Search

CA-3042023-C - FIRE RESISTANT GYPSUM BOARD COMPRISING EXPANDABLE GRAPHITE AND RELATED METHODS AND SLURRIES

CA3042023CCA 3042023 CCA3042023 CCA 3042023CCA-3042023-C

Abstract

Disclosed are a gypsum board, and related slurries and methods. The gypsum board comprises a gypsum layer disposed between two cover sheets. The gypsum layer comprises a crystalline matrix of set gypsum and expandable graphite. The expandable graphite exhibits volume expansion at high temperatures. Optionally, unexpanded vermiculite can also be included in the gypsum layer to provide an expansion component at even higher temperatures. Because of synergy between the expandable graphite and unexpanded vermiculite in accordance with some embodiments, less vermiculite can be included in the board than in conventional board that contained vermiculite. The board desirably can pass one or more fire-related tests, and is a fire-rated board in some embodiments.

Inventors

  • Qinghua Li
  • Naveen PUNATI
  • Mark Antosh
  • Weixin D. Song

Assignees

  • UNITED STATES GYPSUM COMPANY

Dates

Publication Date
20260505
Application Date
20171027
Priority Date
20161101

Claims (12)

  1. CLAIM(S): 50 1. A gypsum board comprising a gypsum layer disposed between two cover sheets, the gypsum layer comprising a crystalline matrix of set gypsum, unexpanded vermiculite, and expandable graphite, wherein the weight ratio of expandable graphite to unexpanded vermiculite is from about 10:90 to about 70:30, and wherein the gypsum board has a High Temperature Shrinkage (S) of about 10% or less in the z direction when heated to about 1560 °F (850 °C), according to ASTM C1795-15, and wherein the expandable graphite has a particle size of from 40 mesh to 100 mesh.
  2. 2. The gypsum board of claim 1, wherein the gypsum layer is further formed from an unexpanded vermiculite in an amount of from about 1% to about 15% by weight of the set gypsum.
  3. 3. The gypsum board of any one of claims 1 or 2, wherein the expandable graphite is present in an amount of from about 0.1 % to about 10% by weight of the set gypsum.
  4. 4. The gypsum board of any one of claims 1-3, wherein the expandable graphite has an expansion onset temperature of from about 250 °F (120 °C) to about 750 °F (400 °C).
  5. 5. A slurry comprising water, stucco, unexpanded vermiculite, and expandable graphite, wherein the weight ratio of expandable graphite to unexpanded vermiculite is from about 10:90 to about 70:30, and wherein, when the slurry is cast and dried as board, the board has a High Temperature Shrinkage (S) in the x-y directions of about 5% or less when heated to about 1560 °F (850 °C) according to ASTM C1795-15, and wherein the expandable graphite has a particle size of from 40 mesh to 100 mesh.
  6. 6. The slurry of claim 5, wherein the slurry further comprises an unexpanded vermiculite in an amount of from about 0% to about 20% by weight of the stucco, and the expandable graphite is present in an amount of from about 0.1% to about 10% by weight of the stucco.
  7. 7. 51 The slurry of claims 5 or 6, wherein the expandable graphite has a density of from about 20 pcf to about 120 pcf.
  8. 8. (a) A method of making gypsum board comprising: mixing at least water, stucco, unexpanded vermiculite, and expandable graphite to form a slurry, wherein the weight ratio of expandable graphite to unexpanded vermiculite is from about 10:90 to about 70:30; (b) disposing the slurry between a first cover sheet and a second cover sheet to form a board precursor; (c) (d) cutting the board precursor into a board; and drying the board; wherein the gypsum board has a High Temperature Shrinkage (S) according to ASTM C1795-15 of about 10% or less in the z direction, when heated to about 1560 °F (850 °C), and wherein the expandable graphite has a particle size of from 40 mesh to 100 mesh.
  9. 9. The method of claim 8, wherein: the slurry further optionally includes unexpanded vermiculite in an amount of from about 0% to about 20% by weight of the stucco; the expandable graphite is present in an amount of from about 0.1% to about 10% by weight of the stucco; and the expandable graphite has an expansion onset temperature of from about 250 °F (120 °C) to about 750 °F (400 °C).
  10. 10. The gypsum board of claim 1, wherein the weight ratio of expandable graphite to unexpanded vermiculite is from about 20:80 to about 40:60.
  11. 11. The slurry of claim 5, wherein the weight ratio of expandable graphite to unexpanded vermiculite is from about 20:80 to about 40:60.
  12. 12. The method of claim 8, wherein the weight ratio of expandable graphite to unexpanded vermiculite is from about 20:80 to about 40:60.

