be made to the accompanying drawings, which are not necessarily drawn to scale.

[0013] Figure 1A is an exemplary diagram of a gypsum panel cross section comprising two slate coat layers.

[0014] Figure IB is an exemplary diagram of a gypsum panel cross section comprising one slate coat layer.

[0015] Figure 2 is an exemplary graph showing a particle size distribution profile for a stucco slurry including a recycled calcium sulfate material.

[0016] Figure 3 is an exemplary graph showing a wet density response of stucco slurries with varying amounts of a recycled calcium sulfate material.

[0017] Figure 4 illustrates an exemplary contour plot showing wet densities of stucco slurries including varying amounts of PGA and varying amounts of a recycled calcium sulfate material.

[0018] Figure 5 is an exemplary graph showing a dispersant response of stucco slurries with varying amounts of a recycled calcium sulfate material.

[0019] Figure 6 is an exemplary graph showing a wet density response of stucco slurries with varying amounts of a recycled calcium sulfate material.

[0020] Figure 7 is an exemplary graph showing a wet density response of stucco slurries with varying amounts of a recycled calcium sulfate material and varying amounts of PGA.

[0021] Figure 8 is an exemplary graph showing a dry weight response of stucco slurries with varying amounts of a recycled calcium sulfate material and varying amounts of PGA.DETAILED DESCRIPTION

[0022] The presently disclosed subj ect matter will now be described more fully hereinafter. However, many modifications and other embodiments of the presently disclosed subject matter set forth herein will come to mind to one skilled in the art to which the presently disclosed subject matter pertains having the benefit of the teachings presented in the foregoing descriptions. Therefore, it is to be understood that the presently disclosed subject matter is not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. In other words, the subject matter described herein covers all alternatives, modifications, and equivalents. In the event that one or more of the incorporated literature, patents, and similar materials differs from or contradicts this application, including but not limited to defined terms,term usage, described techniques, or the like, this application controls. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in this field. All publications, patent applications, patents, and other references mentioned herein are incorporated by reference in their entirety.

[0023] It is understood that where a parameter range is provided, all integers and ranges within that range, and tenths and hundredths thereof, are also provided by the embodiments. For example, “5-10%” includes 5%, 6%, 7%, 8%, 9%, and 10%; 5.0%, 5.1%, 5.2%....9.8%, 9.9%, and 10.0%; and 5.00%, 5.01%, 5.02%....9.98%, 9.99%, and 10.00%, as well as, for example, 6-9%, 8-10%, 5. l%-9.9%, and 5.01%-9.99%. Similarly, where a list is presented, unless stated otherwise, it is to be understood that each individual element of that list, and every combination of components of that list, is a separate embodiment. For example, “1, 2, 3, 4, and 5” encompasses, among numerous embodiments, 1; 2; 3; 1 and 2; 3 and 5; 1, 3, and 5; and 1, 2, 4, and 5.

[0024] As used herein, “about” means within a statistically meaningful range of a value or values such as a stated concentration, length, molecular weight, pH, sequence identity, time frame, temperature or volume. Such a value or range can be within an order of magnitude, typically within 20%, more typically within 10%, and even more typically within 5% of a given value or range. The allowable variation encompassed by “about” will depend upon the particular system under study, and can be readily appreciated by one of skill in the art.

[0025] As used herein, “a gypsum core layer” means a core layer including at least a calcium sulfate dihydrate material. A gypsum core layer may include one or more calcium sulfate dihydrate materials.

[0026] As used herein, “a core layer” means a layer in a panel that provides substantial contributes to the structure of the panel. In some examples, a core layer may substantially contribute to one or more other properties of a panel, such as fire resistance, noncombustibility, one or more acoustic properties, one or more thermal properties, or any combination thereof.

[0027] As used herein, “a calcium sulfate material” means a material including calcium sulfate in at least one hydration phase. For example, calcium sulfate may be associated with multiple hydration phases and a calcium sulfate material may include calcium sulfate in one or multiple hydration phases. In other words, a calcium sulfate material may include calcium sulfate (e.g., a compound having the chemical formula CaSC ) and / or a hydrate thereof. In some non-limiting examples, a calcium sulfate material includes calcium sulfate dihydrate (referred to herein as gypsum), calcium sulfate hemihydrate (referred to herein as stucco),anhydrous calcium sulfate (referred to herein as anhydrite), soluble anhydrite, insoluble anhydrite, or any combination thereof.

[0028] As used herein, “a defoaming agent” means a compound or an element that is capable of preventing the formation of and / or reducing a quantity of trapped air pockets (referred to as foam) and / or a size of trapped air pockets in a material. In some examples, a defoaming agent is referred to as an antifoaming agent. In some examples, a defoaming agent may reduce a quantity of trapped air pockets in a material by rupturing a portion of the air pockets. In a non-limiting example, a defoaming agent may rupture a trapped air pocket (also referred to as a bubble) by attaching to a portion of the wall of the bubble and causing a surface tension gradient. The surface tension gradient may thin the wall of the bubble thereby increasing a likelihood of the bubble rupturing. Non-limiting examples of defoaming agents include silicon-based defoamers, mineral oil-based defoamers, polyether or polyol-based defoamers, alkyl aryl sulfonates, and fatty acid esters.

[0029] As used herein, “a silicon-based defoamer” means a defoaming agent that includes a silicon material. Non-limiting examples of silicon materials include siloxane, polysiloxane, polydimethylsiloxane, and silicon glycol copolymers.

[0030] As used herein, “a foaming agent” means a compound or an element that is capable of forming foam in a material. In some instances, a foaming agent is capable of forming foam that enhanced strength of a gypsum board and / or reduced density of the gypsum board. Nonlimiting examples of foaming agents include anionic surfactants, such as sulfonic acid salts, alcohol sulfates, alkylbenzene sulfonates, phosphoric acid esters, and carboxylic acid salts.

[0031] As used herein, “a propylene glycol alginate additive” means an additive that includes propylene glycol alginate (PGA) and / or a derivative thereof.

[0032] As used herein, “a recycled gypsum source” means a material, substance, or byproduct that includes gypsum and at least one other material from which gypsum can be extracted. In a non-limiting example, a recycled gypsum source includes gypsum waste.

[0033] As used herein, “gypsum waste” means a material, substance, or byproduct that includes gypsum and has been discarded or rendered no longer useful. A non-limiting example of gypsum waste includes a gypsum panel or portion thereof, which has been discarded, such as in a landfill. A gypsum panel is also referred to as drywall, wallboard, gypsum board, plasterboard, dry lining, or sheet rock.

[0034] As used herein, “a non-recycled gypsum source” means gypsum rock or a material from which gypsum can be formed through hydration. A non-limiting example of a material from which gypsum can be formed through hydration includes stucco.

[0035] All concentration percentages described herein are in terms of weight percentage, unless otherwise indicated.

[0036] Gypsum panels, systems of panels, and methods for their manufacture, are provided herein. The gypsum panels exhibit decreased defoaming during and after manufacturing, as a final product. In particular, the gypsum panels described herein include a PGA additive in at least the core layer, in an amount effective to obtain the desired reduction in defoaming. It has been discovered that the presence of a PGA additive in at least the core layer of a gypsum panel may reduce the amount of defoaming and stabilize a wet density of the gypsum panel. Further, the gypsum panels may include a PGA additive in one or more other layers of the gypsum panel, such as one or more slate coat layers. In some examples, a PGA additive may lead to thickening of materials to which the PGA additive is added and may have a relatively low viscosity (e.g., relative to other thickeners). In some examples, such as examples in which a PGA additive is added to a material that includes foam, the PGA additive may stabilize the foam. For example, the PGA additive may reduce a likelihood of foam being ruptured, such as via a defoaming agent. In other words, a PGA additive may act as a low viscosity thickener and foam stabilizer.

[0037] The gypsum panels, systems of panels, and methods for their manufacturing, as described herein, generally relate to the use of a PGA additive (e.g., PGA), which acts as a low viscosity thickener and foam stabilizer, to enable an increase an amount of gypsum waste containing siloxane in gypsum panels (e.g., lightweight gypsum panels) without incurring defoaming effects.

