HK1146013A - Mat-faced gypsum board and method of making thereof - Google Patents

Abstract

A mat-faced gypsum board and method of making thereof is provided having a particulate matter applied on an inner surface of the facer mat and extending partially into the mat from the inner surface thereof. The particulate matter, which is preferably a hydratable powder such as calcium sulfate hemihydrate, minimizes and, preferably, prevents bleed through of a gypsum slurry during formation of the gypsum board.

Description

Mat-faced gypsum board and method of making same

Cross reference to related applications

This patent application claims the benefit of U.S. provisional patent application No. 60/951,400, filed on 7/23/2007 and U.S. patent application No. 12/176,200, filed on 7/18/2008, which are incorporated herein by reference.

Technical Field

The present invention relates to gypsum board and in particular mat faced gypsum board, and methods of making the same.

Background

Wallboard having a gypsum-based core reinforced with a facing material or scrim on a major exterior surface is well known in the art. These gypsum boards are commonly used to form interior or exterior walls, elevator shafts, stairwells, ceilings, and roof shingles, to name a few. In some cases, paper veneer is used with the gypsum-based core. In other cases, fibrous mats are used as facing materials, such as non-woven fiberglass mats. In particular, glass mat faced gypsum board is often used as part of an exterior insulation finishing system (EIFS system) as well as other applications.

The use of such fibrous mats to make gypsum board can be difficult because the aqueous gypsum slurry tends to leak or bleed through the holes in the fibrous mat while the slurry is still in a liquid state. This problem of gel penetration is particularly pronounced when the slurry is deposited onto the fibrous mat prior to entering the board-forming head. Slurry strike-through can result in undesirable gypsum on the outer surface of the fibrous mat and gypsum build-up on rolls or other machine equipment. The accumulation of gypsum on the rolls requires periodic shutdown of the machine for removal because the gypsum on the rolls can migrate to the outer surface of the fiber mat and/or cause problems with marks on the fiber web as it enters the forming head. The gypsum on the outer surface of the pad can reduce the tackiness of the finish coating and present an unpleasant appearance to the consumer.

Various attempts have been made to prevent or minimize bleed through of gypsum slurries. For example, it has been suggested to vary the slurry viscosity by using viscosity control agents to minimize the ability of the slurry to leak through the web. It has also been proposed to provide the outer surface of the mesh with a resin or other coating to block the pores in the fiber mesh to limit gel penetration. Other efforts have focused on altering the characteristics of the fiber web itself. For example, it has been suggested to use a fiber mesh consisting of glass fibers having a specific diameter between 10 and 15 microns with a specific extrusion ratio, the mesh having more than 1.85lb/100ft²A specific basis weight of (a). Other web modifications suggest the use of fibrous mats composed of a blend of staple fibers and microfibers (with an average diameter of 1 micron or less) to block the through-sizing of the slurry. Other proposals include increasing the thickness of the fibrous mat or altering the surface characteristics of the mat fibers to reduce their wettability. See, for example, U.S. patent nos. 4,186,236, 4,388,366, 4,637,951, 4,681,798, 4,810,569 and 6,001,496, and U.S. patent application publication No. 2007/0148430 a1 and european patent application No. EP 1801278 a 1. However, these proposed solutions may require additional processing steps, incorporate other materials, change the slurry characteristics to an undesirable range, and/or specify the use of custom or non-standard fiber mats. In many cases, the techniques suggested above to limit gel permeation are undesirable for various cost, technical, and other reasons.

Accordingly, there is a need in the art to provide gypsum boards and methods of making the same in which the gypsum slurry has minimal or preferably no strikethrough during the manufacture of the gypsum board.

Disclosure of Invention

In one aspect, the present invention provides a method of forming a gypsum board, the method comprising providing a porous substrate having an interior surface; applying a particulate matter to an inner surface of a porous substrate, thereby forming a powder faced substrate; depositing an aqueous gypsum slurry onto at least a portion of the applied particulate matter on the inner surface of the powder-faced substrate, thereby forming a slurry-coated substrate, wherein the particulate matter fills a portion of the pores in the porous substrate to impede penetration of the gypsum slurry therethrough; and allowing the slurry to coat the substrate to form a gypsum board.

In another aspect, the present invention provides a mat-faced gypsum board comprising a gypsum-based core, a fibrous mat having an inner surface facing at least one side of the gypsum-based core, and a hydrated particulate material located on and extending partially into the inner surface of the fibrous mat, wherein the hydrated particulate material is supplied separately from the gypsum-based core.

