High salt gypsum wallboard containing salt absorbents and methods of making same

1. A gypsum board comprising:

a core comprising a central core layer and a first densified layer, the core having opposed first and second faces, the core comprising set gypsum, the set gypsum comprising calcium sulfate dihydrate;

a first cover sheet having an outer surface and an inner surface, the first cover sheet inner surface facing the first face of the core, wherein the first cover sheet comprises a first paper cover sheet or a first fiber glass mat;

a second cover sheet having an outer surface and an inner surface, the second cover sheet inner surface facing the second face of the core, wherein the second cover sheet comprises a second paper cover sheet or a second fiber glass mat;

wherein the core is between the first cover sheet and the second cover sheet;

the first densified layer comprising the set gypsum and salt absorbent particles, said salt absorbent particles comprising salt absorbent material, wherein the salt absorbent material comprises zeolite, or hydrotalcite, or a blend of zeolite and hydrotalcite, wherein the first densified layer is between the central core layer and the second cover sheet, wherein opposing sides of the first densified layer respectively contact the central core layer and the second cover sheet;

wherein the central core layer comprises:

at least 60 wt. % of said calcium sulfate dihydrate, and

150 to 4000 parts by weight chloride per 1,000,000 parts by weight of said calcium sulfate dihydrate;

wherein the first densified layer comprises:

at least 60 wt. % of said calcium sulfate dihydrate,

150 to 4000 parts by weight chloride per 1,000,000 parts by weight of said calcium sulfate dihydrate, and

the salt absorbent material in an amount of 0.5 to 10 parts by weight per 100 parts by weight of the set gypsum of the first densified layer;

wherein parts by weight of salt absorbent material per 100 parts by weight of the set gypsum in the central core layer is relatively less than parts by weight of salt absorbent material per 100 parts by weight of the set gypsum in the first densified layer;

wherein the core has a density of about 15 to 55 pounds per cubic foot,

wherein the first densified layer has a density at least 1.1 times a density of the central core layer,

wherein the first densified layer is thinner than the central core layer, and

wherein thickness of the first densified layer is 5% to 25% of the thickness of the gypsum board;

wherein the central core layer has less than 0.01 wt. % zeolite and less than 0.01 wt. % hydrotalcite.

2. The gypsum board of claim 1 ,

the core further comprising a second densified layer comprising set gypsum, wherein the second densified layer is between the central core layer and the first cover sheet, wherein opposing sides of the second densified layer respectively contact the central core layer and the first cover sheet;

wherein the second densified layer comprises:

at least 60 wt. % of said calcium sulfate dihydrate on a dry (water free) basis,

150 to 4000 parts by weight chloride per 1,000,000 parts by weight of said calcium sulfate dihydrate, and

wherein the second densified layer has a density at least 1.1 times density of the central core layer,

wherein the second densified layer is thinner than the central core layer, and

wherein thickness of the second densified layer is 5% to 25% of the thickness of the gypsum board.

3. The gypsum board of claim 2 ,

wherein the second densified layer further comprises salt absorbent particles, said salt absorbent particles comprising zeolite and/or hydrotalcite;

wherein the aqueous second densified layer slurry further comprises:

the zeolite and/or hydrotalcite in an amount of 0.5 to 10 parts by weight per 100 parts by weight of the set gypsum of the second densified layer.

4. The gypsum board of claim 1 , wherein the salt absorbent particles have a D50 median particle size in a range from 0.1 to 100 micrometers.

5. The gypsum board of claim 1 , wherein each absorbent particle is at least 80 wt. % zeolite or hydrotalcite.

6. The gypsum board of claim 1 , wherein the central core layer further comprises 0-0.1 wt. % sodium trimetaphosphate and wherein the first densified layer further comprises 0-0.1 wt. % sodium trimetaphosphate.

7. The gypsum board of claim 1 , wherein the gypsum board core layer has a ratio of mass of pounds per area less than 440 lbs/msf per ⅛ inch of board thickness.

8. The gypsum board of claim 1 , wherein the first densified layer comprises the zeolite.

9. The gypsum board of claim 1 , wherein the first densified layer comprises the hydrotalcite.

10. The gypsum board of claim 1 , wherein the first densified layer comprises zeolite chosen from zeolites type X, zeolites type A, zeolite type Y, FAU zeolites, CHA zeolites, offretite, erionite, mordenite, gmelinite, mazzite, HEU zeolites, ZSM-3, EMT, EMC-2, ZSM-18, ZK5, ZSM-5, ZSM-11, Zeolite Beta, Zeolite type L, and mixtures of two or more of these zeolites.