[0038] Gypsum waste, which may be deposited in landfills, can lead to increased costs for building products manufacturers, state and local municipalities, and landfills. For example, gypsum (calcium sulfate dihydrate) sulfates may be converted into hydrogen sulfide gas by sulfate reducing bacteria. Consequently, gypsum waste, which may be generated from gypsum board plant operations, such as plant line start-ups, product changeovers, or quality issues, or from conventional construction waste streams, may be associated with increased amounts of regulatory scrutiny and exponentially higher cost due to a likelihood of hydrogen sulfide gas generation in moist landfills.

[0039] An amount of gypsum waste going to landfills may be reduced by, for example, extracting gypsum from the waste (e.g., reclaiming the gypsum) and adding the reclaimed gypsum into other (e.g., new) gypsum panels during manufacturing. In some instances, incorporating reclaimed gypsum may reduce gypsum panel manufacturing costs. For example, costs associated with obtaining gypsum from recycled gypsum sources may be lower than costsassociated with obtaining gypsum from non-recycled gypsum sources and, as such, incorporating reclaimed gypsum (also referred to as gypsum obtained from a recycled gypsum source) into gypsum panels during manufacturing may reduce gypsum panel manufacturing costs. In other words, incorporating reclaimed gypsum into gypsum panels may offset gypsum rock cost.

[0040] In some cases, however, incorporating reclaimed gypsum into gypsum panels may be relatively challenging. For example, gypsum from recycled gypsum sources may not be uniform (e.g., with respect to particle size and or one or more other properties). Additionally, in some examples, a recycled gypsum source may include facer material. In such examples, at least a portion of the facer material may be removed prior to incorporation of the reclaimed gypsum into the gypsum panels. Moreover, reclaimed gypsum may be associated with increased water consumption, for example, due to gypsum (e.g., crushed gypsum) having a relatively high capillary action and reclaim gypsum having a smaller particle size and, thus, an increased surface area relative to non-reclaimed gypsum. Consequently, in some cases, incorporating reclaimed gypsum into gypsum panels during manufacturing may lead to increases in an amount of dispersant and / or an amount of water used during manufacturing.

[0041] Additionally, some gypsum products (which may become gypsum waste) are made with siloxane materials, such as siloxane hydrophobic additives, which increase performance in moist environments. Consequently, in some cases, reclaimed gypsum may include siloxane. For example, a reclaimed gypsum board may include siloxane in an amount of about 8 to about 14 pounds per 1,000 square feet (Ib / msf). The use of reclaimed gypsum including siloxane may lead to one or more challenges associated with the manufacturing of gypsum panels (e.g., lightweight gypsum panels, which may be lighter than other types of gypsum panels, such as standard gypsum panels). For example, lightweight gypsum panels may be used in interior applications, such as for the construction of walls and / or ceilings, in which lighter weight materials may provide one or more benefits. In some instances, lightweight gypsum panels may weigh less relative to standard gypsum panels, due to higher amounts of foam. Siloxane may act as a defoaming agent in gypsum slurries (e.g., even in relatively small amounts, such as in an amount ranging from about 0.01 to about 0.5 Ib / msf). For example, siloxane molecules may attach to a wall of foam bubbles in a gypsum slurry causing thin spots in the foam bubble walls due to surface tension gradients. Thin spots of foam bubble walls may increase a likelihood of the foam bubbles rupturing, and thus defoaming. Consequently, siloxane in a gypsum slurry may reduce the amount of foam present in the gypsum slurry, thereby increasing the wet density of the gypsum slurry and the weight of the resulting gypsum panel. The presence of siloxanein reclaimed gypsum may lead to increases in the wet density of gypsum slurries (and thus increases in the weight of the resulting gypsum panels) to which reclaimed gypsum is added. In other words, adding reclaimed gypsum containing siloxane to gypsum slurries (e.g., for manufacturing gypsum panels) may lead to increased defoaming, which increases wet density and panel weight.

[0042] The methods for manufacturing gypsum panels, as described herein, provide for a process that enables gypsum waste, such as post-consumer and post-industrial gypsum board, to be efficiently recycled into gypsum panels through the use of PGA additives, which support stable foams. For example, in accordance with one or more methods described herein, a PGA additive may be included in one or more gypsum slurries, which may counteract an antifoam effect of siloxane in recycled gypsum and, as such, may decrease wet density and panel weight.

[0043] Figure 1A illustrates an exemplary diagram 100 A of a gypsum panel cross section comprising two slate coat layers. In some embodiments, as shown in Figure 1A, a gypsum panel includes a gypsum core 102 and multiple (e.g., two) slate coat layers. For example, the gypsum panel may include a first slate coat layer 104 and a second slate coat layer 106. The first slate coat layer 104 may be present on a first face of the gypsum core 102 opposite the second slate coat layer 106. The second slate coat layer 106 may be present on a second face of the gypsum core 102 opposite the first slate coat layer 104. The gypsum core 102, the first slate coat layer 104, and the second slate coat layer 106 may include gypsum. Accordingly, in some examples, the gypsum core 102, the first slate coat layer 104, and the second slate coat layer 106, may collectively be referred to as gypsum layers. For example, as illustrated in the example of Figure 1 A, gypsum layers 101 may include the first slate coat layer 104, the second slate coat layer 106, and the gypsum core 102. In some embodiments, the gypsum panel also includes a first face layer 108 and / or a second face layer 110 associated with the gypsum layers 101. The first face layer 108 may be present on a first face of the gypsum panel, for example, opposite the second face layer 110. The second face layer 110 may be present on a second face of the gypsum panel, for example, opposite the first face layer 108. In some embodiments, a coating may be disposed on a surface of the first face layer 108 and / or the second face layer 110, for example, prior to combination with a gypsum slurry. In some examples, such as for external surface coatings, a coating may be disposed on a surface of the first face layer 108 and / or the second face layer 110 after combination with the gypsum slurry. The PGA additive may be present in one or more of these layers (e.g., any of these layers), in one or more coatings adjacent to or between any of these layers, in one or more individual components of these layers, or any combination thereof, as discussed in more detail below.

[0044] Figure IB illustrates and exemplary diagram 100B of a gypsum panel cross section comprising one slate coat layer. In some other embodiment, shown in Figure IB, the gypsum panel may include the gypsum core 102 and a single slate coat layer (e.g., the first slate coat layer 104). In some such embodiments, the second surface of the gypsum core 102 may be directly adjacent to the second face layer 110. Thus, in the example of Figure IB, the gypsum layers 101 include the gypsum core 102 and the first slate coat layer 104. In some embodiments, the first face layer 108 and / or the second face layer 110 may include a face material, such as a paper sheet or fiberglass mat (which may be pre-coated offline or online). In some instances, a face layer (e.g., the first face layer 108 and / or the second face layer 110) may be referred to as a facer.

[0045] During manufacturing, a gypsum slurry, or, more simply, a slurry, is formed and deposited on an uncoated surface of a face 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 adhere to a paper facing material or penetrate some portion of the thickness of a fiberglass mat, and provide a mechanical bond for the panel. In at least one embodiment, three gypsum slurries (e.g., three gypsum slurry layers) are applied to form a gypsum panel. For example, to form the gypsum panel depicted in Figure 1 A, a first slate coat slurry, a gypsum core slurry, and a second slate coat slurry may be applied. That is, the first slate coat slurry may be applied to form the first slate coat layer 104, the gypsum core slurry may be applied to form the gypsum core layer 102, and the second slate coat slurry may be applied to form the second slate coat layer 106. In some such embodiments, the first and the second slate coat slurries are identical. In other embodiments, the first and the second slate coat slurries are different from each other.

[0046] In at least one other embodiment, two gypsum slurries (e.g., two gypsum slurry layers) are applied to form a gypsum panel. For example, to form the gypsum panel depicted in Figure IB, the first slate coat slurry and the gypsum core slurry may be applied. That is, the first slate coat slurry may be applied to form the first slate coat layer 104 and the gypsum core slurry may be applied to form the gypsum core layer 102.

[0047] In some embodiments, following the deposition of the gypsum slurry layers 101 (e.g., the gypsum core layer 102 and the first slate coat layer 104 and / or the second slate coat layer 106), a second face layer may be deposited on the slurries prior to curing.