The present invention relates to a mat-faced gypsum board comprising a gypsum-based core, a fibrous mat having an inner surface facing at least one side of the gypsum-based core, and a hydrated particulate material located on and extending partially into the inner surface of the fibrous mat, wherein the hydrated particulate material has a composition different from the composition of the gypsum-based core.

These and other advantages of the invention, as well as additional inventive features, will be apparent from the description of the invention provided herein.

Drawings

FIG. 1 is a schematic illustration of an exemplary board conversion process that minimizes strikethrough of gypsum slurry;

FIG. 2 is a schematic view of a dry particle application system for use in the board converting process of FIG. 1;

FIG. 3 is a perspective view of a slurry deposition station applying dry particles to a portion of a web;

FIG. 4 is a flow diagram of an exemplary sheet forming process;

FIG. 5 is an SEM photograph of a commercially available fiberglass gasket showing a cross-section of the gasket at 50X magnification prior to application of dry particles to the gasket inner surface;

FIG. 6 is an SEM photograph of a top view showing the inside surface of a commercially available fiberglass gasket at 100 Xmagnification prior to application of dry particles to the inside surface of the gasket;

FIG. 7 is an SEM photograph of the commercially available fiberglass mat of FIG. 5 showing the cross-section at 50X magnification after the dry particles have been applied to the inner surface of the mat;

FIG. 8 is an SEM photograph of a top view showing the inside surface of the commercially available fiberglass gasket of FIG. 6 after application of dry particles to the inside surface of the gasket at 100 Xmagnification; and is

FIG. 9 is a photograph of a mat-faced gypsum board prepared with or without dry particles applied to the inside face of the faced mat.

Detailed Description

The present invention provides mat-faced gypsum board and a method of making the same that minimizes and preferably prevents strikethrough of the grout in the mat. Further, the method includes applying a dry particulate substance, such as a dry powder, to the interior surface of a porous substrate used to form a gypsum board facing mat (e.g., a fibrous mat). As used herein, "interior surface" refers to the surface of the porous substrate on which the gypsum slurry is deposited and which otherwise contacts the gypsum core in the finished gypsum board. Preferably, the dry particulate matter is applied immediately prior to depositing the gypsum slurry onto the substrate or mat. One form of dry particulate matter is a hydratable powder or granules that penetrates into the pores or interstices of the porous substrate and is hydrated by excess water in the gypsum slurry. In other words, the particulate matter comprises a hydratable powder, and the water in the aqueous gypsum slurry substantially hydrates the hydratable powder. The hydrated powder then solidifies in the pores or other interstices of the gasket and impedes the penetration of the liquid slurry through the pores or other interstices by blocking or impeding the possible passage of the slurry through the gasket.

The resulting mat faced gypsum board includes a gypsum-based core having a fibrous mat facing on at least one side thereof. The gypsum-based core may optionally comprise a second fibrous mat, wherein the gypsum-based core is disposed between the first fibrous mat and the second fibrous mat. The second fibrous mat may be the same or different from the first fibrous mat. The fibrous mat comprises a powder deposit of particulate matter on the inner surface of the mat at the interface between the gypsum core and the mat. Preferably, the particulate matter extends partially into the fibrous mat from the inner surface such that the outer surface of the fibrous mat is substantially free of the particulate (e.g., free of particulate on the outer surface visible to the naked eye). Although the powder or particles may include similar components to those found in the gypsum core, the particulate matter is applied to the fibrous mat independently of the gypsum core and is not supplied or transferred from the gypsum core. In other words, the composition of the particulate matter is different from that of the gypsum slurry. That is, a typical construction of mat-faced gypsum board involves mechanical locking of the mat to the gypsum core to some extent by the core material permeating the fibrous mat. In this context, the particulate matter is separate from the core material, for example it is preferred that the particulate matter is pre-applied to the fibrous mat prior to application of the core slurry. It will be appreciated, however, that in some cases the particulate matter may be admixed with the infiltrated core material after the board is formed. If the dry particulate matter comprises a preferably hydratable material, the powder, when hydrated or cured, may additionally assist in securing the fibrous mat to the gypsum core by forming additional mechanical locking with the gypsum core in a manner similar to the way the fibrous mat is locked to the core by penetration into the gypsum core.

