Light Weight Gypsum Board

Patent metadata

Field	Value
Publication number	US-2018002233-A1
Application number	US-201715704365-A
Country	US
Kind code	A1
Filing date	Sep 14, 2017
Priority date	Jun 9, 2005
Publication date	Jan 4, 2018
Grant date	—

Abstract

This invention provides low dust low density gypsum wallboard products having high total core void volumes, corresponding to low densities in the range of about 10 to 30 pcf. The wallboards have a set gypsum core formed between two substantially parallel cover sheets, the set gypsum core preferably having a total void volume from about 80% to about 92%, and made from a slurry including stucco, pregelatinized starch, and a naphthalenesulfonate dispersant. The combination of the pregelatinized starch and the naphthalenesulfonate dispersant also provides a glue-like effect in binding the set gypsum crystals together. The wallboard formulation, along with small air bubble voids (and water voids) provides dust control during cutting, sawing, routing, snapping, nailing or screwing down, or drilling of the gypsum-containing products. This invention also provides a method of making the low dust low density gypsum products including the introduction of soap foam in an amount sufficient to form a total void volume, including air voids, preferably from about 80% to about 92% in the set gypsum core, corresponding to a set gypsum core density from about 10 pcf to about 30 pcf. The wallboards produced by the method generate significantly less dust during working.

First claim

1 .- 55 . (canceled)

56 . A light weight gypsum board comprising:
a set gypsum core disposed between two cover sheets; the set gypsum core formed from a slurry comprising water, foam, and stucco; the set gypsum core comprising a gypsum crystal matrix having a pore size distribution comprising (i) water voids having a pore size less than about 5 microns in diameter, (ii) air voids having a pore size of at least about 5 microns and less than about 50 microns in diameter, (iii) air voids having a pore size from about 50 microns to about 100 microns in diameter, and (iv) air voids having a pore size greater than about 100 microns in diameter, the air voids having a pore size greater than about 100 microns in diameter comprising at least about 20% of the total void volume of the set gypsum core, wherein the voids are measured using three-dimensional imaging acquired by X-ray CT-scanning analysis (XMT); the majority of air voids have a diameter of about 100 microns or less; the gypsum crystal matrix is formed such that the set gypsum core has an average core hardness of at least about 11 pounds as determined in accordance with ASTM C-473; and the board having a density of about 35 pcf or less.

57 . The light weight gypsum board of claim 56 , wherein at least about 50% of the total void volume comprises air voids having a pore size greater than about 50 microns in diameter.

58 . The light weight gypsum board of claim 56 , wherein the set gypsum core density is from about 24 pcf to about 35 pcf.

59 . The light weight gypsum board of claim 56 , wherein the set gypsum core density is from about 24 pcf to about 31 pcf.

60 . The light weight gypsum board of claim 58 , wherein the slurry forming the set gypsum core further comprises (i) starch in an amount from about 0.5% to about 10% by weight based on the weight of the stucco, the starch effective to increase the core hardness of the gypsum board relative to the core hardness of the gypsum board without the starch, or (ii) a trimetaphosphate compound chosen from the group consisting of sodium trimetaphosphate, potassium trimetaphosphate, lithium trimetaphosphate, and ammonium trimetaphosphate, the trimetaphosphate compound being present in an amount from about 0.12% to about 0.4% by weight based on the weight of the stucco, or (iii) naphthalenesulfonate dispersant in an amount from about 0.1% to about 3.0% by weight based on the weight of the stucco, or any combination of (i)-(iii).

61 . The light weight gypsum board of claim 60 , wherein the starch is a pregelatinized starch.

62 . The light weight gypsum board of claim 56 , wherein the board, when at a thickness of ½ inch, has (i) a dry weight from about 1000 lb/MSF to about 1400 lb/MSF, or (ii) a nail pull resistance to core hardness ratio from about 4 to about 8, each as determined according to ASTM C473, or (iii) a nail pull resistance of at least about 65 lb, as determined according to ASTM C473, or (iv) an average flexural strength of at least about 36 lb in a machine direction and/or about 107 lb in a cross-machine direction, as determined according to ASTM C473, or any combination of (i)-(iv).