[0048] As used herein, the term "slate coat slurry," and the like, refers to a slurry having a higher wet density than a slurry that forms the gypsum core. In some embodiments, a slate coat is formed from a slurry which lacks a foaming agent, but is otherwise identical to the slurryused to form the gypsum core layer. In some embodiments, the slate coat and / or the gypsum core are formed from a slurry which includes a PGA additive.

[0049] 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.

[0050] Moreover, while embodiments of the present disclosure are described generally with reference to paper facing materials or fiberglass mats as the face layer, 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 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.

[0051] Methods and compositions

[0052] Methods of making gypsum panels containing PGA additives are provided. In particular, these methods may include forming a core slurry by combining stucco, water, and a PGA additive, and setting the core slurry to form a core layer of said gypsum panel.

[0053] The PGA additive is present in a core layer. For example, the PGA additive may be present in a gypsum core slurry use to form a gypsum core layer. The PGA additive may be present in the core layer in an amount of about 0.1 to about 0.615 Ib / msf, for example, for a gypsum panel having a thickness of about 14 inch to about 1 inch. Additionally, or alternatively, the PGA additive may present in the core layer in an amount of about 0.001 to about 0.05 weight percent relative to the calcium sulfate material, in an amount from about 0.005 to about 0.015 weight percent relative to the calcium sulfate material, or in an amount from about 0.007 to about 0.01 weight percent relative to the calcium sulfate material. In some examples, a same slurry may be used to form the core layer and one or more slate coat layers. In some such examples, the PGA additive may be present in the core layer and the one or more slate coat layers. For example, the PGA additive may be present in the core layer and a first slate coat layer. In some other examples, the PGA additive may be present in the core layer, the first slate coat layer, and a second slate coat layer. In at least one embodiment, the core layer, the first slate coat layer, and the second slate coat layer comprise the PGA additive in identicalconcentrations. In at least one other embodiment, the core layer, the first slate coat layer, and the second slate coat layer comprise the PGA additive in different concentrations.

[0054] 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 Ib / msf over a certain thickness of panel, it should be understood that the amount of the relevant material described to be present per area of the panel may be applied to various other panel thicknesses. In certain embodiments, the panels have a thickness from about 14 inch to about 1 inch. For example, the panels may have a thickness of from about 1 / 2 inch to about 3 / 4 inch, such as from about 1 / 2 inch to about 5 / 8 inch, as generally described.

[0055] These methods may be used to produce gypsum panels using reclaimed gypsum and having a reduced wet density, as described herein. In certain embodiments, the gypsum panel comprising a PGA additive has wet density that is about 35 % lower than an otherwise identical panel that does not comprise the PGA additive, as measured by any method described herein. In certain embodiments, the gypsum panel comprising a PGA additive has wet density that is about 35 %, about 18%, about 15%, or about 11% lower than an otherwise identical panel that does not comprise the PGA additive, as measured by any method described herein.

[0056] In some embodiments, gypsum slurries are prepared with a water to calcium sulfate material (e.g., calcium sulfate dihydrate, calcium sulfate hemihydrate, anhydrous calcium sulfate, soluble anhydrite anhydrous calcium sulfate, a combination thereof) in a ratio of 100 parts of stucco to 50-100 parts of water. In some embodiments, a portion of the calcium sulfate material originates from a recycled gypsum source and a remaining portion of the calcium sulfate material originates from a non-recycled gypsum source. In some embodiments, the calcium sulfate material originating from the recycled gypsum source is present in a gypsum slurry (e.g., a gypsum slurry for a core layer and, optionally, one or more slate coat layers) in an amount of about 0.01 to about 15 weight percent of the calcium sulfate material. In some other embodiments, the calcium sulfate material originating from the recycled gypsum source is present in a gypsum slurry (e.g., a gypsum slurry for a core layer and, optionally, one or more slate coat layers) in an amount of about 0.5 to about 10 weight percent of the calcium sulfate material. In some other embodiments, the calcium sulfate material originating from the recycled gypsum source is present in a gypsum slurry (e.g., a gypsum slurry for a core layer and, optionally, one or more slate coat layers) in an amount of about 1 to about 7.5 weight percent of the calcium sulfate material. In some embodiments, the calcium sulfate material comprises calcium sulfate dihydrate, calcium sulfate hemihydrate, anhydrous calcium sulfate,soluble anhydrite, or any combination thereof. In some embodiments, the calcium sulfate material comprises particles. In some such embodiments, an average particle size associated with the particles is about 20 to about 60 microns (pm).

[0057] In some embodiments, a dispersant is present in a core layer and / or at least one slate coat layer. For example, the dispersant may be present in at least one slate coat slurry used to form at least one slate coat layer or a gypsum core slurry use to form a gypsum core layer. The dispersant may present in the at least one slate coat layer and / or the core layer an amount from about 0.5 to about 10 Ib / msf. The dispersant may include a polynaphthalene sulfonate, a lignosulfonate, or a polycarboxylate ether. In some examples, the dispersant may be a calcium or a sodium salt. For example, the dispersant may include sodium polynaphthalene sulfonate, calcium polynaphthalene sulfonate, sodium lignosulfonate, or calcium lignosulfonate.

[0058] In some embodiments, the gypsum slurries of the present disclosure, which may be used to form the gypsum core or the slate coat layers, further includes one or more ingredients or additives to achieve the desired board properties. Various additives are discussed herein and may be used in any combination. In particular, suitable additives may include, but are not limited to, one or more of starch, fiberglass, dispersants, ball mill accelerators, retarders, potash, polyphosphates, and polymer binders.

[0059] For example, a suitable polyphosphate may be included in a gypsum slurry. For example, the polyphosphate may be sodium trimetaphosphate (STMP), sodium hexametaphosphate (SHMP), ammonium polyphosphate (APP). Other suitable phosphate salts may also be used and include other metaphosphate, polyphosphate, and pyrophosphate salts, such as ammonium trimetaphosphate, potassium trimetaphosphate, lithium trimetaphosphate, calcium trimetaphosphate, sodium calcium trimetaphosphate, aluminum trimetaphosphate; ammonium, lithium, or potassium hexametaphosphates; sodium tripolyphosphate, potassium tripolyphosphate, sodium and potassium tripolyphosphate; calcium pyrophosphate, tetrapotassium pyrophosphate, and / or tetrasodium pyrophosphate.

[0060] In some embodiments, a starch is present in the relevant gypsum layer or slurry in an amount of about 0.01 percent to about 1.5 percent, by weight. In some embodiments, the starch is present in the relevant gypsum layer or slurry in an amount of about 0.1 percent to about 0.5 percent, by weight. In some embodiments, the starch is present in the relevant gypsum layer or slurry in an amount of about 0.05 percent to about 0.2 percent, by weight. In some embodiments, the starch is present in the relevant gypsum layer or slurry in an amount of about 1 Ib / msf to about 50 Ib / msf, for a gypsum panel having a thickness of about 14 inch to about 1inch. In some embodiments, the starch is present in the relevant gypsum layer or slurry in an amount of less than, greater than, or about 1 Ib / msf, about 2 Ib / msf, about 3 Ib / msf, about 4 Ib / msf, about 5 Ib / msf, about 6 Ib / msf, about 7 Ib / msf, about 8 Ib / msf, about 9 Ib / msf, about 10 Ib / msf, about 11 Ib / msf, about 12 Ib / msf, about 13 Ib / msf, about 14 Ib / msf, about 15 Ib / msf, about 16 Ib / msf, about 17 Ib / msf, about 18 Ib / msf, about 19 Ib / msf, about 20 Ib / msf, about 21 Ib / msf, about 22 Ib / msf, about 23 Ib / msf, about 24 Ib / msf, about 25 Ib / msf, about 26 Ib / msf, about 27 Ib / msf, about 28 Ib / msf, about 29 Ib / msf, about 30 Ib / msf, about 31 Ib / msf, about 32 Ib / msf, about 33 Ib / msf, about 34 Ib / msf, about 35 Ib / msf, about 36 Ib / msf, about 37 Ib / msf, about 38 Ib / msf, about 39 Ib / msf, about 40 Ib / msf, about 41 Ib / msf, about 42 Ib / msf, about 43 Ib / msf, about 44 Ib / msf, about 45 Ib / msf, about 46 Ib / msf, about 47 Ib / msf, about 48 Ib / msf, about 49 Ib / msf, about 50 Ib / msf, about 51 Ib / msf, about 52 Ib / msf, about 53 Ib / msf, about 54 Ib / msf, about 55 Ib / msf, about 56 Ib / msf, about 57 Ib / msf, about 58 Ib / msf, about 59 Ib / msf, about 60 Ib / msf, about 61 Ib / msf, about 62 Ib / msf, about 63 Ib / msf, about 64 Ib / msf, about 65 Ib / msf, about 66 Ib / msf, about 67 Ib / msf, about 68 Ib / msf, about 69 Ib / msf, or about 70 Ib / msf, for a gypsum panel having a thickness of about 14 inch to about 1 inch, or within a range defined by any two of these values.

