Gypsum composition comprising uncooked starch having mid-range viscosity, and methods and products related thereto
Disclosed are product (e.g., board), slurry, and methods relating to an uncooked starch that can be used to enhance strength in one or more gypsum layers in the board. The uncooked starch has a hot water viscosity of from about 20 BU to about 300 BU according to the HWVA method, and/or a mid-range peak viscosity of from about 120 Brabender Units to about 1000 Brabender Units.
1. A gypsum board comprising:
a set gypsum core disposed between two cover sheets, the core formed from a slurry comprising stucco, water, a migratory starch, and at least one uncooked non-migratory, non-substituted starch having a hot water viscosity of from 20 Brabender Units to 300 Brabender Units when the viscosity is measured by the HWVA method;
wherein the gypsum board has a density of 35 pcf or less;
wherein the board has a nail pull resistance of at least about 72 lb-f according to ASTM 473-10, method B; and
wherein the at least one uncooked, non-migratory, non-substituted starch is included in the slurry in a weight percentage of total starch content in the slurry that is greater than 30%.
2. The gypsum board of claim 1 , wherein the migratory starch is an uncooked starch having a smaller chain length than a chain length of the at least one uncooked, non-substituted, non-migratory starch.
3. The gypsum board of claim 1 , wherein the at least one uncooked, non-substituted, non-migratory starch comprises an uncooked starch having a molecular weight of at least 15,000 Daltons.
4. The gypsum board of claim 3 , wherein the migratory starch has a molecular weight below 6,000 Daltons.
5. The gypsum board of claim 4 , wherein the at least one migratory starch comprises an acid-modified starch.
6. The gypsum board of claim 1 , wherein the uncooked, non-substituted, non-migratory starch is a native cereal starch or a native tuber starch that is chemically modified to provide the hot water viscosity of from 20 Brabender Units to 300 Brabender Units.
7. The gypsum board of claim 1 , wherein the uncooked, non-substituted, non-migratory starch has a hot water viscosity of from about 30 BU to about 200 BU.
8. The gypsum board of claim 1 , wherein the uncooked, non-substituted, non-migratory starch is acid-modified.
9. The gypsum board of claim 1 , wherein the migratory starch has migrated to a paper-core interface of the set gypsum core and at least one of the cover sheets.
10. The gypsum board of claim 1 , wherein the slurry further comprises a polyphosphate.
11. The gypsum board of claim 10 , wherein the slurry further comprises a dispersant.
12. The gypsum board of claim 1 , wherein the at least one uncooked, non-migratory, non-substituted starch is included in the slurry as a weight percentage of total starch content in the slurry that is greater than 60%.
13. The gypsum board of claim 12 , wherein the at least one uncooked, non-migratory, non-substituted starch is included in the slurry in an amount that is greater than 0.5% and less than 2% by weight of the stucco.
14. The gypsum board of claim 1 , wherein the at least one uncooked, non-migratory, non-substituted starch is included in the slurry as a weight percentage of total starch content in the slurry that is greater than 90%.
15. The gypsum board of claim 14 , wherein the at least one uncooked, non-migratory, non-substituted starch is included in the slurry in an amount that is greater than 0.5% and less than 2% by weight of the stucco.
16. A method of forming a gypsum board comprising:
chemically modifying an uncooked non-substituted starch having a hot water viscosity outside of a range of 20 Brabender Units to 300 Brabender Units when the viscosity is measured by the HWVA method to provide a chemically modified uncooked non-substituted starch having a hot water viscosity of from 20 Brabender Units to 300 Brabender Units;
preparing a slurry comprising stucco, water, and the chemically modified uncooked non-substituted starch; and
forming the prepared slurry over a first cover sheet; and
disposing a second cover sheet over the formed prepared slurry,
wherein the formed prepared slurry sets to form a set gypsum core between the first and second cover sheets;
wherein the gypsum board has a density of 35 pcf or less;
wherein the gypsum board has a nail pull resistance of at least about 72 lb-f according to ASTM 473-10, method B; and
wherein the chemically modified uncooked non-substituted starch is included in the slurry in a weight percentage of total starch content in the slurry that is greater than 30%.
17. The method of claim 16 , wherein the uncooked non-substituted starch before said chemically modifying is a native cereal starch or a native tuber starch.
18. The method of claim 16 , wherein said chemically modifying the uncooked non-substituted starch comprises acid-modifying or enzyme modifying the uncooked non-substituted starch to adjust a molecular weight.
19. The method of claim 16 , wherein said chemically modifying the uncooked non-substituted starch comprises acid-modifying to adjust a molecular weight, wherein said acid-modifying is halted by neutralizing an acid.
20. The method of claim 16 , wherein the prepared slurry further comprises an uncooked migratory starch.
21. The method of claim 20 , wherein the uncooked migratory starch is acid-modified.
22. The method of claim 20 ,
wherein the method further comprises drying the set gypsum core, and
wherein during said drying, the migratory uncooked starch migrates to a paper-core interface between the set gypsum core and at least one of the first and second cover sheets.