As noted above, the dry particulate matter preferably comprises, consists essentially of, or consists of a hydratable powder, such as a hydratable inorganic powder. For example, the dry particulate matter may comprise (consist essentially of, or consist of): gypsum-based particles (e.g., water-soluble calcium sulfate anhydrite, calcium sulfate alpha-hemihydrate, calcium sulfate beta-hemihydrate, natural, synthetic or chemically modified calcium sulfate hemihydrate, calcium sulfate dihydrate ("Gypsum", "set Gypsum" or "hydrated Gypsum"), and mixtures thereof), swellable clay(e.g., montmorillonite (montmorillonite), palygorskite (attapulgite), and the like), calcium carbonate, mixtures thereof, and the like. A particularly preferred form of dry particulate matter includes calcium sulfate hemihydrate (stucco) in powder form, including, consisting essentially of, or consisting of, the excess water in the gypsum slurry being used to hydrate (e.g., partially, substantially, or completely) it to calcium sulfate dihydrate (gypsum). Preferably, the average size of the particulate material is from about 10 to about 50 microns (most preferably from about 10 to about 40 microns, from about 10 to about 25 microns, or from about 10 to about 15 microns), and is from about 10 to about 40lb/1000ft²Is applied to the inside of the fibre mat. For example, it may be about 10lb/1000ft²Or higher, about 15lb/1000ft²Or higher, about 20lb/1000ft²Or higher, or about 25lb/1000ft²Or higher rates to apply the particulate material. Typically, the particulate matter may be about 40lb/1000ft²Or lower, e.g., about 35lb/1000ft²Or less, or even about 30lb/1000ft²Or lower ratio. According to further illustration, the particulate material may be about 10 to about 20lb/1000ft²About 10 to about 30lb/1000ft²About 20 to about 30lb/1000ft²About 20 to about 40lb/1000ft²Or from about 30 to about 40lb/1000ft²Is applied. In another aspect of the embodiment, the particulate material may be about 10lb/1000ft²About 15lb/1000ft²Or about 20lb/1000ft²Is applied. However, other application rates and powder sizes may be used depending on the particular fibrous mat, slurry viscosity, and other factors.

In another aspect, the dry particulate matter may additionally include other fillers or additives to provide other functional reinforcement to the gypsum board. For example, the dry particulate material may include an amount of dry polymer or resin that may provide a moisture barrier on the interior surface of the gasket. The additives may include redispersible polymer or resin powders such as acrylic powders, polyvinyl alcohol, vinyl acetate, polyethylene glycol, polyvinyl chloride, copolymers of the resins (i.e., PVA/PVC copolymers), mixtures thereof, and the like. Further, the dry particulate matter may comprise from about 1% to about 30% by weight of the redispersible polymer or resin. These polymers or resins can be redispersed with water in an aqueous gypsum slurry immediately after application to the mat, typically to form resin deposits or other barriers on the interior surface of the mat and/or extending partially into the mat from the interior surface of the mat. It is contemplated that any resin or polymer will not extend through the gasket to the outer surface of the gasket. It has been found that the resin generally improves the trowelability of EIFS or other direct application finishing system materials to gypsum boards, which allows the end user to apply a more uniform surface finish to the exterior surface of the board. While not wishing to be bound by theory, it is believed that the redispersed resin particles can help the surface finish retain moisture so that it can be spread more evenly over the board without the gypsum core absorbing moisture from the external finish during application.

The fibrous mat may comprise any suitable type of polymer or mineral fibers, or combinations thereof. Non-limiting examples of suitable fibers include glass fibers, polyamide fibers, polyaramid fibers, polypropylene fibers, polyester fibers (e.g., polyethylene terephthalate (PET)), polyvinyl alcohol (PVOH), polyvinyl acetate (PVAc), cellulosic fibers (e.g., cotton, rayon, etc.), and the like, and combinations thereof. The fibrous mat may be woven or non-woven; however, non-woven mats are preferred. The nonwoven mat comprises fibers bonded together by a binder. The adhesive may be any adhesive commonly used in the gasket industry. Suitable binders include, but are not limited to, urea formaldehyde, melamine formaldehyde, stearylated melamine formaldehyde, polyester, acrylic, polyvinyl acetate, urea formaldehyde or melamine formaldehyde modified or blended with polyvinyl acetate or acrylic, styrene acrylic polymers, and the like, and combinations thereof. Suitable fibrous mats include commercially available mats used as facing materials for cementitious articles.