[0061] In certain embodiments, a polyphosphate is present in the relevant gypsum layer or slurry in an amount of about 0.01 percent to about 1 percent, by weight. In certain embodiments, the polyphosphate is present in the relevant gypsum layer or slurry in an amount of about 0.01 percent to about 0.5 percent, by weight. In some embodiments, the polyphosphate is present in the relevant gypsum layer or slurry in an amount of about 0.05 percent to about 0.2 percent, by weight. In some embodiments, the polyphosphate is present in the relevant gypsum layer or slurry in an amount of about 1 Ib / msf to about 50 Ib / msf, for a gypsum panel having a thickness of about 14 inch to about 1 inch. In some embodiments, the polyphosphate is present in the relevant gypsum layer or slurry in an amount of less than, greater than, or about 1 Ib / msf, about 2 Ib / msf, about 3 Ib / msf, about 4 Ib / msf, about 5 Ib / msf, about 6 Ib / msf, about 7 Ib / msf, about 8 Ib / msf, about 9 Ib / msf, about 10 Ib / msf, about 11 Ib / msf, about 12 Ib / msf, about 13 Ib / msf, about 14 Ib / msf, about 15 Ib / msf, about 16 Ib / msf, about 17 Ib / msf, about 18 Ib / msf, about 19 Ib / msf, about 20 Ib / msf, about 21 Ib / msf, about 22 Ib / msf, about 23 Ib / msf, about 24 Ib / msf, about 25 Ib / msf, about 26 Ib / msf, about 27 Ib / msf, about 28 Ib / msf, about 29 Ib / msf, about 30 Ib / msf, about 31 Ib / msf, about 32 Ib / msf, about 33 Ib / msf, about 34 Ib / msf, about 35 Ib / msf, about 36 Ib / msf, about 37 Ib / msf, about 38 Ib / msf, about 39 Ib / msf, about 40 Ib / msf, about 41 Ib / msf, about 42 Ib / msf, about 43 Ib / msf, about 44 Ib / msf, about 45 Ib / msf, about 46 Ib / msf, about 47 Ib / msf, about 48 Ib / msf, about 49 Ib / msf, or about 50 Ib / msf, for agypsum panel having a thickness of about 14 inch to about 1 inch, or within a range defined by any two of these values.

[0062] For example, a suitable polymer binder, such as an organic polymer binder may be contained in a gypsum slurry. Suitable polymer binders may include 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 binders may include UV curable monomers and polymers (e.g., epoxy acrylate, urethane acrylate, polyester acrylate). For example, on a dry basis, the polymer binder content in the relevant gypsum layer or slurry may be between 1 Ib / msf to 50 Ib / msf, for a gypsum panel having a thickness of about % inch to 1 inch.

[0063] In certain embodiments, a polymer binder is present in the relevant gypsum layer or slurry in an amount of about 0.01 percent to about 1 percent, by weight. In certain embodiments, the polymer binder is present in the relevant gypsum layer or slurry in an amount of about 0.01 percent to about 0.5 percent, by weight. In some embodiments, the polymer binder is present in the relevant gypsum layer or slurry in an amount of about 0.05 percent to about 0.2 percent, by weight. In some embodiments, the polymer binder is present in the relevant gypsum layer or slurry in an amount of about 1 Ib / msf to about 50 Ib / msf, for a gypsum panel having a thickness of about 14 inch to about 1 inch. In some embodiments, the polymer binder is present in the relevant gypsum layer or slurry in an amount of less than, greater than, or about 1 Ib / msf, about 2 Ib / msf, about 3 Ib / msf, about 4 Ib / msf, about 5 Ib / msf, about 6 Ib / msf, about 7 Ib / msf, about 8 Ib / msf, about 9 Ib / msf, about 10 Ib / msf, about 11 Ib / msf, about 12 Ib / msf, about 13 Ib / msf, about 14 Ib / msf, about 15 Ib / msf, about 16 Ib / msf, about 17 Ib / msf, about 18 Ib / msf, about 19 Ib / msf, about 20 Ib / msf, about 21 Ib / msf, about 22 Ib / msf, about 23 Ib / msf, about 24 Ib / msf, about 25 Ib / msf, about 26 Ib / msf, about 27 Ib / msf, about 28 Ib / msf, about 29 Ib / msf, about 30 Ib / msf, about 31 Ib / msf, about 32 Ib / msf, about 33 Ib / msf, about 34 Ib / msf, about 35 Ib / msf, about 36 Ib / msf, about 37 Ib / msf, about 38 Ib / msf, about 39 Ib / msf, about 40 Ib / msf, about 41 Ib / msf, about 42 Ib / msf, about 43 Ib / msf, about 44 Ib / msf, about 45 Ib / msf, about 46 Ib / msf, about 47 Ib / msf, about 48 Ib / msf, about 49 Ib / msf, or about 50 Ib / msf, for a gypsum panel having a thickness of about 14 inch to about 1 inch, or within a range defined by any two of these values.

[0064] In certain embodiments, each of the slate coat layers is deposited in an amount of from about 5 percent to about 20 percent, by weight, of the gypsum layers. This would meanthat the gypsum core layer comprises about 80 to about 95 percent of the total weight of the gypsum layers, when one slate coat layer is present, and about 60 to about 90 percent of the total weight of the gypsum layers, when two slate coat layers are present. The gypsum slurries may be deposited by any suitable means, such as roll coating.

[0065] In certain embodiments, a gypsum layer or slurry contains one or more additional agents to enhance its performance, such as, but not limited to, wetting agents, moisture resistance agents, fillers, accelerators, set retarders, foaming agents, polyphosphates, and dispersing agents. Various example uses of such further additives will now be described.

[0066] 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, suitable superplasticisers include Melflux 265 IF 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.

[0067] In certain embodiments, a surfactant is present in the relevant gypsum layer or 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 layer or 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 layer or slurry in an amount of about 0.05 percent to about 0.2 percent, by weight. In some embodiments, the surfactant is present in the relevant gypsum layer or slurry in an amount of about 1 Ib / msf to about 50 Ib / msf, for a gypsum panel having a thickness of about 14 inch to about 1 inch. In some embodiments, the surfactant is present in the relevant gypsum layer or slurry in an amount of less than, greater than, or about 1 Ib / msf, about 2 Ib / msf, about 3 Ib / msf, about 4 Ib / msf, about 5 Ib / msf, about 6 Ib / msf, about 7 Ib / msf, about 8 Ib / msf, about 9 Ib / msf, about 10 Ib / msf, about 11 Ib / msf, about 12 Ib / msf, about 13 Ib / msf, about 14 Ib / msf, about 15 Ib / msf, about 16 Ib / msf, about 17 Ib / msf, about 18 Ib / msf, about 19 Ib / msf, about 20 Ib / msf, about 21 Ib / msf, about 22 Ib / msf, about 23 Ib / msf, about 24 Ib / msf, about 25 Ib / msf, about 26 Ib / msf, about 27 Ib / msf, about 28 Ib / msf, about 29 Ib / msf, about 30 Ib / msf, about 31 Ib / msf, about 32 Ib / msf, about 33 Ib / msf, about 34 Ib / msf, about 35 Ib / msf, about 36 Ib / msf, about 37 Ib / msf, about 38 Ib / msf, about 39 Ib / msf, about 40 Ib / msf, about 41 Ib / msf, about 42 Ib / msf, about 43 Ib / msf, about 44 Ib / msf, about 45 Ib / msf, about 46Ib / msf, about 47 Ib / msf, about 48 Ib / msf, about 49 Ib / msf, or about 50 Ib / msf, for a gypsum panel having a thickness of about % inch to about 1 inch, or within a range defined by any two of these values.

