Composite light weight gypsum wallboard
The invention provides a light weight composite gypsum board including a foamed low density set gypsum core, a top non-foamed (or reduced-foamed) bonding high density layer and a bottom non-foamed (or reduced-foamed) bonding high density layer, a top cover sheet bonded to the foamed low density set gypsum core by the top non-foamed (or reduced-foamed) bonding high density layer, and a bottom cover sheet bonded to the foamed low density set gypsum core by the bottom non-foamed (or reduced-foamed) bonding high density layer. The foamed low density set gypsum core is prepared having a density of less than about 30 pcf using soap foam in the gypsum-containing slurry. The combination of components provide a composite gypsum board having light weight and high strength.
1. A composite light weight gypsum composite board comprising:
a foamed low density set gypsum core having a top surface and a bottom surface, the foamed low density set gypsum core made using a gypsum-containing slurry including stucco, from about 0.5% by weight to about 10% by weight pregelatinized starch, and foam,
a top non-foamed high density bonding layer having a thickness of about 2 mils to less than about 7 mils covering the top surface of the foamed low density set gypsum core,
a bottom non-foamed high density bonding layer having a thickness of about 2 mils to less than about 7 mils covering the bottom surface of the foamed low density set gypsum core,
the top and bottom non-foamed high density bonding layers comprising from about 10% by weight to about 16% by weight of the total amount of the gypsum-containing slurry,
a top cover sheet, and
a bottom cover sheet,
wherein the top cover sheet is bonded to the foamed low density set gypsum core by the top non-foamed high density bonding layer, and the bottom cover sheet is bonded to the foamed low density set gypsum core by the bottom non-foamed high density bonding layer, the foamed low density set gypsum core has a density from about 10 pcf to about 27 pcf and the top and bottom non-foamed high density bonding layers have a density from about 60 pcf to about 70 pcf, and wherein the composite board has a dry weight of about 1000 lb/msf or less for a ½ inch thick board, a nail pull resistance of at least about 77 lb/msf, and a core hardness of at least about 11 lb/msf.
2. The composite light weight gypsum board of claim 1 in which the pregelatinized starch is in the form of a pre-dispersion of about 10% by weight in water.
3. The composite light weight gypsum board of claim 1 , wherein the gypsum-containing slurry further comprises a naphthalenesulfonate dispersant present in an amount from about 0.1% by weight to about 3.0% by weight based on the weight of stucco.
4. The composite light weight gypsum board of claim 1 , wherein the gypsum-containing slurry further comprises a naphthalenesulfonate dispersant in the form of an aqueous solution containing from about 40% to about 45% by weight naphthalenesulfonate and the aqueous solution is present in the slurry in an amount from about 0.5% to about 2.5% by weight based on the weight of stucco.
5. The composite light weight gypsum board of claim 1 , wherein the gypsum-containing slurry further comprises sodium trimetaphosphate present in an amount from about 0.12% by weight to about 0.4% by weight based on the weight of stucco.
6. The composite light weight gypsum board of claim 1 , wherein the gypsum-containing slurry further comprises glass fiber present in an amount up to about 0.5% by weight based on the weight of stucco.
7. The composite light weight gypsum board of claim 1 , wherein the gypsum-containing slurry further comprises a waterproofing agent.
8. The composite light weight gypsum board of claim 1 , wherein the foam is soap foam, and the soap is present in an amount from about 0.3 lb/msf to about 0.5 lb/msf.
9. The composite light weight gypsum board of claim 1 , wherein the top cover sheet is paper having a weight of about 60 lb/msf.
10. The composite light weight gypsum board of claim 1 , wherein the top cover sheet is a fibrous mat.
11. The composite light weight gypsum board of claim 10 , wherein the fibrous mat is a nonwoven glass fiber mat.
12. The composite light weight gypsum board of claim 1 , wherein the gypsum-containing slurry has a water/stucco ratio from about 0.7 to about 1.3.
13. A composite light weight gypsum composite board comprising:
a foamed low density set gypsum core having a top surface and a bottom surface, the foamed low density set gypsum core made using a gypsum-containing slurry including stucco, pregelatinized starch, and foam,
a top reduced-foamed high density bonding layer having a thickness of about 2 mils to less than about 7 mils covering the top surface of the foamed low density set gypsum core,
a bottom reduced-foamed high density bonding layer having a thickness of about 2 mils to less than about 7 mils covering the bottom surface of the foamed low density set gypsum core,
a top cover sheet, and
a bottom cover sheet,
wherein the top cover sheet is bonded to the foamed low density set gypsum core by the top reduced-foamed high density bonding layer, and the bottom cover sheet is bonded to the foamed low density set gypsum core by the bottom reduced-foamed high density bonding layer, the foamed low density set gypsum core has a density from about 10 pcf to about 27 pcf and the top and bottom non-foamed high density bonding layers have a density from about 60 pcf to about 70 pcf, and wherein the composite board has a dry weight of about 1000 lb/msf for a ½ inch thick board, a nail pull resistance of at least about 77 lb/msf, and a core hardness of at least about 11 lb/msf.