In one embodiment, the porous fibrous mat is from about 5 to about 20 microns, such as from about 10 to about 20 microns, or even from about 11 to about 16 microns in average diameterA glass fiber mat formed of chopped or continuous glass fibers having a basis weight of about 20lb/1000ft²Or larger. The porous fibrous mat may also comprise microfibers having a diameter of, for example, about 2-8 microns or 4-6 microns. The fibrous mat may also contain fibers having different diameters. For example, the fiberglass mat may comprise about 70% to about 90% fiberglass having a diameter of about 10 to about 20 microns, and about 10% to about 30% fiberglass having a smaller diameter of about 2 to about 15 microns, the mat having a basis weight of about 20lb/1000ft²Or larger. In another embodiment, a fibrous mat may comprise about 70% to about 90% glass fibers having a diameter of about 14 microns or more, or 15 microns or more (e.g., about 14 to about 16 microns), and about 10% to about 30% glass microfibers having a diameter of about 4 to about 6 microns, the mat having a basis weight of about 20lb/1000ft²Or larger. The fibers can have any suitable length. For example, the microfibers may have different lengths. Other fibers are typically about 1 inch or less in length (e.g., about 3/8 inches to 1 inch, or about 1/2 inches to about 3/4 inches). To further illustrate, one such fiberglass mat is formed from about 80% fibers having a diameter of about 16 microns (about 1/2 inches in length) and about 20% fibers having a diameter of about 11 microns (about 1/4 inches in length), the mat having a basis weight of about 22lb/1000ft². Another suitable fiberglass mat is formed from about 90 percent fibers having a diameter of about 16 microns (3/4 inches in length) and about 10 percent fibers having a diameter of about 4 to about 6 microns (different lengths), the mat having a basis weight of about 22lb/1000ft²。

The mat is preferably formed using a thermosetting resin that binds the glass fibers into a non-woven web. Further, the thermosetting resin may be an acrylic resin, such as a blend of melamine formaldehyde with other acrylic resins. The gasket can comprise any suitable amount of binder, for example, about 5-40 wt%, about 10-30 wt%, or about 20-30 wt%. The above-described fibrous mats are but one example of suitable mats that may be used herein. It will be appreciated that other porous and fibrous mats having different compositions may also be utilized using the methods described herein.

The dry particulate matter may be deposited or applied onto the web (i.e., the porous substrate or fibrous mat surface) using any known application method that disperses dry or solid particles onto a moving web. Referring to fig. 1-4, an example of an application system (10) is illustrated in which dry particulate material (12) is deposited from an applicator, feeder or hopper (13) onto the inner surface (14) of a fibrous mat (16) in series between a web spreading station (18) and a slurry mixing tank (20) in a gypsum board conversion line. In this manner, dry particulate matter (12) is applied to the web and then the slurry is immediately deposited (22) onto the web (16) and then into the board forming head (24). The dry particulate matter is then effective to minimize and preferably prevent slurry bleed-through between the slurry deposition site (22) and the board forming head (24).

Further, the applicator (13) may include a table, tray, hopper, feeder, or other container (30) that contains the excess particles (12). Suitable feeders, including vibratory and rotary feeders, are commercially available. The applicator (13) is configured to apply the particles (12) to the web via a tray (30) that is inclined at a predetermined angle to allow a quantity of the particles (12) to sift or free-fall onto the inner surface (14) of the web (16) as the web (16) passes beneath the tray (30). For example, as shown in fig. 2, the table (30) is tilted and vibrated or oscillated to allow the particulate matter to fall or fall off the leading edge (32) of the table. The leading edge (32) may include a metering device (34), such as a crowned wheel, to provide a more controlled application of particulate matter. It should be appreciated that other application methods may be employed to disperse the particulate material onto the web, such as extrusion dies, roller applicators, curtain applicators, and the like. The above description is only one example of how dry particles may be applied to a web. Alternatively, the dry particulate matter may be pre-applied to a web that has been formed by a mat manufacturer, so that the web may simply be unrolled and used in an existing forming apparatus. In this case, it is contemplated that excess particles may be applied to the mesh to compensate for any loss of powder during shipping and/or deployment.

With the preferred particulate materials described above, the particles generally do not adhere, or only lightly adhere, to the mesh after application due to the loose deposition onto the inner surface of the mesh. If desired, the particles (12) can be flattened or spread on the inner surface of the fibrous mat using a screed, doctor blade, nip, brush, roller, and the like. Further, the particles are spread using a brush (40) immediately after they are applied to the mesh, and then the slurry is applied at a slurry tank (20).