[0068] 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 -di oxane, 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).

[0069] In certain embodiments, a moisture resistance or hydrophobizing agent is provided in the gypsum slurry or layers thereof to impart desired moisture resistance and / or processing properties to the panel. For example, the moisture resistance or hydrophobizing agent may include a wax, wax emulsions or co-emulsions, silicone, siloxane, siliconate, or any combination thereof. In certain embodiments, a moisture resistance or hydrophobizing agent is present in the relevant gypsum layer or slurry in an amount of about 0.01 percent to about 1 percent, by weight. In certain embodiments, the moisture resistance or hydrophobizing agent is present in the relevant gypsum layer or slurry in an amount of about 0.01 percent to about 0.5 percent, by weight. In some embodiments, the moisture resistance or hydrophobizing agentis present in the relevant gypsum layer or slurry in an amount of about 0.05 percent to about 0.2 percent, by weight. In some embodiments, the moisture resistance or hydrophobizing agent is present in the relevant gypsum layer or slurry in an amount of about 1 Ib / msf to about 50 Ib / msf, for a gypsum panel having a thickness of about 14 inch to about 1 inch. In some embodiments, the moisture resistance or hydrophobizing agent is present in the relevant gypsum layer or slurry in an amount of less than, greater than, or about 1 Ib / msf, about 2 Ib / msf, about 3 Ib / msf, about 4 Ib / msf, about 5 Ib / msf, about 6 Ib / msf, about 7 Ib / msf, about 8 Ib / msf, about 9 Ib / msf, about 10 Ib / msf, about 11 Ib / msf, about 12 Ib / msf, about 13 Ib / msf, about 14 Ib / msf, about 15 Ib / msf, about 16 Ib / msf, about 17 Ib / msf, about 18 Ib / msf, about 19 Ib / msf, about 20 Ib / msf, about 21 Ib / msf, about 22 Ib / msf, about 23 Ib / msf, about 24 Ib / msf, about 25 Ib / msf, about 26 Ib / msf, about 27 Ib / msf, about 28 Ib / msf, about 29 Ib / msf, about 30 Ib / msf, about 31 Ib / msf, about 32 Ib / msf, about 33 Ib / msf, about 34 Ib / msf, about 35 Ib / msf, about 36 Ib / msf, about 37 Ib / msf, about 38 Ib / msf, about 39 Ib / msf, about 40 Ib / msf, about 41 Ib / msf, about 42 Ib / msf, about 43 Ib / msf, about 44 Ib / msf, about 45 Ib / msf, about 46 Ib / msf, about 47 Ib / msf, about 48 Ib / msf, about 49 Ib / msf, or about 50 Ib / msf, for a gypsum panel having a thickness of about 14 inch to about 1 inch, or within a range defined by any two of these values.

[0070] In certain embodiments, a gypsum slurry layer, and particularly a slate coat layer, may be deposited on a horizontally oriented moving web of facer material, such as pre-coated fibrous mat or paper facing material. A second coated or uncoated web of facer material may be deposited onto the surface of the gypsum slurries (particularly a second slate coat slurry) opposite the first web of facer material, e.g., a non-coated surface of the second web of facer material contacts the gypsum slurry layer. In some embodiments, a moving web of a facer material may be placed on the upper free surface of the gypsum slurry. Thus, the gypsum layers may be sandwiched between two facer materials, none, one or both having a coating. In certain embodiments, allowing the gypsum layer slurries and / or 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).

[0071] A barrier coating may be applied to both face layers, prior to or after drying of the face layers. In some embodiments, the glass mats are pre-coated when they are associated with the slate coat slurry. In some embodiments, depositing a barrier coating onto the second surface of the first coated face layer occurs after setting the first gypsum slurry to form a slate core layer. In some embodiments, the slate coat layer 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 setat room temperature. In some embodiments, infrared heating is used to flash off water and dry the barrier coating.

[0072] Suitable coating materials (i.e., the precursor to the dried mat coating) may 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, ureaformaldehyde 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.

[0073] 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 pm 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 pm particle size; and NEOCAR 820, commercially available from Arkema Coating Resins, which is a hydrophobic modified acrylic latex containing 45% solids by weight, with a 0.07 pm particle size.

[0074] 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, IL); IMSIL A- 10, commercially available from the Cary Company; and TALCRON MP 44-26, commercially available from Specialty Minerals Inc. (Dillon, MT). 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.

[0075] 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.

[0076] 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 HYDROP ALAT 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-p-tolylsulfone, 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.

[0077] Panels and Systems

[0078] Gypsum panels having improved fire resistance and / or physical properties may be made by any of the methods described herein. For example, a gypsum panel may include a gypsum core including set gypsum and a colloidal material including colloidal silica and / or colloidal alumina, in which the colloidal material is present in the gypsum core in an amount greater than one or more other materials and less than the gypsum. As discussed above, the gypsum panel may have a thickness from about 14 inch to about 1 inch. For example, the gypsum panel may have a thickness from about 1 / 2 inch to about 5 / 8 inch.

[0079] In some embodiments, one or more face layers (e.g., the face layer 108 and / or the face layer 110) may include a nonwoven fiberglass mat. For example, the glass fibers may have an average diameter of from about 10 to about 17 pm and an average length of from about 14 inch to about 1 inch. For example, the glass fibers may have an average diameter of 13 pm (i.e., K fibers) and an average length of 3 / 4 inch. In some such embodiments, the nonwoven fiberglass mats may have a basis weight of from about 1.5 pounds to about 6.0 pounds per 100 square feet of the mat, such as 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 other embodiments, the mat facer may be a suitable paper facer material.

[0080] In some embodiments, the gypsum core 102 is present in an amount from about 5 percent to about 20 percent, by weight, of the gypsum layers 101.

[0081] In some embodiments, one or more of the gypsum layers 101 include reinforcing fibers, such as chopped fiberglass fibers or particles. In one embodiment, the gypsum core includes about 1 pound to about 20 pounds of reinforcing fibers per 1000 square feet of panel.For example, the gypsum core and / or one or more other layers may include up to about 6 pounds of reinforcing fibers per 1000 square feet of panel. For example, the gypsum core and / or a slate coat layer may include about 3 pounds of reinforcing fibers per 1000 square feet of panel. The reinforcing fibers may have a diameter between about 10 and about 17 pm and have a length between about 5 and about 18 millimeters.

[0082] A further embodiment is a method of making a gypsum panel, comprising:

[0083] i) providing a gypsum core slurry comprising water, a calcium sulfate material, a defoaming agent, and a propylene glycol alginate additive;

[0084] ii) providing a first face layer; and

[0085] iii) setting the gypsum core slurry on the first face layer to form a gypsum core layer of the gypsum panel.

[0086] In some embodiments, the method further comprises:

[0087] iv) providing a first slate coat slurry comprising water and the calcium sulfate material; and

[0088] v) setting the first slate coat slurry on the first face layer to form a first slate coat layer, wherein the gypsum core slurry is set on the first slate coat layer.

[0089] In some embodiments, the method further comprises:

[0090] vi) providing a second face layer; and

[0091] vii) placing the second face layer on the gypsum core layer.

[0092] In some embodiments, the method further comprises:

[0093] viii) providing a second slate coat slurry, comprising water and the calcium sulfate material; and

[0094] ix) setting the second slate coat slurry on the gypsum core slurry to form a second slate coat layer.

[0095] In some embodiments, the method further comprises:

[0096] x) obtaining a first calcium sulfate material from a recycled gypsum source, wherein the gypsum core slurry comprises the defoaming agent based at least in part on the first calcium sulfate material being obtained from the recycled gypsum source; and

[0097] xi) combining the first calcium sulfate material with a second calcium sulfate material to obtain the calcium sulfate material, wherein the second calcium sulfate material is from a non-recycled gypsum source.