11. The gypsum board of claim 1 , wherein the first densified layer comprises Zeolite Beta, Zeolite 13X or Zeolite 5A.

12. The gypsum board of claim 1 , wherein the first and/or second cover sheets comprise paper sheet.

13. The gypsum board of claim 1 , wherein the first and/or second cover sheets comprise fiberglass mat.

14. The gypsum board of claim 1 , wherein the set gypsum is formed from calcined synthetic gypsum comprising the one or more chloride salts and the chloride salts provide at least a portion of the chloride anions.

15. A wall system comprising framing to which is attached at least one gypsum board of claim 1 , wherein the outer surface of the first cover sheet faces away from the framing.

16. The gypsum board of claim 1 , wherein the central core layer has no zeolite and no hydrotalcite.

17. A gypsum board comprising:

a core comprising a central core layer and a first densified layer, the core having opposed first and second faces, the core comprising set gypsum, the set gypsum comprising calcium sulfate dihydrate;

a first cover sheet having an outer surface and an inner surface, the first cover sheet inner surface facing the first face of the core, wherein the first cover sheet comprises a first paper cover sheet or a first fiber glass mat;

a second cover sheet having an outer surface and an inner surface, the second cover sheet inner surface facing the second face of the core, wherein the second cover sheet comprises a second paper cover sheet or a second fiber glass mat;

wherein the core is between the first cover sheet and the second cover sheet;

the first densified layer comprising the set gypsum and salt absorbent particles, said salt absorbent particles comprising salt absorbent material, wherein said salt absorbent material comprises zeolite, or hydrotalcite, or a blend of zeolite and hydrotalcite, wherein the first densified layer is between the central core layer and the second cover sheet, wherein opposing sides of the first densified layer respectively contact the central core layer and the second cover sheet;

wherein the central core layer results from setting of an aqueous central core layer slurry comprising a mixture of stucco and water between the first cover sheet and the second cover sheet, wherein the stucco comprises calcium sulfate hemihydrate and one or more chloride salts;

wherein the aqueous central core layer slurry is made from:

at least 60 wt. % of said calcium sulfate hemihydrate on a dry (water free) basis,

150 to 4000 parts by weight chloride anion per 1,000,000 parts by weight of said calcium sulfate hemihydrate, and

the water at a weight ratio of the water to the calcium sulfate hemihydrate of 0.2:1 to 1.2:1;

wherein the first densified layer results from setting of an aqueous first densified layer slurry made from the stucco, the salt absorbent particles, and water, wherein the stucco comprises calcium sulfate hemihydrate and one or more chloride salts, and

wherein the aqueous first densified layer slurry is made from:

at least 60 wt. % of said calcium sulfate hemihydrate on a dry (water free) basis,

150 to 4000 parts by weight chloride anion per 1,000,000 parts by weight of said calcium sulfate hemihydrate,

the salt absorbent material in an amount of 0.5 to 10 parts by weight per 100 parts by weight of the stucco for the first densified layer slurry; and

the water at a weight ratio of water to the calcium sulfate hemihydrate of 0.2:1 to 1.2:1;

wherein parts by weight of said salt absorbent material per 100 parts by weight stucco in the aqueous central core layer slurry is relatively less than parts by weight of said salt absorbent material per 100 parts by weight stucco in the aqueous first densified layer slurry,

wherein parts by weight of said salt absorbent material per 100 parts by weight set gypsum in the central core layer is relatively less than parts by weight of said salt absorbent material per 100 parts by weight set gypsum in the first densified layer;

wherein the core has a density of about 15 to 55 pounds per cubic foot,

wherein the first densified layer has a density at least 1.1 times a density of the central core layer,

wherein the first densified layer is thinner than the central core layer, and

wherein thickness of the first densified layer is 5% to 25% of the thickness of the gypsum board;

wherein the central core layer has less than 0.01 wt. % zeolite and less than 0.01 wt. % hydrotalcite.