63 . A light weight gypsum board comprising:
a set gypsum core disposed between two cover sheets; the set gypsum core formed from a slurry comprising water, foam, and stucco; the set gypsum core having a total void volume from about 75% to about 95% of the core volume, at least about 60% of the total void volume comprising air voids having an average air void pore size greater than about 10 microns in diameter, wherein the voids are measured using three-dimensional imaging acquired by X-ray CT-scanning analysis (XMT) imaging; the majority of air voids having a diameter of about 100 microns or less; the set gypsum core having an average core hardness of at least about 11 pounds (about 49 N) as determined in accordance with ASTM C-473; and the board having a density from about 24 pcf to about 35 pcf.

64 . The light weight gypsum board of claim 63 , wherein the set gypsum core density is from about 24 pcf to about 31 pcf.

65 . The light weight gypsum board of claim 63 , wherein at least about 20% of the total void volume comprises air voids having a pore size greater than about 100 microns in diameter.

66 . The light weight gypsum board of claim 63 , wherein at least about 50% of the total void volume comprises air voids having a pore size greater than about 50 microns in diameter.

67 . The light weight gypsum board of claim 63 , the air voids having an average pore size greater than about 20 microns in diameter.

68 . The light weight gypsum board of claim 63 , wherein the set gypsum core has a total void volume from about 80% to about 92% of the core volume.

69 . The light weight gypsum board of claim 63 , wherein the slurry forming the set gypsum core further comprises (i) starch in an amount from about 0.5% to about 10% by weight based on the weight of the stucco, the starch effective to increase the core hardness of the gypsum board relative to the core hardness of the gypsum board without the starch, or (ii) a trimetaphosphate compound chosen from the group consisting of sodium trimetaphosphate, potassium trimetaphosphate, lithium trimetaphosphate, and ammonium trimetaphosphate, the trimetaphosphate compound being present in an amount from about 0.12% to about 0.4% by weight based on the weight of the stucco, or (iii) naphthalenesulfonate dispersant in an amount from about 0.1% to about 3.0% by weight based on the weight of the stucco, or any combination of (i)-(iii).

70 . The light weight gypsum board of claim 69 , wherein the starch is a pregelatinized starch.

71 . The light weight gypsum board of claim 63 , wherein the board, when at a thickness of ½ inch, has (i) a dry weight from about 1000 lb/MSF to about 1400 lb/MSF, or (ii) a nail pull resistance to core hardness ratio from about 4 to about 8, each as determined according to ASTM C473, or (iii) a nail pull resistance of at least about 65 lb, as determined according to ASTM C473, or (iv) an average flexural strength of at least about 36 lb in a machine direction and/or about 107 lb in a cross-machine direction, as determined according to ASTM C473, or any combination of (i)-(iv).

72 . A light weight gypsum board comprising a set gypsum core disposed between two cover sheets, wherein (a) the set gypsum core comprises air voids and water voids, the air voids with a pore size of about 5 microns or greater and water voids with a pore size less than about 5 microns, in a volume ratio of air voids to water voids from about 1.8 to 1 to about 9 to 1, (b) the set gypsum core comprises air voids having a pore size greater than about 100 microns in diameter such that the air voids having a pore size greater than about 100 microns in diameter comprise at least about 20% of the total void volume of the set gypsum core, the majority of air voids having a diameter of about 100 microns or less, wherein the voids are measured using three-dimensional imaging acquired by X-ray CT-scanning analysis (XMT), and (c) the board has a density from about 24 pcf to about 35 pcf, and a ratio of density (pcf) to core hardness (lb) of less than about 3.2.

73 . The light weight gypsum board of claim 72 , wherein the set gypsum core density is from about 24 pcf to about 31 pcf.

74 . The light weight gypsum board of claim 72 , wherein the volume ratio of air voids to water voids is from about 2.3 to 1 to about 9 to 1.

75 . The light weight gypsum board of claim 7

Assignees

• United States Gypsum Co

Inventors

• Yu Qiang
• Song Weixin David

Classifications

• B32B2250/40

  Symmetrical or sandwich layers, e.g. ABA, ABCBA, ABCCBA · CPC title

• B32B13/14

  next to a fibrous or filamentary layer · CPC title

• C04B24/08

  Fats; Fatty oils; Ester type waxes; Higher fatty acids, i.e. having at least seven carbon atoms in an unbroken chain bound to a carboxyl group; Oxidised oils or fats · CPC title

• B32B13/02

  with fibres or particles {being present as additives in the layer} · CPC title

• C04B38/0054

  the pores being microsized or nanosized · CPC title