14. The composite light weight gypsum board of claim 13 , wherein the pregelatinized starch is present in an amount from about 0.5% by weight to about 10% by weight based on the weight of stucco.
15. The composite light weight gypsum board of claim 13 in which the pregelatinized starch is in the form of a pre-dispersion of about 10% by weight in water.
16. The composite light weight gypsum board of claim 13 , wherein the gypsum-containing slurry further comprises a naphthalenesulfonate dispersant present in an amount from about 0.1% by weight to about 3.0% by weight based on the weight of stucco.
17. The composite light weight gypsum board of claim 13 , wherein the gypsum-containing slurry further comprises sodium trimetaphosphate present in an amount from about 0.12% by weight to about 0.4% by weight based on the weight of stucco.
18. The composite light weight gypsum board of claim 13 , wherein the foam is soap foam, and the soap is present in an amount from about 0.2 lb/msf to about 0.7 lb/msf.
19. The composite light weight gypsum board of claim 18 , wherein the top and bottom reduced-foamed high density bonding layers include about 5% by weight or less of the amount of soap used to make the foamed low density set gypsum core.
20. The composite light weight gypsum board of claim 13 , wherein the top cover sheet is paper having a weight of about 60 lb/msf.
21. The composite light weight gypsum board of claim 13 , wherein the foamed low density set gypsum core has a density from about 10 pcf to about 27 pcf.
22. The composite light weight gypsum board of claim 13 , wherein the top and bottom reduced-foamed high density bonding layers have a density from about 45 pcf to about 60 pcf.
23. A composite light weight gypsum composite board having a dry weight of about 1,000 lb./msf or less for a ½ inch thick board comprising:
a foamed low density set gypsum core having a top surface and a bottom surface, the foamed low density set gypsum core made using a gypsum-containing slurry including stucco from about 0.5% by weight to about 10% by weight pregelatinized starch, and foam,
a top non-foamed high density bonding layer having a thickness of about 2 mils to less than about 7 mils covering the top surface of the foamed low density set gypsum core,
a bottom non-foamed high density bonding layer having a thickness of about 2 mils to less than about 7 mils covering the bottom surface of the foamed low density set gypsum core,
the top and bottom non-foamed high density bonding layers comprising from about 10% by weight to about 16% by weight of the total amount of the gypsum-containing slurry,
a top fibrous mat cover sheet, and
a bottom cover sheet,
wherein the top cover sheet is bonded to the foamed low density set gypsum core by the top non-foamed high density bonding layer, and the bottom cover sheet is bonded to the foamed low density set gypsum core by the bottom non-foamed high density bonding layer, the foamed low density set gypsum core has a density from about 10 pcf to about 30 pcf and the top and bottom non-foamed high density bonding layers have a density from about 60 pcf to about 70 pcf.
24. The composite light weight gypsum board of claim 23 in which the pregelatinized starch is in the form of a pre-dispersion of about 10% by weight in water.
25. The composite light weight gypsum board of claim 23 , wherein the gypsum-containing slurry further comprises a naphthalenesulfonate dispersant present in an amount from about 0.1% by weight to about 3.0% by weight based on the weight of stucco.
26. The composite light weight gypsum board of claim 23 , wherein the gypsum-containing slurry further comprises sodium trimetaphosphate present in an amount from about 0.12% by weight to about 0.4% by weight based on the weight of stucco.
27. The composite light weight gypsum board of claim 23 , wherein the foam is soap foam, and the soap is present in an amount from about 0.2 lb/msf to about 0.7 lb/msf.
28. The composite light weight gypsum board of claim 23 , wherein the board has a dry weight from about 900 lb/msf to about 1100 lb/msf.
29. The composite light weight gypsum board of claim 23 , wherein the fibrous mat cover sheet is a nonwoven glass fiber mat.