The particulate material may be applied to only a portion of the fibrous web or may be applied across the entire width of the fibrous web. It has been found that gypsum slurry exhibits the most significant strikethrough when the slurry is deposited onto a web prior to entering the forming head. Thus, the dry particulate matter should be applied to at least a portion (50) of the inner surface (14) of the fibrous mat (16) that contacts the gypsum slurry prior to entering the forming head, as shown in schematic form in fig. 3. In this manner, positioning the dry particulate material may hinder or block slurry penetration through the mesh pores where the particulate matter is most needed. Alternatively, if the dry particulate matter includes other additives to provide other functional properties to the mesh, the dry powder may preferably be applied across the entire or substantially the entire width of the pad (16). Of course, these are merely examples and the dry particulate matter may be applied to any width of the web as desired for a particular application.

Referring to fig. 4, an exemplary method (100) of forming mat-faced gypsum board (102) with minimal, and preferably no, gypsum slurry strike-through is illustrated. The method (100) includes first providing a porous substrate (104), such as a non-woven fiberglass mat. A particulate material (106) is prepared, preferably comprising an inorganic hydratable powder (108) and optionally a redispersible organic resin (110). Particulate matter (106) is then applied (112) to the interior surface of the porous substrate (104). Optionally, the applied particulate matter (106) may be leveled (114) on the inner surface of the substrate to obtain a more uniform application of the particulate matter. An amount of the gypsum slurry is then deposited (116) onto at least a portion of the particulate matter on the inner surface of the porous substrate. The slurry deposited porous substrate is then formed (118) into a gypsum board.

The gypsum core can include any of a variety of additives in addition to gypsum-based materials (e.g., water-soluble calcium sulfate anhydrous, calcium sulfate alpha-hemihydrate, calcium sulfate beta-hemihydrate, natural, synthetic, or chemically modified calcium sulfate hemihydrate, calcium sulfate dihydrate ("gypsum," "set gypsum," or "hydrated gypsum"), and mixtures thereof). The additive may be any additive conventionally used in the manufacture of gypsum or cement board. Such additives include, but are not limited to, structural additives such as mineral wool, continuous or chopped glass fibers (also known as fiberglass), perlite (perlite), clay, vermiculite (vermiculite), calcium carbonate, polyester, and paper fibers; and chemical additives such as hydrophobizing agents, foaming agents, fillers, accelerators, sugars, reinforcing agents (e.g., phosphates, phosphonates, borates, and the like), retarders, binders (e.g., starches and latexes), colorants, fungicides, biocides, and the like. Examples of the use of certain of these and other additives are set forth, for example, in U.S. Pat. nos. 6,342,284, 6,632,550, 6,800,131, 5,643,510, 5,714,001, and 6,774,146, and U.S. patent publication nos. 2004/0231916 a1, 2002/0045074 a1, and 2005/0019618 a 1.

The advantages and embodiments of the mat-faced gypsum board described herein are further illustrated by the following examples; however, the particular materials and amounts thereof recited in these examples, as well as other conditions and details, should not be construed to unduly limit this invention. All percentages are by weight unless otherwise indicated.

The following examples further illustrate the invention but, of course, should not be construed as in any way limiting its scope.

Example 1

This example illustrates the application of particulate matter to the inner surface of a porous substrate to form a powder faced substrate according to the present invention.

At 20lb/1000ft²Ratio (r) dry stucco powder (USG, chicago, illinois) was shaken onto a glass fiber mat (john Manville, denver, colorado) surface. The pad is made from about 80% 16 micron diameter fibers and about 20% 11 micron diameter fibers and has about 22lb/1000ft²Basis weight of (c). SEM analysis using backscattered electron imaging to distinguish stucco from organic binders and glass fibers even though stucco was shaken onto the surface of the shim showed that stucco partially penetrated into the interstices of the shim. Fig. 5 and 6 are SEM images of the gasket before stucco is applied, and fig. 7 and 8 are SEM images of the gasket after stucco is shaken onto the gasket surface. Fig. 5 and 7 show cross-sections of fibrous mats obtained by cutting the mats with razor blades. In the image of fig. 7, stucco is applied to the right side surface (i.e., the interior surface) of the shim. The stucco material is bright particles in the images of fig. 7 and 8 and is shown partially extending into the thickness of the shim and the opposite surface being substantially free of particulate matter (fig. 7 cross-sectional view).

