Gypsum wallboard slurry and method for making the same

Patent metadata

Field	Value
Publication number	US-11274067-B2
Application number	US-202016850467-A
Country	US
Kind code	B2
Filing date	Apr 16, 2020
Priority date	Feb 23, 2011
Publication date	Mar 15, 2022
Grant date	Mar 15, 2022

Abstract

A slurry for manufacturing gypsum board is disclosed. The slurry comprises calcined gypsum, water, a foaming agent, and a thickening agent. The thickening agent of the present disclosure acts to improve the cohesiveness of the slurry without adversely affecting the setting time of the slurry, the paper-to-core bond (wet and dry), or the head of the slurry by acting as a defoaming agent or coalescing agent. Examples of suitable thickening agents include cellulose ether and co-polymers containing varying degrees of polyacrylamide and acrylic acid. A gypsum board and method of forming the slurry and the gypsum board are also disclosed. The gypsum board comprises a gypsum layer formed from the slurry.

First claim

What is claimed is:

1. A gypsum board comprising:
a gypsum layer formed from a gypsum slurry having a composition comprising
calcined gypsum;
water;
an aqueous foam; and
a first thickening agent comprising a polyacrylamide;
wherein the calcined gypsum is present in the gypsum slurry in an amount of from 1785 to 2040 lbs/msf and wherein the gypsum board has a thickness of ⅝″.

2. The gypsum board of claim 1 , wherein the first thickening agent comprises a copolymer of polyacrylamide.

3. The gypsum board of claim 2 , wherein the copolymer includes up to about 40% of acrylic acid.

4. The gypsum board of claim 2 , wherein the copolymer is present in the gypsum slurry in an amount of from −0.005 to 0.05 lbs/msf.

5. The gypsum board of claim 1 , wherein the polyacrylamide is a homopolymer.

6. The gypsum board of claim 1 , wherein the polyacrylamide has a molecular weight of from about 100,000 Daltons to about 1,000,000 Daltons.

7. The gypsum board of claim 1 , further comprising a second thickening agent.

8. The gypsum board of claim 7 , wherein the second thickening agent comprises a pre-gelled starch or day.

9. The gypsum board of claim 1 , wherein the aqueous foam comprises an alkylsulfate compound, water, and air.

10. The gypsum board of claim 1 , further comprising a coalescing agent.

11. The gypsum board of claim 10 , wherein the coalescing agent comprises an EO/PO reverse block copolymer.

12. The gypsum board of claim 10 , wherein the coalescing agent has a cloud point between an initial temperature of the gypsum slurry and a peak temperature of the gypsum slurry during hydration of the calcined gypsum.

13. The gypsum board of claim 12 , wherein the initial temperature is from about 18.0 to about 37.0° C. and the peak temperature is from about 37.0 to about 70.0° C. during hydration of the calcined gypsum.

14. The gypsum board of claim 10 , wherein the coalescing agent is present in an amount of from about 0.02 to about 1.0 lbs per 1000 square feet of the gypsum board.

15. The gypsum board of claim 10 , wherein the aqueous foam comprises a foaming agent and wherein the foaming agent and the coalescing agent are present in a weight ratio of from about 10:0.05 to about 5:1.5.

16. The gypsum board of claim 10 , wherein the aqueous foam comprises a foaming agent and wherein the foaming agent and the coalescing agent are present in a weight ratio of from about 7.5:1 to about 5:1.

17. A method of forming the gypsum board of claim 1 , the method comprising:
combining the calcined gypsum and the water to form a slurry,
initiating thickening of the gypsum slurry upon introduction of the first thickening agent comprising a polyacrylamide to the slurry,
imparting a plurality of bubbles in the slurry by adding foam generated from the aqueous foam wherein the aqueous foam comprises a foaming agent;
forming dihydrous calcium sulfate in a hydration reaction of the calcined gypsum to form a set gypsum board.

18. The gypsum board of claim 1 , wherein the aqueous foam comprises a foaming agent including a stable foaming agent and an unstable foaming agent.

Assignees

• Nat Gypsum Properties Llc
• Gold Bond Building Products Llc

Inventors

• Stav Eli
• Sethuraman Gopalakrisnan
• Miatudila Ma-Ikay
• Fey Karen
• Bailey Joseph J

Classifications

• Y02W30/91

  Use of waste materials as fillers for mortars or concrete · CPC title

• C04B2111/0062

  Gypsum-paper board like materials · CPC title

• C04B38/10 Primary

  by using foaming agents (C04B38/02 takes precedence){or by using mechanical means, e.g. adding preformed foam} · CPC title

• C04B28/14

  containing calcium sulfate cements {(gypsum-paper plates E04C)} · CPC title

• C04B2103/12

  Set accelerators · CPC title