30. A method of making composite light weight gypsum board having a dry weight from about 900 lbs./msf to about 1,100 lbs./msf, comprising the steps of:
(a) mixing a non-foamed gypsum-containing slurry having a density from about 80 pcf to about 85 pcf comprising
water, stucco, pregelatinized starch, and a naphthalenesulfonate dispersant,
wherein the pregelatinized starch is present in an amount from about 0.5% by weight to about 10% by weight based on the weight of stucco, and wherein the naphthalenesulfonate dispersant is present in an amount from about 0.1% to about 3.0% by weight based on the weight of stucco;
(b) depositing from about 6% to about 9% by weight of the total amount of the non-foamed gypsum-containing slurry on a first cover sheet;
(c) adding soap foam to from about 84% to about 90% by weight of the total amount of the non-foamed gypsum-containing slurry to form a foamed gypsum-containing slurry;
(d) depositing the foamed gypsum-containing slurry onto the non-foamed gypsum-containing slurry on the first cover sheet;
(e) depositing from about 4% to about 7% by weight of the total amount of the non-foamed gypsum-containing slurry on a second cover sheet;
(f) placing the non-foamed gypsum-containing slurry-covered surface of the second cover sheet over the deposited foamed gypsum-containing slurry to form a composite light weight gypsum board;
(g) cutting the composite light weight gypsum board after the foamed gypsum-containing slurry has hardened sufficiently for cutting; and
(h) drying the composite light weight gypsum board to provide a foamed low density set gypsum core in the finished composite light weight gypsum board.
31. The method of claim 30 in which the pregelatinized starch is in the form of a pre-dispersion of about 10% by weight in water.
32. The method of claim 30 , wherein the non-foamed gypsum-containing slurry further comprises sodium trimetaphosphate present in an amount from about 0.12% by weight to about 0.4% by weight based on the weight of stucco.
33. The method of claim 30 , wherein the non-foamed gypsum-containing slurry further comprises glass fiber present in an amount up to about 0.5% by weight based on the weight of stucco.
34. The method of claim 30 , wherein the non-foamed gypsum-containing slurry further comprises paper fiber present in an amount up to about 1.0% by weight based on the weight of stucco.
35. The method of claim 30 , wherein the soap foam includes soap present in an amount from about 0.3 lb/msf to about 0.5 lb/msf.
36. The method of claim 30 , wherein the first cover sheet and the second cover sheet are made of paper.
37. The method of claim 30 , wherein the first cover sheet is paper having a weight of about 60 lb/msf.
38. The method of claim 30 , wherein the first cover sheet is a fibrous mat.
39. The method of claim 38 , wherein the fibrous mat is a nonwoven glass fiber mat.
40. The method of claim 30 , wherein the foamed gypsum-containing slurry has a water/stucco ratio from about 0.7 to about 1.3.
41. The method of claim 30 , wherein the pregelatinized starch is corn starch.
42. A composite light weight gypsum board, comprising:
a foamed low density set gypsum core having a top surface and a bottom surface, the foamed low density set gypsum core made using a gypsum-containing slurry comprising water, stucco, pregelatinized corn starch present in an amount of about 6% by weight based on the weight of stucco, a 45% by weight aqueous solution of a naphthalenesulfonate dispersant present in an amount of about 1.2% by weight based on the weight of stucco, sodium trimetaphosphate present in an amount of about 0.3% by weight based on the weight of stucco, paper fiber present in an amount of about 1% based on the weight of stucco, and glass fiber present in an amount of about 0.5% based on the weight of stucco, and soap foam,
a top non-foamed high density bonding layer having a thickness of about 2 mils to less than about 7 mils covering the top surface of the foamed low density set gypsum core,
a bottom non-foamed high density bonding layer having a thickness of about 2 mils to less than about 7 mils covering the bottom surface of the foamed low density set gypsum core,
the top and bottom non-foamed high density bonding layers comprising from about 10% by weight to about 16% by weight of the total amount of the gypsum-containing slurry,
a top paper cover sheet having a weight of about 60 lb/msf, and
a bottom paper cover sheet,
wherein the top cover sheet is bonded to the foamed low density set gypsum core by the top non-foamed high density bonding layer, and the bottom cover sheet is bonded to the foamed low density set gypsum core by the bottom non-foamed high density bonding layer, wherein the foamed low density set gypsum core has a density of about 25 pcf, the top and bottom non-foamed high density bonding layers have a density from about 60 pcf to about 70 pcf and wherein the composite board has a dry weight of about 1000 lb/msf for a ½ inch thick board, a nail pull resistance of at least about 77 lb/msf, and a core hardness of at least about 11 lb/msf.
43. The composite light weight gypsum board of claim 42 in which the pregelatinized corn starch is in the form of a pre-dispersion of about 10% by weight in water.