Description

WO 2018/085130 PCT/0S2017/058643 I FIRE RESISTANT GYPSUM BOARD COMPRISING EXPANDABLE GRAPHITE AND RELATED METHODS AND SLURRIES BACKGROUND [0001] Set gypsum (i.e., calcium sulfate dihydrate) is a well-known material that is used in many products, including panels and other products for building construction and remodeling. One such panel ( often referred to as gypsum board) is in the form of a set gypsum layer sandwiched between two cover sheets (e.g., paper-faced board) and is commonly used in drywall construction of interior walls and ceilings of buildings. One or IO more dense layers, often referred to as "skim coats" may be included on either side of the core, usually at the paper-core interface. [0002] During manufacture of the board, stucco (i.e., calcined gypsum in the form of calcium sulfate hemihydrate and/or calcium sulfate anhydrite), water, and other ingredients as appropriate are mixed, typically in a pin mixer as the term is used in the art. A slurry is 15 formed and discharged from the mixer onto a moving conveyor carrying a cover sheet with one of the skim coats (if present) already applied ( often upstream of the mixer). The slurry is spread over the paper (with skim coat optionally included on the paper). Another cover sheet, with or without skim coat, is applied onto the slurry to form the sandwich structure of desired thickness with the aid of, e.g., a forming plate or the like. The mixture is cast and 20 allowed to harden to form set (i.e., rehydrated) gypsum by reaction of the calcined gypsum with water to form a matrix of crystalline hydrated gypsum (i.e., calcium sulfate dihydrate ). It is the desired hydration of the calcined gypsum that enables the formation of the interlocking matrix of set gypsum crystals, thereby imparting strength to the gypsum structure in the product. Heat is required (e.g., in a kiln) to drive off the remaining free 25 (i.e., unreacted) water to yield a dry product. [0003] One benefit of using gypsum in wallboard is that gypsum has a natural fire resistance property. Should the finished gypsum board be exposed to relatively high temperatures, such as those produced by high temperature flames or gases, portions of the set gypsum layer may absorb sufficient heat to start the release of water from the gypsum 30 dihydrate crystals of the core. The absorption of heat and release of water from the gypsum dihydrate may be sufficient to retard heat transmission through or within the panels for a time. Gypsum board may experience shrinkage of the panel dimensions in one or more WO 2018/085130 PCT/0S2017/058643 2 directions as one result of some or all of these high temperature heating effects, and such shrinkage may cause failures in the structural integrity of the board. [0004] Some gypsum board products are designed to have enhanced fire resistance as compared with the property of the set gypsum alone. For example, Type X board refers to 5 a type of fire rated board gypsum board, such as SHEETROCK® Brand FIRE CODE® Type X board. One example of an additive that enhances the fire resistance of gypsum board is high expansion vermiculite, which can be included in the gypsum slurry for forming the gypsum board, as described in, e.g., U.S. Patent 8,323,785. One drawback is that such vermiculite can be in short supply. Thus, there is a need for alternative fire IO resistance additives. [0005] It will be appreciated that this background description has been created by the inventors to aid the reader, and is not to be taken as a reference to prior art nor as an indication that any of the indicated problems were themselves appreciated in the art. While the described principles can, in some regards and embodiments, alleviate the problems 15 inherent in other systems, it will be appreciated that the scope of the protected innovation is defined by the attached claims, and not by the ability of any embodiments of the disclosure to solve any specific problem noted herein. BRIEF SUMMARY [0006] In one aspect, the disclosure provides a gypsum board comprising a gypsum 20 layer disposed between two cover sheets, the gypsum layer comprising a crystalline matrix of set gypsum and expandable graphite. In some embodiments, the expandable graphite exhibits a volume expansion of at least about two times of its original volume after being heated for one hour at about l l 10°F (600°C). In various embodiments, the gypsum layer exhibits one or more of the following properties: (a) a Thermal Insulation Index (TI) of 25 about 20 minutes or greater according to ASTM Cl 795-15; (b) a High Temperature Shrinkage (S) of about 5% or less (e.g., about 4% or less, about 3% or less, about 2% or less, etc.) in the x-y directions (width-length) according to ASTM Cl 795-15, when heated to about 1560 °F (850 °C); (c) a High Temperature Shrinkage (S) in the z-direction (thickness) of about I 0% or less ( e.g., about 8% or less, about 5% or less, about 3% or less, 30 etc.) according to ASTM Cl 795-15, when heat