Example 2

This example demonstrates the effectiveness of a particulate material applied to the inner surface of a porous substrate to prevent strikethrough of a gypsum slurry.

A 2 "x 4" column of gypsum slurry was dropped onto a glass mat (john majel) located about 2 "below the column. The amount of gypsum was deposited onto two identical portions of the glass mat and each was cast into a small plate portion. A glass shim was spread with a quantity of stucco powder on the shim surface, then at 20lb/1000ft²The slurry is applied at a ratio of (a). The other glass gasket had no dry stucco powder. Each slab was cast successively from the same batch slurry as quickly as possible to minimize any curing or hydration effects. As shown in fig. 9, the glass gasket with the stucco spread thereon (right side sample) exhibited no gypsum strikethrough, while the mortarless glass gasket (left side sample) exhibited gypsum strikethrough.

Example 3

This example illustrates the preparation of mat-faced gypsum board according to the present invention.

At 20lb/1000ft²Ratio (v) dry particulate matter comprising 80% stucco (USG) and 20% redispersible powders polymer (vinyl acetate copolymer, HD1501, Elotex AG, switzerland) was applied to the glass mat to form a particulate filled glass mat. The glass shim comprised about 80% fibers having a diameter of 16 microns and 20% fibers having a diameter of 11 microns, the shim having a basis weight of about 22lb/1000ft². The gypsum slurry is deposited onto a particulate-filled mat and formed into a finished gypsum board. The board does not exhibit gypsum strike-through and has an enhanced ability to accept surface finishes.

Example 4

This example illustrates the preparation of mat-faced gypsum board according to the present invention.

At 20lb/1000ft²A dry particulate material comprising 100% stucco (USG) was applied to the glass mat to form a particulate-filled glass mat. The glass shim comprised about 80% fibers having a diameter of 16 microns and 20% fibers having a diameter of 11 microns, the shim having a basis weight of about 22lb/1000ft². The gypsum slurry is deposited onto a particulate-filled mat and formed into finished gypsum board on a standard gypsum board manufacturing line. For comparison purposes, gypsum board was made using the same gypsum slurry and glass mat on the same manufacturing line, but without applying stucco powder to the mat. The outer surface of the shim of each of the two types of plates was inspected. After making gypsum boards comprising glass mats to which particulate matter was applied, the exterior surfaces were clean and there was no significant gypsum slurry build-up, indicating that particulate-filled glass boards inhibited slurry strike-through. In contrast, after making a panel without particles applied to the glass shim, the outer surface showed slurry strike-through.

It will be understood that various changes in the details, materials, and arrangements of parts and components which have been herein described and illustrated in order to explain the nature of the non-woven material and its method of manufacture may be made by those skilled in the art within the principle and scope of the appended claims.

All references, including publications, patent applications, and patents, cited herein are hereby incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein.

The terms "a" and "an" and "the" and similar referents used in the context of describing the invention (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms "comprising," "having," and "including" are to be construed as open-ended terms (i.e., meaning "including, but not limited to,") unless otherwise noted. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., "such as") provided herein, is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention.

Preferred embodiments of this invention are set forth herein, including the best mode known to the inventors for carrying out the invention. Variations of those preferred embodiments may become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventors expect skilled artisans to employ such variations as appropriate, and the inventors intend for the invention to be practiced otherwise than as specifically described herein. Accordingly, this invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the invention unless otherwise indicated herein or otherwise clearly contradicted by context.

Claims (24)

1. A method of forming a gypsum board, the method comprising:

(a) providing a porous substrate having an inner surface;

(b) applying a particulate matter onto the inner surface of the porous substrate, thereby forming a powder faced substrate;

(c) depositing an aqueous gypsum slurry onto at least a portion of the applied particulate matter on the inner surface of the powder-faced substrate, thereby forming a slurry-coated substrate, wherein the particulate matter fills a portion of the pores in the porous substrate to impede penetration of the gypsum slurry therethrough; and

(d) coating a substrate with the slurry to form the gypsum board.

2. The method of claim 1, wherein the particulate matter comprises a hydratable powder and water from the aqueous gypsum slurry hydrates the hydratable powder.

3. The method of claim 2, wherein the hydratable powder comprises gypsum-based particles.

4. A process according to claim 2 or 3 wherein the hydratable powder comprises a filler selected from calcium carbonate, clay and mixtures thereof.