[0098] The disclosed subject matter is further described in the following non-limiting Examples. It should be understood that these Examples, while indicating example embodiments of the subject matter, are given by way of illustration only.EXAMPLESExample 1: Manufacturing testing

[0099] A first test was conducted based on a standard manufacturing process to determine how a particle size distribution of stucco that originates from a recycled gypsum source, and includes siloxane (Dens® Reclaim), differs from a particle size distribution of stucco that originates from a non-recycled gypsum source. In the example of Figure 2, the recycled gypsum source is referred to as gypsum reclaim and the stucco from the non-recycled gypsum source is referred to as plant stucco.

[0100] In the first test, the gypsum reclaim was subjected to a first grinding process to, for example, separate one or more glass mat facers from gypsum include in the gypsum reclaim. The first grinding process included passing the gypsum reclaim through a turbo grinder separator. The ground gypsum material was then dried in an oven at about 43 °C overnight. The dried particles were subjected to ball milling and ground to a target median size of about 40 pm. The resulting material, which includes the milled and ground particles, was then calcined by placing the material in an oven at about 160°C and stirring the material approximately every 10 minutes until, for example, a combined water percent of the resulting stucco was between about 4 and 7% by weight. As used herein, combined water percent refers to a percentage of chemically combined water in a sample compared to free moisture in the sample as measured using a COMPUTRAC® MAX® 4000XL moisture analyzer. The resulting stucco is referred to as reclaim calcined in lab.

[0101] Figure 2 illustrates an exemplary graph showing a particle size distribution profile for the reclaim calcined in lab relative to the plant stucco. For example, the graph shows a particle size distribution of the reclaim calcined in lab, which was prepared in the first test, compared to a particle size distribution of the plant stucco. As illustrated in the example of Figure 2, the reclaim calcined in lab has a wider particle size distribution than that of the plant stucco. For example, the particle size distribution of the reclaim calcined in lab ranges from about 0.3 pm to about 600 pm, whereas the particle size distribution of the plant stucco ranges from about 4 pm to about 300 pm. As such, the reclaim calcined in lab includes particles include some particles having a smaller diameter than the particles in the plant stucco.Additionally, the reclaim calcined in lab includes other particles having a larger diameter than the particles in the plant stucco.Example 2: Manufacturing testing

[0102] A second test was conducted based on a standard manufacturing process, to determine how stucco from a recycled gypsum source affects wet density of lightweight gypsum panels. That is, the second test was conducted to determine how the wet density of a slurry for lightweight gypsum panels changes with the incorporation of varying amounts of stucco from a recycled gypsum source. For example, in the second test, a wet density of an initial slurry for a lightweight gypsum panel, which includes stucco from a non-recycled gypsum source was determined to be about 54 pounds per cubic foot (pcf). That is, a field slurry wet density of a lightweight gypsum panel was determined to be about 54 pcf, which is approximately equivalent to a wet density of a slurry used to manufacture a 1450-lbs / msf dry lightweight gypsum panel.

[0103] Figure 3 illustrates an exemplary graph showing the wet density response to the stucco from the recycled gypsum source. That is, the graph shows wet densities of slurries for lightweight gypsum panels, which include varying amounts of stucco from a non-recycled gypsum source and varying amounts of stucco from a recycled gypsum source. In the example of Figure 3, the stucco from the recycled gypsum source is referred to as reclaim dense stucco and the stucco from the non-recycled gypsum source is referred to as plant stucco. The reclaim dense stucco was added on a percent of stucco basis (as a weight percent of the total amount of dry stucco added to the slurry) in varying amounts from 0 to about 7.5%. Each condition, which refers to a respective amount of plant stucco and stucco from reclaimed gypsum, was replicated 5 times. That is, each value illustrated in Figure 3 is based on an average of 5 wet density measurements, in which each wet density measurement was of a slurry that included a respective quantity of plant stucco and a respective quantity of stucco from reclaimed gypsum.

[0104] As illustrated in the example of Figure 3, the average wet density of a slurry with 0% of the reclaim dense stucco is about 55% pcf. The average wet density of a slurry with 1.0% by weight of the reclaim dense stucco is about 61% pcf, showing an 11% increase in wet density relative to the slurry with 0% stucco from reclaimed gypsum. The average wet density of a slurry with 2.5% by weight of the reclaim dense stucco is about 63% pcf, showing an 15% increase in wet density relative to the slurry with 0% stucco from reclaimed gypsum. The average wet density of a slurry with 5.0% of the reclaim dense stucco is about 65% pcf, showing an 18% increase in wet density relative to the slurry with 0% stucco from reclaimed gypsum. The average wet density of a slurry with 7.5% of the reclaim dense stucco is about74% pcf, showing a 35% increase in wet density relative to the slurry with 0% stucco from reclaimed gypsum.

[0105] Thus, as illustrated in the example of Figure 3, the addition of reclaim dense stucco, which includes stucco from reclaim containing siloxane, had a statistically significant change in the wet density of the resulting slurry. In other words, as the amount of reclaim dense stucco increased, the wet density of the resulting slurry also increased. It is noted that, while the particle size distribution of the reclaim dense stucco may be wider than that of other stucco obtained using an industrial process (which may have led to some variability), the results presented herein with respect to wet density change were statistically significant across the tests presented herein.Example 3: Manufacturing testing

[0106] A third test was conducted to quantify the effects of PGA on counteracting defoaming due to stucco from a recycled gypsum source for lightweight gypsum panels. Through screening experiments, PGA was determined to effectively mitigate siloxane defoaming effects. That is, PGA was found to be a relatively low viscosity thickener and foam stabilizer capable of mitigating the effects of siloxane and stabilizing the wet density of slurries, for example, for lightweight gypsum panels and / or standard gypsum panels.

[0107] In the third test, PGA was dissolved in about 175 grams of water at varying concentrations. In the third test, the concentration of PGA ranged from about 0.007% to about 0.015% by stucco weight. Additionally, in the third test, a total of 250 grams of stucco was used with varying amounts of stucco from a recycled gypsum source. In the third test, the composition of the slurries ranged from about 250 grams plant stucco with 0 grams of stucco from a recycled gypsum source to about 235 grams of plant stucco and about 15 grams of stucco from a recycled gypsum source. Foam was generated in the slurries using a foaming agent. In the third test, a solution including a foaming agent in a concentration of about 0.5% by stucco weight was used to produce a foam density of about 7 pounds per cubic foot. Additionally, about 25 grams of the produced foam was mixed with each slurry and poured into a 197mL cup. After the foam was mixed with the slurries, the cup was weighed and the wet density was determined for each slurry.

[0108] Figure 4 illustrates an exemplary contour plot showing wet densities of slurries including varying amounts of PGA and varying amounts of stucco from a recycled gypsum source. In the example of Figure 4, the stucco from the recycled gypsum source is referred to as recycle. As illustrated in the example of Figure 4, PGA was effective in mitigating defoaming caused by the siloxane (caused by incorporating recycle into the slurries). Theresults illustrated in the example of Figure 4 were statistically significant, for example, the p- value of the percent recycle was about 0.023 at a 95% confidence interval, which may indicate that the recycle had a significant effect on wet density. Additionally, the p-value of the percent PGA was about 0.004 at a 95% confidence interval, which may indicate that the PGA had a significant effect on mitigating the defoaming effects of the recycle. The data illustrated in the example of Figure 4 was analyzed as a custom fractional factorial in which the R-squared was about 71.20%. The results of the third test indicate that PGA (and additives thereof) effectively mitigate defoaming in stucco slurries (e.g., even in relatively small amounts, such as in an amount ranging from about 0.05% by stucco weight to about 0.15% by stucco weight).Example 4: Manufacturing testing

[0109] A fourth test was conducted to determine how stucco from a recycled gypsum source comprising siloxane affects wet density, setting characteristics, and water demand of lightweight gypsum panels. That is, the fourth test was conducted to determine how the wet density, setting characteristics, and water demand of a slurry for lightweight gypsum panels changes with the incorporation of varying amounts of stucco from a recycled gypsum source. In the fourth test, a control sample was made with about 7-lb / msf of a dispersant (Diloflo CA- 30, available from GEO Specialty Chemicals) and about a 1-lb / msf ball milled accelerator (BMA) to obtain a target wet density of about 49-pcf, a slump of about 7 to about 1-1 / 2-inches, and a gypsum stiffness time of about 50 seconds. The BMA includes a finely ground gypsum, which acts as a seed crystal and accelerates setting characteristics of the slurry. That is, the BMA includes calcium sulfate dihydrate that, when added to calcium sulfate hemihydrate, acts as a seed crystal and accelerates the setting characteristics of the slurry.