18. The gypsum board of claim 17 ,

the core further comprising a second densified layer comprising set gypsum, wherein the second densified layer is between the central core layer and the first cover sheet, wherein opposing sides of the second densified layer respectively contact the central core layer and the first cover sheet;

wherein the second densified layer resulted from setting of an aqueous second densified layer slurry made from stucco and water, wherein the stucco comprises calcium sulfate hemihydrate and one or more chloride salts, and

wherein the aqueous second densified layer slurry is made from:

at least 60 wt. % of said calcium sulfate hemihydrate on a dry (water free) basis,

150 to 4000 parts by weight chloride anion per 1,000,000 parts by weight of said calcium sulfate hemihydrate; and

the water at a weight ratio of water to the calcium sulfate hemihydrate of 0.2:1 to 1.2:1;

wherein the second densified layer has a density at least 1.1 times a density of the core layer,

wherein the second densified layer is thinner than the central core layer, and

wherein thickness of the second densified layer is 5% to 25% of the thickness of the gypsum board.

19. The gypsum board of claim 18 ,

wherein the second densified layer further comprises salt absorbent particles, wherein the salt absorbent particles comprise zeolite and/or hydrotalcite;

wherein the aqueous second densified layer slurry comprises:

zeolite and/or hydrotalcite in an amount of 0.5 to 10 parts by weight per 100 parts by weight of the stucco of the mixture of the second densified layer slurry.

20. A method of making a gypsum board of claim 1 having a core, comprising a central core layer and a first densified layer, the core having opposed first and second faces, the core comprising set gypsum, the set gypsum comprising calcium sulfate dihydrate, wherein the core is between a first cover sheet and a second cover sheet, comprising:

preparing an aqueous central core layer slurry comprising a mixture of stucco and water, wherein the stucco comprises calcium sulfate hemihydrate and one or more chloride salts,

disposing the aqueous central core layer slurry between the first cover sheet and the second cover sheet, wherein the first cover sheet comprises a first paper cover sheet or a first fiber glass mat, wherein the second cover sheet comprises a second paper cover sheet or a second fiber glass mat, and

disposing an aqueous first densified layer slurry comprising a mixture of water and stucco and salt absorbent particles between the second cover sheet and the central core layer to contact the second cover sheet and the central core layer, wherein the salt absorbent particles comprise salt absorbent material, wherein the salt absorbent material comprises zeolite, or hydrotalcite, or a blend of zeolite and hydrotalcite, wherein the stucco comprises calcium sulfate hemihydrate and the one or more chloride salts,

wherein the aqueous central core layer slurry is made from:

at least 60 wt. % said calcium sulfate hemihydrate on a dry (water free) basis,

150 to 4000 parts by weight chloride anion per 1,000,000 parts by weight said calcium sulfate hemihydrate, and

the water at a weight ratio of water to the calcium sulfate hemihydrate of 0.2:1 to 1.2:1; and

wherein the aqueous central core layer slurry is made from:

at least 60 wt. % said calcium sulfate hemihydrate on a dry (water free) basis,

150 to 4000 parts by weight chloride anion per 1,000,000 parts by weight said calcium sulfate hemihydrate,

the salt absorbent material in an amount of 0.5 to 10 parts by weight per 100 parts by weight of the stucco for the first densified layer slurry, and

the water at a weight ratio of water to the calcium sulfate hemihydrate of 0.2:1 to 1.2:1,

allowing the aqueous gypsum central core layer slurry to set to form a central core layer comprising calcium sulfate dihydrate, and allowing the aqueous gypsum first densified layer slurry to set to form a first densified layer comprising calcium sulfate dihydrate and the salt absorbent particles, to form a gypsum board preform comprising the central core layer, the first densified layer, the first cover sheet, and the second cover sheet;

cutting the gypsum board preform to produce the gypsum board; and

drying the gypsum board;

wherein parts by weight of salt absorbent material per 100 parts by weight stucco in the aqueous central core layer slurry is relatively less than parts by weight of salt absorbent material per 100 parts by weight stucco in the aqueous first densified layer slurry,

wherein parts by weight of salt absorbent material per 100 parts by weight set gypsum in the central core layer is relatively less than parts by weight of salt absorbent material per 100 parts by weight set gypsum in the first densified layer;

wherein the aqueous central core layer slurry is less dense than the aqueous first densified layer slurry;

wherein the core has a density of about 15 to 55 pounds per cubic foot,

wherein the first densified layer has a density at least 1.1 times a density of the central core layer,

wherein the first densified layer is thinner than the central core layer, and

wherein thickness of the first densified layer is 5% to 25% of the thickness of the gypsum board;

wherein the central core layer has less than 0.01 wt. % zeolite and less than 0.01 wt. % hydrotalcite.