5. A method as claimed in claim 2 or 3, wherein the hydratable powder comprises calcium sulphate hemihydrate.

6. The method of any one of claims 1-5, wherein the particulate matter comprises redispersible organic particles selected from the group consisting of: acrylics, polyvinyl alcohols, polyethylene glycols, polyvinyl chlorides, vinyl acetates, copolymers thereof, and mixtures thereof.

7. The method of claim 6, wherein the particulate matter comprises from about 1% to about 30% by weight of the redispersible organic particles.

8. The method of claim 1, wherein applying particulate matter further comprises applying about 10lb/1000ft²To about 40lb/1000ft²Is applied to the inner surface of the porous substrate.

9. The method of any one of claims 1-8, wherein the porous substrate is a non-woven fiberglass mat.

10. The method of claim 9, wherein the non-woven fiberglass mat comprises from about 70% to about 90% fiberglass having a diameter of from about 10 microns to about 20 microns and from about 10% to about 30% fiberglass having a minor diameter of from about 5 microns to about 15 microns, the mat having a basis weight of about 20lb/1000ft²Or larger.

11. The method of claim 9, wherein the non-woven fiberglass mat comprises about 80 percent fiberglass having a diameter of about 16 microns and about 20 percent fiberglass having a diameter of about 11 microns, the mat having a basis weight of about 20lb/1000ft²Or larger.

12. The method of any one of claims 1-11, further comprising spreading the applied particulate matter on the inner surface of the porous substrate prior to depositing the aqueous gypsum slurry thereon.

13. The method of any one of claims 1-12, wherein the particulate matter partially extends from the inner surface of the porous substrate into the porous substrate such that an outer surface of the porous substrate opposite the inner surface is substantially free of the particulate matter.

14. A mat-faced gypsum board comprising:

(a) a gypsum-based core material;

(b) a fibrous mat having an inner surface facing at least one side of the gypsum-based core; and

(c) a hydrated particulate material located on the inner surface of the fibrous mat and extending partially into the fibrous mat from the inner surface of the fibrous mat;

wherein the hydrated particulate material is supplied separately from the gypsum-based core material.

15. A mat-faced gypsum board comprising:

(a) a gypsum-based core material;

(b) a fibrous mat having an inner surface facing at least one side of the gypsum-based core; and

(c) a hydrated particulate material located on the inner surface of the fibrous mat and extending partially into the fibrous mat from the inner surface of the fibrous mat;

wherein the composition of the hydrated particulate material is different from the composition of the gypsum-based core material.

16. The mat-faced gypsum board of claim 14 or 15, wherein the hydrated particulate material comprises gypsum-based particulates.

17. The method of claim 14 or 15, wherein the hydrated particulate comprises a filler selected from the group consisting of calcium carbonate, clay, and mixtures thereof.

18. The mat-faced gypsum board of claim 14 or 15, wherein the hydrated particulate material comprises calcium sulfate hemihydrate.

19. The mat-faced gypsum board of any one of claims 14-18, wherein the hydrated particulate material comprises redispersible organic particles selected from the group consisting of: acrylics, polyvinyl alcohols, polyethylene glycols, polyvinyl chlorides, vinyl acetates, copolymers thereof, and mixtures thereof.

20. The mat-faced gypsum board of claim 19, wherein the hydrated particulate material comprises from about 1% to about 30% by weight of the redispersible organic particulate.

21. The mat-faced gypsum board of any one of claims 14-20, wherein the mat-faced gypsum board comprises about 10lb/1000ft²To about 40lb/1000ft²The hydrated particulate material of (a).

22. The mat-faced gypsum board of any one of claims 14-21, wherein the fibrous mat comprises from about 70% to about 90% glass fibers having a diameter of about 15 microns or greater and from about 10% to about 30% glass fibers having a diameter of about 4 microns to 6 microns, the mat having a basis weight of about 20lb/1000ft²Or larger.

23. The mat-faced gypsum board of any one of claims 14-21, wherein the fibrous mat additionally comprises a non-woven fiberglass mat comprising about 80% glass fibers having a diameter of about 16 microns and about 20% glass fibers having a diameter of about 11 microns, the non-woven fiberglass mat having a basis weight of about 22lb/1000ft²Or larger.

24. The mat-faced gypsum board of any one of claims 14-23, wherein the outer surface of the fibrous mat opposite the inner surface thereof is substantially free of the hydrated particulate matter.