[0110] As used herein, “slump” means a slurry flow distance when released from a tube. In some examples, slump is also referred to as slurry fluidity. A slump value corresponds to a diameter of a patty formed from a slurry released from a tube and is used to determine the fluidity of the slurry, for example, with regards to controlling a dispersing agent and as part of an analysis used to determine water or stucco variations. For example, during a slump test, a tube (e.g., a hollow cylindrical container) is filled with a slurry. The tube is then positioned in a manner that allows the slurry to flow out of the tube and form a patty on a surface (e.g., a surface of a glass plate). The slump of the slurry corresponds to a measured diameter of the patty. Varying amounts of stucco from a recycled gypsum source was then added in concentrations of about 0.625% to about 5% by stucco weight. Additionally, varying amounts of the dispersant was added (e.g., as a water demand of the slurry increased the amount of dispersant was increased) to maintain the slump of the control sample.

[0111] Figure 5 illustrates an exemplary graph showing the dispersant response to stucco from the recycled gypsum source. That is, the graph shows the amount of dispersant added to slurries (e.g., for lightweight gypsum panels), which include varying amounts of stucco from a non-recycled gypsum source and varying amounts of stucco from a recycled gypsum source. In the example of Figure 5, the stucco from the recycled gypsum source is referred to as Dens Reclaim. The Dens Reclaim was added on a percent of stucco basis (as a weight percent of the total amount of dry stucco added to the slurry) in varying amounts from 0% to about 5%, in which the slurry with 0% Dens Reclaim corresponds to the control sample. As illustrated in the example of Figure 5, an increase in water demand was observed with higher amounts of Dens Reclaim, which led to an increase in the amount of dispersant used to maintain the slump of the control sample.

[0112] Figure 6 illustrates an exemplary graph showing the wet density response to stucco from a recycled gypsum source. In the example of Figure 6, the stucco from the recycled gypsum source is referred to as Dens Reclaim. That is, the graph shows the wet densities of the slurries in which Dens Reclaim was added in varying amounts from 0% to about 5%. As illustrated in the example of Figure 6, an increase in wet density was observed with higher amounts of dens reclaim, indicating that the Dens Reclaim causes defoaming in the slurries. Additionally, in the fourth test, an acceleration of the set time was observed for slurries with higher amounts of Dens Reclaim, indicating that a lab grinding and calcining process used to obtain the stucco from reclaimed gypsum was relatively inconsistent.

[0113] A gypsum phase analysis showed a larger percentage of calcium sulfate dihydrate (gypsum) present in the slurries with stucco from reclaimed gypsum obtained using the lab grinding and calcining process than a percentage of calcium sulfate dihydrate that may be present in slurries with stucco from a plant process. The larger percentage of calcium sulfate dihydrate lead to a faster set time. Slower set times may be achieved by reducing the amount of the BMA.Example 5: Product testing

[0114] A fifth test was conducted to quantify defoaming and process adjustments for lightweight gypsum panels made from slurries with a PGA additive and stucco from a recycled gypsum source. In the fifth test, PGA was incorporated into slurries using a PGA solution that included PGA in an amount of about 1.25% by weight. The PGA solution was formed by dissolving about 6.25 grams of PGA in about 500-mL of water using a high shear mixer, which produced some foam in the solution. An ultrasonic bath was used to defoam the solution.

[0115] To disperse the PGA powder in the solution, the temperature of the water was raised to around 80 to 90-deg F. Additionally, high shear mixing was used to disperse the PGA powder and to reduce the presence of fish-eyes. As described herein, “fish-eyes” means agglomerates of partially hydrated PGA powder, in which an agglomerate has an outer layer which prevents wetting of particles within the interior of the agglomerate. The high shear mixing increases mixing efficiency and leads to relatively high amounts of foam in the solution. The amount of foam was reduced by lowering the concentration of the PGA in the solution to less than 1% or preferrable less than about 0.5%. In other words, a PGA solution having a PGA concentration of less than about 1% or preferably less than about 0.5% PGA by weight lead to improved mixing efficiency and generate less foam compared to PGA solutions with higher concentrations of PGA. To defoam the PGA solution, the PGA solution was placed in a 30- watt ultrasonic water bath for about 4 to 6 hours. To accelerate the defoaming step a high- powered ultrasonic probe, such as a 600 W LSP-600 ultrasonic liquid processor, may be used to degas the solution in less time than the 30-watt ultrasonic water bath (e.g., to defoam the solution in minutes compared to hours).

[0116] The fifth test utilized an unstable foam former solution, which included a foaming agent (an anionic surfactant, Hyonic PFM 15 available from GEO Specialty Chemicals) in a concentration of about 1.25% by weight. In the fifth test, a control sample was produced using about 3.75-lbs / msf of a dispersant (Diloflo CA-30). A target wet density of the control sample was 52-pcf with a slump of about 7-inches. Varying amounts of stucco from a recycled gypsum source was then added in a concentration of 0% to about 7.5% by stucco weight. Additionally, varying amounts of the dispersant was added to maintain the slump of the control sample. That is, as a water demand of the slurry increased, the amount of dispersant was increased.

[0117] Table 1 illustrates an exemplary table showing the effects of recycled gypsum, PGA, and dispersant on gypsum properties. In the example of Table 1, the stucco from the recycled gypsum source is referred to as reclaim. For each slurry tested, the target dry board weight was 1450 Ibs / msf and the foam former was Hyonic PFM 15. All percentages listed are by weight compared to the total weight of dry stucco added to the slurries.

[0118] Table 1 : Effects of recycled gypsum, PGA, and dispersant on gypsum properties

[0119] As shown in Table 1, for slurries with reclaim in an amount up to about 2.5% by stucco weight (total stucco weight), relatively small amounts of defoaming was observed. Additionally, for slurries with reclaim in an amount up to about 5 to 7.5% by stucco weight, relatively large amounts of defoaming was observed. As shown in Table 1, for the slurries with reclaim in an amount up to about 5% to about 7.5% by stucco weight, defoaming was reduced with the PGA. Additionally, as shown in Table 1, the incorporation of PGA into the slurries lead to an increase in water demand, which led to an increase in the amount of dispersant used to maintain the slump of the control sample. The fifth test indicates that the incorporation of PGA in a concentration of about 0.005% to 0.01% by stucco weight may reduce the amount of defoaming and stabilize a wet density of gypsum panels.

[0120] Figure 7 illustrates an exemplary graph showing the wet density response to stucco from a recycled gypsum source with and without PGA. In the example of Figure 7, the stucco from the recycled gypsum source is referred to as reclaim. The wet densities shown in the example of Figure 7 are also represented in Table 1. As illustrated in the example of Figure 7, the wet density for slurries with reclaim in an amount up to about 5% to about 7.5% by stucco weight was reduced with the PGA.

[0121] Figure 8 illustrates an exemplary graph showing the panel board (dry) weight response to stucco from a recycled gypsum source with and without PGA. In the example of Figure 8, the stucco from the recycled gypsum source is referred to as reclaim. The panel dry weights shown in the example of Figure 8 are also represented in Table 1. As illustrated in the example of Figure 8, the panel dry weight for panels formed using slurries with reclaim in an amount up to about 5% to about 7.5% by stucco weight was reduced with the PGA.

[0122] Although the examples presented herein illustrate the use of PGA in reducing defoaming due to the presence of siloxane, it is to be understood that PGA may be used to reduce the defoaming effects of other defoaming agents, such as other silicon-based defoamers, mineral oil-based defoamers, polyether or polyol-based defoamers, alkyl aryl sulfonates, and fatty acid esters, among other examples of defoaming agents.

[0123] Although the examples presented herein refer to stucco, it is to be understood that slurries for gypsum panels may be produced using one or more calcium sulfate materials, including calcium sulfate dihydrate, calcium sulfate hemihydrate, anhydrous calcium sulfate, soluble anhydrite, or any combination thereof.

[0124] In addition to PGA, one or more other technologies may be used to reduce defoaming including, but not limited to, carboxymethyl celluloses(CMC), sodium carboxymethyl cellulose, gum arabia, and xanthan gum which act as low viscosity thickeners and foam stabilizers. Betaines, amido betaines, and cationic surfactants used as a secondary surfactant to increase the stability of the foam structure. In some examples, the addition of one or more other additives may increase the stability of the foam structure including, but not limited to, sodium fluoride, polyvinyl alcohol(PVA), polyethylene glycol(PEG), nano SiCh, and sodium polyacrylate.

[0125] Many modifications and other embodiments of the subject matter set forth herein will come to mind to one skilled in the art to which the subject matter pertains having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the subject matter is not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation. Each embodiment disclosed herein is contemplated as being applicable to each of the other disclosed embodiments. All combinations and sub-combinations of the various elements described herein are within the scope of the embodiments.

Claims

WHAT IS CLAIMED IS:

1. A gypsum panel, the gypsum panel comprising: a gypsum core layer, the gypsum core layer comprising a calcium sulfate material, a defoaming agent, and a propylene glycol alginate additive.

2. The gypsum panel of claim 1, wherein the defoaming agent comprises a silicon material.

3. The gypsum panel of claim 2, wherein the silicon material comprises siloxane.

4. The gypsum panel of any one of claims 1-3, wherein about 0.01 to about 15 weight percent of the calcium sulfate material originates from a recycled gypsum source.

5. The gypsum panel of any one of claims 1-3, wherein about 0.5 to about 10 weight percent of the calcium sulfate material originates from a recycled gypsum source.

6. The gypsum panel of any one of claims 1-3, wherein about 1 to about 7.5 weight percent of the calcium sulfate material originates from a recycled gypsum source.

7. The gypsum panel of any one of claims 4-6, wherein a remaining weight percent of the calcium sulfate material originates from a non-recycled gypsum source.

8. The gypsum panel of any one of claims 1-7, wherein the calcium sulfate material comprises calcium sulfate dihydrate, calcium sulfate hemihydrate, anhydrous calcium sulfate, soluble anhydrite, or any combination thereof.

9. The gypsum panel of any one of claims 1-8, wherein the propylene glycol alginate additive is present in the gypsum core layer in an amount from about 0.001 to about 0.05 weight percent relative to the calcium sulfate material.

10. The gypsum panel of any one of claims 1-8, wherein the propylene glycol alginate additive is present in the gypsum core layer in an amount from about 0.005 to about 0.015 weight percent relative to the calcium sulfate material.

11. The gypsum panel of any one of claims 1-8, wherein the propylene glycol alginate additive is present in the gypsum core layer in an amount from about 0.007 to about 0.01 weight percent relative to the calcium sulfate material.

12. The gypsum panel of any one of claims 1-8, wherein the propylene glycol alginate additive is present in the gypsum core layer in an amount from about 0.01 to about 0.61 Ib / msf.

13. The gypsum panel of any one of claims 1-12, wherein the gypsum core layer comprises a dispersant.

14. The gypsum panel of claim 13, wherein the dispersant is present in the gypsum core layer in an amount from about 0.5 to about 10 Ib / msf.

15. The gypsum panel of claim 13 or 14, wherein the dispersant comprises a poly naphthalene sulfonate, a lignosulfonate, or a polycarboxylate ether.

16. The gypsum panel of any one of claims 1-15, wherein the gypsum panel comprises a first face layer and a second face layer, and wherein the gypsum core layer is interposed between the first face layer and the second face layer.

17. The gypsum panel of claim 16, wherein the first face layer and the second face layer each comprise a paper facing material.

18. The gypsum panel of claim 16, wherein the first face layer and the second face layer each comprise a glass mat, the glass mat comprising: i) glass fibers; ii) a resin binder; and iii) a mat coating.

19. The gypsum panel of claim 17 or 18, wherein the gypsum panel comprises at least a first slate coat layer interposed between the gypsum core layer and the first face layer.

20. The gypsum panel of claim 19, wherein the gypsum panel comprises a second slate coat layer interposed between the gypsum core layer and the second face layer.

21. The gypsum panel of any one of claims 1-20, wherein the gypsum core layer comprises a foaming agent.

22. The gypsum panel of claim 21, wherein the foaming agent comprises an anionic surfactant.

23. The gypsum panel of any one of claim 1-22, wherein the gypsum panel has a lower wet density, as compared to an otherwise identical gypsum panel that does not comprise the propylene glycol alginate additive.

24. A method of making a gypsum panel, comprising:i) providing a gypsum core slurry comprising water, a calcium sulfate material, a defoaming agent, and a propylene glycol alginate additive; ii) providing a first face layer; and iii) setting the gypsum core slurry on the first face layer to form a gypsum core layer of the gypsum panel.

25. The method of claim 24, further comprising: iv) providing a first slate coat slurry comprising water and the calcium sulfate material; and v) setting the first slate coat slurry on the first face layer to form a first slate coat layer, wherein the gypsum core slurry is set on the first slate coat layer.

26. The method of claim 25, further comprising: vi) providing a second face layer; and vii) placing the second face layer on the gypsum core layer.

27. The method of claim 26, further comprising: viii) providing a second slate coat slurry comprising water and the calcium sulfate material; and ix) setting the second slate coat slurry on the gypsum core layer to form a second slate coat layer, wherein the second face layer is placed on the second slate coat layer.

28. The method of any one of claims 24-27, further comprising: x) obtaining a first calcium sulfate material from a recycled gypsum source, wherein the gypsum core slurry comprises the defoaming agent based at least in part on the first calcium sulfate material being obtained from the recycled gypsum source; and xi) combining the first calcium sulfate material with a second calcium sulfate material to obtain the calcium sulfate material, wherein the second calcium sulfate material is from a non-recycled gypsum source.

29. The method of any one of claims 24-28, wherein the gypsum core slurry comprises a foaming agent.

30. The method of claim 29, wherein the foaming agent comprises an anionic surfactant.

31. The method of claim 29 or 30, wherein the foaming agent is present in the gypsum core slurry in an amount of about 1 to about 2 percent by weight.

32. The method of any one of claims 24-31, wherein the gypsum core slurry comprises a ball milled accelerator.

33. The method of any one of claims 24-32, wherein about 0.01 to about 15 weight percent of the calcium sulfate material originates from a recycled gypsum source.

34. The method of any one of claims 24-32, wherein about 0.5 to about 10 weight percent of the calcium sulfate material originates from a recycled gypsum source.

35. The method of any one of claims 24-32, wherein about 1 to about 7.5 weight percent of the calcium sulfate material originates from a recycled gypsum source.

36. The method of any one of claims 33-35, wherein a remaining weight percent of the calcium sulfate material originates from a non-recycled gypsum source.

37. The method of any one of claims 24-36, wherein the calcium sulfate material comprises calcium sulfate dihydrate, calcium sulfate hemihydrate, anhydrous calcium sulfate, soluble anhydrite, or any combination thereof.

38. The method of any one of claims 24-37, wherein the propylene glycol alginate additive is present in the gypsum core slurry in an amount from about 0.001 to about 0.05 weight percent relative to the calcium sulfate material.

39. The method of any one of claims 24-37, wherein the propylene glycol alginate additive is present in the gypsum core slurry in an amount from about 0.005 to about 0.015 weight percent relative to the calcium sulfate material.

40. The method of any one of claims 24-37, wherein the propylene glycol alginate additive is present in the gypsum core slurry in an amount from about 0.007 to about 0.01 weight percent relative to the calcium sulfate material.

41. The method of any one of claims 24-37, wherein the propylene glycol alginate additive is present in the gypsum core slurry in an amount from about 0.1 to about 0.61 Ib / msf.

42. The method of any one of claims 24-41, wherein the gypsum core slurry comprises a dispersant.

43. The method of claim 42, wherein the dispersant is present in the gypsum core slurry in an amount from about 0.5 to about 10 Ib / msf.

44. The method of claim 42 or 43, wherein the dispersant comprises a polynaphthalene sulfonate, a lignosulfonate, or a polycarboxylate ether.

45. The method of any one of claims 24-44, wherein the first face layer comprises a paper facing material.

46. The method of any one of claims 24-44, wherein the first face layer comprises a glass mat, the glass mat comprising: i) glass fibers; ii) a resin binder; and iii) a mat coating.

47. A gypsum panel made by the method of any one of claims 24-46.

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